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. Version 3.1 and later of @value{NGCC},
1877 the @sc{gnu} C compiler, provides macro information if you are using
1878 the DWARF debugging format, and specify the option @option{-g3}.
1880 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1881 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1882 information on @value{NGCC} options affecting debug information.
1884 You will have the best debugging experience if you use the latest
1885 version of the DWARF debugging format that your compiler supports.
1886 DWARF is currently the most expressive and best supported debugging
1887 format in @value{GDBN}.
1891 @section Starting your Program
1897 @kindex r @r{(@code{run})}
1900 Use the @code{run} command to start your program under @value{GDBN}.
1901 You must first specify the program name (except on VxWorks) with an
1902 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1903 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1904 (@pxref{Files, ,Commands to Specify Files}).
1908 If you are running your program in an execution environment that
1909 supports processes, @code{run} creates an inferior process and makes
1910 that process run your program. In some environments without processes,
1911 @code{run} jumps to the start of your program. Other targets,
1912 like @samp{remote}, are always running. If you get an error
1913 message like this one:
1916 The "remote" target does not support "run".
1917 Try "help target" or "continue".
1921 then use @code{continue} to run your program. You may need @code{load}
1922 first (@pxref{load}).
1924 The execution of a program is affected by certain information it
1925 receives from its superior. @value{GDBN} provides ways to specify this
1926 information, which you must do @emph{before} starting your program. (You
1927 can change it after starting your program, but such changes only affect
1928 your program the next time you start it.) This information may be
1929 divided into four categories:
1932 @item The @emph{arguments.}
1933 Specify the arguments to give your program as the arguments of the
1934 @code{run} command. If a shell is available on your target, the shell
1935 is used to pass the arguments, so that you may use normal conventions
1936 (such as wildcard expansion or variable substitution) in describing
1938 In Unix systems, you can control which shell is used with the
1939 @code{SHELL} environment variable.
1940 @xref{Arguments, ,Your Program's Arguments}.
1942 @item The @emph{environment.}
1943 Your program normally inherits its environment from @value{GDBN}, but you can
1944 use the @value{GDBN} commands @code{set environment} and @code{unset
1945 environment} to change parts of the environment that affect
1946 your program. @xref{Environment, ,Your Program's Environment}.
1948 @item The @emph{working directory.}
1949 Your program inherits its working directory from @value{GDBN}. You can set
1950 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1951 @xref{Working Directory, ,Your Program's Working Directory}.
1953 @item The @emph{standard input and output.}
1954 Your program normally uses the same device for standard input and
1955 standard output as @value{GDBN} is using. You can redirect input and output
1956 in the @code{run} command line, or you can use the @code{tty} command to
1957 set a different device for your program.
1958 @xref{Input/Output, ,Your Program's Input and Output}.
1961 @emph{Warning:} While input and output redirection work, you cannot use
1962 pipes to pass the output of the program you are debugging to another
1963 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1967 When you issue the @code{run} command, your program begins to execute
1968 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1969 of how to arrange for your program to stop. Once your program has
1970 stopped, you may call functions in your program, using the @code{print}
1971 or @code{call} commands. @xref{Data, ,Examining Data}.
1973 If the modification time of your symbol file has changed since the last
1974 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1975 table, and reads it again. When it does this, @value{GDBN} tries to retain
1976 your current breakpoints.
1981 @cindex run to main procedure
1982 The name of the main procedure can vary from language to language.
1983 With C or C@t{++}, the main procedure name is always @code{main}, but
1984 other languages such as Ada do not require a specific name for their
1985 main procedure. The debugger provides a convenient way to start the
1986 execution of the program and to stop at the beginning of the main
1987 procedure, depending on the language used.
1989 The @samp{start} command does the equivalent of setting a temporary
1990 breakpoint at the beginning of the main procedure and then invoking
1991 the @samp{run} command.
1993 @cindex elaboration phase
1994 Some programs contain an @dfn{elaboration} phase where some startup code is
1995 executed before the main procedure is called. This depends on the
1996 languages used to write your program. In C@t{++}, for instance,
1997 constructors for static and global objects are executed before
1998 @code{main} is called. It is therefore possible that the debugger stops
1999 before reaching the main procedure. However, the temporary breakpoint
2000 will remain to halt execution.
2002 Specify the arguments to give to your program as arguments to the
2003 @samp{start} command. These arguments will be given verbatim to the
2004 underlying @samp{run} command. Note that the same arguments will be
2005 reused if no argument is provided during subsequent calls to
2006 @samp{start} or @samp{run}.
2008 It is sometimes necessary to debug the program during elaboration. In
2009 these cases, using the @code{start} command would stop the execution of
2010 your program too late, as the program would have already completed the
2011 elaboration phase. Under these circumstances, insert breakpoints in your
2012 elaboration code before running your program.
2014 @kindex set exec-wrapper
2015 @item set exec-wrapper @var{wrapper}
2016 @itemx show exec-wrapper
2017 @itemx unset exec-wrapper
2018 When @samp{exec-wrapper} is set, the specified wrapper is used to
2019 launch programs for debugging. @value{GDBN} starts your program
2020 with a shell command of the form @kbd{exec @var{wrapper}
2021 @var{program}}. Quoting is added to @var{program} and its
2022 arguments, but not to @var{wrapper}, so you should add quotes if
2023 appropriate for your shell. The wrapper runs until it executes
2024 your program, and then @value{GDBN} takes control.
2026 You can use any program that eventually calls @code{execve} with
2027 its arguments as a wrapper. Several standard Unix utilities do
2028 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2029 with @code{exec "$@@"} will also work.
2031 For example, you can use @code{env} to pass an environment variable to
2032 the debugged program, without setting the variable in your shell's
2036 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2040 This command is available when debugging locally on most targets, excluding
2041 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2043 @kindex set disable-randomization
2044 @item set disable-randomization
2045 @itemx set disable-randomization on
2046 This option (enabled by default in @value{GDBN}) will turn off the native
2047 randomization of the virtual address space of the started program. This option
2048 is useful for multiple debugging sessions to make the execution better
2049 reproducible and memory addresses reusable across debugging sessions.
2051 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2052 On @sc{gnu}/Linux you can get the same behavior using
2055 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2058 @item set disable-randomization off
2059 Leave the behavior of the started executable unchanged. Some bugs rear their
2060 ugly heads only when the program is loaded at certain addresses. If your bug
2061 disappears when you run the program under @value{GDBN}, that might be because
2062 @value{GDBN} by default disables the address randomization on platforms, such
2063 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2064 disable-randomization off} to try to reproduce such elusive bugs.
2066 On targets where it is available, virtual address space randomization
2067 protects the programs against certain kinds of security attacks. In these
2068 cases the attacker needs to know the exact location of a concrete executable
2069 code. Randomizing its location makes it impossible to inject jumps misusing
2070 a code at its expected addresses.
2072 Prelinking shared libraries provides a startup performance advantage but it
2073 makes addresses in these libraries predictable for privileged processes by
2074 having just unprivileged access at the target system. Reading the shared
2075 library binary gives enough information for assembling the malicious code
2076 misusing it. Still even a prelinked shared library can get loaded at a new
2077 random address just requiring the regular relocation process during the
2078 startup. Shared libraries not already prelinked are always loaded at
2079 a randomly chosen address.
2081 Position independent executables (PIE) contain position independent code
2082 similar to the shared libraries and therefore such executables get loaded at
2083 a randomly chosen address upon startup. PIE executables always load even
2084 already prelinked shared libraries at a random address. You can build such
2085 executable using @command{gcc -fPIE -pie}.
2087 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2088 (as long as the randomization is enabled).
2090 @item show disable-randomization
2091 Show the current setting of the explicit disable of the native randomization of
2092 the virtual address space of the started program.
2097 @section Your Program's Arguments
2099 @cindex arguments (to your program)
2100 The arguments to your program can be specified by the arguments of the
2102 They are passed to a shell, which expands wildcard characters and
2103 performs redirection of I/O, and thence to your program. Your
2104 @code{SHELL} environment variable (if it exists) specifies what shell
2105 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2106 the default shell (@file{/bin/sh} on Unix).
2108 On non-Unix systems, the program is usually invoked directly by
2109 @value{GDBN}, which emulates I/O redirection via the appropriate system
2110 calls, and the wildcard characters are expanded by the startup code of
2111 the program, not by the shell.
2113 @code{run} with no arguments uses the same arguments used by the previous
2114 @code{run}, or those set by the @code{set args} command.
2119 Specify the arguments to be used the next time your program is run. If
2120 @code{set args} has no arguments, @code{run} executes your program
2121 with no arguments. Once you have run your program with arguments,
2122 using @code{set args} before the next @code{run} is the only way to run
2123 it again without arguments.
2127 Show the arguments to give your program when it is started.
2131 @section Your Program's Environment
2133 @cindex environment (of your program)
2134 The @dfn{environment} consists of a set of environment variables and
2135 their values. Environment variables conventionally record such things as
2136 your user name, your home directory, your terminal type, and your search
2137 path for programs to run. Usually you set up environment variables with
2138 the shell and they are inherited by all the other programs you run. When
2139 debugging, it can be useful to try running your program with a modified
2140 environment without having to start @value{GDBN} over again.
2144 @item path @var{directory}
2145 Add @var{directory} to the front of the @code{PATH} environment variable
2146 (the search path for executables) that will be passed to your program.
2147 The value of @code{PATH} used by @value{GDBN} does not change.
2148 You may specify several directory names, separated by whitespace or by a
2149 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2150 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2151 is moved to the front, so it is searched sooner.
2153 You can use the string @samp{$cwd} to refer to whatever is the current
2154 working directory at the time @value{GDBN} searches the path. If you
2155 use @samp{.} instead, it refers to the directory where you executed the
2156 @code{path} command. @value{GDBN} replaces @samp{.} in the
2157 @var{directory} argument (with the current path) before adding
2158 @var{directory} to the search path.
2159 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2160 @c document that, since repeating it would be a no-op.
2164 Display the list of search paths for executables (the @code{PATH}
2165 environment variable).
2167 @kindex show environment
2168 @item show environment @r{[}@var{varname}@r{]}
2169 Print the value of environment variable @var{varname} to be given to
2170 your program when it starts. If you do not supply @var{varname},
2171 print the names and values of all environment variables to be given to
2172 your program. You can abbreviate @code{environment} as @code{env}.
2174 @kindex set environment
2175 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2176 Set environment variable @var{varname} to @var{value}. The value
2177 changes for your program only, not for @value{GDBN} itself. @var{value} may
2178 be any string; the values of environment variables are just strings, and
2179 any interpretation is supplied by your program itself. The @var{value}
2180 parameter is optional; if it is eliminated, the variable is set to a
2182 @c "any string" here does not include leading, trailing
2183 @c blanks. Gnu asks: does anyone care?
2185 For example, this command:
2192 tells the debugged program, when subsequently run, that its user is named
2193 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2194 are not actually required.)
2196 @kindex unset environment
2197 @item unset environment @var{varname}
2198 Remove variable @var{varname} from the environment to be passed to your
2199 program. This is different from @samp{set env @var{varname} =};
2200 @code{unset environment} removes the variable from the environment,
2201 rather than assigning it an empty value.
2204 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2206 by your @code{SHELL} environment variable if it exists (or
2207 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2208 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2209 @file{.bashrc} for BASH---any variables you set in that file affect
2210 your program. You may wish to move setting of environment variables to
2211 files that are only run when you sign on, such as @file{.login} or
2214 @node Working Directory
2215 @section Your Program's Working Directory
2217 @cindex working directory (of your program)
2218 Each time you start your program with @code{run}, it inherits its
2219 working directory from the current working directory of @value{GDBN}.
2220 The @value{GDBN} working directory is initially whatever it inherited
2221 from its parent process (typically the shell), but you can specify a new
2222 working directory in @value{GDBN} with the @code{cd} command.
2224 The @value{GDBN} working directory also serves as a default for the commands
2225 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2230 @cindex change working directory
2231 @item cd @var{directory}
2232 Set the @value{GDBN} working directory to @var{directory}.
2236 Print the @value{GDBN} working directory.
2239 It is generally impossible to find the current working directory of
2240 the process being debugged (since a program can change its directory
2241 during its run). If you work on a system where @value{GDBN} is
2242 configured with the @file{/proc} support, you can use the @code{info
2243 proc} command (@pxref{SVR4 Process Information}) to find out the
2244 current working directory of the debuggee.
2247 @section Your Program's Input and Output
2252 By default, the program you run under @value{GDBN} does input and output to
2253 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2254 to its own terminal modes to interact with you, but it records the terminal
2255 modes your program was using and switches back to them when you continue
2256 running your program.
2259 @kindex info terminal
2261 Displays information recorded by @value{GDBN} about the terminal modes your
2265 You can redirect your program's input and/or output using shell
2266 redirection with the @code{run} command. For example,
2273 starts your program, diverting its output to the file @file{outfile}.
2276 @cindex controlling terminal
2277 Another way to specify where your program should do input and output is
2278 with the @code{tty} command. This command accepts a file name as
2279 argument, and causes this file to be the default for future @code{run}
2280 commands. It also resets the controlling terminal for the child
2281 process, for future @code{run} commands. For example,
2288 directs that processes started with subsequent @code{run} commands
2289 default to do input and output on the terminal @file{/dev/ttyb} and have
2290 that as their controlling terminal.
2292 An explicit redirection in @code{run} overrides the @code{tty} command's
2293 effect on the input/output device, but not its effect on the controlling
2296 When you use the @code{tty} command or redirect input in the @code{run}
2297 command, only the input @emph{for your program} is affected. The input
2298 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2299 for @code{set inferior-tty}.
2301 @cindex inferior tty
2302 @cindex set inferior controlling terminal
2303 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2304 display the name of the terminal that will be used for future runs of your
2308 @item set inferior-tty /dev/ttyb
2309 @kindex set inferior-tty
2310 Set the tty for the program being debugged to /dev/ttyb.
2312 @item show inferior-tty
2313 @kindex show inferior-tty
2314 Show the current tty for the program being debugged.
2318 @section Debugging an Already-running Process
2323 @item attach @var{process-id}
2324 This command attaches to a running process---one that was started
2325 outside @value{GDBN}. (@code{info files} shows your active
2326 targets.) The command takes as argument a process ID. The usual way to
2327 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2328 or with the @samp{jobs -l} shell command.
2330 @code{attach} does not repeat if you press @key{RET} a second time after
2331 executing the command.
2334 To use @code{attach}, your program must be running in an environment
2335 which supports processes; for example, @code{attach} does not work for
2336 programs on bare-board targets that lack an operating system. You must
2337 also have permission to send the process a signal.
2339 When you use @code{attach}, the debugger finds the program running in
2340 the process first by looking in the current working directory, then (if
2341 the program is not found) by using the source file search path
2342 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2343 the @code{file} command to load the program. @xref{Files, ,Commands to
2346 The first thing @value{GDBN} does after arranging to debug the specified
2347 process is to stop it. You can examine and modify an attached process
2348 with all the @value{GDBN} commands that are ordinarily available when
2349 you start processes with @code{run}. You can insert breakpoints; you
2350 can step and continue; you can modify storage. If you would rather the
2351 process continue running, you may use the @code{continue} command after
2352 attaching @value{GDBN} to the process.
2357 When you have finished debugging the attached process, you can use the
2358 @code{detach} command to release it from @value{GDBN} control. Detaching
2359 the process continues its execution. After the @code{detach} command,
2360 that process and @value{GDBN} become completely independent once more, and you
2361 are ready to @code{attach} another process or start one with @code{run}.
2362 @code{detach} does not repeat if you press @key{RET} again after
2363 executing the command.
2366 If you exit @value{GDBN} while you have an attached process, you detach
2367 that process. If you use the @code{run} command, you kill that process.
2368 By default, @value{GDBN} asks for confirmation if you try to do either of these
2369 things; you can control whether or not you need to confirm by using the
2370 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2374 @section Killing the Child Process
2379 Kill the child process in which your program is running under @value{GDBN}.
2382 This command is useful if you wish to debug a core dump instead of a
2383 running process. @value{GDBN} ignores any core dump file while your program
2386 On some operating systems, a program cannot be executed outside @value{GDBN}
2387 while you have breakpoints set on it inside @value{GDBN}. You can use the
2388 @code{kill} command in this situation to permit running your program
2389 outside the debugger.
2391 The @code{kill} command is also useful if you wish to recompile and
2392 relink your program, since on many systems it is impossible to modify an
2393 executable file while it is running in a process. In this case, when you
2394 next type @code{run}, @value{GDBN} notices that the file has changed, and
2395 reads the symbol table again (while trying to preserve your current
2396 breakpoint settings).
2398 @node Inferiors and Programs
2399 @section Debugging Multiple Inferiors and Programs
2401 @value{GDBN} lets you run and debug multiple programs in a single
2402 session. In addition, @value{GDBN} on some systems may let you run
2403 several programs simultaneously (otherwise you have to exit from one
2404 before starting another). In the most general case, you can have
2405 multiple threads of execution in each of multiple processes, launched
2406 from multiple executables.
2409 @value{GDBN} represents the state of each program execution with an
2410 object called an @dfn{inferior}. An inferior typically corresponds to
2411 a process, but is more general and applies also to targets that do not
2412 have processes. Inferiors may be created before a process runs, and
2413 may be retained after a process exits. Inferiors have unique
2414 identifiers that are different from process ids. Usually each
2415 inferior will also have its own distinct address space, although some
2416 embedded targets may have several inferiors running in different parts
2417 of a single address space. Each inferior may in turn have multiple
2418 threads running in it.
2420 To find out what inferiors exist at any moment, use @w{@code{info
2424 @kindex info inferiors
2425 @item info inferiors
2426 Print a list of all inferiors currently being managed by @value{GDBN}.
2428 @value{GDBN} displays for each inferior (in this order):
2432 the inferior number assigned by @value{GDBN}
2435 the target system's inferior identifier
2438 the name of the executable the inferior is running.
2443 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2444 indicates the current inferior.
2448 @c end table here to get a little more width for example
2451 (@value{GDBP}) info inferiors
2452 Num Description Executable
2453 2 process 2307 hello
2454 * 1 process 3401 goodbye
2457 To switch focus between inferiors, use the @code{inferior} command:
2460 @kindex inferior @var{infno}
2461 @item inferior @var{infno}
2462 Make inferior number @var{infno} the current inferior. The argument
2463 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2464 in the first field of the @samp{info inferiors} display.
2468 You can get multiple executables into a debugging session via the
2469 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2470 systems @value{GDBN} can add inferiors to the debug session
2471 automatically by following calls to @code{fork} and @code{exec}. To
2472 remove inferiors from the debugging session use the
2473 @w{@code{remove-inferiors}} command.
2476 @kindex add-inferior
2477 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2478 Adds @var{n} inferiors to be run using @var{executable} as the
2479 executable. @var{n} defaults to 1. If no executable is specified,
2480 the inferiors begins empty, with no program. You can still assign or
2481 change the program assigned to the inferior at any time by using the
2482 @code{file} command with the executable name as its argument.
2484 @kindex clone-inferior
2485 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2486 Adds @var{n} inferiors ready to execute the same program as inferior
2487 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2488 number of the current inferior. This is a convenient command when you
2489 want to run another instance of the inferior you are debugging.
2492 (@value{GDBP}) info inferiors
2493 Num Description Executable
2494 * 1 process 29964 helloworld
2495 (@value{GDBP}) clone-inferior
2498 (@value{GDBP}) info inferiors
2499 Num Description Executable
2501 * 1 process 29964 helloworld
2504 You can now simply switch focus to inferior 2 and run it.
2506 @kindex remove-inferiors
2507 @item remove-inferiors @var{infno}@dots{}
2508 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2509 possible to remove an inferior that is running with this command. For
2510 those, use the @code{kill} or @code{detach} command first.
2514 To quit debugging one of the running inferiors that is not the current
2515 inferior, you can either detach from it by using the @w{@code{detach
2516 inferior}} command (allowing it to run independently), or kill it
2517 using the @w{@code{kill inferiors}} command:
2520 @kindex detach inferiors @var{infno}@dots{}
2521 @item detach inferior @var{infno}@dots{}
2522 Detach from the inferior or inferiors identified by @value{GDBN}
2523 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2524 still stays on the list of inferiors shown by @code{info inferiors},
2525 but its Description will show @samp{<null>}.
2527 @kindex kill inferiors @var{infno}@dots{}
2528 @item kill inferiors @var{infno}@dots{}
2529 Kill the inferior or inferiors identified by @value{GDBN} inferior
2530 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2531 stays on the list of inferiors shown by @code{info inferiors}, but its
2532 Description will show @samp{<null>}.
2535 After the successful completion of a command such as @code{detach},
2536 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2537 a normal process exit, the inferior is still valid and listed with
2538 @code{info inferiors}, ready to be restarted.
2541 To be notified when inferiors are started or exit under @value{GDBN}'s
2542 control use @w{@code{set print inferior-events}}:
2545 @kindex set print inferior-events
2546 @cindex print messages on inferior start and exit
2547 @item set print inferior-events
2548 @itemx set print inferior-events on
2549 @itemx set print inferior-events off
2550 The @code{set print inferior-events} command allows you to enable or
2551 disable printing of messages when @value{GDBN} notices that new
2552 inferiors have started or that inferiors have exited or have been
2553 detached. By default, these messages will not be printed.
2555 @kindex show print inferior-events
2556 @item show print inferior-events
2557 Show whether messages will be printed when @value{GDBN} detects that
2558 inferiors have started, exited or have been detached.
2561 Many commands will work the same with multiple programs as with a
2562 single program: e.g., @code{print myglobal} will simply display the
2563 value of @code{myglobal} in the current inferior.
2566 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2567 get more info about the relationship of inferiors, programs, address
2568 spaces in a debug session. You can do that with the @w{@code{maint
2569 info program-spaces}} command.
2572 @kindex maint info program-spaces
2573 @item maint info program-spaces
2574 Print a list of all program spaces currently being managed by
2577 @value{GDBN} displays for each program space (in this order):
2581 the program space number assigned by @value{GDBN}
2584 the name of the executable loaded into the program space, with e.g.,
2585 the @code{file} command.
2590 An asterisk @samp{*} preceding the @value{GDBN} program space number
2591 indicates the current program space.
2593 In addition, below each program space line, @value{GDBN} prints extra
2594 information that isn't suitable to display in tabular form. For
2595 example, the list of inferiors bound to the program space.
2598 (@value{GDBP}) maint info program-spaces
2601 Bound inferiors: ID 1 (process 21561)
2605 Here we can see that no inferior is running the program @code{hello},
2606 while @code{process 21561} is running the program @code{goodbye}. On
2607 some targets, it is possible that multiple inferiors are bound to the
2608 same program space. The most common example is that of debugging both
2609 the parent and child processes of a @code{vfork} call. For example,
2612 (@value{GDBP}) maint info program-spaces
2615 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2618 Here, both inferior 2 and inferior 1 are running in the same program
2619 space as a result of inferior 1 having executed a @code{vfork} call.
2623 @section Debugging Programs with Multiple Threads
2625 @cindex threads of execution
2626 @cindex multiple threads
2627 @cindex switching threads
2628 In some operating systems, such as HP-UX and Solaris, a single program
2629 may have more than one @dfn{thread} of execution. The precise semantics
2630 of threads differ from one operating system to another, but in general
2631 the threads of a single program are akin to multiple processes---except
2632 that they share one address space (that is, they can all examine and
2633 modify the same variables). On the other hand, each thread has its own
2634 registers and execution stack, and perhaps private memory.
2636 @value{GDBN} provides these facilities for debugging multi-thread
2640 @item automatic notification of new threads
2641 @item @samp{thread @var{threadno}}, a command to switch among threads
2642 @item @samp{info threads}, a command to inquire about existing threads
2643 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2644 a command to apply a command to a list of threads
2645 @item thread-specific breakpoints
2646 @item @samp{set print thread-events}, which controls printing of
2647 messages on thread start and exit.
2648 @item @samp{set libthread-db-search-path @var{path}}, which lets
2649 the user specify which @code{libthread_db} to use if the default choice
2650 isn't compatible with the program.
2654 @emph{Warning:} These facilities are not yet available on every
2655 @value{GDBN} configuration where the operating system supports threads.
2656 If your @value{GDBN} does not support threads, these commands have no
2657 effect. For example, a system without thread support shows no output
2658 from @samp{info threads}, and always rejects the @code{thread} command,
2662 (@value{GDBP}) info threads
2663 (@value{GDBP}) thread 1
2664 Thread ID 1 not known. Use the "info threads" command to
2665 see the IDs of currently known threads.
2667 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2668 @c doesn't support threads"?
2671 @cindex focus of debugging
2672 @cindex current thread
2673 The @value{GDBN} thread debugging facility allows you to observe all
2674 threads while your program runs---but whenever @value{GDBN} takes
2675 control, one thread in particular is always the focus of debugging.
2676 This thread is called the @dfn{current thread}. Debugging commands show
2677 program information from the perspective of the current thread.
2679 @cindex @code{New} @var{systag} message
2680 @cindex thread identifier (system)
2681 @c FIXME-implementors!! It would be more helpful if the [New...] message
2682 @c included GDB's numeric thread handle, so you could just go to that
2683 @c thread without first checking `info threads'.
2684 Whenever @value{GDBN} detects a new thread in your program, it displays
2685 the target system's identification for the thread with a message in the
2686 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2687 whose form varies depending on the particular system. For example, on
2688 @sc{gnu}/Linux, you might see
2691 [New Thread 0x41e02940 (LWP 25582)]
2695 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2696 the @var{systag} is simply something like @samp{process 368}, with no
2699 @c FIXME!! (1) Does the [New...] message appear even for the very first
2700 @c thread of a program, or does it only appear for the
2701 @c second---i.e.@: when it becomes obvious we have a multithread
2703 @c (2) *Is* there necessarily a first thread always? Or do some
2704 @c multithread systems permit starting a program with multiple
2705 @c threads ab initio?
2707 @cindex thread number
2708 @cindex thread identifier (GDB)
2709 For debugging purposes, @value{GDBN} associates its own thread
2710 number---always a single integer---with each thread in your program.
2713 @kindex info threads
2714 @item info threads @r{[}@var{id}@dots{}@r{]}
2715 Display a summary of all threads currently in your program. Optional
2716 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2717 means to print information only about the specified thread or threads.
2718 @value{GDBN} displays for each thread (in this order):
2722 the thread number assigned by @value{GDBN}
2725 the target system's thread identifier (@var{systag})
2728 the thread's name, if one is known. A thread can either be named by
2729 the user (see @code{thread name}, below), or, in some cases, by the
2733 the current stack frame summary for that thread
2737 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2738 indicates the current thread.
2742 @c end table here to get a little more width for example
2745 (@value{GDBP}) info threads
2747 3 process 35 thread 27 0x34e5 in sigpause ()
2748 2 process 35 thread 23 0x34e5 in sigpause ()
2749 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2753 On Solaris, you can display more information about user threads with a
2754 Solaris-specific command:
2757 @item maint info sol-threads
2758 @kindex maint info sol-threads
2759 @cindex thread info (Solaris)
2760 Display info on Solaris user threads.
2764 @kindex thread @var{threadno}
2765 @item thread @var{threadno}
2766 Make thread number @var{threadno} the current thread. The command
2767 argument @var{threadno} is the internal @value{GDBN} thread number, as
2768 shown in the first field of the @samp{info threads} display.
2769 @value{GDBN} responds by displaying the system identifier of the thread
2770 you selected, and its current stack frame summary:
2773 (@value{GDBP}) thread 2
2774 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2775 #0 some_function (ignore=0x0) at example.c:8
2776 8 printf ("hello\n");
2780 As with the @samp{[New @dots{}]} message, the form of the text after
2781 @samp{Switching to} depends on your system's conventions for identifying
2784 @vindex $_thread@r{, convenience variable}
2785 The debugger convenience variable @samp{$_thread} contains the number
2786 of the current thread. You may find this useful in writing breakpoint
2787 conditional expressions, command scripts, and so forth. See
2788 @xref{Convenience Vars,, Convenience Variables}, for general
2789 information on convenience variables.
2791 @kindex thread apply
2792 @cindex apply command to several threads
2793 @item thread apply [@var{threadno} | all] @var{command}
2794 The @code{thread apply} command allows you to apply the named
2795 @var{command} to one or more threads. Specify the numbers of the
2796 threads that you want affected with the command argument
2797 @var{threadno}. It can be a single thread number, one of the numbers
2798 shown in the first field of the @samp{info threads} display; or it
2799 could be a range of thread numbers, as in @code{2-4}. To apply a
2800 command to all threads, type @kbd{thread apply all @var{command}}.
2803 @cindex name a thread
2804 @item thread name [@var{name}]
2805 This command assigns a name to the current thread. If no argument is
2806 given, any existing user-specified name is removed. The thread name
2807 appears in the @samp{info threads} display.
2809 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2810 determine the name of the thread as given by the OS. On these
2811 systems, a name specified with @samp{thread name} will override the
2812 system-give name, and removing the user-specified name will cause
2813 @value{GDBN} to once again display the system-specified name.
2816 @cindex search for a thread
2817 @item thread find [@var{regexp}]
2818 Search for and display thread ids whose name or @var{systag}
2819 matches the supplied regular expression.
2821 As well as being the complement to the @samp{thread name} command,
2822 this command also allows you to identify a thread by its target
2823 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2827 (@value{GDBN}) thread find 26688
2828 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2829 (@value{GDBN}) info thread 4
2831 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2834 @kindex set print thread-events
2835 @cindex print messages on thread start and exit
2836 @item set print thread-events
2837 @itemx set print thread-events on
2838 @itemx set print thread-events off
2839 The @code{set print thread-events} command allows you to enable or
2840 disable printing of messages when @value{GDBN} notices that new threads have
2841 started or that threads have exited. By default, these messages will
2842 be printed if detection of these events is supported by the target.
2843 Note that these messages cannot be disabled on all targets.
2845 @kindex show print thread-events
2846 @item show print thread-events
2847 Show whether messages will be printed when @value{GDBN} detects that threads
2848 have started and exited.
2851 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2852 more information about how @value{GDBN} behaves when you stop and start
2853 programs with multiple threads.
2855 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2856 watchpoints in programs with multiple threads.
2859 @kindex set libthread-db-search-path
2860 @cindex search path for @code{libthread_db}
2861 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2862 If this variable is set, @var{path} is a colon-separated list of
2863 directories @value{GDBN} will use to search for @code{libthread_db}.
2864 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2865 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2866 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2869 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2870 @code{libthread_db} library to obtain information about threads in the
2871 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2872 to find @code{libthread_db}.
2874 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2875 refers to the default system directories that are
2876 normally searched for loading shared libraries.
2878 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2879 refers to the directory from which @code{libpthread}
2880 was loaded in the inferior process.
2882 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2883 @value{GDBN} attempts to initialize it with the current inferior process.
2884 If this initialization fails (which could happen because of a version
2885 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2886 will unload @code{libthread_db}, and continue with the next directory.
2887 If none of @code{libthread_db} libraries initialize successfully,
2888 @value{GDBN} will issue a warning and thread debugging will be disabled.
2890 Setting @code{libthread-db-search-path} is currently implemented
2891 only on some platforms.
2893 @kindex show libthread-db-search-path
2894 @item show libthread-db-search-path
2895 Display current libthread_db search path.
2897 @kindex set debug libthread-db
2898 @kindex show debug libthread-db
2899 @cindex debugging @code{libthread_db}
2900 @item set debug libthread-db
2901 @itemx show debug libthread-db
2902 Turns on or off display of @code{libthread_db}-related events.
2903 Use @code{1} to enable, @code{0} to disable.
2907 @section Debugging Forks
2909 @cindex fork, debugging programs which call
2910 @cindex multiple processes
2911 @cindex processes, multiple
2912 On most systems, @value{GDBN} has no special support for debugging
2913 programs which create additional processes using the @code{fork}
2914 function. When a program forks, @value{GDBN} will continue to debug the
2915 parent process and the child process will run unimpeded. If you have
2916 set a breakpoint in any code which the child then executes, the child
2917 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2918 will cause it to terminate.
2920 However, if you want to debug the child process there is a workaround
2921 which isn't too painful. Put a call to @code{sleep} in the code which
2922 the child process executes after the fork. It may be useful to sleep
2923 only if a certain environment variable is set, or a certain file exists,
2924 so that the delay need not occur when you don't want to run @value{GDBN}
2925 on the child. While the child is sleeping, use the @code{ps} program to
2926 get its process ID. Then tell @value{GDBN} (a new invocation of
2927 @value{GDBN} if you are also debugging the parent process) to attach to
2928 the child process (@pxref{Attach}). From that point on you can debug
2929 the child process just like any other process which you attached to.
2931 On some systems, @value{GDBN} provides support for debugging programs that
2932 create additional processes using the @code{fork} or @code{vfork} functions.
2933 Currently, the only platforms with this feature are HP-UX (11.x and later
2934 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2936 By default, when a program forks, @value{GDBN} will continue to debug
2937 the parent process and the child process will run unimpeded.
2939 If you want to follow the child process instead of the parent process,
2940 use the command @w{@code{set follow-fork-mode}}.
2943 @kindex set follow-fork-mode
2944 @item set follow-fork-mode @var{mode}
2945 Set the debugger response to a program call of @code{fork} or
2946 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2947 process. The @var{mode} argument can be:
2951 The original process is debugged after a fork. The child process runs
2952 unimpeded. This is the default.
2955 The new process is debugged after a fork. The parent process runs
2960 @kindex show follow-fork-mode
2961 @item show follow-fork-mode
2962 Display the current debugger response to a @code{fork} or @code{vfork} call.
2965 @cindex debugging multiple processes
2966 On Linux, if you want to debug both the parent and child processes, use the
2967 command @w{@code{set detach-on-fork}}.
2970 @kindex set detach-on-fork
2971 @item set detach-on-fork @var{mode}
2972 Tells gdb whether to detach one of the processes after a fork, or
2973 retain debugger control over them both.
2977 The child process (or parent process, depending on the value of
2978 @code{follow-fork-mode}) will be detached and allowed to run
2979 independently. This is the default.
2982 Both processes will be held under the control of @value{GDBN}.
2983 One process (child or parent, depending on the value of
2984 @code{follow-fork-mode}) is debugged as usual, while the other
2989 @kindex show detach-on-fork
2990 @item show detach-on-fork
2991 Show whether detach-on-fork mode is on/off.
2994 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2995 will retain control of all forked processes (including nested forks).
2996 You can list the forked processes under the control of @value{GDBN} by
2997 using the @w{@code{info inferiors}} command, and switch from one fork
2998 to another by using the @code{inferior} command (@pxref{Inferiors and
2999 Programs, ,Debugging Multiple Inferiors and Programs}).
3001 To quit debugging one of the forked processes, you can either detach
3002 from it by using the @w{@code{detach inferiors}} command (allowing it
3003 to run independently), or kill it using the @w{@code{kill inferiors}}
3004 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3007 If you ask to debug a child process and a @code{vfork} is followed by an
3008 @code{exec}, @value{GDBN} executes the new target up to the first
3009 breakpoint in the new target. If you have a breakpoint set on
3010 @code{main} in your original program, the breakpoint will also be set on
3011 the child process's @code{main}.
3013 On some systems, when a child process is spawned by @code{vfork}, you
3014 cannot debug the child or parent until an @code{exec} call completes.
3016 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3017 call executes, the new target restarts. To restart the parent
3018 process, use the @code{file} command with the parent executable name
3019 as its argument. By default, after an @code{exec} call executes,
3020 @value{GDBN} discards the symbols of the previous executable image.
3021 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3025 @kindex set follow-exec-mode
3026 @item set follow-exec-mode @var{mode}
3028 Set debugger response to a program call of @code{exec}. An
3029 @code{exec} call replaces the program image of a process.
3031 @code{follow-exec-mode} can be:
3035 @value{GDBN} creates a new inferior and rebinds the process to this
3036 new inferior. The program the process was running before the
3037 @code{exec} call can be restarted afterwards by restarting the
3043 (@value{GDBP}) info inferiors
3045 Id Description Executable
3048 process 12020 is executing new program: prog2
3049 Program exited normally.
3050 (@value{GDBP}) info inferiors
3051 Id Description Executable
3057 @value{GDBN} keeps the process bound to the same inferior. The new
3058 executable image replaces the previous executable loaded in the
3059 inferior. Restarting the inferior after the @code{exec} call, with
3060 e.g., the @code{run} command, restarts the executable the process was
3061 running after the @code{exec} call. This is the default mode.
3066 (@value{GDBP}) info inferiors
3067 Id Description Executable
3070 process 12020 is executing new program: prog2
3071 Program exited normally.
3072 (@value{GDBP}) info inferiors
3073 Id Description Executable
3080 You can use the @code{catch} command to make @value{GDBN} stop whenever
3081 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3082 Catchpoints, ,Setting Catchpoints}.
3084 @node Checkpoint/Restart
3085 @section Setting a @emph{Bookmark} to Return to Later
3090 @cindex snapshot of a process
3091 @cindex rewind program state
3093 On certain operating systems@footnote{Currently, only
3094 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3095 program's state, called a @dfn{checkpoint}, and come back to it
3098 Returning to a checkpoint effectively undoes everything that has
3099 happened in the program since the @code{checkpoint} was saved. This
3100 includes changes in memory, registers, and even (within some limits)
3101 system state. Effectively, it is like going back in time to the
3102 moment when the checkpoint was saved.
3104 Thus, if you're stepping thru a program and you think you're
3105 getting close to the point where things go wrong, you can save
3106 a checkpoint. Then, if you accidentally go too far and miss
3107 the critical statement, instead of having to restart your program
3108 from the beginning, you can just go back to the checkpoint and
3109 start again from there.
3111 This can be especially useful if it takes a lot of time or
3112 steps to reach the point where you think the bug occurs.
3114 To use the @code{checkpoint}/@code{restart} method of debugging:
3119 Save a snapshot of the debugged program's current execution state.
3120 The @code{checkpoint} command takes no arguments, but each checkpoint
3121 is assigned a small integer id, similar to a breakpoint id.
3123 @kindex info checkpoints
3124 @item info checkpoints
3125 List the checkpoints that have been saved in the current debugging
3126 session. For each checkpoint, the following information will be
3133 @item Source line, or label
3136 @kindex restart @var{checkpoint-id}
3137 @item restart @var{checkpoint-id}
3138 Restore the program state that was saved as checkpoint number
3139 @var{checkpoint-id}. All program variables, registers, stack frames
3140 etc.@: will be returned to the values that they had when the checkpoint
3141 was saved. In essence, gdb will ``wind back the clock'' to the point
3142 in time when the checkpoint was saved.
3144 Note that breakpoints, @value{GDBN} variables, command history etc.
3145 are not affected by restoring a checkpoint. In general, a checkpoint
3146 only restores things that reside in the program being debugged, not in
3149 @kindex delete checkpoint @var{checkpoint-id}
3150 @item delete checkpoint @var{checkpoint-id}
3151 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3155 Returning to a previously saved checkpoint will restore the user state
3156 of the program being debugged, plus a significant subset of the system
3157 (OS) state, including file pointers. It won't ``un-write'' data from
3158 a file, but it will rewind the file pointer to the previous location,
3159 so that the previously written data can be overwritten. For files
3160 opened in read mode, the pointer will also be restored so that the
3161 previously read data can be read again.
3163 Of course, characters that have been sent to a printer (or other
3164 external device) cannot be ``snatched back'', and characters received
3165 from eg.@: a serial device can be removed from internal program buffers,
3166 but they cannot be ``pushed back'' into the serial pipeline, ready to
3167 be received again. Similarly, the actual contents of files that have
3168 been changed cannot be restored (at this time).
3170 However, within those constraints, you actually can ``rewind'' your
3171 program to a previously saved point in time, and begin debugging it
3172 again --- and you can change the course of events so as to debug a
3173 different execution path this time.
3175 @cindex checkpoints and process id
3176 Finally, there is one bit of internal program state that will be
3177 different when you return to a checkpoint --- the program's process
3178 id. Each checkpoint will have a unique process id (or @var{pid}),
3179 and each will be different from the program's original @var{pid}.
3180 If your program has saved a local copy of its process id, this could
3181 potentially pose a problem.
3183 @subsection A Non-obvious Benefit of Using Checkpoints
3185 On some systems such as @sc{gnu}/Linux, address space randomization
3186 is performed on new processes for security reasons. This makes it
3187 difficult or impossible to set a breakpoint, or watchpoint, on an
3188 absolute address if you have to restart the program, since the
3189 absolute location of a symbol will change from one execution to the
3192 A checkpoint, however, is an @emph{identical} copy of a process.
3193 Therefore if you create a checkpoint at (eg.@:) the start of main,
3194 and simply return to that checkpoint instead of restarting the
3195 process, you can avoid the effects of address randomization and
3196 your symbols will all stay in the same place.
3199 @chapter Stopping and Continuing
3201 The principal purposes of using a debugger are so that you can stop your
3202 program before it terminates; or so that, if your program runs into
3203 trouble, you can investigate and find out why.
3205 Inside @value{GDBN}, your program may stop for any of several reasons,
3206 such as a signal, a breakpoint, or reaching a new line after a
3207 @value{GDBN} command such as @code{step}. You may then examine and
3208 change variables, set new breakpoints or remove old ones, and then
3209 continue execution. Usually, the messages shown by @value{GDBN} provide
3210 ample explanation of the status of your program---but you can also
3211 explicitly request this information at any time.
3214 @kindex info program
3216 Display information about the status of your program: whether it is
3217 running or not, what process it is, and why it stopped.
3221 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3222 * Continuing and Stepping:: Resuming execution
3223 * Skipping Over Functions and Files::
3224 Skipping over functions and files
3226 * Thread Stops:: Stopping and starting multi-thread programs
3230 @section Breakpoints, Watchpoints, and Catchpoints
3233 A @dfn{breakpoint} makes your program stop whenever a certain point in
3234 the program is reached. For each breakpoint, you can add conditions to
3235 control in finer detail whether your program stops. You can set
3236 breakpoints with the @code{break} command and its variants (@pxref{Set
3237 Breaks, ,Setting Breakpoints}), to specify the place where your program
3238 should stop by line number, function name or exact address in the
3241 On some systems, you can set breakpoints in shared libraries before
3242 the executable is run. There is a minor limitation on HP-UX systems:
3243 you must wait until the executable is run in order to set breakpoints
3244 in shared library routines that are not called directly by the program
3245 (for example, routines that are arguments in a @code{pthread_create}
3249 @cindex data breakpoints
3250 @cindex memory tracing
3251 @cindex breakpoint on memory address
3252 @cindex breakpoint on variable modification
3253 A @dfn{watchpoint} is a special breakpoint that stops your program
3254 when the value of an expression changes. The expression may be a value
3255 of a variable, or it could involve values of one or more variables
3256 combined by operators, such as @samp{a + b}. This is sometimes called
3257 @dfn{data breakpoints}. You must use a different command to set
3258 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3259 from that, you can manage a watchpoint like any other breakpoint: you
3260 enable, disable, and delete both breakpoints and watchpoints using the
3263 You can arrange to have values from your program displayed automatically
3264 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3268 @cindex breakpoint on events
3269 A @dfn{catchpoint} is another special breakpoint that stops your program
3270 when a certain kind of event occurs, such as the throwing of a C@t{++}
3271 exception or the loading of a library. As with watchpoints, you use a
3272 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3273 Catchpoints}), but aside from that, you can manage a catchpoint like any
3274 other breakpoint. (To stop when your program receives a signal, use the
3275 @code{handle} command; see @ref{Signals, ,Signals}.)
3277 @cindex breakpoint numbers
3278 @cindex numbers for breakpoints
3279 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3280 catchpoint when you create it; these numbers are successive integers
3281 starting with one. In many of the commands for controlling various
3282 features of breakpoints you use the breakpoint number to say which
3283 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3284 @dfn{disabled}; if disabled, it has no effect on your program until you
3287 @cindex breakpoint ranges
3288 @cindex ranges of breakpoints
3289 Some @value{GDBN} commands accept a range of breakpoints on which to
3290 operate. A breakpoint range is either a single breakpoint number, like
3291 @samp{5}, or two such numbers, in increasing order, separated by a
3292 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3293 all breakpoints in that range are operated on.
3296 * Set Breaks:: Setting breakpoints
3297 * Set Watchpoints:: Setting watchpoints
3298 * Set Catchpoints:: Setting catchpoints
3299 * Delete Breaks:: Deleting breakpoints
3300 * Disabling:: Disabling breakpoints
3301 * Conditions:: Break conditions
3302 * Break Commands:: Breakpoint command lists
3303 * Save Breakpoints:: How to save breakpoints in a file
3304 * Error in Breakpoints:: ``Cannot insert breakpoints''
3305 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3309 @subsection Setting Breakpoints
3311 @c FIXME LMB what does GDB do if no code on line of breakpt?
3312 @c consider in particular declaration with/without initialization.
3314 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3317 @kindex b @r{(@code{break})}
3318 @vindex $bpnum@r{, convenience variable}
3319 @cindex latest breakpoint
3320 Breakpoints are set with the @code{break} command (abbreviated
3321 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3322 number of the breakpoint you've set most recently; see @ref{Convenience
3323 Vars,, Convenience Variables}, for a discussion of what you can do with
3324 convenience variables.
3327 @item break @var{location}
3328 Set a breakpoint at the given @var{location}, which can specify a
3329 function name, a line number, or an address of an instruction.
3330 (@xref{Specify Location}, for a list of all the possible ways to
3331 specify a @var{location}.) The breakpoint will stop your program just
3332 before it executes any of the code in the specified @var{location}.
3334 When using source languages that permit overloading of symbols, such as
3335 C@t{++}, a function name may refer to more than one possible place to break.
3336 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3339 It is also possible to insert a breakpoint that will stop the program
3340 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3341 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3344 When called without any arguments, @code{break} sets a breakpoint at
3345 the next instruction to be executed in the selected stack frame
3346 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3347 innermost, this makes your program stop as soon as control
3348 returns to that frame. This is similar to the effect of a
3349 @code{finish} command in the frame inside the selected frame---except
3350 that @code{finish} does not leave an active breakpoint. If you use
3351 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3352 the next time it reaches the current location; this may be useful
3355 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3356 least one instruction has been executed. If it did not do this, you
3357 would be unable to proceed past a breakpoint without first disabling the
3358 breakpoint. This rule applies whether or not the breakpoint already
3359 existed when your program stopped.
3361 @item break @dots{} if @var{cond}
3362 Set a breakpoint with condition @var{cond}; evaluate the expression
3363 @var{cond} each time the breakpoint is reached, and stop only if the
3364 value is nonzero---that is, if @var{cond} evaluates as true.
3365 @samp{@dots{}} stands for one of the possible arguments described
3366 above (or no argument) specifying where to break. @xref{Conditions,
3367 ,Break Conditions}, for more information on breakpoint conditions.
3370 @item tbreak @var{args}
3371 Set a breakpoint enabled only for one stop. @var{args} are the
3372 same as for the @code{break} command, and the breakpoint is set in the same
3373 way, but the breakpoint is automatically deleted after the first time your
3374 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3377 @cindex hardware breakpoints
3378 @item hbreak @var{args}
3379 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3380 @code{break} command and the breakpoint is set in the same way, but the
3381 breakpoint requires hardware support and some target hardware may not
3382 have this support. The main purpose of this is EPROM/ROM code
3383 debugging, so you can set a breakpoint at an instruction without
3384 changing the instruction. This can be used with the new trap-generation
3385 provided by SPARClite DSU and most x86-based targets. These targets
3386 will generate traps when a program accesses some data or instruction
3387 address that is assigned to the debug registers. However the hardware
3388 breakpoint registers can take a limited number of breakpoints. For
3389 example, on the DSU, only two data breakpoints can be set at a time, and
3390 @value{GDBN} will reject this command if more than two are used. Delete
3391 or disable unused hardware breakpoints before setting new ones
3392 (@pxref{Disabling, ,Disabling Breakpoints}).
3393 @xref{Conditions, ,Break Conditions}.
3394 For remote targets, you can restrict the number of hardware
3395 breakpoints @value{GDBN} will use, see @ref{set remote
3396 hardware-breakpoint-limit}.
3399 @item thbreak @var{args}
3400 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3401 are the same as for the @code{hbreak} command and the breakpoint is set in
3402 the same way. However, like the @code{tbreak} command,
3403 the breakpoint is automatically deleted after the
3404 first time your program stops there. Also, like the @code{hbreak}
3405 command, the breakpoint requires hardware support and some target hardware
3406 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3407 See also @ref{Conditions, ,Break Conditions}.
3410 @cindex regular expression
3411 @cindex breakpoints at functions matching a regexp
3412 @cindex set breakpoints in many functions
3413 @item rbreak @var{regex}
3414 Set breakpoints on all functions matching the regular expression
3415 @var{regex}. This command sets an unconditional breakpoint on all
3416 matches, printing a list of all breakpoints it set. Once these
3417 breakpoints are set, they are treated just like the breakpoints set with
3418 the @code{break} command. You can delete them, disable them, or make
3419 them conditional the same way as any other breakpoint.
3421 The syntax of the regular expression is the standard one used with tools
3422 like @file{grep}. Note that this is different from the syntax used by
3423 shells, so for instance @code{foo*} matches all functions that include
3424 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3425 @code{.*} leading and trailing the regular expression you supply, so to
3426 match only functions that begin with @code{foo}, use @code{^foo}.
3428 @cindex non-member C@t{++} functions, set breakpoint in
3429 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3430 breakpoints on overloaded functions that are not members of any special
3433 @cindex set breakpoints on all functions
3434 The @code{rbreak} command can be used to set breakpoints in
3435 @strong{all} the functions in a program, like this:
3438 (@value{GDBP}) rbreak .
3441 @item rbreak @var{file}:@var{regex}
3442 If @code{rbreak} is called with a filename qualification, it limits
3443 the search for functions matching the given regular expression to the
3444 specified @var{file}. This can be used, for example, to set breakpoints on
3445 every function in a given file:
3448 (@value{GDBP}) rbreak file.c:.
3451 The colon separating the filename qualifier from the regex may
3452 optionally be surrounded by spaces.
3454 @kindex info breakpoints
3455 @cindex @code{$_} and @code{info breakpoints}
3456 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3457 @itemx info break @r{[}@var{n}@dots{}@r{]}
3458 Print a table of all breakpoints, watchpoints, and catchpoints set and
3459 not deleted. Optional argument @var{n} means print information only
3460 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3461 For each breakpoint, following columns are printed:
3464 @item Breakpoint Numbers
3466 Breakpoint, watchpoint, or catchpoint.
3468 Whether the breakpoint is marked to be disabled or deleted when hit.
3469 @item Enabled or Disabled
3470 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3471 that are not enabled.
3473 Where the breakpoint is in your program, as a memory address. For a
3474 pending breakpoint whose address is not yet known, this field will
3475 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3476 library that has the symbol or line referred by breakpoint is loaded.
3477 See below for details. A breakpoint with several locations will
3478 have @samp{<MULTIPLE>} in this field---see below for details.
3480 Where the breakpoint is in the source for your program, as a file and
3481 line number. For a pending breakpoint, the original string passed to
3482 the breakpoint command will be listed as it cannot be resolved until
3483 the appropriate shared library is loaded in the future.
3487 If a breakpoint is conditional, @code{info break} shows the condition on
3488 the line following the affected breakpoint; breakpoint commands, if any,
3489 are listed after that. A pending breakpoint is allowed to have a condition
3490 specified for it. The condition is not parsed for validity until a shared
3491 library is loaded that allows the pending breakpoint to resolve to a
3495 @code{info break} with a breakpoint
3496 number @var{n} as argument lists only that breakpoint. The
3497 convenience variable @code{$_} and the default examining-address for
3498 the @code{x} command are set to the address of the last breakpoint
3499 listed (@pxref{Memory, ,Examining Memory}).
3502 @code{info break} displays a count of the number of times the breakpoint
3503 has been hit. This is especially useful in conjunction with the
3504 @code{ignore} command. You can ignore a large number of breakpoint
3505 hits, look at the breakpoint info to see how many times the breakpoint
3506 was hit, and then run again, ignoring one less than that number. This
3507 will get you quickly to the last hit of that breakpoint.
3510 @value{GDBN} allows you to set any number of breakpoints at the same place in
3511 your program. There is nothing silly or meaningless about this. When
3512 the breakpoints are conditional, this is even useful
3513 (@pxref{Conditions, ,Break Conditions}).
3515 @cindex multiple locations, breakpoints
3516 @cindex breakpoints, multiple locations
3517 It is possible that a breakpoint corresponds to several locations
3518 in your program. Examples of this situation are:
3522 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3523 instances of the function body, used in different cases.
3526 For a C@t{++} template function, a given line in the function can
3527 correspond to any number of instantiations.
3530 For an inlined function, a given source line can correspond to
3531 several places where that function is inlined.
3534 In all those cases, @value{GDBN} will insert a breakpoint at all
3535 the relevant locations@footnote{
3536 As of this writing, multiple-location breakpoints work only if there's
3537 line number information for all the locations. This means that they
3538 will generally not work in system libraries, unless you have debug
3539 info with line numbers for them.}.
3541 A breakpoint with multiple locations is displayed in the breakpoint
3542 table using several rows---one header row, followed by one row for
3543 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3544 address column. The rows for individual locations contain the actual
3545 addresses for locations, and show the functions to which those
3546 locations belong. The number column for a location is of the form
3547 @var{breakpoint-number}.@var{location-number}.
3552 Num Type Disp Enb Address What
3553 1 breakpoint keep y <MULTIPLE>
3555 breakpoint already hit 1 time
3556 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3557 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3560 Each location can be individually enabled or disabled by passing
3561 @var{breakpoint-number}.@var{location-number} as argument to the
3562 @code{enable} and @code{disable} commands. Note that you cannot
3563 delete the individual locations from the list, you can only delete the
3564 entire list of locations that belong to their parent breakpoint (with
3565 the @kbd{delete @var{num}} command, where @var{num} is the number of
3566 the parent breakpoint, 1 in the above example). Disabling or enabling
3567 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3568 that belong to that breakpoint.
3570 @cindex pending breakpoints
3571 It's quite common to have a breakpoint inside a shared library.
3572 Shared libraries can be loaded and unloaded explicitly,
3573 and possibly repeatedly, as the program is executed. To support
3574 this use case, @value{GDBN} updates breakpoint locations whenever
3575 any shared library is loaded or unloaded. Typically, you would
3576 set a breakpoint in a shared library at the beginning of your
3577 debugging session, when the library is not loaded, and when the
3578 symbols from the library are not available. When you try to set
3579 breakpoint, @value{GDBN} will ask you if you want to set
3580 a so called @dfn{pending breakpoint}---breakpoint whose address
3581 is not yet resolved.
3583 After the program is run, whenever a new shared library is loaded,
3584 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3585 shared library contains the symbol or line referred to by some
3586 pending breakpoint, that breakpoint is resolved and becomes an
3587 ordinary breakpoint. When a library is unloaded, all breakpoints
3588 that refer to its symbols or source lines become pending again.
3590 This logic works for breakpoints with multiple locations, too. For
3591 example, if you have a breakpoint in a C@t{++} template function, and
3592 a newly loaded shared library has an instantiation of that template,
3593 a new location is added to the list of locations for the breakpoint.
3595 Except for having unresolved address, pending breakpoints do not
3596 differ from regular breakpoints. You can set conditions or commands,
3597 enable and disable them and perform other breakpoint operations.
3599 @value{GDBN} provides some additional commands for controlling what
3600 happens when the @samp{break} command cannot resolve breakpoint
3601 address specification to an address:
3603 @kindex set breakpoint pending
3604 @kindex show breakpoint pending
3606 @item set breakpoint pending auto
3607 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3608 location, it queries you whether a pending breakpoint should be created.
3610 @item set breakpoint pending on
3611 This indicates that an unrecognized breakpoint location should automatically
3612 result in a pending breakpoint being created.
3614 @item set breakpoint pending off
3615 This indicates that pending breakpoints are not to be created. Any
3616 unrecognized breakpoint location results in an error. This setting does
3617 not affect any pending breakpoints previously created.
3619 @item show breakpoint pending
3620 Show the current behavior setting for creating pending breakpoints.
3623 The settings above only affect the @code{break} command and its
3624 variants. Once breakpoint is set, it will be automatically updated
3625 as shared libraries are loaded and unloaded.
3627 @cindex automatic hardware breakpoints
3628 For some targets, @value{GDBN} can automatically decide if hardware or
3629 software breakpoints should be used, depending on whether the
3630 breakpoint address is read-only or read-write. This applies to
3631 breakpoints set with the @code{break} command as well as to internal
3632 breakpoints set by commands like @code{next} and @code{finish}. For
3633 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3636 You can control this automatic behaviour with the following commands::
3638 @kindex set breakpoint auto-hw
3639 @kindex show breakpoint auto-hw
3641 @item set breakpoint auto-hw on
3642 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3643 will try to use the target memory map to decide if software or hardware
3644 breakpoint must be used.
3646 @item set breakpoint auto-hw off
3647 This indicates @value{GDBN} should not automatically select breakpoint
3648 type. If the target provides a memory map, @value{GDBN} will warn when
3649 trying to set software breakpoint at a read-only address.
3652 @value{GDBN} normally implements breakpoints by replacing the program code
3653 at the breakpoint address with a special instruction, which, when
3654 executed, given control to the debugger. By default, the program
3655 code is so modified only when the program is resumed. As soon as
3656 the program stops, @value{GDBN} restores the original instructions. This
3657 behaviour guards against leaving breakpoints inserted in the
3658 target should gdb abrubptly disconnect. However, with slow remote
3659 targets, inserting and removing breakpoint can reduce the performance.
3660 This behavior can be controlled with the following commands::
3662 @kindex set breakpoint always-inserted
3663 @kindex show breakpoint always-inserted
3665 @item set breakpoint always-inserted off
3666 All breakpoints, including newly added by the user, are inserted in
3667 the target only when the target is resumed. All breakpoints are
3668 removed from the target when it stops.
3670 @item set breakpoint always-inserted on
3671 Causes all breakpoints to be inserted in the target at all times. If
3672 the user adds a new breakpoint, or changes an existing breakpoint, the
3673 breakpoints in the target are updated immediately. A breakpoint is
3674 removed from the target only when breakpoint itself is removed.
3676 @cindex non-stop mode, and @code{breakpoint always-inserted}
3677 @item set breakpoint always-inserted auto
3678 This is the default mode. If @value{GDBN} is controlling the inferior
3679 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3680 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3681 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3682 @code{breakpoint always-inserted} mode is off.
3685 @cindex negative breakpoint numbers
3686 @cindex internal @value{GDBN} breakpoints
3687 @value{GDBN} itself sometimes sets breakpoints in your program for
3688 special purposes, such as proper handling of @code{longjmp} (in C
3689 programs). These internal breakpoints are assigned negative numbers,
3690 starting with @code{-1}; @samp{info breakpoints} does not display them.
3691 You can see these breakpoints with the @value{GDBN} maintenance command
3692 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3695 @node Set Watchpoints
3696 @subsection Setting Watchpoints
3698 @cindex setting watchpoints
3699 You can use a watchpoint to stop execution whenever the value of an
3700 expression changes, without having to predict a particular place where
3701 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3702 The expression may be as simple as the value of a single variable, or
3703 as complex as many variables combined by operators. Examples include:
3707 A reference to the value of a single variable.
3710 An address cast to an appropriate data type. For example,
3711 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3712 address (assuming an @code{int} occupies 4 bytes).
3715 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3716 expression can use any operators valid in the program's native
3717 language (@pxref{Languages}).
3720 You can set a watchpoint on an expression even if the expression can
3721 not be evaluated yet. For instance, you can set a watchpoint on
3722 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3723 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3724 the expression produces a valid value. If the expression becomes
3725 valid in some other way than changing a variable (e.g.@: if the memory
3726 pointed to by @samp{*global_ptr} becomes readable as the result of a
3727 @code{malloc} call), @value{GDBN} may not stop until the next time
3728 the expression changes.
3730 @cindex software watchpoints
3731 @cindex hardware watchpoints
3732 Depending on your system, watchpoints may be implemented in software or
3733 hardware. @value{GDBN} does software watchpointing by single-stepping your
3734 program and testing the variable's value each time, which is hundreds of
3735 times slower than normal execution. (But this may still be worth it, to
3736 catch errors where you have no clue what part of your program is the
3739 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3740 x86-based targets, @value{GDBN} includes support for hardware
3741 watchpoints, which do not slow down the running of your program.
3745 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3746 Set a watchpoint for an expression. @value{GDBN} will break when the
3747 expression @var{expr} is written into by the program and its value
3748 changes. The simplest (and the most popular) use of this command is
3749 to watch the value of a single variable:
3752 (@value{GDBP}) watch foo
3755 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3756 argument, @value{GDBN} breaks only when the thread identified by
3757 @var{threadnum} changes the value of @var{expr}. If any other threads
3758 change the value of @var{expr}, @value{GDBN} will not break. Note
3759 that watchpoints restricted to a single thread in this way only work
3760 with Hardware Watchpoints.
3762 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3763 (see below). The @code{-location} argument tells @value{GDBN} to
3764 instead watch the memory referred to by @var{expr}. In this case,
3765 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3766 and watch the memory at that address. The type of the result is used
3767 to determine the size of the watched memory. If the expression's
3768 result does not have an address, then @value{GDBN} will print an
3771 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3772 of masked watchpoints, if the current architecture supports this
3773 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3774 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3775 to an address to watch. The mask specifies that some bits of an address
3776 (the bits which are reset in the mask) should be ignored when matching
3777 the address accessed by the inferior against the watchpoint address.
3778 Thus, a masked watchpoint watches many addresses simultaneously---those
3779 addresses whose unmasked bits are identical to the unmasked bits in the
3780 watchpoint address. The @code{mask} argument implies @code{-location}.
3784 (@value{GDBP}) watch foo mask 0xffff00ff
3785 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3789 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3790 Set a watchpoint that will break when the value of @var{expr} is read
3794 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3795 Set a watchpoint that will break when @var{expr} is either read from
3796 or written into by the program.
3798 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3799 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3800 This command prints a list of watchpoints, using the same format as
3801 @code{info break} (@pxref{Set Breaks}).
3804 If you watch for a change in a numerically entered address you need to
3805 dereference it, as the address itself is just a constant number which will
3806 never change. @value{GDBN} refuses to create a watchpoint that watches
3807 a never-changing value:
3810 (@value{GDBP}) watch 0x600850
3811 Cannot watch constant value 0x600850.
3812 (@value{GDBP}) watch *(int *) 0x600850
3813 Watchpoint 1: *(int *) 6293584
3816 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3817 watchpoints execute very quickly, and the debugger reports a change in
3818 value at the exact instruction where the change occurs. If @value{GDBN}
3819 cannot set a hardware watchpoint, it sets a software watchpoint, which
3820 executes more slowly and reports the change in value at the next
3821 @emph{statement}, not the instruction, after the change occurs.
3823 @cindex use only software watchpoints
3824 You can force @value{GDBN} to use only software watchpoints with the
3825 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3826 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3827 the underlying system supports them. (Note that hardware-assisted
3828 watchpoints that were set @emph{before} setting
3829 @code{can-use-hw-watchpoints} to zero will still use the hardware
3830 mechanism of watching expression values.)
3833 @item set can-use-hw-watchpoints
3834 @kindex set can-use-hw-watchpoints
3835 Set whether or not to use hardware watchpoints.
3837 @item show can-use-hw-watchpoints
3838 @kindex show can-use-hw-watchpoints
3839 Show the current mode of using hardware watchpoints.
3842 For remote targets, you can restrict the number of hardware
3843 watchpoints @value{GDBN} will use, see @ref{set remote
3844 hardware-breakpoint-limit}.
3846 When you issue the @code{watch} command, @value{GDBN} reports
3849 Hardware watchpoint @var{num}: @var{expr}
3853 if it was able to set a hardware watchpoint.
3855 Currently, the @code{awatch} and @code{rwatch} commands can only set
3856 hardware watchpoints, because accesses to data that don't change the
3857 value of the watched expression cannot be detected without examining
3858 every instruction as it is being executed, and @value{GDBN} does not do
3859 that currently. If @value{GDBN} finds that it is unable to set a
3860 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3861 will print a message like this:
3864 Expression cannot be implemented with read/access watchpoint.
3867 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3868 data type of the watched expression is wider than what a hardware
3869 watchpoint on the target machine can handle. For example, some systems
3870 can only watch regions that are up to 4 bytes wide; on such systems you
3871 cannot set hardware watchpoints for an expression that yields a
3872 double-precision floating-point number (which is typically 8 bytes
3873 wide). As a work-around, it might be possible to break the large region
3874 into a series of smaller ones and watch them with separate watchpoints.
3876 If you set too many hardware watchpoints, @value{GDBN} might be unable
3877 to insert all of them when you resume the execution of your program.
3878 Since the precise number of active watchpoints is unknown until such
3879 time as the program is about to be resumed, @value{GDBN} might not be
3880 able to warn you about this when you set the watchpoints, and the
3881 warning will be printed only when the program is resumed:
3884 Hardware watchpoint @var{num}: Could not insert watchpoint
3888 If this happens, delete or disable some of the watchpoints.
3890 Watching complex expressions that reference many variables can also
3891 exhaust the resources available for hardware-assisted watchpoints.
3892 That's because @value{GDBN} needs to watch every variable in the
3893 expression with separately allocated resources.
3895 If you call a function interactively using @code{print} or @code{call},
3896 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3897 kind of breakpoint or the call completes.
3899 @value{GDBN} automatically deletes watchpoints that watch local
3900 (automatic) variables, or expressions that involve such variables, when
3901 they go out of scope, that is, when the execution leaves the block in
3902 which these variables were defined. In particular, when the program
3903 being debugged terminates, @emph{all} local variables go out of scope,
3904 and so only watchpoints that watch global variables remain set. If you
3905 rerun the program, you will need to set all such watchpoints again. One
3906 way of doing that would be to set a code breakpoint at the entry to the
3907 @code{main} function and when it breaks, set all the watchpoints.
3909 @cindex watchpoints and threads
3910 @cindex threads and watchpoints
3911 In multi-threaded programs, watchpoints will detect changes to the
3912 watched expression from every thread.
3915 @emph{Warning:} In multi-threaded programs, software watchpoints
3916 have only limited usefulness. If @value{GDBN} creates a software
3917 watchpoint, it can only watch the value of an expression @emph{in a
3918 single thread}. If you are confident that the expression can only
3919 change due to the current thread's activity (and if you are also
3920 confident that no other thread can become current), then you can use
3921 software watchpoints as usual. However, @value{GDBN} may not notice
3922 when a non-current thread's activity changes the expression. (Hardware
3923 watchpoints, in contrast, watch an expression in all threads.)
3926 @xref{set remote hardware-watchpoint-limit}.
3928 @node Set Catchpoints
3929 @subsection Setting Catchpoints
3930 @cindex catchpoints, setting
3931 @cindex exception handlers
3932 @cindex event handling
3934 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3935 kinds of program events, such as C@t{++} exceptions or the loading of a
3936 shared library. Use the @code{catch} command to set a catchpoint.
3940 @item catch @var{event}
3941 Stop when @var{event} occurs. @var{event} can be any of the following:
3944 @cindex stop on C@t{++} exceptions
3945 The throwing of a C@t{++} exception.
3948 The catching of a C@t{++} exception.
3951 @cindex Ada exception catching
3952 @cindex catch Ada exceptions
3953 An Ada exception being raised. If an exception name is specified
3954 at the end of the command (eg @code{catch exception Program_Error}),
3955 the debugger will stop only when this specific exception is raised.
3956 Otherwise, the debugger stops execution when any Ada exception is raised.
3958 When inserting an exception catchpoint on a user-defined exception whose
3959 name is identical to one of the exceptions defined by the language, the
3960 fully qualified name must be used as the exception name. Otherwise,
3961 @value{GDBN} will assume that it should stop on the pre-defined exception
3962 rather than the user-defined one. For instance, assuming an exception
3963 called @code{Constraint_Error} is defined in package @code{Pck}, then
3964 the command to use to catch such exceptions is @kbd{catch exception
3965 Pck.Constraint_Error}.
3967 @item exception unhandled
3968 An exception that was raised but is not handled by the program.
3971 A failed Ada assertion.
3974 @cindex break on fork/exec
3975 A call to @code{exec}. This is currently only available for HP-UX
3979 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3980 @cindex break on a system call.
3981 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3982 syscall is a mechanism for application programs to request a service
3983 from the operating system (OS) or one of the OS system services.
3984 @value{GDBN} can catch some or all of the syscalls issued by the
3985 debuggee, and show the related information for each syscall. If no
3986 argument is specified, calls to and returns from all system calls
3989 @var{name} can be any system call name that is valid for the
3990 underlying OS. Just what syscalls are valid depends on the OS. On
3991 GNU and Unix systems, you can find the full list of valid syscall
3992 names on @file{/usr/include/asm/unistd.h}.
3994 @c For MS-Windows, the syscall names and the corresponding numbers
3995 @c can be found, e.g., on this URL:
3996 @c http://www.metasploit.com/users/opcode/syscalls.html
3997 @c but we don't support Windows syscalls yet.
3999 Normally, @value{GDBN} knows in advance which syscalls are valid for
4000 each OS, so you can use the @value{GDBN} command-line completion
4001 facilities (@pxref{Completion,, command completion}) to list the
4004 You may also specify the system call numerically. A syscall's
4005 number is the value passed to the OS's syscall dispatcher to
4006 identify the requested service. When you specify the syscall by its
4007 name, @value{GDBN} uses its database of syscalls to convert the name
4008 into the corresponding numeric code, but using the number directly
4009 may be useful if @value{GDBN}'s database does not have the complete
4010 list of syscalls on your system (e.g., because @value{GDBN} lags
4011 behind the OS upgrades).
4013 The example below illustrates how this command works if you don't provide
4017 (@value{GDBP}) catch syscall
4018 Catchpoint 1 (syscall)
4020 Starting program: /tmp/catch-syscall
4022 Catchpoint 1 (call to syscall 'close'), \
4023 0xffffe424 in __kernel_vsyscall ()
4027 Catchpoint 1 (returned from syscall 'close'), \
4028 0xffffe424 in __kernel_vsyscall ()
4032 Here is an example of catching a system call by name:
4035 (@value{GDBP}) catch syscall chroot
4036 Catchpoint 1 (syscall 'chroot' [61])
4038 Starting program: /tmp/catch-syscall
4040 Catchpoint 1 (call to syscall 'chroot'), \
4041 0xffffe424 in __kernel_vsyscall ()
4045 Catchpoint 1 (returned from syscall 'chroot'), \
4046 0xffffe424 in __kernel_vsyscall ()
4050 An example of specifying a system call numerically. In the case
4051 below, the syscall number has a corresponding entry in the XML
4052 file, so @value{GDBN} finds its name and prints it:
4055 (@value{GDBP}) catch syscall 252
4056 Catchpoint 1 (syscall(s) 'exit_group')
4058 Starting program: /tmp/catch-syscall
4060 Catchpoint 1 (call to syscall 'exit_group'), \
4061 0xffffe424 in __kernel_vsyscall ()
4065 Program exited normally.
4069 However, there can be situations when there is no corresponding name
4070 in XML file for that syscall number. In this case, @value{GDBN} prints
4071 a warning message saying that it was not able to find the syscall name,
4072 but the catchpoint will be set anyway. See the example below:
4075 (@value{GDBP}) catch syscall 764
4076 warning: The number '764' does not represent a known syscall.
4077 Catchpoint 2 (syscall 764)
4081 If you configure @value{GDBN} using the @samp{--without-expat} option,
4082 it will not be able to display syscall names. Also, if your
4083 architecture does not have an XML file describing its system calls,
4084 you will not be able to see the syscall names. It is important to
4085 notice that these two features are used for accessing the syscall
4086 name database. In either case, you will see a warning like this:
4089 (@value{GDBP}) catch syscall
4090 warning: Could not open "syscalls/i386-linux.xml"
4091 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4092 GDB will not be able to display syscall names.
4093 Catchpoint 1 (syscall)
4097 Of course, the file name will change depending on your architecture and system.
4099 Still using the example above, you can also try to catch a syscall by its
4100 number. In this case, you would see something like:
4103 (@value{GDBP}) catch syscall 252
4104 Catchpoint 1 (syscall(s) 252)
4107 Again, in this case @value{GDBN} would not be able to display syscall's names.
4110 A call to @code{fork}. This is currently only available for HP-UX
4114 A call to @code{vfork}. This is currently only available for HP-UX
4119 @item tcatch @var{event}
4120 Set a catchpoint that is enabled only for one stop. The catchpoint is
4121 automatically deleted after the first time the event is caught.
4125 Use the @code{info break} command to list the current catchpoints.
4127 There are currently some limitations to C@t{++} exception handling
4128 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4132 If you call a function interactively, @value{GDBN} normally returns
4133 control to you when the function has finished executing. If the call
4134 raises an exception, however, the call may bypass the mechanism that
4135 returns control to you and cause your program either to abort or to
4136 simply continue running until it hits a breakpoint, catches a signal
4137 that @value{GDBN} is listening for, or exits. This is the case even if
4138 you set a catchpoint for the exception; catchpoints on exceptions are
4139 disabled within interactive calls.
4142 You cannot raise an exception interactively.
4145 You cannot install an exception handler interactively.
4148 @cindex raise exceptions
4149 Sometimes @code{catch} is not the best way to debug exception handling:
4150 if you need to know exactly where an exception is raised, it is better to
4151 stop @emph{before} the exception handler is called, since that way you
4152 can see the stack before any unwinding takes place. If you set a
4153 breakpoint in an exception handler instead, it may not be easy to find
4154 out where the exception was raised.
4156 To stop just before an exception handler is called, you need some
4157 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4158 raised by calling a library function named @code{__raise_exception}
4159 which has the following ANSI C interface:
4162 /* @var{addr} is where the exception identifier is stored.
4163 @var{id} is the exception identifier. */
4164 void __raise_exception (void **addr, void *id);
4168 To make the debugger catch all exceptions before any stack
4169 unwinding takes place, set a breakpoint on @code{__raise_exception}
4170 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4172 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4173 that depends on the value of @var{id}, you can stop your program when
4174 a specific exception is raised. You can use multiple conditional
4175 breakpoints to stop your program when any of a number of exceptions are
4180 @subsection Deleting Breakpoints
4182 @cindex clearing breakpoints, watchpoints, catchpoints
4183 @cindex deleting breakpoints, watchpoints, catchpoints
4184 It is often necessary to eliminate a breakpoint, watchpoint, or
4185 catchpoint once it has done its job and you no longer want your program
4186 to stop there. This is called @dfn{deleting} the breakpoint. A
4187 breakpoint that has been deleted no longer exists; it is forgotten.
4189 With the @code{clear} command you can delete breakpoints according to
4190 where they are in your program. With the @code{delete} command you can
4191 delete individual breakpoints, watchpoints, or catchpoints by specifying
4192 their breakpoint numbers.
4194 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4195 automatically ignores breakpoints on the first instruction to be executed
4196 when you continue execution without changing the execution address.
4201 Delete any breakpoints at the next instruction to be executed in the
4202 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4203 the innermost frame is selected, this is a good way to delete a
4204 breakpoint where your program just stopped.
4206 @item clear @var{location}
4207 Delete any breakpoints set at the specified @var{location}.
4208 @xref{Specify Location}, for the various forms of @var{location}; the
4209 most useful ones are listed below:
4212 @item clear @var{function}
4213 @itemx clear @var{filename}:@var{function}
4214 Delete any breakpoints set at entry to the named @var{function}.
4216 @item clear @var{linenum}
4217 @itemx clear @var{filename}:@var{linenum}
4218 Delete any breakpoints set at or within the code of the specified
4219 @var{linenum} of the specified @var{filename}.
4222 @cindex delete breakpoints
4224 @kindex d @r{(@code{delete})}
4225 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4226 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4227 ranges specified as arguments. If no argument is specified, delete all
4228 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4229 confirm off}). You can abbreviate this command as @code{d}.
4233 @subsection Disabling Breakpoints
4235 @cindex enable/disable a breakpoint
4236 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4237 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4238 it had been deleted, but remembers the information on the breakpoint so
4239 that you can @dfn{enable} it again later.
4241 You disable and enable breakpoints, watchpoints, and catchpoints with
4242 the @code{enable} and @code{disable} commands, optionally specifying
4243 one or more breakpoint numbers as arguments. Use @code{info break} to
4244 print a list of all breakpoints, watchpoints, and catchpoints if you
4245 do not know which numbers to use.
4247 Disabling and enabling a breakpoint that has multiple locations
4248 affects all of its locations.
4250 A breakpoint, watchpoint, or catchpoint can have any of four different
4251 states of enablement:
4255 Enabled. The breakpoint stops your program. A breakpoint set
4256 with the @code{break} command starts out in this state.
4258 Disabled. The breakpoint has no effect on your program.
4260 Enabled once. The breakpoint stops your program, but then becomes
4263 Enabled for deletion. The breakpoint stops your program, but
4264 immediately after it does so it is deleted permanently. A breakpoint
4265 set with the @code{tbreak} command starts out in this state.
4268 You can use the following commands to enable or disable breakpoints,
4269 watchpoints, and catchpoints:
4273 @kindex dis @r{(@code{disable})}
4274 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4275 Disable the specified breakpoints---or all breakpoints, if none are
4276 listed. A disabled breakpoint has no effect but is not forgotten. All
4277 options such as ignore-counts, conditions and commands are remembered in
4278 case the breakpoint is enabled again later. You may abbreviate
4279 @code{disable} as @code{dis}.
4282 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4283 Enable the specified breakpoints (or all defined breakpoints). They
4284 become effective once again in stopping your program.
4286 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4287 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4288 of these breakpoints immediately after stopping your program.
4290 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4291 Enable the specified breakpoints to work once, then die. @value{GDBN}
4292 deletes any of these breakpoints as soon as your program stops there.
4293 Breakpoints set by the @code{tbreak} command start out in this state.
4296 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4297 @c confusing: tbreak is also initially enabled.
4298 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4299 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4300 subsequently, they become disabled or enabled only when you use one of
4301 the commands above. (The command @code{until} can set and delete a
4302 breakpoint of its own, but it does not change the state of your other
4303 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4307 @subsection Break Conditions
4308 @cindex conditional breakpoints
4309 @cindex breakpoint conditions
4311 @c FIXME what is scope of break condition expr? Context where wanted?
4312 @c in particular for a watchpoint?
4313 The simplest sort of breakpoint breaks every time your program reaches a
4314 specified place. You can also specify a @dfn{condition} for a
4315 breakpoint. A condition is just a Boolean expression in your
4316 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4317 a condition evaluates the expression each time your program reaches it,
4318 and your program stops only if the condition is @emph{true}.
4320 This is the converse of using assertions for program validation; in that
4321 situation, you want to stop when the assertion is violated---that is,
4322 when the condition is false. In C, if you want to test an assertion expressed
4323 by the condition @var{assert}, you should set the condition
4324 @samp{! @var{assert}} on the appropriate breakpoint.
4326 Conditions are also accepted for watchpoints; you may not need them,
4327 since a watchpoint is inspecting the value of an expression anyhow---but
4328 it might be simpler, say, to just set a watchpoint on a variable name,
4329 and specify a condition that tests whether the new value is an interesting
4332 Break conditions can have side effects, and may even call functions in
4333 your program. This can be useful, for example, to activate functions
4334 that log program progress, or to use your own print functions to
4335 format special data structures. The effects are completely predictable
4336 unless there is another enabled breakpoint at the same address. (In
4337 that case, @value{GDBN} might see the other breakpoint first and stop your
4338 program without checking the condition of this one.) Note that
4339 breakpoint commands are usually more convenient and flexible than break
4341 purpose of performing side effects when a breakpoint is reached
4342 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4344 Break conditions can be specified when a breakpoint is set, by using
4345 @samp{if} in the arguments to the @code{break} command. @xref{Set
4346 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4347 with the @code{condition} command.
4349 You can also use the @code{if} keyword with the @code{watch} command.
4350 The @code{catch} command does not recognize the @code{if} keyword;
4351 @code{condition} is the only way to impose a further condition on a
4356 @item condition @var{bnum} @var{expression}
4357 Specify @var{expression} as the break condition for breakpoint,
4358 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4359 breakpoint @var{bnum} stops your program only if the value of
4360 @var{expression} is true (nonzero, in C). When you use
4361 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4362 syntactic correctness, and to determine whether symbols in it have
4363 referents in the context of your breakpoint. If @var{expression} uses
4364 symbols not referenced in the context of the breakpoint, @value{GDBN}
4365 prints an error message:
4368 No symbol "foo" in current context.
4373 not actually evaluate @var{expression} at the time the @code{condition}
4374 command (or a command that sets a breakpoint with a condition, like
4375 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4377 @item condition @var{bnum}
4378 Remove the condition from breakpoint number @var{bnum}. It becomes
4379 an ordinary unconditional breakpoint.
4382 @cindex ignore count (of breakpoint)
4383 A special case of a breakpoint condition is to stop only when the
4384 breakpoint has been reached a certain number of times. This is so
4385 useful that there is a special way to do it, using the @dfn{ignore
4386 count} of the breakpoint. Every breakpoint has an ignore count, which
4387 is an integer. Most of the time, the ignore count is zero, and
4388 therefore has no effect. But if your program reaches a breakpoint whose
4389 ignore count is positive, then instead of stopping, it just decrements
4390 the ignore count by one and continues. As a result, if the ignore count
4391 value is @var{n}, the breakpoint does not stop the next @var{n} times
4392 your program reaches it.
4396 @item ignore @var{bnum} @var{count}
4397 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4398 The next @var{count} times the breakpoint is reached, your program's
4399 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4402 To make the breakpoint stop the next time it is reached, specify
4405 When you use @code{continue} to resume execution of your program from a
4406 breakpoint, you can specify an ignore count directly as an argument to
4407 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4408 Stepping,,Continuing and Stepping}.
4410 If a breakpoint has a positive ignore count and a condition, the
4411 condition is not checked. Once the ignore count reaches zero,
4412 @value{GDBN} resumes checking the condition.
4414 You could achieve the effect of the ignore count with a condition such
4415 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4416 is decremented each time. @xref{Convenience Vars, ,Convenience
4420 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4423 @node Break Commands
4424 @subsection Breakpoint Command Lists
4426 @cindex breakpoint commands
4427 You can give any breakpoint (or watchpoint or catchpoint) a series of
4428 commands to execute when your program stops due to that breakpoint. For
4429 example, you might want to print the values of certain expressions, or
4430 enable other breakpoints.
4434 @kindex end@r{ (breakpoint commands)}
4435 @item commands @r{[}@var{range}@dots{}@r{]}
4436 @itemx @dots{} @var{command-list} @dots{}
4438 Specify a list of commands for the given breakpoints. The commands
4439 themselves appear on the following lines. Type a line containing just
4440 @code{end} to terminate the commands.
4442 To remove all commands from a breakpoint, type @code{commands} and
4443 follow it immediately with @code{end}; that is, give no commands.
4445 With no argument, @code{commands} refers to the last breakpoint,
4446 watchpoint, or catchpoint set (not to the breakpoint most recently
4447 encountered). If the most recent breakpoints were set with a single
4448 command, then the @code{commands} will apply to all the breakpoints
4449 set by that command. This applies to breakpoints set by
4450 @code{rbreak}, and also applies when a single @code{break} command
4451 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4455 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4456 disabled within a @var{command-list}.
4458 You can use breakpoint commands to start your program up again. Simply
4459 use the @code{continue} command, or @code{step}, or any other command
4460 that resumes execution.
4462 Any other commands in the command list, after a command that resumes
4463 execution, are ignored. This is because any time you resume execution
4464 (even with a simple @code{next} or @code{step}), you may encounter
4465 another breakpoint---which could have its own command list, leading to
4466 ambiguities about which list to execute.
4469 If the first command you specify in a command list is @code{silent}, the
4470 usual message about stopping at a breakpoint is not printed. This may
4471 be desirable for breakpoints that are to print a specific message and
4472 then continue. If none of the remaining commands print anything, you
4473 see no sign that the breakpoint was reached. @code{silent} is
4474 meaningful only at the beginning of a breakpoint command list.
4476 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4477 print precisely controlled output, and are often useful in silent
4478 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4480 For example, here is how you could use breakpoint commands to print the
4481 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4487 printf "x is %d\n",x
4492 One application for breakpoint commands is to compensate for one bug so
4493 you can test for another. Put a breakpoint just after the erroneous line
4494 of code, give it a condition to detect the case in which something
4495 erroneous has been done, and give it commands to assign correct values
4496 to any variables that need them. End with the @code{continue} command
4497 so that your program does not stop, and start with the @code{silent}
4498 command so that no output is produced. Here is an example:
4509 @node Save Breakpoints
4510 @subsection How to save breakpoints to a file
4512 To save breakpoint definitions to a file use the @w{@code{save
4513 breakpoints}} command.
4516 @kindex save breakpoints
4517 @cindex save breakpoints to a file for future sessions
4518 @item save breakpoints [@var{filename}]
4519 This command saves all current breakpoint definitions together with
4520 their commands and ignore counts, into a file @file{@var{filename}}
4521 suitable for use in a later debugging session. This includes all
4522 types of breakpoints (breakpoints, watchpoints, catchpoints,
4523 tracepoints). To read the saved breakpoint definitions, use the
4524 @code{source} command (@pxref{Command Files}). Note that watchpoints
4525 with expressions involving local variables may fail to be recreated
4526 because it may not be possible to access the context where the
4527 watchpoint is valid anymore. Because the saved breakpoint definitions
4528 are simply a sequence of @value{GDBN} commands that recreate the
4529 breakpoints, you can edit the file in your favorite editing program,
4530 and remove the breakpoint definitions you're not interested in, or
4531 that can no longer be recreated.
4534 @c @ifclear BARETARGET
4535 @node Error in Breakpoints
4536 @subsection ``Cannot insert breakpoints''
4538 If you request too many active hardware-assisted breakpoints and
4539 watchpoints, you will see this error message:
4541 @c FIXME: the precise wording of this message may change; the relevant
4542 @c source change is not committed yet (Sep 3, 1999).
4544 Stopped; cannot insert breakpoints.
4545 You may have requested too many hardware breakpoints and watchpoints.
4549 This message is printed when you attempt to resume the program, since
4550 only then @value{GDBN} knows exactly how many hardware breakpoints and
4551 watchpoints it needs to insert.
4553 When this message is printed, you need to disable or remove some of the
4554 hardware-assisted breakpoints and watchpoints, and then continue.
4556 @node Breakpoint-related Warnings
4557 @subsection ``Breakpoint address adjusted...''
4558 @cindex breakpoint address adjusted
4560 Some processor architectures place constraints on the addresses at
4561 which breakpoints may be placed. For architectures thus constrained,
4562 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4563 with the constraints dictated by the architecture.
4565 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4566 a VLIW architecture in which a number of RISC-like instructions may be
4567 bundled together for parallel execution. The FR-V architecture
4568 constrains the location of a breakpoint instruction within such a
4569 bundle to the instruction with the lowest address. @value{GDBN}
4570 honors this constraint by adjusting a breakpoint's address to the
4571 first in the bundle.
4573 It is not uncommon for optimized code to have bundles which contain
4574 instructions from different source statements, thus it may happen that
4575 a breakpoint's address will be adjusted from one source statement to
4576 another. Since this adjustment may significantly alter @value{GDBN}'s
4577 breakpoint related behavior from what the user expects, a warning is
4578 printed when the breakpoint is first set and also when the breakpoint
4581 A warning like the one below is printed when setting a breakpoint
4582 that's been subject to address adjustment:
4585 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4588 Such warnings are printed both for user settable and @value{GDBN}'s
4589 internal breakpoints. If you see one of these warnings, you should
4590 verify that a breakpoint set at the adjusted address will have the
4591 desired affect. If not, the breakpoint in question may be removed and
4592 other breakpoints may be set which will have the desired behavior.
4593 E.g., it may be sufficient to place the breakpoint at a later
4594 instruction. A conditional breakpoint may also be useful in some
4595 cases to prevent the breakpoint from triggering too often.
4597 @value{GDBN} will also issue a warning when stopping at one of these
4598 adjusted breakpoints:
4601 warning: Breakpoint 1 address previously adjusted from 0x00010414
4605 When this warning is encountered, it may be too late to take remedial
4606 action except in cases where the breakpoint is hit earlier or more
4607 frequently than expected.
4609 @node Continuing and Stepping
4610 @section Continuing and Stepping
4614 @cindex resuming execution
4615 @dfn{Continuing} means resuming program execution until your program
4616 completes normally. In contrast, @dfn{stepping} means executing just
4617 one more ``step'' of your program, where ``step'' may mean either one
4618 line of source code, or one machine instruction (depending on what
4619 particular command you use). Either when continuing or when stepping,
4620 your program may stop even sooner, due to a breakpoint or a signal. (If
4621 it stops due to a signal, you may want to use @code{handle}, or use
4622 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4626 @kindex c @r{(@code{continue})}
4627 @kindex fg @r{(resume foreground execution)}
4628 @item continue @r{[}@var{ignore-count}@r{]}
4629 @itemx c @r{[}@var{ignore-count}@r{]}
4630 @itemx fg @r{[}@var{ignore-count}@r{]}
4631 Resume program execution, at the address where your program last stopped;
4632 any breakpoints set at that address are bypassed. The optional argument
4633 @var{ignore-count} allows you to specify a further number of times to
4634 ignore a breakpoint at this location; its effect is like that of
4635 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4637 The argument @var{ignore-count} is meaningful only when your program
4638 stopped due to a breakpoint. At other times, the argument to
4639 @code{continue} is ignored.
4641 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4642 debugged program is deemed to be the foreground program) are provided
4643 purely for convenience, and have exactly the same behavior as
4647 To resume execution at a different place, you can use @code{return}
4648 (@pxref{Returning, ,Returning from a Function}) to go back to the
4649 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4650 Different Address}) to go to an arbitrary location in your program.
4652 A typical technique for using stepping is to set a breakpoint
4653 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4654 beginning of the function or the section of your program where a problem
4655 is believed to lie, run your program until it stops at that breakpoint,
4656 and then step through the suspect area, examining the variables that are
4657 interesting, until you see the problem happen.
4661 @kindex s @r{(@code{step})}
4663 Continue running your program until control reaches a different source
4664 line, then stop it and return control to @value{GDBN}. This command is
4665 abbreviated @code{s}.
4668 @c "without debugging information" is imprecise; actually "without line
4669 @c numbers in the debugging information". (gcc -g1 has debugging info but
4670 @c not line numbers). But it seems complex to try to make that
4671 @c distinction here.
4672 @emph{Warning:} If you use the @code{step} command while control is
4673 within a function that was compiled without debugging information,
4674 execution proceeds until control reaches a function that does have
4675 debugging information. Likewise, it will not step into a function which
4676 is compiled without debugging information. To step through functions
4677 without debugging information, use the @code{stepi} command, described
4681 The @code{step} command only stops at the first instruction of a source
4682 line. This prevents the multiple stops that could otherwise occur in
4683 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4684 to stop if a function that has debugging information is called within
4685 the line. In other words, @code{step} @emph{steps inside} any functions
4686 called within the line.
4688 Also, the @code{step} command only enters a function if there is line
4689 number information for the function. Otherwise it acts like the
4690 @code{next} command. This avoids problems when using @code{cc -gl}
4691 on MIPS machines. Previously, @code{step} entered subroutines if there
4692 was any debugging information about the routine.
4694 @item step @var{count}
4695 Continue running as in @code{step}, but do so @var{count} times. If a
4696 breakpoint is reached, or a signal not related to stepping occurs before
4697 @var{count} steps, stepping stops right away.
4700 @kindex n @r{(@code{next})}
4701 @item next @r{[}@var{count}@r{]}
4702 Continue to the next source line in the current (innermost) stack frame.
4703 This is similar to @code{step}, but function calls that appear within
4704 the line of code are executed without stopping. Execution stops when
4705 control reaches a different line of code at the original stack level
4706 that was executing when you gave the @code{next} command. This command
4707 is abbreviated @code{n}.
4709 An argument @var{count} is a repeat count, as for @code{step}.
4712 @c FIX ME!! Do we delete this, or is there a way it fits in with
4713 @c the following paragraph? --- Vctoria
4715 @c @code{next} within a function that lacks debugging information acts like
4716 @c @code{step}, but any function calls appearing within the code of the
4717 @c function are executed without stopping.
4719 The @code{next} command only stops at the first instruction of a
4720 source line. This prevents multiple stops that could otherwise occur in
4721 @code{switch} statements, @code{for} loops, etc.
4723 @kindex set step-mode
4725 @cindex functions without line info, and stepping
4726 @cindex stepping into functions with no line info
4727 @itemx set step-mode on
4728 The @code{set step-mode on} command causes the @code{step} command to
4729 stop at the first instruction of a function which contains no debug line
4730 information rather than stepping over it.
4732 This is useful in cases where you may be interested in inspecting the
4733 machine instructions of a function which has no symbolic info and do not
4734 want @value{GDBN} to automatically skip over this function.
4736 @item set step-mode off
4737 Causes the @code{step} command to step over any functions which contains no
4738 debug information. This is the default.
4740 @item show step-mode
4741 Show whether @value{GDBN} will stop in or step over functions without
4742 source line debug information.
4745 @kindex fin @r{(@code{finish})}
4747 Continue running until just after function in the selected stack frame
4748 returns. Print the returned value (if any). This command can be
4749 abbreviated as @code{fin}.
4751 Contrast this with the @code{return} command (@pxref{Returning,
4752 ,Returning from a Function}).
4755 @kindex u @r{(@code{until})}
4756 @cindex run until specified location
4759 Continue running until a source line past the current line, in the
4760 current stack frame, is reached. This command is used to avoid single
4761 stepping through a loop more than once. It is like the @code{next}
4762 command, except that when @code{until} encounters a jump, it
4763 automatically continues execution until the program counter is greater
4764 than the address of the jump.
4766 This means that when you reach the end of a loop after single stepping
4767 though it, @code{until} makes your program continue execution until it
4768 exits the loop. In contrast, a @code{next} command at the end of a loop
4769 simply steps back to the beginning of the loop, which forces you to step
4770 through the next iteration.
4772 @code{until} always stops your program if it attempts to exit the current
4775 @code{until} may produce somewhat counterintuitive results if the order
4776 of machine code does not match the order of the source lines. For
4777 example, in the following excerpt from a debugging session, the @code{f}
4778 (@code{frame}) command shows that execution is stopped at line
4779 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4783 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4785 (@value{GDBP}) until
4786 195 for ( ; argc > 0; NEXTARG) @{
4789 This happened because, for execution efficiency, the compiler had
4790 generated code for the loop closure test at the end, rather than the
4791 start, of the loop---even though the test in a C @code{for}-loop is
4792 written before the body of the loop. The @code{until} command appeared
4793 to step back to the beginning of the loop when it advanced to this
4794 expression; however, it has not really gone to an earlier
4795 statement---not in terms of the actual machine code.
4797 @code{until} with no argument works by means of single
4798 instruction stepping, and hence is slower than @code{until} with an
4801 @item until @var{location}
4802 @itemx u @var{location}
4803 Continue running your program until either the specified location is
4804 reached, or the current stack frame returns. @var{location} is any of
4805 the forms described in @ref{Specify Location}.
4806 This form of the command uses temporary breakpoints, and
4807 hence is quicker than @code{until} without an argument. The specified
4808 location is actually reached only if it is in the current frame. This
4809 implies that @code{until} can be used to skip over recursive function
4810 invocations. For instance in the code below, if the current location is
4811 line @code{96}, issuing @code{until 99} will execute the program up to
4812 line @code{99} in the same invocation of factorial, i.e., after the inner
4813 invocations have returned.
4816 94 int factorial (int value)
4818 96 if (value > 1) @{
4819 97 value *= factorial (value - 1);
4826 @kindex advance @var{location}
4827 @itemx advance @var{location}
4828 Continue running the program up to the given @var{location}. An argument is
4829 required, which should be of one of the forms described in
4830 @ref{Specify Location}.
4831 Execution will also stop upon exit from the current stack
4832 frame. This command is similar to @code{until}, but @code{advance} will
4833 not skip over recursive function calls, and the target location doesn't
4834 have to be in the same frame as the current one.
4838 @kindex si @r{(@code{stepi})}
4840 @itemx stepi @var{arg}
4842 Execute one machine instruction, then stop and return to the debugger.
4844 It is often useful to do @samp{display/i $pc} when stepping by machine
4845 instructions. This makes @value{GDBN} automatically display the next
4846 instruction to be executed, each time your program stops. @xref{Auto
4847 Display,, Automatic Display}.
4849 An argument is a repeat count, as in @code{step}.
4853 @kindex ni @r{(@code{nexti})}
4855 @itemx nexti @var{arg}
4857 Execute one machine instruction, but if it is a function call,
4858 proceed until the function returns.
4860 An argument is a repeat count, as in @code{next}.
4863 @node Skipping Over Functions and Files
4864 @section Skipping Over Functions and Files
4865 @cindex skipping over functions and files
4867 The program you are debugging may contain some functions which are
4868 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
4869 skip a function or all functions in a file when stepping.
4871 For example, consider the following C function:
4882 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
4883 are not interested in stepping through @code{boring}. If you run @code{step}
4884 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
4885 step over both @code{foo} and @code{boring}!
4887 One solution is to @code{step} into @code{boring} and use the @code{finish}
4888 command to immediately exit it. But this can become tedious if @code{boring}
4889 is called from many places.
4891 A more flexible solution is to execute @kbd{skip boring}. This instructs
4892 @value{GDBN} never to step into @code{boring}. Now when you execute
4893 @code{step} at line 103, you'll step over @code{boring} and directly into
4896 You can also instruct @value{GDBN} to skip all functions in a file, with, for
4897 example, @code{skip file boring.c}.
4900 @kindex skip function
4901 @item skip @r{[}@var{linespec}@r{]}
4902 @itemx skip function @r{[}@var{linespec}@r{]}
4903 After running this command, the function named by @var{linespec} or the
4904 function containing the line named by @var{linespec} will be skipped over when
4905 stepping. @xref{Specify Location}.
4907 If you do not specify @var{linespec}, the function you're currently debugging
4910 (If you have a function called @code{file} that you want to skip, use
4911 @kbd{skip function file}.)
4914 @item skip file @r{[}@var{filename}@r{]}
4915 After running this command, any function whose source lives in @var{filename}
4916 will be skipped over when stepping.
4918 If you do not specify @var{filename}, functions whose source lives in the file
4919 you're currently debugging will be skipped.
4922 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
4923 These are the commands for managing your list of skips:
4927 @item info skip @r{[}@var{range}@r{]}
4928 Print details about the specified skip(s). If @var{range} is not specified,
4929 print a table with details about all functions and files marked for skipping.
4930 @code{info skip} prints the following information about each skip:
4934 A number identifying this skip.
4936 The type of this skip, either @samp{function} or @samp{file}.
4937 @item Enabled or Disabled
4938 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
4940 For function skips, this column indicates the address in memory of the function
4941 being skipped. If you've set a function skip on a function which has not yet
4942 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
4943 which has the function is loaded, @code{info skip} will show the function's
4946 For file skips, this field contains the filename being skipped. For functions
4947 skips, this field contains the function name and its line number in the file
4948 where it is defined.
4952 @item skip delete @r{[}@var{range}@r{]}
4953 Delete the specified skip(s). If @var{range} is not specified, delete all
4957 @item skip enable @r{[}@var{range}@r{]}
4958 Enable the specified skip(s). If @var{range} is not specified, enable all
4961 @kindex skip disable
4962 @item skip disable @r{[}@var{range}@r{]}
4963 Disable the specified skip(s). If @var{range} is not specified, disable all
4972 A signal is an asynchronous event that can happen in a program. The
4973 operating system defines the possible kinds of signals, and gives each
4974 kind a name and a number. For example, in Unix @code{SIGINT} is the
4975 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4976 @code{SIGSEGV} is the signal a program gets from referencing a place in
4977 memory far away from all the areas in use; @code{SIGALRM} occurs when
4978 the alarm clock timer goes off (which happens only if your program has
4979 requested an alarm).
4981 @cindex fatal signals
4982 Some signals, including @code{SIGALRM}, are a normal part of the
4983 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4984 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4985 program has not specified in advance some other way to handle the signal.
4986 @code{SIGINT} does not indicate an error in your program, but it is normally
4987 fatal so it can carry out the purpose of the interrupt: to kill the program.
4989 @value{GDBN} has the ability to detect any occurrence of a signal in your
4990 program. You can tell @value{GDBN} in advance what to do for each kind of
4993 @cindex handling signals
4994 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4995 @code{SIGALRM} be silently passed to your program
4996 (so as not to interfere with their role in the program's functioning)
4997 but to stop your program immediately whenever an error signal happens.
4998 You can change these settings with the @code{handle} command.
5001 @kindex info signals
5005 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5006 handle each one. You can use this to see the signal numbers of all
5007 the defined types of signals.
5009 @item info signals @var{sig}
5010 Similar, but print information only about the specified signal number.
5012 @code{info handle} is an alias for @code{info signals}.
5015 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5016 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5017 can be the number of a signal or its name (with or without the
5018 @samp{SIG} at the beginning); a list of signal numbers of the form
5019 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5020 known signals. Optional arguments @var{keywords}, described below,
5021 say what change to make.
5025 The keywords allowed by the @code{handle} command can be abbreviated.
5026 Their full names are:
5030 @value{GDBN} should not stop your program when this signal happens. It may
5031 still print a message telling you that the signal has come in.
5034 @value{GDBN} should stop your program when this signal happens. This implies
5035 the @code{print} keyword as well.
5038 @value{GDBN} should print a message when this signal happens.
5041 @value{GDBN} should not mention the occurrence of the signal at all. This
5042 implies the @code{nostop} keyword as well.
5046 @value{GDBN} should allow your program to see this signal; your program
5047 can handle the signal, or else it may terminate if the signal is fatal
5048 and not handled. @code{pass} and @code{noignore} are synonyms.
5052 @value{GDBN} should not allow your program to see this signal.
5053 @code{nopass} and @code{ignore} are synonyms.
5057 When a signal stops your program, the signal is not visible to the
5059 continue. Your program sees the signal then, if @code{pass} is in
5060 effect for the signal in question @emph{at that time}. In other words,
5061 after @value{GDBN} reports a signal, you can use the @code{handle}
5062 command with @code{pass} or @code{nopass} to control whether your
5063 program sees that signal when you continue.
5065 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5066 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5067 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5070 You can also use the @code{signal} command to prevent your program from
5071 seeing a signal, or cause it to see a signal it normally would not see,
5072 or to give it any signal at any time. For example, if your program stopped
5073 due to some sort of memory reference error, you might store correct
5074 values into the erroneous variables and continue, hoping to see more
5075 execution; but your program would probably terminate immediately as
5076 a result of the fatal signal once it saw the signal. To prevent this,
5077 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5080 @cindex extra signal information
5081 @anchor{extra signal information}
5083 On some targets, @value{GDBN} can inspect extra signal information
5084 associated with the intercepted signal, before it is actually
5085 delivered to the program being debugged. This information is exported
5086 by the convenience variable @code{$_siginfo}, and consists of data
5087 that is passed by the kernel to the signal handler at the time of the
5088 receipt of a signal. The data type of the information itself is
5089 target dependent. You can see the data type using the @code{ptype
5090 $_siginfo} command. On Unix systems, it typically corresponds to the
5091 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5094 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5095 referenced address that raised a segmentation fault.
5099 (@value{GDBP}) continue
5100 Program received signal SIGSEGV, Segmentation fault.
5101 0x0000000000400766 in main ()
5103 (@value{GDBP}) ptype $_siginfo
5110 struct @{...@} _kill;
5111 struct @{...@} _timer;
5113 struct @{...@} _sigchld;
5114 struct @{...@} _sigfault;
5115 struct @{...@} _sigpoll;
5118 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5122 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5123 $1 = (void *) 0x7ffff7ff7000
5127 Depending on target support, @code{$_siginfo} may also be writable.
5130 @section Stopping and Starting Multi-thread Programs
5132 @cindex stopped threads
5133 @cindex threads, stopped
5135 @cindex continuing threads
5136 @cindex threads, continuing
5138 @value{GDBN} supports debugging programs with multiple threads
5139 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5140 are two modes of controlling execution of your program within the
5141 debugger. In the default mode, referred to as @dfn{all-stop mode},
5142 when any thread in your program stops (for example, at a breakpoint
5143 or while being stepped), all other threads in the program are also stopped by
5144 @value{GDBN}. On some targets, @value{GDBN} also supports
5145 @dfn{non-stop mode}, in which other threads can continue to run freely while
5146 you examine the stopped thread in the debugger.
5149 * All-Stop Mode:: All threads stop when GDB takes control
5150 * Non-Stop Mode:: Other threads continue to execute
5151 * Background Execution:: Running your program asynchronously
5152 * Thread-Specific Breakpoints:: Controlling breakpoints
5153 * Interrupted System Calls:: GDB may interfere with system calls
5154 * Observer Mode:: GDB does not alter program behavior
5158 @subsection All-Stop Mode
5160 @cindex all-stop mode
5162 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5163 @emph{all} threads of execution stop, not just the current thread. This
5164 allows you to examine the overall state of the program, including
5165 switching between threads, without worrying that things may change
5168 Conversely, whenever you restart the program, @emph{all} threads start
5169 executing. @emph{This is true even when single-stepping} with commands
5170 like @code{step} or @code{next}.
5172 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5173 Since thread scheduling is up to your debugging target's operating
5174 system (not controlled by @value{GDBN}), other threads may
5175 execute more than one statement while the current thread completes a
5176 single step. Moreover, in general other threads stop in the middle of a
5177 statement, rather than at a clean statement boundary, when the program
5180 You might even find your program stopped in another thread after
5181 continuing or even single-stepping. This happens whenever some other
5182 thread runs into a breakpoint, a signal, or an exception before the
5183 first thread completes whatever you requested.
5185 @cindex automatic thread selection
5186 @cindex switching threads automatically
5187 @cindex threads, automatic switching
5188 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5189 signal, it automatically selects the thread where that breakpoint or
5190 signal happened. @value{GDBN} alerts you to the context switch with a
5191 message such as @samp{[Switching to Thread @var{n}]} to identify the
5194 On some OSes, you can modify @value{GDBN}'s default behavior by
5195 locking the OS scheduler to allow only a single thread to run.
5198 @item set scheduler-locking @var{mode}
5199 @cindex scheduler locking mode
5200 @cindex lock scheduler
5201 Set the scheduler locking mode. If it is @code{off}, then there is no
5202 locking and any thread may run at any time. If @code{on}, then only the
5203 current thread may run when the inferior is resumed. The @code{step}
5204 mode optimizes for single-stepping; it prevents other threads
5205 from preempting the current thread while you are stepping, so that
5206 the focus of debugging does not change unexpectedly.
5207 Other threads only rarely (or never) get a chance to run
5208 when you step. They are more likely to run when you @samp{next} over a
5209 function call, and they are completely free to run when you use commands
5210 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5211 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5212 the current thread away from the thread that you are debugging.
5214 @item show scheduler-locking
5215 Display the current scheduler locking mode.
5218 @cindex resume threads of multiple processes simultaneously
5219 By default, when you issue one of the execution commands such as
5220 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5221 threads of the current inferior to run. For example, if @value{GDBN}
5222 is attached to two inferiors, each with two threads, the
5223 @code{continue} command resumes only the two threads of the current
5224 inferior. This is useful, for example, when you debug a program that
5225 forks and you want to hold the parent stopped (so that, for instance,
5226 it doesn't run to exit), while you debug the child. In other
5227 situations, you may not be interested in inspecting the current state
5228 of any of the processes @value{GDBN} is attached to, and you may want
5229 to resume them all until some breakpoint is hit. In the latter case,
5230 you can instruct @value{GDBN} to allow all threads of all the
5231 inferiors to run with the @w{@code{set schedule-multiple}} command.
5234 @kindex set schedule-multiple
5235 @item set schedule-multiple
5236 Set the mode for allowing threads of multiple processes to be resumed
5237 when an execution command is issued. When @code{on}, all threads of
5238 all processes are allowed to run. When @code{off}, only the threads
5239 of the current process are resumed. The default is @code{off}. The
5240 @code{scheduler-locking} mode takes precedence when set to @code{on},
5241 or while you are stepping and set to @code{step}.
5243 @item show schedule-multiple
5244 Display the current mode for resuming the execution of threads of
5249 @subsection Non-Stop Mode
5251 @cindex non-stop mode
5253 @c This section is really only a place-holder, and needs to be expanded
5254 @c with more details.
5256 For some multi-threaded targets, @value{GDBN} supports an optional
5257 mode of operation in which you can examine stopped program threads in
5258 the debugger while other threads continue to execute freely. This
5259 minimizes intrusion when debugging live systems, such as programs
5260 where some threads have real-time constraints or must continue to
5261 respond to external events. This is referred to as @dfn{non-stop} mode.
5263 In non-stop mode, when a thread stops to report a debugging event,
5264 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5265 threads as well, in contrast to the all-stop mode behavior. Additionally,
5266 execution commands such as @code{continue} and @code{step} apply by default
5267 only to the current thread in non-stop mode, rather than all threads as
5268 in all-stop mode. This allows you to control threads explicitly in
5269 ways that are not possible in all-stop mode --- for example, stepping
5270 one thread while allowing others to run freely, stepping
5271 one thread while holding all others stopped, or stepping several threads
5272 independently and simultaneously.
5274 To enter non-stop mode, use this sequence of commands before you run
5275 or attach to your program:
5278 # Enable the async interface.
5281 # If using the CLI, pagination breaks non-stop.
5284 # Finally, turn it on!
5288 You can use these commands to manipulate the non-stop mode setting:
5291 @kindex set non-stop
5292 @item set non-stop on
5293 Enable selection of non-stop mode.
5294 @item set non-stop off
5295 Disable selection of non-stop mode.
5296 @kindex show non-stop
5298 Show the current non-stop enablement setting.
5301 Note these commands only reflect whether non-stop mode is enabled,
5302 not whether the currently-executing program is being run in non-stop mode.
5303 In particular, the @code{set non-stop} preference is only consulted when
5304 @value{GDBN} starts or connects to the target program, and it is generally
5305 not possible to switch modes once debugging has started. Furthermore,
5306 since not all targets support non-stop mode, even when you have enabled
5307 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5310 In non-stop mode, all execution commands apply only to the current thread
5311 by default. That is, @code{continue} only continues one thread.
5312 To continue all threads, issue @code{continue -a} or @code{c -a}.
5314 You can use @value{GDBN}'s background execution commands
5315 (@pxref{Background Execution}) to run some threads in the background
5316 while you continue to examine or step others from @value{GDBN}.
5317 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5318 always executed asynchronously in non-stop mode.
5320 Suspending execution is done with the @code{interrupt} command when
5321 running in the background, or @kbd{Ctrl-c} during foreground execution.
5322 In all-stop mode, this stops the whole process;
5323 but in non-stop mode the interrupt applies only to the current thread.
5324 To stop the whole program, use @code{interrupt -a}.
5326 Other execution commands do not currently support the @code{-a} option.
5328 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5329 that thread current, as it does in all-stop mode. This is because the
5330 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5331 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5332 changed to a different thread just as you entered a command to operate on the
5333 previously current thread.
5335 @node Background Execution
5336 @subsection Background Execution
5338 @cindex foreground execution
5339 @cindex background execution
5340 @cindex asynchronous execution
5341 @cindex execution, foreground, background and asynchronous
5343 @value{GDBN}'s execution commands have two variants: the normal
5344 foreground (synchronous) behavior, and a background
5345 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5346 the program to report that some thread has stopped before prompting for
5347 another command. In background execution, @value{GDBN} immediately gives
5348 a command prompt so that you can issue other commands while your program runs.
5350 You need to explicitly enable asynchronous mode before you can use
5351 background execution commands. You can use these commands to
5352 manipulate the asynchronous mode setting:
5355 @kindex set target-async
5356 @item set target-async on
5357 Enable asynchronous mode.
5358 @item set target-async off
5359 Disable asynchronous mode.
5360 @kindex show target-async
5361 @item show target-async
5362 Show the current target-async setting.
5365 If the target doesn't support async mode, @value{GDBN} issues an error
5366 message if you attempt to use the background execution commands.
5368 To specify background execution, add a @code{&} to the command. For example,
5369 the background form of the @code{continue} command is @code{continue&}, or
5370 just @code{c&}. The execution commands that accept background execution
5376 @xref{Starting, , Starting your Program}.
5380 @xref{Attach, , Debugging an Already-running Process}.
5384 @xref{Continuing and Stepping, step}.
5388 @xref{Continuing and Stepping, stepi}.
5392 @xref{Continuing and Stepping, next}.
5396 @xref{Continuing and Stepping, nexti}.
5400 @xref{Continuing and Stepping, continue}.
5404 @xref{Continuing and Stepping, finish}.
5408 @xref{Continuing and Stepping, until}.
5412 Background execution is especially useful in conjunction with non-stop
5413 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5414 However, you can also use these commands in the normal all-stop mode with
5415 the restriction that you cannot issue another execution command until the
5416 previous one finishes. Examples of commands that are valid in all-stop
5417 mode while the program is running include @code{help} and @code{info break}.
5419 You can interrupt your program while it is running in the background by
5420 using the @code{interrupt} command.
5427 Suspend execution of the running program. In all-stop mode,
5428 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5429 only the current thread. To stop the whole program in non-stop mode,
5430 use @code{interrupt -a}.
5433 @node Thread-Specific Breakpoints
5434 @subsection Thread-Specific Breakpoints
5436 When your program has multiple threads (@pxref{Threads,, Debugging
5437 Programs with Multiple Threads}), you can choose whether to set
5438 breakpoints on all threads, or on a particular thread.
5441 @cindex breakpoints and threads
5442 @cindex thread breakpoints
5443 @kindex break @dots{} thread @var{threadno}
5444 @item break @var{linespec} thread @var{threadno}
5445 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5446 @var{linespec} specifies source lines; there are several ways of
5447 writing them (@pxref{Specify Location}), but the effect is always to
5448 specify some source line.
5450 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5451 to specify that you only want @value{GDBN} to stop the program when a
5452 particular thread reaches this breakpoint. @var{threadno} is one of the
5453 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5454 column of the @samp{info threads} display.
5456 If you do not specify @samp{thread @var{threadno}} when you set a
5457 breakpoint, the breakpoint applies to @emph{all} threads of your
5460 You can use the @code{thread} qualifier on conditional breakpoints as
5461 well; in this case, place @samp{thread @var{threadno}} before or
5462 after the breakpoint condition, like this:
5465 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5470 @node Interrupted System Calls
5471 @subsection Interrupted System Calls
5473 @cindex thread breakpoints and system calls
5474 @cindex system calls and thread breakpoints
5475 @cindex premature return from system calls
5476 There is an unfortunate side effect when using @value{GDBN} to debug
5477 multi-threaded programs. If one thread stops for a
5478 breakpoint, or for some other reason, and another thread is blocked in a
5479 system call, then the system call may return prematurely. This is a
5480 consequence of the interaction between multiple threads and the signals
5481 that @value{GDBN} uses to implement breakpoints and other events that
5484 To handle this problem, your program should check the return value of
5485 each system call and react appropriately. This is good programming
5488 For example, do not write code like this:
5494 The call to @code{sleep} will return early if a different thread stops
5495 at a breakpoint or for some other reason.
5497 Instead, write this:
5502 unslept = sleep (unslept);
5505 A system call is allowed to return early, so the system is still
5506 conforming to its specification. But @value{GDBN} does cause your
5507 multi-threaded program to behave differently than it would without
5510 Also, @value{GDBN} uses internal breakpoints in the thread library to
5511 monitor certain events such as thread creation and thread destruction.
5512 When such an event happens, a system call in another thread may return
5513 prematurely, even though your program does not appear to stop.
5516 @subsection Observer Mode
5518 If you want to build on non-stop mode and observe program behavior
5519 without any chance of disruption by @value{GDBN}, you can set
5520 variables to disable all of the debugger's attempts to modify state,
5521 whether by writing memory, inserting breakpoints, etc. These operate
5522 at a low level, intercepting operations from all commands.
5524 When all of these are set to @code{off}, then @value{GDBN} is said to
5525 be @dfn{observer mode}. As a convenience, the variable
5526 @code{observer} can be set to disable these, plus enable non-stop
5529 Note that @value{GDBN} will not prevent you from making nonsensical
5530 combinations of these settings. For instance, if you have enabled
5531 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5532 then breakpoints that work by writing trap instructions into the code
5533 stream will still not be able to be placed.
5538 @item set observer on
5539 @itemx set observer off
5540 When set to @code{on}, this disables all the permission variables
5541 below (except for @code{insert-fast-tracepoints}), plus enables
5542 non-stop debugging. Setting this to @code{off} switches back to
5543 normal debugging, though remaining in non-stop mode.
5546 Show whether observer mode is on or off.
5548 @kindex may-write-registers
5549 @item set may-write-registers on
5550 @itemx set may-write-registers off
5551 This controls whether @value{GDBN} will attempt to alter the values of
5552 registers, such as with assignment expressions in @code{print}, or the
5553 @code{jump} command. It defaults to @code{on}.
5555 @item show may-write-registers
5556 Show the current permission to write registers.
5558 @kindex may-write-memory
5559 @item set may-write-memory on
5560 @itemx set may-write-memory off
5561 This controls whether @value{GDBN} will attempt to alter the contents
5562 of memory, such as with assignment expressions in @code{print}. It
5563 defaults to @code{on}.
5565 @item show may-write-memory
5566 Show the current permission to write memory.
5568 @kindex may-insert-breakpoints
5569 @item set may-insert-breakpoints on
5570 @itemx set may-insert-breakpoints off
5571 This controls whether @value{GDBN} will attempt to insert breakpoints.
5572 This affects all breakpoints, including internal breakpoints defined
5573 by @value{GDBN}. It defaults to @code{on}.
5575 @item show may-insert-breakpoints
5576 Show the current permission to insert breakpoints.
5578 @kindex may-insert-tracepoints
5579 @item set may-insert-tracepoints on
5580 @itemx set may-insert-tracepoints off
5581 This controls whether @value{GDBN} will attempt to insert (regular)
5582 tracepoints at the beginning of a tracing experiment. It affects only
5583 non-fast tracepoints, fast tracepoints being under the control of
5584 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5586 @item show may-insert-tracepoints
5587 Show the current permission to insert tracepoints.
5589 @kindex may-insert-fast-tracepoints
5590 @item set may-insert-fast-tracepoints on
5591 @itemx set may-insert-fast-tracepoints off
5592 This controls whether @value{GDBN} will attempt to insert fast
5593 tracepoints at the beginning of a tracing experiment. It affects only
5594 fast tracepoints, regular (non-fast) tracepoints being under the
5595 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5597 @item show may-insert-fast-tracepoints
5598 Show the current permission to insert fast tracepoints.
5600 @kindex may-interrupt
5601 @item set may-interrupt on
5602 @itemx set may-interrupt off
5603 This controls whether @value{GDBN} will attempt to interrupt or stop
5604 program execution. When this variable is @code{off}, the
5605 @code{interrupt} command will have no effect, nor will
5606 @kbd{Ctrl-c}. It defaults to @code{on}.
5608 @item show may-interrupt
5609 Show the current permission to interrupt or stop the program.
5613 @node Reverse Execution
5614 @chapter Running programs backward
5615 @cindex reverse execution
5616 @cindex running programs backward
5618 When you are debugging a program, it is not unusual to realize that
5619 you have gone too far, and some event of interest has already happened.
5620 If the target environment supports it, @value{GDBN} can allow you to
5621 ``rewind'' the program by running it backward.
5623 A target environment that supports reverse execution should be able
5624 to ``undo'' the changes in machine state that have taken place as the
5625 program was executing normally. Variables, registers etc.@: should
5626 revert to their previous values. Obviously this requires a great
5627 deal of sophistication on the part of the target environment; not
5628 all target environments can support reverse execution.
5630 When a program is executed in reverse, the instructions that
5631 have most recently been executed are ``un-executed'', in reverse
5632 order. The program counter runs backward, following the previous
5633 thread of execution in reverse. As each instruction is ``un-executed'',
5634 the values of memory and/or registers that were changed by that
5635 instruction are reverted to their previous states. After executing
5636 a piece of source code in reverse, all side effects of that code
5637 should be ``undone'', and all variables should be returned to their
5638 prior values@footnote{
5639 Note that some side effects are easier to undo than others. For instance,
5640 memory and registers are relatively easy, but device I/O is hard. Some
5641 targets may be able undo things like device I/O, and some may not.
5643 The contract between @value{GDBN} and the reverse executing target
5644 requires only that the target do something reasonable when
5645 @value{GDBN} tells it to execute backwards, and then report the
5646 results back to @value{GDBN}. Whatever the target reports back to
5647 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5648 assumes that the memory and registers that the target reports are in a
5649 consistant state, but @value{GDBN} accepts whatever it is given.
5652 If you are debugging in a target environment that supports
5653 reverse execution, @value{GDBN} provides the following commands.
5656 @kindex reverse-continue
5657 @kindex rc @r{(@code{reverse-continue})}
5658 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5659 @itemx rc @r{[}@var{ignore-count}@r{]}
5660 Beginning at the point where your program last stopped, start executing
5661 in reverse. Reverse execution will stop for breakpoints and synchronous
5662 exceptions (signals), just like normal execution. Behavior of
5663 asynchronous signals depends on the target environment.
5665 @kindex reverse-step
5666 @kindex rs @r{(@code{step})}
5667 @item reverse-step @r{[}@var{count}@r{]}
5668 Run the program backward until control reaches the start of a
5669 different source line; then stop it, and return control to @value{GDBN}.
5671 Like the @code{step} command, @code{reverse-step} will only stop
5672 at the beginning of a source line. It ``un-executes'' the previously
5673 executed source line. If the previous source line included calls to
5674 debuggable functions, @code{reverse-step} will step (backward) into
5675 the called function, stopping at the beginning of the @emph{last}
5676 statement in the called function (typically a return statement).
5678 Also, as with the @code{step} command, if non-debuggable functions are
5679 called, @code{reverse-step} will run thru them backward without stopping.
5681 @kindex reverse-stepi
5682 @kindex rsi @r{(@code{reverse-stepi})}
5683 @item reverse-stepi @r{[}@var{count}@r{]}
5684 Reverse-execute one machine instruction. Note that the instruction
5685 to be reverse-executed is @emph{not} the one pointed to by the program
5686 counter, but the instruction executed prior to that one. For instance,
5687 if the last instruction was a jump, @code{reverse-stepi} will take you
5688 back from the destination of the jump to the jump instruction itself.
5690 @kindex reverse-next
5691 @kindex rn @r{(@code{reverse-next})}
5692 @item reverse-next @r{[}@var{count}@r{]}
5693 Run backward to the beginning of the previous line executed in
5694 the current (innermost) stack frame. If the line contains function
5695 calls, they will be ``un-executed'' without stopping. Starting from
5696 the first line of a function, @code{reverse-next} will take you back
5697 to the caller of that function, @emph{before} the function was called,
5698 just as the normal @code{next} command would take you from the last
5699 line of a function back to its return to its caller
5700 @footnote{Unless the code is too heavily optimized.}.
5702 @kindex reverse-nexti
5703 @kindex rni @r{(@code{reverse-nexti})}
5704 @item reverse-nexti @r{[}@var{count}@r{]}
5705 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5706 in reverse, except that called functions are ``un-executed'' atomically.
5707 That is, if the previously executed instruction was a return from
5708 another function, @code{reverse-nexti} will continue to execute
5709 in reverse until the call to that function (from the current stack
5712 @kindex reverse-finish
5713 @item reverse-finish
5714 Just as the @code{finish} command takes you to the point where the
5715 current function returns, @code{reverse-finish} takes you to the point
5716 where it was called. Instead of ending up at the end of the current
5717 function invocation, you end up at the beginning.
5719 @kindex set exec-direction
5720 @item set exec-direction
5721 Set the direction of target execution.
5722 @itemx set exec-direction reverse
5723 @cindex execute forward or backward in time
5724 @value{GDBN} will perform all execution commands in reverse, until the
5725 exec-direction mode is changed to ``forward''. Affected commands include
5726 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5727 command cannot be used in reverse mode.
5728 @item set exec-direction forward
5729 @value{GDBN} will perform all execution commands in the normal fashion.
5730 This is the default.
5734 @node Process Record and Replay
5735 @chapter Recording Inferior's Execution and Replaying It
5736 @cindex process record and replay
5737 @cindex recording inferior's execution and replaying it
5739 On some platforms, @value{GDBN} provides a special @dfn{process record
5740 and replay} target that can record a log of the process execution, and
5741 replay it later with both forward and reverse execution commands.
5744 When this target is in use, if the execution log includes the record
5745 for the next instruction, @value{GDBN} will debug in @dfn{replay
5746 mode}. In the replay mode, the inferior does not really execute code
5747 instructions. Instead, all the events that normally happen during
5748 code execution are taken from the execution log. While code is not
5749 really executed in replay mode, the values of registers (including the
5750 program counter register) and the memory of the inferior are still
5751 changed as they normally would. Their contents are taken from the
5755 If the record for the next instruction is not in the execution log,
5756 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5757 inferior executes normally, and @value{GDBN} records the execution log
5760 The process record and replay target supports reverse execution
5761 (@pxref{Reverse Execution}), even if the platform on which the
5762 inferior runs does not. However, the reverse execution is limited in
5763 this case by the range of the instructions recorded in the execution
5764 log. In other words, reverse execution on platforms that don't
5765 support it directly can only be done in the replay mode.
5767 When debugging in the reverse direction, @value{GDBN} will work in
5768 replay mode as long as the execution log includes the record for the
5769 previous instruction; otherwise, it will work in record mode, if the
5770 platform supports reverse execution, or stop if not.
5772 For architecture environments that support process record and replay,
5773 @value{GDBN} provides the following commands:
5776 @kindex target record
5780 This command starts the process record and replay target. The process
5781 record and replay target can only debug a process that is already
5782 running. Therefore, you need first to start the process with the
5783 @kbd{run} or @kbd{start} commands, and then start the recording with
5784 the @kbd{target record} command.
5786 Both @code{record} and @code{rec} are aliases of @code{target record}.
5788 @cindex displaced stepping, and process record and replay
5789 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5790 will be automatically disabled when process record and replay target
5791 is started. That's because the process record and replay target
5792 doesn't support displaced stepping.
5794 @cindex non-stop mode, and process record and replay
5795 @cindex asynchronous execution, and process record and replay
5796 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5797 the asynchronous execution mode (@pxref{Background Execution}), the
5798 process record and replay target cannot be started because it doesn't
5799 support these two modes.
5804 Stop the process record and replay target. When process record and
5805 replay target stops, the entire execution log will be deleted and the
5806 inferior will either be terminated, or will remain in its final state.
5808 When you stop the process record and replay target in record mode (at
5809 the end of the execution log), the inferior will be stopped at the
5810 next instruction that would have been recorded. In other words, if
5811 you record for a while and then stop recording, the inferior process
5812 will be left in the same state as if the recording never happened.
5814 On the other hand, if the process record and replay target is stopped
5815 while in replay mode (that is, not at the end of the execution log,
5816 but at some earlier point), the inferior process will become ``live''
5817 at that earlier state, and it will then be possible to continue the
5818 usual ``live'' debugging of the process from that state.
5820 When the inferior process exits, or @value{GDBN} detaches from it,
5821 process record and replay target will automatically stop itself.
5824 @item record save @var{filename}
5825 Save the execution log to a file @file{@var{filename}}.
5826 Default filename is @file{gdb_record.@var{process_id}}, where
5827 @var{process_id} is the process ID of the inferior.
5829 @kindex record restore
5830 @item record restore @var{filename}
5831 Restore the execution log from a file @file{@var{filename}}.
5832 File must have been created with @code{record save}.
5834 @kindex set record insn-number-max
5835 @item set record insn-number-max @var{limit}
5836 Set the limit of instructions to be recorded. Default value is 200000.
5838 If @var{limit} is a positive number, then @value{GDBN} will start
5839 deleting instructions from the log once the number of the record
5840 instructions becomes greater than @var{limit}. For every new recorded
5841 instruction, @value{GDBN} will delete the earliest recorded
5842 instruction to keep the number of recorded instructions at the limit.
5843 (Since deleting recorded instructions loses information, @value{GDBN}
5844 lets you control what happens when the limit is reached, by means of
5845 the @code{stop-at-limit} option, described below.)
5847 If @var{limit} is zero, @value{GDBN} will never delete recorded
5848 instructions from the execution log. The number of recorded
5849 instructions is unlimited in this case.
5851 @kindex show record insn-number-max
5852 @item show record insn-number-max
5853 Show the limit of instructions to be recorded.
5855 @kindex set record stop-at-limit
5856 @item set record stop-at-limit
5857 Control the behavior when the number of recorded instructions reaches
5858 the limit. If ON (the default), @value{GDBN} will stop when the limit
5859 is reached for the first time and ask you whether you want to stop the
5860 inferior or continue running it and recording the execution log. If
5861 you decide to continue recording, each new recorded instruction will
5862 cause the oldest one to be deleted.
5864 If this option is OFF, @value{GDBN} will automatically delete the
5865 oldest record to make room for each new one, without asking.
5867 @kindex show record stop-at-limit
5868 @item show record stop-at-limit
5869 Show the current setting of @code{stop-at-limit}.
5871 @kindex set record memory-query
5872 @item set record memory-query
5873 Control the behavior when @value{GDBN} is unable to record memory
5874 changes caused by an instruction. If ON, @value{GDBN} will query
5875 whether to stop the inferior in that case.
5877 If this option is OFF (the default), @value{GDBN} will automatically
5878 ignore the effect of such instructions on memory. Later, when
5879 @value{GDBN} replays this execution log, it will mark the log of this
5880 instruction as not accessible, and it will not affect the replay
5883 @kindex show record memory-query
5884 @item show record memory-query
5885 Show the current setting of @code{memory-query}.
5889 Show various statistics about the state of process record and its
5890 in-memory execution log buffer, including:
5894 Whether in record mode or replay mode.
5896 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5898 Highest recorded instruction number.
5900 Current instruction about to be replayed (if in replay mode).
5902 Number of instructions contained in the execution log.
5904 Maximum number of instructions that may be contained in the execution log.
5907 @kindex record delete
5910 When record target runs in replay mode (``in the past''), delete the
5911 subsequent execution log and begin to record a new execution log starting
5912 from the current address. This means you will abandon the previously
5913 recorded ``future'' and begin recording a new ``future''.
5918 @chapter Examining the Stack
5920 When your program has stopped, the first thing you need to know is where it
5921 stopped and how it got there.
5924 Each time your program performs a function call, information about the call
5926 That information includes the location of the call in your program,
5927 the arguments of the call,
5928 and the local variables of the function being called.
5929 The information is saved in a block of data called a @dfn{stack frame}.
5930 The stack frames are allocated in a region of memory called the @dfn{call
5933 When your program stops, the @value{GDBN} commands for examining the
5934 stack allow you to see all of this information.
5936 @cindex selected frame
5937 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5938 @value{GDBN} commands refer implicitly to the selected frame. In
5939 particular, whenever you ask @value{GDBN} for the value of a variable in
5940 your program, the value is found in the selected frame. There are
5941 special @value{GDBN} commands to select whichever frame you are
5942 interested in. @xref{Selection, ,Selecting a Frame}.
5944 When your program stops, @value{GDBN} automatically selects the
5945 currently executing frame and describes it briefly, similar to the
5946 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5949 * Frames:: Stack frames
5950 * Backtrace:: Backtraces
5951 * Selection:: Selecting a frame
5952 * Frame Info:: Information on a frame
5957 @section Stack Frames
5959 @cindex frame, definition
5961 The call stack is divided up into contiguous pieces called @dfn{stack
5962 frames}, or @dfn{frames} for short; each frame is the data associated
5963 with one call to one function. The frame contains the arguments given
5964 to the function, the function's local variables, and the address at
5965 which the function is executing.
5967 @cindex initial frame
5968 @cindex outermost frame
5969 @cindex innermost frame
5970 When your program is started, the stack has only one frame, that of the
5971 function @code{main}. This is called the @dfn{initial} frame or the
5972 @dfn{outermost} frame. Each time a function is called, a new frame is
5973 made. Each time a function returns, the frame for that function invocation
5974 is eliminated. If a function is recursive, there can be many frames for
5975 the same function. The frame for the function in which execution is
5976 actually occurring is called the @dfn{innermost} frame. This is the most
5977 recently created of all the stack frames that still exist.
5979 @cindex frame pointer
5980 Inside your program, stack frames are identified by their addresses. A
5981 stack frame consists of many bytes, each of which has its own address; each
5982 kind of computer has a convention for choosing one byte whose
5983 address serves as the address of the frame. Usually this address is kept
5984 in a register called the @dfn{frame pointer register}
5985 (@pxref{Registers, $fp}) while execution is going on in that frame.
5987 @cindex frame number
5988 @value{GDBN} assigns numbers to all existing stack frames, starting with
5989 zero for the innermost frame, one for the frame that called it,
5990 and so on upward. These numbers do not really exist in your program;
5991 they are assigned by @value{GDBN} to give you a way of designating stack
5992 frames in @value{GDBN} commands.
5994 @c The -fomit-frame-pointer below perennially causes hbox overflow
5995 @c underflow problems.
5996 @cindex frameless execution
5997 Some compilers provide a way to compile functions so that they operate
5998 without stack frames. (For example, the @value{NGCC} option
6000 @samp{-fomit-frame-pointer}
6002 generates functions without a frame.)
6003 This is occasionally done with heavily used library functions to save
6004 the frame setup time. @value{GDBN} has limited facilities for dealing
6005 with these function invocations. If the innermost function invocation
6006 has no stack frame, @value{GDBN} nevertheless regards it as though
6007 it had a separate frame, which is numbered zero as usual, allowing
6008 correct tracing of the function call chain. However, @value{GDBN} has
6009 no provision for frameless functions elsewhere in the stack.
6012 @kindex frame@r{, command}
6013 @cindex current stack frame
6014 @item frame @var{args}
6015 The @code{frame} command allows you to move from one stack frame to another,
6016 and to print the stack frame you select. @var{args} may be either the
6017 address of the frame or the stack frame number. Without an argument,
6018 @code{frame} prints the current stack frame.
6020 @kindex select-frame
6021 @cindex selecting frame silently
6023 The @code{select-frame} command allows you to move from one stack frame
6024 to another without printing the frame. This is the silent version of
6032 @cindex call stack traces
6033 A backtrace is a summary of how your program got where it is. It shows one
6034 line per frame, for many frames, starting with the currently executing
6035 frame (frame zero), followed by its caller (frame one), and on up the
6040 @kindex bt @r{(@code{backtrace})}
6043 Print a backtrace of the entire stack: one line per frame for all
6044 frames in the stack.
6046 You can stop the backtrace at any time by typing the system interrupt
6047 character, normally @kbd{Ctrl-c}.
6049 @item backtrace @var{n}
6051 Similar, but print only the innermost @var{n} frames.
6053 @item backtrace -@var{n}
6055 Similar, but print only the outermost @var{n} frames.
6057 @item backtrace full
6059 @itemx bt full @var{n}
6060 @itemx bt full -@var{n}
6061 Print the values of the local variables also. @var{n} specifies the
6062 number of frames to print, as described above.
6067 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6068 are additional aliases for @code{backtrace}.
6070 @cindex multiple threads, backtrace
6071 In a multi-threaded program, @value{GDBN} by default shows the
6072 backtrace only for the current thread. To display the backtrace for
6073 several or all of the threads, use the command @code{thread apply}
6074 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6075 apply all backtrace}, @value{GDBN} will display the backtrace for all
6076 the threads; this is handy when you debug a core dump of a
6077 multi-threaded program.
6079 Each line in the backtrace shows the frame number and the function name.
6080 The program counter value is also shown---unless you use @code{set
6081 print address off}. The backtrace also shows the source file name and
6082 line number, as well as the arguments to the function. The program
6083 counter value is omitted if it is at the beginning of the code for that
6086 Here is an example of a backtrace. It was made with the command
6087 @samp{bt 3}, so it shows the innermost three frames.
6091 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6093 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6094 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6096 (More stack frames follow...)
6101 The display for frame zero does not begin with a program counter
6102 value, indicating that your program has stopped at the beginning of the
6103 code for line @code{993} of @code{builtin.c}.
6106 The value of parameter @code{data} in frame 1 has been replaced by
6107 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6108 only if it is a scalar (integer, pointer, enumeration, etc). See command
6109 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6110 on how to configure the way function parameter values are printed.
6112 @cindex optimized out, in backtrace
6113 @cindex function call arguments, optimized out
6114 If your program was compiled with optimizations, some compilers will
6115 optimize away arguments passed to functions if those arguments are
6116 never used after the call. Such optimizations generate code that
6117 passes arguments through registers, but doesn't store those arguments
6118 in the stack frame. @value{GDBN} has no way of displaying such
6119 arguments in stack frames other than the innermost one. Here's what
6120 such a backtrace might look like:
6124 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6126 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6127 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6129 (More stack frames follow...)
6134 The values of arguments that were not saved in their stack frames are
6135 shown as @samp{<optimized out>}.
6137 If you need to display the values of such optimized-out arguments,
6138 either deduce that from other variables whose values depend on the one
6139 you are interested in, or recompile without optimizations.
6141 @cindex backtrace beyond @code{main} function
6142 @cindex program entry point
6143 @cindex startup code, and backtrace
6144 Most programs have a standard user entry point---a place where system
6145 libraries and startup code transition into user code. For C this is
6146 @code{main}@footnote{
6147 Note that embedded programs (the so-called ``free-standing''
6148 environment) are not required to have a @code{main} function as the
6149 entry point. They could even have multiple entry points.}.
6150 When @value{GDBN} finds the entry function in a backtrace
6151 it will terminate the backtrace, to avoid tracing into highly
6152 system-specific (and generally uninteresting) code.
6154 If you need to examine the startup code, or limit the number of levels
6155 in a backtrace, you can change this behavior:
6158 @item set backtrace past-main
6159 @itemx set backtrace past-main on
6160 @kindex set backtrace
6161 Backtraces will continue past the user entry point.
6163 @item set backtrace past-main off
6164 Backtraces will stop when they encounter the user entry point. This is the
6167 @item show backtrace past-main
6168 @kindex show backtrace
6169 Display the current user entry point backtrace policy.
6171 @item set backtrace past-entry
6172 @itemx set backtrace past-entry on
6173 Backtraces will continue past the internal entry point of an application.
6174 This entry point is encoded by the linker when the application is built,
6175 and is likely before the user entry point @code{main} (or equivalent) is called.
6177 @item set backtrace past-entry off
6178 Backtraces will stop when they encounter the internal entry point of an
6179 application. This is the default.
6181 @item show backtrace past-entry
6182 Display the current internal entry point backtrace policy.
6184 @item set backtrace limit @var{n}
6185 @itemx set backtrace limit 0
6186 @cindex backtrace limit
6187 Limit the backtrace to @var{n} levels. A value of zero means
6190 @item show backtrace limit
6191 Display the current limit on backtrace levels.
6195 @section Selecting a Frame
6197 Most commands for examining the stack and other data in your program work on
6198 whichever stack frame is selected at the moment. Here are the commands for
6199 selecting a stack frame; all of them finish by printing a brief description
6200 of the stack frame just selected.
6203 @kindex frame@r{, selecting}
6204 @kindex f @r{(@code{frame})}
6207 Select frame number @var{n}. Recall that frame zero is the innermost
6208 (currently executing) frame, frame one is the frame that called the
6209 innermost one, and so on. The highest-numbered frame is the one for
6212 @item frame @var{addr}
6214 Select the frame at address @var{addr}. This is useful mainly if the
6215 chaining of stack frames has been damaged by a bug, making it
6216 impossible for @value{GDBN} to assign numbers properly to all frames. In
6217 addition, this can be useful when your program has multiple stacks and
6218 switches between them.
6220 On the SPARC architecture, @code{frame} needs two addresses to
6221 select an arbitrary frame: a frame pointer and a stack pointer.
6223 On the MIPS and Alpha architecture, it needs two addresses: a stack
6224 pointer and a program counter.
6226 On the 29k architecture, it needs three addresses: a register stack
6227 pointer, a program counter, and a memory stack pointer.
6231 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6232 advances toward the outermost frame, to higher frame numbers, to frames
6233 that have existed longer. @var{n} defaults to one.
6236 @kindex do @r{(@code{down})}
6238 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6239 advances toward the innermost frame, to lower frame numbers, to frames
6240 that were created more recently. @var{n} defaults to one. You may
6241 abbreviate @code{down} as @code{do}.
6244 All of these commands end by printing two lines of output describing the
6245 frame. The first line shows the frame number, the function name, the
6246 arguments, and the source file and line number of execution in that
6247 frame. The second line shows the text of that source line.
6255 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6257 10 read_input_file (argv[i]);
6261 After such a printout, the @code{list} command with no arguments
6262 prints ten lines centered on the point of execution in the frame.
6263 You can also edit the program at the point of execution with your favorite
6264 editing program by typing @code{edit}.
6265 @xref{List, ,Printing Source Lines},
6269 @kindex down-silently
6271 @item up-silently @var{n}
6272 @itemx down-silently @var{n}
6273 These two commands are variants of @code{up} and @code{down},
6274 respectively; they differ in that they do their work silently, without
6275 causing display of the new frame. They are intended primarily for use
6276 in @value{GDBN} command scripts, where the output might be unnecessary and
6281 @section Information About a Frame
6283 There are several other commands to print information about the selected
6289 When used without any argument, this command does not change which
6290 frame is selected, but prints a brief description of the currently
6291 selected stack frame. It can be abbreviated @code{f}. With an
6292 argument, this command is used to select a stack frame.
6293 @xref{Selection, ,Selecting a Frame}.
6296 @kindex info f @r{(@code{info frame})}
6299 This command prints a verbose description of the selected stack frame,
6304 the address of the frame
6306 the address of the next frame down (called by this frame)
6308 the address of the next frame up (caller of this frame)
6310 the language in which the source code corresponding to this frame is written
6312 the address of the frame's arguments
6314 the address of the frame's local variables
6316 the program counter saved in it (the address of execution in the caller frame)
6318 which registers were saved in the frame
6321 @noindent The verbose description is useful when
6322 something has gone wrong that has made the stack format fail to fit
6323 the usual conventions.
6325 @item info frame @var{addr}
6326 @itemx info f @var{addr}
6327 Print a verbose description of the frame at address @var{addr}, without
6328 selecting that frame. The selected frame remains unchanged by this
6329 command. This requires the same kind of address (more than one for some
6330 architectures) that you specify in the @code{frame} command.
6331 @xref{Selection, ,Selecting a Frame}.
6335 Print the arguments of the selected frame, each on a separate line.
6339 Print the local variables of the selected frame, each on a separate
6340 line. These are all variables (declared either static or automatic)
6341 accessible at the point of execution of the selected frame.
6344 @cindex catch exceptions, list active handlers
6345 @cindex exception handlers, how to list
6347 Print a list of all the exception handlers that are active in the
6348 current stack frame at the current point of execution. To see other
6349 exception handlers, visit the associated frame (using the @code{up},
6350 @code{down}, or @code{frame} commands); then type @code{info catch}.
6351 @xref{Set Catchpoints, , Setting Catchpoints}.
6357 @chapter Examining Source Files
6359 @value{GDBN} can print parts of your program's source, since the debugging
6360 information recorded in the program tells @value{GDBN} what source files were
6361 used to build it. When your program stops, @value{GDBN} spontaneously prints
6362 the line where it stopped. Likewise, when you select a stack frame
6363 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6364 execution in that frame has stopped. You can print other portions of
6365 source files by explicit command.
6367 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6368 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6369 @value{GDBN} under @sc{gnu} Emacs}.
6372 * List:: Printing source lines
6373 * Specify Location:: How to specify code locations
6374 * Edit:: Editing source files
6375 * Search:: Searching source files
6376 * Source Path:: Specifying source directories
6377 * Machine Code:: Source and machine code
6381 @section Printing Source Lines
6384 @kindex l @r{(@code{list})}
6385 To print lines from a source file, use the @code{list} command
6386 (abbreviated @code{l}). By default, ten lines are printed.
6387 There are several ways to specify what part of the file you want to
6388 print; see @ref{Specify Location}, for the full list.
6390 Here are the forms of the @code{list} command most commonly used:
6393 @item list @var{linenum}
6394 Print lines centered around line number @var{linenum} in the
6395 current source file.
6397 @item list @var{function}
6398 Print lines centered around the beginning of function
6402 Print more lines. If the last lines printed were printed with a
6403 @code{list} command, this prints lines following the last lines
6404 printed; however, if the last line printed was a solitary line printed
6405 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6406 Stack}), this prints lines centered around that line.
6409 Print lines just before the lines last printed.
6412 @cindex @code{list}, how many lines to display
6413 By default, @value{GDBN} prints ten source lines with any of these forms of
6414 the @code{list} command. You can change this using @code{set listsize}:
6417 @kindex set listsize
6418 @item set listsize @var{count}
6419 Make the @code{list} command display @var{count} source lines (unless
6420 the @code{list} argument explicitly specifies some other number).
6422 @kindex show listsize
6424 Display the number of lines that @code{list} prints.
6427 Repeating a @code{list} command with @key{RET} discards the argument,
6428 so it is equivalent to typing just @code{list}. This is more useful
6429 than listing the same lines again. An exception is made for an
6430 argument of @samp{-}; that argument is preserved in repetition so that
6431 each repetition moves up in the source file.
6433 In general, the @code{list} command expects you to supply zero, one or two
6434 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6435 of writing them (@pxref{Specify Location}), but the effect is always
6436 to specify some source line.
6438 Here is a complete description of the possible arguments for @code{list}:
6441 @item list @var{linespec}
6442 Print lines centered around the line specified by @var{linespec}.
6444 @item list @var{first},@var{last}
6445 Print lines from @var{first} to @var{last}. Both arguments are
6446 linespecs. When a @code{list} command has two linespecs, and the
6447 source file of the second linespec is omitted, this refers to
6448 the same source file as the first linespec.
6450 @item list ,@var{last}
6451 Print lines ending with @var{last}.
6453 @item list @var{first},
6454 Print lines starting with @var{first}.
6457 Print lines just after the lines last printed.
6460 Print lines just before the lines last printed.
6463 As described in the preceding table.
6466 @node Specify Location
6467 @section Specifying a Location
6468 @cindex specifying location
6471 Several @value{GDBN} commands accept arguments that specify a location
6472 of your program's code. Since @value{GDBN} is a source-level
6473 debugger, a location usually specifies some line in the source code;
6474 for that reason, locations are also known as @dfn{linespecs}.
6476 Here are all the different ways of specifying a code location that
6477 @value{GDBN} understands:
6481 Specifies the line number @var{linenum} of the current source file.
6484 @itemx +@var{offset}
6485 Specifies the line @var{offset} lines before or after the @dfn{current
6486 line}. For the @code{list} command, the current line is the last one
6487 printed; for the breakpoint commands, this is the line at which
6488 execution stopped in the currently selected @dfn{stack frame}
6489 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6490 used as the second of the two linespecs in a @code{list} command,
6491 this specifies the line @var{offset} lines up or down from the first
6494 @item @var{filename}:@var{linenum}
6495 Specifies the line @var{linenum} in the source file @var{filename}.
6497 @item @var{function}
6498 Specifies the line that begins the body of the function @var{function}.
6499 For example, in C, this is the line with the open brace.
6501 @item @var{function}:@var{label}
6502 Specifies the line where @var{label} appears in @var{function}.
6504 @item @var{filename}:@var{function}
6505 Specifies the line that begins the body of the function @var{function}
6506 in the file @var{filename}. You only need the file name with a
6507 function name to avoid ambiguity when there are identically named
6508 functions in different source files.
6511 Specifies the line at which the label named @var{label} appears.
6512 @value{GDBN} searches for the label in the function corresponding to
6513 the currently selected stack frame. If there is no current selected
6514 stack frame (for instance, if the inferior is not running), then
6515 @value{GDBN} will not search for a label.
6517 @item *@var{address}
6518 Specifies the program address @var{address}. For line-oriented
6519 commands, such as @code{list} and @code{edit}, this specifies a source
6520 line that contains @var{address}. For @code{break} and other
6521 breakpoint oriented commands, this can be used to set breakpoints in
6522 parts of your program which do not have debugging information or
6525 Here @var{address} may be any expression valid in the current working
6526 language (@pxref{Languages, working language}) that specifies a code
6527 address. In addition, as a convenience, @value{GDBN} extends the
6528 semantics of expressions used in locations to cover the situations
6529 that frequently happen during debugging. Here are the various forms
6533 @item @var{expression}
6534 Any expression valid in the current working language.
6536 @item @var{funcaddr}
6537 An address of a function or procedure derived from its name. In C,
6538 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6539 simply the function's name @var{function} (and actually a special case
6540 of a valid expression). In Pascal and Modula-2, this is
6541 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6542 (although the Pascal form also works).
6544 This form specifies the address of the function's first instruction,
6545 before the stack frame and arguments have been set up.
6547 @item '@var{filename}'::@var{funcaddr}
6548 Like @var{funcaddr} above, but also specifies the name of the source
6549 file explicitly. This is useful if the name of the function does not
6550 specify the function unambiguously, e.g., if there are several
6551 functions with identical names in different source files.
6558 @section Editing Source Files
6559 @cindex editing source files
6562 @kindex e @r{(@code{edit})}
6563 To edit the lines in a source file, use the @code{edit} command.
6564 The editing program of your choice
6565 is invoked with the current line set to
6566 the active line in the program.
6567 Alternatively, there are several ways to specify what part of the file you
6568 want to print if you want to see other parts of the program:
6571 @item edit @var{location}
6572 Edit the source file specified by @code{location}. Editing starts at
6573 that @var{location}, e.g., at the specified source line of the
6574 specified file. @xref{Specify Location}, for all the possible forms
6575 of the @var{location} argument; here are the forms of the @code{edit}
6576 command most commonly used:
6579 @item edit @var{number}
6580 Edit the current source file with @var{number} as the active line number.
6582 @item edit @var{function}
6583 Edit the file containing @var{function} at the beginning of its definition.
6588 @subsection Choosing your Editor
6589 You can customize @value{GDBN} to use any editor you want
6591 The only restriction is that your editor (say @code{ex}), recognizes the
6592 following command-line syntax:
6594 ex +@var{number} file
6596 The optional numeric value +@var{number} specifies the number of the line in
6597 the file where to start editing.}.
6598 By default, it is @file{@value{EDITOR}}, but you can change this
6599 by setting the environment variable @code{EDITOR} before using
6600 @value{GDBN}. For example, to configure @value{GDBN} to use the
6601 @code{vi} editor, you could use these commands with the @code{sh} shell:
6607 or in the @code{csh} shell,
6609 setenv EDITOR /usr/bin/vi
6614 @section Searching Source Files
6615 @cindex searching source files
6617 There are two commands for searching through the current source file for a
6622 @kindex forward-search
6623 @item forward-search @var{regexp}
6624 @itemx search @var{regexp}
6625 The command @samp{forward-search @var{regexp}} checks each line,
6626 starting with the one following the last line listed, for a match for
6627 @var{regexp}. It lists the line that is found. You can use the
6628 synonym @samp{search @var{regexp}} or abbreviate the command name as
6631 @kindex reverse-search
6632 @item reverse-search @var{regexp}
6633 The command @samp{reverse-search @var{regexp}} checks each line, starting
6634 with the one before the last line listed and going backward, for a match
6635 for @var{regexp}. It lists the line that is found. You can abbreviate
6636 this command as @code{rev}.
6640 @section Specifying Source Directories
6643 @cindex directories for source files
6644 Executable programs sometimes do not record the directories of the source
6645 files from which they were compiled, just the names. Even when they do,
6646 the directories could be moved between the compilation and your debugging
6647 session. @value{GDBN} has a list of directories to search for source files;
6648 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6649 it tries all the directories in the list, in the order they are present
6650 in the list, until it finds a file with the desired name.
6652 For example, suppose an executable references the file
6653 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6654 @file{/mnt/cross}. The file is first looked up literally; if this
6655 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6656 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6657 message is printed. @value{GDBN} does not look up the parts of the
6658 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6659 Likewise, the subdirectories of the source path are not searched: if
6660 the source path is @file{/mnt/cross}, and the binary refers to
6661 @file{foo.c}, @value{GDBN} would not find it under
6662 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6664 Plain file names, relative file names with leading directories, file
6665 names containing dots, etc.@: are all treated as described above; for
6666 instance, if the source path is @file{/mnt/cross}, and the source file
6667 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6668 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6669 that---@file{/mnt/cross/foo.c}.
6671 Note that the executable search path is @emph{not} used to locate the
6674 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6675 any information it has cached about where source files are found and where
6676 each line is in the file.
6680 When you start @value{GDBN}, its source path includes only @samp{cdir}
6681 and @samp{cwd}, in that order.
6682 To add other directories, use the @code{directory} command.
6684 The search path is used to find both program source files and @value{GDBN}
6685 script files (read using the @samp{-command} option and @samp{source} command).
6687 In addition to the source path, @value{GDBN} provides a set of commands
6688 that manage a list of source path substitution rules. A @dfn{substitution
6689 rule} specifies how to rewrite source directories stored in the program's
6690 debug information in case the sources were moved to a different
6691 directory between compilation and debugging. A rule is made of
6692 two strings, the first specifying what needs to be rewritten in
6693 the path, and the second specifying how it should be rewritten.
6694 In @ref{set substitute-path}, we name these two parts @var{from} and
6695 @var{to} respectively. @value{GDBN} does a simple string replacement
6696 of @var{from} with @var{to} at the start of the directory part of the
6697 source file name, and uses that result instead of the original file
6698 name to look up the sources.
6700 Using the previous example, suppose the @file{foo-1.0} tree has been
6701 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6702 @value{GDBN} to replace @file{/usr/src} in all source path names with
6703 @file{/mnt/cross}. The first lookup will then be
6704 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6705 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6706 substitution rule, use the @code{set substitute-path} command
6707 (@pxref{set substitute-path}).
6709 To avoid unexpected substitution results, a rule is applied only if the
6710 @var{from} part of the directory name ends at a directory separator.
6711 For instance, a rule substituting @file{/usr/source} into
6712 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6713 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6714 is applied only at the beginning of the directory name, this rule will
6715 not be applied to @file{/root/usr/source/baz.c} either.
6717 In many cases, you can achieve the same result using the @code{directory}
6718 command. However, @code{set substitute-path} can be more efficient in
6719 the case where the sources are organized in a complex tree with multiple
6720 subdirectories. With the @code{directory} command, you need to add each
6721 subdirectory of your project. If you moved the entire tree while
6722 preserving its internal organization, then @code{set substitute-path}
6723 allows you to direct the debugger to all the sources with one single
6726 @code{set substitute-path} is also more than just a shortcut command.
6727 The source path is only used if the file at the original location no
6728 longer exists. On the other hand, @code{set substitute-path} modifies
6729 the debugger behavior to look at the rewritten location instead. So, if
6730 for any reason a source file that is not relevant to your executable is
6731 located at the original location, a substitution rule is the only
6732 method available to point @value{GDBN} at the new location.
6734 @cindex @samp{--with-relocated-sources}
6735 @cindex default source path substitution
6736 You can configure a default source path substitution rule by
6737 configuring @value{GDBN} with the
6738 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6739 should be the name of a directory under @value{GDBN}'s configured
6740 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6741 directory names in debug information under @var{dir} will be adjusted
6742 automatically if the installed @value{GDBN} is moved to a new
6743 location. This is useful if @value{GDBN}, libraries or executables
6744 with debug information and corresponding source code are being moved
6748 @item directory @var{dirname} @dots{}
6749 @item dir @var{dirname} @dots{}
6750 Add directory @var{dirname} to the front of the source path. Several
6751 directory names may be given to this command, separated by @samp{:}
6752 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6753 part of absolute file names) or
6754 whitespace. You may specify a directory that is already in the source
6755 path; this moves it forward, so @value{GDBN} searches it sooner.
6759 @vindex $cdir@r{, convenience variable}
6760 @vindex $cwd@r{, convenience variable}
6761 @cindex compilation directory
6762 @cindex current directory
6763 @cindex working directory
6764 @cindex directory, current
6765 @cindex directory, compilation
6766 You can use the string @samp{$cdir} to refer to the compilation
6767 directory (if one is recorded), and @samp{$cwd} to refer to the current
6768 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6769 tracks the current working directory as it changes during your @value{GDBN}
6770 session, while the latter is immediately expanded to the current
6771 directory at the time you add an entry to the source path.
6774 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6776 @c RET-repeat for @code{directory} is explicitly disabled, but since
6777 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6779 @item set directories @var{path-list}
6780 @kindex set directories
6781 Set the source path to @var{path-list}.
6782 @samp{$cdir:$cwd} are added if missing.
6784 @item show directories
6785 @kindex show directories
6786 Print the source path: show which directories it contains.
6788 @anchor{set substitute-path}
6789 @item set substitute-path @var{from} @var{to}
6790 @kindex set substitute-path
6791 Define a source path substitution rule, and add it at the end of the
6792 current list of existing substitution rules. If a rule with the same
6793 @var{from} was already defined, then the old rule is also deleted.
6795 For example, if the file @file{/foo/bar/baz.c} was moved to
6796 @file{/mnt/cross/baz.c}, then the command
6799 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6803 will tell @value{GDBN} to replace @samp{/usr/src} with
6804 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6805 @file{baz.c} even though it was moved.
6807 In the case when more than one substitution rule have been defined,
6808 the rules are evaluated one by one in the order where they have been
6809 defined. The first one matching, if any, is selected to perform
6812 For instance, if we had entered the following commands:
6815 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6816 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6820 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6821 @file{/mnt/include/defs.h} by using the first rule. However, it would
6822 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6823 @file{/mnt/src/lib/foo.c}.
6826 @item unset substitute-path [path]
6827 @kindex unset substitute-path
6828 If a path is specified, search the current list of substitution rules
6829 for a rule that would rewrite that path. Delete that rule if found.
6830 A warning is emitted by the debugger if no rule could be found.
6832 If no path is specified, then all substitution rules are deleted.
6834 @item show substitute-path [path]
6835 @kindex show substitute-path
6836 If a path is specified, then print the source path substitution rule
6837 which would rewrite that path, if any.
6839 If no path is specified, then print all existing source path substitution
6844 If your source path is cluttered with directories that are no longer of
6845 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6846 versions of source. You can correct the situation as follows:
6850 Use @code{directory} with no argument to reset the source path to its default value.
6853 Use @code{directory} with suitable arguments to reinstall the
6854 directories you want in the source path. You can add all the
6855 directories in one command.
6859 @section Source and Machine Code
6860 @cindex source line and its code address
6862 You can use the command @code{info line} to map source lines to program
6863 addresses (and vice versa), and the command @code{disassemble} to display
6864 a range of addresses as machine instructions. You can use the command
6865 @code{set disassemble-next-line} to set whether to disassemble next
6866 source line when execution stops. When run under @sc{gnu} Emacs
6867 mode, the @code{info line} command causes the arrow to point to the
6868 line specified. Also, @code{info line} prints addresses in symbolic form as
6873 @item info line @var{linespec}
6874 Print the starting and ending addresses of the compiled code for
6875 source line @var{linespec}. You can specify source lines in any of
6876 the ways documented in @ref{Specify Location}.
6879 For example, we can use @code{info line} to discover the location of
6880 the object code for the first line of function
6881 @code{m4_changequote}:
6883 @c FIXME: I think this example should also show the addresses in
6884 @c symbolic form, as they usually would be displayed.
6886 (@value{GDBP}) info line m4_changequote
6887 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6891 @cindex code address and its source line
6892 We can also inquire (using @code{*@var{addr}} as the form for
6893 @var{linespec}) what source line covers a particular address:
6895 (@value{GDBP}) info line *0x63ff
6896 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6899 @cindex @code{$_} and @code{info line}
6900 @cindex @code{x} command, default address
6901 @kindex x@r{(examine), and} info line
6902 After @code{info line}, the default address for the @code{x} command
6903 is changed to the starting address of the line, so that @samp{x/i} is
6904 sufficient to begin examining the machine code (@pxref{Memory,
6905 ,Examining Memory}). Also, this address is saved as the value of the
6906 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6911 @cindex assembly instructions
6912 @cindex instructions, assembly
6913 @cindex machine instructions
6914 @cindex listing machine instructions
6916 @itemx disassemble /m
6917 @itemx disassemble /r
6918 This specialized command dumps a range of memory as machine
6919 instructions. It can also print mixed source+disassembly by specifying
6920 the @code{/m} modifier and print the raw instructions in hex as well as
6921 in symbolic form by specifying the @code{/r}.
6922 The default memory range is the function surrounding the
6923 program counter of the selected frame. A single argument to this
6924 command is a program counter value; @value{GDBN} dumps the function
6925 surrounding this value. When two arguments are given, they should
6926 be separated by a comma, possibly surrounded by whitespace. The
6927 arguments specify a range of addresses to dump, in one of two forms:
6930 @item @var{start},@var{end}
6931 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6932 @item @var{start},+@var{length}
6933 the addresses from @var{start} (inclusive) to
6934 @code{@var{start}+@var{length}} (exclusive).
6938 When 2 arguments are specified, the name of the function is also
6939 printed (since there could be several functions in the given range).
6941 The argument(s) can be any expression yielding a numeric value, such as
6942 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6944 If the range of memory being disassembled contains current program counter,
6945 the instruction at that location is shown with a @code{=>} marker.
6948 The following example shows the disassembly of a range of addresses of
6949 HP PA-RISC 2.0 code:
6952 (@value{GDBP}) disas 0x32c4, 0x32e4
6953 Dump of assembler code from 0x32c4 to 0x32e4:
6954 0x32c4 <main+204>: addil 0,dp
6955 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6956 0x32cc <main+212>: ldil 0x3000,r31
6957 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6958 0x32d4 <main+220>: ldo 0(r31),rp
6959 0x32d8 <main+224>: addil -0x800,dp
6960 0x32dc <main+228>: ldo 0x588(r1),r26
6961 0x32e0 <main+232>: ldil 0x3000,r31
6962 End of assembler dump.
6965 Here is an example showing mixed source+assembly for Intel x86, when the
6966 program is stopped just after function prologue:
6969 (@value{GDBP}) disas /m main
6970 Dump of assembler code for function main:
6972 0x08048330 <+0>: push %ebp
6973 0x08048331 <+1>: mov %esp,%ebp
6974 0x08048333 <+3>: sub $0x8,%esp
6975 0x08048336 <+6>: and $0xfffffff0,%esp
6976 0x08048339 <+9>: sub $0x10,%esp
6978 6 printf ("Hello.\n");
6979 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6980 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6984 0x08048348 <+24>: mov $0x0,%eax
6985 0x0804834d <+29>: leave
6986 0x0804834e <+30>: ret
6988 End of assembler dump.
6991 Here is another example showing raw instructions in hex for AMD x86-64,
6994 (gdb) disas /r 0x400281,+10
6995 Dump of assembler code from 0x400281 to 0x40028b:
6996 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6997 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6998 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6999 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7000 End of assembler dump.
7003 Some architectures have more than one commonly-used set of instruction
7004 mnemonics or other syntax.
7006 For programs that were dynamically linked and use shared libraries,
7007 instructions that call functions or branch to locations in the shared
7008 libraries might show a seemingly bogus location---it's actually a
7009 location of the relocation table. On some architectures, @value{GDBN}
7010 might be able to resolve these to actual function names.
7013 @kindex set disassembly-flavor
7014 @cindex Intel disassembly flavor
7015 @cindex AT&T disassembly flavor
7016 @item set disassembly-flavor @var{instruction-set}
7017 Select the instruction set to use when disassembling the
7018 program via the @code{disassemble} or @code{x/i} commands.
7020 Currently this command is only defined for the Intel x86 family. You
7021 can set @var{instruction-set} to either @code{intel} or @code{att}.
7022 The default is @code{att}, the AT&T flavor used by default by Unix
7023 assemblers for x86-based targets.
7025 @kindex show disassembly-flavor
7026 @item show disassembly-flavor
7027 Show the current setting of the disassembly flavor.
7031 @kindex set disassemble-next-line
7032 @kindex show disassemble-next-line
7033 @item set disassemble-next-line
7034 @itemx show disassemble-next-line
7035 Control whether or not @value{GDBN} will disassemble the next source
7036 line or instruction when execution stops. If ON, @value{GDBN} will
7037 display disassembly of the next source line when execution of the
7038 program being debugged stops. This is @emph{in addition} to
7039 displaying the source line itself, which @value{GDBN} always does if
7040 possible. If the next source line cannot be displayed for some reason
7041 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7042 info in the debug info), @value{GDBN} will display disassembly of the
7043 next @emph{instruction} instead of showing the next source line. If
7044 AUTO, @value{GDBN} will display disassembly of next instruction only
7045 if the source line cannot be displayed. This setting causes
7046 @value{GDBN} to display some feedback when you step through a function
7047 with no line info or whose source file is unavailable. The default is
7048 OFF, which means never display the disassembly of the next line or
7054 @chapter Examining Data
7056 @cindex printing data
7057 @cindex examining data
7060 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
7061 @c document because it is nonstandard... Under Epoch it displays in a
7062 @c different window or something like that.
7063 The usual way to examine data in your program is with the @code{print}
7064 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7065 evaluates and prints the value of an expression of the language your
7066 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7067 Different Languages}). It may also print the expression using a
7068 Python-based pretty-printer (@pxref{Pretty Printing}).
7071 @item print @var{expr}
7072 @itemx print /@var{f} @var{expr}
7073 @var{expr} is an expression (in the source language). By default the
7074 value of @var{expr} is printed in a format appropriate to its data type;
7075 you can choose a different format by specifying @samp{/@var{f}}, where
7076 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7080 @itemx print /@var{f}
7081 @cindex reprint the last value
7082 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7083 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7084 conveniently inspect the same value in an alternative format.
7087 A more low-level way of examining data is with the @code{x} command.
7088 It examines data in memory at a specified address and prints it in a
7089 specified format. @xref{Memory, ,Examining Memory}.
7091 If you are interested in information about types, or about how the
7092 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7093 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7097 * Expressions:: Expressions
7098 * Ambiguous Expressions:: Ambiguous Expressions
7099 * Variables:: Program variables
7100 * Arrays:: Artificial arrays
7101 * Output Formats:: Output formats
7102 * Memory:: Examining memory
7103 * Auto Display:: Automatic display
7104 * Print Settings:: Print settings
7105 * Pretty Printing:: Python pretty printing
7106 * Value History:: Value history
7107 * Convenience Vars:: Convenience variables
7108 * Registers:: Registers
7109 * Floating Point Hardware:: Floating point hardware
7110 * Vector Unit:: Vector Unit
7111 * OS Information:: Auxiliary data provided by operating system
7112 * Memory Region Attributes:: Memory region attributes
7113 * Dump/Restore Files:: Copy between memory and a file
7114 * Core File Generation:: Cause a program dump its core
7115 * Character Sets:: Debugging programs that use a different
7116 character set than GDB does
7117 * Caching Remote Data:: Data caching for remote targets
7118 * Searching Memory:: Searching memory for a sequence of bytes
7122 @section Expressions
7125 @code{print} and many other @value{GDBN} commands accept an expression and
7126 compute its value. Any kind of constant, variable or operator defined
7127 by the programming language you are using is valid in an expression in
7128 @value{GDBN}. This includes conditional expressions, function calls,
7129 casts, and string constants. It also includes preprocessor macros, if
7130 you compiled your program to include this information; see
7133 @cindex arrays in expressions
7134 @value{GDBN} supports array constants in expressions input by
7135 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7136 you can use the command @code{print @{1, 2, 3@}} to create an array
7137 of three integers. If you pass an array to a function or assign it
7138 to a program variable, @value{GDBN} copies the array to memory that
7139 is @code{malloc}ed in the target program.
7141 Because C is so widespread, most of the expressions shown in examples in
7142 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7143 Languages}, for information on how to use expressions in other
7146 In this section, we discuss operators that you can use in @value{GDBN}
7147 expressions regardless of your programming language.
7149 @cindex casts, in expressions
7150 Casts are supported in all languages, not just in C, because it is so
7151 useful to cast a number into a pointer in order to examine a structure
7152 at that address in memory.
7153 @c FIXME: casts supported---Mod2 true?
7155 @value{GDBN} supports these operators, in addition to those common
7156 to programming languages:
7160 @samp{@@} is a binary operator for treating parts of memory as arrays.
7161 @xref{Arrays, ,Artificial Arrays}, for more information.
7164 @samp{::} allows you to specify a variable in terms of the file or
7165 function where it is defined. @xref{Variables, ,Program Variables}.
7167 @cindex @{@var{type}@}
7168 @cindex type casting memory
7169 @cindex memory, viewing as typed object
7170 @cindex casts, to view memory
7171 @item @{@var{type}@} @var{addr}
7172 Refers to an object of type @var{type} stored at address @var{addr} in
7173 memory. @var{addr} may be any expression whose value is an integer or
7174 pointer (but parentheses are required around binary operators, just as in
7175 a cast). This construct is allowed regardless of what kind of data is
7176 normally supposed to reside at @var{addr}.
7179 @node Ambiguous Expressions
7180 @section Ambiguous Expressions
7181 @cindex ambiguous expressions
7183 Expressions can sometimes contain some ambiguous elements. For instance,
7184 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7185 a single function name to be defined several times, for application in
7186 different contexts. This is called @dfn{overloading}. Another example
7187 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7188 templates and is typically instantiated several times, resulting in
7189 the same function name being defined in different contexts.
7191 In some cases and depending on the language, it is possible to adjust
7192 the expression to remove the ambiguity. For instance in C@t{++}, you
7193 can specify the signature of the function you want to break on, as in
7194 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7195 qualified name of your function often makes the expression unambiguous
7198 When an ambiguity that needs to be resolved is detected, the debugger
7199 has the capability to display a menu of numbered choices for each
7200 possibility, and then waits for the selection with the prompt @samp{>}.
7201 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7202 aborts the current command. If the command in which the expression was
7203 used allows more than one choice to be selected, the next option in the
7204 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7207 For example, the following session excerpt shows an attempt to set a
7208 breakpoint at the overloaded symbol @code{String::after}.
7209 We choose three particular definitions of that function name:
7211 @c FIXME! This is likely to change to show arg type lists, at least
7214 (@value{GDBP}) b String::after
7217 [2] file:String.cc; line number:867
7218 [3] file:String.cc; line number:860
7219 [4] file:String.cc; line number:875
7220 [5] file:String.cc; line number:853
7221 [6] file:String.cc; line number:846
7222 [7] file:String.cc; line number:735
7224 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7225 Breakpoint 2 at 0xb344: file String.cc, line 875.
7226 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7227 Multiple breakpoints were set.
7228 Use the "delete" command to delete unwanted
7235 @kindex set multiple-symbols
7236 @item set multiple-symbols @var{mode}
7237 @cindex multiple-symbols menu
7239 This option allows you to adjust the debugger behavior when an expression
7242 By default, @var{mode} is set to @code{all}. If the command with which
7243 the expression is used allows more than one choice, then @value{GDBN}
7244 automatically selects all possible choices. For instance, inserting
7245 a breakpoint on a function using an ambiguous name results in a breakpoint
7246 inserted on each possible match. However, if a unique choice must be made,
7247 then @value{GDBN} uses the menu to help you disambiguate the expression.
7248 For instance, printing the address of an overloaded function will result
7249 in the use of the menu.
7251 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7252 when an ambiguity is detected.
7254 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7255 an error due to the ambiguity and the command is aborted.
7257 @kindex show multiple-symbols
7258 @item show multiple-symbols
7259 Show the current value of the @code{multiple-symbols} setting.
7263 @section Program Variables
7265 The most common kind of expression to use is the name of a variable
7268 Variables in expressions are understood in the selected stack frame
7269 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7273 global (or file-static)
7280 visible according to the scope rules of the
7281 programming language from the point of execution in that frame
7284 @noindent This means that in the function
7299 you can examine and use the variable @code{a} whenever your program is
7300 executing within the function @code{foo}, but you can only use or
7301 examine the variable @code{b} while your program is executing inside
7302 the block where @code{b} is declared.
7304 @cindex variable name conflict
7305 There is an exception: you can refer to a variable or function whose
7306 scope is a single source file even if the current execution point is not
7307 in this file. But it is possible to have more than one such variable or
7308 function with the same name (in different source files). If that
7309 happens, referring to that name has unpredictable effects. If you wish,
7310 you can specify a static variable in a particular function or file,
7311 using the colon-colon (@code{::}) notation:
7313 @cindex colon-colon, context for variables/functions
7315 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7316 @cindex @code{::}, context for variables/functions
7319 @var{file}::@var{variable}
7320 @var{function}::@var{variable}
7324 Here @var{file} or @var{function} is the name of the context for the
7325 static @var{variable}. In the case of file names, you can use quotes to
7326 make sure @value{GDBN} parses the file name as a single word---for example,
7327 to print a global value of @code{x} defined in @file{f2.c}:
7330 (@value{GDBP}) p 'f2.c'::x
7333 @cindex C@t{++} scope resolution
7334 This use of @samp{::} is very rarely in conflict with the very similar
7335 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7336 scope resolution operator in @value{GDBN} expressions.
7337 @c FIXME: Um, so what happens in one of those rare cases where it's in
7340 @cindex wrong values
7341 @cindex variable values, wrong
7342 @cindex function entry/exit, wrong values of variables
7343 @cindex optimized code, wrong values of variables
7345 @emph{Warning:} Occasionally, a local variable may appear to have the
7346 wrong value at certain points in a function---just after entry to a new
7347 scope, and just before exit.
7349 You may see this problem when you are stepping by machine instructions.
7350 This is because, on most machines, it takes more than one instruction to
7351 set up a stack frame (including local variable definitions); if you are
7352 stepping by machine instructions, variables may appear to have the wrong
7353 values until the stack frame is completely built. On exit, it usually
7354 also takes more than one machine instruction to destroy a stack frame;
7355 after you begin stepping through that group of instructions, local
7356 variable definitions may be gone.
7358 This may also happen when the compiler does significant optimizations.
7359 To be sure of always seeing accurate values, turn off all optimization
7362 @cindex ``No symbol "foo" in current context''
7363 Another possible effect of compiler optimizations is to optimize
7364 unused variables out of existence, or assign variables to registers (as
7365 opposed to memory addresses). Depending on the support for such cases
7366 offered by the debug info format used by the compiler, @value{GDBN}
7367 might not be able to display values for such local variables. If that
7368 happens, @value{GDBN} will print a message like this:
7371 No symbol "foo" in current context.
7374 To solve such problems, either recompile without optimizations, or use a
7375 different debug info format, if the compiler supports several such
7376 formats. @xref{Compilation}, for more information on choosing compiler
7377 options. @xref{C, ,C and C@t{++}}, for more information about debug
7378 info formats that are best suited to C@t{++} programs.
7380 If you ask to print an object whose contents are unknown to
7381 @value{GDBN}, e.g., because its data type is not completely specified
7382 by the debug information, @value{GDBN} will say @samp{<incomplete
7383 type>}. @xref{Symbols, incomplete type}, for more about this.
7385 If you append @kbd{@@entry} string to a function parameter name you get its
7386 value at the time the function got called. If the value is not available an
7387 error message is printed. Entry values are available only with some compilers.
7388 Entry values are normally also printed at the function parameter list according
7389 to @ref{set print entry-values}.
7392 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7398 (gdb) print i@@entry
7402 Strings are identified as arrays of @code{char} values without specified
7403 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7404 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7405 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7406 defines literal string type @code{"char"} as @code{char} without a sign.
7411 signed char var1[] = "A";
7414 You get during debugging
7419 $2 = @{65 'A', 0 '\0'@}
7423 @section Artificial Arrays
7425 @cindex artificial array
7427 @kindex @@@r{, referencing memory as an array}
7428 It is often useful to print out several successive objects of the
7429 same type in memory; a section of an array, or an array of
7430 dynamically determined size for which only a pointer exists in the
7433 You can do this by referring to a contiguous span of memory as an
7434 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7435 operand of @samp{@@} should be the first element of the desired array
7436 and be an individual object. The right operand should be the desired length
7437 of the array. The result is an array value whose elements are all of
7438 the type of the left argument. The first element is actually the left
7439 argument; the second element comes from bytes of memory immediately
7440 following those that hold the first element, and so on. Here is an
7441 example. If a program says
7444 int *array = (int *) malloc (len * sizeof (int));
7448 you can print the contents of @code{array} with
7454 The left operand of @samp{@@} must reside in memory. Array values made
7455 with @samp{@@} in this way behave just like other arrays in terms of
7456 subscripting, and are coerced to pointers when used in expressions.
7457 Artificial arrays most often appear in expressions via the value history
7458 (@pxref{Value History, ,Value History}), after printing one out.
7460 Another way to create an artificial array is to use a cast.
7461 This re-interprets a value as if it were an array.
7462 The value need not be in memory:
7464 (@value{GDBP}) p/x (short[2])0x12345678
7465 $1 = @{0x1234, 0x5678@}
7468 As a convenience, if you leave the array length out (as in
7469 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7470 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7472 (@value{GDBP}) p/x (short[])0x12345678
7473 $2 = @{0x1234, 0x5678@}
7476 Sometimes the artificial array mechanism is not quite enough; in
7477 moderately complex data structures, the elements of interest may not
7478 actually be adjacent---for example, if you are interested in the values
7479 of pointers in an array. One useful work-around in this situation is
7480 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7481 Variables}) as a counter in an expression that prints the first
7482 interesting value, and then repeat that expression via @key{RET}. For
7483 instance, suppose you have an array @code{dtab} of pointers to
7484 structures, and you are interested in the values of a field @code{fv}
7485 in each structure. Here is an example of what you might type:
7495 @node Output Formats
7496 @section Output Formats
7498 @cindex formatted output
7499 @cindex output formats
7500 By default, @value{GDBN} prints a value according to its data type. Sometimes
7501 this is not what you want. For example, you might want to print a number
7502 in hex, or a pointer in decimal. Or you might want to view data in memory
7503 at a certain address as a character string or as an instruction. To do
7504 these things, specify an @dfn{output format} when you print a value.
7506 The simplest use of output formats is to say how to print a value
7507 already computed. This is done by starting the arguments of the
7508 @code{print} command with a slash and a format letter. The format
7509 letters supported are:
7513 Regard the bits of the value as an integer, and print the integer in
7517 Print as integer in signed decimal.
7520 Print as integer in unsigned decimal.
7523 Print as integer in octal.
7526 Print as integer in binary. The letter @samp{t} stands for ``two''.
7527 @footnote{@samp{b} cannot be used because these format letters are also
7528 used with the @code{x} command, where @samp{b} stands for ``byte'';
7529 see @ref{Memory,,Examining Memory}.}
7532 @cindex unknown address, locating
7533 @cindex locate address
7534 Print as an address, both absolute in hexadecimal and as an offset from
7535 the nearest preceding symbol. You can use this format used to discover
7536 where (in what function) an unknown address is located:
7539 (@value{GDBP}) p/a 0x54320
7540 $3 = 0x54320 <_initialize_vx+396>
7544 The command @code{info symbol 0x54320} yields similar results.
7545 @xref{Symbols, info symbol}.
7548 Regard as an integer and print it as a character constant. This
7549 prints both the numerical value and its character representation. The
7550 character representation is replaced with the octal escape @samp{\nnn}
7551 for characters outside the 7-bit @sc{ascii} range.
7553 Without this format, @value{GDBN} displays @code{char},
7554 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7555 constants. Single-byte members of vectors are displayed as integer
7559 Regard the bits of the value as a floating point number and print
7560 using typical floating point syntax.
7563 @cindex printing strings
7564 @cindex printing byte arrays
7565 Regard as a string, if possible. With this format, pointers to single-byte
7566 data are displayed as null-terminated strings and arrays of single-byte data
7567 are displayed as fixed-length strings. Other values are displayed in their
7570 Without this format, @value{GDBN} displays pointers to and arrays of
7571 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7572 strings. Single-byte members of a vector are displayed as an integer
7576 @cindex raw printing
7577 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7578 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7579 Printing}). This typically results in a higher-level display of the
7580 value's contents. The @samp{r} format bypasses any Python
7581 pretty-printer which might exist.
7584 For example, to print the program counter in hex (@pxref{Registers}), type
7591 Note that no space is required before the slash; this is because command
7592 names in @value{GDBN} cannot contain a slash.
7594 To reprint the last value in the value history with a different format,
7595 you can use the @code{print} command with just a format and no
7596 expression. For example, @samp{p/x} reprints the last value in hex.
7599 @section Examining Memory
7601 You can use the command @code{x} (for ``examine'') to examine memory in
7602 any of several formats, independently of your program's data types.
7604 @cindex examining memory
7606 @kindex x @r{(examine memory)}
7607 @item x/@var{nfu} @var{addr}
7610 Use the @code{x} command to examine memory.
7613 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7614 much memory to display and how to format it; @var{addr} is an
7615 expression giving the address where you want to start displaying memory.
7616 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7617 Several commands set convenient defaults for @var{addr}.
7620 @item @var{n}, the repeat count
7621 The repeat count is a decimal integer; the default is 1. It specifies
7622 how much memory (counting by units @var{u}) to display.
7623 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7626 @item @var{f}, the display format
7627 The display format is one of the formats used by @code{print}
7628 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7629 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7630 The default is @samp{x} (hexadecimal) initially. The default changes
7631 each time you use either @code{x} or @code{print}.
7633 @item @var{u}, the unit size
7634 The unit size is any of
7640 Halfwords (two bytes).
7642 Words (four bytes). This is the initial default.
7644 Giant words (eight bytes).
7647 Each time you specify a unit size with @code{x}, that size becomes the
7648 default unit the next time you use @code{x}. For the @samp{i} format,
7649 the unit size is ignored and is normally not written. For the @samp{s} format,
7650 the unit size defaults to @samp{b}, unless it is explicitly given.
7651 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7652 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7653 Note that the results depend on the programming language of the
7654 current compilation unit. If the language is C, the @samp{s}
7655 modifier will use the UTF-16 encoding while @samp{w} will use
7656 UTF-32. The encoding is set by the programming language and cannot
7659 @item @var{addr}, starting display address
7660 @var{addr} is the address where you want @value{GDBN} to begin displaying
7661 memory. The expression need not have a pointer value (though it may);
7662 it is always interpreted as an integer address of a byte of memory.
7663 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7664 @var{addr} is usually just after the last address examined---but several
7665 other commands also set the default address: @code{info breakpoints} (to
7666 the address of the last breakpoint listed), @code{info line} (to the
7667 starting address of a line), and @code{print} (if you use it to display
7668 a value from memory).
7671 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7672 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7673 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7674 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7675 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7677 Since the letters indicating unit sizes are all distinct from the
7678 letters specifying output formats, you do not have to remember whether
7679 unit size or format comes first; either order works. The output
7680 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7681 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7683 Even though the unit size @var{u} is ignored for the formats @samp{s}
7684 and @samp{i}, you might still want to use a count @var{n}; for example,
7685 @samp{3i} specifies that you want to see three machine instructions,
7686 including any operands. For convenience, especially when used with
7687 the @code{display} command, the @samp{i} format also prints branch delay
7688 slot instructions, if any, beyond the count specified, which immediately
7689 follow the last instruction that is within the count. The command
7690 @code{disassemble} gives an alternative way of inspecting machine
7691 instructions; see @ref{Machine Code,,Source and Machine Code}.
7693 All the defaults for the arguments to @code{x} are designed to make it
7694 easy to continue scanning memory with minimal specifications each time
7695 you use @code{x}. For example, after you have inspected three machine
7696 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7697 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7698 the repeat count @var{n} is used again; the other arguments default as
7699 for successive uses of @code{x}.
7701 When examining machine instructions, the instruction at current program
7702 counter is shown with a @code{=>} marker. For example:
7705 (@value{GDBP}) x/5i $pc-6
7706 0x804837f <main+11>: mov %esp,%ebp
7707 0x8048381 <main+13>: push %ecx
7708 0x8048382 <main+14>: sub $0x4,%esp
7709 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7710 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7713 @cindex @code{$_}, @code{$__}, and value history
7714 The addresses and contents printed by the @code{x} command are not saved
7715 in the value history because there is often too much of them and they
7716 would get in the way. Instead, @value{GDBN} makes these values available for
7717 subsequent use in expressions as values of the convenience variables
7718 @code{$_} and @code{$__}. After an @code{x} command, the last address
7719 examined is available for use in expressions in the convenience variable
7720 @code{$_}. The contents of that address, as examined, are available in
7721 the convenience variable @code{$__}.
7723 If the @code{x} command has a repeat count, the address and contents saved
7724 are from the last memory unit printed; this is not the same as the last
7725 address printed if several units were printed on the last line of output.
7727 @cindex remote memory comparison
7728 @cindex verify remote memory image
7729 When you are debugging a program running on a remote target machine
7730 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7731 remote machine's memory against the executable file you downloaded to
7732 the target. The @code{compare-sections} command is provided for such
7736 @kindex compare-sections
7737 @item compare-sections @r{[}@var{section-name}@r{]}
7738 Compare the data of a loadable section @var{section-name} in the
7739 executable file of the program being debugged with the same section in
7740 the remote machine's memory, and report any mismatches. With no
7741 arguments, compares all loadable sections. This command's
7742 availability depends on the target's support for the @code{"qCRC"}
7747 @section Automatic Display
7748 @cindex automatic display
7749 @cindex display of expressions
7751 If you find that you want to print the value of an expression frequently
7752 (to see how it changes), you might want to add it to the @dfn{automatic
7753 display list} so that @value{GDBN} prints its value each time your program stops.
7754 Each expression added to the list is given a number to identify it;
7755 to remove an expression from the list, you specify that number.
7756 The automatic display looks like this:
7760 3: bar[5] = (struct hack *) 0x3804
7764 This display shows item numbers, expressions and their current values. As with
7765 displays you request manually using @code{x} or @code{print}, you can
7766 specify the output format you prefer; in fact, @code{display} decides
7767 whether to use @code{print} or @code{x} depending your format
7768 specification---it uses @code{x} if you specify either the @samp{i}
7769 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7773 @item display @var{expr}
7774 Add the expression @var{expr} to the list of expressions to display
7775 each time your program stops. @xref{Expressions, ,Expressions}.
7777 @code{display} does not repeat if you press @key{RET} again after using it.
7779 @item display/@var{fmt} @var{expr}
7780 For @var{fmt} specifying only a display format and not a size or
7781 count, add the expression @var{expr} to the auto-display list but
7782 arrange to display it each time in the specified format @var{fmt}.
7783 @xref{Output Formats,,Output Formats}.
7785 @item display/@var{fmt} @var{addr}
7786 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7787 number of units, add the expression @var{addr} as a memory address to
7788 be examined each time your program stops. Examining means in effect
7789 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7792 For example, @samp{display/i $pc} can be helpful, to see the machine
7793 instruction about to be executed each time execution stops (@samp{$pc}
7794 is a common name for the program counter; @pxref{Registers, ,Registers}).
7797 @kindex delete display
7799 @item undisplay @var{dnums}@dots{}
7800 @itemx delete display @var{dnums}@dots{}
7801 Remove items from the list of expressions to display. Specify the
7802 numbers of the displays that you want affected with the command
7803 argument @var{dnums}. It can be a single display number, one of the
7804 numbers shown in the first field of the @samp{info display} display;
7805 or it could be a range of display numbers, as in @code{2-4}.
7807 @code{undisplay} does not repeat if you press @key{RET} after using it.
7808 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7810 @kindex disable display
7811 @item disable display @var{dnums}@dots{}
7812 Disable the display of item numbers @var{dnums}. A disabled display
7813 item is not printed automatically, but is not forgotten. It may be
7814 enabled again later. Specify the numbers of the displays that you
7815 want affected with the command argument @var{dnums}. It can be a
7816 single display number, one of the numbers shown in the first field of
7817 the @samp{info display} display; or it could be a range of display
7818 numbers, as in @code{2-4}.
7820 @kindex enable display
7821 @item enable display @var{dnums}@dots{}
7822 Enable display of item numbers @var{dnums}. It becomes effective once
7823 again in auto display of its expression, until you specify otherwise.
7824 Specify the numbers of the displays that you want affected with the
7825 command argument @var{dnums}. It can be a single display number, one
7826 of the numbers shown in the first field of the @samp{info display}
7827 display; or it could be a range of display numbers, as in @code{2-4}.
7830 Display the current values of the expressions on the list, just as is
7831 done when your program stops.
7833 @kindex info display
7835 Print the list of expressions previously set up to display
7836 automatically, each one with its item number, but without showing the
7837 values. This includes disabled expressions, which are marked as such.
7838 It also includes expressions which would not be displayed right now
7839 because they refer to automatic variables not currently available.
7842 @cindex display disabled out of scope
7843 If a display expression refers to local variables, then it does not make
7844 sense outside the lexical context for which it was set up. Such an
7845 expression is disabled when execution enters a context where one of its
7846 variables is not defined. For example, if you give the command
7847 @code{display last_char} while inside a function with an argument
7848 @code{last_char}, @value{GDBN} displays this argument while your program
7849 continues to stop inside that function. When it stops elsewhere---where
7850 there is no variable @code{last_char}---the display is disabled
7851 automatically. The next time your program stops where @code{last_char}
7852 is meaningful, you can enable the display expression once again.
7854 @node Print Settings
7855 @section Print Settings
7857 @cindex format options
7858 @cindex print settings
7859 @value{GDBN} provides the following ways to control how arrays, structures,
7860 and symbols are printed.
7863 These settings are useful for debugging programs in any language:
7867 @item set print address
7868 @itemx set print address on
7869 @cindex print/don't print memory addresses
7870 @value{GDBN} prints memory addresses showing the location of stack
7871 traces, structure values, pointer values, breakpoints, and so forth,
7872 even when it also displays the contents of those addresses. The default
7873 is @code{on}. For example, this is what a stack frame display looks like with
7874 @code{set print address on}:
7879 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7881 530 if (lquote != def_lquote)
7885 @item set print address off
7886 Do not print addresses when displaying their contents. For example,
7887 this is the same stack frame displayed with @code{set print address off}:
7891 (@value{GDBP}) set print addr off
7893 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7894 530 if (lquote != def_lquote)
7898 You can use @samp{set print address off} to eliminate all machine
7899 dependent displays from the @value{GDBN} interface. For example, with
7900 @code{print address off}, you should get the same text for backtraces on
7901 all machines---whether or not they involve pointer arguments.
7904 @item show print address
7905 Show whether or not addresses are to be printed.
7908 When @value{GDBN} prints a symbolic address, it normally prints the
7909 closest earlier symbol plus an offset. If that symbol does not uniquely
7910 identify the address (for example, it is a name whose scope is a single
7911 source file), you may need to clarify. One way to do this is with
7912 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7913 you can set @value{GDBN} to print the source file and line number when
7914 it prints a symbolic address:
7917 @item set print symbol-filename on
7918 @cindex source file and line of a symbol
7919 @cindex symbol, source file and line
7920 Tell @value{GDBN} to print the source file name and line number of a
7921 symbol in the symbolic form of an address.
7923 @item set print symbol-filename off
7924 Do not print source file name and line number of a symbol. This is the
7927 @item show print symbol-filename
7928 Show whether or not @value{GDBN} will print the source file name and
7929 line number of a symbol in the symbolic form of an address.
7932 Another situation where it is helpful to show symbol filenames and line
7933 numbers is when disassembling code; @value{GDBN} shows you the line
7934 number and source file that corresponds to each instruction.
7936 Also, you may wish to see the symbolic form only if the address being
7937 printed is reasonably close to the closest earlier symbol:
7940 @item set print max-symbolic-offset @var{max-offset}
7941 @cindex maximum value for offset of closest symbol
7942 Tell @value{GDBN} to only display the symbolic form of an address if the
7943 offset between the closest earlier symbol and the address is less than
7944 @var{max-offset}. The default is 0, which tells @value{GDBN}
7945 to always print the symbolic form of an address if any symbol precedes it.
7947 @item show print max-symbolic-offset
7948 Ask how large the maximum offset is that @value{GDBN} prints in a
7952 @cindex wild pointer, interpreting
7953 @cindex pointer, finding referent
7954 If you have a pointer and you are not sure where it points, try
7955 @samp{set print symbol-filename on}. Then you can determine the name
7956 and source file location of the variable where it points, using
7957 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7958 For example, here @value{GDBN} shows that a variable @code{ptt} points
7959 at another variable @code{t}, defined in @file{hi2.c}:
7962 (@value{GDBP}) set print symbol-filename on
7963 (@value{GDBP}) p/a ptt
7964 $4 = 0xe008 <t in hi2.c>
7968 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7969 does not show the symbol name and filename of the referent, even with
7970 the appropriate @code{set print} options turned on.
7973 Other settings control how different kinds of objects are printed:
7976 @item set print array
7977 @itemx set print array on
7978 @cindex pretty print arrays
7979 Pretty print arrays. This format is more convenient to read,
7980 but uses more space. The default is off.
7982 @item set print array off
7983 Return to compressed format for arrays.
7985 @item show print array
7986 Show whether compressed or pretty format is selected for displaying
7989 @cindex print array indexes
7990 @item set print array-indexes
7991 @itemx set print array-indexes on
7992 Print the index of each element when displaying arrays. May be more
7993 convenient to locate a given element in the array or quickly find the
7994 index of a given element in that printed array. The default is off.
7996 @item set print array-indexes off
7997 Stop printing element indexes when displaying arrays.
7999 @item show print array-indexes
8000 Show whether the index of each element is printed when displaying
8003 @item set print elements @var{number-of-elements}
8004 @cindex number of array elements to print
8005 @cindex limit on number of printed array elements
8006 Set a limit on how many elements of an array @value{GDBN} will print.
8007 If @value{GDBN} is printing a large array, it stops printing after it has
8008 printed the number of elements set by the @code{set print elements} command.
8009 This limit also applies to the display of strings.
8010 When @value{GDBN} starts, this limit is set to 200.
8011 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8013 @item show print elements
8014 Display the number of elements of a large array that @value{GDBN} will print.
8015 If the number is 0, then the printing is unlimited.
8017 @item set print frame-arguments @var{value}
8018 @kindex set print frame-arguments
8019 @cindex printing frame argument values
8020 @cindex print all frame argument values
8021 @cindex print frame argument values for scalars only
8022 @cindex do not print frame argument values
8023 This command allows to control how the values of arguments are printed
8024 when the debugger prints a frame (@pxref{Frames}). The possible
8029 The values of all arguments are printed.
8032 Print the value of an argument only if it is a scalar. The value of more
8033 complex arguments such as arrays, structures, unions, etc, is replaced
8034 by @code{@dots{}}. This is the default. Here is an example where
8035 only scalar arguments are shown:
8038 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8043 None of the argument values are printed. Instead, the value of each argument
8044 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8047 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8052 By default, only scalar arguments are printed. This command can be used
8053 to configure the debugger to print the value of all arguments, regardless
8054 of their type. However, it is often advantageous to not print the value
8055 of more complex parameters. For instance, it reduces the amount of
8056 information printed in each frame, making the backtrace more readable.
8057 Also, it improves performance when displaying Ada frames, because
8058 the computation of large arguments can sometimes be CPU-intensive,
8059 especially in large applications. Setting @code{print frame-arguments}
8060 to @code{scalars} (the default) or @code{none} avoids this computation,
8061 thus speeding up the display of each Ada frame.
8063 @item show print frame-arguments
8064 Show how the value of arguments should be displayed when printing a frame.
8066 @anchor{set print entry-values}
8067 @item set print entry-values @var{value}
8068 @kindex set print entry-values
8069 Set printing of frame argument values at function entry. In some cases
8070 @value{GDBN} can determine the value of function argument which was passed by
8071 the function caller, even if the value was modified inside the called function
8072 and therefore is different. With optimized code, the current value could be
8073 unavailable, but the entry value may still be known.
8075 The default value is @code{default} (see below for its description). Older
8076 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8077 this feature will behave in the @code{default} setting the same way as with the
8080 This functionality is currently supported only by DWARF 2 debugging format and
8081 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8082 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8085 The @var{value} parameter can be one of the following:
8089 Print only actual parameter values, never print values from function entry
8093 #0 different (val=6)
8094 #0 lost (val=<optimized out>)
8096 #0 invalid (val=<optimized out>)
8100 Print only parameter values from function entry point. The actual parameter
8101 values are never printed.
8103 #0 equal (val@@entry=5)
8104 #0 different (val@@entry=5)
8105 #0 lost (val@@entry=5)
8106 #0 born (val@@entry=<optimized out>)
8107 #0 invalid (val@@entry=<optimized out>)
8111 Print only parameter values from function entry point. If value from function
8112 entry point is not known while the actual value is known, print the actual
8113 value for such parameter.
8115 #0 equal (val@@entry=5)
8116 #0 different (val@@entry=5)
8117 #0 lost (val@@entry=5)
8119 #0 invalid (val@@entry=<optimized out>)
8123 Print actual parameter values. If actual parameter value is not known while
8124 value from function entry point is known, print the entry point value for such
8128 #0 different (val=6)
8129 #0 lost (val@@entry=5)
8131 #0 invalid (val=<optimized out>)
8135 Always print both the actual parameter value and its value from function entry
8136 point, even if values of one or both are not available due to compiler
8139 #0 equal (val=5, val@@entry=5)
8140 #0 different (val=6, val@@entry=5)
8141 #0 lost (val=<optimized out>, val@@entry=5)
8142 #0 born (val=10, val@@entry=<optimized out>)
8143 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8147 Print the actual parameter value if it is known and also its value from
8148 function entry point if it is known. If neither is known, print for the actual
8149 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8150 values are known and identical, print the shortened
8151 @code{param=param@@entry=VALUE} notation.
8153 #0 equal (val=val@@entry=5)
8154 #0 different (val=6, val@@entry=5)
8155 #0 lost (val@@entry=5)
8157 #0 invalid (val=<optimized out>)
8161 Always print the actual parameter value. Print also its value from function
8162 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8163 if both values are known and identical, print the shortened
8164 @code{param=param@@entry=VALUE} notation.
8166 #0 equal (val=val@@entry=5)
8167 #0 different (val=6, val@@entry=5)
8168 #0 lost (val=<optimized out>, val@@entry=5)
8170 #0 invalid (val=<optimized out>)
8174 For analysis messages on possible failures of frame argument values at function
8175 entry resolution see @ref{set debug entry-values}.
8177 @item show print entry-values
8178 Show the method being used for printing of frame argument values at function
8181 @item set print repeats
8182 @cindex repeated array elements
8183 Set the threshold for suppressing display of repeated array
8184 elements. When the number of consecutive identical elements of an
8185 array exceeds the threshold, @value{GDBN} prints the string
8186 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8187 identical repetitions, instead of displaying the identical elements
8188 themselves. Setting the threshold to zero will cause all elements to
8189 be individually printed. The default threshold is 10.
8191 @item show print repeats
8192 Display the current threshold for printing repeated identical
8195 @item set print null-stop
8196 @cindex @sc{null} elements in arrays
8197 Cause @value{GDBN} to stop printing the characters of an array when the first
8198 @sc{null} is encountered. This is useful when large arrays actually
8199 contain only short strings.
8202 @item show print null-stop
8203 Show whether @value{GDBN} stops printing an array on the first
8204 @sc{null} character.
8206 @item set print pretty on
8207 @cindex print structures in indented form
8208 @cindex indentation in structure display
8209 Cause @value{GDBN} to print structures in an indented format with one member
8210 per line, like this:
8225 @item set print pretty off
8226 Cause @value{GDBN} to print structures in a compact format, like this:
8230 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8231 meat = 0x54 "Pork"@}
8236 This is the default format.
8238 @item show print pretty
8239 Show which format @value{GDBN} is using to print structures.
8241 @item set print sevenbit-strings on
8242 @cindex eight-bit characters in strings
8243 @cindex octal escapes in strings
8244 Print using only seven-bit characters; if this option is set,
8245 @value{GDBN} displays any eight-bit characters (in strings or
8246 character values) using the notation @code{\}@var{nnn}. This setting is
8247 best if you are working in English (@sc{ascii}) and you use the
8248 high-order bit of characters as a marker or ``meta'' bit.
8250 @item set print sevenbit-strings off
8251 Print full eight-bit characters. This allows the use of more
8252 international character sets, and is the default.
8254 @item show print sevenbit-strings
8255 Show whether or not @value{GDBN} is printing only seven-bit characters.
8257 @item set print union on
8258 @cindex unions in structures, printing
8259 Tell @value{GDBN} to print unions which are contained in structures
8260 and other unions. This is the default setting.
8262 @item set print union off
8263 Tell @value{GDBN} not to print unions which are contained in
8264 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8267 @item show print union
8268 Ask @value{GDBN} whether or not it will print unions which are contained in
8269 structures and other unions.
8271 For example, given the declarations
8274 typedef enum @{Tree, Bug@} Species;
8275 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8276 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8287 struct thing foo = @{Tree, @{Acorn@}@};
8291 with @code{set print union on} in effect @samp{p foo} would print
8294 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8298 and with @code{set print union off} in effect it would print
8301 $1 = @{it = Tree, form = @{...@}@}
8305 @code{set print union} affects programs written in C-like languages
8311 These settings are of interest when debugging C@t{++} programs:
8314 @cindex demangling C@t{++} names
8315 @item set print demangle
8316 @itemx set print demangle on
8317 Print C@t{++} names in their source form rather than in the encoded
8318 (``mangled'') form passed to the assembler and linker for type-safe
8319 linkage. The default is on.
8321 @item show print demangle
8322 Show whether C@t{++} names are printed in mangled or demangled form.
8324 @item set print asm-demangle
8325 @itemx set print asm-demangle on
8326 Print C@t{++} names in their source form rather than their mangled form, even
8327 in assembler code printouts such as instruction disassemblies.
8330 @item show print asm-demangle
8331 Show whether C@t{++} names in assembly listings are printed in mangled
8334 @cindex C@t{++} symbol decoding style
8335 @cindex symbol decoding style, C@t{++}
8336 @kindex set demangle-style
8337 @item set demangle-style @var{style}
8338 Choose among several encoding schemes used by different compilers to
8339 represent C@t{++} names. The choices for @var{style} are currently:
8343 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8346 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8347 This is the default.
8350 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8353 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8356 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8357 @strong{Warning:} this setting alone is not sufficient to allow
8358 debugging @code{cfront}-generated executables. @value{GDBN} would
8359 require further enhancement to permit that.
8362 If you omit @var{style}, you will see a list of possible formats.
8364 @item show demangle-style
8365 Display the encoding style currently in use for decoding C@t{++} symbols.
8367 @item set print object
8368 @itemx set print object on
8369 @cindex derived type of an object, printing
8370 @cindex display derived types
8371 When displaying a pointer to an object, identify the @emph{actual}
8372 (derived) type of the object rather than the @emph{declared} type, using
8373 the virtual function table. Note that the virtual function table is
8374 required---this feature can only work for objects that have run-time
8375 type identification; a single virtual method in the object's declared
8378 @item set print object off
8379 Display only the declared type of objects, without reference to the
8380 virtual function table. This is the default setting.
8382 @item show print object
8383 Show whether actual, or declared, object types are displayed.
8385 @item set print static-members
8386 @itemx set print static-members on
8387 @cindex static members of C@t{++} objects
8388 Print static members when displaying a C@t{++} object. The default is on.
8390 @item set print static-members off
8391 Do not print static members when displaying a C@t{++} object.
8393 @item show print static-members
8394 Show whether C@t{++} static members are printed or not.
8396 @item set print pascal_static-members
8397 @itemx set print pascal_static-members on
8398 @cindex static members of Pascal objects
8399 @cindex Pascal objects, static members display
8400 Print static members when displaying a Pascal object. The default is on.
8402 @item set print pascal_static-members off
8403 Do not print static members when displaying a Pascal object.
8405 @item show print pascal_static-members
8406 Show whether Pascal static members are printed or not.
8408 @c These don't work with HP ANSI C++ yet.
8409 @item set print vtbl
8410 @itemx set print vtbl on
8411 @cindex pretty print C@t{++} virtual function tables
8412 @cindex virtual functions (C@t{++}) display
8413 @cindex VTBL display
8414 Pretty print C@t{++} virtual function tables. The default is off.
8415 (The @code{vtbl} commands do not work on programs compiled with the HP
8416 ANSI C@t{++} compiler (@code{aCC}).)
8418 @item set print vtbl off
8419 Do not pretty print C@t{++} virtual function tables.
8421 @item show print vtbl
8422 Show whether C@t{++} virtual function tables are pretty printed, or not.
8425 @node Pretty Printing
8426 @section Pretty Printing
8428 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8429 Python code. It greatly simplifies the display of complex objects. This
8430 mechanism works for both MI and the CLI.
8433 * Pretty-Printer Introduction:: Introduction to pretty-printers
8434 * Pretty-Printer Example:: An example pretty-printer
8435 * Pretty-Printer Commands:: Pretty-printer commands
8438 @node Pretty-Printer Introduction
8439 @subsection Pretty-Printer Introduction
8441 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8442 registered for the value. If there is then @value{GDBN} invokes the
8443 pretty-printer to print the value. Otherwise the value is printed normally.
8445 Pretty-printers are normally named. This makes them easy to manage.
8446 The @samp{info pretty-printer} command will list all the installed
8447 pretty-printers with their names.
8448 If a pretty-printer can handle multiple data types, then its
8449 @dfn{subprinters} are the printers for the individual data types.
8450 Each such subprinter has its own name.
8451 The format of the name is @var{printer-name};@var{subprinter-name}.
8453 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8454 Typically they are automatically loaded and registered when the corresponding
8455 debug information is loaded, thus making them available without having to
8456 do anything special.
8458 There are three places where a pretty-printer can be registered.
8462 Pretty-printers registered globally are available when debugging
8466 Pretty-printers registered with a program space are available only
8467 when debugging that program.
8468 @xref{Progspaces In Python}, for more details on program spaces in Python.
8471 Pretty-printers registered with an objfile are loaded and unloaded
8472 with the corresponding objfile (e.g., shared library).
8473 @xref{Objfiles In Python}, for more details on objfiles in Python.
8476 @xref{Selecting Pretty-Printers}, for further information on how
8477 pretty-printers are selected,
8479 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8482 @node Pretty-Printer Example
8483 @subsection Pretty-Printer Example
8485 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8488 (@value{GDBP}) print s
8490 static npos = 4294967295,
8492 <std::allocator<char>> = @{
8493 <__gnu_cxx::new_allocator<char>> = @{
8494 <No data fields>@}, <No data fields>
8496 members of std::basic_string<char, std::char_traits<char>,
8497 std::allocator<char> >::_Alloc_hider:
8498 _M_p = 0x804a014 "abcd"
8503 With a pretty-printer for @code{std::string} only the contents are printed:
8506 (@value{GDBP}) print s
8510 @node Pretty-Printer Commands
8511 @subsection Pretty-Printer Commands
8512 @cindex pretty-printer commands
8515 @kindex info pretty-printer
8516 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8517 Print the list of installed pretty-printers.
8518 This includes disabled pretty-printers, which are marked as such.
8520 @var{object-regexp} is a regular expression matching the objects
8521 whose pretty-printers to list.
8522 Objects can be @code{global}, the program space's file
8523 (@pxref{Progspaces In Python}),
8524 and the object files within that program space (@pxref{Objfiles In Python}).
8525 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8526 looks up a printer from these three objects.
8528 @var{name-regexp} is a regular expression matching the name of the printers
8531 @kindex disable pretty-printer
8532 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8533 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8534 A disabled pretty-printer is not forgotten, it may be enabled again later.
8536 @kindex enable pretty-printer
8537 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8538 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8543 Suppose we have three pretty-printers installed: one from library1.so
8544 named @code{foo} that prints objects of type @code{foo}, and
8545 another from library2.so named @code{bar} that prints two types of objects,
8546 @code{bar1} and @code{bar2}.
8549 (gdb) info pretty-printer
8556 (gdb) info pretty-printer library2
8561 (gdb) disable pretty-printer library1
8563 2 of 3 printers enabled
8564 (gdb) info pretty-printer
8571 (gdb) disable pretty-printer library2 bar:bar1
8573 1 of 3 printers enabled
8574 (gdb) info pretty-printer library2
8581 (gdb) disable pretty-printer library2 bar
8583 0 of 3 printers enabled
8584 (gdb) info pretty-printer library2
8593 Note that for @code{bar} the entire printer can be disabled,
8594 as can each individual subprinter.
8597 @section Value History
8599 @cindex value history
8600 @cindex history of values printed by @value{GDBN}
8601 Values printed by the @code{print} command are saved in the @value{GDBN}
8602 @dfn{value history}. This allows you to refer to them in other expressions.
8603 Values are kept until the symbol table is re-read or discarded
8604 (for example with the @code{file} or @code{symbol-file} commands).
8605 When the symbol table changes, the value history is discarded,
8606 since the values may contain pointers back to the types defined in the
8611 @cindex history number
8612 The values printed are given @dfn{history numbers} by which you can
8613 refer to them. These are successive integers starting with one.
8614 @code{print} shows you the history number assigned to a value by
8615 printing @samp{$@var{num} = } before the value; here @var{num} is the
8618 To refer to any previous value, use @samp{$} followed by the value's
8619 history number. The way @code{print} labels its output is designed to
8620 remind you of this. Just @code{$} refers to the most recent value in
8621 the history, and @code{$$} refers to the value before that.
8622 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8623 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8624 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8626 For example, suppose you have just printed a pointer to a structure and
8627 want to see the contents of the structure. It suffices to type
8633 If you have a chain of structures where the component @code{next} points
8634 to the next one, you can print the contents of the next one with this:
8641 You can print successive links in the chain by repeating this
8642 command---which you can do by just typing @key{RET}.
8644 Note that the history records values, not expressions. If the value of
8645 @code{x} is 4 and you type these commands:
8653 then the value recorded in the value history by the @code{print} command
8654 remains 4 even though the value of @code{x} has changed.
8659 Print the last ten values in the value history, with their item numbers.
8660 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8661 values} does not change the history.
8663 @item show values @var{n}
8664 Print ten history values centered on history item number @var{n}.
8667 Print ten history values just after the values last printed. If no more
8668 values are available, @code{show values +} produces no display.
8671 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8672 same effect as @samp{show values +}.
8674 @node Convenience Vars
8675 @section Convenience Variables
8677 @cindex convenience variables
8678 @cindex user-defined variables
8679 @value{GDBN} provides @dfn{convenience variables} that you can use within
8680 @value{GDBN} to hold on to a value and refer to it later. These variables
8681 exist entirely within @value{GDBN}; they are not part of your program, and
8682 setting a convenience variable has no direct effect on further execution
8683 of your program. That is why you can use them freely.
8685 Convenience variables are prefixed with @samp{$}. Any name preceded by
8686 @samp{$} can be used for a convenience variable, unless it is one of
8687 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8688 (Value history references, in contrast, are @emph{numbers} preceded
8689 by @samp{$}. @xref{Value History, ,Value History}.)
8691 You can save a value in a convenience variable with an assignment
8692 expression, just as you would set a variable in your program.
8696 set $foo = *object_ptr
8700 would save in @code{$foo} the value contained in the object pointed to by
8703 Using a convenience variable for the first time creates it, but its
8704 value is @code{void} until you assign a new value. You can alter the
8705 value with another assignment at any time.
8707 Convenience variables have no fixed types. You can assign a convenience
8708 variable any type of value, including structures and arrays, even if
8709 that variable already has a value of a different type. The convenience
8710 variable, when used as an expression, has the type of its current value.
8713 @kindex show convenience
8714 @cindex show all user variables
8715 @item show convenience
8716 Print a list of convenience variables used so far, and their values.
8717 Abbreviated @code{show conv}.
8719 @kindex init-if-undefined
8720 @cindex convenience variables, initializing
8721 @item init-if-undefined $@var{variable} = @var{expression}
8722 Set a convenience variable if it has not already been set. This is useful
8723 for user-defined commands that keep some state. It is similar, in concept,
8724 to using local static variables with initializers in C (except that
8725 convenience variables are global). It can also be used to allow users to
8726 override default values used in a command script.
8728 If the variable is already defined then the expression is not evaluated so
8729 any side-effects do not occur.
8732 One of the ways to use a convenience variable is as a counter to be
8733 incremented or a pointer to be advanced. For example, to print
8734 a field from successive elements of an array of structures:
8738 print bar[$i++]->contents
8742 Repeat that command by typing @key{RET}.
8744 Some convenience variables are created automatically by @value{GDBN} and given
8745 values likely to be useful.
8748 @vindex $_@r{, convenience variable}
8750 The variable @code{$_} is automatically set by the @code{x} command to
8751 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8752 commands which provide a default address for @code{x} to examine also
8753 set @code{$_} to that address; these commands include @code{info line}
8754 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8755 except when set by the @code{x} command, in which case it is a pointer
8756 to the type of @code{$__}.
8758 @vindex $__@r{, convenience variable}
8760 The variable @code{$__} is automatically set by the @code{x} command
8761 to the value found in the last address examined. Its type is chosen
8762 to match the format in which the data was printed.
8765 @vindex $_exitcode@r{, convenience variable}
8766 The variable @code{$_exitcode} is automatically set to the exit code when
8767 the program being debugged terminates.
8770 @vindex $_sdata@r{, inspect, convenience variable}
8771 The variable @code{$_sdata} contains extra collected static tracepoint
8772 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8773 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8774 if extra static tracepoint data has not been collected.
8777 @vindex $_siginfo@r{, convenience variable}
8778 The variable @code{$_siginfo} contains extra signal information
8779 (@pxref{extra signal information}). Note that @code{$_siginfo}
8780 could be empty, if the application has not yet received any signals.
8781 For example, it will be empty before you execute the @code{run} command.
8784 @vindex $_tlb@r{, convenience variable}
8785 The variable @code{$_tlb} is automatically set when debugging
8786 applications running on MS-Windows in native mode or connected to
8787 gdbserver that supports the @code{qGetTIBAddr} request.
8788 @xref{General Query Packets}.
8789 This variable contains the address of the thread information block.
8793 On HP-UX systems, if you refer to a function or variable name that
8794 begins with a dollar sign, @value{GDBN} searches for a user or system
8795 name first, before it searches for a convenience variable.
8797 @cindex convenience functions
8798 @value{GDBN} also supplies some @dfn{convenience functions}. These
8799 have a syntax similar to convenience variables. A convenience
8800 function can be used in an expression just like an ordinary function;
8801 however, a convenience function is implemented internally to
8806 @kindex help function
8807 @cindex show all convenience functions
8808 Print a list of all convenience functions.
8815 You can refer to machine register contents, in expressions, as variables
8816 with names starting with @samp{$}. The names of registers are different
8817 for each machine; use @code{info registers} to see the names used on
8821 @kindex info registers
8822 @item info registers
8823 Print the names and values of all registers except floating-point
8824 and vector registers (in the selected stack frame).
8826 @kindex info all-registers
8827 @cindex floating point registers
8828 @item info all-registers
8829 Print the names and values of all registers, including floating-point
8830 and vector registers (in the selected stack frame).
8832 @item info registers @var{regname} @dots{}
8833 Print the @dfn{relativized} value of each specified register @var{regname}.
8834 As discussed in detail below, register values are normally relative to
8835 the selected stack frame. @var{regname} may be any register name valid on
8836 the machine you are using, with or without the initial @samp{$}.
8839 @cindex stack pointer register
8840 @cindex program counter register
8841 @cindex process status register
8842 @cindex frame pointer register
8843 @cindex standard registers
8844 @value{GDBN} has four ``standard'' register names that are available (in
8845 expressions) on most machines---whenever they do not conflict with an
8846 architecture's canonical mnemonics for registers. The register names
8847 @code{$pc} and @code{$sp} are used for the program counter register and
8848 the stack pointer. @code{$fp} is used for a register that contains a
8849 pointer to the current stack frame, and @code{$ps} is used for a
8850 register that contains the processor status. For example,
8851 you could print the program counter in hex with
8858 or print the instruction to be executed next with
8865 or add four to the stack pointer@footnote{This is a way of removing
8866 one word from the stack, on machines where stacks grow downward in
8867 memory (most machines, nowadays). This assumes that the innermost
8868 stack frame is selected; setting @code{$sp} is not allowed when other
8869 stack frames are selected. To pop entire frames off the stack,
8870 regardless of machine architecture, use @code{return};
8871 see @ref{Returning, ,Returning from a Function}.} with
8877 Whenever possible, these four standard register names are available on
8878 your machine even though the machine has different canonical mnemonics,
8879 so long as there is no conflict. The @code{info registers} command
8880 shows the canonical names. For example, on the SPARC, @code{info
8881 registers} displays the processor status register as @code{$psr} but you
8882 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8883 is an alias for the @sc{eflags} register.
8885 @value{GDBN} always considers the contents of an ordinary register as an
8886 integer when the register is examined in this way. Some machines have
8887 special registers which can hold nothing but floating point; these
8888 registers are considered to have floating point values. There is no way
8889 to refer to the contents of an ordinary register as floating point value
8890 (although you can @emph{print} it as a floating point value with
8891 @samp{print/f $@var{regname}}).
8893 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8894 means that the data format in which the register contents are saved by
8895 the operating system is not the same one that your program normally
8896 sees. For example, the registers of the 68881 floating point
8897 coprocessor are always saved in ``extended'' (raw) format, but all C
8898 programs expect to work with ``double'' (virtual) format. In such
8899 cases, @value{GDBN} normally works with the virtual format only (the format
8900 that makes sense for your program), but the @code{info registers} command
8901 prints the data in both formats.
8903 @cindex SSE registers (x86)
8904 @cindex MMX registers (x86)
8905 Some machines have special registers whose contents can be interpreted
8906 in several different ways. For example, modern x86-based machines
8907 have SSE and MMX registers that can hold several values packed
8908 together in several different formats. @value{GDBN} refers to such
8909 registers in @code{struct} notation:
8912 (@value{GDBP}) print $xmm1
8914 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8915 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8916 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8917 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8918 v4_int32 = @{0, 20657912, 11, 13@},
8919 v2_int64 = @{88725056443645952, 55834574859@},
8920 uint128 = 0x0000000d0000000b013b36f800000000
8925 To set values of such registers, you need to tell @value{GDBN} which
8926 view of the register you wish to change, as if you were assigning
8927 value to a @code{struct} member:
8930 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8933 Normally, register values are relative to the selected stack frame
8934 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8935 value that the register would contain if all stack frames farther in
8936 were exited and their saved registers restored. In order to see the
8937 true contents of hardware registers, you must select the innermost
8938 frame (with @samp{frame 0}).
8940 However, @value{GDBN} must deduce where registers are saved, from the machine
8941 code generated by your compiler. If some registers are not saved, or if
8942 @value{GDBN} is unable to locate the saved registers, the selected stack
8943 frame makes no difference.
8945 @node Floating Point Hardware
8946 @section Floating Point Hardware
8947 @cindex floating point
8949 Depending on the configuration, @value{GDBN} may be able to give
8950 you more information about the status of the floating point hardware.
8955 Display hardware-dependent information about the floating
8956 point unit. The exact contents and layout vary depending on the
8957 floating point chip. Currently, @samp{info float} is supported on
8958 the ARM and x86 machines.
8962 @section Vector Unit
8965 Depending on the configuration, @value{GDBN} may be able to give you
8966 more information about the status of the vector unit.
8971 Display information about the vector unit. The exact contents and
8972 layout vary depending on the hardware.
8975 @node OS Information
8976 @section Operating System Auxiliary Information
8977 @cindex OS information
8979 @value{GDBN} provides interfaces to useful OS facilities that can help
8980 you debug your program.
8982 @cindex @code{ptrace} system call
8983 @cindex @code{struct user} contents
8984 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8985 machines), it interfaces with the inferior via the @code{ptrace}
8986 system call. The operating system creates a special sata structure,
8987 called @code{struct user}, for this interface. You can use the
8988 command @code{info udot} to display the contents of this data
8994 Display the contents of the @code{struct user} maintained by the OS
8995 kernel for the program being debugged. @value{GDBN} displays the
8996 contents of @code{struct user} as a list of hex numbers, similar to
8997 the @code{examine} command.
9000 @cindex auxiliary vector
9001 @cindex vector, auxiliary
9002 Some operating systems supply an @dfn{auxiliary vector} to programs at
9003 startup. This is akin to the arguments and environment that you
9004 specify for a program, but contains a system-dependent variety of
9005 binary values that tell system libraries important details about the
9006 hardware, operating system, and process. Each value's purpose is
9007 identified by an integer tag; the meanings are well-known but system-specific.
9008 Depending on the configuration and operating system facilities,
9009 @value{GDBN} may be able to show you this information. For remote
9010 targets, this functionality may further depend on the remote stub's
9011 support of the @samp{qXfer:auxv:read} packet, see
9012 @ref{qXfer auxiliary vector read}.
9017 Display the auxiliary vector of the inferior, which can be either a
9018 live process or a core dump file. @value{GDBN} prints each tag value
9019 numerically, and also shows names and text descriptions for recognized
9020 tags. Some values in the vector are numbers, some bit masks, and some
9021 pointers to strings or other data. @value{GDBN} displays each value in the
9022 most appropriate form for a recognized tag, and in hexadecimal for
9023 an unrecognized tag.
9026 On some targets, @value{GDBN} can access operating-system-specific information
9027 and display it to user, without interpretation. For remote targets,
9028 this functionality depends on the remote stub's support of the
9029 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9034 List the types of OS information available for the target. If the
9035 target does not return a list of possible types, this command will
9038 @kindex info os processes
9039 @item info os processes
9040 Display the list of processes on the target. For each process,
9041 @value{GDBN} prints the process identifier, the name of the user, and
9042 the command corresponding to the process.
9045 @node Memory Region Attributes
9046 @section Memory Region Attributes
9047 @cindex memory region attributes
9049 @dfn{Memory region attributes} allow you to describe special handling
9050 required by regions of your target's memory. @value{GDBN} uses
9051 attributes to determine whether to allow certain types of memory
9052 accesses; whether to use specific width accesses; and whether to cache
9053 target memory. By default the description of memory regions is
9054 fetched from the target (if the current target supports this), but the
9055 user can override the fetched regions.
9057 Defined memory regions can be individually enabled and disabled. When a
9058 memory region is disabled, @value{GDBN} uses the default attributes when
9059 accessing memory in that region. Similarly, if no memory regions have
9060 been defined, @value{GDBN} uses the default attributes when accessing
9063 When a memory region is defined, it is given a number to identify it;
9064 to enable, disable, or remove a memory region, you specify that number.
9068 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9069 Define a memory region bounded by @var{lower} and @var{upper} with
9070 attributes @var{attributes}@dots{}, and add it to the list of regions
9071 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9072 case: it is treated as the target's maximum memory address.
9073 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9076 Discard any user changes to the memory regions and use target-supplied
9077 regions, if available, or no regions if the target does not support.
9080 @item delete mem @var{nums}@dots{}
9081 Remove memory regions @var{nums}@dots{} from the list of regions
9082 monitored by @value{GDBN}.
9085 @item disable mem @var{nums}@dots{}
9086 Disable monitoring of memory regions @var{nums}@dots{}.
9087 A disabled memory region is not forgotten.
9088 It may be enabled again later.
9091 @item enable mem @var{nums}@dots{}
9092 Enable monitoring of memory regions @var{nums}@dots{}.
9096 Print a table of all defined memory regions, with the following columns
9100 @item Memory Region Number
9101 @item Enabled or Disabled.
9102 Enabled memory regions are marked with @samp{y}.
9103 Disabled memory regions are marked with @samp{n}.
9106 The address defining the inclusive lower bound of the memory region.
9109 The address defining the exclusive upper bound of the memory region.
9112 The list of attributes set for this memory region.
9117 @subsection Attributes
9119 @subsubsection Memory Access Mode
9120 The access mode attributes set whether @value{GDBN} may make read or
9121 write accesses to a memory region.
9123 While these attributes prevent @value{GDBN} from performing invalid
9124 memory accesses, they do nothing to prevent the target system, I/O DMA,
9125 etc.@: from accessing memory.
9129 Memory is read only.
9131 Memory is write only.
9133 Memory is read/write. This is the default.
9136 @subsubsection Memory Access Size
9137 The access size attribute tells @value{GDBN} to use specific sized
9138 accesses in the memory region. Often memory mapped device registers
9139 require specific sized accesses. If no access size attribute is
9140 specified, @value{GDBN} may use accesses of any size.
9144 Use 8 bit memory accesses.
9146 Use 16 bit memory accesses.
9148 Use 32 bit memory accesses.
9150 Use 64 bit memory accesses.
9153 @c @subsubsection Hardware/Software Breakpoints
9154 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9155 @c will use hardware or software breakpoints for the internal breakpoints
9156 @c used by the step, next, finish, until, etc. commands.
9160 @c Always use hardware breakpoints
9161 @c @item swbreak (default)
9164 @subsubsection Data Cache
9165 The data cache attributes set whether @value{GDBN} will cache target
9166 memory. While this generally improves performance by reducing debug
9167 protocol overhead, it can lead to incorrect results because @value{GDBN}
9168 does not know about volatile variables or memory mapped device
9173 Enable @value{GDBN} to cache target memory.
9175 Disable @value{GDBN} from caching target memory. This is the default.
9178 @subsection Memory Access Checking
9179 @value{GDBN} can be instructed to refuse accesses to memory that is
9180 not explicitly described. This can be useful if accessing such
9181 regions has undesired effects for a specific target, or to provide
9182 better error checking. The following commands control this behaviour.
9185 @kindex set mem inaccessible-by-default
9186 @item set mem inaccessible-by-default [on|off]
9187 If @code{on} is specified, make @value{GDBN} treat memory not
9188 explicitly described by the memory ranges as non-existent and refuse accesses
9189 to such memory. The checks are only performed if there's at least one
9190 memory range defined. If @code{off} is specified, make @value{GDBN}
9191 treat the memory not explicitly described by the memory ranges as RAM.
9192 The default value is @code{on}.
9193 @kindex show mem inaccessible-by-default
9194 @item show mem inaccessible-by-default
9195 Show the current handling of accesses to unknown memory.
9199 @c @subsubsection Memory Write Verification
9200 @c The memory write verification attributes set whether @value{GDBN}
9201 @c will re-reads data after each write to verify the write was successful.
9205 @c @item noverify (default)
9208 @node Dump/Restore Files
9209 @section Copy Between Memory and a File
9210 @cindex dump/restore files
9211 @cindex append data to a file
9212 @cindex dump data to a file
9213 @cindex restore data from a file
9215 You can use the commands @code{dump}, @code{append}, and
9216 @code{restore} to copy data between target memory and a file. The
9217 @code{dump} and @code{append} commands write data to a file, and the
9218 @code{restore} command reads data from a file back into the inferior's
9219 memory. Files may be in binary, Motorola S-record, Intel hex, or
9220 Tektronix Hex format; however, @value{GDBN} can only append to binary
9226 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9227 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9228 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9229 or the value of @var{expr}, to @var{filename} in the given format.
9231 The @var{format} parameter may be any one of:
9238 Motorola S-record format.
9240 Tektronix Hex format.
9243 @value{GDBN} uses the same definitions of these formats as the
9244 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9245 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9249 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9250 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9251 Append the contents of memory from @var{start_addr} to @var{end_addr},
9252 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9253 (@value{GDBN} can only append data to files in raw binary form.)
9256 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9257 Restore the contents of file @var{filename} into memory. The
9258 @code{restore} command can automatically recognize any known @sc{bfd}
9259 file format, except for raw binary. To restore a raw binary file you
9260 must specify the optional keyword @code{binary} after the filename.
9262 If @var{bias} is non-zero, its value will be added to the addresses
9263 contained in the file. Binary files always start at address zero, so
9264 they will be restored at address @var{bias}. Other bfd files have
9265 a built-in location; they will be restored at offset @var{bias}
9268 If @var{start} and/or @var{end} are non-zero, then only data between
9269 file offset @var{start} and file offset @var{end} will be restored.
9270 These offsets are relative to the addresses in the file, before
9271 the @var{bias} argument is applied.
9275 @node Core File Generation
9276 @section How to Produce a Core File from Your Program
9277 @cindex dump core from inferior
9279 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9280 image of a running process and its process status (register values
9281 etc.). Its primary use is post-mortem debugging of a program that
9282 crashed while it ran outside a debugger. A program that crashes
9283 automatically produces a core file, unless this feature is disabled by
9284 the user. @xref{Files}, for information on invoking @value{GDBN} in
9285 the post-mortem debugging mode.
9287 Occasionally, you may wish to produce a core file of the program you
9288 are debugging in order to preserve a snapshot of its state.
9289 @value{GDBN} has a special command for that.
9293 @kindex generate-core-file
9294 @item generate-core-file [@var{file}]
9295 @itemx gcore [@var{file}]
9296 Produce a core dump of the inferior process. The optional argument
9297 @var{file} specifies the file name where to put the core dump. If not
9298 specified, the file name defaults to @file{core.@var{pid}}, where
9299 @var{pid} is the inferior process ID.
9301 Note that this command is implemented only for some systems (as of
9302 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9305 @node Character Sets
9306 @section Character Sets
9307 @cindex character sets
9309 @cindex translating between character sets
9310 @cindex host character set
9311 @cindex target character set
9313 If the program you are debugging uses a different character set to
9314 represent characters and strings than the one @value{GDBN} uses itself,
9315 @value{GDBN} can automatically translate between the character sets for
9316 you. The character set @value{GDBN} uses we call the @dfn{host
9317 character set}; the one the inferior program uses we call the
9318 @dfn{target character set}.
9320 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9321 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9322 remote protocol (@pxref{Remote Debugging}) to debug a program
9323 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9324 then the host character set is Latin-1, and the target character set is
9325 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9326 target-charset EBCDIC-US}, then @value{GDBN} translates between
9327 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9328 character and string literals in expressions.
9330 @value{GDBN} has no way to automatically recognize which character set
9331 the inferior program uses; you must tell it, using the @code{set
9332 target-charset} command, described below.
9334 Here are the commands for controlling @value{GDBN}'s character set
9338 @item set target-charset @var{charset}
9339 @kindex set target-charset
9340 Set the current target character set to @var{charset}. To display the
9341 list of supported target character sets, type
9342 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9344 @item set host-charset @var{charset}
9345 @kindex set host-charset
9346 Set the current host character set to @var{charset}.
9348 By default, @value{GDBN} uses a host character set appropriate to the
9349 system it is running on; you can override that default using the
9350 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9351 automatically determine the appropriate host character set. In this
9352 case, @value{GDBN} uses @samp{UTF-8}.
9354 @value{GDBN} can only use certain character sets as its host character
9355 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9356 @value{GDBN} will list the host character sets it supports.
9358 @item set charset @var{charset}
9360 Set the current host and target character sets to @var{charset}. As
9361 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9362 @value{GDBN} will list the names of the character sets that can be used
9363 for both host and target.
9366 @kindex show charset
9367 Show the names of the current host and target character sets.
9369 @item show host-charset
9370 @kindex show host-charset
9371 Show the name of the current host character set.
9373 @item show target-charset
9374 @kindex show target-charset
9375 Show the name of the current target character set.
9377 @item set target-wide-charset @var{charset}
9378 @kindex set target-wide-charset
9379 Set the current target's wide character set to @var{charset}. This is
9380 the character set used by the target's @code{wchar_t} type. To
9381 display the list of supported wide character sets, type
9382 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9384 @item show target-wide-charset
9385 @kindex show target-wide-charset
9386 Show the name of the current target's wide character set.
9389 Here is an example of @value{GDBN}'s character set support in action.
9390 Assume that the following source code has been placed in the file
9391 @file{charset-test.c}:
9397 = @{72, 101, 108, 108, 111, 44, 32, 119,
9398 111, 114, 108, 100, 33, 10, 0@};
9399 char ibm1047_hello[]
9400 = @{200, 133, 147, 147, 150, 107, 64, 166,
9401 150, 153, 147, 132, 90, 37, 0@};
9405 printf ("Hello, world!\n");
9409 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9410 containing the string @samp{Hello, world!} followed by a newline,
9411 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9413 We compile the program, and invoke the debugger on it:
9416 $ gcc -g charset-test.c -o charset-test
9417 $ gdb -nw charset-test
9418 GNU gdb 2001-12-19-cvs
9419 Copyright 2001 Free Software Foundation, Inc.
9424 We can use the @code{show charset} command to see what character sets
9425 @value{GDBN} is currently using to interpret and display characters and
9429 (@value{GDBP}) show charset
9430 The current host and target character set is `ISO-8859-1'.
9434 For the sake of printing this manual, let's use @sc{ascii} as our
9435 initial character set:
9437 (@value{GDBP}) set charset ASCII
9438 (@value{GDBP}) show charset
9439 The current host and target character set is `ASCII'.
9443 Let's assume that @sc{ascii} is indeed the correct character set for our
9444 host system --- in other words, let's assume that if @value{GDBN} prints
9445 characters using the @sc{ascii} character set, our terminal will display
9446 them properly. Since our current target character set is also
9447 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9450 (@value{GDBP}) print ascii_hello
9451 $1 = 0x401698 "Hello, world!\n"
9452 (@value{GDBP}) print ascii_hello[0]
9457 @value{GDBN} uses the target character set for character and string
9458 literals you use in expressions:
9461 (@value{GDBP}) print '+'
9466 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9469 @value{GDBN} relies on the user to tell it which character set the
9470 target program uses. If we print @code{ibm1047_hello} while our target
9471 character set is still @sc{ascii}, we get jibberish:
9474 (@value{GDBP}) print ibm1047_hello
9475 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9476 (@value{GDBP}) print ibm1047_hello[0]
9481 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9482 @value{GDBN} tells us the character sets it supports:
9485 (@value{GDBP}) set target-charset
9486 ASCII EBCDIC-US IBM1047 ISO-8859-1
9487 (@value{GDBP}) set target-charset
9490 We can select @sc{ibm1047} as our target character set, and examine the
9491 program's strings again. Now the @sc{ascii} string is wrong, but
9492 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9493 target character set, @sc{ibm1047}, to the host character set,
9494 @sc{ascii}, and they display correctly:
9497 (@value{GDBP}) set target-charset IBM1047
9498 (@value{GDBP}) show charset
9499 The current host character set is `ASCII'.
9500 The current target character set is `IBM1047'.
9501 (@value{GDBP}) print ascii_hello
9502 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9503 (@value{GDBP}) print ascii_hello[0]
9505 (@value{GDBP}) print ibm1047_hello
9506 $8 = 0x4016a8 "Hello, world!\n"
9507 (@value{GDBP}) print ibm1047_hello[0]
9512 As above, @value{GDBN} uses the target character set for character and
9513 string literals you use in expressions:
9516 (@value{GDBP}) print '+'
9521 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9524 @node Caching Remote Data
9525 @section Caching Data of Remote Targets
9526 @cindex caching data of remote targets
9528 @value{GDBN} caches data exchanged between the debugger and a
9529 remote target (@pxref{Remote Debugging}). Such caching generally improves
9530 performance, because it reduces the overhead of the remote protocol by
9531 bundling memory reads and writes into large chunks. Unfortunately, simply
9532 caching everything would lead to incorrect results, since @value{GDBN}
9533 does not necessarily know anything about volatile values, memory-mapped I/O
9534 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9535 memory can be changed @emph{while} a gdb command is executing.
9536 Therefore, by default, @value{GDBN} only caches data
9537 known to be on the stack@footnote{In non-stop mode, it is moderately
9538 rare for a running thread to modify the stack of a stopped thread
9539 in a way that would interfere with a backtrace, and caching of
9540 stack reads provides a significant speed up of remote backtraces.}.
9541 Other regions of memory can be explicitly marked as
9542 cacheable; see @pxref{Memory Region Attributes}.
9545 @kindex set remotecache
9546 @item set remotecache on
9547 @itemx set remotecache off
9548 This option no longer does anything; it exists for compatibility
9551 @kindex show remotecache
9552 @item show remotecache
9553 Show the current state of the obsolete remotecache flag.
9555 @kindex set stack-cache
9556 @item set stack-cache on
9557 @itemx set stack-cache off
9558 Enable or disable caching of stack accesses. When @code{ON}, use
9559 caching. By default, this option is @code{ON}.
9561 @kindex show stack-cache
9562 @item show stack-cache
9563 Show the current state of data caching for memory accesses.
9566 @item info dcache @r{[}line@r{]}
9567 Print the information about the data cache performance. The
9568 information displayed includes the dcache width and depth, and for
9569 each cache line, its number, address, and how many times it was
9570 referenced. This command is useful for debugging the data cache
9573 If a line number is specified, the contents of that line will be
9576 @item set dcache size @var{size}
9578 @kindex set dcache size
9579 Set maximum number of entries in dcache (dcache depth above).
9581 @item set dcache line-size @var{line-size}
9582 @cindex dcache line-size
9583 @kindex set dcache line-size
9584 Set number of bytes each dcache entry caches (dcache width above).
9585 Must be a power of 2.
9587 @item show dcache size
9588 @kindex show dcache size
9589 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
9591 @item show dcache line-size
9592 @kindex show dcache line-size
9593 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
9597 @node Searching Memory
9598 @section Search Memory
9599 @cindex searching memory
9601 Memory can be searched for a particular sequence of bytes with the
9602 @code{find} command.
9606 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9607 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9608 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9609 etc. The search begins at address @var{start_addr} and continues for either
9610 @var{len} bytes or through to @var{end_addr} inclusive.
9613 @var{s} and @var{n} are optional parameters.
9614 They may be specified in either order, apart or together.
9617 @item @var{s}, search query size
9618 The size of each search query value.
9624 halfwords (two bytes)
9628 giant words (eight bytes)
9631 All values are interpreted in the current language.
9632 This means, for example, that if the current source language is C/C@t{++}
9633 then searching for the string ``hello'' includes the trailing '\0'.
9635 If the value size is not specified, it is taken from the
9636 value's type in the current language.
9637 This is useful when one wants to specify the search
9638 pattern as a mixture of types.
9639 Note that this means, for example, that in the case of C-like languages
9640 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9641 which is typically four bytes.
9643 @item @var{n}, maximum number of finds
9644 The maximum number of matches to print. The default is to print all finds.
9647 You can use strings as search values. Quote them with double-quotes
9649 The string value is copied into the search pattern byte by byte,
9650 regardless of the endianness of the target and the size specification.
9652 The address of each match found is printed as well as a count of the
9653 number of matches found.
9655 The address of the last value found is stored in convenience variable
9657 A count of the number of matches is stored in @samp{$numfound}.
9659 For example, if stopped at the @code{printf} in this function:
9665 static char hello[] = "hello-hello";
9666 static struct @{ char c; short s; int i; @}
9667 __attribute__ ((packed)) mixed
9668 = @{ 'c', 0x1234, 0x87654321 @};
9669 printf ("%s\n", hello);
9674 you get during debugging:
9677 (gdb) find &hello[0], +sizeof(hello), "hello"
9678 0x804956d <hello.1620+6>
9680 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9681 0x8049567 <hello.1620>
9682 0x804956d <hello.1620+6>
9684 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9685 0x8049567 <hello.1620>
9687 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9688 0x8049560 <mixed.1625>
9690 (gdb) print $numfound
9693 $2 = (void *) 0x8049560
9696 @node Optimized Code
9697 @chapter Debugging Optimized Code
9698 @cindex optimized code, debugging
9699 @cindex debugging optimized code
9701 Almost all compilers support optimization. With optimization
9702 disabled, the compiler generates assembly code that corresponds
9703 directly to your source code, in a simplistic way. As the compiler
9704 applies more powerful optimizations, the generated assembly code
9705 diverges from your original source code. With help from debugging
9706 information generated by the compiler, @value{GDBN} can map from
9707 the running program back to constructs from your original source.
9709 @value{GDBN} is more accurate with optimization disabled. If you
9710 can recompile without optimization, it is easier to follow the
9711 progress of your program during debugging. But, there are many cases
9712 where you may need to debug an optimized version.
9714 When you debug a program compiled with @samp{-g -O}, remember that the
9715 optimizer has rearranged your code; the debugger shows you what is
9716 really there. Do not be too surprised when the execution path does not
9717 exactly match your source file! An extreme example: if you define a
9718 variable, but never use it, @value{GDBN} never sees that
9719 variable---because the compiler optimizes it out of existence.
9721 Some things do not work as well with @samp{-g -O} as with just
9722 @samp{-g}, particularly on machines with instruction scheduling. If in
9723 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9724 please report it to us as a bug (including a test case!).
9725 @xref{Variables}, for more information about debugging optimized code.
9728 * Inline Functions:: How @value{GDBN} presents inlining
9729 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
9732 @node Inline Functions
9733 @section Inline Functions
9734 @cindex inline functions, debugging
9736 @dfn{Inlining} is an optimization that inserts a copy of the function
9737 body directly at each call site, instead of jumping to a shared
9738 routine. @value{GDBN} displays inlined functions just like
9739 non-inlined functions. They appear in backtraces. You can view their
9740 arguments and local variables, step into them with @code{step}, skip
9741 them with @code{next}, and escape from them with @code{finish}.
9742 You can check whether a function was inlined by using the
9743 @code{info frame} command.
9745 For @value{GDBN} to support inlined functions, the compiler must
9746 record information about inlining in the debug information ---
9747 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9748 other compilers do also. @value{GDBN} only supports inlined functions
9749 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9750 do not emit two required attributes (@samp{DW_AT_call_file} and
9751 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9752 function calls with earlier versions of @value{NGCC}. It instead
9753 displays the arguments and local variables of inlined functions as
9754 local variables in the caller.
9756 The body of an inlined function is directly included at its call site;
9757 unlike a non-inlined function, there are no instructions devoted to
9758 the call. @value{GDBN} still pretends that the call site and the
9759 start of the inlined function are different instructions. Stepping to
9760 the call site shows the call site, and then stepping again shows
9761 the first line of the inlined function, even though no additional
9762 instructions are executed.
9764 This makes source-level debugging much clearer; you can see both the
9765 context of the call and then the effect of the call. Only stepping by
9766 a single instruction using @code{stepi} or @code{nexti} does not do
9767 this; single instruction steps always show the inlined body.
9769 There are some ways that @value{GDBN} does not pretend that inlined
9770 function calls are the same as normal calls:
9774 You cannot set breakpoints on inlined functions. @value{GDBN}
9775 either reports that there is no symbol with that name, or else sets the
9776 breakpoint only on non-inlined copies of the function. This limitation
9777 will be removed in a future version of @value{GDBN}; until then,
9778 set a breakpoint by line number on the first line of the inlined
9782 Setting breakpoints at the call site of an inlined function may not
9783 work, because the call site does not contain any code. @value{GDBN}
9784 may incorrectly move the breakpoint to the next line of the enclosing
9785 function, after the call. This limitation will be removed in a future
9786 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9787 or inside the inlined function instead.
9790 @value{GDBN} cannot locate the return value of inlined calls after
9791 using the @code{finish} command. This is a limitation of compiler-generated
9792 debugging information; after @code{finish}, you can step to the next line
9793 and print a variable where your program stored the return value.
9797 @node Tail Call Frames
9798 @section Tail Call Frames
9799 @cindex tail call frames, debugging
9801 Function @code{B} can call function @code{C} in its very last statement. In
9802 unoptimized compilation the call of @code{C} is immediately followed by return
9803 instruction at the end of @code{B} code. Optimizing compiler may replace the
9804 call and return in function @code{B} into one jump to function @code{C}
9805 instead. Such use of a jump instruction is called @dfn{tail call}.
9807 During execution of function @code{C}, there will be no indication in the
9808 function call stack frames that it was tail-called from @code{B}. If function
9809 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
9810 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
9811 some cases @value{GDBN} can determine that @code{C} was tail-called from
9812 @code{B}, and it will then create fictitious call frame for that, with the
9813 return address set up as if @code{B} called @code{C} normally.
9815 This functionality is currently supported only by DWARF 2 debugging format and
9816 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9817 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9820 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
9821 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
9825 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
9827 Stack level 1, frame at 0x7fffffffda30:
9828 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
9829 tail call frame, caller of frame at 0x7fffffffda30
9830 source language c++.
9831 Arglist at unknown address.
9832 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
9835 The detection of all the possible code path executions can find them ambiguous.
9836 There is no execution history stored (possible @ref{Reverse Execution} is never
9837 used for this purpose) and the last known caller could have reached the known
9838 callee by multiple different jump sequences. In such case @value{GDBN} still
9839 tries to show at least all the unambiguous top tail callers and all the
9840 unambiguous bottom tail calees, if any.
9843 @anchor{set debug entry-values}
9844 @item set debug entry-values
9845 @kindex set debug entry-values
9846 When set to on, enables printing of analysis messages for both frame argument
9847 values at function entry and tail calls. It will show all the possible valid
9848 tail calls code paths it has considered. It will also print the intersection
9849 of them with the final unambiguous (possibly partial or even empty) code path
9852 @item show debug entry-values
9853 @kindex show debug entry-values
9854 Show the current state of analysis messages printing for both frame argument
9855 values at function entry and tail calls.
9858 The analysis messages for tail calls can for example show why the virtual tail
9859 call frame for function @code{c} has not been recognized (due to the indirect
9860 reference by variable @code{x}):
9863 static void __attribute__((noinline, noclone)) c (void);
9864 void (*x) (void) = c;
9865 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9866 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
9867 int main (void) @{ x (); return 0; @}
9869 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
9870 DW_TAG_GNU_call_site 0x40039a in main
9872 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9875 #1 0x000000000040039a in main () at t.c:5
9878 Another possibility is an ambiguous virtual tail call frames resolution:
9882 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
9883 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
9884 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
9885 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
9886 static void __attribute__((noinline, noclone)) b (void)
9887 @{ if (i) c (); else e (); @}
9888 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
9889 int main (void) @{ a (); return 0; @}
9891 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
9892 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
9893 tailcall: reduced: 0x4004d2(a) |
9896 #1 0x00000000004004d2 in a () at t.c:8
9897 #2 0x0000000000400395 in main () at t.c:9
9900 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
9901 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
9903 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
9904 @ifset HAVE_MAKEINFO_CLICK
9906 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
9907 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
9909 @ifclear HAVE_MAKEINFO_CLICK
9911 @set CALLSEQ1B @value{CALLSEQ1A}
9912 @set CALLSEQ2B @value{CALLSEQ2A}
9915 Frames #0 and #2 are real, #1 is a virtual tail call frame.
9916 The code can have possible execution paths @value{CALLSEQ1B} or
9917 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
9919 @code{initial:} state shows some random possible calling sequence @value{GDBN}
9920 has found. It then finds another possible calling sequcen - that one is
9921 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
9922 printed as the @code{reduced:} calling sequence. That one could have many
9923 futher @code{compare:} and @code{reduced:} statements as long as there remain
9924 any non-ambiguous sequence entries.
9926 For the frame of function @code{b} in both cases there are different possible
9927 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
9928 also ambigous. The only non-ambiguous frame is the one for function @code{a},
9929 therefore this one is displayed to the user while the ambiguous frames are
9932 There can be also reasons why printing of frame argument values at function
9937 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
9938 static void __attribute__((noinline, noclone)) a (int i);
9939 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
9940 static void __attribute__((noinline, noclone)) a (int i)
9941 @{ if (i) b (i - 1); else c (0); @}
9942 int main (void) @{ a (5); return 0; @}
9945 #0 c (i=i@@entry=0) at t.c:2
9946 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
9947 function "a" at 0x400420 can call itself via tail calls
9948 i=<optimized out>) at t.c:6
9949 #2 0x000000000040036e in main () at t.c:7
9952 @value{GDBN} cannot find out from the inferior state if and how many times did
9953 function @code{a} call itself (via function @code{b}) as these calls would be
9954 tail calls. Such tail calls would modify thue @code{i} variable, therefore
9955 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
9956 prints @code{<optimized out>} instead.
9959 @chapter C Preprocessor Macros
9961 Some languages, such as C and C@t{++}, provide a way to define and invoke
9962 ``preprocessor macros'' which expand into strings of tokens.
9963 @value{GDBN} can evaluate expressions containing macro invocations, show
9964 the result of macro expansion, and show a macro's definition, including
9965 where it was defined.
9967 You may need to compile your program specially to provide @value{GDBN}
9968 with information about preprocessor macros. Most compilers do not
9969 include macros in their debugging information, even when you compile
9970 with the @option{-g} flag. @xref{Compilation}.
9972 A program may define a macro at one point, remove that definition later,
9973 and then provide a different definition after that. Thus, at different
9974 points in the program, a macro may have different definitions, or have
9975 no definition at all. If there is a current stack frame, @value{GDBN}
9976 uses the macros in scope at that frame's source code line. Otherwise,
9977 @value{GDBN} uses the macros in scope at the current listing location;
9980 Whenever @value{GDBN} evaluates an expression, it always expands any
9981 macro invocations present in the expression. @value{GDBN} also provides
9982 the following commands for working with macros explicitly.
9986 @kindex macro expand
9987 @cindex macro expansion, showing the results of preprocessor
9988 @cindex preprocessor macro expansion, showing the results of
9989 @cindex expanding preprocessor macros
9990 @item macro expand @var{expression}
9991 @itemx macro exp @var{expression}
9992 Show the results of expanding all preprocessor macro invocations in
9993 @var{expression}. Since @value{GDBN} simply expands macros, but does
9994 not parse the result, @var{expression} need not be a valid expression;
9995 it can be any string of tokens.
9998 @item macro expand-once @var{expression}
9999 @itemx macro exp1 @var{expression}
10000 @cindex expand macro once
10001 @i{(This command is not yet implemented.)} Show the results of
10002 expanding those preprocessor macro invocations that appear explicitly in
10003 @var{expression}. Macro invocations appearing in that expansion are
10004 left unchanged. This command allows you to see the effect of a
10005 particular macro more clearly, without being confused by further
10006 expansions. Since @value{GDBN} simply expands macros, but does not
10007 parse the result, @var{expression} need not be a valid expression; it
10008 can be any string of tokens.
10011 @cindex macro definition, showing
10012 @cindex definition of a macro, showing
10013 @cindex macros, from debug info
10014 @item info macro [-a|-all] [--] @var{macro}
10015 Show the current definition or all definitions of the named @var{macro},
10016 and describe the source location or compiler command-line where that
10017 definition was established. The optional double dash is to signify the end of
10018 argument processing and the beginning of @var{macro} for non C-like macros where
10019 the macro may begin with a hyphen.
10021 @kindex info macros
10022 @item info macros @var{linespec}
10023 Show all macro definitions that are in effect at the location specified
10024 by @var{linespec}, and describe the source location or compiler
10025 command-line where those definitions were established.
10027 @kindex macro define
10028 @cindex user-defined macros
10029 @cindex defining macros interactively
10030 @cindex macros, user-defined
10031 @item macro define @var{macro} @var{replacement-list}
10032 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10033 Introduce a definition for a preprocessor macro named @var{macro},
10034 invocations of which are replaced by the tokens given in
10035 @var{replacement-list}. The first form of this command defines an
10036 ``object-like'' macro, which takes no arguments; the second form
10037 defines a ``function-like'' macro, which takes the arguments given in
10040 A definition introduced by this command is in scope in every
10041 expression evaluated in @value{GDBN}, until it is removed with the
10042 @code{macro undef} command, described below. The definition overrides
10043 all definitions for @var{macro} present in the program being debugged,
10044 as well as any previous user-supplied definition.
10046 @kindex macro undef
10047 @item macro undef @var{macro}
10048 Remove any user-supplied definition for the macro named @var{macro}.
10049 This command only affects definitions provided with the @code{macro
10050 define} command, described above; it cannot remove definitions present
10051 in the program being debugged.
10055 List all the macros defined using the @code{macro define} command.
10058 @cindex macros, example of debugging with
10059 Here is a transcript showing the above commands in action. First, we
10060 show our source files:
10065 #include "sample.h"
10068 #define ADD(x) (M + x)
10073 printf ("Hello, world!\n");
10075 printf ("We're so creative.\n");
10077 printf ("Goodbye, world!\n");
10084 Now, we compile the program using the @sc{gnu} C compiler,
10085 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10086 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10087 and @option{-gdwarf-4}; we recommend always choosing the most recent
10088 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10089 includes information about preprocessor macros in the debugging
10093 $ gcc -gdwarf-2 -g3 sample.c -o sample
10097 Now, we start @value{GDBN} on our sample program:
10101 GNU gdb 2002-05-06-cvs
10102 Copyright 2002 Free Software Foundation, Inc.
10103 GDB is free software, @dots{}
10107 We can expand macros and examine their definitions, even when the
10108 program is not running. @value{GDBN} uses the current listing position
10109 to decide which macro definitions are in scope:
10112 (@value{GDBP}) list main
10115 5 #define ADD(x) (M + x)
10120 10 printf ("Hello, world!\n");
10122 12 printf ("We're so creative.\n");
10123 (@value{GDBP}) info macro ADD
10124 Defined at /home/jimb/gdb/macros/play/sample.c:5
10125 #define ADD(x) (M + x)
10126 (@value{GDBP}) info macro Q
10127 Defined at /home/jimb/gdb/macros/play/sample.h:1
10128 included at /home/jimb/gdb/macros/play/sample.c:2
10130 (@value{GDBP}) macro expand ADD(1)
10131 expands to: (42 + 1)
10132 (@value{GDBP}) macro expand-once ADD(1)
10133 expands to: once (M + 1)
10137 In the example above, note that @code{macro expand-once} expands only
10138 the macro invocation explicit in the original text --- the invocation of
10139 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10140 which was introduced by @code{ADD}.
10142 Once the program is running, @value{GDBN} uses the macro definitions in
10143 force at the source line of the current stack frame:
10146 (@value{GDBP}) break main
10147 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10149 Starting program: /home/jimb/gdb/macros/play/sample
10151 Breakpoint 1, main () at sample.c:10
10152 10 printf ("Hello, world!\n");
10156 At line 10, the definition of the macro @code{N} at line 9 is in force:
10159 (@value{GDBP}) info macro N
10160 Defined at /home/jimb/gdb/macros/play/sample.c:9
10162 (@value{GDBP}) macro expand N Q M
10163 expands to: 28 < 42
10164 (@value{GDBP}) print N Q M
10169 As we step over directives that remove @code{N}'s definition, and then
10170 give it a new definition, @value{GDBN} finds the definition (or lack
10171 thereof) in force at each point:
10174 (@value{GDBP}) next
10176 12 printf ("We're so creative.\n");
10177 (@value{GDBP}) info macro N
10178 The symbol `N' has no definition as a C/C++ preprocessor macro
10179 at /home/jimb/gdb/macros/play/sample.c:12
10180 (@value{GDBP}) next
10182 14 printf ("Goodbye, world!\n");
10183 (@value{GDBP}) info macro N
10184 Defined at /home/jimb/gdb/macros/play/sample.c:13
10186 (@value{GDBP}) macro expand N Q M
10187 expands to: 1729 < 42
10188 (@value{GDBP}) print N Q M
10193 In addition to source files, macros can be defined on the compilation command
10194 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10195 such a way, @value{GDBN} displays the location of their definition as line zero
10196 of the source file submitted to the compiler.
10199 (@value{GDBP}) info macro __STDC__
10200 Defined at /home/jimb/gdb/macros/play/sample.c:0
10207 @chapter Tracepoints
10208 @c This chapter is based on the documentation written by Michael
10209 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10211 @cindex tracepoints
10212 In some applications, it is not feasible for the debugger to interrupt
10213 the program's execution long enough for the developer to learn
10214 anything helpful about its behavior. If the program's correctness
10215 depends on its real-time behavior, delays introduced by a debugger
10216 might cause the program to change its behavior drastically, or perhaps
10217 fail, even when the code itself is correct. It is useful to be able
10218 to observe the program's behavior without interrupting it.
10220 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10221 specify locations in the program, called @dfn{tracepoints}, and
10222 arbitrary expressions to evaluate when those tracepoints are reached.
10223 Later, using the @code{tfind} command, you can examine the values
10224 those expressions had when the program hit the tracepoints. The
10225 expressions may also denote objects in memory---structures or arrays,
10226 for example---whose values @value{GDBN} should record; while visiting
10227 a particular tracepoint, you may inspect those objects as if they were
10228 in memory at that moment. However, because @value{GDBN} records these
10229 values without interacting with you, it can do so quickly and
10230 unobtrusively, hopefully not disturbing the program's behavior.
10232 The tracepoint facility is currently available only for remote
10233 targets. @xref{Targets}. In addition, your remote target must know
10234 how to collect trace data. This functionality is implemented in the
10235 remote stub; however, none of the stubs distributed with @value{GDBN}
10236 support tracepoints as of this writing. The format of the remote
10237 packets used to implement tracepoints are described in @ref{Tracepoint
10240 It is also possible to get trace data from a file, in a manner reminiscent
10241 of corefiles; you specify the filename, and use @code{tfind} to search
10242 through the file. @xref{Trace Files}, for more details.
10244 This chapter describes the tracepoint commands and features.
10247 * Set Tracepoints::
10248 * Analyze Collected Data::
10249 * Tracepoint Variables::
10253 @node Set Tracepoints
10254 @section Commands to Set Tracepoints
10256 Before running such a @dfn{trace experiment}, an arbitrary number of
10257 tracepoints can be set. A tracepoint is actually a special type of
10258 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10259 standard breakpoint commands. For instance, as with breakpoints,
10260 tracepoint numbers are successive integers starting from one, and many
10261 of the commands associated with tracepoints take the tracepoint number
10262 as their argument, to identify which tracepoint to work on.
10264 For each tracepoint, you can specify, in advance, some arbitrary set
10265 of data that you want the target to collect in the trace buffer when
10266 it hits that tracepoint. The collected data can include registers,
10267 local variables, or global data. Later, you can use @value{GDBN}
10268 commands to examine the values these data had at the time the
10269 tracepoint was hit.
10271 Tracepoints do not support every breakpoint feature. Ignore counts on
10272 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10273 commands when they are hit. Tracepoints may not be thread-specific
10276 @cindex fast tracepoints
10277 Some targets may support @dfn{fast tracepoints}, which are inserted in
10278 a different way (such as with a jump instead of a trap), that is
10279 faster but possibly restricted in where they may be installed.
10281 @cindex static tracepoints
10282 @cindex markers, static tracepoints
10283 @cindex probing markers, static tracepoints
10284 Regular and fast tracepoints are dynamic tracing facilities, meaning
10285 that they can be used to insert tracepoints at (almost) any location
10286 in the target. Some targets may also support controlling @dfn{static
10287 tracepoints} from @value{GDBN}. With static tracing, a set of
10288 instrumentation points, also known as @dfn{markers}, are embedded in
10289 the target program, and can be activated or deactivated by name or
10290 address. These are usually placed at locations which facilitate
10291 investigating what the target is actually doing. @value{GDBN}'s
10292 support for static tracing includes being able to list instrumentation
10293 points, and attach them with @value{GDBN} defined high level
10294 tracepoints that expose the whole range of convenience of
10295 @value{GDBN}'s tracepoints support. Namely, support for collecting
10296 registers values and values of global or local (to the instrumentation
10297 point) variables; tracepoint conditions and trace state variables.
10298 The act of installing a @value{GDBN} static tracepoint on an
10299 instrumentation point, or marker, is referred to as @dfn{probing} a
10300 static tracepoint marker.
10302 @code{gdbserver} supports tracepoints on some target systems.
10303 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10305 This section describes commands to set tracepoints and associated
10306 conditions and actions.
10309 * Create and Delete Tracepoints::
10310 * Enable and Disable Tracepoints::
10311 * Tracepoint Passcounts::
10312 * Tracepoint Conditions::
10313 * Trace State Variables::
10314 * Tracepoint Actions::
10315 * Listing Tracepoints::
10316 * Listing Static Tracepoint Markers::
10317 * Starting and Stopping Trace Experiments::
10318 * Tracepoint Restrictions::
10321 @node Create and Delete Tracepoints
10322 @subsection Create and Delete Tracepoints
10325 @cindex set tracepoint
10327 @item trace @var{location}
10328 The @code{trace} command is very similar to the @code{break} command.
10329 Its argument @var{location} can be a source line, a function name, or
10330 an address in the target program. @xref{Specify Location}. The
10331 @code{trace} command defines a tracepoint, which is a point in the
10332 target program where the debugger will briefly stop, collect some
10333 data, and then allow the program to continue. Setting a tracepoint or
10334 changing its actions takes effect immediately if the remote stub
10335 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
10337 If remote stub doesn't support the @samp{InstallInTrace} feature, all
10338 these changes don't take effect until the next @code{tstart}
10339 command, and once a trace experiment is running, further changes will
10340 not have any effect until the next trace experiment starts.
10342 Here are some examples of using the @code{trace} command:
10345 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
10347 (@value{GDBP}) @b{trace +2} // 2 lines forward
10349 (@value{GDBP}) @b{trace my_function} // first source line of function
10351 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
10353 (@value{GDBP}) @b{trace *0x2117c4} // an address
10357 You can abbreviate @code{trace} as @code{tr}.
10359 @item trace @var{location} if @var{cond}
10360 Set a tracepoint with condition @var{cond}; evaluate the expression
10361 @var{cond} each time the tracepoint is reached, and collect data only
10362 if the value is nonzero---that is, if @var{cond} evaluates as true.
10363 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
10364 information on tracepoint conditions.
10366 @item ftrace @var{location} [ if @var{cond} ]
10367 @cindex set fast tracepoint
10368 @cindex fast tracepoints, setting
10370 The @code{ftrace} command sets a fast tracepoint. For targets that
10371 support them, fast tracepoints will use a more efficient but possibly
10372 less general technique to trigger data collection, such as a jump
10373 instruction instead of a trap, or some sort of hardware support. It
10374 may not be possible to create a fast tracepoint at the desired
10375 location, in which case the command will exit with an explanatory
10378 @value{GDBN} handles arguments to @code{ftrace} exactly as for
10381 On 32-bit x86-architecture systems, fast tracepoints normally need to
10382 be placed at an instruction that is 5 bytes or longer, but can be
10383 placed at 4-byte instructions if the low 64K of memory of the target
10384 program is available to install trampolines. Some Unix-type systems,
10385 such as @sc{gnu}/Linux, exclude low addresses from the program's
10386 address space; but for instance with the Linux kernel it is possible
10387 to let @value{GDBN} use this area by doing a @command{sysctl} command
10388 to set the @code{mmap_min_addr} kernel parameter, as in
10391 sudo sysctl -w vm.mmap_min_addr=32768
10395 which sets the low address to 32K, which leaves plenty of room for
10396 trampolines. The minimum address should be set to a page boundary.
10398 @item strace @var{location} [ if @var{cond} ]
10399 @cindex set static tracepoint
10400 @cindex static tracepoints, setting
10401 @cindex probe static tracepoint marker
10403 The @code{strace} command sets a static tracepoint. For targets that
10404 support it, setting a static tracepoint probes a static
10405 instrumentation point, or marker, found at @var{location}. It may not
10406 be possible to set a static tracepoint at the desired location, in
10407 which case the command will exit with an explanatory message.
10409 @value{GDBN} handles arguments to @code{strace} exactly as for
10410 @code{trace}, with the addition that the user can also specify
10411 @code{-m @var{marker}} as @var{location}. This probes the marker
10412 identified by the @var{marker} string identifier. This identifier
10413 depends on the static tracepoint backend library your program is
10414 using. You can find all the marker identifiers in the @samp{ID} field
10415 of the @code{info static-tracepoint-markers} command output.
10416 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
10417 Markers}. For example, in the following small program using the UST
10423 trace_mark(ust, bar33, "str %s", "FOOBAZ");
10428 the marker id is composed of joining the first two arguments to the
10429 @code{trace_mark} call with a slash, which translates to:
10432 (@value{GDBP}) info static-tracepoint-markers
10433 Cnt Enb ID Address What
10434 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
10440 so you may probe the marker above with:
10443 (@value{GDBP}) strace -m ust/bar33
10446 Static tracepoints accept an extra collect action --- @code{collect
10447 $_sdata}. This collects arbitrary user data passed in the probe point
10448 call to the tracing library. In the UST example above, you'll see
10449 that the third argument to @code{trace_mark} is a printf-like format
10450 string. The user data is then the result of running that formating
10451 string against the following arguments. Note that @code{info
10452 static-tracepoint-markers} command output lists that format string in
10453 the @samp{Data:} field.
10455 You can inspect this data when analyzing the trace buffer, by printing
10456 the $_sdata variable like any other variable available to
10457 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
10460 @cindex last tracepoint number
10461 @cindex recent tracepoint number
10462 @cindex tracepoint number
10463 The convenience variable @code{$tpnum} records the tracepoint number
10464 of the most recently set tracepoint.
10466 @kindex delete tracepoint
10467 @cindex tracepoint deletion
10468 @item delete tracepoint @r{[}@var{num}@r{]}
10469 Permanently delete one or more tracepoints. With no argument, the
10470 default is to delete all tracepoints. Note that the regular
10471 @code{delete} command can remove tracepoints also.
10476 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10478 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10482 You can abbreviate this command as @code{del tr}.
10485 @node Enable and Disable Tracepoints
10486 @subsection Enable and Disable Tracepoints
10488 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10491 @kindex disable tracepoint
10492 @item disable tracepoint @r{[}@var{num}@r{]}
10493 Disable tracepoint @var{num}, or all tracepoints if no argument
10494 @var{num} is given. A disabled tracepoint will have no effect during
10495 a trace experiment, but it is not forgotten. You can re-enable
10496 a disabled tracepoint using the @code{enable tracepoint} command.
10497 If the command is issued during a trace experiment and the debug target
10498 has support for disabling tracepoints during a trace experiment, then the
10499 change will be effective immediately. Otherwise, it will be applied to the
10500 next trace experiment.
10502 @kindex enable tracepoint
10503 @item enable tracepoint @r{[}@var{num}@r{]}
10504 Enable tracepoint @var{num}, or all tracepoints. If this command is
10505 issued during a trace experiment and the debug target supports enabling
10506 tracepoints during a trace experiment, then the enabled tracepoints will
10507 become effective immediately. Otherwise, they will become effective the
10508 next time a trace experiment is run.
10511 @node Tracepoint Passcounts
10512 @subsection Tracepoint Passcounts
10516 @cindex tracepoint pass count
10517 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10518 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10519 automatically stop a trace experiment. If a tracepoint's passcount is
10520 @var{n}, then the trace experiment will be automatically stopped on
10521 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10522 @var{num} is not specified, the @code{passcount} command sets the
10523 passcount of the most recently defined tracepoint. If no passcount is
10524 given, the trace experiment will run until stopped explicitly by the
10530 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10531 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10533 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10534 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10535 (@value{GDBP}) @b{trace foo}
10536 (@value{GDBP}) @b{pass 3}
10537 (@value{GDBP}) @b{trace bar}
10538 (@value{GDBP}) @b{pass 2}
10539 (@value{GDBP}) @b{trace baz}
10540 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10541 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10542 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10543 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10547 @node Tracepoint Conditions
10548 @subsection Tracepoint Conditions
10549 @cindex conditional tracepoints
10550 @cindex tracepoint conditions
10552 The simplest sort of tracepoint collects data every time your program
10553 reaches a specified place. You can also specify a @dfn{condition} for
10554 a tracepoint. A condition is just a Boolean expression in your
10555 programming language (@pxref{Expressions, ,Expressions}). A
10556 tracepoint with a condition evaluates the expression each time your
10557 program reaches it, and data collection happens only if the condition
10560 Tracepoint conditions can be specified when a tracepoint is set, by
10561 using @samp{if} in the arguments to the @code{trace} command.
10562 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10563 also be set or changed at any time with the @code{condition} command,
10564 just as with breakpoints.
10566 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10567 the conditional expression itself. Instead, @value{GDBN} encodes the
10568 expression into an agent expression (@pxref{Agent Expressions})
10569 suitable for execution on the target, independently of @value{GDBN}.
10570 Global variables become raw memory locations, locals become stack
10571 accesses, and so forth.
10573 For instance, suppose you have a function that is usually called
10574 frequently, but should not be called after an error has occurred. You
10575 could use the following tracepoint command to collect data about calls
10576 of that function that happen while the error code is propagating
10577 through the program; an unconditional tracepoint could end up
10578 collecting thousands of useless trace frames that you would have to
10582 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10585 @node Trace State Variables
10586 @subsection Trace State Variables
10587 @cindex trace state variables
10589 A @dfn{trace state variable} is a special type of variable that is
10590 created and managed by target-side code. The syntax is the same as
10591 that for GDB's convenience variables (a string prefixed with ``$''),
10592 but they are stored on the target. They must be created explicitly,
10593 using a @code{tvariable} command. They are always 64-bit signed
10596 Trace state variables are remembered by @value{GDBN}, and downloaded
10597 to the target along with tracepoint information when the trace
10598 experiment starts. There are no intrinsic limits on the number of
10599 trace state variables, beyond memory limitations of the target.
10601 @cindex convenience variables, and trace state variables
10602 Although trace state variables are managed by the target, you can use
10603 them in print commands and expressions as if they were convenience
10604 variables; @value{GDBN} will get the current value from the target
10605 while the trace experiment is running. Trace state variables share
10606 the same namespace as other ``$'' variables, which means that you
10607 cannot have trace state variables with names like @code{$23} or
10608 @code{$pc}, nor can you have a trace state variable and a convenience
10609 variable with the same name.
10613 @item tvariable $@var{name} [ = @var{expression} ]
10615 The @code{tvariable} command creates a new trace state variable named
10616 @code{$@var{name}}, and optionally gives it an initial value of
10617 @var{expression}. @var{expression} is evaluated when this command is
10618 entered; the result will be converted to an integer if possible,
10619 otherwise @value{GDBN} will report an error. A subsequent
10620 @code{tvariable} command specifying the same name does not create a
10621 variable, but instead assigns the supplied initial value to the
10622 existing variable of that name, overwriting any previous initial
10623 value. The default initial value is 0.
10625 @item info tvariables
10626 @kindex info tvariables
10627 List all the trace state variables along with their initial values.
10628 Their current values may also be displayed, if the trace experiment is
10631 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10632 @kindex delete tvariable
10633 Delete the given trace state variables, or all of them if no arguments
10638 @node Tracepoint Actions
10639 @subsection Tracepoint Action Lists
10643 @cindex tracepoint actions
10644 @item actions @r{[}@var{num}@r{]}
10645 This command will prompt for a list of actions to be taken when the
10646 tracepoint is hit. If the tracepoint number @var{num} is not
10647 specified, this command sets the actions for the one that was most
10648 recently defined (so that you can define a tracepoint and then say
10649 @code{actions} without bothering about its number). You specify the
10650 actions themselves on the following lines, one action at a time, and
10651 terminate the actions list with a line containing just @code{end}. So
10652 far, the only defined actions are @code{collect}, @code{teval}, and
10653 @code{while-stepping}.
10655 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10656 Commands, ,Breakpoint Command Lists}), except that only the defined
10657 actions are allowed; any other @value{GDBN} command is rejected.
10659 @cindex remove actions from a tracepoint
10660 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10661 and follow it immediately with @samp{end}.
10664 (@value{GDBP}) @b{collect @var{data}} // collect some data
10666 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10668 (@value{GDBP}) @b{end} // signals the end of actions.
10671 In the following example, the action list begins with @code{collect}
10672 commands indicating the things to be collected when the tracepoint is
10673 hit. Then, in order to single-step and collect additional data
10674 following the tracepoint, a @code{while-stepping} command is used,
10675 followed by the list of things to be collected after each step in a
10676 sequence of single steps. The @code{while-stepping} command is
10677 terminated by its own separate @code{end} command. Lastly, the action
10678 list is terminated by an @code{end} command.
10681 (@value{GDBP}) @b{trace foo}
10682 (@value{GDBP}) @b{actions}
10683 Enter actions for tracepoint 1, one per line:
10686 > while-stepping 12
10687 > collect $pc, arr[i]
10692 @kindex collect @r{(tracepoints)}
10693 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
10694 Collect values of the given expressions when the tracepoint is hit.
10695 This command accepts a comma-separated list of any valid expressions.
10696 In addition to global, static, or local variables, the following
10697 special arguments are supported:
10701 Collect all registers.
10704 Collect all function arguments.
10707 Collect all local variables.
10710 Collect the return address. This is helpful if you want to see more
10714 @vindex $_sdata@r{, collect}
10715 Collect static tracepoint marker specific data. Only available for
10716 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10717 Lists}. On the UST static tracepoints library backend, an
10718 instrumentation point resembles a @code{printf} function call. The
10719 tracing library is able to collect user specified data formatted to a
10720 character string using the format provided by the programmer that
10721 instrumented the program. Other backends have similar mechanisms.
10722 Here's an example of a UST marker call:
10725 const char master_name[] = "$your_name";
10726 trace_mark(channel1, marker1, "hello %s", master_name)
10729 In this case, collecting @code{$_sdata} collects the string
10730 @samp{hello $yourname}. When analyzing the trace buffer, you can
10731 inspect @samp{$_sdata} like any other variable available to
10735 You can give several consecutive @code{collect} commands, each one
10736 with a single argument, or one @code{collect} command with several
10737 arguments separated by commas; the effect is the same.
10739 The optional @var{mods} changes the usual handling of the arguments.
10740 @code{s} requests that pointers to chars be handled as strings, in
10741 particular collecting the contents of the memory being pointed at, up
10742 to the first zero. The upper bound is by default the value of the
10743 @code{print elements} variable; if @code{s} is followed by a decimal
10744 number, that is the upper bound instead. So for instance
10745 @samp{collect/s25 mystr} collects as many as 25 characters at
10748 The command @code{info scope} (@pxref{Symbols, info scope}) is
10749 particularly useful for figuring out what data to collect.
10751 @kindex teval @r{(tracepoints)}
10752 @item teval @var{expr1}, @var{expr2}, @dots{}
10753 Evaluate the given expressions when the tracepoint is hit. This
10754 command accepts a comma-separated list of expressions. The results
10755 are discarded, so this is mainly useful for assigning values to trace
10756 state variables (@pxref{Trace State Variables}) without adding those
10757 values to the trace buffer, as would be the case if the @code{collect}
10760 @kindex while-stepping @r{(tracepoints)}
10761 @item while-stepping @var{n}
10762 Perform @var{n} single-step instruction traces after the tracepoint,
10763 collecting new data after each step. The @code{while-stepping}
10764 command is followed by the list of what to collect while stepping
10765 (followed by its own @code{end} command):
10768 > while-stepping 12
10769 > collect $regs, myglobal
10775 Note that @code{$pc} is not automatically collected by
10776 @code{while-stepping}; you need to explicitly collect that register if
10777 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10780 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10781 @kindex set default-collect
10782 @cindex default collection action
10783 This variable is a list of expressions to collect at each tracepoint
10784 hit. It is effectively an additional @code{collect} action prepended
10785 to every tracepoint action list. The expressions are parsed
10786 individually for each tracepoint, so for instance a variable named
10787 @code{xyz} may be interpreted as a global for one tracepoint, and a
10788 local for another, as appropriate to the tracepoint's location.
10790 @item show default-collect
10791 @kindex show default-collect
10792 Show the list of expressions that are collected by default at each
10797 @node Listing Tracepoints
10798 @subsection Listing Tracepoints
10801 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10802 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10803 @cindex information about tracepoints
10804 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10805 Display information about the tracepoint @var{num}. If you don't
10806 specify a tracepoint number, displays information about all the
10807 tracepoints defined so far. The format is similar to that used for
10808 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10809 command, simply restricting itself to tracepoints.
10811 A tracepoint's listing may include additional information specific to
10816 its passcount as given by the @code{passcount @var{n}} command
10820 (@value{GDBP}) @b{info trace}
10821 Num Type Disp Enb Address What
10822 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10824 collect globfoo, $regs
10833 This command can be abbreviated @code{info tp}.
10836 @node Listing Static Tracepoint Markers
10837 @subsection Listing Static Tracepoint Markers
10840 @kindex info static-tracepoint-markers
10841 @cindex information about static tracepoint markers
10842 @item info static-tracepoint-markers
10843 Display information about all static tracepoint markers defined in the
10846 For each marker, the following columns are printed:
10850 An incrementing counter, output to help readability. This is not a
10853 The marker ID, as reported by the target.
10854 @item Enabled or Disabled
10855 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10856 that are not enabled.
10858 Where the marker is in your program, as a memory address.
10860 Where the marker is in the source for your program, as a file and line
10861 number. If the debug information included in the program does not
10862 allow @value{GDBN} to locate the source of the marker, this column
10863 will be left blank.
10867 In addition, the following information may be printed for each marker:
10871 User data passed to the tracing library by the marker call. In the
10872 UST backend, this is the format string passed as argument to the
10874 @item Static tracepoints probing the marker
10875 The list of static tracepoints attached to the marker.
10879 (@value{GDBP}) info static-tracepoint-markers
10880 Cnt ID Enb Address What
10881 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10882 Data: number1 %d number2 %d
10883 Probed by static tracepoints: #2
10884 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10890 @node Starting and Stopping Trace Experiments
10891 @subsection Starting and Stopping Trace Experiments
10895 @cindex start a new trace experiment
10896 @cindex collected data discarded
10898 This command takes no arguments. It starts the trace experiment, and
10899 begins collecting data. This has the side effect of discarding all
10900 the data collected in the trace buffer during the previous trace
10904 @cindex stop a running trace experiment
10906 This command takes no arguments. It ends the trace experiment, and
10907 stops collecting data.
10909 @strong{Note}: a trace experiment and data collection may stop
10910 automatically if any tracepoint's passcount is reached
10911 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10914 @cindex status of trace data collection
10915 @cindex trace experiment, status of
10917 This command displays the status of the current trace data
10921 Here is an example of the commands we described so far:
10924 (@value{GDBP}) @b{trace gdb_c_test}
10925 (@value{GDBP}) @b{actions}
10926 Enter actions for tracepoint #1, one per line.
10927 > collect $regs,$locals,$args
10928 > while-stepping 11
10932 (@value{GDBP}) @b{tstart}
10933 [time passes @dots{}]
10934 (@value{GDBP}) @b{tstop}
10937 @anchor{disconnected tracing}
10938 @cindex disconnected tracing
10939 You can choose to continue running the trace experiment even if
10940 @value{GDBN} disconnects from the target, voluntarily or
10941 involuntarily. For commands such as @code{detach}, the debugger will
10942 ask what you want to do with the trace. But for unexpected
10943 terminations (@value{GDBN} crash, network outage), it would be
10944 unfortunate to lose hard-won trace data, so the variable
10945 @code{disconnected-tracing} lets you decide whether the trace should
10946 continue running without @value{GDBN}.
10949 @item set disconnected-tracing on
10950 @itemx set disconnected-tracing off
10951 @kindex set disconnected-tracing
10952 Choose whether a tracing run should continue to run if @value{GDBN}
10953 has disconnected from the target. Note that @code{detach} or
10954 @code{quit} will ask you directly what to do about a running trace no
10955 matter what this variable's setting, so the variable is mainly useful
10956 for handling unexpected situations, such as loss of the network.
10958 @item show disconnected-tracing
10959 @kindex show disconnected-tracing
10960 Show the current choice for disconnected tracing.
10964 When you reconnect to the target, the trace experiment may or may not
10965 still be running; it might have filled the trace buffer in the
10966 meantime, or stopped for one of the other reasons. If it is running,
10967 it will continue after reconnection.
10969 Upon reconnection, the target will upload information about the
10970 tracepoints in effect. @value{GDBN} will then compare that
10971 information to the set of tracepoints currently defined, and attempt
10972 to match them up, allowing for the possibility that the numbers may
10973 have changed due to creation and deletion in the meantime. If one of
10974 the target's tracepoints does not match any in @value{GDBN}, the
10975 debugger will create a new tracepoint, so that you have a number with
10976 which to specify that tracepoint. This matching-up process is
10977 necessarily heuristic, and it may result in useless tracepoints being
10978 created; you may simply delete them if they are of no use.
10980 @cindex circular trace buffer
10981 If your target agent supports a @dfn{circular trace buffer}, then you
10982 can run a trace experiment indefinitely without filling the trace
10983 buffer; when space runs out, the agent deletes already-collected trace
10984 frames, oldest first, until there is enough room to continue
10985 collecting. This is especially useful if your tracepoints are being
10986 hit too often, and your trace gets terminated prematurely because the
10987 buffer is full. To ask for a circular trace buffer, simply set
10988 @samp{circular-trace-buffer} to on. You can set this at any time,
10989 including during tracing; if the agent can do it, it will change
10990 buffer handling on the fly, otherwise it will not take effect until
10994 @item set circular-trace-buffer on
10995 @itemx set circular-trace-buffer off
10996 @kindex set circular-trace-buffer
10997 Choose whether a tracing run should use a linear or circular buffer
10998 for trace data. A linear buffer will not lose any trace data, but may
10999 fill up prematurely, while a circular buffer will discard old trace
11000 data, but it will have always room for the latest tracepoint hits.
11002 @item show circular-trace-buffer
11003 @kindex show circular-trace-buffer
11004 Show the current choice for the trace buffer. Note that this may not
11005 match the agent's current buffer handling, nor is it guaranteed to
11006 match the setting that might have been in effect during a past run,
11007 for instance if you are looking at frames from a trace file.
11011 @node Tracepoint Restrictions
11012 @subsection Tracepoint Restrictions
11014 @cindex tracepoint restrictions
11015 There are a number of restrictions on the use of tracepoints. As
11016 described above, tracepoint data gathering occurs on the target
11017 without interaction from @value{GDBN}. Thus the full capabilities of
11018 the debugger are not available during data gathering, and then at data
11019 examination time, you will be limited by only having what was
11020 collected. The following items describe some common problems, but it
11021 is not exhaustive, and you may run into additional difficulties not
11027 Tracepoint expressions are intended to gather objects (lvalues). Thus
11028 the full flexibility of GDB's expression evaluator is not available.
11029 You cannot call functions, cast objects to aggregate types, access
11030 convenience variables or modify values (except by assignment to trace
11031 state variables). Some language features may implicitly call
11032 functions (for instance Objective-C fields with accessors), and therefore
11033 cannot be collected either.
11036 Collection of local variables, either individually or in bulk with
11037 @code{$locals} or @code{$args}, during @code{while-stepping} may
11038 behave erratically. The stepping action may enter a new scope (for
11039 instance by stepping into a function), or the location of the variable
11040 may change (for instance it is loaded into a register). The
11041 tracepoint data recorded uses the location information for the
11042 variables that is correct for the tracepoint location. When the
11043 tracepoint is created, it is not possible, in general, to determine
11044 where the steps of a @code{while-stepping} sequence will advance the
11045 program---particularly if a conditional branch is stepped.
11048 Collection of an incompletely-initialized or partially-destroyed object
11049 may result in something that @value{GDBN} cannot display, or displays
11050 in a misleading way.
11053 When @value{GDBN} displays a pointer to character it automatically
11054 dereferences the pointer to also display characters of the string
11055 being pointed to. However, collecting the pointer during tracing does
11056 not automatically collect the string. You need to explicitly
11057 dereference the pointer and provide size information if you want to
11058 collect not only the pointer, but the memory pointed to. For example,
11059 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11063 It is not possible to collect a complete stack backtrace at a
11064 tracepoint. Instead, you may collect the registers and a few hundred
11065 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11066 (adjust to use the name of the actual stack pointer register on your
11067 target architecture, and the amount of stack you wish to capture).
11068 Then the @code{backtrace} command will show a partial backtrace when
11069 using a trace frame. The number of stack frames that can be examined
11070 depends on the sizes of the frames in the collected stack. Note that
11071 if you ask for a block so large that it goes past the bottom of the
11072 stack, the target agent may report an error trying to read from an
11076 If you do not collect registers at a tracepoint, @value{GDBN} can
11077 infer that the value of @code{$pc} must be the same as the address of
11078 the tracepoint and use that when you are looking at a trace frame
11079 for that tracepoint. However, this cannot work if the tracepoint has
11080 multiple locations (for instance if it was set in a function that was
11081 inlined), or if it has a @code{while-stepping} loop. In those cases
11082 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11087 @node Analyze Collected Data
11088 @section Using the Collected Data
11090 After the tracepoint experiment ends, you use @value{GDBN} commands
11091 for examining the trace data. The basic idea is that each tracepoint
11092 collects a trace @dfn{snapshot} every time it is hit and another
11093 snapshot every time it single-steps. All these snapshots are
11094 consecutively numbered from zero and go into a buffer, and you can
11095 examine them later. The way you examine them is to @dfn{focus} on a
11096 specific trace snapshot. When the remote stub is focused on a trace
11097 snapshot, it will respond to all @value{GDBN} requests for memory and
11098 registers by reading from the buffer which belongs to that snapshot,
11099 rather than from @emph{real} memory or registers of the program being
11100 debugged. This means that @strong{all} @value{GDBN} commands
11101 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11102 behave as if we were currently debugging the program state as it was
11103 when the tracepoint occurred. Any requests for data that are not in
11104 the buffer will fail.
11107 * tfind:: How to select a trace snapshot
11108 * tdump:: How to display all data for a snapshot
11109 * save tracepoints:: How to save tracepoints for a future run
11113 @subsection @code{tfind @var{n}}
11116 @cindex select trace snapshot
11117 @cindex find trace snapshot
11118 The basic command for selecting a trace snapshot from the buffer is
11119 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11120 counting from zero. If no argument @var{n} is given, the next
11121 snapshot is selected.
11123 Here are the various forms of using the @code{tfind} command.
11127 Find the first snapshot in the buffer. This is a synonym for
11128 @code{tfind 0} (since 0 is the number of the first snapshot).
11131 Stop debugging trace snapshots, resume @emph{live} debugging.
11134 Same as @samp{tfind none}.
11137 No argument means find the next trace snapshot.
11140 Find the previous trace snapshot before the current one. This permits
11141 retracing earlier steps.
11143 @item tfind tracepoint @var{num}
11144 Find the next snapshot associated with tracepoint @var{num}. Search
11145 proceeds forward from the last examined trace snapshot. If no
11146 argument @var{num} is given, it means find the next snapshot collected
11147 for the same tracepoint as the current snapshot.
11149 @item tfind pc @var{addr}
11150 Find the next snapshot associated with the value @var{addr} of the
11151 program counter. Search proceeds forward from the last examined trace
11152 snapshot. If no argument @var{addr} is given, it means find the next
11153 snapshot with the same value of PC as the current snapshot.
11155 @item tfind outside @var{addr1}, @var{addr2}
11156 Find the next snapshot whose PC is outside the given range of
11157 addresses (exclusive).
11159 @item tfind range @var{addr1}, @var{addr2}
11160 Find the next snapshot whose PC is between @var{addr1} and
11161 @var{addr2} (inclusive).
11163 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11164 Find the next snapshot associated with the source line @var{n}. If
11165 the optional argument @var{file} is given, refer to line @var{n} in
11166 that source file. Search proceeds forward from the last examined
11167 trace snapshot. If no argument @var{n} is given, it means find the
11168 next line other than the one currently being examined; thus saying
11169 @code{tfind line} repeatedly can appear to have the same effect as
11170 stepping from line to line in a @emph{live} debugging session.
11173 The default arguments for the @code{tfind} commands are specifically
11174 designed to make it easy to scan through the trace buffer. For
11175 instance, @code{tfind} with no argument selects the next trace
11176 snapshot, and @code{tfind -} with no argument selects the previous
11177 trace snapshot. So, by giving one @code{tfind} command, and then
11178 simply hitting @key{RET} repeatedly you can examine all the trace
11179 snapshots in order. Or, by saying @code{tfind -} and then hitting
11180 @key{RET} repeatedly you can examine the snapshots in reverse order.
11181 The @code{tfind line} command with no argument selects the snapshot
11182 for the next source line executed. The @code{tfind pc} command with
11183 no argument selects the next snapshot with the same program counter
11184 (PC) as the current frame. The @code{tfind tracepoint} command with
11185 no argument selects the next trace snapshot collected by the same
11186 tracepoint as the current one.
11188 In addition to letting you scan through the trace buffer manually,
11189 these commands make it easy to construct @value{GDBN} scripts that
11190 scan through the trace buffer and print out whatever collected data
11191 you are interested in. Thus, if we want to examine the PC, FP, and SP
11192 registers from each trace frame in the buffer, we can say this:
11195 (@value{GDBP}) @b{tfind start}
11196 (@value{GDBP}) @b{while ($trace_frame != -1)}
11197 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11198 $trace_frame, $pc, $sp, $fp
11202 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11203 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11204 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11205 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11206 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11207 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11208 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11209 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11210 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11211 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11212 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11215 Or, if we want to examine the variable @code{X} at each source line in
11219 (@value{GDBP}) @b{tfind start}
11220 (@value{GDBP}) @b{while ($trace_frame != -1)}
11221 > printf "Frame %d, X == %d\n", $trace_frame, X
11231 @subsection @code{tdump}
11233 @cindex dump all data collected at tracepoint
11234 @cindex tracepoint data, display
11236 This command takes no arguments. It prints all the data collected at
11237 the current trace snapshot.
11240 (@value{GDBP}) @b{trace 444}
11241 (@value{GDBP}) @b{actions}
11242 Enter actions for tracepoint #2, one per line:
11243 > collect $regs, $locals, $args, gdb_long_test
11246 (@value{GDBP}) @b{tstart}
11248 (@value{GDBP}) @b{tfind line 444}
11249 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11251 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11253 (@value{GDBP}) @b{tdump}
11254 Data collected at tracepoint 2, trace frame 1:
11255 d0 0xc4aa0085 -995491707
11259 d4 0x71aea3d 119204413
11262 d7 0x380035 3670069
11263 a0 0x19e24a 1696330
11264 a1 0x3000668 50333288
11266 a3 0x322000 3284992
11267 a4 0x3000698 50333336
11268 a5 0x1ad3cc 1758156
11269 fp 0x30bf3c 0x30bf3c
11270 sp 0x30bf34 0x30bf34
11272 pc 0x20b2c8 0x20b2c8
11276 p = 0x20e5b4 "gdb-test"
11283 gdb_long_test = 17 '\021'
11288 @code{tdump} works by scanning the tracepoint's current collection
11289 actions and printing the value of each expression listed. So
11290 @code{tdump} can fail, if after a run, you change the tracepoint's
11291 actions to mention variables that were not collected during the run.
11293 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11294 uses the collected value of @code{$pc} to distinguish between trace
11295 frames that were collected at the tracepoint hit, and frames that were
11296 collected while stepping. This allows it to correctly choose whether
11297 to display the basic list of collections, or the collections from the
11298 body of the while-stepping loop. However, if @code{$pc} was not collected,
11299 then @code{tdump} will always attempt to dump using the basic collection
11300 list, and may fail if a while-stepping frame does not include all the
11301 same data that is collected at the tracepoint hit.
11302 @c This is getting pretty arcane, example would be good.
11304 @node save tracepoints
11305 @subsection @code{save tracepoints @var{filename}}
11306 @kindex save tracepoints
11307 @kindex save-tracepoints
11308 @cindex save tracepoints for future sessions
11310 This command saves all current tracepoint definitions together with
11311 their actions and passcounts, into a file @file{@var{filename}}
11312 suitable for use in a later debugging session. To read the saved
11313 tracepoint definitions, use the @code{source} command (@pxref{Command
11314 Files}). The @w{@code{save-tracepoints}} command is a deprecated
11315 alias for @w{@code{save tracepoints}}
11317 @node Tracepoint Variables
11318 @section Convenience Variables for Tracepoints
11319 @cindex tracepoint variables
11320 @cindex convenience variables for tracepoints
11323 @vindex $trace_frame
11324 @item (int) $trace_frame
11325 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
11326 snapshot is selected.
11328 @vindex $tracepoint
11329 @item (int) $tracepoint
11330 The tracepoint for the current trace snapshot.
11332 @vindex $trace_line
11333 @item (int) $trace_line
11334 The line number for the current trace snapshot.
11336 @vindex $trace_file
11337 @item (char []) $trace_file
11338 The source file for the current trace snapshot.
11340 @vindex $trace_func
11341 @item (char []) $trace_func
11342 The name of the function containing @code{$tracepoint}.
11345 Note: @code{$trace_file} is not suitable for use in @code{printf},
11346 use @code{output} instead.
11348 Here's a simple example of using these convenience variables for
11349 stepping through all the trace snapshots and printing some of their
11350 data. Note that these are not the same as trace state variables,
11351 which are managed by the target.
11354 (@value{GDBP}) @b{tfind start}
11356 (@value{GDBP}) @b{while $trace_frame != -1}
11357 > output $trace_file
11358 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
11364 @section Using Trace Files
11365 @cindex trace files
11367 In some situations, the target running a trace experiment may no
11368 longer be available; perhaps it crashed, or the hardware was needed
11369 for a different activity. To handle these cases, you can arrange to
11370 dump the trace data into a file, and later use that file as a source
11371 of trace data, via the @code{target tfile} command.
11376 @item tsave [ -r ] @var{filename}
11377 Save the trace data to @var{filename}. By default, this command
11378 assumes that @var{filename} refers to the host filesystem, so if
11379 necessary @value{GDBN} will copy raw trace data up from the target and
11380 then save it. If the target supports it, you can also supply the
11381 optional argument @code{-r} (``remote'') to direct the target to save
11382 the data directly into @var{filename} in its own filesystem, which may be
11383 more efficient if the trace buffer is very large. (Note, however, that
11384 @code{target tfile} can only read from files accessible to the host.)
11386 @kindex target tfile
11388 @item target tfile @var{filename}
11389 Use the file named @var{filename} as a source of trace data. Commands
11390 that examine data work as they do with a live target, but it is not
11391 possible to run any new trace experiments. @code{tstatus} will report
11392 the state of the trace run at the moment the data was saved, as well
11393 as the current trace frame you are examining. @var{filename} must be
11394 on a filesystem accessible to the host.
11399 @chapter Debugging Programs That Use Overlays
11402 If your program is too large to fit completely in your target system's
11403 memory, you can sometimes use @dfn{overlays} to work around this
11404 problem. @value{GDBN} provides some support for debugging programs that
11408 * How Overlays Work:: A general explanation of overlays.
11409 * Overlay Commands:: Managing overlays in @value{GDBN}.
11410 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
11411 mapped by asking the inferior.
11412 * Overlay Sample Program:: A sample program using overlays.
11415 @node How Overlays Work
11416 @section How Overlays Work
11417 @cindex mapped overlays
11418 @cindex unmapped overlays
11419 @cindex load address, overlay's
11420 @cindex mapped address
11421 @cindex overlay area
11423 Suppose you have a computer whose instruction address space is only 64
11424 kilobytes long, but which has much more memory which can be accessed by
11425 other means: special instructions, segment registers, or memory
11426 management hardware, for example. Suppose further that you want to
11427 adapt a program which is larger than 64 kilobytes to run on this system.
11429 One solution is to identify modules of your program which are relatively
11430 independent, and need not call each other directly; call these modules
11431 @dfn{overlays}. Separate the overlays from the main program, and place
11432 their machine code in the larger memory. Place your main program in
11433 instruction memory, but leave at least enough space there to hold the
11434 largest overlay as well.
11436 Now, to call a function located in an overlay, you must first copy that
11437 overlay's machine code from the large memory into the space set aside
11438 for it in the instruction memory, and then jump to its entry point
11441 @c NB: In the below the mapped area's size is greater or equal to the
11442 @c size of all overlays. This is intentional to remind the developer
11443 @c that overlays don't necessarily need to be the same size.
11447 Data Instruction Larger
11448 Address Space Address Space Address Space
11449 +-----------+ +-----------+ +-----------+
11451 +-----------+ +-----------+ +-----------+<-- overlay 1
11452 | program | | main | .----| overlay 1 | load address
11453 | variables | | program | | +-----------+
11454 | and heap | | | | | |
11455 +-----------+ | | | +-----------+<-- overlay 2
11456 | | +-----------+ | | | load address
11457 +-----------+ | | | .-| overlay 2 |
11459 mapped --->+-----------+ | | +-----------+
11460 address | | | | | |
11461 | overlay | <-' | | |
11462 | area | <---' +-----------+<-- overlay 3
11463 | | <---. | | load address
11464 +-----------+ `--| overlay 3 |
11471 @anchor{A code overlay}A code overlay
11475 The diagram (@pxref{A code overlay}) shows a system with separate data
11476 and instruction address spaces. To map an overlay, the program copies
11477 its code from the larger address space to the instruction address space.
11478 Since the overlays shown here all use the same mapped address, only one
11479 may be mapped at a time. For a system with a single address space for
11480 data and instructions, the diagram would be similar, except that the
11481 program variables and heap would share an address space with the main
11482 program and the overlay area.
11484 An overlay loaded into instruction memory and ready for use is called a
11485 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11486 instruction memory. An overlay not present (or only partially present)
11487 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11488 is its address in the larger memory. The mapped address is also called
11489 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11490 called the @dfn{load memory address}, or @dfn{LMA}.
11492 Unfortunately, overlays are not a completely transparent way to adapt a
11493 program to limited instruction memory. They introduce a new set of
11494 global constraints you must keep in mind as you design your program:
11499 Before calling or returning to a function in an overlay, your program
11500 must make sure that overlay is actually mapped. Otherwise, the call or
11501 return will transfer control to the right address, but in the wrong
11502 overlay, and your program will probably crash.
11505 If the process of mapping an overlay is expensive on your system, you
11506 will need to choose your overlays carefully to minimize their effect on
11507 your program's performance.
11510 The executable file you load onto your system must contain each
11511 overlay's instructions, appearing at the overlay's load address, not its
11512 mapped address. However, each overlay's instructions must be relocated
11513 and its symbols defined as if the overlay were at its mapped address.
11514 You can use GNU linker scripts to specify different load and relocation
11515 addresses for pieces of your program; see @ref{Overlay Description,,,
11516 ld.info, Using ld: the GNU linker}.
11519 The procedure for loading executable files onto your system must be able
11520 to load their contents into the larger address space as well as the
11521 instruction and data spaces.
11525 The overlay system described above is rather simple, and could be
11526 improved in many ways:
11531 If your system has suitable bank switch registers or memory management
11532 hardware, you could use those facilities to make an overlay's load area
11533 contents simply appear at their mapped address in instruction space.
11534 This would probably be faster than copying the overlay to its mapped
11535 area in the usual way.
11538 If your overlays are small enough, you could set aside more than one
11539 overlay area, and have more than one overlay mapped at a time.
11542 You can use overlays to manage data, as well as instructions. In
11543 general, data overlays are even less transparent to your design than
11544 code overlays: whereas code overlays only require care when you call or
11545 return to functions, data overlays require care every time you access
11546 the data. Also, if you change the contents of a data overlay, you
11547 must copy its contents back out to its load address before you can copy a
11548 different data overlay into the same mapped area.
11553 @node Overlay Commands
11554 @section Overlay Commands
11556 To use @value{GDBN}'s overlay support, each overlay in your program must
11557 correspond to a separate section of the executable file. The section's
11558 virtual memory address and load memory address must be the overlay's
11559 mapped and load addresses. Identifying overlays with sections allows
11560 @value{GDBN} to determine the appropriate address of a function or
11561 variable, depending on whether the overlay is mapped or not.
11563 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11564 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11569 Disable @value{GDBN}'s overlay support. When overlay support is
11570 disabled, @value{GDBN} assumes that all functions and variables are
11571 always present at their mapped addresses. By default, @value{GDBN}'s
11572 overlay support is disabled.
11574 @item overlay manual
11575 @cindex manual overlay debugging
11576 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11577 relies on you to tell it which overlays are mapped, and which are not,
11578 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11579 commands described below.
11581 @item overlay map-overlay @var{overlay}
11582 @itemx overlay map @var{overlay}
11583 @cindex map an overlay
11584 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11585 be the name of the object file section containing the overlay. When an
11586 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11587 functions and variables at their mapped addresses. @value{GDBN} assumes
11588 that any other overlays whose mapped ranges overlap that of
11589 @var{overlay} are now unmapped.
11591 @item overlay unmap-overlay @var{overlay}
11592 @itemx overlay unmap @var{overlay}
11593 @cindex unmap an overlay
11594 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11595 must be the name of the object file section containing the overlay.
11596 When an overlay is unmapped, @value{GDBN} assumes it can find the
11597 overlay's functions and variables at their load addresses.
11600 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11601 consults a data structure the overlay manager maintains in the inferior
11602 to see which overlays are mapped. For details, see @ref{Automatic
11603 Overlay Debugging}.
11605 @item overlay load-target
11606 @itemx overlay load
11607 @cindex reloading the overlay table
11608 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11609 re-reads the table @value{GDBN} automatically each time the inferior
11610 stops, so this command should only be necessary if you have changed the
11611 overlay mapping yourself using @value{GDBN}. This command is only
11612 useful when using automatic overlay debugging.
11614 @item overlay list-overlays
11615 @itemx overlay list
11616 @cindex listing mapped overlays
11617 Display a list of the overlays currently mapped, along with their mapped
11618 addresses, load addresses, and sizes.
11622 Normally, when @value{GDBN} prints a code address, it includes the name
11623 of the function the address falls in:
11626 (@value{GDBP}) print main
11627 $3 = @{int ()@} 0x11a0 <main>
11630 When overlay debugging is enabled, @value{GDBN} recognizes code in
11631 unmapped overlays, and prints the names of unmapped functions with
11632 asterisks around them. For example, if @code{foo} is a function in an
11633 unmapped overlay, @value{GDBN} prints it this way:
11636 (@value{GDBP}) overlay list
11637 No sections are mapped.
11638 (@value{GDBP}) print foo
11639 $5 = @{int (int)@} 0x100000 <*foo*>
11642 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11646 (@value{GDBP}) overlay list
11647 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11648 mapped at 0x1016 - 0x104a
11649 (@value{GDBP}) print foo
11650 $6 = @{int (int)@} 0x1016 <foo>
11653 When overlay debugging is enabled, @value{GDBN} can find the correct
11654 address for functions and variables in an overlay, whether or not the
11655 overlay is mapped. This allows most @value{GDBN} commands, like
11656 @code{break} and @code{disassemble}, to work normally, even on unmapped
11657 code. However, @value{GDBN}'s breakpoint support has some limitations:
11661 @cindex breakpoints in overlays
11662 @cindex overlays, setting breakpoints in
11663 You can set breakpoints in functions in unmapped overlays, as long as
11664 @value{GDBN} can write to the overlay at its load address.
11666 @value{GDBN} can not set hardware or simulator-based breakpoints in
11667 unmapped overlays. However, if you set a breakpoint at the end of your
11668 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11669 you are using manual overlay management), @value{GDBN} will re-set its
11670 breakpoints properly.
11674 @node Automatic Overlay Debugging
11675 @section Automatic Overlay Debugging
11676 @cindex automatic overlay debugging
11678 @value{GDBN} can automatically track which overlays are mapped and which
11679 are not, given some simple co-operation from the overlay manager in the
11680 inferior. If you enable automatic overlay debugging with the
11681 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11682 looks in the inferior's memory for certain variables describing the
11683 current state of the overlays.
11685 Here are the variables your overlay manager must define to support
11686 @value{GDBN}'s automatic overlay debugging:
11690 @item @code{_ovly_table}:
11691 This variable must be an array of the following structures:
11696 /* The overlay's mapped address. */
11699 /* The size of the overlay, in bytes. */
11700 unsigned long size;
11702 /* The overlay's load address. */
11705 /* Non-zero if the overlay is currently mapped;
11707 unsigned long mapped;
11711 @item @code{_novlys}:
11712 This variable must be a four-byte signed integer, holding the total
11713 number of elements in @code{_ovly_table}.
11717 To decide whether a particular overlay is mapped or not, @value{GDBN}
11718 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11719 @code{lma} members equal the VMA and LMA of the overlay's section in the
11720 executable file. When @value{GDBN} finds a matching entry, it consults
11721 the entry's @code{mapped} member to determine whether the overlay is
11724 In addition, your overlay manager may define a function called
11725 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11726 will silently set a breakpoint there. If the overlay manager then
11727 calls this function whenever it has changed the overlay table, this
11728 will enable @value{GDBN} to accurately keep track of which overlays
11729 are in program memory, and update any breakpoints that may be set
11730 in overlays. This will allow breakpoints to work even if the
11731 overlays are kept in ROM or other non-writable memory while they
11732 are not being executed.
11734 @node Overlay Sample Program
11735 @section Overlay Sample Program
11736 @cindex overlay example program
11738 When linking a program which uses overlays, you must place the overlays
11739 at their load addresses, while relocating them to run at their mapped
11740 addresses. To do this, you must write a linker script (@pxref{Overlay
11741 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11742 since linker scripts are specific to a particular host system, target
11743 architecture, and target memory layout, this manual cannot provide
11744 portable sample code demonstrating @value{GDBN}'s overlay support.
11746 However, the @value{GDBN} source distribution does contain an overlaid
11747 program, with linker scripts for a few systems, as part of its test
11748 suite. The program consists of the following files from
11749 @file{gdb/testsuite/gdb.base}:
11753 The main program file.
11755 A simple overlay manager, used by @file{overlays.c}.
11760 Overlay modules, loaded and used by @file{overlays.c}.
11763 Linker scripts for linking the test program on the @code{d10v-elf}
11764 and @code{m32r-elf} targets.
11767 You can build the test program using the @code{d10v-elf} GCC
11768 cross-compiler like this:
11771 $ d10v-elf-gcc -g -c overlays.c
11772 $ d10v-elf-gcc -g -c ovlymgr.c
11773 $ d10v-elf-gcc -g -c foo.c
11774 $ d10v-elf-gcc -g -c bar.c
11775 $ d10v-elf-gcc -g -c baz.c
11776 $ d10v-elf-gcc -g -c grbx.c
11777 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11778 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11781 The build process is identical for any other architecture, except that
11782 you must substitute the appropriate compiler and linker script for the
11783 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11787 @chapter Using @value{GDBN} with Different Languages
11790 Although programming languages generally have common aspects, they are
11791 rarely expressed in the same manner. For instance, in ANSI C,
11792 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11793 Modula-2, it is accomplished by @code{p^}. Values can also be
11794 represented (and displayed) differently. Hex numbers in C appear as
11795 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11797 @cindex working language
11798 Language-specific information is built into @value{GDBN} for some languages,
11799 allowing you to express operations like the above in your program's
11800 native language, and allowing @value{GDBN} to output values in a manner
11801 consistent with the syntax of your program's native language. The
11802 language you use to build expressions is called the @dfn{working
11806 * Setting:: Switching between source languages
11807 * Show:: Displaying the language
11808 * Checks:: Type and range checks
11809 * Supported Languages:: Supported languages
11810 * Unsupported Languages:: Unsupported languages
11814 @section Switching Between Source Languages
11816 There are two ways to control the working language---either have @value{GDBN}
11817 set it automatically, or select it manually yourself. You can use the
11818 @code{set language} command for either purpose. On startup, @value{GDBN}
11819 defaults to setting the language automatically. The working language is
11820 used to determine how expressions you type are interpreted, how values
11823 In addition to the working language, every source file that
11824 @value{GDBN} knows about has its own working language. For some object
11825 file formats, the compiler might indicate which language a particular
11826 source file is in. However, most of the time @value{GDBN} infers the
11827 language from the name of the file. The language of a source file
11828 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11829 show each frame appropriately for its own language. There is no way to
11830 set the language of a source file from within @value{GDBN}, but you can
11831 set the language associated with a filename extension. @xref{Show, ,
11832 Displaying the Language}.
11834 This is most commonly a problem when you use a program, such
11835 as @code{cfront} or @code{f2c}, that generates C but is written in
11836 another language. In that case, make the
11837 program use @code{#line} directives in its C output; that way
11838 @value{GDBN} will know the correct language of the source code of the original
11839 program, and will display that source code, not the generated C code.
11842 * Filenames:: Filename extensions and languages.
11843 * Manually:: Setting the working language manually
11844 * Automatically:: Having @value{GDBN} infer the source language
11848 @subsection List of Filename Extensions and Languages
11850 If a source file name ends in one of the following extensions, then
11851 @value{GDBN} infers that its language is the one indicated.
11869 C@t{++} source file
11875 Objective-C source file
11879 Fortran source file
11882 Modula-2 source file
11886 Assembler source file. This actually behaves almost like C, but
11887 @value{GDBN} does not skip over function prologues when stepping.
11890 In addition, you may set the language associated with a filename
11891 extension. @xref{Show, , Displaying the Language}.
11894 @subsection Setting the Working Language
11896 If you allow @value{GDBN} to set the language automatically,
11897 expressions are interpreted the same way in your debugging session and
11900 @kindex set language
11901 If you wish, you may set the language manually. To do this, issue the
11902 command @samp{set language @var{lang}}, where @var{lang} is the name of
11903 a language, such as
11904 @code{c} or @code{modula-2}.
11905 For a list of the supported languages, type @samp{set language}.
11907 Setting the language manually prevents @value{GDBN} from updating the working
11908 language automatically. This can lead to confusion if you try
11909 to debug a program when the working language is not the same as the
11910 source language, when an expression is acceptable to both
11911 languages---but means different things. For instance, if the current
11912 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11920 might not have the effect you intended. In C, this means to add
11921 @code{b} and @code{c} and place the result in @code{a}. The result
11922 printed would be the value of @code{a}. In Modula-2, this means to compare
11923 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11925 @node Automatically
11926 @subsection Having @value{GDBN} Infer the Source Language
11928 To have @value{GDBN} set the working language automatically, use
11929 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11930 then infers the working language. That is, when your program stops in a
11931 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11932 working language to the language recorded for the function in that
11933 frame. If the language for a frame is unknown (that is, if the function
11934 or block corresponding to the frame was defined in a source file that
11935 does not have a recognized extension), the current working language is
11936 not changed, and @value{GDBN} issues a warning.
11938 This may not seem necessary for most programs, which are written
11939 entirely in one source language. However, program modules and libraries
11940 written in one source language can be used by a main program written in
11941 a different source language. Using @samp{set language auto} in this
11942 case frees you from having to set the working language manually.
11945 @section Displaying the Language
11947 The following commands help you find out which language is the
11948 working language, and also what language source files were written in.
11951 @item show language
11952 @kindex show language
11953 Display the current working language. This is the
11954 language you can use with commands such as @code{print} to
11955 build and compute expressions that may involve variables in your program.
11958 @kindex info frame@r{, show the source language}
11959 Display the source language for this frame. This language becomes the
11960 working language if you use an identifier from this frame.
11961 @xref{Frame Info, ,Information about a Frame}, to identify the other
11962 information listed here.
11965 @kindex info source@r{, show the source language}
11966 Display the source language of this source file.
11967 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11968 information listed here.
11971 In unusual circumstances, you may have source files with extensions
11972 not in the standard list. You can then set the extension associated
11973 with a language explicitly:
11976 @item set extension-language @var{ext} @var{language}
11977 @kindex set extension-language
11978 Tell @value{GDBN} that source files with extension @var{ext} are to be
11979 assumed as written in the source language @var{language}.
11981 @item info extensions
11982 @kindex info extensions
11983 List all the filename extensions and the associated languages.
11987 @section Type and Range Checking
11990 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11991 checking are included, but they do not yet have any effect. This
11992 section documents the intended facilities.
11994 @c FIXME remove warning when type/range code added
11996 Some languages are designed to guard you against making seemingly common
11997 errors through a series of compile- and run-time checks. These include
11998 checking the type of arguments to functions and operators, and making
11999 sure mathematical overflows are caught at run time. Checks such as
12000 these help to ensure a program's correctness once it has been compiled
12001 by eliminating type mismatches, and providing active checks for range
12002 errors when your program is running.
12004 @value{GDBN} can check for conditions like the above if you wish.
12005 Although @value{GDBN} does not check the statements in your program,
12006 it can check expressions entered directly into @value{GDBN} for
12007 evaluation via the @code{print} command, for example. As with the
12008 working language, @value{GDBN} can also decide whether or not to check
12009 automatically based on your program's source language.
12010 @xref{Supported Languages, ,Supported Languages}, for the default
12011 settings of supported languages.
12014 * Type Checking:: An overview of type checking
12015 * Range Checking:: An overview of range checking
12018 @cindex type checking
12019 @cindex checks, type
12020 @node Type Checking
12021 @subsection An Overview of Type Checking
12023 Some languages, such as Modula-2, are strongly typed, meaning that the
12024 arguments to operators and functions have to be of the correct type,
12025 otherwise an error occurs. These checks prevent type mismatch
12026 errors from ever causing any run-time problems. For example,
12034 The second example fails because the @code{CARDINAL} 1 is not
12035 type-compatible with the @code{REAL} 2.3.
12037 For the expressions you use in @value{GDBN} commands, you can tell the
12038 @value{GDBN} type checker to skip checking;
12039 to treat any mismatches as errors and abandon the expression;
12040 or to only issue warnings when type mismatches occur,
12041 but evaluate the expression anyway. When you choose the last of
12042 these, @value{GDBN} evaluates expressions like the second example above, but
12043 also issues a warning.
12045 Even if you turn type checking off, there may be other reasons
12046 related to type that prevent @value{GDBN} from evaluating an expression.
12047 For instance, @value{GDBN} does not know how to add an @code{int} and
12048 a @code{struct foo}. These particular type errors have nothing to do
12049 with the language in use, and usually arise from expressions, such as
12050 the one described above, which make little sense to evaluate anyway.
12052 Each language defines to what degree it is strict about type. For
12053 instance, both Modula-2 and C require the arguments to arithmetical
12054 operators to be numbers. In C, enumerated types and pointers can be
12055 represented as numbers, so that they are valid arguments to mathematical
12056 operators. @xref{Supported Languages, ,Supported Languages}, for further
12057 details on specific languages.
12059 @value{GDBN} provides some additional commands for controlling the type checker:
12061 @kindex set check type
12062 @kindex show check type
12064 @item set check type auto
12065 Set type checking on or off based on the current working language.
12066 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12069 @item set check type on
12070 @itemx set check type off
12071 Set type checking on or off, overriding the default setting for the
12072 current working language. Issue a warning if the setting does not
12073 match the language default. If any type mismatches occur in
12074 evaluating an expression while type checking is on, @value{GDBN} prints a
12075 message and aborts evaluation of the expression.
12077 @item set check type warn
12078 Cause the type checker to issue warnings, but to always attempt to
12079 evaluate the expression. Evaluating the expression may still
12080 be impossible for other reasons. For example, @value{GDBN} cannot add
12081 numbers and structures.
12084 Show the current setting of the type checker, and whether or not @value{GDBN}
12085 is setting it automatically.
12088 @cindex range checking
12089 @cindex checks, range
12090 @node Range Checking
12091 @subsection An Overview of Range Checking
12093 In some languages (such as Modula-2), it is an error to exceed the
12094 bounds of a type; this is enforced with run-time checks. Such range
12095 checking is meant to ensure program correctness by making sure
12096 computations do not overflow, or indices on an array element access do
12097 not exceed the bounds of the array.
12099 For expressions you use in @value{GDBN} commands, you can tell
12100 @value{GDBN} to treat range errors in one of three ways: ignore them,
12101 always treat them as errors and abandon the expression, or issue
12102 warnings but evaluate the expression anyway.
12104 A range error can result from numerical overflow, from exceeding an
12105 array index bound, or when you type a constant that is not a member
12106 of any type. Some languages, however, do not treat overflows as an
12107 error. In many implementations of C, mathematical overflow causes the
12108 result to ``wrap around'' to lower values---for example, if @var{m} is
12109 the largest integer value, and @var{s} is the smallest, then
12112 @var{m} + 1 @result{} @var{s}
12115 This, too, is specific to individual languages, and in some cases
12116 specific to individual compilers or machines. @xref{Supported Languages, ,
12117 Supported Languages}, for further details on specific languages.
12119 @value{GDBN} provides some additional commands for controlling the range checker:
12121 @kindex set check range
12122 @kindex show check range
12124 @item set check range auto
12125 Set range checking on or off based on the current working language.
12126 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12129 @item set check range on
12130 @itemx set check range off
12131 Set range checking on or off, overriding the default setting for the
12132 current working language. A warning is issued if the setting does not
12133 match the language default. If a range error occurs and range checking is on,
12134 then a message is printed and evaluation of the expression is aborted.
12136 @item set check range warn
12137 Output messages when the @value{GDBN} range checker detects a range error,
12138 but attempt to evaluate the expression anyway. Evaluating the
12139 expression may still be impossible for other reasons, such as accessing
12140 memory that the process does not own (a typical example from many Unix
12144 Show the current setting of the range checker, and whether or not it is
12145 being set automatically by @value{GDBN}.
12148 @node Supported Languages
12149 @section Supported Languages
12151 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
12152 assembly, Modula-2, and Ada.
12153 @c This is false ...
12154 Some @value{GDBN} features may be used in expressions regardless of the
12155 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12156 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12157 ,Expressions}) can be used with the constructs of any supported
12160 The following sections detail to what degree each source language is
12161 supported by @value{GDBN}. These sections are not meant to be language
12162 tutorials or references, but serve only as a reference guide to what the
12163 @value{GDBN} expression parser accepts, and what input and output
12164 formats should look like for different languages. There are many good
12165 books written on each of these languages; please look to these for a
12166 language reference or tutorial.
12169 * C:: C and C@t{++}
12171 * Objective-C:: Objective-C
12172 * OpenCL C:: OpenCL C
12173 * Fortran:: Fortran
12175 * Modula-2:: Modula-2
12180 @subsection C and C@t{++}
12182 @cindex C and C@t{++}
12183 @cindex expressions in C or C@t{++}
12185 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12186 to both languages. Whenever this is the case, we discuss those languages
12190 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12191 @cindex @sc{gnu} C@t{++}
12192 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12193 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12194 effectively, you must compile your C@t{++} programs with a supported
12195 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12196 compiler (@code{aCC}).
12199 * C Operators:: C and C@t{++} operators
12200 * C Constants:: C and C@t{++} constants
12201 * C Plus Plus Expressions:: C@t{++} expressions
12202 * C Defaults:: Default settings for C and C@t{++}
12203 * C Checks:: C and C@t{++} type and range checks
12204 * Debugging C:: @value{GDBN} and C
12205 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12206 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12210 @subsubsection C and C@t{++} Operators
12212 @cindex C and C@t{++} operators
12214 Operators must be defined on values of specific types. For instance,
12215 @code{+} is defined on numbers, but not on structures. Operators are
12216 often defined on groups of types.
12218 For the purposes of C and C@t{++}, the following definitions hold:
12223 @emph{Integral types} include @code{int} with any of its storage-class
12224 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12227 @emph{Floating-point types} include @code{float}, @code{double}, and
12228 @code{long double} (if supported by the target platform).
12231 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12234 @emph{Scalar types} include all of the above.
12239 The following operators are supported. They are listed here
12240 in order of increasing precedence:
12244 The comma or sequencing operator. Expressions in a comma-separated list
12245 are evaluated from left to right, with the result of the entire
12246 expression being the last expression evaluated.
12249 Assignment. The value of an assignment expression is the value
12250 assigned. Defined on scalar types.
12253 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12254 and translated to @w{@code{@var{a} = @var{a op b}}}.
12255 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12256 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12257 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12260 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12261 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12265 Logical @sc{or}. Defined on integral types.
12268 Logical @sc{and}. Defined on integral types.
12271 Bitwise @sc{or}. Defined on integral types.
12274 Bitwise exclusive-@sc{or}. Defined on integral types.
12277 Bitwise @sc{and}. Defined on integral types.
12280 Equality and inequality. Defined on scalar types. The value of these
12281 expressions is 0 for false and non-zero for true.
12283 @item <@r{, }>@r{, }<=@r{, }>=
12284 Less than, greater than, less than or equal, greater than or equal.
12285 Defined on scalar types. The value of these expressions is 0 for false
12286 and non-zero for true.
12289 left shift, and right shift. Defined on integral types.
12292 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12295 Addition and subtraction. Defined on integral types, floating-point types and
12298 @item *@r{, }/@r{, }%
12299 Multiplication, division, and modulus. Multiplication and division are
12300 defined on integral and floating-point types. Modulus is defined on
12304 Increment and decrement. When appearing before a variable, the
12305 operation is performed before the variable is used in an expression;
12306 when appearing after it, the variable's value is used before the
12307 operation takes place.
12310 Pointer dereferencing. Defined on pointer types. Same precedence as
12314 Address operator. Defined on variables. Same precedence as @code{++}.
12316 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
12317 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
12318 to examine the address
12319 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
12323 Negative. Defined on integral and floating-point types. Same
12324 precedence as @code{++}.
12327 Logical negation. Defined on integral types. Same precedence as
12331 Bitwise complement operator. Defined on integral types. Same precedence as
12336 Structure member, and pointer-to-structure member. For convenience,
12337 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
12338 pointer based on the stored type information.
12339 Defined on @code{struct} and @code{union} data.
12342 Dereferences of pointers to members.
12345 Array indexing. @code{@var{a}[@var{i}]} is defined as
12346 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
12349 Function parameter list. Same precedence as @code{->}.
12352 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
12353 and @code{class} types.
12356 Doubled colons also represent the @value{GDBN} scope operator
12357 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
12361 If an operator is redefined in the user code, @value{GDBN} usually
12362 attempts to invoke the redefined version instead of using the operator's
12363 predefined meaning.
12366 @subsubsection C and C@t{++} Constants
12368 @cindex C and C@t{++} constants
12370 @value{GDBN} allows you to express the constants of C and C@t{++} in the
12375 Integer constants are a sequence of digits. Octal constants are
12376 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
12377 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
12378 @samp{l}, specifying that the constant should be treated as a
12382 Floating point constants are a sequence of digits, followed by a decimal
12383 point, followed by a sequence of digits, and optionally followed by an
12384 exponent. An exponent is of the form:
12385 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
12386 sequence of digits. The @samp{+} is optional for positive exponents.
12387 A floating-point constant may also end with a letter @samp{f} or
12388 @samp{F}, specifying that the constant should be treated as being of
12389 the @code{float} (as opposed to the default @code{double}) type; or with
12390 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
12394 Enumerated constants consist of enumerated identifiers, or their
12395 integral equivalents.
12398 Character constants are a single character surrounded by single quotes
12399 (@code{'}), or a number---the ordinal value of the corresponding character
12400 (usually its @sc{ascii} value). Within quotes, the single character may
12401 be represented by a letter or by @dfn{escape sequences}, which are of
12402 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
12403 of the character's ordinal value; or of the form @samp{\@var{x}}, where
12404 @samp{@var{x}} is a predefined special character---for example,
12405 @samp{\n} for newline.
12407 Wide character constants can be written by prefixing a character
12408 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
12409 form of @samp{x}. The target wide character set is used when
12410 computing the value of this constant (@pxref{Character Sets}).
12413 String constants are a sequence of character constants surrounded by
12414 double quotes (@code{"}). Any valid character constant (as described
12415 above) may appear. Double quotes within the string must be preceded by
12416 a backslash, so for instance @samp{"a\"b'c"} is a string of five
12419 Wide string constants can be written by prefixing a string constant
12420 with @samp{L}, as in C. The target wide character set is used when
12421 computing the value of this constant (@pxref{Character Sets}).
12424 Pointer constants are an integral value. You can also write pointers
12425 to constants using the C operator @samp{&}.
12428 Array constants are comma-separated lists surrounded by braces @samp{@{}
12429 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
12430 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
12431 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
12434 @node C Plus Plus Expressions
12435 @subsubsection C@t{++} Expressions
12437 @cindex expressions in C@t{++}
12438 @value{GDBN} expression handling can interpret most C@t{++} expressions.
12440 @cindex debugging C@t{++} programs
12441 @cindex C@t{++} compilers
12442 @cindex debug formats and C@t{++}
12443 @cindex @value{NGCC} and C@t{++}
12445 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
12446 the proper compiler and the proper debug format. Currently,
12447 @value{GDBN} works best when debugging C@t{++} code that is compiled
12448 with the most recent version of @value{NGCC} possible. The DWARF
12449 debugging format is preferred; @value{NGCC} defaults to this on most
12450 popular platforms. Other compilers and/or debug formats are likely to
12451 work badly or not at all when using @value{GDBN} to debug C@t{++}
12452 code. @xref{Compilation}.
12457 @cindex member functions
12459 Member function calls are allowed; you can use expressions like
12462 count = aml->GetOriginal(x, y)
12465 @vindex this@r{, inside C@t{++} member functions}
12466 @cindex namespace in C@t{++}
12468 While a member function is active (in the selected stack frame), your
12469 expressions have the same namespace available as the member function;
12470 that is, @value{GDBN} allows implicit references to the class instance
12471 pointer @code{this} following the same rules as C@t{++}. @code{using}
12472 declarations in the current scope are also respected by @value{GDBN}.
12474 @cindex call overloaded functions
12475 @cindex overloaded functions, calling
12476 @cindex type conversions in C@t{++}
12478 You can call overloaded functions; @value{GDBN} resolves the function
12479 call to the right definition, with some restrictions. @value{GDBN} does not
12480 perform overload resolution involving user-defined type conversions,
12481 calls to constructors, or instantiations of templates that do not exist
12482 in the program. It also cannot handle ellipsis argument lists or
12485 It does perform integral conversions and promotions, floating-point
12486 promotions, arithmetic conversions, pointer conversions, conversions of
12487 class objects to base classes, and standard conversions such as those of
12488 functions or arrays to pointers; it requires an exact match on the
12489 number of function arguments.
12491 Overload resolution is always performed, unless you have specified
12492 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12493 ,@value{GDBN} Features for C@t{++}}.
12495 You must specify @code{set overload-resolution off} in order to use an
12496 explicit function signature to call an overloaded function, as in
12498 p 'foo(char,int)'('x', 13)
12501 The @value{GDBN} command-completion facility can simplify this;
12502 see @ref{Completion, ,Command Completion}.
12504 @cindex reference declarations
12506 @value{GDBN} understands variables declared as C@t{++} references; you can use
12507 them in expressions just as you do in C@t{++} source---they are automatically
12510 In the parameter list shown when @value{GDBN} displays a frame, the values of
12511 reference variables are not displayed (unlike other variables); this
12512 avoids clutter, since references are often used for large structures.
12513 The @emph{address} of a reference variable is always shown, unless
12514 you have specified @samp{set print address off}.
12517 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12518 expressions can use it just as expressions in your program do. Since
12519 one scope may be defined in another, you can use @code{::} repeatedly if
12520 necessary, for example in an expression like
12521 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12522 resolving name scope by reference to source files, in both C and C@t{++}
12523 debugging (@pxref{Variables, ,Program Variables}).
12526 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
12531 @subsubsection C and C@t{++} Defaults
12533 @cindex C and C@t{++} defaults
12535 If you allow @value{GDBN} to set type and range checking automatically, they
12536 both default to @code{off} whenever the working language changes to
12537 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12538 selects the working language.
12540 If you allow @value{GDBN} to set the language automatically, it
12541 recognizes source files whose names end with @file{.c}, @file{.C}, or
12542 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12543 these files, it sets the working language to C or C@t{++}.
12544 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12545 for further details.
12547 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12548 @c unimplemented. If (b) changes, it might make sense to let this node
12549 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12552 @subsubsection C and C@t{++} Type and Range Checks
12554 @cindex C and C@t{++} checks
12556 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12557 is not used. However, if you turn type checking on, @value{GDBN}
12558 considers two variables type equivalent if:
12562 The two variables are structured and have the same structure, union, or
12566 The two variables have the same type name, or types that have been
12567 declared equivalent through @code{typedef}.
12570 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12573 The two @code{struct}, @code{union}, or @code{enum} variables are
12574 declared in the same declaration. (Note: this may not be true for all C
12579 Range checking, if turned on, is done on mathematical operations. Array
12580 indices are not checked, since they are often used to index a pointer
12581 that is not itself an array.
12584 @subsubsection @value{GDBN} and C
12586 The @code{set print union} and @code{show print union} commands apply to
12587 the @code{union} type. When set to @samp{on}, any @code{union} that is
12588 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12589 appears as @samp{@{...@}}.
12591 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12592 with pointers and a memory allocation function. @xref{Expressions,
12595 @node Debugging C Plus Plus
12596 @subsubsection @value{GDBN} Features for C@t{++}
12598 @cindex commands for C@t{++}
12600 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12601 designed specifically for use with C@t{++}. Here is a summary:
12604 @cindex break in overloaded functions
12605 @item @r{breakpoint menus}
12606 When you want a breakpoint in a function whose name is overloaded,
12607 @value{GDBN} has the capability to display a menu of possible breakpoint
12608 locations to help you specify which function definition you want.
12609 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12611 @cindex overloading in C@t{++}
12612 @item rbreak @var{regex}
12613 Setting breakpoints using regular expressions is helpful for setting
12614 breakpoints on overloaded functions that are not members of any special
12616 @xref{Set Breaks, ,Setting Breakpoints}.
12618 @cindex C@t{++} exception handling
12621 Debug C@t{++} exception handling using these commands. @xref{Set
12622 Catchpoints, , Setting Catchpoints}.
12624 @cindex inheritance
12625 @item ptype @var{typename}
12626 Print inheritance relationships as well as other information for type
12628 @xref{Symbols, ,Examining the Symbol Table}.
12630 @cindex C@t{++} symbol display
12631 @item set print demangle
12632 @itemx show print demangle
12633 @itemx set print asm-demangle
12634 @itemx show print asm-demangle
12635 Control whether C@t{++} symbols display in their source form, both when
12636 displaying code as C@t{++} source and when displaying disassemblies.
12637 @xref{Print Settings, ,Print Settings}.
12639 @item set print object
12640 @itemx show print object
12641 Choose whether to print derived (actual) or declared types of objects.
12642 @xref{Print Settings, ,Print Settings}.
12644 @item set print vtbl
12645 @itemx show print vtbl
12646 Control the format for printing virtual function tables.
12647 @xref{Print Settings, ,Print Settings}.
12648 (The @code{vtbl} commands do not work on programs compiled with the HP
12649 ANSI C@t{++} compiler (@code{aCC}).)
12651 @kindex set overload-resolution
12652 @cindex overloaded functions, overload resolution
12653 @item set overload-resolution on
12654 Enable overload resolution for C@t{++} expression evaluation. The default
12655 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12656 and searches for a function whose signature matches the argument types,
12657 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12658 Expressions, ,C@t{++} Expressions}, for details).
12659 If it cannot find a match, it emits a message.
12661 @item set overload-resolution off
12662 Disable overload resolution for C@t{++} expression evaluation. For
12663 overloaded functions that are not class member functions, @value{GDBN}
12664 chooses the first function of the specified name that it finds in the
12665 symbol table, whether or not its arguments are of the correct type. For
12666 overloaded functions that are class member functions, @value{GDBN}
12667 searches for a function whose signature @emph{exactly} matches the
12670 @kindex show overload-resolution
12671 @item show overload-resolution
12672 Show the current setting of overload resolution.
12674 @item @r{Overloaded symbol names}
12675 You can specify a particular definition of an overloaded symbol, using
12676 the same notation that is used to declare such symbols in C@t{++}: type
12677 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12678 also use the @value{GDBN} command-line word completion facilities to list the
12679 available choices, or to finish the type list for you.
12680 @xref{Completion,, Command Completion}, for details on how to do this.
12683 @node Decimal Floating Point
12684 @subsubsection Decimal Floating Point format
12685 @cindex decimal floating point format
12687 @value{GDBN} can examine, set and perform computations with numbers in
12688 decimal floating point format, which in the C language correspond to the
12689 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12690 specified by the extension to support decimal floating-point arithmetic.
12692 There are two encodings in use, depending on the architecture: BID (Binary
12693 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12694 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12697 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12698 to manipulate decimal floating point numbers, it is not possible to convert
12699 (using a cast, for example) integers wider than 32-bit to decimal float.
12701 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12702 point computations, error checking in decimal float operations ignores
12703 underflow, overflow and divide by zero exceptions.
12705 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12706 to inspect @code{_Decimal128} values stored in floating point registers.
12707 See @ref{PowerPC,,PowerPC} for more details.
12713 @value{GDBN} can be used to debug programs written in D and compiled with
12714 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12715 specific feature --- dynamic arrays.
12718 @subsection Objective-C
12720 @cindex Objective-C
12721 This section provides information about some commands and command
12722 options that are useful for debugging Objective-C code. See also
12723 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12724 few more commands specific to Objective-C support.
12727 * Method Names in Commands::
12728 * The Print Command with Objective-C::
12731 @node Method Names in Commands
12732 @subsubsection Method Names in Commands
12734 The following commands have been extended to accept Objective-C method
12735 names as line specifications:
12737 @kindex clear@r{, and Objective-C}
12738 @kindex break@r{, and Objective-C}
12739 @kindex info line@r{, and Objective-C}
12740 @kindex jump@r{, and Objective-C}
12741 @kindex list@r{, and Objective-C}
12745 @item @code{info line}
12750 A fully qualified Objective-C method name is specified as
12753 -[@var{Class} @var{methodName}]
12756 where the minus sign is used to indicate an instance method and a
12757 plus sign (not shown) is used to indicate a class method. The class
12758 name @var{Class} and method name @var{methodName} are enclosed in
12759 brackets, similar to the way messages are specified in Objective-C
12760 source code. For example, to set a breakpoint at the @code{create}
12761 instance method of class @code{Fruit} in the program currently being
12765 break -[Fruit create]
12768 To list ten program lines around the @code{initialize} class method,
12772 list +[NSText initialize]
12775 In the current version of @value{GDBN}, the plus or minus sign is
12776 required. In future versions of @value{GDBN}, the plus or minus
12777 sign will be optional, but you can use it to narrow the search. It
12778 is also possible to specify just a method name:
12784 You must specify the complete method name, including any colons. If
12785 your program's source files contain more than one @code{create} method,
12786 you'll be presented with a numbered list of classes that implement that
12787 method. Indicate your choice by number, or type @samp{0} to exit if
12790 As another example, to clear a breakpoint established at the
12791 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12794 clear -[NSWindow makeKeyAndOrderFront:]
12797 @node The Print Command with Objective-C
12798 @subsubsection The Print Command With Objective-C
12799 @cindex Objective-C, print objects
12800 @kindex print-object
12801 @kindex po @r{(@code{print-object})}
12803 The print command has also been extended to accept methods. For example:
12806 print -[@var{object} hash]
12809 @cindex print an Objective-C object description
12810 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12812 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12813 and print the result. Also, an additional command has been added,
12814 @code{print-object} or @code{po} for short, which is meant to print
12815 the description of an object. However, this command may only work
12816 with certain Objective-C libraries that have a particular hook
12817 function, @code{_NSPrintForDebugger}, defined.
12820 @subsection OpenCL C
12823 This section provides information about @value{GDBN}s OpenCL C support.
12826 * OpenCL C Datatypes::
12827 * OpenCL C Expressions::
12828 * OpenCL C Operators::
12831 @node OpenCL C Datatypes
12832 @subsubsection OpenCL C Datatypes
12834 @cindex OpenCL C Datatypes
12835 @value{GDBN} supports the builtin scalar and vector datatypes specified
12836 by OpenCL 1.1. In addition the half- and double-precision floating point
12837 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12838 extensions are also known to @value{GDBN}.
12840 @node OpenCL C Expressions
12841 @subsubsection OpenCL C Expressions
12843 @cindex OpenCL C Expressions
12844 @value{GDBN} supports accesses to vector components including the access as
12845 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12846 supported by @value{GDBN} can be used as well.
12848 @node OpenCL C Operators
12849 @subsubsection OpenCL C Operators
12851 @cindex OpenCL C Operators
12852 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12856 @subsection Fortran
12857 @cindex Fortran-specific support in @value{GDBN}
12859 @value{GDBN} can be used to debug programs written in Fortran, but it
12860 currently supports only the features of Fortran 77 language.
12862 @cindex trailing underscore, in Fortran symbols
12863 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12864 among them) append an underscore to the names of variables and
12865 functions. When you debug programs compiled by those compilers, you
12866 will need to refer to variables and functions with a trailing
12870 * Fortran Operators:: Fortran operators and expressions
12871 * Fortran Defaults:: Default settings for Fortran
12872 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12875 @node Fortran Operators
12876 @subsubsection Fortran Operators and Expressions
12878 @cindex Fortran operators and expressions
12880 Operators must be defined on values of specific types. For instance,
12881 @code{+} is defined on numbers, but not on characters or other non-
12882 arithmetic types. Operators are often defined on groups of types.
12886 The exponentiation operator. It raises the first operand to the power
12890 The range operator. Normally used in the form of array(low:high) to
12891 represent a section of array.
12894 The access component operator. Normally used to access elements in derived
12895 types. Also suitable for unions. As unions aren't part of regular Fortran,
12896 this can only happen when accessing a register that uses a gdbarch-defined
12900 @node Fortran Defaults
12901 @subsubsection Fortran Defaults
12903 @cindex Fortran Defaults
12905 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12906 default uses case-insensitive matches for Fortran symbols. You can
12907 change that with the @samp{set case-insensitive} command, see
12908 @ref{Symbols}, for the details.
12910 @node Special Fortran Commands
12911 @subsubsection Special Fortran Commands
12913 @cindex Special Fortran commands
12915 @value{GDBN} has some commands to support Fortran-specific features,
12916 such as displaying common blocks.
12919 @cindex @code{COMMON} blocks, Fortran
12920 @kindex info common
12921 @item info common @r{[}@var{common-name}@r{]}
12922 This command prints the values contained in the Fortran @code{COMMON}
12923 block whose name is @var{common-name}. With no argument, the names of
12924 all @code{COMMON} blocks visible at the current program location are
12931 @cindex Pascal support in @value{GDBN}, limitations
12932 Debugging Pascal programs which use sets, subranges, file variables, or
12933 nested functions does not currently work. @value{GDBN} does not support
12934 entering expressions, printing values, or similar features using Pascal
12937 The Pascal-specific command @code{set print pascal_static-members}
12938 controls whether static members of Pascal objects are displayed.
12939 @xref{Print Settings, pascal_static-members}.
12942 @subsection Modula-2
12944 @cindex Modula-2, @value{GDBN} support
12946 The extensions made to @value{GDBN} to support Modula-2 only support
12947 output from the @sc{gnu} Modula-2 compiler (which is currently being
12948 developed). Other Modula-2 compilers are not currently supported, and
12949 attempting to debug executables produced by them is most likely
12950 to give an error as @value{GDBN} reads in the executable's symbol
12953 @cindex expressions in Modula-2
12955 * M2 Operators:: Built-in operators
12956 * Built-In Func/Proc:: Built-in functions and procedures
12957 * M2 Constants:: Modula-2 constants
12958 * M2 Types:: Modula-2 types
12959 * M2 Defaults:: Default settings for Modula-2
12960 * Deviations:: Deviations from standard Modula-2
12961 * M2 Checks:: Modula-2 type and range checks
12962 * M2 Scope:: The scope operators @code{::} and @code{.}
12963 * GDB/M2:: @value{GDBN} and Modula-2
12967 @subsubsection Operators
12968 @cindex Modula-2 operators
12970 Operators must be defined on values of specific types. For instance,
12971 @code{+} is defined on numbers, but not on structures. Operators are
12972 often defined on groups of types. For the purposes of Modula-2, the
12973 following definitions hold:
12978 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12982 @emph{Character types} consist of @code{CHAR} and its subranges.
12985 @emph{Floating-point types} consist of @code{REAL}.
12988 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12992 @emph{Scalar types} consist of all of the above.
12995 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12998 @emph{Boolean types} consist of @code{BOOLEAN}.
13002 The following operators are supported, and appear in order of
13003 increasing precedence:
13007 Function argument or array index separator.
13010 Assignment. The value of @var{var} @code{:=} @var{value} is
13014 Less than, greater than on integral, floating-point, or enumerated
13018 Less than or equal to, greater than or equal to
13019 on integral, floating-point and enumerated types, or set inclusion on
13020 set types. Same precedence as @code{<}.
13022 @item =@r{, }<>@r{, }#
13023 Equality and two ways of expressing inequality, valid on scalar types.
13024 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13025 available for inequality, since @code{#} conflicts with the script
13029 Set membership. Defined on set types and the types of their members.
13030 Same precedence as @code{<}.
13033 Boolean disjunction. Defined on boolean types.
13036 Boolean conjunction. Defined on boolean types.
13039 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13042 Addition and subtraction on integral and floating-point types, or union
13043 and difference on set types.
13046 Multiplication on integral and floating-point types, or set intersection
13050 Division on floating-point types, or symmetric set difference on set
13051 types. Same precedence as @code{*}.
13054 Integer division and remainder. Defined on integral types. Same
13055 precedence as @code{*}.
13058 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13061 Pointer dereferencing. Defined on pointer types.
13064 Boolean negation. Defined on boolean types. Same precedence as
13068 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13069 precedence as @code{^}.
13072 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13075 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13079 @value{GDBN} and Modula-2 scope operators.
13083 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13084 treats the use of the operator @code{IN}, or the use of operators
13085 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13086 @code{<=}, and @code{>=} on sets as an error.
13090 @node Built-In Func/Proc
13091 @subsubsection Built-in Functions and Procedures
13092 @cindex Modula-2 built-ins
13094 Modula-2 also makes available several built-in procedures and functions.
13095 In describing these, the following metavariables are used:
13100 represents an @code{ARRAY} variable.
13103 represents a @code{CHAR} constant or variable.
13106 represents a variable or constant of integral type.
13109 represents an identifier that belongs to a set. Generally used in the
13110 same function with the metavariable @var{s}. The type of @var{s} should
13111 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13114 represents a variable or constant of integral or floating-point type.
13117 represents a variable or constant of floating-point type.
13123 represents a variable.
13126 represents a variable or constant of one of many types. See the
13127 explanation of the function for details.
13130 All Modula-2 built-in procedures also return a result, described below.
13134 Returns the absolute value of @var{n}.
13137 If @var{c} is a lower case letter, it returns its upper case
13138 equivalent, otherwise it returns its argument.
13141 Returns the character whose ordinal value is @var{i}.
13144 Decrements the value in the variable @var{v} by one. Returns the new value.
13146 @item DEC(@var{v},@var{i})
13147 Decrements the value in the variable @var{v} by @var{i}. Returns the
13150 @item EXCL(@var{m},@var{s})
13151 Removes the element @var{m} from the set @var{s}. Returns the new
13154 @item FLOAT(@var{i})
13155 Returns the floating point equivalent of the integer @var{i}.
13157 @item HIGH(@var{a})
13158 Returns the index of the last member of @var{a}.
13161 Increments the value in the variable @var{v} by one. Returns the new value.
13163 @item INC(@var{v},@var{i})
13164 Increments the value in the variable @var{v} by @var{i}. Returns the
13167 @item INCL(@var{m},@var{s})
13168 Adds the element @var{m} to the set @var{s} if it is not already
13169 there. Returns the new set.
13172 Returns the maximum value of the type @var{t}.
13175 Returns the minimum value of the type @var{t}.
13178 Returns boolean TRUE if @var{i} is an odd number.
13181 Returns the ordinal value of its argument. For example, the ordinal
13182 value of a character is its @sc{ascii} value (on machines supporting the
13183 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13184 integral, character and enumerated types.
13186 @item SIZE(@var{x})
13187 Returns the size of its argument. @var{x} can be a variable or a type.
13189 @item TRUNC(@var{r})
13190 Returns the integral part of @var{r}.
13192 @item TSIZE(@var{x})
13193 Returns the size of its argument. @var{x} can be a variable or a type.
13195 @item VAL(@var{t},@var{i})
13196 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13200 @emph{Warning:} Sets and their operations are not yet supported, so
13201 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13205 @cindex Modula-2 constants
13207 @subsubsection Constants
13209 @value{GDBN} allows you to express the constants of Modula-2 in the following
13215 Integer constants are simply a sequence of digits. When used in an
13216 expression, a constant is interpreted to be type-compatible with the
13217 rest of the expression. Hexadecimal integers are specified by a
13218 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13221 Floating point constants appear as a sequence of digits, followed by a
13222 decimal point and another sequence of digits. An optional exponent can
13223 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13224 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13225 digits of the floating point constant must be valid decimal (base 10)
13229 Character constants consist of a single character enclosed by a pair of
13230 like quotes, either single (@code{'}) or double (@code{"}). They may
13231 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13232 followed by a @samp{C}.
13235 String constants consist of a sequence of characters enclosed by a
13236 pair of like quotes, either single (@code{'}) or double (@code{"}).
13237 Escape sequences in the style of C are also allowed. @xref{C
13238 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13242 Enumerated constants consist of an enumerated identifier.
13245 Boolean constants consist of the identifiers @code{TRUE} and
13249 Pointer constants consist of integral values only.
13252 Set constants are not yet supported.
13256 @subsubsection Modula-2 Types
13257 @cindex Modula-2 types
13259 Currently @value{GDBN} can print the following data types in Modula-2
13260 syntax: array types, record types, set types, pointer types, procedure
13261 types, enumerated types, subrange types and base types. You can also
13262 print the contents of variables declared using these type.
13263 This section gives a number of simple source code examples together with
13264 sample @value{GDBN} sessions.
13266 The first example contains the following section of code:
13275 and you can request @value{GDBN} to interrogate the type and value of
13276 @code{r} and @code{s}.
13279 (@value{GDBP}) print s
13281 (@value{GDBP}) ptype s
13283 (@value{GDBP}) print r
13285 (@value{GDBP}) ptype r
13290 Likewise if your source code declares @code{s} as:
13294 s: SET ['A'..'Z'] ;
13298 then you may query the type of @code{s} by:
13301 (@value{GDBP}) ptype s
13302 type = SET ['A'..'Z']
13306 Note that at present you cannot interactively manipulate set
13307 expressions using the debugger.
13309 The following example shows how you might declare an array in Modula-2
13310 and how you can interact with @value{GDBN} to print its type and contents:
13314 s: ARRAY [-10..10] OF CHAR ;
13318 (@value{GDBP}) ptype s
13319 ARRAY [-10..10] OF CHAR
13322 Note that the array handling is not yet complete and although the type
13323 is printed correctly, expression handling still assumes that all
13324 arrays have a lower bound of zero and not @code{-10} as in the example
13327 Here are some more type related Modula-2 examples:
13331 colour = (blue, red, yellow, green) ;
13332 t = [blue..yellow] ;
13340 The @value{GDBN} interaction shows how you can query the data type
13341 and value of a variable.
13344 (@value{GDBP}) print s
13346 (@value{GDBP}) ptype t
13347 type = [blue..yellow]
13351 In this example a Modula-2 array is declared and its contents
13352 displayed. Observe that the contents are written in the same way as
13353 their @code{C} counterparts.
13357 s: ARRAY [1..5] OF CARDINAL ;
13363 (@value{GDBP}) print s
13364 $1 = @{1, 0, 0, 0, 0@}
13365 (@value{GDBP}) ptype s
13366 type = ARRAY [1..5] OF CARDINAL
13369 The Modula-2 language interface to @value{GDBN} also understands
13370 pointer types as shown in this example:
13374 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
13381 and you can request that @value{GDBN} describes the type of @code{s}.
13384 (@value{GDBP}) ptype s
13385 type = POINTER TO ARRAY [1..5] OF CARDINAL
13388 @value{GDBN} handles compound types as we can see in this example.
13389 Here we combine array types, record types, pointer types and subrange
13400 myarray = ARRAY myrange OF CARDINAL ;
13401 myrange = [-2..2] ;
13403 s: POINTER TO ARRAY myrange OF foo ;
13407 and you can ask @value{GDBN} to describe the type of @code{s} as shown
13411 (@value{GDBP}) ptype s
13412 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
13415 f3 : ARRAY [-2..2] OF CARDINAL;
13420 @subsubsection Modula-2 Defaults
13421 @cindex Modula-2 defaults
13423 If type and range checking are set automatically by @value{GDBN}, they
13424 both default to @code{on} whenever the working language changes to
13425 Modula-2. This happens regardless of whether you or @value{GDBN}
13426 selected the working language.
13428 If you allow @value{GDBN} to set the language automatically, then entering
13429 code compiled from a file whose name ends with @file{.mod} sets the
13430 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
13431 Infer the Source Language}, for further details.
13434 @subsubsection Deviations from Standard Modula-2
13435 @cindex Modula-2, deviations from
13437 A few changes have been made to make Modula-2 programs easier to debug.
13438 This is done primarily via loosening its type strictness:
13442 Unlike in standard Modula-2, pointer constants can be formed by
13443 integers. This allows you to modify pointer variables during
13444 debugging. (In standard Modula-2, the actual address contained in a
13445 pointer variable is hidden from you; it can only be modified
13446 through direct assignment to another pointer variable or expression that
13447 returned a pointer.)
13450 C escape sequences can be used in strings and characters to represent
13451 non-printable characters. @value{GDBN} prints out strings with these
13452 escape sequences embedded. Single non-printable characters are
13453 printed using the @samp{CHR(@var{nnn})} format.
13456 The assignment operator (@code{:=}) returns the value of its right-hand
13460 All built-in procedures both modify @emph{and} return their argument.
13464 @subsubsection Modula-2 Type and Range Checks
13465 @cindex Modula-2 checks
13468 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13471 @c FIXME remove warning when type/range checks added
13473 @value{GDBN} considers two Modula-2 variables type equivalent if:
13477 They are of types that have been declared equivalent via a @code{TYPE
13478 @var{t1} = @var{t2}} statement
13481 They have been declared on the same line. (Note: This is true of the
13482 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13485 As long as type checking is enabled, any attempt to combine variables
13486 whose types are not equivalent is an error.
13488 Range checking is done on all mathematical operations, assignment, array
13489 index bounds, and all built-in functions and procedures.
13492 @subsubsection The Scope Operators @code{::} and @code{.}
13494 @cindex @code{.}, Modula-2 scope operator
13495 @cindex colon, doubled as scope operator
13497 @vindex colon-colon@r{, in Modula-2}
13498 @c Info cannot handle :: but TeX can.
13501 @vindex ::@r{, in Modula-2}
13504 There are a few subtle differences between the Modula-2 scope operator
13505 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13510 @var{module} . @var{id}
13511 @var{scope} :: @var{id}
13515 where @var{scope} is the name of a module or a procedure,
13516 @var{module} the name of a module, and @var{id} is any declared
13517 identifier within your program, except another module.
13519 Using the @code{::} operator makes @value{GDBN} search the scope
13520 specified by @var{scope} for the identifier @var{id}. If it is not
13521 found in the specified scope, then @value{GDBN} searches all scopes
13522 enclosing the one specified by @var{scope}.
13524 Using the @code{.} operator makes @value{GDBN} search the current scope for
13525 the identifier specified by @var{id} that was imported from the
13526 definition module specified by @var{module}. With this operator, it is
13527 an error if the identifier @var{id} was not imported from definition
13528 module @var{module}, or if @var{id} is not an identifier in
13532 @subsubsection @value{GDBN} and Modula-2
13534 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13535 Five subcommands of @code{set print} and @code{show print} apply
13536 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13537 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13538 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13539 analogue in Modula-2.
13541 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13542 with any language, is not useful with Modula-2. Its
13543 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13544 created in Modula-2 as they can in C or C@t{++}. However, because an
13545 address can be specified by an integral constant, the construct
13546 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13548 @cindex @code{#} in Modula-2
13549 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13550 interpreted as the beginning of a comment. Use @code{<>} instead.
13556 The extensions made to @value{GDBN} for Ada only support
13557 output from the @sc{gnu} Ada (GNAT) compiler.
13558 Other Ada compilers are not currently supported, and
13559 attempting to debug executables produced by them is most likely
13563 @cindex expressions in Ada
13565 * Ada Mode Intro:: General remarks on the Ada syntax
13566 and semantics supported by Ada mode
13568 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13569 * Additions to Ada:: Extensions of the Ada expression syntax.
13570 * Stopping Before Main Program:: Debugging the program during elaboration.
13571 * Ada Tasks:: Listing and setting breakpoints in tasks.
13572 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13573 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13575 * Ada Glitches:: Known peculiarities of Ada mode.
13578 @node Ada Mode Intro
13579 @subsubsection Introduction
13580 @cindex Ada mode, general
13582 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13583 syntax, with some extensions.
13584 The philosophy behind the design of this subset is
13588 That @value{GDBN} should provide basic literals and access to operations for
13589 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13590 leaving more sophisticated computations to subprograms written into the
13591 program (which therefore may be called from @value{GDBN}).
13594 That type safety and strict adherence to Ada language restrictions
13595 are not particularly important to the @value{GDBN} user.
13598 That brevity is important to the @value{GDBN} user.
13601 Thus, for brevity, the debugger acts as if all names declared in
13602 user-written packages are directly visible, even if they are not visible
13603 according to Ada rules, thus making it unnecessary to fully qualify most
13604 names with their packages, regardless of context. Where this causes
13605 ambiguity, @value{GDBN} asks the user's intent.
13607 The debugger will start in Ada mode if it detects an Ada main program.
13608 As for other languages, it will enter Ada mode when stopped in a program that
13609 was translated from an Ada source file.
13611 While in Ada mode, you may use `@t{--}' for comments. This is useful
13612 mostly for documenting command files. The standard @value{GDBN} comment
13613 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13614 middle (to allow based literals).
13616 The debugger supports limited overloading. Given a subprogram call in which
13617 the function symbol has multiple definitions, it will use the number of
13618 actual parameters and some information about their types to attempt to narrow
13619 the set of definitions. It also makes very limited use of context, preferring
13620 procedures to functions in the context of the @code{call} command, and
13621 functions to procedures elsewhere.
13623 @node Omissions from Ada
13624 @subsubsection Omissions from Ada
13625 @cindex Ada, omissions from
13627 Here are the notable omissions from the subset:
13631 Only a subset of the attributes are supported:
13635 @t{'First}, @t{'Last}, and @t{'Length}
13636 on array objects (not on types and subtypes).
13639 @t{'Min} and @t{'Max}.
13642 @t{'Pos} and @t{'Val}.
13648 @t{'Range} on array objects (not subtypes), but only as the right
13649 operand of the membership (@code{in}) operator.
13652 @t{'Access}, @t{'Unchecked_Access}, and
13653 @t{'Unrestricted_Access} (a GNAT extension).
13661 @code{Characters.Latin_1} are not available and
13662 concatenation is not implemented. Thus, escape characters in strings are
13663 not currently available.
13666 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13667 equality of representations. They will generally work correctly
13668 for strings and arrays whose elements have integer or enumeration types.
13669 They may not work correctly for arrays whose element
13670 types have user-defined equality, for arrays of real values
13671 (in particular, IEEE-conformant floating point, because of negative
13672 zeroes and NaNs), and for arrays whose elements contain unused bits with
13673 indeterminate values.
13676 The other component-by-component array operations (@code{and}, @code{or},
13677 @code{xor}, @code{not}, and relational tests other than equality)
13678 are not implemented.
13681 @cindex array aggregates (Ada)
13682 @cindex record aggregates (Ada)
13683 @cindex aggregates (Ada)
13684 There is limited support for array and record aggregates. They are
13685 permitted only on the right sides of assignments, as in these examples:
13688 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13689 (@value{GDBP}) set An_Array := (1, others => 0)
13690 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13691 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13692 (@value{GDBP}) set A_Record := (1, "Peter", True);
13693 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13697 discriminant's value by assigning an aggregate has an
13698 undefined effect if that discriminant is used within the record.
13699 However, you can first modify discriminants by directly assigning to
13700 them (which normally would not be allowed in Ada), and then performing an
13701 aggregate assignment. For example, given a variable @code{A_Rec}
13702 declared to have a type such as:
13705 type Rec (Len : Small_Integer := 0) is record
13707 Vals : IntArray (1 .. Len);
13711 you can assign a value with a different size of @code{Vals} with two
13715 (@value{GDBP}) set A_Rec.Len := 4
13716 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13719 As this example also illustrates, @value{GDBN} is very loose about the usual
13720 rules concerning aggregates. You may leave out some of the
13721 components of an array or record aggregate (such as the @code{Len}
13722 component in the assignment to @code{A_Rec} above); they will retain their
13723 original values upon assignment. You may freely use dynamic values as
13724 indices in component associations. You may even use overlapping or
13725 redundant component associations, although which component values are
13726 assigned in such cases is not defined.
13729 Calls to dispatching subprograms are not implemented.
13732 The overloading algorithm is much more limited (i.e., less selective)
13733 than that of real Ada. It makes only limited use of the context in
13734 which a subexpression appears to resolve its meaning, and it is much
13735 looser in its rules for allowing type matches. As a result, some
13736 function calls will be ambiguous, and the user will be asked to choose
13737 the proper resolution.
13740 The @code{new} operator is not implemented.
13743 Entry calls are not implemented.
13746 Aside from printing, arithmetic operations on the native VAX floating-point
13747 formats are not supported.
13750 It is not possible to slice a packed array.
13753 The names @code{True} and @code{False}, when not part of a qualified name,
13754 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13756 Should your program
13757 redefine these names in a package or procedure (at best a dubious practice),
13758 you will have to use fully qualified names to access their new definitions.
13761 @node Additions to Ada
13762 @subsubsection Additions to Ada
13763 @cindex Ada, deviations from
13765 As it does for other languages, @value{GDBN} makes certain generic
13766 extensions to Ada (@pxref{Expressions}):
13770 If the expression @var{E} is a variable residing in memory (typically
13771 a local variable or array element) and @var{N} is a positive integer,
13772 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13773 @var{N}-1 adjacent variables following it in memory as an array. In
13774 Ada, this operator is generally not necessary, since its prime use is
13775 in displaying parts of an array, and slicing will usually do this in
13776 Ada. However, there are occasional uses when debugging programs in
13777 which certain debugging information has been optimized away.
13780 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13781 appears in function or file @var{B}.'' When @var{B} is a file name,
13782 you must typically surround it in single quotes.
13785 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13786 @var{type} that appears at address @var{addr}.''
13789 A name starting with @samp{$} is a convenience variable
13790 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13793 In addition, @value{GDBN} provides a few other shortcuts and outright
13794 additions specific to Ada:
13798 The assignment statement is allowed as an expression, returning
13799 its right-hand operand as its value. Thus, you may enter
13802 (@value{GDBP}) set x := y + 3
13803 (@value{GDBP}) print A(tmp := y + 1)
13807 The semicolon is allowed as an ``operator,'' returning as its value
13808 the value of its right-hand operand.
13809 This allows, for example,
13810 complex conditional breaks:
13813 (@value{GDBP}) break f
13814 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13818 Rather than use catenation and symbolic character names to introduce special
13819 characters into strings, one may instead use a special bracket notation,
13820 which is also used to print strings. A sequence of characters of the form
13821 @samp{["@var{XX}"]} within a string or character literal denotes the
13822 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13823 sequence of characters @samp{["""]} also denotes a single quotation mark
13824 in strings. For example,
13826 "One line.["0a"]Next line.["0a"]"
13829 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13833 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13834 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13838 (@value{GDBP}) print 'max(x, y)
13842 When printing arrays, @value{GDBN} uses positional notation when the
13843 array has a lower bound of 1, and uses a modified named notation otherwise.
13844 For example, a one-dimensional array of three integers with a lower bound
13845 of 3 might print as
13852 That is, in contrast to valid Ada, only the first component has a @code{=>}
13856 You may abbreviate attributes in expressions with any unique,
13857 multi-character subsequence of
13858 their names (an exact match gets preference).
13859 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13860 in place of @t{a'length}.
13863 @cindex quoting Ada internal identifiers
13864 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13865 to lower case. The GNAT compiler uses upper-case characters for
13866 some of its internal identifiers, which are normally of no interest to users.
13867 For the rare occasions when you actually have to look at them,
13868 enclose them in angle brackets to avoid the lower-case mapping.
13871 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13875 Printing an object of class-wide type or dereferencing an
13876 access-to-class-wide value will display all the components of the object's
13877 specific type (as indicated by its run-time tag). Likewise, component
13878 selection on such a value will operate on the specific type of the
13883 @node Stopping Before Main Program
13884 @subsubsection Stopping at the Very Beginning
13886 @cindex breakpointing Ada elaboration code
13887 It is sometimes necessary to debug the program during elaboration, and
13888 before reaching the main procedure.
13889 As defined in the Ada Reference
13890 Manual, the elaboration code is invoked from a procedure called
13891 @code{adainit}. To run your program up to the beginning of
13892 elaboration, simply use the following two commands:
13893 @code{tbreak adainit} and @code{run}.
13896 @subsubsection Extensions for Ada Tasks
13897 @cindex Ada, tasking
13899 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13900 @value{GDBN} provides the following task-related commands:
13905 This command shows a list of current Ada tasks, as in the following example:
13912 (@value{GDBP}) info tasks
13913 ID TID P-ID Pri State Name
13914 1 8088000 0 15 Child Activation Wait main_task
13915 2 80a4000 1 15 Accept Statement b
13916 3 809a800 1 15 Child Activation Wait a
13917 * 4 80ae800 3 15 Runnable c
13922 In this listing, the asterisk before the last task indicates it to be the
13923 task currently being inspected.
13927 Represents @value{GDBN}'s internal task number.
13933 The parent's task ID (@value{GDBN}'s internal task number).
13936 The base priority of the task.
13939 Current state of the task.
13943 The task has been created but has not been activated. It cannot be
13947 The task is not blocked for any reason known to Ada. (It may be waiting
13948 for a mutex, though.) It is conceptually "executing" in normal mode.
13951 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13952 that were waiting on terminate alternatives have been awakened and have
13953 terminated themselves.
13955 @item Child Activation Wait
13956 The task is waiting for created tasks to complete activation.
13958 @item Accept Statement
13959 The task is waiting on an accept or selective wait statement.
13961 @item Waiting on entry call
13962 The task is waiting on an entry call.
13964 @item Async Select Wait
13965 The task is waiting to start the abortable part of an asynchronous
13969 The task is waiting on a select statement with only a delay
13972 @item Child Termination Wait
13973 The task is sleeping having completed a master within itself, and is
13974 waiting for the tasks dependent on that master to become terminated or
13975 waiting on a terminate Phase.
13977 @item Wait Child in Term Alt
13978 The task is sleeping waiting for tasks on terminate alternatives to
13979 finish terminating.
13981 @item Accepting RV with @var{taskno}
13982 The task is accepting a rendez-vous with the task @var{taskno}.
13986 Name of the task in the program.
13990 @kindex info task @var{taskno}
13991 @item info task @var{taskno}
13992 This command shows detailled informations on the specified task, as in
13993 the following example:
13998 (@value{GDBP}) info tasks
13999 ID TID P-ID Pri State Name
14000 1 8077880 0 15 Child Activation Wait main_task
14001 * 2 807c468 1 15 Runnable task_1
14002 (@value{GDBP}) info task 2
14003 Ada Task: 0x807c468
14006 Parent: 1 (main_task)
14012 @kindex task@r{ (Ada)}
14013 @cindex current Ada task ID
14014 This command prints the ID of the current task.
14020 (@value{GDBP}) info tasks
14021 ID TID P-ID Pri State Name
14022 1 8077870 0 15 Child Activation Wait main_task
14023 * 2 807c458 1 15 Runnable t
14024 (@value{GDBP}) task
14025 [Current task is 2]
14028 @item task @var{taskno}
14029 @cindex Ada task switching
14030 This command is like the @code{thread @var{threadno}}
14031 command (@pxref{Threads}). It switches the context of debugging
14032 from the current task to the given task.
14038 (@value{GDBP}) info tasks
14039 ID TID P-ID Pri State Name
14040 1 8077870 0 15 Child Activation Wait main_task
14041 * 2 807c458 1 15 Runnable t
14042 (@value{GDBP}) task 1
14043 [Switching to task 1]
14044 #0 0x8067726 in pthread_cond_wait ()
14046 #0 0x8067726 in pthread_cond_wait ()
14047 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14048 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14049 #3 0x806153e in system.tasking.stages.activate_tasks ()
14050 #4 0x804aacc in un () at un.adb:5
14053 @item break @var{linespec} task @var{taskno}
14054 @itemx break @var{linespec} task @var{taskno} if @dots{}
14055 @cindex breakpoints and tasks, in Ada
14056 @cindex task breakpoints, in Ada
14057 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14058 These commands are like the @code{break @dots{} thread @dots{}}
14059 command (@pxref{Thread Stops}).
14060 @var{linespec} specifies source lines, as described
14061 in @ref{Specify Location}.
14063 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14064 to specify that you only want @value{GDBN} to stop the program when a
14065 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14066 numeric task identifiers assigned by @value{GDBN}, shown in the first
14067 column of the @samp{info tasks} display.
14069 If you do not specify @samp{task @var{taskno}} when you set a
14070 breakpoint, the breakpoint applies to @emph{all} tasks of your
14073 You can use the @code{task} qualifier on conditional breakpoints as
14074 well; in this case, place @samp{task @var{taskno}} before the
14075 breakpoint condition (before the @code{if}).
14083 (@value{GDBP}) info tasks
14084 ID TID P-ID Pri State Name
14085 1 140022020 0 15 Child Activation Wait main_task
14086 2 140045060 1 15 Accept/Select Wait t2
14087 3 140044840 1 15 Runnable t1
14088 * 4 140056040 1 15 Runnable t3
14089 (@value{GDBP}) b 15 task 2
14090 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14091 (@value{GDBP}) cont
14096 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14098 (@value{GDBP}) info tasks
14099 ID TID P-ID Pri State Name
14100 1 140022020 0 15 Child Activation Wait main_task
14101 * 2 140045060 1 15 Runnable t2
14102 3 140044840 1 15 Runnable t1
14103 4 140056040 1 15 Delay Sleep t3
14107 @node Ada Tasks and Core Files
14108 @subsubsection Tasking Support when Debugging Core Files
14109 @cindex Ada tasking and core file debugging
14111 When inspecting a core file, as opposed to debugging a live program,
14112 tasking support may be limited or even unavailable, depending on
14113 the platform being used.
14114 For instance, on x86-linux, the list of tasks is available, but task
14115 switching is not supported. On Tru64, however, task switching will work
14118 On certain platforms, including Tru64, the debugger needs to perform some
14119 memory writes in order to provide Ada tasking support. When inspecting
14120 a core file, this means that the core file must be opened with read-write
14121 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14122 Under these circumstances, you should make a backup copy of the core
14123 file before inspecting it with @value{GDBN}.
14125 @node Ravenscar Profile
14126 @subsubsection Tasking Support when using the Ravenscar Profile
14127 @cindex Ravenscar Profile
14129 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14130 specifically designed for systems with safety-critical real-time
14134 @kindex set ravenscar task-switching on
14135 @cindex task switching with program using Ravenscar Profile
14136 @item set ravenscar task-switching on
14137 Allows task switching when debugging a program that uses the Ravenscar
14138 Profile. This is the default.
14140 @kindex set ravenscar task-switching off
14141 @item set ravenscar task-switching off
14142 Turn off task switching when debugging a program that uses the Ravenscar
14143 Profile. This is mostly intended to disable the code that adds support
14144 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14145 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14146 To be effective, this command should be run before the program is started.
14148 @kindex show ravenscar task-switching
14149 @item show ravenscar task-switching
14150 Show whether it is possible to switch from task to task in a program
14151 using the Ravenscar Profile.
14156 @subsubsection Known Peculiarities of Ada Mode
14157 @cindex Ada, problems
14159 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14160 we know of several problems with and limitations of Ada mode in
14162 some of which will be fixed with planned future releases of the debugger
14163 and the GNU Ada compiler.
14167 Static constants that the compiler chooses not to materialize as objects in
14168 storage are invisible to the debugger.
14171 Named parameter associations in function argument lists are ignored (the
14172 argument lists are treated as positional).
14175 Many useful library packages are currently invisible to the debugger.
14178 Fixed-point arithmetic, conversions, input, and output is carried out using
14179 floating-point arithmetic, and may give results that only approximate those on
14183 The GNAT compiler never generates the prefix @code{Standard} for any of
14184 the standard symbols defined by the Ada language. @value{GDBN} knows about
14185 this: it will strip the prefix from names when you use it, and will never
14186 look for a name you have so qualified among local symbols, nor match against
14187 symbols in other packages or subprograms. If you have
14188 defined entities anywhere in your program other than parameters and
14189 local variables whose simple names match names in @code{Standard},
14190 GNAT's lack of qualification here can cause confusion. When this happens,
14191 you can usually resolve the confusion
14192 by qualifying the problematic names with package
14193 @code{Standard} explicitly.
14196 Older versions of the compiler sometimes generate erroneous debugging
14197 information, resulting in the debugger incorrectly printing the value
14198 of affected entities. In some cases, the debugger is able to work
14199 around an issue automatically. In other cases, the debugger is able
14200 to work around the issue, but the work-around has to be specifically
14203 @kindex set ada trust-PAD-over-XVS
14204 @kindex show ada trust-PAD-over-XVS
14207 @item set ada trust-PAD-over-XVS on
14208 Configure GDB to strictly follow the GNAT encoding when computing the
14209 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14210 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14211 a complete description of the encoding used by the GNAT compiler).
14212 This is the default.
14214 @item set ada trust-PAD-over-XVS off
14215 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14216 sometimes prints the wrong value for certain entities, changing @code{ada
14217 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14218 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14219 @code{off}, but this incurs a slight performance penalty, so it is
14220 recommended to leave this setting to @code{on} unless necessary.
14224 @node Unsupported Languages
14225 @section Unsupported Languages
14227 @cindex unsupported languages
14228 @cindex minimal language
14229 In addition to the other fully-supported programming languages,
14230 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14231 It does not represent a real programming language, but provides a set
14232 of capabilities close to what the C or assembly languages provide.
14233 This should allow most simple operations to be performed while debugging
14234 an application that uses a language currently not supported by @value{GDBN}.
14236 If the language is set to @code{auto}, @value{GDBN} will automatically
14237 select this language if the current frame corresponds to an unsupported
14241 @chapter Examining the Symbol Table
14243 The commands described in this chapter allow you to inquire about the
14244 symbols (names of variables, functions and types) defined in your
14245 program. This information is inherent in the text of your program and
14246 does not change as your program executes. @value{GDBN} finds it in your
14247 program's symbol table, in the file indicated when you started @value{GDBN}
14248 (@pxref{File Options, ,Choosing Files}), or by one of the
14249 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14251 @cindex symbol names
14252 @cindex names of symbols
14253 @cindex quoting names
14254 Occasionally, you may need to refer to symbols that contain unusual
14255 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14256 most frequent case is in referring to static variables in other
14257 source files (@pxref{Variables,,Program Variables}). File names
14258 are recorded in object files as debugging symbols, but @value{GDBN} would
14259 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14260 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14261 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14268 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14271 @cindex case-insensitive symbol names
14272 @cindex case sensitivity in symbol names
14273 @kindex set case-sensitive
14274 @item set case-sensitive on
14275 @itemx set case-sensitive off
14276 @itemx set case-sensitive auto
14277 Normally, when @value{GDBN} looks up symbols, it matches their names
14278 with case sensitivity determined by the current source language.
14279 Occasionally, you may wish to control that. The command @code{set
14280 case-sensitive} lets you do that by specifying @code{on} for
14281 case-sensitive matches or @code{off} for case-insensitive ones. If
14282 you specify @code{auto}, case sensitivity is reset to the default
14283 suitable for the source language. The default is case-sensitive
14284 matches for all languages except for Fortran, for which the default is
14285 case-insensitive matches.
14287 @kindex show case-sensitive
14288 @item show case-sensitive
14289 This command shows the current setting of case sensitivity for symbols
14292 @kindex info address
14293 @cindex address of a symbol
14294 @item info address @var{symbol}
14295 Describe where the data for @var{symbol} is stored. For a register
14296 variable, this says which register it is kept in. For a non-register
14297 local variable, this prints the stack-frame offset at which the variable
14300 Note the contrast with @samp{print &@var{symbol}}, which does not work
14301 at all for a register variable, and for a stack local variable prints
14302 the exact address of the current instantiation of the variable.
14304 @kindex info symbol
14305 @cindex symbol from address
14306 @cindex closest symbol and offset for an address
14307 @item info symbol @var{addr}
14308 Print the name of a symbol which is stored at the address @var{addr}.
14309 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
14310 nearest symbol and an offset from it:
14313 (@value{GDBP}) info symbol 0x54320
14314 _initialize_vx + 396 in section .text
14318 This is the opposite of the @code{info address} command. You can use
14319 it to find out the name of a variable or a function given its address.
14321 For dynamically linked executables, the name of executable or shared
14322 library containing the symbol is also printed:
14325 (@value{GDBP}) info symbol 0x400225
14326 _start + 5 in section .text of /tmp/a.out
14327 (@value{GDBP}) info symbol 0x2aaaac2811cf
14328 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
14332 @item whatis [@var{arg}]
14333 Print the data type of @var{arg}, which can be either an expression
14334 or a name of a data type. With no argument, print the data type of
14335 @code{$}, the last value in the value history.
14337 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
14338 is not actually evaluated, and any side-effecting operations (such as
14339 assignments or function calls) inside it do not take place.
14341 If @var{arg} is a variable or an expression, @code{whatis} prints its
14342 literal type as it is used in the source code. If the type was
14343 defined using a @code{typedef}, @code{whatis} will @emph{not} print
14344 the data type underlying the @code{typedef}. If the type of the
14345 variable or the expression is a compound data type, such as
14346 @code{struct} or @code{class}, @code{whatis} never prints their
14347 fields or methods. It just prints the @code{struct}/@code{class}
14348 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
14349 such a compound data type, use @code{ptype}.
14351 If @var{arg} is a type name that was defined using @code{typedef},
14352 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
14353 Unrolling means that @code{whatis} will show the underlying type used
14354 in the @code{typedef} declaration of @var{arg}. However, if that
14355 underlying type is also a @code{typedef}, @code{whatis} will not
14358 For C code, the type names may also have the form @samp{class
14359 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
14360 @var{union-tag}} or @samp{enum @var{enum-tag}}.
14363 @item ptype [@var{arg}]
14364 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
14365 detailed description of the type, instead of just the name of the type.
14366 @xref{Expressions, ,Expressions}.
14368 Contrary to @code{whatis}, @code{ptype} always unrolls any
14369 @code{typedef}s in its argument declaration, whether the argument is
14370 a variable, expression, or a data type. This means that @code{ptype}
14371 of a variable or an expression will not print literally its type as
14372 present in the source code---use @code{whatis} for that. @code{typedef}s at
14373 the pointer or reference targets are also unrolled. Only @code{typedef}s of
14374 fields, methods and inner @code{class typedef}s of @code{struct}s,
14375 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
14377 For example, for this variable declaration:
14380 typedef double real_t;
14381 struct complex @{ real_t real; double imag; @};
14382 typedef struct complex complex_t;
14384 real_t *real_pointer_var;
14388 the two commands give this output:
14392 (@value{GDBP}) whatis var
14394 (@value{GDBP}) ptype var
14395 type = struct complex @{
14399 (@value{GDBP}) whatis complex_t
14400 type = struct complex
14401 (@value{GDBP}) whatis struct complex
14402 type = struct complex
14403 (@value{GDBP}) ptype struct complex
14404 type = struct complex @{
14408 (@value{GDBP}) whatis real_pointer_var
14410 (@value{GDBP}) ptype real_pointer_var
14416 As with @code{whatis}, using @code{ptype} without an argument refers to
14417 the type of @code{$}, the last value in the value history.
14419 @cindex incomplete type
14420 Sometimes, programs use opaque data types or incomplete specifications
14421 of complex data structure. If the debug information included in the
14422 program does not allow @value{GDBN} to display a full declaration of
14423 the data type, it will say @samp{<incomplete type>}. For example,
14424 given these declarations:
14428 struct foo *fooptr;
14432 but no definition for @code{struct foo} itself, @value{GDBN} will say:
14435 (@value{GDBP}) ptype foo
14436 $1 = <incomplete type>
14440 ``Incomplete type'' is C terminology for data types that are not
14441 completely specified.
14444 @item info types @var{regexp}
14446 Print a brief description of all types whose names match the regular
14447 expression @var{regexp} (or all types in your program, if you supply
14448 no argument). Each complete typename is matched as though it were a
14449 complete line; thus, @samp{i type value} gives information on all
14450 types in your program whose names include the string @code{value}, but
14451 @samp{i type ^value$} gives information only on types whose complete
14452 name is @code{value}.
14454 This command differs from @code{ptype} in two ways: first, like
14455 @code{whatis}, it does not print a detailed description; second, it
14456 lists all source files where a type is defined.
14459 @cindex local variables
14460 @item info scope @var{location}
14461 List all the variables local to a particular scope. This command
14462 accepts a @var{location} argument---a function name, a source line, or
14463 an address preceded by a @samp{*}, and prints all the variables local
14464 to the scope defined by that location. (@xref{Specify Location}, for
14465 details about supported forms of @var{location}.) For example:
14468 (@value{GDBP}) @b{info scope command_line_handler}
14469 Scope for command_line_handler:
14470 Symbol rl is an argument at stack/frame offset 8, length 4.
14471 Symbol linebuffer is in static storage at address 0x150a18, length 4.
14472 Symbol linelength is in static storage at address 0x150a1c, length 4.
14473 Symbol p is a local variable in register $esi, length 4.
14474 Symbol p1 is a local variable in register $ebx, length 4.
14475 Symbol nline is a local variable in register $edx, length 4.
14476 Symbol repeat is a local variable at frame offset -8, length 4.
14480 This command is especially useful for determining what data to collect
14481 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14484 @kindex info source
14486 Show information about the current source file---that is, the source file for
14487 the function containing the current point of execution:
14490 the name of the source file, and the directory containing it,
14492 the directory it was compiled in,
14494 its length, in lines,
14496 which programming language it is written in,
14498 whether the executable includes debugging information for that file, and
14499 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14501 whether the debugging information includes information about
14502 preprocessor macros.
14506 @kindex info sources
14508 Print the names of all source files in your program for which there is
14509 debugging information, organized into two lists: files whose symbols
14510 have already been read, and files whose symbols will be read when needed.
14512 @kindex info functions
14513 @item info functions
14514 Print the names and data types of all defined functions.
14516 @item info functions @var{regexp}
14517 Print the names and data types of all defined functions
14518 whose names contain a match for regular expression @var{regexp}.
14519 Thus, @samp{info fun step} finds all functions whose names
14520 include @code{step}; @samp{info fun ^step} finds those whose names
14521 start with @code{step}. If a function name contains characters
14522 that conflict with the regular expression language (e.g.@:
14523 @samp{operator*()}), they may be quoted with a backslash.
14525 @kindex info variables
14526 @item info variables
14527 Print the names and data types of all variables that are defined
14528 outside of functions (i.e.@: excluding local variables).
14530 @item info variables @var{regexp}
14531 Print the names and data types of all variables (except for local
14532 variables) whose names contain a match for regular expression
14535 @kindex info classes
14536 @cindex Objective-C, classes and selectors
14538 @itemx info classes @var{regexp}
14539 Display all Objective-C classes in your program, or
14540 (with the @var{regexp} argument) all those matching a particular regular
14543 @kindex info selectors
14544 @item info selectors
14545 @itemx info selectors @var{regexp}
14546 Display all Objective-C selectors in your program, or
14547 (with the @var{regexp} argument) all those matching a particular regular
14551 This was never implemented.
14552 @kindex info methods
14554 @itemx info methods @var{regexp}
14555 The @code{info methods} command permits the user to examine all defined
14556 methods within C@t{++} program, or (with the @var{regexp} argument) a
14557 specific set of methods found in the various C@t{++} classes. Many
14558 C@t{++} classes provide a large number of methods. Thus, the output
14559 from the @code{ptype} command can be overwhelming and hard to use. The
14560 @code{info-methods} command filters the methods, printing only those
14561 which match the regular-expression @var{regexp}.
14564 @cindex reloading symbols
14565 Some systems allow individual object files that make up your program to
14566 be replaced without stopping and restarting your program. For example,
14567 in VxWorks you can simply recompile a defective object file and keep on
14568 running. If you are running on one of these systems, you can allow
14569 @value{GDBN} to reload the symbols for automatically relinked modules:
14572 @kindex set symbol-reloading
14573 @item set symbol-reloading on
14574 Replace symbol definitions for the corresponding source file when an
14575 object file with a particular name is seen again.
14577 @item set symbol-reloading off
14578 Do not replace symbol definitions when encountering object files of the
14579 same name more than once. This is the default state; if you are not
14580 running on a system that permits automatic relinking of modules, you
14581 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14582 may discard symbols when linking large programs, that may contain
14583 several modules (from different directories or libraries) with the same
14586 @kindex show symbol-reloading
14587 @item show symbol-reloading
14588 Show the current @code{on} or @code{off} setting.
14591 @cindex opaque data types
14592 @kindex set opaque-type-resolution
14593 @item set opaque-type-resolution on
14594 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14595 declared as a pointer to a @code{struct}, @code{class}, or
14596 @code{union}---for example, @code{struct MyType *}---that is used in one
14597 source file although the full declaration of @code{struct MyType} is in
14598 another source file. The default is on.
14600 A change in the setting of this subcommand will not take effect until
14601 the next time symbols for a file are loaded.
14603 @item set opaque-type-resolution off
14604 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14605 is printed as follows:
14607 @{<no data fields>@}
14610 @kindex show opaque-type-resolution
14611 @item show opaque-type-resolution
14612 Show whether opaque types are resolved or not.
14614 @kindex maint print symbols
14615 @cindex symbol dump
14616 @kindex maint print psymbols
14617 @cindex partial symbol dump
14618 @item maint print symbols @var{filename}
14619 @itemx maint print psymbols @var{filename}
14620 @itemx maint print msymbols @var{filename}
14621 Write a dump of debugging symbol data into the file @var{filename}.
14622 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14623 symbols with debugging data are included. If you use @samp{maint print
14624 symbols}, @value{GDBN} includes all the symbols for which it has already
14625 collected full details: that is, @var{filename} reflects symbols for
14626 only those files whose symbols @value{GDBN} has read. You can use the
14627 command @code{info sources} to find out which files these are. If you
14628 use @samp{maint print psymbols} instead, the dump shows information about
14629 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14630 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14631 @samp{maint print msymbols} dumps just the minimal symbol information
14632 required for each object file from which @value{GDBN} has read some symbols.
14633 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14634 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14636 @kindex maint info symtabs
14637 @kindex maint info psymtabs
14638 @cindex listing @value{GDBN}'s internal symbol tables
14639 @cindex symbol tables, listing @value{GDBN}'s internal
14640 @cindex full symbol tables, listing @value{GDBN}'s internal
14641 @cindex partial symbol tables, listing @value{GDBN}'s internal
14642 @item maint info symtabs @r{[} @var{regexp} @r{]}
14643 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14645 List the @code{struct symtab} or @code{struct partial_symtab}
14646 structures whose names match @var{regexp}. If @var{regexp} is not
14647 given, list them all. The output includes expressions which you can
14648 copy into a @value{GDBN} debugging this one to examine a particular
14649 structure in more detail. For example:
14652 (@value{GDBP}) maint info psymtabs dwarf2read
14653 @{ objfile /home/gnu/build/gdb/gdb
14654 ((struct objfile *) 0x82e69d0)
14655 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14656 ((struct partial_symtab *) 0x8474b10)
14659 text addresses 0x814d3c8 -- 0x8158074
14660 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14661 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14662 dependencies (none)
14665 (@value{GDBP}) maint info symtabs
14669 We see that there is one partial symbol table whose filename contains
14670 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14671 and we see that @value{GDBN} has not read in any symtabs yet at all.
14672 If we set a breakpoint on a function, that will cause @value{GDBN} to
14673 read the symtab for the compilation unit containing that function:
14676 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14677 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14679 (@value{GDBP}) maint info symtabs
14680 @{ objfile /home/gnu/build/gdb/gdb
14681 ((struct objfile *) 0x82e69d0)
14682 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14683 ((struct symtab *) 0x86c1f38)
14686 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14687 linetable ((struct linetable *) 0x8370fa0)
14688 debugformat DWARF 2
14697 @chapter Altering Execution
14699 Once you think you have found an error in your program, you might want to
14700 find out for certain whether correcting the apparent error would lead to
14701 correct results in the rest of the run. You can find the answer by
14702 experiment, using the @value{GDBN} features for altering execution of the
14705 For example, you can store new values into variables or memory
14706 locations, give your program a signal, restart it at a different
14707 address, or even return prematurely from a function.
14710 * Assignment:: Assignment to variables
14711 * Jumping:: Continuing at a different address
14712 * Signaling:: Giving your program a signal
14713 * Returning:: Returning from a function
14714 * Calling:: Calling your program's functions
14715 * Patching:: Patching your program
14719 @section Assignment to Variables
14722 @cindex setting variables
14723 To alter the value of a variable, evaluate an assignment expression.
14724 @xref{Expressions, ,Expressions}. For example,
14731 stores the value 4 into the variable @code{x}, and then prints the
14732 value of the assignment expression (which is 4).
14733 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14734 information on operators in supported languages.
14736 @kindex set variable
14737 @cindex variables, setting
14738 If you are not interested in seeing the value of the assignment, use the
14739 @code{set} command instead of the @code{print} command. @code{set} is
14740 really the same as @code{print} except that the expression's value is
14741 not printed and is not put in the value history (@pxref{Value History,
14742 ,Value History}). The expression is evaluated only for its effects.
14744 If the beginning of the argument string of the @code{set} command
14745 appears identical to a @code{set} subcommand, use the @code{set
14746 variable} command instead of just @code{set}. This command is identical
14747 to @code{set} except for its lack of subcommands. For example, if your
14748 program has a variable @code{width}, you get an error if you try to set
14749 a new value with just @samp{set width=13}, because @value{GDBN} has the
14750 command @code{set width}:
14753 (@value{GDBP}) whatis width
14755 (@value{GDBP}) p width
14757 (@value{GDBP}) set width=47
14758 Invalid syntax in expression.
14762 The invalid expression, of course, is @samp{=47}. In
14763 order to actually set the program's variable @code{width}, use
14766 (@value{GDBP}) set var width=47
14769 Because the @code{set} command has many subcommands that can conflict
14770 with the names of program variables, it is a good idea to use the
14771 @code{set variable} command instead of just @code{set}. For example, if
14772 your program has a variable @code{g}, you run into problems if you try
14773 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14774 the command @code{set gnutarget}, abbreviated @code{set g}:
14778 (@value{GDBP}) whatis g
14782 (@value{GDBP}) set g=4
14786 The program being debugged has been started already.
14787 Start it from the beginning? (y or n) y
14788 Starting program: /home/smith/cc_progs/a.out
14789 "/home/smith/cc_progs/a.out": can't open to read symbols:
14790 Invalid bfd target.
14791 (@value{GDBP}) show g
14792 The current BFD target is "=4".
14797 The program variable @code{g} did not change, and you silently set the
14798 @code{gnutarget} to an invalid value. In order to set the variable
14802 (@value{GDBP}) set var g=4
14805 @value{GDBN} allows more implicit conversions in assignments than C; you can
14806 freely store an integer value into a pointer variable or vice versa,
14807 and you can convert any structure to any other structure that is the
14808 same length or shorter.
14809 @comment FIXME: how do structs align/pad in these conversions?
14810 @comment /doc@cygnus.com 18dec1990
14812 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14813 construct to generate a value of specified type at a specified address
14814 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14815 to memory location @code{0x83040} as an integer (which implies a certain size
14816 and representation in memory), and
14819 set @{int@}0x83040 = 4
14823 stores the value 4 into that memory location.
14826 @section Continuing at a Different Address
14828 Ordinarily, when you continue your program, you do so at the place where
14829 it stopped, with the @code{continue} command. You can instead continue at
14830 an address of your own choosing, with the following commands:
14834 @item jump @var{linespec}
14835 @itemx jump @var{location}
14836 Resume execution at line @var{linespec} or at address given by
14837 @var{location}. Execution stops again immediately if there is a
14838 breakpoint there. @xref{Specify Location}, for a description of the
14839 different forms of @var{linespec} and @var{location}. It is common
14840 practice to use the @code{tbreak} command in conjunction with
14841 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14843 The @code{jump} command does not change the current stack frame, or
14844 the stack pointer, or the contents of any memory location or any
14845 register other than the program counter. If line @var{linespec} is in
14846 a different function from the one currently executing, the results may
14847 be bizarre if the two functions expect different patterns of arguments or
14848 of local variables. For this reason, the @code{jump} command requests
14849 confirmation if the specified line is not in the function currently
14850 executing. However, even bizarre results are predictable if you are
14851 well acquainted with the machine-language code of your program.
14854 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14855 On many systems, you can get much the same effect as the @code{jump}
14856 command by storing a new value into the register @code{$pc}. The
14857 difference is that this does not start your program running; it only
14858 changes the address of where it @emph{will} run when you continue. For
14866 makes the next @code{continue} command or stepping command execute at
14867 address @code{0x485}, rather than at the address where your program stopped.
14868 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14870 The most common occasion to use the @code{jump} command is to back
14871 up---perhaps with more breakpoints set---over a portion of a program
14872 that has already executed, in order to examine its execution in more
14877 @section Giving your Program a Signal
14878 @cindex deliver a signal to a program
14882 @item signal @var{signal}
14883 Resume execution where your program stopped, but immediately give it the
14884 signal @var{signal}. @var{signal} can be the name or the number of a
14885 signal. For example, on many systems @code{signal 2} and @code{signal
14886 SIGINT} are both ways of sending an interrupt signal.
14888 Alternatively, if @var{signal} is zero, continue execution without
14889 giving a signal. This is useful when your program stopped on account of
14890 a signal and would ordinary see the signal when resumed with the
14891 @code{continue} command; @samp{signal 0} causes it to resume without a
14894 @code{signal} does not repeat when you press @key{RET} a second time
14895 after executing the command.
14899 Invoking the @code{signal} command is not the same as invoking the
14900 @code{kill} utility from the shell. Sending a signal with @code{kill}
14901 causes @value{GDBN} to decide what to do with the signal depending on
14902 the signal handling tables (@pxref{Signals}). The @code{signal} command
14903 passes the signal directly to your program.
14907 @section Returning from a Function
14910 @cindex returning from a function
14913 @itemx return @var{expression}
14914 You can cancel execution of a function call with the @code{return}
14915 command. If you give an
14916 @var{expression} argument, its value is used as the function's return
14920 When you use @code{return}, @value{GDBN} discards the selected stack frame
14921 (and all frames within it). You can think of this as making the
14922 discarded frame return prematurely. If you wish to specify a value to
14923 be returned, give that value as the argument to @code{return}.
14925 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14926 Frame}), and any other frames inside of it, leaving its caller as the
14927 innermost remaining frame. That frame becomes selected. The
14928 specified value is stored in the registers used for returning values
14931 The @code{return} command does not resume execution; it leaves the
14932 program stopped in the state that would exist if the function had just
14933 returned. In contrast, the @code{finish} command (@pxref{Continuing
14934 and Stepping, ,Continuing and Stepping}) resumes execution until the
14935 selected stack frame returns naturally.
14937 @value{GDBN} needs to know how the @var{expression} argument should be set for
14938 the inferior. The concrete registers assignment depends on the OS ABI and the
14939 type being returned by the selected stack frame. For example it is common for
14940 OS ABI to return floating point values in FPU registers while integer values in
14941 CPU registers. Still some ABIs return even floating point values in CPU
14942 registers. Larger integer widths (such as @code{long long int}) also have
14943 specific placement rules. @value{GDBN} already knows the OS ABI from its
14944 current target so it needs to find out also the type being returned to make the
14945 assignment into the right register(s).
14947 Normally, the selected stack frame has debug info. @value{GDBN} will always
14948 use the debug info instead of the implicit type of @var{expression} when the
14949 debug info is available. For example, if you type @kbd{return -1}, and the
14950 function in the current stack frame is declared to return a @code{long long
14951 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14952 into a @code{long long int}:
14955 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14957 (@value{GDBP}) return -1
14958 Make func return now? (y or n) y
14959 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14960 43 printf ("result=%lld\n", func ());
14964 However, if the selected stack frame does not have a debug info, e.g., if the
14965 function was compiled without debug info, @value{GDBN} has to find out the type
14966 to return from user. Specifying a different type by mistake may set the value
14967 in different inferior registers than the caller code expects. For example,
14968 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14969 of a @code{long long int} result for a debug info less function (on 32-bit
14970 architectures). Therefore the user is required to specify the return type by
14971 an appropriate cast explicitly:
14974 Breakpoint 2, 0x0040050b in func ()
14975 (@value{GDBP}) return -1
14976 Return value type not available for selected stack frame.
14977 Please use an explicit cast of the value to return.
14978 (@value{GDBP}) return (long long int) -1
14979 Make selected stack frame return now? (y or n) y
14980 #0 0x00400526 in main ()
14985 @section Calling Program Functions
14988 @cindex calling functions
14989 @cindex inferior functions, calling
14990 @item print @var{expr}
14991 Evaluate the expression @var{expr} and display the resulting value.
14992 @var{expr} may include calls to functions in the program being
14996 @item call @var{expr}
14997 Evaluate the expression @var{expr} without displaying @code{void}
15000 You can use this variant of the @code{print} command if you want to
15001 execute a function from your program that does not return anything
15002 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15003 with @code{void} returned values that @value{GDBN} will otherwise
15004 print. If the result is not void, it is printed and saved in the
15008 It is possible for the function you call via the @code{print} or
15009 @code{call} command to generate a signal (e.g., if there's a bug in
15010 the function, or if you passed it incorrect arguments). What happens
15011 in that case is controlled by the @code{set unwindonsignal} command.
15013 Similarly, with a C@t{++} program it is possible for the function you
15014 call via the @code{print} or @code{call} command to generate an
15015 exception that is not handled due to the constraints of the dummy
15016 frame. In this case, any exception that is raised in the frame, but has
15017 an out-of-frame exception handler will not be found. GDB builds a
15018 dummy-frame for the inferior function call, and the unwinder cannot
15019 seek for exception handlers outside of this dummy-frame. What happens
15020 in that case is controlled by the
15021 @code{set unwind-on-terminating-exception} command.
15024 @item set unwindonsignal
15025 @kindex set unwindonsignal
15026 @cindex unwind stack in called functions
15027 @cindex call dummy stack unwinding
15028 Set unwinding of the stack if a signal is received while in a function
15029 that @value{GDBN} called in the program being debugged. If set to on,
15030 @value{GDBN} unwinds the stack it created for the call and restores
15031 the context to what it was before the call. If set to off (the
15032 default), @value{GDBN} stops in the frame where the signal was
15035 @item show unwindonsignal
15036 @kindex show unwindonsignal
15037 Show the current setting of stack unwinding in the functions called by
15040 @item set unwind-on-terminating-exception
15041 @kindex set unwind-on-terminating-exception
15042 @cindex unwind stack in called functions with unhandled exceptions
15043 @cindex call dummy stack unwinding on unhandled exception.
15044 Set unwinding of the stack if a C@t{++} exception is raised, but left
15045 unhandled while in a function that @value{GDBN} called in the program being
15046 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15047 it created for the call and restores the context to what it was before
15048 the call. If set to off, @value{GDBN} the exception is delivered to
15049 the default C@t{++} exception handler and the inferior terminated.
15051 @item show unwind-on-terminating-exception
15052 @kindex show unwind-on-terminating-exception
15053 Show the current setting of stack unwinding in the functions called by
15058 @cindex weak alias functions
15059 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15060 for another function. In such case, @value{GDBN} might not pick up
15061 the type information, including the types of the function arguments,
15062 which causes @value{GDBN} to call the inferior function incorrectly.
15063 As a result, the called function will function erroneously and may
15064 even crash. A solution to that is to use the name of the aliased
15068 @section Patching Programs
15070 @cindex patching binaries
15071 @cindex writing into executables
15072 @cindex writing into corefiles
15074 By default, @value{GDBN} opens the file containing your program's
15075 executable code (or the corefile) read-only. This prevents accidental
15076 alterations to machine code; but it also prevents you from intentionally
15077 patching your program's binary.
15079 If you'd like to be able to patch the binary, you can specify that
15080 explicitly with the @code{set write} command. For example, you might
15081 want to turn on internal debugging flags, or even to make emergency
15087 @itemx set write off
15088 If you specify @samp{set write on}, @value{GDBN} opens executable and
15089 core files for both reading and writing; if you specify @kbd{set write
15090 off} (the default), @value{GDBN} opens them read-only.
15092 If you have already loaded a file, you must load it again (using the
15093 @code{exec-file} or @code{core-file} command) after changing @code{set
15094 write}, for your new setting to take effect.
15098 Display whether executable files and core files are opened for writing
15099 as well as reading.
15103 @chapter @value{GDBN} Files
15105 @value{GDBN} needs to know the file name of the program to be debugged,
15106 both in order to read its symbol table and in order to start your
15107 program. To debug a core dump of a previous run, you must also tell
15108 @value{GDBN} the name of the core dump file.
15111 * Files:: Commands to specify files
15112 * Separate Debug Files:: Debugging information in separate files
15113 * Index Files:: Index files speed up GDB
15114 * Symbol Errors:: Errors reading symbol files
15115 * Data Files:: GDB data files
15119 @section Commands to Specify Files
15121 @cindex symbol table
15122 @cindex core dump file
15124 You may want to specify executable and core dump file names. The usual
15125 way to do this is at start-up time, using the arguments to
15126 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15127 Out of @value{GDBN}}).
15129 Occasionally it is necessary to change to a different file during a
15130 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15131 specify a file you want to use. Or you are debugging a remote target
15132 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15133 Program}). In these situations the @value{GDBN} commands to specify
15134 new files are useful.
15137 @cindex executable file
15139 @item file @var{filename}
15140 Use @var{filename} as the program to be debugged. It is read for its
15141 symbols and for the contents of pure memory. It is also the program
15142 executed when you use the @code{run} command. If you do not specify a
15143 directory and the file is not found in the @value{GDBN} working directory,
15144 @value{GDBN} uses the environment variable @code{PATH} as a list of
15145 directories to search, just as the shell does when looking for a program
15146 to run. You can change the value of this variable, for both @value{GDBN}
15147 and your program, using the @code{path} command.
15149 @cindex unlinked object files
15150 @cindex patching object files
15151 You can load unlinked object @file{.o} files into @value{GDBN} using
15152 the @code{file} command. You will not be able to ``run'' an object
15153 file, but you can disassemble functions and inspect variables. Also,
15154 if the underlying BFD functionality supports it, you could use
15155 @kbd{gdb -write} to patch object files using this technique. Note
15156 that @value{GDBN} can neither interpret nor modify relocations in this
15157 case, so branches and some initialized variables will appear to go to
15158 the wrong place. But this feature is still handy from time to time.
15161 @code{file} with no argument makes @value{GDBN} discard any information it
15162 has on both executable file and the symbol table.
15165 @item exec-file @r{[} @var{filename} @r{]}
15166 Specify that the program to be run (but not the symbol table) is found
15167 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15168 if necessary to locate your program. Omitting @var{filename} means to
15169 discard information on the executable file.
15171 @kindex symbol-file
15172 @item symbol-file @r{[} @var{filename} @r{]}
15173 Read symbol table information from file @var{filename}. @code{PATH} is
15174 searched when necessary. Use the @code{file} command to get both symbol
15175 table and program to run from the same file.
15177 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15178 program's symbol table.
15180 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15181 some breakpoints and auto-display expressions. This is because they may
15182 contain pointers to the internal data recording symbols and data types,
15183 which are part of the old symbol table data being discarded inside
15186 @code{symbol-file} does not repeat if you press @key{RET} again after
15189 When @value{GDBN} is configured for a particular environment, it
15190 understands debugging information in whatever format is the standard
15191 generated for that environment; you may use either a @sc{gnu} compiler, or
15192 other compilers that adhere to the local conventions.
15193 Best results are usually obtained from @sc{gnu} compilers; for example,
15194 using @code{@value{NGCC}} you can generate debugging information for
15197 For most kinds of object files, with the exception of old SVR3 systems
15198 using COFF, the @code{symbol-file} command does not normally read the
15199 symbol table in full right away. Instead, it scans the symbol table
15200 quickly to find which source files and which symbols are present. The
15201 details are read later, one source file at a time, as they are needed.
15203 The purpose of this two-stage reading strategy is to make @value{GDBN}
15204 start up faster. For the most part, it is invisible except for
15205 occasional pauses while the symbol table details for a particular source
15206 file are being read. (The @code{set verbose} command can turn these
15207 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15208 Warnings and Messages}.)
15210 We have not implemented the two-stage strategy for COFF yet. When the
15211 symbol table is stored in COFF format, @code{symbol-file} reads the
15212 symbol table data in full right away. Note that ``stabs-in-COFF''
15213 still does the two-stage strategy, since the debug info is actually
15217 @cindex reading symbols immediately
15218 @cindex symbols, reading immediately
15219 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15220 @itemx file @r{[} -readnow @r{]} @var{filename}
15221 You can override the @value{GDBN} two-stage strategy for reading symbol
15222 tables by using the @samp{-readnow} option with any of the commands that
15223 load symbol table information, if you want to be sure @value{GDBN} has the
15224 entire symbol table available.
15226 @c FIXME: for now no mention of directories, since this seems to be in
15227 @c flux. 13mar1992 status is that in theory GDB would look either in
15228 @c current dir or in same dir as myprog; but issues like competing
15229 @c GDB's, or clutter in system dirs, mean that in practice right now
15230 @c only current dir is used. FFish says maybe a special GDB hierarchy
15231 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15235 @item core-file @r{[}@var{filename}@r{]}
15237 Specify the whereabouts of a core dump file to be used as the ``contents
15238 of memory''. Traditionally, core files contain only some parts of the
15239 address space of the process that generated them; @value{GDBN} can access the
15240 executable file itself for other parts.
15242 @code{core-file} with no argument specifies that no core file is
15245 Note that the core file is ignored when your program is actually running
15246 under @value{GDBN}. So, if you have been running your program and you
15247 wish to debug a core file instead, you must kill the subprocess in which
15248 the program is running. To do this, use the @code{kill} command
15249 (@pxref{Kill Process, ,Killing the Child Process}).
15251 @kindex add-symbol-file
15252 @cindex dynamic linking
15253 @item add-symbol-file @var{filename} @var{address}
15254 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15255 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15256 The @code{add-symbol-file} command reads additional symbol table
15257 information from the file @var{filename}. You would use this command
15258 when @var{filename} has been dynamically loaded (by some other means)
15259 into the program that is running. @var{address} should be the memory
15260 address at which the file has been loaded; @value{GDBN} cannot figure
15261 this out for itself. You can additionally specify an arbitrary number
15262 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15263 section name and base address for that section. You can specify any
15264 @var{address} as an expression.
15266 The symbol table of the file @var{filename} is added to the symbol table
15267 originally read with the @code{symbol-file} command. You can use the
15268 @code{add-symbol-file} command any number of times; the new symbol data
15269 thus read keeps adding to the old. To discard all old symbol data
15270 instead, use the @code{symbol-file} command without any arguments.
15272 @cindex relocatable object files, reading symbols from
15273 @cindex object files, relocatable, reading symbols from
15274 @cindex reading symbols from relocatable object files
15275 @cindex symbols, reading from relocatable object files
15276 @cindex @file{.o} files, reading symbols from
15277 Although @var{filename} is typically a shared library file, an
15278 executable file, or some other object file which has been fully
15279 relocated for loading into a process, you can also load symbolic
15280 information from relocatable @file{.o} files, as long as:
15284 the file's symbolic information refers only to linker symbols defined in
15285 that file, not to symbols defined by other object files,
15287 every section the file's symbolic information refers to has actually
15288 been loaded into the inferior, as it appears in the file, and
15290 you can determine the address at which every section was loaded, and
15291 provide these to the @code{add-symbol-file} command.
15295 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15296 relocatable files into an already running program; such systems
15297 typically make the requirements above easy to meet. However, it's
15298 important to recognize that many native systems use complex link
15299 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15300 assembly, for example) that make the requirements difficult to meet. In
15301 general, one cannot assume that using @code{add-symbol-file} to read a
15302 relocatable object file's symbolic information will have the same effect
15303 as linking the relocatable object file into the program in the normal
15306 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
15308 @kindex add-symbol-file-from-memory
15309 @cindex @code{syscall DSO}
15310 @cindex load symbols from memory
15311 @item add-symbol-file-from-memory @var{address}
15312 Load symbols from the given @var{address} in a dynamically loaded
15313 object file whose image is mapped directly into the inferior's memory.
15314 For example, the Linux kernel maps a @code{syscall DSO} into each
15315 process's address space; this DSO provides kernel-specific code for
15316 some system calls. The argument can be any expression whose
15317 evaluation yields the address of the file's shared object file header.
15318 For this command to work, you must have used @code{symbol-file} or
15319 @code{exec-file} commands in advance.
15321 @kindex add-shared-symbol-files
15323 @item add-shared-symbol-files @var{library-file}
15324 @itemx assf @var{library-file}
15325 The @code{add-shared-symbol-files} command can currently be used only
15326 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
15327 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
15328 @value{GDBN} automatically looks for shared libraries, however if
15329 @value{GDBN} does not find yours, you can invoke
15330 @code{add-shared-symbol-files}. It takes one argument: the shared
15331 library's file name. @code{assf} is a shorthand alias for
15332 @code{add-shared-symbol-files}.
15335 @item section @var{section} @var{addr}
15336 The @code{section} command changes the base address of the named
15337 @var{section} of the exec file to @var{addr}. This can be used if the
15338 exec file does not contain section addresses, (such as in the
15339 @code{a.out} format), or when the addresses specified in the file
15340 itself are wrong. Each section must be changed separately. The
15341 @code{info files} command, described below, lists all the sections and
15345 @kindex info target
15348 @code{info files} and @code{info target} are synonymous; both print the
15349 current target (@pxref{Targets, ,Specifying a Debugging Target}),
15350 including the names of the executable and core dump files currently in
15351 use by @value{GDBN}, and the files from which symbols were loaded. The
15352 command @code{help target} lists all possible targets rather than
15355 @kindex maint info sections
15356 @item maint info sections
15357 Another command that can give you extra information about program sections
15358 is @code{maint info sections}. In addition to the section information
15359 displayed by @code{info files}, this command displays the flags and file
15360 offset of each section in the executable and core dump files. In addition,
15361 @code{maint info sections} provides the following command options (which
15362 may be arbitrarily combined):
15366 Display sections for all loaded object files, including shared libraries.
15367 @item @var{sections}
15368 Display info only for named @var{sections}.
15369 @item @var{section-flags}
15370 Display info only for sections for which @var{section-flags} are true.
15371 The section flags that @value{GDBN} currently knows about are:
15374 Section will have space allocated in the process when loaded.
15375 Set for all sections except those containing debug information.
15377 Section will be loaded from the file into the child process memory.
15378 Set for pre-initialized code and data, clear for @code{.bss} sections.
15380 Section needs to be relocated before loading.
15382 Section cannot be modified by the child process.
15384 Section contains executable code only.
15386 Section contains data only (no executable code).
15388 Section will reside in ROM.
15390 Section contains data for constructor/destructor lists.
15392 Section is not empty.
15394 An instruction to the linker to not output the section.
15395 @item COFF_SHARED_LIBRARY
15396 A notification to the linker that the section contains
15397 COFF shared library information.
15399 Section contains common symbols.
15402 @kindex set trust-readonly-sections
15403 @cindex read-only sections
15404 @item set trust-readonly-sections on
15405 Tell @value{GDBN} that readonly sections in your object file
15406 really are read-only (i.e.@: that their contents will not change).
15407 In that case, @value{GDBN} can fetch values from these sections
15408 out of the object file, rather than from the target program.
15409 For some targets (notably embedded ones), this can be a significant
15410 enhancement to debugging performance.
15412 The default is off.
15414 @item set trust-readonly-sections off
15415 Tell @value{GDBN} not to trust readonly sections. This means that
15416 the contents of the section might change while the program is running,
15417 and must therefore be fetched from the target when needed.
15419 @item show trust-readonly-sections
15420 Show the current setting of trusting readonly sections.
15423 All file-specifying commands allow both absolute and relative file names
15424 as arguments. @value{GDBN} always converts the file name to an absolute file
15425 name and remembers it that way.
15427 @cindex shared libraries
15428 @anchor{Shared Libraries}
15429 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
15430 and IBM RS/6000 AIX shared libraries.
15432 On MS-Windows @value{GDBN} must be linked with the Expat library to support
15433 shared libraries. @xref{Expat}.
15435 @value{GDBN} automatically loads symbol definitions from shared libraries
15436 when you use the @code{run} command, or when you examine a core file.
15437 (Before you issue the @code{run} command, @value{GDBN} does not understand
15438 references to a function in a shared library, however---unless you are
15439 debugging a core file).
15441 On HP-UX, if the program loads a library explicitly, @value{GDBN}
15442 automatically loads the symbols at the time of the @code{shl_load} call.
15444 @c FIXME: some @value{GDBN} release may permit some refs to undef
15445 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
15446 @c FIXME...lib; check this from time to time when updating manual
15448 There are times, however, when you may wish to not automatically load
15449 symbol definitions from shared libraries, such as when they are
15450 particularly large or there are many of them.
15452 To control the automatic loading of shared library symbols, use the
15456 @kindex set auto-solib-add
15457 @item set auto-solib-add @var{mode}
15458 If @var{mode} is @code{on}, symbols from all shared object libraries
15459 will be loaded automatically when the inferior begins execution, you
15460 attach to an independently started inferior, or when the dynamic linker
15461 informs @value{GDBN} that a new library has been loaded. If @var{mode}
15462 is @code{off}, symbols must be loaded manually, using the
15463 @code{sharedlibrary} command. The default value is @code{on}.
15465 @cindex memory used for symbol tables
15466 If your program uses lots of shared libraries with debug info that
15467 takes large amounts of memory, you can decrease the @value{GDBN}
15468 memory footprint by preventing it from automatically loading the
15469 symbols from shared libraries. To that end, type @kbd{set
15470 auto-solib-add off} before running the inferior, then load each
15471 library whose debug symbols you do need with @kbd{sharedlibrary
15472 @var{regexp}}, where @var{regexp} is a regular expression that matches
15473 the libraries whose symbols you want to be loaded.
15475 @kindex show auto-solib-add
15476 @item show auto-solib-add
15477 Display the current autoloading mode.
15480 @cindex load shared library
15481 To explicitly load shared library symbols, use the @code{sharedlibrary}
15485 @kindex info sharedlibrary
15487 @item info share @var{regex}
15488 @itemx info sharedlibrary @var{regex}
15489 Print the names of the shared libraries which are currently loaded
15490 that match @var{regex}. If @var{regex} is omitted then print
15491 all shared libraries that are loaded.
15493 @kindex sharedlibrary
15495 @item sharedlibrary @var{regex}
15496 @itemx share @var{regex}
15497 Load shared object library symbols for files matching a
15498 Unix regular expression.
15499 As with files loaded automatically, it only loads shared libraries
15500 required by your program for a core file or after typing @code{run}. If
15501 @var{regex} is omitted all shared libraries required by your program are
15504 @item nosharedlibrary
15505 @kindex nosharedlibrary
15506 @cindex unload symbols from shared libraries
15507 Unload all shared object library symbols. This discards all symbols
15508 that have been loaded from all shared libraries. Symbols from shared
15509 libraries that were loaded by explicit user requests are not
15513 Sometimes you may wish that @value{GDBN} stops and gives you control
15514 when any of shared library events happen. Use the @code{set
15515 stop-on-solib-events} command for this:
15518 @item set stop-on-solib-events
15519 @kindex set stop-on-solib-events
15520 This command controls whether @value{GDBN} should give you control
15521 when the dynamic linker notifies it about some shared library event.
15522 The most common event of interest is loading or unloading of a new
15525 @item show stop-on-solib-events
15526 @kindex show stop-on-solib-events
15527 Show whether @value{GDBN} stops and gives you control when shared
15528 library events happen.
15531 Shared libraries are also supported in many cross or remote debugging
15532 configurations. @value{GDBN} needs to have access to the target's libraries;
15533 this can be accomplished either by providing copies of the libraries
15534 on the host system, or by asking @value{GDBN} to automatically retrieve the
15535 libraries from the target. If copies of the target libraries are
15536 provided, they need to be the same as the target libraries, although the
15537 copies on the target can be stripped as long as the copies on the host are
15540 @cindex where to look for shared libraries
15541 For remote debugging, you need to tell @value{GDBN} where the target
15542 libraries are, so that it can load the correct copies---otherwise, it
15543 may try to load the host's libraries. @value{GDBN} has two variables
15544 to specify the search directories for target libraries.
15547 @cindex prefix for shared library file names
15548 @cindex system root, alternate
15549 @kindex set solib-absolute-prefix
15550 @kindex set sysroot
15551 @item set sysroot @var{path}
15552 Use @var{path} as the system root for the program being debugged. Any
15553 absolute shared library paths will be prefixed with @var{path}; many
15554 runtime loaders store the absolute paths to the shared library in the
15555 target program's memory. If you use @code{set sysroot} to find shared
15556 libraries, they need to be laid out in the same way that they are on
15557 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15560 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15561 retrieve the target libraries from the remote system. This is only
15562 supported when using a remote target that supports the @code{remote get}
15563 command (@pxref{File Transfer,,Sending files to a remote system}).
15564 The part of @var{path} following the initial @file{remote:}
15565 (if present) is used as system root prefix on the remote file system.
15566 @footnote{If you want to specify a local system root using a directory
15567 that happens to be named @file{remote:}, you need to use some equivalent
15568 variant of the name like @file{./remote:}.}
15570 For targets with an MS-DOS based filesystem, such as MS-Windows and
15571 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15572 absolute file name with @var{path}. But first, on Unix hosts,
15573 @value{GDBN} converts all backslash directory separators into forward
15574 slashes, because the backslash is not a directory separator on Unix:
15577 c:\foo\bar.dll @result{} c:/foo/bar.dll
15580 Then, @value{GDBN} attempts prefixing the target file name with
15581 @var{path}, and looks for the resulting file name in the host file
15585 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15588 If that does not find the shared library, @value{GDBN} tries removing
15589 the @samp{:} character from the drive spec, both for convenience, and,
15590 for the case of the host file system not supporting file names with
15594 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15597 This makes it possible to have a system root that mirrors a target
15598 with more than one drive. E.g., you may want to setup your local
15599 copies of the target system shared libraries like so (note @samp{c} vs
15603 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15604 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15605 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15609 and point the system root at @file{/path/to/sysroot}, so that
15610 @value{GDBN} can find the correct copies of both
15611 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15613 If that still does not find the shared library, @value{GDBN} tries
15614 removing the whole drive spec from the target file name:
15617 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15620 This last lookup makes it possible to not care about the drive name,
15621 if you don't want or need to.
15623 The @code{set solib-absolute-prefix} command is an alias for @code{set
15626 @cindex default system root
15627 @cindex @samp{--with-sysroot}
15628 You can set the default system root by using the configure-time
15629 @samp{--with-sysroot} option. If the system root is inside
15630 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15631 @samp{--exec-prefix}), then the default system root will be updated
15632 automatically if the installed @value{GDBN} is moved to a new
15635 @kindex show sysroot
15637 Display the current shared library prefix.
15639 @kindex set solib-search-path
15640 @item set solib-search-path @var{path}
15641 If this variable is set, @var{path} is a colon-separated list of
15642 directories to search for shared libraries. @samp{solib-search-path}
15643 is used after @samp{sysroot} fails to locate the library, or if the
15644 path to the library is relative instead of absolute. If you want to
15645 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15646 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15647 finding your host's libraries. @samp{sysroot} is preferred; setting
15648 it to a nonexistent directory may interfere with automatic loading
15649 of shared library symbols.
15651 @kindex show solib-search-path
15652 @item show solib-search-path
15653 Display the current shared library search path.
15655 @cindex DOS file-name semantics of file names.
15656 @kindex set target-file-system-kind (unix|dos-based|auto)
15657 @kindex show target-file-system-kind
15658 @item set target-file-system-kind @var{kind}
15659 Set assumed file system kind for target reported file names.
15661 Shared library file names as reported by the target system may not
15662 make sense as is on the system @value{GDBN} is running on. For
15663 example, when remote debugging a target that has MS-DOS based file
15664 system semantics, from a Unix host, the target may be reporting to
15665 @value{GDBN} a list of loaded shared libraries with file names such as
15666 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15667 drive letters, so the @samp{c:\} prefix is not normally understood as
15668 indicating an absolute file name, and neither is the backslash
15669 normally considered a directory separator character. In that case,
15670 the native file system would interpret this whole absolute file name
15671 as a relative file name with no directory components. This would make
15672 it impossible to point @value{GDBN} at a copy of the remote target's
15673 shared libraries on the host using @code{set sysroot}, and impractical
15674 with @code{set solib-search-path}. Setting
15675 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15676 to interpret such file names similarly to how the target would, and to
15677 map them to file names valid on @value{GDBN}'s native file system
15678 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15679 to one of the supported file system kinds. In that case, @value{GDBN}
15680 tries to determine the appropriate file system variant based on the
15681 current target's operating system (@pxref{ABI, ,Configuring the
15682 Current ABI}). The supported file system settings are:
15686 Instruct @value{GDBN} to assume the target file system is of Unix
15687 kind. Only file names starting the forward slash (@samp{/}) character
15688 are considered absolute, and the directory separator character is also
15692 Instruct @value{GDBN} to assume the target file system is DOS based.
15693 File names starting with either a forward slash, or a drive letter
15694 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15695 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15696 considered directory separators.
15699 Instruct @value{GDBN} to use the file system kind associated with the
15700 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15701 This is the default.
15706 @node Separate Debug Files
15707 @section Debugging Information in Separate Files
15708 @cindex separate debugging information files
15709 @cindex debugging information in separate files
15710 @cindex @file{.debug} subdirectories
15711 @cindex debugging information directory, global
15712 @cindex global debugging information directory
15713 @cindex build ID, and separate debugging files
15714 @cindex @file{.build-id} directory
15716 @value{GDBN} allows you to put a program's debugging information in a
15717 file separate from the executable itself, in a way that allows
15718 @value{GDBN} to find and load the debugging information automatically.
15719 Since debugging information can be very large---sometimes larger
15720 than the executable code itself---some systems distribute debugging
15721 information for their executables in separate files, which users can
15722 install only when they need to debug a problem.
15724 @value{GDBN} supports two ways of specifying the separate debug info
15729 The executable contains a @dfn{debug link} that specifies the name of
15730 the separate debug info file. The separate debug file's name is
15731 usually @file{@var{executable}.debug}, where @var{executable} is the
15732 name of the corresponding executable file without leading directories
15733 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15734 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15735 checksum for the debug file, which @value{GDBN} uses to validate that
15736 the executable and the debug file came from the same build.
15739 The executable contains a @dfn{build ID}, a unique bit string that is
15740 also present in the corresponding debug info file. (This is supported
15741 only on some operating systems, notably those which use the ELF format
15742 for binary files and the @sc{gnu} Binutils.) For more details about
15743 this feature, see the description of the @option{--build-id}
15744 command-line option in @ref{Options, , Command Line Options, ld.info,
15745 The GNU Linker}. The debug info file's name is not specified
15746 explicitly by the build ID, but can be computed from the build ID, see
15750 Depending on the way the debug info file is specified, @value{GDBN}
15751 uses two different methods of looking for the debug file:
15755 For the ``debug link'' method, @value{GDBN} looks up the named file in
15756 the directory of the executable file, then in a subdirectory of that
15757 directory named @file{.debug}, and finally under the global debug
15758 directory, in a subdirectory whose name is identical to the leading
15759 directories of the executable's absolute file name.
15762 For the ``build ID'' method, @value{GDBN} looks in the
15763 @file{.build-id} subdirectory of the global debug directory for a file
15764 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15765 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15766 are the rest of the bit string. (Real build ID strings are 32 or more
15767 hex characters, not 10.)
15770 So, for example, suppose you ask @value{GDBN} to debug
15771 @file{/usr/bin/ls}, which has a debug link that specifies the
15772 file @file{ls.debug}, and a build ID whose value in hex is
15773 @code{abcdef1234}. If the global debug directory is
15774 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15775 debug information files, in the indicated order:
15779 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15781 @file{/usr/bin/ls.debug}
15783 @file{/usr/bin/.debug/ls.debug}
15785 @file{/usr/lib/debug/usr/bin/ls.debug}.
15788 You can set the global debugging info directory's name, and view the
15789 name @value{GDBN} is currently using.
15793 @kindex set debug-file-directory
15794 @item set debug-file-directory @var{directories}
15795 Set the directories which @value{GDBN} searches for separate debugging
15796 information files to @var{directory}. Multiple directory components can be set
15797 concatenating them by a directory separator.
15799 @kindex show debug-file-directory
15800 @item show debug-file-directory
15801 Show the directories @value{GDBN} searches for separate debugging
15806 @cindex @code{.gnu_debuglink} sections
15807 @cindex debug link sections
15808 A debug link is a special section of the executable file named
15809 @code{.gnu_debuglink}. The section must contain:
15813 A filename, with any leading directory components removed, followed by
15816 zero to three bytes of padding, as needed to reach the next four-byte
15817 boundary within the section, and
15819 a four-byte CRC checksum, stored in the same endianness used for the
15820 executable file itself. The checksum is computed on the debugging
15821 information file's full contents by the function given below, passing
15822 zero as the @var{crc} argument.
15825 Any executable file format can carry a debug link, as long as it can
15826 contain a section named @code{.gnu_debuglink} with the contents
15829 @cindex @code{.note.gnu.build-id} sections
15830 @cindex build ID sections
15831 The build ID is a special section in the executable file (and in other
15832 ELF binary files that @value{GDBN} may consider). This section is
15833 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15834 It contains unique identification for the built files---the ID remains
15835 the same across multiple builds of the same build tree. The default
15836 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15837 content for the build ID string. The same section with an identical
15838 value is present in the original built binary with symbols, in its
15839 stripped variant, and in the separate debugging information file.
15841 The debugging information file itself should be an ordinary
15842 executable, containing a full set of linker symbols, sections, and
15843 debugging information. The sections of the debugging information file
15844 should have the same names, addresses, and sizes as the original file,
15845 but they need not contain any data---much like a @code{.bss} section
15846 in an ordinary executable.
15848 The @sc{gnu} binary utilities (Binutils) package includes the
15849 @samp{objcopy} utility that can produce
15850 the separated executable / debugging information file pairs using the
15851 following commands:
15854 @kbd{objcopy --only-keep-debug foo foo.debug}
15859 These commands remove the debugging
15860 information from the executable file @file{foo} and place it in the file
15861 @file{foo.debug}. You can use the first, second or both methods to link the
15866 The debug link method needs the following additional command to also leave
15867 behind a debug link in @file{foo}:
15870 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15873 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15874 a version of the @code{strip} command such that the command @kbd{strip foo -f
15875 foo.debug} has the same functionality as the two @code{objcopy} commands and
15876 the @code{ln -s} command above, together.
15879 Build ID gets embedded into the main executable using @code{ld --build-id} or
15880 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15881 compatibility fixes for debug files separation are present in @sc{gnu} binary
15882 utilities (Binutils) package since version 2.18.
15887 @cindex CRC algorithm definition
15888 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15889 IEEE 802.3 using the polynomial:
15891 @c TexInfo requires naked braces for multi-digit exponents for Tex
15892 @c output, but this causes HTML output to barf. HTML has to be set using
15893 @c raw commands. So we end up having to specify this equation in 2
15898 <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>
15899 + <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
15905 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15906 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15910 The function is computed byte at a time, taking the least
15911 significant bit of each byte first. The initial pattern
15912 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15913 the final result is inverted to ensure trailing zeros also affect the
15916 @emph{Note:} This is the same CRC polynomial as used in handling the
15917 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15918 , @value{GDBN} Remote Serial Protocol}). However in the
15919 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15920 significant bit first, and the result is not inverted, so trailing
15921 zeros have no effect on the CRC value.
15923 To complete the description, we show below the code of the function
15924 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15925 initially supplied @code{crc} argument means that an initial call to
15926 this function passing in zero will start computing the CRC using
15929 @kindex gnu_debuglink_crc32
15932 gnu_debuglink_crc32 (unsigned long crc,
15933 unsigned char *buf, size_t len)
15935 static const unsigned long crc32_table[256] =
15937 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15938 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15939 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15940 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15941 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15942 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15943 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15944 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15945 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15946 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15947 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15948 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15949 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15950 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15951 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15952 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15953 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15954 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15955 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15956 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15957 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15958 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15959 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15960 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15961 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15962 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15963 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15964 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15965 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15966 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15967 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15968 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15969 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15970 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15971 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15972 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15973 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15974 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15975 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15976 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15977 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15978 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15979 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15980 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15981 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15982 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15983 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15984 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15985 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15986 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15987 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15990 unsigned char *end;
15992 crc = ~crc & 0xffffffff;
15993 for (end = buf + len; buf < end; ++buf)
15994 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15995 return ~crc & 0xffffffff;
16000 This computation does not apply to the ``build ID'' method.
16004 @section Index Files Speed Up @value{GDBN}
16005 @cindex index files
16006 @cindex @samp{.gdb_index} section
16008 When @value{GDBN} finds a symbol file, it scans the symbols in the
16009 file in order to construct an internal symbol table. This lets most
16010 @value{GDBN} operations work quickly---at the cost of a delay early
16011 on. For large programs, this delay can be quite lengthy, so
16012 @value{GDBN} provides a way to build an index, which speeds up
16015 The index is stored as a section in the symbol file. @value{GDBN} can
16016 write the index to a file, then you can put it into the symbol file
16017 using @command{objcopy}.
16019 To create an index file, use the @code{save gdb-index} command:
16022 @item save gdb-index @var{directory}
16023 @kindex save gdb-index
16024 Create an index file for each symbol file currently known by
16025 @value{GDBN}. Each file is named after its corresponding symbol file,
16026 with @samp{.gdb-index} appended, and is written into the given
16030 Once you have created an index file you can merge it into your symbol
16031 file, here named @file{symfile}, using @command{objcopy}:
16034 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16035 --set-section-flags .gdb_index=readonly symfile symfile
16038 There are currently some limitation on indices. They only work when
16039 for DWARF debugging information, not stabs. And, they do not
16040 currently work for programs using Ada.
16042 @node Symbol Errors
16043 @section Errors Reading Symbol Files
16045 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16046 such as symbol types it does not recognize, or known bugs in compiler
16047 output. By default, @value{GDBN} does not notify you of such problems, since
16048 they are relatively common and primarily of interest to people
16049 debugging compilers. If you are interested in seeing information
16050 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16051 only one message about each such type of problem, no matter how many
16052 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16053 to see how many times the problems occur, with the @code{set
16054 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16057 The messages currently printed, and their meanings, include:
16060 @item inner block not inside outer block in @var{symbol}
16062 The symbol information shows where symbol scopes begin and end
16063 (such as at the start of a function or a block of statements). This
16064 error indicates that an inner scope block is not fully contained
16065 in its outer scope blocks.
16067 @value{GDBN} circumvents the problem by treating the inner block as if it had
16068 the same scope as the outer block. In the error message, @var{symbol}
16069 may be shown as ``@code{(don't know)}'' if the outer block is not a
16072 @item block at @var{address} out of order
16074 The symbol information for symbol scope blocks should occur in
16075 order of increasing addresses. This error indicates that it does not
16078 @value{GDBN} does not circumvent this problem, and has trouble
16079 locating symbols in the source file whose symbols it is reading. (You
16080 can often determine what source file is affected by specifying
16081 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16084 @item bad block start address patched
16086 The symbol information for a symbol scope block has a start address
16087 smaller than the address of the preceding source line. This is known
16088 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16090 @value{GDBN} circumvents the problem by treating the symbol scope block as
16091 starting on the previous source line.
16093 @item bad string table offset in symbol @var{n}
16096 Symbol number @var{n} contains a pointer into the string table which is
16097 larger than the size of the string table.
16099 @value{GDBN} circumvents the problem by considering the symbol to have the
16100 name @code{foo}, which may cause other problems if many symbols end up
16103 @item unknown symbol type @code{0x@var{nn}}
16105 The symbol information contains new data types that @value{GDBN} does
16106 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16107 uncomprehended information, in hexadecimal.
16109 @value{GDBN} circumvents the error by ignoring this symbol information.
16110 This usually allows you to debug your program, though certain symbols
16111 are not accessible. If you encounter such a problem and feel like
16112 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16113 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16114 and examine @code{*bufp} to see the symbol.
16116 @item stub type has NULL name
16118 @value{GDBN} could not find the full definition for a struct or class.
16120 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16121 The symbol information for a C@t{++} member function is missing some
16122 information that recent versions of the compiler should have output for
16125 @item info mismatch between compiler and debugger
16127 @value{GDBN} could not parse a type specification output by the compiler.
16132 @section GDB Data Files
16134 @cindex prefix for data files
16135 @value{GDBN} will sometimes read an auxiliary data file. These files
16136 are kept in a directory known as the @dfn{data directory}.
16138 You can set the data directory's name, and view the name @value{GDBN}
16139 is currently using.
16142 @kindex set data-directory
16143 @item set data-directory @var{directory}
16144 Set the directory which @value{GDBN} searches for auxiliary data files
16145 to @var{directory}.
16147 @kindex show data-directory
16148 @item show data-directory
16149 Show the directory @value{GDBN} searches for auxiliary data files.
16152 @cindex default data directory
16153 @cindex @samp{--with-gdb-datadir}
16154 You can set the default data directory by using the configure-time
16155 @samp{--with-gdb-datadir} option. If the data directory is inside
16156 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16157 @samp{--exec-prefix}), then the default data directory will be updated
16158 automatically if the installed @value{GDBN} is moved to a new
16161 The data directory may also be specified with the
16162 @code{--data-directory} command line option.
16163 @xref{Mode Options}.
16166 @chapter Specifying a Debugging Target
16168 @cindex debugging target
16169 A @dfn{target} is the execution environment occupied by your program.
16171 Often, @value{GDBN} runs in the same host environment as your program;
16172 in that case, the debugging target is specified as a side effect when
16173 you use the @code{file} or @code{core} commands. When you need more
16174 flexibility---for example, running @value{GDBN} on a physically separate
16175 host, or controlling a standalone system over a serial port or a
16176 realtime system over a TCP/IP connection---you can use the @code{target}
16177 command to specify one of the target types configured for @value{GDBN}
16178 (@pxref{Target Commands, ,Commands for Managing Targets}).
16180 @cindex target architecture
16181 It is possible to build @value{GDBN} for several different @dfn{target
16182 architectures}. When @value{GDBN} is built like that, you can choose
16183 one of the available architectures with the @kbd{set architecture}
16187 @kindex set architecture
16188 @kindex show architecture
16189 @item set architecture @var{arch}
16190 This command sets the current target architecture to @var{arch}. The
16191 value of @var{arch} can be @code{"auto"}, in addition to one of the
16192 supported architectures.
16194 @item show architecture
16195 Show the current target architecture.
16197 @item set processor
16199 @kindex set processor
16200 @kindex show processor
16201 These are alias commands for, respectively, @code{set architecture}
16202 and @code{show architecture}.
16206 * Active Targets:: Active targets
16207 * Target Commands:: Commands for managing targets
16208 * Byte Order:: Choosing target byte order
16211 @node Active Targets
16212 @section Active Targets
16214 @cindex stacking targets
16215 @cindex active targets
16216 @cindex multiple targets
16218 There are multiple classes of targets such as: processes, executable files or
16219 recording sessions. Core files belong to the process class, making core file
16220 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16221 on multiple active targets, one in each class. This allows you to (for
16222 example) start a process and inspect its activity, while still having access to
16223 the executable file after the process finishes. Or if you start process
16224 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16225 presented a virtual layer of the recording target, while the process target
16226 remains stopped at the chronologically last point of the process execution.
16228 Use the @code{core-file} and @code{exec-file} commands to select a new core
16229 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16230 specify as a target a process that is already running, use the @code{attach}
16231 command (@pxref{Attach, ,Debugging an Already-running Process}).
16233 @node Target Commands
16234 @section Commands for Managing Targets
16237 @item target @var{type} @var{parameters}
16238 Connects the @value{GDBN} host environment to a target machine or
16239 process. A target is typically a protocol for talking to debugging
16240 facilities. You use the argument @var{type} to specify the type or
16241 protocol of the target machine.
16243 Further @var{parameters} are interpreted by the target protocol, but
16244 typically include things like device names or host names to connect
16245 with, process numbers, and baud rates.
16247 The @code{target} command does not repeat if you press @key{RET} again
16248 after executing the command.
16250 @kindex help target
16252 Displays the names of all targets available. To display targets
16253 currently selected, use either @code{info target} or @code{info files}
16254 (@pxref{Files, ,Commands to Specify Files}).
16256 @item help target @var{name}
16257 Describe a particular target, including any parameters necessary to
16260 @kindex set gnutarget
16261 @item set gnutarget @var{args}
16262 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
16263 knows whether it is reading an @dfn{executable},
16264 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
16265 with the @code{set gnutarget} command. Unlike most @code{target} commands,
16266 with @code{gnutarget} the @code{target} refers to a program, not a machine.
16269 @emph{Warning:} To specify a file format with @code{set gnutarget},
16270 you must know the actual BFD name.
16274 @xref{Files, , Commands to Specify Files}.
16276 @kindex show gnutarget
16277 @item show gnutarget
16278 Use the @code{show gnutarget} command to display what file format
16279 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
16280 @value{GDBN} will determine the file format for each file automatically,
16281 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
16284 @cindex common targets
16285 Here are some common targets (available, or not, depending on the GDB
16290 @item target exec @var{program}
16291 @cindex executable file target
16292 An executable file. @samp{target exec @var{program}} is the same as
16293 @samp{exec-file @var{program}}.
16295 @item target core @var{filename}
16296 @cindex core dump file target
16297 A core dump file. @samp{target core @var{filename}} is the same as
16298 @samp{core-file @var{filename}}.
16300 @item target remote @var{medium}
16301 @cindex remote target
16302 A remote system connected to @value{GDBN} via a serial line or network
16303 connection. This command tells @value{GDBN} to use its own remote
16304 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
16306 For example, if you have a board connected to @file{/dev/ttya} on the
16307 machine running @value{GDBN}, you could say:
16310 target remote /dev/ttya
16313 @code{target remote} supports the @code{load} command. This is only
16314 useful if you have some other way of getting the stub to the target
16315 system, and you can put it somewhere in memory where it won't get
16316 clobbered by the download.
16318 @item target sim @r{[}@var{simargs}@r{]} @dots{}
16319 @cindex built-in simulator target
16320 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
16328 works; however, you cannot assume that a specific memory map, device
16329 drivers, or even basic I/O is available, although some simulators do
16330 provide these. For info about any processor-specific simulator details,
16331 see the appropriate section in @ref{Embedded Processors, ,Embedded
16336 Some configurations may include these targets as well:
16340 @item target nrom @var{dev}
16341 @cindex NetROM ROM emulator target
16342 NetROM ROM emulator. This target only supports downloading.
16346 Different targets are available on different configurations of @value{GDBN};
16347 your configuration may have more or fewer targets.
16349 Many remote targets require you to download the executable's code once
16350 you've successfully established a connection. You may wish to control
16351 various aspects of this process.
16356 @kindex set hash@r{, for remote monitors}
16357 @cindex hash mark while downloading
16358 This command controls whether a hash mark @samp{#} is displayed while
16359 downloading a file to the remote monitor. If on, a hash mark is
16360 displayed after each S-record is successfully downloaded to the
16364 @kindex show hash@r{, for remote monitors}
16365 Show the current status of displaying the hash mark.
16367 @item set debug monitor
16368 @kindex set debug monitor
16369 @cindex display remote monitor communications
16370 Enable or disable display of communications messages between
16371 @value{GDBN} and the remote monitor.
16373 @item show debug monitor
16374 @kindex show debug monitor
16375 Show the current status of displaying communications between
16376 @value{GDBN} and the remote monitor.
16381 @kindex load @var{filename}
16382 @item load @var{filename}
16384 Depending on what remote debugging facilities are configured into
16385 @value{GDBN}, the @code{load} command may be available. Where it exists, it
16386 is meant to make @var{filename} (an executable) available for debugging
16387 on the remote system---by downloading, or dynamic linking, for example.
16388 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
16389 the @code{add-symbol-file} command.
16391 If your @value{GDBN} does not have a @code{load} command, attempting to
16392 execute it gets the error message ``@code{You can't do that when your
16393 target is @dots{}}''
16395 The file is loaded at whatever address is specified in the executable.
16396 For some object file formats, you can specify the load address when you
16397 link the program; for other formats, like a.out, the object file format
16398 specifies a fixed address.
16399 @c FIXME! This would be a good place for an xref to the GNU linker doc.
16401 Depending on the remote side capabilities, @value{GDBN} may be able to
16402 load programs into flash memory.
16404 @code{load} does not repeat if you press @key{RET} again after using it.
16408 @section Choosing Target Byte Order
16410 @cindex choosing target byte order
16411 @cindex target byte order
16413 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
16414 offer the ability to run either big-endian or little-endian byte
16415 orders. Usually the executable or symbol will include a bit to
16416 designate the endian-ness, and you will not need to worry about
16417 which to use. However, you may still find it useful to adjust
16418 @value{GDBN}'s idea of processor endian-ness manually.
16422 @item set endian big
16423 Instruct @value{GDBN} to assume the target is big-endian.
16425 @item set endian little
16426 Instruct @value{GDBN} to assume the target is little-endian.
16428 @item set endian auto
16429 Instruct @value{GDBN} to use the byte order associated with the
16433 Display @value{GDBN}'s current idea of the target byte order.
16437 Note that these commands merely adjust interpretation of symbolic
16438 data on the host, and that they have absolutely no effect on the
16442 @node Remote Debugging
16443 @chapter Debugging Remote Programs
16444 @cindex remote debugging
16446 If you are trying to debug a program running on a machine that cannot run
16447 @value{GDBN} in the usual way, it is often useful to use remote debugging.
16448 For example, you might use remote debugging on an operating system kernel,
16449 or on a small system which does not have a general purpose operating system
16450 powerful enough to run a full-featured debugger.
16452 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
16453 to make this work with particular debugging targets. In addition,
16454 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
16455 but not specific to any particular target system) which you can use if you
16456 write the remote stubs---the code that runs on the remote system to
16457 communicate with @value{GDBN}.
16459 Other remote targets may be available in your
16460 configuration of @value{GDBN}; use @code{help target} to list them.
16463 * Connecting:: Connecting to a remote target
16464 * File Transfer:: Sending files to a remote system
16465 * Server:: Using the gdbserver program
16466 * Remote Configuration:: Remote configuration
16467 * Remote Stub:: Implementing a remote stub
16471 @section Connecting to a Remote Target
16473 On the @value{GDBN} host machine, you will need an unstripped copy of
16474 your program, since @value{GDBN} needs symbol and debugging information.
16475 Start up @value{GDBN} as usual, using the name of the local copy of your
16476 program as the first argument.
16478 @cindex @code{target remote}
16479 @value{GDBN} can communicate with the target over a serial line, or
16480 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16481 each case, @value{GDBN} uses the same protocol for debugging your
16482 program; only the medium carrying the debugging packets varies. The
16483 @code{target remote} command establishes a connection to the target.
16484 Its arguments indicate which medium to use:
16488 @item target remote @var{serial-device}
16489 @cindex serial line, @code{target remote}
16490 Use @var{serial-device} to communicate with the target. For example,
16491 to use a serial line connected to the device named @file{/dev/ttyb}:
16494 target remote /dev/ttyb
16497 If you're using a serial line, you may want to give @value{GDBN} the
16498 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16499 (@pxref{Remote Configuration, set remotebaud}) before the
16500 @code{target} command.
16502 @item target remote @code{@var{host}:@var{port}}
16503 @itemx target remote @code{tcp:@var{host}:@var{port}}
16504 @cindex @acronym{TCP} port, @code{target remote}
16505 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16506 The @var{host} may be either a host name or a numeric @acronym{IP}
16507 address; @var{port} must be a decimal number. The @var{host} could be
16508 the target machine itself, if it is directly connected to the net, or
16509 it might be a terminal server which in turn has a serial line to the
16512 For example, to connect to port 2828 on a terminal server named
16516 target remote manyfarms:2828
16519 If your remote target is actually running on the same machine as your
16520 debugger session (e.g.@: a simulator for your target running on the
16521 same host), you can omit the hostname. For example, to connect to
16522 port 1234 on your local machine:
16525 target remote :1234
16529 Note that the colon is still required here.
16531 @item target remote @code{udp:@var{host}:@var{port}}
16532 @cindex @acronym{UDP} port, @code{target remote}
16533 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16534 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16537 target remote udp:manyfarms:2828
16540 When using a @acronym{UDP} connection for remote debugging, you should
16541 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16542 can silently drop packets on busy or unreliable networks, which will
16543 cause havoc with your debugging session.
16545 @item target remote | @var{command}
16546 @cindex pipe, @code{target remote} to
16547 Run @var{command} in the background and communicate with it using a
16548 pipe. The @var{command} is a shell command, to be parsed and expanded
16549 by the system's command shell, @code{/bin/sh}; it should expect remote
16550 protocol packets on its standard input, and send replies on its
16551 standard output. You could use this to run a stand-alone simulator
16552 that speaks the remote debugging protocol, to make net connections
16553 using programs like @code{ssh}, or for other similar tricks.
16555 If @var{command} closes its standard output (perhaps by exiting),
16556 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16557 program has already exited, this will have no effect.)
16561 Once the connection has been established, you can use all the usual
16562 commands to examine and change data. The remote program is already
16563 running; you can use @kbd{step} and @kbd{continue}, and you do not
16564 need to use @kbd{run}.
16566 @cindex interrupting remote programs
16567 @cindex remote programs, interrupting
16568 Whenever @value{GDBN} is waiting for the remote program, if you type the
16569 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16570 program. This may or may not succeed, depending in part on the hardware
16571 and the serial drivers the remote system uses. If you type the
16572 interrupt character once again, @value{GDBN} displays this prompt:
16575 Interrupted while waiting for the program.
16576 Give up (and stop debugging it)? (y or n)
16579 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16580 (If you decide you want to try again later, you can use @samp{target
16581 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16582 goes back to waiting.
16585 @kindex detach (remote)
16587 When you have finished debugging the remote program, you can use the
16588 @code{detach} command to release it from @value{GDBN} control.
16589 Detaching from the target normally resumes its execution, but the results
16590 will depend on your particular remote stub. After the @code{detach}
16591 command, @value{GDBN} is free to connect to another target.
16595 The @code{disconnect} command behaves like @code{detach}, except that
16596 the target is generally not resumed. It will wait for @value{GDBN}
16597 (this instance or another one) to connect and continue debugging. After
16598 the @code{disconnect} command, @value{GDBN} is again free to connect to
16601 @cindex send command to remote monitor
16602 @cindex extend @value{GDBN} for remote targets
16603 @cindex add new commands for external monitor
16605 @item monitor @var{cmd}
16606 This command allows you to send arbitrary commands directly to the
16607 remote monitor. Since @value{GDBN} doesn't care about the commands it
16608 sends like this, this command is the way to extend @value{GDBN}---you
16609 can add new commands that only the external monitor will understand
16613 @node File Transfer
16614 @section Sending files to a remote system
16615 @cindex remote target, file transfer
16616 @cindex file transfer
16617 @cindex sending files to remote systems
16619 Some remote targets offer the ability to transfer files over the same
16620 connection used to communicate with @value{GDBN}. This is convenient
16621 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16622 running @code{gdbserver} over a network interface. For other targets,
16623 e.g.@: embedded devices with only a single serial port, this may be
16624 the only way to upload or download files.
16626 Not all remote targets support these commands.
16630 @item remote put @var{hostfile} @var{targetfile}
16631 Copy file @var{hostfile} from the host system (the machine running
16632 @value{GDBN}) to @var{targetfile} on the target system.
16635 @item remote get @var{targetfile} @var{hostfile}
16636 Copy file @var{targetfile} from the target system to @var{hostfile}
16637 on the host system.
16639 @kindex remote delete
16640 @item remote delete @var{targetfile}
16641 Delete @var{targetfile} from the target system.
16646 @section Using the @code{gdbserver} Program
16649 @cindex remote connection without stubs
16650 @code{gdbserver} is a control program for Unix-like systems, which
16651 allows you to connect your program with a remote @value{GDBN} via
16652 @code{target remote}---but without linking in the usual debugging stub.
16654 @code{gdbserver} is not a complete replacement for the debugging stubs,
16655 because it requires essentially the same operating-system facilities
16656 that @value{GDBN} itself does. In fact, a system that can run
16657 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16658 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16659 because it is a much smaller program than @value{GDBN} itself. It is
16660 also easier to port than all of @value{GDBN}, so you may be able to get
16661 started more quickly on a new system by using @code{gdbserver}.
16662 Finally, if you develop code for real-time systems, you may find that
16663 the tradeoffs involved in real-time operation make it more convenient to
16664 do as much development work as possible on another system, for example
16665 by cross-compiling. You can use @code{gdbserver} to make a similar
16666 choice for debugging.
16668 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16669 or a TCP connection, using the standard @value{GDBN} remote serial
16673 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16674 Do not run @code{gdbserver} connected to any public network; a
16675 @value{GDBN} connection to @code{gdbserver} provides access to the
16676 target system with the same privileges as the user running
16680 @subsection Running @code{gdbserver}
16681 @cindex arguments, to @code{gdbserver}
16682 @cindex @code{gdbserver}, command-line arguments
16684 Run @code{gdbserver} on the target system. You need a copy of the
16685 program you want to debug, including any libraries it requires.
16686 @code{gdbserver} does not need your program's symbol table, so you can
16687 strip the program if necessary to save space. @value{GDBN} on the host
16688 system does all the symbol handling.
16690 To use the server, you must tell it how to communicate with @value{GDBN};
16691 the name of your program; and the arguments for your program. The usual
16695 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16698 @var{comm} is either a device name (to use a serial line) or a TCP
16699 hostname and portnumber. For example, to debug Emacs with the argument
16700 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16704 target> gdbserver /dev/com1 emacs foo.txt
16707 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16710 To use a TCP connection instead of a serial line:
16713 target> gdbserver host:2345 emacs foo.txt
16716 The only difference from the previous example is the first argument,
16717 specifying that you are communicating with the host @value{GDBN} via
16718 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16719 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16720 (Currently, the @samp{host} part is ignored.) You can choose any number
16721 you want for the port number as long as it does not conflict with any
16722 TCP ports already in use on the target system (for example, @code{23} is
16723 reserved for @code{telnet}).@footnote{If you choose a port number that
16724 conflicts with another service, @code{gdbserver} prints an error message
16725 and exits.} You must use the same port number with the host @value{GDBN}
16726 @code{target remote} command.
16728 @subsubsection Attaching to a Running Program
16729 @cindex attach to a program, @code{gdbserver}
16730 @cindex @option{--attach}, @code{gdbserver} option
16732 On some targets, @code{gdbserver} can also attach to running programs.
16733 This is accomplished via the @code{--attach} argument. The syntax is:
16736 target> gdbserver --attach @var{comm} @var{pid}
16739 @var{pid} is the process ID of a currently running process. It isn't necessary
16740 to point @code{gdbserver} at a binary for the running process.
16743 You can debug processes by name instead of process ID if your target has the
16744 @code{pidof} utility:
16747 target> gdbserver --attach @var{comm} `pidof @var{program}`
16750 In case more than one copy of @var{program} is running, or @var{program}
16751 has multiple threads, most versions of @code{pidof} support the
16752 @code{-s} option to only return the first process ID.
16754 @subsubsection Multi-Process Mode for @code{gdbserver}
16755 @cindex @code{gdbserver}, multiple processes
16756 @cindex multiple processes with @code{gdbserver}
16758 When you connect to @code{gdbserver} using @code{target remote},
16759 @code{gdbserver} debugs the specified program only once. When the
16760 program exits, or you detach from it, @value{GDBN} closes the connection
16761 and @code{gdbserver} exits.
16763 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16764 enters multi-process mode. When the debugged program exits, or you
16765 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16766 though no program is running. The @code{run} and @code{attach}
16767 commands instruct @code{gdbserver} to run or attach to a new program.
16768 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16769 remote exec-file}) to select the program to run. Command line
16770 arguments are supported, except for wildcard expansion and I/O
16771 redirection (@pxref{Arguments}).
16773 @cindex @option{--multi}, @code{gdbserver} option
16774 To start @code{gdbserver} without supplying an initial command to run
16775 or process ID to attach, use the @option{--multi} command line option.
16776 Then you can connect using @kbd{target extended-remote} and start
16777 the program you want to debug.
16779 In multi-process mode @code{gdbserver} does not automatically exit unless you
16780 use the option @option{--once}. You can terminate it by using
16781 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16782 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16783 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16784 @option{--multi} option to @code{gdbserver} has no influence on that.
16786 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
16788 This section applies only when @code{gdbserver} is run to listen on a TCP port.
16790 @code{gdbserver} normally terminates after all of its debugged processes have
16791 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
16792 extended-remote}, @code{gdbserver} stays running even with no processes left.
16793 @value{GDBN} normally terminates the spawned debugged process on its exit,
16794 which normally also terminates @code{gdbserver} in the @kbd{target remote}
16795 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
16796 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
16797 stays running even in the @kbd{target remote} mode.
16799 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
16800 Such reconnecting is useful for features like @ref{disconnected tracing}. For
16801 completeness, at most one @value{GDBN} can be connected at a time.
16803 @cindex @option{--once}, @code{gdbserver} option
16804 By default, @code{gdbserver} keeps the listening TCP port open, so that
16805 additional connections are possible. However, if you start @code{gdbserver}
16806 with the @option{--once} option, it will stop listening for any further
16807 connection attempts after connecting to the first @value{GDBN} session. This
16808 means no further connections to @code{gdbserver} will be possible after the
16809 first one. It also means @code{gdbserver} will terminate after the first
16810 connection with remote @value{GDBN} has closed, even for unexpectedly closed
16811 connections and even in the @kbd{target extended-remote} mode. The
16812 @option{--once} option allows reusing the same port number for connecting to
16813 multiple instances of @code{gdbserver} running on the same host, since each
16814 instance closes its port after the first connection.
16816 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16818 @cindex @option{--debug}, @code{gdbserver} option
16819 The @option{--debug} option tells @code{gdbserver} to display extra
16820 status information about the debugging process.
16821 @cindex @option{--remote-debug}, @code{gdbserver} option
16822 The @option{--remote-debug} option tells @code{gdbserver} to display
16823 remote protocol debug output. These options are intended for
16824 @code{gdbserver} development and for bug reports to the developers.
16826 @cindex @option{--wrapper}, @code{gdbserver} option
16827 The @option{--wrapper} option specifies a wrapper to launch programs
16828 for debugging. The option should be followed by the name of the
16829 wrapper, then any command-line arguments to pass to the wrapper, then
16830 @kbd{--} indicating the end of the wrapper arguments.
16832 @code{gdbserver} runs the specified wrapper program with a combined
16833 command line including the wrapper arguments, then the name of the
16834 program to debug, then any arguments to the program. The wrapper
16835 runs until it executes your program, and then @value{GDBN} gains control.
16837 You can use any program that eventually calls @code{execve} with
16838 its arguments as a wrapper. Several standard Unix utilities do
16839 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16840 with @code{exec "$@@"} will also work.
16842 For example, you can use @code{env} to pass an environment variable to
16843 the debugged program, without setting the variable in @code{gdbserver}'s
16847 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16850 @subsection Connecting to @code{gdbserver}
16852 Run @value{GDBN} on the host system.
16854 First make sure you have the necessary symbol files. Load symbols for
16855 your application using the @code{file} command before you connect. Use
16856 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16857 was compiled with the correct sysroot using @code{--with-sysroot}).
16859 The symbol file and target libraries must exactly match the executable
16860 and libraries on the target, with one exception: the files on the host
16861 system should not be stripped, even if the files on the target system
16862 are. Mismatched or missing files will lead to confusing results
16863 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16864 files may also prevent @code{gdbserver} from debugging multi-threaded
16867 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16868 For TCP connections, you must start up @code{gdbserver} prior to using
16869 the @code{target remote} command. Otherwise you may get an error whose
16870 text depends on the host system, but which usually looks something like
16871 @samp{Connection refused}. Don't use the @code{load}
16872 command in @value{GDBN} when using @code{gdbserver}, since the program is
16873 already on the target.
16875 @subsection Monitor Commands for @code{gdbserver}
16876 @cindex monitor commands, for @code{gdbserver}
16877 @anchor{Monitor Commands for gdbserver}
16879 During a @value{GDBN} session using @code{gdbserver}, you can use the
16880 @code{monitor} command to send special requests to @code{gdbserver}.
16881 Here are the available commands.
16885 List the available monitor commands.
16887 @item monitor set debug 0
16888 @itemx monitor set debug 1
16889 Disable or enable general debugging messages.
16891 @item monitor set remote-debug 0
16892 @itemx monitor set remote-debug 1
16893 Disable or enable specific debugging messages associated with the remote
16894 protocol (@pxref{Remote Protocol}).
16896 @item monitor set libthread-db-search-path [PATH]
16897 @cindex gdbserver, search path for @code{libthread_db}
16898 When this command is issued, @var{path} is a colon-separated list of
16899 directories to search for @code{libthread_db} (@pxref{Threads,,set
16900 libthread-db-search-path}). If you omit @var{path},
16901 @samp{libthread-db-search-path} will be reset to its default value.
16903 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
16904 not supported in @code{gdbserver}.
16907 Tell gdbserver to exit immediately. This command should be followed by
16908 @code{disconnect} to close the debugging session. @code{gdbserver} will
16909 detach from any attached processes and kill any processes it created.
16910 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16911 of a multi-process mode debug session.
16915 @subsection Tracepoints support in @code{gdbserver}
16916 @cindex tracepoints support in @code{gdbserver}
16918 On some targets, @code{gdbserver} supports tracepoints, fast
16919 tracepoints and static tracepoints.
16921 For fast or static tracepoints to work, a special library called the
16922 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16923 This library is built and distributed as an integral part of
16924 @code{gdbserver}. In addition, support for static tracepoints
16925 requires building the in-process agent library with static tracepoints
16926 support. At present, the UST (LTTng Userspace Tracer,
16927 @url{http://lttng.org/ust}) tracing engine is supported. This support
16928 is automatically available if UST development headers are found in the
16929 standard include path when @code{gdbserver} is built, or if
16930 @code{gdbserver} was explicitly configured using @option{--with-ust}
16931 to point at such headers. You can explicitly disable the support
16932 using @option{--with-ust=no}.
16934 There are several ways to load the in-process agent in your program:
16937 @item Specifying it as dependency at link time
16939 You can link your program dynamically with the in-process agent
16940 library. On most systems, this is accomplished by adding
16941 @code{-linproctrace} to the link command.
16943 @item Using the system's preloading mechanisms
16945 You can force loading the in-process agent at startup time by using
16946 your system's support for preloading shared libraries. Many Unixes
16947 support the concept of preloading user defined libraries. In most
16948 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16949 in the environment. See also the description of @code{gdbserver}'s
16950 @option{--wrapper} command line option.
16952 @item Using @value{GDBN} to force loading the agent at run time
16954 On some systems, you can force the inferior to load a shared library,
16955 by calling a dynamic loader function in the inferior that takes care
16956 of dynamically looking up and loading a shared library. On most Unix
16957 systems, the function is @code{dlopen}. You'll use the @code{call}
16958 command for that. For example:
16961 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16964 Note that on most Unix systems, for the @code{dlopen} function to be
16965 available, the program needs to be linked with @code{-ldl}.
16968 On systems that have a userspace dynamic loader, like most Unix
16969 systems, when you connect to @code{gdbserver} using @code{target
16970 remote}, you'll find that the program is stopped at the dynamic
16971 loader's entry point, and no shared library has been loaded in the
16972 program's address space yet, including the in-process agent. In that
16973 case, before being able to use any of the fast or static tracepoints
16974 features, you need to let the loader run and load the shared
16975 libraries. The simplest way to do that is to run the program to the
16976 main procedure. E.g., if debugging a C or C@t{++} program, start
16977 @code{gdbserver} like so:
16980 $ gdbserver :9999 myprogram
16983 Start GDB and connect to @code{gdbserver} like so, and run to main:
16987 (@value{GDBP}) target remote myhost:9999
16988 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16989 (@value{GDBP}) b main
16990 (@value{GDBP}) continue
16993 The in-process tracing agent library should now be loaded into the
16994 process; you can confirm it with the @code{info sharedlibrary}
16995 command, which will list @file{libinproctrace.so} as loaded in the
16996 process. You are now ready to install fast tracepoints, list static
16997 tracepoint markers, probe static tracepoints markers, and start
17000 @node Remote Configuration
17001 @section Remote Configuration
17004 @kindex show remote
17005 This section documents the configuration options available when
17006 debugging remote programs. For the options related to the File I/O
17007 extensions of the remote protocol, see @ref{system,
17008 system-call-allowed}.
17011 @item set remoteaddresssize @var{bits}
17012 @cindex address size for remote targets
17013 @cindex bits in remote address
17014 Set the maximum size of address in a memory packet to the specified
17015 number of bits. @value{GDBN} will mask off the address bits above
17016 that number, when it passes addresses to the remote target. The
17017 default value is the number of bits in the target's address.
17019 @item show remoteaddresssize
17020 Show the current value of remote address size in bits.
17022 @item set remotebaud @var{n}
17023 @cindex baud rate for remote targets
17024 Set the baud rate for the remote serial I/O to @var{n} baud. The
17025 value is used to set the speed of the serial port used for debugging
17028 @item show remotebaud
17029 Show the current speed of the remote connection.
17031 @item set remotebreak
17032 @cindex interrupt remote programs
17033 @cindex BREAK signal instead of Ctrl-C
17034 @anchor{set remotebreak}
17035 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17036 when you type @kbd{Ctrl-c} to interrupt the program running
17037 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17038 character instead. The default is off, since most remote systems
17039 expect to see @samp{Ctrl-C} as the interrupt signal.
17041 @item show remotebreak
17042 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17043 interrupt the remote program.
17045 @item set remoteflow on
17046 @itemx set remoteflow off
17047 @kindex set remoteflow
17048 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17049 on the serial port used to communicate to the remote target.
17051 @item show remoteflow
17052 @kindex show remoteflow
17053 Show the current setting of hardware flow control.
17055 @item set remotelogbase @var{base}
17056 Set the base (a.k.a.@: radix) of logging serial protocol
17057 communications to @var{base}. Supported values of @var{base} are:
17058 @code{ascii}, @code{octal}, and @code{hex}. The default is
17061 @item show remotelogbase
17062 Show the current setting of the radix for logging remote serial
17065 @item set remotelogfile @var{file}
17066 @cindex record serial communications on file
17067 Record remote serial communications on the named @var{file}. The
17068 default is not to record at all.
17070 @item show remotelogfile.
17071 Show the current setting of the file name on which to record the
17072 serial communications.
17074 @item set remotetimeout @var{num}
17075 @cindex timeout for serial communications
17076 @cindex remote timeout
17077 Set the timeout limit to wait for the remote target to respond to
17078 @var{num} seconds. The default is 2 seconds.
17080 @item show remotetimeout
17081 Show the current number of seconds to wait for the remote target
17084 @cindex limit hardware breakpoints and watchpoints
17085 @cindex remote target, limit break- and watchpoints
17086 @anchor{set remote hardware-watchpoint-limit}
17087 @anchor{set remote hardware-breakpoint-limit}
17088 @item set remote hardware-watchpoint-limit @var{limit}
17089 @itemx set remote hardware-breakpoint-limit @var{limit}
17090 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17091 watchpoints. A limit of -1, the default, is treated as unlimited.
17093 @cindex limit hardware watchpoints length
17094 @cindex remote target, limit watchpoints length
17095 @anchor{set remote hardware-watchpoint-length-limit}
17096 @item set remote hardware-watchpoint-length-limit @var{limit}
17097 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17098 a remote hardware watchpoint. A limit of -1, the default, is treated
17101 @item show remote hardware-watchpoint-length-limit
17102 Show the current limit (in bytes) of the maximum length of
17103 a remote hardware watchpoint.
17105 @item set remote exec-file @var{filename}
17106 @itemx show remote exec-file
17107 @anchor{set remote exec-file}
17108 @cindex executable file, for remote target
17109 Select the file used for @code{run} with @code{target
17110 extended-remote}. This should be set to a filename valid on the
17111 target system. If it is not set, the target will use a default
17112 filename (e.g.@: the last program run).
17114 @item set remote interrupt-sequence
17115 @cindex interrupt remote programs
17116 @cindex select Ctrl-C, BREAK or BREAK-g
17117 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
17118 @samp{BREAK-g} as the
17119 sequence to the remote target in order to interrupt the execution.
17120 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
17121 is high level of serial line for some certain time.
17122 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
17123 It is @code{BREAK} signal followed by character @code{g}.
17125 @item show interrupt-sequence
17126 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
17127 is sent by @value{GDBN} to interrupt the remote program.
17128 @code{BREAK-g} is BREAK signal followed by @code{g} and
17129 also known as Magic SysRq g.
17131 @item set remote interrupt-on-connect
17132 @cindex send interrupt-sequence on start
17133 Specify whether interrupt-sequence is sent to remote target when
17134 @value{GDBN} connects to it. This is mostly needed when you debug
17135 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
17136 which is known as Magic SysRq g in order to connect @value{GDBN}.
17138 @item show interrupt-on-connect
17139 Show whether interrupt-sequence is sent
17140 to remote target when @value{GDBN} connects to it.
17144 @item set tcp auto-retry on
17145 @cindex auto-retry, for remote TCP target
17146 Enable auto-retry for remote TCP connections. This is useful if the remote
17147 debugging agent is launched in parallel with @value{GDBN}; there is a race
17148 condition because the agent may not become ready to accept the connection
17149 before @value{GDBN} attempts to connect. When auto-retry is
17150 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17151 to establish the connection using the timeout specified by
17152 @code{set tcp connect-timeout}.
17154 @item set tcp auto-retry off
17155 Do not auto-retry failed TCP connections.
17157 @item show tcp auto-retry
17158 Show the current auto-retry setting.
17160 @item set tcp connect-timeout @var{seconds}
17161 @cindex connection timeout, for remote TCP target
17162 @cindex timeout, for remote target connection
17163 Set the timeout for establishing a TCP connection to the remote target to
17164 @var{seconds}. The timeout affects both polling to retry failed connections
17165 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17166 that are merely slow to complete, and represents an approximate cumulative
17169 @item show tcp connect-timeout
17170 Show the current connection timeout setting.
17173 @cindex remote packets, enabling and disabling
17174 The @value{GDBN} remote protocol autodetects the packets supported by
17175 your debugging stub. If you need to override the autodetection, you
17176 can use these commands to enable or disable individual packets. Each
17177 packet can be set to @samp{on} (the remote target supports this
17178 packet), @samp{off} (the remote target does not support this packet),
17179 or @samp{auto} (detect remote target support for this packet). They
17180 all default to @samp{auto}. For more information about each packet,
17181 see @ref{Remote Protocol}.
17183 During normal use, you should not have to use any of these commands.
17184 If you do, that may be a bug in your remote debugging stub, or a bug
17185 in @value{GDBN}. You may want to report the problem to the
17186 @value{GDBN} developers.
17188 For each packet @var{name}, the command to enable or disable the
17189 packet is @code{set remote @var{name}-packet}. The available settings
17192 @multitable @columnfractions 0.28 0.32 0.25
17195 @tab Related Features
17197 @item @code{fetch-register}
17199 @tab @code{info registers}
17201 @item @code{set-register}
17205 @item @code{binary-download}
17207 @tab @code{load}, @code{set}
17209 @item @code{read-aux-vector}
17210 @tab @code{qXfer:auxv:read}
17211 @tab @code{info auxv}
17213 @item @code{symbol-lookup}
17214 @tab @code{qSymbol}
17215 @tab Detecting multiple threads
17217 @item @code{attach}
17218 @tab @code{vAttach}
17221 @item @code{verbose-resume}
17223 @tab Stepping or resuming multiple threads
17229 @item @code{software-breakpoint}
17233 @item @code{hardware-breakpoint}
17237 @item @code{write-watchpoint}
17241 @item @code{read-watchpoint}
17245 @item @code{access-watchpoint}
17249 @item @code{target-features}
17250 @tab @code{qXfer:features:read}
17251 @tab @code{set architecture}
17253 @item @code{library-info}
17254 @tab @code{qXfer:libraries:read}
17255 @tab @code{info sharedlibrary}
17257 @item @code{memory-map}
17258 @tab @code{qXfer:memory-map:read}
17259 @tab @code{info mem}
17261 @item @code{read-sdata-object}
17262 @tab @code{qXfer:sdata:read}
17263 @tab @code{print $_sdata}
17265 @item @code{read-spu-object}
17266 @tab @code{qXfer:spu:read}
17267 @tab @code{info spu}
17269 @item @code{write-spu-object}
17270 @tab @code{qXfer:spu:write}
17271 @tab @code{info spu}
17273 @item @code{read-siginfo-object}
17274 @tab @code{qXfer:siginfo:read}
17275 @tab @code{print $_siginfo}
17277 @item @code{write-siginfo-object}
17278 @tab @code{qXfer:siginfo:write}
17279 @tab @code{set $_siginfo}
17281 @item @code{threads}
17282 @tab @code{qXfer:threads:read}
17283 @tab @code{info threads}
17285 @item @code{get-thread-local-@*storage-address}
17286 @tab @code{qGetTLSAddr}
17287 @tab Displaying @code{__thread} variables
17289 @item @code{get-thread-information-block-address}
17290 @tab @code{qGetTIBAddr}
17291 @tab Display MS-Windows Thread Information Block.
17293 @item @code{search-memory}
17294 @tab @code{qSearch:memory}
17297 @item @code{supported-packets}
17298 @tab @code{qSupported}
17299 @tab Remote communications parameters
17301 @item @code{pass-signals}
17302 @tab @code{QPassSignals}
17303 @tab @code{handle @var{signal}}
17305 @item @code{hostio-close-packet}
17306 @tab @code{vFile:close}
17307 @tab @code{remote get}, @code{remote put}
17309 @item @code{hostio-open-packet}
17310 @tab @code{vFile:open}
17311 @tab @code{remote get}, @code{remote put}
17313 @item @code{hostio-pread-packet}
17314 @tab @code{vFile:pread}
17315 @tab @code{remote get}, @code{remote put}
17317 @item @code{hostio-pwrite-packet}
17318 @tab @code{vFile:pwrite}
17319 @tab @code{remote get}, @code{remote put}
17321 @item @code{hostio-unlink-packet}
17322 @tab @code{vFile:unlink}
17323 @tab @code{remote delete}
17325 @item @code{noack-packet}
17326 @tab @code{QStartNoAckMode}
17327 @tab Packet acknowledgment
17329 @item @code{osdata}
17330 @tab @code{qXfer:osdata:read}
17331 @tab @code{info os}
17333 @item @code{query-attached}
17334 @tab @code{qAttached}
17335 @tab Querying remote process attach state.
17337 @item @code{traceframe-info}
17338 @tab @code{qXfer:traceframe-info:read}
17339 @tab Traceframe info
17341 @item @code{install-in-trace}
17342 @tab @code{InstallInTrace}
17343 @tab Install tracepoint in tracing
17345 @item @code{disable-randomization}
17346 @tab @code{QDisableRandomization}
17347 @tab @code{set disable-randomization}
17351 @section Implementing a Remote Stub
17353 @cindex debugging stub, example
17354 @cindex remote stub, example
17355 @cindex stub example, remote debugging
17356 The stub files provided with @value{GDBN} implement the target side of the
17357 communication protocol, and the @value{GDBN} side is implemented in the
17358 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
17359 these subroutines to communicate, and ignore the details. (If you're
17360 implementing your own stub file, you can still ignore the details: start
17361 with one of the existing stub files. @file{sparc-stub.c} is the best
17362 organized, and therefore the easiest to read.)
17364 @cindex remote serial debugging, overview
17365 To debug a program running on another machine (the debugging
17366 @dfn{target} machine), you must first arrange for all the usual
17367 prerequisites for the program to run by itself. For example, for a C
17372 A startup routine to set up the C runtime environment; these usually
17373 have a name like @file{crt0}. The startup routine may be supplied by
17374 your hardware supplier, or you may have to write your own.
17377 A C subroutine library to support your program's
17378 subroutine calls, notably managing input and output.
17381 A way of getting your program to the other machine---for example, a
17382 download program. These are often supplied by the hardware
17383 manufacturer, but you may have to write your own from hardware
17387 The next step is to arrange for your program to use a serial port to
17388 communicate with the machine where @value{GDBN} is running (the @dfn{host}
17389 machine). In general terms, the scheme looks like this:
17393 @value{GDBN} already understands how to use this protocol; when everything
17394 else is set up, you can simply use the @samp{target remote} command
17395 (@pxref{Targets,,Specifying a Debugging Target}).
17397 @item On the target,
17398 you must link with your program a few special-purpose subroutines that
17399 implement the @value{GDBN} remote serial protocol. The file containing these
17400 subroutines is called a @dfn{debugging stub}.
17402 On certain remote targets, you can use an auxiliary program
17403 @code{gdbserver} instead of linking a stub into your program.
17404 @xref{Server,,Using the @code{gdbserver} Program}, for details.
17407 The debugging stub is specific to the architecture of the remote
17408 machine; for example, use @file{sparc-stub.c} to debug programs on
17411 @cindex remote serial stub list
17412 These working remote stubs are distributed with @value{GDBN}:
17417 @cindex @file{i386-stub.c}
17420 For Intel 386 and compatible architectures.
17423 @cindex @file{m68k-stub.c}
17424 @cindex Motorola 680x0
17426 For Motorola 680x0 architectures.
17429 @cindex @file{sh-stub.c}
17432 For Renesas SH architectures.
17435 @cindex @file{sparc-stub.c}
17437 For @sc{sparc} architectures.
17439 @item sparcl-stub.c
17440 @cindex @file{sparcl-stub.c}
17443 For Fujitsu @sc{sparclite} architectures.
17447 The @file{README} file in the @value{GDBN} distribution may list other
17448 recently added stubs.
17451 * Stub Contents:: What the stub can do for you
17452 * Bootstrapping:: What you must do for the stub
17453 * Debug Session:: Putting it all together
17456 @node Stub Contents
17457 @subsection What the Stub Can Do for You
17459 @cindex remote serial stub
17460 The debugging stub for your architecture supplies these three
17464 @item set_debug_traps
17465 @findex set_debug_traps
17466 @cindex remote serial stub, initialization
17467 This routine arranges for @code{handle_exception} to run when your
17468 program stops. You must call this subroutine explicitly near the
17469 beginning of your program.
17471 @item handle_exception
17472 @findex handle_exception
17473 @cindex remote serial stub, main routine
17474 This is the central workhorse, but your program never calls it
17475 explicitly---the setup code arranges for @code{handle_exception} to
17476 run when a trap is triggered.
17478 @code{handle_exception} takes control when your program stops during
17479 execution (for example, on a breakpoint), and mediates communications
17480 with @value{GDBN} on the host machine. This is where the communications
17481 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
17482 representative on the target machine. It begins by sending summary
17483 information on the state of your program, then continues to execute,
17484 retrieving and transmitting any information @value{GDBN} needs, until you
17485 execute a @value{GDBN} command that makes your program resume; at that point,
17486 @code{handle_exception} returns control to your own code on the target
17490 @cindex @code{breakpoint} subroutine, remote
17491 Use this auxiliary subroutine to make your program contain a
17492 breakpoint. Depending on the particular situation, this may be the only
17493 way for @value{GDBN} to get control. For instance, if your target
17494 machine has some sort of interrupt button, you won't need to call this;
17495 pressing the interrupt button transfers control to
17496 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
17497 simply receiving characters on the serial port may also trigger a trap;
17498 again, in that situation, you don't need to call @code{breakpoint} from
17499 your own program---simply running @samp{target remote} from the host
17500 @value{GDBN} session gets control.
17502 Call @code{breakpoint} if none of these is true, or if you simply want
17503 to make certain your program stops at a predetermined point for the
17504 start of your debugging session.
17507 @node Bootstrapping
17508 @subsection What You Must Do for the Stub
17510 @cindex remote stub, support routines
17511 The debugging stubs that come with @value{GDBN} are set up for a particular
17512 chip architecture, but they have no information about the rest of your
17513 debugging target machine.
17515 First of all you need to tell the stub how to communicate with the
17519 @item int getDebugChar()
17520 @findex getDebugChar
17521 Write this subroutine to read a single character from the serial port.
17522 It may be identical to @code{getchar} for your target system; a
17523 different name is used to allow you to distinguish the two if you wish.
17525 @item void putDebugChar(int)
17526 @findex putDebugChar
17527 Write this subroutine to write a single character to the serial port.
17528 It may be identical to @code{putchar} for your target system; a
17529 different name is used to allow you to distinguish the two if you wish.
17532 @cindex control C, and remote debugging
17533 @cindex interrupting remote targets
17534 If you want @value{GDBN} to be able to stop your program while it is
17535 running, you need to use an interrupt-driven serial driver, and arrange
17536 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
17537 character). That is the character which @value{GDBN} uses to tell the
17538 remote system to stop.
17540 Getting the debugging target to return the proper status to @value{GDBN}
17541 probably requires changes to the standard stub; one quick and dirty way
17542 is to just execute a breakpoint instruction (the ``dirty'' part is that
17543 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17545 Other routines you need to supply are:
17548 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17549 @findex exceptionHandler
17550 Write this function to install @var{exception_address} in the exception
17551 handling tables. You need to do this because the stub does not have any
17552 way of knowing what the exception handling tables on your target system
17553 are like (for example, the processor's table might be in @sc{rom},
17554 containing entries which point to a table in @sc{ram}).
17555 @var{exception_number} is the exception number which should be changed;
17556 its meaning is architecture-dependent (for example, different numbers
17557 might represent divide by zero, misaligned access, etc). When this
17558 exception occurs, control should be transferred directly to
17559 @var{exception_address}, and the processor state (stack, registers,
17560 and so on) should be just as it is when a processor exception occurs. So if
17561 you want to use a jump instruction to reach @var{exception_address}, it
17562 should be a simple jump, not a jump to subroutine.
17564 For the 386, @var{exception_address} should be installed as an interrupt
17565 gate so that interrupts are masked while the handler runs. The gate
17566 should be at privilege level 0 (the most privileged level). The
17567 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17568 help from @code{exceptionHandler}.
17570 @item void flush_i_cache()
17571 @findex flush_i_cache
17572 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17573 instruction cache, if any, on your target machine. If there is no
17574 instruction cache, this subroutine may be a no-op.
17576 On target machines that have instruction caches, @value{GDBN} requires this
17577 function to make certain that the state of your program is stable.
17581 You must also make sure this library routine is available:
17584 @item void *memset(void *, int, int)
17586 This is the standard library function @code{memset} that sets an area of
17587 memory to a known value. If you have one of the free versions of
17588 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17589 either obtain it from your hardware manufacturer, or write your own.
17592 If you do not use the GNU C compiler, you may need other standard
17593 library subroutines as well; this varies from one stub to another,
17594 but in general the stubs are likely to use any of the common library
17595 subroutines which @code{@value{NGCC}} generates as inline code.
17598 @node Debug Session
17599 @subsection Putting it All Together
17601 @cindex remote serial debugging summary
17602 In summary, when your program is ready to debug, you must follow these
17607 Make sure you have defined the supporting low-level routines
17608 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17610 @code{getDebugChar}, @code{putDebugChar},
17611 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17615 Insert these lines near the top of your program:
17623 For the 680x0 stub only, you need to provide a variable called
17624 @code{exceptionHook}. Normally you just use:
17627 void (*exceptionHook)() = 0;
17631 but if before calling @code{set_debug_traps}, you set it to point to a
17632 function in your program, that function is called when
17633 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17634 error). The function indicated by @code{exceptionHook} is called with
17635 one parameter: an @code{int} which is the exception number.
17638 Compile and link together: your program, the @value{GDBN} debugging stub for
17639 your target architecture, and the supporting subroutines.
17642 Make sure you have a serial connection between your target machine and
17643 the @value{GDBN} host, and identify the serial port on the host.
17646 @c The "remote" target now provides a `load' command, so we should
17647 @c document that. FIXME.
17648 Download your program to your target machine (or get it there by
17649 whatever means the manufacturer provides), and start it.
17652 Start @value{GDBN} on the host, and connect to the target
17653 (@pxref{Connecting,,Connecting to a Remote Target}).
17657 @node Configurations
17658 @chapter Configuration-Specific Information
17660 While nearly all @value{GDBN} commands are available for all native and
17661 cross versions of the debugger, there are some exceptions. This chapter
17662 describes things that are only available in certain configurations.
17664 There are three major categories of configurations: native
17665 configurations, where the host and target are the same, embedded
17666 operating system configurations, which are usually the same for several
17667 different processor architectures, and bare embedded processors, which
17668 are quite different from each other.
17673 * Embedded Processors::
17680 This section describes details specific to particular native
17685 * BSD libkvm Interface:: Debugging BSD kernel memory images
17686 * SVR4 Process Information:: SVR4 process information
17687 * DJGPP Native:: Features specific to the DJGPP port
17688 * Cygwin Native:: Features specific to the Cygwin port
17689 * Hurd Native:: Features specific to @sc{gnu} Hurd
17690 * Neutrino:: Features specific to QNX Neutrino
17691 * Darwin:: Features specific to Darwin
17697 On HP-UX systems, if you refer to a function or variable name that
17698 begins with a dollar sign, @value{GDBN} searches for a user or system
17699 name first, before it searches for a convenience variable.
17702 @node BSD libkvm Interface
17703 @subsection BSD libkvm Interface
17706 @cindex kernel memory image
17707 @cindex kernel crash dump
17709 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17710 interface that provides a uniform interface for accessing kernel virtual
17711 memory images, including live systems and crash dumps. @value{GDBN}
17712 uses this interface to allow you to debug live kernels and kernel crash
17713 dumps on many native BSD configurations. This is implemented as a
17714 special @code{kvm} debugging target. For debugging a live system, load
17715 the currently running kernel into @value{GDBN} and connect to the
17719 (@value{GDBP}) @b{target kvm}
17722 For debugging crash dumps, provide the file name of the crash dump as an
17726 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17729 Once connected to the @code{kvm} target, the following commands are
17735 Set current context from the @dfn{Process Control Block} (PCB) address.
17738 Set current context from proc address. This command isn't available on
17739 modern FreeBSD systems.
17742 @node SVR4 Process Information
17743 @subsection SVR4 Process Information
17745 @cindex examine process image
17746 @cindex process info via @file{/proc}
17748 Many versions of SVR4 and compatible systems provide a facility called
17749 @samp{/proc} that can be used to examine the image of a running
17750 process using file-system subroutines. If @value{GDBN} is configured
17751 for an operating system with this facility, the command @code{info
17752 proc} is available to report information about the process running
17753 your program, or about any process running on your system. @code{info
17754 proc} works only on SVR4 systems that include the @code{procfs} code.
17755 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17756 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17762 @itemx info proc @var{process-id}
17763 Summarize available information about any running process. If a
17764 process ID is specified by @var{process-id}, display information about
17765 that process; otherwise display information about the program being
17766 debugged. The summary includes the debugged process ID, the command
17767 line used to invoke it, its current working directory, and its
17768 executable file's absolute file name.
17770 On some systems, @var{process-id} can be of the form
17771 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17772 within a process. If the optional @var{pid} part is missing, it means
17773 a thread from the process being debugged (the leading @samp{/} still
17774 needs to be present, or else @value{GDBN} will interpret the number as
17775 a process ID rather than a thread ID).
17777 @item info proc mappings
17778 @cindex memory address space mappings
17779 Report the memory address space ranges accessible in the program, with
17780 information on whether the process has read, write, or execute access
17781 rights to each range. On @sc{gnu}/Linux systems, each memory range
17782 includes the object file which is mapped to that range, instead of the
17783 memory access rights to that range.
17785 @item info proc stat
17786 @itemx info proc status
17787 @cindex process detailed status information
17788 These subcommands are specific to @sc{gnu}/Linux systems. They show
17789 the process-related information, including the user ID and group ID;
17790 how many threads are there in the process; its virtual memory usage;
17791 the signals that are pending, blocked, and ignored; its TTY; its
17792 consumption of system and user time; its stack size; its @samp{nice}
17793 value; etc. For more information, see the @samp{proc} man page
17794 (type @kbd{man 5 proc} from your shell prompt).
17796 @item info proc all
17797 Show all the information about the process described under all of the
17798 above @code{info proc} subcommands.
17801 @comment These sub-options of 'info proc' were not included when
17802 @comment procfs.c was re-written. Keep their descriptions around
17803 @comment against the day when someone finds the time to put them back in.
17804 @kindex info proc times
17805 @item info proc times
17806 Starting time, user CPU time, and system CPU time for your program and
17809 @kindex info proc id
17811 Report on the process IDs related to your program: its own process ID,
17812 the ID of its parent, the process group ID, and the session ID.
17815 @item set procfs-trace
17816 @kindex set procfs-trace
17817 @cindex @code{procfs} API calls
17818 This command enables and disables tracing of @code{procfs} API calls.
17820 @item show procfs-trace
17821 @kindex show procfs-trace
17822 Show the current state of @code{procfs} API call tracing.
17824 @item set procfs-file @var{file}
17825 @kindex set procfs-file
17826 Tell @value{GDBN} to write @code{procfs} API trace to the named
17827 @var{file}. @value{GDBN} appends the trace info to the previous
17828 contents of the file. The default is to display the trace on the
17831 @item show procfs-file
17832 @kindex show procfs-file
17833 Show the file to which @code{procfs} API trace is written.
17835 @item proc-trace-entry
17836 @itemx proc-trace-exit
17837 @itemx proc-untrace-entry
17838 @itemx proc-untrace-exit
17839 @kindex proc-trace-entry
17840 @kindex proc-trace-exit
17841 @kindex proc-untrace-entry
17842 @kindex proc-untrace-exit
17843 These commands enable and disable tracing of entries into and exits
17844 from the @code{syscall} interface.
17847 @kindex info pidlist
17848 @cindex process list, QNX Neutrino
17849 For QNX Neutrino only, this command displays the list of all the
17850 processes and all the threads within each process.
17853 @kindex info meminfo
17854 @cindex mapinfo list, QNX Neutrino
17855 For QNX Neutrino only, this command displays the list of all mapinfos.
17859 @subsection Features for Debugging @sc{djgpp} Programs
17860 @cindex @sc{djgpp} debugging
17861 @cindex native @sc{djgpp} debugging
17862 @cindex MS-DOS-specific commands
17865 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17866 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17867 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17868 top of real-mode DOS systems and their emulations.
17870 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17871 defines a few commands specific to the @sc{djgpp} port. This
17872 subsection describes those commands.
17877 This is a prefix of @sc{djgpp}-specific commands which print
17878 information about the target system and important OS structures.
17881 @cindex MS-DOS system info
17882 @cindex free memory information (MS-DOS)
17883 @item info dos sysinfo
17884 This command displays assorted information about the underlying
17885 platform: the CPU type and features, the OS version and flavor, the
17886 DPMI version, and the available conventional and DPMI memory.
17891 @cindex segment descriptor tables
17892 @cindex descriptor tables display
17894 @itemx info dos ldt
17895 @itemx info dos idt
17896 These 3 commands display entries from, respectively, Global, Local,
17897 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17898 tables are data structures which store a descriptor for each segment
17899 that is currently in use. The segment's selector is an index into a
17900 descriptor table; the table entry for that index holds the
17901 descriptor's base address and limit, and its attributes and access
17904 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17905 segment (used for both data and the stack), and a DOS segment (which
17906 allows access to DOS/BIOS data structures and absolute addresses in
17907 conventional memory). However, the DPMI host will usually define
17908 additional segments in order to support the DPMI environment.
17910 @cindex garbled pointers
17911 These commands allow to display entries from the descriptor tables.
17912 Without an argument, all entries from the specified table are
17913 displayed. An argument, which should be an integer expression, means
17914 display a single entry whose index is given by the argument. For
17915 example, here's a convenient way to display information about the
17916 debugged program's data segment:
17919 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17920 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17924 This comes in handy when you want to see whether a pointer is outside
17925 the data segment's limit (i.e.@: @dfn{garbled}).
17927 @cindex page tables display (MS-DOS)
17929 @itemx info dos pte
17930 These two commands display entries from, respectively, the Page
17931 Directory and the Page Tables. Page Directories and Page Tables are
17932 data structures which control how virtual memory addresses are mapped
17933 into physical addresses. A Page Table includes an entry for every
17934 page of memory that is mapped into the program's address space; there
17935 may be several Page Tables, each one holding up to 4096 entries. A
17936 Page Directory has up to 4096 entries, one each for every Page Table
17937 that is currently in use.
17939 Without an argument, @kbd{info dos pde} displays the entire Page
17940 Directory, and @kbd{info dos pte} displays all the entries in all of
17941 the Page Tables. An argument, an integer expression, given to the
17942 @kbd{info dos pde} command means display only that entry from the Page
17943 Directory table. An argument given to the @kbd{info dos pte} command
17944 means display entries from a single Page Table, the one pointed to by
17945 the specified entry in the Page Directory.
17947 @cindex direct memory access (DMA) on MS-DOS
17948 These commands are useful when your program uses @dfn{DMA} (Direct
17949 Memory Access), which needs physical addresses to program the DMA
17952 These commands are supported only with some DPMI servers.
17954 @cindex physical address from linear address
17955 @item info dos address-pte @var{addr}
17956 This command displays the Page Table entry for a specified linear
17957 address. The argument @var{addr} is a linear address which should
17958 already have the appropriate segment's base address added to it,
17959 because this command accepts addresses which may belong to @emph{any}
17960 segment. For example, here's how to display the Page Table entry for
17961 the page where a variable @code{i} is stored:
17964 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17965 @exdent @code{Page Table entry for address 0x11a00d30:}
17966 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17970 This says that @code{i} is stored at offset @code{0xd30} from the page
17971 whose physical base address is @code{0x02698000}, and shows all the
17972 attributes of that page.
17974 Note that you must cast the addresses of variables to a @code{char *},
17975 since otherwise the value of @code{__djgpp_base_address}, the base
17976 address of all variables and functions in a @sc{djgpp} program, will
17977 be added using the rules of C pointer arithmetics: if @code{i} is
17978 declared an @code{int}, @value{GDBN} will add 4 times the value of
17979 @code{__djgpp_base_address} to the address of @code{i}.
17981 Here's another example, it displays the Page Table entry for the
17985 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17986 @exdent @code{Page Table entry for address 0x29110:}
17987 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17991 (The @code{+ 3} offset is because the transfer buffer's address is the
17992 3rd member of the @code{_go32_info_block} structure.) The output
17993 clearly shows that this DPMI server maps the addresses in conventional
17994 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17995 linear (@code{0x29110}) addresses are identical.
17997 This command is supported only with some DPMI servers.
18000 @cindex DOS serial data link, remote debugging
18001 In addition to native debugging, the DJGPP port supports remote
18002 debugging via a serial data link. The following commands are specific
18003 to remote serial debugging in the DJGPP port of @value{GDBN}.
18006 @kindex set com1base
18007 @kindex set com1irq
18008 @kindex set com2base
18009 @kindex set com2irq
18010 @kindex set com3base
18011 @kindex set com3irq
18012 @kindex set com4base
18013 @kindex set com4irq
18014 @item set com1base @var{addr}
18015 This command sets the base I/O port address of the @file{COM1} serial
18018 @item set com1irq @var{irq}
18019 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
18020 for the @file{COM1} serial port.
18022 There are similar commands @samp{set com2base}, @samp{set com3irq},
18023 etc.@: for setting the port address and the @code{IRQ} lines for the
18026 @kindex show com1base
18027 @kindex show com1irq
18028 @kindex show com2base
18029 @kindex show com2irq
18030 @kindex show com3base
18031 @kindex show com3irq
18032 @kindex show com4base
18033 @kindex show com4irq
18034 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18035 display the current settings of the base address and the @code{IRQ}
18036 lines used by the COM ports.
18039 @kindex info serial
18040 @cindex DOS serial port status
18041 This command prints the status of the 4 DOS serial ports. For each
18042 port, it prints whether it's active or not, its I/O base address and
18043 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18044 counts of various errors encountered so far.
18048 @node Cygwin Native
18049 @subsection Features for Debugging MS Windows PE Executables
18050 @cindex MS Windows debugging
18051 @cindex native Cygwin debugging
18052 @cindex Cygwin-specific commands
18054 @value{GDBN} supports native debugging of MS Windows programs, including
18055 DLLs with and without symbolic debugging information.
18057 @cindex Ctrl-BREAK, MS-Windows
18058 @cindex interrupt debuggee on MS-Windows
18059 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18060 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18061 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18062 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18063 sequence, which can be used to interrupt the debuggee even if it
18066 There are various additional Cygwin-specific commands, described in
18067 this section. Working with DLLs that have no debugging symbols is
18068 described in @ref{Non-debug DLL Symbols}.
18073 This is a prefix of MS Windows-specific commands which print
18074 information about the target system and important OS structures.
18076 @item info w32 selector
18077 This command displays information returned by
18078 the Win32 API @code{GetThreadSelectorEntry} function.
18079 It takes an optional argument that is evaluated to
18080 a long value to give the information about this given selector.
18081 Without argument, this command displays information
18082 about the six segment registers.
18084 @item info w32 thread-information-block
18085 This command displays thread specific information stored in the
18086 Thread Information Block (readable on the X86 CPU family using @code{$fs}
18087 selector for 32-bit programs and @code{$gs} for 64-bit programs).
18091 This is a Cygwin-specific alias of @code{info shared}.
18093 @kindex dll-symbols
18095 This command loads symbols from a dll similarly to
18096 add-sym command but without the need to specify a base address.
18098 @kindex set cygwin-exceptions
18099 @cindex debugging the Cygwin DLL
18100 @cindex Cygwin DLL, debugging
18101 @item set cygwin-exceptions @var{mode}
18102 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
18103 happen inside the Cygwin DLL. If @var{mode} is @code{off},
18104 @value{GDBN} will delay recognition of exceptions, and may ignore some
18105 exceptions which seem to be caused by internal Cygwin DLL
18106 ``bookkeeping''. This option is meant primarily for debugging the
18107 Cygwin DLL itself; the default value is @code{off} to avoid annoying
18108 @value{GDBN} users with false @code{SIGSEGV} signals.
18110 @kindex show cygwin-exceptions
18111 @item show cygwin-exceptions
18112 Displays whether @value{GDBN} will break on exceptions that happen
18113 inside the Cygwin DLL itself.
18115 @kindex set new-console
18116 @item set new-console @var{mode}
18117 If @var{mode} is @code{on} the debuggee will
18118 be started in a new console on next start.
18119 If @var{mode} is @code{off}, the debuggee will
18120 be started in the same console as the debugger.
18122 @kindex show new-console
18123 @item show new-console
18124 Displays whether a new console is used
18125 when the debuggee is started.
18127 @kindex set new-group
18128 @item set new-group @var{mode}
18129 This boolean value controls whether the debuggee should
18130 start a new group or stay in the same group as the debugger.
18131 This affects the way the Windows OS handles
18134 @kindex show new-group
18135 @item show new-group
18136 Displays current value of new-group boolean.
18138 @kindex set debugevents
18139 @item set debugevents
18140 This boolean value adds debug output concerning kernel events related
18141 to the debuggee seen by the debugger. This includes events that
18142 signal thread and process creation and exit, DLL loading and
18143 unloading, console interrupts, and debugging messages produced by the
18144 Windows @code{OutputDebugString} API call.
18146 @kindex set debugexec
18147 @item set debugexec
18148 This boolean value adds debug output concerning execute events
18149 (such as resume thread) seen by the debugger.
18151 @kindex set debugexceptions
18152 @item set debugexceptions
18153 This boolean value adds debug output concerning exceptions in the
18154 debuggee seen by the debugger.
18156 @kindex set debugmemory
18157 @item set debugmemory
18158 This boolean value adds debug output concerning debuggee memory reads
18159 and writes by the debugger.
18163 This boolean values specifies whether the debuggee is called
18164 via a shell or directly (default value is on).
18168 Displays if the debuggee will be started with a shell.
18173 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18176 @node Non-debug DLL Symbols
18177 @subsubsection Support for DLLs without Debugging Symbols
18178 @cindex DLLs with no debugging symbols
18179 @cindex Minimal symbols and DLLs
18181 Very often on windows, some of the DLLs that your program relies on do
18182 not include symbolic debugging information (for example,
18183 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18184 symbols in a DLL, it relies on the minimal amount of symbolic
18185 information contained in the DLL's export table. This section
18186 describes working with such symbols, known internally to @value{GDBN} as
18187 ``minimal symbols''.
18189 Note that before the debugged program has started execution, no DLLs
18190 will have been loaded. The easiest way around this problem is simply to
18191 start the program --- either by setting a breakpoint or letting the
18192 program run once to completion. It is also possible to force
18193 @value{GDBN} to load a particular DLL before starting the executable ---
18194 see the shared library information in @ref{Files}, or the
18195 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18196 explicitly loading symbols from a DLL with no debugging information will
18197 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18198 which may adversely affect symbol lookup performance.
18200 @subsubsection DLL Name Prefixes
18202 In keeping with the naming conventions used by the Microsoft debugging
18203 tools, DLL export symbols are made available with a prefix based on the
18204 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18205 also entered into the symbol table, so @code{CreateFileA} is often
18206 sufficient. In some cases there will be name clashes within a program
18207 (particularly if the executable itself includes full debugging symbols)
18208 necessitating the use of the fully qualified name when referring to the
18209 contents of the DLL. Use single-quotes around the name to avoid the
18210 exclamation mark (``!'') being interpreted as a language operator.
18212 Note that the internal name of the DLL may be all upper-case, even
18213 though the file name of the DLL is lower-case, or vice-versa. Since
18214 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
18215 some confusion. If in doubt, try the @code{info functions} and
18216 @code{info variables} commands or even @code{maint print msymbols}
18217 (@pxref{Symbols}). Here's an example:
18220 (@value{GDBP}) info function CreateFileA
18221 All functions matching regular expression "CreateFileA":
18223 Non-debugging symbols:
18224 0x77e885f4 CreateFileA
18225 0x77e885f4 KERNEL32!CreateFileA
18229 (@value{GDBP}) info function !
18230 All functions matching regular expression "!":
18232 Non-debugging symbols:
18233 0x6100114c cygwin1!__assert
18234 0x61004034 cygwin1!_dll_crt0@@0
18235 0x61004240 cygwin1!dll_crt0(per_process *)
18239 @subsubsection Working with Minimal Symbols
18241 Symbols extracted from a DLL's export table do not contain very much
18242 type information. All that @value{GDBN} can do is guess whether a symbol
18243 refers to a function or variable depending on the linker section that
18244 contains the symbol. Also note that the actual contents of the memory
18245 contained in a DLL are not available unless the program is running. This
18246 means that you cannot examine the contents of a variable or disassemble
18247 a function within a DLL without a running program.
18249 Variables are generally treated as pointers and dereferenced
18250 automatically. For this reason, it is often necessary to prefix a
18251 variable name with the address-of operator (``&'') and provide explicit
18252 type information in the command. Here's an example of the type of
18256 (@value{GDBP}) print 'cygwin1!__argv'
18261 (@value{GDBP}) x 'cygwin1!__argv'
18262 0x10021610: "\230y\""
18265 And two possible solutions:
18268 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
18269 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
18273 (@value{GDBP}) x/2x &'cygwin1!__argv'
18274 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
18275 (@value{GDBP}) x/x 0x10021608
18276 0x10021608: 0x0022fd98
18277 (@value{GDBP}) x/s 0x0022fd98
18278 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
18281 Setting a break point within a DLL is possible even before the program
18282 starts execution. However, under these circumstances, @value{GDBN} can't
18283 examine the initial instructions of the function in order to skip the
18284 function's frame set-up code. You can work around this by using ``*&''
18285 to set the breakpoint at a raw memory address:
18288 (@value{GDBP}) break *&'python22!PyOS_Readline'
18289 Breakpoint 1 at 0x1e04eff0
18292 The author of these extensions is not entirely convinced that setting a
18293 break point within a shared DLL like @file{kernel32.dll} is completely
18297 @subsection Commands Specific to @sc{gnu} Hurd Systems
18298 @cindex @sc{gnu} Hurd debugging
18300 This subsection describes @value{GDBN} commands specific to the
18301 @sc{gnu} Hurd native debugging.
18306 @kindex set signals@r{, Hurd command}
18307 @kindex set sigs@r{, Hurd command}
18308 This command toggles the state of inferior signal interception by
18309 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
18310 affected by this command. @code{sigs} is a shorthand alias for
18315 @kindex show signals@r{, Hurd command}
18316 @kindex show sigs@r{, Hurd command}
18317 Show the current state of intercepting inferior's signals.
18319 @item set signal-thread
18320 @itemx set sigthread
18321 @kindex set signal-thread
18322 @kindex set sigthread
18323 This command tells @value{GDBN} which thread is the @code{libc} signal
18324 thread. That thread is run when a signal is delivered to a running
18325 process. @code{set sigthread} is the shorthand alias of @code{set
18328 @item show signal-thread
18329 @itemx show sigthread
18330 @kindex show signal-thread
18331 @kindex show sigthread
18332 These two commands show which thread will run when the inferior is
18333 delivered a signal.
18336 @kindex set stopped@r{, Hurd command}
18337 This commands tells @value{GDBN} that the inferior process is stopped,
18338 as with the @code{SIGSTOP} signal. The stopped process can be
18339 continued by delivering a signal to it.
18342 @kindex show stopped@r{, Hurd command}
18343 This command shows whether @value{GDBN} thinks the debuggee is
18346 @item set exceptions
18347 @kindex set exceptions@r{, Hurd command}
18348 Use this command to turn off trapping of exceptions in the inferior.
18349 When exception trapping is off, neither breakpoints nor
18350 single-stepping will work. To restore the default, set exception
18353 @item show exceptions
18354 @kindex show exceptions@r{, Hurd command}
18355 Show the current state of trapping exceptions in the inferior.
18357 @item set task pause
18358 @kindex set task@r{, Hurd commands}
18359 @cindex task attributes (@sc{gnu} Hurd)
18360 @cindex pause current task (@sc{gnu} Hurd)
18361 This command toggles task suspension when @value{GDBN} has control.
18362 Setting it to on takes effect immediately, and the task is suspended
18363 whenever @value{GDBN} gets control. Setting it to off will take
18364 effect the next time the inferior is continued. If this option is set
18365 to off, you can use @code{set thread default pause on} or @code{set
18366 thread pause on} (see below) to pause individual threads.
18368 @item show task pause
18369 @kindex show task@r{, Hurd commands}
18370 Show the current state of task suspension.
18372 @item set task detach-suspend-count
18373 @cindex task suspend count
18374 @cindex detach from task, @sc{gnu} Hurd
18375 This command sets the suspend count the task will be left with when
18376 @value{GDBN} detaches from it.
18378 @item show task detach-suspend-count
18379 Show the suspend count the task will be left with when detaching.
18381 @item set task exception-port
18382 @itemx set task excp
18383 @cindex task exception port, @sc{gnu} Hurd
18384 This command sets the task exception port to which @value{GDBN} will
18385 forward exceptions. The argument should be the value of the @dfn{send
18386 rights} of the task. @code{set task excp} is a shorthand alias.
18388 @item set noninvasive
18389 @cindex noninvasive task options
18390 This command switches @value{GDBN} to a mode that is the least
18391 invasive as far as interfering with the inferior is concerned. This
18392 is the same as using @code{set task pause}, @code{set exceptions}, and
18393 @code{set signals} to values opposite to the defaults.
18395 @item info send-rights
18396 @itemx info receive-rights
18397 @itemx info port-rights
18398 @itemx info port-sets
18399 @itemx info dead-names
18402 @cindex send rights, @sc{gnu} Hurd
18403 @cindex receive rights, @sc{gnu} Hurd
18404 @cindex port rights, @sc{gnu} Hurd
18405 @cindex port sets, @sc{gnu} Hurd
18406 @cindex dead names, @sc{gnu} Hurd
18407 These commands display information about, respectively, send rights,
18408 receive rights, port rights, port sets, and dead names of a task.
18409 There are also shorthand aliases: @code{info ports} for @code{info
18410 port-rights} and @code{info psets} for @code{info port-sets}.
18412 @item set thread pause
18413 @kindex set thread@r{, Hurd command}
18414 @cindex thread properties, @sc{gnu} Hurd
18415 @cindex pause current thread (@sc{gnu} Hurd)
18416 This command toggles current thread suspension when @value{GDBN} has
18417 control. Setting it to on takes effect immediately, and the current
18418 thread is suspended whenever @value{GDBN} gets control. Setting it to
18419 off will take effect the next time the inferior is continued.
18420 Normally, this command has no effect, since when @value{GDBN} has
18421 control, the whole task is suspended. However, if you used @code{set
18422 task pause off} (see above), this command comes in handy to suspend
18423 only the current thread.
18425 @item show thread pause
18426 @kindex show thread@r{, Hurd command}
18427 This command shows the state of current thread suspension.
18429 @item set thread run
18430 This command sets whether the current thread is allowed to run.
18432 @item show thread run
18433 Show whether the current thread is allowed to run.
18435 @item set thread detach-suspend-count
18436 @cindex thread suspend count, @sc{gnu} Hurd
18437 @cindex detach from thread, @sc{gnu} Hurd
18438 This command sets the suspend count @value{GDBN} will leave on a
18439 thread when detaching. This number is relative to the suspend count
18440 found by @value{GDBN} when it notices the thread; use @code{set thread
18441 takeover-suspend-count} to force it to an absolute value.
18443 @item show thread detach-suspend-count
18444 Show the suspend count @value{GDBN} will leave on the thread when
18447 @item set thread exception-port
18448 @itemx set thread excp
18449 Set the thread exception port to which to forward exceptions. This
18450 overrides the port set by @code{set task exception-port} (see above).
18451 @code{set thread excp} is the shorthand alias.
18453 @item set thread takeover-suspend-count
18454 Normally, @value{GDBN}'s thread suspend counts are relative to the
18455 value @value{GDBN} finds when it notices each thread. This command
18456 changes the suspend counts to be absolute instead.
18458 @item set thread default
18459 @itemx show thread default
18460 @cindex thread default settings, @sc{gnu} Hurd
18461 Each of the above @code{set thread} commands has a @code{set thread
18462 default} counterpart (e.g., @code{set thread default pause}, @code{set
18463 thread default exception-port}, etc.). The @code{thread default}
18464 variety of commands sets the default thread properties for all
18465 threads; you can then change the properties of individual threads with
18466 the non-default commands.
18471 @subsection QNX Neutrino
18472 @cindex QNX Neutrino
18474 @value{GDBN} provides the following commands specific to the QNX
18478 @item set debug nto-debug
18479 @kindex set debug nto-debug
18480 When set to on, enables debugging messages specific to the QNX
18483 @item show debug nto-debug
18484 @kindex show debug nto-debug
18485 Show the current state of QNX Neutrino messages.
18492 @value{GDBN} provides the following commands specific to the Darwin target:
18495 @item set debug darwin @var{num}
18496 @kindex set debug darwin
18497 When set to a non zero value, enables debugging messages specific to
18498 the Darwin support. Higher values produce more verbose output.
18500 @item show debug darwin
18501 @kindex show debug darwin
18502 Show the current state of Darwin messages.
18504 @item set debug mach-o @var{num}
18505 @kindex set debug mach-o
18506 When set to a non zero value, enables debugging messages while
18507 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
18508 file format used on Darwin for object and executable files.) Higher
18509 values produce more verbose output. This is a command to diagnose
18510 problems internal to @value{GDBN} and should not be needed in normal
18513 @item show debug mach-o
18514 @kindex show debug mach-o
18515 Show the current state of Mach-O file messages.
18517 @item set mach-exceptions on
18518 @itemx set mach-exceptions off
18519 @kindex set mach-exceptions
18520 On Darwin, faults are first reported as a Mach exception and are then
18521 mapped to a Posix signal. Use this command to turn on trapping of
18522 Mach exceptions in the inferior. This might be sometimes useful to
18523 better understand the cause of a fault. The default is off.
18525 @item show mach-exceptions
18526 @kindex show mach-exceptions
18527 Show the current state of exceptions trapping.
18532 @section Embedded Operating Systems
18534 This section describes configurations involving the debugging of
18535 embedded operating systems that are available for several different
18539 * VxWorks:: Using @value{GDBN} with VxWorks
18542 @value{GDBN} includes the ability to debug programs running on
18543 various real-time operating systems.
18546 @subsection Using @value{GDBN} with VxWorks
18552 @kindex target vxworks
18553 @item target vxworks @var{machinename}
18554 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18555 is the target system's machine name or IP address.
18559 On VxWorks, @code{load} links @var{filename} dynamically on the
18560 current target system as well as adding its symbols in @value{GDBN}.
18562 @value{GDBN} enables developers to spawn and debug tasks running on networked
18563 VxWorks targets from a Unix host. Already-running tasks spawned from
18564 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18565 both the Unix host and on the VxWorks target. The program
18566 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18567 installed with the name @code{vxgdb}, to distinguish it from a
18568 @value{GDBN} for debugging programs on the host itself.)
18571 @item VxWorks-timeout @var{args}
18572 @kindex vxworks-timeout
18573 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18574 This option is set by the user, and @var{args} represents the number of
18575 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18576 your VxWorks target is a slow software simulator or is on the far side
18577 of a thin network line.
18580 The following information on connecting to VxWorks was current when
18581 this manual was produced; newer releases of VxWorks may use revised
18584 @findex INCLUDE_RDB
18585 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18586 to include the remote debugging interface routines in the VxWorks
18587 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18588 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18589 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18590 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18591 information on configuring and remaking VxWorks, see the manufacturer's
18593 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18595 Once you have included @file{rdb.a} in your VxWorks system image and set
18596 your Unix execution search path to find @value{GDBN}, you are ready to
18597 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18598 @code{vxgdb}, depending on your installation).
18600 @value{GDBN} comes up showing the prompt:
18607 * VxWorks Connection:: Connecting to VxWorks
18608 * VxWorks Download:: VxWorks download
18609 * VxWorks Attach:: Running tasks
18612 @node VxWorks Connection
18613 @subsubsection Connecting to VxWorks
18615 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18616 network. To connect to a target whose host name is ``@code{tt}'', type:
18619 (vxgdb) target vxworks tt
18623 @value{GDBN} displays messages like these:
18626 Attaching remote machine across net...
18631 @value{GDBN} then attempts to read the symbol tables of any object modules
18632 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18633 these files by searching the directories listed in the command search
18634 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18635 to find an object file, it displays a message such as:
18638 prog.o: No such file or directory.
18641 When this happens, add the appropriate directory to the search path with
18642 the @value{GDBN} command @code{path}, and execute the @code{target}
18645 @node VxWorks Download
18646 @subsubsection VxWorks Download
18648 @cindex download to VxWorks
18649 If you have connected to the VxWorks target and you want to debug an
18650 object that has not yet been loaded, you can use the @value{GDBN}
18651 @code{load} command to download a file from Unix to VxWorks
18652 incrementally. The object file given as an argument to the @code{load}
18653 command is actually opened twice: first by the VxWorks target in order
18654 to download the code, then by @value{GDBN} in order to read the symbol
18655 table. This can lead to problems if the current working directories on
18656 the two systems differ. If both systems have NFS mounted the same
18657 filesystems, you can avoid these problems by using absolute paths.
18658 Otherwise, it is simplest to set the working directory on both systems
18659 to the directory in which the object file resides, and then to reference
18660 the file by its name, without any path. For instance, a program
18661 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18662 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18663 program, type this on VxWorks:
18666 -> cd "@var{vxpath}/vw/demo/rdb"
18670 Then, in @value{GDBN}, type:
18673 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18674 (vxgdb) load prog.o
18677 @value{GDBN} displays a response similar to this:
18680 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18683 You can also use the @code{load} command to reload an object module
18684 after editing and recompiling the corresponding source file. Note that
18685 this makes @value{GDBN} delete all currently-defined breakpoints,
18686 auto-displays, and convenience variables, and to clear the value
18687 history. (This is necessary in order to preserve the integrity of
18688 debugger's data structures that reference the target system's symbol
18691 @node VxWorks Attach
18692 @subsubsection Running Tasks
18694 @cindex running VxWorks tasks
18695 You can also attach to an existing task using the @code{attach} command as
18699 (vxgdb) attach @var{task}
18703 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18704 or suspended when you attach to it. Running tasks are suspended at
18705 the time of attachment.
18707 @node Embedded Processors
18708 @section Embedded Processors
18710 This section goes into details specific to particular embedded
18713 @cindex send command to simulator
18714 Whenever a specific embedded processor has a simulator, @value{GDBN}
18715 allows to send an arbitrary command to the simulator.
18718 @item sim @var{command}
18719 @kindex sim@r{, a command}
18720 Send an arbitrary @var{command} string to the simulator. Consult the
18721 documentation for the specific simulator in use for information about
18722 acceptable commands.
18728 * M32R/D:: Renesas M32R/D
18729 * M68K:: Motorola M68K
18730 * MicroBlaze:: Xilinx MicroBlaze
18731 * MIPS Embedded:: MIPS Embedded
18732 * OpenRISC 1000:: OpenRisc 1000
18733 * PA:: HP PA Embedded
18734 * PowerPC Embedded:: PowerPC Embedded
18735 * Sparclet:: Tsqware Sparclet
18736 * Sparclite:: Fujitsu Sparclite
18737 * Z8000:: Zilog Z8000
18740 * Super-H:: Renesas Super-H
18749 @item target rdi @var{dev}
18750 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18751 use this target to communicate with both boards running the Angel
18752 monitor, or with the EmbeddedICE JTAG debug device.
18755 @item target rdp @var{dev}
18760 @value{GDBN} provides the following ARM-specific commands:
18763 @item set arm disassembler
18765 This commands selects from a list of disassembly styles. The
18766 @code{"std"} style is the standard style.
18768 @item show arm disassembler
18770 Show the current disassembly style.
18772 @item set arm apcs32
18773 @cindex ARM 32-bit mode
18774 This command toggles ARM operation mode between 32-bit and 26-bit.
18776 @item show arm apcs32
18777 Display the current usage of the ARM 32-bit mode.
18779 @item set arm fpu @var{fputype}
18780 This command sets the ARM floating-point unit (FPU) type. The
18781 argument @var{fputype} can be one of these:
18785 Determine the FPU type by querying the OS ABI.
18787 Software FPU, with mixed-endian doubles on little-endian ARM
18790 GCC-compiled FPA co-processor.
18792 Software FPU with pure-endian doubles.
18798 Show the current type of the FPU.
18801 This command forces @value{GDBN} to use the specified ABI.
18804 Show the currently used ABI.
18806 @item set arm fallback-mode (arm|thumb|auto)
18807 @value{GDBN} uses the symbol table, when available, to determine
18808 whether instructions are ARM or Thumb. This command controls
18809 @value{GDBN}'s default behavior when the symbol table is not
18810 available. The default is @samp{auto}, which causes @value{GDBN} to
18811 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18814 @item show arm fallback-mode
18815 Show the current fallback instruction mode.
18817 @item set arm force-mode (arm|thumb|auto)
18818 This command overrides use of the symbol table to determine whether
18819 instructions are ARM or Thumb. The default is @samp{auto}, which
18820 causes @value{GDBN} to use the symbol table and then the setting
18821 of @samp{set arm fallback-mode}.
18823 @item show arm force-mode
18824 Show the current forced instruction mode.
18826 @item set debug arm
18827 Toggle whether to display ARM-specific debugging messages from the ARM
18828 target support subsystem.
18830 @item show debug arm
18831 Show whether ARM-specific debugging messages are enabled.
18834 The following commands are available when an ARM target is debugged
18835 using the RDI interface:
18838 @item rdilogfile @r{[}@var{file}@r{]}
18840 @cindex ADP (Angel Debugger Protocol) logging
18841 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18842 With an argument, sets the log file to the specified @var{file}. With
18843 no argument, show the current log file name. The default log file is
18846 @item rdilogenable @r{[}@var{arg}@r{]}
18847 @kindex rdilogenable
18848 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18849 enables logging, with an argument 0 or @code{"no"} disables it. With
18850 no arguments displays the current setting. When logging is enabled,
18851 ADP packets exchanged between @value{GDBN} and the RDI target device
18852 are logged to a file.
18854 @item set rdiromatzero
18855 @kindex set rdiromatzero
18856 @cindex ROM at zero address, RDI
18857 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18858 vector catching is disabled, so that zero address can be used. If off
18859 (the default), vector catching is enabled. For this command to take
18860 effect, it needs to be invoked prior to the @code{target rdi} command.
18862 @item show rdiromatzero
18863 @kindex show rdiromatzero
18864 Show the current setting of ROM at zero address.
18866 @item set rdiheartbeat
18867 @kindex set rdiheartbeat
18868 @cindex RDI heartbeat
18869 Enable or disable RDI heartbeat packets. It is not recommended to
18870 turn on this option, since it confuses ARM and EPI JTAG interface, as
18871 well as the Angel monitor.
18873 @item show rdiheartbeat
18874 @kindex show rdiheartbeat
18875 Show the setting of RDI heartbeat packets.
18879 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18880 The @value{GDBN} ARM simulator accepts the following optional arguments.
18883 @item --swi-support=@var{type}
18884 Tell the simulator which SWI interfaces to support.
18885 @var{type} may be a comma separated list of the following values.
18886 The default value is @code{all}.
18899 @subsection Renesas M32R/D and M32R/SDI
18902 @kindex target m32r
18903 @item target m32r @var{dev}
18904 Renesas M32R/D ROM monitor.
18906 @kindex target m32rsdi
18907 @item target m32rsdi @var{dev}
18908 Renesas M32R SDI server, connected via parallel port to the board.
18911 The following @value{GDBN} commands are specific to the M32R monitor:
18914 @item set download-path @var{path}
18915 @kindex set download-path
18916 @cindex find downloadable @sc{srec} files (M32R)
18917 Set the default path for finding downloadable @sc{srec} files.
18919 @item show download-path
18920 @kindex show download-path
18921 Show the default path for downloadable @sc{srec} files.
18923 @item set board-address @var{addr}
18924 @kindex set board-address
18925 @cindex M32-EVA target board address
18926 Set the IP address for the M32R-EVA target board.
18928 @item show board-address
18929 @kindex show board-address
18930 Show the current IP address of the target board.
18932 @item set server-address @var{addr}
18933 @kindex set server-address
18934 @cindex download server address (M32R)
18935 Set the IP address for the download server, which is the @value{GDBN}'s
18938 @item show server-address
18939 @kindex show server-address
18940 Display the IP address of the download server.
18942 @item upload @r{[}@var{file}@r{]}
18943 @kindex upload@r{, M32R}
18944 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18945 upload capability. If no @var{file} argument is given, the current
18946 executable file is uploaded.
18948 @item tload @r{[}@var{file}@r{]}
18949 @kindex tload@r{, M32R}
18950 Test the @code{upload} command.
18953 The following commands are available for M32R/SDI:
18958 @cindex reset SDI connection, M32R
18959 This command resets the SDI connection.
18963 This command shows the SDI connection status.
18966 @kindex debug_chaos
18967 @cindex M32R/Chaos debugging
18968 Instructs the remote that M32R/Chaos debugging is to be used.
18970 @item use_debug_dma
18971 @kindex use_debug_dma
18972 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18975 @kindex use_mon_code
18976 Instructs the remote to use the MON_CODE method of accessing memory.
18979 @kindex use_ib_break
18980 Instructs the remote to set breakpoints by IB break.
18982 @item use_dbt_break
18983 @kindex use_dbt_break
18984 Instructs the remote to set breakpoints by DBT.
18990 The Motorola m68k configuration includes ColdFire support, and a
18991 target command for the following ROM monitor.
18995 @kindex target dbug
18996 @item target dbug @var{dev}
18997 dBUG ROM monitor for Motorola ColdFire.
19002 @subsection MicroBlaze
19003 @cindex Xilinx MicroBlaze
19004 @cindex XMD, Xilinx Microprocessor Debugger
19006 The MicroBlaze is a soft-core processor supported on various Xilinx
19007 FPGAs, such as Spartan or Virtex series. Boards with these processors
19008 usually have JTAG ports which connect to a host system running the Xilinx
19009 Embedded Development Kit (EDK) or Software Development Kit (SDK).
19010 This host system is used to download the configuration bitstream to
19011 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
19012 communicates with the target board using the JTAG interface and
19013 presents a @code{gdbserver} interface to the board. By default
19014 @code{xmd} uses port @code{1234}. (While it is possible to change
19015 this default port, it requires the use of undocumented @code{xmd}
19016 commands. Contact Xilinx support if you need to do this.)
19018 Use these GDB commands to connect to the MicroBlaze target processor.
19021 @item target remote :1234
19022 Use this command to connect to the target if you are running @value{GDBN}
19023 on the same system as @code{xmd}.
19025 @item target remote @var{xmd-host}:1234
19026 Use this command to connect to the target if it is connected to @code{xmd}
19027 running on a different system named @var{xmd-host}.
19030 Use this command to download a program to the MicroBlaze target.
19032 @item set debug microblaze @var{n}
19033 Enable MicroBlaze-specific debugging messages if non-zero.
19035 @item show debug microblaze @var{n}
19036 Show MicroBlaze-specific debugging level.
19039 @node MIPS Embedded
19040 @subsection MIPS Embedded
19042 @cindex MIPS boards
19043 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
19044 MIPS board attached to a serial line. This is available when
19045 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
19048 Use these @value{GDBN} commands to specify the connection to your target board:
19051 @item target mips @var{port}
19052 @kindex target mips @var{port}
19053 To run a program on the board, start up @code{@value{GDBP}} with the
19054 name of your program as the argument. To connect to the board, use the
19055 command @samp{target mips @var{port}}, where @var{port} is the name of
19056 the serial port connected to the board. If the program has not already
19057 been downloaded to the board, you may use the @code{load} command to
19058 download it. You can then use all the usual @value{GDBN} commands.
19060 For example, this sequence connects to the target board through a serial
19061 port, and loads and runs a program called @var{prog} through the
19065 host$ @value{GDBP} @var{prog}
19066 @value{GDBN} is free software and @dots{}
19067 (@value{GDBP}) target mips /dev/ttyb
19068 (@value{GDBP}) load @var{prog}
19072 @item target mips @var{hostname}:@var{portnumber}
19073 On some @value{GDBN} host configurations, you can specify a TCP
19074 connection (for instance, to a serial line managed by a terminal
19075 concentrator) instead of a serial port, using the syntax
19076 @samp{@var{hostname}:@var{portnumber}}.
19078 @item target pmon @var{port}
19079 @kindex target pmon @var{port}
19082 @item target ddb @var{port}
19083 @kindex target ddb @var{port}
19084 NEC's DDB variant of PMON for Vr4300.
19086 @item target lsi @var{port}
19087 @kindex target lsi @var{port}
19088 LSI variant of PMON.
19090 @kindex target r3900
19091 @item target r3900 @var{dev}
19092 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19094 @kindex target array
19095 @item target array @var{dev}
19096 Array Tech LSI33K RAID controller board.
19102 @value{GDBN} also supports these special commands for MIPS targets:
19105 @item set mipsfpu double
19106 @itemx set mipsfpu single
19107 @itemx set mipsfpu none
19108 @itemx set mipsfpu auto
19109 @itemx show mipsfpu
19110 @kindex set mipsfpu
19111 @kindex show mipsfpu
19112 @cindex MIPS remote floating point
19113 @cindex floating point, MIPS remote
19114 If your target board does not support the MIPS floating point
19115 coprocessor, you should use the command @samp{set mipsfpu none} (if you
19116 need this, you may wish to put the command in your @value{GDBN} init
19117 file). This tells @value{GDBN} how to find the return value of
19118 functions which return floating point values. It also allows
19119 @value{GDBN} to avoid saving the floating point registers when calling
19120 functions on the board. If you are using a floating point coprocessor
19121 with only single precision floating point support, as on the @sc{r4650}
19122 processor, use the command @samp{set mipsfpu single}. The default
19123 double precision floating point coprocessor may be selected using
19124 @samp{set mipsfpu double}.
19126 In previous versions the only choices were double precision or no
19127 floating point, so @samp{set mipsfpu on} will select double precision
19128 and @samp{set mipsfpu off} will select no floating point.
19130 As usual, you can inquire about the @code{mipsfpu} variable with
19131 @samp{show mipsfpu}.
19133 @item set timeout @var{seconds}
19134 @itemx set retransmit-timeout @var{seconds}
19135 @itemx show timeout
19136 @itemx show retransmit-timeout
19137 @cindex @code{timeout}, MIPS protocol
19138 @cindex @code{retransmit-timeout}, MIPS protocol
19139 @kindex set timeout
19140 @kindex show timeout
19141 @kindex set retransmit-timeout
19142 @kindex show retransmit-timeout
19143 You can control the timeout used while waiting for a packet, in the MIPS
19144 remote protocol, with the @code{set timeout @var{seconds}} command. The
19145 default is 5 seconds. Similarly, you can control the timeout used while
19146 waiting for an acknowledgment of a packet with the @code{set
19147 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19148 You can inspect both values with @code{show timeout} and @code{show
19149 retransmit-timeout}. (These commands are @emph{only} available when
19150 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
19152 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19153 is waiting for your program to stop. In that case, @value{GDBN} waits
19154 forever because it has no way of knowing how long the program is going
19155 to run before stopping.
19157 @item set syn-garbage-limit @var{num}
19158 @kindex set syn-garbage-limit@r{, MIPS remote}
19159 @cindex synchronize with remote MIPS target
19160 Limit the maximum number of characters @value{GDBN} should ignore when
19161 it tries to synchronize with the remote target. The default is 10
19162 characters. Setting the limit to -1 means there's no limit.
19164 @item show syn-garbage-limit
19165 @kindex show syn-garbage-limit@r{, MIPS remote}
19166 Show the current limit on the number of characters to ignore when
19167 trying to synchronize with the remote system.
19169 @item set monitor-prompt @var{prompt}
19170 @kindex set monitor-prompt@r{, MIPS remote}
19171 @cindex remote monitor prompt
19172 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19173 remote monitor. The default depends on the target:
19183 @item show monitor-prompt
19184 @kindex show monitor-prompt@r{, MIPS remote}
19185 Show the current strings @value{GDBN} expects as the prompt from the
19188 @item set monitor-warnings
19189 @kindex set monitor-warnings@r{, MIPS remote}
19190 Enable or disable monitor warnings about hardware breakpoints. This
19191 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19192 display warning messages whose codes are returned by the @code{lsi}
19193 PMON monitor for breakpoint commands.
19195 @item show monitor-warnings
19196 @kindex show monitor-warnings@r{, MIPS remote}
19197 Show the current setting of printing monitor warnings.
19199 @item pmon @var{command}
19200 @kindex pmon@r{, MIPS remote}
19201 @cindex send PMON command
19202 This command allows sending an arbitrary @var{command} string to the
19203 monitor. The monitor must be in debug mode for this to work.
19206 @node OpenRISC 1000
19207 @subsection OpenRISC 1000
19208 @cindex OpenRISC 1000
19210 @cindex or1k boards
19211 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19212 about platform and commands.
19216 @kindex target jtag
19217 @item target jtag jtag://@var{host}:@var{port}
19219 Connects to remote JTAG server.
19220 JTAG remote server can be either an or1ksim or JTAG server,
19221 connected via parallel port to the board.
19223 Example: @code{target jtag jtag://localhost:9999}
19226 @item or1ksim @var{command}
19227 If connected to @code{or1ksim} OpenRISC 1000 Architectural
19228 Simulator, proprietary commands can be executed.
19230 @kindex info or1k spr
19231 @item info or1k spr
19232 Displays spr groups.
19234 @item info or1k spr @var{group}
19235 @itemx info or1k spr @var{groupno}
19236 Displays register names in selected group.
19238 @item info or1k spr @var{group} @var{register}
19239 @itemx info or1k spr @var{register}
19240 @itemx info or1k spr @var{groupno} @var{registerno}
19241 @itemx info or1k spr @var{registerno}
19242 Shows information about specified spr register.
19245 @item spr @var{group} @var{register} @var{value}
19246 @itemx spr @var{register @var{value}}
19247 @itemx spr @var{groupno} @var{registerno @var{value}}
19248 @itemx spr @var{registerno @var{value}}
19249 Writes @var{value} to specified spr register.
19252 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
19253 It is very similar to @value{GDBN} trace, except it does not interfere with normal
19254 program execution and is thus much faster. Hardware breakpoints/watchpoint
19255 triggers can be set using:
19258 Load effective address/data
19260 Store effective address/data
19262 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
19267 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
19268 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
19270 @code{htrace} commands:
19271 @cindex OpenRISC 1000 htrace
19274 @item hwatch @var{conditional}
19275 Set hardware watchpoint on combination of Load/Store Effective Address(es)
19276 or Data. For example:
19278 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19280 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19284 Display information about current HW trace configuration.
19286 @item htrace trigger @var{conditional}
19287 Set starting criteria for HW trace.
19289 @item htrace qualifier @var{conditional}
19290 Set acquisition qualifier for HW trace.
19292 @item htrace stop @var{conditional}
19293 Set HW trace stopping criteria.
19295 @item htrace record [@var{data}]*
19296 Selects the data to be recorded, when qualifier is met and HW trace was
19299 @item htrace enable
19300 @itemx htrace disable
19301 Enables/disables the HW trace.
19303 @item htrace rewind [@var{filename}]
19304 Clears currently recorded trace data.
19306 If filename is specified, new trace file is made and any newly collected data
19307 will be written there.
19309 @item htrace print [@var{start} [@var{len}]]
19310 Prints trace buffer, using current record configuration.
19312 @item htrace mode continuous
19313 Set continuous trace mode.
19315 @item htrace mode suspend
19316 Set suspend trace mode.
19320 @node PowerPC Embedded
19321 @subsection PowerPC Embedded
19323 @cindex DVC register
19324 @value{GDBN} supports using the DVC (Data Value Compare) register to
19325 implement in hardware simple hardware watchpoint conditions of the form:
19328 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
19329 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
19332 The DVC register will be automatically used when @value{GDBN} detects
19333 such pattern in a condition expression, and the created watchpoint uses one
19334 debug register (either the @code{exact-watchpoints} option is on and the
19335 variable is scalar, or the variable has a length of one byte). This feature
19336 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
19339 When running on PowerPC embedded processors, @value{GDBN} automatically uses
19340 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
19341 in which case watchpoints using only one debug register are created when
19342 watching variables of scalar types.
19344 You can create an artificial array to watch an arbitrary memory
19345 region using one of the following commands (@pxref{Expressions}):
19348 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
19349 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
19352 PowerPC embedded processors support masked watchpoints. See the discussion
19353 about the @code{mask} argument in @ref{Set Watchpoints}.
19355 @cindex ranged breakpoint
19356 PowerPC embedded processors support hardware accelerated
19357 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
19358 the inferior whenever it executes an instruction at any address within
19359 the range it specifies. To set a ranged breakpoint in @value{GDBN},
19360 use the @code{break-range} command.
19362 @value{GDBN} provides the following PowerPC-specific commands:
19365 @kindex break-range
19366 @item break-range @var{start-location}, @var{end-location}
19367 Set a breakpoint for an address range.
19368 @var{start-location} and @var{end-location} can specify a function name,
19369 a line number, an offset of lines from the current line or from the start
19370 location, or an address of an instruction (see @ref{Specify Location},
19371 for a list of all the possible ways to specify a @var{location}.)
19372 The breakpoint will stop execution of the inferior whenever it
19373 executes an instruction at any address within the specified range,
19374 (including @var{start-location} and @var{end-location}.)
19376 @kindex set powerpc
19377 @item set powerpc soft-float
19378 @itemx show powerpc soft-float
19379 Force @value{GDBN} to use (or not use) a software floating point calling
19380 convention. By default, @value{GDBN} selects the calling convention based
19381 on the selected architecture and the provided executable file.
19383 @item set powerpc vector-abi
19384 @itemx show powerpc vector-abi
19385 Force @value{GDBN} to use the specified calling convention for vector
19386 arguments and return values. The valid options are @samp{auto};
19387 @samp{generic}, to avoid vector registers even if they are present;
19388 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
19389 registers. By default, @value{GDBN} selects the calling convention
19390 based on the selected architecture and the provided executable file.
19392 @item set powerpc exact-watchpoints
19393 @itemx show powerpc exact-watchpoints
19394 Allow @value{GDBN} to use only one debug register when watching a variable
19395 of scalar type, thus assuming that the variable is accessed through the
19396 address of its first byte.
19398 @kindex target dink32
19399 @item target dink32 @var{dev}
19400 DINK32 ROM monitor.
19402 @kindex target ppcbug
19403 @item target ppcbug @var{dev}
19404 @kindex target ppcbug1
19405 @item target ppcbug1 @var{dev}
19406 PPCBUG ROM monitor for PowerPC.
19409 @item target sds @var{dev}
19410 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
19413 @cindex SDS protocol
19414 The following commands specific to the SDS protocol are supported
19418 @item set sdstimeout @var{nsec}
19419 @kindex set sdstimeout
19420 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
19421 default is 2 seconds.
19423 @item show sdstimeout
19424 @kindex show sdstimeout
19425 Show the current value of the SDS timeout.
19427 @item sds @var{command}
19428 @kindex sds@r{, a command}
19429 Send the specified @var{command} string to the SDS monitor.
19434 @subsection HP PA Embedded
19438 @kindex target op50n
19439 @item target op50n @var{dev}
19440 OP50N monitor, running on an OKI HPPA board.
19442 @kindex target w89k
19443 @item target w89k @var{dev}
19444 W89K monitor, running on a Winbond HPPA board.
19449 @subsection Tsqware Sparclet
19453 @value{GDBN} enables developers to debug tasks running on
19454 Sparclet targets from a Unix host.
19455 @value{GDBN} uses code that runs on
19456 both the Unix host and on the Sparclet target. The program
19457 @code{@value{GDBP}} is installed and executed on the Unix host.
19460 @item remotetimeout @var{args}
19461 @kindex remotetimeout
19462 @value{GDBN} supports the option @code{remotetimeout}.
19463 This option is set by the user, and @var{args} represents the number of
19464 seconds @value{GDBN} waits for responses.
19467 @cindex compiling, on Sparclet
19468 When compiling for debugging, include the options @samp{-g} to get debug
19469 information and @samp{-Ttext} to relocate the program to where you wish to
19470 load it on the target. You may also want to add the options @samp{-n} or
19471 @samp{-N} in order to reduce the size of the sections. Example:
19474 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
19477 You can use @code{objdump} to verify that the addresses are what you intended:
19480 sparclet-aout-objdump --headers --syms prog
19483 @cindex running, on Sparclet
19485 your Unix execution search path to find @value{GDBN}, you are ready to
19486 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
19487 (or @code{sparclet-aout-gdb}, depending on your installation).
19489 @value{GDBN} comes up showing the prompt:
19496 * Sparclet File:: Setting the file to debug
19497 * Sparclet Connection:: Connecting to Sparclet
19498 * Sparclet Download:: Sparclet download
19499 * Sparclet Execution:: Running and debugging
19502 @node Sparclet File
19503 @subsubsection Setting File to Debug
19505 The @value{GDBN} command @code{file} lets you choose with program to debug.
19508 (gdbslet) file prog
19512 @value{GDBN} then attempts to read the symbol table of @file{prog}.
19513 @value{GDBN} locates
19514 the file by searching the directories listed in the command search
19516 If the file was compiled with debug information (option @samp{-g}), source
19517 files will be searched as well.
19518 @value{GDBN} locates
19519 the source files by searching the directories listed in the directory search
19520 path (@pxref{Environment, ,Your Program's Environment}).
19522 to find a file, it displays a message such as:
19525 prog: No such file or directory.
19528 When this happens, add the appropriate directories to the search paths with
19529 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
19530 @code{target} command again.
19532 @node Sparclet Connection
19533 @subsubsection Connecting to Sparclet
19535 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
19536 To connect to a target on serial port ``@code{ttya}'', type:
19539 (gdbslet) target sparclet /dev/ttya
19540 Remote target sparclet connected to /dev/ttya
19541 main () at ../prog.c:3
19545 @value{GDBN} displays messages like these:
19551 @node Sparclet Download
19552 @subsubsection Sparclet Download
19554 @cindex download to Sparclet
19555 Once connected to the Sparclet target,
19556 you can use the @value{GDBN}
19557 @code{load} command to download the file from the host to the target.
19558 The file name and load offset should be given as arguments to the @code{load}
19560 Since the file format is aout, the program must be loaded to the starting
19561 address. You can use @code{objdump} to find out what this value is. The load
19562 offset is an offset which is added to the VMA (virtual memory address)
19563 of each of the file's sections.
19564 For instance, if the program
19565 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19566 and bss at 0x12010170, in @value{GDBN}, type:
19569 (gdbslet) load prog 0x12010000
19570 Loading section .text, size 0xdb0 vma 0x12010000
19573 If the code is loaded at a different address then what the program was linked
19574 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19575 to tell @value{GDBN} where to map the symbol table.
19577 @node Sparclet Execution
19578 @subsubsection Running and Debugging
19580 @cindex running and debugging Sparclet programs
19581 You can now begin debugging the task using @value{GDBN}'s execution control
19582 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19583 manual for the list of commands.
19587 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19589 Starting program: prog
19590 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19591 3 char *symarg = 0;
19593 4 char *execarg = "hello!";
19598 @subsection Fujitsu Sparclite
19602 @kindex target sparclite
19603 @item target sparclite @var{dev}
19604 Fujitsu sparclite boards, used only for the purpose of loading.
19605 You must use an additional command to debug the program.
19606 For example: target remote @var{dev} using @value{GDBN} standard
19612 @subsection Zilog Z8000
19615 @cindex simulator, Z8000
19616 @cindex Zilog Z8000 simulator
19618 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19621 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19622 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19623 segmented variant). The simulator recognizes which architecture is
19624 appropriate by inspecting the object code.
19627 @item target sim @var{args}
19629 @kindex target sim@r{, with Z8000}
19630 Debug programs on a simulated CPU. If the simulator supports setup
19631 options, specify them via @var{args}.
19635 After specifying this target, you can debug programs for the simulated
19636 CPU in the same style as programs for your host computer; use the
19637 @code{file} command to load a new program image, the @code{run} command
19638 to run your program, and so on.
19640 As well as making available all the usual machine registers
19641 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19642 additional items of information as specially named registers:
19647 Counts clock-ticks in the simulator.
19650 Counts instructions run in the simulator.
19653 Execution time in 60ths of a second.
19657 You can refer to these values in @value{GDBN} expressions with the usual
19658 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19659 conditional breakpoint that suspends only after at least 5000
19660 simulated clock ticks.
19663 @subsection Atmel AVR
19666 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19667 following AVR-specific commands:
19670 @item info io_registers
19671 @kindex info io_registers@r{, AVR}
19672 @cindex I/O registers (Atmel AVR)
19673 This command displays information about the AVR I/O registers. For
19674 each register, @value{GDBN} prints its number and value.
19681 When configured for debugging CRIS, @value{GDBN} provides the
19682 following CRIS-specific commands:
19685 @item set cris-version @var{ver}
19686 @cindex CRIS version
19687 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19688 The CRIS version affects register names and sizes. This command is useful in
19689 case autodetection of the CRIS version fails.
19691 @item show cris-version
19692 Show the current CRIS version.
19694 @item set cris-dwarf2-cfi
19695 @cindex DWARF-2 CFI and CRIS
19696 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19697 Change to @samp{off} when using @code{gcc-cris} whose version is below
19700 @item show cris-dwarf2-cfi
19701 Show the current state of using DWARF-2 CFI.
19703 @item set cris-mode @var{mode}
19705 Set the current CRIS mode to @var{mode}. It should only be changed when
19706 debugging in guru mode, in which case it should be set to
19707 @samp{guru} (the default is @samp{normal}).
19709 @item show cris-mode
19710 Show the current CRIS mode.
19714 @subsection Renesas Super-H
19717 For the Renesas Super-H processor, @value{GDBN} provides these
19722 @kindex regs@r{, Super-H}
19723 Show the values of all Super-H registers.
19725 @item set sh calling-convention @var{convention}
19726 @kindex set sh calling-convention
19727 Set the calling-convention used when calling functions from @value{GDBN}.
19728 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19729 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19730 convention. If the DWARF-2 information of the called function specifies
19731 that the function follows the Renesas calling convention, the function
19732 is called using the Renesas calling convention. If the calling convention
19733 is set to @samp{renesas}, the Renesas calling convention is always used,
19734 regardless of the DWARF-2 information. This can be used to override the
19735 default of @samp{gcc} if debug information is missing, or the compiler
19736 does not emit the DWARF-2 calling convention entry for a function.
19738 @item show sh calling-convention
19739 @kindex show sh calling-convention
19740 Show the current calling convention setting.
19745 @node Architectures
19746 @section Architectures
19748 This section describes characteristics of architectures that affect
19749 all uses of @value{GDBN} with the architecture, both native and cross.
19756 * HPPA:: HP PA architecture
19757 * SPU:: Cell Broadband Engine SPU architecture
19762 @subsection x86 Architecture-specific Issues
19765 @item set struct-convention @var{mode}
19766 @kindex set struct-convention
19767 @cindex struct return convention
19768 @cindex struct/union returned in registers
19769 Set the convention used by the inferior to return @code{struct}s and
19770 @code{union}s from functions to @var{mode}. Possible values of
19771 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19772 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19773 are returned on the stack, while @code{"reg"} means that a
19774 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19775 be returned in a register.
19777 @item show struct-convention
19778 @kindex show struct-convention
19779 Show the current setting of the convention to return @code{struct}s
19788 @kindex set rstack_high_address
19789 @cindex AMD 29K register stack
19790 @cindex register stack, AMD29K
19791 @item set rstack_high_address @var{address}
19792 On AMD 29000 family processors, registers are saved in a separate
19793 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19794 extent of this stack. Normally, @value{GDBN} just assumes that the
19795 stack is ``large enough''. This may result in @value{GDBN} referencing
19796 memory locations that do not exist. If necessary, you can get around
19797 this problem by specifying the ending address of the register stack with
19798 the @code{set rstack_high_address} command. The argument should be an
19799 address, which you probably want to precede with @samp{0x} to specify in
19802 @kindex show rstack_high_address
19803 @item show rstack_high_address
19804 Display the current limit of the register stack, on AMD 29000 family
19812 See the following section.
19817 @cindex stack on Alpha
19818 @cindex stack on MIPS
19819 @cindex Alpha stack
19821 Alpha- and MIPS-based computers use an unusual stack frame, which
19822 sometimes requires @value{GDBN} to search backward in the object code to
19823 find the beginning of a function.
19825 @cindex response time, MIPS debugging
19826 To improve response time (especially for embedded applications, where
19827 @value{GDBN} may be restricted to a slow serial line for this search)
19828 you may want to limit the size of this search, using one of these
19832 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19833 @item set heuristic-fence-post @var{limit}
19834 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19835 search for the beginning of a function. A value of @var{0} (the
19836 default) means there is no limit. However, except for @var{0}, the
19837 larger the limit the more bytes @code{heuristic-fence-post} must search
19838 and therefore the longer it takes to run. You should only need to use
19839 this command when debugging a stripped executable.
19841 @item show heuristic-fence-post
19842 Display the current limit.
19846 These commands are available @emph{only} when @value{GDBN} is configured
19847 for debugging programs on Alpha or MIPS processors.
19849 Several MIPS-specific commands are available when debugging MIPS
19853 @item set mips abi @var{arg}
19854 @kindex set mips abi
19855 @cindex set ABI for MIPS
19856 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19857 values of @var{arg} are:
19861 The default ABI associated with the current binary (this is the
19871 @item show mips abi
19872 @kindex show mips abi
19873 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19876 @itemx show mipsfpu
19877 @xref{MIPS Embedded, set mipsfpu}.
19879 @item set mips mask-address @var{arg}
19880 @kindex set mips mask-address
19881 @cindex MIPS addresses, masking
19882 This command determines whether the most-significant 32 bits of 64-bit
19883 MIPS addresses are masked off. The argument @var{arg} can be
19884 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19885 setting, which lets @value{GDBN} determine the correct value.
19887 @item show mips mask-address
19888 @kindex show mips mask-address
19889 Show whether the upper 32 bits of MIPS addresses are masked off or
19892 @item set remote-mips64-transfers-32bit-regs
19893 @kindex set remote-mips64-transfers-32bit-regs
19894 This command controls compatibility with 64-bit MIPS targets that
19895 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19896 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19897 and 64 bits for other registers, set this option to @samp{on}.
19899 @item show remote-mips64-transfers-32bit-regs
19900 @kindex show remote-mips64-transfers-32bit-regs
19901 Show the current setting of compatibility with older MIPS 64 targets.
19903 @item set debug mips
19904 @kindex set debug mips
19905 This command turns on and off debugging messages for the MIPS-specific
19906 target code in @value{GDBN}.
19908 @item show debug mips
19909 @kindex show debug mips
19910 Show the current setting of MIPS debugging messages.
19916 @cindex HPPA support
19918 When @value{GDBN} is debugging the HP PA architecture, it provides the
19919 following special commands:
19922 @item set debug hppa
19923 @kindex set debug hppa
19924 This command determines whether HPPA architecture-specific debugging
19925 messages are to be displayed.
19927 @item show debug hppa
19928 Show whether HPPA debugging messages are displayed.
19930 @item maint print unwind @var{address}
19931 @kindex maint print unwind@r{, HPPA}
19932 This command displays the contents of the unwind table entry at the
19933 given @var{address}.
19939 @subsection Cell Broadband Engine SPU architecture
19940 @cindex Cell Broadband Engine
19943 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19944 it provides the following special commands:
19947 @item info spu event
19949 Display SPU event facility status. Shows current event mask
19950 and pending event status.
19952 @item info spu signal
19953 Display SPU signal notification facility status. Shows pending
19954 signal-control word and signal notification mode of both signal
19955 notification channels.
19957 @item info spu mailbox
19958 Display SPU mailbox facility status. Shows all pending entries,
19959 in order of processing, in each of the SPU Write Outbound,
19960 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19963 Display MFC DMA status. Shows all pending commands in the MFC
19964 DMA queue. For each entry, opcode, tag, class IDs, effective
19965 and local store addresses and transfer size are shown.
19967 @item info spu proxydma
19968 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19969 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19970 and local store addresses and transfer size are shown.
19974 When @value{GDBN} is debugging a combined PowerPC/SPU application
19975 on the Cell Broadband Engine, it provides in addition the following
19979 @item set spu stop-on-load @var{arg}
19981 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19982 will give control to the user when a new SPE thread enters its @code{main}
19983 function. The default is @code{off}.
19985 @item show spu stop-on-load
19987 Show whether to stop for new SPE threads.
19989 @item set spu auto-flush-cache @var{arg}
19990 Set whether to automatically flush the software-managed cache. When set to
19991 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19992 cache to be flushed whenever SPE execution stops. This provides a consistent
19993 view of PowerPC memory that is accessed via the cache. If an application
19994 does not use the software-managed cache, this option has no effect.
19996 @item show spu auto-flush-cache
19997 Show whether to automatically flush the software-managed cache.
20002 @subsection PowerPC
20003 @cindex PowerPC architecture
20005 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
20006 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
20007 numbers stored in the floating point registers. These values must be stored
20008 in two consecutive registers, always starting at an even register like
20009 @code{f0} or @code{f2}.
20011 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
20012 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
20013 @code{f2} and @code{f3} for @code{$dl1} and so on.
20015 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
20016 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
20019 @node Controlling GDB
20020 @chapter Controlling @value{GDBN}
20022 You can alter the way @value{GDBN} interacts with you by using the
20023 @code{set} command. For commands controlling how @value{GDBN} displays
20024 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20029 * Editing:: Command editing
20030 * Command History:: Command history
20031 * Screen Size:: Screen size
20032 * Numbers:: Numbers
20033 * ABI:: Configuring the current ABI
20034 * Messages/Warnings:: Optional warnings and messages
20035 * Debugging Output:: Optional messages about internal happenings
20036 * Other Misc Settings:: Other Miscellaneous Settings
20044 @value{GDBN} indicates its readiness to read a command by printing a string
20045 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20046 can change the prompt string with the @code{set prompt} command. For
20047 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20048 the prompt in one of the @value{GDBN} sessions so that you can always tell
20049 which one you are talking to.
20051 @emph{Note:} @code{set prompt} does not add a space for you after the
20052 prompt you set. This allows you to set a prompt which ends in a space
20053 or a prompt that does not.
20057 @item set prompt @var{newprompt}
20058 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20060 @kindex show prompt
20062 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20065 Versions of @value{GDBN} that ship with Python scripting enabled have
20066 prompt extensions. The commands for interacting with these extensions
20070 @kindex set extended-prompt
20071 @item set extended-prompt @var{prompt}
20072 Set an extended prompt that allows for substitutions.
20073 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20074 substitution. Any escape sequences specified as part of the prompt
20075 string are replaced with the corresponding strings each time the prompt
20081 set extended-prompt Current working directory: \w (gdb)
20084 Note that when an extended-prompt is set, it takes control of the
20085 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20087 @kindex show extended-prompt
20088 @item show extended-prompt
20089 Prints the extended prompt. Any escape sequences specified as part of
20090 the prompt string with @code{set extended-prompt}, are replaced with the
20091 corresponding strings each time the prompt is displayed.
20095 @section Command Editing
20097 @cindex command line editing
20099 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
20100 @sc{gnu} library provides consistent behavior for programs which provide a
20101 command line interface to the user. Advantages are @sc{gnu} Emacs-style
20102 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
20103 substitution, and a storage and recall of command history across
20104 debugging sessions.
20106 You may control the behavior of command line editing in @value{GDBN} with the
20107 command @code{set}.
20110 @kindex set editing
20113 @itemx set editing on
20114 Enable command line editing (enabled by default).
20116 @item set editing off
20117 Disable command line editing.
20119 @kindex show editing
20121 Show whether command line editing is enabled.
20124 @ifset SYSTEM_READLINE
20125 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
20127 @ifclear SYSTEM_READLINE
20128 @xref{Command Line Editing},
20130 for more details about the Readline
20131 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
20132 encouraged to read that chapter.
20134 @node Command History
20135 @section Command History
20136 @cindex command history
20138 @value{GDBN} can keep track of the commands you type during your
20139 debugging sessions, so that you can be certain of precisely what
20140 happened. Use these commands to manage the @value{GDBN} command
20143 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20144 package, to provide the history facility.
20145 @ifset SYSTEM_READLINE
20146 @xref{Using History Interactively, , , history, GNU History Library},
20148 @ifclear SYSTEM_READLINE
20149 @xref{Using History Interactively},
20151 for the detailed description of the History library.
20153 To issue a command to @value{GDBN} without affecting certain aspects of
20154 the state which is seen by users, prefix it with @samp{server }
20155 (@pxref{Server Prefix}). This
20156 means that this command will not affect the command history, nor will it
20157 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20158 pressed on a line by itself.
20160 @cindex @code{server}, command prefix
20161 The server prefix does not affect the recording of values into the value
20162 history; to print a value without recording it into the value history,
20163 use the @code{output} command instead of the @code{print} command.
20165 Here is the description of @value{GDBN} commands related to command
20169 @cindex history substitution
20170 @cindex history file
20171 @kindex set history filename
20172 @cindex @env{GDBHISTFILE}, environment variable
20173 @item set history filename @var{fname}
20174 Set the name of the @value{GDBN} command history file to @var{fname}.
20175 This is the file where @value{GDBN} reads an initial command history
20176 list, and where it writes the command history from this session when it
20177 exits. You can access this list through history expansion or through
20178 the history command editing characters listed below. This file defaults
20179 to the value of the environment variable @code{GDBHISTFILE}, or to
20180 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20183 @cindex save command history
20184 @kindex set history save
20185 @item set history save
20186 @itemx set history save on
20187 Record command history in a file, whose name may be specified with the
20188 @code{set history filename} command. By default, this option is disabled.
20190 @item set history save off
20191 Stop recording command history in a file.
20193 @cindex history size
20194 @kindex set history size
20195 @cindex @env{HISTSIZE}, environment variable
20196 @item set history size @var{size}
20197 Set the number of commands which @value{GDBN} keeps in its history list.
20198 This defaults to the value of the environment variable
20199 @code{HISTSIZE}, or to 256 if this variable is not set.
20202 History expansion assigns special meaning to the character @kbd{!}.
20203 @ifset SYSTEM_READLINE
20204 @xref{Event Designators, , , history, GNU History Library},
20206 @ifclear SYSTEM_READLINE
20207 @xref{Event Designators},
20211 @cindex history expansion, turn on/off
20212 Since @kbd{!} is also the logical not operator in C, history expansion
20213 is off by default. If you decide to enable history expansion with the
20214 @code{set history expansion on} command, you may sometimes need to
20215 follow @kbd{!} (when it is used as logical not, in an expression) with
20216 a space or a tab to prevent it from being expanded. The readline
20217 history facilities do not attempt substitution on the strings
20218 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20220 The commands to control history expansion are:
20223 @item set history expansion on
20224 @itemx set history expansion
20225 @kindex set history expansion
20226 Enable history expansion. History expansion is off by default.
20228 @item set history expansion off
20229 Disable history expansion.
20232 @kindex show history
20234 @itemx show history filename
20235 @itemx show history save
20236 @itemx show history size
20237 @itemx show history expansion
20238 These commands display the state of the @value{GDBN} history parameters.
20239 @code{show history} by itself displays all four states.
20244 @kindex show commands
20245 @cindex show last commands
20246 @cindex display command history
20247 @item show commands
20248 Display the last ten commands in the command history.
20250 @item show commands @var{n}
20251 Print ten commands centered on command number @var{n}.
20253 @item show commands +
20254 Print ten commands just after the commands last printed.
20258 @section Screen Size
20259 @cindex size of screen
20260 @cindex pauses in output
20262 Certain commands to @value{GDBN} may produce large amounts of
20263 information output to the screen. To help you read all of it,
20264 @value{GDBN} pauses and asks you for input at the end of each page of
20265 output. Type @key{RET} when you want to continue the output, or @kbd{q}
20266 to discard the remaining output. Also, the screen width setting
20267 determines when to wrap lines of output. Depending on what is being
20268 printed, @value{GDBN} tries to break the line at a readable place,
20269 rather than simply letting it overflow onto the following line.
20271 Normally @value{GDBN} knows the size of the screen from the terminal
20272 driver software. For example, on Unix @value{GDBN} uses the termcap data base
20273 together with the value of the @code{TERM} environment variable and the
20274 @code{stty rows} and @code{stty cols} settings. If this is not correct,
20275 you can override it with the @code{set height} and @code{set
20282 @kindex show height
20283 @item set height @var{lpp}
20285 @itemx set width @var{cpl}
20287 These @code{set} commands specify a screen height of @var{lpp} lines and
20288 a screen width of @var{cpl} characters. The associated @code{show}
20289 commands display the current settings.
20291 If you specify a height of zero lines, @value{GDBN} does not pause during
20292 output no matter how long the output is. This is useful if output is to a
20293 file or to an editor buffer.
20295 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
20296 from wrapping its output.
20298 @item set pagination on
20299 @itemx set pagination off
20300 @kindex set pagination
20301 Turn the output pagination on or off; the default is on. Turning
20302 pagination off is the alternative to @code{set height 0}. Note that
20303 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
20304 Options, -batch}) also automatically disables pagination.
20306 @item show pagination
20307 @kindex show pagination
20308 Show the current pagination mode.
20313 @cindex number representation
20314 @cindex entering numbers
20316 You can always enter numbers in octal, decimal, or hexadecimal in
20317 @value{GDBN} by the usual conventions: octal numbers begin with
20318 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
20319 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
20320 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
20321 10; likewise, the default display for numbers---when no particular
20322 format is specified---is base 10. You can change the default base for
20323 both input and output with the commands described below.
20326 @kindex set input-radix
20327 @item set input-radix @var{base}
20328 Set the default base for numeric input. Supported choices
20329 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20330 specified either unambiguously or using the current input radix; for
20334 set input-radix 012
20335 set input-radix 10.
20336 set input-radix 0xa
20340 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
20341 leaves the input radix unchanged, no matter what it was, since
20342 @samp{10}, being without any leading or trailing signs of its base, is
20343 interpreted in the current radix. Thus, if the current radix is 16,
20344 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
20347 @kindex set output-radix
20348 @item set output-radix @var{base}
20349 Set the default base for numeric display. Supported choices
20350 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20351 specified either unambiguously or using the current input radix.
20353 @kindex show input-radix
20354 @item show input-radix
20355 Display the current default base for numeric input.
20357 @kindex show output-radix
20358 @item show output-radix
20359 Display the current default base for numeric display.
20361 @item set radix @r{[}@var{base}@r{]}
20365 These commands set and show the default base for both input and output
20366 of numbers. @code{set radix} sets the radix of input and output to
20367 the same base; without an argument, it resets the radix back to its
20368 default value of 10.
20373 @section Configuring the Current ABI
20375 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
20376 application automatically. However, sometimes you need to override its
20377 conclusions. Use these commands to manage @value{GDBN}'s view of the
20384 One @value{GDBN} configuration can debug binaries for multiple operating
20385 system targets, either via remote debugging or native emulation.
20386 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
20387 but you can override its conclusion using the @code{set osabi} command.
20388 One example where this is useful is in debugging of binaries which use
20389 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
20390 not have the same identifying marks that the standard C library for your
20395 Show the OS ABI currently in use.
20398 With no argument, show the list of registered available OS ABI's.
20400 @item set osabi @var{abi}
20401 Set the current OS ABI to @var{abi}.
20404 @cindex float promotion
20406 Generally, the way that an argument of type @code{float} is passed to a
20407 function depends on whether the function is prototyped. For a prototyped
20408 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
20409 according to the architecture's convention for @code{float}. For unprototyped
20410 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
20411 @code{double} and then passed.
20413 Unfortunately, some forms of debug information do not reliably indicate whether
20414 a function is prototyped. If @value{GDBN} calls a function that is not marked
20415 as prototyped, it consults @kbd{set coerce-float-to-double}.
20418 @kindex set coerce-float-to-double
20419 @item set coerce-float-to-double
20420 @itemx set coerce-float-to-double on
20421 Arguments of type @code{float} will be promoted to @code{double} when passed
20422 to an unprototyped function. This is the default setting.
20424 @item set coerce-float-to-double off
20425 Arguments of type @code{float} will be passed directly to unprototyped
20428 @kindex show coerce-float-to-double
20429 @item show coerce-float-to-double
20430 Show the current setting of promoting @code{float} to @code{double}.
20434 @kindex show cp-abi
20435 @value{GDBN} needs to know the ABI used for your program's C@t{++}
20436 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
20437 used to build your application. @value{GDBN} only fully supports
20438 programs with a single C@t{++} ABI; if your program contains code using
20439 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
20440 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
20441 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
20442 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
20443 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
20444 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
20449 Show the C@t{++} ABI currently in use.
20452 With no argument, show the list of supported C@t{++} ABI's.
20454 @item set cp-abi @var{abi}
20455 @itemx set cp-abi auto
20456 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
20459 @node Messages/Warnings
20460 @section Optional Warnings and Messages
20462 @cindex verbose operation
20463 @cindex optional warnings
20464 By default, @value{GDBN} is silent about its inner workings. If you are
20465 running on a slow machine, you may want to use the @code{set verbose}
20466 command. This makes @value{GDBN} tell you when it does a lengthy
20467 internal operation, so you will not think it has crashed.
20469 Currently, the messages controlled by @code{set verbose} are those
20470 which announce that the symbol table for a source file is being read;
20471 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
20474 @kindex set verbose
20475 @item set verbose on
20476 Enables @value{GDBN} output of certain informational messages.
20478 @item set verbose off
20479 Disables @value{GDBN} output of certain informational messages.
20481 @kindex show verbose
20483 Displays whether @code{set verbose} is on or off.
20486 By default, if @value{GDBN} encounters bugs in the symbol table of an
20487 object file, it is silent; but if you are debugging a compiler, you may
20488 find this information useful (@pxref{Symbol Errors, ,Errors Reading
20493 @kindex set complaints
20494 @item set complaints @var{limit}
20495 Permits @value{GDBN} to output @var{limit} complaints about each type of
20496 unusual symbols before becoming silent about the problem. Set
20497 @var{limit} to zero to suppress all complaints; set it to a large number
20498 to prevent complaints from being suppressed.
20500 @kindex show complaints
20501 @item show complaints
20502 Displays how many symbol complaints @value{GDBN} is permitted to produce.
20506 @anchor{confirmation requests}
20507 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
20508 lot of stupid questions to confirm certain commands. For example, if
20509 you try to run a program which is already running:
20513 The program being debugged has been started already.
20514 Start it from the beginning? (y or n)
20517 If you are willing to unflinchingly face the consequences of your own
20518 commands, you can disable this ``feature'':
20522 @kindex set confirm
20524 @cindex confirmation
20525 @cindex stupid questions
20526 @item set confirm off
20527 Disables confirmation requests. Note that running @value{GDBN} with
20528 the @option{--batch} option (@pxref{Mode Options, -batch}) also
20529 automatically disables confirmation requests.
20531 @item set confirm on
20532 Enables confirmation requests (the default).
20534 @kindex show confirm
20536 Displays state of confirmation requests.
20540 @cindex command tracing
20541 If you need to debug user-defined commands or sourced files you may find it
20542 useful to enable @dfn{command tracing}. In this mode each command will be
20543 printed as it is executed, prefixed with one or more @samp{+} symbols, the
20544 quantity denoting the call depth of each command.
20547 @kindex set trace-commands
20548 @cindex command scripts, debugging
20549 @item set trace-commands on
20550 Enable command tracing.
20551 @item set trace-commands off
20552 Disable command tracing.
20553 @item show trace-commands
20554 Display the current state of command tracing.
20557 @node Debugging Output
20558 @section Optional Messages about Internal Happenings
20559 @cindex optional debugging messages
20561 @value{GDBN} has commands that enable optional debugging messages from
20562 various @value{GDBN} subsystems; normally these commands are of
20563 interest to @value{GDBN} maintainers, or when reporting a bug. This
20564 section documents those commands.
20567 @kindex set exec-done-display
20568 @item set exec-done-display
20569 Turns on or off the notification of asynchronous commands'
20570 completion. When on, @value{GDBN} will print a message when an
20571 asynchronous command finishes its execution. The default is off.
20572 @kindex show exec-done-display
20573 @item show exec-done-display
20574 Displays the current setting of asynchronous command completion
20577 @cindex gdbarch debugging info
20578 @cindex architecture debugging info
20579 @item set debug arch
20580 Turns on or off display of gdbarch debugging info. The default is off
20582 @item show debug arch
20583 Displays the current state of displaying gdbarch debugging info.
20584 @item set debug aix-thread
20585 @cindex AIX threads
20586 Display debugging messages about inner workings of the AIX thread
20588 @item show debug aix-thread
20589 Show the current state of AIX thread debugging info display.
20590 @item set debug check-physname
20592 Check the results of the ``physname'' computation. When reading DWARF
20593 debugging information for C@t{++}, @value{GDBN} attempts to compute
20594 each entity's name. @value{GDBN} can do this computation in two
20595 different ways, depending on exactly what information is present.
20596 When enabled, this setting causes @value{GDBN} to compute the names
20597 both ways and display any discrepancies.
20598 @item show debug check-physname
20599 Show the current state of ``physname'' checking.
20600 @item set debug dwarf2-die
20601 @cindex DWARF2 DIEs
20602 Dump DWARF2 DIEs after they are read in.
20603 The value is the number of nesting levels to print.
20604 A value of zero turns off the display.
20605 @item show debug dwarf2-die
20606 Show the current state of DWARF2 DIE debugging.
20607 @item set debug displaced
20608 @cindex displaced stepping debugging info
20609 Turns on or off display of @value{GDBN} debugging info for the
20610 displaced stepping support. The default is off.
20611 @item show debug displaced
20612 Displays the current state of displaying @value{GDBN} debugging info
20613 related to displaced stepping.
20614 @item set debug event
20615 @cindex event debugging info
20616 Turns on or off display of @value{GDBN} event debugging info. The
20618 @item show debug event
20619 Displays the current state of displaying @value{GDBN} event debugging
20621 @item set debug expression
20622 @cindex expression debugging info
20623 Turns on or off display of debugging info about @value{GDBN}
20624 expression parsing. The default is off.
20625 @item show debug expression
20626 Displays the current state of displaying debugging info about
20627 @value{GDBN} expression parsing.
20628 @item set debug frame
20629 @cindex frame debugging info
20630 Turns on or off display of @value{GDBN} frame debugging info. The
20632 @item show debug frame
20633 Displays the current state of displaying @value{GDBN} frame debugging
20635 @item set debug gnu-nat
20636 @cindex @sc{gnu}/Hurd debug messages
20637 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20638 @item show debug gnu-nat
20639 Show the current state of @sc{gnu}/Hurd debugging messages.
20640 @item set debug infrun
20641 @cindex inferior debugging info
20642 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20643 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20644 for implementing operations such as single-stepping the inferior.
20645 @item show debug infrun
20646 Displays the current state of @value{GDBN} inferior debugging.
20647 @item set debug jit
20648 @cindex just-in-time compilation, debugging messages
20649 Turns on or off debugging messages from JIT debug support.
20650 @item show debug jit
20651 Displays the current state of @value{GDBN} JIT debugging.
20652 @item set debug lin-lwp
20653 @cindex @sc{gnu}/Linux LWP debug messages
20654 @cindex Linux lightweight processes
20655 Turns on or off debugging messages from the Linux LWP debug support.
20656 @item show debug lin-lwp
20657 Show the current state of Linux LWP debugging messages.
20658 @item set debug observer
20659 @cindex observer debugging info
20660 Turns on or off display of @value{GDBN} observer debugging. This
20661 includes info such as the notification of observable events.
20662 @item show debug observer
20663 Displays the current state of observer debugging.
20664 @item set debug overload
20665 @cindex C@t{++} overload debugging info
20666 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20667 info. This includes info such as ranking of functions, etc. The default
20669 @item show debug overload
20670 Displays the current state of displaying @value{GDBN} C@t{++} overload
20672 @cindex expression parser, debugging info
20673 @cindex debug expression parser
20674 @item set debug parser
20675 Turns on or off the display of expression parser debugging output.
20676 Internally, this sets the @code{yydebug} variable in the expression
20677 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20678 details. The default is off.
20679 @item show debug parser
20680 Show the current state of expression parser debugging.
20681 @cindex packets, reporting on stdout
20682 @cindex serial connections, debugging
20683 @cindex debug remote protocol
20684 @cindex remote protocol debugging
20685 @cindex display remote packets
20686 @item set debug remote
20687 Turns on or off display of reports on all packets sent back and forth across
20688 the serial line to the remote machine. The info is printed on the
20689 @value{GDBN} standard output stream. The default is off.
20690 @item show debug remote
20691 Displays the state of display of remote packets.
20692 @item set debug serial
20693 Turns on or off display of @value{GDBN} serial debugging info. The
20695 @item show debug serial
20696 Displays the current state of displaying @value{GDBN} serial debugging
20698 @item set debug solib-frv
20699 @cindex FR-V shared-library debugging
20700 Turns on or off debugging messages for FR-V shared-library code.
20701 @item show debug solib-frv
20702 Display the current state of FR-V shared-library code debugging
20704 @item set debug target
20705 @cindex target debugging info
20706 Turns on or off display of @value{GDBN} target debugging info. This info
20707 includes what is going on at the target level of GDB, as it happens. The
20708 default is 0. Set it to 1 to track events, and to 2 to also track the
20709 value of large memory transfers. Changes to this flag do not take effect
20710 until the next time you connect to a target or use the @code{run} command.
20711 @item show debug target
20712 Displays the current state of displaying @value{GDBN} target debugging
20714 @item set debug timestamp
20715 @cindex timestampping debugging info
20716 Turns on or off display of timestamps with @value{GDBN} debugging info.
20717 When enabled, seconds and microseconds are displayed before each debugging
20719 @item show debug timestamp
20720 Displays the current state of displaying timestamps with @value{GDBN}
20722 @item set debugvarobj
20723 @cindex variable object debugging info
20724 Turns on or off display of @value{GDBN} variable object debugging
20725 info. The default is off.
20726 @item show debugvarobj
20727 Displays the current state of displaying @value{GDBN} variable object
20729 @item set debug xml
20730 @cindex XML parser debugging
20731 Turns on or off debugging messages for built-in XML parsers.
20732 @item show debug xml
20733 Displays the current state of XML debugging messages.
20736 @node Other Misc Settings
20737 @section Other Miscellaneous Settings
20738 @cindex miscellaneous settings
20741 @kindex set interactive-mode
20742 @item set interactive-mode
20743 If @code{on}, forces @value{GDBN} to assume that GDB was started
20744 in a terminal. In practice, this means that @value{GDBN} should wait
20745 for the user to answer queries generated by commands entered at
20746 the command prompt. If @code{off}, forces @value{GDBN} to operate
20747 in the opposite mode, and it uses the default answers to all queries.
20748 If @code{auto} (the default), @value{GDBN} tries to determine whether
20749 its standard input is a terminal, and works in interactive-mode if it
20750 is, non-interactively otherwise.
20752 In the vast majority of cases, the debugger should be able to guess
20753 correctly which mode should be used. But this setting can be useful
20754 in certain specific cases, such as running a MinGW @value{GDBN}
20755 inside a cygwin window.
20757 @kindex show interactive-mode
20758 @item show interactive-mode
20759 Displays whether the debugger is operating in interactive mode or not.
20762 @node Extending GDB
20763 @chapter Extending @value{GDBN}
20764 @cindex extending GDB
20766 @value{GDBN} provides three mechanisms for extension. The first is based
20767 on composition of @value{GDBN} commands, the second is based on the
20768 Python scripting language, and the third is for defining new aliases of
20771 To facilitate the use of the first two extensions, @value{GDBN} is capable
20772 of evaluating the contents of a file. When doing so, @value{GDBN}
20773 can recognize which scripting language is being used by looking at
20774 the filename extension. Files with an unrecognized filename extension
20775 are always treated as a @value{GDBN} Command Files.
20776 @xref{Command Files,, Command files}.
20778 You can control how @value{GDBN} evaluates these files with the following
20782 @kindex set script-extension
20783 @kindex show script-extension
20784 @item set script-extension off
20785 All scripts are always evaluated as @value{GDBN} Command Files.
20787 @item set script-extension soft
20788 The debugger determines the scripting language based on filename
20789 extension. If this scripting language is supported, @value{GDBN}
20790 evaluates the script using that language. Otherwise, it evaluates
20791 the file as a @value{GDBN} Command File.
20793 @item set script-extension strict
20794 The debugger determines the scripting language based on filename
20795 extension, and evaluates the script using that language. If the
20796 language is not supported, then the evaluation fails.
20798 @item show script-extension
20799 Display the current value of the @code{script-extension} option.
20804 * Sequences:: Canned Sequences of Commands
20805 * Python:: Scripting @value{GDBN} using Python
20806 * Aliases:: Creating new spellings of existing commands
20810 @section Canned Sequences of Commands
20812 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20813 Command Lists}), @value{GDBN} provides two ways to store sequences of
20814 commands for execution as a unit: user-defined commands and command
20818 * Define:: How to define your own commands
20819 * Hooks:: Hooks for user-defined commands
20820 * Command Files:: How to write scripts of commands to be stored in a file
20821 * Output:: Commands for controlled output
20825 @subsection User-defined Commands
20827 @cindex user-defined command
20828 @cindex arguments, to user-defined commands
20829 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20830 which you assign a new name as a command. This is done with the
20831 @code{define} command. User commands may accept up to 10 arguments
20832 separated by whitespace. Arguments are accessed within the user command
20833 via @code{$arg0@dots{}$arg9}. A trivial example:
20837 print $arg0 + $arg1 + $arg2
20842 To execute the command use:
20849 This defines the command @code{adder}, which prints the sum of
20850 its three arguments. Note the arguments are text substitutions, so they may
20851 reference variables, use complex expressions, or even perform inferior
20854 @cindex argument count in user-defined commands
20855 @cindex how many arguments (user-defined commands)
20856 In addition, @code{$argc} may be used to find out how many arguments have
20857 been passed. This expands to a number in the range 0@dots{}10.
20862 print $arg0 + $arg1
20865 print $arg0 + $arg1 + $arg2
20873 @item define @var{commandname}
20874 Define a command named @var{commandname}. If there is already a command
20875 by that name, you are asked to confirm that you want to redefine it.
20876 @var{commandname} may be a bare command name consisting of letters,
20877 numbers, dashes, and underscores. It may also start with any predefined
20878 prefix command. For example, @samp{define target my-target} creates
20879 a user-defined @samp{target my-target} command.
20881 The definition of the command is made up of other @value{GDBN} command lines,
20882 which are given following the @code{define} command. The end of these
20883 commands is marked by a line containing @code{end}.
20886 @kindex end@r{ (user-defined commands)}
20887 @item document @var{commandname}
20888 Document the user-defined command @var{commandname}, so that it can be
20889 accessed by @code{help}. The command @var{commandname} must already be
20890 defined. This command reads lines of documentation just as @code{define}
20891 reads the lines of the command definition, ending with @code{end}.
20892 After the @code{document} command is finished, @code{help} on command
20893 @var{commandname} displays the documentation you have written.
20895 You may use the @code{document} command again to change the
20896 documentation of a command. Redefining the command with @code{define}
20897 does not change the documentation.
20899 @kindex dont-repeat
20900 @cindex don't repeat command
20902 Used inside a user-defined command, this tells @value{GDBN} that this
20903 command should not be repeated when the user hits @key{RET}
20904 (@pxref{Command Syntax, repeat last command}).
20906 @kindex help user-defined
20907 @item help user-defined
20908 List all user-defined commands, with the first line of the documentation
20913 @itemx show user @var{commandname}
20914 Display the @value{GDBN} commands used to define @var{commandname} (but
20915 not its documentation). If no @var{commandname} is given, display the
20916 definitions for all user-defined commands.
20918 @cindex infinite recursion in user-defined commands
20919 @kindex show max-user-call-depth
20920 @kindex set max-user-call-depth
20921 @item show max-user-call-depth
20922 @itemx set max-user-call-depth
20923 The value of @code{max-user-call-depth} controls how many recursion
20924 levels are allowed in user-defined commands before @value{GDBN} suspects an
20925 infinite recursion and aborts the command.
20928 In addition to the above commands, user-defined commands frequently
20929 use control flow commands, described in @ref{Command Files}.
20931 When user-defined commands are executed, the
20932 commands of the definition are not printed. An error in any command
20933 stops execution of the user-defined command.
20935 If used interactively, commands that would ask for confirmation proceed
20936 without asking when used inside a user-defined command. Many @value{GDBN}
20937 commands that normally print messages to say what they are doing omit the
20938 messages when used in a user-defined command.
20941 @subsection User-defined Command Hooks
20942 @cindex command hooks
20943 @cindex hooks, for commands
20944 @cindex hooks, pre-command
20947 You may define @dfn{hooks}, which are a special kind of user-defined
20948 command. Whenever you run the command @samp{foo}, if the user-defined
20949 command @samp{hook-foo} exists, it is executed (with no arguments)
20950 before that command.
20952 @cindex hooks, post-command
20954 A hook may also be defined which is run after the command you executed.
20955 Whenever you run the command @samp{foo}, if the user-defined command
20956 @samp{hookpost-foo} exists, it is executed (with no arguments) after
20957 that command. Post-execution hooks may exist simultaneously with
20958 pre-execution hooks, for the same command.
20960 It is valid for a hook to call the command which it hooks. If this
20961 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
20963 @c It would be nice if hookpost could be passed a parameter indicating
20964 @c if the command it hooks executed properly or not. FIXME!
20966 @kindex stop@r{, a pseudo-command}
20967 In addition, a pseudo-command, @samp{stop} exists. Defining
20968 (@samp{hook-stop}) makes the associated commands execute every time
20969 execution stops in your program: before breakpoint commands are run,
20970 displays are printed, or the stack frame is printed.
20972 For example, to ignore @code{SIGALRM} signals while
20973 single-stepping, but treat them normally during normal execution,
20978 handle SIGALRM nopass
20982 handle SIGALRM pass
20985 define hook-continue
20986 handle SIGALRM pass
20990 As a further example, to hook at the beginning and end of the @code{echo}
20991 command, and to add extra text to the beginning and end of the message,
20999 define hookpost-echo
21003 (@value{GDBP}) echo Hello World
21004 <<<---Hello World--->>>
21009 You can define a hook for any single-word command in @value{GDBN}, but
21010 not for command aliases; you should define a hook for the basic command
21011 name, e.g.@: @code{backtrace} rather than @code{bt}.
21012 @c FIXME! So how does Joe User discover whether a command is an alias
21014 You can hook a multi-word command by adding @code{hook-} or
21015 @code{hookpost-} to the last word of the command, e.g.@:
21016 @samp{define target hook-remote} to add a hook to @samp{target remote}.
21018 If an error occurs during the execution of your hook, execution of
21019 @value{GDBN} commands stops and @value{GDBN} issues a prompt
21020 (before the command that you actually typed had a chance to run).
21022 If you try to define a hook which does not match any known command, you
21023 get a warning from the @code{define} command.
21025 @node Command Files
21026 @subsection Command Files
21028 @cindex command files
21029 @cindex scripting commands
21030 A command file for @value{GDBN} is a text file made of lines that are
21031 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
21032 also be included. An empty line in a command file does nothing; it
21033 does not mean to repeat the last command, as it would from the
21036 You can request the execution of a command file with the @code{source}
21037 command. Note that the @code{source} command is also used to evaluate
21038 scripts that are not Command Files. The exact behavior can be configured
21039 using the @code{script-extension} setting.
21040 @xref{Extending GDB,, Extending GDB}.
21044 @cindex execute commands from a file
21045 @item source [-s] [-v] @var{filename}
21046 Execute the command file @var{filename}.
21049 The lines in a command file are generally executed sequentially,
21050 unless the order of execution is changed by one of the
21051 @emph{flow-control commands} described below. The commands are not
21052 printed as they are executed. An error in any command terminates
21053 execution of the command file and control is returned to the console.
21055 @value{GDBN} first searches for @var{filename} in the current directory.
21056 If the file is not found there, and @var{filename} does not specify a
21057 directory, then @value{GDBN} also looks for the file on the source search path
21058 (specified with the @samp{directory} command);
21059 except that @file{$cdir} is not searched because the compilation directory
21060 is not relevant to scripts.
21062 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
21063 on the search path even if @var{filename} specifies a directory.
21064 The search is done by appending @var{filename} to each element of the
21065 search path. So, for example, if @var{filename} is @file{mylib/myscript}
21066 and the search path contains @file{/home/user} then @value{GDBN} will
21067 look for the script @file{/home/user/mylib/myscript}.
21068 The search is also done if @var{filename} is an absolute path.
21069 For example, if @var{filename} is @file{/tmp/myscript} and
21070 the search path contains @file{/home/user} then @value{GDBN} will
21071 look for the script @file{/home/user/tmp/myscript}.
21072 For DOS-like systems, if @var{filename} contains a drive specification,
21073 it is stripped before concatenation. For example, if @var{filename} is
21074 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
21075 will look for the script @file{c:/tmp/myscript}.
21077 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
21078 each command as it is executed. The option must be given before
21079 @var{filename}, and is interpreted as part of the filename anywhere else.
21081 Commands that would ask for confirmation if used interactively proceed
21082 without asking when used in a command file. Many @value{GDBN} commands that
21083 normally print messages to say what they are doing omit the messages
21084 when called from command files.
21086 @value{GDBN} also accepts command input from standard input. In this
21087 mode, normal output goes to standard output and error output goes to
21088 standard error. Errors in a command file supplied on standard input do
21089 not terminate execution of the command file---execution continues with
21093 gdb < cmds > log 2>&1
21096 (The syntax above will vary depending on the shell used.) This example
21097 will execute commands from the file @file{cmds}. All output and errors
21098 would be directed to @file{log}.
21100 Since commands stored on command files tend to be more general than
21101 commands typed interactively, they frequently need to deal with
21102 complicated situations, such as different or unexpected values of
21103 variables and symbols, changes in how the program being debugged is
21104 built, etc. @value{GDBN} provides a set of flow-control commands to
21105 deal with these complexities. Using these commands, you can write
21106 complex scripts that loop over data structures, execute commands
21107 conditionally, etc.
21114 This command allows to include in your script conditionally executed
21115 commands. The @code{if} command takes a single argument, which is an
21116 expression to evaluate. It is followed by a series of commands that
21117 are executed only if the expression is true (its value is nonzero).
21118 There can then optionally be an @code{else} line, followed by a series
21119 of commands that are only executed if the expression was false. The
21120 end of the list is marked by a line containing @code{end}.
21124 This command allows to write loops. Its syntax is similar to
21125 @code{if}: the command takes a single argument, which is an expression
21126 to evaluate, and must be followed by the commands to execute, one per
21127 line, terminated by an @code{end}. These commands are called the
21128 @dfn{body} of the loop. The commands in the body of @code{while} are
21129 executed repeatedly as long as the expression evaluates to true.
21133 This command exits the @code{while} loop in whose body it is included.
21134 Execution of the script continues after that @code{while}s @code{end}
21137 @kindex loop_continue
21138 @item loop_continue
21139 This command skips the execution of the rest of the body of commands
21140 in the @code{while} loop in whose body it is included. Execution
21141 branches to the beginning of the @code{while} loop, where it evaluates
21142 the controlling expression.
21144 @kindex end@r{ (if/else/while commands)}
21146 Terminate the block of commands that are the body of @code{if},
21147 @code{else}, or @code{while} flow-control commands.
21152 @subsection Commands for Controlled Output
21154 During the execution of a command file or a user-defined command, normal
21155 @value{GDBN} output is suppressed; the only output that appears is what is
21156 explicitly printed by the commands in the definition. This section
21157 describes three commands useful for generating exactly the output you
21162 @item echo @var{text}
21163 @c I do not consider backslash-space a standard C escape sequence
21164 @c because it is not in ANSI.
21165 Print @var{text}. Nonprinting characters can be included in
21166 @var{text} using C escape sequences, such as @samp{\n} to print a
21167 newline. @strong{No newline is printed unless you specify one.}
21168 In addition to the standard C escape sequences, a backslash followed
21169 by a space stands for a space. This is useful for displaying a
21170 string with spaces at the beginning or the end, since leading and
21171 trailing spaces are otherwise trimmed from all arguments.
21172 To print @samp{@w{ }and foo =@w{ }}, use the command
21173 @samp{echo \@w{ }and foo = \@w{ }}.
21175 A backslash at the end of @var{text} can be used, as in C, to continue
21176 the command onto subsequent lines. For example,
21179 echo This is some text\n\
21180 which is continued\n\
21181 onto several lines.\n
21184 produces the same output as
21187 echo This is some text\n
21188 echo which is continued\n
21189 echo onto several lines.\n
21193 @item output @var{expression}
21194 Print the value of @var{expression} and nothing but that value: no
21195 newlines, no @samp{$@var{nn} = }. The value is not entered in the
21196 value history either. @xref{Expressions, ,Expressions}, for more information
21199 @item output/@var{fmt} @var{expression}
21200 Print the value of @var{expression} in format @var{fmt}. You can use
21201 the same formats as for @code{print}. @xref{Output Formats,,Output
21202 Formats}, for more information.
21205 @item printf @var{template}, @var{expressions}@dots{}
21206 Print the values of one or more @var{expressions} under the control of
21207 the string @var{template}. To print several values, make
21208 @var{expressions} be a comma-separated list of individual expressions,
21209 which may be either numbers or pointers. Their values are printed as
21210 specified by @var{template}, exactly as a C program would do by
21211 executing the code below:
21214 printf (@var{template}, @var{expressions}@dots{});
21217 As in @code{C} @code{printf}, ordinary characters in @var{template}
21218 are printed verbatim, while @dfn{conversion specification} introduced
21219 by the @samp{%} character cause subsequent @var{expressions} to be
21220 evaluated, their values converted and formatted according to type and
21221 style information encoded in the conversion specifications, and then
21224 For example, you can print two values in hex like this:
21227 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
21230 @code{printf} supports all the standard @code{C} conversion
21231 specifications, including the flags and modifiers between the @samp{%}
21232 character and the conversion letter, with the following exceptions:
21236 The argument-ordering modifiers, such as @samp{2$}, are not supported.
21239 The modifier @samp{*} is not supported for specifying precision or
21243 The @samp{'} flag (for separation of digits into groups according to
21244 @code{LC_NUMERIC'}) is not supported.
21247 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
21251 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
21254 The conversion letters @samp{a} and @samp{A} are not supported.
21258 Note that the @samp{ll} type modifier is supported only if the
21259 underlying @code{C} implementation used to build @value{GDBN} supports
21260 the @code{long long int} type, and the @samp{L} type modifier is
21261 supported only if @code{long double} type is available.
21263 As in @code{C}, @code{printf} supports simple backslash-escape
21264 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
21265 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
21266 single character. Octal and hexadecimal escape sequences are not
21269 Additionally, @code{printf} supports conversion specifications for DFP
21270 (@dfn{Decimal Floating Point}) types using the following length modifiers
21271 together with a floating point specifier.
21276 @samp{H} for printing @code{Decimal32} types.
21279 @samp{D} for printing @code{Decimal64} types.
21282 @samp{DD} for printing @code{Decimal128} types.
21285 If the underlying @code{C} implementation used to build @value{GDBN} has
21286 support for the three length modifiers for DFP types, other modifiers
21287 such as width and precision will also be available for @value{GDBN} to use.
21289 In case there is no such @code{C} support, no additional modifiers will be
21290 available and the value will be printed in the standard way.
21292 Here's an example of printing DFP types using the above conversion letters:
21294 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
21298 @item eval @var{template}, @var{expressions}@dots{}
21299 Convert the values of one or more @var{expressions} under the control of
21300 the string @var{template} to a command line, and call it.
21305 @section Scripting @value{GDBN} using Python
21306 @cindex python scripting
21307 @cindex scripting with python
21309 You can script @value{GDBN} using the @uref{http://www.python.org/,
21310 Python programming language}. This feature is available only if
21311 @value{GDBN} was configured using @option{--with-python}.
21313 @cindex python directory
21314 Python scripts used by @value{GDBN} should be installed in
21315 @file{@var{data-directory}/python}, where @var{data-directory} is
21316 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
21317 This directory, known as the @dfn{python directory},
21318 is automatically added to the Python Search Path in order to allow
21319 the Python interpreter to locate all scripts installed at this location.
21321 Additionally, @value{GDBN} commands and convenience functions which
21322 are written in Python and are located in the
21323 @file{@var{data-directory}/python/gdb/command} or
21324 @file{@var{data-directory}/python/gdb/function} directories are
21325 automatically imported when @value{GDBN} starts.
21328 * Python Commands:: Accessing Python from @value{GDBN}.
21329 * Python API:: Accessing @value{GDBN} from Python.
21330 * Auto-loading:: Automatically loading Python code.
21331 * Python modules:: Python modules provided by @value{GDBN}.
21334 @node Python Commands
21335 @subsection Python Commands
21336 @cindex python commands
21337 @cindex commands to access python
21339 @value{GDBN} provides one command for accessing the Python interpreter,
21340 and one related setting:
21344 @item python @r{[}@var{code}@r{]}
21345 The @code{python} command can be used to evaluate Python code.
21347 If given an argument, the @code{python} command will evaluate the
21348 argument as a Python command. For example:
21351 (@value{GDBP}) python print 23
21355 If you do not provide an argument to @code{python}, it will act as a
21356 multi-line command, like @code{define}. In this case, the Python
21357 script is made up of subsequent command lines, given after the
21358 @code{python} command. This command list is terminated using a line
21359 containing @code{end}. For example:
21362 (@value{GDBP}) python
21364 End with a line saying just "end".
21370 @kindex maint set python print-stack
21371 @item maint set python print-stack
21372 This command is now deprecated. Instead use @code{set python
21375 @kindex set python print-stack
21376 @item set python print-stack
21377 By default, @value{GDBN} will not print a stack trace when an error
21378 occurs in a Python script. This can be controlled using @code{set
21379 python print-stack}: if @code{on}, then Python stack printing is
21380 enabled; if @code{off}, the default, then Python stack printing is
21384 It is also possible to execute a Python script from the @value{GDBN}
21388 @item source @file{script-name}
21389 The script name must end with @samp{.py} and @value{GDBN} must be configured
21390 to recognize the script language based on filename extension using
21391 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
21393 @item python execfile ("script-name")
21394 This method is based on the @code{execfile} Python built-in function,
21395 and thus is always available.
21399 @subsection Python API
21401 @cindex programming in python
21403 @cindex python stdout
21404 @cindex python pagination
21405 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
21406 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
21407 A Python program which outputs to one of these streams may have its
21408 output interrupted by the user (@pxref{Screen Size}). In this
21409 situation, a Python @code{KeyboardInterrupt} exception is thrown.
21412 * Basic Python:: Basic Python Functions.
21413 * Exception Handling:: How Python exceptions are translated.
21414 * Values From Inferior:: Python representation of values.
21415 * Types In Python:: Python representation of types.
21416 * Pretty Printing API:: Pretty-printing values.
21417 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
21418 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
21419 * Inferiors In Python:: Python representation of inferiors (processes)
21420 * Events In Python:: Listening for events from @value{GDBN}.
21421 * Threads In Python:: Accessing inferior threads from Python.
21422 * Commands In Python:: Implementing new commands in Python.
21423 * Parameters In Python:: Adding new @value{GDBN} parameters.
21424 * Functions In Python:: Writing new convenience functions.
21425 * Progspaces In Python:: Program spaces.
21426 * Objfiles In Python:: Object files.
21427 * Frames In Python:: Accessing inferior stack frames from Python.
21428 * Blocks In Python:: Accessing frame blocks from Python.
21429 * Symbols In Python:: Python representation of symbols.
21430 * Symbol Tables In Python:: Python representation of symbol tables.
21431 * Lazy Strings In Python:: Python representation of lazy strings.
21432 * Breakpoints In Python:: Manipulating breakpoints using Python.
21436 @subsubsection Basic Python
21438 @cindex python functions
21439 @cindex python module
21441 @value{GDBN} introduces a new Python module, named @code{gdb}. All
21442 methods and classes added by @value{GDBN} are placed in this module.
21443 @value{GDBN} automatically @code{import}s the @code{gdb} module for
21444 use in all scripts evaluated by the @code{python} command.
21446 @findex gdb.PYTHONDIR
21447 @defvar gdb.PYTHONDIR
21448 A string containing the python directory (@pxref{Python}).
21451 @findex gdb.execute
21452 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
21453 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
21454 If a GDB exception happens while @var{command} runs, it is
21455 translated as described in @ref{Exception Handling,,Exception Handling}.
21457 @var{from_tty} specifies whether @value{GDBN} ought to consider this
21458 command as having originated from the user invoking it interactively.
21459 It must be a boolean value. If omitted, it defaults to @code{False}.
21461 By default, any output produced by @var{command} is sent to
21462 @value{GDBN}'s standard output. If the @var{to_string} parameter is
21463 @code{True}, then output will be collected by @code{gdb.execute} and
21464 returned as a string. The default is @code{False}, in which case the
21465 return value is @code{None}. If @var{to_string} is @code{True}, the
21466 @value{GDBN} virtual terminal will be temporarily set to unlimited width
21467 and height, and its pagination will be disabled; @pxref{Screen Size}.
21470 @findex gdb.breakpoints
21471 @defun gdb.breakpoints ()
21472 Return a sequence holding all of @value{GDBN}'s breakpoints.
21473 @xref{Breakpoints In Python}, for more information.
21476 @findex gdb.parameter
21477 @defun gdb.parameter (parameter)
21478 Return the value of a @value{GDBN} parameter. @var{parameter} is a
21479 string naming the parameter to look up; @var{parameter} may contain
21480 spaces if the parameter has a multi-part name. For example,
21481 @samp{print object} is a valid parameter name.
21483 If the named parameter does not exist, this function throws a
21484 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
21485 parameter's value is converted to a Python value of the appropriate
21486 type, and returned.
21489 @findex gdb.history
21490 @defun gdb.history (number)
21491 Return a value from @value{GDBN}'s value history (@pxref{Value
21492 History}). @var{number} indicates which history element to return.
21493 If @var{number} is negative, then @value{GDBN} will take its absolute value
21494 and count backward from the last element (i.e., the most recent element) to
21495 find the value to return. If @var{number} is zero, then @value{GDBN} will
21496 return the most recent element. If the element specified by @var{number}
21497 doesn't exist in the value history, a @code{gdb.error} exception will be
21500 If no exception is raised, the return value is always an instance of
21501 @code{gdb.Value} (@pxref{Values From Inferior}).
21504 @findex gdb.parse_and_eval
21505 @defun gdb.parse_and_eval (expression)
21506 Parse @var{expression} as an expression in the current language,
21507 evaluate it, and return the result as a @code{gdb.Value}.
21508 @var{expression} must be a string.
21510 This function can be useful when implementing a new command
21511 (@pxref{Commands In Python}), as it provides a way to parse the
21512 command's argument as an expression. It is also useful simply to
21513 compute values, for example, it is the only way to get the value of a
21514 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
21517 @findex gdb.post_event
21518 @defun gdb.post_event (event)
21519 Put @var{event}, a callable object taking no arguments, into
21520 @value{GDBN}'s internal event queue. This callable will be invoked at
21521 some later point, during @value{GDBN}'s event processing. Events
21522 posted using @code{post_event} will be run in the order in which they
21523 were posted; however, there is no way to know when they will be
21524 processed relative to other events inside @value{GDBN}.
21526 @value{GDBN} is not thread-safe. If your Python program uses multiple
21527 threads, you must be careful to only call @value{GDBN}-specific
21528 functions in the main @value{GDBN} thread. @code{post_event} ensures
21532 (@value{GDBP}) python
21536 > def __init__(self, message):
21537 > self.message = message;
21538 > def __call__(self):
21539 > gdb.write(self.message)
21541 >class MyThread1 (threading.Thread):
21543 > gdb.post_event(Writer("Hello "))
21545 >class MyThread2 (threading.Thread):
21547 > gdb.post_event(Writer("World\n"))
21549 >MyThread1().start()
21550 >MyThread2().start()
21552 (@value{GDBP}) Hello World
21557 @defun gdb.write (string @r{[}, stream{]})
21558 Print a string to @value{GDBN}'s paginated output stream. The
21559 optional @var{stream} determines the stream to print to. The default
21560 stream is @value{GDBN}'s standard output stream. Possible stream
21567 @value{GDBN}'s standard output stream.
21572 @value{GDBN}'s standard error stream.
21577 @value{GDBN}'s log stream (@pxref{Logging Output}).
21580 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
21581 call this function and will automatically direct the output to the
21586 @defun gdb.flush ()
21587 Flush the buffer of a @value{GDBN} paginated stream so that the
21588 contents are displayed immediately. @value{GDBN} will flush the
21589 contents of a stream automatically when it encounters a newline in the
21590 buffer. The optional @var{stream} determines the stream to flush. The
21591 default stream is @value{GDBN}'s standard output stream. Possible
21598 @value{GDBN}'s standard output stream.
21603 @value{GDBN}'s standard error stream.
21608 @value{GDBN}'s log stream (@pxref{Logging Output}).
21612 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21613 call this function for the relevant stream.
21616 @findex gdb.target_charset
21617 @defun gdb.target_charset ()
21618 Return the name of the current target character set (@pxref{Character
21619 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21620 that @samp{auto} is never returned.
21623 @findex gdb.target_wide_charset
21624 @defun gdb.target_wide_charset ()
21625 Return the name of the current target wide character set
21626 (@pxref{Character Sets}). This differs from
21627 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21631 @findex gdb.solib_name
21632 @defun gdb.solib_name (address)
21633 Return the name of the shared library holding the given @var{address}
21634 as a string, or @code{None}.
21637 @findex gdb.decode_line
21638 @defun gdb.decode_line @r{[}expression@r{]}
21639 Return locations of the line specified by @var{expression}, or of the
21640 current line if no argument was given. This function returns a Python
21641 tuple containing two elements. The first element contains a string
21642 holding any unparsed section of @var{expression} (or @code{None} if
21643 the expression has been fully parsed). The second element contains
21644 either @code{None} or another tuple that contains all the locations
21645 that match the expression represented as @code{gdb.Symtab_and_line}
21646 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21647 provided, it is decoded the way that @value{GDBN}'s inbuilt
21648 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21651 @defun gdb.prompt_hook (current_prompt)
21652 @anchor{prompt_hook}
21654 If @var{prompt_hook} is callable, @value{GDBN} will call the method
21655 assigned to this operation before a prompt is displayed by
21658 The parameter @code{current_prompt} contains the current @value{GDBN}
21659 prompt. This method must return a Python string, or @code{None}. If
21660 a string is returned, the @value{GDBN} prompt will be set to that
21661 string. If @code{None} is returned, @value{GDBN} will continue to use
21662 the current prompt.
21664 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
21665 such as those used by readline for command input, and annotation
21666 related prompts are prohibited from being changed.
21669 @node Exception Handling
21670 @subsubsection Exception Handling
21671 @cindex python exceptions
21672 @cindex exceptions, python
21674 When executing the @code{python} command, Python exceptions
21675 uncaught within the Python code are translated to calls to
21676 @value{GDBN} error-reporting mechanism. If the command that called
21677 @code{python} does not handle the error, @value{GDBN} will
21678 terminate it and print an error message containing the Python
21679 exception name, the associated value, and the Python call stack
21680 backtrace at the point where the exception was raised. Example:
21683 (@value{GDBP}) python print foo
21684 Traceback (most recent call last):
21685 File "<string>", line 1, in <module>
21686 NameError: name 'foo' is not defined
21689 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21690 Python code are converted to Python exceptions. The type of the
21691 Python exception depends on the error.
21695 This is the base class for most exceptions generated by @value{GDBN}.
21696 It is derived from @code{RuntimeError}, for compatibility with earlier
21697 versions of @value{GDBN}.
21699 If an error occurring in @value{GDBN} does not fit into some more
21700 specific category, then the generated exception will have this type.
21702 @item gdb.MemoryError
21703 This is a subclass of @code{gdb.error} which is thrown when an
21704 operation tried to access invalid memory in the inferior.
21706 @item KeyboardInterrupt
21707 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21708 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21711 In all cases, your exception handler will see the @value{GDBN} error
21712 message as its value and the Python call stack backtrace at the Python
21713 statement closest to where the @value{GDBN} error occured as the
21716 @findex gdb.GdbError
21717 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21718 it is useful to be able to throw an exception that doesn't cause a
21719 traceback to be printed. For example, the user may have invoked the
21720 command incorrectly. Use the @code{gdb.GdbError} exception
21721 to handle this case. Example:
21725 >class HelloWorld (gdb.Command):
21726 > """Greet the whole world."""
21727 > def __init__ (self):
21728 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21729 > def invoke (self, args, from_tty):
21730 > argv = gdb.string_to_argv (args)
21731 > if len (argv) != 0:
21732 > raise gdb.GdbError ("hello-world takes no arguments")
21733 > print "Hello, World!"
21736 (gdb) hello-world 42
21737 hello-world takes no arguments
21740 @node Values From Inferior
21741 @subsubsection Values From Inferior
21742 @cindex values from inferior, with Python
21743 @cindex python, working with values from inferior
21745 @cindex @code{gdb.Value}
21746 @value{GDBN} provides values it obtains from the inferior program in
21747 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21748 for its internal bookkeeping of the inferior's values, and for
21749 fetching values when necessary.
21751 Inferior values that are simple scalars can be used directly in
21752 Python expressions that are valid for the value's data type. Here's
21753 an example for an integer or floating-point value @code{some_val}:
21760 As result of this, @code{bar} will also be a @code{gdb.Value} object
21761 whose values are of the same type as those of @code{some_val}.
21763 Inferior values that are structures or instances of some class can
21764 be accessed using the Python @dfn{dictionary syntax}. For example, if
21765 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21766 can access its @code{foo} element with:
21769 bar = some_val['foo']
21772 Again, @code{bar} will also be a @code{gdb.Value} object.
21774 A @code{gdb.Value} that represents a function can be executed via
21775 inferior function call. Any arguments provided to the call must match
21776 the function's prototype, and must be provided in the order specified
21779 For example, @code{some_val} is a @code{gdb.Value} instance
21780 representing a function that takes two integers as arguments. To
21781 execute this function, call it like so:
21784 result = some_val (10,20)
21787 Any values returned from a function call will be stored as a
21790 The following attributes are provided:
21793 @defvar Value.address
21794 If this object is addressable, this read-only attribute holds a
21795 @code{gdb.Value} object representing the address. Otherwise,
21796 this attribute holds @code{None}.
21799 @cindex optimized out value in Python
21800 @defvar Value.is_optimized_out
21801 This read-only boolean attribute is true if the compiler optimized out
21802 this value, thus it is not available for fetching from the inferior.
21806 The type of this @code{gdb.Value}. The value of this attribute is a
21807 @code{gdb.Type} object (@pxref{Types In Python}).
21810 @defvar Value.dynamic_type
21811 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21812 type information (@acronym{RTTI}) to determine the dynamic type of the
21813 value. If this value is of class type, it will return the class in
21814 which the value is embedded, if any. If this value is of pointer or
21815 reference to a class type, it will compute the dynamic type of the
21816 referenced object, and return a pointer or reference to that type,
21817 respectively. In all other cases, it will return the value's static
21820 Note that this feature will only work when debugging a C@t{++} program
21821 that includes @acronym{RTTI} for the object in question. Otherwise,
21822 it will just return the static type of the value as in @kbd{ptype foo}
21823 (@pxref{Symbols, ptype}).
21826 @defvar Value.is_lazy
21827 The value of this read-only boolean attribute is @code{True} if this
21828 @code{gdb.Value} has not yet been fetched from the inferior.
21829 @value{GDBN} does not fetch values until necessary, for efficiency.
21833 myval = gdb.parse_and_eval ('somevar')
21836 The value of @code{somevar} is not fetched at this time. It will be
21837 fetched when the value is needed, or when the @code{fetch_lazy}
21842 The following methods are provided:
21845 @defun Value.__init__ (@var{val})
21846 Many Python values can be converted directly to a @code{gdb.Value} via
21847 this object initializer. Specifically:
21850 @item Python boolean
21851 A Python boolean is converted to the boolean type from the current
21854 @item Python integer
21855 A Python integer is converted to the C @code{long} type for the
21856 current architecture.
21859 A Python long is converted to the C @code{long long} type for the
21860 current architecture.
21863 A Python float is converted to the C @code{double} type for the
21864 current architecture.
21866 @item Python string
21867 A Python string is converted to a target string, using the current
21870 @item @code{gdb.Value}
21871 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
21873 @item @code{gdb.LazyString}
21874 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
21875 Python}), then the lazy string's @code{value} method is called, and
21876 its result is used.
21880 @defun Value.cast (type)
21881 Return a new instance of @code{gdb.Value} that is the result of
21882 casting this instance to the type described by @var{type}, which must
21883 be a @code{gdb.Type} object. If the cast cannot be performed for some
21884 reason, this method throws an exception.
21887 @defun Value.dereference ()
21888 For pointer data types, this method returns a new @code{gdb.Value} object
21889 whose contents is the object pointed to by the pointer. For example, if
21890 @code{foo} is a C pointer to an @code{int}, declared in your C program as
21897 then you can use the corresponding @code{gdb.Value} to access what
21898 @code{foo} points to like this:
21901 bar = foo.dereference ()
21904 The result @code{bar} will be a @code{gdb.Value} object holding the
21905 value pointed to by @code{foo}.
21908 @defun Value.dynamic_cast (type)
21909 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
21910 operator were used. Consult a C@t{++} reference for details.
21913 @defun Value.reinterpret_cast (type)
21914 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
21915 operator were used. Consult a C@t{++} reference for details.
21918 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
21919 If this @code{gdb.Value} represents a string, then this method
21920 converts the contents to a Python string. Otherwise, this method will
21921 throw an exception.
21923 Strings are recognized in a language-specific way; whether a given
21924 @code{gdb.Value} represents a string is determined by the current
21927 For C-like languages, a value is a string if it is a pointer to or an
21928 array of characters or ints. The string is assumed to be terminated
21929 by a zero of the appropriate width. However if the optional length
21930 argument is given, the string will be converted to that given length,
21931 ignoring any embedded zeros that the string may contain.
21933 If the optional @var{encoding} argument is given, it must be a string
21934 naming the encoding of the string in the @code{gdb.Value}, such as
21935 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
21936 the same encodings as the corresponding argument to Python's
21937 @code{string.decode} method, and the Python codec machinery will be used
21938 to convert the string. If @var{encoding} is not given, or if
21939 @var{encoding} is the empty string, then either the @code{target-charset}
21940 (@pxref{Character Sets}) will be used, or a language-specific encoding
21941 will be used, if the current language is able to supply one.
21943 The optional @var{errors} argument is the same as the corresponding
21944 argument to Python's @code{string.decode} method.
21946 If the optional @var{length} argument is given, the string will be
21947 fetched and converted to the given length.
21950 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
21951 If this @code{gdb.Value} represents a string, then this method
21952 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
21953 In Python}). Otherwise, this method will throw an exception.
21955 If the optional @var{encoding} argument is given, it must be a string
21956 naming the encoding of the @code{gdb.LazyString}. Some examples are:
21957 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
21958 @var{encoding} argument is an encoding that @value{GDBN} does
21959 recognize, @value{GDBN} will raise an error.
21961 When a lazy string is printed, the @value{GDBN} encoding machinery is
21962 used to convert the string during printing. If the optional
21963 @var{encoding} argument is not provided, or is an empty string,
21964 @value{GDBN} will automatically select the encoding most suitable for
21965 the string type. For further information on encoding in @value{GDBN}
21966 please see @ref{Character Sets}.
21968 If the optional @var{length} argument is given, the string will be
21969 fetched and encoded to the length of characters specified. If
21970 the @var{length} argument is not provided, the string will be fetched
21971 and encoded until a null of appropriate width is found.
21974 @defun Value.fetch_lazy ()
21975 If the @code{gdb.Value} object is currently a lazy value
21976 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
21977 fetched from the inferior. Any errors that occur in the process
21978 will produce a Python exception.
21980 If the @code{gdb.Value} object is not a lazy value, this method
21983 This method does not return a value.
21988 @node Types In Python
21989 @subsubsection Types In Python
21990 @cindex types in Python
21991 @cindex Python, working with types
21994 @value{GDBN} represents types from the inferior using the class
21997 The following type-related functions are available in the @code{gdb}
22000 @findex gdb.lookup_type
22001 @defun gdb.lookup_type (name @r{[}, block@r{]})
22002 This function looks up a type by name. @var{name} is the name of the
22003 type to look up. It must be a string.
22005 If @var{block} is given, then @var{name} is looked up in that scope.
22006 Otherwise, it is searched for globally.
22008 Ordinarily, this function will return an instance of @code{gdb.Type}.
22009 If the named type cannot be found, it will throw an exception.
22012 If the type is a structure or class type, or an enum type, the fields
22013 of that type can be accessed using the Python @dfn{dictionary syntax}.
22014 For example, if @code{some_type} is a @code{gdb.Type} instance holding
22015 a structure type, you can access its @code{foo} field with:
22018 bar = some_type['foo']
22021 @code{bar} will be a @code{gdb.Field} object; see below under the
22022 description of the @code{Type.fields} method for a description of the
22023 @code{gdb.Field} class.
22025 An instance of @code{Type} has the following attributes:
22029 The type code for this type. The type code will be one of the
22030 @code{TYPE_CODE_} constants defined below.
22033 @defvar Type.sizeof
22034 The size of this type, in target @code{char} units. Usually, a
22035 target's @code{char} type will be an 8-bit byte. However, on some
22036 unusual platforms, this type may have a different size.
22040 The tag name for this type. The tag name is the name after
22041 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
22042 languages have this concept. If this type has no tag name, then
22043 @code{None} is returned.
22047 The following methods are provided:
22050 @defun Type.fields ()
22051 For structure and union types, this method returns the fields. Range
22052 types have two fields, the minimum and maximum values. Enum types
22053 have one field per enum constant. Function and method types have one
22054 field per parameter. The base types of C@t{++} classes are also
22055 represented as fields. If the type has no fields, or does not fit
22056 into one of these categories, an empty sequence will be returned.
22058 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
22061 This attribute is not available for @code{static} fields (as in
22062 C@t{++} or Java). For non-@code{static} fields, the value is the bit
22063 position of the field. For @code{enum} fields, the value is the
22064 enumeration member's integer representation.
22067 The name of the field, or @code{None} for anonymous fields.
22070 This is @code{True} if the field is artificial, usually meaning that
22071 it was provided by the compiler and not the user. This attribute is
22072 always provided, and is @code{False} if the field is not artificial.
22074 @item is_base_class
22075 This is @code{True} if the field represents a base class of a C@t{++}
22076 structure. This attribute is always provided, and is @code{False}
22077 if the field is not a base class of the type that is the argument of
22078 @code{fields}, or if that type was not a C@t{++} class.
22081 If the field is packed, or is a bitfield, then this will have a
22082 non-zero value, which is the size of the field in bits. Otherwise,
22083 this will be zero; in this case the field's size is given by its type.
22086 The type of the field. This is usually an instance of @code{Type},
22087 but it can be @code{None} in some situations.
22091 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
22092 Return a new @code{gdb.Type} object which represents an array of this
22093 type. If one argument is given, it is the inclusive upper bound of
22094 the array; in this case the lower bound is zero. If two arguments are
22095 given, the first argument is the lower bound of the array, and the
22096 second argument is the upper bound of the array. An array's length
22097 must not be negative, but the bounds can be.
22100 @defun Type.const ()
22101 Return a new @code{gdb.Type} object which represents a
22102 @code{const}-qualified variant of this type.
22105 @defun Type.volatile ()
22106 Return a new @code{gdb.Type} object which represents a
22107 @code{volatile}-qualified variant of this type.
22110 @defun Type.unqualified ()
22111 Return a new @code{gdb.Type} object which represents an unqualified
22112 variant of this type. That is, the result is neither @code{const} nor
22116 @defun Type.range ()
22117 Return a Python @code{Tuple} object that contains two elements: the
22118 low bound of the argument type and the high bound of that type. If
22119 the type does not have a range, @value{GDBN} will raise a
22120 @code{gdb.error} exception (@pxref{Exception Handling}).
22123 @defun Type.reference ()
22124 Return a new @code{gdb.Type} object which represents a reference to this
22128 @defun Type.pointer ()
22129 Return a new @code{gdb.Type} object which represents a pointer to this
22133 @defun Type.strip_typedefs ()
22134 Return a new @code{gdb.Type} that represents the real type,
22135 after removing all layers of typedefs.
22138 @defun Type.target ()
22139 Return a new @code{gdb.Type} object which represents the target type
22142 For a pointer type, the target type is the type of the pointed-to
22143 object. For an array type (meaning C-like arrays), the target type is
22144 the type of the elements of the array. For a function or method type,
22145 the target type is the type of the return value. For a complex type,
22146 the target type is the type of the elements. For a typedef, the
22147 target type is the aliased type.
22149 If the type does not have a target, this method will throw an
22153 @defun Type.template_argument (n @r{[}, block@r{]})
22154 If this @code{gdb.Type} is an instantiation of a template, this will
22155 return a new @code{gdb.Type} which represents the type of the
22156 @var{n}th template argument.
22158 If this @code{gdb.Type} is not a template type, this will throw an
22159 exception. Ordinarily, only C@t{++} code will have template types.
22161 If @var{block} is given, then @var{name} is looked up in that scope.
22162 Otherwise, it is searched for globally.
22167 Each type has a code, which indicates what category this type falls
22168 into. The available type categories are represented by constants
22169 defined in the @code{gdb} module:
22172 @findex TYPE_CODE_PTR
22173 @findex gdb.TYPE_CODE_PTR
22174 @item gdb.TYPE_CODE_PTR
22175 The type is a pointer.
22177 @findex TYPE_CODE_ARRAY
22178 @findex gdb.TYPE_CODE_ARRAY
22179 @item gdb.TYPE_CODE_ARRAY
22180 The type is an array.
22182 @findex TYPE_CODE_STRUCT
22183 @findex gdb.TYPE_CODE_STRUCT
22184 @item gdb.TYPE_CODE_STRUCT
22185 The type is a structure.
22187 @findex TYPE_CODE_UNION
22188 @findex gdb.TYPE_CODE_UNION
22189 @item gdb.TYPE_CODE_UNION
22190 The type is a union.
22192 @findex TYPE_CODE_ENUM
22193 @findex gdb.TYPE_CODE_ENUM
22194 @item gdb.TYPE_CODE_ENUM
22195 The type is an enum.
22197 @findex TYPE_CODE_FLAGS
22198 @findex gdb.TYPE_CODE_FLAGS
22199 @item gdb.TYPE_CODE_FLAGS
22200 A bit flags type, used for things such as status registers.
22202 @findex TYPE_CODE_FUNC
22203 @findex gdb.TYPE_CODE_FUNC
22204 @item gdb.TYPE_CODE_FUNC
22205 The type is a function.
22207 @findex TYPE_CODE_INT
22208 @findex gdb.TYPE_CODE_INT
22209 @item gdb.TYPE_CODE_INT
22210 The type is an integer type.
22212 @findex TYPE_CODE_FLT
22213 @findex gdb.TYPE_CODE_FLT
22214 @item gdb.TYPE_CODE_FLT
22215 A floating point type.
22217 @findex TYPE_CODE_VOID
22218 @findex gdb.TYPE_CODE_VOID
22219 @item gdb.TYPE_CODE_VOID
22220 The special type @code{void}.
22222 @findex TYPE_CODE_SET
22223 @findex gdb.TYPE_CODE_SET
22224 @item gdb.TYPE_CODE_SET
22227 @findex TYPE_CODE_RANGE
22228 @findex gdb.TYPE_CODE_RANGE
22229 @item gdb.TYPE_CODE_RANGE
22230 A range type, that is, an integer type with bounds.
22232 @findex TYPE_CODE_STRING
22233 @findex gdb.TYPE_CODE_STRING
22234 @item gdb.TYPE_CODE_STRING
22235 A string type. Note that this is only used for certain languages with
22236 language-defined string types; C strings are not represented this way.
22238 @findex TYPE_CODE_BITSTRING
22239 @findex gdb.TYPE_CODE_BITSTRING
22240 @item gdb.TYPE_CODE_BITSTRING
22243 @findex TYPE_CODE_ERROR
22244 @findex gdb.TYPE_CODE_ERROR
22245 @item gdb.TYPE_CODE_ERROR
22246 An unknown or erroneous type.
22248 @findex TYPE_CODE_METHOD
22249 @findex gdb.TYPE_CODE_METHOD
22250 @item gdb.TYPE_CODE_METHOD
22251 A method type, as found in C@t{++} or Java.
22253 @findex TYPE_CODE_METHODPTR
22254 @findex gdb.TYPE_CODE_METHODPTR
22255 @item gdb.TYPE_CODE_METHODPTR
22256 A pointer-to-member-function.
22258 @findex TYPE_CODE_MEMBERPTR
22259 @findex gdb.TYPE_CODE_MEMBERPTR
22260 @item gdb.TYPE_CODE_MEMBERPTR
22261 A pointer-to-member.
22263 @findex TYPE_CODE_REF
22264 @findex gdb.TYPE_CODE_REF
22265 @item gdb.TYPE_CODE_REF
22268 @findex TYPE_CODE_CHAR
22269 @findex gdb.TYPE_CODE_CHAR
22270 @item gdb.TYPE_CODE_CHAR
22273 @findex TYPE_CODE_BOOL
22274 @findex gdb.TYPE_CODE_BOOL
22275 @item gdb.TYPE_CODE_BOOL
22278 @findex TYPE_CODE_COMPLEX
22279 @findex gdb.TYPE_CODE_COMPLEX
22280 @item gdb.TYPE_CODE_COMPLEX
22281 A complex float type.
22283 @findex TYPE_CODE_TYPEDEF
22284 @findex gdb.TYPE_CODE_TYPEDEF
22285 @item gdb.TYPE_CODE_TYPEDEF
22286 A typedef to some other type.
22288 @findex TYPE_CODE_NAMESPACE
22289 @findex gdb.TYPE_CODE_NAMESPACE
22290 @item gdb.TYPE_CODE_NAMESPACE
22291 A C@t{++} namespace.
22293 @findex TYPE_CODE_DECFLOAT
22294 @findex gdb.TYPE_CODE_DECFLOAT
22295 @item gdb.TYPE_CODE_DECFLOAT
22296 A decimal floating point type.
22298 @findex TYPE_CODE_INTERNAL_FUNCTION
22299 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
22300 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
22301 A function internal to @value{GDBN}. This is the type used to represent
22302 convenience functions.
22305 Further support for types is provided in the @code{gdb.types}
22306 Python module (@pxref{gdb.types}).
22308 @node Pretty Printing API
22309 @subsubsection Pretty Printing API
22311 An example output is provided (@pxref{Pretty Printing}).
22313 A pretty-printer is just an object that holds a value and implements a
22314 specific interface, defined here.
22316 @defun pretty_printer.children (self)
22317 @value{GDBN} will call this method on a pretty-printer to compute the
22318 children of the pretty-printer's value.
22320 This method must return an object conforming to the Python iterator
22321 protocol. Each item returned by the iterator must be a tuple holding
22322 two elements. The first element is the ``name'' of the child; the
22323 second element is the child's value. The value can be any Python
22324 object which is convertible to a @value{GDBN} value.
22326 This method is optional. If it does not exist, @value{GDBN} will act
22327 as though the value has no children.
22330 @defun pretty_printer.display_hint (self)
22331 The CLI may call this method and use its result to change the
22332 formatting of a value. The result will also be supplied to an MI
22333 consumer as a @samp{displayhint} attribute of the variable being
22336 This method is optional. If it does exist, this method must return a
22339 Some display hints are predefined by @value{GDBN}:
22343 Indicate that the object being printed is ``array-like''. The CLI
22344 uses this to respect parameters such as @code{set print elements} and
22345 @code{set print array}.
22348 Indicate that the object being printed is ``map-like'', and that the
22349 children of this value can be assumed to alternate between keys and
22353 Indicate that the object being printed is ``string-like''. If the
22354 printer's @code{to_string} method returns a Python string of some
22355 kind, then @value{GDBN} will call its internal language-specific
22356 string-printing function to format the string. For the CLI this means
22357 adding quotation marks, possibly escaping some characters, respecting
22358 @code{set print elements}, and the like.
22362 @defun pretty_printer.to_string (self)
22363 @value{GDBN} will call this method to display the string
22364 representation of the value passed to the object's constructor.
22366 When printing from the CLI, if the @code{to_string} method exists,
22367 then @value{GDBN} will prepend its result to the values returned by
22368 @code{children}. Exactly how this formatting is done is dependent on
22369 the display hint, and may change as more hints are added. Also,
22370 depending on the print settings (@pxref{Print Settings}), the CLI may
22371 print just the result of @code{to_string} in a stack trace, omitting
22372 the result of @code{children}.
22374 If this method returns a string, it is printed verbatim.
22376 Otherwise, if this method returns an instance of @code{gdb.Value},
22377 then @value{GDBN} prints this value. This may result in a call to
22378 another pretty-printer.
22380 If instead the method returns a Python value which is convertible to a
22381 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
22382 the resulting value. Again, this may result in a call to another
22383 pretty-printer. Python scalars (integers, floats, and booleans) and
22384 strings are convertible to @code{gdb.Value}; other types are not.
22386 Finally, if this method returns @code{None} then no further operations
22387 are peformed in this method and nothing is printed.
22389 If the result is not one of these types, an exception is raised.
22392 @value{GDBN} provides a function which can be used to look up the
22393 default pretty-printer for a @code{gdb.Value}:
22395 @findex gdb.default_visualizer
22396 @defun gdb.default_visualizer (value)
22397 This function takes a @code{gdb.Value} object as an argument. If a
22398 pretty-printer for this value exists, then it is returned. If no such
22399 printer exists, then this returns @code{None}.
22402 @node Selecting Pretty-Printers
22403 @subsubsection Selecting Pretty-Printers
22405 The Python list @code{gdb.pretty_printers} contains an array of
22406 functions or callable objects that have been registered via addition
22407 as a pretty-printer. Printers in this list are called @code{global}
22408 printers, they're available when debugging all inferiors.
22409 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
22410 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
22413 Each function on these lists is passed a single @code{gdb.Value}
22414 argument and should return a pretty-printer object conforming to the
22415 interface definition above (@pxref{Pretty Printing API}). If a function
22416 cannot create a pretty-printer for the value, it should return
22419 @value{GDBN} first checks the @code{pretty_printers} attribute of each
22420 @code{gdb.Objfile} in the current program space and iteratively calls
22421 each enabled lookup routine in the list for that @code{gdb.Objfile}
22422 until it receives a pretty-printer object.
22423 If no pretty-printer is found in the objfile lists, @value{GDBN} then
22424 searches the pretty-printer list of the current program space,
22425 calling each enabled function until an object is returned.
22426 After these lists have been exhausted, it tries the global
22427 @code{gdb.pretty_printers} list, again calling each enabled function until an
22428 object is returned.
22430 The order in which the objfiles are searched is not specified. For a
22431 given list, functions are always invoked from the head of the list,
22432 and iterated over sequentially until the end of the list, or a printer
22433 object is returned.
22435 For various reasons a pretty-printer may not work.
22436 For example, the underlying data structure may have changed and
22437 the pretty-printer is out of date.
22439 The consequences of a broken pretty-printer are severe enough that
22440 @value{GDBN} provides support for enabling and disabling individual
22441 printers. For example, if @code{print frame-arguments} is on,
22442 a backtrace can become highly illegible if any argument is printed
22443 with a broken printer.
22445 Pretty-printers are enabled and disabled by attaching an @code{enabled}
22446 attribute to the registered function or callable object. If this attribute
22447 is present and its value is @code{False}, the printer is disabled, otherwise
22448 the printer is enabled.
22450 @node Writing a Pretty-Printer
22451 @subsubsection Writing a Pretty-Printer
22452 @cindex writing a pretty-printer
22454 A pretty-printer consists of two parts: a lookup function to detect
22455 if the type is supported, and the printer itself.
22457 Here is an example showing how a @code{std::string} printer might be
22458 written. @xref{Pretty Printing API}, for details on the API this class
22462 class StdStringPrinter(object):
22463 "Print a std::string"
22465 def __init__(self, val):
22468 def to_string(self):
22469 return self.val['_M_dataplus']['_M_p']
22471 def display_hint(self):
22475 And here is an example showing how a lookup function for the printer
22476 example above might be written.
22479 def str_lookup_function(val):
22480 lookup_tag = val.type.tag
22481 if lookup_tag == None:
22483 regex = re.compile("^std::basic_string<char,.*>$")
22484 if regex.match(lookup_tag):
22485 return StdStringPrinter(val)
22489 The example lookup function extracts the value's type, and attempts to
22490 match it to a type that it can pretty-print. If it is a type the
22491 printer can pretty-print, it will return a printer object. If not, it
22492 returns @code{None}.
22494 We recommend that you put your core pretty-printers into a Python
22495 package. If your pretty-printers are for use with a library, we
22496 further recommend embedding a version number into the package name.
22497 This practice will enable @value{GDBN} to load multiple versions of
22498 your pretty-printers at the same time, because they will have
22501 You should write auto-loaded code (@pxref{Auto-loading}) such that it
22502 can be evaluated multiple times without changing its meaning. An
22503 ideal auto-load file will consist solely of @code{import}s of your
22504 printer modules, followed by a call to a register pretty-printers with
22505 the current objfile.
22507 Taken as a whole, this approach will scale nicely to multiple
22508 inferiors, each potentially using a different library version.
22509 Embedding a version number in the Python package name will ensure that
22510 @value{GDBN} is able to load both sets of printers simultaneously.
22511 Then, because the search for pretty-printers is done by objfile, and
22512 because your auto-loaded code took care to register your library's
22513 printers with a specific objfile, @value{GDBN} will find the correct
22514 printers for the specific version of the library used by each
22517 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
22518 this code might appear in @code{gdb.libstdcxx.v6}:
22521 def register_printers(objfile):
22522 objfile.pretty_printers.add(str_lookup_function)
22526 And then the corresponding contents of the auto-load file would be:
22529 import gdb.libstdcxx.v6
22530 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
22533 The previous example illustrates a basic pretty-printer.
22534 There are a few things that can be improved on.
22535 The printer doesn't have a name, making it hard to identify in a
22536 list of installed printers. The lookup function has a name, but
22537 lookup functions can have arbitrary, even identical, names.
22539 Second, the printer only handles one type, whereas a library typically has
22540 several types. One could install a lookup function for each desired type
22541 in the library, but one could also have a single lookup function recognize
22542 several types. The latter is the conventional way this is handled.
22543 If a pretty-printer can handle multiple data types, then its
22544 @dfn{subprinters} are the printers for the individual data types.
22546 The @code{gdb.printing} module provides a formal way of solving these
22547 problems (@pxref{gdb.printing}).
22548 Here is another example that handles multiple types.
22550 These are the types we are going to pretty-print:
22553 struct foo @{ int a, b; @};
22554 struct bar @{ struct foo x, y; @};
22557 Here are the printers:
22561 """Print a foo object."""
22563 def __init__(self, val):
22566 def to_string(self):
22567 return ("a=<" + str(self.val["a"]) +
22568 "> b=<" + str(self.val["b"]) + ">")
22571 """Print a bar object."""
22573 def __init__(self, val):
22576 def to_string(self):
22577 return ("x=<" + str(self.val["x"]) +
22578 "> y=<" + str(self.val["y"]) + ">")
22581 This example doesn't need a lookup function, that is handled by the
22582 @code{gdb.printing} module. Instead a function is provided to build up
22583 the object that handles the lookup.
22586 import gdb.printing
22588 def build_pretty_printer():
22589 pp = gdb.printing.RegexpCollectionPrettyPrinter(
22591 pp.add_printer('foo', '^foo$', fooPrinter)
22592 pp.add_printer('bar', '^bar$', barPrinter)
22596 And here is the autoload support:
22599 import gdb.printing
22601 gdb.printing.register_pretty_printer(
22602 gdb.current_objfile(),
22603 my_library.build_pretty_printer())
22606 Finally, when this printer is loaded into @value{GDBN}, here is the
22607 corresponding output of @samp{info pretty-printer}:
22610 (gdb) info pretty-printer
22617 @node Inferiors In Python
22618 @subsubsection Inferiors In Python
22619 @cindex inferiors in Python
22621 @findex gdb.Inferior
22622 Programs which are being run under @value{GDBN} are called inferiors
22623 (@pxref{Inferiors and Programs}). Python scripts can access
22624 information about and manipulate inferiors controlled by @value{GDBN}
22625 via objects of the @code{gdb.Inferior} class.
22627 The following inferior-related functions are available in the @code{gdb}
22630 @defun gdb.inferiors ()
22631 Return a tuple containing all inferior objects.
22634 @defun gdb.selected_inferior ()
22635 Return an object representing the current inferior.
22638 A @code{gdb.Inferior} object has the following attributes:
22641 @defvar Inferior.num
22642 ID of inferior, as assigned by GDB.
22645 @defvar Inferior.pid
22646 Process ID of the inferior, as assigned by the underlying operating
22650 @defvar Inferior.was_attached
22651 Boolean signaling whether the inferior was created using `attach', or
22652 started by @value{GDBN} itself.
22656 A @code{gdb.Inferior} object has the following methods:
22659 @defun Inferior.is_valid ()
22660 Returns @code{True} if the @code{gdb.Inferior} object is valid,
22661 @code{False} if not. A @code{gdb.Inferior} object will become invalid
22662 if the inferior no longer exists within @value{GDBN}. All other
22663 @code{gdb.Inferior} methods will throw an exception if it is invalid
22664 at the time the method is called.
22667 @defun Inferior.threads ()
22668 This method returns a tuple holding all the threads which are valid
22669 when it is called. If there are no valid threads, the method will
22670 return an empty tuple.
22673 @findex gdb.read_memory
22674 @defun Inferior.read_memory (address, length)
22675 Read @var{length} bytes of memory from the inferior, starting at
22676 @var{address}. Returns a buffer object, which behaves much like an array
22677 or a string. It can be modified and given to the @code{gdb.write_memory}
22681 @findex gdb.write_memory
22682 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
22683 Write the contents of @var{buffer} to the inferior, starting at
22684 @var{address}. The @var{buffer} parameter must be a Python object
22685 which supports the buffer protocol, i.e., a string, an array or the
22686 object returned from @code{gdb.read_memory}. If given, @var{length}
22687 determines the number of bytes from @var{buffer} to be written.
22690 @findex gdb.search_memory
22691 @defun Inferior.search_memory (address, length, pattern)
22692 Search a region of the inferior memory starting at @var{address} with
22693 the given @var{length} using the search pattern supplied in
22694 @var{pattern}. The @var{pattern} parameter must be a Python object
22695 which supports the buffer protocol, i.e., a string, an array or the
22696 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22697 containing the address where the pattern was found, or @code{None} if
22698 the pattern could not be found.
22702 @node Events In Python
22703 @subsubsection Events In Python
22704 @cindex inferior events in Python
22706 @value{GDBN} provides a general event facility so that Python code can be
22707 notified of various state changes, particularly changes that occur in
22710 An @dfn{event} is just an object that describes some state change. The
22711 type of the object and its attributes will vary depending on the details
22712 of the change. All the existing events are described below.
22714 In order to be notified of an event, you must register an event handler
22715 with an @dfn{event registry}. An event registry is an object in the
22716 @code{gdb.events} module which dispatches particular events. A registry
22717 provides methods to register and unregister event handlers:
22720 @defun EventRegistry.connect (object)
22721 Add the given callable @var{object} to the registry. This object will be
22722 called when an event corresponding to this registry occurs.
22725 @defun EventRegistry.disconnect (object)
22726 Remove the given @var{object} from the registry. Once removed, the object
22727 will no longer receive notifications of events.
22731 Here is an example:
22734 def exit_handler (event):
22735 print "event type: exit"
22736 print "exit code: %d" % (event.exit_code)
22738 gdb.events.exited.connect (exit_handler)
22741 In the above example we connect our handler @code{exit_handler} to the
22742 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22743 called when the inferior exits. The argument @dfn{event} in this example is
22744 of type @code{gdb.ExitedEvent}. As you can see in the example the
22745 @code{ExitedEvent} object has an attribute which indicates the exit code of
22748 The following is a listing of the event registries that are available and
22749 details of the events they emit:
22754 Emits @code{gdb.ThreadEvent}.
22756 Some events can be thread specific when @value{GDBN} is running in non-stop
22757 mode. When represented in Python, these events all extend
22758 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22759 events which are emitted by this or other modules might extend this event.
22760 Examples of these events are @code{gdb.BreakpointEvent} and
22761 @code{gdb.ContinueEvent}.
22764 @defvar ThreadEvent.inferior_thread
22765 In non-stop mode this attribute will be set to the specific thread which was
22766 involved in the emitted event. Otherwise, it will be set to @code{None}.
22770 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22772 This event indicates that the inferior has been continued after a stop. For
22773 inherited attribute refer to @code{gdb.ThreadEvent} above.
22775 @item events.exited
22776 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22777 @code{events.ExitedEvent} has two attributes:
22779 @defvar ExitedEvent.exit_code
22780 An integer representing the exit code, if available, which the inferior
22781 has returned. (The exit code could be unavailable if, for example,
22782 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
22783 the attribute does not exist.
22785 @defvar ExitedEvent inferior
22786 A reference to the inferior which triggered the @code{exited} event.
22791 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
22793 Indicates that the inferior has stopped. All events emitted by this registry
22794 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
22795 will indicate the stopped thread when @value{GDBN} is running in non-stop
22796 mode. Refer to @code{gdb.ThreadEvent} above for more details.
22798 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
22800 This event indicates that the inferior or one of its threads has received as
22801 signal. @code{gdb.SignalEvent} has the following attributes:
22804 @defvar SignalEvent.stop_signal
22805 A string representing the signal received by the inferior. A list of possible
22806 signal values can be obtained by running the command @code{info signals} in
22807 the @value{GDBN} command prompt.
22811 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22813 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
22814 been hit, and has the following attributes:
22817 @defvar BreakpointEvent.breakpoints
22818 A sequence containing references to all the breakpoints (type
22819 @code{gdb.Breakpoint}) that were hit.
22820 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22822 @defvar BreakpointEvent.breakpoint
22823 A reference to the first breakpoint that was hit.
22824 This function is maintained for backward compatibility and is now deprecated
22825 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
22829 @item events.new_objfile
22830 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
22831 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
22834 @defvar NewObjFileEvent.new_objfile
22835 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
22836 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
22842 @node Threads In Python
22843 @subsubsection Threads In Python
22844 @cindex threads in python
22846 @findex gdb.InferiorThread
22847 Python scripts can access information about, and manipulate inferior threads
22848 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
22850 The following thread-related functions are available in the @code{gdb}
22853 @findex gdb.selected_thread
22854 @defun gdb.selected_thread ()
22855 This function returns the thread object for the selected thread. If there
22856 is no selected thread, this will return @code{None}.
22859 A @code{gdb.InferiorThread} object has the following attributes:
22862 @defvar InferiorThread.name
22863 The name of the thread. If the user specified a name using
22864 @code{thread name}, then this returns that name. Otherwise, if an
22865 OS-supplied name is available, then it is returned. Otherwise, this
22866 returns @code{None}.
22868 This attribute can be assigned to. The new value must be a string
22869 object, which sets the new name, or @code{None}, which removes any
22870 user-specified thread name.
22873 @defvar InferiorThread.num
22874 ID of the thread, as assigned by GDB.
22877 @defvar InferiorThread.ptid
22878 ID of the thread, as assigned by the operating system. This attribute is a
22879 tuple containing three integers. The first is the Process ID (PID); the second
22880 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
22881 Either the LWPID or TID may be 0, which indicates that the operating system
22882 does not use that identifier.
22886 A @code{gdb.InferiorThread} object has the following methods:
22889 @defun InferiorThread.is_valid ()
22890 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
22891 @code{False} if not. A @code{gdb.InferiorThread} object will become
22892 invalid if the thread exits, or the inferior that the thread belongs
22893 is deleted. All other @code{gdb.InferiorThread} methods will throw an
22894 exception if it is invalid at the time the method is called.
22897 @defun InferiorThread.switch ()
22898 This changes @value{GDBN}'s currently selected thread to the one represented
22902 @defun InferiorThread.is_stopped ()
22903 Return a Boolean indicating whether the thread is stopped.
22906 @defun InferiorThread.is_running ()
22907 Return a Boolean indicating whether the thread is running.
22910 @defun InferiorThread.is_exited ()
22911 Return a Boolean indicating whether the thread is exited.
22915 @node Commands In Python
22916 @subsubsection Commands In Python
22918 @cindex commands in python
22919 @cindex python commands
22920 You can implement new @value{GDBN} CLI commands in Python. A CLI
22921 command is implemented using an instance of the @code{gdb.Command}
22922 class, most commonly using a subclass.
22924 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
22925 The object initializer for @code{Command} registers the new command
22926 with @value{GDBN}. This initializer is normally invoked from the
22927 subclass' own @code{__init__} method.
22929 @var{name} is the name of the command. If @var{name} consists of
22930 multiple words, then the initial words are looked for as prefix
22931 commands. In this case, if one of the prefix commands does not exist,
22932 an exception is raised.
22934 There is no support for multi-line commands.
22936 @var{command_class} should be one of the @samp{COMMAND_} constants
22937 defined below. This argument tells @value{GDBN} how to categorize the
22938 new command in the help system.
22940 @var{completer_class} is an optional argument. If given, it should be
22941 one of the @samp{COMPLETE_} constants defined below. This argument
22942 tells @value{GDBN} how to perform completion for this command. If not
22943 given, @value{GDBN} will attempt to complete using the object's
22944 @code{complete} method (see below); if no such method is found, an
22945 error will occur when completion is attempted.
22947 @var{prefix} is an optional argument. If @code{True}, then the new
22948 command is a prefix command; sub-commands of this command may be
22951 The help text for the new command is taken from the Python
22952 documentation string for the command's class, if there is one. If no
22953 documentation string is provided, the default value ``This command is
22954 not documented.'' is used.
22957 @cindex don't repeat Python command
22958 @defun Command.dont_repeat ()
22959 By default, a @value{GDBN} command is repeated when the user enters a
22960 blank line at the command prompt. A command can suppress this
22961 behavior by invoking the @code{dont_repeat} method. This is similar
22962 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
22965 @defun Command.invoke (argument, from_tty)
22966 This method is called by @value{GDBN} when this command is invoked.
22968 @var{argument} is a string. It is the argument to the command, after
22969 leading and trailing whitespace has been stripped.
22971 @var{from_tty} is a boolean argument. When true, this means that the
22972 command was entered by the user at the terminal; when false it means
22973 that the command came from elsewhere.
22975 If this method throws an exception, it is turned into a @value{GDBN}
22976 @code{error} call. Otherwise, the return value is ignored.
22978 @findex gdb.string_to_argv
22979 To break @var{argument} up into an argv-like string use
22980 @code{gdb.string_to_argv}. This function behaves identically to
22981 @value{GDBN}'s internal argument lexer @code{buildargv}.
22982 It is recommended to use this for consistency.
22983 Arguments are separated by spaces and may be quoted.
22987 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
22988 ['1', '2 "3', '4 "5', "6 '7"]
22993 @cindex completion of Python commands
22994 @defun Command.complete (text, word)
22995 This method is called by @value{GDBN} when the user attempts
22996 completion on this command. All forms of completion are handled by
22997 this method, that is, the @key{TAB} and @key{M-?} key bindings
22998 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
23001 The arguments @var{text} and @var{word} are both strings. @var{text}
23002 holds the complete command line up to the cursor's location.
23003 @var{word} holds the last word of the command line; this is computed
23004 using a word-breaking heuristic.
23006 The @code{complete} method can return several values:
23009 If the return value is a sequence, the contents of the sequence are
23010 used as the completions. It is up to @code{complete} to ensure that the
23011 contents actually do complete the word. A zero-length sequence is
23012 allowed, it means that there were no completions available. Only
23013 string elements of the sequence are used; other elements in the
23014 sequence are ignored.
23017 If the return value is one of the @samp{COMPLETE_} constants defined
23018 below, then the corresponding @value{GDBN}-internal completion
23019 function is invoked, and its result is used.
23022 All other results are treated as though there were no available
23027 When a new command is registered, it must be declared as a member of
23028 some general class of commands. This is used to classify top-level
23029 commands in the on-line help system; note that prefix commands are not
23030 listed under their own category but rather that of their top-level
23031 command. The available classifications are represented by constants
23032 defined in the @code{gdb} module:
23035 @findex COMMAND_NONE
23036 @findex gdb.COMMAND_NONE
23037 @item gdb.COMMAND_NONE
23038 The command does not belong to any particular class. A command in
23039 this category will not be displayed in any of the help categories.
23041 @findex COMMAND_RUNNING
23042 @findex gdb.COMMAND_RUNNING
23043 @item gdb.COMMAND_RUNNING
23044 The command is related to running the inferior. For example,
23045 @code{start}, @code{step}, and @code{continue} are in this category.
23046 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
23047 commands in this category.
23049 @findex COMMAND_DATA
23050 @findex gdb.COMMAND_DATA
23051 @item gdb.COMMAND_DATA
23052 The command is related to data or variables. For example,
23053 @code{call}, @code{find}, and @code{print} are in this category. Type
23054 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
23057 @findex COMMAND_STACK
23058 @findex gdb.COMMAND_STACK
23059 @item gdb.COMMAND_STACK
23060 The command has to do with manipulation of the stack. For example,
23061 @code{backtrace}, @code{frame}, and @code{return} are in this
23062 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
23063 list of commands in this category.
23065 @findex COMMAND_FILES
23066 @findex gdb.COMMAND_FILES
23067 @item gdb.COMMAND_FILES
23068 This class is used for file-related commands. For example,
23069 @code{file}, @code{list} and @code{section} are in this category.
23070 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
23071 commands in this category.
23073 @findex COMMAND_SUPPORT
23074 @findex gdb.COMMAND_SUPPORT
23075 @item gdb.COMMAND_SUPPORT
23076 This should be used for ``support facilities'', generally meaning
23077 things that are useful to the user when interacting with @value{GDBN},
23078 but not related to the state of the inferior. For example,
23079 @code{help}, @code{make}, and @code{shell} are in this category. Type
23080 @kbd{help support} at the @value{GDBN} prompt to see a list of
23081 commands in this category.
23083 @findex COMMAND_STATUS
23084 @findex gdb.COMMAND_STATUS
23085 @item gdb.COMMAND_STATUS
23086 The command is an @samp{info}-related command, that is, related to the
23087 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
23088 and @code{show} are in this category. Type @kbd{help status} at the
23089 @value{GDBN} prompt to see a list of commands in this category.
23091 @findex COMMAND_BREAKPOINTS
23092 @findex gdb.COMMAND_BREAKPOINTS
23093 @item gdb.COMMAND_BREAKPOINTS
23094 The command has to do with breakpoints. For example, @code{break},
23095 @code{clear}, and @code{delete} are in this category. Type @kbd{help
23096 breakpoints} at the @value{GDBN} prompt to see a list of commands in
23099 @findex COMMAND_TRACEPOINTS
23100 @findex gdb.COMMAND_TRACEPOINTS
23101 @item gdb.COMMAND_TRACEPOINTS
23102 The command has to do with tracepoints. For example, @code{trace},
23103 @code{actions}, and @code{tfind} are in this category. Type
23104 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
23105 commands in this category.
23107 @findex COMMAND_OBSCURE
23108 @findex gdb.COMMAND_OBSCURE
23109 @item gdb.COMMAND_OBSCURE
23110 The command is only used in unusual circumstances, or is not of
23111 general interest to users. For example, @code{checkpoint},
23112 @code{fork}, and @code{stop} are in this category. Type @kbd{help
23113 obscure} at the @value{GDBN} prompt to see a list of commands in this
23116 @findex COMMAND_MAINTENANCE
23117 @findex gdb.COMMAND_MAINTENANCE
23118 @item gdb.COMMAND_MAINTENANCE
23119 The command is only useful to @value{GDBN} maintainers. The
23120 @code{maintenance} and @code{flushregs} commands are in this category.
23121 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
23122 commands in this category.
23125 A new command can use a predefined completion function, either by
23126 specifying it via an argument at initialization, or by returning it
23127 from the @code{complete} method. These predefined completion
23128 constants are all defined in the @code{gdb} module:
23131 @findex COMPLETE_NONE
23132 @findex gdb.COMPLETE_NONE
23133 @item gdb.COMPLETE_NONE
23134 This constant means that no completion should be done.
23136 @findex COMPLETE_FILENAME
23137 @findex gdb.COMPLETE_FILENAME
23138 @item gdb.COMPLETE_FILENAME
23139 This constant means that filename completion should be performed.
23141 @findex COMPLETE_LOCATION
23142 @findex gdb.COMPLETE_LOCATION
23143 @item gdb.COMPLETE_LOCATION
23144 This constant means that location completion should be done.
23145 @xref{Specify Location}.
23147 @findex COMPLETE_COMMAND
23148 @findex gdb.COMPLETE_COMMAND
23149 @item gdb.COMPLETE_COMMAND
23150 This constant means that completion should examine @value{GDBN}
23153 @findex COMPLETE_SYMBOL
23154 @findex gdb.COMPLETE_SYMBOL
23155 @item gdb.COMPLETE_SYMBOL
23156 This constant means that completion should be done using symbol names
23160 The following code snippet shows how a trivial CLI command can be
23161 implemented in Python:
23164 class HelloWorld (gdb.Command):
23165 """Greet the whole world."""
23167 def __init__ (self):
23168 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
23170 def invoke (self, arg, from_tty):
23171 print "Hello, World!"
23176 The last line instantiates the class, and is necessary to trigger the
23177 registration of the command with @value{GDBN}. Depending on how the
23178 Python code is read into @value{GDBN}, you may need to import the
23179 @code{gdb} module explicitly.
23181 @node Parameters In Python
23182 @subsubsection Parameters In Python
23184 @cindex parameters in python
23185 @cindex python parameters
23186 @tindex gdb.Parameter
23188 You can implement new @value{GDBN} parameters using Python. A new
23189 parameter is implemented as an instance of the @code{gdb.Parameter}
23192 Parameters are exposed to the user via the @code{set} and
23193 @code{show} commands. @xref{Help}.
23195 There are many parameters that already exist and can be set in
23196 @value{GDBN}. Two examples are: @code{set follow fork} and
23197 @code{set charset}. Setting these parameters influences certain
23198 behavior in @value{GDBN}. Similarly, you can define parameters that
23199 can be used to influence behavior in custom Python scripts and commands.
23201 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
23202 The object initializer for @code{Parameter} registers the new
23203 parameter with @value{GDBN}. This initializer is normally invoked
23204 from the subclass' own @code{__init__} method.
23206 @var{name} is the name of the new parameter. If @var{name} consists
23207 of multiple words, then the initial words are looked for as prefix
23208 parameters. An example of this can be illustrated with the
23209 @code{set print} set of parameters. If @var{name} is
23210 @code{print foo}, then @code{print} will be searched as the prefix
23211 parameter. In this case the parameter can subsequently be accessed in
23212 @value{GDBN} as @code{set print foo}.
23214 If @var{name} consists of multiple words, and no prefix parameter group
23215 can be found, an exception is raised.
23217 @var{command-class} should be one of the @samp{COMMAND_} constants
23218 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
23219 categorize the new parameter in the help system.
23221 @var{parameter-class} should be one of the @samp{PARAM_} constants
23222 defined below. This argument tells @value{GDBN} the type of the new
23223 parameter; this information is used for input validation and
23226 If @var{parameter-class} is @code{PARAM_ENUM}, then
23227 @var{enum-sequence} must be a sequence of strings. These strings
23228 represent the possible values for the parameter.
23230 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
23231 of a fourth argument will cause an exception to be thrown.
23233 The help text for the new parameter is taken from the Python
23234 documentation string for the parameter's class, if there is one. If
23235 there is no documentation string, a default value is used.
23238 @defvar Parameter.set_doc
23239 If this attribute exists, and is a string, then its value is used as
23240 the help text for this parameter's @code{set} command. The value is
23241 examined when @code{Parameter.__init__} is invoked; subsequent changes
23245 @defvar Parameter.show_doc
23246 If this attribute exists, and is a string, then its value is used as
23247 the help text for this parameter's @code{show} command. The value is
23248 examined when @code{Parameter.__init__} is invoked; subsequent changes
23252 @defvar Parameter.value
23253 The @code{value} attribute holds the underlying value of the
23254 parameter. It can be read and assigned to just as any other
23255 attribute. @value{GDBN} does validation when assignments are made.
23258 There are two methods that should be implemented in any
23259 @code{Parameter} class. These are:
23261 @defun Parameter.get_set_string (self)
23262 @value{GDBN} will call this method when a @var{parameter}'s value has
23263 been changed via the @code{set} API (for example, @kbd{set foo off}).
23264 The @code{value} attribute has already been populated with the new
23265 value and may be used in output. This method must return a string.
23268 @defun Parameter.get_show_string (self, svalue)
23269 @value{GDBN} will call this method when a @var{parameter}'s
23270 @code{show} API has been invoked (for example, @kbd{show foo}). The
23271 argument @code{svalue} receives the string representation of the
23272 current value. This method must return a string.
23275 When a new parameter is defined, its type must be specified. The
23276 available types are represented by constants defined in the @code{gdb}
23280 @findex PARAM_BOOLEAN
23281 @findex gdb.PARAM_BOOLEAN
23282 @item gdb.PARAM_BOOLEAN
23283 The value is a plain boolean. The Python boolean values, @code{True}
23284 and @code{False} are the only valid values.
23286 @findex PARAM_AUTO_BOOLEAN
23287 @findex gdb.PARAM_AUTO_BOOLEAN
23288 @item gdb.PARAM_AUTO_BOOLEAN
23289 The value has three possible states: true, false, and @samp{auto}. In
23290 Python, true and false are represented using boolean constants, and
23291 @samp{auto} is represented using @code{None}.
23293 @findex PARAM_UINTEGER
23294 @findex gdb.PARAM_UINTEGER
23295 @item gdb.PARAM_UINTEGER
23296 The value is an unsigned integer. The value of 0 should be
23297 interpreted to mean ``unlimited''.
23299 @findex PARAM_INTEGER
23300 @findex gdb.PARAM_INTEGER
23301 @item gdb.PARAM_INTEGER
23302 The value is a signed integer. The value of 0 should be interpreted
23303 to mean ``unlimited''.
23305 @findex PARAM_STRING
23306 @findex gdb.PARAM_STRING
23307 @item gdb.PARAM_STRING
23308 The value is a string. When the user modifies the string, any escape
23309 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
23310 translated into corresponding characters and encoded into the current
23313 @findex PARAM_STRING_NOESCAPE
23314 @findex gdb.PARAM_STRING_NOESCAPE
23315 @item gdb.PARAM_STRING_NOESCAPE
23316 The value is a string. When the user modifies the string, escapes are
23317 passed through untranslated.
23319 @findex PARAM_OPTIONAL_FILENAME
23320 @findex gdb.PARAM_OPTIONAL_FILENAME
23321 @item gdb.PARAM_OPTIONAL_FILENAME
23322 The value is a either a filename (a string), or @code{None}.
23324 @findex PARAM_FILENAME
23325 @findex gdb.PARAM_FILENAME
23326 @item gdb.PARAM_FILENAME
23327 The value is a filename. This is just like
23328 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
23330 @findex PARAM_ZINTEGER
23331 @findex gdb.PARAM_ZINTEGER
23332 @item gdb.PARAM_ZINTEGER
23333 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
23334 is interpreted as itself.
23337 @findex gdb.PARAM_ENUM
23338 @item gdb.PARAM_ENUM
23339 The value is a string, which must be one of a collection string
23340 constants provided when the parameter is created.
23343 @node Functions In Python
23344 @subsubsection Writing new convenience functions
23346 @cindex writing convenience functions
23347 @cindex convenience functions in python
23348 @cindex python convenience functions
23349 @tindex gdb.Function
23351 You can implement new convenience functions (@pxref{Convenience Vars})
23352 in Python. A convenience function is an instance of a subclass of the
23353 class @code{gdb.Function}.
23355 @defun Function.__init__ (name)
23356 The initializer for @code{Function} registers the new function with
23357 @value{GDBN}. The argument @var{name} is the name of the function,
23358 a string. The function will be visible to the user as a convenience
23359 variable of type @code{internal function}, whose name is the same as
23360 the given @var{name}.
23362 The documentation for the new function is taken from the documentation
23363 string for the new class.
23366 @defun Function.invoke (@var{*args})
23367 When a convenience function is evaluated, its arguments are converted
23368 to instances of @code{gdb.Value}, and then the function's
23369 @code{invoke} method is called. Note that @value{GDBN} does not
23370 predetermine the arity of convenience functions. Instead, all
23371 available arguments are passed to @code{invoke}, following the
23372 standard Python calling convention. In particular, a convenience
23373 function can have default values for parameters without ill effect.
23375 The return value of this method is used as its value in the enclosing
23376 expression. If an ordinary Python value is returned, it is converted
23377 to a @code{gdb.Value} following the usual rules.
23380 The following code snippet shows how a trivial convenience function can
23381 be implemented in Python:
23384 class Greet (gdb.Function):
23385 """Return string to greet someone.
23386 Takes a name as argument."""
23388 def __init__ (self):
23389 super (Greet, self).__init__ ("greet")
23391 def invoke (self, name):
23392 return "Hello, %s!" % name.string ()
23397 The last line instantiates the class, and is necessary to trigger the
23398 registration of the function with @value{GDBN}. Depending on how the
23399 Python code is read into @value{GDBN}, you may need to import the
23400 @code{gdb} module explicitly.
23402 @node Progspaces In Python
23403 @subsubsection Program Spaces In Python
23405 @cindex progspaces in python
23406 @tindex gdb.Progspace
23408 A program space, or @dfn{progspace}, represents a symbolic view
23409 of an address space.
23410 It consists of all of the objfiles of the program.
23411 @xref{Objfiles In Python}.
23412 @xref{Inferiors and Programs, program spaces}, for more details
23413 about program spaces.
23415 The following progspace-related functions are available in the
23418 @findex gdb.current_progspace
23419 @defun gdb.current_progspace ()
23420 This function returns the program space of the currently selected inferior.
23421 @xref{Inferiors and Programs}.
23424 @findex gdb.progspaces
23425 @defun gdb.progspaces ()
23426 Return a sequence of all the progspaces currently known to @value{GDBN}.
23429 Each progspace is represented by an instance of the @code{gdb.Progspace}
23432 @defvar Progspace.filename
23433 The file name of the progspace as a string.
23436 @defvar Progspace.pretty_printers
23437 The @code{pretty_printers} attribute is a list of functions. It is
23438 used to look up pretty-printers. A @code{Value} is passed to each
23439 function in order; if the function returns @code{None}, then the
23440 search continues. Otherwise, the return value should be an object
23441 which is used to format the value. @xref{Pretty Printing API}, for more
23445 @node Objfiles In Python
23446 @subsubsection Objfiles In Python
23448 @cindex objfiles in python
23449 @tindex gdb.Objfile
23451 @value{GDBN} loads symbols for an inferior from various
23452 symbol-containing files (@pxref{Files}). These include the primary
23453 executable file, any shared libraries used by the inferior, and any
23454 separate debug info files (@pxref{Separate Debug Files}).
23455 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
23457 The following objfile-related functions are available in the
23460 @findex gdb.current_objfile
23461 @defun gdb.current_objfile ()
23462 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
23463 sets the ``current objfile'' to the corresponding objfile. This
23464 function returns the current objfile. If there is no current objfile,
23465 this function returns @code{None}.
23468 @findex gdb.objfiles
23469 @defun gdb.objfiles ()
23470 Return a sequence of all the objfiles current known to @value{GDBN}.
23471 @xref{Objfiles In Python}.
23474 Each objfile is represented by an instance of the @code{gdb.Objfile}
23477 @defvar Objfile.filename
23478 The file name of the objfile as a string.
23481 @defvar Objfile.pretty_printers
23482 The @code{pretty_printers} attribute is a list of functions. It is
23483 used to look up pretty-printers. A @code{Value} is passed to each
23484 function in order; if the function returns @code{None}, then the
23485 search continues. Otherwise, the return value should be an object
23486 which is used to format the value. @xref{Pretty Printing API}, for more
23490 A @code{gdb.Objfile} object has the following methods:
23492 @defun Objfile.is_valid ()
23493 Returns @code{True} if the @code{gdb.Objfile} object is valid,
23494 @code{False} if not. A @code{gdb.Objfile} object can become invalid
23495 if the object file it refers to is not loaded in @value{GDBN} any
23496 longer. All other @code{gdb.Objfile} methods will throw an exception
23497 if it is invalid at the time the method is called.
23500 @node Frames In Python
23501 @subsubsection Accessing inferior stack frames from Python.
23503 @cindex frames in python
23504 When the debugged program stops, @value{GDBN} is able to analyze its call
23505 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
23506 represents a frame in the stack. A @code{gdb.Frame} object is only valid
23507 while its corresponding frame exists in the inferior's stack. If you try
23508 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
23509 exception (@pxref{Exception Handling}).
23511 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
23515 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
23519 The following frame-related functions are available in the @code{gdb} module:
23521 @findex gdb.selected_frame
23522 @defun gdb.selected_frame ()
23523 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
23526 @findex gdb.newest_frame
23527 @defun gdb.newest_frame ()
23528 Return the newest frame object for the selected thread.
23531 @defun gdb.frame_stop_reason_string (reason)
23532 Return a string explaining the reason why @value{GDBN} stopped unwinding
23533 frames, as expressed by the given @var{reason} code (an integer, see the
23534 @code{unwind_stop_reason} method further down in this section).
23537 A @code{gdb.Frame} object has the following methods:
23540 @defun Frame.is_valid ()
23541 Returns true if the @code{gdb.Frame} object is valid, false if not.
23542 A frame object can become invalid if the frame it refers to doesn't
23543 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
23544 an exception if it is invalid at the time the method is called.
23547 @defun Frame.name ()
23548 Returns the function name of the frame, or @code{None} if it can't be
23552 @defun Frame.type ()
23553 Returns the type of the frame. The value can be one of:
23555 @item gdb.NORMAL_FRAME
23556 An ordinary stack frame.
23558 @item gdb.DUMMY_FRAME
23559 A fake stack frame that was created by @value{GDBN} when performing an
23560 inferior function call.
23562 @item gdb.INLINE_FRAME
23563 A frame representing an inlined function. The function was inlined
23564 into a @code{gdb.NORMAL_FRAME} that is older than this one.
23566 @item gdb.TAILCALL_FRAME
23567 A frame representing a tail call. @xref{Tail Call Frames}.
23569 @item gdb.SIGTRAMP_FRAME
23570 A signal trampoline frame. This is the frame created by the OS when
23571 it calls into a signal handler.
23573 @item gdb.ARCH_FRAME
23574 A fake stack frame representing a cross-architecture call.
23576 @item gdb.SENTINEL_FRAME
23577 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
23582 @defun Frame.unwind_stop_reason ()
23583 Return an integer representing the reason why it's not possible to find
23584 more frames toward the outermost frame. Use
23585 @code{gdb.frame_stop_reason_string} to convert the value returned by this
23586 function to a string. The value can be one of:
23589 @item gdb.FRAME_UNWIND_NO_REASON
23590 No particular reason (older frames should be available).
23592 @item gdb.FRAME_UNWIND_NULL_ID
23593 The previous frame's analyzer returns an invalid result.
23595 @item gdb.FRAME_UNWIND_OUTERMOST
23596 This frame is the outermost.
23598 @item gdb.FRAME_UNWIND_UNAVAILABLE
23599 Cannot unwind further, because that would require knowing the
23600 values of registers or memory that have not been collected.
23602 @item gdb.FRAME_UNWIND_INNER_ID
23603 This frame ID looks like it ought to belong to a NEXT frame,
23604 but we got it for a PREV frame. Normally, this is a sign of
23605 unwinder failure. It could also indicate stack corruption.
23607 @item gdb.FRAME_UNWIND_SAME_ID
23608 This frame has the same ID as the previous one. That means
23609 that unwinding further would almost certainly give us another
23610 frame with exactly the same ID, so break the chain. Normally,
23611 this is a sign of unwinder failure. It could also indicate
23614 @item gdb.FRAME_UNWIND_NO_SAVED_PC
23615 The frame unwinder did not find any saved PC, but we needed
23616 one to unwind further.
23618 @item gdb.FRAME_UNWIND_FIRST_ERROR
23619 Any stop reason greater or equal to this value indicates some kind
23620 of error. This special value facilitates writing code that tests
23621 for errors in unwinding in a way that will work correctly even if
23622 the list of the other values is modified in future @value{GDBN}
23623 versions. Using it, you could write:
23625 reason = gdb.selected_frame().unwind_stop_reason ()
23626 reason_str = gdb.frame_stop_reason_string (reason)
23627 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
23628 print "An error occured: %s" % reason_str
23635 Returns the frame's resume address.
23638 @defun Frame.block ()
23639 Return the frame's code block. @xref{Blocks In Python}.
23642 @defun Frame.function ()
23643 Return the symbol for the function corresponding to this frame.
23644 @xref{Symbols In Python}.
23647 @defun Frame.older ()
23648 Return the frame that called this frame.
23651 @defun Frame.newer ()
23652 Return the frame called by this frame.
23655 @defun Frame.find_sal ()
23656 Return the frame's symtab and line object.
23657 @xref{Symbol Tables In Python}.
23660 @defun Frame.read_var (variable @r{[}, block@r{]})
23661 Return the value of @var{variable} in this frame. If the optional
23662 argument @var{block} is provided, search for the variable from that
23663 block; otherwise start at the frame's current block (which is
23664 determined by the frame's current program counter). @var{variable}
23665 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
23666 @code{gdb.Block} object.
23669 @defun Frame.select ()
23670 Set this frame to be the selected frame. @xref{Stack, ,Examining the
23675 @node Blocks In Python
23676 @subsubsection Accessing frame blocks from Python.
23678 @cindex blocks in python
23681 Within each frame, @value{GDBN} maintains information on each block
23682 stored in that frame. These blocks are organized hierarchically, and
23683 are represented individually in Python as a @code{gdb.Block}.
23684 Please see @ref{Frames In Python}, for a more in-depth discussion on
23685 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
23686 detailed technical information on @value{GDBN}'s book-keeping of the
23689 The following block-related functions are available in the @code{gdb}
23692 @findex gdb.block_for_pc
23693 @defun gdb.block_for_pc (pc)
23694 Return the @code{gdb.Block} containing the given @var{pc} value. If the
23695 block cannot be found for the @var{pc} value specified, the function
23696 will return @code{None}.
23699 A @code{gdb.Block} object has the following methods:
23702 @defun Block.is_valid ()
23703 Returns @code{True} if the @code{gdb.Block} object is valid,
23704 @code{False} if not. A block object can become invalid if the block it
23705 refers to doesn't exist anymore in the inferior. All other
23706 @code{gdb.Block} methods will throw an exception if it is invalid at
23707 the time the method is called. This method is also made available to
23708 the Python iterator object that @code{gdb.Block} provides in an iteration
23709 context and via the Python @code{iter} built-in function.
23713 A @code{gdb.Block} object has the following attributes:
23716 @defvar Block.start
23717 The start address of the block. This attribute is not writable.
23721 The end address of the block. This attribute is not writable.
23724 @defvar Block.function
23725 The name of the block represented as a @code{gdb.Symbol}. If the
23726 block is not named, then this attribute holds @code{None}. This
23727 attribute is not writable.
23730 @defvar Block.superblock
23731 The block containing this block. If this parent block does not exist,
23732 this attribute holds @code{None}. This attribute is not writable.
23735 @defvar Block.global_block
23736 The global block associated with this block. This attribute is not
23740 @defvar Block.static_block
23741 The static block associated with this block. This attribute is not
23745 @defvar Block.is_global
23746 @code{True} if the @code{gdb.Block} object is a global block,
23747 @code{False} if not. This attribute is not
23751 @defvar Block.is_static
23752 @code{True} if the @code{gdb.Block} object is a static block,
23753 @code{False} if not. This attribute is not writable.
23757 @node Symbols In Python
23758 @subsubsection Python representation of Symbols.
23760 @cindex symbols in python
23763 @value{GDBN} represents every variable, function and type as an
23764 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
23765 Similarly, Python represents these symbols in @value{GDBN} with the
23766 @code{gdb.Symbol} object.
23768 The following symbol-related functions are available in the @code{gdb}
23771 @findex gdb.lookup_symbol
23772 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
23773 This function searches for a symbol by name. The search scope can be
23774 restricted to the parameters defined in the optional domain and block
23777 @var{name} is the name of the symbol. It must be a string. The
23778 optional @var{block} argument restricts the search to symbols visible
23779 in that @var{block}. The @var{block} argument must be a
23780 @code{gdb.Block} object. If omitted, the block for the current frame
23781 is used. The optional @var{domain} argument restricts
23782 the search to the domain type. The @var{domain} argument must be a
23783 domain constant defined in the @code{gdb} module and described later
23786 The result is a tuple of two elements.
23787 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
23789 If the symbol is found, the second element is @code{True} if the symbol
23790 is a field of a method's object (e.g., @code{this} in C@t{++}),
23791 otherwise it is @code{False}.
23792 If the symbol is not found, the second element is @code{False}.
23795 @findex gdb.lookup_global_symbol
23796 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
23797 This function searches for a global symbol by name.
23798 The search scope can be restricted to by the domain argument.
23800 @var{name} is the name of the symbol. It must be a string.
23801 The optional @var{domain} argument restricts the search to the domain type.
23802 The @var{domain} argument must be a domain constant defined in the @code{gdb}
23803 module and described later in this chapter.
23805 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
23809 A @code{gdb.Symbol} object has the following attributes:
23812 @defvar Symbol.type
23813 The type of the symbol or @code{None} if no type is recorded.
23814 This attribute is represented as a @code{gdb.Type} object.
23815 @xref{Types In Python}. This attribute is not writable.
23818 @defvar Symbol.symtab
23819 The symbol table in which the symbol appears. This attribute is
23820 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
23821 Python}. This attribute is not writable.
23824 @defvar Symbol.name
23825 The name of the symbol as a string. This attribute is not writable.
23828 @defvar Symbol.linkage_name
23829 The name of the symbol, as used by the linker (i.e., may be mangled).
23830 This attribute is not writable.
23833 @defvar Symbol.print_name
23834 The name of the symbol in a form suitable for output. This is either
23835 @code{name} or @code{linkage_name}, depending on whether the user
23836 asked @value{GDBN} to display demangled or mangled names.
23839 @defvar Symbol.addr_class
23840 The address class of the symbol. This classifies how to find the value
23841 of a symbol. Each address class is a constant defined in the
23842 @code{gdb} module and described later in this chapter.
23845 @defvar Symbol.is_argument
23846 @code{True} if the symbol is an argument of a function.
23849 @defvar Symbol.is_constant
23850 @code{True} if the symbol is a constant.
23853 @defvar Symbol.is_function
23854 @code{True} if the symbol is a function or a method.
23857 @defvar Symbol.is_variable
23858 @code{True} if the symbol is a variable.
23862 A @code{gdb.Symbol} object has the following methods:
23865 @defun Symbol.is_valid ()
23866 Returns @code{True} if the @code{gdb.Symbol} object is valid,
23867 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
23868 the symbol it refers to does not exist in @value{GDBN} any longer.
23869 All other @code{gdb.Symbol} methods will throw an exception if it is
23870 invalid at the time the method is called.
23874 The available domain categories in @code{gdb.Symbol} are represented
23875 as constants in the @code{gdb} module:
23878 @findex SYMBOL_UNDEF_DOMAIN
23879 @findex gdb.SYMBOL_UNDEF_DOMAIN
23880 @item gdb.SYMBOL_UNDEF_DOMAIN
23881 This is used when a domain has not been discovered or none of the
23882 following domains apply. This usually indicates an error either
23883 in the symbol information or in @value{GDBN}'s handling of symbols.
23884 @findex SYMBOL_VAR_DOMAIN
23885 @findex gdb.SYMBOL_VAR_DOMAIN
23886 @item gdb.SYMBOL_VAR_DOMAIN
23887 This domain contains variables, function names, typedef names and enum
23889 @findex SYMBOL_STRUCT_DOMAIN
23890 @findex gdb.SYMBOL_STRUCT_DOMAIN
23891 @item gdb.SYMBOL_STRUCT_DOMAIN
23892 This domain holds struct, union and enum type names.
23893 @findex SYMBOL_LABEL_DOMAIN
23894 @findex gdb.SYMBOL_LABEL_DOMAIN
23895 @item gdb.SYMBOL_LABEL_DOMAIN
23896 This domain contains names of labels (for gotos).
23897 @findex SYMBOL_VARIABLES_DOMAIN
23898 @findex gdb.SYMBOL_VARIABLES_DOMAIN
23899 @item gdb.SYMBOL_VARIABLES_DOMAIN
23900 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
23901 contains everything minus functions and types.
23902 @findex SYMBOL_FUNCTIONS_DOMAIN
23903 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
23904 @item gdb.SYMBOL_FUNCTION_DOMAIN
23905 This domain contains all functions.
23906 @findex SYMBOL_TYPES_DOMAIN
23907 @findex gdb.SYMBOL_TYPES_DOMAIN
23908 @item gdb.SYMBOL_TYPES_DOMAIN
23909 This domain contains all types.
23912 The available address class categories in @code{gdb.Symbol} are represented
23913 as constants in the @code{gdb} module:
23916 @findex SYMBOL_LOC_UNDEF
23917 @findex gdb.SYMBOL_LOC_UNDEF
23918 @item gdb.SYMBOL_LOC_UNDEF
23919 If this is returned by address class, it indicates an error either in
23920 the symbol information or in @value{GDBN}'s handling of symbols.
23921 @findex SYMBOL_LOC_CONST
23922 @findex gdb.SYMBOL_LOC_CONST
23923 @item gdb.SYMBOL_LOC_CONST
23924 Value is constant int.
23925 @findex SYMBOL_LOC_STATIC
23926 @findex gdb.SYMBOL_LOC_STATIC
23927 @item gdb.SYMBOL_LOC_STATIC
23928 Value is at a fixed address.
23929 @findex SYMBOL_LOC_REGISTER
23930 @findex gdb.SYMBOL_LOC_REGISTER
23931 @item gdb.SYMBOL_LOC_REGISTER
23932 Value is in a register.
23933 @findex SYMBOL_LOC_ARG
23934 @findex gdb.SYMBOL_LOC_ARG
23935 @item gdb.SYMBOL_LOC_ARG
23936 Value is an argument. This value is at the offset stored within the
23937 symbol inside the frame's argument list.
23938 @findex SYMBOL_LOC_REF_ARG
23939 @findex gdb.SYMBOL_LOC_REF_ARG
23940 @item gdb.SYMBOL_LOC_REF_ARG
23941 Value address is stored in the frame's argument list. Just like
23942 @code{LOC_ARG} except that the value's address is stored at the
23943 offset, not the value itself.
23944 @findex SYMBOL_LOC_REGPARM_ADDR
23945 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
23946 @item gdb.SYMBOL_LOC_REGPARM_ADDR
23947 Value is a specified register. Just like @code{LOC_REGISTER} except
23948 the register holds the address of the argument instead of the argument
23950 @findex SYMBOL_LOC_LOCAL
23951 @findex gdb.SYMBOL_LOC_LOCAL
23952 @item gdb.SYMBOL_LOC_LOCAL
23953 Value is a local variable.
23954 @findex SYMBOL_LOC_TYPEDEF
23955 @findex gdb.SYMBOL_LOC_TYPEDEF
23956 @item gdb.SYMBOL_LOC_TYPEDEF
23957 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
23959 @findex SYMBOL_LOC_BLOCK
23960 @findex gdb.SYMBOL_LOC_BLOCK
23961 @item gdb.SYMBOL_LOC_BLOCK
23963 @findex SYMBOL_LOC_CONST_BYTES
23964 @findex gdb.SYMBOL_LOC_CONST_BYTES
23965 @item gdb.SYMBOL_LOC_CONST_BYTES
23966 Value is a byte-sequence.
23967 @findex SYMBOL_LOC_UNRESOLVED
23968 @findex gdb.SYMBOL_LOC_UNRESOLVED
23969 @item gdb.SYMBOL_LOC_UNRESOLVED
23970 Value is at a fixed address, but the address of the variable has to be
23971 determined from the minimal symbol table whenever the variable is
23973 @findex SYMBOL_LOC_OPTIMIZED_OUT
23974 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
23975 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
23976 The value does not actually exist in the program.
23977 @findex SYMBOL_LOC_COMPUTED
23978 @findex gdb.SYMBOL_LOC_COMPUTED
23979 @item gdb.SYMBOL_LOC_COMPUTED
23980 The value's address is a computed location.
23983 @node Symbol Tables In Python
23984 @subsubsection Symbol table representation in Python.
23986 @cindex symbol tables in python
23988 @tindex gdb.Symtab_and_line
23990 Access to symbol table data maintained by @value{GDBN} on the inferior
23991 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
23992 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
23993 from the @code{find_sal} method in @code{gdb.Frame} object.
23994 @xref{Frames In Python}.
23996 For more information on @value{GDBN}'s symbol table management, see
23997 @ref{Symbols, ,Examining the Symbol Table}, for more information.
23999 A @code{gdb.Symtab_and_line} object has the following attributes:
24002 @defvar Symtab_and_line.symtab
24003 The symbol table object (@code{gdb.Symtab}) for this frame.
24004 This attribute is not writable.
24007 @defvar Symtab_and_line.pc
24008 Indicates the current program counter address. This attribute is not
24012 @defvar Symtab_and_line.line
24013 Indicates the current line number for this object. This
24014 attribute is not writable.
24018 A @code{gdb.Symtab_and_line} object has the following methods:
24021 @defun Symtab_and_line.is_valid ()
24022 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
24023 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
24024 invalid if the Symbol table and line object it refers to does not
24025 exist in @value{GDBN} any longer. All other
24026 @code{gdb.Symtab_and_line} methods will throw an exception if it is
24027 invalid at the time the method is called.
24031 A @code{gdb.Symtab} object has the following attributes:
24034 @defvar Symtab.filename
24035 The symbol table's source filename. This attribute is not writable.
24038 @defvar Symtab.objfile
24039 The symbol table's backing object file. @xref{Objfiles In Python}.
24040 This attribute is not writable.
24044 A @code{gdb.Symtab} object has the following methods:
24047 @defun Symtab.is_valid ()
24048 Returns @code{True} if the @code{gdb.Symtab} object is valid,
24049 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
24050 the symbol table it refers to does not exist in @value{GDBN} any
24051 longer. All other @code{gdb.Symtab} methods will throw an exception
24052 if it is invalid at the time the method is called.
24055 @defun Symtab.fullname ()
24056 Return the symbol table's source absolute file name.
24060 @node Breakpoints In Python
24061 @subsubsection Manipulating breakpoints using Python
24063 @cindex breakpoints in python
24064 @tindex gdb.Breakpoint
24066 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
24069 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
24070 Create a new breakpoint. @var{spec} is a string naming the
24071 location of the breakpoint, or an expression that defines a
24072 watchpoint. The contents can be any location recognized by the
24073 @code{break} command, or in the case of a watchpoint, by the @code{watch}
24074 command. The optional @var{type} denotes the breakpoint to create
24075 from the types defined later in this chapter. This argument can be
24076 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
24077 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
24078 allows the breakpoint to become invisible to the user. The breakpoint
24079 will neither be reported when created, nor will it be listed in the
24080 output from @code{info breakpoints} (but will be listed with the
24081 @code{maint info breakpoints} command). The optional @var{wp_class}
24082 argument defines the class of watchpoint to create, if @var{type} is
24083 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
24084 assumed to be a @code{gdb.WP_WRITE} class.
24087 @defun Breakpoint.stop (self)
24088 The @code{gdb.Breakpoint} class can be sub-classed and, in
24089 particular, you may choose to implement the @code{stop} method.
24090 If this method is defined as a sub-class of @code{gdb.Breakpoint},
24091 it will be called when the inferior reaches any location of a
24092 breakpoint which instantiates that sub-class. If the method returns
24093 @code{True}, the inferior will be stopped at the location of the
24094 breakpoint, otherwise the inferior will continue.
24096 If there are multiple breakpoints at the same location with a
24097 @code{stop} method, each one will be called regardless of the
24098 return status of the previous. This ensures that all @code{stop}
24099 methods have a chance to execute at that location. In this scenario
24100 if one of the methods returns @code{True} but the others return
24101 @code{False}, the inferior will still be stopped.
24103 You should not alter the execution state of the inferior (i.e.@:, step,
24104 next, etc.), alter the current frame context (i.e.@:, change the current
24105 active frame), or alter, add or delete any breakpoint. As a general
24106 rule, you should not alter any data within @value{GDBN} or the inferior
24109 Example @code{stop} implementation:
24112 class MyBreakpoint (gdb.Breakpoint):
24114 inf_val = gdb.parse_and_eval("foo")
24121 The available watchpoint types represented by constants are defined in the
24126 @findex gdb.WP_READ
24128 Read only watchpoint.
24131 @findex gdb.WP_WRITE
24133 Write only watchpoint.
24136 @findex gdb.WP_ACCESS
24137 @item gdb.WP_ACCESS
24138 Read/Write watchpoint.
24141 @defun Breakpoint.is_valid ()
24142 Return @code{True} if this @code{Breakpoint} object is valid,
24143 @code{False} otherwise. A @code{Breakpoint} object can become invalid
24144 if the user deletes the breakpoint. In this case, the object still
24145 exists, but the underlying breakpoint does not. In the cases of
24146 watchpoint scope, the watchpoint remains valid even if execution of the
24147 inferior leaves the scope of that watchpoint.
24150 @defun Breakpoint.delete
24151 Permanently deletes the @value{GDBN} breakpoint. This also
24152 invalidates the Python @code{Breakpoint} object. Any further access
24153 to this object's attributes or methods will raise an error.
24156 @defvar Breakpoint.enabled
24157 This attribute is @code{True} if the breakpoint is enabled, and
24158 @code{False} otherwise. This attribute is writable.
24161 @defvar Breakpoint.silent
24162 This attribute is @code{True} if the breakpoint is silent, and
24163 @code{False} otherwise. This attribute is writable.
24165 Note that a breakpoint can also be silent if it has commands and the
24166 first command is @code{silent}. This is not reported by the
24167 @code{silent} attribute.
24170 @defvar Breakpoint.thread
24171 If the breakpoint is thread-specific, this attribute holds the thread
24172 id. If the breakpoint is not thread-specific, this attribute is
24173 @code{None}. This attribute is writable.
24176 @defvar Breakpoint.task
24177 If the breakpoint is Ada task-specific, this attribute holds the Ada task
24178 id. If the breakpoint is not task-specific (or the underlying
24179 language is not Ada), this attribute is @code{None}. This attribute
24183 @defvar Breakpoint.ignore_count
24184 This attribute holds the ignore count for the breakpoint, an integer.
24185 This attribute is writable.
24188 @defvar Breakpoint.number
24189 This attribute holds the breakpoint's number --- the identifier used by
24190 the user to manipulate the breakpoint. This attribute is not writable.
24193 @defvar Breakpoint.type
24194 This attribute holds the breakpoint's type --- the identifier used to
24195 determine the actual breakpoint type or use-case. This attribute is not
24199 @defvar Breakpoint.visible
24200 This attribute tells whether the breakpoint is visible to the user
24201 when set, or when the @samp{info breakpoints} command is run. This
24202 attribute is not writable.
24205 The available types are represented by constants defined in the @code{gdb}
24209 @findex BP_BREAKPOINT
24210 @findex gdb.BP_BREAKPOINT
24211 @item gdb.BP_BREAKPOINT
24212 Normal code breakpoint.
24214 @findex BP_WATCHPOINT
24215 @findex gdb.BP_WATCHPOINT
24216 @item gdb.BP_WATCHPOINT
24217 Watchpoint breakpoint.
24219 @findex BP_HARDWARE_WATCHPOINT
24220 @findex gdb.BP_HARDWARE_WATCHPOINT
24221 @item gdb.BP_HARDWARE_WATCHPOINT
24222 Hardware assisted watchpoint.
24224 @findex BP_READ_WATCHPOINT
24225 @findex gdb.BP_READ_WATCHPOINT
24226 @item gdb.BP_READ_WATCHPOINT
24227 Hardware assisted read watchpoint.
24229 @findex BP_ACCESS_WATCHPOINT
24230 @findex gdb.BP_ACCESS_WATCHPOINT
24231 @item gdb.BP_ACCESS_WATCHPOINT
24232 Hardware assisted access watchpoint.
24235 @defvar Breakpoint.hit_count
24236 This attribute holds the hit count for the breakpoint, an integer.
24237 This attribute is writable, but currently it can only be set to zero.
24240 @defvar Breakpoint.location
24241 This attribute holds the location of the breakpoint, as specified by
24242 the user. It is a string. If the breakpoint does not have a location
24243 (that is, it is a watchpoint) the attribute's value is @code{None}. This
24244 attribute is not writable.
24247 @defvar Breakpoint.expression
24248 This attribute holds a breakpoint expression, as specified by
24249 the user. It is a string. If the breakpoint does not have an
24250 expression (the breakpoint is not a watchpoint) the attribute's value
24251 is @code{None}. This attribute is not writable.
24254 @defvar Breakpoint.condition
24255 This attribute holds the condition of the breakpoint, as specified by
24256 the user. It is a string. If there is no condition, this attribute's
24257 value is @code{None}. This attribute is writable.
24260 @defvar Breakpoint.commands
24261 This attribute holds the commands attached to the breakpoint. If
24262 there are commands, this attribute's value is a string holding all the
24263 commands, separated by newlines. If there are no commands, this
24264 attribute is @code{None}. This attribute is not writable.
24267 @node Lazy Strings In Python
24268 @subsubsection Python representation of lazy strings.
24270 @cindex lazy strings in python
24271 @tindex gdb.LazyString
24273 A @dfn{lazy string} is a string whose contents is not retrieved or
24274 encoded until it is needed.
24276 A @code{gdb.LazyString} is represented in @value{GDBN} as an
24277 @code{address} that points to a region of memory, an @code{encoding}
24278 that will be used to encode that region of memory, and a @code{length}
24279 to delimit the region of memory that represents the string. The
24280 difference between a @code{gdb.LazyString} and a string wrapped within
24281 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
24282 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
24283 retrieved and encoded during printing, while a @code{gdb.Value}
24284 wrapping a string is immediately retrieved and encoded on creation.
24286 A @code{gdb.LazyString} object has the following functions:
24288 @defun LazyString.value ()
24289 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
24290 will point to the string in memory, but will lose all the delayed
24291 retrieval, encoding and handling that @value{GDBN} applies to a
24292 @code{gdb.LazyString}.
24295 @defvar LazyString.address
24296 This attribute holds the address of the string. This attribute is not
24300 @defvar LazyString.length
24301 This attribute holds the length of the string in characters. If the
24302 length is -1, then the string will be fetched and encoded up to the
24303 first null of appropriate width. This attribute is not writable.
24306 @defvar LazyString.encoding
24307 This attribute holds the encoding that will be applied to the string
24308 when the string is printed by @value{GDBN}. If the encoding is not
24309 set, or contains an empty string, then @value{GDBN} will select the
24310 most appropriate encoding when the string is printed. This attribute
24314 @defvar LazyString.type
24315 This attribute holds the type that is represented by the lazy string's
24316 type. For a lazy string this will always be a pointer type. To
24317 resolve this to the lazy string's character type, use the type's
24318 @code{target} method. @xref{Types In Python}. This attribute is not
24323 @subsection Auto-loading
24324 @cindex auto-loading, Python
24326 When a new object file is read (for example, due to the @code{file}
24327 command, or because the inferior has loaded a shared library),
24328 @value{GDBN} will look for Python support scripts in several ways:
24329 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
24332 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
24333 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
24334 * Which flavor to choose?::
24337 The auto-loading feature is useful for supplying application-specific
24338 debugging commands and scripts.
24340 Auto-loading can be enabled or disabled,
24341 and the list of auto-loaded scripts can be printed.
24344 @kindex set auto-load-scripts
24345 @item set auto-load-scripts [yes|no]
24346 Enable or disable the auto-loading of Python scripts.
24348 @kindex show auto-load-scripts
24349 @item show auto-load-scripts
24350 Show whether auto-loading of Python scripts is enabled or disabled.
24352 @kindex info auto-load-scripts
24353 @cindex print list of auto-loaded scripts
24354 @item info auto-load-scripts [@var{regexp}]
24355 Print the list of all scripts that @value{GDBN} auto-loaded.
24357 Also printed is the list of scripts that were mentioned in
24358 the @code{.debug_gdb_scripts} section and were not found
24359 (@pxref{.debug_gdb_scripts section}).
24360 This is useful because their names are not printed when @value{GDBN}
24361 tries to load them and fails. There may be many of them, and printing
24362 an error message for each one is problematic.
24364 If @var{regexp} is supplied only scripts with matching names are printed.
24369 (gdb) info auto-load-scripts
24371 Yes py-section-script.py
24372 full name: /tmp/py-section-script.py
24373 Missing my-foo-pretty-printers.py
24377 When reading an auto-loaded file, @value{GDBN} sets the
24378 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
24379 function (@pxref{Objfiles In Python}). This can be useful for
24380 registering objfile-specific pretty-printers.
24382 @node objfile-gdb.py file
24383 @subsubsection The @file{@var{objfile}-gdb.py} file
24384 @cindex @file{@var{objfile}-gdb.py}
24386 When a new object file is read, @value{GDBN} looks for
24387 a file named @file{@var{objfile}-gdb.py},
24388 where @var{objfile} is the object file's real name, formed by ensuring
24389 that the file name is absolute, following all symlinks, and resolving
24390 @code{.} and @code{..} components. If this file exists and is
24391 readable, @value{GDBN} will evaluate it as a Python script.
24393 If this file does not exist, and if the parameter
24394 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
24395 then @value{GDBN} will look for @var{real-name} in all of the
24396 directories mentioned in the value of @code{debug-file-directory}.
24398 Finally, if this file does not exist, then @value{GDBN} will look for
24399 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
24400 @var{data-directory} is @value{GDBN}'s data directory (available via
24401 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
24402 is the object file's real name, as described above.
24404 @value{GDBN} does not track which files it has already auto-loaded this way.
24405 @value{GDBN} will load the associated script every time the corresponding
24406 @var{objfile} is opened.
24407 So your @file{-gdb.py} file should be careful to avoid errors if it
24408 is evaluated more than once.
24410 @node .debug_gdb_scripts section
24411 @subsubsection The @code{.debug_gdb_scripts} section
24412 @cindex @code{.debug_gdb_scripts} section
24414 For systems using file formats like ELF and COFF,
24415 when @value{GDBN} loads a new object file
24416 it will look for a special section named @samp{.debug_gdb_scripts}.
24417 If this section exists, its contents is a list of names of scripts to load.
24419 @value{GDBN} will look for each specified script file first in the
24420 current directory and then along the source search path
24421 (@pxref{Source Path, ,Specifying Source Directories}),
24422 except that @file{$cdir} is not searched, since the compilation
24423 directory is not relevant to scripts.
24425 Entries can be placed in section @code{.debug_gdb_scripts} with,
24426 for example, this GCC macro:
24429 /* Note: The "MS" section flags are to remove duplicates. */
24430 #define DEFINE_GDB_SCRIPT(script_name) \
24432 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24434 .asciz \"" script_name "\"\n\
24440 Then one can reference the macro in a header or source file like this:
24443 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
24446 The script name may include directories if desired.
24448 If the macro is put in a header, any application or library
24449 using this header will get a reference to the specified script.
24451 @node Which flavor to choose?
24452 @subsubsection Which flavor to choose?
24454 Given the multiple ways of auto-loading Python scripts, it might not always
24455 be clear which one to choose. This section provides some guidance.
24457 Benefits of the @file{-gdb.py} way:
24461 Can be used with file formats that don't support multiple sections.
24464 Ease of finding scripts for public libraries.
24466 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24467 in the source search path.
24468 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24469 isn't a source directory in which to find the script.
24472 Doesn't require source code additions.
24475 Benefits of the @code{.debug_gdb_scripts} way:
24479 Works with static linking.
24481 Scripts for libraries done the @file{-gdb.py} way require an objfile to
24482 trigger their loading. When an application is statically linked the only
24483 objfile available is the executable, and it is cumbersome to attach all the
24484 scripts from all the input libraries to the executable's @file{-gdb.py} script.
24487 Works with classes that are entirely inlined.
24489 Some classes can be entirely inlined, and thus there may not be an associated
24490 shared library to attach a @file{-gdb.py} script to.
24493 Scripts needn't be copied out of the source tree.
24495 In some circumstances, apps can be built out of large collections of internal
24496 libraries, and the build infrastructure necessary to install the
24497 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
24498 cumbersome. It may be easier to specify the scripts in the
24499 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24500 top of the source tree to the source search path.
24503 @node Python modules
24504 @subsection Python modules
24505 @cindex python modules
24507 @value{GDBN} comes with several modules to assist writing Python code.
24510 * gdb.printing:: Building and registering pretty-printers.
24511 * gdb.types:: Utilities for working with types.
24512 * gdb.prompt:: Utilities for prompt value substitution.
24516 @subsubsection gdb.printing
24517 @cindex gdb.printing
24519 This module provides a collection of utilities for working with
24523 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
24524 This class specifies the API that makes @samp{info pretty-printer},
24525 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
24526 Pretty-printers should generally inherit from this class.
24528 @item SubPrettyPrinter (@var{name})
24529 For printers that handle multiple types, this class specifies the
24530 corresponding API for the subprinters.
24532 @item RegexpCollectionPrettyPrinter (@var{name})
24533 Utility class for handling multiple printers, all recognized via
24534 regular expressions.
24535 @xref{Writing a Pretty-Printer}, for an example.
24537 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
24538 Register @var{printer} with the pretty-printer list of @var{obj}.
24539 If @var{replace} is @code{True} then any existing copy of the printer
24540 is replaced. Otherwise a @code{RuntimeError} exception is raised
24541 if a printer with the same name already exists.
24545 @subsubsection gdb.types
24548 This module provides a collection of utilities for working with
24549 @code{gdb.Types} objects.
24552 @item get_basic_type (@var{type})
24553 Return @var{type} with const and volatile qualifiers stripped,
24554 and with typedefs and C@t{++} references converted to the underlying type.
24559 typedef const int const_int;
24561 const_int& foo_ref (foo);
24562 int main () @{ return 0; @}
24569 (gdb) python import gdb.types
24570 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
24571 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
24575 @item has_field (@var{type}, @var{field})
24576 Return @code{True} if @var{type}, assumed to be a type with fields
24577 (e.g., a structure or union), has field @var{field}.
24579 @item make_enum_dict (@var{enum_type})
24580 Return a Python @code{dictionary} type produced from @var{enum_type}.
24582 @item deep_items (@var{type})
24583 Returns a Python iterator similar to the standard
24584 @code{gdb.Type.iteritems} method, except that the iterator returned
24585 by @code{deep_items} will recursively traverse anonymous struct or
24586 union fields. For example:
24600 Then in @value{GDBN}:
24602 (@value{GDBP}) python import gdb.types
24603 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
24604 (@value{GDBP}) python print struct_a.keys ()
24606 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
24607 @{['a', 'b0', 'b1']@}
24613 @subsubsection gdb.prompt
24616 This module provides a method for prompt value-substitution.
24619 @item substitute_prompt (@var{string})
24620 Return @var{string} with escape sequences substituted by values. Some
24621 escape sequences take arguments. You can specify arguments inside
24622 ``@{@}'' immediately following the escape sequence.
24624 The escape sequences you can pass to this function are:
24628 Substitute a backslash.
24630 Substitute an ESC character.
24632 Substitute the selected frame; an argument names a frame parameter.
24634 Substitute a newline.
24636 Substitute a parameter's value; the argument names the parameter.
24638 Substitute a carriage return.
24640 Substitute the selected thread; an argument names a thread parameter.
24642 Substitute the version of GDB.
24644 Substitute the current working directory.
24646 Begin a sequence of non-printing characters. These sequences are
24647 typically used with the ESC character, and are not counted in the string
24648 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
24649 blue-colored ``(gdb)'' prompt where the length is five.
24651 End a sequence of non-printing characters.
24657 substitute_prompt (``frame: \f,
24658 print arguments: \p@{print frame-arguments@}'')
24661 @exdent will return the string:
24664 "frame: main, print arguments: scalars"
24669 @section Creating new spellings of existing commands
24670 @cindex aliases for commands
24672 It is often useful to define alternate spellings of existing commands.
24673 For example, if a new @value{GDBN} command defined in Python has
24674 a long name to type, it is handy to have an abbreviated version of it
24675 that involves less typing.
24677 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24678 of the @samp{step} command even though it is otherwise an ambiguous
24679 abbreviation of other commands like @samp{set} and @samp{show}.
24681 Aliases are also used to provide shortened or more common versions
24682 of multi-word commands. For example, @value{GDBN} provides the
24683 @samp{tty} alias of the @samp{set inferior-tty} command.
24685 You can define a new alias with the @samp{alias} command.
24690 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24694 @var{ALIAS} specifies the name of the new alias.
24695 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24698 @var{COMMAND} specifies the name of an existing command
24699 that is being aliased.
24701 The @samp{-a} option specifies that the new alias is an abbreviation
24702 of the command. Abbreviations are not shown in command
24703 lists displayed by the @samp{help} command.
24705 The @samp{--} option specifies the end of options,
24706 and is useful when @var{ALIAS} begins with a dash.
24708 Here is a simple example showing how to make an abbreviation
24709 of a command so that there is less to type.
24710 Suppose you were tired of typing @samp{disas}, the current
24711 shortest unambiguous abbreviation of the @samp{disassemble} command
24712 and you wanted an even shorter version named @samp{di}.
24713 The following will accomplish this.
24716 (gdb) alias -a di = disas
24719 Note that aliases are different from user-defined commands.
24720 With a user-defined command, you also need to write documentation
24721 for it with the @samp{document} command.
24722 An alias automatically picks up the documentation of the existing command.
24724 Here is an example where we make @samp{elms} an abbreviation of
24725 @samp{elements} in the @samp{set print elements} command.
24726 This is to show that you can make an abbreviation of any part
24730 (gdb) alias -a set print elms = set print elements
24731 (gdb) alias -a show print elms = show print elements
24732 (gdb) set p elms 20
24734 Limit on string chars or array elements to print is 200.
24737 Note that if you are defining an alias of a @samp{set} command,
24738 and you want to have an alias for the corresponding @samp{show}
24739 command, then you need to define the latter separately.
24741 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24742 @var{ALIAS}, just as they are normally.
24745 (gdb) alias -a set pr elms = set p ele
24748 Finally, here is an example showing the creation of a one word
24749 alias for a more complex command.
24750 This creates alias @samp{spe} of the command @samp{set print elements}.
24753 (gdb) alias spe = set print elements
24758 @chapter Command Interpreters
24759 @cindex command interpreters
24761 @value{GDBN} supports multiple command interpreters, and some command
24762 infrastructure to allow users or user interface writers to switch
24763 between interpreters or run commands in other interpreters.
24765 @value{GDBN} currently supports two command interpreters, the console
24766 interpreter (sometimes called the command-line interpreter or @sc{cli})
24767 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24768 describes both of these interfaces in great detail.
24770 By default, @value{GDBN} will start with the console interpreter.
24771 However, the user may choose to start @value{GDBN} with another
24772 interpreter by specifying the @option{-i} or @option{--interpreter}
24773 startup options. Defined interpreters include:
24777 @cindex console interpreter
24778 The traditional console or command-line interpreter. This is the most often
24779 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24780 @value{GDBN} will use this interpreter.
24783 @cindex mi interpreter
24784 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24785 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24786 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24790 @cindex mi2 interpreter
24791 The current @sc{gdb/mi} interface.
24794 @cindex mi1 interpreter
24795 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24799 @cindex invoke another interpreter
24800 The interpreter being used by @value{GDBN} may not be dynamically
24801 switched at runtime. Although possible, this could lead to a very
24802 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24803 enters the command "interpreter-set console" in a console view,
24804 @value{GDBN} would switch to using the console interpreter, rendering
24805 the IDE inoperable!
24807 @kindex interpreter-exec
24808 Although you may only choose a single interpreter at startup, you may execute
24809 commands in any interpreter from the current interpreter using the appropriate
24810 command. If you are running the console interpreter, simply use the
24811 @code{interpreter-exec} command:
24814 interpreter-exec mi "-data-list-register-names"
24817 @sc{gdb/mi} has a similar command, although it is only available in versions of
24818 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24821 @chapter @value{GDBN} Text User Interface
24823 @cindex Text User Interface
24826 * TUI Overview:: TUI overview
24827 * TUI Keys:: TUI key bindings
24828 * TUI Single Key Mode:: TUI single key mode
24829 * TUI Commands:: TUI-specific commands
24830 * TUI Configuration:: TUI configuration variables
24833 The @value{GDBN} Text User Interface (TUI) is a terminal
24834 interface which uses the @code{curses} library to show the source
24835 file, the assembly output, the program registers and @value{GDBN}
24836 commands in separate text windows. The TUI mode is supported only
24837 on platforms where a suitable version of the @code{curses} library
24840 @pindex @value{GDBTUI}
24841 The TUI mode is enabled by default when you invoke @value{GDBN} as
24842 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
24843 You can also switch in and out of TUI mode while @value{GDBN} runs by
24844 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24845 @xref{TUI Keys, ,TUI Key Bindings}.
24848 @section TUI Overview
24850 In TUI mode, @value{GDBN} can display several text windows:
24854 This window is the @value{GDBN} command window with the @value{GDBN}
24855 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24856 managed using readline.
24859 The source window shows the source file of the program. The current
24860 line and active breakpoints are displayed in this window.
24863 The assembly window shows the disassembly output of the program.
24866 This window shows the processor registers. Registers are highlighted
24867 when their values change.
24870 The source and assembly windows show the current program position
24871 by highlighting the current line and marking it with a @samp{>} marker.
24872 Breakpoints are indicated with two markers. The first marker
24873 indicates the breakpoint type:
24877 Breakpoint which was hit at least once.
24880 Breakpoint which was never hit.
24883 Hardware breakpoint which was hit at least once.
24886 Hardware breakpoint which was never hit.
24889 The second marker indicates whether the breakpoint is enabled or not:
24893 Breakpoint is enabled.
24896 Breakpoint is disabled.
24899 The source, assembly and register windows are updated when the current
24900 thread changes, when the frame changes, or when the program counter
24903 These windows are not all visible at the same time. The command
24904 window is always visible. The others can be arranged in several
24915 source and assembly,
24918 source and registers, or
24921 assembly and registers.
24924 A status line above the command window shows the following information:
24928 Indicates the current @value{GDBN} target.
24929 (@pxref{Targets, ,Specifying a Debugging Target}).
24932 Gives the current process or thread number.
24933 When no process is being debugged, this field is set to @code{No process}.
24936 Gives the current function name for the selected frame.
24937 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24938 When there is no symbol corresponding to the current program counter,
24939 the string @code{??} is displayed.
24942 Indicates the current line number for the selected frame.
24943 When the current line number is not known, the string @code{??} is displayed.
24946 Indicates the current program counter address.
24950 @section TUI Key Bindings
24951 @cindex TUI key bindings
24953 The TUI installs several key bindings in the readline keymaps
24954 @ifset SYSTEM_READLINE
24955 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24957 @ifclear SYSTEM_READLINE
24958 (@pxref{Command Line Editing}).
24960 The following key bindings are installed for both TUI mode and the
24961 @value{GDBN} standard mode.
24970 Enter or leave the TUI mode. When leaving the TUI mode,
24971 the curses window management stops and @value{GDBN} operates using
24972 its standard mode, writing on the terminal directly. When reentering
24973 the TUI mode, control is given back to the curses windows.
24974 The screen is then refreshed.
24978 Use a TUI layout with only one window. The layout will
24979 either be @samp{source} or @samp{assembly}. When the TUI mode
24980 is not active, it will switch to the TUI mode.
24982 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24986 Use a TUI layout with at least two windows. When the current
24987 layout already has two windows, the next layout with two windows is used.
24988 When a new layout is chosen, one window will always be common to the
24989 previous layout and the new one.
24991 Think of it as the Emacs @kbd{C-x 2} binding.
24995 Change the active window. The TUI associates several key bindings
24996 (like scrolling and arrow keys) with the active window. This command
24997 gives the focus to the next TUI window.
24999 Think of it as the Emacs @kbd{C-x o} binding.
25003 Switch in and out of the TUI SingleKey mode that binds single
25004 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25007 The following key bindings only work in the TUI mode:
25012 Scroll the active window one page up.
25016 Scroll the active window one page down.
25020 Scroll the active window one line up.
25024 Scroll the active window one line down.
25028 Scroll the active window one column left.
25032 Scroll the active window one column right.
25036 Refresh the screen.
25039 Because the arrow keys scroll the active window in the TUI mode, they
25040 are not available for their normal use by readline unless the command
25041 window has the focus. When another window is active, you must use
25042 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25043 and @kbd{C-f} to control the command window.
25045 @node TUI Single Key Mode
25046 @section TUI Single Key Mode
25047 @cindex TUI single key mode
25049 The TUI also provides a @dfn{SingleKey} mode, which binds several
25050 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25051 switch into this mode, where the following key bindings are used:
25054 @kindex c @r{(SingleKey TUI key)}
25058 @kindex d @r{(SingleKey TUI key)}
25062 @kindex f @r{(SingleKey TUI key)}
25066 @kindex n @r{(SingleKey TUI key)}
25070 @kindex q @r{(SingleKey TUI key)}
25072 exit the SingleKey mode.
25074 @kindex r @r{(SingleKey TUI key)}
25078 @kindex s @r{(SingleKey TUI key)}
25082 @kindex u @r{(SingleKey TUI key)}
25086 @kindex v @r{(SingleKey TUI key)}
25090 @kindex w @r{(SingleKey TUI key)}
25095 Other keys temporarily switch to the @value{GDBN} command prompt.
25096 The key that was pressed is inserted in the editing buffer so that
25097 it is possible to type most @value{GDBN} commands without interaction
25098 with the TUI SingleKey mode. Once the command is entered the TUI
25099 SingleKey mode is restored. The only way to permanently leave
25100 this mode is by typing @kbd{q} or @kbd{C-x s}.
25104 @section TUI-specific Commands
25105 @cindex TUI commands
25107 The TUI has specific commands to control the text windows.
25108 These commands are always available, even when @value{GDBN} is not in
25109 the TUI mode. When @value{GDBN} is in the standard mode, most
25110 of these commands will automatically switch to the TUI mode.
25112 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25113 terminal, or @value{GDBN} has been started with the machine interface
25114 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25115 these commands will fail with an error, because it would not be
25116 possible or desirable to enable curses window management.
25121 List and give the size of all displayed windows.
25125 Display the next layout.
25128 Display the previous layout.
25131 Display the source window only.
25134 Display the assembly window only.
25137 Display the source and assembly window.
25140 Display the register window together with the source or assembly window.
25144 Make the next window active for scrolling.
25147 Make the previous window active for scrolling.
25150 Make the source window active for scrolling.
25153 Make the assembly window active for scrolling.
25156 Make the register window active for scrolling.
25159 Make the command window active for scrolling.
25163 Refresh the screen. This is similar to typing @kbd{C-L}.
25165 @item tui reg float
25167 Show the floating point registers in the register window.
25169 @item tui reg general
25170 Show the general registers in the register window.
25173 Show the next register group. The list of register groups as well as
25174 their order is target specific. The predefined register groups are the
25175 following: @code{general}, @code{float}, @code{system}, @code{vector},
25176 @code{all}, @code{save}, @code{restore}.
25178 @item tui reg system
25179 Show the system registers in the register window.
25183 Update the source window and the current execution point.
25185 @item winheight @var{name} +@var{count}
25186 @itemx winheight @var{name} -@var{count}
25188 Change the height of the window @var{name} by @var{count}
25189 lines. Positive counts increase the height, while negative counts
25192 @item tabset @var{nchars}
25194 Set the width of tab stops to be @var{nchars} characters.
25197 @node TUI Configuration
25198 @section TUI Configuration Variables
25199 @cindex TUI configuration variables
25201 Several configuration variables control the appearance of TUI windows.
25204 @item set tui border-kind @var{kind}
25205 @kindex set tui border-kind
25206 Select the border appearance for the source, assembly and register windows.
25207 The possible values are the following:
25210 Use a space character to draw the border.
25213 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25216 Use the Alternate Character Set to draw the border. The border is
25217 drawn using character line graphics if the terminal supports them.
25220 @item set tui border-mode @var{mode}
25221 @kindex set tui border-mode
25222 @itemx set tui active-border-mode @var{mode}
25223 @kindex set tui active-border-mode
25224 Select the display attributes for the borders of the inactive windows
25225 or the active window. The @var{mode} can be one of the following:
25228 Use normal attributes to display the border.
25234 Use reverse video mode.
25237 Use half bright mode.
25239 @item half-standout
25240 Use half bright and standout mode.
25243 Use extra bright or bold mode.
25245 @item bold-standout
25246 Use extra bright or bold and standout mode.
25251 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25254 @cindex @sc{gnu} Emacs
25255 A special interface allows you to use @sc{gnu} Emacs to view (and
25256 edit) the source files for the program you are debugging with
25259 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25260 executable file you want to debug as an argument. This command starts
25261 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25262 created Emacs buffer.
25263 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25265 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25270 All ``terminal'' input and output goes through an Emacs buffer, called
25273 This applies both to @value{GDBN} commands and their output, and to the input
25274 and output done by the program you are debugging.
25276 This is useful because it means that you can copy the text of previous
25277 commands and input them again; you can even use parts of the output
25280 All the facilities of Emacs' Shell mode are available for interacting
25281 with your program. In particular, you can send signals the usual
25282 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25286 @value{GDBN} displays source code through Emacs.
25288 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25289 source file for that frame and puts an arrow (@samp{=>}) at the
25290 left margin of the current line. Emacs uses a separate buffer for
25291 source display, and splits the screen to show both your @value{GDBN} session
25294 Explicit @value{GDBN} @code{list} or search commands still produce output as
25295 usual, but you probably have no reason to use them from Emacs.
25298 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25299 a graphical mode, enabled by default, which provides further buffers
25300 that can control the execution and describe the state of your program.
25301 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25303 If you specify an absolute file name when prompted for the @kbd{M-x
25304 gdb} argument, then Emacs sets your current working directory to where
25305 your program resides. If you only specify the file name, then Emacs
25306 sets your current working directory to the directory associated
25307 with the previous buffer. In this case, @value{GDBN} may find your
25308 program by searching your environment's @code{PATH} variable, but on
25309 some operating systems it might not find the source. So, although the
25310 @value{GDBN} input and output session proceeds normally, the auxiliary
25311 buffer does not display the current source and line of execution.
25313 The initial working directory of @value{GDBN} is printed on the top
25314 line of the GUD buffer and this serves as a default for the commands
25315 that specify files for @value{GDBN} to operate on. @xref{Files,
25316 ,Commands to Specify Files}.
25318 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25319 need to call @value{GDBN} by a different name (for example, if you
25320 keep several configurations around, with different names) you can
25321 customize the Emacs variable @code{gud-gdb-command-name} to run the
25324 In the GUD buffer, you can use these special Emacs commands in
25325 addition to the standard Shell mode commands:
25329 Describe the features of Emacs' GUD Mode.
25332 Execute to another source line, like the @value{GDBN} @code{step} command; also
25333 update the display window to show the current file and location.
25336 Execute to next source line in this function, skipping all function
25337 calls, like the @value{GDBN} @code{next} command. Then update the display window
25338 to show the current file and location.
25341 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25342 display window accordingly.
25345 Execute until exit from the selected stack frame, like the @value{GDBN}
25346 @code{finish} command.
25349 Continue execution of your program, like the @value{GDBN} @code{continue}
25353 Go up the number of frames indicated by the numeric argument
25354 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25355 like the @value{GDBN} @code{up} command.
25358 Go down the number of frames indicated by the numeric argument, like the
25359 @value{GDBN} @code{down} command.
25362 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25363 tells @value{GDBN} to set a breakpoint on the source line point is on.
25365 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25366 separate frame which shows a backtrace when the GUD buffer is current.
25367 Move point to any frame in the stack and type @key{RET} to make it
25368 become the current frame and display the associated source in the
25369 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25370 selected frame become the current one. In graphical mode, the
25371 speedbar displays watch expressions.
25373 If you accidentally delete the source-display buffer, an easy way to get
25374 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25375 request a frame display; when you run under Emacs, this recreates
25376 the source buffer if necessary to show you the context of the current
25379 The source files displayed in Emacs are in ordinary Emacs buffers
25380 which are visiting the source files in the usual way. You can edit
25381 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25382 communicates with Emacs in terms of line numbers. If you add or
25383 delete lines from the text, the line numbers that @value{GDBN} knows cease
25384 to correspond properly with the code.
25386 A more detailed description of Emacs' interaction with @value{GDBN} is
25387 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25390 @c The following dropped because Epoch is nonstandard. Reactivate
25391 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
25393 @kindex Emacs Epoch environment
25397 Version 18 of @sc{gnu} Emacs has a built-in window system
25398 called the @code{epoch}
25399 environment. Users of this environment can use a new command,
25400 @code{inspect} which performs identically to @code{print} except that
25401 each value is printed in its own window.
25406 @chapter The @sc{gdb/mi} Interface
25408 @unnumberedsec Function and Purpose
25410 @cindex @sc{gdb/mi}, its purpose
25411 @sc{gdb/mi} is a line based machine oriented text interface to
25412 @value{GDBN} and is activated by specifying using the
25413 @option{--interpreter} command line option (@pxref{Mode Options}). It
25414 is specifically intended to support the development of systems which
25415 use the debugger as just one small component of a larger system.
25417 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25418 in the form of a reference manual.
25420 Note that @sc{gdb/mi} is still under construction, so some of the
25421 features described below are incomplete and subject to change
25422 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25424 @unnumberedsec Notation and Terminology
25426 @cindex notational conventions, for @sc{gdb/mi}
25427 This chapter uses the following notation:
25431 @code{|} separates two alternatives.
25434 @code{[ @var{something} ]} indicates that @var{something} is optional:
25435 it may or may not be given.
25438 @code{( @var{group} )*} means that @var{group} inside the parentheses
25439 may repeat zero or more times.
25442 @code{( @var{group} )+} means that @var{group} inside the parentheses
25443 may repeat one or more times.
25446 @code{"@var{string}"} means a literal @var{string}.
25450 @heading Dependencies
25454 * GDB/MI General Design::
25455 * GDB/MI Command Syntax::
25456 * GDB/MI Compatibility with CLI::
25457 * GDB/MI Development and Front Ends::
25458 * GDB/MI Output Records::
25459 * GDB/MI Simple Examples::
25460 * GDB/MI Command Description Format::
25461 * GDB/MI Breakpoint Commands::
25462 * GDB/MI Program Context::
25463 * GDB/MI Thread Commands::
25464 * GDB/MI Ada Tasking Commands::
25465 * GDB/MI Program Execution::
25466 * GDB/MI Stack Manipulation::
25467 * GDB/MI Variable Objects::
25468 * GDB/MI Data Manipulation::
25469 * GDB/MI Tracepoint Commands::
25470 * GDB/MI Symbol Query::
25471 * GDB/MI File Commands::
25473 * GDB/MI Kod Commands::
25474 * GDB/MI Memory Overlay Commands::
25475 * GDB/MI Signal Handling Commands::
25477 * GDB/MI Target Manipulation::
25478 * GDB/MI File Transfer Commands::
25479 * GDB/MI Miscellaneous Commands::
25482 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25483 @node GDB/MI General Design
25484 @section @sc{gdb/mi} General Design
25485 @cindex GDB/MI General Design
25487 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25488 parts---commands sent to @value{GDBN}, responses to those commands
25489 and notifications. Each command results in exactly one response,
25490 indicating either successful completion of the command, or an error.
25491 For the commands that do not resume the target, the response contains the
25492 requested information. For the commands that resume the target, the
25493 response only indicates whether the target was successfully resumed.
25494 Notifications is the mechanism for reporting changes in the state of the
25495 target, or in @value{GDBN} state, that cannot conveniently be associated with
25496 a command and reported as part of that command response.
25498 The important examples of notifications are:
25502 Exec notifications. These are used to report changes in
25503 target state---when a target is resumed, or stopped. It would not
25504 be feasible to include this information in response of resuming
25505 commands, because one resume commands can result in multiple events in
25506 different threads. Also, quite some time may pass before any event
25507 happens in the target, while a frontend needs to know whether the resuming
25508 command itself was successfully executed.
25511 Console output, and status notifications. Console output
25512 notifications are used to report output of CLI commands, as well as
25513 diagnostics for other commands. Status notifications are used to
25514 report the progress of a long-running operation. Naturally, including
25515 this information in command response would mean no output is produced
25516 until the command is finished, which is undesirable.
25519 General notifications. Commands may have various side effects on
25520 the @value{GDBN} or target state beyond their official purpose. For example,
25521 a command may change the selected thread. Although such changes can
25522 be included in command response, using notification allows for more
25523 orthogonal frontend design.
25527 There's no guarantee that whenever an MI command reports an error,
25528 @value{GDBN} or the target are in any specific state, and especially,
25529 the state is not reverted to the state before the MI command was
25530 processed. Therefore, whenever an MI command results in an error,
25531 we recommend that the frontend refreshes all the information shown in
25532 the user interface.
25536 * Context management::
25537 * Asynchronous and non-stop modes::
25541 @node Context management
25542 @subsection Context management
25544 In most cases when @value{GDBN} accesses the target, this access is
25545 done in context of a specific thread and frame (@pxref{Frames}).
25546 Often, even when accessing global data, the target requires that a thread
25547 be specified. The CLI interface maintains the selected thread and frame,
25548 and supplies them to target on each command. This is convenient,
25549 because a command line user would not want to specify that information
25550 explicitly on each command, and because user interacts with
25551 @value{GDBN} via a single terminal, so no confusion is possible as
25552 to what thread and frame are the current ones.
25554 In the case of MI, the concept of selected thread and frame is less
25555 useful. First, a frontend can easily remember this information
25556 itself. Second, a graphical frontend can have more than one window,
25557 each one used for debugging a different thread, and the frontend might
25558 want to access additional threads for internal purposes. This
25559 increases the risk that by relying on implicitly selected thread, the
25560 frontend may be operating on a wrong one. Therefore, each MI command
25561 should explicitly specify which thread and frame to operate on. To
25562 make it possible, each MI command accepts the @samp{--thread} and
25563 @samp{--frame} options, the value to each is @value{GDBN} identifier
25564 for thread and frame to operate on.
25566 Usually, each top-level window in a frontend allows the user to select
25567 a thread and a frame, and remembers the user selection for further
25568 operations. However, in some cases @value{GDBN} may suggest that the
25569 current thread be changed. For example, when stopping on a breakpoint
25570 it is reasonable to switch to the thread where breakpoint is hit. For
25571 another example, if the user issues the CLI @samp{thread} command via
25572 the frontend, it is desirable to change the frontend's selected thread to the
25573 one specified by user. @value{GDBN} communicates the suggestion to
25574 change current thread using the @samp{=thread-selected} notification.
25575 No such notification is available for the selected frame at the moment.
25577 Note that historically, MI shares the selected thread with CLI, so
25578 frontends used the @code{-thread-select} to execute commands in the
25579 right context. However, getting this to work right is cumbersome. The
25580 simplest way is for frontend to emit @code{-thread-select} command
25581 before every command. This doubles the number of commands that need
25582 to be sent. The alternative approach is to suppress @code{-thread-select}
25583 if the selected thread in @value{GDBN} is supposed to be identical to the
25584 thread the frontend wants to operate on. However, getting this
25585 optimization right can be tricky. In particular, if the frontend
25586 sends several commands to @value{GDBN}, and one of the commands changes the
25587 selected thread, then the behaviour of subsequent commands will
25588 change. So, a frontend should either wait for response from such
25589 problematic commands, or explicitly add @code{-thread-select} for
25590 all subsequent commands. No frontend is known to do this exactly
25591 right, so it is suggested to just always pass the @samp{--thread} and
25592 @samp{--frame} options.
25594 @node Asynchronous and non-stop modes
25595 @subsection Asynchronous command execution and non-stop mode
25597 On some targets, @value{GDBN} is capable of processing MI commands
25598 even while the target is running. This is called @dfn{asynchronous
25599 command execution} (@pxref{Background Execution}). The frontend may
25600 specify a preferrence for asynchronous execution using the
25601 @code{-gdb-set target-async 1} command, which should be emitted before
25602 either running the executable or attaching to the target. After the
25603 frontend has started the executable or attached to the target, it can
25604 find if asynchronous execution is enabled using the
25605 @code{-list-target-features} command.
25607 Even if @value{GDBN} can accept a command while target is running,
25608 many commands that access the target do not work when the target is
25609 running. Therefore, asynchronous command execution is most useful
25610 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25611 it is possible to examine the state of one thread, while other threads
25614 When a given thread is running, MI commands that try to access the
25615 target in the context of that thread may not work, or may work only on
25616 some targets. In particular, commands that try to operate on thread's
25617 stack will not work, on any target. Commands that read memory, or
25618 modify breakpoints, may work or not work, depending on the target. Note
25619 that even commands that operate on global state, such as @code{print},
25620 @code{set}, and breakpoint commands, still access the target in the
25621 context of a specific thread, so frontend should try to find a
25622 stopped thread and perform the operation on that thread (using the
25623 @samp{--thread} option).
25625 Which commands will work in the context of a running thread is
25626 highly target dependent. However, the two commands
25627 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25628 to find the state of a thread, will always work.
25630 @node Thread groups
25631 @subsection Thread groups
25632 @value{GDBN} may be used to debug several processes at the same time.
25633 On some platfroms, @value{GDBN} may support debugging of several
25634 hardware systems, each one having several cores with several different
25635 processes running on each core. This section describes the MI
25636 mechanism to support such debugging scenarios.
25638 The key observation is that regardless of the structure of the
25639 target, MI can have a global list of threads, because most commands that
25640 accept the @samp{--thread} option do not need to know what process that
25641 thread belongs to. Therefore, it is not necessary to introduce
25642 neither additional @samp{--process} option, nor an notion of the
25643 current process in the MI interface. The only strictly new feature
25644 that is required is the ability to find how the threads are grouped
25647 To allow the user to discover such grouping, and to support arbitrary
25648 hierarchy of machines/cores/processes, MI introduces the concept of a
25649 @dfn{thread group}. Thread group is a collection of threads and other
25650 thread groups. A thread group always has a string identifier, a type,
25651 and may have additional attributes specific to the type. A new
25652 command, @code{-list-thread-groups}, returns the list of top-level
25653 thread groups, which correspond to processes that @value{GDBN} is
25654 debugging at the moment. By passing an identifier of a thread group
25655 to the @code{-list-thread-groups} command, it is possible to obtain
25656 the members of specific thread group.
25658 To allow the user to easily discover processes, and other objects, he
25659 wishes to debug, a concept of @dfn{available thread group} is
25660 introduced. Available thread group is an thread group that
25661 @value{GDBN} is not debugging, but that can be attached to, using the
25662 @code{-target-attach} command. The list of available top-level thread
25663 groups can be obtained using @samp{-list-thread-groups --available}.
25664 In general, the content of a thread group may be only retrieved only
25665 after attaching to that thread group.
25667 Thread groups are related to inferiors (@pxref{Inferiors and
25668 Programs}). Each inferior corresponds to a thread group of a special
25669 type @samp{process}, and some additional operations are permitted on
25670 such thread groups.
25672 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25673 @node GDB/MI Command Syntax
25674 @section @sc{gdb/mi} Command Syntax
25677 * GDB/MI Input Syntax::
25678 * GDB/MI Output Syntax::
25681 @node GDB/MI Input Syntax
25682 @subsection @sc{gdb/mi} Input Syntax
25684 @cindex input syntax for @sc{gdb/mi}
25685 @cindex @sc{gdb/mi}, input syntax
25687 @item @var{command} @expansion{}
25688 @code{@var{cli-command} | @var{mi-command}}
25690 @item @var{cli-command} @expansion{}
25691 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25692 @var{cli-command} is any existing @value{GDBN} CLI command.
25694 @item @var{mi-command} @expansion{}
25695 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25696 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25698 @item @var{token} @expansion{}
25699 "any sequence of digits"
25701 @item @var{option} @expansion{}
25702 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25704 @item @var{parameter} @expansion{}
25705 @code{@var{non-blank-sequence} | @var{c-string}}
25707 @item @var{operation} @expansion{}
25708 @emph{any of the operations described in this chapter}
25710 @item @var{non-blank-sequence} @expansion{}
25711 @emph{anything, provided it doesn't contain special characters such as
25712 "-", @var{nl}, """ and of course " "}
25714 @item @var{c-string} @expansion{}
25715 @code{""" @var{seven-bit-iso-c-string-content} """}
25717 @item @var{nl} @expansion{}
25726 The CLI commands are still handled by the @sc{mi} interpreter; their
25727 output is described below.
25730 The @code{@var{token}}, when present, is passed back when the command
25734 Some @sc{mi} commands accept optional arguments as part of the parameter
25735 list. Each option is identified by a leading @samp{-} (dash) and may be
25736 followed by an optional argument parameter. Options occur first in the
25737 parameter list and can be delimited from normal parameters using
25738 @samp{--} (this is useful when some parameters begin with a dash).
25745 We want easy access to the existing CLI syntax (for debugging).
25748 We want it to be easy to spot a @sc{mi} operation.
25751 @node GDB/MI Output Syntax
25752 @subsection @sc{gdb/mi} Output Syntax
25754 @cindex output syntax of @sc{gdb/mi}
25755 @cindex @sc{gdb/mi}, output syntax
25756 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25757 followed, optionally, by a single result record. This result record
25758 is for the most recent command. The sequence of output records is
25759 terminated by @samp{(gdb)}.
25761 If an input command was prefixed with a @code{@var{token}} then the
25762 corresponding output for that command will also be prefixed by that same
25766 @item @var{output} @expansion{}
25767 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25769 @item @var{result-record} @expansion{}
25770 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25772 @item @var{out-of-band-record} @expansion{}
25773 @code{@var{async-record} | @var{stream-record}}
25775 @item @var{async-record} @expansion{}
25776 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25778 @item @var{exec-async-output} @expansion{}
25779 @code{[ @var{token} ] "*" @var{async-output}}
25781 @item @var{status-async-output} @expansion{}
25782 @code{[ @var{token} ] "+" @var{async-output}}
25784 @item @var{notify-async-output} @expansion{}
25785 @code{[ @var{token} ] "=" @var{async-output}}
25787 @item @var{async-output} @expansion{}
25788 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
25790 @item @var{result-class} @expansion{}
25791 @code{"done" | "running" | "connected" | "error" | "exit"}
25793 @item @var{async-class} @expansion{}
25794 @code{"stopped" | @var{others}} (where @var{others} will be added
25795 depending on the needs---this is still in development).
25797 @item @var{result} @expansion{}
25798 @code{ @var{variable} "=" @var{value}}
25800 @item @var{variable} @expansion{}
25801 @code{ @var{string} }
25803 @item @var{value} @expansion{}
25804 @code{ @var{const} | @var{tuple} | @var{list} }
25806 @item @var{const} @expansion{}
25807 @code{@var{c-string}}
25809 @item @var{tuple} @expansion{}
25810 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25812 @item @var{list} @expansion{}
25813 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25814 @var{result} ( "," @var{result} )* "]" }
25816 @item @var{stream-record} @expansion{}
25817 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25819 @item @var{console-stream-output} @expansion{}
25820 @code{"~" @var{c-string}}
25822 @item @var{target-stream-output} @expansion{}
25823 @code{"@@" @var{c-string}}
25825 @item @var{log-stream-output} @expansion{}
25826 @code{"&" @var{c-string}}
25828 @item @var{nl} @expansion{}
25831 @item @var{token} @expansion{}
25832 @emph{any sequence of digits}.
25840 All output sequences end in a single line containing a period.
25843 The @code{@var{token}} is from the corresponding request. Note that
25844 for all async output, while the token is allowed by the grammar and
25845 may be output by future versions of @value{GDBN} for select async
25846 output messages, it is generally omitted. Frontends should treat
25847 all async output as reporting general changes in the state of the
25848 target and there should be no need to associate async output to any
25852 @cindex status output in @sc{gdb/mi}
25853 @var{status-async-output} contains on-going status information about the
25854 progress of a slow operation. It can be discarded. All status output is
25855 prefixed by @samp{+}.
25858 @cindex async output in @sc{gdb/mi}
25859 @var{exec-async-output} contains asynchronous state change on the target
25860 (stopped, started, disappeared). All async output is prefixed by
25864 @cindex notify output in @sc{gdb/mi}
25865 @var{notify-async-output} contains supplementary information that the
25866 client should handle (e.g., a new breakpoint information). All notify
25867 output is prefixed by @samp{=}.
25870 @cindex console output in @sc{gdb/mi}
25871 @var{console-stream-output} is output that should be displayed as is in the
25872 console. It is the textual response to a CLI command. All the console
25873 output is prefixed by @samp{~}.
25876 @cindex target output in @sc{gdb/mi}
25877 @var{target-stream-output} is the output produced by the target program.
25878 All the target output is prefixed by @samp{@@}.
25881 @cindex log output in @sc{gdb/mi}
25882 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25883 instance messages that should be displayed as part of an error log. All
25884 the log output is prefixed by @samp{&}.
25887 @cindex list output in @sc{gdb/mi}
25888 New @sc{gdb/mi} commands should only output @var{lists} containing
25894 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25895 details about the various output records.
25897 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25898 @node GDB/MI Compatibility with CLI
25899 @section @sc{gdb/mi} Compatibility with CLI
25901 @cindex compatibility, @sc{gdb/mi} and CLI
25902 @cindex @sc{gdb/mi}, compatibility with CLI
25904 For the developers convenience CLI commands can be entered directly,
25905 but there may be some unexpected behaviour. For example, commands
25906 that query the user will behave as if the user replied yes, breakpoint
25907 command lists are not executed and some CLI commands, such as
25908 @code{if}, @code{when} and @code{define}, prompt for further input with
25909 @samp{>}, which is not valid MI output.
25911 This feature may be removed at some stage in the future and it is
25912 recommended that front ends use the @code{-interpreter-exec} command
25913 (@pxref{-interpreter-exec}).
25915 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25916 @node GDB/MI Development and Front Ends
25917 @section @sc{gdb/mi} Development and Front Ends
25918 @cindex @sc{gdb/mi} development
25920 The application which takes the MI output and presents the state of the
25921 program being debugged to the user is called a @dfn{front end}.
25923 Although @sc{gdb/mi} is still incomplete, it is currently being used
25924 by a variety of front ends to @value{GDBN}. This makes it difficult
25925 to introduce new functionality without breaking existing usage. This
25926 section tries to minimize the problems by describing how the protocol
25929 Some changes in MI need not break a carefully designed front end, and
25930 for these the MI version will remain unchanged. The following is a
25931 list of changes that may occur within one level, so front ends should
25932 parse MI output in a way that can handle them:
25936 New MI commands may be added.
25939 New fields may be added to the output of any MI command.
25942 The range of values for fields with specified values, e.g.,
25943 @code{in_scope} (@pxref{-var-update}) may be extended.
25945 @c The format of field's content e.g type prefix, may change so parse it
25946 @c at your own risk. Yes, in general?
25948 @c The order of fields may change? Shouldn't really matter but it might
25949 @c resolve inconsistencies.
25952 If the changes are likely to break front ends, the MI version level
25953 will be increased by one. This will allow the front end to parse the
25954 output according to the MI version. Apart from mi0, new versions of
25955 @value{GDBN} will not support old versions of MI and it will be the
25956 responsibility of the front end to work with the new one.
25958 @c Starting with mi3, add a new command -mi-version that prints the MI
25961 The best way to avoid unexpected changes in MI that might break your front
25962 end is to make your project known to @value{GDBN} developers and
25963 follow development on @email{gdb@@sourceware.org} and
25964 @email{gdb-patches@@sourceware.org}.
25965 @cindex mailing lists
25967 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25968 @node GDB/MI Output Records
25969 @section @sc{gdb/mi} Output Records
25972 * GDB/MI Result Records::
25973 * GDB/MI Stream Records::
25974 * GDB/MI Async Records::
25975 * GDB/MI Frame Information::
25976 * GDB/MI Thread Information::
25977 * GDB/MI Ada Exception Information::
25980 @node GDB/MI Result Records
25981 @subsection @sc{gdb/mi} Result Records
25983 @cindex result records in @sc{gdb/mi}
25984 @cindex @sc{gdb/mi}, result records
25985 In addition to a number of out-of-band notifications, the response to a
25986 @sc{gdb/mi} command includes one of the following result indications:
25990 @item "^done" [ "," @var{results} ]
25991 The synchronous operation was successful, @code{@var{results}} are the return
25996 This result record is equivalent to @samp{^done}. Historically, it
25997 was output instead of @samp{^done} if the command has resumed the
25998 target. This behaviour is maintained for backward compatibility, but
25999 all frontends should treat @samp{^done} and @samp{^running}
26000 identically and rely on the @samp{*running} output record to determine
26001 which threads are resumed.
26005 @value{GDBN} has connected to a remote target.
26007 @item "^error" "," @var{c-string}
26009 The operation failed. The @code{@var{c-string}} contains the corresponding
26014 @value{GDBN} has terminated.
26018 @node GDB/MI Stream Records
26019 @subsection @sc{gdb/mi} Stream Records
26021 @cindex @sc{gdb/mi}, stream records
26022 @cindex stream records in @sc{gdb/mi}
26023 @value{GDBN} internally maintains a number of output streams: the console, the
26024 target, and the log. The output intended for each of these streams is
26025 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26027 Each stream record begins with a unique @dfn{prefix character} which
26028 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26029 Syntax}). In addition to the prefix, each stream record contains a
26030 @code{@var{string-output}}. This is either raw text (with an implicit new
26031 line) or a quoted C string (which does not contain an implicit newline).
26034 @item "~" @var{string-output}
26035 The console output stream contains text that should be displayed in the
26036 CLI console window. It contains the textual responses to CLI commands.
26038 @item "@@" @var{string-output}
26039 The target output stream contains any textual output from the running
26040 target. This is only present when GDB's event loop is truly
26041 asynchronous, which is currently only the case for remote targets.
26043 @item "&" @var{string-output}
26044 The log stream contains debugging messages being produced by @value{GDBN}'s
26048 @node GDB/MI Async Records
26049 @subsection @sc{gdb/mi} Async Records
26051 @cindex async records in @sc{gdb/mi}
26052 @cindex @sc{gdb/mi}, async records
26053 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26054 additional changes that have occurred. Those changes can either be a
26055 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26056 target activity (e.g., target stopped).
26058 The following is the list of possible async records:
26062 @item *running,thread-id="@var{thread}"
26063 The target is now running. The @var{thread} field tells which
26064 specific thread is now running, and can be @samp{all} if all threads
26065 are running. The frontend should assume that no interaction with a
26066 running thread is possible after this notification is produced.
26067 The frontend should not assume that this notification is output
26068 only once for any command. @value{GDBN} may emit this notification
26069 several times, either for different threads, because it cannot resume
26070 all threads together, or even for a single thread, if the thread must
26071 be stepped though some code before letting it run freely.
26073 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26074 The target has stopped. The @var{reason} field can have one of the
26078 @item breakpoint-hit
26079 A breakpoint was reached.
26080 @item watchpoint-trigger
26081 A watchpoint was triggered.
26082 @item read-watchpoint-trigger
26083 A read watchpoint was triggered.
26084 @item access-watchpoint-trigger
26085 An access watchpoint was triggered.
26086 @item function-finished
26087 An -exec-finish or similar CLI command was accomplished.
26088 @item location-reached
26089 An -exec-until or similar CLI command was accomplished.
26090 @item watchpoint-scope
26091 A watchpoint has gone out of scope.
26092 @item end-stepping-range
26093 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26094 similar CLI command was accomplished.
26095 @item exited-signalled
26096 The inferior exited because of a signal.
26098 The inferior exited.
26099 @item exited-normally
26100 The inferior exited normally.
26101 @item signal-received
26102 A signal was received by the inferior.
26105 The @var{id} field identifies the thread that directly caused the stop
26106 -- for example by hitting a breakpoint. Depending on whether all-stop
26107 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26108 stop all threads, or only the thread that directly triggered the stop.
26109 If all threads are stopped, the @var{stopped} field will have the
26110 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26111 field will be a list of thread identifiers. Presently, this list will
26112 always include a single thread, but frontend should be prepared to see
26113 several threads in the list. The @var{core} field reports the
26114 processor core on which the stop event has happened. This field may be absent
26115 if such information is not available.
26117 @item =thread-group-added,id="@var{id}"
26118 @itemx =thread-group-removed,id="@var{id}"
26119 A thread group was either added or removed. The @var{id} field
26120 contains the @value{GDBN} identifier of the thread group. When a thread
26121 group is added, it generally might not be associated with a running
26122 process. When a thread group is removed, its id becomes invalid and
26123 cannot be used in any way.
26125 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26126 A thread group became associated with a running program,
26127 either because the program was just started or the thread group
26128 was attached to a program. The @var{id} field contains the
26129 @value{GDBN} identifier of the thread group. The @var{pid} field
26130 contains process identifier, specific to the operating system.
26132 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26133 A thread group is no longer associated with a running program,
26134 either because the program has exited, or because it was detached
26135 from. The @var{id} field contains the @value{GDBN} identifier of the
26136 thread group. @var{code} is the exit code of the inferior; it exists
26137 only when the inferior exited with some code.
26139 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26140 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26141 A thread either was created, or has exited. The @var{id} field
26142 contains the @value{GDBN} identifier of the thread. The @var{gid}
26143 field identifies the thread group this thread belongs to.
26145 @item =thread-selected,id="@var{id}"
26146 Informs that the selected thread was changed as result of the last
26147 command. This notification is not emitted as result of @code{-thread-select}
26148 command but is emitted whenever an MI command that is not documented
26149 to change the selected thread actually changes it. In particular,
26150 invoking, directly or indirectly (via user-defined command), the CLI
26151 @code{thread} command, will generate this notification.
26153 We suggest that in response to this notification, front ends
26154 highlight the selected thread and cause subsequent commands to apply to
26157 @item =library-loaded,...
26158 Reports that a new library file was loaded by the program. This
26159 notification has 4 fields---@var{id}, @var{target-name},
26160 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26161 opaque identifier of the library. For remote debugging case,
26162 @var{target-name} and @var{host-name} fields give the name of the
26163 library file on the target, and on the host respectively. For native
26164 debugging, both those fields have the same value. The
26165 @var{symbols-loaded} field is emitted only for backward compatibility
26166 and should not be relied on to convey any useful information. The
26167 @var{thread-group} field, if present, specifies the id of the thread
26168 group in whose context the library was loaded. If the field is
26169 absent, it means the library was loaded in the context of all present
26172 @item =library-unloaded,...
26173 Reports that a library was unloaded by the program. This notification
26174 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26175 the same meaning as for the @code{=library-loaded} notification.
26176 The @var{thread-group} field, if present, specifies the id of the
26177 thread group in whose context the library was unloaded. If the field is
26178 absent, it means the library was unloaded in the context of all present
26181 @item =breakpoint-created,bkpt=@{...@}
26182 @itemx =breakpoint-modified,bkpt=@{...@}
26183 @itemx =breakpoint-deleted,bkpt=@{...@}
26184 Reports that a breakpoint was created, modified, or deleted,
26185 respectively. Only user-visible breakpoints are reported to the MI
26188 The @var{bkpt} argument is of the same form as returned by the various
26189 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
26191 Note that if a breakpoint is emitted in the result record of a
26192 command, then it will not also be emitted in an async record.
26196 @node GDB/MI Frame Information
26197 @subsection @sc{gdb/mi} Frame Information
26199 Response from many MI commands includes an information about stack
26200 frame. This information is a tuple that may have the following
26205 The level of the stack frame. The innermost frame has the level of
26206 zero. This field is always present.
26209 The name of the function corresponding to the frame. This field may
26210 be absent if @value{GDBN} is unable to determine the function name.
26213 The code address for the frame. This field is always present.
26216 The name of the source files that correspond to the frame's code
26217 address. This field may be absent.
26220 The source line corresponding to the frames' code address. This field
26224 The name of the binary file (either executable or shared library) the
26225 corresponds to the frame's code address. This field may be absent.
26229 @node GDB/MI Thread Information
26230 @subsection @sc{gdb/mi} Thread Information
26232 Whenever @value{GDBN} has to report an information about a thread, it
26233 uses a tuple with the following fields:
26237 The numeric id assigned to the thread by @value{GDBN}. This field is
26241 Target-specific string identifying the thread. This field is always present.
26244 Additional information about the thread provided by the target.
26245 It is supposed to be human-readable and not interpreted by the
26246 frontend. This field is optional.
26249 Either @samp{stopped} or @samp{running}, depending on whether the
26250 thread is presently running. This field is always present.
26253 The value of this field is an integer number of the processor core the
26254 thread was last seen on. This field is optional.
26257 @node GDB/MI Ada Exception Information
26258 @subsection @sc{gdb/mi} Ada Exception Information
26260 Whenever a @code{*stopped} record is emitted because the program
26261 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26262 @value{GDBN} provides the name of the exception that was raised via
26263 the @code{exception-name} field.
26265 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26266 @node GDB/MI Simple Examples
26267 @section Simple Examples of @sc{gdb/mi} Interaction
26268 @cindex @sc{gdb/mi}, simple examples
26270 This subsection presents several simple examples of interaction using
26271 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26272 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26273 the output received from @sc{gdb/mi}.
26275 Note the line breaks shown in the examples are here only for
26276 readability, they don't appear in the real output.
26278 @subheading Setting a Breakpoint
26280 Setting a breakpoint generates synchronous output which contains detailed
26281 information of the breakpoint.
26284 -> -break-insert main
26285 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26286 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26287 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
26291 @subheading Program Execution
26293 Program execution generates asynchronous records and MI gives the
26294 reason that execution stopped.
26300 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26301 frame=@{addr="0x08048564",func="main",
26302 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26303 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26308 <- *stopped,reason="exited-normally"
26312 @subheading Quitting @value{GDBN}
26314 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26322 Please note that @samp{^exit} is printed immediately, but it might
26323 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26324 performs necessary cleanups, including killing programs being debugged
26325 or disconnecting from debug hardware, so the frontend should wait till
26326 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26327 fails to exit in reasonable time.
26329 @subheading A Bad Command
26331 Here's what happens if you pass a non-existent command:
26335 <- ^error,msg="Undefined MI command: rubbish"
26340 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26341 @node GDB/MI Command Description Format
26342 @section @sc{gdb/mi} Command Description Format
26344 The remaining sections describe blocks of commands. Each block of
26345 commands is laid out in a fashion similar to this section.
26347 @subheading Motivation
26349 The motivation for this collection of commands.
26351 @subheading Introduction
26353 A brief introduction to this collection of commands as a whole.
26355 @subheading Commands
26357 For each command in the block, the following is described:
26359 @subsubheading Synopsis
26362 -command @var{args}@dots{}
26365 @subsubheading Result
26367 @subsubheading @value{GDBN} Command
26369 The corresponding @value{GDBN} CLI command(s), if any.
26371 @subsubheading Example
26373 Example(s) formatted for readability. Some of the described commands have
26374 not been implemented yet and these are labeled N.A.@: (not available).
26377 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26378 @node GDB/MI Breakpoint Commands
26379 @section @sc{gdb/mi} Breakpoint Commands
26381 @cindex breakpoint commands for @sc{gdb/mi}
26382 @cindex @sc{gdb/mi}, breakpoint commands
26383 This section documents @sc{gdb/mi} commands for manipulating
26386 @subheading The @code{-break-after} Command
26387 @findex -break-after
26389 @subsubheading Synopsis
26392 -break-after @var{number} @var{count}
26395 The breakpoint number @var{number} is not in effect until it has been
26396 hit @var{count} times. To see how this is reflected in the output of
26397 the @samp{-break-list} command, see the description of the
26398 @samp{-break-list} command below.
26400 @subsubheading @value{GDBN} Command
26402 The corresponding @value{GDBN} command is @samp{ignore}.
26404 @subsubheading Example
26409 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26410 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26411 fullname="/home/foo/hello.c",line="5",times="0"@}
26418 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26419 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26420 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26421 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26422 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26423 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26424 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26425 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26426 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26427 line="5",times="0",ignore="3"@}]@}
26432 @subheading The @code{-break-catch} Command
26433 @findex -break-catch
26436 @subheading The @code{-break-commands} Command
26437 @findex -break-commands
26439 @subsubheading Synopsis
26442 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26445 Specifies the CLI commands that should be executed when breakpoint
26446 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26447 are the commands. If no command is specified, any previously-set
26448 commands are cleared. @xref{Break Commands}. Typical use of this
26449 functionality is tracing a program, that is, printing of values of
26450 some variables whenever breakpoint is hit and then continuing.
26452 @subsubheading @value{GDBN} Command
26454 The corresponding @value{GDBN} command is @samp{commands}.
26456 @subsubheading Example
26461 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26462 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26463 fullname="/home/foo/hello.c",line="5",times="0"@}
26465 -break-commands 1 "print v" "continue"
26470 @subheading The @code{-break-condition} Command
26471 @findex -break-condition
26473 @subsubheading Synopsis
26476 -break-condition @var{number} @var{expr}
26479 Breakpoint @var{number} will stop the program only if the condition in
26480 @var{expr} is true. The condition becomes part of the
26481 @samp{-break-list} output (see the description of the @samp{-break-list}
26484 @subsubheading @value{GDBN} Command
26486 The corresponding @value{GDBN} command is @samp{condition}.
26488 @subsubheading Example
26492 -break-condition 1 1
26496 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26497 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26498 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26499 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26500 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26501 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26502 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26503 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26504 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26505 line="5",cond="1",times="0",ignore="3"@}]@}
26509 @subheading The @code{-break-delete} Command
26510 @findex -break-delete
26512 @subsubheading Synopsis
26515 -break-delete ( @var{breakpoint} )+
26518 Delete the breakpoint(s) whose number(s) are specified in the argument
26519 list. This is obviously reflected in the breakpoint list.
26521 @subsubheading @value{GDBN} Command
26523 The corresponding @value{GDBN} command is @samp{delete}.
26525 @subsubheading Example
26533 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26534 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26535 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26536 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26537 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26538 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26539 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26544 @subheading The @code{-break-disable} Command
26545 @findex -break-disable
26547 @subsubheading Synopsis
26550 -break-disable ( @var{breakpoint} )+
26553 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26554 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26556 @subsubheading @value{GDBN} Command
26558 The corresponding @value{GDBN} command is @samp{disable}.
26560 @subsubheading Example
26568 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26569 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26570 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26571 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26572 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26573 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26574 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26575 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26576 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26577 line="5",times="0"@}]@}
26581 @subheading The @code{-break-enable} Command
26582 @findex -break-enable
26584 @subsubheading Synopsis
26587 -break-enable ( @var{breakpoint} )+
26590 Enable (previously disabled) @var{breakpoint}(s).
26592 @subsubheading @value{GDBN} Command
26594 The corresponding @value{GDBN} command is @samp{enable}.
26596 @subsubheading Example
26604 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26605 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26606 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26607 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26608 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26609 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26610 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26611 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26612 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26613 line="5",times="0"@}]@}
26617 @subheading The @code{-break-info} Command
26618 @findex -break-info
26620 @subsubheading Synopsis
26623 -break-info @var{breakpoint}
26627 Get information about a single breakpoint.
26629 @subsubheading @value{GDBN} Command
26631 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26633 @subsubheading Example
26636 @subheading The @code{-break-insert} Command
26637 @findex -break-insert
26639 @subsubheading Synopsis
26642 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26643 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26644 [ -p @var{thread} ] [ @var{location} ]
26648 If specified, @var{location}, can be one of:
26655 @item filename:linenum
26656 @item filename:function
26660 The possible optional parameters of this command are:
26664 Insert a temporary breakpoint.
26666 Insert a hardware breakpoint.
26667 @item -c @var{condition}
26668 Make the breakpoint conditional on @var{condition}.
26669 @item -i @var{ignore-count}
26670 Initialize the @var{ignore-count}.
26672 If @var{location} cannot be parsed (for example if it
26673 refers to unknown files or functions), create a pending
26674 breakpoint. Without this flag, @value{GDBN} will report
26675 an error, and won't create a breakpoint, if @var{location}
26678 Create a disabled breakpoint.
26680 Create a tracepoint. @xref{Tracepoints}. When this parameter
26681 is used together with @samp{-h}, a fast tracepoint is created.
26684 @subsubheading Result
26686 The result is in the form:
26689 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
26690 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
26691 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
26692 times="@var{times}"@}
26696 where @var{number} is the @value{GDBN} number for this breakpoint,
26697 @var{funcname} is the name of the function where the breakpoint was
26698 inserted, @var{filename} is the name of the source file which contains
26699 this function, @var{lineno} is the source line number within that file
26700 and @var{times} the number of times that the breakpoint has been hit
26701 (always 0 for -break-insert but may be greater for -break-info or -break-list
26702 which use the same output).
26704 Note: this format is open to change.
26705 @c An out-of-band breakpoint instead of part of the result?
26707 @subsubheading @value{GDBN} Command
26709 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26710 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
26712 @subsubheading Example
26717 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26718 fullname="/home/foo/recursive2.c,line="4",times="0"@}
26720 -break-insert -t foo
26721 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26722 fullname="/home/foo/recursive2.c,line="11",times="0"@}
26725 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26726 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26727 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26728 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26729 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26730 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26731 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26732 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26733 addr="0x0001072c", func="main",file="recursive2.c",
26734 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
26735 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26736 addr="0x00010774",func="foo",file="recursive2.c",
26737 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
26739 -break-insert -r foo.*
26740 ~int foo(int, int);
26741 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26742 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
26746 @subheading The @code{-break-list} Command
26747 @findex -break-list
26749 @subsubheading Synopsis
26755 Displays the list of inserted breakpoints, showing the following fields:
26759 number of the breakpoint
26761 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26763 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26766 is the breakpoint enabled or no: @samp{y} or @samp{n}
26768 memory location at which the breakpoint is set
26770 logical location of the breakpoint, expressed by function name, file
26773 number of times the breakpoint has been hit
26776 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26777 @code{body} field is an empty list.
26779 @subsubheading @value{GDBN} Command
26781 The corresponding @value{GDBN} command is @samp{info break}.
26783 @subsubheading Example
26788 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26789 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26790 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26791 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26792 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26793 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26794 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26795 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26796 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
26797 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26798 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26799 line="13",times="0"@}]@}
26803 Here's an example of the result when there are no breakpoints:
26808 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26809 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26810 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26811 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26812 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26813 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26814 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26819 @subheading The @code{-break-passcount} Command
26820 @findex -break-passcount
26822 @subsubheading Synopsis
26825 -break-passcount @var{tracepoint-number} @var{passcount}
26828 Set the passcount for tracepoint @var{tracepoint-number} to
26829 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26830 is not a tracepoint, error is emitted. This corresponds to CLI
26831 command @samp{passcount}.
26833 @subheading The @code{-break-watch} Command
26834 @findex -break-watch
26836 @subsubheading Synopsis
26839 -break-watch [ -a | -r ]
26842 Create a watchpoint. With the @samp{-a} option it will create an
26843 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26844 read from or on a write to the memory location. With the @samp{-r}
26845 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26846 trigger only when the memory location is accessed for reading. Without
26847 either of the options, the watchpoint created is a regular watchpoint,
26848 i.e., it will trigger when the memory location is accessed for writing.
26849 @xref{Set Watchpoints, , Setting Watchpoints}.
26851 Note that @samp{-break-list} will report a single list of watchpoints and
26852 breakpoints inserted.
26854 @subsubheading @value{GDBN} Command
26856 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26859 @subsubheading Example
26861 Setting a watchpoint on a variable in the @code{main} function:
26866 ^done,wpt=@{number="2",exp="x"@}
26871 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26872 value=@{old="-268439212",new="55"@},
26873 frame=@{func="main",args=[],file="recursive2.c",
26874 fullname="/home/foo/bar/recursive2.c",line="5"@}
26878 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26879 the program execution twice: first for the variable changing value, then
26880 for the watchpoint going out of scope.
26885 ^done,wpt=@{number="5",exp="C"@}
26890 *stopped,reason="watchpoint-trigger",
26891 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
26892 frame=@{func="callee4",args=[],
26893 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26894 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26899 *stopped,reason="watchpoint-scope",wpnum="5",
26900 frame=@{func="callee3",args=[@{name="strarg",
26901 value="0x11940 \"A string argument.\""@}],
26902 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26903 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26907 Listing breakpoints and watchpoints, at different points in the program
26908 execution. Note that once the watchpoint goes out of scope, it is
26914 ^done,wpt=@{number="2",exp="C"@}
26917 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26918 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26919 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26920 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26921 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26922 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26923 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26924 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26925 addr="0x00010734",func="callee4",
26926 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26927 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
26928 bkpt=@{number="2",type="watchpoint",disp="keep",
26929 enabled="y",addr="",what="C",times="0"@}]@}
26934 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
26935 value=@{old="-276895068",new="3"@},
26936 frame=@{func="callee4",args=[],
26937 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26938 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26941 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26942 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26943 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26944 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26945 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26946 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26947 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26948 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26949 addr="0x00010734",func="callee4",
26950 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26951 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
26952 bkpt=@{number="2",type="watchpoint",disp="keep",
26953 enabled="y",addr="",what="C",times="-5"@}]@}
26957 ^done,reason="watchpoint-scope",wpnum="2",
26958 frame=@{func="callee3",args=[@{name="strarg",
26959 value="0x11940 \"A string argument.\""@}],
26960 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26961 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26964 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26965 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26966 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26967 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26968 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26969 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26970 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26971 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26972 addr="0x00010734",func="callee4",
26973 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26974 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
26979 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26980 @node GDB/MI Program Context
26981 @section @sc{gdb/mi} Program Context
26983 @subheading The @code{-exec-arguments} Command
26984 @findex -exec-arguments
26987 @subsubheading Synopsis
26990 -exec-arguments @var{args}
26993 Set the inferior program arguments, to be used in the next
26996 @subsubheading @value{GDBN} Command
26998 The corresponding @value{GDBN} command is @samp{set args}.
27000 @subsubheading Example
27004 -exec-arguments -v word
27011 @subheading The @code{-exec-show-arguments} Command
27012 @findex -exec-show-arguments
27014 @subsubheading Synopsis
27017 -exec-show-arguments
27020 Print the arguments of the program.
27022 @subsubheading @value{GDBN} Command
27024 The corresponding @value{GDBN} command is @samp{show args}.
27026 @subsubheading Example
27031 @subheading The @code{-environment-cd} Command
27032 @findex -environment-cd
27034 @subsubheading Synopsis
27037 -environment-cd @var{pathdir}
27040 Set @value{GDBN}'s working directory.
27042 @subsubheading @value{GDBN} Command
27044 The corresponding @value{GDBN} command is @samp{cd}.
27046 @subsubheading Example
27050 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27056 @subheading The @code{-environment-directory} Command
27057 @findex -environment-directory
27059 @subsubheading Synopsis
27062 -environment-directory [ -r ] [ @var{pathdir} ]+
27065 Add directories @var{pathdir} to beginning of search path for source files.
27066 If the @samp{-r} option is used, the search path is reset to the default
27067 search path. If directories @var{pathdir} are supplied in addition to the
27068 @samp{-r} option, the search path is first reset and then addition
27070 Multiple directories may be specified, separated by blanks. Specifying
27071 multiple directories in a single command
27072 results in the directories added to the beginning of the
27073 search path in the same order they were presented in the command.
27074 If blanks are needed as
27075 part of a directory name, double-quotes should be used around
27076 the name. In the command output, the path will show up separated
27077 by the system directory-separator character. The directory-separator
27078 character must not be used
27079 in any directory name.
27080 If no directories are specified, the current search path is displayed.
27082 @subsubheading @value{GDBN} Command
27084 The corresponding @value{GDBN} command is @samp{dir}.
27086 @subsubheading Example
27090 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27091 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27093 -environment-directory ""
27094 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27096 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27097 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27099 -environment-directory -r
27100 ^done,source-path="$cdir:$cwd"
27105 @subheading The @code{-environment-path} Command
27106 @findex -environment-path
27108 @subsubheading Synopsis
27111 -environment-path [ -r ] [ @var{pathdir} ]+
27114 Add directories @var{pathdir} to beginning of search path for object files.
27115 If the @samp{-r} option is used, the search path is reset to the original
27116 search path that existed at gdb start-up. If directories @var{pathdir} are
27117 supplied in addition to the
27118 @samp{-r} option, the search path is first reset and then addition
27120 Multiple directories may be specified, separated by blanks. Specifying
27121 multiple directories in a single command
27122 results in the directories added to the beginning of the
27123 search path in the same order they were presented in the command.
27124 If blanks are needed as
27125 part of a directory name, double-quotes should be used around
27126 the name. In the command output, the path will show up separated
27127 by the system directory-separator character. The directory-separator
27128 character must not be used
27129 in any directory name.
27130 If no directories are specified, the current path is displayed.
27133 @subsubheading @value{GDBN} Command
27135 The corresponding @value{GDBN} command is @samp{path}.
27137 @subsubheading Example
27142 ^done,path="/usr/bin"
27144 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27145 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27147 -environment-path -r /usr/local/bin
27148 ^done,path="/usr/local/bin:/usr/bin"
27153 @subheading The @code{-environment-pwd} Command
27154 @findex -environment-pwd
27156 @subsubheading Synopsis
27162 Show the current working directory.
27164 @subsubheading @value{GDBN} Command
27166 The corresponding @value{GDBN} command is @samp{pwd}.
27168 @subsubheading Example
27173 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27177 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27178 @node GDB/MI Thread Commands
27179 @section @sc{gdb/mi} Thread Commands
27182 @subheading The @code{-thread-info} Command
27183 @findex -thread-info
27185 @subsubheading Synopsis
27188 -thread-info [ @var{thread-id} ]
27191 Reports information about either a specific thread, if
27192 the @var{thread-id} parameter is present, or about all
27193 threads. When printing information about all threads,
27194 also reports the current thread.
27196 @subsubheading @value{GDBN} Command
27198 The @samp{info thread} command prints the same information
27201 @subsubheading Result
27203 The result is a list of threads. The following attributes are
27204 defined for a given thread:
27208 This field exists only for the current thread. It has the value @samp{*}.
27211 The identifier that @value{GDBN} uses to refer to the thread.
27214 The identifier that the target uses to refer to the thread.
27217 Extra information about the thread, in a target-specific format. This
27221 The name of the thread. If the user specified a name using the
27222 @code{thread name} command, then this name is given. Otherwise, if
27223 @value{GDBN} can extract the thread name from the target, then that
27224 name is given. If @value{GDBN} cannot find the thread name, then this
27228 The stack frame currently executing in the thread.
27231 The thread's state. The @samp{state} field may have the following
27236 The thread is stopped. Frame information is available for stopped
27240 The thread is running. There's no frame information for running
27246 If @value{GDBN} can find the CPU core on which this thread is running,
27247 then this field is the core identifier. This field is optional.
27251 @subsubheading Example
27256 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27257 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27258 args=[]@},state="running"@},
27259 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27260 frame=@{level="0",addr="0x0804891f",func="foo",
27261 args=[@{name="i",value="10"@}],
27262 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27263 state="running"@}],
27264 current-thread-id="1"
27268 @subheading The @code{-thread-list-ids} Command
27269 @findex -thread-list-ids
27271 @subsubheading Synopsis
27277 Produces a list of the currently known @value{GDBN} thread ids. At the
27278 end of the list it also prints the total number of such threads.
27280 This command is retained for historical reasons, the
27281 @code{-thread-info} command should be used instead.
27283 @subsubheading @value{GDBN} Command
27285 Part of @samp{info threads} supplies the same information.
27287 @subsubheading Example
27292 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27293 current-thread-id="1",number-of-threads="3"
27298 @subheading The @code{-thread-select} Command
27299 @findex -thread-select
27301 @subsubheading Synopsis
27304 -thread-select @var{threadnum}
27307 Make @var{threadnum} the current thread. It prints the number of the new
27308 current thread, and the topmost frame for that thread.
27310 This command is deprecated in favor of explicitly using the
27311 @samp{--thread} option to each command.
27313 @subsubheading @value{GDBN} Command
27315 The corresponding @value{GDBN} command is @samp{thread}.
27317 @subsubheading Example
27324 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27325 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27329 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27330 number-of-threads="3"
27333 ^done,new-thread-id="3",
27334 frame=@{level="0",func="vprintf",
27335 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27336 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27340 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27341 @node GDB/MI Ada Tasking Commands
27342 @section @sc{gdb/mi} Ada Tasking Commands
27344 @subheading The @code{-ada-task-info} Command
27345 @findex -ada-task-info
27347 @subsubheading Synopsis
27350 -ada-task-info [ @var{task-id} ]
27353 Reports information about either a specific Ada task, if the
27354 @var{task-id} parameter is present, or about all Ada tasks.
27356 @subsubheading @value{GDBN} Command
27358 The @samp{info tasks} command prints the same information
27359 about all Ada tasks (@pxref{Ada Tasks}).
27361 @subsubheading Result
27363 The result is a table of Ada tasks. The following columns are
27364 defined for each Ada task:
27368 This field exists only for the current thread. It has the value @samp{*}.
27371 The identifier that @value{GDBN} uses to refer to the Ada task.
27374 The identifier that the target uses to refer to the Ada task.
27377 The identifier of the thread corresponding to the Ada task.
27379 This field should always exist, as Ada tasks are always implemented
27380 on top of a thread. But if @value{GDBN} cannot find this corresponding
27381 thread for any reason, the field is omitted.
27384 This field exists only when the task was created by another task.
27385 In this case, it provides the ID of the parent task.
27388 The base priority of the task.
27391 The current state of the task. For a detailed description of the
27392 possible states, see @ref{Ada Tasks}.
27395 The name of the task.
27399 @subsubheading Example
27403 ^done,tasks=@{nr_rows="3",nr_cols="8",
27404 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27405 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27406 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27407 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27408 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27409 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27410 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27411 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27412 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27413 state="Child Termination Wait",name="main_task"@}]@}
27417 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27418 @node GDB/MI Program Execution
27419 @section @sc{gdb/mi} Program Execution
27421 These are the asynchronous commands which generate the out-of-band
27422 record @samp{*stopped}. Currently @value{GDBN} only really executes
27423 asynchronously with remote targets and this interaction is mimicked in
27426 @subheading The @code{-exec-continue} Command
27427 @findex -exec-continue
27429 @subsubheading Synopsis
27432 -exec-continue [--reverse] [--all|--thread-group N]
27435 Resumes the execution of the inferior program, which will continue
27436 to execute until it reaches a debugger stop event. If the
27437 @samp{--reverse} option is specified, execution resumes in reverse until
27438 it reaches a stop event. Stop events may include
27441 breakpoints or watchpoints
27443 signals or exceptions
27445 the end of the process (or its beginning under @samp{--reverse})
27447 the end or beginning of a replay log if one is being used.
27449 In all-stop mode (@pxref{All-Stop
27450 Mode}), may resume only one thread, or all threads, depending on the
27451 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27452 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27453 ignored in all-stop mode. If the @samp{--thread-group} options is
27454 specified, then all threads in that thread group are resumed.
27456 @subsubheading @value{GDBN} Command
27458 The corresponding @value{GDBN} corresponding is @samp{continue}.
27460 @subsubheading Example
27467 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27468 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27474 @subheading The @code{-exec-finish} Command
27475 @findex -exec-finish
27477 @subsubheading Synopsis
27480 -exec-finish [--reverse]
27483 Resumes the execution of the inferior program until the current
27484 function is exited. Displays the results returned by the function.
27485 If the @samp{--reverse} option is specified, resumes the reverse
27486 execution of the inferior program until the point where current
27487 function was called.
27489 @subsubheading @value{GDBN} Command
27491 The corresponding @value{GDBN} command is @samp{finish}.
27493 @subsubheading Example
27495 Function returning @code{void}.
27502 *stopped,reason="function-finished",frame=@{func="main",args=[],
27503 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27507 Function returning other than @code{void}. The name of the internal
27508 @value{GDBN} variable storing the result is printed, together with the
27515 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27516 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27517 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27518 gdb-result-var="$1",return-value="0"
27523 @subheading The @code{-exec-interrupt} Command
27524 @findex -exec-interrupt
27526 @subsubheading Synopsis
27529 -exec-interrupt [--all|--thread-group N]
27532 Interrupts the background execution of the target. Note how the token
27533 associated with the stop message is the one for the execution command
27534 that has been interrupted. The token for the interrupt itself only
27535 appears in the @samp{^done} output. If the user is trying to
27536 interrupt a non-running program, an error message will be printed.
27538 Note that when asynchronous execution is enabled, this command is
27539 asynchronous just like other execution commands. That is, first the
27540 @samp{^done} response will be printed, and the target stop will be
27541 reported after that using the @samp{*stopped} notification.
27543 In non-stop mode, only the context thread is interrupted by default.
27544 All threads (in all inferiors) will be interrupted if the
27545 @samp{--all} option is specified. If the @samp{--thread-group}
27546 option is specified, all threads in that group will be interrupted.
27548 @subsubheading @value{GDBN} Command
27550 The corresponding @value{GDBN} command is @samp{interrupt}.
27552 @subsubheading Example
27563 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27564 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27565 fullname="/home/foo/bar/try.c",line="13"@}
27570 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27574 @subheading The @code{-exec-jump} Command
27577 @subsubheading Synopsis
27580 -exec-jump @var{location}
27583 Resumes execution of the inferior program at the location specified by
27584 parameter. @xref{Specify Location}, for a description of the
27585 different forms of @var{location}.
27587 @subsubheading @value{GDBN} Command
27589 The corresponding @value{GDBN} command is @samp{jump}.
27591 @subsubheading Example
27594 -exec-jump foo.c:10
27595 *running,thread-id="all"
27600 @subheading The @code{-exec-next} Command
27603 @subsubheading Synopsis
27606 -exec-next [--reverse]
27609 Resumes execution of the inferior program, stopping when the beginning
27610 of the next source line is reached.
27612 If the @samp{--reverse} option is specified, resumes reverse execution
27613 of the inferior program, stopping at the beginning of the previous
27614 source line. If you issue this command on the first line of a
27615 function, it will take you back to the caller of that function, to the
27616 source line where the function was called.
27619 @subsubheading @value{GDBN} Command
27621 The corresponding @value{GDBN} command is @samp{next}.
27623 @subsubheading Example
27629 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27634 @subheading The @code{-exec-next-instruction} Command
27635 @findex -exec-next-instruction
27637 @subsubheading Synopsis
27640 -exec-next-instruction [--reverse]
27643 Executes one machine instruction. If the instruction is a function
27644 call, continues until the function returns. If the program stops at an
27645 instruction in the middle of a source line, the address will be
27648 If the @samp{--reverse} option is specified, resumes reverse execution
27649 of the inferior program, stopping at the previous instruction. If the
27650 previously executed instruction was a return from another function,
27651 it will continue to execute in reverse until the call to that function
27652 (from the current stack frame) is reached.
27654 @subsubheading @value{GDBN} Command
27656 The corresponding @value{GDBN} command is @samp{nexti}.
27658 @subsubheading Example
27662 -exec-next-instruction
27666 *stopped,reason="end-stepping-range",
27667 addr="0x000100d4",line="5",file="hello.c"
27672 @subheading The @code{-exec-return} Command
27673 @findex -exec-return
27675 @subsubheading Synopsis
27681 Makes current function return immediately. Doesn't execute the inferior.
27682 Displays the new current frame.
27684 @subsubheading @value{GDBN} Command
27686 The corresponding @value{GDBN} command is @samp{return}.
27688 @subsubheading Example
27692 200-break-insert callee4
27693 200^done,bkpt=@{number="1",addr="0x00010734",
27694 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27699 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27700 frame=@{func="callee4",args=[],
27701 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27702 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27708 111^done,frame=@{level="0",func="callee3",
27709 args=[@{name="strarg",
27710 value="0x11940 \"A string argument.\""@}],
27711 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27712 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27717 @subheading The @code{-exec-run} Command
27720 @subsubheading Synopsis
27723 -exec-run [--all | --thread-group N]
27726 Starts execution of the inferior from the beginning. The inferior
27727 executes until either a breakpoint is encountered or the program
27728 exits. In the latter case the output will include an exit code, if
27729 the program has exited exceptionally.
27731 When no option is specified, the current inferior is started. If the
27732 @samp{--thread-group} option is specified, it should refer to a thread
27733 group of type @samp{process}, and that thread group will be started.
27734 If the @samp{--all} option is specified, then all inferiors will be started.
27736 @subsubheading @value{GDBN} Command
27738 The corresponding @value{GDBN} command is @samp{run}.
27740 @subsubheading Examples
27745 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27750 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27751 frame=@{func="main",args=[],file="recursive2.c",
27752 fullname="/home/foo/bar/recursive2.c",line="4"@}
27757 Program exited normally:
27765 *stopped,reason="exited-normally"
27770 Program exited exceptionally:
27778 *stopped,reason="exited",exit-code="01"
27782 Another way the program can terminate is if it receives a signal such as
27783 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27787 *stopped,reason="exited-signalled",signal-name="SIGINT",
27788 signal-meaning="Interrupt"
27792 @c @subheading -exec-signal
27795 @subheading The @code{-exec-step} Command
27798 @subsubheading Synopsis
27801 -exec-step [--reverse]
27804 Resumes execution of the inferior program, stopping when the beginning
27805 of the next source line is reached, if the next source line is not a
27806 function call. If it is, stop at the first instruction of the called
27807 function. If the @samp{--reverse} option is specified, resumes reverse
27808 execution of the inferior program, stopping at the beginning of the
27809 previously executed source line.
27811 @subsubheading @value{GDBN} Command
27813 The corresponding @value{GDBN} command is @samp{step}.
27815 @subsubheading Example
27817 Stepping into a function:
27823 *stopped,reason="end-stepping-range",
27824 frame=@{func="foo",args=[@{name="a",value="10"@},
27825 @{name="b",value="0"@}],file="recursive2.c",
27826 fullname="/home/foo/bar/recursive2.c",line="11"@}
27836 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
27841 @subheading The @code{-exec-step-instruction} Command
27842 @findex -exec-step-instruction
27844 @subsubheading Synopsis
27847 -exec-step-instruction [--reverse]
27850 Resumes the inferior which executes one machine instruction. If the
27851 @samp{--reverse} option is specified, resumes reverse execution of the
27852 inferior program, stopping at the previously executed instruction.
27853 The output, once @value{GDBN} has stopped, will vary depending on
27854 whether we have stopped in the middle of a source line or not. In the
27855 former case, the address at which the program stopped will be printed
27858 @subsubheading @value{GDBN} Command
27860 The corresponding @value{GDBN} command is @samp{stepi}.
27862 @subsubheading Example
27866 -exec-step-instruction
27870 *stopped,reason="end-stepping-range",
27871 frame=@{func="foo",args=[],file="try.c",
27872 fullname="/home/foo/bar/try.c",line="10"@}
27874 -exec-step-instruction
27878 *stopped,reason="end-stepping-range",
27879 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
27880 fullname="/home/foo/bar/try.c",line="10"@}
27885 @subheading The @code{-exec-until} Command
27886 @findex -exec-until
27888 @subsubheading Synopsis
27891 -exec-until [ @var{location} ]
27894 Executes the inferior until the @var{location} specified in the
27895 argument is reached. If there is no argument, the inferior executes
27896 until a source line greater than the current one is reached. The
27897 reason for stopping in this case will be @samp{location-reached}.
27899 @subsubheading @value{GDBN} Command
27901 The corresponding @value{GDBN} command is @samp{until}.
27903 @subsubheading Example
27907 -exec-until recursive2.c:6
27911 *stopped,reason="location-reached",frame=@{func="main",args=[],
27912 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
27917 @subheading -file-clear
27918 Is this going away????
27921 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27922 @node GDB/MI Stack Manipulation
27923 @section @sc{gdb/mi} Stack Manipulation Commands
27926 @subheading The @code{-stack-info-frame} Command
27927 @findex -stack-info-frame
27929 @subsubheading Synopsis
27935 Get info on the selected frame.
27937 @subsubheading @value{GDBN} Command
27939 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
27940 (without arguments).
27942 @subsubheading Example
27947 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
27948 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27949 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
27953 @subheading The @code{-stack-info-depth} Command
27954 @findex -stack-info-depth
27956 @subsubheading Synopsis
27959 -stack-info-depth [ @var{max-depth} ]
27962 Return the depth of the stack. If the integer argument @var{max-depth}
27963 is specified, do not count beyond @var{max-depth} frames.
27965 @subsubheading @value{GDBN} Command
27967 There's no equivalent @value{GDBN} command.
27969 @subsubheading Example
27971 For a stack with frame levels 0 through 11:
27978 -stack-info-depth 4
27981 -stack-info-depth 12
27984 -stack-info-depth 11
27987 -stack-info-depth 13
27992 @subheading The @code{-stack-list-arguments} Command
27993 @findex -stack-list-arguments
27995 @subsubheading Synopsis
27998 -stack-list-arguments @var{print-values}
27999 [ @var{low-frame} @var{high-frame} ]
28002 Display a list of the arguments for the frames between @var{low-frame}
28003 and @var{high-frame} (inclusive). If @var{low-frame} and
28004 @var{high-frame} are not provided, list the arguments for the whole
28005 call stack. If the two arguments are equal, show the single frame
28006 at the corresponding level. It is an error if @var{low-frame} is
28007 larger than the actual number of frames. On the other hand,
28008 @var{high-frame} may be larger than the actual number of frames, in
28009 which case only existing frames will be returned.
28011 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28012 the variables; if it is 1 or @code{--all-values}, print also their
28013 values; and if it is 2 or @code{--simple-values}, print the name,
28014 type and value for simple data types, and the name and type for arrays,
28015 structures and unions.
28017 Use of this command to obtain arguments in a single frame is
28018 deprecated in favor of the @samp{-stack-list-variables} command.
28020 @subsubheading @value{GDBN} Command
28022 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28023 @samp{gdb_get_args} command which partially overlaps with the
28024 functionality of @samp{-stack-list-arguments}.
28026 @subsubheading Example
28033 frame=@{level="0",addr="0x00010734",func="callee4",
28034 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28035 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28036 frame=@{level="1",addr="0x0001076c",func="callee3",
28037 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28038 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28039 frame=@{level="2",addr="0x0001078c",func="callee2",
28040 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28041 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28042 frame=@{level="3",addr="0x000107b4",func="callee1",
28043 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28044 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28045 frame=@{level="4",addr="0x000107e0",func="main",
28046 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28047 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28049 -stack-list-arguments 0
28052 frame=@{level="0",args=[]@},
28053 frame=@{level="1",args=[name="strarg"]@},
28054 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28055 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28056 frame=@{level="4",args=[]@}]
28058 -stack-list-arguments 1
28061 frame=@{level="0",args=[]@},
28063 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28064 frame=@{level="2",args=[
28065 @{name="intarg",value="2"@},
28066 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28067 @{frame=@{level="3",args=[
28068 @{name="intarg",value="2"@},
28069 @{name="strarg",value="0x11940 \"A string argument.\""@},
28070 @{name="fltarg",value="3.5"@}]@},
28071 frame=@{level="4",args=[]@}]
28073 -stack-list-arguments 0 2 2
28074 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28076 -stack-list-arguments 1 2 2
28077 ^done,stack-args=[frame=@{level="2",
28078 args=[@{name="intarg",value="2"@},
28079 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28083 @c @subheading -stack-list-exception-handlers
28086 @subheading The @code{-stack-list-frames} Command
28087 @findex -stack-list-frames
28089 @subsubheading Synopsis
28092 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
28095 List the frames currently on the stack. For each frame it displays the
28100 The frame number, 0 being the topmost frame, i.e., the innermost function.
28102 The @code{$pc} value for that frame.
28106 File name of the source file where the function lives.
28107 @item @var{fullname}
28108 The full file name of the source file where the function lives.
28110 Line number corresponding to the @code{$pc}.
28112 The shared library where this function is defined. This is only given
28113 if the frame's function is not known.
28116 If invoked without arguments, this command prints a backtrace for the
28117 whole stack. If given two integer arguments, it shows the frames whose
28118 levels are between the two arguments (inclusive). If the two arguments
28119 are equal, it shows the single frame at the corresponding level. It is
28120 an error if @var{low-frame} is larger than the actual number of
28121 frames. On the other hand, @var{high-frame} may be larger than the
28122 actual number of frames, in which case only existing frames will be returned.
28124 @subsubheading @value{GDBN} Command
28126 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28128 @subsubheading Example
28130 Full stack backtrace:
28136 [frame=@{level="0",addr="0x0001076c",func="foo",
28137 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28138 frame=@{level="1",addr="0x000107a4",func="foo",
28139 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28140 frame=@{level="2",addr="0x000107a4",func="foo",
28141 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28142 frame=@{level="3",addr="0x000107a4",func="foo",
28143 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28144 frame=@{level="4",addr="0x000107a4",func="foo",
28145 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28146 frame=@{level="5",addr="0x000107a4",func="foo",
28147 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28148 frame=@{level="6",addr="0x000107a4",func="foo",
28149 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28150 frame=@{level="7",addr="0x000107a4",func="foo",
28151 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28152 frame=@{level="8",addr="0x000107a4",func="foo",
28153 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28154 frame=@{level="9",addr="0x000107a4",func="foo",
28155 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28156 frame=@{level="10",addr="0x000107a4",func="foo",
28157 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28158 frame=@{level="11",addr="0x00010738",func="main",
28159 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28163 Show frames between @var{low_frame} and @var{high_frame}:
28167 -stack-list-frames 3 5
28169 [frame=@{level="3",addr="0x000107a4",func="foo",
28170 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28171 frame=@{level="4",addr="0x000107a4",func="foo",
28172 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28173 frame=@{level="5",addr="0x000107a4",func="foo",
28174 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28178 Show a single frame:
28182 -stack-list-frames 3 3
28184 [frame=@{level="3",addr="0x000107a4",func="foo",
28185 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28190 @subheading The @code{-stack-list-locals} Command
28191 @findex -stack-list-locals
28193 @subsubheading Synopsis
28196 -stack-list-locals @var{print-values}
28199 Display the local variable names for the selected frame. If
28200 @var{print-values} is 0 or @code{--no-values}, print only the names of
28201 the variables; if it is 1 or @code{--all-values}, print also their
28202 values; and if it is 2 or @code{--simple-values}, print the name,
28203 type and value for simple data types, and the name and type for arrays,
28204 structures and unions. In this last case, a frontend can immediately
28205 display the value of simple data types and create variable objects for
28206 other data types when the user wishes to explore their values in
28209 This command is deprecated in favor of the
28210 @samp{-stack-list-variables} command.
28212 @subsubheading @value{GDBN} Command
28214 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28216 @subsubheading Example
28220 -stack-list-locals 0
28221 ^done,locals=[name="A",name="B",name="C"]
28223 -stack-list-locals --all-values
28224 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28225 @{name="C",value="@{1, 2, 3@}"@}]
28226 -stack-list-locals --simple-values
28227 ^done,locals=[@{name="A",type="int",value="1"@},
28228 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28232 @subheading The @code{-stack-list-variables} Command
28233 @findex -stack-list-variables
28235 @subsubheading Synopsis
28238 -stack-list-variables @var{print-values}
28241 Display the names of local variables and function arguments for the selected frame. If
28242 @var{print-values} is 0 or @code{--no-values}, print only the names of
28243 the variables; if it is 1 or @code{--all-values}, print also their
28244 values; and if it is 2 or @code{--simple-values}, print the name,
28245 type and value for simple data types, and the name and type for arrays,
28246 structures and unions.
28248 @subsubheading Example
28252 -stack-list-variables --thread 1 --frame 0 --all-values
28253 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28258 @subheading The @code{-stack-select-frame} Command
28259 @findex -stack-select-frame
28261 @subsubheading Synopsis
28264 -stack-select-frame @var{framenum}
28267 Change the selected frame. Select a different frame @var{framenum} on
28270 This command in deprecated in favor of passing the @samp{--frame}
28271 option to every command.
28273 @subsubheading @value{GDBN} Command
28275 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28276 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28278 @subsubheading Example
28282 -stack-select-frame 2
28287 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28288 @node GDB/MI Variable Objects
28289 @section @sc{gdb/mi} Variable Objects
28293 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28295 For the implementation of a variable debugger window (locals, watched
28296 expressions, etc.), we are proposing the adaptation of the existing code
28297 used by @code{Insight}.
28299 The two main reasons for that are:
28303 It has been proven in practice (it is already on its second generation).
28306 It will shorten development time (needless to say how important it is
28310 The original interface was designed to be used by Tcl code, so it was
28311 slightly changed so it could be used through @sc{gdb/mi}. This section
28312 describes the @sc{gdb/mi} operations that will be available and gives some
28313 hints about their use.
28315 @emph{Note}: In addition to the set of operations described here, we
28316 expect the @sc{gui} implementation of a variable window to require, at
28317 least, the following operations:
28320 @item @code{-gdb-show} @code{output-radix}
28321 @item @code{-stack-list-arguments}
28322 @item @code{-stack-list-locals}
28323 @item @code{-stack-select-frame}
28328 @subheading Introduction to Variable Objects
28330 @cindex variable objects in @sc{gdb/mi}
28332 Variable objects are "object-oriented" MI interface for examining and
28333 changing values of expressions. Unlike some other MI interfaces that
28334 work with expressions, variable objects are specifically designed for
28335 simple and efficient presentation in the frontend. A variable object
28336 is identified by string name. When a variable object is created, the
28337 frontend specifies the expression for that variable object. The
28338 expression can be a simple variable, or it can be an arbitrary complex
28339 expression, and can even involve CPU registers. After creating a
28340 variable object, the frontend can invoke other variable object
28341 operations---for example to obtain or change the value of a variable
28342 object, or to change display format.
28344 Variable objects have hierarchical tree structure. Any variable object
28345 that corresponds to a composite type, such as structure in C, has
28346 a number of child variable objects, for example corresponding to each
28347 element of a structure. A child variable object can itself have
28348 children, recursively. Recursion ends when we reach
28349 leaf variable objects, which always have built-in types. Child variable
28350 objects are created only by explicit request, so if a frontend
28351 is not interested in the children of a particular variable object, no
28352 child will be created.
28354 For a leaf variable object it is possible to obtain its value as a
28355 string, or set the value from a string. String value can be also
28356 obtained for a non-leaf variable object, but it's generally a string
28357 that only indicates the type of the object, and does not list its
28358 contents. Assignment to a non-leaf variable object is not allowed.
28360 A frontend does not need to read the values of all variable objects each time
28361 the program stops. Instead, MI provides an update command that lists all
28362 variable objects whose values has changed since the last update
28363 operation. This considerably reduces the amount of data that must
28364 be transferred to the frontend. As noted above, children variable
28365 objects are created on demand, and only leaf variable objects have a
28366 real value. As result, gdb will read target memory only for leaf
28367 variables that frontend has created.
28369 The automatic update is not always desirable. For example, a frontend
28370 might want to keep a value of some expression for future reference,
28371 and never update it. For another example, fetching memory is
28372 relatively slow for embedded targets, so a frontend might want
28373 to disable automatic update for the variables that are either not
28374 visible on the screen, or ``closed''. This is possible using so
28375 called ``frozen variable objects''. Such variable objects are never
28376 implicitly updated.
28378 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28379 fixed variable object, the expression is parsed when the variable
28380 object is created, including associating identifiers to specific
28381 variables. The meaning of expression never changes. For a floating
28382 variable object the values of variables whose names appear in the
28383 expressions are re-evaluated every time in the context of the current
28384 frame. Consider this example:
28389 struct work_state state;
28396 If a fixed variable object for the @code{state} variable is created in
28397 this function, and we enter the recursive call, the variable
28398 object will report the value of @code{state} in the top-level
28399 @code{do_work} invocation. On the other hand, a floating variable
28400 object will report the value of @code{state} in the current frame.
28402 If an expression specified when creating a fixed variable object
28403 refers to a local variable, the variable object becomes bound to the
28404 thread and frame in which the variable object is created. When such
28405 variable object is updated, @value{GDBN} makes sure that the
28406 thread/frame combination the variable object is bound to still exists,
28407 and re-evaluates the variable object in context of that thread/frame.
28409 The following is the complete set of @sc{gdb/mi} operations defined to
28410 access this functionality:
28412 @multitable @columnfractions .4 .6
28413 @item @strong{Operation}
28414 @tab @strong{Description}
28416 @item @code{-enable-pretty-printing}
28417 @tab enable Python-based pretty-printing
28418 @item @code{-var-create}
28419 @tab create a variable object
28420 @item @code{-var-delete}
28421 @tab delete the variable object and/or its children
28422 @item @code{-var-set-format}
28423 @tab set the display format of this variable
28424 @item @code{-var-show-format}
28425 @tab show the display format of this variable
28426 @item @code{-var-info-num-children}
28427 @tab tells how many children this object has
28428 @item @code{-var-list-children}
28429 @tab return a list of the object's children
28430 @item @code{-var-info-type}
28431 @tab show the type of this variable object
28432 @item @code{-var-info-expression}
28433 @tab print parent-relative expression that this variable object represents
28434 @item @code{-var-info-path-expression}
28435 @tab print full expression that this variable object represents
28436 @item @code{-var-show-attributes}
28437 @tab is this variable editable? does it exist here?
28438 @item @code{-var-evaluate-expression}
28439 @tab get the value of this variable
28440 @item @code{-var-assign}
28441 @tab set the value of this variable
28442 @item @code{-var-update}
28443 @tab update the variable and its children
28444 @item @code{-var-set-frozen}
28445 @tab set frozeness attribute
28446 @item @code{-var-set-update-range}
28447 @tab set range of children to display on update
28450 In the next subsection we describe each operation in detail and suggest
28451 how it can be used.
28453 @subheading Description And Use of Operations on Variable Objects
28455 @subheading The @code{-enable-pretty-printing} Command
28456 @findex -enable-pretty-printing
28459 -enable-pretty-printing
28462 @value{GDBN} allows Python-based visualizers to affect the output of the
28463 MI variable object commands. However, because there was no way to
28464 implement this in a fully backward-compatible way, a front end must
28465 request that this functionality be enabled.
28467 Once enabled, this feature cannot be disabled.
28469 Note that if Python support has not been compiled into @value{GDBN},
28470 this command will still succeed (and do nothing).
28472 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28473 may work differently in future versions of @value{GDBN}.
28475 @subheading The @code{-var-create} Command
28476 @findex -var-create
28478 @subsubheading Synopsis
28481 -var-create @{@var{name} | "-"@}
28482 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28485 This operation creates a variable object, which allows the monitoring of
28486 a variable, the result of an expression, a memory cell or a CPU
28489 The @var{name} parameter is the string by which the object can be
28490 referenced. It must be unique. If @samp{-} is specified, the varobj
28491 system will generate a string ``varNNNNNN'' automatically. It will be
28492 unique provided that one does not specify @var{name} of that format.
28493 The command fails if a duplicate name is found.
28495 The frame under which the expression should be evaluated can be
28496 specified by @var{frame-addr}. A @samp{*} indicates that the current
28497 frame should be used. A @samp{@@} indicates that a floating variable
28498 object must be created.
28500 @var{expression} is any expression valid on the current language set (must not
28501 begin with a @samp{*}), or one of the following:
28505 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28508 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28511 @samp{$@var{regname}} --- a CPU register name
28514 @cindex dynamic varobj
28515 A varobj's contents may be provided by a Python-based pretty-printer. In this
28516 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28517 have slightly different semantics in some cases. If the
28518 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28519 will never create a dynamic varobj. This ensures backward
28520 compatibility for existing clients.
28522 @subsubheading Result
28524 This operation returns attributes of the newly-created varobj. These
28529 The name of the varobj.
28532 The number of children of the varobj. This number is not necessarily
28533 reliable for a dynamic varobj. Instead, you must examine the
28534 @samp{has_more} attribute.
28537 The varobj's scalar value. For a varobj whose type is some sort of
28538 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28539 will not be interesting.
28542 The varobj's type. This is a string representation of the type, as
28543 would be printed by the @value{GDBN} CLI.
28546 If a variable object is bound to a specific thread, then this is the
28547 thread's identifier.
28550 For a dynamic varobj, this indicates whether there appear to be any
28551 children available. For a non-dynamic varobj, this will be 0.
28554 This attribute will be present and have the value @samp{1} if the
28555 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28556 then this attribute will not be present.
28559 A dynamic varobj can supply a display hint to the front end. The
28560 value comes directly from the Python pretty-printer object's
28561 @code{display_hint} method. @xref{Pretty Printing API}.
28564 Typical output will look like this:
28567 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28568 has_more="@var{has_more}"
28572 @subheading The @code{-var-delete} Command
28573 @findex -var-delete
28575 @subsubheading Synopsis
28578 -var-delete [ -c ] @var{name}
28581 Deletes a previously created variable object and all of its children.
28582 With the @samp{-c} option, just deletes the children.
28584 Returns an error if the object @var{name} is not found.
28587 @subheading The @code{-var-set-format} Command
28588 @findex -var-set-format
28590 @subsubheading Synopsis
28593 -var-set-format @var{name} @var{format-spec}
28596 Sets the output format for the value of the object @var{name} to be
28599 @anchor{-var-set-format}
28600 The syntax for the @var{format-spec} is as follows:
28603 @var{format-spec} @expansion{}
28604 @{binary | decimal | hexadecimal | octal | natural@}
28607 The natural format is the default format choosen automatically
28608 based on the variable type (like decimal for an @code{int}, hex
28609 for pointers, etc.).
28611 For a variable with children, the format is set only on the
28612 variable itself, and the children are not affected.
28614 @subheading The @code{-var-show-format} Command
28615 @findex -var-show-format
28617 @subsubheading Synopsis
28620 -var-show-format @var{name}
28623 Returns the format used to display the value of the object @var{name}.
28626 @var{format} @expansion{}
28631 @subheading The @code{-var-info-num-children} Command
28632 @findex -var-info-num-children
28634 @subsubheading Synopsis
28637 -var-info-num-children @var{name}
28640 Returns the number of children of a variable object @var{name}:
28646 Note that this number is not completely reliable for a dynamic varobj.
28647 It will return the current number of children, but more children may
28651 @subheading The @code{-var-list-children} Command
28652 @findex -var-list-children
28654 @subsubheading Synopsis
28657 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28659 @anchor{-var-list-children}
28661 Return a list of the children of the specified variable object and
28662 create variable objects for them, if they do not already exist. With
28663 a single argument or if @var{print-values} has a value of 0 or
28664 @code{--no-values}, print only the names of the variables; if
28665 @var{print-values} is 1 or @code{--all-values}, also print their
28666 values; and if it is 2 or @code{--simple-values} print the name and
28667 value for simple data types and just the name for arrays, structures
28670 @var{from} and @var{to}, if specified, indicate the range of children
28671 to report. If @var{from} or @var{to} is less than zero, the range is
28672 reset and all children will be reported. Otherwise, children starting
28673 at @var{from} (zero-based) and up to and excluding @var{to} will be
28676 If a child range is requested, it will only affect the current call to
28677 @code{-var-list-children}, but not future calls to @code{-var-update}.
28678 For this, you must instead use @code{-var-set-update-range}. The
28679 intent of this approach is to enable a front end to implement any
28680 update approach it likes; for example, scrolling a view may cause the
28681 front end to request more children with @code{-var-list-children}, and
28682 then the front end could call @code{-var-set-update-range} with a
28683 different range to ensure that future updates are restricted to just
28686 For each child the following results are returned:
28691 Name of the variable object created for this child.
28694 The expression to be shown to the user by the front end to designate this child.
28695 For example this may be the name of a structure member.
28697 For a dynamic varobj, this value cannot be used to form an
28698 expression. There is no way to do this at all with a dynamic varobj.
28700 For C/C@t{++} structures there are several pseudo children returned to
28701 designate access qualifiers. For these pseudo children @var{exp} is
28702 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28703 type and value are not present.
28705 A dynamic varobj will not report the access qualifying
28706 pseudo-children, regardless of the language. This information is not
28707 available at all with a dynamic varobj.
28710 Number of children this child has. For a dynamic varobj, this will be
28714 The type of the child.
28717 If values were requested, this is the value.
28720 If this variable object is associated with a thread, this is the thread id.
28721 Otherwise this result is not present.
28724 If the variable object is frozen, this variable will be present with a value of 1.
28727 The result may have its own attributes:
28731 A dynamic varobj can supply a display hint to the front end. The
28732 value comes directly from the Python pretty-printer object's
28733 @code{display_hint} method. @xref{Pretty Printing API}.
28736 This is an integer attribute which is nonzero if there are children
28737 remaining after the end of the selected range.
28740 @subsubheading Example
28744 -var-list-children n
28745 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28746 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28748 -var-list-children --all-values n
28749 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28750 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28754 @subheading The @code{-var-info-type} Command
28755 @findex -var-info-type
28757 @subsubheading Synopsis
28760 -var-info-type @var{name}
28763 Returns the type of the specified variable @var{name}. The type is
28764 returned as a string in the same format as it is output by the
28768 type=@var{typename}
28772 @subheading The @code{-var-info-expression} Command
28773 @findex -var-info-expression
28775 @subsubheading Synopsis
28778 -var-info-expression @var{name}
28781 Returns a string that is suitable for presenting this
28782 variable object in user interface. The string is generally
28783 not valid expression in the current language, and cannot be evaluated.
28785 For example, if @code{a} is an array, and variable object
28786 @code{A} was created for @code{a}, then we'll get this output:
28789 (gdb) -var-info-expression A.1
28790 ^done,lang="C",exp="1"
28794 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
28796 Note that the output of the @code{-var-list-children} command also
28797 includes those expressions, so the @code{-var-info-expression} command
28800 @subheading The @code{-var-info-path-expression} Command
28801 @findex -var-info-path-expression
28803 @subsubheading Synopsis
28806 -var-info-path-expression @var{name}
28809 Returns an expression that can be evaluated in the current
28810 context and will yield the same value that a variable object has.
28811 Compare this with the @code{-var-info-expression} command, which
28812 result can be used only for UI presentation. Typical use of
28813 the @code{-var-info-path-expression} command is creating a
28814 watchpoint from a variable object.
28816 This command is currently not valid for children of a dynamic varobj,
28817 and will give an error when invoked on one.
28819 For example, suppose @code{C} is a C@t{++} class, derived from class
28820 @code{Base}, and that the @code{Base} class has a member called
28821 @code{m_size}. Assume a variable @code{c} is has the type of
28822 @code{C} and a variable object @code{C} was created for variable
28823 @code{c}. Then, we'll get this output:
28825 (gdb) -var-info-path-expression C.Base.public.m_size
28826 ^done,path_expr=((Base)c).m_size)
28829 @subheading The @code{-var-show-attributes} Command
28830 @findex -var-show-attributes
28832 @subsubheading Synopsis
28835 -var-show-attributes @var{name}
28838 List attributes of the specified variable object @var{name}:
28841 status=@var{attr} [ ( ,@var{attr} )* ]
28845 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
28847 @subheading The @code{-var-evaluate-expression} Command
28848 @findex -var-evaluate-expression
28850 @subsubheading Synopsis
28853 -var-evaluate-expression [-f @var{format-spec}] @var{name}
28856 Evaluates the expression that is represented by the specified variable
28857 object and returns its value as a string. The format of the string
28858 can be specified with the @samp{-f} option. The possible values of
28859 this option are the same as for @code{-var-set-format}
28860 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
28861 the current display format will be used. The current display format
28862 can be changed using the @code{-var-set-format} command.
28868 Note that one must invoke @code{-var-list-children} for a variable
28869 before the value of a child variable can be evaluated.
28871 @subheading The @code{-var-assign} Command
28872 @findex -var-assign
28874 @subsubheading Synopsis
28877 -var-assign @var{name} @var{expression}
28880 Assigns the value of @var{expression} to the variable object specified
28881 by @var{name}. The object must be @samp{editable}. If the variable's
28882 value is altered by the assign, the variable will show up in any
28883 subsequent @code{-var-update} list.
28885 @subsubheading Example
28893 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
28897 @subheading The @code{-var-update} Command
28898 @findex -var-update
28900 @subsubheading Synopsis
28903 -var-update [@var{print-values}] @{@var{name} | "*"@}
28906 Reevaluate the expressions corresponding to the variable object
28907 @var{name} and all its direct and indirect children, and return the
28908 list of variable objects whose values have changed; @var{name} must
28909 be a root variable object. Here, ``changed'' means that the result of
28910 @code{-var-evaluate-expression} before and after the
28911 @code{-var-update} is different. If @samp{*} is used as the variable
28912 object names, all existing variable objects are updated, except
28913 for frozen ones (@pxref{-var-set-frozen}). The option
28914 @var{print-values} determines whether both names and values, or just
28915 names are printed. The possible values of this option are the same
28916 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
28917 recommended to use the @samp{--all-values} option, to reduce the
28918 number of MI commands needed on each program stop.
28920 With the @samp{*} parameter, if a variable object is bound to a
28921 currently running thread, it will not be updated, without any
28924 If @code{-var-set-update-range} was previously used on a varobj, then
28925 only the selected range of children will be reported.
28927 @code{-var-update} reports all the changed varobjs in a tuple named
28930 Each item in the change list is itself a tuple holding:
28934 The name of the varobj.
28937 If values were requested for this update, then this field will be
28938 present and will hold the value of the varobj.
28941 @anchor{-var-update}
28942 This field is a string which may take one of three values:
28946 The variable object's current value is valid.
28949 The variable object does not currently hold a valid value but it may
28950 hold one in the future if its associated expression comes back into
28954 The variable object no longer holds a valid value.
28955 This can occur when the executable file being debugged has changed,
28956 either through recompilation or by using the @value{GDBN} @code{file}
28957 command. The front end should normally choose to delete these variable
28961 In the future new values may be added to this list so the front should
28962 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
28965 This is only present if the varobj is still valid. If the type
28966 changed, then this will be the string @samp{true}; otherwise it will
28970 If the varobj's type changed, then this field will be present and will
28973 @item new_num_children
28974 For a dynamic varobj, if the number of children changed, or if the
28975 type changed, this will be the new number of children.
28977 The @samp{numchild} field in other varobj responses is generally not
28978 valid for a dynamic varobj -- it will show the number of children that
28979 @value{GDBN} knows about, but because dynamic varobjs lazily
28980 instantiate their children, this will not reflect the number of
28981 children which may be available.
28983 The @samp{new_num_children} attribute only reports changes to the
28984 number of children known by @value{GDBN}. This is the only way to
28985 detect whether an update has removed children (which necessarily can
28986 only happen at the end of the update range).
28989 The display hint, if any.
28992 This is an integer value, which will be 1 if there are more children
28993 available outside the varobj's update range.
28996 This attribute will be present and have the value @samp{1} if the
28997 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28998 then this attribute will not be present.
29001 If new children were added to a dynamic varobj within the selected
29002 update range (as set by @code{-var-set-update-range}), then they will
29003 be listed in this attribute.
29006 @subsubheading Example
29013 -var-update --all-values var1
29014 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29015 type_changed="false"@}]
29019 @subheading The @code{-var-set-frozen} Command
29020 @findex -var-set-frozen
29021 @anchor{-var-set-frozen}
29023 @subsubheading Synopsis
29026 -var-set-frozen @var{name} @var{flag}
29029 Set the frozenness flag on the variable object @var{name}. The
29030 @var{flag} parameter should be either @samp{1} to make the variable
29031 frozen or @samp{0} to make it unfrozen. If a variable object is
29032 frozen, then neither itself, nor any of its children, are
29033 implicitly updated by @code{-var-update} of
29034 a parent variable or by @code{-var-update *}. Only
29035 @code{-var-update} of the variable itself will update its value and
29036 values of its children. After a variable object is unfrozen, it is
29037 implicitly updated by all subsequent @code{-var-update} operations.
29038 Unfreezing a variable does not update it, only subsequent
29039 @code{-var-update} does.
29041 @subsubheading Example
29045 -var-set-frozen V 1
29050 @subheading The @code{-var-set-update-range} command
29051 @findex -var-set-update-range
29052 @anchor{-var-set-update-range}
29054 @subsubheading Synopsis
29057 -var-set-update-range @var{name} @var{from} @var{to}
29060 Set the range of children to be returned by future invocations of
29061 @code{-var-update}.
29063 @var{from} and @var{to} indicate the range of children to report. If
29064 @var{from} or @var{to} is less than zero, the range is reset and all
29065 children will be reported. Otherwise, children starting at @var{from}
29066 (zero-based) and up to and excluding @var{to} will be reported.
29068 @subsubheading Example
29072 -var-set-update-range V 1 2
29076 @subheading The @code{-var-set-visualizer} command
29077 @findex -var-set-visualizer
29078 @anchor{-var-set-visualizer}
29080 @subsubheading Synopsis
29083 -var-set-visualizer @var{name} @var{visualizer}
29086 Set a visualizer for the variable object @var{name}.
29088 @var{visualizer} is the visualizer to use. The special value
29089 @samp{None} means to disable any visualizer in use.
29091 If not @samp{None}, @var{visualizer} must be a Python expression.
29092 This expression must evaluate to a callable object which accepts a
29093 single argument. @value{GDBN} will call this object with the value of
29094 the varobj @var{name} as an argument (this is done so that the same
29095 Python pretty-printing code can be used for both the CLI and MI).
29096 When called, this object must return an object which conforms to the
29097 pretty-printing interface (@pxref{Pretty Printing API}).
29099 The pre-defined function @code{gdb.default_visualizer} may be used to
29100 select a visualizer by following the built-in process
29101 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29102 a varobj is created, and so ordinarily is not needed.
29104 This feature is only available if Python support is enabled. The MI
29105 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
29106 can be used to check this.
29108 @subsubheading Example
29110 Resetting the visualizer:
29114 -var-set-visualizer V None
29118 Reselecting the default (type-based) visualizer:
29122 -var-set-visualizer V gdb.default_visualizer
29126 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29127 can be used to instantiate this class for a varobj:
29131 -var-set-visualizer V "lambda val: SomeClass()"
29135 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29136 @node GDB/MI Data Manipulation
29137 @section @sc{gdb/mi} Data Manipulation
29139 @cindex data manipulation, in @sc{gdb/mi}
29140 @cindex @sc{gdb/mi}, data manipulation
29141 This section describes the @sc{gdb/mi} commands that manipulate data:
29142 examine memory and registers, evaluate expressions, etc.
29144 @c REMOVED FROM THE INTERFACE.
29145 @c @subheading -data-assign
29146 @c Change the value of a program variable. Plenty of side effects.
29147 @c @subsubheading GDB Command
29149 @c @subsubheading Example
29152 @subheading The @code{-data-disassemble} Command
29153 @findex -data-disassemble
29155 @subsubheading Synopsis
29159 [ -s @var{start-addr} -e @var{end-addr} ]
29160 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29168 @item @var{start-addr}
29169 is the beginning address (or @code{$pc})
29170 @item @var{end-addr}
29172 @item @var{filename}
29173 is the name of the file to disassemble
29174 @item @var{linenum}
29175 is the line number to disassemble around
29177 is the number of disassembly lines to be produced. If it is -1,
29178 the whole function will be disassembled, in case no @var{end-addr} is
29179 specified. If @var{end-addr} is specified as a non-zero value, and
29180 @var{lines} is lower than the number of disassembly lines between
29181 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29182 displayed; if @var{lines} is higher than the number of lines between
29183 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29186 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29187 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29188 mixed source and disassembly with raw opcodes).
29191 @subsubheading Result
29193 The output for each instruction is composed of four fields:
29202 Note that whatever included in the instruction field, is not manipulated
29203 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
29205 @subsubheading @value{GDBN} Command
29207 There's no direct mapping from this command to the CLI.
29209 @subsubheading Example
29211 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29215 -data-disassemble -s $pc -e "$pc + 20" -- 0
29218 @{address="0x000107c0",func-name="main",offset="4",
29219 inst="mov 2, %o0"@},
29220 @{address="0x000107c4",func-name="main",offset="8",
29221 inst="sethi %hi(0x11800), %o2"@},
29222 @{address="0x000107c8",func-name="main",offset="12",
29223 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29224 @{address="0x000107cc",func-name="main",offset="16",
29225 inst="sethi %hi(0x11800), %o2"@},
29226 @{address="0x000107d0",func-name="main",offset="20",
29227 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29231 Disassemble the whole @code{main} function. Line 32 is part of
29235 -data-disassemble -f basics.c -l 32 -- 0
29237 @{address="0x000107bc",func-name="main",offset="0",
29238 inst="save %sp, -112, %sp"@},
29239 @{address="0x000107c0",func-name="main",offset="4",
29240 inst="mov 2, %o0"@},
29241 @{address="0x000107c4",func-name="main",offset="8",
29242 inst="sethi %hi(0x11800), %o2"@},
29244 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29245 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29249 Disassemble 3 instructions from the start of @code{main}:
29253 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29255 @{address="0x000107bc",func-name="main",offset="0",
29256 inst="save %sp, -112, %sp"@},
29257 @{address="0x000107c0",func-name="main",offset="4",
29258 inst="mov 2, %o0"@},
29259 @{address="0x000107c4",func-name="main",offset="8",
29260 inst="sethi %hi(0x11800), %o2"@}]
29264 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29268 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29270 src_and_asm_line=@{line="31",
29271 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29272 testsuite/gdb.mi/basics.c",line_asm_insn=[
29273 @{address="0x000107bc",func-name="main",offset="0",
29274 inst="save %sp, -112, %sp"@}]@},
29275 src_and_asm_line=@{line="32",
29276 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29277 testsuite/gdb.mi/basics.c",line_asm_insn=[
29278 @{address="0x000107c0",func-name="main",offset="4",
29279 inst="mov 2, %o0"@},
29280 @{address="0x000107c4",func-name="main",offset="8",
29281 inst="sethi %hi(0x11800), %o2"@}]@}]
29286 @subheading The @code{-data-evaluate-expression} Command
29287 @findex -data-evaluate-expression
29289 @subsubheading Synopsis
29292 -data-evaluate-expression @var{expr}
29295 Evaluate @var{expr} as an expression. The expression could contain an
29296 inferior function call. The function call will execute synchronously.
29297 If the expression contains spaces, it must be enclosed in double quotes.
29299 @subsubheading @value{GDBN} Command
29301 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29302 @samp{call}. In @code{gdbtk} only, there's a corresponding
29303 @samp{gdb_eval} command.
29305 @subsubheading Example
29307 In the following example, the numbers that precede the commands are the
29308 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29309 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29313 211-data-evaluate-expression A
29316 311-data-evaluate-expression &A
29317 311^done,value="0xefffeb7c"
29319 411-data-evaluate-expression A+3
29322 511-data-evaluate-expression "A + 3"
29328 @subheading The @code{-data-list-changed-registers} Command
29329 @findex -data-list-changed-registers
29331 @subsubheading Synopsis
29334 -data-list-changed-registers
29337 Display a list of the registers that have changed.
29339 @subsubheading @value{GDBN} Command
29341 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29342 has the corresponding command @samp{gdb_changed_register_list}.
29344 @subsubheading Example
29346 On a PPC MBX board:
29354 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29355 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29358 -data-list-changed-registers
29359 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29360 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29361 "24","25","26","27","28","30","31","64","65","66","67","69"]
29366 @subheading The @code{-data-list-register-names} Command
29367 @findex -data-list-register-names
29369 @subsubheading Synopsis
29372 -data-list-register-names [ ( @var{regno} )+ ]
29375 Show a list of register names for the current target. If no arguments
29376 are given, it shows a list of the names of all the registers. If
29377 integer numbers are given as arguments, it will print a list of the
29378 names of the registers corresponding to the arguments. To ensure
29379 consistency between a register name and its number, the output list may
29380 include empty register names.
29382 @subsubheading @value{GDBN} Command
29384 @value{GDBN} does not have a command which corresponds to
29385 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29386 corresponding command @samp{gdb_regnames}.
29388 @subsubheading Example
29390 For the PPC MBX board:
29393 -data-list-register-names
29394 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29395 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29396 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29397 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29398 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29399 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29400 "", "pc","ps","cr","lr","ctr","xer"]
29402 -data-list-register-names 1 2 3
29403 ^done,register-names=["r1","r2","r3"]
29407 @subheading The @code{-data-list-register-values} Command
29408 @findex -data-list-register-values
29410 @subsubheading Synopsis
29413 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
29416 Display the registers' contents. @var{fmt} is the format according to
29417 which the registers' contents are to be returned, followed by an optional
29418 list of numbers specifying the registers to display. A missing list of
29419 numbers indicates that the contents of all the registers must be returned.
29421 Allowed formats for @var{fmt} are:
29438 @subsubheading @value{GDBN} Command
29440 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29441 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29443 @subsubheading Example
29445 For a PPC MBX board (note: line breaks are for readability only, they
29446 don't appear in the actual output):
29450 -data-list-register-values r 64 65
29451 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29452 @{number="65",value="0x00029002"@}]
29454 -data-list-register-values x
29455 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29456 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29457 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29458 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29459 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29460 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29461 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29462 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29463 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29464 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29465 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29466 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29467 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29468 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29469 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29470 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29471 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29472 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29473 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29474 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29475 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29476 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29477 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29478 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29479 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29480 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29481 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29482 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29483 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29484 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29485 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29486 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29487 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29488 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29489 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29490 @{number="69",value="0x20002b03"@}]
29495 @subheading The @code{-data-read-memory} Command
29496 @findex -data-read-memory
29498 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29500 @subsubheading Synopsis
29503 -data-read-memory [ -o @var{byte-offset} ]
29504 @var{address} @var{word-format} @var{word-size}
29505 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29512 @item @var{address}
29513 An expression specifying the address of the first memory word to be
29514 read. Complex expressions containing embedded white space should be
29515 quoted using the C convention.
29517 @item @var{word-format}
29518 The format to be used to print the memory words. The notation is the
29519 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29522 @item @var{word-size}
29523 The size of each memory word in bytes.
29525 @item @var{nr-rows}
29526 The number of rows in the output table.
29528 @item @var{nr-cols}
29529 The number of columns in the output table.
29532 If present, indicates that each row should include an @sc{ascii} dump. The
29533 value of @var{aschar} is used as a padding character when a byte is not a
29534 member of the printable @sc{ascii} character set (printable @sc{ascii}
29535 characters are those whose code is between 32 and 126, inclusively).
29537 @item @var{byte-offset}
29538 An offset to add to the @var{address} before fetching memory.
29541 This command displays memory contents as a table of @var{nr-rows} by
29542 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29543 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29544 (returned as @samp{total-bytes}). Should less than the requested number
29545 of bytes be returned by the target, the missing words are identified
29546 using @samp{N/A}. The number of bytes read from the target is returned
29547 in @samp{nr-bytes} and the starting address used to read memory in
29550 The address of the next/previous row or page is available in
29551 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29554 @subsubheading @value{GDBN} Command
29556 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29557 @samp{gdb_get_mem} memory read command.
29559 @subsubheading Example
29561 Read six bytes of memory starting at @code{bytes+6} but then offset by
29562 @code{-6} bytes. Format as three rows of two columns. One byte per
29563 word. Display each word in hex.
29567 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29568 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29569 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29570 prev-page="0x0000138a",memory=[
29571 @{addr="0x00001390",data=["0x00","0x01"]@},
29572 @{addr="0x00001392",data=["0x02","0x03"]@},
29573 @{addr="0x00001394",data=["0x04","0x05"]@}]
29577 Read two bytes of memory starting at address @code{shorts + 64} and
29578 display as a single word formatted in decimal.
29582 5-data-read-memory shorts+64 d 2 1 1
29583 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29584 next-row="0x00001512",prev-row="0x0000150e",
29585 next-page="0x00001512",prev-page="0x0000150e",memory=[
29586 @{addr="0x00001510",data=["128"]@}]
29590 Read thirty two bytes of memory starting at @code{bytes+16} and format
29591 as eight rows of four columns. Include a string encoding with @samp{x}
29592 used as the non-printable character.
29596 4-data-read-memory bytes+16 x 1 8 4 x
29597 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29598 next-row="0x000013c0",prev-row="0x0000139c",
29599 next-page="0x000013c0",prev-page="0x00001380",memory=[
29600 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29601 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29602 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29603 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29604 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29605 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29606 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29607 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29611 @subheading The @code{-data-read-memory-bytes} Command
29612 @findex -data-read-memory-bytes
29614 @subsubheading Synopsis
29617 -data-read-memory-bytes [ -o @var{byte-offset} ]
29618 @var{address} @var{count}
29625 @item @var{address}
29626 An expression specifying the address of the first memory word to be
29627 read. Complex expressions containing embedded white space should be
29628 quoted using the C convention.
29631 The number of bytes to read. This should be an integer literal.
29633 @item @var{byte-offset}
29634 The offsets in bytes relative to @var{address} at which to start
29635 reading. This should be an integer literal. This option is provided
29636 so that a frontend is not required to first evaluate address and then
29637 perform address arithmetics itself.
29641 This command attempts to read all accessible memory regions in the
29642 specified range. First, all regions marked as unreadable in the memory
29643 map (if one is defined) will be skipped. @xref{Memory Region
29644 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29645 regions. For each one, if reading full region results in an errors,
29646 @value{GDBN} will try to read a subset of the region.
29648 In general, every single byte in the region may be readable or not,
29649 and the only way to read every readable byte is to try a read at
29650 every address, which is not practical. Therefore, @value{GDBN} will
29651 attempt to read all accessible bytes at either beginning or the end
29652 of the region, using a binary division scheme. This heuristic works
29653 well for reading accross a memory map boundary. Note that if a region
29654 has a readable range that is neither at the beginning or the end,
29655 @value{GDBN} will not read it.
29657 The result record (@pxref{GDB/MI Result Records}) that is output of
29658 the command includes a field named @samp{memory} whose content is a
29659 list of tuples. Each tuple represent a successfully read memory block
29660 and has the following fields:
29664 The start address of the memory block, as hexadecimal literal.
29667 The end address of the memory block, as hexadecimal literal.
29670 The offset of the memory block, as hexadecimal literal, relative to
29671 the start address passed to @code{-data-read-memory-bytes}.
29674 The contents of the memory block, in hex.
29680 @subsubheading @value{GDBN} Command
29682 The corresponding @value{GDBN} command is @samp{x}.
29684 @subsubheading Example
29688 -data-read-memory-bytes &a 10
29689 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29691 contents="01000000020000000300"@}]
29696 @subheading The @code{-data-write-memory-bytes} Command
29697 @findex -data-write-memory-bytes
29699 @subsubheading Synopsis
29702 -data-write-memory-bytes @var{address} @var{contents}
29709 @item @var{address}
29710 An expression specifying the address of the first memory word to be
29711 read. Complex expressions containing embedded white space should be
29712 quoted using the C convention.
29714 @item @var{contents}
29715 The hex-encoded bytes to write.
29719 @subsubheading @value{GDBN} Command
29721 There's no corresponding @value{GDBN} command.
29723 @subsubheading Example
29727 -data-write-memory-bytes &a "aabbccdd"
29733 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29734 @node GDB/MI Tracepoint Commands
29735 @section @sc{gdb/mi} Tracepoint Commands
29737 The commands defined in this section implement MI support for
29738 tracepoints. For detailed introduction, see @ref{Tracepoints}.
29740 @subheading The @code{-trace-find} Command
29741 @findex -trace-find
29743 @subsubheading Synopsis
29746 -trace-find @var{mode} [@var{parameters}@dots{}]
29749 Find a trace frame using criteria defined by @var{mode} and
29750 @var{parameters}. The following table lists permissible
29751 modes and their parameters. For details of operation, see @ref{tfind}.
29756 No parameters are required. Stops examining trace frames.
29759 An integer is required as parameter. Selects tracepoint frame with
29762 @item tracepoint-number
29763 An integer is required as parameter. Finds next
29764 trace frame that corresponds to tracepoint with the specified number.
29767 An address is required as parameter. Finds
29768 next trace frame that corresponds to any tracepoint at the specified
29771 @item pc-inside-range
29772 Two addresses are required as parameters. Finds next trace
29773 frame that corresponds to a tracepoint at an address inside the
29774 specified range. Both bounds are considered to be inside the range.
29776 @item pc-outside-range
29777 Two addresses are required as parameters. Finds
29778 next trace frame that corresponds to a tracepoint at an address outside
29779 the specified range. Both bounds are considered to be inside the range.
29782 Line specification is required as parameter. @xref{Specify Location}.
29783 Finds next trace frame that corresponds to a tracepoint at
29784 the specified location.
29788 If @samp{none} was passed as @var{mode}, the response does not
29789 have fields. Otherwise, the response may have the following fields:
29793 This field has either @samp{0} or @samp{1} as the value, depending
29794 on whether a matching tracepoint was found.
29797 The index of the found traceframe. This field is present iff
29798 the @samp{found} field has value of @samp{1}.
29801 The index of the found tracepoint. This field is present iff
29802 the @samp{found} field has value of @samp{1}.
29805 The information about the frame corresponding to the found trace
29806 frame. This field is present only if a trace frame was found.
29807 @xref{GDB/MI Frame Information}, for description of this field.
29811 @subsubheading @value{GDBN} Command
29813 The corresponding @value{GDBN} command is @samp{tfind}.
29815 @subheading -trace-define-variable
29816 @findex -trace-define-variable
29818 @subsubheading Synopsis
29821 -trace-define-variable @var{name} [ @var{value} ]
29824 Create trace variable @var{name} if it does not exist. If
29825 @var{value} is specified, sets the initial value of the specified
29826 trace variable to that value. Note that the @var{name} should start
29827 with the @samp{$} character.
29829 @subsubheading @value{GDBN} Command
29831 The corresponding @value{GDBN} command is @samp{tvariable}.
29833 @subheading -trace-list-variables
29834 @findex -trace-list-variables
29836 @subsubheading Synopsis
29839 -trace-list-variables
29842 Return a table of all defined trace variables. Each element of the
29843 table has the following fields:
29847 The name of the trace variable. This field is always present.
29850 The initial value. This is a 64-bit signed integer. This
29851 field is always present.
29854 The value the trace variable has at the moment. This is a 64-bit
29855 signed integer. This field is absent iff current value is
29856 not defined, for example if the trace was never run, or is
29861 @subsubheading @value{GDBN} Command
29863 The corresponding @value{GDBN} command is @samp{tvariables}.
29865 @subsubheading Example
29869 -trace-list-variables
29870 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
29871 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
29872 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
29873 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
29874 body=[variable=@{name="$trace_timestamp",initial="0"@}
29875 variable=@{name="$foo",initial="10",current="15"@}]@}
29879 @subheading -trace-save
29880 @findex -trace-save
29882 @subsubheading Synopsis
29885 -trace-save [-r ] @var{filename}
29888 Saves the collected trace data to @var{filename}. Without the
29889 @samp{-r} option, the data is downloaded from the target and saved
29890 in a local file. With the @samp{-r} option the target is asked
29891 to perform the save.
29893 @subsubheading @value{GDBN} Command
29895 The corresponding @value{GDBN} command is @samp{tsave}.
29898 @subheading -trace-start
29899 @findex -trace-start
29901 @subsubheading Synopsis
29907 Starts a tracing experiments. The result of this command does not
29910 @subsubheading @value{GDBN} Command
29912 The corresponding @value{GDBN} command is @samp{tstart}.
29914 @subheading -trace-status
29915 @findex -trace-status
29917 @subsubheading Synopsis
29923 Obtains the status of a tracing experiment. The result may include
29924 the following fields:
29929 May have a value of either @samp{0}, when no tracing operations are
29930 supported, @samp{1}, when all tracing operations are supported, or
29931 @samp{file} when examining trace file. In the latter case, examining
29932 of trace frame is possible but new tracing experiement cannot be
29933 started. This field is always present.
29936 May have a value of either @samp{0} or @samp{1} depending on whether
29937 tracing experiement is in progress on target. This field is present
29938 if @samp{supported} field is not @samp{0}.
29941 Report the reason why the tracing was stopped last time. This field
29942 may be absent iff tracing was never stopped on target yet. The
29943 value of @samp{request} means the tracing was stopped as result of
29944 the @code{-trace-stop} command. The value of @samp{overflow} means
29945 the tracing buffer is full. The value of @samp{disconnection} means
29946 tracing was automatically stopped when @value{GDBN} has disconnected.
29947 The value of @samp{passcount} means tracing was stopped when a
29948 tracepoint was passed a maximal number of times for that tracepoint.
29949 This field is present if @samp{supported} field is not @samp{0}.
29951 @item stopping-tracepoint
29952 The number of tracepoint whose passcount as exceeded. This field is
29953 present iff the @samp{stop-reason} field has the value of
29957 @itemx frames-created
29958 The @samp{frames} field is a count of the total number of trace frames
29959 in the trace buffer, while @samp{frames-created} is the total created
29960 during the run, including ones that were discarded, such as when a
29961 circular trace buffer filled up. Both fields are optional.
29965 These fields tell the current size of the tracing buffer and the
29966 remaining space. These fields are optional.
29969 The value of the circular trace buffer flag. @code{1} means that the
29970 trace buffer is circular and old trace frames will be discarded if
29971 necessary to make room, @code{0} means that the trace buffer is linear
29975 The value of the disconnected tracing flag. @code{1} means that
29976 tracing will continue after @value{GDBN} disconnects, @code{0} means
29977 that the trace run will stop.
29981 @subsubheading @value{GDBN} Command
29983 The corresponding @value{GDBN} command is @samp{tstatus}.
29985 @subheading -trace-stop
29986 @findex -trace-stop
29988 @subsubheading Synopsis
29994 Stops a tracing experiment. The result of this command has the same
29995 fields as @code{-trace-status}, except that the @samp{supported} and
29996 @samp{running} fields are not output.
29998 @subsubheading @value{GDBN} Command
30000 The corresponding @value{GDBN} command is @samp{tstop}.
30003 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30004 @node GDB/MI Symbol Query
30005 @section @sc{gdb/mi} Symbol Query Commands
30009 @subheading The @code{-symbol-info-address} Command
30010 @findex -symbol-info-address
30012 @subsubheading Synopsis
30015 -symbol-info-address @var{symbol}
30018 Describe where @var{symbol} is stored.
30020 @subsubheading @value{GDBN} Command
30022 The corresponding @value{GDBN} command is @samp{info address}.
30024 @subsubheading Example
30028 @subheading The @code{-symbol-info-file} Command
30029 @findex -symbol-info-file
30031 @subsubheading Synopsis
30037 Show the file for the symbol.
30039 @subsubheading @value{GDBN} Command
30041 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30042 @samp{gdb_find_file}.
30044 @subsubheading Example
30048 @subheading The @code{-symbol-info-function} Command
30049 @findex -symbol-info-function
30051 @subsubheading Synopsis
30054 -symbol-info-function
30057 Show which function the symbol lives in.
30059 @subsubheading @value{GDBN} Command
30061 @samp{gdb_get_function} in @code{gdbtk}.
30063 @subsubheading Example
30067 @subheading The @code{-symbol-info-line} Command
30068 @findex -symbol-info-line
30070 @subsubheading Synopsis
30076 Show the core addresses of the code for a source line.
30078 @subsubheading @value{GDBN} Command
30080 The corresponding @value{GDBN} command is @samp{info line}.
30081 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30083 @subsubheading Example
30087 @subheading The @code{-symbol-info-symbol} Command
30088 @findex -symbol-info-symbol
30090 @subsubheading Synopsis
30093 -symbol-info-symbol @var{addr}
30096 Describe what symbol is at location @var{addr}.
30098 @subsubheading @value{GDBN} Command
30100 The corresponding @value{GDBN} command is @samp{info symbol}.
30102 @subsubheading Example
30106 @subheading The @code{-symbol-list-functions} Command
30107 @findex -symbol-list-functions
30109 @subsubheading Synopsis
30112 -symbol-list-functions
30115 List the functions in the executable.
30117 @subsubheading @value{GDBN} Command
30119 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30120 @samp{gdb_search} in @code{gdbtk}.
30122 @subsubheading Example
30127 @subheading The @code{-symbol-list-lines} Command
30128 @findex -symbol-list-lines
30130 @subsubheading Synopsis
30133 -symbol-list-lines @var{filename}
30136 Print the list of lines that contain code and their associated program
30137 addresses for the given source filename. The entries are sorted in
30138 ascending PC order.
30140 @subsubheading @value{GDBN} Command
30142 There is no corresponding @value{GDBN} command.
30144 @subsubheading Example
30147 -symbol-list-lines basics.c
30148 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30154 @subheading The @code{-symbol-list-types} Command
30155 @findex -symbol-list-types
30157 @subsubheading Synopsis
30163 List all the type names.
30165 @subsubheading @value{GDBN} Command
30167 The corresponding commands are @samp{info types} in @value{GDBN},
30168 @samp{gdb_search} in @code{gdbtk}.
30170 @subsubheading Example
30174 @subheading The @code{-symbol-list-variables} Command
30175 @findex -symbol-list-variables
30177 @subsubheading Synopsis
30180 -symbol-list-variables
30183 List all the global and static variable names.
30185 @subsubheading @value{GDBN} Command
30187 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30189 @subsubheading Example
30193 @subheading The @code{-symbol-locate} Command
30194 @findex -symbol-locate
30196 @subsubheading Synopsis
30202 @subsubheading @value{GDBN} Command
30204 @samp{gdb_loc} in @code{gdbtk}.
30206 @subsubheading Example
30210 @subheading The @code{-symbol-type} Command
30211 @findex -symbol-type
30213 @subsubheading Synopsis
30216 -symbol-type @var{variable}
30219 Show type of @var{variable}.
30221 @subsubheading @value{GDBN} Command
30223 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30224 @samp{gdb_obj_variable}.
30226 @subsubheading Example
30231 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30232 @node GDB/MI File Commands
30233 @section @sc{gdb/mi} File Commands
30235 This section describes the GDB/MI commands to specify executable file names
30236 and to read in and obtain symbol table information.
30238 @subheading The @code{-file-exec-and-symbols} Command
30239 @findex -file-exec-and-symbols
30241 @subsubheading Synopsis
30244 -file-exec-and-symbols @var{file}
30247 Specify the executable file to be debugged. This file is the one from
30248 which the symbol table is also read. If no file is specified, the
30249 command clears the executable and symbol information. If breakpoints
30250 are set when using this command with no arguments, @value{GDBN} will produce
30251 error messages. Otherwise, no output is produced, except a completion
30254 @subsubheading @value{GDBN} Command
30256 The corresponding @value{GDBN} command is @samp{file}.
30258 @subsubheading Example
30262 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30268 @subheading The @code{-file-exec-file} Command
30269 @findex -file-exec-file
30271 @subsubheading Synopsis
30274 -file-exec-file @var{file}
30277 Specify the executable file to be debugged. Unlike
30278 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30279 from this file. If used without argument, @value{GDBN} clears the information
30280 about the executable file. No output is produced, except a completion
30283 @subsubheading @value{GDBN} Command
30285 The corresponding @value{GDBN} command is @samp{exec-file}.
30287 @subsubheading Example
30291 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30298 @subheading The @code{-file-list-exec-sections} Command
30299 @findex -file-list-exec-sections
30301 @subsubheading Synopsis
30304 -file-list-exec-sections
30307 List the sections of the current executable file.
30309 @subsubheading @value{GDBN} Command
30311 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30312 information as this command. @code{gdbtk} has a corresponding command
30313 @samp{gdb_load_info}.
30315 @subsubheading Example
30320 @subheading The @code{-file-list-exec-source-file} Command
30321 @findex -file-list-exec-source-file
30323 @subsubheading Synopsis
30326 -file-list-exec-source-file
30329 List the line number, the current source file, and the absolute path
30330 to the current source file for the current executable. The macro
30331 information field has a value of @samp{1} or @samp{0} depending on
30332 whether or not the file includes preprocessor macro information.
30334 @subsubheading @value{GDBN} Command
30336 The @value{GDBN} equivalent is @samp{info source}
30338 @subsubheading Example
30342 123-file-list-exec-source-file
30343 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30348 @subheading The @code{-file-list-exec-source-files} Command
30349 @findex -file-list-exec-source-files
30351 @subsubheading Synopsis
30354 -file-list-exec-source-files
30357 List the source files for the current executable.
30359 It will always output the filename, but only when @value{GDBN} can find
30360 the absolute file name of a source file, will it output the fullname.
30362 @subsubheading @value{GDBN} Command
30364 The @value{GDBN} equivalent is @samp{info sources}.
30365 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30367 @subsubheading Example
30370 -file-list-exec-source-files
30372 @{file=foo.c,fullname=/home/foo.c@},
30373 @{file=/home/bar.c,fullname=/home/bar.c@},
30374 @{file=gdb_could_not_find_fullpath.c@}]
30379 @subheading The @code{-file-list-shared-libraries} Command
30380 @findex -file-list-shared-libraries
30382 @subsubheading Synopsis
30385 -file-list-shared-libraries
30388 List the shared libraries in the program.
30390 @subsubheading @value{GDBN} Command
30392 The corresponding @value{GDBN} command is @samp{info shared}.
30394 @subsubheading Example
30398 @subheading The @code{-file-list-symbol-files} Command
30399 @findex -file-list-symbol-files
30401 @subsubheading Synopsis
30404 -file-list-symbol-files
30409 @subsubheading @value{GDBN} Command
30411 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30413 @subsubheading Example
30418 @subheading The @code{-file-symbol-file} Command
30419 @findex -file-symbol-file
30421 @subsubheading Synopsis
30424 -file-symbol-file @var{file}
30427 Read symbol table info from the specified @var{file} argument. When
30428 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30429 produced, except for a completion notification.
30431 @subsubheading @value{GDBN} Command
30433 The corresponding @value{GDBN} command is @samp{symbol-file}.
30435 @subsubheading Example
30439 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30445 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30446 @node GDB/MI Memory Overlay Commands
30447 @section @sc{gdb/mi} Memory Overlay Commands
30449 The memory overlay commands are not implemented.
30451 @c @subheading -overlay-auto
30453 @c @subheading -overlay-list-mapping-state
30455 @c @subheading -overlay-list-overlays
30457 @c @subheading -overlay-map
30459 @c @subheading -overlay-off
30461 @c @subheading -overlay-on
30463 @c @subheading -overlay-unmap
30465 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30466 @node GDB/MI Signal Handling Commands
30467 @section @sc{gdb/mi} Signal Handling Commands
30469 Signal handling commands are not implemented.
30471 @c @subheading -signal-handle
30473 @c @subheading -signal-list-handle-actions
30475 @c @subheading -signal-list-signal-types
30479 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30480 @node GDB/MI Target Manipulation
30481 @section @sc{gdb/mi} Target Manipulation Commands
30484 @subheading The @code{-target-attach} Command
30485 @findex -target-attach
30487 @subsubheading Synopsis
30490 -target-attach @var{pid} | @var{gid} | @var{file}
30493 Attach to a process @var{pid} or a file @var{file} outside of
30494 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30495 group, the id previously returned by
30496 @samp{-list-thread-groups --available} must be used.
30498 @subsubheading @value{GDBN} Command
30500 The corresponding @value{GDBN} command is @samp{attach}.
30502 @subsubheading Example
30506 =thread-created,id="1"
30507 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30513 @subheading The @code{-target-compare-sections} Command
30514 @findex -target-compare-sections
30516 @subsubheading Synopsis
30519 -target-compare-sections [ @var{section} ]
30522 Compare data of section @var{section} on target to the exec file.
30523 Without the argument, all sections are compared.
30525 @subsubheading @value{GDBN} Command
30527 The @value{GDBN} equivalent is @samp{compare-sections}.
30529 @subsubheading Example
30534 @subheading The @code{-target-detach} Command
30535 @findex -target-detach
30537 @subsubheading Synopsis
30540 -target-detach [ @var{pid} | @var{gid} ]
30543 Detach from the remote target which normally resumes its execution.
30544 If either @var{pid} or @var{gid} is specified, detaches from either
30545 the specified process, or specified thread group. There's no output.
30547 @subsubheading @value{GDBN} Command
30549 The corresponding @value{GDBN} command is @samp{detach}.
30551 @subsubheading Example
30561 @subheading The @code{-target-disconnect} Command
30562 @findex -target-disconnect
30564 @subsubheading Synopsis
30570 Disconnect from the remote target. There's no output and the target is
30571 generally not resumed.
30573 @subsubheading @value{GDBN} Command
30575 The corresponding @value{GDBN} command is @samp{disconnect}.
30577 @subsubheading Example
30587 @subheading The @code{-target-download} Command
30588 @findex -target-download
30590 @subsubheading Synopsis
30596 Loads the executable onto the remote target.
30597 It prints out an update message every half second, which includes the fields:
30601 The name of the section.
30603 The size of what has been sent so far for that section.
30605 The size of the section.
30607 The total size of what was sent so far (the current and the previous sections).
30609 The size of the overall executable to download.
30613 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30614 @sc{gdb/mi} Output Syntax}).
30616 In addition, it prints the name and size of the sections, as they are
30617 downloaded. These messages include the following fields:
30621 The name of the section.
30623 The size of the section.
30625 The size of the overall executable to download.
30629 At the end, a summary is printed.
30631 @subsubheading @value{GDBN} Command
30633 The corresponding @value{GDBN} command is @samp{load}.
30635 @subsubheading Example
30637 Note: each status message appears on a single line. Here the messages
30638 have been broken down so that they can fit onto a page.
30643 +download,@{section=".text",section-size="6668",total-size="9880"@}
30644 +download,@{section=".text",section-sent="512",section-size="6668",
30645 total-sent="512",total-size="9880"@}
30646 +download,@{section=".text",section-sent="1024",section-size="6668",
30647 total-sent="1024",total-size="9880"@}
30648 +download,@{section=".text",section-sent="1536",section-size="6668",
30649 total-sent="1536",total-size="9880"@}
30650 +download,@{section=".text",section-sent="2048",section-size="6668",
30651 total-sent="2048",total-size="9880"@}
30652 +download,@{section=".text",section-sent="2560",section-size="6668",
30653 total-sent="2560",total-size="9880"@}
30654 +download,@{section=".text",section-sent="3072",section-size="6668",
30655 total-sent="3072",total-size="9880"@}
30656 +download,@{section=".text",section-sent="3584",section-size="6668",
30657 total-sent="3584",total-size="9880"@}
30658 +download,@{section=".text",section-sent="4096",section-size="6668",
30659 total-sent="4096",total-size="9880"@}
30660 +download,@{section=".text",section-sent="4608",section-size="6668",
30661 total-sent="4608",total-size="9880"@}
30662 +download,@{section=".text",section-sent="5120",section-size="6668",
30663 total-sent="5120",total-size="9880"@}
30664 +download,@{section=".text",section-sent="5632",section-size="6668",
30665 total-sent="5632",total-size="9880"@}
30666 +download,@{section=".text",section-sent="6144",section-size="6668",
30667 total-sent="6144",total-size="9880"@}
30668 +download,@{section=".text",section-sent="6656",section-size="6668",
30669 total-sent="6656",total-size="9880"@}
30670 +download,@{section=".init",section-size="28",total-size="9880"@}
30671 +download,@{section=".fini",section-size="28",total-size="9880"@}
30672 +download,@{section=".data",section-size="3156",total-size="9880"@}
30673 +download,@{section=".data",section-sent="512",section-size="3156",
30674 total-sent="7236",total-size="9880"@}
30675 +download,@{section=".data",section-sent="1024",section-size="3156",
30676 total-sent="7748",total-size="9880"@}
30677 +download,@{section=".data",section-sent="1536",section-size="3156",
30678 total-sent="8260",total-size="9880"@}
30679 +download,@{section=".data",section-sent="2048",section-size="3156",
30680 total-sent="8772",total-size="9880"@}
30681 +download,@{section=".data",section-sent="2560",section-size="3156",
30682 total-sent="9284",total-size="9880"@}
30683 +download,@{section=".data",section-sent="3072",section-size="3156",
30684 total-sent="9796",total-size="9880"@}
30685 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30692 @subheading The @code{-target-exec-status} Command
30693 @findex -target-exec-status
30695 @subsubheading Synopsis
30698 -target-exec-status
30701 Provide information on the state of the target (whether it is running or
30702 not, for instance).
30704 @subsubheading @value{GDBN} Command
30706 There's no equivalent @value{GDBN} command.
30708 @subsubheading Example
30712 @subheading The @code{-target-list-available-targets} Command
30713 @findex -target-list-available-targets
30715 @subsubheading Synopsis
30718 -target-list-available-targets
30721 List the possible targets to connect to.
30723 @subsubheading @value{GDBN} Command
30725 The corresponding @value{GDBN} command is @samp{help target}.
30727 @subsubheading Example
30731 @subheading The @code{-target-list-current-targets} Command
30732 @findex -target-list-current-targets
30734 @subsubheading Synopsis
30737 -target-list-current-targets
30740 Describe the current target.
30742 @subsubheading @value{GDBN} Command
30744 The corresponding information is printed by @samp{info file} (among
30747 @subsubheading Example
30751 @subheading The @code{-target-list-parameters} Command
30752 @findex -target-list-parameters
30754 @subsubheading Synopsis
30757 -target-list-parameters
30763 @subsubheading @value{GDBN} Command
30767 @subsubheading Example
30771 @subheading The @code{-target-select} Command
30772 @findex -target-select
30774 @subsubheading Synopsis
30777 -target-select @var{type} @var{parameters @dots{}}
30780 Connect @value{GDBN} to the remote target. This command takes two args:
30784 The type of target, for instance @samp{remote}, etc.
30785 @item @var{parameters}
30786 Device names, host names and the like. @xref{Target Commands, ,
30787 Commands for Managing Targets}, for more details.
30790 The output is a connection notification, followed by the address at
30791 which the target program is, in the following form:
30794 ^connected,addr="@var{address}",func="@var{function name}",
30795 args=[@var{arg list}]
30798 @subsubheading @value{GDBN} Command
30800 The corresponding @value{GDBN} command is @samp{target}.
30802 @subsubheading Example
30806 -target-select remote /dev/ttya
30807 ^connected,addr="0xfe00a300",func="??",args=[]
30811 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30812 @node GDB/MI File Transfer Commands
30813 @section @sc{gdb/mi} File Transfer Commands
30816 @subheading The @code{-target-file-put} Command
30817 @findex -target-file-put
30819 @subsubheading Synopsis
30822 -target-file-put @var{hostfile} @var{targetfile}
30825 Copy file @var{hostfile} from the host system (the machine running
30826 @value{GDBN}) to @var{targetfile} on the target system.
30828 @subsubheading @value{GDBN} Command
30830 The corresponding @value{GDBN} command is @samp{remote put}.
30832 @subsubheading Example
30836 -target-file-put localfile remotefile
30842 @subheading The @code{-target-file-get} Command
30843 @findex -target-file-get
30845 @subsubheading Synopsis
30848 -target-file-get @var{targetfile} @var{hostfile}
30851 Copy file @var{targetfile} from the target system to @var{hostfile}
30852 on the host system.
30854 @subsubheading @value{GDBN} Command
30856 The corresponding @value{GDBN} command is @samp{remote get}.
30858 @subsubheading Example
30862 -target-file-get remotefile localfile
30868 @subheading The @code{-target-file-delete} Command
30869 @findex -target-file-delete
30871 @subsubheading Synopsis
30874 -target-file-delete @var{targetfile}
30877 Delete @var{targetfile} from the target system.
30879 @subsubheading @value{GDBN} Command
30881 The corresponding @value{GDBN} command is @samp{remote delete}.
30883 @subsubheading Example
30887 -target-file-delete remotefile
30893 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30894 @node GDB/MI Miscellaneous Commands
30895 @section Miscellaneous @sc{gdb/mi} Commands
30897 @c @subheading -gdb-complete
30899 @subheading The @code{-gdb-exit} Command
30902 @subsubheading Synopsis
30908 Exit @value{GDBN} immediately.
30910 @subsubheading @value{GDBN} Command
30912 Approximately corresponds to @samp{quit}.
30914 @subsubheading Example
30924 @subheading The @code{-exec-abort} Command
30925 @findex -exec-abort
30927 @subsubheading Synopsis
30933 Kill the inferior running program.
30935 @subsubheading @value{GDBN} Command
30937 The corresponding @value{GDBN} command is @samp{kill}.
30939 @subsubheading Example
30944 @subheading The @code{-gdb-set} Command
30947 @subsubheading Synopsis
30953 Set an internal @value{GDBN} variable.
30954 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
30956 @subsubheading @value{GDBN} Command
30958 The corresponding @value{GDBN} command is @samp{set}.
30960 @subsubheading Example
30970 @subheading The @code{-gdb-show} Command
30973 @subsubheading Synopsis
30979 Show the current value of a @value{GDBN} variable.
30981 @subsubheading @value{GDBN} Command
30983 The corresponding @value{GDBN} command is @samp{show}.
30985 @subsubheading Example
30994 @c @subheading -gdb-source
30997 @subheading The @code{-gdb-version} Command
30998 @findex -gdb-version
31000 @subsubheading Synopsis
31006 Show version information for @value{GDBN}. Used mostly in testing.
31008 @subsubheading @value{GDBN} Command
31010 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31011 default shows this information when you start an interactive session.
31013 @subsubheading Example
31015 @c This example modifies the actual output from GDB to avoid overfull
31021 ~Copyright 2000 Free Software Foundation, Inc.
31022 ~GDB is free software, covered by the GNU General Public License, and
31023 ~you are welcome to change it and/or distribute copies of it under
31024 ~ certain conditions.
31025 ~Type "show copying" to see the conditions.
31026 ~There is absolutely no warranty for GDB. Type "show warranty" for
31028 ~This GDB was configured as
31029 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31034 @subheading The @code{-list-features} Command
31035 @findex -list-features
31037 Returns a list of particular features of the MI protocol that
31038 this version of gdb implements. A feature can be a command,
31039 or a new field in an output of some command, or even an
31040 important bugfix. While a frontend can sometimes detect presence
31041 of a feature at runtime, it is easier to perform detection at debugger
31044 The command returns a list of strings, with each string naming an
31045 available feature. Each returned string is just a name, it does not
31046 have any internal structure. The list of possible feature names
31052 (gdb) -list-features
31053 ^done,result=["feature1","feature2"]
31056 The current list of features is:
31059 @item frozen-varobjs
31060 Indicates support for the @code{-var-set-frozen} command, as well
31061 as possible presense of the @code{frozen} field in the output
31062 of @code{-varobj-create}.
31063 @item pending-breakpoints
31064 Indicates support for the @option{-f} option to the @code{-break-insert}
31067 Indicates Python scripting support, Python-based
31068 pretty-printing commands, and possible presence of the
31069 @samp{display_hint} field in the output of @code{-var-list-children}
31071 Indicates support for the @code{-thread-info} command.
31072 @item data-read-memory-bytes
31073 Indicates support for the @code{-data-read-memory-bytes} and the
31074 @code{-data-write-memory-bytes} commands.
31075 @item breakpoint-notifications
31076 Indicates that changes to breakpoints and breakpoints created via the
31077 CLI will be announced via async records.
31078 @item ada-task-info
31079 Indicates support for the @code{-ada-task-info} command.
31082 @subheading The @code{-list-target-features} Command
31083 @findex -list-target-features
31085 Returns a list of particular features that are supported by the
31086 target. Those features affect the permitted MI commands, but
31087 unlike the features reported by the @code{-list-features} command, the
31088 features depend on which target GDB is using at the moment. Whenever
31089 a target can change, due to commands such as @code{-target-select},
31090 @code{-target-attach} or @code{-exec-run}, the list of target features
31091 may change, and the frontend should obtain it again.
31095 (gdb) -list-features
31096 ^done,result=["async"]
31099 The current list of features is:
31103 Indicates that the target is capable of asynchronous command
31104 execution, which means that @value{GDBN} will accept further commands
31105 while the target is running.
31108 Indicates that the target is capable of reverse execution.
31109 @xref{Reverse Execution}, for more information.
31113 @subheading The @code{-list-thread-groups} Command
31114 @findex -list-thread-groups
31116 @subheading Synopsis
31119 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31122 Lists thread groups (@pxref{Thread groups}). When a single thread
31123 group is passed as the argument, lists the children of that group.
31124 When several thread group are passed, lists information about those
31125 thread groups. Without any parameters, lists information about all
31126 top-level thread groups.
31128 Normally, thread groups that are being debugged are reported.
31129 With the @samp{--available} option, @value{GDBN} reports thread groups
31130 available on the target.
31132 The output of this command may have either a @samp{threads} result or
31133 a @samp{groups} result. The @samp{thread} result has a list of tuples
31134 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31135 Information}). The @samp{groups} result has a list of tuples as value,
31136 each tuple describing a thread group. If top-level groups are
31137 requested (that is, no parameter is passed), or when several groups
31138 are passed, the output always has a @samp{groups} result. The format
31139 of the @samp{group} result is described below.
31141 To reduce the number of roundtrips it's possible to list thread groups
31142 together with their children, by passing the @samp{--recurse} option
31143 and the recursion depth. Presently, only recursion depth of 1 is
31144 permitted. If this option is present, then every reported thread group
31145 will also include its children, either as @samp{group} or
31146 @samp{threads} field.
31148 In general, any combination of option and parameters is permitted, with
31149 the following caveats:
31153 When a single thread group is passed, the output will typically
31154 be the @samp{threads} result. Because threads may not contain
31155 anything, the @samp{recurse} option will be ignored.
31158 When the @samp{--available} option is passed, limited information may
31159 be available. In particular, the list of threads of a process might
31160 be inaccessible. Further, specifying specific thread groups might
31161 not give any performance advantage over listing all thread groups.
31162 The frontend should assume that @samp{-list-thread-groups --available}
31163 is always an expensive operation and cache the results.
31167 The @samp{groups} result is a list of tuples, where each tuple may
31168 have the following fields:
31172 Identifier of the thread group. This field is always present.
31173 The identifier is an opaque string; frontends should not try to
31174 convert it to an integer, even though it might look like one.
31177 The type of the thread group. At present, only @samp{process} is a
31181 The target-specific process identifier. This field is only present
31182 for thread groups of type @samp{process} and only if the process exists.
31185 The number of children this thread group has. This field may be
31186 absent for an available thread group.
31189 This field has a list of tuples as value, each tuple describing a
31190 thread. It may be present if the @samp{--recurse} option is
31191 specified, and it's actually possible to obtain the threads.
31194 This field is a list of integers, each identifying a core that one
31195 thread of the group is running on. This field may be absent if
31196 such information is not available.
31199 The name of the executable file that corresponds to this thread group.
31200 The field is only present for thread groups of type @samp{process},
31201 and only if there is a corresponding executable file.
31205 @subheading Example
31209 -list-thread-groups
31210 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31211 -list-thread-groups 17
31212 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31213 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31214 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31215 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31216 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31217 -list-thread-groups --available
31218 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31219 -list-thread-groups --available --recurse 1
31220 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31221 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31222 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31223 -list-thread-groups --available --recurse 1 17 18
31224 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31225 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31226 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31230 @subheading The @code{-add-inferior} Command
31231 @findex -add-inferior
31233 @subheading Synopsis
31239 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31240 inferior is not associated with any executable. Such association may
31241 be established with the @samp{-file-exec-and-symbols} command
31242 (@pxref{GDB/MI File Commands}). The command response has a single
31243 field, @samp{thread-group}, whose value is the identifier of the
31244 thread group corresponding to the new inferior.
31246 @subheading Example
31251 ^done,thread-group="i3"
31254 @subheading The @code{-interpreter-exec} Command
31255 @findex -interpreter-exec
31257 @subheading Synopsis
31260 -interpreter-exec @var{interpreter} @var{command}
31262 @anchor{-interpreter-exec}
31264 Execute the specified @var{command} in the given @var{interpreter}.
31266 @subheading @value{GDBN} Command
31268 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31270 @subheading Example
31274 -interpreter-exec console "break main"
31275 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31276 &"During symbol reading, bad structure-type format.\n"
31277 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31282 @subheading The @code{-inferior-tty-set} Command
31283 @findex -inferior-tty-set
31285 @subheading Synopsis
31288 -inferior-tty-set /dev/pts/1
31291 Set terminal for future runs of the program being debugged.
31293 @subheading @value{GDBN} Command
31295 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31297 @subheading Example
31301 -inferior-tty-set /dev/pts/1
31306 @subheading The @code{-inferior-tty-show} Command
31307 @findex -inferior-tty-show
31309 @subheading Synopsis
31315 Show terminal for future runs of program being debugged.
31317 @subheading @value{GDBN} Command
31319 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31321 @subheading Example
31325 -inferior-tty-set /dev/pts/1
31329 ^done,inferior_tty_terminal="/dev/pts/1"
31333 @subheading The @code{-enable-timings} Command
31334 @findex -enable-timings
31336 @subheading Synopsis
31339 -enable-timings [yes | no]
31342 Toggle the printing of the wallclock, user and system times for an MI
31343 command as a field in its output. This command is to help frontend
31344 developers optimize the performance of their code. No argument is
31345 equivalent to @samp{yes}.
31347 @subheading @value{GDBN} Command
31351 @subheading Example
31359 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31360 addr="0x080484ed",func="main",file="myprog.c",
31361 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
31362 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31370 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31371 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31372 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31373 fullname="/home/nickrob/myprog.c",line="73"@}
31378 @chapter @value{GDBN} Annotations
31380 This chapter describes annotations in @value{GDBN}. Annotations were
31381 designed to interface @value{GDBN} to graphical user interfaces or other
31382 similar programs which want to interact with @value{GDBN} at a
31383 relatively high level.
31385 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31389 This is Edition @value{EDITION}, @value{DATE}.
31393 * Annotations Overview:: What annotations are; the general syntax.
31394 * Server Prefix:: Issuing a command without affecting user state.
31395 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31396 * Errors:: Annotations for error messages.
31397 * Invalidation:: Some annotations describe things now invalid.
31398 * Annotations for Running::
31399 Whether the program is running, how it stopped, etc.
31400 * Source Annotations:: Annotations describing source code.
31403 @node Annotations Overview
31404 @section What is an Annotation?
31405 @cindex annotations
31407 Annotations start with a newline character, two @samp{control-z}
31408 characters, and the name of the annotation. If there is no additional
31409 information associated with this annotation, the name of the annotation
31410 is followed immediately by a newline. If there is additional
31411 information, the name of the annotation is followed by a space, the
31412 additional information, and a newline. The additional information
31413 cannot contain newline characters.
31415 Any output not beginning with a newline and two @samp{control-z}
31416 characters denotes literal output from @value{GDBN}. Currently there is
31417 no need for @value{GDBN} to output a newline followed by two
31418 @samp{control-z} characters, but if there was such a need, the
31419 annotations could be extended with an @samp{escape} annotation which
31420 means those three characters as output.
31422 The annotation @var{level}, which is specified using the
31423 @option{--annotate} command line option (@pxref{Mode Options}), controls
31424 how much information @value{GDBN} prints together with its prompt,
31425 values of expressions, source lines, and other types of output. Level 0
31426 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31427 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31428 for programs that control @value{GDBN}, and level 2 annotations have
31429 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31430 Interface, annotate, GDB's Obsolete Annotations}).
31433 @kindex set annotate
31434 @item set annotate @var{level}
31435 The @value{GDBN} command @code{set annotate} sets the level of
31436 annotations to the specified @var{level}.
31438 @item show annotate
31439 @kindex show annotate
31440 Show the current annotation level.
31443 This chapter describes level 3 annotations.
31445 A simple example of starting up @value{GDBN} with annotations is:
31448 $ @kbd{gdb --annotate=3}
31450 Copyright 2003 Free Software Foundation, Inc.
31451 GDB is free software, covered by the GNU General Public License,
31452 and you are welcome to change it and/or distribute copies of it
31453 under certain conditions.
31454 Type "show copying" to see the conditions.
31455 There is absolutely no warranty for GDB. Type "show warranty"
31457 This GDB was configured as "i386-pc-linux-gnu"
31468 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31469 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31470 denotes a @samp{control-z} character) are annotations; the rest is
31471 output from @value{GDBN}.
31473 @node Server Prefix
31474 @section The Server Prefix
31475 @cindex server prefix
31477 If you prefix a command with @samp{server } then it will not affect
31478 the command history, nor will it affect @value{GDBN}'s notion of which
31479 command to repeat if @key{RET} is pressed on a line by itself. This
31480 means that commands can be run behind a user's back by a front-end in
31481 a transparent manner.
31483 The @code{server } prefix does not affect the recording of values into
31484 the value history; to print a value without recording it into the
31485 value history, use the @code{output} command instead of the
31486 @code{print} command.
31488 Using this prefix also disables confirmation requests
31489 (@pxref{confirmation requests}).
31492 @section Annotation for @value{GDBN} Input
31494 @cindex annotations for prompts
31495 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31496 to know when to send output, when the output from a given command is
31499 Different kinds of input each have a different @dfn{input type}. Each
31500 input type has three annotations: a @code{pre-} annotation, which
31501 denotes the beginning of any prompt which is being output, a plain
31502 annotation, which denotes the end of the prompt, and then a @code{post-}
31503 annotation which denotes the end of any echo which may (or may not) be
31504 associated with the input. For example, the @code{prompt} input type
31505 features the following annotations:
31513 The input types are
31516 @findex pre-prompt annotation
31517 @findex prompt annotation
31518 @findex post-prompt annotation
31520 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31522 @findex pre-commands annotation
31523 @findex commands annotation
31524 @findex post-commands annotation
31526 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31527 command. The annotations are repeated for each command which is input.
31529 @findex pre-overload-choice annotation
31530 @findex overload-choice annotation
31531 @findex post-overload-choice annotation
31532 @item overload-choice
31533 When @value{GDBN} wants the user to select between various overloaded functions.
31535 @findex pre-query annotation
31536 @findex query annotation
31537 @findex post-query annotation
31539 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31541 @findex pre-prompt-for-continue annotation
31542 @findex prompt-for-continue annotation
31543 @findex post-prompt-for-continue annotation
31544 @item prompt-for-continue
31545 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31546 expect this to work well; instead use @code{set height 0} to disable
31547 prompting. This is because the counting of lines is buggy in the
31548 presence of annotations.
31553 @cindex annotations for errors, warnings and interrupts
31555 @findex quit annotation
31560 This annotation occurs right before @value{GDBN} responds to an interrupt.
31562 @findex error annotation
31567 This annotation occurs right before @value{GDBN} responds to an error.
31569 Quit and error annotations indicate that any annotations which @value{GDBN} was
31570 in the middle of may end abruptly. For example, if a
31571 @code{value-history-begin} annotation is followed by a @code{error}, one
31572 cannot expect to receive the matching @code{value-history-end}. One
31573 cannot expect not to receive it either, however; an error annotation
31574 does not necessarily mean that @value{GDBN} is immediately returning all the way
31577 @findex error-begin annotation
31578 A quit or error annotation may be preceded by
31584 Any output between that and the quit or error annotation is the error
31587 Warning messages are not yet annotated.
31588 @c If we want to change that, need to fix warning(), type_error(),
31589 @c range_error(), and possibly other places.
31592 @section Invalidation Notices
31594 @cindex annotations for invalidation messages
31595 The following annotations say that certain pieces of state may have
31599 @findex frames-invalid annotation
31600 @item ^Z^Zframes-invalid
31602 The frames (for example, output from the @code{backtrace} command) may
31605 @findex breakpoints-invalid annotation
31606 @item ^Z^Zbreakpoints-invalid
31608 The breakpoints may have changed. For example, the user just added or
31609 deleted a breakpoint.
31612 @node Annotations for Running
31613 @section Running the Program
31614 @cindex annotations for running programs
31616 @findex starting annotation
31617 @findex stopping annotation
31618 When the program starts executing due to a @value{GDBN} command such as
31619 @code{step} or @code{continue},
31625 is output. When the program stops,
31631 is output. Before the @code{stopped} annotation, a variety of
31632 annotations describe how the program stopped.
31635 @findex exited annotation
31636 @item ^Z^Zexited @var{exit-status}
31637 The program exited, and @var{exit-status} is the exit status (zero for
31638 successful exit, otherwise nonzero).
31640 @findex signalled annotation
31641 @findex signal-name annotation
31642 @findex signal-name-end annotation
31643 @findex signal-string annotation
31644 @findex signal-string-end annotation
31645 @item ^Z^Zsignalled
31646 The program exited with a signal. After the @code{^Z^Zsignalled}, the
31647 annotation continues:
31653 ^Z^Zsignal-name-end
31657 ^Z^Zsignal-string-end
31662 where @var{name} is the name of the signal, such as @code{SIGILL} or
31663 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
31664 as @code{Illegal Instruction} or @code{Segmentation fault}.
31665 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
31666 user's benefit and have no particular format.
31668 @findex signal annotation
31670 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
31671 just saying that the program received the signal, not that it was
31672 terminated with it.
31674 @findex breakpoint annotation
31675 @item ^Z^Zbreakpoint @var{number}
31676 The program hit breakpoint number @var{number}.
31678 @findex watchpoint annotation
31679 @item ^Z^Zwatchpoint @var{number}
31680 The program hit watchpoint number @var{number}.
31683 @node Source Annotations
31684 @section Displaying Source
31685 @cindex annotations for source display
31687 @findex source annotation
31688 The following annotation is used instead of displaying source code:
31691 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
31694 where @var{filename} is an absolute file name indicating which source
31695 file, @var{line} is the line number within that file (where 1 is the
31696 first line in the file), @var{character} is the character position
31697 within the file (where 0 is the first character in the file) (for most
31698 debug formats this will necessarily point to the beginning of a line),
31699 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
31700 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
31701 @var{addr} is the address in the target program associated with the
31702 source which is being displayed. @var{addr} is in the form @samp{0x}
31703 followed by one or more lowercase hex digits (note that this does not
31704 depend on the language).
31706 @node JIT Interface
31707 @chapter JIT Compilation Interface
31708 @cindex just-in-time compilation
31709 @cindex JIT compilation interface
31711 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
31712 interface. A JIT compiler is a program or library that generates native
31713 executable code at runtime and executes it, usually in order to achieve good
31714 performance while maintaining platform independence.
31716 Programs that use JIT compilation are normally difficult to debug because
31717 portions of their code are generated at runtime, instead of being loaded from
31718 object files, which is where @value{GDBN} normally finds the program's symbols
31719 and debug information. In order to debug programs that use JIT compilation,
31720 @value{GDBN} has an interface that allows the program to register in-memory
31721 symbol files with @value{GDBN} at runtime.
31723 If you are using @value{GDBN} to debug a program that uses this interface, then
31724 it should work transparently so long as you have not stripped the binary. If
31725 you are developing a JIT compiler, then the interface is documented in the rest
31726 of this chapter. At this time, the only known client of this interface is the
31729 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
31730 JIT compiler communicates with @value{GDBN} by writing data into a global
31731 variable and calling a fuction at a well-known symbol. When @value{GDBN}
31732 attaches, it reads a linked list of symbol files from the global variable to
31733 find existing code, and puts a breakpoint in the function so that it can find
31734 out about additional code.
31737 * Declarations:: Relevant C struct declarations
31738 * Registering Code:: Steps to register code
31739 * Unregistering Code:: Steps to unregister code
31743 @section JIT Declarations
31745 These are the relevant struct declarations that a C program should include to
31746 implement the interface:
31756 struct jit_code_entry
31758 struct jit_code_entry *next_entry;
31759 struct jit_code_entry *prev_entry;
31760 const char *symfile_addr;
31761 uint64_t symfile_size;
31764 struct jit_descriptor
31767 /* This type should be jit_actions_t, but we use uint32_t
31768 to be explicit about the bitwidth. */
31769 uint32_t action_flag;
31770 struct jit_code_entry *relevant_entry;
31771 struct jit_code_entry *first_entry;
31774 /* GDB puts a breakpoint in this function. */
31775 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
31777 /* Make sure to specify the version statically, because the
31778 debugger may check the version before we can set it. */
31779 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
31782 If the JIT is multi-threaded, then it is important that the JIT synchronize any
31783 modifications to this global data properly, which can easily be done by putting
31784 a global mutex around modifications to these structures.
31786 @node Registering Code
31787 @section Registering Code
31789 To register code with @value{GDBN}, the JIT should follow this protocol:
31793 Generate an object file in memory with symbols and other desired debug
31794 information. The file must include the virtual addresses of the sections.
31797 Create a code entry for the file, which gives the start and size of the symbol
31801 Add it to the linked list in the JIT descriptor.
31804 Point the relevant_entry field of the descriptor at the entry.
31807 Set @code{action_flag} to @code{JIT_REGISTER} and call
31808 @code{__jit_debug_register_code}.
31811 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
31812 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
31813 new code. However, the linked list must still be maintained in order to allow
31814 @value{GDBN} to attach to a running process and still find the symbol files.
31816 @node Unregistering Code
31817 @section Unregistering Code
31819 If code is freed, then the JIT should use the following protocol:
31823 Remove the code entry corresponding to the code from the linked list.
31826 Point the @code{relevant_entry} field of the descriptor at the code entry.
31829 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
31830 @code{__jit_debug_register_code}.
31833 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
31834 and the JIT will leak the memory used for the associated symbol files.
31837 @chapter Reporting Bugs in @value{GDBN}
31838 @cindex bugs in @value{GDBN}
31839 @cindex reporting bugs in @value{GDBN}
31841 Your bug reports play an essential role in making @value{GDBN} reliable.
31843 Reporting a bug may help you by bringing a solution to your problem, or it
31844 may not. But in any case the principal function of a bug report is to help
31845 the entire community by making the next version of @value{GDBN} work better. Bug
31846 reports are your contribution to the maintenance of @value{GDBN}.
31848 In order for a bug report to serve its purpose, you must include the
31849 information that enables us to fix the bug.
31852 * Bug Criteria:: Have you found a bug?
31853 * Bug Reporting:: How to report bugs
31857 @section Have You Found a Bug?
31858 @cindex bug criteria
31860 If you are not sure whether you have found a bug, here are some guidelines:
31863 @cindex fatal signal
31864 @cindex debugger crash
31865 @cindex crash of debugger
31867 If the debugger gets a fatal signal, for any input whatever, that is a
31868 @value{GDBN} bug. Reliable debuggers never crash.
31870 @cindex error on valid input
31872 If @value{GDBN} produces an error message for valid input, that is a
31873 bug. (Note that if you're cross debugging, the problem may also be
31874 somewhere in the connection to the target.)
31876 @cindex invalid input
31878 If @value{GDBN} does not produce an error message for invalid input,
31879 that is a bug. However, you should note that your idea of
31880 ``invalid input'' might be our idea of ``an extension'' or ``support
31881 for traditional practice''.
31884 If you are an experienced user of debugging tools, your suggestions
31885 for improvement of @value{GDBN} are welcome in any case.
31888 @node Bug Reporting
31889 @section How to Report Bugs
31890 @cindex bug reports
31891 @cindex @value{GDBN} bugs, reporting
31893 A number of companies and individuals offer support for @sc{gnu} products.
31894 If you obtained @value{GDBN} from a support organization, we recommend you
31895 contact that organization first.
31897 You can find contact information for many support companies and
31898 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
31900 @c should add a web page ref...
31903 @ifset BUGURL_DEFAULT
31904 In any event, we also recommend that you submit bug reports for
31905 @value{GDBN}. The preferred method is to submit them directly using
31906 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
31907 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
31910 @strong{Do not send bug reports to @samp{info-gdb}, or to
31911 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
31912 not want to receive bug reports. Those that do have arranged to receive
31915 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
31916 serves as a repeater. The mailing list and the newsgroup carry exactly
31917 the same messages. Often people think of posting bug reports to the
31918 newsgroup instead of mailing them. This appears to work, but it has one
31919 problem which can be crucial: a newsgroup posting often lacks a mail
31920 path back to the sender. Thus, if we need to ask for more information,
31921 we may be unable to reach you. For this reason, it is better to send
31922 bug reports to the mailing list.
31924 @ifclear BUGURL_DEFAULT
31925 In any event, we also recommend that you submit bug reports for
31926 @value{GDBN} to @value{BUGURL}.
31930 The fundamental principle of reporting bugs usefully is this:
31931 @strong{report all the facts}. If you are not sure whether to state a
31932 fact or leave it out, state it!
31934 Often people omit facts because they think they know what causes the
31935 problem and assume that some details do not matter. Thus, you might
31936 assume that the name of the variable you use in an example does not matter.
31937 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
31938 stray memory reference which happens to fetch from the location where that
31939 name is stored in memory; perhaps, if the name were different, the contents
31940 of that location would fool the debugger into doing the right thing despite
31941 the bug. Play it safe and give a specific, complete example. That is the
31942 easiest thing for you to do, and the most helpful.
31944 Keep in mind that the purpose of a bug report is to enable us to fix the
31945 bug. It may be that the bug has been reported previously, but neither
31946 you nor we can know that unless your bug report is complete and
31949 Sometimes people give a few sketchy facts and ask, ``Does this ring a
31950 bell?'' Those bug reports are useless, and we urge everyone to
31951 @emph{refuse to respond to them} except to chide the sender to report
31954 To enable us to fix the bug, you should include all these things:
31958 The version of @value{GDBN}. @value{GDBN} announces it if you start
31959 with no arguments; you can also print it at any time using @code{show
31962 Without this, we will not know whether there is any point in looking for
31963 the bug in the current version of @value{GDBN}.
31966 The type of machine you are using, and the operating system name and
31970 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
31971 ``@value{GCC}--2.8.1''.
31974 What compiler (and its version) was used to compile the program you are
31975 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
31976 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
31977 to get this information; for other compilers, see the documentation for
31981 The command arguments you gave the compiler to compile your example and
31982 observe the bug. For example, did you use @samp{-O}? To guarantee
31983 you will not omit something important, list them all. A copy of the
31984 Makefile (or the output from make) is sufficient.
31986 If we were to try to guess the arguments, we would probably guess wrong
31987 and then we might not encounter the bug.
31990 A complete input script, and all necessary source files, that will
31994 A description of what behavior you observe that you believe is
31995 incorrect. For example, ``It gets a fatal signal.''
31997 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
31998 will certainly notice it. But if the bug is incorrect output, we might
31999 not notice unless it is glaringly wrong. You might as well not give us
32000 a chance to make a mistake.
32002 Even if the problem you experience is a fatal signal, you should still
32003 say so explicitly. Suppose something strange is going on, such as, your
32004 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32005 the C library on your system. (This has happened!) Your copy might
32006 crash and ours would not. If you told us to expect a crash, then when
32007 ours fails to crash, we would know that the bug was not happening for
32008 us. If you had not told us to expect a crash, then we would not be able
32009 to draw any conclusion from our observations.
32012 @cindex recording a session script
32013 To collect all this information, you can use a session recording program
32014 such as @command{script}, which is available on many Unix systems.
32015 Just run your @value{GDBN} session inside @command{script} and then
32016 include the @file{typescript} file with your bug report.
32018 Another way to record a @value{GDBN} session is to run @value{GDBN}
32019 inside Emacs and then save the entire buffer to a file.
32022 If you wish to suggest changes to the @value{GDBN} source, send us context
32023 diffs. If you even discuss something in the @value{GDBN} source, refer to
32024 it by context, not by line number.
32026 The line numbers in our development sources will not match those in your
32027 sources. Your line numbers would convey no useful information to us.
32031 Here are some things that are not necessary:
32035 A description of the envelope of the bug.
32037 Often people who encounter a bug spend a lot of time investigating
32038 which changes to the input file will make the bug go away and which
32039 changes will not affect it.
32041 This is often time consuming and not very useful, because the way we
32042 will find the bug is by running a single example under the debugger
32043 with breakpoints, not by pure deduction from a series of examples.
32044 We recommend that you save your time for something else.
32046 Of course, if you can find a simpler example to report @emph{instead}
32047 of the original one, that is a convenience for us. Errors in the
32048 output will be easier to spot, running under the debugger will take
32049 less time, and so on.
32051 However, simplification is not vital; if you do not want to do this,
32052 report the bug anyway and send us the entire test case you used.
32055 A patch for the bug.
32057 A patch for the bug does help us if it is a good one. But do not omit
32058 the necessary information, such as the test case, on the assumption that
32059 a patch is all we need. We might see problems with your patch and decide
32060 to fix the problem another way, or we might not understand it at all.
32062 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32063 construct an example that will make the program follow a certain path
32064 through the code. If you do not send us the example, we will not be able
32065 to construct one, so we will not be able to verify that the bug is fixed.
32067 And if we cannot understand what bug you are trying to fix, or why your
32068 patch should be an improvement, we will not install it. A test case will
32069 help us to understand.
32072 A guess about what the bug is or what it depends on.
32074 Such guesses are usually wrong. Even we cannot guess right about such
32075 things without first using the debugger to find the facts.
32078 @c The readline documentation is distributed with the readline code
32079 @c and consists of the two following files:
32082 @c Use -I with makeinfo to point to the appropriate directory,
32083 @c environment var TEXINPUTS with TeX.
32084 @ifclear SYSTEM_READLINE
32085 @include rluser.texi
32086 @include hsuser.texi
32090 @appendix In Memoriam
32092 The @value{GDBN} project mourns the loss of the following long-time
32097 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32098 to Free Software in general. Outside of @value{GDBN}, he was known in
32099 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32101 @item Michael Snyder
32102 Michael was one of the Global Maintainers of the @value{GDBN} project,
32103 with contributions recorded as early as 1996, until 2011. In addition
32104 to his day to day participation, he was a large driving force behind
32105 adding Reverse Debugging to @value{GDBN}.
32108 Beyond their technical contributions to the project, they were also
32109 enjoyable members of the Free Software Community. We will miss them.
32111 @node Formatting Documentation
32112 @appendix Formatting Documentation
32114 @cindex @value{GDBN} reference card
32115 @cindex reference card
32116 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32117 for printing with PostScript or Ghostscript, in the @file{gdb}
32118 subdirectory of the main source directory@footnote{In
32119 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32120 release.}. If you can use PostScript or Ghostscript with your printer,
32121 you can print the reference card immediately with @file{refcard.ps}.
32123 The release also includes the source for the reference card. You
32124 can format it, using @TeX{}, by typing:
32130 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32131 mode on US ``letter'' size paper;
32132 that is, on a sheet 11 inches wide by 8.5 inches
32133 high. You will need to specify this form of printing as an option to
32134 your @sc{dvi} output program.
32136 @cindex documentation
32138 All the documentation for @value{GDBN} comes as part of the machine-readable
32139 distribution. The documentation is written in Texinfo format, which is
32140 a documentation system that uses a single source file to produce both
32141 on-line information and a printed manual. You can use one of the Info
32142 formatting commands to create the on-line version of the documentation
32143 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32145 @value{GDBN} includes an already formatted copy of the on-line Info
32146 version of this manual in the @file{gdb} subdirectory. The main Info
32147 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32148 subordinate files matching @samp{gdb.info*} in the same directory. If
32149 necessary, you can print out these files, or read them with any editor;
32150 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32151 Emacs or the standalone @code{info} program, available as part of the
32152 @sc{gnu} Texinfo distribution.
32154 If you want to format these Info files yourself, you need one of the
32155 Info formatting programs, such as @code{texinfo-format-buffer} or
32158 If you have @code{makeinfo} installed, and are in the top level
32159 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32160 version @value{GDBVN}), you can make the Info file by typing:
32167 If you want to typeset and print copies of this manual, you need @TeX{},
32168 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32169 Texinfo definitions file.
32171 @TeX{} is a typesetting program; it does not print files directly, but
32172 produces output files called @sc{dvi} files. To print a typeset
32173 document, you need a program to print @sc{dvi} files. If your system
32174 has @TeX{} installed, chances are it has such a program. The precise
32175 command to use depends on your system; @kbd{lpr -d} is common; another
32176 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32177 require a file name without any extension or a @samp{.dvi} extension.
32179 @TeX{} also requires a macro definitions file called
32180 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32181 written in Texinfo format. On its own, @TeX{} cannot either read or
32182 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32183 and is located in the @file{gdb-@var{version-number}/texinfo}
32186 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32187 typeset and print this manual. First switch to the @file{gdb}
32188 subdirectory of the main source directory (for example, to
32189 @file{gdb-@value{GDBVN}/gdb}) and type:
32195 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32197 @node Installing GDB
32198 @appendix Installing @value{GDBN}
32199 @cindex installation
32202 * Requirements:: Requirements for building @value{GDBN}
32203 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32204 * Separate Objdir:: Compiling @value{GDBN} in another directory
32205 * Config Names:: Specifying names for hosts and targets
32206 * Configure Options:: Summary of options for configure
32207 * System-wide configuration:: Having a system-wide init file
32211 @section Requirements for Building @value{GDBN}
32212 @cindex building @value{GDBN}, requirements for
32214 Building @value{GDBN} requires various tools and packages to be available.
32215 Other packages will be used only if they are found.
32217 @heading Tools/Packages Necessary for Building @value{GDBN}
32219 @item ISO C90 compiler
32220 @value{GDBN} is written in ISO C90. It should be buildable with any
32221 working C90 compiler, e.g.@: GCC.
32225 @heading Tools/Packages Optional for Building @value{GDBN}
32229 @value{GDBN} can use the Expat XML parsing library. This library may be
32230 included with your operating system distribution; if it is not, you
32231 can get the latest version from @url{http://expat.sourceforge.net}.
32232 The @file{configure} script will search for this library in several
32233 standard locations; if it is installed in an unusual path, you can
32234 use the @option{--with-libexpat-prefix} option to specify its location.
32240 Remote protocol memory maps (@pxref{Memory Map Format})
32242 Target descriptions (@pxref{Target Descriptions})
32244 Remote shared library lists (@pxref{Library List Format})
32246 MS-Windows shared libraries (@pxref{Shared Libraries})
32248 Traceframe info (@pxref{Traceframe Info Format})
32252 @cindex compressed debug sections
32253 @value{GDBN} will use the @samp{zlib} library, if available, to read
32254 compressed debug sections. Some linkers, such as GNU gold, are capable
32255 of producing binaries with compressed debug sections. If @value{GDBN}
32256 is compiled with @samp{zlib}, it will be able to read the debug
32257 information in such binaries.
32259 The @samp{zlib} library is likely included with your operating system
32260 distribution; if it is not, you can get the latest version from
32261 @url{http://zlib.net}.
32264 @value{GDBN}'s features related to character sets (@pxref{Character
32265 Sets}) require a functioning @code{iconv} implementation. If you are
32266 on a GNU system, then this is provided by the GNU C Library. Some
32267 other systems also provide a working @code{iconv}.
32269 If @value{GDBN} is using the @code{iconv} program which is installed
32270 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32271 This is done with @option{--with-iconv-bin} which specifies the
32272 directory that contains the @code{iconv} program.
32274 On systems without @code{iconv}, you can install GNU Libiconv. If you
32275 have previously installed Libiconv, you can use the
32276 @option{--with-libiconv-prefix} option to configure.
32278 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32279 arrange to build Libiconv if a directory named @file{libiconv} appears
32280 in the top-most source directory. If Libiconv is built this way, and
32281 if the operating system does not provide a suitable @code{iconv}
32282 implementation, then the just-built library will automatically be used
32283 by @value{GDBN}. One easy way to set this up is to download GNU
32284 Libiconv, unpack it, and then rename the directory holding the
32285 Libiconv source code to @samp{libiconv}.
32288 @node Running Configure
32289 @section Invoking the @value{GDBN} @file{configure} Script
32290 @cindex configuring @value{GDBN}
32291 @value{GDBN} comes with a @file{configure} script that automates the process
32292 of preparing @value{GDBN} for installation; you can then use @code{make} to
32293 build the @code{gdb} program.
32295 @c irrelevant in info file; it's as current as the code it lives with.
32296 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
32297 look at the @file{README} file in the sources; we may have improved the
32298 installation procedures since publishing this manual.}
32301 The @value{GDBN} distribution includes all the source code you need for
32302 @value{GDBN} in a single directory, whose name is usually composed by
32303 appending the version number to @samp{gdb}.
32305 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
32306 @file{gdb-@value{GDBVN}} directory. That directory contains:
32309 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
32310 script for configuring @value{GDBN} and all its supporting libraries
32312 @item gdb-@value{GDBVN}/gdb
32313 the source specific to @value{GDBN} itself
32315 @item gdb-@value{GDBVN}/bfd
32316 source for the Binary File Descriptor library
32318 @item gdb-@value{GDBVN}/include
32319 @sc{gnu} include files
32321 @item gdb-@value{GDBVN}/libiberty
32322 source for the @samp{-liberty} free software library
32324 @item gdb-@value{GDBVN}/opcodes
32325 source for the library of opcode tables and disassemblers
32327 @item gdb-@value{GDBVN}/readline
32328 source for the @sc{gnu} command-line interface
32330 @item gdb-@value{GDBVN}/glob
32331 source for the @sc{gnu} filename pattern-matching subroutine
32333 @item gdb-@value{GDBVN}/mmalloc
32334 source for the @sc{gnu} memory-mapped malloc package
32337 The simplest way to configure and build @value{GDBN} is to run @file{configure}
32338 from the @file{gdb-@var{version-number}} source directory, which in
32339 this example is the @file{gdb-@value{GDBVN}} directory.
32341 First switch to the @file{gdb-@var{version-number}} source directory
32342 if you are not already in it; then run @file{configure}. Pass the
32343 identifier for the platform on which @value{GDBN} will run as an
32349 cd gdb-@value{GDBVN}
32350 ./configure @var{host}
32355 where @var{host} is an identifier such as @samp{sun4} or
32356 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
32357 (You can often leave off @var{host}; @file{configure} tries to guess the
32358 correct value by examining your system.)
32360 Running @samp{configure @var{host}} and then running @code{make} builds the
32361 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
32362 libraries, then @code{gdb} itself. The configured source files, and the
32363 binaries, are left in the corresponding source directories.
32366 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
32367 system does not recognize this automatically when you run a different
32368 shell, you may need to run @code{sh} on it explicitly:
32371 sh configure @var{host}
32374 If you run @file{configure} from a directory that contains source
32375 directories for multiple libraries or programs, such as the
32376 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
32378 creates configuration files for every directory level underneath (unless
32379 you tell it not to, with the @samp{--norecursion} option).
32381 You should run the @file{configure} script from the top directory in the
32382 source tree, the @file{gdb-@var{version-number}} directory. If you run
32383 @file{configure} from one of the subdirectories, you will configure only
32384 that subdirectory. That is usually not what you want. In particular,
32385 if you run the first @file{configure} from the @file{gdb} subdirectory
32386 of the @file{gdb-@var{version-number}} directory, you will omit the
32387 configuration of @file{bfd}, @file{readline}, and other sibling
32388 directories of the @file{gdb} subdirectory. This leads to build errors
32389 about missing include files such as @file{bfd/bfd.h}.
32391 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
32392 However, you should make sure that the shell on your path (named by
32393 the @samp{SHELL} environment variable) is publicly readable. Remember
32394 that @value{GDBN} uses the shell to start your program---some systems refuse to
32395 let @value{GDBN} debug child processes whose programs are not readable.
32397 @node Separate Objdir
32398 @section Compiling @value{GDBN} in Another Directory
32400 If you want to run @value{GDBN} versions for several host or target machines,
32401 you need a different @code{gdb} compiled for each combination of
32402 host and target. @file{configure} is designed to make this easy by
32403 allowing you to generate each configuration in a separate subdirectory,
32404 rather than in the source directory. If your @code{make} program
32405 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
32406 @code{make} in each of these directories builds the @code{gdb}
32407 program specified there.
32409 To build @code{gdb} in a separate directory, run @file{configure}
32410 with the @samp{--srcdir} option to specify where to find the source.
32411 (You also need to specify a path to find @file{configure}
32412 itself from your working directory. If the path to @file{configure}
32413 would be the same as the argument to @samp{--srcdir}, you can leave out
32414 the @samp{--srcdir} option; it is assumed.)
32416 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
32417 separate directory for a Sun 4 like this:
32421 cd gdb-@value{GDBVN}
32424 ../gdb-@value{GDBVN}/configure sun4
32429 When @file{configure} builds a configuration using a remote source
32430 directory, it creates a tree for the binaries with the same structure
32431 (and using the same names) as the tree under the source directory. In
32432 the example, you'd find the Sun 4 library @file{libiberty.a} in the
32433 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
32434 @file{gdb-sun4/gdb}.
32436 Make sure that your path to the @file{configure} script has just one
32437 instance of @file{gdb} in it. If your path to @file{configure} looks
32438 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
32439 one subdirectory of @value{GDBN}, not the whole package. This leads to
32440 build errors about missing include files such as @file{bfd/bfd.h}.
32442 One popular reason to build several @value{GDBN} configurations in separate
32443 directories is to configure @value{GDBN} for cross-compiling (where
32444 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
32445 programs that run on another machine---the @dfn{target}).
32446 You specify a cross-debugging target by
32447 giving the @samp{--target=@var{target}} option to @file{configure}.
32449 When you run @code{make} to build a program or library, you must run
32450 it in a configured directory---whatever directory you were in when you
32451 called @file{configure} (or one of its subdirectories).
32453 The @code{Makefile} that @file{configure} generates in each source
32454 directory also runs recursively. If you type @code{make} in a source
32455 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
32456 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
32457 will build all the required libraries, and then build GDB.
32459 When you have multiple hosts or targets configured in separate
32460 directories, you can run @code{make} on them in parallel (for example,
32461 if they are NFS-mounted on each of the hosts); they will not interfere
32465 @section Specifying Names for Hosts and Targets
32467 The specifications used for hosts and targets in the @file{configure}
32468 script are based on a three-part naming scheme, but some short predefined
32469 aliases are also supported. The full naming scheme encodes three pieces
32470 of information in the following pattern:
32473 @var{architecture}-@var{vendor}-@var{os}
32476 For example, you can use the alias @code{sun4} as a @var{host} argument,
32477 or as the value for @var{target} in a @code{--target=@var{target}}
32478 option. The equivalent full name is @samp{sparc-sun-sunos4}.
32480 The @file{configure} script accompanying @value{GDBN} does not provide
32481 any query facility to list all supported host and target names or
32482 aliases. @file{configure} calls the Bourne shell script
32483 @code{config.sub} to map abbreviations to full names; you can read the
32484 script, if you wish, or you can use it to test your guesses on
32485 abbreviations---for example:
32488 % sh config.sub i386-linux
32490 % sh config.sub alpha-linux
32491 alpha-unknown-linux-gnu
32492 % sh config.sub hp9k700
32494 % sh config.sub sun4
32495 sparc-sun-sunos4.1.1
32496 % sh config.sub sun3
32497 m68k-sun-sunos4.1.1
32498 % sh config.sub i986v
32499 Invalid configuration `i986v': machine `i986v' not recognized
32503 @code{config.sub} is also distributed in the @value{GDBN} source
32504 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
32506 @node Configure Options
32507 @section @file{configure} Options
32509 Here is a summary of the @file{configure} options and arguments that
32510 are most often useful for building @value{GDBN}. @file{configure} also has
32511 several other options not listed here. @inforef{What Configure
32512 Does,,configure.info}, for a full explanation of @file{configure}.
32515 configure @r{[}--help@r{]}
32516 @r{[}--prefix=@var{dir}@r{]}
32517 @r{[}--exec-prefix=@var{dir}@r{]}
32518 @r{[}--srcdir=@var{dirname}@r{]}
32519 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
32520 @r{[}--target=@var{target}@r{]}
32525 You may introduce options with a single @samp{-} rather than
32526 @samp{--} if you prefer; but you may abbreviate option names if you use
32531 Display a quick summary of how to invoke @file{configure}.
32533 @item --prefix=@var{dir}
32534 Configure the source to install programs and files under directory
32537 @item --exec-prefix=@var{dir}
32538 Configure the source to install programs under directory
32541 @c avoid splitting the warning from the explanation:
32543 @item --srcdir=@var{dirname}
32544 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
32545 @code{make} that implements the @code{VPATH} feature.}@*
32546 Use this option to make configurations in directories separate from the
32547 @value{GDBN} source directories. Among other things, you can use this to
32548 build (or maintain) several configurations simultaneously, in separate
32549 directories. @file{configure} writes configuration-specific files in
32550 the current directory, but arranges for them to use the source in the
32551 directory @var{dirname}. @file{configure} creates directories under
32552 the working directory in parallel to the source directories below
32555 @item --norecursion
32556 Configure only the directory level where @file{configure} is executed; do not
32557 propagate configuration to subdirectories.
32559 @item --target=@var{target}
32560 Configure @value{GDBN} for cross-debugging programs running on the specified
32561 @var{target}. Without this option, @value{GDBN} is configured to debug
32562 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
32564 There is no convenient way to generate a list of all available targets.
32566 @item @var{host} @dots{}
32567 Configure @value{GDBN} to run on the specified @var{host}.
32569 There is no convenient way to generate a list of all available hosts.
32572 There are many other options available as well, but they are generally
32573 needed for special purposes only.
32575 @node System-wide configuration
32576 @section System-wide configuration and settings
32577 @cindex system-wide init file
32579 @value{GDBN} can be configured to have a system-wide init file;
32580 this file will be read and executed at startup (@pxref{Startup, , What
32581 @value{GDBN} does during startup}).
32583 Here is the corresponding configure option:
32586 @item --with-system-gdbinit=@var{file}
32587 Specify that the default location of the system-wide init file is
32591 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
32592 it may be subject to relocation. Two possible cases:
32596 If the default location of this init file contains @file{$prefix},
32597 it will be subject to relocation. Suppose that the configure options
32598 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
32599 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
32600 init file is looked for as @file{$install/etc/gdbinit} instead of
32601 @file{$prefix/etc/gdbinit}.
32604 By contrast, if the default location does not contain the prefix,
32605 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
32606 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
32607 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
32608 wherever @value{GDBN} is installed.
32611 @node Maintenance Commands
32612 @appendix Maintenance Commands
32613 @cindex maintenance commands
32614 @cindex internal commands
32616 In addition to commands intended for @value{GDBN} users, @value{GDBN}
32617 includes a number of commands intended for @value{GDBN} developers,
32618 that are not documented elsewhere in this manual. These commands are
32619 provided here for reference. (For commands that turn on debugging
32620 messages, see @ref{Debugging Output}.)
32623 @kindex maint agent
32624 @kindex maint agent-eval
32625 @item maint agent @var{expression}
32626 @itemx maint agent-eval @var{expression}
32627 Translate the given @var{expression} into remote agent bytecodes.
32628 This command is useful for debugging the Agent Expression mechanism
32629 (@pxref{Agent Expressions}). The @samp{agent} version produces an
32630 expression useful for data collection, such as by tracepoints, while
32631 @samp{maint agent-eval} produces an expression that evaluates directly
32632 to a result. For instance, a collection expression for @code{globa +
32633 globb} will include bytecodes to record four bytes of memory at each
32634 of the addresses of @code{globa} and @code{globb}, while discarding
32635 the result of the addition, while an evaluation expression will do the
32636 addition and return the sum.
32638 @kindex maint info breakpoints
32639 @item @anchor{maint info breakpoints}maint info breakpoints
32640 Using the same format as @samp{info breakpoints}, display both the
32641 breakpoints you've set explicitly, and those @value{GDBN} is using for
32642 internal purposes. Internal breakpoints are shown with negative
32643 breakpoint numbers. The type column identifies what kind of breakpoint
32648 Normal, explicitly set breakpoint.
32651 Normal, explicitly set watchpoint.
32654 Internal breakpoint, used to handle correctly stepping through
32655 @code{longjmp} calls.
32657 @item longjmp resume
32658 Internal breakpoint at the target of a @code{longjmp}.
32661 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
32664 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
32667 Shared library events.
32671 @kindex set displaced-stepping
32672 @kindex show displaced-stepping
32673 @cindex displaced stepping support
32674 @cindex out-of-line single-stepping
32675 @item set displaced-stepping
32676 @itemx show displaced-stepping
32677 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
32678 if the target supports it. Displaced stepping is a way to single-step
32679 over breakpoints without removing them from the inferior, by executing
32680 an out-of-line copy of the instruction that was originally at the
32681 breakpoint location. It is also known as out-of-line single-stepping.
32684 @item set displaced-stepping on
32685 If the target architecture supports it, @value{GDBN} will use
32686 displaced stepping to step over breakpoints.
32688 @item set displaced-stepping off
32689 @value{GDBN} will not use displaced stepping to step over breakpoints,
32690 even if such is supported by the target architecture.
32692 @cindex non-stop mode, and @samp{set displaced-stepping}
32693 @item set displaced-stepping auto
32694 This is the default mode. @value{GDBN} will use displaced stepping
32695 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
32696 architecture supports displaced stepping.
32699 @kindex maint check-symtabs
32700 @item maint check-symtabs
32701 Check the consistency of psymtabs and symtabs.
32703 @kindex maint cplus first_component
32704 @item maint cplus first_component @var{name}
32705 Print the first C@t{++} class/namespace component of @var{name}.
32707 @kindex maint cplus namespace
32708 @item maint cplus namespace
32709 Print the list of possible C@t{++} namespaces.
32711 @kindex maint demangle
32712 @item maint demangle @var{name}
32713 Demangle a C@t{++} or Objective-C mangled @var{name}.
32715 @kindex maint deprecate
32716 @kindex maint undeprecate
32717 @cindex deprecated commands
32718 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
32719 @itemx maint undeprecate @var{command}
32720 Deprecate or undeprecate the named @var{command}. Deprecated commands
32721 cause @value{GDBN} to issue a warning when you use them. The optional
32722 argument @var{replacement} says which newer command should be used in
32723 favor of the deprecated one; if it is given, @value{GDBN} will mention
32724 the replacement as part of the warning.
32726 @kindex maint dump-me
32727 @item maint dump-me
32728 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
32729 Cause a fatal signal in the debugger and force it to dump its core.
32730 This is supported only on systems which support aborting a program
32731 with the @code{SIGQUIT} signal.
32733 @kindex maint internal-error
32734 @kindex maint internal-warning
32735 @item maint internal-error @r{[}@var{message-text}@r{]}
32736 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
32737 Cause @value{GDBN} to call the internal function @code{internal_error}
32738 or @code{internal_warning} and hence behave as though an internal error
32739 or internal warning has been detected. In addition to reporting the
32740 internal problem, these functions give the user the opportunity to
32741 either quit @value{GDBN} or create a core file of the current
32742 @value{GDBN} session.
32744 These commands take an optional parameter @var{message-text} that is
32745 used as the text of the error or warning message.
32747 Here's an example of using @code{internal-error}:
32750 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
32751 @dots{}/maint.c:121: internal-error: testing, 1, 2
32752 A problem internal to GDB has been detected. Further
32753 debugging may prove unreliable.
32754 Quit this debugging session? (y or n) @kbd{n}
32755 Create a core file? (y or n) @kbd{n}
32759 @cindex @value{GDBN} internal error
32760 @cindex internal errors, control of @value{GDBN} behavior
32762 @kindex maint set internal-error
32763 @kindex maint show internal-error
32764 @kindex maint set internal-warning
32765 @kindex maint show internal-warning
32766 @item maint set internal-error @var{action} [ask|yes|no]
32767 @itemx maint show internal-error @var{action}
32768 @itemx maint set internal-warning @var{action} [ask|yes|no]
32769 @itemx maint show internal-warning @var{action}
32770 When @value{GDBN} reports an internal problem (error or warning) it
32771 gives the user the opportunity to both quit @value{GDBN} and create a
32772 core file of the current @value{GDBN} session. These commands let you
32773 override the default behaviour for each particular @var{action},
32774 described in the table below.
32778 You can specify that @value{GDBN} should always (yes) or never (no)
32779 quit. The default is to ask the user what to do.
32782 You can specify that @value{GDBN} should always (yes) or never (no)
32783 create a core file. The default is to ask the user what to do.
32786 @kindex maint packet
32787 @item maint packet @var{text}
32788 If @value{GDBN} is talking to an inferior via the serial protocol,
32789 then this command sends the string @var{text} to the inferior, and
32790 displays the response packet. @value{GDBN} supplies the initial
32791 @samp{$} character, the terminating @samp{#} character, and the
32794 @kindex maint print architecture
32795 @item maint print architecture @r{[}@var{file}@r{]}
32796 Print the entire architecture configuration. The optional argument
32797 @var{file} names the file where the output goes.
32799 @kindex maint print c-tdesc
32800 @item maint print c-tdesc
32801 Print the current target description (@pxref{Target Descriptions}) as
32802 a C source file. The created source file can be used in @value{GDBN}
32803 when an XML parser is not available to parse the description.
32805 @kindex maint print dummy-frames
32806 @item maint print dummy-frames
32807 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
32810 (@value{GDBP}) @kbd{b add}
32812 (@value{GDBP}) @kbd{print add(2,3)}
32813 Breakpoint 2, add (a=2, b=3) at @dots{}
32815 The program being debugged stopped while in a function called from GDB.
32817 (@value{GDBP}) @kbd{maint print dummy-frames}
32818 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
32819 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
32820 call_lo=0x01014000 call_hi=0x01014001
32824 Takes an optional file parameter.
32826 @kindex maint print registers
32827 @kindex maint print raw-registers
32828 @kindex maint print cooked-registers
32829 @kindex maint print register-groups
32830 @kindex maint print remote-registers
32831 @item maint print registers @r{[}@var{file}@r{]}
32832 @itemx maint print raw-registers @r{[}@var{file}@r{]}
32833 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
32834 @itemx maint print register-groups @r{[}@var{file}@r{]}
32835 @itemx maint print remote-registers @r{[}@var{file}@r{]}
32836 Print @value{GDBN}'s internal register data structures.
32838 The command @code{maint print raw-registers} includes the contents of
32839 the raw register cache; the command @code{maint print
32840 cooked-registers} includes the (cooked) value of all registers,
32841 including registers which aren't available on the target nor visible
32842 to user; the command @code{maint print register-groups} includes the
32843 groups that each register is a member of; and the command @code{maint
32844 print remote-registers} includes the remote target's register numbers
32845 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
32846 @value{GDBN} Internals}.
32848 These commands take an optional parameter, a file name to which to
32849 write the information.
32851 @kindex maint print reggroups
32852 @item maint print reggroups @r{[}@var{file}@r{]}
32853 Print @value{GDBN}'s internal register group data structures. The
32854 optional argument @var{file} tells to what file to write the
32857 The register groups info looks like this:
32860 (@value{GDBP}) @kbd{maint print reggroups}
32873 This command forces @value{GDBN} to flush its internal register cache.
32875 @kindex maint print objfiles
32876 @cindex info for known object files
32877 @item maint print objfiles
32878 Print a dump of all known object files. For each object file, this
32879 command prints its name, address in memory, and all of its psymtabs
32882 @kindex maint print section-scripts
32883 @cindex info for known .debug_gdb_scripts-loaded scripts
32884 @item maint print section-scripts [@var{regexp}]
32885 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
32886 If @var{regexp} is specified, only print scripts loaded by object files
32887 matching @var{regexp}.
32888 For each script, this command prints its name as specified in the objfile,
32889 and the full path if known.
32890 @xref{.debug_gdb_scripts section}.
32892 @kindex maint print statistics
32893 @cindex bcache statistics
32894 @item maint print statistics
32895 This command prints, for each object file in the program, various data
32896 about that object file followed by the byte cache (@dfn{bcache})
32897 statistics for the object file. The objfile data includes the number
32898 of minimal, partial, full, and stabs symbols, the number of types
32899 defined by the objfile, the number of as yet unexpanded psym tables,
32900 the number of line tables and string tables, and the amount of memory
32901 used by the various tables. The bcache statistics include the counts,
32902 sizes, and counts of duplicates of all and unique objects, max,
32903 average, and median entry size, total memory used and its overhead and
32904 savings, and various measures of the hash table size and chain
32907 @kindex maint print target-stack
32908 @cindex target stack description
32909 @item maint print target-stack
32910 A @dfn{target} is an interface between the debugger and a particular
32911 kind of file or process. Targets can be stacked in @dfn{strata},
32912 so that more than one target can potentially respond to a request.
32913 In particular, memory accesses will walk down the stack of targets
32914 until they find a target that is interested in handling that particular
32917 This command prints a short description of each layer that was pushed on
32918 the @dfn{target stack}, starting from the top layer down to the bottom one.
32920 @kindex maint print type
32921 @cindex type chain of a data type
32922 @item maint print type @var{expr}
32923 Print the type chain for a type specified by @var{expr}. The argument
32924 can be either a type name or a symbol. If it is a symbol, the type of
32925 that symbol is described. The type chain produced by this command is
32926 a recursive definition of the data type as stored in @value{GDBN}'s
32927 data structures, including its flags and contained types.
32929 @kindex maint set dwarf2 always-disassemble
32930 @kindex maint show dwarf2 always-disassemble
32931 @item maint set dwarf2 always-disassemble
32932 @item maint show dwarf2 always-disassemble
32933 Control the behavior of @code{info address} when using DWARF debugging
32936 The default is @code{off}, which means that @value{GDBN} should try to
32937 describe a variable's location in an easily readable format. When
32938 @code{on}, @value{GDBN} will instead display the DWARF location
32939 expression in an assembly-like format. Note that some locations are
32940 too complex for @value{GDBN} to describe simply; in this case you will
32941 always see the disassembly form.
32943 Here is an example of the resulting disassembly:
32946 (gdb) info addr argc
32947 Symbol "argc" is a complex DWARF expression:
32951 For more information on these expressions, see
32952 @uref{http://www.dwarfstd.org/, the DWARF standard}.
32954 @kindex maint set dwarf2 max-cache-age
32955 @kindex maint show dwarf2 max-cache-age
32956 @item maint set dwarf2 max-cache-age
32957 @itemx maint show dwarf2 max-cache-age
32958 Control the DWARF 2 compilation unit cache.
32960 @cindex DWARF 2 compilation units cache
32961 In object files with inter-compilation-unit references, such as those
32962 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
32963 reader needs to frequently refer to previously read compilation units.
32964 This setting controls how long a compilation unit will remain in the
32965 cache if it is not referenced. A higher limit means that cached
32966 compilation units will be stored in memory longer, and more total
32967 memory will be used. Setting it to zero disables caching, which will
32968 slow down @value{GDBN} startup, but reduce memory consumption.
32970 @kindex maint set profile
32971 @kindex maint show profile
32972 @cindex profiling GDB
32973 @item maint set profile
32974 @itemx maint show profile
32975 Control profiling of @value{GDBN}.
32977 Profiling will be disabled until you use the @samp{maint set profile}
32978 command to enable it. When you enable profiling, the system will begin
32979 collecting timing and execution count data; when you disable profiling or
32980 exit @value{GDBN}, the results will be written to a log file. Remember that
32981 if you use profiling, @value{GDBN} will overwrite the profiling log file
32982 (often called @file{gmon.out}). If you have a record of important profiling
32983 data in a @file{gmon.out} file, be sure to move it to a safe location.
32985 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
32986 compiled with the @samp{-pg} compiler option.
32988 @kindex maint set show-debug-regs
32989 @kindex maint show show-debug-regs
32990 @cindex hardware debug registers
32991 @item maint set show-debug-regs
32992 @itemx maint show show-debug-regs
32993 Control whether to show variables that mirror the hardware debug
32994 registers. Use @code{ON} to enable, @code{OFF} to disable. If
32995 enabled, the debug registers values are shown when @value{GDBN} inserts or
32996 removes a hardware breakpoint or watchpoint, and when the inferior
32997 triggers a hardware-assisted breakpoint or watchpoint.
32999 @kindex maint set show-all-tib
33000 @kindex maint show show-all-tib
33001 @item maint set show-all-tib
33002 @itemx maint show show-all-tib
33003 Control whether to show all non zero areas within a 1k block starting
33004 at thread local base, when using the @samp{info w32 thread-information-block}
33007 @kindex maint space
33008 @cindex memory used by commands
33010 Control whether to display memory usage for each command. If set to a
33011 nonzero value, @value{GDBN} will display how much memory each command
33012 took, following the command's own output. This can also be requested
33013 by invoking @value{GDBN} with the @option{--statistics} command-line
33014 switch (@pxref{Mode Options}).
33017 @cindex time of command execution
33019 Control whether to display the execution time of @value{GDBN} for each command.
33020 If set to a nonzero value, @value{GDBN} will display how much time it
33021 took to execute each command, following the command's own output.
33022 Both CPU time and wallclock time are printed.
33023 Printing both is useful when trying to determine whether the cost is
33024 CPU or, e.g., disk/network, latency.
33025 Note that the CPU time printed is for @value{GDBN} only, it does not include
33026 the execution time of the inferior because there's no mechanism currently
33027 to compute how much time was spent by @value{GDBN} and how much time was
33028 spent by the program been debugged.
33029 This can also be requested by invoking @value{GDBN} with the
33030 @option{--statistics} command-line switch (@pxref{Mode Options}).
33032 @kindex maint translate-address
33033 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33034 Find the symbol stored at the location specified by the address
33035 @var{addr} and an optional section name @var{section}. If found,
33036 @value{GDBN} prints the name of the closest symbol and an offset from
33037 the symbol's location to the specified address. This is similar to
33038 the @code{info address} command (@pxref{Symbols}), except that this
33039 command also allows to find symbols in other sections.
33041 If section was not specified, the section in which the symbol was found
33042 is also printed. For dynamically linked executables, the name of
33043 executable or shared library containing the symbol is printed as well.
33047 The following command is useful for non-interactive invocations of
33048 @value{GDBN}, such as in the test suite.
33051 @item set watchdog @var{nsec}
33052 @kindex set watchdog
33053 @cindex watchdog timer
33054 @cindex timeout for commands
33055 Set the maximum number of seconds @value{GDBN} will wait for the
33056 target operation to finish. If this time expires, @value{GDBN}
33057 reports and error and the command is aborted.
33059 @item show watchdog
33060 Show the current setting of the target wait timeout.
33063 @node Remote Protocol
33064 @appendix @value{GDBN} Remote Serial Protocol
33069 * Stop Reply Packets::
33070 * General Query Packets::
33071 * Architecture-Specific Protocol Details::
33072 * Tracepoint Packets::
33073 * Host I/O Packets::
33075 * Notification Packets::
33076 * Remote Non-Stop::
33077 * Packet Acknowledgment::
33079 * File-I/O Remote Protocol Extension::
33080 * Library List Format::
33081 * Memory Map Format::
33082 * Thread List Format::
33083 * Traceframe Info Format::
33089 There may be occasions when you need to know something about the
33090 protocol---for example, if there is only one serial port to your target
33091 machine, you might want your program to do something special if it
33092 recognizes a packet meant for @value{GDBN}.
33094 In the examples below, @samp{->} and @samp{<-} are used to indicate
33095 transmitted and received data, respectively.
33097 @cindex protocol, @value{GDBN} remote serial
33098 @cindex serial protocol, @value{GDBN} remote
33099 @cindex remote serial protocol
33100 All @value{GDBN} commands and responses (other than acknowledgments
33101 and notifications, see @ref{Notification Packets}) are sent as a
33102 @var{packet}. A @var{packet} is introduced with the character
33103 @samp{$}, the actual @var{packet-data}, and the terminating character
33104 @samp{#} followed by a two-digit @var{checksum}:
33107 @code{$}@var{packet-data}@code{#}@var{checksum}
33111 @cindex checksum, for @value{GDBN} remote
33113 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33114 characters between the leading @samp{$} and the trailing @samp{#} (an
33115 eight bit unsigned checksum).
33117 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33118 specification also included an optional two-digit @var{sequence-id}:
33121 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33124 @cindex sequence-id, for @value{GDBN} remote
33126 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33127 has never output @var{sequence-id}s. Stubs that handle packets added
33128 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33130 When either the host or the target machine receives a packet, the first
33131 response expected is an acknowledgment: either @samp{+} (to indicate
33132 the package was received correctly) or @samp{-} (to request
33136 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33141 The @samp{+}/@samp{-} acknowledgments can be disabled
33142 once a connection is established.
33143 @xref{Packet Acknowledgment}, for details.
33145 The host (@value{GDBN}) sends @var{command}s, and the target (the
33146 debugging stub incorporated in your program) sends a @var{response}. In
33147 the case of step and continue @var{command}s, the response is only sent
33148 when the operation has completed, and the target has again stopped all
33149 threads in all attached processes. This is the default all-stop mode
33150 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
33151 execution mode; see @ref{Remote Non-Stop}, for details.
33153 @var{packet-data} consists of a sequence of characters with the
33154 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
33157 @cindex remote protocol, field separator
33158 Fields within the packet should be separated using @samp{,} @samp{;} or
33159 @samp{:}. Except where otherwise noted all numbers are represented in
33160 @sc{hex} with leading zeros suppressed.
33162 Implementors should note that prior to @value{GDBN} 5.0, the character
33163 @samp{:} could not appear as the third character in a packet (as it
33164 would potentially conflict with the @var{sequence-id}).
33166 @cindex remote protocol, binary data
33167 @anchor{Binary Data}
33168 Binary data in most packets is encoded either as two hexadecimal
33169 digits per byte of binary data. This allowed the traditional remote
33170 protocol to work over connections which were only seven-bit clean.
33171 Some packets designed more recently assume an eight-bit clean
33172 connection, and use a more efficient encoding to send and receive
33175 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
33176 as an escape character. Any escaped byte is transmitted as the escape
33177 character followed by the original character XORed with @code{0x20}.
33178 For example, the byte @code{0x7d} would be transmitted as the two
33179 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
33180 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
33181 @samp{@}}) must always be escaped. Responses sent by the stub
33182 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
33183 is not interpreted as the start of a run-length encoded sequence
33186 Response @var{data} can be run-length encoded to save space.
33187 Run-length encoding replaces runs of identical characters with one
33188 instance of the repeated character, followed by a @samp{*} and a
33189 repeat count. The repeat count is itself sent encoded, to avoid
33190 binary characters in @var{data}: a value of @var{n} is sent as
33191 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
33192 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
33193 code 32) for a repeat count of 3. (This is because run-length
33194 encoding starts to win for counts 3 or more.) Thus, for example,
33195 @samp{0* } is a run-length encoding of ``0000'': the space character
33196 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
33199 The printable characters @samp{#} and @samp{$} or with a numeric value
33200 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
33201 seven repeats (@samp{$}) can be expanded using a repeat count of only
33202 five (@samp{"}). For example, @samp{00000000} can be encoded as
33205 The error response returned for some packets includes a two character
33206 error number. That number is not well defined.
33208 @cindex empty response, for unsupported packets
33209 For any @var{command} not supported by the stub, an empty response
33210 (@samp{$#00}) should be returned. That way it is possible to extend the
33211 protocol. A newer @value{GDBN} can tell if a packet is supported based
33214 At a minimum, a stub is required to support the @samp{g} and @samp{G}
33215 commands for register access, and the @samp{m} and @samp{M} commands
33216 for memory access. Stubs that only control single-threaded targets
33217 can implement run control with the @samp{c} (continue), and @samp{s}
33218 (step) commands. Stubs that support multi-threading targets should
33219 support the @samp{vCont} command. All other commands are optional.
33224 The following table provides a complete list of all currently defined
33225 @var{command}s and their corresponding response @var{data}.
33226 @xref{File-I/O Remote Protocol Extension}, for details about the File
33227 I/O extension of the remote protocol.
33229 Each packet's description has a template showing the packet's overall
33230 syntax, followed by an explanation of the packet's meaning. We
33231 include spaces in some of the templates for clarity; these are not
33232 part of the packet's syntax. No @value{GDBN} packet uses spaces to
33233 separate its components. For example, a template like @samp{foo
33234 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
33235 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
33236 @var{baz}. @value{GDBN} does not transmit a space character between the
33237 @samp{foo} and the @var{bar}, or between the @var{bar} and the
33240 @cindex @var{thread-id}, in remote protocol
33241 @anchor{thread-id syntax}
33242 Several packets and replies include a @var{thread-id} field to identify
33243 a thread. Normally these are positive numbers with a target-specific
33244 interpretation, formatted as big-endian hex strings. A @var{thread-id}
33245 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
33248 In addition, the remote protocol supports a multiprocess feature in
33249 which the @var{thread-id} syntax is extended to optionally include both
33250 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
33251 The @var{pid} (process) and @var{tid} (thread) components each have the
33252 format described above: a positive number with target-specific
33253 interpretation formatted as a big-endian hex string, literal @samp{-1}
33254 to indicate all processes or threads (respectively), or @samp{0} to
33255 indicate an arbitrary process or thread. Specifying just a process, as
33256 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
33257 error to specify all processes but a specific thread, such as
33258 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
33259 for those packets and replies explicitly documented to include a process
33260 ID, rather than a @var{thread-id}.
33262 The multiprocess @var{thread-id} syntax extensions are only used if both
33263 @value{GDBN} and the stub report support for the @samp{multiprocess}
33264 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
33267 Note that all packet forms beginning with an upper- or lower-case
33268 letter, other than those described here, are reserved for future use.
33270 Here are the packet descriptions.
33275 @cindex @samp{!} packet
33276 @anchor{extended mode}
33277 Enable extended mode. In extended mode, the remote server is made
33278 persistent. The @samp{R} packet is used to restart the program being
33284 The remote target both supports and has enabled extended mode.
33288 @cindex @samp{?} packet
33289 Indicate the reason the target halted. The reply is the same as for
33290 step and continue. This packet has a special interpretation when the
33291 target is in non-stop mode; see @ref{Remote Non-Stop}.
33294 @xref{Stop Reply Packets}, for the reply specifications.
33296 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
33297 @cindex @samp{A} packet
33298 Initialized @code{argv[]} array passed into program. @var{arglen}
33299 specifies the number of bytes in the hex encoded byte stream
33300 @var{arg}. See @code{gdbserver} for more details.
33305 The arguments were set.
33311 @cindex @samp{b} packet
33312 (Don't use this packet; its behavior is not well-defined.)
33313 Change the serial line speed to @var{baud}.
33315 JTC: @emph{When does the transport layer state change? When it's
33316 received, or after the ACK is transmitted. In either case, there are
33317 problems if the command or the acknowledgment packet is dropped.}
33319 Stan: @emph{If people really wanted to add something like this, and get
33320 it working for the first time, they ought to modify ser-unix.c to send
33321 some kind of out-of-band message to a specially-setup stub and have the
33322 switch happen "in between" packets, so that from remote protocol's point
33323 of view, nothing actually happened.}
33325 @item B @var{addr},@var{mode}
33326 @cindex @samp{B} packet
33327 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
33328 breakpoint at @var{addr}.
33330 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
33331 (@pxref{insert breakpoint or watchpoint packet}).
33333 @cindex @samp{bc} packet
33336 Backward continue. Execute the target system in reverse. No parameter.
33337 @xref{Reverse Execution}, for more information.
33340 @xref{Stop Reply Packets}, for the reply specifications.
33342 @cindex @samp{bs} packet
33345 Backward single step. Execute one instruction in reverse. No parameter.
33346 @xref{Reverse Execution}, for more information.
33349 @xref{Stop Reply Packets}, for the reply specifications.
33351 @item c @r{[}@var{addr}@r{]}
33352 @cindex @samp{c} packet
33353 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
33354 resume at current address.
33356 This packet is deprecated for multi-threading support. @xref{vCont
33360 @xref{Stop Reply Packets}, for the reply specifications.
33362 @item C @var{sig}@r{[};@var{addr}@r{]}
33363 @cindex @samp{C} packet
33364 Continue with signal @var{sig} (hex signal number). If
33365 @samp{;@var{addr}} is omitted, resume at same address.
33367 This packet is deprecated for multi-threading support. @xref{vCont
33371 @xref{Stop Reply Packets}, for the reply specifications.
33374 @cindex @samp{d} packet
33377 Don't use this packet; instead, define a general set packet
33378 (@pxref{General Query Packets}).
33382 @cindex @samp{D} packet
33383 The first form of the packet is used to detach @value{GDBN} from the
33384 remote system. It is sent to the remote target
33385 before @value{GDBN} disconnects via the @code{detach} command.
33387 The second form, including a process ID, is used when multiprocess
33388 protocol extensions are enabled (@pxref{multiprocess extensions}), to
33389 detach only a specific process. The @var{pid} is specified as a
33390 big-endian hex string.
33400 @item F @var{RC},@var{EE},@var{CF};@var{XX}
33401 @cindex @samp{F} packet
33402 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
33403 This is part of the File-I/O protocol extension. @xref{File-I/O
33404 Remote Protocol Extension}, for the specification.
33407 @anchor{read registers packet}
33408 @cindex @samp{g} packet
33409 Read general registers.
33413 @item @var{XX@dots{}}
33414 Each byte of register data is described by two hex digits. The bytes
33415 with the register are transmitted in target byte order. The size of
33416 each register and their position within the @samp{g} packet are
33417 determined by the @value{GDBN} internal gdbarch functions
33418 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
33419 specification of several standard @samp{g} packets is specified below.
33421 When reading registers from a trace frame (@pxref{Analyze Collected
33422 Data,,Using the Collected Data}), the stub may also return a string of
33423 literal @samp{x}'s in place of the register data digits, to indicate
33424 that the corresponding register has not been collected, thus its value
33425 is unavailable. For example, for an architecture with 4 registers of
33426 4 bytes each, the following reply indicates to @value{GDBN} that
33427 registers 0 and 2 have not been collected, while registers 1 and 3
33428 have been collected, and both have zero value:
33432 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
33439 @item G @var{XX@dots{}}
33440 @cindex @samp{G} packet
33441 Write general registers. @xref{read registers packet}, for a
33442 description of the @var{XX@dots{}} data.
33452 @item H @var{op} @var{thread-id}
33453 @cindex @samp{H} packet
33454 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
33455 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
33456 it should be @samp{c} for step and continue operations (note that this
33457 is deprecated, supporting the @samp{vCont} command is a better
33458 option), @samp{g} for other operations. The thread designator
33459 @var{thread-id} has the format and interpretation described in
33460 @ref{thread-id syntax}.
33471 @c 'H': How restrictive (or permissive) is the thread model. If a
33472 @c thread is selected and stopped, are other threads allowed
33473 @c to continue to execute? As I mentioned above, I think the
33474 @c semantics of each command when a thread is selected must be
33475 @c described. For example:
33477 @c 'g': If the stub supports threads and a specific thread is
33478 @c selected, returns the register block from that thread;
33479 @c otherwise returns current registers.
33481 @c 'G' If the stub supports threads and a specific thread is
33482 @c selected, sets the registers of the register block of
33483 @c that thread; otherwise sets current registers.
33485 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
33486 @anchor{cycle step packet}
33487 @cindex @samp{i} packet
33488 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
33489 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
33490 step starting at that address.
33493 @cindex @samp{I} packet
33494 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
33498 @cindex @samp{k} packet
33501 FIXME: @emph{There is no description of how to operate when a specific
33502 thread context has been selected (i.e.@: does 'k' kill only that
33505 @item m @var{addr},@var{length}
33506 @cindex @samp{m} packet
33507 Read @var{length} bytes of memory starting at address @var{addr}.
33508 Note that @var{addr} may not be aligned to any particular boundary.
33510 The stub need not use any particular size or alignment when gathering
33511 data from memory for the response; even if @var{addr} is word-aligned
33512 and @var{length} is a multiple of the word size, the stub is free to
33513 use byte accesses, or not. For this reason, this packet may not be
33514 suitable for accessing memory-mapped I/O devices.
33515 @cindex alignment of remote memory accesses
33516 @cindex size of remote memory accesses
33517 @cindex memory, alignment and size of remote accesses
33521 @item @var{XX@dots{}}
33522 Memory contents; each byte is transmitted as a two-digit hexadecimal
33523 number. The reply may contain fewer bytes than requested if the
33524 server was able to read only part of the region of memory.
33529 @item M @var{addr},@var{length}:@var{XX@dots{}}
33530 @cindex @samp{M} packet
33531 Write @var{length} bytes of memory starting at address @var{addr}.
33532 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
33533 hexadecimal number.
33540 for an error (this includes the case where only part of the data was
33545 @cindex @samp{p} packet
33546 Read the value of register @var{n}; @var{n} is in hex.
33547 @xref{read registers packet}, for a description of how the returned
33548 register value is encoded.
33552 @item @var{XX@dots{}}
33553 the register's value
33557 Indicating an unrecognized @var{query}.
33560 @item P @var{n@dots{}}=@var{r@dots{}}
33561 @anchor{write register packet}
33562 @cindex @samp{P} packet
33563 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
33564 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
33565 digits for each byte in the register (target byte order).
33575 @item q @var{name} @var{params}@dots{}
33576 @itemx Q @var{name} @var{params}@dots{}
33577 @cindex @samp{q} packet
33578 @cindex @samp{Q} packet
33579 General query (@samp{q}) and set (@samp{Q}). These packets are
33580 described fully in @ref{General Query Packets}.
33583 @cindex @samp{r} packet
33584 Reset the entire system.
33586 Don't use this packet; use the @samp{R} packet instead.
33589 @cindex @samp{R} packet
33590 Restart the program being debugged. @var{XX}, while needed, is ignored.
33591 This packet is only available in extended mode (@pxref{extended mode}).
33593 The @samp{R} packet has no reply.
33595 @item s @r{[}@var{addr}@r{]}
33596 @cindex @samp{s} packet
33597 Single step. @var{addr} is the address at which to resume. If
33598 @var{addr} is omitted, resume at same address.
33600 This packet is deprecated for multi-threading support. @xref{vCont
33604 @xref{Stop Reply Packets}, for the reply specifications.
33606 @item S @var{sig}@r{[};@var{addr}@r{]}
33607 @anchor{step with signal packet}
33608 @cindex @samp{S} packet
33609 Step with signal. This is analogous to the @samp{C} packet, but
33610 requests a single-step, rather than a normal resumption of execution.
33612 This packet is deprecated for multi-threading support. @xref{vCont
33616 @xref{Stop Reply Packets}, for the reply specifications.
33618 @item t @var{addr}:@var{PP},@var{MM}
33619 @cindex @samp{t} packet
33620 Search backwards starting at address @var{addr} for a match with pattern
33621 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
33622 @var{addr} must be at least 3 digits.
33624 @item T @var{thread-id}
33625 @cindex @samp{T} packet
33626 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
33631 thread is still alive
33637 Packets starting with @samp{v} are identified by a multi-letter name,
33638 up to the first @samp{;} or @samp{?} (or the end of the packet).
33640 @item vAttach;@var{pid}
33641 @cindex @samp{vAttach} packet
33642 Attach to a new process with the specified process ID @var{pid}.
33643 The process ID is a
33644 hexadecimal integer identifying the process. In all-stop mode, all
33645 threads in the attached process are stopped; in non-stop mode, it may be
33646 attached without being stopped if that is supported by the target.
33648 @c In non-stop mode, on a successful vAttach, the stub should set the
33649 @c current thread to a thread of the newly-attached process. After
33650 @c attaching, GDB queries for the attached process's thread ID with qC.
33651 @c Also note that, from a user perspective, whether or not the
33652 @c target is stopped on attach in non-stop mode depends on whether you
33653 @c use the foreground or background version of the attach command, not
33654 @c on what vAttach does; GDB does the right thing with respect to either
33655 @c stopping or restarting threads.
33657 This packet is only available in extended mode (@pxref{extended mode}).
33663 @item @r{Any stop packet}
33664 for success in all-stop mode (@pxref{Stop Reply Packets})
33666 for success in non-stop mode (@pxref{Remote Non-Stop})
33669 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
33670 @cindex @samp{vCont} packet
33671 @anchor{vCont packet}
33672 Resume the inferior, specifying different actions for each thread.
33673 If an action is specified with no @var{thread-id}, then it is applied to any
33674 threads that don't have a specific action specified; if no default action is
33675 specified then other threads should remain stopped in all-stop mode and
33676 in their current state in non-stop mode.
33677 Specifying multiple
33678 default actions is an error; specifying no actions is also an error.
33679 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
33681 Currently supported actions are:
33687 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
33691 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
33696 The optional argument @var{addr} normally associated with the
33697 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
33698 not supported in @samp{vCont}.
33700 The @samp{t} action is only relevant in non-stop mode
33701 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
33702 A stop reply should be generated for any affected thread not already stopped.
33703 When a thread is stopped by means of a @samp{t} action,
33704 the corresponding stop reply should indicate that the thread has stopped with
33705 signal @samp{0}, regardless of whether the target uses some other signal
33706 as an implementation detail.
33709 @xref{Stop Reply Packets}, for the reply specifications.
33712 @cindex @samp{vCont?} packet
33713 Request a list of actions supported by the @samp{vCont} packet.
33717 @item vCont@r{[};@var{action}@dots{}@r{]}
33718 The @samp{vCont} packet is supported. Each @var{action} is a supported
33719 command in the @samp{vCont} packet.
33721 The @samp{vCont} packet is not supported.
33724 @item vFile:@var{operation}:@var{parameter}@dots{}
33725 @cindex @samp{vFile} packet
33726 Perform a file operation on the target system. For details,
33727 see @ref{Host I/O Packets}.
33729 @item vFlashErase:@var{addr},@var{length}
33730 @cindex @samp{vFlashErase} packet
33731 Direct the stub to erase @var{length} bytes of flash starting at
33732 @var{addr}. The region may enclose any number of flash blocks, but
33733 its start and end must fall on block boundaries, as indicated by the
33734 flash block size appearing in the memory map (@pxref{Memory Map
33735 Format}). @value{GDBN} groups flash memory programming operations
33736 together, and sends a @samp{vFlashDone} request after each group; the
33737 stub is allowed to delay erase operation until the @samp{vFlashDone}
33738 packet is received.
33740 The stub must support @samp{vCont} if it reports support for
33741 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
33742 this case @samp{vCont} actions can be specified to apply to all threads
33743 in a process by using the @samp{p@var{pid}.-1} form of the
33754 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
33755 @cindex @samp{vFlashWrite} packet
33756 Direct the stub to write data to flash address @var{addr}. The data
33757 is passed in binary form using the same encoding as for the @samp{X}
33758 packet (@pxref{Binary Data}). The memory ranges specified by
33759 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
33760 not overlap, and must appear in order of increasing addresses
33761 (although @samp{vFlashErase} packets for higher addresses may already
33762 have been received; the ordering is guaranteed only between
33763 @samp{vFlashWrite} packets). If a packet writes to an address that was
33764 neither erased by a preceding @samp{vFlashErase} packet nor by some other
33765 target-specific method, the results are unpredictable.
33773 for vFlashWrite addressing non-flash memory
33779 @cindex @samp{vFlashDone} packet
33780 Indicate to the stub that flash programming operation is finished.
33781 The stub is permitted to delay or batch the effects of a group of
33782 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
33783 @samp{vFlashDone} packet is received. The contents of the affected
33784 regions of flash memory are unpredictable until the @samp{vFlashDone}
33785 request is completed.
33787 @item vKill;@var{pid}
33788 @cindex @samp{vKill} packet
33789 Kill the process with the specified process ID. @var{pid} is a
33790 hexadecimal integer identifying the process. This packet is used in
33791 preference to @samp{k} when multiprocess protocol extensions are
33792 supported; see @ref{multiprocess extensions}.
33802 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
33803 @cindex @samp{vRun} packet
33804 Run the program @var{filename}, passing it each @var{argument} on its
33805 command line. The file and arguments are hex-encoded strings. If
33806 @var{filename} is an empty string, the stub may use a default program
33807 (e.g.@: the last program run). The program is created in the stopped
33810 @c FIXME: What about non-stop mode?
33812 This packet is only available in extended mode (@pxref{extended mode}).
33818 @item @r{Any stop packet}
33819 for success (@pxref{Stop Reply Packets})
33823 @anchor{vStopped packet}
33824 @cindex @samp{vStopped} packet
33826 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
33827 reply and prompt for the stub to report another one.
33831 @item @r{Any stop packet}
33832 if there is another unreported stop event (@pxref{Stop Reply Packets})
33834 if there are no unreported stop events
33837 @item X @var{addr},@var{length}:@var{XX@dots{}}
33839 @cindex @samp{X} packet
33840 Write data to memory, where the data is transmitted in binary.
33841 @var{addr} is address, @var{length} is number of bytes,
33842 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
33852 @item z @var{type},@var{addr},@var{kind}
33853 @itemx Z @var{type},@var{addr},@var{kind}
33854 @anchor{insert breakpoint or watchpoint packet}
33855 @cindex @samp{z} packet
33856 @cindex @samp{Z} packets
33857 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
33858 watchpoint starting at address @var{address} of kind @var{kind}.
33860 Each breakpoint and watchpoint packet @var{type} is documented
33863 @emph{Implementation notes: A remote target shall return an empty string
33864 for an unrecognized breakpoint or watchpoint packet @var{type}. A
33865 remote target shall support either both or neither of a given
33866 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
33867 avoid potential problems with duplicate packets, the operations should
33868 be implemented in an idempotent way.}
33870 @item z0,@var{addr},@var{kind}
33871 @itemx Z0,@var{addr},@var{kind}
33872 @cindex @samp{z0} packet
33873 @cindex @samp{Z0} packet
33874 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
33875 @var{addr} of type @var{kind}.
33877 A memory breakpoint is implemented by replacing the instruction at
33878 @var{addr} with a software breakpoint or trap instruction. The
33879 @var{kind} is target-specific and typically indicates the size of
33880 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
33881 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
33882 architectures have additional meanings for @var{kind};
33883 see @ref{Architecture-Specific Protocol Details}.
33885 @emph{Implementation note: It is possible for a target to copy or move
33886 code that contains memory breakpoints (e.g., when implementing
33887 overlays). The behavior of this packet, in the presence of such a
33888 target, is not defined.}
33900 @item z1,@var{addr},@var{kind}
33901 @itemx Z1,@var{addr},@var{kind}
33902 @cindex @samp{z1} packet
33903 @cindex @samp{Z1} packet
33904 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
33905 address @var{addr}.
33907 A hardware breakpoint is implemented using a mechanism that is not
33908 dependant on being able to modify the target's memory. @var{kind}
33909 has the same meaning as in @samp{Z0} packets.
33911 @emph{Implementation note: A hardware breakpoint is not affected by code
33924 @item z2,@var{addr},@var{kind}
33925 @itemx Z2,@var{addr},@var{kind}
33926 @cindex @samp{z2} packet
33927 @cindex @samp{Z2} packet
33928 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
33929 @var{kind} is interpreted as the number of bytes to watch.
33941 @item z3,@var{addr},@var{kind}
33942 @itemx Z3,@var{addr},@var{kind}
33943 @cindex @samp{z3} packet
33944 @cindex @samp{Z3} packet
33945 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
33946 @var{kind} is interpreted as the number of bytes to watch.
33958 @item z4,@var{addr},@var{kind}
33959 @itemx Z4,@var{addr},@var{kind}
33960 @cindex @samp{z4} packet
33961 @cindex @samp{Z4} packet
33962 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
33963 @var{kind} is interpreted as the number of bytes to watch.
33977 @node Stop Reply Packets
33978 @section Stop Reply Packets
33979 @cindex stop reply packets
33981 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
33982 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
33983 receive any of the below as a reply. Except for @samp{?}
33984 and @samp{vStopped}, that reply is only returned
33985 when the target halts. In the below the exact meaning of @dfn{signal
33986 number} is defined by the header @file{include/gdb/signals.h} in the
33987 @value{GDBN} source code.
33989 As in the description of request packets, we include spaces in the
33990 reply templates for clarity; these are not part of the reply packet's
33991 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
33997 The program received signal number @var{AA} (a two-digit hexadecimal
33998 number). This is equivalent to a @samp{T} response with no
33999 @var{n}:@var{r} pairs.
34001 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
34002 @cindex @samp{T} packet reply
34003 The program received signal number @var{AA} (a two-digit hexadecimal
34004 number). This is equivalent to an @samp{S} response, except that the
34005 @samp{@var{n}:@var{r}} pairs can carry values of important registers
34006 and other information directly in the stop reply packet, reducing
34007 round-trip latency. Single-step and breakpoint traps are reported
34008 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
34012 If @var{n} is a hexadecimal number, it is a register number, and the
34013 corresponding @var{r} gives that register's value. @var{r} is a
34014 series of bytes in target byte order, with each byte given by a
34015 two-digit hex number.
34018 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
34019 the stopped thread, as specified in @ref{thread-id syntax}.
34022 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
34023 the core on which the stop event was detected.
34026 If @var{n} is a recognized @dfn{stop reason}, it describes a more
34027 specific event that stopped the target. The currently defined stop
34028 reasons are listed below. @var{aa} should be @samp{05}, the trap
34029 signal. At most one stop reason should be present.
34032 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34033 and go on to the next; this allows us to extend the protocol in the
34037 The currently defined stop reasons are:
34043 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34046 @cindex shared library events, remote reply
34048 The packet indicates that the loaded libraries have changed.
34049 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34050 list of loaded libraries. @var{r} is ignored.
34052 @cindex replay log events, remote reply
34054 The packet indicates that the target cannot continue replaying
34055 logged execution events, because it has reached the end (or the
34056 beginning when executing backward) of the log. The value of @var{r}
34057 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34058 for more information.
34062 @itemx W @var{AA} ; process:@var{pid}
34063 The process exited, and @var{AA} is the exit status. This is only
34064 applicable to certain targets.
34066 The second form of the response, including the process ID of the exited
34067 process, can be used only when @value{GDBN} has reported support for
34068 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34069 The @var{pid} is formatted as a big-endian hex string.
34072 @itemx X @var{AA} ; process:@var{pid}
34073 The process terminated with signal @var{AA}.
34075 The second form of the response, including the process ID of the
34076 terminated process, can be used only when @value{GDBN} has reported
34077 support for multiprocess protocol extensions; see @ref{multiprocess
34078 extensions}. The @var{pid} is formatted as a big-endian hex string.
34080 @item O @var{XX}@dots{}
34081 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34082 written as the program's console output. This can happen at any time
34083 while the program is running and the debugger should continue to wait
34084 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34086 @item F @var{call-id},@var{parameter}@dots{}
34087 @var{call-id} is the identifier which says which host system call should
34088 be called. This is just the name of the function. Translation into the
34089 correct system call is only applicable as it's defined in @value{GDBN}.
34090 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
34093 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
34094 this very system call.
34096 The target replies with this packet when it expects @value{GDBN} to
34097 call a host system call on behalf of the target. @value{GDBN} replies
34098 with an appropriate @samp{F} packet and keeps up waiting for the next
34099 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
34100 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
34101 Protocol Extension}, for more details.
34105 @node General Query Packets
34106 @section General Query Packets
34107 @cindex remote query requests
34109 Packets starting with @samp{q} are @dfn{general query packets};
34110 packets starting with @samp{Q} are @dfn{general set packets}. General
34111 query and set packets are a semi-unified form for retrieving and
34112 sending information to and from the stub.
34114 The initial letter of a query or set packet is followed by a name
34115 indicating what sort of thing the packet applies to. For example,
34116 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
34117 definitions with the stub. These packet names follow some
34122 The name must not contain commas, colons or semicolons.
34124 Most @value{GDBN} query and set packets have a leading upper case
34127 The names of custom vendor packets should use a company prefix, in
34128 lower case, followed by a period. For example, packets designed at
34129 the Acme Corporation might begin with @samp{qacme.foo} (for querying
34130 foos) or @samp{Qacme.bar} (for setting bars).
34133 The name of a query or set packet should be separated from any
34134 parameters by a @samp{:}; the parameters themselves should be
34135 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
34136 full packet name, and check for a separator or the end of the packet,
34137 in case two packet names share a common prefix. New packets should not begin
34138 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
34139 packets predate these conventions, and have arguments without any terminator
34140 for the packet name; we suspect they are in widespread use in places that
34141 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
34142 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
34145 Like the descriptions of the other packets, each description here
34146 has a template showing the packet's overall syntax, followed by an
34147 explanation of the packet's meaning. We include spaces in some of the
34148 templates for clarity; these are not part of the packet's syntax. No
34149 @value{GDBN} packet uses spaces to separate its components.
34151 Here are the currently defined query and set packets:
34155 @item QAllow:@var{op}:@var{val}@dots{}
34156 @cindex @samp{QAllow} packet
34157 Specify which operations @value{GDBN} expects to request of the
34158 target, as a semicolon-separated list of operation name and value
34159 pairs. Possible values for @var{op} include @samp{WriteReg},
34160 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
34161 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
34162 indicating that @value{GDBN} will not request the operation, or 1,
34163 indicating that it may. (The target can then use this to set up its
34164 own internals optimally, for instance if the debugger never expects to
34165 insert breakpoints, it may not need to install its own trap handler.)
34168 @cindex current thread, remote request
34169 @cindex @samp{qC} packet
34170 Return the current thread ID.
34174 @item QC @var{thread-id}
34175 Where @var{thread-id} is a thread ID as documented in
34176 @ref{thread-id syntax}.
34177 @item @r{(anything else)}
34178 Any other reply implies the old thread ID.
34181 @item qCRC:@var{addr},@var{length}
34182 @cindex CRC of memory block, remote request
34183 @cindex @samp{qCRC} packet
34184 Compute the CRC checksum of a block of memory using CRC-32 defined in
34185 IEEE 802.3. The CRC is computed byte at a time, taking the most
34186 significant bit of each byte first. The initial pattern code
34187 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
34189 @emph{Note:} This is the same CRC used in validating separate debug
34190 files (@pxref{Separate Debug Files, , Debugging Information in Separate
34191 Files}). However the algorithm is slightly different. When validating
34192 separate debug files, the CRC is computed taking the @emph{least}
34193 significant bit of each byte first, and the final result is inverted to
34194 detect trailing zeros.
34199 An error (such as memory fault)
34200 @item C @var{crc32}
34201 The specified memory region's checksum is @var{crc32}.
34204 @item QDisableRandomization:@var{value}
34205 @cindex disable address space randomization, remote request
34206 @cindex @samp{QDisableRandomization} packet
34207 Some target operating systems will randomize the virtual address space
34208 of the inferior process as a security feature, but provide a feature
34209 to disable such randomization, e.g.@: to allow for a more deterministic
34210 debugging experience. On such systems, this packet with a @var{value}
34211 of 1 directs the target to disable address space randomization for
34212 processes subsequently started via @samp{vRun} packets, while a packet
34213 with a @var{value} of 0 tells the target to enable address space
34216 This packet is only available in extended mode (@pxref{extended mode}).
34221 The request succeeded.
34224 An error occurred. @var{nn} are hex digits.
34227 An empty reply indicates that @samp{QDisableRandomization} is not supported
34231 This packet is not probed by default; the remote stub must request it,
34232 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34233 This should only be done on targets that actually support disabling
34234 address space randomization.
34237 @itemx qsThreadInfo
34238 @cindex list active threads, remote request
34239 @cindex @samp{qfThreadInfo} packet
34240 @cindex @samp{qsThreadInfo} packet
34241 Obtain a list of all active thread IDs from the target (OS). Since there
34242 may be too many active threads to fit into one reply packet, this query
34243 works iteratively: it may require more than one query/reply sequence to
34244 obtain the entire list of threads. The first query of the sequence will
34245 be the @samp{qfThreadInfo} query; subsequent queries in the
34246 sequence will be the @samp{qsThreadInfo} query.
34248 NOTE: This packet replaces the @samp{qL} query (see below).
34252 @item m @var{thread-id}
34254 @item m @var{thread-id},@var{thread-id}@dots{}
34255 a comma-separated list of thread IDs
34257 (lower case letter @samp{L}) denotes end of list.
34260 In response to each query, the target will reply with a list of one or
34261 more thread IDs, separated by commas.
34262 @value{GDBN} will respond to each reply with a request for more thread
34263 ids (using the @samp{qs} form of the query), until the target responds
34264 with @samp{l} (lower-case ell, for @dfn{last}).
34265 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
34268 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
34269 @cindex get thread-local storage address, remote request
34270 @cindex @samp{qGetTLSAddr} packet
34271 Fetch the address associated with thread local storage specified
34272 by @var{thread-id}, @var{offset}, and @var{lm}.
34274 @var{thread-id} is the thread ID associated with the
34275 thread for which to fetch the TLS address. @xref{thread-id syntax}.
34277 @var{offset} is the (big endian, hex encoded) offset associated with the
34278 thread local variable. (This offset is obtained from the debug
34279 information associated with the variable.)
34281 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
34282 load module associated with the thread local storage. For example,
34283 a @sc{gnu}/Linux system will pass the link map address of the shared
34284 object associated with the thread local storage under consideration.
34285 Other operating environments may choose to represent the load module
34286 differently, so the precise meaning of this parameter will vary.
34290 @item @var{XX}@dots{}
34291 Hex encoded (big endian) bytes representing the address of the thread
34292 local storage requested.
34295 An error occurred. @var{nn} are hex digits.
34298 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
34301 @item qGetTIBAddr:@var{thread-id}
34302 @cindex get thread information block address
34303 @cindex @samp{qGetTIBAddr} packet
34304 Fetch address of the Windows OS specific Thread Information Block.
34306 @var{thread-id} is the thread ID associated with the thread.
34310 @item @var{XX}@dots{}
34311 Hex encoded (big endian) bytes representing the linear address of the
34312 thread information block.
34315 An error occured. This means that either the thread was not found, or the
34316 address could not be retrieved.
34319 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
34322 @item qL @var{startflag} @var{threadcount} @var{nextthread}
34323 Obtain thread information from RTOS. Where: @var{startflag} (one hex
34324 digit) is one to indicate the first query and zero to indicate a
34325 subsequent query; @var{threadcount} (two hex digits) is the maximum
34326 number of threads the response packet can contain; and @var{nextthread}
34327 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
34328 returned in the response as @var{argthread}.
34330 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
34334 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
34335 Where: @var{count} (two hex digits) is the number of threads being
34336 returned; @var{done} (one hex digit) is zero to indicate more threads
34337 and one indicates no further threads; @var{argthreadid} (eight hex
34338 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
34339 is a sequence of thread IDs from the target. @var{threadid} (eight hex
34340 digits). See @code{remote.c:parse_threadlist_response()}.
34344 @cindex section offsets, remote request
34345 @cindex @samp{qOffsets} packet
34346 Get section offsets that the target used when relocating the downloaded
34351 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
34352 Relocate the @code{Text} section by @var{xxx} from its original address.
34353 Relocate the @code{Data} section by @var{yyy} from its original address.
34354 If the object file format provides segment information (e.g.@: @sc{elf}
34355 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
34356 segments by the supplied offsets.
34358 @emph{Note: while a @code{Bss} offset may be included in the response,
34359 @value{GDBN} ignores this and instead applies the @code{Data} offset
34360 to the @code{Bss} section.}
34362 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
34363 Relocate the first segment of the object file, which conventionally
34364 contains program code, to a starting address of @var{xxx}. If
34365 @samp{DataSeg} is specified, relocate the second segment, which
34366 conventionally contains modifiable data, to a starting address of
34367 @var{yyy}. @value{GDBN} will report an error if the object file
34368 does not contain segment information, or does not contain at least
34369 as many segments as mentioned in the reply. Extra segments are
34370 kept at fixed offsets relative to the last relocated segment.
34373 @item qP @var{mode} @var{thread-id}
34374 @cindex thread information, remote request
34375 @cindex @samp{qP} packet
34376 Returns information on @var{thread-id}. Where: @var{mode} is a hex
34377 encoded 32 bit mode; @var{thread-id} is a thread ID
34378 (@pxref{thread-id syntax}).
34380 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
34383 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
34387 @cindex non-stop mode, remote request
34388 @cindex @samp{QNonStop} packet
34390 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
34391 @xref{Remote Non-Stop}, for more information.
34396 The request succeeded.
34399 An error occurred. @var{nn} are hex digits.
34402 An empty reply indicates that @samp{QNonStop} is not supported by
34406 This packet is not probed by default; the remote stub must request it,
34407 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34408 Use of this packet is controlled by the @code{set non-stop} command;
34409 @pxref{Non-Stop Mode}.
34411 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34412 @cindex pass signals to inferior, remote request
34413 @cindex @samp{QPassSignals} packet
34414 @anchor{QPassSignals}
34415 Each listed @var{signal} should be passed directly to the inferior process.
34416 Signals are numbered identically to continue packets and stop replies
34417 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
34418 strictly greater than the previous item. These signals do not need to stop
34419 the inferior, or be reported to @value{GDBN}. All other signals should be
34420 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
34421 combine; any earlier @samp{QPassSignals} list is completely replaced by the
34422 new list. This packet improves performance when using @samp{handle
34423 @var{signal} nostop noprint pass}.
34428 The request succeeded.
34431 An error occurred. @var{nn} are hex digits.
34434 An empty reply indicates that @samp{QPassSignals} is not supported by
34438 Use of this packet is controlled by the @code{set remote pass-signals}
34439 command (@pxref{Remote Configuration, set remote pass-signals}).
34440 This packet is not probed by default; the remote stub must request it,
34441 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34443 @item qRcmd,@var{command}
34444 @cindex execute remote command, remote request
34445 @cindex @samp{qRcmd} packet
34446 @var{command} (hex encoded) is passed to the local interpreter for
34447 execution. Invalid commands should be reported using the output
34448 string. Before the final result packet, the target may also respond
34449 with a number of intermediate @samp{O@var{output}} console output
34450 packets. @emph{Implementors should note that providing access to a
34451 stubs's interpreter may have security implications}.
34456 A command response with no output.
34458 A command response with the hex encoded output string @var{OUTPUT}.
34460 Indicate a badly formed request.
34462 An empty reply indicates that @samp{qRcmd} is not recognized.
34465 (Note that the @code{qRcmd} packet's name is separated from the
34466 command by a @samp{,}, not a @samp{:}, contrary to the naming
34467 conventions above. Please don't use this packet as a model for new
34470 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
34471 @cindex searching memory, in remote debugging
34472 @cindex @samp{qSearch:memory} packet
34473 @anchor{qSearch memory}
34474 Search @var{length} bytes at @var{address} for @var{search-pattern}.
34475 @var{address} and @var{length} are encoded in hex.
34476 @var{search-pattern} is a sequence of bytes, hex encoded.
34481 The pattern was not found.
34483 The pattern was found at @var{address}.
34485 A badly formed request or an error was encountered while searching memory.
34487 An empty reply indicates that @samp{qSearch:memory} is not recognized.
34490 @item QStartNoAckMode
34491 @cindex @samp{QStartNoAckMode} packet
34492 @anchor{QStartNoAckMode}
34493 Request that the remote stub disable the normal @samp{+}/@samp{-}
34494 protocol acknowledgments (@pxref{Packet Acknowledgment}).
34499 The stub has switched to no-acknowledgment mode.
34500 @value{GDBN} acknowledges this reponse,
34501 but neither the stub nor @value{GDBN} shall send or expect further
34502 @samp{+}/@samp{-} acknowledgments in the current connection.
34504 An empty reply indicates that the stub does not support no-acknowledgment mode.
34507 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
34508 @cindex supported packets, remote query
34509 @cindex features of the remote protocol
34510 @cindex @samp{qSupported} packet
34511 @anchor{qSupported}
34512 Tell the remote stub about features supported by @value{GDBN}, and
34513 query the stub for features it supports. This packet allows
34514 @value{GDBN} and the remote stub to take advantage of each others'
34515 features. @samp{qSupported} also consolidates multiple feature probes
34516 at startup, to improve @value{GDBN} performance---a single larger
34517 packet performs better than multiple smaller probe packets on
34518 high-latency links. Some features may enable behavior which must not
34519 be on by default, e.g.@: because it would confuse older clients or
34520 stubs. Other features may describe packets which could be
34521 automatically probed for, but are not. These features must be
34522 reported before @value{GDBN} will use them. This ``default
34523 unsupported'' behavior is not appropriate for all packets, but it
34524 helps to keep the initial connection time under control with new
34525 versions of @value{GDBN} which support increasing numbers of packets.
34529 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
34530 The stub supports or does not support each returned @var{stubfeature},
34531 depending on the form of each @var{stubfeature} (see below for the
34534 An empty reply indicates that @samp{qSupported} is not recognized,
34535 or that no features needed to be reported to @value{GDBN}.
34538 The allowed forms for each feature (either a @var{gdbfeature} in the
34539 @samp{qSupported} packet, or a @var{stubfeature} in the response)
34543 @item @var{name}=@var{value}
34544 The remote protocol feature @var{name} is supported, and associated
34545 with the specified @var{value}. The format of @var{value} depends
34546 on the feature, but it must not include a semicolon.
34548 The remote protocol feature @var{name} is supported, and does not
34549 need an associated value.
34551 The remote protocol feature @var{name} is not supported.
34553 The remote protocol feature @var{name} may be supported, and
34554 @value{GDBN} should auto-detect support in some other way when it is
34555 needed. This form will not be used for @var{gdbfeature} notifications,
34556 but may be used for @var{stubfeature} responses.
34559 Whenever the stub receives a @samp{qSupported} request, the
34560 supplied set of @value{GDBN} features should override any previous
34561 request. This allows @value{GDBN} to put the stub in a known
34562 state, even if the stub had previously been communicating with
34563 a different version of @value{GDBN}.
34565 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
34570 This feature indicates whether @value{GDBN} supports multiprocess
34571 extensions to the remote protocol. @value{GDBN} does not use such
34572 extensions unless the stub also reports that it supports them by
34573 including @samp{multiprocess+} in its @samp{qSupported} reply.
34574 @xref{multiprocess extensions}, for details.
34577 This feature indicates that @value{GDBN} supports the XML target
34578 description. If the stub sees @samp{xmlRegisters=} with target
34579 specific strings separated by a comma, it will report register
34583 This feature indicates whether @value{GDBN} supports the
34584 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
34585 instruction reply packet}).
34588 Stubs should ignore any unknown values for
34589 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
34590 packet supports receiving packets of unlimited length (earlier
34591 versions of @value{GDBN} may reject overly long responses). Additional values
34592 for @var{gdbfeature} may be defined in the future to let the stub take
34593 advantage of new features in @value{GDBN}, e.g.@: incompatible
34594 improvements in the remote protocol---the @samp{multiprocess} feature is
34595 an example of such a feature. The stub's reply should be independent
34596 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
34597 describes all the features it supports, and then the stub replies with
34598 all the features it supports.
34600 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
34601 responses, as long as each response uses one of the standard forms.
34603 Some features are flags. A stub which supports a flag feature
34604 should respond with a @samp{+} form response. Other features
34605 require values, and the stub should respond with an @samp{=}
34608 Each feature has a default value, which @value{GDBN} will use if
34609 @samp{qSupported} is not available or if the feature is not mentioned
34610 in the @samp{qSupported} response. The default values are fixed; a
34611 stub is free to omit any feature responses that match the defaults.
34613 Not all features can be probed, but for those which can, the probing
34614 mechanism is useful: in some cases, a stub's internal
34615 architecture may not allow the protocol layer to know some information
34616 about the underlying target in advance. This is especially common in
34617 stubs which may be configured for multiple targets.
34619 These are the currently defined stub features and their properties:
34621 @multitable @columnfractions 0.35 0.2 0.12 0.2
34622 @c NOTE: The first row should be @headitem, but we do not yet require
34623 @c a new enough version of Texinfo (4.7) to use @headitem.
34625 @tab Value Required
34629 @item @samp{PacketSize}
34634 @item @samp{qXfer:auxv:read}
34639 @item @samp{qXfer:features:read}
34644 @item @samp{qXfer:libraries:read}
34649 @item @samp{qXfer:memory-map:read}
34654 @item @samp{qXfer:sdata:read}
34659 @item @samp{qXfer:spu:read}
34664 @item @samp{qXfer:spu:write}
34669 @item @samp{qXfer:siginfo:read}
34674 @item @samp{qXfer:siginfo:write}
34679 @item @samp{qXfer:threads:read}
34684 @item @samp{qXfer:traceframe-info:read}
34689 @item @samp{qXfer:fdpic:read}
34694 @item @samp{QNonStop}
34699 @item @samp{QPassSignals}
34704 @item @samp{QStartNoAckMode}
34709 @item @samp{multiprocess}
34714 @item @samp{ConditionalTracepoints}
34719 @item @samp{ReverseContinue}
34724 @item @samp{ReverseStep}
34729 @item @samp{TracepointSource}
34734 @item @samp{QAllow}
34739 @item @samp{QDisableRandomization}
34744 @item @samp{EnableDisableTracepoints}
34749 @item @samp{tracenz}
34756 These are the currently defined stub features, in more detail:
34759 @cindex packet size, remote protocol
34760 @item PacketSize=@var{bytes}
34761 The remote stub can accept packets up to at least @var{bytes} in
34762 length. @value{GDBN} will send packets up to this size for bulk
34763 transfers, and will never send larger packets. This is a limit on the
34764 data characters in the packet, including the frame and checksum.
34765 There is no trailing NUL byte in a remote protocol packet; if the stub
34766 stores packets in a NUL-terminated format, it should allow an extra
34767 byte in its buffer for the NUL. If this stub feature is not supported,
34768 @value{GDBN} guesses based on the size of the @samp{g} packet response.
34770 @item qXfer:auxv:read
34771 The remote stub understands the @samp{qXfer:auxv:read} packet
34772 (@pxref{qXfer auxiliary vector read}).
34774 @item qXfer:features:read
34775 The remote stub understands the @samp{qXfer:features:read} packet
34776 (@pxref{qXfer target description read}).
34778 @item qXfer:libraries:read
34779 The remote stub understands the @samp{qXfer:libraries:read} packet
34780 (@pxref{qXfer library list read}).
34782 @item qXfer:memory-map:read
34783 The remote stub understands the @samp{qXfer:memory-map:read} packet
34784 (@pxref{qXfer memory map read}).
34786 @item qXfer:sdata:read
34787 The remote stub understands the @samp{qXfer:sdata:read} packet
34788 (@pxref{qXfer sdata read}).
34790 @item qXfer:spu:read
34791 The remote stub understands the @samp{qXfer:spu:read} packet
34792 (@pxref{qXfer spu read}).
34794 @item qXfer:spu:write
34795 The remote stub understands the @samp{qXfer:spu:write} packet
34796 (@pxref{qXfer spu write}).
34798 @item qXfer:siginfo:read
34799 The remote stub understands the @samp{qXfer:siginfo:read} packet
34800 (@pxref{qXfer siginfo read}).
34802 @item qXfer:siginfo:write
34803 The remote stub understands the @samp{qXfer:siginfo:write} packet
34804 (@pxref{qXfer siginfo write}).
34806 @item qXfer:threads:read
34807 The remote stub understands the @samp{qXfer:threads:read} packet
34808 (@pxref{qXfer threads read}).
34810 @item qXfer:traceframe-info:read
34811 The remote stub understands the @samp{qXfer:traceframe-info:read}
34812 packet (@pxref{qXfer traceframe info read}).
34814 @item qXfer:fdpic:read
34815 The remote stub understands the @samp{qXfer:fdpic:read}
34816 packet (@pxref{qXfer fdpic loadmap read}).
34819 The remote stub understands the @samp{QNonStop} packet
34820 (@pxref{QNonStop}).
34823 The remote stub understands the @samp{QPassSignals} packet
34824 (@pxref{QPassSignals}).
34826 @item QStartNoAckMode
34827 The remote stub understands the @samp{QStartNoAckMode} packet and
34828 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
34831 @anchor{multiprocess extensions}
34832 @cindex multiprocess extensions, in remote protocol
34833 The remote stub understands the multiprocess extensions to the remote
34834 protocol syntax. The multiprocess extensions affect the syntax of
34835 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
34836 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
34837 replies. Note that reporting this feature indicates support for the
34838 syntactic extensions only, not that the stub necessarily supports
34839 debugging of more than one process at a time. The stub must not use
34840 multiprocess extensions in packet replies unless @value{GDBN} has also
34841 indicated it supports them in its @samp{qSupported} request.
34843 @item qXfer:osdata:read
34844 The remote stub understands the @samp{qXfer:osdata:read} packet
34845 ((@pxref{qXfer osdata read}).
34847 @item ConditionalTracepoints
34848 The remote stub accepts and implements conditional expressions defined
34849 for tracepoints (@pxref{Tracepoint Conditions}).
34851 @item ReverseContinue
34852 The remote stub accepts and implements the reverse continue packet
34856 The remote stub accepts and implements the reverse step packet
34859 @item TracepointSource
34860 The remote stub understands the @samp{QTDPsrc} packet that supplies
34861 the source form of tracepoint definitions.
34864 The remote stub understands the @samp{QAllow} packet.
34866 @item QDisableRandomization
34867 The remote stub understands the @samp{QDisableRandomization} packet.
34869 @item StaticTracepoint
34870 @cindex static tracepoints, in remote protocol
34871 The remote stub supports static tracepoints.
34873 @item InstallInTrace
34874 @anchor{install tracepoint in tracing}
34875 The remote stub supports installing tracepoint in tracing.
34877 @item EnableDisableTracepoints
34878 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
34879 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
34880 to be enabled and disabled while a trace experiment is running.
34883 @cindex string tracing, in remote protocol
34884 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
34885 See @ref{Bytecode Descriptions} for details about the bytecode.
34890 @cindex symbol lookup, remote request
34891 @cindex @samp{qSymbol} packet
34892 Notify the target that @value{GDBN} is prepared to serve symbol lookup
34893 requests. Accept requests from the target for the values of symbols.
34898 The target does not need to look up any (more) symbols.
34899 @item qSymbol:@var{sym_name}
34900 The target requests the value of symbol @var{sym_name} (hex encoded).
34901 @value{GDBN} may provide the value by using the
34902 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
34906 @item qSymbol:@var{sym_value}:@var{sym_name}
34907 Set the value of @var{sym_name} to @var{sym_value}.
34909 @var{sym_name} (hex encoded) is the name of a symbol whose value the
34910 target has previously requested.
34912 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
34913 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
34919 The target does not need to look up any (more) symbols.
34920 @item qSymbol:@var{sym_name}
34921 The target requests the value of a new symbol @var{sym_name} (hex
34922 encoded). @value{GDBN} will continue to supply the values of symbols
34923 (if available), until the target ceases to request them.
34928 @item QTDisconnected
34935 @itemx qTMinFTPILen
34937 @xref{Tracepoint Packets}.
34939 @item qThreadExtraInfo,@var{thread-id}
34940 @cindex thread attributes info, remote request
34941 @cindex @samp{qThreadExtraInfo} packet
34942 Obtain a printable string description of a thread's attributes from
34943 the target OS. @var{thread-id} is a thread ID;
34944 see @ref{thread-id syntax}. This
34945 string may contain anything that the target OS thinks is interesting
34946 for @value{GDBN} to tell the user about the thread. The string is
34947 displayed in @value{GDBN}'s @code{info threads} display. Some
34948 examples of possible thread extra info strings are @samp{Runnable}, or
34949 @samp{Blocked on Mutex}.
34953 @item @var{XX}@dots{}
34954 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
34955 comprising the printable string containing the extra information about
34956 the thread's attributes.
34959 (Note that the @code{qThreadExtraInfo} packet's name is separated from
34960 the command by a @samp{,}, not a @samp{:}, contrary to the naming
34961 conventions above. Please don't use this packet as a model for new
34978 @xref{Tracepoint Packets}.
34980 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
34981 @cindex read special object, remote request
34982 @cindex @samp{qXfer} packet
34983 @anchor{qXfer read}
34984 Read uninterpreted bytes from the target's special data area
34985 identified by the keyword @var{object}. Request @var{length} bytes
34986 starting at @var{offset} bytes into the data. The content and
34987 encoding of @var{annex} is specific to @var{object}; it can supply
34988 additional details about what data to access.
34990 Here are the specific requests of this form defined so far. All
34991 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
34992 formats, listed below.
34995 @item qXfer:auxv:read::@var{offset},@var{length}
34996 @anchor{qXfer auxiliary vector read}
34997 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
34998 auxiliary vector}. Note @var{annex} must be empty.
35000 This packet is not probed by default; the remote stub must request it,
35001 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35003 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
35004 @anchor{qXfer target description read}
35005 Access the @dfn{target description}. @xref{Target Descriptions}. The
35006 annex specifies which XML document to access. The main description is
35007 always loaded from the @samp{target.xml} annex.
35009 This packet is not probed by default; the remote stub must request it,
35010 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35012 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
35013 @anchor{qXfer library list read}
35014 Access the target's list of loaded libraries. @xref{Library List Format}.
35015 The annex part of the generic @samp{qXfer} packet must be empty
35016 (@pxref{qXfer read}).
35018 Targets which maintain a list of libraries in the program's memory do
35019 not need to implement this packet; it is designed for platforms where
35020 the operating system manages the list of loaded libraries.
35022 This packet is not probed by default; the remote stub must request it,
35023 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35025 @item qXfer:memory-map:read::@var{offset},@var{length}
35026 @anchor{qXfer memory map read}
35027 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
35028 annex part of the generic @samp{qXfer} packet must be empty
35029 (@pxref{qXfer read}).
35031 This packet is not probed by default; the remote stub must request it,
35032 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35034 @item qXfer:sdata:read::@var{offset},@var{length}
35035 @anchor{qXfer sdata read}
35037 Read contents of the extra collected static tracepoint marker
35038 information. The annex part of the generic @samp{qXfer} packet must
35039 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
35042 This packet is not probed by default; the remote stub must request it,
35043 by supplying an appropriate @samp{qSupported} response
35044 (@pxref{qSupported}).
35046 @item qXfer:siginfo:read::@var{offset},@var{length}
35047 @anchor{qXfer siginfo read}
35048 Read contents of the extra signal information on the target
35049 system. The annex part of the generic @samp{qXfer} packet must be
35050 empty (@pxref{qXfer read}).
35052 This packet is not probed by default; the remote stub must request it,
35053 by supplying an appropriate @samp{qSupported} response
35054 (@pxref{qSupported}).
35056 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
35057 @anchor{qXfer spu read}
35058 Read contents of an @code{spufs} file on the target system. The
35059 annex specifies which file to read; it must be of the form
35060 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35061 in the target process, and @var{name} identifes the @code{spufs} file
35062 in that context to be accessed.
35064 This packet is not probed by default; the remote stub must request it,
35065 by supplying an appropriate @samp{qSupported} response
35066 (@pxref{qSupported}).
35068 @item qXfer:threads:read::@var{offset},@var{length}
35069 @anchor{qXfer threads read}
35070 Access the list of threads on target. @xref{Thread List Format}. The
35071 annex part of the generic @samp{qXfer} packet must be empty
35072 (@pxref{qXfer read}).
35074 This packet is not probed by default; the remote stub must request it,
35075 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35077 @item qXfer:traceframe-info:read::@var{offset},@var{length}
35078 @anchor{qXfer traceframe info read}
35080 Return a description of the current traceframe's contents.
35081 @xref{Traceframe Info Format}. The annex part of the generic
35082 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35084 This packet is not probed by default; the remote stub must request it,
35085 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35087 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
35088 @anchor{qXfer fdpic loadmap read}
35089 Read contents of @code{loadmap}s on the target system. The
35090 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
35091 executable @code{loadmap} or interpreter @code{loadmap} to read.
35093 This packet is not probed by default; the remote stub must request it,
35094 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35096 @item qXfer:osdata:read::@var{offset},@var{length}
35097 @anchor{qXfer osdata read}
35098 Access the target's @dfn{operating system information}.
35099 @xref{Operating System Information}.
35106 Data @var{data} (@pxref{Binary Data}) has been read from the
35107 target. There may be more data at a higher address (although
35108 it is permitted to return @samp{m} even for the last valid
35109 block of data, as long as at least one byte of data was read).
35110 @var{data} may have fewer bytes than the @var{length} in the
35114 Data @var{data} (@pxref{Binary Data}) has been read from the target.
35115 There is no more data to be read. @var{data} may have fewer bytes
35116 than the @var{length} in the request.
35119 The @var{offset} in the request is at the end of the data.
35120 There is no more data to be read.
35123 The request was malformed, or @var{annex} was invalid.
35126 The offset was invalid, or there was an error encountered reading the data.
35127 @var{nn} is a hex-encoded @code{errno} value.
35130 An empty reply indicates the @var{object} string was not recognized by
35131 the stub, or that the object does not support reading.
35134 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
35135 @cindex write data into object, remote request
35136 @anchor{qXfer write}
35137 Write uninterpreted bytes into the target's special data area
35138 identified by the keyword @var{object}, starting at @var{offset} bytes
35139 into the data. @var{data}@dots{} is the binary-encoded data
35140 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
35141 is specific to @var{object}; it can supply additional details about what data
35144 Here are the specific requests of this form defined so far. All
35145 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
35146 formats, listed below.
35149 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
35150 @anchor{qXfer siginfo write}
35151 Write @var{data} to the extra signal information on the target system.
35152 The annex part of the generic @samp{qXfer} packet must be
35153 empty (@pxref{qXfer write}).
35155 This packet is not probed by default; the remote stub must request it,
35156 by supplying an appropriate @samp{qSupported} response
35157 (@pxref{qSupported}).
35159 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
35160 @anchor{qXfer spu write}
35161 Write @var{data} to an @code{spufs} file on the target system. The
35162 annex specifies which file to write; it must be of the form
35163 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35164 in the target process, and @var{name} identifes the @code{spufs} file
35165 in that context to be accessed.
35167 This packet is not probed by default; the remote stub must request it,
35168 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35174 @var{nn} (hex encoded) is the number of bytes written.
35175 This may be fewer bytes than supplied in the request.
35178 The request was malformed, or @var{annex} was invalid.
35181 The offset was invalid, or there was an error encountered writing the data.
35182 @var{nn} is a hex-encoded @code{errno} value.
35185 An empty reply indicates the @var{object} string was not
35186 recognized by the stub, or that the object does not support writing.
35189 @item qXfer:@var{object}:@var{operation}:@dots{}
35190 Requests of this form may be added in the future. When a stub does
35191 not recognize the @var{object} keyword, or its support for
35192 @var{object} does not recognize the @var{operation} keyword, the stub
35193 must respond with an empty packet.
35195 @item qAttached:@var{pid}
35196 @cindex query attached, remote request
35197 @cindex @samp{qAttached} packet
35198 Return an indication of whether the remote server attached to an
35199 existing process or created a new process. When the multiprocess
35200 protocol extensions are supported (@pxref{multiprocess extensions}),
35201 @var{pid} is an integer in hexadecimal format identifying the target
35202 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
35203 the query packet will be simplified as @samp{qAttached}.
35205 This query is used, for example, to know whether the remote process
35206 should be detached or killed when a @value{GDBN} session is ended with
35207 the @code{quit} command.
35212 The remote server attached to an existing process.
35214 The remote server created a new process.
35216 A badly formed request or an error was encountered.
35221 @node Architecture-Specific Protocol Details
35222 @section Architecture-Specific Protocol Details
35224 This section describes how the remote protocol is applied to specific
35225 target architectures. Also see @ref{Standard Target Features}, for
35226 details of XML target descriptions for each architecture.
35230 @subsubsection Breakpoint Kinds
35232 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
35237 16-bit Thumb mode breakpoint.
35240 32-bit Thumb mode (Thumb-2) breakpoint.
35243 32-bit ARM mode breakpoint.
35249 @subsubsection Register Packet Format
35251 The following @code{g}/@code{G} packets have previously been defined.
35252 In the below, some thirty-two bit registers are transferred as
35253 sixty-four bits. Those registers should be zero/sign extended (which?)
35254 to fill the space allocated. Register bytes are transferred in target
35255 byte order. The two nibbles within a register byte are transferred
35256 most-significant - least-significant.
35262 All registers are transferred as thirty-two bit quantities in the order:
35263 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
35264 registers; fsr; fir; fp.
35268 All registers are transferred as sixty-four bit quantities (including
35269 thirty-two bit registers such as @code{sr}). The ordering is the same
35274 @node Tracepoint Packets
35275 @section Tracepoint Packets
35276 @cindex tracepoint packets
35277 @cindex packets, tracepoint
35279 Here we describe the packets @value{GDBN} uses to implement
35280 tracepoints (@pxref{Tracepoints}).
35284 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
35285 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
35286 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
35287 the tracepoint is disabled. @var{step} is the tracepoint's step
35288 count, and @var{pass} is its pass count. If an @samp{F} is present,
35289 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
35290 the number of bytes that the target should copy elsewhere to make room
35291 for the tracepoint. If an @samp{X} is present, it introduces a
35292 tracepoint condition, which consists of a hexadecimal length, followed
35293 by a comma and hex-encoded bytes, in a manner similar to action
35294 encodings as described below. If the trailing @samp{-} is present,
35295 further @samp{QTDP} packets will follow to specify this tracepoint's
35301 The packet was understood and carried out.
35303 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35305 The packet was not recognized.
35308 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
35309 Define actions to be taken when a tracepoint is hit. @var{n} and
35310 @var{addr} must be the same as in the initial @samp{QTDP} packet for
35311 this tracepoint. This packet may only be sent immediately after
35312 another @samp{QTDP} packet that ended with a @samp{-}. If the
35313 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
35314 specifying more actions for this tracepoint.
35316 In the series of action packets for a given tracepoint, at most one
35317 can have an @samp{S} before its first @var{action}. If such a packet
35318 is sent, it and the following packets define ``while-stepping''
35319 actions. Any prior packets define ordinary actions --- that is, those
35320 taken when the tracepoint is first hit. If no action packet has an
35321 @samp{S}, then all the packets in the series specify ordinary
35322 tracepoint actions.
35324 The @samp{@var{action}@dots{}} portion of the packet is a series of
35325 actions, concatenated without separators. Each action has one of the
35331 Collect the registers whose bits are set in @var{mask}. @var{mask} is
35332 a hexadecimal number whose @var{i}'th bit is set if register number
35333 @var{i} should be collected. (The least significant bit is numbered
35334 zero.) Note that @var{mask} may be any number of digits long; it may
35335 not fit in a 32-bit word.
35337 @item M @var{basereg},@var{offset},@var{len}
35338 Collect @var{len} bytes of memory starting at the address in register
35339 number @var{basereg}, plus @var{offset}. If @var{basereg} is
35340 @samp{-1}, then the range has a fixed address: @var{offset} is the
35341 address of the lowest byte to collect. The @var{basereg},
35342 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
35343 values (the @samp{-1} value for @var{basereg} is a special case).
35345 @item X @var{len},@var{expr}
35346 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
35347 it directs. @var{expr} is an agent expression, as described in
35348 @ref{Agent Expressions}. Each byte of the expression is encoded as a
35349 two-digit hex number in the packet; @var{len} is the number of bytes
35350 in the expression (and thus one-half the number of hex digits in the
35355 Any number of actions may be packed together in a single @samp{QTDP}
35356 packet, as long as the packet does not exceed the maximum packet
35357 length (400 bytes, for many stubs). There may be only one @samp{R}
35358 action per tracepoint, and it must precede any @samp{M} or @samp{X}
35359 actions. Any registers referred to by @samp{M} and @samp{X} actions
35360 must be collected by a preceding @samp{R} action. (The
35361 ``while-stepping'' actions are treated as if they were attached to a
35362 separate tracepoint, as far as these restrictions are concerned.)
35367 The packet was understood and carried out.
35369 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35371 The packet was not recognized.
35374 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
35375 @cindex @samp{QTDPsrc} packet
35376 Specify a source string of tracepoint @var{n} at address @var{addr}.
35377 This is useful to get accurate reproduction of the tracepoints
35378 originally downloaded at the beginning of the trace run. @var{type}
35379 is the name of the tracepoint part, such as @samp{cond} for the
35380 tracepoint's conditional expression (see below for a list of types), while
35381 @var{bytes} is the string, encoded in hexadecimal.
35383 @var{start} is the offset of the @var{bytes} within the overall source
35384 string, while @var{slen} is the total length of the source string.
35385 This is intended for handling source strings that are longer than will
35386 fit in a single packet.
35387 @c Add detailed example when this info is moved into a dedicated
35388 @c tracepoint descriptions section.
35390 The available string types are @samp{at} for the location,
35391 @samp{cond} for the conditional, and @samp{cmd} for an action command.
35392 @value{GDBN} sends a separate packet for each command in the action
35393 list, in the same order in which the commands are stored in the list.
35395 The target does not need to do anything with source strings except
35396 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
35399 Although this packet is optional, and @value{GDBN} will only send it
35400 if the target replies with @samp{TracepointSource} @xref{General
35401 Query Packets}, it makes both disconnected tracing and trace files
35402 much easier to use. Otherwise the user must be careful that the
35403 tracepoints in effect while looking at trace frames are identical to
35404 the ones in effect during the trace run; even a small discrepancy
35405 could cause @samp{tdump} not to work, or a particular trace frame not
35408 @item QTDV:@var{n}:@var{value}
35409 @cindex define trace state variable, remote request
35410 @cindex @samp{QTDV} packet
35411 Create a new trace state variable, number @var{n}, with an initial
35412 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
35413 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
35414 the option of not using this packet for initial values of zero; the
35415 target should simply create the trace state variables as they are
35416 mentioned in expressions.
35418 @item QTFrame:@var{n}
35419 Select the @var{n}'th tracepoint frame from the buffer, and use the
35420 register and memory contents recorded there to answer subsequent
35421 request packets from @value{GDBN}.
35423 A successful reply from the stub indicates that the stub has found the
35424 requested frame. The response is a series of parts, concatenated
35425 without separators, describing the frame we selected. Each part has
35426 one of the following forms:
35430 The selected frame is number @var{n} in the trace frame buffer;
35431 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
35432 was no frame matching the criteria in the request packet.
35435 The selected trace frame records a hit of tracepoint number @var{t};
35436 @var{t} is a hexadecimal number.
35440 @item QTFrame:pc:@var{addr}
35441 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35442 currently selected frame whose PC is @var{addr};
35443 @var{addr} is a hexadecimal number.
35445 @item QTFrame:tdp:@var{t}
35446 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35447 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
35448 is a hexadecimal number.
35450 @item QTFrame:range:@var{start}:@var{end}
35451 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35452 currently selected frame whose PC is between @var{start} (inclusive)
35453 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
35456 @item QTFrame:outside:@var{start}:@var{end}
35457 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
35458 frame @emph{outside} the given range of addresses (exclusive).
35461 This packet requests the minimum length of instruction at which a fast
35462 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
35463 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
35464 it depends on the target system being able to create trampolines in
35465 the first 64K of memory, which might or might not be possible for that
35466 system. So the reply to this packet will be 4 if it is able to
35473 The minimum instruction length is currently unknown.
35475 The minimum instruction length is @var{length}, where @var{length} is greater
35476 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
35477 that a fast tracepoint may be placed on any instruction regardless of size.
35479 An error has occurred.
35481 An empty reply indicates that the request is not supported by the stub.
35485 Begin the tracepoint experiment. Begin collecting data from
35486 tracepoint hits in the trace frame buffer. This packet supports the
35487 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
35488 instruction reply packet}).
35491 End the tracepoint experiment. Stop collecting trace frames.
35493 @item QTEnable:@var{n}:@var{addr}
35495 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
35496 experiment. If the tracepoint was previously disabled, then collection
35497 of data from it will resume.
35499 @item QTDisable:@var{n}:@var{addr}
35501 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
35502 experiment. No more data will be collected from the tracepoint unless
35503 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
35506 Clear the table of tracepoints, and empty the trace frame buffer.
35508 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
35509 Establish the given ranges of memory as ``transparent''. The stub
35510 will answer requests for these ranges from memory's current contents,
35511 if they were not collected as part of the tracepoint hit.
35513 @value{GDBN} uses this to mark read-only regions of memory, like those
35514 containing program code. Since these areas never change, they should
35515 still have the same contents they did when the tracepoint was hit, so
35516 there's no reason for the stub to refuse to provide their contents.
35518 @item QTDisconnected:@var{value}
35519 Set the choice to what to do with the tracing run when @value{GDBN}
35520 disconnects from the target. A @var{value} of 1 directs the target to
35521 continue the tracing run, while 0 tells the target to stop tracing if
35522 @value{GDBN} is no longer in the picture.
35525 Ask the stub if there is a trace experiment running right now.
35527 The reply has the form:
35531 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
35532 @var{running} is a single digit @code{1} if the trace is presently
35533 running, or @code{0} if not. It is followed by semicolon-separated
35534 optional fields that an agent may use to report additional status.
35538 If the trace is not running, the agent may report any of several
35539 explanations as one of the optional fields:
35544 No trace has been run yet.
35547 The trace was stopped by a user-originated stop command.
35550 The trace stopped because the trace buffer filled up.
35552 @item tdisconnected:0
35553 The trace stopped because @value{GDBN} disconnected from the target.
35555 @item tpasscount:@var{tpnum}
35556 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
35558 @item terror:@var{text}:@var{tpnum}
35559 The trace stopped because tracepoint @var{tpnum} had an error. The
35560 string @var{text} is available to describe the nature of the error
35561 (for instance, a divide by zero in the condition expression).
35562 @var{text} is hex encoded.
35565 The trace stopped for some other reason.
35569 Additional optional fields supply statistical and other information.
35570 Although not required, they are extremely useful for users monitoring
35571 the progress of a trace run. If a trace has stopped, and these
35572 numbers are reported, they must reflect the state of the just-stopped
35577 @item tframes:@var{n}
35578 The number of trace frames in the buffer.
35580 @item tcreated:@var{n}
35581 The total number of trace frames created during the run. This may
35582 be larger than the trace frame count, if the buffer is circular.
35584 @item tsize:@var{n}
35585 The total size of the trace buffer, in bytes.
35587 @item tfree:@var{n}
35588 The number of bytes still unused in the buffer.
35590 @item circular:@var{n}
35591 The value of the circular trace buffer flag. @code{1} means that the
35592 trace buffer is circular and old trace frames will be discarded if
35593 necessary to make room, @code{0} means that the trace buffer is linear
35596 @item disconn:@var{n}
35597 The value of the disconnected tracing flag. @code{1} means that
35598 tracing will continue after @value{GDBN} disconnects, @code{0} means
35599 that the trace run will stop.
35603 @item qTV:@var{var}
35604 @cindex trace state variable value, remote request
35605 @cindex @samp{qTV} packet
35606 Ask the stub for the value of the trace state variable number @var{var}.
35611 The value of the variable is @var{value}. This will be the current
35612 value of the variable if the user is examining a running target, or a
35613 saved value if the variable was collected in the trace frame that the
35614 user is looking at. Note that multiple requests may result in
35615 different reply values, such as when requesting values while the
35616 program is running.
35619 The value of the variable is unknown. This would occur, for example,
35620 if the user is examining a trace frame in which the requested variable
35626 These packets request data about tracepoints that are being used by
35627 the target. @value{GDBN} sends @code{qTfP} to get the first piece
35628 of data, and multiple @code{qTsP} to get additional pieces. Replies
35629 to these packets generally take the form of the @code{QTDP} packets
35630 that define tracepoints. (FIXME add detailed syntax)
35634 These packets request data about trace state variables that are on the
35635 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
35636 and multiple @code{qTsV} to get additional variables. Replies to
35637 these packets follow the syntax of the @code{QTDV} packets that define
35638 trace state variables.
35642 These packets request data about static tracepoint markers that exist
35643 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
35644 first piece of data, and multiple @code{qTsSTM} to get additional
35645 pieces. Replies to these packets take the following form:
35649 @item m @var{address}:@var{id}:@var{extra}
35651 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
35652 a comma-separated list of markers
35654 (lower case letter @samp{L}) denotes end of list.
35656 An error occurred. @var{nn} are hex digits.
35658 An empty reply indicates that the request is not supported by the
35662 @var{address} is encoded in hex.
35663 @var{id} and @var{extra} are strings encoded in hex.
35665 In response to each query, the target will reply with a list of one or
35666 more markers, separated by commas. @value{GDBN} will respond to each
35667 reply with a request for more markers (using the @samp{qs} form of the
35668 query), until the target responds with @samp{l} (lower-case ell, for
35671 @item qTSTMat:@var{address}
35672 This packets requests data about static tracepoint markers in the
35673 target program at @var{address}. Replies to this packet follow the
35674 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
35675 tracepoint markers.
35677 @item QTSave:@var{filename}
35678 This packet directs the target to save trace data to the file name
35679 @var{filename} in the target's filesystem. @var{filename} is encoded
35680 as a hex string; the interpretation of the file name (relative vs
35681 absolute, wild cards, etc) is up to the target.
35683 @item qTBuffer:@var{offset},@var{len}
35684 Return up to @var{len} bytes of the current contents of trace buffer,
35685 starting at @var{offset}. The trace buffer is treated as if it were
35686 a contiguous collection of traceframes, as per the trace file format.
35687 The reply consists as many hex-encoded bytes as the target can deliver
35688 in a packet; it is not an error to return fewer than were asked for.
35689 A reply consisting of just @code{l} indicates that no bytes are
35692 @item QTBuffer:circular:@var{value}
35693 This packet directs the target to use a circular trace buffer if
35694 @var{value} is 1, or a linear buffer if the value is 0.
35698 @subsection Relocate instruction reply packet
35699 When installing fast tracepoints in memory, the target may need to
35700 relocate the instruction currently at the tracepoint address to a
35701 different address in memory. For most instructions, a simple copy is
35702 enough, but, for example, call instructions that implicitly push the
35703 return address on the stack, and relative branches or other
35704 PC-relative instructions require offset adjustment, so that the effect
35705 of executing the instruction at a different address is the same as if
35706 it had executed in the original location.
35708 In response to several of the tracepoint packets, the target may also
35709 respond with a number of intermediate @samp{qRelocInsn} request
35710 packets before the final result packet, to have @value{GDBN} handle
35711 this relocation operation. If a packet supports this mechanism, its
35712 documentation will explicitly say so. See for example the above
35713 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
35714 format of the request is:
35717 @item qRelocInsn:@var{from};@var{to}
35719 This requests @value{GDBN} to copy instruction at address @var{from}
35720 to address @var{to}, possibly adjusted so that executing the
35721 instruction at @var{to} has the same effect as executing it at
35722 @var{from}. @value{GDBN} writes the adjusted instruction to target
35723 memory starting at @var{to}.
35728 @item qRelocInsn:@var{adjusted_size}
35729 Informs the stub the relocation is complete. @var{adjusted_size} is
35730 the length in bytes of resulting relocated instruction sequence.
35732 A badly formed request was detected, or an error was encountered while
35733 relocating the instruction.
35736 @node Host I/O Packets
35737 @section Host I/O Packets
35738 @cindex Host I/O, remote protocol
35739 @cindex file transfer, remote protocol
35741 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
35742 operations on the far side of a remote link. For example, Host I/O is
35743 used to upload and download files to a remote target with its own
35744 filesystem. Host I/O uses the same constant values and data structure
35745 layout as the target-initiated File-I/O protocol. However, the
35746 Host I/O packets are structured differently. The target-initiated
35747 protocol relies on target memory to store parameters and buffers.
35748 Host I/O requests are initiated by @value{GDBN}, and the
35749 target's memory is not involved. @xref{File-I/O Remote Protocol
35750 Extension}, for more details on the target-initiated protocol.
35752 The Host I/O request packets all encode a single operation along with
35753 its arguments. They have this format:
35757 @item vFile:@var{operation}: @var{parameter}@dots{}
35758 @var{operation} is the name of the particular request; the target
35759 should compare the entire packet name up to the second colon when checking
35760 for a supported operation. The format of @var{parameter} depends on
35761 the operation. Numbers are always passed in hexadecimal. Negative
35762 numbers have an explicit minus sign (i.e.@: two's complement is not
35763 used). Strings (e.g.@: filenames) are encoded as a series of
35764 hexadecimal bytes. The last argument to a system call may be a
35765 buffer of escaped binary data (@pxref{Binary Data}).
35769 The valid responses to Host I/O packets are:
35773 @item F @var{result} [, @var{errno}] [; @var{attachment}]
35774 @var{result} is the integer value returned by this operation, usually
35775 non-negative for success and -1 for errors. If an error has occured,
35776 @var{errno} will be included in the result. @var{errno} will have a
35777 value defined by the File-I/O protocol (@pxref{Errno Values}). For
35778 operations which return data, @var{attachment} supplies the data as a
35779 binary buffer. Binary buffers in response packets are escaped in the
35780 normal way (@pxref{Binary Data}). See the individual packet
35781 documentation for the interpretation of @var{result} and
35785 An empty response indicates that this operation is not recognized.
35789 These are the supported Host I/O operations:
35792 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
35793 Open a file at @var{pathname} and return a file descriptor for it, or
35794 return -1 if an error occurs. @var{pathname} is a string,
35795 @var{flags} is an integer indicating a mask of open flags
35796 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
35797 of mode bits to use if the file is created (@pxref{mode_t Values}).
35798 @xref{open}, for details of the open flags and mode values.
35800 @item vFile:close: @var{fd}
35801 Close the open file corresponding to @var{fd} and return 0, or
35802 -1 if an error occurs.
35804 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
35805 Read data from the open file corresponding to @var{fd}. Up to
35806 @var{count} bytes will be read from the file, starting at @var{offset}
35807 relative to the start of the file. The target may read fewer bytes;
35808 common reasons include packet size limits and an end-of-file
35809 condition. The number of bytes read is returned. Zero should only be
35810 returned for a successful read at the end of the file, or if
35811 @var{count} was zero.
35813 The data read should be returned as a binary attachment on success.
35814 If zero bytes were read, the response should include an empty binary
35815 attachment (i.e.@: a trailing semicolon). The return value is the
35816 number of target bytes read; the binary attachment may be longer if
35817 some characters were escaped.
35819 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
35820 Write @var{data} (a binary buffer) to the open file corresponding
35821 to @var{fd}. Start the write at @var{offset} from the start of the
35822 file. Unlike many @code{write} system calls, there is no
35823 separate @var{count} argument; the length of @var{data} in the
35824 packet is used. @samp{vFile:write} returns the number of bytes written,
35825 which may be shorter than the length of @var{data}, or -1 if an
35828 @item vFile:unlink: @var{pathname}
35829 Delete the file at @var{pathname} on the target. Return 0,
35830 or -1 if an error occurs. @var{pathname} is a string.
35835 @section Interrupts
35836 @cindex interrupts (remote protocol)
35838 When a program on the remote target is running, @value{GDBN} may
35839 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
35840 a @code{BREAK} followed by @code{g},
35841 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
35843 The precise meaning of @code{BREAK} is defined by the transport
35844 mechanism and may, in fact, be undefined. @value{GDBN} does not
35845 currently define a @code{BREAK} mechanism for any of the network
35846 interfaces except for TCP, in which case @value{GDBN} sends the
35847 @code{telnet} BREAK sequence.
35849 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
35850 transport mechanisms. It is represented by sending the single byte
35851 @code{0x03} without any of the usual packet overhead described in
35852 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
35853 transmitted as part of a packet, it is considered to be packet data
35854 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
35855 (@pxref{X packet}), used for binary downloads, may include an unescaped
35856 @code{0x03} as part of its packet.
35858 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
35859 When Linux kernel receives this sequence from serial port,
35860 it stops execution and connects to gdb.
35862 Stubs are not required to recognize these interrupt mechanisms and the
35863 precise meaning associated with receipt of the interrupt is
35864 implementation defined. If the target supports debugging of multiple
35865 threads and/or processes, it should attempt to interrupt all
35866 currently-executing threads and processes.
35867 If the stub is successful at interrupting the
35868 running program, it should send one of the stop
35869 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
35870 of successfully stopping the program in all-stop mode, and a stop reply
35871 for each stopped thread in non-stop mode.
35872 Interrupts received while the
35873 program is stopped are discarded.
35875 @node Notification Packets
35876 @section Notification Packets
35877 @cindex notification packets
35878 @cindex packets, notification
35880 The @value{GDBN} remote serial protocol includes @dfn{notifications},
35881 packets that require no acknowledgment. Both the GDB and the stub
35882 may send notifications (although the only notifications defined at
35883 present are sent by the stub). Notifications carry information
35884 without incurring the round-trip latency of an acknowledgment, and so
35885 are useful for low-impact communications where occasional packet loss
35888 A notification packet has the form @samp{% @var{data} #
35889 @var{checksum}}, where @var{data} is the content of the notification,
35890 and @var{checksum} is a checksum of @var{data}, computed and formatted
35891 as for ordinary @value{GDBN} packets. A notification's @var{data}
35892 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
35893 receiving a notification, the recipient sends no @samp{+} or @samp{-}
35894 to acknowledge the notification's receipt or to report its corruption.
35896 Every notification's @var{data} begins with a name, which contains no
35897 colon characters, followed by a colon character.
35899 Recipients should silently ignore corrupted notifications and
35900 notifications they do not understand. Recipients should restart
35901 timeout periods on receipt of a well-formed notification, whether or
35902 not they understand it.
35904 Senders should only send the notifications described here when this
35905 protocol description specifies that they are permitted. In the
35906 future, we may extend the protocol to permit existing notifications in
35907 new contexts; this rule helps older senders avoid confusing newer
35910 (Older versions of @value{GDBN} ignore bytes received until they see
35911 the @samp{$} byte that begins an ordinary packet, so new stubs may
35912 transmit notifications without fear of confusing older clients. There
35913 are no notifications defined for @value{GDBN} to send at the moment, but we
35914 assume that most older stubs would ignore them, as well.)
35916 The following notification packets from the stub to @value{GDBN} are
35920 @item Stop: @var{reply}
35921 Report an asynchronous stop event in non-stop mode.
35922 The @var{reply} has the form of a stop reply, as
35923 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
35924 for information on how these notifications are acknowledged by
35928 @node Remote Non-Stop
35929 @section Remote Protocol Support for Non-Stop Mode
35931 @value{GDBN}'s remote protocol supports non-stop debugging of
35932 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
35933 supports non-stop mode, it should report that to @value{GDBN} by including
35934 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
35936 @value{GDBN} typically sends a @samp{QNonStop} packet only when
35937 establishing a new connection with the stub. Entering non-stop mode
35938 does not alter the state of any currently-running threads, but targets
35939 must stop all threads in any already-attached processes when entering
35940 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
35941 probe the target state after a mode change.
35943 In non-stop mode, when an attached process encounters an event that
35944 would otherwise be reported with a stop reply, it uses the
35945 asynchronous notification mechanism (@pxref{Notification Packets}) to
35946 inform @value{GDBN}. In contrast to all-stop mode, where all threads
35947 in all processes are stopped when a stop reply is sent, in non-stop
35948 mode only the thread reporting the stop event is stopped. That is,
35949 when reporting a @samp{S} or @samp{T} response to indicate completion
35950 of a step operation, hitting a breakpoint, or a fault, only the
35951 affected thread is stopped; any other still-running threads continue
35952 to run. When reporting a @samp{W} or @samp{X} response, all running
35953 threads belonging to other attached processes continue to run.
35955 Only one stop reply notification at a time may be pending; if
35956 additional stop events occur before @value{GDBN} has acknowledged the
35957 previous notification, they must be queued by the stub for later
35958 synchronous transmission in response to @samp{vStopped} packets from
35959 @value{GDBN}. Because the notification mechanism is unreliable,
35960 the stub is permitted to resend a stop reply notification
35961 if it believes @value{GDBN} may not have received it. @value{GDBN}
35962 ignores additional stop reply notifications received before it has
35963 finished processing a previous notification and the stub has completed
35964 sending any queued stop events.
35966 Otherwise, @value{GDBN} must be prepared to receive a stop reply
35967 notification at any time. Specifically, they may appear when
35968 @value{GDBN} is not otherwise reading input from the stub, or when
35969 @value{GDBN} is expecting to read a normal synchronous response or a
35970 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
35971 Notification packets are distinct from any other communication from
35972 the stub so there is no ambiguity.
35974 After receiving a stop reply notification, @value{GDBN} shall
35975 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
35976 as a regular, synchronous request to the stub. Such acknowledgment
35977 is not required to happen immediately, as @value{GDBN} is permitted to
35978 send other, unrelated packets to the stub first, which the stub should
35981 Upon receiving a @samp{vStopped} packet, if the stub has other queued
35982 stop events to report to @value{GDBN}, it shall respond by sending a
35983 normal stop reply response. @value{GDBN} shall then send another
35984 @samp{vStopped} packet to solicit further responses; again, it is
35985 permitted to send other, unrelated packets as well which the stub
35986 should process normally.
35988 If the stub receives a @samp{vStopped} packet and there are no
35989 additional stop events to report, the stub shall return an @samp{OK}
35990 response. At this point, if further stop events occur, the stub shall
35991 send a new stop reply notification, @value{GDBN} shall accept the
35992 notification, and the process shall be repeated.
35994 In non-stop mode, the target shall respond to the @samp{?} packet as
35995 follows. First, any incomplete stop reply notification/@samp{vStopped}
35996 sequence in progress is abandoned. The target must begin a new
35997 sequence reporting stop events for all stopped threads, whether or not
35998 it has previously reported those events to @value{GDBN}. The first
35999 stop reply is sent as a synchronous reply to the @samp{?} packet, and
36000 subsequent stop replies are sent as responses to @samp{vStopped} packets
36001 using the mechanism described above. The target must not send
36002 asynchronous stop reply notifications until the sequence is complete.
36003 If all threads are running when the target receives the @samp{?} packet,
36004 or if the target is not attached to any process, it shall respond
36007 @node Packet Acknowledgment
36008 @section Packet Acknowledgment
36010 @cindex acknowledgment, for @value{GDBN} remote
36011 @cindex packet acknowledgment, for @value{GDBN} remote
36012 By default, when either the host or the target machine receives a packet,
36013 the first response expected is an acknowledgment: either @samp{+} (to indicate
36014 the package was received correctly) or @samp{-} (to request retransmission).
36015 This mechanism allows the @value{GDBN} remote protocol to operate over
36016 unreliable transport mechanisms, such as a serial line.
36018 In cases where the transport mechanism is itself reliable (such as a pipe or
36019 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
36020 It may be desirable to disable them in that case to reduce communication
36021 overhead, or for other reasons. This can be accomplished by means of the
36022 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
36024 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
36025 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
36026 and response format still includes the normal checksum, as described in
36027 @ref{Overview}, but the checksum may be ignored by the receiver.
36029 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
36030 no-acknowledgment mode, it should report that to @value{GDBN}
36031 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
36032 @pxref{qSupported}.
36033 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
36034 disabled via the @code{set remote noack-packet off} command
36035 (@pxref{Remote Configuration}),
36036 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
36037 Only then may the stub actually turn off packet acknowledgments.
36038 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
36039 response, which can be safely ignored by the stub.
36041 Note that @code{set remote noack-packet} command only affects negotiation
36042 between @value{GDBN} and the stub when subsequent connections are made;
36043 it does not affect the protocol acknowledgment state for any current
36045 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
36046 new connection is established,
36047 there is also no protocol request to re-enable the acknowledgments
36048 for the current connection, once disabled.
36053 Example sequence of a target being re-started. Notice how the restart
36054 does not get any direct output:
36059 @emph{target restarts}
36062 <- @code{T001:1234123412341234}
36066 Example sequence of a target being stepped by a single instruction:
36069 -> @code{G1445@dots{}}
36074 <- @code{T001:1234123412341234}
36078 <- @code{1455@dots{}}
36082 @node File-I/O Remote Protocol Extension
36083 @section File-I/O Remote Protocol Extension
36084 @cindex File-I/O remote protocol extension
36087 * File-I/O Overview::
36088 * Protocol Basics::
36089 * The F Request Packet::
36090 * The F Reply Packet::
36091 * The Ctrl-C Message::
36093 * List of Supported Calls::
36094 * Protocol-specific Representation of Datatypes::
36096 * File-I/O Examples::
36099 @node File-I/O Overview
36100 @subsection File-I/O Overview
36101 @cindex file-i/o overview
36103 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
36104 target to use the host's file system and console I/O to perform various
36105 system calls. System calls on the target system are translated into a
36106 remote protocol packet to the host system, which then performs the needed
36107 actions and returns a response packet to the target system.
36108 This simulates file system operations even on targets that lack file systems.
36110 The protocol is defined to be independent of both the host and target systems.
36111 It uses its own internal representation of datatypes and values. Both
36112 @value{GDBN} and the target's @value{GDBN} stub are responsible for
36113 translating the system-dependent value representations into the internal
36114 protocol representations when data is transmitted.
36116 The communication is synchronous. A system call is possible only when
36117 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
36118 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
36119 the target is stopped to allow deterministic access to the target's
36120 memory. Therefore File-I/O is not interruptible by target signals. On
36121 the other hand, it is possible to interrupt File-I/O by a user interrupt
36122 (@samp{Ctrl-C}) within @value{GDBN}.
36124 The target's request to perform a host system call does not finish
36125 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
36126 after finishing the system call, the target returns to continuing the
36127 previous activity (continue, step). No additional continue or step
36128 request from @value{GDBN} is required.
36131 (@value{GDBP}) continue
36132 <- target requests 'system call X'
36133 target is stopped, @value{GDBN} executes system call
36134 -> @value{GDBN} returns result
36135 ... target continues, @value{GDBN} returns to wait for the target
36136 <- target hits breakpoint and sends a Txx packet
36139 The protocol only supports I/O on the console and to regular files on
36140 the host file system. Character or block special devices, pipes,
36141 named pipes, sockets or any other communication method on the host
36142 system are not supported by this protocol.
36144 File I/O is not supported in non-stop mode.
36146 @node Protocol Basics
36147 @subsection Protocol Basics
36148 @cindex protocol basics, file-i/o
36150 The File-I/O protocol uses the @code{F} packet as the request as well
36151 as reply packet. Since a File-I/O system call can only occur when
36152 @value{GDBN} is waiting for a response from the continuing or stepping target,
36153 the File-I/O request is a reply that @value{GDBN} has to expect as a result
36154 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
36155 This @code{F} packet contains all information needed to allow @value{GDBN}
36156 to call the appropriate host system call:
36160 A unique identifier for the requested system call.
36163 All parameters to the system call. Pointers are given as addresses
36164 in the target memory address space. Pointers to strings are given as
36165 pointer/length pair. Numerical values are given as they are.
36166 Numerical control flags are given in a protocol-specific representation.
36170 At this point, @value{GDBN} has to perform the following actions.
36174 If the parameters include pointer values to data needed as input to a
36175 system call, @value{GDBN} requests this data from the target with a
36176 standard @code{m} packet request. This additional communication has to be
36177 expected by the target implementation and is handled as any other @code{m}
36181 @value{GDBN} translates all value from protocol representation to host
36182 representation as needed. Datatypes are coerced into the host types.
36185 @value{GDBN} calls the system call.
36188 It then coerces datatypes back to protocol representation.
36191 If the system call is expected to return data in buffer space specified
36192 by pointer parameters to the call, the data is transmitted to the
36193 target using a @code{M} or @code{X} packet. This packet has to be expected
36194 by the target implementation and is handled as any other @code{M} or @code{X}
36199 Eventually @value{GDBN} replies with another @code{F} packet which contains all
36200 necessary information for the target to continue. This at least contains
36207 @code{errno}, if has been changed by the system call.
36214 After having done the needed type and value coercion, the target continues
36215 the latest continue or step action.
36217 @node The F Request Packet
36218 @subsection The @code{F} Request Packet
36219 @cindex file-i/o request packet
36220 @cindex @code{F} request packet
36222 The @code{F} request packet has the following format:
36225 @item F@var{call-id},@var{parameter@dots{}}
36227 @var{call-id} is the identifier to indicate the host system call to be called.
36228 This is just the name of the function.
36230 @var{parameter@dots{}} are the parameters to the system call.
36231 Parameters are hexadecimal integer values, either the actual values in case
36232 of scalar datatypes, pointers to target buffer space in case of compound
36233 datatypes and unspecified memory areas, or pointer/length pairs in case
36234 of string parameters. These are appended to the @var{call-id} as a
36235 comma-delimited list. All values are transmitted in ASCII
36236 string representation, pointer/length pairs separated by a slash.
36242 @node The F Reply Packet
36243 @subsection The @code{F} Reply Packet
36244 @cindex file-i/o reply packet
36245 @cindex @code{F} reply packet
36247 The @code{F} reply packet has the following format:
36251 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
36253 @var{retcode} is the return code of the system call as hexadecimal value.
36255 @var{errno} is the @code{errno} set by the call, in protocol-specific
36257 This parameter can be omitted if the call was successful.
36259 @var{Ctrl-C flag} is only sent if the user requested a break. In this
36260 case, @var{errno} must be sent as well, even if the call was successful.
36261 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
36268 or, if the call was interrupted before the host call has been performed:
36275 assuming 4 is the protocol-specific representation of @code{EINTR}.
36280 @node The Ctrl-C Message
36281 @subsection The @samp{Ctrl-C} Message
36282 @cindex ctrl-c message, in file-i/o protocol
36284 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
36285 reply packet (@pxref{The F Reply Packet}),
36286 the target should behave as if it had
36287 gotten a break message. The meaning for the target is ``system call
36288 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
36289 (as with a break message) and return to @value{GDBN} with a @code{T02}
36292 It's important for the target to know in which
36293 state the system call was interrupted. There are two possible cases:
36297 The system call hasn't been performed on the host yet.
36300 The system call on the host has been finished.
36304 These two states can be distinguished by the target by the value of the
36305 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
36306 call hasn't been performed. This is equivalent to the @code{EINTR} handling
36307 on POSIX systems. In any other case, the target may presume that the
36308 system call has been finished --- successfully or not --- and should behave
36309 as if the break message arrived right after the system call.
36311 @value{GDBN} must behave reliably. If the system call has not been called
36312 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
36313 @code{errno} in the packet. If the system call on the host has been finished
36314 before the user requests a break, the full action must be finished by
36315 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
36316 The @code{F} packet may only be sent when either nothing has happened
36317 or the full action has been completed.
36320 @subsection Console I/O
36321 @cindex console i/o as part of file-i/o
36323 By default and if not explicitly closed by the target system, the file
36324 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
36325 on the @value{GDBN} console is handled as any other file output operation
36326 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
36327 by @value{GDBN} so that after the target read request from file descriptor
36328 0 all following typing is buffered until either one of the following
36333 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
36335 system call is treated as finished.
36338 The user presses @key{RET}. This is treated as end of input with a trailing
36342 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
36343 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
36347 If the user has typed more characters than fit in the buffer given to
36348 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
36349 either another @code{read(0, @dots{})} is requested by the target, or debugging
36350 is stopped at the user's request.
36353 @node List of Supported Calls
36354 @subsection List of Supported Calls
36355 @cindex list of supported file-i/o calls
36372 @unnumberedsubsubsec open
36373 @cindex open, file-i/o system call
36378 int open(const char *pathname, int flags);
36379 int open(const char *pathname, int flags, mode_t mode);
36383 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
36386 @var{flags} is the bitwise @code{OR} of the following values:
36390 If the file does not exist it will be created. The host
36391 rules apply as far as file ownership and time stamps
36395 When used with @code{O_CREAT}, if the file already exists it is
36396 an error and open() fails.
36399 If the file already exists and the open mode allows
36400 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
36401 truncated to zero length.
36404 The file is opened in append mode.
36407 The file is opened for reading only.
36410 The file is opened for writing only.
36413 The file is opened for reading and writing.
36417 Other bits are silently ignored.
36421 @var{mode} is the bitwise @code{OR} of the following values:
36425 User has read permission.
36428 User has write permission.
36431 Group has read permission.
36434 Group has write permission.
36437 Others have read permission.
36440 Others have write permission.
36444 Other bits are silently ignored.
36447 @item Return value:
36448 @code{open} returns the new file descriptor or -1 if an error
36455 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
36458 @var{pathname} refers to a directory.
36461 The requested access is not allowed.
36464 @var{pathname} was too long.
36467 A directory component in @var{pathname} does not exist.
36470 @var{pathname} refers to a device, pipe, named pipe or socket.
36473 @var{pathname} refers to a file on a read-only filesystem and
36474 write access was requested.
36477 @var{pathname} is an invalid pointer value.
36480 No space on device to create the file.
36483 The process already has the maximum number of files open.
36486 The limit on the total number of files open on the system
36490 The call was interrupted by the user.
36496 @unnumberedsubsubsec close
36497 @cindex close, file-i/o system call
36506 @samp{Fclose,@var{fd}}
36508 @item Return value:
36509 @code{close} returns zero on success, or -1 if an error occurred.
36515 @var{fd} isn't a valid open file descriptor.
36518 The call was interrupted by the user.
36524 @unnumberedsubsubsec read
36525 @cindex read, file-i/o system call
36530 int read(int fd, void *buf, unsigned int count);
36534 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
36536 @item Return value:
36537 On success, the number of bytes read is returned.
36538 Zero indicates end of file. If count is zero, read
36539 returns zero as well. On error, -1 is returned.
36545 @var{fd} is not a valid file descriptor or is not open for
36549 @var{bufptr} is an invalid pointer value.
36552 The call was interrupted by the user.
36558 @unnumberedsubsubsec write
36559 @cindex write, file-i/o system call
36564 int write(int fd, const void *buf, unsigned int count);
36568 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
36570 @item Return value:
36571 On success, the number of bytes written are returned.
36572 Zero indicates nothing was written. On error, -1
36579 @var{fd} is not a valid file descriptor or is not open for
36583 @var{bufptr} is an invalid pointer value.
36586 An attempt was made to write a file that exceeds the
36587 host-specific maximum file size allowed.
36590 No space on device to write the data.
36593 The call was interrupted by the user.
36599 @unnumberedsubsubsec lseek
36600 @cindex lseek, file-i/o system call
36605 long lseek (int fd, long offset, int flag);
36609 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
36611 @var{flag} is one of:
36615 The offset is set to @var{offset} bytes.
36618 The offset is set to its current location plus @var{offset}
36622 The offset is set to the size of the file plus @var{offset}
36626 @item Return value:
36627 On success, the resulting unsigned offset in bytes from
36628 the beginning of the file is returned. Otherwise, a
36629 value of -1 is returned.
36635 @var{fd} is not a valid open file descriptor.
36638 @var{fd} is associated with the @value{GDBN} console.
36641 @var{flag} is not a proper value.
36644 The call was interrupted by the user.
36650 @unnumberedsubsubsec rename
36651 @cindex rename, file-i/o system call
36656 int rename(const char *oldpath, const char *newpath);
36660 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
36662 @item Return value:
36663 On success, zero is returned. On error, -1 is returned.
36669 @var{newpath} is an existing directory, but @var{oldpath} is not a
36673 @var{newpath} is a non-empty directory.
36676 @var{oldpath} or @var{newpath} is a directory that is in use by some
36680 An attempt was made to make a directory a subdirectory
36684 A component used as a directory in @var{oldpath} or new
36685 path is not a directory. Or @var{oldpath} is a directory
36686 and @var{newpath} exists but is not a directory.
36689 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
36692 No access to the file or the path of the file.
36696 @var{oldpath} or @var{newpath} was too long.
36699 A directory component in @var{oldpath} or @var{newpath} does not exist.
36702 The file is on a read-only filesystem.
36705 The device containing the file has no room for the new
36709 The call was interrupted by the user.
36715 @unnumberedsubsubsec unlink
36716 @cindex unlink, file-i/o system call
36721 int unlink(const char *pathname);
36725 @samp{Funlink,@var{pathnameptr}/@var{len}}
36727 @item Return value:
36728 On success, zero is returned. On error, -1 is returned.
36734 No access to the file or the path of the file.
36737 The system does not allow unlinking of directories.
36740 The file @var{pathname} cannot be unlinked because it's
36741 being used by another process.
36744 @var{pathnameptr} is an invalid pointer value.
36747 @var{pathname} was too long.
36750 A directory component in @var{pathname} does not exist.
36753 A component of the path is not a directory.
36756 The file is on a read-only filesystem.
36759 The call was interrupted by the user.
36765 @unnumberedsubsubsec stat/fstat
36766 @cindex fstat, file-i/o system call
36767 @cindex stat, file-i/o system call
36772 int stat(const char *pathname, struct stat *buf);
36773 int fstat(int fd, struct stat *buf);
36777 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
36778 @samp{Ffstat,@var{fd},@var{bufptr}}
36780 @item Return value:
36781 On success, zero is returned. On error, -1 is returned.
36787 @var{fd} is not a valid open file.
36790 A directory component in @var{pathname} does not exist or the
36791 path is an empty string.
36794 A component of the path is not a directory.
36797 @var{pathnameptr} is an invalid pointer value.
36800 No access to the file or the path of the file.
36803 @var{pathname} was too long.
36806 The call was interrupted by the user.
36812 @unnumberedsubsubsec gettimeofday
36813 @cindex gettimeofday, file-i/o system call
36818 int gettimeofday(struct timeval *tv, void *tz);
36822 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
36824 @item Return value:
36825 On success, 0 is returned, -1 otherwise.
36831 @var{tz} is a non-NULL pointer.
36834 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
36840 @unnumberedsubsubsec isatty
36841 @cindex isatty, file-i/o system call
36846 int isatty(int fd);
36850 @samp{Fisatty,@var{fd}}
36852 @item Return value:
36853 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
36859 The call was interrupted by the user.
36864 Note that the @code{isatty} call is treated as a special case: it returns
36865 1 to the target if the file descriptor is attached
36866 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
36867 would require implementing @code{ioctl} and would be more complex than
36872 @unnumberedsubsubsec system
36873 @cindex system, file-i/o system call
36878 int system(const char *command);
36882 @samp{Fsystem,@var{commandptr}/@var{len}}
36884 @item Return value:
36885 If @var{len} is zero, the return value indicates whether a shell is
36886 available. A zero return value indicates a shell is not available.
36887 For non-zero @var{len}, the value returned is -1 on error and the
36888 return status of the command otherwise. Only the exit status of the
36889 command is returned, which is extracted from the host's @code{system}
36890 return value by calling @code{WEXITSTATUS(retval)}. In case
36891 @file{/bin/sh} could not be executed, 127 is returned.
36897 The call was interrupted by the user.
36902 @value{GDBN} takes over the full task of calling the necessary host calls
36903 to perform the @code{system} call. The return value of @code{system} on
36904 the host is simplified before it's returned
36905 to the target. Any termination signal information from the child process
36906 is discarded, and the return value consists
36907 entirely of the exit status of the called command.
36909 Due to security concerns, the @code{system} call is by default refused
36910 by @value{GDBN}. The user has to allow this call explicitly with the
36911 @code{set remote system-call-allowed 1} command.
36914 @item set remote system-call-allowed
36915 @kindex set remote system-call-allowed
36916 Control whether to allow the @code{system} calls in the File I/O
36917 protocol for the remote target. The default is zero (disabled).
36919 @item show remote system-call-allowed
36920 @kindex show remote system-call-allowed
36921 Show whether the @code{system} calls are allowed in the File I/O
36925 @node Protocol-specific Representation of Datatypes
36926 @subsection Protocol-specific Representation of Datatypes
36927 @cindex protocol-specific representation of datatypes, in file-i/o protocol
36930 * Integral Datatypes::
36932 * Memory Transfer::
36937 @node Integral Datatypes
36938 @unnumberedsubsubsec Integral Datatypes
36939 @cindex integral datatypes, in file-i/o protocol
36941 The integral datatypes used in the system calls are @code{int},
36942 @code{unsigned int}, @code{long}, @code{unsigned long},
36943 @code{mode_t}, and @code{time_t}.
36945 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
36946 implemented as 32 bit values in this protocol.
36948 @code{long} and @code{unsigned long} are implemented as 64 bit types.
36950 @xref{Limits}, for corresponding MIN and MAX values (similar to those
36951 in @file{limits.h}) to allow range checking on host and target.
36953 @code{time_t} datatypes are defined as seconds since the Epoch.
36955 All integral datatypes transferred as part of a memory read or write of a
36956 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
36959 @node Pointer Values
36960 @unnumberedsubsubsec Pointer Values
36961 @cindex pointer values, in file-i/o protocol
36963 Pointers to target data are transmitted as they are. An exception
36964 is made for pointers to buffers for which the length isn't
36965 transmitted as part of the function call, namely strings. Strings
36966 are transmitted as a pointer/length pair, both as hex values, e.g.@:
36973 which is a pointer to data of length 18 bytes at position 0x1aaf.
36974 The length is defined as the full string length in bytes, including
36975 the trailing null byte. For example, the string @code{"hello world"}
36976 at address 0x123456 is transmitted as
36982 @node Memory Transfer
36983 @unnumberedsubsubsec Memory Transfer
36984 @cindex memory transfer, in file-i/o protocol
36986 Structured data which is transferred using a memory read or write (for
36987 example, a @code{struct stat}) is expected to be in a protocol-specific format
36988 with all scalar multibyte datatypes being big endian. Translation to
36989 this representation needs to be done both by the target before the @code{F}
36990 packet is sent, and by @value{GDBN} before
36991 it transfers memory to the target. Transferred pointers to structured
36992 data should point to the already-coerced data at any time.
36996 @unnumberedsubsubsec struct stat
36997 @cindex struct stat, in file-i/o protocol
36999 The buffer of type @code{struct stat} used by the target and @value{GDBN}
37000 is defined as follows:
37004 unsigned int st_dev; /* device */
37005 unsigned int st_ino; /* inode */
37006 mode_t st_mode; /* protection */
37007 unsigned int st_nlink; /* number of hard links */
37008 unsigned int st_uid; /* user ID of owner */
37009 unsigned int st_gid; /* group ID of owner */
37010 unsigned int st_rdev; /* device type (if inode device) */
37011 unsigned long st_size; /* total size, in bytes */
37012 unsigned long st_blksize; /* blocksize for filesystem I/O */
37013 unsigned long st_blocks; /* number of blocks allocated */
37014 time_t st_atime; /* time of last access */
37015 time_t st_mtime; /* time of last modification */
37016 time_t st_ctime; /* time of last change */
37020 The integral datatypes conform to the definitions given in the
37021 appropriate section (see @ref{Integral Datatypes}, for details) so this
37022 structure is of size 64 bytes.
37024 The values of several fields have a restricted meaning and/or
37030 A value of 0 represents a file, 1 the console.
37033 No valid meaning for the target. Transmitted unchanged.
37036 Valid mode bits are described in @ref{Constants}. Any other
37037 bits have currently no meaning for the target.
37042 No valid meaning for the target. Transmitted unchanged.
37047 These values have a host and file system dependent
37048 accuracy. Especially on Windows hosts, the file system may not
37049 support exact timing values.
37052 The target gets a @code{struct stat} of the above representation and is
37053 responsible for coercing it to the target representation before
37056 Note that due to size differences between the host, target, and protocol
37057 representations of @code{struct stat} members, these members could eventually
37058 get truncated on the target.
37060 @node struct timeval
37061 @unnumberedsubsubsec struct timeval
37062 @cindex struct timeval, in file-i/o protocol
37064 The buffer of type @code{struct timeval} used by the File-I/O protocol
37065 is defined as follows:
37069 time_t tv_sec; /* second */
37070 long tv_usec; /* microsecond */
37074 The integral datatypes conform to the definitions given in the
37075 appropriate section (see @ref{Integral Datatypes}, for details) so this
37076 structure is of size 8 bytes.
37079 @subsection Constants
37080 @cindex constants, in file-i/o protocol
37082 The following values are used for the constants inside of the
37083 protocol. @value{GDBN} and target are responsible for translating these
37084 values before and after the call as needed.
37095 @unnumberedsubsubsec Open Flags
37096 @cindex open flags, in file-i/o protocol
37098 All values are given in hexadecimal representation.
37110 @node mode_t Values
37111 @unnumberedsubsubsec mode_t Values
37112 @cindex mode_t values, in file-i/o protocol
37114 All values are given in octal representation.
37131 @unnumberedsubsubsec Errno Values
37132 @cindex errno values, in file-i/o protocol
37134 All values are given in decimal representation.
37159 @code{EUNKNOWN} is used as a fallback error value if a host system returns
37160 any error value not in the list of supported error numbers.
37163 @unnumberedsubsubsec Lseek Flags
37164 @cindex lseek flags, in file-i/o protocol
37173 @unnumberedsubsubsec Limits
37174 @cindex limits, in file-i/o protocol
37176 All values are given in decimal representation.
37179 INT_MIN -2147483648
37181 UINT_MAX 4294967295
37182 LONG_MIN -9223372036854775808
37183 LONG_MAX 9223372036854775807
37184 ULONG_MAX 18446744073709551615
37187 @node File-I/O Examples
37188 @subsection File-I/O Examples
37189 @cindex file-i/o examples
37191 Example sequence of a write call, file descriptor 3, buffer is at target
37192 address 0x1234, 6 bytes should be written:
37195 <- @code{Fwrite,3,1234,6}
37196 @emph{request memory read from target}
37199 @emph{return "6 bytes written"}
37203 Example sequence of a read call, file descriptor 3, buffer is at target
37204 address 0x1234, 6 bytes should be read:
37207 <- @code{Fread,3,1234,6}
37208 @emph{request memory write to target}
37209 -> @code{X1234,6:XXXXXX}
37210 @emph{return "6 bytes read"}
37214 Example sequence of a read call, call fails on the host due to invalid
37215 file descriptor (@code{EBADF}):
37218 <- @code{Fread,3,1234,6}
37222 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
37226 <- @code{Fread,3,1234,6}
37231 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
37235 <- @code{Fread,3,1234,6}
37236 -> @code{X1234,6:XXXXXX}
37240 @node Library List Format
37241 @section Library List Format
37242 @cindex library list format, remote protocol
37244 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
37245 same process as your application to manage libraries. In this case,
37246 @value{GDBN} can use the loader's symbol table and normal memory
37247 operations to maintain a list of shared libraries. On other
37248 platforms, the operating system manages loaded libraries.
37249 @value{GDBN} can not retrieve the list of currently loaded libraries
37250 through memory operations, so it uses the @samp{qXfer:libraries:read}
37251 packet (@pxref{qXfer library list read}) instead. The remote stub
37252 queries the target's operating system and reports which libraries
37255 The @samp{qXfer:libraries:read} packet returns an XML document which
37256 lists loaded libraries and their offsets. Each library has an
37257 associated name and one or more segment or section base addresses,
37258 which report where the library was loaded in memory.
37260 For the common case of libraries that are fully linked binaries, the
37261 library should have a list of segments. If the target supports
37262 dynamic linking of a relocatable object file, its library XML element
37263 should instead include a list of allocated sections. The segment or
37264 section bases are start addresses, not relocation offsets; they do not
37265 depend on the library's link-time base addresses.
37267 @value{GDBN} must be linked with the Expat library to support XML
37268 library lists. @xref{Expat}.
37270 A simple memory map, with one loaded library relocated by a single
37271 offset, looks like this:
37275 <library name="/lib/libc.so.6">
37276 <segment address="0x10000000"/>
37281 Another simple memory map, with one loaded library with three
37282 allocated sections (.text, .data, .bss), looks like this:
37286 <library name="sharedlib.o">
37287 <section address="0x10000000"/>
37288 <section address="0x20000000"/>
37289 <section address="0x30000000"/>
37294 The format of a library list is described by this DTD:
37297 <!-- library-list: Root element with versioning -->
37298 <!ELEMENT library-list (library)*>
37299 <!ATTLIST library-list version CDATA #FIXED "1.0">
37300 <!ELEMENT library (segment*, section*)>
37301 <!ATTLIST library name CDATA #REQUIRED>
37302 <!ELEMENT segment EMPTY>
37303 <!ATTLIST segment address CDATA #REQUIRED>
37304 <!ELEMENT section EMPTY>
37305 <!ATTLIST section address CDATA #REQUIRED>
37308 In addition, segments and section descriptors cannot be mixed within a
37309 single library element, and you must supply at least one segment or
37310 section for each library.
37312 @node Memory Map Format
37313 @section Memory Map Format
37314 @cindex memory map format
37316 To be able to write into flash memory, @value{GDBN} needs to obtain a
37317 memory map from the target. This section describes the format of the
37320 The memory map is obtained using the @samp{qXfer:memory-map:read}
37321 (@pxref{qXfer memory map read}) packet and is an XML document that
37322 lists memory regions.
37324 @value{GDBN} must be linked with the Expat library to support XML
37325 memory maps. @xref{Expat}.
37327 The top-level structure of the document is shown below:
37330 <?xml version="1.0"?>
37331 <!DOCTYPE memory-map
37332 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37333 "http://sourceware.org/gdb/gdb-memory-map.dtd">
37339 Each region can be either:
37344 A region of RAM starting at @var{addr} and extending for @var{length}
37348 <memory type="ram" start="@var{addr}" length="@var{length}"/>
37353 A region of read-only memory:
37356 <memory type="rom" start="@var{addr}" length="@var{length}"/>
37361 A region of flash memory, with erasure blocks @var{blocksize}
37365 <memory type="flash" start="@var{addr}" length="@var{length}">
37366 <property name="blocksize">@var{blocksize}</property>
37372 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
37373 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
37374 packets to write to addresses in such ranges.
37376 The formal DTD for memory map format is given below:
37379 <!-- ................................................... -->
37380 <!-- Memory Map XML DTD ................................ -->
37381 <!-- File: memory-map.dtd .............................. -->
37382 <!-- .................................... .............. -->
37383 <!-- memory-map.dtd -->
37384 <!-- memory-map: Root element with versioning -->
37385 <!ELEMENT memory-map (memory | property)>
37386 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
37387 <!ELEMENT memory (property)>
37388 <!-- memory: Specifies a memory region,
37389 and its type, or device. -->
37390 <!ATTLIST memory type CDATA #REQUIRED
37391 start CDATA #REQUIRED
37392 length CDATA #REQUIRED
37393 device CDATA #IMPLIED>
37394 <!-- property: Generic attribute tag -->
37395 <!ELEMENT property (#PCDATA | property)*>
37396 <!ATTLIST property name CDATA #REQUIRED>
37399 @node Thread List Format
37400 @section Thread List Format
37401 @cindex thread list format
37403 To efficiently update the list of threads and their attributes,
37404 @value{GDBN} issues the @samp{qXfer:threads:read} packet
37405 (@pxref{qXfer threads read}) and obtains the XML document with
37406 the following structure:
37409 <?xml version="1.0"?>
37411 <thread id="id" core="0">
37412 ... description ...
37417 Each @samp{thread} element must have the @samp{id} attribute that
37418 identifies the thread (@pxref{thread-id syntax}). The
37419 @samp{core} attribute, if present, specifies which processor core
37420 the thread was last executing on. The content of the of @samp{thread}
37421 element is interpreted as human-readable auxilliary information.
37423 @node Traceframe Info Format
37424 @section Traceframe Info Format
37425 @cindex traceframe info format
37427 To be able to know which objects in the inferior can be examined when
37428 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
37429 memory ranges, registers and trace state variables that have been
37430 collected in a traceframe.
37432 This list is obtained using the @samp{qXfer:traceframe-info:read}
37433 (@pxref{qXfer traceframe info read}) packet and is an XML document.
37435 @value{GDBN} must be linked with the Expat library to support XML
37436 traceframe info discovery. @xref{Expat}.
37438 The top-level structure of the document is shown below:
37441 <?xml version="1.0"?>
37442 <!DOCTYPE traceframe-info
37443 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37444 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
37450 Each traceframe block can be either:
37455 A region of collected memory starting at @var{addr} and extending for
37456 @var{length} bytes from there:
37459 <memory start="@var{addr}" length="@var{length}"/>
37464 The formal DTD for the traceframe info format is given below:
37467 <!ELEMENT traceframe-info (memory)* >
37468 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
37470 <!ELEMENT memory EMPTY>
37471 <!ATTLIST memory start CDATA #REQUIRED
37472 length CDATA #REQUIRED>
37475 @include agentexpr.texi
37477 @node Target Descriptions
37478 @appendix Target Descriptions
37479 @cindex target descriptions
37481 One of the challenges of using @value{GDBN} to debug embedded systems
37482 is that there are so many minor variants of each processor
37483 architecture in use. It is common practice for vendors to start with
37484 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
37485 and then make changes to adapt it to a particular market niche. Some
37486 architectures have hundreds of variants, available from dozens of
37487 vendors. This leads to a number of problems:
37491 With so many different customized processors, it is difficult for
37492 the @value{GDBN} maintainers to keep up with the changes.
37494 Since individual variants may have short lifetimes or limited
37495 audiences, it may not be worthwhile to carry information about every
37496 variant in the @value{GDBN} source tree.
37498 When @value{GDBN} does support the architecture of the embedded system
37499 at hand, the task of finding the correct architecture name to give the
37500 @command{set architecture} command can be error-prone.
37503 To address these problems, the @value{GDBN} remote protocol allows a
37504 target system to not only identify itself to @value{GDBN}, but to
37505 actually describe its own features. This lets @value{GDBN} support
37506 processor variants it has never seen before --- to the extent that the
37507 descriptions are accurate, and that @value{GDBN} understands them.
37509 @value{GDBN} must be linked with the Expat library to support XML
37510 target descriptions. @xref{Expat}.
37513 * Retrieving Descriptions:: How descriptions are fetched from a target.
37514 * Target Description Format:: The contents of a target description.
37515 * Predefined Target Types:: Standard types available for target
37517 * Standard Target Features:: Features @value{GDBN} knows about.
37520 @node Retrieving Descriptions
37521 @section Retrieving Descriptions
37523 Target descriptions can be read from the target automatically, or
37524 specified by the user manually. The default behavior is to read the
37525 description from the target. @value{GDBN} retrieves it via the remote
37526 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
37527 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
37528 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
37529 XML document, of the form described in @ref{Target Description
37532 Alternatively, you can specify a file to read for the target description.
37533 If a file is set, the target will not be queried. The commands to
37534 specify a file are:
37537 @cindex set tdesc filename
37538 @item set tdesc filename @var{path}
37539 Read the target description from @var{path}.
37541 @cindex unset tdesc filename
37542 @item unset tdesc filename
37543 Do not read the XML target description from a file. @value{GDBN}
37544 will use the description supplied by the current target.
37546 @cindex show tdesc filename
37547 @item show tdesc filename
37548 Show the filename to read for a target description, if any.
37552 @node Target Description Format
37553 @section Target Description Format
37554 @cindex target descriptions, XML format
37556 A target description annex is an @uref{http://www.w3.org/XML/, XML}
37557 document which complies with the Document Type Definition provided in
37558 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
37559 means you can use generally available tools like @command{xmllint} to
37560 check that your feature descriptions are well-formed and valid.
37561 However, to help people unfamiliar with XML write descriptions for
37562 their targets, we also describe the grammar here.
37564 Target descriptions can identify the architecture of the remote target
37565 and (for some architectures) provide information about custom register
37566 sets. They can also identify the OS ABI of the remote target.
37567 @value{GDBN} can use this information to autoconfigure for your
37568 target, or to warn you if you connect to an unsupported target.
37570 Here is a simple target description:
37573 <target version="1.0">
37574 <architecture>i386:x86-64</architecture>
37579 This minimal description only says that the target uses
37580 the x86-64 architecture.
37582 A target description has the following overall form, with [ ] marking
37583 optional elements and @dots{} marking repeatable elements. The elements
37584 are explained further below.
37587 <?xml version="1.0"?>
37588 <!DOCTYPE target SYSTEM "gdb-target.dtd">
37589 <target version="1.0">
37590 @r{[}@var{architecture}@r{]}
37591 @r{[}@var{osabi}@r{]}
37592 @r{[}@var{compatible}@r{]}
37593 @r{[}@var{feature}@dots{}@r{]}
37598 The description is generally insensitive to whitespace and line
37599 breaks, under the usual common-sense rules. The XML version
37600 declaration and document type declaration can generally be omitted
37601 (@value{GDBN} does not require them), but specifying them may be
37602 useful for XML validation tools. The @samp{version} attribute for
37603 @samp{<target>} may also be omitted, but we recommend
37604 including it; if future versions of @value{GDBN} use an incompatible
37605 revision of @file{gdb-target.dtd}, they will detect and report
37606 the version mismatch.
37608 @subsection Inclusion
37609 @cindex target descriptions, inclusion
37612 @cindex <xi:include>
37615 It can sometimes be valuable to split a target description up into
37616 several different annexes, either for organizational purposes, or to
37617 share files between different possible target descriptions. You can
37618 divide a description into multiple files by replacing any element of
37619 the target description with an inclusion directive of the form:
37622 <xi:include href="@var{document}"/>
37626 When @value{GDBN} encounters an element of this form, it will retrieve
37627 the named XML @var{document}, and replace the inclusion directive with
37628 the contents of that document. If the current description was read
37629 using @samp{qXfer}, then so will be the included document;
37630 @var{document} will be interpreted as the name of an annex. If the
37631 current description was read from a file, @value{GDBN} will look for
37632 @var{document} as a file in the same directory where it found the
37633 original description.
37635 @subsection Architecture
37636 @cindex <architecture>
37638 An @samp{<architecture>} element has this form:
37641 <architecture>@var{arch}</architecture>
37644 @var{arch} is one of the architectures from the set accepted by
37645 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
37648 @cindex @code{<osabi>}
37650 This optional field was introduced in @value{GDBN} version 7.0.
37651 Previous versions of @value{GDBN} ignore it.
37653 An @samp{<osabi>} element has this form:
37656 <osabi>@var{abi-name}</osabi>
37659 @var{abi-name} is an OS ABI name from the same selection accepted by
37660 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
37662 @subsection Compatible Architecture
37663 @cindex @code{<compatible>}
37665 This optional field was introduced in @value{GDBN} version 7.0.
37666 Previous versions of @value{GDBN} ignore it.
37668 A @samp{<compatible>} element has this form:
37671 <compatible>@var{arch}</compatible>
37674 @var{arch} is one of the architectures from the set accepted by
37675 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
37677 A @samp{<compatible>} element is used to specify that the target
37678 is able to run binaries in some other than the main target architecture
37679 given by the @samp{<architecture>} element. For example, on the
37680 Cell Broadband Engine, the main architecture is @code{powerpc:common}
37681 or @code{powerpc:common64}, but the system is able to run binaries
37682 in the @code{spu} architecture as well. The way to describe this
37683 capability with @samp{<compatible>} is as follows:
37686 <architecture>powerpc:common</architecture>
37687 <compatible>spu</compatible>
37690 @subsection Features
37693 Each @samp{<feature>} describes some logical portion of the target
37694 system. Features are currently used to describe available CPU
37695 registers and the types of their contents. A @samp{<feature>} element
37699 <feature name="@var{name}">
37700 @r{[}@var{type}@dots{}@r{]}
37706 Each feature's name should be unique within the description. The name
37707 of a feature does not matter unless @value{GDBN} has some special
37708 knowledge of the contents of that feature; if it does, the feature
37709 should have its standard name. @xref{Standard Target Features}.
37713 Any register's value is a collection of bits which @value{GDBN} must
37714 interpret. The default interpretation is a two's complement integer,
37715 but other types can be requested by name in the register description.
37716 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
37717 Target Types}), and the description can define additional composite types.
37719 Each type element must have an @samp{id} attribute, which gives
37720 a unique (within the containing @samp{<feature>}) name to the type.
37721 Types must be defined before they are used.
37724 Some targets offer vector registers, which can be treated as arrays
37725 of scalar elements. These types are written as @samp{<vector>} elements,
37726 specifying the array element type, @var{type}, and the number of elements,
37730 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
37734 If a register's value is usefully viewed in multiple ways, define it
37735 with a union type containing the useful representations. The
37736 @samp{<union>} element contains one or more @samp{<field>} elements,
37737 each of which has a @var{name} and a @var{type}:
37740 <union id="@var{id}">
37741 <field name="@var{name}" type="@var{type}"/>
37747 If a register's value is composed from several separate values, define
37748 it with a structure type. There are two forms of the @samp{<struct>}
37749 element; a @samp{<struct>} element must either contain only bitfields
37750 or contain no bitfields. If the structure contains only bitfields,
37751 its total size in bytes must be specified, each bitfield must have an
37752 explicit start and end, and bitfields are automatically assigned an
37753 integer type. The field's @var{start} should be less than or
37754 equal to its @var{end}, and zero represents the least significant bit.
37757 <struct id="@var{id}" size="@var{size}">
37758 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
37763 If the structure contains no bitfields, then each field has an
37764 explicit type, and no implicit padding is added.
37767 <struct id="@var{id}">
37768 <field name="@var{name}" type="@var{type}"/>
37774 If a register's value is a series of single-bit flags, define it with
37775 a flags type. The @samp{<flags>} element has an explicit @var{size}
37776 and contains one or more @samp{<field>} elements. Each field has a
37777 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
37781 <flags id="@var{id}" size="@var{size}">
37782 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
37787 @subsection Registers
37790 Each register is represented as an element with this form:
37793 <reg name="@var{name}"
37794 bitsize="@var{size}"
37795 @r{[}regnum="@var{num}"@r{]}
37796 @r{[}save-restore="@var{save-restore}"@r{]}
37797 @r{[}type="@var{type}"@r{]}
37798 @r{[}group="@var{group}"@r{]}/>
37802 The components are as follows:
37807 The register's name; it must be unique within the target description.
37810 The register's size, in bits.
37813 The register's number. If omitted, a register's number is one greater
37814 than that of the previous register (either in the current feature or in
37815 a preceding feature); the first register in the target description
37816 defaults to zero. This register number is used to read or write
37817 the register; e.g.@: it is used in the remote @code{p} and @code{P}
37818 packets, and registers appear in the @code{g} and @code{G} packets
37819 in order of increasing register number.
37822 Whether the register should be preserved across inferior function
37823 calls; this must be either @code{yes} or @code{no}. The default is
37824 @code{yes}, which is appropriate for most registers except for
37825 some system control registers; this is not related to the target's
37829 The type of the register. @var{type} may be a predefined type, a type
37830 defined in the current feature, or one of the special types @code{int}
37831 and @code{float}. @code{int} is an integer type of the correct size
37832 for @var{bitsize}, and @code{float} is a floating point type (in the
37833 architecture's normal floating point format) of the correct size for
37834 @var{bitsize}. The default is @code{int}.
37837 The register group to which this register belongs. @var{group} must
37838 be either @code{general}, @code{float}, or @code{vector}. If no
37839 @var{group} is specified, @value{GDBN} will not display the register
37840 in @code{info registers}.
37844 @node Predefined Target Types
37845 @section Predefined Target Types
37846 @cindex target descriptions, predefined types
37848 Type definitions in the self-description can build up composite types
37849 from basic building blocks, but can not define fundamental types. Instead,
37850 standard identifiers are provided by @value{GDBN} for the fundamental
37851 types. The currently supported types are:
37860 Signed integer types holding the specified number of bits.
37867 Unsigned integer types holding the specified number of bits.
37871 Pointers to unspecified code and data. The program counter and
37872 any dedicated return address register may be marked as code
37873 pointers; printing a code pointer converts it into a symbolic
37874 address. The stack pointer and any dedicated address registers
37875 may be marked as data pointers.
37878 Single precision IEEE floating point.
37881 Double precision IEEE floating point.
37884 The 12-byte extended precision format used by ARM FPA registers.
37887 The 10-byte extended precision format used by x87 registers.
37890 32bit @sc{eflags} register used by x86.
37893 32bit @sc{mxcsr} register used by x86.
37897 @node Standard Target Features
37898 @section Standard Target Features
37899 @cindex target descriptions, standard features
37901 A target description must contain either no registers or all the
37902 target's registers. If the description contains no registers, then
37903 @value{GDBN} will assume a default register layout, selected based on
37904 the architecture. If the description contains any registers, the
37905 default layout will not be used; the standard registers must be
37906 described in the target description, in such a way that @value{GDBN}
37907 can recognize them.
37909 This is accomplished by giving specific names to feature elements
37910 which contain standard registers. @value{GDBN} will look for features
37911 with those names and verify that they contain the expected registers;
37912 if any known feature is missing required registers, or if any required
37913 feature is missing, @value{GDBN} will reject the target
37914 description. You can add additional registers to any of the
37915 standard features --- @value{GDBN} will display them just as if
37916 they were added to an unrecognized feature.
37918 This section lists the known features and their expected contents.
37919 Sample XML documents for these features are included in the
37920 @value{GDBN} source tree, in the directory @file{gdb/features}.
37922 Names recognized by @value{GDBN} should include the name of the
37923 company or organization which selected the name, and the overall
37924 architecture to which the feature applies; so e.g.@: the feature
37925 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
37927 The names of registers are not case sensitive for the purpose
37928 of recognizing standard features, but @value{GDBN} will only display
37929 registers using the capitalization used in the description.
37936 * PowerPC Features::
37942 @subsection ARM Features
37943 @cindex target descriptions, ARM features
37945 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
37947 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
37948 @samp{lr}, @samp{pc}, and @samp{cpsr}.
37950 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
37951 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
37952 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
37955 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
37956 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
37958 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
37959 it should contain at least registers @samp{wR0} through @samp{wR15} and
37960 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
37961 @samp{wCSSF}, and @samp{wCASF} registers are optional.
37963 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
37964 should contain at least registers @samp{d0} through @samp{d15}. If
37965 they are present, @samp{d16} through @samp{d31} should also be included.
37966 @value{GDBN} will synthesize the single-precision registers from
37967 halves of the double-precision registers.
37969 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
37970 need to contain registers; it instructs @value{GDBN} to display the
37971 VFP double-precision registers as vectors and to synthesize the
37972 quad-precision registers from pairs of double-precision registers.
37973 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
37974 be present and include 32 double-precision registers.
37976 @node i386 Features
37977 @subsection i386 Features
37978 @cindex target descriptions, i386 features
37980 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
37981 targets. It should describe the following registers:
37985 @samp{eax} through @samp{edi} plus @samp{eip} for i386
37987 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
37989 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
37990 @samp{fs}, @samp{gs}
37992 @samp{st0} through @samp{st7}
37994 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
37995 @samp{foseg}, @samp{fooff} and @samp{fop}
37998 The register sets may be different, depending on the target.
38000 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
38001 describe registers:
38005 @samp{xmm0} through @samp{xmm7} for i386
38007 @samp{xmm0} through @samp{xmm15} for amd64
38012 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
38013 @samp{org.gnu.gdb.i386.sse} feature. It should
38014 describe the upper 128 bits of @sc{ymm} registers:
38018 @samp{ymm0h} through @samp{ymm7h} for i386
38020 @samp{ymm0h} through @samp{ymm15h} for amd64
38023 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
38024 describe a single register, @samp{orig_eax}.
38026 @node MIPS Features
38027 @subsection MIPS Features
38028 @cindex target descriptions, MIPS features
38030 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
38031 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
38032 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
38035 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
38036 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
38037 registers. They may be 32-bit or 64-bit depending on the target.
38039 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
38040 it may be optional in a future version of @value{GDBN}. It should
38041 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
38042 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
38044 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
38045 contain a single register, @samp{restart}, which is used by the
38046 Linux kernel to control restartable syscalls.
38048 @node M68K Features
38049 @subsection M68K Features
38050 @cindex target descriptions, M68K features
38053 @item @samp{org.gnu.gdb.m68k.core}
38054 @itemx @samp{org.gnu.gdb.coldfire.core}
38055 @itemx @samp{org.gnu.gdb.fido.core}
38056 One of those features must be always present.
38057 The feature that is present determines which flavor of m68k is
38058 used. The feature that is present should contain registers
38059 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
38060 @samp{sp}, @samp{ps} and @samp{pc}.
38062 @item @samp{org.gnu.gdb.coldfire.fp}
38063 This feature is optional. If present, it should contain registers
38064 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
38068 @node PowerPC Features
38069 @subsection PowerPC Features
38070 @cindex target descriptions, PowerPC features
38072 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
38073 targets. It should contain registers @samp{r0} through @samp{r31},
38074 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
38075 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
38077 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
38078 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
38080 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
38081 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
38084 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
38085 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
38086 will combine these registers with the floating point registers
38087 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
38088 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
38089 through @samp{vs63}, the set of vector registers for POWER7.
38091 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
38092 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
38093 @samp{spefscr}. SPE targets should provide 32-bit registers in
38094 @samp{org.gnu.gdb.power.core} and provide the upper halves in
38095 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
38096 these to present registers @samp{ev0} through @samp{ev31} to the
38099 @node TIC6x Features
38100 @subsection TMS320C6x Features
38101 @cindex target descriptions, TIC6x features
38102 @cindex target descriptions, TMS320C6x features
38103 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
38104 targets. It should contain registers @samp{A0} through @samp{A15},
38105 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
38107 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
38108 contain registers @samp{A16} through @samp{A31} and @samp{B16}
38109 through @samp{B31}.
38111 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
38112 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
38114 @node Operating System Information
38115 @appendix Operating System Information
38116 @cindex operating system information
38122 Users of @value{GDBN} often wish to obtain information about the state of
38123 the operating system running on the target---for example the list of
38124 processes, or the list of open files. This section describes the
38125 mechanism that makes it possible. This mechanism is similar to the
38126 target features mechanism (@pxref{Target Descriptions}), but focuses
38127 on a different aspect of target.
38129 Operating system information is retrived from the target via the
38130 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
38131 read}). The object name in the request should be @samp{osdata}, and
38132 the @var{annex} identifies the data to be fetched.
38135 @appendixsection Process list
38136 @cindex operating system information, process list
38138 When requesting the process list, the @var{annex} field in the
38139 @samp{qXfer} request should be @samp{processes}. The returned data is
38140 an XML document. The formal syntax of this document is defined in
38141 @file{gdb/features/osdata.dtd}.
38143 An example document is:
38146 <?xml version="1.0"?>
38147 <!DOCTYPE target SYSTEM "osdata.dtd">
38148 <osdata type="processes">
38150 <column name="pid">1</column>
38151 <column name="user">root</column>
38152 <column name="command">/sbin/init</column>
38153 <column name="cores">1,2,3</column>
38158 Each item should include a column whose name is @samp{pid}. The value
38159 of that column should identify the process on the target. The
38160 @samp{user} and @samp{command} columns are optional, and will be
38161 displayed by @value{GDBN}. The @samp{cores} column, if present,
38162 should contain a comma-separated list of cores that this process
38163 is running on. Target may provide additional columns,
38164 which @value{GDBN} currently ignores.
38166 @node Trace File Format
38167 @appendix Trace File Format
38168 @cindex trace file format
38170 The trace file comes in three parts: a header, a textual description
38171 section, and a trace frame section with binary data.
38173 The header has the form @code{\x7fTRACE0\n}. The first byte is
38174 @code{0x7f} so as to indicate that the file contains binary data,
38175 while the @code{0} is a version number that may have different values
38178 The description section consists of multiple lines of @sc{ascii} text
38179 separated by newline characters (@code{0xa}). The lines may include a
38180 variety of optional descriptive or context-setting information, such
38181 as tracepoint definitions or register set size. @value{GDBN} will
38182 ignore any line that it does not recognize. An empty line marks the end
38185 @c FIXME add some specific types of data
38187 The trace frame section consists of a number of consecutive frames.
38188 Each frame begins with a two-byte tracepoint number, followed by a
38189 four-byte size giving the amount of data in the frame. The data in
38190 the frame consists of a number of blocks, each introduced by a
38191 character indicating its type (at least register, memory, and trace
38192 state variable). The data in this section is raw binary, not a
38193 hexadecimal or other encoding; its endianness matches the target's
38196 @c FIXME bi-arch may require endianness/arch info in description section
38199 @item R @var{bytes}
38200 Register block. The number and ordering of bytes matches that of a
38201 @code{g} packet in the remote protocol. Note that these are the
38202 actual bytes, in target order and @value{GDBN} register order, not a
38203 hexadecimal encoding.
38205 @item M @var{address} @var{length} @var{bytes}...
38206 Memory block. This is a contiguous block of memory, at the 8-byte
38207 address @var{address}, with a 2-byte length @var{length}, followed by
38208 @var{length} bytes.
38210 @item V @var{number} @var{value}
38211 Trace state variable block. This records the 8-byte signed value
38212 @var{value} of trace state variable numbered @var{number}.
38216 Future enhancements of the trace file format may include additional types
38219 @node Index Section Format
38220 @appendix @code{.gdb_index} section format
38221 @cindex .gdb_index section format
38222 @cindex index section format
38224 This section documents the index section that is created by @code{save
38225 gdb-index} (@pxref{Index Files}). The index section is
38226 DWARF-specific; some knowledge of DWARF is assumed in this
38229 The mapped index file format is designed to be directly
38230 @code{mmap}able on any architecture. In most cases, a datum is
38231 represented using a little-endian 32-bit integer value, called an
38232 @code{offset_type}. Big endian machines must byte-swap the values
38233 before using them. Exceptions to this rule are noted. The data is
38234 laid out such that alignment is always respected.
38236 A mapped index consists of several areas, laid out in order.
38240 The file header. This is a sequence of values, of @code{offset_type}
38241 unless otherwise noted:
38245 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
38246 Version 4 differs by its hashing function.
38249 The offset, from the start of the file, of the CU list.
38252 The offset, from the start of the file, of the types CU list. Note
38253 that this area can be empty, in which case this offset will be equal
38254 to the next offset.
38257 The offset, from the start of the file, of the address area.
38260 The offset, from the start of the file, of the symbol table.
38263 The offset, from the start of the file, of the constant pool.
38267 The CU list. This is a sequence of pairs of 64-bit little-endian
38268 values, sorted by the CU offset. The first element in each pair is
38269 the offset of a CU in the @code{.debug_info} section. The second
38270 element in each pair is the length of that CU. References to a CU
38271 elsewhere in the map are done using a CU index, which is just the
38272 0-based index into this table. Note that if there are type CUs, then
38273 conceptually CUs and type CUs form a single list for the purposes of
38277 The types CU list. This is a sequence of triplets of 64-bit
38278 little-endian values. In a triplet, the first value is the CU offset,
38279 the second value is the type offset in the CU, and the third value is
38280 the type signature. The types CU list is not sorted.
38283 The address area. The address area consists of a sequence of address
38284 entries. Each address entry has three elements:
38288 The low address. This is a 64-bit little-endian value.
38291 The high address. This is a 64-bit little-endian value. Like
38292 @code{DW_AT_high_pc}, the value is one byte beyond the end.
38295 The CU index. This is an @code{offset_type} value.
38299 The symbol table. This is an open-addressed hash table. The size of
38300 the hash table is always a power of 2.
38302 Each slot in the hash table consists of a pair of @code{offset_type}
38303 values. The first value is the offset of the symbol's name in the
38304 constant pool. The second value is the offset of the CU vector in the
38307 If both values are 0, then this slot in the hash table is empty. This
38308 is ok because while 0 is a valid constant pool index, it cannot be a
38309 valid index for both a string and a CU vector.
38311 The hash value for a table entry is computed by applying an
38312 iterative hash function to the symbol's name. Starting with an
38313 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
38314 the string is incorporated into the hash using the formula depending on the
38319 The formula is @code{r = r * 67 + c - 113}.
38322 The formula is @code{r = r * 67 + tolower (c) - 113}.
38325 The terminating @samp{\0} is not incorporated into the hash.
38327 The step size used in the hash table is computed via
38328 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
38329 value, and @samp{size} is the size of the hash table. The step size
38330 is used to find the next candidate slot when handling a hash
38333 The names of C@t{++} symbols in the hash table are canonicalized. We
38334 don't currently have a simple description of the canonicalization
38335 algorithm; if you intend to create new index sections, you must read
38339 The constant pool. This is simply a bunch of bytes. It is organized
38340 so that alignment is correct: CU vectors are stored first, followed by
38343 A CU vector in the constant pool is a sequence of @code{offset_type}
38344 values. The first value is the number of CU indices in the vector.
38345 Each subsequent value is the index of a CU in the CU list. This
38346 element in the hash table is used to indicate which CUs define the
38349 A string in the constant pool is zero-terminated.
38354 @node GNU Free Documentation License
38355 @appendix GNU Free Documentation License
38364 % I think something like @colophon should be in texinfo. In the
38366 \long\def\colophon{\hbox to0pt{}\vfill
38367 \centerline{The body of this manual is set in}
38368 \centerline{\fontname\tenrm,}
38369 \centerline{with headings in {\bf\fontname\tenbf}}
38370 \centerline{and examples in {\tt\fontname\tentt}.}
38371 \centerline{{\it\fontname\tenit\/},}
38372 \centerline{{\bf\fontname\tenbf}, and}
38373 \centerline{{\sl\fontname\tensl\/}}
38374 \centerline{are used for emphasis.}\vfill}
38376 % Blame: doc@cygnus.com, 1991.