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.
1351 @cindex shell escape
1352 @item shell @var{command-string}
1353 @itemx !@var{command-string}
1354 Invoke a standard shell to execute @var{command-string}.
1355 Note that no space is needed between @code{!} and @var{command-string}.
1356 If it exists, the environment variable @code{SHELL} determines which
1357 shell to run. Otherwise @value{GDBN} uses the default shell
1358 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1361 The utility @code{make} is often needed in development environments.
1362 You do not have to use the @code{shell} command for this purpose in
1367 @cindex calling make
1368 @item make @var{make-args}
1369 Execute the @code{make} program with the specified
1370 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1373 @node Logging Output
1374 @section Logging Output
1375 @cindex logging @value{GDBN} output
1376 @cindex save @value{GDBN} output to a file
1378 You may want to save the output of @value{GDBN} commands to a file.
1379 There are several commands to control @value{GDBN}'s logging.
1383 @item set logging on
1385 @item set logging off
1387 @cindex logging file name
1388 @item set logging file @var{file}
1389 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1390 @item set logging overwrite [on|off]
1391 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1392 you want @code{set logging on} to overwrite the logfile instead.
1393 @item set logging redirect [on|off]
1394 By default, @value{GDBN} output will go to both the terminal and the logfile.
1395 Set @code{redirect} if you want output to go only to the log file.
1396 @kindex show logging
1398 Show the current values of the logging settings.
1402 @chapter @value{GDBN} Commands
1404 You can abbreviate a @value{GDBN} command to the first few letters of the command
1405 name, if that abbreviation is unambiguous; and you can repeat certain
1406 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1407 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1408 show you the alternatives available, if there is more than one possibility).
1411 * Command Syntax:: How to give commands to @value{GDBN}
1412 * Completion:: Command completion
1413 * Help:: How to ask @value{GDBN} for help
1416 @node Command Syntax
1417 @section Command Syntax
1419 A @value{GDBN} command is a single line of input. There is no limit on
1420 how long it can be. It starts with a command name, which is followed by
1421 arguments whose meaning depends on the command name. For example, the
1422 command @code{step} accepts an argument which is the number of times to
1423 step, as in @samp{step 5}. You can also use the @code{step} command
1424 with no arguments. Some commands do not allow any arguments.
1426 @cindex abbreviation
1427 @value{GDBN} command names may always be truncated if that abbreviation is
1428 unambiguous. Other possible command abbreviations are listed in the
1429 documentation for individual commands. In some cases, even ambiguous
1430 abbreviations are allowed; for example, @code{s} is specially defined as
1431 equivalent to @code{step} even though there are other commands whose
1432 names start with @code{s}. You can test abbreviations by using them as
1433 arguments to the @code{help} command.
1435 @cindex repeating commands
1436 @kindex RET @r{(repeat last command)}
1437 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1438 repeat the previous command. Certain commands (for example, @code{run})
1439 will not repeat this way; these are commands whose unintentional
1440 repetition might cause trouble and which you are unlikely to want to
1441 repeat. User-defined commands can disable this feature; see
1442 @ref{Define, dont-repeat}.
1444 The @code{list} and @code{x} commands, when you repeat them with
1445 @key{RET}, construct new arguments rather than repeating
1446 exactly as typed. This permits easy scanning of source or memory.
1448 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1449 output, in a way similar to the common utility @code{more}
1450 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1451 @key{RET} too many in this situation, @value{GDBN} disables command
1452 repetition after any command that generates this sort of display.
1454 @kindex # @r{(a comment)}
1456 Any text from a @kbd{#} to the end of the line is a comment; it does
1457 nothing. This is useful mainly in command files (@pxref{Command
1458 Files,,Command Files}).
1460 @cindex repeating command sequences
1461 @kindex Ctrl-o @r{(operate-and-get-next)}
1462 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1463 commands. This command accepts the current line, like @key{RET}, and
1464 then fetches the next line relative to the current line from the history
1468 @section Command Completion
1471 @cindex word completion
1472 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1473 only one possibility; it can also show you what the valid possibilities
1474 are for the next word in a command, at any time. This works for @value{GDBN}
1475 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1477 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1478 of a word. If there is only one possibility, @value{GDBN} fills in the
1479 word, and waits for you to finish the command (or press @key{RET} to
1480 enter it). For example, if you type
1482 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1483 @c complete accuracy in these examples; space introduced for clarity.
1484 @c If texinfo enhancements make it unnecessary, it would be nice to
1485 @c replace " @key" by "@key" in the following...
1487 (@value{GDBP}) info bre @key{TAB}
1491 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1492 the only @code{info} subcommand beginning with @samp{bre}:
1495 (@value{GDBP}) info breakpoints
1499 You can either press @key{RET} at this point, to run the @code{info
1500 breakpoints} command, or backspace and enter something else, if
1501 @samp{breakpoints} does not look like the command you expected. (If you
1502 were sure you wanted @code{info breakpoints} in the first place, you
1503 might as well just type @key{RET} immediately after @samp{info bre},
1504 to exploit command abbreviations rather than command completion).
1506 If there is more than one possibility for the next word when you press
1507 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1508 characters and try again, or just press @key{TAB} a second time;
1509 @value{GDBN} displays all the possible completions for that word. For
1510 example, you might want to set a breakpoint on a subroutine whose name
1511 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1512 just sounds the bell. Typing @key{TAB} again displays all the
1513 function names in your program that begin with those characters, for
1517 (@value{GDBP}) b make_ @key{TAB}
1518 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1519 make_a_section_from_file make_environ
1520 make_abs_section make_function_type
1521 make_blockvector make_pointer_type
1522 make_cleanup make_reference_type
1523 make_command make_symbol_completion_list
1524 (@value{GDBP}) b make_
1528 After displaying the available possibilities, @value{GDBN} copies your
1529 partial input (@samp{b make_} in the example) so you can finish the
1532 If you just want to see the list of alternatives in the first place, you
1533 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1534 means @kbd{@key{META} ?}. You can type this either by holding down a
1535 key designated as the @key{META} shift on your keyboard (if there is
1536 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1538 @cindex quotes in commands
1539 @cindex completion of quoted strings
1540 Sometimes the string you need, while logically a ``word'', may contain
1541 parentheses or other characters that @value{GDBN} normally excludes from
1542 its notion of a word. To permit word completion to work in this
1543 situation, you may enclose words in @code{'} (single quote marks) in
1544 @value{GDBN} commands.
1546 The most likely situation where you might need this is in typing the
1547 name of a C@t{++} function. This is because C@t{++} allows function
1548 overloading (multiple definitions of the same function, distinguished
1549 by argument type). For example, when you want to set a breakpoint you
1550 may need to distinguish whether you mean the version of @code{name}
1551 that takes an @code{int} parameter, @code{name(int)}, or the version
1552 that takes a @code{float} parameter, @code{name(float)}. To use the
1553 word-completion facilities in this situation, type a single quote
1554 @code{'} at the beginning of the function name. This alerts
1555 @value{GDBN} that it may need to consider more information than usual
1556 when you press @key{TAB} or @kbd{M-?} to request word completion:
1559 (@value{GDBP}) b 'bubble( @kbd{M-?}
1560 bubble(double,double) bubble(int,int)
1561 (@value{GDBP}) b 'bubble(
1564 In some cases, @value{GDBN} can tell that completing a name requires using
1565 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1566 completing as much as it can) if you do not type the quote in the first
1570 (@value{GDBP}) b bub @key{TAB}
1571 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1572 (@value{GDBP}) b 'bubble(
1576 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1577 you have not yet started typing the argument list when you ask for
1578 completion on an overloaded symbol.
1580 For more information about overloaded functions, see @ref{C Plus Plus
1581 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1582 overload-resolution off} to disable overload resolution;
1583 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1585 @cindex completion of structure field names
1586 @cindex structure field name completion
1587 @cindex completion of union field names
1588 @cindex union field name completion
1589 When completing in an expression which looks up a field in a
1590 structure, @value{GDBN} also tries@footnote{The completer can be
1591 confused by certain kinds of invalid expressions. Also, it only
1592 examines the static type of the expression, not the dynamic type.} to
1593 limit completions to the field names available in the type of the
1597 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1598 magic to_fputs to_rewind
1599 to_data to_isatty to_write
1600 to_delete to_put to_write_async_safe
1605 This is because the @code{gdb_stdout} is a variable of the type
1606 @code{struct ui_file} that is defined in @value{GDBN} sources as
1613 ui_file_flush_ftype *to_flush;
1614 ui_file_write_ftype *to_write;
1615 ui_file_write_async_safe_ftype *to_write_async_safe;
1616 ui_file_fputs_ftype *to_fputs;
1617 ui_file_read_ftype *to_read;
1618 ui_file_delete_ftype *to_delete;
1619 ui_file_isatty_ftype *to_isatty;
1620 ui_file_rewind_ftype *to_rewind;
1621 ui_file_put_ftype *to_put;
1628 @section Getting Help
1629 @cindex online documentation
1632 You can always ask @value{GDBN} itself for information on its commands,
1633 using the command @code{help}.
1636 @kindex h @r{(@code{help})}
1639 You can use @code{help} (abbreviated @code{h}) with no arguments to
1640 display a short list of named classes of commands:
1644 List of classes of commands:
1646 aliases -- Aliases of other commands
1647 breakpoints -- Making program stop at certain points
1648 data -- Examining data
1649 files -- Specifying and examining files
1650 internals -- Maintenance commands
1651 obscure -- Obscure features
1652 running -- Running the program
1653 stack -- Examining the stack
1654 status -- Status inquiries
1655 support -- Support facilities
1656 tracepoints -- Tracing of program execution without
1657 stopping the program
1658 user-defined -- User-defined commands
1660 Type "help" followed by a class name for a list of
1661 commands in that class.
1662 Type "help" followed by command name for full
1664 Command name abbreviations are allowed if unambiguous.
1667 @c the above line break eliminates huge line overfull...
1669 @item help @var{class}
1670 Using one of the general help classes as an argument, you can get a
1671 list of the individual commands in that class. For example, here is the
1672 help display for the class @code{status}:
1675 (@value{GDBP}) help status
1680 @c Line break in "show" line falsifies real output, but needed
1681 @c to fit in smallbook page size.
1682 info -- Generic command for showing things
1683 about the program being debugged
1684 show -- Generic command for showing things
1687 Type "help" followed by command name for full
1689 Command name abbreviations are allowed if unambiguous.
1693 @item help @var{command}
1694 With a command name as @code{help} argument, @value{GDBN} displays a
1695 short paragraph on how to use that command.
1698 @item apropos @var{args}
1699 The @code{apropos} command searches through all of the @value{GDBN}
1700 commands, and their documentation, for the regular expression specified in
1701 @var{args}. It prints out all matches found. For example:
1712 set symbol-reloading -- Set dynamic symbol table reloading
1713 multiple times in one run
1714 show symbol-reloading -- Show dynamic symbol table reloading
1715 multiple times in one run
1720 @item complete @var{args}
1721 The @code{complete @var{args}} command lists all the possible completions
1722 for the beginning of a command. Use @var{args} to specify the beginning of the
1723 command you want completed. For example:
1729 @noindent results in:
1740 @noindent This is intended for use by @sc{gnu} Emacs.
1743 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1744 and @code{show} to inquire about the state of your program, or the state
1745 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1746 manual introduces each of them in the appropriate context. The listings
1747 under @code{info} and under @code{show} in the Index point to
1748 all the sub-commands. @xref{Index}.
1753 @kindex i @r{(@code{info})}
1755 This command (abbreviated @code{i}) is for describing the state of your
1756 program. For example, you can show the arguments passed to a function
1757 with @code{info args}, list the registers currently in use with @code{info
1758 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1759 You can get a complete list of the @code{info} sub-commands with
1760 @w{@code{help info}}.
1764 You can assign the result of an expression to an environment variable with
1765 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1766 @code{set prompt $}.
1770 In contrast to @code{info}, @code{show} is for describing the state of
1771 @value{GDBN} itself.
1772 You can change most of the things you can @code{show}, by using the
1773 related command @code{set}; for example, you can control what number
1774 system is used for displays with @code{set radix}, or simply inquire
1775 which is currently in use with @code{show radix}.
1778 To display all the settable parameters and their current
1779 values, you can use @code{show} with no arguments; you may also use
1780 @code{info set}. Both commands produce the same display.
1781 @c FIXME: "info set" violates the rule that "info" is for state of
1782 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1783 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1787 Here are three miscellaneous @code{show} subcommands, all of which are
1788 exceptional in lacking corresponding @code{set} commands:
1791 @kindex show version
1792 @cindex @value{GDBN} version number
1794 Show what version of @value{GDBN} is running. You should include this
1795 information in @value{GDBN} bug-reports. If multiple versions of
1796 @value{GDBN} are in use at your site, you may need to determine which
1797 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1798 commands are introduced, and old ones may wither away. Also, many
1799 system vendors ship variant versions of @value{GDBN}, and there are
1800 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1801 The version number is the same as the one announced when you start
1804 @kindex show copying
1805 @kindex info copying
1806 @cindex display @value{GDBN} copyright
1809 Display information about permission for copying @value{GDBN}.
1811 @kindex show warranty
1812 @kindex info warranty
1814 @itemx info warranty
1815 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1816 if your version of @value{GDBN} comes with one.
1821 @chapter Running Programs Under @value{GDBN}
1823 When you run a program under @value{GDBN}, you must first generate
1824 debugging information when you compile it.
1826 You may start @value{GDBN} with its arguments, if any, in an environment
1827 of your choice. If you are doing native debugging, you may redirect
1828 your program's input and output, debug an already running process, or
1829 kill a child process.
1832 * Compilation:: Compiling for debugging
1833 * Starting:: Starting your program
1834 * Arguments:: Your program's arguments
1835 * Environment:: Your program's environment
1837 * Working Directory:: Your program's working directory
1838 * Input/Output:: Your program's input and output
1839 * Attach:: Debugging an already-running process
1840 * Kill Process:: Killing the child process
1842 * Inferiors and Programs:: Debugging multiple inferiors and programs
1843 * Threads:: Debugging programs with multiple threads
1844 * Forks:: Debugging forks
1845 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1849 @section Compiling for Debugging
1851 In order to debug a program effectively, you need to generate
1852 debugging information when you compile it. This debugging information
1853 is stored in the object file; it describes the data type of each
1854 variable or function and the correspondence between source line numbers
1855 and addresses in the executable code.
1857 To request debugging information, specify the @samp{-g} option when you run
1860 Programs that are to be shipped to your customers are compiled with
1861 optimizations, using the @samp{-O} compiler option. However, some
1862 compilers are unable to handle the @samp{-g} and @samp{-O} options
1863 together. Using those compilers, you cannot generate optimized
1864 executables containing debugging information.
1866 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1867 without @samp{-O}, making it possible to debug optimized code. We
1868 recommend that you @emph{always} use @samp{-g} whenever you compile a
1869 program. You may think your program is correct, but there is no sense
1870 in pushing your luck. For more information, see @ref{Optimized Code}.
1872 Older versions of the @sc{gnu} C compiler permitted a variant option
1873 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1874 format; if your @sc{gnu} C compiler has this option, do not use it.
1876 @value{GDBN} knows about preprocessor macros and can show you their
1877 expansion (@pxref{Macros}). Most compilers do not include information
1878 about preprocessor macros in the debugging information if you specify
1879 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1880 the @sc{gnu} C compiler, provides macro information if you are using
1881 the DWARF debugging format, and specify the option @option{-g3}.
1883 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1884 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1885 information on @value{NGCC} options affecting debug information.
1887 You will have the best debugging experience if you use the latest
1888 version of the DWARF debugging format that your compiler supports.
1889 DWARF is currently the most expressive and best supported debugging
1890 format in @value{GDBN}.
1894 @section Starting your Program
1900 @kindex r @r{(@code{run})}
1903 Use the @code{run} command to start your program under @value{GDBN}.
1904 You must first specify the program name (except on VxWorks) with an
1905 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1906 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1907 (@pxref{Files, ,Commands to Specify Files}).
1911 If you are running your program in an execution environment that
1912 supports processes, @code{run} creates an inferior process and makes
1913 that process run your program. In some environments without processes,
1914 @code{run} jumps to the start of your program. Other targets,
1915 like @samp{remote}, are always running. If you get an error
1916 message like this one:
1919 The "remote" target does not support "run".
1920 Try "help target" or "continue".
1924 then use @code{continue} to run your program. You may need @code{load}
1925 first (@pxref{load}).
1927 The execution of a program is affected by certain information it
1928 receives from its superior. @value{GDBN} provides ways to specify this
1929 information, which you must do @emph{before} starting your program. (You
1930 can change it after starting your program, but such changes only affect
1931 your program the next time you start it.) This information may be
1932 divided into four categories:
1935 @item The @emph{arguments.}
1936 Specify the arguments to give your program as the arguments of the
1937 @code{run} command. If a shell is available on your target, the shell
1938 is used to pass the arguments, so that you may use normal conventions
1939 (such as wildcard expansion or variable substitution) in describing
1941 In Unix systems, you can control which shell is used with the
1942 @code{SHELL} environment variable.
1943 @xref{Arguments, ,Your Program's Arguments}.
1945 @item The @emph{environment.}
1946 Your program normally inherits its environment from @value{GDBN}, but you can
1947 use the @value{GDBN} commands @code{set environment} and @code{unset
1948 environment} to change parts of the environment that affect
1949 your program. @xref{Environment, ,Your Program's Environment}.
1951 @item The @emph{working directory.}
1952 Your program inherits its working directory from @value{GDBN}. You can set
1953 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1954 @xref{Working Directory, ,Your Program's Working Directory}.
1956 @item The @emph{standard input and output.}
1957 Your program normally uses the same device for standard input and
1958 standard output as @value{GDBN} is using. You can redirect input and output
1959 in the @code{run} command line, or you can use the @code{tty} command to
1960 set a different device for your program.
1961 @xref{Input/Output, ,Your Program's Input and Output}.
1964 @emph{Warning:} While input and output redirection work, you cannot use
1965 pipes to pass the output of the program you are debugging to another
1966 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1970 When you issue the @code{run} command, your program begins to execute
1971 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1972 of how to arrange for your program to stop. Once your program has
1973 stopped, you may call functions in your program, using the @code{print}
1974 or @code{call} commands. @xref{Data, ,Examining Data}.
1976 If the modification time of your symbol file has changed since the last
1977 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1978 table, and reads it again. When it does this, @value{GDBN} tries to retain
1979 your current breakpoints.
1984 @cindex run to main procedure
1985 The name of the main procedure can vary from language to language.
1986 With C or C@t{++}, the main procedure name is always @code{main}, but
1987 other languages such as Ada do not require a specific name for their
1988 main procedure. The debugger provides a convenient way to start the
1989 execution of the program and to stop at the beginning of the main
1990 procedure, depending on the language used.
1992 The @samp{start} command does the equivalent of setting a temporary
1993 breakpoint at the beginning of the main procedure and then invoking
1994 the @samp{run} command.
1996 @cindex elaboration phase
1997 Some programs contain an @dfn{elaboration} phase where some startup code is
1998 executed before the main procedure is called. This depends on the
1999 languages used to write your program. In C@t{++}, for instance,
2000 constructors for static and global objects are executed before
2001 @code{main} is called. It is therefore possible that the debugger stops
2002 before reaching the main procedure. However, the temporary breakpoint
2003 will remain to halt execution.
2005 Specify the arguments to give to your program as arguments to the
2006 @samp{start} command. These arguments will be given verbatim to the
2007 underlying @samp{run} command. Note that the same arguments will be
2008 reused if no argument is provided during subsequent calls to
2009 @samp{start} or @samp{run}.
2011 It is sometimes necessary to debug the program during elaboration. In
2012 these cases, using the @code{start} command would stop the execution of
2013 your program too late, as the program would have already completed the
2014 elaboration phase. Under these circumstances, insert breakpoints in your
2015 elaboration code before running your program.
2017 @kindex set exec-wrapper
2018 @item set exec-wrapper @var{wrapper}
2019 @itemx show exec-wrapper
2020 @itemx unset exec-wrapper
2021 When @samp{exec-wrapper} is set, the specified wrapper is used to
2022 launch programs for debugging. @value{GDBN} starts your program
2023 with a shell command of the form @kbd{exec @var{wrapper}
2024 @var{program}}. Quoting is added to @var{program} and its
2025 arguments, but not to @var{wrapper}, so you should add quotes if
2026 appropriate for your shell. The wrapper runs until it executes
2027 your program, and then @value{GDBN} takes control.
2029 You can use any program that eventually calls @code{execve} with
2030 its arguments as a wrapper. Several standard Unix utilities do
2031 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2032 with @code{exec "$@@"} will also work.
2034 For example, you can use @code{env} to pass an environment variable to
2035 the debugged program, without setting the variable in your shell's
2039 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2043 This command is available when debugging locally on most targets, excluding
2044 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2046 @kindex set disable-randomization
2047 @item set disable-randomization
2048 @itemx set disable-randomization on
2049 This option (enabled by default in @value{GDBN}) will turn off the native
2050 randomization of the virtual address space of the started program. This option
2051 is useful for multiple debugging sessions to make the execution better
2052 reproducible and memory addresses reusable across debugging sessions.
2054 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2055 On @sc{gnu}/Linux you can get the same behavior using
2058 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2061 @item set disable-randomization off
2062 Leave the behavior of the started executable unchanged. Some bugs rear their
2063 ugly heads only when the program is loaded at certain addresses. If your bug
2064 disappears when you run the program under @value{GDBN}, that might be because
2065 @value{GDBN} by default disables the address randomization on platforms, such
2066 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2067 disable-randomization off} to try to reproduce such elusive bugs.
2069 On targets where it is available, virtual address space randomization
2070 protects the programs against certain kinds of security attacks. In these
2071 cases the attacker needs to know the exact location of a concrete executable
2072 code. Randomizing its location makes it impossible to inject jumps misusing
2073 a code at its expected addresses.
2075 Prelinking shared libraries provides a startup performance advantage but it
2076 makes addresses in these libraries predictable for privileged processes by
2077 having just unprivileged access at the target system. Reading the shared
2078 library binary gives enough information for assembling the malicious code
2079 misusing it. Still even a prelinked shared library can get loaded at a new
2080 random address just requiring the regular relocation process during the
2081 startup. Shared libraries not already prelinked are always loaded at
2082 a randomly chosen address.
2084 Position independent executables (PIE) contain position independent code
2085 similar to the shared libraries and therefore such executables get loaded at
2086 a randomly chosen address upon startup. PIE executables always load even
2087 already prelinked shared libraries at a random address. You can build such
2088 executable using @command{gcc -fPIE -pie}.
2090 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2091 (as long as the randomization is enabled).
2093 @item show disable-randomization
2094 Show the current setting of the explicit disable of the native randomization of
2095 the virtual address space of the started program.
2100 @section Your Program's Arguments
2102 @cindex arguments (to your program)
2103 The arguments to your program can be specified by the arguments of the
2105 They are passed to a shell, which expands wildcard characters and
2106 performs redirection of I/O, and thence to your program. Your
2107 @code{SHELL} environment variable (if it exists) specifies what shell
2108 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2109 the default shell (@file{/bin/sh} on Unix).
2111 On non-Unix systems, the program is usually invoked directly by
2112 @value{GDBN}, which emulates I/O redirection via the appropriate system
2113 calls, and the wildcard characters are expanded by the startup code of
2114 the program, not by the shell.
2116 @code{run} with no arguments uses the same arguments used by the previous
2117 @code{run}, or those set by the @code{set args} command.
2122 Specify the arguments to be used the next time your program is run. If
2123 @code{set args} has no arguments, @code{run} executes your program
2124 with no arguments. Once you have run your program with arguments,
2125 using @code{set args} before the next @code{run} is the only way to run
2126 it again without arguments.
2130 Show the arguments to give your program when it is started.
2134 @section Your Program's Environment
2136 @cindex environment (of your program)
2137 The @dfn{environment} consists of a set of environment variables and
2138 their values. Environment variables conventionally record such things as
2139 your user name, your home directory, your terminal type, and your search
2140 path for programs to run. Usually you set up environment variables with
2141 the shell and they are inherited by all the other programs you run. When
2142 debugging, it can be useful to try running your program with a modified
2143 environment without having to start @value{GDBN} over again.
2147 @item path @var{directory}
2148 Add @var{directory} to the front of the @code{PATH} environment variable
2149 (the search path for executables) that will be passed to your program.
2150 The value of @code{PATH} used by @value{GDBN} does not change.
2151 You may specify several directory names, separated by whitespace or by a
2152 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2153 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2154 is moved to the front, so it is searched sooner.
2156 You can use the string @samp{$cwd} to refer to whatever is the current
2157 working directory at the time @value{GDBN} searches the path. If you
2158 use @samp{.} instead, it refers to the directory where you executed the
2159 @code{path} command. @value{GDBN} replaces @samp{.} in the
2160 @var{directory} argument (with the current path) before adding
2161 @var{directory} to the search path.
2162 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2163 @c document that, since repeating it would be a no-op.
2167 Display the list of search paths for executables (the @code{PATH}
2168 environment variable).
2170 @kindex show environment
2171 @item show environment @r{[}@var{varname}@r{]}
2172 Print the value of environment variable @var{varname} to be given to
2173 your program when it starts. If you do not supply @var{varname},
2174 print the names and values of all environment variables to be given to
2175 your program. You can abbreviate @code{environment} as @code{env}.
2177 @kindex set environment
2178 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2179 Set environment variable @var{varname} to @var{value}. The value
2180 changes for your program only, not for @value{GDBN} itself. @var{value} may
2181 be any string; the values of environment variables are just strings, and
2182 any interpretation is supplied by your program itself. The @var{value}
2183 parameter is optional; if it is eliminated, the variable is set to a
2185 @c "any string" here does not include leading, trailing
2186 @c blanks. Gnu asks: does anyone care?
2188 For example, this command:
2195 tells the debugged program, when subsequently run, that its user is named
2196 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2197 are not actually required.)
2199 @kindex unset environment
2200 @item unset environment @var{varname}
2201 Remove variable @var{varname} from the environment to be passed to your
2202 program. This is different from @samp{set env @var{varname} =};
2203 @code{unset environment} removes the variable from the environment,
2204 rather than assigning it an empty value.
2207 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2209 by your @code{SHELL} environment variable if it exists (or
2210 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2211 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2212 @file{.bashrc} for BASH---any variables you set in that file affect
2213 your program. You may wish to move setting of environment variables to
2214 files that are only run when you sign on, such as @file{.login} or
2217 @node Working Directory
2218 @section Your Program's Working Directory
2220 @cindex working directory (of your program)
2221 Each time you start your program with @code{run}, it inherits its
2222 working directory from the current working directory of @value{GDBN}.
2223 The @value{GDBN} working directory is initially whatever it inherited
2224 from its parent process (typically the shell), but you can specify a new
2225 working directory in @value{GDBN} with the @code{cd} command.
2227 The @value{GDBN} working directory also serves as a default for the commands
2228 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2233 @cindex change working directory
2234 @item cd @var{directory}
2235 Set the @value{GDBN} working directory to @var{directory}.
2239 Print the @value{GDBN} working directory.
2242 It is generally impossible to find the current working directory of
2243 the process being debugged (since a program can change its directory
2244 during its run). If you work on a system where @value{GDBN} is
2245 configured with the @file{/proc} support, you can use the @code{info
2246 proc} command (@pxref{SVR4 Process Information}) to find out the
2247 current working directory of the debuggee.
2250 @section Your Program's Input and Output
2255 By default, the program you run under @value{GDBN} does input and output to
2256 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2257 to its own terminal modes to interact with you, but it records the terminal
2258 modes your program was using and switches back to them when you continue
2259 running your program.
2262 @kindex info terminal
2264 Displays information recorded by @value{GDBN} about the terminal modes your
2268 You can redirect your program's input and/or output using shell
2269 redirection with the @code{run} command. For example,
2276 starts your program, diverting its output to the file @file{outfile}.
2279 @cindex controlling terminal
2280 Another way to specify where your program should do input and output is
2281 with the @code{tty} command. This command accepts a file name as
2282 argument, and causes this file to be the default for future @code{run}
2283 commands. It also resets the controlling terminal for the child
2284 process, for future @code{run} commands. For example,
2291 directs that processes started with subsequent @code{run} commands
2292 default to do input and output on the terminal @file{/dev/ttyb} and have
2293 that as their controlling terminal.
2295 An explicit redirection in @code{run} overrides the @code{tty} command's
2296 effect on the input/output device, but not its effect on the controlling
2299 When you use the @code{tty} command or redirect input in the @code{run}
2300 command, only the input @emph{for your program} is affected. The input
2301 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2302 for @code{set inferior-tty}.
2304 @cindex inferior tty
2305 @cindex set inferior controlling terminal
2306 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2307 display the name of the terminal that will be used for future runs of your
2311 @item set inferior-tty /dev/ttyb
2312 @kindex set inferior-tty
2313 Set the tty for the program being debugged to /dev/ttyb.
2315 @item show inferior-tty
2316 @kindex show inferior-tty
2317 Show the current tty for the program being debugged.
2321 @section Debugging an Already-running Process
2326 @item attach @var{process-id}
2327 This command attaches to a running process---one that was started
2328 outside @value{GDBN}. (@code{info files} shows your active
2329 targets.) The command takes as argument a process ID. The usual way to
2330 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2331 or with the @samp{jobs -l} shell command.
2333 @code{attach} does not repeat if you press @key{RET} a second time after
2334 executing the command.
2337 To use @code{attach}, your program must be running in an environment
2338 which supports processes; for example, @code{attach} does not work for
2339 programs on bare-board targets that lack an operating system. You must
2340 also have permission to send the process a signal.
2342 When you use @code{attach}, the debugger finds the program running in
2343 the process first by looking in the current working directory, then (if
2344 the program is not found) by using the source file search path
2345 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2346 the @code{file} command to load the program. @xref{Files, ,Commands to
2349 The first thing @value{GDBN} does after arranging to debug the specified
2350 process is to stop it. You can examine and modify an attached process
2351 with all the @value{GDBN} commands that are ordinarily available when
2352 you start processes with @code{run}. You can insert breakpoints; you
2353 can step and continue; you can modify storage. If you would rather the
2354 process continue running, you may use the @code{continue} command after
2355 attaching @value{GDBN} to the process.
2360 When you have finished debugging the attached process, you can use the
2361 @code{detach} command to release it from @value{GDBN} control. Detaching
2362 the process continues its execution. After the @code{detach} command,
2363 that process and @value{GDBN} become completely independent once more, and you
2364 are ready to @code{attach} another process or start one with @code{run}.
2365 @code{detach} does not repeat if you press @key{RET} again after
2366 executing the command.
2369 If you exit @value{GDBN} while you have an attached process, you detach
2370 that process. If you use the @code{run} command, you kill that process.
2371 By default, @value{GDBN} asks for confirmation if you try to do either of these
2372 things; you can control whether or not you need to confirm by using the
2373 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2377 @section Killing the Child Process
2382 Kill the child process in which your program is running under @value{GDBN}.
2385 This command is useful if you wish to debug a core dump instead of a
2386 running process. @value{GDBN} ignores any core dump file while your program
2389 On some operating systems, a program cannot be executed outside @value{GDBN}
2390 while you have breakpoints set on it inside @value{GDBN}. You can use the
2391 @code{kill} command in this situation to permit running your program
2392 outside the debugger.
2394 The @code{kill} command is also useful if you wish to recompile and
2395 relink your program, since on many systems it is impossible to modify an
2396 executable file while it is running in a process. In this case, when you
2397 next type @code{run}, @value{GDBN} notices that the file has changed, and
2398 reads the symbol table again (while trying to preserve your current
2399 breakpoint settings).
2401 @node Inferiors and Programs
2402 @section Debugging Multiple Inferiors and Programs
2404 @value{GDBN} lets you run and debug multiple programs in a single
2405 session. In addition, @value{GDBN} on some systems may let you run
2406 several programs simultaneously (otherwise you have to exit from one
2407 before starting another). In the most general case, you can have
2408 multiple threads of execution in each of multiple processes, launched
2409 from multiple executables.
2412 @value{GDBN} represents the state of each program execution with an
2413 object called an @dfn{inferior}. An inferior typically corresponds to
2414 a process, but is more general and applies also to targets that do not
2415 have processes. Inferiors may be created before a process runs, and
2416 may be retained after a process exits. Inferiors have unique
2417 identifiers that are different from process ids. Usually each
2418 inferior will also have its own distinct address space, although some
2419 embedded targets may have several inferiors running in different parts
2420 of a single address space. Each inferior may in turn have multiple
2421 threads running in it.
2423 To find out what inferiors exist at any moment, use @w{@code{info
2427 @kindex info inferiors
2428 @item info inferiors
2429 Print a list of all inferiors currently being managed by @value{GDBN}.
2431 @value{GDBN} displays for each inferior (in this order):
2435 the inferior number assigned by @value{GDBN}
2438 the target system's inferior identifier
2441 the name of the executable the inferior is running.
2446 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2447 indicates the current inferior.
2451 @c end table here to get a little more width for example
2454 (@value{GDBP}) info inferiors
2455 Num Description Executable
2456 2 process 2307 hello
2457 * 1 process 3401 goodbye
2460 To switch focus between inferiors, use the @code{inferior} command:
2463 @kindex inferior @var{infno}
2464 @item inferior @var{infno}
2465 Make inferior number @var{infno} the current inferior. The argument
2466 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2467 in the first field of the @samp{info inferiors} display.
2471 You can get multiple executables into a debugging session via the
2472 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2473 systems @value{GDBN} can add inferiors to the debug session
2474 automatically by following calls to @code{fork} and @code{exec}. To
2475 remove inferiors from the debugging session use the
2476 @w{@code{remove-inferiors}} command.
2479 @kindex add-inferior
2480 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2481 Adds @var{n} inferiors to be run using @var{executable} as the
2482 executable. @var{n} defaults to 1. If no executable is specified,
2483 the inferiors begins empty, with no program. You can still assign or
2484 change the program assigned to the inferior at any time by using the
2485 @code{file} command with the executable name as its argument.
2487 @kindex clone-inferior
2488 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2489 Adds @var{n} inferiors ready to execute the same program as inferior
2490 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2491 number of the current inferior. This is a convenient command when you
2492 want to run another instance of the inferior you are debugging.
2495 (@value{GDBP}) info inferiors
2496 Num Description Executable
2497 * 1 process 29964 helloworld
2498 (@value{GDBP}) clone-inferior
2501 (@value{GDBP}) info inferiors
2502 Num Description Executable
2504 * 1 process 29964 helloworld
2507 You can now simply switch focus to inferior 2 and run it.
2509 @kindex remove-inferiors
2510 @item remove-inferiors @var{infno}@dots{}
2511 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2512 possible to remove an inferior that is running with this command. For
2513 those, use the @code{kill} or @code{detach} command first.
2517 To quit debugging one of the running inferiors that is not the current
2518 inferior, you can either detach from it by using the @w{@code{detach
2519 inferior}} command (allowing it to run independently), or kill it
2520 using the @w{@code{kill inferiors}} command:
2523 @kindex detach inferiors @var{infno}@dots{}
2524 @item detach inferior @var{infno}@dots{}
2525 Detach from the inferior or inferiors identified by @value{GDBN}
2526 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2527 still stays on the list of inferiors shown by @code{info inferiors},
2528 but its Description will show @samp{<null>}.
2530 @kindex kill inferiors @var{infno}@dots{}
2531 @item kill inferiors @var{infno}@dots{}
2532 Kill the inferior or inferiors identified by @value{GDBN} inferior
2533 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2534 stays on the list of inferiors shown by @code{info inferiors}, but its
2535 Description will show @samp{<null>}.
2538 After the successful completion of a command such as @code{detach},
2539 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2540 a normal process exit, the inferior is still valid and listed with
2541 @code{info inferiors}, ready to be restarted.
2544 To be notified when inferiors are started or exit under @value{GDBN}'s
2545 control use @w{@code{set print inferior-events}}:
2548 @kindex set print inferior-events
2549 @cindex print messages on inferior start and exit
2550 @item set print inferior-events
2551 @itemx set print inferior-events on
2552 @itemx set print inferior-events off
2553 The @code{set print inferior-events} command allows you to enable or
2554 disable printing of messages when @value{GDBN} notices that new
2555 inferiors have started or that inferiors have exited or have been
2556 detached. By default, these messages will not be printed.
2558 @kindex show print inferior-events
2559 @item show print inferior-events
2560 Show whether messages will be printed when @value{GDBN} detects that
2561 inferiors have started, exited or have been detached.
2564 Many commands will work the same with multiple programs as with a
2565 single program: e.g., @code{print myglobal} will simply display the
2566 value of @code{myglobal} in the current inferior.
2569 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2570 get more info about the relationship of inferiors, programs, address
2571 spaces in a debug session. You can do that with the @w{@code{maint
2572 info program-spaces}} command.
2575 @kindex maint info program-spaces
2576 @item maint info program-spaces
2577 Print a list of all program spaces currently being managed by
2580 @value{GDBN} displays for each program space (in this order):
2584 the program space number assigned by @value{GDBN}
2587 the name of the executable loaded into the program space, with e.g.,
2588 the @code{file} command.
2593 An asterisk @samp{*} preceding the @value{GDBN} program space number
2594 indicates the current program space.
2596 In addition, below each program space line, @value{GDBN} prints extra
2597 information that isn't suitable to display in tabular form. For
2598 example, the list of inferiors bound to the program space.
2601 (@value{GDBP}) maint info program-spaces
2604 Bound inferiors: ID 1 (process 21561)
2608 Here we can see that no inferior is running the program @code{hello},
2609 while @code{process 21561} is running the program @code{goodbye}. On
2610 some targets, it is possible that multiple inferiors are bound to the
2611 same program space. The most common example is that of debugging both
2612 the parent and child processes of a @code{vfork} call. For example,
2615 (@value{GDBP}) maint info program-spaces
2618 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2621 Here, both inferior 2 and inferior 1 are running in the same program
2622 space as a result of inferior 1 having executed a @code{vfork} call.
2626 @section Debugging Programs with Multiple Threads
2628 @cindex threads of execution
2629 @cindex multiple threads
2630 @cindex switching threads
2631 In some operating systems, such as HP-UX and Solaris, a single program
2632 may have more than one @dfn{thread} of execution. The precise semantics
2633 of threads differ from one operating system to another, but in general
2634 the threads of a single program are akin to multiple processes---except
2635 that they share one address space (that is, they can all examine and
2636 modify the same variables). On the other hand, each thread has its own
2637 registers and execution stack, and perhaps private memory.
2639 @value{GDBN} provides these facilities for debugging multi-thread
2643 @item automatic notification of new threads
2644 @item @samp{thread @var{threadno}}, a command to switch among threads
2645 @item @samp{info threads}, a command to inquire about existing threads
2646 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2647 a command to apply a command to a list of threads
2648 @item thread-specific breakpoints
2649 @item @samp{set print thread-events}, which controls printing of
2650 messages on thread start and exit.
2651 @item @samp{set libthread-db-search-path @var{path}}, which lets
2652 the user specify which @code{libthread_db} to use if the default choice
2653 isn't compatible with the program.
2657 @emph{Warning:} These facilities are not yet available on every
2658 @value{GDBN} configuration where the operating system supports threads.
2659 If your @value{GDBN} does not support threads, these commands have no
2660 effect. For example, a system without thread support shows no output
2661 from @samp{info threads}, and always rejects the @code{thread} command,
2665 (@value{GDBP}) info threads
2666 (@value{GDBP}) thread 1
2667 Thread ID 1 not known. Use the "info threads" command to
2668 see the IDs of currently known threads.
2670 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2671 @c doesn't support threads"?
2674 @cindex focus of debugging
2675 @cindex current thread
2676 The @value{GDBN} thread debugging facility allows you to observe all
2677 threads while your program runs---but whenever @value{GDBN} takes
2678 control, one thread in particular is always the focus of debugging.
2679 This thread is called the @dfn{current thread}. Debugging commands show
2680 program information from the perspective of the current thread.
2682 @cindex @code{New} @var{systag} message
2683 @cindex thread identifier (system)
2684 @c FIXME-implementors!! It would be more helpful if the [New...] message
2685 @c included GDB's numeric thread handle, so you could just go to that
2686 @c thread without first checking `info threads'.
2687 Whenever @value{GDBN} detects a new thread in your program, it displays
2688 the target system's identification for the thread with a message in the
2689 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2690 whose form varies depending on the particular system. For example, on
2691 @sc{gnu}/Linux, you might see
2694 [New Thread 0x41e02940 (LWP 25582)]
2698 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2699 the @var{systag} is simply something like @samp{process 368}, with no
2702 @c FIXME!! (1) Does the [New...] message appear even for the very first
2703 @c thread of a program, or does it only appear for the
2704 @c second---i.e.@: when it becomes obvious we have a multithread
2706 @c (2) *Is* there necessarily a first thread always? Or do some
2707 @c multithread systems permit starting a program with multiple
2708 @c threads ab initio?
2710 @cindex thread number
2711 @cindex thread identifier (GDB)
2712 For debugging purposes, @value{GDBN} associates its own thread
2713 number---always a single integer---with each thread in your program.
2716 @kindex info threads
2717 @item info threads @r{[}@var{id}@dots{}@r{]}
2718 Display a summary of all threads currently in your program. Optional
2719 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2720 means to print information only about the specified thread or threads.
2721 @value{GDBN} displays for each thread (in this order):
2725 the thread number assigned by @value{GDBN}
2728 the target system's thread identifier (@var{systag})
2731 the thread's name, if one is known. A thread can either be named by
2732 the user (see @code{thread name}, below), or, in some cases, by the
2736 the current stack frame summary for that thread
2740 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2741 indicates the current thread.
2745 @c end table here to get a little more width for example
2748 (@value{GDBP}) info threads
2750 3 process 35 thread 27 0x34e5 in sigpause ()
2751 2 process 35 thread 23 0x34e5 in sigpause ()
2752 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2756 On Solaris, you can display more information about user threads with a
2757 Solaris-specific command:
2760 @item maint info sol-threads
2761 @kindex maint info sol-threads
2762 @cindex thread info (Solaris)
2763 Display info on Solaris user threads.
2767 @kindex thread @var{threadno}
2768 @item thread @var{threadno}
2769 Make thread number @var{threadno} the current thread. The command
2770 argument @var{threadno} is the internal @value{GDBN} thread number, as
2771 shown in the first field of the @samp{info threads} display.
2772 @value{GDBN} responds by displaying the system identifier of the thread
2773 you selected, and its current stack frame summary:
2776 (@value{GDBP}) thread 2
2777 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2778 #0 some_function (ignore=0x0) at example.c:8
2779 8 printf ("hello\n");
2783 As with the @samp{[New @dots{}]} message, the form of the text after
2784 @samp{Switching to} depends on your system's conventions for identifying
2787 @vindex $_thread@r{, convenience variable}
2788 The debugger convenience variable @samp{$_thread} contains the number
2789 of the current thread. You may find this useful in writing breakpoint
2790 conditional expressions, command scripts, and so forth. See
2791 @xref{Convenience Vars,, Convenience Variables}, for general
2792 information on convenience variables.
2794 @kindex thread apply
2795 @cindex apply command to several threads
2796 @item thread apply [@var{threadno} | all] @var{command}
2797 The @code{thread apply} command allows you to apply the named
2798 @var{command} to one or more threads. Specify the numbers of the
2799 threads that you want affected with the command argument
2800 @var{threadno}. It can be a single thread number, one of the numbers
2801 shown in the first field of the @samp{info threads} display; or it
2802 could be a range of thread numbers, as in @code{2-4}. To apply a
2803 command to all threads, type @kbd{thread apply all @var{command}}.
2806 @cindex name a thread
2807 @item thread name [@var{name}]
2808 This command assigns a name to the current thread. If no argument is
2809 given, any existing user-specified name is removed. The thread name
2810 appears in the @samp{info threads} display.
2812 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2813 determine the name of the thread as given by the OS. On these
2814 systems, a name specified with @samp{thread name} will override the
2815 system-give name, and removing the user-specified name will cause
2816 @value{GDBN} to once again display the system-specified name.
2819 @cindex search for a thread
2820 @item thread find [@var{regexp}]
2821 Search for and display thread ids whose name or @var{systag}
2822 matches the supplied regular expression.
2824 As well as being the complement to the @samp{thread name} command,
2825 this command also allows you to identify a thread by its target
2826 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2830 (@value{GDBN}) thread find 26688
2831 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2832 (@value{GDBN}) info thread 4
2834 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2837 @kindex set print thread-events
2838 @cindex print messages on thread start and exit
2839 @item set print thread-events
2840 @itemx set print thread-events on
2841 @itemx set print thread-events off
2842 The @code{set print thread-events} command allows you to enable or
2843 disable printing of messages when @value{GDBN} notices that new threads have
2844 started or that threads have exited. By default, these messages will
2845 be printed if detection of these events is supported by the target.
2846 Note that these messages cannot be disabled on all targets.
2848 @kindex show print thread-events
2849 @item show print thread-events
2850 Show whether messages will be printed when @value{GDBN} detects that threads
2851 have started and exited.
2854 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2855 more information about how @value{GDBN} behaves when you stop and start
2856 programs with multiple threads.
2858 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2859 watchpoints in programs with multiple threads.
2862 @kindex set libthread-db-search-path
2863 @cindex search path for @code{libthread_db}
2864 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2865 If this variable is set, @var{path} is a colon-separated list of
2866 directories @value{GDBN} will use to search for @code{libthread_db}.
2867 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2868 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2869 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2872 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2873 @code{libthread_db} library to obtain information about threads in the
2874 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2875 to find @code{libthread_db}.
2877 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2878 refers to the default system directories that are
2879 normally searched for loading shared libraries.
2881 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2882 refers to the directory from which @code{libpthread}
2883 was loaded in the inferior process.
2885 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2886 @value{GDBN} attempts to initialize it with the current inferior process.
2887 If this initialization fails (which could happen because of a version
2888 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2889 will unload @code{libthread_db}, and continue with the next directory.
2890 If none of @code{libthread_db} libraries initialize successfully,
2891 @value{GDBN} will issue a warning and thread debugging will be disabled.
2893 Setting @code{libthread-db-search-path} is currently implemented
2894 only on some platforms.
2896 @kindex show libthread-db-search-path
2897 @item show libthread-db-search-path
2898 Display current libthread_db search path.
2900 @kindex set debug libthread-db
2901 @kindex show debug libthread-db
2902 @cindex debugging @code{libthread_db}
2903 @item set debug libthread-db
2904 @itemx show debug libthread-db
2905 Turns on or off display of @code{libthread_db}-related events.
2906 Use @code{1} to enable, @code{0} to disable.
2910 @section Debugging Forks
2912 @cindex fork, debugging programs which call
2913 @cindex multiple processes
2914 @cindex processes, multiple
2915 On most systems, @value{GDBN} has no special support for debugging
2916 programs which create additional processes using the @code{fork}
2917 function. When a program forks, @value{GDBN} will continue to debug the
2918 parent process and the child process will run unimpeded. If you have
2919 set a breakpoint in any code which the child then executes, the child
2920 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2921 will cause it to terminate.
2923 However, if you want to debug the child process there is a workaround
2924 which isn't too painful. Put a call to @code{sleep} in the code which
2925 the child process executes after the fork. It may be useful to sleep
2926 only if a certain environment variable is set, or a certain file exists,
2927 so that the delay need not occur when you don't want to run @value{GDBN}
2928 on the child. While the child is sleeping, use the @code{ps} program to
2929 get its process ID. Then tell @value{GDBN} (a new invocation of
2930 @value{GDBN} if you are also debugging the parent process) to attach to
2931 the child process (@pxref{Attach}). From that point on you can debug
2932 the child process just like any other process which you attached to.
2934 On some systems, @value{GDBN} provides support for debugging programs that
2935 create additional processes using the @code{fork} or @code{vfork} functions.
2936 Currently, the only platforms with this feature are HP-UX (11.x and later
2937 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2939 By default, when a program forks, @value{GDBN} will continue to debug
2940 the parent process and the child process will run unimpeded.
2942 If you want to follow the child process instead of the parent process,
2943 use the command @w{@code{set follow-fork-mode}}.
2946 @kindex set follow-fork-mode
2947 @item set follow-fork-mode @var{mode}
2948 Set the debugger response to a program call of @code{fork} or
2949 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2950 process. The @var{mode} argument can be:
2954 The original process is debugged after a fork. The child process runs
2955 unimpeded. This is the default.
2958 The new process is debugged after a fork. The parent process runs
2963 @kindex show follow-fork-mode
2964 @item show follow-fork-mode
2965 Display the current debugger response to a @code{fork} or @code{vfork} call.
2968 @cindex debugging multiple processes
2969 On Linux, if you want to debug both the parent and child processes, use the
2970 command @w{@code{set detach-on-fork}}.
2973 @kindex set detach-on-fork
2974 @item set detach-on-fork @var{mode}
2975 Tells gdb whether to detach one of the processes after a fork, or
2976 retain debugger control over them both.
2980 The child process (or parent process, depending on the value of
2981 @code{follow-fork-mode}) will be detached and allowed to run
2982 independently. This is the default.
2985 Both processes will be held under the control of @value{GDBN}.
2986 One process (child or parent, depending on the value of
2987 @code{follow-fork-mode}) is debugged as usual, while the other
2992 @kindex show detach-on-fork
2993 @item show detach-on-fork
2994 Show whether detach-on-fork mode is on/off.
2997 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2998 will retain control of all forked processes (including nested forks).
2999 You can list the forked processes under the control of @value{GDBN} by
3000 using the @w{@code{info inferiors}} command, and switch from one fork
3001 to another by using the @code{inferior} command (@pxref{Inferiors and
3002 Programs, ,Debugging Multiple Inferiors and Programs}).
3004 To quit debugging one of the forked processes, you can either detach
3005 from it by using the @w{@code{detach inferiors}} command (allowing it
3006 to run independently), or kill it using the @w{@code{kill inferiors}}
3007 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3010 If you ask to debug a child process and a @code{vfork} is followed by an
3011 @code{exec}, @value{GDBN} executes the new target up to the first
3012 breakpoint in the new target. If you have a breakpoint set on
3013 @code{main} in your original program, the breakpoint will also be set on
3014 the child process's @code{main}.
3016 On some systems, when a child process is spawned by @code{vfork}, you
3017 cannot debug the child or parent until an @code{exec} call completes.
3019 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3020 call executes, the new target restarts. To restart the parent
3021 process, use the @code{file} command with the parent executable name
3022 as its argument. By default, after an @code{exec} call executes,
3023 @value{GDBN} discards the symbols of the previous executable image.
3024 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3028 @kindex set follow-exec-mode
3029 @item set follow-exec-mode @var{mode}
3031 Set debugger response to a program call of @code{exec}. An
3032 @code{exec} call replaces the program image of a process.
3034 @code{follow-exec-mode} can be:
3038 @value{GDBN} creates a new inferior and rebinds the process to this
3039 new inferior. The program the process was running before the
3040 @code{exec} call can be restarted afterwards by restarting the
3046 (@value{GDBP}) info inferiors
3048 Id Description Executable
3051 process 12020 is executing new program: prog2
3052 Program exited normally.
3053 (@value{GDBP}) info inferiors
3054 Id Description Executable
3060 @value{GDBN} keeps the process bound to the same inferior. The new
3061 executable image replaces the previous executable loaded in the
3062 inferior. Restarting the inferior after the @code{exec} call, with
3063 e.g., the @code{run} command, restarts the executable the process was
3064 running after the @code{exec} call. This is the default mode.
3069 (@value{GDBP}) info inferiors
3070 Id Description Executable
3073 process 12020 is executing new program: prog2
3074 Program exited normally.
3075 (@value{GDBP}) info inferiors
3076 Id Description Executable
3083 You can use the @code{catch} command to make @value{GDBN} stop whenever
3084 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3085 Catchpoints, ,Setting Catchpoints}.
3087 @node Checkpoint/Restart
3088 @section Setting a @emph{Bookmark} to Return to Later
3093 @cindex snapshot of a process
3094 @cindex rewind program state
3096 On certain operating systems@footnote{Currently, only
3097 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3098 program's state, called a @dfn{checkpoint}, and come back to it
3101 Returning to a checkpoint effectively undoes everything that has
3102 happened in the program since the @code{checkpoint} was saved. This
3103 includes changes in memory, registers, and even (within some limits)
3104 system state. Effectively, it is like going back in time to the
3105 moment when the checkpoint was saved.
3107 Thus, if you're stepping thru a program and you think you're
3108 getting close to the point where things go wrong, you can save
3109 a checkpoint. Then, if you accidentally go too far and miss
3110 the critical statement, instead of having to restart your program
3111 from the beginning, you can just go back to the checkpoint and
3112 start again from there.
3114 This can be especially useful if it takes a lot of time or
3115 steps to reach the point where you think the bug occurs.
3117 To use the @code{checkpoint}/@code{restart} method of debugging:
3122 Save a snapshot of the debugged program's current execution state.
3123 The @code{checkpoint} command takes no arguments, but each checkpoint
3124 is assigned a small integer id, similar to a breakpoint id.
3126 @kindex info checkpoints
3127 @item info checkpoints
3128 List the checkpoints that have been saved in the current debugging
3129 session. For each checkpoint, the following information will be
3136 @item Source line, or label
3139 @kindex restart @var{checkpoint-id}
3140 @item restart @var{checkpoint-id}
3141 Restore the program state that was saved as checkpoint number
3142 @var{checkpoint-id}. All program variables, registers, stack frames
3143 etc.@: will be returned to the values that they had when the checkpoint
3144 was saved. In essence, gdb will ``wind back the clock'' to the point
3145 in time when the checkpoint was saved.
3147 Note that breakpoints, @value{GDBN} variables, command history etc.
3148 are not affected by restoring a checkpoint. In general, a checkpoint
3149 only restores things that reside in the program being debugged, not in
3152 @kindex delete checkpoint @var{checkpoint-id}
3153 @item delete checkpoint @var{checkpoint-id}
3154 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3158 Returning to a previously saved checkpoint will restore the user state
3159 of the program being debugged, plus a significant subset of the system
3160 (OS) state, including file pointers. It won't ``un-write'' data from
3161 a file, but it will rewind the file pointer to the previous location,
3162 so that the previously written data can be overwritten. For files
3163 opened in read mode, the pointer will also be restored so that the
3164 previously read data can be read again.
3166 Of course, characters that have been sent to a printer (or other
3167 external device) cannot be ``snatched back'', and characters received
3168 from eg.@: a serial device can be removed from internal program buffers,
3169 but they cannot be ``pushed back'' into the serial pipeline, ready to
3170 be received again. Similarly, the actual contents of files that have
3171 been changed cannot be restored (at this time).
3173 However, within those constraints, you actually can ``rewind'' your
3174 program to a previously saved point in time, and begin debugging it
3175 again --- and you can change the course of events so as to debug a
3176 different execution path this time.
3178 @cindex checkpoints and process id
3179 Finally, there is one bit of internal program state that will be
3180 different when you return to a checkpoint --- the program's process
3181 id. Each checkpoint will have a unique process id (or @var{pid}),
3182 and each will be different from the program's original @var{pid}.
3183 If your program has saved a local copy of its process id, this could
3184 potentially pose a problem.
3186 @subsection A Non-obvious Benefit of Using Checkpoints
3188 On some systems such as @sc{gnu}/Linux, address space randomization
3189 is performed on new processes for security reasons. This makes it
3190 difficult or impossible to set a breakpoint, or watchpoint, on an
3191 absolute address if you have to restart the program, since the
3192 absolute location of a symbol will change from one execution to the
3195 A checkpoint, however, is an @emph{identical} copy of a process.
3196 Therefore if you create a checkpoint at (eg.@:) the start of main,
3197 and simply return to that checkpoint instead of restarting the
3198 process, you can avoid the effects of address randomization and
3199 your symbols will all stay in the same place.
3202 @chapter Stopping and Continuing
3204 The principal purposes of using a debugger are so that you can stop your
3205 program before it terminates; or so that, if your program runs into
3206 trouble, you can investigate and find out why.
3208 Inside @value{GDBN}, your program may stop for any of several reasons,
3209 such as a signal, a breakpoint, or reaching a new line after a
3210 @value{GDBN} command such as @code{step}. You may then examine and
3211 change variables, set new breakpoints or remove old ones, and then
3212 continue execution. Usually, the messages shown by @value{GDBN} provide
3213 ample explanation of the status of your program---but you can also
3214 explicitly request this information at any time.
3217 @kindex info program
3219 Display information about the status of your program: whether it is
3220 running or not, what process it is, and why it stopped.
3224 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3225 * Continuing and Stepping:: Resuming execution
3226 * Skipping Over Functions and Files::
3227 Skipping over functions and files
3229 * Thread Stops:: Stopping and starting multi-thread programs
3233 @section Breakpoints, Watchpoints, and Catchpoints
3236 A @dfn{breakpoint} makes your program stop whenever a certain point in
3237 the program is reached. For each breakpoint, you can add conditions to
3238 control in finer detail whether your program stops. You can set
3239 breakpoints with the @code{break} command and its variants (@pxref{Set
3240 Breaks, ,Setting Breakpoints}), to specify the place where your program
3241 should stop by line number, function name or exact address in the
3244 On some systems, you can set breakpoints in shared libraries before
3245 the executable is run. There is a minor limitation on HP-UX systems:
3246 you must wait until the executable is run in order to set breakpoints
3247 in shared library routines that are not called directly by the program
3248 (for example, routines that are arguments in a @code{pthread_create}
3252 @cindex data breakpoints
3253 @cindex memory tracing
3254 @cindex breakpoint on memory address
3255 @cindex breakpoint on variable modification
3256 A @dfn{watchpoint} is a special breakpoint that stops your program
3257 when the value of an expression changes. The expression may be a value
3258 of a variable, or it could involve values of one or more variables
3259 combined by operators, such as @samp{a + b}. This is sometimes called
3260 @dfn{data breakpoints}. You must use a different command to set
3261 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3262 from that, you can manage a watchpoint like any other breakpoint: you
3263 enable, disable, and delete both breakpoints and watchpoints using the
3266 You can arrange to have values from your program displayed automatically
3267 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3271 @cindex breakpoint on events
3272 A @dfn{catchpoint} is another special breakpoint that stops your program
3273 when a certain kind of event occurs, such as the throwing of a C@t{++}
3274 exception or the loading of a library. As with watchpoints, you use a
3275 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3276 Catchpoints}), but aside from that, you can manage a catchpoint like any
3277 other breakpoint. (To stop when your program receives a signal, use the
3278 @code{handle} command; see @ref{Signals, ,Signals}.)
3280 @cindex breakpoint numbers
3281 @cindex numbers for breakpoints
3282 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3283 catchpoint when you create it; these numbers are successive integers
3284 starting with one. In many of the commands for controlling various
3285 features of breakpoints you use the breakpoint number to say which
3286 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3287 @dfn{disabled}; if disabled, it has no effect on your program until you
3290 @cindex breakpoint ranges
3291 @cindex ranges of breakpoints
3292 Some @value{GDBN} commands accept a range of breakpoints on which to
3293 operate. A breakpoint range is either a single breakpoint number, like
3294 @samp{5}, or two such numbers, in increasing order, separated by a
3295 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3296 all breakpoints in that range are operated on.
3299 * Set Breaks:: Setting breakpoints
3300 * Set Watchpoints:: Setting watchpoints
3301 * Set Catchpoints:: Setting catchpoints
3302 * Delete Breaks:: Deleting breakpoints
3303 * Disabling:: Disabling breakpoints
3304 * Conditions:: Break conditions
3305 * Break Commands:: Breakpoint command lists
3306 * Save Breakpoints:: How to save breakpoints in a file
3307 * Error in Breakpoints:: ``Cannot insert breakpoints''
3308 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3312 @subsection Setting Breakpoints
3314 @c FIXME LMB what does GDB do if no code on line of breakpt?
3315 @c consider in particular declaration with/without initialization.
3317 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3320 @kindex b @r{(@code{break})}
3321 @vindex $bpnum@r{, convenience variable}
3322 @cindex latest breakpoint
3323 Breakpoints are set with the @code{break} command (abbreviated
3324 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3325 number of the breakpoint you've set most recently; see @ref{Convenience
3326 Vars,, Convenience Variables}, for a discussion of what you can do with
3327 convenience variables.
3330 @item break @var{location}
3331 Set a breakpoint at the given @var{location}, which can specify a
3332 function name, a line number, or an address of an instruction.
3333 (@xref{Specify Location}, for a list of all the possible ways to
3334 specify a @var{location}.) The breakpoint will stop your program just
3335 before it executes any of the code in the specified @var{location}.
3337 When using source languages that permit overloading of symbols, such as
3338 C@t{++}, a function name may refer to more than one possible place to break.
3339 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3342 It is also possible to insert a breakpoint that will stop the program
3343 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3344 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3347 When called without any arguments, @code{break} sets a breakpoint at
3348 the next instruction to be executed in the selected stack frame
3349 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3350 innermost, this makes your program stop as soon as control
3351 returns to that frame. This is similar to the effect of a
3352 @code{finish} command in the frame inside the selected frame---except
3353 that @code{finish} does not leave an active breakpoint. If you use
3354 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3355 the next time it reaches the current location; this may be useful
3358 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3359 least one instruction has been executed. If it did not do this, you
3360 would be unable to proceed past a breakpoint without first disabling the
3361 breakpoint. This rule applies whether or not the breakpoint already
3362 existed when your program stopped.
3364 @item break @dots{} if @var{cond}
3365 Set a breakpoint with condition @var{cond}; evaluate the expression
3366 @var{cond} each time the breakpoint is reached, and stop only if the
3367 value is nonzero---that is, if @var{cond} evaluates as true.
3368 @samp{@dots{}} stands for one of the possible arguments described
3369 above (or no argument) specifying where to break. @xref{Conditions,
3370 ,Break Conditions}, for more information on breakpoint conditions.
3373 @item tbreak @var{args}
3374 Set a breakpoint enabled only for one stop. @var{args} are the
3375 same as for the @code{break} command, and the breakpoint is set in the same
3376 way, but the breakpoint is automatically deleted after the first time your
3377 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3380 @cindex hardware breakpoints
3381 @item hbreak @var{args}
3382 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3383 @code{break} command and the breakpoint is set in the same way, but the
3384 breakpoint requires hardware support and some target hardware may not
3385 have this support. The main purpose of this is EPROM/ROM code
3386 debugging, so you can set a breakpoint at an instruction without
3387 changing the instruction. This can be used with the new trap-generation
3388 provided by SPARClite DSU and most x86-based targets. These targets
3389 will generate traps when a program accesses some data or instruction
3390 address that is assigned to the debug registers. However the hardware
3391 breakpoint registers can take a limited number of breakpoints. For
3392 example, on the DSU, only two data breakpoints can be set at a time, and
3393 @value{GDBN} will reject this command if more than two are used. Delete
3394 or disable unused hardware breakpoints before setting new ones
3395 (@pxref{Disabling, ,Disabling Breakpoints}).
3396 @xref{Conditions, ,Break Conditions}.
3397 For remote targets, you can restrict the number of hardware
3398 breakpoints @value{GDBN} will use, see @ref{set remote
3399 hardware-breakpoint-limit}.
3402 @item thbreak @var{args}
3403 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3404 are the same as for the @code{hbreak} command and the breakpoint is set in
3405 the same way. However, like the @code{tbreak} command,
3406 the breakpoint is automatically deleted after the
3407 first time your program stops there. Also, like the @code{hbreak}
3408 command, the breakpoint requires hardware support and some target hardware
3409 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3410 See also @ref{Conditions, ,Break Conditions}.
3413 @cindex regular expression
3414 @cindex breakpoints at functions matching a regexp
3415 @cindex set breakpoints in many functions
3416 @item rbreak @var{regex}
3417 Set breakpoints on all functions matching the regular expression
3418 @var{regex}. This command sets an unconditional breakpoint on all
3419 matches, printing a list of all breakpoints it set. Once these
3420 breakpoints are set, they are treated just like the breakpoints set with
3421 the @code{break} command. You can delete them, disable them, or make
3422 them conditional the same way as any other breakpoint.
3424 The syntax of the regular expression is the standard one used with tools
3425 like @file{grep}. Note that this is different from the syntax used by
3426 shells, so for instance @code{foo*} matches all functions that include
3427 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3428 @code{.*} leading and trailing the regular expression you supply, so to
3429 match only functions that begin with @code{foo}, use @code{^foo}.
3431 @cindex non-member C@t{++} functions, set breakpoint in
3432 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3433 breakpoints on overloaded functions that are not members of any special
3436 @cindex set breakpoints on all functions
3437 The @code{rbreak} command can be used to set breakpoints in
3438 @strong{all} the functions in a program, like this:
3441 (@value{GDBP}) rbreak .
3444 @item rbreak @var{file}:@var{regex}
3445 If @code{rbreak} is called with a filename qualification, it limits
3446 the search for functions matching the given regular expression to the
3447 specified @var{file}. This can be used, for example, to set breakpoints on
3448 every function in a given file:
3451 (@value{GDBP}) rbreak file.c:.
3454 The colon separating the filename qualifier from the regex may
3455 optionally be surrounded by spaces.
3457 @kindex info breakpoints
3458 @cindex @code{$_} and @code{info breakpoints}
3459 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3460 @itemx info break @r{[}@var{n}@dots{}@r{]}
3461 Print a table of all breakpoints, watchpoints, and catchpoints set and
3462 not deleted. Optional argument @var{n} means print information only
3463 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3464 For each breakpoint, following columns are printed:
3467 @item Breakpoint Numbers
3469 Breakpoint, watchpoint, or catchpoint.
3471 Whether the breakpoint is marked to be disabled or deleted when hit.
3472 @item Enabled or Disabled
3473 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3474 that are not enabled.
3476 Where the breakpoint is in your program, as a memory address. For a
3477 pending breakpoint whose address is not yet known, this field will
3478 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3479 library that has the symbol or line referred by breakpoint is loaded.
3480 See below for details. A breakpoint with several locations will
3481 have @samp{<MULTIPLE>} in this field---see below for details.
3483 Where the breakpoint is in the source for your program, as a file and
3484 line number. For a pending breakpoint, the original string passed to
3485 the breakpoint command will be listed as it cannot be resolved until
3486 the appropriate shared library is loaded in the future.
3490 If a breakpoint is conditional, @code{info break} shows the condition on
3491 the line following the affected breakpoint; breakpoint commands, if any,
3492 are listed after that. A pending breakpoint is allowed to have a condition
3493 specified for it. The condition is not parsed for validity until a shared
3494 library is loaded that allows the pending breakpoint to resolve to a
3498 @code{info break} with a breakpoint
3499 number @var{n} as argument lists only that breakpoint. The
3500 convenience variable @code{$_} and the default examining-address for
3501 the @code{x} command are set to the address of the last breakpoint
3502 listed (@pxref{Memory, ,Examining Memory}).
3505 @code{info break} displays a count of the number of times the breakpoint
3506 has been hit. This is especially useful in conjunction with the
3507 @code{ignore} command. You can ignore a large number of breakpoint
3508 hits, look at the breakpoint info to see how many times the breakpoint
3509 was hit, and then run again, ignoring one less than that number. This
3510 will get you quickly to the last hit of that breakpoint.
3513 @value{GDBN} allows you to set any number of breakpoints at the same place in
3514 your program. There is nothing silly or meaningless about this. When
3515 the breakpoints are conditional, this is even useful
3516 (@pxref{Conditions, ,Break Conditions}).
3518 @cindex multiple locations, breakpoints
3519 @cindex breakpoints, multiple locations
3520 It is possible that a breakpoint corresponds to several locations
3521 in your program. Examples of this situation are:
3525 Multiple functions in the program may have the same name.
3528 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3529 instances of the function body, used in different cases.
3532 For a C@t{++} template function, a given line in the function can
3533 correspond to any number of instantiations.
3536 For an inlined function, a given source line can correspond to
3537 several places where that function is inlined.
3540 In all those cases, @value{GDBN} will insert a breakpoint at all
3541 the relevant locations.
3543 A breakpoint with multiple locations is displayed in the breakpoint
3544 table using several rows---one header row, followed by one row for
3545 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3546 address column. The rows for individual locations contain the actual
3547 addresses for locations, and show the functions to which those
3548 locations belong. The number column for a location is of the form
3549 @var{breakpoint-number}.@var{location-number}.
3554 Num Type Disp Enb Address What
3555 1 breakpoint keep y <MULTIPLE>
3557 breakpoint already hit 1 time
3558 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3559 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3562 Each location can be individually enabled or disabled by passing
3563 @var{breakpoint-number}.@var{location-number} as argument to the
3564 @code{enable} and @code{disable} commands. Note that you cannot
3565 delete the individual locations from the list, you can only delete the
3566 entire list of locations that belong to their parent breakpoint (with
3567 the @kbd{delete @var{num}} command, where @var{num} is the number of
3568 the parent breakpoint, 1 in the above example). Disabling or enabling
3569 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3570 that belong to that breakpoint.
3572 @cindex pending breakpoints
3573 It's quite common to have a breakpoint inside a shared library.
3574 Shared libraries can be loaded and unloaded explicitly,
3575 and possibly repeatedly, as the program is executed. To support
3576 this use case, @value{GDBN} updates breakpoint locations whenever
3577 any shared library is loaded or unloaded. Typically, you would
3578 set a breakpoint in a shared library at the beginning of your
3579 debugging session, when the library is not loaded, and when the
3580 symbols from the library are not available. When you try to set
3581 breakpoint, @value{GDBN} will ask you if you want to set
3582 a so called @dfn{pending breakpoint}---breakpoint whose address
3583 is not yet resolved.
3585 After the program is run, whenever a new shared library is loaded,
3586 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3587 shared library contains the symbol or line referred to by some
3588 pending breakpoint, that breakpoint is resolved and becomes an
3589 ordinary breakpoint. When a library is unloaded, all breakpoints
3590 that refer to its symbols or source lines become pending again.
3592 This logic works for breakpoints with multiple locations, too. For
3593 example, if you have a breakpoint in a C@t{++} template function, and
3594 a newly loaded shared library has an instantiation of that template,
3595 a new location is added to the list of locations for the breakpoint.
3597 Except for having unresolved address, pending breakpoints do not
3598 differ from regular breakpoints. You can set conditions or commands,
3599 enable and disable them and perform other breakpoint operations.
3601 @value{GDBN} provides some additional commands for controlling what
3602 happens when the @samp{break} command cannot resolve breakpoint
3603 address specification to an address:
3605 @kindex set breakpoint pending
3606 @kindex show breakpoint pending
3608 @item set breakpoint pending auto
3609 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3610 location, it queries you whether a pending breakpoint should be created.
3612 @item set breakpoint pending on
3613 This indicates that an unrecognized breakpoint location should automatically
3614 result in a pending breakpoint being created.
3616 @item set breakpoint pending off
3617 This indicates that pending breakpoints are not to be created. Any
3618 unrecognized breakpoint location results in an error. This setting does
3619 not affect any pending breakpoints previously created.
3621 @item show breakpoint pending
3622 Show the current behavior setting for creating pending breakpoints.
3625 The settings above only affect the @code{break} command and its
3626 variants. Once breakpoint is set, it will be automatically updated
3627 as shared libraries are loaded and unloaded.
3629 @cindex automatic hardware breakpoints
3630 For some targets, @value{GDBN} can automatically decide if hardware or
3631 software breakpoints should be used, depending on whether the
3632 breakpoint address is read-only or read-write. This applies to
3633 breakpoints set with the @code{break} command as well as to internal
3634 breakpoints set by commands like @code{next} and @code{finish}. For
3635 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3638 You can control this automatic behaviour with the following commands::
3640 @kindex set breakpoint auto-hw
3641 @kindex show breakpoint auto-hw
3643 @item set breakpoint auto-hw on
3644 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3645 will try to use the target memory map to decide if software or hardware
3646 breakpoint must be used.
3648 @item set breakpoint auto-hw off
3649 This indicates @value{GDBN} should not automatically select breakpoint
3650 type. If the target provides a memory map, @value{GDBN} will warn when
3651 trying to set software breakpoint at a read-only address.
3654 @value{GDBN} normally implements breakpoints by replacing the program code
3655 at the breakpoint address with a special instruction, which, when
3656 executed, given control to the debugger. By default, the program
3657 code is so modified only when the program is resumed. As soon as
3658 the program stops, @value{GDBN} restores the original instructions. This
3659 behaviour guards against leaving breakpoints inserted in the
3660 target should gdb abrubptly disconnect. However, with slow remote
3661 targets, inserting and removing breakpoint can reduce the performance.
3662 This behavior can be controlled with the following commands::
3664 @kindex set breakpoint always-inserted
3665 @kindex show breakpoint always-inserted
3667 @item set breakpoint always-inserted off
3668 All breakpoints, including newly added by the user, are inserted in
3669 the target only when the target is resumed. All breakpoints are
3670 removed from the target when it stops.
3672 @item set breakpoint always-inserted on
3673 Causes all breakpoints to be inserted in the target at all times. If
3674 the user adds a new breakpoint, or changes an existing breakpoint, the
3675 breakpoints in the target are updated immediately. A breakpoint is
3676 removed from the target only when breakpoint itself is removed.
3678 @cindex non-stop mode, and @code{breakpoint always-inserted}
3679 @item set breakpoint always-inserted auto
3680 This is the default mode. If @value{GDBN} is controlling the inferior
3681 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3682 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3683 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3684 @code{breakpoint always-inserted} mode is off.
3687 @cindex negative breakpoint numbers
3688 @cindex internal @value{GDBN} breakpoints
3689 @value{GDBN} itself sometimes sets breakpoints in your program for
3690 special purposes, such as proper handling of @code{longjmp} (in C
3691 programs). These internal breakpoints are assigned negative numbers,
3692 starting with @code{-1}; @samp{info breakpoints} does not display them.
3693 You can see these breakpoints with the @value{GDBN} maintenance command
3694 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3697 @node Set Watchpoints
3698 @subsection Setting Watchpoints
3700 @cindex setting watchpoints
3701 You can use a watchpoint to stop execution whenever the value of an
3702 expression changes, without having to predict a particular place where
3703 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3704 The expression may be as simple as the value of a single variable, or
3705 as complex as many variables combined by operators. Examples include:
3709 A reference to the value of a single variable.
3712 An address cast to an appropriate data type. For example,
3713 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3714 address (assuming an @code{int} occupies 4 bytes).
3717 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3718 expression can use any operators valid in the program's native
3719 language (@pxref{Languages}).
3722 You can set a watchpoint on an expression even if the expression can
3723 not be evaluated yet. For instance, you can set a watchpoint on
3724 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3725 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3726 the expression produces a valid value. If the expression becomes
3727 valid in some other way than changing a variable (e.g.@: if the memory
3728 pointed to by @samp{*global_ptr} becomes readable as the result of a
3729 @code{malloc} call), @value{GDBN} may not stop until the next time
3730 the expression changes.
3732 @cindex software watchpoints
3733 @cindex hardware watchpoints
3734 Depending on your system, watchpoints may be implemented in software or
3735 hardware. @value{GDBN} does software watchpointing by single-stepping your
3736 program and testing the variable's value each time, which is hundreds of
3737 times slower than normal execution. (But this may still be worth it, to
3738 catch errors where you have no clue what part of your program is the
3741 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3742 x86-based targets, @value{GDBN} includes support for hardware
3743 watchpoints, which do not slow down the running of your program.
3747 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3748 Set a watchpoint for an expression. @value{GDBN} will break when the
3749 expression @var{expr} is written into by the program and its value
3750 changes. The simplest (and the most popular) use of this command is
3751 to watch the value of a single variable:
3754 (@value{GDBP}) watch foo
3757 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3758 argument, @value{GDBN} breaks only when the thread identified by
3759 @var{threadnum} changes the value of @var{expr}. If any other threads
3760 change the value of @var{expr}, @value{GDBN} will not break. Note
3761 that watchpoints restricted to a single thread in this way only work
3762 with Hardware Watchpoints.
3764 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3765 (see below). The @code{-location} argument tells @value{GDBN} to
3766 instead watch the memory referred to by @var{expr}. In this case,
3767 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3768 and watch the memory at that address. The type of the result is used
3769 to determine the size of the watched memory. If the expression's
3770 result does not have an address, then @value{GDBN} will print an
3773 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3774 of masked watchpoints, if the current architecture supports this
3775 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3776 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3777 to an address to watch. The mask specifies that some bits of an address
3778 (the bits which are reset in the mask) should be ignored when matching
3779 the address accessed by the inferior against the watchpoint address.
3780 Thus, a masked watchpoint watches many addresses simultaneously---those
3781 addresses whose unmasked bits are identical to the unmasked bits in the
3782 watchpoint address. The @code{mask} argument implies @code{-location}.
3786 (@value{GDBP}) watch foo mask 0xffff00ff
3787 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3791 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3792 Set a watchpoint that will break when the value of @var{expr} is read
3796 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3797 Set a watchpoint that will break when @var{expr} is either read from
3798 or written into by the program.
3800 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3801 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3802 This command prints a list of watchpoints, using the same format as
3803 @code{info break} (@pxref{Set Breaks}).
3806 If you watch for a change in a numerically entered address you need to
3807 dereference it, as the address itself is just a constant number which will
3808 never change. @value{GDBN} refuses to create a watchpoint that watches
3809 a never-changing value:
3812 (@value{GDBP}) watch 0x600850
3813 Cannot watch constant value 0x600850.
3814 (@value{GDBP}) watch *(int *) 0x600850
3815 Watchpoint 1: *(int *) 6293584
3818 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3819 watchpoints execute very quickly, and the debugger reports a change in
3820 value at the exact instruction where the change occurs. If @value{GDBN}
3821 cannot set a hardware watchpoint, it sets a software watchpoint, which
3822 executes more slowly and reports the change in value at the next
3823 @emph{statement}, not the instruction, after the change occurs.
3825 @cindex use only software watchpoints
3826 You can force @value{GDBN} to use only software watchpoints with the
3827 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3828 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3829 the underlying system supports them. (Note that hardware-assisted
3830 watchpoints that were set @emph{before} setting
3831 @code{can-use-hw-watchpoints} to zero will still use the hardware
3832 mechanism of watching expression values.)
3835 @item set can-use-hw-watchpoints
3836 @kindex set can-use-hw-watchpoints
3837 Set whether or not to use hardware watchpoints.
3839 @item show can-use-hw-watchpoints
3840 @kindex show can-use-hw-watchpoints
3841 Show the current mode of using hardware watchpoints.
3844 For remote targets, you can restrict the number of hardware
3845 watchpoints @value{GDBN} will use, see @ref{set remote
3846 hardware-breakpoint-limit}.
3848 When you issue the @code{watch} command, @value{GDBN} reports
3851 Hardware watchpoint @var{num}: @var{expr}
3855 if it was able to set a hardware watchpoint.
3857 Currently, the @code{awatch} and @code{rwatch} commands can only set
3858 hardware watchpoints, because accesses to data that don't change the
3859 value of the watched expression cannot be detected without examining
3860 every instruction as it is being executed, and @value{GDBN} does not do
3861 that currently. If @value{GDBN} finds that it is unable to set a
3862 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3863 will print a message like this:
3866 Expression cannot be implemented with read/access watchpoint.
3869 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3870 data type of the watched expression is wider than what a hardware
3871 watchpoint on the target machine can handle. For example, some systems
3872 can only watch regions that are up to 4 bytes wide; on such systems you
3873 cannot set hardware watchpoints for an expression that yields a
3874 double-precision floating-point number (which is typically 8 bytes
3875 wide). As a work-around, it might be possible to break the large region
3876 into a series of smaller ones and watch them with separate watchpoints.
3878 If you set too many hardware watchpoints, @value{GDBN} might be unable
3879 to insert all of them when you resume the execution of your program.
3880 Since the precise number of active watchpoints is unknown until such
3881 time as the program is about to be resumed, @value{GDBN} might not be
3882 able to warn you about this when you set the watchpoints, and the
3883 warning will be printed only when the program is resumed:
3886 Hardware watchpoint @var{num}: Could not insert watchpoint
3890 If this happens, delete or disable some of the watchpoints.
3892 Watching complex expressions that reference many variables can also
3893 exhaust the resources available for hardware-assisted watchpoints.
3894 That's because @value{GDBN} needs to watch every variable in the
3895 expression with separately allocated resources.
3897 If you call a function interactively using @code{print} or @code{call},
3898 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3899 kind of breakpoint or the call completes.
3901 @value{GDBN} automatically deletes watchpoints that watch local
3902 (automatic) variables, or expressions that involve such variables, when
3903 they go out of scope, that is, when the execution leaves the block in
3904 which these variables were defined. In particular, when the program
3905 being debugged terminates, @emph{all} local variables go out of scope,
3906 and so only watchpoints that watch global variables remain set. If you
3907 rerun the program, you will need to set all such watchpoints again. One
3908 way of doing that would be to set a code breakpoint at the entry to the
3909 @code{main} function and when it breaks, set all the watchpoints.
3911 @cindex watchpoints and threads
3912 @cindex threads and watchpoints
3913 In multi-threaded programs, watchpoints will detect changes to the
3914 watched expression from every thread.
3917 @emph{Warning:} In multi-threaded programs, software watchpoints
3918 have only limited usefulness. If @value{GDBN} creates a software
3919 watchpoint, it can only watch the value of an expression @emph{in a
3920 single thread}. If you are confident that the expression can only
3921 change due to the current thread's activity (and if you are also
3922 confident that no other thread can become current), then you can use
3923 software watchpoints as usual. However, @value{GDBN} may not notice
3924 when a non-current thread's activity changes the expression. (Hardware
3925 watchpoints, in contrast, watch an expression in all threads.)
3928 @xref{set remote hardware-watchpoint-limit}.
3930 @node Set Catchpoints
3931 @subsection Setting Catchpoints
3932 @cindex catchpoints, setting
3933 @cindex exception handlers
3934 @cindex event handling
3936 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3937 kinds of program events, such as C@t{++} exceptions or the loading of a
3938 shared library. Use the @code{catch} command to set a catchpoint.
3942 @item catch @var{event}
3943 Stop when @var{event} occurs. @var{event} can be any of the following:
3946 @cindex stop on C@t{++} exceptions
3947 The throwing of a C@t{++} exception.
3950 The catching of a C@t{++} exception.
3953 @cindex Ada exception catching
3954 @cindex catch Ada exceptions
3955 An Ada exception being raised. If an exception name is specified
3956 at the end of the command (eg @code{catch exception Program_Error}),
3957 the debugger will stop only when this specific exception is raised.
3958 Otherwise, the debugger stops execution when any Ada exception is raised.
3960 When inserting an exception catchpoint on a user-defined exception whose
3961 name is identical to one of the exceptions defined by the language, the
3962 fully qualified name must be used as the exception name. Otherwise,
3963 @value{GDBN} will assume that it should stop on the pre-defined exception
3964 rather than the user-defined one. For instance, assuming an exception
3965 called @code{Constraint_Error} is defined in package @code{Pck}, then
3966 the command to use to catch such exceptions is @kbd{catch exception
3967 Pck.Constraint_Error}.
3969 @item exception unhandled
3970 An exception that was raised but is not handled by the program.
3973 A failed Ada assertion.
3976 @cindex break on fork/exec
3977 A call to @code{exec}. This is currently only available for HP-UX
3981 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3982 @cindex break on a system call.
3983 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3984 syscall is a mechanism for application programs to request a service
3985 from the operating system (OS) or one of the OS system services.
3986 @value{GDBN} can catch some or all of the syscalls issued by the
3987 debuggee, and show the related information for each syscall. If no
3988 argument is specified, calls to and returns from all system calls
3991 @var{name} can be any system call name that is valid for the
3992 underlying OS. Just what syscalls are valid depends on the OS. On
3993 GNU and Unix systems, you can find the full list of valid syscall
3994 names on @file{/usr/include/asm/unistd.h}.
3996 @c For MS-Windows, the syscall names and the corresponding numbers
3997 @c can be found, e.g., on this URL:
3998 @c http://www.metasploit.com/users/opcode/syscalls.html
3999 @c but we don't support Windows syscalls yet.
4001 Normally, @value{GDBN} knows in advance which syscalls are valid for
4002 each OS, so you can use the @value{GDBN} command-line completion
4003 facilities (@pxref{Completion,, command completion}) to list the
4006 You may also specify the system call numerically. A syscall's
4007 number is the value passed to the OS's syscall dispatcher to
4008 identify the requested service. When you specify the syscall by its
4009 name, @value{GDBN} uses its database of syscalls to convert the name
4010 into the corresponding numeric code, but using the number directly
4011 may be useful if @value{GDBN}'s database does not have the complete
4012 list of syscalls on your system (e.g., because @value{GDBN} lags
4013 behind the OS upgrades).
4015 The example below illustrates how this command works if you don't provide
4019 (@value{GDBP}) catch syscall
4020 Catchpoint 1 (syscall)
4022 Starting program: /tmp/catch-syscall
4024 Catchpoint 1 (call to syscall 'close'), \
4025 0xffffe424 in __kernel_vsyscall ()
4029 Catchpoint 1 (returned from syscall 'close'), \
4030 0xffffe424 in __kernel_vsyscall ()
4034 Here is an example of catching a system call by name:
4037 (@value{GDBP}) catch syscall chroot
4038 Catchpoint 1 (syscall 'chroot' [61])
4040 Starting program: /tmp/catch-syscall
4042 Catchpoint 1 (call to syscall 'chroot'), \
4043 0xffffe424 in __kernel_vsyscall ()
4047 Catchpoint 1 (returned from syscall 'chroot'), \
4048 0xffffe424 in __kernel_vsyscall ()
4052 An example of specifying a system call numerically. In the case
4053 below, the syscall number has a corresponding entry in the XML
4054 file, so @value{GDBN} finds its name and prints it:
4057 (@value{GDBP}) catch syscall 252
4058 Catchpoint 1 (syscall(s) 'exit_group')
4060 Starting program: /tmp/catch-syscall
4062 Catchpoint 1 (call to syscall 'exit_group'), \
4063 0xffffe424 in __kernel_vsyscall ()
4067 Program exited normally.
4071 However, there can be situations when there is no corresponding name
4072 in XML file for that syscall number. In this case, @value{GDBN} prints
4073 a warning message saying that it was not able to find the syscall name,
4074 but the catchpoint will be set anyway. See the example below:
4077 (@value{GDBP}) catch syscall 764
4078 warning: The number '764' does not represent a known syscall.
4079 Catchpoint 2 (syscall 764)
4083 If you configure @value{GDBN} using the @samp{--without-expat} option,
4084 it will not be able to display syscall names. Also, if your
4085 architecture does not have an XML file describing its system calls,
4086 you will not be able to see the syscall names. It is important to
4087 notice that these two features are used for accessing the syscall
4088 name database. In either case, you will see a warning like this:
4091 (@value{GDBP}) catch syscall
4092 warning: Could not open "syscalls/i386-linux.xml"
4093 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4094 GDB will not be able to display syscall names.
4095 Catchpoint 1 (syscall)
4099 Of course, the file name will change depending on your architecture and system.
4101 Still using the example above, you can also try to catch a syscall by its
4102 number. In this case, you would see something like:
4105 (@value{GDBP}) catch syscall 252
4106 Catchpoint 1 (syscall(s) 252)
4109 Again, in this case @value{GDBN} would not be able to display syscall's names.
4112 A call to @code{fork}. This is currently only available for HP-UX
4116 A call to @code{vfork}. This is currently only available for HP-UX
4121 @item tcatch @var{event}
4122 Set a catchpoint that is enabled only for one stop. The catchpoint is
4123 automatically deleted after the first time the event is caught.
4127 Use the @code{info break} command to list the current catchpoints.
4129 There are currently some limitations to C@t{++} exception handling
4130 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4134 If you call a function interactively, @value{GDBN} normally returns
4135 control to you when the function has finished executing. If the call
4136 raises an exception, however, the call may bypass the mechanism that
4137 returns control to you and cause your program either to abort or to
4138 simply continue running until it hits a breakpoint, catches a signal
4139 that @value{GDBN} is listening for, or exits. This is the case even if
4140 you set a catchpoint for the exception; catchpoints on exceptions are
4141 disabled within interactive calls.
4144 You cannot raise an exception interactively.
4147 You cannot install an exception handler interactively.
4150 @cindex raise exceptions
4151 Sometimes @code{catch} is not the best way to debug exception handling:
4152 if you need to know exactly where an exception is raised, it is better to
4153 stop @emph{before} the exception handler is called, since that way you
4154 can see the stack before any unwinding takes place. If you set a
4155 breakpoint in an exception handler instead, it may not be easy to find
4156 out where the exception was raised.
4158 To stop just before an exception handler is called, you need some
4159 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4160 raised by calling a library function named @code{__raise_exception}
4161 which has the following ANSI C interface:
4164 /* @var{addr} is where the exception identifier is stored.
4165 @var{id} is the exception identifier. */
4166 void __raise_exception (void **addr, void *id);
4170 To make the debugger catch all exceptions before any stack
4171 unwinding takes place, set a breakpoint on @code{__raise_exception}
4172 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4174 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4175 that depends on the value of @var{id}, you can stop your program when
4176 a specific exception is raised. You can use multiple conditional
4177 breakpoints to stop your program when any of a number of exceptions are
4182 @subsection Deleting Breakpoints
4184 @cindex clearing breakpoints, watchpoints, catchpoints
4185 @cindex deleting breakpoints, watchpoints, catchpoints
4186 It is often necessary to eliminate a breakpoint, watchpoint, or
4187 catchpoint once it has done its job and you no longer want your program
4188 to stop there. This is called @dfn{deleting} the breakpoint. A
4189 breakpoint that has been deleted no longer exists; it is forgotten.
4191 With the @code{clear} command you can delete breakpoints according to
4192 where they are in your program. With the @code{delete} command you can
4193 delete individual breakpoints, watchpoints, or catchpoints by specifying
4194 their breakpoint numbers.
4196 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4197 automatically ignores breakpoints on the first instruction to be executed
4198 when you continue execution without changing the execution address.
4203 Delete any breakpoints at the next instruction to be executed in the
4204 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4205 the innermost frame is selected, this is a good way to delete a
4206 breakpoint where your program just stopped.
4208 @item clear @var{location}
4209 Delete any breakpoints set at the specified @var{location}.
4210 @xref{Specify Location}, for the various forms of @var{location}; the
4211 most useful ones are listed below:
4214 @item clear @var{function}
4215 @itemx clear @var{filename}:@var{function}
4216 Delete any breakpoints set at entry to the named @var{function}.
4218 @item clear @var{linenum}
4219 @itemx clear @var{filename}:@var{linenum}
4220 Delete any breakpoints set at or within the code of the specified
4221 @var{linenum} of the specified @var{filename}.
4224 @cindex delete breakpoints
4226 @kindex d @r{(@code{delete})}
4227 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4228 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4229 ranges specified as arguments. If no argument is specified, delete all
4230 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4231 confirm off}). You can abbreviate this command as @code{d}.
4235 @subsection Disabling Breakpoints
4237 @cindex enable/disable a breakpoint
4238 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4239 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4240 it had been deleted, but remembers the information on the breakpoint so
4241 that you can @dfn{enable} it again later.
4243 You disable and enable breakpoints, watchpoints, and catchpoints with
4244 the @code{enable} and @code{disable} commands, optionally specifying
4245 one or more breakpoint numbers as arguments. Use @code{info break} to
4246 print a list of all breakpoints, watchpoints, and catchpoints if you
4247 do not know which numbers to use.
4249 Disabling and enabling a breakpoint that has multiple locations
4250 affects all of its locations.
4252 A breakpoint, watchpoint, or catchpoint can have any of four different
4253 states of enablement:
4257 Enabled. The breakpoint stops your program. A breakpoint set
4258 with the @code{break} command starts out in this state.
4260 Disabled. The breakpoint has no effect on your program.
4262 Enabled once. The breakpoint stops your program, but then becomes
4265 Enabled for deletion. The breakpoint stops your program, but
4266 immediately after it does so it is deleted permanently. A breakpoint
4267 set with the @code{tbreak} command starts out in this state.
4270 You can use the following commands to enable or disable breakpoints,
4271 watchpoints, and catchpoints:
4275 @kindex dis @r{(@code{disable})}
4276 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4277 Disable the specified breakpoints---or all breakpoints, if none are
4278 listed. A disabled breakpoint has no effect but is not forgotten. All
4279 options such as ignore-counts, conditions and commands are remembered in
4280 case the breakpoint is enabled again later. You may abbreviate
4281 @code{disable} as @code{dis}.
4284 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4285 Enable the specified breakpoints (or all defined breakpoints). They
4286 become effective once again in stopping your program.
4288 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4289 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4290 of these breakpoints immediately after stopping your program.
4292 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4293 Enable the specified breakpoints to work once, then die. @value{GDBN}
4294 deletes any of these breakpoints as soon as your program stops there.
4295 Breakpoints set by the @code{tbreak} command start out in this state.
4298 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4299 @c confusing: tbreak is also initially enabled.
4300 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4301 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4302 subsequently, they become disabled or enabled only when you use one of
4303 the commands above. (The command @code{until} can set and delete a
4304 breakpoint of its own, but it does not change the state of your other
4305 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4309 @subsection Break Conditions
4310 @cindex conditional breakpoints
4311 @cindex breakpoint conditions
4313 @c FIXME what is scope of break condition expr? Context where wanted?
4314 @c in particular for a watchpoint?
4315 The simplest sort of breakpoint breaks every time your program reaches a
4316 specified place. You can also specify a @dfn{condition} for a
4317 breakpoint. A condition is just a Boolean expression in your
4318 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4319 a condition evaluates the expression each time your program reaches it,
4320 and your program stops only if the condition is @emph{true}.
4322 This is the converse of using assertions for program validation; in that
4323 situation, you want to stop when the assertion is violated---that is,
4324 when the condition is false. In C, if you want to test an assertion expressed
4325 by the condition @var{assert}, you should set the condition
4326 @samp{! @var{assert}} on the appropriate breakpoint.
4328 Conditions are also accepted for watchpoints; you may not need them,
4329 since a watchpoint is inspecting the value of an expression anyhow---but
4330 it might be simpler, say, to just set a watchpoint on a variable name,
4331 and specify a condition that tests whether the new value is an interesting
4334 Break conditions can have side effects, and may even call functions in
4335 your program. This can be useful, for example, to activate functions
4336 that log program progress, or to use your own print functions to
4337 format special data structures. The effects are completely predictable
4338 unless there is another enabled breakpoint at the same address. (In
4339 that case, @value{GDBN} might see the other breakpoint first and stop your
4340 program without checking the condition of this one.) Note that
4341 breakpoint commands are usually more convenient and flexible than break
4343 purpose of performing side effects when a breakpoint is reached
4344 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4346 Break conditions can be specified when a breakpoint is set, by using
4347 @samp{if} in the arguments to the @code{break} command. @xref{Set
4348 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4349 with the @code{condition} command.
4351 You can also use the @code{if} keyword with the @code{watch} command.
4352 The @code{catch} command does not recognize the @code{if} keyword;
4353 @code{condition} is the only way to impose a further condition on a
4358 @item condition @var{bnum} @var{expression}
4359 Specify @var{expression} as the break condition for breakpoint,
4360 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4361 breakpoint @var{bnum} stops your program only if the value of
4362 @var{expression} is true (nonzero, in C). When you use
4363 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4364 syntactic correctness, and to determine whether symbols in it have
4365 referents in the context of your breakpoint. If @var{expression} uses
4366 symbols not referenced in the context of the breakpoint, @value{GDBN}
4367 prints an error message:
4370 No symbol "foo" in current context.
4375 not actually evaluate @var{expression} at the time the @code{condition}
4376 command (or a command that sets a breakpoint with a condition, like
4377 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4379 @item condition @var{bnum}
4380 Remove the condition from breakpoint number @var{bnum}. It becomes
4381 an ordinary unconditional breakpoint.
4384 @cindex ignore count (of breakpoint)
4385 A special case of a breakpoint condition is to stop only when the
4386 breakpoint has been reached a certain number of times. This is so
4387 useful that there is a special way to do it, using the @dfn{ignore
4388 count} of the breakpoint. Every breakpoint has an ignore count, which
4389 is an integer. Most of the time, the ignore count is zero, and
4390 therefore has no effect. But if your program reaches a breakpoint whose
4391 ignore count is positive, then instead of stopping, it just decrements
4392 the ignore count by one and continues. As a result, if the ignore count
4393 value is @var{n}, the breakpoint does not stop the next @var{n} times
4394 your program reaches it.
4398 @item ignore @var{bnum} @var{count}
4399 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4400 The next @var{count} times the breakpoint is reached, your program's
4401 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4404 To make the breakpoint stop the next time it is reached, specify
4407 When you use @code{continue} to resume execution of your program from a
4408 breakpoint, you can specify an ignore count directly as an argument to
4409 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4410 Stepping,,Continuing and Stepping}.
4412 If a breakpoint has a positive ignore count and a condition, the
4413 condition is not checked. Once the ignore count reaches zero,
4414 @value{GDBN} resumes checking the condition.
4416 You could achieve the effect of the ignore count with a condition such
4417 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4418 is decremented each time. @xref{Convenience Vars, ,Convenience
4422 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4425 @node Break Commands
4426 @subsection Breakpoint Command Lists
4428 @cindex breakpoint commands
4429 You can give any breakpoint (or watchpoint or catchpoint) a series of
4430 commands to execute when your program stops due to that breakpoint. For
4431 example, you might want to print the values of certain expressions, or
4432 enable other breakpoints.
4436 @kindex end@r{ (breakpoint commands)}
4437 @item commands @r{[}@var{range}@dots{}@r{]}
4438 @itemx @dots{} @var{command-list} @dots{}
4440 Specify a list of commands for the given breakpoints. The commands
4441 themselves appear on the following lines. Type a line containing just
4442 @code{end} to terminate the commands.
4444 To remove all commands from a breakpoint, type @code{commands} and
4445 follow it immediately with @code{end}; that is, give no commands.
4447 With no argument, @code{commands} refers to the last breakpoint,
4448 watchpoint, or catchpoint set (not to the breakpoint most recently
4449 encountered). If the most recent breakpoints were set with a single
4450 command, then the @code{commands} will apply to all the breakpoints
4451 set by that command. This applies to breakpoints set by
4452 @code{rbreak}, and also applies when a single @code{break} command
4453 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4457 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4458 disabled within a @var{command-list}.
4460 You can use breakpoint commands to start your program up again. Simply
4461 use the @code{continue} command, or @code{step}, or any other command
4462 that resumes execution.
4464 Any other commands in the command list, after a command that resumes
4465 execution, are ignored. This is because any time you resume execution
4466 (even with a simple @code{next} or @code{step}), you may encounter
4467 another breakpoint---which could have its own command list, leading to
4468 ambiguities about which list to execute.
4471 If the first command you specify in a command list is @code{silent}, the
4472 usual message about stopping at a breakpoint is not printed. This may
4473 be desirable for breakpoints that are to print a specific message and
4474 then continue. If none of the remaining commands print anything, you
4475 see no sign that the breakpoint was reached. @code{silent} is
4476 meaningful only at the beginning of a breakpoint command list.
4478 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4479 print precisely controlled output, and are often useful in silent
4480 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4482 For example, here is how you could use breakpoint commands to print the
4483 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4489 printf "x is %d\n",x
4494 One application for breakpoint commands is to compensate for one bug so
4495 you can test for another. Put a breakpoint just after the erroneous line
4496 of code, give it a condition to detect the case in which something
4497 erroneous has been done, and give it commands to assign correct values
4498 to any variables that need them. End with the @code{continue} command
4499 so that your program does not stop, and start with the @code{silent}
4500 command so that no output is produced. Here is an example:
4511 @node Save Breakpoints
4512 @subsection How to save breakpoints to a file
4514 To save breakpoint definitions to a file use the @w{@code{save
4515 breakpoints}} command.
4518 @kindex save breakpoints
4519 @cindex save breakpoints to a file for future sessions
4520 @item save breakpoints [@var{filename}]
4521 This command saves all current breakpoint definitions together with
4522 their commands and ignore counts, into a file @file{@var{filename}}
4523 suitable for use in a later debugging session. This includes all
4524 types of breakpoints (breakpoints, watchpoints, catchpoints,
4525 tracepoints). To read the saved breakpoint definitions, use the
4526 @code{source} command (@pxref{Command Files}). Note that watchpoints
4527 with expressions involving local variables may fail to be recreated
4528 because it may not be possible to access the context where the
4529 watchpoint is valid anymore. Because the saved breakpoint definitions
4530 are simply a sequence of @value{GDBN} commands that recreate the
4531 breakpoints, you can edit the file in your favorite editing program,
4532 and remove the breakpoint definitions you're not interested in, or
4533 that can no longer be recreated.
4536 @c @ifclear BARETARGET
4537 @node Error in Breakpoints
4538 @subsection ``Cannot insert breakpoints''
4540 If you request too many active hardware-assisted breakpoints and
4541 watchpoints, you will see this error message:
4543 @c FIXME: the precise wording of this message may change; the relevant
4544 @c source change is not committed yet (Sep 3, 1999).
4546 Stopped; cannot insert breakpoints.
4547 You may have requested too many hardware breakpoints and watchpoints.
4551 This message is printed when you attempt to resume the program, since
4552 only then @value{GDBN} knows exactly how many hardware breakpoints and
4553 watchpoints it needs to insert.
4555 When this message is printed, you need to disable or remove some of the
4556 hardware-assisted breakpoints and watchpoints, and then continue.
4558 @node Breakpoint-related Warnings
4559 @subsection ``Breakpoint address adjusted...''
4560 @cindex breakpoint address adjusted
4562 Some processor architectures place constraints on the addresses at
4563 which breakpoints may be placed. For architectures thus constrained,
4564 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4565 with the constraints dictated by the architecture.
4567 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4568 a VLIW architecture in which a number of RISC-like instructions may be
4569 bundled together for parallel execution. The FR-V architecture
4570 constrains the location of a breakpoint instruction within such a
4571 bundle to the instruction with the lowest address. @value{GDBN}
4572 honors this constraint by adjusting a breakpoint's address to the
4573 first in the bundle.
4575 It is not uncommon for optimized code to have bundles which contain
4576 instructions from different source statements, thus it may happen that
4577 a breakpoint's address will be adjusted from one source statement to
4578 another. Since this adjustment may significantly alter @value{GDBN}'s
4579 breakpoint related behavior from what the user expects, a warning is
4580 printed when the breakpoint is first set and also when the breakpoint
4583 A warning like the one below is printed when setting a breakpoint
4584 that's been subject to address adjustment:
4587 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4590 Such warnings are printed both for user settable and @value{GDBN}'s
4591 internal breakpoints. If you see one of these warnings, you should
4592 verify that a breakpoint set at the adjusted address will have the
4593 desired affect. If not, the breakpoint in question may be removed and
4594 other breakpoints may be set which will have the desired behavior.
4595 E.g., it may be sufficient to place the breakpoint at a later
4596 instruction. A conditional breakpoint may also be useful in some
4597 cases to prevent the breakpoint from triggering too often.
4599 @value{GDBN} will also issue a warning when stopping at one of these
4600 adjusted breakpoints:
4603 warning: Breakpoint 1 address previously adjusted from 0x00010414
4607 When this warning is encountered, it may be too late to take remedial
4608 action except in cases where the breakpoint is hit earlier or more
4609 frequently than expected.
4611 @node Continuing and Stepping
4612 @section Continuing and Stepping
4616 @cindex resuming execution
4617 @dfn{Continuing} means resuming program execution until your program
4618 completes normally. In contrast, @dfn{stepping} means executing just
4619 one more ``step'' of your program, where ``step'' may mean either one
4620 line of source code, or one machine instruction (depending on what
4621 particular command you use). Either when continuing or when stepping,
4622 your program may stop even sooner, due to a breakpoint or a signal. (If
4623 it stops due to a signal, you may want to use @code{handle}, or use
4624 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4628 @kindex c @r{(@code{continue})}
4629 @kindex fg @r{(resume foreground execution)}
4630 @item continue @r{[}@var{ignore-count}@r{]}
4631 @itemx c @r{[}@var{ignore-count}@r{]}
4632 @itemx fg @r{[}@var{ignore-count}@r{]}
4633 Resume program execution, at the address where your program last stopped;
4634 any breakpoints set at that address are bypassed. The optional argument
4635 @var{ignore-count} allows you to specify a further number of times to
4636 ignore a breakpoint at this location; its effect is like that of
4637 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4639 The argument @var{ignore-count} is meaningful only when your program
4640 stopped due to a breakpoint. At other times, the argument to
4641 @code{continue} is ignored.
4643 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4644 debugged program is deemed to be the foreground program) are provided
4645 purely for convenience, and have exactly the same behavior as
4649 To resume execution at a different place, you can use @code{return}
4650 (@pxref{Returning, ,Returning from a Function}) to go back to the
4651 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4652 Different Address}) to go to an arbitrary location in your program.
4654 A typical technique for using stepping is to set a breakpoint
4655 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4656 beginning of the function or the section of your program where a problem
4657 is believed to lie, run your program until it stops at that breakpoint,
4658 and then step through the suspect area, examining the variables that are
4659 interesting, until you see the problem happen.
4663 @kindex s @r{(@code{step})}
4665 Continue running your program until control reaches a different source
4666 line, then stop it and return control to @value{GDBN}. This command is
4667 abbreviated @code{s}.
4670 @c "without debugging information" is imprecise; actually "without line
4671 @c numbers in the debugging information". (gcc -g1 has debugging info but
4672 @c not line numbers). But it seems complex to try to make that
4673 @c distinction here.
4674 @emph{Warning:} If you use the @code{step} command while control is
4675 within a function that was compiled without debugging information,
4676 execution proceeds until control reaches a function that does have
4677 debugging information. Likewise, it will not step into a function which
4678 is compiled without debugging information. To step through functions
4679 without debugging information, use the @code{stepi} command, described
4683 The @code{step} command only stops at the first instruction of a source
4684 line. This prevents the multiple stops that could otherwise occur in
4685 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4686 to stop if a function that has debugging information is called within
4687 the line. In other words, @code{step} @emph{steps inside} any functions
4688 called within the line.
4690 Also, the @code{step} command only enters a function if there is line
4691 number information for the function. Otherwise it acts like the
4692 @code{next} command. This avoids problems when using @code{cc -gl}
4693 on MIPS machines. Previously, @code{step} entered subroutines if there
4694 was any debugging information about the routine.
4696 @item step @var{count}
4697 Continue running as in @code{step}, but do so @var{count} times. If a
4698 breakpoint is reached, or a signal not related to stepping occurs before
4699 @var{count} steps, stepping stops right away.
4702 @kindex n @r{(@code{next})}
4703 @item next @r{[}@var{count}@r{]}
4704 Continue to the next source line in the current (innermost) stack frame.
4705 This is similar to @code{step}, but function calls that appear within
4706 the line of code are executed without stopping. Execution stops when
4707 control reaches a different line of code at the original stack level
4708 that was executing when you gave the @code{next} command. This command
4709 is abbreviated @code{n}.
4711 An argument @var{count} is a repeat count, as for @code{step}.
4714 @c FIX ME!! Do we delete this, or is there a way it fits in with
4715 @c the following paragraph? --- Vctoria
4717 @c @code{next} within a function that lacks debugging information acts like
4718 @c @code{step}, but any function calls appearing within the code of the
4719 @c function are executed without stopping.
4721 The @code{next} command only stops at the first instruction of a
4722 source line. This prevents multiple stops that could otherwise occur in
4723 @code{switch} statements, @code{for} loops, etc.
4725 @kindex set step-mode
4727 @cindex functions without line info, and stepping
4728 @cindex stepping into functions with no line info
4729 @itemx set step-mode on
4730 The @code{set step-mode on} command causes the @code{step} command to
4731 stop at the first instruction of a function which contains no debug line
4732 information rather than stepping over it.
4734 This is useful in cases where you may be interested in inspecting the
4735 machine instructions of a function which has no symbolic info and do not
4736 want @value{GDBN} to automatically skip over this function.
4738 @item set step-mode off
4739 Causes the @code{step} command to step over any functions which contains no
4740 debug information. This is the default.
4742 @item show step-mode
4743 Show whether @value{GDBN} will stop in or step over functions without
4744 source line debug information.
4747 @kindex fin @r{(@code{finish})}
4749 Continue running until just after function in the selected stack frame
4750 returns. Print the returned value (if any). This command can be
4751 abbreviated as @code{fin}.
4753 Contrast this with the @code{return} command (@pxref{Returning,
4754 ,Returning from a Function}).
4757 @kindex u @r{(@code{until})}
4758 @cindex run until specified location
4761 Continue running until a source line past the current line, in the
4762 current stack frame, is reached. This command is used to avoid single
4763 stepping through a loop more than once. It is like the @code{next}
4764 command, except that when @code{until} encounters a jump, it
4765 automatically continues execution until the program counter is greater
4766 than the address of the jump.
4768 This means that when you reach the end of a loop after single stepping
4769 though it, @code{until} makes your program continue execution until it
4770 exits the loop. In contrast, a @code{next} command at the end of a loop
4771 simply steps back to the beginning of the loop, which forces you to step
4772 through the next iteration.
4774 @code{until} always stops your program if it attempts to exit the current
4777 @code{until} may produce somewhat counterintuitive results if the order
4778 of machine code does not match the order of the source lines. For
4779 example, in the following excerpt from a debugging session, the @code{f}
4780 (@code{frame}) command shows that execution is stopped at line
4781 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4785 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4787 (@value{GDBP}) until
4788 195 for ( ; argc > 0; NEXTARG) @{
4791 This happened because, for execution efficiency, the compiler had
4792 generated code for the loop closure test at the end, rather than the
4793 start, of the loop---even though the test in a C @code{for}-loop is
4794 written before the body of the loop. The @code{until} command appeared
4795 to step back to the beginning of the loop when it advanced to this
4796 expression; however, it has not really gone to an earlier
4797 statement---not in terms of the actual machine code.
4799 @code{until} with no argument works by means of single
4800 instruction stepping, and hence is slower than @code{until} with an
4803 @item until @var{location}
4804 @itemx u @var{location}
4805 Continue running your program until either the specified location is
4806 reached, or the current stack frame returns. @var{location} is any of
4807 the forms described in @ref{Specify Location}.
4808 This form of the command uses temporary breakpoints, and
4809 hence is quicker than @code{until} without an argument. The specified
4810 location is actually reached only if it is in the current frame. This
4811 implies that @code{until} can be used to skip over recursive function
4812 invocations. For instance in the code below, if the current location is
4813 line @code{96}, issuing @code{until 99} will execute the program up to
4814 line @code{99} in the same invocation of factorial, i.e., after the inner
4815 invocations have returned.
4818 94 int factorial (int value)
4820 96 if (value > 1) @{
4821 97 value *= factorial (value - 1);
4828 @kindex advance @var{location}
4829 @itemx advance @var{location}
4830 Continue running the program up to the given @var{location}. An argument is
4831 required, which should be of one of the forms described in
4832 @ref{Specify Location}.
4833 Execution will also stop upon exit from the current stack
4834 frame. This command is similar to @code{until}, but @code{advance} will
4835 not skip over recursive function calls, and the target location doesn't
4836 have to be in the same frame as the current one.
4840 @kindex si @r{(@code{stepi})}
4842 @itemx stepi @var{arg}
4844 Execute one machine instruction, then stop and return to the debugger.
4846 It is often useful to do @samp{display/i $pc} when stepping by machine
4847 instructions. This makes @value{GDBN} automatically display the next
4848 instruction to be executed, each time your program stops. @xref{Auto
4849 Display,, Automatic Display}.
4851 An argument is a repeat count, as in @code{step}.
4855 @kindex ni @r{(@code{nexti})}
4857 @itemx nexti @var{arg}
4859 Execute one machine instruction, but if it is a function call,
4860 proceed until the function returns.
4862 An argument is a repeat count, as in @code{next}.
4865 @node Skipping Over Functions and Files
4866 @section Skipping Over Functions and Files
4867 @cindex skipping over functions and files
4869 The program you are debugging may contain some functions which are
4870 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
4871 skip a function or all functions in a file when stepping.
4873 For example, consider the following C function:
4884 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
4885 are not interested in stepping through @code{boring}. If you run @code{step}
4886 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
4887 step over both @code{foo} and @code{boring}!
4889 One solution is to @code{step} into @code{boring} and use the @code{finish}
4890 command to immediately exit it. But this can become tedious if @code{boring}
4891 is called from many places.
4893 A more flexible solution is to execute @kbd{skip boring}. This instructs
4894 @value{GDBN} never to step into @code{boring}. Now when you execute
4895 @code{step} at line 103, you'll step over @code{boring} and directly into
4898 You can also instruct @value{GDBN} to skip all functions in a file, with, for
4899 example, @code{skip file boring.c}.
4902 @kindex skip function
4903 @item skip @r{[}@var{linespec}@r{]}
4904 @itemx skip function @r{[}@var{linespec}@r{]}
4905 After running this command, the function named by @var{linespec} or the
4906 function containing the line named by @var{linespec} will be skipped over when
4907 stepping. @xref{Specify Location}.
4909 If you do not specify @var{linespec}, the function you're currently debugging
4912 (If you have a function called @code{file} that you want to skip, use
4913 @kbd{skip function file}.)
4916 @item skip file @r{[}@var{filename}@r{]}
4917 After running this command, any function whose source lives in @var{filename}
4918 will be skipped over when stepping.
4920 If you do not specify @var{filename}, functions whose source lives in the file
4921 you're currently debugging will be skipped.
4924 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
4925 These are the commands for managing your list of skips:
4929 @item info skip @r{[}@var{range}@r{]}
4930 Print details about the specified skip(s). If @var{range} is not specified,
4931 print a table with details about all functions and files marked for skipping.
4932 @code{info skip} prints the following information about each skip:
4936 A number identifying this skip.
4938 The type of this skip, either @samp{function} or @samp{file}.
4939 @item Enabled or Disabled
4940 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
4942 For function skips, this column indicates the address in memory of the function
4943 being skipped. If you've set a function skip on a function which has not yet
4944 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
4945 which has the function is loaded, @code{info skip} will show the function's
4948 For file skips, this field contains the filename being skipped. For functions
4949 skips, this field contains the function name and its line number in the file
4950 where it is defined.
4954 @item skip delete @r{[}@var{range}@r{]}
4955 Delete the specified skip(s). If @var{range} is not specified, delete all
4959 @item skip enable @r{[}@var{range}@r{]}
4960 Enable the specified skip(s). If @var{range} is not specified, enable all
4963 @kindex skip disable
4964 @item skip disable @r{[}@var{range}@r{]}
4965 Disable the specified skip(s). If @var{range} is not specified, disable all
4974 A signal is an asynchronous event that can happen in a program. The
4975 operating system defines the possible kinds of signals, and gives each
4976 kind a name and a number. For example, in Unix @code{SIGINT} is the
4977 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4978 @code{SIGSEGV} is the signal a program gets from referencing a place in
4979 memory far away from all the areas in use; @code{SIGALRM} occurs when
4980 the alarm clock timer goes off (which happens only if your program has
4981 requested an alarm).
4983 @cindex fatal signals
4984 Some signals, including @code{SIGALRM}, are a normal part of the
4985 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4986 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4987 program has not specified in advance some other way to handle the signal.
4988 @code{SIGINT} does not indicate an error in your program, but it is normally
4989 fatal so it can carry out the purpose of the interrupt: to kill the program.
4991 @value{GDBN} has the ability to detect any occurrence of a signal in your
4992 program. You can tell @value{GDBN} in advance what to do for each kind of
4995 @cindex handling signals
4996 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4997 @code{SIGALRM} be silently passed to your program
4998 (so as not to interfere with their role in the program's functioning)
4999 but to stop your program immediately whenever an error signal happens.
5000 You can change these settings with the @code{handle} command.
5003 @kindex info signals
5007 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5008 handle each one. You can use this to see the signal numbers of all
5009 the defined types of signals.
5011 @item info signals @var{sig}
5012 Similar, but print information only about the specified signal number.
5014 @code{info handle} is an alias for @code{info signals}.
5017 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5018 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5019 can be the number of a signal or its name (with or without the
5020 @samp{SIG} at the beginning); a list of signal numbers of the form
5021 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5022 known signals. Optional arguments @var{keywords}, described below,
5023 say what change to make.
5027 The keywords allowed by the @code{handle} command can be abbreviated.
5028 Their full names are:
5032 @value{GDBN} should not stop your program when this signal happens. It may
5033 still print a message telling you that the signal has come in.
5036 @value{GDBN} should stop your program when this signal happens. This implies
5037 the @code{print} keyword as well.
5040 @value{GDBN} should print a message when this signal happens.
5043 @value{GDBN} should not mention the occurrence of the signal at all. This
5044 implies the @code{nostop} keyword as well.
5048 @value{GDBN} should allow your program to see this signal; your program
5049 can handle the signal, or else it may terminate if the signal is fatal
5050 and not handled. @code{pass} and @code{noignore} are synonyms.
5054 @value{GDBN} should not allow your program to see this signal.
5055 @code{nopass} and @code{ignore} are synonyms.
5059 When a signal stops your program, the signal is not visible to the
5061 continue. Your program sees the signal then, if @code{pass} is in
5062 effect for the signal in question @emph{at that time}. In other words,
5063 after @value{GDBN} reports a signal, you can use the @code{handle}
5064 command with @code{pass} or @code{nopass} to control whether your
5065 program sees that signal when you continue.
5067 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5068 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5069 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5072 You can also use the @code{signal} command to prevent your program from
5073 seeing a signal, or cause it to see a signal it normally would not see,
5074 or to give it any signal at any time. For example, if your program stopped
5075 due to some sort of memory reference error, you might store correct
5076 values into the erroneous variables and continue, hoping to see more
5077 execution; but your program would probably terminate immediately as
5078 a result of the fatal signal once it saw the signal. To prevent this,
5079 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5082 @cindex extra signal information
5083 @anchor{extra signal information}
5085 On some targets, @value{GDBN} can inspect extra signal information
5086 associated with the intercepted signal, before it is actually
5087 delivered to the program being debugged. This information is exported
5088 by the convenience variable @code{$_siginfo}, and consists of data
5089 that is passed by the kernel to the signal handler at the time of the
5090 receipt of a signal. The data type of the information itself is
5091 target dependent. You can see the data type using the @code{ptype
5092 $_siginfo} command. On Unix systems, it typically corresponds to the
5093 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5096 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5097 referenced address that raised a segmentation fault.
5101 (@value{GDBP}) continue
5102 Program received signal SIGSEGV, Segmentation fault.
5103 0x0000000000400766 in main ()
5105 (@value{GDBP}) ptype $_siginfo
5112 struct @{...@} _kill;
5113 struct @{...@} _timer;
5115 struct @{...@} _sigchld;
5116 struct @{...@} _sigfault;
5117 struct @{...@} _sigpoll;
5120 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5124 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5125 $1 = (void *) 0x7ffff7ff7000
5129 Depending on target support, @code{$_siginfo} may also be writable.
5132 @section Stopping and Starting Multi-thread Programs
5134 @cindex stopped threads
5135 @cindex threads, stopped
5137 @cindex continuing threads
5138 @cindex threads, continuing
5140 @value{GDBN} supports debugging programs with multiple threads
5141 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5142 are two modes of controlling execution of your program within the
5143 debugger. In the default mode, referred to as @dfn{all-stop mode},
5144 when any thread in your program stops (for example, at a breakpoint
5145 or while being stepped), all other threads in the program are also stopped by
5146 @value{GDBN}. On some targets, @value{GDBN} also supports
5147 @dfn{non-stop mode}, in which other threads can continue to run freely while
5148 you examine the stopped thread in the debugger.
5151 * All-Stop Mode:: All threads stop when GDB takes control
5152 * Non-Stop Mode:: Other threads continue to execute
5153 * Background Execution:: Running your program asynchronously
5154 * Thread-Specific Breakpoints:: Controlling breakpoints
5155 * Interrupted System Calls:: GDB may interfere with system calls
5156 * Observer Mode:: GDB does not alter program behavior
5160 @subsection All-Stop Mode
5162 @cindex all-stop mode
5164 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5165 @emph{all} threads of execution stop, not just the current thread. This
5166 allows you to examine the overall state of the program, including
5167 switching between threads, without worrying that things may change
5170 Conversely, whenever you restart the program, @emph{all} threads start
5171 executing. @emph{This is true even when single-stepping} with commands
5172 like @code{step} or @code{next}.
5174 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5175 Since thread scheduling is up to your debugging target's operating
5176 system (not controlled by @value{GDBN}), other threads may
5177 execute more than one statement while the current thread completes a
5178 single step. Moreover, in general other threads stop in the middle of a
5179 statement, rather than at a clean statement boundary, when the program
5182 You might even find your program stopped in another thread after
5183 continuing or even single-stepping. This happens whenever some other
5184 thread runs into a breakpoint, a signal, or an exception before the
5185 first thread completes whatever you requested.
5187 @cindex automatic thread selection
5188 @cindex switching threads automatically
5189 @cindex threads, automatic switching
5190 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5191 signal, it automatically selects the thread where that breakpoint or
5192 signal happened. @value{GDBN} alerts you to the context switch with a
5193 message such as @samp{[Switching to Thread @var{n}]} to identify the
5196 On some OSes, you can modify @value{GDBN}'s default behavior by
5197 locking the OS scheduler to allow only a single thread to run.
5200 @item set scheduler-locking @var{mode}
5201 @cindex scheduler locking mode
5202 @cindex lock scheduler
5203 Set the scheduler locking mode. If it is @code{off}, then there is no
5204 locking and any thread may run at any time. If @code{on}, then only the
5205 current thread may run when the inferior is resumed. The @code{step}
5206 mode optimizes for single-stepping; it prevents other threads
5207 from preempting the current thread while you are stepping, so that
5208 the focus of debugging does not change unexpectedly.
5209 Other threads only rarely (or never) get a chance to run
5210 when you step. They are more likely to run when you @samp{next} over a
5211 function call, and they are completely free to run when you use commands
5212 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5213 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5214 the current thread away from the thread that you are debugging.
5216 @item show scheduler-locking
5217 Display the current scheduler locking mode.
5220 @cindex resume threads of multiple processes simultaneously
5221 By default, when you issue one of the execution commands such as
5222 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5223 threads of the current inferior to run. For example, if @value{GDBN}
5224 is attached to two inferiors, each with two threads, the
5225 @code{continue} command resumes only the two threads of the current
5226 inferior. This is useful, for example, when you debug a program that
5227 forks and you want to hold the parent stopped (so that, for instance,
5228 it doesn't run to exit), while you debug the child. In other
5229 situations, you may not be interested in inspecting the current state
5230 of any of the processes @value{GDBN} is attached to, and you may want
5231 to resume them all until some breakpoint is hit. In the latter case,
5232 you can instruct @value{GDBN} to allow all threads of all the
5233 inferiors to run with the @w{@code{set schedule-multiple}} command.
5236 @kindex set schedule-multiple
5237 @item set schedule-multiple
5238 Set the mode for allowing threads of multiple processes to be resumed
5239 when an execution command is issued. When @code{on}, all threads of
5240 all processes are allowed to run. When @code{off}, only the threads
5241 of the current process are resumed. The default is @code{off}. The
5242 @code{scheduler-locking} mode takes precedence when set to @code{on},
5243 or while you are stepping and set to @code{step}.
5245 @item show schedule-multiple
5246 Display the current mode for resuming the execution of threads of
5251 @subsection Non-Stop Mode
5253 @cindex non-stop mode
5255 @c This section is really only a place-holder, and needs to be expanded
5256 @c with more details.
5258 For some multi-threaded targets, @value{GDBN} supports an optional
5259 mode of operation in which you can examine stopped program threads in
5260 the debugger while other threads continue to execute freely. This
5261 minimizes intrusion when debugging live systems, such as programs
5262 where some threads have real-time constraints or must continue to
5263 respond to external events. This is referred to as @dfn{non-stop} mode.
5265 In non-stop mode, when a thread stops to report a debugging event,
5266 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5267 threads as well, in contrast to the all-stop mode behavior. Additionally,
5268 execution commands such as @code{continue} and @code{step} apply by default
5269 only to the current thread in non-stop mode, rather than all threads as
5270 in all-stop mode. This allows you to control threads explicitly in
5271 ways that are not possible in all-stop mode --- for example, stepping
5272 one thread while allowing others to run freely, stepping
5273 one thread while holding all others stopped, or stepping several threads
5274 independently and simultaneously.
5276 To enter non-stop mode, use this sequence of commands before you run
5277 or attach to your program:
5280 # Enable the async interface.
5283 # If using the CLI, pagination breaks non-stop.
5286 # Finally, turn it on!
5290 You can use these commands to manipulate the non-stop mode setting:
5293 @kindex set non-stop
5294 @item set non-stop on
5295 Enable selection of non-stop mode.
5296 @item set non-stop off
5297 Disable selection of non-stop mode.
5298 @kindex show non-stop
5300 Show the current non-stop enablement setting.
5303 Note these commands only reflect whether non-stop mode is enabled,
5304 not whether the currently-executing program is being run in non-stop mode.
5305 In particular, the @code{set non-stop} preference is only consulted when
5306 @value{GDBN} starts or connects to the target program, and it is generally
5307 not possible to switch modes once debugging has started. Furthermore,
5308 since not all targets support non-stop mode, even when you have enabled
5309 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5312 In non-stop mode, all execution commands apply only to the current thread
5313 by default. That is, @code{continue} only continues one thread.
5314 To continue all threads, issue @code{continue -a} or @code{c -a}.
5316 You can use @value{GDBN}'s background execution commands
5317 (@pxref{Background Execution}) to run some threads in the background
5318 while you continue to examine or step others from @value{GDBN}.
5319 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5320 always executed asynchronously in non-stop mode.
5322 Suspending execution is done with the @code{interrupt} command when
5323 running in the background, or @kbd{Ctrl-c} during foreground execution.
5324 In all-stop mode, this stops the whole process;
5325 but in non-stop mode the interrupt applies only to the current thread.
5326 To stop the whole program, use @code{interrupt -a}.
5328 Other execution commands do not currently support the @code{-a} option.
5330 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5331 that thread current, as it does in all-stop mode. This is because the
5332 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5333 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5334 changed to a different thread just as you entered a command to operate on the
5335 previously current thread.
5337 @node Background Execution
5338 @subsection Background Execution
5340 @cindex foreground execution
5341 @cindex background execution
5342 @cindex asynchronous execution
5343 @cindex execution, foreground, background and asynchronous
5345 @value{GDBN}'s execution commands have two variants: the normal
5346 foreground (synchronous) behavior, and a background
5347 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5348 the program to report that some thread has stopped before prompting for
5349 another command. In background execution, @value{GDBN} immediately gives
5350 a command prompt so that you can issue other commands while your program runs.
5352 You need to explicitly enable asynchronous mode before you can use
5353 background execution commands. You can use these commands to
5354 manipulate the asynchronous mode setting:
5357 @kindex set target-async
5358 @item set target-async on
5359 Enable asynchronous mode.
5360 @item set target-async off
5361 Disable asynchronous mode.
5362 @kindex show target-async
5363 @item show target-async
5364 Show the current target-async setting.
5367 If the target doesn't support async mode, @value{GDBN} issues an error
5368 message if you attempt to use the background execution commands.
5370 To specify background execution, add a @code{&} to the command. For example,
5371 the background form of the @code{continue} command is @code{continue&}, or
5372 just @code{c&}. The execution commands that accept background execution
5378 @xref{Starting, , Starting your Program}.
5382 @xref{Attach, , Debugging an Already-running Process}.
5386 @xref{Continuing and Stepping, step}.
5390 @xref{Continuing and Stepping, stepi}.
5394 @xref{Continuing and Stepping, next}.
5398 @xref{Continuing and Stepping, nexti}.
5402 @xref{Continuing and Stepping, continue}.
5406 @xref{Continuing and Stepping, finish}.
5410 @xref{Continuing and Stepping, until}.
5414 Background execution is especially useful in conjunction with non-stop
5415 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5416 However, you can also use these commands in the normal all-stop mode with
5417 the restriction that you cannot issue another execution command until the
5418 previous one finishes. Examples of commands that are valid in all-stop
5419 mode while the program is running include @code{help} and @code{info break}.
5421 You can interrupt your program while it is running in the background by
5422 using the @code{interrupt} command.
5429 Suspend execution of the running program. In all-stop mode,
5430 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5431 only the current thread. To stop the whole program in non-stop mode,
5432 use @code{interrupt -a}.
5435 @node Thread-Specific Breakpoints
5436 @subsection Thread-Specific Breakpoints
5438 When your program has multiple threads (@pxref{Threads,, Debugging
5439 Programs with Multiple Threads}), you can choose whether to set
5440 breakpoints on all threads, or on a particular thread.
5443 @cindex breakpoints and threads
5444 @cindex thread breakpoints
5445 @kindex break @dots{} thread @var{threadno}
5446 @item break @var{linespec} thread @var{threadno}
5447 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5448 @var{linespec} specifies source lines; there are several ways of
5449 writing them (@pxref{Specify Location}), but the effect is always to
5450 specify some source line.
5452 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5453 to specify that you only want @value{GDBN} to stop the program when a
5454 particular thread reaches this breakpoint. @var{threadno} is one of the
5455 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5456 column of the @samp{info threads} display.
5458 If you do not specify @samp{thread @var{threadno}} when you set a
5459 breakpoint, the breakpoint applies to @emph{all} threads of your
5462 You can use the @code{thread} qualifier on conditional breakpoints as
5463 well; in this case, place @samp{thread @var{threadno}} before or
5464 after the breakpoint condition, like this:
5467 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5472 @node Interrupted System Calls
5473 @subsection Interrupted System Calls
5475 @cindex thread breakpoints and system calls
5476 @cindex system calls and thread breakpoints
5477 @cindex premature return from system calls
5478 There is an unfortunate side effect when using @value{GDBN} to debug
5479 multi-threaded programs. If one thread stops for a
5480 breakpoint, or for some other reason, and another thread is blocked in a
5481 system call, then the system call may return prematurely. This is a
5482 consequence of the interaction between multiple threads and the signals
5483 that @value{GDBN} uses to implement breakpoints and other events that
5486 To handle this problem, your program should check the return value of
5487 each system call and react appropriately. This is good programming
5490 For example, do not write code like this:
5496 The call to @code{sleep} will return early if a different thread stops
5497 at a breakpoint or for some other reason.
5499 Instead, write this:
5504 unslept = sleep (unslept);
5507 A system call is allowed to return early, so the system is still
5508 conforming to its specification. But @value{GDBN} does cause your
5509 multi-threaded program to behave differently than it would without
5512 Also, @value{GDBN} uses internal breakpoints in the thread library to
5513 monitor certain events such as thread creation and thread destruction.
5514 When such an event happens, a system call in another thread may return
5515 prematurely, even though your program does not appear to stop.
5518 @subsection Observer Mode
5520 If you want to build on non-stop mode and observe program behavior
5521 without any chance of disruption by @value{GDBN}, you can set
5522 variables to disable all of the debugger's attempts to modify state,
5523 whether by writing memory, inserting breakpoints, etc. These operate
5524 at a low level, intercepting operations from all commands.
5526 When all of these are set to @code{off}, then @value{GDBN} is said to
5527 be @dfn{observer mode}. As a convenience, the variable
5528 @code{observer} can be set to disable these, plus enable non-stop
5531 Note that @value{GDBN} will not prevent you from making nonsensical
5532 combinations of these settings. For instance, if you have enabled
5533 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5534 then breakpoints that work by writing trap instructions into the code
5535 stream will still not be able to be placed.
5540 @item set observer on
5541 @itemx set observer off
5542 When set to @code{on}, this disables all the permission variables
5543 below (except for @code{insert-fast-tracepoints}), plus enables
5544 non-stop debugging. Setting this to @code{off} switches back to
5545 normal debugging, though remaining in non-stop mode.
5548 Show whether observer mode is on or off.
5550 @kindex may-write-registers
5551 @item set may-write-registers on
5552 @itemx set may-write-registers off
5553 This controls whether @value{GDBN} will attempt to alter the values of
5554 registers, such as with assignment expressions in @code{print}, or the
5555 @code{jump} command. It defaults to @code{on}.
5557 @item show may-write-registers
5558 Show the current permission to write registers.
5560 @kindex may-write-memory
5561 @item set may-write-memory on
5562 @itemx set may-write-memory off
5563 This controls whether @value{GDBN} will attempt to alter the contents
5564 of memory, such as with assignment expressions in @code{print}. It
5565 defaults to @code{on}.
5567 @item show may-write-memory
5568 Show the current permission to write memory.
5570 @kindex may-insert-breakpoints
5571 @item set may-insert-breakpoints on
5572 @itemx set may-insert-breakpoints off
5573 This controls whether @value{GDBN} will attempt to insert breakpoints.
5574 This affects all breakpoints, including internal breakpoints defined
5575 by @value{GDBN}. It defaults to @code{on}.
5577 @item show may-insert-breakpoints
5578 Show the current permission to insert breakpoints.
5580 @kindex may-insert-tracepoints
5581 @item set may-insert-tracepoints on
5582 @itemx set may-insert-tracepoints off
5583 This controls whether @value{GDBN} will attempt to insert (regular)
5584 tracepoints at the beginning of a tracing experiment. It affects only
5585 non-fast tracepoints, fast tracepoints being under the control of
5586 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5588 @item show may-insert-tracepoints
5589 Show the current permission to insert tracepoints.
5591 @kindex may-insert-fast-tracepoints
5592 @item set may-insert-fast-tracepoints on
5593 @itemx set may-insert-fast-tracepoints off
5594 This controls whether @value{GDBN} will attempt to insert fast
5595 tracepoints at the beginning of a tracing experiment. It affects only
5596 fast tracepoints, regular (non-fast) tracepoints being under the
5597 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5599 @item show may-insert-fast-tracepoints
5600 Show the current permission to insert fast tracepoints.
5602 @kindex may-interrupt
5603 @item set may-interrupt on
5604 @itemx set may-interrupt off
5605 This controls whether @value{GDBN} will attempt to interrupt or stop
5606 program execution. When this variable is @code{off}, the
5607 @code{interrupt} command will have no effect, nor will
5608 @kbd{Ctrl-c}. It defaults to @code{on}.
5610 @item show may-interrupt
5611 Show the current permission to interrupt or stop the program.
5615 @node Reverse Execution
5616 @chapter Running programs backward
5617 @cindex reverse execution
5618 @cindex running programs backward
5620 When you are debugging a program, it is not unusual to realize that
5621 you have gone too far, and some event of interest has already happened.
5622 If the target environment supports it, @value{GDBN} can allow you to
5623 ``rewind'' the program by running it backward.
5625 A target environment that supports reverse execution should be able
5626 to ``undo'' the changes in machine state that have taken place as the
5627 program was executing normally. Variables, registers etc.@: should
5628 revert to their previous values. Obviously this requires a great
5629 deal of sophistication on the part of the target environment; not
5630 all target environments can support reverse execution.
5632 When a program is executed in reverse, the instructions that
5633 have most recently been executed are ``un-executed'', in reverse
5634 order. The program counter runs backward, following the previous
5635 thread of execution in reverse. As each instruction is ``un-executed'',
5636 the values of memory and/or registers that were changed by that
5637 instruction are reverted to their previous states. After executing
5638 a piece of source code in reverse, all side effects of that code
5639 should be ``undone'', and all variables should be returned to their
5640 prior values@footnote{
5641 Note that some side effects are easier to undo than others. For instance,
5642 memory and registers are relatively easy, but device I/O is hard. Some
5643 targets may be able undo things like device I/O, and some may not.
5645 The contract between @value{GDBN} and the reverse executing target
5646 requires only that the target do something reasonable when
5647 @value{GDBN} tells it to execute backwards, and then report the
5648 results back to @value{GDBN}. Whatever the target reports back to
5649 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5650 assumes that the memory and registers that the target reports are in a
5651 consistant state, but @value{GDBN} accepts whatever it is given.
5654 If you are debugging in a target environment that supports
5655 reverse execution, @value{GDBN} provides the following commands.
5658 @kindex reverse-continue
5659 @kindex rc @r{(@code{reverse-continue})}
5660 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5661 @itemx rc @r{[}@var{ignore-count}@r{]}
5662 Beginning at the point where your program last stopped, start executing
5663 in reverse. Reverse execution will stop for breakpoints and synchronous
5664 exceptions (signals), just like normal execution. Behavior of
5665 asynchronous signals depends on the target environment.
5667 @kindex reverse-step
5668 @kindex rs @r{(@code{step})}
5669 @item reverse-step @r{[}@var{count}@r{]}
5670 Run the program backward until control reaches the start of a
5671 different source line; then stop it, and return control to @value{GDBN}.
5673 Like the @code{step} command, @code{reverse-step} will only stop
5674 at the beginning of a source line. It ``un-executes'' the previously
5675 executed source line. If the previous source line included calls to
5676 debuggable functions, @code{reverse-step} will step (backward) into
5677 the called function, stopping at the beginning of the @emph{last}
5678 statement in the called function (typically a return statement).
5680 Also, as with the @code{step} command, if non-debuggable functions are
5681 called, @code{reverse-step} will run thru them backward without stopping.
5683 @kindex reverse-stepi
5684 @kindex rsi @r{(@code{reverse-stepi})}
5685 @item reverse-stepi @r{[}@var{count}@r{]}
5686 Reverse-execute one machine instruction. Note that the instruction
5687 to be reverse-executed is @emph{not} the one pointed to by the program
5688 counter, but the instruction executed prior to that one. For instance,
5689 if the last instruction was a jump, @code{reverse-stepi} will take you
5690 back from the destination of the jump to the jump instruction itself.
5692 @kindex reverse-next
5693 @kindex rn @r{(@code{reverse-next})}
5694 @item reverse-next @r{[}@var{count}@r{]}
5695 Run backward to the beginning of the previous line executed in
5696 the current (innermost) stack frame. If the line contains function
5697 calls, they will be ``un-executed'' without stopping. Starting from
5698 the first line of a function, @code{reverse-next} will take you back
5699 to the caller of that function, @emph{before} the function was called,
5700 just as the normal @code{next} command would take you from the last
5701 line of a function back to its return to its caller
5702 @footnote{Unless the code is too heavily optimized.}.
5704 @kindex reverse-nexti
5705 @kindex rni @r{(@code{reverse-nexti})}
5706 @item reverse-nexti @r{[}@var{count}@r{]}
5707 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5708 in reverse, except that called functions are ``un-executed'' atomically.
5709 That is, if the previously executed instruction was a return from
5710 another function, @code{reverse-nexti} will continue to execute
5711 in reverse until the call to that function (from the current stack
5714 @kindex reverse-finish
5715 @item reverse-finish
5716 Just as the @code{finish} command takes you to the point where the
5717 current function returns, @code{reverse-finish} takes you to the point
5718 where it was called. Instead of ending up at the end of the current
5719 function invocation, you end up at the beginning.
5721 @kindex set exec-direction
5722 @item set exec-direction
5723 Set the direction of target execution.
5724 @itemx set exec-direction reverse
5725 @cindex execute forward or backward in time
5726 @value{GDBN} will perform all execution commands in reverse, until the
5727 exec-direction mode is changed to ``forward''. Affected commands include
5728 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5729 command cannot be used in reverse mode.
5730 @item set exec-direction forward
5731 @value{GDBN} will perform all execution commands in the normal fashion.
5732 This is the default.
5736 @node Process Record and Replay
5737 @chapter Recording Inferior's Execution and Replaying It
5738 @cindex process record and replay
5739 @cindex recording inferior's execution and replaying it
5741 On some platforms, @value{GDBN} provides a special @dfn{process record
5742 and replay} target that can record a log of the process execution, and
5743 replay it later with both forward and reverse execution commands.
5746 When this target is in use, if the execution log includes the record
5747 for the next instruction, @value{GDBN} will debug in @dfn{replay
5748 mode}. In the replay mode, the inferior does not really execute code
5749 instructions. Instead, all the events that normally happen during
5750 code execution are taken from the execution log. While code is not
5751 really executed in replay mode, the values of registers (including the
5752 program counter register) and the memory of the inferior are still
5753 changed as they normally would. Their contents are taken from the
5757 If the record for the next instruction is not in the execution log,
5758 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5759 inferior executes normally, and @value{GDBN} records the execution log
5762 The process record and replay target supports reverse execution
5763 (@pxref{Reverse Execution}), even if the platform on which the
5764 inferior runs does not. However, the reverse execution is limited in
5765 this case by the range of the instructions recorded in the execution
5766 log. In other words, reverse execution on platforms that don't
5767 support it directly can only be done in the replay mode.
5769 When debugging in the reverse direction, @value{GDBN} will work in
5770 replay mode as long as the execution log includes the record for the
5771 previous instruction; otherwise, it will work in record mode, if the
5772 platform supports reverse execution, or stop if not.
5774 For architecture environments that support process record and replay,
5775 @value{GDBN} provides the following commands:
5778 @kindex target record
5782 This command starts the process record and replay target. The process
5783 record and replay target can only debug a process that is already
5784 running. Therefore, you need first to start the process with the
5785 @kbd{run} or @kbd{start} commands, and then start the recording with
5786 the @kbd{target record} command.
5788 Both @code{record} and @code{rec} are aliases of @code{target record}.
5790 @cindex displaced stepping, and process record and replay
5791 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5792 will be automatically disabled when process record and replay target
5793 is started. That's because the process record and replay target
5794 doesn't support displaced stepping.
5796 @cindex non-stop mode, and process record and replay
5797 @cindex asynchronous execution, and process record and replay
5798 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5799 the asynchronous execution mode (@pxref{Background Execution}), the
5800 process record and replay target cannot be started because it doesn't
5801 support these two modes.
5806 Stop the process record and replay target. When process record and
5807 replay target stops, the entire execution log will be deleted and the
5808 inferior will either be terminated, or will remain in its final state.
5810 When you stop the process record and replay target in record mode (at
5811 the end of the execution log), the inferior will be stopped at the
5812 next instruction that would have been recorded. In other words, if
5813 you record for a while and then stop recording, the inferior process
5814 will be left in the same state as if the recording never happened.
5816 On the other hand, if the process record and replay target is stopped
5817 while in replay mode (that is, not at the end of the execution log,
5818 but at some earlier point), the inferior process will become ``live''
5819 at that earlier state, and it will then be possible to continue the
5820 usual ``live'' debugging of the process from that state.
5822 When the inferior process exits, or @value{GDBN} detaches from it,
5823 process record and replay target will automatically stop itself.
5826 @item record save @var{filename}
5827 Save the execution log to a file @file{@var{filename}}.
5828 Default filename is @file{gdb_record.@var{process_id}}, where
5829 @var{process_id} is the process ID of the inferior.
5831 @kindex record restore
5832 @item record restore @var{filename}
5833 Restore the execution log from a file @file{@var{filename}}.
5834 File must have been created with @code{record save}.
5836 @kindex set record insn-number-max
5837 @item set record insn-number-max @var{limit}
5838 Set the limit of instructions to be recorded. Default value is 200000.
5840 If @var{limit} is a positive number, then @value{GDBN} will start
5841 deleting instructions from the log once the number of the record
5842 instructions becomes greater than @var{limit}. For every new recorded
5843 instruction, @value{GDBN} will delete the earliest recorded
5844 instruction to keep the number of recorded instructions at the limit.
5845 (Since deleting recorded instructions loses information, @value{GDBN}
5846 lets you control what happens when the limit is reached, by means of
5847 the @code{stop-at-limit} option, described below.)
5849 If @var{limit} is zero, @value{GDBN} will never delete recorded
5850 instructions from the execution log. The number of recorded
5851 instructions is unlimited in this case.
5853 @kindex show record insn-number-max
5854 @item show record insn-number-max
5855 Show the limit of instructions to be recorded.
5857 @kindex set record stop-at-limit
5858 @item set record stop-at-limit
5859 Control the behavior when the number of recorded instructions reaches
5860 the limit. If ON (the default), @value{GDBN} will stop when the limit
5861 is reached for the first time and ask you whether you want to stop the
5862 inferior or continue running it and recording the execution log. If
5863 you decide to continue recording, each new recorded instruction will
5864 cause the oldest one to be deleted.
5866 If this option is OFF, @value{GDBN} will automatically delete the
5867 oldest record to make room for each new one, without asking.
5869 @kindex show record stop-at-limit
5870 @item show record stop-at-limit
5871 Show the current setting of @code{stop-at-limit}.
5873 @kindex set record memory-query
5874 @item set record memory-query
5875 Control the behavior when @value{GDBN} is unable to record memory
5876 changes caused by an instruction. If ON, @value{GDBN} will query
5877 whether to stop the inferior in that case.
5879 If this option is OFF (the default), @value{GDBN} will automatically
5880 ignore the effect of such instructions on memory. Later, when
5881 @value{GDBN} replays this execution log, it will mark the log of this
5882 instruction as not accessible, and it will not affect the replay
5885 @kindex show record memory-query
5886 @item show record memory-query
5887 Show the current setting of @code{memory-query}.
5891 Show various statistics about the state of process record and its
5892 in-memory execution log buffer, including:
5896 Whether in record mode or replay mode.
5898 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5900 Highest recorded instruction number.
5902 Current instruction about to be replayed (if in replay mode).
5904 Number of instructions contained in the execution log.
5906 Maximum number of instructions that may be contained in the execution log.
5909 @kindex record delete
5912 When record target runs in replay mode (``in the past''), delete the
5913 subsequent execution log and begin to record a new execution log starting
5914 from the current address. This means you will abandon the previously
5915 recorded ``future'' and begin recording a new ``future''.
5920 @chapter Examining the Stack
5922 When your program has stopped, the first thing you need to know is where it
5923 stopped and how it got there.
5926 Each time your program performs a function call, information about the call
5928 That information includes the location of the call in your program,
5929 the arguments of the call,
5930 and the local variables of the function being called.
5931 The information is saved in a block of data called a @dfn{stack frame}.
5932 The stack frames are allocated in a region of memory called the @dfn{call
5935 When your program stops, the @value{GDBN} commands for examining the
5936 stack allow you to see all of this information.
5938 @cindex selected frame
5939 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5940 @value{GDBN} commands refer implicitly to the selected frame. In
5941 particular, whenever you ask @value{GDBN} for the value of a variable in
5942 your program, the value is found in the selected frame. There are
5943 special @value{GDBN} commands to select whichever frame you are
5944 interested in. @xref{Selection, ,Selecting a Frame}.
5946 When your program stops, @value{GDBN} automatically selects the
5947 currently executing frame and describes it briefly, similar to the
5948 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5951 * Frames:: Stack frames
5952 * Backtrace:: Backtraces
5953 * Selection:: Selecting a frame
5954 * Frame Info:: Information on a frame
5959 @section Stack Frames
5961 @cindex frame, definition
5963 The call stack is divided up into contiguous pieces called @dfn{stack
5964 frames}, or @dfn{frames} for short; each frame is the data associated
5965 with one call to one function. The frame contains the arguments given
5966 to the function, the function's local variables, and the address at
5967 which the function is executing.
5969 @cindex initial frame
5970 @cindex outermost frame
5971 @cindex innermost frame
5972 When your program is started, the stack has only one frame, that of the
5973 function @code{main}. This is called the @dfn{initial} frame or the
5974 @dfn{outermost} frame. Each time a function is called, a new frame is
5975 made. Each time a function returns, the frame for that function invocation
5976 is eliminated. If a function is recursive, there can be many frames for
5977 the same function. The frame for the function in which execution is
5978 actually occurring is called the @dfn{innermost} frame. This is the most
5979 recently created of all the stack frames that still exist.
5981 @cindex frame pointer
5982 Inside your program, stack frames are identified by their addresses. A
5983 stack frame consists of many bytes, each of which has its own address; each
5984 kind of computer has a convention for choosing one byte whose
5985 address serves as the address of the frame. Usually this address is kept
5986 in a register called the @dfn{frame pointer register}
5987 (@pxref{Registers, $fp}) while execution is going on in that frame.
5989 @cindex frame number
5990 @value{GDBN} assigns numbers to all existing stack frames, starting with
5991 zero for the innermost frame, one for the frame that called it,
5992 and so on upward. These numbers do not really exist in your program;
5993 they are assigned by @value{GDBN} to give you a way of designating stack
5994 frames in @value{GDBN} commands.
5996 @c The -fomit-frame-pointer below perennially causes hbox overflow
5997 @c underflow problems.
5998 @cindex frameless execution
5999 Some compilers provide a way to compile functions so that they operate
6000 without stack frames. (For example, the @value{NGCC} option
6002 @samp{-fomit-frame-pointer}
6004 generates functions without a frame.)
6005 This is occasionally done with heavily used library functions to save
6006 the frame setup time. @value{GDBN} has limited facilities for dealing
6007 with these function invocations. If the innermost function invocation
6008 has no stack frame, @value{GDBN} nevertheless regards it as though
6009 it had a separate frame, which is numbered zero as usual, allowing
6010 correct tracing of the function call chain. However, @value{GDBN} has
6011 no provision for frameless functions elsewhere in the stack.
6014 @kindex frame@r{, command}
6015 @cindex current stack frame
6016 @item frame @var{args}
6017 The @code{frame} command allows you to move from one stack frame to another,
6018 and to print the stack frame you select. @var{args} may be either the
6019 address of the frame or the stack frame number. Without an argument,
6020 @code{frame} prints the current stack frame.
6022 @kindex select-frame
6023 @cindex selecting frame silently
6025 The @code{select-frame} command allows you to move from one stack frame
6026 to another without printing the frame. This is the silent version of
6034 @cindex call stack traces
6035 A backtrace is a summary of how your program got where it is. It shows one
6036 line per frame, for many frames, starting with the currently executing
6037 frame (frame zero), followed by its caller (frame one), and on up the
6042 @kindex bt @r{(@code{backtrace})}
6045 Print a backtrace of the entire stack: one line per frame for all
6046 frames in the stack.
6048 You can stop the backtrace at any time by typing the system interrupt
6049 character, normally @kbd{Ctrl-c}.
6051 @item backtrace @var{n}
6053 Similar, but print only the innermost @var{n} frames.
6055 @item backtrace -@var{n}
6057 Similar, but print only the outermost @var{n} frames.
6059 @item backtrace full
6061 @itemx bt full @var{n}
6062 @itemx bt full -@var{n}
6063 Print the values of the local variables also. @var{n} specifies the
6064 number of frames to print, as described above.
6069 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6070 are additional aliases for @code{backtrace}.
6072 @cindex multiple threads, backtrace
6073 In a multi-threaded program, @value{GDBN} by default shows the
6074 backtrace only for the current thread. To display the backtrace for
6075 several or all of the threads, use the command @code{thread apply}
6076 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6077 apply all backtrace}, @value{GDBN} will display the backtrace for all
6078 the threads; this is handy when you debug a core dump of a
6079 multi-threaded program.
6081 Each line in the backtrace shows the frame number and the function name.
6082 The program counter value is also shown---unless you use @code{set
6083 print address off}. The backtrace also shows the source file name and
6084 line number, as well as the arguments to the function. The program
6085 counter value is omitted if it is at the beginning of the code for that
6088 Here is an example of a backtrace. It was made with the command
6089 @samp{bt 3}, so it shows the innermost three frames.
6093 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6095 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6096 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6098 (More stack frames follow...)
6103 The display for frame zero does not begin with a program counter
6104 value, indicating that your program has stopped at the beginning of the
6105 code for line @code{993} of @code{builtin.c}.
6108 The value of parameter @code{data} in frame 1 has been replaced by
6109 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6110 only if it is a scalar (integer, pointer, enumeration, etc). See command
6111 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6112 on how to configure the way function parameter values are printed.
6114 @cindex optimized out, in backtrace
6115 @cindex function call arguments, optimized out
6116 If your program was compiled with optimizations, some compilers will
6117 optimize away arguments passed to functions if those arguments are
6118 never used after the call. Such optimizations generate code that
6119 passes arguments through registers, but doesn't store those arguments
6120 in the stack frame. @value{GDBN} has no way of displaying such
6121 arguments in stack frames other than the innermost one. Here's what
6122 such a backtrace might look like:
6126 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6128 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6129 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6131 (More stack frames follow...)
6136 The values of arguments that were not saved in their stack frames are
6137 shown as @samp{<optimized out>}.
6139 If you need to display the values of such optimized-out arguments,
6140 either deduce that from other variables whose values depend on the one
6141 you are interested in, or recompile without optimizations.
6143 @cindex backtrace beyond @code{main} function
6144 @cindex program entry point
6145 @cindex startup code, and backtrace
6146 Most programs have a standard user entry point---a place where system
6147 libraries and startup code transition into user code. For C this is
6148 @code{main}@footnote{
6149 Note that embedded programs (the so-called ``free-standing''
6150 environment) are not required to have a @code{main} function as the
6151 entry point. They could even have multiple entry points.}.
6152 When @value{GDBN} finds the entry function in a backtrace
6153 it will terminate the backtrace, to avoid tracing into highly
6154 system-specific (and generally uninteresting) code.
6156 If you need to examine the startup code, or limit the number of levels
6157 in a backtrace, you can change this behavior:
6160 @item set backtrace past-main
6161 @itemx set backtrace past-main on
6162 @kindex set backtrace
6163 Backtraces will continue past the user entry point.
6165 @item set backtrace past-main off
6166 Backtraces will stop when they encounter the user entry point. This is the
6169 @item show backtrace past-main
6170 @kindex show backtrace
6171 Display the current user entry point backtrace policy.
6173 @item set backtrace past-entry
6174 @itemx set backtrace past-entry on
6175 Backtraces will continue past the internal entry point of an application.
6176 This entry point is encoded by the linker when the application is built,
6177 and is likely before the user entry point @code{main} (or equivalent) is called.
6179 @item set backtrace past-entry off
6180 Backtraces will stop when they encounter the internal entry point of an
6181 application. This is the default.
6183 @item show backtrace past-entry
6184 Display the current internal entry point backtrace policy.
6186 @item set backtrace limit @var{n}
6187 @itemx set backtrace limit 0
6188 @cindex backtrace limit
6189 Limit the backtrace to @var{n} levels. A value of zero means
6192 @item show backtrace limit
6193 Display the current limit on backtrace levels.
6197 @section Selecting a Frame
6199 Most commands for examining the stack and other data in your program work on
6200 whichever stack frame is selected at the moment. Here are the commands for
6201 selecting a stack frame; all of them finish by printing a brief description
6202 of the stack frame just selected.
6205 @kindex frame@r{, selecting}
6206 @kindex f @r{(@code{frame})}
6209 Select frame number @var{n}. Recall that frame zero is the innermost
6210 (currently executing) frame, frame one is the frame that called the
6211 innermost one, and so on. The highest-numbered frame is the one for
6214 @item frame @var{addr}
6216 Select the frame at address @var{addr}. This is useful mainly if the
6217 chaining of stack frames has been damaged by a bug, making it
6218 impossible for @value{GDBN} to assign numbers properly to all frames. In
6219 addition, this can be useful when your program has multiple stacks and
6220 switches between them.
6222 On the SPARC architecture, @code{frame} needs two addresses to
6223 select an arbitrary frame: a frame pointer and a stack pointer.
6225 On the MIPS and Alpha architecture, it needs two addresses: a stack
6226 pointer and a program counter.
6228 On the 29k architecture, it needs three addresses: a register stack
6229 pointer, a program counter, and a memory stack pointer.
6233 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6234 advances toward the outermost frame, to higher frame numbers, to frames
6235 that have existed longer. @var{n} defaults to one.
6238 @kindex do @r{(@code{down})}
6240 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6241 advances toward the innermost frame, to lower frame numbers, to frames
6242 that were created more recently. @var{n} defaults to one. You may
6243 abbreviate @code{down} as @code{do}.
6246 All of these commands end by printing two lines of output describing the
6247 frame. The first line shows the frame number, the function name, the
6248 arguments, and the source file and line number of execution in that
6249 frame. The second line shows the text of that source line.
6257 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6259 10 read_input_file (argv[i]);
6263 After such a printout, the @code{list} command with no arguments
6264 prints ten lines centered on the point of execution in the frame.
6265 You can also edit the program at the point of execution with your favorite
6266 editing program by typing @code{edit}.
6267 @xref{List, ,Printing Source Lines},
6271 @kindex down-silently
6273 @item up-silently @var{n}
6274 @itemx down-silently @var{n}
6275 These two commands are variants of @code{up} and @code{down},
6276 respectively; they differ in that they do their work silently, without
6277 causing display of the new frame. They are intended primarily for use
6278 in @value{GDBN} command scripts, where the output might be unnecessary and
6283 @section Information About a Frame
6285 There are several other commands to print information about the selected
6291 When used without any argument, this command does not change which
6292 frame is selected, but prints a brief description of the currently
6293 selected stack frame. It can be abbreviated @code{f}. With an
6294 argument, this command is used to select a stack frame.
6295 @xref{Selection, ,Selecting a Frame}.
6298 @kindex info f @r{(@code{info frame})}
6301 This command prints a verbose description of the selected stack frame,
6306 the address of the frame
6308 the address of the next frame down (called by this frame)
6310 the address of the next frame up (caller of this frame)
6312 the language in which the source code corresponding to this frame is written
6314 the address of the frame's arguments
6316 the address of the frame's local variables
6318 the program counter saved in it (the address of execution in the caller frame)
6320 which registers were saved in the frame
6323 @noindent The verbose description is useful when
6324 something has gone wrong that has made the stack format fail to fit
6325 the usual conventions.
6327 @item info frame @var{addr}
6328 @itemx info f @var{addr}
6329 Print a verbose description of the frame at address @var{addr}, without
6330 selecting that frame. The selected frame remains unchanged by this
6331 command. This requires the same kind of address (more than one for some
6332 architectures) that you specify in the @code{frame} command.
6333 @xref{Selection, ,Selecting a Frame}.
6337 Print the arguments of the selected frame, each on a separate line.
6341 Print the local variables of the selected frame, each on a separate
6342 line. These are all variables (declared either static or automatic)
6343 accessible at the point of execution of the selected frame.
6346 @cindex catch exceptions, list active handlers
6347 @cindex exception handlers, how to list
6349 Print a list of all the exception handlers that are active in the
6350 current stack frame at the current point of execution. To see other
6351 exception handlers, visit the associated frame (using the @code{up},
6352 @code{down}, or @code{frame} commands); then type @code{info catch}.
6353 @xref{Set Catchpoints, , Setting Catchpoints}.
6359 @chapter Examining Source Files
6361 @value{GDBN} can print parts of your program's source, since the debugging
6362 information recorded in the program tells @value{GDBN} what source files were
6363 used to build it. When your program stops, @value{GDBN} spontaneously prints
6364 the line where it stopped. Likewise, when you select a stack frame
6365 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6366 execution in that frame has stopped. You can print other portions of
6367 source files by explicit command.
6369 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6370 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6371 @value{GDBN} under @sc{gnu} Emacs}.
6374 * List:: Printing source lines
6375 * Specify Location:: How to specify code locations
6376 * Edit:: Editing source files
6377 * Search:: Searching source files
6378 * Source Path:: Specifying source directories
6379 * Machine Code:: Source and machine code
6383 @section Printing Source Lines
6386 @kindex l @r{(@code{list})}
6387 To print lines from a source file, use the @code{list} command
6388 (abbreviated @code{l}). By default, ten lines are printed.
6389 There are several ways to specify what part of the file you want to
6390 print; see @ref{Specify Location}, for the full list.
6392 Here are the forms of the @code{list} command most commonly used:
6395 @item list @var{linenum}
6396 Print lines centered around line number @var{linenum} in the
6397 current source file.
6399 @item list @var{function}
6400 Print lines centered around the beginning of function
6404 Print more lines. If the last lines printed were printed with a
6405 @code{list} command, this prints lines following the last lines
6406 printed; however, if the last line printed was a solitary line printed
6407 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6408 Stack}), this prints lines centered around that line.
6411 Print lines just before the lines last printed.
6414 @cindex @code{list}, how many lines to display
6415 By default, @value{GDBN} prints ten source lines with any of these forms of
6416 the @code{list} command. You can change this using @code{set listsize}:
6419 @kindex set listsize
6420 @item set listsize @var{count}
6421 Make the @code{list} command display @var{count} source lines (unless
6422 the @code{list} argument explicitly specifies some other number).
6424 @kindex show listsize
6426 Display the number of lines that @code{list} prints.
6429 Repeating a @code{list} command with @key{RET} discards the argument,
6430 so it is equivalent to typing just @code{list}. This is more useful
6431 than listing the same lines again. An exception is made for an
6432 argument of @samp{-}; that argument is preserved in repetition so that
6433 each repetition moves up in the source file.
6435 In general, the @code{list} command expects you to supply zero, one or two
6436 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6437 of writing them (@pxref{Specify Location}), but the effect is always
6438 to specify some source line.
6440 Here is a complete description of the possible arguments for @code{list}:
6443 @item list @var{linespec}
6444 Print lines centered around the line specified by @var{linespec}.
6446 @item list @var{first},@var{last}
6447 Print lines from @var{first} to @var{last}. Both arguments are
6448 linespecs. When a @code{list} command has two linespecs, and the
6449 source file of the second linespec is omitted, this refers to
6450 the same source file as the first linespec.
6452 @item list ,@var{last}
6453 Print lines ending with @var{last}.
6455 @item list @var{first},
6456 Print lines starting with @var{first}.
6459 Print lines just after the lines last printed.
6462 Print lines just before the lines last printed.
6465 As described in the preceding table.
6468 @node Specify Location
6469 @section Specifying a Location
6470 @cindex specifying location
6473 Several @value{GDBN} commands accept arguments that specify a location
6474 of your program's code. Since @value{GDBN} is a source-level
6475 debugger, a location usually specifies some line in the source code;
6476 for that reason, locations are also known as @dfn{linespecs}.
6478 Here are all the different ways of specifying a code location that
6479 @value{GDBN} understands:
6483 Specifies the line number @var{linenum} of the current source file.
6486 @itemx +@var{offset}
6487 Specifies the line @var{offset} lines before or after the @dfn{current
6488 line}. For the @code{list} command, the current line is the last one
6489 printed; for the breakpoint commands, this is the line at which
6490 execution stopped in the currently selected @dfn{stack frame}
6491 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6492 used as the second of the two linespecs in a @code{list} command,
6493 this specifies the line @var{offset} lines up or down from the first
6496 @item @var{filename}:@var{linenum}
6497 Specifies the line @var{linenum} in the source file @var{filename}.
6499 @item @var{function}
6500 Specifies the line that begins the body of the function @var{function}.
6501 For example, in C, this is the line with the open brace.
6503 @item @var{function}:@var{label}
6504 Specifies the line where @var{label} appears in @var{function}.
6506 @item @var{filename}:@var{function}
6507 Specifies the line that begins the body of the function @var{function}
6508 in the file @var{filename}. You only need the file name with a
6509 function name to avoid ambiguity when there are identically named
6510 functions in different source files.
6513 Specifies the line at which the label named @var{label} appears.
6514 @value{GDBN} searches for the label in the function corresponding to
6515 the currently selected stack frame. If there is no current selected
6516 stack frame (for instance, if the inferior is not running), then
6517 @value{GDBN} will not search for a label.
6519 @item *@var{address}
6520 Specifies the program address @var{address}. For line-oriented
6521 commands, such as @code{list} and @code{edit}, this specifies a source
6522 line that contains @var{address}. For @code{break} and other
6523 breakpoint oriented commands, this can be used to set breakpoints in
6524 parts of your program which do not have debugging information or
6527 Here @var{address} may be any expression valid in the current working
6528 language (@pxref{Languages, working language}) that specifies a code
6529 address. In addition, as a convenience, @value{GDBN} extends the
6530 semantics of expressions used in locations to cover the situations
6531 that frequently happen during debugging. Here are the various forms
6535 @item @var{expression}
6536 Any expression valid in the current working language.
6538 @item @var{funcaddr}
6539 An address of a function or procedure derived from its name. In C,
6540 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6541 simply the function's name @var{function} (and actually a special case
6542 of a valid expression). In Pascal and Modula-2, this is
6543 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6544 (although the Pascal form also works).
6546 This form specifies the address of the function's first instruction,
6547 before the stack frame and arguments have been set up.
6549 @item '@var{filename}'::@var{funcaddr}
6550 Like @var{funcaddr} above, but also specifies the name of the source
6551 file explicitly. This is useful if the name of the function does not
6552 specify the function unambiguously, e.g., if there are several
6553 functions with identical names in different source files.
6560 @section Editing Source Files
6561 @cindex editing source files
6564 @kindex e @r{(@code{edit})}
6565 To edit the lines in a source file, use the @code{edit} command.
6566 The editing program of your choice
6567 is invoked with the current line set to
6568 the active line in the program.
6569 Alternatively, there are several ways to specify what part of the file you
6570 want to print if you want to see other parts of the program:
6573 @item edit @var{location}
6574 Edit the source file specified by @code{location}. Editing starts at
6575 that @var{location}, e.g., at the specified source line of the
6576 specified file. @xref{Specify Location}, for all the possible forms
6577 of the @var{location} argument; here are the forms of the @code{edit}
6578 command most commonly used:
6581 @item edit @var{number}
6582 Edit the current source file with @var{number} as the active line number.
6584 @item edit @var{function}
6585 Edit the file containing @var{function} at the beginning of its definition.
6590 @subsection Choosing your Editor
6591 You can customize @value{GDBN} to use any editor you want
6593 The only restriction is that your editor (say @code{ex}), recognizes the
6594 following command-line syntax:
6596 ex +@var{number} file
6598 The optional numeric value +@var{number} specifies the number of the line in
6599 the file where to start editing.}.
6600 By default, it is @file{@value{EDITOR}}, but you can change this
6601 by setting the environment variable @code{EDITOR} before using
6602 @value{GDBN}. For example, to configure @value{GDBN} to use the
6603 @code{vi} editor, you could use these commands with the @code{sh} shell:
6609 or in the @code{csh} shell,
6611 setenv EDITOR /usr/bin/vi
6616 @section Searching Source Files
6617 @cindex searching source files
6619 There are two commands for searching through the current source file for a
6624 @kindex forward-search
6625 @item forward-search @var{regexp}
6626 @itemx search @var{regexp}
6627 The command @samp{forward-search @var{regexp}} checks each line,
6628 starting with the one following the last line listed, for a match for
6629 @var{regexp}. It lists the line that is found. You can use the
6630 synonym @samp{search @var{regexp}} or abbreviate the command name as
6633 @kindex reverse-search
6634 @item reverse-search @var{regexp}
6635 The command @samp{reverse-search @var{regexp}} checks each line, starting
6636 with the one before the last line listed and going backward, for a match
6637 for @var{regexp}. It lists the line that is found. You can abbreviate
6638 this command as @code{rev}.
6642 @section Specifying Source Directories
6645 @cindex directories for source files
6646 Executable programs sometimes do not record the directories of the source
6647 files from which they were compiled, just the names. Even when they do,
6648 the directories could be moved between the compilation and your debugging
6649 session. @value{GDBN} has a list of directories to search for source files;
6650 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6651 it tries all the directories in the list, in the order they are present
6652 in the list, until it finds a file with the desired name.
6654 For example, suppose an executable references the file
6655 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6656 @file{/mnt/cross}. The file is first looked up literally; if this
6657 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6658 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6659 message is printed. @value{GDBN} does not look up the parts of the
6660 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6661 Likewise, the subdirectories of the source path are not searched: if
6662 the source path is @file{/mnt/cross}, and the binary refers to
6663 @file{foo.c}, @value{GDBN} would not find it under
6664 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6666 Plain file names, relative file names with leading directories, file
6667 names containing dots, etc.@: are all treated as described above; for
6668 instance, if the source path is @file{/mnt/cross}, and the source file
6669 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6670 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6671 that---@file{/mnt/cross/foo.c}.
6673 Note that the executable search path is @emph{not} used to locate the
6676 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6677 any information it has cached about where source files are found and where
6678 each line is in the file.
6682 When you start @value{GDBN}, its source path includes only @samp{cdir}
6683 and @samp{cwd}, in that order.
6684 To add other directories, use the @code{directory} command.
6686 The search path is used to find both program source files and @value{GDBN}
6687 script files (read using the @samp{-command} option and @samp{source} command).
6689 In addition to the source path, @value{GDBN} provides a set of commands
6690 that manage a list of source path substitution rules. A @dfn{substitution
6691 rule} specifies how to rewrite source directories stored in the program's
6692 debug information in case the sources were moved to a different
6693 directory between compilation and debugging. A rule is made of
6694 two strings, the first specifying what needs to be rewritten in
6695 the path, and the second specifying how it should be rewritten.
6696 In @ref{set substitute-path}, we name these two parts @var{from} and
6697 @var{to} respectively. @value{GDBN} does a simple string replacement
6698 of @var{from} with @var{to} at the start of the directory part of the
6699 source file name, and uses that result instead of the original file
6700 name to look up the sources.
6702 Using the previous example, suppose the @file{foo-1.0} tree has been
6703 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6704 @value{GDBN} to replace @file{/usr/src} in all source path names with
6705 @file{/mnt/cross}. The first lookup will then be
6706 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6707 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6708 substitution rule, use the @code{set substitute-path} command
6709 (@pxref{set substitute-path}).
6711 To avoid unexpected substitution results, a rule is applied only if the
6712 @var{from} part of the directory name ends at a directory separator.
6713 For instance, a rule substituting @file{/usr/source} into
6714 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6715 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6716 is applied only at the beginning of the directory name, this rule will
6717 not be applied to @file{/root/usr/source/baz.c} either.
6719 In many cases, you can achieve the same result using the @code{directory}
6720 command. However, @code{set substitute-path} can be more efficient in
6721 the case where the sources are organized in a complex tree with multiple
6722 subdirectories. With the @code{directory} command, you need to add each
6723 subdirectory of your project. If you moved the entire tree while
6724 preserving its internal organization, then @code{set substitute-path}
6725 allows you to direct the debugger to all the sources with one single
6728 @code{set substitute-path} is also more than just a shortcut command.
6729 The source path is only used if the file at the original location no
6730 longer exists. On the other hand, @code{set substitute-path} modifies
6731 the debugger behavior to look at the rewritten location instead. So, if
6732 for any reason a source file that is not relevant to your executable is
6733 located at the original location, a substitution rule is the only
6734 method available to point @value{GDBN} at the new location.
6736 @cindex @samp{--with-relocated-sources}
6737 @cindex default source path substitution
6738 You can configure a default source path substitution rule by
6739 configuring @value{GDBN} with the
6740 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6741 should be the name of a directory under @value{GDBN}'s configured
6742 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6743 directory names in debug information under @var{dir} will be adjusted
6744 automatically if the installed @value{GDBN} is moved to a new
6745 location. This is useful if @value{GDBN}, libraries or executables
6746 with debug information and corresponding source code are being moved
6750 @item directory @var{dirname} @dots{}
6751 @item dir @var{dirname} @dots{}
6752 Add directory @var{dirname} to the front of the source path. Several
6753 directory names may be given to this command, separated by @samp{:}
6754 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6755 part of absolute file names) or
6756 whitespace. You may specify a directory that is already in the source
6757 path; this moves it forward, so @value{GDBN} searches it sooner.
6761 @vindex $cdir@r{, convenience variable}
6762 @vindex $cwd@r{, convenience variable}
6763 @cindex compilation directory
6764 @cindex current directory
6765 @cindex working directory
6766 @cindex directory, current
6767 @cindex directory, compilation
6768 You can use the string @samp{$cdir} to refer to the compilation
6769 directory (if one is recorded), and @samp{$cwd} to refer to the current
6770 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6771 tracks the current working directory as it changes during your @value{GDBN}
6772 session, while the latter is immediately expanded to the current
6773 directory at the time you add an entry to the source path.
6776 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6778 @c RET-repeat for @code{directory} is explicitly disabled, but since
6779 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6781 @item set directories @var{path-list}
6782 @kindex set directories
6783 Set the source path to @var{path-list}.
6784 @samp{$cdir:$cwd} are added if missing.
6786 @item show directories
6787 @kindex show directories
6788 Print the source path: show which directories it contains.
6790 @anchor{set substitute-path}
6791 @item set substitute-path @var{from} @var{to}
6792 @kindex set substitute-path
6793 Define a source path substitution rule, and add it at the end of the
6794 current list of existing substitution rules. If a rule with the same
6795 @var{from} was already defined, then the old rule is also deleted.
6797 For example, if the file @file{/foo/bar/baz.c} was moved to
6798 @file{/mnt/cross/baz.c}, then the command
6801 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6805 will tell @value{GDBN} to replace @samp{/usr/src} with
6806 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6807 @file{baz.c} even though it was moved.
6809 In the case when more than one substitution rule have been defined,
6810 the rules are evaluated one by one in the order where they have been
6811 defined. The first one matching, if any, is selected to perform
6814 For instance, if we had entered the following commands:
6817 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6818 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6822 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6823 @file{/mnt/include/defs.h} by using the first rule. However, it would
6824 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6825 @file{/mnt/src/lib/foo.c}.
6828 @item unset substitute-path [path]
6829 @kindex unset substitute-path
6830 If a path is specified, search the current list of substitution rules
6831 for a rule that would rewrite that path. Delete that rule if found.
6832 A warning is emitted by the debugger if no rule could be found.
6834 If no path is specified, then all substitution rules are deleted.
6836 @item show substitute-path [path]
6837 @kindex show substitute-path
6838 If a path is specified, then print the source path substitution rule
6839 which would rewrite that path, if any.
6841 If no path is specified, then print all existing source path substitution
6846 If your source path is cluttered with directories that are no longer of
6847 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6848 versions of source. You can correct the situation as follows:
6852 Use @code{directory} with no argument to reset the source path to its default value.
6855 Use @code{directory} with suitable arguments to reinstall the
6856 directories you want in the source path. You can add all the
6857 directories in one command.
6861 @section Source and Machine Code
6862 @cindex source line and its code address
6864 You can use the command @code{info line} to map source lines to program
6865 addresses (and vice versa), and the command @code{disassemble} to display
6866 a range of addresses as machine instructions. You can use the command
6867 @code{set disassemble-next-line} to set whether to disassemble next
6868 source line when execution stops. When run under @sc{gnu} Emacs
6869 mode, the @code{info line} command causes the arrow to point to the
6870 line specified. Also, @code{info line} prints addresses in symbolic form as
6875 @item info line @var{linespec}
6876 Print the starting and ending addresses of the compiled code for
6877 source line @var{linespec}. You can specify source lines in any of
6878 the ways documented in @ref{Specify Location}.
6881 For example, we can use @code{info line} to discover the location of
6882 the object code for the first line of function
6883 @code{m4_changequote}:
6885 @c FIXME: I think this example should also show the addresses in
6886 @c symbolic form, as they usually would be displayed.
6888 (@value{GDBP}) info line m4_changequote
6889 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6893 @cindex code address and its source line
6894 We can also inquire (using @code{*@var{addr}} as the form for
6895 @var{linespec}) what source line covers a particular address:
6897 (@value{GDBP}) info line *0x63ff
6898 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6901 @cindex @code{$_} and @code{info line}
6902 @cindex @code{x} command, default address
6903 @kindex x@r{(examine), and} info line
6904 After @code{info line}, the default address for the @code{x} command
6905 is changed to the starting address of the line, so that @samp{x/i} is
6906 sufficient to begin examining the machine code (@pxref{Memory,
6907 ,Examining Memory}). Also, this address is saved as the value of the
6908 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6913 @cindex assembly instructions
6914 @cindex instructions, assembly
6915 @cindex machine instructions
6916 @cindex listing machine instructions
6918 @itemx disassemble /m
6919 @itemx disassemble /r
6920 This specialized command dumps a range of memory as machine
6921 instructions. It can also print mixed source+disassembly by specifying
6922 the @code{/m} modifier and print the raw instructions in hex as well as
6923 in symbolic form by specifying the @code{/r}.
6924 The default memory range is the function surrounding the
6925 program counter of the selected frame. A single argument to this
6926 command is a program counter value; @value{GDBN} dumps the function
6927 surrounding this value. When two arguments are given, they should
6928 be separated by a comma, possibly surrounded by whitespace. The
6929 arguments specify a range of addresses to dump, in one of two forms:
6932 @item @var{start},@var{end}
6933 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6934 @item @var{start},+@var{length}
6935 the addresses from @var{start} (inclusive) to
6936 @code{@var{start}+@var{length}} (exclusive).
6940 When 2 arguments are specified, the name of the function is also
6941 printed (since there could be several functions in the given range).
6943 The argument(s) can be any expression yielding a numeric value, such as
6944 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6946 If the range of memory being disassembled contains current program counter,
6947 the instruction at that location is shown with a @code{=>} marker.
6950 The following example shows the disassembly of a range of addresses of
6951 HP PA-RISC 2.0 code:
6954 (@value{GDBP}) disas 0x32c4, 0x32e4
6955 Dump of assembler code from 0x32c4 to 0x32e4:
6956 0x32c4 <main+204>: addil 0,dp
6957 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6958 0x32cc <main+212>: ldil 0x3000,r31
6959 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6960 0x32d4 <main+220>: ldo 0(r31),rp
6961 0x32d8 <main+224>: addil -0x800,dp
6962 0x32dc <main+228>: ldo 0x588(r1),r26
6963 0x32e0 <main+232>: ldil 0x3000,r31
6964 End of assembler dump.
6967 Here is an example showing mixed source+assembly for Intel x86, when the
6968 program is stopped just after function prologue:
6971 (@value{GDBP}) disas /m main
6972 Dump of assembler code for function main:
6974 0x08048330 <+0>: push %ebp
6975 0x08048331 <+1>: mov %esp,%ebp
6976 0x08048333 <+3>: sub $0x8,%esp
6977 0x08048336 <+6>: and $0xfffffff0,%esp
6978 0x08048339 <+9>: sub $0x10,%esp
6980 6 printf ("Hello.\n");
6981 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6982 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6986 0x08048348 <+24>: mov $0x0,%eax
6987 0x0804834d <+29>: leave
6988 0x0804834e <+30>: ret
6990 End of assembler dump.
6993 Here is another example showing raw instructions in hex for AMD x86-64,
6996 (gdb) disas /r 0x400281,+10
6997 Dump of assembler code from 0x400281 to 0x40028b:
6998 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6999 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7000 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7001 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7002 End of assembler dump.
7005 Some architectures have more than one commonly-used set of instruction
7006 mnemonics or other syntax.
7008 For programs that were dynamically linked and use shared libraries,
7009 instructions that call functions or branch to locations in the shared
7010 libraries might show a seemingly bogus location---it's actually a
7011 location of the relocation table. On some architectures, @value{GDBN}
7012 might be able to resolve these to actual function names.
7015 @kindex set disassembly-flavor
7016 @cindex Intel disassembly flavor
7017 @cindex AT&T disassembly flavor
7018 @item set disassembly-flavor @var{instruction-set}
7019 Select the instruction set to use when disassembling the
7020 program via the @code{disassemble} or @code{x/i} commands.
7022 Currently this command is only defined for the Intel x86 family. You
7023 can set @var{instruction-set} to either @code{intel} or @code{att}.
7024 The default is @code{att}, the AT&T flavor used by default by Unix
7025 assemblers for x86-based targets.
7027 @kindex show disassembly-flavor
7028 @item show disassembly-flavor
7029 Show the current setting of the disassembly flavor.
7033 @kindex set disassemble-next-line
7034 @kindex show disassemble-next-line
7035 @item set disassemble-next-line
7036 @itemx show disassemble-next-line
7037 Control whether or not @value{GDBN} will disassemble the next source
7038 line or instruction when execution stops. If ON, @value{GDBN} will
7039 display disassembly of the next source line when execution of the
7040 program being debugged stops. This is @emph{in addition} to
7041 displaying the source line itself, which @value{GDBN} always does if
7042 possible. If the next source line cannot be displayed for some reason
7043 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7044 info in the debug info), @value{GDBN} will display disassembly of the
7045 next @emph{instruction} instead of showing the next source line. If
7046 AUTO, @value{GDBN} will display disassembly of next instruction only
7047 if the source line cannot be displayed. This setting causes
7048 @value{GDBN} to display some feedback when you step through a function
7049 with no line info or whose source file is unavailable. The default is
7050 OFF, which means never display the disassembly of the next line or
7056 @chapter Examining Data
7058 @cindex printing data
7059 @cindex examining data
7062 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
7063 @c document because it is nonstandard... Under Epoch it displays in a
7064 @c different window or something like that.
7065 The usual way to examine data in your program is with the @code{print}
7066 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7067 evaluates and prints the value of an expression of the language your
7068 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7069 Different Languages}). It may also print the expression using a
7070 Python-based pretty-printer (@pxref{Pretty Printing}).
7073 @item print @var{expr}
7074 @itemx print /@var{f} @var{expr}
7075 @var{expr} is an expression (in the source language). By default the
7076 value of @var{expr} is printed in a format appropriate to its data type;
7077 you can choose a different format by specifying @samp{/@var{f}}, where
7078 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7082 @itemx print /@var{f}
7083 @cindex reprint the last value
7084 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7085 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7086 conveniently inspect the same value in an alternative format.
7089 A more low-level way of examining data is with the @code{x} command.
7090 It examines data in memory at a specified address and prints it in a
7091 specified format. @xref{Memory, ,Examining Memory}.
7093 If you are interested in information about types, or about how the
7094 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7095 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7099 * Expressions:: Expressions
7100 * Ambiguous Expressions:: Ambiguous Expressions
7101 * Variables:: Program variables
7102 * Arrays:: Artificial arrays
7103 * Output Formats:: Output formats
7104 * Memory:: Examining memory
7105 * Auto Display:: Automatic display
7106 * Print Settings:: Print settings
7107 * Pretty Printing:: Python pretty printing
7108 * Value History:: Value history
7109 * Convenience Vars:: Convenience variables
7110 * Registers:: Registers
7111 * Floating Point Hardware:: Floating point hardware
7112 * Vector Unit:: Vector Unit
7113 * OS Information:: Auxiliary data provided by operating system
7114 * Memory Region Attributes:: Memory region attributes
7115 * Dump/Restore Files:: Copy between memory and a file
7116 * Core File Generation:: Cause a program dump its core
7117 * Character Sets:: Debugging programs that use a different
7118 character set than GDB does
7119 * Caching Remote Data:: Data caching for remote targets
7120 * Searching Memory:: Searching memory for a sequence of bytes
7124 @section Expressions
7127 @code{print} and many other @value{GDBN} commands accept an expression and
7128 compute its value. Any kind of constant, variable or operator defined
7129 by the programming language you are using is valid in an expression in
7130 @value{GDBN}. This includes conditional expressions, function calls,
7131 casts, and string constants. It also includes preprocessor macros, if
7132 you compiled your program to include this information; see
7135 @cindex arrays in expressions
7136 @value{GDBN} supports array constants in expressions input by
7137 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7138 you can use the command @code{print @{1, 2, 3@}} to create an array
7139 of three integers. If you pass an array to a function or assign it
7140 to a program variable, @value{GDBN} copies the array to memory that
7141 is @code{malloc}ed in the target program.
7143 Because C is so widespread, most of the expressions shown in examples in
7144 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7145 Languages}, for information on how to use expressions in other
7148 In this section, we discuss operators that you can use in @value{GDBN}
7149 expressions regardless of your programming language.
7151 @cindex casts, in expressions
7152 Casts are supported in all languages, not just in C, because it is so
7153 useful to cast a number into a pointer in order to examine a structure
7154 at that address in memory.
7155 @c FIXME: casts supported---Mod2 true?
7157 @value{GDBN} supports these operators, in addition to those common
7158 to programming languages:
7162 @samp{@@} is a binary operator for treating parts of memory as arrays.
7163 @xref{Arrays, ,Artificial Arrays}, for more information.
7166 @samp{::} allows you to specify a variable in terms of the file or
7167 function where it is defined. @xref{Variables, ,Program Variables}.
7169 @cindex @{@var{type}@}
7170 @cindex type casting memory
7171 @cindex memory, viewing as typed object
7172 @cindex casts, to view memory
7173 @item @{@var{type}@} @var{addr}
7174 Refers to an object of type @var{type} stored at address @var{addr} in
7175 memory. @var{addr} may be any expression whose value is an integer or
7176 pointer (but parentheses are required around binary operators, just as in
7177 a cast). This construct is allowed regardless of what kind of data is
7178 normally supposed to reside at @var{addr}.
7181 @node Ambiguous Expressions
7182 @section Ambiguous Expressions
7183 @cindex ambiguous expressions
7185 Expressions can sometimes contain some ambiguous elements. For instance,
7186 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7187 a single function name to be defined several times, for application in
7188 different contexts. This is called @dfn{overloading}. Another example
7189 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7190 templates and is typically instantiated several times, resulting in
7191 the same function name being defined in different contexts.
7193 In some cases and depending on the language, it is possible to adjust
7194 the expression to remove the ambiguity. For instance in C@t{++}, you
7195 can specify the signature of the function you want to break on, as in
7196 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7197 qualified name of your function often makes the expression unambiguous
7200 When an ambiguity that needs to be resolved is detected, the debugger
7201 has the capability to display a menu of numbered choices for each
7202 possibility, and then waits for the selection with the prompt @samp{>}.
7203 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7204 aborts the current command. If the command in which the expression was
7205 used allows more than one choice to be selected, the next option in the
7206 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7209 For example, the following session excerpt shows an attempt to set a
7210 breakpoint at the overloaded symbol @code{String::after}.
7211 We choose three particular definitions of that function name:
7213 @c FIXME! This is likely to change to show arg type lists, at least
7216 (@value{GDBP}) b String::after
7219 [2] file:String.cc; line number:867
7220 [3] file:String.cc; line number:860
7221 [4] file:String.cc; line number:875
7222 [5] file:String.cc; line number:853
7223 [6] file:String.cc; line number:846
7224 [7] file:String.cc; line number:735
7226 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7227 Breakpoint 2 at 0xb344: file String.cc, line 875.
7228 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7229 Multiple breakpoints were set.
7230 Use the "delete" command to delete unwanted
7237 @kindex set multiple-symbols
7238 @item set multiple-symbols @var{mode}
7239 @cindex multiple-symbols menu
7241 This option allows you to adjust the debugger behavior when an expression
7244 By default, @var{mode} is set to @code{all}. If the command with which
7245 the expression is used allows more than one choice, then @value{GDBN}
7246 automatically selects all possible choices. For instance, inserting
7247 a breakpoint on a function using an ambiguous name results in a breakpoint
7248 inserted on each possible match. However, if a unique choice must be made,
7249 then @value{GDBN} uses the menu to help you disambiguate the expression.
7250 For instance, printing the address of an overloaded function will result
7251 in the use of the menu.
7253 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7254 when an ambiguity is detected.
7256 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7257 an error due to the ambiguity and the command is aborted.
7259 @kindex show multiple-symbols
7260 @item show multiple-symbols
7261 Show the current value of the @code{multiple-symbols} setting.
7265 @section Program Variables
7267 The most common kind of expression to use is the name of a variable
7270 Variables in expressions are understood in the selected stack frame
7271 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7275 global (or file-static)
7282 visible according to the scope rules of the
7283 programming language from the point of execution in that frame
7286 @noindent This means that in the function
7301 you can examine and use the variable @code{a} whenever your program is
7302 executing within the function @code{foo}, but you can only use or
7303 examine the variable @code{b} while your program is executing inside
7304 the block where @code{b} is declared.
7306 @cindex variable name conflict
7307 There is an exception: you can refer to a variable or function whose
7308 scope is a single source file even if the current execution point is not
7309 in this file. But it is possible to have more than one such variable or
7310 function with the same name (in different source files). If that
7311 happens, referring to that name has unpredictable effects. If you wish,
7312 you can specify a static variable in a particular function or file,
7313 using the colon-colon (@code{::}) notation:
7315 @cindex colon-colon, context for variables/functions
7317 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7318 @cindex @code{::}, context for variables/functions
7321 @var{file}::@var{variable}
7322 @var{function}::@var{variable}
7326 Here @var{file} or @var{function} is the name of the context for the
7327 static @var{variable}. In the case of file names, you can use quotes to
7328 make sure @value{GDBN} parses the file name as a single word---for example,
7329 to print a global value of @code{x} defined in @file{f2.c}:
7332 (@value{GDBP}) p 'f2.c'::x
7335 @cindex C@t{++} scope resolution
7336 This use of @samp{::} is very rarely in conflict with the very similar
7337 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7338 scope resolution operator in @value{GDBN} expressions.
7339 @c FIXME: Um, so what happens in one of those rare cases where it's in
7342 @cindex wrong values
7343 @cindex variable values, wrong
7344 @cindex function entry/exit, wrong values of variables
7345 @cindex optimized code, wrong values of variables
7347 @emph{Warning:} Occasionally, a local variable may appear to have the
7348 wrong value at certain points in a function---just after entry to a new
7349 scope, and just before exit.
7351 You may see this problem when you are stepping by machine instructions.
7352 This is because, on most machines, it takes more than one instruction to
7353 set up a stack frame (including local variable definitions); if you are
7354 stepping by machine instructions, variables may appear to have the wrong
7355 values until the stack frame is completely built. On exit, it usually
7356 also takes more than one machine instruction to destroy a stack frame;
7357 after you begin stepping through that group of instructions, local
7358 variable definitions may be gone.
7360 This may also happen when the compiler does significant optimizations.
7361 To be sure of always seeing accurate values, turn off all optimization
7364 @cindex ``No symbol "foo" in current context''
7365 Another possible effect of compiler optimizations is to optimize
7366 unused variables out of existence, or assign variables to registers (as
7367 opposed to memory addresses). Depending on the support for such cases
7368 offered by the debug info format used by the compiler, @value{GDBN}
7369 might not be able to display values for such local variables. If that
7370 happens, @value{GDBN} will print a message like this:
7373 No symbol "foo" in current context.
7376 To solve such problems, either recompile without optimizations, or use a
7377 different debug info format, if the compiler supports several such
7378 formats. @xref{Compilation}, for more information on choosing compiler
7379 options. @xref{C, ,C and C@t{++}}, for more information about debug
7380 info formats that are best suited to C@t{++} programs.
7382 If you ask to print an object whose contents are unknown to
7383 @value{GDBN}, e.g., because its data type is not completely specified
7384 by the debug information, @value{GDBN} will say @samp{<incomplete
7385 type>}. @xref{Symbols, incomplete type}, for more about this.
7387 If you append @kbd{@@entry} string to a function parameter name you get its
7388 value at the time the function got called. If the value is not available an
7389 error message is printed. Entry values are available only with some compilers.
7390 Entry values are normally also printed at the function parameter list according
7391 to @ref{set print entry-values}.
7394 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7400 (gdb) print i@@entry
7404 Strings are identified as arrays of @code{char} values without specified
7405 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7406 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7407 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7408 defines literal string type @code{"char"} as @code{char} without a sign.
7413 signed char var1[] = "A";
7416 You get during debugging
7421 $2 = @{65 'A', 0 '\0'@}
7425 @section Artificial Arrays
7427 @cindex artificial array
7429 @kindex @@@r{, referencing memory as an array}
7430 It is often useful to print out several successive objects of the
7431 same type in memory; a section of an array, or an array of
7432 dynamically determined size for which only a pointer exists in the
7435 You can do this by referring to a contiguous span of memory as an
7436 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7437 operand of @samp{@@} should be the first element of the desired array
7438 and be an individual object. The right operand should be the desired length
7439 of the array. The result is an array value whose elements are all of
7440 the type of the left argument. The first element is actually the left
7441 argument; the second element comes from bytes of memory immediately
7442 following those that hold the first element, and so on. Here is an
7443 example. If a program says
7446 int *array = (int *) malloc (len * sizeof (int));
7450 you can print the contents of @code{array} with
7456 The left operand of @samp{@@} must reside in memory. Array values made
7457 with @samp{@@} in this way behave just like other arrays in terms of
7458 subscripting, and are coerced to pointers when used in expressions.
7459 Artificial arrays most often appear in expressions via the value history
7460 (@pxref{Value History, ,Value History}), after printing one out.
7462 Another way to create an artificial array is to use a cast.
7463 This re-interprets a value as if it were an array.
7464 The value need not be in memory:
7466 (@value{GDBP}) p/x (short[2])0x12345678
7467 $1 = @{0x1234, 0x5678@}
7470 As a convenience, if you leave the array length out (as in
7471 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7472 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7474 (@value{GDBP}) p/x (short[])0x12345678
7475 $2 = @{0x1234, 0x5678@}
7478 Sometimes the artificial array mechanism is not quite enough; in
7479 moderately complex data structures, the elements of interest may not
7480 actually be adjacent---for example, if you are interested in the values
7481 of pointers in an array. One useful work-around in this situation is
7482 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7483 Variables}) as a counter in an expression that prints the first
7484 interesting value, and then repeat that expression via @key{RET}. For
7485 instance, suppose you have an array @code{dtab} of pointers to
7486 structures, and you are interested in the values of a field @code{fv}
7487 in each structure. Here is an example of what you might type:
7497 @node Output Formats
7498 @section Output Formats
7500 @cindex formatted output
7501 @cindex output formats
7502 By default, @value{GDBN} prints a value according to its data type. Sometimes
7503 this is not what you want. For example, you might want to print a number
7504 in hex, or a pointer in decimal. Or you might want to view data in memory
7505 at a certain address as a character string or as an instruction. To do
7506 these things, specify an @dfn{output format} when you print a value.
7508 The simplest use of output formats is to say how to print a value
7509 already computed. This is done by starting the arguments of the
7510 @code{print} command with a slash and a format letter. The format
7511 letters supported are:
7515 Regard the bits of the value as an integer, and print the integer in
7519 Print as integer in signed decimal.
7522 Print as integer in unsigned decimal.
7525 Print as integer in octal.
7528 Print as integer in binary. The letter @samp{t} stands for ``two''.
7529 @footnote{@samp{b} cannot be used because these format letters are also
7530 used with the @code{x} command, where @samp{b} stands for ``byte'';
7531 see @ref{Memory,,Examining Memory}.}
7534 @cindex unknown address, locating
7535 @cindex locate address
7536 Print as an address, both absolute in hexadecimal and as an offset from
7537 the nearest preceding symbol. You can use this format used to discover
7538 where (in what function) an unknown address is located:
7541 (@value{GDBP}) p/a 0x54320
7542 $3 = 0x54320 <_initialize_vx+396>
7546 The command @code{info symbol 0x54320} yields similar results.
7547 @xref{Symbols, info symbol}.
7550 Regard as an integer and print it as a character constant. This
7551 prints both the numerical value and its character representation. The
7552 character representation is replaced with the octal escape @samp{\nnn}
7553 for characters outside the 7-bit @sc{ascii} range.
7555 Without this format, @value{GDBN} displays @code{char},
7556 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7557 constants. Single-byte members of vectors are displayed as integer
7561 Regard the bits of the value as a floating point number and print
7562 using typical floating point syntax.
7565 @cindex printing strings
7566 @cindex printing byte arrays
7567 Regard as a string, if possible. With this format, pointers to single-byte
7568 data are displayed as null-terminated strings and arrays of single-byte data
7569 are displayed as fixed-length strings. Other values are displayed in their
7572 Without this format, @value{GDBN} displays pointers to and arrays of
7573 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7574 strings. Single-byte members of a vector are displayed as an integer
7578 @cindex raw printing
7579 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7580 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7581 Printing}). This typically results in a higher-level display of the
7582 value's contents. The @samp{r} format bypasses any Python
7583 pretty-printer which might exist.
7586 For example, to print the program counter in hex (@pxref{Registers}), type
7593 Note that no space is required before the slash; this is because command
7594 names in @value{GDBN} cannot contain a slash.
7596 To reprint the last value in the value history with a different format,
7597 you can use the @code{print} command with just a format and no
7598 expression. For example, @samp{p/x} reprints the last value in hex.
7601 @section Examining Memory
7603 You can use the command @code{x} (for ``examine'') to examine memory in
7604 any of several formats, independently of your program's data types.
7606 @cindex examining memory
7608 @kindex x @r{(examine memory)}
7609 @item x/@var{nfu} @var{addr}
7612 Use the @code{x} command to examine memory.
7615 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7616 much memory to display and how to format it; @var{addr} is an
7617 expression giving the address where you want to start displaying memory.
7618 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7619 Several commands set convenient defaults for @var{addr}.
7622 @item @var{n}, the repeat count
7623 The repeat count is a decimal integer; the default is 1. It specifies
7624 how much memory (counting by units @var{u}) to display.
7625 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7628 @item @var{f}, the display format
7629 The display format is one of the formats used by @code{print}
7630 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7631 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7632 The default is @samp{x} (hexadecimal) initially. The default changes
7633 each time you use either @code{x} or @code{print}.
7635 @item @var{u}, the unit size
7636 The unit size is any of
7642 Halfwords (two bytes).
7644 Words (four bytes). This is the initial default.
7646 Giant words (eight bytes).
7649 Each time you specify a unit size with @code{x}, that size becomes the
7650 default unit the next time you use @code{x}. For the @samp{i} format,
7651 the unit size is ignored and is normally not written. For the @samp{s} format,
7652 the unit size defaults to @samp{b}, unless it is explicitly given.
7653 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7654 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7655 Note that the results depend on the programming language of the
7656 current compilation unit. If the language is C, the @samp{s}
7657 modifier will use the UTF-16 encoding while @samp{w} will use
7658 UTF-32. The encoding is set by the programming language and cannot
7661 @item @var{addr}, starting display address
7662 @var{addr} is the address where you want @value{GDBN} to begin displaying
7663 memory. The expression need not have a pointer value (though it may);
7664 it is always interpreted as an integer address of a byte of memory.
7665 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7666 @var{addr} is usually just after the last address examined---but several
7667 other commands also set the default address: @code{info breakpoints} (to
7668 the address of the last breakpoint listed), @code{info line} (to the
7669 starting address of a line), and @code{print} (if you use it to display
7670 a value from memory).
7673 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7674 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7675 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7676 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7677 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7679 Since the letters indicating unit sizes are all distinct from the
7680 letters specifying output formats, you do not have to remember whether
7681 unit size or format comes first; either order works. The output
7682 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7683 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7685 Even though the unit size @var{u} is ignored for the formats @samp{s}
7686 and @samp{i}, you might still want to use a count @var{n}; for example,
7687 @samp{3i} specifies that you want to see three machine instructions,
7688 including any operands. For convenience, especially when used with
7689 the @code{display} command, the @samp{i} format also prints branch delay
7690 slot instructions, if any, beyond the count specified, which immediately
7691 follow the last instruction that is within the count. The command
7692 @code{disassemble} gives an alternative way of inspecting machine
7693 instructions; see @ref{Machine Code,,Source and Machine Code}.
7695 All the defaults for the arguments to @code{x} are designed to make it
7696 easy to continue scanning memory with minimal specifications each time
7697 you use @code{x}. For example, after you have inspected three machine
7698 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7699 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7700 the repeat count @var{n} is used again; the other arguments default as
7701 for successive uses of @code{x}.
7703 When examining machine instructions, the instruction at current program
7704 counter is shown with a @code{=>} marker. For example:
7707 (@value{GDBP}) x/5i $pc-6
7708 0x804837f <main+11>: mov %esp,%ebp
7709 0x8048381 <main+13>: push %ecx
7710 0x8048382 <main+14>: sub $0x4,%esp
7711 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7712 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7715 @cindex @code{$_}, @code{$__}, and value history
7716 The addresses and contents printed by the @code{x} command are not saved
7717 in the value history because there is often too much of them and they
7718 would get in the way. Instead, @value{GDBN} makes these values available for
7719 subsequent use in expressions as values of the convenience variables
7720 @code{$_} and @code{$__}. After an @code{x} command, the last address
7721 examined is available for use in expressions in the convenience variable
7722 @code{$_}. The contents of that address, as examined, are available in
7723 the convenience variable @code{$__}.
7725 If the @code{x} command has a repeat count, the address and contents saved
7726 are from the last memory unit printed; this is not the same as the last
7727 address printed if several units were printed on the last line of output.
7729 @cindex remote memory comparison
7730 @cindex verify remote memory image
7731 When you are debugging a program running on a remote target machine
7732 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7733 remote machine's memory against the executable file you downloaded to
7734 the target. The @code{compare-sections} command is provided for such
7738 @kindex compare-sections
7739 @item compare-sections @r{[}@var{section-name}@r{]}
7740 Compare the data of a loadable section @var{section-name} in the
7741 executable file of the program being debugged with the same section in
7742 the remote machine's memory, and report any mismatches. With no
7743 arguments, compares all loadable sections. This command's
7744 availability depends on the target's support for the @code{"qCRC"}
7749 @section Automatic Display
7750 @cindex automatic display
7751 @cindex display of expressions
7753 If you find that you want to print the value of an expression frequently
7754 (to see how it changes), you might want to add it to the @dfn{automatic
7755 display list} so that @value{GDBN} prints its value each time your program stops.
7756 Each expression added to the list is given a number to identify it;
7757 to remove an expression from the list, you specify that number.
7758 The automatic display looks like this:
7762 3: bar[5] = (struct hack *) 0x3804
7766 This display shows item numbers, expressions and their current values. As with
7767 displays you request manually using @code{x} or @code{print}, you can
7768 specify the output format you prefer; in fact, @code{display} decides
7769 whether to use @code{print} or @code{x} depending your format
7770 specification---it uses @code{x} if you specify either the @samp{i}
7771 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7775 @item display @var{expr}
7776 Add the expression @var{expr} to the list of expressions to display
7777 each time your program stops. @xref{Expressions, ,Expressions}.
7779 @code{display} does not repeat if you press @key{RET} again after using it.
7781 @item display/@var{fmt} @var{expr}
7782 For @var{fmt} specifying only a display format and not a size or
7783 count, add the expression @var{expr} to the auto-display list but
7784 arrange to display it each time in the specified format @var{fmt}.
7785 @xref{Output Formats,,Output Formats}.
7787 @item display/@var{fmt} @var{addr}
7788 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7789 number of units, add the expression @var{addr} as a memory address to
7790 be examined each time your program stops. Examining means in effect
7791 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7794 For example, @samp{display/i $pc} can be helpful, to see the machine
7795 instruction about to be executed each time execution stops (@samp{$pc}
7796 is a common name for the program counter; @pxref{Registers, ,Registers}).
7799 @kindex delete display
7801 @item undisplay @var{dnums}@dots{}
7802 @itemx delete display @var{dnums}@dots{}
7803 Remove items from the list of expressions to display. Specify the
7804 numbers of the displays that you want affected with the command
7805 argument @var{dnums}. It can be a single display number, one of the
7806 numbers shown in the first field of the @samp{info display} display;
7807 or it could be a range of display numbers, as in @code{2-4}.
7809 @code{undisplay} does not repeat if you press @key{RET} after using it.
7810 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7812 @kindex disable display
7813 @item disable display @var{dnums}@dots{}
7814 Disable the display of item numbers @var{dnums}. A disabled display
7815 item is not printed automatically, but is not forgotten. It may be
7816 enabled again later. Specify the numbers of the displays that you
7817 want affected with the command argument @var{dnums}. It can be a
7818 single display number, one of the numbers shown in the first field of
7819 the @samp{info display} display; or it could be a range of display
7820 numbers, as in @code{2-4}.
7822 @kindex enable display
7823 @item enable display @var{dnums}@dots{}
7824 Enable display of item numbers @var{dnums}. It becomes effective once
7825 again in auto display of its expression, until you specify otherwise.
7826 Specify the numbers of the displays that you want affected with the
7827 command argument @var{dnums}. It can be a single display number, one
7828 of the numbers shown in the first field of the @samp{info display}
7829 display; or it could be a range of display numbers, as in @code{2-4}.
7832 Display the current values of the expressions on the list, just as is
7833 done when your program stops.
7835 @kindex info display
7837 Print the list of expressions previously set up to display
7838 automatically, each one with its item number, but without showing the
7839 values. This includes disabled expressions, which are marked as such.
7840 It also includes expressions which would not be displayed right now
7841 because they refer to automatic variables not currently available.
7844 @cindex display disabled out of scope
7845 If a display expression refers to local variables, then it does not make
7846 sense outside the lexical context for which it was set up. Such an
7847 expression is disabled when execution enters a context where one of its
7848 variables is not defined. For example, if you give the command
7849 @code{display last_char} while inside a function with an argument
7850 @code{last_char}, @value{GDBN} displays this argument while your program
7851 continues to stop inside that function. When it stops elsewhere---where
7852 there is no variable @code{last_char}---the display is disabled
7853 automatically. The next time your program stops where @code{last_char}
7854 is meaningful, you can enable the display expression once again.
7856 @node Print Settings
7857 @section Print Settings
7859 @cindex format options
7860 @cindex print settings
7861 @value{GDBN} provides the following ways to control how arrays, structures,
7862 and symbols are printed.
7865 These settings are useful for debugging programs in any language:
7869 @item set print address
7870 @itemx set print address on
7871 @cindex print/don't print memory addresses
7872 @value{GDBN} prints memory addresses showing the location of stack
7873 traces, structure values, pointer values, breakpoints, and so forth,
7874 even when it also displays the contents of those addresses. The default
7875 is @code{on}. For example, this is what a stack frame display looks like with
7876 @code{set print address on}:
7881 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7883 530 if (lquote != def_lquote)
7887 @item set print address off
7888 Do not print addresses when displaying their contents. For example,
7889 this is the same stack frame displayed with @code{set print address off}:
7893 (@value{GDBP}) set print addr off
7895 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7896 530 if (lquote != def_lquote)
7900 You can use @samp{set print address off} to eliminate all machine
7901 dependent displays from the @value{GDBN} interface. For example, with
7902 @code{print address off}, you should get the same text for backtraces on
7903 all machines---whether or not they involve pointer arguments.
7906 @item show print address
7907 Show whether or not addresses are to be printed.
7910 When @value{GDBN} prints a symbolic address, it normally prints the
7911 closest earlier symbol plus an offset. If that symbol does not uniquely
7912 identify the address (for example, it is a name whose scope is a single
7913 source file), you may need to clarify. One way to do this is with
7914 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7915 you can set @value{GDBN} to print the source file and line number when
7916 it prints a symbolic address:
7919 @item set print symbol-filename on
7920 @cindex source file and line of a symbol
7921 @cindex symbol, source file and line
7922 Tell @value{GDBN} to print the source file name and line number of a
7923 symbol in the symbolic form of an address.
7925 @item set print symbol-filename off
7926 Do not print source file name and line number of a symbol. This is the
7929 @item show print symbol-filename
7930 Show whether or not @value{GDBN} will print the source file name and
7931 line number of a symbol in the symbolic form of an address.
7934 Another situation where it is helpful to show symbol filenames and line
7935 numbers is when disassembling code; @value{GDBN} shows you the line
7936 number and source file that corresponds to each instruction.
7938 Also, you may wish to see the symbolic form only if the address being
7939 printed is reasonably close to the closest earlier symbol:
7942 @item set print max-symbolic-offset @var{max-offset}
7943 @cindex maximum value for offset of closest symbol
7944 Tell @value{GDBN} to only display the symbolic form of an address if the
7945 offset between the closest earlier symbol and the address is less than
7946 @var{max-offset}. The default is 0, which tells @value{GDBN}
7947 to always print the symbolic form of an address if any symbol precedes it.
7949 @item show print max-symbolic-offset
7950 Ask how large the maximum offset is that @value{GDBN} prints in a
7954 @cindex wild pointer, interpreting
7955 @cindex pointer, finding referent
7956 If you have a pointer and you are not sure where it points, try
7957 @samp{set print symbol-filename on}. Then you can determine the name
7958 and source file location of the variable where it points, using
7959 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7960 For example, here @value{GDBN} shows that a variable @code{ptt} points
7961 at another variable @code{t}, defined in @file{hi2.c}:
7964 (@value{GDBP}) set print symbol-filename on
7965 (@value{GDBP}) p/a ptt
7966 $4 = 0xe008 <t in hi2.c>
7970 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7971 does not show the symbol name and filename of the referent, even with
7972 the appropriate @code{set print} options turned on.
7975 Other settings control how different kinds of objects are printed:
7978 @item set print array
7979 @itemx set print array on
7980 @cindex pretty print arrays
7981 Pretty print arrays. This format is more convenient to read,
7982 but uses more space. The default is off.
7984 @item set print array off
7985 Return to compressed format for arrays.
7987 @item show print array
7988 Show whether compressed or pretty format is selected for displaying
7991 @cindex print array indexes
7992 @item set print array-indexes
7993 @itemx set print array-indexes on
7994 Print the index of each element when displaying arrays. May be more
7995 convenient to locate a given element in the array or quickly find the
7996 index of a given element in that printed array. The default is off.
7998 @item set print array-indexes off
7999 Stop printing element indexes when displaying arrays.
8001 @item show print array-indexes
8002 Show whether the index of each element is printed when displaying
8005 @item set print elements @var{number-of-elements}
8006 @cindex number of array elements to print
8007 @cindex limit on number of printed array elements
8008 Set a limit on how many elements of an array @value{GDBN} will print.
8009 If @value{GDBN} is printing a large array, it stops printing after it has
8010 printed the number of elements set by the @code{set print elements} command.
8011 This limit also applies to the display of strings.
8012 When @value{GDBN} starts, this limit is set to 200.
8013 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8015 @item show print elements
8016 Display the number of elements of a large array that @value{GDBN} will print.
8017 If the number is 0, then the printing is unlimited.
8019 @item set print frame-arguments @var{value}
8020 @kindex set print frame-arguments
8021 @cindex printing frame argument values
8022 @cindex print all frame argument values
8023 @cindex print frame argument values for scalars only
8024 @cindex do not print frame argument values
8025 This command allows to control how the values of arguments are printed
8026 when the debugger prints a frame (@pxref{Frames}). The possible
8031 The values of all arguments are printed.
8034 Print the value of an argument only if it is a scalar. The value of more
8035 complex arguments such as arrays, structures, unions, etc, is replaced
8036 by @code{@dots{}}. This is the default. Here is an example where
8037 only scalar arguments are shown:
8040 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8045 None of the argument values are printed. Instead, the value of each argument
8046 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8049 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8054 By default, only scalar arguments are printed. This command can be used
8055 to configure the debugger to print the value of all arguments, regardless
8056 of their type. However, it is often advantageous to not print the value
8057 of more complex parameters. For instance, it reduces the amount of
8058 information printed in each frame, making the backtrace more readable.
8059 Also, it improves performance when displaying Ada frames, because
8060 the computation of large arguments can sometimes be CPU-intensive,
8061 especially in large applications. Setting @code{print frame-arguments}
8062 to @code{scalars} (the default) or @code{none} avoids this computation,
8063 thus speeding up the display of each Ada frame.
8065 @item show print frame-arguments
8066 Show how the value of arguments should be displayed when printing a frame.
8068 @anchor{set print entry-values}
8069 @item set print entry-values @var{value}
8070 @kindex set print entry-values
8071 Set printing of frame argument values at function entry. In some cases
8072 @value{GDBN} can determine the value of function argument which was passed by
8073 the function caller, even if the value was modified inside the called function
8074 and therefore is different. With optimized code, the current value could be
8075 unavailable, but the entry value may still be known.
8077 The default value is @code{default} (see below for its description). Older
8078 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8079 this feature will behave in the @code{default} setting the same way as with the
8082 This functionality is currently supported only by DWARF 2 debugging format and
8083 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8084 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8087 The @var{value} parameter can be one of the following:
8091 Print only actual parameter values, never print values from function entry
8095 #0 different (val=6)
8096 #0 lost (val=<optimized out>)
8098 #0 invalid (val=<optimized out>)
8102 Print only parameter values from function entry point. The actual parameter
8103 values are never printed.
8105 #0 equal (val@@entry=5)
8106 #0 different (val@@entry=5)
8107 #0 lost (val@@entry=5)
8108 #0 born (val@@entry=<optimized out>)
8109 #0 invalid (val@@entry=<optimized out>)
8113 Print only parameter values from function entry point. If value from function
8114 entry point is not known while the actual value is known, print the actual
8115 value for such parameter.
8117 #0 equal (val@@entry=5)
8118 #0 different (val@@entry=5)
8119 #0 lost (val@@entry=5)
8121 #0 invalid (val@@entry=<optimized out>)
8125 Print actual parameter values. If actual parameter value is not known while
8126 value from function entry point is known, print the entry point value for such
8130 #0 different (val=6)
8131 #0 lost (val@@entry=5)
8133 #0 invalid (val=<optimized out>)
8137 Always print both the actual parameter value and its value from function entry
8138 point, even if values of one or both are not available due to compiler
8141 #0 equal (val=5, val@@entry=5)
8142 #0 different (val=6, val@@entry=5)
8143 #0 lost (val=<optimized out>, val@@entry=5)
8144 #0 born (val=10, val@@entry=<optimized out>)
8145 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8149 Print the actual parameter value if it is known and also its value from
8150 function entry point if it is known. If neither is known, print for the actual
8151 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8152 values are known and identical, print the shortened
8153 @code{param=param@@entry=VALUE} notation.
8155 #0 equal (val=val@@entry=5)
8156 #0 different (val=6, val@@entry=5)
8157 #0 lost (val@@entry=5)
8159 #0 invalid (val=<optimized out>)
8163 Always print the actual parameter value. Print also its value from function
8164 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8165 if both values are known and identical, print the shortened
8166 @code{param=param@@entry=VALUE} notation.
8168 #0 equal (val=val@@entry=5)
8169 #0 different (val=6, val@@entry=5)
8170 #0 lost (val=<optimized out>, val@@entry=5)
8172 #0 invalid (val=<optimized out>)
8176 For analysis messages on possible failures of frame argument values at function
8177 entry resolution see @ref{set debug entry-values}.
8179 @item show print entry-values
8180 Show the method being used for printing of frame argument values at function
8183 @item set print repeats
8184 @cindex repeated array elements
8185 Set the threshold for suppressing display of repeated array
8186 elements. When the number of consecutive identical elements of an
8187 array exceeds the threshold, @value{GDBN} prints the string
8188 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8189 identical repetitions, instead of displaying the identical elements
8190 themselves. Setting the threshold to zero will cause all elements to
8191 be individually printed. The default threshold is 10.
8193 @item show print repeats
8194 Display the current threshold for printing repeated identical
8197 @item set print null-stop
8198 @cindex @sc{null} elements in arrays
8199 Cause @value{GDBN} to stop printing the characters of an array when the first
8200 @sc{null} is encountered. This is useful when large arrays actually
8201 contain only short strings.
8204 @item show print null-stop
8205 Show whether @value{GDBN} stops printing an array on the first
8206 @sc{null} character.
8208 @item set print pretty on
8209 @cindex print structures in indented form
8210 @cindex indentation in structure display
8211 Cause @value{GDBN} to print structures in an indented format with one member
8212 per line, like this:
8227 @item set print pretty off
8228 Cause @value{GDBN} to print structures in a compact format, like this:
8232 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8233 meat = 0x54 "Pork"@}
8238 This is the default format.
8240 @item show print pretty
8241 Show which format @value{GDBN} is using to print structures.
8243 @item set print sevenbit-strings on
8244 @cindex eight-bit characters in strings
8245 @cindex octal escapes in strings
8246 Print using only seven-bit characters; if this option is set,
8247 @value{GDBN} displays any eight-bit characters (in strings or
8248 character values) using the notation @code{\}@var{nnn}. This setting is
8249 best if you are working in English (@sc{ascii}) and you use the
8250 high-order bit of characters as a marker or ``meta'' bit.
8252 @item set print sevenbit-strings off
8253 Print full eight-bit characters. This allows the use of more
8254 international character sets, and is the default.
8256 @item show print sevenbit-strings
8257 Show whether or not @value{GDBN} is printing only seven-bit characters.
8259 @item set print union on
8260 @cindex unions in structures, printing
8261 Tell @value{GDBN} to print unions which are contained in structures
8262 and other unions. This is the default setting.
8264 @item set print union off
8265 Tell @value{GDBN} not to print unions which are contained in
8266 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8269 @item show print union
8270 Ask @value{GDBN} whether or not it will print unions which are contained in
8271 structures and other unions.
8273 For example, given the declarations
8276 typedef enum @{Tree, Bug@} Species;
8277 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8278 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8289 struct thing foo = @{Tree, @{Acorn@}@};
8293 with @code{set print union on} in effect @samp{p foo} would print
8296 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8300 and with @code{set print union off} in effect it would print
8303 $1 = @{it = Tree, form = @{...@}@}
8307 @code{set print union} affects programs written in C-like languages
8313 These settings are of interest when debugging C@t{++} programs:
8316 @cindex demangling C@t{++} names
8317 @item set print demangle
8318 @itemx set print demangle on
8319 Print C@t{++} names in their source form rather than in the encoded
8320 (``mangled'') form passed to the assembler and linker for type-safe
8321 linkage. The default is on.
8323 @item show print demangle
8324 Show whether C@t{++} names are printed in mangled or demangled form.
8326 @item set print asm-demangle
8327 @itemx set print asm-demangle on
8328 Print C@t{++} names in their source form rather than their mangled form, even
8329 in assembler code printouts such as instruction disassemblies.
8332 @item show print asm-demangle
8333 Show whether C@t{++} names in assembly listings are printed in mangled
8336 @cindex C@t{++} symbol decoding style
8337 @cindex symbol decoding style, C@t{++}
8338 @kindex set demangle-style
8339 @item set demangle-style @var{style}
8340 Choose among several encoding schemes used by different compilers to
8341 represent C@t{++} names. The choices for @var{style} are currently:
8345 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8348 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8349 This is the default.
8352 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8355 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8358 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8359 @strong{Warning:} this setting alone is not sufficient to allow
8360 debugging @code{cfront}-generated executables. @value{GDBN} would
8361 require further enhancement to permit that.
8364 If you omit @var{style}, you will see a list of possible formats.
8366 @item show demangle-style
8367 Display the encoding style currently in use for decoding C@t{++} symbols.
8369 @item set print object
8370 @itemx set print object on
8371 @cindex derived type of an object, printing
8372 @cindex display derived types
8373 When displaying a pointer to an object, identify the @emph{actual}
8374 (derived) type of the object rather than the @emph{declared} type, using
8375 the virtual function table. Note that the virtual function table is
8376 required---this feature can only work for objects that have run-time
8377 type identification; a single virtual method in the object's declared
8380 @item set print object off
8381 Display only the declared type of objects, without reference to the
8382 virtual function table. This is the default setting.
8384 @item show print object
8385 Show whether actual, or declared, object types are displayed.
8387 @item set print static-members
8388 @itemx set print static-members on
8389 @cindex static members of C@t{++} objects
8390 Print static members when displaying a C@t{++} object. The default is on.
8392 @item set print static-members off
8393 Do not print static members when displaying a C@t{++} object.
8395 @item show print static-members
8396 Show whether C@t{++} static members are printed or not.
8398 @item set print pascal_static-members
8399 @itemx set print pascal_static-members on
8400 @cindex static members of Pascal objects
8401 @cindex Pascal objects, static members display
8402 Print static members when displaying a Pascal object. The default is on.
8404 @item set print pascal_static-members off
8405 Do not print static members when displaying a Pascal object.
8407 @item show print pascal_static-members
8408 Show whether Pascal static members are printed or not.
8410 @c These don't work with HP ANSI C++ yet.
8411 @item set print vtbl
8412 @itemx set print vtbl on
8413 @cindex pretty print C@t{++} virtual function tables
8414 @cindex virtual functions (C@t{++}) display
8415 @cindex VTBL display
8416 Pretty print C@t{++} virtual function tables. The default is off.
8417 (The @code{vtbl} commands do not work on programs compiled with the HP
8418 ANSI C@t{++} compiler (@code{aCC}).)
8420 @item set print vtbl off
8421 Do not pretty print C@t{++} virtual function tables.
8423 @item show print vtbl
8424 Show whether C@t{++} virtual function tables are pretty printed, or not.
8427 @node Pretty Printing
8428 @section Pretty Printing
8430 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8431 Python code. It greatly simplifies the display of complex objects. This
8432 mechanism works for both MI and the CLI.
8435 * Pretty-Printer Introduction:: Introduction to pretty-printers
8436 * Pretty-Printer Example:: An example pretty-printer
8437 * Pretty-Printer Commands:: Pretty-printer commands
8440 @node Pretty-Printer Introduction
8441 @subsection Pretty-Printer Introduction
8443 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8444 registered for the value. If there is then @value{GDBN} invokes the
8445 pretty-printer to print the value. Otherwise the value is printed normally.
8447 Pretty-printers are normally named. This makes them easy to manage.
8448 The @samp{info pretty-printer} command will list all the installed
8449 pretty-printers with their names.
8450 If a pretty-printer can handle multiple data types, then its
8451 @dfn{subprinters} are the printers for the individual data types.
8452 Each such subprinter has its own name.
8453 The format of the name is @var{printer-name};@var{subprinter-name}.
8455 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8456 Typically they are automatically loaded and registered when the corresponding
8457 debug information is loaded, thus making them available without having to
8458 do anything special.
8460 There are three places where a pretty-printer can be registered.
8464 Pretty-printers registered globally are available when debugging
8468 Pretty-printers registered with a program space are available only
8469 when debugging that program.
8470 @xref{Progspaces In Python}, for more details on program spaces in Python.
8473 Pretty-printers registered with an objfile are loaded and unloaded
8474 with the corresponding objfile (e.g., shared library).
8475 @xref{Objfiles In Python}, for more details on objfiles in Python.
8478 @xref{Selecting Pretty-Printers}, for further information on how
8479 pretty-printers are selected,
8481 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8484 @node Pretty-Printer Example
8485 @subsection Pretty-Printer Example
8487 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8490 (@value{GDBP}) print s
8492 static npos = 4294967295,
8494 <std::allocator<char>> = @{
8495 <__gnu_cxx::new_allocator<char>> = @{
8496 <No data fields>@}, <No data fields>
8498 members of std::basic_string<char, std::char_traits<char>,
8499 std::allocator<char> >::_Alloc_hider:
8500 _M_p = 0x804a014 "abcd"
8505 With a pretty-printer for @code{std::string} only the contents are printed:
8508 (@value{GDBP}) print s
8512 @node Pretty-Printer Commands
8513 @subsection Pretty-Printer Commands
8514 @cindex pretty-printer commands
8517 @kindex info pretty-printer
8518 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8519 Print the list of installed pretty-printers.
8520 This includes disabled pretty-printers, which are marked as such.
8522 @var{object-regexp} is a regular expression matching the objects
8523 whose pretty-printers to list.
8524 Objects can be @code{global}, the program space's file
8525 (@pxref{Progspaces In Python}),
8526 and the object files within that program space (@pxref{Objfiles In Python}).
8527 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8528 looks up a printer from these three objects.
8530 @var{name-regexp} is a regular expression matching the name of the printers
8533 @kindex disable pretty-printer
8534 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8535 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8536 A disabled pretty-printer is not forgotten, it may be enabled again later.
8538 @kindex enable pretty-printer
8539 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8540 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8545 Suppose we have three pretty-printers installed: one from library1.so
8546 named @code{foo} that prints objects of type @code{foo}, and
8547 another from library2.so named @code{bar} that prints two types of objects,
8548 @code{bar1} and @code{bar2}.
8551 (gdb) info pretty-printer
8558 (gdb) info pretty-printer library2
8563 (gdb) disable pretty-printer library1
8565 2 of 3 printers enabled
8566 (gdb) info pretty-printer
8573 (gdb) disable pretty-printer library2 bar:bar1
8575 1 of 3 printers enabled
8576 (gdb) info pretty-printer library2
8583 (gdb) disable pretty-printer library2 bar
8585 0 of 3 printers enabled
8586 (gdb) info pretty-printer library2
8595 Note that for @code{bar} the entire printer can be disabled,
8596 as can each individual subprinter.
8599 @section Value History
8601 @cindex value history
8602 @cindex history of values printed by @value{GDBN}
8603 Values printed by the @code{print} command are saved in the @value{GDBN}
8604 @dfn{value history}. This allows you to refer to them in other expressions.
8605 Values are kept until the symbol table is re-read or discarded
8606 (for example with the @code{file} or @code{symbol-file} commands).
8607 When the symbol table changes, the value history is discarded,
8608 since the values may contain pointers back to the types defined in the
8613 @cindex history number
8614 The values printed are given @dfn{history numbers} by which you can
8615 refer to them. These are successive integers starting with one.
8616 @code{print} shows you the history number assigned to a value by
8617 printing @samp{$@var{num} = } before the value; here @var{num} is the
8620 To refer to any previous value, use @samp{$} followed by the value's
8621 history number. The way @code{print} labels its output is designed to
8622 remind you of this. Just @code{$} refers to the most recent value in
8623 the history, and @code{$$} refers to the value before that.
8624 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8625 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8626 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8628 For example, suppose you have just printed a pointer to a structure and
8629 want to see the contents of the structure. It suffices to type
8635 If you have a chain of structures where the component @code{next} points
8636 to the next one, you can print the contents of the next one with this:
8643 You can print successive links in the chain by repeating this
8644 command---which you can do by just typing @key{RET}.
8646 Note that the history records values, not expressions. If the value of
8647 @code{x} is 4 and you type these commands:
8655 then the value recorded in the value history by the @code{print} command
8656 remains 4 even though the value of @code{x} has changed.
8661 Print the last ten values in the value history, with their item numbers.
8662 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8663 values} does not change the history.
8665 @item show values @var{n}
8666 Print ten history values centered on history item number @var{n}.
8669 Print ten history values just after the values last printed. If no more
8670 values are available, @code{show values +} produces no display.
8673 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8674 same effect as @samp{show values +}.
8676 @node Convenience Vars
8677 @section Convenience Variables
8679 @cindex convenience variables
8680 @cindex user-defined variables
8681 @value{GDBN} provides @dfn{convenience variables} that you can use within
8682 @value{GDBN} to hold on to a value and refer to it later. These variables
8683 exist entirely within @value{GDBN}; they are not part of your program, and
8684 setting a convenience variable has no direct effect on further execution
8685 of your program. That is why you can use them freely.
8687 Convenience variables are prefixed with @samp{$}. Any name preceded by
8688 @samp{$} can be used for a convenience variable, unless it is one of
8689 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8690 (Value history references, in contrast, are @emph{numbers} preceded
8691 by @samp{$}. @xref{Value History, ,Value History}.)
8693 You can save a value in a convenience variable with an assignment
8694 expression, just as you would set a variable in your program.
8698 set $foo = *object_ptr
8702 would save in @code{$foo} the value contained in the object pointed to by
8705 Using a convenience variable for the first time creates it, but its
8706 value is @code{void} until you assign a new value. You can alter the
8707 value with another assignment at any time.
8709 Convenience variables have no fixed types. You can assign a convenience
8710 variable any type of value, including structures and arrays, even if
8711 that variable already has a value of a different type. The convenience
8712 variable, when used as an expression, has the type of its current value.
8715 @kindex show convenience
8716 @cindex show all user variables
8717 @item show convenience
8718 Print a list of convenience variables used so far, and their values.
8719 Abbreviated @code{show conv}.
8721 @kindex init-if-undefined
8722 @cindex convenience variables, initializing
8723 @item init-if-undefined $@var{variable} = @var{expression}
8724 Set a convenience variable if it has not already been set. This is useful
8725 for user-defined commands that keep some state. It is similar, in concept,
8726 to using local static variables with initializers in C (except that
8727 convenience variables are global). It can also be used to allow users to
8728 override default values used in a command script.
8730 If the variable is already defined then the expression is not evaluated so
8731 any side-effects do not occur.
8734 One of the ways to use a convenience variable is as a counter to be
8735 incremented or a pointer to be advanced. For example, to print
8736 a field from successive elements of an array of structures:
8740 print bar[$i++]->contents
8744 Repeat that command by typing @key{RET}.
8746 Some convenience variables are created automatically by @value{GDBN} and given
8747 values likely to be useful.
8750 @vindex $_@r{, convenience variable}
8752 The variable @code{$_} is automatically set by the @code{x} command to
8753 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8754 commands which provide a default address for @code{x} to examine also
8755 set @code{$_} to that address; these commands include @code{info line}
8756 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8757 except when set by the @code{x} command, in which case it is a pointer
8758 to the type of @code{$__}.
8760 @vindex $__@r{, convenience variable}
8762 The variable @code{$__} is automatically set by the @code{x} command
8763 to the value found in the last address examined. Its type is chosen
8764 to match the format in which the data was printed.
8767 @vindex $_exitcode@r{, convenience variable}
8768 The variable @code{$_exitcode} is automatically set to the exit code when
8769 the program being debugged terminates.
8772 @vindex $_sdata@r{, inspect, convenience variable}
8773 The variable @code{$_sdata} contains extra collected static tracepoint
8774 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8775 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8776 if extra static tracepoint data has not been collected.
8779 @vindex $_siginfo@r{, convenience variable}
8780 The variable @code{$_siginfo} contains extra signal information
8781 (@pxref{extra signal information}). Note that @code{$_siginfo}
8782 could be empty, if the application has not yet received any signals.
8783 For example, it will be empty before you execute the @code{run} command.
8786 @vindex $_tlb@r{, convenience variable}
8787 The variable @code{$_tlb} is automatically set when debugging
8788 applications running on MS-Windows in native mode or connected to
8789 gdbserver that supports the @code{qGetTIBAddr} request.
8790 @xref{General Query Packets}.
8791 This variable contains the address of the thread information block.
8795 On HP-UX systems, if you refer to a function or variable name that
8796 begins with a dollar sign, @value{GDBN} searches for a user or system
8797 name first, before it searches for a convenience variable.
8799 @cindex convenience functions
8800 @value{GDBN} also supplies some @dfn{convenience functions}. These
8801 have a syntax similar to convenience variables. A convenience
8802 function can be used in an expression just like an ordinary function;
8803 however, a convenience function is implemented internally to
8808 @kindex help function
8809 @cindex show all convenience functions
8810 Print a list of all convenience functions.
8817 You can refer to machine register contents, in expressions, as variables
8818 with names starting with @samp{$}. The names of registers are different
8819 for each machine; use @code{info registers} to see the names used on
8823 @kindex info registers
8824 @item info registers
8825 Print the names and values of all registers except floating-point
8826 and vector registers (in the selected stack frame).
8828 @kindex info all-registers
8829 @cindex floating point registers
8830 @item info all-registers
8831 Print the names and values of all registers, including floating-point
8832 and vector registers (in the selected stack frame).
8834 @item info registers @var{regname} @dots{}
8835 Print the @dfn{relativized} value of each specified register @var{regname}.
8836 As discussed in detail below, register values are normally relative to
8837 the selected stack frame. @var{regname} may be any register name valid on
8838 the machine you are using, with or without the initial @samp{$}.
8841 @cindex stack pointer register
8842 @cindex program counter register
8843 @cindex process status register
8844 @cindex frame pointer register
8845 @cindex standard registers
8846 @value{GDBN} has four ``standard'' register names that are available (in
8847 expressions) on most machines---whenever they do not conflict with an
8848 architecture's canonical mnemonics for registers. The register names
8849 @code{$pc} and @code{$sp} are used for the program counter register and
8850 the stack pointer. @code{$fp} is used for a register that contains a
8851 pointer to the current stack frame, and @code{$ps} is used for a
8852 register that contains the processor status. For example,
8853 you could print the program counter in hex with
8860 or print the instruction to be executed next with
8867 or add four to the stack pointer@footnote{This is a way of removing
8868 one word from the stack, on machines where stacks grow downward in
8869 memory (most machines, nowadays). This assumes that the innermost
8870 stack frame is selected; setting @code{$sp} is not allowed when other
8871 stack frames are selected. To pop entire frames off the stack,
8872 regardless of machine architecture, use @code{return};
8873 see @ref{Returning, ,Returning from a Function}.} with
8879 Whenever possible, these four standard register names are available on
8880 your machine even though the machine has different canonical mnemonics,
8881 so long as there is no conflict. The @code{info registers} command
8882 shows the canonical names. For example, on the SPARC, @code{info
8883 registers} displays the processor status register as @code{$psr} but you
8884 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8885 is an alias for the @sc{eflags} register.
8887 @value{GDBN} always considers the contents of an ordinary register as an
8888 integer when the register is examined in this way. Some machines have
8889 special registers which can hold nothing but floating point; these
8890 registers are considered to have floating point values. There is no way
8891 to refer to the contents of an ordinary register as floating point value
8892 (although you can @emph{print} it as a floating point value with
8893 @samp{print/f $@var{regname}}).
8895 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8896 means that the data format in which the register contents are saved by
8897 the operating system is not the same one that your program normally
8898 sees. For example, the registers of the 68881 floating point
8899 coprocessor are always saved in ``extended'' (raw) format, but all C
8900 programs expect to work with ``double'' (virtual) format. In such
8901 cases, @value{GDBN} normally works with the virtual format only (the format
8902 that makes sense for your program), but the @code{info registers} command
8903 prints the data in both formats.
8905 @cindex SSE registers (x86)
8906 @cindex MMX registers (x86)
8907 Some machines have special registers whose contents can be interpreted
8908 in several different ways. For example, modern x86-based machines
8909 have SSE and MMX registers that can hold several values packed
8910 together in several different formats. @value{GDBN} refers to such
8911 registers in @code{struct} notation:
8914 (@value{GDBP}) print $xmm1
8916 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8917 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8918 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8919 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8920 v4_int32 = @{0, 20657912, 11, 13@},
8921 v2_int64 = @{88725056443645952, 55834574859@},
8922 uint128 = 0x0000000d0000000b013b36f800000000
8927 To set values of such registers, you need to tell @value{GDBN} which
8928 view of the register you wish to change, as if you were assigning
8929 value to a @code{struct} member:
8932 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8935 Normally, register values are relative to the selected stack frame
8936 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8937 value that the register would contain if all stack frames farther in
8938 were exited and their saved registers restored. In order to see the
8939 true contents of hardware registers, you must select the innermost
8940 frame (with @samp{frame 0}).
8942 However, @value{GDBN} must deduce where registers are saved, from the machine
8943 code generated by your compiler. If some registers are not saved, or if
8944 @value{GDBN} is unable to locate the saved registers, the selected stack
8945 frame makes no difference.
8947 @node Floating Point Hardware
8948 @section Floating Point Hardware
8949 @cindex floating point
8951 Depending on the configuration, @value{GDBN} may be able to give
8952 you more information about the status of the floating point hardware.
8957 Display hardware-dependent information about the floating
8958 point unit. The exact contents and layout vary depending on the
8959 floating point chip. Currently, @samp{info float} is supported on
8960 the ARM and x86 machines.
8964 @section Vector Unit
8967 Depending on the configuration, @value{GDBN} may be able to give you
8968 more information about the status of the vector unit.
8973 Display information about the vector unit. The exact contents and
8974 layout vary depending on the hardware.
8977 @node OS Information
8978 @section Operating System Auxiliary Information
8979 @cindex OS information
8981 @value{GDBN} provides interfaces to useful OS facilities that can help
8982 you debug your program.
8984 @cindex @code{ptrace} system call
8985 @cindex @code{struct user} contents
8986 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8987 machines), it interfaces with the inferior via the @code{ptrace}
8988 system call. The operating system creates a special sata structure,
8989 called @code{struct user}, for this interface. You can use the
8990 command @code{info udot} to display the contents of this data
8996 Display the contents of the @code{struct user} maintained by the OS
8997 kernel for the program being debugged. @value{GDBN} displays the
8998 contents of @code{struct user} as a list of hex numbers, similar to
8999 the @code{examine} command.
9002 @cindex auxiliary vector
9003 @cindex vector, auxiliary
9004 Some operating systems supply an @dfn{auxiliary vector} to programs at
9005 startup. This is akin to the arguments and environment that you
9006 specify for a program, but contains a system-dependent variety of
9007 binary values that tell system libraries important details about the
9008 hardware, operating system, and process. Each value's purpose is
9009 identified by an integer tag; the meanings are well-known but system-specific.
9010 Depending on the configuration and operating system facilities,
9011 @value{GDBN} may be able to show you this information. For remote
9012 targets, this functionality may further depend on the remote stub's
9013 support of the @samp{qXfer:auxv:read} packet, see
9014 @ref{qXfer auxiliary vector read}.
9019 Display the auxiliary vector of the inferior, which can be either a
9020 live process or a core dump file. @value{GDBN} prints each tag value
9021 numerically, and also shows names and text descriptions for recognized
9022 tags. Some values in the vector are numbers, some bit masks, and some
9023 pointers to strings or other data. @value{GDBN} displays each value in the
9024 most appropriate form for a recognized tag, and in hexadecimal for
9025 an unrecognized tag.
9028 On some targets, @value{GDBN} can access operating-system-specific information
9029 and display it to user, without interpretation. For remote targets,
9030 this functionality depends on the remote stub's support of the
9031 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9036 List the types of OS information available for the target. If the
9037 target does not return a list of possible types, this command will
9040 @kindex info os processes
9041 @item info os processes
9042 Display the list of processes on the target. For each process,
9043 @value{GDBN} prints the process identifier, the name of the user, and
9044 the command corresponding to the process.
9047 @node Memory Region Attributes
9048 @section Memory Region Attributes
9049 @cindex memory region attributes
9051 @dfn{Memory region attributes} allow you to describe special handling
9052 required by regions of your target's memory. @value{GDBN} uses
9053 attributes to determine whether to allow certain types of memory
9054 accesses; whether to use specific width accesses; and whether to cache
9055 target memory. By default the description of memory regions is
9056 fetched from the target (if the current target supports this), but the
9057 user can override the fetched regions.
9059 Defined memory regions can be individually enabled and disabled. When a
9060 memory region is disabled, @value{GDBN} uses the default attributes when
9061 accessing memory in that region. Similarly, if no memory regions have
9062 been defined, @value{GDBN} uses the default attributes when accessing
9065 When a memory region is defined, it is given a number to identify it;
9066 to enable, disable, or remove a memory region, you specify that number.
9070 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9071 Define a memory region bounded by @var{lower} and @var{upper} with
9072 attributes @var{attributes}@dots{}, and add it to the list of regions
9073 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9074 case: it is treated as the target's maximum memory address.
9075 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9078 Discard any user changes to the memory regions and use target-supplied
9079 regions, if available, or no regions if the target does not support.
9082 @item delete mem @var{nums}@dots{}
9083 Remove memory regions @var{nums}@dots{} from the list of regions
9084 monitored by @value{GDBN}.
9087 @item disable mem @var{nums}@dots{}
9088 Disable monitoring of memory regions @var{nums}@dots{}.
9089 A disabled memory region is not forgotten.
9090 It may be enabled again later.
9093 @item enable mem @var{nums}@dots{}
9094 Enable monitoring of memory regions @var{nums}@dots{}.
9098 Print a table of all defined memory regions, with the following columns
9102 @item Memory Region Number
9103 @item Enabled or Disabled.
9104 Enabled memory regions are marked with @samp{y}.
9105 Disabled memory regions are marked with @samp{n}.
9108 The address defining the inclusive lower bound of the memory region.
9111 The address defining the exclusive upper bound of the memory region.
9114 The list of attributes set for this memory region.
9119 @subsection Attributes
9121 @subsubsection Memory Access Mode
9122 The access mode attributes set whether @value{GDBN} may make read or
9123 write accesses to a memory region.
9125 While these attributes prevent @value{GDBN} from performing invalid
9126 memory accesses, they do nothing to prevent the target system, I/O DMA,
9127 etc.@: from accessing memory.
9131 Memory is read only.
9133 Memory is write only.
9135 Memory is read/write. This is the default.
9138 @subsubsection Memory Access Size
9139 The access size attribute tells @value{GDBN} to use specific sized
9140 accesses in the memory region. Often memory mapped device registers
9141 require specific sized accesses. If no access size attribute is
9142 specified, @value{GDBN} may use accesses of any size.
9146 Use 8 bit memory accesses.
9148 Use 16 bit memory accesses.
9150 Use 32 bit memory accesses.
9152 Use 64 bit memory accesses.
9155 @c @subsubsection Hardware/Software Breakpoints
9156 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9157 @c will use hardware or software breakpoints for the internal breakpoints
9158 @c used by the step, next, finish, until, etc. commands.
9162 @c Always use hardware breakpoints
9163 @c @item swbreak (default)
9166 @subsubsection Data Cache
9167 The data cache attributes set whether @value{GDBN} will cache target
9168 memory. While this generally improves performance by reducing debug
9169 protocol overhead, it can lead to incorrect results because @value{GDBN}
9170 does not know about volatile variables or memory mapped device
9175 Enable @value{GDBN} to cache target memory.
9177 Disable @value{GDBN} from caching target memory. This is the default.
9180 @subsection Memory Access Checking
9181 @value{GDBN} can be instructed to refuse accesses to memory that is
9182 not explicitly described. This can be useful if accessing such
9183 regions has undesired effects for a specific target, or to provide
9184 better error checking. The following commands control this behaviour.
9187 @kindex set mem inaccessible-by-default
9188 @item set mem inaccessible-by-default [on|off]
9189 If @code{on} is specified, make @value{GDBN} treat memory not
9190 explicitly described by the memory ranges as non-existent and refuse accesses
9191 to such memory. The checks are only performed if there's at least one
9192 memory range defined. If @code{off} is specified, make @value{GDBN}
9193 treat the memory not explicitly described by the memory ranges as RAM.
9194 The default value is @code{on}.
9195 @kindex show mem inaccessible-by-default
9196 @item show mem inaccessible-by-default
9197 Show the current handling of accesses to unknown memory.
9201 @c @subsubsection Memory Write Verification
9202 @c The memory write verification attributes set whether @value{GDBN}
9203 @c will re-reads data after each write to verify the write was successful.
9207 @c @item noverify (default)
9210 @node Dump/Restore Files
9211 @section Copy Between Memory and a File
9212 @cindex dump/restore files
9213 @cindex append data to a file
9214 @cindex dump data to a file
9215 @cindex restore data from a file
9217 You can use the commands @code{dump}, @code{append}, and
9218 @code{restore} to copy data between target memory and a file. The
9219 @code{dump} and @code{append} commands write data to a file, and the
9220 @code{restore} command reads data from a file back into the inferior's
9221 memory. Files may be in binary, Motorola S-record, Intel hex, or
9222 Tektronix Hex format; however, @value{GDBN} can only append to binary
9228 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9229 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9230 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9231 or the value of @var{expr}, to @var{filename} in the given format.
9233 The @var{format} parameter may be any one of:
9240 Motorola S-record format.
9242 Tektronix Hex format.
9245 @value{GDBN} uses the same definitions of these formats as the
9246 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9247 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9251 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9252 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9253 Append the contents of memory from @var{start_addr} to @var{end_addr},
9254 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9255 (@value{GDBN} can only append data to files in raw binary form.)
9258 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9259 Restore the contents of file @var{filename} into memory. The
9260 @code{restore} command can automatically recognize any known @sc{bfd}
9261 file format, except for raw binary. To restore a raw binary file you
9262 must specify the optional keyword @code{binary} after the filename.
9264 If @var{bias} is non-zero, its value will be added to the addresses
9265 contained in the file. Binary files always start at address zero, so
9266 they will be restored at address @var{bias}. Other bfd files have
9267 a built-in location; they will be restored at offset @var{bias}
9270 If @var{start} and/or @var{end} are non-zero, then only data between
9271 file offset @var{start} and file offset @var{end} will be restored.
9272 These offsets are relative to the addresses in the file, before
9273 the @var{bias} argument is applied.
9277 @node Core File Generation
9278 @section How to Produce a Core File from Your Program
9279 @cindex dump core from inferior
9281 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9282 image of a running process and its process status (register values
9283 etc.). Its primary use is post-mortem debugging of a program that
9284 crashed while it ran outside a debugger. A program that crashes
9285 automatically produces a core file, unless this feature is disabled by
9286 the user. @xref{Files}, for information on invoking @value{GDBN} in
9287 the post-mortem debugging mode.
9289 Occasionally, you may wish to produce a core file of the program you
9290 are debugging in order to preserve a snapshot of its state.
9291 @value{GDBN} has a special command for that.
9295 @kindex generate-core-file
9296 @item generate-core-file [@var{file}]
9297 @itemx gcore [@var{file}]
9298 Produce a core dump of the inferior process. The optional argument
9299 @var{file} specifies the file name where to put the core dump. If not
9300 specified, the file name defaults to @file{core.@var{pid}}, where
9301 @var{pid} is the inferior process ID.
9303 Note that this command is implemented only for some systems (as of
9304 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9307 @node Character Sets
9308 @section Character Sets
9309 @cindex character sets
9311 @cindex translating between character sets
9312 @cindex host character set
9313 @cindex target character set
9315 If the program you are debugging uses a different character set to
9316 represent characters and strings than the one @value{GDBN} uses itself,
9317 @value{GDBN} can automatically translate between the character sets for
9318 you. The character set @value{GDBN} uses we call the @dfn{host
9319 character set}; the one the inferior program uses we call the
9320 @dfn{target character set}.
9322 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9323 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9324 remote protocol (@pxref{Remote Debugging}) to debug a program
9325 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9326 then the host character set is Latin-1, and the target character set is
9327 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9328 target-charset EBCDIC-US}, then @value{GDBN} translates between
9329 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9330 character and string literals in expressions.
9332 @value{GDBN} has no way to automatically recognize which character set
9333 the inferior program uses; you must tell it, using the @code{set
9334 target-charset} command, described below.
9336 Here are the commands for controlling @value{GDBN}'s character set
9340 @item set target-charset @var{charset}
9341 @kindex set target-charset
9342 Set the current target character set to @var{charset}. To display the
9343 list of supported target character sets, type
9344 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9346 @item set host-charset @var{charset}
9347 @kindex set host-charset
9348 Set the current host character set to @var{charset}.
9350 By default, @value{GDBN} uses a host character set appropriate to the
9351 system it is running on; you can override that default using the
9352 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9353 automatically determine the appropriate host character set. In this
9354 case, @value{GDBN} uses @samp{UTF-8}.
9356 @value{GDBN} can only use certain character sets as its host character
9357 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9358 @value{GDBN} will list the host character sets it supports.
9360 @item set charset @var{charset}
9362 Set the current host and target character sets to @var{charset}. As
9363 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9364 @value{GDBN} will list the names of the character sets that can be used
9365 for both host and target.
9368 @kindex show charset
9369 Show the names of the current host and target character sets.
9371 @item show host-charset
9372 @kindex show host-charset
9373 Show the name of the current host character set.
9375 @item show target-charset
9376 @kindex show target-charset
9377 Show the name of the current target character set.
9379 @item set target-wide-charset @var{charset}
9380 @kindex set target-wide-charset
9381 Set the current target's wide character set to @var{charset}. This is
9382 the character set used by the target's @code{wchar_t} type. To
9383 display the list of supported wide character sets, type
9384 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9386 @item show target-wide-charset
9387 @kindex show target-wide-charset
9388 Show the name of the current target's wide character set.
9391 Here is an example of @value{GDBN}'s character set support in action.
9392 Assume that the following source code has been placed in the file
9393 @file{charset-test.c}:
9399 = @{72, 101, 108, 108, 111, 44, 32, 119,
9400 111, 114, 108, 100, 33, 10, 0@};
9401 char ibm1047_hello[]
9402 = @{200, 133, 147, 147, 150, 107, 64, 166,
9403 150, 153, 147, 132, 90, 37, 0@};
9407 printf ("Hello, world!\n");
9411 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9412 containing the string @samp{Hello, world!} followed by a newline,
9413 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9415 We compile the program, and invoke the debugger on it:
9418 $ gcc -g charset-test.c -o charset-test
9419 $ gdb -nw charset-test
9420 GNU gdb 2001-12-19-cvs
9421 Copyright 2001 Free Software Foundation, Inc.
9426 We can use the @code{show charset} command to see what character sets
9427 @value{GDBN} is currently using to interpret and display characters and
9431 (@value{GDBP}) show charset
9432 The current host and target character set is `ISO-8859-1'.
9436 For the sake of printing this manual, let's use @sc{ascii} as our
9437 initial character set:
9439 (@value{GDBP}) set charset ASCII
9440 (@value{GDBP}) show charset
9441 The current host and target character set is `ASCII'.
9445 Let's assume that @sc{ascii} is indeed the correct character set for our
9446 host system --- in other words, let's assume that if @value{GDBN} prints
9447 characters using the @sc{ascii} character set, our terminal will display
9448 them properly. Since our current target character set is also
9449 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9452 (@value{GDBP}) print ascii_hello
9453 $1 = 0x401698 "Hello, world!\n"
9454 (@value{GDBP}) print ascii_hello[0]
9459 @value{GDBN} uses the target character set for character and string
9460 literals you use in expressions:
9463 (@value{GDBP}) print '+'
9468 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9471 @value{GDBN} relies on the user to tell it which character set the
9472 target program uses. If we print @code{ibm1047_hello} while our target
9473 character set is still @sc{ascii}, we get jibberish:
9476 (@value{GDBP}) print ibm1047_hello
9477 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9478 (@value{GDBP}) print ibm1047_hello[0]
9483 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9484 @value{GDBN} tells us the character sets it supports:
9487 (@value{GDBP}) set target-charset
9488 ASCII EBCDIC-US IBM1047 ISO-8859-1
9489 (@value{GDBP}) set target-charset
9492 We can select @sc{ibm1047} as our target character set, and examine the
9493 program's strings again. Now the @sc{ascii} string is wrong, but
9494 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9495 target character set, @sc{ibm1047}, to the host character set,
9496 @sc{ascii}, and they display correctly:
9499 (@value{GDBP}) set target-charset IBM1047
9500 (@value{GDBP}) show charset
9501 The current host character set is `ASCII'.
9502 The current target character set is `IBM1047'.
9503 (@value{GDBP}) print ascii_hello
9504 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9505 (@value{GDBP}) print ascii_hello[0]
9507 (@value{GDBP}) print ibm1047_hello
9508 $8 = 0x4016a8 "Hello, world!\n"
9509 (@value{GDBP}) print ibm1047_hello[0]
9514 As above, @value{GDBN} uses the target character set for character and
9515 string literals you use in expressions:
9518 (@value{GDBP}) print '+'
9523 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9526 @node Caching Remote Data
9527 @section Caching Data of Remote Targets
9528 @cindex caching data of remote targets
9530 @value{GDBN} caches data exchanged between the debugger and a
9531 remote target (@pxref{Remote Debugging}). Such caching generally improves
9532 performance, because it reduces the overhead of the remote protocol by
9533 bundling memory reads and writes into large chunks. Unfortunately, simply
9534 caching everything would lead to incorrect results, since @value{GDBN}
9535 does not necessarily know anything about volatile values, memory-mapped I/O
9536 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9537 memory can be changed @emph{while} a gdb command is executing.
9538 Therefore, by default, @value{GDBN} only caches data
9539 known to be on the stack@footnote{In non-stop mode, it is moderately
9540 rare for a running thread to modify the stack of a stopped thread
9541 in a way that would interfere with a backtrace, and caching of
9542 stack reads provides a significant speed up of remote backtraces.}.
9543 Other regions of memory can be explicitly marked as
9544 cacheable; see @pxref{Memory Region Attributes}.
9547 @kindex set remotecache
9548 @item set remotecache on
9549 @itemx set remotecache off
9550 This option no longer does anything; it exists for compatibility
9553 @kindex show remotecache
9554 @item show remotecache
9555 Show the current state of the obsolete remotecache flag.
9557 @kindex set stack-cache
9558 @item set stack-cache on
9559 @itemx set stack-cache off
9560 Enable or disable caching of stack accesses. When @code{ON}, use
9561 caching. By default, this option is @code{ON}.
9563 @kindex show stack-cache
9564 @item show stack-cache
9565 Show the current state of data caching for memory accesses.
9568 @item info dcache @r{[}line@r{]}
9569 Print the information about the data cache performance. The
9570 information displayed includes the dcache width and depth, and for
9571 each cache line, its number, address, and how many times it was
9572 referenced. This command is useful for debugging the data cache
9575 If a line number is specified, the contents of that line will be
9578 @item set dcache size @var{size}
9580 @kindex set dcache size
9581 Set maximum number of entries in dcache (dcache depth above).
9583 @item set dcache line-size @var{line-size}
9584 @cindex dcache line-size
9585 @kindex set dcache line-size
9586 Set number of bytes each dcache entry caches (dcache width above).
9587 Must be a power of 2.
9589 @item show dcache size
9590 @kindex show dcache size
9591 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
9593 @item show dcache line-size
9594 @kindex show dcache line-size
9595 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
9599 @node Searching Memory
9600 @section Search Memory
9601 @cindex searching memory
9603 Memory can be searched for a particular sequence of bytes with the
9604 @code{find} command.
9608 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9609 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9610 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9611 etc. The search begins at address @var{start_addr} and continues for either
9612 @var{len} bytes or through to @var{end_addr} inclusive.
9615 @var{s} and @var{n} are optional parameters.
9616 They may be specified in either order, apart or together.
9619 @item @var{s}, search query size
9620 The size of each search query value.
9626 halfwords (two bytes)
9630 giant words (eight bytes)
9633 All values are interpreted in the current language.
9634 This means, for example, that if the current source language is C/C@t{++}
9635 then searching for the string ``hello'' includes the trailing '\0'.
9637 If the value size is not specified, it is taken from the
9638 value's type in the current language.
9639 This is useful when one wants to specify the search
9640 pattern as a mixture of types.
9641 Note that this means, for example, that in the case of C-like languages
9642 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9643 which is typically four bytes.
9645 @item @var{n}, maximum number of finds
9646 The maximum number of matches to print. The default is to print all finds.
9649 You can use strings as search values. Quote them with double-quotes
9651 The string value is copied into the search pattern byte by byte,
9652 regardless of the endianness of the target and the size specification.
9654 The address of each match found is printed as well as a count of the
9655 number of matches found.
9657 The address of the last value found is stored in convenience variable
9659 A count of the number of matches is stored in @samp{$numfound}.
9661 For example, if stopped at the @code{printf} in this function:
9667 static char hello[] = "hello-hello";
9668 static struct @{ char c; short s; int i; @}
9669 __attribute__ ((packed)) mixed
9670 = @{ 'c', 0x1234, 0x87654321 @};
9671 printf ("%s\n", hello);
9676 you get during debugging:
9679 (gdb) find &hello[0], +sizeof(hello), "hello"
9680 0x804956d <hello.1620+6>
9682 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9683 0x8049567 <hello.1620>
9684 0x804956d <hello.1620+6>
9686 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9687 0x8049567 <hello.1620>
9689 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9690 0x8049560 <mixed.1625>
9692 (gdb) print $numfound
9695 $2 = (void *) 0x8049560
9698 @node Optimized Code
9699 @chapter Debugging Optimized Code
9700 @cindex optimized code, debugging
9701 @cindex debugging optimized code
9703 Almost all compilers support optimization. With optimization
9704 disabled, the compiler generates assembly code that corresponds
9705 directly to your source code, in a simplistic way. As the compiler
9706 applies more powerful optimizations, the generated assembly code
9707 diverges from your original source code. With help from debugging
9708 information generated by the compiler, @value{GDBN} can map from
9709 the running program back to constructs from your original source.
9711 @value{GDBN} is more accurate with optimization disabled. If you
9712 can recompile without optimization, it is easier to follow the
9713 progress of your program during debugging. But, there are many cases
9714 where you may need to debug an optimized version.
9716 When you debug a program compiled with @samp{-g -O}, remember that the
9717 optimizer has rearranged your code; the debugger shows you what is
9718 really there. Do not be too surprised when the execution path does not
9719 exactly match your source file! An extreme example: if you define a
9720 variable, but never use it, @value{GDBN} never sees that
9721 variable---because the compiler optimizes it out of existence.
9723 Some things do not work as well with @samp{-g -O} as with just
9724 @samp{-g}, particularly on machines with instruction scheduling. If in
9725 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9726 please report it to us as a bug (including a test case!).
9727 @xref{Variables}, for more information about debugging optimized code.
9730 * Inline Functions:: How @value{GDBN} presents inlining
9731 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
9734 @node Inline Functions
9735 @section Inline Functions
9736 @cindex inline functions, debugging
9738 @dfn{Inlining} is an optimization that inserts a copy of the function
9739 body directly at each call site, instead of jumping to a shared
9740 routine. @value{GDBN} displays inlined functions just like
9741 non-inlined functions. They appear in backtraces. You can view their
9742 arguments and local variables, step into them with @code{step}, skip
9743 them with @code{next}, and escape from them with @code{finish}.
9744 You can check whether a function was inlined by using the
9745 @code{info frame} command.
9747 For @value{GDBN} to support inlined functions, the compiler must
9748 record information about inlining in the debug information ---
9749 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9750 other compilers do also. @value{GDBN} only supports inlined functions
9751 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9752 do not emit two required attributes (@samp{DW_AT_call_file} and
9753 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9754 function calls with earlier versions of @value{NGCC}. It instead
9755 displays the arguments and local variables of inlined functions as
9756 local variables in the caller.
9758 The body of an inlined function is directly included at its call site;
9759 unlike a non-inlined function, there are no instructions devoted to
9760 the call. @value{GDBN} still pretends that the call site and the
9761 start of the inlined function are different instructions. Stepping to
9762 the call site shows the call site, and then stepping again shows
9763 the first line of the inlined function, even though no additional
9764 instructions are executed.
9766 This makes source-level debugging much clearer; you can see both the
9767 context of the call and then the effect of the call. Only stepping by
9768 a single instruction using @code{stepi} or @code{nexti} does not do
9769 this; single instruction steps always show the inlined body.
9771 There are some ways that @value{GDBN} does not pretend that inlined
9772 function calls are the same as normal calls:
9776 You cannot set breakpoints on inlined functions. @value{GDBN}
9777 either reports that there is no symbol with that name, or else sets the
9778 breakpoint only on non-inlined copies of the function. This limitation
9779 will be removed in a future version of @value{GDBN}; until then,
9780 set a breakpoint by line number on the first line of the inlined
9784 Setting breakpoints at the call site of an inlined function may not
9785 work, because the call site does not contain any code. @value{GDBN}
9786 may incorrectly move the breakpoint to the next line of the enclosing
9787 function, after the call. This limitation will be removed in a future
9788 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9789 or inside the inlined function instead.
9792 @value{GDBN} cannot locate the return value of inlined calls after
9793 using the @code{finish} command. This is a limitation of compiler-generated
9794 debugging information; after @code{finish}, you can step to the next line
9795 and print a variable where your program stored the return value.
9799 @node Tail Call Frames
9800 @section Tail Call Frames
9801 @cindex tail call frames, debugging
9803 Function @code{B} can call function @code{C} in its very last statement. In
9804 unoptimized compilation the call of @code{C} is immediately followed by return
9805 instruction at the end of @code{B} code. Optimizing compiler may replace the
9806 call and return in function @code{B} into one jump to function @code{C}
9807 instead. Such use of a jump instruction is called @dfn{tail call}.
9809 During execution of function @code{C}, there will be no indication in the
9810 function call stack frames that it was tail-called from @code{B}. If function
9811 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
9812 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
9813 some cases @value{GDBN} can determine that @code{C} was tail-called from
9814 @code{B}, and it will then create fictitious call frame for that, with the
9815 return address set up as if @code{B} called @code{C} normally.
9817 This functionality is currently supported only by DWARF 2 debugging format and
9818 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9819 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9822 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
9823 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
9827 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
9829 Stack level 1, frame at 0x7fffffffda30:
9830 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
9831 tail call frame, caller of frame at 0x7fffffffda30
9832 source language c++.
9833 Arglist at unknown address.
9834 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
9837 The detection of all the possible code path executions can find them ambiguous.
9838 There is no execution history stored (possible @ref{Reverse Execution} is never
9839 used for this purpose) and the last known caller could have reached the known
9840 callee by multiple different jump sequences. In such case @value{GDBN} still
9841 tries to show at least all the unambiguous top tail callers and all the
9842 unambiguous bottom tail calees, if any.
9845 @anchor{set debug entry-values}
9846 @item set debug entry-values
9847 @kindex set debug entry-values
9848 When set to on, enables printing of analysis messages for both frame argument
9849 values at function entry and tail calls. It will show all the possible valid
9850 tail calls code paths it has considered. It will also print the intersection
9851 of them with the final unambiguous (possibly partial or even empty) code path
9854 @item show debug entry-values
9855 @kindex show debug entry-values
9856 Show the current state of analysis messages printing for both frame argument
9857 values at function entry and tail calls.
9860 The analysis messages for tail calls can for example show why the virtual tail
9861 call frame for function @code{c} has not been recognized (due to the indirect
9862 reference by variable @code{x}):
9865 static void __attribute__((noinline, noclone)) c (void);
9866 void (*x) (void) = c;
9867 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9868 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
9869 int main (void) @{ x (); return 0; @}
9871 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
9872 DW_TAG_GNU_call_site 0x40039a in main
9874 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9877 #1 0x000000000040039a in main () at t.c:5
9880 Another possibility is an ambiguous virtual tail call frames resolution:
9884 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
9885 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
9886 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
9887 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
9888 static void __attribute__((noinline, noclone)) b (void)
9889 @{ if (i) c (); else e (); @}
9890 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
9891 int main (void) @{ a (); return 0; @}
9893 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
9894 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
9895 tailcall: reduced: 0x4004d2(a) |
9898 #1 0x00000000004004d2 in a () at t.c:8
9899 #2 0x0000000000400395 in main () at t.c:9
9902 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
9903 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
9905 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
9906 @ifset HAVE_MAKEINFO_CLICK
9908 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
9909 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
9911 @ifclear HAVE_MAKEINFO_CLICK
9913 @set CALLSEQ1B @value{CALLSEQ1A}
9914 @set CALLSEQ2B @value{CALLSEQ2A}
9917 Frames #0 and #2 are real, #1 is a virtual tail call frame.
9918 The code can have possible execution paths @value{CALLSEQ1B} or
9919 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
9921 @code{initial:} state shows some random possible calling sequence @value{GDBN}
9922 has found. It then finds another possible calling sequcen - that one is
9923 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
9924 printed as the @code{reduced:} calling sequence. That one could have many
9925 futher @code{compare:} and @code{reduced:} statements as long as there remain
9926 any non-ambiguous sequence entries.
9928 For the frame of function @code{b} in both cases there are different possible
9929 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
9930 also ambigous. The only non-ambiguous frame is the one for function @code{a},
9931 therefore this one is displayed to the user while the ambiguous frames are
9934 There can be also reasons why printing of frame argument values at function
9939 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
9940 static void __attribute__((noinline, noclone)) a (int i);
9941 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
9942 static void __attribute__((noinline, noclone)) a (int i)
9943 @{ if (i) b (i - 1); else c (0); @}
9944 int main (void) @{ a (5); return 0; @}
9947 #0 c (i=i@@entry=0) at t.c:2
9948 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
9949 function "a" at 0x400420 can call itself via tail calls
9950 i=<optimized out>) at t.c:6
9951 #2 0x000000000040036e in main () at t.c:7
9954 @value{GDBN} cannot find out from the inferior state if and how many times did
9955 function @code{a} call itself (via function @code{b}) as these calls would be
9956 tail calls. Such tail calls would modify thue @code{i} variable, therefore
9957 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
9958 prints @code{<optimized out>} instead.
9961 @chapter C Preprocessor Macros
9963 Some languages, such as C and C@t{++}, provide a way to define and invoke
9964 ``preprocessor macros'' which expand into strings of tokens.
9965 @value{GDBN} can evaluate expressions containing macro invocations, show
9966 the result of macro expansion, and show a macro's definition, including
9967 where it was defined.
9969 You may need to compile your program specially to provide @value{GDBN}
9970 with information about preprocessor macros. Most compilers do not
9971 include macros in their debugging information, even when you compile
9972 with the @option{-g} flag. @xref{Compilation}.
9974 A program may define a macro at one point, remove that definition later,
9975 and then provide a different definition after that. Thus, at different
9976 points in the program, a macro may have different definitions, or have
9977 no definition at all. If there is a current stack frame, @value{GDBN}
9978 uses the macros in scope at that frame's source code line. Otherwise,
9979 @value{GDBN} uses the macros in scope at the current listing location;
9982 Whenever @value{GDBN} evaluates an expression, it always expands any
9983 macro invocations present in the expression. @value{GDBN} also provides
9984 the following commands for working with macros explicitly.
9988 @kindex macro expand
9989 @cindex macro expansion, showing the results of preprocessor
9990 @cindex preprocessor macro expansion, showing the results of
9991 @cindex expanding preprocessor macros
9992 @item macro expand @var{expression}
9993 @itemx macro exp @var{expression}
9994 Show the results of expanding all preprocessor macro invocations in
9995 @var{expression}. Since @value{GDBN} simply expands macros, but does
9996 not parse the result, @var{expression} need not be a valid expression;
9997 it can be any string of tokens.
10000 @item macro expand-once @var{expression}
10001 @itemx macro exp1 @var{expression}
10002 @cindex expand macro once
10003 @i{(This command is not yet implemented.)} Show the results of
10004 expanding those preprocessor macro invocations that appear explicitly in
10005 @var{expression}. Macro invocations appearing in that expansion are
10006 left unchanged. This command allows you to see the effect of a
10007 particular macro more clearly, without being confused by further
10008 expansions. Since @value{GDBN} simply expands macros, but does not
10009 parse the result, @var{expression} need not be a valid expression; it
10010 can be any string of tokens.
10013 @cindex macro definition, showing
10014 @cindex definition of a macro, showing
10015 @cindex macros, from debug info
10016 @item info macro [-a|-all] [--] @var{macro}
10017 Show the current definition or all definitions of the named @var{macro},
10018 and describe the source location or compiler command-line where that
10019 definition was established. The optional double dash is to signify the end of
10020 argument processing and the beginning of @var{macro} for non C-like macros where
10021 the macro may begin with a hyphen.
10023 @kindex info macros
10024 @item info macros @var{linespec}
10025 Show all macro definitions that are in effect at the location specified
10026 by @var{linespec}, and describe the source location or compiler
10027 command-line where those definitions were established.
10029 @kindex macro define
10030 @cindex user-defined macros
10031 @cindex defining macros interactively
10032 @cindex macros, user-defined
10033 @item macro define @var{macro} @var{replacement-list}
10034 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10035 Introduce a definition for a preprocessor macro named @var{macro},
10036 invocations of which are replaced by the tokens given in
10037 @var{replacement-list}. The first form of this command defines an
10038 ``object-like'' macro, which takes no arguments; the second form
10039 defines a ``function-like'' macro, which takes the arguments given in
10042 A definition introduced by this command is in scope in every
10043 expression evaluated in @value{GDBN}, until it is removed with the
10044 @code{macro undef} command, described below. The definition overrides
10045 all definitions for @var{macro} present in the program being debugged,
10046 as well as any previous user-supplied definition.
10048 @kindex macro undef
10049 @item macro undef @var{macro}
10050 Remove any user-supplied definition for the macro named @var{macro}.
10051 This command only affects definitions provided with the @code{macro
10052 define} command, described above; it cannot remove definitions present
10053 in the program being debugged.
10057 List all the macros defined using the @code{macro define} command.
10060 @cindex macros, example of debugging with
10061 Here is a transcript showing the above commands in action. First, we
10062 show our source files:
10067 #include "sample.h"
10070 #define ADD(x) (M + x)
10075 printf ("Hello, world!\n");
10077 printf ("We're so creative.\n");
10079 printf ("Goodbye, world!\n");
10086 Now, we compile the program using the @sc{gnu} C compiler,
10087 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10088 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10089 and @option{-gdwarf-4}; we recommend always choosing the most recent
10090 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10091 includes information about preprocessor macros in the debugging
10095 $ gcc -gdwarf-2 -g3 sample.c -o sample
10099 Now, we start @value{GDBN} on our sample program:
10103 GNU gdb 2002-05-06-cvs
10104 Copyright 2002 Free Software Foundation, Inc.
10105 GDB is free software, @dots{}
10109 We can expand macros and examine their definitions, even when the
10110 program is not running. @value{GDBN} uses the current listing position
10111 to decide which macro definitions are in scope:
10114 (@value{GDBP}) list main
10117 5 #define ADD(x) (M + x)
10122 10 printf ("Hello, world!\n");
10124 12 printf ("We're so creative.\n");
10125 (@value{GDBP}) info macro ADD
10126 Defined at /home/jimb/gdb/macros/play/sample.c:5
10127 #define ADD(x) (M + x)
10128 (@value{GDBP}) info macro Q
10129 Defined at /home/jimb/gdb/macros/play/sample.h:1
10130 included at /home/jimb/gdb/macros/play/sample.c:2
10132 (@value{GDBP}) macro expand ADD(1)
10133 expands to: (42 + 1)
10134 (@value{GDBP}) macro expand-once ADD(1)
10135 expands to: once (M + 1)
10139 In the example above, note that @code{macro expand-once} expands only
10140 the macro invocation explicit in the original text --- the invocation of
10141 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10142 which was introduced by @code{ADD}.
10144 Once the program is running, @value{GDBN} uses the macro definitions in
10145 force at the source line of the current stack frame:
10148 (@value{GDBP}) break main
10149 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10151 Starting program: /home/jimb/gdb/macros/play/sample
10153 Breakpoint 1, main () at sample.c:10
10154 10 printf ("Hello, world!\n");
10158 At line 10, the definition of the macro @code{N} at line 9 is in force:
10161 (@value{GDBP}) info macro N
10162 Defined at /home/jimb/gdb/macros/play/sample.c:9
10164 (@value{GDBP}) macro expand N Q M
10165 expands to: 28 < 42
10166 (@value{GDBP}) print N Q M
10171 As we step over directives that remove @code{N}'s definition, and then
10172 give it a new definition, @value{GDBN} finds the definition (or lack
10173 thereof) in force at each point:
10176 (@value{GDBP}) next
10178 12 printf ("We're so creative.\n");
10179 (@value{GDBP}) info macro N
10180 The symbol `N' has no definition as a C/C++ preprocessor macro
10181 at /home/jimb/gdb/macros/play/sample.c:12
10182 (@value{GDBP}) next
10184 14 printf ("Goodbye, world!\n");
10185 (@value{GDBP}) info macro N
10186 Defined at /home/jimb/gdb/macros/play/sample.c:13
10188 (@value{GDBP}) macro expand N Q M
10189 expands to: 1729 < 42
10190 (@value{GDBP}) print N Q M
10195 In addition to source files, macros can be defined on the compilation command
10196 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10197 such a way, @value{GDBN} displays the location of their definition as line zero
10198 of the source file submitted to the compiler.
10201 (@value{GDBP}) info macro __STDC__
10202 Defined at /home/jimb/gdb/macros/play/sample.c:0
10209 @chapter Tracepoints
10210 @c This chapter is based on the documentation written by Michael
10211 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10213 @cindex tracepoints
10214 In some applications, it is not feasible for the debugger to interrupt
10215 the program's execution long enough for the developer to learn
10216 anything helpful about its behavior. If the program's correctness
10217 depends on its real-time behavior, delays introduced by a debugger
10218 might cause the program to change its behavior drastically, or perhaps
10219 fail, even when the code itself is correct. It is useful to be able
10220 to observe the program's behavior without interrupting it.
10222 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10223 specify locations in the program, called @dfn{tracepoints}, and
10224 arbitrary expressions to evaluate when those tracepoints are reached.
10225 Later, using the @code{tfind} command, you can examine the values
10226 those expressions had when the program hit the tracepoints. The
10227 expressions may also denote objects in memory---structures or arrays,
10228 for example---whose values @value{GDBN} should record; while visiting
10229 a particular tracepoint, you may inspect those objects as if they were
10230 in memory at that moment. However, because @value{GDBN} records these
10231 values without interacting with you, it can do so quickly and
10232 unobtrusively, hopefully not disturbing the program's behavior.
10234 The tracepoint facility is currently available only for remote
10235 targets. @xref{Targets}. In addition, your remote target must know
10236 how to collect trace data. This functionality is implemented in the
10237 remote stub; however, none of the stubs distributed with @value{GDBN}
10238 support tracepoints as of this writing. The format of the remote
10239 packets used to implement tracepoints are described in @ref{Tracepoint
10242 It is also possible to get trace data from a file, in a manner reminiscent
10243 of corefiles; you specify the filename, and use @code{tfind} to search
10244 through the file. @xref{Trace Files}, for more details.
10246 This chapter describes the tracepoint commands and features.
10249 * Set Tracepoints::
10250 * Analyze Collected Data::
10251 * Tracepoint Variables::
10255 @node Set Tracepoints
10256 @section Commands to Set Tracepoints
10258 Before running such a @dfn{trace experiment}, an arbitrary number of
10259 tracepoints can be set. A tracepoint is actually a special type of
10260 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10261 standard breakpoint commands. For instance, as with breakpoints,
10262 tracepoint numbers are successive integers starting from one, and many
10263 of the commands associated with tracepoints take the tracepoint number
10264 as their argument, to identify which tracepoint to work on.
10266 For each tracepoint, you can specify, in advance, some arbitrary set
10267 of data that you want the target to collect in the trace buffer when
10268 it hits that tracepoint. The collected data can include registers,
10269 local variables, or global data. Later, you can use @value{GDBN}
10270 commands to examine the values these data had at the time the
10271 tracepoint was hit.
10273 Tracepoints do not support every breakpoint feature. Ignore counts on
10274 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10275 commands when they are hit. Tracepoints may not be thread-specific
10278 @cindex fast tracepoints
10279 Some targets may support @dfn{fast tracepoints}, which are inserted in
10280 a different way (such as with a jump instead of a trap), that is
10281 faster but possibly restricted in where they may be installed.
10283 @cindex static tracepoints
10284 @cindex markers, static tracepoints
10285 @cindex probing markers, static tracepoints
10286 Regular and fast tracepoints are dynamic tracing facilities, meaning
10287 that they can be used to insert tracepoints at (almost) any location
10288 in the target. Some targets may also support controlling @dfn{static
10289 tracepoints} from @value{GDBN}. With static tracing, a set of
10290 instrumentation points, also known as @dfn{markers}, are embedded in
10291 the target program, and can be activated or deactivated by name or
10292 address. These are usually placed at locations which facilitate
10293 investigating what the target is actually doing. @value{GDBN}'s
10294 support for static tracing includes being able to list instrumentation
10295 points, and attach them with @value{GDBN} defined high level
10296 tracepoints that expose the whole range of convenience of
10297 @value{GDBN}'s tracepoints support. Namely, support for collecting
10298 registers values and values of global or local (to the instrumentation
10299 point) variables; tracepoint conditions and trace state variables.
10300 The act of installing a @value{GDBN} static tracepoint on an
10301 instrumentation point, or marker, is referred to as @dfn{probing} a
10302 static tracepoint marker.
10304 @code{gdbserver} supports tracepoints on some target systems.
10305 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10307 This section describes commands to set tracepoints and associated
10308 conditions and actions.
10311 * Create and Delete Tracepoints::
10312 * Enable and Disable Tracepoints::
10313 * Tracepoint Passcounts::
10314 * Tracepoint Conditions::
10315 * Trace State Variables::
10316 * Tracepoint Actions::
10317 * Listing Tracepoints::
10318 * Listing Static Tracepoint Markers::
10319 * Starting and Stopping Trace Experiments::
10320 * Tracepoint Restrictions::
10323 @node Create and Delete Tracepoints
10324 @subsection Create and Delete Tracepoints
10327 @cindex set tracepoint
10329 @item trace @var{location}
10330 The @code{trace} command is very similar to the @code{break} command.
10331 Its argument @var{location} can be a source line, a function name, or
10332 an address in the target program. @xref{Specify Location}. The
10333 @code{trace} command defines a tracepoint, which is a point in the
10334 target program where the debugger will briefly stop, collect some
10335 data, and then allow the program to continue. Setting a tracepoint or
10336 changing its actions takes effect immediately if the remote stub
10337 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
10339 If remote stub doesn't support the @samp{InstallInTrace} feature, all
10340 these changes don't take effect until the next @code{tstart}
10341 command, and once a trace experiment is running, further changes will
10342 not have any effect until the next trace experiment starts. In addition,
10343 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
10344 address is not yet resolved. (This is similar to pending breakpoints.)
10345 Pending tracepoints are not downloaded to the target and not installed
10346 until they are resolved. The resolution of pending tracepoints requires
10347 @value{GDBN} support---when debugging with the remote target, and
10348 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
10349 tracing}), pending tracepoints can not be resolved (and downloaded to
10350 the remote stub) while @value{GDBN} is disconnected.
10352 Here are some examples of using the @code{trace} command:
10355 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
10357 (@value{GDBP}) @b{trace +2} // 2 lines forward
10359 (@value{GDBP}) @b{trace my_function} // first source line of function
10361 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
10363 (@value{GDBP}) @b{trace *0x2117c4} // an address
10367 You can abbreviate @code{trace} as @code{tr}.
10369 @item trace @var{location} if @var{cond}
10370 Set a tracepoint with condition @var{cond}; evaluate the expression
10371 @var{cond} each time the tracepoint is reached, and collect data only
10372 if the value is nonzero---that is, if @var{cond} evaluates as true.
10373 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
10374 information on tracepoint conditions.
10376 @item ftrace @var{location} [ if @var{cond} ]
10377 @cindex set fast tracepoint
10378 @cindex fast tracepoints, setting
10380 The @code{ftrace} command sets a fast tracepoint. For targets that
10381 support them, fast tracepoints will use a more efficient but possibly
10382 less general technique to trigger data collection, such as a jump
10383 instruction instead of a trap, or some sort of hardware support. It
10384 may not be possible to create a fast tracepoint at the desired
10385 location, in which case the command will exit with an explanatory
10388 @value{GDBN} handles arguments to @code{ftrace} exactly as for
10391 On 32-bit x86-architecture systems, fast tracepoints normally need to
10392 be placed at an instruction that is 5 bytes or longer, but can be
10393 placed at 4-byte instructions if the low 64K of memory of the target
10394 program is available to install trampolines. Some Unix-type systems,
10395 such as @sc{gnu}/Linux, exclude low addresses from the program's
10396 address space; but for instance with the Linux kernel it is possible
10397 to let @value{GDBN} use this area by doing a @command{sysctl} command
10398 to set the @code{mmap_min_addr} kernel parameter, as in
10401 sudo sysctl -w vm.mmap_min_addr=32768
10405 which sets the low address to 32K, which leaves plenty of room for
10406 trampolines. The minimum address should be set to a page boundary.
10408 @item strace @var{location} [ if @var{cond} ]
10409 @cindex set static tracepoint
10410 @cindex static tracepoints, setting
10411 @cindex probe static tracepoint marker
10413 The @code{strace} command sets a static tracepoint. For targets that
10414 support it, setting a static tracepoint probes a static
10415 instrumentation point, or marker, found at @var{location}. It may not
10416 be possible to set a static tracepoint at the desired location, in
10417 which case the command will exit with an explanatory message.
10419 @value{GDBN} handles arguments to @code{strace} exactly as for
10420 @code{trace}, with the addition that the user can also specify
10421 @code{-m @var{marker}} as @var{location}. This probes the marker
10422 identified by the @var{marker} string identifier. This identifier
10423 depends on the static tracepoint backend library your program is
10424 using. You can find all the marker identifiers in the @samp{ID} field
10425 of the @code{info static-tracepoint-markers} command output.
10426 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
10427 Markers}. For example, in the following small program using the UST
10433 trace_mark(ust, bar33, "str %s", "FOOBAZ");
10438 the marker id is composed of joining the first two arguments to the
10439 @code{trace_mark} call with a slash, which translates to:
10442 (@value{GDBP}) info static-tracepoint-markers
10443 Cnt Enb ID Address What
10444 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
10450 so you may probe the marker above with:
10453 (@value{GDBP}) strace -m ust/bar33
10456 Static tracepoints accept an extra collect action --- @code{collect
10457 $_sdata}. This collects arbitrary user data passed in the probe point
10458 call to the tracing library. In the UST example above, you'll see
10459 that the third argument to @code{trace_mark} is a printf-like format
10460 string. The user data is then the result of running that formating
10461 string against the following arguments. Note that @code{info
10462 static-tracepoint-markers} command output lists that format string in
10463 the @samp{Data:} field.
10465 You can inspect this data when analyzing the trace buffer, by printing
10466 the $_sdata variable like any other variable available to
10467 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
10470 @cindex last tracepoint number
10471 @cindex recent tracepoint number
10472 @cindex tracepoint number
10473 The convenience variable @code{$tpnum} records the tracepoint number
10474 of the most recently set tracepoint.
10476 @kindex delete tracepoint
10477 @cindex tracepoint deletion
10478 @item delete tracepoint @r{[}@var{num}@r{]}
10479 Permanently delete one or more tracepoints. With no argument, the
10480 default is to delete all tracepoints. Note that the regular
10481 @code{delete} command can remove tracepoints also.
10486 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10488 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10492 You can abbreviate this command as @code{del tr}.
10495 @node Enable and Disable Tracepoints
10496 @subsection Enable and Disable Tracepoints
10498 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10501 @kindex disable tracepoint
10502 @item disable tracepoint @r{[}@var{num}@r{]}
10503 Disable tracepoint @var{num}, or all tracepoints if no argument
10504 @var{num} is given. A disabled tracepoint will have no effect during
10505 a trace experiment, but it is not forgotten. You can re-enable
10506 a disabled tracepoint using the @code{enable tracepoint} command.
10507 If the command is issued during a trace experiment and the debug target
10508 has support for disabling tracepoints during a trace experiment, then the
10509 change will be effective immediately. Otherwise, it will be applied to the
10510 next trace experiment.
10512 @kindex enable tracepoint
10513 @item enable tracepoint @r{[}@var{num}@r{]}
10514 Enable tracepoint @var{num}, or all tracepoints. If this command is
10515 issued during a trace experiment and the debug target supports enabling
10516 tracepoints during a trace experiment, then the enabled tracepoints will
10517 become effective immediately. Otherwise, they will become effective the
10518 next time a trace experiment is run.
10521 @node Tracepoint Passcounts
10522 @subsection Tracepoint Passcounts
10526 @cindex tracepoint pass count
10527 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10528 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10529 automatically stop a trace experiment. If a tracepoint's passcount is
10530 @var{n}, then the trace experiment will be automatically stopped on
10531 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10532 @var{num} is not specified, the @code{passcount} command sets the
10533 passcount of the most recently defined tracepoint. If no passcount is
10534 given, the trace experiment will run until stopped explicitly by the
10540 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10541 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10543 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10544 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10545 (@value{GDBP}) @b{trace foo}
10546 (@value{GDBP}) @b{pass 3}
10547 (@value{GDBP}) @b{trace bar}
10548 (@value{GDBP}) @b{pass 2}
10549 (@value{GDBP}) @b{trace baz}
10550 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10551 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10552 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10553 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10557 @node Tracepoint Conditions
10558 @subsection Tracepoint Conditions
10559 @cindex conditional tracepoints
10560 @cindex tracepoint conditions
10562 The simplest sort of tracepoint collects data every time your program
10563 reaches a specified place. You can also specify a @dfn{condition} for
10564 a tracepoint. A condition is just a Boolean expression in your
10565 programming language (@pxref{Expressions, ,Expressions}). A
10566 tracepoint with a condition evaluates the expression each time your
10567 program reaches it, and data collection happens only if the condition
10570 Tracepoint conditions can be specified when a tracepoint is set, by
10571 using @samp{if} in the arguments to the @code{trace} command.
10572 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10573 also be set or changed at any time with the @code{condition} command,
10574 just as with breakpoints.
10576 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10577 the conditional expression itself. Instead, @value{GDBN} encodes the
10578 expression into an agent expression (@pxref{Agent Expressions})
10579 suitable for execution on the target, independently of @value{GDBN}.
10580 Global variables become raw memory locations, locals become stack
10581 accesses, and so forth.
10583 For instance, suppose you have a function that is usually called
10584 frequently, but should not be called after an error has occurred. You
10585 could use the following tracepoint command to collect data about calls
10586 of that function that happen while the error code is propagating
10587 through the program; an unconditional tracepoint could end up
10588 collecting thousands of useless trace frames that you would have to
10592 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10595 @node Trace State Variables
10596 @subsection Trace State Variables
10597 @cindex trace state variables
10599 A @dfn{trace state variable} is a special type of variable that is
10600 created and managed by target-side code. The syntax is the same as
10601 that for GDB's convenience variables (a string prefixed with ``$''),
10602 but they are stored on the target. They must be created explicitly,
10603 using a @code{tvariable} command. They are always 64-bit signed
10606 Trace state variables are remembered by @value{GDBN}, and downloaded
10607 to the target along with tracepoint information when the trace
10608 experiment starts. There are no intrinsic limits on the number of
10609 trace state variables, beyond memory limitations of the target.
10611 @cindex convenience variables, and trace state variables
10612 Although trace state variables are managed by the target, you can use
10613 them in print commands and expressions as if they were convenience
10614 variables; @value{GDBN} will get the current value from the target
10615 while the trace experiment is running. Trace state variables share
10616 the same namespace as other ``$'' variables, which means that you
10617 cannot have trace state variables with names like @code{$23} or
10618 @code{$pc}, nor can you have a trace state variable and a convenience
10619 variable with the same name.
10623 @item tvariable $@var{name} [ = @var{expression} ]
10625 The @code{tvariable} command creates a new trace state variable named
10626 @code{$@var{name}}, and optionally gives it an initial value of
10627 @var{expression}. @var{expression} is evaluated when this command is
10628 entered; the result will be converted to an integer if possible,
10629 otherwise @value{GDBN} will report an error. A subsequent
10630 @code{tvariable} command specifying the same name does not create a
10631 variable, but instead assigns the supplied initial value to the
10632 existing variable of that name, overwriting any previous initial
10633 value. The default initial value is 0.
10635 @item info tvariables
10636 @kindex info tvariables
10637 List all the trace state variables along with their initial values.
10638 Their current values may also be displayed, if the trace experiment is
10641 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10642 @kindex delete tvariable
10643 Delete the given trace state variables, or all of them if no arguments
10648 @node Tracepoint Actions
10649 @subsection Tracepoint Action Lists
10653 @cindex tracepoint actions
10654 @item actions @r{[}@var{num}@r{]}
10655 This command will prompt for a list of actions to be taken when the
10656 tracepoint is hit. If the tracepoint number @var{num} is not
10657 specified, this command sets the actions for the one that was most
10658 recently defined (so that you can define a tracepoint and then say
10659 @code{actions} without bothering about its number). You specify the
10660 actions themselves on the following lines, one action at a time, and
10661 terminate the actions list with a line containing just @code{end}. So
10662 far, the only defined actions are @code{collect}, @code{teval}, and
10663 @code{while-stepping}.
10665 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10666 Commands, ,Breakpoint Command Lists}), except that only the defined
10667 actions are allowed; any other @value{GDBN} command is rejected.
10669 @cindex remove actions from a tracepoint
10670 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10671 and follow it immediately with @samp{end}.
10674 (@value{GDBP}) @b{collect @var{data}} // collect some data
10676 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10678 (@value{GDBP}) @b{end} // signals the end of actions.
10681 In the following example, the action list begins with @code{collect}
10682 commands indicating the things to be collected when the tracepoint is
10683 hit. Then, in order to single-step and collect additional data
10684 following the tracepoint, a @code{while-stepping} command is used,
10685 followed by the list of things to be collected after each step in a
10686 sequence of single steps. The @code{while-stepping} command is
10687 terminated by its own separate @code{end} command. Lastly, the action
10688 list is terminated by an @code{end} command.
10691 (@value{GDBP}) @b{trace foo}
10692 (@value{GDBP}) @b{actions}
10693 Enter actions for tracepoint 1, one per line:
10696 > while-stepping 12
10697 > collect $pc, arr[i]
10702 @kindex collect @r{(tracepoints)}
10703 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
10704 Collect values of the given expressions when the tracepoint is hit.
10705 This command accepts a comma-separated list of any valid expressions.
10706 In addition to global, static, or local variables, the following
10707 special arguments are supported:
10711 Collect all registers.
10714 Collect all function arguments.
10717 Collect all local variables.
10720 Collect the return address. This is helpful if you want to see more
10724 @vindex $_sdata@r{, collect}
10725 Collect static tracepoint marker specific data. Only available for
10726 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10727 Lists}. On the UST static tracepoints library backend, an
10728 instrumentation point resembles a @code{printf} function call. The
10729 tracing library is able to collect user specified data formatted to a
10730 character string using the format provided by the programmer that
10731 instrumented the program. Other backends have similar mechanisms.
10732 Here's an example of a UST marker call:
10735 const char master_name[] = "$your_name";
10736 trace_mark(channel1, marker1, "hello %s", master_name)
10739 In this case, collecting @code{$_sdata} collects the string
10740 @samp{hello $yourname}. When analyzing the trace buffer, you can
10741 inspect @samp{$_sdata} like any other variable available to
10745 You can give several consecutive @code{collect} commands, each one
10746 with a single argument, or one @code{collect} command with several
10747 arguments separated by commas; the effect is the same.
10749 The optional @var{mods} changes the usual handling of the arguments.
10750 @code{s} requests that pointers to chars be handled as strings, in
10751 particular collecting the contents of the memory being pointed at, up
10752 to the first zero. The upper bound is by default the value of the
10753 @code{print elements} variable; if @code{s} is followed by a decimal
10754 number, that is the upper bound instead. So for instance
10755 @samp{collect/s25 mystr} collects as many as 25 characters at
10758 The command @code{info scope} (@pxref{Symbols, info scope}) is
10759 particularly useful for figuring out what data to collect.
10761 @kindex teval @r{(tracepoints)}
10762 @item teval @var{expr1}, @var{expr2}, @dots{}
10763 Evaluate the given expressions when the tracepoint is hit. This
10764 command accepts a comma-separated list of expressions. The results
10765 are discarded, so this is mainly useful for assigning values to trace
10766 state variables (@pxref{Trace State Variables}) without adding those
10767 values to the trace buffer, as would be the case if the @code{collect}
10770 @kindex while-stepping @r{(tracepoints)}
10771 @item while-stepping @var{n}
10772 Perform @var{n} single-step instruction traces after the tracepoint,
10773 collecting new data after each step. The @code{while-stepping}
10774 command is followed by the list of what to collect while stepping
10775 (followed by its own @code{end} command):
10778 > while-stepping 12
10779 > collect $regs, myglobal
10785 Note that @code{$pc} is not automatically collected by
10786 @code{while-stepping}; you need to explicitly collect that register if
10787 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10790 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10791 @kindex set default-collect
10792 @cindex default collection action
10793 This variable is a list of expressions to collect at each tracepoint
10794 hit. It is effectively an additional @code{collect} action prepended
10795 to every tracepoint action list. The expressions are parsed
10796 individually for each tracepoint, so for instance a variable named
10797 @code{xyz} may be interpreted as a global for one tracepoint, and a
10798 local for another, as appropriate to the tracepoint's location.
10800 @item show default-collect
10801 @kindex show default-collect
10802 Show the list of expressions that are collected by default at each
10807 @node Listing Tracepoints
10808 @subsection Listing Tracepoints
10811 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10812 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10813 @cindex information about tracepoints
10814 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10815 Display information about the tracepoint @var{num}. If you don't
10816 specify a tracepoint number, displays information about all the
10817 tracepoints defined so far. The format is similar to that used for
10818 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10819 command, simply restricting itself to tracepoints.
10821 A tracepoint's listing may include additional information specific to
10826 its passcount as given by the @code{passcount @var{n}} command
10830 (@value{GDBP}) @b{info trace}
10831 Num Type Disp Enb Address What
10832 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10834 collect globfoo, $regs
10843 This command can be abbreviated @code{info tp}.
10846 @node Listing Static Tracepoint Markers
10847 @subsection Listing Static Tracepoint Markers
10850 @kindex info static-tracepoint-markers
10851 @cindex information about static tracepoint markers
10852 @item info static-tracepoint-markers
10853 Display information about all static tracepoint markers defined in the
10856 For each marker, the following columns are printed:
10860 An incrementing counter, output to help readability. This is not a
10863 The marker ID, as reported by the target.
10864 @item Enabled or Disabled
10865 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10866 that are not enabled.
10868 Where the marker is in your program, as a memory address.
10870 Where the marker is in the source for your program, as a file and line
10871 number. If the debug information included in the program does not
10872 allow @value{GDBN} to locate the source of the marker, this column
10873 will be left blank.
10877 In addition, the following information may be printed for each marker:
10881 User data passed to the tracing library by the marker call. In the
10882 UST backend, this is the format string passed as argument to the
10884 @item Static tracepoints probing the marker
10885 The list of static tracepoints attached to the marker.
10889 (@value{GDBP}) info static-tracepoint-markers
10890 Cnt ID Enb Address What
10891 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10892 Data: number1 %d number2 %d
10893 Probed by static tracepoints: #2
10894 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10900 @node Starting and Stopping Trace Experiments
10901 @subsection Starting and Stopping Trace Experiments
10904 @kindex tstart [ @var{notes} ]
10905 @cindex start a new trace experiment
10906 @cindex collected data discarded
10908 This command starts the trace experiment, and begins collecting data.
10909 It has the side effect of discarding all the data collected in the
10910 trace buffer during the previous trace experiment. If any arguments
10911 are supplied, they are taken as a note and stored with the trace
10912 experiment's state. The notes may be arbitrary text, and are
10913 especially useful with disconnected tracing in a multi-user context;
10914 the notes can explain what the trace is doing, supply user contact
10915 information, and so forth.
10917 @kindex tstop [ @var{notes} ]
10918 @cindex stop a running trace experiment
10920 This command stops the trace experiment. If any arguments are
10921 supplied, they are recorded with the experiment as a note. This is
10922 useful if you are stopping a trace started by someone else, for
10923 instance if the trace is interfering with the system's behavior and
10924 needs to be stopped quickly.
10926 @strong{Note}: a trace experiment and data collection may stop
10927 automatically if any tracepoint's passcount is reached
10928 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10931 @cindex status of trace data collection
10932 @cindex trace experiment, status of
10934 This command displays the status of the current trace data
10938 Here is an example of the commands we described so far:
10941 (@value{GDBP}) @b{trace gdb_c_test}
10942 (@value{GDBP}) @b{actions}
10943 Enter actions for tracepoint #1, one per line.
10944 > collect $regs,$locals,$args
10945 > while-stepping 11
10949 (@value{GDBP}) @b{tstart}
10950 [time passes @dots{}]
10951 (@value{GDBP}) @b{tstop}
10954 @anchor{disconnected tracing}
10955 @cindex disconnected tracing
10956 You can choose to continue running the trace experiment even if
10957 @value{GDBN} disconnects from the target, voluntarily or
10958 involuntarily. For commands such as @code{detach}, the debugger will
10959 ask what you want to do with the trace. But for unexpected
10960 terminations (@value{GDBN} crash, network outage), it would be
10961 unfortunate to lose hard-won trace data, so the variable
10962 @code{disconnected-tracing} lets you decide whether the trace should
10963 continue running without @value{GDBN}.
10966 @item set disconnected-tracing on
10967 @itemx set disconnected-tracing off
10968 @kindex set disconnected-tracing
10969 Choose whether a tracing run should continue to run if @value{GDBN}
10970 has disconnected from the target. Note that @code{detach} or
10971 @code{quit} will ask you directly what to do about a running trace no
10972 matter what this variable's setting, so the variable is mainly useful
10973 for handling unexpected situations, such as loss of the network.
10975 @item show disconnected-tracing
10976 @kindex show disconnected-tracing
10977 Show the current choice for disconnected tracing.
10981 When you reconnect to the target, the trace experiment may or may not
10982 still be running; it might have filled the trace buffer in the
10983 meantime, or stopped for one of the other reasons. If it is running,
10984 it will continue after reconnection.
10986 Upon reconnection, the target will upload information about the
10987 tracepoints in effect. @value{GDBN} will then compare that
10988 information to the set of tracepoints currently defined, and attempt
10989 to match them up, allowing for the possibility that the numbers may
10990 have changed due to creation and deletion in the meantime. If one of
10991 the target's tracepoints does not match any in @value{GDBN}, the
10992 debugger will create a new tracepoint, so that you have a number with
10993 which to specify that tracepoint. This matching-up process is
10994 necessarily heuristic, and it may result in useless tracepoints being
10995 created; you may simply delete them if they are of no use.
10997 @cindex circular trace buffer
10998 If your target agent supports a @dfn{circular trace buffer}, then you
10999 can run a trace experiment indefinitely without filling the trace
11000 buffer; when space runs out, the agent deletes already-collected trace
11001 frames, oldest first, until there is enough room to continue
11002 collecting. This is especially useful if your tracepoints are being
11003 hit too often, and your trace gets terminated prematurely because the
11004 buffer is full. To ask for a circular trace buffer, simply set
11005 @samp{circular-trace-buffer} to on. You can set this at any time,
11006 including during tracing; if the agent can do it, it will change
11007 buffer handling on the fly, otherwise it will not take effect until
11011 @item set circular-trace-buffer on
11012 @itemx set circular-trace-buffer off
11013 @kindex set circular-trace-buffer
11014 Choose whether a tracing run should use a linear or circular buffer
11015 for trace data. A linear buffer will not lose any trace data, but may
11016 fill up prematurely, while a circular buffer will discard old trace
11017 data, but it will have always room for the latest tracepoint hits.
11019 @item show circular-trace-buffer
11020 @kindex show circular-trace-buffer
11021 Show the current choice for the trace buffer. Note that this may not
11022 match the agent's current buffer handling, nor is it guaranteed to
11023 match the setting that might have been in effect during a past run,
11024 for instance if you are looking at frames from a trace file.
11029 @item set trace-user @var{text}
11030 @kindex set trace-user
11032 @item show trace-user
11033 @kindex show trace-user
11035 @item set trace-notes @var{text}
11036 @kindex set trace-notes
11037 Set the trace run's notes.
11039 @item show trace-notes
11040 @kindex show trace-notes
11041 Show the trace run's notes.
11043 @item set trace-stop-notes @var{text}
11044 @kindex set trace-stop-notes
11045 Set the trace run's stop notes. The handling of the note is as for
11046 @code{tstop} arguments; the set command is convenient way to fix a
11047 stop note that is mistaken or incomplete.
11049 @item show trace-stop-notes
11050 @kindex show trace-stop-notes
11051 Show the trace run's stop notes.
11055 @node Tracepoint Restrictions
11056 @subsection Tracepoint Restrictions
11058 @cindex tracepoint restrictions
11059 There are a number of restrictions on the use of tracepoints. As
11060 described above, tracepoint data gathering occurs on the target
11061 without interaction from @value{GDBN}. Thus the full capabilities of
11062 the debugger are not available during data gathering, and then at data
11063 examination time, you will be limited by only having what was
11064 collected. The following items describe some common problems, but it
11065 is not exhaustive, and you may run into additional difficulties not
11071 Tracepoint expressions are intended to gather objects (lvalues). Thus
11072 the full flexibility of GDB's expression evaluator is not available.
11073 You cannot call functions, cast objects to aggregate types, access
11074 convenience variables or modify values (except by assignment to trace
11075 state variables). Some language features may implicitly call
11076 functions (for instance Objective-C fields with accessors), and therefore
11077 cannot be collected either.
11080 Collection of local variables, either individually or in bulk with
11081 @code{$locals} or @code{$args}, during @code{while-stepping} may
11082 behave erratically. The stepping action may enter a new scope (for
11083 instance by stepping into a function), or the location of the variable
11084 may change (for instance it is loaded into a register). The
11085 tracepoint data recorded uses the location information for the
11086 variables that is correct for the tracepoint location. When the
11087 tracepoint is created, it is not possible, in general, to determine
11088 where the steps of a @code{while-stepping} sequence will advance the
11089 program---particularly if a conditional branch is stepped.
11092 Collection of an incompletely-initialized or partially-destroyed object
11093 may result in something that @value{GDBN} cannot display, or displays
11094 in a misleading way.
11097 When @value{GDBN} displays a pointer to character it automatically
11098 dereferences the pointer to also display characters of the string
11099 being pointed to. However, collecting the pointer during tracing does
11100 not automatically collect the string. You need to explicitly
11101 dereference the pointer and provide size information if you want to
11102 collect not only the pointer, but the memory pointed to. For example,
11103 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11107 It is not possible to collect a complete stack backtrace at a
11108 tracepoint. Instead, you may collect the registers and a few hundred
11109 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11110 (adjust to use the name of the actual stack pointer register on your
11111 target architecture, and the amount of stack you wish to capture).
11112 Then the @code{backtrace} command will show a partial backtrace when
11113 using a trace frame. The number of stack frames that can be examined
11114 depends on the sizes of the frames in the collected stack. Note that
11115 if you ask for a block so large that it goes past the bottom of the
11116 stack, the target agent may report an error trying to read from an
11120 If you do not collect registers at a tracepoint, @value{GDBN} can
11121 infer that the value of @code{$pc} must be the same as the address of
11122 the tracepoint and use that when you are looking at a trace frame
11123 for that tracepoint. However, this cannot work if the tracepoint has
11124 multiple locations (for instance if it was set in a function that was
11125 inlined), or if it has a @code{while-stepping} loop. In those cases
11126 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11131 @node Analyze Collected Data
11132 @section Using the Collected Data
11134 After the tracepoint experiment ends, you use @value{GDBN} commands
11135 for examining the trace data. The basic idea is that each tracepoint
11136 collects a trace @dfn{snapshot} every time it is hit and another
11137 snapshot every time it single-steps. All these snapshots are
11138 consecutively numbered from zero and go into a buffer, and you can
11139 examine them later. The way you examine them is to @dfn{focus} on a
11140 specific trace snapshot. When the remote stub is focused on a trace
11141 snapshot, it will respond to all @value{GDBN} requests for memory and
11142 registers by reading from the buffer which belongs to that snapshot,
11143 rather than from @emph{real} memory or registers of the program being
11144 debugged. This means that @strong{all} @value{GDBN} commands
11145 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11146 behave as if we were currently debugging the program state as it was
11147 when the tracepoint occurred. Any requests for data that are not in
11148 the buffer will fail.
11151 * tfind:: How to select a trace snapshot
11152 * tdump:: How to display all data for a snapshot
11153 * save tracepoints:: How to save tracepoints for a future run
11157 @subsection @code{tfind @var{n}}
11160 @cindex select trace snapshot
11161 @cindex find trace snapshot
11162 The basic command for selecting a trace snapshot from the buffer is
11163 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11164 counting from zero. If no argument @var{n} is given, the next
11165 snapshot is selected.
11167 Here are the various forms of using the @code{tfind} command.
11171 Find the first snapshot in the buffer. This is a synonym for
11172 @code{tfind 0} (since 0 is the number of the first snapshot).
11175 Stop debugging trace snapshots, resume @emph{live} debugging.
11178 Same as @samp{tfind none}.
11181 No argument means find the next trace snapshot.
11184 Find the previous trace snapshot before the current one. This permits
11185 retracing earlier steps.
11187 @item tfind tracepoint @var{num}
11188 Find the next snapshot associated with tracepoint @var{num}. Search
11189 proceeds forward from the last examined trace snapshot. If no
11190 argument @var{num} is given, it means find the next snapshot collected
11191 for the same tracepoint as the current snapshot.
11193 @item tfind pc @var{addr}
11194 Find the next snapshot associated with the value @var{addr} of the
11195 program counter. Search proceeds forward from the last examined trace
11196 snapshot. If no argument @var{addr} is given, it means find the next
11197 snapshot with the same value of PC as the current snapshot.
11199 @item tfind outside @var{addr1}, @var{addr2}
11200 Find the next snapshot whose PC is outside the given range of
11201 addresses (exclusive).
11203 @item tfind range @var{addr1}, @var{addr2}
11204 Find the next snapshot whose PC is between @var{addr1} and
11205 @var{addr2} (inclusive).
11207 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11208 Find the next snapshot associated with the source line @var{n}. If
11209 the optional argument @var{file} is given, refer to line @var{n} in
11210 that source file. Search proceeds forward from the last examined
11211 trace snapshot. If no argument @var{n} is given, it means find the
11212 next line other than the one currently being examined; thus saying
11213 @code{tfind line} repeatedly can appear to have the same effect as
11214 stepping from line to line in a @emph{live} debugging session.
11217 The default arguments for the @code{tfind} commands are specifically
11218 designed to make it easy to scan through the trace buffer. For
11219 instance, @code{tfind} with no argument selects the next trace
11220 snapshot, and @code{tfind -} with no argument selects the previous
11221 trace snapshot. So, by giving one @code{tfind} command, and then
11222 simply hitting @key{RET} repeatedly you can examine all the trace
11223 snapshots in order. Or, by saying @code{tfind -} and then hitting
11224 @key{RET} repeatedly you can examine the snapshots in reverse order.
11225 The @code{tfind line} command with no argument selects the snapshot
11226 for the next source line executed. The @code{tfind pc} command with
11227 no argument selects the next snapshot with the same program counter
11228 (PC) as the current frame. The @code{tfind tracepoint} command with
11229 no argument selects the next trace snapshot collected by the same
11230 tracepoint as the current one.
11232 In addition to letting you scan through the trace buffer manually,
11233 these commands make it easy to construct @value{GDBN} scripts that
11234 scan through the trace buffer and print out whatever collected data
11235 you are interested in. Thus, if we want to examine the PC, FP, and SP
11236 registers from each trace frame in the buffer, we can say this:
11239 (@value{GDBP}) @b{tfind start}
11240 (@value{GDBP}) @b{while ($trace_frame != -1)}
11241 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11242 $trace_frame, $pc, $sp, $fp
11246 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11247 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11248 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11249 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11250 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11251 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11252 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11253 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11254 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11255 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11256 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11259 Or, if we want to examine the variable @code{X} at each source line in
11263 (@value{GDBP}) @b{tfind start}
11264 (@value{GDBP}) @b{while ($trace_frame != -1)}
11265 > printf "Frame %d, X == %d\n", $trace_frame, X
11275 @subsection @code{tdump}
11277 @cindex dump all data collected at tracepoint
11278 @cindex tracepoint data, display
11280 This command takes no arguments. It prints all the data collected at
11281 the current trace snapshot.
11284 (@value{GDBP}) @b{trace 444}
11285 (@value{GDBP}) @b{actions}
11286 Enter actions for tracepoint #2, one per line:
11287 > collect $regs, $locals, $args, gdb_long_test
11290 (@value{GDBP}) @b{tstart}
11292 (@value{GDBP}) @b{tfind line 444}
11293 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11295 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11297 (@value{GDBP}) @b{tdump}
11298 Data collected at tracepoint 2, trace frame 1:
11299 d0 0xc4aa0085 -995491707
11303 d4 0x71aea3d 119204413
11306 d7 0x380035 3670069
11307 a0 0x19e24a 1696330
11308 a1 0x3000668 50333288
11310 a3 0x322000 3284992
11311 a4 0x3000698 50333336
11312 a5 0x1ad3cc 1758156
11313 fp 0x30bf3c 0x30bf3c
11314 sp 0x30bf34 0x30bf34
11316 pc 0x20b2c8 0x20b2c8
11320 p = 0x20e5b4 "gdb-test"
11327 gdb_long_test = 17 '\021'
11332 @code{tdump} works by scanning the tracepoint's current collection
11333 actions and printing the value of each expression listed. So
11334 @code{tdump} can fail, if after a run, you change the tracepoint's
11335 actions to mention variables that were not collected during the run.
11337 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11338 uses the collected value of @code{$pc} to distinguish between trace
11339 frames that were collected at the tracepoint hit, and frames that were
11340 collected while stepping. This allows it to correctly choose whether
11341 to display the basic list of collections, or the collections from the
11342 body of the while-stepping loop. However, if @code{$pc} was not collected,
11343 then @code{tdump} will always attempt to dump using the basic collection
11344 list, and may fail if a while-stepping frame does not include all the
11345 same data that is collected at the tracepoint hit.
11346 @c This is getting pretty arcane, example would be good.
11348 @node save tracepoints
11349 @subsection @code{save tracepoints @var{filename}}
11350 @kindex save tracepoints
11351 @kindex save-tracepoints
11352 @cindex save tracepoints for future sessions
11354 This command saves all current tracepoint definitions together with
11355 their actions and passcounts, into a file @file{@var{filename}}
11356 suitable for use in a later debugging session. To read the saved
11357 tracepoint definitions, use the @code{source} command (@pxref{Command
11358 Files}). The @w{@code{save-tracepoints}} command is a deprecated
11359 alias for @w{@code{save tracepoints}}
11361 @node Tracepoint Variables
11362 @section Convenience Variables for Tracepoints
11363 @cindex tracepoint variables
11364 @cindex convenience variables for tracepoints
11367 @vindex $trace_frame
11368 @item (int) $trace_frame
11369 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
11370 snapshot is selected.
11372 @vindex $tracepoint
11373 @item (int) $tracepoint
11374 The tracepoint for the current trace snapshot.
11376 @vindex $trace_line
11377 @item (int) $trace_line
11378 The line number for the current trace snapshot.
11380 @vindex $trace_file
11381 @item (char []) $trace_file
11382 The source file for the current trace snapshot.
11384 @vindex $trace_func
11385 @item (char []) $trace_func
11386 The name of the function containing @code{$tracepoint}.
11389 Note: @code{$trace_file} is not suitable for use in @code{printf},
11390 use @code{output} instead.
11392 Here's a simple example of using these convenience variables for
11393 stepping through all the trace snapshots and printing some of their
11394 data. Note that these are not the same as trace state variables,
11395 which are managed by the target.
11398 (@value{GDBP}) @b{tfind start}
11400 (@value{GDBP}) @b{while $trace_frame != -1}
11401 > output $trace_file
11402 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
11408 @section Using Trace Files
11409 @cindex trace files
11411 In some situations, the target running a trace experiment may no
11412 longer be available; perhaps it crashed, or the hardware was needed
11413 for a different activity. To handle these cases, you can arrange to
11414 dump the trace data into a file, and later use that file as a source
11415 of trace data, via the @code{target tfile} command.
11420 @item tsave [ -r ] @var{filename}
11421 Save the trace data to @var{filename}. By default, this command
11422 assumes that @var{filename} refers to the host filesystem, so if
11423 necessary @value{GDBN} will copy raw trace data up from the target and
11424 then save it. If the target supports it, you can also supply the
11425 optional argument @code{-r} (``remote'') to direct the target to save
11426 the data directly into @var{filename} in its own filesystem, which may be
11427 more efficient if the trace buffer is very large. (Note, however, that
11428 @code{target tfile} can only read from files accessible to the host.)
11430 @kindex target tfile
11432 @item target tfile @var{filename}
11433 Use the file named @var{filename} as a source of trace data. Commands
11434 that examine data work as they do with a live target, but it is not
11435 possible to run any new trace experiments. @code{tstatus} will report
11436 the state of the trace run at the moment the data was saved, as well
11437 as the current trace frame you are examining. @var{filename} must be
11438 on a filesystem accessible to the host.
11443 @chapter Debugging Programs That Use Overlays
11446 If your program is too large to fit completely in your target system's
11447 memory, you can sometimes use @dfn{overlays} to work around this
11448 problem. @value{GDBN} provides some support for debugging programs that
11452 * How Overlays Work:: A general explanation of overlays.
11453 * Overlay Commands:: Managing overlays in @value{GDBN}.
11454 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
11455 mapped by asking the inferior.
11456 * Overlay Sample Program:: A sample program using overlays.
11459 @node How Overlays Work
11460 @section How Overlays Work
11461 @cindex mapped overlays
11462 @cindex unmapped overlays
11463 @cindex load address, overlay's
11464 @cindex mapped address
11465 @cindex overlay area
11467 Suppose you have a computer whose instruction address space is only 64
11468 kilobytes long, but which has much more memory which can be accessed by
11469 other means: special instructions, segment registers, or memory
11470 management hardware, for example. Suppose further that you want to
11471 adapt a program which is larger than 64 kilobytes to run on this system.
11473 One solution is to identify modules of your program which are relatively
11474 independent, and need not call each other directly; call these modules
11475 @dfn{overlays}. Separate the overlays from the main program, and place
11476 their machine code in the larger memory. Place your main program in
11477 instruction memory, but leave at least enough space there to hold the
11478 largest overlay as well.
11480 Now, to call a function located in an overlay, you must first copy that
11481 overlay's machine code from the large memory into the space set aside
11482 for it in the instruction memory, and then jump to its entry point
11485 @c NB: In the below the mapped area's size is greater or equal to the
11486 @c size of all overlays. This is intentional to remind the developer
11487 @c that overlays don't necessarily need to be the same size.
11491 Data Instruction Larger
11492 Address Space Address Space Address Space
11493 +-----------+ +-----------+ +-----------+
11495 +-----------+ +-----------+ +-----------+<-- overlay 1
11496 | program | | main | .----| overlay 1 | load address
11497 | variables | | program | | +-----------+
11498 | and heap | | | | | |
11499 +-----------+ | | | +-----------+<-- overlay 2
11500 | | +-----------+ | | | load address
11501 +-----------+ | | | .-| overlay 2 |
11503 mapped --->+-----------+ | | +-----------+
11504 address | | | | | |
11505 | overlay | <-' | | |
11506 | area | <---' +-----------+<-- overlay 3
11507 | | <---. | | load address
11508 +-----------+ `--| overlay 3 |
11515 @anchor{A code overlay}A code overlay
11519 The diagram (@pxref{A code overlay}) shows a system with separate data
11520 and instruction address spaces. To map an overlay, the program copies
11521 its code from the larger address space to the instruction address space.
11522 Since the overlays shown here all use the same mapped address, only one
11523 may be mapped at a time. For a system with a single address space for
11524 data and instructions, the diagram would be similar, except that the
11525 program variables and heap would share an address space with the main
11526 program and the overlay area.
11528 An overlay loaded into instruction memory and ready for use is called a
11529 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11530 instruction memory. An overlay not present (or only partially present)
11531 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11532 is its address in the larger memory. The mapped address is also called
11533 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11534 called the @dfn{load memory address}, or @dfn{LMA}.
11536 Unfortunately, overlays are not a completely transparent way to adapt a
11537 program to limited instruction memory. They introduce a new set of
11538 global constraints you must keep in mind as you design your program:
11543 Before calling or returning to a function in an overlay, your program
11544 must make sure that overlay is actually mapped. Otherwise, the call or
11545 return will transfer control to the right address, but in the wrong
11546 overlay, and your program will probably crash.
11549 If the process of mapping an overlay is expensive on your system, you
11550 will need to choose your overlays carefully to minimize their effect on
11551 your program's performance.
11554 The executable file you load onto your system must contain each
11555 overlay's instructions, appearing at the overlay's load address, not its
11556 mapped address. However, each overlay's instructions must be relocated
11557 and its symbols defined as if the overlay were at its mapped address.
11558 You can use GNU linker scripts to specify different load and relocation
11559 addresses for pieces of your program; see @ref{Overlay Description,,,
11560 ld.info, Using ld: the GNU linker}.
11563 The procedure for loading executable files onto your system must be able
11564 to load their contents into the larger address space as well as the
11565 instruction and data spaces.
11569 The overlay system described above is rather simple, and could be
11570 improved in many ways:
11575 If your system has suitable bank switch registers or memory management
11576 hardware, you could use those facilities to make an overlay's load area
11577 contents simply appear at their mapped address in instruction space.
11578 This would probably be faster than copying the overlay to its mapped
11579 area in the usual way.
11582 If your overlays are small enough, you could set aside more than one
11583 overlay area, and have more than one overlay mapped at a time.
11586 You can use overlays to manage data, as well as instructions. In
11587 general, data overlays are even less transparent to your design than
11588 code overlays: whereas code overlays only require care when you call or
11589 return to functions, data overlays require care every time you access
11590 the data. Also, if you change the contents of a data overlay, you
11591 must copy its contents back out to its load address before you can copy a
11592 different data overlay into the same mapped area.
11597 @node Overlay Commands
11598 @section Overlay Commands
11600 To use @value{GDBN}'s overlay support, each overlay in your program must
11601 correspond to a separate section of the executable file. The section's
11602 virtual memory address and load memory address must be the overlay's
11603 mapped and load addresses. Identifying overlays with sections allows
11604 @value{GDBN} to determine the appropriate address of a function or
11605 variable, depending on whether the overlay is mapped or not.
11607 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11608 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11613 Disable @value{GDBN}'s overlay support. When overlay support is
11614 disabled, @value{GDBN} assumes that all functions and variables are
11615 always present at their mapped addresses. By default, @value{GDBN}'s
11616 overlay support is disabled.
11618 @item overlay manual
11619 @cindex manual overlay debugging
11620 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11621 relies on you to tell it which overlays are mapped, and which are not,
11622 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11623 commands described below.
11625 @item overlay map-overlay @var{overlay}
11626 @itemx overlay map @var{overlay}
11627 @cindex map an overlay
11628 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11629 be the name of the object file section containing the overlay. When an
11630 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11631 functions and variables at their mapped addresses. @value{GDBN} assumes
11632 that any other overlays whose mapped ranges overlap that of
11633 @var{overlay} are now unmapped.
11635 @item overlay unmap-overlay @var{overlay}
11636 @itemx overlay unmap @var{overlay}
11637 @cindex unmap an overlay
11638 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11639 must be the name of the object file section containing the overlay.
11640 When an overlay is unmapped, @value{GDBN} assumes it can find the
11641 overlay's functions and variables at their load addresses.
11644 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11645 consults a data structure the overlay manager maintains in the inferior
11646 to see which overlays are mapped. For details, see @ref{Automatic
11647 Overlay Debugging}.
11649 @item overlay load-target
11650 @itemx overlay load
11651 @cindex reloading the overlay table
11652 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11653 re-reads the table @value{GDBN} automatically each time the inferior
11654 stops, so this command should only be necessary if you have changed the
11655 overlay mapping yourself using @value{GDBN}. This command is only
11656 useful when using automatic overlay debugging.
11658 @item overlay list-overlays
11659 @itemx overlay list
11660 @cindex listing mapped overlays
11661 Display a list of the overlays currently mapped, along with their mapped
11662 addresses, load addresses, and sizes.
11666 Normally, when @value{GDBN} prints a code address, it includes the name
11667 of the function the address falls in:
11670 (@value{GDBP}) print main
11671 $3 = @{int ()@} 0x11a0 <main>
11674 When overlay debugging is enabled, @value{GDBN} recognizes code in
11675 unmapped overlays, and prints the names of unmapped functions with
11676 asterisks around them. For example, if @code{foo} is a function in an
11677 unmapped overlay, @value{GDBN} prints it this way:
11680 (@value{GDBP}) overlay list
11681 No sections are mapped.
11682 (@value{GDBP}) print foo
11683 $5 = @{int (int)@} 0x100000 <*foo*>
11686 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11690 (@value{GDBP}) overlay list
11691 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11692 mapped at 0x1016 - 0x104a
11693 (@value{GDBP}) print foo
11694 $6 = @{int (int)@} 0x1016 <foo>
11697 When overlay debugging is enabled, @value{GDBN} can find the correct
11698 address for functions and variables in an overlay, whether or not the
11699 overlay is mapped. This allows most @value{GDBN} commands, like
11700 @code{break} and @code{disassemble}, to work normally, even on unmapped
11701 code. However, @value{GDBN}'s breakpoint support has some limitations:
11705 @cindex breakpoints in overlays
11706 @cindex overlays, setting breakpoints in
11707 You can set breakpoints in functions in unmapped overlays, as long as
11708 @value{GDBN} can write to the overlay at its load address.
11710 @value{GDBN} can not set hardware or simulator-based breakpoints in
11711 unmapped overlays. However, if you set a breakpoint at the end of your
11712 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11713 you are using manual overlay management), @value{GDBN} will re-set its
11714 breakpoints properly.
11718 @node Automatic Overlay Debugging
11719 @section Automatic Overlay Debugging
11720 @cindex automatic overlay debugging
11722 @value{GDBN} can automatically track which overlays are mapped and which
11723 are not, given some simple co-operation from the overlay manager in the
11724 inferior. If you enable automatic overlay debugging with the
11725 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11726 looks in the inferior's memory for certain variables describing the
11727 current state of the overlays.
11729 Here are the variables your overlay manager must define to support
11730 @value{GDBN}'s automatic overlay debugging:
11734 @item @code{_ovly_table}:
11735 This variable must be an array of the following structures:
11740 /* The overlay's mapped address. */
11743 /* The size of the overlay, in bytes. */
11744 unsigned long size;
11746 /* The overlay's load address. */
11749 /* Non-zero if the overlay is currently mapped;
11751 unsigned long mapped;
11755 @item @code{_novlys}:
11756 This variable must be a four-byte signed integer, holding the total
11757 number of elements in @code{_ovly_table}.
11761 To decide whether a particular overlay is mapped or not, @value{GDBN}
11762 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11763 @code{lma} members equal the VMA and LMA of the overlay's section in the
11764 executable file. When @value{GDBN} finds a matching entry, it consults
11765 the entry's @code{mapped} member to determine whether the overlay is
11768 In addition, your overlay manager may define a function called
11769 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11770 will silently set a breakpoint there. If the overlay manager then
11771 calls this function whenever it has changed the overlay table, this
11772 will enable @value{GDBN} to accurately keep track of which overlays
11773 are in program memory, and update any breakpoints that may be set
11774 in overlays. This will allow breakpoints to work even if the
11775 overlays are kept in ROM or other non-writable memory while they
11776 are not being executed.
11778 @node Overlay Sample Program
11779 @section Overlay Sample Program
11780 @cindex overlay example program
11782 When linking a program which uses overlays, you must place the overlays
11783 at their load addresses, while relocating them to run at their mapped
11784 addresses. To do this, you must write a linker script (@pxref{Overlay
11785 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11786 since linker scripts are specific to a particular host system, target
11787 architecture, and target memory layout, this manual cannot provide
11788 portable sample code demonstrating @value{GDBN}'s overlay support.
11790 However, the @value{GDBN} source distribution does contain an overlaid
11791 program, with linker scripts for a few systems, as part of its test
11792 suite. The program consists of the following files from
11793 @file{gdb/testsuite/gdb.base}:
11797 The main program file.
11799 A simple overlay manager, used by @file{overlays.c}.
11804 Overlay modules, loaded and used by @file{overlays.c}.
11807 Linker scripts for linking the test program on the @code{d10v-elf}
11808 and @code{m32r-elf} targets.
11811 You can build the test program using the @code{d10v-elf} GCC
11812 cross-compiler like this:
11815 $ d10v-elf-gcc -g -c overlays.c
11816 $ d10v-elf-gcc -g -c ovlymgr.c
11817 $ d10v-elf-gcc -g -c foo.c
11818 $ d10v-elf-gcc -g -c bar.c
11819 $ d10v-elf-gcc -g -c baz.c
11820 $ d10v-elf-gcc -g -c grbx.c
11821 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11822 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11825 The build process is identical for any other architecture, except that
11826 you must substitute the appropriate compiler and linker script for the
11827 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11831 @chapter Using @value{GDBN} with Different Languages
11834 Although programming languages generally have common aspects, they are
11835 rarely expressed in the same manner. For instance, in ANSI C,
11836 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11837 Modula-2, it is accomplished by @code{p^}. Values can also be
11838 represented (and displayed) differently. Hex numbers in C appear as
11839 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11841 @cindex working language
11842 Language-specific information is built into @value{GDBN} for some languages,
11843 allowing you to express operations like the above in your program's
11844 native language, and allowing @value{GDBN} to output values in a manner
11845 consistent with the syntax of your program's native language. The
11846 language you use to build expressions is called the @dfn{working
11850 * Setting:: Switching between source languages
11851 * Show:: Displaying the language
11852 * Checks:: Type and range checks
11853 * Supported Languages:: Supported languages
11854 * Unsupported Languages:: Unsupported languages
11858 @section Switching Between Source Languages
11860 There are two ways to control the working language---either have @value{GDBN}
11861 set it automatically, or select it manually yourself. You can use the
11862 @code{set language} command for either purpose. On startup, @value{GDBN}
11863 defaults to setting the language automatically. The working language is
11864 used to determine how expressions you type are interpreted, how values
11867 In addition to the working language, every source file that
11868 @value{GDBN} knows about has its own working language. For some object
11869 file formats, the compiler might indicate which language a particular
11870 source file is in. However, most of the time @value{GDBN} infers the
11871 language from the name of the file. The language of a source file
11872 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11873 show each frame appropriately for its own language. There is no way to
11874 set the language of a source file from within @value{GDBN}, but you can
11875 set the language associated with a filename extension. @xref{Show, ,
11876 Displaying the Language}.
11878 This is most commonly a problem when you use a program, such
11879 as @code{cfront} or @code{f2c}, that generates C but is written in
11880 another language. In that case, make the
11881 program use @code{#line} directives in its C output; that way
11882 @value{GDBN} will know the correct language of the source code of the original
11883 program, and will display that source code, not the generated C code.
11886 * Filenames:: Filename extensions and languages.
11887 * Manually:: Setting the working language manually
11888 * Automatically:: Having @value{GDBN} infer the source language
11892 @subsection List of Filename Extensions and Languages
11894 If a source file name ends in one of the following extensions, then
11895 @value{GDBN} infers that its language is the one indicated.
11913 C@t{++} source file
11919 Objective-C source file
11923 Fortran source file
11926 Modula-2 source file
11930 Assembler source file. This actually behaves almost like C, but
11931 @value{GDBN} does not skip over function prologues when stepping.
11934 In addition, you may set the language associated with a filename
11935 extension. @xref{Show, , Displaying the Language}.
11938 @subsection Setting the Working Language
11940 If you allow @value{GDBN} to set the language automatically,
11941 expressions are interpreted the same way in your debugging session and
11944 @kindex set language
11945 If you wish, you may set the language manually. To do this, issue the
11946 command @samp{set language @var{lang}}, where @var{lang} is the name of
11947 a language, such as
11948 @code{c} or @code{modula-2}.
11949 For a list of the supported languages, type @samp{set language}.
11951 Setting the language manually prevents @value{GDBN} from updating the working
11952 language automatically. This can lead to confusion if you try
11953 to debug a program when the working language is not the same as the
11954 source language, when an expression is acceptable to both
11955 languages---but means different things. For instance, if the current
11956 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11964 might not have the effect you intended. In C, this means to add
11965 @code{b} and @code{c} and place the result in @code{a}. The result
11966 printed would be the value of @code{a}. In Modula-2, this means to compare
11967 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11969 @node Automatically
11970 @subsection Having @value{GDBN} Infer the Source Language
11972 To have @value{GDBN} set the working language automatically, use
11973 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11974 then infers the working language. That is, when your program stops in a
11975 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11976 working language to the language recorded for the function in that
11977 frame. If the language for a frame is unknown (that is, if the function
11978 or block corresponding to the frame was defined in a source file that
11979 does not have a recognized extension), the current working language is
11980 not changed, and @value{GDBN} issues a warning.
11982 This may not seem necessary for most programs, which are written
11983 entirely in one source language. However, program modules and libraries
11984 written in one source language can be used by a main program written in
11985 a different source language. Using @samp{set language auto} in this
11986 case frees you from having to set the working language manually.
11989 @section Displaying the Language
11991 The following commands help you find out which language is the
11992 working language, and also what language source files were written in.
11995 @item show language
11996 @kindex show language
11997 Display the current working language. This is the
11998 language you can use with commands such as @code{print} to
11999 build and compute expressions that may involve variables in your program.
12002 @kindex info frame@r{, show the source language}
12003 Display the source language for this frame. This language becomes the
12004 working language if you use an identifier from this frame.
12005 @xref{Frame Info, ,Information about a Frame}, to identify the other
12006 information listed here.
12009 @kindex info source@r{, show the source language}
12010 Display the source language of this source file.
12011 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12012 information listed here.
12015 In unusual circumstances, you may have source files with extensions
12016 not in the standard list. You can then set the extension associated
12017 with a language explicitly:
12020 @item set extension-language @var{ext} @var{language}
12021 @kindex set extension-language
12022 Tell @value{GDBN} that source files with extension @var{ext} are to be
12023 assumed as written in the source language @var{language}.
12025 @item info extensions
12026 @kindex info extensions
12027 List all the filename extensions and the associated languages.
12031 @section Type and Range Checking
12034 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
12035 checking are included, but they do not yet have any effect. This
12036 section documents the intended facilities.
12038 @c FIXME remove warning when type/range code added
12040 Some languages are designed to guard you against making seemingly common
12041 errors through a series of compile- and run-time checks. These include
12042 checking the type of arguments to functions and operators, and making
12043 sure mathematical overflows are caught at run time. Checks such as
12044 these help to ensure a program's correctness once it has been compiled
12045 by eliminating type mismatches, and providing active checks for range
12046 errors when your program is running.
12048 @value{GDBN} can check for conditions like the above if you wish.
12049 Although @value{GDBN} does not check the statements in your program,
12050 it can check expressions entered directly into @value{GDBN} for
12051 evaluation via the @code{print} command, for example. As with the
12052 working language, @value{GDBN} can also decide whether or not to check
12053 automatically based on your program's source language.
12054 @xref{Supported Languages, ,Supported Languages}, for the default
12055 settings of supported languages.
12058 * Type Checking:: An overview of type checking
12059 * Range Checking:: An overview of range checking
12062 @cindex type checking
12063 @cindex checks, type
12064 @node Type Checking
12065 @subsection An Overview of Type Checking
12067 Some languages, such as Modula-2, are strongly typed, meaning that the
12068 arguments to operators and functions have to be of the correct type,
12069 otherwise an error occurs. These checks prevent type mismatch
12070 errors from ever causing any run-time problems. For example,
12078 The second example fails because the @code{CARDINAL} 1 is not
12079 type-compatible with the @code{REAL} 2.3.
12081 For the expressions you use in @value{GDBN} commands, you can tell the
12082 @value{GDBN} type checker to skip checking;
12083 to treat any mismatches as errors and abandon the expression;
12084 or to only issue warnings when type mismatches occur,
12085 but evaluate the expression anyway. When you choose the last of
12086 these, @value{GDBN} evaluates expressions like the second example above, but
12087 also issues a warning.
12089 Even if you turn type checking off, there may be other reasons
12090 related to type that prevent @value{GDBN} from evaluating an expression.
12091 For instance, @value{GDBN} does not know how to add an @code{int} and
12092 a @code{struct foo}. These particular type errors have nothing to do
12093 with the language in use, and usually arise from expressions, such as
12094 the one described above, which make little sense to evaluate anyway.
12096 Each language defines to what degree it is strict about type. For
12097 instance, both Modula-2 and C require the arguments to arithmetical
12098 operators to be numbers. In C, enumerated types and pointers can be
12099 represented as numbers, so that they are valid arguments to mathematical
12100 operators. @xref{Supported Languages, ,Supported Languages}, for further
12101 details on specific languages.
12103 @value{GDBN} provides some additional commands for controlling the type checker:
12105 @kindex set check type
12106 @kindex show check type
12108 @item set check type auto
12109 Set type checking on or off based on the current working language.
12110 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12113 @item set check type on
12114 @itemx set check type off
12115 Set type checking on or off, overriding the default setting for the
12116 current working language. Issue a warning if the setting does not
12117 match the language default. If any type mismatches occur in
12118 evaluating an expression while type checking is on, @value{GDBN} prints a
12119 message and aborts evaluation of the expression.
12121 @item set check type warn
12122 Cause the type checker to issue warnings, but to always attempt to
12123 evaluate the expression. Evaluating the expression may still
12124 be impossible for other reasons. For example, @value{GDBN} cannot add
12125 numbers and structures.
12128 Show the current setting of the type checker, and whether or not @value{GDBN}
12129 is setting it automatically.
12132 @cindex range checking
12133 @cindex checks, range
12134 @node Range Checking
12135 @subsection An Overview of Range Checking
12137 In some languages (such as Modula-2), it is an error to exceed the
12138 bounds of a type; this is enforced with run-time checks. Such range
12139 checking is meant to ensure program correctness by making sure
12140 computations do not overflow, or indices on an array element access do
12141 not exceed the bounds of the array.
12143 For expressions you use in @value{GDBN} commands, you can tell
12144 @value{GDBN} to treat range errors in one of three ways: ignore them,
12145 always treat them as errors and abandon the expression, or issue
12146 warnings but evaluate the expression anyway.
12148 A range error can result from numerical overflow, from exceeding an
12149 array index bound, or when you type a constant that is not a member
12150 of any type. Some languages, however, do not treat overflows as an
12151 error. In many implementations of C, mathematical overflow causes the
12152 result to ``wrap around'' to lower values---for example, if @var{m} is
12153 the largest integer value, and @var{s} is the smallest, then
12156 @var{m} + 1 @result{} @var{s}
12159 This, too, is specific to individual languages, and in some cases
12160 specific to individual compilers or machines. @xref{Supported Languages, ,
12161 Supported Languages}, for further details on specific languages.
12163 @value{GDBN} provides some additional commands for controlling the range checker:
12165 @kindex set check range
12166 @kindex show check range
12168 @item set check range auto
12169 Set range checking on or off based on the current working language.
12170 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12173 @item set check range on
12174 @itemx set check range off
12175 Set range checking on or off, overriding the default setting for the
12176 current working language. A warning is issued if the setting does not
12177 match the language default. If a range error occurs and range checking is on,
12178 then a message is printed and evaluation of the expression is aborted.
12180 @item set check range warn
12181 Output messages when the @value{GDBN} range checker detects a range error,
12182 but attempt to evaluate the expression anyway. Evaluating the
12183 expression may still be impossible for other reasons, such as accessing
12184 memory that the process does not own (a typical example from many Unix
12188 Show the current setting of the range checker, and whether or not it is
12189 being set automatically by @value{GDBN}.
12192 @node Supported Languages
12193 @section Supported Languages
12195 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
12196 assembly, Modula-2, and Ada.
12197 @c This is false ...
12198 Some @value{GDBN} features may be used in expressions regardless of the
12199 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12200 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12201 ,Expressions}) can be used with the constructs of any supported
12204 The following sections detail to what degree each source language is
12205 supported by @value{GDBN}. These sections are not meant to be language
12206 tutorials or references, but serve only as a reference guide to what the
12207 @value{GDBN} expression parser accepts, and what input and output
12208 formats should look like for different languages. There are many good
12209 books written on each of these languages; please look to these for a
12210 language reference or tutorial.
12213 * C:: C and C@t{++}
12215 * Objective-C:: Objective-C
12216 * OpenCL C:: OpenCL C
12217 * Fortran:: Fortran
12219 * Modula-2:: Modula-2
12224 @subsection C and C@t{++}
12226 @cindex C and C@t{++}
12227 @cindex expressions in C or C@t{++}
12229 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12230 to both languages. Whenever this is the case, we discuss those languages
12234 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12235 @cindex @sc{gnu} C@t{++}
12236 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12237 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12238 effectively, you must compile your C@t{++} programs with a supported
12239 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12240 compiler (@code{aCC}).
12243 * C Operators:: C and C@t{++} operators
12244 * C Constants:: C and C@t{++} constants
12245 * C Plus Plus Expressions:: C@t{++} expressions
12246 * C Defaults:: Default settings for C and C@t{++}
12247 * C Checks:: C and C@t{++} type and range checks
12248 * Debugging C:: @value{GDBN} and C
12249 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12250 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12254 @subsubsection C and C@t{++} Operators
12256 @cindex C and C@t{++} operators
12258 Operators must be defined on values of specific types. For instance,
12259 @code{+} is defined on numbers, but not on structures. Operators are
12260 often defined on groups of types.
12262 For the purposes of C and C@t{++}, the following definitions hold:
12267 @emph{Integral types} include @code{int} with any of its storage-class
12268 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12271 @emph{Floating-point types} include @code{float}, @code{double}, and
12272 @code{long double} (if supported by the target platform).
12275 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12278 @emph{Scalar types} include all of the above.
12283 The following operators are supported. They are listed here
12284 in order of increasing precedence:
12288 The comma or sequencing operator. Expressions in a comma-separated list
12289 are evaluated from left to right, with the result of the entire
12290 expression being the last expression evaluated.
12293 Assignment. The value of an assignment expression is the value
12294 assigned. Defined on scalar types.
12297 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12298 and translated to @w{@code{@var{a} = @var{a op b}}}.
12299 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12300 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12301 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12304 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12305 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12309 Logical @sc{or}. Defined on integral types.
12312 Logical @sc{and}. Defined on integral types.
12315 Bitwise @sc{or}. Defined on integral types.
12318 Bitwise exclusive-@sc{or}. Defined on integral types.
12321 Bitwise @sc{and}. Defined on integral types.
12324 Equality and inequality. Defined on scalar types. The value of these
12325 expressions is 0 for false and non-zero for true.
12327 @item <@r{, }>@r{, }<=@r{, }>=
12328 Less than, greater than, less than or equal, greater than or equal.
12329 Defined on scalar types. The value of these expressions is 0 for false
12330 and non-zero for true.
12333 left shift, and right shift. Defined on integral types.
12336 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12339 Addition and subtraction. Defined on integral types, floating-point types and
12342 @item *@r{, }/@r{, }%
12343 Multiplication, division, and modulus. Multiplication and division are
12344 defined on integral and floating-point types. Modulus is defined on
12348 Increment and decrement. When appearing before a variable, the
12349 operation is performed before the variable is used in an expression;
12350 when appearing after it, the variable's value is used before the
12351 operation takes place.
12354 Pointer dereferencing. Defined on pointer types. Same precedence as
12358 Address operator. Defined on variables. Same precedence as @code{++}.
12360 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
12361 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
12362 to examine the address
12363 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
12367 Negative. Defined on integral and floating-point types. Same
12368 precedence as @code{++}.
12371 Logical negation. Defined on integral types. Same precedence as
12375 Bitwise complement operator. Defined on integral types. Same precedence as
12380 Structure member, and pointer-to-structure member. For convenience,
12381 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
12382 pointer based on the stored type information.
12383 Defined on @code{struct} and @code{union} data.
12386 Dereferences of pointers to members.
12389 Array indexing. @code{@var{a}[@var{i}]} is defined as
12390 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
12393 Function parameter list. Same precedence as @code{->}.
12396 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
12397 and @code{class} types.
12400 Doubled colons also represent the @value{GDBN} scope operator
12401 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
12405 If an operator is redefined in the user code, @value{GDBN} usually
12406 attempts to invoke the redefined version instead of using the operator's
12407 predefined meaning.
12410 @subsubsection C and C@t{++} Constants
12412 @cindex C and C@t{++} constants
12414 @value{GDBN} allows you to express the constants of C and C@t{++} in the
12419 Integer constants are a sequence of digits. Octal constants are
12420 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
12421 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
12422 @samp{l}, specifying that the constant should be treated as a
12426 Floating point constants are a sequence of digits, followed by a decimal
12427 point, followed by a sequence of digits, and optionally followed by an
12428 exponent. An exponent is of the form:
12429 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
12430 sequence of digits. The @samp{+} is optional for positive exponents.
12431 A floating-point constant may also end with a letter @samp{f} or
12432 @samp{F}, specifying that the constant should be treated as being of
12433 the @code{float} (as opposed to the default @code{double}) type; or with
12434 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
12438 Enumerated constants consist of enumerated identifiers, or their
12439 integral equivalents.
12442 Character constants are a single character surrounded by single quotes
12443 (@code{'}), or a number---the ordinal value of the corresponding character
12444 (usually its @sc{ascii} value). Within quotes, the single character may
12445 be represented by a letter or by @dfn{escape sequences}, which are of
12446 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
12447 of the character's ordinal value; or of the form @samp{\@var{x}}, where
12448 @samp{@var{x}} is a predefined special character---for example,
12449 @samp{\n} for newline.
12451 Wide character constants can be written by prefixing a character
12452 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
12453 form of @samp{x}. The target wide character set is used when
12454 computing the value of this constant (@pxref{Character Sets}).
12457 String constants are a sequence of character constants surrounded by
12458 double quotes (@code{"}). Any valid character constant (as described
12459 above) may appear. Double quotes within the string must be preceded by
12460 a backslash, so for instance @samp{"a\"b'c"} is a string of five
12463 Wide string constants can be written by prefixing a string constant
12464 with @samp{L}, as in C. The target wide character set is used when
12465 computing the value of this constant (@pxref{Character Sets}).
12468 Pointer constants are an integral value. You can also write pointers
12469 to constants using the C operator @samp{&}.
12472 Array constants are comma-separated lists surrounded by braces @samp{@{}
12473 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
12474 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
12475 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
12478 @node C Plus Plus Expressions
12479 @subsubsection C@t{++} Expressions
12481 @cindex expressions in C@t{++}
12482 @value{GDBN} expression handling can interpret most C@t{++} expressions.
12484 @cindex debugging C@t{++} programs
12485 @cindex C@t{++} compilers
12486 @cindex debug formats and C@t{++}
12487 @cindex @value{NGCC} and C@t{++}
12489 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
12490 the proper compiler and the proper debug format. Currently,
12491 @value{GDBN} works best when debugging C@t{++} code that is compiled
12492 with the most recent version of @value{NGCC} possible. The DWARF
12493 debugging format is preferred; @value{NGCC} defaults to this on most
12494 popular platforms. Other compilers and/or debug formats are likely to
12495 work badly or not at all when using @value{GDBN} to debug C@t{++}
12496 code. @xref{Compilation}.
12501 @cindex member functions
12503 Member function calls are allowed; you can use expressions like
12506 count = aml->GetOriginal(x, y)
12509 @vindex this@r{, inside C@t{++} member functions}
12510 @cindex namespace in C@t{++}
12512 While a member function is active (in the selected stack frame), your
12513 expressions have the same namespace available as the member function;
12514 that is, @value{GDBN} allows implicit references to the class instance
12515 pointer @code{this} following the same rules as C@t{++}. @code{using}
12516 declarations in the current scope are also respected by @value{GDBN}.
12518 @cindex call overloaded functions
12519 @cindex overloaded functions, calling
12520 @cindex type conversions in C@t{++}
12522 You can call overloaded functions; @value{GDBN} resolves the function
12523 call to the right definition, with some restrictions. @value{GDBN} does not
12524 perform overload resolution involving user-defined type conversions,
12525 calls to constructors, or instantiations of templates that do not exist
12526 in the program. It also cannot handle ellipsis argument lists or
12529 It does perform integral conversions and promotions, floating-point
12530 promotions, arithmetic conversions, pointer conversions, conversions of
12531 class objects to base classes, and standard conversions such as those of
12532 functions or arrays to pointers; it requires an exact match on the
12533 number of function arguments.
12535 Overload resolution is always performed, unless you have specified
12536 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12537 ,@value{GDBN} Features for C@t{++}}.
12539 You must specify @code{set overload-resolution off} in order to use an
12540 explicit function signature to call an overloaded function, as in
12542 p 'foo(char,int)'('x', 13)
12545 The @value{GDBN} command-completion facility can simplify this;
12546 see @ref{Completion, ,Command Completion}.
12548 @cindex reference declarations
12550 @value{GDBN} understands variables declared as C@t{++} references; you can use
12551 them in expressions just as you do in C@t{++} source---they are automatically
12554 In the parameter list shown when @value{GDBN} displays a frame, the values of
12555 reference variables are not displayed (unlike other variables); this
12556 avoids clutter, since references are often used for large structures.
12557 The @emph{address} of a reference variable is always shown, unless
12558 you have specified @samp{set print address off}.
12561 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12562 expressions can use it just as expressions in your program do. Since
12563 one scope may be defined in another, you can use @code{::} repeatedly if
12564 necessary, for example in an expression like
12565 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12566 resolving name scope by reference to source files, in both C and C@t{++}
12567 debugging (@pxref{Variables, ,Program Variables}).
12570 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
12575 @subsubsection C and C@t{++} Defaults
12577 @cindex C and C@t{++} defaults
12579 If you allow @value{GDBN} to set type and range checking automatically, they
12580 both default to @code{off} whenever the working language changes to
12581 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12582 selects the working language.
12584 If you allow @value{GDBN} to set the language automatically, it
12585 recognizes source files whose names end with @file{.c}, @file{.C}, or
12586 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12587 these files, it sets the working language to C or C@t{++}.
12588 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12589 for further details.
12591 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12592 @c unimplemented. If (b) changes, it might make sense to let this node
12593 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12596 @subsubsection C and C@t{++} Type and Range Checks
12598 @cindex C and C@t{++} checks
12600 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12601 is not used. However, if you turn type checking on, @value{GDBN}
12602 considers two variables type equivalent if:
12606 The two variables are structured and have the same structure, union, or
12610 The two variables have the same type name, or types that have been
12611 declared equivalent through @code{typedef}.
12614 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12617 The two @code{struct}, @code{union}, or @code{enum} variables are
12618 declared in the same declaration. (Note: this may not be true for all C
12623 Range checking, if turned on, is done on mathematical operations. Array
12624 indices are not checked, since they are often used to index a pointer
12625 that is not itself an array.
12628 @subsubsection @value{GDBN} and C
12630 The @code{set print union} and @code{show print union} commands apply to
12631 the @code{union} type. When set to @samp{on}, any @code{union} that is
12632 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12633 appears as @samp{@{...@}}.
12635 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12636 with pointers and a memory allocation function. @xref{Expressions,
12639 @node Debugging C Plus Plus
12640 @subsubsection @value{GDBN} Features for C@t{++}
12642 @cindex commands for C@t{++}
12644 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12645 designed specifically for use with C@t{++}. Here is a summary:
12648 @cindex break in overloaded functions
12649 @item @r{breakpoint menus}
12650 When you want a breakpoint in a function whose name is overloaded,
12651 @value{GDBN} has the capability to display a menu of possible breakpoint
12652 locations to help you specify which function definition you want.
12653 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12655 @cindex overloading in C@t{++}
12656 @item rbreak @var{regex}
12657 Setting breakpoints using regular expressions is helpful for setting
12658 breakpoints on overloaded functions that are not members of any special
12660 @xref{Set Breaks, ,Setting Breakpoints}.
12662 @cindex C@t{++} exception handling
12665 Debug C@t{++} exception handling using these commands. @xref{Set
12666 Catchpoints, , Setting Catchpoints}.
12668 @cindex inheritance
12669 @item ptype @var{typename}
12670 Print inheritance relationships as well as other information for type
12672 @xref{Symbols, ,Examining the Symbol Table}.
12674 @cindex C@t{++} symbol display
12675 @item set print demangle
12676 @itemx show print demangle
12677 @itemx set print asm-demangle
12678 @itemx show print asm-demangle
12679 Control whether C@t{++} symbols display in their source form, both when
12680 displaying code as C@t{++} source and when displaying disassemblies.
12681 @xref{Print Settings, ,Print Settings}.
12683 @item set print object
12684 @itemx show print object
12685 Choose whether to print derived (actual) or declared types of objects.
12686 @xref{Print Settings, ,Print Settings}.
12688 @item set print vtbl
12689 @itemx show print vtbl
12690 Control the format for printing virtual function tables.
12691 @xref{Print Settings, ,Print Settings}.
12692 (The @code{vtbl} commands do not work on programs compiled with the HP
12693 ANSI C@t{++} compiler (@code{aCC}).)
12695 @kindex set overload-resolution
12696 @cindex overloaded functions, overload resolution
12697 @item set overload-resolution on
12698 Enable overload resolution for C@t{++} expression evaluation. The default
12699 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12700 and searches for a function whose signature matches the argument types,
12701 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12702 Expressions, ,C@t{++} Expressions}, for details).
12703 If it cannot find a match, it emits a message.
12705 @item set overload-resolution off
12706 Disable overload resolution for C@t{++} expression evaluation. For
12707 overloaded functions that are not class member functions, @value{GDBN}
12708 chooses the first function of the specified name that it finds in the
12709 symbol table, whether or not its arguments are of the correct type. For
12710 overloaded functions that are class member functions, @value{GDBN}
12711 searches for a function whose signature @emph{exactly} matches the
12714 @kindex show overload-resolution
12715 @item show overload-resolution
12716 Show the current setting of overload resolution.
12718 @item @r{Overloaded symbol names}
12719 You can specify a particular definition of an overloaded symbol, using
12720 the same notation that is used to declare such symbols in C@t{++}: type
12721 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12722 also use the @value{GDBN} command-line word completion facilities to list the
12723 available choices, or to finish the type list for you.
12724 @xref{Completion,, Command Completion}, for details on how to do this.
12727 @node Decimal Floating Point
12728 @subsubsection Decimal Floating Point format
12729 @cindex decimal floating point format
12731 @value{GDBN} can examine, set and perform computations with numbers in
12732 decimal floating point format, which in the C language correspond to the
12733 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12734 specified by the extension to support decimal floating-point arithmetic.
12736 There are two encodings in use, depending on the architecture: BID (Binary
12737 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12738 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12741 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12742 to manipulate decimal floating point numbers, it is not possible to convert
12743 (using a cast, for example) integers wider than 32-bit to decimal float.
12745 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12746 point computations, error checking in decimal float operations ignores
12747 underflow, overflow and divide by zero exceptions.
12749 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12750 to inspect @code{_Decimal128} values stored in floating point registers.
12751 See @ref{PowerPC,,PowerPC} for more details.
12757 @value{GDBN} can be used to debug programs written in D and compiled with
12758 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12759 specific feature --- dynamic arrays.
12762 @subsection Objective-C
12764 @cindex Objective-C
12765 This section provides information about some commands and command
12766 options that are useful for debugging Objective-C code. See also
12767 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12768 few more commands specific to Objective-C support.
12771 * Method Names in Commands::
12772 * The Print Command with Objective-C::
12775 @node Method Names in Commands
12776 @subsubsection Method Names in Commands
12778 The following commands have been extended to accept Objective-C method
12779 names as line specifications:
12781 @kindex clear@r{, and Objective-C}
12782 @kindex break@r{, and Objective-C}
12783 @kindex info line@r{, and Objective-C}
12784 @kindex jump@r{, and Objective-C}
12785 @kindex list@r{, and Objective-C}
12789 @item @code{info line}
12794 A fully qualified Objective-C method name is specified as
12797 -[@var{Class} @var{methodName}]
12800 where the minus sign is used to indicate an instance method and a
12801 plus sign (not shown) is used to indicate a class method. The class
12802 name @var{Class} and method name @var{methodName} are enclosed in
12803 brackets, similar to the way messages are specified in Objective-C
12804 source code. For example, to set a breakpoint at the @code{create}
12805 instance method of class @code{Fruit} in the program currently being
12809 break -[Fruit create]
12812 To list ten program lines around the @code{initialize} class method,
12816 list +[NSText initialize]
12819 In the current version of @value{GDBN}, the plus or minus sign is
12820 required. In future versions of @value{GDBN}, the plus or minus
12821 sign will be optional, but you can use it to narrow the search. It
12822 is also possible to specify just a method name:
12828 You must specify the complete method name, including any colons. If
12829 your program's source files contain more than one @code{create} method,
12830 you'll be presented with a numbered list of classes that implement that
12831 method. Indicate your choice by number, or type @samp{0} to exit if
12834 As another example, to clear a breakpoint established at the
12835 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12838 clear -[NSWindow makeKeyAndOrderFront:]
12841 @node The Print Command with Objective-C
12842 @subsubsection The Print Command With Objective-C
12843 @cindex Objective-C, print objects
12844 @kindex print-object
12845 @kindex po @r{(@code{print-object})}
12847 The print command has also been extended to accept methods. For example:
12850 print -[@var{object} hash]
12853 @cindex print an Objective-C object description
12854 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12856 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12857 and print the result. Also, an additional command has been added,
12858 @code{print-object} or @code{po} for short, which is meant to print
12859 the description of an object. However, this command may only work
12860 with certain Objective-C libraries that have a particular hook
12861 function, @code{_NSPrintForDebugger}, defined.
12864 @subsection OpenCL C
12867 This section provides information about @value{GDBN}s OpenCL C support.
12870 * OpenCL C Datatypes::
12871 * OpenCL C Expressions::
12872 * OpenCL C Operators::
12875 @node OpenCL C Datatypes
12876 @subsubsection OpenCL C Datatypes
12878 @cindex OpenCL C Datatypes
12879 @value{GDBN} supports the builtin scalar and vector datatypes specified
12880 by OpenCL 1.1. In addition the half- and double-precision floating point
12881 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12882 extensions are also known to @value{GDBN}.
12884 @node OpenCL C Expressions
12885 @subsubsection OpenCL C Expressions
12887 @cindex OpenCL C Expressions
12888 @value{GDBN} supports accesses to vector components including the access as
12889 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12890 supported by @value{GDBN} can be used as well.
12892 @node OpenCL C Operators
12893 @subsubsection OpenCL C Operators
12895 @cindex OpenCL C Operators
12896 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12900 @subsection Fortran
12901 @cindex Fortran-specific support in @value{GDBN}
12903 @value{GDBN} can be used to debug programs written in Fortran, but it
12904 currently supports only the features of Fortran 77 language.
12906 @cindex trailing underscore, in Fortran symbols
12907 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12908 among them) append an underscore to the names of variables and
12909 functions. When you debug programs compiled by those compilers, you
12910 will need to refer to variables and functions with a trailing
12914 * Fortran Operators:: Fortran operators and expressions
12915 * Fortran Defaults:: Default settings for Fortran
12916 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12919 @node Fortran Operators
12920 @subsubsection Fortran Operators and Expressions
12922 @cindex Fortran operators and expressions
12924 Operators must be defined on values of specific types. For instance,
12925 @code{+} is defined on numbers, but not on characters or other non-
12926 arithmetic types. Operators are often defined on groups of types.
12930 The exponentiation operator. It raises the first operand to the power
12934 The range operator. Normally used in the form of array(low:high) to
12935 represent a section of array.
12938 The access component operator. Normally used to access elements in derived
12939 types. Also suitable for unions. As unions aren't part of regular Fortran,
12940 this can only happen when accessing a register that uses a gdbarch-defined
12944 @node Fortran Defaults
12945 @subsubsection Fortran Defaults
12947 @cindex Fortran Defaults
12949 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12950 default uses case-insensitive matches for Fortran symbols. You can
12951 change that with the @samp{set case-insensitive} command, see
12952 @ref{Symbols}, for the details.
12954 @node Special Fortran Commands
12955 @subsubsection Special Fortran Commands
12957 @cindex Special Fortran commands
12959 @value{GDBN} has some commands to support Fortran-specific features,
12960 such as displaying common blocks.
12963 @cindex @code{COMMON} blocks, Fortran
12964 @kindex info common
12965 @item info common @r{[}@var{common-name}@r{]}
12966 This command prints the values contained in the Fortran @code{COMMON}
12967 block whose name is @var{common-name}. With no argument, the names of
12968 all @code{COMMON} blocks visible at the current program location are
12975 @cindex Pascal support in @value{GDBN}, limitations
12976 Debugging Pascal programs which use sets, subranges, file variables, or
12977 nested functions does not currently work. @value{GDBN} does not support
12978 entering expressions, printing values, or similar features using Pascal
12981 The Pascal-specific command @code{set print pascal_static-members}
12982 controls whether static members of Pascal objects are displayed.
12983 @xref{Print Settings, pascal_static-members}.
12986 @subsection Modula-2
12988 @cindex Modula-2, @value{GDBN} support
12990 The extensions made to @value{GDBN} to support Modula-2 only support
12991 output from the @sc{gnu} Modula-2 compiler (which is currently being
12992 developed). Other Modula-2 compilers are not currently supported, and
12993 attempting to debug executables produced by them is most likely
12994 to give an error as @value{GDBN} reads in the executable's symbol
12997 @cindex expressions in Modula-2
12999 * M2 Operators:: Built-in operators
13000 * Built-In Func/Proc:: Built-in functions and procedures
13001 * M2 Constants:: Modula-2 constants
13002 * M2 Types:: Modula-2 types
13003 * M2 Defaults:: Default settings for Modula-2
13004 * Deviations:: Deviations from standard Modula-2
13005 * M2 Checks:: Modula-2 type and range checks
13006 * M2 Scope:: The scope operators @code{::} and @code{.}
13007 * GDB/M2:: @value{GDBN} and Modula-2
13011 @subsubsection Operators
13012 @cindex Modula-2 operators
13014 Operators must be defined on values of specific types. For instance,
13015 @code{+} is defined on numbers, but not on structures. Operators are
13016 often defined on groups of types. For the purposes of Modula-2, the
13017 following definitions hold:
13022 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13026 @emph{Character types} consist of @code{CHAR} and its subranges.
13029 @emph{Floating-point types} consist of @code{REAL}.
13032 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13036 @emph{Scalar types} consist of all of the above.
13039 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13042 @emph{Boolean types} consist of @code{BOOLEAN}.
13046 The following operators are supported, and appear in order of
13047 increasing precedence:
13051 Function argument or array index separator.
13054 Assignment. The value of @var{var} @code{:=} @var{value} is
13058 Less than, greater than on integral, floating-point, or enumerated
13062 Less than or equal to, greater than or equal to
13063 on integral, floating-point and enumerated types, or set inclusion on
13064 set types. Same precedence as @code{<}.
13066 @item =@r{, }<>@r{, }#
13067 Equality and two ways of expressing inequality, valid on scalar types.
13068 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13069 available for inequality, since @code{#} conflicts with the script
13073 Set membership. Defined on set types and the types of their members.
13074 Same precedence as @code{<}.
13077 Boolean disjunction. Defined on boolean types.
13080 Boolean conjunction. Defined on boolean types.
13083 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13086 Addition and subtraction on integral and floating-point types, or union
13087 and difference on set types.
13090 Multiplication on integral and floating-point types, or set intersection
13094 Division on floating-point types, or symmetric set difference on set
13095 types. Same precedence as @code{*}.
13098 Integer division and remainder. Defined on integral types. Same
13099 precedence as @code{*}.
13102 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13105 Pointer dereferencing. Defined on pointer types.
13108 Boolean negation. Defined on boolean types. Same precedence as
13112 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13113 precedence as @code{^}.
13116 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13119 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13123 @value{GDBN} and Modula-2 scope operators.
13127 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13128 treats the use of the operator @code{IN}, or the use of operators
13129 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13130 @code{<=}, and @code{>=} on sets as an error.
13134 @node Built-In Func/Proc
13135 @subsubsection Built-in Functions and Procedures
13136 @cindex Modula-2 built-ins
13138 Modula-2 also makes available several built-in procedures and functions.
13139 In describing these, the following metavariables are used:
13144 represents an @code{ARRAY} variable.
13147 represents a @code{CHAR} constant or variable.
13150 represents a variable or constant of integral type.
13153 represents an identifier that belongs to a set. Generally used in the
13154 same function with the metavariable @var{s}. The type of @var{s} should
13155 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13158 represents a variable or constant of integral or floating-point type.
13161 represents a variable or constant of floating-point type.
13167 represents a variable.
13170 represents a variable or constant of one of many types. See the
13171 explanation of the function for details.
13174 All Modula-2 built-in procedures also return a result, described below.
13178 Returns the absolute value of @var{n}.
13181 If @var{c} is a lower case letter, it returns its upper case
13182 equivalent, otherwise it returns its argument.
13185 Returns the character whose ordinal value is @var{i}.
13188 Decrements the value in the variable @var{v} by one. Returns the new value.
13190 @item DEC(@var{v},@var{i})
13191 Decrements the value in the variable @var{v} by @var{i}. Returns the
13194 @item EXCL(@var{m},@var{s})
13195 Removes the element @var{m} from the set @var{s}. Returns the new
13198 @item FLOAT(@var{i})
13199 Returns the floating point equivalent of the integer @var{i}.
13201 @item HIGH(@var{a})
13202 Returns the index of the last member of @var{a}.
13205 Increments the value in the variable @var{v} by one. Returns the new value.
13207 @item INC(@var{v},@var{i})
13208 Increments the value in the variable @var{v} by @var{i}. Returns the
13211 @item INCL(@var{m},@var{s})
13212 Adds the element @var{m} to the set @var{s} if it is not already
13213 there. Returns the new set.
13216 Returns the maximum value of the type @var{t}.
13219 Returns the minimum value of the type @var{t}.
13222 Returns boolean TRUE if @var{i} is an odd number.
13225 Returns the ordinal value of its argument. For example, the ordinal
13226 value of a character is its @sc{ascii} value (on machines supporting the
13227 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13228 integral, character and enumerated types.
13230 @item SIZE(@var{x})
13231 Returns the size of its argument. @var{x} can be a variable or a type.
13233 @item TRUNC(@var{r})
13234 Returns the integral part of @var{r}.
13236 @item TSIZE(@var{x})
13237 Returns the size of its argument. @var{x} can be a variable or a type.
13239 @item VAL(@var{t},@var{i})
13240 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13244 @emph{Warning:} Sets and their operations are not yet supported, so
13245 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13249 @cindex Modula-2 constants
13251 @subsubsection Constants
13253 @value{GDBN} allows you to express the constants of Modula-2 in the following
13259 Integer constants are simply a sequence of digits. When used in an
13260 expression, a constant is interpreted to be type-compatible with the
13261 rest of the expression. Hexadecimal integers are specified by a
13262 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13265 Floating point constants appear as a sequence of digits, followed by a
13266 decimal point and another sequence of digits. An optional exponent can
13267 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13268 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13269 digits of the floating point constant must be valid decimal (base 10)
13273 Character constants consist of a single character enclosed by a pair of
13274 like quotes, either single (@code{'}) or double (@code{"}). They may
13275 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13276 followed by a @samp{C}.
13279 String constants consist of a sequence of characters enclosed by a
13280 pair of like quotes, either single (@code{'}) or double (@code{"}).
13281 Escape sequences in the style of C are also allowed. @xref{C
13282 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13286 Enumerated constants consist of an enumerated identifier.
13289 Boolean constants consist of the identifiers @code{TRUE} and
13293 Pointer constants consist of integral values only.
13296 Set constants are not yet supported.
13300 @subsubsection Modula-2 Types
13301 @cindex Modula-2 types
13303 Currently @value{GDBN} can print the following data types in Modula-2
13304 syntax: array types, record types, set types, pointer types, procedure
13305 types, enumerated types, subrange types and base types. You can also
13306 print the contents of variables declared using these type.
13307 This section gives a number of simple source code examples together with
13308 sample @value{GDBN} sessions.
13310 The first example contains the following section of code:
13319 and you can request @value{GDBN} to interrogate the type and value of
13320 @code{r} and @code{s}.
13323 (@value{GDBP}) print s
13325 (@value{GDBP}) ptype s
13327 (@value{GDBP}) print r
13329 (@value{GDBP}) ptype r
13334 Likewise if your source code declares @code{s} as:
13338 s: SET ['A'..'Z'] ;
13342 then you may query the type of @code{s} by:
13345 (@value{GDBP}) ptype s
13346 type = SET ['A'..'Z']
13350 Note that at present you cannot interactively manipulate set
13351 expressions using the debugger.
13353 The following example shows how you might declare an array in Modula-2
13354 and how you can interact with @value{GDBN} to print its type and contents:
13358 s: ARRAY [-10..10] OF CHAR ;
13362 (@value{GDBP}) ptype s
13363 ARRAY [-10..10] OF CHAR
13366 Note that the array handling is not yet complete and although the type
13367 is printed correctly, expression handling still assumes that all
13368 arrays have a lower bound of zero and not @code{-10} as in the example
13371 Here are some more type related Modula-2 examples:
13375 colour = (blue, red, yellow, green) ;
13376 t = [blue..yellow] ;
13384 The @value{GDBN} interaction shows how you can query the data type
13385 and value of a variable.
13388 (@value{GDBP}) print s
13390 (@value{GDBP}) ptype t
13391 type = [blue..yellow]
13395 In this example a Modula-2 array is declared and its contents
13396 displayed. Observe that the contents are written in the same way as
13397 their @code{C} counterparts.
13401 s: ARRAY [1..5] OF CARDINAL ;
13407 (@value{GDBP}) print s
13408 $1 = @{1, 0, 0, 0, 0@}
13409 (@value{GDBP}) ptype s
13410 type = ARRAY [1..5] OF CARDINAL
13413 The Modula-2 language interface to @value{GDBN} also understands
13414 pointer types as shown in this example:
13418 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
13425 and you can request that @value{GDBN} describes the type of @code{s}.
13428 (@value{GDBP}) ptype s
13429 type = POINTER TO ARRAY [1..5] OF CARDINAL
13432 @value{GDBN} handles compound types as we can see in this example.
13433 Here we combine array types, record types, pointer types and subrange
13444 myarray = ARRAY myrange OF CARDINAL ;
13445 myrange = [-2..2] ;
13447 s: POINTER TO ARRAY myrange OF foo ;
13451 and you can ask @value{GDBN} to describe the type of @code{s} as shown
13455 (@value{GDBP}) ptype s
13456 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
13459 f3 : ARRAY [-2..2] OF CARDINAL;
13464 @subsubsection Modula-2 Defaults
13465 @cindex Modula-2 defaults
13467 If type and range checking are set automatically by @value{GDBN}, they
13468 both default to @code{on} whenever the working language changes to
13469 Modula-2. This happens regardless of whether you or @value{GDBN}
13470 selected the working language.
13472 If you allow @value{GDBN} to set the language automatically, then entering
13473 code compiled from a file whose name ends with @file{.mod} sets the
13474 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
13475 Infer the Source Language}, for further details.
13478 @subsubsection Deviations from Standard Modula-2
13479 @cindex Modula-2, deviations from
13481 A few changes have been made to make Modula-2 programs easier to debug.
13482 This is done primarily via loosening its type strictness:
13486 Unlike in standard Modula-2, pointer constants can be formed by
13487 integers. This allows you to modify pointer variables during
13488 debugging. (In standard Modula-2, the actual address contained in a
13489 pointer variable is hidden from you; it can only be modified
13490 through direct assignment to another pointer variable or expression that
13491 returned a pointer.)
13494 C escape sequences can be used in strings and characters to represent
13495 non-printable characters. @value{GDBN} prints out strings with these
13496 escape sequences embedded. Single non-printable characters are
13497 printed using the @samp{CHR(@var{nnn})} format.
13500 The assignment operator (@code{:=}) returns the value of its right-hand
13504 All built-in procedures both modify @emph{and} return their argument.
13508 @subsubsection Modula-2 Type and Range Checks
13509 @cindex Modula-2 checks
13512 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13515 @c FIXME remove warning when type/range checks added
13517 @value{GDBN} considers two Modula-2 variables type equivalent if:
13521 They are of types that have been declared equivalent via a @code{TYPE
13522 @var{t1} = @var{t2}} statement
13525 They have been declared on the same line. (Note: This is true of the
13526 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13529 As long as type checking is enabled, any attempt to combine variables
13530 whose types are not equivalent is an error.
13532 Range checking is done on all mathematical operations, assignment, array
13533 index bounds, and all built-in functions and procedures.
13536 @subsubsection The Scope Operators @code{::} and @code{.}
13538 @cindex @code{.}, Modula-2 scope operator
13539 @cindex colon, doubled as scope operator
13541 @vindex colon-colon@r{, in Modula-2}
13542 @c Info cannot handle :: but TeX can.
13545 @vindex ::@r{, in Modula-2}
13548 There are a few subtle differences between the Modula-2 scope operator
13549 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13554 @var{module} . @var{id}
13555 @var{scope} :: @var{id}
13559 where @var{scope} is the name of a module or a procedure,
13560 @var{module} the name of a module, and @var{id} is any declared
13561 identifier within your program, except another module.
13563 Using the @code{::} operator makes @value{GDBN} search the scope
13564 specified by @var{scope} for the identifier @var{id}. If it is not
13565 found in the specified scope, then @value{GDBN} searches all scopes
13566 enclosing the one specified by @var{scope}.
13568 Using the @code{.} operator makes @value{GDBN} search the current scope for
13569 the identifier specified by @var{id} that was imported from the
13570 definition module specified by @var{module}. With this operator, it is
13571 an error if the identifier @var{id} was not imported from definition
13572 module @var{module}, or if @var{id} is not an identifier in
13576 @subsubsection @value{GDBN} and Modula-2
13578 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13579 Five subcommands of @code{set print} and @code{show print} apply
13580 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13581 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13582 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13583 analogue in Modula-2.
13585 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13586 with any language, is not useful with Modula-2. Its
13587 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13588 created in Modula-2 as they can in C or C@t{++}. However, because an
13589 address can be specified by an integral constant, the construct
13590 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13592 @cindex @code{#} in Modula-2
13593 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13594 interpreted as the beginning of a comment. Use @code{<>} instead.
13600 The extensions made to @value{GDBN} for Ada only support
13601 output from the @sc{gnu} Ada (GNAT) compiler.
13602 Other Ada compilers are not currently supported, and
13603 attempting to debug executables produced by them is most likely
13607 @cindex expressions in Ada
13609 * Ada Mode Intro:: General remarks on the Ada syntax
13610 and semantics supported by Ada mode
13612 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13613 * Additions to Ada:: Extensions of the Ada expression syntax.
13614 * Stopping Before Main Program:: Debugging the program during elaboration.
13615 * Ada Tasks:: Listing and setting breakpoints in tasks.
13616 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13617 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13619 * Ada Glitches:: Known peculiarities of Ada mode.
13622 @node Ada Mode Intro
13623 @subsubsection Introduction
13624 @cindex Ada mode, general
13626 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13627 syntax, with some extensions.
13628 The philosophy behind the design of this subset is
13632 That @value{GDBN} should provide basic literals and access to operations for
13633 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13634 leaving more sophisticated computations to subprograms written into the
13635 program (which therefore may be called from @value{GDBN}).
13638 That type safety and strict adherence to Ada language restrictions
13639 are not particularly important to the @value{GDBN} user.
13642 That brevity is important to the @value{GDBN} user.
13645 Thus, for brevity, the debugger acts as if all names declared in
13646 user-written packages are directly visible, even if they are not visible
13647 according to Ada rules, thus making it unnecessary to fully qualify most
13648 names with their packages, regardless of context. Where this causes
13649 ambiguity, @value{GDBN} asks the user's intent.
13651 The debugger will start in Ada mode if it detects an Ada main program.
13652 As for other languages, it will enter Ada mode when stopped in a program that
13653 was translated from an Ada source file.
13655 While in Ada mode, you may use `@t{--}' for comments. This is useful
13656 mostly for documenting command files. The standard @value{GDBN} comment
13657 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13658 middle (to allow based literals).
13660 The debugger supports limited overloading. Given a subprogram call in which
13661 the function symbol has multiple definitions, it will use the number of
13662 actual parameters and some information about their types to attempt to narrow
13663 the set of definitions. It also makes very limited use of context, preferring
13664 procedures to functions in the context of the @code{call} command, and
13665 functions to procedures elsewhere.
13667 @node Omissions from Ada
13668 @subsubsection Omissions from Ada
13669 @cindex Ada, omissions from
13671 Here are the notable omissions from the subset:
13675 Only a subset of the attributes are supported:
13679 @t{'First}, @t{'Last}, and @t{'Length}
13680 on array objects (not on types and subtypes).
13683 @t{'Min} and @t{'Max}.
13686 @t{'Pos} and @t{'Val}.
13692 @t{'Range} on array objects (not subtypes), but only as the right
13693 operand of the membership (@code{in}) operator.
13696 @t{'Access}, @t{'Unchecked_Access}, and
13697 @t{'Unrestricted_Access} (a GNAT extension).
13705 @code{Characters.Latin_1} are not available and
13706 concatenation is not implemented. Thus, escape characters in strings are
13707 not currently available.
13710 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13711 equality of representations. They will generally work correctly
13712 for strings and arrays whose elements have integer or enumeration types.
13713 They may not work correctly for arrays whose element
13714 types have user-defined equality, for arrays of real values
13715 (in particular, IEEE-conformant floating point, because of negative
13716 zeroes and NaNs), and for arrays whose elements contain unused bits with
13717 indeterminate values.
13720 The other component-by-component array operations (@code{and}, @code{or},
13721 @code{xor}, @code{not}, and relational tests other than equality)
13722 are not implemented.
13725 @cindex array aggregates (Ada)
13726 @cindex record aggregates (Ada)
13727 @cindex aggregates (Ada)
13728 There is limited support for array and record aggregates. They are
13729 permitted only on the right sides of assignments, as in these examples:
13732 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13733 (@value{GDBP}) set An_Array := (1, others => 0)
13734 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13735 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13736 (@value{GDBP}) set A_Record := (1, "Peter", True);
13737 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13741 discriminant's value by assigning an aggregate has an
13742 undefined effect if that discriminant is used within the record.
13743 However, you can first modify discriminants by directly assigning to
13744 them (which normally would not be allowed in Ada), and then performing an
13745 aggregate assignment. For example, given a variable @code{A_Rec}
13746 declared to have a type such as:
13749 type Rec (Len : Small_Integer := 0) is record
13751 Vals : IntArray (1 .. Len);
13755 you can assign a value with a different size of @code{Vals} with two
13759 (@value{GDBP}) set A_Rec.Len := 4
13760 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13763 As this example also illustrates, @value{GDBN} is very loose about the usual
13764 rules concerning aggregates. You may leave out some of the
13765 components of an array or record aggregate (such as the @code{Len}
13766 component in the assignment to @code{A_Rec} above); they will retain their
13767 original values upon assignment. You may freely use dynamic values as
13768 indices in component associations. You may even use overlapping or
13769 redundant component associations, although which component values are
13770 assigned in such cases is not defined.
13773 Calls to dispatching subprograms are not implemented.
13776 The overloading algorithm is much more limited (i.e., less selective)
13777 than that of real Ada. It makes only limited use of the context in
13778 which a subexpression appears to resolve its meaning, and it is much
13779 looser in its rules for allowing type matches. As a result, some
13780 function calls will be ambiguous, and the user will be asked to choose
13781 the proper resolution.
13784 The @code{new} operator is not implemented.
13787 Entry calls are not implemented.
13790 Aside from printing, arithmetic operations on the native VAX floating-point
13791 formats are not supported.
13794 It is not possible to slice a packed array.
13797 The names @code{True} and @code{False}, when not part of a qualified name,
13798 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13800 Should your program
13801 redefine these names in a package or procedure (at best a dubious practice),
13802 you will have to use fully qualified names to access their new definitions.
13805 @node Additions to Ada
13806 @subsubsection Additions to Ada
13807 @cindex Ada, deviations from
13809 As it does for other languages, @value{GDBN} makes certain generic
13810 extensions to Ada (@pxref{Expressions}):
13814 If the expression @var{E} is a variable residing in memory (typically
13815 a local variable or array element) and @var{N} is a positive integer,
13816 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13817 @var{N}-1 adjacent variables following it in memory as an array. In
13818 Ada, this operator is generally not necessary, since its prime use is
13819 in displaying parts of an array, and slicing will usually do this in
13820 Ada. However, there are occasional uses when debugging programs in
13821 which certain debugging information has been optimized away.
13824 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13825 appears in function or file @var{B}.'' When @var{B} is a file name,
13826 you must typically surround it in single quotes.
13829 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13830 @var{type} that appears at address @var{addr}.''
13833 A name starting with @samp{$} is a convenience variable
13834 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13837 In addition, @value{GDBN} provides a few other shortcuts and outright
13838 additions specific to Ada:
13842 The assignment statement is allowed as an expression, returning
13843 its right-hand operand as its value. Thus, you may enter
13846 (@value{GDBP}) set x := y + 3
13847 (@value{GDBP}) print A(tmp := y + 1)
13851 The semicolon is allowed as an ``operator,'' returning as its value
13852 the value of its right-hand operand.
13853 This allows, for example,
13854 complex conditional breaks:
13857 (@value{GDBP}) break f
13858 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13862 Rather than use catenation and symbolic character names to introduce special
13863 characters into strings, one may instead use a special bracket notation,
13864 which is also used to print strings. A sequence of characters of the form
13865 @samp{["@var{XX}"]} within a string or character literal denotes the
13866 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13867 sequence of characters @samp{["""]} also denotes a single quotation mark
13868 in strings. For example,
13870 "One line.["0a"]Next line.["0a"]"
13873 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13877 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13878 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13882 (@value{GDBP}) print 'max(x, y)
13886 When printing arrays, @value{GDBN} uses positional notation when the
13887 array has a lower bound of 1, and uses a modified named notation otherwise.
13888 For example, a one-dimensional array of three integers with a lower bound
13889 of 3 might print as
13896 That is, in contrast to valid Ada, only the first component has a @code{=>}
13900 You may abbreviate attributes in expressions with any unique,
13901 multi-character subsequence of
13902 their names (an exact match gets preference).
13903 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13904 in place of @t{a'length}.
13907 @cindex quoting Ada internal identifiers
13908 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13909 to lower case. The GNAT compiler uses upper-case characters for
13910 some of its internal identifiers, which are normally of no interest to users.
13911 For the rare occasions when you actually have to look at them,
13912 enclose them in angle brackets to avoid the lower-case mapping.
13915 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13919 Printing an object of class-wide type or dereferencing an
13920 access-to-class-wide value will display all the components of the object's
13921 specific type (as indicated by its run-time tag). Likewise, component
13922 selection on such a value will operate on the specific type of the
13927 @node Stopping Before Main Program
13928 @subsubsection Stopping at the Very Beginning
13930 @cindex breakpointing Ada elaboration code
13931 It is sometimes necessary to debug the program during elaboration, and
13932 before reaching the main procedure.
13933 As defined in the Ada Reference
13934 Manual, the elaboration code is invoked from a procedure called
13935 @code{adainit}. To run your program up to the beginning of
13936 elaboration, simply use the following two commands:
13937 @code{tbreak adainit} and @code{run}.
13940 @subsubsection Extensions for Ada Tasks
13941 @cindex Ada, tasking
13943 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13944 @value{GDBN} provides the following task-related commands:
13949 This command shows a list of current Ada tasks, as in the following example:
13956 (@value{GDBP}) info tasks
13957 ID TID P-ID Pri State Name
13958 1 8088000 0 15 Child Activation Wait main_task
13959 2 80a4000 1 15 Accept Statement b
13960 3 809a800 1 15 Child Activation Wait a
13961 * 4 80ae800 3 15 Runnable c
13966 In this listing, the asterisk before the last task indicates it to be the
13967 task currently being inspected.
13971 Represents @value{GDBN}'s internal task number.
13977 The parent's task ID (@value{GDBN}'s internal task number).
13980 The base priority of the task.
13983 Current state of the task.
13987 The task has been created but has not been activated. It cannot be
13991 The task is not blocked for any reason known to Ada. (It may be waiting
13992 for a mutex, though.) It is conceptually "executing" in normal mode.
13995 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13996 that were waiting on terminate alternatives have been awakened and have
13997 terminated themselves.
13999 @item Child Activation Wait
14000 The task is waiting for created tasks to complete activation.
14002 @item Accept Statement
14003 The task is waiting on an accept or selective wait statement.
14005 @item Waiting on entry call
14006 The task is waiting on an entry call.
14008 @item Async Select Wait
14009 The task is waiting to start the abortable part of an asynchronous
14013 The task is waiting on a select statement with only a delay
14016 @item Child Termination Wait
14017 The task is sleeping having completed a master within itself, and is
14018 waiting for the tasks dependent on that master to become terminated or
14019 waiting on a terminate Phase.
14021 @item Wait Child in Term Alt
14022 The task is sleeping waiting for tasks on terminate alternatives to
14023 finish terminating.
14025 @item Accepting RV with @var{taskno}
14026 The task is accepting a rendez-vous with the task @var{taskno}.
14030 Name of the task in the program.
14034 @kindex info task @var{taskno}
14035 @item info task @var{taskno}
14036 This command shows detailled informations on the specified task, as in
14037 the following example:
14042 (@value{GDBP}) info tasks
14043 ID TID P-ID Pri State Name
14044 1 8077880 0 15 Child Activation Wait main_task
14045 * 2 807c468 1 15 Runnable task_1
14046 (@value{GDBP}) info task 2
14047 Ada Task: 0x807c468
14050 Parent: 1 (main_task)
14056 @kindex task@r{ (Ada)}
14057 @cindex current Ada task ID
14058 This command prints the ID of the current task.
14064 (@value{GDBP}) info tasks
14065 ID TID P-ID Pri State Name
14066 1 8077870 0 15 Child Activation Wait main_task
14067 * 2 807c458 1 15 Runnable t
14068 (@value{GDBP}) task
14069 [Current task is 2]
14072 @item task @var{taskno}
14073 @cindex Ada task switching
14074 This command is like the @code{thread @var{threadno}}
14075 command (@pxref{Threads}). It switches the context of debugging
14076 from the current task to the given task.
14082 (@value{GDBP}) info tasks
14083 ID TID P-ID Pri State Name
14084 1 8077870 0 15 Child Activation Wait main_task
14085 * 2 807c458 1 15 Runnable t
14086 (@value{GDBP}) task 1
14087 [Switching to task 1]
14088 #0 0x8067726 in pthread_cond_wait ()
14090 #0 0x8067726 in pthread_cond_wait ()
14091 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14092 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14093 #3 0x806153e in system.tasking.stages.activate_tasks ()
14094 #4 0x804aacc in un () at un.adb:5
14097 @item break @var{linespec} task @var{taskno}
14098 @itemx break @var{linespec} task @var{taskno} if @dots{}
14099 @cindex breakpoints and tasks, in Ada
14100 @cindex task breakpoints, in Ada
14101 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14102 These commands are like the @code{break @dots{} thread @dots{}}
14103 command (@pxref{Thread Stops}).
14104 @var{linespec} specifies source lines, as described
14105 in @ref{Specify Location}.
14107 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14108 to specify that you only want @value{GDBN} to stop the program when a
14109 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14110 numeric task identifiers assigned by @value{GDBN}, shown in the first
14111 column of the @samp{info tasks} display.
14113 If you do not specify @samp{task @var{taskno}} when you set a
14114 breakpoint, the breakpoint applies to @emph{all} tasks of your
14117 You can use the @code{task} qualifier on conditional breakpoints as
14118 well; in this case, place @samp{task @var{taskno}} before the
14119 breakpoint condition (before the @code{if}).
14127 (@value{GDBP}) info tasks
14128 ID TID P-ID Pri State Name
14129 1 140022020 0 15 Child Activation Wait main_task
14130 2 140045060 1 15 Accept/Select Wait t2
14131 3 140044840 1 15 Runnable t1
14132 * 4 140056040 1 15 Runnable t3
14133 (@value{GDBP}) b 15 task 2
14134 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14135 (@value{GDBP}) cont
14140 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14142 (@value{GDBP}) info tasks
14143 ID TID P-ID Pri State Name
14144 1 140022020 0 15 Child Activation Wait main_task
14145 * 2 140045060 1 15 Runnable t2
14146 3 140044840 1 15 Runnable t1
14147 4 140056040 1 15 Delay Sleep t3
14151 @node Ada Tasks and Core Files
14152 @subsubsection Tasking Support when Debugging Core Files
14153 @cindex Ada tasking and core file debugging
14155 When inspecting a core file, as opposed to debugging a live program,
14156 tasking support may be limited or even unavailable, depending on
14157 the platform being used.
14158 For instance, on x86-linux, the list of tasks is available, but task
14159 switching is not supported. On Tru64, however, task switching will work
14162 On certain platforms, including Tru64, the debugger needs to perform some
14163 memory writes in order to provide Ada tasking support. When inspecting
14164 a core file, this means that the core file must be opened with read-write
14165 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14166 Under these circumstances, you should make a backup copy of the core
14167 file before inspecting it with @value{GDBN}.
14169 @node Ravenscar Profile
14170 @subsubsection Tasking Support when using the Ravenscar Profile
14171 @cindex Ravenscar Profile
14173 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14174 specifically designed for systems with safety-critical real-time
14178 @kindex set ravenscar task-switching on
14179 @cindex task switching with program using Ravenscar Profile
14180 @item set ravenscar task-switching on
14181 Allows task switching when debugging a program that uses the Ravenscar
14182 Profile. This is the default.
14184 @kindex set ravenscar task-switching off
14185 @item set ravenscar task-switching off
14186 Turn off task switching when debugging a program that uses the Ravenscar
14187 Profile. This is mostly intended to disable the code that adds support
14188 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14189 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14190 To be effective, this command should be run before the program is started.
14192 @kindex show ravenscar task-switching
14193 @item show ravenscar task-switching
14194 Show whether it is possible to switch from task to task in a program
14195 using the Ravenscar Profile.
14200 @subsubsection Known Peculiarities of Ada Mode
14201 @cindex Ada, problems
14203 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14204 we know of several problems with and limitations of Ada mode in
14206 some of which will be fixed with planned future releases of the debugger
14207 and the GNU Ada compiler.
14211 Static constants that the compiler chooses not to materialize as objects in
14212 storage are invisible to the debugger.
14215 Named parameter associations in function argument lists are ignored (the
14216 argument lists are treated as positional).
14219 Many useful library packages are currently invisible to the debugger.
14222 Fixed-point arithmetic, conversions, input, and output is carried out using
14223 floating-point arithmetic, and may give results that only approximate those on
14227 The GNAT compiler never generates the prefix @code{Standard} for any of
14228 the standard symbols defined by the Ada language. @value{GDBN} knows about
14229 this: it will strip the prefix from names when you use it, and will never
14230 look for a name you have so qualified among local symbols, nor match against
14231 symbols in other packages or subprograms. If you have
14232 defined entities anywhere in your program other than parameters and
14233 local variables whose simple names match names in @code{Standard},
14234 GNAT's lack of qualification here can cause confusion. When this happens,
14235 you can usually resolve the confusion
14236 by qualifying the problematic names with package
14237 @code{Standard} explicitly.
14240 Older versions of the compiler sometimes generate erroneous debugging
14241 information, resulting in the debugger incorrectly printing the value
14242 of affected entities. In some cases, the debugger is able to work
14243 around an issue automatically. In other cases, the debugger is able
14244 to work around the issue, but the work-around has to be specifically
14247 @kindex set ada trust-PAD-over-XVS
14248 @kindex show ada trust-PAD-over-XVS
14251 @item set ada trust-PAD-over-XVS on
14252 Configure GDB to strictly follow the GNAT encoding when computing the
14253 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14254 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14255 a complete description of the encoding used by the GNAT compiler).
14256 This is the default.
14258 @item set ada trust-PAD-over-XVS off
14259 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14260 sometimes prints the wrong value for certain entities, changing @code{ada
14261 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14262 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14263 @code{off}, but this incurs a slight performance penalty, so it is
14264 recommended to leave this setting to @code{on} unless necessary.
14268 @node Unsupported Languages
14269 @section Unsupported Languages
14271 @cindex unsupported languages
14272 @cindex minimal language
14273 In addition to the other fully-supported programming languages,
14274 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14275 It does not represent a real programming language, but provides a set
14276 of capabilities close to what the C or assembly languages provide.
14277 This should allow most simple operations to be performed while debugging
14278 an application that uses a language currently not supported by @value{GDBN}.
14280 If the language is set to @code{auto}, @value{GDBN} will automatically
14281 select this language if the current frame corresponds to an unsupported
14285 @chapter Examining the Symbol Table
14287 The commands described in this chapter allow you to inquire about the
14288 symbols (names of variables, functions and types) defined in your
14289 program. This information is inherent in the text of your program and
14290 does not change as your program executes. @value{GDBN} finds it in your
14291 program's symbol table, in the file indicated when you started @value{GDBN}
14292 (@pxref{File Options, ,Choosing Files}), or by one of the
14293 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14295 @cindex symbol names
14296 @cindex names of symbols
14297 @cindex quoting names
14298 Occasionally, you may need to refer to symbols that contain unusual
14299 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14300 most frequent case is in referring to static variables in other
14301 source files (@pxref{Variables,,Program Variables}). File names
14302 are recorded in object files as debugging symbols, but @value{GDBN} would
14303 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14304 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14305 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14312 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14315 @cindex case-insensitive symbol names
14316 @cindex case sensitivity in symbol names
14317 @kindex set case-sensitive
14318 @item set case-sensitive on
14319 @itemx set case-sensitive off
14320 @itemx set case-sensitive auto
14321 Normally, when @value{GDBN} looks up symbols, it matches their names
14322 with case sensitivity determined by the current source language.
14323 Occasionally, you may wish to control that. The command @code{set
14324 case-sensitive} lets you do that by specifying @code{on} for
14325 case-sensitive matches or @code{off} for case-insensitive ones. If
14326 you specify @code{auto}, case sensitivity is reset to the default
14327 suitable for the source language. The default is case-sensitive
14328 matches for all languages except for Fortran, for which the default is
14329 case-insensitive matches.
14331 @kindex show case-sensitive
14332 @item show case-sensitive
14333 This command shows the current setting of case sensitivity for symbols
14336 @kindex info address
14337 @cindex address of a symbol
14338 @item info address @var{symbol}
14339 Describe where the data for @var{symbol} is stored. For a register
14340 variable, this says which register it is kept in. For a non-register
14341 local variable, this prints the stack-frame offset at which the variable
14344 Note the contrast with @samp{print &@var{symbol}}, which does not work
14345 at all for a register variable, and for a stack local variable prints
14346 the exact address of the current instantiation of the variable.
14348 @kindex info symbol
14349 @cindex symbol from address
14350 @cindex closest symbol and offset for an address
14351 @item info symbol @var{addr}
14352 Print the name of a symbol which is stored at the address @var{addr}.
14353 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
14354 nearest symbol and an offset from it:
14357 (@value{GDBP}) info symbol 0x54320
14358 _initialize_vx + 396 in section .text
14362 This is the opposite of the @code{info address} command. You can use
14363 it to find out the name of a variable or a function given its address.
14365 For dynamically linked executables, the name of executable or shared
14366 library containing the symbol is also printed:
14369 (@value{GDBP}) info symbol 0x400225
14370 _start + 5 in section .text of /tmp/a.out
14371 (@value{GDBP}) info symbol 0x2aaaac2811cf
14372 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
14376 @item whatis [@var{arg}]
14377 Print the data type of @var{arg}, which can be either an expression
14378 or a name of a data type. With no argument, print the data type of
14379 @code{$}, the last value in the value history.
14381 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
14382 is not actually evaluated, and any side-effecting operations (such as
14383 assignments or function calls) inside it do not take place.
14385 If @var{arg} is a variable or an expression, @code{whatis} prints its
14386 literal type as it is used in the source code. If the type was
14387 defined using a @code{typedef}, @code{whatis} will @emph{not} print
14388 the data type underlying the @code{typedef}. If the type of the
14389 variable or the expression is a compound data type, such as
14390 @code{struct} or @code{class}, @code{whatis} never prints their
14391 fields or methods. It just prints the @code{struct}/@code{class}
14392 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
14393 such a compound data type, use @code{ptype}.
14395 If @var{arg} is a type name that was defined using @code{typedef},
14396 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
14397 Unrolling means that @code{whatis} will show the underlying type used
14398 in the @code{typedef} declaration of @var{arg}. However, if that
14399 underlying type is also a @code{typedef}, @code{whatis} will not
14402 For C code, the type names may also have the form @samp{class
14403 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
14404 @var{union-tag}} or @samp{enum @var{enum-tag}}.
14407 @item ptype [@var{arg}]
14408 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
14409 detailed description of the type, instead of just the name of the type.
14410 @xref{Expressions, ,Expressions}.
14412 Contrary to @code{whatis}, @code{ptype} always unrolls any
14413 @code{typedef}s in its argument declaration, whether the argument is
14414 a variable, expression, or a data type. This means that @code{ptype}
14415 of a variable or an expression will not print literally its type as
14416 present in the source code---use @code{whatis} for that. @code{typedef}s at
14417 the pointer or reference targets are also unrolled. Only @code{typedef}s of
14418 fields, methods and inner @code{class typedef}s of @code{struct}s,
14419 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
14421 For example, for this variable declaration:
14424 typedef double real_t;
14425 struct complex @{ real_t real; double imag; @};
14426 typedef struct complex complex_t;
14428 real_t *real_pointer_var;
14432 the two commands give this output:
14436 (@value{GDBP}) whatis var
14438 (@value{GDBP}) ptype var
14439 type = struct complex @{
14443 (@value{GDBP}) whatis complex_t
14444 type = struct complex
14445 (@value{GDBP}) whatis struct complex
14446 type = struct complex
14447 (@value{GDBP}) ptype struct complex
14448 type = struct complex @{
14452 (@value{GDBP}) whatis real_pointer_var
14454 (@value{GDBP}) ptype real_pointer_var
14460 As with @code{whatis}, using @code{ptype} without an argument refers to
14461 the type of @code{$}, the last value in the value history.
14463 @cindex incomplete type
14464 Sometimes, programs use opaque data types or incomplete specifications
14465 of complex data structure. If the debug information included in the
14466 program does not allow @value{GDBN} to display a full declaration of
14467 the data type, it will say @samp{<incomplete type>}. For example,
14468 given these declarations:
14472 struct foo *fooptr;
14476 but no definition for @code{struct foo} itself, @value{GDBN} will say:
14479 (@value{GDBP}) ptype foo
14480 $1 = <incomplete type>
14484 ``Incomplete type'' is C terminology for data types that are not
14485 completely specified.
14488 @item info types @var{regexp}
14490 Print a brief description of all types whose names match the regular
14491 expression @var{regexp} (or all types in your program, if you supply
14492 no argument). Each complete typename is matched as though it were a
14493 complete line; thus, @samp{i type value} gives information on all
14494 types in your program whose names include the string @code{value}, but
14495 @samp{i type ^value$} gives information only on types whose complete
14496 name is @code{value}.
14498 This command differs from @code{ptype} in two ways: first, like
14499 @code{whatis}, it does not print a detailed description; second, it
14500 lists all source files where a type is defined.
14503 @cindex local variables
14504 @item info scope @var{location}
14505 List all the variables local to a particular scope. This command
14506 accepts a @var{location} argument---a function name, a source line, or
14507 an address preceded by a @samp{*}, and prints all the variables local
14508 to the scope defined by that location. (@xref{Specify Location}, for
14509 details about supported forms of @var{location}.) For example:
14512 (@value{GDBP}) @b{info scope command_line_handler}
14513 Scope for command_line_handler:
14514 Symbol rl is an argument at stack/frame offset 8, length 4.
14515 Symbol linebuffer is in static storage at address 0x150a18, length 4.
14516 Symbol linelength is in static storage at address 0x150a1c, length 4.
14517 Symbol p is a local variable in register $esi, length 4.
14518 Symbol p1 is a local variable in register $ebx, length 4.
14519 Symbol nline is a local variable in register $edx, length 4.
14520 Symbol repeat is a local variable at frame offset -8, length 4.
14524 This command is especially useful for determining what data to collect
14525 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14528 @kindex info source
14530 Show information about the current source file---that is, the source file for
14531 the function containing the current point of execution:
14534 the name of the source file, and the directory containing it,
14536 the directory it was compiled in,
14538 its length, in lines,
14540 which programming language it is written in,
14542 whether the executable includes debugging information for that file, and
14543 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14545 whether the debugging information includes information about
14546 preprocessor macros.
14550 @kindex info sources
14552 Print the names of all source files in your program for which there is
14553 debugging information, organized into two lists: files whose symbols
14554 have already been read, and files whose symbols will be read when needed.
14556 @kindex info functions
14557 @item info functions
14558 Print the names and data types of all defined functions.
14560 @item info functions @var{regexp}
14561 Print the names and data types of all defined functions
14562 whose names contain a match for regular expression @var{regexp}.
14563 Thus, @samp{info fun step} finds all functions whose names
14564 include @code{step}; @samp{info fun ^step} finds those whose names
14565 start with @code{step}. If a function name contains characters
14566 that conflict with the regular expression language (e.g.@:
14567 @samp{operator*()}), they may be quoted with a backslash.
14569 @kindex info variables
14570 @item info variables
14571 Print the names and data types of all variables that are defined
14572 outside of functions (i.e.@: excluding local variables).
14574 @item info variables @var{regexp}
14575 Print the names and data types of all variables (except for local
14576 variables) whose names contain a match for regular expression
14579 @kindex info classes
14580 @cindex Objective-C, classes and selectors
14582 @itemx info classes @var{regexp}
14583 Display all Objective-C classes in your program, or
14584 (with the @var{regexp} argument) all those matching a particular regular
14587 @kindex info selectors
14588 @item info selectors
14589 @itemx info selectors @var{regexp}
14590 Display all Objective-C selectors in your program, or
14591 (with the @var{regexp} argument) all those matching a particular regular
14595 This was never implemented.
14596 @kindex info methods
14598 @itemx info methods @var{regexp}
14599 The @code{info methods} command permits the user to examine all defined
14600 methods within C@t{++} program, or (with the @var{regexp} argument) a
14601 specific set of methods found in the various C@t{++} classes. Many
14602 C@t{++} classes provide a large number of methods. Thus, the output
14603 from the @code{ptype} command can be overwhelming and hard to use. The
14604 @code{info-methods} command filters the methods, printing only those
14605 which match the regular-expression @var{regexp}.
14608 @cindex reloading symbols
14609 Some systems allow individual object files that make up your program to
14610 be replaced without stopping and restarting your program. For example,
14611 in VxWorks you can simply recompile a defective object file and keep on
14612 running. If you are running on one of these systems, you can allow
14613 @value{GDBN} to reload the symbols for automatically relinked modules:
14616 @kindex set symbol-reloading
14617 @item set symbol-reloading on
14618 Replace symbol definitions for the corresponding source file when an
14619 object file with a particular name is seen again.
14621 @item set symbol-reloading off
14622 Do not replace symbol definitions when encountering object files of the
14623 same name more than once. This is the default state; if you are not
14624 running on a system that permits automatic relinking of modules, you
14625 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14626 may discard symbols when linking large programs, that may contain
14627 several modules (from different directories or libraries) with the same
14630 @kindex show symbol-reloading
14631 @item show symbol-reloading
14632 Show the current @code{on} or @code{off} setting.
14635 @cindex opaque data types
14636 @kindex set opaque-type-resolution
14637 @item set opaque-type-resolution on
14638 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14639 declared as a pointer to a @code{struct}, @code{class}, or
14640 @code{union}---for example, @code{struct MyType *}---that is used in one
14641 source file although the full declaration of @code{struct MyType} is in
14642 another source file. The default is on.
14644 A change in the setting of this subcommand will not take effect until
14645 the next time symbols for a file are loaded.
14647 @item set opaque-type-resolution off
14648 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14649 is printed as follows:
14651 @{<no data fields>@}
14654 @kindex show opaque-type-resolution
14655 @item show opaque-type-resolution
14656 Show whether opaque types are resolved or not.
14658 @kindex maint print symbols
14659 @cindex symbol dump
14660 @kindex maint print psymbols
14661 @cindex partial symbol dump
14662 @item maint print symbols @var{filename}
14663 @itemx maint print psymbols @var{filename}
14664 @itemx maint print msymbols @var{filename}
14665 Write a dump of debugging symbol data into the file @var{filename}.
14666 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14667 symbols with debugging data are included. If you use @samp{maint print
14668 symbols}, @value{GDBN} includes all the symbols for which it has already
14669 collected full details: that is, @var{filename} reflects symbols for
14670 only those files whose symbols @value{GDBN} has read. You can use the
14671 command @code{info sources} to find out which files these are. If you
14672 use @samp{maint print psymbols} instead, the dump shows information about
14673 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14674 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14675 @samp{maint print msymbols} dumps just the minimal symbol information
14676 required for each object file from which @value{GDBN} has read some symbols.
14677 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14678 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14680 @kindex maint info symtabs
14681 @kindex maint info psymtabs
14682 @cindex listing @value{GDBN}'s internal symbol tables
14683 @cindex symbol tables, listing @value{GDBN}'s internal
14684 @cindex full symbol tables, listing @value{GDBN}'s internal
14685 @cindex partial symbol tables, listing @value{GDBN}'s internal
14686 @item maint info symtabs @r{[} @var{regexp} @r{]}
14687 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14689 List the @code{struct symtab} or @code{struct partial_symtab}
14690 structures whose names match @var{regexp}. If @var{regexp} is not
14691 given, list them all. The output includes expressions which you can
14692 copy into a @value{GDBN} debugging this one to examine a particular
14693 structure in more detail. For example:
14696 (@value{GDBP}) maint info psymtabs dwarf2read
14697 @{ objfile /home/gnu/build/gdb/gdb
14698 ((struct objfile *) 0x82e69d0)
14699 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14700 ((struct partial_symtab *) 0x8474b10)
14703 text addresses 0x814d3c8 -- 0x8158074
14704 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14705 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14706 dependencies (none)
14709 (@value{GDBP}) maint info symtabs
14713 We see that there is one partial symbol table whose filename contains
14714 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14715 and we see that @value{GDBN} has not read in any symtabs yet at all.
14716 If we set a breakpoint on a function, that will cause @value{GDBN} to
14717 read the symtab for the compilation unit containing that function:
14720 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14721 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14723 (@value{GDBP}) maint info symtabs
14724 @{ objfile /home/gnu/build/gdb/gdb
14725 ((struct objfile *) 0x82e69d0)
14726 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14727 ((struct symtab *) 0x86c1f38)
14730 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14731 linetable ((struct linetable *) 0x8370fa0)
14732 debugformat DWARF 2
14741 @chapter Altering Execution
14743 Once you think you have found an error in your program, you might want to
14744 find out for certain whether correcting the apparent error would lead to
14745 correct results in the rest of the run. You can find the answer by
14746 experiment, using the @value{GDBN} features for altering execution of the
14749 For example, you can store new values into variables or memory
14750 locations, give your program a signal, restart it at a different
14751 address, or even return prematurely from a function.
14754 * Assignment:: Assignment to variables
14755 * Jumping:: Continuing at a different address
14756 * Signaling:: Giving your program a signal
14757 * Returning:: Returning from a function
14758 * Calling:: Calling your program's functions
14759 * Patching:: Patching your program
14763 @section Assignment to Variables
14766 @cindex setting variables
14767 To alter the value of a variable, evaluate an assignment expression.
14768 @xref{Expressions, ,Expressions}. For example,
14775 stores the value 4 into the variable @code{x}, and then prints the
14776 value of the assignment expression (which is 4).
14777 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14778 information on operators in supported languages.
14780 @kindex set variable
14781 @cindex variables, setting
14782 If you are not interested in seeing the value of the assignment, use the
14783 @code{set} command instead of the @code{print} command. @code{set} is
14784 really the same as @code{print} except that the expression's value is
14785 not printed and is not put in the value history (@pxref{Value History,
14786 ,Value History}). The expression is evaluated only for its effects.
14788 If the beginning of the argument string of the @code{set} command
14789 appears identical to a @code{set} subcommand, use the @code{set
14790 variable} command instead of just @code{set}. This command is identical
14791 to @code{set} except for its lack of subcommands. For example, if your
14792 program has a variable @code{width}, you get an error if you try to set
14793 a new value with just @samp{set width=13}, because @value{GDBN} has the
14794 command @code{set width}:
14797 (@value{GDBP}) whatis width
14799 (@value{GDBP}) p width
14801 (@value{GDBP}) set width=47
14802 Invalid syntax in expression.
14806 The invalid expression, of course, is @samp{=47}. In
14807 order to actually set the program's variable @code{width}, use
14810 (@value{GDBP}) set var width=47
14813 Because the @code{set} command has many subcommands that can conflict
14814 with the names of program variables, it is a good idea to use the
14815 @code{set variable} command instead of just @code{set}. For example, if
14816 your program has a variable @code{g}, you run into problems if you try
14817 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14818 the command @code{set gnutarget}, abbreviated @code{set g}:
14822 (@value{GDBP}) whatis g
14826 (@value{GDBP}) set g=4
14830 The program being debugged has been started already.
14831 Start it from the beginning? (y or n) y
14832 Starting program: /home/smith/cc_progs/a.out
14833 "/home/smith/cc_progs/a.out": can't open to read symbols:
14834 Invalid bfd target.
14835 (@value{GDBP}) show g
14836 The current BFD target is "=4".
14841 The program variable @code{g} did not change, and you silently set the
14842 @code{gnutarget} to an invalid value. In order to set the variable
14846 (@value{GDBP}) set var g=4
14849 @value{GDBN} allows more implicit conversions in assignments than C; you can
14850 freely store an integer value into a pointer variable or vice versa,
14851 and you can convert any structure to any other structure that is the
14852 same length or shorter.
14853 @comment FIXME: how do structs align/pad in these conversions?
14854 @comment /doc@cygnus.com 18dec1990
14856 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14857 construct to generate a value of specified type at a specified address
14858 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14859 to memory location @code{0x83040} as an integer (which implies a certain size
14860 and representation in memory), and
14863 set @{int@}0x83040 = 4
14867 stores the value 4 into that memory location.
14870 @section Continuing at a Different Address
14872 Ordinarily, when you continue your program, you do so at the place where
14873 it stopped, with the @code{continue} command. You can instead continue at
14874 an address of your own choosing, with the following commands:
14878 @item jump @var{linespec}
14879 @itemx jump @var{location}
14880 Resume execution at line @var{linespec} or at address given by
14881 @var{location}. Execution stops again immediately if there is a
14882 breakpoint there. @xref{Specify Location}, for a description of the
14883 different forms of @var{linespec} and @var{location}. It is common
14884 practice to use the @code{tbreak} command in conjunction with
14885 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14887 The @code{jump} command does not change the current stack frame, or
14888 the stack pointer, or the contents of any memory location or any
14889 register other than the program counter. If line @var{linespec} is in
14890 a different function from the one currently executing, the results may
14891 be bizarre if the two functions expect different patterns of arguments or
14892 of local variables. For this reason, the @code{jump} command requests
14893 confirmation if the specified line is not in the function currently
14894 executing. However, even bizarre results are predictable if you are
14895 well acquainted with the machine-language code of your program.
14898 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14899 On many systems, you can get much the same effect as the @code{jump}
14900 command by storing a new value into the register @code{$pc}. The
14901 difference is that this does not start your program running; it only
14902 changes the address of where it @emph{will} run when you continue. For
14910 makes the next @code{continue} command or stepping command execute at
14911 address @code{0x485}, rather than at the address where your program stopped.
14912 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14914 The most common occasion to use the @code{jump} command is to back
14915 up---perhaps with more breakpoints set---over a portion of a program
14916 that has already executed, in order to examine its execution in more
14921 @section Giving your Program a Signal
14922 @cindex deliver a signal to a program
14926 @item signal @var{signal}
14927 Resume execution where your program stopped, but immediately give it the
14928 signal @var{signal}. @var{signal} can be the name or the number of a
14929 signal. For example, on many systems @code{signal 2} and @code{signal
14930 SIGINT} are both ways of sending an interrupt signal.
14932 Alternatively, if @var{signal} is zero, continue execution without
14933 giving a signal. This is useful when your program stopped on account of
14934 a signal and would ordinary see the signal when resumed with the
14935 @code{continue} command; @samp{signal 0} causes it to resume without a
14938 @code{signal} does not repeat when you press @key{RET} a second time
14939 after executing the command.
14943 Invoking the @code{signal} command is not the same as invoking the
14944 @code{kill} utility from the shell. Sending a signal with @code{kill}
14945 causes @value{GDBN} to decide what to do with the signal depending on
14946 the signal handling tables (@pxref{Signals}). The @code{signal} command
14947 passes the signal directly to your program.
14951 @section Returning from a Function
14954 @cindex returning from a function
14957 @itemx return @var{expression}
14958 You can cancel execution of a function call with the @code{return}
14959 command. If you give an
14960 @var{expression} argument, its value is used as the function's return
14964 When you use @code{return}, @value{GDBN} discards the selected stack frame
14965 (and all frames within it). You can think of this as making the
14966 discarded frame return prematurely. If you wish to specify a value to
14967 be returned, give that value as the argument to @code{return}.
14969 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14970 Frame}), and any other frames inside of it, leaving its caller as the
14971 innermost remaining frame. That frame becomes selected. The
14972 specified value is stored in the registers used for returning values
14975 The @code{return} command does not resume execution; it leaves the
14976 program stopped in the state that would exist if the function had just
14977 returned. In contrast, the @code{finish} command (@pxref{Continuing
14978 and Stepping, ,Continuing and Stepping}) resumes execution until the
14979 selected stack frame returns naturally.
14981 @value{GDBN} needs to know how the @var{expression} argument should be set for
14982 the inferior. The concrete registers assignment depends on the OS ABI and the
14983 type being returned by the selected stack frame. For example it is common for
14984 OS ABI to return floating point values in FPU registers while integer values in
14985 CPU registers. Still some ABIs return even floating point values in CPU
14986 registers. Larger integer widths (such as @code{long long int}) also have
14987 specific placement rules. @value{GDBN} already knows the OS ABI from its
14988 current target so it needs to find out also the type being returned to make the
14989 assignment into the right register(s).
14991 Normally, the selected stack frame has debug info. @value{GDBN} will always
14992 use the debug info instead of the implicit type of @var{expression} when the
14993 debug info is available. For example, if you type @kbd{return -1}, and the
14994 function in the current stack frame is declared to return a @code{long long
14995 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14996 into a @code{long long int}:
14999 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15001 (@value{GDBP}) return -1
15002 Make func return now? (y or n) y
15003 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15004 43 printf ("result=%lld\n", func ());
15008 However, if the selected stack frame does not have a debug info, e.g., if the
15009 function was compiled without debug info, @value{GDBN} has to find out the type
15010 to return from user. Specifying a different type by mistake may set the value
15011 in different inferior registers than the caller code expects. For example,
15012 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15013 of a @code{long long int} result for a debug info less function (on 32-bit
15014 architectures). Therefore the user is required to specify the return type by
15015 an appropriate cast explicitly:
15018 Breakpoint 2, 0x0040050b in func ()
15019 (@value{GDBP}) return -1
15020 Return value type not available for selected stack frame.
15021 Please use an explicit cast of the value to return.
15022 (@value{GDBP}) return (long long int) -1
15023 Make selected stack frame return now? (y or n) y
15024 #0 0x00400526 in main ()
15029 @section Calling Program Functions
15032 @cindex calling functions
15033 @cindex inferior functions, calling
15034 @item print @var{expr}
15035 Evaluate the expression @var{expr} and display the resulting value.
15036 @var{expr} may include calls to functions in the program being
15040 @item call @var{expr}
15041 Evaluate the expression @var{expr} without displaying @code{void}
15044 You can use this variant of the @code{print} command if you want to
15045 execute a function from your program that does not return anything
15046 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15047 with @code{void} returned values that @value{GDBN} will otherwise
15048 print. If the result is not void, it is printed and saved in the
15052 It is possible for the function you call via the @code{print} or
15053 @code{call} command to generate a signal (e.g., if there's a bug in
15054 the function, or if you passed it incorrect arguments). What happens
15055 in that case is controlled by the @code{set unwindonsignal} command.
15057 Similarly, with a C@t{++} program it is possible for the function you
15058 call via the @code{print} or @code{call} command to generate an
15059 exception that is not handled due to the constraints of the dummy
15060 frame. In this case, any exception that is raised in the frame, but has
15061 an out-of-frame exception handler will not be found. GDB builds a
15062 dummy-frame for the inferior function call, and the unwinder cannot
15063 seek for exception handlers outside of this dummy-frame. What happens
15064 in that case is controlled by the
15065 @code{set unwind-on-terminating-exception} command.
15068 @item set unwindonsignal
15069 @kindex set unwindonsignal
15070 @cindex unwind stack in called functions
15071 @cindex call dummy stack unwinding
15072 Set unwinding of the stack if a signal is received while in a function
15073 that @value{GDBN} called in the program being debugged. If set to on,
15074 @value{GDBN} unwinds the stack it created for the call and restores
15075 the context to what it was before the call. If set to off (the
15076 default), @value{GDBN} stops in the frame where the signal was
15079 @item show unwindonsignal
15080 @kindex show unwindonsignal
15081 Show the current setting of stack unwinding in the functions called by
15084 @item set unwind-on-terminating-exception
15085 @kindex set unwind-on-terminating-exception
15086 @cindex unwind stack in called functions with unhandled exceptions
15087 @cindex call dummy stack unwinding on unhandled exception.
15088 Set unwinding of the stack if a C@t{++} exception is raised, but left
15089 unhandled while in a function that @value{GDBN} called in the program being
15090 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15091 it created for the call and restores the context to what it was before
15092 the call. If set to off, @value{GDBN} the exception is delivered to
15093 the default C@t{++} exception handler and the inferior terminated.
15095 @item show unwind-on-terminating-exception
15096 @kindex show unwind-on-terminating-exception
15097 Show the current setting of stack unwinding in the functions called by
15102 @cindex weak alias functions
15103 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15104 for another function. In such case, @value{GDBN} might not pick up
15105 the type information, including the types of the function arguments,
15106 which causes @value{GDBN} to call the inferior function incorrectly.
15107 As a result, the called function will function erroneously and may
15108 even crash. A solution to that is to use the name of the aliased
15112 @section Patching Programs
15114 @cindex patching binaries
15115 @cindex writing into executables
15116 @cindex writing into corefiles
15118 By default, @value{GDBN} opens the file containing your program's
15119 executable code (or the corefile) read-only. This prevents accidental
15120 alterations to machine code; but it also prevents you from intentionally
15121 patching your program's binary.
15123 If you'd like to be able to patch the binary, you can specify that
15124 explicitly with the @code{set write} command. For example, you might
15125 want to turn on internal debugging flags, or even to make emergency
15131 @itemx set write off
15132 If you specify @samp{set write on}, @value{GDBN} opens executable and
15133 core files for both reading and writing; if you specify @kbd{set write
15134 off} (the default), @value{GDBN} opens them read-only.
15136 If you have already loaded a file, you must load it again (using the
15137 @code{exec-file} or @code{core-file} command) after changing @code{set
15138 write}, for your new setting to take effect.
15142 Display whether executable files and core files are opened for writing
15143 as well as reading.
15147 @chapter @value{GDBN} Files
15149 @value{GDBN} needs to know the file name of the program to be debugged,
15150 both in order to read its symbol table and in order to start your
15151 program. To debug a core dump of a previous run, you must also tell
15152 @value{GDBN} the name of the core dump file.
15155 * Files:: Commands to specify files
15156 * Separate Debug Files:: Debugging information in separate files
15157 * Index Files:: Index files speed up GDB
15158 * Symbol Errors:: Errors reading symbol files
15159 * Data Files:: GDB data files
15163 @section Commands to Specify Files
15165 @cindex symbol table
15166 @cindex core dump file
15168 You may want to specify executable and core dump file names. The usual
15169 way to do this is at start-up time, using the arguments to
15170 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15171 Out of @value{GDBN}}).
15173 Occasionally it is necessary to change to a different file during a
15174 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15175 specify a file you want to use. Or you are debugging a remote target
15176 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15177 Program}). In these situations the @value{GDBN} commands to specify
15178 new files are useful.
15181 @cindex executable file
15183 @item file @var{filename}
15184 Use @var{filename} as the program to be debugged. It is read for its
15185 symbols and for the contents of pure memory. It is also the program
15186 executed when you use the @code{run} command. If you do not specify a
15187 directory and the file is not found in the @value{GDBN} working directory,
15188 @value{GDBN} uses the environment variable @code{PATH} as a list of
15189 directories to search, just as the shell does when looking for a program
15190 to run. You can change the value of this variable, for both @value{GDBN}
15191 and your program, using the @code{path} command.
15193 @cindex unlinked object files
15194 @cindex patching object files
15195 You can load unlinked object @file{.o} files into @value{GDBN} using
15196 the @code{file} command. You will not be able to ``run'' an object
15197 file, but you can disassemble functions and inspect variables. Also,
15198 if the underlying BFD functionality supports it, you could use
15199 @kbd{gdb -write} to patch object files using this technique. Note
15200 that @value{GDBN} can neither interpret nor modify relocations in this
15201 case, so branches and some initialized variables will appear to go to
15202 the wrong place. But this feature is still handy from time to time.
15205 @code{file} with no argument makes @value{GDBN} discard any information it
15206 has on both executable file and the symbol table.
15209 @item exec-file @r{[} @var{filename} @r{]}
15210 Specify that the program to be run (but not the symbol table) is found
15211 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15212 if necessary to locate your program. Omitting @var{filename} means to
15213 discard information on the executable file.
15215 @kindex symbol-file
15216 @item symbol-file @r{[} @var{filename} @r{]}
15217 Read symbol table information from file @var{filename}. @code{PATH} is
15218 searched when necessary. Use the @code{file} command to get both symbol
15219 table and program to run from the same file.
15221 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15222 program's symbol table.
15224 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15225 some breakpoints and auto-display expressions. This is because they may
15226 contain pointers to the internal data recording symbols and data types,
15227 which are part of the old symbol table data being discarded inside
15230 @code{symbol-file} does not repeat if you press @key{RET} again after
15233 When @value{GDBN} is configured for a particular environment, it
15234 understands debugging information in whatever format is the standard
15235 generated for that environment; you may use either a @sc{gnu} compiler, or
15236 other compilers that adhere to the local conventions.
15237 Best results are usually obtained from @sc{gnu} compilers; for example,
15238 using @code{@value{NGCC}} you can generate debugging information for
15241 For most kinds of object files, with the exception of old SVR3 systems
15242 using COFF, the @code{symbol-file} command does not normally read the
15243 symbol table in full right away. Instead, it scans the symbol table
15244 quickly to find which source files and which symbols are present. The
15245 details are read later, one source file at a time, as they are needed.
15247 The purpose of this two-stage reading strategy is to make @value{GDBN}
15248 start up faster. For the most part, it is invisible except for
15249 occasional pauses while the symbol table details for a particular source
15250 file are being read. (The @code{set verbose} command can turn these
15251 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15252 Warnings and Messages}.)
15254 We have not implemented the two-stage strategy for COFF yet. When the
15255 symbol table is stored in COFF format, @code{symbol-file} reads the
15256 symbol table data in full right away. Note that ``stabs-in-COFF''
15257 still does the two-stage strategy, since the debug info is actually
15261 @cindex reading symbols immediately
15262 @cindex symbols, reading immediately
15263 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15264 @itemx file @r{[} -readnow @r{]} @var{filename}
15265 You can override the @value{GDBN} two-stage strategy for reading symbol
15266 tables by using the @samp{-readnow} option with any of the commands that
15267 load symbol table information, if you want to be sure @value{GDBN} has the
15268 entire symbol table available.
15270 @c FIXME: for now no mention of directories, since this seems to be in
15271 @c flux. 13mar1992 status is that in theory GDB would look either in
15272 @c current dir or in same dir as myprog; but issues like competing
15273 @c GDB's, or clutter in system dirs, mean that in practice right now
15274 @c only current dir is used. FFish says maybe a special GDB hierarchy
15275 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15279 @item core-file @r{[}@var{filename}@r{]}
15281 Specify the whereabouts of a core dump file to be used as the ``contents
15282 of memory''. Traditionally, core files contain only some parts of the
15283 address space of the process that generated them; @value{GDBN} can access the
15284 executable file itself for other parts.
15286 @code{core-file} with no argument specifies that no core file is
15289 Note that the core file is ignored when your program is actually running
15290 under @value{GDBN}. So, if you have been running your program and you
15291 wish to debug a core file instead, you must kill the subprocess in which
15292 the program is running. To do this, use the @code{kill} command
15293 (@pxref{Kill Process, ,Killing the Child Process}).
15295 @kindex add-symbol-file
15296 @cindex dynamic linking
15297 @item add-symbol-file @var{filename} @var{address}
15298 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15299 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15300 The @code{add-symbol-file} command reads additional symbol table
15301 information from the file @var{filename}. You would use this command
15302 when @var{filename} has been dynamically loaded (by some other means)
15303 into the program that is running. @var{address} should be the memory
15304 address at which the file has been loaded; @value{GDBN} cannot figure
15305 this out for itself. You can additionally specify an arbitrary number
15306 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15307 section name and base address for that section. You can specify any
15308 @var{address} as an expression.
15310 The symbol table of the file @var{filename} is added to the symbol table
15311 originally read with the @code{symbol-file} command. You can use the
15312 @code{add-symbol-file} command any number of times; the new symbol data
15313 thus read keeps adding to the old. To discard all old symbol data
15314 instead, use the @code{symbol-file} command without any arguments.
15316 @cindex relocatable object files, reading symbols from
15317 @cindex object files, relocatable, reading symbols from
15318 @cindex reading symbols from relocatable object files
15319 @cindex symbols, reading from relocatable object files
15320 @cindex @file{.o} files, reading symbols from
15321 Although @var{filename} is typically a shared library file, an
15322 executable file, or some other object file which has been fully
15323 relocated for loading into a process, you can also load symbolic
15324 information from relocatable @file{.o} files, as long as:
15328 the file's symbolic information refers only to linker symbols defined in
15329 that file, not to symbols defined by other object files,
15331 every section the file's symbolic information refers to has actually
15332 been loaded into the inferior, as it appears in the file, and
15334 you can determine the address at which every section was loaded, and
15335 provide these to the @code{add-symbol-file} command.
15339 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15340 relocatable files into an already running program; such systems
15341 typically make the requirements above easy to meet. However, it's
15342 important to recognize that many native systems use complex link
15343 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15344 assembly, for example) that make the requirements difficult to meet. In
15345 general, one cannot assume that using @code{add-symbol-file} to read a
15346 relocatable object file's symbolic information will have the same effect
15347 as linking the relocatable object file into the program in the normal
15350 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
15352 @kindex add-symbol-file-from-memory
15353 @cindex @code{syscall DSO}
15354 @cindex load symbols from memory
15355 @item add-symbol-file-from-memory @var{address}
15356 Load symbols from the given @var{address} in a dynamically loaded
15357 object file whose image is mapped directly into the inferior's memory.
15358 For example, the Linux kernel maps a @code{syscall DSO} into each
15359 process's address space; this DSO provides kernel-specific code for
15360 some system calls. The argument can be any expression whose
15361 evaluation yields the address of the file's shared object file header.
15362 For this command to work, you must have used @code{symbol-file} or
15363 @code{exec-file} commands in advance.
15365 @kindex add-shared-symbol-files
15367 @item add-shared-symbol-files @var{library-file}
15368 @itemx assf @var{library-file}
15369 The @code{add-shared-symbol-files} command can currently be used only
15370 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
15371 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
15372 @value{GDBN} automatically looks for shared libraries, however if
15373 @value{GDBN} does not find yours, you can invoke
15374 @code{add-shared-symbol-files}. It takes one argument: the shared
15375 library's file name. @code{assf} is a shorthand alias for
15376 @code{add-shared-symbol-files}.
15379 @item section @var{section} @var{addr}
15380 The @code{section} command changes the base address of the named
15381 @var{section} of the exec file to @var{addr}. This can be used if the
15382 exec file does not contain section addresses, (such as in the
15383 @code{a.out} format), or when the addresses specified in the file
15384 itself are wrong. Each section must be changed separately. The
15385 @code{info files} command, described below, lists all the sections and
15389 @kindex info target
15392 @code{info files} and @code{info target} are synonymous; both print the
15393 current target (@pxref{Targets, ,Specifying a Debugging Target}),
15394 including the names of the executable and core dump files currently in
15395 use by @value{GDBN}, and the files from which symbols were loaded. The
15396 command @code{help target} lists all possible targets rather than
15399 @kindex maint info sections
15400 @item maint info sections
15401 Another command that can give you extra information about program sections
15402 is @code{maint info sections}. In addition to the section information
15403 displayed by @code{info files}, this command displays the flags and file
15404 offset of each section in the executable and core dump files. In addition,
15405 @code{maint info sections} provides the following command options (which
15406 may be arbitrarily combined):
15410 Display sections for all loaded object files, including shared libraries.
15411 @item @var{sections}
15412 Display info only for named @var{sections}.
15413 @item @var{section-flags}
15414 Display info only for sections for which @var{section-flags} are true.
15415 The section flags that @value{GDBN} currently knows about are:
15418 Section will have space allocated in the process when loaded.
15419 Set for all sections except those containing debug information.
15421 Section will be loaded from the file into the child process memory.
15422 Set for pre-initialized code and data, clear for @code{.bss} sections.
15424 Section needs to be relocated before loading.
15426 Section cannot be modified by the child process.
15428 Section contains executable code only.
15430 Section contains data only (no executable code).
15432 Section will reside in ROM.
15434 Section contains data for constructor/destructor lists.
15436 Section is not empty.
15438 An instruction to the linker to not output the section.
15439 @item COFF_SHARED_LIBRARY
15440 A notification to the linker that the section contains
15441 COFF shared library information.
15443 Section contains common symbols.
15446 @kindex set trust-readonly-sections
15447 @cindex read-only sections
15448 @item set trust-readonly-sections on
15449 Tell @value{GDBN} that readonly sections in your object file
15450 really are read-only (i.e.@: that their contents will not change).
15451 In that case, @value{GDBN} can fetch values from these sections
15452 out of the object file, rather than from the target program.
15453 For some targets (notably embedded ones), this can be a significant
15454 enhancement to debugging performance.
15456 The default is off.
15458 @item set trust-readonly-sections off
15459 Tell @value{GDBN} not to trust readonly sections. This means that
15460 the contents of the section might change while the program is running,
15461 and must therefore be fetched from the target when needed.
15463 @item show trust-readonly-sections
15464 Show the current setting of trusting readonly sections.
15467 All file-specifying commands allow both absolute and relative file names
15468 as arguments. @value{GDBN} always converts the file name to an absolute file
15469 name and remembers it that way.
15471 @cindex shared libraries
15472 @anchor{Shared Libraries}
15473 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
15474 and IBM RS/6000 AIX shared libraries.
15476 On MS-Windows @value{GDBN} must be linked with the Expat library to support
15477 shared libraries. @xref{Expat}.
15479 @value{GDBN} automatically loads symbol definitions from shared libraries
15480 when you use the @code{run} command, or when you examine a core file.
15481 (Before you issue the @code{run} command, @value{GDBN} does not understand
15482 references to a function in a shared library, however---unless you are
15483 debugging a core file).
15485 On HP-UX, if the program loads a library explicitly, @value{GDBN}
15486 automatically loads the symbols at the time of the @code{shl_load} call.
15488 @c FIXME: some @value{GDBN} release may permit some refs to undef
15489 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
15490 @c FIXME...lib; check this from time to time when updating manual
15492 There are times, however, when you may wish to not automatically load
15493 symbol definitions from shared libraries, such as when they are
15494 particularly large or there are many of them.
15496 To control the automatic loading of shared library symbols, use the
15500 @kindex set auto-solib-add
15501 @item set auto-solib-add @var{mode}
15502 If @var{mode} is @code{on}, symbols from all shared object libraries
15503 will be loaded automatically when the inferior begins execution, you
15504 attach to an independently started inferior, or when the dynamic linker
15505 informs @value{GDBN} that a new library has been loaded. If @var{mode}
15506 is @code{off}, symbols must be loaded manually, using the
15507 @code{sharedlibrary} command. The default value is @code{on}.
15509 @cindex memory used for symbol tables
15510 If your program uses lots of shared libraries with debug info that
15511 takes large amounts of memory, you can decrease the @value{GDBN}
15512 memory footprint by preventing it from automatically loading the
15513 symbols from shared libraries. To that end, type @kbd{set
15514 auto-solib-add off} before running the inferior, then load each
15515 library whose debug symbols you do need with @kbd{sharedlibrary
15516 @var{regexp}}, where @var{regexp} is a regular expression that matches
15517 the libraries whose symbols you want to be loaded.
15519 @kindex show auto-solib-add
15520 @item show auto-solib-add
15521 Display the current autoloading mode.
15524 @cindex load shared library
15525 To explicitly load shared library symbols, use the @code{sharedlibrary}
15529 @kindex info sharedlibrary
15531 @item info share @var{regex}
15532 @itemx info sharedlibrary @var{regex}
15533 Print the names of the shared libraries which are currently loaded
15534 that match @var{regex}. If @var{regex} is omitted then print
15535 all shared libraries that are loaded.
15537 @kindex sharedlibrary
15539 @item sharedlibrary @var{regex}
15540 @itemx share @var{regex}
15541 Load shared object library symbols for files matching a
15542 Unix regular expression.
15543 As with files loaded automatically, it only loads shared libraries
15544 required by your program for a core file or after typing @code{run}. If
15545 @var{regex} is omitted all shared libraries required by your program are
15548 @item nosharedlibrary
15549 @kindex nosharedlibrary
15550 @cindex unload symbols from shared libraries
15551 Unload all shared object library symbols. This discards all symbols
15552 that have been loaded from all shared libraries. Symbols from shared
15553 libraries that were loaded by explicit user requests are not
15557 Sometimes you may wish that @value{GDBN} stops and gives you control
15558 when any of shared library events happen. Use the @code{set
15559 stop-on-solib-events} command for this:
15562 @item set stop-on-solib-events
15563 @kindex set stop-on-solib-events
15564 This command controls whether @value{GDBN} should give you control
15565 when the dynamic linker notifies it about some shared library event.
15566 The most common event of interest is loading or unloading of a new
15569 @item show stop-on-solib-events
15570 @kindex show stop-on-solib-events
15571 Show whether @value{GDBN} stops and gives you control when shared
15572 library events happen.
15575 Shared libraries are also supported in many cross or remote debugging
15576 configurations. @value{GDBN} needs to have access to the target's libraries;
15577 this can be accomplished either by providing copies of the libraries
15578 on the host system, or by asking @value{GDBN} to automatically retrieve the
15579 libraries from the target. If copies of the target libraries are
15580 provided, they need to be the same as the target libraries, although the
15581 copies on the target can be stripped as long as the copies on the host are
15584 @cindex where to look for shared libraries
15585 For remote debugging, you need to tell @value{GDBN} where the target
15586 libraries are, so that it can load the correct copies---otherwise, it
15587 may try to load the host's libraries. @value{GDBN} has two variables
15588 to specify the search directories for target libraries.
15591 @cindex prefix for shared library file names
15592 @cindex system root, alternate
15593 @kindex set solib-absolute-prefix
15594 @kindex set sysroot
15595 @item set sysroot @var{path}
15596 Use @var{path} as the system root for the program being debugged. Any
15597 absolute shared library paths will be prefixed with @var{path}; many
15598 runtime loaders store the absolute paths to the shared library in the
15599 target program's memory. If you use @code{set sysroot} to find shared
15600 libraries, they need to be laid out in the same way that they are on
15601 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15604 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15605 retrieve the target libraries from the remote system. This is only
15606 supported when using a remote target that supports the @code{remote get}
15607 command (@pxref{File Transfer,,Sending files to a remote system}).
15608 The part of @var{path} following the initial @file{remote:}
15609 (if present) is used as system root prefix on the remote file system.
15610 @footnote{If you want to specify a local system root using a directory
15611 that happens to be named @file{remote:}, you need to use some equivalent
15612 variant of the name like @file{./remote:}.}
15614 For targets with an MS-DOS based filesystem, such as MS-Windows and
15615 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15616 absolute file name with @var{path}. But first, on Unix hosts,
15617 @value{GDBN} converts all backslash directory separators into forward
15618 slashes, because the backslash is not a directory separator on Unix:
15621 c:\foo\bar.dll @result{} c:/foo/bar.dll
15624 Then, @value{GDBN} attempts prefixing the target file name with
15625 @var{path}, and looks for the resulting file name in the host file
15629 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15632 If that does not find the shared library, @value{GDBN} tries removing
15633 the @samp{:} character from the drive spec, both for convenience, and,
15634 for the case of the host file system not supporting file names with
15638 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15641 This makes it possible to have a system root that mirrors a target
15642 with more than one drive. E.g., you may want to setup your local
15643 copies of the target system shared libraries like so (note @samp{c} vs
15647 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15648 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15649 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15653 and point the system root at @file{/path/to/sysroot}, so that
15654 @value{GDBN} can find the correct copies of both
15655 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15657 If that still does not find the shared library, @value{GDBN} tries
15658 removing the whole drive spec from the target file name:
15661 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15664 This last lookup makes it possible to not care about the drive name,
15665 if you don't want or need to.
15667 The @code{set solib-absolute-prefix} command is an alias for @code{set
15670 @cindex default system root
15671 @cindex @samp{--with-sysroot}
15672 You can set the default system root by using the configure-time
15673 @samp{--with-sysroot} option. If the system root is inside
15674 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15675 @samp{--exec-prefix}), then the default system root will be updated
15676 automatically if the installed @value{GDBN} is moved to a new
15679 @kindex show sysroot
15681 Display the current shared library prefix.
15683 @kindex set solib-search-path
15684 @item set solib-search-path @var{path}
15685 If this variable is set, @var{path} is a colon-separated list of
15686 directories to search for shared libraries. @samp{solib-search-path}
15687 is used after @samp{sysroot} fails to locate the library, or if the
15688 path to the library is relative instead of absolute. If you want to
15689 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15690 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15691 finding your host's libraries. @samp{sysroot} is preferred; setting
15692 it to a nonexistent directory may interfere with automatic loading
15693 of shared library symbols.
15695 @kindex show solib-search-path
15696 @item show solib-search-path
15697 Display the current shared library search path.
15699 @cindex DOS file-name semantics of file names.
15700 @kindex set target-file-system-kind (unix|dos-based|auto)
15701 @kindex show target-file-system-kind
15702 @item set target-file-system-kind @var{kind}
15703 Set assumed file system kind for target reported file names.
15705 Shared library file names as reported by the target system may not
15706 make sense as is on the system @value{GDBN} is running on. For
15707 example, when remote debugging a target that has MS-DOS based file
15708 system semantics, from a Unix host, the target may be reporting to
15709 @value{GDBN} a list of loaded shared libraries with file names such as
15710 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15711 drive letters, so the @samp{c:\} prefix is not normally understood as
15712 indicating an absolute file name, and neither is the backslash
15713 normally considered a directory separator character. In that case,
15714 the native file system would interpret this whole absolute file name
15715 as a relative file name with no directory components. This would make
15716 it impossible to point @value{GDBN} at a copy of the remote target's
15717 shared libraries on the host using @code{set sysroot}, and impractical
15718 with @code{set solib-search-path}. Setting
15719 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15720 to interpret such file names similarly to how the target would, and to
15721 map them to file names valid on @value{GDBN}'s native file system
15722 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15723 to one of the supported file system kinds. In that case, @value{GDBN}
15724 tries to determine the appropriate file system variant based on the
15725 current target's operating system (@pxref{ABI, ,Configuring the
15726 Current ABI}). The supported file system settings are:
15730 Instruct @value{GDBN} to assume the target file system is of Unix
15731 kind. Only file names starting the forward slash (@samp{/}) character
15732 are considered absolute, and the directory separator character is also
15736 Instruct @value{GDBN} to assume the target file system is DOS based.
15737 File names starting with either a forward slash, or a drive letter
15738 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15739 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15740 considered directory separators.
15743 Instruct @value{GDBN} to use the file system kind associated with the
15744 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15745 This is the default.
15749 @cindex file name canonicalization
15750 @cindex base name differences
15751 When processing file names provided by the user, @value{GDBN}
15752 frequently needs to compare them to the file names recorded in the
15753 program's debug info. Normally, @value{GDBN} compares just the
15754 @dfn{base names} of the files as strings, which is reasonably fast
15755 even for very large programs. (The base name of a file is the last
15756 portion of its name, after stripping all the leading directories.)
15757 This shortcut in comparison is based upon the assumption that files
15758 cannot have more than one base name. This is usually true, but
15759 references to files that use symlinks or similar filesystem
15760 facilities violate that assumption. If your program records files
15761 using such facilities, or if you provide file names to @value{GDBN}
15762 using symlinks etc., you can set @code{basenames-may-differ} to
15763 @code{true} to instruct @value{GDBN} to completely canonicalize each
15764 pair of file names it needs to compare. This will make file-name
15765 comparisons accurate, but at a price of a significant slowdown.
15768 @item set basenames-may-differ
15769 @kindex set basenames-may-differ
15770 Set whether a source file may have multiple base names.
15772 @item show basenames-may-differ
15773 @kindex show basenames-may-differ
15774 Show whether a source file may have multiple base names.
15777 @node Separate Debug Files
15778 @section Debugging Information in Separate Files
15779 @cindex separate debugging information files
15780 @cindex debugging information in separate files
15781 @cindex @file{.debug} subdirectories
15782 @cindex debugging information directory, global
15783 @cindex global debugging information directory
15784 @cindex build ID, and separate debugging files
15785 @cindex @file{.build-id} directory
15787 @value{GDBN} allows you to put a program's debugging information in a
15788 file separate from the executable itself, in a way that allows
15789 @value{GDBN} to find and load the debugging information automatically.
15790 Since debugging information can be very large---sometimes larger
15791 than the executable code itself---some systems distribute debugging
15792 information for their executables in separate files, which users can
15793 install only when they need to debug a problem.
15795 @value{GDBN} supports two ways of specifying the separate debug info
15800 The executable contains a @dfn{debug link} that specifies the name of
15801 the separate debug info file. The separate debug file's name is
15802 usually @file{@var{executable}.debug}, where @var{executable} is the
15803 name of the corresponding executable file without leading directories
15804 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15805 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15806 checksum for the debug file, which @value{GDBN} uses to validate that
15807 the executable and the debug file came from the same build.
15810 The executable contains a @dfn{build ID}, a unique bit string that is
15811 also present in the corresponding debug info file. (This is supported
15812 only on some operating systems, notably those which use the ELF format
15813 for binary files and the @sc{gnu} Binutils.) For more details about
15814 this feature, see the description of the @option{--build-id}
15815 command-line option in @ref{Options, , Command Line Options, ld.info,
15816 The GNU Linker}. The debug info file's name is not specified
15817 explicitly by the build ID, but can be computed from the build ID, see
15821 Depending on the way the debug info file is specified, @value{GDBN}
15822 uses two different methods of looking for the debug file:
15826 For the ``debug link'' method, @value{GDBN} looks up the named file in
15827 the directory of the executable file, then in a subdirectory of that
15828 directory named @file{.debug}, and finally under the global debug
15829 directory, in a subdirectory whose name is identical to the leading
15830 directories of the executable's absolute file name.
15833 For the ``build ID'' method, @value{GDBN} looks in the
15834 @file{.build-id} subdirectory of the global debug directory for a file
15835 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15836 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15837 are the rest of the bit string. (Real build ID strings are 32 or more
15838 hex characters, not 10.)
15841 So, for example, suppose you ask @value{GDBN} to debug
15842 @file{/usr/bin/ls}, which has a debug link that specifies the
15843 file @file{ls.debug}, and a build ID whose value in hex is
15844 @code{abcdef1234}. If the global debug directory is
15845 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15846 debug information files, in the indicated order:
15850 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15852 @file{/usr/bin/ls.debug}
15854 @file{/usr/bin/.debug/ls.debug}
15856 @file{/usr/lib/debug/usr/bin/ls.debug}.
15859 You can set the global debugging info directory's name, and view the
15860 name @value{GDBN} is currently using.
15864 @kindex set debug-file-directory
15865 @item set debug-file-directory @var{directories}
15866 Set the directories which @value{GDBN} searches for separate debugging
15867 information files to @var{directory}. Multiple directory components can be set
15868 concatenating them by a directory separator.
15870 @kindex show debug-file-directory
15871 @item show debug-file-directory
15872 Show the directories @value{GDBN} searches for separate debugging
15877 @cindex @code{.gnu_debuglink} sections
15878 @cindex debug link sections
15879 A debug link is a special section of the executable file named
15880 @code{.gnu_debuglink}. The section must contain:
15884 A filename, with any leading directory components removed, followed by
15887 zero to three bytes of padding, as needed to reach the next four-byte
15888 boundary within the section, and
15890 a four-byte CRC checksum, stored in the same endianness used for the
15891 executable file itself. The checksum is computed on the debugging
15892 information file's full contents by the function given below, passing
15893 zero as the @var{crc} argument.
15896 Any executable file format can carry a debug link, as long as it can
15897 contain a section named @code{.gnu_debuglink} with the contents
15900 @cindex @code{.note.gnu.build-id} sections
15901 @cindex build ID sections
15902 The build ID is a special section in the executable file (and in other
15903 ELF binary files that @value{GDBN} may consider). This section is
15904 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15905 It contains unique identification for the built files---the ID remains
15906 the same across multiple builds of the same build tree. The default
15907 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15908 content for the build ID string. The same section with an identical
15909 value is present in the original built binary with symbols, in its
15910 stripped variant, and in the separate debugging information file.
15912 The debugging information file itself should be an ordinary
15913 executable, containing a full set of linker symbols, sections, and
15914 debugging information. The sections of the debugging information file
15915 should have the same names, addresses, and sizes as the original file,
15916 but they need not contain any data---much like a @code{.bss} section
15917 in an ordinary executable.
15919 The @sc{gnu} binary utilities (Binutils) package includes the
15920 @samp{objcopy} utility that can produce
15921 the separated executable / debugging information file pairs using the
15922 following commands:
15925 @kbd{objcopy --only-keep-debug foo foo.debug}
15930 These commands remove the debugging
15931 information from the executable file @file{foo} and place it in the file
15932 @file{foo.debug}. You can use the first, second or both methods to link the
15937 The debug link method needs the following additional command to also leave
15938 behind a debug link in @file{foo}:
15941 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15944 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15945 a version of the @code{strip} command such that the command @kbd{strip foo -f
15946 foo.debug} has the same functionality as the two @code{objcopy} commands and
15947 the @code{ln -s} command above, together.
15950 Build ID gets embedded into the main executable using @code{ld --build-id} or
15951 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15952 compatibility fixes for debug files separation are present in @sc{gnu} binary
15953 utilities (Binutils) package since version 2.18.
15958 @cindex CRC algorithm definition
15959 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15960 IEEE 802.3 using the polynomial:
15962 @c TexInfo requires naked braces for multi-digit exponents for Tex
15963 @c output, but this causes HTML output to barf. HTML has to be set using
15964 @c raw commands. So we end up having to specify this equation in 2
15969 <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>
15970 + <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
15976 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15977 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15981 The function is computed byte at a time, taking the least
15982 significant bit of each byte first. The initial pattern
15983 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15984 the final result is inverted to ensure trailing zeros also affect the
15987 @emph{Note:} This is the same CRC polynomial as used in handling the
15988 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15989 , @value{GDBN} Remote Serial Protocol}). However in the
15990 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15991 significant bit first, and the result is not inverted, so trailing
15992 zeros have no effect on the CRC value.
15994 To complete the description, we show below the code of the function
15995 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15996 initially supplied @code{crc} argument means that an initial call to
15997 this function passing in zero will start computing the CRC using
16000 @kindex gnu_debuglink_crc32
16003 gnu_debuglink_crc32 (unsigned long crc,
16004 unsigned char *buf, size_t len)
16006 static const unsigned long crc32_table[256] =
16008 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16009 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16010 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16011 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16012 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16013 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16014 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16015 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16016 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16017 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16018 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16019 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16020 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16021 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16022 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16023 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16024 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16025 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16026 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16027 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16028 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16029 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16030 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16031 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16032 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16033 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16034 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16035 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16036 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16037 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16038 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16039 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16040 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16041 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16042 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16043 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16044 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16045 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16046 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16047 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16048 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16049 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16050 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16051 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16052 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16053 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16054 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16055 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16056 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16057 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16058 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16061 unsigned char *end;
16063 crc = ~crc & 0xffffffff;
16064 for (end = buf + len; buf < end; ++buf)
16065 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
16066 return ~crc & 0xffffffff;
16071 This computation does not apply to the ``build ID'' method.
16075 @section Index Files Speed Up @value{GDBN}
16076 @cindex index files
16077 @cindex @samp{.gdb_index} section
16079 When @value{GDBN} finds a symbol file, it scans the symbols in the
16080 file in order to construct an internal symbol table. This lets most
16081 @value{GDBN} operations work quickly---at the cost of a delay early
16082 on. For large programs, this delay can be quite lengthy, so
16083 @value{GDBN} provides a way to build an index, which speeds up
16086 The index is stored as a section in the symbol file. @value{GDBN} can
16087 write the index to a file, then you can put it into the symbol file
16088 using @command{objcopy}.
16090 To create an index file, use the @code{save gdb-index} command:
16093 @item save gdb-index @var{directory}
16094 @kindex save gdb-index
16095 Create an index file for each symbol file currently known by
16096 @value{GDBN}. Each file is named after its corresponding symbol file,
16097 with @samp{.gdb-index} appended, and is written into the given
16101 Once you have created an index file you can merge it into your symbol
16102 file, here named @file{symfile}, using @command{objcopy}:
16105 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16106 --set-section-flags .gdb_index=readonly symfile symfile
16109 There are currently some limitation on indices. They only work when
16110 for DWARF debugging information, not stabs. And, they do not
16111 currently work for programs using Ada.
16113 @node Symbol Errors
16114 @section Errors Reading Symbol Files
16116 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16117 such as symbol types it does not recognize, or known bugs in compiler
16118 output. By default, @value{GDBN} does not notify you of such problems, since
16119 they are relatively common and primarily of interest to people
16120 debugging compilers. If you are interested in seeing information
16121 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16122 only one message about each such type of problem, no matter how many
16123 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16124 to see how many times the problems occur, with the @code{set
16125 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16128 The messages currently printed, and their meanings, include:
16131 @item inner block not inside outer block in @var{symbol}
16133 The symbol information shows where symbol scopes begin and end
16134 (such as at the start of a function or a block of statements). This
16135 error indicates that an inner scope block is not fully contained
16136 in its outer scope blocks.
16138 @value{GDBN} circumvents the problem by treating the inner block as if it had
16139 the same scope as the outer block. In the error message, @var{symbol}
16140 may be shown as ``@code{(don't know)}'' if the outer block is not a
16143 @item block at @var{address} out of order
16145 The symbol information for symbol scope blocks should occur in
16146 order of increasing addresses. This error indicates that it does not
16149 @value{GDBN} does not circumvent this problem, and has trouble
16150 locating symbols in the source file whose symbols it is reading. (You
16151 can often determine what source file is affected by specifying
16152 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16155 @item bad block start address patched
16157 The symbol information for a symbol scope block has a start address
16158 smaller than the address of the preceding source line. This is known
16159 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16161 @value{GDBN} circumvents the problem by treating the symbol scope block as
16162 starting on the previous source line.
16164 @item bad string table offset in symbol @var{n}
16167 Symbol number @var{n} contains a pointer into the string table which is
16168 larger than the size of the string table.
16170 @value{GDBN} circumvents the problem by considering the symbol to have the
16171 name @code{foo}, which may cause other problems if many symbols end up
16174 @item unknown symbol type @code{0x@var{nn}}
16176 The symbol information contains new data types that @value{GDBN} does
16177 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16178 uncomprehended information, in hexadecimal.
16180 @value{GDBN} circumvents the error by ignoring this symbol information.
16181 This usually allows you to debug your program, though certain symbols
16182 are not accessible. If you encounter such a problem and feel like
16183 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16184 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16185 and examine @code{*bufp} to see the symbol.
16187 @item stub type has NULL name
16189 @value{GDBN} could not find the full definition for a struct or class.
16191 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16192 The symbol information for a C@t{++} member function is missing some
16193 information that recent versions of the compiler should have output for
16196 @item info mismatch between compiler and debugger
16198 @value{GDBN} could not parse a type specification output by the compiler.
16203 @section GDB Data Files
16205 @cindex prefix for data files
16206 @value{GDBN} will sometimes read an auxiliary data file. These files
16207 are kept in a directory known as the @dfn{data directory}.
16209 You can set the data directory's name, and view the name @value{GDBN}
16210 is currently using.
16213 @kindex set data-directory
16214 @item set data-directory @var{directory}
16215 Set the directory which @value{GDBN} searches for auxiliary data files
16216 to @var{directory}.
16218 @kindex show data-directory
16219 @item show data-directory
16220 Show the directory @value{GDBN} searches for auxiliary data files.
16223 @cindex default data directory
16224 @cindex @samp{--with-gdb-datadir}
16225 You can set the default data directory by using the configure-time
16226 @samp{--with-gdb-datadir} option. If the data directory is inside
16227 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16228 @samp{--exec-prefix}), then the default data directory will be updated
16229 automatically if the installed @value{GDBN} is moved to a new
16232 The data directory may also be specified with the
16233 @code{--data-directory} command line option.
16234 @xref{Mode Options}.
16237 @chapter Specifying a Debugging Target
16239 @cindex debugging target
16240 A @dfn{target} is the execution environment occupied by your program.
16242 Often, @value{GDBN} runs in the same host environment as your program;
16243 in that case, the debugging target is specified as a side effect when
16244 you use the @code{file} or @code{core} commands. When you need more
16245 flexibility---for example, running @value{GDBN} on a physically separate
16246 host, or controlling a standalone system over a serial port or a
16247 realtime system over a TCP/IP connection---you can use the @code{target}
16248 command to specify one of the target types configured for @value{GDBN}
16249 (@pxref{Target Commands, ,Commands for Managing Targets}).
16251 @cindex target architecture
16252 It is possible to build @value{GDBN} for several different @dfn{target
16253 architectures}. When @value{GDBN} is built like that, you can choose
16254 one of the available architectures with the @kbd{set architecture}
16258 @kindex set architecture
16259 @kindex show architecture
16260 @item set architecture @var{arch}
16261 This command sets the current target architecture to @var{arch}. The
16262 value of @var{arch} can be @code{"auto"}, in addition to one of the
16263 supported architectures.
16265 @item show architecture
16266 Show the current target architecture.
16268 @item set processor
16270 @kindex set processor
16271 @kindex show processor
16272 These are alias commands for, respectively, @code{set architecture}
16273 and @code{show architecture}.
16277 * Active Targets:: Active targets
16278 * Target Commands:: Commands for managing targets
16279 * Byte Order:: Choosing target byte order
16282 @node Active Targets
16283 @section Active Targets
16285 @cindex stacking targets
16286 @cindex active targets
16287 @cindex multiple targets
16289 There are multiple classes of targets such as: processes, executable files or
16290 recording sessions. Core files belong to the process class, making core file
16291 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16292 on multiple active targets, one in each class. This allows you to (for
16293 example) start a process and inspect its activity, while still having access to
16294 the executable file after the process finishes. Or if you start process
16295 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16296 presented a virtual layer of the recording target, while the process target
16297 remains stopped at the chronologically last point of the process execution.
16299 Use the @code{core-file} and @code{exec-file} commands to select a new core
16300 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16301 specify as a target a process that is already running, use the @code{attach}
16302 command (@pxref{Attach, ,Debugging an Already-running Process}).
16304 @node Target Commands
16305 @section Commands for Managing Targets
16308 @item target @var{type} @var{parameters}
16309 Connects the @value{GDBN} host environment to a target machine or
16310 process. A target is typically a protocol for talking to debugging
16311 facilities. You use the argument @var{type} to specify the type or
16312 protocol of the target machine.
16314 Further @var{parameters} are interpreted by the target protocol, but
16315 typically include things like device names or host names to connect
16316 with, process numbers, and baud rates.
16318 The @code{target} command does not repeat if you press @key{RET} again
16319 after executing the command.
16321 @kindex help target
16323 Displays the names of all targets available. To display targets
16324 currently selected, use either @code{info target} or @code{info files}
16325 (@pxref{Files, ,Commands to Specify Files}).
16327 @item help target @var{name}
16328 Describe a particular target, including any parameters necessary to
16331 @kindex set gnutarget
16332 @item set gnutarget @var{args}
16333 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
16334 knows whether it is reading an @dfn{executable},
16335 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
16336 with the @code{set gnutarget} command. Unlike most @code{target} commands,
16337 with @code{gnutarget} the @code{target} refers to a program, not a machine.
16340 @emph{Warning:} To specify a file format with @code{set gnutarget},
16341 you must know the actual BFD name.
16345 @xref{Files, , Commands to Specify Files}.
16347 @kindex show gnutarget
16348 @item show gnutarget
16349 Use the @code{show gnutarget} command to display what file format
16350 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
16351 @value{GDBN} will determine the file format for each file automatically,
16352 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
16355 @cindex common targets
16356 Here are some common targets (available, or not, depending on the GDB
16361 @item target exec @var{program}
16362 @cindex executable file target
16363 An executable file. @samp{target exec @var{program}} is the same as
16364 @samp{exec-file @var{program}}.
16366 @item target core @var{filename}
16367 @cindex core dump file target
16368 A core dump file. @samp{target core @var{filename}} is the same as
16369 @samp{core-file @var{filename}}.
16371 @item target remote @var{medium}
16372 @cindex remote target
16373 A remote system connected to @value{GDBN} via a serial line or network
16374 connection. This command tells @value{GDBN} to use its own remote
16375 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
16377 For example, if you have a board connected to @file{/dev/ttya} on the
16378 machine running @value{GDBN}, you could say:
16381 target remote /dev/ttya
16384 @code{target remote} supports the @code{load} command. This is only
16385 useful if you have some other way of getting the stub to the target
16386 system, and you can put it somewhere in memory where it won't get
16387 clobbered by the download.
16389 @item target sim @r{[}@var{simargs}@r{]} @dots{}
16390 @cindex built-in simulator target
16391 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
16399 works; however, you cannot assume that a specific memory map, device
16400 drivers, or even basic I/O is available, although some simulators do
16401 provide these. For info about any processor-specific simulator details,
16402 see the appropriate section in @ref{Embedded Processors, ,Embedded
16407 Some configurations may include these targets as well:
16411 @item target nrom @var{dev}
16412 @cindex NetROM ROM emulator target
16413 NetROM ROM emulator. This target only supports downloading.
16417 Different targets are available on different configurations of @value{GDBN};
16418 your configuration may have more or fewer targets.
16420 Many remote targets require you to download the executable's code once
16421 you've successfully established a connection. You may wish to control
16422 various aspects of this process.
16427 @kindex set hash@r{, for remote monitors}
16428 @cindex hash mark while downloading
16429 This command controls whether a hash mark @samp{#} is displayed while
16430 downloading a file to the remote monitor. If on, a hash mark is
16431 displayed after each S-record is successfully downloaded to the
16435 @kindex show hash@r{, for remote monitors}
16436 Show the current status of displaying the hash mark.
16438 @item set debug monitor
16439 @kindex set debug monitor
16440 @cindex display remote monitor communications
16441 Enable or disable display of communications messages between
16442 @value{GDBN} and the remote monitor.
16444 @item show debug monitor
16445 @kindex show debug monitor
16446 Show the current status of displaying communications between
16447 @value{GDBN} and the remote monitor.
16452 @kindex load @var{filename}
16453 @item load @var{filename}
16455 Depending on what remote debugging facilities are configured into
16456 @value{GDBN}, the @code{load} command may be available. Where it exists, it
16457 is meant to make @var{filename} (an executable) available for debugging
16458 on the remote system---by downloading, or dynamic linking, for example.
16459 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
16460 the @code{add-symbol-file} command.
16462 If your @value{GDBN} does not have a @code{load} command, attempting to
16463 execute it gets the error message ``@code{You can't do that when your
16464 target is @dots{}}''
16466 The file is loaded at whatever address is specified in the executable.
16467 For some object file formats, you can specify the load address when you
16468 link the program; for other formats, like a.out, the object file format
16469 specifies a fixed address.
16470 @c FIXME! This would be a good place for an xref to the GNU linker doc.
16472 Depending on the remote side capabilities, @value{GDBN} may be able to
16473 load programs into flash memory.
16475 @code{load} does not repeat if you press @key{RET} again after using it.
16479 @section Choosing Target Byte Order
16481 @cindex choosing target byte order
16482 @cindex target byte order
16484 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
16485 offer the ability to run either big-endian or little-endian byte
16486 orders. Usually the executable or symbol will include a bit to
16487 designate the endian-ness, and you will not need to worry about
16488 which to use. However, you may still find it useful to adjust
16489 @value{GDBN}'s idea of processor endian-ness manually.
16493 @item set endian big
16494 Instruct @value{GDBN} to assume the target is big-endian.
16496 @item set endian little
16497 Instruct @value{GDBN} to assume the target is little-endian.
16499 @item set endian auto
16500 Instruct @value{GDBN} to use the byte order associated with the
16504 Display @value{GDBN}'s current idea of the target byte order.
16508 Note that these commands merely adjust interpretation of symbolic
16509 data on the host, and that they have absolutely no effect on the
16513 @node Remote Debugging
16514 @chapter Debugging Remote Programs
16515 @cindex remote debugging
16517 If you are trying to debug a program running on a machine that cannot run
16518 @value{GDBN} in the usual way, it is often useful to use remote debugging.
16519 For example, you might use remote debugging on an operating system kernel,
16520 or on a small system which does not have a general purpose operating system
16521 powerful enough to run a full-featured debugger.
16523 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
16524 to make this work with particular debugging targets. In addition,
16525 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
16526 but not specific to any particular target system) which you can use if you
16527 write the remote stubs---the code that runs on the remote system to
16528 communicate with @value{GDBN}.
16530 Other remote targets may be available in your
16531 configuration of @value{GDBN}; use @code{help target} to list them.
16534 * Connecting:: Connecting to a remote target
16535 * File Transfer:: Sending files to a remote system
16536 * Server:: Using the gdbserver program
16537 * Remote Configuration:: Remote configuration
16538 * Remote Stub:: Implementing a remote stub
16542 @section Connecting to a Remote Target
16544 On the @value{GDBN} host machine, you will need an unstripped copy of
16545 your program, since @value{GDBN} needs symbol and debugging information.
16546 Start up @value{GDBN} as usual, using the name of the local copy of your
16547 program as the first argument.
16549 @cindex @code{target remote}
16550 @value{GDBN} can communicate with the target over a serial line, or
16551 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16552 each case, @value{GDBN} uses the same protocol for debugging your
16553 program; only the medium carrying the debugging packets varies. The
16554 @code{target remote} command establishes a connection to the target.
16555 Its arguments indicate which medium to use:
16559 @item target remote @var{serial-device}
16560 @cindex serial line, @code{target remote}
16561 Use @var{serial-device} to communicate with the target. For example,
16562 to use a serial line connected to the device named @file{/dev/ttyb}:
16565 target remote /dev/ttyb
16568 If you're using a serial line, you may want to give @value{GDBN} the
16569 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16570 (@pxref{Remote Configuration, set remotebaud}) before the
16571 @code{target} command.
16573 @item target remote @code{@var{host}:@var{port}}
16574 @itemx target remote @code{tcp:@var{host}:@var{port}}
16575 @cindex @acronym{TCP} port, @code{target remote}
16576 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16577 The @var{host} may be either a host name or a numeric @acronym{IP}
16578 address; @var{port} must be a decimal number. The @var{host} could be
16579 the target machine itself, if it is directly connected to the net, or
16580 it might be a terminal server which in turn has a serial line to the
16583 For example, to connect to port 2828 on a terminal server named
16587 target remote manyfarms:2828
16590 If your remote target is actually running on the same machine as your
16591 debugger session (e.g.@: a simulator for your target running on the
16592 same host), you can omit the hostname. For example, to connect to
16593 port 1234 on your local machine:
16596 target remote :1234
16600 Note that the colon is still required here.
16602 @item target remote @code{udp:@var{host}:@var{port}}
16603 @cindex @acronym{UDP} port, @code{target remote}
16604 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16605 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16608 target remote udp:manyfarms:2828
16611 When using a @acronym{UDP} connection for remote debugging, you should
16612 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16613 can silently drop packets on busy or unreliable networks, which will
16614 cause havoc with your debugging session.
16616 @item target remote | @var{command}
16617 @cindex pipe, @code{target remote} to
16618 Run @var{command} in the background and communicate with it using a
16619 pipe. The @var{command} is a shell command, to be parsed and expanded
16620 by the system's command shell, @code{/bin/sh}; it should expect remote
16621 protocol packets on its standard input, and send replies on its
16622 standard output. You could use this to run a stand-alone simulator
16623 that speaks the remote debugging protocol, to make net connections
16624 using programs like @code{ssh}, or for other similar tricks.
16626 If @var{command} closes its standard output (perhaps by exiting),
16627 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16628 program has already exited, this will have no effect.)
16632 Once the connection has been established, you can use all the usual
16633 commands to examine and change data. The remote program is already
16634 running; you can use @kbd{step} and @kbd{continue}, and you do not
16635 need to use @kbd{run}.
16637 @cindex interrupting remote programs
16638 @cindex remote programs, interrupting
16639 Whenever @value{GDBN} is waiting for the remote program, if you type the
16640 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16641 program. This may or may not succeed, depending in part on the hardware
16642 and the serial drivers the remote system uses. If you type the
16643 interrupt character once again, @value{GDBN} displays this prompt:
16646 Interrupted while waiting for the program.
16647 Give up (and stop debugging it)? (y or n)
16650 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16651 (If you decide you want to try again later, you can use @samp{target
16652 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16653 goes back to waiting.
16656 @kindex detach (remote)
16658 When you have finished debugging the remote program, you can use the
16659 @code{detach} command to release it from @value{GDBN} control.
16660 Detaching from the target normally resumes its execution, but the results
16661 will depend on your particular remote stub. After the @code{detach}
16662 command, @value{GDBN} is free to connect to another target.
16666 The @code{disconnect} command behaves like @code{detach}, except that
16667 the target is generally not resumed. It will wait for @value{GDBN}
16668 (this instance or another one) to connect and continue debugging. After
16669 the @code{disconnect} command, @value{GDBN} is again free to connect to
16672 @cindex send command to remote monitor
16673 @cindex extend @value{GDBN} for remote targets
16674 @cindex add new commands for external monitor
16676 @item monitor @var{cmd}
16677 This command allows you to send arbitrary commands directly to the
16678 remote monitor. Since @value{GDBN} doesn't care about the commands it
16679 sends like this, this command is the way to extend @value{GDBN}---you
16680 can add new commands that only the external monitor will understand
16684 @node File Transfer
16685 @section Sending files to a remote system
16686 @cindex remote target, file transfer
16687 @cindex file transfer
16688 @cindex sending files to remote systems
16690 Some remote targets offer the ability to transfer files over the same
16691 connection used to communicate with @value{GDBN}. This is convenient
16692 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16693 running @code{gdbserver} over a network interface. For other targets,
16694 e.g.@: embedded devices with only a single serial port, this may be
16695 the only way to upload or download files.
16697 Not all remote targets support these commands.
16701 @item remote put @var{hostfile} @var{targetfile}
16702 Copy file @var{hostfile} from the host system (the machine running
16703 @value{GDBN}) to @var{targetfile} on the target system.
16706 @item remote get @var{targetfile} @var{hostfile}
16707 Copy file @var{targetfile} from the target system to @var{hostfile}
16708 on the host system.
16710 @kindex remote delete
16711 @item remote delete @var{targetfile}
16712 Delete @var{targetfile} from the target system.
16717 @section Using the @code{gdbserver} Program
16720 @cindex remote connection without stubs
16721 @code{gdbserver} is a control program for Unix-like systems, which
16722 allows you to connect your program with a remote @value{GDBN} via
16723 @code{target remote}---but without linking in the usual debugging stub.
16725 @code{gdbserver} is not a complete replacement for the debugging stubs,
16726 because it requires essentially the same operating-system facilities
16727 that @value{GDBN} itself does. In fact, a system that can run
16728 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16729 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16730 because it is a much smaller program than @value{GDBN} itself. It is
16731 also easier to port than all of @value{GDBN}, so you may be able to get
16732 started more quickly on a new system by using @code{gdbserver}.
16733 Finally, if you develop code for real-time systems, you may find that
16734 the tradeoffs involved in real-time operation make it more convenient to
16735 do as much development work as possible on another system, for example
16736 by cross-compiling. You can use @code{gdbserver} to make a similar
16737 choice for debugging.
16739 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16740 or a TCP connection, using the standard @value{GDBN} remote serial
16744 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16745 Do not run @code{gdbserver} connected to any public network; a
16746 @value{GDBN} connection to @code{gdbserver} provides access to the
16747 target system with the same privileges as the user running
16751 @subsection Running @code{gdbserver}
16752 @cindex arguments, to @code{gdbserver}
16753 @cindex @code{gdbserver}, command-line arguments
16755 Run @code{gdbserver} on the target system. You need a copy of the
16756 program you want to debug, including any libraries it requires.
16757 @code{gdbserver} does not need your program's symbol table, so you can
16758 strip the program if necessary to save space. @value{GDBN} on the host
16759 system does all the symbol handling.
16761 To use the server, you must tell it how to communicate with @value{GDBN};
16762 the name of your program; and the arguments for your program. The usual
16766 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16769 @var{comm} is either a device name (to use a serial line), or a TCP
16770 hostname and portnumber, or @code{-} or @code{stdio} to use
16771 stdin/stdout of @code{gdbserver}.
16772 For example, to debug Emacs with the argument
16773 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16777 target> gdbserver /dev/com1 emacs foo.txt
16780 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16783 To use a TCP connection instead of a serial line:
16786 target> gdbserver host:2345 emacs foo.txt
16789 The only difference from the previous example is the first argument,
16790 specifying that you are communicating with the host @value{GDBN} via
16791 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16792 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16793 (Currently, the @samp{host} part is ignored.) You can choose any number
16794 you want for the port number as long as it does not conflict with any
16795 TCP ports already in use on the target system (for example, @code{23} is
16796 reserved for @code{telnet}).@footnote{If you choose a port number that
16797 conflicts with another service, @code{gdbserver} prints an error message
16798 and exits.} You must use the same port number with the host @value{GDBN}
16799 @code{target remote} command.
16801 The @code{stdio} connection is useful when starting @code{gdbserver}
16805 (gdb) target remote | ssh -T hostname gdbserver - hello
16808 The @samp{-T} option to ssh is provided because we don't need a remote pty,
16809 and we don't want escape-character handling. Ssh does this by default when
16810 a command is provided, the flag is provided to make it explicit.
16811 You could elide it if you want to.
16813 Programs started with stdio-connected gdbserver have @file{/dev/null} for
16814 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
16815 display through a pipe connected to gdbserver.
16816 Both @code{stdout} and @code{stderr} use the same pipe.
16818 @subsubsection Attaching to a Running Program
16819 @cindex attach to a program, @code{gdbserver}
16820 @cindex @option{--attach}, @code{gdbserver} option
16822 On some targets, @code{gdbserver} can also attach to running programs.
16823 This is accomplished via the @code{--attach} argument. The syntax is:
16826 target> gdbserver --attach @var{comm} @var{pid}
16829 @var{pid} is the process ID of a currently running process. It isn't necessary
16830 to point @code{gdbserver} at a binary for the running process.
16833 You can debug processes by name instead of process ID if your target has the
16834 @code{pidof} utility:
16837 target> gdbserver --attach @var{comm} `pidof @var{program}`
16840 In case more than one copy of @var{program} is running, or @var{program}
16841 has multiple threads, most versions of @code{pidof} support the
16842 @code{-s} option to only return the first process ID.
16844 @subsubsection Multi-Process Mode for @code{gdbserver}
16845 @cindex @code{gdbserver}, multiple processes
16846 @cindex multiple processes with @code{gdbserver}
16848 When you connect to @code{gdbserver} using @code{target remote},
16849 @code{gdbserver} debugs the specified program only once. When the
16850 program exits, or you detach from it, @value{GDBN} closes the connection
16851 and @code{gdbserver} exits.
16853 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16854 enters multi-process mode. When the debugged program exits, or you
16855 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16856 though no program is running. The @code{run} and @code{attach}
16857 commands instruct @code{gdbserver} to run or attach to a new program.
16858 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16859 remote exec-file}) to select the program to run. Command line
16860 arguments are supported, except for wildcard expansion and I/O
16861 redirection (@pxref{Arguments}).
16863 @cindex @option{--multi}, @code{gdbserver} option
16864 To start @code{gdbserver} without supplying an initial command to run
16865 or process ID to attach, use the @option{--multi} command line option.
16866 Then you can connect using @kbd{target extended-remote} and start
16867 the program you want to debug.
16869 In multi-process mode @code{gdbserver} does not automatically exit unless you
16870 use the option @option{--once}. You can terminate it by using
16871 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16872 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16873 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16874 @option{--multi} option to @code{gdbserver} has no influence on that.
16876 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
16878 This section applies only when @code{gdbserver} is run to listen on a TCP port.
16880 @code{gdbserver} normally terminates after all of its debugged processes have
16881 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
16882 extended-remote}, @code{gdbserver} stays running even with no processes left.
16883 @value{GDBN} normally terminates the spawned debugged process on its exit,
16884 which normally also terminates @code{gdbserver} in the @kbd{target remote}
16885 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
16886 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
16887 stays running even in the @kbd{target remote} mode.
16889 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
16890 Such reconnecting is useful for features like @ref{disconnected tracing}. For
16891 completeness, at most one @value{GDBN} can be connected at a time.
16893 @cindex @option{--once}, @code{gdbserver} option
16894 By default, @code{gdbserver} keeps the listening TCP port open, so that
16895 additional connections are possible. However, if you start @code{gdbserver}
16896 with the @option{--once} option, it will stop listening for any further
16897 connection attempts after connecting to the first @value{GDBN} session. This
16898 means no further connections to @code{gdbserver} will be possible after the
16899 first one. It also means @code{gdbserver} will terminate after the first
16900 connection with remote @value{GDBN} has closed, even for unexpectedly closed
16901 connections and even in the @kbd{target extended-remote} mode. The
16902 @option{--once} option allows reusing the same port number for connecting to
16903 multiple instances of @code{gdbserver} running on the same host, since each
16904 instance closes its port after the first connection.
16906 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16908 @cindex @option{--debug}, @code{gdbserver} option
16909 The @option{--debug} option tells @code{gdbserver} to display extra
16910 status information about the debugging process.
16911 @cindex @option{--remote-debug}, @code{gdbserver} option
16912 The @option{--remote-debug} option tells @code{gdbserver} to display
16913 remote protocol debug output. These options are intended for
16914 @code{gdbserver} development and for bug reports to the developers.
16916 @cindex @option{--wrapper}, @code{gdbserver} option
16917 The @option{--wrapper} option specifies a wrapper to launch programs
16918 for debugging. The option should be followed by the name of the
16919 wrapper, then any command-line arguments to pass to the wrapper, then
16920 @kbd{--} indicating the end of the wrapper arguments.
16922 @code{gdbserver} runs the specified wrapper program with a combined
16923 command line including the wrapper arguments, then the name of the
16924 program to debug, then any arguments to the program. The wrapper
16925 runs until it executes your program, and then @value{GDBN} gains control.
16927 You can use any program that eventually calls @code{execve} with
16928 its arguments as a wrapper. Several standard Unix utilities do
16929 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16930 with @code{exec "$@@"} will also work.
16932 For example, you can use @code{env} to pass an environment variable to
16933 the debugged program, without setting the variable in @code{gdbserver}'s
16937 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16940 @subsection Connecting to @code{gdbserver}
16942 Run @value{GDBN} on the host system.
16944 First make sure you have the necessary symbol files. Load symbols for
16945 your application using the @code{file} command before you connect. Use
16946 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16947 was compiled with the correct sysroot using @code{--with-sysroot}).
16949 The symbol file and target libraries must exactly match the executable
16950 and libraries on the target, with one exception: the files on the host
16951 system should not be stripped, even if the files on the target system
16952 are. Mismatched or missing files will lead to confusing results
16953 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16954 files may also prevent @code{gdbserver} from debugging multi-threaded
16957 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16958 For TCP connections, you must start up @code{gdbserver} prior to using
16959 the @code{target remote} command. Otherwise you may get an error whose
16960 text depends on the host system, but which usually looks something like
16961 @samp{Connection refused}. Don't use the @code{load}
16962 command in @value{GDBN} when using @code{gdbserver}, since the program is
16963 already on the target.
16965 @subsection Monitor Commands for @code{gdbserver}
16966 @cindex monitor commands, for @code{gdbserver}
16967 @anchor{Monitor Commands for gdbserver}
16969 During a @value{GDBN} session using @code{gdbserver}, you can use the
16970 @code{monitor} command to send special requests to @code{gdbserver}.
16971 Here are the available commands.
16975 List the available monitor commands.
16977 @item monitor set debug 0
16978 @itemx monitor set debug 1
16979 Disable or enable general debugging messages.
16981 @item monitor set remote-debug 0
16982 @itemx monitor set remote-debug 1
16983 Disable or enable specific debugging messages associated with the remote
16984 protocol (@pxref{Remote Protocol}).
16986 @item monitor set libthread-db-search-path [PATH]
16987 @cindex gdbserver, search path for @code{libthread_db}
16988 When this command is issued, @var{path} is a colon-separated list of
16989 directories to search for @code{libthread_db} (@pxref{Threads,,set
16990 libthread-db-search-path}). If you omit @var{path},
16991 @samp{libthread-db-search-path} will be reset to its default value.
16993 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
16994 not supported in @code{gdbserver}.
16997 Tell gdbserver to exit immediately. This command should be followed by
16998 @code{disconnect} to close the debugging session. @code{gdbserver} will
16999 detach from any attached processes and kill any processes it created.
17000 Use @code{monitor exit} to terminate @code{gdbserver} at the end
17001 of a multi-process mode debug session.
17005 @subsection Tracepoints support in @code{gdbserver}
17006 @cindex tracepoints support in @code{gdbserver}
17008 On some targets, @code{gdbserver} supports tracepoints, fast
17009 tracepoints and static tracepoints.
17011 For fast or static tracepoints to work, a special library called the
17012 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
17013 This library is built and distributed as an integral part of
17014 @code{gdbserver}. In addition, support for static tracepoints
17015 requires building the in-process agent library with static tracepoints
17016 support. At present, the UST (LTTng Userspace Tracer,
17017 @url{http://lttng.org/ust}) tracing engine is supported. This support
17018 is automatically available if UST development headers are found in the
17019 standard include path when @code{gdbserver} is built, or if
17020 @code{gdbserver} was explicitly configured using @option{--with-ust}
17021 to point at such headers. You can explicitly disable the support
17022 using @option{--with-ust=no}.
17024 There are several ways to load the in-process agent in your program:
17027 @item Specifying it as dependency at link time
17029 You can link your program dynamically with the in-process agent
17030 library. On most systems, this is accomplished by adding
17031 @code{-linproctrace} to the link command.
17033 @item Using the system's preloading mechanisms
17035 You can force loading the in-process agent at startup time by using
17036 your system's support for preloading shared libraries. Many Unixes
17037 support the concept of preloading user defined libraries. In most
17038 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
17039 in the environment. See also the description of @code{gdbserver}'s
17040 @option{--wrapper} command line option.
17042 @item Using @value{GDBN} to force loading the agent at run time
17044 On some systems, you can force the inferior to load a shared library,
17045 by calling a dynamic loader function in the inferior that takes care
17046 of dynamically looking up and loading a shared library. On most Unix
17047 systems, the function is @code{dlopen}. You'll use the @code{call}
17048 command for that. For example:
17051 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
17054 Note that on most Unix systems, for the @code{dlopen} function to be
17055 available, the program needs to be linked with @code{-ldl}.
17058 On systems that have a userspace dynamic loader, like most Unix
17059 systems, when you connect to @code{gdbserver} using @code{target
17060 remote}, you'll find that the program is stopped at the dynamic
17061 loader's entry point, and no shared library has been loaded in the
17062 program's address space yet, including the in-process agent. In that
17063 case, before being able to use any of the fast or static tracepoints
17064 features, you need to let the loader run and load the shared
17065 libraries. The simplest way to do that is to run the program to the
17066 main procedure. E.g., if debugging a C or C@t{++} program, start
17067 @code{gdbserver} like so:
17070 $ gdbserver :9999 myprogram
17073 Start GDB and connect to @code{gdbserver} like so, and run to main:
17077 (@value{GDBP}) target remote myhost:9999
17078 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
17079 (@value{GDBP}) b main
17080 (@value{GDBP}) continue
17083 The in-process tracing agent library should now be loaded into the
17084 process; you can confirm it with the @code{info sharedlibrary}
17085 command, which will list @file{libinproctrace.so} as loaded in the
17086 process. You are now ready to install fast tracepoints, list static
17087 tracepoint markers, probe static tracepoints markers, and start
17090 @node Remote Configuration
17091 @section Remote Configuration
17094 @kindex show remote
17095 This section documents the configuration options available when
17096 debugging remote programs. For the options related to the File I/O
17097 extensions of the remote protocol, see @ref{system,
17098 system-call-allowed}.
17101 @item set remoteaddresssize @var{bits}
17102 @cindex address size for remote targets
17103 @cindex bits in remote address
17104 Set the maximum size of address in a memory packet to the specified
17105 number of bits. @value{GDBN} will mask off the address bits above
17106 that number, when it passes addresses to the remote target. The
17107 default value is the number of bits in the target's address.
17109 @item show remoteaddresssize
17110 Show the current value of remote address size in bits.
17112 @item set remotebaud @var{n}
17113 @cindex baud rate for remote targets
17114 Set the baud rate for the remote serial I/O to @var{n} baud. The
17115 value is used to set the speed of the serial port used for debugging
17118 @item show remotebaud
17119 Show the current speed of the remote connection.
17121 @item set remotebreak
17122 @cindex interrupt remote programs
17123 @cindex BREAK signal instead of Ctrl-C
17124 @anchor{set remotebreak}
17125 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17126 when you type @kbd{Ctrl-c} to interrupt the program running
17127 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17128 character instead. The default is off, since most remote systems
17129 expect to see @samp{Ctrl-C} as the interrupt signal.
17131 @item show remotebreak
17132 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17133 interrupt the remote program.
17135 @item set remoteflow on
17136 @itemx set remoteflow off
17137 @kindex set remoteflow
17138 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17139 on the serial port used to communicate to the remote target.
17141 @item show remoteflow
17142 @kindex show remoteflow
17143 Show the current setting of hardware flow control.
17145 @item set remotelogbase @var{base}
17146 Set the base (a.k.a.@: radix) of logging serial protocol
17147 communications to @var{base}. Supported values of @var{base} are:
17148 @code{ascii}, @code{octal}, and @code{hex}. The default is
17151 @item show remotelogbase
17152 Show the current setting of the radix for logging remote serial
17155 @item set remotelogfile @var{file}
17156 @cindex record serial communications on file
17157 Record remote serial communications on the named @var{file}. The
17158 default is not to record at all.
17160 @item show remotelogfile.
17161 Show the current setting of the file name on which to record the
17162 serial communications.
17164 @item set remotetimeout @var{num}
17165 @cindex timeout for serial communications
17166 @cindex remote timeout
17167 Set the timeout limit to wait for the remote target to respond to
17168 @var{num} seconds. The default is 2 seconds.
17170 @item show remotetimeout
17171 Show the current number of seconds to wait for the remote target
17174 @cindex limit hardware breakpoints and watchpoints
17175 @cindex remote target, limit break- and watchpoints
17176 @anchor{set remote hardware-watchpoint-limit}
17177 @anchor{set remote hardware-breakpoint-limit}
17178 @item set remote hardware-watchpoint-limit @var{limit}
17179 @itemx set remote hardware-breakpoint-limit @var{limit}
17180 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17181 watchpoints. A limit of -1, the default, is treated as unlimited.
17183 @cindex limit hardware watchpoints length
17184 @cindex remote target, limit watchpoints length
17185 @anchor{set remote hardware-watchpoint-length-limit}
17186 @item set remote hardware-watchpoint-length-limit @var{limit}
17187 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17188 a remote hardware watchpoint. A limit of -1, the default, is treated
17191 @item show remote hardware-watchpoint-length-limit
17192 Show the current limit (in bytes) of the maximum length of
17193 a remote hardware watchpoint.
17195 @item set remote exec-file @var{filename}
17196 @itemx show remote exec-file
17197 @anchor{set remote exec-file}
17198 @cindex executable file, for remote target
17199 Select the file used for @code{run} with @code{target
17200 extended-remote}. This should be set to a filename valid on the
17201 target system. If it is not set, the target will use a default
17202 filename (e.g.@: the last program run).
17204 @item set remote interrupt-sequence
17205 @cindex interrupt remote programs
17206 @cindex select Ctrl-C, BREAK or BREAK-g
17207 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
17208 @samp{BREAK-g} as the
17209 sequence to the remote target in order to interrupt the execution.
17210 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
17211 is high level of serial line for some certain time.
17212 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
17213 It is @code{BREAK} signal followed by character @code{g}.
17215 @item show interrupt-sequence
17216 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
17217 is sent by @value{GDBN} to interrupt the remote program.
17218 @code{BREAK-g} is BREAK signal followed by @code{g} and
17219 also known as Magic SysRq g.
17221 @item set remote interrupt-on-connect
17222 @cindex send interrupt-sequence on start
17223 Specify whether interrupt-sequence is sent to remote target when
17224 @value{GDBN} connects to it. This is mostly needed when you debug
17225 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
17226 which is known as Magic SysRq g in order to connect @value{GDBN}.
17228 @item show interrupt-on-connect
17229 Show whether interrupt-sequence is sent
17230 to remote target when @value{GDBN} connects to it.
17234 @item set tcp auto-retry on
17235 @cindex auto-retry, for remote TCP target
17236 Enable auto-retry for remote TCP connections. This is useful if the remote
17237 debugging agent is launched in parallel with @value{GDBN}; there is a race
17238 condition because the agent may not become ready to accept the connection
17239 before @value{GDBN} attempts to connect. When auto-retry is
17240 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17241 to establish the connection using the timeout specified by
17242 @code{set tcp connect-timeout}.
17244 @item set tcp auto-retry off
17245 Do not auto-retry failed TCP connections.
17247 @item show tcp auto-retry
17248 Show the current auto-retry setting.
17250 @item set tcp connect-timeout @var{seconds}
17251 @cindex connection timeout, for remote TCP target
17252 @cindex timeout, for remote target connection
17253 Set the timeout for establishing a TCP connection to the remote target to
17254 @var{seconds}. The timeout affects both polling to retry failed connections
17255 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17256 that are merely slow to complete, and represents an approximate cumulative
17259 @item show tcp connect-timeout
17260 Show the current connection timeout setting.
17263 @cindex remote packets, enabling and disabling
17264 The @value{GDBN} remote protocol autodetects the packets supported by
17265 your debugging stub. If you need to override the autodetection, you
17266 can use these commands to enable or disable individual packets. Each
17267 packet can be set to @samp{on} (the remote target supports this
17268 packet), @samp{off} (the remote target does not support this packet),
17269 or @samp{auto} (detect remote target support for this packet). They
17270 all default to @samp{auto}. For more information about each packet,
17271 see @ref{Remote Protocol}.
17273 During normal use, you should not have to use any of these commands.
17274 If you do, that may be a bug in your remote debugging stub, or a bug
17275 in @value{GDBN}. You may want to report the problem to the
17276 @value{GDBN} developers.
17278 For each packet @var{name}, the command to enable or disable the
17279 packet is @code{set remote @var{name}-packet}. The available settings
17282 @multitable @columnfractions 0.28 0.32 0.25
17285 @tab Related Features
17287 @item @code{fetch-register}
17289 @tab @code{info registers}
17291 @item @code{set-register}
17295 @item @code{binary-download}
17297 @tab @code{load}, @code{set}
17299 @item @code{read-aux-vector}
17300 @tab @code{qXfer:auxv:read}
17301 @tab @code{info auxv}
17303 @item @code{symbol-lookup}
17304 @tab @code{qSymbol}
17305 @tab Detecting multiple threads
17307 @item @code{attach}
17308 @tab @code{vAttach}
17311 @item @code{verbose-resume}
17313 @tab Stepping or resuming multiple threads
17319 @item @code{software-breakpoint}
17323 @item @code{hardware-breakpoint}
17327 @item @code{write-watchpoint}
17331 @item @code{read-watchpoint}
17335 @item @code{access-watchpoint}
17339 @item @code{target-features}
17340 @tab @code{qXfer:features:read}
17341 @tab @code{set architecture}
17343 @item @code{library-info}
17344 @tab @code{qXfer:libraries:read}
17345 @tab @code{info sharedlibrary}
17347 @item @code{memory-map}
17348 @tab @code{qXfer:memory-map:read}
17349 @tab @code{info mem}
17351 @item @code{read-sdata-object}
17352 @tab @code{qXfer:sdata:read}
17353 @tab @code{print $_sdata}
17355 @item @code{read-spu-object}
17356 @tab @code{qXfer:spu:read}
17357 @tab @code{info spu}
17359 @item @code{write-spu-object}
17360 @tab @code{qXfer:spu:write}
17361 @tab @code{info spu}
17363 @item @code{read-siginfo-object}
17364 @tab @code{qXfer:siginfo:read}
17365 @tab @code{print $_siginfo}
17367 @item @code{write-siginfo-object}
17368 @tab @code{qXfer:siginfo:write}
17369 @tab @code{set $_siginfo}
17371 @item @code{threads}
17372 @tab @code{qXfer:threads:read}
17373 @tab @code{info threads}
17375 @item @code{get-thread-local-@*storage-address}
17376 @tab @code{qGetTLSAddr}
17377 @tab Displaying @code{__thread} variables
17379 @item @code{get-thread-information-block-address}
17380 @tab @code{qGetTIBAddr}
17381 @tab Display MS-Windows Thread Information Block.
17383 @item @code{search-memory}
17384 @tab @code{qSearch:memory}
17387 @item @code{supported-packets}
17388 @tab @code{qSupported}
17389 @tab Remote communications parameters
17391 @item @code{pass-signals}
17392 @tab @code{QPassSignals}
17393 @tab @code{handle @var{signal}}
17395 @item @code{hostio-close-packet}
17396 @tab @code{vFile:close}
17397 @tab @code{remote get}, @code{remote put}
17399 @item @code{hostio-open-packet}
17400 @tab @code{vFile:open}
17401 @tab @code{remote get}, @code{remote put}
17403 @item @code{hostio-pread-packet}
17404 @tab @code{vFile:pread}
17405 @tab @code{remote get}, @code{remote put}
17407 @item @code{hostio-pwrite-packet}
17408 @tab @code{vFile:pwrite}
17409 @tab @code{remote get}, @code{remote put}
17411 @item @code{hostio-unlink-packet}
17412 @tab @code{vFile:unlink}
17413 @tab @code{remote delete}
17415 @item @code{noack-packet}
17416 @tab @code{QStartNoAckMode}
17417 @tab Packet acknowledgment
17419 @item @code{osdata}
17420 @tab @code{qXfer:osdata:read}
17421 @tab @code{info os}
17423 @item @code{query-attached}
17424 @tab @code{qAttached}
17425 @tab Querying remote process attach state.
17427 @item @code{traceframe-info}
17428 @tab @code{qXfer:traceframe-info:read}
17429 @tab Traceframe info
17431 @item @code{install-in-trace}
17432 @tab @code{InstallInTrace}
17433 @tab Install tracepoint in tracing
17435 @item @code{disable-randomization}
17436 @tab @code{QDisableRandomization}
17437 @tab @code{set disable-randomization}
17441 @section Implementing a Remote Stub
17443 @cindex debugging stub, example
17444 @cindex remote stub, example
17445 @cindex stub example, remote debugging
17446 The stub files provided with @value{GDBN} implement the target side of the
17447 communication protocol, and the @value{GDBN} side is implemented in the
17448 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
17449 these subroutines to communicate, and ignore the details. (If you're
17450 implementing your own stub file, you can still ignore the details: start
17451 with one of the existing stub files. @file{sparc-stub.c} is the best
17452 organized, and therefore the easiest to read.)
17454 @cindex remote serial debugging, overview
17455 To debug a program running on another machine (the debugging
17456 @dfn{target} machine), you must first arrange for all the usual
17457 prerequisites for the program to run by itself. For example, for a C
17462 A startup routine to set up the C runtime environment; these usually
17463 have a name like @file{crt0}. The startup routine may be supplied by
17464 your hardware supplier, or you may have to write your own.
17467 A C subroutine library to support your program's
17468 subroutine calls, notably managing input and output.
17471 A way of getting your program to the other machine---for example, a
17472 download program. These are often supplied by the hardware
17473 manufacturer, but you may have to write your own from hardware
17477 The next step is to arrange for your program to use a serial port to
17478 communicate with the machine where @value{GDBN} is running (the @dfn{host}
17479 machine). In general terms, the scheme looks like this:
17483 @value{GDBN} already understands how to use this protocol; when everything
17484 else is set up, you can simply use the @samp{target remote} command
17485 (@pxref{Targets,,Specifying a Debugging Target}).
17487 @item On the target,
17488 you must link with your program a few special-purpose subroutines that
17489 implement the @value{GDBN} remote serial protocol. The file containing these
17490 subroutines is called a @dfn{debugging stub}.
17492 On certain remote targets, you can use an auxiliary program
17493 @code{gdbserver} instead of linking a stub into your program.
17494 @xref{Server,,Using the @code{gdbserver} Program}, for details.
17497 The debugging stub is specific to the architecture of the remote
17498 machine; for example, use @file{sparc-stub.c} to debug programs on
17501 @cindex remote serial stub list
17502 These working remote stubs are distributed with @value{GDBN}:
17507 @cindex @file{i386-stub.c}
17510 For Intel 386 and compatible architectures.
17513 @cindex @file{m68k-stub.c}
17514 @cindex Motorola 680x0
17516 For Motorola 680x0 architectures.
17519 @cindex @file{sh-stub.c}
17522 For Renesas SH architectures.
17525 @cindex @file{sparc-stub.c}
17527 For @sc{sparc} architectures.
17529 @item sparcl-stub.c
17530 @cindex @file{sparcl-stub.c}
17533 For Fujitsu @sc{sparclite} architectures.
17537 The @file{README} file in the @value{GDBN} distribution may list other
17538 recently added stubs.
17541 * Stub Contents:: What the stub can do for you
17542 * Bootstrapping:: What you must do for the stub
17543 * Debug Session:: Putting it all together
17546 @node Stub Contents
17547 @subsection What the Stub Can Do for You
17549 @cindex remote serial stub
17550 The debugging stub for your architecture supplies these three
17554 @item set_debug_traps
17555 @findex set_debug_traps
17556 @cindex remote serial stub, initialization
17557 This routine arranges for @code{handle_exception} to run when your
17558 program stops. You must call this subroutine explicitly in your
17559 program's startup code.
17561 @item handle_exception
17562 @findex handle_exception
17563 @cindex remote serial stub, main routine
17564 This is the central workhorse, but your program never calls it
17565 explicitly---the setup code arranges for @code{handle_exception} to
17566 run when a trap is triggered.
17568 @code{handle_exception} takes control when your program stops during
17569 execution (for example, on a breakpoint), and mediates communications
17570 with @value{GDBN} on the host machine. This is where the communications
17571 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
17572 representative on the target machine. It begins by sending summary
17573 information on the state of your program, then continues to execute,
17574 retrieving and transmitting any information @value{GDBN} needs, until you
17575 execute a @value{GDBN} command that makes your program resume; at that point,
17576 @code{handle_exception} returns control to your own code on the target
17580 @cindex @code{breakpoint} subroutine, remote
17581 Use this auxiliary subroutine to make your program contain a
17582 breakpoint. Depending on the particular situation, this may be the only
17583 way for @value{GDBN} to get control. For instance, if your target
17584 machine has some sort of interrupt button, you won't need to call this;
17585 pressing the interrupt button transfers control to
17586 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
17587 simply receiving characters on the serial port may also trigger a trap;
17588 again, in that situation, you don't need to call @code{breakpoint} from
17589 your own program---simply running @samp{target remote} from the host
17590 @value{GDBN} session gets control.
17592 Call @code{breakpoint} if none of these is true, or if you simply want
17593 to make certain your program stops at a predetermined point for the
17594 start of your debugging session.
17597 @node Bootstrapping
17598 @subsection What You Must Do for the Stub
17600 @cindex remote stub, support routines
17601 The debugging stubs that come with @value{GDBN} are set up for a particular
17602 chip architecture, but they have no information about the rest of your
17603 debugging target machine.
17605 First of all you need to tell the stub how to communicate with the
17609 @item int getDebugChar()
17610 @findex getDebugChar
17611 Write this subroutine to read a single character from the serial port.
17612 It may be identical to @code{getchar} for your target system; a
17613 different name is used to allow you to distinguish the two if you wish.
17615 @item void putDebugChar(int)
17616 @findex putDebugChar
17617 Write this subroutine to write a single character to the serial port.
17618 It may be identical to @code{putchar} for your target system; a
17619 different name is used to allow you to distinguish the two if you wish.
17622 @cindex control C, and remote debugging
17623 @cindex interrupting remote targets
17624 If you want @value{GDBN} to be able to stop your program while it is
17625 running, you need to use an interrupt-driven serial driver, and arrange
17626 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
17627 character). That is the character which @value{GDBN} uses to tell the
17628 remote system to stop.
17630 Getting the debugging target to return the proper status to @value{GDBN}
17631 probably requires changes to the standard stub; one quick and dirty way
17632 is to just execute a breakpoint instruction (the ``dirty'' part is that
17633 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17635 Other routines you need to supply are:
17638 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17639 @findex exceptionHandler
17640 Write this function to install @var{exception_address} in the exception
17641 handling tables. You need to do this because the stub does not have any
17642 way of knowing what the exception handling tables on your target system
17643 are like (for example, the processor's table might be in @sc{rom},
17644 containing entries which point to a table in @sc{ram}).
17645 @var{exception_number} is the exception number which should be changed;
17646 its meaning is architecture-dependent (for example, different numbers
17647 might represent divide by zero, misaligned access, etc). When this
17648 exception occurs, control should be transferred directly to
17649 @var{exception_address}, and the processor state (stack, registers,
17650 and so on) should be just as it is when a processor exception occurs. So if
17651 you want to use a jump instruction to reach @var{exception_address}, it
17652 should be a simple jump, not a jump to subroutine.
17654 For the 386, @var{exception_address} should be installed as an interrupt
17655 gate so that interrupts are masked while the handler runs. The gate
17656 should be at privilege level 0 (the most privileged level). The
17657 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17658 help from @code{exceptionHandler}.
17660 @item void flush_i_cache()
17661 @findex flush_i_cache
17662 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17663 instruction cache, if any, on your target machine. If there is no
17664 instruction cache, this subroutine may be a no-op.
17666 On target machines that have instruction caches, @value{GDBN} requires this
17667 function to make certain that the state of your program is stable.
17671 You must also make sure this library routine is available:
17674 @item void *memset(void *, int, int)
17676 This is the standard library function @code{memset} that sets an area of
17677 memory to a known value. If you have one of the free versions of
17678 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17679 either obtain it from your hardware manufacturer, or write your own.
17682 If you do not use the GNU C compiler, you may need other standard
17683 library subroutines as well; this varies from one stub to another,
17684 but in general the stubs are likely to use any of the common library
17685 subroutines which @code{@value{NGCC}} generates as inline code.
17688 @node Debug Session
17689 @subsection Putting it All Together
17691 @cindex remote serial debugging summary
17692 In summary, when your program is ready to debug, you must follow these
17697 Make sure you have defined the supporting low-level routines
17698 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17700 @code{getDebugChar}, @code{putDebugChar},
17701 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17705 Insert these lines in your program's startup code, before the main
17706 procedure is called:
17713 On some machines, when a breakpoint trap is raised, the hardware
17714 automatically makes the PC point to the instruction after the
17715 breakpoint. If your machine doesn't do that, you may need to adjust
17716 @code{handle_exception} to arrange for it to return to the instruction
17717 after the breakpoint on this first invocation, so that your program
17718 doesn't keep hitting the initial breakpoint instead of making
17722 For the 680x0 stub only, you need to provide a variable called
17723 @code{exceptionHook}. Normally you just use:
17726 void (*exceptionHook)() = 0;
17730 but if before calling @code{set_debug_traps}, you set it to point to a
17731 function in your program, that function is called when
17732 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17733 error). The function indicated by @code{exceptionHook} is called with
17734 one parameter: an @code{int} which is the exception number.
17737 Compile and link together: your program, the @value{GDBN} debugging stub for
17738 your target architecture, and the supporting subroutines.
17741 Make sure you have a serial connection between your target machine and
17742 the @value{GDBN} host, and identify the serial port on the host.
17745 @c The "remote" target now provides a `load' command, so we should
17746 @c document that. FIXME.
17747 Download your program to your target machine (or get it there by
17748 whatever means the manufacturer provides), and start it.
17751 Start @value{GDBN} on the host, and connect to the target
17752 (@pxref{Connecting,,Connecting to a Remote Target}).
17756 @node Configurations
17757 @chapter Configuration-Specific Information
17759 While nearly all @value{GDBN} commands are available for all native and
17760 cross versions of the debugger, there are some exceptions. This chapter
17761 describes things that are only available in certain configurations.
17763 There are three major categories of configurations: native
17764 configurations, where the host and target are the same, embedded
17765 operating system configurations, which are usually the same for several
17766 different processor architectures, and bare embedded processors, which
17767 are quite different from each other.
17772 * Embedded Processors::
17779 This section describes details specific to particular native
17784 * BSD libkvm Interface:: Debugging BSD kernel memory images
17785 * SVR4 Process Information:: SVR4 process information
17786 * DJGPP Native:: Features specific to the DJGPP port
17787 * Cygwin Native:: Features specific to the Cygwin port
17788 * Hurd Native:: Features specific to @sc{gnu} Hurd
17789 * Neutrino:: Features specific to QNX Neutrino
17790 * Darwin:: Features specific to Darwin
17796 On HP-UX systems, if you refer to a function or variable name that
17797 begins with a dollar sign, @value{GDBN} searches for a user or system
17798 name first, before it searches for a convenience variable.
17801 @node BSD libkvm Interface
17802 @subsection BSD libkvm Interface
17805 @cindex kernel memory image
17806 @cindex kernel crash dump
17808 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17809 interface that provides a uniform interface for accessing kernel virtual
17810 memory images, including live systems and crash dumps. @value{GDBN}
17811 uses this interface to allow you to debug live kernels and kernel crash
17812 dumps on many native BSD configurations. This is implemented as a
17813 special @code{kvm} debugging target. For debugging a live system, load
17814 the currently running kernel into @value{GDBN} and connect to the
17818 (@value{GDBP}) @b{target kvm}
17821 For debugging crash dumps, provide the file name of the crash dump as an
17825 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17828 Once connected to the @code{kvm} target, the following commands are
17834 Set current context from the @dfn{Process Control Block} (PCB) address.
17837 Set current context from proc address. This command isn't available on
17838 modern FreeBSD systems.
17841 @node SVR4 Process Information
17842 @subsection SVR4 Process Information
17844 @cindex examine process image
17845 @cindex process info via @file{/proc}
17847 Many versions of SVR4 and compatible systems provide a facility called
17848 @samp{/proc} that can be used to examine the image of a running
17849 process using file-system subroutines. If @value{GDBN} is configured
17850 for an operating system with this facility, the command @code{info
17851 proc} is available to report information about the process running
17852 your program, or about any process running on your system. @code{info
17853 proc} works only on SVR4 systems that include the @code{procfs} code.
17854 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17855 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17861 @itemx info proc @var{process-id}
17862 Summarize available information about any running process. If a
17863 process ID is specified by @var{process-id}, display information about
17864 that process; otherwise display information about the program being
17865 debugged. The summary includes the debugged process ID, the command
17866 line used to invoke it, its current working directory, and its
17867 executable file's absolute file name.
17869 On some systems, @var{process-id} can be of the form
17870 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17871 within a process. If the optional @var{pid} part is missing, it means
17872 a thread from the process being debugged (the leading @samp{/} still
17873 needs to be present, or else @value{GDBN} will interpret the number as
17874 a process ID rather than a thread ID).
17876 @item info proc mappings
17877 @cindex memory address space mappings
17878 Report the memory address space ranges accessible in the program, with
17879 information on whether the process has read, write, or execute access
17880 rights to each range. On @sc{gnu}/Linux systems, each memory range
17881 includes the object file which is mapped to that range, instead of the
17882 memory access rights to that range.
17884 @item info proc stat
17885 @itemx info proc status
17886 @cindex process detailed status information
17887 These subcommands are specific to @sc{gnu}/Linux systems. They show
17888 the process-related information, including the user ID and group ID;
17889 how many threads are there in the process; its virtual memory usage;
17890 the signals that are pending, blocked, and ignored; its TTY; its
17891 consumption of system and user time; its stack size; its @samp{nice}
17892 value; etc. For more information, see the @samp{proc} man page
17893 (type @kbd{man 5 proc} from your shell prompt).
17895 @item info proc all
17896 Show all the information about the process described under all of the
17897 above @code{info proc} subcommands.
17900 @comment These sub-options of 'info proc' were not included when
17901 @comment procfs.c was re-written. Keep their descriptions around
17902 @comment against the day when someone finds the time to put them back in.
17903 @kindex info proc times
17904 @item info proc times
17905 Starting time, user CPU time, and system CPU time for your program and
17908 @kindex info proc id
17910 Report on the process IDs related to your program: its own process ID,
17911 the ID of its parent, the process group ID, and the session ID.
17914 @item set procfs-trace
17915 @kindex set procfs-trace
17916 @cindex @code{procfs} API calls
17917 This command enables and disables tracing of @code{procfs} API calls.
17919 @item show procfs-trace
17920 @kindex show procfs-trace
17921 Show the current state of @code{procfs} API call tracing.
17923 @item set procfs-file @var{file}
17924 @kindex set procfs-file
17925 Tell @value{GDBN} to write @code{procfs} API trace to the named
17926 @var{file}. @value{GDBN} appends the trace info to the previous
17927 contents of the file. The default is to display the trace on the
17930 @item show procfs-file
17931 @kindex show procfs-file
17932 Show the file to which @code{procfs} API trace is written.
17934 @item proc-trace-entry
17935 @itemx proc-trace-exit
17936 @itemx proc-untrace-entry
17937 @itemx proc-untrace-exit
17938 @kindex proc-trace-entry
17939 @kindex proc-trace-exit
17940 @kindex proc-untrace-entry
17941 @kindex proc-untrace-exit
17942 These commands enable and disable tracing of entries into and exits
17943 from the @code{syscall} interface.
17946 @kindex info pidlist
17947 @cindex process list, QNX Neutrino
17948 For QNX Neutrino only, this command displays the list of all the
17949 processes and all the threads within each process.
17952 @kindex info meminfo
17953 @cindex mapinfo list, QNX Neutrino
17954 For QNX Neutrino only, this command displays the list of all mapinfos.
17958 @subsection Features for Debugging @sc{djgpp} Programs
17959 @cindex @sc{djgpp} debugging
17960 @cindex native @sc{djgpp} debugging
17961 @cindex MS-DOS-specific commands
17964 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17965 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17966 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17967 top of real-mode DOS systems and their emulations.
17969 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17970 defines a few commands specific to the @sc{djgpp} port. This
17971 subsection describes those commands.
17976 This is a prefix of @sc{djgpp}-specific commands which print
17977 information about the target system and important OS structures.
17980 @cindex MS-DOS system info
17981 @cindex free memory information (MS-DOS)
17982 @item info dos sysinfo
17983 This command displays assorted information about the underlying
17984 platform: the CPU type and features, the OS version and flavor, the
17985 DPMI version, and the available conventional and DPMI memory.
17990 @cindex segment descriptor tables
17991 @cindex descriptor tables display
17993 @itemx info dos ldt
17994 @itemx info dos idt
17995 These 3 commands display entries from, respectively, Global, Local,
17996 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17997 tables are data structures which store a descriptor for each segment
17998 that is currently in use. The segment's selector is an index into a
17999 descriptor table; the table entry for that index holds the
18000 descriptor's base address and limit, and its attributes and access
18003 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
18004 segment (used for both data and the stack), and a DOS segment (which
18005 allows access to DOS/BIOS data structures and absolute addresses in
18006 conventional memory). However, the DPMI host will usually define
18007 additional segments in order to support the DPMI environment.
18009 @cindex garbled pointers
18010 These commands allow to display entries from the descriptor tables.
18011 Without an argument, all entries from the specified table are
18012 displayed. An argument, which should be an integer expression, means
18013 display a single entry whose index is given by the argument. For
18014 example, here's a convenient way to display information about the
18015 debugged program's data segment:
18018 @exdent @code{(@value{GDBP}) info dos ldt $ds}
18019 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
18023 This comes in handy when you want to see whether a pointer is outside
18024 the data segment's limit (i.e.@: @dfn{garbled}).
18026 @cindex page tables display (MS-DOS)
18028 @itemx info dos pte
18029 These two commands display entries from, respectively, the Page
18030 Directory and the Page Tables. Page Directories and Page Tables are
18031 data structures which control how virtual memory addresses are mapped
18032 into physical addresses. A Page Table includes an entry for every
18033 page of memory that is mapped into the program's address space; there
18034 may be several Page Tables, each one holding up to 4096 entries. A
18035 Page Directory has up to 4096 entries, one each for every Page Table
18036 that is currently in use.
18038 Without an argument, @kbd{info dos pde} displays the entire Page
18039 Directory, and @kbd{info dos pte} displays all the entries in all of
18040 the Page Tables. An argument, an integer expression, given to the
18041 @kbd{info dos pde} command means display only that entry from the Page
18042 Directory table. An argument given to the @kbd{info dos pte} command
18043 means display entries from a single Page Table, the one pointed to by
18044 the specified entry in the Page Directory.
18046 @cindex direct memory access (DMA) on MS-DOS
18047 These commands are useful when your program uses @dfn{DMA} (Direct
18048 Memory Access), which needs physical addresses to program the DMA
18051 These commands are supported only with some DPMI servers.
18053 @cindex physical address from linear address
18054 @item info dos address-pte @var{addr}
18055 This command displays the Page Table entry for a specified linear
18056 address. The argument @var{addr} is a linear address which should
18057 already have the appropriate segment's base address added to it,
18058 because this command accepts addresses which may belong to @emph{any}
18059 segment. For example, here's how to display the Page Table entry for
18060 the page where a variable @code{i} is stored:
18063 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
18064 @exdent @code{Page Table entry for address 0x11a00d30:}
18065 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
18069 This says that @code{i} is stored at offset @code{0xd30} from the page
18070 whose physical base address is @code{0x02698000}, and shows all the
18071 attributes of that page.
18073 Note that you must cast the addresses of variables to a @code{char *},
18074 since otherwise the value of @code{__djgpp_base_address}, the base
18075 address of all variables and functions in a @sc{djgpp} program, will
18076 be added using the rules of C pointer arithmetics: if @code{i} is
18077 declared an @code{int}, @value{GDBN} will add 4 times the value of
18078 @code{__djgpp_base_address} to the address of @code{i}.
18080 Here's another example, it displays the Page Table entry for the
18084 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
18085 @exdent @code{Page Table entry for address 0x29110:}
18086 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
18090 (The @code{+ 3} offset is because the transfer buffer's address is the
18091 3rd member of the @code{_go32_info_block} structure.) The output
18092 clearly shows that this DPMI server maps the addresses in conventional
18093 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
18094 linear (@code{0x29110}) addresses are identical.
18096 This command is supported only with some DPMI servers.
18099 @cindex DOS serial data link, remote debugging
18100 In addition to native debugging, the DJGPP port supports remote
18101 debugging via a serial data link. The following commands are specific
18102 to remote serial debugging in the DJGPP port of @value{GDBN}.
18105 @kindex set com1base
18106 @kindex set com1irq
18107 @kindex set com2base
18108 @kindex set com2irq
18109 @kindex set com3base
18110 @kindex set com3irq
18111 @kindex set com4base
18112 @kindex set com4irq
18113 @item set com1base @var{addr}
18114 This command sets the base I/O port address of the @file{COM1} serial
18117 @item set com1irq @var{irq}
18118 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
18119 for the @file{COM1} serial port.
18121 There are similar commands @samp{set com2base}, @samp{set com3irq},
18122 etc.@: for setting the port address and the @code{IRQ} lines for the
18125 @kindex show com1base
18126 @kindex show com1irq
18127 @kindex show com2base
18128 @kindex show com2irq
18129 @kindex show com3base
18130 @kindex show com3irq
18131 @kindex show com4base
18132 @kindex show com4irq
18133 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18134 display the current settings of the base address and the @code{IRQ}
18135 lines used by the COM ports.
18138 @kindex info serial
18139 @cindex DOS serial port status
18140 This command prints the status of the 4 DOS serial ports. For each
18141 port, it prints whether it's active or not, its I/O base address and
18142 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18143 counts of various errors encountered so far.
18147 @node Cygwin Native
18148 @subsection Features for Debugging MS Windows PE Executables
18149 @cindex MS Windows debugging
18150 @cindex native Cygwin debugging
18151 @cindex Cygwin-specific commands
18153 @value{GDBN} supports native debugging of MS Windows programs, including
18154 DLLs with and without symbolic debugging information.
18156 @cindex Ctrl-BREAK, MS-Windows
18157 @cindex interrupt debuggee on MS-Windows
18158 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18159 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18160 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18161 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18162 sequence, which can be used to interrupt the debuggee even if it
18165 There are various additional Cygwin-specific commands, described in
18166 this section. Working with DLLs that have no debugging symbols is
18167 described in @ref{Non-debug DLL Symbols}.
18172 This is a prefix of MS Windows-specific commands which print
18173 information about the target system and important OS structures.
18175 @item info w32 selector
18176 This command displays information returned by
18177 the Win32 API @code{GetThreadSelectorEntry} function.
18178 It takes an optional argument that is evaluated to
18179 a long value to give the information about this given selector.
18180 Without argument, this command displays information
18181 about the six segment registers.
18183 @item info w32 thread-information-block
18184 This command displays thread specific information stored in the
18185 Thread Information Block (readable on the X86 CPU family using @code{$fs}
18186 selector for 32-bit programs and @code{$gs} for 64-bit programs).
18190 This is a Cygwin-specific alias of @code{info shared}.
18192 @kindex dll-symbols
18194 This command loads symbols from a dll similarly to
18195 add-sym command but without the need to specify a base address.
18197 @kindex set cygwin-exceptions
18198 @cindex debugging the Cygwin DLL
18199 @cindex Cygwin DLL, debugging
18200 @item set cygwin-exceptions @var{mode}
18201 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
18202 happen inside the Cygwin DLL. If @var{mode} is @code{off},
18203 @value{GDBN} will delay recognition of exceptions, and may ignore some
18204 exceptions which seem to be caused by internal Cygwin DLL
18205 ``bookkeeping''. This option is meant primarily for debugging the
18206 Cygwin DLL itself; the default value is @code{off} to avoid annoying
18207 @value{GDBN} users with false @code{SIGSEGV} signals.
18209 @kindex show cygwin-exceptions
18210 @item show cygwin-exceptions
18211 Displays whether @value{GDBN} will break on exceptions that happen
18212 inside the Cygwin DLL itself.
18214 @kindex set new-console
18215 @item set new-console @var{mode}
18216 If @var{mode} is @code{on} the debuggee will
18217 be started in a new console on next start.
18218 If @var{mode} is @code{off}, the debuggee will
18219 be started in the same console as the debugger.
18221 @kindex show new-console
18222 @item show new-console
18223 Displays whether a new console is used
18224 when the debuggee is started.
18226 @kindex set new-group
18227 @item set new-group @var{mode}
18228 This boolean value controls whether the debuggee should
18229 start a new group or stay in the same group as the debugger.
18230 This affects the way the Windows OS handles
18233 @kindex show new-group
18234 @item show new-group
18235 Displays current value of new-group boolean.
18237 @kindex set debugevents
18238 @item set debugevents
18239 This boolean value adds debug output concerning kernel events related
18240 to the debuggee seen by the debugger. This includes events that
18241 signal thread and process creation and exit, DLL loading and
18242 unloading, console interrupts, and debugging messages produced by the
18243 Windows @code{OutputDebugString} API call.
18245 @kindex set debugexec
18246 @item set debugexec
18247 This boolean value adds debug output concerning execute events
18248 (such as resume thread) seen by the debugger.
18250 @kindex set debugexceptions
18251 @item set debugexceptions
18252 This boolean value adds debug output concerning exceptions in the
18253 debuggee seen by the debugger.
18255 @kindex set debugmemory
18256 @item set debugmemory
18257 This boolean value adds debug output concerning debuggee memory reads
18258 and writes by the debugger.
18262 This boolean values specifies whether the debuggee is called
18263 via a shell or directly (default value is on).
18267 Displays if the debuggee will be started with a shell.
18272 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18275 @node Non-debug DLL Symbols
18276 @subsubsection Support for DLLs without Debugging Symbols
18277 @cindex DLLs with no debugging symbols
18278 @cindex Minimal symbols and DLLs
18280 Very often on windows, some of the DLLs that your program relies on do
18281 not include symbolic debugging information (for example,
18282 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18283 symbols in a DLL, it relies on the minimal amount of symbolic
18284 information contained in the DLL's export table. This section
18285 describes working with such symbols, known internally to @value{GDBN} as
18286 ``minimal symbols''.
18288 Note that before the debugged program has started execution, no DLLs
18289 will have been loaded. The easiest way around this problem is simply to
18290 start the program --- either by setting a breakpoint or letting the
18291 program run once to completion. It is also possible to force
18292 @value{GDBN} to load a particular DLL before starting the executable ---
18293 see the shared library information in @ref{Files}, or the
18294 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18295 explicitly loading symbols from a DLL with no debugging information will
18296 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18297 which may adversely affect symbol lookup performance.
18299 @subsubsection DLL Name Prefixes
18301 In keeping with the naming conventions used by the Microsoft debugging
18302 tools, DLL export symbols are made available with a prefix based on the
18303 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18304 also entered into the symbol table, so @code{CreateFileA} is often
18305 sufficient. In some cases there will be name clashes within a program
18306 (particularly if the executable itself includes full debugging symbols)
18307 necessitating the use of the fully qualified name when referring to the
18308 contents of the DLL. Use single-quotes around the name to avoid the
18309 exclamation mark (``!'') being interpreted as a language operator.
18311 Note that the internal name of the DLL may be all upper-case, even
18312 though the file name of the DLL is lower-case, or vice-versa. Since
18313 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
18314 some confusion. If in doubt, try the @code{info functions} and
18315 @code{info variables} commands or even @code{maint print msymbols}
18316 (@pxref{Symbols}). Here's an example:
18319 (@value{GDBP}) info function CreateFileA
18320 All functions matching regular expression "CreateFileA":
18322 Non-debugging symbols:
18323 0x77e885f4 CreateFileA
18324 0x77e885f4 KERNEL32!CreateFileA
18328 (@value{GDBP}) info function !
18329 All functions matching regular expression "!":
18331 Non-debugging symbols:
18332 0x6100114c cygwin1!__assert
18333 0x61004034 cygwin1!_dll_crt0@@0
18334 0x61004240 cygwin1!dll_crt0(per_process *)
18338 @subsubsection Working with Minimal Symbols
18340 Symbols extracted from a DLL's export table do not contain very much
18341 type information. All that @value{GDBN} can do is guess whether a symbol
18342 refers to a function or variable depending on the linker section that
18343 contains the symbol. Also note that the actual contents of the memory
18344 contained in a DLL are not available unless the program is running. This
18345 means that you cannot examine the contents of a variable or disassemble
18346 a function within a DLL without a running program.
18348 Variables are generally treated as pointers and dereferenced
18349 automatically. For this reason, it is often necessary to prefix a
18350 variable name with the address-of operator (``&'') and provide explicit
18351 type information in the command. Here's an example of the type of
18355 (@value{GDBP}) print 'cygwin1!__argv'
18360 (@value{GDBP}) x 'cygwin1!__argv'
18361 0x10021610: "\230y\""
18364 And two possible solutions:
18367 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
18368 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
18372 (@value{GDBP}) x/2x &'cygwin1!__argv'
18373 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
18374 (@value{GDBP}) x/x 0x10021608
18375 0x10021608: 0x0022fd98
18376 (@value{GDBP}) x/s 0x0022fd98
18377 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
18380 Setting a break point within a DLL is possible even before the program
18381 starts execution. However, under these circumstances, @value{GDBN} can't
18382 examine the initial instructions of the function in order to skip the
18383 function's frame set-up code. You can work around this by using ``*&''
18384 to set the breakpoint at a raw memory address:
18387 (@value{GDBP}) break *&'python22!PyOS_Readline'
18388 Breakpoint 1 at 0x1e04eff0
18391 The author of these extensions is not entirely convinced that setting a
18392 break point within a shared DLL like @file{kernel32.dll} is completely
18396 @subsection Commands Specific to @sc{gnu} Hurd Systems
18397 @cindex @sc{gnu} Hurd debugging
18399 This subsection describes @value{GDBN} commands specific to the
18400 @sc{gnu} Hurd native debugging.
18405 @kindex set signals@r{, Hurd command}
18406 @kindex set sigs@r{, Hurd command}
18407 This command toggles the state of inferior signal interception by
18408 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
18409 affected by this command. @code{sigs} is a shorthand alias for
18414 @kindex show signals@r{, Hurd command}
18415 @kindex show sigs@r{, Hurd command}
18416 Show the current state of intercepting inferior's signals.
18418 @item set signal-thread
18419 @itemx set sigthread
18420 @kindex set signal-thread
18421 @kindex set sigthread
18422 This command tells @value{GDBN} which thread is the @code{libc} signal
18423 thread. That thread is run when a signal is delivered to a running
18424 process. @code{set sigthread} is the shorthand alias of @code{set
18427 @item show signal-thread
18428 @itemx show sigthread
18429 @kindex show signal-thread
18430 @kindex show sigthread
18431 These two commands show which thread will run when the inferior is
18432 delivered a signal.
18435 @kindex set stopped@r{, Hurd command}
18436 This commands tells @value{GDBN} that the inferior process is stopped,
18437 as with the @code{SIGSTOP} signal. The stopped process can be
18438 continued by delivering a signal to it.
18441 @kindex show stopped@r{, Hurd command}
18442 This command shows whether @value{GDBN} thinks the debuggee is
18445 @item set exceptions
18446 @kindex set exceptions@r{, Hurd command}
18447 Use this command to turn off trapping of exceptions in the inferior.
18448 When exception trapping is off, neither breakpoints nor
18449 single-stepping will work. To restore the default, set exception
18452 @item show exceptions
18453 @kindex show exceptions@r{, Hurd command}
18454 Show the current state of trapping exceptions in the inferior.
18456 @item set task pause
18457 @kindex set task@r{, Hurd commands}
18458 @cindex task attributes (@sc{gnu} Hurd)
18459 @cindex pause current task (@sc{gnu} Hurd)
18460 This command toggles task suspension when @value{GDBN} has control.
18461 Setting it to on takes effect immediately, and the task is suspended
18462 whenever @value{GDBN} gets control. Setting it to off will take
18463 effect the next time the inferior is continued. If this option is set
18464 to off, you can use @code{set thread default pause on} or @code{set
18465 thread pause on} (see below) to pause individual threads.
18467 @item show task pause
18468 @kindex show task@r{, Hurd commands}
18469 Show the current state of task suspension.
18471 @item set task detach-suspend-count
18472 @cindex task suspend count
18473 @cindex detach from task, @sc{gnu} Hurd
18474 This command sets the suspend count the task will be left with when
18475 @value{GDBN} detaches from it.
18477 @item show task detach-suspend-count
18478 Show the suspend count the task will be left with when detaching.
18480 @item set task exception-port
18481 @itemx set task excp
18482 @cindex task exception port, @sc{gnu} Hurd
18483 This command sets the task exception port to which @value{GDBN} will
18484 forward exceptions. The argument should be the value of the @dfn{send
18485 rights} of the task. @code{set task excp} is a shorthand alias.
18487 @item set noninvasive
18488 @cindex noninvasive task options
18489 This command switches @value{GDBN} to a mode that is the least
18490 invasive as far as interfering with the inferior is concerned. This
18491 is the same as using @code{set task pause}, @code{set exceptions}, and
18492 @code{set signals} to values opposite to the defaults.
18494 @item info send-rights
18495 @itemx info receive-rights
18496 @itemx info port-rights
18497 @itemx info port-sets
18498 @itemx info dead-names
18501 @cindex send rights, @sc{gnu} Hurd
18502 @cindex receive rights, @sc{gnu} Hurd
18503 @cindex port rights, @sc{gnu} Hurd
18504 @cindex port sets, @sc{gnu} Hurd
18505 @cindex dead names, @sc{gnu} Hurd
18506 These commands display information about, respectively, send rights,
18507 receive rights, port rights, port sets, and dead names of a task.
18508 There are also shorthand aliases: @code{info ports} for @code{info
18509 port-rights} and @code{info psets} for @code{info port-sets}.
18511 @item set thread pause
18512 @kindex set thread@r{, Hurd command}
18513 @cindex thread properties, @sc{gnu} Hurd
18514 @cindex pause current thread (@sc{gnu} Hurd)
18515 This command toggles current thread suspension when @value{GDBN} has
18516 control. Setting it to on takes effect immediately, and the current
18517 thread is suspended whenever @value{GDBN} gets control. Setting it to
18518 off will take effect the next time the inferior is continued.
18519 Normally, this command has no effect, since when @value{GDBN} has
18520 control, the whole task is suspended. However, if you used @code{set
18521 task pause off} (see above), this command comes in handy to suspend
18522 only the current thread.
18524 @item show thread pause
18525 @kindex show thread@r{, Hurd command}
18526 This command shows the state of current thread suspension.
18528 @item set thread run
18529 This command sets whether the current thread is allowed to run.
18531 @item show thread run
18532 Show whether the current thread is allowed to run.
18534 @item set thread detach-suspend-count
18535 @cindex thread suspend count, @sc{gnu} Hurd
18536 @cindex detach from thread, @sc{gnu} Hurd
18537 This command sets the suspend count @value{GDBN} will leave on a
18538 thread when detaching. This number is relative to the suspend count
18539 found by @value{GDBN} when it notices the thread; use @code{set thread
18540 takeover-suspend-count} to force it to an absolute value.
18542 @item show thread detach-suspend-count
18543 Show the suspend count @value{GDBN} will leave on the thread when
18546 @item set thread exception-port
18547 @itemx set thread excp
18548 Set the thread exception port to which to forward exceptions. This
18549 overrides the port set by @code{set task exception-port} (see above).
18550 @code{set thread excp} is the shorthand alias.
18552 @item set thread takeover-suspend-count
18553 Normally, @value{GDBN}'s thread suspend counts are relative to the
18554 value @value{GDBN} finds when it notices each thread. This command
18555 changes the suspend counts to be absolute instead.
18557 @item set thread default
18558 @itemx show thread default
18559 @cindex thread default settings, @sc{gnu} Hurd
18560 Each of the above @code{set thread} commands has a @code{set thread
18561 default} counterpart (e.g., @code{set thread default pause}, @code{set
18562 thread default exception-port}, etc.). The @code{thread default}
18563 variety of commands sets the default thread properties for all
18564 threads; you can then change the properties of individual threads with
18565 the non-default commands.
18570 @subsection QNX Neutrino
18571 @cindex QNX Neutrino
18573 @value{GDBN} provides the following commands specific to the QNX
18577 @item set debug nto-debug
18578 @kindex set debug nto-debug
18579 When set to on, enables debugging messages specific to the QNX
18582 @item show debug nto-debug
18583 @kindex show debug nto-debug
18584 Show the current state of QNX Neutrino messages.
18591 @value{GDBN} provides the following commands specific to the Darwin target:
18594 @item set debug darwin @var{num}
18595 @kindex set debug darwin
18596 When set to a non zero value, enables debugging messages specific to
18597 the Darwin support. Higher values produce more verbose output.
18599 @item show debug darwin
18600 @kindex show debug darwin
18601 Show the current state of Darwin messages.
18603 @item set debug mach-o @var{num}
18604 @kindex set debug mach-o
18605 When set to a non zero value, enables debugging messages while
18606 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
18607 file format used on Darwin for object and executable files.) Higher
18608 values produce more verbose output. This is a command to diagnose
18609 problems internal to @value{GDBN} and should not be needed in normal
18612 @item show debug mach-o
18613 @kindex show debug mach-o
18614 Show the current state of Mach-O file messages.
18616 @item set mach-exceptions on
18617 @itemx set mach-exceptions off
18618 @kindex set mach-exceptions
18619 On Darwin, faults are first reported as a Mach exception and are then
18620 mapped to a Posix signal. Use this command to turn on trapping of
18621 Mach exceptions in the inferior. This might be sometimes useful to
18622 better understand the cause of a fault. The default is off.
18624 @item show mach-exceptions
18625 @kindex show mach-exceptions
18626 Show the current state of exceptions trapping.
18631 @section Embedded Operating Systems
18633 This section describes configurations involving the debugging of
18634 embedded operating systems that are available for several different
18638 * VxWorks:: Using @value{GDBN} with VxWorks
18641 @value{GDBN} includes the ability to debug programs running on
18642 various real-time operating systems.
18645 @subsection Using @value{GDBN} with VxWorks
18651 @kindex target vxworks
18652 @item target vxworks @var{machinename}
18653 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18654 is the target system's machine name or IP address.
18658 On VxWorks, @code{load} links @var{filename} dynamically on the
18659 current target system as well as adding its symbols in @value{GDBN}.
18661 @value{GDBN} enables developers to spawn and debug tasks running on networked
18662 VxWorks targets from a Unix host. Already-running tasks spawned from
18663 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18664 both the Unix host and on the VxWorks target. The program
18665 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18666 installed with the name @code{vxgdb}, to distinguish it from a
18667 @value{GDBN} for debugging programs on the host itself.)
18670 @item VxWorks-timeout @var{args}
18671 @kindex vxworks-timeout
18672 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18673 This option is set by the user, and @var{args} represents the number of
18674 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18675 your VxWorks target is a slow software simulator or is on the far side
18676 of a thin network line.
18679 The following information on connecting to VxWorks was current when
18680 this manual was produced; newer releases of VxWorks may use revised
18683 @findex INCLUDE_RDB
18684 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18685 to include the remote debugging interface routines in the VxWorks
18686 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18687 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18688 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18689 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18690 information on configuring and remaking VxWorks, see the manufacturer's
18692 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18694 Once you have included @file{rdb.a} in your VxWorks system image and set
18695 your Unix execution search path to find @value{GDBN}, you are ready to
18696 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18697 @code{vxgdb}, depending on your installation).
18699 @value{GDBN} comes up showing the prompt:
18706 * VxWorks Connection:: Connecting to VxWorks
18707 * VxWorks Download:: VxWorks download
18708 * VxWorks Attach:: Running tasks
18711 @node VxWorks Connection
18712 @subsubsection Connecting to VxWorks
18714 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18715 network. To connect to a target whose host name is ``@code{tt}'', type:
18718 (vxgdb) target vxworks tt
18722 @value{GDBN} displays messages like these:
18725 Attaching remote machine across net...
18730 @value{GDBN} then attempts to read the symbol tables of any object modules
18731 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18732 these files by searching the directories listed in the command search
18733 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18734 to find an object file, it displays a message such as:
18737 prog.o: No such file or directory.
18740 When this happens, add the appropriate directory to the search path with
18741 the @value{GDBN} command @code{path}, and execute the @code{target}
18744 @node VxWorks Download
18745 @subsubsection VxWorks Download
18747 @cindex download to VxWorks
18748 If you have connected to the VxWorks target and you want to debug an
18749 object that has not yet been loaded, you can use the @value{GDBN}
18750 @code{load} command to download a file from Unix to VxWorks
18751 incrementally. The object file given as an argument to the @code{load}
18752 command is actually opened twice: first by the VxWorks target in order
18753 to download the code, then by @value{GDBN} in order to read the symbol
18754 table. This can lead to problems if the current working directories on
18755 the two systems differ. If both systems have NFS mounted the same
18756 filesystems, you can avoid these problems by using absolute paths.
18757 Otherwise, it is simplest to set the working directory on both systems
18758 to the directory in which the object file resides, and then to reference
18759 the file by its name, without any path. For instance, a program
18760 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18761 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18762 program, type this on VxWorks:
18765 -> cd "@var{vxpath}/vw/demo/rdb"
18769 Then, in @value{GDBN}, type:
18772 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18773 (vxgdb) load prog.o
18776 @value{GDBN} displays a response similar to this:
18779 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18782 You can also use the @code{load} command to reload an object module
18783 after editing and recompiling the corresponding source file. Note that
18784 this makes @value{GDBN} delete all currently-defined breakpoints,
18785 auto-displays, and convenience variables, and to clear the value
18786 history. (This is necessary in order to preserve the integrity of
18787 debugger's data structures that reference the target system's symbol
18790 @node VxWorks Attach
18791 @subsubsection Running Tasks
18793 @cindex running VxWorks tasks
18794 You can also attach to an existing task using the @code{attach} command as
18798 (vxgdb) attach @var{task}
18802 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18803 or suspended when you attach to it. Running tasks are suspended at
18804 the time of attachment.
18806 @node Embedded Processors
18807 @section Embedded Processors
18809 This section goes into details specific to particular embedded
18812 @cindex send command to simulator
18813 Whenever a specific embedded processor has a simulator, @value{GDBN}
18814 allows to send an arbitrary command to the simulator.
18817 @item sim @var{command}
18818 @kindex sim@r{, a command}
18819 Send an arbitrary @var{command} string to the simulator. Consult the
18820 documentation for the specific simulator in use for information about
18821 acceptable commands.
18827 * M32R/D:: Renesas M32R/D
18828 * M68K:: Motorola M68K
18829 * MicroBlaze:: Xilinx MicroBlaze
18830 * MIPS Embedded:: MIPS Embedded
18831 * OpenRISC 1000:: OpenRisc 1000
18832 * PA:: HP PA Embedded
18833 * PowerPC Embedded:: PowerPC Embedded
18834 * Sparclet:: Tsqware Sparclet
18835 * Sparclite:: Fujitsu Sparclite
18836 * Z8000:: Zilog Z8000
18839 * Super-H:: Renesas Super-H
18848 @item target rdi @var{dev}
18849 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18850 use this target to communicate with both boards running the Angel
18851 monitor, or with the EmbeddedICE JTAG debug device.
18854 @item target rdp @var{dev}
18859 @value{GDBN} provides the following ARM-specific commands:
18862 @item set arm disassembler
18864 This commands selects from a list of disassembly styles. The
18865 @code{"std"} style is the standard style.
18867 @item show arm disassembler
18869 Show the current disassembly style.
18871 @item set arm apcs32
18872 @cindex ARM 32-bit mode
18873 This command toggles ARM operation mode between 32-bit and 26-bit.
18875 @item show arm apcs32
18876 Display the current usage of the ARM 32-bit mode.
18878 @item set arm fpu @var{fputype}
18879 This command sets the ARM floating-point unit (FPU) type. The
18880 argument @var{fputype} can be one of these:
18884 Determine the FPU type by querying the OS ABI.
18886 Software FPU, with mixed-endian doubles on little-endian ARM
18889 GCC-compiled FPA co-processor.
18891 Software FPU with pure-endian doubles.
18897 Show the current type of the FPU.
18900 This command forces @value{GDBN} to use the specified ABI.
18903 Show the currently used ABI.
18905 @item set arm fallback-mode (arm|thumb|auto)
18906 @value{GDBN} uses the symbol table, when available, to determine
18907 whether instructions are ARM or Thumb. This command controls
18908 @value{GDBN}'s default behavior when the symbol table is not
18909 available. The default is @samp{auto}, which causes @value{GDBN} to
18910 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18913 @item show arm fallback-mode
18914 Show the current fallback instruction mode.
18916 @item set arm force-mode (arm|thumb|auto)
18917 This command overrides use of the symbol table to determine whether
18918 instructions are ARM or Thumb. The default is @samp{auto}, which
18919 causes @value{GDBN} to use the symbol table and then the setting
18920 of @samp{set arm fallback-mode}.
18922 @item show arm force-mode
18923 Show the current forced instruction mode.
18925 @item set debug arm
18926 Toggle whether to display ARM-specific debugging messages from the ARM
18927 target support subsystem.
18929 @item show debug arm
18930 Show whether ARM-specific debugging messages are enabled.
18933 The following commands are available when an ARM target is debugged
18934 using the RDI interface:
18937 @item rdilogfile @r{[}@var{file}@r{]}
18939 @cindex ADP (Angel Debugger Protocol) logging
18940 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18941 With an argument, sets the log file to the specified @var{file}. With
18942 no argument, show the current log file name. The default log file is
18945 @item rdilogenable @r{[}@var{arg}@r{]}
18946 @kindex rdilogenable
18947 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18948 enables logging, with an argument 0 or @code{"no"} disables it. With
18949 no arguments displays the current setting. When logging is enabled,
18950 ADP packets exchanged between @value{GDBN} and the RDI target device
18951 are logged to a file.
18953 @item set rdiromatzero
18954 @kindex set rdiromatzero
18955 @cindex ROM at zero address, RDI
18956 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18957 vector catching is disabled, so that zero address can be used. If off
18958 (the default), vector catching is enabled. For this command to take
18959 effect, it needs to be invoked prior to the @code{target rdi} command.
18961 @item show rdiromatzero
18962 @kindex show rdiromatzero
18963 Show the current setting of ROM at zero address.
18965 @item set rdiheartbeat
18966 @kindex set rdiheartbeat
18967 @cindex RDI heartbeat
18968 Enable or disable RDI heartbeat packets. It is not recommended to
18969 turn on this option, since it confuses ARM and EPI JTAG interface, as
18970 well as the Angel monitor.
18972 @item show rdiheartbeat
18973 @kindex show rdiheartbeat
18974 Show the setting of RDI heartbeat packets.
18978 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18979 The @value{GDBN} ARM simulator accepts the following optional arguments.
18982 @item --swi-support=@var{type}
18983 Tell the simulator which SWI interfaces to support.
18984 @var{type} may be a comma separated list of the following values.
18985 The default value is @code{all}.
18998 @subsection Renesas M32R/D and M32R/SDI
19001 @kindex target m32r
19002 @item target m32r @var{dev}
19003 Renesas M32R/D ROM monitor.
19005 @kindex target m32rsdi
19006 @item target m32rsdi @var{dev}
19007 Renesas M32R SDI server, connected via parallel port to the board.
19010 The following @value{GDBN} commands are specific to the M32R monitor:
19013 @item set download-path @var{path}
19014 @kindex set download-path
19015 @cindex find downloadable @sc{srec} files (M32R)
19016 Set the default path for finding downloadable @sc{srec} files.
19018 @item show download-path
19019 @kindex show download-path
19020 Show the default path for downloadable @sc{srec} files.
19022 @item set board-address @var{addr}
19023 @kindex set board-address
19024 @cindex M32-EVA target board address
19025 Set the IP address for the M32R-EVA target board.
19027 @item show board-address
19028 @kindex show board-address
19029 Show the current IP address of the target board.
19031 @item set server-address @var{addr}
19032 @kindex set server-address
19033 @cindex download server address (M32R)
19034 Set the IP address for the download server, which is the @value{GDBN}'s
19037 @item show server-address
19038 @kindex show server-address
19039 Display the IP address of the download server.
19041 @item upload @r{[}@var{file}@r{]}
19042 @kindex upload@r{, M32R}
19043 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
19044 upload capability. If no @var{file} argument is given, the current
19045 executable file is uploaded.
19047 @item tload @r{[}@var{file}@r{]}
19048 @kindex tload@r{, M32R}
19049 Test the @code{upload} command.
19052 The following commands are available for M32R/SDI:
19057 @cindex reset SDI connection, M32R
19058 This command resets the SDI connection.
19062 This command shows the SDI connection status.
19065 @kindex debug_chaos
19066 @cindex M32R/Chaos debugging
19067 Instructs the remote that M32R/Chaos debugging is to be used.
19069 @item use_debug_dma
19070 @kindex use_debug_dma
19071 Instructs the remote to use the DEBUG_DMA method of accessing memory.
19074 @kindex use_mon_code
19075 Instructs the remote to use the MON_CODE method of accessing memory.
19078 @kindex use_ib_break
19079 Instructs the remote to set breakpoints by IB break.
19081 @item use_dbt_break
19082 @kindex use_dbt_break
19083 Instructs the remote to set breakpoints by DBT.
19089 The Motorola m68k configuration includes ColdFire support, and a
19090 target command for the following ROM monitor.
19094 @kindex target dbug
19095 @item target dbug @var{dev}
19096 dBUG ROM monitor for Motorola ColdFire.
19101 @subsection MicroBlaze
19102 @cindex Xilinx MicroBlaze
19103 @cindex XMD, Xilinx Microprocessor Debugger
19105 The MicroBlaze is a soft-core processor supported on various Xilinx
19106 FPGAs, such as Spartan or Virtex series. Boards with these processors
19107 usually have JTAG ports which connect to a host system running the Xilinx
19108 Embedded Development Kit (EDK) or Software Development Kit (SDK).
19109 This host system is used to download the configuration bitstream to
19110 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
19111 communicates with the target board using the JTAG interface and
19112 presents a @code{gdbserver} interface to the board. By default
19113 @code{xmd} uses port @code{1234}. (While it is possible to change
19114 this default port, it requires the use of undocumented @code{xmd}
19115 commands. Contact Xilinx support if you need to do this.)
19117 Use these GDB commands to connect to the MicroBlaze target processor.
19120 @item target remote :1234
19121 Use this command to connect to the target if you are running @value{GDBN}
19122 on the same system as @code{xmd}.
19124 @item target remote @var{xmd-host}:1234
19125 Use this command to connect to the target if it is connected to @code{xmd}
19126 running on a different system named @var{xmd-host}.
19129 Use this command to download a program to the MicroBlaze target.
19131 @item set debug microblaze @var{n}
19132 Enable MicroBlaze-specific debugging messages if non-zero.
19134 @item show debug microblaze @var{n}
19135 Show MicroBlaze-specific debugging level.
19138 @node MIPS Embedded
19139 @subsection MIPS Embedded
19141 @cindex MIPS boards
19142 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
19143 MIPS board attached to a serial line. This is available when
19144 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
19147 Use these @value{GDBN} commands to specify the connection to your target board:
19150 @item target mips @var{port}
19151 @kindex target mips @var{port}
19152 To run a program on the board, start up @code{@value{GDBP}} with the
19153 name of your program as the argument. To connect to the board, use the
19154 command @samp{target mips @var{port}}, where @var{port} is the name of
19155 the serial port connected to the board. If the program has not already
19156 been downloaded to the board, you may use the @code{load} command to
19157 download it. You can then use all the usual @value{GDBN} commands.
19159 For example, this sequence connects to the target board through a serial
19160 port, and loads and runs a program called @var{prog} through the
19164 host$ @value{GDBP} @var{prog}
19165 @value{GDBN} is free software and @dots{}
19166 (@value{GDBP}) target mips /dev/ttyb
19167 (@value{GDBP}) load @var{prog}
19171 @item target mips @var{hostname}:@var{portnumber}
19172 On some @value{GDBN} host configurations, you can specify a TCP
19173 connection (for instance, to a serial line managed by a terminal
19174 concentrator) instead of a serial port, using the syntax
19175 @samp{@var{hostname}:@var{portnumber}}.
19177 @item target pmon @var{port}
19178 @kindex target pmon @var{port}
19181 @item target ddb @var{port}
19182 @kindex target ddb @var{port}
19183 NEC's DDB variant of PMON for Vr4300.
19185 @item target lsi @var{port}
19186 @kindex target lsi @var{port}
19187 LSI variant of PMON.
19189 @kindex target r3900
19190 @item target r3900 @var{dev}
19191 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19193 @kindex target array
19194 @item target array @var{dev}
19195 Array Tech LSI33K RAID controller board.
19201 @value{GDBN} also supports these special commands for MIPS targets:
19204 @item set mipsfpu double
19205 @itemx set mipsfpu single
19206 @itemx set mipsfpu none
19207 @itemx set mipsfpu auto
19208 @itemx show mipsfpu
19209 @kindex set mipsfpu
19210 @kindex show mipsfpu
19211 @cindex MIPS remote floating point
19212 @cindex floating point, MIPS remote
19213 If your target board does not support the MIPS floating point
19214 coprocessor, you should use the command @samp{set mipsfpu none} (if you
19215 need this, you may wish to put the command in your @value{GDBN} init
19216 file). This tells @value{GDBN} how to find the return value of
19217 functions which return floating point values. It also allows
19218 @value{GDBN} to avoid saving the floating point registers when calling
19219 functions on the board. If you are using a floating point coprocessor
19220 with only single precision floating point support, as on the @sc{r4650}
19221 processor, use the command @samp{set mipsfpu single}. The default
19222 double precision floating point coprocessor may be selected using
19223 @samp{set mipsfpu double}.
19225 In previous versions the only choices were double precision or no
19226 floating point, so @samp{set mipsfpu on} will select double precision
19227 and @samp{set mipsfpu off} will select no floating point.
19229 As usual, you can inquire about the @code{mipsfpu} variable with
19230 @samp{show mipsfpu}.
19232 @item set timeout @var{seconds}
19233 @itemx set retransmit-timeout @var{seconds}
19234 @itemx show timeout
19235 @itemx show retransmit-timeout
19236 @cindex @code{timeout}, MIPS protocol
19237 @cindex @code{retransmit-timeout}, MIPS protocol
19238 @kindex set timeout
19239 @kindex show timeout
19240 @kindex set retransmit-timeout
19241 @kindex show retransmit-timeout
19242 You can control the timeout used while waiting for a packet, in the MIPS
19243 remote protocol, with the @code{set timeout @var{seconds}} command. The
19244 default is 5 seconds. Similarly, you can control the timeout used while
19245 waiting for an acknowledgment of a packet with the @code{set
19246 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19247 You can inspect both values with @code{show timeout} and @code{show
19248 retransmit-timeout}. (These commands are @emph{only} available when
19249 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
19251 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19252 is waiting for your program to stop. In that case, @value{GDBN} waits
19253 forever because it has no way of knowing how long the program is going
19254 to run before stopping.
19256 @item set syn-garbage-limit @var{num}
19257 @kindex set syn-garbage-limit@r{, MIPS remote}
19258 @cindex synchronize with remote MIPS target
19259 Limit the maximum number of characters @value{GDBN} should ignore when
19260 it tries to synchronize with the remote target. The default is 10
19261 characters. Setting the limit to -1 means there's no limit.
19263 @item show syn-garbage-limit
19264 @kindex show syn-garbage-limit@r{, MIPS remote}
19265 Show the current limit on the number of characters to ignore when
19266 trying to synchronize with the remote system.
19268 @item set monitor-prompt @var{prompt}
19269 @kindex set monitor-prompt@r{, MIPS remote}
19270 @cindex remote monitor prompt
19271 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19272 remote monitor. The default depends on the target:
19282 @item show monitor-prompt
19283 @kindex show monitor-prompt@r{, MIPS remote}
19284 Show the current strings @value{GDBN} expects as the prompt from the
19287 @item set monitor-warnings
19288 @kindex set monitor-warnings@r{, MIPS remote}
19289 Enable or disable monitor warnings about hardware breakpoints. This
19290 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19291 display warning messages whose codes are returned by the @code{lsi}
19292 PMON monitor for breakpoint commands.
19294 @item show monitor-warnings
19295 @kindex show monitor-warnings@r{, MIPS remote}
19296 Show the current setting of printing monitor warnings.
19298 @item pmon @var{command}
19299 @kindex pmon@r{, MIPS remote}
19300 @cindex send PMON command
19301 This command allows sending an arbitrary @var{command} string to the
19302 monitor. The monitor must be in debug mode for this to work.
19305 @node OpenRISC 1000
19306 @subsection OpenRISC 1000
19307 @cindex OpenRISC 1000
19309 @cindex or1k boards
19310 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19311 about platform and commands.
19315 @kindex target jtag
19316 @item target jtag jtag://@var{host}:@var{port}
19318 Connects to remote JTAG server.
19319 JTAG remote server can be either an or1ksim or JTAG server,
19320 connected via parallel port to the board.
19322 Example: @code{target jtag jtag://localhost:9999}
19325 @item or1ksim @var{command}
19326 If connected to @code{or1ksim} OpenRISC 1000 Architectural
19327 Simulator, proprietary commands can be executed.
19329 @kindex info or1k spr
19330 @item info or1k spr
19331 Displays spr groups.
19333 @item info or1k spr @var{group}
19334 @itemx info or1k spr @var{groupno}
19335 Displays register names in selected group.
19337 @item info or1k spr @var{group} @var{register}
19338 @itemx info or1k spr @var{register}
19339 @itemx info or1k spr @var{groupno} @var{registerno}
19340 @itemx info or1k spr @var{registerno}
19341 Shows information about specified spr register.
19344 @item spr @var{group} @var{register} @var{value}
19345 @itemx spr @var{register @var{value}}
19346 @itemx spr @var{groupno} @var{registerno @var{value}}
19347 @itemx spr @var{registerno @var{value}}
19348 Writes @var{value} to specified spr register.
19351 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
19352 It is very similar to @value{GDBN} trace, except it does not interfere with normal
19353 program execution and is thus much faster. Hardware breakpoints/watchpoint
19354 triggers can be set using:
19357 Load effective address/data
19359 Store effective address/data
19361 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
19366 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
19367 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
19369 @code{htrace} commands:
19370 @cindex OpenRISC 1000 htrace
19373 @item hwatch @var{conditional}
19374 Set hardware watchpoint on combination of Load/Store Effective Address(es)
19375 or Data. For example:
19377 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19379 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19383 Display information about current HW trace configuration.
19385 @item htrace trigger @var{conditional}
19386 Set starting criteria for HW trace.
19388 @item htrace qualifier @var{conditional}
19389 Set acquisition qualifier for HW trace.
19391 @item htrace stop @var{conditional}
19392 Set HW trace stopping criteria.
19394 @item htrace record [@var{data}]*
19395 Selects the data to be recorded, when qualifier is met and HW trace was
19398 @item htrace enable
19399 @itemx htrace disable
19400 Enables/disables the HW trace.
19402 @item htrace rewind [@var{filename}]
19403 Clears currently recorded trace data.
19405 If filename is specified, new trace file is made and any newly collected data
19406 will be written there.
19408 @item htrace print [@var{start} [@var{len}]]
19409 Prints trace buffer, using current record configuration.
19411 @item htrace mode continuous
19412 Set continuous trace mode.
19414 @item htrace mode suspend
19415 Set suspend trace mode.
19419 @node PowerPC Embedded
19420 @subsection PowerPC Embedded
19422 @cindex DVC register
19423 @value{GDBN} supports using the DVC (Data Value Compare) register to
19424 implement in hardware simple hardware watchpoint conditions of the form:
19427 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
19428 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
19431 The DVC register will be automatically used when @value{GDBN} detects
19432 such pattern in a condition expression, and the created watchpoint uses one
19433 debug register (either the @code{exact-watchpoints} option is on and the
19434 variable is scalar, or the variable has a length of one byte). This feature
19435 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
19438 When running on PowerPC embedded processors, @value{GDBN} automatically uses
19439 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
19440 in which case watchpoints using only one debug register are created when
19441 watching variables of scalar types.
19443 You can create an artificial array to watch an arbitrary memory
19444 region using one of the following commands (@pxref{Expressions}):
19447 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
19448 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
19451 PowerPC embedded processors support masked watchpoints. See the discussion
19452 about the @code{mask} argument in @ref{Set Watchpoints}.
19454 @cindex ranged breakpoint
19455 PowerPC embedded processors support hardware accelerated
19456 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
19457 the inferior whenever it executes an instruction at any address within
19458 the range it specifies. To set a ranged breakpoint in @value{GDBN},
19459 use the @code{break-range} command.
19461 @value{GDBN} provides the following PowerPC-specific commands:
19464 @kindex break-range
19465 @item break-range @var{start-location}, @var{end-location}
19466 Set a breakpoint for an address range.
19467 @var{start-location} and @var{end-location} can specify a function name,
19468 a line number, an offset of lines from the current line or from the start
19469 location, or an address of an instruction (see @ref{Specify Location},
19470 for a list of all the possible ways to specify a @var{location}.)
19471 The breakpoint will stop execution of the inferior whenever it
19472 executes an instruction at any address within the specified range,
19473 (including @var{start-location} and @var{end-location}.)
19475 @kindex set powerpc
19476 @item set powerpc soft-float
19477 @itemx show powerpc soft-float
19478 Force @value{GDBN} to use (or not use) a software floating point calling
19479 convention. By default, @value{GDBN} selects the calling convention based
19480 on the selected architecture and the provided executable file.
19482 @item set powerpc vector-abi
19483 @itemx show powerpc vector-abi
19484 Force @value{GDBN} to use the specified calling convention for vector
19485 arguments and return values. The valid options are @samp{auto};
19486 @samp{generic}, to avoid vector registers even if they are present;
19487 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
19488 registers. By default, @value{GDBN} selects the calling convention
19489 based on the selected architecture and the provided executable file.
19491 @item set powerpc exact-watchpoints
19492 @itemx show powerpc exact-watchpoints
19493 Allow @value{GDBN} to use only one debug register when watching a variable
19494 of scalar type, thus assuming that the variable is accessed through the
19495 address of its first byte.
19497 @kindex target dink32
19498 @item target dink32 @var{dev}
19499 DINK32 ROM monitor.
19501 @kindex target ppcbug
19502 @item target ppcbug @var{dev}
19503 @kindex target ppcbug1
19504 @item target ppcbug1 @var{dev}
19505 PPCBUG ROM monitor for PowerPC.
19508 @item target sds @var{dev}
19509 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
19512 @cindex SDS protocol
19513 The following commands specific to the SDS protocol are supported
19517 @item set sdstimeout @var{nsec}
19518 @kindex set sdstimeout
19519 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
19520 default is 2 seconds.
19522 @item show sdstimeout
19523 @kindex show sdstimeout
19524 Show the current value of the SDS timeout.
19526 @item sds @var{command}
19527 @kindex sds@r{, a command}
19528 Send the specified @var{command} string to the SDS monitor.
19533 @subsection HP PA Embedded
19537 @kindex target op50n
19538 @item target op50n @var{dev}
19539 OP50N monitor, running on an OKI HPPA board.
19541 @kindex target w89k
19542 @item target w89k @var{dev}
19543 W89K monitor, running on a Winbond HPPA board.
19548 @subsection Tsqware Sparclet
19552 @value{GDBN} enables developers to debug tasks running on
19553 Sparclet targets from a Unix host.
19554 @value{GDBN} uses code that runs on
19555 both the Unix host and on the Sparclet target. The program
19556 @code{@value{GDBP}} is installed and executed on the Unix host.
19559 @item remotetimeout @var{args}
19560 @kindex remotetimeout
19561 @value{GDBN} supports the option @code{remotetimeout}.
19562 This option is set by the user, and @var{args} represents the number of
19563 seconds @value{GDBN} waits for responses.
19566 @cindex compiling, on Sparclet
19567 When compiling for debugging, include the options @samp{-g} to get debug
19568 information and @samp{-Ttext} to relocate the program to where you wish to
19569 load it on the target. You may also want to add the options @samp{-n} or
19570 @samp{-N} in order to reduce the size of the sections. Example:
19573 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
19576 You can use @code{objdump} to verify that the addresses are what you intended:
19579 sparclet-aout-objdump --headers --syms prog
19582 @cindex running, on Sparclet
19584 your Unix execution search path to find @value{GDBN}, you are ready to
19585 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
19586 (or @code{sparclet-aout-gdb}, depending on your installation).
19588 @value{GDBN} comes up showing the prompt:
19595 * Sparclet File:: Setting the file to debug
19596 * Sparclet Connection:: Connecting to Sparclet
19597 * Sparclet Download:: Sparclet download
19598 * Sparclet Execution:: Running and debugging
19601 @node Sparclet File
19602 @subsubsection Setting File to Debug
19604 The @value{GDBN} command @code{file} lets you choose with program to debug.
19607 (gdbslet) file prog
19611 @value{GDBN} then attempts to read the symbol table of @file{prog}.
19612 @value{GDBN} locates
19613 the file by searching the directories listed in the command search
19615 If the file was compiled with debug information (option @samp{-g}), source
19616 files will be searched as well.
19617 @value{GDBN} locates
19618 the source files by searching the directories listed in the directory search
19619 path (@pxref{Environment, ,Your Program's Environment}).
19621 to find a file, it displays a message such as:
19624 prog: No such file or directory.
19627 When this happens, add the appropriate directories to the search paths with
19628 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
19629 @code{target} command again.
19631 @node Sparclet Connection
19632 @subsubsection Connecting to Sparclet
19634 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
19635 To connect to a target on serial port ``@code{ttya}'', type:
19638 (gdbslet) target sparclet /dev/ttya
19639 Remote target sparclet connected to /dev/ttya
19640 main () at ../prog.c:3
19644 @value{GDBN} displays messages like these:
19650 @node Sparclet Download
19651 @subsubsection Sparclet Download
19653 @cindex download to Sparclet
19654 Once connected to the Sparclet target,
19655 you can use the @value{GDBN}
19656 @code{load} command to download the file from the host to the target.
19657 The file name and load offset should be given as arguments to the @code{load}
19659 Since the file format is aout, the program must be loaded to the starting
19660 address. You can use @code{objdump} to find out what this value is. The load
19661 offset is an offset which is added to the VMA (virtual memory address)
19662 of each of the file's sections.
19663 For instance, if the program
19664 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19665 and bss at 0x12010170, in @value{GDBN}, type:
19668 (gdbslet) load prog 0x12010000
19669 Loading section .text, size 0xdb0 vma 0x12010000
19672 If the code is loaded at a different address then what the program was linked
19673 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19674 to tell @value{GDBN} where to map the symbol table.
19676 @node Sparclet Execution
19677 @subsubsection Running and Debugging
19679 @cindex running and debugging Sparclet programs
19680 You can now begin debugging the task using @value{GDBN}'s execution control
19681 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19682 manual for the list of commands.
19686 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19688 Starting program: prog
19689 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19690 3 char *symarg = 0;
19692 4 char *execarg = "hello!";
19697 @subsection Fujitsu Sparclite
19701 @kindex target sparclite
19702 @item target sparclite @var{dev}
19703 Fujitsu sparclite boards, used only for the purpose of loading.
19704 You must use an additional command to debug the program.
19705 For example: target remote @var{dev} using @value{GDBN} standard
19711 @subsection Zilog Z8000
19714 @cindex simulator, Z8000
19715 @cindex Zilog Z8000 simulator
19717 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19720 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19721 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19722 segmented variant). The simulator recognizes which architecture is
19723 appropriate by inspecting the object code.
19726 @item target sim @var{args}
19728 @kindex target sim@r{, with Z8000}
19729 Debug programs on a simulated CPU. If the simulator supports setup
19730 options, specify them via @var{args}.
19734 After specifying this target, you can debug programs for the simulated
19735 CPU in the same style as programs for your host computer; use the
19736 @code{file} command to load a new program image, the @code{run} command
19737 to run your program, and so on.
19739 As well as making available all the usual machine registers
19740 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19741 additional items of information as specially named registers:
19746 Counts clock-ticks in the simulator.
19749 Counts instructions run in the simulator.
19752 Execution time in 60ths of a second.
19756 You can refer to these values in @value{GDBN} expressions with the usual
19757 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19758 conditional breakpoint that suspends only after at least 5000
19759 simulated clock ticks.
19762 @subsection Atmel AVR
19765 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19766 following AVR-specific commands:
19769 @item info io_registers
19770 @kindex info io_registers@r{, AVR}
19771 @cindex I/O registers (Atmel AVR)
19772 This command displays information about the AVR I/O registers. For
19773 each register, @value{GDBN} prints its number and value.
19780 When configured for debugging CRIS, @value{GDBN} provides the
19781 following CRIS-specific commands:
19784 @item set cris-version @var{ver}
19785 @cindex CRIS version
19786 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19787 The CRIS version affects register names and sizes. This command is useful in
19788 case autodetection of the CRIS version fails.
19790 @item show cris-version
19791 Show the current CRIS version.
19793 @item set cris-dwarf2-cfi
19794 @cindex DWARF-2 CFI and CRIS
19795 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19796 Change to @samp{off} when using @code{gcc-cris} whose version is below
19799 @item show cris-dwarf2-cfi
19800 Show the current state of using DWARF-2 CFI.
19802 @item set cris-mode @var{mode}
19804 Set the current CRIS mode to @var{mode}. It should only be changed when
19805 debugging in guru mode, in which case it should be set to
19806 @samp{guru} (the default is @samp{normal}).
19808 @item show cris-mode
19809 Show the current CRIS mode.
19813 @subsection Renesas Super-H
19816 For the Renesas Super-H processor, @value{GDBN} provides these
19821 @kindex regs@r{, Super-H}
19822 Show the values of all Super-H registers.
19824 @item set sh calling-convention @var{convention}
19825 @kindex set sh calling-convention
19826 Set the calling-convention used when calling functions from @value{GDBN}.
19827 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19828 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19829 convention. If the DWARF-2 information of the called function specifies
19830 that the function follows the Renesas calling convention, the function
19831 is called using the Renesas calling convention. If the calling convention
19832 is set to @samp{renesas}, the Renesas calling convention is always used,
19833 regardless of the DWARF-2 information. This can be used to override the
19834 default of @samp{gcc} if debug information is missing, or the compiler
19835 does not emit the DWARF-2 calling convention entry for a function.
19837 @item show sh calling-convention
19838 @kindex show sh calling-convention
19839 Show the current calling convention setting.
19844 @node Architectures
19845 @section Architectures
19847 This section describes characteristics of architectures that affect
19848 all uses of @value{GDBN} with the architecture, both native and cross.
19855 * HPPA:: HP PA architecture
19856 * SPU:: Cell Broadband Engine SPU architecture
19861 @subsection x86 Architecture-specific Issues
19864 @item set struct-convention @var{mode}
19865 @kindex set struct-convention
19866 @cindex struct return convention
19867 @cindex struct/union returned in registers
19868 Set the convention used by the inferior to return @code{struct}s and
19869 @code{union}s from functions to @var{mode}. Possible values of
19870 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19871 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19872 are returned on the stack, while @code{"reg"} means that a
19873 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19874 be returned in a register.
19876 @item show struct-convention
19877 @kindex show struct-convention
19878 Show the current setting of the convention to return @code{struct}s
19887 @kindex set rstack_high_address
19888 @cindex AMD 29K register stack
19889 @cindex register stack, AMD29K
19890 @item set rstack_high_address @var{address}
19891 On AMD 29000 family processors, registers are saved in a separate
19892 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19893 extent of this stack. Normally, @value{GDBN} just assumes that the
19894 stack is ``large enough''. This may result in @value{GDBN} referencing
19895 memory locations that do not exist. If necessary, you can get around
19896 this problem by specifying the ending address of the register stack with
19897 the @code{set rstack_high_address} command. The argument should be an
19898 address, which you probably want to precede with @samp{0x} to specify in
19901 @kindex show rstack_high_address
19902 @item show rstack_high_address
19903 Display the current limit of the register stack, on AMD 29000 family
19911 See the following section.
19916 @cindex stack on Alpha
19917 @cindex stack on MIPS
19918 @cindex Alpha stack
19920 Alpha- and MIPS-based computers use an unusual stack frame, which
19921 sometimes requires @value{GDBN} to search backward in the object code to
19922 find the beginning of a function.
19924 @cindex response time, MIPS debugging
19925 To improve response time (especially for embedded applications, where
19926 @value{GDBN} may be restricted to a slow serial line for this search)
19927 you may want to limit the size of this search, using one of these
19931 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19932 @item set heuristic-fence-post @var{limit}
19933 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19934 search for the beginning of a function. A value of @var{0} (the
19935 default) means there is no limit. However, except for @var{0}, the
19936 larger the limit the more bytes @code{heuristic-fence-post} must search
19937 and therefore the longer it takes to run. You should only need to use
19938 this command when debugging a stripped executable.
19940 @item show heuristic-fence-post
19941 Display the current limit.
19945 These commands are available @emph{only} when @value{GDBN} is configured
19946 for debugging programs on Alpha or MIPS processors.
19948 Several MIPS-specific commands are available when debugging MIPS
19952 @item set mips abi @var{arg}
19953 @kindex set mips abi
19954 @cindex set ABI for MIPS
19955 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19956 values of @var{arg} are:
19960 The default ABI associated with the current binary (this is the
19970 @item show mips abi
19971 @kindex show mips abi
19972 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19975 @itemx show mipsfpu
19976 @xref{MIPS Embedded, set mipsfpu}.
19978 @item set mips mask-address @var{arg}
19979 @kindex set mips mask-address
19980 @cindex MIPS addresses, masking
19981 This command determines whether the most-significant 32 bits of 64-bit
19982 MIPS addresses are masked off. The argument @var{arg} can be
19983 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19984 setting, which lets @value{GDBN} determine the correct value.
19986 @item show mips mask-address
19987 @kindex show mips mask-address
19988 Show whether the upper 32 bits of MIPS addresses are masked off or
19991 @item set remote-mips64-transfers-32bit-regs
19992 @kindex set remote-mips64-transfers-32bit-regs
19993 This command controls compatibility with 64-bit MIPS targets that
19994 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19995 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19996 and 64 bits for other registers, set this option to @samp{on}.
19998 @item show remote-mips64-transfers-32bit-regs
19999 @kindex show remote-mips64-transfers-32bit-regs
20000 Show the current setting of compatibility with older MIPS 64 targets.
20002 @item set debug mips
20003 @kindex set debug mips
20004 This command turns on and off debugging messages for the MIPS-specific
20005 target code in @value{GDBN}.
20007 @item show debug mips
20008 @kindex show debug mips
20009 Show the current setting of MIPS debugging messages.
20015 @cindex HPPA support
20017 When @value{GDBN} is debugging the HP PA architecture, it provides the
20018 following special commands:
20021 @item set debug hppa
20022 @kindex set debug hppa
20023 This command determines whether HPPA architecture-specific debugging
20024 messages are to be displayed.
20026 @item show debug hppa
20027 Show whether HPPA debugging messages are displayed.
20029 @item maint print unwind @var{address}
20030 @kindex maint print unwind@r{, HPPA}
20031 This command displays the contents of the unwind table entry at the
20032 given @var{address}.
20038 @subsection Cell Broadband Engine SPU architecture
20039 @cindex Cell Broadband Engine
20042 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
20043 it provides the following special commands:
20046 @item info spu event
20048 Display SPU event facility status. Shows current event mask
20049 and pending event status.
20051 @item info spu signal
20052 Display SPU signal notification facility status. Shows pending
20053 signal-control word and signal notification mode of both signal
20054 notification channels.
20056 @item info spu mailbox
20057 Display SPU mailbox facility status. Shows all pending entries,
20058 in order of processing, in each of the SPU Write Outbound,
20059 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
20062 Display MFC DMA status. Shows all pending commands in the MFC
20063 DMA queue. For each entry, opcode, tag, class IDs, effective
20064 and local store addresses and transfer size are shown.
20066 @item info spu proxydma
20067 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
20068 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
20069 and local store addresses and transfer size are shown.
20073 When @value{GDBN} is debugging a combined PowerPC/SPU application
20074 on the Cell Broadband Engine, it provides in addition the following
20078 @item set spu stop-on-load @var{arg}
20080 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
20081 will give control to the user when a new SPE thread enters its @code{main}
20082 function. The default is @code{off}.
20084 @item show spu stop-on-load
20086 Show whether to stop for new SPE threads.
20088 @item set spu auto-flush-cache @var{arg}
20089 Set whether to automatically flush the software-managed cache. When set to
20090 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
20091 cache to be flushed whenever SPE execution stops. This provides a consistent
20092 view of PowerPC memory that is accessed via the cache. If an application
20093 does not use the software-managed cache, this option has no effect.
20095 @item show spu auto-flush-cache
20096 Show whether to automatically flush the software-managed cache.
20101 @subsection PowerPC
20102 @cindex PowerPC architecture
20104 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
20105 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
20106 numbers stored in the floating point registers. These values must be stored
20107 in two consecutive registers, always starting at an even register like
20108 @code{f0} or @code{f2}.
20110 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
20111 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
20112 @code{f2} and @code{f3} for @code{$dl1} and so on.
20114 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
20115 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
20118 @node Controlling GDB
20119 @chapter Controlling @value{GDBN}
20121 You can alter the way @value{GDBN} interacts with you by using the
20122 @code{set} command. For commands controlling how @value{GDBN} displays
20123 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20128 * Editing:: Command editing
20129 * Command History:: Command history
20130 * Screen Size:: Screen size
20131 * Numbers:: Numbers
20132 * ABI:: Configuring the current ABI
20133 * Messages/Warnings:: Optional warnings and messages
20134 * Debugging Output:: Optional messages about internal happenings
20135 * Other Misc Settings:: Other Miscellaneous Settings
20143 @value{GDBN} indicates its readiness to read a command by printing a string
20144 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20145 can change the prompt string with the @code{set prompt} command. For
20146 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20147 the prompt in one of the @value{GDBN} sessions so that you can always tell
20148 which one you are talking to.
20150 @emph{Note:} @code{set prompt} does not add a space for you after the
20151 prompt you set. This allows you to set a prompt which ends in a space
20152 or a prompt that does not.
20156 @item set prompt @var{newprompt}
20157 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20159 @kindex show prompt
20161 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20164 Versions of @value{GDBN} that ship with Python scripting enabled have
20165 prompt extensions. The commands for interacting with these extensions
20169 @kindex set extended-prompt
20170 @item set extended-prompt @var{prompt}
20171 Set an extended prompt that allows for substitutions.
20172 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20173 substitution. Any escape sequences specified as part of the prompt
20174 string are replaced with the corresponding strings each time the prompt
20180 set extended-prompt Current working directory: \w (gdb)
20183 Note that when an extended-prompt is set, it takes control of the
20184 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20186 @kindex show extended-prompt
20187 @item show extended-prompt
20188 Prints the extended prompt. Any escape sequences specified as part of
20189 the prompt string with @code{set extended-prompt}, are replaced with the
20190 corresponding strings each time the prompt is displayed.
20194 @section Command Editing
20196 @cindex command line editing
20198 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
20199 @sc{gnu} library provides consistent behavior for programs which provide a
20200 command line interface to the user. Advantages are @sc{gnu} Emacs-style
20201 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
20202 substitution, and a storage and recall of command history across
20203 debugging sessions.
20205 You may control the behavior of command line editing in @value{GDBN} with the
20206 command @code{set}.
20209 @kindex set editing
20212 @itemx set editing on
20213 Enable command line editing (enabled by default).
20215 @item set editing off
20216 Disable command line editing.
20218 @kindex show editing
20220 Show whether command line editing is enabled.
20223 @ifset SYSTEM_READLINE
20224 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
20226 @ifclear SYSTEM_READLINE
20227 @xref{Command Line Editing},
20229 for more details about the Readline
20230 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
20231 encouraged to read that chapter.
20233 @node Command History
20234 @section Command History
20235 @cindex command history
20237 @value{GDBN} can keep track of the commands you type during your
20238 debugging sessions, so that you can be certain of precisely what
20239 happened. Use these commands to manage the @value{GDBN} command
20242 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20243 package, to provide the history facility.
20244 @ifset SYSTEM_READLINE
20245 @xref{Using History Interactively, , , history, GNU History Library},
20247 @ifclear SYSTEM_READLINE
20248 @xref{Using History Interactively},
20250 for the detailed description of the History library.
20252 To issue a command to @value{GDBN} without affecting certain aspects of
20253 the state which is seen by users, prefix it with @samp{server }
20254 (@pxref{Server Prefix}). This
20255 means that this command will not affect the command history, nor will it
20256 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20257 pressed on a line by itself.
20259 @cindex @code{server}, command prefix
20260 The server prefix does not affect the recording of values into the value
20261 history; to print a value without recording it into the value history,
20262 use the @code{output} command instead of the @code{print} command.
20264 Here is the description of @value{GDBN} commands related to command
20268 @cindex history substitution
20269 @cindex history file
20270 @kindex set history filename
20271 @cindex @env{GDBHISTFILE}, environment variable
20272 @item set history filename @var{fname}
20273 Set the name of the @value{GDBN} command history file to @var{fname}.
20274 This is the file where @value{GDBN} reads an initial command history
20275 list, and where it writes the command history from this session when it
20276 exits. You can access this list through history expansion or through
20277 the history command editing characters listed below. This file defaults
20278 to the value of the environment variable @code{GDBHISTFILE}, or to
20279 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20282 @cindex save command history
20283 @kindex set history save
20284 @item set history save
20285 @itemx set history save on
20286 Record command history in a file, whose name may be specified with the
20287 @code{set history filename} command. By default, this option is disabled.
20289 @item set history save off
20290 Stop recording command history in a file.
20292 @cindex history size
20293 @kindex set history size
20294 @cindex @env{HISTSIZE}, environment variable
20295 @item set history size @var{size}
20296 Set the number of commands which @value{GDBN} keeps in its history list.
20297 This defaults to the value of the environment variable
20298 @code{HISTSIZE}, or to 256 if this variable is not set.
20301 History expansion assigns special meaning to the character @kbd{!}.
20302 @ifset SYSTEM_READLINE
20303 @xref{Event Designators, , , history, GNU History Library},
20305 @ifclear SYSTEM_READLINE
20306 @xref{Event Designators},
20310 @cindex history expansion, turn on/off
20311 Since @kbd{!} is also the logical not operator in C, history expansion
20312 is off by default. If you decide to enable history expansion with the
20313 @code{set history expansion on} command, you may sometimes need to
20314 follow @kbd{!} (when it is used as logical not, in an expression) with
20315 a space or a tab to prevent it from being expanded. The readline
20316 history facilities do not attempt substitution on the strings
20317 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20319 The commands to control history expansion are:
20322 @item set history expansion on
20323 @itemx set history expansion
20324 @kindex set history expansion
20325 Enable history expansion. History expansion is off by default.
20327 @item set history expansion off
20328 Disable history expansion.
20331 @kindex show history
20333 @itemx show history filename
20334 @itemx show history save
20335 @itemx show history size
20336 @itemx show history expansion
20337 These commands display the state of the @value{GDBN} history parameters.
20338 @code{show history} by itself displays all four states.
20343 @kindex show commands
20344 @cindex show last commands
20345 @cindex display command history
20346 @item show commands
20347 Display the last ten commands in the command history.
20349 @item show commands @var{n}
20350 Print ten commands centered on command number @var{n}.
20352 @item show commands +
20353 Print ten commands just after the commands last printed.
20357 @section Screen Size
20358 @cindex size of screen
20359 @cindex pauses in output
20361 Certain commands to @value{GDBN} may produce large amounts of
20362 information output to the screen. To help you read all of it,
20363 @value{GDBN} pauses and asks you for input at the end of each page of
20364 output. Type @key{RET} when you want to continue the output, or @kbd{q}
20365 to discard the remaining output. Also, the screen width setting
20366 determines when to wrap lines of output. Depending on what is being
20367 printed, @value{GDBN} tries to break the line at a readable place,
20368 rather than simply letting it overflow onto the following line.
20370 Normally @value{GDBN} knows the size of the screen from the terminal
20371 driver software. For example, on Unix @value{GDBN} uses the termcap data base
20372 together with the value of the @code{TERM} environment variable and the
20373 @code{stty rows} and @code{stty cols} settings. If this is not correct,
20374 you can override it with the @code{set height} and @code{set
20381 @kindex show height
20382 @item set height @var{lpp}
20384 @itemx set width @var{cpl}
20386 These @code{set} commands specify a screen height of @var{lpp} lines and
20387 a screen width of @var{cpl} characters. The associated @code{show}
20388 commands display the current settings.
20390 If you specify a height of zero lines, @value{GDBN} does not pause during
20391 output no matter how long the output is. This is useful if output is to a
20392 file or to an editor buffer.
20394 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
20395 from wrapping its output.
20397 @item set pagination on
20398 @itemx set pagination off
20399 @kindex set pagination
20400 Turn the output pagination on or off; the default is on. Turning
20401 pagination off is the alternative to @code{set height 0}. Note that
20402 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
20403 Options, -batch}) also automatically disables pagination.
20405 @item show pagination
20406 @kindex show pagination
20407 Show the current pagination mode.
20412 @cindex number representation
20413 @cindex entering numbers
20415 You can always enter numbers in octal, decimal, or hexadecimal in
20416 @value{GDBN} by the usual conventions: octal numbers begin with
20417 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
20418 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
20419 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
20420 10; likewise, the default display for numbers---when no particular
20421 format is specified---is base 10. You can change the default base for
20422 both input and output with the commands described below.
20425 @kindex set input-radix
20426 @item set input-radix @var{base}
20427 Set the default base for numeric input. Supported choices
20428 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20429 specified either unambiguously or using the current input radix; for
20433 set input-radix 012
20434 set input-radix 10.
20435 set input-radix 0xa
20439 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
20440 leaves the input radix unchanged, no matter what it was, since
20441 @samp{10}, being without any leading or trailing signs of its base, is
20442 interpreted in the current radix. Thus, if the current radix is 16,
20443 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
20446 @kindex set output-radix
20447 @item set output-radix @var{base}
20448 Set the default base for numeric display. Supported choices
20449 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20450 specified either unambiguously or using the current input radix.
20452 @kindex show input-radix
20453 @item show input-radix
20454 Display the current default base for numeric input.
20456 @kindex show output-radix
20457 @item show output-radix
20458 Display the current default base for numeric display.
20460 @item set radix @r{[}@var{base}@r{]}
20464 These commands set and show the default base for both input and output
20465 of numbers. @code{set radix} sets the radix of input and output to
20466 the same base; without an argument, it resets the radix back to its
20467 default value of 10.
20472 @section Configuring the Current ABI
20474 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
20475 application automatically. However, sometimes you need to override its
20476 conclusions. Use these commands to manage @value{GDBN}'s view of the
20483 One @value{GDBN} configuration can debug binaries for multiple operating
20484 system targets, either via remote debugging or native emulation.
20485 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
20486 but you can override its conclusion using the @code{set osabi} command.
20487 One example where this is useful is in debugging of binaries which use
20488 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
20489 not have the same identifying marks that the standard C library for your
20494 Show the OS ABI currently in use.
20497 With no argument, show the list of registered available OS ABI's.
20499 @item set osabi @var{abi}
20500 Set the current OS ABI to @var{abi}.
20503 @cindex float promotion
20505 Generally, the way that an argument of type @code{float} is passed to a
20506 function depends on whether the function is prototyped. For a prototyped
20507 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
20508 according to the architecture's convention for @code{float}. For unprototyped
20509 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
20510 @code{double} and then passed.
20512 Unfortunately, some forms of debug information do not reliably indicate whether
20513 a function is prototyped. If @value{GDBN} calls a function that is not marked
20514 as prototyped, it consults @kbd{set coerce-float-to-double}.
20517 @kindex set coerce-float-to-double
20518 @item set coerce-float-to-double
20519 @itemx set coerce-float-to-double on
20520 Arguments of type @code{float} will be promoted to @code{double} when passed
20521 to an unprototyped function. This is the default setting.
20523 @item set coerce-float-to-double off
20524 Arguments of type @code{float} will be passed directly to unprototyped
20527 @kindex show coerce-float-to-double
20528 @item show coerce-float-to-double
20529 Show the current setting of promoting @code{float} to @code{double}.
20533 @kindex show cp-abi
20534 @value{GDBN} needs to know the ABI used for your program's C@t{++}
20535 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
20536 used to build your application. @value{GDBN} only fully supports
20537 programs with a single C@t{++} ABI; if your program contains code using
20538 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
20539 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
20540 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
20541 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
20542 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
20543 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
20548 Show the C@t{++} ABI currently in use.
20551 With no argument, show the list of supported C@t{++} ABI's.
20553 @item set cp-abi @var{abi}
20554 @itemx set cp-abi auto
20555 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
20558 @node Messages/Warnings
20559 @section Optional Warnings and Messages
20561 @cindex verbose operation
20562 @cindex optional warnings
20563 By default, @value{GDBN} is silent about its inner workings. If you are
20564 running on a slow machine, you may want to use the @code{set verbose}
20565 command. This makes @value{GDBN} tell you when it does a lengthy
20566 internal operation, so you will not think it has crashed.
20568 Currently, the messages controlled by @code{set verbose} are those
20569 which announce that the symbol table for a source file is being read;
20570 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
20573 @kindex set verbose
20574 @item set verbose on
20575 Enables @value{GDBN} output of certain informational messages.
20577 @item set verbose off
20578 Disables @value{GDBN} output of certain informational messages.
20580 @kindex show verbose
20582 Displays whether @code{set verbose} is on or off.
20585 By default, if @value{GDBN} encounters bugs in the symbol table of an
20586 object file, it is silent; but if you are debugging a compiler, you may
20587 find this information useful (@pxref{Symbol Errors, ,Errors Reading
20592 @kindex set complaints
20593 @item set complaints @var{limit}
20594 Permits @value{GDBN} to output @var{limit} complaints about each type of
20595 unusual symbols before becoming silent about the problem. Set
20596 @var{limit} to zero to suppress all complaints; set it to a large number
20597 to prevent complaints from being suppressed.
20599 @kindex show complaints
20600 @item show complaints
20601 Displays how many symbol complaints @value{GDBN} is permitted to produce.
20605 @anchor{confirmation requests}
20606 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
20607 lot of stupid questions to confirm certain commands. For example, if
20608 you try to run a program which is already running:
20612 The program being debugged has been started already.
20613 Start it from the beginning? (y or n)
20616 If you are willing to unflinchingly face the consequences of your own
20617 commands, you can disable this ``feature'':
20621 @kindex set confirm
20623 @cindex confirmation
20624 @cindex stupid questions
20625 @item set confirm off
20626 Disables confirmation requests. Note that running @value{GDBN} with
20627 the @option{--batch} option (@pxref{Mode Options, -batch}) also
20628 automatically disables confirmation requests.
20630 @item set confirm on
20631 Enables confirmation requests (the default).
20633 @kindex show confirm
20635 Displays state of confirmation requests.
20639 @cindex command tracing
20640 If you need to debug user-defined commands or sourced files you may find it
20641 useful to enable @dfn{command tracing}. In this mode each command will be
20642 printed as it is executed, prefixed with one or more @samp{+} symbols, the
20643 quantity denoting the call depth of each command.
20646 @kindex set trace-commands
20647 @cindex command scripts, debugging
20648 @item set trace-commands on
20649 Enable command tracing.
20650 @item set trace-commands off
20651 Disable command tracing.
20652 @item show trace-commands
20653 Display the current state of command tracing.
20656 @node Debugging Output
20657 @section Optional Messages about Internal Happenings
20658 @cindex optional debugging messages
20660 @value{GDBN} has commands that enable optional debugging messages from
20661 various @value{GDBN} subsystems; normally these commands are of
20662 interest to @value{GDBN} maintainers, or when reporting a bug. This
20663 section documents those commands.
20666 @kindex set exec-done-display
20667 @item set exec-done-display
20668 Turns on or off the notification of asynchronous commands'
20669 completion. When on, @value{GDBN} will print a message when an
20670 asynchronous command finishes its execution. The default is off.
20671 @kindex show exec-done-display
20672 @item show exec-done-display
20673 Displays the current setting of asynchronous command completion
20676 @cindex gdbarch debugging info
20677 @cindex architecture debugging info
20678 @item set debug arch
20679 Turns on or off display of gdbarch debugging info. The default is off
20681 @item show debug arch
20682 Displays the current state of displaying gdbarch debugging info.
20683 @item set debug aix-thread
20684 @cindex AIX threads
20685 Display debugging messages about inner workings of the AIX thread
20687 @item show debug aix-thread
20688 Show the current state of AIX thread debugging info display.
20689 @item set debug check-physname
20691 Check the results of the ``physname'' computation. When reading DWARF
20692 debugging information for C@t{++}, @value{GDBN} attempts to compute
20693 each entity's name. @value{GDBN} can do this computation in two
20694 different ways, depending on exactly what information is present.
20695 When enabled, this setting causes @value{GDBN} to compute the names
20696 both ways and display any discrepancies.
20697 @item show debug check-physname
20698 Show the current state of ``physname'' checking.
20699 @item set debug dwarf2-die
20700 @cindex DWARF2 DIEs
20701 Dump DWARF2 DIEs after they are read in.
20702 The value is the number of nesting levels to print.
20703 A value of zero turns off the display.
20704 @item show debug dwarf2-die
20705 Show the current state of DWARF2 DIE debugging.
20706 @item set debug displaced
20707 @cindex displaced stepping debugging info
20708 Turns on or off display of @value{GDBN} debugging info for the
20709 displaced stepping support. The default is off.
20710 @item show debug displaced
20711 Displays the current state of displaying @value{GDBN} debugging info
20712 related to displaced stepping.
20713 @item set debug event
20714 @cindex event debugging info
20715 Turns on or off display of @value{GDBN} event debugging info. The
20717 @item show debug event
20718 Displays the current state of displaying @value{GDBN} event debugging
20720 @item set debug expression
20721 @cindex expression debugging info
20722 Turns on or off display of debugging info about @value{GDBN}
20723 expression parsing. The default is off.
20724 @item show debug expression
20725 Displays the current state of displaying debugging info about
20726 @value{GDBN} expression parsing.
20727 @item set debug frame
20728 @cindex frame debugging info
20729 Turns on or off display of @value{GDBN} frame debugging info. The
20731 @item show debug frame
20732 Displays the current state of displaying @value{GDBN} frame debugging
20734 @item set debug gnu-nat
20735 @cindex @sc{gnu}/Hurd debug messages
20736 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20737 @item show debug gnu-nat
20738 Show the current state of @sc{gnu}/Hurd debugging messages.
20739 @item set debug infrun
20740 @cindex inferior debugging info
20741 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20742 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20743 for implementing operations such as single-stepping the inferior.
20744 @item show debug infrun
20745 Displays the current state of @value{GDBN} inferior debugging.
20746 @item set debug jit
20747 @cindex just-in-time compilation, debugging messages
20748 Turns on or off debugging messages from JIT debug support.
20749 @item show debug jit
20750 Displays the current state of @value{GDBN} JIT debugging.
20751 @item set debug lin-lwp
20752 @cindex @sc{gnu}/Linux LWP debug messages
20753 @cindex Linux lightweight processes
20754 Turns on or off debugging messages from the Linux LWP debug support.
20755 @item show debug lin-lwp
20756 Show the current state of Linux LWP debugging messages.
20757 @item set debug observer
20758 @cindex observer debugging info
20759 Turns on or off display of @value{GDBN} observer debugging. This
20760 includes info such as the notification of observable events.
20761 @item show debug observer
20762 Displays the current state of observer debugging.
20763 @item set debug overload
20764 @cindex C@t{++} overload debugging info
20765 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20766 info. This includes info such as ranking of functions, etc. The default
20768 @item show debug overload
20769 Displays the current state of displaying @value{GDBN} C@t{++} overload
20771 @cindex expression parser, debugging info
20772 @cindex debug expression parser
20773 @item set debug parser
20774 Turns on or off the display of expression parser debugging output.
20775 Internally, this sets the @code{yydebug} variable in the expression
20776 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20777 details. The default is off.
20778 @item show debug parser
20779 Show the current state of expression parser debugging.
20780 @cindex packets, reporting on stdout
20781 @cindex serial connections, debugging
20782 @cindex debug remote protocol
20783 @cindex remote protocol debugging
20784 @cindex display remote packets
20785 @item set debug remote
20786 Turns on or off display of reports on all packets sent back and forth across
20787 the serial line to the remote machine. The info is printed on the
20788 @value{GDBN} standard output stream. The default is off.
20789 @item show debug remote
20790 Displays the state of display of remote packets.
20791 @item set debug serial
20792 Turns on or off display of @value{GDBN} serial debugging info. The
20794 @item show debug serial
20795 Displays the current state of displaying @value{GDBN} serial debugging
20797 @item set debug solib-frv
20798 @cindex FR-V shared-library debugging
20799 Turns on or off debugging messages for FR-V shared-library code.
20800 @item show debug solib-frv
20801 Display the current state of FR-V shared-library code debugging
20803 @item set debug target
20804 @cindex target debugging info
20805 Turns on or off display of @value{GDBN} target debugging info. This info
20806 includes what is going on at the target level of GDB, as it happens. The
20807 default is 0. Set it to 1 to track events, and to 2 to also track the
20808 value of large memory transfers. Changes to this flag do not take effect
20809 until the next time you connect to a target or use the @code{run} command.
20810 @item show debug target
20811 Displays the current state of displaying @value{GDBN} target debugging
20813 @item set debug timestamp
20814 @cindex timestampping debugging info
20815 Turns on or off display of timestamps with @value{GDBN} debugging info.
20816 When enabled, seconds and microseconds are displayed before each debugging
20818 @item show debug timestamp
20819 Displays the current state of displaying timestamps with @value{GDBN}
20821 @item set debugvarobj
20822 @cindex variable object debugging info
20823 Turns on or off display of @value{GDBN} variable object debugging
20824 info. The default is off.
20825 @item show debugvarobj
20826 Displays the current state of displaying @value{GDBN} variable object
20828 @item set debug xml
20829 @cindex XML parser debugging
20830 Turns on or off debugging messages for built-in XML parsers.
20831 @item show debug xml
20832 Displays the current state of XML debugging messages.
20835 @node Other Misc Settings
20836 @section Other Miscellaneous Settings
20837 @cindex miscellaneous settings
20840 @kindex set interactive-mode
20841 @item set interactive-mode
20842 If @code{on}, forces @value{GDBN} to assume that GDB was started
20843 in a terminal. In practice, this means that @value{GDBN} should wait
20844 for the user to answer queries generated by commands entered at
20845 the command prompt. If @code{off}, forces @value{GDBN} to operate
20846 in the opposite mode, and it uses the default answers to all queries.
20847 If @code{auto} (the default), @value{GDBN} tries to determine whether
20848 its standard input is a terminal, and works in interactive-mode if it
20849 is, non-interactively otherwise.
20851 In the vast majority of cases, the debugger should be able to guess
20852 correctly which mode should be used. But this setting can be useful
20853 in certain specific cases, such as running a MinGW @value{GDBN}
20854 inside a cygwin window.
20856 @kindex show interactive-mode
20857 @item show interactive-mode
20858 Displays whether the debugger is operating in interactive mode or not.
20861 @node Extending GDB
20862 @chapter Extending @value{GDBN}
20863 @cindex extending GDB
20865 @value{GDBN} provides three mechanisms for extension. The first is based
20866 on composition of @value{GDBN} commands, the second is based on the
20867 Python scripting language, and the third is for defining new aliases of
20870 To facilitate the use of the first two extensions, @value{GDBN} is capable
20871 of evaluating the contents of a file. When doing so, @value{GDBN}
20872 can recognize which scripting language is being used by looking at
20873 the filename extension. Files with an unrecognized filename extension
20874 are always treated as a @value{GDBN} Command Files.
20875 @xref{Command Files,, Command files}.
20877 You can control how @value{GDBN} evaluates these files with the following
20881 @kindex set script-extension
20882 @kindex show script-extension
20883 @item set script-extension off
20884 All scripts are always evaluated as @value{GDBN} Command Files.
20886 @item set script-extension soft
20887 The debugger determines the scripting language based on filename
20888 extension. If this scripting language is supported, @value{GDBN}
20889 evaluates the script using that language. Otherwise, it evaluates
20890 the file as a @value{GDBN} Command File.
20892 @item set script-extension strict
20893 The debugger determines the scripting language based on filename
20894 extension, and evaluates the script using that language. If the
20895 language is not supported, then the evaluation fails.
20897 @item show script-extension
20898 Display the current value of the @code{script-extension} option.
20903 * Sequences:: Canned Sequences of Commands
20904 * Python:: Scripting @value{GDBN} using Python
20905 * Aliases:: Creating new spellings of existing commands
20909 @section Canned Sequences of Commands
20911 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20912 Command Lists}), @value{GDBN} provides two ways to store sequences of
20913 commands for execution as a unit: user-defined commands and command
20917 * Define:: How to define your own commands
20918 * Hooks:: Hooks for user-defined commands
20919 * Command Files:: How to write scripts of commands to be stored in a file
20920 * Output:: Commands for controlled output
20924 @subsection User-defined Commands
20926 @cindex user-defined command
20927 @cindex arguments, to user-defined commands
20928 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20929 which you assign a new name as a command. This is done with the
20930 @code{define} command. User commands may accept up to 10 arguments
20931 separated by whitespace. Arguments are accessed within the user command
20932 via @code{$arg0@dots{}$arg9}. A trivial example:
20936 print $arg0 + $arg1 + $arg2
20941 To execute the command use:
20948 This defines the command @code{adder}, which prints the sum of
20949 its three arguments. Note the arguments are text substitutions, so they may
20950 reference variables, use complex expressions, or even perform inferior
20953 @cindex argument count in user-defined commands
20954 @cindex how many arguments (user-defined commands)
20955 In addition, @code{$argc} may be used to find out how many arguments have
20956 been passed. This expands to a number in the range 0@dots{}10.
20961 print $arg0 + $arg1
20964 print $arg0 + $arg1 + $arg2
20972 @item define @var{commandname}
20973 Define a command named @var{commandname}. If there is already a command
20974 by that name, you are asked to confirm that you want to redefine it.
20975 @var{commandname} may be a bare command name consisting of letters,
20976 numbers, dashes, and underscores. It may also start with any predefined
20977 prefix command. For example, @samp{define target my-target} creates
20978 a user-defined @samp{target my-target} command.
20980 The definition of the command is made up of other @value{GDBN} command lines,
20981 which are given following the @code{define} command. The end of these
20982 commands is marked by a line containing @code{end}.
20985 @kindex end@r{ (user-defined commands)}
20986 @item document @var{commandname}
20987 Document the user-defined command @var{commandname}, so that it can be
20988 accessed by @code{help}. The command @var{commandname} must already be
20989 defined. This command reads lines of documentation just as @code{define}
20990 reads the lines of the command definition, ending with @code{end}.
20991 After the @code{document} command is finished, @code{help} on command
20992 @var{commandname} displays the documentation you have written.
20994 You may use the @code{document} command again to change the
20995 documentation of a command. Redefining the command with @code{define}
20996 does not change the documentation.
20998 @kindex dont-repeat
20999 @cindex don't repeat command
21001 Used inside a user-defined command, this tells @value{GDBN} that this
21002 command should not be repeated when the user hits @key{RET}
21003 (@pxref{Command Syntax, repeat last command}).
21005 @kindex help user-defined
21006 @item help user-defined
21007 List all user-defined commands, with the first line of the documentation
21012 @itemx show user @var{commandname}
21013 Display the @value{GDBN} commands used to define @var{commandname} (but
21014 not its documentation). If no @var{commandname} is given, display the
21015 definitions for all user-defined commands.
21017 @cindex infinite recursion in user-defined commands
21018 @kindex show max-user-call-depth
21019 @kindex set max-user-call-depth
21020 @item show max-user-call-depth
21021 @itemx set max-user-call-depth
21022 The value of @code{max-user-call-depth} controls how many recursion
21023 levels are allowed in user-defined commands before @value{GDBN} suspects an
21024 infinite recursion and aborts the command.
21027 In addition to the above commands, user-defined commands frequently
21028 use control flow commands, described in @ref{Command Files}.
21030 When user-defined commands are executed, the
21031 commands of the definition are not printed. An error in any command
21032 stops execution of the user-defined command.
21034 If used interactively, commands that would ask for confirmation proceed
21035 without asking when used inside a user-defined command. Many @value{GDBN}
21036 commands that normally print messages to say what they are doing omit the
21037 messages when used in a user-defined command.
21040 @subsection User-defined Command Hooks
21041 @cindex command hooks
21042 @cindex hooks, for commands
21043 @cindex hooks, pre-command
21046 You may define @dfn{hooks}, which are a special kind of user-defined
21047 command. Whenever you run the command @samp{foo}, if the user-defined
21048 command @samp{hook-foo} exists, it is executed (with no arguments)
21049 before that command.
21051 @cindex hooks, post-command
21053 A hook may also be defined which is run after the command you executed.
21054 Whenever you run the command @samp{foo}, if the user-defined command
21055 @samp{hookpost-foo} exists, it is executed (with no arguments) after
21056 that command. Post-execution hooks may exist simultaneously with
21057 pre-execution hooks, for the same command.
21059 It is valid for a hook to call the command which it hooks. If this
21060 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
21062 @c It would be nice if hookpost could be passed a parameter indicating
21063 @c if the command it hooks executed properly or not. FIXME!
21065 @kindex stop@r{, a pseudo-command}
21066 In addition, a pseudo-command, @samp{stop} exists. Defining
21067 (@samp{hook-stop}) makes the associated commands execute every time
21068 execution stops in your program: before breakpoint commands are run,
21069 displays are printed, or the stack frame is printed.
21071 For example, to ignore @code{SIGALRM} signals while
21072 single-stepping, but treat them normally during normal execution,
21077 handle SIGALRM nopass
21081 handle SIGALRM pass
21084 define hook-continue
21085 handle SIGALRM pass
21089 As a further example, to hook at the beginning and end of the @code{echo}
21090 command, and to add extra text to the beginning and end of the message,
21098 define hookpost-echo
21102 (@value{GDBP}) echo Hello World
21103 <<<---Hello World--->>>
21108 You can define a hook for any single-word command in @value{GDBN}, but
21109 not for command aliases; you should define a hook for the basic command
21110 name, e.g.@: @code{backtrace} rather than @code{bt}.
21111 @c FIXME! So how does Joe User discover whether a command is an alias
21113 You can hook a multi-word command by adding @code{hook-} or
21114 @code{hookpost-} to the last word of the command, e.g.@:
21115 @samp{define target hook-remote} to add a hook to @samp{target remote}.
21117 If an error occurs during the execution of your hook, execution of
21118 @value{GDBN} commands stops and @value{GDBN} issues a prompt
21119 (before the command that you actually typed had a chance to run).
21121 If you try to define a hook which does not match any known command, you
21122 get a warning from the @code{define} command.
21124 @node Command Files
21125 @subsection Command Files
21127 @cindex command files
21128 @cindex scripting commands
21129 A command file for @value{GDBN} is a text file made of lines that are
21130 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
21131 also be included. An empty line in a command file does nothing; it
21132 does not mean to repeat the last command, as it would from the
21135 You can request the execution of a command file with the @code{source}
21136 command. Note that the @code{source} command is also used to evaluate
21137 scripts that are not Command Files. The exact behavior can be configured
21138 using the @code{script-extension} setting.
21139 @xref{Extending GDB,, Extending GDB}.
21143 @cindex execute commands from a file
21144 @item source [-s] [-v] @var{filename}
21145 Execute the command file @var{filename}.
21148 The lines in a command file are generally executed sequentially,
21149 unless the order of execution is changed by one of the
21150 @emph{flow-control commands} described below. The commands are not
21151 printed as they are executed. An error in any command terminates
21152 execution of the command file and control is returned to the console.
21154 @value{GDBN} first searches for @var{filename} in the current directory.
21155 If the file is not found there, and @var{filename} does not specify a
21156 directory, then @value{GDBN} also looks for the file on the source search path
21157 (specified with the @samp{directory} command);
21158 except that @file{$cdir} is not searched because the compilation directory
21159 is not relevant to scripts.
21161 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
21162 on the search path even if @var{filename} specifies a directory.
21163 The search is done by appending @var{filename} to each element of the
21164 search path. So, for example, if @var{filename} is @file{mylib/myscript}
21165 and the search path contains @file{/home/user} then @value{GDBN} will
21166 look for the script @file{/home/user/mylib/myscript}.
21167 The search is also done if @var{filename} is an absolute path.
21168 For example, if @var{filename} is @file{/tmp/myscript} and
21169 the search path contains @file{/home/user} then @value{GDBN} will
21170 look for the script @file{/home/user/tmp/myscript}.
21171 For DOS-like systems, if @var{filename} contains a drive specification,
21172 it is stripped before concatenation. For example, if @var{filename} is
21173 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
21174 will look for the script @file{c:/tmp/myscript}.
21176 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
21177 each command as it is executed. The option must be given before
21178 @var{filename}, and is interpreted as part of the filename anywhere else.
21180 Commands that would ask for confirmation if used interactively proceed
21181 without asking when used in a command file. Many @value{GDBN} commands that
21182 normally print messages to say what they are doing omit the messages
21183 when called from command files.
21185 @value{GDBN} also accepts command input from standard input. In this
21186 mode, normal output goes to standard output and error output goes to
21187 standard error. Errors in a command file supplied on standard input do
21188 not terminate execution of the command file---execution continues with
21192 gdb < cmds > log 2>&1
21195 (The syntax above will vary depending on the shell used.) This example
21196 will execute commands from the file @file{cmds}. All output and errors
21197 would be directed to @file{log}.
21199 Since commands stored on command files tend to be more general than
21200 commands typed interactively, they frequently need to deal with
21201 complicated situations, such as different or unexpected values of
21202 variables and symbols, changes in how the program being debugged is
21203 built, etc. @value{GDBN} provides a set of flow-control commands to
21204 deal with these complexities. Using these commands, you can write
21205 complex scripts that loop over data structures, execute commands
21206 conditionally, etc.
21213 This command allows to include in your script conditionally executed
21214 commands. The @code{if} command takes a single argument, which is an
21215 expression to evaluate. It is followed by a series of commands that
21216 are executed only if the expression is true (its value is nonzero).
21217 There can then optionally be an @code{else} line, followed by a series
21218 of commands that are only executed if the expression was false. The
21219 end of the list is marked by a line containing @code{end}.
21223 This command allows to write loops. Its syntax is similar to
21224 @code{if}: the command takes a single argument, which is an expression
21225 to evaluate, and must be followed by the commands to execute, one per
21226 line, terminated by an @code{end}. These commands are called the
21227 @dfn{body} of the loop. The commands in the body of @code{while} are
21228 executed repeatedly as long as the expression evaluates to true.
21232 This command exits the @code{while} loop in whose body it is included.
21233 Execution of the script continues after that @code{while}s @code{end}
21236 @kindex loop_continue
21237 @item loop_continue
21238 This command skips the execution of the rest of the body of commands
21239 in the @code{while} loop in whose body it is included. Execution
21240 branches to the beginning of the @code{while} loop, where it evaluates
21241 the controlling expression.
21243 @kindex end@r{ (if/else/while commands)}
21245 Terminate the block of commands that are the body of @code{if},
21246 @code{else}, or @code{while} flow-control commands.
21251 @subsection Commands for Controlled Output
21253 During the execution of a command file or a user-defined command, normal
21254 @value{GDBN} output is suppressed; the only output that appears is what is
21255 explicitly printed by the commands in the definition. This section
21256 describes three commands useful for generating exactly the output you
21261 @item echo @var{text}
21262 @c I do not consider backslash-space a standard C escape sequence
21263 @c because it is not in ANSI.
21264 Print @var{text}. Nonprinting characters can be included in
21265 @var{text} using C escape sequences, such as @samp{\n} to print a
21266 newline. @strong{No newline is printed unless you specify one.}
21267 In addition to the standard C escape sequences, a backslash followed
21268 by a space stands for a space. This is useful for displaying a
21269 string with spaces at the beginning or the end, since leading and
21270 trailing spaces are otherwise trimmed from all arguments.
21271 To print @samp{@w{ }and foo =@w{ }}, use the command
21272 @samp{echo \@w{ }and foo = \@w{ }}.
21274 A backslash at the end of @var{text} can be used, as in C, to continue
21275 the command onto subsequent lines. For example,
21278 echo This is some text\n\
21279 which is continued\n\
21280 onto several lines.\n
21283 produces the same output as
21286 echo This is some text\n
21287 echo which is continued\n
21288 echo onto several lines.\n
21292 @item output @var{expression}
21293 Print the value of @var{expression} and nothing but that value: no
21294 newlines, no @samp{$@var{nn} = }. The value is not entered in the
21295 value history either. @xref{Expressions, ,Expressions}, for more information
21298 @item output/@var{fmt} @var{expression}
21299 Print the value of @var{expression} in format @var{fmt}. You can use
21300 the same formats as for @code{print}. @xref{Output Formats,,Output
21301 Formats}, for more information.
21304 @item printf @var{template}, @var{expressions}@dots{}
21305 Print the values of one or more @var{expressions} under the control of
21306 the string @var{template}. To print several values, make
21307 @var{expressions} be a comma-separated list of individual expressions,
21308 which may be either numbers or pointers. Their values are printed as
21309 specified by @var{template}, exactly as a C program would do by
21310 executing the code below:
21313 printf (@var{template}, @var{expressions}@dots{});
21316 As in @code{C} @code{printf}, ordinary characters in @var{template}
21317 are printed verbatim, while @dfn{conversion specification} introduced
21318 by the @samp{%} character cause subsequent @var{expressions} to be
21319 evaluated, their values converted and formatted according to type and
21320 style information encoded in the conversion specifications, and then
21323 For example, you can print two values in hex like this:
21326 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
21329 @code{printf} supports all the standard @code{C} conversion
21330 specifications, including the flags and modifiers between the @samp{%}
21331 character and the conversion letter, with the following exceptions:
21335 The argument-ordering modifiers, such as @samp{2$}, are not supported.
21338 The modifier @samp{*} is not supported for specifying precision or
21342 The @samp{'} flag (for separation of digits into groups according to
21343 @code{LC_NUMERIC'}) is not supported.
21346 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
21350 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
21353 The conversion letters @samp{a} and @samp{A} are not supported.
21357 Note that the @samp{ll} type modifier is supported only if the
21358 underlying @code{C} implementation used to build @value{GDBN} supports
21359 the @code{long long int} type, and the @samp{L} type modifier is
21360 supported only if @code{long double} type is available.
21362 As in @code{C}, @code{printf} supports simple backslash-escape
21363 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
21364 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
21365 single character. Octal and hexadecimal escape sequences are not
21368 Additionally, @code{printf} supports conversion specifications for DFP
21369 (@dfn{Decimal Floating Point}) types using the following length modifiers
21370 together with a floating point specifier.
21375 @samp{H} for printing @code{Decimal32} types.
21378 @samp{D} for printing @code{Decimal64} types.
21381 @samp{DD} for printing @code{Decimal128} types.
21384 If the underlying @code{C} implementation used to build @value{GDBN} has
21385 support for the three length modifiers for DFP types, other modifiers
21386 such as width and precision will also be available for @value{GDBN} to use.
21388 In case there is no such @code{C} support, no additional modifiers will be
21389 available and the value will be printed in the standard way.
21391 Here's an example of printing DFP types using the above conversion letters:
21393 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
21397 @item eval @var{template}, @var{expressions}@dots{}
21398 Convert the values of one or more @var{expressions} under the control of
21399 the string @var{template} to a command line, and call it.
21404 @section Scripting @value{GDBN} using Python
21405 @cindex python scripting
21406 @cindex scripting with python
21408 You can script @value{GDBN} using the @uref{http://www.python.org/,
21409 Python programming language}. This feature is available only if
21410 @value{GDBN} was configured using @option{--with-python}.
21412 @cindex python directory
21413 Python scripts used by @value{GDBN} should be installed in
21414 @file{@var{data-directory}/python}, where @var{data-directory} is
21415 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
21416 This directory, known as the @dfn{python directory},
21417 is automatically added to the Python Search Path in order to allow
21418 the Python interpreter to locate all scripts installed at this location.
21420 Additionally, @value{GDBN} commands and convenience functions which
21421 are written in Python and are located in the
21422 @file{@var{data-directory}/python/gdb/command} or
21423 @file{@var{data-directory}/python/gdb/function} directories are
21424 automatically imported when @value{GDBN} starts.
21427 * Python Commands:: Accessing Python from @value{GDBN}.
21428 * Python API:: Accessing @value{GDBN} from Python.
21429 * Auto-loading:: Automatically loading Python code.
21430 * Python modules:: Python modules provided by @value{GDBN}.
21433 @node Python Commands
21434 @subsection Python Commands
21435 @cindex python commands
21436 @cindex commands to access python
21438 @value{GDBN} provides one command for accessing the Python interpreter,
21439 and one related setting:
21443 @item python @r{[}@var{code}@r{]}
21444 The @code{python} command can be used to evaluate Python code.
21446 If given an argument, the @code{python} command will evaluate the
21447 argument as a Python command. For example:
21450 (@value{GDBP}) python print 23
21454 If you do not provide an argument to @code{python}, it will act as a
21455 multi-line command, like @code{define}. In this case, the Python
21456 script is made up of subsequent command lines, given after the
21457 @code{python} command. This command list is terminated using a line
21458 containing @code{end}. For example:
21461 (@value{GDBP}) python
21463 End with a line saying just "end".
21469 @kindex set python print-stack
21470 @item set python print-stack
21471 By default, @value{GDBN} will print only the message component of a
21472 Python exception when an error occurs in a Python script. This can be
21473 controlled using @code{set python print-stack}: if @code{full}, then
21474 full Python stack printing is enabled; if @code{none}, then Python stack
21475 and message printing is disabled; if @code{message}, the default, only
21476 the message component of the error is printed.
21479 It is also possible to execute a Python script from the @value{GDBN}
21483 @item source @file{script-name}
21484 The script name must end with @samp{.py} and @value{GDBN} must be configured
21485 to recognize the script language based on filename extension using
21486 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
21488 @item python execfile ("script-name")
21489 This method is based on the @code{execfile} Python built-in function,
21490 and thus is always available.
21494 @subsection Python API
21496 @cindex programming in python
21498 @cindex python stdout
21499 @cindex python pagination
21500 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
21501 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
21502 A Python program which outputs to one of these streams may have its
21503 output interrupted by the user (@pxref{Screen Size}). In this
21504 situation, a Python @code{KeyboardInterrupt} exception is thrown.
21507 * Basic Python:: Basic Python Functions.
21508 * Exception Handling:: How Python exceptions are translated.
21509 * Values From Inferior:: Python representation of values.
21510 * Types In Python:: Python representation of types.
21511 * Pretty Printing API:: Pretty-printing values.
21512 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
21513 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
21514 * Inferiors In Python:: Python representation of inferiors (processes)
21515 * Events In Python:: Listening for events from @value{GDBN}.
21516 * Threads In Python:: Accessing inferior threads from Python.
21517 * Commands In Python:: Implementing new commands in Python.
21518 * Parameters In Python:: Adding new @value{GDBN} parameters.
21519 * Functions In Python:: Writing new convenience functions.
21520 * Progspaces In Python:: Program spaces.
21521 * Objfiles In Python:: Object files.
21522 * Frames In Python:: Accessing inferior stack frames from Python.
21523 * Blocks In Python:: Accessing frame blocks from Python.
21524 * Symbols In Python:: Python representation of symbols.
21525 * Symbol Tables In Python:: Python representation of symbol tables.
21526 * Lazy Strings In Python:: Python representation of lazy strings.
21527 * Breakpoints In Python:: Manipulating breakpoints using Python.
21528 * Finish Breakpoints in Python:: Setting Breakpoints on function return
21533 @subsubsection Basic Python
21535 @cindex python functions
21536 @cindex python module
21538 @value{GDBN} introduces a new Python module, named @code{gdb}. All
21539 methods and classes added by @value{GDBN} are placed in this module.
21540 @value{GDBN} automatically @code{import}s the @code{gdb} module for
21541 use in all scripts evaluated by the @code{python} command.
21543 @findex gdb.PYTHONDIR
21544 @defvar gdb.PYTHONDIR
21545 A string containing the python directory (@pxref{Python}).
21548 @findex gdb.execute
21549 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
21550 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
21551 If a GDB exception happens while @var{command} runs, it is
21552 translated as described in @ref{Exception Handling,,Exception Handling}.
21554 @var{from_tty} specifies whether @value{GDBN} ought to consider this
21555 command as having originated from the user invoking it interactively.
21556 It must be a boolean value. If omitted, it defaults to @code{False}.
21558 By default, any output produced by @var{command} is sent to
21559 @value{GDBN}'s standard output. If the @var{to_string} parameter is
21560 @code{True}, then output will be collected by @code{gdb.execute} and
21561 returned as a string. The default is @code{False}, in which case the
21562 return value is @code{None}. If @var{to_string} is @code{True}, the
21563 @value{GDBN} virtual terminal will be temporarily set to unlimited width
21564 and height, and its pagination will be disabled; @pxref{Screen Size}.
21567 @findex gdb.breakpoints
21568 @defun gdb.breakpoints ()
21569 Return a sequence holding all of @value{GDBN}'s breakpoints.
21570 @xref{Breakpoints In Python}, for more information.
21573 @findex gdb.parameter
21574 @defun gdb.parameter (parameter)
21575 Return the value of a @value{GDBN} parameter. @var{parameter} is a
21576 string naming the parameter to look up; @var{parameter} may contain
21577 spaces if the parameter has a multi-part name. For example,
21578 @samp{print object} is a valid parameter name.
21580 If the named parameter does not exist, this function throws a
21581 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
21582 parameter's value is converted to a Python value of the appropriate
21583 type, and returned.
21586 @findex gdb.history
21587 @defun gdb.history (number)
21588 Return a value from @value{GDBN}'s value history (@pxref{Value
21589 History}). @var{number} indicates which history element to return.
21590 If @var{number} is negative, then @value{GDBN} will take its absolute value
21591 and count backward from the last element (i.e., the most recent element) to
21592 find the value to return. If @var{number} is zero, then @value{GDBN} will
21593 return the most recent element. If the element specified by @var{number}
21594 doesn't exist in the value history, a @code{gdb.error} exception will be
21597 If no exception is raised, the return value is always an instance of
21598 @code{gdb.Value} (@pxref{Values From Inferior}).
21601 @findex gdb.parse_and_eval
21602 @defun gdb.parse_and_eval (expression)
21603 Parse @var{expression} as an expression in the current language,
21604 evaluate it, and return the result as a @code{gdb.Value}.
21605 @var{expression} must be a string.
21607 This function can be useful when implementing a new command
21608 (@pxref{Commands In Python}), as it provides a way to parse the
21609 command's argument as an expression. It is also useful simply to
21610 compute values, for example, it is the only way to get the value of a
21611 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
21614 @findex gdb.post_event
21615 @defun gdb.post_event (event)
21616 Put @var{event}, a callable object taking no arguments, into
21617 @value{GDBN}'s internal event queue. This callable will be invoked at
21618 some later point, during @value{GDBN}'s event processing. Events
21619 posted using @code{post_event} will be run in the order in which they
21620 were posted; however, there is no way to know when they will be
21621 processed relative to other events inside @value{GDBN}.
21623 @value{GDBN} is not thread-safe. If your Python program uses multiple
21624 threads, you must be careful to only call @value{GDBN}-specific
21625 functions in the main @value{GDBN} thread. @code{post_event} ensures
21629 (@value{GDBP}) python
21633 > def __init__(self, message):
21634 > self.message = message;
21635 > def __call__(self):
21636 > gdb.write(self.message)
21638 >class MyThread1 (threading.Thread):
21640 > gdb.post_event(Writer("Hello "))
21642 >class MyThread2 (threading.Thread):
21644 > gdb.post_event(Writer("World\n"))
21646 >MyThread1().start()
21647 >MyThread2().start()
21649 (@value{GDBP}) Hello World
21654 @defun gdb.write (string @r{[}, stream{]})
21655 Print a string to @value{GDBN}'s paginated output stream. The
21656 optional @var{stream} determines the stream to print to. The default
21657 stream is @value{GDBN}'s standard output stream. Possible stream
21664 @value{GDBN}'s standard output stream.
21669 @value{GDBN}'s standard error stream.
21674 @value{GDBN}'s log stream (@pxref{Logging Output}).
21677 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
21678 call this function and will automatically direct the output to the
21683 @defun gdb.flush ()
21684 Flush the buffer of a @value{GDBN} paginated stream so that the
21685 contents are displayed immediately. @value{GDBN} will flush the
21686 contents of a stream automatically when it encounters a newline in the
21687 buffer. The optional @var{stream} determines the stream to flush. The
21688 default stream is @value{GDBN}'s standard output stream. Possible
21695 @value{GDBN}'s standard output stream.
21700 @value{GDBN}'s standard error stream.
21705 @value{GDBN}'s log stream (@pxref{Logging Output}).
21709 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21710 call this function for the relevant stream.
21713 @findex gdb.target_charset
21714 @defun gdb.target_charset ()
21715 Return the name of the current target character set (@pxref{Character
21716 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21717 that @samp{auto} is never returned.
21720 @findex gdb.target_wide_charset
21721 @defun gdb.target_wide_charset ()
21722 Return the name of the current target wide character set
21723 (@pxref{Character Sets}). This differs from
21724 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21728 @findex gdb.solib_name
21729 @defun gdb.solib_name (address)
21730 Return the name of the shared library holding the given @var{address}
21731 as a string, or @code{None}.
21734 @findex gdb.decode_line
21735 @defun gdb.decode_line @r{[}expression@r{]}
21736 Return locations of the line specified by @var{expression}, or of the
21737 current line if no argument was given. This function returns a Python
21738 tuple containing two elements. The first element contains a string
21739 holding any unparsed section of @var{expression} (or @code{None} if
21740 the expression has been fully parsed). The second element contains
21741 either @code{None} or another tuple that contains all the locations
21742 that match the expression represented as @code{gdb.Symtab_and_line}
21743 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21744 provided, it is decoded the way that @value{GDBN}'s inbuilt
21745 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21748 @defun gdb.prompt_hook (current_prompt)
21749 @anchor{prompt_hook}
21751 If @var{prompt_hook} is callable, @value{GDBN} will call the method
21752 assigned to this operation before a prompt is displayed by
21755 The parameter @code{current_prompt} contains the current @value{GDBN}
21756 prompt. This method must return a Python string, or @code{None}. If
21757 a string is returned, the @value{GDBN} prompt will be set to that
21758 string. If @code{None} is returned, @value{GDBN} will continue to use
21759 the current prompt.
21761 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
21762 such as those used by readline for command input, and annotation
21763 related prompts are prohibited from being changed.
21766 @node Exception Handling
21767 @subsubsection Exception Handling
21768 @cindex python exceptions
21769 @cindex exceptions, python
21771 When executing the @code{python} command, Python exceptions
21772 uncaught within the Python code are translated to calls to
21773 @value{GDBN} error-reporting mechanism. If the command that called
21774 @code{python} does not handle the error, @value{GDBN} will
21775 terminate it and print an error message containing the Python
21776 exception name, the associated value, and the Python call stack
21777 backtrace at the point where the exception was raised. Example:
21780 (@value{GDBP}) python print foo
21781 Traceback (most recent call last):
21782 File "<string>", line 1, in <module>
21783 NameError: name 'foo' is not defined
21786 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21787 Python code are converted to Python exceptions. The type of the
21788 Python exception depends on the error.
21792 This is the base class for most exceptions generated by @value{GDBN}.
21793 It is derived from @code{RuntimeError}, for compatibility with earlier
21794 versions of @value{GDBN}.
21796 If an error occurring in @value{GDBN} does not fit into some more
21797 specific category, then the generated exception will have this type.
21799 @item gdb.MemoryError
21800 This is a subclass of @code{gdb.error} which is thrown when an
21801 operation tried to access invalid memory in the inferior.
21803 @item KeyboardInterrupt
21804 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21805 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21808 In all cases, your exception handler will see the @value{GDBN} error
21809 message as its value and the Python call stack backtrace at the Python
21810 statement closest to where the @value{GDBN} error occured as the
21813 @findex gdb.GdbError
21814 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21815 it is useful to be able to throw an exception that doesn't cause a
21816 traceback to be printed. For example, the user may have invoked the
21817 command incorrectly. Use the @code{gdb.GdbError} exception
21818 to handle this case. Example:
21822 >class HelloWorld (gdb.Command):
21823 > """Greet the whole world."""
21824 > def __init__ (self):
21825 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21826 > def invoke (self, args, from_tty):
21827 > argv = gdb.string_to_argv (args)
21828 > if len (argv) != 0:
21829 > raise gdb.GdbError ("hello-world takes no arguments")
21830 > print "Hello, World!"
21833 (gdb) hello-world 42
21834 hello-world takes no arguments
21837 @node Values From Inferior
21838 @subsubsection Values From Inferior
21839 @cindex values from inferior, with Python
21840 @cindex python, working with values from inferior
21842 @cindex @code{gdb.Value}
21843 @value{GDBN} provides values it obtains from the inferior program in
21844 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21845 for its internal bookkeeping of the inferior's values, and for
21846 fetching values when necessary.
21848 Inferior values that are simple scalars can be used directly in
21849 Python expressions that are valid for the value's data type. Here's
21850 an example for an integer or floating-point value @code{some_val}:
21857 As result of this, @code{bar} will also be a @code{gdb.Value} object
21858 whose values are of the same type as those of @code{some_val}.
21860 Inferior values that are structures or instances of some class can
21861 be accessed using the Python @dfn{dictionary syntax}. For example, if
21862 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21863 can access its @code{foo} element with:
21866 bar = some_val['foo']
21869 Again, @code{bar} will also be a @code{gdb.Value} object.
21871 A @code{gdb.Value} that represents a function can be executed via
21872 inferior function call. Any arguments provided to the call must match
21873 the function's prototype, and must be provided in the order specified
21876 For example, @code{some_val} is a @code{gdb.Value} instance
21877 representing a function that takes two integers as arguments. To
21878 execute this function, call it like so:
21881 result = some_val (10,20)
21884 Any values returned from a function call will be stored as a
21887 The following attributes are provided:
21890 @defvar Value.address
21891 If this object is addressable, this read-only attribute holds a
21892 @code{gdb.Value} object representing the address. Otherwise,
21893 this attribute holds @code{None}.
21896 @cindex optimized out value in Python
21897 @defvar Value.is_optimized_out
21898 This read-only boolean attribute is true if the compiler optimized out
21899 this value, thus it is not available for fetching from the inferior.
21903 The type of this @code{gdb.Value}. The value of this attribute is a
21904 @code{gdb.Type} object (@pxref{Types In Python}).
21907 @defvar Value.dynamic_type
21908 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21909 type information (@acronym{RTTI}) to determine the dynamic type of the
21910 value. If this value is of class type, it will return the class in
21911 which the value is embedded, if any. If this value is of pointer or
21912 reference to a class type, it will compute the dynamic type of the
21913 referenced object, and return a pointer or reference to that type,
21914 respectively. In all other cases, it will return the value's static
21917 Note that this feature will only work when debugging a C@t{++} program
21918 that includes @acronym{RTTI} for the object in question. Otherwise,
21919 it will just return the static type of the value as in @kbd{ptype foo}
21920 (@pxref{Symbols, ptype}).
21923 @defvar Value.is_lazy
21924 The value of this read-only boolean attribute is @code{True} if this
21925 @code{gdb.Value} has not yet been fetched from the inferior.
21926 @value{GDBN} does not fetch values until necessary, for efficiency.
21930 myval = gdb.parse_and_eval ('somevar')
21933 The value of @code{somevar} is not fetched at this time. It will be
21934 fetched when the value is needed, or when the @code{fetch_lazy}
21939 The following methods are provided:
21942 @defun Value.__init__ (@var{val})
21943 Many Python values can be converted directly to a @code{gdb.Value} via
21944 this object initializer. Specifically:
21947 @item Python boolean
21948 A Python boolean is converted to the boolean type from the current
21951 @item Python integer
21952 A Python integer is converted to the C @code{long} type for the
21953 current architecture.
21956 A Python long is converted to the C @code{long long} type for the
21957 current architecture.
21960 A Python float is converted to the C @code{double} type for the
21961 current architecture.
21963 @item Python string
21964 A Python string is converted to a target string, using the current
21967 @item @code{gdb.Value}
21968 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
21970 @item @code{gdb.LazyString}
21971 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
21972 Python}), then the lazy string's @code{value} method is called, and
21973 its result is used.
21977 @defun Value.cast (type)
21978 Return a new instance of @code{gdb.Value} that is the result of
21979 casting this instance to the type described by @var{type}, which must
21980 be a @code{gdb.Type} object. If the cast cannot be performed for some
21981 reason, this method throws an exception.
21984 @defun Value.dereference ()
21985 For pointer data types, this method returns a new @code{gdb.Value} object
21986 whose contents is the object pointed to by the pointer. For example, if
21987 @code{foo} is a C pointer to an @code{int}, declared in your C program as
21994 then you can use the corresponding @code{gdb.Value} to access what
21995 @code{foo} points to like this:
21998 bar = foo.dereference ()
22001 The result @code{bar} will be a @code{gdb.Value} object holding the
22002 value pointed to by @code{foo}.
22005 @defun Value.dynamic_cast (type)
22006 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
22007 operator were used. Consult a C@t{++} reference for details.
22010 @defun Value.reinterpret_cast (type)
22011 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
22012 operator were used. Consult a C@t{++} reference for details.
22015 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
22016 If this @code{gdb.Value} represents a string, then this method
22017 converts the contents to a Python string. Otherwise, this method will
22018 throw an exception.
22020 Strings are recognized in a language-specific way; whether a given
22021 @code{gdb.Value} represents a string is determined by the current
22024 For C-like languages, a value is a string if it is a pointer to or an
22025 array of characters or ints. The string is assumed to be terminated
22026 by a zero of the appropriate width. However if the optional length
22027 argument is given, the string will be converted to that given length,
22028 ignoring any embedded zeros that the string may contain.
22030 If the optional @var{encoding} argument is given, it must be a string
22031 naming the encoding of the string in the @code{gdb.Value}, such as
22032 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
22033 the same encodings as the corresponding argument to Python's
22034 @code{string.decode} method, and the Python codec machinery will be used
22035 to convert the string. If @var{encoding} is not given, or if
22036 @var{encoding} is the empty string, then either the @code{target-charset}
22037 (@pxref{Character Sets}) will be used, or a language-specific encoding
22038 will be used, if the current language is able to supply one.
22040 The optional @var{errors} argument is the same as the corresponding
22041 argument to Python's @code{string.decode} method.
22043 If the optional @var{length} argument is given, the string will be
22044 fetched and converted to the given length.
22047 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
22048 If this @code{gdb.Value} represents a string, then this method
22049 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
22050 In Python}). Otherwise, this method will throw an exception.
22052 If the optional @var{encoding} argument is given, it must be a string
22053 naming the encoding of the @code{gdb.LazyString}. Some examples are:
22054 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
22055 @var{encoding} argument is an encoding that @value{GDBN} does
22056 recognize, @value{GDBN} will raise an error.
22058 When a lazy string is printed, the @value{GDBN} encoding machinery is
22059 used to convert the string during printing. If the optional
22060 @var{encoding} argument is not provided, or is an empty string,
22061 @value{GDBN} will automatically select the encoding most suitable for
22062 the string type. For further information on encoding in @value{GDBN}
22063 please see @ref{Character Sets}.
22065 If the optional @var{length} argument is given, the string will be
22066 fetched and encoded to the length of characters specified. If
22067 the @var{length} argument is not provided, the string will be fetched
22068 and encoded until a null of appropriate width is found.
22071 @defun Value.fetch_lazy ()
22072 If the @code{gdb.Value} object is currently a lazy value
22073 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
22074 fetched from the inferior. Any errors that occur in the process
22075 will produce a Python exception.
22077 If the @code{gdb.Value} object is not a lazy value, this method
22080 This method does not return a value.
22085 @node Types In Python
22086 @subsubsection Types In Python
22087 @cindex types in Python
22088 @cindex Python, working with types
22091 @value{GDBN} represents types from the inferior using the class
22094 The following type-related functions are available in the @code{gdb}
22097 @findex gdb.lookup_type
22098 @defun gdb.lookup_type (name @r{[}, block@r{]})
22099 This function looks up a type by name. @var{name} is the name of the
22100 type to look up. It must be a string.
22102 If @var{block} is given, then @var{name} is looked up in that scope.
22103 Otherwise, it is searched for globally.
22105 Ordinarily, this function will return an instance of @code{gdb.Type}.
22106 If the named type cannot be found, it will throw an exception.
22109 If the type is a structure or class type, or an enum type, the fields
22110 of that type can be accessed using the Python @dfn{dictionary syntax}.
22111 For example, if @code{some_type} is a @code{gdb.Type} instance holding
22112 a structure type, you can access its @code{foo} field with:
22115 bar = some_type['foo']
22118 @code{bar} will be a @code{gdb.Field} object; see below under the
22119 description of the @code{Type.fields} method for a description of the
22120 @code{gdb.Field} class.
22122 An instance of @code{Type} has the following attributes:
22126 The type code for this type. The type code will be one of the
22127 @code{TYPE_CODE_} constants defined below.
22130 @defvar Type.sizeof
22131 The size of this type, in target @code{char} units. Usually, a
22132 target's @code{char} type will be an 8-bit byte. However, on some
22133 unusual platforms, this type may have a different size.
22137 The tag name for this type. The tag name is the name after
22138 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
22139 languages have this concept. If this type has no tag name, then
22140 @code{None} is returned.
22144 The following methods are provided:
22147 @defun Type.fields ()
22148 For structure and union types, this method returns the fields. Range
22149 types have two fields, the minimum and maximum values. Enum types
22150 have one field per enum constant. Function and method types have one
22151 field per parameter. The base types of C@t{++} classes are also
22152 represented as fields. If the type has no fields, or does not fit
22153 into one of these categories, an empty sequence will be returned.
22155 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
22158 This attribute is not available for @code{static} fields (as in
22159 C@t{++} or Java). For non-@code{static} fields, the value is the bit
22160 position of the field. For @code{enum} fields, the value is the
22161 enumeration member's integer representation.
22164 The name of the field, or @code{None} for anonymous fields.
22167 This is @code{True} if the field is artificial, usually meaning that
22168 it was provided by the compiler and not the user. This attribute is
22169 always provided, and is @code{False} if the field is not artificial.
22171 @item is_base_class
22172 This is @code{True} if the field represents a base class of a C@t{++}
22173 structure. This attribute is always provided, and is @code{False}
22174 if the field is not a base class of the type that is the argument of
22175 @code{fields}, or if that type was not a C@t{++} class.
22178 If the field is packed, or is a bitfield, then this will have a
22179 non-zero value, which is the size of the field in bits. Otherwise,
22180 this will be zero; in this case the field's size is given by its type.
22183 The type of the field. This is usually an instance of @code{Type},
22184 but it can be @code{None} in some situations.
22188 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
22189 Return a new @code{gdb.Type} object which represents an array of this
22190 type. If one argument is given, it is the inclusive upper bound of
22191 the array; in this case the lower bound is zero. If two arguments are
22192 given, the first argument is the lower bound of the array, and the
22193 second argument is the upper bound of the array. An array's length
22194 must not be negative, but the bounds can be.
22197 @defun Type.const ()
22198 Return a new @code{gdb.Type} object which represents a
22199 @code{const}-qualified variant of this type.
22202 @defun Type.volatile ()
22203 Return a new @code{gdb.Type} object which represents a
22204 @code{volatile}-qualified variant of this type.
22207 @defun Type.unqualified ()
22208 Return a new @code{gdb.Type} object which represents an unqualified
22209 variant of this type. That is, the result is neither @code{const} nor
22213 @defun Type.range ()
22214 Return a Python @code{Tuple} object that contains two elements: the
22215 low bound of the argument type and the high bound of that type. If
22216 the type does not have a range, @value{GDBN} will raise a
22217 @code{gdb.error} exception (@pxref{Exception Handling}).
22220 @defun Type.reference ()
22221 Return a new @code{gdb.Type} object which represents a reference to this
22225 @defun Type.pointer ()
22226 Return a new @code{gdb.Type} object which represents a pointer to this
22230 @defun Type.strip_typedefs ()
22231 Return a new @code{gdb.Type} that represents the real type,
22232 after removing all layers of typedefs.
22235 @defun Type.target ()
22236 Return a new @code{gdb.Type} object which represents the target type
22239 For a pointer type, the target type is the type of the pointed-to
22240 object. For an array type (meaning C-like arrays), the target type is
22241 the type of the elements of the array. For a function or method type,
22242 the target type is the type of the return value. For a complex type,
22243 the target type is the type of the elements. For a typedef, the
22244 target type is the aliased type.
22246 If the type does not have a target, this method will throw an
22250 @defun Type.template_argument (n @r{[}, block@r{]})
22251 If this @code{gdb.Type} is an instantiation of a template, this will
22252 return a new @code{gdb.Type} which represents the type of the
22253 @var{n}th template argument.
22255 If this @code{gdb.Type} is not a template type, this will throw an
22256 exception. Ordinarily, only C@t{++} code will have template types.
22258 If @var{block} is given, then @var{name} is looked up in that scope.
22259 Otherwise, it is searched for globally.
22264 Each type has a code, which indicates what category this type falls
22265 into. The available type categories are represented by constants
22266 defined in the @code{gdb} module:
22269 @findex TYPE_CODE_PTR
22270 @findex gdb.TYPE_CODE_PTR
22271 @item gdb.TYPE_CODE_PTR
22272 The type is a pointer.
22274 @findex TYPE_CODE_ARRAY
22275 @findex gdb.TYPE_CODE_ARRAY
22276 @item gdb.TYPE_CODE_ARRAY
22277 The type is an array.
22279 @findex TYPE_CODE_STRUCT
22280 @findex gdb.TYPE_CODE_STRUCT
22281 @item gdb.TYPE_CODE_STRUCT
22282 The type is a structure.
22284 @findex TYPE_CODE_UNION
22285 @findex gdb.TYPE_CODE_UNION
22286 @item gdb.TYPE_CODE_UNION
22287 The type is a union.
22289 @findex TYPE_CODE_ENUM
22290 @findex gdb.TYPE_CODE_ENUM
22291 @item gdb.TYPE_CODE_ENUM
22292 The type is an enum.
22294 @findex TYPE_CODE_FLAGS
22295 @findex gdb.TYPE_CODE_FLAGS
22296 @item gdb.TYPE_CODE_FLAGS
22297 A bit flags type, used for things such as status registers.
22299 @findex TYPE_CODE_FUNC
22300 @findex gdb.TYPE_CODE_FUNC
22301 @item gdb.TYPE_CODE_FUNC
22302 The type is a function.
22304 @findex TYPE_CODE_INT
22305 @findex gdb.TYPE_CODE_INT
22306 @item gdb.TYPE_CODE_INT
22307 The type is an integer type.
22309 @findex TYPE_CODE_FLT
22310 @findex gdb.TYPE_CODE_FLT
22311 @item gdb.TYPE_CODE_FLT
22312 A floating point type.
22314 @findex TYPE_CODE_VOID
22315 @findex gdb.TYPE_CODE_VOID
22316 @item gdb.TYPE_CODE_VOID
22317 The special type @code{void}.
22319 @findex TYPE_CODE_SET
22320 @findex gdb.TYPE_CODE_SET
22321 @item gdb.TYPE_CODE_SET
22324 @findex TYPE_CODE_RANGE
22325 @findex gdb.TYPE_CODE_RANGE
22326 @item gdb.TYPE_CODE_RANGE
22327 A range type, that is, an integer type with bounds.
22329 @findex TYPE_CODE_STRING
22330 @findex gdb.TYPE_CODE_STRING
22331 @item gdb.TYPE_CODE_STRING
22332 A string type. Note that this is only used for certain languages with
22333 language-defined string types; C strings are not represented this way.
22335 @findex TYPE_CODE_BITSTRING
22336 @findex gdb.TYPE_CODE_BITSTRING
22337 @item gdb.TYPE_CODE_BITSTRING
22340 @findex TYPE_CODE_ERROR
22341 @findex gdb.TYPE_CODE_ERROR
22342 @item gdb.TYPE_CODE_ERROR
22343 An unknown or erroneous type.
22345 @findex TYPE_CODE_METHOD
22346 @findex gdb.TYPE_CODE_METHOD
22347 @item gdb.TYPE_CODE_METHOD
22348 A method type, as found in C@t{++} or Java.
22350 @findex TYPE_CODE_METHODPTR
22351 @findex gdb.TYPE_CODE_METHODPTR
22352 @item gdb.TYPE_CODE_METHODPTR
22353 A pointer-to-member-function.
22355 @findex TYPE_CODE_MEMBERPTR
22356 @findex gdb.TYPE_CODE_MEMBERPTR
22357 @item gdb.TYPE_CODE_MEMBERPTR
22358 A pointer-to-member.
22360 @findex TYPE_CODE_REF
22361 @findex gdb.TYPE_CODE_REF
22362 @item gdb.TYPE_CODE_REF
22365 @findex TYPE_CODE_CHAR
22366 @findex gdb.TYPE_CODE_CHAR
22367 @item gdb.TYPE_CODE_CHAR
22370 @findex TYPE_CODE_BOOL
22371 @findex gdb.TYPE_CODE_BOOL
22372 @item gdb.TYPE_CODE_BOOL
22375 @findex TYPE_CODE_COMPLEX
22376 @findex gdb.TYPE_CODE_COMPLEX
22377 @item gdb.TYPE_CODE_COMPLEX
22378 A complex float type.
22380 @findex TYPE_CODE_TYPEDEF
22381 @findex gdb.TYPE_CODE_TYPEDEF
22382 @item gdb.TYPE_CODE_TYPEDEF
22383 A typedef to some other type.
22385 @findex TYPE_CODE_NAMESPACE
22386 @findex gdb.TYPE_CODE_NAMESPACE
22387 @item gdb.TYPE_CODE_NAMESPACE
22388 A C@t{++} namespace.
22390 @findex TYPE_CODE_DECFLOAT
22391 @findex gdb.TYPE_CODE_DECFLOAT
22392 @item gdb.TYPE_CODE_DECFLOAT
22393 A decimal floating point type.
22395 @findex TYPE_CODE_INTERNAL_FUNCTION
22396 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
22397 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
22398 A function internal to @value{GDBN}. This is the type used to represent
22399 convenience functions.
22402 Further support for types is provided in the @code{gdb.types}
22403 Python module (@pxref{gdb.types}).
22405 @node Pretty Printing API
22406 @subsubsection Pretty Printing API
22408 An example output is provided (@pxref{Pretty Printing}).
22410 A pretty-printer is just an object that holds a value and implements a
22411 specific interface, defined here.
22413 @defun pretty_printer.children (self)
22414 @value{GDBN} will call this method on a pretty-printer to compute the
22415 children of the pretty-printer's value.
22417 This method must return an object conforming to the Python iterator
22418 protocol. Each item returned by the iterator must be a tuple holding
22419 two elements. The first element is the ``name'' of the child; the
22420 second element is the child's value. The value can be any Python
22421 object which is convertible to a @value{GDBN} value.
22423 This method is optional. If it does not exist, @value{GDBN} will act
22424 as though the value has no children.
22427 @defun pretty_printer.display_hint (self)
22428 The CLI may call this method and use its result to change the
22429 formatting of a value. The result will also be supplied to an MI
22430 consumer as a @samp{displayhint} attribute of the variable being
22433 This method is optional. If it does exist, this method must return a
22436 Some display hints are predefined by @value{GDBN}:
22440 Indicate that the object being printed is ``array-like''. The CLI
22441 uses this to respect parameters such as @code{set print elements} and
22442 @code{set print array}.
22445 Indicate that the object being printed is ``map-like'', and that the
22446 children of this value can be assumed to alternate between keys and
22450 Indicate that the object being printed is ``string-like''. If the
22451 printer's @code{to_string} method returns a Python string of some
22452 kind, then @value{GDBN} will call its internal language-specific
22453 string-printing function to format the string. For the CLI this means
22454 adding quotation marks, possibly escaping some characters, respecting
22455 @code{set print elements}, and the like.
22459 @defun pretty_printer.to_string (self)
22460 @value{GDBN} will call this method to display the string
22461 representation of the value passed to the object's constructor.
22463 When printing from the CLI, if the @code{to_string} method exists,
22464 then @value{GDBN} will prepend its result to the values returned by
22465 @code{children}. Exactly how this formatting is done is dependent on
22466 the display hint, and may change as more hints are added. Also,
22467 depending on the print settings (@pxref{Print Settings}), the CLI may
22468 print just the result of @code{to_string} in a stack trace, omitting
22469 the result of @code{children}.
22471 If this method returns a string, it is printed verbatim.
22473 Otherwise, if this method returns an instance of @code{gdb.Value},
22474 then @value{GDBN} prints this value. This may result in a call to
22475 another pretty-printer.
22477 If instead the method returns a Python value which is convertible to a
22478 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
22479 the resulting value. Again, this may result in a call to another
22480 pretty-printer. Python scalars (integers, floats, and booleans) and
22481 strings are convertible to @code{gdb.Value}; other types are not.
22483 Finally, if this method returns @code{None} then no further operations
22484 are peformed in this method and nothing is printed.
22486 If the result is not one of these types, an exception is raised.
22489 @value{GDBN} provides a function which can be used to look up the
22490 default pretty-printer for a @code{gdb.Value}:
22492 @findex gdb.default_visualizer
22493 @defun gdb.default_visualizer (value)
22494 This function takes a @code{gdb.Value} object as an argument. If a
22495 pretty-printer for this value exists, then it is returned. If no such
22496 printer exists, then this returns @code{None}.
22499 @node Selecting Pretty-Printers
22500 @subsubsection Selecting Pretty-Printers
22502 The Python list @code{gdb.pretty_printers} contains an array of
22503 functions or callable objects that have been registered via addition
22504 as a pretty-printer. Printers in this list are called @code{global}
22505 printers, they're available when debugging all inferiors.
22506 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
22507 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
22510 Each function on these lists is passed a single @code{gdb.Value}
22511 argument and should return a pretty-printer object conforming to the
22512 interface definition above (@pxref{Pretty Printing API}). If a function
22513 cannot create a pretty-printer for the value, it should return
22516 @value{GDBN} first checks the @code{pretty_printers} attribute of each
22517 @code{gdb.Objfile} in the current program space and iteratively calls
22518 each enabled lookup routine in the list for that @code{gdb.Objfile}
22519 until it receives a pretty-printer object.
22520 If no pretty-printer is found in the objfile lists, @value{GDBN} then
22521 searches the pretty-printer list of the current program space,
22522 calling each enabled function until an object is returned.
22523 After these lists have been exhausted, it tries the global
22524 @code{gdb.pretty_printers} list, again calling each enabled function until an
22525 object is returned.
22527 The order in which the objfiles are searched is not specified. For a
22528 given list, functions are always invoked from the head of the list,
22529 and iterated over sequentially until the end of the list, or a printer
22530 object is returned.
22532 For various reasons a pretty-printer may not work.
22533 For example, the underlying data structure may have changed and
22534 the pretty-printer is out of date.
22536 The consequences of a broken pretty-printer are severe enough that
22537 @value{GDBN} provides support for enabling and disabling individual
22538 printers. For example, if @code{print frame-arguments} is on,
22539 a backtrace can become highly illegible if any argument is printed
22540 with a broken printer.
22542 Pretty-printers are enabled and disabled by attaching an @code{enabled}
22543 attribute to the registered function or callable object. If this attribute
22544 is present and its value is @code{False}, the printer is disabled, otherwise
22545 the printer is enabled.
22547 @node Writing a Pretty-Printer
22548 @subsubsection Writing a Pretty-Printer
22549 @cindex writing a pretty-printer
22551 A pretty-printer consists of two parts: a lookup function to detect
22552 if the type is supported, and the printer itself.
22554 Here is an example showing how a @code{std::string} printer might be
22555 written. @xref{Pretty Printing API}, for details on the API this class
22559 class StdStringPrinter(object):
22560 "Print a std::string"
22562 def __init__(self, val):
22565 def to_string(self):
22566 return self.val['_M_dataplus']['_M_p']
22568 def display_hint(self):
22572 And here is an example showing how a lookup function for the printer
22573 example above might be written.
22576 def str_lookup_function(val):
22577 lookup_tag = val.type.tag
22578 if lookup_tag == None:
22580 regex = re.compile("^std::basic_string<char,.*>$")
22581 if regex.match(lookup_tag):
22582 return StdStringPrinter(val)
22586 The example lookup function extracts the value's type, and attempts to
22587 match it to a type that it can pretty-print. If it is a type the
22588 printer can pretty-print, it will return a printer object. If not, it
22589 returns @code{None}.
22591 We recommend that you put your core pretty-printers into a Python
22592 package. If your pretty-printers are for use with a library, we
22593 further recommend embedding a version number into the package name.
22594 This practice will enable @value{GDBN} to load multiple versions of
22595 your pretty-printers at the same time, because they will have
22598 You should write auto-loaded code (@pxref{Auto-loading}) such that it
22599 can be evaluated multiple times without changing its meaning. An
22600 ideal auto-load file will consist solely of @code{import}s of your
22601 printer modules, followed by a call to a register pretty-printers with
22602 the current objfile.
22604 Taken as a whole, this approach will scale nicely to multiple
22605 inferiors, each potentially using a different library version.
22606 Embedding a version number in the Python package name will ensure that
22607 @value{GDBN} is able to load both sets of printers simultaneously.
22608 Then, because the search for pretty-printers is done by objfile, and
22609 because your auto-loaded code took care to register your library's
22610 printers with a specific objfile, @value{GDBN} will find the correct
22611 printers for the specific version of the library used by each
22614 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
22615 this code might appear in @code{gdb.libstdcxx.v6}:
22618 def register_printers(objfile):
22619 objfile.pretty_printers.append(str_lookup_function)
22623 And then the corresponding contents of the auto-load file would be:
22626 import gdb.libstdcxx.v6
22627 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
22630 The previous example illustrates a basic pretty-printer.
22631 There are a few things that can be improved on.
22632 The printer doesn't have a name, making it hard to identify in a
22633 list of installed printers. The lookup function has a name, but
22634 lookup functions can have arbitrary, even identical, names.
22636 Second, the printer only handles one type, whereas a library typically has
22637 several types. One could install a lookup function for each desired type
22638 in the library, but one could also have a single lookup function recognize
22639 several types. The latter is the conventional way this is handled.
22640 If a pretty-printer can handle multiple data types, then its
22641 @dfn{subprinters} are the printers for the individual data types.
22643 The @code{gdb.printing} module provides a formal way of solving these
22644 problems (@pxref{gdb.printing}).
22645 Here is another example that handles multiple types.
22647 These are the types we are going to pretty-print:
22650 struct foo @{ int a, b; @};
22651 struct bar @{ struct foo x, y; @};
22654 Here are the printers:
22658 """Print a foo object."""
22660 def __init__(self, val):
22663 def to_string(self):
22664 return ("a=<" + str(self.val["a"]) +
22665 "> b=<" + str(self.val["b"]) + ">")
22668 """Print a bar object."""
22670 def __init__(self, val):
22673 def to_string(self):
22674 return ("x=<" + str(self.val["x"]) +
22675 "> y=<" + str(self.val["y"]) + ">")
22678 This example doesn't need a lookup function, that is handled by the
22679 @code{gdb.printing} module. Instead a function is provided to build up
22680 the object that handles the lookup.
22683 import gdb.printing
22685 def build_pretty_printer():
22686 pp = gdb.printing.RegexpCollectionPrettyPrinter(
22688 pp.add_printer('foo', '^foo$', fooPrinter)
22689 pp.add_printer('bar', '^bar$', barPrinter)
22693 And here is the autoload support:
22696 import gdb.printing
22698 gdb.printing.register_pretty_printer(
22699 gdb.current_objfile(),
22700 my_library.build_pretty_printer())
22703 Finally, when this printer is loaded into @value{GDBN}, here is the
22704 corresponding output of @samp{info pretty-printer}:
22707 (gdb) info pretty-printer
22714 @node Inferiors In Python
22715 @subsubsection Inferiors In Python
22716 @cindex inferiors in Python
22718 @findex gdb.Inferior
22719 Programs which are being run under @value{GDBN} are called inferiors
22720 (@pxref{Inferiors and Programs}). Python scripts can access
22721 information about and manipulate inferiors controlled by @value{GDBN}
22722 via objects of the @code{gdb.Inferior} class.
22724 The following inferior-related functions are available in the @code{gdb}
22727 @defun gdb.inferiors ()
22728 Return a tuple containing all inferior objects.
22731 @defun gdb.selected_inferior ()
22732 Return an object representing the current inferior.
22735 A @code{gdb.Inferior} object has the following attributes:
22738 @defvar Inferior.num
22739 ID of inferior, as assigned by GDB.
22742 @defvar Inferior.pid
22743 Process ID of the inferior, as assigned by the underlying operating
22747 @defvar Inferior.was_attached
22748 Boolean signaling whether the inferior was created using `attach', or
22749 started by @value{GDBN} itself.
22753 A @code{gdb.Inferior} object has the following methods:
22756 @defun Inferior.is_valid ()
22757 Returns @code{True} if the @code{gdb.Inferior} object is valid,
22758 @code{False} if not. A @code{gdb.Inferior} object will become invalid
22759 if the inferior no longer exists within @value{GDBN}. All other
22760 @code{gdb.Inferior} methods will throw an exception if it is invalid
22761 at the time the method is called.
22764 @defun Inferior.threads ()
22765 This method returns a tuple holding all the threads which are valid
22766 when it is called. If there are no valid threads, the method will
22767 return an empty tuple.
22770 @findex gdb.read_memory
22771 @defun Inferior.read_memory (address, length)
22772 Read @var{length} bytes of memory from the inferior, starting at
22773 @var{address}. Returns a buffer object, which behaves much like an array
22774 or a string. It can be modified and given to the @code{gdb.write_memory}
22778 @findex gdb.write_memory
22779 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
22780 Write the contents of @var{buffer} to the inferior, starting at
22781 @var{address}. The @var{buffer} parameter must be a Python object
22782 which supports the buffer protocol, i.e., a string, an array or the
22783 object returned from @code{gdb.read_memory}. If given, @var{length}
22784 determines the number of bytes from @var{buffer} to be written.
22787 @findex gdb.search_memory
22788 @defun Inferior.search_memory (address, length, pattern)
22789 Search a region of the inferior memory starting at @var{address} with
22790 the given @var{length} using the search pattern supplied in
22791 @var{pattern}. The @var{pattern} parameter must be a Python object
22792 which supports the buffer protocol, i.e., a string, an array or the
22793 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22794 containing the address where the pattern was found, or @code{None} if
22795 the pattern could not be found.
22799 @node Events In Python
22800 @subsubsection Events In Python
22801 @cindex inferior events in Python
22803 @value{GDBN} provides a general event facility so that Python code can be
22804 notified of various state changes, particularly changes that occur in
22807 An @dfn{event} is just an object that describes some state change. The
22808 type of the object and its attributes will vary depending on the details
22809 of the change. All the existing events are described below.
22811 In order to be notified of an event, you must register an event handler
22812 with an @dfn{event registry}. An event registry is an object in the
22813 @code{gdb.events} module which dispatches particular events. A registry
22814 provides methods to register and unregister event handlers:
22817 @defun EventRegistry.connect (object)
22818 Add the given callable @var{object} to the registry. This object will be
22819 called when an event corresponding to this registry occurs.
22822 @defun EventRegistry.disconnect (object)
22823 Remove the given @var{object} from the registry. Once removed, the object
22824 will no longer receive notifications of events.
22828 Here is an example:
22831 def exit_handler (event):
22832 print "event type: exit"
22833 print "exit code: %d" % (event.exit_code)
22835 gdb.events.exited.connect (exit_handler)
22838 In the above example we connect our handler @code{exit_handler} to the
22839 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22840 called when the inferior exits. The argument @dfn{event} in this example is
22841 of type @code{gdb.ExitedEvent}. As you can see in the example the
22842 @code{ExitedEvent} object has an attribute which indicates the exit code of
22845 The following is a listing of the event registries that are available and
22846 details of the events they emit:
22851 Emits @code{gdb.ThreadEvent}.
22853 Some events can be thread specific when @value{GDBN} is running in non-stop
22854 mode. When represented in Python, these events all extend
22855 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22856 events which are emitted by this or other modules might extend this event.
22857 Examples of these events are @code{gdb.BreakpointEvent} and
22858 @code{gdb.ContinueEvent}.
22861 @defvar ThreadEvent.inferior_thread
22862 In non-stop mode this attribute will be set to the specific thread which was
22863 involved in the emitted event. Otherwise, it will be set to @code{None}.
22867 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22869 This event indicates that the inferior has been continued after a stop. For
22870 inherited attribute refer to @code{gdb.ThreadEvent} above.
22872 @item events.exited
22873 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22874 @code{events.ExitedEvent} has two attributes:
22876 @defvar ExitedEvent.exit_code
22877 An integer representing the exit code, if available, which the inferior
22878 has returned. (The exit code could be unavailable if, for example,
22879 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
22880 the attribute does not exist.
22882 @defvar ExitedEvent inferior
22883 A reference to the inferior which triggered the @code{exited} event.
22888 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
22890 Indicates that the inferior has stopped. All events emitted by this registry
22891 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
22892 will indicate the stopped thread when @value{GDBN} is running in non-stop
22893 mode. Refer to @code{gdb.ThreadEvent} above for more details.
22895 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
22897 This event indicates that the inferior or one of its threads has received as
22898 signal. @code{gdb.SignalEvent} has the following attributes:
22901 @defvar SignalEvent.stop_signal
22902 A string representing the signal received by the inferior. A list of possible
22903 signal values can be obtained by running the command @code{info signals} in
22904 the @value{GDBN} command prompt.
22908 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22910 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
22911 been hit, and has the following attributes:
22914 @defvar BreakpointEvent.breakpoints
22915 A sequence containing references to all the breakpoints (type
22916 @code{gdb.Breakpoint}) that were hit.
22917 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22919 @defvar BreakpointEvent.breakpoint
22920 A reference to the first breakpoint that was hit.
22921 This function is maintained for backward compatibility and is now deprecated
22922 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
22926 @item events.new_objfile
22927 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
22928 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
22931 @defvar NewObjFileEvent.new_objfile
22932 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
22933 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
22939 @node Threads In Python
22940 @subsubsection Threads In Python
22941 @cindex threads in python
22943 @findex gdb.InferiorThread
22944 Python scripts can access information about, and manipulate inferior threads
22945 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
22947 The following thread-related functions are available in the @code{gdb}
22950 @findex gdb.selected_thread
22951 @defun gdb.selected_thread ()
22952 This function returns the thread object for the selected thread. If there
22953 is no selected thread, this will return @code{None}.
22956 A @code{gdb.InferiorThread} object has the following attributes:
22959 @defvar InferiorThread.name
22960 The name of the thread. If the user specified a name using
22961 @code{thread name}, then this returns that name. Otherwise, if an
22962 OS-supplied name is available, then it is returned. Otherwise, this
22963 returns @code{None}.
22965 This attribute can be assigned to. The new value must be a string
22966 object, which sets the new name, or @code{None}, which removes any
22967 user-specified thread name.
22970 @defvar InferiorThread.num
22971 ID of the thread, as assigned by GDB.
22974 @defvar InferiorThread.ptid
22975 ID of the thread, as assigned by the operating system. This attribute is a
22976 tuple containing three integers. The first is the Process ID (PID); the second
22977 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
22978 Either the LWPID or TID may be 0, which indicates that the operating system
22979 does not use that identifier.
22983 A @code{gdb.InferiorThread} object has the following methods:
22986 @defun InferiorThread.is_valid ()
22987 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
22988 @code{False} if not. A @code{gdb.InferiorThread} object will become
22989 invalid if the thread exits, or the inferior that the thread belongs
22990 is deleted. All other @code{gdb.InferiorThread} methods will throw an
22991 exception if it is invalid at the time the method is called.
22994 @defun InferiorThread.switch ()
22995 This changes @value{GDBN}'s currently selected thread to the one represented
22999 @defun InferiorThread.is_stopped ()
23000 Return a Boolean indicating whether the thread is stopped.
23003 @defun InferiorThread.is_running ()
23004 Return a Boolean indicating whether the thread is running.
23007 @defun InferiorThread.is_exited ()
23008 Return a Boolean indicating whether the thread is exited.
23012 @node Commands In Python
23013 @subsubsection Commands In Python
23015 @cindex commands in python
23016 @cindex python commands
23017 You can implement new @value{GDBN} CLI commands in Python. A CLI
23018 command is implemented using an instance of the @code{gdb.Command}
23019 class, most commonly using a subclass.
23021 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
23022 The object initializer for @code{Command} registers the new command
23023 with @value{GDBN}. This initializer is normally invoked from the
23024 subclass' own @code{__init__} method.
23026 @var{name} is the name of the command. If @var{name} consists of
23027 multiple words, then the initial words are looked for as prefix
23028 commands. In this case, if one of the prefix commands does not exist,
23029 an exception is raised.
23031 There is no support for multi-line commands.
23033 @var{command_class} should be one of the @samp{COMMAND_} constants
23034 defined below. This argument tells @value{GDBN} how to categorize the
23035 new command in the help system.
23037 @var{completer_class} is an optional argument. If given, it should be
23038 one of the @samp{COMPLETE_} constants defined below. This argument
23039 tells @value{GDBN} how to perform completion for this command. If not
23040 given, @value{GDBN} will attempt to complete using the object's
23041 @code{complete} method (see below); if no such method is found, an
23042 error will occur when completion is attempted.
23044 @var{prefix} is an optional argument. If @code{True}, then the new
23045 command is a prefix command; sub-commands of this command may be
23048 The help text for the new command is taken from the Python
23049 documentation string for the command's class, if there is one. If no
23050 documentation string is provided, the default value ``This command is
23051 not documented.'' is used.
23054 @cindex don't repeat Python command
23055 @defun Command.dont_repeat ()
23056 By default, a @value{GDBN} command is repeated when the user enters a
23057 blank line at the command prompt. A command can suppress this
23058 behavior by invoking the @code{dont_repeat} method. This is similar
23059 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
23062 @defun Command.invoke (argument, from_tty)
23063 This method is called by @value{GDBN} when this command is invoked.
23065 @var{argument} is a string. It is the argument to the command, after
23066 leading and trailing whitespace has been stripped.
23068 @var{from_tty} is a boolean argument. When true, this means that the
23069 command was entered by the user at the terminal; when false it means
23070 that the command came from elsewhere.
23072 If this method throws an exception, it is turned into a @value{GDBN}
23073 @code{error} call. Otherwise, the return value is ignored.
23075 @findex gdb.string_to_argv
23076 To break @var{argument} up into an argv-like string use
23077 @code{gdb.string_to_argv}. This function behaves identically to
23078 @value{GDBN}'s internal argument lexer @code{buildargv}.
23079 It is recommended to use this for consistency.
23080 Arguments are separated by spaces and may be quoted.
23084 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
23085 ['1', '2 "3', '4 "5', "6 '7"]
23090 @cindex completion of Python commands
23091 @defun Command.complete (text, word)
23092 This method is called by @value{GDBN} when the user attempts
23093 completion on this command. All forms of completion are handled by
23094 this method, that is, the @key{TAB} and @key{M-?} key bindings
23095 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
23098 The arguments @var{text} and @var{word} are both strings. @var{text}
23099 holds the complete command line up to the cursor's location.
23100 @var{word} holds the last word of the command line; this is computed
23101 using a word-breaking heuristic.
23103 The @code{complete} method can return several values:
23106 If the return value is a sequence, the contents of the sequence are
23107 used as the completions. It is up to @code{complete} to ensure that the
23108 contents actually do complete the word. A zero-length sequence is
23109 allowed, it means that there were no completions available. Only
23110 string elements of the sequence are used; other elements in the
23111 sequence are ignored.
23114 If the return value is one of the @samp{COMPLETE_} constants defined
23115 below, then the corresponding @value{GDBN}-internal completion
23116 function is invoked, and its result is used.
23119 All other results are treated as though there were no available
23124 When a new command is registered, it must be declared as a member of
23125 some general class of commands. This is used to classify top-level
23126 commands in the on-line help system; note that prefix commands are not
23127 listed under their own category but rather that of their top-level
23128 command. The available classifications are represented by constants
23129 defined in the @code{gdb} module:
23132 @findex COMMAND_NONE
23133 @findex gdb.COMMAND_NONE
23134 @item gdb.COMMAND_NONE
23135 The command does not belong to any particular class. A command in
23136 this category will not be displayed in any of the help categories.
23138 @findex COMMAND_RUNNING
23139 @findex gdb.COMMAND_RUNNING
23140 @item gdb.COMMAND_RUNNING
23141 The command is related to running the inferior. For example,
23142 @code{start}, @code{step}, and @code{continue} are in this category.
23143 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
23144 commands in this category.
23146 @findex COMMAND_DATA
23147 @findex gdb.COMMAND_DATA
23148 @item gdb.COMMAND_DATA
23149 The command is related to data or variables. For example,
23150 @code{call}, @code{find}, and @code{print} are in this category. Type
23151 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
23154 @findex COMMAND_STACK
23155 @findex gdb.COMMAND_STACK
23156 @item gdb.COMMAND_STACK
23157 The command has to do with manipulation of the stack. For example,
23158 @code{backtrace}, @code{frame}, and @code{return} are in this
23159 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
23160 list of commands in this category.
23162 @findex COMMAND_FILES
23163 @findex gdb.COMMAND_FILES
23164 @item gdb.COMMAND_FILES
23165 This class is used for file-related commands. For example,
23166 @code{file}, @code{list} and @code{section} are in this category.
23167 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
23168 commands in this category.
23170 @findex COMMAND_SUPPORT
23171 @findex gdb.COMMAND_SUPPORT
23172 @item gdb.COMMAND_SUPPORT
23173 This should be used for ``support facilities'', generally meaning
23174 things that are useful to the user when interacting with @value{GDBN},
23175 but not related to the state of the inferior. For example,
23176 @code{help}, @code{make}, and @code{shell} are in this category. Type
23177 @kbd{help support} at the @value{GDBN} prompt to see a list of
23178 commands in this category.
23180 @findex COMMAND_STATUS
23181 @findex gdb.COMMAND_STATUS
23182 @item gdb.COMMAND_STATUS
23183 The command is an @samp{info}-related command, that is, related to the
23184 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
23185 and @code{show} are in this category. Type @kbd{help status} at the
23186 @value{GDBN} prompt to see a list of commands in this category.
23188 @findex COMMAND_BREAKPOINTS
23189 @findex gdb.COMMAND_BREAKPOINTS
23190 @item gdb.COMMAND_BREAKPOINTS
23191 The command has to do with breakpoints. For example, @code{break},
23192 @code{clear}, and @code{delete} are in this category. Type @kbd{help
23193 breakpoints} at the @value{GDBN} prompt to see a list of commands in
23196 @findex COMMAND_TRACEPOINTS
23197 @findex gdb.COMMAND_TRACEPOINTS
23198 @item gdb.COMMAND_TRACEPOINTS
23199 The command has to do with tracepoints. For example, @code{trace},
23200 @code{actions}, and @code{tfind} are in this category. Type
23201 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
23202 commands in this category.
23204 @findex COMMAND_OBSCURE
23205 @findex gdb.COMMAND_OBSCURE
23206 @item gdb.COMMAND_OBSCURE
23207 The command is only used in unusual circumstances, or is not of
23208 general interest to users. For example, @code{checkpoint},
23209 @code{fork}, and @code{stop} are in this category. Type @kbd{help
23210 obscure} at the @value{GDBN} prompt to see a list of commands in this
23213 @findex COMMAND_MAINTENANCE
23214 @findex gdb.COMMAND_MAINTENANCE
23215 @item gdb.COMMAND_MAINTENANCE
23216 The command is only useful to @value{GDBN} maintainers. The
23217 @code{maintenance} and @code{flushregs} commands are in this category.
23218 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
23219 commands in this category.
23222 A new command can use a predefined completion function, either by
23223 specifying it via an argument at initialization, or by returning it
23224 from the @code{complete} method. These predefined completion
23225 constants are all defined in the @code{gdb} module:
23228 @findex COMPLETE_NONE
23229 @findex gdb.COMPLETE_NONE
23230 @item gdb.COMPLETE_NONE
23231 This constant means that no completion should be done.
23233 @findex COMPLETE_FILENAME
23234 @findex gdb.COMPLETE_FILENAME
23235 @item gdb.COMPLETE_FILENAME
23236 This constant means that filename completion should be performed.
23238 @findex COMPLETE_LOCATION
23239 @findex gdb.COMPLETE_LOCATION
23240 @item gdb.COMPLETE_LOCATION
23241 This constant means that location completion should be done.
23242 @xref{Specify Location}.
23244 @findex COMPLETE_COMMAND
23245 @findex gdb.COMPLETE_COMMAND
23246 @item gdb.COMPLETE_COMMAND
23247 This constant means that completion should examine @value{GDBN}
23250 @findex COMPLETE_SYMBOL
23251 @findex gdb.COMPLETE_SYMBOL
23252 @item gdb.COMPLETE_SYMBOL
23253 This constant means that completion should be done using symbol names
23257 The following code snippet shows how a trivial CLI command can be
23258 implemented in Python:
23261 class HelloWorld (gdb.Command):
23262 """Greet the whole world."""
23264 def __init__ (self):
23265 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
23267 def invoke (self, arg, from_tty):
23268 print "Hello, World!"
23273 The last line instantiates the class, and is necessary to trigger the
23274 registration of the command with @value{GDBN}. Depending on how the
23275 Python code is read into @value{GDBN}, you may need to import the
23276 @code{gdb} module explicitly.
23278 @node Parameters In Python
23279 @subsubsection Parameters In Python
23281 @cindex parameters in python
23282 @cindex python parameters
23283 @tindex gdb.Parameter
23285 You can implement new @value{GDBN} parameters using Python. A new
23286 parameter is implemented as an instance of the @code{gdb.Parameter}
23289 Parameters are exposed to the user via the @code{set} and
23290 @code{show} commands. @xref{Help}.
23292 There are many parameters that already exist and can be set in
23293 @value{GDBN}. Two examples are: @code{set follow fork} and
23294 @code{set charset}. Setting these parameters influences certain
23295 behavior in @value{GDBN}. Similarly, you can define parameters that
23296 can be used to influence behavior in custom Python scripts and commands.
23298 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
23299 The object initializer for @code{Parameter} registers the new
23300 parameter with @value{GDBN}. This initializer is normally invoked
23301 from the subclass' own @code{__init__} method.
23303 @var{name} is the name of the new parameter. If @var{name} consists
23304 of multiple words, then the initial words are looked for as prefix
23305 parameters. An example of this can be illustrated with the
23306 @code{set print} set of parameters. If @var{name} is
23307 @code{print foo}, then @code{print} will be searched as the prefix
23308 parameter. In this case the parameter can subsequently be accessed in
23309 @value{GDBN} as @code{set print foo}.
23311 If @var{name} consists of multiple words, and no prefix parameter group
23312 can be found, an exception is raised.
23314 @var{command-class} should be one of the @samp{COMMAND_} constants
23315 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
23316 categorize the new parameter in the help system.
23318 @var{parameter-class} should be one of the @samp{PARAM_} constants
23319 defined below. This argument tells @value{GDBN} the type of the new
23320 parameter; this information is used for input validation and
23323 If @var{parameter-class} is @code{PARAM_ENUM}, then
23324 @var{enum-sequence} must be a sequence of strings. These strings
23325 represent the possible values for the parameter.
23327 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
23328 of a fourth argument will cause an exception to be thrown.
23330 The help text for the new parameter is taken from the Python
23331 documentation string for the parameter's class, if there is one. If
23332 there is no documentation string, a default value is used.
23335 @defvar Parameter.set_doc
23336 If this attribute exists, and is a string, then its value is used as
23337 the help text for this parameter's @code{set} command. The value is
23338 examined when @code{Parameter.__init__} is invoked; subsequent changes
23342 @defvar Parameter.show_doc
23343 If this attribute exists, and is a string, then its value is used as
23344 the help text for this parameter's @code{show} command. The value is
23345 examined when @code{Parameter.__init__} is invoked; subsequent changes
23349 @defvar Parameter.value
23350 The @code{value} attribute holds the underlying value of the
23351 parameter. It can be read and assigned to just as any other
23352 attribute. @value{GDBN} does validation when assignments are made.
23355 There are two methods that should be implemented in any
23356 @code{Parameter} class. These are:
23358 @defun Parameter.get_set_string (self)
23359 @value{GDBN} will call this method when a @var{parameter}'s value has
23360 been changed via the @code{set} API (for example, @kbd{set foo off}).
23361 The @code{value} attribute has already been populated with the new
23362 value and may be used in output. This method must return a string.
23365 @defun Parameter.get_show_string (self, svalue)
23366 @value{GDBN} will call this method when a @var{parameter}'s
23367 @code{show} API has been invoked (for example, @kbd{show foo}). The
23368 argument @code{svalue} receives the string representation of the
23369 current value. This method must return a string.
23372 When a new parameter is defined, its type must be specified. The
23373 available types are represented by constants defined in the @code{gdb}
23377 @findex PARAM_BOOLEAN
23378 @findex gdb.PARAM_BOOLEAN
23379 @item gdb.PARAM_BOOLEAN
23380 The value is a plain boolean. The Python boolean values, @code{True}
23381 and @code{False} are the only valid values.
23383 @findex PARAM_AUTO_BOOLEAN
23384 @findex gdb.PARAM_AUTO_BOOLEAN
23385 @item gdb.PARAM_AUTO_BOOLEAN
23386 The value has three possible states: true, false, and @samp{auto}. In
23387 Python, true and false are represented using boolean constants, and
23388 @samp{auto} is represented using @code{None}.
23390 @findex PARAM_UINTEGER
23391 @findex gdb.PARAM_UINTEGER
23392 @item gdb.PARAM_UINTEGER
23393 The value is an unsigned integer. The value of 0 should be
23394 interpreted to mean ``unlimited''.
23396 @findex PARAM_INTEGER
23397 @findex gdb.PARAM_INTEGER
23398 @item gdb.PARAM_INTEGER
23399 The value is a signed integer. The value of 0 should be interpreted
23400 to mean ``unlimited''.
23402 @findex PARAM_STRING
23403 @findex gdb.PARAM_STRING
23404 @item gdb.PARAM_STRING
23405 The value is a string. When the user modifies the string, any escape
23406 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
23407 translated into corresponding characters and encoded into the current
23410 @findex PARAM_STRING_NOESCAPE
23411 @findex gdb.PARAM_STRING_NOESCAPE
23412 @item gdb.PARAM_STRING_NOESCAPE
23413 The value is a string. When the user modifies the string, escapes are
23414 passed through untranslated.
23416 @findex PARAM_OPTIONAL_FILENAME
23417 @findex gdb.PARAM_OPTIONAL_FILENAME
23418 @item gdb.PARAM_OPTIONAL_FILENAME
23419 The value is a either a filename (a string), or @code{None}.
23421 @findex PARAM_FILENAME
23422 @findex gdb.PARAM_FILENAME
23423 @item gdb.PARAM_FILENAME
23424 The value is a filename. This is just like
23425 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
23427 @findex PARAM_ZINTEGER
23428 @findex gdb.PARAM_ZINTEGER
23429 @item gdb.PARAM_ZINTEGER
23430 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
23431 is interpreted as itself.
23434 @findex gdb.PARAM_ENUM
23435 @item gdb.PARAM_ENUM
23436 The value is a string, which must be one of a collection string
23437 constants provided when the parameter is created.
23440 @node Functions In Python
23441 @subsubsection Writing new convenience functions
23443 @cindex writing convenience functions
23444 @cindex convenience functions in python
23445 @cindex python convenience functions
23446 @tindex gdb.Function
23448 You can implement new convenience functions (@pxref{Convenience Vars})
23449 in Python. A convenience function is an instance of a subclass of the
23450 class @code{gdb.Function}.
23452 @defun Function.__init__ (name)
23453 The initializer for @code{Function} registers the new function with
23454 @value{GDBN}. The argument @var{name} is the name of the function,
23455 a string. The function will be visible to the user as a convenience
23456 variable of type @code{internal function}, whose name is the same as
23457 the given @var{name}.
23459 The documentation for the new function is taken from the documentation
23460 string for the new class.
23463 @defun Function.invoke (@var{*args})
23464 When a convenience function is evaluated, its arguments are converted
23465 to instances of @code{gdb.Value}, and then the function's
23466 @code{invoke} method is called. Note that @value{GDBN} does not
23467 predetermine the arity of convenience functions. Instead, all
23468 available arguments are passed to @code{invoke}, following the
23469 standard Python calling convention. In particular, a convenience
23470 function can have default values for parameters without ill effect.
23472 The return value of this method is used as its value in the enclosing
23473 expression. If an ordinary Python value is returned, it is converted
23474 to a @code{gdb.Value} following the usual rules.
23477 The following code snippet shows how a trivial convenience function can
23478 be implemented in Python:
23481 class Greet (gdb.Function):
23482 """Return string to greet someone.
23483 Takes a name as argument."""
23485 def __init__ (self):
23486 super (Greet, self).__init__ ("greet")
23488 def invoke (self, name):
23489 return "Hello, %s!" % name.string ()
23494 The last line instantiates the class, and is necessary to trigger the
23495 registration of the function with @value{GDBN}. Depending on how the
23496 Python code is read into @value{GDBN}, you may need to import the
23497 @code{gdb} module explicitly.
23499 @node Progspaces In Python
23500 @subsubsection Program Spaces In Python
23502 @cindex progspaces in python
23503 @tindex gdb.Progspace
23505 A program space, or @dfn{progspace}, represents a symbolic view
23506 of an address space.
23507 It consists of all of the objfiles of the program.
23508 @xref{Objfiles In Python}.
23509 @xref{Inferiors and Programs, program spaces}, for more details
23510 about program spaces.
23512 The following progspace-related functions are available in the
23515 @findex gdb.current_progspace
23516 @defun gdb.current_progspace ()
23517 This function returns the program space of the currently selected inferior.
23518 @xref{Inferiors and Programs}.
23521 @findex gdb.progspaces
23522 @defun gdb.progspaces ()
23523 Return a sequence of all the progspaces currently known to @value{GDBN}.
23526 Each progspace is represented by an instance of the @code{gdb.Progspace}
23529 @defvar Progspace.filename
23530 The file name of the progspace as a string.
23533 @defvar Progspace.pretty_printers
23534 The @code{pretty_printers} attribute is a list of functions. It is
23535 used to look up pretty-printers. A @code{Value} is passed to each
23536 function in order; if the function returns @code{None}, then the
23537 search continues. Otherwise, the return value should be an object
23538 which is used to format the value. @xref{Pretty Printing API}, for more
23542 @node Objfiles In Python
23543 @subsubsection Objfiles In Python
23545 @cindex objfiles in python
23546 @tindex gdb.Objfile
23548 @value{GDBN} loads symbols for an inferior from various
23549 symbol-containing files (@pxref{Files}). These include the primary
23550 executable file, any shared libraries used by the inferior, and any
23551 separate debug info files (@pxref{Separate Debug Files}).
23552 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
23554 The following objfile-related functions are available in the
23557 @findex gdb.current_objfile
23558 @defun gdb.current_objfile ()
23559 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
23560 sets the ``current objfile'' to the corresponding objfile. This
23561 function returns the current objfile. If there is no current objfile,
23562 this function returns @code{None}.
23565 @findex gdb.objfiles
23566 @defun gdb.objfiles ()
23567 Return a sequence of all the objfiles current known to @value{GDBN}.
23568 @xref{Objfiles In Python}.
23571 Each objfile is represented by an instance of the @code{gdb.Objfile}
23574 @defvar Objfile.filename
23575 The file name of the objfile as a string.
23578 @defvar Objfile.pretty_printers
23579 The @code{pretty_printers} attribute is a list of functions. It is
23580 used to look up pretty-printers. A @code{Value} is passed to each
23581 function in order; if the function returns @code{None}, then the
23582 search continues. Otherwise, the return value should be an object
23583 which is used to format the value. @xref{Pretty Printing API}, for more
23587 A @code{gdb.Objfile} object has the following methods:
23589 @defun Objfile.is_valid ()
23590 Returns @code{True} if the @code{gdb.Objfile} object is valid,
23591 @code{False} if not. A @code{gdb.Objfile} object can become invalid
23592 if the object file it refers to is not loaded in @value{GDBN} any
23593 longer. All other @code{gdb.Objfile} methods will throw an exception
23594 if it is invalid at the time the method is called.
23597 @node Frames In Python
23598 @subsubsection Accessing inferior stack frames from Python.
23600 @cindex frames in python
23601 When the debugged program stops, @value{GDBN} is able to analyze its call
23602 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
23603 represents a frame in the stack. A @code{gdb.Frame} object is only valid
23604 while its corresponding frame exists in the inferior's stack. If you try
23605 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
23606 exception (@pxref{Exception Handling}).
23608 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
23612 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
23616 The following frame-related functions are available in the @code{gdb} module:
23618 @findex gdb.selected_frame
23619 @defun gdb.selected_frame ()
23620 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
23623 @findex gdb.newest_frame
23624 @defun gdb.newest_frame ()
23625 Return the newest frame object for the selected thread.
23628 @defun gdb.frame_stop_reason_string (reason)
23629 Return a string explaining the reason why @value{GDBN} stopped unwinding
23630 frames, as expressed by the given @var{reason} code (an integer, see the
23631 @code{unwind_stop_reason} method further down in this section).
23634 A @code{gdb.Frame} object has the following methods:
23637 @defun Frame.is_valid ()
23638 Returns true if the @code{gdb.Frame} object is valid, false if not.
23639 A frame object can become invalid if the frame it refers to doesn't
23640 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
23641 an exception if it is invalid at the time the method is called.
23644 @defun Frame.name ()
23645 Returns the function name of the frame, or @code{None} if it can't be
23649 @defun Frame.type ()
23650 Returns the type of the frame. The value can be one of:
23652 @item gdb.NORMAL_FRAME
23653 An ordinary stack frame.
23655 @item gdb.DUMMY_FRAME
23656 A fake stack frame that was created by @value{GDBN} when performing an
23657 inferior function call.
23659 @item gdb.INLINE_FRAME
23660 A frame representing an inlined function. The function was inlined
23661 into a @code{gdb.NORMAL_FRAME} that is older than this one.
23663 @item gdb.TAILCALL_FRAME
23664 A frame representing a tail call. @xref{Tail Call Frames}.
23666 @item gdb.SIGTRAMP_FRAME
23667 A signal trampoline frame. This is the frame created by the OS when
23668 it calls into a signal handler.
23670 @item gdb.ARCH_FRAME
23671 A fake stack frame representing a cross-architecture call.
23673 @item gdb.SENTINEL_FRAME
23674 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
23679 @defun Frame.unwind_stop_reason ()
23680 Return an integer representing the reason why it's not possible to find
23681 more frames toward the outermost frame. Use
23682 @code{gdb.frame_stop_reason_string} to convert the value returned by this
23683 function to a string. The value can be one of:
23686 @item gdb.FRAME_UNWIND_NO_REASON
23687 No particular reason (older frames should be available).
23689 @item gdb.FRAME_UNWIND_NULL_ID
23690 The previous frame's analyzer returns an invalid result.
23692 @item gdb.FRAME_UNWIND_OUTERMOST
23693 This frame is the outermost.
23695 @item gdb.FRAME_UNWIND_UNAVAILABLE
23696 Cannot unwind further, because that would require knowing the
23697 values of registers or memory that have not been collected.
23699 @item gdb.FRAME_UNWIND_INNER_ID
23700 This frame ID looks like it ought to belong to a NEXT frame,
23701 but we got it for a PREV frame. Normally, this is a sign of
23702 unwinder failure. It could also indicate stack corruption.
23704 @item gdb.FRAME_UNWIND_SAME_ID
23705 This frame has the same ID as the previous one. That means
23706 that unwinding further would almost certainly give us another
23707 frame with exactly the same ID, so break the chain. Normally,
23708 this is a sign of unwinder failure. It could also indicate
23711 @item gdb.FRAME_UNWIND_NO_SAVED_PC
23712 The frame unwinder did not find any saved PC, but we needed
23713 one to unwind further.
23715 @item gdb.FRAME_UNWIND_FIRST_ERROR
23716 Any stop reason greater or equal to this value indicates some kind
23717 of error. This special value facilitates writing code that tests
23718 for errors in unwinding in a way that will work correctly even if
23719 the list of the other values is modified in future @value{GDBN}
23720 versions. Using it, you could write:
23722 reason = gdb.selected_frame().unwind_stop_reason ()
23723 reason_str = gdb.frame_stop_reason_string (reason)
23724 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
23725 print "An error occured: %s" % reason_str
23732 Returns the frame's resume address.
23735 @defun Frame.block ()
23736 Return the frame's code block. @xref{Blocks In Python}.
23739 @defun Frame.function ()
23740 Return the symbol for the function corresponding to this frame.
23741 @xref{Symbols In Python}.
23744 @defun Frame.older ()
23745 Return the frame that called this frame.
23748 @defun Frame.newer ()
23749 Return the frame called by this frame.
23752 @defun Frame.find_sal ()
23753 Return the frame's symtab and line object.
23754 @xref{Symbol Tables In Python}.
23757 @defun Frame.read_var (variable @r{[}, block@r{]})
23758 Return the value of @var{variable} in this frame. If the optional
23759 argument @var{block} is provided, search for the variable from that
23760 block; otherwise start at the frame's current block (which is
23761 determined by the frame's current program counter). @var{variable}
23762 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
23763 @code{gdb.Block} object.
23766 @defun Frame.select ()
23767 Set this frame to be the selected frame. @xref{Stack, ,Examining the
23772 @node Blocks In Python
23773 @subsubsection Accessing frame blocks from Python.
23775 @cindex blocks in python
23778 Within each frame, @value{GDBN} maintains information on each block
23779 stored in that frame. These blocks are organized hierarchically, and
23780 are represented individually in Python as a @code{gdb.Block}.
23781 Please see @ref{Frames In Python}, for a more in-depth discussion on
23782 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
23783 detailed technical information on @value{GDBN}'s book-keeping of the
23786 The following block-related functions are available in the @code{gdb}
23789 @findex gdb.block_for_pc
23790 @defun gdb.block_for_pc (pc)
23791 Return the @code{gdb.Block} containing the given @var{pc} value. If the
23792 block cannot be found for the @var{pc} value specified, the function
23793 will return @code{None}.
23796 A @code{gdb.Block} object has the following methods:
23799 @defun Block.is_valid ()
23800 Returns @code{True} if the @code{gdb.Block} object is valid,
23801 @code{False} if not. A block object can become invalid if the block it
23802 refers to doesn't exist anymore in the inferior. All other
23803 @code{gdb.Block} methods will throw an exception if it is invalid at
23804 the time the method is called. This method is also made available to
23805 the Python iterator object that @code{gdb.Block} provides in an iteration
23806 context and via the Python @code{iter} built-in function.
23810 A @code{gdb.Block} object has the following attributes:
23813 @defvar Block.start
23814 The start address of the block. This attribute is not writable.
23818 The end address of the block. This attribute is not writable.
23821 @defvar Block.function
23822 The name of the block represented as a @code{gdb.Symbol}. If the
23823 block is not named, then this attribute holds @code{None}. This
23824 attribute is not writable.
23827 @defvar Block.superblock
23828 The block containing this block. If this parent block does not exist,
23829 this attribute holds @code{None}. This attribute is not writable.
23832 @defvar Block.global_block
23833 The global block associated with this block. This attribute is not
23837 @defvar Block.static_block
23838 The static block associated with this block. This attribute is not
23842 @defvar Block.is_global
23843 @code{True} if the @code{gdb.Block} object is a global block,
23844 @code{False} if not. This attribute is not
23848 @defvar Block.is_static
23849 @code{True} if the @code{gdb.Block} object is a static block,
23850 @code{False} if not. This attribute is not writable.
23854 @node Symbols In Python
23855 @subsubsection Python representation of Symbols.
23857 @cindex symbols in python
23860 @value{GDBN} represents every variable, function and type as an
23861 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
23862 Similarly, Python represents these symbols in @value{GDBN} with the
23863 @code{gdb.Symbol} object.
23865 The following symbol-related functions are available in the @code{gdb}
23868 @findex gdb.lookup_symbol
23869 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
23870 This function searches for a symbol by name. The search scope can be
23871 restricted to the parameters defined in the optional domain and block
23874 @var{name} is the name of the symbol. It must be a string. The
23875 optional @var{block} argument restricts the search to symbols visible
23876 in that @var{block}. The @var{block} argument must be a
23877 @code{gdb.Block} object. If omitted, the block for the current frame
23878 is used. The optional @var{domain} argument restricts
23879 the search to the domain type. The @var{domain} argument must be a
23880 domain constant defined in the @code{gdb} module and described later
23883 The result is a tuple of two elements.
23884 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
23886 If the symbol is found, the second element is @code{True} if the symbol
23887 is a field of a method's object (e.g., @code{this} in C@t{++}),
23888 otherwise it is @code{False}.
23889 If the symbol is not found, the second element is @code{False}.
23892 @findex gdb.lookup_global_symbol
23893 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
23894 This function searches for a global symbol by name.
23895 The search scope can be restricted to by the domain argument.
23897 @var{name} is the name of the symbol. It must be a string.
23898 The optional @var{domain} argument restricts the search to the domain type.
23899 The @var{domain} argument must be a domain constant defined in the @code{gdb}
23900 module and described later in this chapter.
23902 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
23906 A @code{gdb.Symbol} object has the following attributes:
23909 @defvar Symbol.type
23910 The type of the symbol or @code{None} if no type is recorded.
23911 This attribute is represented as a @code{gdb.Type} object.
23912 @xref{Types In Python}. This attribute is not writable.
23915 @defvar Symbol.symtab
23916 The symbol table in which the symbol appears. This attribute is
23917 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
23918 Python}. This attribute is not writable.
23921 @defvar Symbol.name
23922 The name of the symbol as a string. This attribute is not writable.
23925 @defvar Symbol.linkage_name
23926 The name of the symbol, as used by the linker (i.e., may be mangled).
23927 This attribute is not writable.
23930 @defvar Symbol.print_name
23931 The name of the symbol in a form suitable for output. This is either
23932 @code{name} or @code{linkage_name}, depending on whether the user
23933 asked @value{GDBN} to display demangled or mangled names.
23936 @defvar Symbol.addr_class
23937 The address class of the symbol. This classifies how to find the value
23938 of a symbol. Each address class is a constant defined in the
23939 @code{gdb} module and described later in this chapter.
23942 @defvar Symbol.is_argument
23943 @code{True} if the symbol is an argument of a function.
23946 @defvar Symbol.is_constant
23947 @code{True} if the symbol is a constant.
23950 @defvar Symbol.is_function
23951 @code{True} if the symbol is a function or a method.
23954 @defvar Symbol.is_variable
23955 @code{True} if the symbol is a variable.
23959 A @code{gdb.Symbol} object has the following methods:
23962 @defun Symbol.is_valid ()
23963 Returns @code{True} if the @code{gdb.Symbol} object is valid,
23964 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
23965 the symbol it refers to does not exist in @value{GDBN} any longer.
23966 All other @code{gdb.Symbol} methods will throw an exception if it is
23967 invalid at the time the method is called.
23971 The available domain categories in @code{gdb.Symbol} are represented
23972 as constants in the @code{gdb} module:
23975 @findex SYMBOL_UNDEF_DOMAIN
23976 @findex gdb.SYMBOL_UNDEF_DOMAIN
23977 @item gdb.SYMBOL_UNDEF_DOMAIN
23978 This is used when a domain has not been discovered or none of the
23979 following domains apply. This usually indicates an error either
23980 in the symbol information or in @value{GDBN}'s handling of symbols.
23981 @findex SYMBOL_VAR_DOMAIN
23982 @findex gdb.SYMBOL_VAR_DOMAIN
23983 @item gdb.SYMBOL_VAR_DOMAIN
23984 This domain contains variables, function names, typedef names and enum
23986 @findex SYMBOL_STRUCT_DOMAIN
23987 @findex gdb.SYMBOL_STRUCT_DOMAIN
23988 @item gdb.SYMBOL_STRUCT_DOMAIN
23989 This domain holds struct, union and enum type names.
23990 @findex SYMBOL_LABEL_DOMAIN
23991 @findex gdb.SYMBOL_LABEL_DOMAIN
23992 @item gdb.SYMBOL_LABEL_DOMAIN
23993 This domain contains names of labels (for gotos).
23994 @findex SYMBOL_VARIABLES_DOMAIN
23995 @findex gdb.SYMBOL_VARIABLES_DOMAIN
23996 @item gdb.SYMBOL_VARIABLES_DOMAIN
23997 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
23998 contains everything minus functions and types.
23999 @findex SYMBOL_FUNCTIONS_DOMAIN
24000 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
24001 @item gdb.SYMBOL_FUNCTION_DOMAIN
24002 This domain contains all functions.
24003 @findex SYMBOL_TYPES_DOMAIN
24004 @findex gdb.SYMBOL_TYPES_DOMAIN
24005 @item gdb.SYMBOL_TYPES_DOMAIN
24006 This domain contains all types.
24009 The available address class categories in @code{gdb.Symbol} are represented
24010 as constants in the @code{gdb} module:
24013 @findex SYMBOL_LOC_UNDEF
24014 @findex gdb.SYMBOL_LOC_UNDEF
24015 @item gdb.SYMBOL_LOC_UNDEF
24016 If this is returned by address class, it indicates an error either in
24017 the symbol information or in @value{GDBN}'s handling of symbols.
24018 @findex SYMBOL_LOC_CONST
24019 @findex gdb.SYMBOL_LOC_CONST
24020 @item gdb.SYMBOL_LOC_CONST
24021 Value is constant int.
24022 @findex SYMBOL_LOC_STATIC
24023 @findex gdb.SYMBOL_LOC_STATIC
24024 @item gdb.SYMBOL_LOC_STATIC
24025 Value is at a fixed address.
24026 @findex SYMBOL_LOC_REGISTER
24027 @findex gdb.SYMBOL_LOC_REGISTER
24028 @item gdb.SYMBOL_LOC_REGISTER
24029 Value is in a register.
24030 @findex SYMBOL_LOC_ARG
24031 @findex gdb.SYMBOL_LOC_ARG
24032 @item gdb.SYMBOL_LOC_ARG
24033 Value is an argument. This value is at the offset stored within the
24034 symbol inside the frame's argument list.
24035 @findex SYMBOL_LOC_REF_ARG
24036 @findex gdb.SYMBOL_LOC_REF_ARG
24037 @item gdb.SYMBOL_LOC_REF_ARG
24038 Value address is stored in the frame's argument list. Just like
24039 @code{LOC_ARG} except that the value's address is stored at the
24040 offset, not the value itself.
24041 @findex SYMBOL_LOC_REGPARM_ADDR
24042 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
24043 @item gdb.SYMBOL_LOC_REGPARM_ADDR
24044 Value is a specified register. Just like @code{LOC_REGISTER} except
24045 the register holds the address of the argument instead of the argument
24047 @findex SYMBOL_LOC_LOCAL
24048 @findex gdb.SYMBOL_LOC_LOCAL
24049 @item gdb.SYMBOL_LOC_LOCAL
24050 Value is a local variable.
24051 @findex SYMBOL_LOC_TYPEDEF
24052 @findex gdb.SYMBOL_LOC_TYPEDEF
24053 @item gdb.SYMBOL_LOC_TYPEDEF
24054 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
24056 @findex SYMBOL_LOC_BLOCK
24057 @findex gdb.SYMBOL_LOC_BLOCK
24058 @item gdb.SYMBOL_LOC_BLOCK
24060 @findex SYMBOL_LOC_CONST_BYTES
24061 @findex gdb.SYMBOL_LOC_CONST_BYTES
24062 @item gdb.SYMBOL_LOC_CONST_BYTES
24063 Value is a byte-sequence.
24064 @findex SYMBOL_LOC_UNRESOLVED
24065 @findex gdb.SYMBOL_LOC_UNRESOLVED
24066 @item gdb.SYMBOL_LOC_UNRESOLVED
24067 Value is at a fixed address, but the address of the variable has to be
24068 determined from the minimal symbol table whenever the variable is
24070 @findex SYMBOL_LOC_OPTIMIZED_OUT
24071 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
24072 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
24073 The value does not actually exist in the program.
24074 @findex SYMBOL_LOC_COMPUTED
24075 @findex gdb.SYMBOL_LOC_COMPUTED
24076 @item gdb.SYMBOL_LOC_COMPUTED
24077 The value's address is a computed location.
24080 @node Symbol Tables In Python
24081 @subsubsection Symbol table representation in Python.
24083 @cindex symbol tables in python
24085 @tindex gdb.Symtab_and_line
24087 Access to symbol table data maintained by @value{GDBN} on the inferior
24088 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
24089 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
24090 from the @code{find_sal} method in @code{gdb.Frame} object.
24091 @xref{Frames In Python}.
24093 For more information on @value{GDBN}'s symbol table management, see
24094 @ref{Symbols, ,Examining the Symbol Table}, for more information.
24096 A @code{gdb.Symtab_and_line} object has the following attributes:
24099 @defvar Symtab_and_line.symtab
24100 The symbol table object (@code{gdb.Symtab}) for this frame.
24101 This attribute is not writable.
24104 @defvar Symtab_and_line.pc
24105 Indicates the current program counter address. This attribute is not
24109 @defvar Symtab_and_line.line
24110 Indicates the current line number for this object. This
24111 attribute is not writable.
24115 A @code{gdb.Symtab_and_line} object has the following methods:
24118 @defun Symtab_and_line.is_valid ()
24119 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
24120 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
24121 invalid if the Symbol table and line object it refers to does not
24122 exist in @value{GDBN} any longer. All other
24123 @code{gdb.Symtab_and_line} methods will throw an exception if it is
24124 invalid at the time the method is called.
24128 A @code{gdb.Symtab} object has the following attributes:
24131 @defvar Symtab.filename
24132 The symbol table's source filename. This attribute is not writable.
24135 @defvar Symtab.objfile
24136 The symbol table's backing object file. @xref{Objfiles In Python}.
24137 This attribute is not writable.
24141 A @code{gdb.Symtab} object has the following methods:
24144 @defun Symtab.is_valid ()
24145 Returns @code{True} if the @code{gdb.Symtab} object is valid,
24146 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
24147 the symbol table it refers to does not exist in @value{GDBN} any
24148 longer. All other @code{gdb.Symtab} methods will throw an exception
24149 if it is invalid at the time the method is called.
24152 @defun Symtab.fullname ()
24153 Return the symbol table's source absolute file name.
24157 @node Breakpoints In Python
24158 @subsubsection Manipulating breakpoints using Python
24160 @cindex breakpoints in python
24161 @tindex gdb.Breakpoint
24163 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
24166 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
24167 Create a new breakpoint. @var{spec} is a string naming the
24168 location of the breakpoint, or an expression that defines a
24169 watchpoint. The contents can be any location recognized by the
24170 @code{break} command, or in the case of a watchpoint, by the @code{watch}
24171 command. The optional @var{type} denotes the breakpoint to create
24172 from the types defined later in this chapter. This argument can be
24173 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
24174 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
24175 allows the breakpoint to become invisible to the user. The breakpoint
24176 will neither be reported when created, nor will it be listed in the
24177 output from @code{info breakpoints} (but will be listed with the
24178 @code{maint info breakpoints} command). The optional @var{wp_class}
24179 argument defines the class of watchpoint to create, if @var{type} is
24180 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
24181 assumed to be a @code{gdb.WP_WRITE} class.
24184 @defun Breakpoint.stop (self)
24185 The @code{gdb.Breakpoint} class can be sub-classed and, in
24186 particular, you may choose to implement the @code{stop} method.
24187 If this method is defined as a sub-class of @code{gdb.Breakpoint},
24188 it will be called when the inferior reaches any location of a
24189 breakpoint which instantiates that sub-class. If the method returns
24190 @code{True}, the inferior will be stopped at the location of the
24191 breakpoint, otherwise the inferior will continue.
24193 If there are multiple breakpoints at the same location with a
24194 @code{stop} method, each one will be called regardless of the
24195 return status of the previous. This ensures that all @code{stop}
24196 methods have a chance to execute at that location. In this scenario
24197 if one of the methods returns @code{True} but the others return
24198 @code{False}, the inferior will still be stopped.
24200 You should not alter the execution state of the inferior (i.e.@:, step,
24201 next, etc.), alter the current frame context (i.e.@:, change the current
24202 active frame), or alter, add or delete any breakpoint. As a general
24203 rule, you should not alter any data within @value{GDBN} or the inferior
24206 Example @code{stop} implementation:
24209 class MyBreakpoint (gdb.Breakpoint):
24211 inf_val = gdb.parse_and_eval("foo")
24218 The available watchpoint types represented by constants are defined in the
24223 @findex gdb.WP_READ
24225 Read only watchpoint.
24228 @findex gdb.WP_WRITE
24230 Write only watchpoint.
24233 @findex gdb.WP_ACCESS
24234 @item gdb.WP_ACCESS
24235 Read/Write watchpoint.
24238 @defun Breakpoint.is_valid ()
24239 Return @code{True} if this @code{Breakpoint} object is valid,
24240 @code{False} otherwise. A @code{Breakpoint} object can become invalid
24241 if the user deletes the breakpoint. In this case, the object still
24242 exists, but the underlying breakpoint does not. In the cases of
24243 watchpoint scope, the watchpoint remains valid even if execution of the
24244 inferior leaves the scope of that watchpoint.
24247 @defun Breakpoint.delete
24248 Permanently deletes the @value{GDBN} breakpoint. This also
24249 invalidates the Python @code{Breakpoint} object. Any further access
24250 to this object's attributes or methods will raise an error.
24253 @defvar Breakpoint.enabled
24254 This attribute is @code{True} if the breakpoint is enabled, and
24255 @code{False} otherwise. This attribute is writable.
24258 @defvar Breakpoint.silent
24259 This attribute is @code{True} if the breakpoint is silent, and
24260 @code{False} otherwise. This attribute is writable.
24262 Note that a breakpoint can also be silent if it has commands and the
24263 first command is @code{silent}. This is not reported by the
24264 @code{silent} attribute.
24267 @defvar Breakpoint.thread
24268 If the breakpoint is thread-specific, this attribute holds the thread
24269 id. If the breakpoint is not thread-specific, this attribute is
24270 @code{None}. This attribute is writable.
24273 @defvar Breakpoint.task
24274 If the breakpoint is Ada task-specific, this attribute holds the Ada task
24275 id. If the breakpoint is not task-specific (or the underlying
24276 language is not Ada), this attribute is @code{None}. This attribute
24280 @defvar Breakpoint.ignore_count
24281 This attribute holds the ignore count for the breakpoint, an integer.
24282 This attribute is writable.
24285 @defvar Breakpoint.number
24286 This attribute holds the breakpoint's number --- the identifier used by
24287 the user to manipulate the breakpoint. This attribute is not writable.
24290 @defvar Breakpoint.type
24291 This attribute holds the breakpoint's type --- the identifier used to
24292 determine the actual breakpoint type or use-case. This attribute is not
24296 @defvar Breakpoint.visible
24297 This attribute tells whether the breakpoint is visible to the user
24298 when set, or when the @samp{info breakpoints} command is run. This
24299 attribute is not writable.
24302 The available types are represented by constants defined in the @code{gdb}
24306 @findex BP_BREAKPOINT
24307 @findex gdb.BP_BREAKPOINT
24308 @item gdb.BP_BREAKPOINT
24309 Normal code breakpoint.
24311 @findex BP_WATCHPOINT
24312 @findex gdb.BP_WATCHPOINT
24313 @item gdb.BP_WATCHPOINT
24314 Watchpoint breakpoint.
24316 @findex BP_HARDWARE_WATCHPOINT
24317 @findex gdb.BP_HARDWARE_WATCHPOINT
24318 @item gdb.BP_HARDWARE_WATCHPOINT
24319 Hardware assisted watchpoint.
24321 @findex BP_READ_WATCHPOINT
24322 @findex gdb.BP_READ_WATCHPOINT
24323 @item gdb.BP_READ_WATCHPOINT
24324 Hardware assisted read watchpoint.
24326 @findex BP_ACCESS_WATCHPOINT
24327 @findex gdb.BP_ACCESS_WATCHPOINT
24328 @item gdb.BP_ACCESS_WATCHPOINT
24329 Hardware assisted access watchpoint.
24332 @defvar Breakpoint.hit_count
24333 This attribute holds the hit count for the breakpoint, an integer.
24334 This attribute is writable, but currently it can only be set to zero.
24337 @defvar Breakpoint.location
24338 This attribute holds the location of the breakpoint, as specified by
24339 the user. It is a string. If the breakpoint does not have a location
24340 (that is, it is a watchpoint) the attribute's value is @code{None}. This
24341 attribute is not writable.
24344 @defvar Breakpoint.expression
24345 This attribute holds a breakpoint expression, as specified by
24346 the user. It is a string. If the breakpoint does not have an
24347 expression (the breakpoint is not a watchpoint) the attribute's value
24348 is @code{None}. This attribute is not writable.
24351 @defvar Breakpoint.condition
24352 This attribute holds the condition of the breakpoint, as specified by
24353 the user. It is a string. If there is no condition, this attribute's
24354 value is @code{None}. This attribute is writable.
24357 @defvar Breakpoint.commands
24358 This attribute holds the commands attached to the breakpoint. If
24359 there are commands, this attribute's value is a string holding all the
24360 commands, separated by newlines. If there are no commands, this
24361 attribute is @code{None}. This attribute is not writable.
24364 @node Finish Breakpoints in Python
24365 @subsubsection Finish Breakpoints
24367 @cindex python finish breakpoints
24368 @tindex gdb.FinishBreakpoint
24370 A finish breakpoint is a temporary breakpoint set at the return address of
24371 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
24372 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
24373 and deleted when the execution will run out of the breakpoint scope (i.e.@:
24374 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
24375 Finish breakpoints are thread specific and must be create with the right
24378 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
24379 Create a finish breakpoint at the return address of the @code{gdb.Frame}
24380 object @var{frame}. If @var{frame} is not provided, this defaults to the
24381 newest frame. The optional @var{internal} argument allows the breakpoint to
24382 become invisible to the user. @xref{Breakpoints In Python}, for further
24383 details about this argument.
24386 @defun FinishBreakpoint.out_of_scope (self)
24387 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
24388 @code{return} command, @dots{}), a function may not properly terminate, and
24389 thus never hit the finish breakpoint. When @value{GDBN} notices such a
24390 situation, the @code{out_of_scope} callback will be triggered.
24392 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
24396 class MyFinishBreakpoint (gdb.FinishBreakpoint)
24398 print "normal finish"
24401 def out_of_scope ():
24402 print "abnormal finish"
24406 @defvar FinishBreakpoint.return_value
24407 When @value{GDBN} is stopped at a finish breakpoint and the frame
24408 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
24409 attribute will contain a @code{gdb.Value} object corresponding to the return
24410 value of the function. The value will be @code{None} if the function return
24411 type is @code{void} or if the return value was not computable. This attribute
24415 @node Lazy Strings In Python
24416 @subsubsection Python representation of lazy strings.
24418 @cindex lazy strings in python
24419 @tindex gdb.LazyString
24421 A @dfn{lazy string} is a string whose contents is not retrieved or
24422 encoded until it is needed.
24424 A @code{gdb.LazyString} is represented in @value{GDBN} as an
24425 @code{address} that points to a region of memory, an @code{encoding}
24426 that will be used to encode that region of memory, and a @code{length}
24427 to delimit the region of memory that represents the string. The
24428 difference between a @code{gdb.LazyString} and a string wrapped within
24429 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
24430 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
24431 retrieved and encoded during printing, while a @code{gdb.Value}
24432 wrapping a string is immediately retrieved and encoded on creation.
24434 A @code{gdb.LazyString} object has the following functions:
24436 @defun LazyString.value ()
24437 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
24438 will point to the string in memory, but will lose all the delayed
24439 retrieval, encoding and handling that @value{GDBN} applies to a
24440 @code{gdb.LazyString}.
24443 @defvar LazyString.address
24444 This attribute holds the address of the string. This attribute is not
24448 @defvar LazyString.length
24449 This attribute holds the length of the string in characters. If the
24450 length is -1, then the string will be fetched and encoded up to the
24451 first null of appropriate width. This attribute is not writable.
24454 @defvar LazyString.encoding
24455 This attribute holds the encoding that will be applied to the string
24456 when the string is printed by @value{GDBN}. If the encoding is not
24457 set, or contains an empty string, then @value{GDBN} will select the
24458 most appropriate encoding when the string is printed. This attribute
24462 @defvar LazyString.type
24463 This attribute holds the type that is represented by the lazy string's
24464 type. For a lazy string this will always be a pointer type. To
24465 resolve this to the lazy string's character type, use the type's
24466 @code{target} method. @xref{Types In Python}. This attribute is not
24471 @subsection Auto-loading
24472 @cindex auto-loading, Python
24474 When a new object file is read (for example, due to the @code{file}
24475 command, or because the inferior has loaded a shared library),
24476 @value{GDBN} will look for Python support scripts in several ways:
24477 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
24480 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
24481 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
24482 * Which flavor to choose?::
24485 The auto-loading feature is useful for supplying application-specific
24486 debugging commands and scripts.
24488 Auto-loading can be enabled or disabled,
24489 and the list of auto-loaded scripts can be printed.
24492 @kindex set auto-load-scripts
24493 @item set auto-load-scripts [yes|no]
24494 Enable or disable the auto-loading of Python scripts.
24496 @kindex show auto-load-scripts
24497 @item show auto-load-scripts
24498 Show whether auto-loading of Python scripts is enabled or disabled.
24500 @kindex info auto-load-scripts
24501 @cindex print list of auto-loaded scripts
24502 @item info auto-load-scripts [@var{regexp}]
24503 Print the list of all scripts that @value{GDBN} auto-loaded.
24505 Also printed is the list of scripts that were mentioned in
24506 the @code{.debug_gdb_scripts} section and were not found
24507 (@pxref{.debug_gdb_scripts section}).
24508 This is useful because their names are not printed when @value{GDBN}
24509 tries to load them and fails. There may be many of them, and printing
24510 an error message for each one is problematic.
24512 If @var{regexp} is supplied only scripts with matching names are printed.
24517 (gdb) info auto-load-scripts
24519 Yes py-section-script.py
24520 full name: /tmp/py-section-script.py
24521 Missing my-foo-pretty-printers.py
24525 When reading an auto-loaded file, @value{GDBN} sets the
24526 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
24527 function (@pxref{Objfiles In Python}). This can be useful for
24528 registering objfile-specific pretty-printers.
24530 @node objfile-gdb.py file
24531 @subsubsection The @file{@var{objfile}-gdb.py} file
24532 @cindex @file{@var{objfile}-gdb.py}
24534 When a new object file is read, @value{GDBN} looks for
24535 a file named @file{@var{objfile}-gdb.py},
24536 where @var{objfile} is the object file's real name, formed by ensuring
24537 that the file name is absolute, following all symlinks, and resolving
24538 @code{.} and @code{..} components. If this file exists and is
24539 readable, @value{GDBN} will evaluate it as a Python script.
24541 If this file does not exist, and if the parameter
24542 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
24543 then @value{GDBN} will look for @var{real-name} in all of the
24544 directories mentioned in the value of @code{debug-file-directory}.
24546 Finally, if this file does not exist, then @value{GDBN} will look for
24547 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
24548 @var{data-directory} is @value{GDBN}'s data directory (available via
24549 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
24550 is the object file's real name, as described above.
24552 @value{GDBN} does not track which files it has already auto-loaded this way.
24553 @value{GDBN} will load the associated script every time the corresponding
24554 @var{objfile} is opened.
24555 So your @file{-gdb.py} file should be careful to avoid errors if it
24556 is evaluated more than once.
24558 @node .debug_gdb_scripts section
24559 @subsubsection The @code{.debug_gdb_scripts} section
24560 @cindex @code{.debug_gdb_scripts} section
24562 For systems using file formats like ELF and COFF,
24563 when @value{GDBN} loads a new object file
24564 it will look for a special section named @samp{.debug_gdb_scripts}.
24565 If this section exists, its contents is a list of names of scripts to load.
24567 @value{GDBN} will look for each specified script file first in the
24568 current directory and then along the source search path
24569 (@pxref{Source Path, ,Specifying Source Directories}),
24570 except that @file{$cdir} is not searched, since the compilation
24571 directory is not relevant to scripts.
24573 Entries can be placed in section @code{.debug_gdb_scripts} with,
24574 for example, this GCC macro:
24577 /* Note: The "MS" section flags are to remove duplicates. */
24578 #define DEFINE_GDB_SCRIPT(script_name) \
24580 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24582 .asciz \"" script_name "\"\n\
24588 Then one can reference the macro in a header or source file like this:
24591 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
24594 The script name may include directories if desired.
24596 If the macro is put in a header, any application or library
24597 using this header will get a reference to the specified script.
24599 @node Which flavor to choose?
24600 @subsubsection Which flavor to choose?
24602 Given the multiple ways of auto-loading Python scripts, it might not always
24603 be clear which one to choose. This section provides some guidance.
24605 Benefits of the @file{-gdb.py} way:
24609 Can be used with file formats that don't support multiple sections.
24612 Ease of finding scripts for public libraries.
24614 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24615 in the source search path.
24616 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24617 isn't a source directory in which to find the script.
24620 Doesn't require source code additions.
24623 Benefits of the @code{.debug_gdb_scripts} way:
24627 Works with static linking.
24629 Scripts for libraries done the @file{-gdb.py} way require an objfile to
24630 trigger their loading. When an application is statically linked the only
24631 objfile available is the executable, and it is cumbersome to attach all the
24632 scripts from all the input libraries to the executable's @file{-gdb.py} script.
24635 Works with classes that are entirely inlined.
24637 Some classes can be entirely inlined, and thus there may not be an associated
24638 shared library to attach a @file{-gdb.py} script to.
24641 Scripts needn't be copied out of the source tree.
24643 In some circumstances, apps can be built out of large collections of internal
24644 libraries, and the build infrastructure necessary to install the
24645 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
24646 cumbersome. It may be easier to specify the scripts in the
24647 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24648 top of the source tree to the source search path.
24651 @node Python modules
24652 @subsection Python modules
24653 @cindex python modules
24655 @value{GDBN} comes with several modules to assist writing Python code.
24658 * gdb.printing:: Building and registering pretty-printers.
24659 * gdb.types:: Utilities for working with types.
24660 * gdb.prompt:: Utilities for prompt value substitution.
24664 @subsubsection gdb.printing
24665 @cindex gdb.printing
24667 This module provides a collection of utilities for working with
24671 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
24672 This class specifies the API that makes @samp{info pretty-printer},
24673 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
24674 Pretty-printers should generally inherit from this class.
24676 @item SubPrettyPrinter (@var{name})
24677 For printers that handle multiple types, this class specifies the
24678 corresponding API for the subprinters.
24680 @item RegexpCollectionPrettyPrinter (@var{name})
24681 Utility class for handling multiple printers, all recognized via
24682 regular expressions.
24683 @xref{Writing a Pretty-Printer}, for an example.
24685 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
24686 Register @var{printer} with the pretty-printer list of @var{obj}.
24687 If @var{replace} is @code{True} then any existing copy of the printer
24688 is replaced. Otherwise a @code{RuntimeError} exception is raised
24689 if a printer with the same name already exists.
24693 @subsubsection gdb.types
24696 This module provides a collection of utilities for working with
24697 @code{gdb.Types} objects.
24700 @item get_basic_type (@var{type})
24701 Return @var{type} with const and volatile qualifiers stripped,
24702 and with typedefs and C@t{++} references converted to the underlying type.
24707 typedef const int const_int;
24709 const_int& foo_ref (foo);
24710 int main () @{ return 0; @}
24717 (gdb) python import gdb.types
24718 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
24719 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
24723 @item has_field (@var{type}, @var{field})
24724 Return @code{True} if @var{type}, assumed to be a type with fields
24725 (e.g., a structure or union), has field @var{field}.
24727 @item make_enum_dict (@var{enum_type})
24728 Return a Python @code{dictionary} type produced from @var{enum_type}.
24730 @item deep_items (@var{type})
24731 Returns a Python iterator similar to the standard
24732 @code{gdb.Type.iteritems} method, except that the iterator returned
24733 by @code{deep_items} will recursively traverse anonymous struct or
24734 union fields. For example:
24748 Then in @value{GDBN}:
24750 (@value{GDBP}) python import gdb.types
24751 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
24752 (@value{GDBP}) python print struct_a.keys ()
24754 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
24755 @{['a', 'b0', 'b1']@}
24761 @subsubsection gdb.prompt
24764 This module provides a method for prompt value-substitution.
24767 @item substitute_prompt (@var{string})
24768 Return @var{string} with escape sequences substituted by values. Some
24769 escape sequences take arguments. You can specify arguments inside
24770 ``@{@}'' immediately following the escape sequence.
24772 The escape sequences you can pass to this function are:
24776 Substitute a backslash.
24778 Substitute an ESC character.
24780 Substitute the selected frame; an argument names a frame parameter.
24782 Substitute a newline.
24784 Substitute a parameter's value; the argument names the parameter.
24786 Substitute a carriage return.
24788 Substitute the selected thread; an argument names a thread parameter.
24790 Substitute the version of GDB.
24792 Substitute the current working directory.
24794 Begin a sequence of non-printing characters. These sequences are
24795 typically used with the ESC character, and are not counted in the string
24796 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
24797 blue-colored ``(gdb)'' prompt where the length is five.
24799 End a sequence of non-printing characters.
24805 substitute_prompt (``frame: \f,
24806 print arguments: \p@{print frame-arguments@}'')
24809 @exdent will return the string:
24812 "frame: main, print arguments: scalars"
24817 @section Creating new spellings of existing commands
24818 @cindex aliases for commands
24820 It is often useful to define alternate spellings of existing commands.
24821 For example, if a new @value{GDBN} command defined in Python has
24822 a long name to type, it is handy to have an abbreviated version of it
24823 that involves less typing.
24825 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24826 of the @samp{step} command even though it is otherwise an ambiguous
24827 abbreviation of other commands like @samp{set} and @samp{show}.
24829 Aliases are also used to provide shortened or more common versions
24830 of multi-word commands. For example, @value{GDBN} provides the
24831 @samp{tty} alias of the @samp{set inferior-tty} command.
24833 You can define a new alias with the @samp{alias} command.
24838 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24842 @var{ALIAS} specifies the name of the new alias.
24843 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24846 @var{COMMAND} specifies the name of an existing command
24847 that is being aliased.
24849 The @samp{-a} option specifies that the new alias is an abbreviation
24850 of the command. Abbreviations are not shown in command
24851 lists displayed by the @samp{help} command.
24853 The @samp{--} option specifies the end of options,
24854 and is useful when @var{ALIAS} begins with a dash.
24856 Here is a simple example showing how to make an abbreviation
24857 of a command so that there is less to type.
24858 Suppose you were tired of typing @samp{disas}, the current
24859 shortest unambiguous abbreviation of the @samp{disassemble} command
24860 and you wanted an even shorter version named @samp{di}.
24861 The following will accomplish this.
24864 (gdb) alias -a di = disas
24867 Note that aliases are different from user-defined commands.
24868 With a user-defined command, you also need to write documentation
24869 for it with the @samp{document} command.
24870 An alias automatically picks up the documentation of the existing command.
24872 Here is an example where we make @samp{elms} an abbreviation of
24873 @samp{elements} in the @samp{set print elements} command.
24874 This is to show that you can make an abbreviation of any part
24878 (gdb) alias -a set print elms = set print elements
24879 (gdb) alias -a show print elms = show print elements
24880 (gdb) set p elms 20
24882 Limit on string chars or array elements to print is 200.
24885 Note that if you are defining an alias of a @samp{set} command,
24886 and you want to have an alias for the corresponding @samp{show}
24887 command, then you need to define the latter separately.
24889 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24890 @var{ALIAS}, just as they are normally.
24893 (gdb) alias -a set pr elms = set p ele
24896 Finally, here is an example showing the creation of a one word
24897 alias for a more complex command.
24898 This creates alias @samp{spe} of the command @samp{set print elements}.
24901 (gdb) alias spe = set print elements
24906 @chapter Command Interpreters
24907 @cindex command interpreters
24909 @value{GDBN} supports multiple command interpreters, and some command
24910 infrastructure to allow users or user interface writers to switch
24911 between interpreters or run commands in other interpreters.
24913 @value{GDBN} currently supports two command interpreters, the console
24914 interpreter (sometimes called the command-line interpreter or @sc{cli})
24915 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24916 describes both of these interfaces in great detail.
24918 By default, @value{GDBN} will start with the console interpreter.
24919 However, the user may choose to start @value{GDBN} with another
24920 interpreter by specifying the @option{-i} or @option{--interpreter}
24921 startup options. Defined interpreters include:
24925 @cindex console interpreter
24926 The traditional console or command-line interpreter. This is the most often
24927 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24928 @value{GDBN} will use this interpreter.
24931 @cindex mi interpreter
24932 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24933 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24934 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24938 @cindex mi2 interpreter
24939 The current @sc{gdb/mi} interface.
24942 @cindex mi1 interpreter
24943 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24947 @cindex invoke another interpreter
24948 The interpreter being used by @value{GDBN} may not be dynamically
24949 switched at runtime. Although possible, this could lead to a very
24950 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24951 enters the command "interpreter-set console" in a console view,
24952 @value{GDBN} would switch to using the console interpreter, rendering
24953 the IDE inoperable!
24955 @kindex interpreter-exec
24956 Although you may only choose a single interpreter at startup, you may execute
24957 commands in any interpreter from the current interpreter using the appropriate
24958 command. If you are running the console interpreter, simply use the
24959 @code{interpreter-exec} command:
24962 interpreter-exec mi "-data-list-register-names"
24965 @sc{gdb/mi} has a similar command, although it is only available in versions of
24966 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24969 @chapter @value{GDBN} Text User Interface
24971 @cindex Text User Interface
24974 * TUI Overview:: TUI overview
24975 * TUI Keys:: TUI key bindings
24976 * TUI Single Key Mode:: TUI single key mode
24977 * TUI Commands:: TUI-specific commands
24978 * TUI Configuration:: TUI configuration variables
24981 The @value{GDBN} Text User Interface (TUI) is a terminal
24982 interface which uses the @code{curses} library to show the source
24983 file, the assembly output, the program registers and @value{GDBN}
24984 commands in separate text windows. The TUI mode is supported only
24985 on platforms where a suitable version of the @code{curses} library
24988 @pindex @value{GDBTUI}
24989 The TUI mode is enabled by default when you invoke @value{GDBN} as
24990 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
24991 You can also switch in and out of TUI mode while @value{GDBN} runs by
24992 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24993 @xref{TUI Keys, ,TUI Key Bindings}.
24996 @section TUI Overview
24998 In TUI mode, @value{GDBN} can display several text windows:
25002 This window is the @value{GDBN} command window with the @value{GDBN}
25003 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25004 managed using readline.
25007 The source window shows the source file of the program. The current
25008 line and active breakpoints are displayed in this window.
25011 The assembly window shows the disassembly output of the program.
25014 This window shows the processor registers. Registers are highlighted
25015 when their values change.
25018 The source and assembly windows show the current program position
25019 by highlighting the current line and marking it with a @samp{>} marker.
25020 Breakpoints are indicated with two markers. The first marker
25021 indicates the breakpoint type:
25025 Breakpoint which was hit at least once.
25028 Breakpoint which was never hit.
25031 Hardware breakpoint which was hit at least once.
25034 Hardware breakpoint which was never hit.
25037 The second marker indicates whether the breakpoint is enabled or not:
25041 Breakpoint is enabled.
25044 Breakpoint is disabled.
25047 The source, assembly and register windows are updated when the current
25048 thread changes, when the frame changes, or when the program counter
25051 These windows are not all visible at the same time. The command
25052 window is always visible. The others can be arranged in several
25063 source and assembly,
25066 source and registers, or
25069 assembly and registers.
25072 A status line above the command window shows the following information:
25076 Indicates the current @value{GDBN} target.
25077 (@pxref{Targets, ,Specifying a Debugging Target}).
25080 Gives the current process or thread number.
25081 When no process is being debugged, this field is set to @code{No process}.
25084 Gives the current function name for the selected frame.
25085 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25086 When there is no symbol corresponding to the current program counter,
25087 the string @code{??} is displayed.
25090 Indicates the current line number for the selected frame.
25091 When the current line number is not known, the string @code{??} is displayed.
25094 Indicates the current program counter address.
25098 @section TUI Key Bindings
25099 @cindex TUI key bindings
25101 The TUI installs several key bindings in the readline keymaps
25102 @ifset SYSTEM_READLINE
25103 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25105 @ifclear SYSTEM_READLINE
25106 (@pxref{Command Line Editing}).
25108 The following key bindings are installed for both TUI mode and the
25109 @value{GDBN} standard mode.
25118 Enter or leave the TUI mode. When leaving the TUI mode,
25119 the curses window management stops and @value{GDBN} operates using
25120 its standard mode, writing on the terminal directly. When reentering
25121 the TUI mode, control is given back to the curses windows.
25122 The screen is then refreshed.
25126 Use a TUI layout with only one window. The layout will
25127 either be @samp{source} or @samp{assembly}. When the TUI mode
25128 is not active, it will switch to the TUI mode.
25130 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25134 Use a TUI layout with at least two windows. When the current
25135 layout already has two windows, the next layout with two windows is used.
25136 When a new layout is chosen, one window will always be common to the
25137 previous layout and the new one.
25139 Think of it as the Emacs @kbd{C-x 2} binding.
25143 Change the active window. The TUI associates several key bindings
25144 (like scrolling and arrow keys) with the active window. This command
25145 gives the focus to the next TUI window.
25147 Think of it as the Emacs @kbd{C-x o} binding.
25151 Switch in and out of the TUI SingleKey mode that binds single
25152 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25155 The following key bindings only work in the TUI mode:
25160 Scroll the active window one page up.
25164 Scroll the active window one page down.
25168 Scroll the active window one line up.
25172 Scroll the active window one line down.
25176 Scroll the active window one column left.
25180 Scroll the active window one column right.
25184 Refresh the screen.
25187 Because the arrow keys scroll the active window in the TUI mode, they
25188 are not available for their normal use by readline unless the command
25189 window has the focus. When another window is active, you must use
25190 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25191 and @kbd{C-f} to control the command window.
25193 @node TUI Single Key Mode
25194 @section TUI Single Key Mode
25195 @cindex TUI single key mode
25197 The TUI also provides a @dfn{SingleKey} mode, which binds several
25198 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25199 switch into this mode, where the following key bindings are used:
25202 @kindex c @r{(SingleKey TUI key)}
25206 @kindex d @r{(SingleKey TUI key)}
25210 @kindex f @r{(SingleKey TUI key)}
25214 @kindex n @r{(SingleKey TUI key)}
25218 @kindex q @r{(SingleKey TUI key)}
25220 exit the SingleKey mode.
25222 @kindex r @r{(SingleKey TUI key)}
25226 @kindex s @r{(SingleKey TUI key)}
25230 @kindex u @r{(SingleKey TUI key)}
25234 @kindex v @r{(SingleKey TUI key)}
25238 @kindex w @r{(SingleKey TUI key)}
25243 Other keys temporarily switch to the @value{GDBN} command prompt.
25244 The key that was pressed is inserted in the editing buffer so that
25245 it is possible to type most @value{GDBN} commands without interaction
25246 with the TUI SingleKey mode. Once the command is entered the TUI
25247 SingleKey mode is restored. The only way to permanently leave
25248 this mode is by typing @kbd{q} or @kbd{C-x s}.
25252 @section TUI-specific Commands
25253 @cindex TUI commands
25255 The TUI has specific commands to control the text windows.
25256 These commands are always available, even when @value{GDBN} is not in
25257 the TUI mode. When @value{GDBN} is in the standard mode, most
25258 of these commands will automatically switch to the TUI mode.
25260 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25261 terminal, or @value{GDBN} has been started with the machine interface
25262 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25263 these commands will fail with an error, because it would not be
25264 possible or desirable to enable curses window management.
25269 List and give the size of all displayed windows.
25273 Display the next layout.
25276 Display the previous layout.
25279 Display the source window only.
25282 Display the assembly window only.
25285 Display the source and assembly window.
25288 Display the register window together with the source or assembly window.
25292 Make the next window active for scrolling.
25295 Make the previous window active for scrolling.
25298 Make the source window active for scrolling.
25301 Make the assembly window active for scrolling.
25304 Make the register window active for scrolling.
25307 Make the command window active for scrolling.
25311 Refresh the screen. This is similar to typing @kbd{C-L}.
25313 @item tui reg float
25315 Show the floating point registers in the register window.
25317 @item tui reg general
25318 Show the general registers in the register window.
25321 Show the next register group. The list of register groups as well as
25322 their order is target specific. The predefined register groups are the
25323 following: @code{general}, @code{float}, @code{system}, @code{vector},
25324 @code{all}, @code{save}, @code{restore}.
25326 @item tui reg system
25327 Show the system registers in the register window.
25331 Update the source window and the current execution point.
25333 @item winheight @var{name} +@var{count}
25334 @itemx winheight @var{name} -@var{count}
25336 Change the height of the window @var{name} by @var{count}
25337 lines. Positive counts increase the height, while negative counts
25340 @item tabset @var{nchars}
25342 Set the width of tab stops to be @var{nchars} characters.
25345 @node TUI Configuration
25346 @section TUI Configuration Variables
25347 @cindex TUI configuration variables
25349 Several configuration variables control the appearance of TUI windows.
25352 @item set tui border-kind @var{kind}
25353 @kindex set tui border-kind
25354 Select the border appearance for the source, assembly and register windows.
25355 The possible values are the following:
25358 Use a space character to draw the border.
25361 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25364 Use the Alternate Character Set to draw the border. The border is
25365 drawn using character line graphics if the terminal supports them.
25368 @item set tui border-mode @var{mode}
25369 @kindex set tui border-mode
25370 @itemx set tui active-border-mode @var{mode}
25371 @kindex set tui active-border-mode
25372 Select the display attributes for the borders of the inactive windows
25373 or the active window. The @var{mode} can be one of the following:
25376 Use normal attributes to display the border.
25382 Use reverse video mode.
25385 Use half bright mode.
25387 @item half-standout
25388 Use half bright and standout mode.
25391 Use extra bright or bold mode.
25393 @item bold-standout
25394 Use extra bright or bold and standout mode.
25399 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25402 @cindex @sc{gnu} Emacs
25403 A special interface allows you to use @sc{gnu} Emacs to view (and
25404 edit) the source files for the program you are debugging with
25407 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25408 executable file you want to debug as an argument. This command starts
25409 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25410 created Emacs buffer.
25411 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25413 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25418 All ``terminal'' input and output goes through an Emacs buffer, called
25421 This applies both to @value{GDBN} commands and their output, and to the input
25422 and output done by the program you are debugging.
25424 This is useful because it means that you can copy the text of previous
25425 commands and input them again; you can even use parts of the output
25428 All the facilities of Emacs' Shell mode are available for interacting
25429 with your program. In particular, you can send signals the usual
25430 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25434 @value{GDBN} displays source code through Emacs.
25436 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25437 source file for that frame and puts an arrow (@samp{=>}) at the
25438 left margin of the current line. Emacs uses a separate buffer for
25439 source display, and splits the screen to show both your @value{GDBN} session
25442 Explicit @value{GDBN} @code{list} or search commands still produce output as
25443 usual, but you probably have no reason to use them from Emacs.
25446 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25447 a graphical mode, enabled by default, which provides further buffers
25448 that can control the execution and describe the state of your program.
25449 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25451 If you specify an absolute file name when prompted for the @kbd{M-x
25452 gdb} argument, then Emacs sets your current working directory to where
25453 your program resides. If you only specify the file name, then Emacs
25454 sets your current working directory to the directory associated
25455 with the previous buffer. In this case, @value{GDBN} may find your
25456 program by searching your environment's @code{PATH} variable, but on
25457 some operating systems it might not find the source. So, although the
25458 @value{GDBN} input and output session proceeds normally, the auxiliary
25459 buffer does not display the current source and line of execution.
25461 The initial working directory of @value{GDBN} is printed on the top
25462 line of the GUD buffer and this serves as a default for the commands
25463 that specify files for @value{GDBN} to operate on. @xref{Files,
25464 ,Commands to Specify Files}.
25466 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25467 need to call @value{GDBN} by a different name (for example, if you
25468 keep several configurations around, with different names) you can
25469 customize the Emacs variable @code{gud-gdb-command-name} to run the
25472 In the GUD buffer, you can use these special Emacs commands in
25473 addition to the standard Shell mode commands:
25477 Describe the features of Emacs' GUD Mode.
25480 Execute to another source line, like the @value{GDBN} @code{step} command; also
25481 update the display window to show the current file and location.
25484 Execute to next source line in this function, skipping all function
25485 calls, like the @value{GDBN} @code{next} command. Then update the display window
25486 to show the current file and location.
25489 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25490 display window accordingly.
25493 Execute until exit from the selected stack frame, like the @value{GDBN}
25494 @code{finish} command.
25497 Continue execution of your program, like the @value{GDBN} @code{continue}
25501 Go up the number of frames indicated by the numeric argument
25502 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25503 like the @value{GDBN} @code{up} command.
25506 Go down the number of frames indicated by the numeric argument, like the
25507 @value{GDBN} @code{down} command.
25510 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25511 tells @value{GDBN} to set a breakpoint on the source line point is on.
25513 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25514 separate frame which shows a backtrace when the GUD buffer is current.
25515 Move point to any frame in the stack and type @key{RET} to make it
25516 become the current frame and display the associated source in the
25517 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25518 selected frame become the current one. In graphical mode, the
25519 speedbar displays watch expressions.
25521 If you accidentally delete the source-display buffer, an easy way to get
25522 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25523 request a frame display; when you run under Emacs, this recreates
25524 the source buffer if necessary to show you the context of the current
25527 The source files displayed in Emacs are in ordinary Emacs buffers
25528 which are visiting the source files in the usual way. You can edit
25529 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25530 communicates with Emacs in terms of line numbers. If you add or
25531 delete lines from the text, the line numbers that @value{GDBN} knows cease
25532 to correspond properly with the code.
25534 A more detailed description of Emacs' interaction with @value{GDBN} is
25535 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25538 @c The following dropped because Epoch is nonstandard. Reactivate
25539 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
25541 @kindex Emacs Epoch environment
25545 Version 18 of @sc{gnu} Emacs has a built-in window system
25546 called the @code{epoch}
25547 environment. Users of this environment can use a new command,
25548 @code{inspect} which performs identically to @code{print} except that
25549 each value is printed in its own window.
25554 @chapter The @sc{gdb/mi} Interface
25556 @unnumberedsec Function and Purpose
25558 @cindex @sc{gdb/mi}, its purpose
25559 @sc{gdb/mi} is a line based machine oriented text interface to
25560 @value{GDBN} and is activated by specifying using the
25561 @option{--interpreter} command line option (@pxref{Mode Options}). It
25562 is specifically intended to support the development of systems which
25563 use the debugger as just one small component of a larger system.
25565 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25566 in the form of a reference manual.
25568 Note that @sc{gdb/mi} is still under construction, so some of the
25569 features described below are incomplete and subject to change
25570 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25572 @unnumberedsec Notation and Terminology
25574 @cindex notational conventions, for @sc{gdb/mi}
25575 This chapter uses the following notation:
25579 @code{|} separates two alternatives.
25582 @code{[ @var{something} ]} indicates that @var{something} is optional:
25583 it may or may not be given.
25586 @code{( @var{group} )*} means that @var{group} inside the parentheses
25587 may repeat zero or more times.
25590 @code{( @var{group} )+} means that @var{group} inside the parentheses
25591 may repeat one or more times.
25594 @code{"@var{string}"} means a literal @var{string}.
25598 @heading Dependencies
25602 * GDB/MI General Design::
25603 * GDB/MI Command Syntax::
25604 * GDB/MI Compatibility with CLI::
25605 * GDB/MI Development and Front Ends::
25606 * GDB/MI Output Records::
25607 * GDB/MI Simple Examples::
25608 * GDB/MI Command Description Format::
25609 * GDB/MI Breakpoint Commands::
25610 * GDB/MI Program Context::
25611 * GDB/MI Thread Commands::
25612 * GDB/MI Ada Tasking Commands::
25613 * GDB/MI Program Execution::
25614 * GDB/MI Stack Manipulation::
25615 * GDB/MI Variable Objects::
25616 * GDB/MI Data Manipulation::
25617 * GDB/MI Tracepoint Commands::
25618 * GDB/MI Symbol Query::
25619 * GDB/MI File Commands::
25621 * GDB/MI Kod Commands::
25622 * GDB/MI Memory Overlay Commands::
25623 * GDB/MI Signal Handling Commands::
25625 * GDB/MI Target Manipulation::
25626 * GDB/MI File Transfer Commands::
25627 * GDB/MI Miscellaneous Commands::
25630 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25631 @node GDB/MI General Design
25632 @section @sc{gdb/mi} General Design
25633 @cindex GDB/MI General Design
25635 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25636 parts---commands sent to @value{GDBN}, responses to those commands
25637 and notifications. Each command results in exactly one response,
25638 indicating either successful completion of the command, or an error.
25639 For the commands that do not resume the target, the response contains the
25640 requested information. For the commands that resume the target, the
25641 response only indicates whether the target was successfully resumed.
25642 Notifications is the mechanism for reporting changes in the state of the
25643 target, or in @value{GDBN} state, that cannot conveniently be associated with
25644 a command and reported as part of that command response.
25646 The important examples of notifications are:
25650 Exec notifications. These are used to report changes in
25651 target state---when a target is resumed, or stopped. It would not
25652 be feasible to include this information in response of resuming
25653 commands, because one resume commands can result in multiple events in
25654 different threads. Also, quite some time may pass before any event
25655 happens in the target, while a frontend needs to know whether the resuming
25656 command itself was successfully executed.
25659 Console output, and status notifications. Console output
25660 notifications are used to report output of CLI commands, as well as
25661 diagnostics for other commands. Status notifications are used to
25662 report the progress of a long-running operation. Naturally, including
25663 this information in command response would mean no output is produced
25664 until the command is finished, which is undesirable.
25667 General notifications. Commands may have various side effects on
25668 the @value{GDBN} or target state beyond their official purpose. For example,
25669 a command may change the selected thread. Although such changes can
25670 be included in command response, using notification allows for more
25671 orthogonal frontend design.
25675 There's no guarantee that whenever an MI command reports an error,
25676 @value{GDBN} or the target are in any specific state, and especially,
25677 the state is not reverted to the state before the MI command was
25678 processed. Therefore, whenever an MI command results in an error,
25679 we recommend that the frontend refreshes all the information shown in
25680 the user interface.
25684 * Context management::
25685 * Asynchronous and non-stop modes::
25689 @node Context management
25690 @subsection Context management
25692 In most cases when @value{GDBN} accesses the target, this access is
25693 done in context of a specific thread and frame (@pxref{Frames}).
25694 Often, even when accessing global data, the target requires that a thread
25695 be specified. The CLI interface maintains the selected thread and frame,
25696 and supplies them to target on each command. This is convenient,
25697 because a command line user would not want to specify that information
25698 explicitly on each command, and because user interacts with
25699 @value{GDBN} via a single terminal, so no confusion is possible as
25700 to what thread and frame are the current ones.
25702 In the case of MI, the concept of selected thread and frame is less
25703 useful. First, a frontend can easily remember this information
25704 itself. Second, a graphical frontend can have more than one window,
25705 each one used for debugging a different thread, and the frontend might
25706 want to access additional threads for internal purposes. This
25707 increases the risk that by relying on implicitly selected thread, the
25708 frontend may be operating on a wrong one. Therefore, each MI command
25709 should explicitly specify which thread and frame to operate on. To
25710 make it possible, each MI command accepts the @samp{--thread} and
25711 @samp{--frame} options, the value to each is @value{GDBN} identifier
25712 for thread and frame to operate on.
25714 Usually, each top-level window in a frontend allows the user to select
25715 a thread and a frame, and remembers the user selection for further
25716 operations. However, in some cases @value{GDBN} may suggest that the
25717 current thread be changed. For example, when stopping on a breakpoint
25718 it is reasonable to switch to the thread where breakpoint is hit. For
25719 another example, if the user issues the CLI @samp{thread} command via
25720 the frontend, it is desirable to change the frontend's selected thread to the
25721 one specified by user. @value{GDBN} communicates the suggestion to
25722 change current thread using the @samp{=thread-selected} notification.
25723 No such notification is available for the selected frame at the moment.
25725 Note that historically, MI shares the selected thread with CLI, so
25726 frontends used the @code{-thread-select} to execute commands in the
25727 right context. However, getting this to work right is cumbersome. The
25728 simplest way is for frontend to emit @code{-thread-select} command
25729 before every command. This doubles the number of commands that need
25730 to be sent. The alternative approach is to suppress @code{-thread-select}
25731 if the selected thread in @value{GDBN} is supposed to be identical to the
25732 thread the frontend wants to operate on. However, getting this
25733 optimization right can be tricky. In particular, if the frontend
25734 sends several commands to @value{GDBN}, and one of the commands changes the
25735 selected thread, then the behaviour of subsequent commands will
25736 change. So, a frontend should either wait for response from such
25737 problematic commands, or explicitly add @code{-thread-select} for
25738 all subsequent commands. No frontend is known to do this exactly
25739 right, so it is suggested to just always pass the @samp{--thread} and
25740 @samp{--frame} options.
25742 @node Asynchronous and non-stop modes
25743 @subsection Asynchronous command execution and non-stop mode
25745 On some targets, @value{GDBN} is capable of processing MI commands
25746 even while the target is running. This is called @dfn{asynchronous
25747 command execution} (@pxref{Background Execution}). The frontend may
25748 specify a preferrence for asynchronous execution using the
25749 @code{-gdb-set target-async 1} command, which should be emitted before
25750 either running the executable or attaching to the target. After the
25751 frontend has started the executable or attached to the target, it can
25752 find if asynchronous execution is enabled using the
25753 @code{-list-target-features} command.
25755 Even if @value{GDBN} can accept a command while target is running,
25756 many commands that access the target do not work when the target is
25757 running. Therefore, asynchronous command execution is most useful
25758 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25759 it is possible to examine the state of one thread, while other threads
25762 When a given thread is running, MI commands that try to access the
25763 target in the context of that thread may not work, or may work only on
25764 some targets. In particular, commands that try to operate on thread's
25765 stack will not work, on any target. Commands that read memory, or
25766 modify breakpoints, may work or not work, depending on the target. Note
25767 that even commands that operate on global state, such as @code{print},
25768 @code{set}, and breakpoint commands, still access the target in the
25769 context of a specific thread, so frontend should try to find a
25770 stopped thread and perform the operation on that thread (using the
25771 @samp{--thread} option).
25773 Which commands will work in the context of a running thread is
25774 highly target dependent. However, the two commands
25775 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25776 to find the state of a thread, will always work.
25778 @node Thread groups
25779 @subsection Thread groups
25780 @value{GDBN} may be used to debug several processes at the same time.
25781 On some platfroms, @value{GDBN} may support debugging of several
25782 hardware systems, each one having several cores with several different
25783 processes running on each core. This section describes the MI
25784 mechanism to support such debugging scenarios.
25786 The key observation is that regardless of the structure of the
25787 target, MI can have a global list of threads, because most commands that
25788 accept the @samp{--thread} option do not need to know what process that
25789 thread belongs to. Therefore, it is not necessary to introduce
25790 neither additional @samp{--process} option, nor an notion of the
25791 current process in the MI interface. The only strictly new feature
25792 that is required is the ability to find how the threads are grouped
25795 To allow the user to discover such grouping, and to support arbitrary
25796 hierarchy of machines/cores/processes, MI introduces the concept of a
25797 @dfn{thread group}. Thread group is a collection of threads and other
25798 thread groups. A thread group always has a string identifier, a type,
25799 and may have additional attributes specific to the type. A new
25800 command, @code{-list-thread-groups}, returns the list of top-level
25801 thread groups, which correspond to processes that @value{GDBN} is
25802 debugging at the moment. By passing an identifier of a thread group
25803 to the @code{-list-thread-groups} command, it is possible to obtain
25804 the members of specific thread group.
25806 To allow the user to easily discover processes, and other objects, he
25807 wishes to debug, a concept of @dfn{available thread group} is
25808 introduced. Available thread group is an thread group that
25809 @value{GDBN} is not debugging, but that can be attached to, using the
25810 @code{-target-attach} command. The list of available top-level thread
25811 groups can be obtained using @samp{-list-thread-groups --available}.
25812 In general, the content of a thread group may be only retrieved only
25813 after attaching to that thread group.
25815 Thread groups are related to inferiors (@pxref{Inferiors and
25816 Programs}). Each inferior corresponds to a thread group of a special
25817 type @samp{process}, and some additional operations are permitted on
25818 such thread groups.
25820 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25821 @node GDB/MI Command Syntax
25822 @section @sc{gdb/mi} Command Syntax
25825 * GDB/MI Input Syntax::
25826 * GDB/MI Output Syntax::
25829 @node GDB/MI Input Syntax
25830 @subsection @sc{gdb/mi} Input Syntax
25832 @cindex input syntax for @sc{gdb/mi}
25833 @cindex @sc{gdb/mi}, input syntax
25835 @item @var{command} @expansion{}
25836 @code{@var{cli-command} | @var{mi-command}}
25838 @item @var{cli-command} @expansion{}
25839 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25840 @var{cli-command} is any existing @value{GDBN} CLI command.
25842 @item @var{mi-command} @expansion{}
25843 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25844 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25846 @item @var{token} @expansion{}
25847 "any sequence of digits"
25849 @item @var{option} @expansion{}
25850 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25852 @item @var{parameter} @expansion{}
25853 @code{@var{non-blank-sequence} | @var{c-string}}
25855 @item @var{operation} @expansion{}
25856 @emph{any of the operations described in this chapter}
25858 @item @var{non-blank-sequence} @expansion{}
25859 @emph{anything, provided it doesn't contain special characters such as
25860 "-", @var{nl}, """ and of course " "}
25862 @item @var{c-string} @expansion{}
25863 @code{""" @var{seven-bit-iso-c-string-content} """}
25865 @item @var{nl} @expansion{}
25874 The CLI commands are still handled by the @sc{mi} interpreter; their
25875 output is described below.
25878 The @code{@var{token}}, when present, is passed back when the command
25882 Some @sc{mi} commands accept optional arguments as part of the parameter
25883 list. Each option is identified by a leading @samp{-} (dash) and may be
25884 followed by an optional argument parameter. Options occur first in the
25885 parameter list and can be delimited from normal parameters using
25886 @samp{--} (this is useful when some parameters begin with a dash).
25893 We want easy access to the existing CLI syntax (for debugging).
25896 We want it to be easy to spot a @sc{mi} operation.
25899 @node GDB/MI Output Syntax
25900 @subsection @sc{gdb/mi} Output Syntax
25902 @cindex output syntax of @sc{gdb/mi}
25903 @cindex @sc{gdb/mi}, output syntax
25904 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25905 followed, optionally, by a single result record. This result record
25906 is for the most recent command. The sequence of output records is
25907 terminated by @samp{(gdb)}.
25909 If an input command was prefixed with a @code{@var{token}} then the
25910 corresponding output for that command will also be prefixed by that same
25914 @item @var{output} @expansion{}
25915 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25917 @item @var{result-record} @expansion{}
25918 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25920 @item @var{out-of-band-record} @expansion{}
25921 @code{@var{async-record} | @var{stream-record}}
25923 @item @var{async-record} @expansion{}
25924 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25926 @item @var{exec-async-output} @expansion{}
25927 @code{[ @var{token} ] "*" @var{async-output}}
25929 @item @var{status-async-output} @expansion{}
25930 @code{[ @var{token} ] "+" @var{async-output}}
25932 @item @var{notify-async-output} @expansion{}
25933 @code{[ @var{token} ] "=" @var{async-output}}
25935 @item @var{async-output} @expansion{}
25936 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
25938 @item @var{result-class} @expansion{}
25939 @code{"done" | "running" | "connected" | "error" | "exit"}
25941 @item @var{async-class} @expansion{}
25942 @code{"stopped" | @var{others}} (where @var{others} will be added
25943 depending on the needs---this is still in development).
25945 @item @var{result} @expansion{}
25946 @code{ @var{variable} "=" @var{value}}
25948 @item @var{variable} @expansion{}
25949 @code{ @var{string} }
25951 @item @var{value} @expansion{}
25952 @code{ @var{const} | @var{tuple} | @var{list} }
25954 @item @var{const} @expansion{}
25955 @code{@var{c-string}}
25957 @item @var{tuple} @expansion{}
25958 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25960 @item @var{list} @expansion{}
25961 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25962 @var{result} ( "," @var{result} )* "]" }
25964 @item @var{stream-record} @expansion{}
25965 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25967 @item @var{console-stream-output} @expansion{}
25968 @code{"~" @var{c-string}}
25970 @item @var{target-stream-output} @expansion{}
25971 @code{"@@" @var{c-string}}
25973 @item @var{log-stream-output} @expansion{}
25974 @code{"&" @var{c-string}}
25976 @item @var{nl} @expansion{}
25979 @item @var{token} @expansion{}
25980 @emph{any sequence of digits}.
25988 All output sequences end in a single line containing a period.
25991 The @code{@var{token}} is from the corresponding request. Note that
25992 for all async output, while the token is allowed by the grammar and
25993 may be output by future versions of @value{GDBN} for select async
25994 output messages, it is generally omitted. Frontends should treat
25995 all async output as reporting general changes in the state of the
25996 target and there should be no need to associate async output to any
26000 @cindex status output in @sc{gdb/mi}
26001 @var{status-async-output} contains on-going status information about the
26002 progress of a slow operation. It can be discarded. All status output is
26003 prefixed by @samp{+}.
26006 @cindex async output in @sc{gdb/mi}
26007 @var{exec-async-output} contains asynchronous state change on the target
26008 (stopped, started, disappeared). All async output is prefixed by
26012 @cindex notify output in @sc{gdb/mi}
26013 @var{notify-async-output} contains supplementary information that the
26014 client should handle (e.g., a new breakpoint information). All notify
26015 output is prefixed by @samp{=}.
26018 @cindex console output in @sc{gdb/mi}
26019 @var{console-stream-output} is output that should be displayed as is in the
26020 console. It is the textual response to a CLI command. All the console
26021 output is prefixed by @samp{~}.
26024 @cindex target output in @sc{gdb/mi}
26025 @var{target-stream-output} is the output produced by the target program.
26026 All the target output is prefixed by @samp{@@}.
26029 @cindex log output in @sc{gdb/mi}
26030 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26031 instance messages that should be displayed as part of an error log. All
26032 the log output is prefixed by @samp{&}.
26035 @cindex list output in @sc{gdb/mi}
26036 New @sc{gdb/mi} commands should only output @var{lists} containing
26042 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26043 details about the various output records.
26045 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26046 @node GDB/MI Compatibility with CLI
26047 @section @sc{gdb/mi} Compatibility with CLI
26049 @cindex compatibility, @sc{gdb/mi} and CLI
26050 @cindex @sc{gdb/mi}, compatibility with CLI
26052 For the developers convenience CLI commands can be entered directly,
26053 but there may be some unexpected behaviour. For example, commands
26054 that query the user will behave as if the user replied yes, breakpoint
26055 command lists are not executed and some CLI commands, such as
26056 @code{if}, @code{when} and @code{define}, prompt for further input with
26057 @samp{>}, which is not valid MI output.
26059 This feature may be removed at some stage in the future and it is
26060 recommended that front ends use the @code{-interpreter-exec} command
26061 (@pxref{-interpreter-exec}).
26063 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26064 @node GDB/MI Development and Front Ends
26065 @section @sc{gdb/mi} Development and Front Ends
26066 @cindex @sc{gdb/mi} development
26068 The application which takes the MI output and presents the state of the
26069 program being debugged to the user is called a @dfn{front end}.
26071 Although @sc{gdb/mi} is still incomplete, it is currently being used
26072 by a variety of front ends to @value{GDBN}. This makes it difficult
26073 to introduce new functionality without breaking existing usage. This
26074 section tries to minimize the problems by describing how the protocol
26077 Some changes in MI need not break a carefully designed front end, and
26078 for these the MI version will remain unchanged. The following is a
26079 list of changes that may occur within one level, so front ends should
26080 parse MI output in a way that can handle them:
26084 New MI commands may be added.
26087 New fields may be added to the output of any MI command.
26090 The range of values for fields with specified values, e.g.,
26091 @code{in_scope} (@pxref{-var-update}) may be extended.
26093 @c The format of field's content e.g type prefix, may change so parse it
26094 @c at your own risk. Yes, in general?
26096 @c The order of fields may change? Shouldn't really matter but it might
26097 @c resolve inconsistencies.
26100 If the changes are likely to break front ends, the MI version level
26101 will be increased by one. This will allow the front end to parse the
26102 output according to the MI version. Apart from mi0, new versions of
26103 @value{GDBN} will not support old versions of MI and it will be the
26104 responsibility of the front end to work with the new one.
26106 @c Starting with mi3, add a new command -mi-version that prints the MI
26109 The best way to avoid unexpected changes in MI that might break your front
26110 end is to make your project known to @value{GDBN} developers and
26111 follow development on @email{gdb@@sourceware.org} and
26112 @email{gdb-patches@@sourceware.org}.
26113 @cindex mailing lists
26115 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26116 @node GDB/MI Output Records
26117 @section @sc{gdb/mi} Output Records
26120 * GDB/MI Result Records::
26121 * GDB/MI Stream Records::
26122 * GDB/MI Async Records::
26123 * GDB/MI Frame Information::
26124 * GDB/MI Thread Information::
26125 * GDB/MI Ada Exception Information::
26128 @node GDB/MI Result Records
26129 @subsection @sc{gdb/mi} Result Records
26131 @cindex result records in @sc{gdb/mi}
26132 @cindex @sc{gdb/mi}, result records
26133 In addition to a number of out-of-band notifications, the response to a
26134 @sc{gdb/mi} command includes one of the following result indications:
26138 @item "^done" [ "," @var{results} ]
26139 The synchronous operation was successful, @code{@var{results}} are the return
26144 This result record is equivalent to @samp{^done}. Historically, it
26145 was output instead of @samp{^done} if the command has resumed the
26146 target. This behaviour is maintained for backward compatibility, but
26147 all frontends should treat @samp{^done} and @samp{^running}
26148 identically and rely on the @samp{*running} output record to determine
26149 which threads are resumed.
26153 @value{GDBN} has connected to a remote target.
26155 @item "^error" "," @var{c-string}
26157 The operation failed. The @code{@var{c-string}} contains the corresponding
26162 @value{GDBN} has terminated.
26166 @node GDB/MI Stream Records
26167 @subsection @sc{gdb/mi} Stream Records
26169 @cindex @sc{gdb/mi}, stream records
26170 @cindex stream records in @sc{gdb/mi}
26171 @value{GDBN} internally maintains a number of output streams: the console, the
26172 target, and the log. The output intended for each of these streams is
26173 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26175 Each stream record begins with a unique @dfn{prefix character} which
26176 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26177 Syntax}). In addition to the prefix, each stream record contains a
26178 @code{@var{string-output}}. This is either raw text (with an implicit new
26179 line) or a quoted C string (which does not contain an implicit newline).
26182 @item "~" @var{string-output}
26183 The console output stream contains text that should be displayed in the
26184 CLI console window. It contains the textual responses to CLI commands.
26186 @item "@@" @var{string-output}
26187 The target output stream contains any textual output from the running
26188 target. This is only present when GDB's event loop is truly
26189 asynchronous, which is currently only the case for remote targets.
26191 @item "&" @var{string-output}
26192 The log stream contains debugging messages being produced by @value{GDBN}'s
26196 @node GDB/MI Async Records
26197 @subsection @sc{gdb/mi} Async Records
26199 @cindex async records in @sc{gdb/mi}
26200 @cindex @sc{gdb/mi}, async records
26201 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26202 additional changes that have occurred. Those changes can either be a
26203 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26204 target activity (e.g., target stopped).
26206 The following is the list of possible async records:
26210 @item *running,thread-id="@var{thread}"
26211 The target is now running. The @var{thread} field tells which
26212 specific thread is now running, and can be @samp{all} if all threads
26213 are running. The frontend should assume that no interaction with a
26214 running thread is possible after this notification is produced.
26215 The frontend should not assume that this notification is output
26216 only once for any command. @value{GDBN} may emit this notification
26217 several times, either for different threads, because it cannot resume
26218 all threads together, or even for a single thread, if the thread must
26219 be stepped though some code before letting it run freely.
26221 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26222 The target has stopped. The @var{reason} field can have one of the
26226 @item breakpoint-hit
26227 A breakpoint was reached.
26228 @item watchpoint-trigger
26229 A watchpoint was triggered.
26230 @item read-watchpoint-trigger
26231 A read watchpoint was triggered.
26232 @item access-watchpoint-trigger
26233 An access watchpoint was triggered.
26234 @item function-finished
26235 An -exec-finish or similar CLI command was accomplished.
26236 @item location-reached
26237 An -exec-until or similar CLI command was accomplished.
26238 @item watchpoint-scope
26239 A watchpoint has gone out of scope.
26240 @item end-stepping-range
26241 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26242 similar CLI command was accomplished.
26243 @item exited-signalled
26244 The inferior exited because of a signal.
26246 The inferior exited.
26247 @item exited-normally
26248 The inferior exited normally.
26249 @item signal-received
26250 A signal was received by the inferior.
26252 The inferior has stopped due to a library being loaded or unloaded.
26253 This can only happen when @code{stop-on-solib-events} (@pxref{Files})
26256 The inferior has forked. This is reported when @code{catch fork}
26257 (@pxref{Set Catchpoints}) has been used.
26259 The inferior has vforked. This is reported in when @code{catch vfork}
26260 (@pxref{Set Catchpoints}) has been used.
26261 @item syscall-entry
26262 The inferior entered a system call. This is reported when @code{catch
26263 syscall} (@pxref{Set Catchpoints}) has been used.
26264 @item syscall-entry
26265 The inferior returned from a system call. This is reported when
26266 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26268 The inferior called @code{exec}. This is reported when @code{catch exec}
26269 (@pxref{Set Catchpoints}) has been used.
26272 The @var{id} field identifies the thread that directly caused the stop
26273 -- for example by hitting a breakpoint. Depending on whether all-stop
26274 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26275 stop all threads, or only the thread that directly triggered the stop.
26276 If all threads are stopped, the @var{stopped} field will have the
26277 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26278 field will be a list of thread identifiers. Presently, this list will
26279 always include a single thread, but frontend should be prepared to see
26280 several threads in the list. The @var{core} field reports the
26281 processor core on which the stop event has happened. This field may be absent
26282 if such information is not available.
26284 @item =thread-group-added,id="@var{id}"
26285 @itemx =thread-group-removed,id="@var{id}"
26286 A thread group was either added or removed. The @var{id} field
26287 contains the @value{GDBN} identifier of the thread group. When a thread
26288 group is added, it generally might not be associated with a running
26289 process. When a thread group is removed, its id becomes invalid and
26290 cannot be used in any way.
26292 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26293 A thread group became associated with a running program,
26294 either because the program was just started or the thread group
26295 was attached to a program. The @var{id} field contains the
26296 @value{GDBN} identifier of the thread group. The @var{pid} field
26297 contains process identifier, specific to the operating system.
26299 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26300 A thread group is no longer associated with a running program,
26301 either because the program has exited, or because it was detached
26302 from. The @var{id} field contains the @value{GDBN} identifier of the
26303 thread group. @var{code} is the exit code of the inferior; it exists
26304 only when the inferior exited with some code.
26306 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26307 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26308 A thread either was created, or has exited. The @var{id} field
26309 contains the @value{GDBN} identifier of the thread. The @var{gid}
26310 field identifies the thread group this thread belongs to.
26312 @item =thread-selected,id="@var{id}"
26313 Informs that the selected thread was changed as result of the last
26314 command. This notification is not emitted as result of @code{-thread-select}
26315 command but is emitted whenever an MI command that is not documented
26316 to change the selected thread actually changes it. In particular,
26317 invoking, directly or indirectly (via user-defined command), the CLI
26318 @code{thread} command, will generate this notification.
26320 We suggest that in response to this notification, front ends
26321 highlight the selected thread and cause subsequent commands to apply to
26324 @item =library-loaded,...
26325 Reports that a new library file was loaded by the program. This
26326 notification has 4 fields---@var{id}, @var{target-name},
26327 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26328 opaque identifier of the library. For remote debugging case,
26329 @var{target-name} and @var{host-name} fields give the name of the
26330 library file on the target, and on the host respectively. For native
26331 debugging, both those fields have the same value. The
26332 @var{symbols-loaded} field is emitted only for backward compatibility
26333 and should not be relied on to convey any useful information. The
26334 @var{thread-group} field, if present, specifies the id of the thread
26335 group in whose context the library was loaded. If the field is
26336 absent, it means the library was loaded in the context of all present
26339 @item =library-unloaded,...
26340 Reports that a library was unloaded by the program. This notification
26341 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26342 the same meaning as for the @code{=library-loaded} notification.
26343 The @var{thread-group} field, if present, specifies the id of the
26344 thread group in whose context the library was unloaded. If the field is
26345 absent, it means the library was unloaded in the context of all present
26348 @item =breakpoint-created,bkpt=@{...@}
26349 @itemx =breakpoint-modified,bkpt=@{...@}
26350 @itemx =breakpoint-deleted,bkpt=@{...@}
26351 Reports that a breakpoint was created, modified, or deleted,
26352 respectively. Only user-visible breakpoints are reported to the MI
26355 The @var{bkpt} argument is of the same form as returned by the various
26356 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
26358 Note that if a breakpoint is emitted in the result record of a
26359 command, then it will not also be emitted in an async record.
26363 @node GDB/MI Frame Information
26364 @subsection @sc{gdb/mi} Frame Information
26366 Response from many MI commands includes an information about stack
26367 frame. This information is a tuple that may have the following
26372 The level of the stack frame. The innermost frame has the level of
26373 zero. This field is always present.
26376 The name of the function corresponding to the frame. This field may
26377 be absent if @value{GDBN} is unable to determine the function name.
26380 The code address for the frame. This field is always present.
26383 The name of the source files that correspond to the frame's code
26384 address. This field may be absent.
26387 The source line corresponding to the frames' code address. This field
26391 The name of the binary file (either executable or shared library) the
26392 corresponds to the frame's code address. This field may be absent.
26396 @node GDB/MI Thread Information
26397 @subsection @sc{gdb/mi} Thread Information
26399 Whenever @value{GDBN} has to report an information about a thread, it
26400 uses a tuple with the following fields:
26404 The numeric id assigned to the thread by @value{GDBN}. This field is
26408 Target-specific string identifying the thread. This field is always present.
26411 Additional information about the thread provided by the target.
26412 It is supposed to be human-readable and not interpreted by the
26413 frontend. This field is optional.
26416 Either @samp{stopped} or @samp{running}, depending on whether the
26417 thread is presently running. This field is always present.
26420 The value of this field is an integer number of the processor core the
26421 thread was last seen on. This field is optional.
26424 @node GDB/MI Ada Exception Information
26425 @subsection @sc{gdb/mi} Ada Exception Information
26427 Whenever a @code{*stopped} record is emitted because the program
26428 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26429 @value{GDBN} provides the name of the exception that was raised via
26430 the @code{exception-name} field.
26432 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26433 @node GDB/MI Simple Examples
26434 @section Simple Examples of @sc{gdb/mi} Interaction
26435 @cindex @sc{gdb/mi}, simple examples
26437 This subsection presents several simple examples of interaction using
26438 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26439 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26440 the output received from @sc{gdb/mi}.
26442 Note the line breaks shown in the examples are here only for
26443 readability, they don't appear in the real output.
26445 @subheading Setting a Breakpoint
26447 Setting a breakpoint generates synchronous output which contains detailed
26448 information of the breakpoint.
26451 -> -break-insert main
26452 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26453 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26454 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
26458 @subheading Program Execution
26460 Program execution generates asynchronous records and MI gives the
26461 reason that execution stopped.
26467 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26468 frame=@{addr="0x08048564",func="main",
26469 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26470 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26475 <- *stopped,reason="exited-normally"
26479 @subheading Quitting @value{GDBN}
26481 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26489 Please note that @samp{^exit} is printed immediately, but it might
26490 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26491 performs necessary cleanups, including killing programs being debugged
26492 or disconnecting from debug hardware, so the frontend should wait till
26493 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26494 fails to exit in reasonable time.
26496 @subheading A Bad Command
26498 Here's what happens if you pass a non-existent command:
26502 <- ^error,msg="Undefined MI command: rubbish"
26507 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26508 @node GDB/MI Command Description Format
26509 @section @sc{gdb/mi} Command Description Format
26511 The remaining sections describe blocks of commands. Each block of
26512 commands is laid out in a fashion similar to this section.
26514 @subheading Motivation
26516 The motivation for this collection of commands.
26518 @subheading Introduction
26520 A brief introduction to this collection of commands as a whole.
26522 @subheading Commands
26524 For each command in the block, the following is described:
26526 @subsubheading Synopsis
26529 -command @var{args}@dots{}
26532 @subsubheading Result
26534 @subsubheading @value{GDBN} Command
26536 The corresponding @value{GDBN} CLI command(s), if any.
26538 @subsubheading Example
26540 Example(s) formatted for readability. Some of the described commands have
26541 not been implemented yet and these are labeled N.A.@: (not available).
26544 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26545 @node GDB/MI Breakpoint Commands
26546 @section @sc{gdb/mi} Breakpoint Commands
26548 @cindex breakpoint commands for @sc{gdb/mi}
26549 @cindex @sc{gdb/mi}, breakpoint commands
26550 This section documents @sc{gdb/mi} commands for manipulating
26553 @subheading The @code{-break-after} Command
26554 @findex -break-after
26556 @subsubheading Synopsis
26559 -break-after @var{number} @var{count}
26562 The breakpoint number @var{number} is not in effect until it has been
26563 hit @var{count} times. To see how this is reflected in the output of
26564 the @samp{-break-list} command, see the description of the
26565 @samp{-break-list} command below.
26567 @subsubheading @value{GDBN} Command
26569 The corresponding @value{GDBN} command is @samp{ignore}.
26571 @subsubheading Example
26576 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26577 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26578 fullname="/home/foo/hello.c",line="5",times="0"@}
26585 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26586 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26587 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26588 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26589 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26590 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26591 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26592 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26593 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26594 line="5",times="0",ignore="3"@}]@}
26599 @subheading The @code{-break-catch} Command
26600 @findex -break-catch
26603 @subheading The @code{-break-commands} Command
26604 @findex -break-commands
26606 @subsubheading Synopsis
26609 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26612 Specifies the CLI commands that should be executed when breakpoint
26613 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26614 are the commands. If no command is specified, any previously-set
26615 commands are cleared. @xref{Break Commands}. Typical use of this
26616 functionality is tracing a program, that is, printing of values of
26617 some variables whenever breakpoint is hit and then continuing.
26619 @subsubheading @value{GDBN} Command
26621 The corresponding @value{GDBN} command is @samp{commands}.
26623 @subsubheading Example
26628 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26629 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26630 fullname="/home/foo/hello.c",line="5",times="0"@}
26632 -break-commands 1 "print v" "continue"
26637 @subheading The @code{-break-condition} Command
26638 @findex -break-condition
26640 @subsubheading Synopsis
26643 -break-condition @var{number} @var{expr}
26646 Breakpoint @var{number} will stop the program only if the condition in
26647 @var{expr} is true. The condition becomes part of the
26648 @samp{-break-list} output (see the description of the @samp{-break-list}
26651 @subsubheading @value{GDBN} Command
26653 The corresponding @value{GDBN} command is @samp{condition}.
26655 @subsubheading Example
26659 -break-condition 1 1
26663 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26664 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26665 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26666 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26667 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26668 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26669 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26670 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26671 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26672 line="5",cond="1",times="0",ignore="3"@}]@}
26676 @subheading The @code{-break-delete} Command
26677 @findex -break-delete
26679 @subsubheading Synopsis
26682 -break-delete ( @var{breakpoint} )+
26685 Delete the breakpoint(s) whose number(s) are specified in the argument
26686 list. This is obviously reflected in the breakpoint list.
26688 @subsubheading @value{GDBN} Command
26690 The corresponding @value{GDBN} command is @samp{delete}.
26692 @subsubheading Example
26700 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26701 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26702 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26703 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26704 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26705 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26706 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26711 @subheading The @code{-break-disable} Command
26712 @findex -break-disable
26714 @subsubheading Synopsis
26717 -break-disable ( @var{breakpoint} )+
26720 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26721 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26723 @subsubheading @value{GDBN} Command
26725 The corresponding @value{GDBN} command is @samp{disable}.
26727 @subsubheading Example
26735 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26736 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26737 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26738 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26739 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26740 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26741 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26742 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26743 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26744 line="5",times="0"@}]@}
26748 @subheading The @code{-break-enable} Command
26749 @findex -break-enable
26751 @subsubheading Synopsis
26754 -break-enable ( @var{breakpoint} )+
26757 Enable (previously disabled) @var{breakpoint}(s).
26759 @subsubheading @value{GDBN} Command
26761 The corresponding @value{GDBN} command is @samp{enable}.
26763 @subsubheading Example
26771 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26772 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26773 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26774 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26775 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26776 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26777 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26778 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26779 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26780 line="5",times="0"@}]@}
26784 @subheading The @code{-break-info} Command
26785 @findex -break-info
26787 @subsubheading Synopsis
26790 -break-info @var{breakpoint}
26794 Get information about a single breakpoint.
26796 @subsubheading @value{GDBN} Command
26798 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26800 @subsubheading Example
26803 @subheading The @code{-break-insert} Command
26804 @findex -break-insert
26806 @subsubheading Synopsis
26809 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26810 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26811 [ -p @var{thread} ] [ @var{location} ]
26815 If specified, @var{location}, can be one of:
26822 @item filename:linenum
26823 @item filename:function
26827 The possible optional parameters of this command are:
26831 Insert a temporary breakpoint.
26833 Insert a hardware breakpoint.
26834 @item -c @var{condition}
26835 Make the breakpoint conditional on @var{condition}.
26836 @item -i @var{ignore-count}
26837 Initialize the @var{ignore-count}.
26839 If @var{location} cannot be parsed (for example if it
26840 refers to unknown files or functions), create a pending
26841 breakpoint. Without this flag, @value{GDBN} will report
26842 an error, and won't create a breakpoint, if @var{location}
26845 Create a disabled breakpoint.
26847 Create a tracepoint. @xref{Tracepoints}. When this parameter
26848 is used together with @samp{-h}, a fast tracepoint is created.
26851 @subsubheading Result
26853 The result is in the form:
26856 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
26857 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
26858 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
26859 times="@var{times}"@}
26863 where @var{number} is the @value{GDBN} number for this breakpoint,
26864 @var{funcname} is the name of the function where the breakpoint was
26865 inserted, @var{filename} is the name of the source file which contains
26866 this function, @var{lineno} is the source line number within that file
26867 and @var{times} the number of times that the breakpoint has been hit
26868 (always 0 for -break-insert but may be greater for -break-info or -break-list
26869 which use the same output).
26871 Note: this format is open to change.
26872 @c An out-of-band breakpoint instead of part of the result?
26874 @subsubheading @value{GDBN} Command
26876 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26877 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
26879 @subsubheading Example
26884 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26885 fullname="/home/foo/recursive2.c,line="4",times="0"@}
26887 -break-insert -t foo
26888 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26889 fullname="/home/foo/recursive2.c,line="11",times="0"@}
26892 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26893 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26894 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26895 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26896 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26897 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26898 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26899 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26900 addr="0x0001072c", func="main",file="recursive2.c",
26901 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
26902 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26903 addr="0x00010774",func="foo",file="recursive2.c",
26904 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
26906 -break-insert -r foo.*
26907 ~int foo(int, int);
26908 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26909 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
26913 @subheading The @code{-break-list} Command
26914 @findex -break-list
26916 @subsubheading Synopsis
26922 Displays the list of inserted breakpoints, showing the following fields:
26926 number of the breakpoint
26928 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26930 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26933 is the breakpoint enabled or no: @samp{y} or @samp{n}
26935 memory location at which the breakpoint is set
26937 logical location of the breakpoint, expressed by function name, file
26940 number of times the breakpoint has been hit
26943 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26944 @code{body} field is an empty list.
26946 @subsubheading @value{GDBN} Command
26948 The corresponding @value{GDBN} command is @samp{info break}.
26950 @subsubheading Example
26955 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26956 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26957 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26958 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26959 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26960 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26961 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26962 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26963 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
26964 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26965 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26966 line="13",times="0"@}]@}
26970 Here's an example of the result when there are no breakpoints:
26975 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26976 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26977 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26978 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26979 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26980 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26981 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26986 @subheading The @code{-break-passcount} Command
26987 @findex -break-passcount
26989 @subsubheading Synopsis
26992 -break-passcount @var{tracepoint-number} @var{passcount}
26995 Set the passcount for tracepoint @var{tracepoint-number} to
26996 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26997 is not a tracepoint, error is emitted. This corresponds to CLI
26998 command @samp{passcount}.
27000 @subheading The @code{-break-watch} Command
27001 @findex -break-watch
27003 @subsubheading Synopsis
27006 -break-watch [ -a | -r ]
27009 Create a watchpoint. With the @samp{-a} option it will create an
27010 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27011 read from or on a write to the memory location. With the @samp{-r}
27012 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27013 trigger only when the memory location is accessed for reading. Without
27014 either of the options, the watchpoint created is a regular watchpoint,
27015 i.e., it will trigger when the memory location is accessed for writing.
27016 @xref{Set Watchpoints, , Setting Watchpoints}.
27018 Note that @samp{-break-list} will report a single list of watchpoints and
27019 breakpoints inserted.
27021 @subsubheading @value{GDBN} Command
27023 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27026 @subsubheading Example
27028 Setting a watchpoint on a variable in the @code{main} function:
27033 ^done,wpt=@{number="2",exp="x"@}
27038 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27039 value=@{old="-268439212",new="55"@},
27040 frame=@{func="main",args=[],file="recursive2.c",
27041 fullname="/home/foo/bar/recursive2.c",line="5"@}
27045 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27046 the program execution twice: first for the variable changing value, then
27047 for the watchpoint going out of scope.
27052 ^done,wpt=@{number="5",exp="C"@}
27057 *stopped,reason="watchpoint-trigger",
27058 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27059 frame=@{func="callee4",args=[],
27060 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27061 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27066 *stopped,reason="watchpoint-scope",wpnum="5",
27067 frame=@{func="callee3",args=[@{name="strarg",
27068 value="0x11940 \"A string argument.\""@}],
27069 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27070 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27074 Listing breakpoints and watchpoints, at different points in the program
27075 execution. Note that once the watchpoint goes out of scope, it is
27081 ^done,wpt=@{number="2",exp="C"@}
27084 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27085 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27086 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27087 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27088 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27089 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27090 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27091 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27092 addr="0x00010734",func="callee4",
27093 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27094 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
27095 bkpt=@{number="2",type="watchpoint",disp="keep",
27096 enabled="y",addr="",what="C",times="0"@}]@}
27101 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27102 value=@{old="-276895068",new="3"@},
27103 frame=@{func="callee4",args=[],
27104 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27105 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27108 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27109 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27110 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27111 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27112 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27113 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27114 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27115 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27116 addr="0x00010734",func="callee4",
27117 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27118 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
27119 bkpt=@{number="2",type="watchpoint",disp="keep",
27120 enabled="y",addr="",what="C",times="-5"@}]@}
27124 ^done,reason="watchpoint-scope",wpnum="2",
27125 frame=@{func="callee3",args=[@{name="strarg",
27126 value="0x11940 \"A string argument.\""@}],
27127 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27128 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27131 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27132 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27133 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27134 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27135 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27136 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27137 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27138 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27139 addr="0x00010734",func="callee4",
27140 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27141 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27146 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27147 @node GDB/MI Program Context
27148 @section @sc{gdb/mi} Program Context
27150 @subheading The @code{-exec-arguments} Command
27151 @findex -exec-arguments
27154 @subsubheading Synopsis
27157 -exec-arguments @var{args}
27160 Set the inferior program arguments, to be used in the next
27163 @subsubheading @value{GDBN} Command
27165 The corresponding @value{GDBN} command is @samp{set args}.
27167 @subsubheading Example
27171 -exec-arguments -v word
27178 @subheading The @code{-exec-show-arguments} Command
27179 @findex -exec-show-arguments
27181 @subsubheading Synopsis
27184 -exec-show-arguments
27187 Print the arguments of the program.
27189 @subsubheading @value{GDBN} Command
27191 The corresponding @value{GDBN} command is @samp{show args}.
27193 @subsubheading Example
27198 @subheading The @code{-environment-cd} Command
27199 @findex -environment-cd
27201 @subsubheading Synopsis
27204 -environment-cd @var{pathdir}
27207 Set @value{GDBN}'s working directory.
27209 @subsubheading @value{GDBN} Command
27211 The corresponding @value{GDBN} command is @samp{cd}.
27213 @subsubheading Example
27217 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27223 @subheading The @code{-environment-directory} Command
27224 @findex -environment-directory
27226 @subsubheading Synopsis
27229 -environment-directory [ -r ] [ @var{pathdir} ]+
27232 Add directories @var{pathdir} to beginning of search path for source files.
27233 If the @samp{-r} option is used, the search path is reset to the default
27234 search path. If directories @var{pathdir} are supplied in addition to the
27235 @samp{-r} option, the search path is first reset and then addition
27237 Multiple directories may be specified, separated by blanks. Specifying
27238 multiple directories in a single command
27239 results in the directories added to the beginning of the
27240 search path in the same order they were presented in the command.
27241 If blanks are needed as
27242 part of a directory name, double-quotes should be used around
27243 the name. In the command output, the path will show up separated
27244 by the system directory-separator character. The directory-separator
27245 character must not be used
27246 in any directory name.
27247 If no directories are specified, the current search path is displayed.
27249 @subsubheading @value{GDBN} Command
27251 The corresponding @value{GDBN} command is @samp{dir}.
27253 @subsubheading Example
27257 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27258 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27260 -environment-directory ""
27261 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27263 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27264 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27266 -environment-directory -r
27267 ^done,source-path="$cdir:$cwd"
27272 @subheading The @code{-environment-path} Command
27273 @findex -environment-path
27275 @subsubheading Synopsis
27278 -environment-path [ -r ] [ @var{pathdir} ]+
27281 Add directories @var{pathdir} to beginning of search path for object files.
27282 If the @samp{-r} option is used, the search path is reset to the original
27283 search path that existed at gdb start-up. If directories @var{pathdir} are
27284 supplied in addition to the
27285 @samp{-r} option, the search path is first reset and then addition
27287 Multiple directories may be specified, separated by blanks. Specifying
27288 multiple directories in a single command
27289 results in the directories added to the beginning of the
27290 search path in the same order they were presented in the command.
27291 If blanks are needed as
27292 part of a directory name, double-quotes should be used around
27293 the name. In the command output, the path will show up separated
27294 by the system directory-separator character. The directory-separator
27295 character must not be used
27296 in any directory name.
27297 If no directories are specified, the current path is displayed.
27300 @subsubheading @value{GDBN} Command
27302 The corresponding @value{GDBN} command is @samp{path}.
27304 @subsubheading Example
27309 ^done,path="/usr/bin"
27311 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27312 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27314 -environment-path -r /usr/local/bin
27315 ^done,path="/usr/local/bin:/usr/bin"
27320 @subheading The @code{-environment-pwd} Command
27321 @findex -environment-pwd
27323 @subsubheading Synopsis
27329 Show the current working directory.
27331 @subsubheading @value{GDBN} Command
27333 The corresponding @value{GDBN} command is @samp{pwd}.
27335 @subsubheading Example
27340 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27344 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27345 @node GDB/MI Thread Commands
27346 @section @sc{gdb/mi} Thread Commands
27349 @subheading The @code{-thread-info} Command
27350 @findex -thread-info
27352 @subsubheading Synopsis
27355 -thread-info [ @var{thread-id} ]
27358 Reports information about either a specific thread, if
27359 the @var{thread-id} parameter is present, or about all
27360 threads. When printing information about all threads,
27361 also reports the current thread.
27363 @subsubheading @value{GDBN} Command
27365 The @samp{info thread} command prints the same information
27368 @subsubheading Result
27370 The result is a list of threads. The following attributes are
27371 defined for a given thread:
27375 This field exists only for the current thread. It has the value @samp{*}.
27378 The identifier that @value{GDBN} uses to refer to the thread.
27381 The identifier that the target uses to refer to the thread.
27384 Extra information about the thread, in a target-specific format. This
27388 The name of the thread. If the user specified a name using the
27389 @code{thread name} command, then this name is given. Otherwise, if
27390 @value{GDBN} can extract the thread name from the target, then that
27391 name is given. If @value{GDBN} cannot find the thread name, then this
27395 The stack frame currently executing in the thread.
27398 The thread's state. The @samp{state} field may have the following
27403 The thread is stopped. Frame information is available for stopped
27407 The thread is running. There's no frame information for running
27413 If @value{GDBN} can find the CPU core on which this thread is running,
27414 then this field is the core identifier. This field is optional.
27418 @subsubheading Example
27423 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27424 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27425 args=[]@},state="running"@},
27426 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27427 frame=@{level="0",addr="0x0804891f",func="foo",
27428 args=[@{name="i",value="10"@}],
27429 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27430 state="running"@}],
27431 current-thread-id="1"
27435 @subheading The @code{-thread-list-ids} Command
27436 @findex -thread-list-ids
27438 @subsubheading Synopsis
27444 Produces a list of the currently known @value{GDBN} thread ids. At the
27445 end of the list it also prints the total number of such threads.
27447 This command is retained for historical reasons, the
27448 @code{-thread-info} command should be used instead.
27450 @subsubheading @value{GDBN} Command
27452 Part of @samp{info threads} supplies the same information.
27454 @subsubheading Example
27459 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27460 current-thread-id="1",number-of-threads="3"
27465 @subheading The @code{-thread-select} Command
27466 @findex -thread-select
27468 @subsubheading Synopsis
27471 -thread-select @var{threadnum}
27474 Make @var{threadnum} the current thread. It prints the number of the new
27475 current thread, and the topmost frame for that thread.
27477 This command is deprecated in favor of explicitly using the
27478 @samp{--thread} option to each command.
27480 @subsubheading @value{GDBN} Command
27482 The corresponding @value{GDBN} command is @samp{thread}.
27484 @subsubheading Example
27491 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27492 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27496 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27497 number-of-threads="3"
27500 ^done,new-thread-id="3",
27501 frame=@{level="0",func="vprintf",
27502 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27503 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27507 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27508 @node GDB/MI Ada Tasking Commands
27509 @section @sc{gdb/mi} Ada Tasking Commands
27511 @subheading The @code{-ada-task-info} Command
27512 @findex -ada-task-info
27514 @subsubheading Synopsis
27517 -ada-task-info [ @var{task-id} ]
27520 Reports information about either a specific Ada task, if the
27521 @var{task-id} parameter is present, or about all Ada tasks.
27523 @subsubheading @value{GDBN} Command
27525 The @samp{info tasks} command prints the same information
27526 about all Ada tasks (@pxref{Ada Tasks}).
27528 @subsubheading Result
27530 The result is a table of Ada tasks. The following columns are
27531 defined for each Ada task:
27535 This field exists only for the current thread. It has the value @samp{*}.
27538 The identifier that @value{GDBN} uses to refer to the Ada task.
27541 The identifier that the target uses to refer to the Ada task.
27544 The identifier of the thread corresponding to the Ada task.
27546 This field should always exist, as Ada tasks are always implemented
27547 on top of a thread. But if @value{GDBN} cannot find this corresponding
27548 thread for any reason, the field is omitted.
27551 This field exists only when the task was created by another task.
27552 In this case, it provides the ID of the parent task.
27555 The base priority of the task.
27558 The current state of the task. For a detailed description of the
27559 possible states, see @ref{Ada Tasks}.
27562 The name of the task.
27566 @subsubheading Example
27570 ^done,tasks=@{nr_rows="3",nr_cols="8",
27571 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27572 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27573 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27574 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27575 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27576 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27577 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27578 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27579 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27580 state="Child Termination Wait",name="main_task"@}]@}
27584 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27585 @node GDB/MI Program Execution
27586 @section @sc{gdb/mi} Program Execution
27588 These are the asynchronous commands which generate the out-of-band
27589 record @samp{*stopped}. Currently @value{GDBN} only really executes
27590 asynchronously with remote targets and this interaction is mimicked in
27593 @subheading The @code{-exec-continue} Command
27594 @findex -exec-continue
27596 @subsubheading Synopsis
27599 -exec-continue [--reverse] [--all|--thread-group N]
27602 Resumes the execution of the inferior program, which will continue
27603 to execute until it reaches a debugger stop event. If the
27604 @samp{--reverse} option is specified, execution resumes in reverse until
27605 it reaches a stop event. Stop events may include
27608 breakpoints or watchpoints
27610 signals or exceptions
27612 the end of the process (or its beginning under @samp{--reverse})
27614 the end or beginning of a replay log if one is being used.
27616 In all-stop mode (@pxref{All-Stop
27617 Mode}), may resume only one thread, or all threads, depending on the
27618 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27619 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27620 ignored in all-stop mode. If the @samp{--thread-group} options is
27621 specified, then all threads in that thread group are resumed.
27623 @subsubheading @value{GDBN} Command
27625 The corresponding @value{GDBN} corresponding is @samp{continue}.
27627 @subsubheading Example
27634 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27635 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27641 @subheading The @code{-exec-finish} Command
27642 @findex -exec-finish
27644 @subsubheading Synopsis
27647 -exec-finish [--reverse]
27650 Resumes the execution of the inferior program until the current
27651 function is exited. Displays the results returned by the function.
27652 If the @samp{--reverse} option is specified, resumes the reverse
27653 execution of the inferior program until the point where current
27654 function was called.
27656 @subsubheading @value{GDBN} Command
27658 The corresponding @value{GDBN} command is @samp{finish}.
27660 @subsubheading Example
27662 Function returning @code{void}.
27669 *stopped,reason="function-finished",frame=@{func="main",args=[],
27670 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27674 Function returning other than @code{void}. The name of the internal
27675 @value{GDBN} variable storing the result is printed, together with the
27682 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27683 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27684 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27685 gdb-result-var="$1",return-value="0"
27690 @subheading The @code{-exec-interrupt} Command
27691 @findex -exec-interrupt
27693 @subsubheading Synopsis
27696 -exec-interrupt [--all|--thread-group N]
27699 Interrupts the background execution of the target. Note how the token
27700 associated with the stop message is the one for the execution command
27701 that has been interrupted. The token for the interrupt itself only
27702 appears in the @samp{^done} output. If the user is trying to
27703 interrupt a non-running program, an error message will be printed.
27705 Note that when asynchronous execution is enabled, this command is
27706 asynchronous just like other execution commands. That is, first the
27707 @samp{^done} response will be printed, and the target stop will be
27708 reported after that using the @samp{*stopped} notification.
27710 In non-stop mode, only the context thread is interrupted by default.
27711 All threads (in all inferiors) will be interrupted if the
27712 @samp{--all} option is specified. If the @samp{--thread-group}
27713 option is specified, all threads in that group will be interrupted.
27715 @subsubheading @value{GDBN} Command
27717 The corresponding @value{GDBN} command is @samp{interrupt}.
27719 @subsubheading Example
27730 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27731 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27732 fullname="/home/foo/bar/try.c",line="13"@}
27737 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27741 @subheading The @code{-exec-jump} Command
27744 @subsubheading Synopsis
27747 -exec-jump @var{location}
27750 Resumes execution of the inferior program at the location specified by
27751 parameter. @xref{Specify Location}, for a description of the
27752 different forms of @var{location}.
27754 @subsubheading @value{GDBN} Command
27756 The corresponding @value{GDBN} command is @samp{jump}.
27758 @subsubheading Example
27761 -exec-jump foo.c:10
27762 *running,thread-id="all"
27767 @subheading The @code{-exec-next} Command
27770 @subsubheading Synopsis
27773 -exec-next [--reverse]
27776 Resumes execution of the inferior program, stopping when the beginning
27777 of the next source line is reached.
27779 If the @samp{--reverse} option is specified, resumes reverse execution
27780 of the inferior program, stopping at the beginning of the previous
27781 source line. If you issue this command on the first line of a
27782 function, it will take you back to the caller of that function, to the
27783 source line where the function was called.
27786 @subsubheading @value{GDBN} Command
27788 The corresponding @value{GDBN} command is @samp{next}.
27790 @subsubheading Example
27796 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27801 @subheading The @code{-exec-next-instruction} Command
27802 @findex -exec-next-instruction
27804 @subsubheading Synopsis
27807 -exec-next-instruction [--reverse]
27810 Executes one machine instruction. If the instruction is a function
27811 call, continues until the function returns. If the program stops at an
27812 instruction in the middle of a source line, the address will be
27815 If the @samp{--reverse} option is specified, resumes reverse execution
27816 of the inferior program, stopping at the previous instruction. If the
27817 previously executed instruction was a return from another function,
27818 it will continue to execute in reverse until the call to that function
27819 (from the current stack frame) is reached.
27821 @subsubheading @value{GDBN} Command
27823 The corresponding @value{GDBN} command is @samp{nexti}.
27825 @subsubheading Example
27829 -exec-next-instruction
27833 *stopped,reason="end-stepping-range",
27834 addr="0x000100d4",line="5",file="hello.c"
27839 @subheading The @code{-exec-return} Command
27840 @findex -exec-return
27842 @subsubheading Synopsis
27848 Makes current function return immediately. Doesn't execute the inferior.
27849 Displays the new current frame.
27851 @subsubheading @value{GDBN} Command
27853 The corresponding @value{GDBN} command is @samp{return}.
27855 @subsubheading Example
27859 200-break-insert callee4
27860 200^done,bkpt=@{number="1",addr="0x00010734",
27861 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27866 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27867 frame=@{func="callee4",args=[],
27868 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27869 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27875 111^done,frame=@{level="0",func="callee3",
27876 args=[@{name="strarg",
27877 value="0x11940 \"A string argument.\""@}],
27878 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27879 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27884 @subheading The @code{-exec-run} Command
27887 @subsubheading Synopsis
27890 -exec-run [--all | --thread-group N]
27893 Starts execution of the inferior from the beginning. The inferior
27894 executes until either a breakpoint is encountered or the program
27895 exits. In the latter case the output will include an exit code, if
27896 the program has exited exceptionally.
27898 When no option is specified, the current inferior is started. If the
27899 @samp{--thread-group} option is specified, it should refer to a thread
27900 group of type @samp{process}, and that thread group will be started.
27901 If the @samp{--all} option is specified, then all inferiors will be started.
27903 @subsubheading @value{GDBN} Command
27905 The corresponding @value{GDBN} command is @samp{run}.
27907 @subsubheading Examples
27912 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27917 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27918 frame=@{func="main",args=[],file="recursive2.c",
27919 fullname="/home/foo/bar/recursive2.c",line="4"@}
27924 Program exited normally:
27932 *stopped,reason="exited-normally"
27937 Program exited exceptionally:
27945 *stopped,reason="exited",exit-code="01"
27949 Another way the program can terminate is if it receives a signal such as
27950 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27954 *stopped,reason="exited-signalled",signal-name="SIGINT",
27955 signal-meaning="Interrupt"
27959 @c @subheading -exec-signal
27962 @subheading The @code{-exec-step} Command
27965 @subsubheading Synopsis
27968 -exec-step [--reverse]
27971 Resumes execution of the inferior program, stopping when the beginning
27972 of the next source line is reached, if the next source line is not a
27973 function call. If it is, stop at the first instruction of the called
27974 function. If the @samp{--reverse} option is specified, resumes reverse
27975 execution of the inferior program, stopping at the beginning of the
27976 previously executed source line.
27978 @subsubheading @value{GDBN} Command
27980 The corresponding @value{GDBN} command is @samp{step}.
27982 @subsubheading Example
27984 Stepping into a function:
27990 *stopped,reason="end-stepping-range",
27991 frame=@{func="foo",args=[@{name="a",value="10"@},
27992 @{name="b",value="0"@}],file="recursive2.c",
27993 fullname="/home/foo/bar/recursive2.c",line="11"@}
28003 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28008 @subheading The @code{-exec-step-instruction} Command
28009 @findex -exec-step-instruction
28011 @subsubheading Synopsis
28014 -exec-step-instruction [--reverse]
28017 Resumes the inferior which executes one machine instruction. If the
28018 @samp{--reverse} option is specified, resumes reverse execution of the
28019 inferior program, stopping at the previously executed instruction.
28020 The output, once @value{GDBN} has stopped, will vary depending on
28021 whether we have stopped in the middle of a source line or not. In the
28022 former case, the address at which the program stopped will be printed
28025 @subsubheading @value{GDBN} Command
28027 The corresponding @value{GDBN} command is @samp{stepi}.
28029 @subsubheading Example
28033 -exec-step-instruction
28037 *stopped,reason="end-stepping-range",
28038 frame=@{func="foo",args=[],file="try.c",
28039 fullname="/home/foo/bar/try.c",line="10"@}
28041 -exec-step-instruction
28045 *stopped,reason="end-stepping-range",
28046 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28047 fullname="/home/foo/bar/try.c",line="10"@}
28052 @subheading The @code{-exec-until} Command
28053 @findex -exec-until
28055 @subsubheading Synopsis
28058 -exec-until [ @var{location} ]
28061 Executes the inferior until the @var{location} specified in the
28062 argument is reached. If there is no argument, the inferior executes
28063 until a source line greater than the current one is reached. The
28064 reason for stopping in this case will be @samp{location-reached}.
28066 @subsubheading @value{GDBN} Command
28068 The corresponding @value{GDBN} command is @samp{until}.
28070 @subsubheading Example
28074 -exec-until recursive2.c:6
28078 *stopped,reason="location-reached",frame=@{func="main",args=[],
28079 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28084 @subheading -file-clear
28085 Is this going away????
28088 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28089 @node GDB/MI Stack Manipulation
28090 @section @sc{gdb/mi} Stack Manipulation Commands
28093 @subheading The @code{-stack-info-frame} Command
28094 @findex -stack-info-frame
28096 @subsubheading Synopsis
28102 Get info on the selected frame.
28104 @subsubheading @value{GDBN} Command
28106 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28107 (without arguments).
28109 @subsubheading Example
28114 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28115 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28116 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28120 @subheading The @code{-stack-info-depth} Command
28121 @findex -stack-info-depth
28123 @subsubheading Synopsis
28126 -stack-info-depth [ @var{max-depth} ]
28129 Return the depth of the stack. If the integer argument @var{max-depth}
28130 is specified, do not count beyond @var{max-depth} frames.
28132 @subsubheading @value{GDBN} Command
28134 There's no equivalent @value{GDBN} command.
28136 @subsubheading Example
28138 For a stack with frame levels 0 through 11:
28145 -stack-info-depth 4
28148 -stack-info-depth 12
28151 -stack-info-depth 11
28154 -stack-info-depth 13
28159 @subheading The @code{-stack-list-arguments} Command
28160 @findex -stack-list-arguments
28162 @subsubheading Synopsis
28165 -stack-list-arguments @var{print-values}
28166 [ @var{low-frame} @var{high-frame} ]
28169 Display a list of the arguments for the frames between @var{low-frame}
28170 and @var{high-frame} (inclusive). If @var{low-frame} and
28171 @var{high-frame} are not provided, list the arguments for the whole
28172 call stack. If the two arguments are equal, show the single frame
28173 at the corresponding level. It is an error if @var{low-frame} is
28174 larger than the actual number of frames. On the other hand,
28175 @var{high-frame} may be larger than the actual number of frames, in
28176 which case only existing frames will be returned.
28178 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28179 the variables; if it is 1 or @code{--all-values}, print also their
28180 values; and if it is 2 or @code{--simple-values}, print the name,
28181 type and value for simple data types, and the name and type for arrays,
28182 structures and unions.
28184 Use of this command to obtain arguments in a single frame is
28185 deprecated in favor of the @samp{-stack-list-variables} command.
28187 @subsubheading @value{GDBN} Command
28189 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28190 @samp{gdb_get_args} command which partially overlaps with the
28191 functionality of @samp{-stack-list-arguments}.
28193 @subsubheading Example
28200 frame=@{level="0",addr="0x00010734",func="callee4",
28201 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28202 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28203 frame=@{level="1",addr="0x0001076c",func="callee3",
28204 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28205 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28206 frame=@{level="2",addr="0x0001078c",func="callee2",
28207 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28208 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28209 frame=@{level="3",addr="0x000107b4",func="callee1",
28210 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28211 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28212 frame=@{level="4",addr="0x000107e0",func="main",
28213 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28214 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28216 -stack-list-arguments 0
28219 frame=@{level="0",args=[]@},
28220 frame=@{level="1",args=[name="strarg"]@},
28221 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28222 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28223 frame=@{level="4",args=[]@}]
28225 -stack-list-arguments 1
28228 frame=@{level="0",args=[]@},
28230 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28231 frame=@{level="2",args=[
28232 @{name="intarg",value="2"@},
28233 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28234 @{frame=@{level="3",args=[
28235 @{name="intarg",value="2"@},
28236 @{name="strarg",value="0x11940 \"A string argument.\""@},
28237 @{name="fltarg",value="3.5"@}]@},
28238 frame=@{level="4",args=[]@}]
28240 -stack-list-arguments 0 2 2
28241 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28243 -stack-list-arguments 1 2 2
28244 ^done,stack-args=[frame=@{level="2",
28245 args=[@{name="intarg",value="2"@},
28246 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28250 @c @subheading -stack-list-exception-handlers
28253 @subheading The @code{-stack-list-frames} Command
28254 @findex -stack-list-frames
28256 @subsubheading Synopsis
28259 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
28262 List the frames currently on the stack. For each frame it displays the
28267 The frame number, 0 being the topmost frame, i.e., the innermost function.
28269 The @code{$pc} value for that frame.
28273 File name of the source file where the function lives.
28274 @item @var{fullname}
28275 The full file name of the source file where the function lives.
28277 Line number corresponding to the @code{$pc}.
28279 The shared library where this function is defined. This is only given
28280 if the frame's function is not known.
28283 If invoked without arguments, this command prints a backtrace for the
28284 whole stack. If given two integer arguments, it shows the frames whose
28285 levels are between the two arguments (inclusive). If the two arguments
28286 are equal, it shows the single frame at the corresponding level. It is
28287 an error if @var{low-frame} is larger than the actual number of
28288 frames. On the other hand, @var{high-frame} may be larger than the
28289 actual number of frames, in which case only existing frames will be returned.
28291 @subsubheading @value{GDBN} Command
28293 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28295 @subsubheading Example
28297 Full stack backtrace:
28303 [frame=@{level="0",addr="0x0001076c",func="foo",
28304 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28305 frame=@{level="1",addr="0x000107a4",func="foo",
28306 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28307 frame=@{level="2",addr="0x000107a4",func="foo",
28308 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28309 frame=@{level="3",addr="0x000107a4",func="foo",
28310 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28311 frame=@{level="4",addr="0x000107a4",func="foo",
28312 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28313 frame=@{level="5",addr="0x000107a4",func="foo",
28314 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28315 frame=@{level="6",addr="0x000107a4",func="foo",
28316 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28317 frame=@{level="7",addr="0x000107a4",func="foo",
28318 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28319 frame=@{level="8",addr="0x000107a4",func="foo",
28320 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28321 frame=@{level="9",addr="0x000107a4",func="foo",
28322 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28323 frame=@{level="10",addr="0x000107a4",func="foo",
28324 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28325 frame=@{level="11",addr="0x00010738",func="main",
28326 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28330 Show frames between @var{low_frame} and @var{high_frame}:
28334 -stack-list-frames 3 5
28336 [frame=@{level="3",addr="0x000107a4",func="foo",
28337 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28338 frame=@{level="4",addr="0x000107a4",func="foo",
28339 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28340 frame=@{level="5",addr="0x000107a4",func="foo",
28341 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28345 Show a single frame:
28349 -stack-list-frames 3 3
28351 [frame=@{level="3",addr="0x000107a4",func="foo",
28352 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28357 @subheading The @code{-stack-list-locals} Command
28358 @findex -stack-list-locals
28360 @subsubheading Synopsis
28363 -stack-list-locals @var{print-values}
28366 Display the local variable names for the selected frame. If
28367 @var{print-values} is 0 or @code{--no-values}, print only the names of
28368 the variables; if it is 1 or @code{--all-values}, print also their
28369 values; and if it is 2 or @code{--simple-values}, print the name,
28370 type and value for simple data types, and the name and type for arrays,
28371 structures and unions. In this last case, a frontend can immediately
28372 display the value of simple data types and create variable objects for
28373 other data types when the user wishes to explore their values in
28376 This command is deprecated in favor of the
28377 @samp{-stack-list-variables} command.
28379 @subsubheading @value{GDBN} Command
28381 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28383 @subsubheading Example
28387 -stack-list-locals 0
28388 ^done,locals=[name="A",name="B",name="C"]
28390 -stack-list-locals --all-values
28391 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28392 @{name="C",value="@{1, 2, 3@}"@}]
28393 -stack-list-locals --simple-values
28394 ^done,locals=[@{name="A",type="int",value="1"@},
28395 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28399 @subheading The @code{-stack-list-variables} Command
28400 @findex -stack-list-variables
28402 @subsubheading Synopsis
28405 -stack-list-variables @var{print-values}
28408 Display the names of local variables and function arguments for the selected frame. If
28409 @var{print-values} is 0 or @code{--no-values}, print only the names of
28410 the variables; if it is 1 or @code{--all-values}, print also their
28411 values; and if it is 2 or @code{--simple-values}, print the name,
28412 type and value for simple data types, and the name and type for arrays,
28413 structures and unions.
28415 @subsubheading Example
28419 -stack-list-variables --thread 1 --frame 0 --all-values
28420 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28425 @subheading The @code{-stack-select-frame} Command
28426 @findex -stack-select-frame
28428 @subsubheading Synopsis
28431 -stack-select-frame @var{framenum}
28434 Change the selected frame. Select a different frame @var{framenum} on
28437 This command in deprecated in favor of passing the @samp{--frame}
28438 option to every command.
28440 @subsubheading @value{GDBN} Command
28442 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28443 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28445 @subsubheading Example
28449 -stack-select-frame 2
28454 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28455 @node GDB/MI Variable Objects
28456 @section @sc{gdb/mi} Variable Objects
28460 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28462 For the implementation of a variable debugger window (locals, watched
28463 expressions, etc.), we are proposing the adaptation of the existing code
28464 used by @code{Insight}.
28466 The two main reasons for that are:
28470 It has been proven in practice (it is already on its second generation).
28473 It will shorten development time (needless to say how important it is
28477 The original interface was designed to be used by Tcl code, so it was
28478 slightly changed so it could be used through @sc{gdb/mi}. This section
28479 describes the @sc{gdb/mi} operations that will be available and gives some
28480 hints about their use.
28482 @emph{Note}: In addition to the set of operations described here, we
28483 expect the @sc{gui} implementation of a variable window to require, at
28484 least, the following operations:
28487 @item @code{-gdb-show} @code{output-radix}
28488 @item @code{-stack-list-arguments}
28489 @item @code{-stack-list-locals}
28490 @item @code{-stack-select-frame}
28495 @subheading Introduction to Variable Objects
28497 @cindex variable objects in @sc{gdb/mi}
28499 Variable objects are "object-oriented" MI interface for examining and
28500 changing values of expressions. Unlike some other MI interfaces that
28501 work with expressions, variable objects are specifically designed for
28502 simple and efficient presentation in the frontend. A variable object
28503 is identified by string name. When a variable object is created, the
28504 frontend specifies the expression for that variable object. The
28505 expression can be a simple variable, or it can be an arbitrary complex
28506 expression, and can even involve CPU registers. After creating a
28507 variable object, the frontend can invoke other variable object
28508 operations---for example to obtain or change the value of a variable
28509 object, or to change display format.
28511 Variable objects have hierarchical tree structure. Any variable object
28512 that corresponds to a composite type, such as structure in C, has
28513 a number of child variable objects, for example corresponding to each
28514 element of a structure. A child variable object can itself have
28515 children, recursively. Recursion ends when we reach
28516 leaf variable objects, which always have built-in types. Child variable
28517 objects are created only by explicit request, so if a frontend
28518 is not interested in the children of a particular variable object, no
28519 child will be created.
28521 For a leaf variable object it is possible to obtain its value as a
28522 string, or set the value from a string. String value can be also
28523 obtained for a non-leaf variable object, but it's generally a string
28524 that only indicates the type of the object, and does not list its
28525 contents. Assignment to a non-leaf variable object is not allowed.
28527 A frontend does not need to read the values of all variable objects each time
28528 the program stops. Instead, MI provides an update command that lists all
28529 variable objects whose values has changed since the last update
28530 operation. This considerably reduces the amount of data that must
28531 be transferred to the frontend. As noted above, children variable
28532 objects are created on demand, and only leaf variable objects have a
28533 real value. As result, gdb will read target memory only for leaf
28534 variables that frontend has created.
28536 The automatic update is not always desirable. For example, a frontend
28537 might want to keep a value of some expression for future reference,
28538 and never update it. For another example, fetching memory is
28539 relatively slow for embedded targets, so a frontend might want
28540 to disable automatic update for the variables that are either not
28541 visible on the screen, or ``closed''. This is possible using so
28542 called ``frozen variable objects''. Such variable objects are never
28543 implicitly updated.
28545 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28546 fixed variable object, the expression is parsed when the variable
28547 object is created, including associating identifiers to specific
28548 variables. The meaning of expression never changes. For a floating
28549 variable object the values of variables whose names appear in the
28550 expressions are re-evaluated every time in the context of the current
28551 frame. Consider this example:
28556 struct work_state state;
28563 If a fixed variable object for the @code{state} variable is created in
28564 this function, and we enter the recursive call, the variable
28565 object will report the value of @code{state} in the top-level
28566 @code{do_work} invocation. On the other hand, a floating variable
28567 object will report the value of @code{state} in the current frame.
28569 If an expression specified when creating a fixed variable object
28570 refers to a local variable, the variable object becomes bound to the
28571 thread and frame in which the variable object is created. When such
28572 variable object is updated, @value{GDBN} makes sure that the
28573 thread/frame combination the variable object is bound to still exists,
28574 and re-evaluates the variable object in context of that thread/frame.
28576 The following is the complete set of @sc{gdb/mi} operations defined to
28577 access this functionality:
28579 @multitable @columnfractions .4 .6
28580 @item @strong{Operation}
28581 @tab @strong{Description}
28583 @item @code{-enable-pretty-printing}
28584 @tab enable Python-based pretty-printing
28585 @item @code{-var-create}
28586 @tab create a variable object
28587 @item @code{-var-delete}
28588 @tab delete the variable object and/or its children
28589 @item @code{-var-set-format}
28590 @tab set the display format of this variable
28591 @item @code{-var-show-format}
28592 @tab show the display format of this variable
28593 @item @code{-var-info-num-children}
28594 @tab tells how many children this object has
28595 @item @code{-var-list-children}
28596 @tab return a list of the object's children
28597 @item @code{-var-info-type}
28598 @tab show the type of this variable object
28599 @item @code{-var-info-expression}
28600 @tab print parent-relative expression that this variable object represents
28601 @item @code{-var-info-path-expression}
28602 @tab print full expression that this variable object represents
28603 @item @code{-var-show-attributes}
28604 @tab is this variable editable? does it exist here?
28605 @item @code{-var-evaluate-expression}
28606 @tab get the value of this variable
28607 @item @code{-var-assign}
28608 @tab set the value of this variable
28609 @item @code{-var-update}
28610 @tab update the variable and its children
28611 @item @code{-var-set-frozen}
28612 @tab set frozeness attribute
28613 @item @code{-var-set-update-range}
28614 @tab set range of children to display on update
28617 In the next subsection we describe each operation in detail and suggest
28618 how it can be used.
28620 @subheading Description And Use of Operations on Variable Objects
28622 @subheading The @code{-enable-pretty-printing} Command
28623 @findex -enable-pretty-printing
28626 -enable-pretty-printing
28629 @value{GDBN} allows Python-based visualizers to affect the output of the
28630 MI variable object commands. However, because there was no way to
28631 implement this in a fully backward-compatible way, a front end must
28632 request that this functionality be enabled.
28634 Once enabled, this feature cannot be disabled.
28636 Note that if Python support has not been compiled into @value{GDBN},
28637 this command will still succeed (and do nothing).
28639 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28640 may work differently in future versions of @value{GDBN}.
28642 @subheading The @code{-var-create} Command
28643 @findex -var-create
28645 @subsubheading Synopsis
28648 -var-create @{@var{name} | "-"@}
28649 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28652 This operation creates a variable object, which allows the monitoring of
28653 a variable, the result of an expression, a memory cell or a CPU
28656 The @var{name} parameter is the string by which the object can be
28657 referenced. It must be unique. If @samp{-} is specified, the varobj
28658 system will generate a string ``varNNNNNN'' automatically. It will be
28659 unique provided that one does not specify @var{name} of that format.
28660 The command fails if a duplicate name is found.
28662 The frame under which the expression should be evaluated can be
28663 specified by @var{frame-addr}. A @samp{*} indicates that the current
28664 frame should be used. A @samp{@@} indicates that a floating variable
28665 object must be created.
28667 @var{expression} is any expression valid on the current language set (must not
28668 begin with a @samp{*}), or one of the following:
28672 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28675 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28678 @samp{$@var{regname}} --- a CPU register name
28681 @cindex dynamic varobj
28682 A varobj's contents may be provided by a Python-based pretty-printer. In this
28683 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28684 have slightly different semantics in some cases. If the
28685 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28686 will never create a dynamic varobj. This ensures backward
28687 compatibility for existing clients.
28689 @subsubheading Result
28691 This operation returns attributes of the newly-created varobj. These
28696 The name of the varobj.
28699 The number of children of the varobj. This number is not necessarily
28700 reliable for a dynamic varobj. Instead, you must examine the
28701 @samp{has_more} attribute.
28704 The varobj's scalar value. For a varobj whose type is some sort of
28705 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28706 will not be interesting.
28709 The varobj's type. This is a string representation of the type, as
28710 would be printed by the @value{GDBN} CLI.
28713 If a variable object is bound to a specific thread, then this is the
28714 thread's identifier.
28717 For a dynamic varobj, this indicates whether there appear to be any
28718 children available. For a non-dynamic varobj, this will be 0.
28721 This attribute will be present and have the value @samp{1} if the
28722 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28723 then this attribute will not be present.
28726 A dynamic varobj can supply a display hint to the front end. The
28727 value comes directly from the Python pretty-printer object's
28728 @code{display_hint} method. @xref{Pretty Printing API}.
28731 Typical output will look like this:
28734 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28735 has_more="@var{has_more}"
28739 @subheading The @code{-var-delete} Command
28740 @findex -var-delete
28742 @subsubheading Synopsis
28745 -var-delete [ -c ] @var{name}
28748 Deletes a previously created variable object and all of its children.
28749 With the @samp{-c} option, just deletes the children.
28751 Returns an error if the object @var{name} is not found.
28754 @subheading The @code{-var-set-format} Command
28755 @findex -var-set-format
28757 @subsubheading Synopsis
28760 -var-set-format @var{name} @var{format-spec}
28763 Sets the output format for the value of the object @var{name} to be
28766 @anchor{-var-set-format}
28767 The syntax for the @var{format-spec} is as follows:
28770 @var{format-spec} @expansion{}
28771 @{binary | decimal | hexadecimal | octal | natural@}
28774 The natural format is the default format choosen automatically
28775 based on the variable type (like decimal for an @code{int}, hex
28776 for pointers, etc.).
28778 For a variable with children, the format is set only on the
28779 variable itself, and the children are not affected.
28781 @subheading The @code{-var-show-format} Command
28782 @findex -var-show-format
28784 @subsubheading Synopsis
28787 -var-show-format @var{name}
28790 Returns the format used to display the value of the object @var{name}.
28793 @var{format} @expansion{}
28798 @subheading The @code{-var-info-num-children} Command
28799 @findex -var-info-num-children
28801 @subsubheading Synopsis
28804 -var-info-num-children @var{name}
28807 Returns the number of children of a variable object @var{name}:
28813 Note that this number is not completely reliable for a dynamic varobj.
28814 It will return the current number of children, but more children may
28818 @subheading The @code{-var-list-children} Command
28819 @findex -var-list-children
28821 @subsubheading Synopsis
28824 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28826 @anchor{-var-list-children}
28828 Return a list of the children of the specified variable object and
28829 create variable objects for them, if they do not already exist. With
28830 a single argument or if @var{print-values} has a value of 0 or
28831 @code{--no-values}, print only the names of the variables; if
28832 @var{print-values} is 1 or @code{--all-values}, also print their
28833 values; and if it is 2 or @code{--simple-values} print the name and
28834 value for simple data types and just the name for arrays, structures
28837 @var{from} and @var{to}, if specified, indicate the range of children
28838 to report. If @var{from} or @var{to} is less than zero, the range is
28839 reset and all children will be reported. Otherwise, children starting
28840 at @var{from} (zero-based) and up to and excluding @var{to} will be
28843 If a child range is requested, it will only affect the current call to
28844 @code{-var-list-children}, but not future calls to @code{-var-update}.
28845 For this, you must instead use @code{-var-set-update-range}. The
28846 intent of this approach is to enable a front end to implement any
28847 update approach it likes; for example, scrolling a view may cause the
28848 front end to request more children with @code{-var-list-children}, and
28849 then the front end could call @code{-var-set-update-range} with a
28850 different range to ensure that future updates are restricted to just
28853 For each child the following results are returned:
28858 Name of the variable object created for this child.
28861 The expression to be shown to the user by the front end to designate this child.
28862 For example this may be the name of a structure member.
28864 For a dynamic varobj, this value cannot be used to form an
28865 expression. There is no way to do this at all with a dynamic varobj.
28867 For C/C@t{++} structures there are several pseudo children returned to
28868 designate access qualifiers. For these pseudo children @var{exp} is
28869 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28870 type and value are not present.
28872 A dynamic varobj will not report the access qualifying
28873 pseudo-children, regardless of the language. This information is not
28874 available at all with a dynamic varobj.
28877 Number of children this child has. For a dynamic varobj, this will be
28881 The type of the child.
28884 If values were requested, this is the value.
28887 If this variable object is associated with a thread, this is the thread id.
28888 Otherwise this result is not present.
28891 If the variable object is frozen, this variable will be present with a value of 1.
28894 The result may have its own attributes:
28898 A dynamic varobj can supply a display hint to the front end. The
28899 value comes directly from the Python pretty-printer object's
28900 @code{display_hint} method. @xref{Pretty Printing API}.
28903 This is an integer attribute which is nonzero if there are children
28904 remaining after the end of the selected range.
28907 @subsubheading Example
28911 -var-list-children n
28912 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28913 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28915 -var-list-children --all-values n
28916 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28917 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28921 @subheading The @code{-var-info-type} Command
28922 @findex -var-info-type
28924 @subsubheading Synopsis
28927 -var-info-type @var{name}
28930 Returns the type of the specified variable @var{name}. The type is
28931 returned as a string in the same format as it is output by the
28935 type=@var{typename}
28939 @subheading The @code{-var-info-expression} Command
28940 @findex -var-info-expression
28942 @subsubheading Synopsis
28945 -var-info-expression @var{name}
28948 Returns a string that is suitable for presenting this
28949 variable object in user interface. The string is generally
28950 not valid expression in the current language, and cannot be evaluated.
28952 For example, if @code{a} is an array, and variable object
28953 @code{A} was created for @code{a}, then we'll get this output:
28956 (gdb) -var-info-expression A.1
28957 ^done,lang="C",exp="1"
28961 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
28963 Note that the output of the @code{-var-list-children} command also
28964 includes those expressions, so the @code{-var-info-expression} command
28967 @subheading The @code{-var-info-path-expression} Command
28968 @findex -var-info-path-expression
28970 @subsubheading Synopsis
28973 -var-info-path-expression @var{name}
28976 Returns an expression that can be evaluated in the current
28977 context and will yield the same value that a variable object has.
28978 Compare this with the @code{-var-info-expression} command, which
28979 result can be used only for UI presentation. Typical use of
28980 the @code{-var-info-path-expression} command is creating a
28981 watchpoint from a variable object.
28983 This command is currently not valid for children of a dynamic varobj,
28984 and will give an error when invoked on one.
28986 For example, suppose @code{C} is a C@t{++} class, derived from class
28987 @code{Base}, and that the @code{Base} class has a member called
28988 @code{m_size}. Assume a variable @code{c} is has the type of
28989 @code{C} and a variable object @code{C} was created for variable
28990 @code{c}. Then, we'll get this output:
28992 (gdb) -var-info-path-expression C.Base.public.m_size
28993 ^done,path_expr=((Base)c).m_size)
28996 @subheading The @code{-var-show-attributes} Command
28997 @findex -var-show-attributes
28999 @subsubheading Synopsis
29002 -var-show-attributes @var{name}
29005 List attributes of the specified variable object @var{name}:
29008 status=@var{attr} [ ( ,@var{attr} )* ]
29012 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29014 @subheading The @code{-var-evaluate-expression} Command
29015 @findex -var-evaluate-expression
29017 @subsubheading Synopsis
29020 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29023 Evaluates the expression that is represented by the specified variable
29024 object and returns its value as a string. The format of the string
29025 can be specified with the @samp{-f} option. The possible values of
29026 this option are the same as for @code{-var-set-format}
29027 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29028 the current display format will be used. The current display format
29029 can be changed using the @code{-var-set-format} command.
29035 Note that one must invoke @code{-var-list-children} for a variable
29036 before the value of a child variable can be evaluated.
29038 @subheading The @code{-var-assign} Command
29039 @findex -var-assign
29041 @subsubheading Synopsis
29044 -var-assign @var{name} @var{expression}
29047 Assigns the value of @var{expression} to the variable object specified
29048 by @var{name}. The object must be @samp{editable}. If the variable's
29049 value is altered by the assign, the variable will show up in any
29050 subsequent @code{-var-update} list.
29052 @subsubheading Example
29060 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29064 @subheading The @code{-var-update} Command
29065 @findex -var-update
29067 @subsubheading Synopsis
29070 -var-update [@var{print-values}] @{@var{name} | "*"@}
29073 Reevaluate the expressions corresponding to the variable object
29074 @var{name} and all its direct and indirect children, and return the
29075 list of variable objects whose values have changed; @var{name} must
29076 be a root variable object. Here, ``changed'' means that the result of
29077 @code{-var-evaluate-expression} before and after the
29078 @code{-var-update} is different. If @samp{*} is used as the variable
29079 object names, all existing variable objects are updated, except
29080 for frozen ones (@pxref{-var-set-frozen}). The option
29081 @var{print-values} determines whether both names and values, or just
29082 names are printed. The possible values of this option are the same
29083 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29084 recommended to use the @samp{--all-values} option, to reduce the
29085 number of MI commands needed on each program stop.
29087 With the @samp{*} parameter, if a variable object is bound to a
29088 currently running thread, it will not be updated, without any
29091 If @code{-var-set-update-range} was previously used on a varobj, then
29092 only the selected range of children will be reported.
29094 @code{-var-update} reports all the changed varobjs in a tuple named
29097 Each item in the change list is itself a tuple holding:
29101 The name of the varobj.
29104 If values were requested for this update, then this field will be
29105 present and will hold the value of the varobj.
29108 @anchor{-var-update}
29109 This field is a string which may take one of three values:
29113 The variable object's current value is valid.
29116 The variable object does not currently hold a valid value but it may
29117 hold one in the future if its associated expression comes back into
29121 The variable object no longer holds a valid value.
29122 This can occur when the executable file being debugged has changed,
29123 either through recompilation or by using the @value{GDBN} @code{file}
29124 command. The front end should normally choose to delete these variable
29128 In the future new values may be added to this list so the front should
29129 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29132 This is only present if the varobj is still valid. If the type
29133 changed, then this will be the string @samp{true}; otherwise it will
29137 If the varobj's type changed, then this field will be present and will
29140 @item new_num_children
29141 For a dynamic varobj, if the number of children changed, or if the
29142 type changed, this will be the new number of children.
29144 The @samp{numchild} field in other varobj responses is generally not
29145 valid for a dynamic varobj -- it will show the number of children that
29146 @value{GDBN} knows about, but because dynamic varobjs lazily
29147 instantiate their children, this will not reflect the number of
29148 children which may be available.
29150 The @samp{new_num_children} attribute only reports changes to the
29151 number of children known by @value{GDBN}. This is the only way to
29152 detect whether an update has removed children (which necessarily can
29153 only happen at the end of the update range).
29156 The display hint, if any.
29159 This is an integer value, which will be 1 if there are more children
29160 available outside the varobj's update range.
29163 This attribute will be present and have the value @samp{1} if the
29164 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29165 then this attribute will not be present.
29168 If new children were added to a dynamic varobj within the selected
29169 update range (as set by @code{-var-set-update-range}), then they will
29170 be listed in this attribute.
29173 @subsubheading Example
29180 -var-update --all-values var1
29181 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29182 type_changed="false"@}]
29186 @subheading The @code{-var-set-frozen} Command
29187 @findex -var-set-frozen
29188 @anchor{-var-set-frozen}
29190 @subsubheading Synopsis
29193 -var-set-frozen @var{name} @var{flag}
29196 Set the frozenness flag on the variable object @var{name}. The
29197 @var{flag} parameter should be either @samp{1} to make the variable
29198 frozen or @samp{0} to make it unfrozen. If a variable object is
29199 frozen, then neither itself, nor any of its children, are
29200 implicitly updated by @code{-var-update} of
29201 a parent variable or by @code{-var-update *}. Only
29202 @code{-var-update} of the variable itself will update its value and
29203 values of its children. After a variable object is unfrozen, it is
29204 implicitly updated by all subsequent @code{-var-update} operations.
29205 Unfreezing a variable does not update it, only subsequent
29206 @code{-var-update} does.
29208 @subsubheading Example
29212 -var-set-frozen V 1
29217 @subheading The @code{-var-set-update-range} command
29218 @findex -var-set-update-range
29219 @anchor{-var-set-update-range}
29221 @subsubheading Synopsis
29224 -var-set-update-range @var{name} @var{from} @var{to}
29227 Set the range of children to be returned by future invocations of
29228 @code{-var-update}.
29230 @var{from} and @var{to} indicate the range of children to report. If
29231 @var{from} or @var{to} is less than zero, the range is reset and all
29232 children will be reported. Otherwise, children starting at @var{from}
29233 (zero-based) and up to and excluding @var{to} will be reported.
29235 @subsubheading Example
29239 -var-set-update-range V 1 2
29243 @subheading The @code{-var-set-visualizer} command
29244 @findex -var-set-visualizer
29245 @anchor{-var-set-visualizer}
29247 @subsubheading Synopsis
29250 -var-set-visualizer @var{name} @var{visualizer}
29253 Set a visualizer for the variable object @var{name}.
29255 @var{visualizer} is the visualizer to use. The special value
29256 @samp{None} means to disable any visualizer in use.
29258 If not @samp{None}, @var{visualizer} must be a Python expression.
29259 This expression must evaluate to a callable object which accepts a
29260 single argument. @value{GDBN} will call this object with the value of
29261 the varobj @var{name} as an argument (this is done so that the same
29262 Python pretty-printing code can be used for both the CLI and MI).
29263 When called, this object must return an object which conforms to the
29264 pretty-printing interface (@pxref{Pretty Printing API}).
29266 The pre-defined function @code{gdb.default_visualizer} may be used to
29267 select a visualizer by following the built-in process
29268 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29269 a varobj is created, and so ordinarily is not needed.
29271 This feature is only available if Python support is enabled. The MI
29272 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
29273 can be used to check this.
29275 @subsubheading Example
29277 Resetting the visualizer:
29281 -var-set-visualizer V None
29285 Reselecting the default (type-based) visualizer:
29289 -var-set-visualizer V gdb.default_visualizer
29293 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29294 can be used to instantiate this class for a varobj:
29298 -var-set-visualizer V "lambda val: SomeClass()"
29302 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29303 @node GDB/MI Data Manipulation
29304 @section @sc{gdb/mi} Data Manipulation
29306 @cindex data manipulation, in @sc{gdb/mi}
29307 @cindex @sc{gdb/mi}, data manipulation
29308 This section describes the @sc{gdb/mi} commands that manipulate data:
29309 examine memory and registers, evaluate expressions, etc.
29311 @c REMOVED FROM THE INTERFACE.
29312 @c @subheading -data-assign
29313 @c Change the value of a program variable. Plenty of side effects.
29314 @c @subsubheading GDB Command
29316 @c @subsubheading Example
29319 @subheading The @code{-data-disassemble} Command
29320 @findex -data-disassemble
29322 @subsubheading Synopsis
29326 [ -s @var{start-addr} -e @var{end-addr} ]
29327 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29335 @item @var{start-addr}
29336 is the beginning address (or @code{$pc})
29337 @item @var{end-addr}
29339 @item @var{filename}
29340 is the name of the file to disassemble
29341 @item @var{linenum}
29342 is the line number to disassemble around
29344 is the number of disassembly lines to be produced. If it is -1,
29345 the whole function will be disassembled, in case no @var{end-addr} is
29346 specified. If @var{end-addr} is specified as a non-zero value, and
29347 @var{lines} is lower than the number of disassembly lines between
29348 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29349 displayed; if @var{lines} is higher than the number of lines between
29350 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29353 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29354 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29355 mixed source and disassembly with raw opcodes).
29358 @subsubheading Result
29360 The output for each instruction is composed of four fields:
29369 Note that whatever included in the instruction field, is not manipulated
29370 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
29372 @subsubheading @value{GDBN} Command
29374 There's no direct mapping from this command to the CLI.
29376 @subsubheading Example
29378 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29382 -data-disassemble -s $pc -e "$pc + 20" -- 0
29385 @{address="0x000107c0",func-name="main",offset="4",
29386 inst="mov 2, %o0"@},
29387 @{address="0x000107c4",func-name="main",offset="8",
29388 inst="sethi %hi(0x11800), %o2"@},
29389 @{address="0x000107c8",func-name="main",offset="12",
29390 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29391 @{address="0x000107cc",func-name="main",offset="16",
29392 inst="sethi %hi(0x11800), %o2"@},
29393 @{address="0x000107d0",func-name="main",offset="20",
29394 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29398 Disassemble the whole @code{main} function. Line 32 is part of
29402 -data-disassemble -f basics.c -l 32 -- 0
29404 @{address="0x000107bc",func-name="main",offset="0",
29405 inst="save %sp, -112, %sp"@},
29406 @{address="0x000107c0",func-name="main",offset="4",
29407 inst="mov 2, %o0"@},
29408 @{address="0x000107c4",func-name="main",offset="8",
29409 inst="sethi %hi(0x11800), %o2"@},
29411 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29412 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29416 Disassemble 3 instructions from the start of @code{main}:
29420 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29422 @{address="0x000107bc",func-name="main",offset="0",
29423 inst="save %sp, -112, %sp"@},
29424 @{address="0x000107c0",func-name="main",offset="4",
29425 inst="mov 2, %o0"@},
29426 @{address="0x000107c4",func-name="main",offset="8",
29427 inst="sethi %hi(0x11800), %o2"@}]
29431 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29435 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29437 src_and_asm_line=@{line="31",
29438 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29439 testsuite/gdb.mi/basics.c",line_asm_insn=[
29440 @{address="0x000107bc",func-name="main",offset="0",
29441 inst="save %sp, -112, %sp"@}]@},
29442 src_and_asm_line=@{line="32",
29443 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29444 testsuite/gdb.mi/basics.c",line_asm_insn=[
29445 @{address="0x000107c0",func-name="main",offset="4",
29446 inst="mov 2, %o0"@},
29447 @{address="0x000107c4",func-name="main",offset="8",
29448 inst="sethi %hi(0x11800), %o2"@}]@}]
29453 @subheading The @code{-data-evaluate-expression} Command
29454 @findex -data-evaluate-expression
29456 @subsubheading Synopsis
29459 -data-evaluate-expression @var{expr}
29462 Evaluate @var{expr} as an expression. The expression could contain an
29463 inferior function call. The function call will execute synchronously.
29464 If the expression contains spaces, it must be enclosed in double quotes.
29466 @subsubheading @value{GDBN} Command
29468 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29469 @samp{call}. In @code{gdbtk} only, there's a corresponding
29470 @samp{gdb_eval} command.
29472 @subsubheading Example
29474 In the following example, the numbers that precede the commands are the
29475 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29476 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29480 211-data-evaluate-expression A
29483 311-data-evaluate-expression &A
29484 311^done,value="0xefffeb7c"
29486 411-data-evaluate-expression A+3
29489 511-data-evaluate-expression "A + 3"
29495 @subheading The @code{-data-list-changed-registers} Command
29496 @findex -data-list-changed-registers
29498 @subsubheading Synopsis
29501 -data-list-changed-registers
29504 Display a list of the registers that have changed.
29506 @subsubheading @value{GDBN} Command
29508 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29509 has the corresponding command @samp{gdb_changed_register_list}.
29511 @subsubheading Example
29513 On a PPC MBX board:
29521 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29522 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29525 -data-list-changed-registers
29526 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29527 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29528 "24","25","26","27","28","30","31","64","65","66","67","69"]
29533 @subheading The @code{-data-list-register-names} Command
29534 @findex -data-list-register-names
29536 @subsubheading Synopsis
29539 -data-list-register-names [ ( @var{regno} )+ ]
29542 Show a list of register names for the current target. If no arguments
29543 are given, it shows a list of the names of all the registers. If
29544 integer numbers are given as arguments, it will print a list of the
29545 names of the registers corresponding to the arguments. To ensure
29546 consistency between a register name and its number, the output list may
29547 include empty register names.
29549 @subsubheading @value{GDBN} Command
29551 @value{GDBN} does not have a command which corresponds to
29552 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29553 corresponding command @samp{gdb_regnames}.
29555 @subsubheading Example
29557 For the PPC MBX board:
29560 -data-list-register-names
29561 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29562 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29563 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29564 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29565 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29566 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29567 "", "pc","ps","cr","lr","ctr","xer"]
29569 -data-list-register-names 1 2 3
29570 ^done,register-names=["r1","r2","r3"]
29574 @subheading The @code{-data-list-register-values} Command
29575 @findex -data-list-register-values
29577 @subsubheading Synopsis
29580 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
29583 Display the registers' contents. @var{fmt} is the format according to
29584 which the registers' contents are to be returned, followed by an optional
29585 list of numbers specifying the registers to display. A missing list of
29586 numbers indicates that the contents of all the registers must be returned.
29588 Allowed formats for @var{fmt} are:
29605 @subsubheading @value{GDBN} Command
29607 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29608 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29610 @subsubheading Example
29612 For a PPC MBX board (note: line breaks are for readability only, they
29613 don't appear in the actual output):
29617 -data-list-register-values r 64 65
29618 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29619 @{number="65",value="0x00029002"@}]
29621 -data-list-register-values x
29622 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29623 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29624 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29625 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29626 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29627 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29628 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29629 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29630 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29631 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29632 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29633 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29634 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29635 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29636 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29637 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29638 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29639 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29640 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29641 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29642 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29643 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29644 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29645 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29646 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29647 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29648 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29649 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29650 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29651 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29652 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29653 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29654 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29655 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29656 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29657 @{number="69",value="0x20002b03"@}]
29662 @subheading The @code{-data-read-memory} Command
29663 @findex -data-read-memory
29665 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29667 @subsubheading Synopsis
29670 -data-read-memory [ -o @var{byte-offset} ]
29671 @var{address} @var{word-format} @var{word-size}
29672 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29679 @item @var{address}
29680 An expression specifying the address of the first memory word to be
29681 read. Complex expressions containing embedded white space should be
29682 quoted using the C convention.
29684 @item @var{word-format}
29685 The format to be used to print the memory words. The notation is the
29686 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29689 @item @var{word-size}
29690 The size of each memory word in bytes.
29692 @item @var{nr-rows}
29693 The number of rows in the output table.
29695 @item @var{nr-cols}
29696 The number of columns in the output table.
29699 If present, indicates that each row should include an @sc{ascii} dump. The
29700 value of @var{aschar} is used as a padding character when a byte is not a
29701 member of the printable @sc{ascii} character set (printable @sc{ascii}
29702 characters are those whose code is between 32 and 126, inclusively).
29704 @item @var{byte-offset}
29705 An offset to add to the @var{address} before fetching memory.
29708 This command displays memory contents as a table of @var{nr-rows} by
29709 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29710 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29711 (returned as @samp{total-bytes}). Should less than the requested number
29712 of bytes be returned by the target, the missing words are identified
29713 using @samp{N/A}. The number of bytes read from the target is returned
29714 in @samp{nr-bytes} and the starting address used to read memory in
29717 The address of the next/previous row or page is available in
29718 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29721 @subsubheading @value{GDBN} Command
29723 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29724 @samp{gdb_get_mem} memory read command.
29726 @subsubheading Example
29728 Read six bytes of memory starting at @code{bytes+6} but then offset by
29729 @code{-6} bytes. Format as three rows of two columns. One byte per
29730 word. Display each word in hex.
29734 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29735 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29736 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29737 prev-page="0x0000138a",memory=[
29738 @{addr="0x00001390",data=["0x00","0x01"]@},
29739 @{addr="0x00001392",data=["0x02","0x03"]@},
29740 @{addr="0x00001394",data=["0x04","0x05"]@}]
29744 Read two bytes of memory starting at address @code{shorts + 64} and
29745 display as a single word formatted in decimal.
29749 5-data-read-memory shorts+64 d 2 1 1
29750 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29751 next-row="0x00001512",prev-row="0x0000150e",
29752 next-page="0x00001512",prev-page="0x0000150e",memory=[
29753 @{addr="0x00001510",data=["128"]@}]
29757 Read thirty two bytes of memory starting at @code{bytes+16} and format
29758 as eight rows of four columns. Include a string encoding with @samp{x}
29759 used as the non-printable character.
29763 4-data-read-memory bytes+16 x 1 8 4 x
29764 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29765 next-row="0x000013c0",prev-row="0x0000139c",
29766 next-page="0x000013c0",prev-page="0x00001380",memory=[
29767 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29768 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29769 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29770 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29771 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29772 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29773 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29774 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29778 @subheading The @code{-data-read-memory-bytes} Command
29779 @findex -data-read-memory-bytes
29781 @subsubheading Synopsis
29784 -data-read-memory-bytes [ -o @var{byte-offset} ]
29785 @var{address} @var{count}
29792 @item @var{address}
29793 An expression specifying the address of the first memory word to be
29794 read. Complex expressions containing embedded white space should be
29795 quoted using the C convention.
29798 The number of bytes to read. This should be an integer literal.
29800 @item @var{byte-offset}
29801 The offsets in bytes relative to @var{address} at which to start
29802 reading. This should be an integer literal. This option is provided
29803 so that a frontend is not required to first evaluate address and then
29804 perform address arithmetics itself.
29808 This command attempts to read all accessible memory regions in the
29809 specified range. First, all regions marked as unreadable in the memory
29810 map (if one is defined) will be skipped. @xref{Memory Region
29811 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29812 regions. For each one, if reading full region results in an errors,
29813 @value{GDBN} will try to read a subset of the region.
29815 In general, every single byte in the region may be readable or not,
29816 and the only way to read every readable byte is to try a read at
29817 every address, which is not practical. Therefore, @value{GDBN} will
29818 attempt to read all accessible bytes at either beginning or the end
29819 of the region, using a binary division scheme. This heuristic works
29820 well for reading accross a memory map boundary. Note that if a region
29821 has a readable range that is neither at the beginning or the end,
29822 @value{GDBN} will not read it.
29824 The result record (@pxref{GDB/MI Result Records}) that is output of
29825 the command includes a field named @samp{memory} whose content is a
29826 list of tuples. Each tuple represent a successfully read memory block
29827 and has the following fields:
29831 The start address of the memory block, as hexadecimal literal.
29834 The end address of the memory block, as hexadecimal literal.
29837 The offset of the memory block, as hexadecimal literal, relative to
29838 the start address passed to @code{-data-read-memory-bytes}.
29841 The contents of the memory block, in hex.
29847 @subsubheading @value{GDBN} Command
29849 The corresponding @value{GDBN} command is @samp{x}.
29851 @subsubheading Example
29855 -data-read-memory-bytes &a 10
29856 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29858 contents="01000000020000000300"@}]
29863 @subheading The @code{-data-write-memory-bytes} Command
29864 @findex -data-write-memory-bytes
29866 @subsubheading Synopsis
29869 -data-write-memory-bytes @var{address} @var{contents}
29876 @item @var{address}
29877 An expression specifying the address of the first memory word to be
29878 read. Complex expressions containing embedded white space should be
29879 quoted using the C convention.
29881 @item @var{contents}
29882 The hex-encoded bytes to write.
29886 @subsubheading @value{GDBN} Command
29888 There's no corresponding @value{GDBN} command.
29890 @subsubheading Example
29894 -data-write-memory-bytes &a "aabbccdd"
29900 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29901 @node GDB/MI Tracepoint Commands
29902 @section @sc{gdb/mi} Tracepoint Commands
29904 The commands defined in this section implement MI support for
29905 tracepoints. For detailed introduction, see @ref{Tracepoints}.
29907 @subheading The @code{-trace-find} Command
29908 @findex -trace-find
29910 @subsubheading Synopsis
29913 -trace-find @var{mode} [@var{parameters}@dots{}]
29916 Find a trace frame using criteria defined by @var{mode} and
29917 @var{parameters}. The following table lists permissible
29918 modes and their parameters. For details of operation, see @ref{tfind}.
29923 No parameters are required. Stops examining trace frames.
29926 An integer is required as parameter. Selects tracepoint frame with
29929 @item tracepoint-number
29930 An integer is required as parameter. Finds next
29931 trace frame that corresponds to tracepoint with the specified number.
29934 An address is required as parameter. Finds
29935 next trace frame that corresponds to any tracepoint at the specified
29938 @item pc-inside-range
29939 Two addresses are required as parameters. Finds next trace
29940 frame that corresponds to a tracepoint at an address inside the
29941 specified range. Both bounds are considered to be inside the range.
29943 @item pc-outside-range
29944 Two addresses are required as parameters. Finds
29945 next trace frame that corresponds to a tracepoint at an address outside
29946 the specified range. Both bounds are considered to be inside the range.
29949 Line specification is required as parameter. @xref{Specify Location}.
29950 Finds next trace frame that corresponds to a tracepoint at
29951 the specified location.
29955 If @samp{none} was passed as @var{mode}, the response does not
29956 have fields. Otherwise, the response may have the following fields:
29960 This field has either @samp{0} or @samp{1} as the value, depending
29961 on whether a matching tracepoint was found.
29964 The index of the found traceframe. This field is present iff
29965 the @samp{found} field has value of @samp{1}.
29968 The index of the found tracepoint. This field is present iff
29969 the @samp{found} field has value of @samp{1}.
29972 The information about the frame corresponding to the found trace
29973 frame. This field is present only if a trace frame was found.
29974 @xref{GDB/MI Frame Information}, for description of this field.
29978 @subsubheading @value{GDBN} Command
29980 The corresponding @value{GDBN} command is @samp{tfind}.
29982 @subheading -trace-define-variable
29983 @findex -trace-define-variable
29985 @subsubheading Synopsis
29988 -trace-define-variable @var{name} [ @var{value} ]
29991 Create trace variable @var{name} if it does not exist. If
29992 @var{value} is specified, sets the initial value of the specified
29993 trace variable to that value. Note that the @var{name} should start
29994 with the @samp{$} character.
29996 @subsubheading @value{GDBN} Command
29998 The corresponding @value{GDBN} command is @samp{tvariable}.
30000 @subheading -trace-list-variables
30001 @findex -trace-list-variables
30003 @subsubheading Synopsis
30006 -trace-list-variables
30009 Return a table of all defined trace variables. Each element of the
30010 table has the following fields:
30014 The name of the trace variable. This field is always present.
30017 The initial value. This is a 64-bit signed integer. This
30018 field is always present.
30021 The value the trace variable has at the moment. This is a 64-bit
30022 signed integer. This field is absent iff current value is
30023 not defined, for example if the trace was never run, or is
30028 @subsubheading @value{GDBN} Command
30030 The corresponding @value{GDBN} command is @samp{tvariables}.
30032 @subsubheading Example
30036 -trace-list-variables
30037 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30038 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30039 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30040 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30041 body=[variable=@{name="$trace_timestamp",initial="0"@}
30042 variable=@{name="$foo",initial="10",current="15"@}]@}
30046 @subheading -trace-save
30047 @findex -trace-save
30049 @subsubheading Synopsis
30052 -trace-save [-r ] @var{filename}
30055 Saves the collected trace data to @var{filename}. Without the
30056 @samp{-r} option, the data is downloaded from the target and saved
30057 in a local file. With the @samp{-r} option the target is asked
30058 to perform the save.
30060 @subsubheading @value{GDBN} Command
30062 The corresponding @value{GDBN} command is @samp{tsave}.
30065 @subheading -trace-start
30066 @findex -trace-start
30068 @subsubheading Synopsis
30074 Starts a tracing experiments. The result of this command does not
30077 @subsubheading @value{GDBN} Command
30079 The corresponding @value{GDBN} command is @samp{tstart}.
30081 @subheading -trace-status
30082 @findex -trace-status
30084 @subsubheading Synopsis
30090 Obtains the status of a tracing experiment. The result may include
30091 the following fields:
30096 May have a value of either @samp{0}, when no tracing operations are
30097 supported, @samp{1}, when all tracing operations are supported, or
30098 @samp{file} when examining trace file. In the latter case, examining
30099 of trace frame is possible but new tracing experiement cannot be
30100 started. This field is always present.
30103 May have a value of either @samp{0} or @samp{1} depending on whether
30104 tracing experiement is in progress on target. This field is present
30105 if @samp{supported} field is not @samp{0}.
30108 Report the reason why the tracing was stopped last time. This field
30109 may be absent iff tracing was never stopped on target yet. The
30110 value of @samp{request} means the tracing was stopped as result of
30111 the @code{-trace-stop} command. The value of @samp{overflow} means
30112 the tracing buffer is full. The value of @samp{disconnection} means
30113 tracing was automatically stopped when @value{GDBN} has disconnected.
30114 The value of @samp{passcount} means tracing was stopped when a
30115 tracepoint was passed a maximal number of times for that tracepoint.
30116 This field is present if @samp{supported} field is not @samp{0}.
30118 @item stopping-tracepoint
30119 The number of tracepoint whose passcount as exceeded. This field is
30120 present iff the @samp{stop-reason} field has the value of
30124 @itemx frames-created
30125 The @samp{frames} field is a count of the total number of trace frames
30126 in the trace buffer, while @samp{frames-created} is the total created
30127 during the run, including ones that were discarded, such as when a
30128 circular trace buffer filled up. Both fields are optional.
30132 These fields tell the current size of the tracing buffer and the
30133 remaining space. These fields are optional.
30136 The value of the circular trace buffer flag. @code{1} means that the
30137 trace buffer is circular and old trace frames will be discarded if
30138 necessary to make room, @code{0} means that the trace buffer is linear
30142 The value of the disconnected tracing flag. @code{1} means that
30143 tracing will continue after @value{GDBN} disconnects, @code{0} means
30144 that the trace run will stop.
30148 @subsubheading @value{GDBN} Command
30150 The corresponding @value{GDBN} command is @samp{tstatus}.
30152 @subheading -trace-stop
30153 @findex -trace-stop
30155 @subsubheading Synopsis
30161 Stops a tracing experiment. The result of this command has the same
30162 fields as @code{-trace-status}, except that the @samp{supported} and
30163 @samp{running} fields are not output.
30165 @subsubheading @value{GDBN} Command
30167 The corresponding @value{GDBN} command is @samp{tstop}.
30170 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30171 @node GDB/MI Symbol Query
30172 @section @sc{gdb/mi} Symbol Query Commands
30176 @subheading The @code{-symbol-info-address} Command
30177 @findex -symbol-info-address
30179 @subsubheading Synopsis
30182 -symbol-info-address @var{symbol}
30185 Describe where @var{symbol} is stored.
30187 @subsubheading @value{GDBN} Command
30189 The corresponding @value{GDBN} command is @samp{info address}.
30191 @subsubheading Example
30195 @subheading The @code{-symbol-info-file} Command
30196 @findex -symbol-info-file
30198 @subsubheading Synopsis
30204 Show the file for the symbol.
30206 @subsubheading @value{GDBN} Command
30208 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30209 @samp{gdb_find_file}.
30211 @subsubheading Example
30215 @subheading The @code{-symbol-info-function} Command
30216 @findex -symbol-info-function
30218 @subsubheading Synopsis
30221 -symbol-info-function
30224 Show which function the symbol lives in.
30226 @subsubheading @value{GDBN} Command
30228 @samp{gdb_get_function} in @code{gdbtk}.
30230 @subsubheading Example
30234 @subheading The @code{-symbol-info-line} Command
30235 @findex -symbol-info-line
30237 @subsubheading Synopsis
30243 Show the core addresses of the code for a source line.
30245 @subsubheading @value{GDBN} Command
30247 The corresponding @value{GDBN} command is @samp{info line}.
30248 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30250 @subsubheading Example
30254 @subheading The @code{-symbol-info-symbol} Command
30255 @findex -symbol-info-symbol
30257 @subsubheading Synopsis
30260 -symbol-info-symbol @var{addr}
30263 Describe what symbol is at location @var{addr}.
30265 @subsubheading @value{GDBN} Command
30267 The corresponding @value{GDBN} command is @samp{info symbol}.
30269 @subsubheading Example
30273 @subheading The @code{-symbol-list-functions} Command
30274 @findex -symbol-list-functions
30276 @subsubheading Synopsis
30279 -symbol-list-functions
30282 List the functions in the executable.
30284 @subsubheading @value{GDBN} Command
30286 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30287 @samp{gdb_search} in @code{gdbtk}.
30289 @subsubheading Example
30294 @subheading The @code{-symbol-list-lines} Command
30295 @findex -symbol-list-lines
30297 @subsubheading Synopsis
30300 -symbol-list-lines @var{filename}
30303 Print the list of lines that contain code and their associated program
30304 addresses for the given source filename. The entries are sorted in
30305 ascending PC order.
30307 @subsubheading @value{GDBN} Command
30309 There is no corresponding @value{GDBN} command.
30311 @subsubheading Example
30314 -symbol-list-lines basics.c
30315 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30321 @subheading The @code{-symbol-list-types} Command
30322 @findex -symbol-list-types
30324 @subsubheading Synopsis
30330 List all the type names.
30332 @subsubheading @value{GDBN} Command
30334 The corresponding commands are @samp{info types} in @value{GDBN},
30335 @samp{gdb_search} in @code{gdbtk}.
30337 @subsubheading Example
30341 @subheading The @code{-symbol-list-variables} Command
30342 @findex -symbol-list-variables
30344 @subsubheading Synopsis
30347 -symbol-list-variables
30350 List all the global and static variable names.
30352 @subsubheading @value{GDBN} Command
30354 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30356 @subsubheading Example
30360 @subheading The @code{-symbol-locate} Command
30361 @findex -symbol-locate
30363 @subsubheading Synopsis
30369 @subsubheading @value{GDBN} Command
30371 @samp{gdb_loc} in @code{gdbtk}.
30373 @subsubheading Example
30377 @subheading The @code{-symbol-type} Command
30378 @findex -symbol-type
30380 @subsubheading Synopsis
30383 -symbol-type @var{variable}
30386 Show type of @var{variable}.
30388 @subsubheading @value{GDBN} Command
30390 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30391 @samp{gdb_obj_variable}.
30393 @subsubheading Example
30398 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30399 @node GDB/MI File Commands
30400 @section @sc{gdb/mi} File Commands
30402 This section describes the GDB/MI commands to specify executable file names
30403 and to read in and obtain symbol table information.
30405 @subheading The @code{-file-exec-and-symbols} Command
30406 @findex -file-exec-and-symbols
30408 @subsubheading Synopsis
30411 -file-exec-and-symbols @var{file}
30414 Specify the executable file to be debugged. This file is the one from
30415 which the symbol table is also read. If no file is specified, the
30416 command clears the executable and symbol information. If breakpoints
30417 are set when using this command with no arguments, @value{GDBN} will produce
30418 error messages. Otherwise, no output is produced, except a completion
30421 @subsubheading @value{GDBN} Command
30423 The corresponding @value{GDBN} command is @samp{file}.
30425 @subsubheading Example
30429 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30435 @subheading The @code{-file-exec-file} Command
30436 @findex -file-exec-file
30438 @subsubheading Synopsis
30441 -file-exec-file @var{file}
30444 Specify the executable file to be debugged. Unlike
30445 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30446 from this file. If used without argument, @value{GDBN} clears the information
30447 about the executable file. No output is produced, except a completion
30450 @subsubheading @value{GDBN} Command
30452 The corresponding @value{GDBN} command is @samp{exec-file}.
30454 @subsubheading Example
30458 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30465 @subheading The @code{-file-list-exec-sections} Command
30466 @findex -file-list-exec-sections
30468 @subsubheading Synopsis
30471 -file-list-exec-sections
30474 List the sections of the current executable file.
30476 @subsubheading @value{GDBN} Command
30478 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30479 information as this command. @code{gdbtk} has a corresponding command
30480 @samp{gdb_load_info}.
30482 @subsubheading Example
30487 @subheading The @code{-file-list-exec-source-file} Command
30488 @findex -file-list-exec-source-file
30490 @subsubheading Synopsis
30493 -file-list-exec-source-file
30496 List the line number, the current source file, and the absolute path
30497 to the current source file for the current executable. The macro
30498 information field has a value of @samp{1} or @samp{0} depending on
30499 whether or not the file includes preprocessor macro information.
30501 @subsubheading @value{GDBN} Command
30503 The @value{GDBN} equivalent is @samp{info source}
30505 @subsubheading Example
30509 123-file-list-exec-source-file
30510 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30515 @subheading The @code{-file-list-exec-source-files} Command
30516 @findex -file-list-exec-source-files
30518 @subsubheading Synopsis
30521 -file-list-exec-source-files
30524 List the source files for the current executable.
30526 It will always output the filename, but only when @value{GDBN} can find
30527 the absolute file name of a source file, will it output the fullname.
30529 @subsubheading @value{GDBN} Command
30531 The @value{GDBN} equivalent is @samp{info sources}.
30532 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30534 @subsubheading Example
30537 -file-list-exec-source-files
30539 @{file=foo.c,fullname=/home/foo.c@},
30540 @{file=/home/bar.c,fullname=/home/bar.c@},
30541 @{file=gdb_could_not_find_fullpath.c@}]
30546 @subheading The @code{-file-list-shared-libraries} Command
30547 @findex -file-list-shared-libraries
30549 @subsubheading Synopsis
30552 -file-list-shared-libraries
30555 List the shared libraries in the program.
30557 @subsubheading @value{GDBN} Command
30559 The corresponding @value{GDBN} command is @samp{info shared}.
30561 @subsubheading Example
30565 @subheading The @code{-file-list-symbol-files} Command
30566 @findex -file-list-symbol-files
30568 @subsubheading Synopsis
30571 -file-list-symbol-files
30576 @subsubheading @value{GDBN} Command
30578 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30580 @subsubheading Example
30585 @subheading The @code{-file-symbol-file} Command
30586 @findex -file-symbol-file
30588 @subsubheading Synopsis
30591 -file-symbol-file @var{file}
30594 Read symbol table info from the specified @var{file} argument. When
30595 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30596 produced, except for a completion notification.
30598 @subsubheading @value{GDBN} Command
30600 The corresponding @value{GDBN} command is @samp{symbol-file}.
30602 @subsubheading Example
30606 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30612 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30613 @node GDB/MI Memory Overlay Commands
30614 @section @sc{gdb/mi} Memory Overlay Commands
30616 The memory overlay commands are not implemented.
30618 @c @subheading -overlay-auto
30620 @c @subheading -overlay-list-mapping-state
30622 @c @subheading -overlay-list-overlays
30624 @c @subheading -overlay-map
30626 @c @subheading -overlay-off
30628 @c @subheading -overlay-on
30630 @c @subheading -overlay-unmap
30632 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30633 @node GDB/MI Signal Handling Commands
30634 @section @sc{gdb/mi} Signal Handling Commands
30636 Signal handling commands are not implemented.
30638 @c @subheading -signal-handle
30640 @c @subheading -signal-list-handle-actions
30642 @c @subheading -signal-list-signal-types
30646 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30647 @node GDB/MI Target Manipulation
30648 @section @sc{gdb/mi} Target Manipulation Commands
30651 @subheading The @code{-target-attach} Command
30652 @findex -target-attach
30654 @subsubheading Synopsis
30657 -target-attach @var{pid} | @var{gid} | @var{file}
30660 Attach to a process @var{pid} or a file @var{file} outside of
30661 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30662 group, the id previously returned by
30663 @samp{-list-thread-groups --available} must be used.
30665 @subsubheading @value{GDBN} Command
30667 The corresponding @value{GDBN} command is @samp{attach}.
30669 @subsubheading Example
30673 =thread-created,id="1"
30674 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30680 @subheading The @code{-target-compare-sections} Command
30681 @findex -target-compare-sections
30683 @subsubheading Synopsis
30686 -target-compare-sections [ @var{section} ]
30689 Compare data of section @var{section} on target to the exec file.
30690 Without the argument, all sections are compared.
30692 @subsubheading @value{GDBN} Command
30694 The @value{GDBN} equivalent is @samp{compare-sections}.
30696 @subsubheading Example
30701 @subheading The @code{-target-detach} Command
30702 @findex -target-detach
30704 @subsubheading Synopsis
30707 -target-detach [ @var{pid} | @var{gid} ]
30710 Detach from the remote target which normally resumes its execution.
30711 If either @var{pid} or @var{gid} is specified, detaches from either
30712 the specified process, or specified thread group. There's no output.
30714 @subsubheading @value{GDBN} Command
30716 The corresponding @value{GDBN} command is @samp{detach}.
30718 @subsubheading Example
30728 @subheading The @code{-target-disconnect} Command
30729 @findex -target-disconnect
30731 @subsubheading Synopsis
30737 Disconnect from the remote target. There's no output and the target is
30738 generally not resumed.
30740 @subsubheading @value{GDBN} Command
30742 The corresponding @value{GDBN} command is @samp{disconnect}.
30744 @subsubheading Example
30754 @subheading The @code{-target-download} Command
30755 @findex -target-download
30757 @subsubheading Synopsis
30763 Loads the executable onto the remote target.
30764 It prints out an update message every half second, which includes the fields:
30768 The name of the section.
30770 The size of what has been sent so far for that section.
30772 The size of the section.
30774 The total size of what was sent so far (the current and the previous sections).
30776 The size of the overall executable to download.
30780 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30781 @sc{gdb/mi} Output Syntax}).
30783 In addition, it prints the name and size of the sections, as they are
30784 downloaded. These messages include the following fields:
30788 The name of the section.
30790 The size of the section.
30792 The size of the overall executable to download.
30796 At the end, a summary is printed.
30798 @subsubheading @value{GDBN} Command
30800 The corresponding @value{GDBN} command is @samp{load}.
30802 @subsubheading Example
30804 Note: each status message appears on a single line. Here the messages
30805 have been broken down so that they can fit onto a page.
30810 +download,@{section=".text",section-size="6668",total-size="9880"@}
30811 +download,@{section=".text",section-sent="512",section-size="6668",
30812 total-sent="512",total-size="9880"@}
30813 +download,@{section=".text",section-sent="1024",section-size="6668",
30814 total-sent="1024",total-size="9880"@}
30815 +download,@{section=".text",section-sent="1536",section-size="6668",
30816 total-sent="1536",total-size="9880"@}
30817 +download,@{section=".text",section-sent="2048",section-size="6668",
30818 total-sent="2048",total-size="9880"@}
30819 +download,@{section=".text",section-sent="2560",section-size="6668",
30820 total-sent="2560",total-size="9880"@}
30821 +download,@{section=".text",section-sent="3072",section-size="6668",
30822 total-sent="3072",total-size="9880"@}
30823 +download,@{section=".text",section-sent="3584",section-size="6668",
30824 total-sent="3584",total-size="9880"@}
30825 +download,@{section=".text",section-sent="4096",section-size="6668",
30826 total-sent="4096",total-size="9880"@}
30827 +download,@{section=".text",section-sent="4608",section-size="6668",
30828 total-sent="4608",total-size="9880"@}
30829 +download,@{section=".text",section-sent="5120",section-size="6668",
30830 total-sent="5120",total-size="9880"@}
30831 +download,@{section=".text",section-sent="5632",section-size="6668",
30832 total-sent="5632",total-size="9880"@}
30833 +download,@{section=".text",section-sent="6144",section-size="6668",
30834 total-sent="6144",total-size="9880"@}
30835 +download,@{section=".text",section-sent="6656",section-size="6668",
30836 total-sent="6656",total-size="9880"@}
30837 +download,@{section=".init",section-size="28",total-size="9880"@}
30838 +download,@{section=".fini",section-size="28",total-size="9880"@}
30839 +download,@{section=".data",section-size="3156",total-size="9880"@}
30840 +download,@{section=".data",section-sent="512",section-size="3156",
30841 total-sent="7236",total-size="9880"@}
30842 +download,@{section=".data",section-sent="1024",section-size="3156",
30843 total-sent="7748",total-size="9880"@}
30844 +download,@{section=".data",section-sent="1536",section-size="3156",
30845 total-sent="8260",total-size="9880"@}
30846 +download,@{section=".data",section-sent="2048",section-size="3156",
30847 total-sent="8772",total-size="9880"@}
30848 +download,@{section=".data",section-sent="2560",section-size="3156",
30849 total-sent="9284",total-size="9880"@}
30850 +download,@{section=".data",section-sent="3072",section-size="3156",
30851 total-sent="9796",total-size="9880"@}
30852 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30859 @subheading The @code{-target-exec-status} Command
30860 @findex -target-exec-status
30862 @subsubheading Synopsis
30865 -target-exec-status
30868 Provide information on the state of the target (whether it is running or
30869 not, for instance).
30871 @subsubheading @value{GDBN} Command
30873 There's no equivalent @value{GDBN} command.
30875 @subsubheading Example
30879 @subheading The @code{-target-list-available-targets} Command
30880 @findex -target-list-available-targets
30882 @subsubheading Synopsis
30885 -target-list-available-targets
30888 List the possible targets to connect to.
30890 @subsubheading @value{GDBN} Command
30892 The corresponding @value{GDBN} command is @samp{help target}.
30894 @subsubheading Example
30898 @subheading The @code{-target-list-current-targets} Command
30899 @findex -target-list-current-targets
30901 @subsubheading Synopsis
30904 -target-list-current-targets
30907 Describe the current target.
30909 @subsubheading @value{GDBN} Command
30911 The corresponding information is printed by @samp{info file} (among
30914 @subsubheading Example
30918 @subheading The @code{-target-list-parameters} Command
30919 @findex -target-list-parameters
30921 @subsubheading Synopsis
30924 -target-list-parameters
30930 @subsubheading @value{GDBN} Command
30934 @subsubheading Example
30938 @subheading The @code{-target-select} Command
30939 @findex -target-select
30941 @subsubheading Synopsis
30944 -target-select @var{type} @var{parameters @dots{}}
30947 Connect @value{GDBN} to the remote target. This command takes two args:
30951 The type of target, for instance @samp{remote}, etc.
30952 @item @var{parameters}
30953 Device names, host names and the like. @xref{Target Commands, ,
30954 Commands for Managing Targets}, for more details.
30957 The output is a connection notification, followed by the address at
30958 which the target program is, in the following form:
30961 ^connected,addr="@var{address}",func="@var{function name}",
30962 args=[@var{arg list}]
30965 @subsubheading @value{GDBN} Command
30967 The corresponding @value{GDBN} command is @samp{target}.
30969 @subsubheading Example
30973 -target-select remote /dev/ttya
30974 ^connected,addr="0xfe00a300",func="??",args=[]
30978 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30979 @node GDB/MI File Transfer Commands
30980 @section @sc{gdb/mi} File Transfer Commands
30983 @subheading The @code{-target-file-put} Command
30984 @findex -target-file-put
30986 @subsubheading Synopsis
30989 -target-file-put @var{hostfile} @var{targetfile}
30992 Copy file @var{hostfile} from the host system (the machine running
30993 @value{GDBN}) to @var{targetfile} on the target system.
30995 @subsubheading @value{GDBN} Command
30997 The corresponding @value{GDBN} command is @samp{remote put}.
30999 @subsubheading Example
31003 -target-file-put localfile remotefile
31009 @subheading The @code{-target-file-get} Command
31010 @findex -target-file-get
31012 @subsubheading Synopsis
31015 -target-file-get @var{targetfile} @var{hostfile}
31018 Copy file @var{targetfile} from the target system to @var{hostfile}
31019 on the host system.
31021 @subsubheading @value{GDBN} Command
31023 The corresponding @value{GDBN} command is @samp{remote get}.
31025 @subsubheading Example
31029 -target-file-get remotefile localfile
31035 @subheading The @code{-target-file-delete} Command
31036 @findex -target-file-delete
31038 @subsubheading Synopsis
31041 -target-file-delete @var{targetfile}
31044 Delete @var{targetfile} from the target system.
31046 @subsubheading @value{GDBN} Command
31048 The corresponding @value{GDBN} command is @samp{remote delete}.
31050 @subsubheading Example
31054 -target-file-delete remotefile
31060 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31061 @node GDB/MI Miscellaneous Commands
31062 @section Miscellaneous @sc{gdb/mi} Commands
31064 @c @subheading -gdb-complete
31066 @subheading The @code{-gdb-exit} Command
31069 @subsubheading Synopsis
31075 Exit @value{GDBN} immediately.
31077 @subsubheading @value{GDBN} Command
31079 Approximately corresponds to @samp{quit}.
31081 @subsubheading Example
31091 @subheading The @code{-exec-abort} Command
31092 @findex -exec-abort
31094 @subsubheading Synopsis
31100 Kill the inferior running program.
31102 @subsubheading @value{GDBN} Command
31104 The corresponding @value{GDBN} command is @samp{kill}.
31106 @subsubheading Example
31111 @subheading The @code{-gdb-set} Command
31114 @subsubheading Synopsis
31120 Set an internal @value{GDBN} variable.
31121 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31123 @subsubheading @value{GDBN} Command
31125 The corresponding @value{GDBN} command is @samp{set}.
31127 @subsubheading Example
31137 @subheading The @code{-gdb-show} Command
31140 @subsubheading Synopsis
31146 Show the current value of a @value{GDBN} variable.
31148 @subsubheading @value{GDBN} Command
31150 The corresponding @value{GDBN} command is @samp{show}.
31152 @subsubheading Example
31161 @c @subheading -gdb-source
31164 @subheading The @code{-gdb-version} Command
31165 @findex -gdb-version
31167 @subsubheading Synopsis
31173 Show version information for @value{GDBN}. Used mostly in testing.
31175 @subsubheading @value{GDBN} Command
31177 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31178 default shows this information when you start an interactive session.
31180 @subsubheading Example
31182 @c This example modifies the actual output from GDB to avoid overfull
31188 ~Copyright 2000 Free Software Foundation, Inc.
31189 ~GDB is free software, covered by the GNU General Public License, and
31190 ~you are welcome to change it and/or distribute copies of it under
31191 ~ certain conditions.
31192 ~Type "show copying" to see the conditions.
31193 ~There is absolutely no warranty for GDB. Type "show warranty" for
31195 ~This GDB was configured as
31196 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31201 @subheading The @code{-list-features} Command
31202 @findex -list-features
31204 Returns a list of particular features of the MI protocol that
31205 this version of gdb implements. A feature can be a command,
31206 or a new field in an output of some command, or even an
31207 important bugfix. While a frontend can sometimes detect presence
31208 of a feature at runtime, it is easier to perform detection at debugger
31211 The command returns a list of strings, with each string naming an
31212 available feature. Each returned string is just a name, it does not
31213 have any internal structure. The list of possible feature names
31219 (gdb) -list-features
31220 ^done,result=["feature1","feature2"]
31223 The current list of features is:
31226 @item frozen-varobjs
31227 Indicates support for the @code{-var-set-frozen} command, as well
31228 as possible presense of the @code{frozen} field in the output
31229 of @code{-varobj-create}.
31230 @item pending-breakpoints
31231 Indicates support for the @option{-f} option to the @code{-break-insert}
31234 Indicates Python scripting support, Python-based
31235 pretty-printing commands, and possible presence of the
31236 @samp{display_hint} field in the output of @code{-var-list-children}
31238 Indicates support for the @code{-thread-info} command.
31239 @item data-read-memory-bytes
31240 Indicates support for the @code{-data-read-memory-bytes} and the
31241 @code{-data-write-memory-bytes} commands.
31242 @item breakpoint-notifications
31243 Indicates that changes to breakpoints and breakpoints created via the
31244 CLI will be announced via async records.
31245 @item ada-task-info
31246 Indicates support for the @code{-ada-task-info} command.
31249 @subheading The @code{-list-target-features} Command
31250 @findex -list-target-features
31252 Returns a list of particular features that are supported by the
31253 target. Those features affect the permitted MI commands, but
31254 unlike the features reported by the @code{-list-features} command, the
31255 features depend on which target GDB is using at the moment. Whenever
31256 a target can change, due to commands such as @code{-target-select},
31257 @code{-target-attach} or @code{-exec-run}, the list of target features
31258 may change, and the frontend should obtain it again.
31262 (gdb) -list-features
31263 ^done,result=["async"]
31266 The current list of features is:
31270 Indicates that the target is capable of asynchronous command
31271 execution, which means that @value{GDBN} will accept further commands
31272 while the target is running.
31275 Indicates that the target is capable of reverse execution.
31276 @xref{Reverse Execution}, for more information.
31280 @subheading The @code{-list-thread-groups} Command
31281 @findex -list-thread-groups
31283 @subheading Synopsis
31286 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31289 Lists thread groups (@pxref{Thread groups}). When a single thread
31290 group is passed as the argument, lists the children of that group.
31291 When several thread group are passed, lists information about those
31292 thread groups. Without any parameters, lists information about all
31293 top-level thread groups.
31295 Normally, thread groups that are being debugged are reported.
31296 With the @samp{--available} option, @value{GDBN} reports thread groups
31297 available on the target.
31299 The output of this command may have either a @samp{threads} result or
31300 a @samp{groups} result. The @samp{thread} result has a list of tuples
31301 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31302 Information}). The @samp{groups} result has a list of tuples as value,
31303 each tuple describing a thread group. If top-level groups are
31304 requested (that is, no parameter is passed), or when several groups
31305 are passed, the output always has a @samp{groups} result. The format
31306 of the @samp{group} result is described below.
31308 To reduce the number of roundtrips it's possible to list thread groups
31309 together with their children, by passing the @samp{--recurse} option
31310 and the recursion depth. Presently, only recursion depth of 1 is
31311 permitted. If this option is present, then every reported thread group
31312 will also include its children, either as @samp{group} or
31313 @samp{threads} field.
31315 In general, any combination of option and parameters is permitted, with
31316 the following caveats:
31320 When a single thread group is passed, the output will typically
31321 be the @samp{threads} result. Because threads may not contain
31322 anything, the @samp{recurse} option will be ignored.
31325 When the @samp{--available} option is passed, limited information may
31326 be available. In particular, the list of threads of a process might
31327 be inaccessible. Further, specifying specific thread groups might
31328 not give any performance advantage over listing all thread groups.
31329 The frontend should assume that @samp{-list-thread-groups --available}
31330 is always an expensive operation and cache the results.
31334 The @samp{groups} result is a list of tuples, where each tuple may
31335 have the following fields:
31339 Identifier of the thread group. This field is always present.
31340 The identifier is an opaque string; frontends should not try to
31341 convert it to an integer, even though it might look like one.
31344 The type of the thread group. At present, only @samp{process} is a
31348 The target-specific process identifier. This field is only present
31349 for thread groups of type @samp{process} and only if the process exists.
31352 The number of children this thread group has. This field may be
31353 absent for an available thread group.
31356 This field has a list of tuples as value, each tuple describing a
31357 thread. It may be present if the @samp{--recurse} option is
31358 specified, and it's actually possible to obtain the threads.
31361 This field is a list of integers, each identifying a core that one
31362 thread of the group is running on. This field may be absent if
31363 such information is not available.
31366 The name of the executable file that corresponds to this thread group.
31367 The field is only present for thread groups of type @samp{process},
31368 and only if there is a corresponding executable file.
31372 @subheading Example
31376 -list-thread-groups
31377 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31378 -list-thread-groups 17
31379 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31380 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31381 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31382 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31383 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31384 -list-thread-groups --available
31385 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31386 -list-thread-groups --available --recurse 1
31387 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31388 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31389 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31390 -list-thread-groups --available --recurse 1 17 18
31391 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31392 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31393 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31397 @subheading The @code{-add-inferior} Command
31398 @findex -add-inferior
31400 @subheading Synopsis
31406 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31407 inferior is not associated with any executable. Such association may
31408 be established with the @samp{-file-exec-and-symbols} command
31409 (@pxref{GDB/MI File Commands}). The command response has a single
31410 field, @samp{thread-group}, whose value is the identifier of the
31411 thread group corresponding to the new inferior.
31413 @subheading Example
31418 ^done,thread-group="i3"
31421 @subheading The @code{-interpreter-exec} Command
31422 @findex -interpreter-exec
31424 @subheading Synopsis
31427 -interpreter-exec @var{interpreter} @var{command}
31429 @anchor{-interpreter-exec}
31431 Execute the specified @var{command} in the given @var{interpreter}.
31433 @subheading @value{GDBN} Command
31435 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31437 @subheading Example
31441 -interpreter-exec console "break main"
31442 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31443 &"During symbol reading, bad structure-type format.\n"
31444 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31449 @subheading The @code{-inferior-tty-set} Command
31450 @findex -inferior-tty-set
31452 @subheading Synopsis
31455 -inferior-tty-set /dev/pts/1
31458 Set terminal for future runs of the program being debugged.
31460 @subheading @value{GDBN} Command
31462 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31464 @subheading Example
31468 -inferior-tty-set /dev/pts/1
31473 @subheading The @code{-inferior-tty-show} Command
31474 @findex -inferior-tty-show
31476 @subheading Synopsis
31482 Show terminal for future runs of program being debugged.
31484 @subheading @value{GDBN} Command
31486 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31488 @subheading Example
31492 -inferior-tty-set /dev/pts/1
31496 ^done,inferior_tty_terminal="/dev/pts/1"
31500 @subheading The @code{-enable-timings} Command
31501 @findex -enable-timings
31503 @subheading Synopsis
31506 -enable-timings [yes | no]
31509 Toggle the printing of the wallclock, user and system times for an MI
31510 command as a field in its output. This command is to help frontend
31511 developers optimize the performance of their code. No argument is
31512 equivalent to @samp{yes}.
31514 @subheading @value{GDBN} Command
31518 @subheading Example
31526 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31527 addr="0x080484ed",func="main",file="myprog.c",
31528 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
31529 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31537 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31538 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31539 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31540 fullname="/home/nickrob/myprog.c",line="73"@}
31545 @chapter @value{GDBN} Annotations
31547 This chapter describes annotations in @value{GDBN}. Annotations were
31548 designed to interface @value{GDBN} to graphical user interfaces or other
31549 similar programs which want to interact with @value{GDBN} at a
31550 relatively high level.
31552 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31556 This is Edition @value{EDITION}, @value{DATE}.
31560 * Annotations Overview:: What annotations are; the general syntax.
31561 * Server Prefix:: Issuing a command without affecting user state.
31562 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31563 * Errors:: Annotations for error messages.
31564 * Invalidation:: Some annotations describe things now invalid.
31565 * Annotations for Running::
31566 Whether the program is running, how it stopped, etc.
31567 * Source Annotations:: Annotations describing source code.
31570 @node Annotations Overview
31571 @section What is an Annotation?
31572 @cindex annotations
31574 Annotations start with a newline character, two @samp{control-z}
31575 characters, and the name of the annotation. If there is no additional
31576 information associated with this annotation, the name of the annotation
31577 is followed immediately by a newline. If there is additional
31578 information, the name of the annotation is followed by a space, the
31579 additional information, and a newline. The additional information
31580 cannot contain newline characters.
31582 Any output not beginning with a newline and two @samp{control-z}
31583 characters denotes literal output from @value{GDBN}. Currently there is
31584 no need for @value{GDBN} to output a newline followed by two
31585 @samp{control-z} characters, but if there was such a need, the
31586 annotations could be extended with an @samp{escape} annotation which
31587 means those three characters as output.
31589 The annotation @var{level}, which is specified using the
31590 @option{--annotate} command line option (@pxref{Mode Options}), controls
31591 how much information @value{GDBN} prints together with its prompt,
31592 values of expressions, source lines, and other types of output. Level 0
31593 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31594 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31595 for programs that control @value{GDBN}, and level 2 annotations have
31596 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31597 Interface, annotate, GDB's Obsolete Annotations}).
31600 @kindex set annotate
31601 @item set annotate @var{level}
31602 The @value{GDBN} command @code{set annotate} sets the level of
31603 annotations to the specified @var{level}.
31605 @item show annotate
31606 @kindex show annotate
31607 Show the current annotation level.
31610 This chapter describes level 3 annotations.
31612 A simple example of starting up @value{GDBN} with annotations is:
31615 $ @kbd{gdb --annotate=3}
31617 Copyright 2003 Free Software Foundation, Inc.
31618 GDB is free software, covered by the GNU General Public License,
31619 and you are welcome to change it and/or distribute copies of it
31620 under certain conditions.
31621 Type "show copying" to see the conditions.
31622 There is absolutely no warranty for GDB. Type "show warranty"
31624 This GDB was configured as "i386-pc-linux-gnu"
31635 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31636 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31637 denotes a @samp{control-z} character) are annotations; the rest is
31638 output from @value{GDBN}.
31640 @node Server Prefix
31641 @section The Server Prefix
31642 @cindex server prefix
31644 If you prefix a command with @samp{server } then it will not affect
31645 the command history, nor will it affect @value{GDBN}'s notion of which
31646 command to repeat if @key{RET} is pressed on a line by itself. This
31647 means that commands can be run behind a user's back by a front-end in
31648 a transparent manner.
31650 The @code{server } prefix does not affect the recording of values into
31651 the value history; to print a value without recording it into the
31652 value history, use the @code{output} command instead of the
31653 @code{print} command.
31655 Using this prefix also disables confirmation requests
31656 (@pxref{confirmation requests}).
31659 @section Annotation for @value{GDBN} Input
31661 @cindex annotations for prompts
31662 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31663 to know when to send output, when the output from a given command is
31666 Different kinds of input each have a different @dfn{input type}. Each
31667 input type has three annotations: a @code{pre-} annotation, which
31668 denotes the beginning of any prompt which is being output, a plain
31669 annotation, which denotes the end of the prompt, and then a @code{post-}
31670 annotation which denotes the end of any echo which may (or may not) be
31671 associated with the input. For example, the @code{prompt} input type
31672 features the following annotations:
31680 The input types are
31683 @findex pre-prompt annotation
31684 @findex prompt annotation
31685 @findex post-prompt annotation
31687 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31689 @findex pre-commands annotation
31690 @findex commands annotation
31691 @findex post-commands annotation
31693 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31694 command. The annotations are repeated for each command which is input.
31696 @findex pre-overload-choice annotation
31697 @findex overload-choice annotation
31698 @findex post-overload-choice annotation
31699 @item overload-choice
31700 When @value{GDBN} wants the user to select between various overloaded functions.
31702 @findex pre-query annotation
31703 @findex query annotation
31704 @findex post-query annotation
31706 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31708 @findex pre-prompt-for-continue annotation
31709 @findex prompt-for-continue annotation
31710 @findex post-prompt-for-continue annotation
31711 @item prompt-for-continue
31712 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31713 expect this to work well; instead use @code{set height 0} to disable
31714 prompting. This is because the counting of lines is buggy in the
31715 presence of annotations.
31720 @cindex annotations for errors, warnings and interrupts
31722 @findex quit annotation
31727 This annotation occurs right before @value{GDBN} responds to an interrupt.
31729 @findex error annotation
31734 This annotation occurs right before @value{GDBN} responds to an error.
31736 Quit and error annotations indicate that any annotations which @value{GDBN} was
31737 in the middle of may end abruptly. For example, if a
31738 @code{value-history-begin} annotation is followed by a @code{error}, one
31739 cannot expect to receive the matching @code{value-history-end}. One
31740 cannot expect not to receive it either, however; an error annotation
31741 does not necessarily mean that @value{GDBN} is immediately returning all the way
31744 @findex error-begin annotation
31745 A quit or error annotation may be preceded by
31751 Any output between that and the quit or error annotation is the error
31754 Warning messages are not yet annotated.
31755 @c If we want to change that, need to fix warning(), type_error(),
31756 @c range_error(), and possibly other places.
31759 @section Invalidation Notices
31761 @cindex annotations for invalidation messages
31762 The following annotations say that certain pieces of state may have
31766 @findex frames-invalid annotation
31767 @item ^Z^Zframes-invalid
31769 The frames (for example, output from the @code{backtrace} command) may
31772 @findex breakpoints-invalid annotation
31773 @item ^Z^Zbreakpoints-invalid
31775 The breakpoints may have changed. For example, the user just added or
31776 deleted a breakpoint.
31779 @node Annotations for Running
31780 @section Running the Program
31781 @cindex annotations for running programs
31783 @findex starting annotation
31784 @findex stopping annotation
31785 When the program starts executing due to a @value{GDBN} command such as
31786 @code{step} or @code{continue},
31792 is output. When the program stops,
31798 is output. Before the @code{stopped} annotation, a variety of
31799 annotations describe how the program stopped.
31802 @findex exited annotation
31803 @item ^Z^Zexited @var{exit-status}
31804 The program exited, and @var{exit-status} is the exit status (zero for
31805 successful exit, otherwise nonzero).
31807 @findex signalled annotation
31808 @findex signal-name annotation
31809 @findex signal-name-end annotation
31810 @findex signal-string annotation
31811 @findex signal-string-end annotation
31812 @item ^Z^Zsignalled
31813 The program exited with a signal. After the @code{^Z^Zsignalled}, the
31814 annotation continues:
31820 ^Z^Zsignal-name-end
31824 ^Z^Zsignal-string-end
31829 where @var{name} is the name of the signal, such as @code{SIGILL} or
31830 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
31831 as @code{Illegal Instruction} or @code{Segmentation fault}.
31832 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
31833 user's benefit and have no particular format.
31835 @findex signal annotation
31837 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
31838 just saying that the program received the signal, not that it was
31839 terminated with it.
31841 @findex breakpoint annotation
31842 @item ^Z^Zbreakpoint @var{number}
31843 The program hit breakpoint number @var{number}.
31845 @findex watchpoint annotation
31846 @item ^Z^Zwatchpoint @var{number}
31847 The program hit watchpoint number @var{number}.
31850 @node Source Annotations
31851 @section Displaying Source
31852 @cindex annotations for source display
31854 @findex source annotation
31855 The following annotation is used instead of displaying source code:
31858 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
31861 where @var{filename} is an absolute file name indicating which source
31862 file, @var{line} is the line number within that file (where 1 is the
31863 first line in the file), @var{character} is the character position
31864 within the file (where 0 is the first character in the file) (for most
31865 debug formats this will necessarily point to the beginning of a line),
31866 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
31867 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
31868 @var{addr} is the address in the target program associated with the
31869 source which is being displayed. @var{addr} is in the form @samp{0x}
31870 followed by one or more lowercase hex digits (note that this does not
31871 depend on the language).
31873 @node JIT Interface
31874 @chapter JIT Compilation Interface
31875 @cindex just-in-time compilation
31876 @cindex JIT compilation interface
31878 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
31879 interface. A JIT compiler is a program or library that generates native
31880 executable code at runtime and executes it, usually in order to achieve good
31881 performance while maintaining platform independence.
31883 Programs that use JIT compilation are normally difficult to debug because
31884 portions of their code are generated at runtime, instead of being loaded from
31885 object files, which is where @value{GDBN} normally finds the program's symbols
31886 and debug information. In order to debug programs that use JIT compilation,
31887 @value{GDBN} has an interface that allows the program to register in-memory
31888 symbol files with @value{GDBN} at runtime.
31890 If you are using @value{GDBN} to debug a program that uses this interface, then
31891 it should work transparently so long as you have not stripped the binary. If
31892 you are developing a JIT compiler, then the interface is documented in the rest
31893 of this chapter. At this time, the only known client of this interface is the
31896 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
31897 JIT compiler communicates with @value{GDBN} by writing data into a global
31898 variable and calling a fuction at a well-known symbol. When @value{GDBN}
31899 attaches, it reads a linked list of symbol files from the global variable to
31900 find existing code, and puts a breakpoint in the function so that it can find
31901 out about additional code.
31904 * Declarations:: Relevant C struct declarations
31905 * Registering Code:: Steps to register code
31906 * Unregistering Code:: Steps to unregister code
31907 * Custom Debug Info:: Emit debug information in a custom format
31911 @section JIT Declarations
31913 These are the relevant struct declarations that a C program should include to
31914 implement the interface:
31924 struct jit_code_entry
31926 struct jit_code_entry *next_entry;
31927 struct jit_code_entry *prev_entry;
31928 const char *symfile_addr;
31929 uint64_t symfile_size;
31932 struct jit_descriptor
31935 /* This type should be jit_actions_t, but we use uint32_t
31936 to be explicit about the bitwidth. */
31937 uint32_t action_flag;
31938 struct jit_code_entry *relevant_entry;
31939 struct jit_code_entry *first_entry;
31942 /* GDB puts a breakpoint in this function. */
31943 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
31945 /* Make sure to specify the version statically, because the
31946 debugger may check the version before we can set it. */
31947 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
31950 If the JIT is multi-threaded, then it is important that the JIT synchronize any
31951 modifications to this global data properly, which can easily be done by putting
31952 a global mutex around modifications to these structures.
31954 @node Registering Code
31955 @section Registering Code
31957 To register code with @value{GDBN}, the JIT should follow this protocol:
31961 Generate an object file in memory with symbols and other desired debug
31962 information. The file must include the virtual addresses of the sections.
31965 Create a code entry for the file, which gives the start and size of the symbol
31969 Add it to the linked list in the JIT descriptor.
31972 Point the relevant_entry field of the descriptor at the entry.
31975 Set @code{action_flag} to @code{JIT_REGISTER} and call
31976 @code{__jit_debug_register_code}.
31979 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
31980 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
31981 new code. However, the linked list must still be maintained in order to allow
31982 @value{GDBN} to attach to a running process and still find the symbol files.
31984 @node Unregistering Code
31985 @section Unregistering Code
31987 If code is freed, then the JIT should use the following protocol:
31991 Remove the code entry corresponding to the code from the linked list.
31994 Point the @code{relevant_entry} field of the descriptor at the code entry.
31997 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
31998 @code{__jit_debug_register_code}.
32001 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32002 and the JIT will leak the memory used for the associated symbol files.
32004 @node Custom Debug Info
32005 @section Custom Debug Info
32006 @cindex custom JIT debug info
32007 @cindex JIT debug info reader
32009 Generating debug information in platform-native file formats (like ELF
32010 or COFF) may be an overkill for JIT compilers; especially if all the
32011 debug info is used for is displaying a meaningful backtrace. The
32012 issue can be resolved by having the JIT writers decide on a debug info
32013 format and also provide a reader that parses the debug info generated
32014 by the JIT compiler. This section gives a brief overview on writing
32015 such a parser. More specific details can be found in the source file
32016 @file{gdb/jit-reader.in}, which is also installed as a header at
32017 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32019 The reader is implemented as a shared object (so this functionality is
32020 not available on platforms which don't allow loading shared objects at
32021 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32022 @code{jit-reader-unload} are provided, to be used to load and unload
32023 the readers from a preconfigured directory. Once loaded, the shared
32024 object is used the parse the debug information emitted by the JIT
32028 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32029 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32032 @node Using JIT Debug Info Readers
32033 @subsection Using JIT Debug Info Readers
32034 @kindex jit-reader-load
32035 @kindex jit-reader-unload
32037 Readers can be loaded and unloaded using the @code{jit-reader-load}
32038 and @code{jit-reader-unload} commands.
32041 @item jit-reader-load @var{reader-name}
32042 Load the JIT reader named @var{reader-name}. On a UNIX system, this
32043 will usually load @file{@var{libdir}/gdb/@var{reader-name}}, where
32044 @var{libdir} is the system library directory, usually
32045 @file{/usr/local/lib}. Only one reader can be active at a time;
32046 trying to load a second reader when one is already loaded will result
32047 in @value{GDBN} reporting an error. A new JIT reader can be loaded by
32048 first unloading the current one using @code{jit-reader-load} and then
32049 invoking @code{jit-reader-load}.
32051 @item jit-reader-unload
32052 Unload the currently loaded JIT reader.
32056 @node Writing JIT Debug Info Readers
32057 @subsection Writing JIT Debug Info Readers
32058 @cindex writing JIT debug info readers
32060 As mentioned, a reader is essentially a shared object conforming to a
32061 certain ABI. This ABI is described in @file{jit-reader.h}.
32063 @file{jit-reader.h} defines the structures, macros and functions
32064 required to write a reader. It is installed (along with
32065 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32066 the system include directory.
32068 Readers need to be released under a GPL compatible license. A reader
32069 can be declared as released under such a license by placing the macro
32070 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32072 The entry point for readers is the symbol @code{gdb_init_reader},
32073 which is expected to be a function with the prototype
32075 @findex gdb_init_reader
32077 extern struct gdb_reader_funcs *gdb_init_reader (void);
32080 @cindex @code{struct gdb_reader_funcs}
32082 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32083 functions. These functions are executed to read the debug info
32084 generated by the JIT compiler (@code{read}), to unwind stack frames
32085 (@code{unwind}) and to create canonical frame IDs
32086 (@code{get_Frame_id}). It also has a callback that is called when the
32087 reader is being unloaded (@code{destroy}). The struct looks like this
32090 struct gdb_reader_funcs
32092 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32093 int reader_version;
32095 /* For use by the reader. */
32098 gdb_read_debug_info *read;
32099 gdb_unwind_frame *unwind;
32100 gdb_get_frame_id *get_frame_id;
32101 gdb_destroy_reader *destroy;
32105 @cindex @code{struct gdb_symbol_callbacks}
32106 @cindex @code{struct gdb_unwind_callbacks}
32108 The callbacks are provided with another set of callbacks by
32109 @value{GDBN} to do their job. For @code{read}, these callbacks are
32110 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32111 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32112 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32113 files and new symbol tables inside those object files. @code{struct
32114 gdb_unwind_callbacks} has callbacks to read registers off the current
32115 frame and to write out the values of the registers in the previous
32116 frame. Both have a callback (@code{target_read}) to read bytes off the
32117 target's address space.
32120 @chapter Reporting Bugs in @value{GDBN}
32121 @cindex bugs in @value{GDBN}
32122 @cindex reporting bugs in @value{GDBN}
32124 Your bug reports play an essential role in making @value{GDBN} reliable.
32126 Reporting a bug may help you by bringing a solution to your problem, or it
32127 may not. But in any case the principal function of a bug report is to help
32128 the entire community by making the next version of @value{GDBN} work better. Bug
32129 reports are your contribution to the maintenance of @value{GDBN}.
32131 In order for a bug report to serve its purpose, you must include the
32132 information that enables us to fix the bug.
32135 * Bug Criteria:: Have you found a bug?
32136 * Bug Reporting:: How to report bugs
32140 @section Have You Found a Bug?
32141 @cindex bug criteria
32143 If you are not sure whether you have found a bug, here are some guidelines:
32146 @cindex fatal signal
32147 @cindex debugger crash
32148 @cindex crash of debugger
32150 If the debugger gets a fatal signal, for any input whatever, that is a
32151 @value{GDBN} bug. Reliable debuggers never crash.
32153 @cindex error on valid input
32155 If @value{GDBN} produces an error message for valid input, that is a
32156 bug. (Note that if you're cross debugging, the problem may also be
32157 somewhere in the connection to the target.)
32159 @cindex invalid input
32161 If @value{GDBN} does not produce an error message for invalid input,
32162 that is a bug. However, you should note that your idea of
32163 ``invalid input'' might be our idea of ``an extension'' or ``support
32164 for traditional practice''.
32167 If you are an experienced user of debugging tools, your suggestions
32168 for improvement of @value{GDBN} are welcome in any case.
32171 @node Bug Reporting
32172 @section How to Report Bugs
32173 @cindex bug reports
32174 @cindex @value{GDBN} bugs, reporting
32176 A number of companies and individuals offer support for @sc{gnu} products.
32177 If you obtained @value{GDBN} from a support organization, we recommend you
32178 contact that organization first.
32180 You can find contact information for many support companies and
32181 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32183 @c should add a web page ref...
32186 @ifset BUGURL_DEFAULT
32187 In any event, we also recommend that you submit bug reports for
32188 @value{GDBN}. The preferred method is to submit them directly using
32189 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32190 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32193 @strong{Do not send bug reports to @samp{info-gdb}, or to
32194 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32195 not want to receive bug reports. Those that do have arranged to receive
32198 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32199 serves as a repeater. The mailing list and the newsgroup carry exactly
32200 the same messages. Often people think of posting bug reports to the
32201 newsgroup instead of mailing them. This appears to work, but it has one
32202 problem which can be crucial: a newsgroup posting often lacks a mail
32203 path back to the sender. Thus, if we need to ask for more information,
32204 we may be unable to reach you. For this reason, it is better to send
32205 bug reports to the mailing list.
32207 @ifclear BUGURL_DEFAULT
32208 In any event, we also recommend that you submit bug reports for
32209 @value{GDBN} to @value{BUGURL}.
32213 The fundamental principle of reporting bugs usefully is this:
32214 @strong{report all the facts}. If you are not sure whether to state a
32215 fact or leave it out, state it!
32217 Often people omit facts because they think they know what causes the
32218 problem and assume that some details do not matter. Thus, you might
32219 assume that the name of the variable you use in an example does not matter.
32220 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32221 stray memory reference which happens to fetch from the location where that
32222 name is stored in memory; perhaps, if the name were different, the contents
32223 of that location would fool the debugger into doing the right thing despite
32224 the bug. Play it safe and give a specific, complete example. That is the
32225 easiest thing for you to do, and the most helpful.
32227 Keep in mind that the purpose of a bug report is to enable us to fix the
32228 bug. It may be that the bug has been reported previously, but neither
32229 you nor we can know that unless your bug report is complete and
32232 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32233 bell?'' Those bug reports are useless, and we urge everyone to
32234 @emph{refuse to respond to them} except to chide the sender to report
32237 To enable us to fix the bug, you should include all these things:
32241 The version of @value{GDBN}. @value{GDBN} announces it if you start
32242 with no arguments; you can also print it at any time using @code{show
32245 Without this, we will not know whether there is any point in looking for
32246 the bug in the current version of @value{GDBN}.
32249 The type of machine you are using, and the operating system name and
32253 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32254 ``@value{GCC}--2.8.1''.
32257 What compiler (and its version) was used to compile the program you are
32258 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32259 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32260 to get this information; for other compilers, see the documentation for
32264 The command arguments you gave the compiler to compile your example and
32265 observe the bug. For example, did you use @samp{-O}? To guarantee
32266 you will not omit something important, list them all. A copy of the
32267 Makefile (or the output from make) is sufficient.
32269 If we were to try to guess the arguments, we would probably guess wrong
32270 and then we might not encounter the bug.
32273 A complete input script, and all necessary source files, that will
32277 A description of what behavior you observe that you believe is
32278 incorrect. For example, ``It gets a fatal signal.''
32280 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32281 will certainly notice it. But if the bug is incorrect output, we might
32282 not notice unless it is glaringly wrong. You might as well not give us
32283 a chance to make a mistake.
32285 Even if the problem you experience is a fatal signal, you should still
32286 say so explicitly. Suppose something strange is going on, such as, your
32287 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32288 the C library on your system. (This has happened!) Your copy might
32289 crash and ours would not. If you told us to expect a crash, then when
32290 ours fails to crash, we would know that the bug was not happening for
32291 us. If you had not told us to expect a crash, then we would not be able
32292 to draw any conclusion from our observations.
32295 @cindex recording a session script
32296 To collect all this information, you can use a session recording program
32297 such as @command{script}, which is available on many Unix systems.
32298 Just run your @value{GDBN} session inside @command{script} and then
32299 include the @file{typescript} file with your bug report.
32301 Another way to record a @value{GDBN} session is to run @value{GDBN}
32302 inside Emacs and then save the entire buffer to a file.
32305 If you wish to suggest changes to the @value{GDBN} source, send us context
32306 diffs. If you even discuss something in the @value{GDBN} source, refer to
32307 it by context, not by line number.
32309 The line numbers in our development sources will not match those in your
32310 sources. Your line numbers would convey no useful information to us.
32314 Here are some things that are not necessary:
32318 A description of the envelope of the bug.
32320 Often people who encounter a bug spend a lot of time investigating
32321 which changes to the input file will make the bug go away and which
32322 changes will not affect it.
32324 This is often time consuming and not very useful, because the way we
32325 will find the bug is by running a single example under the debugger
32326 with breakpoints, not by pure deduction from a series of examples.
32327 We recommend that you save your time for something else.
32329 Of course, if you can find a simpler example to report @emph{instead}
32330 of the original one, that is a convenience for us. Errors in the
32331 output will be easier to spot, running under the debugger will take
32332 less time, and so on.
32334 However, simplification is not vital; if you do not want to do this,
32335 report the bug anyway and send us the entire test case you used.
32338 A patch for the bug.
32340 A patch for the bug does help us if it is a good one. But do not omit
32341 the necessary information, such as the test case, on the assumption that
32342 a patch is all we need. We might see problems with your patch and decide
32343 to fix the problem another way, or we might not understand it at all.
32345 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32346 construct an example that will make the program follow a certain path
32347 through the code. If you do not send us the example, we will not be able
32348 to construct one, so we will not be able to verify that the bug is fixed.
32350 And if we cannot understand what bug you are trying to fix, or why your
32351 patch should be an improvement, we will not install it. A test case will
32352 help us to understand.
32355 A guess about what the bug is or what it depends on.
32357 Such guesses are usually wrong. Even we cannot guess right about such
32358 things without first using the debugger to find the facts.
32361 @c The readline documentation is distributed with the readline code
32362 @c and consists of the two following files:
32365 @c Use -I with makeinfo to point to the appropriate directory,
32366 @c environment var TEXINPUTS with TeX.
32367 @ifclear SYSTEM_READLINE
32368 @include rluser.texi
32369 @include hsuser.texi
32373 @appendix In Memoriam
32375 The @value{GDBN} project mourns the loss of the following long-time
32380 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32381 to Free Software in general. Outside of @value{GDBN}, he was known in
32382 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32384 @item Michael Snyder
32385 Michael was one of the Global Maintainers of the @value{GDBN} project,
32386 with contributions recorded as early as 1996, until 2011. In addition
32387 to his day to day participation, he was a large driving force behind
32388 adding Reverse Debugging to @value{GDBN}.
32391 Beyond their technical contributions to the project, they were also
32392 enjoyable members of the Free Software Community. We will miss them.
32394 @node Formatting Documentation
32395 @appendix Formatting Documentation
32397 @cindex @value{GDBN} reference card
32398 @cindex reference card
32399 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32400 for printing with PostScript or Ghostscript, in the @file{gdb}
32401 subdirectory of the main source directory@footnote{In
32402 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32403 release.}. If you can use PostScript or Ghostscript with your printer,
32404 you can print the reference card immediately with @file{refcard.ps}.
32406 The release also includes the source for the reference card. You
32407 can format it, using @TeX{}, by typing:
32413 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32414 mode on US ``letter'' size paper;
32415 that is, on a sheet 11 inches wide by 8.5 inches
32416 high. You will need to specify this form of printing as an option to
32417 your @sc{dvi} output program.
32419 @cindex documentation
32421 All the documentation for @value{GDBN} comes as part of the machine-readable
32422 distribution. The documentation is written in Texinfo format, which is
32423 a documentation system that uses a single source file to produce both
32424 on-line information and a printed manual. You can use one of the Info
32425 formatting commands to create the on-line version of the documentation
32426 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32428 @value{GDBN} includes an already formatted copy of the on-line Info
32429 version of this manual in the @file{gdb} subdirectory. The main Info
32430 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32431 subordinate files matching @samp{gdb.info*} in the same directory. If
32432 necessary, you can print out these files, or read them with any editor;
32433 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32434 Emacs or the standalone @code{info} program, available as part of the
32435 @sc{gnu} Texinfo distribution.
32437 If you want to format these Info files yourself, you need one of the
32438 Info formatting programs, such as @code{texinfo-format-buffer} or
32441 If you have @code{makeinfo} installed, and are in the top level
32442 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32443 version @value{GDBVN}), you can make the Info file by typing:
32450 If you want to typeset and print copies of this manual, you need @TeX{},
32451 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32452 Texinfo definitions file.
32454 @TeX{} is a typesetting program; it does not print files directly, but
32455 produces output files called @sc{dvi} files. To print a typeset
32456 document, you need a program to print @sc{dvi} files. If your system
32457 has @TeX{} installed, chances are it has such a program. The precise
32458 command to use depends on your system; @kbd{lpr -d} is common; another
32459 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32460 require a file name without any extension or a @samp{.dvi} extension.
32462 @TeX{} also requires a macro definitions file called
32463 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32464 written in Texinfo format. On its own, @TeX{} cannot either read or
32465 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32466 and is located in the @file{gdb-@var{version-number}/texinfo}
32469 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32470 typeset and print this manual. First switch to the @file{gdb}
32471 subdirectory of the main source directory (for example, to
32472 @file{gdb-@value{GDBVN}/gdb}) and type:
32478 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32480 @node Installing GDB
32481 @appendix Installing @value{GDBN}
32482 @cindex installation
32485 * Requirements:: Requirements for building @value{GDBN}
32486 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32487 * Separate Objdir:: Compiling @value{GDBN} in another directory
32488 * Config Names:: Specifying names for hosts and targets
32489 * Configure Options:: Summary of options for configure
32490 * System-wide configuration:: Having a system-wide init file
32494 @section Requirements for Building @value{GDBN}
32495 @cindex building @value{GDBN}, requirements for
32497 Building @value{GDBN} requires various tools and packages to be available.
32498 Other packages will be used only if they are found.
32500 @heading Tools/Packages Necessary for Building @value{GDBN}
32502 @item ISO C90 compiler
32503 @value{GDBN} is written in ISO C90. It should be buildable with any
32504 working C90 compiler, e.g.@: GCC.
32508 @heading Tools/Packages Optional for Building @value{GDBN}
32512 @value{GDBN} can use the Expat XML parsing library. This library may be
32513 included with your operating system distribution; if it is not, you
32514 can get the latest version from @url{http://expat.sourceforge.net}.
32515 The @file{configure} script will search for this library in several
32516 standard locations; if it is installed in an unusual path, you can
32517 use the @option{--with-libexpat-prefix} option to specify its location.
32523 Remote protocol memory maps (@pxref{Memory Map Format})
32525 Target descriptions (@pxref{Target Descriptions})
32527 Remote shared library lists (@xref{Library List Format},
32528 or alternatively @pxref{Library List Format for SVR4 Targets})
32530 MS-Windows shared libraries (@pxref{Shared Libraries})
32532 Traceframe info (@pxref{Traceframe Info Format})
32536 @cindex compressed debug sections
32537 @value{GDBN} will use the @samp{zlib} library, if available, to read
32538 compressed debug sections. Some linkers, such as GNU gold, are capable
32539 of producing binaries with compressed debug sections. If @value{GDBN}
32540 is compiled with @samp{zlib}, it will be able to read the debug
32541 information in such binaries.
32543 The @samp{zlib} library is likely included with your operating system
32544 distribution; if it is not, you can get the latest version from
32545 @url{http://zlib.net}.
32548 @value{GDBN}'s features related to character sets (@pxref{Character
32549 Sets}) require a functioning @code{iconv} implementation. If you are
32550 on a GNU system, then this is provided by the GNU C Library. Some
32551 other systems also provide a working @code{iconv}.
32553 If @value{GDBN} is using the @code{iconv} program which is installed
32554 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32555 This is done with @option{--with-iconv-bin} which specifies the
32556 directory that contains the @code{iconv} program.
32558 On systems without @code{iconv}, you can install GNU Libiconv. If you
32559 have previously installed Libiconv, you can use the
32560 @option{--with-libiconv-prefix} option to configure.
32562 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32563 arrange to build Libiconv if a directory named @file{libiconv} appears
32564 in the top-most source directory. If Libiconv is built this way, and
32565 if the operating system does not provide a suitable @code{iconv}
32566 implementation, then the just-built library will automatically be used
32567 by @value{GDBN}. One easy way to set this up is to download GNU
32568 Libiconv, unpack it, and then rename the directory holding the
32569 Libiconv source code to @samp{libiconv}.
32572 @node Running Configure
32573 @section Invoking the @value{GDBN} @file{configure} Script
32574 @cindex configuring @value{GDBN}
32575 @value{GDBN} comes with a @file{configure} script that automates the process
32576 of preparing @value{GDBN} for installation; you can then use @code{make} to
32577 build the @code{gdb} program.
32579 @c irrelevant in info file; it's as current as the code it lives with.
32580 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
32581 look at the @file{README} file in the sources; we may have improved the
32582 installation procedures since publishing this manual.}
32585 The @value{GDBN} distribution includes all the source code you need for
32586 @value{GDBN} in a single directory, whose name is usually composed by
32587 appending the version number to @samp{gdb}.
32589 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
32590 @file{gdb-@value{GDBVN}} directory. That directory contains:
32593 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
32594 script for configuring @value{GDBN} and all its supporting libraries
32596 @item gdb-@value{GDBVN}/gdb
32597 the source specific to @value{GDBN} itself
32599 @item gdb-@value{GDBVN}/bfd
32600 source for the Binary File Descriptor library
32602 @item gdb-@value{GDBVN}/include
32603 @sc{gnu} include files
32605 @item gdb-@value{GDBVN}/libiberty
32606 source for the @samp{-liberty} free software library
32608 @item gdb-@value{GDBVN}/opcodes
32609 source for the library of opcode tables and disassemblers
32611 @item gdb-@value{GDBVN}/readline
32612 source for the @sc{gnu} command-line interface
32614 @item gdb-@value{GDBVN}/glob
32615 source for the @sc{gnu} filename pattern-matching subroutine
32617 @item gdb-@value{GDBVN}/mmalloc
32618 source for the @sc{gnu} memory-mapped malloc package
32621 The simplest way to configure and build @value{GDBN} is to run @file{configure}
32622 from the @file{gdb-@var{version-number}} source directory, which in
32623 this example is the @file{gdb-@value{GDBVN}} directory.
32625 First switch to the @file{gdb-@var{version-number}} source directory
32626 if you are not already in it; then run @file{configure}. Pass the
32627 identifier for the platform on which @value{GDBN} will run as an
32633 cd gdb-@value{GDBVN}
32634 ./configure @var{host}
32639 where @var{host} is an identifier such as @samp{sun4} or
32640 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
32641 (You can often leave off @var{host}; @file{configure} tries to guess the
32642 correct value by examining your system.)
32644 Running @samp{configure @var{host}} and then running @code{make} builds the
32645 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
32646 libraries, then @code{gdb} itself. The configured source files, and the
32647 binaries, are left in the corresponding source directories.
32650 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
32651 system does not recognize this automatically when you run a different
32652 shell, you may need to run @code{sh} on it explicitly:
32655 sh configure @var{host}
32658 If you run @file{configure} from a directory that contains source
32659 directories for multiple libraries or programs, such as the
32660 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
32662 creates configuration files for every directory level underneath (unless
32663 you tell it not to, with the @samp{--norecursion} option).
32665 You should run the @file{configure} script from the top directory in the
32666 source tree, the @file{gdb-@var{version-number}} directory. If you run
32667 @file{configure} from one of the subdirectories, you will configure only
32668 that subdirectory. That is usually not what you want. In particular,
32669 if you run the first @file{configure} from the @file{gdb} subdirectory
32670 of the @file{gdb-@var{version-number}} directory, you will omit the
32671 configuration of @file{bfd}, @file{readline}, and other sibling
32672 directories of the @file{gdb} subdirectory. This leads to build errors
32673 about missing include files such as @file{bfd/bfd.h}.
32675 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
32676 However, you should make sure that the shell on your path (named by
32677 the @samp{SHELL} environment variable) is publicly readable. Remember
32678 that @value{GDBN} uses the shell to start your program---some systems refuse to
32679 let @value{GDBN} debug child processes whose programs are not readable.
32681 @node Separate Objdir
32682 @section Compiling @value{GDBN} in Another Directory
32684 If you want to run @value{GDBN} versions for several host or target machines,
32685 you need a different @code{gdb} compiled for each combination of
32686 host and target. @file{configure} is designed to make this easy by
32687 allowing you to generate each configuration in a separate subdirectory,
32688 rather than in the source directory. If your @code{make} program
32689 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
32690 @code{make} in each of these directories builds the @code{gdb}
32691 program specified there.
32693 To build @code{gdb} in a separate directory, run @file{configure}
32694 with the @samp{--srcdir} option to specify where to find the source.
32695 (You also need to specify a path to find @file{configure}
32696 itself from your working directory. If the path to @file{configure}
32697 would be the same as the argument to @samp{--srcdir}, you can leave out
32698 the @samp{--srcdir} option; it is assumed.)
32700 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
32701 separate directory for a Sun 4 like this:
32705 cd gdb-@value{GDBVN}
32708 ../gdb-@value{GDBVN}/configure sun4
32713 When @file{configure} builds a configuration using a remote source
32714 directory, it creates a tree for the binaries with the same structure
32715 (and using the same names) as the tree under the source directory. In
32716 the example, you'd find the Sun 4 library @file{libiberty.a} in the
32717 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
32718 @file{gdb-sun4/gdb}.
32720 Make sure that your path to the @file{configure} script has just one
32721 instance of @file{gdb} in it. If your path to @file{configure} looks
32722 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
32723 one subdirectory of @value{GDBN}, not the whole package. This leads to
32724 build errors about missing include files such as @file{bfd/bfd.h}.
32726 One popular reason to build several @value{GDBN} configurations in separate
32727 directories is to configure @value{GDBN} for cross-compiling (where
32728 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
32729 programs that run on another machine---the @dfn{target}).
32730 You specify a cross-debugging target by
32731 giving the @samp{--target=@var{target}} option to @file{configure}.
32733 When you run @code{make} to build a program or library, you must run
32734 it in a configured directory---whatever directory you were in when you
32735 called @file{configure} (or one of its subdirectories).
32737 The @code{Makefile} that @file{configure} generates in each source
32738 directory also runs recursively. If you type @code{make} in a source
32739 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
32740 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
32741 will build all the required libraries, and then build GDB.
32743 When you have multiple hosts or targets configured in separate
32744 directories, you can run @code{make} on them in parallel (for example,
32745 if they are NFS-mounted on each of the hosts); they will not interfere
32749 @section Specifying Names for Hosts and Targets
32751 The specifications used for hosts and targets in the @file{configure}
32752 script are based on a three-part naming scheme, but some short predefined
32753 aliases are also supported. The full naming scheme encodes three pieces
32754 of information in the following pattern:
32757 @var{architecture}-@var{vendor}-@var{os}
32760 For example, you can use the alias @code{sun4} as a @var{host} argument,
32761 or as the value for @var{target} in a @code{--target=@var{target}}
32762 option. The equivalent full name is @samp{sparc-sun-sunos4}.
32764 The @file{configure} script accompanying @value{GDBN} does not provide
32765 any query facility to list all supported host and target names or
32766 aliases. @file{configure} calls the Bourne shell script
32767 @code{config.sub} to map abbreviations to full names; you can read the
32768 script, if you wish, or you can use it to test your guesses on
32769 abbreviations---for example:
32772 % sh config.sub i386-linux
32774 % sh config.sub alpha-linux
32775 alpha-unknown-linux-gnu
32776 % sh config.sub hp9k700
32778 % sh config.sub sun4
32779 sparc-sun-sunos4.1.1
32780 % sh config.sub sun3
32781 m68k-sun-sunos4.1.1
32782 % sh config.sub i986v
32783 Invalid configuration `i986v': machine `i986v' not recognized
32787 @code{config.sub} is also distributed in the @value{GDBN} source
32788 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
32790 @node Configure Options
32791 @section @file{configure} Options
32793 Here is a summary of the @file{configure} options and arguments that
32794 are most often useful for building @value{GDBN}. @file{configure} also has
32795 several other options not listed here. @inforef{What Configure
32796 Does,,configure.info}, for a full explanation of @file{configure}.
32799 configure @r{[}--help@r{]}
32800 @r{[}--prefix=@var{dir}@r{]}
32801 @r{[}--exec-prefix=@var{dir}@r{]}
32802 @r{[}--srcdir=@var{dirname}@r{]}
32803 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
32804 @r{[}--target=@var{target}@r{]}
32809 You may introduce options with a single @samp{-} rather than
32810 @samp{--} if you prefer; but you may abbreviate option names if you use
32815 Display a quick summary of how to invoke @file{configure}.
32817 @item --prefix=@var{dir}
32818 Configure the source to install programs and files under directory
32821 @item --exec-prefix=@var{dir}
32822 Configure the source to install programs under directory
32825 @c avoid splitting the warning from the explanation:
32827 @item --srcdir=@var{dirname}
32828 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
32829 @code{make} that implements the @code{VPATH} feature.}@*
32830 Use this option to make configurations in directories separate from the
32831 @value{GDBN} source directories. Among other things, you can use this to
32832 build (or maintain) several configurations simultaneously, in separate
32833 directories. @file{configure} writes configuration-specific files in
32834 the current directory, but arranges for them to use the source in the
32835 directory @var{dirname}. @file{configure} creates directories under
32836 the working directory in parallel to the source directories below
32839 @item --norecursion
32840 Configure only the directory level where @file{configure} is executed; do not
32841 propagate configuration to subdirectories.
32843 @item --target=@var{target}
32844 Configure @value{GDBN} for cross-debugging programs running on the specified
32845 @var{target}. Without this option, @value{GDBN} is configured to debug
32846 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
32848 There is no convenient way to generate a list of all available targets.
32850 @item @var{host} @dots{}
32851 Configure @value{GDBN} to run on the specified @var{host}.
32853 There is no convenient way to generate a list of all available hosts.
32856 There are many other options available as well, but they are generally
32857 needed for special purposes only.
32859 @node System-wide configuration
32860 @section System-wide configuration and settings
32861 @cindex system-wide init file
32863 @value{GDBN} can be configured to have a system-wide init file;
32864 this file will be read and executed at startup (@pxref{Startup, , What
32865 @value{GDBN} does during startup}).
32867 Here is the corresponding configure option:
32870 @item --with-system-gdbinit=@var{file}
32871 Specify that the default location of the system-wide init file is
32875 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
32876 it may be subject to relocation. Two possible cases:
32880 If the default location of this init file contains @file{$prefix},
32881 it will be subject to relocation. Suppose that the configure options
32882 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
32883 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
32884 init file is looked for as @file{$install/etc/gdbinit} instead of
32885 @file{$prefix/etc/gdbinit}.
32888 By contrast, if the default location does not contain the prefix,
32889 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
32890 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
32891 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
32892 wherever @value{GDBN} is installed.
32895 @node Maintenance Commands
32896 @appendix Maintenance Commands
32897 @cindex maintenance commands
32898 @cindex internal commands
32900 In addition to commands intended for @value{GDBN} users, @value{GDBN}
32901 includes a number of commands intended for @value{GDBN} developers,
32902 that are not documented elsewhere in this manual. These commands are
32903 provided here for reference. (For commands that turn on debugging
32904 messages, see @ref{Debugging Output}.)
32907 @kindex maint agent
32908 @kindex maint agent-eval
32909 @item maint agent @var{expression}
32910 @itemx maint agent-eval @var{expression}
32911 Translate the given @var{expression} into remote agent bytecodes.
32912 This command is useful for debugging the Agent Expression mechanism
32913 (@pxref{Agent Expressions}). The @samp{agent} version produces an
32914 expression useful for data collection, such as by tracepoints, while
32915 @samp{maint agent-eval} produces an expression that evaluates directly
32916 to a result. For instance, a collection expression for @code{globa +
32917 globb} will include bytecodes to record four bytes of memory at each
32918 of the addresses of @code{globa} and @code{globb}, while discarding
32919 the result of the addition, while an evaluation expression will do the
32920 addition and return the sum.
32922 @kindex maint info breakpoints
32923 @item @anchor{maint info breakpoints}maint info breakpoints
32924 Using the same format as @samp{info breakpoints}, display both the
32925 breakpoints you've set explicitly, and those @value{GDBN} is using for
32926 internal purposes. Internal breakpoints are shown with negative
32927 breakpoint numbers. The type column identifies what kind of breakpoint
32932 Normal, explicitly set breakpoint.
32935 Normal, explicitly set watchpoint.
32938 Internal breakpoint, used to handle correctly stepping through
32939 @code{longjmp} calls.
32941 @item longjmp resume
32942 Internal breakpoint at the target of a @code{longjmp}.
32945 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
32948 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
32951 Shared library events.
32955 @kindex set displaced-stepping
32956 @kindex show displaced-stepping
32957 @cindex displaced stepping support
32958 @cindex out-of-line single-stepping
32959 @item set displaced-stepping
32960 @itemx show displaced-stepping
32961 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
32962 if the target supports it. Displaced stepping is a way to single-step
32963 over breakpoints without removing them from the inferior, by executing
32964 an out-of-line copy of the instruction that was originally at the
32965 breakpoint location. It is also known as out-of-line single-stepping.
32968 @item set displaced-stepping on
32969 If the target architecture supports it, @value{GDBN} will use
32970 displaced stepping to step over breakpoints.
32972 @item set displaced-stepping off
32973 @value{GDBN} will not use displaced stepping to step over breakpoints,
32974 even if such is supported by the target architecture.
32976 @cindex non-stop mode, and @samp{set displaced-stepping}
32977 @item set displaced-stepping auto
32978 This is the default mode. @value{GDBN} will use displaced stepping
32979 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
32980 architecture supports displaced stepping.
32983 @kindex maint check-symtabs
32984 @item maint check-symtabs
32985 Check the consistency of psymtabs and symtabs.
32987 @kindex maint cplus first_component
32988 @item maint cplus first_component @var{name}
32989 Print the first C@t{++} class/namespace component of @var{name}.
32991 @kindex maint cplus namespace
32992 @item maint cplus namespace
32993 Print the list of possible C@t{++} namespaces.
32995 @kindex maint demangle
32996 @item maint demangle @var{name}
32997 Demangle a C@t{++} or Objective-C mangled @var{name}.
32999 @kindex maint deprecate
33000 @kindex maint undeprecate
33001 @cindex deprecated commands
33002 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33003 @itemx maint undeprecate @var{command}
33004 Deprecate or undeprecate the named @var{command}. Deprecated commands
33005 cause @value{GDBN} to issue a warning when you use them. The optional
33006 argument @var{replacement} says which newer command should be used in
33007 favor of the deprecated one; if it is given, @value{GDBN} will mention
33008 the replacement as part of the warning.
33010 @kindex maint dump-me
33011 @item maint dump-me
33012 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33013 Cause a fatal signal in the debugger and force it to dump its core.
33014 This is supported only on systems which support aborting a program
33015 with the @code{SIGQUIT} signal.
33017 @kindex maint internal-error
33018 @kindex maint internal-warning
33019 @item maint internal-error @r{[}@var{message-text}@r{]}
33020 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33021 Cause @value{GDBN} to call the internal function @code{internal_error}
33022 or @code{internal_warning} and hence behave as though an internal error
33023 or internal warning has been detected. In addition to reporting the
33024 internal problem, these functions give the user the opportunity to
33025 either quit @value{GDBN} or create a core file of the current
33026 @value{GDBN} session.
33028 These commands take an optional parameter @var{message-text} that is
33029 used as the text of the error or warning message.
33031 Here's an example of using @code{internal-error}:
33034 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33035 @dots{}/maint.c:121: internal-error: testing, 1, 2
33036 A problem internal to GDB has been detected. Further
33037 debugging may prove unreliable.
33038 Quit this debugging session? (y or n) @kbd{n}
33039 Create a core file? (y or n) @kbd{n}
33043 @cindex @value{GDBN} internal error
33044 @cindex internal errors, control of @value{GDBN} behavior
33046 @kindex maint set internal-error
33047 @kindex maint show internal-error
33048 @kindex maint set internal-warning
33049 @kindex maint show internal-warning
33050 @item maint set internal-error @var{action} [ask|yes|no]
33051 @itemx maint show internal-error @var{action}
33052 @itemx maint set internal-warning @var{action} [ask|yes|no]
33053 @itemx maint show internal-warning @var{action}
33054 When @value{GDBN} reports an internal problem (error or warning) it
33055 gives the user the opportunity to both quit @value{GDBN} and create a
33056 core file of the current @value{GDBN} session. These commands let you
33057 override the default behaviour for each particular @var{action},
33058 described in the table below.
33062 You can specify that @value{GDBN} should always (yes) or never (no)
33063 quit. The default is to ask the user what to do.
33066 You can specify that @value{GDBN} should always (yes) or never (no)
33067 create a core file. The default is to ask the user what to do.
33070 @kindex maint packet
33071 @item maint packet @var{text}
33072 If @value{GDBN} is talking to an inferior via the serial protocol,
33073 then this command sends the string @var{text} to the inferior, and
33074 displays the response packet. @value{GDBN} supplies the initial
33075 @samp{$} character, the terminating @samp{#} character, and the
33078 @kindex maint print architecture
33079 @item maint print architecture @r{[}@var{file}@r{]}
33080 Print the entire architecture configuration. The optional argument
33081 @var{file} names the file where the output goes.
33083 @kindex maint print c-tdesc
33084 @item maint print c-tdesc
33085 Print the current target description (@pxref{Target Descriptions}) as
33086 a C source file. The created source file can be used in @value{GDBN}
33087 when an XML parser is not available to parse the description.
33089 @kindex maint print dummy-frames
33090 @item maint print dummy-frames
33091 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33094 (@value{GDBP}) @kbd{b add}
33096 (@value{GDBP}) @kbd{print add(2,3)}
33097 Breakpoint 2, add (a=2, b=3) at @dots{}
33099 The program being debugged stopped while in a function called from GDB.
33101 (@value{GDBP}) @kbd{maint print dummy-frames}
33102 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
33103 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
33104 call_lo=0x01014000 call_hi=0x01014001
33108 Takes an optional file parameter.
33110 @kindex maint print registers
33111 @kindex maint print raw-registers
33112 @kindex maint print cooked-registers
33113 @kindex maint print register-groups
33114 @kindex maint print remote-registers
33115 @item maint print registers @r{[}@var{file}@r{]}
33116 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33117 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33118 @itemx maint print register-groups @r{[}@var{file}@r{]}
33119 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33120 Print @value{GDBN}'s internal register data structures.
33122 The command @code{maint print raw-registers} includes the contents of
33123 the raw register cache; the command @code{maint print
33124 cooked-registers} includes the (cooked) value of all registers,
33125 including registers which aren't available on the target nor visible
33126 to user; the command @code{maint print register-groups} includes the
33127 groups that each register is a member of; and the command @code{maint
33128 print remote-registers} includes the remote target's register numbers
33129 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
33130 @value{GDBN} Internals}.
33132 These commands take an optional parameter, a file name to which to
33133 write the information.
33135 @kindex maint print reggroups
33136 @item maint print reggroups @r{[}@var{file}@r{]}
33137 Print @value{GDBN}'s internal register group data structures. The
33138 optional argument @var{file} tells to what file to write the
33141 The register groups info looks like this:
33144 (@value{GDBP}) @kbd{maint print reggroups}
33157 This command forces @value{GDBN} to flush its internal register cache.
33159 @kindex maint print objfiles
33160 @cindex info for known object files
33161 @item maint print objfiles
33162 Print a dump of all known object files. For each object file, this
33163 command prints its name, address in memory, and all of its psymtabs
33166 @kindex maint print section-scripts
33167 @cindex info for known .debug_gdb_scripts-loaded scripts
33168 @item maint print section-scripts [@var{regexp}]
33169 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33170 If @var{regexp} is specified, only print scripts loaded by object files
33171 matching @var{regexp}.
33172 For each script, this command prints its name as specified in the objfile,
33173 and the full path if known.
33174 @xref{.debug_gdb_scripts section}.
33176 @kindex maint print statistics
33177 @cindex bcache statistics
33178 @item maint print statistics
33179 This command prints, for each object file in the program, various data
33180 about that object file followed by the byte cache (@dfn{bcache})
33181 statistics for the object file. The objfile data includes the number
33182 of minimal, partial, full, and stabs symbols, the number of types
33183 defined by the objfile, the number of as yet unexpanded psym tables,
33184 the number of line tables and string tables, and the amount of memory
33185 used by the various tables. The bcache statistics include the counts,
33186 sizes, and counts of duplicates of all and unique objects, max,
33187 average, and median entry size, total memory used and its overhead and
33188 savings, and various measures of the hash table size and chain
33191 @kindex maint print target-stack
33192 @cindex target stack description
33193 @item maint print target-stack
33194 A @dfn{target} is an interface between the debugger and a particular
33195 kind of file or process. Targets can be stacked in @dfn{strata},
33196 so that more than one target can potentially respond to a request.
33197 In particular, memory accesses will walk down the stack of targets
33198 until they find a target that is interested in handling that particular
33201 This command prints a short description of each layer that was pushed on
33202 the @dfn{target stack}, starting from the top layer down to the bottom one.
33204 @kindex maint print type
33205 @cindex type chain of a data type
33206 @item maint print type @var{expr}
33207 Print the type chain for a type specified by @var{expr}. The argument
33208 can be either a type name or a symbol. If it is a symbol, the type of
33209 that symbol is described. The type chain produced by this command is
33210 a recursive definition of the data type as stored in @value{GDBN}'s
33211 data structures, including its flags and contained types.
33213 @kindex maint set dwarf2 always-disassemble
33214 @kindex maint show dwarf2 always-disassemble
33215 @item maint set dwarf2 always-disassemble
33216 @item maint show dwarf2 always-disassemble
33217 Control the behavior of @code{info address} when using DWARF debugging
33220 The default is @code{off}, which means that @value{GDBN} should try to
33221 describe a variable's location in an easily readable format. When
33222 @code{on}, @value{GDBN} will instead display the DWARF location
33223 expression in an assembly-like format. Note that some locations are
33224 too complex for @value{GDBN} to describe simply; in this case you will
33225 always see the disassembly form.
33227 Here is an example of the resulting disassembly:
33230 (gdb) info addr argc
33231 Symbol "argc" is a complex DWARF expression:
33235 For more information on these expressions, see
33236 @uref{http://www.dwarfstd.org/, the DWARF standard}.
33238 @kindex maint set dwarf2 max-cache-age
33239 @kindex maint show dwarf2 max-cache-age
33240 @item maint set dwarf2 max-cache-age
33241 @itemx maint show dwarf2 max-cache-age
33242 Control the DWARF 2 compilation unit cache.
33244 @cindex DWARF 2 compilation units cache
33245 In object files with inter-compilation-unit references, such as those
33246 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
33247 reader needs to frequently refer to previously read compilation units.
33248 This setting controls how long a compilation unit will remain in the
33249 cache if it is not referenced. A higher limit means that cached
33250 compilation units will be stored in memory longer, and more total
33251 memory will be used. Setting it to zero disables caching, which will
33252 slow down @value{GDBN} startup, but reduce memory consumption.
33254 @kindex maint set profile
33255 @kindex maint show profile
33256 @cindex profiling GDB
33257 @item maint set profile
33258 @itemx maint show profile
33259 Control profiling of @value{GDBN}.
33261 Profiling will be disabled until you use the @samp{maint set profile}
33262 command to enable it. When you enable profiling, the system will begin
33263 collecting timing and execution count data; when you disable profiling or
33264 exit @value{GDBN}, the results will be written to a log file. Remember that
33265 if you use profiling, @value{GDBN} will overwrite the profiling log file
33266 (often called @file{gmon.out}). If you have a record of important profiling
33267 data in a @file{gmon.out} file, be sure to move it to a safe location.
33269 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
33270 compiled with the @samp{-pg} compiler option.
33272 @kindex maint set show-debug-regs
33273 @kindex maint show show-debug-regs
33274 @cindex hardware debug registers
33275 @item maint set show-debug-regs
33276 @itemx maint show show-debug-regs
33277 Control whether to show variables that mirror the hardware debug
33278 registers. Use @code{ON} to enable, @code{OFF} to disable. If
33279 enabled, the debug registers values are shown when @value{GDBN} inserts or
33280 removes a hardware breakpoint or watchpoint, and when the inferior
33281 triggers a hardware-assisted breakpoint or watchpoint.
33283 @kindex maint set show-all-tib
33284 @kindex maint show show-all-tib
33285 @item maint set show-all-tib
33286 @itemx maint show show-all-tib
33287 Control whether to show all non zero areas within a 1k block starting
33288 at thread local base, when using the @samp{info w32 thread-information-block}
33291 @kindex maint space
33292 @cindex memory used by commands
33294 Control whether to display memory usage for each command. If set to a
33295 nonzero value, @value{GDBN} will display how much memory each command
33296 took, following the command's own output. This can also be requested
33297 by invoking @value{GDBN} with the @option{--statistics} command-line
33298 switch (@pxref{Mode Options}).
33301 @cindex time of command execution
33303 Control whether to display the execution time of @value{GDBN} for each command.
33304 If set to a nonzero value, @value{GDBN} will display how much time it
33305 took to execute each command, following the command's own output.
33306 Both CPU time and wallclock time are printed.
33307 Printing both is useful when trying to determine whether the cost is
33308 CPU or, e.g., disk/network, latency.
33309 Note that the CPU time printed is for @value{GDBN} only, it does not include
33310 the execution time of the inferior because there's no mechanism currently
33311 to compute how much time was spent by @value{GDBN} and how much time was
33312 spent by the program been debugged.
33313 This can also be requested by invoking @value{GDBN} with the
33314 @option{--statistics} command-line switch (@pxref{Mode Options}).
33316 @kindex maint translate-address
33317 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33318 Find the symbol stored at the location specified by the address
33319 @var{addr} and an optional section name @var{section}. If found,
33320 @value{GDBN} prints the name of the closest symbol and an offset from
33321 the symbol's location to the specified address. This is similar to
33322 the @code{info address} command (@pxref{Symbols}), except that this
33323 command also allows to find symbols in other sections.
33325 If section was not specified, the section in which the symbol was found
33326 is also printed. For dynamically linked executables, the name of
33327 executable or shared library containing the symbol is printed as well.
33331 The following command is useful for non-interactive invocations of
33332 @value{GDBN}, such as in the test suite.
33335 @item set watchdog @var{nsec}
33336 @kindex set watchdog
33337 @cindex watchdog timer
33338 @cindex timeout for commands
33339 Set the maximum number of seconds @value{GDBN} will wait for the
33340 target operation to finish. If this time expires, @value{GDBN}
33341 reports and error and the command is aborted.
33343 @item show watchdog
33344 Show the current setting of the target wait timeout.
33347 @node Remote Protocol
33348 @appendix @value{GDBN} Remote Serial Protocol
33353 * Stop Reply Packets::
33354 * General Query Packets::
33355 * Architecture-Specific Protocol Details::
33356 * Tracepoint Packets::
33357 * Host I/O Packets::
33359 * Notification Packets::
33360 * Remote Non-Stop::
33361 * Packet Acknowledgment::
33363 * File-I/O Remote Protocol Extension::
33364 * Library List Format::
33365 * Library List Format for SVR4 Targets::
33366 * Memory Map Format::
33367 * Thread List Format::
33368 * Traceframe Info Format::
33374 There may be occasions when you need to know something about the
33375 protocol---for example, if there is only one serial port to your target
33376 machine, you might want your program to do something special if it
33377 recognizes a packet meant for @value{GDBN}.
33379 In the examples below, @samp{->} and @samp{<-} are used to indicate
33380 transmitted and received data, respectively.
33382 @cindex protocol, @value{GDBN} remote serial
33383 @cindex serial protocol, @value{GDBN} remote
33384 @cindex remote serial protocol
33385 All @value{GDBN} commands and responses (other than acknowledgments
33386 and notifications, see @ref{Notification Packets}) are sent as a
33387 @var{packet}. A @var{packet} is introduced with the character
33388 @samp{$}, the actual @var{packet-data}, and the terminating character
33389 @samp{#} followed by a two-digit @var{checksum}:
33392 @code{$}@var{packet-data}@code{#}@var{checksum}
33396 @cindex checksum, for @value{GDBN} remote
33398 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33399 characters between the leading @samp{$} and the trailing @samp{#} (an
33400 eight bit unsigned checksum).
33402 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33403 specification also included an optional two-digit @var{sequence-id}:
33406 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33409 @cindex sequence-id, for @value{GDBN} remote
33411 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33412 has never output @var{sequence-id}s. Stubs that handle packets added
33413 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33415 When either the host or the target machine receives a packet, the first
33416 response expected is an acknowledgment: either @samp{+} (to indicate
33417 the package was received correctly) or @samp{-} (to request
33421 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33426 The @samp{+}/@samp{-} acknowledgments can be disabled
33427 once a connection is established.
33428 @xref{Packet Acknowledgment}, for details.
33430 The host (@value{GDBN}) sends @var{command}s, and the target (the
33431 debugging stub incorporated in your program) sends a @var{response}. In
33432 the case of step and continue @var{command}s, the response is only sent
33433 when the operation has completed, and the target has again stopped all
33434 threads in all attached processes. This is the default all-stop mode
33435 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
33436 execution mode; see @ref{Remote Non-Stop}, for details.
33438 @var{packet-data} consists of a sequence of characters with the
33439 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
33442 @cindex remote protocol, field separator
33443 Fields within the packet should be separated using @samp{,} @samp{;} or
33444 @samp{:}. Except where otherwise noted all numbers are represented in
33445 @sc{hex} with leading zeros suppressed.
33447 Implementors should note that prior to @value{GDBN} 5.0, the character
33448 @samp{:} could not appear as the third character in a packet (as it
33449 would potentially conflict with the @var{sequence-id}).
33451 @cindex remote protocol, binary data
33452 @anchor{Binary Data}
33453 Binary data in most packets is encoded either as two hexadecimal
33454 digits per byte of binary data. This allowed the traditional remote
33455 protocol to work over connections which were only seven-bit clean.
33456 Some packets designed more recently assume an eight-bit clean
33457 connection, and use a more efficient encoding to send and receive
33460 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
33461 as an escape character. Any escaped byte is transmitted as the escape
33462 character followed by the original character XORed with @code{0x20}.
33463 For example, the byte @code{0x7d} would be transmitted as the two
33464 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
33465 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
33466 @samp{@}}) must always be escaped. Responses sent by the stub
33467 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
33468 is not interpreted as the start of a run-length encoded sequence
33471 Response @var{data} can be run-length encoded to save space.
33472 Run-length encoding replaces runs of identical characters with one
33473 instance of the repeated character, followed by a @samp{*} and a
33474 repeat count. The repeat count is itself sent encoded, to avoid
33475 binary characters in @var{data}: a value of @var{n} is sent as
33476 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
33477 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
33478 code 32) for a repeat count of 3. (This is because run-length
33479 encoding starts to win for counts 3 or more.) Thus, for example,
33480 @samp{0* } is a run-length encoding of ``0000'': the space character
33481 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
33484 The printable characters @samp{#} and @samp{$} or with a numeric value
33485 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
33486 seven repeats (@samp{$}) can be expanded using a repeat count of only
33487 five (@samp{"}). For example, @samp{00000000} can be encoded as
33490 The error response returned for some packets includes a two character
33491 error number. That number is not well defined.
33493 @cindex empty response, for unsupported packets
33494 For any @var{command} not supported by the stub, an empty response
33495 (@samp{$#00}) should be returned. That way it is possible to extend the
33496 protocol. A newer @value{GDBN} can tell if a packet is supported based
33499 At a minimum, a stub is required to support the @samp{g} and @samp{G}
33500 commands for register access, and the @samp{m} and @samp{M} commands
33501 for memory access. Stubs that only control single-threaded targets
33502 can implement run control with the @samp{c} (continue), and @samp{s}
33503 (step) commands. Stubs that support multi-threading targets should
33504 support the @samp{vCont} command. All other commands are optional.
33509 The following table provides a complete list of all currently defined
33510 @var{command}s and their corresponding response @var{data}.
33511 @xref{File-I/O Remote Protocol Extension}, for details about the File
33512 I/O extension of the remote protocol.
33514 Each packet's description has a template showing the packet's overall
33515 syntax, followed by an explanation of the packet's meaning. We
33516 include spaces in some of the templates for clarity; these are not
33517 part of the packet's syntax. No @value{GDBN} packet uses spaces to
33518 separate its components. For example, a template like @samp{foo
33519 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
33520 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
33521 @var{baz}. @value{GDBN} does not transmit a space character between the
33522 @samp{foo} and the @var{bar}, or between the @var{bar} and the
33525 @cindex @var{thread-id}, in remote protocol
33526 @anchor{thread-id syntax}
33527 Several packets and replies include a @var{thread-id} field to identify
33528 a thread. Normally these are positive numbers with a target-specific
33529 interpretation, formatted as big-endian hex strings. A @var{thread-id}
33530 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
33533 In addition, the remote protocol supports a multiprocess feature in
33534 which the @var{thread-id} syntax is extended to optionally include both
33535 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
33536 The @var{pid} (process) and @var{tid} (thread) components each have the
33537 format described above: a positive number with target-specific
33538 interpretation formatted as a big-endian hex string, literal @samp{-1}
33539 to indicate all processes or threads (respectively), or @samp{0} to
33540 indicate an arbitrary process or thread. Specifying just a process, as
33541 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
33542 error to specify all processes but a specific thread, such as
33543 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
33544 for those packets and replies explicitly documented to include a process
33545 ID, rather than a @var{thread-id}.
33547 The multiprocess @var{thread-id} syntax extensions are only used if both
33548 @value{GDBN} and the stub report support for the @samp{multiprocess}
33549 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
33552 Note that all packet forms beginning with an upper- or lower-case
33553 letter, other than those described here, are reserved for future use.
33555 Here are the packet descriptions.
33560 @cindex @samp{!} packet
33561 @anchor{extended mode}
33562 Enable extended mode. In extended mode, the remote server is made
33563 persistent. The @samp{R} packet is used to restart the program being
33569 The remote target both supports and has enabled extended mode.
33573 @cindex @samp{?} packet
33574 Indicate the reason the target halted. The reply is the same as for
33575 step and continue. This packet has a special interpretation when the
33576 target is in non-stop mode; see @ref{Remote Non-Stop}.
33579 @xref{Stop Reply Packets}, for the reply specifications.
33581 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
33582 @cindex @samp{A} packet
33583 Initialized @code{argv[]} array passed into program. @var{arglen}
33584 specifies the number of bytes in the hex encoded byte stream
33585 @var{arg}. See @code{gdbserver} for more details.
33590 The arguments were set.
33596 @cindex @samp{b} packet
33597 (Don't use this packet; its behavior is not well-defined.)
33598 Change the serial line speed to @var{baud}.
33600 JTC: @emph{When does the transport layer state change? When it's
33601 received, or after the ACK is transmitted. In either case, there are
33602 problems if the command or the acknowledgment packet is dropped.}
33604 Stan: @emph{If people really wanted to add something like this, and get
33605 it working for the first time, they ought to modify ser-unix.c to send
33606 some kind of out-of-band message to a specially-setup stub and have the
33607 switch happen "in between" packets, so that from remote protocol's point
33608 of view, nothing actually happened.}
33610 @item B @var{addr},@var{mode}
33611 @cindex @samp{B} packet
33612 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
33613 breakpoint at @var{addr}.
33615 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
33616 (@pxref{insert breakpoint or watchpoint packet}).
33618 @cindex @samp{bc} packet
33621 Backward continue. Execute the target system in reverse. No parameter.
33622 @xref{Reverse Execution}, for more information.
33625 @xref{Stop Reply Packets}, for the reply specifications.
33627 @cindex @samp{bs} packet
33630 Backward single step. Execute one instruction in reverse. No parameter.
33631 @xref{Reverse Execution}, for more information.
33634 @xref{Stop Reply Packets}, for the reply specifications.
33636 @item c @r{[}@var{addr}@r{]}
33637 @cindex @samp{c} packet
33638 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
33639 resume at current address.
33641 This packet is deprecated for multi-threading support. @xref{vCont
33645 @xref{Stop Reply Packets}, for the reply specifications.
33647 @item C @var{sig}@r{[};@var{addr}@r{]}
33648 @cindex @samp{C} packet
33649 Continue with signal @var{sig} (hex signal number). If
33650 @samp{;@var{addr}} is omitted, resume at same address.
33652 This packet is deprecated for multi-threading support. @xref{vCont
33656 @xref{Stop Reply Packets}, for the reply specifications.
33659 @cindex @samp{d} packet
33662 Don't use this packet; instead, define a general set packet
33663 (@pxref{General Query Packets}).
33667 @cindex @samp{D} packet
33668 The first form of the packet is used to detach @value{GDBN} from the
33669 remote system. It is sent to the remote target
33670 before @value{GDBN} disconnects via the @code{detach} command.
33672 The second form, including a process ID, is used when multiprocess
33673 protocol extensions are enabled (@pxref{multiprocess extensions}), to
33674 detach only a specific process. The @var{pid} is specified as a
33675 big-endian hex string.
33685 @item F @var{RC},@var{EE},@var{CF};@var{XX}
33686 @cindex @samp{F} packet
33687 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
33688 This is part of the File-I/O protocol extension. @xref{File-I/O
33689 Remote Protocol Extension}, for the specification.
33692 @anchor{read registers packet}
33693 @cindex @samp{g} packet
33694 Read general registers.
33698 @item @var{XX@dots{}}
33699 Each byte of register data is described by two hex digits. The bytes
33700 with the register are transmitted in target byte order. The size of
33701 each register and their position within the @samp{g} packet are
33702 determined by the @value{GDBN} internal gdbarch functions
33703 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
33704 specification of several standard @samp{g} packets is specified below.
33706 When reading registers from a trace frame (@pxref{Analyze Collected
33707 Data,,Using the Collected Data}), the stub may also return a string of
33708 literal @samp{x}'s in place of the register data digits, to indicate
33709 that the corresponding register has not been collected, thus its value
33710 is unavailable. For example, for an architecture with 4 registers of
33711 4 bytes each, the following reply indicates to @value{GDBN} that
33712 registers 0 and 2 have not been collected, while registers 1 and 3
33713 have been collected, and both have zero value:
33717 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
33724 @item G @var{XX@dots{}}
33725 @cindex @samp{G} packet
33726 Write general registers. @xref{read registers packet}, for a
33727 description of the @var{XX@dots{}} data.
33737 @item H @var{op} @var{thread-id}
33738 @cindex @samp{H} packet
33739 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
33740 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
33741 it should be @samp{c} for step and continue operations (note that this
33742 is deprecated, supporting the @samp{vCont} command is a better
33743 option), @samp{g} for other operations. The thread designator
33744 @var{thread-id} has the format and interpretation described in
33745 @ref{thread-id syntax}.
33756 @c 'H': How restrictive (or permissive) is the thread model. If a
33757 @c thread is selected and stopped, are other threads allowed
33758 @c to continue to execute? As I mentioned above, I think the
33759 @c semantics of each command when a thread is selected must be
33760 @c described. For example:
33762 @c 'g': If the stub supports threads and a specific thread is
33763 @c selected, returns the register block from that thread;
33764 @c otherwise returns current registers.
33766 @c 'G' If the stub supports threads and a specific thread is
33767 @c selected, sets the registers of the register block of
33768 @c that thread; otherwise sets current registers.
33770 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
33771 @anchor{cycle step packet}
33772 @cindex @samp{i} packet
33773 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
33774 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
33775 step starting at that address.
33778 @cindex @samp{I} packet
33779 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
33783 @cindex @samp{k} packet
33786 FIXME: @emph{There is no description of how to operate when a specific
33787 thread context has been selected (i.e.@: does 'k' kill only that
33790 @item m @var{addr},@var{length}
33791 @cindex @samp{m} packet
33792 Read @var{length} bytes of memory starting at address @var{addr}.
33793 Note that @var{addr} may not be aligned to any particular boundary.
33795 The stub need not use any particular size or alignment when gathering
33796 data from memory for the response; even if @var{addr} is word-aligned
33797 and @var{length} is a multiple of the word size, the stub is free to
33798 use byte accesses, or not. For this reason, this packet may not be
33799 suitable for accessing memory-mapped I/O devices.
33800 @cindex alignment of remote memory accesses
33801 @cindex size of remote memory accesses
33802 @cindex memory, alignment and size of remote accesses
33806 @item @var{XX@dots{}}
33807 Memory contents; each byte is transmitted as a two-digit hexadecimal
33808 number. The reply may contain fewer bytes than requested if the
33809 server was able to read only part of the region of memory.
33814 @item M @var{addr},@var{length}:@var{XX@dots{}}
33815 @cindex @samp{M} packet
33816 Write @var{length} bytes of memory starting at address @var{addr}.
33817 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
33818 hexadecimal number.
33825 for an error (this includes the case where only part of the data was
33830 @cindex @samp{p} packet
33831 Read the value of register @var{n}; @var{n} is in hex.
33832 @xref{read registers packet}, for a description of how the returned
33833 register value is encoded.
33837 @item @var{XX@dots{}}
33838 the register's value
33842 Indicating an unrecognized @var{query}.
33845 @item P @var{n@dots{}}=@var{r@dots{}}
33846 @anchor{write register packet}
33847 @cindex @samp{P} packet
33848 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
33849 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
33850 digits for each byte in the register (target byte order).
33860 @item q @var{name} @var{params}@dots{}
33861 @itemx Q @var{name} @var{params}@dots{}
33862 @cindex @samp{q} packet
33863 @cindex @samp{Q} packet
33864 General query (@samp{q}) and set (@samp{Q}). These packets are
33865 described fully in @ref{General Query Packets}.
33868 @cindex @samp{r} packet
33869 Reset the entire system.
33871 Don't use this packet; use the @samp{R} packet instead.
33874 @cindex @samp{R} packet
33875 Restart the program being debugged. @var{XX}, while needed, is ignored.
33876 This packet is only available in extended mode (@pxref{extended mode}).
33878 The @samp{R} packet has no reply.
33880 @item s @r{[}@var{addr}@r{]}
33881 @cindex @samp{s} packet
33882 Single step. @var{addr} is the address at which to resume. If
33883 @var{addr} is omitted, resume at same address.
33885 This packet is deprecated for multi-threading support. @xref{vCont
33889 @xref{Stop Reply Packets}, for the reply specifications.
33891 @item S @var{sig}@r{[};@var{addr}@r{]}
33892 @anchor{step with signal packet}
33893 @cindex @samp{S} packet
33894 Step with signal. This is analogous to the @samp{C} packet, but
33895 requests a single-step, rather than a normal resumption of execution.
33897 This packet is deprecated for multi-threading support. @xref{vCont
33901 @xref{Stop Reply Packets}, for the reply specifications.
33903 @item t @var{addr}:@var{PP},@var{MM}
33904 @cindex @samp{t} packet
33905 Search backwards starting at address @var{addr} for a match with pattern
33906 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
33907 @var{addr} must be at least 3 digits.
33909 @item T @var{thread-id}
33910 @cindex @samp{T} packet
33911 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
33916 thread is still alive
33922 Packets starting with @samp{v} are identified by a multi-letter name,
33923 up to the first @samp{;} or @samp{?} (or the end of the packet).
33925 @item vAttach;@var{pid}
33926 @cindex @samp{vAttach} packet
33927 Attach to a new process with the specified process ID @var{pid}.
33928 The process ID is a
33929 hexadecimal integer identifying the process. In all-stop mode, all
33930 threads in the attached process are stopped; in non-stop mode, it may be
33931 attached without being stopped if that is supported by the target.
33933 @c In non-stop mode, on a successful vAttach, the stub should set the
33934 @c current thread to a thread of the newly-attached process. After
33935 @c attaching, GDB queries for the attached process's thread ID with qC.
33936 @c Also note that, from a user perspective, whether or not the
33937 @c target is stopped on attach in non-stop mode depends on whether you
33938 @c use the foreground or background version of the attach command, not
33939 @c on what vAttach does; GDB does the right thing with respect to either
33940 @c stopping or restarting threads.
33942 This packet is only available in extended mode (@pxref{extended mode}).
33948 @item @r{Any stop packet}
33949 for success in all-stop mode (@pxref{Stop Reply Packets})
33951 for success in non-stop mode (@pxref{Remote Non-Stop})
33954 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
33955 @cindex @samp{vCont} packet
33956 @anchor{vCont packet}
33957 Resume the inferior, specifying different actions for each thread.
33958 If an action is specified with no @var{thread-id}, then it is applied to any
33959 threads that don't have a specific action specified; if no default action is
33960 specified then other threads should remain stopped in all-stop mode and
33961 in their current state in non-stop mode.
33962 Specifying multiple
33963 default actions is an error; specifying no actions is also an error.
33964 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
33966 Currently supported actions are:
33972 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
33976 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
33981 The optional argument @var{addr} normally associated with the
33982 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
33983 not supported in @samp{vCont}.
33985 The @samp{t} action is only relevant in non-stop mode
33986 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
33987 A stop reply should be generated for any affected thread not already stopped.
33988 When a thread is stopped by means of a @samp{t} action,
33989 the corresponding stop reply should indicate that the thread has stopped with
33990 signal @samp{0}, regardless of whether the target uses some other signal
33991 as an implementation detail.
33994 @xref{Stop Reply Packets}, for the reply specifications.
33997 @cindex @samp{vCont?} packet
33998 Request a list of actions supported by the @samp{vCont} packet.
34002 @item vCont@r{[};@var{action}@dots{}@r{]}
34003 The @samp{vCont} packet is supported. Each @var{action} is a supported
34004 command in the @samp{vCont} packet.
34006 The @samp{vCont} packet is not supported.
34009 @item vFile:@var{operation}:@var{parameter}@dots{}
34010 @cindex @samp{vFile} packet
34011 Perform a file operation on the target system. For details,
34012 see @ref{Host I/O Packets}.
34014 @item vFlashErase:@var{addr},@var{length}
34015 @cindex @samp{vFlashErase} packet
34016 Direct the stub to erase @var{length} bytes of flash starting at
34017 @var{addr}. The region may enclose any number of flash blocks, but
34018 its start and end must fall on block boundaries, as indicated by the
34019 flash block size appearing in the memory map (@pxref{Memory Map
34020 Format}). @value{GDBN} groups flash memory programming operations
34021 together, and sends a @samp{vFlashDone} request after each group; the
34022 stub is allowed to delay erase operation until the @samp{vFlashDone}
34023 packet is received.
34025 The stub must support @samp{vCont} if it reports support for
34026 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34027 this case @samp{vCont} actions can be specified to apply to all threads
34028 in a process by using the @samp{p@var{pid}.-1} form of the
34039 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34040 @cindex @samp{vFlashWrite} packet
34041 Direct the stub to write data to flash address @var{addr}. The data
34042 is passed in binary form using the same encoding as for the @samp{X}
34043 packet (@pxref{Binary Data}). The memory ranges specified by
34044 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34045 not overlap, and must appear in order of increasing addresses
34046 (although @samp{vFlashErase} packets for higher addresses may already
34047 have been received; the ordering is guaranteed only between
34048 @samp{vFlashWrite} packets). If a packet writes to an address that was
34049 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34050 target-specific method, the results are unpredictable.
34058 for vFlashWrite addressing non-flash memory
34064 @cindex @samp{vFlashDone} packet
34065 Indicate to the stub that flash programming operation is finished.
34066 The stub is permitted to delay or batch the effects of a group of
34067 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34068 @samp{vFlashDone} packet is received. The contents of the affected
34069 regions of flash memory are unpredictable until the @samp{vFlashDone}
34070 request is completed.
34072 @item vKill;@var{pid}
34073 @cindex @samp{vKill} packet
34074 Kill the process with the specified process ID. @var{pid} is a
34075 hexadecimal integer identifying the process. This packet is used in
34076 preference to @samp{k} when multiprocess protocol extensions are
34077 supported; see @ref{multiprocess extensions}.
34087 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34088 @cindex @samp{vRun} packet
34089 Run the program @var{filename}, passing it each @var{argument} on its
34090 command line. The file and arguments are hex-encoded strings. If
34091 @var{filename} is an empty string, the stub may use a default program
34092 (e.g.@: the last program run). The program is created in the stopped
34095 @c FIXME: What about non-stop mode?
34097 This packet is only available in extended mode (@pxref{extended mode}).
34103 @item @r{Any stop packet}
34104 for success (@pxref{Stop Reply Packets})
34108 @anchor{vStopped packet}
34109 @cindex @samp{vStopped} packet
34111 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
34112 reply and prompt for the stub to report another one.
34116 @item @r{Any stop packet}
34117 if there is another unreported stop event (@pxref{Stop Reply Packets})
34119 if there are no unreported stop events
34122 @item X @var{addr},@var{length}:@var{XX@dots{}}
34124 @cindex @samp{X} packet
34125 Write data to memory, where the data is transmitted in binary.
34126 @var{addr} is address, @var{length} is number of bytes,
34127 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
34137 @item z @var{type},@var{addr},@var{kind}
34138 @itemx Z @var{type},@var{addr},@var{kind}
34139 @anchor{insert breakpoint or watchpoint packet}
34140 @cindex @samp{z} packet
34141 @cindex @samp{Z} packets
34142 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
34143 watchpoint starting at address @var{address} of kind @var{kind}.
34145 Each breakpoint and watchpoint packet @var{type} is documented
34148 @emph{Implementation notes: A remote target shall return an empty string
34149 for an unrecognized breakpoint or watchpoint packet @var{type}. A
34150 remote target shall support either both or neither of a given
34151 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
34152 avoid potential problems with duplicate packets, the operations should
34153 be implemented in an idempotent way.}
34155 @item z0,@var{addr},@var{kind}
34156 @itemx Z0,@var{addr},@var{kind}
34157 @cindex @samp{z0} packet
34158 @cindex @samp{Z0} packet
34159 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
34160 @var{addr} of type @var{kind}.
34162 A memory breakpoint is implemented by replacing the instruction at
34163 @var{addr} with a software breakpoint or trap instruction. The
34164 @var{kind} is target-specific and typically indicates the size of
34165 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
34166 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
34167 architectures have additional meanings for @var{kind};
34168 see @ref{Architecture-Specific Protocol Details}.
34170 @emph{Implementation note: It is possible for a target to copy or move
34171 code that contains memory breakpoints (e.g., when implementing
34172 overlays). The behavior of this packet, in the presence of such a
34173 target, is not defined.}
34185 @item z1,@var{addr},@var{kind}
34186 @itemx Z1,@var{addr},@var{kind}
34187 @cindex @samp{z1} packet
34188 @cindex @samp{Z1} packet
34189 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
34190 address @var{addr}.
34192 A hardware breakpoint is implemented using a mechanism that is not
34193 dependant on being able to modify the target's memory. @var{kind}
34194 has the same meaning as in @samp{Z0} packets.
34196 @emph{Implementation note: A hardware breakpoint is not affected by code
34209 @item z2,@var{addr},@var{kind}
34210 @itemx Z2,@var{addr},@var{kind}
34211 @cindex @samp{z2} packet
34212 @cindex @samp{Z2} packet
34213 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
34214 @var{kind} is interpreted as the number of bytes to watch.
34226 @item z3,@var{addr},@var{kind}
34227 @itemx Z3,@var{addr},@var{kind}
34228 @cindex @samp{z3} packet
34229 @cindex @samp{Z3} packet
34230 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
34231 @var{kind} is interpreted as the number of bytes to watch.
34243 @item z4,@var{addr},@var{kind}
34244 @itemx Z4,@var{addr},@var{kind}
34245 @cindex @samp{z4} packet
34246 @cindex @samp{Z4} packet
34247 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
34248 @var{kind} is interpreted as the number of bytes to watch.
34262 @node Stop Reply Packets
34263 @section Stop Reply Packets
34264 @cindex stop reply packets
34266 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
34267 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
34268 receive any of the below as a reply. Except for @samp{?}
34269 and @samp{vStopped}, that reply is only returned
34270 when the target halts. In the below the exact meaning of @dfn{signal
34271 number} is defined by the header @file{include/gdb/signals.h} in the
34272 @value{GDBN} source code.
34274 As in the description of request packets, we include spaces in the
34275 reply templates for clarity; these are not part of the reply packet's
34276 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
34282 The program received signal number @var{AA} (a two-digit hexadecimal
34283 number). This is equivalent to a @samp{T} response with no
34284 @var{n}:@var{r} pairs.
34286 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
34287 @cindex @samp{T} packet reply
34288 The program received signal number @var{AA} (a two-digit hexadecimal
34289 number). This is equivalent to an @samp{S} response, except that the
34290 @samp{@var{n}:@var{r}} pairs can carry values of important registers
34291 and other information directly in the stop reply packet, reducing
34292 round-trip latency. Single-step and breakpoint traps are reported
34293 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
34297 If @var{n} is a hexadecimal number, it is a register number, and the
34298 corresponding @var{r} gives that register's value. @var{r} is a
34299 series of bytes in target byte order, with each byte given by a
34300 two-digit hex number.
34303 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
34304 the stopped thread, as specified in @ref{thread-id syntax}.
34307 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
34308 the core on which the stop event was detected.
34311 If @var{n} is a recognized @dfn{stop reason}, it describes a more
34312 specific event that stopped the target. The currently defined stop
34313 reasons are listed below. @var{aa} should be @samp{05}, the trap
34314 signal. At most one stop reason should be present.
34317 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34318 and go on to the next; this allows us to extend the protocol in the
34322 The currently defined stop reasons are:
34328 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34331 @cindex shared library events, remote reply
34333 The packet indicates that the loaded libraries have changed.
34334 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34335 list of loaded libraries. @var{r} is ignored.
34337 @cindex replay log events, remote reply
34339 The packet indicates that the target cannot continue replaying
34340 logged execution events, because it has reached the end (or the
34341 beginning when executing backward) of the log. The value of @var{r}
34342 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34343 for more information.
34347 @itemx W @var{AA} ; process:@var{pid}
34348 The process exited, and @var{AA} is the exit status. This is only
34349 applicable to certain targets.
34351 The second form of the response, including the process ID of the exited
34352 process, can be used only when @value{GDBN} has reported support for
34353 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34354 The @var{pid} is formatted as a big-endian hex string.
34357 @itemx X @var{AA} ; process:@var{pid}
34358 The process terminated with signal @var{AA}.
34360 The second form of the response, including the process ID of the
34361 terminated process, can be used only when @value{GDBN} has reported
34362 support for multiprocess protocol extensions; see @ref{multiprocess
34363 extensions}. The @var{pid} is formatted as a big-endian hex string.
34365 @item O @var{XX}@dots{}
34366 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34367 written as the program's console output. This can happen at any time
34368 while the program is running and the debugger should continue to wait
34369 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34371 @item F @var{call-id},@var{parameter}@dots{}
34372 @var{call-id} is the identifier which says which host system call should
34373 be called. This is just the name of the function. Translation into the
34374 correct system call is only applicable as it's defined in @value{GDBN}.
34375 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
34378 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
34379 this very system call.
34381 The target replies with this packet when it expects @value{GDBN} to
34382 call a host system call on behalf of the target. @value{GDBN} replies
34383 with an appropriate @samp{F} packet and keeps up waiting for the next
34384 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
34385 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
34386 Protocol Extension}, for more details.
34390 @node General Query Packets
34391 @section General Query Packets
34392 @cindex remote query requests
34394 Packets starting with @samp{q} are @dfn{general query packets};
34395 packets starting with @samp{Q} are @dfn{general set packets}. General
34396 query and set packets are a semi-unified form for retrieving and
34397 sending information to and from the stub.
34399 The initial letter of a query or set packet is followed by a name
34400 indicating what sort of thing the packet applies to. For example,
34401 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
34402 definitions with the stub. These packet names follow some
34407 The name must not contain commas, colons or semicolons.
34409 Most @value{GDBN} query and set packets have a leading upper case
34412 The names of custom vendor packets should use a company prefix, in
34413 lower case, followed by a period. For example, packets designed at
34414 the Acme Corporation might begin with @samp{qacme.foo} (for querying
34415 foos) or @samp{Qacme.bar} (for setting bars).
34418 The name of a query or set packet should be separated from any
34419 parameters by a @samp{:}; the parameters themselves should be
34420 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
34421 full packet name, and check for a separator or the end of the packet,
34422 in case two packet names share a common prefix. New packets should not begin
34423 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
34424 packets predate these conventions, and have arguments without any terminator
34425 for the packet name; we suspect they are in widespread use in places that
34426 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
34427 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
34430 Like the descriptions of the other packets, each description here
34431 has a template showing the packet's overall syntax, followed by an
34432 explanation of the packet's meaning. We include spaces in some of the
34433 templates for clarity; these are not part of the packet's syntax. No
34434 @value{GDBN} packet uses spaces to separate its components.
34436 Here are the currently defined query and set packets:
34440 @item QAllow:@var{op}:@var{val}@dots{}
34441 @cindex @samp{QAllow} packet
34442 Specify which operations @value{GDBN} expects to request of the
34443 target, as a semicolon-separated list of operation name and value
34444 pairs. Possible values for @var{op} include @samp{WriteReg},
34445 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
34446 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
34447 indicating that @value{GDBN} will not request the operation, or 1,
34448 indicating that it may. (The target can then use this to set up its
34449 own internals optimally, for instance if the debugger never expects to
34450 insert breakpoints, it may not need to install its own trap handler.)
34453 @cindex current thread, remote request
34454 @cindex @samp{qC} packet
34455 Return the current thread ID.
34459 @item QC @var{thread-id}
34460 Where @var{thread-id} is a thread ID as documented in
34461 @ref{thread-id syntax}.
34462 @item @r{(anything else)}
34463 Any other reply implies the old thread ID.
34466 @item qCRC:@var{addr},@var{length}
34467 @cindex CRC of memory block, remote request
34468 @cindex @samp{qCRC} packet
34469 Compute the CRC checksum of a block of memory using CRC-32 defined in
34470 IEEE 802.3. The CRC is computed byte at a time, taking the most
34471 significant bit of each byte first. The initial pattern code
34472 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
34474 @emph{Note:} This is the same CRC used in validating separate debug
34475 files (@pxref{Separate Debug Files, , Debugging Information in Separate
34476 Files}). However the algorithm is slightly different. When validating
34477 separate debug files, the CRC is computed taking the @emph{least}
34478 significant bit of each byte first, and the final result is inverted to
34479 detect trailing zeros.
34484 An error (such as memory fault)
34485 @item C @var{crc32}
34486 The specified memory region's checksum is @var{crc32}.
34489 @item QDisableRandomization:@var{value}
34490 @cindex disable address space randomization, remote request
34491 @cindex @samp{QDisableRandomization} packet
34492 Some target operating systems will randomize the virtual address space
34493 of the inferior process as a security feature, but provide a feature
34494 to disable such randomization, e.g.@: to allow for a more deterministic
34495 debugging experience. On such systems, this packet with a @var{value}
34496 of 1 directs the target to disable address space randomization for
34497 processes subsequently started via @samp{vRun} packets, while a packet
34498 with a @var{value} of 0 tells the target to enable address space
34501 This packet is only available in extended mode (@pxref{extended mode}).
34506 The request succeeded.
34509 An error occurred. @var{nn} are hex digits.
34512 An empty reply indicates that @samp{QDisableRandomization} is not supported
34516 This packet is not probed by default; the remote stub must request it,
34517 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34518 This should only be done on targets that actually support disabling
34519 address space randomization.
34522 @itemx qsThreadInfo
34523 @cindex list active threads, remote request
34524 @cindex @samp{qfThreadInfo} packet
34525 @cindex @samp{qsThreadInfo} packet
34526 Obtain a list of all active thread IDs from the target (OS). Since there
34527 may be too many active threads to fit into one reply packet, this query
34528 works iteratively: it may require more than one query/reply sequence to
34529 obtain the entire list of threads. The first query of the sequence will
34530 be the @samp{qfThreadInfo} query; subsequent queries in the
34531 sequence will be the @samp{qsThreadInfo} query.
34533 NOTE: This packet replaces the @samp{qL} query (see below).
34537 @item m @var{thread-id}
34539 @item m @var{thread-id},@var{thread-id}@dots{}
34540 a comma-separated list of thread IDs
34542 (lower case letter @samp{L}) denotes end of list.
34545 In response to each query, the target will reply with a list of one or
34546 more thread IDs, separated by commas.
34547 @value{GDBN} will respond to each reply with a request for more thread
34548 ids (using the @samp{qs} form of the query), until the target responds
34549 with @samp{l} (lower-case ell, for @dfn{last}).
34550 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
34553 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
34554 @cindex get thread-local storage address, remote request
34555 @cindex @samp{qGetTLSAddr} packet
34556 Fetch the address associated with thread local storage specified
34557 by @var{thread-id}, @var{offset}, and @var{lm}.
34559 @var{thread-id} is the thread ID associated with the
34560 thread for which to fetch the TLS address. @xref{thread-id syntax}.
34562 @var{offset} is the (big endian, hex encoded) offset associated with the
34563 thread local variable. (This offset is obtained from the debug
34564 information associated with the variable.)
34566 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
34567 load module associated with the thread local storage. For example,
34568 a @sc{gnu}/Linux system will pass the link map address of the shared
34569 object associated with the thread local storage under consideration.
34570 Other operating environments may choose to represent the load module
34571 differently, so the precise meaning of this parameter will vary.
34575 @item @var{XX}@dots{}
34576 Hex encoded (big endian) bytes representing the address of the thread
34577 local storage requested.
34580 An error occurred. @var{nn} are hex digits.
34583 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
34586 @item qGetTIBAddr:@var{thread-id}
34587 @cindex get thread information block address
34588 @cindex @samp{qGetTIBAddr} packet
34589 Fetch address of the Windows OS specific Thread Information Block.
34591 @var{thread-id} is the thread ID associated with the thread.
34595 @item @var{XX}@dots{}
34596 Hex encoded (big endian) bytes representing the linear address of the
34597 thread information block.
34600 An error occured. This means that either the thread was not found, or the
34601 address could not be retrieved.
34604 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
34607 @item qL @var{startflag} @var{threadcount} @var{nextthread}
34608 Obtain thread information from RTOS. Where: @var{startflag} (one hex
34609 digit) is one to indicate the first query and zero to indicate a
34610 subsequent query; @var{threadcount} (two hex digits) is the maximum
34611 number of threads the response packet can contain; and @var{nextthread}
34612 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
34613 returned in the response as @var{argthread}.
34615 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
34619 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
34620 Where: @var{count} (two hex digits) is the number of threads being
34621 returned; @var{done} (one hex digit) is zero to indicate more threads
34622 and one indicates no further threads; @var{argthreadid} (eight hex
34623 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
34624 is a sequence of thread IDs from the target. @var{threadid} (eight hex
34625 digits). See @code{remote.c:parse_threadlist_response()}.
34629 @cindex section offsets, remote request
34630 @cindex @samp{qOffsets} packet
34631 Get section offsets that the target used when relocating the downloaded
34636 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
34637 Relocate the @code{Text} section by @var{xxx} from its original address.
34638 Relocate the @code{Data} section by @var{yyy} from its original address.
34639 If the object file format provides segment information (e.g.@: @sc{elf}
34640 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
34641 segments by the supplied offsets.
34643 @emph{Note: while a @code{Bss} offset may be included in the response,
34644 @value{GDBN} ignores this and instead applies the @code{Data} offset
34645 to the @code{Bss} section.}
34647 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
34648 Relocate the first segment of the object file, which conventionally
34649 contains program code, to a starting address of @var{xxx}. If
34650 @samp{DataSeg} is specified, relocate the second segment, which
34651 conventionally contains modifiable data, to a starting address of
34652 @var{yyy}. @value{GDBN} will report an error if the object file
34653 does not contain segment information, or does not contain at least
34654 as many segments as mentioned in the reply. Extra segments are
34655 kept at fixed offsets relative to the last relocated segment.
34658 @item qP @var{mode} @var{thread-id}
34659 @cindex thread information, remote request
34660 @cindex @samp{qP} packet
34661 Returns information on @var{thread-id}. Where: @var{mode} is a hex
34662 encoded 32 bit mode; @var{thread-id} is a thread ID
34663 (@pxref{thread-id syntax}).
34665 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
34668 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
34672 @cindex non-stop mode, remote request
34673 @cindex @samp{QNonStop} packet
34675 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
34676 @xref{Remote Non-Stop}, for more information.
34681 The request succeeded.
34684 An error occurred. @var{nn} are hex digits.
34687 An empty reply indicates that @samp{QNonStop} is not supported by
34691 This packet is not probed by default; the remote stub must request it,
34692 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34693 Use of this packet is controlled by the @code{set non-stop} command;
34694 @pxref{Non-Stop Mode}.
34696 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34697 @cindex pass signals to inferior, remote request
34698 @cindex @samp{QPassSignals} packet
34699 @anchor{QPassSignals}
34700 Each listed @var{signal} should be passed directly to the inferior process.
34701 Signals are numbered identically to continue packets and stop replies
34702 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
34703 strictly greater than the previous item. These signals do not need to stop
34704 the inferior, or be reported to @value{GDBN}. All other signals should be
34705 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
34706 combine; any earlier @samp{QPassSignals} list is completely replaced by the
34707 new list. This packet improves performance when using @samp{handle
34708 @var{signal} nostop noprint pass}.
34713 The request succeeded.
34716 An error occurred. @var{nn} are hex digits.
34719 An empty reply indicates that @samp{QPassSignals} is not supported by
34723 Use of this packet is controlled by the @code{set remote pass-signals}
34724 command (@pxref{Remote Configuration, set remote pass-signals}).
34725 This packet is not probed by default; the remote stub must request it,
34726 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34728 @item qRcmd,@var{command}
34729 @cindex execute remote command, remote request
34730 @cindex @samp{qRcmd} packet
34731 @var{command} (hex encoded) is passed to the local interpreter for
34732 execution. Invalid commands should be reported using the output
34733 string. Before the final result packet, the target may also respond
34734 with a number of intermediate @samp{O@var{output}} console output
34735 packets. @emph{Implementors should note that providing access to a
34736 stubs's interpreter may have security implications}.
34741 A command response with no output.
34743 A command response with the hex encoded output string @var{OUTPUT}.
34745 Indicate a badly formed request.
34747 An empty reply indicates that @samp{qRcmd} is not recognized.
34750 (Note that the @code{qRcmd} packet's name is separated from the
34751 command by a @samp{,}, not a @samp{:}, contrary to the naming
34752 conventions above. Please don't use this packet as a model for new
34755 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
34756 @cindex searching memory, in remote debugging
34757 @cindex @samp{qSearch:memory} packet
34758 @anchor{qSearch memory}
34759 Search @var{length} bytes at @var{address} for @var{search-pattern}.
34760 @var{address} and @var{length} are encoded in hex.
34761 @var{search-pattern} is a sequence of bytes, hex encoded.
34766 The pattern was not found.
34768 The pattern was found at @var{address}.
34770 A badly formed request or an error was encountered while searching memory.
34772 An empty reply indicates that @samp{qSearch:memory} is not recognized.
34775 @item QStartNoAckMode
34776 @cindex @samp{QStartNoAckMode} packet
34777 @anchor{QStartNoAckMode}
34778 Request that the remote stub disable the normal @samp{+}/@samp{-}
34779 protocol acknowledgments (@pxref{Packet Acknowledgment}).
34784 The stub has switched to no-acknowledgment mode.
34785 @value{GDBN} acknowledges this reponse,
34786 but neither the stub nor @value{GDBN} shall send or expect further
34787 @samp{+}/@samp{-} acknowledgments in the current connection.
34789 An empty reply indicates that the stub does not support no-acknowledgment mode.
34792 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
34793 @cindex supported packets, remote query
34794 @cindex features of the remote protocol
34795 @cindex @samp{qSupported} packet
34796 @anchor{qSupported}
34797 Tell the remote stub about features supported by @value{GDBN}, and
34798 query the stub for features it supports. This packet allows
34799 @value{GDBN} and the remote stub to take advantage of each others'
34800 features. @samp{qSupported} also consolidates multiple feature probes
34801 at startup, to improve @value{GDBN} performance---a single larger
34802 packet performs better than multiple smaller probe packets on
34803 high-latency links. Some features may enable behavior which must not
34804 be on by default, e.g.@: because it would confuse older clients or
34805 stubs. Other features may describe packets which could be
34806 automatically probed for, but are not. These features must be
34807 reported before @value{GDBN} will use them. This ``default
34808 unsupported'' behavior is not appropriate for all packets, but it
34809 helps to keep the initial connection time under control with new
34810 versions of @value{GDBN} which support increasing numbers of packets.
34814 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
34815 The stub supports or does not support each returned @var{stubfeature},
34816 depending on the form of each @var{stubfeature} (see below for the
34819 An empty reply indicates that @samp{qSupported} is not recognized,
34820 or that no features needed to be reported to @value{GDBN}.
34823 The allowed forms for each feature (either a @var{gdbfeature} in the
34824 @samp{qSupported} packet, or a @var{stubfeature} in the response)
34828 @item @var{name}=@var{value}
34829 The remote protocol feature @var{name} is supported, and associated
34830 with the specified @var{value}. The format of @var{value} depends
34831 on the feature, but it must not include a semicolon.
34833 The remote protocol feature @var{name} is supported, and does not
34834 need an associated value.
34836 The remote protocol feature @var{name} is not supported.
34838 The remote protocol feature @var{name} may be supported, and
34839 @value{GDBN} should auto-detect support in some other way when it is
34840 needed. This form will not be used for @var{gdbfeature} notifications,
34841 but may be used for @var{stubfeature} responses.
34844 Whenever the stub receives a @samp{qSupported} request, the
34845 supplied set of @value{GDBN} features should override any previous
34846 request. This allows @value{GDBN} to put the stub in a known
34847 state, even if the stub had previously been communicating with
34848 a different version of @value{GDBN}.
34850 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
34855 This feature indicates whether @value{GDBN} supports multiprocess
34856 extensions to the remote protocol. @value{GDBN} does not use such
34857 extensions unless the stub also reports that it supports them by
34858 including @samp{multiprocess+} in its @samp{qSupported} reply.
34859 @xref{multiprocess extensions}, for details.
34862 This feature indicates that @value{GDBN} supports the XML target
34863 description. If the stub sees @samp{xmlRegisters=} with target
34864 specific strings separated by a comma, it will report register
34868 This feature indicates whether @value{GDBN} supports the
34869 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
34870 instruction reply packet}).
34873 Stubs should ignore any unknown values for
34874 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
34875 packet supports receiving packets of unlimited length (earlier
34876 versions of @value{GDBN} may reject overly long responses). Additional values
34877 for @var{gdbfeature} may be defined in the future to let the stub take
34878 advantage of new features in @value{GDBN}, e.g.@: incompatible
34879 improvements in the remote protocol---the @samp{multiprocess} feature is
34880 an example of such a feature. The stub's reply should be independent
34881 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
34882 describes all the features it supports, and then the stub replies with
34883 all the features it supports.
34885 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
34886 responses, as long as each response uses one of the standard forms.
34888 Some features are flags. A stub which supports a flag feature
34889 should respond with a @samp{+} form response. Other features
34890 require values, and the stub should respond with an @samp{=}
34893 Each feature has a default value, which @value{GDBN} will use if
34894 @samp{qSupported} is not available or if the feature is not mentioned
34895 in the @samp{qSupported} response. The default values are fixed; a
34896 stub is free to omit any feature responses that match the defaults.
34898 Not all features can be probed, but for those which can, the probing
34899 mechanism is useful: in some cases, a stub's internal
34900 architecture may not allow the protocol layer to know some information
34901 about the underlying target in advance. This is especially common in
34902 stubs which may be configured for multiple targets.
34904 These are the currently defined stub features and their properties:
34906 @multitable @columnfractions 0.35 0.2 0.12 0.2
34907 @c NOTE: The first row should be @headitem, but we do not yet require
34908 @c a new enough version of Texinfo (4.7) to use @headitem.
34910 @tab Value Required
34914 @item @samp{PacketSize}
34919 @item @samp{qXfer:auxv:read}
34924 @item @samp{qXfer:features:read}
34929 @item @samp{qXfer:libraries:read}
34934 @item @samp{qXfer:memory-map:read}
34939 @item @samp{qXfer:sdata:read}
34944 @item @samp{qXfer:spu:read}
34949 @item @samp{qXfer:spu:write}
34954 @item @samp{qXfer:siginfo:read}
34959 @item @samp{qXfer:siginfo:write}
34964 @item @samp{qXfer:threads:read}
34969 @item @samp{qXfer:traceframe-info:read}
34974 @item @samp{qXfer:fdpic:read}
34979 @item @samp{QNonStop}
34984 @item @samp{QPassSignals}
34989 @item @samp{QStartNoAckMode}
34994 @item @samp{multiprocess}
34999 @item @samp{ConditionalTracepoints}
35004 @item @samp{ReverseContinue}
35009 @item @samp{ReverseStep}
35014 @item @samp{TracepointSource}
35019 @item @samp{QAllow}
35024 @item @samp{QDisableRandomization}
35029 @item @samp{EnableDisableTracepoints}
35034 @item @samp{tracenz}
35041 These are the currently defined stub features, in more detail:
35044 @cindex packet size, remote protocol
35045 @item PacketSize=@var{bytes}
35046 The remote stub can accept packets up to at least @var{bytes} in
35047 length. @value{GDBN} will send packets up to this size for bulk
35048 transfers, and will never send larger packets. This is a limit on the
35049 data characters in the packet, including the frame and checksum.
35050 There is no trailing NUL byte in a remote protocol packet; if the stub
35051 stores packets in a NUL-terminated format, it should allow an extra
35052 byte in its buffer for the NUL. If this stub feature is not supported,
35053 @value{GDBN} guesses based on the size of the @samp{g} packet response.
35055 @item qXfer:auxv:read
35056 The remote stub understands the @samp{qXfer:auxv:read} packet
35057 (@pxref{qXfer auxiliary vector read}).
35059 @item qXfer:features:read
35060 The remote stub understands the @samp{qXfer:features:read} packet
35061 (@pxref{qXfer target description read}).
35063 @item qXfer:libraries:read
35064 The remote stub understands the @samp{qXfer:libraries:read} packet
35065 (@pxref{qXfer library list read}).
35067 @item qXfer:libraries-svr4:read
35068 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
35069 (@pxref{qXfer svr4 library list read}).
35071 @item qXfer:memory-map:read
35072 The remote stub understands the @samp{qXfer:memory-map:read} packet
35073 (@pxref{qXfer memory map read}).
35075 @item qXfer:sdata:read
35076 The remote stub understands the @samp{qXfer:sdata:read} packet
35077 (@pxref{qXfer sdata read}).
35079 @item qXfer:spu:read
35080 The remote stub understands the @samp{qXfer:spu:read} packet
35081 (@pxref{qXfer spu read}).
35083 @item qXfer:spu:write
35084 The remote stub understands the @samp{qXfer:spu:write} packet
35085 (@pxref{qXfer spu write}).
35087 @item qXfer:siginfo:read
35088 The remote stub understands the @samp{qXfer:siginfo:read} packet
35089 (@pxref{qXfer siginfo read}).
35091 @item qXfer:siginfo:write
35092 The remote stub understands the @samp{qXfer:siginfo:write} packet
35093 (@pxref{qXfer siginfo write}).
35095 @item qXfer:threads:read
35096 The remote stub understands the @samp{qXfer:threads:read} packet
35097 (@pxref{qXfer threads read}).
35099 @item qXfer:traceframe-info:read
35100 The remote stub understands the @samp{qXfer:traceframe-info:read}
35101 packet (@pxref{qXfer traceframe info read}).
35103 @item qXfer:fdpic:read
35104 The remote stub understands the @samp{qXfer:fdpic:read}
35105 packet (@pxref{qXfer fdpic loadmap read}).
35108 The remote stub understands the @samp{QNonStop} packet
35109 (@pxref{QNonStop}).
35112 The remote stub understands the @samp{QPassSignals} packet
35113 (@pxref{QPassSignals}).
35115 @item QStartNoAckMode
35116 The remote stub understands the @samp{QStartNoAckMode} packet and
35117 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
35120 @anchor{multiprocess extensions}
35121 @cindex multiprocess extensions, in remote protocol
35122 The remote stub understands the multiprocess extensions to the remote
35123 protocol syntax. The multiprocess extensions affect the syntax of
35124 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
35125 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
35126 replies. Note that reporting this feature indicates support for the
35127 syntactic extensions only, not that the stub necessarily supports
35128 debugging of more than one process at a time. The stub must not use
35129 multiprocess extensions in packet replies unless @value{GDBN} has also
35130 indicated it supports them in its @samp{qSupported} request.
35132 @item qXfer:osdata:read
35133 The remote stub understands the @samp{qXfer:osdata:read} packet
35134 ((@pxref{qXfer osdata read}).
35136 @item ConditionalTracepoints
35137 The remote stub accepts and implements conditional expressions defined
35138 for tracepoints (@pxref{Tracepoint Conditions}).
35140 @item ReverseContinue
35141 The remote stub accepts and implements the reverse continue packet
35145 The remote stub accepts and implements the reverse step packet
35148 @item TracepointSource
35149 The remote stub understands the @samp{QTDPsrc} packet that supplies
35150 the source form of tracepoint definitions.
35153 The remote stub understands the @samp{QAllow} packet.
35155 @item QDisableRandomization
35156 The remote stub understands the @samp{QDisableRandomization} packet.
35158 @item StaticTracepoint
35159 @cindex static tracepoints, in remote protocol
35160 The remote stub supports static tracepoints.
35162 @item InstallInTrace
35163 @anchor{install tracepoint in tracing}
35164 The remote stub supports installing tracepoint in tracing.
35166 @item EnableDisableTracepoints
35167 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
35168 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
35169 to be enabled and disabled while a trace experiment is running.
35172 @cindex string tracing, in remote protocol
35173 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
35174 See @ref{Bytecode Descriptions} for details about the bytecode.
35179 @cindex symbol lookup, remote request
35180 @cindex @samp{qSymbol} packet
35181 Notify the target that @value{GDBN} is prepared to serve symbol lookup
35182 requests. Accept requests from the target for the values of symbols.
35187 The target does not need to look up any (more) symbols.
35188 @item qSymbol:@var{sym_name}
35189 The target requests the value of symbol @var{sym_name} (hex encoded).
35190 @value{GDBN} may provide the value by using the
35191 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
35195 @item qSymbol:@var{sym_value}:@var{sym_name}
35196 Set the value of @var{sym_name} to @var{sym_value}.
35198 @var{sym_name} (hex encoded) is the name of a symbol whose value the
35199 target has previously requested.
35201 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
35202 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
35208 The target does not need to look up any (more) symbols.
35209 @item qSymbol:@var{sym_name}
35210 The target requests the value of a new symbol @var{sym_name} (hex
35211 encoded). @value{GDBN} will continue to supply the values of symbols
35212 (if available), until the target ceases to request them.
35217 @item QTDisconnected
35224 @itemx qTMinFTPILen
35226 @xref{Tracepoint Packets}.
35228 @item qThreadExtraInfo,@var{thread-id}
35229 @cindex thread attributes info, remote request
35230 @cindex @samp{qThreadExtraInfo} packet
35231 Obtain a printable string description of a thread's attributes from
35232 the target OS. @var{thread-id} is a thread ID;
35233 see @ref{thread-id syntax}. This
35234 string may contain anything that the target OS thinks is interesting
35235 for @value{GDBN} to tell the user about the thread. The string is
35236 displayed in @value{GDBN}'s @code{info threads} display. Some
35237 examples of possible thread extra info strings are @samp{Runnable}, or
35238 @samp{Blocked on Mutex}.
35242 @item @var{XX}@dots{}
35243 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
35244 comprising the printable string containing the extra information about
35245 the thread's attributes.
35248 (Note that the @code{qThreadExtraInfo} packet's name is separated from
35249 the command by a @samp{,}, not a @samp{:}, contrary to the naming
35250 conventions above. Please don't use this packet as a model for new
35269 @xref{Tracepoint Packets}.
35271 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
35272 @cindex read special object, remote request
35273 @cindex @samp{qXfer} packet
35274 @anchor{qXfer read}
35275 Read uninterpreted bytes from the target's special data area
35276 identified by the keyword @var{object}. Request @var{length} bytes
35277 starting at @var{offset} bytes into the data. The content and
35278 encoding of @var{annex} is specific to @var{object}; it can supply
35279 additional details about what data to access.
35281 Here are the specific requests of this form defined so far. All
35282 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
35283 formats, listed below.
35286 @item qXfer:auxv:read::@var{offset},@var{length}
35287 @anchor{qXfer auxiliary vector read}
35288 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
35289 auxiliary vector}. Note @var{annex} must be empty.
35291 This packet is not probed by default; the remote stub must request it,
35292 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35294 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
35295 @anchor{qXfer target description read}
35296 Access the @dfn{target description}. @xref{Target Descriptions}. The
35297 annex specifies which XML document to access. The main description is
35298 always loaded from the @samp{target.xml} annex.
35300 This packet is not probed by default; the remote stub must request it,
35301 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35303 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
35304 @anchor{qXfer library list read}
35305 Access the target's list of loaded libraries. @xref{Library List Format}.
35306 The annex part of the generic @samp{qXfer} packet must be empty
35307 (@pxref{qXfer read}).
35309 Targets which maintain a list of libraries in the program's memory do
35310 not need to implement this packet; it is designed for platforms where
35311 the operating system manages the list of loaded libraries.
35313 This packet is not probed by default; the remote stub must request it,
35314 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35316 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
35317 @anchor{qXfer svr4 library list read}
35318 Access the target's list of loaded libraries when the target is an SVR4
35319 platform. @xref{Library List Format for SVR4 Targets}. The annex part
35320 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35322 This packet is optional for better performance on SVR4 targets.
35323 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
35325 This packet is not probed by default; the remote stub must request it,
35326 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35328 @item qXfer:memory-map:read::@var{offset},@var{length}
35329 @anchor{qXfer memory map read}
35330 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
35331 annex part of the generic @samp{qXfer} packet must be empty
35332 (@pxref{qXfer read}).
35334 This packet is not probed by default; the remote stub must request it,
35335 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35337 @item qXfer:sdata:read::@var{offset},@var{length}
35338 @anchor{qXfer sdata read}
35340 Read contents of the extra collected static tracepoint marker
35341 information. The annex part of the generic @samp{qXfer} packet must
35342 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
35345 This packet is not probed by default; the remote stub must request it,
35346 by supplying an appropriate @samp{qSupported} response
35347 (@pxref{qSupported}).
35349 @item qXfer:siginfo:read::@var{offset},@var{length}
35350 @anchor{qXfer siginfo read}
35351 Read contents of the extra signal information on the target
35352 system. The annex part of the generic @samp{qXfer} packet must be
35353 empty (@pxref{qXfer read}).
35355 This packet is not probed by default; the remote stub must request it,
35356 by supplying an appropriate @samp{qSupported} response
35357 (@pxref{qSupported}).
35359 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
35360 @anchor{qXfer spu read}
35361 Read contents of an @code{spufs} file on the target system. The
35362 annex specifies which file to read; it must be of the form
35363 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35364 in the target process, and @var{name} identifes the @code{spufs} file
35365 in that context to be accessed.
35367 This packet is not probed by default; the remote stub must request it,
35368 by supplying an appropriate @samp{qSupported} response
35369 (@pxref{qSupported}).
35371 @item qXfer:threads:read::@var{offset},@var{length}
35372 @anchor{qXfer threads read}
35373 Access the list of threads on target. @xref{Thread List Format}. The
35374 annex part of the generic @samp{qXfer} packet must be empty
35375 (@pxref{qXfer read}).
35377 This packet is not probed by default; the remote stub must request it,
35378 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35380 @item qXfer:traceframe-info:read::@var{offset},@var{length}
35381 @anchor{qXfer traceframe info read}
35383 Return a description of the current traceframe's contents.
35384 @xref{Traceframe Info Format}. The annex part of the generic
35385 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35387 This packet is not probed by default; the remote stub must request it,
35388 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35390 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
35391 @anchor{qXfer fdpic loadmap read}
35392 Read contents of @code{loadmap}s on the target system. The
35393 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
35394 executable @code{loadmap} or interpreter @code{loadmap} to read.
35396 This packet is not probed by default; the remote stub must request it,
35397 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35399 @item qXfer:osdata:read::@var{offset},@var{length}
35400 @anchor{qXfer osdata read}
35401 Access the target's @dfn{operating system information}.
35402 @xref{Operating System Information}.
35409 Data @var{data} (@pxref{Binary Data}) has been read from the
35410 target. There may be more data at a higher address (although
35411 it is permitted to return @samp{m} even for the last valid
35412 block of data, as long as at least one byte of data was read).
35413 @var{data} may have fewer bytes than the @var{length} in the
35417 Data @var{data} (@pxref{Binary Data}) has been read from the target.
35418 There is no more data to be read. @var{data} may have fewer bytes
35419 than the @var{length} in the request.
35422 The @var{offset} in the request is at the end of the data.
35423 There is no more data to be read.
35426 The request was malformed, or @var{annex} was invalid.
35429 The offset was invalid, or there was an error encountered reading the data.
35430 @var{nn} is a hex-encoded @code{errno} value.
35433 An empty reply indicates the @var{object} string was not recognized by
35434 the stub, or that the object does not support reading.
35437 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
35438 @cindex write data into object, remote request
35439 @anchor{qXfer write}
35440 Write uninterpreted bytes into the target's special data area
35441 identified by the keyword @var{object}, starting at @var{offset} bytes
35442 into the data. @var{data}@dots{} is the binary-encoded data
35443 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
35444 is specific to @var{object}; it can supply additional details about what data
35447 Here are the specific requests of this form defined so far. All
35448 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
35449 formats, listed below.
35452 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
35453 @anchor{qXfer siginfo write}
35454 Write @var{data} to the extra signal information on the target system.
35455 The annex part of the generic @samp{qXfer} packet must be
35456 empty (@pxref{qXfer write}).
35458 This packet is not probed by default; the remote stub must request it,
35459 by supplying an appropriate @samp{qSupported} response
35460 (@pxref{qSupported}).
35462 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
35463 @anchor{qXfer spu write}
35464 Write @var{data} to an @code{spufs} file on the target system. The
35465 annex specifies which file to write; it must be of the form
35466 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35467 in the target process, and @var{name} identifes the @code{spufs} file
35468 in that context to be accessed.
35470 This packet is not probed by default; the remote stub must request it,
35471 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35477 @var{nn} (hex encoded) is the number of bytes written.
35478 This may be fewer bytes than supplied in the request.
35481 The request was malformed, or @var{annex} was invalid.
35484 The offset was invalid, or there was an error encountered writing the data.
35485 @var{nn} is a hex-encoded @code{errno} value.
35488 An empty reply indicates the @var{object} string was not
35489 recognized by the stub, or that the object does not support writing.
35492 @item qXfer:@var{object}:@var{operation}:@dots{}
35493 Requests of this form may be added in the future. When a stub does
35494 not recognize the @var{object} keyword, or its support for
35495 @var{object} does not recognize the @var{operation} keyword, the stub
35496 must respond with an empty packet.
35498 @item qAttached:@var{pid}
35499 @cindex query attached, remote request
35500 @cindex @samp{qAttached} packet
35501 Return an indication of whether the remote server attached to an
35502 existing process or created a new process. When the multiprocess
35503 protocol extensions are supported (@pxref{multiprocess extensions}),
35504 @var{pid} is an integer in hexadecimal format identifying the target
35505 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
35506 the query packet will be simplified as @samp{qAttached}.
35508 This query is used, for example, to know whether the remote process
35509 should be detached or killed when a @value{GDBN} session is ended with
35510 the @code{quit} command.
35515 The remote server attached to an existing process.
35517 The remote server created a new process.
35519 A badly formed request or an error was encountered.
35524 @node Architecture-Specific Protocol Details
35525 @section Architecture-Specific Protocol Details
35527 This section describes how the remote protocol is applied to specific
35528 target architectures. Also see @ref{Standard Target Features}, for
35529 details of XML target descriptions for each architecture.
35533 @subsubsection Breakpoint Kinds
35535 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
35540 16-bit Thumb mode breakpoint.
35543 32-bit Thumb mode (Thumb-2) breakpoint.
35546 32-bit ARM mode breakpoint.
35552 @subsubsection Register Packet Format
35554 The following @code{g}/@code{G} packets have previously been defined.
35555 In the below, some thirty-two bit registers are transferred as
35556 sixty-four bits. Those registers should be zero/sign extended (which?)
35557 to fill the space allocated. Register bytes are transferred in target
35558 byte order. The two nibbles within a register byte are transferred
35559 most-significant - least-significant.
35565 All registers are transferred as thirty-two bit quantities in the order:
35566 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
35567 registers; fsr; fir; fp.
35571 All registers are transferred as sixty-four bit quantities (including
35572 thirty-two bit registers such as @code{sr}). The ordering is the same
35577 @node Tracepoint Packets
35578 @section Tracepoint Packets
35579 @cindex tracepoint packets
35580 @cindex packets, tracepoint
35582 Here we describe the packets @value{GDBN} uses to implement
35583 tracepoints (@pxref{Tracepoints}).
35587 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
35588 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
35589 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
35590 the tracepoint is disabled. @var{step} is the tracepoint's step
35591 count, and @var{pass} is its pass count. If an @samp{F} is present,
35592 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
35593 the number of bytes that the target should copy elsewhere to make room
35594 for the tracepoint. If an @samp{X} is present, it introduces a
35595 tracepoint condition, which consists of a hexadecimal length, followed
35596 by a comma and hex-encoded bytes, in a manner similar to action
35597 encodings as described below. If the trailing @samp{-} is present,
35598 further @samp{QTDP} packets will follow to specify this tracepoint's
35604 The packet was understood and carried out.
35606 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35608 The packet was not recognized.
35611 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
35612 Define actions to be taken when a tracepoint is hit. @var{n} and
35613 @var{addr} must be the same as in the initial @samp{QTDP} packet for
35614 this tracepoint. This packet may only be sent immediately after
35615 another @samp{QTDP} packet that ended with a @samp{-}. If the
35616 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
35617 specifying more actions for this tracepoint.
35619 In the series of action packets for a given tracepoint, at most one
35620 can have an @samp{S} before its first @var{action}. If such a packet
35621 is sent, it and the following packets define ``while-stepping''
35622 actions. Any prior packets define ordinary actions --- that is, those
35623 taken when the tracepoint is first hit. If no action packet has an
35624 @samp{S}, then all the packets in the series specify ordinary
35625 tracepoint actions.
35627 The @samp{@var{action}@dots{}} portion of the packet is a series of
35628 actions, concatenated without separators. Each action has one of the
35634 Collect the registers whose bits are set in @var{mask}. @var{mask} is
35635 a hexadecimal number whose @var{i}'th bit is set if register number
35636 @var{i} should be collected. (The least significant bit is numbered
35637 zero.) Note that @var{mask} may be any number of digits long; it may
35638 not fit in a 32-bit word.
35640 @item M @var{basereg},@var{offset},@var{len}
35641 Collect @var{len} bytes of memory starting at the address in register
35642 number @var{basereg}, plus @var{offset}. If @var{basereg} is
35643 @samp{-1}, then the range has a fixed address: @var{offset} is the
35644 address of the lowest byte to collect. The @var{basereg},
35645 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
35646 values (the @samp{-1} value for @var{basereg} is a special case).
35648 @item X @var{len},@var{expr}
35649 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
35650 it directs. @var{expr} is an agent expression, as described in
35651 @ref{Agent Expressions}. Each byte of the expression is encoded as a
35652 two-digit hex number in the packet; @var{len} is the number of bytes
35653 in the expression (and thus one-half the number of hex digits in the
35658 Any number of actions may be packed together in a single @samp{QTDP}
35659 packet, as long as the packet does not exceed the maximum packet
35660 length (400 bytes, for many stubs). There may be only one @samp{R}
35661 action per tracepoint, and it must precede any @samp{M} or @samp{X}
35662 actions. Any registers referred to by @samp{M} and @samp{X} actions
35663 must be collected by a preceding @samp{R} action. (The
35664 ``while-stepping'' actions are treated as if they were attached to a
35665 separate tracepoint, as far as these restrictions are concerned.)
35670 The packet was understood and carried out.
35672 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35674 The packet was not recognized.
35677 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
35678 @cindex @samp{QTDPsrc} packet
35679 Specify a source string of tracepoint @var{n} at address @var{addr}.
35680 This is useful to get accurate reproduction of the tracepoints
35681 originally downloaded at the beginning of the trace run. @var{type}
35682 is the name of the tracepoint part, such as @samp{cond} for the
35683 tracepoint's conditional expression (see below for a list of types), while
35684 @var{bytes} is the string, encoded in hexadecimal.
35686 @var{start} is the offset of the @var{bytes} within the overall source
35687 string, while @var{slen} is the total length of the source string.
35688 This is intended for handling source strings that are longer than will
35689 fit in a single packet.
35690 @c Add detailed example when this info is moved into a dedicated
35691 @c tracepoint descriptions section.
35693 The available string types are @samp{at} for the location,
35694 @samp{cond} for the conditional, and @samp{cmd} for an action command.
35695 @value{GDBN} sends a separate packet for each command in the action
35696 list, in the same order in which the commands are stored in the list.
35698 The target does not need to do anything with source strings except
35699 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
35702 Although this packet is optional, and @value{GDBN} will only send it
35703 if the target replies with @samp{TracepointSource} @xref{General
35704 Query Packets}, it makes both disconnected tracing and trace files
35705 much easier to use. Otherwise the user must be careful that the
35706 tracepoints in effect while looking at trace frames are identical to
35707 the ones in effect during the trace run; even a small discrepancy
35708 could cause @samp{tdump} not to work, or a particular trace frame not
35711 @item QTDV:@var{n}:@var{value}
35712 @cindex define trace state variable, remote request
35713 @cindex @samp{QTDV} packet
35714 Create a new trace state variable, number @var{n}, with an initial
35715 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
35716 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
35717 the option of not using this packet for initial values of zero; the
35718 target should simply create the trace state variables as they are
35719 mentioned in expressions.
35721 @item QTFrame:@var{n}
35722 Select the @var{n}'th tracepoint frame from the buffer, and use the
35723 register and memory contents recorded there to answer subsequent
35724 request packets from @value{GDBN}.
35726 A successful reply from the stub indicates that the stub has found the
35727 requested frame. The response is a series of parts, concatenated
35728 without separators, describing the frame we selected. Each part has
35729 one of the following forms:
35733 The selected frame is number @var{n} in the trace frame buffer;
35734 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
35735 was no frame matching the criteria in the request packet.
35738 The selected trace frame records a hit of tracepoint number @var{t};
35739 @var{t} is a hexadecimal number.
35743 @item QTFrame:pc:@var{addr}
35744 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35745 currently selected frame whose PC is @var{addr};
35746 @var{addr} is a hexadecimal number.
35748 @item QTFrame:tdp:@var{t}
35749 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35750 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
35751 is a hexadecimal number.
35753 @item QTFrame:range:@var{start}:@var{end}
35754 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35755 currently selected frame whose PC is between @var{start} (inclusive)
35756 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
35759 @item QTFrame:outside:@var{start}:@var{end}
35760 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
35761 frame @emph{outside} the given range of addresses (exclusive).
35764 This packet requests the minimum length of instruction at which a fast
35765 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
35766 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
35767 it depends on the target system being able to create trampolines in
35768 the first 64K of memory, which might or might not be possible for that
35769 system. So the reply to this packet will be 4 if it is able to
35776 The minimum instruction length is currently unknown.
35778 The minimum instruction length is @var{length}, where @var{length} is greater
35779 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
35780 that a fast tracepoint may be placed on any instruction regardless of size.
35782 An error has occurred.
35784 An empty reply indicates that the request is not supported by the stub.
35788 Begin the tracepoint experiment. Begin collecting data from
35789 tracepoint hits in the trace frame buffer. This packet supports the
35790 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
35791 instruction reply packet}).
35794 End the tracepoint experiment. Stop collecting trace frames.
35796 @item QTEnable:@var{n}:@var{addr}
35798 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
35799 experiment. If the tracepoint was previously disabled, then collection
35800 of data from it will resume.
35802 @item QTDisable:@var{n}:@var{addr}
35804 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
35805 experiment. No more data will be collected from the tracepoint unless
35806 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
35809 Clear the table of tracepoints, and empty the trace frame buffer.
35811 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
35812 Establish the given ranges of memory as ``transparent''. The stub
35813 will answer requests for these ranges from memory's current contents,
35814 if they were not collected as part of the tracepoint hit.
35816 @value{GDBN} uses this to mark read-only regions of memory, like those
35817 containing program code. Since these areas never change, they should
35818 still have the same contents they did when the tracepoint was hit, so
35819 there's no reason for the stub to refuse to provide their contents.
35821 @item QTDisconnected:@var{value}
35822 Set the choice to what to do with the tracing run when @value{GDBN}
35823 disconnects from the target. A @var{value} of 1 directs the target to
35824 continue the tracing run, while 0 tells the target to stop tracing if
35825 @value{GDBN} is no longer in the picture.
35828 Ask the stub if there is a trace experiment running right now.
35830 The reply has the form:
35834 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
35835 @var{running} is a single digit @code{1} if the trace is presently
35836 running, or @code{0} if not. It is followed by semicolon-separated
35837 optional fields that an agent may use to report additional status.
35841 If the trace is not running, the agent may report any of several
35842 explanations as one of the optional fields:
35847 No trace has been run yet.
35849 @item tstop[:@var{text}]:0
35850 The trace was stopped by a user-originated stop command. The optional
35851 @var{text} field is a user-supplied string supplied as part of the
35852 stop command (for instance, an explanation of why the trace was
35853 stopped manually). It is hex-encoded.
35856 The trace stopped because the trace buffer filled up.
35858 @item tdisconnected:0
35859 The trace stopped because @value{GDBN} disconnected from the target.
35861 @item tpasscount:@var{tpnum}
35862 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
35864 @item terror:@var{text}:@var{tpnum}
35865 The trace stopped because tracepoint @var{tpnum} had an error. The
35866 string @var{text} is available to describe the nature of the error
35867 (for instance, a divide by zero in the condition expression).
35868 @var{text} is hex encoded.
35871 The trace stopped for some other reason.
35875 Additional optional fields supply statistical and other information.
35876 Although not required, they are extremely useful for users monitoring
35877 the progress of a trace run. If a trace has stopped, and these
35878 numbers are reported, they must reflect the state of the just-stopped
35883 @item tframes:@var{n}
35884 The number of trace frames in the buffer.
35886 @item tcreated:@var{n}
35887 The total number of trace frames created during the run. This may
35888 be larger than the trace frame count, if the buffer is circular.
35890 @item tsize:@var{n}
35891 The total size of the trace buffer, in bytes.
35893 @item tfree:@var{n}
35894 The number of bytes still unused in the buffer.
35896 @item circular:@var{n}
35897 The value of the circular trace buffer flag. @code{1} means that the
35898 trace buffer is circular and old trace frames will be discarded if
35899 necessary to make room, @code{0} means that the trace buffer is linear
35902 @item disconn:@var{n}
35903 The value of the disconnected tracing flag. @code{1} means that
35904 tracing will continue after @value{GDBN} disconnects, @code{0} means
35905 that the trace run will stop.
35909 @item qTP:@var{tp}:@var{addr}
35910 @cindex tracepoint status, remote request
35911 @cindex @samp{qTP} packet
35912 Ask the stub for the current state of tracepoint number @var{tp} at
35913 address @var{addr}.
35917 @item V@var{hits}:@var{usage}
35918 The tracepoint has been hit @var{hits} times so far during the trace
35919 run, and accounts for @var{usage} in the trace buffer. Note that
35920 @code{while-stepping} steps are not counted as separate hits, but the
35921 steps' space consumption is added into the usage number.
35925 @item qTV:@var{var}
35926 @cindex trace state variable value, remote request
35927 @cindex @samp{qTV} packet
35928 Ask the stub for the value of the trace state variable number @var{var}.
35933 The value of the variable is @var{value}. This will be the current
35934 value of the variable if the user is examining a running target, or a
35935 saved value if the variable was collected in the trace frame that the
35936 user is looking at. Note that multiple requests may result in
35937 different reply values, such as when requesting values while the
35938 program is running.
35941 The value of the variable is unknown. This would occur, for example,
35942 if the user is examining a trace frame in which the requested variable
35948 These packets request data about tracepoints that are being used by
35949 the target. @value{GDBN} sends @code{qTfP} to get the first piece
35950 of data, and multiple @code{qTsP} to get additional pieces. Replies
35951 to these packets generally take the form of the @code{QTDP} packets
35952 that define tracepoints. (FIXME add detailed syntax)
35956 These packets request data about trace state variables that are on the
35957 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
35958 and multiple @code{qTsV} to get additional variables. Replies to
35959 these packets follow the syntax of the @code{QTDV} packets that define
35960 trace state variables.
35964 These packets request data about static tracepoint markers that exist
35965 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
35966 first piece of data, and multiple @code{qTsSTM} to get additional
35967 pieces. Replies to these packets take the following form:
35971 @item m @var{address}:@var{id}:@var{extra}
35973 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
35974 a comma-separated list of markers
35976 (lower case letter @samp{L}) denotes end of list.
35978 An error occurred. @var{nn} are hex digits.
35980 An empty reply indicates that the request is not supported by the
35984 @var{address} is encoded in hex.
35985 @var{id} and @var{extra} are strings encoded in hex.
35987 In response to each query, the target will reply with a list of one or
35988 more markers, separated by commas. @value{GDBN} will respond to each
35989 reply with a request for more markers (using the @samp{qs} form of the
35990 query), until the target responds with @samp{l} (lower-case ell, for
35993 @item qTSTMat:@var{address}
35994 This packets requests data about static tracepoint markers in the
35995 target program at @var{address}. Replies to this packet follow the
35996 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
35997 tracepoint markers.
35999 @item QTSave:@var{filename}
36000 This packet directs the target to save trace data to the file name
36001 @var{filename} in the target's filesystem. @var{filename} is encoded
36002 as a hex string; the interpretation of the file name (relative vs
36003 absolute, wild cards, etc) is up to the target.
36005 @item qTBuffer:@var{offset},@var{len}
36006 Return up to @var{len} bytes of the current contents of trace buffer,
36007 starting at @var{offset}. The trace buffer is treated as if it were
36008 a contiguous collection of traceframes, as per the trace file format.
36009 The reply consists as many hex-encoded bytes as the target can deliver
36010 in a packet; it is not an error to return fewer than were asked for.
36011 A reply consisting of just @code{l} indicates that no bytes are
36014 @item QTBuffer:circular:@var{value}
36015 This packet directs the target to use a circular trace buffer if
36016 @var{value} is 1, or a linear buffer if the value is 0.
36018 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
36019 This packet adds optional textual notes to the trace run. Allowable
36020 types include @code{user}, @code{notes}, and @code{tstop}, the
36021 @var{text} fields are arbitrary strings, hex-encoded.
36025 @subsection Relocate instruction reply packet
36026 When installing fast tracepoints in memory, the target may need to
36027 relocate the instruction currently at the tracepoint address to a
36028 different address in memory. For most instructions, a simple copy is
36029 enough, but, for example, call instructions that implicitly push the
36030 return address on the stack, and relative branches or other
36031 PC-relative instructions require offset adjustment, so that the effect
36032 of executing the instruction at a different address is the same as if
36033 it had executed in the original location.
36035 In response to several of the tracepoint packets, the target may also
36036 respond with a number of intermediate @samp{qRelocInsn} request
36037 packets before the final result packet, to have @value{GDBN} handle
36038 this relocation operation. If a packet supports this mechanism, its
36039 documentation will explicitly say so. See for example the above
36040 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
36041 format of the request is:
36044 @item qRelocInsn:@var{from};@var{to}
36046 This requests @value{GDBN} to copy instruction at address @var{from}
36047 to address @var{to}, possibly adjusted so that executing the
36048 instruction at @var{to} has the same effect as executing it at
36049 @var{from}. @value{GDBN} writes the adjusted instruction to target
36050 memory starting at @var{to}.
36055 @item qRelocInsn:@var{adjusted_size}
36056 Informs the stub the relocation is complete. @var{adjusted_size} is
36057 the length in bytes of resulting relocated instruction sequence.
36059 A badly formed request was detected, or an error was encountered while
36060 relocating the instruction.
36063 @node Host I/O Packets
36064 @section Host I/O Packets
36065 @cindex Host I/O, remote protocol
36066 @cindex file transfer, remote protocol
36068 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
36069 operations on the far side of a remote link. For example, Host I/O is
36070 used to upload and download files to a remote target with its own
36071 filesystem. Host I/O uses the same constant values and data structure
36072 layout as the target-initiated File-I/O protocol. However, the
36073 Host I/O packets are structured differently. The target-initiated
36074 protocol relies on target memory to store parameters and buffers.
36075 Host I/O requests are initiated by @value{GDBN}, and the
36076 target's memory is not involved. @xref{File-I/O Remote Protocol
36077 Extension}, for more details on the target-initiated protocol.
36079 The Host I/O request packets all encode a single operation along with
36080 its arguments. They have this format:
36084 @item vFile:@var{operation}: @var{parameter}@dots{}
36085 @var{operation} is the name of the particular request; the target
36086 should compare the entire packet name up to the second colon when checking
36087 for a supported operation. The format of @var{parameter} depends on
36088 the operation. Numbers are always passed in hexadecimal. Negative
36089 numbers have an explicit minus sign (i.e.@: two's complement is not
36090 used). Strings (e.g.@: filenames) are encoded as a series of
36091 hexadecimal bytes. The last argument to a system call may be a
36092 buffer of escaped binary data (@pxref{Binary Data}).
36096 The valid responses to Host I/O packets are:
36100 @item F @var{result} [, @var{errno}] [; @var{attachment}]
36101 @var{result} is the integer value returned by this operation, usually
36102 non-negative for success and -1 for errors. If an error has occured,
36103 @var{errno} will be included in the result. @var{errno} will have a
36104 value defined by the File-I/O protocol (@pxref{Errno Values}). For
36105 operations which return data, @var{attachment} supplies the data as a
36106 binary buffer. Binary buffers in response packets are escaped in the
36107 normal way (@pxref{Binary Data}). See the individual packet
36108 documentation for the interpretation of @var{result} and
36112 An empty response indicates that this operation is not recognized.
36116 These are the supported Host I/O operations:
36119 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
36120 Open a file at @var{pathname} and return a file descriptor for it, or
36121 return -1 if an error occurs. @var{pathname} is a string,
36122 @var{flags} is an integer indicating a mask of open flags
36123 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
36124 of mode bits to use if the file is created (@pxref{mode_t Values}).
36125 @xref{open}, for details of the open flags and mode values.
36127 @item vFile:close: @var{fd}
36128 Close the open file corresponding to @var{fd} and return 0, or
36129 -1 if an error occurs.
36131 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
36132 Read data from the open file corresponding to @var{fd}. Up to
36133 @var{count} bytes will be read from the file, starting at @var{offset}
36134 relative to the start of the file. The target may read fewer bytes;
36135 common reasons include packet size limits and an end-of-file
36136 condition. The number of bytes read is returned. Zero should only be
36137 returned for a successful read at the end of the file, or if
36138 @var{count} was zero.
36140 The data read should be returned as a binary attachment on success.
36141 If zero bytes were read, the response should include an empty binary
36142 attachment (i.e.@: a trailing semicolon). The return value is the
36143 number of target bytes read; the binary attachment may be longer if
36144 some characters were escaped.
36146 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
36147 Write @var{data} (a binary buffer) to the open file corresponding
36148 to @var{fd}. Start the write at @var{offset} from the start of the
36149 file. Unlike many @code{write} system calls, there is no
36150 separate @var{count} argument; the length of @var{data} in the
36151 packet is used. @samp{vFile:write} returns the number of bytes written,
36152 which may be shorter than the length of @var{data}, or -1 if an
36155 @item vFile:unlink: @var{pathname}
36156 Delete the file at @var{pathname} on the target. Return 0,
36157 or -1 if an error occurs. @var{pathname} is a string.
36162 @section Interrupts
36163 @cindex interrupts (remote protocol)
36165 When a program on the remote target is running, @value{GDBN} may
36166 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
36167 a @code{BREAK} followed by @code{g},
36168 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
36170 The precise meaning of @code{BREAK} is defined by the transport
36171 mechanism and may, in fact, be undefined. @value{GDBN} does not
36172 currently define a @code{BREAK} mechanism for any of the network
36173 interfaces except for TCP, in which case @value{GDBN} sends the
36174 @code{telnet} BREAK sequence.
36176 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
36177 transport mechanisms. It is represented by sending the single byte
36178 @code{0x03} without any of the usual packet overhead described in
36179 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
36180 transmitted as part of a packet, it is considered to be packet data
36181 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
36182 (@pxref{X packet}), used for binary downloads, may include an unescaped
36183 @code{0x03} as part of its packet.
36185 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
36186 When Linux kernel receives this sequence from serial port,
36187 it stops execution and connects to gdb.
36189 Stubs are not required to recognize these interrupt mechanisms and the
36190 precise meaning associated with receipt of the interrupt is
36191 implementation defined. If the target supports debugging of multiple
36192 threads and/or processes, it should attempt to interrupt all
36193 currently-executing threads and processes.
36194 If the stub is successful at interrupting the
36195 running program, it should send one of the stop
36196 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
36197 of successfully stopping the program in all-stop mode, and a stop reply
36198 for each stopped thread in non-stop mode.
36199 Interrupts received while the
36200 program is stopped are discarded.
36202 @node Notification Packets
36203 @section Notification Packets
36204 @cindex notification packets
36205 @cindex packets, notification
36207 The @value{GDBN} remote serial protocol includes @dfn{notifications},
36208 packets that require no acknowledgment. Both the GDB and the stub
36209 may send notifications (although the only notifications defined at
36210 present are sent by the stub). Notifications carry information
36211 without incurring the round-trip latency of an acknowledgment, and so
36212 are useful for low-impact communications where occasional packet loss
36215 A notification packet has the form @samp{% @var{data} #
36216 @var{checksum}}, where @var{data} is the content of the notification,
36217 and @var{checksum} is a checksum of @var{data}, computed and formatted
36218 as for ordinary @value{GDBN} packets. A notification's @var{data}
36219 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
36220 receiving a notification, the recipient sends no @samp{+} or @samp{-}
36221 to acknowledge the notification's receipt or to report its corruption.
36223 Every notification's @var{data} begins with a name, which contains no
36224 colon characters, followed by a colon character.
36226 Recipients should silently ignore corrupted notifications and
36227 notifications they do not understand. Recipients should restart
36228 timeout periods on receipt of a well-formed notification, whether or
36229 not they understand it.
36231 Senders should only send the notifications described here when this
36232 protocol description specifies that they are permitted. In the
36233 future, we may extend the protocol to permit existing notifications in
36234 new contexts; this rule helps older senders avoid confusing newer
36237 (Older versions of @value{GDBN} ignore bytes received until they see
36238 the @samp{$} byte that begins an ordinary packet, so new stubs may
36239 transmit notifications without fear of confusing older clients. There
36240 are no notifications defined for @value{GDBN} to send at the moment, but we
36241 assume that most older stubs would ignore them, as well.)
36243 The following notification packets from the stub to @value{GDBN} are
36247 @item Stop: @var{reply}
36248 Report an asynchronous stop event in non-stop mode.
36249 The @var{reply} has the form of a stop reply, as
36250 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
36251 for information on how these notifications are acknowledged by
36255 @node Remote Non-Stop
36256 @section Remote Protocol Support for Non-Stop Mode
36258 @value{GDBN}'s remote protocol supports non-stop debugging of
36259 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
36260 supports non-stop mode, it should report that to @value{GDBN} by including
36261 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
36263 @value{GDBN} typically sends a @samp{QNonStop} packet only when
36264 establishing a new connection with the stub. Entering non-stop mode
36265 does not alter the state of any currently-running threads, but targets
36266 must stop all threads in any already-attached processes when entering
36267 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
36268 probe the target state after a mode change.
36270 In non-stop mode, when an attached process encounters an event that
36271 would otherwise be reported with a stop reply, it uses the
36272 asynchronous notification mechanism (@pxref{Notification Packets}) to
36273 inform @value{GDBN}. In contrast to all-stop mode, where all threads
36274 in all processes are stopped when a stop reply is sent, in non-stop
36275 mode only the thread reporting the stop event is stopped. That is,
36276 when reporting a @samp{S} or @samp{T} response to indicate completion
36277 of a step operation, hitting a breakpoint, or a fault, only the
36278 affected thread is stopped; any other still-running threads continue
36279 to run. When reporting a @samp{W} or @samp{X} response, all running
36280 threads belonging to other attached processes continue to run.
36282 Only one stop reply notification at a time may be pending; if
36283 additional stop events occur before @value{GDBN} has acknowledged the
36284 previous notification, they must be queued by the stub for later
36285 synchronous transmission in response to @samp{vStopped} packets from
36286 @value{GDBN}. Because the notification mechanism is unreliable,
36287 the stub is permitted to resend a stop reply notification
36288 if it believes @value{GDBN} may not have received it. @value{GDBN}
36289 ignores additional stop reply notifications received before it has
36290 finished processing a previous notification and the stub has completed
36291 sending any queued stop events.
36293 Otherwise, @value{GDBN} must be prepared to receive a stop reply
36294 notification at any time. Specifically, they may appear when
36295 @value{GDBN} is not otherwise reading input from the stub, or when
36296 @value{GDBN} is expecting to read a normal synchronous response or a
36297 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
36298 Notification packets are distinct from any other communication from
36299 the stub so there is no ambiguity.
36301 After receiving a stop reply notification, @value{GDBN} shall
36302 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
36303 as a regular, synchronous request to the stub. Such acknowledgment
36304 is not required to happen immediately, as @value{GDBN} is permitted to
36305 send other, unrelated packets to the stub first, which the stub should
36308 Upon receiving a @samp{vStopped} packet, if the stub has other queued
36309 stop events to report to @value{GDBN}, it shall respond by sending a
36310 normal stop reply response. @value{GDBN} shall then send another
36311 @samp{vStopped} packet to solicit further responses; again, it is
36312 permitted to send other, unrelated packets as well which the stub
36313 should process normally.
36315 If the stub receives a @samp{vStopped} packet and there are no
36316 additional stop events to report, the stub shall return an @samp{OK}
36317 response. At this point, if further stop events occur, the stub shall
36318 send a new stop reply notification, @value{GDBN} shall accept the
36319 notification, and the process shall be repeated.
36321 In non-stop mode, the target shall respond to the @samp{?} packet as
36322 follows. First, any incomplete stop reply notification/@samp{vStopped}
36323 sequence in progress is abandoned. The target must begin a new
36324 sequence reporting stop events for all stopped threads, whether or not
36325 it has previously reported those events to @value{GDBN}. The first
36326 stop reply is sent as a synchronous reply to the @samp{?} packet, and
36327 subsequent stop replies are sent as responses to @samp{vStopped} packets
36328 using the mechanism described above. The target must not send
36329 asynchronous stop reply notifications until the sequence is complete.
36330 If all threads are running when the target receives the @samp{?} packet,
36331 or if the target is not attached to any process, it shall respond
36334 @node Packet Acknowledgment
36335 @section Packet Acknowledgment
36337 @cindex acknowledgment, for @value{GDBN} remote
36338 @cindex packet acknowledgment, for @value{GDBN} remote
36339 By default, when either the host or the target machine receives a packet,
36340 the first response expected is an acknowledgment: either @samp{+} (to indicate
36341 the package was received correctly) or @samp{-} (to request retransmission).
36342 This mechanism allows the @value{GDBN} remote protocol to operate over
36343 unreliable transport mechanisms, such as a serial line.
36345 In cases where the transport mechanism is itself reliable (such as a pipe or
36346 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
36347 It may be desirable to disable them in that case to reduce communication
36348 overhead, or for other reasons. This can be accomplished by means of the
36349 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
36351 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
36352 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
36353 and response format still includes the normal checksum, as described in
36354 @ref{Overview}, but the checksum may be ignored by the receiver.
36356 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
36357 no-acknowledgment mode, it should report that to @value{GDBN}
36358 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
36359 @pxref{qSupported}.
36360 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
36361 disabled via the @code{set remote noack-packet off} command
36362 (@pxref{Remote Configuration}),
36363 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
36364 Only then may the stub actually turn off packet acknowledgments.
36365 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
36366 response, which can be safely ignored by the stub.
36368 Note that @code{set remote noack-packet} command only affects negotiation
36369 between @value{GDBN} and the stub when subsequent connections are made;
36370 it does not affect the protocol acknowledgment state for any current
36372 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
36373 new connection is established,
36374 there is also no protocol request to re-enable the acknowledgments
36375 for the current connection, once disabled.
36380 Example sequence of a target being re-started. Notice how the restart
36381 does not get any direct output:
36386 @emph{target restarts}
36389 <- @code{T001:1234123412341234}
36393 Example sequence of a target being stepped by a single instruction:
36396 -> @code{G1445@dots{}}
36401 <- @code{T001:1234123412341234}
36405 <- @code{1455@dots{}}
36409 @node File-I/O Remote Protocol Extension
36410 @section File-I/O Remote Protocol Extension
36411 @cindex File-I/O remote protocol extension
36414 * File-I/O Overview::
36415 * Protocol Basics::
36416 * The F Request Packet::
36417 * The F Reply Packet::
36418 * The Ctrl-C Message::
36420 * List of Supported Calls::
36421 * Protocol-specific Representation of Datatypes::
36423 * File-I/O Examples::
36426 @node File-I/O Overview
36427 @subsection File-I/O Overview
36428 @cindex file-i/o overview
36430 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
36431 target to use the host's file system and console I/O to perform various
36432 system calls. System calls on the target system are translated into a
36433 remote protocol packet to the host system, which then performs the needed
36434 actions and returns a response packet to the target system.
36435 This simulates file system operations even on targets that lack file systems.
36437 The protocol is defined to be independent of both the host and target systems.
36438 It uses its own internal representation of datatypes and values. Both
36439 @value{GDBN} and the target's @value{GDBN} stub are responsible for
36440 translating the system-dependent value representations into the internal
36441 protocol representations when data is transmitted.
36443 The communication is synchronous. A system call is possible only when
36444 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
36445 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
36446 the target is stopped to allow deterministic access to the target's
36447 memory. Therefore File-I/O is not interruptible by target signals. On
36448 the other hand, it is possible to interrupt File-I/O by a user interrupt
36449 (@samp{Ctrl-C}) within @value{GDBN}.
36451 The target's request to perform a host system call does not finish
36452 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
36453 after finishing the system call, the target returns to continuing the
36454 previous activity (continue, step). No additional continue or step
36455 request from @value{GDBN} is required.
36458 (@value{GDBP}) continue
36459 <- target requests 'system call X'
36460 target is stopped, @value{GDBN} executes system call
36461 -> @value{GDBN} returns result
36462 ... target continues, @value{GDBN} returns to wait for the target
36463 <- target hits breakpoint and sends a Txx packet
36466 The protocol only supports I/O on the console and to regular files on
36467 the host file system. Character or block special devices, pipes,
36468 named pipes, sockets or any other communication method on the host
36469 system are not supported by this protocol.
36471 File I/O is not supported in non-stop mode.
36473 @node Protocol Basics
36474 @subsection Protocol Basics
36475 @cindex protocol basics, file-i/o
36477 The File-I/O protocol uses the @code{F} packet as the request as well
36478 as reply packet. Since a File-I/O system call can only occur when
36479 @value{GDBN} is waiting for a response from the continuing or stepping target,
36480 the File-I/O request is a reply that @value{GDBN} has to expect as a result
36481 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
36482 This @code{F} packet contains all information needed to allow @value{GDBN}
36483 to call the appropriate host system call:
36487 A unique identifier for the requested system call.
36490 All parameters to the system call. Pointers are given as addresses
36491 in the target memory address space. Pointers to strings are given as
36492 pointer/length pair. Numerical values are given as they are.
36493 Numerical control flags are given in a protocol-specific representation.
36497 At this point, @value{GDBN} has to perform the following actions.
36501 If the parameters include pointer values to data needed as input to a
36502 system call, @value{GDBN} requests this data from the target with a
36503 standard @code{m} packet request. This additional communication has to be
36504 expected by the target implementation and is handled as any other @code{m}
36508 @value{GDBN} translates all value from protocol representation to host
36509 representation as needed. Datatypes are coerced into the host types.
36512 @value{GDBN} calls the system call.
36515 It then coerces datatypes back to protocol representation.
36518 If the system call is expected to return data in buffer space specified
36519 by pointer parameters to the call, the data is transmitted to the
36520 target using a @code{M} or @code{X} packet. This packet has to be expected
36521 by the target implementation and is handled as any other @code{M} or @code{X}
36526 Eventually @value{GDBN} replies with another @code{F} packet which contains all
36527 necessary information for the target to continue. This at least contains
36534 @code{errno}, if has been changed by the system call.
36541 After having done the needed type and value coercion, the target continues
36542 the latest continue or step action.
36544 @node The F Request Packet
36545 @subsection The @code{F} Request Packet
36546 @cindex file-i/o request packet
36547 @cindex @code{F} request packet
36549 The @code{F} request packet has the following format:
36552 @item F@var{call-id},@var{parameter@dots{}}
36554 @var{call-id} is the identifier to indicate the host system call to be called.
36555 This is just the name of the function.
36557 @var{parameter@dots{}} are the parameters to the system call.
36558 Parameters are hexadecimal integer values, either the actual values in case
36559 of scalar datatypes, pointers to target buffer space in case of compound
36560 datatypes and unspecified memory areas, or pointer/length pairs in case
36561 of string parameters. These are appended to the @var{call-id} as a
36562 comma-delimited list. All values are transmitted in ASCII
36563 string representation, pointer/length pairs separated by a slash.
36569 @node The F Reply Packet
36570 @subsection The @code{F} Reply Packet
36571 @cindex file-i/o reply packet
36572 @cindex @code{F} reply packet
36574 The @code{F} reply packet has the following format:
36578 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
36580 @var{retcode} is the return code of the system call as hexadecimal value.
36582 @var{errno} is the @code{errno} set by the call, in protocol-specific
36584 This parameter can be omitted if the call was successful.
36586 @var{Ctrl-C flag} is only sent if the user requested a break. In this
36587 case, @var{errno} must be sent as well, even if the call was successful.
36588 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
36595 or, if the call was interrupted before the host call has been performed:
36602 assuming 4 is the protocol-specific representation of @code{EINTR}.
36607 @node The Ctrl-C Message
36608 @subsection The @samp{Ctrl-C} Message
36609 @cindex ctrl-c message, in file-i/o protocol
36611 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
36612 reply packet (@pxref{The F Reply Packet}),
36613 the target should behave as if it had
36614 gotten a break message. The meaning for the target is ``system call
36615 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
36616 (as with a break message) and return to @value{GDBN} with a @code{T02}
36619 It's important for the target to know in which
36620 state the system call was interrupted. There are two possible cases:
36624 The system call hasn't been performed on the host yet.
36627 The system call on the host has been finished.
36631 These two states can be distinguished by the target by the value of the
36632 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
36633 call hasn't been performed. This is equivalent to the @code{EINTR} handling
36634 on POSIX systems. In any other case, the target may presume that the
36635 system call has been finished --- successfully or not --- and should behave
36636 as if the break message arrived right after the system call.
36638 @value{GDBN} must behave reliably. If the system call has not been called
36639 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
36640 @code{errno} in the packet. If the system call on the host has been finished
36641 before the user requests a break, the full action must be finished by
36642 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
36643 The @code{F} packet may only be sent when either nothing has happened
36644 or the full action has been completed.
36647 @subsection Console I/O
36648 @cindex console i/o as part of file-i/o
36650 By default and if not explicitly closed by the target system, the file
36651 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
36652 on the @value{GDBN} console is handled as any other file output operation
36653 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
36654 by @value{GDBN} so that after the target read request from file descriptor
36655 0 all following typing is buffered until either one of the following
36660 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
36662 system call is treated as finished.
36665 The user presses @key{RET}. This is treated as end of input with a trailing
36669 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
36670 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
36674 If the user has typed more characters than fit in the buffer given to
36675 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
36676 either another @code{read(0, @dots{})} is requested by the target, or debugging
36677 is stopped at the user's request.
36680 @node List of Supported Calls
36681 @subsection List of Supported Calls
36682 @cindex list of supported file-i/o calls
36699 @unnumberedsubsubsec open
36700 @cindex open, file-i/o system call
36705 int open(const char *pathname, int flags);
36706 int open(const char *pathname, int flags, mode_t mode);
36710 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
36713 @var{flags} is the bitwise @code{OR} of the following values:
36717 If the file does not exist it will be created. The host
36718 rules apply as far as file ownership and time stamps
36722 When used with @code{O_CREAT}, if the file already exists it is
36723 an error and open() fails.
36726 If the file already exists and the open mode allows
36727 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
36728 truncated to zero length.
36731 The file is opened in append mode.
36734 The file is opened for reading only.
36737 The file is opened for writing only.
36740 The file is opened for reading and writing.
36744 Other bits are silently ignored.
36748 @var{mode} is the bitwise @code{OR} of the following values:
36752 User has read permission.
36755 User has write permission.
36758 Group has read permission.
36761 Group has write permission.
36764 Others have read permission.
36767 Others have write permission.
36771 Other bits are silently ignored.
36774 @item Return value:
36775 @code{open} returns the new file descriptor or -1 if an error
36782 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
36785 @var{pathname} refers to a directory.
36788 The requested access is not allowed.
36791 @var{pathname} was too long.
36794 A directory component in @var{pathname} does not exist.
36797 @var{pathname} refers to a device, pipe, named pipe or socket.
36800 @var{pathname} refers to a file on a read-only filesystem and
36801 write access was requested.
36804 @var{pathname} is an invalid pointer value.
36807 No space on device to create the file.
36810 The process already has the maximum number of files open.
36813 The limit on the total number of files open on the system
36817 The call was interrupted by the user.
36823 @unnumberedsubsubsec close
36824 @cindex close, file-i/o system call
36833 @samp{Fclose,@var{fd}}
36835 @item Return value:
36836 @code{close} returns zero on success, or -1 if an error occurred.
36842 @var{fd} isn't a valid open file descriptor.
36845 The call was interrupted by the user.
36851 @unnumberedsubsubsec read
36852 @cindex read, file-i/o system call
36857 int read(int fd, void *buf, unsigned int count);
36861 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
36863 @item Return value:
36864 On success, the number of bytes read is returned.
36865 Zero indicates end of file. If count is zero, read
36866 returns zero as well. On error, -1 is returned.
36872 @var{fd} is not a valid file descriptor or is not open for
36876 @var{bufptr} is an invalid pointer value.
36879 The call was interrupted by the user.
36885 @unnumberedsubsubsec write
36886 @cindex write, file-i/o system call
36891 int write(int fd, const void *buf, unsigned int count);
36895 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
36897 @item Return value:
36898 On success, the number of bytes written are returned.
36899 Zero indicates nothing was written. On error, -1
36906 @var{fd} is not a valid file descriptor or is not open for
36910 @var{bufptr} is an invalid pointer value.
36913 An attempt was made to write a file that exceeds the
36914 host-specific maximum file size allowed.
36917 No space on device to write the data.
36920 The call was interrupted by the user.
36926 @unnumberedsubsubsec lseek
36927 @cindex lseek, file-i/o system call
36932 long lseek (int fd, long offset, int flag);
36936 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
36938 @var{flag} is one of:
36942 The offset is set to @var{offset} bytes.
36945 The offset is set to its current location plus @var{offset}
36949 The offset is set to the size of the file plus @var{offset}
36953 @item Return value:
36954 On success, the resulting unsigned offset in bytes from
36955 the beginning of the file is returned. Otherwise, a
36956 value of -1 is returned.
36962 @var{fd} is not a valid open file descriptor.
36965 @var{fd} is associated with the @value{GDBN} console.
36968 @var{flag} is not a proper value.
36971 The call was interrupted by the user.
36977 @unnumberedsubsubsec rename
36978 @cindex rename, file-i/o system call
36983 int rename(const char *oldpath, const char *newpath);
36987 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
36989 @item Return value:
36990 On success, zero is returned. On error, -1 is returned.
36996 @var{newpath} is an existing directory, but @var{oldpath} is not a
37000 @var{newpath} is a non-empty directory.
37003 @var{oldpath} or @var{newpath} is a directory that is in use by some
37007 An attempt was made to make a directory a subdirectory
37011 A component used as a directory in @var{oldpath} or new
37012 path is not a directory. Or @var{oldpath} is a directory
37013 and @var{newpath} exists but is not a directory.
37016 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
37019 No access to the file or the path of the file.
37023 @var{oldpath} or @var{newpath} was too long.
37026 A directory component in @var{oldpath} or @var{newpath} does not exist.
37029 The file is on a read-only filesystem.
37032 The device containing the file has no room for the new
37036 The call was interrupted by the user.
37042 @unnumberedsubsubsec unlink
37043 @cindex unlink, file-i/o system call
37048 int unlink(const char *pathname);
37052 @samp{Funlink,@var{pathnameptr}/@var{len}}
37054 @item Return value:
37055 On success, zero is returned. On error, -1 is returned.
37061 No access to the file or the path of the file.
37064 The system does not allow unlinking of directories.
37067 The file @var{pathname} cannot be unlinked because it's
37068 being used by another process.
37071 @var{pathnameptr} is an invalid pointer value.
37074 @var{pathname} was too long.
37077 A directory component in @var{pathname} does not exist.
37080 A component of the path is not a directory.
37083 The file is on a read-only filesystem.
37086 The call was interrupted by the user.
37092 @unnumberedsubsubsec stat/fstat
37093 @cindex fstat, file-i/o system call
37094 @cindex stat, file-i/o system call
37099 int stat(const char *pathname, struct stat *buf);
37100 int fstat(int fd, struct stat *buf);
37104 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
37105 @samp{Ffstat,@var{fd},@var{bufptr}}
37107 @item Return value:
37108 On success, zero is returned. On error, -1 is returned.
37114 @var{fd} is not a valid open file.
37117 A directory component in @var{pathname} does not exist or the
37118 path is an empty string.
37121 A component of the path is not a directory.
37124 @var{pathnameptr} is an invalid pointer value.
37127 No access to the file or the path of the file.
37130 @var{pathname} was too long.
37133 The call was interrupted by the user.
37139 @unnumberedsubsubsec gettimeofday
37140 @cindex gettimeofday, file-i/o system call
37145 int gettimeofday(struct timeval *tv, void *tz);
37149 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
37151 @item Return value:
37152 On success, 0 is returned, -1 otherwise.
37158 @var{tz} is a non-NULL pointer.
37161 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
37167 @unnumberedsubsubsec isatty
37168 @cindex isatty, file-i/o system call
37173 int isatty(int fd);
37177 @samp{Fisatty,@var{fd}}
37179 @item Return value:
37180 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
37186 The call was interrupted by the user.
37191 Note that the @code{isatty} call is treated as a special case: it returns
37192 1 to the target if the file descriptor is attached
37193 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
37194 would require implementing @code{ioctl} and would be more complex than
37199 @unnumberedsubsubsec system
37200 @cindex system, file-i/o system call
37205 int system(const char *command);
37209 @samp{Fsystem,@var{commandptr}/@var{len}}
37211 @item Return value:
37212 If @var{len} is zero, the return value indicates whether a shell is
37213 available. A zero return value indicates a shell is not available.
37214 For non-zero @var{len}, the value returned is -1 on error and the
37215 return status of the command otherwise. Only the exit status of the
37216 command is returned, which is extracted from the host's @code{system}
37217 return value by calling @code{WEXITSTATUS(retval)}. In case
37218 @file{/bin/sh} could not be executed, 127 is returned.
37224 The call was interrupted by the user.
37229 @value{GDBN} takes over the full task of calling the necessary host calls
37230 to perform the @code{system} call. The return value of @code{system} on
37231 the host is simplified before it's returned
37232 to the target. Any termination signal information from the child process
37233 is discarded, and the return value consists
37234 entirely of the exit status of the called command.
37236 Due to security concerns, the @code{system} call is by default refused
37237 by @value{GDBN}. The user has to allow this call explicitly with the
37238 @code{set remote system-call-allowed 1} command.
37241 @item set remote system-call-allowed
37242 @kindex set remote system-call-allowed
37243 Control whether to allow the @code{system} calls in the File I/O
37244 protocol for the remote target. The default is zero (disabled).
37246 @item show remote system-call-allowed
37247 @kindex show remote system-call-allowed
37248 Show whether the @code{system} calls are allowed in the File I/O
37252 @node Protocol-specific Representation of Datatypes
37253 @subsection Protocol-specific Representation of Datatypes
37254 @cindex protocol-specific representation of datatypes, in file-i/o protocol
37257 * Integral Datatypes::
37259 * Memory Transfer::
37264 @node Integral Datatypes
37265 @unnumberedsubsubsec Integral Datatypes
37266 @cindex integral datatypes, in file-i/o protocol
37268 The integral datatypes used in the system calls are @code{int},
37269 @code{unsigned int}, @code{long}, @code{unsigned long},
37270 @code{mode_t}, and @code{time_t}.
37272 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
37273 implemented as 32 bit values in this protocol.
37275 @code{long} and @code{unsigned long} are implemented as 64 bit types.
37277 @xref{Limits}, for corresponding MIN and MAX values (similar to those
37278 in @file{limits.h}) to allow range checking on host and target.
37280 @code{time_t} datatypes are defined as seconds since the Epoch.
37282 All integral datatypes transferred as part of a memory read or write of a
37283 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
37286 @node Pointer Values
37287 @unnumberedsubsubsec Pointer Values
37288 @cindex pointer values, in file-i/o protocol
37290 Pointers to target data are transmitted as they are. An exception
37291 is made for pointers to buffers for which the length isn't
37292 transmitted as part of the function call, namely strings. Strings
37293 are transmitted as a pointer/length pair, both as hex values, e.g.@:
37300 which is a pointer to data of length 18 bytes at position 0x1aaf.
37301 The length is defined as the full string length in bytes, including
37302 the trailing null byte. For example, the string @code{"hello world"}
37303 at address 0x123456 is transmitted as
37309 @node Memory Transfer
37310 @unnumberedsubsubsec Memory Transfer
37311 @cindex memory transfer, in file-i/o protocol
37313 Structured data which is transferred using a memory read or write (for
37314 example, a @code{struct stat}) is expected to be in a protocol-specific format
37315 with all scalar multibyte datatypes being big endian. Translation to
37316 this representation needs to be done both by the target before the @code{F}
37317 packet is sent, and by @value{GDBN} before
37318 it transfers memory to the target. Transferred pointers to structured
37319 data should point to the already-coerced data at any time.
37323 @unnumberedsubsubsec struct stat
37324 @cindex struct stat, in file-i/o protocol
37326 The buffer of type @code{struct stat} used by the target and @value{GDBN}
37327 is defined as follows:
37331 unsigned int st_dev; /* device */
37332 unsigned int st_ino; /* inode */
37333 mode_t st_mode; /* protection */
37334 unsigned int st_nlink; /* number of hard links */
37335 unsigned int st_uid; /* user ID of owner */
37336 unsigned int st_gid; /* group ID of owner */
37337 unsigned int st_rdev; /* device type (if inode device) */
37338 unsigned long st_size; /* total size, in bytes */
37339 unsigned long st_blksize; /* blocksize for filesystem I/O */
37340 unsigned long st_blocks; /* number of blocks allocated */
37341 time_t st_atime; /* time of last access */
37342 time_t st_mtime; /* time of last modification */
37343 time_t st_ctime; /* time of last change */
37347 The integral datatypes conform to the definitions given in the
37348 appropriate section (see @ref{Integral Datatypes}, for details) so this
37349 structure is of size 64 bytes.
37351 The values of several fields have a restricted meaning and/or
37357 A value of 0 represents a file, 1 the console.
37360 No valid meaning for the target. Transmitted unchanged.
37363 Valid mode bits are described in @ref{Constants}. Any other
37364 bits have currently no meaning for the target.
37369 No valid meaning for the target. Transmitted unchanged.
37374 These values have a host and file system dependent
37375 accuracy. Especially on Windows hosts, the file system may not
37376 support exact timing values.
37379 The target gets a @code{struct stat} of the above representation and is
37380 responsible for coercing it to the target representation before
37383 Note that due to size differences between the host, target, and protocol
37384 representations of @code{struct stat} members, these members could eventually
37385 get truncated on the target.
37387 @node struct timeval
37388 @unnumberedsubsubsec struct timeval
37389 @cindex struct timeval, in file-i/o protocol
37391 The buffer of type @code{struct timeval} used by the File-I/O protocol
37392 is defined as follows:
37396 time_t tv_sec; /* second */
37397 long tv_usec; /* microsecond */
37401 The integral datatypes conform to the definitions given in the
37402 appropriate section (see @ref{Integral Datatypes}, for details) so this
37403 structure is of size 8 bytes.
37406 @subsection Constants
37407 @cindex constants, in file-i/o protocol
37409 The following values are used for the constants inside of the
37410 protocol. @value{GDBN} and target are responsible for translating these
37411 values before and after the call as needed.
37422 @unnumberedsubsubsec Open Flags
37423 @cindex open flags, in file-i/o protocol
37425 All values are given in hexadecimal representation.
37437 @node mode_t Values
37438 @unnumberedsubsubsec mode_t Values
37439 @cindex mode_t values, in file-i/o protocol
37441 All values are given in octal representation.
37458 @unnumberedsubsubsec Errno Values
37459 @cindex errno values, in file-i/o protocol
37461 All values are given in decimal representation.
37486 @code{EUNKNOWN} is used as a fallback error value if a host system returns
37487 any error value not in the list of supported error numbers.
37490 @unnumberedsubsubsec Lseek Flags
37491 @cindex lseek flags, in file-i/o protocol
37500 @unnumberedsubsubsec Limits
37501 @cindex limits, in file-i/o protocol
37503 All values are given in decimal representation.
37506 INT_MIN -2147483648
37508 UINT_MAX 4294967295
37509 LONG_MIN -9223372036854775808
37510 LONG_MAX 9223372036854775807
37511 ULONG_MAX 18446744073709551615
37514 @node File-I/O Examples
37515 @subsection File-I/O Examples
37516 @cindex file-i/o examples
37518 Example sequence of a write call, file descriptor 3, buffer is at target
37519 address 0x1234, 6 bytes should be written:
37522 <- @code{Fwrite,3,1234,6}
37523 @emph{request memory read from target}
37526 @emph{return "6 bytes written"}
37530 Example sequence of a read call, file descriptor 3, buffer is at target
37531 address 0x1234, 6 bytes should be read:
37534 <- @code{Fread,3,1234,6}
37535 @emph{request memory write to target}
37536 -> @code{X1234,6:XXXXXX}
37537 @emph{return "6 bytes read"}
37541 Example sequence of a read call, call fails on the host due to invalid
37542 file descriptor (@code{EBADF}):
37545 <- @code{Fread,3,1234,6}
37549 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
37553 <- @code{Fread,3,1234,6}
37558 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
37562 <- @code{Fread,3,1234,6}
37563 -> @code{X1234,6:XXXXXX}
37567 @node Library List Format
37568 @section Library List Format
37569 @cindex library list format, remote protocol
37571 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
37572 same process as your application to manage libraries. In this case,
37573 @value{GDBN} can use the loader's symbol table and normal memory
37574 operations to maintain a list of shared libraries. On other
37575 platforms, the operating system manages loaded libraries.
37576 @value{GDBN} can not retrieve the list of currently loaded libraries
37577 through memory operations, so it uses the @samp{qXfer:libraries:read}
37578 packet (@pxref{qXfer library list read}) instead. The remote stub
37579 queries the target's operating system and reports which libraries
37582 The @samp{qXfer:libraries:read} packet returns an XML document which
37583 lists loaded libraries and their offsets. Each library has an
37584 associated name and one or more segment or section base addresses,
37585 which report where the library was loaded in memory.
37587 For the common case of libraries that are fully linked binaries, the
37588 library should have a list of segments. If the target supports
37589 dynamic linking of a relocatable object file, its library XML element
37590 should instead include a list of allocated sections. The segment or
37591 section bases are start addresses, not relocation offsets; they do not
37592 depend on the library's link-time base addresses.
37594 @value{GDBN} must be linked with the Expat library to support XML
37595 library lists. @xref{Expat}.
37597 A simple memory map, with one loaded library relocated by a single
37598 offset, looks like this:
37602 <library name="/lib/libc.so.6">
37603 <segment address="0x10000000"/>
37608 Another simple memory map, with one loaded library with three
37609 allocated sections (.text, .data, .bss), looks like this:
37613 <library name="sharedlib.o">
37614 <section address="0x10000000"/>
37615 <section address="0x20000000"/>
37616 <section address="0x30000000"/>
37621 The format of a library list is described by this DTD:
37624 <!-- library-list: Root element with versioning -->
37625 <!ELEMENT library-list (library)*>
37626 <!ATTLIST library-list version CDATA #FIXED "1.0">
37627 <!ELEMENT library (segment*, section*)>
37628 <!ATTLIST library name CDATA #REQUIRED>
37629 <!ELEMENT segment EMPTY>
37630 <!ATTLIST segment address CDATA #REQUIRED>
37631 <!ELEMENT section EMPTY>
37632 <!ATTLIST section address CDATA #REQUIRED>
37635 In addition, segments and section descriptors cannot be mixed within a
37636 single library element, and you must supply at least one segment or
37637 section for each library.
37639 @node Library List Format for SVR4 Targets
37640 @section Library List Format for SVR4 Targets
37641 @cindex library list format, remote protocol
37643 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
37644 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
37645 shared libraries. Still a special library list provided by this packet is
37646 more efficient for the @value{GDBN} remote protocol.
37648 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
37649 loaded libraries and their SVR4 linker parameters. For each library on SVR4
37650 target, the following parameters are reported:
37654 @code{name}, the absolute file name from the @code{l_name} field of
37655 @code{struct link_map}.
37657 @code{lm} with address of @code{struct link_map} used for TLS
37658 (Thread Local Storage) access.
37660 @code{l_addr}, the displacement as read from the field @code{l_addr} of
37661 @code{struct link_map}. For prelinked libraries this is not an absolute
37662 memory address. It is a displacement of absolute memory address against
37663 address the file was prelinked to during the library load.
37665 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
37668 Additionally the single @code{main-lm} attribute specifies address of
37669 @code{struct link_map} used for the main executable. This parameter is used
37670 for TLS access and its presence is optional.
37672 @value{GDBN} must be linked with the Expat library to support XML
37673 SVR4 library lists. @xref{Expat}.
37675 A simple memory map, with two loaded libraries (which do not use prelink),
37679 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
37680 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
37682 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
37684 </library-list-svr>
37687 The format of an SVR4 library list is described by this DTD:
37690 <!-- library-list-svr4: Root element with versioning -->
37691 <!ELEMENT library-list-svr4 (library)*>
37692 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
37693 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
37694 <!ELEMENT library EMPTY>
37695 <!ATTLIST library name CDATA #REQUIRED>
37696 <!ATTLIST library lm CDATA #REQUIRED>
37697 <!ATTLIST library l_addr CDATA #REQUIRED>
37698 <!ATTLIST library l_ld CDATA #REQUIRED>
37701 @node Memory Map Format
37702 @section Memory Map Format
37703 @cindex memory map format
37705 To be able to write into flash memory, @value{GDBN} needs to obtain a
37706 memory map from the target. This section describes the format of the
37709 The memory map is obtained using the @samp{qXfer:memory-map:read}
37710 (@pxref{qXfer memory map read}) packet and is an XML document that
37711 lists memory regions.
37713 @value{GDBN} must be linked with the Expat library to support XML
37714 memory maps. @xref{Expat}.
37716 The top-level structure of the document is shown below:
37719 <?xml version="1.0"?>
37720 <!DOCTYPE memory-map
37721 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37722 "http://sourceware.org/gdb/gdb-memory-map.dtd">
37728 Each region can be either:
37733 A region of RAM starting at @var{addr} and extending for @var{length}
37737 <memory type="ram" start="@var{addr}" length="@var{length}"/>
37742 A region of read-only memory:
37745 <memory type="rom" start="@var{addr}" length="@var{length}"/>
37750 A region of flash memory, with erasure blocks @var{blocksize}
37754 <memory type="flash" start="@var{addr}" length="@var{length}">
37755 <property name="blocksize">@var{blocksize}</property>
37761 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
37762 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
37763 packets to write to addresses in such ranges.
37765 The formal DTD for memory map format is given below:
37768 <!-- ................................................... -->
37769 <!-- Memory Map XML DTD ................................ -->
37770 <!-- File: memory-map.dtd .............................. -->
37771 <!-- .................................... .............. -->
37772 <!-- memory-map.dtd -->
37773 <!-- memory-map: Root element with versioning -->
37774 <!ELEMENT memory-map (memory | property)>
37775 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
37776 <!ELEMENT memory (property)>
37777 <!-- memory: Specifies a memory region,
37778 and its type, or device. -->
37779 <!ATTLIST memory type CDATA #REQUIRED
37780 start CDATA #REQUIRED
37781 length CDATA #REQUIRED
37782 device CDATA #IMPLIED>
37783 <!-- property: Generic attribute tag -->
37784 <!ELEMENT property (#PCDATA | property)*>
37785 <!ATTLIST property name CDATA #REQUIRED>
37788 @node Thread List Format
37789 @section Thread List Format
37790 @cindex thread list format
37792 To efficiently update the list of threads and their attributes,
37793 @value{GDBN} issues the @samp{qXfer:threads:read} packet
37794 (@pxref{qXfer threads read}) and obtains the XML document with
37795 the following structure:
37798 <?xml version="1.0"?>
37800 <thread id="id" core="0">
37801 ... description ...
37806 Each @samp{thread} element must have the @samp{id} attribute that
37807 identifies the thread (@pxref{thread-id syntax}). The
37808 @samp{core} attribute, if present, specifies which processor core
37809 the thread was last executing on. The content of the of @samp{thread}
37810 element is interpreted as human-readable auxilliary information.
37812 @node Traceframe Info Format
37813 @section Traceframe Info Format
37814 @cindex traceframe info format
37816 To be able to know which objects in the inferior can be examined when
37817 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
37818 memory ranges, registers and trace state variables that have been
37819 collected in a traceframe.
37821 This list is obtained using the @samp{qXfer:traceframe-info:read}
37822 (@pxref{qXfer traceframe info read}) packet and is an XML document.
37824 @value{GDBN} must be linked with the Expat library to support XML
37825 traceframe info discovery. @xref{Expat}.
37827 The top-level structure of the document is shown below:
37830 <?xml version="1.0"?>
37831 <!DOCTYPE traceframe-info
37832 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37833 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
37839 Each traceframe block can be either:
37844 A region of collected memory starting at @var{addr} and extending for
37845 @var{length} bytes from there:
37848 <memory start="@var{addr}" length="@var{length}"/>
37853 The formal DTD for the traceframe info format is given below:
37856 <!ELEMENT traceframe-info (memory)* >
37857 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
37859 <!ELEMENT memory EMPTY>
37860 <!ATTLIST memory start CDATA #REQUIRED
37861 length CDATA #REQUIRED>
37864 @include agentexpr.texi
37866 @node Target Descriptions
37867 @appendix Target Descriptions
37868 @cindex target descriptions
37870 One of the challenges of using @value{GDBN} to debug embedded systems
37871 is that there are so many minor variants of each processor
37872 architecture in use. It is common practice for vendors to start with
37873 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
37874 and then make changes to adapt it to a particular market niche. Some
37875 architectures have hundreds of variants, available from dozens of
37876 vendors. This leads to a number of problems:
37880 With so many different customized processors, it is difficult for
37881 the @value{GDBN} maintainers to keep up with the changes.
37883 Since individual variants may have short lifetimes or limited
37884 audiences, it may not be worthwhile to carry information about every
37885 variant in the @value{GDBN} source tree.
37887 When @value{GDBN} does support the architecture of the embedded system
37888 at hand, the task of finding the correct architecture name to give the
37889 @command{set architecture} command can be error-prone.
37892 To address these problems, the @value{GDBN} remote protocol allows a
37893 target system to not only identify itself to @value{GDBN}, but to
37894 actually describe its own features. This lets @value{GDBN} support
37895 processor variants it has never seen before --- to the extent that the
37896 descriptions are accurate, and that @value{GDBN} understands them.
37898 @value{GDBN} must be linked with the Expat library to support XML
37899 target descriptions. @xref{Expat}.
37902 * Retrieving Descriptions:: How descriptions are fetched from a target.
37903 * Target Description Format:: The contents of a target description.
37904 * Predefined Target Types:: Standard types available for target
37906 * Standard Target Features:: Features @value{GDBN} knows about.
37909 @node Retrieving Descriptions
37910 @section Retrieving Descriptions
37912 Target descriptions can be read from the target automatically, or
37913 specified by the user manually. The default behavior is to read the
37914 description from the target. @value{GDBN} retrieves it via the remote
37915 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
37916 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
37917 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
37918 XML document, of the form described in @ref{Target Description
37921 Alternatively, you can specify a file to read for the target description.
37922 If a file is set, the target will not be queried. The commands to
37923 specify a file are:
37926 @cindex set tdesc filename
37927 @item set tdesc filename @var{path}
37928 Read the target description from @var{path}.
37930 @cindex unset tdesc filename
37931 @item unset tdesc filename
37932 Do not read the XML target description from a file. @value{GDBN}
37933 will use the description supplied by the current target.
37935 @cindex show tdesc filename
37936 @item show tdesc filename
37937 Show the filename to read for a target description, if any.
37941 @node Target Description Format
37942 @section Target Description Format
37943 @cindex target descriptions, XML format
37945 A target description annex is an @uref{http://www.w3.org/XML/, XML}
37946 document which complies with the Document Type Definition provided in
37947 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
37948 means you can use generally available tools like @command{xmllint} to
37949 check that your feature descriptions are well-formed and valid.
37950 However, to help people unfamiliar with XML write descriptions for
37951 their targets, we also describe the grammar here.
37953 Target descriptions can identify the architecture of the remote target
37954 and (for some architectures) provide information about custom register
37955 sets. They can also identify the OS ABI of the remote target.
37956 @value{GDBN} can use this information to autoconfigure for your
37957 target, or to warn you if you connect to an unsupported target.
37959 Here is a simple target description:
37962 <target version="1.0">
37963 <architecture>i386:x86-64</architecture>
37968 This minimal description only says that the target uses
37969 the x86-64 architecture.
37971 A target description has the following overall form, with [ ] marking
37972 optional elements and @dots{} marking repeatable elements. The elements
37973 are explained further below.
37976 <?xml version="1.0"?>
37977 <!DOCTYPE target SYSTEM "gdb-target.dtd">
37978 <target version="1.0">
37979 @r{[}@var{architecture}@r{]}
37980 @r{[}@var{osabi}@r{]}
37981 @r{[}@var{compatible}@r{]}
37982 @r{[}@var{feature}@dots{}@r{]}
37987 The description is generally insensitive to whitespace and line
37988 breaks, under the usual common-sense rules. The XML version
37989 declaration and document type declaration can generally be omitted
37990 (@value{GDBN} does not require them), but specifying them may be
37991 useful for XML validation tools. The @samp{version} attribute for
37992 @samp{<target>} may also be omitted, but we recommend
37993 including it; if future versions of @value{GDBN} use an incompatible
37994 revision of @file{gdb-target.dtd}, they will detect and report
37995 the version mismatch.
37997 @subsection Inclusion
37998 @cindex target descriptions, inclusion
38001 @cindex <xi:include>
38004 It can sometimes be valuable to split a target description up into
38005 several different annexes, either for organizational purposes, or to
38006 share files between different possible target descriptions. You can
38007 divide a description into multiple files by replacing any element of
38008 the target description with an inclusion directive of the form:
38011 <xi:include href="@var{document}"/>
38015 When @value{GDBN} encounters an element of this form, it will retrieve
38016 the named XML @var{document}, and replace the inclusion directive with
38017 the contents of that document. If the current description was read
38018 using @samp{qXfer}, then so will be the included document;
38019 @var{document} will be interpreted as the name of an annex. If the
38020 current description was read from a file, @value{GDBN} will look for
38021 @var{document} as a file in the same directory where it found the
38022 original description.
38024 @subsection Architecture
38025 @cindex <architecture>
38027 An @samp{<architecture>} element has this form:
38030 <architecture>@var{arch}</architecture>
38033 @var{arch} is one of the architectures from the set accepted by
38034 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38037 @cindex @code{<osabi>}
38039 This optional field was introduced in @value{GDBN} version 7.0.
38040 Previous versions of @value{GDBN} ignore it.
38042 An @samp{<osabi>} element has this form:
38045 <osabi>@var{abi-name}</osabi>
38048 @var{abi-name} is an OS ABI name from the same selection accepted by
38049 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
38051 @subsection Compatible Architecture
38052 @cindex @code{<compatible>}
38054 This optional field was introduced in @value{GDBN} version 7.0.
38055 Previous versions of @value{GDBN} ignore it.
38057 A @samp{<compatible>} element has this form:
38060 <compatible>@var{arch}</compatible>
38063 @var{arch} is one of the architectures from the set accepted by
38064 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38066 A @samp{<compatible>} element is used to specify that the target
38067 is able to run binaries in some other than the main target architecture
38068 given by the @samp{<architecture>} element. For example, on the
38069 Cell Broadband Engine, the main architecture is @code{powerpc:common}
38070 or @code{powerpc:common64}, but the system is able to run binaries
38071 in the @code{spu} architecture as well. The way to describe this
38072 capability with @samp{<compatible>} is as follows:
38075 <architecture>powerpc:common</architecture>
38076 <compatible>spu</compatible>
38079 @subsection Features
38082 Each @samp{<feature>} describes some logical portion of the target
38083 system. Features are currently used to describe available CPU
38084 registers and the types of their contents. A @samp{<feature>} element
38088 <feature name="@var{name}">
38089 @r{[}@var{type}@dots{}@r{]}
38095 Each feature's name should be unique within the description. The name
38096 of a feature does not matter unless @value{GDBN} has some special
38097 knowledge of the contents of that feature; if it does, the feature
38098 should have its standard name. @xref{Standard Target Features}.
38102 Any register's value is a collection of bits which @value{GDBN} must
38103 interpret. The default interpretation is a two's complement integer,
38104 but other types can be requested by name in the register description.
38105 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
38106 Target Types}), and the description can define additional composite types.
38108 Each type element must have an @samp{id} attribute, which gives
38109 a unique (within the containing @samp{<feature>}) name to the type.
38110 Types must be defined before they are used.
38113 Some targets offer vector registers, which can be treated as arrays
38114 of scalar elements. These types are written as @samp{<vector>} elements,
38115 specifying the array element type, @var{type}, and the number of elements,
38119 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
38123 If a register's value is usefully viewed in multiple ways, define it
38124 with a union type containing the useful representations. The
38125 @samp{<union>} element contains one or more @samp{<field>} elements,
38126 each of which has a @var{name} and a @var{type}:
38129 <union id="@var{id}">
38130 <field name="@var{name}" type="@var{type}"/>
38136 If a register's value is composed from several separate values, define
38137 it with a structure type. There are two forms of the @samp{<struct>}
38138 element; a @samp{<struct>} element must either contain only bitfields
38139 or contain no bitfields. If the structure contains only bitfields,
38140 its total size in bytes must be specified, each bitfield must have an
38141 explicit start and end, and bitfields are automatically assigned an
38142 integer type. The field's @var{start} should be less than or
38143 equal to its @var{end}, and zero represents the least significant bit.
38146 <struct id="@var{id}" size="@var{size}">
38147 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38152 If the structure contains no bitfields, then each field has an
38153 explicit type, and no implicit padding is added.
38156 <struct id="@var{id}">
38157 <field name="@var{name}" type="@var{type}"/>
38163 If a register's value is a series of single-bit flags, define it with
38164 a flags type. The @samp{<flags>} element has an explicit @var{size}
38165 and contains one or more @samp{<field>} elements. Each field has a
38166 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
38170 <flags id="@var{id}" size="@var{size}">
38171 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38176 @subsection Registers
38179 Each register is represented as an element with this form:
38182 <reg name="@var{name}"
38183 bitsize="@var{size}"
38184 @r{[}regnum="@var{num}"@r{]}
38185 @r{[}save-restore="@var{save-restore}"@r{]}
38186 @r{[}type="@var{type}"@r{]}
38187 @r{[}group="@var{group}"@r{]}/>
38191 The components are as follows:
38196 The register's name; it must be unique within the target description.
38199 The register's size, in bits.
38202 The register's number. If omitted, a register's number is one greater
38203 than that of the previous register (either in the current feature or in
38204 a preceding feature); the first register in the target description
38205 defaults to zero. This register number is used to read or write
38206 the register; e.g.@: it is used in the remote @code{p} and @code{P}
38207 packets, and registers appear in the @code{g} and @code{G} packets
38208 in order of increasing register number.
38211 Whether the register should be preserved across inferior function
38212 calls; this must be either @code{yes} or @code{no}. The default is
38213 @code{yes}, which is appropriate for most registers except for
38214 some system control registers; this is not related to the target's
38218 The type of the register. @var{type} may be a predefined type, a type
38219 defined in the current feature, or one of the special types @code{int}
38220 and @code{float}. @code{int} is an integer type of the correct size
38221 for @var{bitsize}, and @code{float} is a floating point type (in the
38222 architecture's normal floating point format) of the correct size for
38223 @var{bitsize}. The default is @code{int}.
38226 The register group to which this register belongs. @var{group} must
38227 be either @code{general}, @code{float}, or @code{vector}. If no
38228 @var{group} is specified, @value{GDBN} will not display the register
38229 in @code{info registers}.
38233 @node Predefined Target Types
38234 @section Predefined Target Types
38235 @cindex target descriptions, predefined types
38237 Type definitions in the self-description can build up composite types
38238 from basic building blocks, but can not define fundamental types. Instead,
38239 standard identifiers are provided by @value{GDBN} for the fundamental
38240 types. The currently supported types are:
38249 Signed integer types holding the specified number of bits.
38256 Unsigned integer types holding the specified number of bits.
38260 Pointers to unspecified code and data. The program counter and
38261 any dedicated return address register may be marked as code
38262 pointers; printing a code pointer converts it into a symbolic
38263 address. The stack pointer and any dedicated address registers
38264 may be marked as data pointers.
38267 Single precision IEEE floating point.
38270 Double precision IEEE floating point.
38273 The 12-byte extended precision format used by ARM FPA registers.
38276 The 10-byte extended precision format used by x87 registers.
38279 32bit @sc{eflags} register used by x86.
38282 32bit @sc{mxcsr} register used by x86.
38286 @node Standard Target Features
38287 @section Standard Target Features
38288 @cindex target descriptions, standard features
38290 A target description must contain either no registers or all the
38291 target's registers. If the description contains no registers, then
38292 @value{GDBN} will assume a default register layout, selected based on
38293 the architecture. If the description contains any registers, the
38294 default layout will not be used; the standard registers must be
38295 described in the target description, in such a way that @value{GDBN}
38296 can recognize them.
38298 This is accomplished by giving specific names to feature elements
38299 which contain standard registers. @value{GDBN} will look for features
38300 with those names and verify that they contain the expected registers;
38301 if any known feature is missing required registers, or if any required
38302 feature is missing, @value{GDBN} will reject the target
38303 description. You can add additional registers to any of the
38304 standard features --- @value{GDBN} will display them just as if
38305 they were added to an unrecognized feature.
38307 This section lists the known features and their expected contents.
38308 Sample XML documents for these features are included in the
38309 @value{GDBN} source tree, in the directory @file{gdb/features}.
38311 Names recognized by @value{GDBN} should include the name of the
38312 company or organization which selected the name, and the overall
38313 architecture to which the feature applies; so e.g.@: the feature
38314 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
38316 The names of registers are not case sensitive for the purpose
38317 of recognizing standard features, but @value{GDBN} will only display
38318 registers using the capitalization used in the description.
38325 * PowerPC Features::
38331 @subsection ARM Features
38332 @cindex target descriptions, ARM features
38334 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
38336 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
38337 @samp{lr}, @samp{pc}, and @samp{cpsr}.
38339 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
38340 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
38341 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
38344 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
38345 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
38347 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
38348 it should contain at least registers @samp{wR0} through @samp{wR15} and
38349 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
38350 @samp{wCSSF}, and @samp{wCASF} registers are optional.
38352 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
38353 should contain at least registers @samp{d0} through @samp{d15}. If
38354 they are present, @samp{d16} through @samp{d31} should also be included.
38355 @value{GDBN} will synthesize the single-precision registers from
38356 halves of the double-precision registers.
38358 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
38359 need to contain registers; it instructs @value{GDBN} to display the
38360 VFP double-precision registers as vectors and to synthesize the
38361 quad-precision registers from pairs of double-precision registers.
38362 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
38363 be present and include 32 double-precision registers.
38365 @node i386 Features
38366 @subsection i386 Features
38367 @cindex target descriptions, i386 features
38369 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
38370 targets. It should describe the following registers:
38374 @samp{eax} through @samp{edi} plus @samp{eip} for i386
38376 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
38378 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
38379 @samp{fs}, @samp{gs}
38381 @samp{st0} through @samp{st7}
38383 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
38384 @samp{foseg}, @samp{fooff} and @samp{fop}
38387 The register sets may be different, depending on the target.
38389 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
38390 describe registers:
38394 @samp{xmm0} through @samp{xmm7} for i386
38396 @samp{xmm0} through @samp{xmm15} for amd64
38401 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
38402 @samp{org.gnu.gdb.i386.sse} feature. It should
38403 describe the upper 128 bits of @sc{ymm} registers:
38407 @samp{ymm0h} through @samp{ymm7h} for i386
38409 @samp{ymm0h} through @samp{ymm15h} for amd64
38412 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
38413 describe a single register, @samp{orig_eax}.
38415 @node MIPS Features
38416 @subsection MIPS Features
38417 @cindex target descriptions, MIPS features
38419 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
38420 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
38421 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
38424 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
38425 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
38426 registers. They may be 32-bit or 64-bit depending on the target.
38428 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
38429 it may be optional in a future version of @value{GDBN}. It should
38430 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
38431 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
38433 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
38434 contain a single register, @samp{restart}, which is used by the
38435 Linux kernel to control restartable syscalls.
38437 @node M68K Features
38438 @subsection M68K Features
38439 @cindex target descriptions, M68K features
38442 @item @samp{org.gnu.gdb.m68k.core}
38443 @itemx @samp{org.gnu.gdb.coldfire.core}
38444 @itemx @samp{org.gnu.gdb.fido.core}
38445 One of those features must be always present.
38446 The feature that is present determines which flavor of m68k is
38447 used. The feature that is present should contain registers
38448 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
38449 @samp{sp}, @samp{ps} and @samp{pc}.
38451 @item @samp{org.gnu.gdb.coldfire.fp}
38452 This feature is optional. If present, it should contain registers
38453 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
38457 @node PowerPC Features
38458 @subsection PowerPC Features
38459 @cindex target descriptions, PowerPC features
38461 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
38462 targets. It should contain registers @samp{r0} through @samp{r31},
38463 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
38464 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
38466 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
38467 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
38469 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
38470 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
38473 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
38474 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
38475 will combine these registers with the floating point registers
38476 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
38477 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
38478 through @samp{vs63}, the set of vector registers for POWER7.
38480 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
38481 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
38482 @samp{spefscr}. SPE targets should provide 32-bit registers in
38483 @samp{org.gnu.gdb.power.core} and provide the upper halves in
38484 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
38485 these to present registers @samp{ev0} through @samp{ev31} to the
38488 @node TIC6x Features
38489 @subsection TMS320C6x Features
38490 @cindex target descriptions, TIC6x features
38491 @cindex target descriptions, TMS320C6x features
38492 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
38493 targets. It should contain registers @samp{A0} through @samp{A15},
38494 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
38496 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
38497 contain registers @samp{A16} through @samp{A31} and @samp{B16}
38498 through @samp{B31}.
38500 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
38501 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
38503 @node Operating System Information
38504 @appendix Operating System Information
38505 @cindex operating system information
38511 Users of @value{GDBN} often wish to obtain information about the state of
38512 the operating system running on the target---for example the list of
38513 processes, or the list of open files. This section describes the
38514 mechanism that makes it possible. This mechanism is similar to the
38515 target features mechanism (@pxref{Target Descriptions}), but focuses
38516 on a different aspect of target.
38518 Operating system information is retrived from the target via the
38519 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
38520 read}). The object name in the request should be @samp{osdata}, and
38521 the @var{annex} identifies the data to be fetched.
38524 @appendixsection Process list
38525 @cindex operating system information, process list
38527 When requesting the process list, the @var{annex} field in the
38528 @samp{qXfer} request should be @samp{processes}. The returned data is
38529 an XML document. The formal syntax of this document is defined in
38530 @file{gdb/features/osdata.dtd}.
38532 An example document is:
38535 <?xml version="1.0"?>
38536 <!DOCTYPE target SYSTEM "osdata.dtd">
38537 <osdata type="processes">
38539 <column name="pid">1</column>
38540 <column name="user">root</column>
38541 <column name="command">/sbin/init</column>
38542 <column name="cores">1,2,3</column>
38547 Each item should include a column whose name is @samp{pid}. The value
38548 of that column should identify the process on the target. The
38549 @samp{user} and @samp{command} columns are optional, and will be
38550 displayed by @value{GDBN}. The @samp{cores} column, if present,
38551 should contain a comma-separated list of cores that this process
38552 is running on. Target may provide additional columns,
38553 which @value{GDBN} currently ignores.
38555 @node Trace File Format
38556 @appendix Trace File Format
38557 @cindex trace file format
38559 The trace file comes in three parts: a header, a textual description
38560 section, and a trace frame section with binary data.
38562 The header has the form @code{\x7fTRACE0\n}. The first byte is
38563 @code{0x7f} so as to indicate that the file contains binary data,
38564 while the @code{0} is a version number that may have different values
38567 The description section consists of multiple lines of @sc{ascii} text
38568 separated by newline characters (@code{0xa}). The lines may include a
38569 variety of optional descriptive or context-setting information, such
38570 as tracepoint definitions or register set size. @value{GDBN} will
38571 ignore any line that it does not recognize. An empty line marks the end
38574 @c FIXME add some specific types of data
38576 The trace frame section consists of a number of consecutive frames.
38577 Each frame begins with a two-byte tracepoint number, followed by a
38578 four-byte size giving the amount of data in the frame. The data in
38579 the frame consists of a number of blocks, each introduced by a
38580 character indicating its type (at least register, memory, and trace
38581 state variable). The data in this section is raw binary, not a
38582 hexadecimal or other encoding; its endianness matches the target's
38585 @c FIXME bi-arch may require endianness/arch info in description section
38588 @item R @var{bytes}
38589 Register block. The number and ordering of bytes matches that of a
38590 @code{g} packet in the remote protocol. Note that these are the
38591 actual bytes, in target order and @value{GDBN} register order, not a
38592 hexadecimal encoding.
38594 @item M @var{address} @var{length} @var{bytes}...
38595 Memory block. This is a contiguous block of memory, at the 8-byte
38596 address @var{address}, with a 2-byte length @var{length}, followed by
38597 @var{length} bytes.
38599 @item V @var{number} @var{value}
38600 Trace state variable block. This records the 8-byte signed value
38601 @var{value} of trace state variable numbered @var{number}.
38605 Future enhancements of the trace file format may include additional types
38608 @node Index Section Format
38609 @appendix @code{.gdb_index} section format
38610 @cindex .gdb_index section format
38611 @cindex index section format
38613 This section documents the index section that is created by @code{save
38614 gdb-index} (@pxref{Index Files}). The index section is
38615 DWARF-specific; some knowledge of DWARF is assumed in this
38618 The mapped index file format is designed to be directly
38619 @code{mmap}able on any architecture. In most cases, a datum is
38620 represented using a little-endian 32-bit integer value, called an
38621 @code{offset_type}. Big endian machines must byte-swap the values
38622 before using them. Exceptions to this rule are noted. The data is
38623 laid out such that alignment is always respected.
38625 A mapped index consists of several areas, laid out in order.
38629 The file header. This is a sequence of values, of @code{offset_type}
38630 unless otherwise noted:
38634 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
38635 Version 4 differs by its hashing function.
38638 The offset, from the start of the file, of the CU list.
38641 The offset, from the start of the file, of the types CU list. Note
38642 that this area can be empty, in which case this offset will be equal
38643 to the next offset.
38646 The offset, from the start of the file, of the address area.
38649 The offset, from the start of the file, of the symbol table.
38652 The offset, from the start of the file, of the constant pool.
38656 The CU list. This is a sequence of pairs of 64-bit little-endian
38657 values, sorted by the CU offset. The first element in each pair is
38658 the offset of a CU in the @code{.debug_info} section. The second
38659 element in each pair is the length of that CU. References to a CU
38660 elsewhere in the map are done using a CU index, which is just the
38661 0-based index into this table. Note that if there are type CUs, then
38662 conceptually CUs and type CUs form a single list for the purposes of
38666 The types CU list. This is a sequence of triplets of 64-bit
38667 little-endian values. In a triplet, the first value is the CU offset,
38668 the second value is the type offset in the CU, and the third value is
38669 the type signature. The types CU list is not sorted.
38672 The address area. The address area consists of a sequence of address
38673 entries. Each address entry has three elements:
38677 The low address. This is a 64-bit little-endian value.
38680 The high address. This is a 64-bit little-endian value. Like
38681 @code{DW_AT_high_pc}, the value is one byte beyond the end.
38684 The CU index. This is an @code{offset_type} value.
38688 The symbol table. This is an open-addressed hash table. The size of
38689 the hash table is always a power of 2.
38691 Each slot in the hash table consists of a pair of @code{offset_type}
38692 values. The first value is the offset of the symbol's name in the
38693 constant pool. The second value is the offset of the CU vector in the
38696 If both values are 0, then this slot in the hash table is empty. This
38697 is ok because while 0 is a valid constant pool index, it cannot be a
38698 valid index for both a string and a CU vector.
38700 The hash value for a table entry is computed by applying an
38701 iterative hash function to the symbol's name. Starting with an
38702 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
38703 the string is incorporated into the hash using the formula depending on the
38708 The formula is @code{r = r * 67 + c - 113}.
38711 The formula is @code{r = r * 67 + tolower (c) - 113}.
38714 The terminating @samp{\0} is not incorporated into the hash.
38716 The step size used in the hash table is computed via
38717 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
38718 value, and @samp{size} is the size of the hash table. The step size
38719 is used to find the next candidate slot when handling a hash
38722 The names of C@t{++} symbols in the hash table are canonicalized. We
38723 don't currently have a simple description of the canonicalization
38724 algorithm; if you intend to create new index sections, you must read
38728 The constant pool. This is simply a bunch of bytes. It is organized
38729 so that alignment is correct: CU vectors are stored first, followed by
38732 A CU vector in the constant pool is a sequence of @code{offset_type}
38733 values. The first value is the number of CU indices in the vector.
38734 Each subsequent value is the index of a CU in the CU list. This
38735 element in the hash table is used to indicate which CUs define the
38738 A string in the constant pool is zero-terminated.
38743 @node GNU Free Documentation License
38744 @appendix GNU Free Documentation License
38753 % I think something like @colophon should be in texinfo. In the
38755 \long\def\colophon{\hbox to0pt{}\vfill
38756 \centerline{The body of this manual is set in}
38757 \centerline{\fontname\tenrm,}
38758 \centerline{with headings in {\bf\fontname\tenbf}}
38759 \centerline{and examples in {\tt\fontname\tentt}.}
38760 \centerline{{\it\fontname\tenit\/},}
38761 \centerline{{\bf\fontname\tenbf}, and}
38762 \centerline{{\sl\fontname\tensl\/}}
38763 \centerline{are used for emphasis.}\vfill}
38765 % Blame: doc@cygnus.com, 1991.