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 978-0-9831592-3-0 @*
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_fputs to_rewind
1596 to_data to_isatty to_write
1597 to_delete to_put to_write_async_safe
1602 This is because the @code{gdb_stdout} is a variable of the type
1603 @code{struct ui_file} that is defined in @value{GDBN} sources as
1610 ui_file_flush_ftype *to_flush;
1611 ui_file_write_ftype *to_write;
1612 ui_file_write_async_safe_ftype *to_write_async_safe;
1613 ui_file_fputs_ftype *to_fputs;
1614 ui_file_read_ftype *to_read;
1615 ui_file_delete_ftype *to_delete;
1616 ui_file_isatty_ftype *to_isatty;
1617 ui_file_rewind_ftype *to_rewind;
1618 ui_file_put_ftype *to_put;
1625 @section Getting Help
1626 @cindex online documentation
1629 You can always ask @value{GDBN} itself for information on its commands,
1630 using the command @code{help}.
1633 @kindex h @r{(@code{help})}
1636 You can use @code{help} (abbreviated @code{h}) with no arguments to
1637 display a short list of named classes of commands:
1641 List of classes of commands:
1643 aliases -- Aliases of other commands
1644 breakpoints -- Making program stop at certain points
1645 data -- Examining data
1646 files -- Specifying and examining files
1647 internals -- Maintenance commands
1648 obscure -- Obscure features
1649 running -- Running the program
1650 stack -- Examining the stack
1651 status -- Status inquiries
1652 support -- Support facilities
1653 tracepoints -- Tracing of program execution without
1654 stopping the program
1655 user-defined -- User-defined commands
1657 Type "help" followed by a class name for a list of
1658 commands in that class.
1659 Type "help" followed by command name for full
1661 Command name abbreviations are allowed if unambiguous.
1664 @c the above line break eliminates huge line overfull...
1666 @item help @var{class}
1667 Using one of the general help classes as an argument, you can get a
1668 list of the individual commands in that class. For example, here is the
1669 help display for the class @code{status}:
1672 (@value{GDBP}) help status
1677 @c Line break in "show" line falsifies real output, but needed
1678 @c to fit in smallbook page size.
1679 info -- Generic command for showing things
1680 about the program being debugged
1681 show -- Generic command for showing things
1684 Type "help" followed by command name for full
1686 Command name abbreviations are allowed if unambiguous.
1690 @item help @var{command}
1691 With a command name as @code{help} argument, @value{GDBN} displays a
1692 short paragraph on how to use that command.
1695 @item apropos @var{args}
1696 The @code{apropos} command searches through all of the @value{GDBN}
1697 commands, and their documentation, for the regular expression specified in
1698 @var{args}. It prints out all matches found. For example:
1709 set symbol-reloading -- Set dynamic symbol table reloading
1710 multiple times in one run
1711 show symbol-reloading -- Show dynamic symbol table reloading
1712 multiple times in one run
1717 @item complete @var{args}
1718 The @code{complete @var{args}} command lists all the possible completions
1719 for the beginning of a command. Use @var{args} to specify the beginning of the
1720 command you want completed. For example:
1726 @noindent results in:
1737 @noindent This is intended for use by @sc{gnu} Emacs.
1740 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1741 and @code{show} to inquire about the state of your program, or the state
1742 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1743 manual introduces each of them in the appropriate context. The listings
1744 under @code{info} and under @code{show} in the Index point to
1745 all the sub-commands. @xref{Index}.
1750 @kindex i @r{(@code{info})}
1752 This command (abbreviated @code{i}) is for describing the state of your
1753 program. For example, you can show the arguments passed to a function
1754 with @code{info args}, list the registers currently in use with @code{info
1755 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1756 You can get a complete list of the @code{info} sub-commands with
1757 @w{@code{help info}}.
1761 You can assign the result of an expression to an environment variable with
1762 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1763 @code{set prompt $}.
1767 In contrast to @code{info}, @code{show} is for describing the state of
1768 @value{GDBN} itself.
1769 You can change most of the things you can @code{show}, by using the
1770 related command @code{set}; for example, you can control what number
1771 system is used for displays with @code{set radix}, or simply inquire
1772 which is currently in use with @code{show radix}.
1775 To display all the settable parameters and their current
1776 values, you can use @code{show} with no arguments; you may also use
1777 @code{info set}. Both commands produce the same display.
1778 @c FIXME: "info set" violates the rule that "info" is for state of
1779 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1780 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1784 Here are three miscellaneous @code{show} subcommands, all of which are
1785 exceptional in lacking corresponding @code{set} commands:
1788 @kindex show version
1789 @cindex @value{GDBN} version number
1791 Show what version of @value{GDBN} is running. You should include this
1792 information in @value{GDBN} bug-reports. If multiple versions of
1793 @value{GDBN} are in use at your site, you may need to determine which
1794 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1795 commands are introduced, and old ones may wither away. Also, many
1796 system vendors ship variant versions of @value{GDBN}, and there are
1797 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1798 The version number is the same as the one announced when you start
1801 @kindex show copying
1802 @kindex info copying
1803 @cindex display @value{GDBN} copyright
1806 Display information about permission for copying @value{GDBN}.
1808 @kindex show warranty
1809 @kindex info warranty
1811 @itemx info warranty
1812 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1813 if your version of @value{GDBN} comes with one.
1818 @chapter Running Programs Under @value{GDBN}
1820 When you run a program under @value{GDBN}, you must first generate
1821 debugging information when you compile it.
1823 You may start @value{GDBN} with its arguments, if any, in an environment
1824 of your choice. If you are doing native debugging, you may redirect
1825 your program's input and output, debug an already running process, or
1826 kill a child process.
1829 * Compilation:: Compiling for debugging
1830 * Starting:: Starting your program
1831 * Arguments:: Your program's arguments
1832 * Environment:: Your program's environment
1834 * Working Directory:: Your program's working directory
1835 * Input/Output:: Your program's input and output
1836 * Attach:: Debugging an already-running process
1837 * Kill Process:: Killing the child process
1839 * Inferiors and Programs:: Debugging multiple inferiors and programs
1840 * Threads:: Debugging programs with multiple threads
1841 * Forks:: Debugging forks
1842 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1846 @section Compiling for Debugging
1848 In order to debug a program effectively, you need to generate
1849 debugging information when you compile it. This debugging information
1850 is stored in the object file; it describes the data type of each
1851 variable or function and the correspondence between source line numbers
1852 and addresses in the executable code.
1854 To request debugging information, specify the @samp{-g} option when you run
1857 Programs that are to be shipped to your customers are compiled with
1858 optimizations, using the @samp{-O} compiler option. However, some
1859 compilers are unable to handle the @samp{-g} and @samp{-O} options
1860 together. Using those compilers, you cannot generate optimized
1861 executables containing debugging information.
1863 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1864 without @samp{-O}, making it possible to debug optimized code. We
1865 recommend that you @emph{always} use @samp{-g} whenever you compile a
1866 program. You may think your program is correct, but there is no sense
1867 in pushing your luck. For more information, see @ref{Optimized Code}.
1869 Older versions of the @sc{gnu} C compiler permitted a variant option
1870 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1871 format; if your @sc{gnu} C compiler has this option, do not use it.
1873 @value{GDBN} knows about preprocessor macros and can show you their
1874 expansion (@pxref{Macros}). Most compilers do not include information
1875 about preprocessor macros in the debugging information if you specify
1876 the @option{-g} flag alone, because this information is rather large.
1877 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1878 provides macro information if you specify the options
1879 @option{-gdwarf-2} and @option{-g3}; the former option requests
1880 debugging information in the Dwarf 2 format, and the latter requests
1881 ``extra information''. In the future, we hope to find more compact
1882 ways to represent macro information, so that it can be included with
1887 @section Starting your Program
1893 @kindex r @r{(@code{run})}
1896 Use the @code{run} command to start your program under @value{GDBN}.
1897 You must first specify the program name (except on VxWorks) with an
1898 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1899 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1900 (@pxref{Files, ,Commands to Specify Files}).
1904 If you are running your program in an execution environment that
1905 supports processes, @code{run} creates an inferior process and makes
1906 that process run your program. In some environments without processes,
1907 @code{run} jumps to the start of your program. Other targets,
1908 like @samp{remote}, are always running. If you get an error
1909 message like this one:
1912 The "remote" target does not support "run".
1913 Try "help target" or "continue".
1917 then use @code{continue} to run your program. You may need @code{load}
1918 first (@pxref{load}).
1920 The execution of a program is affected by certain information it
1921 receives from its superior. @value{GDBN} provides ways to specify this
1922 information, which you must do @emph{before} starting your program. (You
1923 can change it after starting your program, but such changes only affect
1924 your program the next time you start it.) This information may be
1925 divided into four categories:
1928 @item The @emph{arguments.}
1929 Specify the arguments to give your program as the arguments of the
1930 @code{run} command. If a shell is available on your target, the shell
1931 is used to pass the arguments, so that you may use normal conventions
1932 (such as wildcard expansion or variable substitution) in describing
1934 In Unix systems, you can control which shell is used with the
1935 @code{SHELL} environment variable.
1936 @xref{Arguments, ,Your Program's Arguments}.
1938 @item The @emph{environment.}
1939 Your program normally inherits its environment from @value{GDBN}, but you can
1940 use the @value{GDBN} commands @code{set environment} and @code{unset
1941 environment} to change parts of the environment that affect
1942 your program. @xref{Environment, ,Your Program's Environment}.
1944 @item The @emph{working directory.}
1945 Your program inherits its working directory from @value{GDBN}. You can set
1946 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1947 @xref{Working Directory, ,Your Program's Working Directory}.
1949 @item The @emph{standard input and output.}
1950 Your program normally uses the same device for standard input and
1951 standard output as @value{GDBN} is using. You can redirect input and output
1952 in the @code{run} command line, or you can use the @code{tty} command to
1953 set a different device for your program.
1954 @xref{Input/Output, ,Your Program's Input and Output}.
1957 @emph{Warning:} While input and output redirection work, you cannot use
1958 pipes to pass the output of the program you are debugging to another
1959 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1963 When you issue the @code{run} command, your program begins to execute
1964 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1965 of how to arrange for your program to stop. Once your program has
1966 stopped, you may call functions in your program, using the @code{print}
1967 or @code{call} commands. @xref{Data, ,Examining Data}.
1969 If the modification time of your symbol file has changed since the last
1970 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1971 table, and reads it again. When it does this, @value{GDBN} tries to retain
1972 your current breakpoints.
1977 @cindex run to main procedure
1978 The name of the main procedure can vary from language to language.
1979 With C or C@t{++}, the main procedure name is always @code{main}, but
1980 other languages such as Ada do not require a specific name for their
1981 main procedure. The debugger provides a convenient way to start the
1982 execution of the program and to stop at the beginning of the main
1983 procedure, depending on the language used.
1985 The @samp{start} command does the equivalent of setting a temporary
1986 breakpoint at the beginning of the main procedure and then invoking
1987 the @samp{run} command.
1989 @cindex elaboration phase
1990 Some programs contain an @dfn{elaboration} phase where some startup code is
1991 executed before the main procedure is called. This depends on the
1992 languages used to write your program. In C@t{++}, for instance,
1993 constructors for static and global objects are executed before
1994 @code{main} is called. It is therefore possible that the debugger stops
1995 before reaching the main procedure. However, the temporary breakpoint
1996 will remain to halt execution.
1998 Specify the arguments to give to your program as arguments to the
1999 @samp{start} command. These arguments will be given verbatim to the
2000 underlying @samp{run} command. Note that the same arguments will be
2001 reused if no argument is provided during subsequent calls to
2002 @samp{start} or @samp{run}.
2004 It is sometimes necessary to debug the program during elaboration. In
2005 these cases, using the @code{start} command would stop the execution of
2006 your program too late, as the program would have already completed the
2007 elaboration phase. Under these circumstances, insert breakpoints in your
2008 elaboration code before running your program.
2010 @kindex set exec-wrapper
2011 @item set exec-wrapper @var{wrapper}
2012 @itemx show exec-wrapper
2013 @itemx unset exec-wrapper
2014 When @samp{exec-wrapper} is set, the specified wrapper is used to
2015 launch programs for debugging. @value{GDBN} starts your program
2016 with a shell command of the form @kbd{exec @var{wrapper}
2017 @var{program}}. Quoting is added to @var{program} and its
2018 arguments, but not to @var{wrapper}, so you should add quotes if
2019 appropriate for your shell. The wrapper runs until it executes
2020 your program, and then @value{GDBN} takes control.
2022 You can use any program that eventually calls @code{execve} with
2023 its arguments as a wrapper. Several standard Unix utilities do
2024 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2025 with @code{exec "$@@"} will also work.
2027 For example, you can use @code{env} to pass an environment variable to
2028 the debugged program, without setting the variable in your shell's
2032 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2036 This command is available when debugging locally on most targets, excluding
2037 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2039 @kindex set disable-randomization
2040 @item set disable-randomization
2041 @itemx set disable-randomization on
2042 This option (enabled by default in @value{GDBN}) will turn off the native
2043 randomization of the virtual address space of the started program. This option
2044 is useful for multiple debugging sessions to make the execution better
2045 reproducible and memory addresses reusable across debugging sessions.
2047 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2051 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2054 @item set disable-randomization off
2055 Leave the behavior of the started executable unchanged. Some bugs rear their
2056 ugly heads only when the program is loaded at certain addresses. If your bug
2057 disappears when you run the program under @value{GDBN}, that might be because
2058 @value{GDBN} by default disables the address randomization on platforms, such
2059 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2060 disable-randomization off} to try to reproduce such elusive bugs.
2062 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2063 It protects the programs against some kinds of security attacks. In these
2064 cases the attacker needs to know the exact location of a concrete executable
2065 code. Randomizing its location makes it impossible to inject jumps misusing
2066 a code at its expected addresses.
2068 Prelinking shared libraries provides a startup performance advantage but it
2069 makes addresses in these libraries predictable for privileged processes by
2070 having just unprivileged access at the target system. Reading the shared
2071 library binary gives enough information for assembling the malicious code
2072 misusing it. Still even a prelinked shared library can get loaded at a new
2073 random address just requiring the regular relocation process during the
2074 startup. Shared libraries not already prelinked are always loaded at
2075 a randomly chosen address.
2077 Position independent executables (PIE) contain position independent code
2078 similar to the shared libraries and therefore such executables get loaded at
2079 a randomly chosen address upon startup. PIE executables always load even
2080 already prelinked shared libraries at a random address. You can build such
2081 executable using @command{gcc -fPIE -pie}.
2083 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2084 (as long as the randomization is enabled).
2086 @item show disable-randomization
2087 Show the current setting of the explicit disable of the native randomization of
2088 the virtual address space of the started program.
2093 @section Your Program's Arguments
2095 @cindex arguments (to your program)
2096 The arguments to your program can be specified by the arguments of the
2098 They are passed to a shell, which expands wildcard characters and
2099 performs redirection of I/O, and thence to your program. Your
2100 @code{SHELL} environment variable (if it exists) specifies what shell
2101 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2102 the default shell (@file{/bin/sh} on Unix).
2104 On non-Unix systems, the program is usually invoked directly by
2105 @value{GDBN}, which emulates I/O redirection via the appropriate system
2106 calls, and the wildcard characters are expanded by the startup code of
2107 the program, not by the shell.
2109 @code{run} with no arguments uses the same arguments used by the previous
2110 @code{run}, or those set by the @code{set args} command.
2115 Specify the arguments to be used the next time your program is run. If
2116 @code{set args} has no arguments, @code{run} executes your program
2117 with no arguments. Once you have run your program with arguments,
2118 using @code{set args} before the next @code{run} is the only way to run
2119 it again without arguments.
2123 Show the arguments to give your program when it is started.
2127 @section Your Program's Environment
2129 @cindex environment (of your program)
2130 The @dfn{environment} consists of a set of environment variables and
2131 their values. Environment variables conventionally record such things as
2132 your user name, your home directory, your terminal type, and your search
2133 path for programs to run. Usually you set up environment variables with
2134 the shell and they are inherited by all the other programs you run. When
2135 debugging, it can be useful to try running your program with a modified
2136 environment without having to start @value{GDBN} over again.
2140 @item path @var{directory}
2141 Add @var{directory} to the front of the @code{PATH} environment variable
2142 (the search path for executables) that will be passed to your program.
2143 The value of @code{PATH} used by @value{GDBN} does not change.
2144 You may specify several directory names, separated by whitespace or by a
2145 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2146 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2147 is moved to the front, so it is searched sooner.
2149 You can use the string @samp{$cwd} to refer to whatever is the current
2150 working directory at the time @value{GDBN} searches the path. If you
2151 use @samp{.} instead, it refers to the directory where you executed the
2152 @code{path} command. @value{GDBN} replaces @samp{.} in the
2153 @var{directory} argument (with the current path) before adding
2154 @var{directory} to the search path.
2155 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2156 @c document that, since repeating it would be a no-op.
2160 Display the list of search paths for executables (the @code{PATH}
2161 environment variable).
2163 @kindex show environment
2164 @item show environment @r{[}@var{varname}@r{]}
2165 Print the value of environment variable @var{varname} to be given to
2166 your program when it starts. If you do not supply @var{varname},
2167 print the names and values of all environment variables to be given to
2168 your program. You can abbreviate @code{environment} as @code{env}.
2170 @kindex set environment
2171 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2172 Set environment variable @var{varname} to @var{value}. The value
2173 changes for your program only, not for @value{GDBN} itself. @var{value} may
2174 be any string; the values of environment variables are just strings, and
2175 any interpretation is supplied by your program itself. The @var{value}
2176 parameter is optional; if it is eliminated, the variable is set to a
2178 @c "any string" here does not include leading, trailing
2179 @c blanks. Gnu asks: does anyone care?
2181 For example, this command:
2188 tells the debugged program, when subsequently run, that its user is named
2189 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2190 are not actually required.)
2192 @kindex unset environment
2193 @item unset environment @var{varname}
2194 Remove variable @var{varname} from the environment to be passed to your
2195 program. This is different from @samp{set env @var{varname} =};
2196 @code{unset environment} removes the variable from the environment,
2197 rather than assigning it an empty value.
2200 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2202 by your @code{SHELL} environment variable if it exists (or
2203 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2204 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2205 @file{.bashrc} for BASH---any variables you set in that file affect
2206 your program. You may wish to move setting of environment variables to
2207 files that are only run when you sign on, such as @file{.login} or
2210 @node Working Directory
2211 @section Your Program's Working Directory
2213 @cindex working directory (of your program)
2214 Each time you start your program with @code{run}, it inherits its
2215 working directory from the current working directory of @value{GDBN}.
2216 The @value{GDBN} working directory is initially whatever it inherited
2217 from its parent process (typically the shell), but you can specify a new
2218 working directory in @value{GDBN} with the @code{cd} command.
2220 The @value{GDBN} working directory also serves as a default for the commands
2221 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2226 @cindex change working directory
2227 @item cd @var{directory}
2228 Set the @value{GDBN} working directory to @var{directory}.
2232 Print the @value{GDBN} working directory.
2235 It is generally impossible to find the current working directory of
2236 the process being debugged (since a program can change its directory
2237 during its run). If you work on a system where @value{GDBN} is
2238 configured with the @file{/proc} support, you can use the @code{info
2239 proc} command (@pxref{SVR4 Process Information}) to find out the
2240 current working directory of the debuggee.
2243 @section Your Program's Input and Output
2248 By default, the program you run under @value{GDBN} does input and output to
2249 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2250 to its own terminal modes to interact with you, but it records the terminal
2251 modes your program was using and switches back to them when you continue
2252 running your program.
2255 @kindex info terminal
2257 Displays information recorded by @value{GDBN} about the terminal modes your
2261 You can redirect your program's input and/or output using shell
2262 redirection with the @code{run} command. For example,
2269 starts your program, diverting its output to the file @file{outfile}.
2272 @cindex controlling terminal
2273 Another way to specify where your program should do input and output is
2274 with the @code{tty} command. This command accepts a file name as
2275 argument, and causes this file to be the default for future @code{run}
2276 commands. It also resets the controlling terminal for the child
2277 process, for future @code{run} commands. For example,
2284 directs that processes started with subsequent @code{run} commands
2285 default to do input and output on the terminal @file{/dev/ttyb} and have
2286 that as their controlling terminal.
2288 An explicit redirection in @code{run} overrides the @code{tty} command's
2289 effect on the input/output device, but not its effect on the controlling
2292 When you use the @code{tty} command or redirect input in the @code{run}
2293 command, only the input @emph{for your program} is affected. The input
2294 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2295 for @code{set inferior-tty}.
2297 @cindex inferior tty
2298 @cindex set inferior controlling terminal
2299 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2300 display the name of the terminal that will be used for future runs of your
2304 @item set inferior-tty /dev/ttyb
2305 @kindex set inferior-tty
2306 Set the tty for the program being debugged to /dev/ttyb.
2308 @item show inferior-tty
2309 @kindex show inferior-tty
2310 Show the current tty for the program being debugged.
2314 @section Debugging an Already-running Process
2319 @item attach @var{process-id}
2320 This command attaches to a running process---one that was started
2321 outside @value{GDBN}. (@code{info files} shows your active
2322 targets.) The command takes as argument a process ID. The usual way to
2323 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2324 or with the @samp{jobs -l} shell command.
2326 @code{attach} does not repeat if you press @key{RET} a second time after
2327 executing the command.
2330 To use @code{attach}, your program must be running in an environment
2331 which supports processes; for example, @code{attach} does not work for
2332 programs on bare-board targets that lack an operating system. You must
2333 also have permission to send the process a signal.
2335 When you use @code{attach}, the debugger finds the program running in
2336 the process first by looking in the current working directory, then (if
2337 the program is not found) by using the source file search path
2338 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2339 the @code{file} command to load the program. @xref{Files, ,Commands to
2342 The first thing @value{GDBN} does after arranging to debug the specified
2343 process is to stop it. You can examine and modify an attached process
2344 with all the @value{GDBN} commands that are ordinarily available when
2345 you start processes with @code{run}. You can insert breakpoints; you
2346 can step and continue; you can modify storage. If you would rather the
2347 process continue running, you may use the @code{continue} command after
2348 attaching @value{GDBN} to the process.
2353 When you have finished debugging the attached process, you can use the
2354 @code{detach} command to release it from @value{GDBN} control. Detaching
2355 the process continues its execution. After the @code{detach} command,
2356 that process and @value{GDBN} become completely independent once more, and you
2357 are ready to @code{attach} another process or start one with @code{run}.
2358 @code{detach} does not repeat if you press @key{RET} again after
2359 executing the command.
2362 If you exit @value{GDBN} while you have an attached process, you detach
2363 that process. If you use the @code{run} command, you kill that process.
2364 By default, @value{GDBN} asks for confirmation if you try to do either of these
2365 things; you can control whether or not you need to confirm by using the
2366 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2370 @section Killing the Child Process
2375 Kill the child process in which your program is running under @value{GDBN}.
2378 This command is useful if you wish to debug a core dump instead of a
2379 running process. @value{GDBN} ignores any core dump file while your program
2382 On some operating systems, a program cannot be executed outside @value{GDBN}
2383 while you have breakpoints set on it inside @value{GDBN}. You can use the
2384 @code{kill} command in this situation to permit running your program
2385 outside the debugger.
2387 The @code{kill} command is also useful if you wish to recompile and
2388 relink your program, since on many systems it is impossible to modify an
2389 executable file while it is running in a process. In this case, when you
2390 next type @code{run}, @value{GDBN} notices that the file has changed, and
2391 reads the symbol table again (while trying to preserve your current
2392 breakpoint settings).
2394 @node Inferiors and Programs
2395 @section Debugging Multiple Inferiors and Programs
2397 @value{GDBN} lets you run and debug multiple programs in a single
2398 session. In addition, @value{GDBN} on some systems may let you run
2399 several programs simultaneously (otherwise you have to exit from one
2400 before starting another). In the most general case, you can have
2401 multiple threads of execution in each of multiple processes, launched
2402 from multiple executables.
2405 @value{GDBN} represents the state of each program execution with an
2406 object called an @dfn{inferior}. An inferior typically corresponds to
2407 a process, but is more general and applies also to targets that do not
2408 have processes. Inferiors may be created before a process runs, and
2409 may be retained after a process exits. Inferiors have unique
2410 identifiers that are different from process ids. Usually each
2411 inferior will also have its own distinct address space, although some
2412 embedded targets may have several inferiors running in different parts
2413 of a single address space. Each inferior may in turn have multiple
2414 threads running in it.
2416 To find out what inferiors exist at any moment, use @w{@code{info
2420 @kindex info inferiors
2421 @item info inferiors
2422 Print a list of all inferiors currently being managed by @value{GDBN}.
2424 @value{GDBN} displays for each inferior (in this order):
2428 the inferior number assigned by @value{GDBN}
2431 the target system's inferior identifier
2434 the name of the executable the inferior is running.
2439 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2440 indicates the current inferior.
2444 @c end table here to get a little more width for example
2447 (@value{GDBP}) info inferiors
2448 Num Description Executable
2449 2 process 2307 hello
2450 * 1 process 3401 goodbye
2453 To switch focus between inferiors, use the @code{inferior} command:
2456 @kindex inferior @var{infno}
2457 @item inferior @var{infno}
2458 Make inferior number @var{infno} the current inferior. The argument
2459 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2460 in the first field of the @samp{info inferiors} display.
2464 You can get multiple executables into a debugging session via the
2465 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2466 systems @value{GDBN} can add inferiors to the debug session
2467 automatically by following calls to @code{fork} and @code{exec}. To
2468 remove inferiors from the debugging session use the
2469 @w{@code{remove-inferiors}} command.
2472 @kindex add-inferior
2473 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2474 Adds @var{n} inferiors to be run using @var{executable} as the
2475 executable. @var{n} defaults to 1. If no executable is specified,
2476 the inferiors begins empty, with no program. You can still assign or
2477 change the program assigned to the inferior at any time by using the
2478 @code{file} command with the executable name as its argument.
2480 @kindex clone-inferior
2481 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2482 Adds @var{n} inferiors ready to execute the same program as inferior
2483 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2484 number of the current inferior. This is a convenient command when you
2485 want to run another instance of the inferior you are debugging.
2488 (@value{GDBP}) info inferiors
2489 Num Description Executable
2490 * 1 process 29964 helloworld
2491 (@value{GDBP}) clone-inferior
2494 (@value{GDBP}) info inferiors
2495 Num Description Executable
2497 * 1 process 29964 helloworld
2500 You can now simply switch focus to inferior 2 and run it.
2502 @kindex remove-inferiors
2503 @item remove-inferiors @var{infno}@dots{}
2504 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2505 possible to remove an inferior that is running with this command. For
2506 those, use the @code{kill} or @code{detach} command first.
2510 To quit debugging one of the running inferiors that is not the current
2511 inferior, you can either detach from it by using the @w{@code{detach
2512 inferior}} command (allowing it to run independently), or kill it
2513 using the @w{@code{kill inferiors}} command:
2516 @kindex detach inferiors @var{infno}@dots{}
2517 @item detach inferior @var{infno}@dots{}
2518 Detach from the inferior or inferiors identified by @value{GDBN}
2519 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2520 still stays on the list of inferiors shown by @code{info inferiors},
2521 but its Description will show @samp{<null>}.
2523 @kindex kill inferiors @var{infno}@dots{}
2524 @item kill inferiors @var{infno}@dots{}
2525 Kill the inferior or inferiors identified by @value{GDBN} inferior
2526 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2527 stays on the list of inferiors shown by @code{info inferiors}, but its
2528 Description will show @samp{<null>}.
2531 After the successful completion of a command such as @code{detach},
2532 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2533 a normal process exit, the inferior is still valid and listed with
2534 @code{info inferiors}, ready to be restarted.
2537 To be notified when inferiors are started or exit under @value{GDBN}'s
2538 control use @w{@code{set print inferior-events}}:
2541 @kindex set print inferior-events
2542 @cindex print messages on inferior start and exit
2543 @item set print inferior-events
2544 @itemx set print inferior-events on
2545 @itemx set print inferior-events off
2546 The @code{set print inferior-events} command allows you to enable or
2547 disable printing of messages when @value{GDBN} notices that new
2548 inferiors have started or that inferiors have exited or have been
2549 detached. By default, these messages will not be printed.
2551 @kindex show print inferior-events
2552 @item show print inferior-events
2553 Show whether messages will be printed when @value{GDBN} detects that
2554 inferiors have started, exited or have been detached.
2557 Many commands will work the same with multiple programs as with a
2558 single program: e.g., @code{print myglobal} will simply display the
2559 value of @code{myglobal} in the current inferior.
2562 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2563 get more info about the relationship of inferiors, programs, address
2564 spaces in a debug session. You can do that with the @w{@code{maint
2565 info program-spaces}} command.
2568 @kindex maint info program-spaces
2569 @item maint info program-spaces
2570 Print a list of all program spaces currently being managed by
2573 @value{GDBN} displays for each program space (in this order):
2577 the program space number assigned by @value{GDBN}
2580 the name of the executable loaded into the program space, with e.g.,
2581 the @code{file} command.
2586 An asterisk @samp{*} preceding the @value{GDBN} program space number
2587 indicates the current program space.
2589 In addition, below each program space line, @value{GDBN} prints extra
2590 information that isn't suitable to display in tabular form. For
2591 example, the list of inferiors bound to the program space.
2594 (@value{GDBP}) maint info program-spaces
2597 Bound inferiors: ID 1 (process 21561)
2601 Here we can see that no inferior is running the program @code{hello},
2602 while @code{process 21561} is running the program @code{goodbye}. On
2603 some targets, it is possible that multiple inferiors are bound to the
2604 same program space. The most common example is that of debugging both
2605 the parent and child processes of a @code{vfork} call. For example,
2608 (@value{GDBP}) maint info program-spaces
2611 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2614 Here, both inferior 2 and inferior 1 are running in the same program
2615 space as a result of inferior 1 having executed a @code{vfork} call.
2619 @section Debugging Programs with Multiple Threads
2621 @cindex threads of execution
2622 @cindex multiple threads
2623 @cindex switching threads
2624 In some operating systems, such as HP-UX and Solaris, a single program
2625 may have more than one @dfn{thread} of execution. The precise semantics
2626 of threads differ from one operating system to another, but in general
2627 the threads of a single program are akin to multiple processes---except
2628 that they share one address space (that is, they can all examine and
2629 modify the same variables). On the other hand, each thread has its own
2630 registers and execution stack, and perhaps private memory.
2632 @value{GDBN} provides these facilities for debugging multi-thread
2636 @item automatic notification of new threads
2637 @item @samp{thread @var{threadno}}, a command to switch among threads
2638 @item @samp{info threads}, a command to inquire about existing threads
2639 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2640 a command to apply a command to a list of threads
2641 @item thread-specific breakpoints
2642 @item @samp{set print thread-events}, which controls printing of
2643 messages on thread start and exit.
2644 @item @samp{set libthread-db-search-path @var{path}}, which lets
2645 the user specify which @code{libthread_db} to use if the default choice
2646 isn't compatible with the program.
2650 @emph{Warning:} These facilities are not yet available on every
2651 @value{GDBN} configuration where the operating system supports threads.
2652 If your @value{GDBN} does not support threads, these commands have no
2653 effect. For example, a system without thread support shows no output
2654 from @samp{info threads}, and always rejects the @code{thread} command,
2658 (@value{GDBP}) info threads
2659 (@value{GDBP}) thread 1
2660 Thread ID 1 not known. Use the "info threads" command to
2661 see the IDs of currently known threads.
2663 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2664 @c doesn't support threads"?
2667 @cindex focus of debugging
2668 @cindex current thread
2669 The @value{GDBN} thread debugging facility allows you to observe all
2670 threads while your program runs---but whenever @value{GDBN} takes
2671 control, one thread in particular is always the focus of debugging.
2672 This thread is called the @dfn{current thread}. Debugging commands show
2673 program information from the perspective of the current thread.
2675 @cindex @code{New} @var{systag} message
2676 @cindex thread identifier (system)
2677 @c FIXME-implementors!! It would be more helpful if the [New...] message
2678 @c included GDB's numeric thread handle, so you could just go to that
2679 @c thread without first checking `info threads'.
2680 Whenever @value{GDBN} detects a new thread in your program, it displays
2681 the target system's identification for the thread with a message in the
2682 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2683 whose form varies depending on the particular system. For example, on
2684 @sc{gnu}/Linux, you might see
2687 [New Thread 0x41e02940 (LWP 25582)]
2691 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2692 the @var{systag} is simply something like @samp{process 368}, with no
2695 @c FIXME!! (1) Does the [New...] message appear even for the very first
2696 @c thread of a program, or does it only appear for the
2697 @c second---i.e.@: when it becomes obvious we have a multithread
2699 @c (2) *Is* there necessarily a first thread always? Or do some
2700 @c multithread systems permit starting a program with multiple
2701 @c threads ab initio?
2703 @cindex thread number
2704 @cindex thread identifier (GDB)
2705 For debugging purposes, @value{GDBN} associates its own thread
2706 number---always a single integer---with each thread in your program.
2709 @kindex info threads
2710 @item info threads @r{[}@var{id}@dots{}@r{]}
2711 Display a summary of all threads currently in your program. Optional
2712 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2713 means to print information only about the specified thread or threads.
2714 @value{GDBN} displays for each thread (in this order):
2718 the thread number assigned by @value{GDBN}
2721 the target system's thread identifier (@var{systag})
2724 the thread's name, if one is known. A thread can either be named by
2725 the user (see @code{thread name}, below), or, in some cases, by the
2729 the current stack frame summary for that thread
2733 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2734 indicates the current thread.
2738 @c end table here to get a little more width for example
2741 (@value{GDBP}) info threads
2743 3 process 35 thread 27 0x34e5 in sigpause ()
2744 2 process 35 thread 23 0x34e5 in sigpause ()
2745 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2749 On Solaris, you can display more information about user threads with a
2750 Solaris-specific command:
2753 @item maint info sol-threads
2754 @kindex maint info sol-threads
2755 @cindex thread info (Solaris)
2756 Display info on Solaris user threads.
2760 @kindex thread @var{threadno}
2761 @item thread @var{threadno}
2762 Make thread number @var{threadno} the current thread. The command
2763 argument @var{threadno} is the internal @value{GDBN} thread number, as
2764 shown in the first field of the @samp{info threads} display.
2765 @value{GDBN} responds by displaying the system identifier of the thread
2766 you selected, and its current stack frame summary:
2769 (@value{GDBP}) thread 2
2770 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2771 #0 some_function (ignore=0x0) at example.c:8
2772 8 printf ("hello\n");
2776 As with the @samp{[New @dots{}]} message, the form of the text after
2777 @samp{Switching to} depends on your system's conventions for identifying
2780 @vindex $_thread@r{, convenience variable}
2781 The debugger convenience variable @samp{$_thread} contains the number
2782 of the current thread. You may find this useful in writing breakpoint
2783 conditional expressions, command scripts, and so forth. See
2784 @xref{Convenience Vars,, Convenience Variables}, for general
2785 information on convenience variables.
2787 @kindex thread apply
2788 @cindex apply command to several threads
2789 @item thread apply [@var{threadno} | all] @var{command}
2790 The @code{thread apply} command allows you to apply the named
2791 @var{command} to one or more threads. Specify the numbers of the
2792 threads that you want affected with the command argument
2793 @var{threadno}. It can be a single thread number, one of the numbers
2794 shown in the first field of the @samp{info threads} display; or it
2795 could be a range of thread numbers, as in @code{2-4}. To apply a
2796 command to all threads, type @kbd{thread apply all @var{command}}.
2799 @cindex name a thread
2800 @item thread name [@var{name}]
2801 This command assigns a name to the current thread. If no argument is
2802 given, any existing user-specified name is removed. The thread name
2803 appears in the @samp{info threads} display.
2805 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2806 determine the name of the thread as given by the OS. On these
2807 systems, a name specified with @samp{thread name} will override the
2808 system-give name, and removing the user-specified name will cause
2809 @value{GDBN} to once again display the system-specified name.
2812 @cindex search for a thread
2813 @item thread find [@var{regexp}]
2814 Search for and display thread ids whose name or @var{systag}
2815 matches the supplied regular expression.
2817 As well as being the complement to the @samp{thread name} command,
2818 this command also allows you to identify a thread by its target
2819 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2823 (@value{GDBN}) thread find 26688
2824 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2825 (@value{GDBN}) info thread 4
2827 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2830 @kindex set print thread-events
2831 @cindex print messages on thread start and exit
2832 @item set print thread-events
2833 @itemx set print thread-events on
2834 @itemx set print thread-events off
2835 The @code{set print thread-events} command allows you to enable or
2836 disable printing of messages when @value{GDBN} notices that new threads have
2837 started or that threads have exited. By default, these messages will
2838 be printed if detection of these events is supported by the target.
2839 Note that these messages cannot be disabled on all targets.
2841 @kindex show print thread-events
2842 @item show print thread-events
2843 Show whether messages will be printed when @value{GDBN} detects that threads
2844 have started and exited.
2847 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2848 more information about how @value{GDBN} behaves when you stop and start
2849 programs with multiple threads.
2851 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2852 watchpoints in programs with multiple threads.
2855 @kindex set libthread-db-search-path
2856 @cindex search path for @code{libthread_db}
2857 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2858 If this variable is set, @var{path} is a colon-separated list of
2859 directories @value{GDBN} will use to search for @code{libthread_db}.
2860 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2861 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2862 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2865 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2866 @code{libthread_db} library to obtain information about threads in the
2867 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2868 to find @code{libthread_db}.
2870 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2871 refers to the default system directories that are
2872 normally searched for loading shared libraries.
2874 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2875 refers to the directory from which @code{libpthread}
2876 was loaded in the inferior process.
2878 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2879 @value{GDBN} attempts to initialize it with the current inferior process.
2880 If this initialization fails (which could happen because of a version
2881 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2882 will unload @code{libthread_db}, and continue with the next directory.
2883 If none of @code{libthread_db} libraries initialize successfully,
2884 @value{GDBN} will issue a warning and thread debugging will be disabled.
2886 Setting @code{libthread-db-search-path} is currently implemented
2887 only on some platforms.
2889 @kindex show libthread-db-search-path
2890 @item show libthread-db-search-path
2891 Display current libthread_db search path.
2893 @kindex set debug libthread-db
2894 @kindex show debug libthread-db
2895 @cindex debugging @code{libthread_db}
2896 @item set debug libthread-db
2897 @itemx show debug libthread-db
2898 Turns on or off display of @code{libthread_db}-related events.
2899 Use @code{1} to enable, @code{0} to disable.
2903 @section Debugging Forks
2905 @cindex fork, debugging programs which call
2906 @cindex multiple processes
2907 @cindex processes, multiple
2908 On most systems, @value{GDBN} has no special support for debugging
2909 programs which create additional processes using the @code{fork}
2910 function. When a program forks, @value{GDBN} will continue to debug the
2911 parent process and the child process will run unimpeded. If you have
2912 set a breakpoint in any code which the child then executes, the child
2913 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2914 will cause it to terminate.
2916 However, if you want to debug the child process there is a workaround
2917 which isn't too painful. Put a call to @code{sleep} in the code which
2918 the child process executes after the fork. It may be useful to sleep
2919 only if a certain environment variable is set, or a certain file exists,
2920 so that the delay need not occur when you don't want to run @value{GDBN}
2921 on the child. While the child is sleeping, use the @code{ps} program to
2922 get its process ID. Then tell @value{GDBN} (a new invocation of
2923 @value{GDBN} if you are also debugging the parent process) to attach to
2924 the child process (@pxref{Attach}). From that point on you can debug
2925 the child process just like any other process which you attached to.
2927 On some systems, @value{GDBN} provides support for debugging programs that
2928 create additional processes using the @code{fork} or @code{vfork} functions.
2929 Currently, the only platforms with this feature are HP-UX (11.x and later
2930 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2932 By default, when a program forks, @value{GDBN} will continue to debug
2933 the parent process and the child process will run unimpeded.
2935 If you want to follow the child process instead of the parent process,
2936 use the command @w{@code{set follow-fork-mode}}.
2939 @kindex set follow-fork-mode
2940 @item set follow-fork-mode @var{mode}
2941 Set the debugger response to a program call of @code{fork} or
2942 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2943 process. The @var{mode} argument can be:
2947 The original process is debugged after a fork. The child process runs
2948 unimpeded. This is the default.
2951 The new process is debugged after a fork. The parent process runs
2956 @kindex show follow-fork-mode
2957 @item show follow-fork-mode
2958 Display the current debugger response to a @code{fork} or @code{vfork} call.
2961 @cindex debugging multiple processes
2962 On Linux, if you want to debug both the parent and child processes, use the
2963 command @w{@code{set detach-on-fork}}.
2966 @kindex set detach-on-fork
2967 @item set detach-on-fork @var{mode}
2968 Tells gdb whether to detach one of the processes after a fork, or
2969 retain debugger control over them both.
2973 The child process (or parent process, depending on the value of
2974 @code{follow-fork-mode}) will be detached and allowed to run
2975 independently. This is the default.
2978 Both processes will be held under the control of @value{GDBN}.
2979 One process (child or parent, depending on the value of
2980 @code{follow-fork-mode}) is debugged as usual, while the other
2985 @kindex show detach-on-fork
2986 @item show detach-on-fork
2987 Show whether detach-on-fork mode is on/off.
2990 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2991 will retain control of all forked processes (including nested forks).
2992 You can list the forked processes under the control of @value{GDBN} by
2993 using the @w{@code{info inferiors}} command, and switch from one fork
2994 to another by using the @code{inferior} command (@pxref{Inferiors and
2995 Programs, ,Debugging Multiple Inferiors and Programs}).
2997 To quit debugging one of the forked processes, you can either detach
2998 from it by using the @w{@code{detach inferiors}} command (allowing it
2999 to run independently), or kill it using the @w{@code{kill inferiors}}
3000 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3003 If you ask to debug a child process and a @code{vfork} is followed by an
3004 @code{exec}, @value{GDBN} executes the new target up to the first
3005 breakpoint in the new target. If you have a breakpoint set on
3006 @code{main} in your original program, the breakpoint will also be set on
3007 the child process's @code{main}.
3009 On some systems, when a child process is spawned by @code{vfork}, you
3010 cannot debug the child or parent until an @code{exec} call completes.
3012 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3013 call executes, the new target restarts. To restart the parent
3014 process, use the @code{file} command with the parent executable name
3015 as its argument. By default, after an @code{exec} call executes,
3016 @value{GDBN} discards the symbols of the previous executable image.
3017 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3021 @kindex set follow-exec-mode
3022 @item set follow-exec-mode @var{mode}
3024 Set debugger response to a program call of @code{exec}. An
3025 @code{exec} call replaces the program image of a process.
3027 @code{follow-exec-mode} can be:
3031 @value{GDBN} creates a new inferior and rebinds the process to this
3032 new inferior. The program the process was running before the
3033 @code{exec} call can be restarted afterwards by restarting the
3039 (@value{GDBP}) info inferiors
3041 Id Description Executable
3044 process 12020 is executing new program: prog2
3045 Program exited normally.
3046 (@value{GDBP}) info inferiors
3047 Id Description Executable
3053 @value{GDBN} keeps the process bound to the same inferior. The new
3054 executable image replaces the previous executable loaded in the
3055 inferior. Restarting the inferior after the @code{exec} call, with
3056 e.g., the @code{run} command, restarts the executable the process was
3057 running after the @code{exec} call. This is the default mode.
3062 (@value{GDBP}) info inferiors
3063 Id Description Executable
3066 process 12020 is executing new program: prog2
3067 Program exited normally.
3068 (@value{GDBP}) info inferiors
3069 Id Description Executable
3076 You can use the @code{catch} command to make @value{GDBN} stop whenever
3077 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3078 Catchpoints, ,Setting Catchpoints}.
3080 @node Checkpoint/Restart
3081 @section Setting a @emph{Bookmark} to Return to Later
3086 @cindex snapshot of a process
3087 @cindex rewind program state
3089 On certain operating systems@footnote{Currently, only
3090 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3091 program's state, called a @dfn{checkpoint}, and come back to it
3094 Returning to a checkpoint effectively undoes everything that has
3095 happened in the program since the @code{checkpoint} was saved. This
3096 includes changes in memory, registers, and even (within some limits)
3097 system state. Effectively, it is like going back in time to the
3098 moment when the checkpoint was saved.
3100 Thus, if you're stepping thru a program and you think you're
3101 getting close to the point where things go wrong, you can save
3102 a checkpoint. Then, if you accidentally go too far and miss
3103 the critical statement, instead of having to restart your program
3104 from the beginning, you can just go back to the checkpoint and
3105 start again from there.
3107 This can be especially useful if it takes a lot of time or
3108 steps to reach the point where you think the bug occurs.
3110 To use the @code{checkpoint}/@code{restart} method of debugging:
3115 Save a snapshot of the debugged program's current execution state.
3116 The @code{checkpoint} command takes no arguments, but each checkpoint
3117 is assigned a small integer id, similar to a breakpoint id.
3119 @kindex info checkpoints
3120 @item info checkpoints
3121 List the checkpoints that have been saved in the current debugging
3122 session. For each checkpoint, the following information will be
3129 @item Source line, or label
3132 @kindex restart @var{checkpoint-id}
3133 @item restart @var{checkpoint-id}
3134 Restore the program state that was saved as checkpoint number
3135 @var{checkpoint-id}. All program variables, registers, stack frames
3136 etc.@: will be returned to the values that they had when the checkpoint
3137 was saved. In essence, gdb will ``wind back the clock'' to the point
3138 in time when the checkpoint was saved.
3140 Note that breakpoints, @value{GDBN} variables, command history etc.
3141 are not affected by restoring a checkpoint. In general, a checkpoint
3142 only restores things that reside in the program being debugged, not in
3145 @kindex delete checkpoint @var{checkpoint-id}
3146 @item delete checkpoint @var{checkpoint-id}
3147 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3151 Returning to a previously saved checkpoint will restore the user state
3152 of the program being debugged, plus a significant subset of the system
3153 (OS) state, including file pointers. It won't ``un-write'' data from
3154 a file, but it will rewind the file pointer to the previous location,
3155 so that the previously written data can be overwritten. For files
3156 opened in read mode, the pointer will also be restored so that the
3157 previously read data can be read again.
3159 Of course, characters that have been sent to a printer (or other
3160 external device) cannot be ``snatched back'', and characters received
3161 from eg.@: a serial device can be removed from internal program buffers,
3162 but they cannot be ``pushed back'' into the serial pipeline, ready to
3163 be received again. Similarly, the actual contents of files that have
3164 been changed cannot be restored (at this time).
3166 However, within those constraints, you actually can ``rewind'' your
3167 program to a previously saved point in time, and begin debugging it
3168 again --- and you can change the course of events so as to debug a
3169 different execution path this time.
3171 @cindex checkpoints and process id
3172 Finally, there is one bit of internal program state that will be
3173 different when you return to a checkpoint --- the program's process
3174 id. Each checkpoint will have a unique process id (or @var{pid}),
3175 and each will be different from the program's original @var{pid}.
3176 If your program has saved a local copy of its process id, this could
3177 potentially pose a problem.
3179 @subsection A Non-obvious Benefit of Using Checkpoints
3181 On some systems such as @sc{gnu}/Linux, address space randomization
3182 is performed on new processes for security reasons. This makes it
3183 difficult or impossible to set a breakpoint, or watchpoint, on an
3184 absolute address if you have to restart the program, since the
3185 absolute location of a symbol will change from one execution to the
3188 A checkpoint, however, is an @emph{identical} copy of a process.
3189 Therefore if you create a checkpoint at (eg.@:) the start of main,
3190 and simply return to that checkpoint instead of restarting the
3191 process, you can avoid the effects of address randomization and
3192 your symbols will all stay in the same place.
3195 @chapter Stopping and Continuing
3197 The principal purposes of using a debugger are so that you can stop your
3198 program before it terminates; or so that, if your program runs into
3199 trouble, you can investigate and find out why.
3201 Inside @value{GDBN}, your program may stop for any of several reasons,
3202 such as a signal, a breakpoint, or reaching a new line after a
3203 @value{GDBN} command such as @code{step}. You may then examine and
3204 change variables, set new breakpoints or remove old ones, and then
3205 continue execution. Usually, the messages shown by @value{GDBN} provide
3206 ample explanation of the status of your program---but you can also
3207 explicitly request this information at any time.
3210 @kindex info program
3212 Display information about the status of your program: whether it is
3213 running or not, what process it is, and why it stopped.
3217 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3218 * Continuing and Stepping:: Resuming execution
3220 * Thread Stops:: Stopping and starting multi-thread programs
3224 @section Breakpoints, Watchpoints, and Catchpoints
3227 A @dfn{breakpoint} makes your program stop whenever a certain point in
3228 the program is reached. For each breakpoint, you can add conditions to
3229 control in finer detail whether your program stops. You can set
3230 breakpoints with the @code{break} command and its variants (@pxref{Set
3231 Breaks, ,Setting Breakpoints}), to specify the place where your program
3232 should stop by line number, function name or exact address in the
3235 On some systems, you can set breakpoints in shared libraries before
3236 the executable is run. There is a minor limitation on HP-UX systems:
3237 you must wait until the executable is run in order to set breakpoints
3238 in shared library routines that are not called directly by the program
3239 (for example, routines that are arguments in a @code{pthread_create}
3243 @cindex data breakpoints
3244 @cindex memory tracing
3245 @cindex breakpoint on memory address
3246 @cindex breakpoint on variable modification
3247 A @dfn{watchpoint} is a special breakpoint that stops your program
3248 when the value of an expression changes. The expression may be a value
3249 of a variable, or it could involve values of one or more variables
3250 combined by operators, such as @samp{a + b}. This is sometimes called
3251 @dfn{data breakpoints}. You must use a different command to set
3252 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3253 from that, you can manage a watchpoint like any other breakpoint: you
3254 enable, disable, and delete both breakpoints and watchpoints using the
3257 You can arrange to have values from your program displayed automatically
3258 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3262 @cindex breakpoint on events
3263 A @dfn{catchpoint} is another special breakpoint that stops your program
3264 when a certain kind of event occurs, such as the throwing of a C@t{++}
3265 exception or the loading of a library. As with watchpoints, you use a
3266 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3267 Catchpoints}), but aside from that, you can manage a catchpoint like any
3268 other breakpoint. (To stop when your program receives a signal, use the
3269 @code{handle} command; see @ref{Signals, ,Signals}.)
3271 @cindex breakpoint numbers
3272 @cindex numbers for breakpoints
3273 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3274 catchpoint when you create it; these numbers are successive integers
3275 starting with one. In many of the commands for controlling various
3276 features of breakpoints you use the breakpoint number to say which
3277 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3278 @dfn{disabled}; if disabled, it has no effect on your program until you
3281 @cindex breakpoint ranges
3282 @cindex ranges of breakpoints
3283 Some @value{GDBN} commands accept a range of breakpoints on which to
3284 operate. A breakpoint range is either a single breakpoint number, like
3285 @samp{5}, or two such numbers, in increasing order, separated by a
3286 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3287 all breakpoints in that range are operated on.
3290 * Set Breaks:: Setting breakpoints
3291 * Set Watchpoints:: Setting watchpoints
3292 * Set Catchpoints:: Setting catchpoints
3293 * Delete Breaks:: Deleting breakpoints
3294 * Disabling:: Disabling breakpoints
3295 * Conditions:: Break conditions
3296 * Break Commands:: Breakpoint command lists
3297 * Save Breakpoints:: How to save breakpoints in a file
3298 * Error in Breakpoints:: ``Cannot insert breakpoints''
3299 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3303 @subsection Setting Breakpoints
3305 @c FIXME LMB what does GDB do if no code on line of breakpt?
3306 @c consider in particular declaration with/without initialization.
3308 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3311 @kindex b @r{(@code{break})}
3312 @vindex $bpnum@r{, convenience variable}
3313 @cindex latest breakpoint
3314 Breakpoints are set with the @code{break} command (abbreviated
3315 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3316 number of the breakpoint you've set most recently; see @ref{Convenience
3317 Vars,, Convenience Variables}, for a discussion of what you can do with
3318 convenience variables.
3321 @item break @var{location}
3322 Set a breakpoint at the given @var{location}, which can specify a
3323 function name, a line number, or an address of an instruction.
3324 (@xref{Specify Location}, for a list of all the possible ways to
3325 specify a @var{location}.) The breakpoint will stop your program just
3326 before it executes any of the code in the specified @var{location}.
3328 When using source languages that permit overloading of symbols, such as
3329 C@t{++}, a function name may refer to more than one possible place to break.
3330 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3333 It is also possible to insert a breakpoint that will stop the program
3334 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3335 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3338 When called without any arguments, @code{break} sets a breakpoint at
3339 the next instruction to be executed in the selected stack frame
3340 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3341 innermost, this makes your program stop as soon as control
3342 returns to that frame. This is similar to the effect of a
3343 @code{finish} command in the frame inside the selected frame---except
3344 that @code{finish} does not leave an active breakpoint. If you use
3345 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3346 the next time it reaches the current location; this may be useful
3349 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3350 least one instruction has been executed. If it did not do this, you
3351 would be unable to proceed past a breakpoint without first disabling the
3352 breakpoint. This rule applies whether or not the breakpoint already
3353 existed when your program stopped.
3355 @item break @dots{} if @var{cond}
3356 Set a breakpoint with condition @var{cond}; evaluate the expression
3357 @var{cond} each time the breakpoint is reached, and stop only if the
3358 value is nonzero---that is, if @var{cond} evaluates as true.
3359 @samp{@dots{}} stands for one of the possible arguments described
3360 above (or no argument) specifying where to break. @xref{Conditions,
3361 ,Break Conditions}, for more information on breakpoint conditions.
3364 @item tbreak @var{args}
3365 Set a breakpoint enabled only for one stop. @var{args} are the
3366 same as for the @code{break} command, and the breakpoint is set in the same
3367 way, but the breakpoint is automatically deleted after the first time your
3368 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3371 @cindex hardware breakpoints
3372 @item hbreak @var{args}
3373 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3374 @code{break} command and the breakpoint is set in the same way, but the
3375 breakpoint requires hardware support and some target hardware may not
3376 have this support. The main purpose of this is EPROM/ROM code
3377 debugging, so you can set a breakpoint at an instruction without
3378 changing the instruction. This can be used with the new trap-generation
3379 provided by SPARClite DSU and most x86-based targets. These targets
3380 will generate traps when a program accesses some data or instruction
3381 address that is assigned to the debug registers. However the hardware
3382 breakpoint registers can take a limited number of breakpoints. For
3383 example, on the DSU, only two data breakpoints can be set at a time, and
3384 @value{GDBN} will reject this command if more than two are used. Delete
3385 or disable unused hardware breakpoints before setting new ones
3386 (@pxref{Disabling, ,Disabling Breakpoints}).
3387 @xref{Conditions, ,Break Conditions}.
3388 For remote targets, you can restrict the number of hardware
3389 breakpoints @value{GDBN} will use, see @ref{set remote
3390 hardware-breakpoint-limit}.
3393 @item thbreak @var{args}
3394 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3395 are the same as for the @code{hbreak} command and the breakpoint is set in
3396 the same way. However, like the @code{tbreak} command,
3397 the breakpoint is automatically deleted after the
3398 first time your program stops there. Also, like the @code{hbreak}
3399 command, the breakpoint requires hardware support and some target hardware
3400 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3401 See also @ref{Conditions, ,Break Conditions}.
3404 @cindex regular expression
3405 @cindex breakpoints at functions matching a regexp
3406 @cindex set breakpoints in many functions
3407 @item rbreak @var{regex}
3408 Set breakpoints on all functions matching the regular expression
3409 @var{regex}. This command sets an unconditional breakpoint on all
3410 matches, printing a list of all breakpoints it set. Once these
3411 breakpoints are set, they are treated just like the breakpoints set with
3412 the @code{break} command. You can delete them, disable them, or make
3413 them conditional the same way as any other breakpoint.
3415 The syntax of the regular expression is the standard one used with tools
3416 like @file{grep}. Note that this is different from the syntax used by
3417 shells, so for instance @code{foo*} matches all functions that include
3418 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3419 @code{.*} leading and trailing the regular expression you supply, so to
3420 match only functions that begin with @code{foo}, use @code{^foo}.
3422 @cindex non-member C@t{++} functions, set breakpoint in
3423 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3424 breakpoints on overloaded functions that are not members of any special
3427 @cindex set breakpoints on all functions
3428 The @code{rbreak} command can be used to set breakpoints in
3429 @strong{all} the functions in a program, like this:
3432 (@value{GDBP}) rbreak .
3435 @item rbreak @var{file}:@var{regex}
3436 If @code{rbreak} is called with a filename qualification, it limits
3437 the search for functions matching the given regular expression to the
3438 specified @var{file}. This can be used, for example, to set breakpoints on
3439 every function in a given file:
3442 (@value{GDBP}) rbreak file.c:.
3445 The colon separating the filename qualifier from the regex may
3446 optionally be surrounded by spaces.
3448 @kindex info breakpoints
3449 @cindex @code{$_} and @code{info breakpoints}
3450 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3451 @itemx info break @r{[}@var{n}@dots{}@r{]}
3452 Print a table of all breakpoints, watchpoints, and catchpoints set and
3453 not deleted. Optional argument @var{n} means print information only
3454 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3455 For each breakpoint, following columns are printed:
3458 @item Breakpoint Numbers
3460 Breakpoint, watchpoint, or catchpoint.
3462 Whether the breakpoint is marked to be disabled or deleted when hit.
3463 @item Enabled or Disabled
3464 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3465 that are not enabled.
3467 Where the breakpoint is in your program, as a memory address. For a
3468 pending breakpoint whose address is not yet known, this field will
3469 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3470 library that has the symbol or line referred by breakpoint is loaded.
3471 See below for details. A breakpoint with several locations will
3472 have @samp{<MULTIPLE>} in this field---see below for details.
3474 Where the breakpoint is in the source for your program, as a file and
3475 line number. For a pending breakpoint, the original string passed to
3476 the breakpoint command will be listed as it cannot be resolved until
3477 the appropriate shared library is loaded in the future.
3481 If a breakpoint is conditional, @code{info break} shows the condition on
3482 the line following the affected breakpoint; breakpoint commands, if any,
3483 are listed after that. A pending breakpoint is allowed to have a condition
3484 specified for it. The condition is not parsed for validity until a shared
3485 library is loaded that allows the pending breakpoint to resolve to a
3489 @code{info break} with a breakpoint
3490 number @var{n} as argument lists only that breakpoint. The
3491 convenience variable @code{$_} and the default examining-address for
3492 the @code{x} command are set to the address of the last breakpoint
3493 listed (@pxref{Memory, ,Examining Memory}).
3496 @code{info break} displays a count of the number of times the breakpoint
3497 has been hit. This is especially useful in conjunction with the
3498 @code{ignore} command. You can ignore a large number of breakpoint
3499 hits, look at the breakpoint info to see how many times the breakpoint
3500 was hit, and then run again, ignoring one less than that number. This
3501 will get you quickly to the last hit of that breakpoint.
3504 @value{GDBN} allows you to set any number of breakpoints at the same place in
3505 your program. There is nothing silly or meaningless about this. When
3506 the breakpoints are conditional, this is even useful
3507 (@pxref{Conditions, ,Break Conditions}).
3509 @cindex multiple locations, breakpoints
3510 @cindex breakpoints, multiple locations
3511 It is possible that a breakpoint corresponds to several locations
3512 in your program. Examples of this situation are:
3516 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3517 instances of the function body, used in different cases.
3520 For a C@t{++} template function, a given line in the function can
3521 correspond to any number of instantiations.
3524 For an inlined function, a given source line can correspond to
3525 several places where that function is inlined.
3528 In all those cases, @value{GDBN} will insert a breakpoint at all
3529 the relevant locations@footnote{
3530 As of this writing, multiple-location breakpoints work only if there's
3531 line number information for all the locations. This means that they
3532 will generally not work in system libraries, unless you have debug
3533 info with line numbers for them.}.
3535 A breakpoint with multiple locations is displayed in the breakpoint
3536 table using several rows---one header row, followed by one row for
3537 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3538 address column. The rows for individual locations contain the actual
3539 addresses for locations, and show the functions to which those
3540 locations belong. The number column for a location is of the form
3541 @var{breakpoint-number}.@var{location-number}.
3546 Num Type Disp Enb Address What
3547 1 breakpoint keep y <MULTIPLE>
3549 breakpoint already hit 1 time
3550 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3551 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3554 Each location can be individually enabled or disabled by passing
3555 @var{breakpoint-number}.@var{location-number} as argument to the
3556 @code{enable} and @code{disable} commands. Note that you cannot
3557 delete the individual locations from the list, you can only delete the
3558 entire list of locations that belong to their parent breakpoint (with
3559 the @kbd{delete @var{num}} command, where @var{num} is the number of
3560 the parent breakpoint, 1 in the above example). Disabling or enabling
3561 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3562 that belong to that breakpoint.
3564 @cindex pending breakpoints
3565 It's quite common to have a breakpoint inside a shared library.
3566 Shared libraries can be loaded and unloaded explicitly,
3567 and possibly repeatedly, as the program is executed. To support
3568 this use case, @value{GDBN} updates breakpoint locations whenever
3569 any shared library is loaded or unloaded. Typically, you would
3570 set a breakpoint in a shared library at the beginning of your
3571 debugging session, when the library is not loaded, and when the
3572 symbols from the library are not available. When you try to set
3573 breakpoint, @value{GDBN} will ask you if you want to set
3574 a so called @dfn{pending breakpoint}---breakpoint whose address
3575 is not yet resolved.
3577 After the program is run, whenever a new shared library is loaded,
3578 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3579 shared library contains the symbol or line referred to by some
3580 pending breakpoint, that breakpoint is resolved and becomes an
3581 ordinary breakpoint. When a library is unloaded, all breakpoints
3582 that refer to its symbols or source lines become pending again.
3584 This logic works for breakpoints with multiple locations, too. For
3585 example, if you have a breakpoint in a C@t{++} template function, and
3586 a newly loaded shared library has an instantiation of that template,
3587 a new location is added to the list of locations for the breakpoint.
3589 Except for having unresolved address, pending breakpoints do not
3590 differ from regular breakpoints. You can set conditions or commands,
3591 enable and disable them and perform other breakpoint operations.
3593 @value{GDBN} provides some additional commands for controlling what
3594 happens when the @samp{break} command cannot resolve breakpoint
3595 address specification to an address:
3597 @kindex set breakpoint pending
3598 @kindex show breakpoint pending
3600 @item set breakpoint pending auto
3601 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3602 location, it queries you whether a pending breakpoint should be created.
3604 @item set breakpoint pending on
3605 This indicates that an unrecognized breakpoint location should automatically
3606 result in a pending breakpoint being created.
3608 @item set breakpoint pending off
3609 This indicates that pending breakpoints are not to be created. Any
3610 unrecognized breakpoint location results in an error. This setting does
3611 not affect any pending breakpoints previously created.
3613 @item show breakpoint pending
3614 Show the current behavior setting for creating pending breakpoints.
3617 The settings above only affect the @code{break} command and its
3618 variants. Once breakpoint is set, it will be automatically updated
3619 as shared libraries are loaded and unloaded.
3621 @cindex automatic hardware breakpoints
3622 For some targets, @value{GDBN} can automatically decide if hardware or
3623 software breakpoints should be used, depending on whether the
3624 breakpoint address is read-only or read-write. This applies to
3625 breakpoints set with the @code{break} command as well as to internal
3626 breakpoints set by commands like @code{next} and @code{finish}. For
3627 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3630 You can control this automatic behaviour with the following commands::
3632 @kindex set breakpoint auto-hw
3633 @kindex show breakpoint auto-hw
3635 @item set breakpoint auto-hw on
3636 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3637 will try to use the target memory map to decide if software or hardware
3638 breakpoint must be used.
3640 @item set breakpoint auto-hw off
3641 This indicates @value{GDBN} should not automatically select breakpoint
3642 type. If the target provides a memory map, @value{GDBN} will warn when
3643 trying to set software breakpoint at a read-only address.
3646 @value{GDBN} normally implements breakpoints by replacing the program code
3647 at the breakpoint address with a special instruction, which, when
3648 executed, given control to the debugger. By default, the program
3649 code is so modified only when the program is resumed. As soon as
3650 the program stops, @value{GDBN} restores the original instructions. This
3651 behaviour guards against leaving breakpoints inserted in the
3652 target should gdb abrubptly disconnect. However, with slow remote
3653 targets, inserting and removing breakpoint can reduce the performance.
3654 This behavior can be controlled with the following commands::
3656 @kindex set breakpoint always-inserted
3657 @kindex show breakpoint always-inserted
3659 @item set breakpoint always-inserted off
3660 All breakpoints, including newly added by the user, are inserted in
3661 the target only when the target is resumed. All breakpoints are
3662 removed from the target when it stops.
3664 @item set breakpoint always-inserted on
3665 Causes all breakpoints to be inserted in the target at all times. If
3666 the user adds a new breakpoint, or changes an existing breakpoint, the
3667 breakpoints in the target are updated immediately. A breakpoint is
3668 removed from the target only when breakpoint itself is removed.
3670 @cindex non-stop mode, and @code{breakpoint always-inserted}
3671 @item set breakpoint always-inserted auto
3672 This is the default mode. If @value{GDBN} is controlling the inferior
3673 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3674 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3675 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3676 @code{breakpoint always-inserted} mode is off.
3679 @cindex negative breakpoint numbers
3680 @cindex internal @value{GDBN} breakpoints
3681 @value{GDBN} itself sometimes sets breakpoints in your program for
3682 special purposes, such as proper handling of @code{longjmp} (in C
3683 programs). These internal breakpoints are assigned negative numbers,
3684 starting with @code{-1}; @samp{info breakpoints} does not display them.
3685 You can see these breakpoints with the @value{GDBN} maintenance command
3686 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3689 @node Set Watchpoints
3690 @subsection Setting Watchpoints
3692 @cindex setting watchpoints
3693 You can use a watchpoint to stop execution whenever the value of an
3694 expression changes, without having to predict a particular place where
3695 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3696 The expression may be as simple as the value of a single variable, or
3697 as complex as many variables combined by operators. Examples include:
3701 A reference to the value of a single variable.
3704 An address cast to an appropriate data type. For example,
3705 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3706 address (assuming an @code{int} occupies 4 bytes).
3709 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3710 expression can use any operators valid in the program's native
3711 language (@pxref{Languages}).
3714 You can set a watchpoint on an expression even if the expression can
3715 not be evaluated yet. For instance, you can set a watchpoint on
3716 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3717 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3718 the expression produces a valid value. If the expression becomes
3719 valid in some other way than changing a variable (e.g.@: if the memory
3720 pointed to by @samp{*global_ptr} becomes readable as the result of a
3721 @code{malloc} call), @value{GDBN} may not stop until the next time
3722 the expression changes.
3724 @cindex software watchpoints
3725 @cindex hardware watchpoints
3726 Depending on your system, watchpoints may be implemented in software or
3727 hardware. @value{GDBN} does software watchpointing by single-stepping your
3728 program and testing the variable's value each time, which is hundreds of
3729 times slower than normal execution. (But this may still be worth it, to
3730 catch errors where you have no clue what part of your program is the
3733 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3734 x86-based targets, @value{GDBN} includes support for hardware
3735 watchpoints, which do not slow down the running of your program.
3739 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3740 Set a watchpoint for an expression. @value{GDBN} will break when the
3741 expression @var{expr} is written into by the program and its value
3742 changes. The simplest (and the most popular) use of this command is
3743 to watch the value of a single variable:
3746 (@value{GDBP}) watch foo
3749 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3750 argument, @value{GDBN} breaks only when the thread identified by
3751 @var{threadnum} changes the value of @var{expr}. If any other threads
3752 change the value of @var{expr}, @value{GDBN} will not break. Note
3753 that watchpoints restricted to a single thread in this way only work
3754 with Hardware Watchpoints.
3756 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3757 (see below). The @code{-location} argument tells @value{GDBN} to
3758 instead watch the memory referred to by @var{expr}. In this case,
3759 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3760 and watch the memory at that address. The type of the result is used
3761 to determine the size of the watched memory. If the expression's
3762 result does not have an address, then @value{GDBN} will print an
3765 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3766 of masked watchpoints, if the current architecture supports this
3767 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3768 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3769 to an address to watch. The mask specifies that some bits of an address
3770 (the bits which are reset in the mask) should be ignored when matching
3771 the address accessed by the inferior against the watchpoint address.
3772 Thus, a masked watchpoint watches many addresses simultaneously---those
3773 addresses whose unmasked bits are identical to the unmasked bits in the
3774 watchpoint address. The @code{mask} argument implies @code{-location}.
3778 (@value{GDBP}) watch foo mask 0xffff00ff
3779 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3783 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3784 Set a watchpoint that will break when the value of @var{expr} is read
3788 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3789 Set a watchpoint that will break when @var{expr} is either read from
3790 or written into by the program.
3792 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3793 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3794 This command prints a list of watchpoints, using the same format as
3795 @code{info break} (@pxref{Set Breaks}).
3798 If you watch for a change in a numerically entered address you need to
3799 dereference it, as the address itself is just a constant number which will
3800 never change. @value{GDBN} refuses to create a watchpoint that watches
3801 a never-changing value:
3804 (@value{GDBP}) watch 0x600850
3805 Cannot watch constant value 0x600850.
3806 (@value{GDBP}) watch *(int *) 0x600850
3807 Watchpoint 1: *(int *) 6293584
3810 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3811 watchpoints execute very quickly, and the debugger reports a change in
3812 value at the exact instruction where the change occurs. If @value{GDBN}
3813 cannot set a hardware watchpoint, it sets a software watchpoint, which
3814 executes more slowly and reports the change in value at the next
3815 @emph{statement}, not the instruction, after the change occurs.
3817 @cindex use only software watchpoints
3818 You can force @value{GDBN} to use only software watchpoints with the
3819 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3820 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3821 the underlying system supports them. (Note that hardware-assisted
3822 watchpoints that were set @emph{before} setting
3823 @code{can-use-hw-watchpoints} to zero will still use the hardware
3824 mechanism of watching expression values.)
3827 @item set can-use-hw-watchpoints
3828 @kindex set can-use-hw-watchpoints
3829 Set whether or not to use hardware watchpoints.
3831 @item show can-use-hw-watchpoints
3832 @kindex show can-use-hw-watchpoints
3833 Show the current mode of using hardware watchpoints.
3836 For remote targets, you can restrict the number of hardware
3837 watchpoints @value{GDBN} will use, see @ref{set remote
3838 hardware-breakpoint-limit}.
3840 When you issue the @code{watch} command, @value{GDBN} reports
3843 Hardware watchpoint @var{num}: @var{expr}
3847 if it was able to set a hardware watchpoint.
3849 Currently, the @code{awatch} and @code{rwatch} commands can only set
3850 hardware watchpoints, because accesses to data that don't change the
3851 value of the watched expression cannot be detected without examining
3852 every instruction as it is being executed, and @value{GDBN} does not do
3853 that currently. If @value{GDBN} finds that it is unable to set a
3854 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3855 will print a message like this:
3858 Expression cannot be implemented with read/access watchpoint.
3861 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3862 data type of the watched expression is wider than what a hardware
3863 watchpoint on the target machine can handle. For example, some systems
3864 can only watch regions that are up to 4 bytes wide; on such systems you
3865 cannot set hardware watchpoints for an expression that yields a
3866 double-precision floating-point number (which is typically 8 bytes
3867 wide). As a work-around, it might be possible to break the large region
3868 into a series of smaller ones and watch them with separate watchpoints.
3870 If you set too many hardware watchpoints, @value{GDBN} might be unable
3871 to insert all of them when you resume the execution of your program.
3872 Since the precise number of active watchpoints is unknown until such
3873 time as the program is about to be resumed, @value{GDBN} might not be
3874 able to warn you about this when you set the watchpoints, and the
3875 warning will be printed only when the program is resumed:
3878 Hardware watchpoint @var{num}: Could not insert watchpoint
3882 If this happens, delete or disable some of the watchpoints.
3884 Watching complex expressions that reference many variables can also
3885 exhaust the resources available for hardware-assisted watchpoints.
3886 That's because @value{GDBN} needs to watch every variable in the
3887 expression with separately allocated resources.
3889 If you call a function interactively using @code{print} or @code{call},
3890 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3891 kind of breakpoint or the call completes.
3893 @value{GDBN} automatically deletes watchpoints that watch local
3894 (automatic) variables, or expressions that involve such variables, when
3895 they go out of scope, that is, when the execution leaves the block in
3896 which these variables were defined. In particular, when the program
3897 being debugged terminates, @emph{all} local variables go out of scope,
3898 and so only watchpoints that watch global variables remain set. If you
3899 rerun the program, you will need to set all such watchpoints again. One
3900 way of doing that would be to set a code breakpoint at the entry to the
3901 @code{main} function and when it breaks, set all the watchpoints.
3903 @cindex watchpoints and threads
3904 @cindex threads and watchpoints
3905 In multi-threaded programs, watchpoints will detect changes to the
3906 watched expression from every thread.
3909 @emph{Warning:} In multi-threaded programs, software watchpoints
3910 have only limited usefulness. If @value{GDBN} creates a software
3911 watchpoint, it can only watch the value of an expression @emph{in a
3912 single thread}. If you are confident that the expression can only
3913 change due to the current thread's activity (and if you are also
3914 confident that no other thread can become current), then you can use
3915 software watchpoints as usual. However, @value{GDBN} may not notice
3916 when a non-current thread's activity changes the expression. (Hardware
3917 watchpoints, in contrast, watch an expression in all threads.)
3920 @xref{set remote hardware-watchpoint-limit}.
3922 @node Set Catchpoints
3923 @subsection Setting Catchpoints
3924 @cindex catchpoints, setting
3925 @cindex exception handlers
3926 @cindex event handling
3928 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3929 kinds of program events, such as C@t{++} exceptions or the loading of a
3930 shared library. Use the @code{catch} command to set a catchpoint.
3934 @item catch @var{event}
3935 Stop when @var{event} occurs. @var{event} can be any of the following:
3938 @cindex stop on C@t{++} exceptions
3939 The throwing of a C@t{++} exception.
3942 The catching of a C@t{++} exception.
3945 @cindex Ada exception catching
3946 @cindex catch Ada exceptions
3947 An Ada exception being raised. If an exception name is specified
3948 at the end of the command (eg @code{catch exception Program_Error}),
3949 the debugger will stop only when this specific exception is raised.
3950 Otherwise, the debugger stops execution when any Ada exception is raised.
3952 When inserting an exception catchpoint on a user-defined exception whose
3953 name is identical to one of the exceptions defined by the language, the
3954 fully qualified name must be used as the exception name. Otherwise,
3955 @value{GDBN} will assume that it should stop on the pre-defined exception
3956 rather than the user-defined one. For instance, assuming an exception
3957 called @code{Constraint_Error} is defined in package @code{Pck}, then
3958 the command to use to catch such exceptions is @kbd{catch exception
3959 Pck.Constraint_Error}.
3961 @item exception unhandled
3962 An exception that was raised but is not handled by the program.
3965 A failed Ada assertion.
3968 @cindex break on fork/exec
3969 A call to @code{exec}. This is currently only available for HP-UX
3973 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3974 @cindex break on a system call.
3975 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3976 syscall is a mechanism for application programs to request a service
3977 from the operating system (OS) or one of the OS system services.
3978 @value{GDBN} can catch some or all of the syscalls issued by the
3979 debuggee, and show the related information for each syscall. If no
3980 argument is specified, calls to and returns from all system calls
3983 @var{name} can be any system call name that is valid for the
3984 underlying OS. Just what syscalls are valid depends on the OS. On
3985 GNU and Unix systems, you can find the full list of valid syscall
3986 names on @file{/usr/include/asm/unistd.h}.
3988 @c For MS-Windows, the syscall names and the corresponding numbers
3989 @c can be found, e.g., on this URL:
3990 @c http://www.metasploit.com/users/opcode/syscalls.html
3991 @c but we don't support Windows syscalls yet.
3993 Normally, @value{GDBN} knows in advance which syscalls are valid for
3994 each OS, so you can use the @value{GDBN} command-line completion
3995 facilities (@pxref{Completion,, command completion}) to list the
3998 You may also specify the system call numerically. A syscall's
3999 number is the value passed to the OS's syscall dispatcher to
4000 identify the requested service. When you specify the syscall by its
4001 name, @value{GDBN} uses its database of syscalls to convert the name
4002 into the corresponding numeric code, but using the number directly
4003 may be useful if @value{GDBN}'s database does not have the complete
4004 list of syscalls on your system (e.g., because @value{GDBN} lags
4005 behind the OS upgrades).
4007 The example below illustrates how this command works if you don't provide
4011 (@value{GDBP}) catch syscall
4012 Catchpoint 1 (syscall)
4014 Starting program: /tmp/catch-syscall
4016 Catchpoint 1 (call to syscall 'close'), \
4017 0xffffe424 in __kernel_vsyscall ()
4021 Catchpoint 1 (returned from syscall 'close'), \
4022 0xffffe424 in __kernel_vsyscall ()
4026 Here is an example of catching a system call by name:
4029 (@value{GDBP}) catch syscall chroot
4030 Catchpoint 1 (syscall 'chroot' [61])
4032 Starting program: /tmp/catch-syscall
4034 Catchpoint 1 (call to syscall 'chroot'), \
4035 0xffffe424 in __kernel_vsyscall ()
4039 Catchpoint 1 (returned from syscall 'chroot'), \
4040 0xffffe424 in __kernel_vsyscall ()
4044 An example of specifying a system call numerically. In the case
4045 below, the syscall number has a corresponding entry in the XML
4046 file, so @value{GDBN} finds its name and prints it:
4049 (@value{GDBP}) catch syscall 252
4050 Catchpoint 1 (syscall(s) 'exit_group')
4052 Starting program: /tmp/catch-syscall
4054 Catchpoint 1 (call to syscall 'exit_group'), \
4055 0xffffe424 in __kernel_vsyscall ()
4059 Program exited normally.
4063 However, there can be situations when there is no corresponding name
4064 in XML file for that syscall number. In this case, @value{GDBN} prints
4065 a warning message saying that it was not able to find the syscall name,
4066 but the catchpoint will be set anyway. See the example below:
4069 (@value{GDBP}) catch syscall 764
4070 warning: The number '764' does not represent a known syscall.
4071 Catchpoint 2 (syscall 764)
4075 If you configure @value{GDBN} using the @samp{--without-expat} option,
4076 it will not be able to display syscall names. Also, if your
4077 architecture does not have an XML file describing its system calls,
4078 you will not be able to see the syscall names. It is important to
4079 notice that these two features are used for accessing the syscall
4080 name database. In either case, you will see a warning like this:
4083 (@value{GDBP}) catch syscall
4084 warning: Could not open "syscalls/i386-linux.xml"
4085 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4086 GDB will not be able to display syscall names.
4087 Catchpoint 1 (syscall)
4091 Of course, the file name will change depending on your architecture and system.
4093 Still using the example above, you can also try to catch a syscall by its
4094 number. In this case, you would see something like:
4097 (@value{GDBP}) catch syscall 252
4098 Catchpoint 1 (syscall(s) 252)
4101 Again, in this case @value{GDBN} would not be able to display syscall's names.
4104 A call to @code{fork}. This is currently only available for HP-UX
4108 A call to @code{vfork}. This is currently only available for HP-UX
4113 @item tcatch @var{event}
4114 Set a catchpoint that is enabled only for one stop. The catchpoint is
4115 automatically deleted after the first time the event is caught.
4119 Use the @code{info break} command to list the current catchpoints.
4121 There are currently some limitations to C@t{++} exception handling
4122 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4126 If you call a function interactively, @value{GDBN} normally returns
4127 control to you when the function has finished executing. If the call
4128 raises an exception, however, the call may bypass the mechanism that
4129 returns control to you and cause your program either to abort or to
4130 simply continue running until it hits a breakpoint, catches a signal
4131 that @value{GDBN} is listening for, or exits. This is the case even if
4132 you set a catchpoint for the exception; catchpoints on exceptions are
4133 disabled within interactive calls.
4136 You cannot raise an exception interactively.
4139 You cannot install an exception handler interactively.
4142 @cindex raise exceptions
4143 Sometimes @code{catch} is not the best way to debug exception handling:
4144 if you need to know exactly where an exception is raised, it is better to
4145 stop @emph{before} the exception handler is called, since that way you
4146 can see the stack before any unwinding takes place. If you set a
4147 breakpoint in an exception handler instead, it may not be easy to find
4148 out where the exception was raised.
4150 To stop just before an exception handler is called, you need some
4151 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4152 raised by calling a library function named @code{__raise_exception}
4153 which has the following ANSI C interface:
4156 /* @var{addr} is where the exception identifier is stored.
4157 @var{id} is the exception identifier. */
4158 void __raise_exception (void **addr, void *id);
4162 To make the debugger catch all exceptions before any stack
4163 unwinding takes place, set a breakpoint on @code{__raise_exception}
4164 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4166 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4167 that depends on the value of @var{id}, you can stop your program when
4168 a specific exception is raised. You can use multiple conditional
4169 breakpoints to stop your program when any of a number of exceptions are
4174 @subsection Deleting Breakpoints
4176 @cindex clearing breakpoints, watchpoints, catchpoints
4177 @cindex deleting breakpoints, watchpoints, catchpoints
4178 It is often necessary to eliminate a breakpoint, watchpoint, or
4179 catchpoint once it has done its job and you no longer want your program
4180 to stop there. This is called @dfn{deleting} the breakpoint. A
4181 breakpoint that has been deleted no longer exists; it is forgotten.
4183 With the @code{clear} command you can delete breakpoints according to
4184 where they are in your program. With the @code{delete} command you can
4185 delete individual breakpoints, watchpoints, or catchpoints by specifying
4186 their breakpoint numbers.
4188 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4189 automatically ignores breakpoints on the first instruction to be executed
4190 when you continue execution without changing the execution address.
4195 Delete any breakpoints at the next instruction to be executed in the
4196 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4197 the innermost frame is selected, this is a good way to delete a
4198 breakpoint where your program just stopped.
4200 @item clear @var{location}
4201 Delete any breakpoints set at the specified @var{location}.
4202 @xref{Specify Location}, for the various forms of @var{location}; the
4203 most useful ones are listed below:
4206 @item clear @var{function}
4207 @itemx clear @var{filename}:@var{function}
4208 Delete any breakpoints set at entry to the named @var{function}.
4210 @item clear @var{linenum}
4211 @itemx clear @var{filename}:@var{linenum}
4212 Delete any breakpoints set at or within the code of the specified
4213 @var{linenum} of the specified @var{filename}.
4216 @cindex delete breakpoints
4218 @kindex d @r{(@code{delete})}
4219 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4220 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4221 ranges specified as arguments. If no argument is specified, delete all
4222 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4223 confirm off}). You can abbreviate this command as @code{d}.
4227 @subsection Disabling Breakpoints
4229 @cindex enable/disable a breakpoint
4230 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4231 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4232 it had been deleted, but remembers the information on the breakpoint so
4233 that you can @dfn{enable} it again later.
4235 You disable and enable breakpoints, watchpoints, and catchpoints with
4236 the @code{enable} and @code{disable} commands, optionally specifying
4237 one or more breakpoint numbers as arguments. Use @code{info break} to
4238 print a list of all breakpoints, watchpoints, and catchpoints if you
4239 do not know which numbers to use.
4241 Disabling and enabling a breakpoint that has multiple locations
4242 affects all of its locations.
4244 A breakpoint, watchpoint, or catchpoint can have any of four different
4245 states of enablement:
4249 Enabled. The breakpoint stops your program. A breakpoint set
4250 with the @code{break} command starts out in this state.
4252 Disabled. The breakpoint has no effect on your program.
4254 Enabled once. The breakpoint stops your program, but then becomes
4257 Enabled for deletion. The breakpoint stops your program, but
4258 immediately after it does so it is deleted permanently. A breakpoint
4259 set with the @code{tbreak} command starts out in this state.
4262 You can use the following commands to enable or disable breakpoints,
4263 watchpoints, and catchpoints:
4267 @kindex dis @r{(@code{disable})}
4268 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4269 Disable the specified breakpoints---or all breakpoints, if none are
4270 listed. A disabled breakpoint has no effect but is not forgotten. All
4271 options such as ignore-counts, conditions and commands are remembered in
4272 case the breakpoint is enabled again later. You may abbreviate
4273 @code{disable} as @code{dis}.
4276 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4277 Enable the specified breakpoints (or all defined breakpoints). They
4278 become effective once again in stopping your program.
4280 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4281 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4282 of these breakpoints immediately after stopping your program.
4284 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4285 Enable the specified breakpoints to work once, then die. @value{GDBN}
4286 deletes any of these breakpoints as soon as your program stops there.
4287 Breakpoints set by the @code{tbreak} command start out in this state.
4290 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4291 @c confusing: tbreak is also initially enabled.
4292 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4293 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4294 subsequently, they become disabled or enabled only when you use one of
4295 the commands above. (The command @code{until} can set and delete a
4296 breakpoint of its own, but it does not change the state of your other
4297 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4301 @subsection Break Conditions
4302 @cindex conditional breakpoints
4303 @cindex breakpoint conditions
4305 @c FIXME what is scope of break condition expr? Context where wanted?
4306 @c in particular for a watchpoint?
4307 The simplest sort of breakpoint breaks every time your program reaches a
4308 specified place. You can also specify a @dfn{condition} for a
4309 breakpoint. A condition is just a Boolean expression in your
4310 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4311 a condition evaluates the expression each time your program reaches it,
4312 and your program stops only if the condition is @emph{true}.
4314 This is the converse of using assertions for program validation; in that
4315 situation, you want to stop when the assertion is violated---that is,
4316 when the condition is false. In C, if you want to test an assertion expressed
4317 by the condition @var{assert}, you should set the condition
4318 @samp{! @var{assert}} on the appropriate breakpoint.
4320 Conditions are also accepted for watchpoints; you may not need them,
4321 since a watchpoint is inspecting the value of an expression anyhow---but
4322 it might be simpler, say, to just set a watchpoint on a variable name,
4323 and specify a condition that tests whether the new value is an interesting
4326 Break conditions can have side effects, and may even call functions in
4327 your program. This can be useful, for example, to activate functions
4328 that log program progress, or to use your own print functions to
4329 format special data structures. The effects are completely predictable
4330 unless there is another enabled breakpoint at the same address. (In
4331 that case, @value{GDBN} might see the other breakpoint first and stop your
4332 program without checking the condition of this one.) Note that
4333 breakpoint commands are usually more convenient and flexible than break
4335 purpose of performing side effects when a breakpoint is reached
4336 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4338 Break conditions can be specified when a breakpoint is set, by using
4339 @samp{if} in the arguments to the @code{break} command. @xref{Set
4340 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4341 with the @code{condition} command.
4343 You can also use the @code{if} keyword with the @code{watch} command.
4344 The @code{catch} command does not recognize the @code{if} keyword;
4345 @code{condition} is the only way to impose a further condition on a
4350 @item condition @var{bnum} @var{expression}
4351 Specify @var{expression} as the break condition for breakpoint,
4352 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4353 breakpoint @var{bnum} stops your program only if the value of
4354 @var{expression} is true (nonzero, in C). When you use
4355 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4356 syntactic correctness, and to determine whether symbols in it have
4357 referents in the context of your breakpoint. If @var{expression} uses
4358 symbols not referenced in the context of the breakpoint, @value{GDBN}
4359 prints an error message:
4362 No symbol "foo" in current context.
4367 not actually evaluate @var{expression} at the time the @code{condition}
4368 command (or a command that sets a breakpoint with a condition, like
4369 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4371 @item condition @var{bnum}
4372 Remove the condition from breakpoint number @var{bnum}. It becomes
4373 an ordinary unconditional breakpoint.
4376 @cindex ignore count (of breakpoint)
4377 A special case of a breakpoint condition is to stop only when the
4378 breakpoint has been reached a certain number of times. This is so
4379 useful that there is a special way to do it, using the @dfn{ignore
4380 count} of the breakpoint. Every breakpoint has an ignore count, which
4381 is an integer. Most of the time, the ignore count is zero, and
4382 therefore has no effect. But if your program reaches a breakpoint whose
4383 ignore count is positive, then instead of stopping, it just decrements
4384 the ignore count by one and continues. As a result, if the ignore count
4385 value is @var{n}, the breakpoint does not stop the next @var{n} times
4386 your program reaches it.
4390 @item ignore @var{bnum} @var{count}
4391 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4392 The next @var{count} times the breakpoint is reached, your program's
4393 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4396 To make the breakpoint stop the next time it is reached, specify
4399 When you use @code{continue} to resume execution of your program from a
4400 breakpoint, you can specify an ignore count directly as an argument to
4401 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4402 Stepping,,Continuing and Stepping}.
4404 If a breakpoint has a positive ignore count and a condition, the
4405 condition is not checked. Once the ignore count reaches zero,
4406 @value{GDBN} resumes checking the condition.
4408 You could achieve the effect of the ignore count with a condition such
4409 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4410 is decremented each time. @xref{Convenience Vars, ,Convenience
4414 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4417 @node Break Commands
4418 @subsection Breakpoint Command Lists
4420 @cindex breakpoint commands
4421 You can give any breakpoint (or watchpoint or catchpoint) a series of
4422 commands to execute when your program stops due to that breakpoint. For
4423 example, you might want to print the values of certain expressions, or
4424 enable other breakpoints.
4428 @kindex end@r{ (breakpoint commands)}
4429 @item commands @r{[}@var{range}@dots{}@r{]}
4430 @itemx @dots{} @var{command-list} @dots{}
4432 Specify a list of commands for the given breakpoints. The commands
4433 themselves appear on the following lines. Type a line containing just
4434 @code{end} to terminate the commands.
4436 To remove all commands from a breakpoint, type @code{commands} and
4437 follow it immediately with @code{end}; that is, give no commands.
4439 With no argument, @code{commands} refers to the last breakpoint,
4440 watchpoint, or catchpoint set (not to the breakpoint most recently
4441 encountered). If the most recent breakpoints were set with a single
4442 command, then the @code{commands} will apply to all the breakpoints
4443 set by that command. This applies to breakpoints set by
4444 @code{rbreak}, and also applies when a single @code{break} command
4445 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4449 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4450 disabled within a @var{command-list}.
4452 You can use breakpoint commands to start your program up again. Simply
4453 use the @code{continue} command, or @code{step}, or any other command
4454 that resumes execution.
4456 Any other commands in the command list, after a command that resumes
4457 execution, are ignored. This is because any time you resume execution
4458 (even with a simple @code{next} or @code{step}), you may encounter
4459 another breakpoint---which could have its own command list, leading to
4460 ambiguities about which list to execute.
4463 If the first command you specify in a command list is @code{silent}, the
4464 usual message about stopping at a breakpoint is not printed. This may
4465 be desirable for breakpoints that are to print a specific message and
4466 then continue. If none of the remaining commands print anything, you
4467 see no sign that the breakpoint was reached. @code{silent} is
4468 meaningful only at the beginning of a breakpoint command list.
4470 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4471 print precisely controlled output, and are often useful in silent
4472 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4474 For example, here is how you could use breakpoint commands to print the
4475 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4481 printf "x is %d\n",x
4486 One application for breakpoint commands is to compensate for one bug so
4487 you can test for another. Put a breakpoint just after the erroneous line
4488 of code, give it a condition to detect the case in which something
4489 erroneous has been done, and give it commands to assign correct values
4490 to any variables that need them. End with the @code{continue} command
4491 so that your program does not stop, and start with the @code{silent}
4492 command so that no output is produced. Here is an example:
4503 @node Save Breakpoints
4504 @subsection How to save breakpoints to a file
4506 To save breakpoint definitions to a file use the @w{@code{save
4507 breakpoints}} command.
4510 @kindex save breakpoints
4511 @cindex save breakpoints to a file for future sessions
4512 @item save breakpoints [@var{filename}]
4513 This command saves all current breakpoint definitions together with
4514 their commands and ignore counts, into a file @file{@var{filename}}
4515 suitable for use in a later debugging session. This includes all
4516 types of breakpoints (breakpoints, watchpoints, catchpoints,
4517 tracepoints). To read the saved breakpoint definitions, use the
4518 @code{source} command (@pxref{Command Files}). Note that watchpoints
4519 with expressions involving local variables may fail to be recreated
4520 because it may not be possible to access the context where the
4521 watchpoint is valid anymore. Because the saved breakpoint definitions
4522 are simply a sequence of @value{GDBN} commands that recreate the
4523 breakpoints, you can edit the file in your favorite editing program,
4524 and remove the breakpoint definitions you're not interested in, or
4525 that can no longer be recreated.
4528 @c @ifclear BARETARGET
4529 @node Error in Breakpoints
4530 @subsection ``Cannot insert breakpoints''
4532 If you request too many active hardware-assisted breakpoints and
4533 watchpoints, you will see this error message:
4535 @c FIXME: the precise wording of this message may change; the relevant
4536 @c source change is not committed yet (Sep 3, 1999).
4538 Stopped; cannot insert breakpoints.
4539 You may have requested too many hardware breakpoints and watchpoints.
4543 This message is printed when you attempt to resume the program, since
4544 only then @value{GDBN} knows exactly how many hardware breakpoints and
4545 watchpoints it needs to insert.
4547 When this message is printed, you need to disable or remove some of the
4548 hardware-assisted breakpoints and watchpoints, and then continue.
4550 @node Breakpoint-related Warnings
4551 @subsection ``Breakpoint address adjusted...''
4552 @cindex breakpoint address adjusted
4554 Some processor architectures place constraints on the addresses at
4555 which breakpoints may be placed. For architectures thus constrained,
4556 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4557 with the constraints dictated by the architecture.
4559 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4560 a VLIW architecture in which a number of RISC-like instructions may be
4561 bundled together for parallel execution. The FR-V architecture
4562 constrains the location of a breakpoint instruction within such a
4563 bundle to the instruction with the lowest address. @value{GDBN}
4564 honors this constraint by adjusting a breakpoint's address to the
4565 first in the bundle.
4567 It is not uncommon for optimized code to have bundles which contain
4568 instructions from different source statements, thus it may happen that
4569 a breakpoint's address will be adjusted from one source statement to
4570 another. Since this adjustment may significantly alter @value{GDBN}'s
4571 breakpoint related behavior from what the user expects, a warning is
4572 printed when the breakpoint is first set and also when the breakpoint
4575 A warning like the one below is printed when setting a breakpoint
4576 that's been subject to address adjustment:
4579 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4582 Such warnings are printed both for user settable and @value{GDBN}'s
4583 internal breakpoints. If you see one of these warnings, you should
4584 verify that a breakpoint set at the adjusted address will have the
4585 desired affect. If not, the breakpoint in question may be removed and
4586 other breakpoints may be set which will have the desired behavior.
4587 E.g., it may be sufficient to place the breakpoint at a later
4588 instruction. A conditional breakpoint may also be useful in some
4589 cases to prevent the breakpoint from triggering too often.
4591 @value{GDBN} will also issue a warning when stopping at one of these
4592 adjusted breakpoints:
4595 warning: Breakpoint 1 address previously adjusted from 0x00010414
4599 When this warning is encountered, it may be too late to take remedial
4600 action except in cases where the breakpoint is hit earlier or more
4601 frequently than expected.
4603 @node Continuing and Stepping
4604 @section Continuing and Stepping
4608 @cindex resuming execution
4609 @dfn{Continuing} means resuming program execution until your program
4610 completes normally. In contrast, @dfn{stepping} means executing just
4611 one more ``step'' of your program, where ``step'' may mean either one
4612 line of source code, or one machine instruction (depending on what
4613 particular command you use). Either when continuing or when stepping,
4614 your program may stop even sooner, due to a breakpoint or a signal. (If
4615 it stops due to a signal, you may want to use @code{handle}, or use
4616 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4620 @kindex c @r{(@code{continue})}
4621 @kindex fg @r{(resume foreground execution)}
4622 @item continue @r{[}@var{ignore-count}@r{]}
4623 @itemx c @r{[}@var{ignore-count}@r{]}
4624 @itemx fg @r{[}@var{ignore-count}@r{]}
4625 Resume program execution, at the address where your program last stopped;
4626 any breakpoints set at that address are bypassed. The optional argument
4627 @var{ignore-count} allows you to specify a further number of times to
4628 ignore a breakpoint at this location; its effect is like that of
4629 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4631 The argument @var{ignore-count} is meaningful only when your program
4632 stopped due to a breakpoint. At other times, the argument to
4633 @code{continue} is ignored.
4635 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4636 debugged program is deemed to be the foreground program) are provided
4637 purely for convenience, and have exactly the same behavior as
4641 To resume execution at a different place, you can use @code{return}
4642 (@pxref{Returning, ,Returning from a Function}) to go back to the
4643 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4644 Different Address}) to go to an arbitrary location in your program.
4646 A typical technique for using stepping is to set a breakpoint
4647 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4648 beginning of the function or the section of your program where a problem
4649 is believed to lie, run your program until it stops at that breakpoint,
4650 and then step through the suspect area, examining the variables that are
4651 interesting, until you see the problem happen.
4655 @kindex s @r{(@code{step})}
4657 Continue running your program until control reaches a different source
4658 line, then stop it and return control to @value{GDBN}. This command is
4659 abbreviated @code{s}.
4662 @c "without debugging information" is imprecise; actually "without line
4663 @c numbers in the debugging information". (gcc -g1 has debugging info but
4664 @c not line numbers). But it seems complex to try to make that
4665 @c distinction here.
4666 @emph{Warning:} If you use the @code{step} command while control is
4667 within a function that was compiled without debugging information,
4668 execution proceeds until control reaches a function that does have
4669 debugging information. Likewise, it will not step into a function which
4670 is compiled without debugging information. To step through functions
4671 without debugging information, use the @code{stepi} command, described
4675 The @code{step} command only stops at the first instruction of a source
4676 line. This prevents the multiple stops that could otherwise occur in
4677 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4678 to stop if a function that has debugging information is called within
4679 the line. In other words, @code{step} @emph{steps inside} any functions
4680 called within the line.
4682 Also, the @code{step} command only enters a function if there is line
4683 number information for the function. Otherwise it acts like the
4684 @code{next} command. This avoids problems when using @code{cc -gl}
4685 on MIPS machines. Previously, @code{step} entered subroutines if there
4686 was any debugging information about the routine.
4688 @item step @var{count}
4689 Continue running as in @code{step}, but do so @var{count} times. If a
4690 breakpoint is reached, or a signal not related to stepping occurs before
4691 @var{count} steps, stepping stops right away.
4694 @kindex n @r{(@code{next})}
4695 @item next @r{[}@var{count}@r{]}
4696 Continue to the next source line in the current (innermost) stack frame.
4697 This is similar to @code{step}, but function calls that appear within
4698 the line of code are executed without stopping. Execution stops when
4699 control reaches a different line of code at the original stack level
4700 that was executing when you gave the @code{next} command. This command
4701 is abbreviated @code{n}.
4703 An argument @var{count} is a repeat count, as for @code{step}.
4706 @c FIX ME!! Do we delete this, or is there a way it fits in with
4707 @c the following paragraph? --- Vctoria
4709 @c @code{next} within a function that lacks debugging information acts like
4710 @c @code{step}, but any function calls appearing within the code of the
4711 @c function are executed without stopping.
4713 The @code{next} command only stops at the first instruction of a
4714 source line. This prevents multiple stops that could otherwise occur in
4715 @code{switch} statements, @code{for} loops, etc.
4717 @kindex set step-mode
4719 @cindex functions without line info, and stepping
4720 @cindex stepping into functions with no line info
4721 @itemx set step-mode on
4722 The @code{set step-mode on} command causes the @code{step} command to
4723 stop at the first instruction of a function which contains no debug line
4724 information rather than stepping over it.
4726 This is useful in cases where you may be interested in inspecting the
4727 machine instructions of a function which has no symbolic info and do not
4728 want @value{GDBN} to automatically skip over this function.
4730 @item set step-mode off
4731 Causes the @code{step} command to step over any functions which contains no
4732 debug information. This is the default.
4734 @item show step-mode
4735 Show whether @value{GDBN} will stop in or step over functions without
4736 source line debug information.
4739 @kindex fin @r{(@code{finish})}
4741 Continue running until just after function in the selected stack frame
4742 returns. Print the returned value (if any). This command can be
4743 abbreviated as @code{fin}.
4745 Contrast this with the @code{return} command (@pxref{Returning,
4746 ,Returning from a Function}).
4749 @kindex u @r{(@code{until})}
4750 @cindex run until specified location
4753 Continue running until a source line past the current line, in the
4754 current stack frame, is reached. This command is used to avoid single
4755 stepping through a loop more than once. It is like the @code{next}
4756 command, except that when @code{until} encounters a jump, it
4757 automatically continues execution until the program counter is greater
4758 than the address of the jump.
4760 This means that when you reach the end of a loop after single stepping
4761 though it, @code{until} makes your program continue execution until it
4762 exits the loop. In contrast, a @code{next} command at the end of a loop
4763 simply steps back to the beginning of the loop, which forces you to step
4764 through the next iteration.
4766 @code{until} always stops your program if it attempts to exit the current
4769 @code{until} may produce somewhat counterintuitive results if the order
4770 of machine code does not match the order of the source lines. For
4771 example, in the following excerpt from a debugging session, the @code{f}
4772 (@code{frame}) command shows that execution is stopped at line
4773 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4777 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4779 (@value{GDBP}) until
4780 195 for ( ; argc > 0; NEXTARG) @{
4783 This happened because, for execution efficiency, the compiler had
4784 generated code for the loop closure test at the end, rather than the
4785 start, of the loop---even though the test in a C @code{for}-loop is
4786 written before the body of the loop. The @code{until} command appeared
4787 to step back to the beginning of the loop when it advanced to this
4788 expression; however, it has not really gone to an earlier
4789 statement---not in terms of the actual machine code.
4791 @code{until} with no argument works by means of single
4792 instruction stepping, and hence is slower than @code{until} with an
4795 @item until @var{location}
4796 @itemx u @var{location}
4797 Continue running your program until either the specified location is
4798 reached, or the current stack frame returns. @var{location} is any of
4799 the forms described in @ref{Specify Location}.
4800 This form of the command uses temporary breakpoints, and
4801 hence is quicker than @code{until} without an argument. The specified
4802 location is actually reached only if it is in the current frame. This
4803 implies that @code{until} can be used to skip over recursive function
4804 invocations. For instance in the code below, if the current location is
4805 line @code{96}, issuing @code{until 99} will execute the program up to
4806 line @code{99} in the same invocation of factorial, i.e., after the inner
4807 invocations have returned.
4810 94 int factorial (int value)
4812 96 if (value > 1) @{
4813 97 value *= factorial (value - 1);
4820 @kindex advance @var{location}
4821 @itemx advance @var{location}
4822 Continue running the program up to the given @var{location}. An argument is
4823 required, which should be of one of the forms described in
4824 @ref{Specify Location}.
4825 Execution will also stop upon exit from the current stack
4826 frame. This command is similar to @code{until}, but @code{advance} will
4827 not skip over recursive function calls, and the target location doesn't
4828 have to be in the same frame as the current one.
4832 @kindex si @r{(@code{stepi})}
4834 @itemx stepi @var{arg}
4836 Execute one machine instruction, then stop and return to the debugger.
4838 It is often useful to do @samp{display/i $pc} when stepping by machine
4839 instructions. This makes @value{GDBN} automatically display the next
4840 instruction to be executed, each time your program stops. @xref{Auto
4841 Display,, Automatic Display}.
4843 An argument is a repeat count, as in @code{step}.
4847 @kindex ni @r{(@code{nexti})}
4849 @itemx nexti @var{arg}
4851 Execute one machine instruction, but if it is a function call,
4852 proceed until the function returns.
4854 An argument is a repeat count, as in @code{next}.
4861 A signal is an asynchronous event that can happen in a program. The
4862 operating system defines the possible kinds of signals, and gives each
4863 kind a name and a number. For example, in Unix @code{SIGINT} is the
4864 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4865 @code{SIGSEGV} is the signal a program gets from referencing a place in
4866 memory far away from all the areas in use; @code{SIGALRM} occurs when
4867 the alarm clock timer goes off (which happens only if your program has
4868 requested an alarm).
4870 @cindex fatal signals
4871 Some signals, including @code{SIGALRM}, are a normal part of the
4872 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4873 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4874 program has not specified in advance some other way to handle the signal.
4875 @code{SIGINT} does not indicate an error in your program, but it is normally
4876 fatal so it can carry out the purpose of the interrupt: to kill the program.
4878 @value{GDBN} has the ability to detect any occurrence of a signal in your
4879 program. You can tell @value{GDBN} in advance what to do for each kind of
4882 @cindex handling signals
4883 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4884 @code{SIGALRM} be silently passed to your program
4885 (so as not to interfere with their role in the program's functioning)
4886 but to stop your program immediately whenever an error signal happens.
4887 You can change these settings with the @code{handle} command.
4890 @kindex info signals
4894 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4895 handle each one. You can use this to see the signal numbers of all
4896 the defined types of signals.
4898 @item info signals @var{sig}
4899 Similar, but print information only about the specified signal number.
4901 @code{info handle} is an alias for @code{info signals}.
4904 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4905 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4906 can be the number of a signal or its name (with or without the
4907 @samp{SIG} at the beginning); a list of signal numbers of the form
4908 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4909 known signals. Optional arguments @var{keywords}, described below,
4910 say what change to make.
4914 The keywords allowed by the @code{handle} command can be abbreviated.
4915 Their full names are:
4919 @value{GDBN} should not stop your program when this signal happens. It may
4920 still print a message telling you that the signal has come in.
4923 @value{GDBN} should stop your program when this signal happens. This implies
4924 the @code{print} keyword as well.
4927 @value{GDBN} should print a message when this signal happens.
4930 @value{GDBN} should not mention the occurrence of the signal at all. This
4931 implies the @code{nostop} keyword as well.
4935 @value{GDBN} should allow your program to see this signal; your program
4936 can handle the signal, or else it may terminate if the signal is fatal
4937 and not handled. @code{pass} and @code{noignore} are synonyms.
4941 @value{GDBN} should not allow your program to see this signal.
4942 @code{nopass} and @code{ignore} are synonyms.
4946 When a signal stops your program, the signal is not visible to the
4948 continue. Your program sees the signal then, if @code{pass} is in
4949 effect for the signal in question @emph{at that time}. In other words,
4950 after @value{GDBN} reports a signal, you can use the @code{handle}
4951 command with @code{pass} or @code{nopass} to control whether your
4952 program sees that signal when you continue.
4954 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4955 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4956 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4959 You can also use the @code{signal} command to prevent your program from
4960 seeing a signal, or cause it to see a signal it normally would not see,
4961 or to give it any signal at any time. For example, if your program stopped
4962 due to some sort of memory reference error, you might store correct
4963 values into the erroneous variables and continue, hoping to see more
4964 execution; but your program would probably terminate immediately as
4965 a result of the fatal signal once it saw the signal. To prevent this,
4966 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4969 @cindex extra signal information
4970 @anchor{extra signal information}
4972 On some targets, @value{GDBN} can inspect extra signal information
4973 associated with the intercepted signal, before it is actually
4974 delivered to the program being debugged. This information is exported
4975 by the convenience variable @code{$_siginfo}, and consists of data
4976 that is passed by the kernel to the signal handler at the time of the
4977 receipt of a signal. The data type of the information itself is
4978 target dependent. You can see the data type using the @code{ptype
4979 $_siginfo} command. On Unix systems, it typically corresponds to the
4980 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4983 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4984 referenced address that raised a segmentation fault.
4988 (@value{GDBP}) continue
4989 Program received signal SIGSEGV, Segmentation fault.
4990 0x0000000000400766 in main ()
4992 (@value{GDBP}) ptype $_siginfo
4999 struct @{...@} _kill;
5000 struct @{...@} _timer;
5002 struct @{...@} _sigchld;
5003 struct @{...@} _sigfault;
5004 struct @{...@} _sigpoll;
5007 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5011 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5012 $1 = (void *) 0x7ffff7ff7000
5016 Depending on target support, @code{$_siginfo} may also be writable.
5019 @section Stopping and Starting Multi-thread Programs
5021 @cindex stopped threads
5022 @cindex threads, stopped
5024 @cindex continuing threads
5025 @cindex threads, continuing
5027 @value{GDBN} supports debugging programs with multiple threads
5028 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5029 are two modes of controlling execution of your program within the
5030 debugger. In the default mode, referred to as @dfn{all-stop mode},
5031 when any thread in your program stops (for example, at a breakpoint
5032 or while being stepped), all other threads in the program are also stopped by
5033 @value{GDBN}. On some targets, @value{GDBN} also supports
5034 @dfn{non-stop mode}, in which other threads can continue to run freely while
5035 you examine the stopped thread in the debugger.
5038 * All-Stop Mode:: All threads stop when GDB takes control
5039 * Non-Stop Mode:: Other threads continue to execute
5040 * Background Execution:: Running your program asynchronously
5041 * Thread-Specific Breakpoints:: Controlling breakpoints
5042 * Interrupted System Calls:: GDB may interfere with system calls
5043 * Observer Mode:: GDB does not alter program behavior
5047 @subsection All-Stop Mode
5049 @cindex all-stop mode
5051 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5052 @emph{all} threads of execution stop, not just the current thread. This
5053 allows you to examine the overall state of the program, including
5054 switching between threads, without worrying that things may change
5057 Conversely, whenever you restart the program, @emph{all} threads start
5058 executing. @emph{This is true even when single-stepping} with commands
5059 like @code{step} or @code{next}.
5061 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5062 Since thread scheduling is up to your debugging target's operating
5063 system (not controlled by @value{GDBN}), other threads may
5064 execute more than one statement while the current thread completes a
5065 single step. Moreover, in general other threads stop in the middle of a
5066 statement, rather than at a clean statement boundary, when the program
5069 You might even find your program stopped in another thread after
5070 continuing or even single-stepping. This happens whenever some other
5071 thread runs into a breakpoint, a signal, or an exception before the
5072 first thread completes whatever you requested.
5074 @cindex automatic thread selection
5075 @cindex switching threads automatically
5076 @cindex threads, automatic switching
5077 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5078 signal, it automatically selects the thread where that breakpoint or
5079 signal happened. @value{GDBN} alerts you to the context switch with a
5080 message such as @samp{[Switching to Thread @var{n}]} to identify the
5083 On some OSes, you can modify @value{GDBN}'s default behavior by
5084 locking the OS scheduler to allow only a single thread to run.
5087 @item set scheduler-locking @var{mode}
5088 @cindex scheduler locking mode
5089 @cindex lock scheduler
5090 Set the scheduler locking mode. If it is @code{off}, then there is no
5091 locking and any thread may run at any time. If @code{on}, then only the
5092 current thread may run when the inferior is resumed. The @code{step}
5093 mode optimizes for single-stepping; it prevents other threads
5094 from preempting the current thread while you are stepping, so that
5095 the focus of debugging does not change unexpectedly.
5096 Other threads only rarely (or never) get a chance to run
5097 when you step. They are more likely to run when you @samp{next} over a
5098 function call, and they are completely free to run when you use commands
5099 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5100 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5101 the current thread away from the thread that you are debugging.
5103 @item show scheduler-locking
5104 Display the current scheduler locking mode.
5107 @cindex resume threads of multiple processes simultaneously
5108 By default, when you issue one of the execution commands such as
5109 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5110 threads of the current inferior to run. For example, if @value{GDBN}
5111 is attached to two inferiors, each with two threads, the
5112 @code{continue} command resumes only the two threads of the current
5113 inferior. This is useful, for example, when you debug a program that
5114 forks and you want to hold the parent stopped (so that, for instance,
5115 it doesn't run to exit), while you debug the child. In other
5116 situations, you may not be interested in inspecting the current state
5117 of any of the processes @value{GDBN} is attached to, and you may want
5118 to resume them all until some breakpoint is hit. In the latter case,
5119 you can instruct @value{GDBN} to allow all threads of all the
5120 inferiors to run with the @w{@code{set schedule-multiple}} command.
5123 @kindex set schedule-multiple
5124 @item set schedule-multiple
5125 Set the mode for allowing threads of multiple processes to be resumed
5126 when an execution command is issued. When @code{on}, all threads of
5127 all processes are allowed to run. When @code{off}, only the threads
5128 of the current process are resumed. The default is @code{off}. The
5129 @code{scheduler-locking} mode takes precedence when set to @code{on},
5130 or while you are stepping and set to @code{step}.
5132 @item show schedule-multiple
5133 Display the current mode for resuming the execution of threads of
5138 @subsection Non-Stop Mode
5140 @cindex non-stop mode
5142 @c This section is really only a place-holder, and needs to be expanded
5143 @c with more details.
5145 For some multi-threaded targets, @value{GDBN} supports an optional
5146 mode of operation in which you can examine stopped program threads in
5147 the debugger while other threads continue to execute freely. This
5148 minimizes intrusion when debugging live systems, such as programs
5149 where some threads have real-time constraints or must continue to
5150 respond to external events. This is referred to as @dfn{non-stop} mode.
5152 In non-stop mode, when a thread stops to report a debugging event,
5153 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5154 threads as well, in contrast to the all-stop mode behavior. Additionally,
5155 execution commands such as @code{continue} and @code{step} apply by default
5156 only to the current thread in non-stop mode, rather than all threads as
5157 in all-stop mode. This allows you to control threads explicitly in
5158 ways that are not possible in all-stop mode --- for example, stepping
5159 one thread while allowing others to run freely, stepping
5160 one thread while holding all others stopped, or stepping several threads
5161 independently and simultaneously.
5163 To enter non-stop mode, use this sequence of commands before you run
5164 or attach to your program:
5167 # Enable the async interface.
5170 # If using the CLI, pagination breaks non-stop.
5173 # Finally, turn it on!
5177 You can use these commands to manipulate the non-stop mode setting:
5180 @kindex set non-stop
5181 @item set non-stop on
5182 Enable selection of non-stop mode.
5183 @item set non-stop off
5184 Disable selection of non-stop mode.
5185 @kindex show non-stop
5187 Show the current non-stop enablement setting.
5190 Note these commands only reflect whether non-stop mode is enabled,
5191 not whether the currently-executing program is being run in non-stop mode.
5192 In particular, the @code{set non-stop} preference is only consulted when
5193 @value{GDBN} starts or connects to the target program, and it is generally
5194 not possible to switch modes once debugging has started. Furthermore,
5195 since not all targets support non-stop mode, even when you have enabled
5196 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5199 In non-stop mode, all execution commands apply only to the current thread
5200 by default. That is, @code{continue} only continues one thread.
5201 To continue all threads, issue @code{continue -a} or @code{c -a}.
5203 You can use @value{GDBN}'s background execution commands
5204 (@pxref{Background Execution}) to run some threads in the background
5205 while you continue to examine or step others from @value{GDBN}.
5206 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5207 always executed asynchronously in non-stop mode.
5209 Suspending execution is done with the @code{interrupt} command when
5210 running in the background, or @kbd{Ctrl-c} during foreground execution.
5211 In all-stop mode, this stops the whole process;
5212 but in non-stop mode the interrupt applies only to the current thread.
5213 To stop the whole program, use @code{interrupt -a}.
5215 Other execution commands do not currently support the @code{-a} option.
5217 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5218 that thread current, as it does in all-stop mode. This is because the
5219 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5220 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5221 changed to a different thread just as you entered a command to operate on the
5222 previously current thread.
5224 @node Background Execution
5225 @subsection Background Execution
5227 @cindex foreground execution
5228 @cindex background execution
5229 @cindex asynchronous execution
5230 @cindex execution, foreground, background and asynchronous
5232 @value{GDBN}'s execution commands have two variants: the normal
5233 foreground (synchronous) behavior, and a background
5234 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5235 the program to report that some thread has stopped before prompting for
5236 another command. In background execution, @value{GDBN} immediately gives
5237 a command prompt so that you can issue other commands while your program runs.
5239 You need to explicitly enable asynchronous mode before you can use
5240 background execution commands. You can use these commands to
5241 manipulate the asynchronous mode setting:
5244 @kindex set target-async
5245 @item set target-async on
5246 Enable asynchronous mode.
5247 @item set target-async off
5248 Disable asynchronous mode.
5249 @kindex show target-async
5250 @item show target-async
5251 Show the current target-async setting.
5254 If the target doesn't support async mode, @value{GDBN} issues an error
5255 message if you attempt to use the background execution commands.
5257 To specify background execution, add a @code{&} to the command. For example,
5258 the background form of the @code{continue} command is @code{continue&}, or
5259 just @code{c&}. The execution commands that accept background execution
5265 @xref{Starting, , Starting your Program}.
5269 @xref{Attach, , Debugging an Already-running Process}.
5273 @xref{Continuing and Stepping, step}.
5277 @xref{Continuing and Stepping, stepi}.
5281 @xref{Continuing and Stepping, next}.
5285 @xref{Continuing and Stepping, nexti}.
5289 @xref{Continuing and Stepping, continue}.
5293 @xref{Continuing and Stepping, finish}.
5297 @xref{Continuing and Stepping, until}.
5301 Background execution is especially useful in conjunction with non-stop
5302 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5303 However, you can also use these commands in the normal all-stop mode with
5304 the restriction that you cannot issue another execution command until the
5305 previous one finishes. Examples of commands that are valid in all-stop
5306 mode while the program is running include @code{help} and @code{info break}.
5308 You can interrupt your program while it is running in the background by
5309 using the @code{interrupt} command.
5316 Suspend execution of the running program. In all-stop mode,
5317 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5318 only the current thread. To stop the whole program in non-stop mode,
5319 use @code{interrupt -a}.
5322 @node Thread-Specific Breakpoints
5323 @subsection Thread-Specific Breakpoints
5325 When your program has multiple threads (@pxref{Threads,, Debugging
5326 Programs with Multiple Threads}), you can choose whether to set
5327 breakpoints on all threads, or on a particular thread.
5330 @cindex breakpoints and threads
5331 @cindex thread breakpoints
5332 @kindex break @dots{} thread @var{threadno}
5333 @item break @var{linespec} thread @var{threadno}
5334 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5335 @var{linespec} specifies source lines; there are several ways of
5336 writing them (@pxref{Specify Location}), but the effect is always to
5337 specify some source line.
5339 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5340 to specify that you only want @value{GDBN} to stop the program when a
5341 particular thread reaches this breakpoint. @var{threadno} is one of the
5342 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5343 column of the @samp{info threads} display.
5345 If you do not specify @samp{thread @var{threadno}} when you set a
5346 breakpoint, the breakpoint applies to @emph{all} threads of your
5349 You can use the @code{thread} qualifier on conditional breakpoints as
5350 well; in this case, place @samp{thread @var{threadno}} before or
5351 after the breakpoint condition, like this:
5354 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5359 @node Interrupted System Calls
5360 @subsection Interrupted System Calls
5362 @cindex thread breakpoints and system calls
5363 @cindex system calls and thread breakpoints
5364 @cindex premature return from system calls
5365 There is an unfortunate side effect when using @value{GDBN} to debug
5366 multi-threaded programs. If one thread stops for a
5367 breakpoint, or for some other reason, and another thread is blocked in a
5368 system call, then the system call may return prematurely. This is a
5369 consequence of the interaction between multiple threads and the signals
5370 that @value{GDBN} uses to implement breakpoints and other events that
5373 To handle this problem, your program should check the return value of
5374 each system call and react appropriately. This is good programming
5377 For example, do not write code like this:
5383 The call to @code{sleep} will return early if a different thread stops
5384 at a breakpoint or for some other reason.
5386 Instead, write this:
5391 unslept = sleep (unslept);
5394 A system call is allowed to return early, so the system is still
5395 conforming to its specification. But @value{GDBN} does cause your
5396 multi-threaded program to behave differently than it would without
5399 Also, @value{GDBN} uses internal breakpoints in the thread library to
5400 monitor certain events such as thread creation and thread destruction.
5401 When such an event happens, a system call in another thread may return
5402 prematurely, even though your program does not appear to stop.
5405 @subsection Observer Mode
5407 If you want to build on non-stop mode and observe program behavior
5408 without any chance of disruption by @value{GDBN}, you can set
5409 variables to disable all of the debugger's attempts to modify state,
5410 whether by writing memory, inserting breakpoints, etc. These operate
5411 at a low level, intercepting operations from all commands.
5413 When all of these are set to @code{off}, then @value{GDBN} is said to
5414 be @dfn{observer mode}. As a convenience, the variable
5415 @code{observer} can be set to disable these, plus enable non-stop
5418 Note that @value{GDBN} will not prevent you from making nonsensical
5419 combinations of these settings. For instance, if you have enabled
5420 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5421 then breakpoints that work by writing trap instructions into the code
5422 stream will still not be able to be placed.
5427 @item set observer on
5428 @itemx set observer off
5429 When set to @code{on}, this disables all the permission variables
5430 below (except for @code{insert-fast-tracepoints}), plus enables
5431 non-stop debugging. Setting this to @code{off} switches back to
5432 normal debugging, though remaining in non-stop mode.
5435 Show whether observer mode is on or off.
5437 @kindex may-write-registers
5438 @item set may-write-registers on
5439 @itemx set may-write-registers off
5440 This controls whether @value{GDBN} will attempt to alter the values of
5441 registers, such as with assignment expressions in @code{print}, or the
5442 @code{jump} command. It defaults to @code{on}.
5444 @item show may-write-registers
5445 Show the current permission to write registers.
5447 @kindex may-write-memory
5448 @item set may-write-memory on
5449 @itemx set may-write-memory off
5450 This controls whether @value{GDBN} will attempt to alter the contents
5451 of memory, such as with assignment expressions in @code{print}. It
5452 defaults to @code{on}.
5454 @item show may-write-memory
5455 Show the current permission to write memory.
5457 @kindex may-insert-breakpoints
5458 @item set may-insert-breakpoints on
5459 @itemx set may-insert-breakpoints off
5460 This controls whether @value{GDBN} will attempt to insert breakpoints.
5461 This affects all breakpoints, including internal breakpoints defined
5462 by @value{GDBN}. It defaults to @code{on}.
5464 @item show may-insert-breakpoints
5465 Show the current permission to insert breakpoints.
5467 @kindex may-insert-tracepoints
5468 @item set may-insert-tracepoints on
5469 @itemx set may-insert-tracepoints off
5470 This controls whether @value{GDBN} will attempt to insert (regular)
5471 tracepoints at the beginning of a tracing experiment. It affects only
5472 non-fast tracepoints, fast tracepoints being under the control of
5473 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5475 @item show may-insert-tracepoints
5476 Show the current permission to insert tracepoints.
5478 @kindex may-insert-fast-tracepoints
5479 @item set may-insert-fast-tracepoints on
5480 @itemx set may-insert-fast-tracepoints off
5481 This controls whether @value{GDBN} will attempt to insert fast
5482 tracepoints at the beginning of a tracing experiment. It affects only
5483 fast tracepoints, regular (non-fast) tracepoints being under the
5484 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5486 @item show may-insert-fast-tracepoints
5487 Show the current permission to insert fast tracepoints.
5489 @kindex may-interrupt
5490 @item set may-interrupt on
5491 @itemx set may-interrupt off
5492 This controls whether @value{GDBN} will attempt to interrupt or stop
5493 program execution. When this variable is @code{off}, the
5494 @code{interrupt} command will have no effect, nor will
5495 @kbd{Ctrl-c}. It defaults to @code{on}.
5497 @item show may-interrupt
5498 Show the current permission to interrupt or stop the program.
5502 @node Reverse Execution
5503 @chapter Running programs backward
5504 @cindex reverse execution
5505 @cindex running programs backward
5507 When you are debugging a program, it is not unusual to realize that
5508 you have gone too far, and some event of interest has already happened.
5509 If the target environment supports it, @value{GDBN} can allow you to
5510 ``rewind'' the program by running it backward.
5512 A target environment that supports reverse execution should be able
5513 to ``undo'' the changes in machine state that have taken place as the
5514 program was executing normally. Variables, registers etc.@: should
5515 revert to their previous values. Obviously this requires a great
5516 deal of sophistication on the part of the target environment; not
5517 all target environments can support reverse execution.
5519 When a program is executed in reverse, the instructions that
5520 have most recently been executed are ``un-executed'', in reverse
5521 order. The program counter runs backward, following the previous
5522 thread of execution in reverse. As each instruction is ``un-executed'',
5523 the values of memory and/or registers that were changed by that
5524 instruction are reverted to their previous states. After executing
5525 a piece of source code in reverse, all side effects of that code
5526 should be ``undone'', and all variables should be returned to their
5527 prior values@footnote{
5528 Note that some side effects are easier to undo than others. For instance,
5529 memory and registers are relatively easy, but device I/O is hard. Some
5530 targets may be able undo things like device I/O, and some may not.
5532 The contract between @value{GDBN} and the reverse executing target
5533 requires only that the target do something reasonable when
5534 @value{GDBN} tells it to execute backwards, and then report the
5535 results back to @value{GDBN}. Whatever the target reports back to
5536 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5537 assumes that the memory and registers that the target reports are in a
5538 consistant state, but @value{GDBN} accepts whatever it is given.
5541 If you are debugging in a target environment that supports
5542 reverse execution, @value{GDBN} provides the following commands.
5545 @kindex reverse-continue
5546 @kindex rc @r{(@code{reverse-continue})}
5547 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5548 @itemx rc @r{[}@var{ignore-count}@r{]}
5549 Beginning at the point where your program last stopped, start executing
5550 in reverse. Reverse execution will stop for breakpoints and synchronous
5551 exceptions (signals), just like normal execution. Behavior of
5552 asynchronous signals depends on the target environment.
5554 @kindex reverse-step
5555 @kindex rs @r{(@code{step})}
5556 @item reverse-step @r{[}@var{count}@r{]}
5557 Run the program backward until control reaches the start of a
5558 different source line; then stop it, and return control to @value{GDBN}.
5560 Like the @code{step} command, @code{reverse-step} will only stop
5561 at the beginning of a source line. It ``un-executes'' the previously
5562 executed source line. If the previous source line included calls to
5563 debuggable functions, @code{reverse-step} will step (backward) into
5564 the called function, stopping at the beginning of the @emph{last}
5565 statement in the called function (typically a return statement).
5567 Also, as with the @code{step} command, if non-debuggable functions are
5568 called, @code{reverse-step} will run thru them backward without stopping.
5570 @kindex reverse-stepi
5571 @kindex rsi @r{(@code{reverse-stepi})}
5572 @item reverse-stepi @r{[}@var{count}@r{]}
5573 Reverse-execute one machine instruction. Note that the instruction
5574 to be reverse-executed is @emph{not} the one pointed to by the program
5575 counter, but the instruction executed prior to that one. For instance,
5576 if the last instruction was a jump, @code{reverse-stepi} will take you
5577 back from the destination of the jump to the jump instruction itself.
5579 @kindex reverse-next
5580 @kindex rn @r{(@code{reverse-next})}
5581 @item reverse-next @r{[}@var{count}@r{]}
5582 Run backward to the beginning of the previous line executed in
5583 the current (innermost) stack frame. If the line contains function
5584 calls, they will be ``un-executed'' without stopping. Starting from
5585 the first line of a function, @code{reverse-next} will take you back
5586 to the caller of that function, @emph{before} the function was called,
5587 just as the normal @code{next} command would take you from the last
5588 line of a function back to its return to its caller
5589 @footnote{Unless the code is too heavily optimized.}.
5591 @kindex reverse-nexti
5592 @kindex rni @r{(@code{reverse-nexti})}
5593 @item reverse-nexti @r{[}@var{count}@r{]}
5594 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5595 in reverse, except that called functions are ``un-executed'' atomically.
5596 That is, if the previously executed instruction was a return from
5597 another function, @code{reverse-nexti} will continue to execute
5598 in reverse until the call to that function (from the current stack
5601 @kindex reverse-finish
5602 @item reverse-finish
5603 Just as the @code{finish} command takes you to the point where the
5604 current function returns, @code{reverse-finish} takes you to the point
5605 where it was called. Instead of ending up at the end of the current
5606 function invocation, you end up at the beginning.
5608 @kindex set exec-direction
5609 @item set exec-direction
5610 Set the direction of target execution.
5611 @itemx set exec-direction reverse
5612 @cindex execute forward or backward in time
5613 @value{GDBN} will perform all execution commands in reverse, until the
5614 exec-direction mode is changed to ``forward''. Affected commands include
5615 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5616 command cannot be used in reverse mode.
5617 @item set exec-direction forward
5618 @value{GDBN} will perform all execution commands in the normal fashion.
5619 This is the default.
5623 @node Process Record and Replay
5624 @chapter Recording Inferior's Execution and Replaying It
5625 @cindex process record and replay
5626 @cindex recording inferior's execution and replaying it
5628 On some platforms, @value{GDBN} provides a special @dfn{process record
5629 and replay} target that can record a log of the process execution, and
5630 replay it later with both forward and reverse execution commands.
5633 When this target is in use, if the execution log includes the record
5634 for the next instruction, @value{GDBN} will debug in @dfn{replay
5635 mode}. In the replay mode, the inferior does not really execute code
5636 instructions. Instead, all the events that normally happen during
5637 code execution are taken from the execution log. While code is not
5638 really executed in replay mode, the values of registers (including the
5639 program counter register) and the memory of the inferior are still
5640 changed as they normally would. Their contents are taken from the
5644 If the record for the next instruction is not in the execution log,
5645 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5646 inferior executes normally, and @value{GDBN} records the execution log
5649 The process record and replay target supports reverse execution
5650 (@pxref{Reverse Execution}), even if the platform on which the
5651 inferior runs does not. However, the reverse execution is limited in
5652 this case by the range of the instructions recorded in the execution
5653 log. In other words, reverse execution on platforms that don't
5654 support it directly can only be done in the replay mode.
5656 When debugging in the reverse direction, @value{GDBN} will work in
5657 replay mode as long as the execution log includes the record for the
5658 previous instruction; otherwise, it will work in record mode, if the
5659 platform supports reverse execution, or stop if not.
5661 For architecture environments that support process record and replay,
5662 @value{GDBN} provides the following commands:
5665 @kindex target record
5669 This command starts the process record and replay target. The process
5670 record and replay target can only debug a process that is already
5671 running. Therefore, you need first to start the process with the
5672 @kbd{run} or @kbd{start} commands, and then start the recording with
5673 the @kbd{target record} command.
5675 Both @code{record} and @code{rec} are aliases of @code{target record}.
5677 @cindex displaced stepping, and process record and replay
5678 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5679 will be automatically disabled when process record and replay target
5680 is started. That's because the process record and replay target
5681 doesn't support displaced stepping.
5683 @cindex non-stop mode, and process record and replay
5684 @cindex asynchronous execution, and process record and replay
5685 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5686 the asynchronous execution mode (@pxref{Background Execution}), the
5687 process record and replay target cannot be started because it doesn't
5688 support these two modes.
5693 Stop the process record and replay target. When process record and
5694 replay target stops, the entire execution log will be deleted and the
5695 inferior will either be terminated, or will remain in its final state.
5697 When you stop the process record and replay target in record mode (at
5698 the end of the execution log), the inferior will be stopped at the
5699 next instruction that would have been recorded. In other words, if
5700 you record for a while and then stop recording, the inferior process
5701 will be left in the same state as if the recording never happened.
5703 On the other hand, if the process record and replay target is stopped
5704 while in replay mode (that is, not at the end of the execution log,
5705 but at some earlier point), the inferior process will become ``live''
5706 at that earlier state, and it will then be possible to continue the
5707 usual ``live'' debugging of the process from that state.
5709 When the inferior process exits, or @value{GDBN} detaches from it,
5710 process record and replay target will automatically stop itself.
5713 @item record save @var{filename}
5714 Save the execution log to a file @file{@var{filename}}.
5715 Default filename is @file{gdb_record.@var{process_id}}, where
5716 @var{process_id} is the process ID of the inferior.
5718 @kindex record restore
5719 @item record restore @var{filename}
5720 Restore the execution log from a file @file{@var{filename}}.
5721 File must have been created with @code{record save}.
5723 @kindex set record insn-number-max
5724 @item set record insn-number-max @var{limit}
5725 Set the limit of instructions to be recorded. Default value is 200000.
5727 If @var{limit} is a positive number, then @value{GDBN} will start
5728 deleting instructions from the log once the number of the record
5729 instructions becomes greater than @var{limit}. For every new recorded
5730 instruction, @value{GDBN} will delete the earliest recorded
5731 instruction to keep the number of recorded instructions at the limit.
5732 (Since deleting recorded instructions loses information, @value{GDBN}
5733 lets you control what happens when the limit is reached, by means of
5734 the @code{stop-at-limit} option, described below.)
5736 If @var{limit} is zero, @value{GDBN} will never delete recorded
5737 instructions from the execution log. The number of recorded
5738 instructions is unlimited in this case.
5740 @kindex show record insn-number-max
5741 @item show record insn-number-max
5742 Show the limit of instructions to be recorded.
5744 @kindex set record stop-at-limit
5745 @item set record stop-at-limit
5746 Control the behavior when the number of recorded instructions reaches
5747 the limit. If ON (the default), @value{GDBN} will stop when the limit
5748 is reached for the first time and ask you whether you want to stop the
5749 inferior or continue running it and recording the execution log. If
5750 you decide to continue recording, each new recorded instruction will
5751 cause the oldest one to be deleted.
5753 If this option is OFF, @value{GDBN} will automatically delete the
5754 oldest record to make room for each new one, without asking.
5756 @kindex show record stop-at-limit
5757 @item show record stop-at-limit
5758 Show the current setting of @code{stop-at-limit}.
5760 @kindex set record memory-query
5761 @item set record memory-query
5762 Control the behavior when @value{GDBN} is unable to record memory
5763 changes caused by an instruction. If ON, @value{GDBN} will query
5764 whether to stop the inferior in that case.
5766 If this option is OFF (the default), @value{GDBN} will automatically
5767 ignore the effect of such instructions on memory. Later, when
5768 @value{GDBN} replays this execution log, it will mark the log of this
5769 instruction as not accessible, and it will not affect the replay
5772 @kindex show record memory-query
5773 @item show record memory-query
5774 Show the current setting of @code{memory-query}.
5778 Show various statistics about the state of process record and its
5779 in-memory execution log buffer, including:
5783 Whether in record mode or replay mode.
5785 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5787 Highest recorded instruction number.
5789 Current instruction about to be replayed (if in replay mode).
5791 Number of instructions contained in the execution log.
5793 Maximum number of instructions that may be contained in the execution log.
5796 @kindex record delete
5799 When record target runs in replay mode (``in the past''), delete the
5800 subsequent execution log and begin to record a new execution log starting
5801 from the current address. This means you will abandon the previously
5802 recorded ``future'' and begin recording a new ``future''.
5807 @chapter Examining the Stack
5809 When your program has stopped, the first thing you need to know is where it
5810 stopped and how it got there.
5813 Each time your program performs a function call, information about the call
5815 That information includes the location of the call in your program,
5816 the arguments of the call,
5817 and the local variables of the function being called.
5818 The information is saved in a block of data called a @dfn{stack frame}.
5819 The stack frames are allocated in a region of memory called the @dfn{call
5822 When your program stops, the @value{GDBN} commands for examining the
5823 stack allow you to see all of this information.
5825 @cindex selected frame
5826 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5827 @value{GDBN} commands refer implicitly to the selected frame. In
5828 particular, whenever you ask @value{GDBN} for the value of a variable in
5829 your program, the value is found in the selected frame. There are
5830 special @value{GDBN} commands to select whichever frame you are
5831 interested in. @xref{Selection, ,Selecting a Frame}.
5833 When your program stops, @value{GDBN} automatically selects the
5834 currently executing frame and describes it briefly, similar to the
5835 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5838 * Frames:: Stack frames
5839 * Backtrace:: Backtraces
5840 * Selection:: Selecting a frame
5841 * Frame Info:: Information on a frame
5846 @section Stack Frames
5848 @cindex frame, definition
5850 The call stack is divided up into contiguous pieces called @dfn{stack
5851 frames}, or @dfn{frames} for short; each frame is the data associated
5852 with one call to one function. The frame contains the arguments given
5853 to the function, the function's local variables, and the address at
5854 which the function is executing.
5856 @cindex initial frame
5857 @cindex outermost frame
5858 @cindex innermost frame
5859 When your program is started, the stack has only one frame, that of the
5860 function @code{main}. This is called the @dfn{initial} frame or the
5861 @dfn{outermost} frame. Each time a function is called, a new frame is
5862 made. Each time a function returns, the frame for that function invocation
5863 is eliminated. If a function is recursive, there can be many frames for
5864 the same function. The frame for the function in which execution is
5865 actually occurring is called the @dfn{innermost} frame. This is the most
5866 recently created of all the stack frames that still exist.
5868 @cindex frame pointer
5869 Inside your program, stack frames are identified by their addresses. A
5870 stack frame consists of many bytes, each of which has its own address; each
5871 kind of computer has a convention for choosing one byte whose
5872 address serves as the address of the frame. Usually this address is kept
5873 in a register called the @dfn{frame pointer register}
5874 (@pxref{Registers, $fp}) while execution is going on in that frame.
5876 @cindex frame number
5877 @value{GDBN} assigns numbers to all existing stack frames, starting with
5878 zero for the innermost frame, one for the frame that called it,
5879 and so on upward. These numbers do not really exist in your program;
5880 they are assigned by @value{GDBN} to give you a way of designating stack
5881 frames in @value{GDBN} commands.
5883 @c The -fomit-frame-pointer below perennially causes hbox overflow
5884 @c underflow problems.
5885 @cindex frameless execution
5886 Some compilers provide a way to compile functions so that they operate
5887 without stack frames. (For example, the @value{NGCC} option
5889 @samp{-fomit-frame-pointer}
5891 generates functions without a frame.)
5892 This is occasionally done with heavily used library functions to save
5893 the frame setup time. @value{GDBN} has limited facilities for dealing
5894 with these function invocations. If the innermost function invocation
5895 has no stack frame, @value{GDBN} nevertheless regards it as though
5896 it had a separate frame, which is numbered zero as usual, allowing
5897 correct tracing of the function call chain. However, @value{GDBN} has
5898 no provision for frameless functions elsewhere in the stack.
5901 @kindex frame@r{, command}
5902 @cindex current stack frame
5903 @item frame @var{args}
5904 The @code{frame} command allows you to move from one stack frame to another,
5905 and to print the stack frame you select. @var{args} may be either the
5906 address of the frame or the stack frame number. Without an argument,
5907 @code{frame} prints the current stack frame.
5909 @kindex select-frame
5910 @cindex selecting frame silently
5912 The @code{select-frame} command allows you to move from one stack frame
5913 to another without printing the frame. This is the silent version of
5921 @cindex call stack traces
5922 A backtrace is a summary of how your program got where it is. It shows one
5923 line per frame, for many frames, starting with the currently executing
5924 frame (frame zero), followed by its caller (frame one), and on up the
5929 @kindex bt @r{(@code{backtrace})}
5932 Print a backtrace of the entire stack: one line per frame for all
5933 frames in the stack.
5935 You can stop the backtrace at any time by typing the system interrupt
5936 character, normally @kbd{Ctrl-c}.
5938 @item backtrace @var{n}
5940 Similar, but print only the innermost @var{n} frames.
5942 @item backtrace -@var{n}
5944 Similar, but print only the outermost @var{n} frames.
5946 @item backtrace full
5948 @itemx bt full @var{n}
5949 @itemx bt full -@var{n}
5950 Print the values of the local variables also. @var{n} specifies the
5951 number of frames to print, as described above.
5956 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5957 are additional aliases for @code{backtrace}.
5959 @cindex multiple threads, backtrace
5960 In a multi-threaded program, @value{GDBN} by default shows the
5961 backtrace only for the current thread. To display the backtrace for
5962 several or all of the threads, use the command @code{thread apply}
5963 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5964 apply all backtrace}, @value{GDBN} will display the backtrace for all
5965 the threads; this is handy when you debug a core dump of a
5966 multi-threaded program.
5968 Each line in the backtrace shows the frame number and the function name.
5969 The program counter value is also shown---unless you use @code{set
5970 print address off}. The backtrace also shows the source file name and
5971 line number, as well as the arguments to the function. The program
5972 counter value is omitted if it is at the beginning of the code for that
5975 Here is an example of a backtrace. It was made with the command
5976 @samp{bt 3}, so it shows the innermost three frames.
5980 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5982 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5983 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5985 (More stack frames follow...)
5990 The display for frame zero does not begin with a program counter
5991 value, indicating that your program has stopped at the beginning of the
5992 code for line @code{993} of @code{builtin.c}.
5995 The value of parameter @code{data} in frame 1 has been replaced by
5996 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5997 only if it is a scalar (integer, pointer, enumeration, etc). See command
5998 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5999 on how to configure the way function parameter values are printed.
6001 @cindex optimized out, in backtrace
6002 @cindex function call arguments, optimized out
6003 If your program was compiled with optimizations, some compilers will
6004 optimize away arguments passed to functions if those arguments are
6005 never used after the call. Such optimizations generate code that
6006 passes arguments through registers, but doesn't store those arguments
6007 in the stack frame. @value{GDBN} has no way of displaying such
6008 arguments in stack frames other than the innermost one. Here's what
6009 such a backtrace might look like:
6013 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6015 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6016 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6018 (More stack frames follow...)
6023 The values of arguments that were not saved in their stack frames are
6024 shown as @samp{<optimized out>}.
6026 If you need to display the values of such optimized-out arguments,
6027 either deduce that from other variables whose values depend on the one
6028 you are interested in, or recompile without optimizations.
6030 @cindex backtrace beyond @code{main} function
6031 @cindex program entry point
6032 @cindex startup code, and backtrace
6033 Most programs have a standard user entry point---a place where system
6034 libraries and startup code transition into user code. For C this is
6035 @code{main}@footnote{
6036 Note that embedded programs (the so-called ``free-standing''
6037 environment) are not required to have a @code{main} function as the
6038 entry point. They could even have multiple entry points.}.
6039 When @value{GDBN} finds the entry function in a backtrace
6040 it will terminate the backtrace, to avoid tracing into highly
6041 system-specific (and generally uninteresting) code.
6043 If you need to examine the startup code, or limit the number of levels
6044 in a backtrace, you can change this behavior:
6047 @item set backtrace past-main
6048 @itemx set backtrace past-main on
6049 @kindex set backtrace
6050 Backtraces will continue past the user entry point.
6052 @item set backtrace past-main off
6053 Backtraces will stop when they encounter the user entry point. This is the
6056 @item show backtrace past-main
6057 @kindex show backtrace
6058 Display the current user entry point backtrace policy.
6060 @item set backtrace past-entry
6061 @itemx set backtrace past-entry on
6062 Backtraces will continue past the internal entry point of an application.
6063 This entry point is encoded by the linker when the application is built,
6064 and is likely before the user entry point @code{main} (or equivalent) is called.
6066 @item set backtrace past-entry off
6067 Backtraces will stop when they encounter the internal entry point of an
6068 application. This is the default.
6070 @item show backtrace past-entry
6071 Display the current internal entry point backtrace policy.
6073 @item set backtrace limit @var{n}
6074 @itemx set backtrace limit 0
6075 @cindex backtrace limit
6076 Limit the backtrace to @var{n} levels. A value of zero means
6079 @item show backtrace limit
6080 Display the current limit on backtrace levels.
6084 @section Selecting a Frame
6086 Most commands for examining the stack and other data in your program work on
6087 whichever stack frame is selected at the moment. Here are the commands for
6088 selecting a stack frame; all of them finish by printing a brief description
6089 of the stack frame just selected.
6092 @kindex frame@r{, selecting}
6093 @kindex f @r{(@code{frame})}
6096 Select frame number @var{n}. Recall that frame zero is the innermost
6097 (currently executing) frame, frame one is the frame that called the
6098 innermost one, and so on. The highest-numbered frame is the one for
6101 @item frame @var{addr}
6103 Select the frame at address @var{addr}. This is useful mainly if the
6104 chaining of stack frames has been damaged by a bug, making it
6105 impossible for @value{GDBN} to assign numbers properly to all frames. In
6106 addition, this can be useful when your program has multiple stacks and
6107 switches between them.
6109 On the SPARC architecture, @code{frame} needs two addresses to
6110 select an arbitrary frame: a frame pointer and a stack pointer.
6112 On the MIPS and Alpha architecture, it needs two addresses: a stack
6113 pointer and a program counter.
6115 On the 29k architecture, it needs three addresses: a register stack
6116 pointer, a program counter, and a memory stack pointer.
6120 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6121 advances toward the outermost frame, to higher frame numbers, to frames
6122 that have existed longer. @var{n} defaults to one.
6125 @kindex do @r{(@code{down})}
6127 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6128 advances toward the innermost frame, to lower frame numbers, to frames
6129 that were created more recently. @var{n} defaults to one. You may
6130 abbreviate @code{down} as @code{do}.
6133 All of these commands end by printing two lines of output describing the
6134 frame. The first line shows the frame number, the function name, the
6135 arguments, and the source file and line number of execution in that
6136 frame. The second line shows the text of that source line.
6144 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6146 10 read_input_file (argv[i]);
6150 After such a printout, the @code{list} command with no arguments
6151 prints ten lines centered on the point of execution in the frame.
6152 You can also edit the program at the point of execution with your favorite
6153 editing program by typing @code{edit}.
6154 @xref{List, ,Printing Source Lines},
6158 @kindex down-silently
6160 @item up-silently @var{n}
6161 @itemx down-silently @var{n}
6162 These two commands are variants of @code{up} and @code{down},
6163 respectively; they differ in that they do their work silently, without
6164 causing display of the new frame. They are intended primarily for use
6165 in @value{GDBN} command scripts, where the output might be unnecessary and
6170 @section Information About a Frame
6172 There are several other commands to print information about the selected
6178 When used without any argument, this command does not change which
6179 frame is selected, but prints a brief description of the currently
6180 selected stack frame. It can be abbreviated @code{f}. With an
6181 argument, this command is used to select a stack frame.
6182 @xref{Selection, ,Selecting a Frame}.
6185 @kindex info f @r{(@code{info frame})}
6188 This command prints a verbose description of the selected stack frame,
6193 the address of the frame
6195 the address of the next frame down (called by this frame)
6197 the address of the next frame up (caller of this frame)
6199 the language in which the source code corresponding to this frame is written
6201 the address of the frame's arguments
6203 the address of the frame's local variables
6205 the program counter saved in it (the address of execution in the caller frame)
6207 which registers were saved in the frame
6210 @noindent The verbose description is useful when
6211 something has gone wrong that has made the stack format fail to fit
6212 the usual conventions.
6214 @item info frame @var{addr}
6215 @itemx info f @var{addr}
6216 Print a verbose description of the frame at address @var{addr}, without
6217 selecting that frame. The selected frame remains unchanged by this
6218 command. This requires the same kind of address (more than one for some
6219 architectures) that you specify in the @code{frame} command.
6220 @xref{Selection, ,Selecting a Frame}.
6224 Print the arguments of the selected frame, each on a separate line.
6228 Print the local variables of the selected frame, each on a separate
6229 line. These are all variables (declared either static or automatic)
6230 accessible at the point of execution of the selected frame.
6233 @cindex catch exceptions, list active handlers
6234 @cindex exception handlers, how to list
6236 Print a list of all the exception handlers that are active in the
6237 current stack frame at the current point of execution. To see other
6238 exception handlers, visit the associated frame (using the @code{up},
6239 @code{down}, or @code{frame} commands); then type @code{info catch}.
6240 @xref{Set Catchpoints, , Setting Catchpoints}.
6246 @chapter Examining Source Files
6248 @value{GDBN} can print parts of your program's source, since the debugging
6249 information recorded in the program tells @value{GDBN} what source files were
6250 used to build it. When your program stops, @value{GDBN} spontaneously prints
6251 the line where it stopped. Likewise, when you select a stack frame
6252 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6253 execution in that frame has stopped. You can print other portions of
6254 source files by explicit command.
6256 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6257 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6258 @value{GDBN} under @sc{gnu} Emacs}.
6261 * List:: Printing source lines
6262 * Specify Location:: How to specify code locations
6263 * Edit:: Editing source files
6264 * Search:: Searching source files
6265 * Source Path:: Specifying source directories
6266 * Machine Code:: Source and machine code
6270 @section Printing Source Lines
6273 @kindex l @r{(@code{list})}
6274 To print lines from a source file, use the @code{list} command
6275 (abbreviated @code{l}). By default, ten lines are printed.
6276 There are several ways to specify what part of the file you want to
6277 print; see @ref{Specify Location}, for the full list.
6279 Here are the forms of the @code{list} command most commonly used:
6282 @item list @var{linenum}
6283 Print lines centered around line number @var{linenum} in the
6284 current source file.
6286 @item list @var{function}
6287 Print lines centered around the beginning of function
6291 Print more lines. If the last lines printed were printed with a
6292 @code{list} command, this prints lines following the last lines
6293 printed; however, if the last line printed was a solitary line printed
6294 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6295 Stack}), this prints lines centered around that line.
6298 Print lines just before the lines last printed.
6301 @cindex @code{list}, how many lines to display
6302 By default, @value{GDBN} prints ten source lines with any of these forms of
6303 the @code{list} command. You can change this using @code{set listsize}:
6306 @kindex set listsize
6307 @item set listsize @var{count}
6308 Make the @code{list} command display @var{count} source lines (unless
6309 the @code{list} argument explicitly specifies some other number).
6311 @kindex show listsize
6313 Display the number of lines that @code{list} prints.
6316 Repeating a @code{list} command with @key{RET} discards the argument,
6317 so it is equivalent to typing just @code{list}. This is more useful
6318 than listing the same lines again. An exception is made for an
6319 argument of @samp{-}; that argument is preserved in repetition so that
6320 each repetition moves up in the source file.
6322 In general, the @code{list} command expects you to supply zero, one or two
6323 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6324 of writing them (@pxref{Specify Location}), but the effect is always
6325 to specify some source line.
6327 Here is a complete description of the possible arguments for @code{list}:
6330 @item list @var{linespec}
6331 Print lines centered around the line specified by @var{linespec}.
6333 @item list @var{first},@var{last}
6334 Print lines from @var{first} to @var{last}. Both arguments are
6335 linespecs. When a @code{list} command has two linespecs, and the
6336 source file of the second linespec is omitted, this refers to
6337 the same source file as the first linespec.
6339 @item list ,@var{last}
6340 Print lines ending with @var{last}.
6342 @item list @var{first},
6343 Print lines starting with @var{first}.
6346 Print lines just after the lines last printed.
6349 Print lines just before the lines last printed.
6352 As described in the preceding table.
6355 @node Specify Location
6356 @section Specifying a Location
6357 @cindex specifying location
6360 Several @value{GDBN} commands accept arguments that specify a location
6361 of your program's code. Since @value{GDBN} is a source-level
6362 debugger, a location usually specifies some line in the source code;
6363 for that reason, locations are also known as @dfn{linespecs}.
6365 Here are all the different ways of specifying a code location that
6366 @value{GDBN} understands:
6370 Specifies the line number @var{linenum} of the current source file.
6373 @itemx +@var{offset}
6374 Specifies the line @var{offset} lines before or after the @dfn{current
6375 line}. For the @code{list} command, the current line is the last one
6376 printed; for the breakpoint commands, this is the line at which
6377 execution stopped in the currently selected @dfn{stack frame}
6378 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6379 used as the second of the two linespecs in a @code{list} command,
6380 this specifies the line @var{offset} lines up or down from the first
6383 @item @var{filename}:@var{linenum}
6384 Specifies the line @var{linenum} in the source file @var{filename}.
6386 @item @var{function}
6387 Specifies the line that begins the body of the function @var{function}.
6388 For example, in C, this is the line with the open brace.
6390 @item @var{function}:@var{label}
6391 Specifies the line where @var{label} appears in @var{function}.
6393 @item @var{filename}:@var{function}
6394 Specifies the line that begins the body of the function @var{function}
6395 in the file @var{filename}. You only need the file name with a
6396 function name to avoid ambiguity when there are identically named
6397 functions in different source files.
6400 Specifies the line at which the label named @var{label} appears.
6401 @value{GDBN} searches for the label in the function corresponding to
6402 the currently selected stack frame. If there is no current selected
6403 stack frame (for instance, if the inferior is not running), then
6404 @value{GDBN} will not search for a label.
6406 @item *@var{address}
6407 Specifies the program address @var{address}. For line-oriented
6408 commands, such as @code{list} and @code{edit}, this specifies a source
6409 line that contains @var{address}. For @code{break} and other
6410 breakpoint oriented commands, this can be used to set breakpoints in
6411 parts of your program which do not have debugging information or
6414 Here @var{address} may be any expression valid in the current working
6415 language (@pxref{Languages, working language}) that specifies a code
6416 address. In addition, as a convenience, @value{GDBN} extends the
6417 semantics of expressions used in locations to cover the situations
6418 that frequently happen during debugging. Here are the various forms
6422 @item @var{expression}
6423 Any expression valid in the current working language.
6425 @item @var{funcaddr}
6426 An address of a function or procedure derived from its name. In C,
6427 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6428 simply the function's name @var{function} (and actually a special case
6429 of a valid expression). In Pascal and Modula-2, this is
6430 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6431 (although the Pascal form also works).
6433 This form specifies the address of the function's first instruction,
6434 before the stack frame and arguments have been set up.
6436 @item '@var{filename}'::@var{funcaddr}
6437 Like @var{funcaddr} above, but also specifies the name of the source
6438 file explicitly. This is useful if the name of the function does not
6439 specify the function unambiguously, e.g., if there are several
6440 functions with identical names in different source files.
6447 @section Editing Source Files
6448 @cindex editing source files
6451 @kindex e @r{(@code{edit})}
6452 To edit the lines in a source file, use the @code{edit} command.
6453 The editing program of your choice
6454 is invoked with the current line set to
6455 the active line in the program.
6456 Alternatively, there are several ways to specify what part of the file you
6457 want to print if you want to see other parts of the program:
6460 @item edit @var{location}
6461 Edit the source file specified by @code{location}. Editing starts at
6462 that @var{location}, e.g., at the specified source line of the
6463 specified file. @xref{Specify Location}, for all the possible forms
6464 of the @var{location} argument; here are the forms of the @code{edit}
6465 command most commonly used:
6468 @item edit @var{number}
6469 Edit the current source file with @var{number} as the active line number.
6471 @item edit @var{function}
6472 Edit the file containing @var{function} at the beginning of its definition.
6477 @subsection Choosing your Editor
6478 You can customize @value{GDBN} to use any editor you want
6480 The only restriction is that your editor (say @code{ex}), recognizes the
6481 following command-line syntax:
6483 ex +@var{number} file
6485 The optional numeric value +@var{number} specifies the number of the line in
6486 the file where to start editing.}.
6487 By default, it is @file{@value{EDITOR}}, but you can change this
6488 by setting the environment variable @code{EDITOR} before using
6489 @value{GDBN}. For example, to configure @value{GDBN} to use the
6490 @code{vi} editor, you could use these commands with the @code{sh} shell:
6496 or in the @code{csh} shell,
6498 setenv EDITOR /usr/bin/vi
6503 @section Searching Source Files
6504 @cindex searching source files
6506 There are two commands for searching through the current source file for a
6511 @kindex forward-search
6512 @item forward-search @var{regexp}
6513 @itemx search @var{regexp}
6514 The command @samp{forward-search @var{regexp}} checks each line,
6515 starting with the one following the last line listed, for a match for
6516 @var{regexp}. It lists the line that is found. You can use the
6517 synonym @samp{search @var{regexp}} or abbreviate the command name as
6520 @kindex reverse-search
6521 @item reverse-search @var{regexp}
6522 The command @samp{reverse-search @var{regexp}} checks each line, starting
6523 with the one before the last line listed and going backward, for a match
6524 for @var{regexp}. It lists the line that is found. You can abbreviate
6525 this command as @code{rev}.
6529 @section Specifying Source Directories
6532 @cindex directories for source files
6533 Executable programs sometimes do not record the directories of the source
6534 files from which they were compiled, just the names. Even when they do,
6535 the directories could be moved between the compilation and your debugging
6536 session. @value{GDBN} has a list of directories to search for source files;
6537 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6538 it tries all the directories in the list, in the order they are present
6539 in the list, until it finds a file with the desired name.
6541 For example, suppose an executable references the file
6542 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6543 @file{/mnt/cross}. The file is first looked up literally; if this
6544 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6545 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6546 message is printed. @value{GDBN} does not look up the parts of the
6547 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6548 Likewise, the subdirectories of the source path are not searched: if
6549 the source path is @file{/mnt/cross}, and the binary refers to
6550 @file{foo.c}, @value{GDBN} would not find it under
6551 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6553 Plain file names, relative file names with leading directories, file
6554 names containing dots, etc.@: are all treated as described above; for
6555 instance, if the source path is @file{/mnt/cross}, and the source file
6556 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6557 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6558 that---@file{/mnt/cross/foo.c}.
6560 Note that the executable search path is @emph{not} used to locate the
6563 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6564 any information it has cached about where source files are found and where
6565 each line is in the file.
6569 When you start @value{GDBN}, its source path includes only @samp{cdir}
6570 and @samp{cwd}, in that order.
6571 To add other directories, use the @code{directory} command.
6573 The search path is used to find both program source files and @value{GDBN}
6574 script files (read using the @samp{-command} option and @samp{source} command).
6576 In addition to the source path, @value{GDBN} provides a set of commands
6577 that manage a list of source path substitution rules. A @dfn{substitution
6578 rule} specifies how to rewrite source directories stored in the program's
6579 debug information in case the sources were moved to a different
6580 directory between compilation and debugging. A rule is made of
6581 two strings, the first specifying what needs to be rewritten in
6582 the path, and the second specifying how it should be rewritten.
6583 In @ref{set substitute-path}, we name these two parts @var{from} and
6584 @var{to} respectively. @value{GDBN} does a simple string replacement
6585 of @var{from} with @var{to} at the start of the directory part of the
6586 source file name, and uses that result instead of the original file
6587 name to look up the sources.
6589 Using the previous example, suppose the @file{foo-1.0} tree has been
6590 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6591 @value{GDBN} to replace @file{/usr/src} in all source path names with
6592 @file{/mnt/cross}. The first lookup will then be
6593 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6594 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6595 substitution rule, use the @code{set substitute-path} command
6596 (@pxref{set substitute-path}).
6598 To avoid unexpected substitution results, a rule is applied only if the
6599 @var{from} part of the directory name ends at a directory separator.
6600 For instance, a rule substituting @file{/usr/source} into
6601 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6602 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6603 is applied only at the beginning of the directory name, this rule will
6604 not be applied to @file{/root/usr/source/baz.c} either.
6606 In many cases, you can achieve the same result using the @code{directory}
6607 command. However, @code{set substitute-path} can be more efficient in
6608 the case where the sources are organized in a complex tree with multiple
6609 subdirectories. With the @code{directory} command, you need to add each
6610 subdirectory of your project. If you moved the entire tree while
6611 preserving its internal organization, then @code{set substitute-path}
6612 allows you to direct the debugger to all the sources with one single
6615 @code{set substitute-path} is also more than just a shortcut command.
6616 The source path is only used if the file at the original location no
6617 longer exists. On the other hand, @code{set substitute-path} modifies
6618 the debugger behavior to look at the rewritten location instead. So, if
6619 for any reason a source file that is not relevant to your executable is
6620 located at the original location, a substitution rule is the only
6621 method available to point @value{GDBN} at the new location.
6623 @cindex @samp{--with-relocated-sources}
6624 @cindex default source path substitution
6625 You can configure a default source path substitution rule by
6626 configuring @value{GDBN} with the
6627 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6628 should be the name of a directory under @value{GDBN}'s configured
6629 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6630 directory names in debug information under @var{dir} will be adjusted
6631 automatically if the installed @value{GDBN} is moved to a new
6632 location. This is useful if @value{GDBN}, libraries or executables
6633 with debug information and corresponding source code are being moved
6637 @item directory @var{dirname} @dots{}
6638 @item dir @var{dirname} @dots{}
6639 Add directory @var{dirname} to the front of the source path. Several
6640 directory names may be given to this command, separated by @samp{:}
6641 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6642 part of absolute file names) or
6643 whitespace. You may specify a directory that is already in the source
6644 path; this moves it forward, so @value{GDBN} searches it sooner.
6648 @vindex $cdir@r{, convenience variable}
6649 @vindex $cwd@r{, convenience variable}
6650 @cindex compilation directory
6651 @cindex current directory
6652 @cindex working directory
6653 @cindex directory, current
6654 @cindex directory, compilation
6655 You can use the string @samp{$cdir} to refer to the compilation
6656 directory (if one is recorded), and @samp{$cwd} to refer to the current
6657 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6658 tracks the current working directory as it changes during your @value{GDBN}
6659 session, while the latter is immediately expanded to the current
6660 directory at the time you add an entry to the source path.
6663 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6665 @c RET-repeat for @code{directory} is explicitly disabled, but since
6666 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6668 @item set directories @var{path-list}
6669 @kindex set directories
6670 Set the source path to @var{path-list}.
6671 @samp{$cdir:$cwd} are added if missing.
6673 @item show directories
6674 @kindex show directories
6675 Print the source path: show which directories it contains.
6677 @anchor{set substitute-path}
6678 @item set substitute-path @var{from} @var{to}
6679 @kindex set substitute-path
6680 Define a source path substitution rule, and add it at the end of the
6681 current list of existing substitution rules. If a rule with the same
6682 @var{from} was already defined, then the old rule is also deleted.
6684 For example, if the file @file{/foo/bar/baz.c} was moved to
6685 @file{/mnt/cross/baz.c}, then the command
6688 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6692 will tell @value{GDBN} to replace @samp{/usr/src} with
6693 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6694 @file{baz.c} even though it was moved.
6696 In the case when more than one substitution rule have been defined,
6697 the rules are evaluated one by one in the order where they have been
6698 defined. The first one matching, if any, is selected to perform
6701 For instance, if we had entered the following commands:
6704 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6705 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6709 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6710 @file{/mnt/include/defs.h} by using the first rule. However, it would
6711 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6712 @file{/mnt/src/lib/foo.c}.
6715 @item unset substitute-path [path]
6716 @kindex unset substitute-path
6717 If a path is specified, search the current list of substitution rules
6718 for a rule that would rewrite that path. Delete that rule if found.
6719 A warning is emitted by the debugger if no rule could be found.
6721 If no path is specified, then all substitution rules are deleted.
6723 @item show substitute-path [path]
6724 @kindex show substitute-path
6725 If a path is specified, then print the source path substitution rule
6726 which would rewrite that path, if any.
6728 If no path is specified, then print all existing source path substitution
6733 If your source path is cluttered with directories that are no longer of
6734 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6735 versions of source. You can correct the situation as follows:
6739 Use @code{directory} with no argument to reset the source path to its default value.
6742 Use @code{directory} with suitable arguments to reinstall the
6743 directories you want in the source path. You can add all the
6744 directories in one command.
6748 @section Source and Machine Code
6749 @cindex source line and its code address
6751 You can use the command @code{info line} to map source lines to program
6752 addresses (and vice versa), and the command @code{disassemble} to display
6753 a range of addresses as machine instructions. You can use the command
6754 @code{set disassemble-next-line} to set whether to disassemble next
6755 source line when execution stops. When run under @sc{gnu} Emacs
6756 mode, the @code{info line} command causes the arrow to point to the
6757 line specified. Also, @code{info line} prints addresses in symbolic form as
6762 @item info line @var{linespec}
6763 Print the starting and ending addresses of the compiled code for
6764 source line @var{linespec}. You can specify source lines in any of
6765 the ways documented in @ref{Specify Location}.
6768 For example, we can use @code{info line} to discover the location of
6769 the object code for the first line of function
6770 @code{m4_changequote}:
6772 @c FIXME: I think this example should also show the addresses in
6773 @c symbolic form, as they usually would be displayed.
6775 (@value{GDBP}) info line m4_changequote
6776 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6780 @cindex code address and its source line
6781 We can also inquire (using @code{*@var{addr}} as the form for
6782 @var{linespec}) what source line covers a particular address:
6784 (@value{GDBP}) info line *0x63ff
6785 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6788 @cindex @code{$_} and @code{info line}
6789 @cindex @code{x} command, default address
6790 @kindex x@r{(examine), and} info line
6791 After @code{info line}, the default address for the @code{x} command
6792 is changed to the starting address of the line, so that @samp{x/i} is
6793 sufficient to begin examining the machine code (@pxref{Memory,
6794 ,Examining Memory}). Also, this address is saved as the value of the
6795 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6800 @cindex assembly instructions
6801 @cindex instructions, assembly
6802 @cindex machine instructions
6803 @cindex listing machine instructions
6805 @itemx disassemble /m
6806 @itemx disassemble /r
6807 This specialized command dumps a range of memory as machine
6808 instructions. It can also print mixed source+disassembly by specifying
6809 the @code{/m} modifier and print the raw instructions in hex as well as
6810 in symbolic form by specifying the @code{/r}.
6811 The default memory range is the function surrounding the
6812 program counter of the selected frame. A single argument to this
6813 command is a program counter value; @value{GDBN} dumps the function
6814 surrounding this value. When two arguments are given, they should
6815 be separated by a comma, possibly surrounded by whitespace. The
6816 arguments specify a range of addresses to dump, in one of two forms:
6819 @item @var{start},@var{end}
6820 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6821 @item @var{start},+@var{length}
6822 the addresses from @var{start} (inclusive) to
6823 @code{@var{start}+@var{length}} (exclusive).
6827 When 2 arguments are specified, the name of the function is also
6828 printed (since there could be several functions in the given range).
6830 The argument(s) can be any expression yielding a numeric value, such as
6831 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6833 If the range of memory being disassembled contains current program counter,
6834 the instruction at that location is shown with a @code{=>} marker.
6837 The following example shows the disassembly of a range of addresses of
6838 HP PA-RISC 2.0 code:
6841 (@value{GDBP}) disas 0x32c4, 0x32e4
6842 Dump of assembler code from 0x32c4 to 0x32e4:
6843 0x32c4 <main+204>: addil 0,dp
6844 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6845 0x32cc <main+212>: ldil 0x3000,r31
6846 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6847 0x32d4 <main+220>: ldo 0(r31),rp
6848 0x32d8 <main+224>: addil -0x800,dp
6849 0x32dc <main+228>: ldo 0x588(r1),r26
6850 0x32e0 <main+232>: ldil 0x3000,r31
6851 End of assembler dump.
6854 Here is an example showing mixed source+assembly for Intel x86, when the
6855 program is stopped just after function prologue:
6858 (@value{GDBP}) disas /m main
6859 Dump of assembler code for function main:
6861 0x08048330 <+0>: push %ebp
6862 0x08048331 <+1>: mov %esp,%ebp
6863 0x08048333 <+3>: sub $0x8,%esp
6864 0x08048336 <+6>: and $0xfffffff0,%esp
6865 0x08048339 <+9>: sub $0x10,%esp
6867 6 printf ("Hello.\n");
6868 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6869 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6873 0x08048348 <+24>: mov $0x0,%eax
6874 0x0804834d <+29>: leave
6875 0x0804834e <+30>: ret
6877 End of assembler dump.
6880 Here is another example showing raw instructions in hex for AMD x86-64,
6883 (gdb) disas /r 0x400281,+10
6884 Dump of assembler code from 0x400281 to 0x40028b:
6885 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6886 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6887 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6888 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
6889 End of assembler dump.
6892 Some architectures have more than one commonly-used set of instruction
6893 mnemonics or other syntax.
6895 For programs that were dynamically linked and use shared libraries,
6896 instructions that call functions or branch to locations in the shared
6897 libraries might show a seemingly bogus location---it's actually a
6898 location of the relocation table. On some architectures, @value{GDBN}
6899 might be able to resolve these to actual function names.
6902 @kindex set disassembly-flavor
6903 @cindex Intel disassembly flavor
6904 @cindex AT&T disassembly flavor
6905 @item set disassembly-flavor @var{instruction-set}
6906 Select the instruction set to use when disassembling the
6907 program via the @code{disassemble} or @code{x/i} commands.
6909 Currently this command is only defined for the Intel x86 family. You
6910 can set @var{instruction-set} to either @code{intel} or @code{att}.
6911 The default is @code{att}, the AT&T flavor used by default by Unix
6912 assemblers for x86-based targets.
6914 @kindex show disassembly-flavor
6915 @item show disassembly-flavor
6916 Show the current setting of the disassembly flavor.
6920 @kindex set disassemble-next-line
6921 @kindex show disassemble-next-line
6922 @item set disassemble-next-line
6923 @itemx show disassemble-next-line
6924 Control whether or not @value{GDBN} will disassemble the next source
6925 line or instruction when execution stops. If ON, @value{GDBN} will
6926 display disassembly of the next source line when execution of the
6927 program being debugged stops. This is @emph{in addition} to
6928 displaying the source line itself, which @value{GDBN} always does if
6929 possible. If the next source line cannot be displayed for some reason
6930 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6931 info in the debug info), @value{GDBN} will display disassembly of the
6932 next @emph{instruction} instead of showing the next source line. If
6933 AUTO, @value{GDBN} will display disassembly of next instruction only
6934 if the source line cannot be displayed. This setting causes
6935 @value{GDBN} to display some feedback when you step through a function
6936 with no line info or whose source file is unavailable. The default is
6937 OFF, which means never display the disassembly of the next line or
6943 @chapter Examining Data
6945 @cindex printing data
6946 @cindex examining data
6949 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6950 @c document because it is nonstandard... Under Epoch it displays in a
6951 @c different window or something like that.
6952 The usual way to examine data in your program is with the @code{print}
6953 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6954 evaluates and prints the value of an expression of the language your
6955 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6956 Different Languages}). It may also print the expression using a
6957 Python-based pretty-printer (@pxref{Pretty Printing}).
6960 @item print @var{expr}
6961 @itemx print /@var{f} @var{expr}
6962 @var{expr} is an expression (in the source language). By default the
6963 value of @var{expr} is printed in a format appropriate to its data type;
6964 you can choose a different format by specifying @samp{/@var{f}}, where
6965 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6969 @itemx print /@var{f}
6970 @cindex reprint the last value
6971 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6972 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6973 conveniently inspect the same value in an alternative format.
6976 A more low-level way of examining data is with the @code{x} command.
6977 It examines data in memory at a specified address and prints it in a
6978 specified format. @xref{Memory, ,Examining Memory}.
6980 If you are interested in information about types, or about how the
6981 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6982 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6986 * Expressions:: Expressions
6987 * Ambiguous Expressions:: Ambiguous Expressions
6988 * Variables:: Program variables
6989 * Arrays:: Artificial arrays
6990 * Output Formats:: Output formats
6991 * Memory:: Examining memory
6992 * Auto Display:: Automatic display
6993 * Print Settings:: Print settings
6994 * Pretty Printing:: Python pretty printing
6995 * Value History:: Value history
6996 * Convenience Vars:: Convenience variables
6997 * Registers:: Registers
6998 * Floating Point Hardware:: Floating point hardware
6999 * Vector Unit:: Vector Unit
7000 * OS Information:: Auxiliary data provided by operating system
7001 * Memory Region Attributes:: Memory region attributes
7002 * Dump/Restore Files:: Copy between memory and a file
7003 * Core File Generation:: Cause a program dump its core
7004 * Character Sets:: Debugging programs that use a different
7005 character set than GDB does
7006 * Caching Remote Data:: Data caching for remote targets
7007 * Searching Memory:: Searching memory for a sequence of bytes
7011 @section Expressions
7014 @code{print} and many other @value{GDBN} commands accept an expression and
7015 compute its value. Any kind of constant, variable or operator defined
7016 by the programming language you are using is valid in an expression in
7017 @value{GDBN}. This includes conditional expressions, function calls,
7018 casts, and string constants. It also includes preprocessor macros, if
7019 you compiled your program to include this information; see
7022 @cindex arrays in expressions
7023 @value{GDBN} supports array constants in expressions input by
7024 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7025 you can use the command @code{print @{1, 2, 3@}} to create an array
7026 of three integers. If you pass an array to a function or assign it
7027 to a program variable, @value{GDBN} copies the array to memory that
7028 is @code{malloc}ed in the target program.
7030 Because C is so widespread, most of the expressions shown in examples in
7031 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7032 Languages}, for information on how to use expressions in other
7035 In this section, we discuss operators that you can use in @value{GDBN}
7036 expressions regardless of your programming language.
7038 @cindex casts, in expressions
7039 Casts are supported in all languages, not just in C, because it is so
7040 useful to cast a number into a pointer in order to examine a structure
7041 at that address in memory.
7042 @c FIXME: casts supported---Mod2 true?
7044 @value{GDBN} supports these operators, in addition to those common
7045 to programming languages:
7049 @samp{@@} is a binary operator for treating parts of memory as arrays.
7050 @xref{Arrays, ,Artificial Arrays}, for more information.
7053 @samp{::} allows you to specify a variable in terms of the file or
7054 function where it is defined. @xref{Variables, ,Program Variables}.
7056 @cindex @{@var{type}@}
7057 @cindex type casting memory
7058 @cindex memory, viewing as typed object
7059 @cindex casts, to view memory
7060 @item @{@var{type}@} @var{addr}
7061 Refers to an object of type @var{type} stored at address @var{addr} in
7062 memory. @var{addr} may be any expression whose value is an integer or
7063 pointer (but parentheses are required around binary operators, just as in
7064 a cast). This construct is allowed regardless of what kind of data is
7065 normally supposed to reside at @var{addr}.
7068 @node Ambiguous Expressions
7069 @section Ambiguous Expressions
7070 @cindex ambiguous expressions
7072 Expressions can sometimes contain some ambiguous elements. For instance,
7073 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7074 a single function name to be defined several times, for application in
7075 different contexts. This is called @dfn{overloading}. Another example
7076 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7077 templates and is typically instantiated several times, resulting in
7078 the same function name being defined in different contexts.
7080 In some cases and depending on the language, it is possible to adjust
7081 the expression to remove the ambiguity. For instance in C@t{++}, you
7082 can specify the signature of the function you want to break on, as in
7083 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7084 qualified name of your function often makes the expression unambiguous
7087 When an ambiguity that needs to be resolved is detected, the debugger
7088 has the capability to display a menu of numbered choices for each
7089 possibility, and then waits for the selection with the prompt @samp{>}.
7090 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7091 aborts the current command. If the command in which the expression was
7092 used allows more than one choice to be selected, the next option in the
7093 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7096 For example, the following session excerpt shows an attempt to set a
7097 breakpoint at the overloaded symbol @code{String::after}.
7098 We choose three particular definitions of that function name:
7100 @c FIXME! This is likely to change to show arg type lists, at least
7103 (@value{GDBP}) b String::after
7106 [2] file:String.cc; line number:867
7107 [3] file:String.cc; line number:860
7108 [4] file:String.cc; line number:875
7109 [5] file:String.cc; line number:853
7110 [6] file:String.cc; line number:846
7111 [7] file:String.cc; line number:735
7113 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7114 Breakpoint 2 at 0xb344: file String.cc, line 875.
7115 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7116 Multiple breakpoints were set.
7117 Use the "delete" command to delete unwanted
7124 @kindex set multiple-symbols
7125 @item set multiple-symbols @var{mode}
7126 @cindex multiple-symbols menu
7128 This option allows you to adjust the debugger behavior when an expression
7131 By default, @var{mode} is set to @code{all}. If the command with which
7132 the expression is used allows more than one choice, then @value{GDBN}
7133 automatically selects all possible choices. For instance, inserting
7134 a breakpoint on a function using an ambiguous name results in a breakpoint
7135 inserted on each possible match. However, if a unique choice must be made,
7136 then @value{GDBN} uses the menu to help you disambiguate the expression.
7137 For instance, printing the address of an overloaded function will result
7138 in the use of the menu.
7140 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7141 when an ambiguity is detected.
7143 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7144 an error due to the ambiguity and the command is aborted.
7146 @kindex show multiple-symbols
7147 @item show multiple-symbols
7148 Show the current value of the @code{multiple-symbols} setting.
7152 @section Program Variables
7154 The most common kind of expression to use is the name of a variable
7157 Variables in expressions are understood in the selected stack frame
7158 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7162 global (or file-static)
7169 visible according to the scope rules of the
7170 programming language from the point of execution in that frame
7173 @noindent This means that in the function
7188 you can examine and use the variable @code{a} whenever your program is
7189 executing within the function @code{foo}, but you can only use or
7190 examine the variable @code{b} while your program is executing inside
7191 the block where @code{b} is declared.
7193 @cindex variable name conflict
7194 There is an exception: you can refer to a variable or function whose
7195 scope is a single source file even if the current execution point is not
7196 in this file. But it is possible to have more than one such variable or
7197 function with the same name (in different source files). If that
7198 happens, referring to that name has unpredictable effects. If you wish,
7199 you can specify a static variable in a particular function or file,
7200 using the colon-colon (@code{::}) notation:
7202 @cindex colon-colon, context for variables/functions
7204 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7205 @cindex @code{::}, context for variables/functions
7208 @var{file}::@var{variable}
7209 @var{function}::@var{variable}
7213 Here @var{file} or @var{function} is the name of the context for the
7214 static @var{variable}. In the case of file names, you can use quotes to
7215 make sure @value{GDBN} parses the file name as a single word---for example,
7216 to print a global value of @code{x} defined in @file{f2.c}:
7219 (@value{GDBP}) p 'f2.c'::x
7222 @cindex C@t{++} scope resolution
7223 This use of @samp{::} is very rarely in conflict with the very similar
7224 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7225 scope resolution operator in @value{GDBN} expressions.
7226 @c FIXME: Um, so what happens in one of those rare cases where it's in
7229 @cindex wrong values
7230 @cindex variable values, wrong
7231 @cindex function entry/exit, wrong values of variables
7232 @cindex optimized code, wrong values of variables
7234 @emph{Warning:} Occasionally, a local variable may appear to have the
7235 wrong value at certain points in a function---just after entry to a new
7236 scope, and just before exit.
7238 You may see this problem when you are stepping by machine instructions.
7239 This is because, on most machines, it takes more than one instruction to
7240 set up a stack frame (including local variable definitions); if you are
7241 stepping by machine instructions, variables may appear to have the wrong
7242 values until the stack frame is completely built. On exit, it usually
7243 also takes more than one machine instruction to destroy a stack frame;
7244 after you begin stepping through that group of instructions, local
7245 variable definitions may be gone.
7247 This may also happen when the compiler does significant optimizations.
7248 To be sure of always seeing accurate values, turn off all optimization
7251 @cindex ``No symbol "foo" in current context''
7252 Another possible effect of compiler optimizations is to optimize
7253 unused variables out of existence, or assign variables to registers (as
7254 opposed to memory addresses). Depending on the support for such cases
7255 offered by the debug info format used by the compiler, @value{GDBN}
7256 might not be able to display values for such local variables. If that
7257 happens, @value{GDBN} will print a message like this:
7260 No symbol "foo" in current context.
7263 To solve such problems, either recompile without optimizations, or use a
7264 different debug info format, if the compiler supports several such
7265 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7266 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7267 produces debug info in a format that is superior to formats such as
7268 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7269 an effective form for debug info. @xref{Debugging Options,,Options
7270 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7271 Compiler Collection (GCC)}.
7272 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7273 that are best suited to C@t{++} programs.
7275 If you ask to print an object whose contents are unknown to
7276 @value{GDBN}, e.g., because its data type is not completely specified
7277 by the debug information, @value{GDBN} will say @samp{<incomplete
7278 type>}. @xref{Symbols, incomplete type}, for more about this.
7280 Strings are identified as arrays of @code{char} values without specified
7281 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7282 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7283 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7284 defines literal string type @code{"char"} as @code{char} without a sign.
7289 signed char var1[] = "A";
7292 You get during debugging
7297 $2 = @{65 'A', 0 '\0'@}
7301 @section Artificial Arrays
7303 @cindex artificial array
7305 @kindex @@@r{, referencing memory as an array}
7306 It is often useful to print out several successive objects of the
7307 same type in memory; a section of an array, or an array of
7308 dynamically determined size for which only a pointer exists in the
7311 You can do this by referring to a contiguous span of memory as an
7312 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7313 operand of @samp{@@} should be the first element of the desired array
7314 and be an individual object. The right operand should be the desired length
7315 of the array. The result is an array value whose elements are all of
7316 the type of the left argument. The first element is actually the left
7317 argument; the second element comes from bytes of memory immediately
7318 following those that hold the first element, and so on. Here is an
7319 example. If a program says
7322 int *array = (int *) malloc (len * sizeof (int));
7326 you can print the contents of @code{array} with
7332 The left operand of @samp{@@} must reside in memory. Array values made
7333 with @samp{@@} in this way behave just like other arrays in terms of
7334 subscripting, and are coerced to pointers when used in expressions.
7335 Artificial arrays most often appear in expressions via the value history
7336 (@pxref{Value History, ,Value History}), after printing one out.
7338 Another way to create an artificial array is to use a cast.
7339 This re-interprets a value as if it were an array.
7340 The value need not be in memory:
7342 (@value{GDBP}) p/x (short[2])0x12345678
7343 $1 = @{0x1234, 0x5678@}
7346 As a convenience, if you leave the array length out (as in
7347 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7348 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7350 (@value{GDBP}) p/x (short[])0x12345678
7351 $2 = @{0x1234, 0x5678@}
7354 Sometimes the artificial array mechanism is not quite enough; in
7355 moderately complex data structures, the elements of interest may not
7356 actually be adjacent---for example, if you are interested in the values
7357 of pointers in an array. One useful work-around in this situation is
7358 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7359 Variables}) as a counter in an expression that prints the first
7360 interesting value, and then repeat that expression via @key{RET}. For
7361 instance, suppose you have an array @code{dtab} of pointers to
7362 structures, and you are interested in the values of a field @code{fv}
7363 in each structure. Here is an example of what you might type:
7373 @node Output Formats
7374 @section Output Formats
7376 @cindex formatted output
7377 @cindex output formats
7378 By default, @value{GDBN} prints a value according to its data type. Sometimes
7379 this is not what you want. For example, you might want to print a number
7380 in hex, or a pointer in decimal. Or you might want to view data in memory
7381 at a certain address as a character string or as an instruction. To do
7382 these things, specify an @dfn{output format} when you print a value.
7384 The simplest use of output formats is to say how to print a value
7385 already computed. This is done by starting the arguments of the
7386 @code{print} command with a slash and a format letter. The format
7387 letters supported are:
7391 Regard the bits of the value as an integer, and print the integer in
7395 Print as integer in signed decimal.
7398 Print as integer in unsigned decimal.
7401 Print as integer in octal.
7404 Print as integer in binary. The letter @samp{t} stands for ``two''.
7405 @footnote{@samp{b} cannot be used because these format letters are also
7406 used with the @code{x} command, where @samp{b} stands for ``byte'';
7407 see @ref{Memory,,Examining Memory}.}
7410 @cindex unknown address, locating
7411 @cindex locate address
7412 Print as an address, both absolute in hexadecimal and as an offset from
7413 the nearest preceding symbol. You can use this format used to discover
7414 where (in what function) an unknown address is located:
7417 (@value{GDBP}) p/a 0x54320
7418 $3 = 0x54320 <_initialize_vx+396>
7422 The command @code{info symbol 0x54320} yields similar results.
7423 @xref{Symbols, info symbol}.
7426 Regard as an integer and print it as a character constant. This
7427 prints both the numerical value and its character representation. The
7428 character representation is replaced with the octal escape @samp{\nnn}
7429 for characters outside the 7-bit @sc{ascii} range.
7431 Without this format, @value{GDBN} displays @code{char},
7432 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7433 constants. Single-byte members of vectors are displayed as integer
7437 Regard the bits of the value as a floating point number and print
7438 using typical floating point syntax.
7441 @cindex printing strings
7442 @cindex printing byte arrays
7443 Regard as a string, if possible. With this format, pointers to single-byte
7444 data are displayed as null-terminated strings and arrays of single-byte data
7445 are displayed as fixed-length strings. Other values are displayed in their
7448 Without this format, @value{GDBN} displays pointers to and arrays of
7449 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7450 strings. Single-byte members of a vector are displayed as an integer
7454 @cindex raw printing
7455 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7456 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7457 Printing}). This typically results in a higher-level display of the
7458 value's contents. The @samp{r} format bypasses any Python
7459 pretty-printer which might exist.
7462 For example, to print the program counter in hex (@pxref{Registers}), type
7469 Note that no space is required before the slash; this is because command
7470 names in @value{GDBN} cannot contain a slash.
7472 To reprint the last value in the value history with a different format,
7473 you can use the @code{print} command with just a format and no
7474 expression. For example, @samp{p/x} reprints the last value in hex.
7477 @section Examining Memory
7479 You can use the command @code{x} (for ``examine'') to examine memory in
7480 any of several formats, independently of your program's data types.
7482 @cindex examining memory
7484 @kindex x @r{(examine memory)}
7485 @item x/@var{nfu} @var{addr}
7488 Use the @code{x} command to examine memory.
7491 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7492 much memory to display and how to format it; @var{addr} is an
7493 expression giving the address where you want to start displaying memory.
7494 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7495 Several commands set convenient defaults for @var{addr}.
7498 @item @var{n}, the repeat count
7499 The repeat count is a decimal integer; the default is 1. It specifies
7500 how much memory (counting by units @var{u}) to display.
7501 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7504 @item @var{f}, the display format
7505 The display format is one of the formats used by @code{print}
7506 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7507 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7508 The default is @samp{x} (hexadecimal) initially. The default changes
7509 each time you use either @code{x} or @code{print}.
7511 @item @var{u}, the unit size
7512 The unit size is any of
7518 Halfwords (two bytes).
7520 Words (four bytes). This is the initial default.
7522 Giant words (eight bytes).
7525 Each time you specify a unit size with @code{x}, that size becomes the
7526 default unit the next time you use @code{x}. For the @samp{i} format,
7527 the unit size is ignored and is normally not written. For the @samp{s} format,
7528 the unit size defaults to @samp{b}, unless it is explicitly given.
7529 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7530 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7531 Note that the results depend on the programming language of the
7532 current compilation unit. If the language is C, the @samp{s}
7533 modifier will use the UTF-16 encoding while @samp{w} will use
7534 UTF-32. The encoding is set by the programming language and cannot
7537 @item @var{addr}, starting display address
7538 @var{addr} is the address where you want @value{GDBN} to begin displaying
7539 memory. The expression need not have a pointer value (though it may);
7540 it is always interpreted as an integer address of a byte of memory.
7541 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7542 @var{addr} is usually just after the last address examined---but several
7543 other commands also set the default address: @code{info breakpoints} (to
7544 the address of the last breakpoint listed), @code{info line} (to the
7545 starting address of a line), and @code{print} (if you use it to display
7546 a value from memory).
7549 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7550 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7551 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7552 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7553 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7555 Since the letters indicating unit sizes are all distinct from the
7556 letters specifying output formats, you do not have to remember whether
7557 unit size or format comes first; either order works. The output
7558 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7559 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7561 Even though the unit size @var{u} is ignored for the formats @samp{s}
7562 and @samp{i}, you might still want to use a count @var{n}; for example,
7563 @samp{3i} specifies that you want to see three machine instructions,
7564 including any operands. For convenience, especially when used with
7565 the @code{display} command, the @samp{i} format also prints branch delay
7566 slot instructions, if any, beyond the count specified, which immediately
7567 follow the last instruction that is within the count. The command
7568 @code{disassemble} gives an alternative way of inspecting machine
7569 instructions; see @ref{Machine Code,,Source and Machine Code}.
7571 All the defaults for the arguments to @code{x} are designed to make it
7572 easy to continue scanning memory with minimal specifications each time
7573 you use @code{x}. For example, after you have inspected three machine
7574 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7575 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7576 the repeat count @var{n} is used again; the other arguments default as
7577 for successive uses of @code{x}.
7579 When examining machine instructions, the instruction at current program
7580 counter is shown with a @code{=>} marker. For example:
7583 (@value{GDBP}) x/5i $pc-6
7584 0x804837f <main+11>: mov %esp,%ebp
7585 0x8048381 <main+13>: push %ecx
7586 0x8048382 <main+14>: sub $0x4,%esp
7587 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7588 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7591 @cindex @code{$_}, @code{$__}, and value history
7592 The addresses and contents printed by the @code{x} command are not saved
7593 in the value history because there is often too much of them and they
7594 would get in the way. Instead, @value{GDBN} makes these values available for
7595 subsequent use in expressions as values of the convenience variables
7596 @code{$_} and @code{$__}. After an @code{x} command, the last address
7597 examined is available for use in expressions in the convenience variable
7598 @code{$_}. The contents of that address, as examined, are available in
7599 the convenience variable @code{$__}.
7601 If the @code{x} command has a repeat count, the address and contents saved
7602 are from the last memory unit printed; this is not the same as the last
7603 address printed if several units were printed on the last line of output.
7605 @cindex remote memory comparison
7606 @cindex verify remote memory image
7607 When you are debugging a program running on a remote target machine
7608 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7609 remote machine's memory against the executable file you downloaded to
7610 the target. The @code{compare-sections} command is provided for such
7614 @kindex compare-sections
7615 @item compare-sections @r{[}@var{section-name}@r{]}
7616 Compare the data of a loadable section @var{section-name} in the
7617 executable file of the program being debugged with the same section in
7618 the remote machine's memory, and report any mismatches. With no
7619 arguments, compares all loadable sections. This command's
7620 availability depends on the target's support for the @code{"qCRC"}
7625 @section Automatic Display
7626 @cindex automatic display
7627 @cindex display of expressions
7629 If you find that you want to print the value of an expression frequently
7630 (to see how it changes), you might want to add it to the @dfn{automatic
7631 display list} so that @value{GDBN} prints its value each time your program stops.
7632 Each expression added to the list is given a number to identify it;
7633 to remove an expression from the list, you specify that number.
7634 The automatic display looks like this:
7638 3: bar[5] = (struct hack *) 0x3804
7642 This display shows item numbers, expressions and their current values. As with
7643 displays you request manually using @code{x} or @code{print}, you can
7644 specify the output format you prefer; in fact, @code{display} decides
7645 whether to use @code{print} or @code{x} depending your format
7646 specification---it uses @code{x} if you specify either the @samp{i}
7647 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7651 @item display @var{expr}
7652 Add the expression @var{expr} to the list of expressions to display
7653 each time your program stops. @xref{Expressions, ,Expressions}.
7655 @code{display} does not repeat if you press @key{RET} again after using it.
7657 @item display/@var{fmt} @var{expr}
7658 For @var{fmt} specifying only a display format and not a size or
7659 count, add the expression @var{expr} to the auto-display list but
7660 arrange to display it each time in the specified format @var{fmt}.
7661 @xref{Output Formats,,Output Formats}.
7663 @item display/@var{fmt} @var{addr}
7664 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7665 number of units, add the expression @var{addr} as a memory address to
7666 be examined each time your program stops. Examining means in effect
7667 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7670 For example, @samp{display/i $pc} can be helpful, to see the machine
7671 instruction about to be executed each time execution stops (@samp{$pc}
7672 is a common name for the program counter; @pxref{Registers, ,Registers}).
7675 @kindex delete display
7677 @item undisplay @var{dnums}@dots{}
7678 @itemx delete display @var{dnums}@dots{}
7679 Remove items from the list of expressions to display. Specify the
7680 numbers of the displays that you want affected with the command
7681 argument @var{dnums}. It can be a single display number, one of the
7682 numbers shown in the first field of the @samp{info display} display;
7683 or it could be a range of display numbers, as in @code{2-4}.
7685 @code{undisplay} does not repeat if you press @key{RET} after using it.
7686 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7688 @kindex disable display
7689 @item disable display @var{dnums}@dots{}
7690 Disable the display of item numbers @var{dnums}. A disabled display
7691 item is not printed automatically, but is not forgotten. It may be
7692 enabled again later. Specify the numbers of the displays that you
7693 want affected with the command argument @var{dnums}. It can be a
7694 single display number, one of the numbers shown in the first field of
7695 the @samp{info display} display; or it could be a range of display
7696 numbers, as in @code{2-4}.
7698 @kindex enable display
7699 @item enable display @var{dnums}@dots{}
7700 Enable display of item numbers @var{dnums}. It becomes effective once
7701 again in auto display of its expression, until you specify otherwise.
7702 Specify the numbers of the displays that you want affected with the
7703 command argument @var{dnums}. It can be a single display number, one
7704 of the numbers shown in the first field of the @samp{info display}
7705 display; or it could be a range of display numbers, as in @code{2-4}.
7708 Display the current values of the expressions on the list, just as is
7709 done when your program stops.
7711 @kindex info display
7713 Print the list of expressions previously set up to display
7714 automatically, each one with its item number, but without showing the
7715 values. This includes disabled expressions, which are marked as such.
7716 It also includes expressions which would not be displayed right now
7717 because they refer to automatic variables not currently available.
7720 @cindex display disabled out of scope
7721 If a display expression refers to local variables, then it does not make
7722 sense outside the lexical context for which it was set up. Such an
7723 expression is disabled when execution enters a context where one of its
7724 variables is not defined. For example, if you give the command
7725 @code{display last_char} while inside a function with an argument
7726 @code{last_char}, @value{GDBN} displays this argument while your program
7727 continues to stop inside that function. When it stops elsewhere---where
7728 there is no variable @code{last_char}---the display is disabled
7729 automatically. The next time your program stops where @code{last_char}
7730 is meaningful, you can enable the display expression once again.
7732 @node Print Settings
7733 @section Print Settings
7735 @cindex format options
7736 @cindex print settings
7737 @value{GDBN} provides the following ways to control how arrays, structures,
7738 and symbols are printed.
7741 These settings are useful for debugging programs in any language:
7745 @item set print address
7746 @itemx set print address on
7747 @cindex print/don't print memory addresses
7748 @value{GDBN} prints memory addresses showing the location of stack
7749 traces, structure values, pointer values, breakpoints, and so forth,
7750 even when it also displays the contents of those addresses. The default
7751 is @code{on}. For example, this is what a stack frame display looks like with
7752 @code{set print address on}:
7757 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7759 530 if (lquote != def_lquote)
7763 @item set print address off
7764 Do not print addresses when displaying their contents. For example,
7765 this is the same stack frame displayed with @code{set print address off}:
7769 (@value{GDBP}) set print addr off
7771 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7772 530 if (lquote != def_lquote)
7776 You can use @samp{set print address off} to eliminate all machine
7777 dependent displays from the @value{GDBN} interface. For example, with
7778 @code{print address off}, you should get the same text for backtraces on
7779 all machines---whether or not they involve pointer arguments.
7782 @item show print address
7783 Show whether or not addresses are to be printed.
7786 When @value{GDBN} prints a symbolic address, it normally prints the
7787 closest earlier symbol plus an offset. If that symbol does not uniquely
7788 identify the address (for example, it is a name whose scope is a single
7789 source file), you may need to clarify. One way to do this is with
7790 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7791 you can set @value{GDBN} to print the source file and line number when
7792 it prints a symbolic address:
7795 @item set print symbol-filename on
7796 @cindex source file and line of a symbol
7797 @cindex symbol, source file and line
7798 Tell @value{GDBN} to print the source file name and line number of a
7799 symbol in the symbolic form of an address.
7801 @item set print symbol-filename off
7802 Do not print source file name and line number of a symbol. This is the
7805 @item show print symbol-filename
7806 Show whether or not @value{GDBN} will print the source file name and
7807 line number of a symbol in the symbolic form of an address.
7810 Another situation where it is helpful to show symbol filenames and line
7811 numbers is when disassembling code; @value{GDBN} shows you the line
7812 number and source file that corresponds to each instruction.
7814 Also, you may wish to see the symbolic form only if the address being
7815 printed is reasonably close to the closest earlier symbol:
7818 @item set print max-symbolic-offset @var{max-offset}
7819 @cindex maximum value for offset of closest symbol
7820 Tell @value{GDBN} to only display the symbolic form of an address if the
7821 offset between the closest earlier symbol and the address is less than
7822 @var{max-offset}. The default is 0, which tells @value{GDBN}
7823 to always print the symbolic form of an address if any symbol precedes it.
7825 @item show print max-symbolic-offset
7826 Ask how large the maximum offset is that @value{GDBN} prints in a
7830 @cindex wild pointer, interpreting
7831 @cindex pointer, finding referent
7832 If you have a pointer and you are not sure where it points, try
7833 @samp{set print symbol-filename on}. Then you can determine the name
7834 and source file location of the variable where it points, using
7835 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7836 For example, here @value{GDBN} shows that a variable @code{ptt} points
7837 at another variable @code{t}, defined in @file{hi2.c}:
7840 (@value{GDBP}) set print symbol-filename on
7841 (@value{GDBP}) p/a ptt
7842 $4 = 0xe008 <t in hi2.c>
7846 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7847 does not show the symbol name and filename of the referent, even with
7848 the appropriate @code{set print} options turned on.
7851 Other settings control how different kinds of objects are printed:
7854 @item set print array
7855 @itemx set print array on
7856 @cindex pretty print arrays
7857 Pretty print arrays. This format is more convenient to read,
7858 but uses more space. The default is off.
7860 @item set print array off
7861 Return to compressed format for arrays.
7863 @item show print array
7864 Show whether compressed or pretty format is selected for displaying
7867 @cindex print array indexes
7868 @item set print array-indexes
7869 @itemx set print array-indexes on
7870 Print the index of each element when displaying arrays. May be more
7871 convenient to locate a given element in the array or quickly find the
7872 index of a given element in that printed array. The default is off.
7874 @item set print array-indexes off
7875 Stop printing element indexes when displaying arrays.
7877 @item show print array-indexes
7878 Show whether the index of each element is printed when displaying
7881 @item set print elements @var{number-of-elements}
7882 @cindex number of array elements to print
7883 @cindex limit on number of printed array elements
7884 Set a limit on how many elements of an array @value{GDBN} will print.
7885 If @value{GDBN} is printing a large array, it stops printing after it has
7886 printed the number of elements set by the @code{set print elements} command.
7887 This limit also applies to the display of strings.
7888 When @value{GDBN} starts, this limit is set to 200.
7889 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7891 @item show print elements
7892 Display the number of elements of a large array that @value{GDBN} will print.
7893 If the number is 0, then the printing is unlimited.
7895 @item set print frame-arguments @var{value}
7896 @kindex set print frame-arguments
7897 @cindex printing frame argument values
7898 @cindex print all frame argument values
7899 @cindex print frame argument values for scalars only
7900 @cindex do not print frame argument values
7901 This command allows to control how the values of arguments are printed
7902 when the debugger prints a frame (@pxref{Frames}). The possible
7907 The values of all arguments are printed.
7910 Print the value of an argument only if it is a scalar. The value of more
7911 complex arguments such as arrays, structures, unions, etc, is replaced
7912 by @code{@dots{}}. This is the default. Here is an example where
7913 only scalar arguments are shown:
7916 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7921 None of the argument values are printed. Instead, the value of each argument
7922 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7925 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7930 By default, only scalar arguments are printed. This command can be used
7931 to configure the debugger to print the value of all arguments, regardless
7932 of their type. However, it is often advantageous to not print the value
7933 of more complex parameters. For instance, it reduces the amount of
7934 information printed in each frame, making the backtrace more readable.
7935 Also, it improves performance when displaying Ada frames, because
7936 the computation of large arguments can sometimes be CPU-intensive,
7937 especially in large applications. Setting @code{print frame-arguments}
7938 to @code{scalars} (the default) or @code{none} avoids this computation,
7939 thus speeding up the display of each Ada frame.
7941 @item show print frame-arguments
7942 Show how the value of arguments should be displayed when printing a frame.
7944 @item set print repeats
7945 @cindex repeated array elements
7946 Set the threshold for suppressing display of repeated array
7947 elements. When the number of consecutive identical elements of an
7948 array exceeds the threshold, @value{GDBN} prints the string
7949 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7950 identical repetitions, instead of displaying the identical elements
7951 themselves. Setting the threshold to zero will cause all elements to
7952 be individually printed. The default threshold is 10.
7954 @item show print repeats
7955 Display the current threshold for printing repeated identical
7958 @item set print null-stop
7959 @cindex @sc{null} elements in arrays
7960 Cause @value{GDBN} to stop printing the characters of an array when the first
7961 @sc{null} is encountered. This is useful when large arrays actually
7962 contain only short strings.
7965 @item show print null-stop
7966 Show whether @value{GDBN} stops printing an array on the first
7967 @sc{null} character.
7969 @item set print pretty on
7970 @cindex print structures in indented form
7971 @cindex indentation in structure display
7972 Cause @value{GDBN} to print structures in an indented format with one member
7973 per line, like this:
7988 @item set print pretty off
7989 Cause @value{GDBN} to print structures in a compact format, like this:
7993 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7994 meat = 0x54 "Pork"@}
7999 This is the default format.
8001 @item show print pretty
8002 Show which format @value{GDBN} is using to print structures.
8004 @item set print sevenbit-strings on
8005 @cindex eight-bit characters in strings
8006 @cindex octal escapes in strings
8007 Print using only seven-bit characters; if this option is set,
8008 @value{GDBN} displays any eight-bit characters (in strings or
8009 character values) using the notation @code{\}@var{nnn}. This setting is
8010 best if you are working in English (@sc{ascii}) and you use the
8011 high-order bit of characters as a marker or ``meta'' bit.
8013 @item set print sevenbit-strings off
8014 Print full eight-bit characters. This allows the use of more
8015 international character sets, and is the default.
8017 @item show print sevenbit-strings
8018 Show whether or not @value{GDBN} is printing only seven-bit characters.
8020 @item set print union on
8021 @cindex unions in structures, printing
8022 Tell @value{GDBN} to print unions which are contained in structures
8023 and other unions. This is the default setting.
8025 @item set print union off
8026 Tell @value{GDBN} not to print unions which are contained in
8027 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8030 @item show print union
8031 Ask @value{GDBN} whether or not it will print unions which are contained in
8032 structures and other unions.
8034 For example, given the declarations
8037 typedef enum @{Tree, Bug@} Species;
8038 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8039 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8050 struct thing foo = @{Tree, @{Acorn@}@};
8054 with @code{set print union on} in effect @samp{p foo} would print
8057 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8061 and with @code{set print union off} in effect it would print
8064 $1 = @{it = Tree, form = @{...@}@}
8068 @code{set print union} affects programs written in C-like languages
8074 These settings are of interest when debugging C@t{++} programs:
8077 @cindex demangling C@t{++} names
8078 @item set print demangle
8079 @itemx set print demangle on
8080 Print C@t{++} names in their source form rather than in the encoded
8081 (``mangled'') form passed to the assembler and linker for type-safe
8082 linkage. The default is on.
8084 @item show print demangle
8085 Show whether C@t{++} names are printed in mangled or demangled form.
8087 @item set print asm-demangle
8088 @itemx set print asm-demangle on
8089 Print C@t{++} names in their source form rather than their mangled form, even
8090 in assembler code printouts such as instruction disassemblies.
8093 @item show print asm-demangle
8094 Show whether C@t{++} names in assembly listings are printed in mangled
8097 @cindex C@t{++} symbol decoding style
8098 @cindex symbol decoding style, C@t{++}
8099 @kindex set demangle-style
8100 @item set demangle-style @var{style}
8101 Choose among several encoding schemes used by different compilers to
8102 represent C@t{++} names. The choices for @var{style} are currently:
8106 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8109 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8110 This is the default.
8113 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8116 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8119 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8120 @strong{Warning:} this setting alone is not sufficient to allow
8121 debugging @code{cfront}-generated executables. @value{GDBN} would
8122 require further enhancement to permit that.
8125 If you omit @var{style}, you will see a list of possible formats.
8127 @item show demangle-style
8128 Display the encoding style currently in use for decoding C@t{++} symbols.
8130 @item set print object
8131 @itemx set print object on
8132 @cindex derived type of an object, printing
8133 @cindex display derived types
8134 When displaying a pointer to an object, identify the @emph{actual}
8135 (derived) type of the object rather than the @emph{declared} type, using
8136 the virtual function table.
8138 @item set print object off
8139 Display only the declared type of objects, without reference to the
8140 virtual function table. This is the default setting.
8142 @item show print object
8143 Show whether actual, or declared, object types are displayed.
8145 @item set print static-members
8146 @itemx set print static-members on
8147 @cindex static members of C@t{++} objects
8148 Print static members when displaying a C@t{++} object. The default is on.
8150 @item set print static-members off
8151 Do not print static members when displaying a C@t{++} object.
8153 @item show print static-members
8154 Show whether C@t{++} static members are printed or not.
8156 @item set print pascal_static-members
8157 @itemx set print pascal_static-members on
8158 @cindex static members of Pascal objects
8159 @cindex Pascal objects, static members display
8160 Print static members when displaying a Pascal object. The default is on.
8162 @item set print pascal_static-members off
8163 Do not print static members when displaying a Pascal object.
8165 @item show print pascal_static-members
8166 Show whether Pascal static members are printed or not.
8168 @c These don't work with HP ANSI C++ yet.
8169 @item set print vtbl
8170 @itemx set print vtbl on
8171 @cindex pretty print C@t{++} virtual function tables
8172 @cindex virtual functions (C@t{++}) display
8173 @cindex VTBL display
8174 Pretty print C@t{++} virtual function tables. The default is off.
8175 (The @code{vtbl} commands do not work on programs compiled with the HP
8176 ANSI C@t{++} compiler (@code{aCC}).)
8178 @item set print vtbl off
8179 Do not pretty print C@t{++} virtual function tables.
8181 @item show print vtbl
8182 Show whether C@t{++} virtual function tables are pretty printed, or not.
8185 @node Pretty Printing
8186 @section Pretty Printing
8188 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8189 Python code. It greatly simplifies the display of complex objects. This
8190 mechanism works for both MI and the CLI.
8193 * Pretty-Printer Introduction:: Introduction to pretty-printers
8194 * Pretty-Printer Example:: An example pretty-printer
8195 * Pretty-Printer Commands:: Pretty-printer commands
8198 @node Pretty-Printer Introduction
8199 @subsection Pretty-Printer Introduction
8201 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8202 registered for the value. If there is then @value{GDBN} invokes the
8203 pretty-printer to print the value. Otherwise the value is printed normally.
8205 Pretty-printers are normally named. This makes them easy to manage.
8206 The @samp{info pretty-printer} command will list all the installed
8207 pretty-printers with their names.
8208 If a pretty-printer can handle multiple data types, then its
8209 @dfn{subprinters} are the printers for the individual data types.
8210 Each such subprinter has its own name.
8211 The format of the name is @var{printer-name};@var{subprinter-name}.
8213 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8214 Typically they are automatically loaded and registered when the corresponding
8215 debug information is loaded, thus making them available without having to
8216 do anything special.
8218 There are three places where a pretty-printer can be registered.
8222 Pretty-printers registered globally are available when debugging
8226 Pretty-printers registered with a program space are available only
8227 when debugging that program.
8228 @xref{Progspaces In Python}, for more details on program spaces in Python.
8231 Pretty-printers registered with an objfile are loaded and unloaded
8232 with the corresponding objfile (e.g., shared library).
8233 @xref{Objfiles In Python}, for more details on objfiles in Python.
8236 @xref{Selecting Pretty-Printers}, for further information on how
8237 pretty-printers are selected,
8239 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8242 @node Pretty-Printer Example
8243 @subsection Pretty-Printer Example
8245 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8248 (@value{GDBP}) print s
8250 static npos = 4294967295,
8252 <std::allocator<char>> = @{
8253 <__gnu_cxx::new_allocator<char>> = @{
8254 <No data fields>@}, <No data fields>
8256 members of std::basic_string<char, std::char_traits<char>,
8257 std::allocator<char> >::_Alloc_hider:
8258 _M_p = 0x804a014 "abcd"
8263 With a pretty-printer for @code{std::string} only the contents are printed:
8266 (@value{GDBP}) print s
8270 @node Pretty-Printer Commands
8271 @subsection Pretty-Printer Commands
8272 @cindex pretty-printer commands
8275 @kindex info pretty-printer
8276 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8277 Print the list of installed pretty-printers.
8278 This includes disabled pretty-printers, which are marked as such.
8280 @var{object-regexp} is a regular expression matching the objects
8281 whose pretty-printers to list.
8282 Objects can be @code{global}, the program space's file
8283 (@pxref{Progspaces In Python}),
8284 and the object files within that program space (@pxref{Objfiles In Python}).
8285 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8286 looks up a printer from these three objects.
8288 @var{name-regexp} is a regular expression matching the name of the printers
8291 @kindex disable pretty-printer
8292 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8293 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8294 A disabled pretty-printer is not forgotten, it may be enabled again later.
8296 @kindex enable pretty-printer
8297 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8298 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8303 Suppose we have three pretty-printers installed: one from library1.so
8304 named @code{foo} that prints objects of type @code{foo}, and
8305 another from library2.so named @code{bar} that prints two types of objects,
8306 @code{bar1} and @code{bar2}.
8309 (gdb) info pretty-printer
8316 (gdb) info pretty-printer library2
8321 (gdb) disable pretty-printer library1
8323 2 of 3 printers enabled
8324 (gdb) info pretty-printer
8331 (gdb) disable pretty-printer library2 bar:bar1
8333 1 of 3 printers enabled
8334 (gdb) info pretty-printer library2
8341 (gdb) disable pretty-printer library2 bar
8343 0 of 3 printers enabled
8344 (gdb) info pretty-printer library2
8353 Note that for @code{bar} the entire printer can be disabled,
8354 as can each individual subprinter.
8357 @section Value History
8359 @cindex value history
8360 @cindex history of values printed by @value{GDBN}
8361 Values printed by the @code{print} command are saved in the @value{GDBN}
8362 @dfn{value history}. This allows you to refer to them in other expressions.
8363 Values are kept until the symbol table is re-read or discarded
8364 (for example with the @code{file} or @code{symbol-file} commands).
8365 When the symbol table changes, the value history is discarded,
8366 since the values may contain pointers back to the types defined in the
8371 @cindex history number
8372 The values printed are given @dfn{history numbers} by which you can
8373 refer to them. These are successive integers starting with one.
8374 @code{print} shows you the history number assigned to a value by
8375 printing @samp{$@var{num} = } before the value; here @var{num} is the
8378 To refer to any previous value, use @samp{$} followed by the value's
8379 history number. The way @code{print} labels its output is designed to
8380 remind you of this. Just @code{$} refers to the most recent value in
8381 the history, and @code{$$} refers to the value before that.
8382 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8383 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8384 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8386 For example, suppose you have just printed a pointer to a structure and
8387 want to see the contents of the structure. It suffices to type
8393 If you have a chain of structures where the component @code{next} points
8394 to the next one, you can print the contents of the next one with this:
8401 You can print successive links in the chain by repeating this
8402 command---which you can do by just typing @key{RET}.
8404 Note that the history records values, not expressions. If the value of
8405 @code{x} is 4 and you type these commands:
8413 then the value recorded in the value history by the @code{print} command
8414 remains 4 even though the value of @code{x} has changed.
8419 Print the last ten values in the value history, with their item numbers.
8420 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8421 values} does not change the history.
8423 @item show values @var{n}
8424 Print ten history values centered on history item number @var{n}.
8427 Print ten history values just after the values last printed. If no more
8428 values are available, @code{show values +} produces no display.
8431 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8432 same effect as @samp{show values +}.
8434 @node Convenience Vars
8435 @section Convenience Variables
8437 @cindex convenience variables
8438 @cindex user-defined variables
8439 @value{GDBN} provides @dfn{convenience variables} that you can use within
8440 @value{GDBN} to hold on to a value and refer to it later. These variables
8441 exist entirely within @value{GDBN}; they are not part of your program, and
8442 setting a convenience variable has no direct effect on further execution
8443 of your program. That is why you can use them freely.
8445 Convenience variables are prefixed with @samp{$}. Any name preceded by
8446 @samp{$} can be used for a convenience variable, unless it is one of
8447 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8448 (Value history references, in contrast, are @emph{numbers} preceded
8449 by @samp{$}. @xref{Value History, ,Value History}.)
8451 You can save a value in a convenience variable with an assignment
8452 expression, just as you would set a variable in your program.
8456 set $foo = *object_ptr
8460 would save in @code{$foo} the value contained in the object pointed to by
8463 Using a convenience variable for the first time creates it, but its
8464 value is @code{void} until you assign a new value. You can alter the
8465 value with another assignment at any time.
8467 Convenience variables have no fixed types. You can assign a convenience
8468 variable any type of value, including structures and arrays, even if
8469 that variable already has a value of a different type. The convenience
8470 variable, when used as an expression, has the type of its current value.
8473 @kindex show convenience
8474 @cindex show all user variables
8475 @item show convenience
8476 Print a list of convenience variables used so far, and their values.
8477 Abbreviated @code{show conv}.
8479 @kindex init-if-undefined
8480 @cindex convenience variables, initializing
8481 @item init-if-undefined $@var{variable} = @var{expression}
8482 Set a convenience variable if it has not already been set. This is useful
8483 for user-defined commands that keep some state. It is similar, in concept,
8484 to using local static variables with initializers in C (except that
8485 convenience variables are global). It can also be used to allow users to
8486 override default values used in a command script.
8488 If the variable is already defined then the expression is not evaluated so
8489 any side-effects do not occur.
8492 One of the ways to use a convenience variable is as a counter to be
8493 incremented or a pointer to be advanced. For example, to print
8494 a field from successive elements of an array of structures:
8498 print bar[$i++]->contents
8502 Repeat that command by typing @key{RET}.
8504 Some convenience variables are created automatically by @value{GDBN} and given
8505 values likely to be useful.
8508 @vindex $_@r{, convenience variable}
8510 The variable @code{$_} is automatically set by the @code{x} command to
8511 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8512 commands which provide a default address for @code{x} to examine also
8513 set @code{$_} to that address; these commands include @code{info line}
8514 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8515 except when set by the @code{x} command, in which case it is a pointer
8516 to the type of @code{$__}.
8518 @vindex $__@r{, convenience variable}
8520 The variable @code{$__} is automatically set by the @code{x} command
8521 to the value found in the last address examined. Its type is chosen
8522 to match the format in which the data was printed.
8525 @vindex $_exitcode@r{, convenience variable}
8526 The variable @code{$_exitcode} is automatically set to the exit code when
8527 the program being debugged terminates.
8530 @vindex $_sdata@r{, inspect, convenience variable}
8531 The variable @code{$_sdata} contains extra collected static tracepoint
8532 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8533 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8534 if extra static tracepoint data has not been collected.
8537 @vindex $_siginfo@r{, convenience variable}
8538 The variable @code{$_siginfo} contains extra signal information
8539 (@pxref{extra signal information}). Note that @code{$_siginfo}
8540 could be empty, if the application has not yet received any signals.
8541 For example, it will be empty before you execute the @code{run} command.
8544 @vindex $_tlb@r{, convenience variable}
8545 The variable @code{$_tlb} is automatically set when debugging
8546 applications running on MS-Windows in native mode or connected to
8547 gdbserver that supports the @code{qGetTIBAddr} request.
8548 @xref{General Query Packets}.
8549 This variable contains the address of the thread information block.
8553 On HP-UX systems, if you refer to a function or variable name that
8554 begins with a dollar sign, @value{GDBN} searches for a user or system
8555 name first, before it searches for a convenience variable.
8557 @cindex convenience functions
8558 @value{GDBN} also supplies some @dfn{convenience functions}. These
8559 have a syntax similar to convenience variables. A convenience
8560 function can be used in an expression just like an ordinary function;
8561 however, a convenience function is implemented internally to
8566 @kindex help function
8567 @cindex show all convenience functions
8568 Print a list of all convenience functions.
8575 You can refer to machine register contents, in expressions, as variables
8576 with names starting with @samp{$}. The names of registers are different
8577 for each machine; use @code{info registers} to see the names used on
8581 @kindex info registers
8582 @item info registers
8583 Print the names and values of all registers except floating-point
8584 and vector registers (in the selected stack frame).
8586 @kindex info all-registers
8587 @cindex floating point registers
8588 @item info all-registers
8589 Print the names and values of all registers, including floating-point
8590 and vector registers (in the selected stack frame).
8592 @item info registers @var{regname} @dots{}
8593 Print the @dfn{relativized} value of each specified register @var{regname}.
8594 As discussed in detail below, register values are normally relative to
8595 the selected stack frame. @var{regname} may be any register name valid on
8596 the machine you are using, with or without the initial @samp{$}.
8599 @cindex stack pointer register
8600 @cindex program counter register
8601 @cindex process status register
8602 @cindex frame pointer register
8603 @cindex standard registers
8604 @value{GDBN} has four ``standard'' register names that are available (in
8605 expressions) on most machines---whenever they do not conflict with an
8606 architecture's canonical mnemonics for registers. The register names
8607 @code{$pc} and @code{$sp} are used for the program counter register and
8608 the stack pointer. @code{$fp} is used for a register that contains a
8609 pointer to the current stack frame, and @code{$ps} is used for a
8610 register that contains the processor status. For example,
8611 you could print the program counter in hex with
8618 or print the instruction to be executed next with
8625 or add four to the stack pointer@footnote{This is a way of removing
8626 one word from the stack, on machines where stacks grow downward in
8627 memory (most machines, nowadays). This assumes that the innermost
8628 stack frame is selected; setting @code{$sp} is not allowed when other
8629 stack frames are selected. To pop entire frames off the stack,
8630 regardless of machine architecture, use @code{return};
8631 see @ref{Returning, ,Returning from a Function}.} with
8637 Whenever possible, these four standard register names are available on
8638 your machine even though the machine has different canonical mnemonics,
8639 so long as there is no conflict. The @code{info registers} command
8640 shows the canonical names. For example, on the SPARC, @code{info
8641 registers} displays the processor status register as @code{$psr} but you
8642 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8643 is an alias for the @sc{eflags} register.
8645 @value{GDBN} always considers the contents of an ordinary register as an
8646 integer when the register is examined in this way. Some machines have
8647 special registers which can hold nothing but floating point; these
8648 registers are considered to have floating point values. There is no way
8649 to refer to the contents of an ordinary register as floating point value
8650 (although you can @emph{print} it as a floating point value with
8651 @samp{print/f $@var{regname}}).
8653 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8654 means that the data format in which the register contents are saved by
8655 the operating system is not the same one that your program normally
8656 sees. For example, the registers of the 68881 floating point
8657 coprocessor are always saved in ``extended'' (raw) format, but all C
8658 programs expect to work with ``double'' (virtual) format. In such
8659 cases, @value{GDBN} normally works with the virtual format only (the format
8660 that makes sense for your program), but the @code{info registers} command
8661 prints the data in both formats.
8663 @cindex SSE registers (x86)
8664 @cindex MMX registers (x86)
8665 Some machines have special registers whose contents can be interpreted
8666 in several different ways. For example, modern x86-based machines
8667 have SSE and MMX registers that can hold several values packed
8668 together in several different formats. @value{GDBN} refers to such
8669 registers in @code{struct} notation:
8672 (@value{GDBP}) print $xmm1
8674 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8675 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8676 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8677 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8678 v4_int32 = @{0, 20657912, 11, 13@},
8679 v2_int64 = @{88725056443645952, 55834574859@},
8680 uint128 = 0x0000000d0000000b013b36f800000000
8685 To set values of such registers, you need to tell @value{GDBN} which
8686 view of the register you wish to change, as if you were assigning
8687 value to a @code{struct} member:
8690 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8693 Normally, register values are relative to the selected stack frame
8694 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8695 value that the register would contain if all stack frames farther in
8696 were exited and their saved registers restored. In order to see the
8697 true contents of hardware registers, you must select the innermost
8698 frame (with @samp{frame 0}).
8700 However, @value{GDBN} must deduce where registers are saved, from the machine
8701 code generated by your compiler. If some registers are not saved, or if
8702 @value{GDBN} is unable to locate the saved registers, the selected stack
8703 frame makes no difference.
8705 @node Floating Point Hardware
8706 @section Floating Point Hardware
8707 @cindex floating point
8709 Depending on the configuration, @value{GDBN} may be able to give
8710 you more information about the status of the floating point hardware.
8715 Display hardware-dependent information about the floating
8716 point unit. The exact contents and layout vary depending on the
8717 floating point chip. Currently, @samp{info float} is supported on
8718 the ARM and x86 machines.
8722 @section Vector Unit
8725 Depending on the configuration, @value{GDBN} may be able to give you
8726 more information about the status of the vector unit.
8731 Display information about the vector unit. The exact contents and
8732 layout vary depending on the hardware.
8735 @node OS Information
8736 @section Operating System Auxiliary Information
8737 @cindex OS information
8739 @value{GDBN} provides interfaces to useful OS facilities that can help
8740 you debug your program.
8742 @cindex @code{ptrace} system call
8743 @cindex @code{struct user} contents
8744 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8745 machines), it interfaces with the inferior via the @code{ptrace}
8746 system call. The operating system creates a special sata structure,
8747 called @code{struct user}, for this interface. You can use the
8748 command @code{info udot} to display the contents of this data
8754 Display the contents of the @code{struct user} maintained by the OS
8755 kernel for the program being debugged. @value{GDBN} displays the
8756 contents of @code{struct user} as a list of hex numbers, similar to
8757 the @code{examine} command.
8760 @cindex auxiliary vector
8761 @cindex vector, auxiliary
8762 Some operating systems supply an @dfn{auxiliary vector} to programs at
8763 startup. This is akin to the arguments and environment that you
8764 specify for a program, but contains a system-dependent variety of
8765 binary values that tell system libraries important details about the
8766 hardware, operating system, and process. Each value's purpose is
8767 identified by an integer tag; the meanings are well-known but system-specific.
8768 Depending on the configuration and operating system facilities,
8769 @value{GDBN} may be able to show you this information. For remote
8770 targets, this functionality may further depend on the remote stub's
8771 support of the @samp{qXfer:auxv:read} packet, see
8772 @ref{qXfer auxiliary vector read}.
8777 Display the auxiliary vector of the inferior, which can be either a
8778 live process or a core dump file. @value{GDBN} prints each tag value
8779 numerically, and also shows names and text descriptions for recognized
8780 tags. Some values in the vector are numbers, some bit masks, and some
8781 pointers to strings or other data. @value{GDBN} displays each value in the
8782 most appropriate form for a recognized tag, and in hexadecimal for
8783 an unrecognized tag.
8786 On some targets, @value{GDBN} can access operating-system-specific information
8787 and display it to user, without interpretation. For remote targets,
8788 this functionality depends on the remote stub's support of the
8789 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8794 List the types of OS information available for the target. If the
8795 target does not return a list of possible types, this command will
8798 @kindex info os processes
8799 @item info os processes
8800 Display the list of processes on the target. For each process,
8801 @value{GDBN} prints the process identifier, the name of the user, and
8802 the command corresponding to the process.
8805 @node Memory Region Attributes
8806 @section Memory Region Attributes
8807 @cindex memory region attributes
8809 @dfn{Memory region attributes} allow you to describe special handling
8810 required by regions of your target's memory. @value{GDBN} uses
8811 attributes to determine whether to allow certain types of memory
8812 accesses; whether to use specific width accesses; and whether to cache
8813 target memory. By default the description of memory regions is
8814 fetched from the target (if the current target supports this), but the
8815 user can override the fetched regions.
8817 Defined memory regions can be individually enabled and disabled. When a
8818 memory region is disabled, @value{GDBN} uses the default attributes when
8819 accessing memory in that region. Similarly, if no memory regions have
8820 been defined, @value{GDBN} uses the default attributes when accessing
8823 When a memory region is defined, it is given a number to identify it;
8824 to enable, disable, or remove a memory region, you specify that number.
8828 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8829 Define a memory region bounded by @var{lower} and @var{upper} with
8830 attributes @var{attributes}@dots{}, and add it to the list of regions
8831 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8832 case: it is treated as the target's maximum memory address.
8833 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8836 Discard any user changes to the memory regions and use target-supplied
8837 regions, if available, or no regions if the target does not support.
8840 @item delete mem @var{nums}@dots{}
8841 Remove memory regions @var{nums}@dots{} from the list of regions
8842 monitored by @value{GDBN}.
8845 @item disable mem @var{nums}@dots{}
8846 Disable monitoring of memory regions @var{nums}@dots{}.
8847 A disabled memory region is not forgotten.
8848 It may be enabled again later.
8851 @item enable mem @var{nums}@dots{}
8852 Enable monitoring of memory regions @var{nums}@dots{}.
8856 Print a table of all defined memory regions, with the following columns
8860 @item Memory Region Number
8861 @item Enabled or Disabled.
8862 Enabled memory regions are marked with @samp{y}.
8863 Disabled memory regions are marked with @samp{n}.
8866 The address defining the inclusive lower bound of the memory region.
8869 The address defining the exclusive upper bound of the memory region.
8872 The list of attributes set for this memory region.
8877 @subsection Attributes
8879 @subsubsection Memory Access Mode
8880 The access mode attributes set whether @value{GDBN} may make read or
8881 write accesses to a memory region.
8883 While these attributes prevent @value{GDBN} from performing invalid
8884 memory accesses, they do nothing to prevent the target system, I/O DMA,
8885 etc.@: from accessing memory.
8889 Memory is read only.
8891 Memory is write only.
8893 Memory is read/write. This is the default.
8896 @subsubsection Memory Access Size
8897 The access size attribute tells @value{GDBN} to use specific sized
8898 accesses in the memory region. Often memory mapped device registers
8899 require specific sized accesses. If no access size attribute is
8900 specified, @value{GDBN} may use accesses of any size.
8904 Use 8 bit memory accesses.
8906 Use 16 bit memory accesses.
8908 Use 32 bit memory accesses.
8910 Use 64 bit memory accesses.
8913 @c @subsubsection Hardware/Software Breakpoints
8914 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8915 @c will use hardware or software breakpoints for the internal breakpoints
8916 @c used by the step, next, finish, until, etc. commands.
8920 @c Always use hardware breakpoints
8921 @c @item swbreak (default)
8924 @subsubsection Data Cache
8925 The data cache attributes set whether @value{GDBN} will cache target
8926 memory. While this generally improves performance by reducing debug
8927 protocol overhead, it can lead to incorrect results because @value{GDBN}
8928 does not know about volatile variables or memory mapped device
8933 Enable @value{GDBN} to cache target memory.
8935 Disable @value{GDBN} from caching target memory. This is the default.
8938 @subsection Memory Access Checking
8939 @value{GDBN} can be instructed to refuse accesses to memory that is
8940 not explicitly described. This can be useful if accessing such
8941 regions has undesired effects for a specific target, or to provide
8942 better error checking. The following commands control this behaviour.
8945 @kindex set mem inaccessible-by-default
8946 @item set mem inaccessible-by-default [on|off]
8947 If @code{on} is specified, make @value{GDBN} treat memory not
8948 explicitly described by the memory ranges as non-existent and refuse accesses
8949 to such memory. The checks are only performed if there's at least one
8950 memory range defined. If @code{off} is specified, make @value{GDBN}
8951 treat the memory not explicitly described by the memory ranges as RAM.
8952 The default value is @code{on}.
8953 @kindex show mem inaccessible-by-default
8954 @item show mem inaccessible-by-default
8955 Show the current handling of accesses to unknown memory.
8959 @c @subsubsection Memory Write Verification
8960 @c The memory write verification attributes set whether @value{GDBN}
8961 @c will re-reads data after each write to verify the write was successful.
8965 @c @item noverify (default)
8968 @node Dump/Restore Files
8969 @section Copy Between Memory and a File
8970 @cindex dump/restore files
8971 @cindex append data to a file
8972 @cindex dump data to a file
8973 @cindex restore data from a file
8975 You can use the commands @code{dump}, @code{append}, and
8976 @code{restore} to copy data between target memory and a file. The
8977 @code{dump} and @code{append} commands write data to a file, and the
8978 @code{restore} command reads data from a file back into the inferior's
8979 memory. Files may be in binary, Motorola S-record, Intel hex, or
8980 Tektronix Hex format; however, @value{GDBN} can only append to binary
8986 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8987 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8988 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8989 or the value of @var{expr}, to @var{filename} in the given format.
8991 The @var{format} parameter may be any one of:
8998 Motorola S-record format.
9000 Tektronix Hex format.
9003 @value{GDBN} uses the same definitions of these formats as the
9004 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9005 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9009 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9010 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9011 Append the contents of memory from @var{start_addr} to @var{end_addr},
9012 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9013 (@value{GDBN} can only append data to files in raw binary form.)
9016 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9017 Restore the contents of file @var{filename} into memory. The
9018 @code{restore} command can automatically recognize any known @sc{bfd}
9019 file format, except for raw binary. To restore a raw binary file you
9020 must specify the optional keyword @code{binary} after the filename.
9022 If @var{bias} is non-zero, its value will be added to the addresses
9023 contained in the file. Binary files always start at address zero, so
9024 they will be restored at address @var{bias}. Other bfd files have
9025 a built-in location; they will be restored at offset @var{bias}
9028 If @var{start} and/or @var{end} are non-zero, then only data between
9029 file offset @var{start} and file offset @var{end} will be restored.
9030 These offsets are relative to the addresses in the file, before
9031 the @var{bias} argument is applied.
9035 @node Core File Generation
9036 @section How to Produce a Core File from Your Program
9037 @cindex dump core from inferior
9039 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9040 image of a running process and its process status (register values
9041 etc.). Its primary use is post-mortem debugging of a program that
9042 crashed while it ran outside a debugger. A program that crashes
9043 automatically produces a core file, unless this feature is disabled by
9044 the user. @xref{Files}, for information on invoking @value{GDBN} in
9045 the post-mortem debugging mode.
9047 Occasionally, you may wish to produce a core file of the program you
9048 are debugging in order to preserve a snapshot of its state.
9049 @value{GDBN} has a special command for that.
9053 @kindex generate-core-file
9054 @item generate-core-file [@var{file}]
9055 @itemx gcore [@var{file}]
9056 Produce a core dump of the inferior process. The optional argument
9057 @var{file} specifies the file name where to put the core dump. If not
9058 specified, the file name defaults to @file{core.@var{pid}}, where
9059 @var{pid} is the inferior process ID.
9061 Note that this command is implemented only for some systems (as of
9062 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9065 @node Character Sets
9066 @section Character Sets
9067 @cindex character sets
9069 @cindex translating between character sets
9070 @cindex host character set
9071 @cindex target character set
9073 If the program you are debugging uses a different character set to
9074 represent characters and strings than the one @value{GDBN} uses itself,
9075 @value{GDBN} can automatically translate between the character sets for
9076 you. The character set @value{GDBN} uses we call the @dfn{host
9077 character set}; the one the inferior program uses we call the
9078 @dfn{target character set}.
9080 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9081 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9082 remote protocol (@pxref{Remote Debugging}) to debug a program
9083 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9084 then the host character set is Latin-1, and the target character set is
9085 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9086 target-charset EBCDIC-US}, then @value{GDBN} translates between
9087 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9088 character and string literals in expressions.
9090 @value{GDBN} has no way to automatically recognize which character set
9091 the inferior program uses; you must tell it, using the @code{set
9092 target-charset} command, described below.
9094 Here are the commands for controlling @value{GDBN}'s character set
9098 @item set target-charset @var{charset}
9099 @kindex set target-charset
9100 Set the current target character set to @var{charset}. To display the
9101 list of supported target character sets, type
9102 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9104 @item set host-charset @var{charset}
9105 @kindex set host-charset
9106 Set the current host character set to @var{charset}.
9108 By default, @value{GDBN} uses a host character set appropriate to the
9109 system it is running on; you can override that default using the
9110 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9111 automatically determine the appropriate host character set. In this
9112 case, @value{GDBN} uses @samp{UTF-8}.
9114 @value{GDBN} can only use certain character sets as its host character
9115 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9116 @value{GDBN} will list the host character sets it supports.
9118 @item set charset @var{charset}
9120 Set the current host and target character sets to @var{charset}. As
9121 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9122 @value{GDBN} will list the names of the character sets that can be used
9123 for both host and target.
9126 @kindex show charset
9127 Show the names of the current host and target character sets.
9129 @item show host-charset
9130 @kindex show host-charset
9131 Show the name of the current host character set.
9133 @item show target-charset
9134 @kindex show target-charset
9135 Show the name of the current target character set.
9137 @item set target-wide-charset @var{charset}
9138 @kindex set target-wide-charset
9139 Set the current target's wide character set to @var{charset}. This is
9140 the character set used by the target's @code{wchar_t} type. To
9141 display the list of supported wide character sets, type
9142 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9144 @item show target-wide-charset
9145 @kindex show target-wide-charset
9146 Show the name of the current target's wide character set.
9149 Here is an example of @value{GDBN}'s character set support in action.
9150 Assume that the following source code has been placed in the file
9151 @file{charset-test.c}:
9157 = @{72, 101, 108, 108, 111, 44, 32, 119,
9158 111, 114, 108, 100, 33, 10, 0@};
9159 char ibm1047_hello[]
9160 = @{200, 133, 147, 147, 150, 107, 64, 166,
9161 150, 153, 147, 132, 90, 37, 0@};
9165 printf ("Hello, world!\n");
9169 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9170 containing the string @samp{Hello, world!} followed by a newline,
9171 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9173 We compile the program, and invoke the debugger on it:
9176 $ gcc -g charset-test.c -o charset-test
9177 $ gdb -nw charset-test
9178 GNU gdb 2001-12-19-cvs
9179 Copyright 2001 Free Software Foundation, Inc.
9184 We can use the @code{show charset} command to see what character sets
9185 @value{GDBN} is currently using to interpret and display characters and
9189 (@value{GDBP}) show charset
9190 The current host and target character set is `ISO-8859-1'.
9194 For the sake of printing this manual, let's use @sc{ascii} as our
9195 initial character set:
9197 (@value{GDBP}) set charset ASCII
9198 (@value{GDBP}) show charset
9199 The current host and target character set is `ASCII'.
9203 Let's assume that @sc{ascii} is indeed the correct character set for our
9204 host system --- in other words, let's assume that if @value{GDBN} prints
9205 characters using the @sc{ascii} character set, our terminal will display
9206 them properly. Since our current target character set is also
9207 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9210 (@value{GDBP}) print ascii_hello
9211 $1 = 0x401698 "Hello, world!\n"
9212 (@value{GDBP}) print ascii_hello[0]
9217 @value{GDBN} uses the target character set for character and string
9218 literals you use in expressions:
9221 (@value{GDBP}) print '+'
9226 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9229 @value{GDBN} relies on the user to tell it which character set the
9230 target program uses. If we print @code{ibm1047_hello} while our target
9231 character set is still @sc{ascii}, we get jibberish:
9234 (@value{GDBP}) print ibm1047_hello
9235 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9236 (@value{GDBP}) print ibm1047_hello[0]
9241 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9242 @value{GDBN} tells us the character sets it supports:
9245 (@value{GDBP}) set target-charset
9246 ASCII EBCDIC-US IBM1047 ISO-8859-1
9247 (@value{GDBP}) set target-charset
9250 We can select @sc{ibm1047} as our target character set, and examine the
9251 program's strings again. Now the @sc{ascii} string is wrong, but
9252 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9253 target character set, @sc{ibm1047}, to the host character set,
9254 @sc{ascii}, and they display correctly:
9257 (@value{GDBP}) set target-charset IBM1047
9258 (@value{GDBP}) show charset
9259 The current host character set is `ASCII'.
9260 The current target character set is `IBM1047'.
9261 (@value{GDBP}) print ascii_hello
9262 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9263 (@value{GDBP}) print ascii_hello[0]
9265 (@value{GDBP}) print ibm1047_hello
9266 $8 = 0x4016a8 "Hello, world!\n"
9267 (@value{GDBP}) print ibm1047_hello[0]
9272 As above, @value{GDBN} uses the target character set for character and
9273 string literals you use in expressions:
9276 (@value{GDBP}) print '+'
9281 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9284 @node Caching Remote Data
9285 @section Caching Data of Remote Targets
9286 @cindex caching data of remote targets
9288 @value{GDBN} caches data exchanged between the debugger and a
9289 remote target (@pxref{Remote Debugging}). Such caching generally improves
9290 performance, because it reduces the overhead of the remote protocol by
9291 bundling memory reads and writes into large chunks. Unfortunately, simply
9292 caching everything would lead to incorrect results, since @value{GDBN}
9293 does not necessarily know anything about volatile values, memory-mapped I/O
9294 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9295 memory can be changed @emph{while} a gdb command is executing.
9296 Therefore, by default, @value{GDBN} only caches data
9297 known to be on the stack@footnote{In non-stop mode, it is moderately
9298 rare for a running thread to modify the stack of a stopped thread
9299 in a way that would interfere with a backtrace, and caching of
9300 stack reads provides a significant speed up of remote backtraces.}.
9301 Other regions of memory can be explicitly marked as
9302 cacheable; see @pxref{Memory Region Attributes}.
9305 @kindex set remotecache
9306 @item set remotecache on
9307 @itemx set remotecache off
9308 This option no longer does anything; it exists for compatibility
9311 @kindex show remotecache
9312 @item show remotecache
9313 Show the current state of the obsolete remotecache flag.
9315 @kindex set stack-cache
9316 @item set stack-cache on
9317 @itemx set stack-cache off
9318 Enable or disable caching of stack accesses. When @code{ON}, use
9319 caching. By default, this option is @code{ON}.
9321 @kindex show stack-cache
9322 @item show stack-cache
9323 Show the current state of data caching for memory accesses.
9326 @item info dcache @r{[}line@r{]}
9327 Print the information about the data cache performance. The
9328 information displayed includes the dcache width and depth, and for
9329 each cache line, its number, address, and how many times it was
9330 referenced. This command is useful for debugging the data cache
9333 If a line number is specified, the contents of that line will be
9336 @item set dcache size @var{size}
9338 @kindex set dcache size
9339 Set maximum number of entries in dcache (dcache depth above).
9341 @item set dcache line-size @var{line-size}
9342 @cindex dcache line-size
9343 @kindex set dcache line-size
9344 Set number of bytes each dcache entry caches (dcache width above).
9345 Must be a power of 2.
9347 @item show dcache size
9348 @kindex show dcache size
9349 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
9351 @item show dcache line-size
9352 @kindex show dcache line-size
9353 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
9357 @node Searching Memory
9358 @section Search Memory
9359 @cindex searching memory
9361 Memory can be searched for a particular sequence of bytes with the
9362 @code{find} command.
9366 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9367 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9368 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9369 etc. The search begins at address @var{start_addr} and continues for either
9370 @var{len} bytes or through to @var{end_addr} inclusive.
9373 @var{s} and @var{n} are optional parameters.
9374 They may be specified in either order, apart or together.
9377 @item @var{s}, search query size
9378 The size of each search query value.
9384 halfwords (two bytes)
9388 giant words (eight bytes)
9391 All values are interpreted in the current language.
9392 This means, for example, that if the current source language is C/C@t{++}
9393 then searching for the string ``hello'' includes the trailing '\0'.
9395 If the value size is not specified, it is taken from the
9396 value's type in the current language.
9397 This is useful when one wants to specify the search
9398 pattern as a mixture of types.
9399 Note that this means, for example, that in the case of C-like languages
9400 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9401 which is typically four bytes.
9403 @item @var{n}, maximum number of finds
9404 The maximum number of matches to print. The default is to print all finds.
9407 You can use strings as search values. Quote them with double-quotes
9409 The string value is copied into the search pattern byte by byte,
9410 regardless of the endianness of the target and the size specification.
9412 The address of each match found is printed as well as a count of the
9413 number of matches found.
9415 The address of the last value found is stored in convenience variable
9417 A count of the number of matches is stored in @samp{$numfound}.
9419 For example, if stopped at the @code{printf} in this function:
9425 static char hello[] = "hello-hello";
9426 static struct @{ char c; short s; int i; @}
9427 __attribute__ ((packed)) mixed
9428 = @{ 'c', 0x1234, 0x87654321 @};
9429 printf ("%s\n", hello);
9434 you get during debugging:
9437 (gdb) find &hello[0], +sizeof(hello), "hello"
9438 0x804956d <hello.1620+6>
9440 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9441 0x8049567 <hello.1620>
9442 0x804956d <hello.1620+6>
9444 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9445 0x8049567 <hello.1620>
9447 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9448 0x8049560 <mixed.1625>
9450 (gdb) print $numfound
9453 $2 = (void *) 0x8049560
9456 @node Optimized Code
9457 @chapter Debugging Optimized Code
9458 @cindex optimized code, debugging
9459 @cindex debugging optimized code
9461 Almost all compilers support optimization. With optimization
9462 disabled, the compiler generates assembly code that corresponds
9463 directly to your source code, in a simplistic way. As the compiler
9464 applies more powerful optimizations, the generated assembly code
9465 diverges from your original source code. With help from debugging
9466 information generated by the compiler, @value{GDBN} can map from
9467 the running program back to constructs from your original source.
9469 @value{GDBN} is more accurate with optimization disabled. If you
9470 can recompile without optimization, it is easier to follow the
9471 progress of your program during debugging. But, there are many cases
9472 where you may need to debug an optimized version.
9474 When you debug a program compiled with @samp{-g -O}, remember that the
9475 optimizer has rearranged your code; the debugger shows you what is
9476 really there. Do not be too surprised when the execution path does not
9477 exactly match your source file! An extreme example: if you define a
9478 variable, but never use it, @value{GDBN} never sees that
9479 variable---because the compiler optimizes it out of existence.
9481 Some things do not work as well with @samp{-g -O} as with just
9482 @samp{-g}, particularly on machines with instruction scheduling. If in
9483 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9484 please report it to us as a bug (including a test case!).
9485 @xref{Variables}, for more information about debugging optimized code.
9488 * Inline Functions:: How @value{GDBN} presents inlining
9491 @node Inline Functions
9492 @section Inline Functions
9493 @cindex inline functions, debugging
9495 @dfn{Inlining} is an optimization that inserts a copy of the function
9496 body directly at each call site, instead of jumping to a shared
9497 routine. @value{GDBN} displays inlined functions just like
9498 non-inlined functions. They appear in backtraces. You can view their
9499 arguments and local variables, step into them with @code{step}, skip
9500 them with @code{next}, and escape from them with @code{finish}.
9501 You can check whether a function was inlined by using the
9502 @code{info frame} command.
9504 For @value{GDBN} to support inlined functions, the compiler must
9505 record information about inlining in the debug information ---
9506 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9507 other compilers do also. @value{GDBN} only supports inlined functions
9508 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9509 do not emit two required attributes (@samp{DW_AT_call_file} and
9510 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9511 function calls with earlier versions of @value{NGCC}. It instead
9512 displays the arguments and local variables of inlined functions as
9513 local variables in the caller.
9515 The body of an inlined function is directly included at its call site;
9516 unlike a non-inlined function, there are no instructions devoted to
9517 the call. @value{GDBN} still pretends that the call site and the
9518 start of the inlined function are different instructions. Stepping to
9519 the call site shows the call site, and then stepping again shows
9520 the first line of the inlined function, even though no additional
9521 instructions are executed.
9523 This makes source-level debugging much clearer; you can see both the
9524 context of the call and then the effect of the call. Only stepping by
9525 a single instruction using @code{stepi} or @code{nexti} does not do
9526 this; single instruction steps always show the inlined body.
9528 There are some ways that @value{GDBN} does not pretend that inlined
9529 function calls are the same as normal calls:
9533 You cannot set breakpoints on inlined functions. @value{GDBN}
9534 either reports that there is no symbol with that name, or else sets the
9535 breakpoint only on non-inlined copies of the function. This limitation
9536 will be removed in a future version of @value{GDBN}; until then,
9537 set a breakpoint by line number on the first line of the inlined
9541 Setting breakpoints at the call site of an inlined function may not
9542 work, because the call site does not contain any code. @value{GDBN}
9543 may incorrectly move the breakpoint to the next line of the enclosing
9544 function, after the call. This limitation will be removed in a future
9545 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9546 or inside the inlined function instead.
9549 @value{GDBN} cannot locate the return value of inlined calls after
9550 using the @code{finish} command. This is a limitation of compiler-generated
9551 debugging information; after @code{finish}, you can step to the next line
9552 and print a variable where your program stored the return value.
9558 @chapter C Preprocessor Macros
9560 Some languages, such as C and C@t{++}, provide a way to define and invoke
9561 ``preprocessor macros'' which expand into strings of tokens.
9562 @value{GDBN} can evaluate expressions containing macro invocations, show
9563 the result of macro expansion, and show a macro's definition, including
9564 where it was defined.
9566 You may need to compile your program specially to provide @value{GDBN}
9567 with information about preprocessor macros. Most compilers do not
9568 include macros in their debugging information, even when you compile
9569 with the @option{-g} flag. @xref{Compilation}.
9571 A program may define a macro at one point, remove that definition later,
9572 and then provide a different definition after that. Thus, at different
9573 points in the program, a macro may have different definitions, or have
9574 no definition at all. If there is a current stack frame, @value{GDBN}
9575 uses the macros in scope at that frame's source code line. Otherwise,
9576 @value{GDBN} uses the macros in scope at the current listing location;
9579 Whenever @value{GDBN} evaluates an expression, it always expands any
9580 macro invocations present in the expression. @value{GDBN} also provides
9581 the following commands for working with macros explicitly.
9585 @kindex macro expand
9586 @cindex macro expansion, showing the results of preprocessor
9587 @cindex preprocessor macro expansion, showing the results of
9588 @cindex expanding preprocessor macros
9589 @item macro expand @var{expression}
9590 @itemx macro exp @var{expression}
9591 Show the results of expanding all preprocessor macro invocations in
9592 @var{expression}. Since @value{GDBN} simply expands macros, but does
9593 not parse the result, @var{expression} need not be a valid expression;
9594 it can be any string of tokens.
9597 @item macro expand-once @var{expression}
9598 @itemx macro exp1 @var{expression}
9599 @cindex expand macro once
9600 @i{(This command is not yet implemented.)} Show the results of
9601 expanding those preprocessor macro invocations that appear explicitly in
9602 @var{expression}. Macro invocations appearing in that expansion are
9603 left unchanged. This command allows you to see the effect of a
9604 particular macro more clearly, without being confused by further
9605 expansions. Since @value{GDBN} simply expands macros, but does not
9606 parse the result, @var{expression} need not be a valid expression; it
9607 can be any string of tokens.
9610 @cindex macro definition, showing
9611 @cindex definition of a macro, showing
9612 @cindex macros, from debug info
9613 @item info macro @var{macro}
9614 Show the current definition of the named @var{macro}, and describe the
9615 source location or compiler command-line where that definition was established.
9618 @item info macros @var{linespec}
9619 Show all macro definitions that are in effect at the location specified
9620 by @var{linespec}, and describe the source location or compiler
9621 command-line where those definitions were established.
9623 @kindex info definitions
9624 @item info definitions @var{macro}
9625 Show all definitions of the named @var{macro} that are defined in the current
9626 compilation unit, and describe the source location or compiler command-line
9627 where those definitions were established.
9629 @kindex macro define
9630 @cindex user-defined macros
9631 @cindex defining macros interactively
9632 @cindex macros, user-defined
9633 @item macro define @var{macro} @var{replacement-list}
9634 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9635 Introduce a definition for a preprocessor macro named @var{macro},
9636 invocations of which are replaced by the tokens given in
9637 @var{replacement-list}. The first form of this command defines an
9638 ``object-like'' macro, which takes no arguments; the second form
9639 defines a ``function-like'' macro, which takes the arguments given in
9642 A definition introduced by this command is in scope in every
9643 expression evaluated in @value{GDBN}, until it is removed with the
9644 @code{macro undef} command, described below. The definition overrides
9645 all definitions for @var{macro} present in the program being debugged,
9646 as well as any previous user-supplied definition.
9649 @item macro undef @var{macro}
9650 Remove any user-supplied definition for the macro named @var{macro}.
9651 This command only affects definitions provided with the @code{macro
9652 define} command, described above; it cannot remove definitions present
9653 in the program being debugged.
9657 List all the macros defined using the @code{macro define} command.
9660 @cindex macros, example of debugging with
9661 Here is a transcript showing the above commands in action. First, we
9662 show our source files:
9670 #define ADD(x) (M + x)
9675 printf ("Hello, world!\n");
9677 printf ("We're so creative.\n");
9679 printf ("Goodbye, world!\n");
9686 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9687 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9688 compiler includes information about preprocessor macros in the debugging
9692 $ gcc -gdwarf-2 -g3 sample.c -o sample
9696 Now, we start @value{GDBN} on our sample program:
9700 GNU gdb 2002-05-06-cvs
9701 Copyright 2002 Free Software Foundation, Inc.
9702 GDB is free software, @dots{}
9706 We can expand macros and examine their definitions, even when the
9707 program is not running. @value{GDBN} uses the current listing position
9708 to decide which macro definitions are in scope:
9711 (@value{GDBP}) list main
9714 5 #define ADD(x) (M + x)
9719 10 printf ("Hello, world!\n");
9721 12 printf ("We're so creative.\n");
9722 (@value{GDBP}) info macro ADD
9723 Defined at /home/jimb/gdb/macros/play/sample.c:5
9724 #define ADD(x) (M + x)
9725 (@value{GDBP}) info macro Q
9726 Defined at /home/jimb/gdb/macros/play/sample.h:1
9727 included at /home/jimb/gdb/macros/play/sample.c:2
9729 (@value{GDBP}) macro expand ADD(1)
9730 expands to: (42 + 1)
9731 (@value{GDBP}) macro expand-once ADD(1)
9732 expands to: once (M + 1)
9736 In the example above, note that @code{macro expand-once} expands only
9737 the macro invocation explicit in the original text --- the invocation of
9738 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9739 which was introduced by @code{ADD}.
9741 Once the program is running, @value{GDBN} uses the macro definitions in
9742 force at the source line of the current stack frame:
9745 (@value{GDBP}) break main
9746 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9748 Starting program: /home/jimb/gdb/macros/play/sample
9750 Breakpoint 1, main () at sample.c:10
9751 10 printf ("Hello, world!\n");
9755 At line 10, the definition of the macro @code{N} at line 9 is in force:
9758 (@value{GDBP}) info macro N
9759 Defined at /home/jimb/gdb/macros/play/sample.c:9
9761 (@value{GDBP}) macro expand N Q M
9763 (@value{GDBP}) print N Q M
9768 As we step over directives that remove @code{N}'s definition, and then
9769 give it a new definition, @value{GDBN} finds the definition (or lack
9770 thereof) in force at each point:
9775 12 printf ("We're so creative.\n");
9776 (@value{GDBP}) info macro N
9777 The symbol `N' has no definition as a C/C++ preprocessor macro
9778 at /home/jimb/gdb/macros/play/sample.c:12
9781 14 printf ("Goodbye, world!\n");
9782 (@value{GDBP}) info macro N
9783 Defined at /home/jimb/gdb/macros/play/sample.c:13
9785 (@value{GDBP}) macro expand N Q M
9786 expands to: 1729 < 42
9787 (@value{GDBP}) print N Q M
9792 In addition to source files, macros can be defined on the compilation command
9793 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9794 such a way, @value{GDBN} displays the location of their definition as line zero
9795 of the source file submitted to the compiler.
9798 (@value{GDBP}) info macro __STDC__
9799 Defined at /home/jimb/gdb/macros/play/sample.c:0
9806 @chapter Tracepoints
9807 @c This chapter is based on the documentation written by Michael
9808 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9811 In some applications, it is not feasible for the debugger to interrupt
9812 the program's execution long enough for the developer to learn
9813 anything helpful about its behavior. If the program's correctness
9814 depends on its real-time behavior, delays introduced by a debugger
9815 might cause the program to change its behavior drastically, or perhaps
9816 fail, even when the code itself is correct. It is useful to be able
9817 to observe the program's behavior without interrupting it.
9819 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9820 specify locations in the program, called @dfn{tracepoints}, and
9821 arbitrary expressions to evaluate when those tracepoints are reached.
9822 Later, using the @code{tfind} command, you can examine the values
9823 those expressions had when the program hit the tracepoints. The
9824 expressions may also denote objects in memory---structures or arrays,
9825 for example---whose values @value{GDBN} should record; while visiting
9826 a particular tracepoint, you may inspect those objects as if they were
9827 in memory at that moment. However, because @value{GDBN} records these
9828 values without interacting with you, it can do so quickly and
9829 unobtrusively, hopefully not disturbing the program's behavior.
9831 The tracepoint facility is currently available only for remote
9832 targets. @xref{Targets}. In addition, your remote target must know
9833 how to collect trace data. This functionality is implemented in the
9834 remote stub; however, none of the stubs distributed with @value{GDBN}
9835 support tracepoints as of this writing. The format of the remote
9836 packets used to implement tracepoints are described in @ref{Tracepoint
9839 It is also possible to get trace data from a file, in a manner reminiscent
9840 of corefiles; you specify the filename, and use @code{tfind} to search
9841 through the file. @xref{Trace Files}, for more details.
9843 This chapter describes the tracepoint commands and features.
9847 * Analyze Collected Data::
9848 * Tracepoint Variables::
9852 @node Set Tracepoints
9853 @section Commands to Set Tracepoints
9855 Before running such a @dfn{trace experiment}, an arbitrary number of
9856 tracepoints can be set. A tracepoint is actually a special type of
9857 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9858 standard breakpoint commands. For instance, as with breakpoints,
9859 tracepoint numbers are successive integers starting from one, and many
9860 of the commands associated with tracepoints take the tracepoint number
9861 as their argument, to identify which tracepoint to work on.
9863 For each tracepoint, you can specify, in advance, some arbitrary set
9864 of data that you want the target to collect in the trace buffer when
9865 it hits that tracepoint. The collected data can include registers,
9866 local variables, or global data. Later, you can use @value{GDBN}
9867 commands to examine the values these data had at the time the
9870 Tracepoints do not support every breakpoint feature. Ignore counts on
9871 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9872 commands when they are hit. Tracepoints may not be thread-specific
9875 @cindex fast tracepoints
9876 Some targets may support @dfn{fast tracepoints}, which are inserted in
9877 a different way (such as with a jump instead of a trap), that is
9878 faster but possibly restricted in where they may be installed.
9880 @cindex static tracepoints
9881 @cindex markers, static tracepoints
9882 @cindex probing markers, static tracepoints
9883 Regular and fast tracepoints are dynamic tracing facilities, meaning
9884 that they can be used to insert tracepoints at (almost) any location
9885 in the target. Some targets may also support controlling @dfn{static
9886 tracepoints} from @value{GDBN}. With static tracing, a set of
9887 instrumentation points, also known as @dfn{markers}, are embedded in
9888 the target program, and can be activated or deactivated by name or
9889 address. These are usually placed at locations which facilitate
9890 investigating what the target is actually doing. @value{GDBN}'s
9891 support for static tracing includes being able to list instrumentation
9892 points, and attach them with @value{GDBN} defined high level
9893 tracepoints that expose the whole range of convenience of
9894 @value{GDBN}'s tracepoints support. Namely, support for collecting
9895 registers values and values of global or local (to the instrumentation
9896 point) variables; tracepoint conditions and trace state variables.
9897 The act of installing a @value{GDBN} static tracepoint on an
9898 instrumentation point, or marker, is referred to as @dfn{probing} a
9899 static tracepoint marker.
9901 @code{gdbserver} supports tracepoints on some target systems.
9902 @xref{Server,,Tracepoints support in @code{gdbserver}}.
9904 This section describes commands to set tracepoints and associated
9905 conditions and actions.
9908 * Create and Delete Tracepoints::
9909 * Enable and Disable Tracepoints::
9910 * Tracepoint Passcounts::
9911 * Tracepoint Conditions::
9912 * Trace State Variables::
9913 * Tracepoint Actions::
9914 * Listing Tracepoints::
9915 * Listing Static Tracepoint Markers::
9916 * Starting and Stopping Trace Experiments::
9917 * Tracepoint Restrictions::
9920 @node Create and Delete Tracepoints
9921 @subsection Create and Delete Tracepoints
9924 @cindex set tracepoint
9926 @item trace @var{location}
9927 The @code{trace} command is very similar to the @code{break} command.
9928 Its argument @var{location} can be a source line, a function name, or
9929 an address in the target program. @xref{Specify Location}. The
9930 @code{trace} command defines a tracepoint, which is a point in the
9931 target program where the debugger will briefly stop, collect some
9932 data, and then allow the program to continue. Setting a tracepoint or
9933 changing its actions doesn't take effect until the next @code{tstart}
9934 command, and once a trace experiment is running, further changes will
9935 not have any effect until the next trace experiment starts.
9937 Here are some examples of using the @code{trace} command:
9940 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9942 (@value{GDBP}) @b{trace +2} // 2 lines forward
9944 (@value{GDBP}) @b{trace my_function} // first source line of function
9946 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9948 (@value{GDBP}) @b{trace *0x2117c4} // an address
9952 You can abbreviate @code{trace} as @code{tr}.
9954 @item trace @var{location} if @var{cond}
9955 Set a tracepoint with condition @var{cond}; evaluate the expression
9956 @var{cond} each time the tracepoint is reached, and collect data only
9957 if the value is nonzero---that is, if @var{cond} evaluates as true.
9958 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9959 information on tracepoint conditions.
9961 @item ftrace @var{location} [ if @var{cond} ]
9962 @cindex set fast tracepoint
9963 @cindex fast tracepoints, setting
9965 The @code{ftrace} command sets a fast tracepoint. For targets that
9966 support them, fast tracepoints will use a more efficient but possibly
9967 less general technique to trigger data collection, such as a jump
9968 instruction instead of a trap, or some sort of hardware support. It
9969 may not be possible to create a fast tracepoint at the desired
9970 location, in which case the command will exit with an explanatory
9973 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9976 @item strace @var{location} [ if @var{cond} ]
9977 @cindex set static tracepoint
9978 @cindex static tracepoints, setting
9979 @cindex probe static tracepoint marker
9981 The @code{strace} command sets a static tracepoint. For targets that
9982 support it, setting a static tracepoint probes a static
9983 instrumentation point, or marker, found at @var{location}. It may not
9984 be possible to set a static tracepoint at the desired location, in
9985 which case the command will exit with an explanatory message.
9987 @value{GDBN} handles arguments to @code{strace} exactly as for
9988 @code{trace}, with the addition that the user can also specify
9989 @code{-m @var{marker}} as @var{location}. This probes the marker
9990 identified by the @var{marker} string identifier. This identifier
9991 depends on the static tracepoint backend library your program is
9992 using. You can find all the marker identifiers in the @samp{ID} field
9993 of the @code{info static-tracepoint-markers} command output.
9994 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
9995 Markers}. For example, in the following small program using the UST
10001 trace_mark(ust, bar33, "str %s", "FOOBAZ");
10006 the marker id is composed of joining the first two arguments to the
10007 @code{trace_mark} call with a slash, which translates to:
10010 (@value{GDBP}) info static-tracepoint-markers
10011 Cnt Enb ID Address What
10012 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
10018 so you may probe the marker above with:
10021 (@value{GDBP}) strace -m ust/bar33
10024 Static tracepoints accept an extra collect action --- @code{collect
10025 $_sdata}. This collects arbitrary user data passed in the probe point
10026 call to the tracing library. In the UST example above, you'll see
10027 that the third argument to @code{trace_mark} is a printf-like format
10028 string. The user data is then the result of running that formating
10029 string against the following arguments. Note that @code{info
10030 static-tracepoint-markers} command output lists that format string in
10031 the @samp{Data:} field.
10033 You can inspect this data when analyzing the trace buffer, by printing
10034 the $_sdata variable like any other variable available to
10035 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
10038 @cindex last tracepoint number
10039 @cindex recent tracepoint number
10040 @cindex tracepoint number
10041 The convenience variable @code{$tpnum} records the tracepoint number
10042 of the most recently set tracepoint.
10044 @kindex delete tracepoint
10045 @cindex tracepoint deletion
10046 @item delete tracepoint @r{[}@var{num}@r{]}
10047 Permanently delete one or more tracepoints. With no argument, the
10048 default is to delete all tracepoints. Note that the regular
10049 @code{delete} command can remove tracepoints also.
10054 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10056 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10060 You can abbreviate this command as @code{del tr}.
10063 @node Enable and Disable Tracepoints
10064 @subsection Enable and Disable Tracepoints
10066 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10069 @kindex disable tracepoint
10070 @item disable tracepoint @r{[}@var{num}@r{]}
10071 Disable tracepoint @var{num}, or all tracepoints if no argument
10072 @var{num} is given. A disabled tracepoint will have no effect during
10073 a trace experiment, but it is not forgotten. You can re-enable
10074 a disabled tracepoint using the @code{enable tracepoint} command.
10075 If the command is issued during a trace experiment and the debug target
10076 has support for disabling tracepoints during a trace experiment, then the
10077 change will be effective immediately. Otherwise, it will be applied to the
10078 next trace experiment.
10080 @kindex enable tracepoint
10081 @item enable tracepoint @r{[}@var{num}@r{]}
10082 Enable tracepoint @var{num}, or all tracepoints. If this command is
10083 issued during a trace experiment and the debug target supports enabling
10084 tracepoints during a trace experiment, then the enabled tracepoints will
10085 become effective immediately. Otherwise, they will become effective the
10086 next time a trace experiment is run.
10089 @node Tracepoint Passcounts
10090 @subsection Tracepoint Passcounts
10094 @cindex tracepoint pass count
10095 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10096 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10097 automatically stop a trace experiment. If a tracepoint's passcount is
10098 @var{n}, then the trace experiment will be automatically stopped on
10099 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10100 @var{num} is not specified, the @code{passcount} command sets the
10101 passcount of the most recently defined tracepoint. If no passcount is
10102 given, the trace experiment will run until stopped explicitly by the
10108 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10109 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10111 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10112 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10113 (@value{GDBP}) @b{trace foo}
10114 (@value{GDBP}) @b{pass 3}
10115 (@value{GDBP}) @b{trace bar}
10116 (@value{GDBP}) @b{pass 2}
10117 (@value{GDBP}) @b{trace baz}
10118 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10119 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10120 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10121 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10125 @node Tracepoint Conditions
10126 @subsection Tracepoint Conditions
10127 @cindex conditional tracepoints
10128 @cindex tracepoint conditions
10130 The simplest sort of tracepoint collects data every time your program
10131 reaches a specified place. You can also specify a @dfn{condition} for
10132 a tracepoint. A condition is just a Boolean expression in your
10133 programming language (@pxref{Expressions, ,Expressions}). A
10134 tracepoint with a condition evaluates the expression each time your
10135 program reaches it, and data collection happens only if the condition
10138 Tracepoint conditions can be specified when a tracepoint is set, by
10139 using @samp{if} in the arguments to the @code{trace} command.
10140 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10141 also be set or changed at any time with the @code{condition} command,
10142 just as with breakpoints.
10144 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10145 the conditional expression itself. Instead, @value{GDBN} encodes the
10146 expression into an agent expression (@pxref{Agent Expressions})
10147 suitable for execution on the target, independently of @value{GDBN}.
10148 Global variables become raw memory locations, locals become stack
10149 accesses, and so forth.
10151 For instance, suppose you have a function that is usually called
10152 frequently, but should not be called after an error has occurred. You
10153 could use the following tracepoint command to collect data about calls
10154 of that function that happen while the error code is propagating
10155 through the program; an unconditional tracepoint could end up
10156 collecting thousands of useless trace frames that you would have to
10160 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10163 @node Trace State Variables
10164 @subsection Trace State Variables
10165 @cindex trace state variables
10167 A @dfn{trace state variable} is a special type of variable that is
10168 created and managed by target-side code. The syntax is the same as
10169 that for GDB's convenience variables (a string prefixed with ``$''),
10170 but they are stored on the target. They must be created explicitly,
10171 using a @code{tvariable} command. They are always 64-bit signed
10174 Trace state variables are remembered by @value{GDBN}, and downloaded
10175 to the target along with tracepoint information when the trace
10176 experiment starts. There are no intrinsic limits on the number of
10177 trace state variables, beyond memory limitations of the target.
10179 @cindex convenience variables, and trace state variables
10180 Although trace state variables are managed by the target, you can use
10181 them in print commands and expressions as if they were convenience
10182 variables; @value{GDBN} will get the current value from the target
10183 while the trace experiment is running. Trace state variables share
10184 the same namespace as other ``$'' variables, which means that you
10185 cannot have trace state variables with names like @code{$23} or
10186 @code{$pc}, nor can you have a trace state variable and a convenience
10187 variable with the same name.
10191 @item tvariable $@var{name} [ = @var{expression} ]
10193 The @code{tvariable} command creates a new trace state variable named
10194 @code{$@var{name}}, and optionally gives it an initial value of
10195 @var{expression}. @var{expression} is evaluated when this command is
10196 entered; the result will be converted to an integer if possible,
10197 otherwise @value{GDBN} will report an error. A subsequent
10198 @code{tvariable} command specifying the same name does not create a
10199 variable, but instead assigns the supplied initial value to the
10200 existing variable of that name, overwriting any previous initial
10201 value. The default initial value is 0.
10203 @item info tvariables
10204 @kindex info tvariables
10205 List all the trace state variables along with their initial values.
10206 Their current values may also be displayed, if the trace experiment is
10209 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10210 @kindex delete tvariable
10211 Delete the given trace state variables, or all of them if no arguments
10216 @node Tracepoint Actions
10217 @subsection Tracepoint Action Lists
10221 @cindex tracepoint actions
10222 @item actions @r{[}@var{num}@r{]}
10223 This command will prompt for a list of actions to be taken when the
10224 tracepoint is hit. If the tracepoint number @var{num} is not
10225 specified, this command sets the actions for the one that was most
10226 recently defined (so that you can define a tracepoint and then say
10227 @code{actions} without bothering about its number). You specify the
10228 actions themselves on the following lines, one action at a time, and
10229 terminate the actions list with a line containing just @code{end}. So
10230 far, the only defined actions are @code{collect}, @code{teval}, and
10231 @code{while-stepping}.
10233 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10234 Commands, ,Breakpoint Command Lists}), except that only the defined
10235 actions are allowed; any other @value{GDBN} command is rejected.
10237 @cindex remove actions from a tracepoint
10238 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10239 and follow it immediately with @samp{end}.
10242 (@value{GDBP}) @b{collect @var{data}} // collect some data
10244 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10246 (@value{GDBP}) @b{end} // signals the end of actions.
10249 In the following example, the action list begins with @code{collect}
10250 commands indicating the things to be collected when the tracepoint is
10251 hit. Then, in order to single-step and collect additional data
10252 following the tracepoint, a @code{while-stepping} command is used,
10253 followed by the list of things to be collected after each step in a
10254 sequence of single steps. The @code{while-stepping} command is
10255 terminated by its own separate @code{end} command. Lastly, the action
10256 list is terminated by an @code{end} command.
10259 (@value{GDBP}) @b{trace foo}
10260 (@value{GDBP}) @b{actions}
10261 Enter actions for tracepoint 1, one per line:
10264 > while-stepping 12
10265 > collect $pc, arr[i]
10270 @kindex collect @r{(tracepoints)}
10271 @item collect @var{expr1}, @var{expr2}, @dots{}
10272 Collect values of the given expressions when the tracepoint is hit.
10273 This command accepts a comma-separated list of any valid expressions.
10274 In addition to global, static, or local variables, the following
10275 special arguments are supported:
10279 Collect all registers.
10282 Collect all function arguments.
10285 Collect all local variables.
10288 @vindex $_sdata@r{, collect}
10289 Collect static tracepoint marker specific data. Only available for
10290 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10291 Lists}. On the UST static tracepoints library backend, an
10292 instrumentation point resembles a @code{printf} function call. The
10293 tracing library is able to collect user specified data formatted to a
10294 character string using the format provided by the programmer that
10295 instrumented the program. Other backends have similar mechanisms.
10296 Here's an example of a UST marker call:
10299 const char master_name[] = "$your_name";
10300 trace_mark(channel1, marker1, "hello %s", master_name)
10303 In this case, collecting @code{$_sdata} collects the string
10304 @samp{hello $yourname}. When analyzing the trace buffer, you can
10305 inspect @samp{$_sdata} like any other variable available to
10309 You can give several consecutive @code{collect} commands, each one
10310 with a single argument, or one @code{collect} command with several
10311 arguments separated by commas; the effect is the same.
10313 The command @code{info scope} (@pxref{Symbols, info scope}) is
10314 particularly useful for figuring out what data to collect.
10316 @kindex teval @r{(tracepoints)}
10317 @item teval @var{expr1}, @var{expr2}, @dots{}
10318 Evaluate the given expressions when the tracepoint is hit. This
10319 command accepts a comma-separated list of expressions. The results
10320 are discarded, so this is mainly useful for assigning values to trace
10321 state variables (@pxref{Trace State Variables}) without adding those
10322 values to the trace buffer, as would be the case if the @code{collect}
10325 @kindex while-stepping @r{(tracepoints)}
10326 @item while-stepping @var{n}
10327 Perform @var{n} single-step instruction traces after the tracepoint,
10328 collecting new data after each step. The @code{while-stepping}
10329 command is followed by the list of what to collect while stepping
10330 (followed by its own @code{end} command):
10333 > while-stepping 12
10334 > collect $regs, myglobal
10340 Note that @code{$pc} is not automatically collected by
10341 @code{while-stepping}; you need to explicitly collect that register if
10342 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10345 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10346 @kindex set default-collect
10347 @cindex default collection action
10348 This variable is a list of expressions to collect at each tracepoint
10349 hit. It is effectively an additional @code{collect} action prepended
10350 to every tracepoint action list. The expressions are parsed
10351 individually for each tracepoint, so for instance a variable named
10352 @code{xyz} may be interpreted as a global for one tracepoint, and a
10353 local for another, as appropriate to the tracepoint's location.
10355 @item show default-collect
10356 @kindex show default-collect
10357 Show the list of expressions that are collected by default at each
10362 @node Listing Tracepoints
10363 @subsection Listing Tracepoints
10366 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10367 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10368 @cindex information about tracepoints
10369 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10370 Display information about the tracepoint @var{num}. If you don't
10371 specify a tracepoint number, displays information about all the
10372 tracepoints defined so far. The format is similar to that used for
10373 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10374 command, simply restricting itself to tracepoints.
10376 A tracepoint's listing may include additional information specific to
10381 its passcount as given by the @code{passcount @var{n}} command
10385 (@value{GDBP}) @b{info trace}
10386 Num Type Disp Enb Address What
10387 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10389 collect globfoo, $regs
10398 This command can be abbreviated @code{info tp}.
10401 @node Listing Static Tracepoint Markers
10402 @subsection Listing Static Tracepoint Markers
10405 @kindex info static-tracepoint-markers
10406 @cindex information about static tracepoint markers
10407 @item info static-tracepoint-markers
10408 Display information about all static tracepoint markers defined in the
10411 For each marker, the following columns are printed:
10415 An incrementing counter, output to help readability. This is not a
10418 The marker ID, as reported by the target.
10419 @item Enabled or Disabled
10420 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10421 that are not enabled.
10423 Where the marker is in your program, as a memory address.
10425 Where the marker is in the source for your program, as a file and line
10426 number. If the debug information included in the program does not
10427 allow @value{GDBN} to locate the source of the marker, this column
10428 will be left blank.
10432 In addition, the following information may be printed for each marker:
10436 User data passed to the tracing library by the marker call. In the
10437 UST backend, this is the format string passed as argument to the
10439 @item Static tracepoints probing the marker
10440 The list of static tracepoints attached to the marker.
10444 (@value{GDBP}) info static-tracepoint-markers
10445 Cnt ID Enb Address What
10446 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10447 Data: number1 %d number2 %d
10448 Probed by static tracepoints: #2
10449 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10455 @node Starting and Stopping Trace Experiments
10456 @subsection Starting and Stopping Trace Experiments
10460 @cindex start a new trace experiment
10461 @cindex collected data discarded
10463 This command takes no arguments. It starts the trace experiment, and
10464 begins collecting data. This has the side effect of discarding all
10465 the data collected in the trace buffer during the previous trace
10469 @cindex stop a running trace experiment
10471 This command takes no arguments. It ends the trace experiment, and
10472 stops collecting data.
10474 @strong{Note}: a trace experiment and data collection may stop
10475 automatically if any tracepoint's passcount is reached
10476 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10479 @cindex status of trace data collection
10480 @cindex trace experiment, status of
10482 This command displays the status of the current trace data
10486 Here is an example of the commands we described so far:
10489 (@value{GDBP}) @b{trace gdb_c_test}
10490 (@value{GDBP}) @b{actions}
10491 Enter actions for tracepoint #1, one per line.
10492 > collect $regs,$locals,$args
10493 > while-stepping 11
10497 (@value{GDBP}) @b{tstart}
10498 [time passes @dots{}]
10499 (@value{GDBP}) @b{tstop}
10502 @anchor{disconnected tracing}
10503 @cindex disconnected tracing
10504 You can choose to continue running the trace experiment even if
10505 @value{GDBN} disconnects from the target, voluntarily or
10506 involuntarily. For commands such as @code{detach}, the debugger will
10507 ask what you want to do with the trace. But for unexpected
10508 terminations (@value{GDBN} crash, network outage), it would be
10509 unfortunate to lose hard-won trace data, so the variable
10510 @code{disconnected-tracing} lets you decide whether the trace should
10511 continue running without @value{GDBN}.
10514 @item set disconnected-tracing on
10515 @itemx set disconnected-tracing off
10516 @kindex set disconnected-tracing
10517 Choose whether a tracing run should continue to run if @value{GDBN}
10518 has disconnected from the target. Note that @code{detach} or
10519 @code{quit} will ask you directly what to do about a running trace no
10520 matter what this variable's setting, so the variable is mainly useful
10521 for handling unexpected situations, such as loss of the network.
10523 @item show disconnected-tracing
10524 @kindex show disconnected-tracing
10525 Show the current choice for disconnected tracing.
10529 When you reconnect to the target, the trace experiment may or may not
10530 still be running; it might have filled the trace buffer in the
10531 meantime, or stopped for one of the other reasons. If it is running,
10532 it will continue after reconnection.
10534 Upon reconnection, the target will upload information about the
10535 tracepoints in effect. @value{GDBN} will then compare that
10536 information to the set of tracepoints currently defined, and attempt
10537 to match them up, allowing for the possibility that the numbers may
10538 have changed due to creation and deletion in the meantime. If one of
10539 the target's tracepoints does not match any in @value{GDBN}, the
10540 debugger will create a new tracepoint, so that you have a number with
10541 which to specify that tracepoint. This matching-up process is
10542 necessarily heuristic, and it may result in useless tracepoints being
10543 created; you may simply delete them if they are of no use.
10545 @cindex circular trace buffer
10546 If your target agent supports a @dfn{circular trace buffer}, then you
10547 can run a trace experiment indefinitely without filling the trace
10548 buffer; when space runs out, the agent deletes already-collected trace
10549 frames, oldest first, until there is enough room to continue
10550 collecting. This is especially useful if your tracepoints are being
10551 hit too often, and your trace gets terminated prematurely because the
10552 buffer is full. To ask for a circular trace buffer, simply set
10553 @samp{circular-trace-buffer} to on. You can set this at any time,
10554 including during tracing; if the agent can do it, it will change
10555 buffer handling on the fly, otherwise it will not take effect until
10559 @item set circular-trace-buffer on
10560 @itemx set circular-trace-buffer off
10561 @kindex set circular-trace-buffer
10562 Choose whether a tracing run should use a linear or circular buffer
10563 for trace data. A linear buffer will not lose any trace data, but may
10564 fill up prematurely, while a circular buffer will discard old trace
10565 data, but it will have always room for the latest tracepoint hits.
10567 @item show circular-trace-buffer
10568 @kindex show circular-trace-buffer
10569 Show the current choice for the trace buffer. Note that this may not
10570 match the agent's current buffer handling, nor is it guaranteed to
10571 match the setting that might have been in effect during a past run,
10572 for instance if you are looking at frames from a trace file.
10576 @node Tracepoint Restrictions
10577 @subsection Tracepoint Restrictions
10579 @cindex tracepoint restrictions
10580 There are a number of restrictions on the use of tracepoints. As
10581 described above, tracepoint data gathering occurs on the target
10582 without interaction from @value{GDBN}. Thus the full capabilities of
10583 the debugger are not available during data gathering, and then at data
10584 examination time, you will be limited by only having what was
10585 collected. The following items describe some common problems, but it
10586 is not exhaustive, and you may run into additional difficulties not
10592 Tracepoint expressions are intended to gather objects (lvalues). Thus
10593 the full flexibility of GDB's expression evaluator is not available.
10594 You cannot call functions, cast objects to aggregate types, access
10595 convenience variables or modify values (except by assignment to trace
10596 state variables). Some language features may implicitly call
10597 functions (for instance Objective-C fields with accessors), and therefore
10598 cannot be collected either.
10601 Collection of local variables, either individually or in bulk with
10602 @code{$locals} or @code{$args}, during @code{while-stepping} may
10603 behave erratically. The stepping action may enter a new scope (for
10604 instance by stepping into a function), or the location of the variable
10605 may change (for instance it is loaded into a register). The
10606 tracepoint data recorded uses the location information for the
10607 variables that is correct for the tracepoint location. When the
10608 tracepoint is created, it is not possible, in general, to determine
10609 where the steps of a @code{while-stepping} sequence will advance the
10610 program---particularly if a conditional branch is stepped.
10613 Collection of an incompletely-initialized or partially-destroyed object
10614 may result in something that @value{GDBN} cannot display, or displays
10615 in a misleading way.
10618 When @value{GDBN} displays a pointer to character it automatically
10619 dereferences the pointer to also display characters of the string
10620 being pointed to. However, collecting the pointer during tracing does
10621 not automatically collect the string. You need to explicitly
10622 dereference the pointer and provide size information if you want to
10623 collect not only the pointer, but the memory pointed to. For example,
10624 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10628 It is not possible to collect a complete stack backtrace at a
10629 tracepoint. Instead, you may collect the registers and a few hundred
10630 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
10631 (adjust to use the name of the actual stack pointer register on your
10632 target architecture, and the amount of stack you wish to capture).
10633 Then the @code{backtrace} command will show a partial backtrace when
10634 using a trace frame. The number of stack frames that can be examined
10635 depends on the sizes of the frames in the collected stack. Note that
10636 if you ask for a block so large that it goes past the bottom of the
10637 stack, the target agent may report an error trying to read from an
10641 If you do not collect registers at a tracepoint, @value{GDBN} can
10642 infer that the value of @code{$pc} must be the same as the address of
10643 the tracepoint and use that when you are looking at a trace frame
10644 for that tracepoint. However, this cannot work if the tracepoint has
10645 multiple locations (for instance if it was set in a function that was
10646 inlined), or if it has a @code{while-stepping} loop. In those cases
10647 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10652 @node Analyze Collected Data
10653 @section Using the Collected Data
10655 After the tracepoint experiment ends, you use @value{GDBN} commands
10656 for examining the trace data. The basic idea is that each tracepoint
10657 collects a trace @dfn{snapshot} every time it is hit and another
10658 snapshot every time it single-steps. All these snapshots are
10659 consecutively numbered from zero and go into a buffer, and you can
10660 examine them later. The way you examine them is to @dfn{focus} on a
10661 specific trace snapshot. When the remote stub is focused on a trace
10662 snapshot, it will respond to all @value{GDBN} requests for memory and
10663 registers by reading from the buffer which belongs to that snapshot,
10664 rather than from @emph{real} memory or registers of the program being
10665 debugged. This means that @strong{all} @value{GDBN} commands
10666 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10667 behave as if we were currently debugging the program state as it was
10668 when the tracepoint occurred. Any requests for data that are not in
10669 the buffer will fail.
10672 * tfind:: How to select a trace snapshot
10673 * tdump:: How to display all data for a snapshot
10674 * save tracepoints:: How to save tracepoints for a future run
10678 @subsection @code{tfind @var{n}}
10681 @cindex select trace snapshot
10682 @cindex find trace snapshot
10683 The basic command for selecting a trace snapshot from the buffer is
10684 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10685 counting from zero. If no argument @var{n} is given, the next
10686 snapshot is selected.
10688 Here are the various forms of using the @code{tfind} command.
10692 Find the first snapshot in the buffer. This is a synonym for
10693 @code{tfind 0} (since 0 is the number of the first snapshot).
10696 Stop debugging trace snapshots, resume @emph{live} debugging.
10699 Same as @samp{tfind none}.
10702 No argument means find the next trace snapshot.
10705 Find the previous trace snapshot before the current one. This permits
10706 retracing earlier steps.
10708 @item tfind tracepoint @var{num}
10709 Find the next snapshot associated with tracepoint @var{num}. Search
10710 proceeds forward from the last examined trace snapshot. If no
10711 argument @var{num} is given, it means find the next snapshot collected
10712 for the same tracepoint as the current snapshot.
10714 @item tfind pc @var{addr}
10715 Find the next snapshot associated with the value @var{addr} of the
10716 program counter. Search proceeds forward from the last examined trace
10717 snapshot. If no argument @var{addr} is given, it means find the next
10718 snapshot with the same value of PC as the current snapshot.
10720 @item tfind outside @var{addr1}, @var{addr2}
10721 Find the next snapshot whose PC is outside the given range of
10722 addresses (exclusive).
10724 @item tfind range @var{addr1}, @var{addr2}
10725 Find the next snapshot whose PC is between @var{addr1} and
10726 @var{addr2} (inclusive).
10728 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10729 Find the next snapshot associated with the source line @var{n}. If
10730 the optional argument @var{file} is given, refer to line @var{n} in
10731 that source file. Search proceeds forward from the last examined
10732 trace snapshot. If no argument @var{n} is given, it means find the
10733 next line other than the one currently being examined; thus saying
10734 @code{tfind line} repeatedly can appear to have the same effect as
10735 stepping from line to line in a @emph{live} debugging session.
10738 The default arguments for the @code{tfind} commands are specifically
10739 designed to make it easy to scan through the trace buffer. For
10740 instance, @code{tfind} with no argument selects the next trace
10741 snapshot, and @code{tfind -} with no argument selects the previous
10742 trace snapshot. So, by giving one @code{tfind} command, and then
10743 simply hitting @key{RET} repeatedly you can examine all the trace
10744 snapshots in order. Or, by saying @code{tfind -} and then hitting
10745 @key{RET} repeatedly you can examine the snapshots in reverse order.
10746 The @code{tfind line} command with no argument selects the snapshot
10747 for the next source line executed. The @code{tfind pc} command with
10748 no argument selects the next snapshot with the same program counter
10749 (PC) as the current frame. The @code{tfind tracepoint} command with
10750 no argument selects the next trace snapshot collected by the same
10751 tracepoint as the current one.
10753 In addition to letting you scan through the trace buffer manually,
10754 these commands make it easy to construct @value{GDBN} scripts that
10755 scan through the trace buffer and print out whatever collected data
10756 you are interested in. Thus, if we want to examine the PC, FP, and SP
10757 registers from each trace frame in the buffer, we can say this:
10760 (@value{GDBP}) @b{tfind start}
10761 (@value{GDBP}) @b{while ($trace_frame != -1)}
10762 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10763 $trace_frame, $pc, $sp, $fp
10767 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10768 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10769 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10770 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10771 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10772 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10773 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10774 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10775 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10776 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10777 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10780 Or, if we want to examine the variable @code{X} at each source line in
10784 (@value{GDBP}) @b{tfind start}
10785 (@value{GDBP}) @b{while ($trace_frame != -1)}
10786 > printf "Frame %d, X == %d\n", $trace_frame, X
10796 @subsection @code{tdump}
10798 @cindex dump all data collected at tracepoint
10799 @cindex tracepoint data, display
10801 This command takes no arguments. It prints all the data collected at
10802 the current trace snapshot.
10805 (@value{GDBP}) @b{trace 444}
10806 (@value{GDBP}) @b{actions}
10807 Enter actions for tracepoint #2, one per line:
10808 > collect $regs, $locals, $args, gdb_long_test
10811 (@value{GDBP}) @b{tstart}
10813 (@value{GDBP}) @b{tfind line 444}
10814 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10816 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10818 (@value{GDBP}) @b{tdump}
10819 Data collected at tracepoint 2, trace frame 1:
10820 d0 0xc4aa0085 -995491707
10824 d4 0x71aea3d 119204413
10827 d7 0x380035 3670069
10828 a0 0x19e24a 1696330
10829 a1 0x3000668 50333288
10831 a3 0x322000 3284992
10832 a4 0x3000698 50333336
10833 a5 0x1ad3cc 1758156
10834 fp 0x30bf3c 0x30bf3c
10835 sp 0x30bf34 0x30bf34
10837 pc 0x20b2c8 0x20b2c8
10841 p = 0x20e5b4 "gdb-test"
10848 gdb_long_test = 17 '\021'
10853 @code{tdump} works by scanning the tracepoint's current collection
10854 actions and printing the value of each expression listed. So
10855 @code{tdump} can fail, if after a run, you change the tracepoint's
10856 actions to mention variables that were not collected during the run.
10858 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10859 uses the collected value of @code{$pc} to distinguish between trace
10860 frames that were collected at the tracepoint hit, and frames that were
10861 collected while stepping. This allows it to correctly choose whether
10862 to display the basic list of collections, or the collections from the
10863 body of the while-stepping loop. However, if @code{$pc} was not collected,
10864 then @code{tdump} will always attempt to dump using the basic collection
10865 list, and may fail if a while-stepping frame does not include all the
10866 same data that is collected at the tracepoint hit.
10867 @c This is getting pretty arcane, example would be good.
10869 @node save tracepoints
10870 @subsection @code{save tracepoints @var{filename}}
10871 @kindex save tracepoints
10872 @kindex save-tracepoints
10873 @cindex save tracepoints for future sessions
10875 This command saves all current tracepoint definitions together with
10876 their actions and passcounts, into a file @file{@var{filename}}
10877 suitable for use in a later debugging session. To read the saved
10878 tracepoint definitions, use the @code{source} command (@pxref{Command
10879 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10880 alias for @w{@code{save tracepoints}}
10882 @node Tracepoint Variables
10883 @section Convenience Variables for Tracepoints
10884 @cindex tracepoint variables
10885 @cindex convenience variables for tracepoints
10888 @vindex $trace_frame
10889 @item (int) $trace_frame
10890 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10891 snapshot is selected.
10893 @vindex $tracepoint
10894 @item (int) $tracepoint
10895 The tracepoint for the current trace snapshot.
10897 @vindex $trace_line
10898 @item (int) $trace_line
10899 The line number for the current trace snapshot.
10901 @vindex $trace_file
10902 @item (char []) $trace_file
10903 The source file for the current trace snapshot.
10905 @vindex $trace_func
10906 @item (char []) $trace_func
10907 The name of the function containing @code{$tracepoint}.
10910 Note: @code{$trace_file} is not suitable for use in @code{printf},
10911 use @code{output} instead.
10913 Here's a simple example of using these convenience variables for
10914 stepping through all the trace snapshots and printing some of their
10915 data. Note that these are not the same as trace state variables,
10916 which are managed by the target.
10919 (@value{GDBP}) @b{tfind start}
10921 (@value{GDBP}) @b{while $trace_frame != -1}
10922 > output $trace_file
10923 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10929 @section Using Trace Files
10930 @cindex trace files
10932 In some situations, the target running a trace experiment may no
10933 longer be available; perhaps it crashed, or the hardware was needed
10934 for a different activity. To handle these cases, you can arrange to
10935 dump the trace data into a file, and later use that file as a source
10936 of trace data, via the @code{target tfile} command.
10941 @item tsave [ -r ] @var{filename}
10942 Save the trace data to @var{filename}. By default, this command
10943 assumes that @var{filename} refers to the host filesystem, so if
10944 necessary @value{GDBN} will copy raw trace data up from the target and
10945 then save it. If the target supports it, you can also supply the
10946 optional argument @code{-r} (``remote'') to direct the target to save
10947 the data directly into @var{filename} in its own filesystem, which may be
10948 more efficient if the trace buffer is very large. (Note, however, that
10949 @code{target tfile} can only read from files accessible to the host.)
10951 @kindex target tfile
10953 @item target tfile @var{filename}
10954 Use the file named @var{filename} as a source of trace data. Commands
10955 that examine data work as they do with a live target, but it is not
10956 possible to run any new trace experiments. @code{tstatus} will report
10957 the state of the trace run at the moment the data was saved, as well
10958 as the current trace frame you are examining. @var{filename} must be
10959 on a filesystem accessible to the host.
10964 @chapter Debugging Programs That Use Overlays
10967 If your program is too large to fit completely in your target system's
10968 memory, you can sometimes use @dfn{overlays} to work around this
10969 problem. @value{GDBN} provides some support for debugging programs that
10973 * How Overlays Work:: A general explanation of overlays.
10974 * Overlay Commands:: Managing overlays in @value{GDBN}.
10975 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10976 mapped by asking the inferior.
10977 * Overlay Sample Program:: A sample program using overlays.
10980 @node How Overlays Work
10981 @section How Overlays Work
10982 @cindex mapped overlays
10983 @cindex unmapped overlays
10984 @cindex load address, overlay's
10985 @cindex mapped address
10986 @cindex overlay area
10988 Suppose you have a computer whose instruction address space is only 64
10989 kilobytes long, but which has much more memory which can be accessed by
10990 other means: special instructions, segment registers, or memory
10991 management hardware, for example. Suppose further that you want to
10992 adapt a program which is larger than 64 kilobytes to run on this system.
10994 One solution is to identify modules of your program which are relatively
10995 independent, and need not call each other directly; call these modules
10996 @dfn{overlays}. Separate the overlays from the main program, and place
10997 their machine code in the larger memory. Place your main program in
10998 instruction memory, but leave at least enough space there to hold the
10999 largest overlay as well.
11001 Now, to call a function located in an overlay, you must first copy that
11002 overlay's machine code from the large memory into the space set aside
11003 for it in the instruction memory, and then jump to its entry point
11006 @c NB: In the below the mapped area's size is greater or equal to the
11007 @c size of all overlays. This is intentional to remind the developer
11008 @c that overlays don't necessarily need to be the same size.
11012 Data Instruction Larger
11013 Address Space Address Space Address Space
11014 +-----------+ +-----------+ +-----------+
11016 +-----------+ +-----------+ +-----------+<-- overlay 1
11017 | program | | main | .----| overlay 1 | load address
11018 | variables | | program | | +-----------+
11019 | and heap | | | | | |
11020 +-----------+ | | | +-----------+<-- overlay 2
11021 | | +-----------+ | | | load address
11022 +-----------+ | | | .-| overlay 2 |
11024 mapped --->+-----------+ | | +-----------+
11025 address | | | | | |
11026 | overlay | <-' | | |
11027 | area | <---' +-----------+<-- overlay 3
11028 | | <---. | | load address
11029 +-----------+ `--| overlay 3 |
11036 @anchor{A code overlay}A code overlay
11040 The diagram (@pxref{A code overlay}) shows a system with separate data
11041 and instruction address spaces. To map an overlay, the program copies
11042 its code from the larger address space to the instruction address space.
11043 Since the overlays shown here all use the same mapped address, only one
11044 may be mapped at a time. For a system with a single address space for
11045 data and instructions, the diagram would be similar, except that the
11046 program variables and heap would share an address space with the main
11047 program and the overlay area.
11049 An overlay loaded into instruction memory and ready for use is called a
11050 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11051 instruction memory. An overlay not present (or only partially present)
11052 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11053 is its address in the larger memory. The mapped address is also called
11054 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11055 called the @dfn{load memory address}, or @dfn{LMA}.
11057 Unfortunately, overlays are not a completely transparent way to adapt a
11058 program to limited instruction memory. They introduce a new set of
11059 global constraints you must keep in mind as you design your program:
11064 Before calling or returning to a function in an overlay, your program
11065 must make sure that overlay is actually mapped. Otherwise, the call or
11066 return will transfer control to the right address, but in the wrong
11067 overlay, and your program will probably crash.
11070 If the process of mapping an overlay is expensive on your system, you
11071 will need to choose your overlays carefully to minimize their effect on
11072 your program's performance.
11075 The executable file you load onto your system must contain each
11076 overlay's instructions, appearing at the overlay's load address, not its
11077 mapped address. However, each overlay's instructions must be relocated
11078 and its symbols defined as if the overlay were at its mapped address.
11079 You can use GNU linker scripts to specify different load and relocation
11080 addresses for pieces of your program; see @ref{Overlay Description,,,
11081 ld.info, Using ld: the GNU linker}.
11084 The procedure for loading executable files onto your system must be able
11085 to load their contents into the larger address space as well as the
11086 instruction and data spaces.
11090 The overlay system described above is rather simple, and could be
11091 improved in many ways:
11096 If your system has suitable bank switch registers or memory management
11097 hardware, you could use those facilities to make an overlay's load area
11098 contents simply appear at their mapped address in instruction space.
11099 This would probably be faster than copying the overlay to its mapped
11100 area in the usual way.
11103 If your overlays are small enough, you could set aside more than one
11104 overlay area, and have more than one overlay mapped at a time.
11107 You can use overlays to manage data, as well as instructions. In
11108 general, data overlays are even less transparent to your design than
11109 code overlays: whereas code overlays only require care when you call or
11110 return to functions, data overlays require care every time you access
11111 the data. Also, if you change the contents of a data overlay, you
11112 must copy its contents back out to its load address before you can copy a
11113 different data overlay into the same mapped area.
11118 @node Overlay Commands
11119 @section Overlay Commands
11121 To use @value{GDBN}'s overlay support, each overlay in your program must
11122 correspond to a separate section of the executable file. The section's
11123 virtual memory address and load memory address must be the overlay's
11124 mapped and load addresses. Identifying overlays with sections allows
11125 @value{GDBN} to determine the appropriate address of a function or
11126 variable, depending on whether the overlay is mapped or not.
11128 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11129 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11134 Disable @value{GDBN}'s overlay support. When overlay support is
11135 disabled, @value{GDBN} assumes that all functions and variables are
11136 always present at their mapped addresses. By default, @value{GDBN}'s
11137 overlay support is disabled.
11139 @item overlay manual
11140 @cindex manual overlay debugging
11141 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11142 relies on you to tell it which overlays are mapped, and which are not,
11143 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11144 commands described below.
11146 @item overlay map-overlay @var{overlay}
11147 @itemx overlay map @var{overlay}
11148 @cindex map an overlay
11149 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11150 be the name of the object file section containing the overlay. When an
11151 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11152 functions and variables at their mapped addresses. @value{GDBN} assumes
11153 that any other overlays whose mapped ranges overlap that of
11154 @var{overlay} are now unmapped.
11156 @item overlay unmap-overlay @var{overlay}
11157 @itemx overlay unmap @var{overlay}
11158 @cindex unmap an overlay
11159 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11160 must be the name of the object file section containing the overlay.
11161 When an overlay is unmapped, @value{GDBN} assumes it can find the
11162 overlay's functions and variables at their load addresses.
11165 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11166 consults a data structure the overlay manager maintains in the inferior
11167 to see which overlays are mapped. For details, see @ref{Automatic
11168 Overlay Debugging}.
11170 @item overlay load-target
11171 @itemx overlay load
11172 @cindex reloading the overlay table
11173 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11174 re-reads the table @value{GDBN} automatically each time the inferior
11175 stops, so this command should only be necessary if you have changed the
11176 overlay mapping yourself using @value{GDBN}. This command is only
11177 useful when using automatic overlay debugging.
11179 @item overlay list-overlays
11180 @itemx overlay list
11181 @cindex listing mapped overlays
11182 Display a list of the overlays currently mapped, along with their mapped
11183 addresses, load addresses, and sizes.
11187 Normally, when @value{GDBN} prints a code address, it includes the name
11188 of the function the address falls in:
11191 (@value{GDBP}) print main
11192 $3 = @{int ()@} 0x11a0 <main>
11195 When overlay debugging is enabled, @value{GDBN} recognizes code in
11196 unmapped overlays, and prints the names of unmapped functions with
11197 asterisks around them. For example, if @code{foo} is a function in an
11198 unmapped overlay, @value{GDBN} prints it this way:
11201 (@value{GDBP}) overlay list
11202 No sections are mapped.
11203 (@value{GDBP}) print foo
11204 $5 = @{int (int)@} 0x100000 <*foo*>
11207 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11211 (@value{GDBP}) overlay list
11212 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11213 mapped at 0x1016 - 0x104a
11214 (@value{GDBP}) print foo
11215 $6 = @{int (int)@} 0x1016 <foo>
11218 When overlay debugging is enabled, @value{GDBN} can find the correct
11219 address for functions and variables in an overlay, whether or not the
11220 overlay is mapped. This allows most @value{GDBN} commands, like
11221 @code{break} and @code{disassemble}, to work normally, even on unmapped
11222 code. However, @value{GDBN}'s breakpoint support has some limitations:
11226 @cindex breakpoints in overlays
11227 @cindex overlays, setting breakpoints in
11228 You can set breakpoints in functions in unmapped overlays, as long as
11229 @value{GDBN} can write to the overlay at its load address.
11231 @value{GDBN} can not set hardware or simulator-based breakpoints in
11232 unmapped overlays. However, if you set a breakpoint at the end of your
11233 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11234 you are using manual overlay management), @value{GDBN} will re-set its
11235 breakpoints properly.
11239 @node Automatic Overlay Debugging
11240 @section Automatic Overlay Debugging
11241 @cindex automatic overlay debugging
11243 @value{GDBN} can automatically track which overlays are mapped and which
11244 are not, given some simple co-operation from the overlay manager in the
11245 inferior. If you enable automatic overlay debugging with the
11246 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11247 looks in the inferior's memory for certain variables describing the
11248 current state of the overlays.
11250 Here are the variables your overlay manager must define to support
11251 @value{GDBN}'s automatic overlay debugging:
11255 @item @code{_ovly_table}:
11256 This variable must be an array of the following structures:
11261 /* The overlay's mapped address. */
11264 /* The size of the overlay, in bytes. */
11265 unsigned long size;
11267 /* The overlay's load address. */
11270 /* Non-zero if the overlay is currently mapped;
11272 unsigned long mapped;
11276 @item @code{_novlys}:
11277 This variable must be a four-byte signed integer, holding the total
11278 number of elements in @code{_ovly_table}.
11282 To decide whether a particular overlay is mapped or not, @value{GDBN}
11283 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11284 @code{lma} members equal the VMA and LMA of the overlay's section in the
11285 executable file. When @value{GDBN} finds a matching entry, it consults
11286 the entry's @code{mapped} member to determine whether the overlay is
11289 In addition, your overlay manager may define a function called
11290 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11291 will silently set a breakpoint there. If the overlay manager then
11292 calls this function whenever it has changed the overlay table, this
11293 will enable @value{GDBN} to accurately keep track of which overlays
11294 are in program memory, and update any breakpoints that may be set
11295 in overlays. This will allow breakpoints to work even if the
11296 overlays are kept in ROM or other non-writable memory while they
11297 are not being executed.
11299 @node Overlay Sample Program
11300 @section Overlay Sample Program
11301 @cindex overlay example program
11303 When linking a program which uses overlays, you must place the overlays
11304 at their load addresses, while relocating them to run at their mapped
11305 addresses. To do this, you must write a linker script (@pxref{Overlay
11306 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11307 since linker scripts are specific to a particular host system, target
11308 architecture, and target memory layout, this manual cannot provide
11309 portable sample code demonstrating @value{GDBN}'s overlay support.
11311 However, the @value{GDBN} source distribution does contain an overlaid
11312 program, with linker scripts for a few systems, as part of its test
11313 suite. The program consists of the following files from
11314 @file{gdb/testsuite/gdb.base}:
11318 The main program file.
11320 A simple overlay manager, used by @file{overlays.c}.
11325 Overlay modules, loaded and used by @file{overlays.c}.
11328 Linker scripts for linking the test program on the @code{d10v-elf}
11329 and @code{m32r-elf} targets.
11332 You can build the test program using the @code{d10v-elf} GCC
11333 cross-compiler like this:
11336 $ d10v-elf-gcc -g -c overlays.c
11337 $ d10v-elf-gcc -g -c ovlymgr.c
11338 $ d10v-elf-gcc -g -c foo.c
11339 $ d10v-elf-gcc -g -c bar.c
11340 $ d10v-elf-gcc -g -c baz.c
11341 $ d10v-elf-gcc -g -c grbx.c
11342 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11343 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11346 The build process is identical for any other architecture, except that
11347 you must substitute the appropriate compiler and linker script for the
11348 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11352 @chapter Using @value{GDBN} with Different Languages
11355 Although programming languages generally have common aspects, they are
11356 rarely expressed in the same manner. For instance, in ANSI C,
11357 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11358 Modula-2, it is accomplished by @code{p^}. Values can also be
11359 represented (and displayed) differently. Hex numbers in C appear as
11360 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11362 @cindex working language
11363 Language-specific information is built into @value{GDBN} for some languages,
11364 allowing you to express operations like the above in your program's
11365 native language, and allowing @value{GDBN} to output values in a manner
11366 consistent with the syntax of your program's native language. The
11367 language you use to build expressions is called the @dfn{working
11371 * Setting:: Switching between source languages
11372 * Show:: Displaying the language
11373 * Checks:: Type and range checks
11374 * Supported Languages:: Supported languages
11375 * Unsupported Languages:: Unsupported languages
11379 @section Switching Between Source Languages
11381 There are two ways to control the working language---either have @value{GDBN}
11382 set it automatically, or select it manually yourself. You can use the
11383 @code{set language} command for either purpose. On startup, @value{GDBN}
11384 defaults to setting the language automatically. The working language is
11385 used to determine how expressions you type are interpreted, how values
11388 In addition to the working language, every source file that
11389 @value{GDBN} knows about has its own working language. For some object
11390 file formats, the compiler might indicate which language a particular
11391 source file is in. However, most of the time @value{GDBN} infers the
11392 language from the name of the file. The language of a source file
11393 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11394 show each frame appropriately for its own language. There is no way to
11395 set the language of a source file from within @value{GDBN}, but you can
11396 set the language associated with a filename extension. @xref{Show, ,
11397 Displaying the Language}.
11399 This is most commonly a problem when you use a program, such
11400 as @code{cfront} or @code{f2c}, that generates C but is written in
11401 another language. In that case, make the
11402 program use @code{#line} directives in its C output; that way
11403 @value{GDBN} will know the correct language of the source code of the original
11404 program, and will display that source code, not the generated C code.
11407 * Filenames:: Filename extensions and languages.
11408 * Manually:: Setting the working language manually
11409 * Automatically:: Having @value{GDBN} infer the source language
11413 @subsection List of Filename Extensions and Languages
11415 If a source file name ends in one of the following extensions, then
11416 @value{GDBN} infers that its language is the one indicated.
11434 C@t{++} source file
11440 Objective-C source file
11444 Fortran source file
11447 Modula-2 source file
11451 Assembler source file. This actually behaves almost like C, but
11452 @value{GDBN} does not skip over function prologues when stepping.
11455 In addition, you may set the language associated with a filename
11456 extension. @xref{Show, , Displaying the Language}.
11459 @subsection Setting the Working Language
11461 If you allow @value{GDBN} to set the language automatically,
11462 expressions are interpreted the same way in your debugging session and
11465 @kindex set language
11466 If you wish, you may set the language manually. To do this, issue the
11467 command @samp{set language @var{lang}}, where @var{lang} is the name of
11468 a language, such as
11469 @code{c} or @code{modula-2}.
11470 For a list of the supported languages, type @samp{set language}.
11472 Setting the language manually prevents @value{GDBN} from updating the working
11473 language automatically. This can lead to confusion if you try
11474 to debug a program when the working language is not the same as the
11475 source language, when an expression is acceptable to both
11476 languages---but means different things. For instance, if the current
11477 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11485 might not have the effect you intended. In C, this means to add
11486 @code{b} and @code{c} and place the result in @code{a}. The result
11487 printed would be the value of @code{a}. In Modula-2, this means to compare
11488 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11490 @node Automatically
11491 @subsection Having @value{GDBN} Infer the Source Language
11493 To have @value{GDBN} set the working language automatically, use
11494 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11495 then infers the working language. That is, when your program stops in a
11496 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11497 working language to the language recorded for the function in that
11498 frame. If the language for a frame is unknown (that is, if the function
11499 or block corresponding to the frame was defined in a source file that
11500 does not have a recognized extension), the current working language is
11501 not changed, and @value{GDBN} issues a warning.
11503 This may not seem necessary for most programs, which are written
11504 entirely in one source language. However, program modules and libraries
11505 written in one source language can be used by a main program written in
11506 a different source language. Using @samp{set language auto} in this
11507 case frees you from having to set the working language manually.
11510 @section Displaying the Language
11512 The following commands help you find out which language is the
11513 working language, and also what language source files were written in.
11516 @item show language
11517 @kindex show language
11518 Display the current working language. This is the
11519 language you can use with commands such as @code{print} to
11520 build and compute expressions that may involve variables in your program.
11523 @kindex info frame@r{, show the source language}
11524 Display the source language for this frame. This language becomes the
11525 working language if you use an identifier from this frame.
11526 @xref{Frame Info, ,Information about a Frame}, to identify the other
11527 information listed here.
11530 @kindex info source@r{, show the source language}
11531 Display the source language of this source file.
11532 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11533 information listed here.
11536 In unusual circumstances, you may have source files with extensions
11537 not in the standard list. You can then set the extension associated
11538 with a language explicitly:
11541 @item set extension-language @var{ext} @var{language}
11542 @kindex set extension-language
11543 Tell @value{GDBN} that source files with extension @var{ext} are to be
11544 assumed as written in the source language @var{language}.
11546 @item info extensions
11547 @kindex info extensions
11548 List all the filename extensions and the associated languages.
11552 @section Type and Range Checking
11555 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11556 checking are included, but they do not yet have any effect. This
11557 section documents the intended facilities.
11559 @c FIXME remove warning when type/range code added
11561 Some languages are designed to guard you against making seemingly common
11562 errors through a series of compile- and run-time checks. These include
11563 checking the type of arguments to functions and operators, and making
11564 sure mathematical overflows are caught at run time. Checks such as
11565 these help to ensure a program's correctness once it has been compiled
11566 by eliminating type mismatches, and providing active checks for range
11567 errors when your program is running.
11569 @value{GDBN} can check for conditions like the above if you wish.
11570 Although @value{GDBN} does not check the statements in your program,
11571 it can check expressions entered directly into @value{GDBN} for
11572 evaluation via the @code{print} command, for example. As with the
11573 working language, @value{GDBN} can also decide whether or not to check
11574 automatically based on your program's source language.
11575 @xref{Supported Languages, ,Supported Languages}, for the default
11576 settings of supported languages.
11579 * Type Checking:: An overview of type checking
11580 * Range Checking:: An overview of range checking
11583 @cindex type checking
11584 @cindex checks, type
11585 @node Type Checking
11586 @subsection An Overview of Type Checking
11588 Some languages, such as Modula-2, are strongly typed, meaning that the
11589 arguments to operators and functions have to be of the correct type,
11590 otherwise an error occurs. These checks prevent type mismatch
11591 errors from ever causing any run-time problems. For example,
11599 The second example fails because the @code{CARDINAL} 1 is not
11600 type-compatible with the @code{REAL} 2.3.
11602 For the expressions you use in @value{GDBN} commands, you can tell the
11603 @value{GDBN} type checker to skip checking;
11604 to treat any mismatches as errors and abandon the expression;
11605 or to only issue warnings when type mismatches occur,
11606 but evaluate the expression anyway. When you choose the last of
11607 these, @value{GDBN} evaluates expressions like the second example above, but
11608 also issues a warning.
11610 Even if you turn type checking off, there may be other reasons
11611 related to type that prevent @value{GDBN} from evaluating an expression.
11612 For instance, @value{GDBN} does not know how to add an @code{int} and
11613 a @code{struct foo}. These particular type errors have nothing to do
11614 with the language in use, and usually arise from expressions, such as
11615 the one described above, which make little sense to evaluate anyway.
11617 Each language defines to what degree it is strict about type. For
11618 instance, both Modula-2 and C require the arguments to arithmetical
11619 operators to be numbers. In C, enumerated types and pointers can be
11620 represented as numbers, so that they are valid arguments to mathematical
11621 operators. @xref{Supported Languages, ,Supported Languages}, for further
11622 details on specific languages.
11624 @value{GDBN} provides some additional commands for controlling the type checker:
11626 @kindex set check type
11627 @kindex show check type
11629 @item set check type auto
11630 Set type checking on or off based on the current working language.
11631 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11634 @item set check type on
11635 @itemx set check type off
11636 Set type checking on or off, overriding the default setting for the
11637 current working language. Issue a warning if the setting does not
11638 match the language default. If any type mismatches occur in
11639 evaluating an expression while type checking is on, @value{GDBN} prints a
11640 message and aborts evaluation of the expression.
11642 @item set check type warn
11643 Cause the type checker to issue warnings, but to always attempt to
11644 evaluate the expression. Evaluating the expression may still
11645 be impossible for other reasons. For example, @value{GDBN} cannot add
11646 numbers and structures.
11649 Show the current setting of the type checker, and whether or not @value{GDBN}
11650 is setting it automatically.
11653 @cindex range checking
11654 @cindex checks, range
11655 @node Range Checking
11656 @subsection An Overview of Range Checking
11658 In some languages (such as Modula-2), it is an error to exceed the
11659 bounds of a type; this is enforced with run-time checks. Such range
11660 checking is meant to ensure program correctness by making sure
11661 computations do not overflow, or indices on an array element access do
11662 not exceed the bounds of the array.
11664 For expressions you use in @value{GDBN} commands, you can tell
11665 @value{GDBN} to treat range errors in one of three ways: ignore them,
11666 always treat them as errors and abandon the expression, or issue
11667 warnings but evaluate the expression anyway.
11669 A range error can result from numerical overflow, from exceeding an
11670 array index bound, or when you type a constant that is not a member
11671 of any type. Some languages, however, do not treat overflows as an
11672 error. In many implementations of C, mathematical overflow causes the
11673 result to ``wrap around'' to lower values---for example, if @var{m} is
11674 the largest integer value, and @var{s} is the smallest, then
11677 @var{m} + 1 @result{} @var{s}
11680 This, too, is specific to individual languages, and in some cases
11681 specific to individual compilers or machines. @xref{Supported Languages, ,
11682 Supported Languages}, for further details on specific languages.
11684 @value{GDBN} provides some additional commands for controlling the range checker:
11686 @kindex set check range
11687 @kindex show check range
11689 @item set check range auto
11690 Set range checking on or off based on the current working language.
11691 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11694 @item set check range on
11695 @itemx set check range off
11696 Set range checking on or off, overriding the default setting for the
11697 current working language. A warning is issued if the setting does not
11698 match the language default. If a range error occurs and range checking is on,
11699 then a message is printed and evaluation of the expression is aborted.
11701 @item set check range warn
11702 Output messages when the @value{GDBN} range checker detects a range error,
11703 but attempt to evaluate the expression anyway. Evaluating the
11704 expression may still be impossible for other reasons, such as accessing
11705 memory that the process does not own (a typical example from many Unix
11709 Show the current setting of the range checker, and whether or not it is
11710 being set automatically by @value{GDBN}.
11713 @node Supported Languages
11714 @section Supported Languages
11716 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
11717 assembly, Modula-2, and Ada.
11718 @c This is false ...
11719 Some @value{GDBN} features may be used in expressions regardless of the
11720 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11721 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11722 ,Expressions}) can be used with the constructs of any supported
11725 The following sections detail to what degree each source language is
11726 supported by @value{GDBN}. These sections are not meant to be language
11727 tutorials or references, but serve only as a reference guide to what the
11728 @value{GDBN} expression parser accepts, and what input and output
11729 formats should look like for different languages. There are many good
11730 books written on each of these languages; please look to these for a
11731 language reference or tutorial.
11734 * C:: C and C@t{++}
11736 * Objective-C:: Objective-C
11737 * OpenCL C:: OpenCL C
11738 * Fortran:: Fortran
11740 * Modula-2:: Modula-2
11745 @subsection C and C@t{++}
11747 @cindex C and C@t{++}
11748 @cindex expressions in C or C@t{++}
11750 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11751 to both languages. Whenever this is the case, we discuss those languages
11755 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11756 @cindex @sc{gnu} C@t{++}
11757 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11758 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11759 effectively, you must compile your C@t{++} programs with a supported
11760 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11761 compiler (@code{aCC}).
11763 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11764 format; if it doesn't work on your system, try the stabs+ debugging
11765 format. You can select those formats explicitly with the @code{g++}
11766 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11767 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11768 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11771 * C Operators:: C and C@t{++} operators
11772 * C Constants:: C and C@t{++} constants
11773 * C Plus Plus Expressions:: C@t{++} expressions
11774 * C Defaults:: Default settings for C and C@t{++}
11775 * C Checks:: C and C@t{++} type and range checks
11776 * Debugging C:: @value{GDBN} and C
11777 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11778 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11782 @subsubsection C and C@t{++} Operators
11784 @cindex C and C@t{++} operators
11786 Operators must be defined on values of specific types. For instance,
11787 @code{+} is defined on numbers, but not on structures. Operators are
11788 often defined on groups of types.
11790 For the purposes of C and C@t{++}, the following definitions hold:
11795 @emph{Integral types} include @code{int} with any of its storage-class
11796 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11799 @emph{Floating-point types} include @code{float}, @code{double}, and
11800 @code{long double} (if supported by the target platform).
11803 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11806 @emph{Scalar types} include all of the above.
11811 The following operators are supported. They are listed here
11812 in order of increasing precedence:
11816 The comma or sequencing operator. Expressions in a comma-separated list
11817 are evaluated from left to right, with the result of the entire
11818 expression being the last expression evaluated.
11821 Assignment. The value of an assignment expression is the value
11822 assigned. Defined on scalar types.
11825 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11826 and translated to @w{@code{@var{a} = @var{a op b}}}.
11827 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11828 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11829 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11832 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11833 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11837 Logical @sc{or}. Defined on integral types.
11840 Logical @sc{and}. Defined on integral types.
11843 Bitwise @sc{or}. Defined on integral types.
11846 Bitwise exclusive-@sc{or}. Defined on integral types.
11849 Bitwise @sc{and}. Defined on integral types.
11852 Equality and inequality. Defined on scalar types. The value of these
11853 expressions is 0 for false and non-zero for true.
11855 @item <@r{, }>@r{, }<=@r{, }>=
11856 Less than, greater than, less than or equal, greater than or equal.
11857 Defined on scalar types. The value of these expressions is 0 for false
11858 and non-zero for true.
11861 left shift, and right shift. Defined on integral types.
11864 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11867 Addition and subtraction. Defined on integral types, floating-point types and
11870 @item *@r{, }/@r{, }%
11871 Multiplication, division, and modulus. Multiplication and division are
11872 defined on integral and floating-point types. Modulus is defined on
11876 Increment and decrement. When appearing before a variable, the
11877 operation is performed before the variable is used in an expression;
11878 when appearing after it, the variable's value is used before the
11879 operation takes place.
11882 Pointer dereferencing. Defined on pointer types. Same precedence as
11886 Address operator. Defined on variables. Same precedence as @code{++}.
11888 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11889 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11890 to examine the address
11891 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11895 Negative. Defined on integral and floating-point types. Same
11896 precedence as @code{++}.
11899 Logical negation. Defined on integral types. Same precedence as
11903 Bitwise complement operator. Defined on integral types. Same precedence as
11908 Structure member, and pointer-to-structure member. For convenience,
11909 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11910 pointer based on the stored type information.
11911 Defined on @code{struct} and @code{union} data.
11914 Dereferences of pointers to members.
11917 Array indexing. @code{@var{a}[@var{i}]} is defined as
11918 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11921 Function parameter list. Same precedence as @code{->}.
11924 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11925 and @code{class} types.
11928 Doubled colons also represent the @value{GDBN} scope operator
11929 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11933 If an operator is redefined in the user code, @value{GDBN} usually
11934 attempts to invoke the redefined version instead of using the operator's
11935 predefined meaning.
11938 @subsubsection C and C@t{++} Constants
11940 @cindex C and C@t{++} constants
11942 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11947 Integer constants are a sequence of digits. Octal constants are
11948 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11949 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11950 @samp{l}, specifying that the constant should be treated as a
11954 Floating point constants are a sequence of digits, followed by a decimal
11955 point, followed by a sequence of digits, and optionally followed by an
11956 exponent. An exponent is of the form:
11957 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11958 sequence of digits. The @samp{+} is optional for positive exponents.
11959 A floating-point constant may also end with a letter @samp{f} or
11960 @samp{F}, specifying that the constant should be treated as being of
11961 the @code{float} (as opposed to the default @code{double}) type; or with
11962 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11966 Enumerated constants consist of enumerated identifiers, or their
11967 integral equivalents.
11970 Character constants are a single character surrounded by single quotes
11971 (@code{'}), or a number---the ordinal value of the corresponding character
11972 (usually its @sc{ascii} value). Within quotes, the single character may
11973 be represented by a letter or by @dfn{escape sequences}, which are of
11974 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11975 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11976 @samp{@var{x}} is a predefined special character---for example,
11977 @samp{\n} for newline.
11980 String constants are a sequence of character constants surrounded by
11981 double quotes (@code{"}). Any valid character constant (as described
11982 above) may appear. Double quotes within the string must be preceded by
11983 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11987 Pointer constants are an integral value. You can also write pointers
11988 to constants using the C operator @samp{&}.
11991 Array constants are comma-separated lists surrounded by braces @samp{@{}
11992 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11993 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11994 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11997 @node C Plus Plus Expressions
11998 @subsubsection C@t{++} Expressions
12000 @cindex expressions in C@t{++}
12001 @value{GDBN} expression handling can interpret most C@t{++} expressions.
12003 @cindex debugging C@t{++} programs
12004 @cindex C@t{++} compilers
12005 @cindex debug formats and C@t{++}
12006 @cindex @value{NGCC} and C@t{++}
12008 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
12009 proper compiler and the proper debug format. Currently, @value{GDBN}
12010 works best when debugging C@t{++} code that is compiled with
12011 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
12012 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
12013 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
12014 stabs+ as their default debug format, so you usually don't need to
12015 specify a debug format explicitly. Other compilers and/or debug formats
12016 are likely to work badly or not at all when using @value{GDBN} to debug
12022 @cindex member functions
12024 Member function calls are allowed; you can use expressions like
12027 count = aml->GetOriginal(x, y)
12030 @vindex this@r{, inside C@t{++} member functions}
12031 @cindex namespace in C@t{++}
12033 While a member function is active (in the selected stack frame), your
12034 expressions have the same namespace available as the member function;
12035 that is, @value{GDBN} allows implicit references to the class instance
12036 pointer @code{this} following the same rules as C@t{++}.
12038 @cindex call overloaded functions
12039 @cindex overloaded functions, calling
12040 @cindex type conversions in C@t{++}
12042 You can call overloaded functions; @value{GDBN} resolves the function
12043 call to the right definition, with some restrictions. @value{GDBN} does not
12044 perform overload resolution involving user-defined type conversions,
12045 calls to constructors, or instantiations of templates that do not exist
12046 in the program. It also cannot handle ellipsis argument lists or
12049 It does perform integral conversions and promotions, floating-point
12050 promotions, arithmetic conversions, pointer conversions, conversions of
12051 class objects to base classes, and standard conversions such as those of
12052 functions or arrays to pointers; it requires an exact match on the
12053 number of function arguments.
12055 Overload resolution is always performed, unless you have specified
12056 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12057 ,@value{GDBN} Features for C@t{++}}.
12059 You must specify @code{set overload-resolution off} in order to use an
12060 explicit function signature to call an overloaded function, as in
12062 p 'foo(char,int)'('x', 13)
12065 The @value{GDBN} command-completion facility can simplify this;
12066 see @ref{Completion, ,Command Completion}.
12068 @cindex reference declarations
12070 @value{GDBN} understands variables declared as C@t{++} references; you can use
12071 them in expressions just as you do in C@t{++} source---they are automatically
12074 In the parameter list shown when @value{GDBN} displays a frame, the values of
12075 reference variables are not displayed (unlike other variables); this
12076 avoids clutter, since references are often used for large structures.
12077 The @emph{address} of a reference variable is always shown, unless
12078 you have specified @samp{set print address off}.
12081 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12082 expressions can use it just as expressions in your program do. Since
12083 one scope may be defined in another, you can use @code{::} repeatedly if
12084 necessary, for example in an expression like
12085 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12086 resolving name scope by reference to source files, in both C and C@t{++}
12087 debugging (@pxref{Variables, ,Program Variables}).
12090 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
12091 calling virtual functions correctly, printing out virtual bases of
12092 objects, calling functions in a base subobject, casting objects, and
12093 invoking user-defined operators.
12096 @subsubsection C and C@t{++} Defaults
12098 @cindex C and C@t{++} defaults
12100 If you allow @value{GDBN} to set type and range checking automatically, they
12101 both default to @code{off} whenever the working language changes to
12102 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12103 selects the working language.
12105 If you allow @value{GDBN} to set the language automatically, it
12106 recognizes source files whose names end with @file{.c}, @file{.C}, or
12107 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12108 these files, it sets the working language to C or C@t{++}.
12109 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12110 for further details.
12112 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12113 @c unimplemented. If (b) changes, it might make sense to let this node
12114 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12117 @subsubsection C and C@t{++} Type and Range Checks
12119 @cindex C and C@t{++} checks
12121 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12122 is not used. However, if you turn type checking on, @value{GDBN}
12123 considers two variables type equivalent if:
12127 The two variables are structured and have the same structure, union, or
12131 The two variables have the same type name, or types that have been
12132 declared equivalent through @code{typedef}.
12135 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12138 The two @code{struct}, @code{union}, or @code{enum} variables are
12139 declared in the same declaration. (Note: this may not be true for all C
12144 Range checking, if turned on, is done on mathematical operations. Array
12145 indices are not checked, since they are often used to index a pointer
12146 that is not itself an array.
12149 @subsubsection @value{GDBN} and C
12151 The @code{set print union} and @code{show print union} commands apply to
12152 the @code{union} type. When set to @samp{on}, any @code{union} that is
12153 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12154 appears as @samp{@{...@}}.
12156 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12157 with pointers and a memory allocation function. @xref{Expressions,
12160 @node Debugging C Plus Plus
12161 @subsubsection @value{GDBN} Features for C@t{++}
12163 @cindex commands for C@t{++}
12165 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12166 designed specifically for use with C@t{++}. Here is a summary:
12169 @cindex break in overloaded functions
12170 @item @r{breakpoint menus}
12171 When you want a breakpoint in a function whose name is overloaded,
12172 @value{GDBN} has the capability to display a menu of possible breakpoint
12173 locations to help you specify which function definition you want.
12174 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12176 @cindex overloading in C@t{++}
12177 @item rbreak @var{regex}
12178 Setting breakpoints using regular expressions is helpful for setting
12179 breakpoints on overloaded functions that are not members of any special
12181 @xref{Set Breaks, ,Setting Breakpoints}.
12183 @cindex C@t{++} exception handling
12186 Debug C@t{++} exception handling using these commands. @xref{Set
12187 Catchpoints, , Setting Catchpoints}.
12189 @cindex inheritance
12190 @item ptype @var{typename}
12191 Print inheritance relationships as well as other information for type
12193 @xref{Symbols, ,Examining the Symbol Table}.
12195 @cindex C@t{++} symbol display
12196 @item set print demangle
12197 @itemx show print demangle
12198 @itemx set print asm-demangle
12199 @itemx show print asm-demangle
12200 Control whether C@t{++} symbols display in their source form, both when
12201 displaying code as C@t{++} source and when displaying disassemblies.
12202 @xref{Print Settings, ,Print Settings}.
12204 @item set print object
12205 @itemx show print object
12206 Choose whether to print derived (actual) or declared types of objects.
12207 @xref{Print Settings, ,Print Settings}.
12209 @item set print vtbl
12210 @itemx show print vtbl
12211 Control the format for printing virtual function tables.
12212 @xref{Print Settings, ,Print Settings}.
12213 (The @code{vtbl} commands do not work on programs compiled with the HP
12214 ANSI C@t{++} compiler (@code{aCC}).)
12216 @kindex set overload-resolution
12217 @cindex overloaded functions, overload resolution
12218 @item set overload-resolution on
12219 Enable overload resolution for C@t{++} expression evaluation. The default
12220 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12221 and searches for a function whose signature matches the argument types,
12222 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12223 Expressions, ,C@t{++} Expressions}, for details).
12224 If it cannot find a match, it emits a message.
12226 @item set overload-resolution off
12227 Disable overload resolution for C@t{++} expression evaluation. For
12228 overloaded functions that are not class member functions, @value{GDBN}
12229 chooses the first function of the specified name that it finds in the
12230 symbol table, whether or not its arguments are of the correct type. For
12231 overloaded functions that are class member functions, @value{GDBN}
12232 searches for a function whose signature @emph{exactly} matches the
12235 @kindex show overload-resolution
12236 @item show overload-resolution
12237 Show the current setting of overload resolution.
12239 @item @r{Overloaded symbol names}
12240 You can specify a particular definition of an overloaded symbol, using
12241 the same notation that is used to declare such symbols in C@t{++}: type
12242 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12243 also use the @value{GDBN} command-line word completion facilities to list the
12244 available choices, or to finish the type list for you.
12245 @xref{Completion,, Command Completion}, for details on how to do this.
12248 @node Decimal Floating Point
12249 @subsubsection Decimal Floating Point format
12250 @cindex decimal floating point format
12252 @value{GDBN} can examine, set and perform computations with numbers in
12253 decimal floating point format, which in the C language correspond to the
12254 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12255 specified by the extension to support decimal floating-point arithmetic.
12257 There are two encodings in use, depending on the architecture: BID (Binary
12258 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12259 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12262 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12263 to manipulate decimal floating point numbers, it is not possible to convert
12264 (using a cast, for example) integers wider than 32-bit to decimal float.
12266 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12267 point computations, error checking in decimal float operations ignores
12268 underflow, overflow and divide by zero exceptions.
12270 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12271 to inspect @code{_Decimal128} values stored in floating point registers.
12272 See @ref{PowerPC,,PowerPC} for more details.
12278 @value{GDBN} can be used to debug programs written in D and compiled with
12279 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12280 specific feature --- dynamic arrays.
12283 @subsection Objective-C
12285 @cindex Objective-C
12286 This section provides information about some commands and command
12287 options that are useful for debugging Objective-C code. See also
12288 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12289 few more commands specific to Objective-C support.
12292 * Method Names in Commands::
12293 * The Print Command with Objective-C::
12296 @node Method Names in Commands
12297 @subsubsection Method Names in Commands
12299 The following commands have been extended to accept Objective-C method
12300 names as line specifications:
12302 @kindex clear@r{, and Objective-C}
12303 @kindex break@r{, and Objective-C}
12304 @kindex info line@r{, and Objective-C}
12305 @kindex jump@r{, and Objective-C}
12306 @kindex list@r{, and Objective-C}
12310 @item @code{info line}
12315 A fully qualified Objective-C method name is specified as
12318 -[@var{Class} @var{methodName}]
12321 where the minus sign is used to indicate an instance method and a
12322 plus sign (not shown) is used to indicate a class method. The class
12323 name @var{Class} and method name @var{methodName} are enclosed in
12324 brackets, similar to the way messages are specified in Objective-C
12325 source code. For example, to set a breakpoint at the @code{create}
12326 instance method of class @code{Fruit} in the program currently being
12330 break -[Fruit create]
12333 To list ten program lines around the @code{initialize} class method,
12337 list +[NSText initialize]
12340 In the current version of @value{GDBN}, the plus or minus sign is
12341 required. In future versions of @value{GDBN}, the plus or minus
12342 sign will be optional, but you can use it to narrow the search. It
12343 is also possible to specify just a method name:
12349 You must specify the complete method name, including any colons. If
12350 your program's source files contain more than one @code{create} method,
12351 you'll be presented with a numbered list of classes that implement that
12352 method. Indicate your choice by number, or type @samp{0} to exit if
12355 As another example, to clear a breakpoint established at the
12356 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12359 clear -[NSWindow makeKeyAndOrderFront:]
12362 @node The Print Command with Objective-C
12363 @subsubsection The Print Command With Objective-C
12364 @cindex Objective-C, print objects
12365 @kindex print-object
12366 @kindex po @r{(@code{print-object})}
12368 The print command has also been extended to accept methods. For example:
12371 print -[@var{object} hash]
12374 @cindex print an Objective-C object description
12375 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12377 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12378 and print the result. Also, an additional command has been added,
12379 @code{print-object} or @code{po} for short, which is meant to print
12380 the description of an object. However, this command may only work
12381 with certain Objective-C libraries that have a particular hook
12382 function, @code{_NSPrintForDebugger}, defined.
12385 @subsection OpenCL C
12388 This section provides information about @value{GDBN}s OpenCL C support.
12391 * OpenCL C Datatypes::
12392 * OpenCL C Expressions::
12393 * OpenCL C Operators::
12396 @node OpenCL C Datatypes
12397 @subsubsection OpenCL C Datatypes
12399 @cindex OpenCL C Datatypes
12400 @value{GDBN} supports the builtin scalar and vector datatypes specified
12401 by OpenCL 1.1. In addition the half- and double-precision floating point
12402 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12403 extensions are also known to @value{GDBN}.
12405 @node OpenCL C Expressions
12406 @subsubsection OpenCL C Expressions
12408 @cindex OpenCL C Expressions
12409 @value{GDBN} supports accesses to vector components including the access as
12410 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12411 supported by @value{GDBN} can be used as well.
12413 @node OpenCL C Operators
12414 @subsubsection OpenCL C Operators
12416 @cindex OpenCL C Operators
12417 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12421 @subsection Fortran
12422 @cindex Fortran-specific support in @value{GDBN}
12424 @value{GDBN} can be used to debug programs written in Fortran, but it
12425 currently supports only the features of Fortran 77 language.
12427 @cindex trailing underscore, in Fortran symbols
12428 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12429 among them) append an underscore to the names of variables and
12430 functions. When you debug programs compiled by those compilers, you
12431 will need to refer to variables and functions with a trailing
12435 * Fortran Operators:: Fortran operators and expressions
12436 * Fortran Defaults:: Default settings for Fortran
12437 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12440 @node Fortran Operators
12441 @subsubsection Fortran Operators and Expressions
12443 @cindex Fortran operators and expressions
12445 Operators must be defined on values of specific types. For instance,
12446 @code{+} is defined on numbers, but not on characters or other non-
12447 arithmetic types. Operators are often defined on groups of types.
12451 The exponentiation operator. It raises the first operand to the power
12455 The range operator. Normally used in the form of array(low:high) to
12456 represent a section of array.
12459 The access component operator. Normally used to access elements in derived
12460 types. Also suitable for unions. As unions aren't part of regular Fortran,
12461 this can only happen when accessing a register that uses a gdbarch-defined
12465 @node Fortran Defaults
12466 @subsubsection Fortran Defaults
12468 @cindex Fortran Defaults
12470 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12471 default uses case-insensitive matches for Fortran symbols. You can
12472 change that with the @samp{set case-insensitive} command, see
12473 @ref{Symbols}, for the details.
12475 @node Special Fortran Commands
12476 @subsubsection Special Fortran Commands
12478 @cindex Special Fortran commands
12480 @value{GDBN} has some commands to support Fortran-specific features,
12481 such as displaying common blocks.
12484 @cindex @code{COMMON} blocks, Fortran
12485 @kindex info common
12486 @item info common @r{[}@var{common-name}@r{]}
12487 This command prints the values contained in the Fortran @code{COMMON}
12488 block whose name is @var{common-name}. With no argument, the names of
12489 all @code{COMMON} blocks visible at the current program location are
12496 @cindex Pascal support in @value{GDBN}, limitations
12497 Debugging Pascal programs which use sets, subranges, file variables, or
12498 nested functions does not currently work. @value{GDBN} does not support
12499 entering expressions, printing values, or similar features using Pascal
12502 The Pascal-specific command @code{set print pascal_static-members}
12503 controls whether static members of Pascal objects are displayed.
12504 @xref{Print Settings, pascal_static-members}.
12507 @subsection Modula-2
12509 @cindex Modula-2, @value{GDBN} support
12511 The extensions made to @value{GDBN} to support Modula-2 only support
12512 output from the @sc{gnu} Modula-2 compiler (which is currently being
12513 developed). Other Modula-2 compilers are not currently supported, and
12514 attempting to debug executables produced by them is most likely
12515 to give an error as @value{GDBN} reads in the executable's symbol
12518 @cindex expressions in Modula-2
12520 * M2 Operators:: Built-in operators
12521 * Built-In Func/Proc:: Built-in functions and procedures
12522 * M2 Constants:: Modula-2 constants
12523 * M2 Types:: Modula-2 types
12524 * M2 Defaults:: Default settings for Modula-2
12525 * Deviations:: Deviations from standard Modula-2
12526 * M2 Checks:: Modula-2 type and range checks
12527 * M2 Scope:: The scope operators @code{::} and @code{.}
12528 * GDB/M2:: @value{GDBN} and Modula-2
12532 @subsubsection Operators
12533 @cindex Modula-2 operators
12535 Operators must be defined on values of specific types. For instance,
12536 @code{+} is defined on numbers, but not on structures. Operators are
12537 often defined on groups of types. For the purposes of Modula-2, the
12538 following definitions hold:
12543 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12547 @emph{Character types} consist of @code{CHAR} and its subranges.
12550 @emph{Floating-point types} consist of @code{REAL}.
12553 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12557 @emph{Scalar types} consist of all of the above.
12560 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12563 @emph{Boolean types} consist of @code{BOOLEAN}.
12567 The following operators are supported, and appear in order of
12568 increasing precedence:
12572 Function argument or array index separator.
12575 Assignment. The value of @var{var} @code{:=} @var{value} is
12579 Less than, greater than on integral, floating-point, or enumerated
12583 Less than or equal to, greater than or equal to
12584 on integral, floating-point and enumerated types, or set inclusion on
12585 set types. Same precedence as @code{<}.
12587 @item =@r{, }<>@r{, }#
12588 Equality and two ways of expressing inequality, valid on scalar types.
12589 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12590 available for inequality, since @code{#} conflicts with the script
12594 Set membership. Defined on set types and the types of their members.
12595 Same precedence as @code{<}.
12598 Boolean disjunction. Defined on boolean types.
12601 Boolean conjunction. Defined on boolean types.
12604 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12607 Addition and subtraction on integral and floating-point types, or union
12608 and difference on set types.
12611 Multiplication on integral and floating-point types, or set intersection
12615 Division on floating-point types, or symmetric set difference on set
12616 types. Same precedence as @code{*}.
12619 Integer division and remainder. Defined on integral types. Same
12620 precedence as @code{*}.
12623 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12626 Pointer dereferencing. Defined on pointer types.
12629 Boolean negation. Defined on boolean types. Same precedence as
12633 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12634 precedence as @code{^}.
12637 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12640 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12644 @value{GDBN} and Modula-2 scope operators.
12648 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12649 treats the use of the operator @code{IN}, or the use of operators
12650 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12651 @code{<=}, and @code{>=} on sets as an error.
12655 @node Built-In Func/Proc
12656 @subsubsection Built-in Functions and Procedures
12657 @cindex Modula-2 built-ins
12659 Modula-2 also makes available several built-in procedures and functions.
12660 In describing these, the following metavariables are used:
12665 represents an @code{ARRAY} variable.
12668 represents a @code{CHAR} constant or variable.
12671 represents a variable or constant of integral type.
12674 represents an identifier that belongs to a set. Generally used in the
12675 same function with the metavariable @var{s}. The type of @var{s} should
12676 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12679 represents a variable or constant of integral or floating-point type.
12682 represents a variable or constant of floating-point type.
12688 represents a variable.
12691 represents a variable or constant of one of many types. See the
12692 explanation of the function for details.
12695 All Modula-2 built-in procedures also return a result, described below.
12699 Returns the absolute value of @var{n}.
12702 If @var{c} is a lower case letter, it returns its upper case
12703 equivalent, otherwise it returns its argument.
12706 Returns the character whose ordinal value is @var{i}.
12709 Decrements the value in the variable @var{v} by one. Returns the new value.
12711 @item DEC(@var{v},@var{i})
12712 Decrements the value in the variable @var{v} by @var{i}. Returns the
12715 @item EXCL(@var{m},@var{s})
12716 Removes the element @var{m} from the set @var{s}. Returns the new
12719 @item FLOAT(@var{i})
12720 Returns the floating point equivalent of the integer @var{i}.
12722 @item HIGH(@var{a})
12723 Returns the index of the last member of @var{a}.
12726 Increments the value in the variable @var{v} by one. Returns the new value.
12728 @item INC(@var{v},@var{i})
12729 Increments the value in the variable @var{v} by @var{i}. Returns the
12732 @item INCL(@var{m},@var{s})
12733 Adds the element @var{m} to the set @var{s} if it is not already
12734 there. Returns the new set.
12737 Returns the maximum value of the type @var{t}.
12740 Returns the minimum value of the type @var{t}.
12743 Returns boolean TRUE if @var{i} is an odd number.
12746 Returns the ordinal value of its argument. For example, the ordinal
12747 value of a character is its @sc{ascii} value (on machines supporting the
12748 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12749 integral, character and enumerated types.
12751 @item SIZE(@var{x})
12752 Returns the size of its argument. @var{x} can be a variable or a type.
12754 @item TRUNC(@var{r})
12755 Returns the integral part of @var{r}.
12757 @item TSIZE(@var{x})
12758 Returns the size of its argument. @var{x} can be a variable or a type.
12760 @item VAL(@var{t},@var{i})
12761 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12765 @emph{Warning:} Sets and their operations are not yet supported, so
12766 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12770 @cindex Modula-2 constants
12772 @subsubsection Constants
12774 @value{GDBN} allows you to express the constants of Modula-2 in the following
12780 Integer constants are simply a sequence of digits. When used in an
12781 expression, a constant is interpreted to be type-compatible with the
12782 rest of the expression. Hexadecimal integers are specified by a
12783 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12786 Floating point constants appear as a sequence of digits, followed by a
12787 decimal point and another sequence of digits. An optional exponent can
12788 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12789 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12790 digits of the floating point constant must be valid decimal (base 10)
12794 Character constants consist of a single character enclosed by a pair of
12795 like quotes, either single (@code{'}) or double (@code{"}). They may
12796 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12797 followed by a @samp{C}.
12800 String constants consist of a sequence of characters enclosed by a
12801 pair of like quotes, either single (@code{'}) or double (@code{"}).
12802 Escape sequences in the style of C are also allowed. @xref{C
12803 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12807 Enumerated constants consist of an enumerated identifier.
12810 Boolean constants consist of the identifiers @code{TRUE} and
12814 Pointer constants consist of integral values only.
12817 Set constants are not yet supported.
12821 @subsubsection Modula-2 Types
12822 @cindex Modula-2 types
12824 Currently @value{GDBN} can print the following data types in Modula-2
12825 syntax: array types, record types, set types, pointer types, procedure
12826 types, enumerated types, subrange types and base types. You can also
12827 print the contents of variables declared using these type.
12828 This section gives a number of simple source code examples together with
12829 sample @value{GDBN} sessions.
12831 The first example contains the following section of code:
12840 and you can request @value{GDBN} to interrogate the type and value of
12841 @code{r} and @code{s}.
12844 (@value{GDBP}) print s
12846 (@value{GDBP}) ptype s
12848 (@value{GDBP}) print r
12850 (@value{GDBP}) ptype r
12855 Likewise if your source code declares @code{s} as:
12859 s: SET ['A'..'Z'] ;
12863 then you may query the type of @code{s} by:
12866 (@value{GDBP}) ptype s
12867 type = SET ['A'..'Z']
12871 Note that at present you cannot interactively manipulate set
12872 expressions using the debugger.
12874 The following example shows how you might declare an array in Modula-2
12875 and how you can interact with @value{GDBN} to print its type and contents:
12879 s: ARRAY [-10..10] OF CHAR ;
12883 (@value{GDBP}) ptype s
12884 ARRAY [-10..10] OF CHAR
12887 Note that the array handling is not yet complete and although the type
12888 is printed correctly, expression handling still assumes that all
12889 arrays have a lower bound of zero and not @code{-10} as in the example
12892 Here are some more type related Modula-2 examples:
12896 colour = (blue, red, yellow, green) ;
12897 t = [blue..yellow] ;
12905 The @value{GDBN} interaction shows how you can query the data type
12906 and value of a variable.
12909 (@value{GDBP}) print s
12911 (@value{GDBP}) ptype t
12912 type = [blue..yellow]
12916 In this example a Modula-2 array is declared and its contents
12917 displayed. Observe that the contents are written in the same way as
12918 their @code{C} counterparts.
12922 s: ARRAY [1..5] OF CARDINAL ;
12928 (@value{GDBP}) print s
12929 $1 = @{1, 0, 0, 0, 0@}
12930 (@value{GDBP}) ptype s
12931 type = ARRAY [1..5] OF CARDINAL
12934 The Modula-2 language interface to @value{GDBN} also understands
12935 pointer types as shown in this example:
12939 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12946 and you can request that @value{GDBN} describes the type of @code{s}.
12949 (@value{GDBP}) ptype s
12950 type = POINTER TO ARRAY [1..5] OF CARDINAL
12953 @value{GDBN} handles compound types as we can see in this example.
12954 Here we combine array types, record types, pointer types and subrange
12965 myarray = ARRAY myrange OF CARDINAL ;
12966 myrange = [-2..2] ;
12968 s: POINTER TO ARRAY myrange OF foo ;
12972 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12976 (@value{GDBP}) ptype s
12977 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12980 f3 : ARRAY [-2..2] OF CARDINAL;
12985 @subsubsection Modula-2 Defaults
12986 @cindex Modula-2 defaults
12988 If type and range checking are set automatically by @value{GDBN}, they
12989 both default to @code{on} whenever the working language changes to
12990 Modula-2. This happens regardless of whether you or @value{GDBN}
12991 selected the working language.
12993 If you allow @value{GDBN} to set the language automatically, then entering
12994 code compiled from a file whose name ends with @file{.mod} sets the
12995 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12996 Infer the Source Language}, for further details.
12999 @subsubsection Deviations from Standard Modula-2
13000 @cindex Modula-2, deviations from
13002 A few changes have been made to make Modula-2 programs easier to debug.
13003 This is done primarily via loosening its type strictness:
13007 Unlike in standard Modula-2, pointer constants can be formed by
13008 integers. This allows you to modify pointer variables during
13009 debugging. (In standard Modula-2, the actual address contained in a
13010 pointer variable is hidden from you; it can only be modified
13011 through direct assignment to another pointer variable or expression that
13012 returned a pointer.)
13015 C escape sequences can be used in strings and characters to represent
13016 non-printable characters. @value{GDBN} prints out strings with these
13017 escape sequences embedded. Single non-printable characters are
13018 printed using the @samp{CHR(@var{nnn})} format.
13021 The assignment operator (@code{:=}) returns the value of its right-hand
13025 All built-in procedures both modify @emph{and} return their argument.
13029 @subsubsection Modula-2 Type and Range Checks
13030 @cindex Modula-2 checks
13033 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13036 @c FIXME remove warning when type/range checks added
13038 @value{GDBN} considers two Modula-2 variables type equivalent if:
13042 They are of types that have been declared equivalent via a @code{TYPE
13043 @var{t1} = @var{t2}} statement
13046 They have been declared on the same line. (Note: This is true of the
13047 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13050 As long as type checking is enabled, any attempt to combine variables
13051 whose types are not equivalent is an error.
13053 Range checking is done on all mathematical operations, assignment, array
13054 index bounds, and all built-in functions and procedures.
13057 @subsubsection The Scope Operators @code{::} and @code{.}
13059 @cindex @code{.}, Modula-2 scope operator
13060 @cindex colon, doubled as scope operator
13062 @vindex colon-colon@r{, in Modula-2}
13063 @c Info cannot handle :: but TeX can.
13066 @vindex ::@r{, in Modula-2}
13069 There are a few subtle differences between the Modula-2 scope operator
13070 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13075 @var{module} . @var{id}
13076 @var{scope} :: @var{id}
13080 where @var{scope} is the name of a module or a procedure,
13081 @var{module} the name of a module, and @var{id} is any declared
13082 identifier within your program, except another module.
13084 Using the @code{::} operator makes @value{GDBN} search the scope
13085 specified by @var{scope} for the identifier @var{id}. If it is not
13086 found in the specified scope, then @value{GDBN} searches all scopes
13087 enclosing the one specified by @var{scope}.
13089 Using the @code{.} operator makes @value{GDBN} search the current scope for
13090 the identifier specified by @var{id} that was imported from the
13091 definition module specified by @var{module}. With this operator, it is
13092 an error if the identifier @var{id} was not imported from definition
13093 module @var{module}, or if @var{id} is not an identifier in
13097 @subsubsection @value{GDBN} and Modula-2
13099 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13100 Five subcommands of @code{set print} and @code{show print} apply
13101 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13102 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13103 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13104 analogue in Modula-2.
13106 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13107 with any language, is not useful with Modula-2. Its
13108 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13109 created in Modula-2 as they can in C or C@t{++}. However, because an
13110 address can be specified by an integral constant, the construct
13111 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13113 @cindex @code{#} in Modula-2
13114 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13115 interpreted as the beginning of a comment. Use @code{<>} instead.
13121 The extensions made to @value{GDBN} for Ada only support
13122 output from the @sc{gnu} Ada (GNAT) compiler.
13123 Other Ada compilers are not currently supported, and
13124 attempting to debug executables produced by them is most likely
13128 @cindex expressions in Ada
13130 * Ada Mode Intro:: General remarks on the Ada syntax
13131 and semantics supported by Ada mode
13133 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13134 * Additions to Ada:: Extensions of the Ada expression syntax.
13135 * Stopping Before Main Program:: Debugging the program during elaboration.
13136 * Ada Tasks:: Listing and setting breakpoints in tasks.
13137 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13138 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13140 * Ada Glitches:: Known peculiarities of Ada mode.
13143 @node Ada Mode Intro
13144 @subsubsection Introduction
13145 @cindex Ada mode, general
13147 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13148 syntax, with some extensions.
13149 The philosophy behind the design of this subset is
13153 That @value{GDBN} should provide basic literals and access to operations for
13154 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13155 leaving more sophisticated computations to subprograms written into the
13156 program (which therefore may be called from @value{GDBN}).
13159 That type safety and strict adherence to Ada language restrictions
13160 are not particularly important to the @value{GDBN} user.
13163 That brevity is important to the @value{GDBN} user.
13166 Thus, for brevity, the debugger acts as if all names declared in
13167 user-written packages are directly visible, even if they are not visible
13168 according to Ada rules, thus making it unnecessary to fully qualify most
13169 names with their packages, regardless of context. Where this causes
13170 ambiguity, @value{GDBN} asks the user's intent.
13172 The debugger will start in Ada mode if it detects an Ada main program.
13173 As for other languages, it will enter Ada mode when stopped in a program that
13174 was translated from an Ada source file.
13176 While in Ada mode, you may use `@t{--}' for comments. This is useful
13177 mostly for documenting command files. The standard @value{GDBN} comment
13178 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13179 middle (to allow based literals).
13181 The debugger supports limited overloading. Given a subprogram call in which
13182 the function symbol has multiple definitions, it will use the number of
13183 actual parameters and some information about their types to attempt to narrow
13184 the set of definitions. It also makes very limited use of context, preferring
13185 procedures to functions in the context of the @code{call} command, and
13186 functions to procedures elsewhere.
13188 @node Omissions from Ada
13189 @subsubsection Omissions from Ada
13190 @cindex Ada, omissions from
13192 Here are the notable omissions from the subset:
13196 Only a subset of the attributes are supported:
13200 @t{'First}, @t{'Last}, and @t{'Length}
13201 on array objects (not on types and subtypes).
13204 @t{'Min} and @t{'Max}.
13207 @t{'Pos} and @t{'Val}.
13213 @t{'Range} on array objects (not subtypes), but only as the right
13214 operand of the membership (@code{in}) operator.
13217 @t{'Access}, @t{'Unchecked_Access}, and
13218 @t{'Unrestricted_Access} (a GNAT extension).
13226 @code{Characters.Latin_1} are not available and
13227 concatenation is not implemented. Thus, escape characters in strings are
13228 not currently available.
13231 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13232 equality of representations. They will generally work correctly
13233 for strings and arrays whose elements have integer or enumeration types.
13234 They may not work correctly for arrays whose element
13235 types have user-defined equality, for arrays of real values
13236 (in particular, IEEE-conformant floating point, because of negative
13237 zeroes and NaNs), and for arrays whose elements contain unused bits with
13238 indeterminate values.
13241 The other component-by-component array operations (@code{and}, @code{or},
13242 @code{xor}, @code{not}, and relational tests other than equality)
13243 are not implemented.
13246 @cindex array aggregates (Ada)
13247 @cindex record aggregates (Ada)
13248 @cindex aggregates (Ada)
13249 There is limited support for array and record aggregates. They are
13250 permitted only on the right sides of assignments, as in these examples:
13253 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13254 (@value{GDBP}) set An_Array := (1, others => 0)
13255 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13256 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13257 (@value{GDBP}) set A_Record := (1, "Peter", True);
13258 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13262 discriminant's value by assigning an aggregate has an
13263 undefined effect if that discriminant is used within the record.
13264 However, you can first modify discriminants by directly assigning to
13265 them (which normally would not be allowed in Ada), and then performing an
13266 aggregate assignment. For example, given a variable @code{A_Rec}
13267 declared to have a type such as:
13270 type Rec (Len : Small_Integer := 0) is record
13272 Vals : IntArray (1 .. Len);
13276 you can assign a value with a different size of @code{Vals} with two
13280 (@value{GDBP}) set A_Rec.Len := 4
13281 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13284 As this example also illustrates, @value{GDBN} is very loose about the usual
13285 rules concerning aggregates. You may leave out some of the
13286 components of an array or record aggregate (such as the @code{Len}
13287 component in the assignment to @code{A_Rec} above); they will retain their
13288 original values upon assignment. You may freely use dynamic values as
13289 indices in component associations. You may even use overlapping or
13290 redundant component associations, although which component values are
13291 assigned in such cases is not defined.
13294 Calls to dispatching subprograms are not implemented.
13297 The overloading algorithm is much more limited (i.e., less selective)
13298 than that of real Ada. It makes only limited use of the context in
13299 which a subexpression appears to resolve its meaning, and it is much
13300 looser in its rules for allowing type matches. As a result, some
13301 function calls will be ambiguous, and the user will be asked to choose
13302 the proper resolution.
13305 The @code{new} operator is not implemented.
13308 Entry calls are not implemented.
13311 Aside from printing, arithmetic operations on the native VAX floating-point
13312 formats are not supported.
13315 It is not possible to slice a packed array.
13318 The names @code{True} and @code{False}, when not part of a qualified name,
13319 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13321 Should your program
13322 redefine these names in a package or procedure (at best a dubious practice),
13323 you will have to use fully qualified names to access their new definitions.
13326 @node Additions to Ada
13327 @subsubsection Additions to Ada
13328 @cindex Ada, deviations from
13330 As it does for other languages, @value{GDBN} makes certain generic
13331 extensions to Ada (@pxref{Expressions}):
13335 If the expression @var{E} is a variable residing in memory (typically
13336 a local variable or array element) and @var{N} is a positive integer,
13337 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13338 @var{N}-1 adjacent variables following it in memory as an array. In
13339 Ada, this operator is generally not necessary, since its prime use is
13340 in displaying parts of an array, and slicing will usually do this in
13341 Ada. However, there are occasional uses when debugging programs in
13342 which certain debugging information has been optimized away.
13345 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13346 appears in function or file @var{B}.'' When @var{B} is a file name,
13347 you must typically surround it in single quotes.
13350 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13351 @var{type} that appears at address @var{addr}.''
13354 A name starting with @samp{$} is a convenience variable
13355 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13358 In addition, @value{GDBN} provides a few other shortcuts and outright
13359 additions specific to Ada:
13363 The assignment statement is allowed as an expression, returning
13364 its right-hand operand as its value. Thus, you may enter
13367 (@value{GDBP}) set x := y + 3
13368 (@value{GDBP}) print A(tmp := y + 1)
13372 The semicolon is allowed as an ``operator,'' returning as its value
13373 the value of its right-hand operand.
13374 This allows, for example,
13375 complex conditional breaks:
13378 (@value{GDBP}) break f
13379 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13383 Rather than use catenation and symbolic character names to introduce special
13384 characters into strings, one may instead use a special bracket notation,
13385 which is also used to print strings. A sequence of characters of the form
13386 @samp{["@var{XX}"]} within a string or character literal denotes the
13387 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13388 sequence of characters @samp{["""]} also denotes a single quotation mark
13389 in strings. For example,
13391 "One line.["0a"]Next line.["0a"]"
13394 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13398 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13399 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13403 (@value{GDBP}) print 'max(x, y)
13407 When printing arrays, @value{GDBN} uses positional notation when the
13408 array has a lower bound of 1, and uses a modified named notation otherwise.
13409 For example, a one-dimensional array of three integers with a lower bound
13410 of 3 might print as
13417 That is, in contrast to valid Ada, only the first component has a @code{=>}
13421 You may abbreviate attributes in expressions with any unique,
13422 multi-character subsequence of
13423 their names (an exact match gets preference).
13424 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13425 in place of @t{a'length}.
13428 @cindex quoting Ada internal identifiers
13429 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13430 to lower case. The GNAT compiler uses upper-case characters for
13431 some of its internal identifiers, which are normally of no interest to users.
13432 For the rare occasions when you actually have to look at them,
13433 enclose them in angle brackets to avoid the lower-case mapping.
13436 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13440 Printing an object of class-wide type or dereferencing an
13441 access-to-class-wide value will display all the components of the object's
13442 specific type (as indicated by its run-time tag). Likewise, component
13443 selection on such a value will operate on the specific type of the
13448 @node Stopping Before Main Program
13449 @subsubsection Stopping at the Very Beginning
13451 @cindex breakpointing Ada elaboration code
13452 It is sometimes necessary to debug the program during elaboration, and
13453 before reaching the main procedure.
13454 As defined in the Ada Reference
13455 Manual, the elaboration code is invoked from a procedure called
13456 @code{adainit}. To run your program up to the beginning of
13457 elaboration, simply use the following two commands:
13458 @code{tbreak adainit} and @code{run}.
13461 @subsubsection Extensions for Ada Tasks
13462 @cindex Ada, tasking
13464 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13465 @value{GDBN} provides the following task-related commands:
13470 This command shows a list of current Ada tasks, as in the following example:
13477 (@value{GDBP}) info tasks
13478 ID TID P-ID Pri State Name
13479 1 8088000 0 15 Child Activation Wait main_task
13480 2 80a4000 1 15 Accept Statement b
13481 3 809a800 1 15 Child Activation Wait a
13482 * 4 80ae800 3 15 Runnable c
13487 In this listing, the asterisk before the last task indicates it to be the
13488 task currently being inspected.
13492 Represents @value{GDBN}'s internal task number.
13498 The parent's task ID (@value{GDBN}'s internal task number).
13501 The base priority of the task.
13504 Current state of the task.
13508 The task has been created but has not been activated. It cannot be
13512 The task is not blocked for any reason known to Ada. (It may be waiting
13513 for a mutex, though.) It is conceptually "executing" in normal mode.
13516 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13517 that were waiting on terminate alternatives have been awakened and have
13518 terminated themselves.
13520 @item Child Activation Wait
13521 The task is waiting for created tasks to complete activation.
13523 @item Accept Statement
13524 The task is waiting on an accept or selective wait statement.
13526 @item Waiting on entry call
13527 The task is waiting on an entry call.
13529 @item Async Select Wait
13530 The task is waiting to start the abortable part of an asynchronous
13534 The task is waiting on a select statement with only a delay
13537 @item Child Termination Wait
13538 The task is sleeping having completed a master within itself, and is
13539 waiting for the tasks dependent on that master to become terminated or
13540 waiting on a terminate Phase.
13542 @item Wait Child in Term Alt
13543 The task is sleeping waiting for tasks on terminate alternatives to
13544 finish terminating.
13546 @item Accepting RV with @var{taskno}
13547 The task is accepting a rendez-vous with the task @var{taskno}.
13551 Name of the task in the program.
13555 @kindex info task @var{taskno}
13556 @item info task @var{taskno}
13557 This command shows detailled informations on the specified task, as in
13558 the following example:
13563 (@value{GDBP}) info tasks
13564 ID TID P-ID Pri State Name
13565 1 8077880 0 15 Child Activation Wait main_task
13566 * 2 807c468 1 15 Runnable task_1
13567 (@value{GDBP}) info task 2
13568 Ada Task: 0x807c468
13571 Parent: 1 (main_task)
13577 @kindex task@r{ (Ada)}
13578 @cindex current Ada task ID
13579 This command prints the ID of the current task.
13585 (@value{GDBP}) info tasks
13586 ID TID P-ID Pri State Name
13587 1 8077870 0 15 Child Activation Wait main_task
13588 * 2 807c458 1 15 Runnable t
13589 (@value{GDBP}) task
13590 [Current task is 2]
13593 @item task @var{taskno}
13594 @cindex Ada task switching
13595 This command is like the @code{thread @var{threadno}}
13596 command (@pxref{Threads}). It switches the context of debugging
13597 from the current task to the given task.
13603 (@value{GDBP}) info tasks
13604 ID TID P-ID Pri State Name
13605 1 8077870 0 15 Child Activation Wait main_task
13606 * 2 807c458 1 15 Runnable t
13607 (@value{GDBP}) task 1
13608 [Switching to task 1]
13609 #0 0x8067726 in pthread_cond_wait ()
13611 #0 0x8067726 in pthread_cond_wait ()
13612 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13613 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13614 #3 0x806153e in system.tasking.stages.activate_tasks ()
13615 #4 0x804aacc in un () at un.adb:5
13618 @item break @var{linespec} task @var{taskno}
13619 @itemx break @var{linespec} task @var{taskno} if @dots{}
13620 @cindex breakpoints and tasks, in Ada
13621 @cindex task breakpoints, in Ada
13622 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13623 These commands are like the @code{break @dots{} thread @dots{}}
13624 command (@pxref{Thread Stops}).
13625 @var{linespec} specifies source lines, as described
13626 in @ref{Specify Location}.
13628 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13629 to specify that you only want @value{GDBN} to stop the program when a
13630 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13631 numeric task identifiers assigned by @value{GDBN}, shown in the first
13632 column of the @samp{info tasks} display.
13634 If you do not specify @samp{task @var{taskno}} when you set a
13635 breakpoint, the breakpoint applies to @emph{all} tasks of your
13638 You can use the @code{task} qualifier on conditional breakpoints as
13639 well; in this case, place @samp{task @var{taskno}} before the
13640 breakpoint condition (before the @code{if}).
13648 (@value{GDBP}) info tasks
13649 ID TID P-ID Pri State Name
13650 1 140022020 0 15 Child Activation Wait main_task
13651 2 140045060 1 15 Accept/Select Wait t2
13652 3 140044840 1 15 Runnable t1
13653 * 4 140056040 1 15 Runnable t3
13654 (@value{GDBP}) b 15 task 2
13655 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13656 (@value{GDBP}) cont
13661 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13663 (@value{GDBP}) info tasks
13664 ID TID P-ID Pri State Name
13665 1 140022020 0 15 Child Activation Wait main_task
13666 * 2 140045060 1 15 Runnable t2
13667 3 140044840 1 15 Runnable t1
13668 4 140056040 1 15 Delay Sleep t3
13672 @node Ada Tasks and Core Files
13673 @subsubsection Tasking Support when Debugging Core Files
13674 @cindex Ada tasking and core file debugging
13676 When inspecting a core file, as opposed to debugging a live program,
13677 tasking support may be limited or even unavailable, depending on
13678 the platform being used.
13679 For instance, on x86-linux, the list of tasks is available, but task
13680 switching is not supported. On Tru64, however, task switching will work
13683 On certain platforms, including Tru64, the debugger needs to perform some
13684 memory writes in order to provide Ada tasking support. When inspecting
13685 a core file, this means that the core file must be opened with read-write
13686 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13687 Under these circumstances, you should make a backup copy of the core
13688 file before inspecting it with @value{GDBN}.
13690 @node Ravenscar Profile
13691 @subsubsection Tasking Support when using the Ravenscar Profile
13692 @cindex Ravenscar Profile
13694 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
13695 specifically designed for systems with safety-critical real-time
13699 @kindex set ravenscar task-switching on
13700 @cindex task switching with program using Ravenscar Profile
13701 @item set ravenscar task-switching on
13702 Allows task switching when debugging a program that uses the Ravenscar
13703 Profile. This is the default.
13705 @kindex set ravenscar task-switching off
13706 @item set ravenscar task-switching off
13707 Turn off task switching when debugging a program that uses the Ravenscar
13708 Profile. This is mostly intended to disable the code that adds support
13709 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
13710 the Ravenscar runtime is preventing @value{GDBN} from working properly.
13711 To be effective, this command should be run before the program is started.
13713 @kindex show ravenscar task-switching
13714 @item show ravenscar task-switching
13715 Show whether it is possible to switch from task to task in a program
13716 using the Ravenscar Profile.
13721 @subsubsection Known Peculiarities of Ada Mode
13722 @cindex Ada, problems
13724 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13725 we know of several problems with and limitations of Ada mode in
13727 some of which will be fixed with planned future releases of the debugger
13728 and the GNU Ada compiler.
13732 Static constants that the compiler chooses not to materialize as objects in
13733 storage are invisible to the debugger.
13736 Named parameter associations in function argument lists are ignored (the
13737 argument lists are treated as positional).
13740 Many useful library packages are currently invisible to the debugger.
13743 Fixed-point arithmetic, conversions, input, and output is carried out using
13744 floating-point arithmetic, and may give results that only approximate those on
13748 The GNAT compiler never generates the prefix @code{Standard} for any of
13749 the standard symbols defined by the Ada language. @value{GDBN} knows about
13750 this: it will strip the prefix from names when you use it, and will never
13751 look for a name you have so qualified among local symbols, nor match against
13752 symbols in other packages or subprograms. If you have
13753 defined entities anywhere in your program other than parameters and
13754 local variables whose simple names match names in @code{Standard},
13755 GNAT's lack of qualification here can cause confusion. When this happens,
13756 you can usually resolve the confusion
13757 by qualifying the problematic names with package
13758 @code{Standard} explicitly.
13761 Older versions of the compiler sometimes generate erroneous debugging
13762 information, resulting in the debugger incorrectly printing the value
13763 of affected entities. In some cases, the debugger is able to work
13764 around an issue automatically. In other cases, the debugger is able
13765 to work around the issue, but the work-around has to be specifically
13768 @kindex set ada trust-PAD-over-XVS
13769 @kindex show ada trust-PAD-over-XVS
13772 @item set ada trust-PAD-over-XVS on
13773 Configure GDB to strictly follow the GNAT encoding when computing the
13774 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13775 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13776 a complete description of the encoding used by the GNAT compiler).
13777 This is the default.
13779 @item set ada trust-PAD-over-XVS off
13780 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13781 sometimes prints the wrong value for certain entities, changing @code{ada
13782 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13783 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13784 @code{off}, but this incurs a slight performance penalty, so it is
13785 recommended to leave this setting to @code{on} unless necessary.
13789 @node Unsupported Languages
13790 @section Unsupported Languages
13792 @cindex unsupported languages
13793 @cindex minimal language
13794 In addition to the other fully-supported programming languages,
13795 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13796 It does not represent a real programming language, but provides a set
13797 of capabilities close to what the C or assembly languages provide.
13798 This should allow most simple operations to be performed while debugging
13799 an application that uses a language currently not supported by @value{GDBN}.
13801 If the language is set to @code{auto}, @value{GDBN} will automatically
13802 select this language if the current frame corresponds to an unsupported
13806 @chapter Examining the Symbol Table
13808 The commands described in this chapter allow you to inquire about the
13809 symbols (names of variables, functions and types) defined in your
13810 program. This information is inherent in the text of your program and
13811 does not change as your program executes. @value{GDBN} finds it in your
13812 program's symbol table, in the file indicated when you started @value{GDBN}
13813 (@pxref{File Options, ,Choosing Files}), or by one of the
13814 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13816 @cindex symbol names
13817 @cindex names of symbols
13818 @cindex quoting names
13819 Occasionally, you may need to refer to symbols that contain unusual
13820 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13821 most frequent case is in referring to static variables in other
13822 source files (@pxref{Variables,,Program Variables}). File names
13823 are recorded in object files as debugging symbols, but @value{GDBN} would
13824 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13825 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13826 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13833 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13836 @cindex case-insensitive symbol names
13837 @cindex case sensitivity in symbol names
13838 @kindex set case-sensitive
13839 @item set case-sensitive on
13840 @itemx set case-sensitive off
13841 @itemx set case-sensitive auto
13842 Normally, when @value{GDBN} looks up symbols, it matches their names
13843 with case sensitivity determined by the current source language.
13844 Occasionally, you may wish to control that. The command @code{set
13845 case-sensitive} lets you do that by specifying @code{on} for
13846 case-sensitive matches or @code{off} for case-insensitive ones. If
13847 you specify @code{auto}, case sensitivity is reset to the default
13848 suitable for the source language. The default is case-sensitive
13849 matches for all languages except for Fortran, for which the default is
13850 case-insensitive matches.
13852 @kindex show case-sensitive
13853 @item show case-sensitive
13854 This command shows the current setting of case sensitivity for symbols
13857 @kindex info address
13858 @cindex address of a symbol
13859 @item info address @var{symbol}
13860 Describe where the data for @var{symbol} is stored. For a register
13861 variable, this says which register it is kept in. For a non-register
13862 local variable, this prints the stack-frame offset at which the variable
13865 Note the contrast with @samp{print &@var{symbol}}, which does not work
13866 at all for a register variable, and for a stack local variable prints
13867 the exact address of the current instantiation of the variable.
13869 @kindex info symbol
13870 @cindex symbol from address
13871 @cindex closest symbol and offset for an address
13872 @item info symbol @var{addr}
13873 Print the name of a symbol which is stored at the address @var{addr}.
13874 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13875 nearest symbol and an offset from it:
13878 (@value{GDBP}) info symbol 0x54320
13879 _initialize_vx + 396 in section .text
13883 This is the opposite of the @code{info address} command. You can use
13884 it to find out the name of a variable or a function given its address.
13886 For dynamically linked executables, the name of executable or shared
13887 library containing the symbol is also printed:
13890 (@value{GDBP}) info symbol 0x400225
13891 _start + 5 in section .text of /tmp/a.out
13892 (@value{GDBP}) info symbol 0x2aaaac2811cf
13893 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13897 @item whatis [@var{arg}]
13898 Print the data type of @var{arg}, which can be either an expression
13899 or a name of a data type. With no argument, print the data type of
13900 @code{$}, the last value in the value history.
13902 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
13903 is not actually evaluated, and any side-effecting operations (such as
13904 assignments or function calls) inside it do not take place.
13906 If @var{arg} is a variable or an expression, @code{whatis} prints its
13907 literal type as it is used in the source code. If the type was
13908 defined using a @code{typedef}, @code{whatis} will @emph{not} print
13909 the data type underlying the @code{typedef}. If the type of the
13910 variable or the expression is a compound data type, such as
13911 @code{struct} or @code{class}, @code{whatis} never prints their
13912 fields or methods. It just prints the @code{struct}/@code{class}
13913 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
13914 such a compound data type, use @code{ptype}.
13916 If @var{arg} is a type name that was defined using @code{typedef},
13917 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
13918 Unrolling means that @code{whatis} will show the underlying type used
13919 in the @code{typedef} declaration of @var{arg}. However, if that
13920 underlying type is also a @code{typedef}, @code{whatis} will not
13923 For C code, the type names may also have the form @samp{class
13924 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
13925 @var{union-tag}} or @samp{enum @var{enum-tag}}.
13928 @item ptype [@var{arg}]
13929 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13930 detailed description of the type, instead of just the name of the type.
13931 @xref{Expressions, ,Expressions}.
13933 Contrary to @code{whatis}, @code{ptype} always unrolls any
13934 @code{typedef}s in its argument declaration, whether the argument is
13935 a variable, expression, or a data type. This means that @code{ptype}
13936 of a variable or an expression will not print literally its type as
13937 present in the source code---use @code{whatis} for that. @code{typedef}s at
13938 the pointer or reference targets are also unrolled. Only @code{typedef}s of
13939 fields, methods and inner @code{class typedef}s of @code{struct}s,
13940 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
13942 For example, for this variable declaration:
13945 typedef double real_t;
13946 struct complex @{ real_t real; double imag; @};
13947 typedef struct complex complex_t;
13949 real_t *real_pointer_var;
13953 the two commands give this output:
13957 (@value{GDBP}) whatis var
13959 (@value{GDBP}) ptype var
13960 type = struct complex @{
13964 (@value{GDBP}) whatis complex_t
13965 type = struct complex
13966 (@value{GDBP}) whatis struct complex
13967 type = struct complex
13968 (@value{GDBP}) ptype struct complex
13969 type = struct complex @{
13973 (@value{GDBP}) whatis real_pointer_var
13975 (@value{GDBP}) ptype real_pointer_var
13981 As with @code{whatis}, using @code{ptype} without an argument refers to
13982 the type of @code{$}, the last value in the value history.
13984 @cindex incomplete type
13985 Sometimes, programs use opaque data types or incomplete specifications
13986 of complex data structure. If the debug information included in the
13987 program does not allow @value{GDBN} to display a full declaration of
13988 the data type, it will say @samp{<incomplete type>}. For example,
13989 given these declarations:
13993 struct foo *fooptr;
13997 but no definition for @code{struct foo} itself, @value{GDBN} will say:
14000 (@value{GDBP}) ptype foo
14001 $1 = <incomplete type>
14005 ``Incomplete type'' is C terminology for data types that are not
14006 completely specified.
14009 @item info types @var{regexp}
14011 Print a brief description of all types whose names match the regular
14012 expression @var{regexp} (or all types in your program, if you supply
14013 no argument). Each complete typename is matched as though it were a
14014 complete line; thus, @samp{i type value} gives information on all
14015 types in your program whose names include the string @code{value}, but
14016 @samp{i type ^value$} gives information only on types whose complete
14017 name is @code{value}.
14019 This command differs from @code{ptype} in two ways: first, like
14020 @code{whatis}, it does not print a detailed description; second, it
14021 lists all source files where a type is defined.
14024 @cindex local variables
14025 @item info scope @var{location}
14026 List all the variables local to a particular scope. This command
14027 accepts a @var{location} argument---a function name, a source line, or
14028 an address preceded by a @samp{*}, and prints all the variables local
14029 to the scope defined by that location. (@xref{Specify Location}, for
14030 details about supported forms of @var{location}.) For example:
14033 (@value{GDBP}) @b{info scope command_line_handler}
14034 Scope for command_line_handler:
14035 Symbol rl is an argument at stack/frame offset 8, length 4.
14036 Symbol linebuffer is in static storage at address 0x150a18, length 4.
14037 Symbol linelength is in static storage at address 0x150a1c, length 4.
14038 Symbol p is a local variable in register $esi, length 4.
14039 Symbol p1 is a local variable in register $ebx, length 4.
14040 Symbol nline is a local variable in register $edx, length 4.
14041 Symbol repeat is a local variable at frame offset -8, length 4.
14045 This command is especially useful for determining what data to collect
14046 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14049 @kindex info source
14051 Show information about the current source file---that is, the source file for
14052 the function containing the current point of execution:
14055 the name of the source file, and the directory containing it,
14057 the directory it was compiled in,
14059 its length, in lines,
14061 which programming language it is written in,
14063 whether the executable includes debugging information for that file, and
14064 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14066 whether the debugging information includes information about
14067 preprocessor macros.
14071 @kindex info sources
14073 Print the names of all source files in your program for which there is
14074 debugging information, organized into two lists: files whose symbols
14075 have already been read, and files whose symbols will be read when needed.
14077 @kindex info functions
14078 @item info functions
14079 Print the names and data types of all defined functions.
14081 @item info functions @var{regexp}
14082 Print the names and data types of all defined functions
14083 whose names contain a match for regular expression @var{regexp}.
14084 Thus, @samp{info fun step} finds all functions whose names
14085 include @code{step}; @samp{info fun ^step} finds those whose names
14086 start with @code{step}. If a function name contains characters
14087 that conflict with the regular expression language (e.g.@:
14088 @samp{operator*()}), they may be quoted with a backslash.
14090 @kindex info variables
14091 @item info variables
14092 Print the names and data types of all variables that are defined
14093 outside of functions (i.e.@: excluding local variables).
14095 @item info variables @var{regexp}
14096 Print the names and data types of all variables (except for local
14097 variables) whose names contain a match for regular expression
14100 @kindex info classes
14101 @cindex Objective-C, classes and selectors
14103 @itemx info classes @var{regexp}
14104 Display all Objective-C classes in your program, or
14105 (with the @var{regexp} argument) all those matching a particular regular
14108 @kindex info selectors
14109 @item info selectors
14110 @itemx info selectors @var{regexp}
14111 Display all Objective-C selectors in your program, or
14112 (with the @var{regexp} argument) all those matching a particular regular
14116 This was never implemented.
14117 @kindex info methods
14119 @itemx info methods @var{regexp}
14120 The @code{info methods} command permits the user to examine all defined
14121 methods within C@t{++} program, or (with the @var{regexp} argument) a
14122 specific set of methods found in the various C@t{++} classes. Many
14123 C@t{++} classes provide a large number of methods. Thus, the output
14124 from the @code{ptype} command can be overwhelming and hard to use. The
14125 @code{info-methods} command filters the methods, printing only those
14126 which match the regular-expression @var{regexp}.
14129 @cindex reloading symbols
14130 Some systems allow individual object files that make up your program to
14131 be replaced without stopping and restarting your program. For example,
14132 in VxWorks you can simply recompile a defective object file and keep on
14133 running. If you are running on one of these systems, you can allow
14134 @value{GDBN} to reload the symbols for automatically relinked modules:
14137 @kindex set symbol-reloading
14138 @item set symbol-reloading on
14139 Replace symbol definitions for the corresponding source file when an
14140 object file with a particular name is seen again.
14142 @item set symbol-reloading off
14143 Do not replace symbol definitions when encountering object files of the
14144 same name more than once. This is the default state; if you are not
14145 running on a system that permits automatic relinking of modules, you
14146 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14147 may discard symbols when linking large programs, that may contain
14148 several modules (from different directories or libraries) with the same
14151 @kindex show symbol-reloading
14152 @item show symbol-reloading
14153 Show the current @code{on} or @code{off} setting.
14156 @cindex opaque data types
14157 @kindex set opaque-type-resolution
14158 @item set opaque-type-resolution on
14159 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14160 declared as a pointer to a @code{struct}, @code{class}, or
14161 @code{union}---for example, @code{struct MyType *}---that is used in one
14162 source file although the full declaration of @code{struct MyType} is in
14163 another source file. The default is on.
14165 A change in the setting of this subcommand will not take effect until
14166 the next time symbols for a file are loaded.
14168 @item set opaque-type-resolution off
14169 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14170 is printed as follows:
14172 @{<no data fields>@}
14175 @kindex show opaque-type-resolution
14176 @item show opaque-type-resolution
14177 Show whether opaque types are resolved or not.
14179 @kindex maint print symbols
14180 @cindex symbol dump
14181 @kindex maint print psymbols
14182 @cindex partial symbol dump
14183 @item maint print symbols @var{filename}
14184 @itemx maint print psymbols @var{filename}
14185 @itemx maint print msymbols @var{filename}
14186 Write a dump of debugging symbol data into the file @var{filename}.
14187 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14188 symbols with debugging data are included. If you use @samp{maint print
14189 symbols}, @value{GDBN} includes all the symbols for which it has already
14190 collected full details: that is, @var{filename} reflects symbols for
14191 only those files whose symbols @value{GDBN} has read. You can use the
14192 command @code{info sources} to find out which files these are. If you
14193 use @samp{maint print psymbols} instead, the dump shows information about
14194 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14195 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14196 @samp{maint print msymbols} dumps just the minimal symbol information
14197 required for each object file from which @value{GDBN} has read some symbols.
14198 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14199 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14201 @kindex maint info symtabs
14202 @kindex maint info psymtabs
14203 @cindex listing @value{GDBN}'s internal symbol tables
14204 @cindex symbol tables, listing @value{GDBN}'s internal
14205 @cindex full symbol tables, listing @value{GDBN}'s internal
14206 @cindex partial symbol tables, listing @value{GDBN}'s internal
14207 @item maint info symtabs @r{[} @var{regexp} @r{]}
14208 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14210 List the @code{struct symtab} or @code{struct partial_symtab}
14211 structures whose names match @var{regexp}. If @var{regexp} is not
14212 given, list them all. The output includes expressions which you can
14213 copy into a @value{GDBN} debugging this one to examine a particular
14214 structure in more detail. For example:
14217 (@value{GDBP}) maint info psymtabs dwarf2read
14218 @{ objfile /home/gnu/build/gdb/gdb
14219 ((struct objfile *) 0x82e69d0)
14220 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14221 ((struct partial_symtab *) 0x8474b10)
14224 text addresses 0x814d3c8 -- 0x8158074
14225 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14226 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14227 dependencies (none)
14230 (@value{GDBP}) maint info symtabs
14234 We see that there is one partial symbol table whose filename contains
14235 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14236 and we see that @value{GDBN} has not read in any symtabs yet at all.
14237 If we set a breakpoint on a function, that will cause @value{GDBN} to
14238 read the symtab for the compilation unit containing that function:
14241 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14242 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14244 (@value{GDBP}) maint info symtabs
14245 @{ objfile /home/gnu/build/gdb/gdb
14246 ((struct objfile *) 0x82e69d0)
14247 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14248 ((struct symtab *) 0x86c1f38)
14251 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14252 linetable ((struct linetable *) 0x8370fa0)
14253 debugformat DWARF 2
14262 @chapter Altering Execution
14264 Once you think you have found an error in your program, you might want to
14265 find out for certain whether correcting the apparent error would lead to
14266 correct results in the rest of the run. You can find the answer by
14267 experiment, using the @value{GDBN} features for altering execution of the
14270 For example, you can store new values into variables or memory
14271 locations, give your program a signal, restart it at a different
14272 address, or even return prematurely from a function.
14275 * Assignment:: Assignment to variables
14276 * Jumping:: Continuing at a different address
14277 * Signaling:: Giving your program a signal
14278 * Returning:: Returning from a function
14279 * Calling:: Calling your program's functions
14280 * Patching:: Patching your program
14284 @section Assignment to Variables
14287 @cindex setting variables
14288 To alter the value of a variable, evaluate an assignment expression.
14289 @xref{Expressions, ,Expressions}. For example,
14296 stores the value 4 into the variable @code{x}, and then prints the
14297 value of the assignment expression (which is 4).
14298 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14299 information on operators in supported languages.
14301 @kindex set variable
14302 @cindex variables, setting
14303 If you are not interested in seeing the value of the assignment, use the
14304 @code{set} command instead of the @code{print} command. @code{set} is
14305 really the same as @code{print} except that the expression's value is
14306 not printed and is not put in the value history (@pxref{Value History,
14307 ,Value History}). The expression is evaluated only for its effects.
14309 If the beginning of the argument string of the @code{set} command
14310 appears identical to a @code{set} subcommand, use the @code{set
14311 variable} command instead of just @code{set}. This command is identical
14312 to @code{set} except for its lack of subcommands. For example, if your
14313 program has a variable @code{width}, you get an error if you try to set
14314 a new value with just @samp{set width=13}, because @value{GDBN} has the
14315 command @code{set width}:
14318 (@value{GDBP}) whatis width
14320 (@value{GDBP}) p width
14322 (@value{GDBP}) set width=47
14323 Invalid syntax in expression.
14327 The invalid expression, of course, is @samp{=47}. In
14328 order to actually set the program's variable @code{width}, use
14331 (@value{GDBP}) set var width=47
14334 Because the @code{set} command has many subcommands that can conflict
14335 with the names of program variables, it is a good idea to use the
14336 @code{set variable} command instead of just @code{set}. For example, if
14337 your program has a variable @code{g}, you run into problems if you try
14338 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14339 the command @code{set gnutarget}, abbreviated @code{set g}:
14343 (@value{GDBP}) whatis g
14347 (@value{GDBP}) set g=4
14351 The program being debugged has been started already.
14352 Start it from the beginning? (y or n) y
14353 Starting program: /home/smith/cc_progs/a.out
14354 "/home/smith/cc_progs/a.out": can't open to read symbols:
14355 Invalid bfd target.
14356 (@value{GDBP}) show g
14357 The current BFD target is "=4".
14362 The program variable @code{g} did not change, and you silently set the
14363 @code{gnutarget} to an invalid value. In order to set the variable
14367 (@value{GDBP}) set var g=4
14370 @value{GDBN} allows more implicit conversions in assignments than C; you can
14371 freely store an integer value into a pointer variable or vice versa,
14372 and you can convert any structure to any other structure that is the
14373 same length or shorter.
14374 @comment FIXME: how do structs align/pad in these conversions?
14375 @comment /doc@cygnus.com 18dec1990
14377 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14378 construct to generate a value of specified type at a specified address
14379 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14380 to memory location @code{0x83040} as an integer (which implies a certain size
14381 and representation in memory), and
14384 set @{int@}0x83040 = 4
14388 stores the value 4 into that memory location.
14391 @section Continuing at a Different Address
14393 Ordinarily, when you continue your program, you do so at the place where
14394 it stopped, with the @code{continue} command. You can instead continue at
14395 an address of your own choosing, with the following commands:
14399 @item jump @var{linespec}
14400 @itemx jump @var{location}
14401 Resume execution at line @var{linespec} or at address given by
14402 @var{location}. Execution stops again immediately if there is a
14403 breakpoint there. @xref{Specify Location}, for a description of the
14404 different forms of @var{linespec} and @var{location}. It is common
14405 practice to use the @code{tbreak} command in conjunction with
14406 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14408 The @code{jump} command does not change the current stack frame, or
14409 the stack pointer, or the contents of any memory location or any
14410 register other than the program counter. If line @var{linespec} is in
14411 a different function from the one currently executing, the results may
14412 be bizarre if the two functions expect different patterns of arguments or
14413 of local variables. For this reason, the @code{jump} command requests
14414 confirmation if the specified line is not in the function currently
14415 executing. However, even bizarre results are predictable if you are
14416 well acquainted with the machine-language code of your program.
14419 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14420 On many systems, you can get much the same effect as the @code{jump}
14421 command by storing a new value into the register @code{$pc}. The
14422 difference is that this does not start your program running; it only
14423 changes the address of where it @emph{will} run when you continue. For
14431 makes the next @code{continue} command or stepping command execute at
14432 address @code{0x485}, rather than at the address where your program stopped.
14433 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14435 The most common occasion to use the @code{jump} command is to back
14436 up---perhaps with more breakpoints set---over a portion of a program
14437 that has already executed, in order to examine its execution in more
14442 @section Giving your Program a Signal
14443 @cindex deliver a signal to a program
14447 @item signal @var{signal}
14448 Resume execution where your program stopped, but immediately give it the
14449 signal @var{signal}. @var{signal} can be the name or the number of a
14450 signal. For example, on many systems @code{signal 2} and @code{signal
14451 SIGINT} are both ways of sending an interrupt signal.
14453 Alternatively, if @var{signal} is zero, continue execution without
14454 giving a signal. This is useful when your program stopped on account of
14455 a signal and would ordinary see the signal when resumed with the
14456 @code{continue} command; @samp{signal 0} causes it to resume without a
14459 @code{signal} does not repeat when you press @key{RET} a second time
14460 after executing the command.
14464 Invoking the @code{signal} command is not the same as invoking the
14465 @code{kill} utility from the shell. Sending a signal with @code{kill}
14466 causes @value{GDBN} to decide what to do with the signal depending on
14467 the signal handling tables (@pxref{Signals}). The @code{signal} command
14468 passes the signal directly to your program.
14472 @section Returning from a Function
14475 @cindex returning from a function
14478 @itemx return @var{expression}
14479 You can cancel execution of a function call with the @code{return}
14480 command. If you give an
14481 @var{expression} argument, its value is used as the function's return
14485 When you use @code{return}, @value{GDBN} discards the selected stack frame
14486 (and all frames within it). You can think of this as making the
14487 discarded frame return prematurely. If you wish to specify a value to
14488 be returned, give that value as the argument to @code{return}.
14490 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14491 Frame}), and any other frames inside of it, leaving its caller as the
14492 innermost remaining frame. That frame becomes selected. The
14493 specified value is stored in the registers used for returning values
14496 The @code{return} command does not resume execution; it leaves the
14497 program stopped in the state that would exist if the function had just
14498 returned. In contrast, the @code{finish} command (@pxref{Continuing
14499 and Stepping, ,Continuing and Stepping}) resumes execution until the
14500 selected stack frame returns naturally.
14502 @value{GDBN} needs to know how the @var{expression} argument should be set for
14503 the inferior. The concrete registers assignment depends on the OS ABI and the
14504 type being returned by the selected stack frame. For example it is common for
14505 OS ABI to return floating point values in FPU registers while integer values in
14506 CPU registers. Still some ABIs return even floating point values in CPU
14507 registers. Larger integer widths (such as @code{long long int}) also have
14508 specific placement rules. @value{GDBN} already knows the OS ABI from its
14509 current target so it needs to find out also the type being returned to make the
14510 assignment into the right register(s).
14512 Normally, the selected stack frame has debug info. @value{GDBN} will always
14513 use the debug info instead of the implicit type of @var{expression} when the
14514 debug info is available. For example, if you type @kbd{return -1}, and the
14515 function in the current stack frame is declared to return a @code{long long
14516 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14517 into a @code{long long int}:
14520 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14522 (@value{GDBP}) return -1
14523 Make func return now? (y or n) y
14524 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14525 43 printf ("result=%lld\n", func ());
14529 However, if the selected stack frame does not have a debug info, e.g., if the
14530 function was compiled without debug info, @value{GDBN} has to find out the type
14531 to return from user. Specifying a different type by mistake may set the value
14532 in different inferior registers than the caller code expects. For example,
14533 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14534 of a @code{long long int} result for a debug info less function (on 32-bit
14535 architectures). Therefore the user is required to specify the return type by
14536 an appropriate cast explicitly:
14539 Breakpoint 2, 0x0040050b in func ()
14540 (@value{GDBP}) return -1
14541 Return value type not available for selected stack frame.
14542 Please use an explicit cast of the value to return.
14543 (@value{GDBP}) return (long long int) -1
14544 Make selected stack frame return now? (y or n) y
14545 #0 0x00400526 in main ()
14550 @section Calling Program Functions
14553 @cindex calling functions
14554 @cindex inferior functions, calling
14555 @item print @var{expr}
14556 Evaluate the expression @var{expr} and display the resulting value.
14557 @var{expr} may include calls to functions in the program being
14561 @item call @var{expr}
14562 Evaluate the expression @var{expr} without displaying @code{void}
14565 You can use this variant of the @code{print} command if you want to
14566 execute a function from your program that does not return anything
14567 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14568 with @code{void} returned values that @value{GDBN} will otherwise
14569 print. If the result is not void, it is printed and saved in the
14573 It is possible for the function you call via the @code{print} or
14574 @code{call} command to generate a signal (e.g., if there's a bug in
14575 the function, or if you passed it incorrect arguments). What happens
14576 in that case is controlled by the @code{set unwindonsignal} command.
14578 Similarly, with a C@t{++} program it is possible for the function you
14579 call via the @code{print} or @code{call} command to generate an
14580 exception that is not handled due to the constraints of the dummy
14581 frame. In this case, any exception that is raised in the frame, but has
14582 an out-of-frame exception handler will not be found. GDB builds a
14583 dummy-frame for the inferior function call, and the unwinder cannot
14584 seek for exception handlers outside of this dummy-frame. What happens
14585 in that case is controlled by the
14586 @code{set unwind-on-terminating-exception} command.
14589 @item set unwindonsignal
14590 @kindex set unwindonsignal
14591 @cindex unwind stack in called functions
14592 @cindex call dummy stack unwinding
14593 Set unwinding of the stack if a signal is received while in a function
14594 that @value{GDBN} called in the program being debugged. If set to on,
14595 @value{GDBN} unwinds the stack it created for the call and restores
14596 the context to what it was before the call. If set to off (the
14597 default), @value{GDBN} stops in the frame where the signal was
14600 @item show unwindonsignal
14601 @kindex show unwindonsignal
14602 Show the current setting of stack unwinding in the functions called by
14605 @item set unwind-on-terminating-exception
14606 @kindex set unwind-on-terminating-exception
14607 @cindex unwind stack in called functions with unhandled exceptions
14608 @cindex call dummy stack unwinding on unhandled exception.
14609 Set unwinding of the stack if a C@t{++} exception is raised, but left
14610 unhandled while in a function that @value{GDBN} called in the program being
14611 debugged. If set to on (the default), @value{GDBN} unwinds the stack
14612 it created for the call and restores the context to what it was before
14613 the call. If set to off, @value{GDBN} the exception is delivered to
14614 the default C@t{++} exception handler and the inferior terminated.
14616 @item show unwind-on-terminating-exception
14617 @kindex show unwind-on-terminating-exception
14618 Show the current setting of stack unwinding in the functions called by
14623 @cindex weak alias functions
14624 Sometimes, a function you wish to call is actually a @dfn{weak alias}
14625 for another function. In such case, @value{GDBN} might not pick up
14626 the type information, including the types of the function arguments,
14627 which causes @value{GDBN} to call the inferior function incorrectly.
14628 As a result, the called function will function erroneously and may
14629 even crash. A solution to that is to use the name of the aliased
14633 @section Patching Programs
14635 @cindex patching binaries
14636 @cindex writing into executables
14637 @cindex writing into corefiles
14639 By default, @value{GDBN} opens the file containing your program's
14640 executable code (or the corefile) read-only. This prevents accidental
14641 alterations to machine code; but it also prevents you from intentionally
14642 patching your program's binary.
14644 If you'd like to be able to patch the binary, you can specify that
14645 explicitly with the @code{set write} command. For example, you might
14646 want to turn on internal debugging flags, or even to make emergency
14652 @itemx set write off
14653 If you specify @samp{set write on}, @value{GDBN} opens executable and
14654 core files for both reading and writing; if you specify @kbd{set write
14655 off} (the default), @value{GDBN} opens them read-only.
14657 If you have already loaded a file, you must load it again (using the
14658 @code{exec-file} or @code{core-file} command) after changing @code{set
14659 write}, for your new setting to take effect.
14663 Display whether executable files and core files are opened for writing
14664 as well as reading.
14668 @chapter @value{GDBN} Files
14670 @value{GDBN} needs to know the file name of the program to be debugged,
14671 both in order to read its symbol table and in order to start your
14672 program. To debug a core dump of a previous run, you must also tell
14673 @value{GDBN} the name of the core dump file.
14676 * Files:: Commands to specify files
14677 * Separate Debug Files:: Debugging information in separate files
14678 * Index Files:: Index files speed up GDB
14679 * Symbol Errors:: Errors reading symbol files
14680 * Data Files:: GDB data files
14684 @section Commands to Specify Files
14686 @cindex symbol table
14687 @cindex core dump file
14689 You may want to specify executable and core dump file names. The usual
14690 way to do this is at start-up time, using the arguments to
14691 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
14692 Out of @value{GDBN}}).
14694 Occasionally it is necessary to change to a different file during a
14695 @value{GDBN} session. Or you may run @value{GDBN} and forget to
14696 specify a file you want to use. Or you are debugging a remote target
14697 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
14698 Program}). In these situations the @value{GDBN} commands to specify
14699 new files are useful.
14702 @cindex executable file
14704 @item file @var{filename}
14705 Use @var{filename} as the program to be debugged. It is read for its
14706 symbols and for the contents of pure memory. It is also the program
14707 executed when you use the @code{run} command. If you do not specify a
14708 directory and the file is not found in the @value{GDBN} working directory,
14709 @value{GDBN} uses the environment variable @code{PATH} as a list of
14710 directories to search, just as the shell does when looking for a program
14711 to run. You can change the value of this variable, for both @value{GDBN}
14712 and your program, using the @code{path} command.
14714 @cindex unlinked object files
14715 @cindex patching object files
14716 You can load unlinked object @file{.o} files into @value{GDBN} using
14717 the @code{file} command. You will not be able to ``run'' an object
14718 file, but you can disassemble functions and inspect variables. Also,
14719 if the underlying BFD functionality supports it, you could use
14720 @kbd{gdb -write} to patch object files using this technique. Note
14721 that @value{GDBN} can neither interpret nor modify relocations in this
14722 case, so branches and some initialized variables will appear to go to
14723 the wrong place. But this feature is still handy from time to time.
14726 @code{file} with no argument makes @value{GDBN} discard any information it
14727 has on both executable file and the symbol table.
14730 @item exec-file @r{[} @var{filename} @r{]}
14731 Specify that the program to be run (but not the symbol table) is found
14732 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14733 if necessary to locate your program. Omitting @var{filename} means to
14734 discard information on the executable file.
14736 @kindex symbol-file
14737 @item symbol-file @r{[} @var{filename} @r{]}
14738 Read symbol table information from file @var{filename}. @code{PATH} is
14739 searched when necessary. Use the @code{file} command to get both symbol
14740 table and program to run from the same file.
14742 @code{symbol-file} with no argument clears out @value{GDBN} information on your
14743 program's symbol table.
14745 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
14746 some breakpoints and auto-display expressions. This is because they may
14747 contain pointers to the internal data recording symbols and data types,
14748 which are part of the old symbol table data being discarded inside
14751 @code{symbol-file} does not repeat if you press @key{RET} again after
14754 When @value{GDBN} is configured for a particular environment, it
14755 understands debugging information in whatever format is the standard
14756 generated for that environment; you may use either a @sc{gnu} compiler, or
14757 other compilers that adhere to the local conventions.
14758 Best results are usually obtained from @sc{gnu} compilers; for example,
14759 using @code{@value{NGCC}} you can generate debugging information for
14762 For most kinds of object files, with the exception of old SVR3 systems
14763 using COFF, the @code{symbol-file} command does not normally read the
14764 symbol table in full right away. Instead, it scans the symbol table
14765 quickly to find which source files and which symbols are present. The
14766 details are read later, one source file at a time, as they are needed.
14768 The purpose of this two-stage reading strategy is to make @value{GDBN}
14769 start up faster. For the most part, it is invisible except for
14770 occasional pauses while the symbol table details for a particular source
14771 file are being read. (The @code{set verbose} command can turn these
14772 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
14773 Warnings and Messages}.)
14775 We have not implemented the two-stage strategy for COFF yet. When the
14776 symbol table is stored in COFF format, @code{symbol-file} reads the
14777 symbol table data in full right away. Note that ``stabs-in-COFF''
14778 still does the two-stage strategy, since the debug info is actually
14782 @cindex reading symbols immediately
14783 @cindex symbols, reading immediately
14784 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14785 @itemx file @r{[} -readnow @r{]} @var{filename}
14786 You can override the @value{GDBN} two-stage strategy for reading symbol
14787 tables by using the @samp{-readnow} option with any of the commands that
14788 load symbol table information, if you want to be sure @value{GDBN} has the
14789 entire symbol table available.
14791 @c FIXME: for now no mention of directories, since this seems to be in
14792 @c flux. 13mar1992 status is that in theory GDB would look either in
14793 @c current dir or in same dir as myprog; but issues like competing
14794 @c GDB's, or clutter in system dirs, mean that in practice right now
14795 @c only current dir is used. FFish says maybe a special GDB hierarchy
14796 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14800 @item core-file @r{[}@var{filename}@r{]}
14802 Specify the whereabouts of a core dump file to be used as the ``contents
14803 of memory''. Traditionally, core files contain only some parts of the
14804 address space of the process that generated them; @value{GDBN} can access the
14805 executable file itself for other parts.
14807 @code{core-file} with no argument specifies that no core file is
14810 Note that the core file is ignored when your program is actually running
14811 under @value{GDBN}. So, if you have been running your program and you
14812 wish to debug a core file instead, you must kill the subprocess in which
14813 the program is running. To do this, use the @code{kill} command
14814 (@pxref{Kill Process, ,Killing the Child Process}).
14816 @kindex add-symbol-file
14817 @cindex dynamic linking
14818 @item add-symbol-file @var{filename} @var{address}
14819 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14820 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14821 The @code{add-symbol-file} command reads additional symbol table
14822 information from the file @var{filename}. You would use this command
14823 when @var{filename} has been dynamically loaded (by some other means)
14824 into the program that is running. @var{address} should be the memory
14825 address at which the file has been loaded; @value{GDBN} cannot figure
14826 this out for itself. You can additionally specify an arbitrary number
14827 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14828 section name and base address for that section. You can specify any
14829 @var{address} as an expression.
14831 The symbol table of the file @var{filename} is added to the symbol table
14832 originally read with the @code{symbol-file} command. You can use the
14833 @code{add-symbol-file} command any number of times; the new symbol data
14834 thus read keeps adding to the old. To discard all old symbol data
14835 instead, use the @code{symbol-file} command without any arguments.
14837 @cindex relocatable object files, reading symbols from
14838 @cindex object files, relocatable, reading symbols from
14839 @cindex reading symbols from relocatable object files
14840 @cindex symbols, reading from relocatable object files
14841 @cindex @file{.o} files, reading symbols from
14842 Although @var{filename} is typically a shared library file, an
14843 executable file, or some other object file which has been fully
14844 relocated for loading into a process, you can also load symbolic
14845 information from relocatable @file{.o} files, as long as:
14849 the file's symbolic information refers only to linker symbols defined in
14850 that file, not to symbols defined by other object files,
14852 every section the file's symbolic information refers to has actually
14853 been loaded into the inferior, as it appears in the file, and
14855 you can determine the address at which every section was loaded, and
14856 provide these to the @code{add-symbol-file} command.
14860 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14861 relocatable files into an already running program; such systems
14862 typically make the requirements above easy to meet. However, it's
14863 important to recognize that many native systems use complex link
14864 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14865 assembly, for example) that make the requirements difficult to meet. In
14866 general, one cannot assume that using @code{add-symbol-file} to read a
14867 relocatable object file's symbolic information will have the same effect
14868 as linking the relocatable object file into the program in the normal
14871 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14873 @kindex add-symbol-file-from-memory
14874 @cindex @code{syscall DSO}
14875 @cindex load symbols from memory
14876 @item add-symbol-file-from-memory @var{address}
14877 Load symbols from the given @var{address} in a dynamically loaded
14878 object file whose image is mapped directly into the inferior's memory.
14879 For example, the Linux kernel maps a @code{syscall DSO} into each
14880 process's address space; this DSO provides kernel-specific code for
14881 some system calls. The argument can be any expression whose
14882 evaluation yields the address of the file's shared object file header.
14883 For this command to work, you must have used @code{symbol-file} or
14884 @code{exec-file} commands in advance.
14886 @kindex add-shared-symbol-files
14888 @item add-shared-symbol-files @var{library-file}
14889 @itemx assf @var{library-file}
14890 The @code{add-shared-symbol-files} command can currently be used only
14891 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14892 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14893 @value{GDBN} automatically looks for shared libraries, however if
14894 @value{GDBN} does not find yours, you can invoke
14895 @code{add-shared-symbol-files}. It takes one argument: the shared
14896 library's file name. @code{assf} is a shorthand alias for
14897 @code{add-shared-symbol-files}.
14900 @item section @var{section} @var{addr}
14901 The @code{section} command changes the base address of the named
14902 @var{section} of the exec file to @var{addr}. This can be used if the
14903 exec file does not contain section addresses, (such as in the
14904 @code{a.out} format), or when the addresses specified in the file
14905 itself are wrong. Each section must be changed separately. The
14906 @code{info files} command, described below, lists all the sections and
14910 @kindex info target
14913 @code{info files} and @code{info target} are synonymous; both print the
14914 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14915 including the names of the executable and core dump files currently in
14916 use by @value{GDBN}, and the files from which symbols were loaded. The
14917 command @code{help target} lists all possible targets rather than
14920 @kindex maint info sections
14921 @item maint info sections
14922 Another command that can give you extra information about program sections
14923 is @code{maint info sections}. In addition to the section information
14924 displayed by @code{info files}, this command displays the flags and file
14925 offset of each section in the executable and core dump files. In addition,
14926 @code{maint info sections} provides the following command options (which
14927 may be arbitrarily combined):
14931 Display sections for all loaded object files, including shared libraries.
14932 @item @var{sections}
14933 Display info only for named @var{sections}.
14934 @item @var{section-flags}
14935 Display info only for sections for which @var{section-flags} are true.
14936 The section flags that @value{GDBN} currently knows about are:
14939 Section will have space allocated in the process when loaded.
14940 Set for all sections except those containing debug information.
14942 Section will be loaded from the file into the child process memory.
14943 Set for pre-initialized code and data, clear for @code{.bss} sections.
14945 Section needs to be relocated before loading.
14947 Section cannot be modified by the child process.
14949 Section contains executable code only.
14951 Section contains data only (no executable code).
14953 Section will reside in ROM.
14955 Section contains data for constructor/destructor lists.
14957 Section is not empty.
14959 An instruction to the linker to not output the section.
14960 @item COFF_SHARED_LIBRARY
14961 A notification to the linker that the section contains
14962 COFF shared library information.
14964 Section contains common symbols.
14967 @kindex set trust-readonly-sections
14968 @cindex read-only sections
14969 @item set trust-readonly-sections on
14970 Tell @value{GDBN} that readonly sections in your object file
14971 really are read-only (i.e.@: that their contents will not change).
14972 In that case, @value{GDBN} can fetch values from these sections
14973 out of the object file, rather than from the target program.
14974 For some targets (notably embedded ones), this can be a significant
14975 enhancement to debugging performance.
14977 The default is off.
14979 @item set trust-readonly-sections off
14980 Tell @value{GDBN} not to trust readonly sections. This means that
14981 the contents of the section might change while the program is running,
14982 and must therefore be fetched from the target when needed.
14984 @item show trust-readonly-sections
14985 Show the current setting of trusting readonly sections.
14988 All file-specifying commands allow both absolute and relative file names
14989 as arguments. @value{GDBN} always converts the file name to an absolute file
14990 name and remembers it that way.
14992 @cindex shared libraries
14993 @anchor{Shared Libraries}
14994 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14995 and IBM RS/6000 AIX shared libraries.
14997 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14998 shared libraries. @xref{Expat}.
15000 @value{GDBN} automatically loads symbol definitions from shared libraries
15001 when you use the @code{run} command, or when you examine a core file.
15002 (Before you issue the @code{run} command, @value{GDBN} does not understand
15003 references to a function in a shared library, however---unless you are
15004 debugging a core file).
15006 On HP-UX, if the program loads a library explicitly, @value{GDBN}
15007 automatically loads the symbols at the time of the @code{shl_load} call.
15009 @c FIXME: some @value{GDBN} release may permit some refs to undef
15010 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
15011 @c FIXME...lib; check this from time to time when updating manual
15013 There are times, however, when you may wish to not automatically load
15014 symbol definitions from shared libraries, such as when they are
15015 particularly large or there are many of them.
15017 To control the automatic loading of shared library symbols, use the
15021 @kindex set auto-solib-add
15022 @item set auto-solib-add @var{mode}
15023 If @var{mode} is @code{on}, symbols from all shared object libraries
15024 will be loaded automatically when the inferior begins execution, you
15025 attach to an independently started inferior, or when the dynamic linker
15026 informs @value{GDBN} that a new library has been loaded. If @var{mode}
15027 is @code{off}, symbols must be loaded manually, using the
15028 @code{sharedlibrary} command. The default value is @code{on}.
15030 @cindex memory used for symbol tables
15031 If your program uses lots of shared libraries with debug info that
15032 takes large amounts of memory, you can decrease the @value{GDBN}
15033 memory footprint by preventing it from automatically loading the
15034 symbols from shared libraries. To that end, type @kbd{set
15035 auto-solib-add off} before running the inferior, then load each
15036 library whose debug symbols you do need with @kbd{sharedlibrary
15037 @var{regexp}}, where @var{regexp} is a regular expression that matches
15038 the libraries whose symbols you want to be loaded.
15040 @kindex show auto-solib-add
15041 @item show auto-solib-add
15042 Display the current autoloading mode.
15045 @cindex load shared library
15046 To explicitly load shared library symbols, use the @code{sharedlibrary}
15050 @kindex info sharedlibrary
15052 @item info share @var{regex}
15053 @itemx info sharedlibrary @var{regex}
15054 Print the names of the shared libraries which are currently loaded
15055 that match @var{regex}. If @var{regex} is omitted then print
15056 all shared libraries that are loaded.
15058 @kindex sharedlibrary
15060 @item sharedlibrary @var{regex}
15061 @itemx share @var{regex}
15062 Load shared object library symbols for files matching a
15063 Unix regular expression.
15064 As with files loaded automatically, it only loads shared libraries
15065 required by your program for a core file or after typing @code{run}. If
15066 @var{regex} is omitted all shared libraries required by your program are
15069 @item nosharedlibrary
15070 @kindex nosharedlibrary
15071 @cindex unload symbols from shared libraries
15072 Unload all shared object library symbols. This discards all symbols
15073 that have been loaded from all shared libraries. Symbols from shared
15074 libraries that were loaded by explicit user requests are not
15078 Sometimes you may wish that @value{GDBN} stops and gives you control
15079 when any of shared library events happen. Use the @code{set
15080 stop-on-solib-events} command for this:
15083 @item set stop-on-solib-events
15084 @kindex set stop-on-solib-events
15085 This command controls whether @value{GDBN} should give you control
15086 when the dynamic linker notifies it about some shared library event.
15087 The most common event of interest is loading or unloading of a new
15090 @item show stop-on-solib-events
15091 @kindex show stop-on-solib-events
15092 Show whether @value{GDBN} stops and gives you control when shared
15093 library events happen.
15096 Shared libraries are also supported in many cross or remote debugging
15097 configurations. @value{GDBN} needs to have access to the target's libraries;
15098 this can be accomplished either by providing copies of the libraries
15099 on the host system, or by asking @value{GDBN} to automatically retrieve the
15100 libraries from the target. If copies of the target libraries are
15101 provided, they need to be the same as the target libraries, although the
15102 copies on the target can be stripped as long as the copies on the host are
15105 @cindex where to look for shared libraries
15106 For remote debugging, you need to tell @value{GDBN} where the target
15107 libraries are, so that it can load the correct copies---otherwise, it
15108 may try to load the host's libraries. @value{GDBN} has two variables
15109 to specify the search directories for target libraries.
15112 @cindex prefix for shared library file names
15113 @cindex system root, alternate
15114 @kindex set solib-absolute-prefix
15115 @kindex set sysroot
15116 @item set sysroot @var{path}
15117 Use @var{path} as the system root for the program being debugged. Any
15118 absolute shared library paths will be prefixed with @var{path}; many
15119 runtime loaders store the absolute paths to the shared library in the
15120 target program's memory. If you use @code{set sysroot} to find shared
15121 libraries, they need to be laid out in the same way that they are on
15122 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15125 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15126 retrieve the target libraries from the remote system. This is only
15127 supported when using a remote target that supports the @code{remote get}
15128 command (@pxref{File Transfer,,Sending files to a remote system}).
15129 The part of @var{path} following the initial @file{remote:}
15130 (if present) is used as system root prefix on the remote file system.
15131 @footnote{If you want to specify a local system root using a directory
15132 that happens to be named @file{remote:}, you need to use some equivalent
15133 variant of the name like @file{./remote:}.}
15135 For targets with an MS-DOS based filesystem, such as MS-Windows and
15136 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15137 absolute file name with @var{path}. But first, on Unix hosts,
15138 @value{GDBN} converts all backslash directory separators into forward
15139 slashes, because the backslash is not a directory separator on Unix:
15142 c:\foo\bar.dll @result{} c:/foo/bar.dll
15145 Then, @value{GDBN} attempts prefixing the target file name with
15146 @var{path}, and looks for the resulting file name in the host file
15150 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15153 If that does not find the shared library, @value{GDBN} tries removing
15154 the @samp{:} character from the drive spec, both for convenience, and,
15155 for the case of the host file system not supporting file names with
15159 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15162 This makes it possible to have a system root that mirrors a target
15163 with more than one drive. E.g., you may want to setup your local
15164 copies of the target system shared libraries like so (note @samp{c} vs
15168 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15169 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15170 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15174 and point the system root at @file{/path/to/sysroot}, so that
15175 @value{GDBN} can find the correct copies of both
15176 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15178 If that still does not find the shared library, @value{GDBN} tries
15179 removing the whole drive spec from the target file name:
15182 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15185 This last lookup makes it possible to not care about the drive name,
15186 if you don't want or need to.
15188 The @code{set solib-absolute-prefix} command is an alias for @code{set
15191 @cindex default system root
15192 @cindex @samp{--with-sysroot}
15193 You can set the default system root by using the configure-time
15194 @samp{--with-sysroot} option. If the system root is inside
15195 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15196 @samp{--exec-prefix}), then the default system root will be updated
15197 automatically if the installed @value{GDBN} is moved to a new
15200 @kindex show sysroot
15202 Display the current shared library prefix.
15204 @kindex set solib-search-path
15205 @item set solib-search-path @var{path}
15206 If this variable is set, @var{path} is a colon-separated list of
15207 directories to search for shared libraries. @samp{solib-search-path}
15208 is used after @samp{sysroot} fails to locate the library, or if the
15209 path to the library is relative instead of absolute. If you want to
15210 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15211 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15212 finding your host's libraries. @samp{sysroot} is preferred; setting
15213 it to a nonexistent directory may interfere with automatic loading
15214 of shared library symbols.
15216 @kindex show solib-search-path
15217 @item show solib-search-path
15218 Display the current shared library search path.
15220 @cindex DOS file-name semantics of file names.
15221 @kindex set target-file-system-kind (unix|dos-based|auto)
15222 @kindex show target-file-system-kind
15223 @item set target-file-system-kind @var{kind}
15224 Set assumed file system kind for target reported file names.
15226 Shared library file names as reported by the target system may not
15227 make sense as is on the system @value{GDBN} is running on. For
15228 example, when remote debugging a target that has MS-DOS based file
15229 system semantics, from a Unix host, the target may be reporting to
15230 @value{GDBN} a list of loaded shared libraries with file names such as
15231 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15232 drive letters, so the @samp{c:\} prefix is not normally understood as
15233 indicating an absolute file name, and neither is the backslash
15234 normally considered a directory separator character. In that case,
15235 the native file system would interpret this whole absolute file name
15236 as a relative file name with no directory components. This would make
15237 it impossible to point @value{GDBN} at a copy of the remote target's
15238 shared libraries on the host using @code{set sysroot}, and impractical
15239 with @code{set solib-search-path}. Setting
15240 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15241 to interpret such file names similarly to how the target would, and to
15242 map them to file names valid on @value{GDBN}'s native file system
15243 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15244 to one of the supported file system kinds. In that case, @value{GDBN}
15245 tries to determine the appropriate file system variant based on the
15246 current target's operating system (@pxref{ABI, ,Configuring the
15247 Current ABI}). The supported file system settings are:
15251 Instruct @value{GDBN} to assume the target file system is of Unix
15252 kind. Only file names starting the forward slash (@samp{/}) character
15253 are considered absolute, and the directory separator character is also
15257 Instruct @value{GDBN} to assume the target file system is DOS based.
15258 File names starting with either a forward slash, or a drive letter
15259 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15260 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15261 considered directory separators.
15264 Instruct @value{GDBN} to use the file system kind associated with the
15265 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15266 This is the default.
15271 @node Separate Debug Files
15272 @section Debugging Information in Separate Files
15273 @cindex separate debugging information files
15274 @cindex debugging information in separate files
15275 @cindex @file{.debug} subdirectories
15276 @cindex debugging information directory, global
15277 @cindex global debugging information directory
15278 @cindex build ID, and separate debugging files
15279 @cindex @file{.build-id} directory
15281 @value{GDBN} allows you to put a program's debugging information in a
15282 file separate from the executable itself, in a way that allows
15283 @value{GDBN} to find and load the debugging information automatically.
15284 Since debugging information can be very large---sometimes larger
15285 than the executable code itself---some systems distribute debugging
15286 information for their executables in separate files, which users can
15287 install only when they need to debug a problem.
15289 @value{GDBN} supports two ways of specifying the separate debug info
15294 The executable contains a @dfn{debug link} that specifies the name of
15295 the separate debug info file. The separate debug file's name is
15296 usually @file{@var{executable}.debug}, where @var{executable} is the
15297 name of the corresponding executable file without leading directories
15298 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15299 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15300 checksum for the debug file, which @value{GDBN} uses to validate that
15301 the executable and the debug file came from the same build.
15304 The executable contains a @dfn{build ID}, a unique bit string that is
15305 also present in the corresponding debug info file. (This is supported
15306 only on some operating systems, notably those which use the ELF format
15307 for binary files and the @sc{gnu} Binutils.) For more details about
15308 this feature, see the description of the @option{--build-id}
15309 command-line option in @ref{Options, , Command Line Options, ld.info,
15310 The GNU Linker}. The debug info file's name is not specified
15311 explicitly by the build ID, but can be computed from the build ID, see
15315 Depending on the way the debug info file is specified, @value{GDBN}
15316 uses two different methods of looking for the debug file:
15320 For the ``debug link'' method, @value{GDBN} looks up the named file in
15321 the directory of the executable file, then in a subdirectory of that
15322 directory named @file{.debug}, and finally under the global debug
15323 directory, in a subdirectory whose name is identical to the leading
15324 directories of the executable's absolute file name.
15327 For the ``build ID'' method, @value{GDBN} looks in the
15328 @file{.build-id} subdirectory of the global debug directory for a file
15329 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15330 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15331 are the rest of the bit string. (Real build ID strings are 32 or more
15332 hex characters, not 10.)
15335 So, for example, suppose you ask @value{GDBN} to debug
15336 @file{/usr/bin/ls}, which has a debug link that specifies the
15337 file @file{ls.debug}, and a build ID whose value in hex is
15338 @code{abcdef1234}. If the global debug directory is
15339 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15340 debug information files, in the indicated order:
15344 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15346 @file{/usr/bin/ls.debug}
15348 @file{/usr/bin/.debug/ls.debug}
15350 @file{/usr/lib/debug/usr/bin/ls.debug}.
15353 You can set the global debugging info directory's name, and view the
15354 name @value{GDBN} is currently using.
15358 @kindex set debug-file-directory
15359 @item set debug-file-directory @var{directories}
15360 Set the directories which @value{GDBN} searches for separate debugging
15361 information files to @var{directory}. Multiple directory components can be set
15362 concatenating them by a directory separator.
15364 @kindex show debug-file-directory
15365 @item show debug-file-directory
15366 Show the directories @value{GDBN} searches for separate debugging
15371 @cindex @code{.gnu_debuglink} sections
15372 @cindex debug link sections
15373 A debug link is a special section of the executable file named
15374 @code{.gnu_debuglink}. The section must contain:
15378 A filename, with any leading directory components removed, followed by
15381 zero to three bytes of padding, as needed to reach the next four-byte
15382 boundary within the section, and
15384 a four-byte CRC checksum, stored in the same endianness used for the
15385 executable file itself. The checksum is computed on the debugging
15386 information file's full contents by the function given below, passing
15387 zero as the @var{crc} argument.
15390 Any executable file format can carry a debug link, as long as it can
15391 contain a section named @code{.gnu_debuglink} with the contents
15394 @cindex @code{.note.gnu.build-id} sections
15395 @cindex build ID sections
15396 The build ID is a special section in the executable file (and in other
15397 ELF binary files that @value{GDBN} may consider). This section is
15398 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15399 It contains unique identification for the built files---the ID remains
15400 the same across multiple builds of the same build tree. The default
15401 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15402 content for the build ID string. The same section with an identical
15403 value is present in the original built binary with symbols, in its
15404 stripped variant, and in the separate debugging information file.
15406 The debugging information file itself should be an ordinary
15407 executable, containing a full set of linker symbols, sections, and
15408 debugging information. The sections of the debugging information file
15409 should have the same names, addresses, and sizes as the original file,
15410 but they need not contain any data---much like a @code{.bss} section
15411 in an ordinary executable.
15413 The @sc{gnu} binary utilities (Binutils) package includes the
15414 @samp{objcopy} utility that can produce
15415 the separated executable / debugging information file pairs using the
15416 following commands:
15419 @kbd{objcopy --only-keep-debug foo foo.debug}
15424 These commands remove the debugging
15425 information from the executable file @file{foo} and place it in the file
15426 @file{foo.debug}. You can use the first, second or both methods to link the
15431 The debug link method needs the following additional command to also leave
15432 behind a debug link in @file{foo}:
15435 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15438 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15439 a version of the @code{strip} command such that the command @kbd{strip foo -f
15440 foo.debug} has the same functionality as the two @code{objcopy} commands and
15441 the @code{ln -s} command above, together.
15444 Build ID gets embedded into the main executable using @code{ld --build-id} or
15445 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15446 compatibility fixes for debug files separation are present in @sc{gnu} binary
15447 utilities (Binutils) package since version 2.18.
15452 @cindex CRC algorithm definition
15453 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15454 IEEE 802.3 using the polynomial:
15456 @c TexInfo requires naked braces for multi-digit exponents for Tex
15457 @c output, but this causes HTML output to barf. HTML has to be set using
15458 @c raw commands. So we end up having to specify this equation in 2
15463 <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>
15464 + <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
15470 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15471 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15475 The function is computed byte at a time, taking the least
15476 significant bit of each byte first. The initial pattern
15477 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15478 the final result is inverted to ensure trailing zeros also affect the
15481 @emph{Note:} This is the same CRC polynomial as used in handling the
15482 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15483 , @value{GDBN} Remote Serial Protocol}). However in the
15484 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15485 significant bit first, and the result is not inverted, so trailing
15486 zeros have no effect on the CRC value.
15488 To complete the description, we show below the code of the function
15489 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15490 initially supplied @code{crc} argument means that an initial call to
15491 this function passing in zero will start computing the CRC using
15494 @kindex gnu_debuglink_crc32
15497 gnu_debuglink_crc32 (unsigned long crc,
15498 unsigned char *buf, size_t len)
15500 static const unsigned long crc32_table[256] =
15502 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15503 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15504 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15505 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15506 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15507 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15508 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15509 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15510 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15511 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15512 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15513 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15514 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15515 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15516 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15517 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15518 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15519 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15520 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15521 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15522 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15523 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15524 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15525 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15526 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15527 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15528 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15529 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15530 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15531 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15532 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15533 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15534 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15535 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15536 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15537 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15538 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15539 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15540 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15541 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15542 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15543 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15544 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15545 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15546 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15547 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15548 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15549 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15550 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15551 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15552 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15555 unsigned char *end;
15557 crc = ~crc & 0xffffffff;
15558 for (end = buf + len; buf < end; ++buf)
15559 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15560 return ~crc & 0xffffffff;
15565 This computation does not apply to the ``build ID'' method.
15569 @section Index Files Speed Up @value{GDBN}
15570 @cindex index files
15571 @cindex @samp{.gdb_index} section
15573 When @value{GDBN} finds a symbol file, it scans the symbols in the
15574 file in order to construct an internal symbol table. This lets most
15575 @value{GDBN} operations work quickly---at the cost of a delay early
15576 on. For large programs, this delay can be quite lengthy, so
15577 @value{GDBN} provides a way to build an index, which speeds up
15580 The index is stored as a section in the symbol file. @value{GDBN} can
15581 write the index to a file, then you can put it into the symbol file
15582 using @command{objcopy}.
15584 To create an index file, use the @code{save gdb-index} command:
15587 @item save gdb-index @var{directory}
15588 @kindex save gdb-index
15589 Create an index file for each symbol file currently known by
15590 @value{GDBN}. Each file is named after its corresponding symbol file,
15591 with @samp{.gdb-index} appended, and is written into the given
15595 Once you have created an index file you can merge it into your symbol
15596 file, here named @file{symfile}, using @command{objcopy}:
15599 $ objcopy --add-section .gdb_index=symfile.gdb-index \
15600 --set-section-flags .gdb_index=readonly symfile symfile
15603 There are currently some limitation on indices. They only work when
15604 for DWARF debugging information, not stabs. And, they do not
15605 currently work for programs using Ada.
15607 @node Symbol Errors
15608 @section Errors Reading Symbol Files
15610 While reading a symbol file, @value{GDBN} occasionally encounters problems,
15611 such as symbol types it does not recognize, or known bugs in compiler
15612 output. By default, @value{GDBN} does not notify you of such problems, since
15613 they are relatively common and primarily of interest to people
15614 debugging compilers. If you are interested in seeing information
15615 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
15616 only one message about each such type of problem, no matter how many
15617 times the problem occurs; or you can ask @value{GDBN} to print more messages,
15618 to see how many times the problems occur, with the @code{set
15619 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
15622 The messages currently printed, and their meanings, include:
15625 @item inner block not inside outer block in @var{symbol}
15627 The symbol information shows where symbol scopes begin and end
15628 (such as at the start of a function or a block of statements). This
15629 error indicates that an inner scope block is not fully contained
15630 in its outer scope blocks.
15632 @value{GDBN} circumvents the problem by treating the inner block as if it had
15633 the same scope as the outer block. In the error message, @var{symbol}
15634 may be shown as ``@code{(don't know)}'' if the outer block is not a
15637 @item block at @var{address} out of order
15639 The symbol information for symbol scope blocks should occur in
15640 order of increasing addresses. This error indicates that it does not
15643 @value{GDBN} does not circumvent this problem, and has trouble
15644 locating symbols in the source file whose symbols it is reading. (You
15645 can often determine what source file is affected by specifying
15646 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
15649 @item bad block start address patched
15651 The symbol information for a symbol scope block has a start address
15652 smaller than the address of the preceding source line. This is known
15653 to occur in the SunOS 4.1.1 (and earlier) C compiler.
15655 @value{GDBN} circumvents the problem by treating the symbol scope block as
15656 starting on the previous source line.
15658 @item bad string table offset in symbol @var{n}
15661 Symbol number @var{n} contains a pointer into the string table which is
15662 larger than the size of the string table.
15664 @value{GDBN} circumvents the problem by considering the symbol to have the
15665 name @code{foo}, which may cause other problems if many symbols end up
15668 @item unknown symbol type @code{0x@var{nn}}
15670 The symbol information contains new data types that @value{GDBN} does
15671 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
15672 uncomprehended information, in hexadecimal.
15674 @value{GDBN} circumvents the error by ignoring this symbol information.
15675 This usually allows you to debug your program, though certain symbols
15676 are not accessible. If you encounter such a problem and feel like
15677 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
15678 on @code{complain}, then go up to the function @code{read_dbx_symtab}
15679 and examine @code{*bufp} to see the symbol.
15681 @item stub type has NULL name
15683 @value{GDBN} could not find the full definition for a struct or class.
15685 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
15686 The symbol information for a C@t{++} member function is missing some
15687 information that recent versions of the compiler should have output for
15690 @item info mismatch between compiler and debugger
15692 @value{GDBN} could not parse a type specification output by the compiler.
15697 @section GDB Data Files
15699 @cindex prefix for data files
15700 @value{GDBN} will sometimes read an auxiliary data file. These files
15701 are kept in a directory known as the @dfn{data directory}.
15703 You can set the data directory's name, and view the name @value{GDBN}
15704 is currently using.
15707 @kindex set data-directory
15708 @item set data-directory @var{directory}
15709 Set the directory which @value{GDBN} searches for auxiliary data files
15710 to @var{directory}.
15712 @kindex show data-directory
15713 @item show data-directory
15714 Show the directory @value{GDBN} searches for auxiliary data files.
15717 @cindex default data directory
15718 @cindex @samp{--with-gdb-datadir}
15719 You can set the default data directory by using the configure-time
15720 @samp{--with-gdb-datadir} option. If the data directory is inside
15721 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15722 @samp{--exec-prefix}), then the default data directory will be updated
15723 automatically if the installed @value{GDBN} is moved to a new
15726 The data directory may also be specified with the
15727 @code{--data-directory} command line option.
15728 @xref{Mode Options}.
15731 @chapter Specifying a Debugging Target
15733 @cindex debugging target
15734 A @dfn{target} is the execution environment occupied by your program.
15736 Often, @value{GDBN} runs in the same host environment as your program;
15737 in that case, the debugging target is specified as a side effect when
15738 you use the @code{file} or @code{core} commands. When you need more
15739 flexibility---for example, running @value{GDBN} on a physically separate
15740 host, or controlling a standalone system over a serial port or a
15741 realtime system over a TCP/IP connection---you can use the @code{target}
15742 command to specify one of the target types configured for @value{GDBN}
15743 (@pxref{Target Commands, ,Commands for Managing Targets}).
15745 @cindex target architecture
15746 It is possible to build @value{GDBN} for several different @dfn{target
15747 architectures}. When @value{GDBN} is built like that, you can choose
15748 one of the available architectures with the @kbd{set architecture}
15752 @kindex set architecture
15753 @kindex show architecture
15754 @item set architecture @var{arch}
15755 This command sets the current target architecture to @var{arch}. The
15756 value of @var{arch} can be @code{"auto"}, in addition to one of the
15757 supported architectures.
15759 @item show architecture
15760 Show the current target architecture.
15762 @item set processor
15764 @kindex set processor
15765 @kindex show processor
15766 These are alias commands for, respectively, @code{set architecture}
15767 and @code{show architecture}.
15771 * Active Targets:: Active targets
15772 * Target Commands:: Commands for managing targets
15773 * Byte Order:: Choosing target byte order
15776 @node Active Targets
15777 @section Active Targets
15779 @cindex stacking targets
15780 @cindex active targets
15781 @cindex multiple targets
15783 There are multiple classes of targets such as: processes, executable files or
15784 recording sessions. Core files belong to the process class, making core file
15785 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
15786 on multiple active targets, one in each class. This allows you to (for
15787 example) start a process and inspect its activity, while still having access to
15788 the executable file after the process finishes. Or if you start process
15789 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
15790 presented a virtual layer of the recording target, while the process target
15791 remains stopped at the chronologically last point of the process execution.
15793 Use the @code{core-file} and @code{exec-file} commands to select a new core
15794 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
15795 specify as a target a process that is already running, use the @code{attach}
15796 command (@pxref{Attach, ,Debugging an Already-running Process}).
15798 @node Target Commands
15799 @section Commands for Managing Targets
15802 @item target @var{type} @var{parameters}
15803 Connects the @value{GDBN} host environment to a target machine or
15804 process. A target is typically a protocol for talking to debugging
15805 facilities. You use the argument @var{type} to specify the type or
15806 protocol of the target machine.
15808 Further @var{parameters} are interpreted by the target protocol, but
15809 typically include things like device names or host names to connect
15810 with, process numbers, and baud rates.
15812 The @code{target} command does not repeat if you press @key{RET} again
15813 after executing the command.
15815 @kindex help target
15817 Displays the names of all targets available. To display targets
15818 currently selected, use either @code{info target} or @code{info files}
15819 (@pxref{Files, ,Commands to Specify Files}).
15821 @item help target @var{name}
15822 Describe a particular target, including any parameters necessary to
15825 @kindex set gnutarget
15826 @item set gnutarget @var{args}
15827 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15828 knows whether it is reading an @dfn{executable},
15829 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15830 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15831 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15834 @emph{Warning:} To specify a file format with @code{set gnutarget},
15835 you must know the actual BFD name.
15839 @xref{Files, , Commands to Specify Files}.
15841 @kindex show gnutarget
15842 @item show gnutarget
15843 Use the @code{show gnutarget} command to display what file format
15844 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15845 @value{GDBN} will determine the file format for each file automatically,
15846 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15849 @cindex common targets
15850 Here are some common targets (available, or not, depending on the GDB
15855 @item target exec @var{program}
15856 @cindex executable file target
15857 An executable file. @samp{target exec @var{program}} is the same as
15858 @samp{exec-file @var{program}}.
15860 @item target core @var{filename}
15861 @cindex core dump file target
15862 A core dump file. @samp{target core @var{filename}} is the same as
15863 @samp{core-file @var{filename}}.
15865 @item target remote @var{medium}
15866 @cindex remote target
15867 A remote system connected to @value{GDBN} via a serial line or network
15868 connection. This command tells @value{GDBN} to use its own remote
15869 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15871 For example, if you have a board connected to @file{/dev/ttya} on the
15872 machine running @value{GDBN}, you could say:
15875 target remote /dev/ttya
15878 @code{target remote} supports the @code{load} command. This is only
15879 useful if you have some other way of getting the stub to the target
15880 system, and you can put it somewhere in memory where it won't get
15881 clobbered by the download.
15883 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15884 @cindex built-in simulator target
15885 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15893 works; however, you cannot assume that a specific memory map, device
15894 drivers, or even basic I/O is available, although some simulators do
15895 provide these. For info about any processor-specific simulator details,
15896 see the appropriate section in @ref{Embedded Processors, ,Embedded
15901 Some configurations may include these targets as well:
15905 @item target nrom @var{dev}
15906 @cindex NetROM ROM emulator target
15907 NetROM ROM emulator. This target only supports downloading.
15911 Different targets are available on different configurations of @value{GDBN};
15912 your configuration may have more or fewer targets.
15914 Many remote targets require you to download the executable's code once
15915 you've successfully established a connection. You may wish to control
15916 various aspects of this process.
15921 @kindex set hash@r{, for remote monitors}
15922 @cindex hash mark while downloading
15923 This command controls whether a hash mark @samp{#} is displayed while
15924 downloading a file to the remote monitor. If on, a hash mark is
15925 displayed after each S-record is successfully downloaded to the
15929 @kindex show hash@r{, for remote monitors}
15930 Show the current status of displaying the hash mark.
15932 @item set debug monitor
15933 @kindex set debug monitor
15934 @cindex display remote monitor communications
15935 Enable or disable display of communications messages between
15936 @value{GDBN} and the remote monitor.
15938 @item show debug monitor
15939 @kindex show debug monitor
15940 Show the current status of displaying communications between
15941 @value{GDBN} and the remote monitor.
15946 @kindex load @var{filename}
15947 @item load @var{filename}
15949 Depending on what remote debugging facilities are configured into
15950 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15951 is meant to make @var{filename} (an executable) available for debugging
15952 on the remote system---by downloading, or dynamic linking, for example.
15953 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15954 the @code{add-symbol-file} command.
15956 If your @value{GDBN} does not have a @code{load} command, attempting to
15957 execute it gets the error message ``@code{You can't do that when your
15958 target is @dots{}}''
15960 The file is loaded at whatever address is specified in the executable.
15961 For some object file formats, you can specify the load address when you
15962 link the program; for other formats, like a.out, the object file format
15963 specifies a fixed address.
15964 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15966 Depending on the remote side capabilities, @value{GDBN} may be able to
15967 load programs into flash memory.
15969 @code{load} does not repeat if you press @key{RET} again after using it.
15973 @section Choosing Target Byte Order
15975 @cindex choosing target byte order
15976 @cindex target byte order
15978 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15979 offer the ability to run either big-endian or little-endian byte
15980 orders. Usually the executable or symbol will include a bit to
15981 designate the endian-ness, and you will not need to worry about
15982 which to use. However, you may still find it useful to adjust
15983 @value{GDBN}'s idea of processor endian-ness manually.
15987 @item set endian big
15988 Instruct @value{GDBN} to assume the target is big-endian.
15990 @item set endian little
15991 Instruct @value{GDBN} to assume the target is little-endian.
15993 @item set endian auto
15994 Instruct @value{GDBN} to use the byte order associated with the
15998 Display @value{GDBN}'s current idea of the target byte order.
16002 Note that these commands merely adjust interpretation of symbolic
16003 data on the host, and that they have absolutely no effect on the
16007 @node Remote Debugging
16008 @chapter Debugging Remote Programs
16009 @cindex remote debugging
16011 If you are trying to debug a program running on a machine that cannot run
16012 @value{GDBN} in the usual way, it is often useful to use remote debugging.
16013 For example, you might use remote debugging on an operating system kernel,
16014 or on a small system which does not have a general purpose operating system
16015 powerful enough to run a full-featured debugger.
16017 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
16018 to make this work with particular debugging targets. In addition,
16019 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
16020 but not specific to any particular target system) which you can use if you
16021 write the remote stubs---the code that runs on the remote system to
16022 communicate with @value{GDBN}.
16024 Other remote targets may be available in your
16025 configuration of @value{GDBN}; use @code{help target} to list them.
16028 * Connecting:: Connecting to a remote target
16029 * File Transfer:: Sending files to a remote system
16030 * Server:: Using the gdbserver program
16031 * Remote Configuration:: Remote configuration
16032 * Remote Stub:: Implementing a remote stub
16036 @section Connecting to a Remote Target
16038 On the @value{GDBN} host machine, you will need an unstripped copy of
16039 your program, since @value{GDBN} needs symbol and debugging information.
16040 Start up @value{GDBN} as usual, using the name of the local copy of your
16041 program as the first argument.
16043 @cindex @code{target remote}
16044 @value{GDBN} can communicate with the target over a serial line, or
16045 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16046 each case, @value{GDBN} uses the same protocol for debugging your
16047 program; only the medium carrying the debugging packets varies. The
16048 @code{target remote} command establishes a connection to the target.
16049 Its arguments indicate which medium to use:
16053 @item target remote @var{serial-device}
16054 @cindex serial line, @code{target remote}
16055 Use @var{serial-device} to communicate with the target. For example,
16056 to use a serial line connected to the device named @file{/dev/ttyb}:
16059 target remote /dev/ttyb
16062 If you're using a serial line, you may want to give @value{GDBN} the
16063 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16064 (@pxref{Remote Configuration, set remotebaud}) before the
16065 @code{target} command.
16067 @item target remote @code{@var{host}:@var{port}}
16068 @itemx target remote @code{tcp:@var{host}:@var{port}}
16069 @cindex @acronym{TCP} port, @code{target remote}
16070 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16071 The @var{host} may be either a host name or a numeric @acronym{IP}
16072 address; @var{port} must be a decimal number. The @var{host} could be
16073 the target machine itself, if it is directly connected to the net, or
16074 it might be a terminal server which in turn has a serial line to the
16077 For example, to connect to port 2828 on a terminal server named
16081 target remote manyfarms:2828
16084 If your remote target is actually running on the same machine as your
16085 debugger session (e.g.@: a simulator for your target running on the
16086 same host), you can omit the hostname. For example, to connect to
16087 port 1234 on your local machine:
16090 target remote :1234
16094 Note that the colon is still required here.
16096 @item target remote @code{udp:@var{host}:@var{port}}
16097 @cindex @acronym{UDP} port, @code{target remote}
16098 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16099 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16102 target remote udp:manyfarms:2828
16105 When using a @acronym{UDP} connection for remote debugging, you should
16106 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16107 can silently drop packets on busy or unreliable networks, which will
16108 cause havoc with your debugging session.
16110 @item target remote | @var{command}
16111 @cindex pipe, @code{target remote} to
16112 Run @var{command} in the background and communicate with it using a
16113 pipe. The @var{command} is a shell command, to be parsed and expanded
16114 by the system's command shell, @code{/bin/sh}; it should expect remote
16115 protocol packets on its standard input, and send replies on its
16116 standard output. You could use this to run a stand-alone simulator
16117 that speaks the remote debugging protocol, to make net connections
16118 using programs like @code{ssh}, or for other similar tricks.
16120 If @var{command} closes its standard output (perhaps by exiting),
16121 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16122 program has already exited, this will have no effect.)
16126 Once the connection has been established, you can use all the usual
16127 commands to examine and change data. The remote program is already
16128 running; you can use @kbd{step} and @kbd{continue}, and you do not
16129 need to use @kbd{run}.
16131 @cindex interrupting remote programs
16132 @cindex remote programs, interrupting
16133 Whenever @value{GDBN} is waiting for the remote program, if you type the
16134 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16135 program. This may or may not succeed, depending in part on the hardware
16136 and the serial drivers the remote system uses. If you type the
16137 interrupt character once again, @value{GDBN} displays this prompt:
16140 Interrupted while waiting for the program.
16141 Give up (and stop debugging it)? (y or n)
16144 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16145 (If you decide you want to try again later, you can use @samp{target
16146 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16147 goes back to waiting.
16150 @kindex detach (remote)
16152 When you have finished debugging the remote program, you can use the
16153 @code{detach} command to release it from @value{GDBN} control.
16154 Detaching from the target normally resumes its execution, but the results
16155 will depend on your particular remote stub. After the @code{detach}
16156 command, @value{GDBN} is free to connect to another target.
16160 The @code{disconnect} command behaves like @code{detach}, except that
16161 the target is generally not resumed. It will wait for @value{GDBN}
16162 (this instance or another one) to connect and continue debugging. After
16163 the @code{disconnect} command, @value{GDBN} is again free to connect to
16166 @cindex send command to remote monitor
16167 @cindex extend @value{GDBN} for remote targets
16168 @cindex add new commands for external monitor
16170 @item monitor @var{cmd}
16171 This command allows you to send arbitrary commands directly to the
16172 remote monitor. Since @value{GDBN} doesn't care about the commands it
16173 sends like this, this command is the way to extend @value{GDBN}---you
16174 can add new commands that only the external monitor will understand
16178 @node File Transfer
16179 @section Sending files to a remote system
16180 @cindex remote target, file transfer
16181 @cindex file transfer
16182 @cindex sending files to remote systems
16184 Some remote targets offer the ability to transfer files over the same
16185 connection used to communicate with @value{GDBN}. This is convenient
16186 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16187 running @code{gdbserver} over a network interface. For other targets,
16188 e.g.@: embedded devices with only a single serial port, this may be
16189 the only way to upload or download files.
16191 Not all remote targets support these commands.
16195 @item remote put @var{hostfile} @var{targetfile}
16196 Copy file @var{hostfile} from the host system (the machine running
16197 @value{GDBN}) to @var{targetfile} on the target system.
16200 @item remote get @var{targetfile} @var{hostfile}
16201 Copy file @var{targetfile} from the target system to @var{hostfile}
16202 on the host system.
16204 @kindex remote delete
16205 @item remote delete @var{targetfile}
16206 Delete @var{targetfile} from the target system.
16211 @section Using the @code{gdbserver} Program
16214 @cindex remote connection without stubs
16215 @code{gdbserver} is a control program for Unix-like systems, which
16216 allows you to connect your program with a remote @value{GDBN} via
16217 @code{target remote}---but without linking in the usual debugging stub.
16219 @code{gdbserver} is not a complete replacement for the debugging stubs,
16220 because it requires essentially the same operating-system facilities
16221 that @value{GDBN} itself does. In fact, a system that can run
16222 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16223 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16224 because it is a much smaller program than @value{GDBN} itself. It is
16225 also easier to port than all of @value{GDBN}, so you may be able to get
16226 started more quickly on a new system by using @code{gdbserver}.
16227 Finally, if you develop code for real-time systems, you may find that
16228 the tradeoffs involved in real-time operation make it more convenient to
16229 do as much development work as possible on another system, for example
16230 by cross-compiling. You can use @code{gdbserver} to make a similar
16231 choice for debugging.
16233 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16234 or a TCP connection, using the standard @value{GDBN} remote serial
16238 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16239 Do not run @code{gdbserver} connected to any public network; a
16240 @value{GDBN} connection to @code{gdbserver} provides access to the
16241 target system with the same privileges as the user running
16245 @subsection Running @code{gdbserver}
16246 @cindex arguments, to @code{gdbserver}
16247 @cindex @code{gdbserver}, command-line arguments
16249 Run @code{gdbserver} on the target system. You need a copy of the
16250 program you want to debug, including any libraries it requires.
16251 @code{gdbserver} does not need your program's symbol table, so you can
16252 strip the program if necessary to save space. @value{GDBN} on the host
16253 system does all the symbol handling.
16255 To use the server, you must tell it how to communicate with @value{GDBN};
16256 the name of your program; and the arguments for your program. The usual
16260 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16263 @var{comm} is either a device name (to use a serial line) or a TCP
16264 hostname and portnumber. For example, to debug Emacs with the argument
16265 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16269 target> gdbserver /dev/com1 emacs foo.txt
16272 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16275 To use a TCP connection instead of a serial line:
16278 target> gdbserver host:2345 emacs foo.txt
16281 The only difference from the previous example is the first argument,
16282 specifying that you are communicating with the host @value{GDBN} via
16283 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16284 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16285 (Currently, the @samp{host} part is ignored.) You can choose any number
16286 you want for the port number as long as it does not conflict with any
16287 TCP ports already in use on the target system (for example, @code{23} is
16288 reserved for @code{telnet}).@footnote{If you choose a port number that
16289 conflicts with another service, @code{gdbserver} prints an error message
16290 and exits.} You must use the same port number with the host @value{GDBN}
16291 @code{target remote} command.
16293 @subsubsection Attaching to a Running Program
16294 @cindex attach to a program, @code{gdbserver}
16295 @cindex @option{--attach}, @code{gdbserver} option
16297 On some targets, @code{gdbserver} can also attach to running programs.
16298 This is accomplished via the @code{--attach} argument. The syntax is:
16301 target> gdbserver --attach @var{comm} @var{pid}
16304 @var{pid} is the process ID of a currently running process. It isn't necessary
16305 to point @code{gdbserver} at a binary for the running process.
16308 You can debug processes by name instead of process ID if your target has the
16309 @code{pidof} utility:
16312 target> gdbserver --attach @var{comm} `pidof @var{program}`
16315 In case more than one copy of @var{program} is running, or @var{program}
16316 has multiple threads, most versions of @code{pidof} support the
16317 @code{-s} option to only return the first process ID.
16319 @subsubsection Multi-Process Mode for @code{gdbserver}
16320 @cindex @code{gdbserver}, multiple processes
16321 @cindex multiple processes with @code{gdbserver}
16323 When you connect to @code{gdbserver} using @code{target remote},
16324 @code{gdbserver} debugs the specified program only once. When the
16325 program exits, or you detach from it, @value{GDBN} closes the connection
16326 and @code{gdbserver} exits.
16328 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16329 enters multi-process mode. When the debugged program exits, or you
16330 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16331 though no program is running. The @code{run} and @code{attach}
16332 commands instruct @code{gdbserver} to run or attach to a new program.
16333 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16334 remote exec-file}) to select the program to run. Command line
16335 arguments are supported, except for wildcard expansion and I/O
16336 redirection (@pxref{Arguments}).
16338 @cindex @option{--multi}, @code{gdbserver} option
16339 To start @code{gdbserver} without supplying an initial command to run
16340 or process ID to attach, use the @option{--multi} command line option.
16341 Then you can connect using @kbd{target extended-remote} and start
16342 the program you want to debug.
16344 In multi-process mode @code{gdbserver} does not automatically exit unless you
16345 use the option @option{--once}. You can terminate it by using
16346 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16347 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16348 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16349 @option{--multi} option to @code{gdbserver} has no influence on that.
16351 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
16353 This section applies only when @code{gdbserver} is run to listen on a TCP port.
16355 @code{gdbserver} normally terminates after all of its debugged processes have
16356 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
16357 extended-remote}, @code{gdbserver} stays running even with no processes left.
16358 @value{GDBN} normally terminates the spawned debugged process on its exit,
16359 which normally also terminates @code{gdbserver} in the @kbd{target remote}
16360 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
16361 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
16362 stays running even in the @kbd{target remote} mode.
16364 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
16365 Such reconnecting is useful for features like @ref{disconnected tracing}. For
16366 completeness, at most one @value{GDBN} can be connected at a time.
16368 @cindex @option{--once}, @code{gdbserver} option
16369 By default, @code{gdbserver} keeps the listening TCP port open, so that
16370 additional connections are possible. However, if you start @code{gdbserver}
16371 with the @option{--once} option, it will stop listening for any further
16372 connection attempts after connecting to the first @value{GDBN} session. This
16373 means no further connections to @code{gdbserver} will be possible after the
16374 first one. It also means @code{gdbserver} will terminate after the first
16375 connection with remote @value{GDBN} has closed, even for unexpectedly closed
16376 connections and even in the @kbd{target extended-remote} mode. The
16377 @option{--once} option allows reusing the same port number for connecting to
16378 multiple instances of @code{gdbserver} running on the same host, since each
16379 instance closes its port after the first connection.
16381 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16383 @cindex @option{--debug}, @code{gdbserver} option
16384 The @option{--debug} option tells @code{gdbserver} to display extra
16385 status information about the debugging process.
16386 @cindex @option{--remote-debug}, @code{gdbserver} option
16387 The @option{--remote-debug} option tells @code{gdbserver} to display
16388 remote protocol debug output. These options are intended for
16389 @code{gdbserver} development and for bug reports to the developers.
16391 @cindex @option{--wrapper}, @code{gdbserver} option
16392 The @option{--wrapper} option specifies a wrapper to launch programs
16393 for debugging. The option should be followed by the name of the
16394 wrapper, then any command-line arguments to pass to the wrapper, then
16395 @kbd{--} indicating the end of the wrapper arguments.
16397 @code{gdbserver} runs the specified wrapper program with a combined
16398 command line including the wrapper arguments, then the name of the
16399 program to debug, then any arguments to the program. The wrapper
16400 runs until it executes your program, and then @value{GDBN} gains control.
16402 You can use any program that eventually calls @code{execve} with
16403 its arguments as a wrapper. Several standard Unix utilities do
16404 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16405 with @code{exec "$@@"} will also work.
16407 For example, you can use @code{env} to pass an environment variable to
16408 the debugged program, without setting the variable in @code{gdbserver}'s
16412 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16415 @subsection Connecting to @code{gdbserver}
16417 Run @value{GDBN} on the host system.
16419 First make sure you have the necessary symbol files. Load symbols for
16420 your application using the @code{file} command before you connect. Use
16421 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16422 was compiled with the correct sysroot using @code{--with-sysroot}).
16424 The symbol file and target libraries must exactly match the executable
16425 and libraries on the target, with one exception: the files on the host
16426 system should not be stripped, even if the files on the target system
16427 are. Mismatched or missing files will lead to confusing results
16428 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16429 files may also prevent @code{gdbserver} from debugging multi-threaded
16432 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16433 For TCP connections, you must start up @code{gdbserver} prior to using
16434 the @code{target remote} command. Otherwise you may get an error whose
16435 text depends on the host system, but which usually looks something like
16436 @samp{Connection refused}. Don't use the @code{load}
16437 command in @value{GDBN} when using @code{gdbserver}, since the program is
16438 already on the target.
16440 @subsection Monitor Commands for @code{gdbserver}
16441 @cindex monitor commands, for @code{gdbserver}
16442 @anchor{Monitor Commands for gdbserver}
16444 During a @value{GDBN} session using @code{gdbserver}, you can use the
16445 @code{monitor} command to send special requests to @code{gdbserver}.
16446 Here are the available commands.
16450 List the available monitor commands.
16452 @item monitor set debug 0
16453 @itemx monitor set debug 1
16454 Disable or enable general debugging messages.
16456 @item monitor set remote-debug 0
16457 @itemx monitor set remote-debug 1
16458 Disable or enable specific debugging messages associated with the remote
16459 protocol (@pxref{Remote Protocol}).
16461 @item monitor set libthread-db-search-path [PATH]
16462 @cindex gdbserver, search path for @code{libthread_db}
16463 When this command is issued, @var{path} is a colon-separated list of
16464 directories to search for @code{libthread_db} (@pxref{Threads,,set
16465 libthread-db-search-path}). If you omit @var{path},
16466 @samp{libthread-db-search-path} will be reset to its default value.
16468 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
16469 not supported in @code{gdbserver}.
16472 Tell gdbserver to exit immediately. This command should be followed by
16473 @code{disconnect} to close the debugging session. @code{gdbserver} will
16474 detach from any attached processes and kill any processes it created.
16475 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16476 of a multi-process mode debug session.
16480 @subsection Tracepoints support in @code{gdbserver}
16481 @cindex tracepoints support in @code{gdbserver}
16483 On some targets, @code{gdbserver} supports tracepoints, fast
16484 tracepoints and static tracepoints.
16486 For fast or static tracepoints to work, a special library called the
16487 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16488 This library is built and distributed as an integral part of
16489 @code{gdbserver}. In addition, support for static tracepoints
16490 requires building the in-process agent library with static tracepoints
16491 support. At present, the UST (LTTng Userspace Tracer,
16492 @url{http://lttng.org/ust}) tracing engine is supported. This support
16493 is automatically available if UST development headers are found in the
16494 standard include path when @code{gdbserver} is built, or if
16495 @code{gdbserver} was explicitly configured using @option{--with-ust}
16496 to point at such headers. You can explicitly disable the support
16497 using @option{--with-ust=no}.
16499 There are several ways to load the in-process agent in your program:
16502 @item Specifying it as dependency at link time
16504 You can link your program dynamically with the in-process agent
16505 library. On most systems, this is accomplished by adding
16506 @code{-linproctrace} to the link command.
16508 @item Using the system's preloading mechanisms
16510 You can force loading the in-process agent at startup time by using
16511 your system's support for preloading shared libraries. Many Unixes
16512 support the concept of preloading user defined libraries. In most
16513 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16514 in the environment. See also the description of @code{gdbserver}'s
16515 @option{--wrapper} command line option.
16517 @item Using @value{GDBN} to force loading the agent at run time
16519 On some systems, you can force the inferior to load a shared library,
16520 by calling a dynamic loader function in the inferior that takes care
16521 of dynamically looking up and loading a shared library. On most Unix
16522 systems, the function is @code{dlopen}. You'll use the @code{call}
16523 command for that. For example:
16526 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16529 Note that on most Unix systems, for the @code{dlopen} function to be
16530 available, the program needs to be linked with @code{-ldl}.
16533 On systems that have a userspace dynamic loader, like most Unix
16534 systems, when you connect to @code{gdbserver} using @code{target
16535 remote}, you'll find that the program is stopped at the dynamic
16536 loader's entry point, and no shared library has been loaded in the
16537 program's address space yet, including the in-process agent. In that
16538 case, before being able to use any of the fast or static tracepoints
16539 features, you need to let the loader run and load the shared
16540 libraries. The simplest way to do that is to run the program to the
16541 main procedure. E.g., if debugging a C or C@t{++} program, start
16542 @code{gdbserver} like so:
16545 $ gdbserver :9999 myprogram
16548 Start GDB and connect to @code{gdbserver} like so, and run to main:
16552 (@value{GDBP}) target remote myhost:9999
16553 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16554 (@value{GDBP}) b main
16555 (@value{GDBP}) continue
16558 The in-process tracing agent library should now be loaded into the
16559 process; you can confirm it with the @code{info sharedlibrary}
16560 command, which will list @file{libinproctrace.so} as loaded in the
16561 process. You are now ready to install fast tracepoints, list static
16562 tracepoint markers, probe static tracepoints markers, and start
16565 @node Remote Configuration
16566 @section Remote Configuration
16569 @kindex show remote
16570 This section documents the configuration options available when
16571 debugging remote programs. For the options related to the File I/O
16572 extensions of the remote protocol, see @ref{system,
16573 system-call-allowed}.
16576 @item set remoteaddresssize @var{bits}
16577 @cindex address size for remote targets
16578 @cindex bits in remote address
16579 Set the maximum size of address in a memory packet to the specified
16580 number of bits. @value{GDBN} will mask off the address bits above
16581 that number, when it passes addresses to the remote target. The
16582 default value is the number of bits in the target's address.
16584 @item show remoteaddresssize
16585 Show the current value of remote address size in bits.
16587 @item set remotebaud @var{n}
16588 @cindex baud rate for remote targets
16589 Set the baud rate for the remote serial I/O to @var{n} baud. The
16590 value is used to set the speed of the serial port used for debugging
16593 @item show remotebaud
16594 Show the current speed of the remote connection.
16596 @item set remotebreak
16597 @cindex interrupt remote programs
16598 @cindex BREAK signal instead of Ctrl-C
16599 @anchor{set remotebreak}
16600 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
16601 when you type @kbd{Ctrl-c} to interrupt the program running
16602 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
16603 character instead. The default is off, since most remote systems
16604 expect to see @samp{Ctrl-C} as the interrupt signal.
16606 @item show remotebreak
16607 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
16608 interrupt the remote program.
16610 @item set remoteflow on
16611 @itemx set remoteflow off
16612 @kindex set remoteflow
16613 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
16614 on the serial port used to communicate to the remote target.
16616 @item show remoteflow
16617 @kindex show remoteflow
16618 Show the current setting of hardware flow control.
16620 @item set remotelogbase @var{base}
16621 Set the base (a.k.a.@: radix) of logging serial protocol
16622 communications to @var{base}. Supported values of @var{base} are:
16623 @code{ascii}, @code{octal}, and @code{hex}. The default is
16626 @item show remotelogbase
16627 Show the current setting of the radix for logging remote serial
16630 @item set remotelogfile @var{file}
16631 @cindex record serial communications on file
16632 Record remote serial communications on the named @var{file}. The
16633 default is not to record at all.
16635 @item show remotelogfile.
16636 Show the current setting of the file name on which to record the
16637 serial communications.
16639 @item set remotetimeout @var{num}
16640 @cindex timeout for serial communications
16641 @cindex remote timeout
16642 Set the timeout limit to wait for the remote target to respond to
16643 @var{num} seconds. The default is 2 seconds.
16645 @item show remotetimeout
16646 Show the current number of seconds to wait for the remote target
16649 @cindex limit hardware breakpoints and watchpoints
16650 @cindex remote target, limit break- and watchpoints
16651 @anchor{set remote hardware-watchpoint-limit}
16652 @anchor{set remote hardware-breakpoint-limit}
16653 @item set remote hardware-watchpoint-limit @var{limit}
16654 @itemx set remote hardware-breakpoint-limit @var{limit}
16655 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
16656 watchpoints. A limit of -1, the default, is treated as unlimited.
16658 @cindex limit hardware watchpoints length
16659 @cindex remote target, limit watchpoints length
16660 @anchor{set remote hardware-watchpoint-length-limit}
16661 @item set remote hardware-watchpoint-length-limit @var{limit}
16662 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
16663 a remote hardware watchpoint. A limit of -1, the default, is treated
16666 @item show remote hardware-watchpoint-length-limit
16667 Show the current limit (in bytes) of the maximum length of
16668 a remote hardware watchpoint.
16670 @item set remote exec-file @var{filename}
16671 @itemx show remote exec-file
16672 @anchor{set remote exec-file}
16673 @cindex executable file, for remote target
16674 Select the file used for @code{run} with @code{target
16675 extended-remote}. This should be set to a filename valid on the
16676 target system. If it is not set, the target will use a default
16677 filename (e.g.@: the last program run).
16679 @item set remote interrupt-sequence
16680 @cindex interrupt remote programs
16681 @cindex select Ctrl-C, BREAK or BREAK-g
16682 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
16683 @samp{BREAK-g} as the
16684 sequence to the remote target in order to interrupt the execution.
16685 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
16686 is high level of serial line for some certain time.
16687 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
16688 It is @code{BREAK} signal followed by character @code{g}.
16690 @item show interrupt-sequence
16691 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
16692 is sent by @value{GDBN} to interrupt the remote program.
16693 @code{BREAK-g} is BREAK signal followed by @code{g} and
16694 also known as Magic SysRq g.
16696 @item set remote interrupt-on-connect
16697 @cindex send interrupt-sequence on start
16698 Specify whether interrupt-sequence is sent to remote target when
16699 @value{GDBN} connects to it. This is mostly needed when you debug
16700 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
16701 which is known as Magic SysRq g in order to connect @value{GDBN}.
16703 @item show interrupt-on-connect
16704 Show whether interrupt-sequence is sent
16705 to remote target when @value{GDBN} connects to it.
16709 @item set tcp auto-retry on
16710 @cindex auto-retry, for remote TCP target
16711 Enable auto-retry for remote TCP connections. This is useful if the remote
16712 debugging agent is launched in parallel with @value{GDBN}; there is a race
16713 condition because the agent may not become ready to accept the connection
16714 before @value{GDBN} attempts to connect. When auto-retry is
16715 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
16716 to establish the connection using the timeout specified by
16717 @code{set tcp connect-timeout}.
16719 @item set tcp auto-retry off
16720 Do not auto-retry failed TCP connections.
16722 @item show tcp auto-retry
16723 Show the current auto-retry setting.
16725 @item set tcp connect-timeout @var{seconds}
16726 @cindex connection timeout, for remote TCP target
16727 @cindex timeout, for remote target connection
16728 Set the timeout for establishing a TCP connection to the remote target to
16729 @var{seconds}. The timeout affects both polling to retry failed connections
16730 (enabled by @code{set tcp auto-retry on}) and waiting for connections
16731 that are merely slow to complete, and represents an approximate cumulative
16734 @item show tcp connect-timeout
16735 Show the current connection timeout setting.
16738 @cindex remote packets, enabling and disabling
16739 The @value{GDBN} remote protocol autodetects the packets supported by
16740 your debugging stub. If you need to override the autodetection, you
16741 can use these commands to enable or disable individual packets. Each
16742 packet can be set to @samp{on} (the remote target supports this
16743 packet), @samp{off} (the remote target does not support this packet),
16744 or @samp{auto} (detect remote target support for this packet). They
16745 all default to @samp{auto}. For more information about each packet,
16746 see @ref{Remote Protocol}.
16748 During normal use, you should not have to use any of these commands.
16749 If you do, that may be a bug in your remote debugging stub, or a bug
16750 in @value{GDBN}. You may want to report the problem to the
16751 @value{GDBN} developers.
16753 For each packet @var{name}, the command to enable or disable the
16754 packet is @code{set remote @var{name}-packet}. The available settings
16757 @multitable @columnfractions 0.28 0.32 0.25
16760 @tab Related Features
16762 @item @code{fetch-register}
16764 @tab @code{info registers}
16766 @item @code{set-register}
16770 @item @code{binary-download}
16772 @tab @code{load}, @code{set}
16774 @item @code{read-aux-vector}
16775 @tab @code{qXfer:auxv:read}
16776 @tab @code{info auxv}
16778 @item @code{symbol-lookup}
16779 @tab @code{qSymbol}
16780 @tab Detecting multiple threads
16782 @item @code{attach}
16783 @tab @code{vAttach}
16786 @item @code{verbose-resume}
16788 @tab Stepping or resuming multiple threads
16794 @item @code{software-breakpoint}
16798 @item @code{hardware-breakpoint}
16802 @item @code{write-watchpoint}
16806 @item @code{read-watchpoint}
16810 @item @code{access-watchpoint}
16814 @item @code{target-features}
16815 @tab @code{qXfer:features:read}
16816 @tab @code{set architecture}
16818 @item @code{library-info}
16819 @tab @code{qXfer:libraries:read}
16820 @tab @code{info sharedlibrary}
16822 @item @code{memory-map}
16823 @tab @code{qXfer:memory-map:read}
16824 @tab @code{info mem}
16826 @item @code{read-sdata-object}
16827 @tab @code{qXfer:sdata:read}
16828 @tab @code{print $_sdata}
16830 @item @code{read-spu-object}
16831 @tab @code{qXfer:spu:read}
16832 @tab @code{info spu}
16834 @item @code{write-spu-object}
16835 @tab @code{qXfer:spu:write}
16836 @tab @code{info spu}
16838 @item @code{read-siginfo-object}
16839 @tab @code{qXfer:siginfo:read}
16840 @tab @code{print $_siginfo}
16842 @item @code{write-siginfo-object}
16843 @tab @code{qXfer:siginfo:write}
16844 @tab @code{set $_siginfo}
16846 @item @code{threads}
16847 @tab @code{qXfer:threads:read}
16848 @tab @code{info threads}
16850 @item @code{get-thread-local-@*storage-address}
16851 @tab @code{qGetTLSAddr}
16852 @tab Displaying @code{__thread} variables
16854 @item @code{get-thread-information-block-address}
16855 @tab @code{qGetTIBAddr}
16856 @tab Display MS-Windows Thread Information Block.
16858 @item @code{search-memory}
16859 @tab @code{qSearch:memory}
16862 @item @code{supported-packets}
16863 @tab @code{qSupported}
16864 @tab Remote communications parameters
16866 @item @code{pass-signals}
16867 @tab @code{QPassSignals}
16868 @tab @code{handle @var{signal}}
16870 @item @code{hostio-close-packet}
16871 @tab @code{vFile:close}
16872 @tab @code{remote get}, @code{remote put}
16874 @item @code{hostio-open-packet}
16875 @tab @code{vFile:open}
16876 @tab @code{remote get}, @code{remote put}
16878 @item @code{hostio-pread-packet}
16879 @tab @code{vFile:pread}
16880 @tab @code{remote get}, @code{remote put}
16882 @item @code{hostio-pwrite-packet}
16883 @tab @code{vFile:pwrite}
16884 @tab @code{remote get}, @code{remote put}
16886 @item @code{hostio-unlink-packet}
16887 @tab @code{vFile:unlink}
16888 @tab @code{remote delete}
16890 @item @code{noack-packet}
16891 @tab @code{QStartNoAckMode}
16892 @tab Packet acknowledgment
16894 @item @code{osdata}
16895 @tab @code{qXfer:osdata:read}
16896 @tab @code{info os}
16898 @item @code{query-attached}
16899 @tab @code{qAttached}
16900 @tab Querying remote process attach state.
16902 @item @code{traceframe-info}
16903 @tab @code{qXfer:traceframe-info:read}
16904 @tab Traceframe info
16908 @section Implementing a Remote Stub
16910 @cindex debugging stub, example
16911 @cindex remote stub, example
16912 @cindex stub example, remote debugging
16913 The stub files provided with @value{GDBN} implement the target side of the
16914 communication protocol, and the @value{GDBN} side is implemented in the
16915 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16916 these subroutines to communicate, and ignore the details. (If you're
16917 implementing your own stub file, you can still ignore the details: start
16918 with one of the existing stub files. @file{sparc-stub.c} is the best
16919 organized, and therefore the easiest to read.)
16921 @cindex remote serial debugging, overview
16922 To debug a program running on another machine (the debugging
16923 @dfn{target} machine), you must first arrange for all the usual
16924 prerequisites for the program to run by itself. For example, for a C
16929 A startup routine to set up the C runtime environment; these usually
16930 have a name like @file{crt0}. The startup routine may be supplied by
16931 your hardware supplier, or you may have to write your own.
16934 A C subroutine library to support your program's
16935 subroutine calls, notably managing input and output.
16938 A way of getting your program to the other machine---for example, a
16939 download program. These are often supplied by the hardware
16940 manufacturer, but you may have to write your own from hardware
16944 The next step is to arrange for your program to use a serial port to
16945 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16946 machine). In general terms, the scheme looks like this:
16950 @value{GDBN} already understands how to use this protocol; when everything
16951 else is set up, you can simply use the @samp{target remote} command
16952 (@pxref{Targets,,Specifying a Debugging Target}).
16954 @item On the target,
16955 you must link with your program a few special-purpose subroutines that
16956 implement the @value{GDBN} remote serial protocol. The file containing these
16957 subroutines is called a @dfn{debugging stub}.
16959 On certain remote targets, you can use an auxiliary program
16960 @code{gdbserver} instead of linking a stub into your program.
16961 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16964 The debugging stub is specific to the architecture of the remote
16965 machine; for example, use @file{sparc-stub.c} to debug programs on
16968 @cindex remote serial stub list
16969 These working remote stubs are distributed with @value{GDBN}:
16974 @cindex @file{i386-stub.c}
16977 For Intel 386 and compatible architectures.
16980 @cindex @file{m68k-stub.c}
16981 @cindex Motorola 680x0
16983 For Motorola 680x0 architectures.
16986 @cindex @file{sh-stub.c}
16989 For Renesas SH architectures.
16992 @cindex @file{sparc-stub.c}
16994 For @sc{sparc} architectures.
16996 @item sparcl-stub.c
16997 @cindex @file{sparcl-stub.c}
17000 For Fujitsu @sc{sparclite} architectures.
17004 The @file{README} file in the @value{GDBN} distribution may list other
17005 recently added stubs.
17008 * Stub Contents:: What the stub can do for you
17009 * Bootstrapping:: What you must do for the stub
17010 * Debug Session:: Putting it all together
17013 @node Stub Contents
17014 @subsection What the Stub Can Do for You
17016 @cindex remote serial stub
17017 The debugging stub for your architecture supplies these three
17021 @item set_debug_traps
17022 @findex set_debug_traps
17023 @cindex remote serial stub, initialization
17024 This routine arranges for @code{handle_exception} to run when your
17025 program stops. You must call this subroutine explicitly near the
17026 beginning of your program.
17028 @item handle_exception
17029 @findex handle_exception
17030 @cindex remote serial stub, main routine
17031 This is the central workhorse, but your program never calls it
17032 explicitly---the setup code arranges for @code{handle_exception} to
17033 run when a trap is triggered.
17035 @code{handle_exception} takes control when your program stops during
17036 execution (for example, on a breakpoint), and mediates communications
17037 with @value{GDBN} on the host machine. This is where the communications
17038 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
17039 representative on the target machine. It begins by sending summary
17040 information on the state of your program, then continues to execute,
17041 retrieving and transmitting any information @value{GDBN} needs, until you
17042 execute a @value{GDBN} command that makes your program resume; at that point,
17043 @code{handle_exception} returns control to your own code on the target
17047 @cindex @code{breakpoint} subroutine, remote
17048 Use this auxiliary subroutine to make your program contain a
17049 breakpoint. Depending on the particular situation, this may be the only
17050 way for @value{GDBN} to get control. For instance, if your target
17051 machine has some sort of interrupt button, you won't need to call this;
17052 pressing the interrupt button transfers control to
17053 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
17054 simply receiving characters on the serial port may also trigger a trap;
17055 again, in that situation, you don't need to call @code{breakpoint} from
17056 your own program---simply running @samp{target remote} from the host
17057 @value{GDBN} session gets control.
17059 Call @code{breakpoint} if none of these is true, or if you simply want
17060 to make certain your program stops at a predetermined point for the
17061 start of your debugging session.
17064 @node Bootstrapping
17065 @subsection What You Must Do for the Stub
17067 @cindex remote stub, support routines
17068 The debugging stubs that come with @value{GDBN} are set up for a particular
17069 chip architecture, but they have no information about the rest of your
17070 debugging target machine.
17072 First of all you need to tell the stub how to communicate with the
17076 @item int getDebugChar()
17077 @findex getDebugChar
17078 Write this subroutine to read a single character from the serial port.
17079 It may be identical to @code{getchar} for your target system; a
17080 different name is used to allow you to distinguish the two if you wish.
17082 @item void putDebugChar(int)
17083 @findex putDebugChar
17084 Write this subroutine to write a single character to the serial port.
17085 It may be identical to @code{putchar} for your target system; a
17086 different name is used to allow you to distinguish the two if you wish.
17089 @cindex control C, and remote debugging
17090 @cindex interrupting remote targets
17091 If you want @value{GDBN} to be able to stop your program while it is
17092 running, you need to use an interrupt-driven serial driver, and arrange
17093 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
17094 character). That is the character which @value{GDBN} uses to tell the
17095 remote system to stop.
17097 Getting the debugging target to return the proper status to @value{GDBN}
17098 probably requires changes to the standard stub; one quick and dirty way
17099 is to just execute a breakpoint instruction (the ``dirty'' part is that
17100 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17102 Other routines you need to supply are:
17105 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17106 @findex exceptionHandler
17107 Write this function to install @var{exception_address} in the exception
17108 handling tables. You need to do this because the stub does not have any
17109 way of knowing what the exception handling tables on your target system
17110 are like (for example, the processor's table might be in @sc{rom},
17111 containing entries which point to a table in @sc{ram}).
17112 @var{exception_number} is the exception number which should be changed;
17113 its meaning is architecture-dependent (for example, different numbers
17114 might represent divide by zero, misaligned access, etc). When this
17115 exception occurs, control should be transferred directly to
17116 @var{exception_address}, and the processor state (stack, registers,
17117 and so on) should be just as it is when a processor exception occurs. So if
17118 you want to use a jump instruction to reach @var{exception_address}, it
17119 should be a simple jump, not a jump to subroutine.
17121 For the 386, @var{exception_address} should be installed as an interrupt
17122 gate so that interrupts are masked while the handler runs. The gate
17123 should be at privilege level 0 (the most privileged level). The
17124 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17125 help from @code{exceptionHandler}.
17127 @item void flush_i_cache()
17128 @findex flush_i_cache
17129 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17130 instruction cache, if any, on your target machine. If there is no
17131 instruction cache, this subroutine may be a no-op.
17133 On target machines that have instruction caches, @value{GDBN} requires this
17134 function to make certain that the state of your program is stable.
17138 You must also make sure this library routine is available:
17141 @item void *memset(void *, int, int)
17143 This is the standard library function @code{memset} that sets an area of
17144 memory to a known value. If you have one of the free versions of
17145 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17146 either obtain it from your hardware manufacturer, or write your own.
17149 If you do not use the GNU C compiler, you may need other standard
17150 library subroutines as well; this varies from one stub to another,
17151 but in general the stubs are likely to use any of the common library
17152 subroutines which @code{@value{NGCC}} generates as inline code.
17155 @node Debug Session
17156 @subsection Putting it All Together
17158 @cindex remote serial debugging summary
17159 In summary, when your program is ready to debug, you must follow these
17164 Make sure you have defined the supporting low-level routines
17165 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17167 @code{getDebugChar}, @code{putDebugChar},
17168 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17172 Insert these lines near the top of your program:
17180 For the 680x0 stub only, you need to provide a variable called
17181 @code{exceptionHook}. Normally you just use:
17184 void (*exceptionHook)() = 0;
17188 but if before calling @code{set_debug_traps}, you set it to point to a
17189 function in your program, that function is called when
17190 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17191 error). The function indicated by @code{exceptionHook} is called with
17192 one parameter: an @code{int} which is the exception number.
17195 Compile and link together: your program, the @value{GDBN} debugging stub for
17196 your target architecture, and the supporting subroutines.
17199 Make sure you have a serial connection between your target machine and
17200 the @value{GDBN} host, and identify the serial port on the host.
17203 @c The "remote" target now provides a `load' command, so we should
17204 @c document that. FIXME.
17205 Download your program to your target machine (or get it there by
17206 whatever means the manufacturer provides), and start it.
17209 Start @value{GDBN} on the host, and connect to the target
17210 (@pxref{Connecting,,Connecting to a Remote Target}).
17214 @node Configurations
17215 @chapter Configuration-Specific Information
17217 While nearly all @value{GDBN} commands are available for all native and
17218 cross versions of the debugger, there are some exceptions. This chapter
17219 describes things that are only available in certain configurations.
17221 There are three major categories of configurations: native
17222 configurations, where the host and target are the same, embedded
17223 operating system configurations, which are usually the same for several
17224 different processor architectures, and bare embedded processors, which
17225 are quite different from each other.
17230 * Embedded Processors::
17237 This section describes details specific to particular native
17242 * BSD libkvm Interface:: Debugging BSD kernel memory images
17243 * SVR4 Process Information:: SVR4 process information
17244 * DJGPP Native:: Features specific to the DJGPP port
17245 * Cygwin Native:: Features specific to the Cygwin port
17246 * Hurd Native:: Features specific to @sc{gnu} Hurd
17247 * Neutrino:: Features specific to QNX Neutrino
17248 * Darwin:: Features specific to Darwin
17254 On HP-UX systems, if you refer to a function or variable name that
17255 begins with a dollar sign, @value{GDBN} searches for a user or system
17256 name first, before it searches for a convenience variable.
17259 @node BSD libkvm Interface
17260 @subsection BSD libkvm Interface
17263 @cindex kernel memory image
17264 @cindex kernel crash dump
17266 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17267 interface that provides a uniform interface for accessing kernel virtual
17268 memory images, including live systems and crash dumps. @value{GDBN}
17269 uses this interface to allow you to debug live kernels and kernel crash
17270 dumps on many native BSD configurations. This is implemented as a
17271 special @code{kvm} debugging target. For debugging a live system, load
17272 the currently running kernel into @value{GDBN} and connect to the
17276 (@value{GDBP}) @b{target kvm}
17279 For debugging crash dumps, provide the file name of the crash dump as an
17283 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17286 Once connected to the @code{kvm} target, the following commands are
17292 Set current context from the @dfn{Process Control Block} (PCB) address.
17295 Set current context from proc address. This command isn't available on
17296 modern FreeBSD systems.
17299 @node SVR4 Process Information
17300 @subsection SVR4 Process Information
17302 @cindex examine process image
17303 @cindex process info via @file{/proc}
17305 Many versions of SVR4 and compatible systems provide a facility called
17306 @samp{/proc} that can be used to examine the image of a running
17307 process using file-system subroutines. If @value{GDBN} is configured
17308 for an operating system with this facility, the command @code{info
17309 proc} is available to report information about the process running
17310 your program, or about any process running on your system. @code{info
17311 proc} works only on SVR4 systems that include the @code{procfs} code.
17312 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17313 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17319 @itemx info proc @var{process-id}
17320 Summarize available information about any running process. If a
17321 process ID is specified by @var{process-id}, display information about
17322 that process; otherwise display information about the program being
17323 debugged. The summary includes the debugged process ID, the command
17324 line used to invoke it, its current working directory, and its
17325 executable file's absolute file name.
17327 On some systems, @var{process-id} can be of the form
17328 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17329 within a process. If the optional @var{pid} part is missing, it means
17330 a thread from the process being debugged (the leading @samp{/} still
17331 needs to be present, or else @value{GDBN} will interpret the number as
17332 a process ID rather than a thread ID).
17334 @item info proc mappings
17335 @cindex memory address space mappings
17336 Report the memory address space ranges accessible in the program, with
17337 information on whether the process has read, write, or execute access
17338 rights to each range. On @sc{gnu}/Linux systems, each memory range
17339 includes the object file which is mapped to that range, instead of the
17340 memory access rights to that range.
17342 @item info proc stat
17343 @itemx info proc status
17344 @cindex process detailed status information
17345 These subcommands are specific to @sc{gnu}/Linux systems. They show
17346 the process-related information, including the user ID and group ID;
17347 how many threads are there in the process; its virtual memory usage;
17348 the signals that are pending, blocked, and ignored; its TTY; its
17349 consumption of system and user time; its stack size; its @samp{nice}
17350 value; etc. For more information, see the @samp{proc} man page
17351 (type @kbd{man 5 proc} from your shell prompt).
17353 @item info proc all
17354 Show all the information about the process described under all of the
17355 above @code{info proc} subcommands.
17358 @comment These sub-options of 'info proc' were not included when
17359 @comment procfs.c was re-written. Keep their descriptions around
17360 @comment against the day when someone finds the time to put them back in.
17361 @kindex info proc times
17362 @item info proc times
17363 Starting time, user CPU time, and system CPU time for your program and
17366 @kindex info proc id
17368 Report on the process IDs related to your program: its own process ID,
17369 the ID of its parent, the process group ID, and the session ID.
17372 @item set procfs-trace
17373 @kindex set procfs-trace
17374 @cindex @code{procfs} API calls
17375 This command enables and disables tracing of @code{procfs} API calls.
17377 @item show procfs-trace
17378 @kindex show procfs-trace
17379 Show the current state of @code{procfs} API call tracing.
17381 @item set procfs-file @var{file}
17382 @kindex set procfs-file
17383 Tell @value{GDBN} to write @code{procfs} API trace to the named
17384 @var{file}. @value{GDBN} appends the trace info to the previous
17385 contents of the file. The default is to display the trace on the
17388 @item show procfs-file
17389 @kindex show procfs-file
17390 Show the file to which @code{procfs} API trace is written.
17392 @item proc-trace-entry
17393 @itemx proc-trace-exit
17394 @itemx proc-untrace-entry
17395 @itemx proc-untrace-exit
17396 @kindex proc-trace-entry
17397 @kindex proc-trace-exit
17398 @kindex proc-untrace-entry
17399 @kindex proc-untrace-exit
17400 These commands enable and disable tracing of entries into and exits
17401 from the @code{syscall} interface.
17404 @kindex info pidlist
17405 @cindex process list, QNX Neutrino
17406 For QNX Neutrino only, this command displays the list of all the
17407 processes and all the threads within each process.
17410 @kindex info meminfo
17411 @cindex mapinfo list, QNX Neutrino
17412 For QNX Neutrino only, this command displays the list of all mapinfos.
17416 @subsection Features for Debugging @sc{djgpp} Programs
17417 @cindex @sc{djgpp} debugging
17418 @cindex native @sc{djgpp} debugging
17419 @cindex MS-DOS-specific commands
17422 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17423 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17424 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17425 top of real-mode DOS systems and their emulations.
17427 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17428 defines a few commands specific to the @sc{djgpp} port. This
17429 subsection describes those commands.
17434 This is a prefix of @sc{djgpp}-specific commands which print
17435 information about the target system and important OS structures.
17438 @cindex MS-DOS system info
17439 @cindex free memory information (MS-DOS)
17440 @item info dos sysinfo
17441 This command displays assorted information about the underlying
17442 platform: the CPU type and features, the OS version and flavor, the
17443 DPMI version, and the available conventional and DPMI memory.
17448 @cindex segment descriptor tables
17449 @cindex descriptor tables display
17451 @itemx info dos ldt
17452 @itemx info dos idt
17453 These 3 commands display entries from, respectively, Global, Local,
17454 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17455 tables are data structures which store a descriptor for each segment
17456 that is currently in use. The segment's selector is an index into a
17457 descriptor table; the table entry for that index holds the
17458 descriptor's base address and limit, and its attributes and access
17461 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17462 segment (used for both data and the stack), and a DOS segment (which
17463 allows access to DOS/BIOS data structures and absolute addresses in
17464 conventional memory). However, the DPMI host will usually define
17465 additional segments in order to support the DPMI environment.
17467 @cindex garbled pointers
17468 These commands allow to display entries from the descriptor tables.
17469 Without an argument, all entries from the specified table are
17470 displayed. An argument, which should be an integer expression, means
17471 display a single entry whose index is given by the argument. For
17472 example, here's a convenient way to display information about the
17473 debugged program's data segment:
17476 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17477 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17481 This comes in handy when you want to see whether a pointer is outside
17482 the data segment's limit (i.e.@: @dfn{garbled}).
17484 @cindex page tables display (MS-DOS)
17486 @itemx info dos pte
17487 These two commands display entries from, respectively, the Page
17488 Directory and the Page Tables. Page Directories and Page Tables are
17489 data structures which control how virtual memory addresses are mapped
17490 into physical addresses. A Page Table includes an entry for every
17491 page of memory that is mapped into the program's address space; there
17492 may be several Page Tables, each one holding up to 4096 entries. A
17493 Page Directory has up to 4096 entries, one each for every Page Table
17494 that is currently in use.
17496 Without an argument, @kbd{info dos pde} displays the entire Page
17497 Directory, and @kbd{info dos pte} displays all the entries in all of
17498 the Page Tables. An argument, an integer expression, given to the
17499 @kbd{info dos pde} command means display only that entry from the Page
17500 Directory table. An argument given to the @kbd{info dos pte} command
17501 means display entries from a single Page Table, the one pointed to by
17502 the specified entry in the Page Directory.
17504 @cindex direct memory access (DMA) on MS-DOS
17505 These commands are useful when your program uses @dfn{DMA} (Direct
17506 Memory Access), which needs physical addresses to program the DMA
17509 These commands are supported only with some DPMI servers.
17511 @cindex physical address from linear address
17512 @item info dos address-pte @var{addr}
17513 This command displays the Page Table entry for a specified linear
17514 address. The argument @var{addr} is a linear address which should
17515 already have the appropriate segment's base address added to it,
17516 because this command accepts addresses which may belong to @emph{any}
17517 segment. For example, here's how to display the Page Table entry for
17518 the page where a variable @code{i} is stored:
17521 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17522 @exdent @code{Page Table entry for address 0x11a00d30:}
17523 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17527 This says that @code{i} is stored at offset @code{0xd30} from the page
17528 whose physical base address is @code{0x02698000}, and shows all the
17529 attributes of that page.
17531 Note that you must cast the addresses of variables to a @code{char *},
17532 since otherwise the value of @code{__djgpp_base_address}, the base
17533 address of all variables and functions in a @sc{djgpp} program, will
17534 be added using the rules of C pointer arithmetics: if @code{i} is
17535 declared an @code{int}, @value{GDBN} will add 4 times the value of
17536 @code{__djgpp_base_address} to the address of @code{i}.
17538 Here's another example, it displays the Page Table entry for the
17542 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17543 @exdent @code{Page Table entry for address 0x29110:}
17544 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17548 (The @code{+ 3} offset is because the transfer buffer's address is the
17549 3rd member of the @code{_go32_info_block} structure.) The output
17550 clearly shows that this DPMI server maps the addresses in conventional
17551 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17552 linear (@code{0x29110}) addresses are identical.
17554 This command is supported only with some DPMI servers.
17557 @cindex DOS serial data link, remote debugging
17558 In addition to native debugging, the DJGPP port supports remote
17559 debugging via a serial data link. The following commands are specific
17560 to remote serial debugging in the DJGPP port of @value{GDBN}.
17563 @kindex set com1base
17564 @kindex set com1irq
17565 @kindex set com2base
17566 @kindex set com2irq
17567 @kindex set com3base
17568 @kindex set com3irq
17569 @kindex set com4base
17570 @kindex set com4irq
17571 @item set com1base @var{addr}
17572 This command sets the base I/O port address of the @file{COM1} serial
17575 @item set com1irq @var{irq}
17576 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17577 for the @file{COM1} serial port.
17579 There are similar commands @samp{set com2base}, @samp{set com3irq},
17580 etc.@: for setting the port address and the @code{IRQ} lines for the
17583 @kindex show com1base
17584 @kindex show com1irq
17585 @kindex show com2base
17586 @kindex show com2irq
17587 @kindex show com3base
17588 @kindex show com3irq
17589 @kindex show com4base
17590 @kindex show com4irq
17591 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
17592 display the current settings of the base address and the @code{IRQ}
17593 lines used by the COM ports.
17596 @kindex info serial
17597 @cindex DOS serial port status
17598 This command prints the status of the 4 DOS serial ports. For each
17599 port, it prints whether it's active or not, its I/O base address and
17600 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
17601 counts of various errors encountered so far.
17605 @node Cygwin Native
17606 @subsection Features for Debugging MS Windows PE Executables
17607 @cindex MS Windows debugging
17608 @cindex native Cygwin debugging
17609 @cindex Cygwin-specific commands
17611 @value{GDBN} supports native debugging of MS Windows programs, including
17612 DLLs with and without symbolic debugging information.
17614 @cindex Ctrl-BREAK, MS-Windows
17615 @cindex interrupt debuggee on MS-Windows
17616 MS-Windows programs that call @code{SetConsoleMode} to switch off the
17617 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
17618 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
17619 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
17620 sequence, which can be used to interrupt the debuggee even if it
17623 There are various additional Cygwin-specific commands, described in
17624 this section. Working with DLLs that have no debugging symbols is
17625 described in @ref{Non-debug DLL Symbols}.
17630 This is a prefix of MS Windows-specific commands which print
17631 information about the target system and important OS structures.
17633 @item info w32 selector
17634 This command displays information returned by
17635 the Win32 API @code{GetThreadSelectorEntry} function.
17636 It takes an optional argument that is evaluated to
17637 a long value to give the information about this given selector.
17638 Without argument, this command displays information
17639 about the six segment registers.
17641 @item info w32 thread-information-block
17642 This command displays thread specific information stored in the
17643 Thread Information Block (readable on the X86 CPU family using @code{$fs}
17644 selector for 32-bit programs and @code{$gs} for 64-bit programs).
17648 This is a Cygwin-specific alias of @code{info shared}.
17650 @kindex dll-symbols
17652 This command loads symbols from a dll similarly to
17653 add-sym command but without the need to specify a base address.
17655 @kindex set cygwin-exceptions
17656 @cindex debugging the Cygwin DLL
17657 @cindex Cygwin DLL, debugging
17658 @item set cygwin-exceptions @var{mode}
17659 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
17660 happen inside the Cygwin DLL. If @var{mode} is @code{off},
17661 @value{GDBN} will delay recognition of exceptions, and may ignore some
17662 exceptions which seem to be caused by internal Cygwin DLL
17663 ``bookkeeping''. This option is meant primarily for debugging the
17664 Cygwin DLL itself; the default value is @code{off} to avoid annoying
17665 @value{GDBN} users with false @code{SIGSEGV} signals.
17667 @kindex show cygwin-exceptions
17668 @item show cygwin-exceptions
17669 Displays whether @value{GDBN} will break on exceptions that happen
17670 inside the Cygwin DLL itself.
17672 @kindex set new-console
17673 @item set new-console @var{mode}
17674 If @var{mode} is @code{on} the debuggee will
17675 be started in a new console on next start.
17676 If @var{mode} is @code{off}, the debuggee will
17677 be started in the same console as the debugger.
17679 @kindex show new-console
17680 @item show new-console
17681 Displays whether a new console is used
17682 when the debuggee is started.
17684 @kindex set new-group
17685 @item set new-group @var{mode}
17686 This boolean value controls whether the debuggee should
17687 start a new group or stay in the same group as the debugger.
17688 This affects the way the Windows OS handles
17691 @kindex show new-group
17692 @item show new-group
17693 Displays current value of new-group boolean.
17695 @kindex set debugevents
17696 @item set debugevents
17697 This boolean value adds debug output concerning kernel events related
17698 to the debuggee seen by the debugger. This includes events that
17699 signal thread and process creation and exit, DLL loading and
17700 unloading, console interrupts, and debugging messages produced by the
17701 Windows @code{OutputDebugString} API call.
17703 @kindex set debugexec
17704 @item set debugexec
17705 This boolean value adds debug output concerning execute events
17706 (such as resume thread) seen by the debugger.
17708 @kindex set debugexceptions
17709 @item set debugexceptions
17710 This boolean value adds debug output concerning exceptions in the
17711 debuggee seen by the debugger.
17713 @kindex set debugmemory
17714 @item set debugmemory
17715 This boolean value adds debug output concerning debuggee memory reads
17716 and writes by the debugger.
17720 This boolean values specifies whether the debuggee is called
17721 via a shell or directly (default value is on).
17725 Displays if the debuggee will be started with a shell.
17730 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
17733 @node Non-debug DLL Symbols
17734 @subsubsection Support for DLLs without Debugging Symbols
17735 @cindex DLLs with no debugging symbols
17736 @cindex Minimal symbols and DLLs
17738 Very often on windows, some of the DLLs that your program relies on do
17739 not include symbolic debugging information (for example,
17740 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
17741 symbols in a DLL, it relies on the minimal amount of symbolic
17742 information contained in the DLL's export table. This section
17743 describes working with such symbols, known internally to @value{GDBN} as
17744 ``minimal symbols''.
17746 Note that before the debugged program has started execution, no DLLs
17747 will have been loaded. The easiest way around this problem is simply to
17748 start the program --- either by setting a breakpoint or letting the
17749 program run once to completion. It is also possible to force
17750 @value{GDBN} to load a particular DLL before starting the executable ---
17751 see the shared library information in @ref{Files}, or the
17752 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
17753 explicitly loading symbols from a DLL with no debugging information will
17754 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
17755 which may adversely affect symbol lookup performance.
17757 @subsubsection DLL Name Prefixes
17759 In keeping with the naming conventions used by the Microsoft debugging
17760 tools, DLL export symbols are made available with a prefix based on the
17761 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
17762 also entered into the symbol table, so @code{CreateFileA} is often
17763 sufficient. In some cases there will be name clashes within a program
17764 (particularly if the executable itself includes full debugging symbols)
17765 necessitating the use of the fully qualified name when referring to the
17766 contents of the DLL. Use single-quotes around the name to avoid the
17767 exclamation mark (``!'') being interpreted as a language operator.
17769 Note that the internal name of the DLL may be all upper-case, even
17770 though the file name of the DLL is lower-case, or vice-versa. Since
17771 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
17772 some confusion. If in doubt, try the @code{info functions} and
17773 @code{info variables} commands or even @code{maint print msymbols}
17774 (@pxref{Symbols}). Here's an example:
17777 (@value{GDBP}) info function CreateFileA
17778 All functions matching regular expression "CreateFileA":
17780 Non-debugging symbols:
17781 0x77e885f4 CreateFileA
17782 0x77e885f4 KERNEL32!CreateFileA
17786 (@value{GDBP}) info function !
17787 All functions matching regular expression "!":
17789 Non-debugging symbols:
17790 0x6100114c cygwin1!__assert
17791 0x61004034 cygwin1!_dll_crt0@@0
17792 0x61004240 cygwin1!dll_crt0(per_process *)
17796 @subsubsection Working with Minimal Symbols
17798 Symbols extracted from a DLL's export table do not contain very much
17799 type information. All that @value{GDBN} can do is guess whether a symbol
17800 refers to a function or variable depending on the linker section that
17801 contains the symbol. Also note that the actual contents of the memory
17802 contained in a DLL are not available unless the program is running. This
17803 means that you cannot examine the contents of a variable or disassemble
17804 a function within a DLL without a running program.
17806 Variables are generally treated as pointers and dereferenced
17807 automatically. For this reason, it is often necessary to prefix a
17808 variable name with the address-of operator (``&'') and provide explicit
17809 type information in the command. Here's an example of the type of
17813 (@value{GDBP}) print 'cygwin1!__argv'
17818 (@value{GDBP}) x 'cygwin1!__argv'
17819 0x10021610: "\230y\""
17822 And two possible solutions:
17825 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
17826 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
17830 (@value{GDBP}) x/2x &'cygwin1!__argv'
17831 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
17832 (@value{GDBP}) x/x 0x10021608
17833 0x10021608: 0x0022fd98
17834 (@value{GDBP}) x/s 0x0022fd98
17835 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
17838 Setting a break point within a DLL is possible even before the program
17839 starts execution. However, under these circumstances, @value{GDBN} can't
17840 examine the initial instructions of the function in order to skip the
17841 function's frame set-up code. You can work around this by using ``*&''
17842 to set the breakpoint at a raw memory address:
17845 (@value{GDBP}) break *&'python22!PyOS_Readline'
17846 Breakpoint 1 at 0x1e04eff0
17849 The author of these extensions is not entirely convinced that setting a
17850 break point within a shared DLL like @file{kernel32.dll} is completely
17854 @subsection Commands Specific to @sc{gnu} Hurd Systems
17855 @cindex @sc{gnu} Hurd debugging
17857 This subsection describes @value{GDBN} commands specific to the
17858 @sc{gnu} Hurd native debugging.
17863 @kindex set signals@r{, Hurd command}
17864 @kindex set sigs@r{, Hurd command}
17865 This command toggles the state of inferior signal interception by
17866 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
17867 affected by this command. @code{sigs} is a shorthand alias for
17872 @kindex show signals@r{, Hurd command}
17873 @kindex show sigs@r{, Hurd command}
17874 Show the current state of intercepting inferior's signals.
17876 @item set signal-thread
17877 @itemx set sigthread
17878 @kindex set signal-thread
17879 @kindex set sigthread
17880 This command tells @value{GDBN} which thread is the @code{libc} signal
17881 thread. That thread is run when a signal is delivered to a running
17882 process. @code{set sigthread} is the shorthand alias of @code{set
17885 @item show signal-thread
17886 @itemx show sigthread
17887 @kindex show signal-thread
17888 @kindex show sigthread
17889 These two commands show which thread will run when the inferior is
17890 delivered a signal.
17893 @kindex set stopped@r{, Hurd command}
17894 This commands tells @value{GDBN} that the inferior process is stopped,
17895 as with the @code{SIGSTOP} signal. The stopped process can be
17896 continued by delivering a signal to it.
17899 @kindex show stopped@r{, Hurd command}
17900 This command shows whether @value{GDBN} thinks the debuggee is
17903 @item set exceptions
17904 @kindex set exceptions@r{, Hurd command}
17905 Use this command to turn off trapping of exceptions in the inferior.
17906 When exception trapping is off, neither breakpoints nor
17907 single-stepping will work. To restore the default, set exception
17910 @item show exceptions
17911 @kindex show exceptions@r{, Hurd command}
17912 Show the current state of trapping exceptions in the inferior.
17914 @item set task pause
17915 @kindex set task@r{, Hurd commands}
17916 @cindex task attributes (@sc{gnu} Hurd)
17917 @cindex pause current task (@sc{gnu} Hurd)
17918 This command toggles task suspension when @value{GDBN} has control.
17919 Setting it to on takes effect immediately, and the task is suspended
17920 whenever @value{GDBN} gets control. Setting it to off will take
17921 effect the next time the inferior is continued. If this option is set
17922 to off, you can use @code{set thread default pause on} or @code{set
17923 thread pause on} (see below) to pause individual threads.
17925 @item show task pause
17926 @kindex show task@r{, Hurd commands}
17927 Show the current state of task suspension.
17929 @item set task detach-suspend-count
17930 @cindex task suspend count
17931 @cindex detach from task, @sc{gnu} Hurd
17932 This command sets the suspend count the task will be left with when
17933 @value{GDBN} detaches from it.
17935 @item show task detach-suspend-count
17936 Show the suspend count the task will be left with when detaching.
17938 @item set task exception-port
17939 @itemx set task excp
17940 @cindex task exception port, @sc{gnu} Hurd
17941 This command sets the task exception port to which @value{GDBN} will
17942 forward exceptions. The argument should be the value of the @dfn{send
17943 rights} of the task. @code{set task excp} is a shorthand alias.
17945 @item set noninvasive
17946 @cindex noninvasive task options
17947 This command switches @value{GDBN} to a mode that is the least
17948 invasive as far as interfering with the inferior is concerned. This
17949 is the same as using @code{set task pause}, @code{set exceptions}, and
17950 @code{set signals} to values opposite to the defaults.
17952 @item info send-rights
17953 @itemx info receive-rights
17954 @itemx info port-rights
17955 @itemx info port-sets
17956 @itemx info dead-names
17959 @cindex send rights, @sc{gnu} Hurd
17960 @cindex receive rights, @sc{gnu} Hurd
17961 @cindex port rights, @sc{gnu} Hurd
17962 @cindex port sets, @sc{gnu} Hurd
17963 @cindex dead names, @sc{gnu} Hurd
17964 These commands display information about, respectively, send rights,
17965 receive rights, port rights, port sets, and dead names of a task.
17966 There are also shorthand aliases: @code{info ports} for @code{info
17967 port-rights} and @code{info psets} for @code{info port-sets}.
17969 @item set thread pause
17970 @kindex set thread@r{, Hurd command}
17971 @cindex thread properties, @sc{gnu} Hurd
17972 @cindex pause current thread (@sc{gnu} Hurd)
17973 This command toggles current thread suspension when @value{GDBN} has
17974 control. Setting it to on takes effect immediately, and the current
17975 thread is suspended whenever @value{GDBN} gets control. Setting it to
17976 off will take effect the next time the inferior is continued.
17977 Normally, this command has no effect, since when @value{GDBN} has
17978 control, the whole task is suspended. However, if you used @code{set
17979 task pause off} (see above), this command comes in handy to suspend
17980 only the current thread.
17982 @item show thread pause
17983 @kindex show thread@r{, Hurd command}
17984 This command shows the state of current thread suspension.
17986 @item set thread run
17987 This command sets whether the current thread is allowed to run.
17989 @item show thread run
17990 Show whether the current thread is allowed to run.
17992 @item set thread detach-suspend-count
17993 @cindex thread suspend count, @sc{gnu} Hurd
17994 @cindex detach from thread, @sc{gnu} Hurd
17995 This command sets the suspend count @value{GDBN} will leave on a
17996 thread when detaching. This number is relative to the suspend count
17997 found by @value{GDBN} when it notices the thread; use @code{set thread
17998 takeover-suspend-count} to force it to an absolute value.
18000 @item show thread detach-suspend-count
18001 Show the suspend count @value{GDBN} will leave on the thread when
18004 @item set thread exception-port
18005 @itemx set thread excp
18006 Set the thread exception port to which to forward exceptions. This
18007 overrides the port set by @code{set task exception-port} (see above).
18008 @code{set thread excp} is the shorthand alias.
18010 @item set thread takeover-suspend-count
18011 Normally, @value{GDBN}'s thread suspend counts are relative to the
18012 value @value{GDBN} finds when it notices each thread. This command
18013 changes the suspend counts to be absolute instead.
18015 @item set thread default
18016 @itemx show thread default
18017 @cindex thread default settings, @sc{gnu} Hurd
18018 Each of the above @code{set thread} commands has a @code{set thread
18019 default} counterpart (e.g., @code{set thread default pause}, @code{set
18020 thread default exception-port}, etc.). The @code{thread default}
18021 variety of commands sets the default thread properties for all
18022 threads; you can then change the properties of individual threads with
18023 the non-default commands.
18028 @subsection QNX Neutrino
18029 @cindex QNX Neutrino
18031 @value{GDBN} provides the following commands specific to the QNX
18035 @item set debug nto-debug
18036 @kindex set debug nto-debug
18037 When set to on, enables debugging messages specific to the QNX
18040 @item show debug nto-debug
18041 @kindex show debug nto-debug
18042 Show the current state of QNX Neutrino messages.
18049 @value{GDBN} provides the following commands specific to the Darwin target:
18052 @item set debug darwin @var{num}
18053 @kindex set debug darwin
18054 When set to a non zero value, enables debugging messages specific to
18055 the Darwin support. Higher values produce more verbose output.
18057 @item show debug darwin
18058 @kindex show debug darwin
18059 Show the current state of Darwin messages.
18061 @item set debug mach-o @var{num}
18062 @kindex set debug mach-o
18063 When set to a non zero value, enables debugging messages while
18064 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
18065 file format used on Darwin for object and executable files.) Higher
18066 values produce more verbose output. This is a command to diagnose
18067 problems internal to @value{GDBN} and should not be needed in normal
18070 @item show debug mach-o
18071 @kindex show debug mach-o
18072 Show the current state of Mach-O file messages.
18074 @item set mach-exceptions on
18075 @itemx set mach-exceptions off
18076 @kindex set mach-exceptions
18077 On Darwin, faults are first reported as a Mach exception and are then
18078 mapped to a Posix signal. Use this command to turn on trapping of
18079 Mach exceptions in the inferior. This might be sometimes useful to
18080 better understand the cause of a fault. The default is off.
18082 @item show mach-exceptions
18083 @kindex show mach-exceptions
18084 Show the current state of exceptions trapping.
18089 @section Embedded Operating Systems
18091 This section describes configurations involving the debugging of
18092 embedded operating systems that are available for several different
18096 * VxWorks:: Using @value{GDBN} with VxWorks
18099 @value{GDBN} includes the ability to debug programs running on
18100 various real-time operating systems.
18103 @subsection Using @value{GDBN} with VxWorks
18109 @kindex target vxworks
18110 @item target vxworks @var{machinename}
18111 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18112 is the target system's machine name or IP address.
18116 On VxWorks, @code{load} links @var{filename} dynamically on the
18117 current target system as well as adding its symbols in @value{GDBN}.
18119 @value{GDBN} enables developers to spawn and debug tasks running on networked
18120 VxWorks targets from a Unix host. Already-running tasks spawned from
18121 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18122 both the Unix host and on the VxWorks target. The program
18123 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18124 installed with the name @code{vxgdb}, to distinguish it from a
18125 @value{GDBN} for debugging programs on the host itself.)
18128 @item VxWorks-timeout @var{args}
18129 @kindex vxworks-timeout
18130 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18131 This option is set by the user, and @var{args} represents the number of
18132 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18133 your VxWorks target is a slow software simulator or is on the far side
18134 of a thin network line.
18137 The following information on connecting to VxWorks was current when
18138 this manual was produced; newer releases of VxWorks may use revised
18141 @findex INCLUDE_RDB
18142 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18143 to include the remote debugging interface routines in the VxWorks
18144 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18145 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18146 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18147 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18148 information on configuring and remaking VxWorks, see the manufacturer's
18150 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18152 Once you have included @file{rdb.a} in your VxWorks system image and set
18153 your Unix execution search path to find @value{GDBN}, you are ready to
18154 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18155 @code{vxgdb}, depending on your installation).
18157 @value{GDBN} comes up showing the prompt:
18164 * VxWorks Connection:: Connecting to VxWorks
18165 * VxWorks Download:: VxWorks download
18166 * VxWorks Attach:: Running tasks
18169 @node VxWorks Connection
18170 @subsubsection Connecting to VxWorks
18172 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18173 network. To connect to a target whose host name is ``@code{tt}'', type:
18176 (vxgdb) target vxworks tt
18180 @value{GDBN} displays messages like these:
18183 Attaching remote machine across net...
18188 @value{GDBN} then attempts to read the symbol tables of any object modules
18189 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18190 these files by searching the directories listed in the command search
18191 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18192 to find an object file, it displays a message such as:
18195 prog.o: No such file or directory.
18198 When this happens, add the appropriate directory to the search path with
18199 the @value{GDBN} command @code{path}, and execute the @code{target}
18202 @node VxWorks Download
18203 @subsubsection VxWorks Download
18205 @cindex download to VxWorks
18206 If you have connected to the VxWorks target and you want to debug an
18207 object that has not yet been loaded, you can use the @value{GDBN}
18208 @code{load} command to download a file from Unix to VxWorks
18209 incrementally. The object file given as an argument to the @code{load}
18210 command is actually opened twice: first by the VxWorks target in order
18211 to download the code, then by @value{GDBN} in order to read the symbol
18212 table. This can lead to problems if the current working directories on
18213 the two systems differ. If both systems have NFS mounted the same
18214 filesystems, you can avoid these problems by using absolute paths.
18215 Otherwise, it is simplest to set the working directory on both systems
18216 to the directory in which the object file resides, and then to reference
18217 the file by its name, without any path. For instance, a program
18218 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18219 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18220 program, type this on VxWorks:
18223 -> cd "@var{vxpath}/vw/demo/rdb"
18227 Then, in @value{GDBN}, type:
18230 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18231 (vxgdb) load prog.o
18234 @value{GDBN} displays a response similar to this:
18237 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18240 You can also use the @code{load} command to reload an object module
18241 after editing and recompiling the corresponding source file. Note that
18242 this makes @value{GDBN} delete all currently-defined breakpoints,
18243 auto-displays, and convenience variables, and to clear the value
18244 history. (This is necessary in order to preserve the integrity of
18245 debugger's data structures that reference the target system's symbol
18248 @node VxWorks Attach
18249 @subsubsection Running Tasks
18251 @cindex running VxWorks tasks
18252 You can also attach to an existing task using the @code{attach} command as
18256 (vxgdb) attach @var{task}
18260 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18261 or suspended when you attach to it. Running tasks are suspended at
18262 the time of attachment.
18264 @node Embedded Processors
18265 @section Embedded Processors
18267 This section goes into details specific to particular embedded
18270 @cindex send command to simulator
18271 Whenever a specific embedded processor has a simulator, @value{GDBN}
18272 allows to send an arbitrary command to the simulator.
18275 @item sim @var{command}
18276 @kindex sim@r{, a command}
18277 Send an arbitrary @var{command} string to the simulator. Consult the
18278 documentation for the specific simulator in use for information about
18279 acceptable commands.
18285 * M32R/D:: Renesas M32R/D
18286 * M68K:: Motorola M68K
18287 * MicroBlaze:: Xilinx MicroBlaze
18288 * MIPS Embedded:: MIPS Embedded
18289 * OpenRISC 1000:: OpenRisc 1000
18290 * PA:: HP PA Embedded
18291 * PowerPC Embedded:: PowerPC Embedded
18292 * Sparclet:: Tsqware Sparclet
18293 * Sparclite:: Fujitsu Sparclite
18294 * Z8000:: Zilog Z8000
18297 * Super-H:: Renesas Super-H
18306 @item target rdi @var{dev}
18307 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18308 use this target to communicate with both boards running the Angel
18309 monitor, or with the EmbeddedICE JTAG debug device.
18312 @item target rdp @var{dev}
18317 @value{GDBN} provides the following ARM-specific commands:
18320 @item set arm disassembler
18322 This commands selects from a list of disassembly styles. The
18323 @code{"std"} style is the standard style.
18325 @item show arm disassembler
18327 Show the current disassembly style.
18329 @item set arm apcs32
18330 @cindex ARM 32-bit mode
18331 This command toggles ARM operation mode between 32-bit and 26-bit.
18333 @item show arm apcs32
18334 Display the current usage of the ARM 32-bit mode.
18336 @item set arm fpu @var{fputype}
18337 This command sets the ARM floating-point unit (FPU) type. The
18338 argument @var{fputype} can be one of these:
18342 Determine the FPU type by querying the OS ABI.
18344 Software FPU, with mixed-endian doubles on little-endian ARM
18347 GCC-compiled FPA co-processor.
18349 Software FPU with pure-endian doubles.
18355 Show the current type of the FPU.
18358 This command forces @value{GDBN} to use the specified ABI.
18361 Show the currently used ABI.
18363 @item set arm fallback-mode (arm|thumb|auto)
18364 @value{GDBN} uses the symbol table, when available, to determine
18365 whether instructions are ARM or Thumb. This command controls
18366 @value{GDBN}'s default behavior when the symbol table is not
18367 available. The default is @samp{auto}, which causes @value{GDBN} to
18368 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18371 @item show arm fallback-mode
18372 Show the current fallback instruction mode.
18374 @item set arm force-mode (arm|thumb|auto)
18375 This command overrides use of the symbol table to determine whether
18376 instructions are ARM or Thumb. The default is @samp{auto}, which
18377 causes @value{GDBN} to use the symbol table and then the setting
18378 of @samp{set arm fallback-mode}.
18380 @item show arm force-mode
18381 Show the current forced instruction mode.
18383 @item set debug arm
18384 Toggle whether to display ARM-specific debugging messages from the ARM
18385 target support subsystem.
18387 @item show debug arm
18388 Show whether ARM-specific debugging messages are enabled.
18391 The following commands are available when an ARM target is debugged
18392 using the RDI interface:
18395 @item rdilogfile @r{[}@var{file}@r{]}
18397 @cindex ADP (Angel Debugger Protocol) logging
18398 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18399 With an argument, sets the log file to the specified @var{file}. With
18400 no argument, show the current log file name. The default log file is
18403 @item rdilogenable @r{[}@var{arg}@r{]}
18404 @kindex rdilogenable
18405 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18406 enables logging, with an argument 0 or @code{"no"} disables it. With
18407 no arguments displays the current setting. When logging is enabled,
18408 ADP packets exchanged between @value{GDBN} and the RDI target device
18409 are logged to a file.
18411 @item set rdiromatzero
18412 @kindex set rdiromatzero
18413 @cindex ROM at zero address, RDI
18414 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18415 vector catching is disabled, so that zero address can be used. If off
18416 (the default), vector catching is enabled. For this command to take
18417 effect, it needs to be invoked prior to the @code{target rdi} command.
18419 @item show rdiromatzero
18420 @kindex show rdiromatzero
18421 Show the current setting of ROM at zero address.
18423 @item set rdiheartbeat
18424 @kindex set rdiheartbeat
18425 @cindex RDI heartbeat
18426 Enable or disable RDI heartbeat packets. It is not recommended to
18427 turn on this option, since it confuses ARM and EPI JTAG interface, as
18428 well as the Angel monitor.
18430 @item show rdiheartbeat
18431 @kindex show rdiheartbeat
18432 Show the setting of RDI heartbeat packets.
18436 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18437 The @value{GDBN} ARM simulator accepts the following optional arguments.
18440 @item --swi-support=@var{type}
18441 Tell the simulator which SWI interfaces to support.
18442 @var{type} may be a comma separated list of the following values.
18443 The default value is @code{all}.
18456 @subsection Renesas M32R/D and M32R/SDI
18459 @kindex target m32r
18460 @item target m32r @var{dev}
18461 Renesas M32R/D ROM monitor.
18463 @kindex target m32rsdi
18464 @item target m32rsdi @var{dev}
18465 Renesas M32R SDI server, connected via parallel port to the board.
18468 The following @value{GDBN} commands are specific to the M32R monitor:
18471 @item set download-path @var{path}
18472 @kindex set download-path
18473 @cindex find downloadable @sc{srec} files (M32R)
18474 Set the default path for finding downloadable @sc{srec} files.
18476 @item show download-path
18477 @kindex show download-path
18478 Show the default path for downloadable @sc{srec} files.
18480 @item set board-address @var{addr}
18481 @kindex set board-address
18482 @cindex M32-EVA target board address
18483 Set the IP address for the M32R-EVA target board.
18485 @item show board-address
18486 @kindex show board-address
18487 Show the current IP address of the target board.
18489 @item set server-address @var{addr}
18490 @kindex set server-address
18491 @cindex download server address (M32R)
18492 Set the IP address for the download server, which is the @value{GDBN}'s
18495 @item show server-address
18496 @kindex show server-address
18497 Display the IP address of the download server.
18499 @item upload @r{[}@var{file}@r{]}
18500 @kindex upload@r{, M32R}
18501 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18502 upload capability. If no @var{file} argument is given, the current
18503 executable file is uploaded.
18505 @item tload @r{[}@var{file}@r{]}
18506 @kindex tload@r{, M32R}
18507 Test the @code{upload} command.
18510 The following commands are available for M32R/SDI:
18515 @cindex reset SDI connection, M32R
18516 This command resets the SDI connection.
18520 This command shows the SDI connection status.
18523 @kindex debug_chaos
18524 @cindex M32R/Chaos debugging
18525 Instructs the remote that M32R/Chaos debugging is to be used.
18527 @item use_debug_dma
18528 @kindex use_debug_dma
18529 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18532 @kindex use_mon_code
18533 Instructs the remote to use the MON_CODE method of accessing memory.
18536 @kindex use_ib_break
18537 Instructs the remote to set breakpoints by IB break.
18539 @item use_dbt_break
18540 @kindex use_dbt_break
18541 Instructs the remote to set breakpoints by DBT.
18547 The Motorola m68k configuration includes ColdFire support, and a
18548 target command for the following ROM monitor.
18552 @kindex target dbug
18553 @item target dbug @var{dev}
18554 dBUG ROM monitor for Motorola ColdFire.
18559 @subsection MicroBlaze
18560 @cindex Xilinx MicroBlaze
18561 @cindex XMD, Xilinx Microprocessor Debugger
18563 The MicroBlaze is a soft-core processor supported on various Xilinx
18564 FPGAs, such as Spartan or Virtex series. Boards with these processors
18565 usually have JTAG ports which connect to a host system running the Xilinx
18566 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18567 This host system is used to download the configuration bitstream to
18568 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18569 communicates with the target board using the JTAG interface and
18570 presents a @code{gdbserver} interface to the board. By default
18571 @code{xmd} uses port @code{1234}. (While it is possible to change
18572 this default port, it requires the use of undocumented @code{xmd}
18573 commands. Contact Xilinx support if you need to do this.)
18575 Use these GDB commands to connect to the MicroBlaze target processor.
18578 @item target remote :1234
18579 Use this command to connect to the target if you are running @value{GDBN}
18580 on the same system as @code{xmd}.
18582 @item target remote @var{xmd-host}:1234
18583 Use this command to connect to the target if it is connected to @code{xmd}
18584 running on a different system named @var{xmd-host}.
18587 Use this command to download a program to the MicroBlaze target.
18589 @item set debug microblaze @var{n}
18590 Enable MicroBlaze-specific debugging messages if non-zero.
18592 @item show debug microblaze @var{n}
18593 Show MicroBlaze-specific debugging level.
18596 @node MIPS Embedded
18597 @subsection MIPS Embedded
18599 @cindex MIPS boards
18600 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
18601 MIPS board attached to a serial line. This is available when
18602 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
18605 Use these @value{GDBN} commands to specify the connection to your target board:
18608 @item target mips @var{port}
18609 @kindex target mips @var{port}
18610 To run a program on the board, start up @code{@value{GDBP}} with the
18611 name of your program as the argument. To connect to the board, use the
18612 command @samp{target mips @var{port}}, where @var{port} is the name of
18613 the serial port connected to the board. If the program has not already
18614 been downloaded to the board, you may use the @code{load} command to
18615 download it. You can then use all the usual @value{GDBN} commands.
18617 For example, this sequence connects to the target board through a serial
18618 port, and loads and runs a program called @var{prog} through the
18622 host$ @value{GDBP} @var{prog}
18623 @value{GDBN} is free software and @dots{}
18624 (@value{GDBP}) target mips /dev/ttyb
18625 (@value{GDBP}) load @var{prog}
18629 @item target mips @var{hostname}:@var{portnumber}
18630 On some @value{GDBN} host configurations, you can specify a TCP
18631 connection (for instance, to a serial line managed by a terminal
18632 concentrator) instead of a serial port, using the syntax
18633 @samp{@var{hostname}:@var{portnumber}}.
18635 @item target pmon @var{port}
18636 @kindex target pmon @var{port}
18639 @item target ddb @var{port}
18640 @kindex target ddb @var{port}
18641 NEC's DDB variant of PMON for Vr4300.
18643 @item target lsi @var{port}
18644 @kindex target lsi @var{port}
18645 LSI variant of PMON.
18647 @kindex target r3900
18648 @item target r3900 @var{dev}
18649 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
18651 @kindex target array
18652 @item target array @var{dev}
18653 Array Tech LSI33K RAID controller board.
18659 @value{GDBN} also supports these special commands for MIPS targets:
18662 @item set mipsfpu double
18663 @itemx set mipsfpu single
18664 @itemx set mipsfpu none
18665 @itemx set mipsfpu auto
18666 @itemx show mipsfpu
18667 @kindex set mipsfpu
18668 @kindex show mipsfpu
18669 @cindex MIPS remote floating point
18670 @cindex floating point, MIPS remote
18671 If your target board does not support the MIPS floating point
18672 coprocessor, you should use the command @samp{set mipsfpu none} (if you
18673 need this, you may wish to put the command in your @value{GDBN} init
18674 file). This tells @value{GDBN} how to find the return value of
18675 functions which return floating point values. It also allows
18676 @value{GDBN} to avoid saving the floating point registers when calling
18677 functions on the board. If you are using a floating point coprocessor
18678 with only single precision floating point support, as on the @sc{r4650}
18679 processor, use the command @samp{set mipsfpu single}. The default
18680 double precision floating point coprocessor may be selected using
18681 @samp{set mipsfpu double}.
18683 In previous versions the only choices were double precision or no
18684 floating point, so @samp{set mipsfpu on} will select double precision
18685 and @samp{set mipsfpu off} will select no floating point.
18687 As usual, you can inquire about the @code{mipsfpu} variable with
18688 @samp{show mipsfpu}.
18690 @item set timeout @var{seconds}
18691 @itemx set retransmit-timeout @var{seconds}
18692 @itemx show timeout
18693 @itemx show retransmit-timeout
18694 @cindex @code{timeout}, MIPS protocol
18695 @cindex @code{retransmit-timeout}, MIPS protocol
18696 @kindex set timeout
18697 @kindex show timeout
18698 @kindex set retransmit-timeout
18699 @kindex show retransmit-timeout
18700 You can control the timeout used while waiting for a packet, in the MIPS
18701 remote protocol, with the @code{set timeout @var{seconds}} command. The
18702 default is 5 seconds. Similarly, you can control the timeout used while
18703 waiting for an acknowledgment of a packet with the @code{set
18704 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
18705 You can inspect both values with @code{show timeout} and @code{show
18706 retransmit-timeout}. (These commands are @emph{only} available when
18707 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
18709 The timeout set by @code{set timeout} does not apply when @value{GDBN}
18710 is waiting for your program to stop. In that case, @value{GDBN} waits
18711 forever because it has no way of knowing how long the program is going
18712 to run before stopping.
18714 @item set syn-garbage-limit @var{num}
18715 @kindex set syn-garbage-limit@r{, MIPS remote}
18716 @cindex synchronize with remote MIPS target
18717 Limit the maximum number of characters @value{GDBN} should ignore when
18718 it tries to synchronize with the remote target. The default is 10
18719 characters. Setting the limit to -1 means there's no limit.
18721 @item show syn-garbage-limit
18722 @kindex show syn-garbage-limit@r{, MIPS remote}
18723 Show the current limit on the number of characters to ignore when
18724 trying to synchronize with the remote system.
18726 @item set monitor-prompt @var{prompt}
18727 @kindex set monitor-prompt@r{, MIPS remote}
18728 @cindex remote monitor prompt
18729 Tell @value{GDBN} to expect the specified @var{prompt} string from the
18730 remote monitor. The default depends on the target:
18740 @item show monitor-prompt
18741 @kindex show monitor-prompt@r{, MIPS remote}
18742 Show the current strings @value{GDBN} expects as the prompt from the
18745 @item set monitor-warnings
18746 @kindex set monitor-warnings@r{, MIPS remote}
18747 Enable or disable monitor warnings about hardware breakpoints. This
18748 has effect only for the @code{lsi} target. When on, @value{GDBN} will
18749 display warning messages whose codes are returned by the @code{lsi}
18750 PMON monitor for breakpoint commands.
18752 @item show monitor-warnings
18753 @kindex show monitor-warnings@r{, MIPS remote}
18754 Show the current setting of printing monitor warnings.
18756 @item pmon @var{command}
18757 @kindex pmon@r{, MIPS remote}
18758 @cindex send PMON command
18759 This command allows sending an arbitrary @var{command} string to the
18760 monitor. The monitor must be in debug mode for this to work.
18763 @node OpenRISC 1000
18764 @subsection OpenRISC 1000
18765 @cindex OpenRISC 1000
18767 @cindex or1k boards
18768 See OR1k Architecture document (@uref{www.opencores.org}) for more information
18769 about platform and commands.
18773 @kindex target jtag
18774 @item target jtag jtag://@var{host}:@var{port}
18776 Connects to remote JTAG server.
18777 JTAG remote server can be either an or1ksim or JTAG server,
18778 connected via parallel port to the board.
18780 Example: @code{target jtag jtag://localhost:9999}
18783 @item or1ksim @var{command}
18784 If connected to @code{or1ksim} OpenRISC 1000 Architectural
18785 Simulator, proprietary commands can be executed.
18787 @kindex info or1k spr
18788 @item info or1k spr
18789 Displays spr groups.
18791 @item info or1k spr @var{group}
18792 @itemx info or1k spr @var{groupno}
18793 Displays register names in selected group.
18795 @item info or1k spr @var{group} @var{register}
18796 @itemx info or1k spr @var{register}
18797 @itemx info or1k spr @var{groupno} @var{registerno}
18798 @itemx info or1k spr @var{registerno}
18799 Shows information about specified spr register.
18802 @item spr @var{group} @var{register} @var{value}
18803 @itemx spr @var{register @var{value}}
18804 @itemx spr @var{groupno} @var{registerno @var{value}}
18805 @itemx spr @var{registerno @var{value}}
18806 Writes @var{value} to specified spr register.
18809 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
18810 It is very similar to @value{GDBN} trace, except it does not interfere with normal
18811 program execution and is thus much faster. Hardware breakpoints/watchpoint
18812 triggers can be set using:
18815 Load effective address/data
18817 Store effective address/data
18819 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
18824 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
18825 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
18827 @code{htrace} commands:
18828 @cindex OpenRISC 1000 htrace
18831 @item hwatch @var{conditional}
18832 Set hardware watchpoint on combination of Load/Store Effective Address(es)
18833 or Data. For example:
18835 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18837 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18841 Display information about current HW trace configuration.
18843 @item htrace trigger @var{conditional}
18844 Set starting criteria for HW trace.
18846 @item htrace qualifier @var{conditional}
18847 Set acquisition qualifier for HW trace.
18849 @item htrace stop @var{conditional}
18850 Set HW trace stopping criteria.
18852 @item htrace record [@var{data}]*
18853 Selects the data to be recorded, when qualifier is met and HW trace was
18856 @item htrace enable
18857 @itemx htrace disable
18858 Enables/disables the HW trace.
18860 @item htrace rewind [@var{filename}]
18861 Clears currently recorded trace data.
18863 If filename is specified, new trace file is made and any newly collected data
18864 will be written there.
18866 @item htrace print [@var{start} [@var{len}]]
18867 Prints trace buffer, using current record configuration.
18869 @item htrace mode continuous
18870 Set continuous trace mode.
18872 @item htrace mode suspend
18873 Set suspend trace mode.
18877 @node PowerPC Embedded
18878 @subsection PowerPC Embedded
18880 @cindex DVC register
18881 @value{GDBN} supports using the DVC (Data Value Compare) register to
18882 implement in hardware simple hardware watchpoint conditions of the form:
18885 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
18886 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
18889 The DVC register will be automatically used when @value{GDBN} detects
18890 such pattern in a condition expression, and the created watchpoint uses one
18891 debug register (either the @code{exact-watchpoints} option is on and the
18892 variable is scalar, or the variable has a length of one byte). This feature
18893 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
18896 When running on PowerPC embedded processors, @value{GDBN} automatically uses
18897 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
18898 in which case watchpoints using only one debug register are created when
18899 watching variables of scalar types.
18901 You can create an artificial array to watch an arbitrary memory
18902 region using one of the following commands (@pxref{Expressions}):
18905 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
18906 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
18909 PowerPC embedded processors support masked watchpoints. See the discussion
18910 about the @code{mask} argument in @ref{Set Watchpoints}.
18912 @cindex ranged breakpoint
18913 PowerPC embedded processors support hardware accelerated
18914 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
18915 the inferior whenever it executes an instruction at any address within
18916 the range it specifies. To set a ranged breakpoint in @value{GDBN},
18917 use the @code{break-range} command.
18919 @value{GDBN} provides the following PowerPC-specific commands:
18922 @kindex break-range
18923 @item break-range @var{start-location}, @var{end-location}
18924 Set a breakpoint for an address range.
18925 @var{start-location} and @var{end-location} can specify a function name,
18926 a line number, an offset of lines from the current line or from the start
18927 location, or an address of an instruction (see @ref{Specify Location},
18928 for a list of all the possible ways to specify a @var{location}.)
18929 The breakpoint will stop execution of the inferior whenever it
18930 executes an instruction at any address within the specified range,
18931 (including @var{start-location} and @var{end-location}.)
18933 @kindex set powerpc
18934 @item set powerpc soft-float
18935 @itemx show powerpc soft-float
18936 Force @value{GDBN} to use (or not use) a software floating point calling
18937 convention. By default, @value{GDBN} selects the calling convention based
18938 on the selected architecture and the provided executable file.
18940 @item set powerpc vector-abi
18941 @itemx show powerpc vector-abi
18942 Force @value{GDBN} to use the specified calling convention for vector
18943 arguments and return values. The valid options are @samp{auto};
18944 @samp{generic}, to avoid vector registers even if they are present;
18945 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
18946 registers. By default, @value{GDBN} selects the calling convention
18947 based on the selected architecture and the provided executable file.
18949 @item set powerpc exact-watchpoints
18950 @itemx show powerpc exact-watchpoints
18951 Allow @value{GDBN} to use only one debug register when watching a variable
18952 of scalar type, thus assuming that the variable is accessed through the
18953 address of its first byte.
18955 @kindex target dink32
18956 @item target dink32 @var{dev}
18957 DINK32 ROM monitor.
18959 @kindex target ppcbug
18960 @item target ppcbug @var{dev}
18961 @kindex target ppcbug1
18962 @item target ppcbug1 @var{dev}
18963 PPCBUG ROM monitor for PowerPC.
18966 @item target sds @var{dev}
18967 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18970 @cindex SDS protocol
18971 The following commands specific to the SDS protocol are supported
18975 @item set sdstimeout @var{nsec}
18976 @kindex set sdstimeout
18977 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18978 default is 2 seconds.
18980 @item show sdstimeout
18981 @kindex show sdstimeout
18982 Show the current value of the SDS timeout.
18984 @item sds @var{command}
18985 @kindex sds@r{, a command}
18986 Send the specified @var{command} string to the SDS monitor.
18991 @subsection HP PA Embedded
18995 @kindex target op50n
18996 @item target op50n @var{dev}
18997 OP50N monitor, running on an OKI HPPA board.
18999 @kindex target w89k
19000 @item target w89k @var{dev}
19001 W89K monitor, running on a Winbond HPPA board.
19006 @subsection Tsqware Sparclet
19010 @value{GDBN} enables developers to debug tasks running on
19011 Sparclet targets from a Unix host.
19012 @value{GDBN} uses code that runs on
19013 both the Unix host and on the Sparclet target. The program
19014 @code{@value{GDBP}} is installed and executed on the Unix host.
19017 @item remotetimeout @var{args}
19018 @kindex remotetimeout
19019 @value{GDBN} supports the option @code{remotetimeout}.
19020 This option is set by the user, and @var{args} represents the number of
19021 seconds @value{GDBN} waits for responses.
19024 @cindex compiling, on Sparclet
19025 When compiling for debugging, include the options @samp{-g} to get debug
19026 information and @samp{-Ttext} to relocate the program to where you wish to
19027 load it on the target. You may also want to add the options @samp{-n} or
19028 @samp{-N} in order to reduce the size of the sections. Example:
19031 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
19034 You can use @code{objdump} to verify that the addresses are what you intended:
19037 sparclet-aout-objdump --headers --syms prog
19040 @cindex running, on Sparclet
19042 your Unix execution search path to find @value{GDBN}, you are ready to
19043 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
19044 (or @code{sparclet-aout-gdb}, depending on your installation).
19046 @value{GDBN} comes up showing the prompt:
19053 * Sparclet File:: Setting the file to debug
19054 * Sparclet Connection:: Connecting to Sparclet
19055 * Sparclet Download:: Sparclet download
19056 * Sparclet Execution:: Running and debugging
19059 @node Sparclet File
19060 @subsubsection Setting File to Debug
19062 The @value{GDBN} command @code{file} lets you choose with program to debug.
19065 (gdbslet) file prog
19069 @value{GDBN} then attempts to read the symbol table of @file{prog}.
19070 @value{GDBN} locates
19071 the file by searching the directories listed in the command search
19073 If the file was compiled with debug information (option @samp{-g}), source
19074 files will be searched as well.
19075 @value{GDBN} locates
19076 the source files by searching the directories listed in the directory search
19077 path (@pxref{Environment, ,Your Program's Environment}).
19079 to find a file, it displays a message such as:
19082 prog: No such file or directory.
19085 When this happens, add the appropriate directories to the search paths with
19086 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
19087 @code{target} command again.
19089 @node Sparclet Connection
19090 @subsubsection Connecting to Sparclet
19092 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
19093 To connect to a target on serial port ``@code{ttya}'', type:
19096 (gdbslet) target sparclet /dev/ttya
19097 Remote target sparclet connected to /dev/ttya
19098 main () at ../prog.c:3
19102 @value{GDBN} displays messages like these:
19108 @node Sparclet Download
19109 @subsubsection Sparclet Download
19111 @cindex download to Sparclet
19112 Once connected to the Sparclet target,
19113 you can use the @value{GDBN}
19114 @code{load} command to download the file from the host to the target.
19115 The file name and load offset should be given as arguments to the @code{load}
19117 Since the file format is aout, the program must be loaded to the starting
19118 address. You can use @code{objdump} to find out what this value is. The load
19119 offset is an offset which is added to the VMA (virtual memory address)
19120 of each of the file's sections.
19121 For instance, if the program
19122 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19123 and bss at 0x12010170, in @value{GDBN}, type:
19126 (gdbslet) load prog 0x12010000
19127 Loading section .text, size 0xdb0 vma 0x12010000
19130 If the code is loaded at a different address then what the program was linked
19131 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19132 to tell @value{GDBN} where to map the symbol table.
19134 @node Sparclet Execution
19135 @subsubsection Running and Debugging
19137 @cindex running and debugging Sparclet programs
19138 You can now begin debugging the task using @value{GDBN}'s execution control
19139 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19140 manual for the list of commands.
19144 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19146 Starting program: prog
19147 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19148 3 char *symarg = 0;
19150 4 char *execarg = "hello!";
19155 @subsection Fujitsu Sparclite
19159 @kindex target sparclite
19160 @item target sparclite @var{dev}
19161 Fujitsu sparclite boards, used only for the purpose of loading.
19162 You must use an additional command to debug the program.
19163 For example: target remote @var{dev} using @value{GDBN} standard
19169 @subsection Zilog Z8000
19172 @cindex simulator, Z8000
19173 @cindex Zilog Z8000 simulator
19175 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19178 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19179 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19180 segmented variant). The simulator recognizes which architecture is
19181 appropriate by inspecting the object code.
19184 @item target sim @var{args}
19186 @kindex target sim@r{, with Z8000}
19187 Debug programs on a simulated CPU. If the simulator supports setup
19188 options, specify them via @var{args}.
19192 After specifying this target, you can debug programs for the simulated
19193 CPU in the same style as programs for your host computer; use the
19194 @code{file} command to load a new program image, the @code{run} command
19195 to run your program, and so on.
19197 As well as making available all the usual machine registers
19198 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19199 additional items of information as specially named registers:
19204 Counts clock-ticks in the simulator.
19207 Counts instructions run in the simulator.
19210 Execution time in 60ths of a second.
19214 You can refer to these values in @value{GDBN} expressions with the usual
19215 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19216 conditional breakpoint that suspends only after at least 5000
19217 simulated clock ticks.
19220 @subsection Atmel AVR
19223 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19224 following AVR-specific commands:
19227 @item info io_registers
19228 @kindex info io_registers@r{, AVR}
19229 @cindex I/O registers (Atmel AVR)
19230 This command displays information about the AVR I/O registers. For
19231 each register, @value{GDBN} prints its number and value.
19238 When configured for debugging CRIS, @value{GDBN} provides the
19239 following CRIS-specific commands:
19242 @item set cris-version @var{ver}
19243 @cindex CRIS version
19244 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19245 The CRIS version affects register names and sizes. This command is useful in
19246 case autodetection of the CRIS version fails.
19248 @item show cris-version
19249 Show the current CRIS version.
19251 @item set cris-dwarf2-cfi
19252 @cindex DWARF-2 CFI and CRIS
19253 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19254 Change to @samp{off} when using @code{gcc-cris} whose version is below
19257 @item show cris-dwarf2-cfi
19258 Show the current state of using DWARF-2 CFI.
19260 @item set cris-mode @var{mode}
19262 Set the current CRIS mode to @var{mode}. It should only be changed when
19263 debugging in guru mode, in which case it should be set to
19264 @samp{guru} (the default is @samp{normal}).
19266 @item show cris-mode
19267 Show the current CRIS mode.
19271 @subsection Renesas Super-H
19274 For the Renesas Super-H processor, @value{GDBN} provides these
19279 @kindex regs@r{, Super-H}
19280 Show the values of all Super-H registers.
19282 @item set sh calling-convention @var{convention}
19283 @kindex set sh calling-convention
19284 Set the calling-convention used when calling functions from @value{GDBN}.
19285 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19286 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19287 convention. If the DWARF-2 information of the called function specifies
19288 that the function follows the Renesas calling convention, the function
19289 is called using the Renesas calling convention. If the calling convention
19290 is set to @samp{renesas}, the Renesas calling convention is always used,
19291 regardless of the DWARF-2 information. This can be used to override the
19292 default of @samp{gcc} if debug information is missing, or the compiler
19293 does not emit the DWARF-2 calling convention entry for a function.
19295 @item show sh calling-convention
19296 @kindex show sh calling-convention
19297 Show the current calling convention setting.
19302 @node Architectures
19303 @section Architectures
19305 This section describes characteristics of architectures that affect
19306 all uses of @value{GDBN} with the architecture, both native and cross.
19313 * HPPA:: HP PA architecture
19314 * SPU:: Cell Broadband Engine SPU architecture
19319 @subsection x86 Architecture-specific Issues
19322 @item set struct-convention @var{mode}
19323 @kindex set struct-convention
19324 @cindex struct return convention
19325 @cindex struct/union returned in registers
19326 Set the convention used by the inferior to return @code{struct}s and
19327 @code{union}s from functions to @var{mode}. Possible values of
19328 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19329 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19330 are returned on the stack, while @code{"reg"} means that a
19331 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19332 be returned in a register.
19334 @item show struct-convention
19335 @kindex show struct-convention
19336 Show the current setting of the convention to return @code{struct}s
19345 @kindex set rstack_high_address
19346 @cindex AMD 29K register stack
19347 @cindex register stack, AMD29K
19348 @item set rstack_high_address @var{address}
19349 On AMD 29000 family processors, registers are saved in a separate
19350 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19351 extent of this stack. Normally, @value{GDBN} just assumes that the
19352 stack is ``large enough''. This may result in @value{GDBN} referencing
19353 memory locations that do not exist. If necessary, you can get around
19354 this problem by specifying the ending address of the register stack with
19355 the @code{set rstack_high_address} command. The argument should be an
19356 address, which you probably want to precede with @samp{0x} to specify in
19359 @kindex show rstack_high_address
19360 @item show rstack_high_address
19361 Display the current limit of the register stack, on AMD 29000 family
19369 See the following section.
19374 @cindex stack on Alpha
19375 @cindex stack on MIPS
19376 @cindex Alpha stack
19378 Alpha- and MIPS-based computers use an unusual stack frame, which
19379 sometimes requires @value{GDBN} to search backward in the object code to
19380 find the beginning of a function.
19382 @cindex response time, MIPS debugging
19383 To improve response time (especially for embedded applications, where
19384 @value{GDBN} may be restricted to a slow serial line for this search)
19385 you may want to limit the size of this search, using one of these
19389 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19390 @item set heuristic-fence-post @var{limit}
19391 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19392 search for the beginning of a function. A value of @var{0} (the
19393 default) means there is no limit. However, except for @var{0}, the
19394 larger the limit the more bytes @code{heuristic-fence-post} must search
19395 and therefore the longer it takes to run. You should only need to use
19396 this command when debugging a stripped executable.
19398 @item show heuristic-fence-post
19399 Display the current limit.
19403 These commands are available @emph{only} when @value{GDBN} is configured
19404 for debugging programs on Alpha or MIPS processors.
19406 Several MIPS-specific commands are available when debugging MIPS
19410 @item set mips abi @var{arg}
19411 @kindex set mips abi
19412 @cindex set ABI for MIPS
19413 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19414 values of @var{arg} are:
19418 The default ABI associated with the current binary (this is the
19429 @item show mips abi
19430 @kindex show mips abi
19431 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19434 @itemx show mipsfpu
19435 @xref{MIPS Embedded, set mipsfpu}.
19437 @item set mips mask-address @var{arg}
19438 @kindex set mips mask-address
19439 @cindex MIPS addresses, masking
19440 This command determines whether the most-significant 32 bits of 64-bit
19441 MIPS addresses are masked off. The argument @var{arg} can be
19442 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19443 setting, which lets @value{GDBN} determine the correct value.
19445 @item show mips mask-address
19446 @kindex show mips mask-address
19447 Show whether the upper 32 bits of MIPS addresses are masked off or
19450 @item set remote-mips64-transfers-32bit-regs
19451 @kindex set remote-mips64-transfers-32bit-regs
19452 This command controls compatibility with 64-bit MIPS targets that
19453 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19454 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19455 and 64 bits for other registers, set this option to @samp{on}.
19457 @item show remote-mips64-transfers-32bit-regs
19458 @kindex show remote-mips64-transfers-32bit-regs
19459 Show the current setting of compatibility with older MIPS 64 targets.
19461 @item set debug mips
19462 @kindex set debug mips
19463 This command turns on and off debugging messages for the MIPS-specific
19464 target code in @value{GDBN}.
19466 @item show debug mips
19467 @kindex show debug mips
19468 Show the current setting of MIPS debugging messages.
19474 @cindex HPPA support
19476 When @value{GDBN} is debugging the HP PA architecture, it provides the
19477 following special commands:
19480 @item set debug hppa
19481 @kindex set debug hppa
19482 This command determines whether HPPA architecture-specific debugging
19483 messages are to be displayed.
19485 @item show debug hppa
19486 Show whether HPPA debugging messages are displayed.
19488 @item maint print unwind @var{address}
19489 @kindex maint print unwind@r{, HPPA}
19490 This command displays the contents of the unwind table entry at the
19491 given @var{address}.
19497 @subsection Cell Broadband Engine SPU architecture
19498 @cindex Cell Broadband Engine
19501 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19502 it provides the following special commands:
19505 @item info spu event
19507 Display SPU event facility status. Shows current event mask
19508 and pending event status.
19510 @item info spu signal
19511 Display SPU signal notification facility status. Shows pending
19512 signal-control word and signal notification mode of both signal
19513 notification channels.
19515 @item info spu mailbox
19516 Display SPU mailbox facility status. Shows all pending entries,
19517 in order of processing, in each of the SPU Write Outbound,
19518 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19521 Display MFC DMA status. Shows all pending commands in the MFC
19522 DMA queue. For each entry, opcode, tag, class IDs, effective
19523 and local store addresses and transfer size are shown.
19525 @item info spu proxydma
19526 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19527 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19528 and local store addresses and transfer size are shown.
19532 When @value{GDBN} is debugging a combined PowerPC/SPU application
19533 on the Cell Broadband Engine, it provides in addition the following
19537 @item set spu stop-on-load @var{arg}
19539 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19540 will give control to the user when a new SPE thread enters its @code{main}
19541 function. The default is @code{off}.
19543 @item show spu stop-on-load
19545 Show whether to stop for new SPE threads.
19547 @item set spu auto-flush-cache @var{arg}
19548 Set whether to automatically flush the software-managed cache. When set to
19549 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19550 cache to be flushed whenever SPE execution stops. This provides a consistent
19551 view of PowerPC memory that is accessed via the cache. If an application
19552 does not use the software-managed cache, this option has no effect.
19554 @item show spu auto-flush-cache
19555 Show whether to automatically flush the software-managed cache.
19560 @subsection PowerPC
19561 @cindex PowerPC architecture
19563 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19564 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19565 numbers stored in the floating point registers. These values must be stored
19566 in two consecutive registers, always starting at an even register like
19567 @code{f0} or @code{f2}.
19569 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19570 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19571 @code{f2} and @code{f3} for @code{$dl1} and so on.
19573 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19574 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19577 @node Controlling GDB
19578 @chapter Controlling @value{GDBN}
19580 You can alter the way @value{GDBN} interacts with you by using the
19581 @code{set} command. For commands controlling how @value{GDBN} displays
19582 data, see @ref{Print Settings, ,Print Settings}. Other settings are
19587 * Editing:: Command editing
19588 * Command History:: Command history
19589 * Screen Size:: Screen size
19590 * Numbers:: Numbers
19591 * ABI:: Configuring the current ABI
19592 * Messages/Warnings:: Optional warnings and messages
19593 * Debugging Output:: Optional messages about internal happenings
19594 * Other Misc Settings:: Other Miscellaneous Settings
19602 @value{GDBN} indicates its readiness to read a command by printing a string
19603 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
19604 can change the prompt string with the @code{set prompt} command. For
19605 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
19606 the prompt in one of the @value{GDBN} sessions so that you can always tell
19607 which one you are talking to.
19609 @emph{Note:} @code{set prompt} does not add a space for you after the
19610 prompt you set. This allows you to set a prompt which ends in a space
19611 or a prompt that does not.
19615 @item set prompt @var{newprompt}
19616 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
19618 @kindex show prompt
19620 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
19623 Versions of @value{GDBN} that ship with Python scripting enabled have
19624 prompt extensions. The commands for interacting with these extensions
19628 @kindex set extended-prompt
19629 @item set extended-prompt @var{prompt}
19630 Set an extended prompt that allows for substitutions.
19631 @xref{gdb.prompt}, for a list of escape sequences that can be used for
19632 substitution. Any escape sequences specified as part of the prompt
19633 string are replaced with the corresponding strings each time the prompt
19639 set extended-prompt Current working directory: \w (gdb)
19642 Note that when an extended-prompt is set, it takes control of the
19643 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
19645 @kindex show extended-prompt
19646 @item show extended-prompt
19647 Prints the extended prompt. Any escape sequences specified as part of
19648 the prompt string with @code{set extended-prompt}, are replaced with the
19649 corresponding strings each time the prompt is displayed.
19653 @section Command Editing
19655 @cindex command line editing
19657 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
19658 @sc{gnu} library provides consistent behavior for programs which provide a
19659 command line interface to the user. Advantages are @sc{gnu} Emacs-style
19660 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
19661 substitution, and a storage and recall of command history across
19662 debugging sessions.
19664 You may control the behavior of command line editing in @value{GDBN} with the
19665 command @code{set}.
19668 @kindex set editing
19671 @itemx set editing on
19672 Enable command line editing (enabled by default).
19674 @item set editing off
19675 Disable command line editing.
19677 @kindex show editing
19679 Show whether command line editing is enabled.
19682 @ifset SYSTEM_READLINE
19683 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
19685 @ifclear SYSTEM_READLINE
19686 @xref{Command Line Editing},
19688 for more details about the Readline
19689 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
19690 encouraged to read that chapter.
19692 @node Command History
19693 @section Command History
19694 @cindex command history
19696 @value{GDBN} can keep track of the commands you type during your
19697 debugging sessions, so that you can be certain of precisely what
19698 happened. Use these commands to manage the @value{GDBN} command
19701 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
19702 package, to provide the history facility.
19703 @ifset SYSTEM_READLINE
19704 @xref{Using History Interactively, , , history, GNU History Library},
19706 @ifclear SYSTEM_READLINE
19707 @xref{Using History Interactively},
19709 for the detailed description of the History library.
19711 To issue a command to @value{GDBN} without affecting certain aspects of
19712 the state which is seen by users, prefix it with @samp{server }
19713 (@pxref{Server Prefix}). This
19714 means that this command will not affect the command history, nor will it
19715 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19716 pressed on a line by itself.
19718 @cindex @code{server}, command prefix
19719 The server prefix does not affect the recording of values into the value
19720 history; to print a value without recording it into the value history,
19721 use the @code{output} command instead of the @code{print} command.
19723 Here is the description of @value{GDBN} commands related to command
19727 @cindex history substitution
19728 @cindex history file
19729 @kindex set history filename
19730 @cindex @env{GDBHISTFILE}, environment variable
19731 @item set history filename @var{fname}
19732 Set the name of the @value{GDBN} command history file to @var{fname}.
19733 This is the file where @value{GDBN} reads an initial command history
19734 list, and where it writes the command history from this session when it
19735 exits. You can access this list through history expansion or through
19736 the history command editing characters listed below. This file defaults
19737 to the value of the environment variable @code{GDBHISTFILE}, or to
19738 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
19741 @cindex save command history
19742 @kindex set history save
19743 @item set history save
19744 @itemx set history save on
19745 Record command history in a file, whose name may be specified with the
19746 @code{set history filename} command. By default, this option is disabled.
19748 @item set history save off
19749 Stop recording command history in a file.
19751 @cindex history size
19752 @kindex set history size
19753 @cindex @env{HISTSIZE}, environment variable
19754 @item set history size @var{size}
19755 Set the number of commands which @value{GDBN} keeps in its history list.
19756 This defaults to the value of the environment variable
19757 @code{HISTSIZE}, or to 256 if this variable is not set.
19760 History expansion assigns special meaning to the character @kbd{!}.
19761 @ifset SYSTEM_READLINE
19762 @xref{Event Designators, , , history, GNU History Library},
19764 @ifclear SYSTEM_READLINE
19765 @xref{Event Designators},
19769 @cindex history expansion, turn on/off
19770 Since @kbd{!} is also the logical not operator in C, history expansion
19771 is off by default. If you decide to enable history expansion with the
19772 @code{set history expansion on} command, you may sometimes need to
19773 follow @kbd{!} (when it is used as logical not, in an expression) with
19774 a space or a tab to prevent it from being expanded. The readline
19775 history facilities do not attempt substitution on the strings
19776 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
19778 The commands to control history expansion are:
19781 @item set history expansion on
19782 @itemx set history expansion
19783 @kindex set history expansion
19784 Enable history expansion. History expansion is off by default.
19786 @item set history expansion off
19787 Disable history expansion.
19790 @kindex show history
19792 @itemx show history filename
19793 @itemx show history save
19794 @itemx show history size
19795 @itemx show history expansion
19796 These commands display the state of the @value{GDBN} history parameters.
19797 @code{show history} by itself displays all four states.
19802 @kindex show commands
19803 @cindex show last commands
19804 @cindex display command history
19805 @item show commands
19806 Display the last ten commands in the command history.
19808 @item show commands @var{n}
19809 Print ten commands centered on command number @var{n}.
19811 @item show commands +
19812 Print ten commands just after the commands last printed.
19816 @section Screen Size
19817 @cindex size of screen
19818 @cindex pauses in output
19820 Certain commands to @value{GDBN} may produce large amounts of
19821 information output to the screen. To help you read all of it,
19822 @value{GDBN} pauses and asks you for input at the end of each page of
19823 output. Type @key{RET} when you want to continue the output, or @kbd{q}
19824 to discard the remaining output. Also, the screen width setting
19825 determines when to wrap lines of output. Depending on what is being
19826 printed, @value{GDBN} tries to break the line at a readable place,
19827 rather than simply letting it overflow onto the following line.
19829 Normally @value{GDBN} knows the size of the screen from the terminal
19830 driver software. For example, on Unix @value{GDBN} uses the termcap data base
19831 together with the value of the @code{TERM} environment variable and the
19832 @code{stty rows} and @code{stty cols} settings. If this is not correct,
19833 you can override it with the @code{set height} and @code{set
19840 @kindex show height
19841 @item set height @var{lpp}
19843 @itemx set width @var{cpl}
19845 These @code{set} commands specify a screen height of @var{lpp} lines and
19846 a screen width of @var{cpl} characters. The associated @code{show}
19847 commands display the current settings.
19849 If you specify a height of zero lines, @value{GDBN} does not pause during
19850 output no matter how long the output is. This is useful if output is to a
19851 file or to an editor buffer.
19853 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
19854 from wrapping its output.
19856 @item set pagination on
19857 @itemx set pagination off
19858 @kindex set pagination
19859 Turn the output pagination on or off; the default is on. Turning
19860 pagination off is the alternative to @code{set height 0}. Note that
19861 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
19862 Options, -batch}) also automatically disables pagination.
19864 @item show pagination
19865 @kindex show pagination
19866 Show the current pagination mode.
19871 @cindex number representation
19872 @cindex entering numbers
19874 You can always enter numbers in octal, decimal, or hexadecimal in
19875 @value{GDBN} by the usual conventions: octal numbers begin with
19876 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
19877 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
19878 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
19879 10; likewise, the default display for numbers---when no particular
19880 format is specified---is base 10. You can change the default base for
19881 both input and output with the commands described below.
19884 @kindex set input-radix
19885 @item set input-radix @var{base}
19886 Set the default base for numeric input. Supported choices
19887 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19888 specified either unambiguously or using the current input radix; for
19892 set input-radix 012
19893 set input-radix 10.
19894 set input-radix 0xa
19898 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
19899 leaves the input radix unchanged, no matter what it was, since
19900 @samp{10}, being without any leading or trailing signs of its base, is
19901 interpreted in the current radix. Thus, if the current radix is 16,
19902 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
19905 @kindex set output-radix
19906 @item set output-radix @var{base}
19907 Set the default base for numeric display. Supported choices
19908 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19909 specified either unambiguously or using the current input radix.
19911 @kindex show input-radix
19912 @item show input-radix
19913 Display the current default base for numeric input.
19915 @kindex show output-radix
19916 @item show output-radix
19917 Display the current default base for numeric display.
19919 @item set radix @r{[}@var{base}@r{]}
19923 These commands set and show the default base for both input and output
19924 of numbers. @code{set radix} sets the radix of input and output to
19925 the same base; without an argument, it resets the radix back to its
19926 default value of 10.
19931 @section Configuring the Current ABI
19933 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
19934 application automatically. However, sometimes you need to override its
19935 conclusions. Use these commands to manage @value{GDBN}'s view of the
19942 One @value{GDBN} configuration can debug binaries for multiple operating
19943 system targets, either via remote debugging or native emulation.
19944 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
19945 but you can override its conclusion using the @code{set osabi} command.
19946 One example where this is useful is in debugging of binaries which use
19947 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
19948 not have the same identifying marks that the standard C library for your
19953 Show the OS ABI currently in use.
19956 With no argument, show the list of registered available OS ABI's.
19958 @item set osabi @var{abi}
19959 Set the current OS ABI to @var{abi}.
19962 @cindex float promotion
19964 Generally, the way that an argument of type @code{float} is passed to a
19965 function depends on whether the function is prototyped. For a prototyped
19966 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
19967 according to the architecture's convention for @code{float}. For unprototyped
19968 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
19969 @code{double} and then passed.
19971 Unfortunately, some forms of debug information do not reliably indicate whether
19972 a function is prototyped. If @value{GDBN} calls a function that is not marked
19973 as prototyped, it consults @kbd{set coerce-float-to-double}.
19976 @kindex set coerce-float-to-double
19977 @item set coerce-float-to-double
19978 @itemx set coerce-float-to-double on
19979 Arguments of type @code{float} will be promoted to @code{double} when passed
19980 to an unprototyped function. This is the default setting.
19982 @item set coerce-float-to-double off
19983 Arguments of type @code{float} will be passed directly to unprototyped
19986 @kindex show coerce-float-to-double
19987 @item show coerce-float-to-double
19988 Show the current setting of promoting @code{float} to @code{double}.
19992 @kindex show cp-abi
19993 @value{GDBN} needs to know the ABI used for your program's C@t{++}
19994 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
19995 used to build your application. @value{GDBN} only fully supports
19996 programs with a single C@t{++} ABI; if your program contains code using
19997 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
19998 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
19999 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
20000 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
20001 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
20002 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
20007 Show the C@t{++} ABI currently in use.
20010 With no argument, show the list of supported C@t{++} ABI's.
20012 @item set cp-abi @var{abi}
20013 @itemx set cp-abi auto
20014 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
20017 @node Messages/Warnings
20018 @section Optional Warnings and Messages
20020 @cindex verbose operation
20021 @cindex optional warnings
20022 By default, @value{GDBN} is silent about its inner workings. If you are
20023 running on a slow machine, you may want to use the @code{set verbose}
20024 command. This makes @value{GDBN} tell you when it does a lengthy
20025 internal operation, so you will not think it has crashed.
20027 Currently, the messages controlled by @code{set verbose} are those
20028 which announce that the symbol table for a source file is being read;
20029 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
20032 @kindex set verbose
20033 @item set verbose on
20034 Enables @value{GDBN} output of certain informational messages.
20036 @item set verbose off
20037 Disables @value{GDBN} output of certain informational messages.
20039 @kindex show verbose
20041 Displays whether @code{set verbose} is on or off.
20044 By default, if @value{GDBN} encounters bugs in the symbol table of an
20045 object file, it is silent; but if you are debugging a compiler, you may
20046 find this information useful (@pxref{Symbol Errors, ,Errors Reading
20051 @kindex set complaints
20052 @item set complaints @var{limit}
20053 Permits @value{GDBN} to output @var{limit} complaints about each type of
20054 unusual symbols before becoming silent about the problem. Set
20055 @var{limit} to zero to suppress all complaints; set it to a large number
20056 to prevent complaints from being suppressed.
20058 @kindex show complaints
20059 @item show complaints
20060 Displays how many symbol complaints @value{GDBN} is permitted to produce.
20064 @anchor{confirmation requests}
20065 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
20066 lot of stupid questions to confirm certain commands. For example, if
20067 you try to run a program which is already running:
20071 The program being debugged has been started already.
20072 Start it from the beginning? (y or n)
20075 If you are willing to unflinchingly face the consequences of your own
20076 commands, you can disable this ``feature'':
20080 @kindex set confirm
20082 @cindex confirmation
20083 @cindex stupid questions
20084 @item set confirm off
20085 Disables confirmation requests. Note that running @value{GDBN} with
20086 the @option{--batch} option (@pxref{Mode Options, -batch}) also
20087 automatically disables confirmation requests.
20089 @item set confirm on
20090 Enables confirmation requests (the default).
20092 @kindex show confirm
20094 Displays state of confirmation requests.
20098 @cindex command tracing
20099 If you need to debug user-defined commands or sourced files you may find it
20100 useful to enable @dfn{command tracing}. In this mode each command will be
20101 printed as it is executed, prefixed with one or more @samp{+} symbols, the
20102 quantity denoting the call depth of each command.
20105 @kindex set trace-commands
20106 @cindex command scripts, debugging
20107 @item set trace-commands on
20108 Enable command tracing.
20109 @item set trace-commands off
20110 Disable command tracing.
20111 @item show trace-commands
20112 Display the current state of command tracing.
20115 @node Debugging Output
20116 @section Optional Messages about Internal Happenings
20117 @cindex optional debugging messages
20119 @value{GDBN} has commands that enable optional debugging messages from
20120 various @value{GDBN} subsystems; normally these commands are of
20121 interest to @value{GDBN} maintainers, or when reporting a bug. This
20122 section documents those commands.
20125 @kindex set exec-done-display
20126 @item set exec-done-display
20127 Turns on or off the notification of asynchronous commands'
20128 completion. When on, @value{GDBN} will print a message when an
20129 asynchronous command finishes its execution. The default is off.
20130 @kindex show exec-done-display
20131 @item show exec-done-display
20132 Displays the current setting of asynchronous command completion
20135 @cindex gdbarch debugging info
20136 @cindex architecture debugging info
20137 @item set debug arch
20138 Turns on or off display of gdbarch debugging info. The default is off
20140 @item show debug arch
20141 Displays the current state of displaying gdbarch debugging info.
20142 @item set debug aix-thread
20143 @cindex AIX threads
20144 Display debugging messages about inner workings of the AIX thread
20146 @item show debug aix-thread
20147 Show the current state of AIX thread debugging info display.
20148 @item set debug check-physname
20150 Check the results of the ``physname'' computation. When reading DWARF
20151 debugging information for C@t{++}, @value{GDBN} attempts to compute
20152 each entity's name. @value{GDBN} can do this computation in two
20153 different ways, depending on exactly what information is present.
20154 When enabled, this setting causes @value{GDBN} to compute the names
20155 both ways and display any discrepancies.
20156 @item show debug check-physname
20157 Show the current state of ``physname'' checking.
20158 @item set debug dwarf2-die
20159 @cindex DWARF2 DIEs
20160 Dump DWARF2 DIEs after they are read in.
20161 The value is the number of nesting levels to print.
20162 A value of zero turns off the display.
20163 @item show debug dwarf2-die
20164 Show the current state of DWARF2 DIE debugging.
20165 @item set debug displaced
20166 @cindex displaced stepping debugging info
20167 Turns on or off display of @value{GDBN} debugging info for the
20168 displaced stepping support. The default is off.
20169 @item show debug displaced
20170 Displays the current state of displaying @value{GDBN} debugging info
20171 related to displaced stepping.
20172 @item set debug event
20173 @cindex event debugging info
20174 Turns on or off display of @value{GDBN} event debugging info. The
20176 @item show debug event
20177 Displays the current state of displaying @value{GDBN} event debugging
20179 @item set debug expression
20180 @cindex expression debugging info
20181 Turns on or off display of debugging info about @value{GDBN}
20182 expression parsing. The default is off.
20183 @item show debug expression
20184 Displays the current state of displaying debugging info about
20185 @value{GDBN} expression parsing.
20186 @item set debug frame
20187 @cindex frame debugging info
20188 Turns on or off display of @value{GDBN} frame debugging info. The
20190 @item show debug frame
20191 Displays the current state of displaying @value{GDBN} frame debugging
20193 @item set debug gnu-nat
20194 @cindex @sc{gnu}/Hurd debug messages
20195 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20196 @item show debug gnu-nat
20197 Show the current state of @sc{gnu}/Hurd debugging messages.
20198 @item set debug infrun
20199 @cindex inferior debugging info
20200 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20201 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20202 for implementing operations such as single-stepping the inferior.
20203 @item show debug infrun
20204 Displays the current state of @value{GDBN} inferior debugging.
20205 @item set debug jit
20206 @cindex just-in-time compilation, debugging messages
20207 Turns on or off debugging messages from JIT debug support.
20208 @item show debug jit
20209 Displays the current state of @value{GDBN} JIT debugging.
20210 @item set debug lin-lwp
20211 @cindex @sc{gnu}/Linux LWP debug messages
20212 @cindex Linux lightweight processes
20213 Turns on or off debugging messages from the Linux LWP debug support.
20214 @item show debug lin-lwp
20215 Show the current state of Linux LWP debugging messages.
20216 @item set debug observer
20217 @cindex observer debugging info
20218 Turns on or off display of @value{GDBN} observer debugging. This
20219 includes info such as the notification of observable events.
20220 @item show debug observer
20221 Displays the current state of observer debugging.
20222 @item set debug overload
20223 @cindex C@t{++} overload debugging info
20224 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20225 info. This includes info such as ranking of functions, etc. The default
20227 @item show debug overload
20228 Displays the current state of displaying @value{GDBN} C@t{++} overload
20230 @cindex expression parser, debugging info
20231 @cindex debug expression parser
20232 @item set debug parser
20233 Turns on or off the display of expression parser debugging output.
20234 Internally, this sets the @code{yydebug} variable in the expression
20235 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20236 details. The default is off.
20237 @item show debug parser
20238 Show the current state of expression parser debugging.
20239 @cindex packets, reporting on stdout
20240 @cindex serial connections, debugging
20241 @cindex debug remote protocol
20242 @cindex remote protocol debugging
20243 @cindex display remote packets
20244 @item set debug remote
20245 Turns on or off display of reports on all packets sent back and forth across
20246 the serial line to the remote machine. The info is printed on the
20247 @value{GDBN} standard output stream. The default is off.
20248 @item show debug remote
20249 Displays the state of display of remote packets.
20250 @item set debug serial
20251 Turns on or off display of @value{GDBN} serial debugging info. The
20253 @item show debug serial
20254 Displays the current state of displaying @value{GDBN} serial debugging
20256 @item set debug solib-frv
20257 @cindex FR-V shared-library debugging
20258 Turns on or off debugging messages for FR-V shared-library code.
20259 @item show debug solib-frv
20260 Display the current state of FR-V shared-library code debugging
20262 @item set debug target
20263 @cindex target debugging info
20264 Turns on or off display of @value{GDBN} target debugging info. This info
20265 includes what is going on at the target level of GDB, as it happens. The
20266 default is 0. Set it to 1 to track events, and to 2 to also track the
20267 value of large memory transfers. Changes to this flag do not take effect
20268 until the next time you connect to a target or use the @code{run} command.
20269 @item show debug target
20270 Displays the current state of displaying @value{GDBN} target debugging
20272 @item set debug timestamp
20273 @cindex timestampping debugging info
20274 Turns on or off display of timestamps with @value{GDBN} debugging info.
20275 When enabled, seconds and microseconds are displayed before each debugging
20277 @item show debug timestamp
20278 Displays the current state of displaying timestamps with @value{GDBN}
20280 @item set debugvarobj
20281 @cindex variable object debugging info
20282 Turns on or off display of @value{GDBN} variable object debugging
20283 info. The default is off.
20284 @item show debugvarobj
20285 Displays the current state of displaying @value{GDBN} variable object
20287 @item set debug xml
20288 @cindex XML parser debugging
20289 Turns on or off debugging messages for built-in XML parsers.
20290 @item show debug xml
20291 Displays the current state of XML debugging messages.
20294 @node Other Misc Settings
20295 @section Other Miscellaneous Settings
20296 @cindex miscellaneous settings
20299 @kindex set interactive-mode
20300 @item set interactive-mode
20301 If @code{on}, forces @value{GDBN} to assume that GDB was started
20302 in a terminal. In practice, this means that @value{GDBN} should wait
20303 for the user to answer queries generated by commands entered at
20304 the command prompt. If @code{off}, forces @value{GDBN} to operate
20305 in the opposite mode, and it uses the default answers to all queries.
20306 If @code{auto} (the default), @value{GDBN} tries to determine whether
20307 its standard input is a terminal, and works in interactive-mode if it
20308 is, non-interactively otherwise.
20310 In the vast majority of cases, the debugger should be able to guess
20311 correctly which mode should be used. But this setting can be useful
20312 in certain specific cases, such as running a MinGW @value{GDBN}
20313 inside a cygwin window.
20315 @kindex show interactive-mode
20316 @item show interactive-mode
20317 Displays whether the debugger is operating in interactive mode or not.
20320 @node Extending GDB
20321 @chapter Extending @value{GDBN}
20322 @cindex extending GDB
20324 @value{GDBN} provides two mechanisms for extension. The first is based
20325 on composition of @value{GDBN} commands, and the second is based on the
20326 Python scripting language.
20328 To facilitate the use of these extensions, @value{GDBN} is capable
20329 of evaluating the contents of a file. When doing so, @value{GDBN}
20330 can recognize which scripting language is being used by looking at
20331 the filename extension. Files with an unrecognized filename extension
20332 are always treated as a @value{GDBN} Command Files.
20333 @xref{Command Files,, Command files}.
20335 You can control how @value{GDBN} evaluates these files with the following
20339 @kindex set script-extension
20340 @kindex show script-extension
20341 @item set script-extension off
20342 All scripts are always evaluated as @value{GDBN} Command Files.
20344 @item set script-extension soft
20345 The debugger determines the scripting language based on filename
20346 extension. If this scripting language is supported, @value{GDBN}
20347 evaluates the script using that language. Otherwise, it evaluates
20348 the file as a @value{GDBN} Command File.
20350 @item set script-extension strict
20351 The debugger determines the scripting language based on filename
20352 extension, and evaluates the script using that language. If the
20353 language is not supported, then the evaluation fails.
20355 @item show script-extension
20356 Display the current value of the @code{script-extension} option.
20361 * Sequences:: Canned Sequences of Commands
20362 * Python:: Scripting @value{GDBN} using Python
20366 @section Canned Sequences of Commands
20368 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20369 Command Lists}), @value{GDBN} provides two ways to store sequences of
20370 commands for execution as a unit: user-defined commands and command
20374 * Define:: How to define your own commands
20375 * Hooks:: Hooks for user-defined commands
20376 * Command Files:: How to write scripts of commands to be stored in a file
20377 * Output:: Commands for controlled output
20381 @subsection User-defined Commands
20383 @cindex user-defined command
20384 @cindex arguments, to user-defined commands
20385 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20386 which you assign a new name as a command. This is done with the
20387 @code{define} command. User commands may accept up to 10 arguments
20388 separated by whitespace. Arguments are accessed within the user command
20389 via @code{$arg0@dots{}$arg9}. A trivial example:
20393 print $arg0 + $arg1 + $arg2
20398 To execute the command use:
20405 This defines the command @code{adder}, which prints the sum of
20406 its three arguments. Note the arguments are text substitutions, so they may
20407 reference variables, use complex expressions, or even perform inferior
20410 @cindex argument count in user-defined commands
20411 @cindex how many arguments (user-defined commands)
20412 In addition, @code{$argc} may be used to find out how many arguments have
20413 been passed. This expands to a number in the range 0@dots{}10.
20418 print $arg0 + $arg1
20421 print $arg0 + $arg1 + $arg2
20429 @item define @var{commandname}
20430 Define a command named @var{commandname}. If there is already a command
20431 by that name, you are asked to confirm that you want to redefine it.
20432 @var{commandname} may be a bare command name consisting of letters,
20433 numbers, dashes, and underscores. It may also start with any predefined
20434 prefix command. For example, @samp{define target my-target} creates
20435 a user-defined @samp{target my-target} command.
20437 The definition of the command is made up of other @value{GDBN} command lines,
20438 which are given following the @code{define} command. The end of these
20439 commands is marked by a line containing @code{end}.
20442 @kindex end@r{ (user-defined commands)}
20443 @item document @var{commandname}
20444 Document the user-defined command @var{commandname}, so that it can be
20445 accessed by @code{help}. The command @var{commandname} must already be
20446 defined. This command reads lines of documentation just as @code{define}
20447 reads the lines of the command definition, ending with @code{end}.
20448 After the @code{document} command is finished, @code{help} on command
20449 @var{commandname} displays the documentation you have written.
20451 You may use the @code{document} command again to change the
20452 documentation of a command. Redefining the command with @code{define}
20453 does not change the documentation.
20455 @kindex dont-repeat
20456 @cindex don't repeat command
20458 Used inside a user-defined command, this tells @value{GDBN} that this
20459 command should not be repeated when the user hits @key{RET}
20460 (@pxref{Command Syntax, repeat last command}).
20462 @kindex help user-defined
20463 @item help user-defined
20464 List all user-defined commands, with the first line of the documentation
20469 @itemx show user @var{commandname}
20470 Display the @value{GDBN} commands used to define @var{commandname} (but
20471 not its documentation). If no @var{commandname} is given, display the
20472 definitions for all user-defined commands.
20474 @cindex infinite recursion in user-defined commands
20475 @kindex show max-user-call-depth
20476 @kindex set max-user-call-depth
20477 @item show max-user-call-depth
20478 @itemx set max-user-call-depth
20479 The value of @code{max-user-call-depth} controls how many recursion
20480 levels are allowed in user-defined commands before @value{GDBN} suspects an
20481 infinite recursion and aborts the command.
20484 In addition to the above commands, user-defined commands frequently
20485 use control flow commands, described in @ref{Command Files}.
20487 When user-defined commands are executed, the
20488 commands of the definition are not printed. An error in any command
20489 stops execution of the user-defined command.
20491 If used interactively, commands that would ask for confirmation proceed
20492 without asking when used inside a user-defined command. Many @value{GDBN}
20493 commands that normally print messages to say what they are doing omit the
20494 messages when used in a user-defined command.
20497 @subsection User-defined Command Hooks
20498 @cindex command hooks
20499 @cindex hooks, for commands
20500 @cindex hooks, pre-command
20503 You may define @dfn{hooks}, which are a special kind of user-defined
20504 command. Whenever you run the command @samp{foo}, if the user-defined
20505 command @samp{hook-foo} exists, it is executed (with no arguments)
20506 before that command.
20508 @cindex hooks, post-command
20510 A hook may also be defined which is run after the command you executed.
20511 Whenever you run the command @samp{foo}, if the user-defined command
20512 @samp{hookpost-foo} exists, it is executed (with no arguments) after
20513 that command. Post-execution hooks may exist simultaneously with
20514 pre-execution hooks, for the same command.
20516 It is valid for a hook to call the command which it hooks. If this
20517 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
20519 @c It would be nice if hookpost could be passed a parameter indicating
20520 @c if the command it hooks executed properly or not. FIXME!
20522 @kindex stop@r{, a pseudo-command}
20523 In addition, a pseudo-command, @samp{stop} exists. Defining
20524 (@samp{hook-stop}) makes the associated commands execute every time
20525 execution stops in your program: before breakpoint commands are run,
20526 displays are printed, or the stack frame is printed.
20528 For example, to ignore @code{SIGALRM} signals while
20529 single-stepping, but treat them normally during normal execution,
20534 handle SIGALRM nopass
20538 handle SIGALRM pass
20541 define hook-continue
20542 handle SIGALRM pass
20546 As a further example, to hook at the beginning and end of the @code{echo}
20547 command, and to add extra text to the beginning and end of the message,
20555 define hookpost-echo
20559 (@value{GDBP}) echo Hello World
20560 <<<---Hello World--->>>
20565 You can define a hook for any single-word command in @value{GDBN}, but
20566 not for command aliases; you should define a hook for the basic command
20567 name, e.g.@: @code{backtrace} rather than @code{bt}.
20568 @c FIXME! So how does Joe User discover whether a command is an alias
20570 You can hook a multi-word command by adding @code{hook-} or
20571 @code{hookpost-} to the last word of the command, e.g.@:
20572 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20574 If an error occurs during the execution of your hook, execution of
20575 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20576 (before the command that you actually typed had a chance to run).
20578 If you try to define a hook which does not match any known command, you
20579 get a warning from the @code{define} command.
20581 @node Command Files
20582 @subsection Command Files
20584 @cindex command files
20585 @cindex scripting commands
20586 A command file for @value{GDBN} is a text file made of lines that are
20587 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
20588 also be included. An empty line in a command file does nothing; it
20589 does not mean to repeat the last command, as it would from the
20592 You can request the execution of a command file with the @code{source}
20593 command. Note that the @code{source} command is also used to evaluate
20594 scripts that are not Command Files. The exact behavior can be configured
20595 using the @code{script-extension} setting.
20596 @xref{Extending GDB,, Extending GDB}.
20600 @cindex execute commands from a file
20601 @item source [-s] [-v] @var{filename}
20602 Execute the command file @var{filename}.
20605 The lines in a command file are generally executed sequentially,
20606 unless the order of execution is changed by one of the
20607 @emph{flow-control commands} described below. The commands are not
20608 printed as they are executed. An error in any command terminates
20609 execution of the command file and control is returned to the console.
20611 @value{GDBN} first searches for @var{filename} in the current directory.
20612 If the file is not found there, and @var{filename} does not specify a
20613 directory, then @value{GDBN} also looks for the file on the source search path
20614 (specified with the @samp{directory} command);
20615 except that @file{$cdir} is not searched because the compilation directory
20616 is not relevant to scripts.
20618 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
20619 on the search path even if @var{filename} specifies a directory.
20620 The search is done by appending @var{filename} to each element of the
20621 search path. So, for example, if @var{filename} is @file{mylib/myscript}
20622 and the search path contains @file{/home/user} then @value{GDBN} will
20623 look for the script @file{/home/user/mylib/myscript}.
20624 The search is also done if @var{filename} is an absolute path.
20625 For example, if @var{filename} is @file{/tmp/myscript} and
20626 the search path contains @file{/home/user} then @value{GDBN} will
20627 look for the script @file{/home/user/tmp/myscript}.
20628 For DOS-like systems, if @var{filename} contains a drive specification,
20629 it is stripped before concatenation. For example, if @var{filename} is
20630 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
20631 will look for the script @file{c:/tmp/myscript}.
20633 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
20634 each command as it is executed. The option must be given before
20635 @var{filename}, and is interpreted as part of the filename anywhere else.
20637 Commands that would ask for confirmation if used interactively proceed
20638 without asking when used in a command file. Many @value{GDBN} commands that
20639 normally print messages to say what they are doing omit the messages
20640 when called from command files.
20642 @value{GDBN} also accepts command input from standard input. In this
20643 mode, normal output goes to standard output and error output goes to
20644 standard error. Errors in a command file supplied on standard input do
20645 not terminate execution of the command file---execution continues with
20649 gdb < cmds > log 2>&1
20652 (The syntax above will vary depending on the shell used.) This example
20653 will execute commands from the file @file{cmds}. All output and errors
20654 would be directed to @file{log}.
20656 Since commands stored on command files tend to be more general than
20657 commands typed interactively, they frequently need to deal with
20658 complicated situations, such as different or unexpected values of
20659 variables and symbols, changes in how the program being debugged is
20660 built, etc. @value{GDBN} provides a set of flow-control commands to
20661 deal with these complexities. Using these commands, you can write
20662 complex scripts that loop over data structures, execute commands
20663 conditionally, etc.
20670 This command allows to include in your script conditionally executed
20671 commands. The @code{if} command takes a single argument, which is an
20672 expression to evaluate. It is followed by a series of commands that
20673 are executed only if the expression is true (its value is nonzero).
20674 There can then optionally be an @code{else} line, followed by a series
20675 of commands that are only executed if the expression was false. The
20676 end of the list is marked by a line containing @code{end}.
20680 This command allows to write loops. Its syntax is similar to
20681 @code{if}: the command takes a single argument, which is an expression
20682 to evaluate, and must be followed by the commands to execute, one per
20683 line, terminated by an @code{end}. These commands are called the
20684 @dfn{body} of the loop. The commands in the body of @code{while} are
20685 executed repeatedly as long as the expression evaluates to true.
20689 This command exits the @code{while} loop in whose body it is included.
20690 Execution of the script continues after that @code{while}s @code{end}
20693 @kindex loop_continue
20694 @item loop_continue
20695 This command skips the execution of the rest of the body of commands
20696 in the @code{while} loop in whose body it is included. Execution
20697 branches to the beginning of the @code{while} loop, where it evaluates
20698 the controlling expression.
20700 @kindex end@r{ (if/else/while commands)}
20702 Terminate the block of commands that are the body of @code{if},
20703 @code{else}, or @code{while} flow-control commands.
20708 @subsection Commands for Controlled Output
20710 During the execution of a command file or a user-defined command, normal
20711 @value{GDBN} output is suppressed; the only output that appears is what is
20712 explicitly printed by the commands in the definition. This section
20713 describes three commands useful for generating exactly the output you
20718 @item echo @var{text}
20719 @c I do not consider backslash-space a standard C escape sequence
20720 @c because it is not in ANSI.
20721 Print @var{text}. Nonprinting characters can be included in
20722 @var{text} using C escape sequences, such as @samp{\n} to print a
20723 newline. @strong{No newline is printed unless you specify one.}
20724 In addition to the standard C escape sequences, a backslash followed
20725 by a space stands for a space. This is useful for displaying a
20726 string with spaces at the beginning or the end, since leading and
20727 trailing spaces are otherwise trimmed from all arguments.
20728 To print @samp{@w{ }and foo =@w{ }}, use the command
20729 @samp{echo \@w{ }and foo = \@w{ }}.
20731 A backslash at the end of @var{text} can be used, as in C, to continue
20732 the command onto subsequent lines. For example,
20735 echo This is some text\n\
20736 which is continued\n\
20737 onto several lines.\n
20740 produces the same output as
20743 echo This is some text\n
20744 echo which is continued\n
20745 echo onto several lines.\n
20749 @item output @var{expression}
20750 Print the value of @var{expression} and nothing but that value: no
20751 newlines, no @samp{$@var{nn} = }. The value is not entered in the
20752 value history either. @xref{Expressions, ,Expressions}, for more information
20755 @item output/@var{fmt} @var{expression}
20756 Print the value of @var{expression} in format @var{fmt}. You can use
20757 the same formats as for @code{print}. @xref{Output Formats,,Output
20758 Formats}, for more information.
20761 @item printf @var{template}, @var{expressions}@dots{}
20762 Print the values of one or more @var{expressions} under the control of
20763 the string @var{template}. To print several values, make
20764 @var{expressions} be a comma-separated list of individual expressions,
20765 which may be either numbers or pointers. Their values are printed as
20766 specified by @var{template}, exactly as a C program would do by
20767 executing the code below:
20770 printf (@var{template}, @var{expressions}@dots{});
20773 As in @code{C} @code{printf}, ordinary characters in @var{template}
20774 are printed verbatim, while @dfn{conversion specification} introduced
20775 by the @samp{%} character cause subsequent @var{expressions} to be
20776 evaluated, their values converted and formatted according to type and
20777 style information encoded in the conversion specifications, and then
20780 For example, you can print two values in hex like this:
20783 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
20786 @code{printf} supports all the standard @code{C} conversion
20787 specifications, including the flags and modifiers between the @samp{%}
20788 character and the conversion letter, with the following exceptions:
20792 The argument-ordering modifiers, such as @samp{2$}, are not supported.
20795 The modifier @samp{*} is not supported for specifying precision or
20799 The @samp{'} flag (for separation of digits into groups according to
20800 @code{LC_NUMERIC'}) is not supported.
20803 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
20807 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
20810 The conversion letters @samp{a} and @samp{A} are not supported.
20814 Note that the @samp{ll} type modifier is supported only if the
20815 underlying @code{C} implementation used to build @value{GDBN} supports
20816 the @code{long long int} type, and the @samp{L} type modifier is
20817 supported only if @code{long double} type is available.
20819 As in @code{C}, @code{printf} supports simple backslash-escape
20820 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
20821 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
20822 single character. Octal and hexadecimal escape sequences are not
20825 Additionally, @code{printf} supports conversion specifications for DFP
20826 (@dfn{Decimal Floating Point}) types using the following length modifiers
20827 together with a floating point specifier.
20832 @samp{H} for printing @code{Decimal32} types.
20835 @samp{D} for printing @code{Decimal64} types.
20838 @samp{DD} for printing @code{Decimal128} types.
20841 If the underlying @code{C} implementation used to build @value{GDBN} has
20842 support for the three length modifiers for DFP types, other modifiers
20843 such as width and precision will also be available for @value{GDBN} to use.
20845 In case there is no such @code{C} support, no additional modifiers will be
20846 available and the value will be printed in the standard way.
20848 Here's an example of printing DFP types using the above conversion letters:
20850 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
20854 @item eval @var{template}, @var{expressions}@dots{}
20855 Convert the values of one or more @var{expressions} under the control of
20856 the string @var{template} to a command line, and call it.
20861 @section Scripting @value{GDBN} using Python
20862 @cindex python scripting
20863 @cindex scripting with python
20865 You can script @value{GDBN} using the @uref{http://www.python.org/,
20866 Python programming language}. This feature is available only if
20867 @value{GDBN} was configured using @option{--with-python}.
20869 @cindex python directory
20870 Python scripts used by @value{GDBN} should be installed in
20871 @file{@var{data-directory}/python}, where @var{data-directory} is
20872 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
20873 This directory, known as the @dfn{python directory},
20874 is automatically added to the Python Search Path in order to allow
20875 the Python interpreter to locate all scripts installed at this location.
20877 Additionally, @value{GDBN} commands and convenience functions which
20878 are written in Python and are located in the
20879 @file{@var{data-directory}/python/gdb/command} or
20880 @file{@var{data-directory}/python/gdb/function} directories are
20881 automatically imported when @value{GDBN} starts.
20884 * Python Commands:: Accessing Python from @value{GDBN}.
20885 * Python API:: Accessing @value{GDBN} from Python.
20886 * Auto-loading:: Automatically loading Python code.
20887 * Python modules:: Python modules provided by @value{GDBN}.
20890 @node Python Commands
20891 @subsection Python Commands
20892 @cindex python commands
20893 @cindex commands to access python
20895 @value{GDBN} provides one command for accessing the Python interpreter,
20896 and one related setting:
20900 @item python @r{[}@var{code}@r{]}
20901 The @code{python} command can be used to evaluate Python code.
20903 If given an argument, the @code{python} command will evaluate the
20904 argument as a Python command. For example:
20907 (@value{GDBP}) python print 23
20911 If you do not provide an argument to @code{python}, it will act as a
20912 multi-line command, like @code{define}. In this case, the Python
20913 script is made up of subsequent command lines, given after the
20914 @code{python} command. This command list is terminated using a line
20915 containing @code{end}. For example:
20918 (@value{GDBP}) python
20920 End with a line saying just "end".
20926 @kindex maint set python print-stack
20927 @item maint set python print-stack
20928 This command is now deprecated. Instead use @code{set python
20931 @kindex set python print-stack
20932 @item set python print-stack
20933 By default, @value{GDBN} will not print a stack trace when an error
20934 occurs in a Python script. This can be controlled using @code{set
20935 python print-stack}: if @code{on}, then Python stack printing is
20936 enabled; if @code{off}, the default, then Python stack printing is
20940 It is also possible to execute a Python script from the @value{GDBN}
20944 @item source @file{script-name}
20945 The script name must end with @samp{.py} and @value{GDBN} must be configured
20946 to recognize the script language based on filename extension using
20947 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
20949 @item python execfile ("script-name")
20950 This method is based on the @code{execfile} Python built-in function,
20951 and thus is always available.
20955 @subsection Python API
20957 @cindex programming in python
20959 @cindex python stdout
20960 @cindex python pagination
20961 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
20962 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
20963 A Python program which outputs to one of these streams may have its
20964 output interrupted by the user (@pxref{Screen Size}). In this
20965 situation, a Python @code{KeyboardInterrupt} exception is thrown.
20968 * Basic Python:: Basic Python Functions.
20969 * Exception Handling:: How Python exceptions are translated.
20970 * Values From Inferior:: Python representation of values.
20971 * Types In Python:: Python representation of types.
20972 * Pretty Printing API:: Pretty-printing values.
20973 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
20974 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
20975 * Inferiors In Python:: Python representation of inferiors (processes)
20976 * Events In Python:: Listening for events from @value{GDBN}.
20977 * Threads In Python:: Accessing inferior threads from Python.
20978 * Commands In Python:: Implementing new commands in Python.
20979 * Parameters In Python:: Adding new @value{GDBN} parameters.
20980 * Functions In Python:: Writing new convenience functions.
20981 * Progspaces In Python:: Program spaces.
20982 * Objfiles In Python:: Object files.
20983 * Frames In Python:: Accessing inferior stack frames from Python.
20984 * Blocks In Python:: Accessing frame blocks from Python.
20985 * Symbols In Python:: Python representation of symbols.
20986 * Symbol Tables In Python:: Python representation of symbol tables.
20987 * Lazy Strings In Python:: Python representation of lazy strings.
20988 * Breakpoints In Python:: Manipulating breakpoints using Python.
20992 @subsubsection Basic Python
20994 @cindex python functions
20995 @cindex python module
20997 @value{GDBN} introduces a new Python module, named @code{gdb}. All
20998 methods and classes added by @value{GDBN} are placed in this module.
20999 @value{GDBN} automatically @code{import}s the @code{gdb} module for
21000 use in all scripts evaluated by the @code{python} command.
21002 @findex gdb.PYTHONDIR
21003 @defvar gdb.PYTHONDIR
21004 A string containing the python directory (@pxref{Python}).
21007 @findex gdb.execute
21008 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
21009 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
21010 If a GDB exception happens while @var{command} runs, it is
21011 translated as described in @ref{Exception Handling,,Exception Handling}.
21013 @var{from_tty} specifies whether @value{GDBN} ought to consider this
21014 command as having originated from the user invoking it interactively.
21015 It must be a boolean value. If omitted, it defaults to @code{False}.
21017 By default, any output produced by @var{command} is sent to
21018 @value{GDBN}'s standard output. If the @var{to_string} parameter is
21019 @code{True}, then output will be collected by @code{gdb.execute} and
21020 returned as a string. The default is @code{False}, in which case the
21021 return value is @code{None}. If @var{to_string} is @code{True}, the
21022 @value{GDBN} virtual terminal will be temporarily set to unlimited width
21023 and height, and its pagination will be disabled; @pxref{Screen Size}.
21026 @findex gdb.breakpoints
21027 @defun gdb.breakpoints ()
21028 Return a sequence holding all of @value{GDBN}'s breakpoints.
21029 @xref{Breakpoints In Python}, for more information.
21032 @findex gdb.parameter
21033 @defun gdb.parameter (parameter)
21034 Return the value of a @value{GDBN} parameter. @var{parameter} is a
21035 string naming the parameter to look up; @var{parameter} may contain
21036 spaces if the parameter has a multi-part name. For example,
21037 @samp{print object} is a valid parameter name.
21039 If the named parameter does not exist, this function throws a
21040 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
21041 parameter's value is converted to a Python value of the appropriate
21042 type, and returned.
21045 @findex gdb.history
21046 @defun gdb.history (number)
21047 Return a value from @value{GDBN}'s value history (@pxref{Value
21048 History}). @var{number} indicates which history element to return.
21049 If @var{number} is negative, then @value{GDBN} will take its absolute value
21050 and count backward from the last element (i.e., the most recent element) to
21051 find the value to return. If @var{number} is zero, then @value{GDBN} will
21052 return the most recent element. If the element specified by @var{number}
21053 doesn't exist in the value history, a @code{gdb.error} exception will be
21056 If no exception is raised, the return value is always an instance of
21057 @code{gdb.Value} (@pxref{Values From Inferior}).
21060 @findex gdb.parse_and_eval
21061 @defun gdb.parse_and_eval (expression)
21062 Parse @var{expression} as an expression in the current language,
21063 evaluate it, and return the result as a @code{gdb.Value}.
21064 @var{expression} must be a string.
21066 This function can be useful when implementing a new command
21067 (@pxref{Commands In Python}), as it provides a way to parse the
21068 command's argument as an expression. It is also useful simply to
21069 compute values, for example, it is the only way to get the value of a
21070 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
21073 @findex gdb.post_event
21074 @defun gdb.post_event (event)
21075 Put @var{event}, a callable object taking no arguments, into
21076 @value{GDBN}'s internal event queue. This callable will be invoked at
21077 some later point, during @value{GDBN}'s event processing. Events
21078 posted using @code{post_event} will be run in the order in which they
21079 were posted; however, there is no way to know when they will be
21080 processed relative to other events inside @value{GDBN}.
21082 @value{GDBN} is not thread-safe. If your Python program uses multiple
21083 threads, you must be careful to only call @value{GDBN}-specific
21084 functions in the main @value{GDBN} thread. @code{post_event} ensures
21088 (@value{GDBP}) python
21092 > def __init__(self, message):
21093 > self.message = message;
21094 > def __call__(self):
21095 > gdb.write(self.message)
21097 >class MyThread1 (threading.Thread):
21099 > gdb.post_event(Writer("Hello "))
21101 >class MyThread2 (threading.Thread):
21103 > gdb.post_event(Writer("World\n"))
21105 >MyThread1().start()
21106 >MyThread2().start()
21108 (@value{GDBP}) Hello World
21113 @defun gdb.write (string @r{[}, stream{]})
21114 Print a string to @value{GDBN}'s paginated output stream. The
21115 optional @var{stream} determines the stream to print to. The default
21116 stream is @value{GDBN}'s standard output stream. Possible stream
21123 @value{GDBN}'s standard output stream.
21128 @value{GDBN}'s standard error stream.
21133 @value{GDBN}'s log stream (@pxref{Logging Output}).
21136 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
21137 call this function and will automatically direct the output to the
21142 @defun gdb.flush ()
21143 Flush the buffer of a @value{GDBN} paginated stream so that the
21144 contents are displayed immediately. @value{GDBN} will flush the
21145 contents of a stream automatically when it encounters a newline in the
21146 buffer. The optional @var{stream} determines the stream to flush. The
21147 default stream is @value{GDBN}'s standard output stream. Possible
21154 @value{GDBN}'s standard output stream.
21159 @value{GDBN}'s standard error stream.
21164 @value{GDBN}'s log stream (@pxref{Logging Output}).
21168 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21169 call this function for the relevant stream.
21172 @findex gdb.target_charset
21173 @defun gdb.target_charset ()
21174 Return the name of the current target character set (@pxref{Character
21175 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21176 that @samp{auto} is never returned.
21179 @findex gdb.target_wide_charset
21180 @defun gdb.target_wide_charset ()
21181 Return the name of the current target wide character set
21182 (@pxref{Character Sets}). This differs from
21183 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21187 @findex gdb.solib_name
21188 @defun gdb.solib_name (address)
21189 Return the name of the shared library holding the given @var{address}
21190 as a string, or @code{None}.
21193 @findex gdb.decode_line
21194 @defun gdb.decode_line @r{[}expression@r{]}
21195 Return locations of the line specified by @var{expression}, or of the
21196 current line if no argument was given. This function returns a Python
21197 tuple containing two elements. The first element contains a string
21198 holding any unparsed section of @var{expression} (or @code{None} if
21199 the expression has been fully parsed). The second element contains
21200 either @code{None} or another tuple that contains all the locations
21201 that match the expression represented as @code{gdb.Symtab_and_line}
21202 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21203 provided, it is decoded the way that @value{GDBN}'s inbuilt
21204 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21207 @defun gdb.prompt_hook (current_prompt)
21208 @anchor{prompt_hook}
21210 If @var{prompt_hook} is callable, @value{GDBN} will call the method
21211 assigned to this operation before a prompt is displayed by
21214 The parameter @code{current_prompt} contains the current @value{GDBN}
21215 prompt. This method must return a Python string, or @code{None}. If
21216 a string is returned, the @value{GDBN} prompt will be set to that
21217 string. If @code{None} is returned, @value{GDBN} will continue to use
21218 the current prompt.
21220 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
21221 such as those used by readline for command input, and annotation
21222 related prompts are prohibited from being changed.
21225 @node Exception Handling
21226 @subsubsection Exception Handling
21227 @cindex python exceptions
21228 @cindex exceptions, python
21230 When executing the @code{python} command, Python exceptions
21231 uncaught within the Python code are translated to calls to
21232 @value{GDBN} error-reporting mechanism. If the command that called
21233 @code{python} does not handle the error, @value{GDBN} will
21234 terminate it and print an error message containing the Python
21235 exception name, the associated value, and the Python call stack
21236 backtrace at the point where the exception was raised. Example:
21239 (@value{GDBP}) python print foo
21240 Traceback (most recent call last):
21241 File "<string>", line 1, in <module>
21242 NameError: name 'foo' is not defined
21245 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21246 Python code are converted to Python exceptions. The type of the
21247 Python exception depends on the error.
21251 This is the base class for most exceptions generated by @value{GDBN}.
21252 It is derived from @code{RuntimeError}, for compatibility with earlier
21253 versions of @value{GDBN}.
21255 If an error occurring in @value{GDBN} does not fit into some more
21256 specific category, then the generated exception will have this type.
21258 @item gdb.MemoryError
21259 This is a subclass of @code{gdb.error} which is thrown when an
21260 operation tried to access invalid memory in the inferior.
21262 @item KeyboardInterrupt
21263 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21264 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21267 In all cases, your exception handler will see the @value{GDBN} error
21268 message as its value and the Python call stack backtrace at the Python
21269 statement closest to where the @value{GDBN} error occured as the
21272 @findex gdb.GdbError
21273 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21274 it is useful to be able to throw an exception that doesn't cause a
21275 traceback to be printed. For example, the user may have invoked the
21276 command incorrectly. Use the @code{gdb.GdbError} exception
21277 to handle this case. Example:
21281 >class HelloWorld (gdb.Command):
21282 > """Greet the whole world."""
21283 > def __init__ (self):
21284 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21285 > def invoke (self, args, from_tty):
21286 > argv = gdb.string_to_argv (args)
21287 > if len (argv) != 0:
21288 > raise gdb.GdbError ("hello-world takes no arguments")
21289 > print "Hello, World!"
21292 (gdb) hello-world 42
21293 hello-world takes no arguments
21296 @node Values From Inferior
21297 @subsubsection Values From Inferior
21298 @cindex values from inferior, with Python
21299 @cindex python, working with values from inferior
21301 @cindex @code{gdb.Value}
21302 @value{GDBN} provides values it obtains from the inferior program in
21303 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21304 for its internal bookkeeping of the inferior's values, and for
21305 fetching values when necessary.
21307 Inferior values that are simple scalars can be used directly in
21308 Python expressions that are valid for the value's data type. Here's
21309 an example for an integer or floating-point value @code{some_val}:
21316 As result of this, @code{bar} will also be a @code{gdb.Value} object
21317 whose values are of the same type as those of @code{some_val}.
21319 Inferior values that are structures or instances of some class can
21320 be accessed using the Python @dfn{dictionary syntax}. For example, if
21321 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21322 can access its @code{foo} element with:
21325 bar = some_val['foo']
21328 Again, @code{bar} will also be a @code{gdb.Value} object.
21330 A @code{gdb.Value} that represents a function can be executed via
21331 inferior function call. Any arguments provided to the call must match
21332 the function's prototype, and must be provided in the order specified
21335 For example, @code{some_val} is a @code{gdb.Value} instance
21336 representing a function that takes two integers as arguments. To
21337 execute this function, call it like so:
21340 result = some_val (10,20)
21343 Any values returned from a function call will be stored as a
21346 The following attributes are provided:
21349 @defvar Value.address
21350 If this object is addressable, this read-only attribute holds a
21351 @code{gdb.Value} object representing the address. Otherwise,
21352 this attribute holds @code{None}.
21355 @cindex optimized out value in Python
21356 @defvar Value.is_optimized_out
21357 This read-only boolean attribute is true if the compiler optimized out
21358 this value, thus it is not available for fetching from the inferior.
21362 The type of this @code{gdb.Value}. The value of this attribute is a
21363 @code{gdb.Type} object (@pxref{Types In Python}).
21366 @defvar Value.dynamic_type
21367 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21368 type information (@acronym{RTTI}) to determine the dynamic type of the
21369 value. If this value is of class type, it will return the class in
21370 which the value is embedded, if any. If this value is of pointer or
21371 reference to a class type, it will compute the dynamic type of the
21372 referenced object, and return a pointer or reference to that type,
21373 respectively. In all other cases, it will return the value's static
21376 Note that this feature will only work when debugging a C@t{++} program
21377 that includes @acronym{RTTI} for the object in question. Otherwise,
21378 it will just return the static type of the value as in @kbd{ptype foo}
21379 (@pxref{Symbols, ptype}).
21383 The following methods are provided:
21386 @defun Value.__init__ (@var{val})
21387 Many Python values can be converted directly to a @code{gdb.Value} via
21388 this object initializer. Specifically:
21391 @item Python boolean
21392 A Python boolean is converted to the boolean type from the current
21395 @item Python integer
21396 A Python integer is converted to the C @code{long} type for the
21397 current architecture.
21400 A Python long is converted to the C @code{long long} type for the
21401 current architecture.
21404 A Python float is converted to the C @code{double} type for the
21405 current architecture.
21407 @item Python string
21408 A Python string is converted to a target string, using the current
21411 @item @code{gdb.Value}
21412 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
21414 @item @code{gdb.LazyString}
21415 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
21416 Python}), then the lazy string's @code{value} method is called, and
21417 its result is used.
21421 @defun Value.cast (type)
21422 Return a new instance of @code{gdb.Value} that is the result of
21423 casting this instance to the type described by @var{type}, which must
21424 be a @code{gdb.Type} object. If the cast cannot be performed for some
21425 reason, this method throws an exception.
21428 @defun Value.dereference ()
21429 For pointer data types, this method returns a new @code{gdb.Value} object
21430 whose contents is the object pointed to by the pointer. For example, if
21431 @code{foo} is a C pointer to an @code{int}, declared in your C program as
21438 then you can use the corresponding @code{gdb.Value} to access what
21439 @code{foo} points to like this:
21442 bar = foo.dereference ()
21445 The result @code{bar} will be a @code{gdb.Value} object holding the
21446 value pointed to by @code{foo}.
21449 @defun Value.dynamic_cast (type)
21450 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
21451 operator were used. Consult a C@t{++} reference for details.
21454 @defun Value.reinterpret_cast (type)
21455 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
21456 operator were used. Consult a C@t{++} reference for details.
21459 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
21460 If this @code{gdb.Value} represents a string, then this method
21461 converts the contents to a Python string. Otherwise, this method will
21462 throw an exception.
21464 Strings are recognized in a language-specific way; whether a given
21465 @code{gdb.Value} represents a string is determined by the current
21468 For C-like languages, a value is a string if it is a pointer to or an
21469 array of characters or ints. The string is assumed to be terminated
21470 by a zero of the appropriate width. However if the optional length
21471 argument is given, the string will be converted to that given length,
21472 ignoring any embedded zeros that the string may contain.
21474 If the optional @var{encoding} argument is given, it must be a string
21475 naming the encoding of the string in the @code{gdb.Value}, such as
21476 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
21477 the same encodings as the corresponding argument to Python's
21478 @code{string.decode} method, and the Python codec machinery will be used
21479 to convert the string. If @var{encoding} is not given, or if
21480 @var{encoding} is the empty string, then either the @code{target-charset}
21481 (@pxref{Character Sets}) will be used, or a language-specific encoding
21482 will be used, if the current language is able to supply one.
21484 The optional @var{errors} argument is the same as the corresponding
21485 argument to Python's @code{string.decode} method.
21487 If the optional @var{length} argument is given, the string will be
21488 fetched and converted to the given length.
21491 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
21492 If this @code{gdb.Value} represents a string, then this method
21493 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
21494 In Python}). Otherwise, this method will throw an exception.
21496 If the optional @var{encoding} argument is given, it must be a string
21497 naming the encoding of the @code{gdb.LazyString}. Some examples are:
21498 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
21499 @var{encoding} argument is an encoding that @value{GDBN} does
21500 recognize, @value{GDBN} will raise an error.
21502 When a lazy string is printed, the @value{GDBN} encoding machinery is
21503 used to convert the string during printing. If the optional
21504 @var{encoding} argument is not provided, or is an empty string,
21505 @value{GDBN} will automatically select the encoding most suitable for
21506 the string type. For further information on encoding in @value{GDBN}
21507 please see @ref{Character Sets}.
21509 If the optional @var{length} argument is given, the string will be
21510 fetched and encoded to the length of characters specified. If
21511 the @var{length} argument is not provided, the string will be fetched
21512 and encoded until a null of appropriate width is found.
21516 @node Types In Python
21517 @subsubsection Types In Python
21518 @cindex types in Python
21519 @cindex Python, working with types
21522 @value{GDBN} represents types from the inferior using the class
21525 The following type-related functions are available in the @code{gdb}
21528 @findex gdb.lookup_type
21529 @defun gdb.lookup_type (name @r{[}, block@r{]})
21530 This function looks up a type by name. @var{name} is the name of the
21531 type to look up. It must be a string.
21533 If @var{block} is given, then @var{name} is looked up in that scope.
21534 Otherwise, it is searched for globally.
21536 Ordinarily, this function will return an instance of @code{gdb.Type}.
21537 If the named type cannot be found, it will throw an exception.
21540 An instance of @code{Type} has the following attributes:
21544 The type code for this type. The type code will be one of the
21545 @code{TYPE_CODE_} constants defined below.
21548 @defvar Type.sizeof
21549 The size of this type, in target @code{char} units. Usually, a
21550 target's @code{char} type will be an 8-bit byte. However, on some
21551 unusual platforms, this type may have a different size.
21555 The tag name for this type. The tag name is the name after
21556 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
21557 languages have this concept. If this type has no tag name, then
21558 @code{None} is returned.
21562 The following methods are provided:
21565 @defun Type.fields ()
21566 For structure and union types, this method returns the fields. Range
21567 types have two fields, the minimum and maximum values. Enum types
21568 have one field per enum constant. Function and method types have one
21569 field per parameter. The base types of C@t{++} classes are also
21570 represented as fields. If the type has no fields, or does not fit
21571 into one of these categories, an empty sequence will be returned.
21573 Each field is an object, with some pre-defined attributes:
21576 This attribute is not available for @code{static} fields (as in
21577 C@t{++} or Java). For non-@code{static} fields, the value is the bit
21578 position of the field. For @code{enum} fields, the value is the
21579 enumeration member's integer representation.
21582 The name of the field, or @code{None} for anonymous fields.
21585 This is @code{True} if the field is artificial, usually meaning that
21586 it was provided by the compiler and not the user. This attribute is
21587 always provided, and is @code{False} if the field is not artificial.
21589 @item is_base_class
21590 This is @code{True} if the field represents a base class of a C@t{++}
21591 structure. This attribute is always provided, and is @code{False}
21592 if the field is not a base class of the type that is the argument of
21593 @code{fields}, or if that type was not a C@t{++} class.
21596 If the field is packed, or is a bitfield, then this will have a
21597 non-zero value, which is the size of the field in bits. Otherwise,
21598 this will be zero; in this case the field's size is given by its type.
21601 The type of the field. This is usually an instance of @code{Type},
21602 but it can be @code{None} in some situations.
21606 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
21607 Return a new @code{gdb.Type} object which represents an array of this
21608 type. If one argument is given, it is the inclusive upper bound of
21609 the array; in this case the lower bound is zero. If two arguments are
21610 given, the first argument is the lower bound of the array, and the
21611 second argument is the upper bound of the array. An array's length
21612 must not be negative, but the bounds can be.
21615 @defun Type.const ()
21616 Return a new @code{gdb.Type} object which represents a
21617 @code{const}-qualified variant of this type.
21620 @defun Type.volatile ()
21621 Return a new @code{gdb.Type} object which represents a
21622 @code{volatile}-qualified variant of this type.
21625 @defun Type.unqualified ()
21626 Return a new @code{gdb.Type} object which represents an unqualified
21627 variant of this type. That is, the result is neither @code{const} nor
21631 @defun Type.range ()
21632 Return a Python @code{Tuple} object that contains two elements: the
21633 low bound of the argument type and the high bound of that type. If
21634 the type does not have a range, @value{GDBN} will raise a
21635 @code{gdb.error} exception (@pxref{Exception Handling}).
21638 @defun Type.reference ()
21639 Return a new @code{gdb.Type} object which represents a reference to this
21643 @defun Type.pointer ()
21644 Return a new @code{gdb.Type} object which represents a pointer to this
21648 @defun Type.strip_typedefs ()
21649 Return a new @code{gdb.Type} that represents the real type,
21650 after removing all layers of typedefs.
21653 @defun Type.target ()
21654 Return a new @code{gdb.Type} object which represents the target type
21657 For a pointer type, the target type is the type of the pointed-to
21658 object. For an array type (meaning C-like arrays), the target type is
21659 the type of the elements of the array. For a function or method type,
21660 the target type is the type of the return value. For a complex type,
21661 the target type is the type of the elements. For a typedef, the
21662 target type is the aliased type.
21664 If the type does not have a target, this method will throw an
21668 @defun Type.template_argument (n @r{[}, block@r{]})
21669 If this @code{gdb.Type} is an instantiation of a template, this will
21670 return a new @code{gdb.Type} which represents the type of the
21671 @var{n}th template argument.
21673 If this @code{gdb.Type} is not a template type, this will throw an
21674 exception. Ordinarily, only C@t{++} code will have template types.
21676 If @var{block} is given, then @var{name} is looked up in that scope.
21677 Otherwise, it is searched for globally.
21682 Each type has a code, which indicates what category this type falls
21683 into. The available type categories are represented by constants
21684 defined in the @code{gdb} module:
21687 @findex TYPE_CODE_PTR
21688 @findex gdb.TYPE_CODE_PTR
21689 @item gdb.TYPE_CODE_PTR
21690 The type is a pointer.
21692 @findex TYPE_CODE_ARRAY
21693 @findex gdb.TYPE_CODE_ARRAY
21694 @item gdb.TYPE_CODE_ARRAY
21695 The type is an array.
21697 @findex TYPE_CODE_STRUCT
21698 @findex gdb.TYPE_CODE_STRUCT
21699 @item gdb.TYPE_CODE_STRUCT
21700 The type is a structure.
21702 @findex TYPE_CODE_UNION
21703 @findex gdb.TYPE_CODE_UNION
21704 @item gdb.TYPE_CODE_UNION
21705 The type is a union.
21707 @findex TYPE_CODE_ENUM
21708 @findex gdb.TYPE_CODE_ENUM
21709 @item gdb.TYPE_CODE_ENUM
21710 The type is an enum.
21712 @findex TYPE_CODE_FLAGS
21713 @findex gdb.TYPE_CODE_FLAGS
21714 @item gdb.TYPE_CODE_FLAGS
21715 A bit flags type, used for things such as status registers.
21717 @findex TYPE_CODE_FUNC
21718 @findex gdb.TYPE_CODE_FUNC
21719 @item gdb.TYPE_CODE_FUNC
21720 The type is a function.
21722 @findex TYPE_CODE_INT
21723 @findex gdb.TYPE_CODE_INT
21724 @item gdb.TYPE_CODE_INT
21725 The type is an integer type.
21727 @findex TYPE_CODE_FLT
21728 @findex gdb.TYPE_CODE_FLT
21729 @item gdb.TYPE_CODE_FLT
21730 A floating point type.
21732 @findex TYPE_CODE_VOID
21733 @findex gdb.TYPE_CODE_VOID
21734 @item gdb.TYPE_CODE_VOID
21735 The special type @code{void}.
21737 @findex TYPE_CODE_SET
21738 @findex gdb.TYPE_CODE_SET
21739 @item gdb.TYPE_CODE_SET
21742 @findex TYPE_CODE_RANGE
21743 @findex gdb.TYPE_CODE_RANGE
21744 @item gdb.TYPE_CODE_RANGE
21745 A range type, that is, an integer type with bounds.
21747 @findex TYPE_CODE_STRING
21748 @findex gdb.TYPE_CODE_STRING
21749 @item gdb.TYPE_CODE_STRING
21750 A string type. Note that this is only used for certain languages with
21751 language-defined string types; C strings are not represented this way.
21753 @findex TYPE_CODE_BITSTRING
21754 @findex gdb.TYPE_CODE_BITSTRING
21755 @item gdb.TYPE_CODE_BITSTRING
21758 @findex TYPE_CODE_ERROR
21759 @findex gdb.TYPE_CODE_ERROR
21760 @item gdb.TYPE_CODE_ERROR
21761 An unknown or erroneous type.
21763 @findex TYPE_CODE_METHOD
21764 @findex gdb.TYPE_CODE_METHOD
21765 @item gdb.TYPE_CODE_METHOD
21766 A method type, as found in C@t{++} or Java.
21768 @findex TYPE_CODE_METHODPTR
21769 @findex gdb.TYPE_CODE_METHODPTR
21770 @item gdb.TYPE_CODE_METHODPTR
21771 A pointer-to-member-function.
21773 @findex TYPE_CODE_MEMBERPTR
21774 @findex gdb.TYPE_CODE_MEMBERPTR
21775 @item gdb.TYPE_CODE_MEMBERPTR
21776 A pointer-to-member.
21778 @findex TYPE_CODE_REF
21779 @findex gdb.TYPE_CODE_REF
21780 @item gdb.TYPE_CODE_REF
21783 @findex TYPE_CODE_CHAR
21784 @findex gdb.TYPE_CODE_CHAR
21785 @item gdb.TYPE_CODE_CHAR
21788 @findex TYPE_CODE_BOOL
21789 @findex gdb.TYPE_CODE_BOOL
21790 @item gdb.TYPE_CODE_BOOL
21793 @findex TYPE_CODE_COMPLEX
21794 @findex gdb.TYPE_CODE_COMPLEX
21795 @item gdb.TYPE_CODE_COMPLEX
21796 A complex float type.
21798 @findex TYPE_CODE_TYPEDEF
21799 @findex gdb.TYPE_CODE_TYPEDEF
21800 @item gdb.TYPE_CODE_TYPEDEF
21801 A typedef to some other type.
21803 @findex TYPE_CODE_NAMESPACE
21804 @findex gdb.TYPE_CODE_NAMESPACE
21805 @item gdb.TYPE_CODE_NAMESPACE
21806 A C@t{++} namespace.
21808 @findex TYPE_CODE_DECFLOAT
21809 @findex gdb.TYPE_CODE_DECFLOAT
21810 @item gdb.TYPE_CODE_DECFLOAT
21811 A decimal floating point type.
21813 @findex TYPE_CODE_INTERNAL_FUNCTION
21814 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
21815 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
21816 A function internal to @value{GDBN}. This is the type used to represent
21817 convenience functions.
21820 Further support for types is provided in the @code{gdb.types}
21821 Python module (@pxref{gdb.types}).
21823 @node Pretty Printing API
21824 @subsubsection Pretty Printing API
21826 An example output is provided (@pxref{Pretty Printing}).
21828 A pretty-printer is just an object that holds a value and implements a
21829 specific interface, defined here.
21831 @defun pretty_printer.children (self)
21832 @value{GDBN} will call this method on a pretty-printer to compute the
21833 children of the pretty-printer's value.
21835 This method must return an object conforming to the Python iterator
21836 protocol. Each item returned by the iterator must be a tuple holding
21837 two elements. The first element is the ``name'' of the child; the
21838 second element is the child's value. The value can be any Python
21839 object which is convertible to a @value{GDBN} value.
21841 This method is optional. If it does not exist, @value{GDBN} will act
21842 as though the value has no children.
21845 @defun pretty_printer.display_hint (self)
21846 The CLI may call this method and use its result to change the
21847 formatting of a value. The result will also be supplied to an MI
21848 consumer as a @samp{displayhint} attribute of the variable being
21851 This method is optional. If it does exist, this method must return a
21854 Some display hints are predefined by @value{GDBN}:
21858 Indicate that the object being printed is ``array-like''. The CLI
21859 uses this to respect parameters such as @code{set print elements} and
21860 @code{set print array}.
21863 Indicate that the object being printed is ``map-like'', and that the
21864 children of this value can be assumed to alternate between keys and
21868 Indicate that the object being printed is ``string-like''. If the
21869 printer's @code{to_string} method returns a Python string of some
21870 kind, then @value{GDBN} will call its internal language-specific
21871 string-printing function to format the string. For the CLI this means
21872 adding quotation marks, possibly escaping some characters, respecting
21873 @code{set print elements}, and the like.
21877 @defun pretty_printer.to_string (self)
21878 @value{GDBN} will call this method to display the string
21879 representation of the value passed to the object's constructor.
21881 When printing from the CLI, if the @code{to_string} method exists,
21882 then @value{GDBN} will prepend its result to the values returned by
21883 @code{children}. Exactly how this formatting is done is dependent on
21884 the display hint, and may change as more hints are added. Also,
21885 depending on the print settings (@pxref{Print Settings}), the CLI may
21886 print just the result of @code{to_string} in a stack trace, omitting
21887 the result of @code{children}.
21889 If this method returns a string, it is printed verbatim.
21891 Otherwise, if this method returns an instance of @code{gdb.Value},
21892 then @value{GDBN} prints this value. This may result in a call to
21893 another pretty-printer.
21895 If instead the method returns a Python value which is convertible to a
21896 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
21897 the resulting value. Again, this may result in a call to another
21898 pretty-printer. Python scalars (integers, floats, and booleans) and
21899 strings are convertible to @code{gdb.Value}; other types are not.
21901 Finally, if this method returns @code{None} then no further operations
21902 are peformed in this method and nothing is printed.
21904 If the result is not one of these types, an exception is raised.
21907 @value{GDBN} provides a function which can be used to look up the
21908 default pretty-printer for a @code{gdb.Value}:
21910 @findex gdb.default_visualizer
21911 @defun gdb.default_visualizer (value)
21912 This function takes a @code{gdb.Value} object as an argument. If a
21913 pretty-printer for this value exists, then it is returned. If no such
21914 printer exists, then this returns @code{None}.
21917 @node Selecting Pretty-Printers
21918 @subsubsection Selecting Pretty-Printers
21920 The Python list @code{gdb.pretty_printers} contains an array of
21921 functions or callable objects that have been registered via addition
21922 as a pretty-printer. Printers in this list are called @code{global}
21923 printers, they're available when debugging all inferiors.
21924 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
21925 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
21928 Each function on these lists is passed a single @code{gdb.Value}
21929 argument and should return a pretty-printer object conforming to the
21930 interface definition above (@pxref{Pretty Printing API}). If a function
21931 cannot create a pretty-printer for the value, it should return
21934 @value{GDBN} first checks the @code{pretty_printers} attribute of each
21935 @code{gdb.Objfile} in the current program space and iteratively calls
21936 each enabled lookup routine in the list for that @code{gdb.Objfile}
21937 until it receives a pretty-printer object.
21938 If no pretty-printer is found in the objfile lists, @value{GDBN} then
21939 searches the pretty-printer list of the current program space,
21940 calling each enabled function until an object is returned.
21941 After these lists have been exhausted, it tries the global
21942 @code{gdb.pretty_printers} list, again calling each enabled function until an
21943 object is returned.
21945 The order in which the objfiles are searched is not specified. For a
21946 given list, functions are always invoked from the head of the list,
21947 and iterated over sequentially until the end of the list, or a printer
21948 object is returned.
21950 For various reasons a pretty-printer may not work.
21951 For example, the underlying data structure may have changed and
21952 the pretty-printer is out of date.
21954 The consequences of a broken pretty-printer are severe enough that
21955 @value{GDBN} provides support for enabling and disabling individual
21956 printers. For example, if @code{print frame-arguments} is on,
21957 a backtrace can become highly illegible if any argument is printed
21958 with a broken printer.
21960 Pretty-printers are enabled and disabled by attaching an @code{enabled}
21961 attribute to the registered function or callable object. If this attribute
21962 is present and its value is @code{False}, the printer is disabled, otherwise
21963 the printer is enabled.
21965 @node Writing a Pretty-Printer
21966 @subsubsection Writing a Pretty-Printer
21967 @cindex writing a pretty-printer
21969 A pretty-printer consists of two parts: a lookup function to detect
21970 if the type is supported, and the printer itself.
21972 Here is an example showing how a @code{std::string} printer might be
21973 written. @xref{Pretty Printing API}, for details on the API this class
21977 class StdStringPrinter(object):
21978 "Print a std::string"
21980 def __init__(self, val):
21983 def to_string(self):
21984 return self.val['_M_dataplus']['_M_p']
21986 def display_hint(self):
21990 And here is an example showing how a lookup function for the printer
21991 example above might be written.
21994 def str_lookup_function(val):
21995 lookup_tag = val.type.tag
21996 if lookup_tag == None:
21998 regex = re.compile("^std::basic_string<char,.*>$")
21999 if regex.match(lookup_tag):
22000 return StdStringPrinter(val)
22004 The example lookup function extracts the value's type, and attempts to
22005 match it to a type that it can pretty-print. If it is a type the
22006 printer can pretty-print, it will return a printer object. If not, it
22007 returns @code{None}.
22009 We recommend that you put your core pretty-printers into a Python
22010 package. If your pretty-printers are for use with a library, we
22011 further recommend embedding a version number into the package name.
22012 This practice will enable @value{GDBN} to load multiple versions of
22013 your pretty-printers at the same time, because they will have
22016 You should write auto-loaded code (@pxref{Auto-loading}) such that it
22017 can be evaluated multiple times without changing its meaning. An
22018 ideal auto-load file will consist solely of @code{import}s of your
22019 printer modules, followed by a call to a register pretty-printers with
22020 the current objfile.
22022 Taken as a whole, this approach will scale nicely to multiple
22023 inferiors, each potentially using a different library version.
22024 Embedding a version number in the Python package name will ensure that
22025 @value{GDBN} is able to load both sets of printers simultaneously.
22026 Then, because the search for pretty-printers is done by objfile, and
22027 because your auto-loaded code took care to register your library's
22028 printers with a specific objfile, @value{GDBN} will find the correct
22029 printers for the specific version of the library used by each
22032 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
22033 this code might appear in @code{gdb.libstdcxx.v6}:
22036 def register_printers(objfile):
22037 objfile.pretty_printers.add(str_lookup_function)
22041 And then the corresponding contents of the auto-load file would be:
22044 import gdb.libstdcxx.v6
22045 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
22048 The previous example illustrates a basic pretty-printer.
22049 There are a few things that can be improved on.
22050 The printer doesn't have a name, making it hard to identify in a
22051 list of installed printers. The lookup function has a name, but
22052 lookup functions can have arbitrary, even identical, names.
22054 Second, the printer only handles one type, whereas a library typically has
22055 several types. One could install a lookup function for each desired type
22056 in the library, but one could also have a single lookup function recognize
22057 several types. The latter is the conventional way this is handled.
22058 If a pretty-printer can handle multiple data types, then its
22059 @dfn{subprinters} are the printers for the individual data types.
22061 The @code{gdb.printing} module provides a formal way of solving these
22062 problems (@pxref{gdb.printing}).
22063 Here is another example that handles multiple types.
22065 These are the types we are going to pretty-print:
22068 struct foo @{ int a, b; @};
22069 struct bar @{ struct foo x, y; @};
22072 Here are the printers:
22076 """Print a foo object."""
22078 def __init__(self, val):
22081 def to_string(self):
22082 return ("a=<" + str(self.val["a"]) +
22083 "> b=<" + str(self.val["b"]) + ">")
22086 """Print a bar object."""
22088 def __init__(self, val):
22091 def to_string(self):
22092 return ("x=<" + str(self.val["x"]) +
22093 "> y=<" + str(self.val["y"]) + ">")
22096 This example doesn't need a lookup function, that is handled by the
22097 @code{gdb.printing} module. Instead a function is provided to build up
22098 the object that handles the lookup.
22101 import gdb.printing
22103 def build_pretty_printer():
22104 pp = gdb.printing.RegexpCollectionPrettyPrinter(
22106 pp.add_printer('foo', '^foo$', fooPrinter)
22107 pp.add_printer('bar', '^bar$', barPrinter)
22111 And here is the autoload support:
22114 import gdb.printing
22116 gdb.printing.register_pretty_printer(
22117 gdb.current_objfile(),
22118 my_library.build_pretty_printer())
22121 Finally, when this printer is loaded into @value{GDBN}, here is the
22122 corresponding output of @samp{info pretty-printer}:
22125 (gdb) info pretty-printer
22132 @node Inferiors In Python
22133 @subsubsection Inferiors In Python
22134 @cindex inferiors in Python
22136 @findex gdb.Inferior
22137 Programs which are being run under @value{GDBN} are called inferiors
22138 (@pxref{Inferiors and Programs}). Python scripts can access
22139 information about and manipulate inferiors controlled by @value{GDBN}
22140 via objects of the @code{gdb.Inferior} class.
22142 The following inferior-related functions are available in the @code{gdb}
22145 @defun gdb.inferiors ()
22146 Return a tuple containing all inferior objects.
22149 @defun gdb.selected_inferior ()
22150 Return an object representing the current inferior.
22153 A @code{gdb.Inferior} object has the following attributes:
22156 @defvar Inferior.num
22157 ID of inferior, as assigned by GDB.
22160 @defvar Inferior.pid
22161 Process ID of the inferior, as assigned by the underlying operating
22165 @defvar Inferior.was_attached
22166 Boolean signaling whether the inferior was created using `attach', or
22167 started by @value{GDBN} itself.
22171 A @code{gdb.Inferior} object has the following methods:
22174 @defun Inferior.is_valid ()
22175 Returns @code{True} if the @code{gdb.Inferior} object is valid,
22176 @code{False} if not. A @code{gdb.Inferior} object will become invalid
22177 if the inferior no longer exists within @value{GDBN}. All other
22178 @code{gdb.Inferior} methods will throw an exception if it is invalid
22179 at the time the method is called.
22182 @defun Inferior.threads ()
22183 This method returns a tuple holding all the threads which are valid
22184 when it is called. If there are no valid threads, the method will
22185 return an empty tuple.
22188 @findex gdb.read_memory
22189 @defun Inferior.read_memory (address, length)
22190 Read @var{length} bytes of memory from the inferior, starting at
22191 @var{address}. Returns a buffer object, which behaves much like an array
22192 or a string. It can be modified and given to the @code{gdb.write_memory}
22196 @findex gdb.write_memory
22197 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
22198 Write the contents of @var{buffer} to the inferior, starting at
22199 @var{address}. The @var{buffer} parameter must be a Python object
22200 which supports the buffer protocol, i.e., a string, an array or the
22201 object returned from @code{gdb.read_memory}. If given, @var{length}
22202 determines the number of bytes from @var{buffer} to be written.
22205 @findex gdb.search_memory
22206 @defun Inferior.search_memory (address, length, pattern)
22207 Search a region of the inferior memory starting at @var{address} with
22208 the given @var{length} using the search pattern supplied in
22209 @var{pattern}. The @var{pattern} parameter must be a Python object
22210 which supports the buffer protocol, i.e., a string, an array or the
22211 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22212 containing the address where the pattern was found, or @code{None} if
22213 the pattern could not be found.
22217 @node Events In Python
22218 @subsubsection Events In Python
22219 @cindex inferior events in Python
22221 @value{GDBN} provides a general event facility so that Python code can be
22222 notified of various state changes, particularly changes that occur in
22225 An @dfn{event} is just an object that describes some state change. The
22226 type of the object and its attributes will vary depending on the details
22227 of the change. All the existing events are described below.
22229 In order to be notified of an event, you must register an event handler
22230 with an @dfn{event registry}. An event registry is an object in the
22231 @code{gdb.events} module which dispatches particular events. A registry
22232 provides methods to register and unregister event handlers:
22235 @defun EventRegistry.connect (object)
22236 Add the given callable @var{object} to the registry. This object will be
22237 called when an event corresponding to this registry occurs.
22240 @defun EventRegistry.disconnect (object)
22241 Remove the given @var{object} from the registry. Once removed, the object
22242 will no longer receive notifications of events.
22246 Here is an example:
22249 def exit_handler (event):
22250 print "event type: exit"
22251 print "exit code: %d" % (event.exit_code)
22253 gdb.events.exited.connect (exit_handler)
22256 In the above example we connect our handler @code{exit_handler} to the
22257 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22258 called when the inferior exits. The argument @dfn{event} in this example is
22259 of type @code{gdb.ExitedEvent}. As you can see in the example the
22260 @code{ExitedEvent} object has an attribute which indicates the exit code of
22263 The following is a listing of the event registries that are available and
22264 details of the events they emit:
22269 Emits @code{gdb.ThreadEvent}.
22271 Some events can be thread specific when @value{GDBN} is running in non-stop
22272 mode. When represented in Python, these events all extend
22273 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22274 events which are emitted by this or other modules might extend this event.
22275 Examples of these events are @code{gdb.BreakpointEvent} and
22276 @code{gdb.ContinueEvent}.
22279 @defvar ThreadEvent.inferior_thread
22280 In non-stop mode this attribute will be set to the specific thread which was
22281 involved in the emitted event. Otherwise, it will be set to @code{None}.
22285 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22287 This event indicates that the inferior has been continued after a stop. For
22288 inherited attribute refer to @code{gdb.ThreadEvent} above.
22290 @item events.exited
22291 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22292 @code{events.ExitedEvent} has one optional attribute. This attribute
22293 will exist only in the case that the inferior exited with some
22296 @defvar ExitedEvent.exit_code
22297 An integer representing the exit code which the inferior has returned.
22302 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
22304 Indicates that the inferior has stopped. All events emitted by this registry
22305 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
22306 will indicate the stopped thread when @value{GDBN} is running in non-stop
22307 mode. Refer to @code{gdb.ThreadEvent} above for more details.
22309 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
22311 This event indicates that the inferior or one of its threads has received as
22312 signal. @code{gdb.SignalEvent} has the following attributes:
22315 @defvar SignalEvent.stop_signal
22316 A string representing the signal received by the inferior. A list of possible
22317 signal values can be obtained by running the command @code{info signals} in
22318 the @value{GDBN} command prompt.
22322 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22324 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
22325 been hit, and has the following attributes:
22328 @defvar BreakpointEvent.breakpoints
22329 A sequence containing references to all the breakpoints (type
22330 @code{gdb.Breakpoint}) that were hit.
22331 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22333 @defvar BreakpointEvent.breakpoint
22334 A reference to the first breakpoint that was hit.
22335 This function is maintained for backward compatibility and is now deprecated
22336 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
22342 @node Threads In Python
22343 @subsubsection Threads In Python
22344 @cindex threads in python
22346 @findex gdb.InferiorThread
22347 Python scripts can access information about, and manipulate inferior threads
22348 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
22350 The following thread-related functions are available in the @code{gdb}
22353 @findex gdb.selected_thread
22354 @defun gdb.selected_thread ()
22355 This function returns the thread object for the selected thread. If there
22356 is no selected thread, this will return @code{None}.
22359 A @code{gdb.InferiorThread} object has the following attributes:
22362 @defvar InferiorThread.name
22363 The name of the thread. If the user specified a name using
22364 @code{thread name}, then this returns that name. Otherwise, if an
22365 OS-supplied name is available, then it is returned. Otherwise, this
22366 returns @code{None}.
22368 This attribute can be assigned to. The new value must be a string
22369 object, which sets the new name, or @code{None}, which removes any
22370 user-specified thread name.
22373 @defvar InferiorThread.num
22374 ID of the thread, as assigned by GDB.
22377 @defvar InferiorThread.ptid
22378 ID of the thread, as assigned by the operating system. This attribute is a
22379 tuple containing three integers. The first is the Process ID (PID); the second
22380 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
22381 Either the LWPID or TID may be 0, which indicates that the operating system
22382 does not use that identifier.
22386 A @code{gdb.InferiorThread} object has the following methods:
22389 @defun InferiorThread.is_valid ()
22390 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
22391 @code{False} if not. A @code{gdb.InferiorThread} object will become
22392 invalid if the thread exits, or the inferior that the thread belongs
22393 is deleted. All other @code{gdb.InferiorThread} methods will throw an
22394 exception if it is invalid at the time the method is called.
22397 @defun InferiorThread.switch ()
22398 This changes @value{GDBN}'s currently selected thread to the one represented
22402 @defun InferiorThread.is_stopped ()
22403 Return a Boolean indicating whether the thread is stopped.
22406 @defun InferiorThread.is_running ()
22407 Return a Boolean indicating whether the thread is running.
22410 @defun InferiorThread.is_exited ()
22411 Return a Boolean indicating whether the thread is exited.
22415 @node Commands In Python
22416 @subsubsection Commands In Python
22418 @cindex commands in python
22419 @cindex python commands
22420 You can implement new @value{GDBN} CLI commands in Python. A CLI
22421 command is implemented using an instance of the @code{gdb.Command}
22422 class, most commonly using a subclass.
22424 @defun Command.__init__ (name, @var{command_class} @r{[}, var{completer_class} @r{[}, var{prefix}@r{]]})
22425 The object initializer for @code{Command} registers the new command
22426 with @value{GDBN}. This initializer is normally invoked from the
22427 subclass' own @code{__init__} method.
22429 @var{name} is the name of the command. If @var{name} consists of
22430 multiple words, then the initial words are looked for as prefix
22431 commands. In this case, if one of the prefix commands does not exist,
22432 an exception is raised.
22434 There is no support for multi-line commands.
22436 @var{command_class} should be one of the @samp{COMMAND_} constants
22437 defined below. This argument tells @value{GDBN} how to categorize the
22438 new command in the help system.
22440 @var{completer_class} is an optional argument. If given, it should be
22441 one of the @samp{COMPLETE_} constants defined below. This argument
22442 tells @value{GDBN} how to perform completion for this command. If not
22443 given, @value{GDBN} will attempt to complete using the object's
22444 @code{complete} method (see below); if no such method is found, an
22445 error will occur when completion is attempted.
22447 @var{prefix} is an optional argument. If @code{True}, then the new
22448 command is a prefix command; sub-commands of this command may be
22451 The help text for the new command is taken from the Python
22452 documentation string for the command's class, if there is one. If no
22453 documentation string is provided, the default value ``This command is
22454 not documented.'' is used.
22457 @cindex don't repeat Python command
22458 @defun Command.dont_repeat ()
22459 By default, a @value{GDBN} command is repeated when the user enters a
22460 blank line at the command prompt. A command can suppress this
22461 behavior by invoking the @code{dont_repeat} method. This is similar
22462 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
22465 @defun Command.invoke (argument, from_tty)
22466 This method is called by @value{GDBN} when this command is invoked.
22468 @var{argument} is a string. It is the argument to the command, after
22469 leading and trailing whitespace has been stripped.
22471 @var{from_tty} is a boolean argument. When true, this means that the
22472 command was entered by the user at the terminal; when false it means
22473 that the command came from elsewhere.
22475 If this method throws an exception, it is turned into a @value{GDBN}
22476 @code{error} call. Otherwise, the return value is ignored.
22478 @findex gdb.string_to_argv
22479 To break @var{argument} up into an argv-like string use
22480 @code{gdb.string_to_argv}. This function behaves identically to
22481 @value{GDBN}'s internal argument lexer @code{buildargv}.
22482 It is recommended to use this for consistency.
22483 Arguments are separated by spaces and may be quoted.
22487 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
22488 ['1', '2 "3', '4 "5', "6 '7"]
22493 @cindex completion of Python commands
22494 @defun Command.complete (text, word)
22495 This method is called by @value{GDBN} when the user attempts
22496 completion on this command. All forms of completion are handled by
22497 this method, that is, the @key{TAB} and @key{M-?} key bindings
22498 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
22501 The arguments @var{text} and @var{word} are both strings. @var{text}
22502 holds the complete command line up to the cursor's location.
22503 @var{word} holds the last word of the command line; this is computed
22504 using a word-breaking heuristic.
22506 The @code{complete} method can return several values:
22509 If the return value is a sequence, the contents of the sequence are
22510 used as the completions. It is up to @code{complete} to ensure that the
22511 contents actually do complete the word. A zero-length sequence is
22512 allowed, it means that there were no completions available. Only
22513 string elements of the sequence are used; other elements in the
22514 sequence are ignored.
22517 If the return value is one of the @samp{COMPLETE_} constants defined
22518 below, then the corresponding @value{GDBN}-internal completion
22519 function is invoked, and its result is used.
22522 All other results are treated as though there were no available
22527 When a new command is registered, it must be declared as a member of
22528 some general class of commands. This is used to classify top-level
22529 commands in the on-line help system; note that prefix commands are not
22530 listed under their own category but rather that of their top-level
22531 command. The available classifications are represented by constants
22532 defined in the @code{gdb} module:
22535 @findex COMMAND_NONE
22536 @findex gdb.COMMAND_NONE
22537 @item gdb.COMMAND_NONE
22538 The command does not belong to any particular class. A command in
22539 this category will not be displayed in any of the help categories.
22541 @findex COMMAND_RUNNING
22542 @findex gdb.COMMAND_RUNNING
22543 @item gdb.COMMAND_RUNNING
22544 The command is related to running the inferior. For example,
22545 @code{start}, @code{step}, and @code{continue} are in this category.
22546 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
22547 commands in this category.
22549 @findex COMMAND_DATA
22550 @findex gdb.COMMAND_DATA
22551 @item gdb.COMMAND_DATA
22552 The command is related to data or variables. For example,
22553 @code{call}, @code{find}, and @code{print} are in this category. Type
22554 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
22557 @findex COMMAND_STACK
22558 @findex gdb.COMMAND_STACK
22559 @item gdb.COMMAND_STACK
22560 The command has to do with manipulation of the stack. For example,
22561 @code{backtrace}, @code{frame}, and @code{return} are in this
22562 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
22563 list of commands in this category.
22565 @findex COMMAND_FILES
22566 @findex gdb.COMMAND_FILES
22567 @item gdb.COMMAND_FILES
22568 This class is used for file-related commands. For example,
22569 @code{file}, @code{list} and @code{section} are in this category.
22570 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
22571 commands in this category.
22573 @findex COMMAND_SUPPORT
22574 @findex gdb.COMMAND_SUPPORT
22575 @item gdb.COMMAND_SUPPORT
22576 This should be used for ``support facilities'', generally meaning
22577 things that are useful to the user when interacting with @value{GDBN},
22578 but not related to the state of the inferior. For example,
22579 @code{help}, @code{make}, and @code{shell} are in this category. Type
22580 @kbd{help support} at the @value{GDBN} prompt to see a list of
22581 commands in this category.
22583 @findex COMMAND_STATUS
22584 @findex gdb.COMMAND_STATUS
22585 @item gdb.COMMAND_STATUS
22586 The command is an @samp{info}-related command, that is, related to the
22587 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
22588 and @code{show} are in this category. Type @kbd{help status} at the
22589 @value{GDBN} prompt to see a list of commands in this category.
22591 @findex COMMAND_BREAKPOINTS
22592 @findex gdb.COMMAND_BREAKPOINTS
22593 @item gdb.COMMAND_BREAKPOINTS
22594 The command has to do with breakpoints. For example, @code{break},
22595 @code{clear}, and @code{delete} are in this category. Type @kbd{help
22596 breakpoints} at the @value{GDBN} prompt to see a list of commands in
22599 @findex COMMAND_TRACEPOINTS
22600 @findex gdb.COMMAND_TRACEPOINTS
22601 @item gdb.COMMAND_TRACEPOINTS
22602 The command has to do with tracepoints. For example, @code{trace},
22603 @code{actions}, and @code{tfind} are in this category. Type
22604 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
22605 commands in this category.
22607 @findex COMMAND_OBSCURE
22608 @findex gdb.COMMAND_OBSCURE
22609 @item gdb.COMMAND_OBSCURE
22610 The command is only used in unusual circumstances, or is not of
22611 general interest to users. For example, @code{checkpoint},
22612 @code{fork}, and @code{stop} are in this category. Type @kbd{help
22613 obscure} at the @value{GDBN} prompt to see a list of commands in this
22616 @findex COMMAND_MAINTENANCE
22617 @findex gdb.COMMAND_MAINTENANCE
22618 @item gdb.COMMAND_MAINTENANCE
22619 The command is only useful to @value{GDBN} maintainers. The
22620 @code{maintenance} and @code{flushregs} commands are in this category.
22621 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
22622 commands in this category.
22625 A new command can use a predefined completion function, either by
22626 specifying it via an argument at initialization, or by returning it
22627 from the @code{complete} method. These predefined completion
22628 constants are all defined in the @code{gdb} module:
22631 @findex COMPLETE_NONE
22632 @findex gdb.COMPLETE_NONE
22633 @item gdb.COMPLETE_NONE
22634 This constant means that no completion should be done.
22636 @findex COMPLETE_FILENAME
22637 @findex gdb.COMPLETE_FILENAME
22638 @item gdb.COMPLETE_FILENAME
22639 This constant means that filename completion should be performed.
22641 @findex COMPLETE_LOCATION
22642 @findex gdb.COMPLETE_LOCATION
22643 @item gdb.COMPLETE_LOCATION
22644 This constant means that location completion should be done.
22645 @xref{Specify Location}.
22647 @findex COMPLETE_COMMAND
22648 @findex gdb.COMPLETE_COMMAND
22649 @item gdb.COMPLETE_COMMAND
22650 This constant means that completion should examine @value{GDBN}
22653 @findex COMPLETE_SYMBOL
22654 @findex gdb.COMPLETE_SYMBOL
22655 @item gdb.COMPLETE_SYMBOL
22656 This constant means that completion should be done using symbol names
22660 The following code snippet shows how a trivial CLI command can be
22661 implemented in Python:
22664 class HelloWorld (gdb.Command):
22665 """Greet the whole world."""
22667 def __init__ (self):
22668 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
22670 def invoke (self, arg, from_tty):
22671 print "Hello, World!"
22676 The last line instantiates the class, and is necessary to trigger the
22677 registration of the command with @value{GDBN}. Depending on how the
22678 Python code is read into @value{GDBN}, you may need to import the
22679 @code{gdb} module explicitly.
22681 @node Parameters In Python
22682 @subsubsection Parameters In Python
22684 @cindex parameters in python
22685 @cindex python parameters
22686 @tindex gdb.Parameter
22688 You can implement new @value{GDBN} parameters using Python. A new
22689 parameter is implemented as an instance of the @code{gdb.Parameter}
22692 Parameters are exposed to the user via the @code{set} and
22693 @code{show} commands. @xref{Help}.
22695 There are many parameters that already exist and can be set in
22696 @value{GDBN}. Two examples are: @code{set follow fork} and
22697 @code{set charset}. Setting these parameters influences certain
22698 behavior in @value{GDBN}. Similarly, you can define parameters that
22699 can be used to influence behavior in custom Python scripts and commands.
22701 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
22702 The object initializer for @code{Parameter} registers the new
22703 parameter with @value{GDBN}. This initializer is normally invoked
22704 from the subclass' own @code{__init__} method.
22706 @var{name} is the name of the new parameter. If @var{name} consists
22707 of multiple words, then the initial words are looked for as prefix
22708 parameters. An example of this can be illustrated with the
22709 @code{set print} set of parameters. If @var{name} is
22710 @code{print foo}, then @code{print} will be searched as the prefix
22711 parameter. In this case the parameter can subsequently be accessed in
22712 @value{GDBN} as @code{set print foo}.
22714 If @var{name} consists of multiple words, and no prefix parameter group
22715 can be found, an exception is raised.
22717 @var{command-class} should be one of the @samp{COMMAND_} constants
22718 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
22719 categorize the new parameter in the help system.
22721 @var{parameter-class} should be one of the @samp{PARAM_} constants
22722 defined below. This argument tells @value{GDBN} the type of the new
22723 parameter; this information is used for input validation and
22726 If @var{parameter-class} is @code{PARAM_ENUM}, then
22727 @var{enum-sequence} must be a sequence of strings. These strings
22728 represent the possible values for the parameter.
22730 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
22731 of a fourth argument will cause an exception to be thrown.
22733 The help text for the new parameter is taken from the Python
22734 documentation string for the parameter's class, if there is one. If
22735 there is no documentation string, a default value is used.
22738 @defvar Parameter.set_doc
22739 If this attribute exists, and is a string, then its value is used as
22740 the help text for this parameter's @code{set} command. The value is
22741 examined when @code{Parameter.__init__} is invoked; subsequent changes
22745 @defvar Parameter.show_doc
22746 If this attribute exists, and is a string, then its value is used as
22747 the help text for this parameter's @code{show} command. The value is
22748 examined when @code{Parameter.__init__} is invoked; subsequent changes
22752 @defvar Parameter.value
22753 The @code{value} attribute holds the underlying value of the
22754 parameter. It can be read and assigned to just as any other
22755 attribute. @value{GDBN} does validation when assignments are made.
22758 There are two methods that should be implemented in any
22759 @code{Parameter} class. These are:
22761 @defun Parameter.get_set_string (self)
22762 @value{GDBN} will call this method when a @var{parameter}'s value has
22763 been changed via the @code{set} API (for example, @kbd{set foo off}).
22764 The @code{value} attribute has already been populated with the new
22765 value and may be used in output. This method must return a string.
22768 @defun Parameter.get_show_string (self, svalue)
22769 @value{GDBN} will call this method when a @var{parameter}'s
22770 @code{show} API has been invoked (for example, @kbd{show foo}). The
22771 argument @code{svalue} receives the string representation of the
22772 current value. This method must return a string.
22775 When a new parameter is defined, its type must be specified. The
22776 available types are represented by constants defined in the @code{gdb}
22780 @findex PARAM_BOOLEAN
22781 @findex gdb.PARAM_BOOLEAN
22782 @item gdb.PARAM_BOOLEAN
22783 The value is a plain boolean. The Python boolean values, @code{True}
22784 and @code{False} are the only valid values.
22786 @findex PARAM_AUTO_BOOLEAN
22787 @findex gdb.PARAM_AUTO_BOOLEAN
22788 @item gdb.PARAM_AUTO_BOOLEAN
22789 The value has three possible states: true, false, and @samp{auto}. In
22790 Python, true and false are represented using boolean constants, and
22791 @samp{auto} is represented using @code{None}.
22793 @findex PARAM_UINTEGER
22794 @findex gdb.PARAM_UINTEGER
22795 @item gdb.PARAM_UINTEGER
22796 The value is an unsigned integer. The value of 0 should be
22797 interpreted to mean ``unlimited''.
22799 @findex PARAM_INTEGER
22800 @findex gdb.PARAM_INTEGER
22801 @item gdb.PARAM_INTEGER
22802 The value is a signed integer. The value of 0 should be interpreted
22803 to mean ``unlimited''.
22805 @findex PARAM_STRING
22806 @findex gdb.PARAM_STRING
22807 @item gdb.PARAM_STRING
22808 The value is a string. When the user modifies the string, any escape
22809 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
22810 translated into corresponding characters and encoded into the current
22813 @findex PARAM_STRING_NOESCAPE
22814 @findex gdb.PARAM_STRING_NOESCAPE
22815 @item gdb.PARAM_STRING_NOESCAPE
22816 The value is a string. When the user modifies the string, escapes are
22817 passed through untranslated.
22819 @findex PARAM_OPTIONAL_FILENAME
22820 @findex gdb.PARAM_OPTIONAL_FILENAME
22821 @item gdb.PARAM_OPTIONAL_FILENAME
22822 The value is a either a filename (a string), or @code{None}.
22824 @findex PARAM_FILENAME
22825 @findex gdb.PARAM_FILENAME
22826 @item gdb.PARAM_FILENAME
22827 The value is a filename. This is just like
22828 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
22830 @findex PARAM_ZINTEGER
22831 @findex gdb.PARAM_ZINTEGER
22832 @item gdb.PARAM_ZINTEGER
22833 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
22834 is interpreted as itself.
22837 @findex gdb.PARAM_ENUM
22838 @item gdb.PARAM_ENUM
22839 The value is a string, which must be one of a collection string
22840 constants provided when the parameter is created.
22843 @node Functions In Python
22844 @subsubsection Writing new convenience functions
22846 @cindex writing convenience functions
22847 @cindex convenience functions in python
22848 @cindex python convenience functions
22849 @tindex gdb.Function
22851 You can implement new convenience functions (@pxref{Convenience Vars})
22852 in Python. A convenience function is an instance of a subclass of the
22853 class @code{gdb.Function}.
22855 @defun Function.__init__ (name)
22856 The initializer for @code{Function} registers the new function with
22857 @value{GDBN}. The argument @var{name} is the name of the function,
22858 a string. The function will be visible to the user as a convenience
22859 variable of type @code{internal function}, whose name is the same as
22860 the given @var{name}.
22862 The documentation for the new function is taken from the documentation
22863 string for the new class.
22866 @defun Function.invoke (@var{*args})
22867 When a convenience function is evaluated, its arguments are converted
22868 to instances of @code{gdb.Value}, and then the function's
22869 @code{invoke} method is called. Note that @value{GDBN} does not
22870 predetermine the arity of convenience functions. Instead, all
22871 available arguments are passed to @code{invoke}, following the
22872 standard Python calling convention. In particular, a convenience
22873 function can have default values for parameters without ill effect.
22875 The return value of this method is used as its value in the enclosing
22876 expression. If an ordinary Python value is returned, it is converted
22877 to a @code{gdb.Value} following the usual rules.
22880 The following code snippet shows how a trivial convenience function can
22881 be implemented in Python:
22884 class Greet (gdb.Function):
22885 """Return string to greet someone.
22886 Takes a name as argument."""
22888 def __init__ (self):
22889 super (Greet, self).__init__ ("greet")
22891 def invoke (self, name):
22892 return "Hello, %s!" % name.string ()
22897 The last line instantiates the class, and is necessary to trigger the
22898 registration of the function with @value{GDBN}. Depending on how the
22899 Python code is read into @value{GDBN}, you may need to import the
22900 @code{gdb} module explicitly.
22902 @node Progspaces In Python
22903 @subsubsection Program Spaces In Python
22905 @cindex progspaces in python
22906 @tindex gdb.Progspace
22908 A program space, or @dfn{progspace}, represents a symbolic view
22909 of an address space.
22910 It consists of all of the objfiles of the program.
22911 @xref{Objfiles In Python}.
22912 @xref{Inferiors and Programs, program spaces}, for more details
22913 about program spaces.
22915 The following progspace-related functions are available in the
22918 @findex gdb.current_progspace
22919 @defun gdb.current_progspace ()
22920 This function returns the program space of the currently selected inferior.
22921 @xref{Inferiors and Programs}.
22924 @findex gdb.progspaces
22925 @defun gdb.progspaces ()
22926 Return a sequence of all the progspaces currently known to @value{GDBN}.
22929 Each progspace is represented by an instance of the @code{gdb.Progspace}
22932 @defvar Progspace.filename
22933 The file name of the progspace as a string.
22936 @defvar Progspace.pretty_printers
22937 The @code{pretty_printers} attribute is a list of functions. It is
22938 used to look up pretty-printers. A @code{Value} is passed to each
22939 function in order; if the function returns @code{None}, then the
22940 search continues. Otherwise, the return value should be an object
22941 which is used to format the value. @xref{Pretty Printing API}, for more
22945 @node Objfiles In Python
22946 @subsubsection Objfiles In Python
22948 @cindex objfiles in python
22949 @tindex gdb.Objfile
22951 @value{GDBN} loads symbols for an inferior from various
22952 symbol-containing files (@pxref{Files}). These include the primary
22953 executable file, any shared libraries used by the inferior, and any
22954 separate debug info files (@pxref{Separate Debug Files}).
22955 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
22957 The following objfile-related functions are available in the
22960 @findex gdb.current_objfile
22961 @defun gdb.current_objfile ()
22962 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
22963 sets the ``current objfile'' to the corresponding objfile. This
22964 function returns the current objfile. If there is no current objfile,
22965 this function returns @code{None}.
22968 @findex gdb.objfiles
22969 @defun gdb.objfiles ()
22970 Return a sequence of all the objfiles current known to @value{GDBN}.
22971 @xref{Objfiles In Python}.
22974 Each objfile is represented by an instance of the @code{gdb.Objfile}
22977 @defvar Objfile.filename
22978 The file name of the objfile as a string.
22981 @defvar Objfile.pretty_printers
22982 The @code{pretty_printers} attribute is a list of functions. It is
22983 used to look up pretty-printers. A @code{Value} is passed to each
22984 function in order; if the function returns @code{None}, then the
22985 search continues. Otherwise, the return value should be an object
22986 which is used to format the value. @xref{Pretty Printing API}, for more
22990 A @code{gdb.Objfile} object has the following methods:
22992 @defun Objfile.is_valid ()
22993 Returns @code{True} if the @code{gdb.Objfile} object is valid,
22994 @code{False} if not. A @code{gdb.Objfile} object can become invalid
22995 if the object file it refers to is not loaded in @value{GDBN} any
22996 longer. All other @code{gdb.Objfile} methods will throw an exception
22997 if it is invalid at the time the method is called.
23000 @node Frames In Python
23001 @subsubsection Accessing inferior stack frames from Python.
23003 @cindex frames in python
23004 When the debugged program stops, @value{GDBN} is able to analyze its call
23005 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
23006 represents a frame in the stack. A @code{gdb.Frame} object is only valid
23007 while its corresponding frame exists in the inferior's stack. If you try
23008 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
23009 exception (@pxref{Exception Handling}).
23011 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
23015 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
23019 The following frame-related functions are available in the @code{gdb} module:
23021 @findex gdb.selected_frame
23022 @defun gdb.selected_frame ()
23023 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
23026 @findex gdb.newest_frame
23027 @defun gdb.newest_frame ()
23028 Return the newest frame object for the selected thread.
23031 @defun gdb.frame_stop_reason_string (reason)
23032 Return a string explaining the reason why @value{GDBN} stopped unwinding
23033 frames, as expressed by the given @var{reason} code (an integer, see the
23034 @code{unwind_stop_reason} method further down in this section).
23037 A @code{gdb.Frame} object has the following methods:
23040 @defun Frame.is_valid ()
23041 Returns true if the @code{gdb.Frame} object is valid, false if not.
23042 A frame object can become invalid if the frame it refers to doesn't
23043 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
23044 an exception if it is invalid at the time the method is called.
23047 @defun Frame.name ()
23048 Returns the function name of the frame, or @code{None} if it can't be
23052 @defun Frame.type ()
23053 Returns the type of the frame. The value can be one of:
23055 @item gdb.NORMAL_FRAME
23056 An ordinary stack frame.
23058 @item gdb.DUMMY_FRAME
23059 A fake stack frame that was created by @value{GDBN} when performing an
23060 inferior function call.
23062 @item gdb.INLINE_FRAME
23063 A frame representing an inlined function. The function was inlined
23064 into a @code{gdb.NORMAL_FRAME} that is older than this one.
23066 @item gdb.SIGTRAMP_FRAME
23067 A signal trampoline frame. This is the frame created by the OS when
23068 it calls into a signal handler.
23070 @item gdb.ARCH_FRAME
23071 A fake stack frame representing a cross-architecture call.
23073 @item gdb.SENTINEL_FRAME
23074 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
23079 @defun Frame.unwind_stop_reason ()
23080 Return an integer representing the reason why it's not possible to find
23081 more frames toward the outermost frame. Use
23082 @code{gdb.frame_stop_reason_string} to convert the value returned by this
23083 function to a string.
23087 Returns the frame's resume address.
23090 @defun Frame.block ()
23091 Return the frame's code block. @xref{Blocks In Python}.
23094 @defun Frame.function ()
23095 Return the symbol for the function corresponding to this frame.
23096 @xref{Symbols In Python}.
23099 @defun Frame.older ()
23100 Return the frame that called this frame.
23103 @defun Frame.newer ()
23104 Return the frame called by this frame.
23107 @defun Frame.find_sal ()
23108 Return the frame's symtab and line object.
23109 @xref{Symbol Tables In Python}.
23112 @defun Frame.read_var (variable @r{[}, block@r{]})
23113 Return the value of @var{variable} in this frame. If the optional
23114 argument @var{block} is provided, search for the variable from that
23115 block; otherwise start at the frame's current block (which is
23116 determined by the frame's current program counter). @var{variable}
23117 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
23118 @code{gdb.Block} object.
23121 @defun Frame.select ()
23122 Set this frame to be the selected frame. @xref{Stack, ,Examining the
23127 @node Blocks In Python
23128 @subsubsection Accessing frame blocks from Python.
23130 @cindex blocks in python
23133 Within each frame, @value{GDBN} maintains information on each block
23134 stored in that frame. These blocks are organized hierarchically, and
23135 are represented individually in Python as a @code{gdb.Block}.
23136 Please see @ref{Frames In Python}, for a more in-depth discussion on
23137 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
23138 detailed technical information on @value{GDBN}'s book-keeping of the
23141 The following block-related functions are available in the @code{gdb}
23144 @findex gdb.block_for_pc
23145 @defun gdb.block_for_pc (pc)
23146 Return the @code{gdb.Block} containing the given @var{pc} value. If the
23147 block cannot be found for the @var{pc} value specified, the function
23148 will return @code{None}.
23151 A @code{gdb.Block} object has the following methods:
23154 @defun Block.is_valid ()
23155 Returns @code{True} if the @code{gdb.Block} object is valid,
23156 @code{False} if not. A block object can become invalid if the block it
23157 refers to doesn't exist anymore in the inferior. All other
23158 @code{gdb.Block} methods will throw an exception if it is invalid at
23159 the time the method is called. This method is also made available to
23160 the Python iterator object that @code{gdb.Block} provides in an iteration
23161 context and via the Python @code{iter} built-in function.
23165 A @code{gdb.Block} object has the following attributes:
23168 @defvar Block.start
23169 The start address of the block. This attribute is not writable.
23173 The end address of the block. This attribute is not writable.
23176 @defvar Block.function
23177 The name of the block represented as a @code{gdb.Symbol}. If the
23178 block is not named, then this attribute holds @code{None}. This
23179 attribute is not writable.
23182 @defvar Block.superblock
23183 The block containing this block. If this parent block does not exist,
23184 this attribute holds @code{None}. This attribute is not writable.
23188 @node Symbols In Python
23189 @subsubsection Python representation of Symbols.
23191 @cindex symbols in python
23194 @value{GDBN} represents every variable, function and type as an
23195 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
23196 Similarly, Python represents these symbols in @value{GDBN} with the
23197 @code{gdb.Symbol} object.
23199 The following symbol-related functions are available in the @code{gdb}
23202 @findex gdb.lookup_symbol
23203 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
23204 This function searches for a symbol by name. The search scope can be
23205 restricted to the parameters defined in the optional domain and block
23208 @var{name} is the name of the symbol. It must be a string. The
23209 optional @var{block} argument restricts the search to symbols visible
23210 in that @var{block}. The @var{block} argument must be a
23211 @code{gdb.Block} object. If omitted, the block for the current frame
23212 is used. The optional @var{domain} argument restricts
23213 the search to the domain type. The @var{domain} argument must be a
23214 domain constant defined in the @code{gdb} module and described later
23217 The result is a tuple of two elements.
23218 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
23220 If the symbol is found, the second element is @code{True} if the symbol
23221 is a field of a method's object (e.g., @code{this} in C@t{++}),
23222 otherwise it is @code{False}.
23223 If the symbol is not found, the second element is @code{False}.
23226 @findex gdb.lookup_global_symbol
23227 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
23228 This function searches for a global symbol by name.
23229 The search scope can be restricted to by the domain argument.
23231 @var{name} is the name of the symbol. It must be a string.
23232 The optional @var{domain} argument restricts the search to the domain type.
23233 The @var{domain} argument must be a domain constant defined in the @code{gdb}
23234 module and described later in this chapter.
23236 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
23240 A @code{gdb.Symbol} object has the following attributes:
23243 @defvar Symbol.type
23244 The type of the symbol or @code{None} if no type is recorded.
23245 This attribute is represented as a @code{gdb.Type} object.
23246 @xref{Types In Python}. This attribute is not writable.
23249 @defvar Symbol.symtab
23250 The symbol table in which the symbol appears. This attribute is
23251 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
23252 Python}. This attribute is not writable.
23255 @defvar Symbol.name
23256 The name of the symbol as a string. This attribute is not writable.
23259 @defvar Symbol.linkage_name
23260 The name of the symbol, as used by the linker (i.e., may be mangled).
23261 This attribute is not writable.
23264 @defvar Symbol.print_name
23265 The name of the symbol in a form suitable for output. This is either
23266 @code{name} or @code{linkage_name}, depending on whether the user
23267 asked @value{GDBN} to display demangled or mangled names.
23270 @defvar Symbol.addr_class
23271 The address class of the symbol. This classifies how to find the value
23272 of a symbol. Each address class is a constant defined in the
23273 @code{gdb} module and described later in this chapter.
23276 @defvar Symbol.is_argument
23277 @code{True} if the symbol is an argument of a function.
23280 @defvar Symbol.is_constant
23281 @code{True} if the symbol is a constant.
23284 @defvar Symbol.is_function
23285 @code{True} if the symbol is a function or a method.
23288 @defvar Symbol.is_variable
23289 @code{True} if the symbol is a variable.
23293 A @code{gdb.Symbol} object has the following methods:
23296 @defun Symbol.is_valid ()
23297 Returns @code{True} if the @code{gdb.Symbol} object is valid,
23298 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
23299 the symbol it refers to does not exist in @value{GDBN} any longer.
23300 All other @code{gdb.Symbol} methods will throw an exception if it is
23301 invalid at the time the method is called.
23305 The available domain categories in @code{gdb.Symbol} are represented
23306 as constants in the @code{gdb} module:
23309 @findex SYMBOL_UNDEF_DOMAIN
23310 @findex gdb.SYMBOL_UNDEF_DOMAIN
23311 @item gdb.SYMBOL_UNDEF_DOMAIN
23312 This is used when a domain has not been discovered or none of the
23313 following domains apply. This usually indicates an error either
23314 in the symbol information or in @value{GDBN}'s handling of symbols.
23315 @findex SYMBOL_VAR_DOMAIN
23316 @findex gdb.SYMBOL_VAR_DOMAIN
23317 @item gdb.SYMBOL_VAR_DOMAIN
23318 This domain contains variables, function names, typedef names and enum
23320 @findex SYMBOL_STRUCT_DOMAIN
23321 @findex gdb.SYMBOL_STRUCT_DOMAIN
23322 @item gdb.SYMBOL_STRUCT_DOMAIN
23323 This domain holds struct, union and enum type names.
23324 @findex SYMBOL_LABEL_DOMAIN
23325 @findex gdb.SYMBOL_LABEL_DOMAIN
23326 @item gdb.SYMBOL_LABEL_DOMAIN
23327 This domain contains names of labels (for gotos).
23328 @findex SYMBOL_VARIABLES_DOMAIN
23329 @findex gdb.SYMBOL_VARIABLES_DOMAIN
23330 @item gdb.SYMBOL_VARIABLES_DOMAIN
23331 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
23332 contains everything minus functions and types.
23333 @findex SYMBOL_FUNCTIONS_DOMAIN
23334 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
23335 @item gdb.SYMBOL_FUNCTION_DOMAIN
23336 This domain contains all functions.
23337 @findex SYMBOL_TYPES_DOMAIN
23338 @findex gdb.SYMBOL_TYPES_DOMAIN
23339 @item gdb.SYMBOL_TYPES_DOMAIN
23340 This domain contains all types.
23343 The available address class categories in @code{gdb.Symbol} are represented
23344 as constants in the @code{gdb} module:
23347 @findex SYMBOL_LOC_UNDEF
23348 @findex gdb.SYMBOL_LOC_UNDEF
23349 @item gdb.SYMBOL_LOC_UNDEF
23350 If this is returned by address class, it indicates an error either in
23351 the symbol information or in @value{GDBN}'s handling of symbols.
23352 @findex SYMBOL_LOC_CONST
23353 @findex gdb.SYMBOL_LOC_CONST
23354 @item gdb.SYMBOL_LOC_CONST
23355 Value is constant int.
23356 @findex SYMBOL_LOC_STATIC
23357 @findex gdb.SYMBOL_LOC_STATIC
23358 @item gdb.SYMBOL_LOC_STATIC
23359 Value is at a fixed address.
23360 @findex SYMBOL_LOC_REGISTER
23361 @findex gdb.SYMBOL_LOC_REGISTER
23362 @item gdb.SYMBOL_LOC_REGISTER
23363 Value is in a register.
23364 @findex SYMBOL_LOC_ARG
23365 @findex gdb.SYMBOL_LOC_ARG
23366 @item gdb.SYMBOL_LOC_ARG
23367 Value is an argument. This value is at the offset stored within the
23368 symbol inside the frame's argument list.
23369 @findex SYMBOL_LOC_REF_ARG
23370 @findex gdb.SYMBOL_LOC_REF_ARG
23371 @item gdb.SYMBOL_LOC_REF_ARG
23372 Value address is stored in the frame's argument list. Just like
23373 @code{LOC_ARG} except that the value's address is stored at the
23374 offset, not the value itself.
23375 @findex SYMBOL_LOC_REGPARM_ADDR
23376 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
23377 @item gdb.SYMBOL_LOC_REGPARM_ADDR
23378 Value is a specified register. Just like @code{LOC_REGISTER} except
23379 the register holds the address of the argument instead of the argument
23381 @findex SYMBOL_LOC_LOCAL
23382 @findex gdb.SYMBOL_LOC_LOCAL
23383 @item gdb.SYMBOL_LOC_LOCAL
23384 Value is a local variable.
23385 @findex SYMBOL_LOC_TYPEDEF
23386 @findex gdb.SYMBOL_LOC_TYPEDEF
23387 @item gdb.SYMBOL_LOC_TYPEDEF
23388 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
23390 @findex SYMBOL_LOC_BLOCK
23391 @findex gdb.SYMBOL_LOC_BLOCK
23392 @item gdb.SYMBOL_LOC_BLOCK
23394 @findex SYMBOL_LOC_CONST_BYTES
23395 @findex gdb.SYMBOL_LOC_CONST_BYTES
23396 @item gdb.SYMBOL_LOC_CONST_BYTES
23397 Value is a byte-sequence.
23398 @findex SYMBOL_LOC_UNRESOLVED
23399 @findex gdb.SYMBOL_LOC_UNRESOLVED
23400 @item gdb.SYMBOL_LOC_UNRESOLVED
23401 Value is at a fixed address, but the address of the variable has to be
23402 determined from the minimal symbol table whenever the variable is
23404 @findex SYMBOL_LOC_OPTIMIZED_OUT
23405 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
23406 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
23407 The value does not actually exist in the program.
23408 @findex SYMBOL_LOC_COMPUTED
23409 @findex gdb.SYMBOL_LOC_COMPUTED
23410 @item gdb.SYMBOL_LOC_COMPUTED
23411 The value's address is a computed location.
23414 @node Symbol Tables In Python
23415 @subsubsection Symbol table representation in Python.
23417 @cindex symbol tables in python
23419 @tindex gdb.Symtab_and_line
23421 Access to symbol table data maintained by @value{GDBN} on the inferior
23422 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
23423 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
23424 from the @code{find_sal} method in @code{gdb.Frame} object.
23425 @xref{Frames In Python}.
23427 For more information on @value{GDBN}'s symbol table management, see
23428 @ref{Symbols, ,Examining the Symbol Table}, for more information.
23430 A @code{gdb.Symtab_and_line} object has the following attributes:
23433 @defvar Symtab_and_line.symtab
23434 The symbol table object (@code{gdb.Symtab}) for this frame.
23435 This attribute is not writable.
23438 @defvar Symtab_and_line.pc
23439 Indicates the current program counter address. This attribute is not
23443 @defvar Symtab_and_line.line
23444 Indicates the current line number for this object. This
23445 attribute is not writable.
23449 A @code{gdb.Symtab_and_line} object has the following methods:
23452 @defun Symtab_and_line.is_valid ()
23453 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
23454 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
23455 invalid if the Symbol table and line object it refers to does not
23456 exist in @value{GDBN} any longer. All other
23457 @code{gdb.Symtab_and_line} methods will throw an exception if it is
23458 invalid at the time the method is called.
23462 A @code{gdb.Symtab} object has the following attributes:
23465 @defvar Symtab.filename
23466 The symbol table's source filename. This attribute is not writable.
23469 @defvar Symtab.objfile
23470 The symbol table's backing object file. @xref{Objfiles In Python}.
23471 This attribute is not writable.
23475 A @code{gdb.Symtab} object has the following methods:
23478 @defun Symtab.is_valid ()
23479 Returns @code{True} if the @code{gdb.Symtab} object is valid,
23480 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
23481 the symbol table it refers to does not exist in @value{GDBN} any
23482 longer. All other @code{gdb.Symtab} methods will throw an exception
23483 if it is invalid at the time the method is called.
23486 @defun Symtab.fullname ()
23487 Return the symbol table's source absolute file name.
23491 @node Breakpoints In Python
23492 @subsubsection Manipulating breakpoints using Python
23494 @cindex breakpoints in python
23495 @tindex gdb.Breakpoint
23497 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
23500 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
23501 Create a new breakpoint. @var{spec} is a string naming the
23502 location of the breakpoint, or an expression that defines a
23503 watchpoint. The contents can be any location recognized by the
23504 @code{break} command, or in the case of a watchpoint, by the @code{watch}
23505 command. The optional @var{type} denotes the breakpoint to create
23506 from the types defined later in this chapter. This argument can be
23507 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
23508 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
23509 allows the breakpoint to become invisible to the user. The breakpoint
23510 will neither be reported when created, nor will it be listed in the
23511 output from @code{info breakpoints} (but will be listed with the
23512 @code{maint info breakpoints} command). The optional @var{wp_class}
23513 argument defines the class of watchpoint to create, if @var{type} is
23514 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
23515 assumed to be a @code{gdb.WP_WRITE} class.
23518 @defun Breakpoint.stop (self)
23519 The @code{gdb.Breakpoint} class can be sub-classed and, in
23520 particular, you may choose to implement the @code{stop} method.
23521 If this method is defined as a sub-class of @code{gdb.Breakpoint},
23522 it will be called when the inferior reaches any location of a
23523 breakpoint which instantiates that sub-class. If the method returns
23524 @code{True}, the inferior will be stopped at the location of the
23525 breakpoint, otherwise the inferior will continue.
23527 If there are multiple breakpoints at the same location with a
23528 @code{stop} method, each one will be called regardless of the
23529 return status of the previous. This ensures that all @code{stop}
23530 methods have a chance to execute at that location. In this scenario
23531 if one of the methods returns @code{True} but the others return
23532 @code{False}, the inferior will still be stopped.
23534 Example @code{stop} implementation:
23537 class MyBreakpoint (gdb.Breakpoint):
23539 inf_val = gdb.parse_and_eval("foo")
23546 The available watchpoint types represented by constants are defined in the
23551 @findex gdb.WP_READ
23553 Read only watchpoint.
23556 @findex gdb.WP_WRITE
23558 Write only watchpoint.
23561 @findex gdb.WP_ACCESS
23562 @item gdb.WP_ACCESS
23563 Read/Write watchpoint.
23566 @defun Breakpoint.is_valid ()
23567 Return @code{True} if this @code{Breakpoint} object is valid,
23568 @code{False} otherwise. A @code{Breakpoint} object can become invalid
23569 if the user deletes the breakpoint. In this case, the object still
23570 exists, but the underlying breakpoint does not. In the cases of
23571 watchpoint scope, the watchpoint remains valid even if execution of the
23572 inferior leaves the scope of that watchpoint.
23575 @defun Breakpoint.delete
23576 Permanently deletes the @value{GDBN} breakpoint. This also
23577 invalidates the Python @code{Breakpoint} object. Any further access
23578 to this object's attributes or methods will raise an error.
23581 @defvar Breakpoint.enabled
23582 This attribute is @code{True} if the breakpoint is enabled, and
23583 @code{False} otherwise. This attribute is writable.
23586 @defvar Breakpoint.silent
23587 This attribute is @code{True} if the breakpoint is silent, and
23588 @code{False} otherwise. This attribute is writable.
23590 Note that a breakpoint can also be silent if it has commands and the
23591 first command is @code{silent}. This is not reported by the
23592 @code{silent} attribute.
23595 @defvar Breakpoint.thread
23596 If the breakpoint is thread-specific, this attribute holds the thread
23597 id. If the breakpoint is not thread-specific, this attribute is
23598 @code{None}. This attribute is writable.
23601 @defvar Breakpoint.task
23602 If the breakpoint is Ada task-specific, this attribute holds the Ada task
23603 id. If the breakpoint is not task-specific (or the underlying
23604 language is not Ada), this attribute is @code{None}. This attribute
23608 @defvar Breakpoint.ignore_count
23609 This attribute holds the ignore count for the breakpoint, an integer.
23610 This attribute is writable.
23613 @defvar Breakpoint.number
23614 This attribute holds the breakpoint's number --- the identifier used by
23615 the user to manipulate the breakpoint. This attribute is not writable.
23618 @defvar Breakpoint.type
23619 This attribute holds the breakpoint's type --- the identifier used to
23620 determine the actual breakpoint type or use-case. This attribute is not
23624 @defvar Breakpoint.visible
23625 This attribute tells whether the breakpoint is visible to the user
23626 when set, or when the @samp{info breakpoints} command is run. This
23627 attribute is not writable.
23630 The available types are represented by constants defined in the @code{gdb}
23634 @findex BP_BREAKPOINT
23635 @findex gdb.BP_BREAKPOINT
23636 @item gdb.BP_BREAKPOINT
23637 Normal code breakpoint.
23639 @findex BP_WATCHPOINT
23640 @findex gdb.BP_WATCHPOINT
23641 @item gdb.BP_WATCHPOINT
23642 Watchpoint breakpoint.
23644 @findex BP_HARDWARE_WATCHPOINT
23645 @findex gdb.BP_HARDWARE_WATCHPOINT
23646 @item gdb.BP_HARDWARE_WATCHPOINT
23647 Hardware assisted watchpoint.
23649 @findex BP_READ_WATCHPOINT
23650 @findex gdb.BP_READ_WATCHPOINT
23651 @item gdb.BP_READ_WATCHPOINT
23652 Hardware assisted read watchpoint.
23654 @findex BP_ACCESS_WATCHPOINT
23655 @findex gdb.BP_ACCESS_WATCHPOINT
23656 @item gdb.BP_ACCESS_WATCHPOINT
23657 Hardware assisted access watchpoint.
23660 @defvar Breakpoint.hit_count
23661 This attribute holds the hit count for the breakpoint, an integer.
23662 This attribute is writable, but currently it can only be set to zero.
23665 @defvar Breakpoint.location
23666 This attribute holds the location of the breakpoint, as specified by
23667 the user. It is a string. If the breakpoint does not have a location
23668 (that is, it is a watchpoint) the attribute's value is @code{None}. This
23669 attribute is not writable.
23672 @defvar Breakpoint.expression
23673 This attribute holds a breakpoint expression, as specified by
23674 the user. It is a string. If the breakpoint does not have an
23675 expression (the breakpoint is not a watchpoint) the attribute's value
23676 is @code{None}. This attribute is not writable.
23679 @defvar Breakpoint.condition
23680 This attribute holds the condition of the breakpoint, as specified by
23681 the user. It is a string. If there is no condition, this attribute's
23682 value is @code{None}. This attribute is writable.
23685 @defvar Breakpoint.commands
23686 This attribute holds the commands attached to the breakpoint. If
23687 there are commands, this attribute's value is a string holding all the
23688 commands, separated by newlines. If there are no commands, this
23689 attribute is @code{None}. This attribute is not writable.
23692 @node Lazy Strings In Python
23693 @subsubsection Python representation of lazy strings.
23695 @cindex lazy strings in python
23696 @tindex gdb.LazyString
23698 A @dfn{lazy string} is a string whose contents is not retrieved or
23699 encoded until it is needed.
23701 A @code{gdb.LazyString} is represented in @value{GDBN} as an
23702 @code{address} that points to a region of memory, an @code{encoding}
23703 that will be used to encode that region of memory, and a @code{length}
23704 to delimit the region of memory that represents the string. The
23705 difference between a @code{gdb.LazyString} and a string wrapped within
23706 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
23707 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
23708 retrieved and encoded during printing, while a @code{gdb.Value}
23709 wrapping a string is immediately retrieved and encoded on creation.
23711 A @code{gdb.LazyString} object has the following functions:
23713 @defun LazyString.value ()
23714 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
23715 will point to the string in memory, but will lose all the delayed
23716 retrieval, encoding and handling that @value{GDBN} applies to a
23717 @code{gdb.LazyString}.
23720 @defvar LazyString.address
23721 This attribute holds the address of the string. This attribute is not
23725 @defvar LazyString.length
23726 This attribute holds the length of the string in characters. If the
23727 length is -1, then the string will be fetched and encoded up to the
23728 first null of appropriate width. This attribute is not writable.
23731 @defvar LazyString.encoding
23732 This attribute holds the encoding that will be applied to the string
23733 when the string is printed by @value{GDBN}. If the encoding is not
23734 set, or contains an empty string, then @value{GDBN} will select the
23735 most appropriate encoding when the string is printed. This attribute
23739 @defvar LazyString.type
23740 This attribute holds the type that is represented by the lazy string's
23741 type. For a lazy string this will always be a pointer type. To
23742 resolve this to the lazy string's character type, use the type's
23743 @code{target} method. @xref{Types In Python}. This attribute is not
23748 @subsection Auto-loading
23749 @cindex auto-loading, Python
23751 When a new object file is read (for example, due to the @code{file}
23752 command, or because the inferior has loaded a shared library),
23753 @value{GDBN} will look for Python support scripts in several ways:
23754 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
23757 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
23758 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
23759 * Which flavor to choose?::
23762 The auto-loading feature is useful for supplying application-specific
23763 debugging commands and scripts.
23765 Auto-loading can be enabled or disabled,
23766 and the list of auto-loaded scripts can be printed.
23769 @kindex set auto-load-scripts
23770 @item set auto-load-scripts [yes|no]
23771 Enable or disable the auto-loading of Python scripts.
23773 @kindex show auto-load-scripts
23774 @item show auto-load-scripts
23775 Show whether auto-loading of Python scripts is enabled or disabled.
23777 @kindex info auto-load-scripts
23778 @cindex print list of auto-loaded scripts
23779 @item info auto-load-scripts [@var{regexp}]
23780 Print the list of all scripts that @value{GDBN} auto-loaded.
23782 Also printed is the list of scripts that were mentioned in
23783 the @code{.debug_gdb_scripts} section and were not found
23784 (@pxref{.debug_gdb_scripts section}).
23785 This is useful because their names are not printed when @value{GDBN}
23786 tries to load them and fails. There may be many of them, and printing
23787 an error message for each one is problematic.
23789 If @var{regexp} is supplied only scripts with matching names are printed.
23794 (gdb) info auto-load-scripts
23796 Yes py-section-script.py
23797 full name: /tmp/py-section-script.py
23798 Missing my-foo-pretty-printers.py
23802 When reading an auto-loaded file, @value{GDBN} sets the
23803 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
23804 function (@pxref{Objfiles In Python}). This can be useful for
23805 registering objfile-specific pretty-printers.
23807 @node objfile-gdb.py file
23808 @subsubsection The @file{@var{objfile}-gdb.py} file
23809 @cindex @file{@var{objfile}-gdb.py}
23811 When a new object file is read, @value{GDBN} looks for
23812 a file named @file{@var{objfile}-gdb.py},
23813 where @var{objfile} is the object file's real name, formed by ensuring
23814 that the file name is absolute, following all symlinks, and resolving
23815 @code{.} and @code{..} components. If this file exists and is
23816 readable, @value{GDBN} will evaluate it as a Python script.
23818 If this file does not exist, and if the parameter
23819 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
23820 then @value{GDBN} will look for @var{real-name} in all of the
23821 directories mentioned in the value of @code{debug-file-directory}.
23823 Finally, if this file does not exist, then @value{GDBN} will look for
23824 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
23825 @var{data-directory} is @value{GDBN}'s data directory (available via
23826 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
23827 is the object file's real name, as described above.
23829 @value{GDBN} does not track which files it has already auto-loaded this way.
23830 @value{GDBN} will load the associated script every time the corresponding
23831 @var{objfile} is opened.
23832 So your @file{-gdb.py} file should be careful to avoid errors if it
23833 is evaluated more than once.
23835 @node .debug_gdb_scripts section
23836 @subsubsection The @code{.debug_gdb_scripts} section
23837 @cindex @code{.debug_gdb_scripts} section
23839 For systems using file formats like ELF and COFF,
23840 when @value{GDBN} loads a new object file
23841 it will look for a special section named @samp{.debug_gdb_scripts}.
23842 If this section exists, its contents is a list of names of scripts to load.
23844 @value{GDBN} will look for each specified script file first in the
23845 current directory and then along the source search path
23846 (@pxref{Source Path, ,Specifying Source Directories}),
23847 except that @file{$cdir} is not searched, since the compilation
23848 directory is not relevant to scripts.
23850 Entries can be placed in section @code{.debug_gdb_scripts} with,
23851 for example, this GCC macro:
23854 /* Note: The "MS" section flags are to remove duplicates. */
23855 #define DEFINE_GDB_SCRIPT(script_name) \
23857 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
23859 .asciz \"" script_name "\"\n\
23865 Then one can reference the macro in a header or source file like this:
23868 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
23871 The script name may include directories if desired.
23873 If the macro is put in a header, any application or library
23874 using this header will get a reference to the specified script.
23876 @node Which flavor to choose?
23877 @subsubsection Which flavor to choose?
23879 Given the multiple ways of auto-loading Python scripts, it might not always
23880 be clear which one to choose. This section provides some guidance.
23882 Benefits of the @file{-gdb.py} way:
23886 Can be used with file formats that don't support multiple sections.
23889 Ease of finding scripts for public libraries.
23891 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
23892 in the source search path.
23893 For publicly installed libraries, e.g., @file{libstdc++}, there typically
23894 isn't a source directory in which to find the script.
23897 Doesn't require source code additions.
23900 Benefits of the @code{.debug_gdb_scripts} way:
23904 Works with static linking.
23906 Scripts for libraries done the @file{-gdb.py} way require an objfile to
23907 trigger their loading. When an application is statically linked the only
23908 objfile available is the executable, and it is cumbersome to attach all the
23909 scripts from all the input libraries to the executable's @file{-gdb.py} script.
23912 Works with classes that are entirely inlined.
23914 Some classes can be entirely inlined, and thus there may not be an associated
23915 shared library to attach a @file{-gdb.py} script to.
23918 Scripts needn't be copied out of the source tree.
23920 In some circumstances, apps can be built out of large collections of internal
23921 libraries, and the build infrastructure necessary to install the
23922 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
23923 cumbersome. It may be easier to specify the scripts in the
23924 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
23925 top of the source tree to the source search path.
23928 @node Python modules
23929 @subsection Python modules
23930 @cindex python modules
23932 @value{GDBN} comes with several modules to assist writing Python code.
23935 * gdb.printing:: Building and registering pretty-printers.
23936 * gdb.types:: Utilities for working with types.
23937 * gdb.prompt:: Utilities for prompt value substitution.
23941 @subsubsection gdb.printing
23942 @cindex gdb.printing
23944 This module provides a collection of utilities for working with
23948 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
23949 This class specifies the API that makes @samp{info pretty-printer},
23950 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
23951 Pretty-printers should generally inherit from this class.
23953 @item SubPrettyPrinter (@var{name})
23954 For printers that handle multiple types, this class specifies the
23955 corresponding API for the subprinters.
23957 @item RegexpCollectionPrettyPrinter (@var{name})
23958 Utility class for handling multiple printers, all recognized via
23959 regular expressions.
23960 @xref{Writing a Pretty-Printer}, for an example.
23962 @item register_pretty_printer (@var{obj}, @var{printer})
23963 Register @var{printer} with the pretty-printer list of @var{obj}.
23967 @subsubsection gdb.types
23970 This module provides a collection of utilities for working with
23971 @code{gdb.Types} objects.
23974 @item get_basic_type (@var{type})
23975 Return @var{type} with const and volatile qualifiers stripped,
23976 and with typedefs and C@t{++} references converted to the underlying type.
23981 typedef const int const_int;
23983 const_int& foo_ref (foo);
23984 int main () @{ return 0; @}
23991 (gdb) python import gdb.types
23992 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
23993 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
23997 @item has_field (@var{type}, @var{field})
23998 Return @code{True} if @var{type}, assumed to be a type with fields
23999 (e.g., a structure or union), has field @var{field}.
24001 @item make_enum_dict (@var{enum_type})
24002 Return a Python @code{dictionary} type produced from @var{enum_type}.
24006 @subsubsection gdb.prompt
24009 This module provides a method for prompt value-substitution.
24012 @item substitute_prompt (@var{string})
24013 Return @var{string} with escape sequences substituted by values. Some
24014 escape sequences take arguments. You can specify arguments inside
24015 ``@{@}'' immediately following the escape sequence.
24017 The escape sequences you can pass to this function are:
24021 Substitute a backslash.
24023 Substitute an ESC character.
24025 Substitute the selected frame; an argument names a frame parameter.
24027 Substitute a newline.
24029 Substitute a parameter's value; the argument names the parameter.
24031 Substitute a carriage return.
24033 Substitute the selected thread; an argument names a thread parameter.
24035 Substitute the version of GDB.
24037 Substitute the current working directory.
24039 Begin a sequence of non-printing characters. These sequences are
24040 typically used with the ESC character, and are not counted in the string
24041 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
24042 blue-colored ``(gdb)'' prompt where the length is five.
24044 End a sequence of non-printing characters.
24050 substitute_prompt (``frame: \f,
24051 print arguments: \p@{print frame-arguments@}'')
24054 @exdent will return the string:
24057 "frame: main, print arguments: scalars"
24062 @chapter Command Interpreters
24063 @cindex command interpreters
24065 @value{GDBN} supports multiple command interpreters, and some command
24066 infrastructure to allow users or user interface writers to switch
24067 between interpreters or run commands in other interpreters.
24069 @value{GDBN} currently supports two command interpreters, the console
24070 interpreter (sometimes called the command-line interpreter or @sc{cli})
24071 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24072 describes both of these interfaces in great detail.
24074 By default, @value{GDBN} will start with the console interpreter.
24075 However, the user may choose to start @value{GDBN} with another
24076 interpreter by specifying the @option{-i} or @option{--interpreter}
24077 startup options. Defined interpreters include:
24081 @cindex console interpreter
24082 The traditional console or command-line interpreter. This is the most often
24083 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24084 @value{GDBN} will use this interpreter.
24087 @cindex mi interpreter
24088 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24089 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24090 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24094 @cindex mi2 interpreter
24095 The current @sc{gdb/mi} interface.
24098 @cindex mi1 interpreter
24099 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24103 @cindex invoke another interpreter
24104 The interpreter being used by @value{GDBN} may not be dynamically
24105 switched at runtime. Although possible, this could lead to a very
24106 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24107 enters the command "interpreter-set console" in a console view,
24108 @value{GDBN} would switch to using the console interpreter, rendering
24109 the IDE inoperable!
24111 @kindex interpreter-exec
24112 Although you may only choose a single interpreter at startup, you may execute
24113 commands in any interpreter from the current interpreter using the appropriate
24114 command. If you are running the console interpreter, simply use the
24115 @code{interpreter-exec} command:
24118 interpreter-exec mi "-data-list-register-names"
24121 @sc{gdb/mi} has a similar command, although it is only available in versions of
24122 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24125 @chapter @value{GDBN} Text User Interface
24127 @cindex Text User Interface
24130 * TUI Overview:: TUI overview
24131 * TUI Keys:: TUI key bindings
24132 * TUI Single Key Mode:: TUI single key mode
24133 * TUI Commands:: TUI-specific commands
24134 * TUI Configuration:: TUI configuration variables
24137 The @value{GDBN} Text User Interface (TUI) is a terminal
24138 interface which uses the @code{curses} library to show the source
24139 file, the assembly output, the program registers and @value{GDBN}
24140 commands in separate text windows. The TUI mode is supported only
24141 on platforms where a suitable version of the @code{curses} library
24144 @pindex @value{GDBTUI}
24145 The TUI mode is enabled by default when you invoke @value{GDBN} as
24146 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
24147 You can also switch in and out of TUI mode while @value{GDBN} runs by
24148 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24149 @xref{TUI Keys, ,TUI Key Bindings}.
24152 @section TUI Overview
24154 In TUI mode, @value{GDBN} can display several text windows:
24158 This window is the @value{GDBN} command window with the @value{GDBN}
24159 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24160 managed using readline.
24163 The source window shows the source file of the program. The current
24164 line and active breakpoints are displayed in this window.
24167 The assembly window shows the disassembly output of the program.
24170 This window shows the processor registers. Registers are highlighted
24171 when their values change.
24174 The source and assembly windows show the current program position
24175 by highlighting the current line and marking it with a @samp{>} marker.
24176 Breakpoints are indicated with two markers. The first marker
24177 indicates the breakpoint type:
24181 Breakpoint which was hit at least once.
24184 Breakpoint which was never hit.
24187 Hardware breakpoint which was hit at least once.
24190 Hardware breakpoint which was never hit.
24193 The second marker indicates whether the breakpoint is enabled or not:
24197 Breakpoint is enabled.
24200 Breakpoint is disabled.
24203 The source, assembly and register windows are updated when the current
24204 thread changes, when the frame changes, or when the program counter
24207 These windows are not all visible at the same time. The command
24208 window is always visible. The others can be arranged in several
24219 source and assembly,
24222 source and registers, or
24225 assembly and registers.
24228 A status line above the command window shows the following information:
24232 Indicates the current @value{GDBN} target.
24233 (@pxref{Targets, ,Specifying a Debugging Target}).
24236 Gives the current process or thread number.
24237 When no process is being debugged, this field is set to @code{No process}.
24240 Gives the current function name for the selected frame.
24241 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24242 When there is no symbol corresponding to the current program counter,
24243 the string @code{??} is displayed.
24246 Indicates the current line number for the selected frame.
24247 When the current line number is not known, the string @code{??} is displayed.
24250 Indicates the current program counter address.
24254 @section TUI Key Bindings
24255 @cindex TUI key bindings
24257 The TUI installs several key bindings in the readline keymaps
24258 @ifset SYSTEM_READLINE
24259 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24261 @ifclear SYSTEM_READLINE
24262 (@pxref{Command Line Editing}).
24264 The following key bindings are installed for both TUI mode and the
24265 @value{GDBN} standard mode.
24274 Enter or leave the TUI mode. When leaving the TUI mode,
24275 the curses window management stops and @value{GDBN} operates using
24276 its standard mode, writing on the terminal directly. When reentering
24277 the TUI mode, control is given back to the curses windows.
24278 The screen is then refreshed.
24282 Use a TUI layout with only one window. The layout will
24283 either be @samp{source} or @samp{assembly}. When the TUI mode
24284 is not active, it will switch to the TUI mode.
24286 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24290 Use a TUI layout with at least two windows. When the current
24291 layout already has two windows, the next layout with two windows is used.
24292 When a new layout is chosen, one window will always be common to the
24293 previous layout and the new one.
24295 Think of it as the Emacs @kbd{C-x 2} binding.
24299 Change the active window. The TUI associates several key bindings
24300 (like scrolling and arrow keys) with the active window. This command
24301 gives the focus to the next TUI window.
24303 Think of it as the Emacs @kbd{C-x o} binding.
24307 Switch in and out of the TUI SingleKey mode that binds single
24308 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24311 The following key bindings only work in the TUI mode:
24316 Scroll the active window one page up.
24320 Scroll the active window one page down.
24324 Scroll the active window one line up.
24328 Scroll the active window one line down.
24332 Scroll the active window one column left.
24336 Scroll the active window one column right.
24340 Refresh the screen.
24343 Because the arrow keys scroll the active window in the TUI mode, they
24344 are not available for their normal use by readline unless the command
24345 window has the focus. When another window is active, you must use
24346 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24347 and @kbd{C-f} to control the command window.
24349 @node TUI Single Key Mode
24350 @section TUI Single Key Mode
24351 @cindex TUI single key mode
24353 The TUI also provides a @dfn{SingleKey} mode, which binds several
24354 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24355 switch into this mode, where the following key bindings are used:
24358 @kindex c @r{(SingleKey TUI key)}
24362 @kindex d @r{(SingleKey TUI key)}
24366 @kindex f @r{(SingleKey TUI key)}
24370 @kindex n @r{(SingleKey TUI key)}
24374 @kindex q @r{(SingleKey TUI key)}
24376 exit the SingleKey mode.
24378 @kindex r @r{(SingleKey TUI key)}
24382 @kindex s @r{(SingleKey TUI key)}
24386 @kindex u @r{(SingleKey TUI key)}
24390 @kindex v @r{(SingleKey TUI key)}
24394 @kindex w @r{(SingleKey TUI key)}
24399 Other keys temporarily switch to the @value{GDBN} command prompt.
24400 The key that was pressed is inserted in the editing buffer so that
24401 it is possible to type most @value{GDBN} commands without interaction
24402 with the TUI SingleKey mode. Once the command is entered the TUI
24403 SingleKey mode is restored. The only way to permanently leave
24404 this mode is by typing @kbd{q} or @kbd{C-x s}.
24408 @section TUI-specific Commands
24409 @cindex TUI commands
24411 The TUI has specific commands to control the text windows.
24412 These commands are always available, even when @value{GDBN} is not in
24413 the TUI mode. When @value{GDBN} is in the standard mode, most
24414 of these commands will automatically switch to the TUI mode.
24416 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24417 terminal, or @value{GDBN} has been started with the machine interface
24418 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24419 these commands will fail with an error, because it would not be
24420 possible or desirable to enable curses window management.
24425 List and give the size of all displayed windows.
24429 Display the next layout.
24432 Display the previous layout.
24435 Display the source window only.
24438 Display the assembly window only.
24441 Display the source and assembly window.
24444 Display the register window together with the source or assembly window.
24448 Make the next window active for scrolling.
24451 Make the previous window active for scrolling.
24454 Make the source window active for scrolling.
24457 Make the assembly window active for scrolling.
24460 Make the register window active for scrolling.
24463 Make the command window active for scrolling.
24467 Refresh the screen. This is similar to typing @kbd{C-L}.
24469 @item tui reg float
24471 Show the floating point registers in the register window.
24473 @item tui reg general
24474 Show the general registers in the register window.
24477 Show the next register group. The list of register groups as well as
24478 their order is target specific. The predefined register groups are the
24479 following: @code{general}, @code{float}, @code{system}, @code{vector},
24480 @code{all}, @code{save}, @code{restore}.
24482 @item tui reg system
24483 Show the system registers in the register window.
24487 Update the source window and the current execution point.
24489 @item winheight @var{name} +@var{count}
24490 @itemx winheight @var{name} -@var{count}
24492 Change the height of the window @var{name} by @var{count}
24493 lines. Positive counts increase the height, while negative counts
24496 @item tabset @var{nchars}
24498 Set the width of tab stops to be @var{nchars} characters.
24501 @node TUI Configuration
24502 @section TUI Configuration Variables
24503 @cindex TUI configuration variables
24505 Several configuration variables control the appearance of TUI windows.
24508 @item set tui border-kind @var{kind}
24509 @kindex set tui border-kind
24510 Select the border appearance for the source, assembly and register windows.
24511 The possible values are the following:
24514 Use a space character to draw the border.
24517 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
24520 Use the Alternate Character Set to draw the border. The border is
24521 drawn using character line graphics if the terminal supports them.
24524 @item set tui border-mode @var{mode}
24525 @kindex set tui border-mode
24526 @itemx set tui active-border-mode @var{mode}
24527 @kindex set tui active-border-mode
24528 Select the display attributes for the borders of the inactive windows
24529 or the active window. The @var{mode} can be one of the following:
24532 Use normal attributes to display the border.
24538 Use reverse video mode.
24541 Use half bright mode.
24543 @item half-standout
24544 Use half bright and standout mode.
24547 Use extra bright or bold mode.
24549 @item bold-standout
24550 Use extra bright or bold and standout mode.
24555 @chapter Using @value{GDBN} under @sc{gnu} Emacs
24558 @cindex @sc{gnu} Emacs
24559 A special interface allows you to use @sc{gnu} Emacs to view (and
24560 edit) the source files for the program you are debugging with
24563 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
24564 executable file you want to debug as an argument. This command starts
24565 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
24566 created Emacs buffer.
24567 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
24569 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
24574 All ``terminal'' input and output goes through an Emacs buffer, called
24577 This applies both to @value{GDBN} commands and their output, and to the input
24578 and output done by the program you are debugging.
24580 This is useful because it means that you can copy the text of previous
24581 commands and input them again; you can even use parts of the output
24584 All the facilities of Emacs' Shell mode are available for interacting
24585 with your program. In particular, you can send signals the usual
24586 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
24590 @value{GDBN} displays source code through Emacs.
24592 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
24593 source file for that frame and puts an arrow (@samp{=>}) at the
24594 left margin of the current line. Emacs uses a separate buffer for
24595 source display, and splits the screen to show both your @value{GDBN} session
24598 Explicit @value{GDBN} @code{list} or search commands still produce output as
24599 usual, but you probably have no reason to use them from Emacs.
24602 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
24603 a graphical mode, enabled by default, which provides further buffers
24604 that can control the execution and describe the state of your program.
24605 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
24607 If you specify an absolute file name when prompted for the @kbd{M-x
24608 gdb} argument, then Emacs sets your current working directory to where
24609 your program resides. If you only specify the file name, then Emacs
24610 sets your current working directory to the directory associated
24611 with the previous buffer. In this case, @value{GDBN} may find your
24612 program by searching your environment's @code{PATH} variable, but on
24613 some operating systems it might not find the source. So, although the
24614 @value{GDBN} input and output session proceeds normally, the auxiliary
24615 buffer does not display the current source and line of execution.
24617 The initial working directory of @value{GDBN} is printed on the top
24618 line of the GUD buffer and this serves as a default for the commands
24619 that specify files for @value{GDBN} to operate on. @xref{Files,
24620 ,Commands to Specify Files}.
24622 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
24623 need to call @value{GDBN} by a different name (for example, if you
24624 keep several configurations around, with different names) you can
24625 customize the Emacs variable @code{gud-gdb-command-name} to run the
24628 In the GUD buffer, you can use these special Emacs commands in
24629 addition to the standard Shell mode commands:
24633 Describe the features of Emacs' GUD Mode.
24636 Execute to another source line, like the @value{GDBN} @code{step} command; also
24637 update the display window to show the current file and location.
24640 Execute to next source line in this function, skipping all function
24641 calls, like the @value{GDBN} @code{next} command. Then update the display window
24642 to show the current file and location.
24645 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
24646 display window accordingly.
24649 Execute until exit from the selected stack frame, like the @value{GDBN}
24650 @code{finish} command.
24653 Continue execution of your program, like the @value{GDBN} @code{continue}
24657 Go up the number of frames indicated by the numeric argument
24658 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
24659 like the @value{GDBN} @code{up} command.
24662 Go down the number of frames indicated by the numeric argument, like the
24663 @value{GDBN} @code{down} command.
24666 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
24667 tells @value{GDBN} to set a breakpoint on the source line point is on.
24669 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
24670 separate frame which shows a backtrace when the GUD buffer is current.
24671 Move point to any frame in the stack and type @key{RET} to make it
24672 become the current frame and display the associated source in the
24673 source buffer. Alternatively, click @kbd{Mouse-2} to make the
24674 selected frame become the current one. In graphical mode, the
24675 speedbar displays watch expressions.
24677 If you accidentally delete the source-display buffer, an easy way to get
24678 it back is to type the command @code{f} in the @value{GDBN} buffer, to
24679 request a frame display; when you run under Emacs, this recreates
24680 the source buffer if necessary to show you the context of the current
24683 The source files displayed in Emacs are in ordinary Emacs buffers
24684 which are visiting the source files in the usual way. You can edit
24685 the files with these buffers if you wish; but keep in mind that @value{GDBN}
24686 communicates with Emacs in terms of line numbers. If you add or
24687 delete lines from the text, the line numbers that @value{GDBN} knows cease
24688 to correspond properly with the code.
24690 A more detailed description of Emacs' interaction with @value{GDBN} is
24691 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
24694 @c The following dropped because Epoch is nonstandard. Reactivate
24695 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
24697 @kindex Emacs Epoch environment
24701 Version 18 of @sc{gnu} Emacs has a built-in window system
24702 called the @code{epoch}
24703 environment. Users of this environment can use a new command,
24704 @code{inspect} which performs identically to @code{print} except that
24705 each value is printed in its own window.
24710 @chapter The @sc{gdb/mi} Interface
24712 @unnumberedsec Function and Purpose
24714 @cindex @sc{gdb/mi}, its purpose
24715 @sc{gdb/mi} is a line based machine oriented text interface to
24716 @value{GDBN} and is activated by specifying using the
24717 @option{--interpreter} command line option (@pxref{Mode Options}). It
24718 is specifically intended to support the development of systems which
24719 use the debugger as just one small component of a larger system.
24721 This chapter is a specification of the @sc{gdb/mi} interface. It is written
24722 in the form of a reference manual.
24724 Note that @sc{gdb/mi} is still under construction, so some of the
24725 features described below are incomplete and subject to change
24726 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
24728 @unnumberedsec Notation and Terminology
24730 @cindex notational conventions, for @sc{gdb/mi}
24731 This chapter uses the following notation:
24735 @code{|} separates two alternatives.
24738 @code{[ @var{something} ]} indicates that @var{something} is optional:
24739 it may or may not be given.
24742 @code{( @var{group} )*} means that @var{group} inside the parentheses
24743 may repeat zero or more times.
24746 @code{( @var{group} )+} means that @var{group} inside the parentheses
24747 may repeat one or more times.
24750 @code{"@var{string}"} means a literal @var{string}.
24754 @heading Dependencies
24758 * GDB/MI General Design::
24759 * GDB/MI Command Syntax::
24760 * GDB/MI Compatibility with CLI::
24761 * GDB/MI Development and Front Ends::
24762 * GDB/MI Output Records::
24763 * GDB/MI Simple Examples::
24764 * GDB/MI Command Description Format::
24765 * GDB/MI Breakpoint Commands::
24766 * GDB/MI Program Context::
24767 * GDB/MI Thread Commands::
24768 * GDB/MI Program Execution::
24769 * GDB/MI Stack Manipulation::
24770 * GDB/MI Variable Objects::
24771 * GDB/MI Data Manipulation::
24772 * GDB/MI Tracepoint Commands::
24773 * GDB/MI Symbol Query::
24774 * GDB/MI File Commands::
24776 * GDB/MI Kod Commands::
24777 * GDB/MI Memory Overlay Commands::
24778 * GDB/MI Signal Handling Commands::
24780 * GDB/MI Target Manipulation::
24781 * GDB/MI File Transfer Commands::
24782 * GDB/MI Miscellaneous Commands::
24785 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24786 @node GDB/MI General Design
24787 @section @sc{gdb/mi} General Design
24788 @cindex GDB/MI General Design
24790 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
24791 parts---commands sent to @value{GDBN}, responses to those commands
24792 and notifications. Each command results in exactly one response,
24793 indicating either successful completion of the command, or an error.
24794 For the commands that do not resume the target, the response contains the
24795 requested information. For the commands that resume the target, the
24796 response only indicates whether the target was successfully resumed.
24797 Notifications is the mechanism for reporting changes in the state of the
24798 target, or in @value{GDBN} state, that cannot conveniently be associated with
24799 a command and reported as part of that command response.
24801 The important examples of notifications are:
24805 Exec notifications. These are used to report changes in
24806 target state---when a target is resumed, or stopped. It would not
24807 be feasible to include this information in response of resuming
24808 commands, because one resume commands can result in multiple events in
24809 different threads. Also, quite some time may pass before any event
24810 happens in the target, while a frontend needs to know whether the resuming
24811 command itself was successfully executed.
24814 Console output, and status notifications. Console output
24815 notifications are used to report output of CLI commands, as well as
24816 diagnostics for other commands. Status notifications are used to
24817 report the progress of a long-running operation. Naturally, including
24818 this information in command response would mean no output is produced
24819 until the command is finished, which is undesirable.
24822 General notifications. Commands may have various side effects on
24823 the @value{GDBN} or target state beyond their official purpose. For example,
24824 a command may change the selected thread. Although such changes can
24825 be included in command response, using notification allows for more
24826 orthogonal frontend design.
24830 There's no guarantee that whenever an MI command reports an error,
24831 @value{GDBN} or the target are in any specific state, and especially,
24832 the state is not reverted to the state before the MI command was
24833 processed. Therefore, whenever an MI command results in an error,
24834 we recommend that the frontend refreshes all the information shown in
24835 the user interface.
24839 * Context management::
24840 * Asynchronous and non-stop modes::
24844 @node Context management
24845 @subsection Context management
24847 In most cases when @value{GDBN} accesses the target, this access is
24848 done in context of a specific thread and frame (@pxref{Frames}).
24849 Often, even when accessing global data, the target requires that a thread
24850 be specified. The CLI interface maintains the selected thread and frame,
24851 and supplies them to target on each command. This is convenient,
24852 because a command line user would not want to specify that information
24853 explicitly on each command, and because user interacts with
24854 @value{GDBN} via a single terminal, so no confusion is possible as
24855 to what thread and frame are the current ones.
24857 In the case of MI, the concept of selected thread and frame is less
24858 useful. First, a frontend can easily remember this information
24859 itself. Second, a graphical frontend can have more than one window,
24860 each one used for debugging a different thread, and the frontend might
24861 want to access additional threads for internal purposes. This
24862 increases the risk that by relying on implicitly selected thread, the
24863 frontend may be operating on a wrong one. Therefore, each MI command
24864 should explicitly specify which thread and frame to operate on. To
24865 make it possible, each MI command accepts the @samp{--thread} and
24866 @samp{--frame} options, the value to each is @value{GDBN} identifier
24867 for thread and frame to operate on.
24869 Usually, each top-level window in a frontend allows the user to select
24870 a thread and a frame, and remembers the user selection for further
24871 operations. However, in some cases @value{GDBN} may suggest that the
24872 current thread be changed. For example, when stopping on a breakpoint
24873 it is reasonable to switch to the thread where breakpoint is hit. For
24874 another example, if the user issues the CLI @samp{thread} command via
24875 the frontend, it is desirable to change the frontend's selected thread to the
24876 one specified by user. @value{GDBN} communicates the suggestion to
24877 change current thread using the @samp{=thread-selected} notification.
24878 No such notification is available for the selected frame at the moment.
24880 Note that historically, MI shares the selected thread with CLI, so
24881 frontends used the @code{-thread-select} to execute commands in the
24882 right context. However, getting this to work right is cumbersome. The
24883 simplest way is for frontend to emit @code{-thread-select} command
24884 before every command. This doubles the number of commands that need
24885 to be sent. The alternative approach is to suppress @code{-thread-select}
24886 if the selected thread in @value{GDBN} is supposed to be identical to the
24887 thread the frontend wants to operate on. However, getting this
24888 optimization right can be tricky. In particular, if the frontend
24889 sends several commands to @value{GDBN}, and one of the commands changes the
24890 selected thread, then the behaviour of subsequent commands will
24891 change. So, a frontend should either wait for response from such
24892 problematic commands, or explicitly add @code{-thread-select} for
24893 all subsequent commands. No frontend is known to do this exactly
24894 right, so it is suggested to just always pass the @samp{--thread} and
24895 @samp{--frame} options.
24897 @node Asynchronous and non-stop modes
24898 @subsection Asynchronous command execution and non-stop mode
24900 On some targets, @value{GDBN} is capable of processing MI commands
24901 even while the target is running. This is called @dfn{asynchronous
24902 command execution} (@pxref{Background Execution}). The frontend may
24903 specify a preferrence for asynchronous execution using the
24904 @code{-gdb-set target-async 1} command, which should be emitted before
24905 either running the executable or attaching to the target. After the
24906 frontend has started the executable or attached to the target, it can
24907 find if asynchronous execution is enabled using the
24908 @code{-list-target-features} command.
24910 Even if @value{GDBN} can accept a command while target is running,
24911 many commands that access the target do not work when the target is
24912 running. Therefore, asynchronous command execution is most useful
24913 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
24914 it is possible to examine the state of one thread, while other threads
24917 When a given thread is running, MI commands that try to access the
24918 target in the context of that thread may not work, or may work only on
24919 some targets. In particular, commands that try to operate on thread's
24920 stack will not work, on any target. Commands that read memory, or
24921 modify breakpoints, may work or not work, depending on the target. Note
24922 that even commands that operate on global state, such as @code{print},
24923 @code{set}, and breakpoint commands, still access the target in the
24924 context of a specific thread, so frontend should try to find a
24925 stopped thread and perform the operation on that thread (using the
24926 @samp{--thread} option).
24928 Which commands will work in the context of a running thread is
24929 highly target dependent. However, the two commands
24930 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
24931 to find the state of a thread, will always work.
24933 @node Thread groups
24934 @subsection Thread groups
24935 @value{GDBN} may be used to debug several processes at the same time.
24936 On some platfroms, @value{GDBN} may support debugging of several
24937 hardware systems, each one having several cores with several different
24938 processes running on each core. This section describes the MI
24939 mechanism to support such debugging scenarios.
24941 The key observation is that regardless of the structure of the
24942 target, MI can have a global list of threads, because most commands that
24943 accept the @samp{--thread} option do not need to know what process that
24944 thread belongs to. Therefore, it is not necessary to introduce
24945 neither additional @samp{--process} option, nor an notion of the
24946 current process in the MI interface. The only strictly new feature
24947 that is required is the ability to find how the threads are grouped
24950 To allow the user to discover such grouping, and to support arbitrary
24951 hierarchy of machines/cores/processes, MI introduces the concept of a
24952 @dfn{thread group}. Thread group is a collection of threads and other
24953 thread groups. A thread group always has a string identifier, a type,
24954 and may have additional attributes specific to the type. A new
24955 command, @code{-list-thread-groups}, returns the list of top-level
24956 thread groups, which correspond to processes that @value{GDBN} is
24957 debugging at the moment. By passing an identifier of a thread group
24958 to the @code{-list-thread-groups} command, it is possible to obtain
24959 the members of specific thread group.
24961 To allow the user to easily discover processes, and other objects, he
24962 wishes to debug, a concept of @dfn{available thread group} is
24963 introduced. Available thread group is an thread group that
24964 @value{GDBN} is not debugging, but that can be attached to, using the
24965 @code{-target-attach} command. The list of available top-level thread
24966 groups can be obtained using @samp{-list-thread-groups --available}.
24967 In general, the content of a thread group may be only retrieved only
24968 after attaching to that thread group.
24970 Thread groups are related to inferiors (@pxref{Inferiors and
24971 Programs}). Each inferior corresponds to a thread group of a special
24972 type @samp{process}, and some additional operations are permitted on
24973 such thread groups.
24975 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24976 @node GDB/MI Command Syntax
24977 @section @sc{gdb/mi} Command Syntax
24980 * GDB/MI Input Syntax::
24981 * GDB/MI Output Syntax::
24984 @node GDB/MI Input Syntax
24985 @subsection @sc{gdb/mi} Input Syntax
24987 @cindex input syntax for @sc{gdb/mi}
24988 @cindex @sc{gdb/mi}, input syntax
24990 @item @var{command} @expansion{}
24991 @code{@var{cli-command} | @var{mi-command}}
24993 @item @var{cli-command} @expansion{}
24994 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
24995 @var{cli-command} is any existing @value{GDBN} CLI command.
24997 @item @var{mi-command} @expansion{}
24998 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
24999 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25001 @item @var{token} @expansion{}
25002 "any sequence of digits"
25004 @item @var{option} @expansion{}
25005 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25007 @item @var{parameter} @expansion{}
25008 @code{@var{non-blank-sequence} | @var{c-string}}
25010 @item @var{operation} @expansion{}
25011 @emph{any of the operations described in this chapter}
25013 @item @var{non-blank-sequence} @expansion{}
25014 @emph{anything, provided it doesn't contain special characters such as
25015 "-", @var{nl}, """ and of course " "}
25017 @item @var{c-string} @expansion{}
25018 @code{""" @var{seven-bit-iso-c-string-content} """}
25020 @item @var{nl} @expansion{}
25029 The CLI commands are still handled by the @sc{mi} interpreter; their
25030 output is described below.
25033 The @code{@var{token}}, when present, is passed back when the command
25037 Some @sc{mi} commands accept optional arguments as part of the parameter
25038 list. Each option is identified by a leading @samp{-} (dash) and may be
25039 followed by an optional argument parameter. Options occur first in the
25040 parameter list and can be delimited from normal parameters using
25041 @samp{--} (this is useful when some parameters begin with a dash).
25048 We want easy access to the existing CLI syntax (for debugging).
25051 We want it to be easy to spot a @sc{mi} operation.
25054 @node GDB/MI Output Syntax
25055 @subsection @sc{gdb/mi} Output Syntax
25057 @cindex output syntax of @sc{gdb/mi}
25058 @cindex @sc{gdb/mi}, output syntax
25059 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25060 followed, optionally, by a single result record. This result record
25061 is for the most recent command. The sequence of output records is
25062 terminated by @samp{(gdb)}.
25064 If an input command was prefixed with a @code{@var{token}} then the
25065 corresponding output for that command will also be prefixed by that same
25069 @item @var{output} @expansion{}
25070 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25072 @item @var{result-record} @expansion{}
25073 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25075 @item @var{out-of-band-record} @expansion{}
25076 @code{@var{async-record} | @var{stream-record}}
25078 @item @var{async-record} @expansion{}
25079 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25081 @item @var{exec-async-output} @expansion{}
25082 @code{[ @var{token} ] "*" @var{async-output}}
25084 @item @var{status-async-output} @expansion{}
25085 @code{[ @var{token} ] "+" @var{async-output}}
25087 @item @var{notify-async-output} @expansion{}
25088 @code{[ @var{token} ] "=" @var{async-output}}
25090 @item @var{async-output} @expansion{}
25091 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
25093 @item @var{result-class} @expansion{}
25094 @code{"done" | "running" | "connected" | "error" | "exit"}
25096 @item @var{async-class} @expansion{}
25097 @code{"stopped" | @var{others}} (where @var{others} will be added
25098 depending on the needs---this is still in development).
25100 @item @var{result} @expansion{}
25101 @code{ @var{variable} "=" @var{value}}
25103 @item @var{variable} @expansion{}
25104 @code{ @var{string} }
25106 @item @var{value} @expansion{}
25107 @code{ @var{const} | @var{tuple} | @var{list} }
25109 @item @var{const} @expansion{}
25110 @code{@var{c-string}}
25112 @item @var{tuple} @expansion{}
25113 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25115 @item @var{list} @expansion{}
25116 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25117 @var{result} ( "," @var{result} )* "]" }
25119 @item @var{stream-record} @expansion{}
25120 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25122 @item @var{console-stream-output} @expansion{}
25123 @code{"~" @var{c-string}}
25125 @item @var{target-stream-output} @expansion{}
25126 @code{"@@" @var{c-string}}
25128 @item @var{log-stream-output} @expansion{}
25129 @code{"&" @var{c-string}}
25131 @item @var{nl} @expansion{}
25134 @item @var{token} @expansion{}
25135 @emph{any sequence of digits}.
25143 All output sequences end in a single line containing a period.
25146 The @code{@var{token}} is from the corresponding request. Note that
25147 for all async output, while the token is allowed by the grammar and
25148 may be output by future versions of @value{GDBN} for select async
25149 output messages, it is generally omitted. Frontends should treat
25150 all async output as reporting general changes in the state of the
25151 target and there should be no need to associate async output to any
25155 @cindex status output in @sc{gdb/mi}
25156 @var{status-async-output} contains on-going status information about the
25157 progress of a slow operation. It can be discarded. All status output is
25158 prefixed by @samp{+}.
25161 @cindex async output in @sc{gdb/mi}
25162 @var{exec-async-output} contains asynchronous state change on the target
25163 (stopped, started, disappeared). All async output is prefixed by
25167 @cindex notify output in @sc{gdb/mi}
25168 @var{notify-async-output} contains supplementary information that the
25169 client should handle (e.g., a new breakpoint information). All notify
25170 output is prefixed by @samp{=}.
25173 @cindex console output in @sc{gdb/mi}
25174 @var{console-stream-output} is output that should be displayed as is in the
25175 console. It is the textual response to a CLI command. All the console
25176 output is prefixed by @samp{~}.
25179 @cindex target output in @sc{gdb/mi}
25180 @var{target-stream-output} is the output produced by the target program.
25181 All the target output is prefixed by @samp{@@}.
25184 @cindex log output in @sc{gdb/mi}
25185 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25186 instance messages that should be displayed as part of an error log. All
25187 the log output is prefixed by @samp{&}.
25190 @cindex list output in @sc{gdb/mi}
25191 New @sc{gdb/mi} commands should only output @var{lists} containing
25197 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25198 details about the various output records.
25200 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25201 @node GDB/MI Compatibility with CLI
25202 @section @sc{gdb/mi} Compatibility with CLI
25204 @cindex compatibility, @sc{gdb/mi} and CLI
25205 @cindex @sc{gdb/mi}, compatibility with CLI
25207 For the developers convenience CLI commands can be entered directly,
25208 but there may be some unexpected behaviour. For example, commands
25209 that query the user will behave as if the user replied yes, breakpoint
25210 command lists are not executed and some CLI commands, such as
25211 @code{if}, @code{when} and @code{define}, prompt for further input with
25212 @samp{>}, which is not valid MI output.
25214 This feature may be removed at some stage in the future and it is
25215 recommended that front ends use the @code{-interpreter-exec} command
25216 (@pxref{-interpreter-exec}).
25218 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25219 @node GDB/MI Development and Front Ends
25220 @section @sc{gdb/mi} Development and Front Ends
25221 @cindex @sc{gdb/mi} development
25223 The application which takes the MI output and presents the state of the
25224 program being debugged to the user is called a @dfn{front end}.
25226 Although @sc{gdb/mi} is still incomplete, it is currently being used
25227 by a variety of front ends to @value{GDBN}. This makes it difficult
25228 to introduce new functionality without breaking existing usage. This
25229 section tries to minimize the problems by describing how the protocol
25232 Some changes in MI need not break a carefully designed front end, and
25233 for these the MI version will remain unchanged. The following is a
25234 list of changes that may occur within one level, so front ends should
25235 parse MI output in a way that can handle them:
25239 New MI commands may be added.
25242 New fields may be added to the output of any MI command.
25245 The range of values for fields with specified values, e.g.,
25246 @code{in_scope} (@pxref{-var-update}) may be extended.
25248 @c The format of field's content e.g type prefix, may change so parse it
25249 @c at your own risk. Yes, in general?
25251 @c The order of fields may change? Shouldn't really matter but it might
25252 @c resolve inconsistencies.
25255 If the changes are likely to break front ends, the MI version level
25256 will be increased by one. This will allow the front end to parse the
25257 output according to the MI version. Apart from mi0, new versions of
25258 @value{GDBN} will not support old versions of MI and it will be the
25259 responsibility of the front end to work with the new one.
25261 @c Starting with mi3, add a new command -mi-version that prints the MI
25264 The best way to avoid unexpected changes in MI that might break your front
25265 end is to make your project known to @value{GDBN} developers and
25266 follow development on @email{gdb@@sourceware.org} and
25267 @email{gdb-patches@@sourceware.org}.
25268 @cindex mailing lists
25270 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25271 @node GDB/MI Output Records
25272 @section @sc{gdb/mi} Output Records
25275 * GDB/MI Result Records::
25276 * GDB/MI Stream Records::
25277 * GDB/MI Async Records::
25278 * GDB/MI Frame Information::
25279 * GDB/MI Thread Information::
25280 * GDB/MI Ada Exception Information::
25283 @node GDB/MI Result Records
25284 @subsection @sc{gdb/mi} Result Records
25286 @cindex result records in @sc{gdb/mi}
25287 @cindex @sc{gdb/mi}, result records
25288 In addition to a number of out-of-band notifications, the response to a
25289 @sc{gdb/mi} command includes one of the following result indications:
25293 @item "^done" [ "," @var{results} ]
25294 The synchronous operation was successful, @code{@var{results}} are the return
25299 This result record is equivalent to @samp{^done}. Historically, it
25300 was output instead of @samp{^done} if the command has resumed the
25301 target. This behaviour is maintained for backward compatibility, but
25302 all frontends should treat @samp{^done} and @samp{^running}
25303 identically and rely on the @samp{*running} output record to determine
25304 which threads are resumed.
25308 @value{GDBN} has connected to a remote target.
25310 @item "^error" "," @var{c-string}
25312 The operation failed. The @code{@var{c-string}} contains the corresponding
25317 @value{GDBN} has terminated.
25321 @node GDB/MI Stream Records
25322 @subsection @sc{gdb/mi} Stream Records
25324 @cindex @sc{gdb/mi}, stream records
25325 @cindex stream records in @sc{gdb/mi}
25326 @value{GDBN} internally maintains a number of output streams: the console, the
25327 target, and the log. The output intended for each of these streams is
25328 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25330 Each stream record begins with a unique @dfn{prefix character} which
25331 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25332 Syntax}). In addition to the prefix, each stream record contains a
25333 @code{@var{string-output}}. This is either raw text (with an implicit new
25334 line) or a quoted C string (which does not contain an implicit newline).
25337 @item "~" @var{string-output}
25338 The console output stream contains text that should be displayed in the
25339 CLI console window. It contains the textual responses to CLI commands.
25341 @item "@@" @var{string-output}
25342 The target output stream contains any textual output from the running
25343 target. This is only present when GDB's event loop is truly
25344 asynchronous, which is currently only the case for remote targets.
25346 @item "&" @var{string-output}
25347 The log stream contains debugging messages being produced by @value{GDBN}'s
25351 @node GDB/MI Async Records
25352 @subsection @sc{gdb/mi} Async Records
25354 @cindex async records in @sc{gdb/mi}
25355 @cindex @sc{gdb/mi}, async records
25356 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25357 additional changes that have occurred. Those changes can either be a
25358 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25359 target activity (e.g., target stopped).
25361 The following is the list of possible async records:
25365 @item *running,thread-id="@var{thread}"
25366 The target is now running. The @var{thread} field tells which
25367 specific thread is now running, and can be @samp{all} if all threads
25368 are running. The frontend should assume that no interaction with a
25369 running thread is possible after this notification is produced.
25370 The frontend should not assume that this notification is output
25371 only once for any command. @value{GDBN} may emit this notification
25372 several times, either for different threads, because it cannot resume
25373 all threads together, or even for a single thread, if the thread must
25374 be stepped though some code before letting it run freely.
25376 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25377 The target has stopped. The @var{reason} field can have one of the
25381 @item breakpoint-hit
25382 A breakpoint was reached.
25383 @item watchpoint-trigger
25384 A watchpoint was triggered.
25385 @item read-watchpoint-trigger
25386 A read watchpoint was triggered.
25387 @item access-watchpoint-trigger
25388 An access watchpoint was triggered.
25389 @item function-finished
25390 An -exec-finish or similar CLI command was accomplished.
25391 @item location-reached
25392 An -exec-until or similar CLI command was accomplished.
25393 @item watchpoint-scope
25394 A watchpoint has gone out of scope.
25395 @item end-stepping-range
25396 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25397 similar CLI command was accomplished.
25398 @item exited-signalled
25399 The inferior exited because of a signal.
25401 The inferior exited.
25402 @item exited-normally
25403 The inferior exited normally.
25404 @item signal-received
25405 A signal was received by the inferior.
25408 The @var{id} field identifies the thread that directly caused the stop
25409 -- for example by hitting a breakpoint. Depending on whether all-stop
25410 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25411 stop all threads, or only the thread that directly triggered the stop.
25412 If all threads are stopped, the @var{stopped} field will have the
25413 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25414 field will be a list of thread identifiers. Presently, this list will
25415 always include a single thread, but frontend should be prepared to see
25416 several threads in the list. The @var{core} field reports the
25417 processor core on which the stop event has happened. This field may be absent
25418 if such information is not available.
25420 @item =thread-group-added,id="@var{id}"
25421 @itemx =thread-group-removed,id="@var{id}"
25422 A thread group was either added or removed. The @var{id} field
25423 contains the @value{GDBN} identifier of the thread group. When a thread
25424 group is added, it generally might not be associated with a running
25425 process. When a thread group is removed, its id becomes invalid and
25426 cannot be used in any way.
25428 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25429 A thread group became associated with a running program,
25430 either because the program was just started or the thread group
25431 was attached to a program. The @var{id} field contains the
25432 @value{GDBN} identifier of the thread group. The @var{pid} field
25433 contains process identifier, specific to the operating system.
25435 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
25436 A thread group is no longer associated with a running program,
25437 either because the program has exited, or because it was detached
25438 from. The @var{id} field contains the @value{GDBN} identifier of the
25439 thread group. @var{code} is the exit code of the inferior; it exists
25440 only when the inferior exited with some code.
25442 @item =thread-created,id="@var{id}",group-id="@var{gid}"
25443 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
25444 A thread either was created, or has exited. The @var{id} field
25445 contains the @value{GDBN} identifier of the thread. The @var{gid}
25446 field identifies the thread group this thread belongs to.
25448 @item =thread-selected,id="@var{id}"
25449 Informs that the selected thread was changed as result of the last
25450 command. This notification is not emitted as result of @code{-thread-select}
25451 command but is emitted whenever an MI command that is not documented
25452 to change the selected thread actually changes it. In particular,
25453 invoking, directly or indirectly (via user-defined command), the CLI
25454 @code{thread} command, will generate this notification.
25456 We suggest that in response to this notification, front ends
25457 highlight the selected thread and cause subsequent commands to apply to
25460 @item =library-loaded,...
25461 Reports that a new library file was loaded by the program. This
25462 notification has 4 fields---@var{id}, @var{target-name},
25463 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
25464 opaque identifier of the library. For remote debugging case,
25465 @var{target-name} and @var{host-name} fields give the name of the
25466 library file on the target, and on the host respectively. For native
25467 debugging, both those fields have the same value. The
25468 @var{symbols-loaded} field is emitted only for backward compatibility
25469 and should not be relied on to convey any useful information. The
25470 @var{thread-group} field, if present, specifies the id of the thread
25471 group in whose context the library was loaded. If the field is
25472 absent, it means the library was loaded in the context of all present
25475 @item =library-unloaded,...
25476 Reports that a library was unloaded by the program. This notification
25477 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
25478 the same meaning as for the @code{=library-loaded} notification.
25479 The @var{thread-group} field, if present, specifies the id of the
25480 thread group in whose context the library was unloaded. If the field is
25481 absent, it means the library was unloaded in the context of all present
25484 @item =breakpoint-created,bkpt=@{...@}
25485 @itemx =breakpoint-modified,bkpt=@{...@}
25486 @itemx =breakpoint-deleted,bkpt=@{...@}
25487 Reports that a breakpoint was created, modified, or deleted,
25488 respectively. Only user-visible breakpoints are reported to the MI
25491 The @var{bkpt} argument is of the same form as returned by the various
25492 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
25494 Note that if a breakpoint is emitted in the result record of a
25495 command, then it will not also be emitted in an async record.
25499 @node GDB/MI Frame Information
25500 @subsection @sc{gdb/mi} Frame Information
25502 Response from many MI commands includes an information about stack
25503 frame. This information is a tuple that may have the following
25508 The level of the stack frame. The innermost frame has the level of
25509 zero. This field is always present.
25512 The name of the function corresponding to the frame. This field may
25513 be absent if @value{GDBN} is unable to determine the function name.
25516 The code address for the frame. This field is always present.
25519 The name of the source files that correspond to the frame's code
25520 address. This field may be absent.
25523 The source line corresponding to the frames' code address. This field
25527 The name of the binary file (either executable or shared library) the
25528 corresponds to the frame's code address. This field may be absent.
25532 @node GDB/MI Thread Information
25533 @subsection @sc{gdb/mi} Thread Information
25535 Whenever @value{GDBN} has to report an information about a thread, it
25536 uses a tuple with the following fields:
25540 The numeric id assigned to the thread by @value{GDBN}. This field is
25544 Target-specific string identifying the thread. This field is always present.
25547 Additional information about the thread provided by the target.
25548 It is supposed to be human-readable and not interpreted by the
25549 frontend. This field is optional.
25552 Either @samp{stopped} or @samp{running}, depending on whether the
25553 thread is presently running. This field is always present.
25556 The value of this field is an integer number of the processor core the
25557 thread was last seen on. This field is optional.
25560 @node GDB/MI Ada Exception Information
25561 @subsection @sc{gdb/mi} Ada Exception Information
25563 Whenever a @code{*stopped} record is emitted because the program
25564 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
25565 @value{GDBN} provides the name of the exception that was raised via
25566 the @code{exception-name} field.
25568 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25569 @node GDB/MI Simple Examples
25570 @section Simple Examples of @sc{gdb/mi} Interaction
25571 @cindex @sc{gdb/mi}, simple examples
25573 This subsection presents several simple examples of interaction using
25574 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
25575 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
25576 the output received from @sc{gdb/mi}.
25578 Note the line breaks shown in the examples are here only for
25579 readability, they don't appear in the real output.
25581 @subheading Setting a Breakpoint
25583 Setting a breakpoint generates synchronous output which contains detailed
25584 information of the breakpoint.
25587 -> -break-insert main
25588 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25589 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25590 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
25594 @subheading Program Execution
25596 Program execution generates asynchronous records and MI gives the
25597 reason that execution stopped.
25603 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
25604 frame=@{addr="0x08048564",func="main",
25605 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
25606 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
25611 <- *stopped,reason="exited-normally"
25615 @subheading Quitting @value{GDBN}
25617 Quitting @value{GDBN} just prints the result class @samp{^exit}.
25625 Please note that @samp{^exit} is printed immediately, but it might
25626 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
25627 performs necessary cleanups, including killing programs being debugged
25628 or disconnecting from debug hardware, so the frontend should wait till
25629 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
25630 fails to exit in reasonable time.
25632 @subheading A Bad Command
25634 Here's what happens if you pass a non-existent command:
25638 <- ^error,msg="Undefined MI command: rubbish"
25643 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25644 @node GDB/MI Command Description Format
25645 @section @sc{gdb/mi} Command Description Format
25647 The remaining sections describe blocks of commands. Each block of
25648 commands is laid out in a fashion similar to this section.
25650 @subheading Motivation
25652 The motivation for this collection of commands.
25654 @subheading Introduction
25656 A brief introduction to this collection of commands as a whole.
25658 @subheading Commands
25660 For each command in the block, the following is described:
25662 @subsubheading Synopsis
25665 -command @var{args}@dots{}
25668 @subsubheading Result
25670 @subsubheading @value{GDBN} Command
25672 The corresponding @value{GDBN} CLI command(s), if any.
25674 @subsubheading Example
25676 Example(s) formatted for readability. Some of the described commands have
25677 not been implemented yet and these are labeled N.A.@: (not available).
25680 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25681 @node GDB/MI Breakpoint Commands
25682 @section @sc{gdb/mi} Breakpoint Commands
25684 @cindex breakpoint commands for @sc{gdb/mi}
25685 @cindex @sc{gdb/mi}, breakpoint commands
25686 This section documents @sc{gdb/mi} commands for manipulating
25689 @subheading The @code{-break-after} Command
25690 @findex -break-after
25692 @subsubheading Synopsis
25695 -break-after @var{number} @var{count}
25698 The breakpoint number @var{number} is not in effect until it has been
25699 hit @var{count} times. To see how this is reflected in the output of
25700 the @samp{-break-list} command, see the description of the
25701 @samp{-break-list} command below.
25703 @subsubheading @value{GDBN} Command
25705 The corresponding @value{GDBN} command is @samp{ignore}.
25707 @subsubheading Example
25712 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25713 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25714 fullname="/home/foo/hello.c",line="5",times="0"@}
25721 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25722 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25723 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25724 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25725 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25726 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25727 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25728 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25729 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25730 line="5",times="0",ignore="3"@}]@}
25735 @subheading The @code{-break-catch} Command
25736 @findex -break-catch
25739 @subheading The @code{-break-commands} Command
25740 @findex -break-commands
25742 @subsubheading Synopsis
25745 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
25748 Specifies the CLI commands that should be executed when breakpoint
25749 @var{number} is hit. The parameters @var{command1} to @var{commandN}
25750 are the commands. If no command is specified, any previously-set
25751 commands are cleared. @xref{Break Commands}. Typical use of this
25752 functionality is tracing a program, that is, printing of values of
25753 some variables whenever breakpoint is hit and then continuing.
25755 @subsubheading @value{GDBN} Command
25757 The corresponding @value{GDBN} command is @samp{commands}.
25759 @subsubheading Example
25764 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25765 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25766 fullname="/home/foo/hello.c",line="5",times="0"@}
25768 -break-commands 1 "print v" "continue"
25773 @subheading The @code{-break-condition} Command
25774 @findex -break-condition
25776 @subsubheading Synopsis
25779 -break-condition @var{number} @var{expr}
25782 Breakpoint @var{number} will stop the program only if the condition in
25783 @var{expr} is true. The condition becomes part of the
25784 @samp{-break-list} output (see the description of the @samp{-break-list}
25787 @subsubheading @value{GDBN} Command
25789 The corresponding @value{GDBN} command is @samp{condition}.
25791 @subsubheading Example
25795 -break-condition 1 1
25799 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25800 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25801 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25802 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25803 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25804 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25805 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25806 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25807 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25808 line="5",cond="1",times="0",ignore="3"@}]@}
25812 @subheading The @code{-break-delete} Command
25813 @findex -break-delete
25815 @subsubheading Synopsis
25818 -break-delete ( @var{breakpoint} )+
25821 Delete the breakpoint(s) whose number(s) are specified in the argument
25822 list. This is obviously reflected in the breakpoint list.
25824 @subsubheading @value{GDBN} Command
25826 The corresponding @value{GDBN} command is @samp{delete}.
25828 @subsubheading Example
25836 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25837 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25838 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25839 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25840 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25841 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25842 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25847 @subheading The @code{-break-disable} Command
25848 @findex -break-disable
25850 @subsubheading Synopsis
25853 -break-disable ( @var{breakpoint} )+
25856 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
25857 break list is now set to @samp{n} for the named @var{breakpoint}(s).
25859 @subsubheading @value{GDBN} Command
25861 The corresponding @value{GDBN} command is @samp{disable}.
25863 @subsubheading Example
25871 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25872 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25873 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25874 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25875 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25876 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25877 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25878 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
25879 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25880 line="5",times="0"@}]@}
25884 @subheading The @code{-break-enable} Command
25885 @findex -break-enable
25887 @subsubheading Synopsis
25890 -break-enable ( @var{breakpoint} )+
25893 Enable (previously disabled) @var{breakpoint}(s).
25895 @subsubheading @value{GDBN} Command
25897 The corresponding @value{GDBN} command is @samp{enable}.
25899 @subsubheading Example
25907 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25908 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25909 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25910 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25911 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25912 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25913 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25914 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
25915 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25916 line="5",times="0"@}]@}
25920 @subheading The @code{-break-info} Command
25921 @findex -break-info
25923 @subsubheading Synopsis
25926 -break-info @var{breakpoint}
25930 Get information about a single breakpoint.
25932 @subsubheading @value{GDBN} Command
25934 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
25936 @subsubheading Example
25939 @subheading The @code{-break-insert} Command
25940 @findex -break-insert
25942 @subsubheading Synopsis
25945 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
25946 [ -c @var{condition} ] [ -i @var{ignore-count} ]
25947 [ -p @var{thread} ] [ @var{location} ]
25951 If specified, @var{location}, can be one of:
25958 @item filename:linenum
25959 @item filename:function
25963 The possible optional parameters of this command are:
25967 Insert a temporary breakpoint.
25969 Insert a hardware breakpoint.
25970 @item -c @var{condition}
25971 Make the breakpoint conditional on @var{condition}.
25972 @item -i @var{ignore-count}
25973 Initialize the @var{ignore-count}.
25975 If @var{location} cannot be parsed (for example if it
25976 refers to unknown files or functions), create a pending
25977 breakpoint. Without this flag, @value{GDBN} will report
25978 an error, and won't create a breakpoint, if @var{location}
25981 Create a disabled breakpoint.
25983 Create a tracepoint. @xref{Tracepoints}. When this parameter
25984 is used together with @samp{-h}, a fast tracepoint is created.
25987 @subsubheading Result
25989 The result is in the form:
25992 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
25993 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
25994 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
25995 times="@var{times}"@}
25999 where @var{number} is the @value{GDBN} number for this breakpoint,
26000 @var{funcname} is the name of the function where the breakpoint was
26001 inserted, @var{filename} is the name of the source file which contains
26002 this function, @var{lineno} is the source line number within that file
26003 and @var{times} the number of times that the breakpoint has been hit
26004 (always 0 for -break-insert but may be greater for -break-info or -break-list
26005 which use the same output).
26007 Note: this format is open to change.
26008 @c An out-of-band breakpoint instead of part of the result?
26010 @subsubheading @value{GDBN} Command
26012 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26013 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
26015 @subsubheading Example
26020 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26021 fullname="/home/foo/recursive2.c,line="4",times="0"@}
26023 -break-insert -t foo
26024 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26025 fullname="/home/foo/recursive2.c,line="11",times="0"@}
26028 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26029 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26030 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26031 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26032 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26033 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26034 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26035 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26036 addr="0x0001072c", func="main",file="recursive2.c",
26037 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
26038 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26039 addr="0x00010774",func="foo",file="recursive2.c",
26040 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
26042 -break-insert -r foo.*
26043 ~int foo(int, int);
26044 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26045 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
26049 @subheading The @code{-break-list} Command
26050 @findex -break-list
26052 @subsubheading Synopsis
26058 Displays the list of inserted breakpoints, showing the following fields:
26062 number of the breakpoint
26064 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26066 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26069 is the breakpoint enabled or no: @samp{y} or @samp{n}
26071 memory location at which the breakpoint is set
26073 logical location of the breakpoint, expressed by function name, file
26076 number of times the breakpoint has been hit
26079 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26080 @code{body} field is an empty list.
26082 @subsubheading @value{GDBN} Command
26084 The corresponding @value{GDBN} command is @samp{info break}.
26086 @subsubheading Example
26091 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26092 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26093 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26094 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26095 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26096 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26097 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26098 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26099 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
26100 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26101 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26102 line="13",times="0"@}]@}
26106 Here's an example of the result when there are no breakpoints:
26111 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26112 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26113 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26114 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26115 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26116 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26117 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26122 @subheading The @code{-break-passcount} Command
26123 @findex -break-passcount
26125 @subsubheading Synopsis
26128 -break-passcount @var{tracepoint-number} @var{passcount}
26131 Set the passcount for tracepoint @var{tracepoint-number} to
26132 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26133 is not a tracepoint, error is emitted. This corresponds to CLI
26134 command @samp{passcount}.
26136 @subheading The @code{-break-watch} Command
26137 @findex -break-watch
26139 @subsubheading Synopsis
26142 -break-watch [ -a | -r ]
26145 Create a watchpoint. With the @samp{-a} option it will create an
26146 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26147 read from or on a write to the memory location. With the @samp{-r}
26148 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26149 trigger only when the memory location is accessed for reading. Without
26150 either of the options, the watchpoint created is a regular watchpoint,
26151 i.e., it will trigger when the memory location is accessed for writing.
26152 @xref{Set Watchpoints, , Setting Watchpoints}.
26154 Note that @samp{-break-list} will report a single list of watchpoints and
26155 breakpoints inserted.
26157 @subsubheading @value{GDBN} Command
26159 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26162 @subsubheading Example
26164 Setting a watchpoint on a variable in the @code{main} function:
26169 ^done,wpt=@{number="2",exp="x"@}
26174 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26175 value=@{old="-268439212",new="55"@},
26176 frame=@{func="main",args=[],file="recursive2.c",
26177 fullname="/home/foo/bar/recursive2.c",line="5"@}
26181 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26182 the program execution twice: first for the variable changing value, then
26183 for the watchpoint going out of scope.
26188 ^done,wpt=@{number="5",exp="C"@}
26193 *stopped,reason="watchpoint-trigger",
26194 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
26195 frame=@{func="callee4",args=[],
26196 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26197 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26202 *stopped,reason="watchpoint-scope",wpnum="5",
26203 frame=@{func="callee3",args=[@{name="strarg",
26204 value="0x11940 \"A string argument.\""@}],
26205 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26206 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26210 Listing breakpoints and watchpoints, at different points in the program
26211 execution. Note that once the watchpoint goes out of scope, it is
26217 ^done,wpt=@{number="2",exp="C"@}
26220 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26221 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26222 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26223 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26224 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26225 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26226 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26227 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26228 addr="0x00010734",func="callee4",
26229 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26230 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
26231 bkpt=@{number="2",type="watchpoint",disp="keep",
26232 enabled="y",addr="",what="C",times="0"@}]@}
26237 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
26238 value=@{old="-276895068",new="3"@},
26239 frame=@{func="callee4",args=[],
26240 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26241 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26244 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26245 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26246 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26247 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26248 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26249 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26250 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26251 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26252 addr="0x00010734",func="callee4",
26253 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26254 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
26255 bkpt=@{number="2",type="watchpoint",disp="keep",
26256 enabled="y",addr="",what="C",times="-5"@}]@}
26260 ^done,reason="watchpoint-scope",wpnum="2",
26261 frame=@{func="callee3",args=[@{name="strarg",
26262 value="0x11940 \"A string argument.\""@}],
26263 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26264 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26267 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26268 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26269 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26270 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26271 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26272 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26273 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26274 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26275 addr="0x00010734",func="callee4",
26276 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26277 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
26282 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26283 @node GDB/MI Program Context
26284 @section @sc{gdb/mi} Program Context
26286 @subheading The @code{-exec-arguments} Command
26287 @findex -exec-arguments
26290 @subsubheading Synopsis
26293 -exec-arguments @var{args}
26296 Set the inferior program arguments, to be used in the next
26299 @subsubheading @value{GDBN} Command
26301 The corresponding @value{GDBN} command is @samp{set args}.
26303 @subsubheading Example
26307 -exec-arguments -v word
26314 @subheading The @code{-exec-show-arguments} Command
26315 @findex -exec-show-arguments
26317 @subsubheading Synopsis
26320 -exec-show-arguments
26323 Print the arguments of the program.
26325 @subsubheading @value{GDBN} Command
26327 The corresponding @value{GDBN} command is @samp{show args}.
26329 @subsubheading Example
26334 @subheading The @code{-environment-cd} Command
26335 @findex -environment-cd
26337 @subsubheading Synopsis
26340 -environment-cd @var{pathdir}
26343 Set @value{GDBN}'s working directory.
26345 @subsubheading @value{GDBN} Command
26347 The corresponding @value{GDBN} command is @samp{cd}.
26349 @subsubheading Example
26353 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26359 @subheading The @code{-environment-directory} Command
26360 @findex -environment-directory
26362 @subsubheading Synopsis
26365 -environment-directory [ -r ] [ @var{pathdir} ]+
26368 Add directories @var{pathdir} to beginning of search path for source files.
26369 If the @samp{-r} option is used, the search path is reset to the default
26370 search path. If directories @var{pathdir} are supplied in addition to the
26371 @samp{-r} option, the search path is first reset and then addition
26373 Multiple directories may be specified, separated by blanks. Specifying
26374 multiple directories in a single command
26375 results in the directories added to the beginning of the
26376 search path in the same order they were presented in the command.
26377 If blanks are needed as
26378 part of a directory name, double-quotes should be used around
26379 the name. In the command output, the path will show up separated
26380 by the system directory-separator character. The directory-separator
26381 character must not be used
26382 in any directory name.
26383 If no directories are specified, the current search path is displayed.
26385 @subsubheading @value{GDBN} Command
26387 The corresponding @value{GDBN} command is @samp{dir}.
26389 @subsubheading Example
26393 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26394 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26396 -environment-directory ""
26397 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26399 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
26400 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
26402 -environment-directory -r
26403 ^done,source-path="$cdir:$cwd"
26408 @subheading The @code{-environment-path} Command
26409 @findex -environment-path
26411 @subsubheading Synopsis
26414 -environment-path [ -r ] [ @var{pathdir} ]+
26417 Add directories @var{pathdir} to beginning of search path for object files.
26418 If the @samp{-r} option is used, the search path is reset to the original
26419 search path that existed at gdb start-up. If directories @var{pathdir} are
26420 supplied in addition to the
26421 @samp{-r} option, the search path is first reset and then addition
26423 Multiple directories may be specified, separated by blanks. Specifying
26424 multiple directories in a single command
26425 results in the directories added to the beginning of the
26426 search path in the same order they were presented in the command.
26427 If blanks are needed as
26428 part of a directory name, double-quotes should be used around
26429 the name. In the command output, the path will show up separated
26430 by the system directory-separator character. The directory-separator
26431 character must not be used
26432 in any directory name.
26433 If no directories are specified, the current path is displayed.
26436 @subsubheading @value{GDBN} Command
26438 The corresponding @value{GDBN} command is @samp{path}.
26440 @subsubheading Example
26445 ^done,path="/usr/bin"
26447 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
26448 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
26450 -environment-path -r /usr/local/bin
26451 ^done,path="/usr/local/bin:/usr/bin"
26456 @subheading The @code{-environment-pwd} Command
26457 @findex -environment-pwd
26459 @subsubheading Synopsis
26465 Show the current working directory.
26467 @subsubheading @value{GDBN} Command
26469 The corresponding @value{GDBN} command is @samp{pwd}.
26471 @subsubheading Example
26476 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
26480 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26481 @node GDB/MI Thread Commands
26482 @section @sc{gdb/mi} Thread Commands
26485 @subheading The @code{-thread-info} Command
26486 @findex -thread-info
26488 @subsubheading Synopsis
26491 -thread-info [ @var{thread-id} ]
26494 Reports information about either a specific thread, if
26495 the @var{thread-id} parameter is present, or about all
26496 threads. When printing information about all threads,
26497 also reports the current thread.
26499 @subsubheading @value{GDBN} Command
26501 The @samp{info thread} command prints the same information
26504 @subsubheading Result
26506 The result is a list of threads. The following attributes are
26507 defined for a given thread:
26511 This field exists only for the current thread. It has the value @samp{*}.
26514 The identifier that @value{GDBN} uses to refer to the thread.
26517 The identifier that the target uses to refer to the thread.
26520 Extra information about the thread, in a target-specific format. This
26524 The name of the thread. If the user specified a name using the
26525 @code{thread name} command, then this name is given. Otherwise, if
26526 @value{GDBN} can extract the thread name from the target, then that
26527 name is given. If @value{GDBN} cannot find the thread name, then this
26531 The stack frame currently executing in the thread.
26534 The thread's state. The @samp{state} field may have the following
26539 The thread is stopped. Frame information is available for stopped
26543 The thread is running. There's no frame information for running
26549 If @value{GDBN} can find the CPU core on which this thread is running,
26550 then this field is the core identifier. This field is optional.
26554 @subsubheading Example
26559 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
26560 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
26561 args=[]@},state="running"@},
26562 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
26563 frame=@{level="0",addr="0x0804891f",func="foo",
26564 args=[@{name="i",value="10"@}],
26565 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
26566 state="running"@}],
26567 current-thread-id="1"
26571 @subheading The @code{-thread-list-ids} Command
26572 @findex -thread-list-ids
26574 @subsubheading Synopsis
26580 Produces a list of the currently known @value{GDBN} thread ids. At the
26581 end of the list it also prints the total number of such threads.
26583 This command is retained for historical reasons, the
26584 @code{-thread-info} command should be used instead.
26586 @subsubheading @value{GDBN} Command
26588 Part of @samp{info threads} supplies the same information.
26590 @subsubheading Example
26595 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26596 current-thread-id="1",number-of-threads="3"
26601 @subheading The @code{-thread-select} Command
26602 @findex -thread-select
26604 @subsubheading Synopsis
26607 -thread-select @var{threadnum}
26610 Make @var{threadnum} the current thread. It prints the number of the new
26611 current thread, and the topmost frame for that thread.
26613 This command is deprecated in favor of explicitly using the
26614 @samp{--thread} option to each command.
26616 @subsubheading @value{GDBN} Command
26618 The corresponding @value{GDBN} command is @samp{thread}.
26620 @subsubheading Example
26627 *stopped,reason="end-stepping-range",thread-id="2",line="187",
26628 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
26632 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26633 number-of-threads="3"
26636 ^done,new-thread-id="3",
26637 frame=@{level="0",func="vprintf",
26638 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
26639 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
26643 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26644 @node GDB/MI Program Execution
26645 @section @sc{gdb/mi} Program Execution
26647 These are the asynchronous commands which generate the out-of-band
26648 record @samp{*stopped}. Currently @value{GDBN} only really executes
26649 asynchronously with remote targets and this interaction is mimicked in
26652 @subheading The @code{-exec-continue} Command
26653 @findex -exec-continue
26655 @subsubheading Synopsis
26658 -exec-continue [--reverse] [--all|--thread-group N]
26661 Resumes the execution of the inferior program, which will continue
26662 to execute until it reaches a debugger stop event. If the
26663 @samp{--reverse} option is specified, execution resumes in reverse until
26664 it reaches a stop event. Stop events may include
26667 breakpoints or watchpoints
26669 signals or exceptions
26671 the end of the process (or its beginning under @samp{--reverse})
26673 the end or beginning of a replay log if one is being used.
26675 In all-stop mode (@pxref{All-Stop
26676 Mode}), may resume only one thread, or all threads, depending on the
26677 value of the @samp{scheduler-locking} variable. If @samp{--all} is
26678 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
26679 ignored in all-stop mode. If the @samp{--thread-group} options is
26680 specified, then all threads in that thread group are resumed.
26682 @subsubheading @value{GDBN} Command
26684 The corresponding @value{GDBN} corresponding is @samp{continue}.
26686 @subsubheading Example
26693 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
26694 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
26700 @subheading The @code{-exec-finish} Command
26701 @findex -exec-finish
26703 @subsubheading Synopsis
26706 -exec-finish [--reverse]
26709 Resumes the execution of the inferior program until the current
26710 function is exited. Displays the results returned by the function.
26711 If the @samp{--reverse} option is specified, resumes the reverse
26712 execution of the inferior program until the point where current
26713 function was called.
26715 @subsubheading @value{GDBN} Command
26717 The corresponding @value{GDBN} command is @samp{finish}.
26719 @subsubheading Example
26721 Function returning @code{void}.
26728 *stopped,reason="function-finished",frame=@{func="main",args=[],
26729 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
26733 Function returning other than @code{void}. The name of the internal
26734 @value{GDBN} variable storing the result is printed, together with the
26741 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
26742 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
26743 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26744 gdb-result-var="$1",return-value="0"
26749 @subheading The @code{-exec-interrupt} Command
26750 @findex -exec-interrupt
26752 @subsubheading Synopsis
26755 -exec-interrupt [--all|--thread-group N]
26758 Interrupts the background execution of the target. Note how the token
26759 associated with the stop message is the one for the execution command
26760 that has been interrupted. The token for the interrupt itself only
26761 appears in the @samp{^done} output. If the user is trying to
26762 interrupt a non-running program, an error message will be printed.
26764 Note that when asynchronous execution is enabled, this command is
26765 asynchronous just like other execution commands. That is, first the
26766 @samp{^done} response will be printed, and the target stop will be
26767 reported after that using the @samp{*stopped} notification.
26769 In non-stop mode, only the context thread is interrupted by default.
26770 All threads (in all inferiors) will be interrupted if the
26771 @samp{--all} option is specified. If the @samp{--thread-group}
26772 option is specified, all threads in that group will be interrupted.
26774 @subsubheading @value{GDBN} Command
26776 The corresponding @value{GDBN} command is @samp{interrupt}.
26778 @subsubheading Example
26789 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
26790 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
26791 fullname="/home/foo/bar/try.c",line="13"@}
26796 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
26800 @subheading The @code{-exec-jump} Command
26803 @subsubheading Synopsis
26806 -exec-jump @var{location}
26809 Resumes execution of the inferior program at the location specified by
26810 parameter. @xref{Specify Location}, for a description of the
26811 different forms of @var{location}.
26813 @subsubheading @value{GDBN} Command
26815 The corresponding @value{GDBN} command is @samp{jump}.
26817 @subsubheading Example
26820 -exec-jump foo.c:10
26821 *running,thread-id="all"
26826 @subheading The @code{-exec-next} Command
26829 @subsubheading Synopsis
26832 -exec-next [--reverse]
26835 Resumes execution of the inferior program, stopping when the beginning
26836 of the next source line is reached.
26838 If the @samp{--reverse} option is specified, resumes reverse execution
26839 of the inferior program, stopping at the beginning of the previous
26840 source line. If you issue this command on the first line of a
26841 function, it will take you back to the caller of that function, to the
26842 source line where the function was called.
26845 @subsubheading @value{GDBN} Command
26847 The corresponding @value{GDBN} command is @samp{next}.
26849 @subsubheading Example
26855 *stopped,reason="end-stepping-range",line="8",file="hello.c"
26860 @subheading The @code{-exec-next-instruction} Command
26861 @findex -exec-next-instruction
26863 @subsubheading Synopsis
26866 -exec-next-instruction [--reverse]
26869 Executes one machine instruction. If the instruction is a function
26870 call, continues until the function returns. If the program stops at an
26871 instruction in the middle of a source line, the address will be
26874 If the @samp{--reverse} option is specified, resumes reverse execution
26875 of the inferior program, stopping at the previous instruction. If the
26876 previously executed instruction was a return from another function,
26877 it will continue to execute in reverse until the call to that function
26878 (from the current stack frame) is reached.
26880 @subsubheading @value{GDBN} Command
26882 The corresponding @value{GDBN} command is @samp{nexti}.
26884 @subsubheading Example
26888 -exec-next-instruction
26892 *stopped,reason="end-stepping-range",
26893 addr="0x000100d4",line="5",file="hello.c"
26898 @subheading The @code{-exec-return} Command
26899 @findex -exec-return
26901 @subsubheading Synopsis
26907 Makes current function return immediately. Doesn't execute the inferior.
26908 Displays the new current frame.
26910 @subsubheading @value{GDBN} Command
26912 The corresponding @value{GDBN} command is @samp{return}.
26914 @subsubheading Example
26918 200-break-insert callee4
26919 200^done,bkpt=@{number="1",addr="0x00010734",
26920 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
26925 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
26926 frame=@{func="callee4",args=[],
26927 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26928 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
26934 111^done,frame=@{level="0",func="callee3",
26935 args=[@{name="strarg",
26936 value="0x11940 \"A string argument.\""@}],
26937 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26938 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26943 @subheading The @code{-exec-run} Command
26946 @subsubheading Synopsis
26949 -exec-run [--all | --thread-group N]
26952 Starts execution of the inferior from the beginning. The inferior
26953 executes until either a breakpoint is encountered or the program
26954 exits. In the latter case the output will include an exit code, if
26955 the program has exited exceptionally.
26957 When no option is specified, the current inferior is started. If the
26958 @samp{--thread-group} option is specified, it should refer to a thread
26959 group of type @samp{process}, and that thread group will be started.
26960 If the @samp{--all} option is specified, then all inferiors will be started.
26962 @subsubheading @value{GDBN} Command
26964 The corresponding @value{GDBN} command is @samp{run}.
26966 @subsubheading Examples
26971 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
26976 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
26977 frame=@{func="main",args=[],file="recursive2.c",
26978 fullname="/home/foo/bar/recursive2.c",line="4"@}
26983 Program exited normally:
26991 *stopped,reason="exited-normally"
26996 Program exited exceptionally:
27004 *stopped,reason="exited",exit-code="01"
27008 Another way the program can terminate is if it receives a signal such as
27009 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27013 *stopped,reason="exited-signalled",signal-name="SIGINT",
27014 signal-meaning="Interrupt"
27018 @c @subheading -exec-signal
27021 @subheading The @code{-exec-step} Command
27024 @subsubheading Synopsis
27027 -exec-step [--reverse]
27030 Resumes execution of the inferior program, stopping when the beginning
27031 of the next source line is reached, if the next source line is not a
27032 function call. If it is, stop at the first instruction of the called
27033 function. If the @samp{--reverse} option is specified, resumes reverse
27034 execution of the inferior program, stopping at the beginning of the
27035 previously executed source line.
27037 @subsubheading @value{GDBN} Command
27039 The corresponding @value{GDBN} command is @samp{step}.
27041 @subsubheading Example
27043 Stepping into a function:
27049 *stopped,reason="end-stepping-range",
27050 frame=@{func="foo",args=[@{name="a",value="10"@},
27051 @{name="b",value="0"@}],file="recursive2.c",
27052 fullname="/home/foo/bar/recursive2.c",line="11"@}
27062 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
27067 @subheading The @code{-exec-step-instruction} Command
27068 @findex -exec-step-instruction
27070 @subsubheading Synopsis
27073 -exec-step-instruction [--reverse]
27076 Resumes the inferior which executes one machine instruction. If the
27077 @samp{--reverse} option is specified, resumes reverse execution of the
27078 inferior program, stopping at the previously executed instruction.
27079 The output, once @value{GDBN} has stopped, will vary depending on
27080 whether we have stopped in the middle of a source line or not. In the
27081 former case, the address at which the program stopped will be printed
27084 @subsubheading @value{GDBN} Command
27086 The corresponding @value{GDBN} command is @samp{stepi}.
27088 @subsubheading Example
27092 -exec-step-instruction
27096 *stopped,reason="end-stepping-range",
27097 frame=@{func="foo",args=[],file="try.c",
27098 fullname="/home/foo/bar/try.c",line="10"@}
27100 -exec-step-instruction
27104 *stopped,reason="end-stepping-range",
27105 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
27106 fullname="/home/foo/bar/try.c",line="10"@}
27111 @subheading The @code{-exec-until} Command
27112 @findex -exec-until
27114 @subsubheading Synopsis
27117 -exec-until [ @var{location} ]
27120 Executes the inferior until the @var{location} specified in the
27121 argument is reached. If there is no argument, the inferior executes
27122 until a source line greater than the current one is reached. The
27123 reason for stopping in this case will be @samp{location-reached}.
27125 @subsubheading @value{GDBN} Command
27127 The corresponding @value{GDBN} command is @samp{until}.
27129 @subsubheading Example
27133 -exec-until recursive2.c:6
27137 *stopped,reason="location-reached",frame=@{func="main",args=[],
27138 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
27143 @subheading -file-clear
27144 Is this going away????
27147 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27148 @node GDB/MI Stack Manipulation
27149 @section @sc{gdb/mi} Stack Manipulation Commands
27152 @subheading The @code{-stack-info-frame} Command
27153 @findex -stack-info-frame
27155 @subsubheading Synopsis
27161 Get info on the selected frame.
27163 @subsubheading @value{GDBN} Command
27165 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
27166 (without arguments).
27168 @subsubheading Example
27173 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
27174 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27175 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
27179 @subheading The @code{-stack-info-depth} Command
27180 @findex -stack-info-depth
27182 @subsubheading Synopsis
27185 -stack-info-depth [ @var{max-depth} ]
27188 Return the depth of the stack. If the integer argument @var{max-depth}
27189 is specified, do not count beyond @var{max-depth} frames.
27191 @subsubheading @value{GDBN} Command
27193 There's no equivalent @value{GDBN} command.
27195 @subsubheading Example
27197 For a stack with frame levels 0 through 11:
27204 -stack-info-depth 4
27207 -stack-info-depth 12
27210 -stack-info-depth 11
27213 -stack-info-depth 13
27218 @subheading The @code{-stack-list-arguments} Command
27219 @findex -stack-list-arguments
27221 @subsubheading Synopsis
27224 -stack-list-arguments @var{print-values}
27225 [ @var{low-frame} @var{high-frame} ]
27228 Display a list of the arguments for the frames between @var{low-frame}
27229 and @var{high-frame} (inclusive). If @var{low-frame} and
27230 @var{high-frame} are not provided, list the arguments for the whole
27231 call stack. If the two arguments are equal, show the single frame
27232 at the corresponding level. It is an error if @var{low-frame} is
27233 larger than the actual number of frames. On the other hand,
27234 @var{high-frame} may be larger than the actual number of frames, in
27235 which case only existing frames will be returned.
27237 If @var{print-values} is 0 or @code{--no-values}, print only the names of
27238 the variables; if it is 1 or @code{--all-values}, print also their
27239 values; and if it is 2 or @code{--simple-values}, print the name,
27240 type and value for simple data types, and the name and type for arrays,
27241 structures and unions.
27243 Use of this command to obtain arguments in a single frame is
27244 deprecated in favor of the @samp{-stack-list-variables} command.
27246 @subsubheading @value{GDBN} Command
27248 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
27249 @samp{gdb_get_args} command which partially overlaps with the
27250 functionality of @samp{-stack-list-arguments}.
27252 @subsubheading Example
27259 frame=@{level="0",addr="0x00010734",func="callee4",
27260 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27261 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
27262 frame=@{level="1",addr="0x0001076c",func="callee3",
27263 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27264 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
27265 frame=@{level="2",addr="0x0001078c",func="callee2",
27266 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27267 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
27268 frame=@{level="3",addr="0x000107b4",func="callee1",
27269 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27270 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
27271 frame=@{level="4",addr="0x000107e0",func="main",
27272 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27273 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
27275 -stack-list-arguments 0
27278 frame=@{level="0",args=[]@},
27279 frame=@{level="1",args=[name="strarg"]@},
27280 frame=@{level="2",args=[name="intarg",name="strarg"]@},
27281 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
27282 frame=@{level="4",args=[]@}]
27284 -stack-list-arguments 1
27287 frame=@{level="0",args=[]@},
27289 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27290 frame=@{level="2",args=[
27291 @{name="intarg",value="2"@},
27292 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27293 @{frame=@{level="3",args=[
27294 @{name="intarg",value="2"@},
27295 @{name="strarg",value="0x11940 \"A string argument.\""@},
27296 @{name="fltarg",value="3.5"@}]@},
27297 frame=@{level="4",args=[]@}]
27299 -stack-list-arguments 0 2 2
27300 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
27302 -stack-list-arguments 1 2 2
27303 ^done,stack-args=[frame=@{level="2",
27304 args=[@{name="intarg",value="2"@},
27305 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
27309 @c @subheading -stack-list-exception-handlers
27312 @subheading The @code{-stack-list-frames} Command
27313 @findex -stack-list-frames
27315 @subsubheading Synopsis
27318 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
27321 List the frames currently on the stack. For each frame it displays the
27326 The frame number, 0 being the topmost frame, i.e., the innermost function.
27328 The @code{$pc} value for that frame.
27332 File name of the source file where the function lives.
27333 @item @var{fullname}
27334 The full file name of the source file where the function lives.
27336 Line number corresponding to the @code{$pc}.
27338 The shared library where this function is defined. This is only given
27339 if the frame's function is not known.
27342 If invoked without arguments, this command prints a backtrace for the
27343 whole stack. If given two integer arguments, it shows the frames whose
27344 levels are between the two arguments (inclusive). If the two arguments
27345 are equal, it shows the single frame at the corresponding level. It is
27346 an error if @var{low-frame} is larger than the actual number of
27347 frames. On the other hand, @var{high-frame} may be larger than the
27348 actual number of frames, in which case only existing frames will be returned.
27350 @subsubheading @value{GDBN} Command
27352 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
27354 @subsubheading Example
27356 Full stack backtrace:
27362 [frame=@{level="0",addr="0x0001076c",func="foo",
27363 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
27364 frame=@{level="1",addr="0x000107a4",func="foo",
27365 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27366 frame=@{level="2",addr="0x000107a4",func="foo",
27367 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27368 frame=@{level="3",addr="0x000107a4",func="foo",
27369 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27370 frame=@{level="4",addr="0x000107a4",func="foo",
27371 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27372 frame=@{level="5",addr="0x000107a4",func="foo",
27373 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27374 frame=@{level="6",addr="0x000107a4",func="foo",
27375 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27376 frame=@{level="7",addr="0x000107a4",func="foo",
27377 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27378 frame=@{level="8",addr="0x000107a4",func="foo",
27379 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27380 frame=@{level="9",addr="0x000107a4",func="foo",
27381 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27382 frame=@{level="10",addr="0x000107a4",func="foo",
27383 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27384 frame=@{level="11",addr="0x00010738",func="main",
27385 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
27389 Show frames between @var{low_frame} and @var{high_frame}:
27393 -stack-list-frames 3 5
27395 [frame=@{level="3",addr="0x000107a4",func="foo",
27396 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27397 frame=@{level="4",addr="0x000107a4",func="foo",
27398 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27399 frame=@{level="5",addr="0x000107a4",func="foo",
27400 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27404 Show a single frame:
27408 -stack-list-frames 3 3
27410 [frame=@{level="3",addr="0x000107a4",func="foo",
27411 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27416 @subheading The @code{-stack-list-locals} Command
27417 @findex -stack-list-locals
27419 @subsubheading Synopsis
27422 -stack-list-locals @var{print-values}
27425 Display the local variable names for the selected frame. If
27426 @var{print-values} is 0 or @code{--no-values}, print only the names of
27427 the variables; if it is 1 or @code{--all-values}, print also their
27428 values; and if it is 2 or @code{--simple-values}, print the name,
27429 type and value for simple data types, and the name and type for arrays,
27430 structures and unions. In this last case, a frontend can immediately
27431 display the value of simple data types and create variable objects for
27432 other data types when the user wishes to explore their values in
27435 This command is deprecated in favor of the
27436 @samp{-stack-list-variables} command.
27438 @subsubheading @value{GDBN} Command
27440 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
27442 @subsubheading Example
27446 -stack-list-locals 0
27447 ^done,locals=[name="A",name="B",name="C"]
27449 -stack-list-locals --all-values
27450 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
27451 @{name="C",value="@{1, 2, 3@}"@}]
27452 -stack-list-locals --simple-values
27453 ^done,locals=[@{name="A",type="int",value="1"@},
27454 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
27458 @subheading The @code{-stack-list-variables} Command
27459 @findex -stack-list-variables
27461 @subsubheading Synopsis
27464 -stack-list-variables @var{print-values}
27467 Display the names of local variables and function arguments for the selected frame. If
27468 @var{print-values} is 0 or @code{--no-values}, print only the names of
27469 the variables; if it is 1 or @code{--all-values}, print also their
27470 values; and if it is 2 or @code{--simple-values}, print the name,
27471 type and value for simple data types, and the name and type for arrays,
27472 structures and unions.
27474 @subsubheading Example
27478 -stack-list-variables --thread 1 --frame 0 --all-values
27479 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
27484 @subheading The @code{-stack-select-frame} Command
27485 @findex -stack-select-frame
27487 @subsubheading Synopsis
27490 -stack-select-frame @var{framenum}
27493 Change the selected frame. Select a different frame @var{framenum} on
27496 This command in deprecated in favor of passing the @samp{--frame}
27497 option to every command.
27499 @subsubheading @value{GDBN} Command
27501 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
27502 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
27504 @subsubheading Example
27508 -stack-select-frame 2
27513 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27514 @node GDB/MI Variable Objects
27515 @section @sc{gdb/mi} Variable Objects
27519 @subheading Motivation for Variable Objects in @sc{gdb/mi}
27521 For the implementation of a variable debugger window (locals, watched
27522 expressions, etc.), we are proposing the adaptation of the existing code
27523 used by @code{Insight}.
27525 The two main reasons for that are:
27529 It has been proven in practice (it is already on its second generation).
27532 It will shorten development time (needless to say how important it is
27536 The original interface was designed to be used by Tcl code, so it was
27537 slightly changed so it could be used through @sc{gdb/mi}. This section
27538 describes the @sc{gdb/mi} operations that will be available and gives some
27539 hints about their use.
27541 @emph{Note}: In addition to the set of operations described here, we
27542 expect the @sc{gui} implementation of a variable window to require, at
27543 least, the following operations:
27546 @item @code{-gdb-show} @code{output-radix}
27547 @item @code{-stack-list-arguments}
27548 @item @code{-stack-list-locals}
27549 @item @code{-stack-select-frame}
27554 @subheading Introduction to Variable Objects
27556 @cindex variable objects in @sc{gdb/mi}
27558 Variable objects are "object-oriented" MI interface for examining and
27559 changing values of expressions. Unlike some other MI interfaces that
27560 work with expressions, variable objects are specifically designed for
27561 simple and efficient presentation in the frontend. A variable object
27562 is identified by string name. When a variable object is created, the
27563 frontend specifies the expression for that variable object. The
27564 expression can be a simple variable, or it can be an arbitrary complex
27565 expression, and can even involve CPU registers. After creating a
27566 variable object, the frontend can invoke other variable object
27567 operations---for example to obtain or change the value of a variable
27568 object, or to change display format.
27570 Variable objects have hierarchical tree structure. Any variable object
27571 that corresponds to a composite type, such as structure in C, has
27572 a number of child variable objects, for example corresponding to each
27573 element of a structure. A child variable object can itself have
27574 children, recursively. Recursion ends when we reach
27575 leaf variable objects, which always have built-in types. Child variable
27576 objects are created only by explicit request, so if a frontend
27577 is not interested in the children of a particular variable object, no
27578 child will be created.
27580 For a leaf variable object it is possible to obtain its value as a
27581 string, or set the value from a string. String value can be also
27582 obtained for a non-leaf variable object, but it's generally a string
27583 that only indicates the type of the object, and does not list its
27584 contents. Assignment to a non-leaf variable object is not allowed.
27586 A frontend does not need to read the values of all variable objects each time
27587 the program stops. Instead, MI provides an update command that lists all
27588 variable objects whose values has changed since the last update
27589 operation. This considerably reduces the amount of data that must
27590 be transferred to the frontend. As noted above, children variable
27591 objects are created on demand, and only leaf variable objects have a
27592 real value. As result, gdb will read target memory only for leaf
27593 variables that frontend has created.
27595 The automatic update is not always desirable. For example, a frontend
27596 might want to keep a value of some expression for future reference,
27597 and never update it. For another example, fetching memory is
27598 relatively slow for embedded targets, so a frontend might want
27599 to disable automatic update for the variables that are either not
27600 visible on the screen, or ``closed''. This is possible using so
27601 called ``frozen variable objects''. Such variable objects are never
27602 implicitly updated.
27604 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
27605 fixed variable object, the expression is parsed when the variable
27606 object is created, including associating identifiers to specific
27607 variables. The meaning of expression never changes. For a floating
27608 variable object the values of variables whose names appear in the
27609 expressions are re-evaluated every time in the context of the current
27610 frame. Consider this example:
27615 struct work_state state;
27622 If a fixed variable object for the @code{state} variable is created in
27623 this function, and we enter the recursive call, the variable
27624 object will report the value of @code{state} in the top-level
27625 @code{do_work} invocation. On the other hand, a floating variable
27626 object will report the value of @code{state} in the current frame.
27628 If an expression specified when creating a fixed variable object
27629 refers to a local variable, the variable object becomes bound to the
27630 thread and frame in which the variable object is created. When such
27631 variable object is updated, @value{GDBN} makes sure that the
27632 thread/frame combination the variable object is bound to still exists,
27633 and re-evaluates the variable object in context of that thread/frame.
27635 The following is the complete set of @sc{gdb/mi} operations defined to
27636 access this functionality:
27638 @multitable @columnfractions .4 .6
27639 @item @strong{Operation}
27640 @tab @strong{Description}
27642 @item @code{-enable-pretty-printing}
27643 @tab enable Python-based pretty-printing
27644 @item @code{-var-create}
27645 @tab create a variable object
27646 @item @code{-var-delete}
27647 @tab delete the variable object and/or its children
27648 @item @code{-var-set-format}
27649 @tab set the display format of this variable
27650 @item @code{-var-show-format}
27651 @tab show the display format of this variable
27652 @item @code{-var-info-num-children}
27653 @tab tells how many children this object has
27654 @item @code{-var-list-children}
27655 @tab return a list of the object's children
27656 @item @code{-var-info-type}
27657 @tab show the type of this variable object
27658 @item @code{-var-info-expression}
27659 @tab print parent-relative expression that this variable object represents
27660 @item @code{-var-info-path-expression}
27661 @tab print full expression that this variable object represents
27662 @item @code{-var-show-attributes}
27663 @tab is this variable editable? does it exist here?
27664 @item @code{-var-evaluate-expression}
27665 @tab get the value of this variable
27666 @item @code{-var-assign}
27667 @tab set the value of this variable
27668 @item @code{-var-update}
27669 @tab update the variable and its children
27670 @item @code{-var-set-frozen}
27671 @tab set frozeness attribute
27672 @item @code{-var-set-update-range}
27673 @tab set range of children to display on update
27676 In the next subsection we describe each operation in detail and suggest
27677 how it can be used.
27679 @subheading Description And Use of Operations on Variable Objects
27681 @subheading The @code{-enable-pretty-printing} Command
27682 @findex -enable-pretty-printing
27685 -enable-pretty-printing
27688 @value{GDBN} allows Python-based visualizers to affect the output of the
27689 MI variable object commands. However, because there was no way to
27690 implement this in a fully backward-compatible way, a front end must
27691 request that this functionality be enabled.
27693 Once enabled, this feature cannot be disabled.
27695 Note that if Python support has not been compiled into @value{GDBN},
27696 this command will still succeed (and do nothing).
27698 This feature is currently (as of @value{GDBN} 7.0) experimental, and
27699 may work differently in future versions of @value{GDBN}.
27701 @subheading The @code{-var-create} Command
27702 @findex -var-create
27704 @subsubheading Synopsis
27707 -var-create @{@var{name} | "-"@}
27708 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
27711 This operation creates a variable object, which allows the monitoring of
27712 a variable, the result of an expression, a memory cell or a CPU
27715 The @var{name} parameter is the string by which the object can be
27716 referenced. It must be unique. If @samp{-} is specified, the varobj
27717 system will generate a string ``varNNNNNN'' automatically. It will be
27718 unique provided that one does not specify @var{name} of that format.
27719 The command fails if a duplicate name is found.
27721 The frame under which the expression should be evaluated can be
27722 specified by @var{frame-addr}. A @samp{*} indicates that the current
27723 frame should be used. A @samp{@@} indicates that a floating variable
27724 object must be created.
27726 @var{expression} is any expression valid on the current language set (must not
27727 begin with a @samp{*}), or one of the following:
27731 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
27734 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
27737 @samp{$@var{regname}} --- a CPU register name
27740 @cindex dynamic varobj
27741 A varobj's contents may be provided by a Python-based pretty-printer. In this
27742 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
27743 have slightly different semantics in some cases. If the
27744 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
27745 will never create a dynamic varobj. This ensures backward
27746 compatibility for existing clients.
27748 @subsubheading Result
27750 This operation returns attributes of the newly-created varobj. These
27755 The name of the varobj.
27758 The number of children of the varobj. This number is not necessarily
27759 reliable for a dynamic varobj. Instead, you must examine the
27760 @samp{has_more} attribute.
27763 The varobj's scalar value. For a varobj whose type is some sort of
27764 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
27765 will not be interesting.
27768 The varobj's type. This is a string representation of the type, as
27769 would be printed by the @value{GDBN} CLI.
27772 If a variable object is bound to a specific thread, then this is the
27773 thread's identifier.
27776 For a dynamic varobj, this indicates whether there appear to be any
27777 children available. For a non-dynamic varobj, this will be 0.
27780 This attribute will be present and have the value @samp{1} if the
27781 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
27782 then this attribute will not be present.
27785 A dynamic varobj can supply a display hint to the front end. The
27786 value comes directly from the Python pretty-printer object's
27787 @code{display_hint} method. @xref{Pretty Printing API}.
27790 Typical output will look like this:
27793 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
27794 has_more="@var{has_more}"
27798 @subheading The @code{-var-delete} Command
27799 @findex -var-delete
27801 @subsubheading Synopsis
27804 -var-delete [ -c ] @var{name}
27807 Deletes a previously created variable object and all of its children.
27808 With the @samp{-c} option, just deletes the children.
27810 Returns an error if the object @var{name} is not found.
27813 @subheading The @code{-var-set-format} Command
27814 @findex -var-set-format
27816 @subsubheading Synopsis
27819 -var-set-format @var{name} @var{format-spec}
27822 Sets the output format for the value of the object @var{name} to be
27825 @anchor{-var-set-format}
27826 The syntax for the @var{format-spec} is as follows:
27829 @var{format-spec} @expansion{}
27830 @{binary | decimal | hexadecimal | octal | natural@}
27833 The natural format is the default format choosen automatically
27834 based on the variable type (like decimal for an @code{int}, hex
27835 for pointers, etc.).
27837 For a variable with children, the format is set only on the
27838 variable itself, and the children are not affected.
27840 @subheading The @code{-var-show-format} Command
27841 @findex -var-show-format
27843 @subsubheading Synopsis
27846 -var-show-format @var{name}
27849 Returns the format used to display the value of the object @var{name}.
27852 @var{format} @expansion{}
27857 @subheading The @code{-var-info-num-children} Command
27858 @findex -var-info-num-children
27860 @subsubheading Synopsis
27863 -var-info-num-children @var{name}
27866 Returns the number of children of a variable object @var{name}:
27872 Note that this number is not completely reliable for a dynamic varobj.
27873 It will return the current number of children, but more children may
27877 @subheading The @code{-var-list-children} Command
27878 @findex -var-list-children
27880 @subsubheading Synopsis
27883 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
27885 @anchor{-var-list-children}
27887 Return a list of the children of the specified variable object and
27888 create variable objects for them, if they do not already exist. With
27889 a single argument or if @var{print-values} has a value of 0 or
27890 @code{--no-values}, print only the names of the variables; if
27891 @var{print-values} is 1 or @code{--all-values}, also print their
27892 values; and if it is 2 or @code{--simple-values} print the name and
27893 value for simple data types and just the name for arrays, structures
27896 @var{from} and @var{to}, if specified, indicate the range of children
27897 to report. If @var{from} or @var{to} is less than zero, the range is
27898 reset and all children will be reported. Otherwise, children starting
27899 at @var{from} (zero-based) and up to and excluding @var{to} will be
27902 If a child range is requested, it will only affect the current call to
27903 @code{-var-list-children}, but not future calls to @code{-var-update}.
27904 For this, you must instead use @code{-var-set-update-range}. The
27905 intent of this approach is to enable a front end to implement any
27906 update approach it likes; for example, scrolling a view may cause the
27907 front end to request more children with @code{-var-list-children}, and
27908 then the front end could call @code{-var-set-update-range} with a
27909 different range to ensure that future updates are restricted to just
27912 For each child the following results are returned:
27917 Name of the variable object created for this child.
27920 The expression to be shown to the user by the front end to designate this child.
27921 For example this may be the name of a structure member.
27923 For a dynamic varobj, this value cannot be used to form an
27924 expression. There is no way to do this at all with a dynamic varobj.
27926 For C/C@t{++} structures there are several pseudo children returned to
27927 designate access qualifiers. For these pseudo children @var{exp} is
27928 @samp{public}, @samp{private}, or @samp{protected}. In this case the
27929 type and value are not present.
27931 A dynamic varobj will not report the access qualifying
27932 pseudo-children, regardless of the language. This information is not
27933 available at all with a dynamic varobj.
27936 Number of children this child has. For a dynamic varobj, this will be
27940 The type of the child.
27943 If values were requested, this is the value.
27946 If this variable object is associated with a thread, this is the thread id.
27947 Otherwise this result is not present.
27950 If the variable object is frozen, this variable will be present with a value of 1.
27953 The result may have its own attributes:
27957 A dynamic varobj can supply a display hint to the front end. The
27958 value comes directly from the Python pretty-printer object's
27959 @code{display_hint} method. @xref{Pretty Printing API}.
27962 This is an integer attribute which is nonzero if there are children
27963 remaining after the end of the selected range.
27966 @subsubheading Example
27970 -var-list-children n
27971 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
27972 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
27974 -var-list-children --all-values n
27975 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
27976 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
27980 @subheading The @code{-var-info-type} Command
27981 @findex -var-info-type
27983 @subsubheading Synopsis
27986 -var-info-type @var{name}
27989 Returns the type of the specified variable @var{name}. The type is
27990 returned as a string in the same format as it is output by the
27994 type=@var{typename}
27998 @subheading The @code{-var-info-expression} Command
27999 @findex -var-info-expression
28001 @subsubheading Synopsis
28004 -var-info-expression @var{name}
28007 Returns a string that is suitable for presenting this
28008 variable object in user interface. The string is generally
28009 not valid expression in the current language, and cannot be evaluated.
28011 For example, if @code{a} is an array, and variable object
28012 @code{A} was created for @code{a}, then we'll get this output:
28015 (gdb) -var-info-expression A.1
28016 ^done,lang="C",exp="1"
28020 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
28022 Note that the output of the @code{-var-list-children} command also
28023 includes those expressions, so the @code{-var-info-expression} command
28026 @subheading The @code{-var-info-path-expression} Command
28027 @findex -var-info-path-expression
28029 @subsubheading Synopsis
28032 -var-info-path-expression @var{name}
28035 Returns an expression that can be evaluated in the current
28036 context and will yield the same value that a variable object has.
28037 Compare this with the @code{-var-info-expression} command, which
28038 result can be used only for UI presentation. Typical use of
28039 the @code{-var-info-path-expression} command is creating a
28040 watchpoint from a variable object.
28042 This command is currently not valid for children of a dynamic varobj,
28043 and will give an error when invoked on one.
28045 For example, suppose @code{C} is a C@t{++} class, derived from class
28046 @code{Base}, and that the @code{Base} class has a member called
28047 @code{m_size}. Assume a variable @code{c} is has the type of
28048 @code{C} and a variable object @code{C} was created for variable
28049 @code{c}. Then, we'll get this output:
28051 (gdb) -var-info-path-expression C.Base.public.m_size
28052 ^done,path_expr=((Base)c).m_size)
28055 @subheading The @code{-var-show-attributes} Command
28056 @findex -var-show-attributes
28058 @subsubheading Synopsis
28061 -var-show-attributes @var{name}
28064 List attributes of the specified variable object @var{name}:
28067 status=@var{attr} [ ( ,@var{attr} )* ]
28071 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
28073 @subheading The @code{-var-evaluate-expression} Command
28074 @findex -var-evaluate-expression
28076 @subsubheading Synopsis
28079 -var-evaluate-expression [-f @var{format-spec}] @var{name}
28082 Evaluates the expression that is represented by the specified variable
28083 object and returns its value as a string. The format of the string
28084 can be specified with the @samp{-f} option. The possible values of
28085 this option are the same as for @code{-var-set-format}
28086 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
28087 the current display format will be used. The current display format
28088 can be changed using the @code{-var-set-format} command.
28094 Note that one must invoke @code{-var-list-children} for a variable
28095 before the value of a child variable can be evaluated.
28097 @subheading The @code{-var-assign} Command
28098 @findex -var-assign
28100 @subsubheading Synopsis
28103 -var-assign @var{name} @var{expression}
28106 Assigns the value of @var{expression} to the variable object specified
28107 by @var{name}. The object must be @samp{editable}. If the variable's
28108 value is altered by the assign, the variable will show up in any
28109 subsequent @code{-var-update} list.
28111 @subsubheading Example
28119 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
28123 @subheading The @code{-var-update} Command
28124 @findex -var-update
28126 @subsubheading Synopsis
28129 -var-update [@var{print-values}] @{@var{name} | "*"@}
28132 Reevaluate the expressions corresponding to the variable object
28133 @var{name} and all its direct and indirect children, and return the
28134 list of variable objects whose values have changed; @var{name} must
28135 be a root variable object. Here, ``changed'' means that the result of
28136 @code{-var-evaluate-expression} before and after the
28137 @code{-var-update} is different. If @samp{*} is used as the variable
28138 object names, all existing variable objects are updated, except
28139 for frozen ones (@pxref{-var-set-frozen}). The option
28140 @var{print-values} determines whether both names and values, or just
28141 names are printed. The possible values of this option are the same
28142 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
28143 recommended to use the @samp{--all-values} option, to reduce the
28144 number of MI commands needed on each program stop.
28146 With the @samp{*} parameter, if a variable object is bound to a
28147 currently running thread, it will not be updated, without any
28150 If @code{-var-set-update-range} was previously used on a varobj, then
28151 only the selected range of children will be reported.
28153 @code{-var-update} reports all the changed varobjs in a tuple named
28156 Each item in the change list is itself a tuple holding:
28160 The name of the varobj.
28163 If values were requested for this update, then this field will be
28164 present and will hold the value of the varobj.
28167 @anchor{-var-update}
28168 This field is a string which may take one of three values:
28172 The variable object's current value is valid.
28175 The variable object does not currently hold a valid value but it may
28176 hold one in the future if its associated expression comes back into
28180 The variable object no longer holds a valid value.
28181 This can occur when the executable file being debugged has changed,
28182 either through recompilation or by using the @value{GDBN} @code{file}
28183 command. The front end should normally choose to delete these variable
28187 In the future new values may be added to this list so the front should
28188 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
28191 This is only present if the varobj is still valid. If the type
28192 changed, then this will be the string @samp{true}; otherwise it will
28196 If the varobj's type changed, then this field will be present and will
28199 @item new_num_children
28200 For a dynamic varobj, if the number of children changed, or if the
28201 type changed, this will be the new number of children.
28203 The @samp{numchild} field in other varobj responses is generally not
28204 valid for a dynamic varobj -- it will show the number of children that
28205 @value{GDBN} knows about, but because dynamic varobjs lazily
28206 instantiate their children, this will not reflect the number of
28207 children which may be available.
28209 The @samp{new_num_children} attribute only reports changes to the
28210 number of children known by @value{GDBN}. This is the only way to
28211 detect whether an update has removed children (which necessarily can
28212 only happen at the end of the update range).
28215 The display hint, if any.
28218 This is an integer value, which will be 1 if there are more children
28219 available outside the varobj's update range.
28222 This attribute will be present and have the value @samp{1} if the
28223 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28224 then this attribute will not be present.
28227 If new children were added to a dynamic varobj within the selected
28228 update range (as set by @code{-var-set-update-range}), then they will
28229 be listed in this attribute.
28232 @subsubheading Example
28239 -var-update --all-values var1
28240 ^done,changelist=[@{name="var1",value="3",in_scope="true",
28241 type_changed="false"@}]
28245 @subheading The @code{-var-set-frozen} Command
28246 @findex -var-set-frozen
28247 @anchor{-var-set-frozen}
28249 @subsubheading Synopsis
28252 -var-set-frozen @var{name} @var{flag}
28255 Set the frozenness flag on the variable object @var{name}. The
28256 @var{flag} parameter should be either @samp{1} to make the variable
28257 frozen or @samp{0} to make it unfrozen. If a variable object is
28258 frozen, then neither itself, nor any of its children, are
28259 implicitly updated by @code{-var-update} of
28260 a parent variable or by @code{-var-update *}. Only
28261 @code{-var-update} of the variable itself will update its value and
28262 values of its children. After a variable object is unfrozen, it is
28263 implicitly updated by all subsequent @code{-var-update} operations.
28264 Unfreezing a variable does not update it, only subsequent
28265 @code{-var-update} does.
28267 @subsubheading Example
28271 -var-set-frozen V 1
28276 @subheading The @code{-var-set-update-range} command
28277 @findex -var-set-update-range
28278 @anchor{-var-set-update-range}
28280 @subsubheading Synopsis
28283 -var-set-update-range @var{name} @var{from} @var{to}
28286 Set the range of children to be returned by future invocations of
28287 @code{-var-update}.
28289 @var{from} and @var{to} indicate the range of children to report. If
28290 @var{from} or @var{to} is less than zero, the range is reset and all
28291 children will be reported. Otherwise, children starting at @var{from}
28292 (zero-based) and up to and excluding @var{to} will be reported.
28294 @subsubheading Example
28298 -var-set-update-range V 1 2
28302 @subheading The @code{-var-set-visualizer} command
28303 @findex -var-set-visualizer
28304 @anchor{-var-set-visualizer}
28306 @subsubheading Synopsis
28309 -var-set-visualizer @var{name} @var{visualizer}
28312 Set a visualizer for the variable object @var{name}.
28314 @var{visualizer} is the visualizer to use. The special value
28315 @samp{None} means to disable any visualizer in use.
28317 If not @samp{None}, @var{visualizer} must be a Python expression.
28318 This expression must evaluate to a callable object which accepts a
28319 single argument. @value{GDBN} will call this object with the value of
28320 the varobj @var{name} as an argument (this is done so that the same
28321 Python pretty-printing code can be used for both the CLI and MI).
28322 When called, this object must return an object which conforms to the
28323 pretty-printing interface (@pxref{Pretty Printing API}).
28325 The pre-defined function @code{gdb.default_visualizer} may be used to
28326 select a visualizer by following the built-in process
28327 (@pxref{Selecting Pretty-Printers}). This is done automatically when
28328 a varobj is created, and so ordinarily is not needed.
28330 This feature is only available if Python support is enabled. The MI
28331 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
28332 can be used to check this.
28334 @subsubheading Example
28336 Resetting the visualizer:
28340 -var-set-visualizer V None
28344 Reselecting the default (type-based) visualizer:
28348 -var-set-visualizer V gdb.default_visualizer
28352 Suppose @code{SomeClass} is a visualizer class. A lambda expression
28353 can be used to instantiate this class for a varobj:
28357 -var-set-visualizer V "lambda val: SomeClass()"
28361 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28362 @node GDB/MI Data Manipulation
28363 @section @sc{gdb/mi} Data Manipulation
28365 @cindex data manipulation, in @sc{gdb/mi}
28366 @cindex @sc{gdb/mi}, data manipulation
28367 This section describes the @sc{gdb/mi} commands that manipulate data:
28368 examine memory and registers, evaluate expressions, etc.
28370 @c REMOVED FROM THE INTERFACE.
28371 @c @subheading -data-assign
28372 @c Change the value of a program variable. Plenty of side effects.
28373 @c @subsubheading GDB Command
28375 @c @subsubheading Example
28378 @subheading The @code{-data-disassemble} Command
28379 @findex -data-disassemble
28381 @subsubheading Synopsis
28385 [ -s @var{start-addr} -e @var{end-addr} ]
28386 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
28394 @item @var{start-addr}
28395 is the beginning address (or @code{$pc})
28396 @item @var{end-addr}
28398 @item @var{filename}
28399 is the name of the file to disassemble
28400 @item @var{linenum}
28401 is the line number to disassemble around
28403 is the number of disassembly lines to be produced. If it is -1,
28404 the whole function will be disassembled, in case no @var{end-addr} is
28405 specified. If @var{end-addr} is specified as a non-zero value, and
28406 @var{lines} is lower than the number of disassembly lines between
28407 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
28408 displayed; if @var{lines} is higher than the number of lines between
28409 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
28412 is either 0 (meaning only disassembly), 1 (meaning mixed source and
28413 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
28414 mixed source and disassembly with raw opcodes).
28417 @subsubheading Result
28419 The output for each instruction is composed of four fields:
28428 Note that whatever included in the instruction field, is not manipulated
28429 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
28431 @subsubheading @value{GDBN} Command
28433 There's no direct mapping from this command to the CLI.
28435 @subsubheading Example
28437 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
28441 -data-disassemble -s $pc -e "$pc + 20" -- 0
28444 @{address="0x000107c0",func-name="main",offset="4",
28445 inst="mov 2, %o0"@},
28446 @{address="0x000107c4",func-name="main",offset="8",
28447 inst="sethi %hi(0x11800), %o2"@},
28448 @{address="0x000107c8",func-name="main",offset="12",
28449 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
28450 @{address="0x000107cc",func-name="main",offset="16",
28451 inst="sethi %hi(0x11800), %o2"@},
28452 @{address="0x000107d0",func-name="main",offset="20",
28453 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
28457 Disassemble the whole @code{main} function. Line 32 is part of
28461 -data-disassemble -f basics.c -l 32 -- 0
28463 @{address="0x000107bc",func-name="main",offset="0",
28464 inst="save %sp, -112, %sp"@},
28465 @{address="0x000107c0",func-name="main",offset="4",
28466 inst="mov 2, %o0"@},
28467 @{address="0x000107c4",func-name="main",offset="8",
28468 inst="sethi %hi(0x11800), %o2"@},
28470 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
28471 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
28475 Disassemble 3 instructions from the start of @code{main}:
28479 -data-disassemble -f basics.c -l 32 -n 3 -- 0
28481 @{address="0x000107bc",func-name="main",offset="0",
28482 inst="save %sp, -112, %sp"@},
28483 @{address="0x000107c0",func-name="main",offset="4",
28484 inst="mov 2, %o0"@},
28485 @{address="0x000107c4",func-name="main",offset="8",
28486 inst="sethi %hi(0x11800), %o2"@}]
28490 Disassemble 3 instructions from the start of @code{main} in mixed mode:
28494 -data-disassemble -f basics.c -l 32 -n 3 -- 1
28496 src_and_asm_line=@{line="31",
28497 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
28498 testsuite/gdb.mi/basics.c",line_asm_insn=[
28499 @{address="0x000107bc",func-name="main",offset="0",
28500 inst="save %sp, -112, %sp"@}]@},
28501 src_and_asm_line=@{line="32",
28502 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
28503 testsuite/gdb.mi/basics.c",line_asm_insn=[
28504 @{address="0x000107c0",func-name="main",offset="4",
28505 inst="mov 2, %o0"@},
28506 @{address="0x000107c4",func-name="main",offset="8",
28507 inst="sethi %hi(0x11800), %o2"@}]@}]
28512 @subheading The @code{-data-evaluate-expression} Command
28513 @findex -data-evaluate-expression
28515 @subsubheading Synopsis
28518 -data-evaluate-expression @var{expr}
28521 Evaluate @var{expr} as an expression. The expression could contain an
28522 inferior function call. The function call will execute synchronously.
28523 If the expression contains spaces, it must be enclosed in double quotes.
28525 @subsubheading @value{GDBN} Command
28527 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
28528 @samp{call}. In @code{gdbtk} only, there's a corresponding
28529 @samp{gdb_eval} command.
28531 @subsubheading Example
28533 In the following example, the numbers that precede the commands are the
28534 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
28535 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
28539 211-data-evaluate-expression A
28542 311-data-evaluate-expression &A
28543 311^done,value="0xefffeb7c"
28545 411-data-evaluate-expression A+3
28548 511-data-evaluate-expression "A + 3"
28554 @subheading The @code{-data-list-changed-registers} Command
28555 @findex -data-list-changed-registers
28557 @subsubheading Synopsis
28560 -data-list-changed-registers
28563 Display a list of the registers that have changed.
28565 @subsubheading @value{GDBN} Command
28567 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
28568 has the corresponding command @samp{gdb_changed_register_list}.
28570 @subsubheading Example
28572 On a PPC MBX board:
28580 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
28581 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
28584 -data-list-changed-registers
28585 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
28586 "10","11","13","14","15","16","17","18","19","20","21","22","23",
28587 "24","25","26","27","28","30","31","64","65","66","67","69"]
28592 @subheading The @code{-data-list-register-names} Command
28593 @findex -data-list-register-names
28595 @subsubheading Synopsis
28598 -data-list-register-names [ ( @var{regno} )+ ]
28601 Show a list of register names for the current target. If no arguments
28602 are given, it shows a list of the names of all the registers. If
28603 integer numbers are given as arguments, it will print a list of the
28604 names of the registers corresponding to the arguments. To ensure
28605 consistency between a register name and its number, the output list may
28606 include empty register names.
28608 @subsubheading @value{GDBN} Command
28610 @value{GDBN} does not have a command which corresponds to
28611 @samp{-data-list-register-names}. In @code{gdbtk} there is a
28612 corresponding command @samp{gdb_regnames}.
28614 @subsubheading Example
28616 For the PPC MBX board:
28619 -data-list-register-names
28620 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
28621 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
28622 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
28623 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
28624 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
28625 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
28626 "", "pc","ps","cr","lr","ctr","xer"]
28628 -data-list-register-names 1 2 3
28629 ^done,register-names=["r1","r2","r3"]
28633 @subheading The @code{-data-list-register-values} Command
28634 @findex -data-list-register-values
28636 @subsubheading Synopsis
28639 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
28642 Display the registers' contents. @var{fmt} is the format according to
28643 which the registers' contents are to be returned, followed by an optional
28644 list of numbers specifying the registers to display. A missing list of
28645 numbers indicates that the contents of all the registers must be returned.
28647 Allowed formats for @var{fmt} are:
28664 @subsubheading @value{GDBN} Command
28666 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
28667 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
28669 @subsubheading Example
28671 For a PPC MBX board (note: line breaks are for readability only, they
28672 don't appear in the actual output):
28676 -data-list-register-values r 64 65
28677 ^done,register-values=[@{number="64",value="0xfe00a300"@},
28678 @{number="65",value="0x00029002"@}]
28680 -data-list-register-values x
28681 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
28682 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
28683 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
28684 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
28685 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
28686 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
28687 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
28688 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
28689 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
28690 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
28691 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
28692 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
28693 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
28694 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
28695 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
28696 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
28697 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
28698 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
28699 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
28700 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
28701 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
28702 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
28703 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
28704 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
28705 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
28706 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
28707 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
28708 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
28709 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
28710 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
28711 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
28712 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
28713 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
28714 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
28715 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
28716 @{number="69",value="0x20002b03"@}]
28721 @subheading The @code{-data-read-memory} Command
28722 @findex -data-read-memory
28724 This command is deprecated, use @code{-data-read-memory-bytes} instead.
28726 @subsubheading Synopsis
28729 -data-read-memory [ -o @var{byte-offset} ]
28730 @var{address} @var{word-format} @var{word-size}
28731 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
28738 @item @var{address}
28739 An expression specifying the address of the first memory word to be
28740 read. Complex expressions containing embedded white space should be
28741 quoted using the C convention.
28743 @item @var{word-format}
28744 The format to be used to print the memory words. The notation is the
28745 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
28748 @item @var{word-size}
28749 The size of each memory word in bytes.
28751 @item @var{nr-rows}
28752 The number of rows in the output table.
28754 @item @var{nr-cols}
28755 The number of columns in the output table.
28758 If present, indicates that each row should include an @sc{ascii} dump. The
28759 value of @var{aschar} is used as a padding character when a byte is not a
28760 member of the printable @sc{ascii} character set (printable @sc{ascii}
28761 characters are those whose code is between 32 and 126, inclusively).
28763 @item @var{byte-offset}
28764 An offset to add to the @var{address} before fetching memory.
28767 This command displays memory contents as a table of @var{nr-rows} by
28768 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
28769 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
28770 (returned as @samp{total-bytes}). Should less than the requested number
28771 of bytes be returned by the target, the missing words are identified
28772 using @samp{N/A}. The number of bytes read from the target is returned
28773 in @samp{nr-bytes} and the starting address used to read memory in
28776 The address of the next/previous row or page is available in
28777 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
28780 @subsubheading @value{GDBN} Command
28782 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
28783 @samp{gdb_get_mem} memory read command.
28785 @subsubheading Example
28787 Read six bytes of memory starting at @code{bytes+6} but then offset by
28788 @code{-6} bytes. Format as three rows of two columns. One byte per
28789 word. Display each word in hex.
28793 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
28794 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
28795 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
28796 prev-page="0x0000138a",memory=[
28797 @{addr="0x00001390",data=["0x00","0x01"]@},
28798 @{addr="0x00001392",data=["0x02","0x03"]@},
28799 @{addr="0x00001394",data=["0x04","0x05"]@}]
28803 Read two bytes of memory starting at address @code{shorts + 64} and
28804 display as a single word formatted in decimal.
28808 5-data-read-memory shorts+64 d 2 1 1
28809 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
28810 next-row="0x00001512",prev-row="0x0000150e",
28811 next-page="0x00001512",prev-page="0x0000150e",memory=[
28812 @{addr="0x00001510",data=["128"]@}]
28816 Read thirty two bytes of memory starting at @code{bytes+16} and format
28817 as eight rows of four columns. Include a string encoding with @samp{x}
28818 used as the non-printable character.
28822 4-data-read-memory bytes+16 x 1 8 4 x
28823 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
28824 next-row="0x000013c0",prev-row="0x0000139c",
28825 next-page="0x000013c0",prev-page="0x00001380",memory=[
28826 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
28827 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
28828 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
28829 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
28830 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
28831 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
28832 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
28833 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
28837 @subheading The @code{-data-read-memory-bytes} Command
28838 @findex -data-read-memory-bytes
28840 @subsubheading Synopsis
28843 -data-read-memory-bytes [ -o @var{byte-offset} ]
28844 @var{address} @var{count}
28851 @item @var{address}
28852 An expression specifying the address of the first memory word to be
28853 read. Complex expressions containing embedded white space should be
28854 quoted using the C convention.
28857 The number of bytes to read. This should be an integer literal.
28859 @item @var{byte-offset}
28860 The offsets in bytes relative to @var{address} at which to start
28861 reading. This should be an integer literal. This option is provided
28862 so that a frontend is not required to first evaluate address and then
28863 perform address arithmetics itself.
28867 This command attempts to read all accessible memory regions in the
28868 specified range. First, all regions marked as unreadable in the memory
28869 map (if one is defined) will be skipped. @xref{Memory Region
28870 Attributes}. Second, @value{GDBN} will attempt to read the remaining
28871 regions. For each one, if reading full region results in an errors,
28872 @value{GDBN} will try to read a subset of the region.
28874 In general, every single byte in the region may be readable or not,
28875 and the only way to read every readable byte is to try a read at
28876 every address, which is not practical. Therefore, @value{GDBN} will
28877 attempt to read all accessible bytes at either beginning or the end
28878 of the region, using a binary division scheme. This heuristic works
28879 well for reading accross a memory map boundary. Note that if a region
28880 has a readable range that is neither at the beginning or the end,
28881 @value{GDBN} will not read it.
28883 The result record (@pxref{GDB/MI Result Records}) that is output of
28884 the command includes a field named @samp{memory} whose content is a
28885 list of tuples. Each tuple represent a successfully read memory block
28886 and has the following fields:
28890 The start address of the memory block, as hexadecimal literal.
28893 The end address of the memory block, as hexadecimal literal.
28896 The offset of the memory block, as hexadecimal literal, relative to
28897 the start address passed to @code{-data-read-memory-bytes}.
28900 The contents of the memory block, in hex.
28906 @subsubheading @value{GDBN} Command
28908 The corresponding @value{GDBN} command is @samp{x}.
28910 @subsubheading Example
28914 -data-read-memory-bytes &a 10
28915 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
28917 contents="01000000020000000300"@}]
28922 @subheading The @code{-data-write-memory-bytes} Command
28923 @findex -data-write-memory-bytes
28925 @subsubheading Synopsis
28928 -data-write-memory-bytes @var{address} @var{contents}
28935 @item @var{address}
28936 An expression specifying the address of the first memory word to be
28937 read. Complex expressions containing embedded white space should be
28938 quoted using the C convention.
28940 @item @var{contents}
28941 The hex-encoded bytes to write.
28945 @subsubheading @value{GDBN} Command
28947 There's no corresponding @value{GDBN} command.
28949 @subsubheading Example
28953 -data-write-memory-bytes &a "aabbccdd"
28959 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28960 @node GDB/MI Tracepoint Commands
28961 @section @sc{gdb/mi} Tracepoint Commands
28963 The commands defined in this section implement MI support for
28964 tracepoints. For detailed introduction, see @ref{Tracepoints}.
28966 @subheading The @code{-trace-find} Command
28967 @findex -trace-find
28969 @subsubheading Synopsis
28972 -trace-find @var{mode} [@var{parameters}@dots{}]
28975 Find a trace frame using criteria defined by @var{mode} and
28976 @var{parameters}. The following table lists permissible
28977 modes and their parameters. For details of operation, see @ref{tfind}.
28982 No parameters are required. Stops examining trace frames.
28985 An integer is required as parameter. Selects tracepoint frame with
28988 @item tracepoint-number
28989 An integer is required as parameter. Finds next
28990 trace frame that corresponds to tracepoint with the specified number.
28993 An address is required as parameter. Finds
28994 next trace frame that corresponds to any tracepoint at the specified
28997 @item pc-inside-range
28998 Two addresses are required as parameters. Finds next trace
28999 frame that corresponds to a tracepoint at an address inside the
29000 specified range. Both bounds are considered to be inside the range.
29002 @item pc-outside-range
29003 Two addresses are required as parameters. Finds
29004 next trace frame that corresponds to a tracepoint at an address outside
29005 the specified range. Both bounds are considered to be inside the range.
29008 Line specification is required as parameter. @xref{Specify Location}.
29009 Finds next trace frame that corresponds to a tracepoint at
29010 the specified location.
29014 If @samp{none} was passed as @var{mode}, the response does not
29015 have fields. Otherwise, the response may have the following fields:
29019 This field has either @samp{0} or @samp{1} as the value, depending
29020 on whether a matching tracepoint was found.
29023 The index of the found traceframe. This field is present iff
29024 the @samp{found} field has value of @samp{1}.
29027 The index of the found tracepoint. This field is present iff
29028 the @samp{found} field has value of @samp{1}.
29031 The information about the frame corresponding to the found trace
29032 frame. This field is present only if a trace frame was found.
29033 @xref{GDB/MI Frame Information}, for description of this field.
29037 @subsubheading @value{GDBN} Command
29039 The corresponding @value{GDBN} command is @samp{tfind}.
29041 @subheading -trace-define-variable
29042 @findex -trace-define-variable
29044 @subsubheading Synopsis
29047 -trace-define-variable @var{name} [ @var{value} ]
29050 Create trace variable @var{name} if it does not exist. If
29051 @var{value} is specified, sets the initial value of the specified
29052 trace variable to that value. Note that the @var{name} should start
29053 with the @samp{$} character.
29055 @subsubheading @value{GDBN} Command
29057 The corresponding @value{GDBN} command is @samp{tvariable}.
29059 @subheading -trace-list-variables
29060 @findex -trace-list-variables
29062 @subsubheading Synopsis
29065 -trace-list-variables
29068 Return a table of all defined trace variables. Each element of the
29069 table has the following fields:
29073 The name of the trace variable. This field is always present.
29076 The initial value. This is a 64-bit signed integer. This
29077 field is always present.
29080 The value the trace variable has at the moment. This is a 64-bit
29081 signed integer. This field is absent iff current value is
29082 not defined, for example if the trace was never run, or is
29087 @subsubheading @value{GDBN} Command
29089 The corresponding @value{GDBN} command is @samp{tvariables}.
29091 @subsubheading Example
29095 -trace-list-variables
29096 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
29097 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
29098 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
29099 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
29100 body=[variable=@{name="$trace_timestamp",initial="0"@}
29101 variable=@{name="$foo",initial="10",current="15"@}]@}
29105 @subheading -trace-save
29106 @findex -trace-save
29108 @subsubheading Synopsis
29111 -trace-save [-r ] @var{filename}
29114 Saves the collected trace data to @var{filename}. Without the
29115 @samp{-r} option, the data is downloaded from the target and saved
29116 in a local file. With the @samp{-r} option the target is asked
29117 to perform the save.
29119 @subsubheading @value{GDBN} Command
29121 The corresponding @value{GDBN} command is @samp{tsave}.
29124 @subheading -trace-start
29125 @findex -trace-start
29127 @subsubheading Synopsis
29133 Starts a tracing experiments. The result of this command does not
29136 @subsubheading @value{GDBN} Command
29138 The corresponding @value{GDBN} command is @samp{tstart}.
29140 @subheading -trace-status
29141 @findex -trace-status
29143 @subsubheading Synopsis
29149 Obtains the status of a tracing experiment. The result may include
29150 the following fields:
29155 May have a value of either @samp{0}, when no tracing operations are
29156 supported, @samp{1}, when all tracing operations are supported, or
29157 @samp{file} when examining trace file. In the latter case, examining
29158 of trace frame is possible but new tracing experiement cannot be
29159 started. This field is always present.
29162 May have a value of either @samp{0} or @samp{1} depending on whether
29163 tracing experiement is in progress on target. This field is present
29164 if @samp{supported} field is not @samp{0}.
29167 Report the reason why the tracing was stopped last time. This field
29168 may be absent iff tracing was never stopped on target yet. The
29169 value of @samp{request} means the tracing was stopped as result of
29170 the @code{-trace-stop} command. The value of @samp{overflow} means
29171 the tracing buffer is full. The value of @samp{disconnection} means
29172 tracing was automatically stopped when @value{GDBN} has disconnected.
29173 The value of @samp{passcount} means tracing was stopped when a
29174 tracepoint was passed a maximal number of times for that tracepoint.
29175 This field is present if @samp{supported} field is not @samp{0}.
29177 @item stopping-tracepoint
29178 The number of tracepoint whose passcount as exceeded. This field is
29179 present iff the @samp{stop-reason} field has the value of
29183 @itemx frames-created
29184 The @samp{frames} field is a count of the total number of trace frames
29185 in the trace buffer, while @samp{frames-created} is the total created
29186 during the run, including ones that were discarded, such as when a
29187 circular trace buffer filled up. Both fields are optional.
29191 These fields tell the current size of the tracing buffer and the
29192 remaining space. These fields are optional.
29195 The value of the circular trace buffer flag. @code{1} means that the
29196 trace buffer is circular and old trace frames will be discarded if
29197 necessary to make room, @code{0} means that the trace buffer is linear
29201 The value of the disconnected tracing flag. @code{1} means that
29202 tracing will continue after @value{GDBN} disconnects, @code{0} means
29203 that the trace run will stop.
29207 @subsubheading @value{GDBN} Command
29209 The corresponding @value{GDBN} command is @samp{tstatus}.
29211 @subheading -trace-stop
29212 @findex -trace-stop
29214 @subsubheading Synopsis
29220 Stops a tracing experiment. The result of this command has the same
29221 fields as @code{-trace-status}, except that the @samp{supported} and
29222 @samp{running} fields are not output.
29224 @subsubheading @value{GDBN} Command
29226 The corresponding @value{GDBN} command is @samp{tstop}.
29229 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29230 @node GDB/MI Symbol Query
29231 @section @sc{gdb/mi} Symbol Query Commands
29235 @subheading The @code{-symbol-info-address} Command
29236 @findex -symbol-info-address
29238 @subsubheading Synopsis
29241 -symbol-info-address @var{symbol}
29244 Describe where @var{symbol} is stored.
29246 @subsubheading @value{GDBN} Command
29248 The corresponding @value{GDBN} command is @samp{info address}.
29250 @subsubheading Example
29254 @subheading The @code{-symbol-info-file} Command
29255 @findex -symbol-info-file
29257 @subsubheading Synopsis
29263 Show the file for the symbol.
29265 @subsubheading @value{GDBN} Command
29267 There's no equivalent @value{GDBN} command. @code{gdbtk} has
29268 @samp{gdb_find_file}.
29270 @subsubheading Example
29274 @subheading The @code{-symbol-info-function} Command
29275 @findex -symbol-info-function
29277 @subsubheading Synopsis
29280 -symbol-info-function
29283 Show which function the symbol lives in.
29285 @subsubheading @value{GDBN} Command
29287 @samp{gdb_get_function} in @code{gdbtk}.
29289 @subsubheading Example
29293 @subheading The @code{-symbol-info-line} Command
29294 @findex -symbol-info-line
29296 @subsubheading Synopsis
29302 Show the core addresses of the code for a source line.
29304 @subsubheading @value{GDBN} Command
29306 The corresponding @value{GDBN} command is @samp{info line}.
29307 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
29309 @subsubheading Example
29313 @subheading The @code{-symbol-info-symbol} Command
29314 @findex -symbol-info-symbol
29316 @subsubheading Synopsis
29319 -symbol-info-symbol @var{addr}
29322 Describe what symbol is at location @var{addr}.
29324 @subsubheading @value{GDBN} Command
29326 The corresponding @value{GDBN} command is @samp{info symbol}.
29328 @subsubheading Example
29332 @subheading The @code{-symbol-list-functions} Command
29333 @findex -symbol-list-functions
29335 @subsubheading Synopsis
29338 -symbol-list-functions
29341 List the functions in the executable.
29343 @subsubheading @value{GDBN} Command
29345 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
29346 @samp{gdb_search} in @code{gdbtk}.
29348 @subsubheading Example
29353 @subheading The @code{-symbol-list-lines} Command
29354 @findex -symbol-list-lines
29356 @subsubheading Synopsis
29359 -symbol-list-lines @var{filename}
29362 Print the list of lines that contain code and their associated program
29363 addresses for the given source filename. The entries are sorted in
29364 ascending PC order.
29366 @subsubheading @value{GDBN} Command
29368 There is no corresponding @value{GDBN} command.
29370 @subsubheading Example
29373 -symbol-list-lines basics.c
29374 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
29380 @subheading The @code{-symbol-list-types} Command
29381 @findex -symbol-list-types
29383 @subsubheading Synopsis
29389 List all the type names.
29391 @subsubheading @value{GDBN} Command
29393 The corresponding commands are @samp{info types} in @value{GDBN},
29394 @samp{gdb_search} in @code{gdbtk}.
29396 @subsubheading Example
29400 @subheading The @code{-symbol-list-variables} Command
29401 @findex -symbol-list-variables
29403 @subsubheading Synopsis
29406 -symbol-list-variables
29409 List all the global and static variable names.
29411 @subsubheading @value{GDBN} Command
29413 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
29415 @subsubheading Example
29419 @subheading The @code{-symbol-locate} Command
29420 @findex -symbol-locate
29422 @subsubheading Synopsis
29428 @subsubheading @value{GDBN} Command
29430 @samp{gdb_loc} in @code{gdbtk}.
29432 @subsubheading Example
29436 @subheading The @code{-symbol-type} Command
29437 @findex -symbol-type
29439 @subsubheading Synopsis
29442 -symbol-type @var{variable}
29445 Show type of @var{variable}.
29447 @subsubheading @value{GDBN} Command
29449 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
29450 @samp{gdb_obj_variable}.
29452 @subsubheading Example
29457 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29458 @node GDB/MI File Commands
29459 @section @sc{gdb/mi} File Commands
29461 This section describes the GDB/MI commands to specify executable file names
29462 and to read in and obtain symbol table information.
29464 @subheading The @code{-file-exec-and-symbols} Command
29465 @findex -file-exec-and-symbols
29467 @subsubheading Synopsis
29470 -file-exec-and-symbols @var{file}
29473 Specify the executable file to be debugged. This file is the one from
29474 which the symbol table is also read. If no file is specified, the
29475 command clears the executable and symbol information. If breakpoints
29476 are set when using this command with no arguments, @value{GDBN} will produce
29477 error messages. Otherwise, no output is produced, except a completion
29480 @subsubheading @value{GDBN} Command
29482 The corresponding @value{GDBN} command is @samp{file}.
29484 @subsubheading Example
29488 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29494 @subheading The @code{-file-exec-file} Command
29495 @findex -file-exec-file
29497 @subsubheading Synopsis
29500 -file-exec-file @var{file}
29503 Specify the executable file to be debugged. Unlike
29504 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
29505 from this file. If used without argument, @value{GDBN} clears the information
29506 about the executable file. No output is produced, except a completion
29509 @subsubheading @value{GDBN} Command
29511 The corresponding @value{GDBN} command is @samp{exec-file}.
29513 @subsubheading Example
29517 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29524 @subheading The @code{-file-list-exec-sections} Command
29525 @findex -file-list-exec-sections
29527 @subsubheading Synopsis
29530 -file-list-exec-sections
29533 List the sections of the current executable file.
29535 @subsubheading @value{GDBN} Command
29537 The @value{GDBN} command @samp{info file} shows, among the rest, the same
29538 information as this command. @code{gdbtk} has a corresponding command
29539 @samp{gdb_load_info}.
29541 @subsubheading Example
29546 @subheading The @code{-file-list-exec-source-file} Command
29547 @findex -file-list-exec-source-file
29549 @subsubheading Synopsis
29552 -file-list-exec-source-file
29555 List the line number, the current source file, and the absolute path
29556 to the current source file for the current executable. The macro
29557 information field has a value of @samp{1} or @samp{0} depending on
29558 whether or not the file includes preprocessor macro information.
29560 @subsubheading @value{GDBN} Command
29562 The @value{GDBN} equivalent is @samp{info source}
29564 @subsubheading Example
29568 123-file-list-exec-source-file
29569 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
29574 @subheading The @code{-file-list-exec-source-files} Command
29575 @findex -file-list-exec-source-files
29577 @subsubheading Synopsis
29580 -file-list-exec-source-files
29583 List the source files for the current executable.
29585 It will always output the filename, but only when @value{GDBN} can find
29586 the absolute file name of a source file, will it output the fullname.
29588 @subsubheading @value{GDBN} Command
29590 The @value{GDBN} equivalent is @samp{info sources}.
29591 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
29593 @subsubheading Example
29596 -file-list-exec-source-files
29598 @{file=foo.c,fullname=/home/foo.c@},
29599 @{file=/home/bar.c,fullname=/home/bar.c@},
29600 @{file=gdb_could_not_find_fullpath.c@}]
29605 @subheading The @code{-file-list-shared-libraries} Command
29606 @findex -file-list-shared-libraries
29608 @subsubheading Synopsis
29611 -file-list-shared-libraries
29614 List the shared libraries in the program.
29616 @subsubheading @value{GDBN} Command
29618 The corresponding @value{GDBN} command is @samp{info shared}.
29620 @subsubheading Example
29624 @subheading The @code{-file-list-symbol-files} Command
29625 @findex -file-list-symbol-files
29627 @subsubheading Synopsis
29630 -file-list-symbol-files
29635 @subsubheading @value{GDBN} Command
29637 The corresponding @value{GDBN} command is @samp{info file} (part of it).
29639 @subsubheading Example
29644 @subheading The @code{-file-symbol-file} Command
29645 @findex -file-symbol-file
29647 @subsubheading Synopsis
29650 -file-symbol-file @var{file}
29653 Read symbol table info from the specified @var{file} argument. When
29654 used without arguments, clears @value{GDBN}'s symbol table info. No output is
29655 produced, except for a completion notification.
29657 @subsubheading @value{GDBN} Command
29659 The corresponding @value{GDBN} command is @samp{symbol-file}.
29661 @subsubheading Example
29665 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29671 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29672 @node GDB/MI Memory Overlay Commands
29673 @section @sc{gdb/mi} Memory Overlay Commands
29675 The memory overlay commands are not implemented.
29677 @c @subheading -overlay-auto
29679 @c @subheading -overlay-list-mapping-state
29681 @c @subheading -overlay-list-overlays
29683 @c @subheading -overlay-map
29685 @c @subheading -overlay-off
29687 @c @subheading -overlay-on
29689 @c @subheading -overlay-unmap
29691 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29692 @node GDB/MI Signal Handling Commands
29693 @section @sc{gdb/mi} Signal Handling Commands
29695 Signal handling commands are not implemented.
29697 @c @subheading -signal-handle
29699 @c @subheading -signal-list-handle-actions
29701 @c @subheading -signal-list-signal-types
29705 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29706 @node GDB/MI Target Manipulation
29707 @section @sc{gdb/mi} Target Manipulation Commands
29710 @subheading The @code{-target-attach} Command
29711 @findex -target-attach
29713 @subsubheading Synopsis
29716 -target-attach @var{pid} | @var{gid} | @var{file}
29719 Attach to a process @var{pid} or a file @var{file} outside of
29720 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
29721 group, the id previously returned by
29722 @samp{-list-thread-groups --available} must be used.
29724 @subsubheading @value{GDBN} Command
29726 The corresponding @value{GDBN} command is @samp{attach}.
29728 @subsubheading Example
29732 =thread-created,id="1"
29733 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
29739 @subheading The @code{-target-compare-sections} Command
29740 @findex -target-compare-sections
29742 @subsubheading Synopsis
29745 -target-compare-sections [ @var{section} ]
29748 Compare data of section @var{section} on target to the exec file.
29749 Without the argument, all sections are compared.
29751 @subsubheading @value{GDBN} Command
29753 The @value{GDBN} equivalent is @samp{compare-sections}.
29755 @subsubheading Example
29760 @subheading The @code{-target-detach} Command
29761 @findex -target-detach
29763 @subsubheading Synopsis
29766 -target-detach [ @var{pid} | @var{gid} ]
29769 Detach from the remote target which normally resumes its execution.
29770 If either @var{pid} or @var{gid} is specified, detaches from either
29771 the specified process, or specified thread group. There's no output.
29773 @subsubheading @value{GDBN} Command
29775 The corresponding @value{GDBN} command is @samp{detach}.
29777 @subsubheading Example
29787 @subheading The @code{-target-disconnect} Command
29788 @findex -target-disconnect
29790 @subsubheading Synopsis
29796 Disconnect from the remote target. There's no output and the target is
29797 generally not resumed.
29799 @subsubheading @value{GDBN} Command
29801 The corresponding @value{GDBN} command is @samp{disconnect}.
29803 @subsubheading Example
29813 @subheading The @code{-target-download} Command
29814 @findex -target-download
29816 @subsubheading Synopsis
29822 Loads the executable onto the remote target.
29823 It prints out an update message every half second, which includes the fields:
29827 The name of the section.
29829 The size of what has been sent so far for that section.
29831 The size of the section.
29833 The total size of what was sent so far (the current and the previous sections).
29835 The size of the overall executable to download.
29839 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
29840 @sc{gdb/mi} Output Syntax}).
29842 In addition, it prints the name and size of the sections, as they are
29843 downloaded. These messages include the following fields:
29847 The name of the section.
29849 The size of the section.
29851 The size of the overall executable to download.
29855 At the end, a summary is printed.
29857 @subsubheading @value{GDBN} Command
29859 The corresponding @value{GDBN} command is @samp{load}.
29861 @subsubheading Example
29863 Note: each status message appears on a single line. Here the messages
29864 have been broken down so that they can fit onto a page.
29869 +download,@{section=".text",section-size="6668",total-size="9880"@}
29870 +download,@{section=".text",section-sent="512",section-size="6668",
29871 total-sent="512",total-size="9880"@}
29872 +download,@{section=".text",section-sent="1024",section-size="6668",
29873 total-sent="1024",total-size="9880"@}
29874 +download,@{section=".text",section-sent="1536",section-size="6668",
29875 total-sent="1536",total-size="9880"@}
29876 +download,@{section=".text",section-sent="2048",section-size="6668",
29877 total-sent="2048",total-size="9880"@}
29878 +download,@{section=".text",section-sent="2560",section-size="6668",
29879 total-sent="2560",total-size="9880"@}
29880 +download,@{section=".text",section-sent="3072",section-size="6668",
29881 total-sent="3072",total-size="9880"@}
29882 +download,@{section=".text",section-sent="3584",section-size="6668",
29883 total-sent="3584",total-size="9880"@}
29884 +download,@{section=".text",section-sent="4096",section-size="6668",
29885 total-sent="4096",total-size="9880"@}
29886 +download,@{section=".text",section-sent="4608",section-size="6668",
29887 total-sent="4608",total-size="9880"@}
29888 +download,@{section=".text",section-sent="5120",section-size="6668",
29889 total-sent="5120",total-size="9880"@}
29890 +download,@{section=".text",section-sent="5632",section-size="6668",
29891 total-sent="5632",total-size="9880"@}
29892 +download,@{section=".text",section-sent="6144",section-size="6668",
29893 total-sent="6144",total-size="9880"@}
29894 +download,@{section=".text",section-sent="6656",section-size="6668",
29895 total-sent="6656",total-size="9880"@}
29896 +download,@{section=".init",section-size="28",total-size="9880"@}
29897 +download,@{section=".fini",section-size="28",total-size="9880"@}
29898 +download,@{section=".data",section-size="3156",total-size="9880"@}
29899 +download,@{section=".data",section-sent="512",section-size="3156",
29900 total-sent="7236",total-size="9880"@}
29901 +download,@{section=".data",section-sent="1024",section-size="3156",
29902 total-sent="7748",total-size="9880"@}
29903 +download,@{section=".data",section-sent="1536",section-size="3156",
29904 total-sent="8260",total-size="9880"@}
29905 +download,@{section=".data",section-sent="2048",section-size="3156",
29906 total-sent="8772",total-size="9880"@}
29907 +download,@{section=".data",section-sent="2560",section-size="3156",
29908 total-sent="9284",total-size="9880"@}
29909 +download,@{section=".data",section-sent="3072",section-size="3156",
29910 total-sent="9796",total-size="9880"@}
29911 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
29918 @subheading The @code{-target-exec-status} Command
29919 @findex -target-exec-status
29921 @subsubheading Synopsis
29924 -target-exec-status
29927 Provide information on the state of the target (whether it is running or
29928 not, for instance).
29930 @subsubheading @value{GDBN} Command
29932 There's no equivalent @value{GDBN} command.
29934 @subsubheading Example
29938 @subheading The @code{-target-list-available-targets} Command
29939 @findex -target-list-available-targets
29941 @subsubheading Synopsis
29944 -target-list-available-targets
29947 List the possible targets to connect to.
29949 @subsubheading @value{GDBN} Command
29951 The corresponding @value{GDBN} command is @samp{help target}.
29953 @subsubheading Example
29957 @subheading The @code{-target-list-current-targets} Command
29958 @findex -target-list-current-targets
29960 @subsubheading Synopsis
29963 -target-list-current-targets
29966 Describe the current target.
29968 @subsubheading @value{GDBN} Command
29970 The corresponding information is printed by @samp{info file} (among
29973 @subsubheading Example
29977 @subheading The @code{-target-list-parameters} Command
29978 @findex -target-list-parameters
29980 @subsubheading Synopsis
29983 -target-list-parameters
29989 @subsubheading @value{GDBN} Command
29993 @subsubheading Example
29997 @subheading The @code{-target-select} Command
29998 @findex -target-select
30000 @subsubheading Synopsis
30003 -target-select @var{type} @var{parameters @dots{}}
30006 Connect @value{GDBN} to the remote target. This command takes two args:
30010 The type of target, for instance @samp{remote}, etc.
30011 @item @var{parameters}
30012 Device names, host names and the like. @xref{Target Commands, ,
30013 Commands for Managing Targets}, for more details.
30016 The output is a connection notification, followed by the address at
30017 which the target program is, in the following form:
30020 ^connected,addr="@var{address}",func="@var{function name}",
30021 args=[@var{arg list}]
30024 @subsubheading @value{GDBN} Command
30026 The corresponding @value{GDBN} command is @samp{target}.
30028 @subsubheading Example
30032 -target-select remote /dev/ttya
30033 ^connected,addr="0xfe00a300",func="??",args=[]
30037 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30038 @node GDB/MI File Transfer Commands
30039 @section @sc{gdb/mi} File Transfer Commands
30042 @subheading The @code{-target-file-put} Command
30043 @findex -target-file-put
30045 @subsubheading Synopsis
30048 -target-file-put @var{hostfile} @var{targetfile}
30051 Copy file @var{hostfile} from the host system (the machine running
30052 @value{GDBN}) to @var{targetfile} on the target system.
30054 @subsubheading @value{GDBN} Command
30056 The corresponding @value{GDBN} command is @samp{remote put}.
30058 @subsubheading Example
30062 -target-file-put localfile remotefile
30068 @subheading The @code{-target-file-get} Command
30069 @findex -target-file-get
30071 @subsubheading Synopsis
30074 -target-file-get @var{targetfile} @var{hostfile}
30077 Copy file @var{targetfile} from the target system to @var{hostfile}
30078 on the host system.
30080 @subsubheading @value{GDBN} Command
30082 The corresponding @value{GDBN} command is @samp{remote get}.
30084 @subsubheading Example
30088 -target-file-get remotefile localfile
30094 @subheading The @code{-target-file-delete} Command
30095 @findex -target-file-delete
30097 @subsubheading Synopsis
30100 -target-file-delete @var{targetfile}
30103 Delete @var{targetfile} from the target system.
30105 @subsubheading @value{GDBN} Command
30107 The corresponding @value{GDBN} command is @samp{remote delete}.
30109 @subsubheading Example
30113 -target-file-delete remotefile
30119 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30120 @node GDB/MI Miscellaneous Commands
30121 @section Miscellaneous @sc{gdb/mi} Commands
30123 @c @subheading -gdb-complete
30125 @subheading The @code{-gdb-exit} Command
30128 @subsubheading Synopsis
30134 Exit @value{GDBN} immediately.
30136 @subsubheading @value{GDBN} Command
30138 Approximately corresponds to @samp{quit}.
30140 @subsubheading Example
30150 @subheading The @code{-exec-abort} Command
30151 @findex -exec-abort
30153 @subsubheading Synopsis
30159 Kill the inferior running program.
30161 @subsubheading @value{GDBN} Command
30163 The corresponding @value{GDBN} command is @samp{kill}.
30165 @subsubheading Example
30170 @subheading The @code{-gdb-set} Command
30173 @subsubheading Synopsis
30179 Set an internal @value{GDBN} variable.
30180 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
30182 @subsubheading @value{GDBN} Command
30184 The corresponding @value{GDBN} command is @samp{set}.
30186 @subsubheading Example
30196 @subheading The @code{-gdb-show} Command
30199 @subsubheading Synopsis
30205 Show the current value of a @value{GDBN} variable.
30207 @subsubheading @value{GDBN} Command
30209 The corresponding @value{GDBN} command is @samp{show}.
30211 @subsubheading Example
30220 @c @subheading -gdb-source
30223 @subheading The @code{-gdb-version} Command
30224 @findex -gdb-version
30226 @subsubheading Synopsis
30232 Show version information for @value{GDBN}. Used mostly in testing.
30234 @subsubheading @value{GDBN} Command
30236 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
30237 default shows this information when you start an interactive session.
30239 @subsubheading Example
30241 @c This example modifies the actual output from GDB to avoid overfull
30247 ~Copyright 2000 Free Software Foundation, Inc.
30248 ~GDB is free software, covered by the GNU General Public License, and
30249 ~you are welcome to change it and/or distribute copies of it under
30250 ~ certain conditions.
30251 ~Type "show copying" to see the conditions.
30252 ~There is absolutely no warranty for GDB. Type "show warranty" for
30254 ~This GDB was configured as
30255 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
30260 @subheading The @code{-list-features} Command
30261 @findex -list-features
30263 Returns a list of particular features of the MI protocol that
30264 this version of gdb implements. A feature can be a command,
30265 or a new field in an output of some command, or even an
30266 important bugfix. While a frontend can sometimes detect presence
30267 of a feature at runtime, it is easier to perform detection at debugger
30270 The command returns a list of strings, with each string naming an
30271 available feature. Each returned string is just a name, it does not
30272 have any internal structure. The list of possible feature names
30278 (gdb) -list-features
30279 ^done,result=["feature1","feature2"]
30282 The current list of features is:
30285 @item frozen-varobjs
30286 Indicates presence of the @code{-var-set-frozen} command, as well
30287 as possible presense of the @code{frozen} field in the output
30288 of @code{-varobj-create}.
30289 @item pending-breakpoints
30290 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
30292 Indicates presence of Python scripting support, Python-based
30293 pretty-printing commands, and possible presence of the
30294 @samp{display_hint} field in the output of @code{-var-list-children}
30296 Indicates presence of the @code{-thread-info} command.
30297 @item data-read-memory-bytes
30298 Indicates presense of the @code{-data-read-memory-bytes} and the
30299 @code{-data-write-memory-bytes} commands.
30300 @item breakpoint-notifications
30301 Indicates that changes to breakpoints and breakpoints created via the
30302 CLI will be announced via async records.
30306 @subheading The @code{-list-target-features} Command
30307 @findex -list-target-features
30309 Returns a list of particular features that are supported by the
30310 target. Those features affect the permitted MI commands, but
30311 unlike the features reported by the @code{-list-features} command, the
30312 features depend on which target GDB is using at the moment. Whenever
30313 a target can change, due to commands such as @code{-target-select},
30314 @code{-target-attach} or @code{-exec-run}, the list of target features
30315 may change, and the frontend should obtain it again.
30319 (gdb) -list-features
30320 ^done,result=["async"]
30323 The current list of features is:
30327 Indicates that the target is capable of asynchronous command
30328 execution, which means that @value{GDBN} will accept further commands
30329 while the target is running.
30332 Indicates that the target is capable of reverse execution.
30333 @xref{Reverse Execution}, for more information.
30337 @subheading The @code{-list-thread-groups} Command
30338 @findex -list-thread-groups
30340 @subheading Synopsis
30343 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
30346 Lists thread groups (@pxref{Thread groups}). When a single thread
30347 group is passed as the argument, lists the children of that group.
30348 When several thread group are passed, lists information about those
30349 thread groups. Without any parameters, lists information about all
30350 top-level thread groups.
30352 Normally, thread groups that are being debugged are reported.
30353 With the @samp{--available} option, @value{GDBN} reports thread groups
30354 available on the target.
30356 The output of this command may have either a @samp{threads} result or
30357 a @samp{groups} result. The @samp{thread} result has a list of tuples
30358 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
30359 Information}). The @samp{groups} result has a list of tuples as value,
30360 each tuple describing a thread group. If top-level groups are
30361 requested (that is, no parameter is passed), or when several groups
30362 are passed, the output always has a @samp{groups} result. The format
30363 of the @samp{group} result is described below.
30365 To reduce the number of roundtrips it's possible to list thread groups
30366 together with their children, by passing the @samp{--recurse} option
30367 and the recursion depth. Presently, only recursion depth of 1 is
30368 permitted. If this option is present, then every reported thread group
30369 will also include its children, either as @samp{group} or
30370 @samp{threads} field.
30372 In general, any combination of option and parameters is permitted, with
30373 the following caveats:
30377 When a single thread group is passed, the output will typically
30378 be the @samp{threads} result. Because threads may not contain
30379 anything, the @samp{recurse} option will be ignored.
30382 When the @samp{--available} option is passed, limited information may
30383 be available. In particular, the list of threads of a process might
30384 be inaccessible. Further, specifying specific thread groups might
30385 not give any performance advantage over listing all thread groups.
30386 The frontend should assume that @samp{-list-thread-groups --available}
30387 is always an expensive operation and cache the results.
30391 The @samp{groups} result is a list of tuples, where each tuple may
30392 have the following fields:
30396 Identifier of the thread group. This field is always present.
30397 The identifier is an opaque string; frontends should not try to
30398 convert it to an integer, even though it might look like one.
30401 The type of the thread group. At present, only @samp{process} is a
30405 The target-specific process identifier. This field is only present
30406 for thread groups of type @samp{process} and only if the process exists.
30409 The number of children this thread group has. This field may be
30410 absent for an available thread group.
30413 This field has a list of tuples as value, each tuple describing a
30414 thread. It may be present if the @samp{--recurse} option is
30415 specified, and it's actually possible to obtain the threads.
30418 This field is a list of integers, each identifying a core that one
30419 thread of the group is running on. This field may be absent if
30420 such information is not available.
30423 The name of the executable file that corresponds to this thread group.
30424 The field is only present for thread groups of type @samp{process},
30425 and only if there is a corresponding executable file.
30429 @subheading Example
30433 -list-thread-groups
30434 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
30435 -list-thread-groups 17
30436 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
30437 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
30438 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
30439 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
30440 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
30441 -list-thread-groups --available
30442 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
30443 -list-thread-groups --available --recurse 1
30444 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
30445 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
30446 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
30447 -list-thread-groups --available --recurse 1 17 18
30448 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
30449 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
30450 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
30454 @subheading The @code{-add-inferior} Command
30455 @findex -add-inferior
30457 @subheading Synopsis
30463 Creates a new inferior (@pxref{Inferiors and Programs}). The created
30464 inferior is not associated with any executable. Such association may
30465 be established with the @samp{-file-exec-and-symbols} command
30466 (@pxref{GDB/MI File Commands}). The command response has a single
30467 field, @samp{thread-group}, whose value is the identifier of the
30468 thread group corresponding to the new inferior.
30470 @subheading Example
30475 ^done,thread-group="i3"
30478 @subheading The @code{-interpreter-exec} Command
30479 @findex -interpreter-exec
30481 @subheading Synopsis
30484 -interpreter-exec @var{interpreter} @var{command}
30486 @anchor{-interpreter-exec}
30488 Execute the specified @var{command} in the given @var{interpreter}.
30490 @subheading @value{GDBN} Command
30492 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
30494 @subheading Example
30498 -interpreter-exec console "break main"
30499 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
30500 &"During symbol reading, bad structure-type format.\n"
30501 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
30506 @subheading The @code{-inferior-tty-set} Command
30507 @findex -inferior-tty-set
30509 @subheading Synopsis
30512 -inferior-tty-set /dev/pts/1
30515 Set terminal for future runs of the program being debugged.
30517 @subheading @value{GDBN} Command
30519 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
30521 @subheading Example
30525 -inferior-tty-set /dev/pts/1
30530 @subheading The @code{-inferior-tty-show} Command
30531 @findex -inferior-tty-show
30533 @subheading Synopsis
30539 Show terminal for future runs of program being debugged.
30541 @subheading @value{GDBN} Command
30543 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
30545 @subheading Example
30549 -inferior-tty-set /dev/pts/1
30553 ^done,inferior_tty_terminal="/dev/pts/1"
30557 @subheading The @code{-enable-timings} Command
30558 @findex -enable-timings
30560 @subheading Synopsis
30563 -enable-timings [yes | no]
30566 Toggle the printing of the wallclock, user and system times for an MI
30567 command as a field in its output. This command is to help frontend
30568 developers optimize the performance of their code. No argument is
30569 equivalent to @samp{yes}.
30571 @subheading @value{GDBN} Command
30575 @subheading Example
30583 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30584 addr="0x080484ed",func="main",file="myprog.c",
30585 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
30586 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
30594 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
30595 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
30596 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
30597 fullname="/home/nickrob/myprog.c",line="73"@}
30602 @chapter @value{GDBN} Annotations
30604 This chapter describes annotations in @value{GDBN}. Annotations were
30605 designed to interface @value{GDBN} to graphical user interfaces or other
30606 similar programs which want to interact with @value{GDBN} at a
30607 relatively high level.
30609 The annotation mechanism has largely been superseded by @sc{gdb/mi}
30613 This is Edition @value{EDITION}, @value{DATE}.
30617 * Annotations Overview:: What annotations are; the general syntax.
30618 * Server Prefix:: Issuing a command without affecting user state.
30619 * Prompting:: Annotations marking @value{GDBN}'s need for input.
30620 * Errors:: Annotations for error messages.
30621 * Invalidation:: Some annotations describe things now invalid.
30622 * Annotations for Running::
30623 Whether the program is running, how it stopped, etc.
30624 * Source Annotations:: Annotations describing source code.
30627 @node Annotations Overview
30628 @section What is an Annotation?
30629 @cindex annotations
30631 Annotations start with a newline character, two @samp{control-z}
30632 characters, and the name of the annotation. If there is no additional
30633 information associated with this annotation, the name of the annotation
30634 is followed immediately by a newline. If there is additional
30635 information, the name of the annotation is followed by a space, the
30636 additional information, and a newline. The additional information
30637 cannot contain newline characters.
30639 Any output not beginning with a newline and two @samp{control-z}
30640 characters denotes literal output from @value{GDBN}. Currently there is
30641 no need for @value{GDBN} to output a newline followed by two
30642 @samp{control-z} characters, but if there was such a need, the
30643 annotations could be extended with an @samp{escape} annotation which
30644 means those three characters as output.
30646 The annotation @var{level}, which is specified using the
30647 @option{--annotate} command line option (@pxref{Mode Options}), controls
30648 how much information @value{GDBN} prints together with its prompt,
30649 values of expressions, source lines, and other types of output. Level 0
30650 is for no annotations, level 1 is for use when @value{GDBN} is run as a
30651 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
30652 for programs that control @value{GDBN}, and level 2 annotations have
30653 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
30654 Interface, annotate, GDB's Obsolete Annotations}).
30657 @kindex set annotate
30658 @item set annotate @var{level}
30659 The @value{GDBN} command @code{set annotate} sets the level of
30660 annotations to the specified @var{level}.
30662 @item show annotate
30663 @kindex show annotate
30664 Show the current annotation level.
30667 This chapter describes level 3 annotations.
30669 A simple example of starting up @value{GDBN} with annotations is:
30672 $ @kbd{gdb --annotate=3}
30674 Copyright 2003 Free Software Foundation, Inc.
30675 GDB is free software, covered by the GNU General Public License,
30676 and you are welcome to change it and/or distribute copies of it
30677 under certain conditions.
30678 Type "show copying" to see the conditions.
30679 There is absolutely no warranty for GDB. Type "show warranty"
30681 This GDB was configured as "i386-pc-linux-gnu"
30692 Here @samp{quit} is input to @value{GDBN}; the rest is output from
30693 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
30694 denotes a @samp{control-z} character) are annotations; the rest is
30695 output from @value{GDBN}.
30697 @node Server Prefix
30698 @section The Server Prefix
30699 @cindex server prefix
30701 If you prefix a command with @samp{server } then it will not affect
30702 the command history, nor will it affect @value{GDBN}'s notion of which
30703 command to repeat if @key{RET} is pressed on a line by itself. This
30704 means that commands can be run behind a user's back by a front-end in
30705 a transparent manner.
30707 The @code{server } prefix does not affect the recording of values into
30708 the value history; to print a value without recording it into the
30709 value history, use the @code{output} command instead of the
30710 @code{print} command.
30712 Using this prefix also disables confirmation requests
30713 (@pxref{confirmation requests}).
30716 @section Annotation for @value{GDBN} Input
30718 @cindex annotations for prompts
30719 When @value{GDBN} prompts for input, it annotates this fact so it is possible
30720 to know when to send output, when the output from a given command is
30723 Different kinds of input each have a different @dfn{input type}. Each
30724 input type has three annotations: a @code{pre-} annotation, which
30725 denotes the beginning of any prompt which is being output, a plain
30726 annotation, which denotes the end of the prompt, and then a @code{post-}
30727 annotation which denotes the end of any echo which may (or may not) be
30728 associated with the input. For example, the @code{prompt} input type
30729 features the following annotations:
30737 The input types are
30740 @findex pre-prompt annotation
30741 @findex prompt annotation
30742 @findex post-prompt annotation
30744 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
30746 @findex pre-commands annotation
30747 @findex commands annotation
30748 @findex post-commands annotation
30750 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
30751 command. The annotations are repeated for each command which is input.
30753 @findex pre-overload-choice annotation
30754 @findex overload-choice annotation
30755 @findex post-overload-choice annotation
30756 @item overload-choice
30757 When @value{GDBN} wants the user to select between various overloaded functions.
30759 @findex pre-query annotation
30760 @findex query annotation
30761 @findex post-query annotation
30763 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
30765 @findex pre-prompt-for-continue annotation
30766 @findex prompt-for-continue annotation
30767 @findex post-prompt-for-continue annotation
30768 @item prompt-for-continue
30769 When @value{GDBN} is asking the user to press return to continue. Note: Don't
30770 expect this to work well; instead use @code{set height 0} to disable
30771 prompting. This is because the counting of lines is buggy in the
30772 presence of annotations.
30777 @cindex annotations for errors, warnings and interrupts
30779 @findex quit annotation
30784 This annotation occurs right before @value{GDBN} responds to an interrupt.
30786 @findex error annotation
30791 This annotation occurs right before @value{GDBN} responds to an error.
30793 Quit and error annotations indicate that any annotations which @value{GDBN} was
30794 in the middle of may end abruptly. For example, if a
30795 @code{value-history-begin} annotation is followed by a @code{error}, one
30796 cannot expect to receive the matching @code{value-history-end}. One
30797 cannot expect not to receive it either, however; an error annotation
30798 does not necessarily mean that @value{GDBN} is immediately returning all the way
30801 @findex error-begin annotation
30802 A quit or error annotation may be preceded by
30808 Any output between that and the quit or error annotation is the error
30811 Warning messages are not yet annotated.
30812 @c If we want to change that, need to fix warning(), type_error(),
30813 @c range_error(), and possibly other places.
30816 @section Invalidation Notices
30818 @cindex annotations for invalidation messages
30819 The following annotations say that certain pieces of state may have
30823 @findex frames-invalid annotation
30824 @item ^Z^Zframes-invalid
30826 The frames (for example, output from the @code{backtrace} command) may
30829 @findex breakpoints-invalid annotation
30830 @item ^Z^Zbreakpoints-invalid
30832 The breakpoints may have changed. For example, the user just added or
30833 deleted a breakpoint.
30836 @node Annotations for Running
30837 @section Running the Program
30838 @cindex annotations for running programs
30840 @findex starting annotation
30841 @findex stopping annotation
30842 When the program starts executing due to a @value{GDBN} command such as
30843 @code{step} or @code{continue},
30849 is output. When the program stops,
30855 is output. Before the @code{stopped} annotation, a variety of
30856 annotations describe how the program stopped.
30859 @findex exited annotation
30860 @item ^Z^Zexited @var{exit-status}
30861 The program exited, and @var{exit-status} is the exit status (zero for
30862 successful exit, otherwise nonzero).
30864 @findex signalled annotation
30865 @findex signal-name annotation
30866 @findex signal-name-end annotation
30867 @findex signal-string annotation
30868 @findex signal-string-end annotation
30869 @item ^Z^Zsignalled
30870 The program exited with a signal. After the @code{^Z^Zsignalled}, the
30871 annotation continues:
30877 ^Z^Zsignal-name-end
30881 ^Z^Zsignal-string-end
30886 where @var{name} is the name of the signal, such as @code{SIGILL} or
30887 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
30888 as @code{Illegal Instruction} or @code{Segmentation fault}.
30889 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
30890 user's benefit and have no particular format.
30892 @findex signal annotation
30894 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
30895 just saying that the program received the signal, not that it was
30896 terminated with it.
30898 @findex breakpoint annotation
30899 @item ^Z^Zbreakpoint @var{number}
30900 The program hit breakpoint number @var{number}.
30902 @findex watchpoint annotation
30903 @item ^Z^Zwatchpoint @var{number}
30904 The program hit watchpoint number @var{number}.
30907 @node Source Annotations
30908 @section Displaying Source
30909 @cindex annotations for source display
30911 @findex source annotation
30912 The following annotation is used instead of displaying source code:
30915 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
30918 where @var{filename} is an absolute file name indicating which source
30919 file, @var{line} is the line number within that file (where 1 is the
30920 first line in the file), @var{character} is the character position
30921 within the file (where 0 is the first character in the file) (for most
30922 debug formats this will necessarily point to the beginning of a line),
30923 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
30924 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
30925 @var{addr} is the address in the target program associated with the
30926 source which is being displayed. @var{addr} is in the form @samp{0x}
30927 followed by one or more lowercase hex digits (note that this does not
30928 depend on the language).
30930 @node JIT Interface
30931 @chapter JIT Compilation Interface
30932 @cindex just-in-time compilation
30933 @cindex JIT compilation interface
30935 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
30936 interface. A JIT compiler is a program or library that generates native
30937 executable code at runtime and executes it, usually in order to achieve good
30938 performance while maintaining platform independence.
30940 Programs that use JIT compilation are normally difficult to debug because
30941 portions of their code are generated at runtime, instead of being loaded from
30942 object files, which is where @value{GDBN} normally finds the program's symbols
30943 and debug information. In order to debug programs that use JIT compilation,
30944 @value{GDBN} has an interface that allows the program to register in-memory
30945 symbol files with @value{GDBN} at runtime.
30947 If you are using @value{GDBN} to debug a program that uses this interface, then
30948 it should work transparently so long as you have not stripped the binary. If
30949 you are developing a JIT compiler, then the interface is documented in the rest
30950 of this chapter. At this time, the only known client of this interface is the
30953 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
30954 JIT compiler communicates with @value{GDBN} by writing data into a global
30955 variable and calling a fuction at a well-known symbol. When @value{GDBN}
30956 attaches, it reads a linked list of symbol files from the global variable to
30957 find existing code, and puts a breakpoint in the function so that it can find
30958 out about additional code.
30961 * Declarations:: Relevant C struct declarations
30962 * Registering Code:: Steps to register code
30963 * Unregistering Code:: Steps to unregister code
30967 @section JIT Declarations
30969 These are the relevant struct declarations that a C program should include to
30970 implement the interface:
30980 struct jit_code_entry
30982 struct jit_code_entry *next_entry;
30983 struct jit_code_entry *prev_entry;
30984 const char *symfile_addr;
30985 uint64_t symfile_size;
30988 struct jit_descriptor
30991 /* This type should be jit_actions_t, but we use uint32_t
30992 to be explicit about the bitwidth. */
30993 uint32_t action_flag;
30994 struct jit_code_entry *relevant_entry;
30995 struct jit_code_entry *first_entry;
30998 /* GDB puts a breakpoint in this function. */
30999 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
31001 /* Make sure to specify the version statically, because the
31002 debugger may check the version before we can set it. */
31003 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
31006 If the JIT is multi-threaded, then it is important that the JIT synchronize any
31007 modifications to this global data properly, which can easily be done by putting
31008 a global mutex around modifications to these structures.
31010 @node Registering Code
31011 @section Registering Code
31013 To register code with @value{GDBN}, the JIT should follow this protocol:
31017 Generate an object file in memory with symbols and other desired debug
31018 information. The file must include the virtual addresses of the sections.
31021 Create a code entry for the file, which gives the start and size of the symbol
31025 Add it to the linked list in the JIT descriptor.
31028 Point the relevant_entry field of the descriptor at the entry.
31031 Set @code{action_flag} to @code{JIT_REGISTER} and call
31032 @code{__jit_debug_register_code}.
31035 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
31036 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
31037 new code. However, the linked list must still be maintained in order to allow
31038 @value{GDBN} to attach to a running process and still find the symbol files.
31040 @node Unregistering Code
31041 @section Unregistering Code
31043 If code is freed, then the JIT should use the following protocol:
31047 Remove the code entry corresponding to the code from the linked list.
31050 Point the @code{relevant_entry} field of the descriptor at the code entry.
31053 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
31054 @code{__jit_debug_register_code}.
31057 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
31058 and the JIT will leak the memory used for the associated symbol files.
31061 @chapter Reporting Bugs in @value{GDBN}
31062 @cindex bugs in @value{GDBN}
31063 @cindex reporting bugs in @value{GDBN}
31065 Your bug reports play an essential role in making @value{GDBN} reliable.
31067 Reporting a bug may help you by bringing a solution to your problem, or it
31068 may not. But in any case the principal function of a bug report is to help
31069 the entire community by making the next version of @value{GDBN} work better. Bug
31070 reports are your contribution to the maintenance of @value{GDBN}.
31072 In order for a bug report to serve its purpose, you must include the
31073 information that enables us to fix the bug.
31076 * Bug Criteria:: Have you found a bug?
31077 * Bug Reporting:: How to report bugs
31081 @section Have You Found a Bug?
31082 @cindex bug criteria
31084 If you are not sure whether you have found a bug, here are some guidelines:
31087 @cindex fatal signal
31088 @cindex debugger crash
31089 @cindex crash of debugger
31091 If the debugger gets a fatal signal, for any input whatever, that is a
31092 @value{GDBN} bug. Reliable debuggers never crash.
31094 @cindex error on valid input
31096 If @value{GDBN} produces an error message for valid input, that is a
31097 bug. (Note that if you're cross debugging, the problem may also be
31098 somewhere in the connection to the target.)
31100 @cindex invalid input
31102 If @value{GDBN} does not produce an error message for invalid input,
31103 that is a bug. However, you should note that your idea of
31104 ``invalid input'' might be our idea of ``an extension'' or ``support
31105 for traditional practice''.
31108 If you are an experienced user of debugging tools, your suggestions
31109 for improvement of @value{GDBN} are welcome in any case.
31112 @node Bug Reporting
31113 @section How to Report Bugs
31114 @cindex bug reports
31115 @cindex @value{GDBN} bugs, reporting
31117 A number of companies and individuals offer support for @sc{gnu} products.
31118 If you obtained @value{GDBN} from a support organization, we recommend you
31119 contact that organization first.
31121 You can find contact information for many support companies and
31122 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
31124 @c should add a web page ref...
31127 @ifset BUGURL_DEFAULT
31128 In any event, we also recommend that you submit bug reports for
31129 @value{GDBN}. The preferred method is to submit them directly using
31130 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
31131 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
31134 @strong{Do not send bug reports to @samp{info-gdb}, or to
31135 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
31136 not want to receive bug reports. Those that do have arranged to receive
31139 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
31140 serves as a repeater. The mailing list and the newsgroup carry exactly
31141 the same messages. Often people think of posting bug reports to the
31142 newsgroup instead of mailing them. This appears to work, but it has one
31143 problem which can be crucial: a newsgroup posting often lacks a mail
31144 path back to the sender. Thus, if we need to ask for more information,
31145 we may be unable to reach you. For this reason, it is better to send
31146 bug reports to the mailing list.
31148 @ifclear BUGURL_DEFAULT
31149 In any event, we also recommend that you submit bug reports for
31150 @value{GDBN} to @value{BUGURL}.
31154 The fundamental principle of reporting bugs usefully is this:
31155 @strong{report all the facts}. If you are not sure whether to state a
31156 fact or leave it out, state it!
31158 Often people omit facts because they think they know what causes the
31159 problem and assume that some details do not matter. Thus, you might
31160 assume that the name of the variable you use in an example does not matter.
31161 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
31162 stray memory reference which happens to fetch from the location where that
31163 name is stored in memory; perhaps, if the name were different, the contents
31164 of that location would fool the debugger into doing the right thing despite
31165 the bug. Play it safe and give a specific, complete example. That is the
31166 easiest thing for you to do, and the most helpful.
31168 Keep in mind that the purpose of a bug report is to enable us to fix the
31169 bug. It may be that the bug has been reported previously, but neither
31170 you nor we can know that unless your bug report is complete and
31173 Sometimes people give a few sketchy facts and ask, ``Does this ring a
31174 bell?'' Those bug reports are useless, and we urge everyone to
31175 @emph{refuse to respond to them} except to chide the sender to report
31178 To enable us to fix the bug, you should include all these things:
31182 The version of @value{GDBN}. @value{GDBN} announces it if you start
31183 with no arguments; you can also print it at any time using @code{show
31186 Without this, we will not know whether there is any point in looking for
31187 the bug in the current version of @value{GDBN}.
31190 The type of machine you are using, and the operating system name and
31194 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
31195 ``@value{GCC}--2.8.1''.
31198 What compiler (and its version) was used to compile the program you are
31199 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
31200 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
31201 to get this information; for other compilers, see the documentation for
31205 The command arguments you gave the compiler to compile your example and
31206 observe the bug. For example, did you use @samp{-O}? To guarantee
31207 you will not omit something important, list them all. A copy of the
31208 Makefile (or the output from make) is sufficient.
31210 If we were to try to guess the arguments, we would probably guess wrong
31211 and then we might not encounter the bug.
31214 A complete input script, and all necessary source files, that will
31218 A description of what behavior you observe that you believe is
31219 incorrect. For example, ``It gets a fatal signal.''
31221 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
31222 will certainly notice it. But if the bug is incorrect output, we might
31223 not notice unless it is glaringly wrong. You might as well not give us
31224 a chance to make a mistake.
31226 Even if the problem you experience is a fatal signal, you should still
31227 say so explicitly. Suppose something strange is going on, such as, your
31228 copy of @value{GDBN} is out of synch, or you have encountered a bug in
31229 the C library on your system. (This has happened!) Your copy might
31230 crash and ours would not. If you told us to expect a crash, then when
31231 ours fails to crash, we would know that the bug was not happening for
31232 us. If you had not told us to expect a crash, then we would not be able
31233 to draw any conclusion from our observations.
31236 @cindex recording a session script
31237 To collect all this information, you can use a session recording program
31238 such as @command{script}, which is available on many Unix systems.
31239 Just run your @value{GDBN} session inside @command{script} and then
31240 include the @file{typescript} file with your bug report.
31242 Another way to record a @value{GDBN} session is to run @value{GDBN}
31243 inside Emacs and then save the entire buffer to a file.
31246 If you wish to suggest changes to the @value{GDBN} source, send us context
31247 diffs. If you even discuss something in the @value{GDBN} source, refer to
31248 it by context, not by line number.
31250 The line numbers in our development sources will not match those in your
31251 sources. Your line numbers would convey no useful information to us.
31255 Here are some things that are not necessary:
31259 A description of the envelope of the bug.
31261 Often people who encounter a bug spend a lot of time investigating
31262 which changes to the input file will make the bug go away and which
31263 changes will not affect it.
31265 This is often time consuming and not very useful, because the way we
31266 will find the bug is by running a single example under the debugger
31267 with breakpoints, not by pure deduction from a series of examples.
31268 We recommend that you save your time for something else.
31270 Of course, if you can find a simpler example to report @emph{instead}
31271 of the original one, that is a convenience for us. Errors in the
31272 output will be easier to spot, running under the debugger will take
31273 less time, and so on.
31275 However, simplification is not vital; if you do not want to do this,
31276 report the bug anyway and send us the entire test case you used.
31279 A patch for the bug.
31281 A patch for the bug does help us if it is a good one. But do not omit
31282 the necessary information, such as the test case, on the assumption that
31283 a patch is all we need. We might see problems with your patch and decide
31284 to fix the problem another way, or we might not understand it at all.
31286 Sometimes with a program as complicated as @value{GDBN} it is very hard to
31287 construct an example that will make the program follow a certain path
31288 through the code. If you do not send us the example, we will not be able
31289 to construct one, so we will not be able to verify that the bug is fixed.
31291 And if we cannot understand what bug you are trying to fix, or why your
31292 patch should be an improvement, we will not install it. A test case will
31293 help us to understand.
31296 A guess about what the bug is or what it depends on.
31298 Such guesses are usually wrong. Even we cannot guess right about such
31299 things without first using the debugger to find the facts.
31302 @c The readline documentation is distributed with the readline code
31303 @c and consists of the two following files:
31306 @c Use -I with makeinfo to point to the appropriate directory,
31307 @c environment var TEXINPUTS with TeX.
31308 @ifclear SYSTEM_READLINE
31309 @include rluser.texi
31310 @include hsuser.texi
31314 @appendix In Memoriam
31316 The @value{GDBN} project mourns the loss of the following long-time
31321 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
31322 to Free Software in general. Outside of @value{GDBN}, he was known in
31323 the Amiga world for his series of Fish Disks, and the GeekGadget project.
31325 @item Michael Snyder
31326 Michael was one of the Global Maintainers of the @value{GDBN} project,
31327 with contributions recorded as early as 1996, until 2011. In addition
31328 to his day to day participation, he was a large driving force behind
31329 adding Reverse Debugging to @value{GDBN}.
31332 Beyond their technical contributions to the project, they were also
31333 enjoyable members of the Free Software Community. We will miss them.
31335 @node Formatting Documentation
31336 @appendix Formatting Documentation
31338 @cindex @value{GDBN} reference card
31339 @cindex reference card
31340 The @value{GDBN} 4 release includes an already-formatted reference card, ready
31341 for printing with PostScript or Ghostscript, in the @file{gdb}
31342 subdirectory of the main source directory@footnote{In
31343 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
31344 release.}. If you can use PostScript or Ghostscript with your printer,
31345 you can print the reference card immediately with @file{refcard.ps}.
31347 The release also includes the source for the reference card. You
31348 can format it, using @TeX{}, by typing:
31354 The @value{GDBN} reference card is designed to print in @dfn{landscape}
31355 mode on US ``letter'' size paper;
31356 that is, on a sheet 11 inches wide by 8.5 inches
31357 high. You will need to specify this form of printing as an option to
31358 your @sc{dvi} output program.
31360 @cindex documentation
31362 All the documentation for @value{GDBN} comes as part of the machine-readable
31363 distribution. The documentation is written in Texinfo format, which is
31364 a documentation system that uses a single source file to produce both
31365 on-line information and a printed manual. You can use one of the Info
31366 formatting commands to create the on-line version of the documentation
31367 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
31369 @value{GDBN} includes an already formatted copy of the on-line Info
31370 version of this manual in the @file{gdb} subdirectory. The main Info
31371 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
31372 subordinate files matching @samp{gdb.info*} in the same directory. If
31373 necessary, you can print out these files, or read them with any editor;
31374 but they are easier to read using the @code{info} subsystem in @sc{gnu}
31375 Emacs or the standalone @code{info} program, available as part of the
31376 @sc{gnu} Texinfo distribution.
31378 If you want to format these Info files yourself, you need one of the
31379 Info formatting programs, such as @code{texinfo-format-buffer} or
31382 If you have @code{makeinfo} installed, and are in the top level
31383 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
31384 version @value{GDBVN}), you can make the Info file by typing:
31391 If you want to typeset and print copies of this manual, you need @TeX{},
31392 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
31393 Texinfo definitions file.
31395 @TeX{} is a typesetting program; it does not print files directly, but
31396 produces output files called @sc{dvi} files. To print a typeset
31397 document, you need a program to print @sc{dvi} files. If your system
31398 has @TeX{} installed, chances are it has such a program. The precise
31399 command to use depends on your system; @kbd{lpr -d} is common; another
31400 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
31401 require a file name without any extension or a @samp{.dvi} extension.
31403 @TeX{} also requires a macro definitions file called
31404 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
31405 written in Texinfo format. On its own, @TeX{} cannot either read or
31406 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
31407 and is located in the @file{gdb-@var{version-number}/texinfo}
31410 If you have @TeX{} and a @sc{dvi} printer program installed, you can
31411 typeset and print this manual. First switch to the @file{gdb}
31412 subdirectory of the main source directory (for example, to
31413 @file{gdb-@value{GDBVN}/gdb}) and type:
31419 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
31421 @node Installing GDB
31422 @appendix Installing @value{GDBN}
31423 @cindex installation
31426 * Requirements:: Requirements for building @value{GDBN}
31427 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
31428 * Separate Objdir:: Compiling @value{GDBN} in another directory
31429 * Config Names:: Specifying names for hosts and targets
31430 * Configure Options:: Summary of options for configure
31431 * System-wide configuration:: Having a system-wide init file
31435 @section Requirements for Building @value{GDBN}
31436 @cindex building @value{GDBN}, requirements for
31438 Building @value{GDBN} requires various tools and packages to be available.
31439 Other packages will be used only if they are found.
31441 @heading Tools/Packages Necessary for Building @value{GDBN}
31443 @item ISO C90 compiler
31444 @value{GDBN} is written in ISO C90. It should be buildable with any
31445 working C90 compiler, e.g.@: GCC.
31449 @heading Tools/Packages Optional for Building @value{GDBN}
31453 @value{GDBN} can use the Expat XML parsing library. This library may be
31454 included with your operating system distribution; if it is not, you
31455 can get the latest version from @url{http://expat.sourceforge.net}.
31456 The @file{configure} script will search for this library in several
31457 standard locations; if it is installed in an unusual path, you can
31458 use the @option{--with-libexpat-prefix} option to specify its location.
31464 Remote protocol memory maps (@pxref{Memory Map Format})
31466 Target descriptions (@pxref{Target Descriptions})
31468 Remote shared library lists (@pxref{Library List Format})
31470 MS-Windows shared libraries (@pxref{Shared Libraries})
31472 Traceframe info (@pxref{Traceframe Info Format})
31476 @cindex compressed debug sections
31477 @value{GDBN} will use the @samp{zlib} library, if available, to read
31478 compressed debug sections. Some linkers, such as GNU gold, are capable
31479 of producing binaries with compressed debug sections. If @value{GDBN}
31480 is compiled with @samp{zlib}, it will be able to read the debug
31481 information in such binaries.
31483 The @samp{zlib} library is likely included with your operating system
31484 distribution; if it is not, you can get the latest version from
31485 @url{http://zlib.net}.
31488 @value{GDBN}'s features related to character sets (@pxref{Character
31489 Sets}) require a functioning @code{iconv} implementation. If you are
31490 on a GNU system, then this is provided by the GNU C Library. Some
31491 other systems also provide a working @code{iconv}.
31493 If @value{GDBN} is using the @code{iconv} program which is installed
31494 in a non-standard place, you will need to tell @value{GDBN} where to find it.
31495 This is done with @option{--with-iconv-bin} which specifies the
31496 directory that contains the @code{iconv} program.
31498 On systems without @code{iconv}, you can install GNU Libiconv. If you
31499 have previously installed Libiconv, you can use the
31500 @option{--with-libiconv-prefix} option to configure.
31502 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
31503 arrange to build Libiconv if a directory named @file{libiconv} appears
31504 in the top-most source directory. If Libiconv is built this way, and
31505 if the operating system does not provide a suitable @code{iconv}
31506 implementation, then the just-built library will automatically be used
31507 by @value{GDBN}. One easy way to set this up is to download GNU
31508 Libiconv, unpack it, and then rename the directory holding the
31509 Libiconv source code to @samp{libiconv}.
31512 @node Running Configure
31513 @section Invoking the @value{GDBN} @file{configure} Script
31514 @cindex configuring @value{GDBN}
31515 @value{GDBN} comes with a @file{configure} script that automates the process
31516 of preparing @value{GDBN} for installation; you can then use @code{make} to
31517 build the @code{gdb} program.
31519 @c irrelevant in info file; it's as current as the code it lives with.
31520 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
31521 look at the @file{README} file in the sources; we may have improved the
31522 installation procedures since publishing this manual.}
31525 The @value{GDBN} distribution includes all the source code you need for
31526 @value{GDBN} in a single directory, whose name is usually composed by
31527 appending the version number to @samp{gdb}.
31529 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
31530 @file{gdb-@value{GDBVN}} directory. That directory contains:
31533 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
31534 script for configuring @value{GDBN} and all its supporting libraries
31536 @item gdb-@value{GDBVN}/gdb
31537 the source specific to @value{GDBN} itself
31539 @item gdb-@value{GDBVN}/bfd
31540 source for the Binary File Descriptor library
31542 @item gdb-@value{GDBVN}/include
31543 @sc{gnu} include files
31545 @item gdb-@value{GDBVN}/libiberty
31546 source for the @samp{-liberty} free software library
31548 @item gdb-@value{GDBVN}/opcodes
31549 source for the library of opcode tables and disassemblers
31551 @item gdb-@value{GDBVN}/readline
31552 source for the @sc{gnu} command-line interface
31554 @item gdb-@value{GDBVN}/glob
31555 source for the @sc{gnu} filename pattern-matching subroutine
31557 @item gdb-@value{GDBVN}/mmalloc
31558 source for the @sc{gnu} memory-mapped malloc package
31561 The simplest way to configure and build @value{GDBN} is to run @file{configure}
31562 from the @file{gdb-@var{version-number}} source directory, which in
31563 this example is the @file{gdb-@value{GDBVN}} directory.
31565 First switch to the @file{gdb-@var{version-number}} source directory
31566 if you are not already in it; then run @file{configure}. Pass the
31567 identifier for the platform on which @value{GDBN} will run as an
31573 cd gdb-@value{GDBVN}
31574 ./configure @var{host}
31579 where @var{host} is an identifier such as @samp{sun4} or
31580 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
31581 (You can often leave off @var{host}; @file{configure} tries to guess the
31582 correct value by examining your system.)
31584 Running @samp{configure @var{host}} and then running @code{make} builds the
31585 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
31586 libraries, then @code{gdb} itself. The configured source files, and the
31587 binaries, are left in the corresponding source directories.
31590 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
31591 system does not recognize this automatically when you run a different
31592 shell, you may need to run @code{sh} on it explicitly:
31595 sh configure @var{host}
31598 If you run @file{configure} from a directory that contains source
31599 directories for multiple libraries or programs, such as the
31600 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
31602 creates configuration files for every directory level underneath (unless
31603 you tell it not to, with the @samp{--norecursion} option).
31605 You should run the @file{configure} script from the top directory in the
31606 source tree, the @file{gdb-@var{version-number}} directory. If you run
31607 @file{configure} from one of the subdirectories, you will configure only
31608 that subdirectory. That is usually not what you want. In particular,
31609 if you run the first @file{configure} from the @file{gdb} subdirectory
31610 of the @file{gdb-@var{version-number}} directory, you will omit the
31611 configuration of @file{bfd}, @file{readline}, and other sibling
31612 directories of the @file{gdb} subdirectory. This leads to build errors
31613 about missing include files such as @file{bfd/bfd.h}.
31615 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
31616 However, you should make sure that the shell on your path (named by
31617 the @samp{SHELL} environment variable) is publicly readable. Remember
31618 that @value{GDBN} uses the shell to start your program---some systems refuse to
31619 let @value{GDBN} debug child processes whose programs are not readable.
31621 @node Separate Objdir
31622 @section Compiling @value{GDBN} in Another Directory
31624 If you want to run @value{GDBN} versions for several host or target machines,
31625 you need a different @code{gdb} compiled for each combination of
31626 host and target. @file{configure} is designed to make this easy by
31627 allowing you to generate each configuration in a separate subdirectory,
31628 rather than in the source directory. If your @code{make} program
31629 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
31630 @code{make} in each of these directories builds the @code{gdb}
31631 program specified there.
31633 To build @code{gdb} in a separate directory, run @file{configure}
31634 with the @samp{--srcdir} option to specify where to find the source.
31635 (You also need to specify a path to find @file{configure}
31636 itself from your working directory. If the path to @file{configure}
31637 would be the same as the argument to @samp{--srcdir}, you can leave out
31638 the @samp{--srcdir} option; it is assumed.)
31640 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
31641 separate directory for a Sun 4 like this:
31645 cd gdb-@value{GDBVN}
31648 ../gdb-@value{GDBVN}/configure sun4
31653 When @file{configure} builds a configuration using a remote source
31654 directory, it creates a tree for the binaries with the same structure
31655 (and using the same names) as the tree under the source directory. In
31656 the example, you'd find the Sun 4 library @file{libiberty.a} in the
31657 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
31658 @file{gdb-sun4/gdb}.
31660 Make sure that your path to the @file{configure} script has just one
31661 instance of @file{gdb} in it. If your path to @file{configure} looks
31662 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
31663 one subdirectory of @value{GDBN}, not the whole package. This leads to
31664 build errors about missing include files such as @file{bfd/bfd.h}.
31666 One popular reason to build several @value{GDBN} configurations in separate
31667 directories is to configure @value{GDBN} for cross-compiling (where
31668 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
31669 programs that run on another machine---the @dfn{target}).
31670 You specify a cross-debugging target by
31671 giving the @samp{--target=@var{target}} option to @file{configure}.
31673 When you run @code{make} to build a program or library, you must run
31674 it in a configured directory---whatever directory you were in when you
31675 called @file{configure} (or one of its subdirectories).
31677 The @code{Makefile} that @file{configure} generates in each source
31678 directory also runs recursively. If you type @code{make} in a source
31679 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
31680 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
31681 will build all the required libraries, and then build GDB.
31683 When you have multiple hosts or targets configured in separate
31684 directories, you can run @code{make} on them in parallel (for example,
31685 if they are NFS-mounted on each of the hosts); they will not interfere
31689 @section Specifying Names for Hosts and Targets
31691 The specifications used for hosts and targets in the @file{configure}
31692 script are based on a three-part naming scheme, but some short predefined
31693 aliases are also supported. The full naming scheme encodes three pieces
31694 of information in the following pattern:
31697 @var{architecture}-@var{vendor}-@var{os}
31700 For example, you can use the alias @code{sun4} as a @var{host} argument,
31701 or as the value for @var{target} in a @code{--target=@var{target}}
31702 option. The equivalent full name is @samp{sparc-sun-sunos4}.
31704 The @file{configure} script accompanying @value{GDBN} does not provide
31705 any query facility to list all supported host and target names or
31706 aliases. @file{configure} calls the Bourne shell script
31707 @code{config.sub} to map abbreviations to full names; you can read the
31708 script, if you wish, or you can use it to test your guesses on
31709 abbreviations---for example:
31712 % sh config.sub i386-linux
31714 % sh config.sub alpha-linux
31715 alpha-unknown-linux-gnu
31716 % sh config.sub hp9k700
31718 % sh config.sub sun4
31719 sparc-sun-sunos4.1.1
31720 % sh config.sub sun3
31721 m68k-sun-sunos4.1.1
31722 % sh config.sub i986v
31723 Invalid configuration `i986v': machine `i986v' not recognized
31727 @code{config.sub} is also distributed in the @value{GDBN} source
31728 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
31730 @node Configure Options
31731 @section @file{configure} Options
31733 Here is a summary of the @file{configure} options and arguments that
31734 are most often useful for building @value{GDBN}. @file{configure} also has
31735 several other options not listed here. @inforef{What Configure
31736 Does,,configure.info}, for a full explanation of @file{configure}.
31739 configure @r{[}--help@r{]}
31740 @r{[}--prefix=@var{dir}@r{]}
31741 @r{[}--exec-prefix=@var{dir}@r{]}
31742 @r{[}--srcdir=@var{dirname}@r{]}
31743 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
31744 @r{[}--target=@var{target}@r{]}
31749 You may introduce options with a single @samp{-} rather than
31750 @samp{--} if you prefer; but you may abbreviate option names if you use
31755 Display a quick summary of how to invoke @file{configure}.
31757 @item --prefix=@var{dir}
31758 Configure the source to install programs and files under directory
31761 @item --exec-prefix=@var{dir}
31762 Configure the source to install programs under directory
31765 @c avoid splitting the warning from the explanation:
31767 @item --srcdir=@var{dirname}
31768 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
31769 @code{make} that implements the @code{VPATH} feature.}@*
31770 Use this option to make configurations in directories separate from the
31771 @value{GDBN} source directories. Among other things, you can use this to
31772 build (or maintain) several configurations simultaneously, in separate
31773 directories. @file{configure} writes configuration-specific files in
31774 the current directory, but arranges for them to use the source in the
31775 directory @var{dirname}. @file{configure} creates directories under
31776 the working directory in parallel to the source directories below
31779 @item --norecursion
31780 Configure only the directory level where @file{configure} is executed; do not
31781 propagate configuration to subdirectories.
31783 @item --target=@var{target}
31784 Configure @value{GDBN} for cross-debugging programs running on the specified
31785 @var{target}. Without this option, @value{GDBN} is configured to debug
31786 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
31788 There is no convenient way to generate a list of all available targets.
31790 @item @var{host} @dots{}
31791 Configure @value{GDBN} to run on the specified @var{host}.
31793 There is no convenient way to generate a list of all available hosts.
31796 There are many other options available as well, but they are generally
31797 needed for special purposes only.
31799 @node System-wide configuration
31800 @section System-wide configuration and settings
31801 @cindex system-wide init file
31803 @value{GDBN} can be configured to have a system-wide init file;
31804 this file will be read and executed at startup (@pxref{Startup, , What
31805 @value{GDBN} does during startup}).
31807 Here is the corresponding configure option:
31810 @item --with-system-gdbinit=@var{file}
31811 Specify that the default location of the system-wide init file is
31815 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
31816 it may be subject to relocation. Two possible cases:
31820 If the default location of this init file contains @file{$prefix},
31821 it will be subject to relocation. Suppose that the configure options
31822 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
31823 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
31824 init file is looked for as @file{$install/etc/gdbinit} instead of
31825 @file{$prefix/etc/gdbinit}.
31828 By contrast, if the default location does not contain the prefix,
31829 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
31830 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
31831 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
31832 wherever @value{GDBN} is installed.
31835 @node Maintenance Commands
31836 @appendix Maintenance Commands
31837 @cindex maintenance commands
31838 @cindex internal commands
31840 In addition to commands intended for @value{GDBN} users, @value{GDBN}
31841 includes a number of commands intended for @value{GDBN} developers,
31842 that are not documented elsewhere in this manual. These commands are
31843 provided here for reference. (For commands that turn on debugging
31844 messages, see @ref{Debugging Output}.)
31847 @kindex maint agent
31848 @kindex maint agent-eval
31849 @item maint agent @var{expression}
31850 @itemx maint agent-eval @var{expression}
31851 Translate the given @var{expression} into remote agent bytecodes.
31852 This command is useful for debugging the Agent Expression mechanism
31853 (@pxref{Agent Expressions}). The @samp{agent} version produces an
31854 expression useful for data collection, such as by tracepoints, while
31855 @samp{maint agent-eval} produces an expression that evaluates directly
31856 to a result. For instance, a collection expression for @code{globa +
31857 globb} will include bytecodes to record four bytes of memory at each
31858 of the addresses of @code{globa} and @code{globb}, while discarding
31859 the result of the addition, while an evaluation expression will do the
31860 addition and return the sum.
31862 @kindex maint info breakpoints
31863 @item @anchor{maint info breakpoints}maint info breakpoints
31864 Using the same format as @samp{info breakpoints}, display both the
31865 breakpoints you've set explicitly, and those @value{GDBN} is using for
31866 internal purposes. Internal breakpoints are shown with negative
31867 breakpoint numbers. The type column identifies what kind of breakpoint
31872 Normal, explicitly set breakpoint.
31875 Normal, explicitly set watchpoint.
31878 Internal breakpoint, used to handle correctly stepping through
31879 @code{longjmp} calls.
31881 @item longjmp resume
31882 Internal breakpoint at the target of a @code{longjmp}.
31885 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
31888 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
31891 Shared library events.
31895 @kindex set displaced-stepping
31896 @kindex show displaced-stepping
31897 @cindex displaced stepping support
31898 @cindex out-of-line single-stepping
31899 @item set displaced-stepping
31900 @itemx show displaced-stepping
31901 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
31902 if the target supports it. Displaced stepping is a way to single-step
31903 over breakpoints without removing them from the inferior, by executing
31904 an out-of-line copy of the instruction that was originally at the
31905 breakpoint location. It is also known as out-of-line single-stepping.
31908 @item set displaced-stepping on
31909 If the target architecture supports it, @value{GDBN} will use
31910 displaced stepping to step over breakpoints.
31912 @item set displaced-stepping off
31913 @value{GDBN} will not use displaced stepping to step over breakpoints,
31914 even if such is supported by the target architecture.
31916 @cindex non-stop mode, and @samp{set displaced-stepping}
31917 @item set displaced-stepping auto
31918 This is the default mode. @value{GDBN} will use displaced stepping
31919 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
31920 architecture supports displaced stepping.
31923 @kindex maint check-symtabs
31924 @item maint check-symtabs
31925 Check the consistency of psymtabs and symtabs.
31927 @kindex maint cplus first_component
31928 @item maint cplus first_component @var{name}
31929 Print the first C@t{++} class/namespace component of @var{name}.
31931 @kindex maint cplus namespace
31932 @item maint cplus namespace
31933 Print the list of possible C@t{++} namespaces.
31935 @kindex maint demangle
31936 @item maint demangle @var{name}
31937 Demangle a C@t{++} or Objective-C mangled @var{name}.
31939 @kindex maint deprecate
31940 @kindex maint undeprecate
31941 @cindex deprecated commands
31942 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
31943 @itemx maint undeprecate @var{command}
31944 Deprecate or undeprecate the named @var{command}. Deprecated commands
31945 cause @value{GDBN} to issue a warning when you use them. The optional
31946 argument @var{replacement} says which newer command should be used in
31947 favor of the deprecated one; if it is given, @value{GDBN} will mention
31948 the replacement as part of the warning.
31950 @kindex maint dump-me
31951 @item maint dump-me
31952 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
31953 Cause a fatal signal in the debugger and force it to dump its core.
31954 This is supported only on systems which support aborting a program
31955 with the @code{SIGQUIT} signal.
31957 @kindex maint internal-error
31958 @kindex maint internal-warning
31959 @item maint internal-error @r{[}@var{message-text}@r{]}
31960 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
31961 Cause @value{GDBN} to call the internal function @code{internal_error}
31962 or @code{internal_warning} and hence behave as though an internal error
31963 or internal warning has been detected. In addition to reporting the
31964 internal problem, these functions give the user the opportunity to
31965 either quit @value{GDBN} or create a core file of the current
31966 @value{GDBN} session.
31968 These commands take an optional parameter @var{message-text} that is
31969 used as the text of the error or warning message.
31971 Here's an example of using @code{internal-error}:
31974 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
31975 @dots{}/maint.c:121: internal-error: testing, 1, 2
31976 A problem internal to GDB has been detected. Further
31977 debugging may prove unreliable.
31978 Quit this debugging session? (y or n) @kbd{n}
31979 Create a core file? (y or n) @kbd{n}
31983 @cindex @value{GDBN} internal error
31984 @cindex internal errors, control of @value{GDBN} behavior
31986 @kindex maint set internal-error
31987 @kindex maint show internal-error
31988 @kindex maint set internal-warning
31989 @kindex maint show internal-warning
31990 @item maint set internal-error @var{action} [ask|yes|no]
31991 @itemx maint show internal-error @var{action}
31992 @itemx maint set internal-warning @var{action} [ask|yes|no]
31993 @itemx maint show internal-warning @var{action}
31994 When @value{GDBN} reports an internal problem (error or warning) it
31995 gives the user the opportunity to both quit @value{GDBN} and create a
31996 core file of the current @value{GDBN} session. These commands let you
31997 override the default behaviour for each particular @var{action},
31998 described in the table below.
32002 You can specify that @value{GDBN} should always (yes) or never (no)
32003 quit. The default is to ask the user what to do.
32006 You can specify that @value{GDBN} should always (yes) or never (no)
32007 create a core file. The default is to ask the user what to do.
32010 @kindex maint packet
32011 @item maint packet @var{text}
32012 If @value{GDBN} is talking to an inferior via the serial protocol,
32013 then this command sends the string @var{text} to the inferior, and
32014 displays the response packet. @value{GDBN} supplies the initial
32015 @samp{$} character, the terminating @samp{#} character, and the
32018 @kindex maint print architecture
32019 @item maint print architecture @r{[}@var{file}@r{]}
32020 Print the entire architecture configuration. The optional argument
32021 @var{file} names the file where the output goes.
32023 @kindex maint print c-tdesc
32024 @item maint print c-tdesc
32025 Print the current target description (@pxref{Target Descriptions}) as
32026 a C source file. The created source file can be used in @value{GDBN}
32027 when an XML parser is not available to parse the description.
32029 @kindex maint print dummy-frames
32030 @item maint print dummy-frames
32031 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
32034 (@value{GDBP}) @kbd{b add}
32036 (@value{GDBP}) @kbd{print add(2,3)}
32037 Breakpoint 2, add (a=2, b=3) at @dots{}
32039 The program being debugged stopped while in a function called from GDB.
32041 (@value{GDBP}) @kbd{maint print dummy-frames}
32042 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
32043 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
32044 call_lo=0x01014000 call_hi=0x01014001
32048 Takes an optional file parameter.
32050 @kindex maint print registers
32051 @kindex maint print raw-registers
32052 @kindex maint print cooked-registers
32053 @kindex maint print register-groups
32054 @kindex maint print remote-registers
32055 @item maint print registers @r{[}@var{file}@r{]}
32056 @itemx maint print raw-registers @r{[}@var{file}@r{]}
32057 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
32058 @itemx maint print register-groups @r{[}@var{file}@r{]}
32059 @itemx maint print remote-registers @r{[}@var{file}@r{]}
32060 Print @value{GDBN}'s internal register data structures.
32062 The command @code{maint print raw-registers} includes the contents of
32063 the raw register cache; the command @code{maint print
32064 cooked-registers} includes the (cooked) value of all registers,
32065 including registers which aren't available on the target nor visible
32066 to user; the command @code{maint print register-groups} includes the
32067 groups that each register is a member of; and the command @code{maint
32068 print remote-registers} includes the remote target's register numbers
32069 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
32070 @value{GDBN} Internals}.
32072 These commands take an optional parameter, a file name to which to
32073 write the information.
32075 @kindex maint print reggroups
32076 @item maint print reggroups @r{[}@var{file}@r{]}
32077 Print @value{GDBN}'s internal register group data structures. The
32078 optional argument @var{file} tells to what file to write the
32081 The register groups info looks like this:
32084 (@value{GDBP}) @kbd{maint print reggroups}
32097 This command forces @value{GDBN} to flush its internal register cache.
32099 @kindex maint print objfiles
32100 @cindex info for known object files
32101 @item maint print objfiles
32102 Print a dump of all known object files. For each object file, this
32103 command prints its name, address in memory, and all of its psymtabs
32106 @kindex maint print section-scripts
32107 @cindex info for known .debug_gdb_scripts-loaded scripts
32108 @item maint print section-scripts [@var{regexp}]
32109 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
32110 If @var{regexp} is specified, only print scripts loaded by object files
32111 matching @var{regexp}.
32112 For each script, this command prints its name as specified in the objfile,
32113 and the full path if known.
32114 @xref{.debug_gdb_scripts section}.
32116 @kindex maint print statistics
32117 @cindex bcache statistics
32118 @item maint print statistics
32119 This command prints, for each object file in the program, various data
32120 about that object file followed by the byte cache (@dfn{bcache})
32121 statistics for the object file. The objfile data includes the number
32122 of minimal, partial, full, and stabs symbols, the number of types
32123 defined by the objfile, the number of as yet unexpanded psym tables,
32124 the number of line tables and string tables, and the amount of memory
32125 used by the various tables. The bcache statistics include the counts,
32126 sizes, and counts of duplicates of all and unique objects, max,
32127 average, and median entry size, total memory used and its overhead and
32128 savings, and various measures of the hash table size and chain
32131 @kindex maint print target-stack
32132 @cindex target stack description
32133 @item maint print target-stack
32134 A @dfn{target} is an interface between the debugger and a particular
32135 kind of file or process. Targets can be stacked in @dfn{strata},
32136 so that more than one target can potentially respond to a request.
32137 In particular, memory accesses will walk down the stack of targets
32138 until they find a target that is interested in handling that particular
32141 This command prints a short description of each layer that was pushed on
32142 the @dfn{target stack}, starting from the top layer down to the bottom one.
32144 @kindex maint print type
32145 @cindex type chain of a data type
32146 @item maint print type @var{expr}
32147 Print the type chain for a type specified by @var{expr}. The argument
32148 can be either a type name or a symbol. If it is a symbol, the type of
32149 that symbol is described. The type chain produced by this command is
32150 a recursive definition of the data type as stored in @value{GDBN}'s
32151 data structures, including its flags and contained types.
32153 @kindex maint set dwarf2 always-disassemble
32154 @kindex maint show dwarf2 always-disassemble
32155 @item maint set dwarf2 always-disassemble
32156 @item maint show dwarf2 always-disassemble
32157 Control the behavior of @code{info address} when using DWARF debugging
32160 The default is @code{off}, which means that @value{GDBN} should try to
32161 describe a variable's location in an easily readable format. When
32162 @code{on}, @value{GDBN} will instead display the DWARF location
32163 expression in an assembly-like format. Note that some locations are
32164 too complex for @value{GDBN} to describe simply; in this case you will
32165 always see the disassembly form.
32167 Here is an example of the resulting disassembly:
32170 (gdb) info addr argc
32171 Symbol "argc" is a complex DWARF expression:
32175 For more information on these expressions, see
32176 @uref{http://www.dwarfstd.org/, the DWARF standard}.
32178 @kindex maint set dwarf2 max-cache-age
32179 @kindex maint show dwarf2 max-cache-age
32180 @item maint set dwarf2 max-cache-age
32181 @itemx maint show dwarf2 max-cache-age
32182 Control the DWARF 2 compilation unit cache.
32184 @cindex DWARF 2 compilation units cache
32185 In object files with inter-compilation-unit references, such as those
32186 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
32187 reader needs to frequently refer to previously read compilation units.
32188 This setting controls how long a compilation unit will remain in the
32189 cache if it is not referenced. A higher limit means that cached
32190 compilation units will be stored in memory longer, and more total
32191 memory will be used. Setting it to zero disables caching, which will
32192 slow down @value{GDBN} startup, but reduce memory consumption.
32194 @kindex maint set profile
32195 @kindex maint show profile
32196 @cindex profiling GDB
32197 @item maint set profile
32198 @itemx maint show profile
32199 Control profiling of @value{GDBN}.
32201 Profiling will be disabled until you use the @samp{maint set profile}
32202 command to enable it. When you enable profiling, the system will begin
32203 collecting timing and execution count data; when you disable profiling or
32204 exit @value{GDBN}, the results will be written to a log file. Remember that
32205 if you use profiling, @value{GDBN} will overwrite the profiling log file
32206 (often called @file{gmon.out}). If you have a record of important profiling
32207 data in a @file{gmon.out} file, be sure to move it to a safe location.
32209 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
32210 compiled with the @samp{-pg} compiler option.
32212 @kindex maint set show-debug-regs
32213 @kindex maint show show-debug-regs
32214 @cindex hardware debug registers
32215 @item maint set show-debug-regs
32216 @itemx maint show show-debug-regs
32217 Control whether to show variables that mirror the hardware debug
32218 registers. Use @code{ON} to enable, @code{OFF} to disable. If
32219 enabled, the debug registers values are shown when @value{GDBN} inserts or
32220 removes a hardware breakpoint or watchpoint, and when the inferior
32221 triggers a hardware-assisted breakpoint or watchpoint.
32223 @kindex maint set show-all-tib
32224 @kindex maint show show-all-tib
32225 @item maint set show-all-tib
32226 @itemx maint show show-all-tib
32227 Control whether to show all non zero areas within a 1k block starting
32228 at thread local base, when using the @samp{info w32 thread-information-block}
32231 @kindex maint space
32232 @cindex memory used by commands
32234 Control whether to display memory usage for each command. If set to a
32235 nonzero value, @value{GDBN} will display how much memory each command
32236 took, following the command's own output. This can also be requested
32237 by invoking @value{GDBN} with the @option{--statistics} command-line
32238 switch (@pxref{Mode Options}).
32241 @cindex time of command execution
32243 Control whether to display the execution time for each command. If
32244 set to a nonzero value, @value{GDBN} will display how much time it
32245 took to execute each command, following the command's own output.
32246 The time is not printed for the commands that run the target, since
32247 there's no mechanism currently to compute how much time was spend
32248 by @value{GDBN} and how much time was spend by the program been debugged.
32249 it's not possibly currently
32250 This can also be requested by invoking @value{GDBN} with the
32251 @option{--statistics} command-line switch (@pxref{Mode Options}).
32253 @kindex maint translate-address
32254 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
32255 Find the symbol stored at the location specified by the address
32256 @var{addr} and an optional section name @var{section}. If found,
32257 @value{GDBN} prints the name of the closest symbol and an offset from
32258 the symbol's location to the specified address. This is similar to
32259 the @code{info address} command (@pxref{Symbols}), except that this
32260 command also allows to find symbols in other sections.
32262 If section was not specified, the section in which the symbol was found
32263 is also printed. For dynamically linked executables, the name of
32264 executable or shared library containing the symbol is printed as well.
32268 The following command is useful for non-interactive invocations of
32269 @value{GDBN}, such as in the test suite.
32272 @item set watchdog @var{nsec}
32273 @kindex set watchdog
32274 @cindex watchdog timer
32275 @cindex timeout for commands
32276 Set the maximum number of seconds @value{GDBN} will wait for the
32277 target operation to finish. If this time expires, @value{GDBN}
32278 reports and error and the command is aborted.
32280 @item show watchdog
32281 Show the current setting of the target wait timeout.
32284 @node Remote Protocol
32285 @appendix @value{GDBN} Remote Serial Protocol
32290 * Stop Reply Packets::
32291 * General Query Packets::
32292 * Architecture-Specific Protocol Details::
32293 * Tracepoint Packets::
32294 * Host I/O Packets::
32296 * Notification Packets::
32297 * Remote Non-Stop::
32298 * Packet Acknowledgment::
32300 * File-I/O Remote Protocol Extension::
32301 * Library List Format::
32302 * Memory Map Format::
32303 * Thread List Format::
32304 * Traceframe Info Format::
32310 There may be occasions when you need to know something about the
32311 protocol---for example, if there is only one serial port to your target
32312 machine, you might want your program to do something special if it
32313 recognizes a packet meant for @value{GDBN}.
32315 In the examples below, @samp{->} and @samp{<-} are used to indicate
32316 transmitted and received data, respectively.
32318 @cindex protocol, @value{GDBN} remote serial
32319 @cindex serial protocol, @value{GDBN} remote
32320 @cindex remote serial protocol
32321 All @value{GDBN} commands and responses (other than acknowledgments
32322 and notifications, see @ref{Notification Packets}) are sent as a
32323 @var{packet}. A @var{packet} is introduced with the character
32324 @samp{$}, the actual @var{packet-data}, and the terminating character
32325 @samp{#} followed by a two-digit @var{checksum}:
32328 @code{$}@var{packet-data}@code{#}@var{checksum}
32332 @cindex checksum, for @value{GDBN} remote
32334 The two-digit @var{checksum} is computed as the modulo 256 sum of all
32335 characters between the leading @samp{$} and the trailing @samp{#} (an
32336 eight bit unsigned checksum).
32338 Implementors should note that prior to @value{GDBN} 5.0 the protocol
32339 specification also included an optional two-digit @var{sequence-id}:
32342 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
32345 @cindex sequence-id, for @value{GDBN} remote
32347 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
32348 has never output @var{sequence-id}s. Stubs that handle packets added
32349 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
32351 When either the host or the target machine receives a packet, the first
32352 response expected is an acknowledgment: either @samp{+} (to indicate
32353 the package was received correctly) or @samp{-} (to request
32357 -> @code{$}@var{packet-data}@code{#}@var{checksum}
32362 The @samp{+}/@samp{-} acknowledgments can be disabled
32363 once a connection is established.
32364 @xref{Packet Acknowledgment}, for details.
32366 The host (@value{GDBN}) sends @var{command}s, and the target (the
32367 debugging stub incorporated in your program) sends a @var{response}. In
32368 the case of step and continue @var{command}s, the response is only sent
32369 when the operation has completed, and the target has again stopped all
32370 threads in all attached processes. This is the default all-stop mode
32371 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
32372 execution mode; see @ref{Remote Non-Stop}, for details.
32374 @var{packet-data} consists of a sequence of characters with the
32375 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
32378 @cindex remote protocol, field separator
32379 Fields within the packet should be separated using @samp{,} @samp{;} or
32380 @samp{:}. Except where otherwise noted all numbers are represented in
32381 @sc{hex} with leading zeros suppressed.
32383 Implementors should note that prior to @value{GDBN} 5.0, the character
32384 @samp{:} could not appear as the third character in a packet (as it
32385 would potentially conflict with the @var{sequence-id}).
32387 @cindex remote protocol, binary data
32388 @anchor{Binary Data}
32389 Binary data in most packets is encoded either as two hexadecimal
32390 digits per byte of binary data. This allowed the traditional remote
32391 protocol to work over connections which were only seven-bit clean.
32392 Some packets designed more recently assume an eight-bit clean
32393 connection, and use a more efficient encoding to send and receive
32396 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
32397 as an escape character. Any escaped byte is transmitted as the escape
32398 character followed by the original character XORed with @code{0x20}.
32399 For example, the byte @code{0x7d} would be transmitted as the two
32400 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
32401 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
32402 @samp{@}}) must always be escaped. Responses sent by the stub
32403 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
32404 is not interpreted as the start of a run-length encoded sequence
32407 Response @var{data} can be run-length encoded to save space.
32408 Run-length encoding replaces runs of identical characters with one
32409 instance of the repeated character, followed by a @samp{*} and a
32410 repeat count. The repeat count is itself sent encoded, to avoid
32411 binary characters in @var{data}: a value of @var{n} is sent as
32412 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
32413 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
32414 code 32) for a repeat count of 3. (This is because run-length
32415 encoding starts to win for counts 3 or more.) Thus, for example,
32416 @samp{0* } is a run-length encoding of ``0000'': the space character
32417 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
32420 The printable characters @samp{#} and @samp{$} or with a numeric value
32421 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
32422 seven repeats (@samp{$}) can be expanded using a repeat count of only
32423 five (@samp{"}). For example, @samp{00000000} can be encoded as
32426 The error response returned for some packets includes a two character
32427 error number. That number is not well defined.
32429 @cindex empty response, for unsupported packets
32430 For any @var{command} not supported by the stub, an empty response
32431 (@samp{$#00}) should be returned. That way it is possible to extend the
32432 protocol. A newer @value{GDBN} can tell if a packet is supported based
32435 At a minimum, a stub is required to support the @samp{g} and @samp{G}
32436 commands for register access, and the @samp{m} and @samp{M} commands
32437 for memory access. Stubs that only control single-threaded targets
32438 can implement run control with the @samp{c} (continue), and @samp{s}
32439 (step) commands. Stubs that support multi-threading targets should
32440 support the @samp{vCont} command. All other commands are optional.
32445 The following table provides a complete list of all currently defined
32446 @var{command}s and their corresponding response @var{data}.
32447 @xref{File-I/O Remote Protocol Extension}, for details about the File
32448 I/O extension of the remote protocol.
32450 Each packet's description has a template showing the packet's overall
32451 syntax, followed by an explanation of the packet's meaning. We
32452 include spaces in some of the templates for clarity; these are not
32453 part of the packet's syntax. No @value{GDBN} packet uses spaces to
32454 separate its components. For example, a template like @samp{foo
32455 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
32456 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
32457 @var{baz}. @value{GDBN} does not transmit a space character between the
32458 @samp{foo} and the @var{bar}, or between the @var{bar} and the
32461 @cindex @var{thread-id}, in remote protocol
32462 @anchor{thread-id syntax}
32463 Several packets and replies include a @var{thread-id} field to identify
32464 a thread. Normally these are positive numbers with a target-specific
32465 interpretation, formatted as big-endian hex strings. A @var{thread-id}
32466 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
32469 In addition, the remote protocol supports a multiprocess feature in
32470 which the @var{thread-id} syntax is extended to optionally include both
32471 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
32472 The @var{pid} (process) and @var{tid} (thread) components each have the
32473 format described above: a positive number with target-specific
32474 interpretation formatted as a big-endian hex string, literal @samp{-1}
32475 to indicate all processes or threads (respectively), or @samp{0} to
32476 indicate an arbitrary process or thread. Specifying just a process, as
32477 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
32478 error to specify all processes but a specific thread, such as
32479 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
32480 for those packets and replies explicitly documented to include a process
32481 ID, rather than a @var{thread-id}.
32483 The multiprocess @var{thread-id} syntax extensions are only used if both
32484 @value{GDBN} and the stub report support for the @samp{multiprocess}
32485 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
32488 Note that all packet forms beginning with an upper- or lower-case
32489 letter, other than those described here, are reserved for future use.
32491 Here are the packet descriptions.
32496 @cindex @samp{!} packet
32497 @anchor{extended mode}
32498 Enable extended mode. In extended mode, the remote server is made
32499 persistent. The @samp{R} packet is used to restart the program being
32505 The remote target both supports and has enabled extended mode.
32509 @cindex @samp{?} packet
32510 Indicate the reason the target halted. The reply is the same as for
32511 step and continue. This packet has a special interpretation when the
32512 target is in non-stop mode; see @ref{Remote Non-Stop}.
32515 @xref{Stop Reply Packets}, for the reply specifications.
32517 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
32518 @cindex @samp{A} packet
32519 Initialized @code{argv[]} array passed into program. @var{arglen}
32520 specifies the number of bytes in the hex encoded byte stream
32521 @var{arg}. See @code{gdbserver} for more details.
32526 The arguments were set.
32532 @cindex @samp{b} packet
32533 (Don't use this packet; its behavior is not well-defined.)
32534 Change the serial line speed to @var{baud}.
32536 JTC: @emph{When does the transport layer state change? When it's
32537 received, or after the ACK is transmitted. In either case, there are
32538 problems if the command or the acknowledgment packet is dropped.}
32540 Stan: @emph{If people really wanted to add something like this, and get
32541 it working for the first time, they ought to modify ser-unix.c to send
32542 some kind of out-of-band message to a specially-setup stub and have the
32543 switch happen "in between" packets, so that from remote protocol's point
32544 of view, nothing actually happened.}
32546 @item B @var{addr},@var{mode}
32547 @cindex @samp{B} packet
32548 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
32549 breakpoint at @var{addr}.
32551 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
32552 (@pxref{insert breakpoint or watchpoint packet}).
32554 @cindex @samp{bc} packet
32557 Backward continue. Execute the target system in reverse. No parameter.
32558 @xref{Reverse Execution}, for more information.
32561 @xref{Stop Reply Packets}, for the reply specifications.
32563 @cindex @samp{bs} packet
32566 Backward single step. Execute one instruction in reverse. No parameter.
32567 @xref{Reverse Execution}, for more information.
32570 @xref{Stop Reply Packets}, for the reply specifications.
32572 @item c @r{[}@var{addr}@r{]}
32573 @cindex @samp{c} packet
32574 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
32575 resume at current address.
32577 This packet is deprecated for multi-threading support. @xref{vCont
32581 @xref{Stop Reply Packets}, for the reply specifications.
32583 @item C @var{sig}@r{[};@var{addr}@r{]}
32584 @cindex @samp{C} packet
32585 Continue with signal @var{sig} (hex signal number). If
32586 @samp{;@var{addr}} is omitted, resume at same address.
32588 This packet is deprecated for multi-threading support. @xref{vCont
32592 @xref{Stop Reply Packets}, for the reply specifications.
32595 @cindex @samp{d} packet
32598 Don't use this packet; instead, define a general set packet
32599 (@pxref{General Query Packets}).
32603 @cindex @samp{D} packet
32604 The first form of the packet is used to detach @value{GDBN} from the
32605 remote system. It is sent to the remote target
32606 before @value{GDBN} disconnects via the @code{detach} command.
32608 The second form, including a process ID, is used when multiprocess
32609 protocol extensions are enabled (@pxref{multiprocess extensions}), to
32610 detach only a specific process. The @var{pid} is specified as a
32611 big-endian hex string.
32621 @item F @var{RC},@var{EE},@var{CF};@var{XX}
32622 @cindex @samp{F} packet
32623 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
32624 This is part of the File-I/O protocol extension. @xref{File-I/O
32625 Remote Protocol Extension}, for the specification.
32628 @anchor{read registers packet}
32629 @cindex @samp{g} packet
32630 Read general registers.
32634 @item @var{XX@dots{}}
32635 Each byte of register data is described by two hex digits. The bytes
32636 with the register are transmitted in target byte order. The size of
32637 each register and their position within the @samp{g} packet are
32638 determined by the @value{GDBN} internal gdbarch functions
32639 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
32640 specification of several standard @samp{g} packets is specified below.
32642 When reading registers from a trace frame (@pxref{Analyze Collected
32643 Data,,Using the Collected Data}), the stub may also return a string of
32644 literal @samp{x}'s in place of the register data digits, to indicate
32645 that the corresponding register has not been collected, thus its value
32646 is unavailable. For example, for an architecture with 4 registers of
32647 4 bytes each, the following reply indicates to @value{GDBN} that
32648 registers 0 and 2 have not been collected, while registers 1 and 3
32649 have been collected, and both have zero value:
32653 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
32660 @item G @var{XX@dots{}}
32661 @cindex @samp{G} packet
32662 Write general registers. @xref{read registers packet}, for a
32663 description of the @var{XX@dots{}} data.
32673 @item H @var{op} @var{thread-id}
32674 @cindex @samp{H} packet
32675 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
32676 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
32677 it should be @samp{c} for step and continue operations (note that this
32678 is deprecated, supporting the @samp{vCont} command is a better
32679 option), @samp{g} for other operations. The thread designator
32680 @var{thread-id} has the format and interpretation described in
32681 @ref{thread-id syntax}.
32692 @c 'H': How restrictive (or permissive) is the thread model. If a
32693 @c thread is selected and stopped, are other threads allowed
32694 @c to continue to execute? As I mentioned above, I think the
32695 @c semantics of each command when a thread is selected must be
32696 @c described. For example:
32698 @c 'g': If the stub supports threads and a specific thread is
32699 @c selected, returns the register block from that thread;
32700 @c otherwise returns current registers.
32702 @c 'G' If the stub supports threads and a specific thread is
32703 @c selected, sets the registers of the register block of
32704 @c that thread; otherwise sets current registers.
32706 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
32707 @anchor{cycle step packet}
32708 @cindex @samp{i} packet
32709 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
32710 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
32711 step starting at that address.
32714 @cindex @samp{I} packet
32715 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
32719 @cindex @samp{k} packet
32722 FIXME: @emph{There is no description of how to operate when a specific
32723 thread context has been selected (i.e.@: does 'k' kill only that
32726 @item m @var{addr},@var{length}
32727 @cindex @samp{m} packet
32728 Read @var{length} bytes of memory starting at address @var{addr}.
32729 Note that @var{addr} may not be aligned to any particular boundary.
32731 The stub need not use any particular size or alignment when gathering
32732 data from memory for the response; even if @var{addr} is word-aligned
32733 and @var{length} is a multiple of the word size, the stub is free to
32734 use byte accesses, or not. For this reason, this packet may not be
32735 suitable for accessing memory-mapped I/O devices.
32736 @cindex alignment of remote memory accesses
32737 @cindex size of remote memory accesses
32738 @cindex memory, alignment and size of remote accesses
32742 @item @var{XX@dots{}}
32743 Memory contents; each byte is transmitted as a two-digit hexadecimal
32744 number. The reply may contain fewer bytes than requested if the
32745 server was able to read only part of the region of memory.
32750 @item M @var{addr},@var{length}:@var{XX@dots{}}
32751 @cindex @samp{M} packet
32752 Write @var{length} bytes of memory starting at address @var{addr}.
32753 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
32754 hexadecimal number.
32761 for an error (this includes the case where only part of the data was
32766 @cindex @samp{p} packet
32767 Read the value of register @var{n}; @var{n} is in hex.
32768 @xref{read registers packet}, for a description of how the returned
32769 register value is encoded.
32773 @item @var{XX@dots{}}
32774 the register's value
32778 Indicating an unrecognized @var{query}.
32781 @item P @var{n@dots{}}=@var{r@dots{}}
32782 @anchor{write register packet}
32783 @cindex @samp{P} packet
32784 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
32785 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
32786 digits for each byte in the register (target byte order).
32796 @item q @var{name} @var{params}@dots{}
32797 @itemx Q @var{name} @var{params}@dots{}
32798 @cindex @samp{q} packet
32799 @cindex @samp{Q} packet
32800 General query (@samp{q}) and set (@samp{Q}). These packets are
32801 described fully in @ref{General Query Packets}.
32804 @cindex @samp{r} packet
32805 Reset the entire system.
32807 Don't use this packet; use the @samp{R} packet instead.
32810 @cindex @samp{R} packet
32811 Restart the program being debugged. @var{XX}, while needed, is ignored.
32812 This packet is only available in extended mode (@pxref{extended mode}).
32814 The @samp{R} packet has no reply.
32816 @item s @r{[}@var{addr}@r{]}
32817 @cindex @samp{s} packet
32818 Single step. @var{addr} is the address at which to resume. If
32819 @var{addr} is omitted, resume at same address.
32821 This packet is deprecated for multi-threading support. @xref{vCont
32825 @xref{Stop Reply Packets}, for the reply specifications.
32827 @item S @var{sig}@r{[};@var{addr}@r{]}
32828 @anchor{step with signal packet}
32829 @cindex @samp{S} packet
32830 Step with signal. This is analogous to the @samp{C} packet, but
32831 requests a single-step, rather than a normal resumption of execution.
32833 This packet is deprecated for multi-threading support. @xref{vCont
32837 @xref{Stop Reply Packets}, for the reply specifications.
32839 @item t @var{addr}:@var{PP},@var{MM}
32840 @cindex @samp{t} packet
32841 Search backwards starting at address @var{addr} for a match with pattern
32842 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
32843 @var{addr} must be at least 3 digits.
32845 @item T @var{thread-id}
32846 @cindex @samp{T} packet
32847 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
32852 thread is still alive
32858 Packets starting with @samp{v} are identified by a multi-letter name,
32859 up to the first @samp{;} or @samp{?} (or the end of the packet).
32861 @item vAttach;@var{pid}
32862 @cindex @samp{vAttach} packet
32863 Attach to a new process with the specified process ID @var{pid}.
32864 The process ID is a
32865 hexadecimal integer identifying the process. In all-stop mode, all
32866 threads in the attached process are stopped; in non-stop mode, it may be
32867 attached without being stopped if that is supported by the target.
32869 @c In non-stop mode, on a successful vAttach, the stub should set the
32870 @c current thread to a thread of the newly-attached process. After
32871 @c attaching, GDB queries for the attached process's thread ID with qC.
32872 @c Also note that, from a user perspective, whether or not the
32873 @c target is stopped on attach in non-stop mode depends on whether you
32874 @c use the foreground or background version of the attach command, not
32875 @c on what vAttach does; GDB does the right thing with respect to either
32876 @c stopping or restarting threads.
32878 This packet is only available in extended mode (@pxref{extended mode}).
32884 @item @r{Any stop packet}
32885 for success in all-stop mode (@pxref{Stop Reply Packets})
32887 for success in non-stop mode (@pxref{Remote Non-Stop})
32890 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
32891 @cindex @samp{vCont} packet
32892 @anchor{vCont packet}
32893 Resume the inferior, specifying different actions for each thread.
32894 If an action is specified with no @var{thread-id}, then it is applied to any
32895 threads that don't have a specific action specified; if no default action is
32896 specified then other threads should remain stopped in all-stop mode and
32897 in their current state in non-stop mode.
32898 Specifying multiple
32899 default actions is an error; specifying no actions is also an error.
32900 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
32902 Currently supported actions are:
32908 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
32912 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
32917 The optional argument @var{addr} normally associated with the
32918 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
32919 not supported in @samp{vCont}.
32921 The @samp{t} action is only relevant in non-stop mode
32922 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
32923 A stop reply should be generated for any affected thread not already stopped.
32924 When a thread is stopped by means of a @samp{t} action,
32925 the corresponding stop reply should indicate that the thread has stopped with
32926 signal @samp{0}, regardless of whether the target uses some other signal
32927 as an implementation detail.
32930 @xref{Stop Reply Packets}, for the reply specifications.
32933 @cindex @samp{vCont?} packet
32934 Request a list of actions supported by the @samp{vCont} packet.
32938 @item vCont@r{[};@var{action}@dots{}@r{]}
32939 The @samp{vCont} packet is supported. Each @var{action} is a supported
32940 command in the @samp{vCont} packet.
32942 The @samp{vCont} packet is not supported.
32945 @item vFile:@var{operation}:@var{parameter}@dots{}
32946 @cindex @samp{vFile} packet
32947 Perform a file operation on the target system. For details,
32948 see @ref{Host I/O Packets}.
32950 @item vFlashErase:@var{addr},@var{length}
32951 @cindex @samp{vFlashErase} packet
32952 Direct the stub to erase @var{length} bytes of flash starting at
32953 @var{addr}. The region may enclose any number of flash blocks, but
32954 its start and end must fall on block boundaries, as indicated by the
32955 flash block size appearing in the memory map (@pxref{Memory Map
32956 Format}). @value{GDBN} groups flash memory programming operations
32957 together, and sends a @samp{vFlashDone} request after each group; the
32958 stub is allowed to delay erase operation until the @samp{vFlashDone}
32959 packet is received.
32961 The stub must support @samp{vCont} if it reports support for
32962 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
32963 this case @samp{vCont} actions can be specified to apply to all threads
32964 in a process by using the @samp{p@var{pid}.-1} form of the
32975 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
32976 @cindex @samp{vFlashWrite} packet
32977 Direct the stub to write data to flash address @var{addr}. The data
32978 is passed in binary form using the same encoding as for the @samp{X}
32979 packet (@pxref{Binary Data}). The memory ranges specified by
32980 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
32981 not overlap, and must appear in order of increasing addresses
32982 (although @samp{vFlashErase} packets for higher addresses may already
32983 have been received; the ordering is guaranteed only between
32984 @samp{vFlashWrite} packets). If a packet writes to an address that was
32985 neither erased by a preceding @samp{vFlashErase} packet nor by some other
32986 target-specific method, the results are unpredictable.
32994 for vFlashWrite addressing non-flash memory
33000 @cindex @samp{vFlashDone} packet
33001 Indicate to the stub that flash programming operation is finished.
33002 The stub is permitted to delay or batch the effects of a group of
33003 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
33004 @samp{vFlashDone} packet is received. The contents of the affected
33005 regions of flash memory are unpredictable until the @samp{vFlashDone}
33006 request is completed.
33008 @item vKill;@var{pid}
33009 @cindex @samp{vKill} packet
33010 Kill the process with the specified process ID. @var{pid} is a
33011 hexadecimal integer identifying the process. This packet is used in
33012 preference to @samp{k} when multiprocess protocol extensions are
33013 supported; see @ref{multiprocess extensions}.
33023 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
33024 @cindex @samp{vRun} packet
33025 Run the program @var{filename}, passing it each @var{argument} on its
33026 command line. The file and arguments are hex-encoded strings. If
33027 @var{filename} is an empty string, the stub may use a default program
33028 (e.g.@: the last program run). The program is created in the stopped
33031 @c FIXME: What about non-stop mode?
33033 This packet is only available in extended mode (@pxref{extended mode}).
33039 @item @r{Any stop packet}
33040 for success (@pxref{Stop Reply Packets})
33044 @anchor{vStopped packet}
33045 @cindex @samp{vStopped} packet
33047 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
33048 reply and prompt for the stub to report another one.
33052 @item @r{Any stop packet}
33053 if there is another unreported stop event (@pxref{Stop Reply Packets})
33055 if there are no unreported stop events
33058 @item X @var{addr},@var{length}:@var{XX@dots{}}
33060 @cindex @samp{X} packet
33061 Write data to memory, where the data is transmitted in binary.
33062 @var{addr} is address, @var{length} is number of bytes,
33063 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
33073 @item z @var{type},@var{addr},@var{kind}
33074 @itemx Z @var{type},@var{addr},@var{kind}
33075 @anchor{insert breakpoint or watchpoint packet}
33076 @cindex @samp{z} packet
33077 @cindex @samp{Z} packets
33078 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
33079 watchpoint starting at address @var{address} of kind @var{kind}.
33081 Each breakpoint and watchpoint packet @var{type} is documented
33084 @emph{Implementation notes: A remote target shall return an empty string
33085 for an unrecognized breakpoint or watchpoint packet @var{type}. A
33086 remote target shall support either both or neither of a given
33087 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
33088 avoid potential problems with duplicate packets, the operations should
33089 be implemented in an idempotent way.}
33091 @item z0,@var{addr},@var{kind}
33092 @itemx Z0,@var{addr},@var{kind}
33093 @cindex @samp{z0} packet
33094 @cindex @samp{Z0} packet
33095 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
33096 @var{addr} of type @var{kind}.
33098 A memory breakpoint is implemented by replacing the instruction at
33099 @var{addr} with a software breakpoint or trap instruction. The
33100 @var{kind} is target-specific and typically indicates the size of
33101 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
33102 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
33103 architectures have additional meanings for @var{kind};
33104 see @ref{Architecture-Specific Protocol Details}.
33106 @emph{Implementation note: It is possible for a target to copy or move
33107 code that contains memory breakpoints (e.g., when implementing
33108 overlays). The behavior of this packet, in the presence of such a
33109 target, is not defined.}
33121 @item z1,@var{addr},@var{kind}
33122 @itemx Z1,@var{addr},@var{kind}
33123 @cindex @samp{z1} packet
33124 @cindex @samp{Z1} packet
33125 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
33126 address @var{addr}.
33128 A hardware breakpoint is implemented using a mechanism that is not
33129 dependant on being able to modify the target's memory. @var{kind}
33130 has the same meaning as in @samp{Z0} packets.
33132 @emph{Implementation note: A hardware breakpoint is not affected by code
33145 @item z2,@var{addr},@var{kind}
33146 @itemx Z2,@var{addr},@var{kind}
33147 @cindex @samp{z2} packet
33148 @cindex @samp{Z2} packet
33149 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
33150 @var{kind} is interpreted as the number of bytes to watch.
33162 @item z3,@var{addr},@var{kind}
33163 @itemx Z3,@var{addr},@var{kind}
33164 @cindex @samp{z3} packet
33165 @cindex @samp{Z3} packet
33166 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
33167 @var{kind} is interpreted as the number of bytes to watch.
33179 @item z4,@var{addr},@var{kind}
33180 @itemx Z4,@var{addr},@var{kind}
33181 @cindex @samp{z4} packet
33182 @cindex @samp{Z4} packet
33183 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
33184 @var{kind} is interpreted as the number of bytes to watch.
33198 @node Stop Reply Packets
33199 @section Stop Reply Packets
33200 @cindex stop reply packets
33202 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
33203 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
33204 receive any of the below as a reply. Except for @samp{?}
33205 and @samp{vStopped}, that reply is only returned
33206 when the target halts. In the below the exact meaning of @dfn{signal
33207 number} is defined by the header @file{include/gdb/signals.h} in the
33208 @value{GDBN} source code.
33210 As in the description of request packets, we include spaces in the
33211 reply templates for clarity; these are not part of the reply packet's
33212 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
33218 The program received signal number @var{AA} (a two-digit hexadecimal
33219 number). This is equivalent to a @samp{T} response with no
33220 @var{n}:@var{r} pairs.
33222 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
33223 @cindex @samp{T} packet reply
33224 The program received signal number @var{AA} (a two-digit hexadecimal
33225 number). This is equivalent to an @samp{S} response, except that the
33226 @samp{@var{n}:@var{r}} pairs can carry values of important registers
33227 and other information directly in the stop reply packet, reducing
33228 round-trip latency. Single-step and breakpoint traps are reported
33229 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
33233 If @var{n} is a hexadecimal number, it is a register number, and the
33234 corresponding @var{r} gives that register's value. @var{r} is a
33235 series of bytes in target byte order, with each byte given by a
33236 two-digit hex number.
33239 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
33240 the stopped thread, as specified in @ref{thread-id syntax}.
33243 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
33244 the core on which the stop event was detected.
33247 If @var{n} is a recognized @dfn{stop reason}, it describes a more
33248 specific event that stopped the target. The currently defined stop
33249 reasons are listed below. @var{aa} should be @samp{05}, the trap
33250 signal. At most one stop reason should be present.
33253 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
33254 and go on to the next; this allows us to extend the protocol in the
33258 The currently defined stop reasons are:
33264 The packet indicates a watchpoint hit, and @var{r} is the data address, in
33267 @cindex shared library events, remote reply
33269 The packet indicates that the loaded libraries have changed.
33270 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
33271 list of loaded libraries. @var{r} is ignored.
33273 @cindex replay log events, remote reply
33275 The packet indicates that the target cannot continue replaying
33276 logged execution events, because it has reached the end (or the
33277 beginning when executing backward) of the log. The value of @var{r}
33278 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
33279 for more information.
33283 @itemx W @var{AA} ; process:@var{pid}
33284 The process exited, and @var{AA} is the exit status. This is only
33285 applicable to certain targets.
33287 The second form of the response, including the process ID of the exited
33288 process, can be used only when @value{GDBN} has reported support for
33289 multiprocess protocol extensions; see @ref{multiprocess extensions}.
33290 The @var{pid} is formatted as a big-endian hex string.
33293 @itemx X @var{AA} ; process:@var{pid}
33294 The process terminated with signal @var{AA}.
33296 The second form of the response, including the process ID of the
33297 terminated process, can be used only when @value{GDBN} has reported
33298 support for multiprocess protocol extensions; see @ref{multiprocess
33299 extensions}. The @var{pid} is formatted as a big-endian hex string.
33301 @item O @var{XX}@dots{}
33302 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
33303 written as the program's console output. This can happen at any time
33304 while the program is running and the debugger should continue to wait
33305 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
33307 @item F @var{call-id},@var{parameter}@dots{}
33308 @var{call-id} is the identifier which says which host system call should
33309 be called. This is just the name of the function. Translation into the
33310 correct system call is only applicable as it's defined in @value{GDBN}.
33311 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
33314 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
33315 this very system call.
33317 The target replies with this packet when it expects @value{GDBN} to
33318 call a host system call on behalf of the target. @value{GDBN} replies
33319 with an appropriate @samp{F} packet and keeps up waiting for the next
33320 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
33321 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
33322 Protocol Extension}, for more details.
33326 @node General Query Packets
33327 @section General Query Packets
33328 @cindex remote query requests
33330 Packets starting with @samp{q} are @dfn{general query packets};
33331 packets starting with @samp{Q} are @dfn{general set packets}. General
33332 query and set packets are a semi-unified form for retrieving and
33333 sending information to and from the stub.
33335 The initial letter of a query or set packet is followed by a name
33336 indicating what sort of thing the packet applies to. For example,
33337 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
33338 definitions with the stub. These packet names follow some
33343 The name must not contain commas, colons or semicolons.
33345 Most @value{GDBN} query and set packets have a leading upper case
33348 The names of custom vendor packets should use a company prefix, in
33349 lower case, followed by a period. For example, packets designed at
33350 the Acme Corporation might begin with @samp{qacme.foo} (for querying
33351 foos) or @samp{Qacme.bar} (for setting bars).
33354 The name of a query or set packet should be separated from any
33355 parameters by a @samp{:}; the parameters themselves should be
33356 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
33357 full packet name, and check for a separator or the end of the packet,
33358 in case two packet names share a common prefix. New packets should not begin
33359 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
33360 packets predate these conventions, and have arguments without any terminator
33361 for the packet name; we suspect they are in widespread use in places that
33362 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
33363 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
33366 Like the descriptions of the other packets, each description here
33367 has a template showing the packet's overall syntax, followed by an
33368 explanation of the packet's meaning. We include spaces in some of the
33369 templates for clarity; these are not part of the packet's syntax. No
33370 @value{GDBN} packet uses spaces to separate its components.
33372 Here are the currently defined query and set packets:
33376 @item QAllow:@var{op}:@var{val}@dots{}
33377 @cindex @samp{QAllow} packet
33378 Specify which operations @value{GDBN} expects to request of the
33379 target, as a semicolon-separated list of operation name and value
33380 pairs. Possible values for @var{op} include @samp{WriteReg},
33381 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
33382 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
33383 indicating that @value{GDBN} will not request the operation, or 1,
33384 indicating that it may. (The target can then use this to set up its
33385 own internals optimally, for instance if the debugger never expects to
33386 insert breakpoints, it may not need to install its own trap handler.)
33389 @cindex current thread, remote request
33390 @cindex @samp{qC} packet
33391 Return the current thread ID.
33395 @item QC @var{thread-id}
33396 Where @var{thread-id} is a thread ID as documented in
33397 @ref{thread-id syntax}.
33398 @item @r{(anything else)}
33399 Any other reply implies the old thread ID.
33402 @item qCRC:@var{addr},@var{length}
33403 @cindex CRC of memory block, remote request
33404 @cindex @samp{qCRC} packet
33405 Compute the CRC checksum of a block of memory using CRC-32 defined in
33406 IEEE 802.3. The CRC is computed byte at a time, taking the most
33407 significant bit of each byte first. The initial pattern code
33408 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
33410 @emph{Note:} This is the same CRC used in validating separate debug
33411 files (@pxref{Separate Debug Files, , Debugging Information in Separate
33412 Files}). However the algorithm is slightly different. When validating
33413 separate debug files, the CRC is computed taking the @emph{least}
33414 significant bit of each byte first, and the final result is inverted to
33415 detect trailing zeros.
33420 An error (such as memory fault)
33421 @item C @var{crc32}
33422 The specified memory region's checksum is @var{crc32}.
33426 @itemx qsThreadInfo
33427 @cindex list active threads, remote request
33428 @cindex @samp{qfThreadInfo} packet
33429 @cindex @samp{qsThreadInfo} packet
33430 Obtain a list of all active thread IDs from the target (OS). Since there
33431 may be too many active threads to fit into one reply packet, this query
33432 works iteratively: it may require more than one query/reply sequence to
33433 obtain the entire list of threads. The first query of the sequence will
33434 be the @samp{qfThreadInfo} query; subsequent queries in the
33435 sequence will be the @samp{qsThreadInfo} query.
33437 NOTE: This packet replaces the @samp{qL} query (see below).
33441 @item m @var{thread-id}
33443 @item m @var{thread-id},@var{thread-id}@dots{}
33444 a comma-separated list of thread IDs
33446 (lower case letter @samp{L}) denotes end of list.
33449 In response to each query, the target will reply with a list of one or
33450 more thread IDs, separated by commas.
33451 @value{GDBN} will respond to each reply with a request for more thread
33452 ids (using the @samp{qs} form of the query), until the target responds
33453 with @samp{l} (lower-case ell, for @dfn{last}).
33454 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
33457 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
33458 @cindex get thread-local storage address, remote request
33459 @cindex @samp{qGetTLSAddr} packet
33460 Fetch the address associated with thread local storage specified
33461 by @var{thread-id}, @var{offset}, and @var{lm}.
33463 @var{thread-id} is the thread ID associated with the
33464 thread for which to fetch the TLS address. @xref{thread-id syntax}.
33466 @var{offset} is the (big endian, hex encoded) offset associated with the
33467 thread local variable. (This offset is obtained from the debug
33468 information associated with the variable.)
33470 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
33471 load module associated with the thread local storage. For example,
33472 a @sc{gnu}/Linux system will pass the link map address of the shared
33473 object associated with the thread local storage under consideration.
33474 Other operating environments may choose to represent the load module
33475 differently, so the precise meaning of this parameter will vary.
33479 @item @var{XX}@dots{}
33480 Hex encoded (big endian) bytes representing the address of the thread
33481 local storage requested.
33484 An error occurred. @var{nn} are hex digits.
33487 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
33490 @item qGetTIBAddr:@var{thread-id}
33491 @cindex get thread information block address
33492 @cindex @samp{qGetTIBAddr} packet
33493 Fetch address of the Windows OS specific Thread Information Block.
33495 @var{thread-id} is the thread ID associated with the thread.
33499 @item @var{XX}@dots{}
33500 Hex encoded (big endian) bytes representing the linear address of the
33501 thread information block.
33504 An error occured. This means that either the thread was not found, or the
33505 address could not be retrieved.
33508 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
33511 @item qL @var{startflag} @var{threadcount} @var{nextthread}
33512 Obtain thread information from RTOS. Where: @var{startflag} (one hex
33513 digit) is one to indicate the first query and zero to indicate a
33514 subsequent query; @var{threadcount} (two hex digits) is the maximum
33515 number of threads the response packet can contain; and @var{nextthread}
33516 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
33517 returned in the response as @var{argthread}.
33519 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
33523 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
33524 Where: @var{count} (two hex digits) is the number of threads being
33525 returned; @var{done} (one hex digit) is zero to indicate more threads
33526 and one indicates no further threads; @var{argthreadid} (eight hex
33527 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
33528 is a sequence of thread IDs from the target. @var{threadid} (eight hex
33529 digits). See @code{remote.c:parse_threadlist_response()}.
33533 @cindex section offsets, remote request
33534 @cindex @samp{qOffsets} packet
33535 Get section offsets that the target used when relocating the downloaded
33540 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
33541 Relocate the @code{Text} section by @var{xxx} from its original address.
33542 Relocate the @code{Data} section by @var{yyy} from its original address.
33543 If the object file format provides segment information (e.g.@: @sc{elf}
33544 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
33545 segments by the supplied offsets.
33547 @emph{Note: while a @code{Bss} offset may be included in the response,
33548 @value{GDBN} ignores this and instead applies the @code{Data} offset
33549 to the @code{Bss} section.}
33551 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
33552 Relocate the first segment of the object file, which conventionally
33553 contains program code, to a starting address of @var{xxx}. If
33554 @samp{DataSeg} is specified, relocate the second segment, which
33555 conventionally contains modifiable data, to a starting address of
33556 @var{yyy}. @value{GDBN} will report an error if the object file
33557 does not contain segment information, or does not contain at least
33558 as many segments as mentioned in the reply. Extra segments are
33559 kept at fixed offsets relative to the last relocated segment.
33562 @item qP @var{mode} @var{thread-id}
33563 @cindex thread information, remote request
33564 @cindex @samp{qP} packet
33565 Returns information on @var{thread-id}. Where: @var{mode} is a hex
33566 encoded 32 bit mode; @var{thread-id} is a thread ID
33567 (@pxref{thread-id syntax}).
33569 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
33572 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
33576 @cindex non-stop mode, remote request
33577 @cindex @samp{QNonStop} packet
33579 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
33580 @xref{Remote Non-Stop}, for more information.
33585 The request succeeded.
33588 An error occurred. @var{nn} are hex digits.
33591 An empty reply indicates that @samp{QNonStop} is not supported by
33595 This packet is not probed by default; the remote stub must request it,
33596 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33597 Use of this packet is controlled by the @code{set non-stop} command;
33598 @pxref{Non-Stop Mode}.
33600 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
33601 @cindex pass signals to inferior, remote request
33602 @cindex @samp{QPassSignals} packet
33603 @anchor{QPassSignals}
33604 Each listed @var{signal} should be passed directly to the inferior process.
33605 Signals are numbered identically to continue packets and stop replies
33606 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
33607 strictly greater than the previous item. These signals do not need to stop
33608 the inferior, or be reported to @value{GDBN}. All other signals should be
33609 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
33610 combine; any earlier @samp{QPassSignals} list is completely replaced by the
33611 new list. This packet improves performance when using @samp{handle
33612 @var{signal} nostop noprint pass}.
33617 The request succeeded.
33620 An error occurred. @var{nn} are hex digits.
33623 An empty reply indicates that @samp{QPassSignals} is not supported by
33627 Use of this packet is controlled by the @code{set remote pass-signals}
33628 command (@pxref{Remote Configuration, set remote pass-signals}).
33629 This packet is not probed by default; the remote stub must request it,
33630 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33632 @item qRcmd,@var{command}
33633 @cindex execute remote command, remote request
33634 @cindex @samp{qRcmd} packet
33635 @var{command} (hex encoded) is passed to the local interpreter for
33636 execution. Invalid commands should be reported using the output
33637 string. Before the final result packet, the target may also respond
33638 with a number of intermediate @samp{O@var{output}} console output
33639 packets. @emph{Implementors should note that providing access to a
33640 stubs's interpreter may have security implications}.
33645 A command response with no output.
33647 A command response with the hex encoded output string @var{OUTPUT}.
33649 Indicate a badly formed request.
33651 An empty reply indicates that @samp{qRcmd} is not recognized.
33654 (Note that the @code{qRcmd} packet's name is separated from the
33655 command by a @samp{,}, not a @samp{:}, contrary to the naming
33656 conventions above. Please don't use this packet as a model for new
33659 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
33660 @cindex searching memory, in remote debugging
33661 @cindex @samp{qSearch:memory} packet
33662 @anchor{qSearch memory}
33663 Search @var{length} bytes at @var{address} for @var{search-pattern}.
33664 @var{address} and @var{length} are encoded in hex.
33665 @var{search-pattern} is a sequence of bytes, hex encoded.
33670 The pattern was not found.
33672 The pattern was found at @var{address}.
33674 A badly formed request or an error was encountered while searching memory.
33676 An empty reply indicates that @samp{qSearch:memory} is not recognized.
33679 @item QStartNoAckMode
33680 @cindex @samp{QStartNoAckMode} packet
33681 @anchor{QStartNoAckMode}
33682 Request that the remote stub disable the normal @samp{+}/@samp{-}
33683 protocol acknowledgments (@pxref{Packet Acknowledgment}).
33688 The stub has switched to no-acknowledgment mode.
33689 @value{GDBN} acknowledges this reponse,
33690 but neither the stub nor @value{GDBN} shall send or expect further
33691 @samp{+}/@samp{-} acknowledgments in the current connection.
33693 An empty reply indicates that the stub does not support no-acknowledgment mode.
33696 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
33697 @cindex supported packets, remote query
33698 @cindex features of the remote protocol
33699 @cindex @samp{qSupported} packet
33700 @anchor{qSupported}
33701 Tell the remote stub about features supported by @value{GDBN}, and
33702 query the stub for features it supports. This packet allows
33703 @value{GDBN} and the remote stub to take advantage of each others'
33704 features. @samp{qSupported} also consolidates multiple feature probes
33705 at startup, to improve @value{GDBN} performance---a single larger
33706 packet performs better than multiple smaller probe packets on
33707 high-latency links. Some features may enable behavior which must not
33708 be on by default, e.g.@: because it would confuse older clients or
33709 stubs. Other features may describe packets which could be
33710 automatically probed for, but are not. These features must be
33711 reported before @value{GDBN} will use them. This ``default
33712 unsupported'' behavior is not appropriate for all packets, but it
33713 helps to keep the initial connection time under control with new
33714 versions of @value{GDBN} which support increasing numbers of packets.
33718 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
33719 The stub supports or does not support each returned @var{stubfeature},
33720 depending on the form of each @var{stubfeature} (see below for the
33723 An empty reply indicates that @samp{qSupported} is not recognized,
33724 or that no features needed to be reported to @value{GDBN}.
33727 The allowed forms for each feature (either a @var{gdbfeature} in the
33728 @samp{qSupported} packet, or a @var{stubfeature} in the response)
33732 @item @var{name}=@var{value}
33733 The remote protocol feature @var{name} is supported, and associated
33734 with the specified @var{value}. The format of @var{value} depends
33735 on the feature, but it must not include a semicolon.
33737 The remote protocol feature @var{name} is supported, and does not
33738 need an associated value.
33740 The remote protocol feature @var{name} is not supported.
33742 The remote protocol feature @var{name} may be supported, and
33743 @value{GDBN} should auto-detect support in some other way when it is
33744 needed. This form will not be used for @var{gdbfeature} notifications,
33745 but may be used for @var{stubfeature} responses.
33748 Whenever the stub receives a @samp{qSupported} request, the
33749 supplied set of @value{GDBN} features should override any previous
33750 request. This allows @value{GDBN} to put the stub in a known
33751 state, even if the stub had previously been communicating with
33752 a different version of @value{GDBN}.
33754 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
33759 This feature indicates whether @value{GDBN} supports multiprocess
33760 extensions to the remote protocol. @value{GDBN} does not use such
33761 extensions unless the stub also reports that it supports them by
33762 including @samp{multiprocess+} in its @samp{qSupported} reply.
33763 @xref{multiprocess extensions}, for details.
33766 This feature indicates that @value{GDBN} supports the XML target
33767 description. If the stub sees @samp{xmlRegisters=} with target
33768 specific strings separated by a comma, it will report register
33772 This feature indicates whether @value{GDBN} supports the
33773 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
33774 instruction reply packet}).
33777 Stubs should ignore any unknown values for
33778 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
33779 packet supports receiving packets of unlimited length (earlier
33780 versions of @value{GDBN} may reject overly long responses). Additional values
33781 for @var{gdbfeature} may be defined in the future to let the stub take
33782 advantage of new features in @value{GDBN}, e.g.@: incompatible
33783 improvements in the remote protocol---the @samp{multiprocess} feature is
33784 an example of such a feature. The stub's reply should be independent
33785 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
33786 describes all the features it supports, and then the stub replies with
33787 all the features it supports.
33789 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
33790 responses, as long as each response uses one of the standard forms.
33792 Some features are flags. A stub which supports a flag feature
33793 should respond with a @samp{+} form response. Other features
33794 require values, and the stub should respond with an @samp{=}
33797 Each feature has a default value, which @value{GDBN} will use if
33798 @samp{qSupported} is not available or if the feature is not mentioned
33799 in the @samp{qSupported} response. The default values are fixed; a
33800 stub is free to omit any feature responses that match the defaults.
33802 Not all features can be probed, but for those which can, the probing
33803 mechanism is useful: in some cases, a stub's internal
33804 architecture may not allow the protocol layer to know some information
33805 about the underlying target in advance. This is especially common in
33806 stubs which may be configured for multiple targets.
33808 These are the currently defined stub features and their properties:
33810 @multitable @columnfractions 0.35 0.2 0.12 0.2
33811 @c NOTE: The first row should be @headitem, but we do not yet require
33812 @c a new enough version of Texinfo (4.7) to use @headitem.
33814 @tab Value Required
33818 @item @samp{PacketSize}
33823 @item @samp{qXfer:auxv:read}
33828 @item @samp{qXfer:features:read}
33833 @item @samp{qXfer:libraries:read}
33838 @item @samp{qXfer:memory-map:read}
33843 @item @samp{qXfer:sdata:read}
33848 @item @samp{qXfer:spu:read}
33853 @item @samp{qXfer:spu:write}
33858 @item @samp{qXfer:siginfo:read}
33863 @item @samp{qXfer:siginfo:write}
33868 @item @samp{qXfer:threads:read}
33873 @item @samp{qXfer:traceframe-info:read}
33878 @item @samp{qXfer:fdpic:read}
33883 @item @samp{QNonStop}
33888 @item @samp{QPassSignals}
33893 @item @samp{QStartNoAckMode}
33898 @item @samp{multiprocess}
33903 @item @samp{ConditionalTracepoints}
33908 @item @samp{ReverseContinue}
33913 @item @samp{ReverseStep}
33918 @item @samp{TracepointSource}
33923 @item @samp{QAllow}
33928 @item @samp{EnableDisableTracepoints}
33935 These are the currently defined stub features, in more detail:
33938 @cindex packet size, remote protocol
33939 @item PacketSize=@var{bytes}
33940 The remote stub can accept packets up to at least @var{bytes} in
33941 length. @value{GDBN} will send packets up to this size for bulk
33942 transfers, and will never send larger packets. This is a limit on the
33943 data characters in the packet, including the frame and checksum.
33944 There is no trailing NUL byte in a remote protocol packet; if the stub
33945 stores packets in a NUL-terminated format, it should allow an extra
33946 byte in its buffer for the NUL. If this stub feature is not supported,
33947 @value{GDBN} guesses based on the size of the @samp{g} packet response.
33949 @item qXfer:auxv:read
33950 The remote stub understands the @samp{qXfer:auxv:read} packet
33951 (@pxref{qXfer auxiliary vector read}).
33953 @item qXfer:features:read
33954 The remote stub understands the @samp{qXfer:features:read} packet
33955 (@pxref{qXfer target description read}).
33957 @item qXfer:libraries:read
33958 The remote stub understands the @samp{qXfer:libraries:read} packet
33959 (@pxref{qXfer library list read}).
33961 @item qXfer:memory-map:read
33962 The remote stub understands the @samp{qXfer:memory-map:read} packet
33963 (@pxref{qXfer memory map read}).
33965 @item qXfer:sdata:read
33966 The remote stub understands the @samp{qXfer:sdata:read} packet
33967 (@pxref{qXfer sdata read}).
33969 @item qXfer:spu:read
33970 The remote stub understands the @samp{qXfer:spu:read} packet
33971 (@pxref{qXfer spu read}).
33973 @item qXfer:spu:write
33974 The remote stub understands the @samp{qXfer:spu:write} packet
33975 (@pxref{qXfer spu write}).
33977 @item qXfer:siginfo:read
33978 The remote stub understands the @samp{qXfer:siginfo:read} packet
33979 (@pxref{qXfer siginfo read}).
33981 @item qXfer:siginfo:write
33982 The remote stub understands the @samp{qXfer:siginfo:write} packet
33983 (@pxref{qXfer siginfo write}).
33985 @item qXfer:threads:read
33986 The remote stub understands the @samp{qXfer:threads:read} packet
33987 (@pxref{qXfer threads read}).
33989 @item qXfer:traceframe-info:read
33990 The remote stub understands the @samp{qXfer:traceframe-info:read}
33991 packet (@pxref{qXfer traceframe info read}).
33993 @item qXfer:fdpic:read
33994 The remote stub understands the @samp{qXfer:fdpic:read}
33995 packet (@pxref{qXfer fdpic loadmap read}).
33998 The remote stub understands the @samp{QNonStop} packet
33999 (@pxref{QNonStop}).
34002 The remote stub understands the @samp{QPassSignals} packet
34003 (@pxref{QPassSignals}).
34005 @item QStartNoAckMode
34006 The remote stub understands the @samp{QStartNoAckMode} packet and
34007 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
34010 @anchor{multiprocess extensions}
34011 @cindex multiprocess extensions, in remote protocol
34012 The remote stub understands the multiprocess extensions to the remote
34013 protocol syntax. The multiprocess extensions affect the syntax of
34014 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
34015 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
34016 replies. Note that reporting this feature indicates support for the
34017 syntactic extensions only, not that the stub necessarily supports
34018 debugging of more than one process at a time. The stub must not use
34019 multiprocess extensions in packet replies unless @value{GDBN} has also
34020 indicated it supports them in its @samp{qSupported} request.
34022 @item qXfer:osdata:read
34023 The remote stub understands the @samp{qXfer:osdata:read} packet
34024 ((@pxref{qXfer osdata read}).
34026 @item ConditionalTracepoints
34027 The remote stub accepts and implements conditional expressions defined
34028 for tracepoints (@pxref{Tracepoint Conditions}).
34030 @item ReverseContinue
34031 The remote stub accepts and implements the reverse continue packet
34035 The remote stub accepts and implements the reverse step packet
34038 @item TracepointSource
34039 The remote stub understands the @samp{QTDPsrc} packet that supplies
34040 the source form of tracepoint definitions.
34043 The remote stub understands the @samp{QAllow} packet.
34045 @item StaticTracepoint
34046 @cindex static tracepoints, in remote protocol
34047 The remote stub supports static tracepoints.
34049 @item EnableDisableTracepoints
34050 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
34051 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
34052 to be enabled and disabled while a trace experiment is running.
34057 @cindex symbol lookup, remote request
34058 @cindex @samp{qSymbol} packet
34059 Notify the target that @value{GDBN} is prepared to serve symbol lookup
34060 requests. Accept requests from the target for the values of symbols.
34065 The target does not need to look up any (more) symbols.
34066 @item qSymbol:@var{sym_name}
34067 The target requests the value of symbol @var{sym_name} (hex encoded).
34068 @value{GDBN} may provide the value by using the
34069 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
34073 @item qSymbol:@var{sym_value}:@var{sym_name}
34074 Set the value of @var{sym_name} to @var{sym_value}.
34076 @var{sym_name} (hex encoded) is the name of a symbol whose value the
34077 target has previously requested.
34079 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
34080 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
34086 The target does not need to look up any (more) symbols.
34087 @item qSymbol:@var{sym_name}
34088 The target requests the value of a new symbol @var{sym_name} (hex
34089 encoded). @value{GDBN} will continue to supply the values of symbols
34090 (if available), until the target ceases to request them.
34095 @item QTDisconnected
34102 @xref{Tracepoint Packets}.
34104 @item qThreadExtraInfo,@var{thread-id}
34105 @cindex thread attributes info, remote request
34106 @cindex @samp{qThreadExtraInfo} packet
34107 Obtain a printable string description of a thread's attributes from
34108 the target OS. @var{thread-id} is a thread ID;
34109 see @ref{thread-id syntax}. This
34110 string may contain anything that the target OS thinks is interesting
34111 for @value{GDBN} to tell the user about the thread. The string is
34112 displayed in @value{GDBN}'s @code{info threads} display. Some
34113 examples of possible thread extra info strings are @samp{Runnable}, or
34114 @samp{Blocked on Mutex}.
34118 @item @var{XX}@dots{}
34119 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
34120 comprising the printable string containing the extra information about
34121 the thread's attributes.
34124 (Note that the @code{qThreadExtraInfo} packet's name is separated from
34125 the command by a @samp{,}, not a @samp{:}, contrary to the naming
34126 conventions above. Please don't use this packet as a model for new
34143 @xref{Tracepoint Packets}.
34145 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
34146 @cindex read special object, remote request
34147 @cindex @samp{qXfer} packet
34148 @anchor{qXfer read}
34149 Read uninterpreted bytes from the target's special data area
34150 identified by the keyword @var{object}. Request @var{length} bytes
34151 starting at @var{offset} bytes into the data. The content and
34152 encoding of @var{annex} is specific to @var{object}; it can supply
34153 additional details about what data to access.
34155 Here are the specific requests of this form defined so far. All
34156 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
34157 formats, listed below.
34160 @item qXfer:auxv:read::@var{offset},@var{length}
34161 @anchor{qXfer auxiliary vector read}
34162 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
34163 auxiliary vector}. Note @var{annex} must be empty.
34165 This packet is not probed by default; the remote stub must request it,
34166 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34168 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
34169 @anchor{qXfer target description read}
34170 Access the @dfn{target description}. @xref{Target Descriptions}. The
34171 annex specifies which XML document to access. The main description is
34172 always loaded from the @samp{target.xml} annex.
34174 This packet is not probed by default; the remote stub must request it,
34175 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34177 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
34178 @anchor{qXfer library list read}
34179 Access the target's list of loaded libraries. @xref{Library List Format}.
34180 The annex part of the generic @samp{qXfer} packet must be empty
34181 (@pxref{qXfer read}).
34183 Targets which maintain a list of libraries in the program's memory do
34184 not need to implement this packet; it is designed for platforms where
34185 the operating system manages the list of loaded libraries.
34187 This packet is not probed by default; the remote stub must request it,
34188 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34190 @item qXfer:memory-map:read::@var{offset},@var{length}
34191 @anchor{qXfer memory map read}
34192 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
34193 annex part of the generic @samp{qXfer} packet must be empty
34194 (@pxref{qXfer read}).
34196 This packet is not probed by default; the remote stub must request it,
34197 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34199 @item qXfer:sdata:read::@var{offset},@var{length}
34200 @anchor{qXfer sdata read}
34202 Read contents of the extra collected static tracepoint marker
34203 information. The annex part of the generic @samp{qXfer} packet must
34204 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
34207 This packet is not probed by default; the remote stub must request it,
34208 by supplying an appropriate @samp{qSupported} response
34209 (@pxref{qSupported}).
34211 @item qXfer:siginfo:read::@var{offset},@var{length}
34212 @anchor{qXfer siginfo read}
34213 Read contents of the extra signal information on the target
34214 system. The annex part of the generic @samp{qXfer} packet must be
34215 empty (@pxref{qXfer read}).
34217 This packet is not probed by default; the remote stub must request it,
34218 by supplying an appropriate @samp{qSupported} response
34219 (@pxref{qSupported}).
34221 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
34222 @anchor{qXfer spu read}
34223 Read contents of an @code{spufs} file on the target system. The
34224 annex specifies which file to read; it must be of the form
34225 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
34226 in the target process, and @var{name} identifes the @code{spufs} file
34227 in that context to be accessed.
34229 This packet is not probed by default; the remote stub must request it,
34230 by supplying an appropriate @samp{qSupported} response
34231 (@pxref{qSupported}).
34233 @item qXfer:threads:read::@var{offset},@var{length}
34234 @anchor{qXfer threads read}
34235 Access the list of threads on target. @xref{Thread List Format}. The
34236 annex part of the generic @samp{qXfer} packet must be empty
34237 (@pxref{qXfer read}).
34239 This packet is not probed by default; the remote stub must request it,
34240 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34242 @item qXfer:traceframe-info:read::@var{offset},@var{length}
34243 @anchor{qXfer traceframe info read}
34245 Return a description of the current traceframe's contents.
34246 @xref{Traceframe Info Format}. The annex part of the generic
34247 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
34249 This packet is not probed by default; the remote stub must request it,
34250 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34252 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
34253 @anchor{qXfer fdpic loadmap read}
34254 Read contents of @code{loadmap}s on the target system. The
34255 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
34256 executable @code{loadmap} or interpreter @code{loadmap} to read.
34258 This packet is not probed by default; the remote stub must request it,
34259 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34261 @item qXfer:osdata:read::@var{offset},@var{length}
34262 @anchor{qXfer osdata read}
34263 Access the target's @dfn{operating system information}.
34264 @xref{Operating System Information}.
34271 Data @var{data} (@pxref{Binary Data}) has been read from the
34272 target. There may be more data at a higher address (although
34273 it is permitted to return @samp{m} even for the last valid
34274 block of data, as long as at least one byte of data was read).
34275 @var{data} may have fewer bytes than the @var{length} in the
34279 Data @var{data} (@pxref{Binary Data}) has been read from the target.
34280 There is no more data to be read. @var{data} may have fewer bytes
34281 than the @var{length} in the request.
34284 The @var{offset} in the request is at the end of the data.
34285 There is no more data to be read.
34288 The request was malformed, or @var{annex} was invalid.
34291 The offset was invalid, or there was an error encountered reading the data.
34292 @var{nn} is a hex-encoded @code{errno} value.
34295 An empty reply indicates the @var{object} string was not recognized by
34296 the stub, or that the object does not support reading.
34299 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
34300 @cindex write data into object, remote request
34301 @anchor{qXfer write}
34302 Write uninterpreted bytes into the target's special data area
34303 identified by the keyword @var{object}, starting at @var{offset} bytes
34304 into the data. @var{data}@dots{} is the binary-encoded data
34305 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
34306 is specific to @var{object}; it can supply additional details about what data
34309 Here are the specific requests of this form defined so far. All
34310 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
34311 formats, listed below.
34314 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
34315 @anchor{qXfer siginfo write}
34316 Write @var{data} to the extra signal information on the target system.
34317 The annex part of the generic @samp{qXfer} packet must be
34318 empty (@pxref{qXfer write}).
34320 This packet is not probed by default; the remote stub must request it,
34321 by supplying an appropriate @samp{qSupported} response
34322 (@pxref{qSupported}).
34324 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
34325 @anchor{qXfer spu write}
34326 Write @var{data} to an @code{spufs} file on the target system. The
34327 annex specifies which file to write; it must be of the form
34328 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
34329 in the target process, and @var{name} identifes the @code{spufs} file
34330 in that context to be accessed.
34332 This packet is not probed by default; the remote stub must request it,
34333 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34339 @var{nn} (hex encoded) is the number of bytes written.
34340 This may be fewer bytes than supplied in the request.
34343 The request was malformed, or @var{annex} was invalid.
34346 The offset was invalid, or there was an error encountered writing the data.
34347 @var{nn} is a hex-encoded @code{errno} value.
34350 An empty reply indicates the @var{object} string was not
34351 recognized by the stub, or that the object does not support writing.
34354 @item qXfer:@var{object}:@var{operation}:@dots{}
34355 Requests of this form may be added in the future. When a stub does
34356 not recognize the @var{object} keyword, or its support for
34357 @var{object} does not recognize the @var{operation} keyword, the stub
34358 must respond with an empty packet.
34360 @item qAttached:@var{pid}
34361 @cindex query attached, remote request
34362 @cindex @samp{qAttached} packet
34363 Return an indication of whether the remote server attached to an
34364 existing process or created a new process. When the multiprocess
34365 protocol extensions are supported (@pxref{multiprocess extensions}),
34366 @var{pid} is an integer in hexadecimal format identifying the target
34367 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
34368 the query packet will be simplified as @samp{qAttached}.
34370 This query is used, for example, to know whether the remote process
34371 should be detached or killed when a @value{GDBN} session is ended with
34372 the @code{quit} command.
34377 The remote server attached to an existing process.
34379 The remote server created a new process.
34381 A badly formed request or an error was encountered.
34386 @node Architecture-Specific Protocol Details
34387 @section Architecture-Specific Protocol Details
34389 This section describes how the remote protocol is applied to specific
34390 target architectures. Also see @ref{Standard Target Features}, for
34391 details of XML target descriptions for each architecture.
34395 @subsubsection Breakpoint Kinds
34397 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
34402 16-bit Thumb mode breakpoint.
34405 32-bit Thumb mode (Thumb-2) breakpoint.
34408 32-bit ARM mode breakpoint.
34414 @subsubsection Register Packet Format
34416 The following @code{g}/@code{G} packets have previously been defined.
34417 In the below, some thirty-two bit registers are transferred as
34418 sixty-four bits. Those registers should be zero/sign extended (which?)
34419 to fill the space allocated. Register bytes are transferred in target
34420 byte order. The two nibbles within a register byte are transferred
34421 most-significant - least-significant.
34427 All registers are transferred as thirty-two bit quantities in the order:
34428 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
34429 registers; fsr; fir; fp.
34433 All registers are transferred as sixty-four bit quantities (including
34434 thirty-two bit registers such as @code{sr}). The ordering is the same
34439 @node Tracepoint Packets
34440 @section Tracepoint Packets
34441 @cindex tracepoint packets
34442 @cindex packets, tracepoint
34444 Here we describe the packets @value{GDBN} uses to implement
34445 tracepoints (@pxref{Tracepoints}).
34449 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
34450 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
34451 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
34452 the tracepoint is disabled. @var{step} is the tracepoint's step
34453 count, and @var{pass} is its pass count. If an @samp{F} is present,
34454 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
34455 the number of bytes that the target should copy elsewhere to make room
34456 for the tracepoint. If an @samp{X} is present, it introduces a
34457 tracepoint condition, which consists of a hexadecimal length, followed
34458 by a comma and hex-encoded bytes, in a manner similar to action
34459 encodings as described below. If the trailing @samp{-} is present,
34460 further @samp{QTDP} packets will follow to specify this tracepoint's
34466 The packet was understood and carried out.
34468 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
34470 The packet was not recognized.
34473 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
34474 Define actions to be taken when a tracepoint is hit. @var{n} and
34475 @var{addr} must be the same as in the initial @samp{QTDP} packet for
34476 this tracepoint. This packet may only be sent immediately after
34477 another @samp{QTDP} packet that ended with a @samp{-}. If the
34478 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
34479 specifying more actions for this tracepoint.
34481 In the series of action packets for a given tracepoint, at most one
34482 can have an @samp{S} before its first @var{action}. If such a packet
34483 is sent, it and the following packets define ``while-stepping''
34484 actions. Any prior packets define ordinary actions --- that is, those
34485 taken when the tracepoint is first hit. If no action packet has an
34486 @samp{S}, then all the packets in the series specify ordinary
34487 tracepoint actions.
34489 The @samp{@var{action}@dots{}} portion of the packet is a series of
34490 actions, concatenated without separators. Each action has one of the
34496 Collect the registers whose bits are set in @var{mask}. @var{mask} is
34497 a hexadecimal number whose @var{i}'th bit is set if register number
34498 @var{i} should be collected. (The least significant bit is numbered
34499 zero.) Note that @var{mask} may be any number of digits long; it may
34500 not fit in a 32-bit word.
34502 @item M @var{basereg},@var{offset},@var{len}
34503 Collect @var{len} bytes of memory starting at the address in register
34504 number @var{basereg}, plus @var{offset}. If @var{basereg} is
34505 @samp{-1}, then the range has a fixed address: @var{offset} is the
34506 address of the lowest byte to collect. The @var{basereg},
34507 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
34508 values (the @samp{-1} value for @var{basereg} is a special case).
34510 @item X @var{len},@var{expr}
34511 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
34512 it directs. @var{expr} is an agent expression, as described in
34513 @ref{Agent Expressions}. Each byte of the expression is encoded as a
34514 two-digit hex number in the packet; @var{len} is the number of bytes
34515 in the expression (and thus one-half the number of hex digits in the
34520 Any number of actions may be packed together in a single @samp{QTDP}
34521 packet, as long as the packet does not exceed the maximum packet
34522 length (400 bytes, for many stubs). There may be only one @samp{R}
34523 action per tracepoint, and it must precede any @samp{M} or @samp{X}
34524 actions. Any registers referred to by @samp{M} and @samp{X} actions
34525 must be collected by a preceding @samp{R} action. (The
34526 ``while-stepping'' actions are treated as if they were attached to a
34527 separate tracepoint, as far as these restrictions are concerned.)
34532 The packet was understood and carried out.
34534 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
34536 The packet was not recognized.
34539 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
34540 @cindex @samp{QTDPsrc} packet
34541 Specify a source string of tracepoint @var{n} at address @var{addr}.
34542 This is useful to get accurate reproduction of the tracepoints
34543 originally downloaded at the beginning of the trace run. @var{type}
34544 is the name of the tracepoint part, such as @samp{cond} for the
34545 tracepoint's conditional expression (see below for a list of types), while
34546 @var{bytes} is the string, encoded in hexadecimal.
34548 @var{start} is the offset of the @var{bytes} within the overall source
34549 string, while @var{slen} is the total length of the source string.
34550 This is intended for handling source strings that are longer than will
34551 fit in a single packet.
34552 @c Add detailed example when this info is moved into a dedicated
34553 @c tracepoint descriptions section.
34555 The available string types are @samp{at} for the location,
34556 @samp{cond} for the conditional, and @samp{cmd} for an action command.
34557 @value{GDBN} sends a separate packet for each command in the action
34558 list, in the same order in which the commands are stored in the list.
34560 The target does not need to do anything with source strings except
34561 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
34564 Although this packet is optional, and @value{GDBN} will only send it
34565 if the target replies with @samp{TracepointSource} @xref{General
34566 Query Packets}, it makes both disconnected tracing and trace files
34567 much easier to use. Otherwise the user must be careful that the
34568 tracepoints in effect while looking at trace frames are identical to
34569 the ones in effect during the trace run; even a small discrepancy
34570 could cause @samp{tdump} not to work, or a particular trace frame not
34573 @item QTDV:@var{n}:@var{value}
34574 @cindex define trace state variable, remote request
34575 @cindex @samp{QTDV} packet
34576 Create a new trace state variable, number @var{n}, with an initial
34577 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
34578 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
34579 the option of not using this packet for initial values of zero; the
34580 target should simply create the trace state variables as they are
34581 mentioned in expressions.
34583 @item QTFrame:@var{n}
34584 Select the @var{n}'th tracepoint frame from the buffer, and use the
34585 register and memory contents recorded there to answer subsequent
34586 request packets from @value{GDBN}.
34588 A successful reply from the stub indicates that the stub has found the
34589 requested frame. The response is a series of parts, concatenated
34590 without separators, describing the frame we selected. Each part has
34591 one of the following forms:
34595 The selected frame is number @var{n} in the trace frame buffer;
34596 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
34597 was no frame matching the criteria in the request packet.
34600 The selected trace frame records a hit of tracepoint number @var{t};
34601 @var{t} is a hexadecimal number.
34605 @item QTFrame:pc:@var{addr}
34606 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
34607 currently selected frame whose PC is @var{addr};
34608 @var{addr} is a hexadecimal number.
34610 @item QTFrame:tdp:@var{t}
34611 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
34612 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
34613 is a hexadecimal number.
34615 @item QTFrame:range:@var{start}:@var{end}
34616 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
34617 currently selected frame whose PC is between @var{start} (inclusive)
34618 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
34621 @item QTFrame:outside:@var{start}:@var{end}
34622 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
34623 frame @emph{outside} the given range of addresses (exclusive).
34626 Begin the tracepoint experiment. Begin collecting data from
34627 tracepoint hits in the trace frame buffer. This packet supports the
34628 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
34629 instruction reply packet}).
34632 End the tracepoint experiment. Stop collecting trace frames.
34634 @item QTEnable:@var{n}:@var{addr}
34636 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
34637 experiment. If the tracepoint was previously disabled, then collection
34638 of data from it will resume.
34640 @item QTDisable:@var{n}:@var{addr}
34642 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
34643 experiment. No more data will be collected from the tracepoint unless
34644 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
34647 Clear the table of tracepoints, and empty the trace frame buffer.
34649 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
34650 Establish the given ranges of memory as ``transparent''. The stub
34651 will answer requests for these ranges from memory's current contents,
34652 if they were not collected as part of the tracepoint hit.
34654 @value{GDBN} uses this to mark read-only regions of memory, like those
34655 containing program code. Since these areas never change, they should
34656 still have the same contents they did when the tracepoint was hit, so
34657 there's no reason for the stub to refuse to provide their contents.
34659 @item QTDisconnected:@var{value}
34660 Set the choice to what to do with the tracing run when @value{GDBN}
34661 disconnects from the target. A @var{value} of 1 directs the target to
34662 continue the tracing run, while 0 tells the target to stop tracing if
34663 @value{GDBN} is no longer in the picture.
34666 Ask the stub if there is a trace experiment running right now.
34668 The reply has the form:
34672 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
34673 @var{running} is a single digit @code{1} if the trace is presently
34674 running, or @code{0} if not. It is followed by semicolon-separated
34675 optional fields that an agent may use to report additional status.
34679 If the trace is not running, the agent may report any of several
34680 explanations as one of the optional fields:
34685 No trace has been run yet.
34688 The trace was stopped by a user-originated stop command.
34691 The trace stopped because the trace buffer filled up.
34693 @item tdisconnected:0
34694 The trace stopped because @value{GDBN} disconnected from the target.
34696 @item tpasscount:@var{tpnum}
34697 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
34699 @item terror:@var{text}:@var{tpnum}
34700 The trace stopped because tracepoint @var{tpnum} had an error. The
34701 string @var{text} is available to describe the nature of the error
34702 (for instance, a divide by zero in the condition expression).
34703 @var{text} is hex encoded.
34706 The trace stopped for some other reason.
34710 Additional optional fields supply statistical and other information.
34711 Although not required, they are extremely useful for users monitoring
34712 the progress of a trace run. If a trace has stopped, and these
34713 numbers are reported, they must reflect the state of the just-stopped
34718 @item tframes:@var{n}
34719 The number of trace frames in the buffer.
34721 @item tcreated:@var{n}
34722 The total number of trace frames created during the run. This may
34723 be larger than the trace frame count, if the buffer is circular.
34725 @item tsize:@var{n}
34726 The total size of the trace buffer, in bytes.
34728 @item tfree:@var{n}
34729 The number of bytes still unused in the buffer.
34731 @item circular:@var{n}
34732 The value of the circular trace buffer flag. @code{1} means that the
34733 trace buffer is circular and old trace frames will be discarded if
34734 necessary to make room, @code{0} means that the trace buffer is linear
34737 @item disconn:@var{n}
34738 The value of the disconnected tracing flag. @code{1} means that
34739 tracing will continue after @value{GDBN} disconnects, @code{0} means
34740 that the trace run will stop.
34744 @item qTV:@var{var}
34745 @cindex trace state variable value, remote request
34746 @cindex @samp{qTV} packet
34747 Ask the stub for the value of the trace state variable number @var{var}.
34752 The value of the variable is @var{value}. This will be the current
34753 value of the variable if the user is examining a running target, or a
34754 saved value if the variable was collected in the trace frame that the
34755 user is looking at. Note that multiple requests may result in
34756 different reply values, such as when requesting values while the
34757 program is running.
34760 The value of the variable is unknown. This would occur, for example,
34761 if the user is examining a trace frame in which the requested variable
34767 These packets request data about tracepoints that are being used by
34768 the target. @value{GDBN} sends @code{qTfP} to get the first piece
34769 of data, and multiple @code{qTsP} to get additional pieces. Replies
34770 to these packets generally take the form of the @code{QTDP} packets
34771 that define tracepoints. (FIXME add detailed syntax)
34775 These packets request data about trace state variables that are on the
34776 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
34777 and multiple @code{qTsV} to get additional variables. Replies to
34778 these packets follow the syntax of the @code{QTDV} packets that define
34779 trace state variables.
34783 These packets request data about static tracepoint markers that exist
34784 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
34785 first piece of data, and multiple @code{qTsSTM} to get additional
34786 pieces. Replies to these packets take the following form:
34790 @item m @var{address}:@var{id}:@var{extra}
34792 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
34793 a comma-separated list of markers
34795 (lower case letter @samp{L}) denotes end of list.
34797 An error occurred. @var{nn} are hex digits.
34799 An empty reply indicates that the request is not supported by the
34803 @var{address} is encoded in hex.
34804 @var{id} and @var{extra} are strings encoded in hex.
34806 In response to each query, the target will reply with a list of one or
34807 more markers, separated by commas. @value{GDBN} will respond to each
34808 reply with a request for more markers (using the @samp{qs} form of the
34809 query), until the target responds with @samp{l} (lower-case ell, for
34812 @item qTSTMat:@var{address}
34813 This packets requests data about static tracepoint markers in the
34814 target program at @var{address}. Replies to this packet follow the
34815 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
34816 tracepoint markers.
34818 @item QTSave:@var{filename}
34819 This packet directs the target to save trace data to the file name
34820 @var{filename} in the target's filesystem. @var{filename} is encoded
34821 as a hex string; the interpretation of the file name (relative vs
34822 absolute, wild cards, etc) is up to the target.
34824 @item qTBuffer:@var{offset},@var{len}
34825 Return up to @var{len} bytes of the current contents of trace buffer,
34826 starting at @var{offset}. The trace buffer is treated as if it were
34827 a contiguous collection of traceframes, as per the trace file format.
34828 The reply consists as many hex-encoded bytes as the target can deliver
34829 in a packet; it is not an error to return fewer than were asked for.
34830 A reply consisting of just @code{l} indicates that no bytes are
34833 @item QTBuffer:circular:@var{value}
34834 This packet directs the target to use a circular trace buffer if
34835 @var{value} is 1, or a linear buffer if the value is 0.
34839 @subsection Relocate instruction reply packet
34840 When installing fast tracepoints in memory, the target may need to
34841 relocate the instruction currently at the tracepoint address to a
34842 different address in memory. For most instructions, a simple copy is
34843 enough, but, for example, call instructions that implicitly push the
34844 return address on the stack, and relative branches or other
34845 PC-relative instructions require offset adjustment, so that the effect
34846 of executing the instruction at a different address is the same as if
34847 it had executed in the original location.
34849 In response to several of the tracepoint packets, the target may also
34850 respond with a number of intermediate @samp{qRelocInsn} request
34851 packets before the final result packet, to have @value{GDBN} handle
34852 this relocation operation. If a packet supports this mechanism, its
34853 documentation will explicitly say so. See for example the above
34854 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
34855 format of the request is:
34858 @item qRelocInsn:@var{from};@var{to}
34860 This requests @value{GDBN} to copy instruction at address @var{from}
34861 to address @var{to}, possibly adjusted so that executing the
34862 instruction at @var{to} has the same effect as executing it at
34863 @var{from}. @value{GDBN} writes the adjusted instruction to target
34864 memory starting at @var{to}.
34869 @item qRelocInsn:@var{adjusted_size}
34870 Informs the stub the relocation is complete. @var{adjusted_size} is
34871 the length in bytes of resulting relocated instruction sequence.
34873 A badly formed request was detected, or an error was encountered while
34874 relocating the instruction.
34877 @node Host I/O Packets
34878 @section Host I/O Packets
34879 @cindex Host I/O, remote protocol
34880 @cindex file transfer, remote protocol
34882 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
34883 operations on the far side of a remote link. For example, Host I/O is
34884 used to upload and download files to a remote target with its own
34885 filesystem. Host I/O uses the same constant values and data structure
34886 layout as the target-initiated File-I/O protocol. However, the
34887 Host I/O packets are structured differently. The target-initiated
34888 protocol relies on target memory to store parameters and buffers.
34889 Host I/O requests are initiated by @value{GDBN}, and the
34890 target's memory is not involved. @xref{File-I/O Remote Protocol
34891 Extension}, for more details on the target-initiated protocol.
34893 The Host I/O request packets all encode a single operation along with
34894 its arguments. They have this format:
34898 @item vFile:@var{operation}: @var{parameter}@dots{}
34899 @var{operation} is the name of the particular request; the target
34900 should compare the entire packet name up to the second colon when checking
34901 for a supported operation. The format of @var{parameter} depends on
34902 the operation. Numbers are always passed in hexadecimal. Negative
34903 numbers have an explicit minus sign (i.e.@: two's complement is not
34904 used). Strings (e.g.@: filenames) are encoded as a series of
34905 hexadecimal bytes. The last argument to a system call may be a
34906 buffer of escaped binary data (@pxref{Binary Data}).
34910 The valid responses to Host I/O packets are:
34914 @item F @var{result} [, @var{errno}] [; @var{attachment}]
34915 @var{result} is the integer value returned by this operation, usually
34916 non-negative for success and -1 for errors. If an error has occured,
34917 @var{errno} will be included in the result. @var{errno} will have a
34918 value defined by the File-I/O protocol (@pxref{Errno Values}). For
34919 operations which return data, @var{attachment} supplies the data as a
34920 binary buffer. Binary buffers in response packets are escaped in the
34921 normal way (@pxref{Binary Data}). See the individual packet
34922 documentation for the interpretation of @var{result} and
34926 An empty response indicates that this operation is not recognized.
34930 These are the supported Host I/O operations:
34933 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
34934 Open a file at @var{pathname} and return a file descriptor for it, or
34935 return -1 if an error occurs. @var{pathname} is a string,
34936 @var{flags} is an integer indicating a mask of open flags
34937 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
34938 of mode bits to use if the file is created (@pxref{mode_t Values}).
34939 @xref{open}, for details of the open flags and mode values.
34941 @item vFile:close: @var{fd}
34942 Close the open file corresponding to @var{fd} and return 0, or
34943 -1 if an error occurs.
34945 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
34946 Read data from the open file corresponding to @var{fd}. Up to
34947 @var{count} bytes will be read from the file, starting at @var{offset}
34948 relative to the start of the file. The target may read fewer bytes;
34949 common reasons include packet size limits and an end-of-file
34950 condition. The number of bytes read is returned. Zero should only be
34951 returned for a successful read at the end of the file, or if
34952 @var{count} was zero.
34954 The data read should be returned as a binary attachment on success.
34955 If zero bytes were read, the response should include an empty binary
34956 attachment (i.e.@: a trailing semicolon). The return value is the
34957 number of target bytes read; the binary attachment may be longer if
34958 some characters were escaped.
34960 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
34961 Write @var{data} (a binary buffer) to the open file corresponding
34962 to @var{fd}. Start the write at @var{offset} from the start of the
34963 file. Unlike many @code{write} system calls, there is no
34964 separate @var{count} argument; the length of @var{data} in the
34965 packet is used. @samp{vFile:write} returns the number of bytes written,
34966 which may be shorter than the length of @var{data}, or -1 if an
34969 @item vFile:unlink: @var{pathname}
34970 Delete the file at @var{pathname} on the target. Return 0,
34971 or -1 if an error occurs. @var{pathname} is a string.
34976 @section Interrupts
34977 @cindex interrupts (remote protocol)
34979 When a program on the remote target is running, @value{GDBN} may
34980 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
34981 a @code{BREAK} followed by @code{g},
34982 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
34984 The precise meaning of @code{BREAK} is defined by the transport
34985 mechanism and may, in fact, be undefined. @value{GDBN} does not
34986 currently define a @code{BREAK} mechanism for any of the network
34987 interfaces except for TCP, in which case @value{GDBN} sends the
34988 @code{telnet} BREAK sequence.
34990 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
34991 transport mechanisms. It is represented by sending the single byte
34992 @code{0x03} without any of the usual packet overhead described in
34993 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
34994 transmitted as part of a packet, it is considered to be packet data
34995 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
34996 (@pxref{X packet}), used for binary downloads, may include an unescaped
34997 @code{0x03} as part of its packet.
34999 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
35000 When Linux kernel receives this sequence from serial port,
35001 it stops execution and connects to gdb.
35003 Stubs are not required to recognize these interrupt mechanisms and the
35004 precise meaning associated with receipt of the interrupt is
35005 implementation defined. If the target supports debugging of multiple
35006 threads and/or processes, it should attempt to interrupt all
35007 currently-executing threads and processes.
35008 If the stub is successful at interrupting the
35009 running program, it should send one of the stop
35010 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
35011 of successfully stopping the program in all-stop mode, and a stop reply
35012 for each stopped thread in non-stop mode.
35013 Interrupts received while the
35014 program is stopped are discarded.
35016 @node Notification Packets
35017 @section Notification Packets
35018 @cindex notification packets
35019 @cindex packets, notification
35021 The @value{GDBN} remote serial protocol includes @dfn{notifications},
35022 packets that require no acknowledgment. Both the GDB and the stub
35023 may send notifications (although the only notifications defined at
35024 present are sent by the stub). Notifications carry information
35025 without incurring the round-trip latency of an acknowledgment, and so
35026 are useful for low-impact communications where occasional packet loss
35029 A notification packet has the form @samp{% @var{data} #
35030 @var{checksum}}, where @var{data} is the content of the notification,
35031 and @var{checksum} is a checksum of @var{data}, computed and formatted
35032 as for ordinary @value{GDBN} packets. A notification's @var{data}
35033 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
35034 receiving a notification, the recipient sends no @samp{+} or @samp{-}
35035 to acknowledge the notification's receipt or to report its corruption.
35037 Every notification's @var{data} begins with a name, which contains no
35038 colon characters, followed by a colon character.
35040 Recipients should silently ignore corrupted notifications and
35041 notifications they do not understand. Recipients should restart
35042 timeout periods on receipt of a well-formed notification, whether or
35043 not they understand it.
35045 Senders should only send the notifications described here when this
35046 protocol description specifies that they are permitted. In the
35047 future, we may extend the protocol to permit existing notifications in
35048 new contexts; this rule helps older senders avoid confusing newer
35051 (Older versions of @value{GDBN} ignore bytes received until they see
35052 the @samp{$} byte that begins an ordinary packet, so new stubs may
35053 transmit notifications without fear of confusing older clients. There
35054 are no notifications defined for @value{GDBN} to send at the moment, but we
35055 assume that most older stubs would ignore them, as well.)
35057 The following notification packets from the stub to @value{GDBN} are
35061 @item Stop: @var{reply}
35062 Report an asynchronous stop event in non-stop mode.
35063 The @var{reply} has the form of a stop reply, as
35064 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
35065 for information on how these notifications are acknowledged by
35069 @node Remote Non-Stop
35070 @section Remote Protocol Support for Non-Stop Mode
35072 @value{GDBN}'s remote protocol supports non-stop debugging of
35073 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
35074 supports non-stop mode, it should report that to @value{GDBN} by including
35075 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
35077 @value{GDBN} typically sends a @samp{QNonStop} packet only when
35078 establishing a new connection with the stub. Entering non-stop mode
35079 does not alter the state of any currently-running threads, but targets
35080 must stop all threads in any already-attached processes when entering
35081 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
35082 probe the target state after a mode change.
35084 In non-stop mode, when an attached process encounters an event that
35085 would otherwise be reported with a stop reply, it uses the
35086 asynchronous notification mechanism (@pxref{Notification Packets}) to
35087 inform @value{GDBN}. In contrast to all-stop mode, where all threads
35088 in all processes are stopped when a stop reply is sent, in non-stop
35089 mode only the thread reporting the stop event is stopped. That is,
35090 when reporting a @samp{S} or @samp{T} response to indicate completion
35091 of a step operation, hitting a breakpoint, or a fault, only the
35092 affected thread is stopped; any other still-running threads continue
35093 to run. When reporting a @samp{W} or @samp{X} response, all running
35094 threads belonging to other attached processes continue to run.
35096 Only one stop reply notification at a time may be pending; if
35097 additional stop events occur before @value{GDBN} has acknowledged the
35098 previous notification, they must be queued by the stub for later
35099 synchronous transmission in response to @samp{vStopped} packets from
35100 @value{GDBN}. Because the notification mechanism is unreliable,
35101 the stub is permitted to resend a stop reply notification
35102 if it believes @value{GDBN} may not have received it. @value{GDBN}
35103 ignores additional stop reply notifications received before it has
35104 finished processing a previous notification and the stub has completed
35105 sending any queued stop events.
35107 Otherwise, @value{GDBN} must be prepared to receive a stop reply
35108 notification at any time. Specifically, they may appear when
35109 @value{GDBN} is not otherwise reading input from the stub, or when
35110 @value{GDBN} is expecting to read a normal synchronous response or a
35111 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
35112 Notification packets are distinct from any other communication from
35113 the stub so there is no ambiguity.
35115 After receiving a stop reply notification, @value{GDBN} shall
35116 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
35117 as a regular, synchronous request to the stub. Such acknowledgment
35118 is not required to happen immediately, as @value{GDBN} is permitted to
35119 send other, unrelated packets to the stub first, which the stub should
35122 Upon receiving a @samp{vStopped} packet, if the stub has other queued
35123 stop events to report to @value{GDBN}, it shall respond by sending a
35124 normal stop reply response. @value{GDBN} shall then send another
35125 @samp{vStopped} packet to solicit further responses; again, it is
35126 permitted to send other, unrelated packets as well which the stub
35127 should process normally.
35129 If the stub receives a @samp{vStopped} packet and there are no
35130 additional stop events to report, the stub shall return an @samp{OK}
35131 response. At this point, if further stop events occur, the stub shall
35132 send a new stop reply notification, @value{GDBN} shall accept the
35133 notification, and the process shall be repeated.
35135 In non-stop mode, the target shall respond to the @samp{?} packet as
35136 follows. First, any incomplete stop reply notification/@samp{vStopped}
35137 sequence in progress is abandoned. The target must begin a new
35138 sequence reporting stop events for all stopped threads, whether or not
35139 it has previously reported those events to @value{GDBN}. The first
35140 stop reply is sent as a synchronous reply to the @samp{?} packet, and
35141 subsequent stop replies are sent as responses to @samp{vStopped} packets
35142 using the mechanism described above. The target must not send
35143 asynchronous stop reply notifications until the sequence is complete.
35144 If all threads are running when the target receives the @samp{?} packet,
35145 or if the target is not attached to any process, it shall respond
35148 @node Packet Acknowledgment
35149 @section Packet Acknowledgment
35151 @cindex acknowledgment, for @value{GDBN} remote
35152 @cindex packet acknowledgment, for @value{GDBN} remote
35153 By default, when either the host or the target machine receives a packet,
35154 the first response expected is an acknowledgment: either @samp{+} (to indicate
35155 the package was received correctly) or @samp{-} (to request retransmission).
35156 This mechanism allows the @value{GDBN} remote protocol to operate over
35157 unreliable transport mechanisms, such as a serial line.
35159 In cases where the transport mechanism is itself reliable (such as a pipe or
35160 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
35161 It may be desirable to disable them in that case to reduce communication
35162 overhead, or for other reasons. This can be accomplished by means of the
35163 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
35165 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
35166 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
35167 and response format still includes the normal checksum, as described in
35168 @ref{Overview}, but the checksum may be ignored by the receiver.
35170 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
35171 no-acknowledgment mode, it should report that to @value{GDBN}
35172 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
35173 @pxref{qSupported}.
35174 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
35175 disabled via the @code{set remote noack-packet off} command
35176 (@pxref{Remote Configuration}),
35177 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
35178 Only then may the stub actually turn off packet acknowledgments.
35179 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
35180 response, which can be safely ignored by the stub.
35182 Note that @code{set remote noack-packet} command only affects negotiation
35183 between @value{GDBN} and the stub when subsequent connections are made;
35184 it does not affect the protocol acknowledgment state for any current
35186 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
35187 new connection is established,
35188 there is also no protocol request to re-enable the acknowledgments
35189 for the current connection, once disabled.
35194 Example sequence of a target being re-started. Notice how the restart
35195 does not get any direct output:
35200 @emph{target restarts}
35203 <- @code{T001:1234123412341234}
35207 Example sequence of a target being stepped by a single instruction:
35210 -> @code{G1445@dots{}}
35215 <- @code{T001:1234123412341234}
35219 <- @code{1455@dots{}}
35223 @node File-I/O Remote Protocol Extension
35224 @section File-I/O Remote Protocol Extension
35225 @cindex File-I/O remote protocol extension
35228 * File-I/O Overview::
35229 * Protocol Basics::
35230 * The F Request Packet::
35231 * The F Reply Packet::
35232 * The Ctrl-C Message::
35234 * List of Supported Calls::
35235 * Protocol-specific Representation of Datatypes::
35237 * File-I/O Examples::
35240 @node File-I/O Overview
35241 @subsection File-I/O Overview
35242 @cindex file-i/o overview
35244 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
35245 target to use the host's file system and console I/O to perform various
35246 system calls. System calls on the target system are translated into a
35247 remote protocol packet to the host system, which then performs the needed
35248 actions and returns a response packet to the target system.
35249 This simulates file system operations even on targets that lack file systems.
35251 The protocol is defined to be independent of both the host and target systems.
35252 It uses its own internal representation of datatypes and values. Both
35253 @value{GDBN} and the target's @value{GDBN} stub are responsible for
35254 translating the system-dependent value representations into the internal
35255 protocol representations when data is transmitted.
35257 The communication is synchronous. A system call is possible only when
35258 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
35259 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
35260 the target is stopped to allow deterministic access to the target's
35261 memory. Therefore File-I/O is not interruptible by target signals. On
35262 the other hand, it is possible to interrupt File-I/O by a user interrupt
35263 (@samp{Ctrl-C}) within @value{GDBN}.
35265 The target's request to perform a host system call does not finish
35266 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
35267 after finishing the system call, the target returns to continuing the
35268 previous activity (continue, step). No additional continue or step
35269 request from @value{GDBN} is required.
35272 (@value{GDBP}) continue
35273 <- target requests 'system call X'
35274 target is stopped, @value{GDBN} executes system call
35275 -> @value{GDBN} returns result
35276 ... target continues, @value{GDBN} returns to wait for the target
35277 <- target hits breakpoint and sends a Txx packet
35280 The protocol only supports I/O on the console and to regular files on
35281 the host file system. Character or block special devices, pipes,
35282 named pipes, sockets or any other communication method on the host
35283 system are not supported by this protocol.
35285 File I/O is not supported in non-stop mode.
35287 @node Protocol Basics
35288 @subsection Protocol Basics
35289 @cindex protocol basics, file-i/o
35291 The File-I/O protocol uses the @code{F} packet as the request as well
35292 as reply packet. Since a File-I/O system call can only occur when
35293 @value{GDBN} is waiting for a response from the continuing or stepping target,
35294 the File-I/O request is a reply that @value{GDBN} has to expect as a result
35295 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
35296 This @code{F} packet contains all information needed to allow @value{GDBN}
35297 to call the appropriate host system call:
35301 A unique identifier for the requested system call.
35304 All parameters to the system call. Pointers are given as addresses
35305 in the target memory address space. Pointers to strings are given as
35306 pointer/length pair. Numerical values are given as they are.
35307 Numerical control flags are given in a protocol-specific representation.
35311 At this point, @value{GDBN} has to perform the following actions.
35315 If the parameters include pointer values to data needed as input to a
35316 system call, @value{GDBN} requests this data from the target with a
35317 standard @code{m} packet request. This additional communication has to be
35318 expected by the target implementation and is handled as any other @code{m}
35322 @value{GDBN} translates all value from protocol representation to host
35323 representation as needed. Datatypes are coerced into the host types.
35326 @value{GDBN} calls the system call.
35329 It then coerces datatypes back to protocol representation.
35332 If the system call is expected to return data in buffer space specified
35333 by pointer parameters to the call, the data is transmitted to the
35334 target using a @code{M} or @code{X} packet. This packet has to be expected
35335 by the target implementation and is handled as any other @code{M} or @code{X}
35340 Eventually @value{GDBN} replies with another @code{F} packet which contains all
35341 necessary information for the target to continue. This at least contains
35348 @code{errno}, if has been changed by the system call.
35355 After having done the needed type and value coercion, the target continues
35356 the latest continue or step action.
35358 @node The F Request Packet
35359 @subsection The @code{F} Request Packet
35360 @cindex file-i/o request packet
35361 @cindex @code{F} request packet
35363 The @code{F} request packet has the following format:
35366 @item F@var{call-id},@var{parameter@dots{}}
35368 @var{call-id} is the identifier to indicate the host system call to be called.
35369 This is just the name of the function.
35371 @var{parameter@dots{}} are the parameters to the system call.
35372 Parameters are hexadecimal integer values, either the actual values in case
35373 of scalar datatypes, pointers to target buffer space in case of compound
35374 datatypes and unspecified memory areas, or pointer/length pairs in case
35375 of string parameters. These are appended to the @var{call-id} as a
35376 comma-delimited list. All values are transmitted in ASCII
35377 string representation, pointer/length pairs separated by a slash.
35383 @node The F Reply Packet
35384 @subsection The @code{F} Reply Packet
35385 @cindex file-i/o reply packet
35386 @cindex @code{F} reply packet
35388 The @code{F} reply packet has the following format:
35392 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
35394 @var{retcode} is the return code of the system call as hexadecimal value.
35396 @var{errno} is the @code{errno} set by the call, in protocol-specific
35398 This parameter can be omitted if the call was successful.
35400 @var{Ctrl-C flag} is only sent if the user requested a break. In this
35401 case, @var{errno} must be sent as well, even if the call was successful.
35402 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
35409 or, if the call was interrupted before the host call has been performed:
35416 assuming 4 is the protocol-specific representation of @code{EINTR}.
35421 @node The Ctrl-C Message
35422 @subsection The @samp{Ctrl-C} Message
35423 @cindex ctrl-c message, in file-i/o protocol
35425 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
35426 reply packet (@pxref{The F Reply Packet}),
35427 the target should behave as if it had
35428 gotten a break message. The meaning for the target is ``system call
35429 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
35430 (as with a break message) and return to @value{GDBN} with a @code{T02}
35433 It's important for the target to know in which
35434 state the system call was interrupted. There are two possible cases:
35438 The system call hasn't been performed on the host yet.
35441 The system call on the host has been finished.
35445 These two states can be distinguished by the target by the value of the
35446 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
35447 call hasn't been performed. This is equivalent to the @code{EINTR} handling
35448 on POSIX systems. In any other case, the target may presume that the
35449 system call has been finished --- successfully or not --- and should behave
35450 as if the break message arrived right after the system call.
35452 @value{GDBN} must behave reliably. If the system call has not been called
35453 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
35454 @code{errno} in the packet. If the system call on the host has been finished
35455 before the user requests a break, the full action must be finished by
35456 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
35457 The @code{F} packet may only be sent when either nothing has happened
35458 or the full action has been completed.
35461 @subsection Console I/O
35462 @cindex console i/o as part of file-i/o
35464 By default and if not explicitly closed by the target system, the file
35465 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
35466 on the @value{GDBN} console is handled as any other file output operation
35467 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
35468 by @value{GDBN} so that after the target read request from file descriptor
35469 0 all following typing is buffered until either one of the following
35474 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
35476 system call is treated as finished.
35479 The user presses @key{RET}. This is treated as end of input with a trailing
35483 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
35484 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
35488 If the user has typed more characters than fit in the buffer given to
35489 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
35490 either another @code{read(0, @dots{})} is requested by the target, or debugging
35491 is stopped at the user's request.
35494 @node List of Supported Calls
35495 @subsection List of Supported Calls
35496 @cindex list of supported file-i/o calls
35513 @unnumberedsubsubsec open
35514 @cindex open, file-i/o system call
35519 int open(const char *pathname, int flags);
35520 int open(const char *pathname, int flags, mode_t mode);
35524 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
35527 @var{flags} is the bitwise @code{OR} of the following values:
35531 If the file does not exist it will be created. The host
35532 rules apply as far as file ownership and time stamps
35536 When used with @code{O_CREAT}, if the file already exists it is
35537 an error and open() fails.
35540 If the file already exists and the open mode allows
35541 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
35542 truncated to zero length.
35545 The file is opened in append mode.
35548 The file is opened for reading only.
35551 The file is opened for writing only.
35554 The file is opened for reading and writing.
35558 Other bits are silently ignored.
35562 @var{mode} is the bitwise @code{OR} of the following values:
35566 User has read permission.
35569 User has write permission.
35572 Group has read permission.
35575 Group has write permission.
35578 Others have read permission.
35581 Others have write permission.
35585 Other bits are silently ignored.
35588 @item Return value:
35589 @code{open} returns the new file descriptor or -1 if an error
35596 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
35599 @var{pathname} refers to a directory.
35602 The requested access is not allowed.
35605 @var{pathname} was too long.
35608 A directory component in @var{pathname} does not exist.
35611 @var{pathname} refers to a device, pipe, named pipe or socket.
35614 @var{pathname} refers to a file on a read-only filesystem and
35615 write access was requested.
35618 @var{pathname} is an invalid pointer value.
35621 No space on device to create the file.
35624 The process already has the maximum number of files open.
35627 The limit on the total number of files open on the system
35631 The call was interrupted by the user.
35637 @unnumberedsubsubsec close
35638 @cindex close, file-i/o system call
35647 @samp{Fclose,@var{fd}}
35649 @item Return value:
35650 @code{close} returns zero on success, or -1 if an error occurred.
35656 @var{fd} isn't a valid open file descriptor.
35659 The call was interrupted by the user.
35665 @unnumberedsubsubsec read
35666 @cindex read, file-i/o system call
35671 int read(int fd, void *buf, unsigned int count);
35675 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
35677 @item Return value:
35678 On success, the number of bytes read is returned.
35679 Zero indicates end of file. If count is zero, read
35680 returns zero as well. On error, -1 is returned.
35686 @var{fd} is not a valid file descriptor or is not open for
35690 @var{bufptr} is an invalid pointer value.
35693 The call was interrupted by the user.
35699 @unnumberedsubsubsec write
35700 @cindex write, file-i/o system call
35705 int write(int fd, const void *buf, unsigned int count);
35709 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
35711 @item Return value:
35712 On success, the number of bytes written are returned.
35713 Zero indicates nothing was written. On error, -1
35720 @var{fd} is not a valid file descriptor or is not open for
35724 @var{bufptr} is an invalid pointer value.
35727 An attempt was made to write a file that exceeds the
35728 host-specific maximum file size allowed.
35731 No space on device to write the data.
35734 The call was interrupted by the user.
35740 @unnumberedsubsubsec lseek
35741 @cindex lseek, file-i/o system call
35746 long lseek (int fd, long offset, int flag);
35750 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
35752 @var{flag} is one of:
35756 The offset is set to @var{offset} bytes.
35759 The offset is set to its current location plus @var{offset}
35763 The offset is set to the size of the file plus @var{offset}
35767 @item Return value:
35768 On success, the resulting unsigned offset in bytes from
35769 the beginning of the file is returned. Otherwise, a
35770 value of -1 is returned.
35776 @var{fd} is not a valid open file descriptor.
35779 @var{fd} is associated with the @value{GDBN} console.
35782 @var{flag} is not a proper value.
35785 The call was interrupted by the user.
35791 @unnumberedsubsubsec rename
35792 @cindex rename, file-i/o system call
35797 int rename(const char *oldpath, const char *newpath);
35801 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
35803 @item Return value:
35804 On success, zero is returned. On error, -1 is returned.
35810 @var{newpath} is an existing directory, but @var{oldpath} is not a
35814 @var{newpath} is a non-empty directory.
35817 @var{oldpath} or @var{newpath} is a directory that is in use by some
35821 An attempt was made to make a directory a subdirectory
35825 A component used as a directory in @var{oldpath} or new
35826 path is not a directory. Or @var{oldpath} is a directory
35827 and @var{newpath} exists but is not a directory.
35830 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
35833 No access to the file or the path of the file.
35837 @var{oldpath} or @var{newpath} was too long.
35840 A directory component in @var{oldpath} or @var{newpath} does not exist.
35843 The file is on a read-only filesystem.
35846 The device containing the file has no room for the new
35850 The call was interrupted by the user.
35856 @unnumberedsubsubsec unlink
35857 @cindex unlink, file-i/o system call
35862 int unlink(const char *pathname);
35866 @samp{Funlink,@var{pathnameptr}/@var{len}}
35868 @item Return value:
35869 On success, zero is returned. On error, -1 is returned.
35875 No access to the file or the path of the file.
35878 The system does not allow unlinking of directories.
35881 The file @var{pathname} cannot be unlinked because it's
35882 being used by another process.
35885 @var{pathnameptr} is an invalid pointer value.
35888 @var{pathname} was too long.
35891 A directory component in @var{pathname} does not exist.
35894 A component of the path is not a directory.
35897 The file is on a read-only filesystem.
35900 The call was interrupted by the user.
35906 @unnumberedsubsubsec stat/fstat
35907 @cindex fstat, file-i/o system call
35908 @cindex stat, file-i/o system call
35913 int stat(const char *pathname, struct stat *buf);
35914 int fstat(int fd, struct stat *buf);
35918 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
35919 @samp{Ffstat,@var{fd},@var{bufptr}}
35921 @item Return value:
35922 On success, zero is returned. On error, -1 is returned.
35928 @var{fd} is not a valid open file.
35931 A directory component in @var{pathname} does not exist or the
35932 path is an empty string.
35935 A component of the path is not a directory.
35938 @var{pathnameptr} is an invalid pointer value.
35941 No access to the file or the path of the file.
35944 @var{pathname} was too long.
35947 The call was interrupted by the user.
35953 @unnumberedsubsubsec gettimeofday
35954 @cindex gettimeofday, file-i/o system call
35959 int gettimeofday(struct timeval *tv, void *tz);
35963 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
35965 @item Return value:
35966 On success, 0 is returned, -1 otherwise.
35972 @var{tz} is a non-NULL pointer.
35975 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
35981 @unnumberedsubsubsec isatty
35982 @cindex isatty, file-i/o system call
35987 int isatty(int fd);
35991 @samp{Fisatty,@var{fd}}
35993 @item Return value:
35994 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
36000 The call was interrupted by the user.
36005 Note that the @code{isatty} call is treated as a special case: it returns
36006 1 to the target if the file descriptor is attached
36007 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
36008 would require implementing @code{ioctl} and would be more complex than
36013 @unnumberedsubsubsec system
36014 @cindex system, file-i/o system call
36019 int system(const char *command);
36023 @samp{Fsystem,@var{commandptr}/@var{len}}
36025 @item Return value:
36026 If @var{len} is zero, the return value indicates whether a shell is
36027 available. A zero return value indicates a shell is not available.
36028 For non-zero @var{len}, the value returned is -1 on error and the
36029 return status of the command otherwise. Only the exit status of the
36030 command is returned, which is extracted from the host's @code{system}
36031 return value by calling @code{WEXITSTATUS(retval)}. In case
36032 @file{/bin/sh} could not be executed, 127 is returned.
36038 The call was interrupted by the user.
36043 @value{GDBN} takes over the full task of calling the necessary host calls
36044 to perform the @code{system} call. The return value of @code{system} on
36045 the host is simplified before it's returned
36046 to the target. Any termination signal information from the child process
36047 is discarded, and the return value consists
36048 entirely of the exit status of the called command.
36050 Due to security concerns, the @code{system} call is by default refused
36051 by @value{GDBN}. The user has to allow this call explicitly with the
36052 @code{set remote system-call-allowed 1} command.
36055 @item set remote system-call-allowed
36056 @kindex set remote system-call-allowed
36057 Control whether to allow the @code{system} calls in the File I/O
36058 protocol for the remote target. The default is zero (disabled).
36060 @item show remote system-call-allowed
36061 @kindex show remote system-call-allowed
36062 Show whether the @code{system} calls are allowed in the File I/O
36066 @node Protocol-specific Representation of Datatypes
36067 @subsection Protocol-specific Representation of Datatypes
36068 @cindex protocol-specific representation of datatypes, in file-i/o protocol
36071 * Integral Datatypes::
36073 * Memory Transfer::
36078 @node Integral Datatypes
36079 @unnumberedsubsubsec Integral Datatypes
36080 @cindex integral datatypes, in file-i/o protocol
36082 The integral datatypes used in the system calls are @code{int},
36083 @code{unsigned int}, @code{long}, @code{unsigned long},
36084 @code{mode_t}, and @code{time_t}.
36086 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
36087 implemented as 32 bit values in this protocol.
36089 @code{long} and @code{unsigned long} are implemented as 64 bit types.
36091 @xref{Limits}, for corresponding MIN and MAX values (similar to those
36092 in @file{limits.h}) to allow range checking on host and target.
36094 @code{time_t} datatypes are defined as seconds since the Epoch.
36096 All integral datatypes transferred as part of a memory read or write of a
36097 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
36100 @node Pointer Values
36101 @unnumberedsubsubsec Pointer Values
36102 @cindex pointer values, in file-i/o protocol
36104 Pointers to target data are transmitted as they are. An exception
36105 is made for pointers to buffers for which the length isn't
36106 transmitted as part of the function call, namely strings. Strings
36107 are transmitted as a pointer/length pair, both as hex values, e.g.@:
36114 which is a pointer to data of length 18 bytes at position 0x1aaf.
36115 The length is defined as the full string length in bytes, including
36116 the trailing null byte. For example, the string @code{"hello world"}
36117 at address 0x123456 is transmitted as
36123 @node Memory Transfer
36124 @unnumberedsubsubsec Memory Transfer
36125 @cindex memory transfer, in file-i/o protocol
36127 Structured data which is transferred using a memory read or write (for
36128 example, a @code{struct stat}) is expected to be in a protocol-specific format
36129 with all scalar multibyte datatypes being big endian. Translation to
36130 this representation needs to be done both by the target before the @code{F}
36131 packet is sent, and by @value{GDBN} before
36132 it transfers memory to the target. Transferred pointers to structured
36133 data should point to the already-coerced data at any time.
36137 @unnumberedsubsubsec struct stat
36138 @cindex struct stat, in file-i/o protocol
36140 The buffer of type @code{struct stat} used by the target and @value{GDBN}
36141 is defined as follows:
36145 unsigned int st_dev; /* device */
36146 unsigned int st_ino; /* inode */
36147 mode_t st_mode; /* protection */
36148 unsigned int st_nlink; /* number of hard links */
36149 unsigned int st_uid; /* user ID of owner */
36150 unsigned int st_gid; /* group ID of owner */
36151 unsigned int st_rdev; /* device type (if inode device) */
36152 unsigned long st_size; /* total size, in bytes */
36153 unsigned long st_blksize; /* blocksize for filesystem I/O */
36154 unsigned long st_blocks; /* number of blocks allocated */
36155 time_t st_atime; /* time of last access */
36156 time_t st_mtime; /* time of last modification */
36157 time_t st_ctime; /* time of last change */
36161 The integral datatypes conform to the definitions given in the
36162 appropriate section (see @ref{Integral Datatypes}, for details) so this
36163 structure is of size 64 bytes.
36165 The values of several fields have a restricted meaning and/or
36171 A value of 0 represents a file, 1 the console.
36174 No valid meaning for the target. Transmitted unchanged.
36177 Valid mode bits are described in @ref{Constants}. Any other
36178 bits have currently no meaning for the target.
36183 No valid meaning for the target. Transmitted unchanged.
36188 These values have a host and file system dependent
36189 accuracy. Especially on Windows hosts, the file system may not
36190 support exact timing values.
36193 The target gets a @code{struct stat} of the above representation and is
36194 responsible for coercing it to the target representation before
36197 Note that due to size differences between the host, target, and protocol
36198 representations of @code{struct stat} members, these members could eventually
36199 get truncated on the target.
36201 @node struct timeval
36202 @unnumberedsubsubsec struct timeval
36203 @cindex struct timeval, in file-i/o protocol
36205 The buffer of type @code{struct timeval} used by the File-I/O protocol
36206 is defined as follows:
36210 time_t tv_sec; /* second */
36211 long tv_usec; /* microsecond */
36215 The integral datatypes conform to the definitions given in the
36216 appropriate section (see @ref{Integral Datatypes}, for details) so this
36217 structure is of size 8 bytes.
36220 @subsection Constants
36221 @cindex constants, in file-i/o protocol
36223 The following values are used for the constants inside of the
36224 protocol. @value{GDBN} and target are responsible for translating these
36225 values before and after the call as needed.
36236 @unnumberedsubsubsec Open Flags
36237 @cindex open flags, in file-i/o protocol
36239 All values are given in hexadecimal representation.
36251 @node mode_t Values
36252 @unnumberedsubsubsec mode_t Values
36253 @cindex mode_t values, in file-i/o protocol
36255 All values are given in octal representation.
36272 @unnumberedsubsubsec Errno Values
36273 @cindex errno values, in file-i/o protocol
36275 All values are given in decimal representation.
36300 @code{EUNKNOWN} is used as a fallback error value if a host system returns
36301 any error value not in the list of supported error numbers.
36304 @unnumberedsubsubsec Lseek Flags
36305 @cindex lseek flags, in file-i/o protocol
36314 @unnumberedsubsubsec Limits
36315 @cindex limits, in file-i/o protocol
36317 All values are given in decimal representation.
36320 INT_MIN -2147483648
36322 UINT_MAX 4294967295
36323 LONG_MIN -9223372036854775808
36324 LONG_MAX 9223372036854775807
36325 ULONG_MAX 18446744073709551615
36328 @node File-I/O Examples
36329 @subsection File-I/O Examples
36330 @cindex file-i/o examples
36332 Example sequence of a write call, file descriptor 3, buffer is at target
36333 address 0x1234, 6 bytes should be written:
36336 <- @code{Fwrite,3,1234,6}
36337 @emph{request memory read from target}
36340 @emph{return "6 bytes written"}
36344 Example sequence of a read call, file descriptor 3, buffer is at target
36345 address 0x1234, 6 bytes should be read:
36348 <- @code{Fread,3,1234,6}
36349 @emph{request memory write to target}
36350 -> @code{X1234,6:XXXXXX}
36351 @emph{return "6 bytes read"}
36355 Example sequence of a read call, call fails on the host due to invalid
36356 file descriptor (@code{EBADF}):
36359 <- @code{Fread,3,1234,6}
36363 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
36367 <- @code{Fread,3,1234,6}
36372 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
36376 <- @code{Fread,3,1234,6}
36377 -> @code{X1234,6:XXXXXX}
36381 @node Library List Format
36382 @section Library List Format
36383 @cindex library list format, remote protocol
36385 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
36386 same process as your application to manage libraries. In this case,
36387 @value{GDBN} can use the loader's symbol table and normal memory
36388 operations to maintain a list of shared libraries. On other
36389 platforms, the operating system manages loaded libraries.
36390 @value{GDBN} can not retrieve the list of currently loaded libraries
36391 through memory operations, so it uses the @samp{qXfer:libraries:read}
36392 packet (@pxref{qXfer library list read}) instead. The remote stub
36393 queries the target's operating system and reports which libraries
36396 The @samp{qXfer:libraries:read} packet returns an XML document which
36397 lists loaded libraries and their offsets. Each library has an
36398 associated name and one or more segment or section base addresses,
36399 which report where the library was loaded in memory.
36401 For the common case of libraries that are fully linked binaries, the
36402 library should have a list of segments. If the target supports
36403 dynamic linking of a relocatable object file, its library XML element
36404 should instead include a list of allocated sections. The segment or
36405 section bases are start addresses, not relocation offsets; they do not
36406 depend on the library's link-time base addresses.
36408 @value{GDBN} must be linked with the Expat library to support XML
36409 library lists. @xref{Expat}.
36411 A simple memory map, with one loaded library relocated by a single
36412 offset, looks like this:
36416 <library name="/lib/libc.so.6">
36417 <segment address="0x10000000"/>
36422 Another simple memory map, with one loaded library with three
36423 allocated sections (.text, .data, .bss), looks like this:
36427 <library name="sharedlib.o">
36428 <section address="0x10000000"/>
36429 <section address="0x20000000"/>
36430 <section address="0x30000000"/>
36435 The format of a library list is described by this DTD:
36438 <!-- library-list: Root element with versioning -->
36439 <!ELEMENT library-list (library)*>
36440 <!ATTLIST library-list version CDATA #FIXED "1.0">
36441 <!ELEMENT library (segment*, section*)>
36442 <!ATTLIST library name CDATA #REQUIRED>
36443 <!ELEMENT segment EMPTY>
36444 <!ATTLIST segment address CDATA #REQUIRED>
36445 <!ELEMENT section EMPTY>
36446 <!ATTLIST section address CDATA #REQUIRED>
36449 In addition, segments and section descriptors cannot be mixed within a
36450 single library element, and you must supply at least one segment or
36451 section for each library.
36453 @node Memory Map Format
36454 @section Memory Map Format
36455 @cindex memory map format
36457 To be able to write into flash memory, @value{GDBN} needs to obtain a
36458 memory map from the target. This section describes the format of the
36461 The memory map is obtained using the @samp{qXfer:memory-map:read}
36462 (@pxref{qXfer memory map read}) packet and is an XML document that
36463 lists memory regions.
36465 @value{GDBN} must be linked with the Expat library to support XML
36466 memory maps. @xref{Expat}.
36468 The top-level structure of the document is shown below:
36471 <?xml version="1.0"?>
36472 <!DOCTYPE memory-map
36473 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
36474 "http://sourceware.org/gdb/gdb-memory-map.dtd">
36480 Each region can be either:
36485 A region of RAM starting at @var{addr} and extending for @var{length}
36489 <memory type="ram" start="@var{addr}" length="@var{length}"/>
36494 A region of read-only memory:
36497 <memory type="rom" start="@var{addr}" length="@var{length}"/>
36502 A region of flash memory, with erasure blocks @var{blocksize}
36506 <memory type="flash" start="@var{addr}" length="@var{length}">
36507 <property name="blocksize">@var{blocksize}</property>
36513 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
36514 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
36515 packets to write to addresses in such ranges.
36517 The formal DTD for memory map format is given below:
36520 <!-- ................................................... -->
36521 <!-- Memory Map XML DTD ................................ -->
36522 <!-- File: memory-map.dtd .............................. -->
36523 <!-- .................................... .............. -->
36524 <!-- memory-map.dtd -->
36525 <!-- memory-map: Root element with versioning -->
36526 <!ELEMENT memory-map (memory | property)>
36527 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
36528 <!ELEMENT memory (property)>
36529 <!-- memory: Specifies a memory region,
36530 and its type, or device. -->
36531 <!ATTLIST memory type CDATA #REQUIRED
36532 start CDATA #REQUIRED
36533 length CDATA #REQUIRED
36534 device CDATA #IMPLIED>
36535 <!-- property: Generic attribute tag -->
36536 <!ELEMENT property (#PCDATA | property)*>
36537 <!ATTLIST property name CDATA #REQUIRED>
36540 @node Thread List Format
36541 @section Thread List Format
36542 @cindex thread list format
36544 To efficiently update the list of threads and their attributes,
36545 @value{GDBN} issues the @samp{qXfer:threads:read} packet
36546 (@pxref{qXfer threads read}) and obtains the XML document with
36547 the following structure:
36550 <?xml version="1.0"?>
36552 <thread id="id" core="0">
36553 ... description ...
36558 Each @samp{thread} element must have the @samp{id} attribute that
36559 identifies the thread (@pxref{thread-id syntax}). The
36560 @samp{core} attribute, if present, specifies which processor core
36561 the thread was last executing on. The content of the of @samp{thread}
36562 element is interpreted as human-readable auxilliary information.
36564 @node Traceframe Info Format
36565 @section Traceframe Info Format
36566 @cindex traceframe info format
36568 To be able to know which objects in the inferior can be examined when
36569 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
36570 memory ranges, registers and trace state variables that have been
36571 collected in a traceframe.
36573 This list is obtained using the @samp{qXfer:traceframe-info:read}
36574 (@pxref{qXfer traceframe info read}) packet and is an XML document.
36576 @value{GDBN} must be linked with the Expat library to support XML
36577 traceframe info discovery. @xref{Expat}.
36579 The top-level structure of the document is shown below:
36582 <?xml version="1.0"?>
36583 <!DOCTYPE traceframe-info
36584 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
36585 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
36591 Each traceframe block can be either:
36596 A region of collected memory starting at @var{addr} and extending for
36597 @var{length} bytes from there:
36600 <memory start="@var{addr}" length="@var{length}"/>
36605 The formal DTD for the traceframe info format is given below:
36608 <!ELEMENT traceframe-info (memory)* >
36609 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
36611 <!ELEMENT memory EMPTY>
36612 <!ATTLIST memory start CDATA #REQUIRED
36613 length CDATA #REQUIRED>
36616 @include agentexpr.texi
36618 @node Target Descriptions
36619 @appendix Target Descriptions
36620 @cindex target descriptions
36622 One of the challenges of using @value{GDBN} to debug embedded systems
36623 is that there are so many minor variants of each processor
36624 architecture in use. It is common practice for vendors to start with
36625 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
36626 and then make changes to adapt it to a particular market niche. Some
36627 architectures have hundreds of variants, available from dozens of
36628 vendors. This leads to a number of problems:
36632 With so many different customized processors, it is difficult for
36633 the @value{GDBN} maintainers to keep up with the changes.
36635 Since individual variants may have short lifetimes or limited
36636 audiences, it may not be worthwhile to carry information about every
36637 variant in the @value{GDBN} source tree.
36639 When @value{GDBN} does support the architecture of the embedded system
36640 at hand, the task of finding the correct architecture name to give the
36641 @command{set architecture} command can be error-prone.
36644 To address these problems, the @value{GDBN} remote protocol allows a
36645 target system to not only identify itself to @value{GDBN}, but to
36646 actually describe its own features. This lets @value{GDBN} support
36647 processor variants it has never seen before --- to the extent that the
36648 descriptions are accurate, and that @value{GDBN} understands them.
36650 @value{GDBN} must be linked with the Expat library to support XML
36651 target descriptions. @xref{Expat}.
36654 * Retrieving Descriptions:: How descriptions are fetched from a target.
36655 * Target Description Format:: The contents of a target description.
36656 * Predefined Target Types:: Standard types available for target
36658 * Standard Target Features:: Features @value{GDBN} knows about.
36661 @node Retrieving Descriptions
36662 @section Retrieving Descriptions
36664 Target descriptions can be read from the target automatically, or
36665 specified by the user manually. The default behavior is to read the
36666 description from the target. @value{GDBN} retrieves it via the remote
36667 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
36668 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
36669 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
36670 XML document, of the form described in @ref{Target Description
36673 Alternatively, you can specify a file to read for the target description.
36674 If a file is set, the target will not be queried. The commands to
36675 specify a file are:
36678 @cindex set tdesc filename
36679 @item set tdesc filename @var{path}
36680 Read the target description from @var{path}.
36682 @cindex unset tdesc filename
36683 @item unset tdesc filename
36684 Do not read the XML target description from a file. @value{GDBN}
36685 will use the description supplied by the current target.
36687 @cindex show tdesc filename
36688 @item show tdesc filename
36689 Show the filename to read for a target description, if any.
36693 @node Target Description Format
36694 @section Target Description Format
36695 @cindex target descriptions, XML format
36697 A target description annex is an @uref{http://www.w3.org/XML/, XML}
36698 document which complies with the Document Type Definition provided in
36699 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
36700 means you can use generally available tools like @command{xmllint} to
36701 check that your feature descriptions are well-formed and valid.
36702 However, to help people unfamiliar with XML write descriptions for
36703 their targets, we also describe the grammar here.
36705 Target descriptions can identify the architecture of the remote target
36706 and (for some architectures) provide information about custom register
36707 sets. They can also identify the OS ABI of the remote target.
36708 @value{GDBN} can use this information to autoconfigure for your
36709 target, or to warn you if you connect to an unsupported target.
36711 Here is a simple target description:
36714 <target version="1.0">
36715 <architecture>i386:x86-64</architecture>
36720 This minimal description only says that the target uses
36721 the x86-64 architecture.
36723 A target description has the following overall form, with [ ] marking
36724 optional elements and @dots{} marking repeatable elements. The elements
36725 are explained further below.
36728 <?xml version="1.0"?>
36729 <!DOCTYPE target SYSTEM "gdb-target.dtd">
36730 <target version="1.0">
36731 @r{[}@var{architecture}@r{]}
36732 @r{[}@var{osabi}@r{]}
36733 @r{[}@var{compatible}@r{]}
36734 @r{[}@var{feature}@dots{}@r{]}
36739 The description is generally insensitive to whitespace and line
36740 breaks, under the usual common-sense rules. The XML version
36741 declaration and document type declaration can generally be omitted
36742 (@value{GDBN} does not require them), but specifying them may be
36743 useful for XML validation tools. The @samp{version} attribute for
36744 @samp{<target>} may also be omitted, but we recommend
36745 including it; if future versions of @value{GDBN} use an incompatible
36746 revision of @file{gdb-target.dtd}, they will detect and report
36747 the version mismatch.
36749 @subsection Inclusion
36750 @cindex target descriptions, inclusion
36753 @cindex <xi:include>
36756 It can sometimes be valuable to split a target description up into
36757 several different annexes, either for organizational purposes, or to
36758 share files between different possible target descriptions. You can
36759 divide a description into multiple files by replacing any element of
36760 the target description with an inclusion directive of the form:
36763 <xi:include href="@var{document}"/>
36767 When @value{GDBN} encounters an element of this form, it will retrieve
36768 the named XML @var{document}, and replace the inclusion directive with
36769 the contents of that document. If the current description was read
36770 using @samp{qXfer}, then so will be the included document;
36771 @var{document} will be interpreted as the name of an annex. If the
36772 current description was read from a file, @value{GDBN} will look for
36773 @var{document} as a file in the same directory where it found the
36774 original description.
36776 @subsection Architecture
36777 @cindex <architecture>
36779 An @samp{<architecture>} element has this form:
36782 <architecture>@var{arch}</architecture>
36785 @var{arch} is one of the architectures from the set accepted by
36786 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
36789 @cindex @code{<osabi>}
36791 This optional field was introduced in @value{GDBN} version 7.0.
36792 Previous versions of @value{GDBN} ignore it.
36794 An @samp{<osabi>} element has this form:
36797 <osabi>@var{abi-name}</osabi>
36800 @var{abi-name} is an OS ABI name from the same selection accepted by
36801 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
36803 @subsection Compatible Architecture
36804 @cindex @code{<compatible>}
36806 This optional field was introduced in @value{GDBN} version 7.0.
36807 Previous versions of @value{GDBN} ignore it.
36809 A @samp{<compatible>} element has this form:
36812 <compatible>@var{arch}</compatible>
36815 @var{arch} is one of the architectures from the set accepted by
36816 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
36818 A @samp{<compatible>} element is used to specify that the target
36819 is able to run binaries in some other than the main target architecture
36820 given by the @samp{<architecture>} element. For example, on the
36821 Cell Broadband Engine, the main architecture is @code{powerpc:common}
36822 or @code{powerpc:common64}, but the system is able to run binaries
36823 in the @code{spu} architecture as well. The way to describe this
36824 capability with @samp{<compatible>} is as follows:
36827 <architecture>powerpc:common</architecture>
36828 <compatible>spu</compatible>
36831 @subsection Features
36834 Each @samp{<feature>} describes some logical portion of the target
36835 system. Features are currently used to describe available CPU
36836 registers and the types of their contents. A @samp{<feature>} element
36840 <feature name="@var{name}">
36841 @r{[}@var{type}@dots{}@r{]}
36847 Each feature's name should be unique within the description. The name
36848 of a feature does not matter unless @value{GDBN} has some special
36849 knowledge of the contents of that feature; if it does, the feature
36850 should have its standard name. @xref{Standard Target Features}.
36854 Any register's value is a collection of bits which @value{GDBN} must
36855 interpret. The default interpretation is a two's complement integer,
36856 but other types can be requested by name in the register description.
36857 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
36858 Target Types}), and the description can define additional composite types.
36860 Each type element must have an @samp{id} attribute, which gives
36861 a unique (within the containing @samp{<feature>}) name to the type.
36862 Types must be defined before they are used.
36865 Some targets offer vector registers, which can be treated as arrays
36866 of scalar elements. These types are written as @samp{<vector>} elements,
36867 specifying the array element type, @var{type}, and the number of elements,
36871 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
36875 If a register's value is usefully viewed in multiple ways, define it
36876 with a union type containing the useful representations. The
36877 @samp{<union>} element contains one or more @samp{<field>} elements,
36878 each of which has a @var{name} and a @var{type}:
36881 <union id="@var{id}">
36882 <field name="@var{name}" type="@var{type}"/>
36888 If a register's value is composed from several separate values, define
36889 it with a structure type. There are two forms of the @samp{<struct>}
36890 element; a @samp{<struct>} element must either contain only bitfields
36891 or contain no bitfields. If the structure contains only bitfields,
36892 its total size in bytes must be specified, each bitfield must have an
36893 explicit start and end, and bitfields are automatically assigned an
36894 integer type. The field's @var{start} should be less than or
36895 equal to its @var{end}, and zero represents the least significant bit.
36898 <struct id="@var{id}" size="@var{size}">
36899 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
36904 If the structure contains no bitfields, then each field has an
36905 explicit type, and no implicit padding is added.
36908 <struct id="@var{id}">
36909 <field name="@var{name}" type="@var{type}"/>
36915 If a register's value is a series of single-bit flags, define it with
36916 a flags type. The @samp{<flags>} element has an explicit @var{size}
36917 and contains one or more @samp{<field>} elements. Each field has a
36918 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
36922 <flags id="@var{id}" size="@var{size}">
36923 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
36928 @subsection Registers
36931 Each register is represented as an element with this form:
36934 <reg name="@var{name}"
36935 bitsize="@var{size}"
36936 @r{[}regnum="@var{num}"@r{]}
36937 @r{[}save-restore="@var{save-restore}"@r{]}
36938 @r{[}type="@var{type}"@r{]}
36939 @r{[}group="@var{group}"@r{]}/>
36943 The components are as follows:
36948 The register's name; it must be unique within the target description.
36951 The register's size, in bits.
36954 The register's number. If omitted, a register's number is one greater
36955 than that of the previous register (either in the current feature or in
36956 a preceding feature); the first register in the target description
36957 defaults to zero. This register number is used to read or write
36958 the register; e.g.@: it is used in the remote @code{p} and @code{P}
36959 packets, and registers appear in the @code{g} and @code{G} packets
36960 in order of increasing register number.
36963 Whether the register should be preserved across inferior function
36964 calls; this must be either @code{yes} or @code{no}. The default is
36965 @code{yes}, which is appropriate for most registers except for
36966 some system control registers; this is not related to the target's
36970 The type of the register. @var{type} may be a predefined type, a type
36971 defined in the current feature, or one of the special types @code{int}
36972 and @code{float}. @code{int} is an integer type of the correct size
36973 for @var{bitsize}, and @code{float} is a floating point type (in the
36974 architecture's normal floating point format) of the correct size for
36975 @var{bitsize}. The default is @code{int}.
36978 The register group to which this register belongs. @var{group} must
36979 be either @code{general}, @code{float}, or @code{vector}. If no
36980 @var{group} is specified, @value{GDBN} will not display the register
36981 in @code{info registers}.
36985 @node Predefined Target Types
36986 @section Predefined Target Types
36987 @cindex target descriptions, predefined types
36989 Type definitions in the self-description can build up composite types
36990 from basic building blocks, but can not define fundamental types. Instead,
36991 standard identifiers are provided by @value{GDBN} for the fundamental
36992 types. The currently supported types are:
37001 Signed integer types holding the specified number of bits.
37008 Unsigned integer types holding the specified number of bits.
37012 Pointers to unspecified code and data. The program counter and
37013 any dedicated return address register may be marked as code
37014 pointers; printing a code pointer converts it into a symbolic
37015 address. The stack pointer and any dedicated address registers
37016 may be marked as data pointers.
37019 Single precision IEEE floating point.
37022 Double precision IEEE floating point.
37025 The 12-byte extended precision format used by ARM FPA registers.
37028 The 10-byte extended precision format used by x87 registers.
37031 32bit @sc{eflags} register used by x86.
37034 32bit @sc{mxcsr} register used by x86.
37038 @node Standard Target Features
37039 @section Standard Target Features
37040 @cindex target descriptions, standard features
37042 A target description must contain either no registers or all the
37043 target's registers. If the description contains no registers, then
37044 @value{GDBN} will assume a default register layout, selected based on
37045 the architecture. If the description contains any registers, the
37046 default layout will not be used; the standard registers must be
37047 described in the target description, in such a way that @value{GDBN}
37048 can recognize them.
37050 This is accomplished by giving specific names to feature elements
37051 which contain standard registers. @value{GDBN} will look for features
37052 with those names and verify that they contain the expected registers;
37053 if any known feature is missing required registers, or if any required
37054 feature is missing, @value{GDBN} will reject the target
37055 description. You can add additional registers to any of the
37056 standard features --- @value{GDBN} will display them just as if
37057 they were added to an unrecognized feature.
37059 This section lists the known features and their expected contents.
37060 Sample XML documents for these features are included in the
37061 @value{GDBN} source tree, in the directory @file{gdb/features}.
37063 Names recognized by @value{GDBN} should include the name of the
37064 company or organization which selected the name, and the overall
37065 architecture to which the feature applies; so e.g.@: the feature
37066 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
37068 The names of registers are not case sensitive for the purpose
37069 of recognizing standard features, but @value{GDBN} will only display
37070 registers using the capitalization used in the description.
37077 * PowerPC Features::
37083 @subsection ARM Features
37084 @cindex target descriptions, ARM features
37086 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
37088 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
37089 @samp{lr}, @samp{pc}, and @samp{cpsr}.
37091 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
37092 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
37093 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
37096 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
37097 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
37099 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
37100 it should contain at least registers @samp{wR0} through @samp{wR15} and
37101 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
37102 @samp{wCSSF}, and @samp{wCASF} registers are optional.
37104 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
37105 should contain at least registers @samp{d0} through @samp{d15}. If
37106 they are present, @samp{d16} through @samp{d31} should also be included.
37107 @value{GDBN} will synthesize the single-precision registers from
37108 halves of the double-precision registers.
37110 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
37111 need to contain registers; it instructs @value{GDBN} to display the
37112 VFP double-precision registers as vectors and to synthesize the
37113 quad-precision registers from pairs of double-precision registers.
37114 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
37115 be present and include 32 double-precision registers.
37117 @node i386 Features
37118 @subsection i386 Features
37119 @cindex target descriptions, i386 features
37121 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
37122 targets. It should describe the following registers:
37126 @samp{eax} through @samp{edi} plus @samp{eip} for i386
37128 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
37130 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
37131 @samp{fs}, @samp{gs}
37133 @samp{st0} through @samp{st7}
37135 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
37136 @samp{foseg}, @samp{fooff} and @samp{fop}
37139 The register sets may be different, depending on the target.
37141 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
37142 describe registers:
37146 @samp{xmm0} through @samp{xmm7} for i386
37148 @samp{xmm0} through @samp{xmm15} for amd64
37153 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
37154 @samp{org.gnu.gdb.i386.sse} feature. It should
37155 describe the upper 128 bits of @sc{ymm} registers:
37159 @samp{ymm0h} through @samp{ymm7h} for i386
37161 @samp{ymm0h} through @samp{ymm15h} for amd64
37164 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
37165 describe a single register, @samp{orig_eax}.
37167 @node MIPS Features
37168 @subsection MIPS Features
37169 @cindex target descriptions, MIPS features
37171 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
37172 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
37173 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
37176 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
37177 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
37178 registers. They may be 32-bit or 64-bit depending on the target.
37180 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
37181 it may be optional in a future version of @value{GDBN}. It should
37182 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
37183 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
37185 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
37186 contain a single register, @samp{restart}, which is used by the
37187 Linux kernel to control restartable syscalls.
37189 @node M68K Features
37190 @subsection M68K Features
37191 @cindex target descriptions, M68K features
37194 @item @samp{org.gnu.gdb.m68k.core}
37195 @itemx @samp{org.gnu.gdb.coldfire.core}
37196 @itemx @samp{org.gnu.gdb.fido.core}
37197 One of those features must be always present.
37198 The feature that is present determines which flavor of m68k is
37199 used. The feature that is present should contain registers
37200 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
37201 @samp{sp}, @samp{ps} and @samp{pc}.
37203 @item @samp{org.gnu.gdb.coldfire.fp}
37204 This feature is optional. If present, it should contain registers
37205 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
37209 @node PowerPC Features
37210 @subsection PowerPC Features
37211 @cindex target descriptions, PowerPC features
37213 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
37214 targets. It should contain registers @samp{r0} through @samp{r31},
37215 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
37216 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
37218 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
37219 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
37221 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
37222 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
37225 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
37226 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
37227 will combine these registers with the floating point registers
37228 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
37229 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
37230 through @samp{vs63}, the set of vector registers for POWER7.
37232 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
37233 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
37234 @samp{spefscr}. SPE targets should provide 32-bit registers in
37235 @samp{org.gnu.gdb.power.core} and provide the upper halves in
37236 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
37237 these to present registers @samp{ev0} through @samp{ev31} to the
37240 @node TIC6x Features
37241 @subsection TMS320C6x Features
37242 @cindex target descriptions, TIC6x features
37243 @cindex target descriptions, TMS320C6x features
37244 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
37245 targets. It should contain registers @samp{A0} through @samp{A15},
37246 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
37248 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
37249 contain registers @samp{A16} through @samp{A31} and @samp{B16}
37250 through @samp{B31}.
37252 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
37253 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
37255 @node Operating System Information
37256 @appendix Operating System Information
37257 @cindex operating system information
37263 Users of @value{GDBN} often wish to obtain information about the state of
37264 the operating system running on the target---for example the list of
37265 processes, or the list of open files. This section describes the
37266 mechanism that makes it possible. This mechanism is similar to the
37267 target features mechanism (@pxref{Target Descriptions}), but focuses
37268 on a different aspect of target.
37270 Operating system information is retrived from the target via the
37271 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
37272 read}). The object name in the request should be @samp{osdata}, and
37273 the @var{annex} identifies the data to be fetched.
37276 @appendixsection Process list
37277 @cindex operating system information, process list
37279 When requesting the process list, the @var{annex} field in the
37280 @samp{qXfer} request should be @samp{processes}. The returned data is
37281 an XML document. The formal syntax of this document is defined in
37282 @file{gdb/features/osdata.dtd}.
37284 An example document is:
37287 <?xml version="1.0"?>
37288 <!DOCTYPE target SYSTEM "osdata.dtd">
37289 <osdata type="processes">
37291 <column name="pid">1</column>
37292 <column name="user">root</column>
37293 <column name="command">/sbin/init</column>
37294 <column name="cores">1,2,3</column>
37299 Each item should include a column whose name is @samp{pid}. The value
37300 of that column should identify the process on the target. The
37301 @samp{user} and @samp{command} columns are optional, and will be
37302 displayed by @value{GDBN}. The @samp{cores} column, if present,
37303 should contain a comma-separated list of cores that this process
37304 is running on. Target may provide additional columns,
37305 which @value{GDBN} currently ignores.
37307 @node Trace File Format
37308 @appendix Trace File Format
37309 @cindex trace file format
37311 The trace file comes in three parts: a header, a textual description
37312 section, and a trace frame section with binary data.
37314 The header has the form @code{\x7fTRACE0\n}. The first byte is
37315 @code{0x7f} so as to indicate that the file contains binary data,
37316 while the @code{0} is a version number that may have different values
37319 The description section consists of multiple lines of @sc{ascii} text
37320 separated by newline characters (@code{0xa}). The lines may include a
37321 variety of optional descriptive or context-setting information, such
37322 as tracepoint definitions or register set size. @value{GDBN} will
37323 ignore any line that it does not recognize. An empty line marks the end
37326 @c FIXME add some specific types of data
37328 The trace frame section consists of a number of consecutive frames.
37329 Each frame begins with a two-byte tracepoint number, followed by a
37330 four-byte size giving the amount of data in the frame. The data in
37331 the frame consists of a number of blocks, each introduced by a
37332 character indicating its type (at least register, memory, and trace
37333 state variable). The data in this section is raw binary, not a
37334 hexadecimal or other encoding; its endianness matches the target's
37337 @c FIXME bi-arch may require endianness/arch info in description section
37340 @item R @var{bytes}
37341 Register block. The number and ordering of bytes matches that of a
37342 @code{g} packet in the remote protocol. Note that these are the
37343 actual bytes, in target order and @value{GDBN} register order, not a
37344 hexadecimal encoding.
37346 @item M @var{address} @var{length} @var{bytes}...
37347 Memory block. This is a contiguous block of memory, at the 8-byte
37348 address @var{address}, with a 2-byte length @var{length}, followed by
37349 @var{length} bytes.
37351 @item V @var{number} @var{value}
37352 Trace state variable block. This records the 8-byte signed value
37353 @var{value} of trace state variable numbered @var{number}.
37357 Future enhancements of the trace file format may include additional types
37360 @node Index Section Format
37361 @appendix @code{.gdb_index} section format
37362 @cindex .gdb_index section format
37363 @cindex index section format
37365 This section documents the index section that is created by @code{save
37366 gdb-index} (@pxref{Index Files}). The index section is
37367 DWARF-specific; some knowledge of DWARF is assumed in this
37370 The mapped index file format is designed to be directly
37371 @code{mmap}able on any architecture. In most cases, a datum is
37372 represented using a little-endian 32-bit integer value, called an
37373 @code{offset_type}. Big endian machines must byte-swap the values
37374 before using them. Exceptions to this rule are noted. The data is
37375 laid out such that alignment is always respected.
37377 A mapped index consists of several areas, laid out in order.
37381 The file header. This is a sequence of values, of @code{offset_type}
37382 unless otherwise noted:
37386 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
37387 Version 4 differs by its hashing function.
37390 The offset, from the start of the file, of the CU list.
37393 The offset, from the start of the file, of the types CU list. Note
37394 that this area can be empty, in which case this offset will be equal
37395 to the next offset.
37398 The offset, from the start of the file, of the address area.
37401 The offset, from the start of the file, of the symbol table.
37404 The offset, from the start of the file, of the constant pool.
37408 The CU list. This is a sequence of pairs of 64-bit little-endian
37409 values, sorted by the CU offset. The first element in each pair is
37410 the offset of a CU in the @code{.debug_info} section. The second
37411 element in each pair is the length of that CU. References to a CU
37412 elsewhere in the map are done using a CU index, which is just the
37413 0-based index into this table. Note that if there are type CUs, then
37414 conceptually CUs and type CUs form a single list for the purposes of
37418 The types CU list. This is a sequence of triplets of 64-bit
37419 little-endian values. In a triplet, the first value is the CU offset,
37420 the second value is the type offset in the CU, and the third value is
37421 the type signature. The types CU list is not sorted.
37424 The address area. The address area consists of a sequence of address
37425 entries. Each address entry has three elements:
37429 The low address. This is a 64-bit little-endian value.
37432 The high address. This is a 64-bit little-endian value. Like
37433 @code{DW_AT_high_pc}, the value is one byte beyond the end.
37436 The CU index. This is an @code{offset_type} value.
37440 The symbol table. This is an open-addressed hash table. The size of
37441 the hash table is always a power of 2.
37443 Each slot in the hash table consists of a pair of @code{offset_type}
37444 values. The first value is the offset of the symbol's name in the
37445 constant pool. The second value is the offset of the CU vector in the
37448 If both values are 0, then this slot in the hash table is empty. This
37449 is ok because while 0 is a valid constant pool index, it cannot be a
37450 valid index for both a string and a CU vector.
37452 The hash value for a table entry is computed by applying an
37453 iterative hash function to the symbol's name. Starting with an
37454 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
37455 the string is incorporated into the hash using the formula depending on the
37460 The formula is @code{r = r * 67 + c - 113}.
37463 The formula is @code{r = r * 67 + tolower (c) - 113}.
37466 The terminating @samp{\0} is not incorporated into the hash.
37468 The step size used in the hash table is computed via
37469 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
37470 value, and @samp{size} is the size of the hash table. The step size
37471 is used to find the next candidate slot when handling a hash
37474 The names of C@t{++} symbols in the hash table are canonicalized. We
37475 don't currently have a simple description of the canonicalization
37476 algorithm; if you intend to create new index sections, you must read
37480 The constant pool. This is simply a bunch of bytes. It is organized
37481 so that alignment is correct: CU vectors are stored first, followed by
37484 A CU vector in the constant pool is a sequence of @code{offset_type}
37485 values. The first value is the number of CU indices in the vector.
37486 Each subsequent value is the index of a CU in the CU list. This
37487 element in the hash table is used to indicate which CUs define the
37490 A string in the constant pool is zero-terminated.
37495 @node GNU Free Documentation License
37496 @appendix GNU Free Documentation License
37505 % I think something like @colophon should be in texinfo. In the
37507 \long\def\colophon{\hbox to0pt{}\vfill
37508 \centerline{The body of this manual is set in}
37509 \centerline{\fontname\tenrm,}
37510 \centerline{with headings in {\bf\fontname\tenbf}}
37511 \centerline{and examples in {\tt\fontname\tentt}.}
37512 \centerline{{\it\fontname\tenit\/},}
37513 \centerline{{\bf\fontname\tenbf}, and}
37514 \centerline{{\sl\fontname\tensl\/}}
37515 \centerline{are used for emphasis.}\vfill}
37517 % Blame: doc@cygnus.com, 1991.