1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2013 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
11 @settitle Debugging with @value{GDBN}
12 @setchapternewpage odd
21 @c To avoid file-name clashes between index.html and Index.html, when
22 @c the manual is produced on a Posix host and then moved to a
23 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
24 @c indices into two: Concept Index and all the rest.
28 @c readline appendices use @vindex, @findex and @ftable,
29 @c annotate.texi and gdbmi use @findex.
33 @c !!set GDB manual's edition---not the same as GDB version!
34 @c This is updated by GNU Press.
37 @c !!set GDB edit command default editor
40 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
42 @c This is a dir.info fragment to support semi-automated addition of
43 @c manuals to an info tree.
44 @dircategory Software development
46 * Gdb: (gdb). The GNU debugger.
50 Copyright @copyright{} 1988-2013 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) 1988-2013 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.
159 * In-Process Agent:: In-Process Agent
161 * GDB Bugs:: Reporting bugs in @value{GDBN}
163 @ifset SYSTEM_READLINE
164 * Command Line Editing: (rluserman). Command Line Editing
165 * Using History Interactively: (history). Using History Interactively
167 @ifclear SYSTEM_READLINE
168 * Command Line Editing:: Command Line Editing
169 * Using History Interactively:: Using History Interactively
171 * In Memoriam:: In Memoriam
172 * Formatting Documentation:: How to format and print @value{GDBN} documentation
173 * Installing GDB:: Installing GDB
174 * Maintenance Commands:: Maintenance Commands
175 * Remote Protocol:: GDB Remote Serial Protocol
176 * Agent Expressions:: The GDB Agent Expression Mechanism
177 * Target Descriptions:: How targets can describe themselves to
179 * Operating System Information:: Getting additional information from
181 * Trace File Format:: GDB trace file format
182 * Index Section Format:: .gdb_index section format
183 * Copying:: GNU General Public License says
184 how you can copy and share GDB
185 * GNU Free Documentation License:: The license for this documentation
186 * Concept Index:: Index of @value{GDBN} concepts
187 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
188 functions, and Python data types
196 @unnumbered Summary of @value{GDBN}
198 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
199 going on ``inside'' another program while it executes---or what another
200 program was doing at the moment it crashed.
202 @value{GDBN} can do four main kinds of things (plus other things in support of
203 these) to help you catch bugs in the act:
207 Start your program, specifying anything that might affect its behavior.
210 Make your program stop on specified conditions.
213 Examine what has happened, when your program has stopped.
216 Change things in your program, so you can experiment with correcting the
217 effects of one bug and go on to learn about another.
220 You can use @value{GDBN} to debug programs written in C and C@t{++}.
221 For more information, see @ref{Supported Languages,,Supported Languages}.
222 For more information, see @ref{C,,C and C++}.
224 Support for D is partial. For information on D, see
228 Support for Modula-2 is partial. For information on Modula-2, see
229 @ref{Modula-2,,Modula-2}.
231 Support for OpenCL C is partial. For information on OpenCL C, see
232 @ref{OpenCL C,,OpenCL C}.
235 Debugging Pascal programs which use sets, subranges, file variables, or
236 nested functions does not currently work. @value{GDBN} does not support
237 entering expressions, printing values, or similar features using Pascal
241 @value{GDBN} can be used to debug programs written in Fortran, although
242 it may be necessary to refer to some variables with a trailing
245 @value{GDBN} can be used to debug programs written in Objective-C,
246 using either the Apple/NeXT or the GNU Objective-C runtime.
249 * Free Software:: Freely redistributable software
250 * Free Documentation:: Free Software Needs Free Documentation
251 * Contributors:: Contributors to GDB
255 @unnumberedsec Free Software
257 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
258 General Public License
259 (GPL). The GPL gives you the freedom to copy or adapt a licensed
260 program---but every person getting a copy also gets with it the
261 freedom to modify that copy (which means that they must get access to
262 the source code), and the freedom to distribute further copies.
263 Typical software companies use copyrights to limit your freedoms; the
264 Free Software Foundation uses the GPL to preserve these freedoms.
266 Fundamentally, the General Public License is a license which says that
267 you have these freedoms and that you cannot take these freedoms away
270 @node Free Documentation
271 @unnumberedsec Free Software Needs Free Documentation
273 The biggest deficiency in the free software community today is not in
274 the software---it is the lack of good free documentation that we can
275 include with the free software. Many of our most important
276 programs do not come with free reference manuals and free introductory
277 texts. Documentation is an essential part of any software package;
278 when an important free software package does not come with a free
279 manual and a free tutorial, that is a major gap. We have many such
282 Consider Perl, for instance. The tutorial manuals that people
283 normally use are non-free. How did this come about? Because the
284 authors of those manuals published them with restrictive terms---no
285 copying, no modification, source files not available---which exclude
286 them from the free software world.
288 That wasn't the first time this sort of thing happened, and it was far
289 from the last. Many times we have heard a GNU user eagerly describe a
290 manual that he is writing, his intended contribution to the community,
291 only to learn that he had ruined everything by signing a publication
292 contract to make it non-free.
294 Free documentation, like free software, is a matter of freedom, not
295 price. The problem with the non-free manual is not that publishers
296 charge a price for printed copies---that in itself is fine. (The Free
297 Software Foundation sells printed copies of manuals, too.) The
298 problem is the restrictions on the use of the manual. Free manuals
299 are available in source code form, and give you permission to copy and
300 modify. Non-free manuals do not allow this.
302 The criteria of freedom for a free manual are roughly the same as for
303 free software. Redistribution (including the normal kinds of
304 commercial redistribution) must be permitted, so that the manual can
305 accompany every copy of the program, both on-line and on paper.
307 Permission for modification of the technical content is crucial too.
308 When people modify the software, adding or changing features, if they
309 are conscientious they will change the manual too---so they can
310 provide accurate and clear documentation for the modified program. A
311 manual that leaves you no choice but to write a new manual to document
312 a changed version of the program is not really available to our
315 Some kinds of limits on the way modification is handled are
316 acceptable. For example, requirements to preserve the original
317 author's copyright notice, the distribution terms, or the list of
318 authors, are ok. It is also no problem to require modified versions
319 to include notice that they were modified. Even entire sections that
320 may not be deleted or changed are acceptable, as long as they deal
321 with nontechnical topics (like this one). These kinds of restrictions
322 are acceptable because they don't obstruct the community's normal use
325 However, it must be possible to modify all the @emph{technical}
326 content of the manual, and then distribute the result in all the usual
327 media, through all the usual channels. Otherwise, the restrictions
328 obstruct the use of the manual, it is not free, and we need another
329 manual to replace it.
331 Please spread the word about this issue. Our community continues to
332 lose manuals to proprietary publishing. If we spread the word that
333 free software needs free reference manuals and free tutorials, perhaps
334 the next person who wants to contribute by writing documentation will
335 realize, before it is too late, that only free manuals contribute to
336 the free software community.
338 If you are writing documentation, please insist on publishing it under
339 the GNU Free Documentation License or another free documentation
340 license. Remember that this decision requires your approval---you
341 don't have to let the publisher decide. Some commercial publishers
342 will use a free license if you insist, but they will not propose the
343 option; it is up to you to raise the issue and say firmly that this is
344 what you want. If the publisher you are dealing with refuses, please
345 try other publishers. If you're not sure whether a proposed license
346 is free, write to @email{licensing@@gnu.org}.
348 You can encourage commercial publishers to sell more free, copylefted
349 manuals and tutorials by buying them, and particularly by buying
350 copies from the publishers that paid for their writing or for major
351 improvements. Meanwhile, try to avoid buying non-free documentation
352 at all. Check the distribution terms of a manual before you buy it,
353 and insist that whoever seeks your business must respect your freedom.
354 Check the history of the book, and try to reward the publishers that
355 have paid or pay the authors to work on it.
357 The Free Software Foundation maintains a list of free documentation
358 published by other publishers, at
359 @url{http://www.fsf.org/doc/other-free-books.html}.
362 @unnumberedsec Contributors to @value{GDBN}
364 Richard Stallman was the original author of @value{GDBN}, and of many
365 other @sc{gnu} programs. Many others have contributed to its
366 development. This section attempts to credit major contributors. One
367 of the virtues of free software is that everyone is free to contribute
368 to it; with regret, we cannot actually acknowledge everyone here. The
369 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
370 blow-by-blow account.
372 Changes much prior to version 2.0 are lost in the mists of time.
375 @emph{Plea:} Additions to this section are particularly welcome. If you
376 or your friends (or enemies, to be evenhanded) have been unfairly
377 omitted from this list, we would like to add your names!
380 So that they may not regard their many labors as thankless, we
381 particularly thank those who shepherded @value{GDBN} through major
383 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
384 Jim Blandy (release 4.18);
385 Jason Molenda (release 4.17);
386 Stan Shebs (release 4.14);
387 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
388 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
389 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
390 Jim Kingdon (releases 3.5, 3.4, and 3.3);
391 and Randy Smith (releases 3.2, 3.1, and 3.0).
393 Richard Stallman, assisted at various times by Peter TerMaat, Chris
394 Hanson, and Richard Mlynarik, handled releases through 2.8.
396 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
397 in @value{GDBN}, with significant additional contributions from Per
398 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
399 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
400 much general update work leading to release 3.0).
402 @value{GDBN} uses the BFD subroutine library to examine multiple
403 object-file formats; BFD was a joint project of David V.
404 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
406 David Johnson wrote the original COFF support; Pace Willison did
407 the original support for encapsulated COFF.
409 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
411 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
412 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
414 Jean-Daniel Fekete contributed Sun 386i support.
415 Chris Hanson improved the HP9000 support.
416 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
417 David Johnson contributed Encore Umax support.
418 Jyrki Kuoppala contributed Altos 3068 support.
419 Jeff Law contributed HP PA and SOM support.
420 Keith Packard contributed NS32K support.
421 Doug Rabson contributed Acorn Risc Machine support.
422 Bob Rusk contributed Harris Nighthawk CX-UX support.
423 Chris Smith contributed Convex support (and Fortran debugging).
424 Jonathan Stone contributed Pyramid support.
425 Michael Tiemann contributed SPARC support.
426 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
427 Pace Willison contributed Intel 386 support.
428 Jay Vosburgh contributed Symmetry support.
429 Marko Mlinar contributed OpenRISC 1000 support.
431 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
433 Rich Schaefer and Peter Schauer helped with support of SunOS shared
436 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
437 about several machine instruction sets.
439 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
440 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
441 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
442 and RDI targets, respectively.
444 Brian Fox is the author of the readline libraries providing
445 command-line editing and command history.
447 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
448 Modula-2 support, and contributed the Languages chapter of this manual.
450 Fred Fish wrote most of the support for Unix System Vr4.
451 He also enhanced the command-completion support to cover C@t{++} overloaded
454 Hitachi America (now Renesas America), Ltd. sponsored the support for
455 H8/300, H8/500, and Super-H processors.
457 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
459 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
462 Toshiba sponsored the support for the TX39 Mips processor.
464 Matsushita sponsored the support for the MN10200 and MN10300 processors.
466 Fujitsu sponsored the support for SPARClite and FR30 processors.
468 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
471 Michael Snyder added support for tracepoints.
473 Stu Grossman wrote gdbserver.
475 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
476 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
478 The following people at the Hewlett-Packard Company contributed
479 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
480 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
481 compiler, and the Text User Interface (nee Terminal User Interface):
482 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
483 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
484 provided HP-specific information in this manual.
486 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
487 Robert Hoehne made significant contributions to the DJGPP port.
489 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
490 development since 1991. Cygnus engineers who have worked on @value{GDBN}
491 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
492 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
493 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
494 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
495 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
496 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
497 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
498 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
499 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
500 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
501 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
502 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
503 Zuhn have made contributions both large and small.
505 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
506 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
508 Jim Blandy added support for preprocessor macros, while working for Red
511 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
512 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
513 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
514 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
515 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
516 with the migration of old architectures to this new framework.
518 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
519 unwinder framework, this consisting of a fresh new design featuring
520 frame IDs, independent frame sniffers, and the sentinel frame. Mark
521 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
522 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
523 trad unwinders. The architecture-specific changes, each involving a
524 complete rewrite of the architecture's frame code, were carried out by
525 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
526 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
527 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
528 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
531 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
532 Tensilica, Inc.@: contributed support for Xtensa processors. Others
533 who have worked on the Xtensa port of @value{GDBN} in the past include
534 Steve Tjiang, John Newlin, and Scott Foehner.
536 Michael Eager and staff of Xilinx, Inc., contributed support for the
537 Xilinx MicroBlaze architecture.
540 @chapter A Sample @value{GDBN} Session
542 You can use this manual at your leisure to read all about @value{GDBN}.
543 However, a handful of commands are enough to get started using the
544 debugger. This chapter illustrates those commands.
547 In this sample session, we emphasize user input like this: @b{input},
548 to make it easier to pick out from the surrounding output.
551 @c FIXME: this example may not be appropriate for some configs, where
552 @c FIXME...primary interest is in remote use.
554 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
555 processor) exhibits the following bug: sometimes, when we change its
556 quote strings from the default, the commands used to capture one macro
557 definition within another stop working. In the following short @code{m4}
558 session, we define a macro @code{foo} which expands to @code{0000}; we
559 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
560 same thing. However, when we change the open quote string to
561 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
562 procedure fails to define a new synonym @code{baz}:
571 @b{define(bar,defn(`foo'))}
575 @b{changequote(<QUOTE>,<UNQUOTE>)}
577 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
580 m4: End of input: 0: fatal error: EOF in string
584 Let us use @value{GDBN} to try to see what is going on.
587 $ @b{@value{GDBP} m4}
588 @c FIXME: this falsifies the exact text played out, to permit smallbook
589 @c FIXME... format to come out better.
590 @value{GDBN} is free software and you are welcome to distribute copies
591 of it under certain conditions; type "show copying" to see
593 There is absolutely no warranty for @value{GDBN}; type "show warranty"
596 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
601 @value{GDBN} reads only enough symbol data to know where to find the
602 rest when needed; as a result, the first prompt comes up very quickly.
603 We now tell @value{GDBN} to use a narrower display width than usual, so
604 that examples fit in this manual.
607 (@value{GDBP}) @b{set width 70}
611 We need to see how the @code{m4} built-in @code{changequote} works.
612 Having looked at the source, we know the relevant subroutine is
613 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
614 @code{break} command.
617 (@value{GDBP}) @b{break m4_changequote}
618 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
622 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
623 control; as long as control does not reach the @code{m4_changequote}
624 subroutine, the program runs as usual:
627 (@value{GDBP}) @b{run}
628 Starting program: /work/Editorial/gdb/gnu/m4/m4
636 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
637 suspends execution of @code{m4}, displaying information about the
638 context where it stops.
641 @b{changequote(<QUOTE>,<UNQUOTE>)}
643 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
645 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
649 Now we use the command @code{n} (@code{next}) to advance execution to
650 the next line of the current function.
654 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
659 @code{set_quotes} looks like a promising subroutine. We can go into it
660 by using the command @code{s} (@code{step}) instead of @code{next}.
661 @code{step} goes to the next line to be executed in @emph{any}
662 subroutine, so it steps into @code{set_quotes}.
666 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
668 530 if (lquote != def_lquote)
672 The display that shows the subroutine where @code{m4} is now
673 suspended (and its arguments) is called a stack frame display. It
674 shows a summary of the stack. We can use the @code{backtrace}
675 command (which can also be spelled @code{bt}), to see where we are
676 in the stack as a whole: the @code{backtrace} command displays a
677 stack frame for each active subroutine.
680 (@value{GDBP}) @b{bt}
681 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
683 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
685 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
686 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
688 #4 0x79dc in expand_input () at macro.c:40
689 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
693 We step through a few more lines to see what happens. The first two
694 times, we can use @samp{s}; the next two times we use @code{n} to avoid
695 falling into the @code{xstrdup} subroutine.
699 0x3b5c 532 if (rquote != def_rquote)
701 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
702 def_lquote : xstrdup(lq);
704 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
707 538 len_lquote = strlen(rquote);
711 The last line displayed looks a little odd; we can examine the variables
712 @code{lquote} and @code{rquote} to see if they are in fact the new left
713 and right quotes we specified. We use the command @code{p}
714 (@code{print}) to see their values.
717 (@value{GDBP}) @b{p lquote}
718 $1 = 0x35d40 "<QUOTE>"
719 (@value{GDBP}) @b{p rquote}
720 $2 = 0x35d50 "<UNQUOTE>"
724 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
725 To look at some context, we can display ten lines of source
726 surrounding the current line with the @code{l} (@code{list}) command.
732 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
734 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
737 538 len_lquote = strlen(rquote);
738 539 len_rquote = strlen(lquote);
745 Let us step past the two lines that set @code{len_lquote} and
746 @code{len_rquote}, and then examine the values of those variables.
750 539 len_rquote = strlen(lquote);
753 (@value{GDBP}) @b{p len_lquote}
755 (@value{GDBP}) @b{p len_rquote}
760 That certainly looks wrong, assuming @code{len_lquote} and
761 @code{len_rquote} are meant to be the lengths of @code{lquote} and
762 @code{rquote} respectively. We can set them to better values using
763 the @code{p} command, since it can print the value of
764 any expression---and that expression can include subroutine calls and
768 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
770 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
775 Is that enough to fix the problem of using the new quotes with the
776 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
777 executing with the @code{c} (@code{continue}) command, and then try the
778 example that caused trouble initially:
784 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
791 Success! The new quotes now work just as well as the default ones. The
792 problem seems to have been just the two typos defining the wrong
793 lengths. We allow @code{m4} exit by giving it an EOF as input:
797 Program exited normally.
801 The message @samp{Program exited normally.} is from @value{GDBN}; it
802 indicates @code{m4} has finished executing. We can end our @value{GDBN}
803 session with the @value{GDBN} @code{quit} command.
806 (@value{GDBP}) @b{quit}
810 @chapter Getting In and Out of @value{GDBN}
812 This chapter discusses how to start @value{GDBN}, and how to get out of it.
816 type @samp{@value{GDBP}} to start @value{GDBN}.
818 type @kbd{quit} or @kbd{Ctrl-d} to exit.
822 * Invoking GDB:: How to start @value{GDBN}
823 * Quitting GDB:: How to quit @value{GDBN}
824 * Shell Commands:: How to use shell commands inside @value{GDBN}
825 * Logging Output:: How to log @value{GDBN}'s output to a file
829 @section Invoking @value{GDBN}
831 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
832 @value{GDBN} reads commands from the terminal until you tell it to exit.
834 You can also run @code{@value{GDBP}} with a variety of arguments and options,
835 to specify more of your debugging environment at the outset.
837 The command-line options described here are designed
838 to cover a variety of situations; in some environments, some of these
839 options may effectively be unavailable.
841 The most usual way to start @value{GDBN} is with one argument,
842 specifying an executable program:
845 @value{GDBP} @var{program}
849 You can also start with both an executable program and a core file
853 @value{GDBP} @var{program} @var{core}
856 You can, instead, specify a process ID as a second argument, if you want
857 to debug a running process:
860 @value{GDBP} @var{program} 1234
864 would attach @value{GDBN} to process @code{1234} (unless you also have a file
865 named @file{1234}; @value{GDBN} does check for a core file first).
867 Taking advantage of the second command-line argument requires a fairly
868 complete operating system; when you use @value{GDBN} as a remote
869 debugger attached to a bare board, there may not be any notion of
870 ``process'', and there is often no way to get a core dump. @value{GDBN}
871 will warn you if it is unable to attach or to read core dumps.
873 You can optionally have @code{@value{GDBP}} pass any arguments after the
874 executable file to the inferior using @code{--args}. This option stops
877 @value{GDBP} --args gcc -O2 -c foo.c
879 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
880 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
882 You can run @code{@value{GDBP}} without printing the front material, which describes
883 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
890 You can further control how @value{GDBN} starts up by using command-line
891 options. @value{GDBN} itself can remind you of the options available.
901 to display all available options and briefly describe their use
902 (@samp{@value{GDBP} -h} is a shorter equivalent).
904 All options and command line arguments you give are processed
905 in sequential order. The order makes a difference when the
906 @samp{-x} option is used.
910 * File Options:: Choosing files
911 * Mode Options:: Choosing modes
912 * Startup:: What @value{GDBN} does during startup
916 @subsection Choosing Files
918 When @value{GDBN} starts, it reads any arguments other than options as
919 specifying an executable file and core file (or process ID). This is
920 the same as if the arguments were specified by the @samp{-se} and
921 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
922 first argument that does not have an associated option flag as
923 equivalent to the @samp{-se} option followed by that argument; and the
924 second argument that does not have an associated option flag, if any, as
925 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
926 If the second argument begins with a decimal digit, @value{GDBN} will
927 first attempt to attach to it as a process, and if that fails, attempt
928 to open it as a corefile. If you have a corefile whose name begins with
929 a digit, you can prevent @value{GDBN} from treating it as a pid by
930 prefixing it with @file{./}, e.g.@: @file{./12345}.
932 If @value{GDBN} has not been configured to included core file support,
933 such as for most embedded targets, then it will complain about a second
934 argument and ignore it.
936 Many options have both long and short forms; both are shown in the
937 following list. @value{GDBN} also recognizes the long forms if you truncate
938 them, so long as enough of the option is present to be unambiguous.
939 (If you prefer, you can flag option arguments with @samp{--} rather
940 than @samp{-}, though we illustrate the more usual convention.)
942 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
943 @c way, both those who look for -foo and --foo in the index, will find
947 @item -symbols @var{file}
949 @cindex @code{--symbols}
951 Read symbol table from file @var{file}.
953 @item -exec @var{file}
955 @cindex @code{--exec}
957 Use file @var{file} as the executable file to execute when appropriate,
958 and for examining pure data in conjunction with a core dump.
962 Read symbol table from file @var{file} and use it as the executable
965 @item -core @var{file}
967 @cindex @code{--core}
969 Use file @var{file} as a core dump to examine.
971 @item -pid @var{number}
972 @itemx -p @var{number}
975 Connect to process ID @var{number}, as with the @code{attach} command.
977 @item -command @var{file}
979 @cindex @code{--command}
981 Execute commands from file @var{file}. The contents of this file is
982 evaluated exactly as the @code{source} command would.
983 @xref{Command Files,, Command files}.
985 @item -eval-command @var{command}
986 @itemx -ex @var{command}
987 @cindex @code{--eval-command}
989 Execute a single @value{GDBN} command.
991 This option may be used multiple times to call multiple commands. It may
992 also be interleaved with @samp{-command} as required.
995 @value{GDBP} -ex 'target sim' -ex 'load' \
996 -x setbreakpoints -ex 'run' a.out
999 @item -init-command @var{file}
1000 @itemx -ix @var{file}
1001 @cindex @code{--init-command}
1003 Execute commands from file @var{file} before loading the inferior (but
1004 after loading gdbinit files).
1007 @item -init-eval-command @var{command}
1008 @itemx -iex @var{command}
1009 @cindex @code{--init-eval-command}
1011 Execute a single @value{GDBN} command before loading the inferior (but
1012 after loading gdbinit files).
1015 @item -directory @var{directory}
1016 @itemx -d @var{directory}
1017 @cindex @code{--directory}
1019 Add @var{directory} to the path to search for source and script files.
1023 @cindex @code{--readnow}
1025 Read each symbol file's entire symbol table immediately, rather than
1026 the default, which is to read it incrementally as it is needed.
1027 This makes startup slower, but makes future operations faster.
1032 @subsection Choosing Modes
1034 You can run @value{GDBN} in various alternative modes---for example, in
1035 batch mode or quiet mode.
1043 Do not execute commands found in any initialization file.
1044 There are three init files, loaded in the following order:
1047 @item @file{system.gdbinit}
1048 This is the system-wide init file.
1049 Its location is specified with the @code{--with-system-gdbinit}
1050 configure option (@pxref{System-wide configuration}).
1051 It is loaded first when @value{GDBN} starts, before command line options
1052 have been processed.
1053 @item @file{~/.gdbinit}
1054 This is the init file in your home directory.
1055 It is loaded next, after @file{system.gdbinit}, and before
1056 command options have been processed.
1057 @item @file{./.gdbinit}
1058 This is the init file in the current directory.
1059 It is loaded last, after command line options other than @code{-x} and
1060 @code{-ex} have been processed. Command line options @code{-x} and
1061 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1064 For further documentation on startup processing, @xref{Startup}.
1065 For documentation on how to write command files,
1066 @xref{Command Files,,Command Files}.
1071 Do not execute commands found in @file{~/.gdbinit}, the init file
1072 in your home directory.
1078 @cindex @code{--quiet}
1079 @cindex @code{--silent}
1081 ``Quiet''. Do not print the introductory and copyright messages. These
1082 messages are also suppressed in batch mode.
1085 @cindex @code{--batch}
1086 Run in batch mode. Exit with status @code{0} after processing all the
1087 command files specified with @samp{-x} (and all commands from
1088 initialization files, if not inhibited with @samp{-n}). Exit with
1089 nonzero status if an error occurs in executing the @value{GDBN} commands
1090 in the command files. Batch mode also disables pagination, sets unlimited
1091 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1092 off} were in effect (@pxref{Messages/Warnings}).
1094 Batch mode may be useful for running @value{GDBN} as a filter, for
1095 example to download and run a program on another computer; in order to
1096 make this more useful, the message
1099 Program exited normally.
1103 (which is ordinarily issued whenever a program running under
1104 @value{GDBN} control terminates) is not issued when running in batch
1108 @cindex @code{--batch-silent}
1109 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1110 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1111 unaffected). This is much quieter than @samp{-silent} and would be useless
1112 for an interactive session.
1114 This is particularly useful when using targets that give @samp{Loading section}
1115 messages, for example.
1117 Note that targets that give their output via @value{GDBN}, as opposed to
1118 writing directly to @code{stdout}, will also be made silent.
1120 @item -return-child-result
1121 @cindex @code{--return-child-result}
1122 The return code from @value{GDBN} will be the return code from the child
1123 process (the process being debugged), with the following exceptions:
1127 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1128 internal error. In this case the exit code is the same as it would have been
1129 without @samp{-return-child-result}.
1131 The user quits with an explicit value. E.g., @samp{quit 1}.
1133 The child process never runs, or is not allowed to terminate, in which case
1134 the exit code will be -1.
1137 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1138 when @value{GDBN} is being used as a remote program loader or simulator
1143 @cindex @code{--nowindows}
1145 ``No windows''. If @value{GDBN} comes with a graphical user interface
1146 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1147 interface. If no GUI is available, this option has no effect.
1151 @cindex @code{--windows}
1153 If @value{GDBN} includes a GUI, then this option requires it to be
1156 @item -cd @var{directory}
1158 Run @value{GDBN} using @var{directory} as its working directory,
1159 instead of the current directory.
1161 @item -data-directory @var{directory}
1162 @cindex @code{--data-directory}
1163 Run @value{GDBN} using @var{directory} as its data directory.
1164 The data directory is where @value{GDBN} searches for its
1165 auxiliary files. @xref{Data Files}.
1169 @cindex @code{--fullname}
1171 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1172 subprocess. It tells @value{GDBN} to output the full file name and line
1173 number in a standard, recognizable fashion each time a stack frame is
1174 displayed (which includes each time your program stops). This
1175 recognizable format looks like two @samp{\032} characters, followed by
1176 the file name, line number and character position separated by colons,
1177 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1178 @samp{\032} characters as a signal to display the source code for the
1181 @item -annotate @var{level}
1182 @cindex @code{--annotate}
1183 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1184 effect is identical to using @samp{set annotate @var{level}}
1185 (@pxref{Annotations}). The annotation @var{level} controls how much
1186 information @value{GDBN} prints together with its prompt, values of
1187 expressions, source lines, and other types of output. Level 0 is the
1188 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1189 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1190 that control @value{GDBN}, and level 2 has been deprecated.
1192 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1196 @cindex @code{--args}
1197 Change interpretation of command line so that arguments following the
1198 executable file are passed as command line arguments to the inferior.
1199 This option stops option processing.
1201 @item -baud @var{bps}
1203 @cindex @code{--baud}
1205 Set the line speed (baud rate or bits per second) of any serial
1206 interface used by @value{GDBN} for remote debugging.
1208 @item -l @var{timeout}
1210 Set the timeout (in seconds) of any communication used by @value{GDBN}
1211 for remote debugging.
1213 @item -tty @var{device}
1214 @itemx -t @var{device}
1215 @cindex @code{--tty}
1217 Run using @var{device} for your program's standard input and output.
1218 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1220 @c resolve the situation of these eventually
1222 @cindex @code{--tui}
1223 Activate the @dfn{Text User Interface} when starting. The Text User
1224 Interface manages several text windows on the terminal, showing
1225 source, assembly, registers and @value{GDBN} command outputs
1226 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1227 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1228 Using @value{GDBN} under @sc{gnu} Emacs}).
1231 @c @cindex @code{--xdb}
1232 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1233 @c For information, see the file @file{xdb_trans.html}, which is usually
1234 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1237 @item -interpreter @var{interp}
1238 @cindex @code{--interpreter}
1239 Use the interpreter @var{interp} for interface with the controlling
1240 program or device. This option is meant to be set by programs which
1241 communicate with @value{GDBN} using it as a back end.
1242 @xref{Interpreters, , Command Interpreters}.
1244 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1245 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1246 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1247 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1248 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1249 @sc{gdb/mi} interfaces are no longer supported.
1252 @cindex @code{--write}
1253 Open the executable and core files for both reading and writing. This
1254 is equivalent to the @samp{set write on} command inside @value{GDBN}
1258 @cindex @code{--statistics}
1259 This option causes @value{GDBN} to print statistics about time and
1260 memory usage after it completes each command and returns to the prompt.
1263 @cindex @code{--version}
1264 This option causes @value{GDBN} to print its version number and
1265 no-warranty blurb, and exit.
1270 @subsection What @value{GDBN} Does During Startup
1271 @cindex @value{GDBN} startup
1273 Here's the description of what @value{GDBN} does during session startup:
1277 Sets up the command interpreter as specified by the command line
1278 (@pxref{Mode Options, interpreter}).
1282 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1283 used when building @value{GDBN}; @pxref{System-wide configuration,
1284 ,System-wide configuration and settings}) and executes all the commands in
1287 @anchor{Home Directory Init File}
1289 Reads the init file (if any) in your home directory@footnote{On
1290 DOS/Windows systems, the home directory is the one pointed to by the
1291 @code{HOME} environment variable.} and executes all the commands in
1294 @anchor{Option -init-eval-command}
1296 Executes commands and command files specified by the @samp{-iex} and
1297 @samp{-ix} options in their specified order. Usually you should use the
1298 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1299 settings before @value{GDBN} init files get executed and before inferior
1303 Processes command line options and operands.
1305 @anchor{Init File in the Current Directory during Startup}
1307 Reads and executes the commands from init file (if any) in the current
1308 working directory as long as @samp{set auto-load local-gdbinit} is set to
1309 @samp{on} (@pxref{Init File in the Current Directory}).
1310 This is only done if the current directory is
1311 different from your home directory. Thus, you can have more than one
1312 init file, one generic in your home directory, and another, specific
1313 to the program you are debugging, in the directory where you invoke
1317 If the command line specified a program to debug, or a process to
1318 attach to, or a core file, @value{GDBN} loads any auto-loaded
1319 scripts provided for the program or for its loaded shared libraries.
1320 @xref{Auto-loading}.
1322 If you wish to disable the auto-loading during startup,
1323 you must do something like the following:
1326 $ gdb -iex "set auto-load python-scripts off" myprogram
1329 Option @samp{-ex} does not work because the auto-loading is then turned
1333 Executes commands and command files specified by the @samp{-ex} and
1334 @samp{-x} options in their specified order. @xref{Command Files}, for
1335 more details about @value{GDBN} command files.
1338 Reads the command history recorded in the @dfn{history file}.
1339 @xref{Command History}, for more details about the command history and the
1340 files where @value{GDBN} records it.
1343 Init files use the same syntax as @dfn{command files} (@pxref{Command
1344 Files}) and are processed by @value{GDBN} in the same way. The init
1345 file in your home directory can set options (such as @samp{set
1346 complaints}) that affect subsequent processing of command line options
1347 and operands. Init files are not executed if you use the @samp{-nx}
1348 option (@pxref{Mode Options, ,Choosing Modes}).
1350 To display the list of init files loaded by gdb at startup, you
1351 can use @kbd{gdb --help}.
1353 @cindex init file name
1354 @cindex @file{.gdbinit}
1355 @cindex @file{gdb.ini}
1356 The @value{GDBN} init files are normally called @file{.gdbinit}.
1357 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1358 the limitations of file names imposed by DOS filesystems. The Windows
1359 port of @value{GDBN} uses the standard name, but if it finds a
1360 @file{gdb.ini} file in your home directory, it warns you about that
1361 and suggests to rename the file to the standard name.
1365 @section Quitting @value{GDBN}
1366 @cindex exiting @value{GDBN}
1367 @cindex leaving @value{GDBN}
1370 @kindex quit @r{[}@var{expression}@r{]}
1371 @kindex q @r{(@code{quit})}
1372 @item quit @r{[}@var{expression}@r{]}
1374 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1375 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1376 do not supply @var{expression}, @value{GDBN} will terminate normally;
1377 otherwise it will terminate using the result of @var{expression} as the
1382 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1383 terminates the action of any @value{GDBN} command that is in progress and
1384 returns to @value{GDBN} command level. It is safe to type the interrupt
1385 character at any time because @value{GDBN} does not allow it to take effect
1386 until a time when it is safe.
1388 If you have been using @value{GDBN} to control an attached process or
1389 device, you can release it with the @code{detach} command
1390 (@pxref{Attach, ,Debugging an Already-running Process}).
1392 @node Shell Commands
1393 @section Shell Commands
1395 If you need to execute occasional shell commands during your
1396 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1397 just use the @code{shell} command.
1402 @cindex shell escape
1403 @item shell @var{command-string}
1404 @itemx !@var{command-string}
1405 Invoke a standard shell to execute @var{command-string}.
1406 Note that no space is needed between @code{!} and @var{command-string}.
1407 If it exists, the environment variable @code{SHELL} determines which
1408 shell to run. Otherwise @value{GDBN} uses the default shell
1409 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1412 The utility @code{make} is often needed in development environments.
1413 You do not have to use the @code{shell} command for this purpose in
1418 @cindex calling make
1419 @item make @var{make-args}
1420 Execute the @code{make} program with the specified
1421 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1424 @node Logging Output
1425 @section Logging Output
1426 @cindex logging @value{GDBN} output
1427 @cindex save @value{GDBN} output to a file
1429 You may want to save the output of @value{GDBN} commands to a file.
1430 There are several commands to control @value{GDBN}'s logging.
1434 @item set logging on
1436 @item set logging off
1438 @cindex logging file name
1439 @item set logging file @var{file}
1440 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1441 @item set logging overwrite [on|off]
1442 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1443 you want @code{set logging on} to overwrite the logfile instead.
1444 @item set logging redirect [on|off]
1445 By default, @value{GDBN} output will go to both the terminal and the logfile.
1446 Set @code{redirect} if you want output to go only to the log file.
1447 @kindex show logging
1449 Show the current values of the logging settings.
1453 @chapter @value{GDBN} Commands
1455 You can abbreviate a @value{GDBN} command to the first few letters of the command
1456 name, if that abbreviation is unambiguous; and you can repeat certain
1457 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1458 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1459 show you the alternatives available, if there is more than one possibility).
1462 * Command Syntax:: How to give commands to @value{GDBN}
1463 * Completion:: Command completion
1464 * Help:: How to ask @value{GDBN} for help
1467 @node Command Syntax
1468 @section Command Syntax
1470 A @value{GDBN} command is a single line of input. There is no limit on
1471 how long it can be. It starts with a command name, which is followed by
1472 arguments whose meaning depends on the command name. For example, the
1473 command @code{step} accepts an argument which is the number of times to
1474 step, as in @samp{step 5}. You can also use the @code{step} command
1475 with no arguments. Some commands do not allow any arguments.
1477 @cindex abbreviation
1478 @value{GDBN} command names may always be truncated if that abbreviation is
1479 unambiguous. Other possible command abbreviations are listed in the
1480 documentation for individual commands. In some cases, even ambiguous
1481 abbreviations are allowed; for example, @code{s} is specially defined as
1482 equivalent to @code{step} even though there are other commands whose
1483 names start with @code{s}. You can test abbreviations by using them as
1484 arguments to the @code{help} command.
1486 @cindex repeating commands
1487 @kindex RET @r{(repeat last command)}
1488 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1489 repeat the previous command. Certain commands (for example, @code{run})
1490 will not repeat this way; these are commands whose unintentional
1491 repetition might cause trouble and which you are unlikely to want to
1492 repeat. User-defined commands can disable this feature; see
1493 @ref{Define, dont-repeat}.
1495 The @code{list} and @code{x} commands, when you repeat them with
1496 @key{RET}, construct new arguments rather than repeating
1497 exactly as typed. This permits easy scanning of source or memory.
1499 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1500 output, in a way similar to the common utility @code{more}
1501 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1502 @key{RET} too many in this situation, @value{GDBN} disables command
1503 repetition after any command that generates this sort of display.
1505 @kindex # @r{(a comment)}
1507 Any text from a @kbd{#} to the end of the line is a comment; it does
1508 nothing. This is useful mainly in command files (@pxref{Command
1509 Files,,Command Files}).
1511 @cindex repeating command sequences
1512 @kindex Ctrl-o @r{(operate-and-get-next)}
1513 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1514 commands. This command accepts the current line, like @key{RET}, and
1515 then fetches the next line relative to the current line from the history
1519 @section Command Completion
1522 @cindex word completion
1523 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1524 only one possibility; it can also show you what the valid possibilities
1525 are for the next word in a command, at any time. This works for @value{GDBN}
1526 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1528 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1529 of a word. If there is only one possibility, @value{GDBN} fills in the
1530 word, and waits for you to finish the command (or press @key{RET} to
1531 enter it). For example, if you type
1533 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1534 @c complete accuracy in these examples; space introduced for clarity.
1535 @c If texinfo enhancements make it unnecessary, it would be nice to
1536 @c replace " @key" by "@key" in the following...
1538 (@value{GDBP}) info bre @key{TAB}
1542 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1543 the only @code{info} subcommand beginning with @samp{bre}:
1546 (@value{GDBP}) info breakpoints
1550 You can either press @key{RET} at this point, to run the @code{info
1551 breakpoints} command, or backspace and enter something else, if
1552 @samp{breakpoints} does not look like the command you expected. (If you
1553 were sure you wanted @code{info breakpoints} in the first place, you
1554 might as well just type @key{RET} immediately after @samp{info bre},
1555 to exploit command abbreviations rather than command completion).
1557 If there is more than one possibility for the next word when you press
1558 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1559 characters and try again, or just press @key{TAB} a second time;
1560 @value{GDBN} displays all the possible completions for that word. For
1561 example, you might want to set a breakpoint on a subroutine whose name
1562 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1563 just sounds the bell. Typing @key{TAB} again displays all the
1564 function names in your program that begin with those characters, for
1568 (@value{GDBP}) b make_ @key{TAB}
1569 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1570 make_a_section_from_file make_environ
1571 make_abs_section make_function_type
1572 make_blockvector make_pointer_type
1573 make_cleanup make_reference_type
1574 make_command make_symbol_completion_list
1575 (@value{GDBP}) b make_
1579 After displaying the available possibilities, @value{GDBN} copies your
1580 partial input (@samp{b make_} in the example) so you can finish the
1583 If you just want to see the list of alternatives in the first place, you
1584 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1585 means @kbd{@key{META} ?}. You can type this either by holding down a
1586 key designated as the @key{META} shift on your keyboard (if there is
1587 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1589 @cindex quotes in commands
1590 @cindex completion of quoted strings
1591 Sometimes the string you need, while logically a ``word'', may contain
1592 parentheses or other characters that @value{GDBN} normally excludes from
1593 its notion of a word. To permit word completion to work in this
1594 situation, you may enclose words in @code{'} (single quote marks) in
1595 @value{GDBN} commands.
1597 The most likely situation where you might need this is in typing the
1598 name of a C@t{++} function. This is because C@t{++} allows function
1599 overloading (multiple definitions of the same function, distinguished
1600 by argument type). For example, when you want to set a breakpoint you
1601 may need to distinguish whether you mean the version of @code{name}
1602 that takes an @code{int} parameter, @code{name(int)}, or the version
1603 that takes a @code{float} parameter, @code{name(float)}. To use the
1604 word-completion facilities in this situation, type a single quote
1605 @code{'} at the beginning of the function name. This alerts
1606 @value{GDBN} that it may need to consider more information than usual
1607 when you press @key{TAB} or @kbd{M-?} to request word completion:
1610 (@value{GDBP}) b 'bubble( @kbd{M-?}
1611 bubble(double,double) bubble(int,int)
1612 (@value{GDBP}) b 'bubble(
1615 In some cases, @value{GDBN} can tell that completing a name requires using
1616 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1617 completing as much as it can) if you do not type the quote in the first
1621 (@value{GDBP}) b bub @key{TAB}
1622 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1623 (@value{GDBP}) b 'bubble(
1627 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1628 you have not yet started typing the argument list when you ask for
1629 completion on an overloaded symbol.
1631 For more information about overloaded functions, see @ref{C Plus Plus
1632 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1633 overload-resolution off} to disable overload resolution;
1634 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1636 @cindex completion of structure field names
1637 @cindex structure field name completion
1638 @cindex completion of union field names
1639 @cindex union field name completion
1640 When completing in an expression which looks up a field in a
1641 structure, @value{GDBN} also tries@footnote{The completer can be
1642 confused by certain kinds of invalid expressions. Also, it only
1643 examines the static type of the expression, not the dynamic type.} to
1644 limit completions to the field names available in the type of the
1648 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1649 magic to_fputs to_rewind
1650 to_data to_isatty to_write
1651 to_delete to_put to_write_async_safe
1656 This is because the @code{gdb_stdout} is a variable of the type
1657 @code{struct ui_file} that is defined in @value{GDBN} sources as
1664 ui_file_flush_ftype *to_flush;
1665 ui_file_write_ftype *to_write;
1666 ui_file_write_async_safe_ftype *to_write_async_safe;
1667 ui_file_fputs_ftype *to_fputs;
1668 ui_file_read_ftype *to_read;
1669 ui_file_delete_ftype *to_delete;
1670 ui_file_isatty_ftype *to_isatty;
1671 ui_file_rewind_ftype *to_rewind;
1672 ui_file_put_ftype *to_put;
1679 @section Getting Help
1680 @cindex online documentation
1683 You can always ask @value{GDBN} itself for information on its commands,
1684 using the command @code{help}.
1687 @kindex h @r{(@code{help})}
1690 You can use @code{help} (abbreviated @code{h}) with no arguments to
1691 display a short list of named classes of commands:
1695 List of classes of commands:
1697 aliases -- Aliases of other commands
1698 breakpoints -- Making program stop at certain points
1699 data -- Examining data
1700 files -- Specifying and examining files
1701 internals -- Maintenance commands
1702 obscure -- Obscure features
1703 running -- Running the program
1704 stack -- Examining the stack
1705 status -- Status inquiries
1706 support -- Support facilities
1707 tracepoints -- Tracing of program execution without
1708 stopping the program
1709 user-defined -- User-defined commands
1711 Type "help" followed by a class name for a list of
1712 commands in that class.
1713 Type "help" followed by command name for full
1715 Command name abbreviations are allowed if unambiguous.
1718 @c the above line break eliminates huge line overfull...
1720 @item help @var{class}
1721 Using one of the general help classes as an argument, you can get a
1722 list of the individual commands in that class. For example, here is the
1723 help display for the class @code{status}:
1726 (@value{GDBP}) help status
1731 @c Line break in "show" line falsifies real output, but needed
1732 @c to fit in smallbook page size.
1733 info -- Generic command for showing things
1734 about the program being debugged
1735 show -- Generic command for showing things
1738 Type "help" followed by command name for full
1740 Command name abbreviations are allowed if unambiguous.
1744 @item help @var{command}
1745 With a command name as @code{help} argument, @value{GDBN} displays a
1746 short paragraph on how to use that command.
1749 @item apropos @var{args}
1750 The @code{apropos} command searches through all of the @value{GDBN}
1751 commands, and their documentation, for the regular expression specified in
1752 @var{args}. It prints out all matches found. For example:
1763 alias -- Define a new command that is an alias of an existing command
1764 aliases -- Aliases of other commands
1765 d -- Delete some breakpoints or auto-display expressions
1766 del -- Delete some breakpoints or auto-display expressions
1767 delete -- Delete some breakpoints or auto-display expressions
1772 @item complete @var{args}
1773 The @code{complete @var{args}} command lists all the possible completions
1774 for the beginning of a command. Use @var{args} to specify the beginning of the
1775 command you want completed. For example:
1781 @noindent results in:
1792 @noindent This is intended for use by @sc{gnu} Emacs.
1795 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1796 and @code{show} to inquire about the state of your program, or the state
1797 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1798 manual introduces each of them in the appropriate context. The listings
1799 under @code{info} and under @code{show} in the Command, Variable, and
1800 Function Index point to all the sub-commands. @xref{Command and Variable
1806 @kindex i @r{(@code{info})}
1808 This command (abbreviated @code{i}) is for describing the state of your
1809 program. For example, you can show the arguments passed to a function
1810 with @code{info args}, list the registers currently in use with @code{info
1811 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1812 You can get a complete list of the @code{info} sub-commands with
1813 @w{@code{help info}}.
1817 You can assign the result of an expression to an environment variable with
1818 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1819 @code{set prompt $}.
1823 In contrast to @code{info}, @code{show} is for describing the state of
1824 @value{GDBN} itself.
1825 You can change most of the things you can @code{show}, by using the
1826 related command @code{set}; for example, you can control what number
1827 system is used for displays with @code{set radix}, or simply inquire
1828 which is currently in use with @code{show radix}.
1831 To display all the settable parameters and their current
1832 values, you can use @code{show} with no arguments; you may also use
1833 @code{info set}. Both commands produce the same display.
1834 @c FIXME: "info set" violates the rule that "info" is for state of
1835 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1836 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1840 Here are three miscellaneous @code{show} subcommands, all of which are
1841 exceptional in lacking corresponding @code{set} commands:
1844 @kindex show version
1845 @cindex @value{GDBN} version number
1847 Show what version of @value{GDBN} is running. You should include this
1848 information in @value{GDBN} bug-reports. If multiple versions of
1849 @value{GDBN} are in use at your site, you may need to determine which
1850 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1851 commands are introduced, and old ones may wither away. Also, many
1852 system vendors ship variant versions of @value{GDBN}, and there are
1853 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1854 The version number is the same as the one announced when you start
1857 @kindex show copying
1858 @kindex info copying
1859 @cindex display @value{GDBN} copyright
1862 Display information about permission for copying @value{GDBN}.
1864 @kindex show warranty
1865 @kindex info warranty
1867 @itemx info warranty
1868 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1869 if your version of @value{GDBN} comes with one.
1874 @chapter Running Programs Under @value{GDBN}
1876 When you run a program under @value{GDBN}, you must first generate
1877 debugging information when you compile it.
1879 You may start @value{GDBN} with its arguments, if any, in an environment
1880 of your choice. If you are doing native debugging, you may redirect
1881 your program's input and output, debug an already running process, or
1882 kill a child process.
1885 * Compilation:: Compiling for debugging
1886 * Starting:: Starting your program
1887 * Arguments:: Your program's arguments
1888 * Environment:: Your program's environment
1890 * Working Directory:: Your program's working directory
1891 * Input/Output:: Your program's input and output
1892 * Attach:: Debugging an already-running process
1893 * Kill Process:: Killing the child process
1895 * Inferiors and Programs:: Debugging multiple inferiors and programs
1896 * Threads:: Debugging programs with multiple threads
1897 * Forks:: Debugging forks
1898 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1902 @section Compiling for Debugging
1904 In order to debug a program effectively, you need to generate
1905 debugging information when you compile it. This debugging information
1906 is stored in the object file; it describes the data type of each
1907 variable or function and the correspondence between source line numbers
1908 and addresses in the executable code.
1910 To request debugging information, specify the @samp{-g} option when you run
1913 Programs that are to be shipped to your customers are compiled with
1914 optimizations, using the @samp{-O} compiler option. However, some
1915 compilers are unable to handle the @samp{-g} and @samp{-O} options
1916 together. Using those compilers, you cannot generate optimized
1917 executables containing debugging information.
1919 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1920 without @samp{-O}, making it possible to debug optimized code. We
1921 recommend that you @emph{always} use @samp{-g} whenever you compile a
1922 program. You may think your program is correct, but there is no sense
1923 in pushing your luck. For more information, see @ref{Optimized Code}.
1925 Older versions of the @sc{gnu} C compiler permitted a variant option
1926 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1927 format; if your @sc{gnu} C compiler has this option, do not use it.
1929 @value{GDBN} knows about preprocessor macros and can show you their
1930 expansion (@pxref{Macros}). Most compilers do not include information
1931 about preprocessor macros in the debugging information if you specify
1932 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1933 the @sc{gnu} C compiler, provides macro information if you are using
1934 the DWARF debugging format, and specify the option @option{-g3}.
1936 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1937 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1938 information on @value{NGCC} options affecting debug information.
1940 You will have the best debugging experience if you use the latest
1941 version of the DWARF debugging format that your compiler supports.
1942 DWARF is currently the most expressive and best supported debugging
1943 format in @value{GDBN}.
1947 @section Starting your Program
1953 @kindex r @r{(@code{run})}
1956 Use the @code{run} command to start your program under @value{GDBN}.
1957 You must first specify the program name (except on VxWorks) with an
1958 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1959 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1960 (@pxref{Files, ,Commands to Specify Files}).
1964 If you are running your program in an execution environment that
1965 supports processes, @code{run} creates an inferior process and makes
1966 that process run your program. In some environments without processes,
1967 @code{run} jumps to the start of your program. Other targets,
1968 like @samp{remote}, are always running. If you get an error
1969 message like this one:
1972 The "remote" target does not support "run".
1973 Try "help target" or "continue".
1977 then use @code{continue} to run your program. You may need @code{load}
1978 first (@pxref{load}).
1980 The execution of a program is affected by certain information it
1981 receives from its superior. @value{GDBN} provides ways to specify this
1982 information, which you must do @emph{before} starting your program. (You
1983 can change it after starting your program, but such changes only affect
1984 your program the next time you start it.) This information may be
1985 divided into four categories:
1988 @item The @emph{arguments.}
1989 Specify the arguments to give your program as the arguments of the
1990 @code{run} command. If a shell is available on your target, the shell
1991 is used to pass the arguments, so that you may use normal conventions
1992 (such as wildcard expansion or variable substitution) in describing
1994 In Unix systems, you can control which shell is used with the
1995 @code{SHELL} environment variable.
1996 @xref{Arguments, ,Your Program's Arguments}.
1998 @item The @emph{environment.}
1999 Your program normally inherits its environment from @value{GDBN}, but you can
2000 use the @value{GDBN} commands @code{set environment} and @code{unset
2001 environment} to change parts of the environment that affect
2002 your program. @xref{Environment, ,Your Program's Environment}.
2004 @item The @emph{working directory.}
2005 Your program inherits its working directory from @value{GDBN}. You can set
2006 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2007 @xref{Working Directory, ,Your Program's Working Directory}.
2009 @item The @emph{standard input and output.}
2010 Your program normally uses the same device for standard input and
2011 standard output as @value{GDBN} is using. You can redirect input and output
2012 in the @code{run} command line, or you can use the @code{tty} command to
2013 set a different device for your program.
2014 @xref{Input/Output, ,Your Program's Input and Output}.
2017 @emph{Warning:} While input and output redirection work, you cannot use
2018 pipes to pass the output of the program you are debugging to another
2019 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2023 When you issue the @code{run} command, your program begins to execute
2024 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2025 of how to arrange for your program to stop. Once your program has
2026 stopped, you may call functions in your program, using the @code{print}
2027 or @code{call} commands. @xref{Data, ,Examining Data}.
2029 If the modification time of your symbol file has changed since the last
2030 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2031 table, and reads it again. When it does this, @value{GDBN} tries to retain
2032 your current breakpoints.
2037 @cindex run to main procedure
2038 The name of the main procedure can vary from language to language.
2039 With C or C@t{++}, the main procedure name is always @code{main}, but
2040 other languages such as Ada do not require a specific name for their
2041 main procedure. The debugger provides a convenient way to start the
2042 execution of the program and to stop at the beginning of the main
2043 procedure, depending on the language used.
2045 The @samp{start} command does the equivalent of setting a temporary
2046 breakpoint at the beginning of the main procedure and then invoking
2047 the @samp{run} command.
2049 @cindex elaboration phase
2050 Some programs contain an @dfn{elaboration} phase where some startup code is
2051 executed before the main procedure is called. This depends on the
2052 languages used to write your program. In C@t{++}, for instance,
2053 constructors for static and global objects are executed before
2054 @code{main} is called. It is therefore possible that the debugger stops
2055 before reaching the main procedure. However, the temporary breakpoint
2056 will remain to halt execution.
2058 Specify the arguments to give to your program as arguments to the
2059 @samp{start} command. These arguments will be given verbatim to the
2060 underlying @samp{run} command. Note that the same arguments will be
2061 reused if no argument is provided during subsequent calls to
2062 @samp{start} or @samp{run}.
2064 It is sometimes necessary to debug the program during elaboration. In
2065 these cases, using the @code{start} command would stop the execution of
2066 your program too late, as the program would have already completed the
2067 elaboration phase. Under these circumstances, insert breakpoints in your
2068 elaboration code before running your program.
2070 @kindex set exec-wrapper
2071 @item set exec-wrapper @var{wrapper}
2072 @itemx show exec-wrapper
2073 @itemx unset exec-wrapper
2074 When @samp{exec-wrapper} is set, the specified wrapper is used to
2075 launch programs for debugging. @value{GDBN} starts your program
2076 with a shell command of the form @kbd{exec @var{wrapper}
2077 @var{program}}. Quoting is added to @var{program} and its
2078 arguments, but not to @var{wrapper}, so you should add quotes if
2079 appropriate for your shell. The wrapper runs until it executes
2080 your program, and then @value{GDBN} takes control.
2082 You can use any program that eventually calls @code{execve} with
2083 its arguments as a wrapper. Several standard Unix utilities do
2084 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2085 with @code{exec "$@@"} will also work.
2087 For example, you can use @code{env} to pass an environment variable to
2088 the debugged program, without setting the variable in your shell's
2092 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2096 This command is available when debugging locally on most targets, excluding
2097 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2099 @kindex set disable-randomization
2100 @item set disable-randomization
2101 @itemx set disable-randomization on
2102 This option (enabled by default in @value{GDBN}) will turn off the native
2103 randomization of the virtual address space of the started program. This option
2104 is useful for multiple debugging sessions to make the execution better
2105 reproducible and memory addresses reusable across debugging sessions.
2107 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2108 On @sc{gnu}/Linux you can get the same behavior using
2111 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2114 @item set disable-randomization off
2115 Leave the behavior of the started executable unchanged. Some bugs rear their
2116 ugly heads only when the program is loaded at certain addresses. If your bug
2117 disappears when you run the program under @value{GDBN}, that might be because
2118 @value{GDBN} by default disables the address randomization on platforms, such
2119 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2120 disable-randomization off} to try to reproduce such elusive bugs.
2122 On targets where it is available, virtual address space randomization
2123 protects the programs against certain kinds of security attacks. In these
2124 cases the attacker needs to know the exact location of a concrete executable
2125 code. Randomizing its location makes it impossible to inject jumps misusing
2126 a code at its expected addresses.
2128 Prelinking shared libraries provides a startup performance advantage but it
2129 makes addresses in these libraries predictable for privileged processes by
2130 having just unprivileged access at the target system. Reading the shared
2131 library binary gives enough information for assembling the malicious code
2132 misusing it. Still even a prelinked shared library can get loaded at a new
2133 random address just requiring the regular relocation process during the
2134 startup. Shared libraries not already prelinked are always loaded at
2135 a randomly chosen address.
2137 Position independent executables (PIE) contain position independent code
2138 similar to the shared libraries and therefore such executables get loaded at
2139 a randomly chosen address upon startup. PIE executables always load even
2140 already prelinked shared libraries at a random address. You can build such
2141 executable using @command{gcc -fPIE -pie}.
2143 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2144 (as long as the randomization is enabled).
2146 @item show disable-randomization
2147 Show the current setting of the explicit disable of the native randomization of
2148 the virtual address space of the started program.
2153 @section Your Program's Arguments
2155 @cindex arguments (to your program)
2156 The arguments to your program can be specified by the arguments of the
2158 They are passed to a shell, which expands wildcard characters and
2159 performs redirection of I/O, and thence to your program. Your
2160 @code{SHELL} environment variable (if it exists) specifies what shell
2161 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2162 the default shell (@file{/bin/sh} on Unix).
2164 On non-Unix systems, the program is usually invoked directly by
2165 @value{GDBN}, which emulates I/O redirection via the appropriate system
2166 calls, and the wildcard characters are expanded by the startup code of
2167 the program, not by the shell.
2169 @code{run} with no arguments uses the same arguments used by the previous
2170 @code{run}, or those set by the @code{set args} command.
2175 Specify the arguments to be used the next time your program is run. If
2176 @code{set args} has no arguments, @code{run} executes your program
2177 with no arguments. Once you have run your program with arguments,
2178 using @code{set args} before the next @code{run} is the only way to run
2179 it again without arguments.
2183 Show the arguments to give your program when it is started.
2187 @section Your Program's Environment
2189 @cindex environment (of your program)
2190 The @dfn{environment} consists of a set of environment variables and
2191 their values. Environment variables conventionally record such things as
2192 your user name, your home directory, your terminal type, and your search
2193 path for programs to run. Usually you set up environment variables with
2194 the shell and they are inherited by all the other programs you run. When
2195 debugging, it can be useful to try running your program with a modified
2196 environment without having to start @value{GDBN} over again.
2200 @item path @var{directory}
2201 Add @var{directory} to the front of the @code{PATH} environment variable
2202 (the search path for executables) that will be passed to your program.
2203 The value of @code{PATH} used by @value{GDBN} does not change.
2204 You may specify several directory names, separated by whitespace or by a
2205 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2206 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2207 is moved to the front, so it is searched sooner.
2209 You can use the string @samp{$cwd} to refer to whatever is the current
2210 working directory at the time @value{GDBN} searches the path. If you
2211 use @samp{.} instead, it refers to the directory where you executed the
2212 @code{path} command. @value{GDBN} replaces @samp{.} in the
2213 @var{directory} argument (with the current path) before adding
2214 @var{directory} to the search path.
2215 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2216 @c document that, since repeating it would be a no-op.
2220 Display the list of search paths for executables (the @code{PATH}
2221 environment variable).
2223 @kindex show environment
2224 @item show environment @r{[}@var{varname}@r{]}
2225 Print the value of environment variable @var{varname} to be given to
2226 your program when it starts. If you do not supply @var{varname},
2227 print the names and values of all environment variables to be given to
2228 your program. You can abbreviate @code{environment} as @code{env}.
2230 @kindex set environment
2231 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2232 Set environment variable @var{varname} to @var{value}. The value
2233 changes for your program only, not for @value{GDBN} itself. @var{value} may
2234 be any string; the values of environment variables are just strings, and
2235 any interpretation is supplied by your program itself. The @var{value}
2236 parameter is optional; if it is eliminated, the variable is set to a
2238 @c "any string" here does not include leading, trailing
2239 @c blanks. Gnu asks: does anyone care?
2241 For example, this command:
2248 tells the debugged program, when subsequently run, that its user is named
2249 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2250 are not actually required.)
2252 @kindex unset environment
2253 @item unset environment @var{varname}
2254 Remove variable @var{varname} from the environment to be passed to your
2255 program. This is different from @samp{set env @var{varname} =};
2256 @code{unset environment} removes the variable from the environment,
2257 rather than assigning it an empty value.
2260 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2262 by your @code{SHELL} environment variable if it exists (or
2263 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2264 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2265 @file{.bashrc} for BASH---any variables you set in that file affect
2266 your program. You may wish to move setting of environment variables to
2267 files that are only run when you sign on, such as @file{.login} or
2270 @node Working Directory
2271 @section Your Program's Working Directory
2273 @cindex working directory (of your program)
2274 Each time you start your program with @code{run}, it inherits its
2275 working directory from the current working directory of @value{GDBN}.
2276 The @value{GDBN} working directory is initially whatever it inherited
2277 from its parent process (typically the shell), but you can specify a new
2278 working directory in @value{GDBN} with the @code{cd} command.
2280 The @value{GDBN} working directory also serves as a default for the commands
2281 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2286 @cindex change working directory
2287 @item cd @r{[}@var{directory}@r{]}
2288 Set the @value{GDBN} working directory to @var{directory}. If not
2289 given, @var{directory} uses @file{'~'}.
2293 Print the @value{GDBN} working directory.
2296 It is generally impossible to find the current working directory of
2297 the process being debugged (since a program can change its directory
2298 during its run). If you work on a system where @value{GDBN} is
2299 configured with the @file{/proc} support, you can use the @code{info
2300 proc} command (@pxref{SVR4 Process Information}) to find out the
2301 current working directory of the debuggee.
2304 @section Your Program's Input and Output
2309 By default, the program you run under @value{GDBN} does input and output to
2310 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2311 to its own terminal modes to interact with you, but it records the terminal
2312 modes your program was using and switches back to them when you continue
2313 running your program.
2316 @kindex info terminal
2318 Displays information recorded by @value{GDBN} about the terminal modes your
2322 You can redirect your program's input and/or output using shell
2323 redirection with the @code{run} command. For example,
2330 starts your program, diverting its output to the file @file{outfile}.
2333 @cindex controlling terminal
2334 Another way to specify where your program should do input and output is
2335 with the @code{tty} command. This command accepts a file name as
2336 argument, and causes this file to be the default for future @code{run}
2337 commands. It also resets the controlling terminal for the child
2338 process, for future @code{run} commands. For example,
2345 directs that processes started with subsequent @code{run} commands
2346 default to do input and output on the terminal @file{/dev/ttyb} and have
2347 that as their controlling terminal.
2349 An explicit redirection in @code{run} overrides the @code{tty} command's
2350 effect on the input/output device, but not its effect on the controlling
2353 When you use the @code{tty} command or redirect input in the @code{run}
2354 command, only the input @emph{for your program} is affected. The input
2355 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2356 for @code{set inferior-tty}.
2358 @cindex inferior tty
2359 @cindex set inferior controlling terminal
2360 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2361 display the name of the terminal that will be used for future runs of your
2365 @item set inferior-tty /dev/ttyb
2366 @kindex set inferior-tty
2367 Set the tty for the program being debugged to /dev/ttyb.
2369 @item show inferior-tty
2370 @kindex show inferior-tty
2371 Show the current tty for the program being debugged.
2375 @section Debugging an Already-running Process
2380 @item attach @var{process-id}
2381 This command attaches to a running process---one that was started
2382 outside @value{GDBN}. (@code{info files} shows your active
2383 targets.) The command takes as argument a process ID. The usual way to
2384 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2385 or with the @samp{jobs -l} shell command.
2387 @code{attach} does not repeat if you press @key{RET} a second time after
2388 executing the command.
2391 To use @code{attach}, your program must be running in an environment
2392 which supports processes; for example, @code{attach} does not work for
2393 programs on bare-board targets that lack an operating system. You must
2394 also have permission to send the process a signal.
2396 When you use @code{attach}, the debugger finds the program running in
2397 the process first by looking in the current working directory, then (if
2398 the program is not found) by using the source file search path
2399 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2400 the @code{file} command to load the program. @xref{Files, ,Commands to
2403 The first thing @value{GDBN} does after arranging to debug the specified
2404 process is to stop it. You can examine and modify an attached process
2405 with all the @value{GDBN} commands that are ordinarily available when
2406 you start processes with @code{run}. You can insert breakpoints; you
2407 can step and continue; you can modify storage. If you would rather the
2408 process continue running, you may use the @code{continue} command after
2409 attaching @value{GDBN} to the process.
2414 When you have finished debugging the attached process, you can use the
2415 @code{detach} command to release it from @value{GDBN} control. Detaching
2416 the process continues its execution. After the @code{detach} command,
2417 that process and @value{GDBN} become completely independent once more, and you
2418 are ready to @code{attach} another process or start one with @code{run}.
2419 @code{detach} does not repeat if you press @key{RET} again after
2420 executing the command.
2423 If you exit @value{GDBN} while you have an attached process, you detach
2424 that process. If you use the @code{run} command, you kill that process.
2425 By default, @value{GDBN} asks for confirmation if you try to do either of these
2426 things; you can control whether or not you need to confirm by using the
2427 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2431 @section Killing the Child Process
2436 Kill the child process in which your program is running under @value{GDBN}.
2439 This command is useful if you wish to debug a core dump instead of a
2440 running process. @value{GDBN} ignores any core dump file while your program
2443 On some operating systems, a program cannot be executed outside @value{GDBN}
2444 while you have breakpoints set on it inside @value{GDBN}. You can use the
2445 @code{kill} command in this situation to permit running your program
2446 outside the debugger.
2448 The @code{kill} command is also useful if you wish to recompile and
2449 relink your program, since on many systems it is impossible to modify an
2450 executable file while it is running in a process. In this case, when you
2451 next type @code{run}, @value{GDBN} notices that the file has changed, and
2452 reads the symbol table again (while trying to preserve your current
2453 breakpoint settings).
2455 @node Inferiors and Programs
2456 @section Debugging Multiple Inferiors and Programs
2458 @value{GDBN} lets you run and debug multiple programs in a single
2459 session. In addition, @value{GDBN} on some systems may let you run
2460 several programs simultaneously (otherwise you have to exit from one
2461 before starting another). In the most general case, you can have
2462 multiple threads of execution in each of multiple processes, launched
2463 from multiple executables.
2466 @value{GDBN} represents the state of each program execution with an
2467 object called an @dfn{inferior}. An inferior typically corresponds to
2468 a process, but is more general and applies also to targets that do not
2469 have processes. Inferiors may be created before a process runs, and
2470 may be retained after a process exits. Inferiors have unique
2471 identifiers that are different from process ids. Usually each
2472 inferior will also have its own distinct address space, although some
2473 embedded targets may have several inferiors running in different parts
2474 of a single address space. Each inferior may in turn have multiple
2475 threads running in it.
2477 To find out what inferiors exist at any moment, use @w{@code{info
2481 @kindex info inferiors
2482 @item info inferiors
2483 Print a list of all inferiors currently being managed by @value{GDBN}.
2485 @value{GDBN} displays for each inferior (in this order):
2489 the inferior number assigned by @value{GDBN}
2492 the target system's inferior identifier
2495 the name of the executable the inferior is running.
2500 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2501 indicates the current inferior.
2505 @c end table here to get a little more width for example
2508 (@value{GDBP}) info inferiors
2509 Num Description Executable
2510 2 process 2307 hello
2511 * 1 process 3401 goodbye
2514 To switch focus between inferiors, use the @code{inferior} command:
2517 @kindex inferior @var{infno}
2518 @item inferior @var{infno}
2519 Make inferior number @var{infno} the current inferior. The argument
2520 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2521 in the first field of the @samp{info inferiors} display.
2525 You can get multiple executables into a debugging session via the
2526 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2527 systems @value{GDBN} can add inferiors to the debug session
2528 automatically by following calls to @code{fork} and @code{exec}. To
2529 remove inferiors from the debugging session use the
2530 @w{@code{remove-inferiors}} command.
2533 @kindex add-inferior
2534 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2535 Adds @var{n} inferiors to be run using @var{executable} as the
2536 executable. @var{n} defaults to 1. If no executable is specified,
2537 the inferiors begins empty, with no program. You can still assign or
2538 change the program assigned to the inferior at any time by using the
2539 @code{file} command with the executable name as its argument.
2541 @kindex clone-inferior
2542 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2543 Adds @var{n} inferiors ready to execute the same program as inferior
2544 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2545 number of the current inferior. This is a convenient command when you
2546 want to run another instance of the inferior you are debugging.
2549 (@value{GDBP}) info inferiors
2550 Num Description Executable
2551 * 1 process 29964 helloworld
2552 (@value{GDBP}) clone-inferior
2555 (@value{GDBP}) info inferiors
2556 Num Description Executable
2558 * 1 process 29964 helloworld
2561 You can now simply switch focus to inferior 2 and run it.
2563 @kindex remove-inferiors
2564 @item remove-inferiors @var{infno}@dots{}
2565 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2566 possible to remove an inferior that is running with this command. For
2567 those, use the @code{kill} or @code{detach} command first.
2571 To quit debugging one of the running inferiors that is not the current
2572 inferior, you can either detach from it by using the @w{@code{detach
2573 inferior}} command (allowing it to run independently), or kill it
2574 using the @w{@code{kill inferiors}} command:
2577 @kindex detach inferiors @var{infno}@dots{}
2578 @item detach inferior @var{infno}@dots{}
2579 Detach from the inferior or inferiors identified by @value{GDBN}
2580 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2581 still stays on the list of inferiors shown by @code{info inferiors},
2582 but its Description will show @samp{<null>}.
2584 @kindex kill inferiors @var{infno}@dots{}
2585 @item kill inferiors @var{infno}@dots{}
2586 Kill the inferior or inferiors identified by @value{GDBN} inferior
2587 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2588 stays on the list of inferiors shown by @code{info inferiors}, but its
2589 Description will show @samp{<null>}.
2592 After the successful completion of a command such as @code{detach},
2593 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2594 a normal process exit, the inferior is still valid and listed with
2595 @code{info inferiors}, ready to be restarted.
2598 To be notified when inferiors are started or exit under @value{GDBN}'s
2599 control use @w{@code{set print inferior-events}}:
2602 @kindex set print inferior-events
2603 @cindex print messages on inferior start and exit
2604 @item set print inferior-events
2605 @itemx set print inferior-events on
2606 @itemx set print inferior-events off
2607 The @code{set print inferior-events} command allows you to enable or
2608 disable printing of messages when @value{GDBN} notices that new
2609 inferiors have started or that inferiors have exited or have been
2610 detached. By default, these messages will not be printed.
2612 @kindex show print inferior-events
2613 @item show print inferior-events
2614 Show whether messages will be printed when @value{GDBN} detects that
2615 inferiors have started, exited or have been detached.
2618 Many commands will work the same with multiple programs as with a
2619 single program: e.g., @code{print myglobal} will simply display the
2620 value of @code{myglobal} in the current inferior.
2623 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2624 get more info about the relationship of inferiors, programs, address
2625 spaces in a debug session. You can do that with the @w{@code{maint
2626 info program-spaces}} command.
2629 @kindex maint info program-spaces
2630 @item maint info program-spaces
2631 Print a list of all program spaces currently being managed by
2634 @value{GDBN} displays for each program space (in this order):
2638 the program space number assigned by @value{GDBN}
2641 the name of the executable loaded into the program space, with e.g.,
2642 the @code{file} command.
2647 An asterisk @samp{*} preceding the @value{GDBN} program space number
2648 indicates the current program space.
2650 In addition, below each program space line, @value{GDBN} prints extra
2651 information that isn't suitable to display in tabular form. For
2652 example, the list of inferiors bound to the program space.
2655 (@value{GDBP}) maint info program-spaces
2658 Bound inferiors: ID 1 (process 21561)
2662 Here we can see that no inferior is running the program @code{hello},
2663 while @code{process 21561} is running the program @code{goodbye}. On
2664 some targets, it is possible that multiple inferiors are bound to the
2665 same program space. The most common example is that of debugging both
2666 the parent and child processes of a @code{vfork} call. For example,
2669 (@value{GDBP}) maint info program-spaces
2672 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2675 Here, both inferior 2 and inferior 1 are running in the same program
2676 space as a result of inferior 1 having executed a @code{vfork} call.
2680 @section Debugging Programs with Multiple Threads
2682 @cindex threads of execution
2683 @cindex multiple threads
2684 @cindex switching threads
2685 In some operating systems, such as HP-UX and Solaris, a single program
2686 may have more than one @dfn{thread} of execution. The precise semantics
2687 of threads differ from one operating system to another, but in general
2688 the threads of a single program are akin to multiple processes---except
2689 that they share one address space (that is, they can all examine and
2690 modify the same variables). On the other hand, each thread has its own
2691 registers and execution stack, and perhaps private memory.
2693 @value{GDBN} provides these facilities for debugging multi-thread
2697 @item automatic notification of new threads
2698 @item @samp{thread @var{threadno}}, a command to switch among threads
2699 @item @samp{info threads}, a command to inquire about existing threads
2700 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2701 a command to apply a command to a list of threads
2702 @item thread-specific breakpoints
2703 @item @samp{set print thread-events}, which controls printing of
2704 messages on thread start and exit.
2705 @item @samp{set libthread-db-search-path @var{path}}, which lets
2706 the user specify which @code{libthread_db} to use if the default choice
2707 isn't compatible with the program.
2711 @emph{Warning:} These facilities are not yet available on every
2712 @value{GDBN} configuration where the operating system supports threads.
2713 If your @value{GDBN} does not support threads, these commands have no
2714 effect. For example, a system without thread support shows no output
2715 from @samp{info threads}, and always rejects the @code{thread} command,
2719 (@value{GDBP}) info threads
2720 (@value{GDBP}) thread 1
2721 Thread ID 1 not known. Use the "info threads" command to
2722 see the IDs of currently known threads.
2724 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2725 @c doesn't support threads"?
2728 @cindex focus of debugging
2729 @cindex current thread
2730 The @value{GDBN} thread debugging facility allows you to observe all
2731 threads while your program runs---but whenever @value{GDBN} takes
2732 control, one thread in particular is always the focus of debugging.
2733 This thread is called the @dfn{current thread}. Debugging commands show
2734 program information from the perspective of the current thread.
2736 @cindex @code{New} @var{systag} message
2737 @cindex thread identifier (system)
2738 @c FIXME-implementors!! It would be more helpful if the [New...] message
2739 @c included GDB's numeric thread handle, so you could just go to that
2740 @c thread without first checking `info threads'.
2741 Whenever @value{GDBN} detects a new thread in your program, it displays
2742 the target system's identification for the thread with a message in the
2743 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2744 whose form varies depending on the particular system. For example, on
2745 @sc{gnu}/Linux, you might see
2748 [New Thread 0x41e02940 (LWP 25582)]
2752 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2753 the @var{systag} is simply something like @samp{process 368}, with no
2756 @c FIXME!! (1) Does the [New...] message appear even for the very first
2757 @c thread of a program, or does it only appear for the
2758 @c second---i.e.@: when it becomes obvious we have a multithread
2760 @c (2) *Is* there necessarily a first thread always? Or do some
2761 @c multithread systems permit starting a program with multiple
2762 @c threads ab initio?
2764 @cindex thread number
2765 @cindex thread identifier (GDB)
2766 For debugging purposes, @value{GDBN} associates its own thread
2767 number---always a single integer---with each thread in your program.
2770 @kindex info threads
2771 @item info threads @r{[}@var{id}@dots{}@r{]}
2772 Display a summary of all threads currently in your program. Optional
2773 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2774 means to print information only about the specified thread or threads.
2775 @value{GDBN} displays for each thread (in this order):
2779 the thread number assigned by @value{GDBN}
2782 the target system's thread identifier (@var{systag})
2785 the thread's name, if one is known. A thread can either be named by
2786 the user (see @code{thread name}, below), or, in some cases, by the
2790 the current stack frame summary for that thread
2794 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2795 indicates the current thread.
2799 @c end table here to get a little more width for example
2802 (@value{GDBP}) info threads
2804 3 process 35 thread 27 0x34e5 in sigpause ()
2805 2 process 35 thread 23 0x34e5 in sigpause ()
2806 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2810 On Solaris, you can display more information about user threads with a
2811 Solaris-specific command:
2814 @item maint info sol-threads
2815 @kindex maint info sol-threads
2816 @cindex thread info (Solaris)
2817 Display info on Solaris user threads.
2821 @kindex thread @var{threadno}
2822 @item thread @var{threadno}
2823 Make thread number @var{threadno} the current thread. The command
2824 argument @var{threadno} is the internal @value{GDBN} thread number, as
2825 shown in the first field of the @samp{info threads} display.
2826 @value{GDBN} responds by displaying the system identifier of the thread
2827 you selected, and its current stack frame summary:
2830 (@value{GDBP}) thread 2
2831 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2832 #0 some_function (ignore=0x0) at example.c:8
2833 8 printf ("hello\n");
2837 As with the @samp{[New @dots{}]} message, the form of the text after
2838 @samp{Switching to} depends on your system's conventions for identifying
2841 @vindex $_thread@r{, convenience variable}
2842 The debugger convenience variable @samp{$_thread} contains the number
2843 of the current thread. You may find this useful in writing breakpoint
2844 conditional expressions, command scripts, and so forth. See
2845 @xref{Convenience Vars,, Convenience Variables}, for general
2846 information on convenience variables.
2848 @kindex thread apply
2849 @cindex apply command to several threads
2850 @item thread apply [@var{threadno} | all] @var{command}
2851 The @code{thread apply} command allows you to apply the named
2852 @var{command} to one or more threads. Specify the numbers of the
2853 threads that you want affected with the command argument
2854 @var{threadno}. It can be a single thread number, one of the numbers
2855 shown in the first field of the @samp{info threads} display; or it
2856 could be a range of thread numbers, as in @code{2-4}. To apply a
2857 command to all threads, type @kbd{thread apply all @var{command}}.
2860 @cindex name a thread
2861 @item thread name [@var{name}]
2862 This command assigns a name to the current thread. If no argument is
2863 given, any existing user-specified name is removed. The thread name
2864 appears in the @samp{info threads} display.
2866 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2867 determine the name of the thread as given by the OS. On these
2868 systems, a name specified with @samp{thread name} will override the
2869 system-give name, and removing the user-specified name will cause
2870 @value{GDBN} to once again display the system-specified name.
2873 @cindex search for a thread
2874 @item thread find [@var{regexp}]
2875 Search for and display thread ids whose name or @var{systag}
2876 matches the supplied regular expression.
2878 As well as being the complement to the @samp{thread name} command,
2879 this command also allows you to identify a thread by its target
2880 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2884 (@value{GDBN}) thread find 26688
2885 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2886 (@value{GDBN}) info thread 4
2888 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2891 @kindex set print thread-events
2892 @cindex print messages on thread start and exit
2893 @item set print thread-events
2894 @itemx set print thread-events on
2895 @itemx set print thread-events off
2896 The @code{set print thread-events} command allows you to enable or
2897 disable printing of messages when @value{GDBN} notices that new threads have
2898 started or that threads have exited. By default, these messages will
2899 be printed if detection of these events is supported by the target.
2900 Note that these messages cannot be disabled on all targets.
2902 @kindex show print thread-events
2903 @item show print thread-events
2904 Show whether messages will be printed when @value{GDBN} detects that threads
2905 have started and exited.
2908 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2909 more information about how @value{GDBN} behaves when you stop and start
2910 programs with multiple threads.
2912 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2913 watchpoints in programs with multiple threads.
2915 @anchor{set libthread-db-search-path}
2917 @kindex set libthread-db-search-path
2918 @cindex search path for @code{libthread_db}
2919 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2920 If this variable is set, @var{path} is a colon-separated list of
2921 directories @value{GDBN} will use to search for @code{libthread_db}.
2922 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2923 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2924 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2927 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2928 @code{libthread_db} library to obtain information about threads in the
2929 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2930 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
2931 specific thread debugging library loading is enabled
2932 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
2934 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2935 refers to the default system directories that are
2936 normally searched for loading shared libraries. The @samp{$sdir} entry
2937 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
2938 (@pxref{libthread_db.so.1 file}).
2940 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2941 refers to the directory from which @code{libpthread}
2942 was loaded in the inferior process.
2944 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2945 @value{GDBN} attempts to initialize it with the current inferior process.
2946 If this initialization fails (which could happen because of a version
2947 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2948 will unload @code{libthread_db}, and continue with the next directory.
2949 If none of @code{libthread_db} libraries initialize successfully,
2950 @value{GDBN} will issue a warning and thread debugging will be disabled.
2952 Setting @code{libthread-db-search-path} is currently implemented
2953 only on some platforms.
2955 @kindex show libthread-db-search-path
2956 @item show libthread-db-search-path
2957 Display current libthread_db search path.
2959 @kindex set debug libthread-db
2960 @kindex show debug libthread-db
2961 @cindex debugging @code{libthread_db}
2962 @item set debug libthread-db
2963 @itemx show debug libthread-db
2964 Turns on or off display of @code{libthread_db}-related events.
2965 Use @code{1} to enable, @code{0} to disable.
2969 @section Debugging Forks
2971 @cindex fork, debugging programs which call
2972 @cindex multiple processes
2973 @cindex processes, multiple
2974 On most systems, @value{GDBN} has no special support for debugging
2975 programs which create additional processes using the @code{fork}
2976 function. When a program forks, @value{GDBN} will continue to debug the
2977 parent process and the child process will run unimpeded. If you have
2978 set a breakpoint in any code which the child then executes, the child
2979 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2980 will cause it to terminate.
2982 However, if you want to debug the child process there is a workaround
2983 which isn't too painful. Put a call to @code{sleep} in the code which
2984 the child process executes after the fork. It may be useful to sleep
2985 only if a certain environment variable is set, or a certain file exists,
2986 so that the delay need not occur when you don't want to run @value{GDBN}
2987 on the child. While the child is sleeping, use the @code{ps} program to
2988 get its process ID. Then tell @value{GDBN} (a new invocation of
2989 @value{GDBN} if you are also debugging the parent process) to attach to
2990 the child process (@pxref{Attach}). From that point on you can debug
2991 the child process just like any other process which you attached to.
2993 On some systems, @value{GDBN} provides support for debugging programs that
2994 create additional processes using the @code{fork} or @code{vfork} functions.
2995 Currently, the only platforms with this feature are HP-UX (11.x and later
2996 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2998 By default, when a program forks, @value{GDBN} will continue to debug
2999 the parent process and the child process will run unimpeded.
3001 If you want to follow the child process instead of the parent process,
3002 use the command @w{@code{set follow-fork-mode}}.
3005 @kindex set follow-fork-mode
3006 @item set follow-fork-mode @var{mode}
3007 Set the debugger response to a program call of @code{fork} or
3008 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3009 process. The @var{mode} argument can be:
3013 The original process is debugged after a fork. The child process runs
3014 unimpeded. This is the default.
3017 The new process is debugged after a fork. The parent process runs
3022 @kindex show follow-fork-mode
3023 @item show follow-fork-mode
3024 Display the current debugger response to a @code{fork} or @code{vfork} call.
3027 @cindex debugging multiple processes
3028 On Linux, if you want to debug both the parent and child processes, use the
3029 command @w{@code{set detach-on-fork}}.
3032 @kindex set detach-on-fork
3033 @item set detach-on-fork @var{mode}
3034 Tells gdb whether to detach one of the processes after a fork, or
3035 retain debugger control over them both.
3039 The child process (or parent process, depending on the value of
3040 @code{follow-fork-mode}) will be detached and allowed to run
3041 independently. This is the default.
3044 Both processes will be held under the control of @value{GDBN}.
3045 One process (child or parent, depending on the value of
3046 @code{follow-fork-mode}) is debugged as usual, while the other
3051 @kindex show detach-on-fork
3052 @item show detach-on-fork
3053 Show whether detach-on-fork mode is on/off.
3056 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3057 will retain control of all forked processes (including nested forks).
3058 You can list the forked processes under the control of @value{GDBN} by
3059 using the @w{@code{info inferiors}} command, and switch from one fork
3060 to another by using the @code{inferior} command (@pxref{Inferiors and
3061 Programs, ,Debugging Multiple Inferiors and Programs}).
3063 To quit debugging one of the forked processes, you can either detach
3064 from it by using the @w{@code{detach inferiors}} command (allowing it
3065 to run independently), or kill it using the @w{@code{kill inferiors}}
3066 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3069 If you ask to debug a child process and a @code{vfork} is followed by an
3070 @code{exec}, @value{GDBN} executes the new target up to the first
3071 breakpoint in the new target. If you have a breakpoint set on
3072 @code{main} in your original program, the breakpoint will also be set on
3073 the child process's @code{main}.
3075 On some systems, when a child process is spawned by @code{vfork}, you
3076 cannot debug the child or parent until an @code{exec} call completes.
3078 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3079 call executes, the new target restarts. To restart the parent
3080 process, use the @code{file} command with the parent executable name
3081 as its argument. By default, after an @code{exec} call executes,
3082 @value{GDBN} discards the symbols of the previous executable image.
3083 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3087 @kindex set follow-exec-mode
3088 @item set follow-exec-mode @var{mode}
3090 Set debugger response to a program call of @code{exec}. An
3091 @code{exec} call replaces the program image of a process.
3093 @code{follow-exec-mode} can be:
3097 @value{GDBN} creates a new inferior and rebinds the process to this
3098 new inferior. The program the process was running before the
3099 @code{exec} call can be restarted afterwards by restarting the
3105 (@value{GDBP}) info inferiors
3107 Id Description Executable
3110 process 12020 is executing new program: prog2
3111 Program exited normally.
3112 (@value{GDBP}) info inferiors
3113 Id Description Executable
3119 @value{GDBN} keeps the process bound to the same inferior. The new
3120 executable image replaces the previous executable loaded in the
3121 inferior. Restarting the inferior after the @code{exec} call, with
3122 e.g., the @code{run} command, restarts the executable the process was
3123 running after the @code{exec} call. This is the default mode.
3128 (@value{GDBP}) info inferiors
3129 Id Description Executable
3132 process 12020 is executing new program: prog2
3133 Program exited normally.
3134 (@value{GDBP}) info inferiors
3135 Id Description Executable
3142 You can use the @code{catch} command to make @value{GDBN} stop whenever
3143 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3144 Catchpoints, ,Setting Catchpoints}.
3146 @node Checkpoint/Restart
3147 @section Setting a @emph{Bookmark} to Return to Later
3152 @cindex snapshot of a process
3153 @cindex rewind program state
3155 On certain operating systems@footnote{Currently, only
3156 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3157 program's state, called a @dfn{checkpoint}, and come back to it
3160 Returning to a checkpoint effectively undoes everything that has
3161 happened in the program since the @code{checkpoint} was saved. This
3162 includes changes in memory, registers, and even (within some limits)
3163 system state. Effectively, it is like going back in time to the
3164 moment when the checkpoint was saved.
3166 Thus, if you're stepping thru a program and you think you're
3167 getting close to the point where things go wrong, you can save
3168 a checkpoint. Then, if you accidentally go too far and miss
3169 the critical statement, instead of having to restart your program
3170 from the beginning, you can just go back to the checkpoint and
3171 start again from there.
3173 This can be especially useful if it takes a lot of time or
3174 steps to reach the point where you think the bug occurs.
3176 To use the @code{checkpoint}/@code{restart} method of debugging:
3181 Save a snapshot of the debugged program's current execution state.
3182 The @code{checkpoint} command takes no arguments, but each checkpoint
3183 is assigned a small integer id, similar to a breakpoint id.
3185 @kindex info checkpoints
3186 @item info checkpoints
3187 List the checkpoints that have been saved in the current debugging
3188 session. For each checkpoint, the following information will be
3195 @item Source line, or label
3198 @kindex restart @var{checkpoint-id}
3199 @item restart @var{checkpoint-id}
3200 Restore the program state that was saved as checkpoint number
3201 @var{checkpoint-id}. All program variables, registers, stack frames
3202 etc.@: will be returned to the values that they had when the checkpoint
3203 was saved. In essence, gdb will ``wind back the clock'' to the point
3204 in time when the checkpoint was saved.
3206 Note that breakpoints, @value{GDBN} variables, command history etc.
3207 are not affected by restoring a checkpoint. In general, a checkpoint
3208 only restores things that reside in the program being debugged, not in
3211 @kindex delete checkpoint @var{checkpoint-id}
3212 @item delete checkpoint @var{checkpoint-id}
3213 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3217 Returning to a previously saved checkpoint will restore the user state
3218 of the program being debugged, plus a significant subset of the system
3219 (OS) state, including file pointers. It won't ``un-write'' data from
3220 a file, but it will rewind the file pointer to the previous location,
3221 so that the previously written data can be overwritten. For files
3222 opened in read mode, the pointer will also be restored so that the
3223 previously read data can be read again.
3225 Of course, characters that have been sent to a printer (or other
3226 external device) cannot be ``snatched back'', and characters received
3227 from eg.@: a serial device can be removed from internal program buffers,
3228 but they cannot be ``pushed back'' into the serial pipeline, ready to
3229 be received again. Similarly, the actual contents of files that have
3230 been changed cannot be restored (at this time).
3232 However, within those constraints, you actually can ``rewind'' your
3233 program to a previously saved point in time, and begin debugging it
3234 again --- and you can change the course of events so as to debug a
3235 different execution path this time.
3237 @cindex checkpoints and process id
3238 Finally, there is one bit of internal program state that will be
3239 different when you return to a checkpoint --- the program's process
3240 id. Each checkpoint will have a unique process id (or @var{pid}),
3241 and each will be different from the program's original @var{pid}.
3242 If your program has saved a local copy of its process id, this could
3243 potentially pose a problem.
3245 @subsection A Non-obvious Benefit of Using Checkpoints
3247 On some systems such as @sc{gnu}/Linux, address space randomization
3248 is performed on new processes for security reasons. This makes it
3249 difficult or impossible to set a breakpoint, or watchpoint, on an
3250 absolute address if you have to restart the program, since the
3251 absolute location of a symbol will change from one execution to the
3254 A checkpoint, however, is an @emph{identical} copy of a process.
3255 Therefore if you create a checkpoint at (eg.@:) the start of main,
3256 and simply return to that checkpoint instead of restarting the
3257 process, you can avoid the effects of address randomization and
3258 your symbols will all stay in the same place.
3261 @chapter Stopping and Continuing
3263 The principal purposes of using a debugger are so that you can stop your
3264 program before it terminates; or so that, if your program runs into
3265 trouble, you can investigate and find out why.
3267 Inside @value{GDBN}, your program may stop for any of several reasons,
3268 such as a signal, a breakpoint, or reaching a new line after a
3269 @value{GDBN} command such as @code{step}. You may then examine and
3270 change variables, set new breakpoints or remove old ones, and then
3271 continue execution. Usually, the messages shown by @value{GDBN} provide
3272 ample explanation of the status of your program---but you can also
3273 explicitly request this information at any time.
3276 @kindex info program
3278 Display information about the status of your program: whether it is
3279 running or not, what process it is, and why it stopped.
3283 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3284 * Continuing and Stepping:: Resuming execution
3285 * Skipping Over Functions and Files::
3286 Skipping over functions and files
3288 * Thread Stops:: Stopping and starting multi-thread programs
3292 @section Breakpoints, Watchpoints, and Catchpoints
3295 A @dfn{breakpoint} makes your program stop whenever a certain point in
3296 the program is reached. For each breakpoint, you can add conditions to
3297 control in finer detail whether your program stops. You can set
3298 breakpoints with the @code{break} command and its variants (@pxref{Set
3299 Breaks, ,Setting Breakpoints}), to specify the place where your program
3300 should stop by line number, function name or exact address in the
3303 On some systems, you can set breakpoints in shared libraries before
3304 the executable is run. There is a minor limitation on HP-UX systems:
3305 you must wait until the executable is run in order to set breakpoints
3306 in shared library routines that are not called directly by the program
3307 (for example, routines that are arguments in a @code{pthread_create}
3311 @cindex data breakpoints
3312 @cindex memory tracing
3313 @cindex breakpoint on memory address
3314 @cindex breakpoint on variable modification
3315 A @dfn{watchpoint} is a special breakpoint that stops your program
3316 when the value of an expression changes. The expression may be a value
3317 of a variable, or it could involve values of one or more variables
3318 combined by operators, such as @samp{a + b}. This is sometimes called
3319 @dfn{data breakpoints}. You must use a different command to set
3320 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3321 from that, you can manage a watchpoint like any other breakpoint: you
3322 enable, disable, and delete both breakpoints and watchpoints using the
3325 You can arrange to have values from your program displayed automatically
3326 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3330 @cindex breakpoint on events
3331 A @dfn{catchpoint} is another special breakpoint that stops your program
3332 when a certain kind of event occurs, such as the throwing of a C@t{++}
3333 exception or the loading of a library. As with watchpoints, you use a
3334 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3335 Catchpoints}), but aside from that, you can manage a catchpoint like any
3336 other breakpoint. (To stop when your program receives a signal, use the
3337 @code{handle} command; see @ref{Signals, ,Signals}.)
3339 @cindex breakpoint numbers
3340 @cindex numbers for breakpoints
3341 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3342 catchpoint when you create it; these numbers are successive integers
3343 starting with one. In many of the commands for controlling various
3344 features of breakpoints you use the breakpoint number to say which
3345 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3346 @dfn{disabled}; if disabled, it has no effect on your program until you
3349 @cindex breakpoint ranges
3350 @cindex ranges of breakpoints
3351 Some @value{GDBN} commands accept a range of breakpoints on which to
3352 operate. A breakpoint range is either a single breakpoint number, like
3353 @samp{5}, or two such numbers, in increasing order, separated by a
3354 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3355 all breakpoints in that range are operated on.
3358 * Set Breaks:: Setting breakpoints
3359 * Set Watchpoints:: Setting watchpoints
3360 * Set Catchpoints:: Setting catchpoints
3361 * Delete Breaks:: Deleting breakpoints
3362 * Disabling:: Disabling breakpoints
3363 * Conditions:: Break conditions
3364 * Break Commands:: Breakpoint command lists
3365 * Dynamic Printf:: Dynamic printf
3366 * Save Breakpoints:: How to save breakpoints in a file
3367 * Static Probe Points:: Listing static probe points
3368 * Error in Breakpoints:: ``Cannot insert breakpoints''
3369 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3373 @subsection Setting Breakpoints
3375 @c FIXME LMB what does GDB do if no code on line of breakpt?
3376 @c consider in particular declaration with/without initialization.
3378 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3381 @kindex b @r{(@code{break})}
3382 @vindex $bpnum@r{, convenience variable}
3383 @cindex latest breakpoint
3384 Breakpoints are set with the @code{break} command (abbreviated
3385 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3386 number of the breakpoint you've set most recently; see @ref{Convenience
3387 Vars,, Convenience Variables}, for a discussion of what you can do with
3388 convenience variables.
3391 @item break @var{location}
3392 Set a breakpoint at the given @var{location}, which can specify a
3393 function name, a line number, or an address of an instruction.
3394 (@xref{Specify Location}, for a list of all the possible ways to
3395 specify a @var{location}.) The breakpoint will stop your program just
3396 before it executes any of the code in the specified @var{location}.
3398 When using source languages that permit overloading of symbols, such as
3399 C@t{++}, a function name may refer to more than one possible place to break.
3400 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3403 It is also possible to insert a breakpoint that will stop the program
3404 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3405 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3408 When called without any arguments, @code{break} sets a breakpoint at
3409 the next instruction to be executed in the selected stack frame
3410 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3411 innermost, this makes your program stop as soon as control
3412 returns to that frame. This is similar to the effect of a
3413 @code{finish} command in the frame inside the selected frame---except
3414 that @code{finish} does not leave an active breakpoint. If you use
3415 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3416 the next time it reaches the current location; this may be useful
3419 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3420 least one instruction has been executed. If it did not do this, you
3421 would be unable to proceed past a breakpoint without first disabling the
3422 breakpoint. This rule applies whether or not the breakpoint already
3423 existed when your program stopped.
3425 @item break @dots{} if @var{cond}
3426 Set a breakpoint with condition @var{cond}; evaluate the expression
3427 @var{cond} each time the breakpoint is reached, and stop only if the
3428 value is nonzero---that is, if @var{cond} evaluates as true.
3429 @samp{@dots{}} stands for one of the possible arguments described
3430 above (or no argument) specifying where to break. @xref{Conditions,
3431 ,Break Conditions}, for more information on breakpoint conditions.
3434 @item tbreak @var{args}
3435 Set a breakpoint enabled only for one stop. @var{args} are the
3436 same as for the @code{break} command, and the breakpoint is set in the same
3437 way, but the breakpoint is automatically deleted after the first time your
3438 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3441 @cindex hardware breakpoints
3442 @item hbreak @var{args}
3443 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3444 @code{break} command and the breakpoint is set in the same way, but the
3445 breakpoint requires hardware support and some target hardware may not
3446 have this support. The main purpose of this is EPROM/ROM code
3447 debugging, so you can set a breakpoint at an instruction without
3448 changing the instruction. This can be used with the new trap-generation
3449 provided by SPARClite DSU and most x86-based targets. These targets
3450 will generate traps when a program accesses some data or instruction
3451 address that is assigned to the debug registers. However the hardware
3452 breakpoint registers can take a limited number of breakpoints. For
3453 example, on the DSU, only two data breakpoints can be set at a time, and
3454 @value{GDBN} will reject this command if more than two are used. Delete
3455 or disable unused hardware breakpoints before setting new ones
3456 (@pxref{Disabling, ,Disabling Breakpoints}).
3457 @xref{Conditions, ,Break Conditions}.
3458 For remote targets, you can restrict the number of hardware
3459 breakpoints @value{GDBN} will use, see @ref{set remote
3460 hardware-breakpoint-limit}.
3463 @item thbreak @var{args}
3464 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3465 are the same as for the @code{hbreak} command and the breakpoint is set in
3466 the same way. However, like the @code{tbreak} command,
3467 the breakpoint is automatically deleted after the
3468 first time your program stops there. Also, like the @code{hbreak}
3469 command, the breakpoint requires hardware support and some target hardware
3470 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3471 See also @ref{Conditions, ,Break Conditions}.
3474 @cindex regular expression
3475 @cindex breakpoints at functions matching a regexp
3476 @cindex set breakpoints in many functions
3477 @item rbreak @var{regex}
3478 Set breakpoints on all functions matching the regular expression
3479 @var{regex}. This command sets an unconditional breakpoint on all
3480 matches, printing a list of all breakpoints it set. Once these
3481 breakpoints are set, they are treated just like the breakpoints set with
3482 the @code{break} command. You can delete them, disable them, or make
3483 them conditional the same way as any other breakpoint.
3485 The syntax of the regular expression is the standard one used with tools
3486 like @file{grep}. Note that this is different from the syntax used by
3487 shells, so for instance @code{foo*} matches all functions that include
3488 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3489 @code{.*} leading and trailing the regular expression you supply, so to
3490 match only functions that begin with @code{foo}, use @code{^foo}.
3492 @cindex non-member C@t{++} functions, set breakpoint in
3493 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3494 breakpoints on overloaded functions that are not members of any special
3497 @cindex set breakpoints on all functions
3498 The @code{rbreak} command can be used to set breakpoints in
3499 @strong{all} the functions in a program, like this:
3502 (@value{GDBP}) rbreak .
3505 @item rbreak @var{file}:@var{regex}
3506 If @code{rbreak} is called with a filename qualification, it limits
3507 the search for functions matching the given regular expression to the
3508 specified @var{file}. This can be used, for example, to set breakpoints on
3509 every function in a given file:
3512 (@value{GDBP}) rbreak file.c:.
3515 The colon separating the filename qualifier from the regex may
3516 optionally be surrounded by spaces.
3518 @kindex info breakpoints
3519 @cindex @code{$_} and @code{info breakpoints}
3520 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3521 @itemx info break @r{[}@var{n}@dots{}@r{]}
3522 Print a table of all breakpoints, watchpoints, and catchpoints set and
3523 not deleted. Optional argument @var{n} means print information only
3524 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3525 For each breakpoint, following columns are printed:
3528 @item Breakpoint Numbers
3530 Breakpoint, watchpoint, or catchpoint.
3532 Whether the breakpoint is marked to be disabled or deleted when hit.
3533 @item Enabled or Disabled
3534 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3535 that are not enabled.
3537 Where the breakpoint is in your program, as a memory address. For a
3538 pending breakpoint whose address is not yet known, this field will
3539 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3540 library that has the symbol or line referred by breakpoint is loaded.
3541 See below for details. A breakpoint with several locations will
3542 have @samp{<MULTIPLE>} in this field---see below for details.
3544 Where the breakpoint is in the source for your program, as a file and
3545 line number. For a pending breakpoint, the original string passed to
3546 the breakpoint command will be listed as it cannot be resolved until
3547 the appropriate shared library is loaded in the future.
3551 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3552 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3553 @value{GDBN} on the host's side. If it is ``target'', then the condition
3554 is evaluated by the target. The @code{info break} command shows
3555 the condition on the line following the affected breakpoint, together with
3556 its condition evaluation mode in between parentheses.
3558 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3559 allowed to have a condition specified for it. The condition is not parsed for
3560 validity until a shared library is loaded that allows the pending
3561 breakpoint to resolve to a valid location.
3564 @code{info break} with a breakpoint
3565 number @var{n} as argument lists only that breakpoint. The
3566 convenience variable @code{$_} and the default examining-address for
3567 the @code{x} command are set to the address of the last breakpoint
3568 listed (@pxref{Memory, ,Examining Memory}).
3571 @code{info break} displays a count of the number of times the breakpoint
3572 has been hit. This is especially useful in conjunction with the
3573 @code{ignore} command. You can ignore a large number of breakpoint
3574 hits, look at the breakpoint info to see how many times the breakpoint
3575 was hit, and then run again, ignoring one less than that number. This
3576 will get you quickly to the last hit of that breakpoint.
3579 For a breakpoints with an enable count (xref) greater than 1,
3580 @code{info break} also displays that count.
3584 @value{GDBN} allows you to set any number of breakpoints at the same place in
3585 your program. There is nothing silly or meaningless about this. When
3586 the breakpoints are conditional, this is even useful
3587 (@pxref{Conditions, ,Break Conditions}).
3589 @cindex multiple locations, breakpoints
3590 @cindex breakpoints, multiple locations
3591 It is possible that a breakpoint corresponds to several locations
3592 in your program. Examples of this situation are:
3596 Multiple functions in the program may have the same name.
3599 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3600 instances of the function body, used in different cases.
3603 For a C@t{++} template function, a given line in the function can
3604 correspond to any number of instantiations.
3607 For an inlined function, a given source line can correspond to
3608 several places where that function is inlined.
3611 In all those cases, @value{GDBN} will insert a breakpoint at all
3612 the relevant locations.
3614 A breakpoint with multiple locations is displayed in the breakpoint
3615 table using several rows---one header row, followed by one row for
3616 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3617 address column. The rows for individual locations contain the actual
3618 addresses for locations, and show the functions to which those
3619 locations belong. The number column for a location is of the form
3620 @var{breakpoint-number}.@var{location-number}.
3625 Num Type Disp Enb Address What
3626 1 breakpoint keep y <MULTIPLE>
3628 breakpoint already hit 1 time
3629 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3630 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3633 Each location can be individually enabled or disabled by passing
3634 @var{breakpoint-number}.@var{location-number} as argument to the
3635 @code{enable} and @code{disable} commands. Note that you cannot
3636 delete the individual locations from the list, you can only delete the
3637 entire list of locations that belong to their parent breakpoint (with
3638 the @kbd{delete @var{num}} command, where @var{num} is the number of
3639 the parent breakpoint, 1 in the above example). Disabling or enabling
3640 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3641 that belong to that breakpoint.
3643 @cindex pending breakpoints
3644 It's quite common to have a breakpoint inside a shared library.
3645 Shared libraries can be loaded and unloaded explicitly,
3646 and possibly repeatedly, as the program is executed. To support
3647 this use case, @value{GDBN} updates breakpoint locations whenever
3648 any shared library is loaded or unloaded. Typically, you would
3649 set a breakpoint in a shared library at the beginning of your
3650 debugging session, when the library is not loaded, and when the
3651 symbols from the library are not available. When you try to set
3652 breakpoint, @value{GDBN} will ask you if you want to set
3653 a so called @dfn{pending breakpoint}---breakpoint whose address
3654 is not yet resolved.
3656 After the program is run, whenever a new shared library is loaded,
3657 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3658 shared library contains the symbol or line referred to by some
3659 pending breakpoint, that breakpoint is resolved and becomes an
3660 ordinary breakpoint. When a library is unloaded, all breakpoints
3661 that refer to its symbols or source lines become pending again.
3663 This logic works for breakpoints with multiple locations, too. For
3664 example, if you have a breakpoint in a C@t{++} template function, and
3665 a newly loaded shared library has an instantiation of that template,
3666 a new location is added to the list of locations for the breakpoint.
3668 Except for having unresolved address, pending breakpoints do not
3669 differ from regular breakpoints. You can set conditions or commands,
3670 enable and disable them and perform other breakpoint operations.
3672 @value{GDBN} provides some additional commands for controlling what
3673 happens when the @samp{break} command cannot resolve breakpoint
3674 address specification to an address:
3676 @kindex set breakpoint pending
3677 @kindex show breakpoint pending
3679 @item set breakpoint pending auto
3680 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3681 location, it queries you whether a pending breakpoint should be created.
3683 @item set breakpoint pending on
3684 This indicates that an unrecognized breakpoint location should automatically
3685 result in a pending breakpoint being created.
3687 @item set breakpoint pending off
3688 This indicates that pending breakpoints are not to be created. Any
3689 unrecognized breakpoint location results in an error. This setting does
3690 not affect any pending breakpoints previously created.
3692 @item show breakpoint pending
3693 Show the current behavior setting for creating pending breakpoints.
3696 The settings above only affect the @code{break} command and its
3697 variants. Once breakpoint is set, it will be automatically updated
3698 as shared libraries are loaded and unloaded.
3700 @cindex automatic hardware breakpoints
3701 For some targets, @value{GDBN} can automatically decide if hardware or
3702 software breakpoints should be used, depending on whether the
3703 breakpoint address is read-only or read-write. This applies to
3704 breakpoints set with the @code{break} command as well as to internal
3705 breakpoints set by commands like @code{next} and @code{finish}. For
3706 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3709 You can control this automatic behaviour with the following commands::
3711 @kindex set breakpoint auto-hw
3712 @kindex show breakpoint auto-hw
3714 @item set breakpoint auto-hw on
3715 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3716 will try to use the target memory map to decide if software or hardware
3717 breakpoint must be used.
3719 @item set breakpoint auto-hw off
3720 This indicates @value{GDBN} should not automatically select breakpoint
3721 type. If the target provides a memory map, @value{GDBN} will warn when
3722 trying to set software breakpoint at a read-only address.
3725 @value{GDBN} normally implements breakpoints by replacing the program code
3726 at the breakpoint address with a special instruction, which, when
3727 executed, given control to the debugger. By default, the program
3728 code is so modified only when the program is resumed. As soon as
3729 the program stops, @value{GDBN} restores the original instructions. This
3730 behaviour guards against leaving breakpoints inserted in the
3731 target should gdb abrubptly disconnect. However, with slow remote
3732 targets, inserting and removing breakpoint can reduce the performance.
3733 This behavior can be controlled with the following commands::
3735 @kindex set breakpoint always-inserted
3736 @kindex show breakpoint always-inserted
3738 @item set breakpoint always-inserted off
3739 All breakpoints, including newly added by the user, are inserted in
3740 the target only when the target is resumed. All breakpoints are
3741 removed from the target when it stops.
3743 @item set breakpoint always-inserted on
3744 Causes all breakpoints to be inserted in the target at all times. If
3745 the user adds a new breakpoint, or changes an existing breakpoint, the
3746 breakpoints in the target are updated immediately. A breakpoint is
3747 removed from the target only when breakpoint itself is removed.
3749 @cindex non-stop mode, and @code{breakpoint always-inserted}
3750 @item set breakpoint always-inserted auto
3751 This is the default mode. If @value{GDBN} is controlling the inferior
3752 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3753 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3754 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3755 @code{breakpoint always-inserted} mode is off.
3758 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3759 when a breakpoint breaks. If the condition is true, then the process being
3760 debugged stops, otherwise the process is resumed.
3762 If the target supports evaluating conditions on its end, @value{GDBN} may
3763 download the breakpoint, together with its conditions, to it.
3765 This feature can be controlled via the following commands:
3767 @kindex set breakpoint condition-evaluation
3768 @kindex show breakpoint condition-evaluation
3770 @item set breakpoint condition-evaluation host
3771 This option commands @value{GDBN} to evaluate the breakpoint
3772 conditions on the host's side. Unconditional breakpoints are sent to
3773 the target which in turn receives the triggers and reports them back to GDB
3774 for condition evaluation. This is the standard evaluation mode.
3776 @item set breakpoint condition-evaluation target
3777 This option commands @value{GDBN} to download breakpoint conditions
3778 to the target at the moment of their insertion. The target
3779 is responsible for evaluating the conditional expression and reporting
3780 breakpoint stop events back to @value{GDBN} whenever the condition
3781 is true. Due to limitations of target-side evaluation, some conditions
3782 cannot be evaluated there, e.g., conditions that depend on local data
3783 that is only known to the host. Examples include
3784 conditional expressions involving convenience variables, complex types
3785 that cannot be handled by the agent expression parser and expressions
3786 that are too long to be sent over to the target, specially when the
3787 target is a remote system. In these cases, the conditions will be
3788 evaluated by @value{GDBN}.
3790 @item set breakpoint condition-evaluation auto
3791 This is the default mode. If the target supports evaluating breakpoint
3792 conditions on its end, @value{GDBN} will download breakpoint conditions to
3793 the target (limitations mentioned previously apply). If the target does
3794 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3795 to evaluating all these conditions on the host's side.
3799 @cindex negative breakpoint numbers
3800 @cindex internal @value{GDBN} breakpoints
3801 @value{GDBN} itself sometimes sets breakpoints in your program for
3802 special purposes, such as proper handling of @code{longjmp} (in C
3803 programs). These internal breakpoints are assigned negative numbers,
3804 starting with @code{-1}; @samp{info breakpoints} does not display them.
3805 You can see these breakpoints with the @value{GDBN} maintenance command
3806 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3809 @node Set Watchpoints
3810 @subsection Setting Watchpoints
3812 @cindex setting watchpoints
3813 You can use a watchpoint to stop execution whenever the value of an
3814 expression changes, without having to predict a particular place where
3815 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3816 The expression may be as simple as the value of a single variable, or
3817 as complex as many variables combined by operators. Examples include:
3821 A reference to the value of a single variable.
3824 An address cast to an appropriate data type. For example,
3825 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3826 address (assuming an @code{int} occupies 4 bytes).
3829 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3830 expression can use any operators valid in the program's native
3831 language (@pxref{Languages}).
3834 You can set a watchpoint on an expression even if the expression can
3835 not be evaluated yet. For instance, you can set a watchpoint on
3836 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3837 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3838 the expression produces a valid value. If the expression becomes
3839 valid in some other way than changing a variable (e.g.@: if the memory
3840 pointed to by @samp{*global_ptr} becomes readable as the result of a
3841 @code{malloc} call), @value{GDBN} may not stop until the next time
3842 the expression changes.
3844 @cindex software watchpoints
3845 @cindex hardware watchpoints
3846 Depending on your system, watchpoints may be implemented in software or
3847 hardware. @value{GDBN} does software watchpointing by single-stepping your
3848 program and testing the variable's value each time, which is hundreds of
3849 times slower than normal execution. (But this may still be worth it, to
3850 catch errors where you have no clue what part of your program is the
3853 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3854 x86-based targets, @value{GDBN} includes support for hardware
3855 watchpoints, which do not slow down the running of your program.
3859 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3860 Set a watchpoint for an expression. @value{GDBN} will break when the
3861 expression @var{expr} is written into by the program and its value
3862 changes. The simplest (and the most popular) use of this command is
3863 to watch the value of a single variable:
3866 (@value{GDBP}) watch foo
3869 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3870 argument, @value{GDBN} breaks only when the thread identified by
3871 @var{threadnum} changes the value of @var{expr}. If any other threads
3872 change the value of @var{expr}, @value{GDBN} will not break. Note
3873 that watchpoints restricted to a single thread in this way only work
3874 with Hardware Watchpoints.
3876 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3877 (see below). The @code{-location} argument tells @value{GDBN} to
3878 instead watch the memory referred to by @var{expr}. In this case,
3879 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3880 and watch the memory at that address. The type of the result is used
3881 to determine the size of the watched memory. If the expression's
3882 result does not have an address, then @value{GDBN} will print an
3885 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3886 of masked watchpoints, if the current architecture supports this
3887 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3888 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3889 to an address to watch. The mask specifies that some bits of an address
3890 (the bits which are reset in the mask) should be ignored when matching
3891 the address accessed by the inferior against the watchpoint address.
3892 Thus, a masked watchpoint watches many addresses simultaneously---those
3893 addresses whose unmasked bits are identical to the unmasked bits in the
3894 watchpoint address. The @code{mask} argument implies @code{-location}.
3898 (@value{GDBP}) watch foo mask 0xffff00ff
3899 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3903 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3904 Set a watchpoint that will break when the value of @var{expr} is read
3908 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3909 Set a watchpoint that will break when @var{expr} is either read from
3910 or written into by the program.
3912 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3913 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3914 This command prints a list of watchpoints, using the same format as
3915 @code{info break} (@pxref{Set Breaks}).
3918 If you watch for a change in a numerically entered address you need to
3919 dereference it, as the address itself is just a constant number which will
3920 never change. @value{GDBN} refuses to create a watchpoint that watches
3921 a never-changing value:
3924 (@value{GDBP}) watch 0x600850
3925 Cannot watch constant value 0x600850.
3926 (@value{GDBP}) watch *(int *) 0x600850
3927 Watchpoint 1: *(int *) 6293584
3930 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3931 watchpoints execute very quickly, and the debugger reports a change in
3932 value at the exact instruction where the change occurs. If @value{GDBN}
3933 cannot set a hardware watchpoint, it sets a software watchpoint, which
3934 executes more slowly and reports the change in value at the next
3935 @emph{statement}, not the instruction, after the change occurs.
3937 @cindex use only software watchpoints
3938 You can force @value{GDBN} to use only software watchpoints with the
3939 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3940 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3941 the underlying system supports them. (Note that hardware-assisted
3942 watchpoints that were set @emph{before} setting
3943 @code{can-use-hw-watchpoints} to zero will still use the hardware
3944 mechanism of watching expression values.)
3947 @item set can-use-hw-watchpoints
3948 @kindex set can-use-hw-watchpoints
3949 Set whether or not to use hardware watchpoints.
3951 @item show can-use-hw-watchpoints
3952 @kindex show can-use-hw-watchpoints
3953 Show the current mode of using hardware watchpoints.
3956 For remote targets, you can restrict the number of hardware
3957 watchpoints @value{GDBN} will use, see @ref{set remote
3958 hardware-breakpoint-limit}.
3960 When you issue the @code{watch} command, @value{GDBN} reports
3963 Hardware watchpoint @var{num}: @var{expr}
3967 if it was able to set a hardware watchpoint.
3969 Currently, the @code{awatch} and @code{rwatch} commands can only set
3970 hardware watchpoints, because accesses to data that don't change the
3971 value of the watched expression cannot be detected without examining
3972 every instruction as it is being executed, and @value{GDBN} does not do
3973 that currently. If @value{GDBN} finds that it is unable to set a
3974 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3975 will print a message like this:
3978 Expression cannot be implemented with read/access watchpoint.
3981 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3982 data type of the watched expression is wider than what a hardware
3983 watchpoint on the target machine can handle. For example, some systems
3984 can only watch regions that are up to 4 bytes wide; on such systems you
3985 cannot set hardware watchpoints for an expression that yields a
3986 double-precision floating-point number (which is typically 8 bytes
3987 wide). As a work-around, it might be possible to break the large region
3988 into a series of smaller ones and watch them with separate watchpoints.
3990 If you set too many hardware watchpoints, @value{GDBN} might be unable
3991 to insert all of them when you resume the execution of your program.
3992 Since the precise number of active watchpoints is unknown until such
3993 time as the program is about to be resumed, @value{GDBN} might not be
3994 able to warn you about this when you set the watchpoints, and the
3995 warning will be printed only when the program is resumed:
3998 Hardware watchpoint @var{num}: Could not insert watchpoint
4002 If this happens, delete or disable some of the watchpoints.
4004 Watching complex expressions that reference many variables can also
4005 exhaust the resources available for hardware-assisted watchpoints.
4006 That's because @value{GDBN} needs to watch every variable in the
4007 expression with separately allocated resources.
4009 If you call a function interactively using @code{print} or @code{call},
4010 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4011 kind of breakpoint or the call completes.
4013 @value{GDBN} automatically deletes watchpoints that watch local
4014 (automatic) variables, or expressions that involve such variables, when
4015 they go out of scope, that is, when the execution leaves the block in
4016 which these variables were defined. In particular, when the program
4017 being debugged terminates, @emph{all} local variables go out of scope,
4018 and so only watchpoints that watch global variables remain set. If you
4019 rerun the program, you will need to set all such watchpoints again. One
4020 way of doing that would be to set a code breakpoint at the entry to the
4021 @code{main} function and when it breaks, set all the watchpoints.
4023 @cindex watchpoints and threads
4024 @cindex threads and watchpoints
4025 In multi-threaded programs, watchpoints will detect changes to the
4026 watched expression from every thread.
4029 @emph{Warning:} In multi-threaded programs, software watchpoints
4030 have only limited usefulness. If @value{GDBN} creates a software
4031 watchpoint, it can only watch the value of an expression @emph{in a
4032 single thread}. If you are confident that the expression can only
4033 change due to the current thread's activity (and if you are also
4034 confident that no other thread can become current), then you can use
4035 software watchpoints as usual. However, @value{GDBN} may not notice
4036 when a non-current thread's activity changes the expression. (Hardware
4037 watchpoints, in contrast, watch an expression in all threads.)
4040 @xref{set remote hardware-watchpoint-limit}.
4042 @node Set Catchpoints
4043 @subsection Setting Catchpoints
4044 @cindex catchpoints, setting
4045 @cindex exception handlers
4046 @cindex event handling
4048 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4049 kinds of program events, such as C@t{++} exceptions or the loading of a
4050 shared library. Use the @code{catch} command to set a catchpoint.
4054 @item catch @var{event}
4055 Stop when @var{event} occurs. @var{event} can be any of the following:
4058 @cindex stop on C@t{++} exceptions
4059 The throwing of a C@t{++} exception.
4062 The catching of a C@t{++} exception.
4065 @cindex Ada exception catching
4066 @cindex catch Ada exceptions
4067 An Ada exception being raised. If an exception name is specified
4068 at the end of the command (eg @code{catch exception Program_Error}),
4069 the debugger will stop only when this specific exception is raised.
4070 Otherwise, the debugger stops execution when any Ada exception is raised.
4072 When inserting an exception catchpoint on a user-defined exception whose
4073 name is identical to one of the exceptions defined by the language, the
4074 fully qualified name must be used as the exception name. Otherwise,
4075 @value{GDBN} will assume that it should stop on the pre-defined exception
4076 rather than the user-defined one. For instance, assuming an exception
4077 called @code{Constraint_Error} is defined in package @code{Pck}, then
4078 the command to use to catch such exceptions is @kbd{catch exception
4079 Pck.Constraint_Error}.
4081 @item exception unhandled
4082 An exception that was raised but is not handled by the program.
4085 A failed Ada assertion.
4088 @cindex break on fork/exec
4089 A call to @code{exec}. This is currently only available for HP-UX
4093 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4094 @cindex break on a system call.
4095 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4096 syscall is a mechanism for application programs to request a service
4097 from the operating system (OS) or one of the OS system services.
4098 @value{GDBN} can catch some or all of the syscalls issued by the
4099 debuggee, and show the related information for each syscall. If no
4100 argument is specified, calls to and returns from all system calls
4103 @var{name} can be any system call name that is valid for the
4104 underlying OS. Just what syscalls are valid depends on the OS. On
4105 GNU and Unix systems, you can find the full list of valid syscall
4106 names on @file{/usr/include/asm/unistd.h}.
4108 @c For MS-Windows, the syscall names and the corresponding numbers
4109 @c can be found, e.g., on this URL:
4110 @c http://www.metasploit.com/users/opcode/syscalls.html
4111 @c but we don't support Windows syscalls yet.
4113 Normally, @value{GDBN} knows in advance which syscalls are valid for
4114 each OS, so you can use the @value{GDBN} command-line completion
4115 facilities (@pxref{Completion,, command completion}) to list the
4118 You may also specify the system call numerically. A syscall's
4119 number is the value passed to the OS's syscall dispatcher to
4120 identify the requested service. When you specify the syscall by its
4121 name, @value{GDBN} uses its database of syscalls to convert the name
4122 into the corresponding numeric code, but using the number directly
4123 may be useful if @value{GDBN}'s database does not have the complete
4124 list of syscalls on your system (e.g., because @value{GDBN} lags
4125 behind the OS upgrades).
4127 The example below illustrates how this command works if you don't provide
4131 (@value{GDBP}) catch syscall
4132 Catchpoint 1 (syscall)
4134 Starting program: /tmp/catch-syscall
4136 Catchpoint 1 (call to syscall 'close'), \
4137 0xffffe424 in __kernel_vsyscall ()
4141 Catchpoint 1 (returned from syscall 'close'), \
4142 0xffffe424 in __kernel_vsyscall ()
4146 Here is an example of catching a system call by name:
4149 (@value{GDBP}) catch syscall chroot
4150 Catchpoint 1 (syscall 'chroot' [61])
4152 Starting program: /tmp/catch-syscall
4154 Catchpoint 1 (call to syscall 'chroot'), \
4155 0xffffe424 in __kernel_vsyscall ()
4159 Catchpoint 1 (returned from syscall 'chroot'), \
4160 0xffffe424 in __kernel_vsyscall ()
4164 An example of specifying a system call numerically. In the case
4165 below, the syscall number has a corresponding entry in the XML
4166 file, so @value{GDBN} finds its name and prints it:
4169 (@value{GDBP}) catch syscall 252
4170 Catchpoint 1 (syscall(s) 'exit_group')
4172 Starting program: /tmp/catch-syscall
4174 Catchpoint 1 (call to syscall 'exit_group'), \
4175 0xffffe424 in __kernel_vsyscall ()
4179 Program exited normally.
4183 However, there can be situations when there is no corresponding name
4184 in XML file for that syscall number. In this case, @value{GDBN} prints
4185 a warning message saying that it was not able to find the syscall name,
4186 but the catchpoint will be set anyway. See the example below:
4189 (@value{GDBP}) catch syscall 764
4190 warning: The number '764' does not represent a known syscall.
4191 Catchpoint 2 (syscall 764)
4195 If you configure @value{GDBN} using the @samp{--without-expat} option,
4196 it will not be able to display syscall names. Also, if your
4197 architecture does not have an XML file describing its system calls,
4198 you will not be able to see the syscall names. It is important to
4199 notice that these two features are used for accessing the syscall
4200 name database. In either case, you will see a warning like this:
4203 (@value{GDBP}) catch syscall
4204 warning: Could not open "syscalls/i386-linux.xml"
4205 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4206 GDB will not be able to display syscall names.
4207 Catchpoint 1 (syscall)
4211 Of course, the file name will change depending on your architecture and system.
4213 Still using the example above, you can also try to catch a syscall by its
4214 number. In this case, you would see something like:
4217 (@value{GDBP}) catch syscall 252
4218 Catchpoint 1 (syscall(s) 252)
4221 Again, in this case @value{GDBN} would not be able to display syscall's names.
4224 A call to @code{fork}. This is currently only available for HP-UX
4228 A call to @code{vfork}. This is currently only available for HP-UX
4231 @item load @r{[}regexp@r{]}
4232 @itemx unload @r{[}regexp@r{]}
4233 The loading or unloading of a shared library. If @var{regexp} is
4234 given, then the catchpoint will stop only if the regular expression
4235 matches one of the affected libraries.
4237 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4238 The delivery of a signal.
4240 With no arguments, this catchpoint will catch any signal that is not
4241 used internally by @value{GDBN}, specifically, all signals except
4242 @samp{SIGTRAP} and @samp{SIGINT}.
4244 With the argument @samp{all}, all signals, including those used by
4245 @value{GDBN}, will be caught. This argument cannot be used with other
4248 Otherwise, the arguments are a list of signal names as given to
4249 @code{handle} (@pxref{Signals}). Only signals specified in this list
4252 One reason that @code{catch signal} can be more useful than
4253 @code{handle} is that you can attach commands and conditions to the
4256 When a signal is caught by a catchpoint, the signal's @code{stop} and
4257 @code{print} settings, as specified by @code{handle}, are ignored.
4258 However, whether the signal is still delivered to the inferior depends
4259 on the @code{pass} setting; this can be changed in the catchpoint's
4264 @item tcatch @var{event}
4265 Set a catchpoint that is enabled only for one stop. The catchpoint is
4266 automatically deleted after the first time the event is caught.
4270 Use the @code{info break} command to list the current catchpoints.
4272 There are currently some limitations to C@t{++} exception handling
4273 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4277 If you call a function interactively, @value{GDBN} normally returns
4278 control to you when the function has finished executing. If the call
4279 raises an exception, however, the call may bypass the mechanism that
4280 returns control to you and cause your program either to abort or to
4281 simply continue running until it hits a breakpoint, catches a signal
4282 that @value{GDBN} is listening for, or exits. This is the case even if
4283 you set a catchpoint for the exception; catchpoints on exceptions are
4284 disabled within interactive calls.
4287 You cannot raise an exception interactively.
4290 You cannot install an exception handler interactively.
4293 @cindex raise exceptions
4294 Sometimes @code{catch} is not the best way to debug exception handling:
4295 if you need to know exactly where an exception is raised, it is better to
4296 stop @emph{before} the exception handler is called, since that way you
4297 can see the stack before any unwinding takes place. If you set a
4298 breakpoint in an exception handler instead, it may not be easy to find
4299 out where the exception was raised.
4301 To stop just before an exception handler is called, you need some
4302 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4303 raised by calling a library function named @code{__raise_exception}
4304 which has the following ANSI C interface:
4307 /* @var{addr} is where the exception identifier is stored.
4308 @var{id} is the exception identifier. */
4309 void __raise_exception (void **addr, void *id);
4313 To make the debugger catch all exceptions before any stack
4314 unwinding takes place, set a breakpoint on @code{__raise_exception}
4315 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4317 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4318 that depends on the value of @var{id}, you can stop your program when
4319 a specific exception is raised. You can use multiple conditional
4320 breakpoints to stop your program when any of a number of exceptions are
4325 @subsection Deleting Breakpoints
4327 @cindex clearing breakpoints, watchpoints, catchpoints
4328 @cindex deleting breakpoints, watchpoints, catchpoints
4329 It is often necessary to eliminate a breakpoint, watchpoint, or
4330 catchpoint once it has done its job and you no longer want your program
4331 to stop there. This is called @dfn{deleting} the breakpoint. A
4332 breakpoint that has been deleted no longer exists; it is forgotten.
4334 With the @code{clear} command you can delete breakpoints according to
4335 where they are in your program. With the @code{delete} command you can
4336 delete individual breakpoints, watchpoints, or catchpoints by specifying
4337 their breakpoint numbers.
4339 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4340 automatically ignores breakpoints on the first instruction to be executed
4341 when you continue execution without changing the execution address.
4346 Delete any breakpoints at the next instruction to be executed in the
4347 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4348 the innermost frame is selected, this is a good way to delete a
4349 breakpoint where your program just stopped.
4351 @item clear @var{location}
4352 Delete any breakpoints set at the specified @var{location}.
4353 @xref{Specify Location}, for the various forms of @var{location}; the
4354 most useful ones are listed below:
4357 @item clear @var{function}
4358 @itemx clear @var{filename}:@var{function}
4359 Delete any breakpoints set at entry to the named @var{function}.
4361 @item clear @var{linenum}
4362 @itemx clear @var{filename}:@var{linenum}
4363 Delete any breakpoints set at or within the code of the specified
4364 @var{linenum} of the specified @var{filename}.
4367 @cindex delete breakpoints
4369 @kindex d @r{(@code{delete})}
4370 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4371 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4372 ranges specified as arguments. If no argument is specified, delete all
4373 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4374 confirm off}). You can abbreviate this command as @code{d}.
4378 @subsection Disabling Breakpoints
4380 @cindex enable/disable a breakpoint
4381 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4382 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4383 it had been deleted, but remembers the information on the breakpoint so
4384 that you can @dfn{enable} it again later.
4386 You disable and enable breakpoints, watchpoints, and catchpoints with
4387 the @code{enable} and @code{disable} commands, optionally specifying
4388 one or more breakpoint numbers as arguments. Use @code{info break} to
4389 print a list of all breakpoints, watchpoints, and catchpoints if you
4390 do not know which numbers to use.
4392 Disabling and enabling a breakpoint that has multiple locations
4393 affects all of its locations.
4395 A breakpoint, watchpoint, or catchpoint can have any of several
4396 different states of enablement:
4400 Enabled. The breakpoint stops your program. A breakpoint set
4401 with the @code{break} command starts out in this state.
4403 Disabled. The breakpoint has no effect on your program.
4405 Enabled once. The breakpoint stops your program, but then becomes
4408 Enabled for a count. The breakpoint stops your program for the next
4409 N times, then becomes disabled.
4411 Enabled for deletion. The breakpoint stops your program, but
4412 immediately after it does so it is deleted permanently. A breakpoint
4413 set with the @code{tbreak} command starts out in this state.
4416 You can use the following commands to enable or disable breakpoints,
4417 watchpoints, and catchpoints:
4421 @kindex dis @r{(@code{disable})}
4422 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4423 Disable the specified breakpoints---or all breakpoints, if none are
4424 listed. A disabled breakpoint has no effect but is not forgotten. All
4425 options such as ignore-counts, conditions and commands are remembered in
4426 case the breakpoint is enabled again later. You may abbreviate
4427 @code{disable} as @code{dis}.
4430 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4431 Enable the specified breakpoints (or all defined breakpoints). They
4432 become effective once again in stopping your program.
4434 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4435 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4436 of these breakpoints immediately after stopping your program.
4438 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4439 Enable the specified breakpoints temporarily. @value{GDBN} records
4440 @var{count} with each of the specified breakpoints, and decrements a
4441 breakpoint's count when it is hit. When any count reaches 0,
4442 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4443 count (@pxref{Conditions, ,Break Conditions}), that will be
4444 decremented to 0 before @var{count} is affected.
4446 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4447 Enable the specified breakpoints to work once, then die. @value{GDBN}
4448 deletes any of these breakpoints as soon as your program stops there.
4449 Breakpoints set by the @code{tbreak} command start out in this state.
4452 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4453 @c confusing: tbreak is also initially enabled.
4454 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4455 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4456 subsequently, they become disabled or enabled only when you use one of
4457 the commands above. (The command @code{until} can set and delete a
4458 breakpoint of its own, but it does not change the state of your other
4459 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4463 @subsection Break Conditions
4464 @cindex conditional breakpoints
4465 @cindex breakpoint conditions
4467 @c FIXME what is scope of break condition expr? Context where wanted?
4468 @c in particular for a watchpoint?
4469 The simplest sort of breakpoint breaks every time your program reaches a
4470 specified place. You can also specify a @dfn{condition} for a
4471 breakpoint. A condition is just a Boolean expression in your
4472 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4473 a condition evaluates the expression each time your program reaches it,
4474 and your program stops only if the condition is @emph{true}.
4476 This is the converse of using assertions for program validation; in that
4477 situation, you want to stop when the assertion is violated---that is,
4478 when the condition is false. In C, if you want to test an assertion expressed
4479 by the condition @var{assert}, you should set the condition
4480 @samp{! @var{assert}} on the appropriate breakpoint.
4482 Conditions are also accepted for watchpoints; you may not need them,
4483 since a watchpoint is inspecting the value of an expression anyhow---but
4484 it might be simpler, say, to just set a watchpoint on a variable name,
4485 and specify a condition that tests whether the new value is an interesting
4488 Break conditions can have side effects, and may even call functions in
4489 your program. This can be useful, for example, to activate functions
4490 that log program progress, or to use your own print functions to
4491 format special data structures. The effects are completely predictable
4492 unless there is another enabled breakpoint at the same address. (In
4493 that case, @value{GDBN} might see the other breakpoint first and stop your
4494 program without checking the condition of this one.) Note that
4495 breakpoint commands are usually more convenient and flexible than break
4497 purpose of performing side effects when a breakpoint is reached
4498 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4500 Breakpoint conditions can also be evaluated on the target's side if
4501 the target supports it. Instead of evaluating the conditions locally,
4502 @value{GDBN} encodes the expression into an agent expression
4503 (@pxref{Agent Expressions}) suitable for execution on the target,
4504 independently of @value{GDBN}. Global variables become raw memory
4505 locations, locals become stack accesses, and so forth.
4507 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4508 when its condition evaluates to true. This mechanism may provide faster
4509 response times depending on the performance characteristics of the target
4510 since it does not need to keep @value{GDBN} informed about
4511 every breakpoint trigger, even those with false conditions.
4513 Break conditions can be specified when a breakpoint is set, by using
4514 @samp{if} in the arguments to the @code{break} command. @xref{Set
4515 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4516 with the @code{condition} command.
4518 You can also use the @code{if} keyword with the @code{watch} command.
4519 The @code{catch} command does not recognize the @code{if} keyword;
4520 @code{condition} is the only way to impose a further condition on a
4525 @item condition @var{bnum} @var{expression}
4526 Specify @var{expression} as the break condition for breakpoint,
4527 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4528 breakpoint @var{bnum} stops your program only if the value of
4529 @var{expression} is true (nonzero, in C). When you use
4530 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4531 syntactic correctness, and to determine whether symbols in it have
4532 referents in the context of your breakpoint. If @var{expression} uses
4533 symbols not referenced in the context of the breakpoint, @value{GDBN}
4534 prints an error message:
4537 No symbol "foo" in current context.
4542 not actually evaluate @var{expression} at the time the @code{condition}
4543 command (or a command that sets a breakpoint with a condition, like
4544 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4546 @item condition @var{bnum}
4547 Remove the condition from breakpoint number @var{bnum}. It becomes
4548 an ordinary unconditional breakpoint.
4551 @cindex ignore count (of breakpoint)
4552 A special case of a breakpoint condition is to stop only when the
4553 breakpoint has been reached a certain number of times. This is so
4554 useful that there is a special way to do it, using the @dfn{ignore
4555 count} of the breakpoint. Every breakpoint has an ignore count, which
4556 is an integer. Most of the time, the ignore count is zero, and
4557 therefore has no effect. But if your program reaches a breakpoint whose
4558 ignore count is positive, then instead of stopping, it just decrements
4559 the ignore count by one and continues. As a result, if the ignore count
4560 value is @var{n}, the breakpoint does not stop the next @var{n} times
4561 your program reaches it.
4565 @item ignore @var{bnum} @var{count}
4566 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4567 The next @var{count} times the breakpoint is reached, your program's
4568 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4571 To make the breakpoint stop the next time it is reached, specify
4574 When you use @code{continue} to resume execution of your program from a
4575 breakpoint, you can specify an ignore count directly as an argument to
4576 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4577 Stepping,,Continuing and Stepping}.
4579 If a breakpoint has a positive ignore count and a condition, the
4580 condition is not checked. Once the ignore count reaches zero,
4581 @value{GDBN} resumes checking the condition.
4583 You could achieve the effect of the ignore count with a condition such
4584 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4585 is decremented each time. @xref{Convenience Vars, ,Convenience
4589 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4592 @node Break Commands
4593 @subsection Breakpoint Command Lists
4595 @cindex breakpoint commands
4596 You can give any breakpoint (or watchpoint or catchpoint) a series of
4597 commands to execute when your program stops due to that breakpoint. For
4598 example, you might want to print the values of certain expressions, or
4599 enable other breakpoints.
4603 @kindex end@r{ (breakpoint commands)}
4604 @item commands @r{[}@var{range}@dots{}@r{]}
4605 @itemx @dots{} @var{command-list} @dots{}
4607 Specify a list of commands for the given breakpoints. The commands
4608 themselves appear on the following lines. Type a line containing just
4609 @code{end} to terminate the commands.
4611 To remove all commands from a breakpoint, type @code{commands} and
4612 follow it immediately with @code{end}; that is, give no commands.
4614 With no argument, @code{commands} refers to the last breakpoint,
4615 watchpoint, or catchpoint set (not to the breakpoint most recently
4616 encountered). If the most recent breakpoints were set with a single
4617 command, then the @code{commands} will apply to all the breakpoints
4618 set by that command. This applies to breakpoints set by
4619 @code{rbreak}, and also applies when a single @code{break} command
4620 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4624 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4625 disabled within a @var{command-list}.
4627 You can use breakpoint commands to start your program up again. Simply
4628 use the @code{continue} command, or @code{step}, or any other command
4629 that resumes execution.
4631 Any other commands in the command list, after a command that resumes
4632 execution, are ignored. This is because any time you resume execution
4633 (even with a simple @code{next} or @code{step}), you may encounter
4634 another breakpoint---which could have its own command list, leading to
4635 ambiguities about which list to execute.
4638 If the first command you specify in a command list is @code{silent}, the
4639 usual message about stopping at a breakpoint is not printed. This may
4640 be desirable for breakpoints that are to print a specific message and
4641 then continue. If none of the remaining commands print anything, you
4642 see no sign that the breakpoint was reached. @code{silent} is
4643 meaningful only at the beginning of a breakpoint command list.
4645 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4646 print precisely controlled output, and are often useful in silent
4647 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4649 For example, here is how you could use breakpoint commands to print the
4650 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4656 printf "x is %d\n",x
4661 One application for breakpoint commands is to compensate for one bug so
4662 you can test for another. Put a breakpoint just after the erroneous line
4663 of code, give it a condition to detect the case in which something
4664 erroneous has been done, and give it commands to assign correct values
4665 to any variables that need them. End with the @code{continue} command
4666 so that your program does not stop, and start with the @code{silent}
4667 command so that no output is produced. Here is an example:
4678 @node Dynamic Printf
4679 @subsection Dynamic Printf
4681 @cindex dynamic printf
4683 The dynamic printf command @code{dprintf} combines a breakpoint with
4684 formatted printing of your program's data to give you the effect of
4685 inserting @code{printf} calls into your program on-the-fly, without
4686 having to recompile it.
4688 In its most basic form, the output goes to the GDB console. However,
4689 you can set the variable @code{dprintf-style} for alternate handling.
4690 For instance, you can ask to format the output by calling your
4691 program's @code{printf} function. This has the advantage that the
4692 characters go to the program's output device, so they can recorded in
4693 redirects to files and so forth.
4695 If you are doing remote debugging with a stub or agent, you can also
4696 ask to have the printf handled by the remote agent. In addition to
4697 ensuring that the output goes to the remote program's device along
4698 with any other output the program might produce, you can also ask that
4699 the dprintf remain active even after disconnecting from the remote
4700 target. Using the stub/agent is also more efficient, as it can do
4701 everything without needing to communicate with @value{GDBN}.
4705 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4706 Whenever execution reaches @var{location}, print the values of one or
4707 more @var{expressions} under the control of the string @var{template}.
4708 To print several values, separate them with commas.
4710 @item set dprintf-style @var{style}
4711 Set the dprintf output to be handled in one of several different
4712 styles enumerated below. A change of style affects all existing
4713 dynamic printfs immediately. (If you need individual control over the
4714 print commands, simply define normal breakpoints with
4715 explicitly-supplied command lists.)
4718 @kindex dprintf-style gdb
4719 Handle the output using the @value{GDBN} @code{printf} command.
4722 @kindex dprintf-style call
4723 Handle the output by calling a function in your program (normally
4727 @kindex dprintf-style agent
4728 Have the remote debugging agent (such as @code{gdbserver}) handle
4729 the output itself. This style is only available for agents that
4730 support running commands on the target.
4732 @item set dprintf-function @var{function}
4733 Set the function to call if the dprintf style is @code{call}. By
4734 default its value is @code{printf}. You may set it to any expression.
4735 that @value{GDBN} can evaluate to a function, as per the @code{call}
4738 @item set dprintf-channel @var{channel}
4739 Set a ``channel'' for dprintf. If set to a non-empty value,
4740 @value{GDBN} will evaluate it as an expression and pass the result as
4741 a first argument to the @code{dprintf-function}, in the manner of
4742 @code{fprintf} and similar functions. Otherwise, the dprintf format
4743 string will be the first argument, in the manner of @code{printf}.
4745 As an example, if you wanted @code{dprintf} output to go to a logfile
4746 that is a standard I/O stream assigned to the variable @code{mylog},
4747 you could do the following:
4750 (gdb) set dprintf-style call
4751 (gdb) set dprintf-function fprintf
4752 (gdb) set dprintf-channel mylog
4753 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4754 Dprintf 1 at 0x123456: file main.c, line 25.
4756 1 dprintf keep y 0x00123456 in main at main.c:25
4757 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4762 Note that the @code{info break} displays the dynamic printf commands
4763 as normal breakpoint commands; you can thus easily see the effect of
4764 the variable settings.
4766 @item set disconnected-dprintf on
4767 @itemx set disconnected-dprintf off
4768 @kindex set disconnected-dprintf
4769 Choose whether @code{dprintf} commands should continue to run if
4770 @value{GDBN} has disconnected from the target. This only applies
4771 if the @code{dprintf-style} is @code{agent}.
4773 @item show disconnected-dprintf off
4774 @kindex show disconnected-dprintf
4775 Show the current choice for disconnected @code{dprintf}.
4779 @value{GDBN} does not check the validity of function and channel,
4780 relying on you to supply values that are meaningful for the contexts
4781 in which they are being used. For instance, the function and channel
4782 may be the values of local variables, but if that is the case, then
4783 all enabled dynamic prints must be at locations within the scope of
4784 those locals. If evaluation fails, @value{GDBN} will report an error.
4786 @node Save Breakpoints
4787 @subsection How to save breakpoints to a file
4789 To save breakpoint definitions to a file use the @w{@code{save
4790 breakpoints}} command.
4793 @kindex save breakpoints
4794 @cindex save breakpoints to a file for future sessions
4795 @item save breakpoints [@var{filename}]
4796 This command saves all current breakpoint definitions together with
4797 their commands and ignore counts, into a file @file{@var{filename}}
4798 suitable for use in a later debugging session. This includes all
4799 types of breakpoints (breakpoints, watchpoints, catchpoints,
4800 tracepoints). To read the saved breakpoint definitions, use the
4801 @code{source} command (@pxref{Command Files}). Note that watchpoints
4802 with expressions involving local variables may fail to be recreated
4803 because it may not be possible to access the context where the
4804 watchpoint is valid anymore. Because the saved breakpoint definitions
4805 are simply a sequence of @value{GDBN} commands that recreate the
4806 breakpoints, you can edit the file in your favorite editing program,
4807 and remove the breakpoint definitions you're not interested in, or
4808 that can no longer be recreated.
4811 @node Static Probe Points
4812 @subsection Static Probe Points
4814 @cindex static probe point, SystemTap
4815 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4816 for Statically Defined Tracing, and the probes are designed to have a tiny
4817 runtime code and data footprint, and no dynamic relocations. They are
4818 usable from assembly, C and C@t{++} languages. See
4819 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4820 for a good reference on how the @acronym{SDT} probes are implemented.
4822 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4823 @acronym{SDT} probes are supported on ELF-compatible systems. See
4824 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4825 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4826 in your applications.
4828 @cindex semaphores on static probe points
4829 Some probes have an associated semaphore variable; for instance, this
4830 happens automatically if you defined your probe using a DTrace-style
4831 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4832 automatically enable it when you specify a breakpoint using the
4833 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4834 location by some other method (e.g., @code{break file:line}), then
4835 @value{GDBN} will not automatically set the semaphore.
4837 You can examine the available static static probes using @code{info
4838 probes}, with optional arguments:
4842 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4843 If given, @var{provider} is a regular expression used to match against provider
4844 names when selecting which probes to list. If omitted, probes by all
4845 probes from all providers are listed.
4847 If given, @var{name} is a regular expression to match against probe names
4848 when selecting which probes to list. If omitted, probe names are not
4849 considered when deciding whether to display them.
4851 If given, @var{objfile} is a regular expression used to select which
4852 object files (executable or shared libraries) to examine. If not
4853 given, all object files are considered.
4855 @item info probes all
4856 List the available static probes, from all types.
4859 @vindex $_probe_arg@r{, convenience variable}
4860 A probe may specify up to twelve arguments. These are available at the
4861 point at which the probe is defined---that is, when the current PC is
4862 at the probe's location. The arguments are available using the
4863 convenience variables (@pxref{Convenience Vars})
4864 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4865 an integer of the appropriate size; types are not preserved. The
4866 convenience variable @code{$_probe_argc} holds the number of arguments
4867 at the current probe point.
4869 These variables are always available, but attempts to access them at
4870 any location other than a probe point will cause @value{GDBN} to give
4874 @c @ifclear BARETARGET
4875 @node Error in Breakpoints
4876 @subsection ``Cannot insert breakpoints''
4878 If you request too many active hardware-assisted breakpoints and
4879 watchpoints, you will see this error message:
4881 @c FIXME: the precise wording of this message may change; the relevant
4882 @c source change is not committed yet (Sep 3, 1999).
4884 Stopped; cannot insert breakpoints.
4885 You may have requested too many hardware breakpoints and watchpoints.
4889 This message is printed when you attempt to resume the program, since
4890 only then @value{GDBN} knows exactly how many hardware breakpoints and
4891 watchpoints it needs to insert.
4893 When this message is printed, you need to disable or remove some of the
4894 hardware-assisted breakpoints and watchpoints, and then continue.
4896 @node Breakpoint-related Warnings
4897 @subsection ``Breakpoint address adjusted...''
4898 @cindex breakpoint address adjusted
4900 Some processor architectures place constraints on the addresses at
4901 which breakpoints may be placed. For architectures thus constrained,
4902 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4903 with the constraints dictated by the architecture.
4905 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4906 a VLIW architecture in which a number of RISC-like instructions may be
4907 bundled together for parallel execution. The FR-V architecture
4908 constrains the location of a breakpoint instruction within such a
4909 bundle to the instruction with the lowest address. @value{GDBN}
4910 honors this constraint by adjusting a breakpoint's address to the
4911 first in the bundle.
4913 It is not uncommon for optimized code to have bundles which contain
4914 instructions from different source statements, thus it may happen that
4915 a breakpoint's address will be adjusted from one source statement to
4916 another. Since this adjustment may significantly alter @value{GDBN}'s
4917 breakpoint related behavior from what the user expects, a warning is
4918 printed when the breakpoint is first set and also when the breakpoint
4921 A warning like the one below is printed when setting a breakpoint
4922 that's been subject to address adjustment:
4925 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4928 Such warnings are printed both for user settable and @value{GDBN}'s
4929 internal breakpoints. If you see one of these warnings, you should
4930 verify that a breakpoint set at the adjusted address will have the
4931 desired affect. If not, the breakpoint in question may be removed and
4932 other breakpoints may be set which will have the desired behavior.
4933 E.g., it may be sufficient to place the breakpoint at a later
4934 instruction. A conditional breakpoint may also be useful in some
4935 cases to prevent the breakpoint from triggering too often.
4937 @value{GDBN} will also issue a warning when stopping at one of these
4938 adjusted breakpoints:
4941 warning: Breakpoint 1 address previously adjusted from 0x00010414
4945 When this warning is encountered, it may be too late to take remedial
4946 action except in cases where the breakpoint is hit earlier or more
4947 frequently than expected.
4949 @node Continuing and Stepping
4950 @section Continuing and Stepping
4954 @cindex resuming execution
4955 @dfn{Continuing} means resuming program execution until your program
4956 completes normally. In contrast, @dfn{stepping} means executing just
4957 one more ``step'' of your program, where ``step'' may mean either one
4958 line of source code, or one machine instruction (depending on what
4959 particular command you use). Either when continuing or when stepping,
4960 your program may stop even sooner, due to a breakpoint or a signal. (If
4961 it stops due to a signal, you may want to use @code{handle}, or use
4962 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4966 @kindex c @r{(@code{continue})}
4967 @kindex fg @r{(resume foreground execution)}
4968 @item continue @r{[}@var{ignore-count}@r{]}
4969 @itemx c @r{[}@var{ignore-count}@r{]}
4970 @itemx fg @r{[}@var{ignore-count}@r{]}
4971 Resume program execution, at the address where your program last stopped;
4972 any breakpoints set at that address are bypassed. The optional argument
4973 @var{ignore-count} allows you to specify a further number of times to
4974 ignore a breakpoint at this location; its effect is like that of
4975 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4977 The argument @var{ignore-count} is meaningful only when your program
4978 stopped due to a breakpoint. At other times, the argument to
4979 @code{continue} is ignored.
4981 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4982 debugged program is deemed to be the foreground program) are provided
4983 purely for convenience, and have exactly the same behavior as
4987 To resume execution at a different place, you can use @code{return}
4988 (@pxref{Returning, ,Returning from a Function}) to go back to the
4989 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4990 Different Address}) to go to an arbitrary location in your program.
4992 A typical technique for using stepping is to set a breakpoint
4993 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4994 beginning of the function or the section of your program where a problem
4995 is believed to lie, run your program until it stops at that breakpoint,
4996 and then step through the suspect area, examining the variables that are
4997 interesting, until you see the problem happen.
5001 @kindex s @r{(@code{step})}
5003 Continue running your program until control reaches a different source
5004 line, then stop it and return control to @value{GDBN}. This command is
5005 abbreviated @code{s}.
5008 @c "without debugging information" is imprecise; actually "without line
5009 @c numbers in the debugging information". (gcc -g1 has debugging info but
5010 @c not line numbers). But it seems complex to try to make that
5011 @c distinction here.
5012 @emph{Warning:} If you use the @code{step} command while control is
5013 within a function that was compiled without debugging information,
5014 execution proceeds until control reaches a function that does have
5015 debugging information. Likewise, it will not step into a function which
5016 is compiled without debugging information. To step through functions
5017 without debugging information, use the @code{stepi} command, described
5021 The @code{step} command only stops at the first instruction of a source
5022 line. This prevents the multiple stops that could otherwise occur in
5023 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5024 to stop if a function that has debugging information is called within
5025 the line. In other words, @code{step} @emph{steps inside} any functions
5026 called within the line.
5028 Also, the @code{step} command only enters a function if there is line
5029 number information for the function. Otherwise it acts like the
5030 @code{next} command. This avoids problems when using @code{cc -gl}
5031 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5032 was any debugging information about the routine.
5034 @item step @var{count}
5035 Continue running as in @code{step}, but do so @var{count} times. If a
5036 breakpoint is reached, or a signal not related to stepping occurs before
5037 @var{count} steps, stepping stops right away.
5040 @kindex n @r{(@code{next})}
5041 @item next @r{[}@var{count}@r{]}
5042 Continue to the next source line in the current (innermost) stack frame.
5043 This is similar to @code{step}, but function calls that appear within
5044 the line of code are executed without stopping. Execution stops when
5045 control reaches a different line of code at the original stack level
5046 that was executing when you gave the @code{next} command. This command
5047 is abbreviated @code{n}.
5049 An argument @var{count} is a repeat count, as for @code{step}.
5052 @c FIX ME!! Do we delete this, or is there a way it fits in with
5053 @c the following paragraph? --- Vctoria
5055 @c @code{next} within a function that lacks debugging information acts like
5056 @c @code{step}, but any function calls appearing within the code of the
5057 @c function are executed without stopping.
5059 The @code{next} command only stops at the first instruction of a
5060 source line. This prevents multiple stops that could otherwise occur in
5061 @code{switch} statements, @code{for} loops, etc.
5063 @kindex set step-mode
5065 @cindex functions without line info, and stepping
5066 @cindex stepping into functions with no line info
5067 @itemx set step-mode on
5068 The @code{set step-mode on} command causes the @code{step} command to
5069 stop at the first instruction of a function which contains no debug line
5070 information rather than stepping over it.
5072 This is useful in cases where you may be interested in inspecting the
5073 machine instructions of a function which has no symbolic info and do not
5074 want @value{GDBN} to automatically skip over this function.
5076 @item set step-mode off
5077 Causes the @code{step} command to step over any functions which contains no
5078 debug information. This is the default.
5080 @item show step-mode
5081 Show whether @value{GDBN} will stop in or step over functions without
5082 source line debug information.
5085 @kindex fin @r{(@code{finish})}
5087 Continue running until just after function in the selected stack frame
5088 returns. Print the returned value (if any). This command can be
5089 abbreviated as @code{fin}.
5091 Contrast this with the @code{return} command (@pxref{Returning,
5092 ,Returning from a Function}).
5095 @kindex u @r{(@code{until})}
5096 @cindex run until specified location
5099 Continue running until a source line past the current line, in the
5100 current stack frame, is reached. This command is used to avoid single
5101 stepping through a loop more than once. It is like the @code{next}
5102 command, except that when @code{until} encounters a jump, it
5103 automatically continues execution until the program counter is greater
5104 than the address of the jump.
5106 This means that when you reach the end of a loop after single stepping
5107 though it, @code{until} makes your program continue execution until it
5108 exits the loop. In contrast, a @code{next} command at the end of a loop
5109 simply steps back to the beginning of the loop, which forces you to step
5110 through the next iteration.
5112 @code{until} always stops your program if it attempts to exit the current
5115 @code{until} may produce somewhat counterintuitive results if the order
5116 of machine code does not match the order of the source lines. For
5117 example, in the following excerpt from a debugging session, the @code{f}
5118 (@code{frame}) command shows that execution is stopped at line
5119 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5123 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5125 (@value{GDBP}) until
5126 195 for ( ; argc > 0; NEXTARG) @{
5129 This happened because, for execution efficiency, the compiler had
5130 generated code for the loop closure test at the end, rather than the
5131 start, of the loop---even though the test in a C @code{for}-loop is
5132 written before the body of the loop. The @code{until} command appeared
5133 to step back to the beginning of the loop when it advanced to this
5134 expression; however, it has not really gone to an earlier
5135 statement---not in terms of the actual machine code.
5137 @code{until} with no argument works by means of single
5138 instruction stepping, and hence is slower than @code{until} with an
5141 @item until @var{location}
5142 @itemx u @var{location}
5143 Continue running your program until either the specified location is
5144 reached, or the current stack frame returns. @var{location} is any of
5145 the forms described in @ref{Specify Location}.
5146 This form of the command uses temporary breakpoints, and
5147 hence is quicker than @code{until} without an argument. The specified
5148 location is actually reached only if it is in the current frame. This
5149 implies that @code{until} can be used to skip over recursive function
5150 invocations. For instance in the code below, if the current location is
5151 line @code{96}, issuing @code{until 99} will execute the program up to
5152 line @code{99} in the same invocation of factorial, i.e., after the inner
5153 invocations have returned.
5156 94 int factorial (int value)
5158 96 if (value > 1) @{
5159 97 value *= factorial (value - 1);
5166 @kindex advance @var{location}
5167 @item advance @var{location}
5168 Continue running the program up to the given @var{location}. An argument is
5169 required, which should be of one of the forms described in
5170 @ref{Specify Location}.
5171 Execution will also stop upon exit from the current stack
5172 frame. This command is similar to @code{until}, but @code{advance} will
5173 not skip over recursive function calls, and the target location doesn't
5174 have to be in the same frame as the current one.
5178 @kindex si @r{(@code{stepi})}
5180 @itemx stepi @var{arg}
5182 Execute one machine instruction, then stop and return to the debugger.
5184 It is often useful to do @samp{display/i $pc} when stepping by machine
5185 instructions. This makes @value{GDBN} automatically display the next
5186 instruction to be executed, each time your program stops. @xref{Auto
5187 Display,, Automatic Display}.
5189 An argument is a repeat count, as in @code{step}.
5193 @kindex ni @r{(@code{nexti})}
5195 @itemx nexti @var{arg}
5197 Execute one machine instruction, but if it is a function call,
5198 proceed until the function returns.
5200 An argument is a repeat count, as in @code{next}.
5203 @node Skipping Over Functions and Files
5204 @section Skipping Over Functions and Files
5205 @cindex skipping over functions and files
5207 The program you are debugging may contain some functions which are
5208 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5209 skip a function or all functions in a file when stepping.
5211 For example, consider the following C function:
5222 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5223 are not interested in stepping through @code{boring}. If you run @code{step}
5224 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5225 step over both @code{foo} and @code{boring}!
5227 One solution is to @code{step} into @code{boring} and use the @code{finish}
5228 command to immediately exit it. But this can become tedious if @code{boring}
5229 is called from many places.
5231 A more flexible solution is to execute @kbd{skip boring}. This instructs
5232 @value{GDBN} never to step into @code{boring}. Now when you execute
5233 @code{step} at line 103, you'll step over @code{boring} and directly into
5236 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5237 example, @code{skip file boring.c}.
5240 @kindex skip function
5241 @item skip @r{[}@var{linespec}@r{]}
5242 @itemx skip function @r{[}@var{linespec}@r{]}
5243 After running this command, the function named by @var{linespec} or the
5244 function containing the line named by @var{linespec} will be skipped over when
5245 stepping. @xref{Specify Location}.
5247 If you do not specify @var{linespec}, the function you're currently debugging
5250 (If you have a function called @code{file} that you want to skip, use
5251 @kbd{skip function file}.)
5254 @item skip file @r{[}@var{filename}@r{]}
5255 After running this command, any function whose source lives in @var{filename}
5256 will be skipped over when stepping.
5258 If you do not specify @var{filename}, functions whose source lives in the file
5259 you're currently debugging will be skipped.
5262 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5263 These are the commands for managing your list of skips:
5267 @item info skip @r{[}@var{range}@r{]}
5268 Print details about the specified skip(s). If @var{range} is not specified,
5269 print a table with details about all functions and files marked for skipping.
5270 @code{info skip} prints the following information about each skip:
5274 A number identifying this skip.
5276 The type of this skip, either @samp{function} or @samp{file}.
5277 @item Enabled or Disabled
5278 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5280 For function skips, this column indicates the address in memory of the function
5281 being skipped. If you've set a function skip on a function which has not yet
5282 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5283 which has the function is loaded, @code{info skip} will show the function's
5286 For file skips, this field contains the filename being skipped. For functions
5287 skips, this field contains the function name and its line number in the file
5288 where it is defined.
5292 @item skip delete @r{[}@var{range}@r{]}
5293 Delete the specified skip(s). If @var{range} is not specified, delete all
5297 @item skip enable @r{[}@var{range}@r{]}
5298 Enable the specified skip(s). If @var{range} is not specified, enable all
5301 @kindex skip disable
5302 @item skip disable @r{[}@var{range}@r{]}
5303 Disable the specified skip(s). If @var{range} is not specified, disable all
5312 A signal is an asynchronous event that can happen in a program. The
5313 operating system defines the possible kinds of signals, and gives each
5314 kind a name and a number. For example, in Unix @code{SIGINT} is the
5315 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5316 @code{SIGSEGV} is the signal a program gets from referencing a place in
5317 memory far away from all the areas in use; @code{SIGALRM} occurs when
5318 the alarm clock timer goes off (which happens only if your program has
5319 requested an alarm).
5321 @cindex fatal signals
5322 Some signals, including @code{SIGALRM}, are a normal part of the
5323 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5324 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5325 program has not specified in advance some other way to handle the signal.
5326 @code{SIGINT} does not indicate an error in your program, but it is normally
5327 fatal so it can carry out the purpose of the interrupt: to kill the program.
5329 @value{GDBN} has the ability to detect any occurrence of a signal in your
5330 program. You can tell @value{GDBN} in advance what to do for each kind of
5333 @cindex handling signals
5334 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5335 @code{SIGALRM} be silently passed to your program
5336 (so as not to interfere with their role in the program's functioning)
5337 but to stop your program immediately whenever an error signal happens.
5338 You can change these settings with the @code{handle} command.
5341 @kindex info signals
5345 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5346 handle each one. You can use this to see the signal numbers of all
5347 the defined types of signals.
5349 @item info signals @var{sig}
5350 Similar, but print information only about the specified signal number.
5352 @code{info handle} is an alias for @code{info signals}.
5354 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5355 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5356 for details about this command.
5359 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5360 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5361 can be the number of a signal or its name (with or without the
5362 @samp{SIG} at the beginning); a list of signal numbers of the form
5363 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5364 known signals. Optional arguments @var{keywords}, described below,
5365 say what change to make.
5369 The keywords allowed by the @code{handle} command can be abbreviated.
5370 Their full names are:
5374 @value{GDBN} should not stop your program when this signal happens. It may
5375 still print a message telling you that the signal has come in.
5378 @value{GDBN} should stop your program when this signal happens. This implies
5379 the @code{print} keyword as well.
5382 @value{GDBN} should print a message when this signal happens.
5385 @value{GDBN} should not mention the occurrence of the signal at all. This
5386 implies the @code{nostop} keyword as well.
5390 @value{GDBN} should allow your program to see this signal; your program
5391 can handle the signal, or else it may terminate if the signal is fatal
5392 and not handled. @code{pass} and @code{noignore} are synonyms.
5396 @value{GDBN} should not allow your program to see this signal.
5397 @code{nopass} and @code{ignore} are synonyms.
5401 When a signal stops your program, the signal is not visible to the
5403 continue. Your program sees the signal then, if @code{pass} is in
5404 effect for the signal in question @emph{at that time}. In other words,
5405 after @value{GDBN} reports a signal, you can use the @code{handle}
5406 command with @code{pass} or @code{nopass} to control whether your
5407 program sees that signal when you continue.
5409 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5410 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5411 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5414 You can also use the @code{signal} command to prevent your program from
5415 seeing a signal, or cause it to see a signal it normally would not see,
5416 or to give it any signal at any time. For example, if your program stopped
5417 due to some sort of memory reference error, you might store correct
5418 values into the erroneous variables and continue, hoping to see more
5419 execution; but your program would probably terminate immediately as
5420 a result of the fatal signal once it saw the signal. To prevent this,
5421 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5424 @cindex extra signal information
5425 @anchor{extra signal information}
5427 On some targets, @value{GDBN} can inspect extra signal information
5428 associated with the intercepted signal, before it is actually
5429 delivered to the program being debugged. This information is exported
5430 by the convenience variable @code{$_siginfo}, and consists of data
5431 that is passed by the kernel to the signal handler at the time of the
5432 receipt of a signal. The data type of the information itself is
5433 target dependent. You can see the data type using the @code{ptype
5434 $_siginfo} command. On Unix systems, it typically corresponds to the
5435 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5438 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5439 referenced address that raised a segmentation fault.
5443 (@value{GDBP}) continue
5444 Program received signal SIGSEGV, Segmentation fault.
5445 0x0000000000400766 in main ()
5447 (@value{GDBP}) ptype $_siginfo
5454 struct @{...@} _kill;
5455 struct @{...@} _timer;
5457 struct @{...@} _sigchld;
5458 struct @{...@} _sigfault;
5459 struct @{...@} _sigpoll;
5462 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5466 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5467 $1 = (void *) 0x7ffff7ff7000
5471 Depending on target support, @code{$_siginfo} may also be writable.
5474 @section Stopping and Starting Multi-thread Programs
5476 @cindex stopped threads
5477 @cindex threads, stopped
5479 @cindex continuing threads
5480 @cindex threads, continuing
5482 @value{GDBN} supports debugging programs with multiple threads
5483 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5484 are two modes of controlling execution of your program within the
5485 debugger. In the default mode, referred to as @dfn{all-stop mode},
5486 when any thread in your program stops (for example, at a breakpoint
5487 or while being stepped), all other threads in the program are also stopped by
5488 @value{GDBN}. On some targets, @value{GDBN} also supports
5489 @dfn{non-stop mode}, in which other threads can continue to run freely while
5490 you examine the stopped thread in the debugger.
5493 * All-Stop Mode:: All threads stop when GDB takes control
5494 * Non-Stop Mode:: Other threads continue to execute
5495 * Background Execution:: Running your program asynchronously
5496 * Thread-Specific Breakpoints:: Controlling breakpoints
5497 * Interrupted System Calls:: GDB may interfere with system calls
5498 * Observer Mode:: GDB does not alter program behavior
5502 @subsection All-Stop Mode
5504 @cindex all-stop mode
5506 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5507 @emph{all} threads of execution stop, not just the current thread. This
5508 allows you to examine the overall state of the program, including
5509 switching between threads, without worrying that things may change
5512 Conversely, whenever you restart the program, @emph{all} threads start
5513 executing. @emph{This is true even when single-stepping} with commands
5514 like @code{step} or @code{next}.
5516 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5517 Since thread scheduling is up to your debugging target's operating
5518 system (not controlled by @value{GDBN}), other threads may
5519 execute more than one statement while the current thread completes a
5520 single step. Moreover, in general other threads stop in the middle of a
5521 statement, rather than at a clean statement boundary, when the program
5524 You might even find your program stopped in another thread after
5525 continuing or even single-stepping. This happens whenever some other
5526 thread runs into a breakpoint, a signal, or an exception before the
5527 first thread completes whatever you requested.
5529 @cindex automatic thread selection
5530 @cindex switching threads automatically
5531 @cindex threads, automatic switching
5532 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5533 signal, it automatically selects the thread where that breakpoint or
5534 signal happened. @value{GDBN} alerts you to the context switch with a
5535 message such as @samp{[Switching to Thread @var{n}]} to identify the
5538 On some OSes, you can modify @value{GDBN}'s default behavior by
5539 locking the OS scheduler to allow only a single thread to run.
5542 @item set scheduler-locking @var{mode}
5543 @cindex scheduler locking mode
5544 @cindex lock scheduler
5545 Set the scheduler locking mode. If it is @code{off}, then there is no
5546 locking and any thread may run at any time. If @code{on}, then only the
5547 current thread may run when the inferior is resumed. The @code{step}
5548 mode optimizes for single-stepping; it prevents other threads
5549 from preempting the current thread while you are stepping, so that
5550 the focus of debugging does not change unexpectedly.
5551 Other threads only rarely (or never) get a chance to run
5552 when you step. They are more likely to run when you @samp{next} over a
5553 function call, and they are completely free to run when you use commands
5554 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5555 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5556 the current thread away from the thread that you are debugging.
5558 @item show scheduler-locking
5559 Display the current scheduler locking mode.
5562 @cindex resume threads of multiple processes simultaneously
5563 By default, when you issue one of the execution commands such as
5564 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5565 threads of the current inferior to run. For example, if @value{GDBN}
5566 is attached to two inferiors, each with two threads, the
5567 @code{continue} command resumes only the two threads of the current
5568 inferior. This is useful, for example, when you debug a program that
5569 forks and you want to hold the parent stopped (so that, for instance,
5570 it doesn't run to exit), while you debug the child. In other
5571 situations, you may not be interested in inspecting the current state
5572 of any of the processes @value{GDBN} is attached to, and you may want
5573 to resume them all until some breakpoint is hit. In the latter case,
5574 you can instruct @value{GDBN} to allow all threads of all the
5575 inferiors to run with the @w{@code{set schedule-multiple}} command.
5578 @kindex set schedule-multiple
5579 @item set schedule-multiple
5580 Set the mode for allowing threads of multiple processes to be resumed
5581 when an execution command is issued. When @code{on}, all threads of
5582 all processes are allowed to run. When @code{off}, only the threads
5583 of the current process are resumed. The default is @code{off}. The
5584 @code{scheduler-locking} mode takes precedence when set to @code{on},
5585 or while you are stepping and set to @code{step}.
5587 @item show schedule-multiple
5588 Display the current mode for resuming the execution of threads of
5593 @subsection Non-Stop Mode
5595 @cindex non-stop mode
5597 @c This section is really only a place-holder, and needs to be expanded
5598 @c with more details.
5600 For some multi-threaded targets, @value{GDBN} supports an optional
5601 mode of operation in which you can examine stopped program threads in
5602 the debugger while other threads continue to execute freely. This
5603 minimizes intrusion when debugging live systems, such as programs
5604 where some threads have real-time constraints or must continue to
5605 respond to external events. This is referred to as @dfn{non-stop} mode.
5607 In non-stop mode, when a thread stops to report a debugging event,
5608 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5609 threads as well, in contrast to the all-stop mode behavior. Additionally,
5610 execution commands such as @code{continue} and @code{step} apply by default
5611 only to the current thread in non-stop mode, rather than all threads as
5612 in all-stop mode. This allows you to control threads explicitly in
5613 ways that are not possible in all-stop mode --- for example, stepping
5614 one thread while allowing others to run freely, stepping
5615 one thread while holding all others stopped, or stepping several threads
5616 independently and simultaneously.
5618 To enter non-stop mode, use this sequence of commands before you run
5619 or attach to your program:
5622 # Enable the async interface.
5625 # If using the CLI, pagination breaks non-stop.
5628 # Finally, turn it on!
5632 You can use these commands to manipulate the non-stop mode setting:
5635 @kindex set non-stop
5636 @item set non-stop on
5637 Enable selection of non-stop mode.
5638 @item set non-stop off
5639 Disable selection of non-stop mode.
5640 @kindex show non-stop
5642 Show the current non-stop enablement setting.
5645 Note these commands only reflect whether non-stop mode is enabled,
5646 not whether the currently-executing program is being run in non-stop mode.
5647 In particular, the @code{set non-stop} preference is only consulted when
5648 @value{GDBN} starts or connects to the target program, and it is generally
5649 not possible to switch modes once debugging has started. Furthermore,
5650 since not all targets support non-stop mode, even when you have enabled
5651 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5654 In non-stop mode, all execution commands apply only to the current thread
5655 by default. That is, @code{continue} only continues one thread.
5656 To continue all threads, issue @code{continue -a} or @code{c -a}.
5658 You can use @value{GDBN}'s background execution commands
5659 (@pxref{Background Execution}) to run some threads in the background
5660 while you continue to examine or step others from @value{GDBN}.
5661 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5662 always executed asynchronously in non-stop mode.
5664 Suspending execution is done with the @code{interrupt} command when
5665 running in the background, or @kbd{Ctrl-c} during foreground execution.
5666 In all-stop mode, this stops the whole process;
5667 but in non-stop mode the interrupt applies only to the current thread.
5668 To stop the whole program, use @code{interrupt -a}.
5670 Other execution commands do not currently support the @code{-a} option.
5672 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5673 that thread current, as it does in all-stop mode. This is because the
5674 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5675 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5676 changed to a different thread just as you entered a command to operate on the
5677 previously current thread.
5679 @node Background Execution
5680 @subsection Background Execution
5682 @cindex foreground execution
5683 @cindex background execution
5684 @cindex asynchronous execution
5685 @cindex execution, foreground, background and asynchronous
5687 @value{GDBN}'s execution commands have two variants: the normal
5688 foreground (synchronous) behavior, and a background
5689 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5690 the program to report that some thread has stopped before prompting for
5691 another command. In background execution, @value{GDBN} immediately gives
5692 a command prompt so that you can issue other commands while your program runs.
5694 You need to explicitly enable asynchronous mode before you can use
5695 background execution commands. You can use these commands to
5696 manipulate the asynchronous mode setting:
5699 @kindex set target-async
5700 @item set target-async on
5701 Enable asynchronous mode.
5702 @item set target-async off
5703 Disable asynchronous mode.
5704 @kindex show target-async
5705 @item show target-async
5706 Show the current target-async setting.
5709 If the target doesn't support async mode, @value{GDBN} issues an error
5710 message if you attempt to use the background execution commands.
5712 To specify background execution, add a @code{&} to the command. For example,
5713 the background form of the @code{continue} command is @code{continue&}, or
5714 just @code{c&}. The execution commands that accept background execution
5720 @xref{Starting, , Starting your Program}.
5724 @xref{Attach, , Debugging an Already-running Process}.
5728 @xref{Continuing and Stepping, step}.
5732 @xref{Continuing and Stepping, stepi}.
5736 @xref{Continuing and Stepping, next}.
5740 @xref{Continuing and Stepping, nexti}.
5744 @xref{Continuing and Stepping, continue}.
5748 @xref{Continuing and Stepping, finish}.
5752 @xref{Continuing and Stepping, until}.
5756 Background execution is especially useful in conjunction with non-stop
5757 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5758 However, you can also use these commands in the normal all-stop mode with
5759 the restriction that you cannot issue another execution command until the
5760 previous one finishes. Examples of commands that are valid in all-stop
5761 mode while the program is running include @code{help} and @code{info break}.
5763 You can interrupt your program while it is running in the background by
5764 using the @code{interrupt} command.
5771 Suspend execution of the running program. In all-stop mode,
5772 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5773 only the current thread. To stop the whole program in non-stop mode,
5774 use @code{interrupt -a}.
5777 @node Thread-Specific Breakpoints
5778 @subsection Thread-Specific Breakpoints
5780 When your program has multiple threads (@pxref{Threads,, Debugging
5781 Programs with Multiple Threads}), you can choose whether to set
5782 breakpoints on all threads, or on a particular thread.
5785 @cindex breakpoints and threads
5786 @cindex thread breakpoints
5787 @kindex break @dots{} thread @var{threadno}
5788 @item break @var{linespec} thread @var{threadno}
5789 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5790 @var{linespec} specifies source lines; there are several ways of
5791 writing them (@pxref{Specify Location}), but the effect is always to
5792 specify some source line.
5794 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5795 to specify that you only want @value{GDBN} to stop the program when a
5796 particular thread reaches this breakpoint. @var{threadno} is one of the
5797 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5798 column of the @samp{info threads} display.
5800 If you do not specify @samp{thread @var{threadno}} when you set a
5801 breakpoint, the breakpoint applies to @emph{all} threads of your
5804 You can use the @code{thread} qualifier on conditional breakpoints as
5805 well; in this case, place @samp{thread @var{threadno}} before or
5806 after the breakpoint condition, like this:
5809 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5814 @node Interrupted System Calls
5815 @subsection Interrupted System Calls
5817 @cindex thread breakpoints and system calls
5818 @cindex system calls and thread breakpoints
5819 @cindex premature return from system calls
5820 There is an unfortunate side effect when using @value{GDBN} to debug
5821 multi-threaded programs. If one thread stops for a
5822 breakpoint, or for some other reason, and another thread is blocked in a
5823 system call, then the system call may return prematurely. This is a
5824 consequence of the interaction between multiple threads and the signals
5825 that @value{GDBN} uses to implement breakpoints and other events that
5828 To handle this problem, your program should check the return value of
5829 each system call and react appropriately. This is good programming
5832 For example, do not write code like this:
5838 The call to @code{sleep} will return early if a different thread stops
5839 at a breakpoint or for some other reason.
5841 Instead, write this:
5846 unslept = sleep (unslept);
5849 A system call is allowed to return early, so the system is still
5850 conforming to its specification. But @value{GDBN} does cause your
5851 multi-threaded program to behave differently than it would without
5854 Also, @value{GDBN} uses internal breakpoints in the thread library to
5855 monitor certain events such as thread creation and thread destruction.
5856 When such an event happens, a system call in another thread may return
5857 prematurely, even though your program does not appear to stop.
5860 @subsection Observer Mode
5862 If you want to build on non-stop mode and observe program behavior
5863 without any chance of disruption by @value{GDBN}, you can set
5864 variables to disable all of the debugger's attempts to modify state,
5865 whether by writing memory, inserting breakpoints, etc. These operate
5866 at a low level, intercepting operations from all commands.
5868 When all of these are set to @code{off}, then @value{GDBN} is said to
5869 be @dfn{observer mode}. As a convenience, the variable
5870 @code{observer} can be set to disable these, plus enable non-stop
5873 Note that @value{GDBN} will not prevent you from making nonsensical
5874 combinations of these settings. For instance, if you have enabled
5875 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5876 then breakpoints that work by writing trap instructions into the code
5877 stream will still not be able to be placed.
5882 @item set observer on
5883 @itemx set observer off
5884 When set to @code{on}, this disables all the permission variables
5885 below (except for @code{insert-fast-tracepoints}), plus enables
5886 non-stop debugging. Setting this to @code{off} switches back to
5887 normal debugging, though remaining in non-stop mode.
5890 Show whether observer mode is on or off.
5892 @kindex may-write-registers
5893 @item set may-write-registers on
5894 @itemx set may-write-registers off
5895 This controls whether @value{GDBN} will attempt to alter the values of
5896 registers, such as with assignment expressions in @code{print}, or the
5897 @code{jump} command. It defaults to @code{on}.
5899 @item show may-write-registers
5900 Show the current permission to write registers.
5902 @kindex may-write-memory
5903 @item set may-write-memory on
5904 @itemx set may-write-memory off
5905 This controls whether @value{GDBN} will attempt to alter the contents
5906 of memory, such as with assignment expressions in @code{print}. It
5907 defaults to @code{on}.
5909 @item show may-write-memory
5910 Show the current permission to write memory.
5912 @kindex may-insert-breakpoints
5913 @item set may-insert-breakpoints on
5914 @itemx set may-insert-breakpoints off
5915 This controls whether @value{GDBN} will attempt to insert breakpoints.
5916 This affects all breakpoints, including internal breakpoints defined
5917 by @value{GDBN}. It defaults to @code{on}.
5919 @item show may-insert-breakpoints
5920 Show the current permission to insert breakpoints.
5922 @kindex may-insert-tracepoints
5923 @item set may-insert-tracepoints on
5924 @itemx set may-insert-tracepoints off
5925 This controls whether @value{GDBN} will attempt to insert (regular)
5926 tracepoints at the beginning of a tracing experiment. It affects only
5927 non-fast tracepoints, fast tracepoints being under the control of
5928 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5930 @item show may-insert-tracepoints
5931 Show the current permission to insert tracepoints.
5933 @kindex may-insert-fast-tracepoints
5934 @item set may-insert-fast-tracepoints on
5935 @itemx set may-insert-fast-tracepoints off
5936 This controls whether @value{GDBN} will attempt to insert fast
5937 tracepoints at the beginning of a tracing experiment. It affects only
5938 fast tracepoints, regular (non-fast) tracepoints being under the
5939 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5941 @item show may-insert-fast-tracepoints
5942 Show the current permission to insert fast tracepoints.
5944 @kindex may-interrupt
5945 @item set may-interrupt on
5946 @itemx set may-interrupt off
5947 This controls whether @value{GDBN} will attempt to interrupt or stop
5948 program execution. When this variable is @code{off}, the
5949 @code{interrupt} command will have no effect, nor will
5950 @kbd{Ctrl-c}. It defaults to @code{on}.
5952 @item show may-interrupt
5953 Show the current permission to interrupt or stop the program.
5957 @node Reverse Execution
5958 @chapter Running programs backward
5959 @cindex reverse execution
5960 @cindex running programs backward
5962 When you are debugging a program, it is not unusual to realize that
5963 you have gone too far, and some event of interest has already happened.
5964 If the target environment supports it, @value{GDBN} can allow you to
5965 ``rewind'' the program by running it backward.
5967 A target environment that supports reverse execution should be able
5968 to ``undo'' the changes in machine state that have taken place as the
5969 program was executing normally. Variables, registers etc.@: should
5970 revert to their previous values. Obviously this requires a great
5971 deal of sophistication on the part of the target environment; not
5972 all target environments can support reverse execution.
5974 When a program is executed in reverse, the instructions that
5975 have most recently been executed are ``un-executed'', in reverse
5976 order. The program counter runs backward, following the previous
5977 thread of execution in reverse. As each instruction is ``un-executed'',
5978 the values of memory and/or registers that were changed by that
5979 instruction are reverted to their previous states. After executing
5980 a piece of source code in reverse, all side effects of that code
5981 should be ``undone'', and all variables should be returned to their
5982 prior values@footnote{
5983 Note that some side effects are easier to undo than others. For instance,
5984 memory and registers are relatively easy, but device I/O is hard. Some
5985 targets may be able undo things like device I/O, and some may not.
5987 The contract between @value{GDBN} and the reverse executing target
5988 requires only that the target do something reasonable when
5989 @value{GDBN} tells it to execute backwards, and then report the
5990 results back to @value{GDBN}. Whatever the target reports back to
5991 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5992 assumes that the memory and registers that the target reports are in a
5993 consistant state, but @value{GDBN} accepts whatever it is given.
5996 If you are debugging in a target environment that supports
5997 reverse execution, @value{GDBN} provides the following commands.
6000 @kindex reverse-continue
6001 @kindex rc @r{(@code{reverse-continue})}
6002 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6003 @itemx rc @r{[}@var{ignore-count}@r{]}
6004 Beginning at the point where your program last stopped, start executing
6005 in reverse. Reverse execution will stop for breakpoints and synchronous
6006 exceptions (signals), just like normal execution. Behavior of
6007 asynchronous signals depends on the target environment.
6009 @kindex reverse-step
6010 @kindex rs @r{(@code{step})}
6011 @item reverse-step @r{[}@var{count}@r{]}
6012 Run the program backward until control reaches the start of a
6013 different source line; then stop it, and return control to @value{GDBN}.
6015 Like the @code{step} command, @code{reverse-step} will only stop
6016 at the beginning of a source line. It ``un-executes'' the previously
6017 executed source line. If the previous source line included calls to
6018 debuggable functions, @code{reverse-step} will step (backward) into
6019 the called function, stopping at the beginning of the @emph{last}
6020 statement in the called function (typically a return statement).
6022 Also, as with the @code{step} command, if non-debuggable functions are
6023 called, @code{reverse-step} will run thru them backward without stopping.
6025 @kindex reverse-stepi
6026 @kindex rsi @r{(@code{reverse-stepi})}
6027 @item reverse-stepi @r{[}@var{count}@r{]}
6028 Reverse-execute one machine instruction. Note that the instruction
6029 to be reverse-executed is @emph{not} the one pointed to by the program
6030 counter, but the instruction executed prior to that one. For instance,
6031 if the last instruction was a jump, @code{reverse-stepi} will take you
6032 back from the destination of the jump to the jump instruction itself.
6034 @kindex reverse-next
6035 @kindex rn @r{(@code{reverse-next})}
6036 @item reverse-next @r{[}@var{count}@r{]}
6037 Run backward to the beginning of the previous line executed in
6038 the current (innermost) stack frame. If the line contains function
6039 calls, they will be ``un-executed'' without stopping. Starting from
6040 the first line of a function, @code{reverse-next} will take you back
6041 to the caller of that function, @emph{before} the function was called,
6042 just as the normal @code{next} command would take you from the last
6043 line of a function back to its return to its caller
6044 @footnote{Unless the code is too heavily optimized.}.
6046 @kindex reverse-nexti
6047 @kindex rni @r{(@code{reverse-nexti})}
6048 @item reverse-nexti @r{[}@var{count}@r{]}
6049 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6050 in reverse, except that called functions are ``un-executed'' atomically.
6051 That is, if the previously executed instruction was a return from
6052 another function, @code{reverse-nexti} will continue to execute
6053 in reverse until the call to that function (from the current stack
6056 @kindex reverse-finish
6057 @item reverse-finish
6058 Just as the @code{finish} command takes you to the point where the
6059 current function returns, @code{reverse-finish} takes you to the point
6060 where it was called. Instead of ending up at the end of the current
6061 function invocation, you end up at the beginning.
6063 @kindex set exec-direction
6064 @item set exec-direction
6065 Set the direction of target execution.
6066 @item set exec-direction reverse
6067 @cindex execute forward or backward in time
6068 @value{GDBN} will perform all execution commands in reverse, until the
6069 exec-direction mode is changed to ``forward''. Affected commands include
6070 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6071 command cannot be used in reverse mode.
6072 @item set exec-direction forward
6073 @value{GDBN} will perform all execution commands in the normal fashion.
6074 This is the default.
6078 @node Process Record and Replay
6079 @chapter Recording Inferior's Execution and Replaying It
6080 @cindex process record and replay
6081 @cindex recording inferior's execution and replaying it
6083 On some platforms, @value{GDBN} provides a special @dfn{process record
6084 and replay} target that can record a log of the process execution, and
6085 replay it later with both forward and reverse execution commands.
6088 When this target is in use, if the execution log includes the record
6089 for the next instruction, @value{GDBN} will debug in @dfn{replay
6090 mode}. In the replay mode, the inferior does not really execute code
6091 instructions. Instead, all the events that normally happen during
6092 code execution are taken from the execution log. While code is not
6093 really executed in replay mode, the values of registers (including the
6094 program counter register) and the memory of the inferior are still
6095 changed as they normally would. Their contents are taken from the
6099 If the record for the next instruction is not in the execution log,
6100 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6101 inferior executes normally, and @value{GDBN} records the execution log
6104 The process record and replay target supports reverse execution
6105 (@pxref{Reverse Execution}), even if the platform on which the
6106 inferior runs does not. However, the reverse execution is limited in
6107 this case by the range of the instructions recorded in the execution
6108 log. In other words, reverse execution on platforms that don't
6109 support it directly can only be done in the replay mode.
6111 When debugging in the reverse direction, @value{GDBN} will work in
6112 replay mode as long as the execution log includes the record for the
6113 previous instruction; otherwise, it will work in record mode, if the
6114 platform supports reverse execution, or stop if not.
6116 For architecture environments that support process record and replay,
6117 @value{GDBN} provides the following commands:
6120 @kindex target record
6124 This command starts the process record and replay target. The process
6125 record and replay target can only debug a process that is already
6126 running. Therefore, you need first to start the process with the
6127 @kbd{run} or @kbd{start} commands, and then start the recording with
6128 the @kbd{target record} command.
6130 Both @code{record} and @code{rec} are aliases of @code{target record}.
6132 @cindex displaced stepping, and process record and replay
6133 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6134 will be automatically disabled when process record and replay target
6135 is started. That's because the process record and replay target
6136 doesn't support displaced stepping.
6138 @cindex non-stop mode, and process record and replay
6139 @cindex asynchronous execution, and process record and replay
6140 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6141 the asynchronous execution mode (@pxref{Background Execution}), the
6142 process record and replay target cannot be started because it doesn't
6143 support these two modes.
6148 Stop the process record and replay target. When process record and
6149 replay target stops, the entire execution log will be deleted and the
6150 inferior will either be terminated, or will remain in its final state.
6152 When you stop the process record and replay target in record mode (at
6153 the end of the execution log), the inferior will be stopped at the
6154 next instruction that would have been recorded. In other words, if
6155 you record for a while and then stop recording, the inferior process
6156 will be left in the same state as if the recording never happened.
6158 On the other hand, if the process record and replay target is stopped
6159 while in replay mode (that is, not at the end of the execution log,
6160 but at some earlier point), the inferior process will become ``live''
6161 at that earlier state, and it will then be possible to continue the
6162 usual ``live'' debugging of the process from that state.
6164 When the inferior process exits, or @value{GDBN} detaches from it,
6165 process record and replay target will automatically stop itself.
6168 @item record save @var{filename}
6169 Save the execution log to a file @file{@var{filename}}.
6170 Default filename is @file{gdb_record.@var{process_id}}, where
6171 @var{process_id} is the process ID of the inferior.
6173 @kindex record restore
6174 @item record restore @var{filename}
6175 Restore the execution log from a file @file{@var{filename}}.
6176 File must have been created with @code{record save}.
6178 @kindex set record insn-number-max
6179 @item set record insn-number-max @var{limit}
6180 Set the limit of instructions to be recorded. Default value is 200000.
6182 If @var{limit} is a positive number, then @value{GDBN} will start
6183 deleting instructions from the log once the number of the record
6184 instructions becomes greater than @var{limit}. For every new recorded
6185 instruction, @value{GDBN} will delete the earliest recorded
6186 instruction to keep the number of recorded instructions at the limit.
6187 (Since deleting recorded instructions loses information, @value{GDBN}
6188 lets you control what happens when the limit is reached, by means of
6189 the @code{stop-at-limit} option, described below.)
6191 If @var{limit} is zero, @value{GDBN} will never delete recorded
6192 instructions from the execution log. The number of recorded
6193 instructions is unlimited in this case.
6195 @kindex show record insn-number-max
6196 @item show record insn-number-max
6197 Show the limit of instructions to be recorded.
6199 @kindex set record stop-at-limit
6200 @item set record stop-at-limit
6201 Control the behavior when the number of recorded instructions reaches
6202 the limit. If ON (the default), @value{GDBN} will stop when the limit
6203 is reached for the first time and ask you whether you want to stop the
6204 inferior or continue running it and recording the execution log. If
6205 you decide to continue recording, each new recorded instruction will
6206 cause the oldest one to be deleted.
6208 If this option is OFF, @value{GDBN} will automatically delete the
6209 oldest record to make room for each new one, without asking.
6211 @kindex show record stop-at-limit
6212 @item show record stop-at-limit
6213 Show the current setting of @code{stop-at-limit}.
6215 @kindex set record memory-query
6216 @item set record memory-query
6217 Control the behavior when @value{GDBN} is unable to record memory
6218 changes caused by an instruction. If ON, @value{GDBN} will query
6219 whether to stop the inferior in that case.
6221 If this option is OFF (the default), @value{GDBN} will automatically
6222 ignore the effect of such instructions on memory. Later, when
6223 @value{GDBN} replays this execution log, it will mark the log of this
6224 instruction as not accessible, and it will not affect the replay
6227 @kindex show record memory-query
6228 @item show record memory-query
6229 Show the current setting of @code{memory-query}.
6233 Show various statistics about the state of process record and its
6234 in-memory execution log buffer, including:
6238 Whether in record mode or replay mode.
6240 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6242 Highest recorded instruction number.
6244 Current instruction about to be replayed (if in replay mode).
6246 Number of instructions contained in the execution log.
6248 Maximum number of instructions that may be contained in the execution log.
6251 @kindex record delete
6254 When record target runs in replay mode (``in the past''), delete the
6255 subsequent execution log and begin to record a new execution log starting
6256 from the current address. This means you will abandon the previously
6257 recorded ``future'' and begin recording a new ``future''.
6262 @chapter Examining the Stack
6264 When your program has stopped, the first thing you need to know is where it
6265 stopped and how it got there.
6268 Each time your program performs a function call, information about the call
6270 That information includes the location of the call in your program,
6271 the arguments of the call,
6272 and the local variables of the function being called.
6273 The information is saved in a block of data called a @dfn{stack frame}.
6274 The stack frames are allocated in a region of memory called the @dfn{call
6277 When your program stops, the @value{GDBN} commands for examining the
6278 stack allow you to see all of this information.
6280 @cindex selected frame
6281 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6282 @value{GDBN} commands refer implicitly to the selected frame. In
6283 particular, whenever you ask @value{GDBN} for the value of a variable in
6284 your program, the value is found in the selected frame. There are
6285 special @value{GDBN} commands to select whichever frame you are
6286 interested in. @xref{Selection, ,Selecting a Frame}.
6288 When your program stops, @value{GDBN} automatically selects the
6289 currently executing frame and describes it briefly, similar to the
6290 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6293 * Frames:: Stack frames
6294 * Backtrace:: Backtraces
6295 * Selection:: Selecting a frame
6296 * Frame Info:: Information on a frame
6301 @section Stack Frames
6303 @cindex frame, definition
6305 The call stack is divided up into contiguous pieces called @dfn{stack
6306 frames}, or @dfn{frames} for short; each frame is the data associated
6307 with one call to one function. The frame contains the arguments given
6308 to the function, the function's local variables, and the address at
6309 which the function is executing.
6311 @cindex initial frame
6312 @cindex outermost frame
6313 @cindex innermost frame
6314 When your program is started, the stack has only one frame, that of the
6315 function @code{main}. This is called the @dfn{initial} frame or the
6316 @dfn{outermost} frame. Each time a function is called, a new frame is
6317 made. Each time a function returns, the frame for that function invocation
6318 is eliminated. If a function is recursive, there can be many frames for
6319 the same function. The frame for the function in which execution is
6320 actually occurring is called the @dfn{innermost} frame. This is the most
6321 recently created of all the stack frames that still exist.
6323 @cindex frame pointer
6324 Inside your program, stack frames are identified by their addresses. A
6325 stack frame consists of many bytes, each of which has its own address; each
6326 kind of computer has a convention for choosing one byte whose
6327 address serves as the address of the frame. Usually this address is kept
6328 in a register called the @dfn{frame pointer register}
6329 (@pxref{Registers, $fp}) while execution is going on in that frame.
6331 @cindex frame number
6332 @value{GDBN} assigns numbers to all existing stack frames, starting with
6333 zero for the innermost frame, one for the frame that called it,
6334 and so on upward. These numbers do not really exist in your program;
6335 they are assigned by @value{GDBN} to give you a way of designating stack
6336 frames in @value{GDBN} commands.
6338 @c The -fomit-frame-pointer below perennially causes hbox overflow
6339 @c underflow problems.
6340 @cindex frameless execution
6341 Some compilers provide a way to compile functions so that they operate
6342 without stack frames. (For example, the @value{NGCC} option
6344 @samp{-fomit-frame-pointer}
6346 generates functions without a frame.)
6347 This is occasionally done with heavily used library functions to save
6348 the frame setup time. @value{GDBN} has limited facilities for dealing
6349 with these function invocations. If the innermost function invocation
6350 has no stack frame, @value{GDBN} nevertheless regards it as though
6351 it had a separate frame, which is numbered zero as usual, allowing
6352 correct tracing of the function call chain. However, @value{GDBN} has
6353 no provision for frameless functions elsewhere in the stack.
6356 @kindex frame@r{, command}
6357 @cindex current stack frame
6358 @item frame @var{args}
6359 The @code{frame} command allows you to move from one stack frame to another,
6360 and to print the stack frame you select. @var{args} may be either the
6361 address of the frame or the stack frame number. Without an argument,
6362 @code{frame} prints the current stack frame.
6364 @kindex select-frame
6365 @cindex selecting frame silently
6367 The @code{select-frame} command allows you to move from one stack frame
6368 to another without printing the frame. This is the silent version of
6376 @cindex call stack traces
6377 A backtrace is a summary of how your program got where it is. It shows one
6378 line per frame, for many frames, starting with the currently executing
6379 frame (frame zero), followed by its caller (frame one), and on up the
6384 @kindex bt @r{(@code{backtrace})}
6387 Print a backtrace of the entire stack: one line per frame for all
6388 frames in the stack.
6390 You can stop the backtrace at any time by typing the system interrupt
6391 character, normally @kbd{Ctrl-c}.
6393 @item backtrace @var{n}
6395 Similar, but print only the innermost @var{n} frames.
6397 @item backtrace -@var{n}
6399 Similar, but print only the outermost @var{n} frames.
6401 @item backtrace full
6403 @itemx bt full @var{n}
6404 @itemx bt full -@var{n}
6405 Print the values of the local variables also. @var{n} specifies the
6406 number of frames to print, as described above.
6411 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6412 are additional aliases for @code{backtrace}.
6414 @cindex multiple threads, backtrace
6415 In a multi-threaded program, @value{GDBN} by default shows the
6416 backtrace only for the current thread. To display the backtrace for
6417 several or all of the threads, use the command @code{thread apply}
6418 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6419 apply all backtrace}, @value{GDBN} will display the backtrace for all
6420 the threads; this is handy when you debug a core dump of a
6421 multi-threaded program.
6423 Each line in the backtrace shows the frame number and the function name.
6424 The program counter value is also shown---unless you use @code{set
6425 print address off}. The backtrace also shows the source file name and
6426 line number, as well as the arguments to the function. The program
6427 counter value is omitted if it is at the beginning of the code for that
6430 Here is an example of a backtrace. It was made with the command
6431 @samp{bt 3}, so it shows the innermost three frames.
6435 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6437 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6438 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6440 (More stack frames follow...)
6445 The display for frame zero does not begin with a program counter
6446 value, indicating that your program has stopped at the beginning of the
6447 code for line @code{993} of @code{builtin.c}.
6450 The value of parameter @code{data} in frame 1 has been replaced by
6451 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6452 only if it is a scalar (integer, pointer, enumeration, etc). See command
6453 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6454 on how to configure the way function parameter values are printed.
6456 @cindex optimized out, in backtrace
6457 @cindex function call arguments, optimized out
6458 If your program was compiled with optimizations, some compilers will
6459 optimize away arguments passed to functions if those arguments are
6460 never used after the call. Such optimizations generate code that
6461 passes arguments through registers, but doesn't store those arguments
6462 in the stack frame. @value{GDBN} has no way of displaying such
6463 arguments in stack frames other than the innermost one. Here's what
6464 such a backtrace might look like:
6468 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6470 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6471 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6473 (More stack frames follow...)
6478 The values of arguments that were not saved in their stack frames are
6479 shown as @samp{<optimized out>}.
6481 If you need to display the values of such optimized-out arguments,
6482 either deduce that from other variables whose values depend on the one
6483 you are interested in, or recompile without optimizations.
6485 @cindex backtrace beyond @code{main} function
6486 @cindex program entry point
6487 @cindex startup code, and backtrace
6488 Most programs have a standard user entry point---a place where system
6489 libraries and startup code transition into user code. For C this is
6490 @code{main}@footnote{
6491 Note that embedded programs (the so-called ``free-standing''
6492 environment) are not required to have a @code{main} function as the
6493 entry point. They could even have multiple entry points.}.
6494 When @value{GDBN} finds the entry function in a backtrace
6495 it will terminate the backtrace, to avoid tracing into highly
6496 system-specific (and generally uninteresting) code.
6498 If you need to examine the startup code, or limit the number of levels
6499 in a backtrace, you can change this behavior:
6502 @item set backtrace past-main
6503 @itemx set backtrace past-main on
6504 @kindex set backtrace
6505 Backtraces will continue past the user entry point.
6507 @item set backtrace past-main off
6508 Backtraces will stop when they encounter the user entry point. This is the
6511 @item show backtrace past-main
6512 @kindex show backtrace
6513 Display the current user entry point backtrace policy.
6515 @item set backtrace past-entry
6516 @itemx set backtrace past-entry on
6517 Backtraces will continue past the internal entry point of an application.
6518 This entry point is encoded by the linker when the application is built,
6519 and is likely before the user entry point @code{main} (or equivalent) is called.
6521 @item set backtrace past-entry off
6522 Backtraces will stop when they encounter the internal entry point of an
6523 application. This is the default.
6525 @item show backtrace past-entry
6526 Display the current internal entry point backtrace policy.
6528 @item set backtrace limit @var{n}
6529 @itemx set backtrace limit 0
6530 @cindex backtrace limit
6531 Limit the backtrace to @var{n} levels. A value of zero means
6534 @item show backtrace limit
6535 Display the current limit on backtrace levels.
6539 @section Selecting a Frame
6541 Most commands for examining the stack and other data in your program work on
6542 whichever stack frame is selected at the moment. Here are the commands for
6543 selecting a stack frame; all of them finish by printing a brief description
6544 of the stack frame just selected.
6547 @kindex frame@r{, selecting}
6548 @kindex f @r{(@code{frame})}
6551 Select frame number @var{n}. Recall that frame zero is the innermost
6552 (currently executing) frame, frame one is the frame that called the
6553 innermost one, and so on. The highest-numbered frame is the one for
6556 @item frame @var{addr}
6558 Select the frame at address @var{addr}. This is useful mainly if the
6559 chaining of stack frames has been damaged by a bug, making it
6560 impossible for @value{GDBN} to assign numbers properly to all frames. In
6561 addition, this can be useful when your program has multiple stacks and
6562 switches between them.
6564 On the SPARC architecture, @code{frame} needs two addresses to
6565 select an arbitrary frame: a frame pointer and a stack pointer.
6567 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
6568 pointer and a program counter.
6570 On the 29k architecture, it needs three addresses: a register stack
6571 pointer, a program counter, and a memory stack pointer.
6575 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6576 advances toward the outermost frame, to higher frame numbers, to frames
6577 that have existed longer. @var{n} defaults to one.
6580 @kindex do @r{(@code{down})}
6582 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6583 advances toward the innermost frame, to lower frame numbers, to frames
6584 that were created more recently. @var{n} defaults to one. You may
6585 abbreviate @code{down} as @code{do}.
6588 All of these commands end by printing two lines of output describing the
6589 frame. The first line shows the frame number, the function name, the
6590 arguments, and the source file and line number of execution in that
6591 frame. The second line shows the text of that source line.
6599 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6601 10 read_input_file (argv[i]);
6605 After such a printout, the @code{list} command with no arguments
6606 prints ten lines centered on the point of execution in the frame.
6607 You can also edit the program at the point of execution with your favorite
6608 editing program by typing @code{edit}.
6609 @xref{List, ,Printing Source Lines},
6613 @kindex down-silently
6615 @item up-silently @var{n}
6616 @itemx down-silently @var{n}
6617 These two commands are variants of @code{up} and @code{down},
6618 respectively; they differ in that they do their work silently, without
6619 causing display of the new frame. They are intended primarily for use
6620 in @value{GDBN} command scripts, where the output might be unnecessary and
6625 @section Information About a Frame
6627 There are several other commands to print information about the selected
6633 When used without any argument, this command does not change which
6634 frame is selected, but prints a brief description of the currently
6635 selected stack frame. It can be abbreviated @code{f}. With an
6636 argument, this command is used to select a stack frame.
6637 @xref{Selection, ,Selecting a Frame}.
6640 @kindex info f @r{(@code{info frame})}
6643 This command prints a verbose description of the selected stack frame,
6648 the address of the frame
6650 the address of the next frame down (called by this frame)
6652 the address of the next frame up (caller of this frame)
6654 the language in which the source code corresponding to this frame is written
6656 the address of the frame's arguments
6658 the address of the frame's local variables
6660 the program counter saved in it (the address of execution in the caller frame)
6662 which registers were saved in the frame
6665 @noindent The verbose description is useful when
6666 something has gone wrong that has made the stack format fail to fit
6667 the usual conventions.
6669 @item info frame @var{addr}
6670 @itemx info f @var{addr}
6671 Print a verbose description of the frame at address @var{addr}, without
6672 selecting that frame. The selected frame remains unchanged by this
6673 command. This requires the same kind of address (more than one for some
6674 architectures) that you specify in the @code{frame} command.
6675 @xref{Selection, ,Selecting a Frame}.
6679 Print the arguments of the selected frame, each on a separate line.
6683 Print the local variables of the selected frame, each on a separate
6684 line. These are all variables (declared either static or automatic)
6685 accessible at the point of execution of the selected frame.
6691 @chapter Examining Source Files
6693 @value{GDBN} can print parts of your program's source, since the debugging
6694 information recorded in the program tells @value{GDBN} what source files were
6695 used to build it. When your program stops, @value{GDBN} spontaneously prints
6696 the line where it stopped. Likewise, when you select a stack frame
6697 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6698 execution in that frame has stopped. You can print other portions of
6699 source files by explicit command.
6701 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6702 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6703 @value{GDBN} under @sc{gnu} Emacs}.
6706 * List:: Printing source lines
6707 * Specify Location:: How to specify code locations
6708 * Edit:: Editing source files
6709 * Search:: Searching source files
6710 * Source Path:: Specifying source directories
6711 * Machine Code:: Source and machine code
6715 @section Printing Source Lines
6718 @kindex l @r{(@code{list})}
6719 To print lines from a source file, use the @code{list} command
6720 (abbreviated @code{l}). By default, ten lines are printed.
6721 There are several ways to specify what part of the file you want to
6722 print; see @ref{Specify Location}, for the full list.
6724 Here are the forms of the @code{list} command most commonly used:
6727 @item list @var{linenum}
6728 Print lines centered around line number @var{linenum} in the
6729 current source file.
6731 @item list @var{function}
6732 Print lines centered around the beginning of function
6736 Print more lines. If the last lines printed were printed with a
6737 @code{list} command, this prints lines following the last lines
6738 printed; however, if the last line printed was a solitary line printed
6739 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6740 Stack}), this prints lines centered around that line.
6743 Print lines just before the lines last printed.
6746 @cindex @code{list}, how many lines to display
6747 By default, @value{GDBN} prints ten source lines with any of these forms of
6748 the @code{list} command. You can change this using @code{set listsize}:
6751 @kindex set listsize
6752 @item set listsize @var{count}
6753 Make the @code{list} command display @var{count} source lines (unless
6754 the @code{list} argument explicitly specifies some other number).
6755 Setting @var{count} to -1 means there's no limit and 0 means suppress
6756 display of source lines.
6758 @kindex show listsize
6760 Display the number of lines that @code{list} prints.
6763 Repeating a @code{list} command with @key{RET} discards the argument,
6764 so it is equivalent to typing just @code{list}. This is more useful
6765 than listing the same lines again. An exception is made for an
6766 argument of @samp{-}; that argument is preserved in repetition so that
6767 each repetition moves up in the source file.
6769 In general, the @code{list} command expects you to supply zero, one or two
6770 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6771 of writing them (@pxref{Specify Location}), but the effect is always
6772 to specify some source line.
6774 Here is a complete description of the possible arguments for @code{list}:
6777 @item list @var{linespec}
6778 Print lines centered around the line specified by @var{linespec}.
6780 @item list @var{first},@var{last}
6781 Print lines from @var{first} to @var{last}. Both arguments are
6782 linespecs. When a @code{list} command has two linespecs, and the
6783 source file of the second linespec is omitted, this refers to
6784 the same source file as the first linespec.
6786 @item list ,@var{last}
6787 Print lines ending with @var{last}.
6789 @item list @var{first},
6790 Print lines starting with @var{first}.
6793 Print lines just after the lines last printed.
6796 Print lines just before the lines last printed.
6799 As described in the preceding table.
6802 @node Specify Location
6803 @section Specifying a Location
6804 @cindex specifying location
6807 Several @value{GDBN} commands accept arguments that specify a location
6808 of your program's code. Since @value{GDBN} is a source-level
6809 debugger, a location usually specifies some line in the source code;
6810 for that reason, locations are also known as @dfn{linespecs}.
6812 Here are all the different ways of specifying a code location that
6813 @value{GDBN} understands:
6817 Specifies the line number @var{linenum} of the current source file.
6820 @itemx +@var{offset}
6821 Specifies the line @var{offset} lines before or after the @dfn{current
6822 line}. For the @code{list} command, the current line is the last one
6823 printed; for the breakpoint commands, this is the line at which
6824 execution stopped in the currently selected @dfn{stack frame}
6825 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6826 used as the second of the two linespecs in a @code{list} command,
6827 this specifies the line @var{offset} lines up or down from the first
6830 @item @var{filename}:@var{linenum}
6831 Specifies the line @var{linenum} in the source file @var{filename}.
6832 If @var{filename} is a relative file name, then it will match any
6833 source file name with the same trailing components. For example, if
6834 @var{filename} is @samp{gcc/expr.c}, then it will match source file
6835 name of @file{/build/trunk/gcc/expr.c}, but not
6836 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
6838 @item @var{function}
6839 Specifies the line that begins the body of the function @var{function}.
6840 For example, in C, this is the line with the open brace.
6842 @item @var{function}:@var{label}
6843 Specifies the line where @var{label} appears in @var{function}.
6845 @item @var{filename}:@var{function}
6846 Specifies the line that begins the body of the function @var{function}
6847 in the file @var{filename}. You only need the file name with a
6848 function name to avoid ambiguity when there are identically named
6849 functions in different source files.
6852 Specifies the line at which the label named @var{label} appears.
6853 @value{GDBN} searches for the label in the function corresponding to
6854 the currently selected stack frame. If there is no current selected
6855 stack frame (for instance, if the inferior is not running), then
6856 @value{GDBN} will not search for a label.
6858 @item *@var{address}
6859 Specifies the program address @var{address}. For line-oriented
6860 commands, such as @code{list} and @code{edit}, this specifies a source
6861 line that contains @var{address}. For @code{break} and other
6862 breakpoint oriented commands, this can be used to set breakpoints in
6863 parts of your program which do not have debugging information or
6866 Here @var{address} may be any expression valid in the current working
6867 language (@pxref{Languages, working language}) that specifies a code
6868 address. In addition, as a convenience, @value{GDBN} extends the
6869 semantics of expressions used in locations to cover the situations
6870 that frequently happen during debugging. Here are the various forms
6874 @item @var{expression}
6875 Any expression valid in the current working language.
6877 @item @var{funcaddr}
6878 An address of a function or procedure derived from its name. In C,
6879 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6880 simply the function's name @var{function} (and actually a special case
6881 of a valid expression). In Pascal and Modula-2, this is
6882 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6883 (although the Pascal form also works).
6885 This form specifies the address of the function's first instruction,
6886 before the stack frame and arguments have been set up.
6888 @item '@var{filename}'::@var{funcaddr}
6889 Like @var{funcaddr} above, but also specifies the name of the source
6890 file explicitly. This is useful if the name of the function does not
6891 specify the function unambiguously, e.g., if there are several
6892 functions with identical names in different source files.
6895 @cindex breakpoint at static probe point
6896 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
6897 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
6898 applications to embed static probes. @xref{Static Probe Points}, for more
6899 information on finding and using static probes. This form of linespec
6900 specifies the location of such a static probe.
6902 If @var{objfile} is given, only probes coming from that shared library
6903 or executable matching @var{objfile} as a regular expression are considered.
6904 If @var{provider} is given, then only probes from that provider are considered.
6905 If several probes match the spec, @value{GDBN} will insert a breakpoint at
6906 each one of those probes.
6912 @section Editing Source Files
6913 @cindex editing source files
6916 @kindex e @r{(@code{edit})}
6917 To edit the lines in a source file, use the @code{edit} command.
6918 The editing program of your choice
6919 is invoked with the current line set to
6920 the active line in the program.
6921 Alternatively, there are several ways to specify what part of the file you
6922 want to print if you want to see other parts of the program:
6925 @item edit @var{location}
6926 Edit the source file specified by @code{location}. Editing starts at
6927 that @var{location}, e.g., at the specified source line of the
6928 specified file. @xref{Specify Location}, for all the possible forms
6929 of the @var{location} argument; here are the forms of the @code{edit}
6930 command most commonly used:
6933 @item edit @var{number}
6934 Edit the current source file with @var{number} as the active line number.
6936 @item edit @var{function}
6937 Edit the file containing @var{function} at the beginning of its definition.
6942 @subsection Choosing your Editor
6943 You can customize @value{GDBN} to use any editor you want
6945 The only restriction is that your editor (say @code{ex}), recognizes the
6946 following command-line syntax:
6948 ex +@var{number} file
6950 The optional numeric value +@var{number} specifies the number of the line in
6951 the file where to start editing.}.
6952 By default, it is @file{@value{EDITOR}}, but you can change this
6953 by setting the environment variable @code{EDITOR} before using
6954 @value{GDBN}. For example, to configure @value{GDBN} to use the
6955 @code{vi} editor, you could use these commands with the @code{sh} shell:
6961 or in the @code{csh} shell,
6963 setenv EDITOR /usr/bin/vi
6968 @section Searching Source Files
6969 @cindex searching source files
6971 There are two commands for searching through the current source file for a
6976 @kindex forward-search
6977 @kindex fo @r{(@code{forward-search})}
6978 @item forward-search @var{regexp}
6979 @itemx search @var{regexp}
6980 The command @samp{forward-search @var{regexp}} checks each line,
6981 starting with the one following the last line listed, for a match for
6982 @var{regexp}. It lists the line that is found. You can use the
6983 synonym @samp{search @var{regexp}} or abbreviate the command name as
6986 @kindex reverse-search
6987 @item reverse-search @var{regexp}
6988 The command @samp{reverse-search @var{regexp}} checks each line, starting
6989 with the one before the last line listed and going backward, for a match
6990 for @var{regexp}. It lists the line that is found. You can abbreviate
6991 this command as @code{rev}.
6995 @section Specifying Source Directories
6998 @cindex directories for source files
6999 Executable programs sometimes do not record the directories of the source
7000 files from which they were compiled, just the names. Even when they do,
7001 the directories could be moved between the compilation and your debugging
7002 session. @value{GDBN} has a list of directories to search for source files;
7003 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7004 it tries all the directories in the list, in the order they are present
7005 in the list, until it finds a file with the desired name.
7007 For example, suppose an executable references the file
7008 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7009 @file{/mnt/cross}. The file is first looked up literally; if this
7010 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7011 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7012 message is printed. @value{GDBN} does not look up the parts of the
7013 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7014 Likewise, the subdirectories of the source path are not searched: if
7015 the source path is @file{/mnt/cross}, and the binary refers to
7016 @file{foo.c}, @value{GDBN} would not find it under
7017 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7019 Plain file names, relative file names with leading directories, file
7020 names containing dots, etc.@: are all treated as described above; for
7021 instance, if the source path is @file{/mnt/cross}, and the source file
7022 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7023 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7024 that---@file{/mnt/cross/foo.c}.
7026 Note that the executable search path is @emph{not} used to locate the
7029 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7030 any information it has cached about where source files are found and where
7031 each line is in the file.
7035 When you start @value{GDBN}, its source path includes only @samp{cdir}
7036 and @samp{cwd}, in that order.
7037 To add other directories, use the @code{directory} command.
7039 The search path is used to find both program source files and @value{GDBN}
7040 script files (read using the @samp{-command} option and @samp{source} command).
7042 In addition to the source path, @value{GDBN} provides a set of commands
7043 that manage a list of source path substitution rules. A @dfn{substitution
7044 rule} specifies how to rewrite source directories stored in the program's
7045 debug information in case the sources were moved to a different
7046 directory between compilation and debugging. A rule is made of
7047 two strings, the first specifying what needs to be rewritten in
7048 the path, and the second specifying how it should be rewritten.
7049 In @ref{set substitute-path}, we name these two parts @var{from} and
7050 @var{to} respectively. @value{GDBN} does a simple string replacement
7051 of @var{from} with @var{to} at the start of the directory part of the
7052 source file name, and uses that result instead of the original file
7053 name to look up the sources.
7055 Using the previous example, suppose the @file{foo-1.0} tree has been
7056 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7057 @value{GDBN} to replace @file{/usr/src} in all source path names with
7058 @file{/mnt/cross}. The first lookup will then be
7059 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7060 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7061 substitution rule, use the @code{set substitute-path} command
7062 (@pxref{set substitute-path}).
7064 To avoid unexpected substitution results, a rule is applied only if the
7065 @var{from} part of the directory name ends at a directory separator.
7066 For instance, a rule substituting @file{/usr/source} into
7067 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7068 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7069 is applied only at the beginning of the directory name, this rule will
7070 not be applied to @file{/root/usr/source/baz.c} either.
7072 In many cases, you can achieve the same result using the @code{directory}
7073 command. However, @code{set substitute-path} can be more efficient in
7074 the case where the sources are organized in a complex tree with multiple
7075 subdirectories. With the @code{directory} command, you need to add each
7076 subdirectory of your project. If you moved the entire tree while
7077 preserving its internal organization, then @code{set substitute-path}
7078 allows you to direct the debugger to all the sources with one single
7081 @code{set substitute-path} is also more than just a shortcut command.
7082 The source path is only used if the file at the original location no
7083 longer exists. On the other hand, @code{set substitute-path} modifies
7084 the debugger behavior to look at the rewritten location instead. So, if
7085 for any reason a source file that is not relevant to your executable is
7086 located at the original location, a substitution rule is the only
7087 method available to point @value{GDBN} at the new location.
7089 @cindex @samp{--with-relocated-sources}
7090 @cindex default source path substitution
7091 You can configure a default source path substitution rule by
7092 configuring @value{GDBN} with the
7093 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7094 should be the name of a directory under @value{GDBN}'s configured
7095 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7096 directory names in debug information under @var{dir} will be adjusted
7097 automatically if the installed @value{GDBN} is moved to a new
7098 location. This is useful if @value{GDBN}, libraries or executables
7099 with debug information and corresponding source code are being moved
7103 @item directory @var{dirname} @dots{}
7104 @item dir @var{dirname} @dots{}
7105 Add directory @var{dirname} to the front of the source path. Several
7106 directory names may be given to this command, separated by @samp{:}
7107 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7108 part of absolute file names) or
7109 whitespace. You may specify a directory that is already in the source
7110 path; this moves it forward, so @value{GDBN} searches it sooner.
7114 @vindex $cdir@r{, convenience variable}
7115 @vindex $cwd@r{, convenience variable}
7116 @cindex compilation directory
7117 @cindex current directory
7118 @cindex working directory
7119 @cindex directory, current
7120 @cindex directory, compilation
7121 You can use the string @samp{$cdir} to refer to the compilation
7122 directory (if one is recorded), and @samp{$cwd} to refer to the current
7123 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7124 tracks the current working directory as it changes during your @value{GDBN}
7125 session, while the latter is immediately expanded to the current
7126 directory at the time you add an entry to the source path.
7129 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7131 @c RET-repeat for @code{directory} is explicitly disabled, but since
7132 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7134 @item set directories @var{path-list}
7135 @kindex set directories
7136 Set the source path to @var{path-list}.
7137 @samp{$cdir:$cwd} are added if missing.
7139 @item show directories
7140 @kindex show directories
7141 Print the source path: show which directories it contains.
7143 @anchor{set substitute-path}
7144 @item set substitute-path @var{from} @var{to}
7145 @kindex set substitute-path
7146 Define a source path substitution rule, and add it at the end of the
7147 current list of existing substitution rules. If a rule with the same
7148 @var{from} was already defined, then the old rule is also deleted.
7150 For example, if the file @file{/foo/bar/baz.c} was moved to
7151 @file{/mnt/cross/baz.c}, then the command
7154 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7158 will tell @value{GDBN} to replace @samp{/usr/src} with
7159 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7160 @file{baz.c} even though it was moved.
7162 In the case when more than one substitution rule have been defined,
7163 the rules are evaluated one by one in the order where they have been
7164 defined. The first one matching, if any, is selected to perform
7167 For instance, if we had entered the following commands:
7170 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7171 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7175 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7176 @file{/mnt/include/defs.h} by using the first rule. However, it would
7177 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7178 @file{/mnt/src/lib/foo.c}.
7181 @item unset substitute-path [path]
7182 @kindex unset substitute-path
7183 If a path is specified, search the current list of substitution rules
7184 for a rule that would rewrite that path. Delete that rule if found.
7185 A warning is emitted by the debugger if no rule could be found.
7187 If no path is specified, then all substitution rules are deleted.
7189 @item show substitute-path [path]
7190 @kindex show substitute-path
7191 If a path is specified, then print the source path substitution rule
7192 which would rewrite that path, if any.
7194 If no path is specified, then print all existing source path substitution
7199 If your source path is cluttered with directories that are no longer of
7200 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7201 versions of source. You can correct the situation as follows:
7205 Use @code{directory} with no argument to reset the source path to its default value.
7208 Use @code{directory} with suitable arguments to reinstall the
7209 directories you want in the source path. You can add all the
7210 directories in one command.
7214 @section Source and Machine Code
7215 @cindex source line and its code address
7217 You can use the command @code{info line} to map source lines to program
7218 addresses (and vice versa), and the command @code{disassemble} to display
7219 a range of addresses as machine instructions. You can use the command
7220 @code{set disassemble-next-line} to set whether to disassemble next
7221 source line when execution stops. When run under @sc{gnu} Emacs
7222 mode, the @code{info line} command causes the arrow to point to the
7223 line specified. Also, @code{info line} prints addresses in symbolic form as
7228 @item info line @var{linespec}
7229 Print the starting and ending addresses of the compiled code for
7230 source line @var{linespec}. You can specify source lines in any of
7231 the ways documented in @ref{Specify Location}.
7234 For example, we can use @code{info line} to discover the location of
7235 the object code for the first line of function
7236 @code{m4_changequote}:
7238 @c FIXME: I think this example should also show the addresses in
7239 @c symbolic form, as they usually would be displayed.
7241 (@value{GDBP}) info line m4_changequote
7242 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7246 @cindex code address and its source line
7247 We can also inquire (using @code{*@var{addr}} as the form for
7248 @var{linespec}) what source line covers a particular address:
7250 (@value{GDBP}) info line *0x63ff
7251 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7254 @cindex @code{$_} and @code{info line}
7255 @cindex @code{x} command, default address
7256 @kindex x@r{(examine), and} info line
7257 After @code{info line}, the default address for the @code{x} command
7258 is changed to the starting address of the line, so that @samp{x/i} is
7259 sufficient to begin examining the machine code (@pxref{Memory,
7260 ,Examining Memory}). Also, this address is saved as the value of the
7261 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7266 @cindex assembly instructions
7267 @cindex instructions, assembly
7268 @cindex machine instructions
7269 @cindex listing machine instructions
7271 @itemx disassemble /m
7272 @itemx disassemble /r
7273 This specialized command dumps a range of memory as machine
7274 instructions. It can also print mixed source+disassembly by specifying
7275 the @code{/m} modifier and print the raw instructions in hex as well as
7276 in symbolic form by specifying the @code{/r}.
7277 The default memory range is the function surrounding the
7278 program counter of the selected frame. A single argument to this
7279 command is a program counter value; @value{GDBN} dumps the function
7280 surrounding this value. When two arguments are given, they should
7281 be separated by a comma, possibly surrounded by whitespace. The
7282 arguments specify a range of addresses to dump, in one of two forms:
7285 @item @var{start},@var{end}
7286 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7287 @item @var{start},+@var{length}
7288 the addresses from @var{start} (inclusive) to
7289 @code{@var{start}+@var{length}} (exclusive).
7293 When 2 arguments are specified, the name of the function is also
7294 printed (since there could be several functions in the given range).
7296 The argument(s) can be any expression yielding a numeric value, such as
7297 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7299 If the range of memory being disassembled contains current program counter,
7300 the instruction at that location is shown with a @code{=>} marker.
7303 The following example shows the disassembly of a range of addresses of
7304 HP PA-RISC 2.0 code:
7307 (@value{GDBP}) disas 0x32c4, 0x32e4
7308 Dump of assembler code from 0x32c4 to 0x32e4:
7309 0x32c4 <main+204>: addil 0,dp
7310 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7311 0x32cc <main+212>: ldil 0x3000,r31
7312 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7313 0x32d4 <main+220>: ldo 0(r31),rp
7314 0x32d8 <main+224>: addil -0x800,dp
7315 0x32dc <main+228>: ldo 0x588(r1),r26
7316 0x32e0 <main+232>: ldil 0x3000,r31
7317 End of assembler dump.
7320 Here is an example showing mixed source+assembly for Intel x86, when the
7321 program is stopped just after function prologue:
7324 (@value{GDBP}) disas /m main
7325 Dump of assembler code for function main:
7327 0x08048330 <+0>: push %ebp
7328 0x08048331 <+1>: mov %esp,%ebp
7329 0x08048333 <+3>: sub $0x8,%esp
7330 0x08048336 <+6>: and $0xfffffff0,%esp
7331 0x08048339 <+9>: sub $0x10,%esp
7333 6 printf ("Hello.\n");
7334 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7335 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7339 0x08048348 <+24>: mov $0x0,%eax
7340 0x0804834d <+29>: leave
7341 0x0804834e <+30>: ret
7343 End of assembler dump.
7346 Here is another example showing raw instructions in hex for AMD x86-64,
7349 (gdb) disas /r 0x400281,+10
7350 Dump of assembler code from 0x400281 to 0x40028b:
7351 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7352 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7353 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7354 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7355 End of assembler dump.
7358 Some architectures have more than one commonly-used set of instruction
7359 mnemonics or other syntax.
7361 For programs that were dynamically linked and use shared libraries,
7362 instructions that call functions or branch to locations in the shared
7363 libraries might show a seemingly bogus location---it's actually a
7364 location of the relocation table. On some architectures, @value{GDBN}
7365 might be able to resolve these to actual function names.
7368 @kindex set disassembly-flavor
7369 @cindex Intel disassembly flavor
7370 @cindex AT&T disassembly flavor
7371 @item set disassembly-flavor @var{instruction-set}
7372 Select the instruction set to use when disassembling the
7373 program via the @code{disassemble} or @code{x/i} commands.
7375 Currently this command is only defined for the Intel x86 family. You
7376 can set @var{instruction-set} to either @code{intel} or @code{att}.
7377 The default is @code{att}, the AT&T flavor used by default by Unix
7378 assemblers for x86-based targets.
7380 @kindex show disassembly-flavor
7381 @item show disassembly-flavor
7382 Show the current setting of the disassembly flavor.
7386 @kindex set disassemble-next-line
7387 @kindex show disassemble-next-line
7388 @item set disassemble-next-line
7389 @itemx show disassemble-next-line
7390 Control whether or not @value{GDBN} will disassemble the next source
7391 line or instruction when execution stops. If ON, @value{GDBN} will
7392 display disassembly of the next source line when execution of the
7393 program being debugged stops. This is @emph{in addition} to
7394 displaying the source line itself, which @value{GDBN} always does if
7395 possible. If the next source line cannot be displayed for some reason
7396 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7397 info in the debug info), @value{GDBN} will display disassembly of the
7398 next @emph{instruction} instead of showing the next source line. If
7399 AUTO, @value{GDBN} will display disassembly of next instruction only
7400 if the source line cannot be displayed. This setting causes
7401 @value{GDBN} to display some feedback when you step through a function
7402 with no line info or whose source file is unavailable. The default is
7403 OFF, which means never display the disassembly of the next line or
7409 @chapter Examining Data
7411 @cindex printing data
7412 @cindex examining data
7415 The usual way to examine data in your program is with the @code{print}
7416 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7417 evaluates and prints the value of an expression of the language your
7418 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7419 Different Languages}). It may also print the expression using a
7420 Python-based pretty-printer (@pxref{Pretty Printing}).
7423 @item print @var{expr}
7424 @itemx print /@var{f} @var{expr}
7425 @var{expr} is an expression (in the source language). By default the
7426 value of @var{expr} is printed in a format appropriate to its data type;
7427 you can choose a different format by specifying @samp{/@var{f}}, where
7428 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7432 @itemx print /@var{f}
7433 @cindex reprint the last value
7434 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7435 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7436 conveniently inspect the same value in an alternative format.
7439 A more low-level way of examining data is with the @code{x} command.
7440 It examines data in memory at a specified address and prints it in a
7441 specified format. @xref{Memory, ,Examining Memory}.
7443 If you are interested in information about types, or about how the
7444 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7445 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7448 @cindex exploring hierarchical data structures
7450 Another way of examining values of expressions and type information is
7451 through the Python extension command @code{explore} (available only if
7452 the @value{GDBN} build is configured with @code{--with-python}). It
7453 offers an interactive way to start at the highest level (or, the most
7454 abstract level) of the data type of an expression (or, the data type
7455 itself) and explore all the way down to leaf scalar values/fields
7456 embedded in the higher level data types.
7459 @item explore @var{arg}
7460 @var{arg} is either an expression (in the source language), or a type
7461 visible in the current context of the program being debugged.
7464 The working of the @code{explore} command can be illustrated with an
7465 example. If a data type @code{struct ComplexStruct} is defined in your
7475 struct ComplexStruct
7477 struct SimpleStruct *ss_p;
7483 followed by variable declarations as
7486 struct SimpleStruct ss = @{ 10, 1.11 @};
7487 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7491 then, the value of the variable @code{cs} can be explored using the
7492 @code{explore} command as follows.
7496 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7497 the following fields:
7499 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7500 arr = <Enter 1 to explore this field of type `int [10]'>
7502 Enter the field number of choice:
7506 Since the fields of @code{cs} are not scalar values, you are being
7507 prompted to chose the field you want to explore. Let's say you choose
7508 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7509 pointer, you will be asked if it is pointing to a single value. From
7510 the declaration of @code{cs} above, it is indeed pointing to a single
7511 value, hence you enter @code{y}. If you enter @code{n}, then you will
7512 be asked if it were pointing to an array of values, in which case this
7513 field will be explored as if it were an array.
7516 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7517 Continue exploring it as a pointer to a single value [y/n]: y
7518 The value of `*(cs.ss_p)' is a struct/class of type `struct
7519 SimpleStruct' with the following fields:
7521 i = 10 .. (Value of type `int')
7522 d = 1.1100000000000001 .. (Value of type `double')
7524 Press enter to return to parent value:
7528 If the field @code{arr} of @code{cs} was chosen for exploration by
7529 entering @code{1} earlier, then since it is as array, you will be
7530 prompted to enter the index of the element in the array that you want
7534 `cs.arr' is an array of `int'.
7535 Enter the index of the element you want to explore in `cs.arr': 5
7537 `(cs.arr)[5]' is a scalar value of type `int'.
7541 Press enter to return to parent value:
7544 In general, at any stage of exploration, you can go deeper towards the
7545 leaf values by responding to the prompts appropriately, or hit the
7546 return key to return to the enclosing data structure (the @i{higher}
7547 level data structure).
7549 Similar to exploring values, you can use the @code{explore} command to
7550 explore types. Instead of specifying a value (which is typically a
7551 variable name or an expression valid in the current context of the
7552 program being debugged), you specify a type name. If you consider the
7553 same example as above, your can explore the type
7554 @code{struct ComplexStruct} by passing the argument
7555 @code{struct ComplexStruct} to the @code{explore} command.
7558 (gdb) explore struct ComplexStruct
7562 By responding to the prompts appropriately in the subsequent interactive
7563 session, you can explore the type @code{struct ComplexStruct} in a
7564 manner similar to how the value @code{cs} was explored in the above
7567 The @code{explore} command also has two sub-commands,
7568 @code{explore value} and @code{explore type}. The former sub-command is
7569 a way to explicitly specify that value exploration of the argument is
7570 being invoked, while the latter is a way to explicitly specify that type
7571 exploration of the argument is being invoked.
7574 @item explore value @var{expr}
7575 @cindex explore value
7576 This sub-command of @code{explore} explores the value of the
7577 expression @var{expr} (if @var{expr} is an expression valid in the
7578 current context of the program being debugged). The behavior of this
7579 command is identical to that of the behavior of the @code{explore}
7580 command being passed the argument @var{expr}.
7582 @item explore type @var{arg}
7583 @cindex explore type
7584 This sub-command of @code{explore} explores the type of @var{arg} (if
7585 @var{arg} is a type visible in the current context of program being
7586 debugged), or the type of the value/expression @var{arg} (if @var{arg}
7587 is an expression valid in the current context of the program being
7588 debugged). If @var{arg} is a type, then the behavior of this command is
7589 identical to that of the @code{explore} command being passed the
7590 argument @var{arg}. If @var{arg} is an expression, then the behavior of
7591 this command will be identical to that of the @code{explore} command
7592 being passed the type of @var{arg} as the argument.
7596 * Expressions:: Expressions
7597 * Ambiguous Expressions:: Ambiguous Expressions
7598 * Variables:: Program variables
7599 * Arrays:: Artificial arrays
7600 * Output Formats:: Output formats
7601 * Memory:: Examining memory
7602 * Auto Display:: Automatic display
7603 * Print Settings:: Print settings
7604 * Pretty Printing:: Python pretty printing
7605 * Value History:: Value history
7606 * Convenience Vars:: Convenience variables
7607 * Convenience Funs:: Convenience functions
7608 * Registers:: Registers
7609 * Floating Point Hardware:: Floating point hardware
7610 * Vector Unit:: Vector Unit
7611 * OS Information:: Auxiliary data provided by operating system
7612 * Memory Region Attributes:: Memory region attributes
7613 * Dump/Restore Files:: Copy between memory and a file
7614 * Core File Generation:: Cause a program dump its core
7615 * Character Sets:: Debugging programs that use a different
7616 character set than GDB does
7617 * Caching Remote Data:: Data caching for remote targets
7618 * Searching Memory:: Searching memory for a sequence of bytes
7622 @section Expressions
7625 @code{print} and many other @value{GDBN} commands accept an expression and
7626 compute its value. Any kind of constant, variable or operator defined
7627 by the programming language you are using is valid in an expression in
7628 @value{GDBN}. This includes conditional expressions, function calls,
7629 casts, and string constants. It also includes preprocessor macros, if
7630 you compiled your program to include this information; see
7633 @cindex arrays in expressions
7634 @value{GDBN} supports array constants in expressions input by
7635 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7636 you can use the command @code{print @{1, 2, 3@}} to create an array
7637 of three integers. If you pass an array to a function or assign it
7638 to a program variable, @value{GDBN} copies the array to memory that
7639 is @code{malloc}ed in the target program.
7641 Because C is so widespread, most of the expressions shown in examples in
7642 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7643 Languages}, for information on how to use expressions in other
7646 In this section, we discuss operators that you can use in @value{GDBN}
7647 expressions regardless of your programming language.
7649 @cindex casts, in expressions
7650 Casts are supported in all languages, not just in C, because it is so
7651 useful to cast a number into a pointer in order to examine a structure
7652 at that address in memory.
7653 @c FIXME: casts supported---Mod2 true?
7655 @value{GDBN} supports these operators, in addition to those common
7656 to programming languages:
7660 @samp{@@} is a binary operator for treating parts of memory as arrays.
7661 @xref{Arrays, ,Artificial Arrays}, for more information.
7664 @samp{::} allows you to specify a variable in terms of the file or
7665 function where it is defined. @xref{Variables, ,Program Variables}.
7667 @cindex @{@var{type}@}
7668 @cindex type casting memory
7669 @cindex memory, viewing as typed object
7670 @cindex casts, to view memory
7671 @item @{@var{type}@} @var{addr}
7672 Refers to an object of type @var{type} stored at address @var{addr} in
7673 memory. @var{addr} may be any expression whose value is an integer or
7674 pointer (but parentheses are required around binary operators, just as in
7675 a cast). This construct is allowed regardless of what kind of data is
7676 normally supposed to reside at @var{addr}.
7679 @node Ambiguous Expressions
7680 @section Ambiguous Expressions
7681 @cindex ambiguous expressions
7683 Expressions can sometimes contain some ambiguous elements. For instance,
7684 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7685 a single function name to be defined several times, for application in
7686 different contexts. This is called @dfn{overloading}. Another example
7687 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7688 templates and is typically instantiated several times, resulting in
7689 the same function name being defined in different contexts.
7691 In some cases and depending on the language, it is possible to adjust
7692 the expression to remove the ambiguity. For instance in C@t{++}, you
7693 can specify the signature of the function you want to break on, as in
7694 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7695 qualified name of your function often makes the expression unambiguous
7698 When an ambiguity that needs to be resolved is detected, the debugger
7699 has the capability to display a menu of numbered choices for each
7700 possibility, and then waits for the selection with the prompt @samp{>}.
7701 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7702 aborts the current command. If the command in which the expression was
7703 used allows more than one choice to be selected, the next option in the
7704 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7707 For example, the following session excerpt shows an attempt to set a
7708 breakpoint at the overloaded symbol @code{String::after}.
7709 We choose three particular definitions of that function name:
7711 @c FIXME! This is likely to change to show arg type lists, at least
7714 (@value{GDBP}) b String::after
7717 [2] file:String.cc; line number:867
7718 [3] file:String.cc; line number:860
7719 [4] file:String.cc; line number:875
7720 [5] file:String.cc; line number:853
7721 [6] file:String.cc; line number:846
7722 [7] file:String.cc; line number:735
7724 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7725 Breakpoint 2 at 0xb344: file String.cc, line 875.
7726 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7727 Multiple breakpoints were set.
7728 Use the "delete" command to delete unwanted
7735 @kindex set multiple-symbols
7736 @item set multiple-symbols @var{mode}
7737 @cindex multiple-symbols menu
7739 This option allows you to adjust the debugger behavior when an expression
7742 By default, @var{mode} is set to @code{all}. If the command with which
7743 the expression is used allows more than one choice, then @value{GDBN}
7744 automatically selects all possible choices. For instance, inserting
7745 a breakpoint on a function using an ambiguous name results in a breakpoint
7746 inserted on each possible match. However, if a unique choice must be made,
7747 then @value{GDBN} uses the menu to help you disambiguate the expression.
7748 For instance, printing the address of an overloaded function will result
7749 in the use of the menu.
7751 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7752 when an ambiguity is detected.
7754 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7755 an error due to the ambiguity and the command is aborted.
7757 @kindex show multiple-symbols
7758 @item show multiple-symbols
7759 Show the current value of the @code{multiple-symbols} setting.
7763 @section Program Variables
7765 The most common kind of expression to use is the name of a variable
7768 Variables in expressions are understood in the selected stack frame
7769 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7773 global (or file-static)
7780 visible according to the scope rules of the
7781 programming language from the point of execution in that frame
7784 @noindent This means that in the function
7799 you can examine and use the variable @code{a} whenever your program is
7800 executing within the function @code{foo}, but you can only use or
7801 examine the variable @code{b} while your program is executing inside
7802 the block where @code{b} is declared.
7804 @cindex variable name conflict
7805 There is an exception: you can refer to a variable or function whose
7806 scope is a single source file even if the current execution point is not
7807 in this file. But it is possible to have more than one such variable or
7808 function with the same name (in different source files). If that
7809 happens, referring to that name has unpredictable effects. If you wish,
7810 you can specify a static variable in a particular function or file by
7811 using the colon-colon (@code{::}) notation:
7813 @cindex colon-colon, context for variables/functions
7815 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7816 @cindex @code{::}, context for variables/functions
7819 @var{file}::@var{variable}
7820 @var{function}::@var{variable}
7824 Here @var{file} or @var{function} is the name of the context for the
7825 static @var{variable}. In the case of file names, you can use quotes to
7826 make sure @value{GDBN} parses the file name as a single word---for example,
7827 to print a global value of @code{x} defined in @file{f2.c}:
7830 (@value{GDBP}) p 'f2.c'::x
7833 The @code{::} notation is normally used for referring to
7834 static variables, since you typically disambiguate uses of local variables
7835 in functions by selecting the appropriate frame and using the
7836 simple name of the variable. However, you may also use this notation
7837 to refer to local variables in frames enclosing the selected frame:
7846 process (a); /* Stop here */
7857 For example, if there is a breakpoint at the commented line,
7858 here is what you might see
7859 when the program stops after executing the call @code{bar(0)}:
7864 (@value{GDBP}) p bar::a
7867 #2 0x080483d0 in foo (a=5) at foobar.c:12
7870 (@value{GDBP}) p bar::a
7874 @cindex C@t{++} scope resolution
7875 These uses of @samp{::} are very rarely in conflict with the very similar
7876 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7877 scope resolution operator in @value{GDBN} expressions.
7878 @c FIXME: Um, so what happens in one of those rare cases where it's in
7881 @cindex wrong values
7882 @cindex variable values, wrong
7883 @cindex function entry/exit, wrong values of variables
7884 @cindex optimized code, wrong values of variables
7886 @emph{Warning:} Occasionally, a local variable may appear to have the
7887 wrong value at certain points in a function---just after entry to a new
7888 scope, and just before exit.
7890 You may see this problem when you are stepping by machine instructions.
7891 This is because, on most machines, it takes more than one instruction to
7892 set up a stack frame (including local variable definitions); if you are
7893 stepping by machine instructions, variables may appear to have the wrong
7894 values until the stack frame is completely built. On exit, it usually
7895 also takes more than one machine instruction to destroy a stack frame;
7896 after you begin stepping through that group of instructions, local
7897 variable definitions may be gone.
7899 This may also happen when the compiler does significant optimizations.
7900 To be sure of always seeing accurate values, turn off all optimization
7903 @cindex ``No symbol "foo" in current context''
7904 Another possible effect of compiler optimizations is to optimize
7905 unused variables out of existence, or assign variables to registers (as
7906 opposed to memory addresses). Depending on the support for such cases
7907 offered by the debug info format used by the compiler, @value{GDBN}
7908 might not be able to display values for such local variables. If that
7909 happens, @value{GDBN} will print a message like this:
7912 No symbol "foo" in current context.
7915 To solve such problems, either recompile without optimizations, or use a
7916 different debug info format, if the compiler supports several such
7917 formats. @xref{Compilation}, for more information on choosing compiler
7918 options. @xref{C, ,C and C@t{++}}, for more information about debug
7919 info formats that are best suited to C@t{++} programs.
7921 If you ask to print an object whose contents are unknown to
7922 @value{GDBN}, e.g., because its data type is not completely specified
7923 by the debug information, @value{GDBN} will say @samp{<incomplete
7924 type>}. @xref{Symbols, incomplete type}, for more about this.
7926 If you append @kbd{@@entry} string to a function parameter name you get its
7927 value at the time the function got called. If the value is not available an
7928 error message is printed. Entry values are available only with some compilers.
7929 Entry values are normally also printed at the function parameter list according
7930 to @ref{set print entry-values}.
7933 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7939 (gdb) print i@@entry
7943 Strings are identified as arrays of @code{char} values without specified
7944 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7945 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7946 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7947 defines literal string type @code{"char"} as @code{char} without a sign.
7952 signed char var1[] = "A";
7955 You get during debugging
7960 $2 = @{65 'A', 0 '\0'@}
7964 @section Artificial Arrays
7966 @cindex artificial array
7968 @kindex @@@r{, referencing memory as an array}
7969 It is often useful to print out several successive objects of the
7970 same type in memory; a section of an array, or an array of
7971 dynamically determined size for which only a pointer exists in the
7974 You can do this by referring to a contiguous span of memory as an
7975 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7976 operand of @samp{@@} should be the first element of the desired array
7977 and be an individual object. The right operand should be the desired length
7978 of the array. The result is an array value whose elements are all of
7979 the type of the left argument. The first element is actually the left
7980 argument; the second element comes from bytes of memory immediately
7981 following those that hold the first element, and so on. Here is an
7982 example. If a program says
7985 int *array = (int *) malloc (len * sizeof (int));
7989 you can print the contents of @code{array} with
7995 The left operand of @samp{@@} must reside in memory. Array values made
7996 with @samp{@@} in this way behave just like other arrays in terms of
7997 subscripting, and are coerced to pointers when used in expressions.
7998 Artificial arrays most often appear in expressions via the value history
7999 (@pxref{Value History, ,Value History}), after printing one out.
8001 Another way to create an artificial array is to use a cast.
8002 This re-interprets a value as if it were an array.
8003 The value need not be in memory:
8005 (@value{GDBP}) p/x (short[2])0x12345678
8006 $1 = @{0x1234, 0x5678@}
8009 As a convenience, if you leave the array length out (as in
8010 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8011 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8013 (@value{GDBP}) p/x (short[])0x12345678
8014 $2 = @{0x1234, 0x5678@}
8017 Sometimes the artificial array mechanism is not quite enough; in
8018 moderately complex data structures, the elements of interest may not
8019 actually be adjacent---for example, if you are interested in the values
8020 of pointers in an array. One useful work-around in this situation is
8021 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8022 Variables}) as a counter in an expression that prints the first
8023 interesting value, and then repeat that expression via @key{RET}. For
8024 instance, suppose you have an array @code{dtab} of pointers to
8025 structures, and you are interested in the values of a field @code{fv}
8026 in each structure. Here is an example of what you might type:
8036 @node Output Formats
8037 @section Output Formats
8039 @cindex formatted output
8040 @cindex output formats
8041 By default, @value{GDBN} prints a value according to its data type. Sometimes
8042 this is not what you want. For example, you might want to print a number
8043 in hex, or a pointer in decimal. Or you might want to view data in memory
8044 at a certain address as a character string or as an instruction. To do
8045 these things, specify an @dfn{output format} when you print a value.
8047 The simplest use of output formats is to say how to print a value
8048 already computed. This is done by starting the arguments of the
8049 @code{print} command with a slash and a format letter. The format
8050 letters supported are:
8054 Regard the bits of the value as an integer, and print the integer in
8058 Print as integer in signed decimal.
8061 Print as integer in unsigned decimal.
8064 Print as integer in octal.
8067 Print as integer in binary. The letter @samp{t} stands for ``two''.
8068 @footnote{@samp{b} cannot be used because these format letters are also
8069 used with the @code{x} command, where @samp{b} stands for ``byte'';
8070 see @ref{Memory,,Examining Memory}.}
8073 @cindex unknown address, locating
8074 @cindex locate address
8075 Print as an address, both absolute in hexadecimal and as an offset from
8076 the nearest preceding symbol. You can use this format used to discover
8077 where (in what function) an unknown address is located:
8080 (@value{GDBP}) p/a 0x54320
8081 $3 = 0x54320 <_initialize_vx+396>
8085 The command @code{info symbol 0x54320} yields similar results.
8086 @xref{Symbols, info symbol}.
8089 Regard as an integer and print it as a character constant. This
8090 prints both the numerical value and its character representation. The
8091 character representation is replaced with the octal escape @samp{\nnn}
8092 for characters outside the 7-bit @sc{ascii} range.
8094 Without this format, @value{GDBN} displays @code{char},
8095 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8096 constants. Single-byte members of vectors are displayed as integer
8100 Regard the bits of the value as a floating point number and print
8101 using typical floating point syntax.
8104 @cindex printing strings
8105 @cindex printing byte arrays
8106 Regard as a string, if possible. With this format, pointers to single-byte
8107 data are displayed as null-terminated strings and arrays of single-byte data
8108 are displayed as fixed-length strings. Other values are displayed in their
8111 Without this format, @value{GDBN} displays pointers to and arrays of
8112 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8113 strings. Single-byte members of a vector are displayed as an integer
8117 @cindex raw printing
8118 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8119 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8120 Printing}). This typically results in a higher-level display of the
8121 value's contents. The @samp{r} format bypasses any Python
8122 pretty-printer which might exist.
8125 For example, to print the program counter in hex (@pxref{Registers}), type
8132 Note that no space is required before the slash; this is because command
8133 names in @value{GDBN} cannot contain a slash.
8135 To reprint the last value in the value history with a different format,
8136 you can use the @code{print} command with just a format and no
8137 expression. For example, @samp{p/x} reprints the last value in hex.
8140 @section Examining Memory
8142 You can use the command @code{x} (for ``examine'') to examine memory in
8143 any of several formats, independently of your program's data types.
8145 @cindex examining memory
8147 @kindex x @r{(examine memory)}
8148 @item x/@var{nfu} @var{addr}
8151 Use the @code{x} command to examine memory.
8154 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8155 much memory to display and how to format it; @var{addr} is an
8156 expression giving the address where you want to start displaying memory.
8157 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8158 Several commands set convenient defaults for @var{addr}.
8161 @item @var{n}, the repeat count
8162 The repeat count is a decimal integer; the default is 1. It specifies
8163 how much memory (counting by units @var{u}) to display.
8164 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8167 @item @var{f}, the display format
8168 The display format is one of the formats used by @code{print}
8169 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8170 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8171 The default is @samp{x} (hexadecimal) initially. The default changes
8172 each time you use either @code{x} or @code{print}.
8174 @item @var{u}, the unit size
8175 The unit size is any of
8181 Halfwords (two bytes).
8183 Words (four bytes). This is the initial default.
8185 Giant words (eight bytes).
8188 Each time you specify a unit size with @code{x}, that size becomes the
8189 default unit the next time you use @code{x}. For the @samp{i} format,
8190 the unit size is ignored and is normally not written. For the @samp{s} format,
8191 the unit size defaults to @samp{b}, unless it is explicitly given.
8192 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8193 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8194 Note that the results depend on the programming language of the
8195 current compilation unit. If the language is C, the @samp{s}
8196 modifier will use the UTF-16 encoding while @samp{w} will use
8197 UTF-32. The encoding is set by the programming language and cannot
8200 @item @var{addr}, starting display address
8201 @var{addr} is the address where you want @value{GDBN} to begin displaying
8202 memory. The expression need not have a pointer value (though it may);
8203 it is always interpreted as an integer address of a byte of memory.
8204 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8205 @var{addr} is usually just after the last address examined---but several
8206 other commands also set the default address: @code{info breakpoints} (to
8207 the address of the last breakpoint listed), @code{info line} (to the
8208 starting address of a line), and @code{print} (if you use it to display
8209 a value from memory).
8212 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8213 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8214 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8215 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8216 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8218 Since the letters indicating unit sizes are all distinct from the
8219 letters specifying output formats, you do not have to remember whether
8220 unit size or format comes first; either order works. The output
8221 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8222 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8224 Even though the unit size @var{u} is ignored for the formats @samp{s}
8225 and @samp{i}, you might still want to use a count @var{n}; for example,
8226 @samp{3i} specifies that you want to see three machine instructions,
8227 including any operands. For convenience, especially when used with
8228 the @code{display} command, the @samp{i} format also prints branch delay
8229 slot instructions, if any, beyond the count specified, which immediately
8230 follow the last instruction that is within the count. The command
8231 @code{disassemble} gives an alternative way of inspecting machine
8232 instructions; see @ref{Machine Code,,Source and Machine Code}.
8234 All the defaults for the arguments to @code{x} are designed to make it
8235 easy to continue scanning memory with minimal specifications each time
8236 you use @code{x}. For example, after you have inspected three machine
8237 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8238 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8239 the repeat count @var{n} is used again; the other arguments default as
8240 for successive uses of @code{x}.
8242 When examining machine instructions, the instruction at current program
8243 counter is shown with a @code{=>} marker. For example:
8246 (@value{GDBP}) x/5i $pc-6
8247 0x804837f <main+11>: mov %esp,%ebp
8248 0x8048381 <main+13>: push %ecx
8249 0x8048382 <main+14>: sub $0x4,%esp
8250 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8251 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8254 @cindex @code{$_}, @code{$__}, and value history
8255 The addresses and contents printed by the @code{x} command are not saved
8256 in the value history because there is often too much of them and they
8257 would get in the way. Instead, @value{GDBN} makes these values available for
8258 subsequent use in expressions as values of the convenience variables
8259 @code{$_} and @code{$__}. After an @code{x} command, the last address
8260 examined is available for use in expressions in the convenience variable
8261 @code{$_}. The contents of that address, as examined, are available in
8262 the convenience variable @code{$__}.
8264 If the @code{x} command has a repeat count, the address and contents saved
8265 are from the last memory unit printed; this is not the same as the last
8266 address printed if several units were printed on the last line of output.
8268 @cindex remote memory comparison
8269 @cindex verify remote memory image
8270 When you are debugging a program running on a remote target machine
8271 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8272 remote machine's memory against the executable file you downloaded to
8273 the target. The @code{compare-sections} command is provided for such
8277 @kindex compare-sections
8278 @item compare-sections @r{[}@var{section-name}@r{]}
8279 Compare the data of a loadable section @var{section-name} in the
8280 executable file of the program being debugged with the same section in
8281 the remote machine's memory, and report any mismatches. With no
8282 arguments, compares all loadable sections. This command's
8283 availability depends on the target's support for the @code{"qCRC"}
8288 @section Automatic Display
8289 @cindex automatic display
8290 @cindex display of expressions
8292 If you find that you want to print the value of an expression frequently
8293 (to see how it changes), you might want to add it to the @dfn{automatic
8294 display list} so that @value{GDBN} prints its value each time your program stops.
8295 Each expression added to the list is given a number to identify it;
8296 to remove an expression from the list, you specify that number.
8297 The automatic display looks like this:
8301 3: bar[5] = (struct hack *) 0x3804
8305 This display shows item numbers, expressions and their current values. As with
8306 displays you request manually using @code{x} or @code{print}, you can
8307 specify the output format you prefer; in fact, @code{display} decides
8308 whether to use @code{print} or @code{x} depending your format
8309 specification---it uses @code{x} if you specify either the @samp{i}
8310 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8314 @item display @var{expr}
8315 Add the expression @var{expr} to the list of expressions to display
8316 each time your program stops. @xref{Expressions, ,Expressions}.
8318 @code{display} does not repeat if you press @key{RET} again after using it.
8320 @item display/@var{fmt} @var{expr}
8321 For @var{fmt} specifying only a display format and not a size or
8322 count, add the expression @var{expr} to the auto-display list but
8323 arrange to display it each time in the specified format @var{fmt}.
8324 @xref{Output Formats,,Output Formats}.
8326 @item display/@var{fmt} @var{addr}
8327 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8328 number of units, add the expression @var{addr} as a memory address to
8329 be examined each time your program stops. Examining means in effect
8330 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8333 For example, @samp{display/i $pc} can be helpful, to see the machine
8334 instruction about to be executed each time execution stops (@samp{$pc}
8335 is a common name for the program counter; @pxref{Registers, ,Registers}).
8338 @kindex delete display
8340 @item undisplay @var{dnums}@dots{}
8341 @itemx delete display @var{dnums}@dots{}
8342 Remove items from the list of expressions to display. Specify the
8343 numbers of the displays that you want affected with the command
8344 argument @var{dnums}. It can be a single display number, one of the
8345 numbers shown in the first field of the @samp{info display} display;
8346 or it could be a range of display numbers, as in @code{2-4}.
8348 @code{undisplay} does not repeat if you press @key{RET} after using it.
8349 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8351 @kindex disable display
8352 @item disable display @var{dnums}@dots{}
8353 Disable the display of item numbers @var{dnums}. A disabled display
8354 item is not printed automatically, but is not forgotten. It may be
8355 enabled again later. Specify the numbers of the displays that you
8356 want affected with the command argument @var{dnums}. It can be a
8357 single display number, one of the numbers shown in the first field of
8358 the @samp{info display} display; or it could be a range of display
8359 numbers, as in @code{2-4}.
8361 @kindex enable display
8362 @item enable display @var{dnums}@dots{}
8363 Enable display of item numbers @var{dnums}. It becomes effective once
8364 again in auto display of its expression, until you specify otherwise.
8365 Specify the numbers of the displays that you want affected with the
8366 command argument @var{dnums}. It can be a single display number, one
8367 of the numbers shown in the first field of the @samp{info display}
8368 display; or it could be a range of display numbers, as in @code{2-4}.
8371 Display the current values of the expressions on the list, just as is
8372 done when your program stops.
8374 @kindex info display
8376 Print the list of expressions previously set up to display
8377 automatically, each one with its item number, but without showing the
8378 values. This includes disabled expressions, which are marked as such.
8379 It also includes expressions which would not be displayed right now
8380 because they refer to automatic variables not currently available.
8383 @cindex display disabled out of scope
8384 If a display expression refers to local variables, then it does not make
8385 sense outside the lexical context for which it was set up. Such an
8386 expression is disabled when execution enters a context where one of its
8387 variables is not defined. For example, if you give the command
8388 @code{display last_char} while inside a function with an argument
8389 @code{last_char}, @value{GDBN} displays this argument while your program
8390 continues to stop inside that function. When it stops elsewhere---where
8391 there is no variable @code{last_char}---the display is disabled
8392 automatically. The next time your program stops where @code{last_char}
8393 is meaningful, you can enable the display expression once again.
8395 @node Print Settings
8396 @section Print Settings
8398 @cindex format options
8399 @cindex print settings
8400 @value{GDBN} provides the following ways to control how arrays, structures,
8401 and symbols are printed.
8404 These settings are useful for debugging programs in any language:
8408 @item set print address
8409 @itemx set print address on
8410 @cindex print/don't print memory addresses
8411 @value{GDBN} prints memory addresses showing the location of stack
8412 traces, structure values, pointer values, breakpoints, and so forth,
8413 even when it also displays the contents of those addresses. The default
8414 is @code{on}. For example, this is what a stack frame display looks like with
8415 @code{set print address on}:
8420 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8422 530 if (lquote != def_lquote)
8426 @item set print address off
8427 Do not print addresses when displaying their contents. For example,
8428 this is the same stack frame displayed with @code{set print address off}:
8432 (@value{GDBP}) set print addr off
8434 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8435 530 if (lquote != def_lquote)
8439 You can use @samp{set print address off} to eliminate all machine
8440 dependent displays from the @value{GDBN} interface. For example, with
8441 @code{print address off}, you should get the same text for backtraces on
8442 all machines---whether or not they involve pointer arguments.
8445 @item show print address
8446 Show whether or not addresses are to be printed.
8449 When @value{GDBN} prints a symbolic address, it normally prints the
8450 closest earlier symbol plus an offset. If that symbol does not uniquely
8451 identify the address (for example, it is a name whose scope is a single
8452 source file), you may need to clarify. One way to do this is with
8453 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8454 you can set @value{GDBN} to print the source file and line number when
8455 it prints a symbolic address:
8458 @item set print symbol-filename on
8459 @cindex source file and line of a symbol
8460 @cindex symbol, source file and line
8461 Tell @value{GDBN} to print the source file name and line number of a
8462 symbol in the symbolic form of an address.
8464 @item set print symbol-filename off
8465 Do not print source file name and line number of a symbol. This is the
8468 @item show print symbol-filename
8469 Show whether or not @value{GDBN} will print the source file name and
8470 line number of a symbol in the symbolic form of an address.
8473 Another situation where it is helpful to show symbol filenames and line
8474 numbers is when disassembling code; @value{GDBN} shows you the line
8475 number and source file that corresponds to each instruction.
8477 Also, you may wish to see the symbolic form only if the address being
8478 printed is reasonably close to the closest earlier symbol:
8481 @item set print max-symbolic-offset @var{max-offset}
8482 @cindex maximum value for offset of closest symbol
8483 Tell @value{GDBN} to only display the symbolic form of an address if the
8484 offset between the closest earlier symbol and the address is less than
8485 @var{max-offset}. The default is 0, which tells @value{GDBN}
8486 to always print the symbolic form of an address if any symbol precedes it.
8488 @item show print max-symbolic-offset
8489 Ask how large the maximum offset is that @value{GDBN} prints in a
8493 @cindex wild pointer, interpreting
8494 @cindex pointer, finding referent
8495 If you have a pointer and you are not sure where it points, try
8496 @samp{set print symbol-filename on}. Then you can determine the name
8497 and source file location of the variable where it points, using
8498 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8499 For example, here @value{GDBN} shows that a variable @code{ptt} points
8500 at another variable @code{t}, defined in @file{hi2.c}:
8503 (@value{GDBP}) set print symbol-filename on
8504 (@value{GDBP}) p/a ptt
8505 $4 = 0xe008 <t in hi2.c>
8509 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8510 does not show the symbol name and filename of the referent, even with
8511 the appropriate @code{set print} options turned on.
8514 You can also enable @samp{/a}-like formatting all the time using
8515 @samp{set print symbol on}:
8518 @item set print symbol on
8519 Tell @value{GDBN} to print the symbol corresponding to an address, if
8522 @item set print symbol off
8523 Tell @value{GDBN} not to print the symbol corresponding to an
8524 address. In this mode, @value{GDBN} will still print the symbol
8525 corresponding to pointers to functions. This is the default.
8527 @item show print symbol
8528 Show whether @value{GDBN} will display the symbol corresponding to an
8532 Other settings control how different kinds of objects are printed:
8535 @item set print array
8536 @itemx set print array on
8537 @cindex pretty print arrays
8538 Pretty print arrays. This format is more convenient to read,
8539 but uses more space. The default is off.
8541 @item set print array off
8542 Return to compressed format for arrays.
8544 @item show print array
8545 Show whether compressed or pretty format is selected for displaying
8548 @cindex print array indexes
8549 @item set print array-indexes
8550 @itemx set print array-indexes on
8551 Print the index of each element when displaying arrays. May be more
8552 convenient to locate a given element in the array or quickly find the
8553 index of a given element in that printed array. The default is off.
8555 @item set print array-indexes off
8556 Stop printing element indexes when displaying arrays.
8558 @item show print array-indexes
8559 Show whether the index of each element is printed when displaying
8562 @item set print elements @var{number-of-elements}
8563 @cindex number of array elements to print
8564 @cindex limit on number of printed array elements
8565 Set a limit on how many elements of an array @value{GDBN} will print.
8566 If @value{GDBN} is printing a large array, it stops printing after it has
8567 printed the number of elements set by the @code{set print elements} command.
8568 This limit also applies to the display of strings.
8569 When @value{GDBN} starts, this limit is set to 200.
8570 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8572 @item show print elements
8573 Display the number of elements of a large array that @value{GDBN} will print.
8574 If the number is 0, then the printing is unlimited.
8576 @item set print frame-arguments @var{value}
8577 @kindex set print frame-arguments
8578 @cindex printing frame argument values
8579 @cindex print all frame argument values
8580 @cindex print frame argument values for scalars only
8581 @cindex do not print frame argument values
8582 This command allows to control how the values of arguments are printed
8583 when the debugger prints a frame (@pxref{Frames}). The possible
8588 The values of all arguments are printed.
8591 Print the value of an argument only if it is a scalar. The value of more
8592 complex arguments such as arrays, structures, unions, etc, is replaced
8593 by @code{@dots{}}. This is the default. Here is an example where
8594 only scalar arguments are shown:
8597 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8602 None of the argument values are printed. Instead, the value of each argument
8603 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8606 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8611 By default, only scalar arguments are printed. This command can be used
8612 to configure the debugger to print the value of all arguments, regardless
8613 of their type. However, it is often advantageous to not print the value
8614 of more complex parameters. For instance, it reduces the amount of
8615 information printed in each frame, making the backtrace more readable.
8616 Also, it improves performance when displaying Ada frames, because
8617 the computation of large arguments can sometimes be CPU-intensive,
8618 especially in large applications. Setting @code{print frame-arguments}
8619 to @code{scalars} (the default) or @code{none} avoids this computation,
8620 thus speeding up the display of each Ada frame.
8622 @item show print frame-arguments
8623 Show how the value of arguments should be displayed when printing a frame.
8625 @anchor{set print entry-values}
8626 @item set print entry-values @var{value}
8627 @kindex set print entry-values
8628 Set printing of frame argument values at function entry. In some cases
8629 @value{GDBN} can determine the value of function argument which was passed by
8630 the function caller, even if the value was modified inside the called function
8631 and therefore is different. With optimized code, the current value could be
8632 unavailable, but the entry value may still be known.
8634 The default value is @code{default} (see below for its description). Older
8635 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8636 this feature will behave in the @code{default} setting the same way as with the
8639 This functionality is currently supported only by DWARF 2 debugging format and
8640 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8641 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8644 The @var{value} parameter can be one of the following:
8648 Print only actual parameter values, never print values from function entry
8652 #0 different (val=6)
8653 #0 lost (val=<optimized out>)
8655 #0 invalid (val=<optimized out>)
8659 Print only parameter values from function entry point. The actual parameter
8660 values are never printed.
8662 #0 equal (val@@entry=5)
8663 #0 different (val@@entry=5)
8664 #0 lost (val@@entry=5)
8665 #0 born (val@@entry=<optimized out>)
8666 #0 invalid (val@@entry=<optimized out>)
8670 Print only parameter values from function entry point. If value from function
8671 entry point is not known while the actual value is known, print the actual
8672 value for such parameter.
8674 #0 equal (val@@entry=5)
8675 #0 different (val@@entry=5)
8676 #0 lost (val@@entry=5)
8678 #0 invalid (val@@entry=<optimized out>)
8682 Print actual parameter values. If actual parameter value is not known while
8683 value from function entry point is known, print the entry point value for such
8687 #0 different (val=6)
8688 #0 lost (val@@entry=5)
8690 #0 invalid (val=<optimized out>)
8694 Always print both the actual parameter value and its value from function entry
8695 point, even if values of one or both are not available due to compiler
8698 #0 equal (val=5, val@@entry=5)
8699 #0 different (val=6, val@@entry=5)
8700 #0 lost (val=<optimized out>, val@@entry=5)
8701 #0 born (val=10, val@@entry=<optimized out>)
8702 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8706 Print the actual parameter value if it is known and also its value from
8707 function entry point if it is known. If neither is known, print for the actual
8708 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8709 values are known and identical, print the shortened
8710 @code{param=param@@entry=VALUE} notation.
8712 #0 equal (val=val@@entry=5)
8713 #0 different (val=6, val@@entry=5)
8714 #0 lost (val@@entry=5)
8716 #0 invalid (val=<optimized out>)
8720 Always print the actual parameter value. Print also its value from function
8721 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8722 if both values are known and identical, print the shortened
8723 @code{param=param@@entry=VALUE} notation.
8725 #0 equal (val=val@@entry=5)
8726 #0 different (val=6, val@@entry=5)
8727 #0 lost (val=<optimized out>, val@@entry=5)
8729 #0 invalid (val=<optimized out>)
8733 For analysis messages on possible failures of frame argument values at function
8734 entry resolution see @ref{set debug entry-values}.
8736 @item show print entry-values
8737 Show the method being used for printing of frame argument values at function
8740 @item set print repeats
8741 @cindex repeated array elements
8742 Set the threshold for suppressing display of repeated array
8743 elements. When the number of consecutive identical elements of an
8744 array exceeds the threshold, @value{GDBN} prints the string
8745 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8746 identical repetitions, instead of displaying the identical elements
8747 themselves. Setting the threshold to zero will cause all elements to
8748 be individually printed. The default threshold is 10.
8750 @item show print repeats
8751 Display the current threshold for printing repeated identical
8754 @item set print null-stop
8755 @cindex @sc{null} elements in arrays
8756 Cause @value{GDBN} to stop printing the characters of an array when the first
8757 @sc{null} is encountered. This is useful when large arrays actually
8758 contain only short strings.
8761 @item show print null-stop
8762 Show whether @value{GDBN} stops printing an array on the first
8763 @sc{null} character.
8765 @item set print pretty on
8766 @cindex print structures in indented form
8767 @cindex indentation in structure display
8768 Cause @value{GDBN} to print structures in an indented format with one member
8769 per line, like this:
8784 @item set print pretty off
8785 Cause @value{GDBN} to print structures in a compact format, like this:
8789 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8790 meat = 0x54 "Pork"@}
8795 This is the default format.
8797 @item show print pretty
8798 Show which format @value{GDBN} is using to print structures.
8800 @item set print sevenbit-strings on
8801 @cindex eight-bit characters in strings
8802 @cindex octal escapes in strings
8803 Print using only seven-bit characters; if this option is set,
8804 @value{GDBN} displays any eight-bit characters (in strings or
8805 character values) using the notation @code{\}@var{nnn}. This setting is
8806 best if you are working in English (@sc{ascii}) and you use the
8807 high-order bit of characters as a marker or ``meta'' bit.
8809 @item set print sevenbit-strings off
8810 Print full eight-bit characters. This allows the use of more
8811 international character sets, and is the default.
8813 @item show print sevenbit-strings
8814 Show whether or not @value{GDBN} is printing only seven-bit characters.
8816 @item set print union on
8817 @cindex unions in structures, printing
8818 Tell @value{GDBN} to print unions which are contained in structures
8819 and other unions. This is the default setting.
8821 @item set print union off
8822 Tell @value{GDBN} not to print unions which are contained in
8823 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8826 @item show print union
8827 Ask @value{GDBN} whether or not it will print unions which are contained in
8828 structures and other unions.
8830 For example, given the declarations
8833 typedef enum @{Tree, Bug@} Species;
8834 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8835 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8846 struct thing foo = @{Tree, @{Acorn@}@};
8850 with @code{set print union on} in effect @samp{p foo} would print
8853 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8857 and with @code{set print union off} in effect it would print
8860 $1 = @{it = Tree, form = @{...@}@}
8864 @code{set print union} affects programs written in C-like languages
8870 These settings are of interest when debugging C@t{++} programs:
8873 @cindex demangling C@t{++} names
8874 @item set print demangle
8875 @itemx set print demangle on
8876 Print C@t{++} names in their source form rather than in the encoded
8877 (``mangled'') form passed to the assembler and linker for type-safe
8878 linkage. The default is on.
8880 @item show print demangle
8881 Show whether C@t{++} names are printed in mangled or demangled form.
8883 @item set print asm-demangle
8884 @itemx set print asm-demangle on
8885 Print C@t{++} names in their source form rather than their mangled form, even
8886 in assembler code printouts such as instruction disassemblies.
8889 @item show print asm-demangle
8890 Show whether C@t{++} names in assembly listings are printed in mangled
8893 @cindex C@t{++} symbol decoding style
8894 @cindex symbol decoding style, C@t{++}
8895 @kindex set demangle-style
8896 @item set demangle-style @var{style}
8897 Choose among several encoding schemes used by different compilers to
8898 represent C@t{++} names. The choices for @var{style} are currently:
8902 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8903 This is the default.
8906 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8909 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8912 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8915 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8916 @strong{Warning:} this setting alone is not sufficient to allow
8917 debugging @code{cfront}-generated executables. @value{GDBN} would
8918 require further enhancement to permit that.
8921 If you omit @var{style}, you will see a list of possible formats.
8923 @item show demangle-style
8924 Display the encoding style currently in use for decoding C@t{++} symbols.
8926 @item set print object
8927 @itemx set print object on
8928 @cindex derived type of an object, printing
8929 @cindex display derived types
8930 When displaying a pointer to an object, identify the @emph{actual}
8931 (derived) type of the object rather than the @emph{declared} type, using
8932 the virtual function table. Note that the virtual function table is
8933 required---this feature can only work for objects that have run-time
8934 type identification; a single virtual method in the object's declared
8935 type is sufficient. Note that this setting is also taken into account when
8936 working with variable objects via MI (@pxref{GDB/MI}).
8938 @item set print object off
8939 Display only the declared type of objects, without reference to the
8940 virtual function table. This is the default setting.
8942 @item show print object
8943 Show whether actual, or declared, object types are displayed.
8945 @item set print static-members
8946 @itemx set print static-members on
8947 @cindex static members of C@t{++} objects
8948 Print static members when displaying a C@t{++} object. The default is on.
8950 @item set print static-members off
8951 Do not print static members when displaying a C@t{++} object.
8953 @item show print static-members
8954 Show whether C@t{++} static members are printed or not.
8956 @item set print pascal_static-members
8957 @itemx set print pascal_static-members on
8958 @cindex static members of Pascal objects
8959 @cindex Pascal objects, static members display
8960 Print static members when displaying a Pascal object. The default is on.
8962 @item set print pascal_static-members off
8963 Do not print static members when displaying a Pascal object.
8965 @item show print pascal_static-members
8966 Show whether Pascal static members are printed or not.
8968 @c These don't work with HP ANSI C++ yet.
8969 @item set print vtbl
8970 @itemx set print vtbl on
8971 @cindex pretty print C@t{++} virtual function tables
8972 @cindex virtual functions (C@t{++}) display
8973 @cindex VTBL display
8974 Pretty print C@t{++} virtual function tables. The default is off.
8975 (The @code{vtbl} commands do not work on programs compiled with the HP
8976 ANSI C@t{++} compiler (@code{aCC}).)
8978 @item set print vtbl off
8979 Do not pretty print C@t{++} virtual function tables.
8981 @item show print vtbl
8982 Show whether C@t{++} virtual function tables are pretty printed, or not.
8985 @node Pretty Printing
8986 @section Pretty Printing
8988 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8989 Python code. It greatly simplifies the display of complex objects. This
8990 mechanism works for both MI and the CLI.
8993 * Pretty-Printer Introduction:: Introduction to pretty-printers
8994 * Pretty-Printer Example:: An example pretty-printer
8995 * Pretty-Printer Commands:: Pretty-printer commands
8998 @node Pretty-Printer Introduction
8999 @subsection Pretty-Printer Introduction
9001 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9002 registered for the value. If there is then @value{GDBN} invokes the
9003 pretty-printer to print the value. Otherwise the value is printed normally.
9005 Pretty-printers are normally named. This makes them easy to manage.
9006 The @samp{info pretty-printer} command will list all the installed
9007 pretty-printers with their names.
9008 If a pretty-printer can handle multiple data types, then its
9009 @dfn{subprinters} are the printers for the individual data types.
9010 Each such subprinter has its own name.
9011 The format of the name is @var{printer-name};@var{subprinter-name}.
9013 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9014 Typically they are automatically loaded and registered when the corresponding
9015 debug information is loaded, thus making them available without having to
9016 do anything special.
9018 There are three places where a pretty-printer can be registered.
9022 Pretty-printers registered globally are available when debugging
9026 Pretty-printers registered with a program space are available only
9027 when debugging that program.
9028 @xref{Progspaces In Python}, for more details on program spaces in Python.
9031 Pretty-printers registered with an objfile are loaded and unloaded
9032 with the corresponding objfile (e.g., shared library).
9033 @xref{Objfiles In Python}, for more details on objfiles in Python.
9036 @xref{Selecting Pretty-Printers}, for further information on how
9037 pretty-printers are selected,
9039 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9042 @node Pretty-Printer Example
9043 @subsection Pretty-Printer Example
9045 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9048 (@value{GDBP}) print s
9050 static npos = 4294967295,
9052 <std::allocator<char>> = @{
9053 <__gnu_cxx::new_allocator<char>> = @{
9054 <No data fields>@}, <No data fields>
9056 members of std::basic_string<char, std::char_traits<char>,
9057 std::allocator<char> >::_Alloc_hider:
9058 _M_p = 0x804a014 "abcd"
9063 With a pretty-printer for @code{std::string} only the contents are printed:
9066 (@value{GDBP}) print s
9070 @node Pretty-Printer Commands
9071 @subsection Pretty-Printer Commands
9072 @cindex pretty-printer commands
9075 @kindex info pretty-printer
9076 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9077 Print the list of installed pretty-printers.
9078 This includes disabled pretty-printers, which are marked as such.
9080 @var{object-regexp} is a regular expression matching the objects
9081 whose pretty-printers to list.
9082 Objects can be @code{global}, the program space's file
9083 (@pxref{Progspaces In Python}),
9084 and the object files within that program space (@pxref{Objfiles In Python}).
9085 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9086 looks up a printer from these three objects.
9088 @var{name-regexp} is a regular expression matching the name of the printers
9091 @kindex disable pretty-printer
9092 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9093 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9094 A disabled pretty-printer is not forgotten, it may be enabled again later.
9096 @kindex enable pretty-printer
9097 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9098 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9103 Suppose we have three pretty-printers installed: one from library1.so
9104 named @code{foo} that prints objects of type @code{foo}, and
9105 another from library2.so named @code{bar} that prints two types of objects,
9106 @code{bar1} and @code{bar2}.
9109 (gdb) info pretty-printer
9116 (gdb) info pretty-printer library2
9121 (gdb) disable pretty-printer library1
9123 2 of 3 printers enabled
9124 (gdb) info pretty-printer
9131 (gdb) disable pretty-printer library2 bar:bar1
9133 1 of 3 printers enabled
9134 (gdb) info pretty-printer library2
9141 (gdb) disable pretty-printer library2 bar
9143 0 of 3 printers enabled
9144 (gdb) info pretty-printer library2
9153 Note that for @code{bar} the entire printer can be disabled,
9154 as can each individual subprinter.
9157 @section Value History
9159 @cindex value history
9160 @cindex history of values printed by @value{GDBN}
9161 Values printed by the @code{print} command are saved in the @value{GDBN}
9162 @dfn{value history}. This allows you to refer to them in other expressions.
9163 Values are kept until the symbol table is re-read or discarded
9164 (for example with the @code{file} or @code{symbol-file} commands).
9165 When the symbol table changes, the value history is discarded,
9166 since the values may contain pointers back to the types defined in the
9171 @cindex history number
9172 The values printed are given @dfn{history numbers} by which you can
9173 refer to them. These are successive integers starting with one.
9174 @code{print} shows you the history number assigned to a value by
9175 printing @samp{$@var{num} = } before the value; here @var{num} is the
9178 To refer to any previous value, use @samp{$} followed by the value's
9179 history number. The way @code{print} labels its output is designed to
9180 remind you of this. Just @code{$} refers to the most recent value in
9181 the history, and @code{$$} refers to the value before that.
9182 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9183 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9184 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9186 For example, suppose you have just printed a pointer to a structure and
9187 want to see the contents of the structure. It suffices to type
9193 If you have a chain of structures where the component @code{next} points
9194 to the next one, you can print the contents of the next one with this:
9201 You can print successive links in the chain by repeating this
9202 command---which you can do by just typing @key{RET}.
9204 Note that the history records values, not expressions. If the value of
9205 @code{x} is 4 and you type these commands:
9213 then the value recorded in the value history by the @code{print} command
9214 remains 4 even though the value of @code{x} has changed.
9219 Print the last ten values in the value history, with their item numbers.
9220 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9221 values} does not change the history.
9223 @item show values @var{n}
9224 Print ten history values centered on history item number @var{n}.
9227 Print ten history values just after the values last printed. If no more
9228 values are available, @code{show values +} produces no display.
9231 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9232 same effect as @samp{show values +}.
9234 @node Convenience Vars
9235 @section Convenience Variables
9237 @cindex convenience variables
9238 @cindex user-defined variables
9239 @value{GDBN} provides @dfn{convenience variables} that you can use within
9240 @value{GDBN} to hold on to a value and refer to it later. These variables
9241 exist entirely within @value{GDBN}; they are not part of your program, and
9242 setting a convenience variable has no direct effect on further execution
9243 of your program. That is why you can use them freely.
9245 Convenience variables are prefixed with @samp{$}. Any name preceded by
9246 @samp{$} can be used for a convenience variable, unless it is one of
9247 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9248 (Value history references, in contrast, are @emph{numbers} preceded
9249 by @samp{$}. @xref{Value History, ,Value History}.)
9251 You can save a value in a convenience variable with an assignment
9252 expression, just as you would set a variable in your program.
9256 set $foo = *object_ptr
9260 would save in @code{$foo} the value contained in the object pointed to by
9263 Using a convenience variable for the first time creates it, but its
9264 value is @code{void} until you assign a new value. You can alter the
9265 value with another assignment at any time.
9267 Convenience variables have no fixed types. You can assign a convenience
9268 variable any type of value, including structures and arrays, even if
9269 that variable already has a value of a different type. The convenience
9270 variable, when used as an expression, has the type of its current value.
9273 @kindex show convenience
9274 @cindex show all user variables and functions
9275 @item show convenience
9276 Print a list of convenience variables used so far, and their values,
9277 as well as a list of the convenience functions.
9278 Abbreviated @code{show conv}.
9280 @kindex init-if-undefined
9281 @cindex convenience variables, initializing
9282 @item init-if-undefined $@var{variable} = @var{expression}
9283 Set a convenience variable if it has not already been set. This is useful
9284 for user-defined commands that keep some state. It is similar, in concept,
9285 to using local static variables with initializers in C (except that
9286 convenience variables are global). It can also be used to allow users to
9287 override default values used in a command script.
9289 If the variable is already defined then the expression is not evaluated so
9290 any side-effects do not occur.
9293 One of the ways to use a convenience variable is as a counter to be
9294 incremented or a pointer to be advanced. For example, to print
9295 a field from successive elements of an array of structures:
9299 print bar[$i++]->contents
9303 Repeat that command by typing @key{RET}.
9305 Some convenience variables are created automatically by @value{GDBN} and given
9306 values likely to be useful.
9309 @vindex $_@r{, convenience variable}
9311 The variable @code{$_} is automatically set by the @code{x} command to
9312 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9313 commands which provide a default address for @code{x} to examine also
9314 set @code{$_} to that address; these commands include @code{info line}
9315 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9316 except when set by the @code{x} command, in which case it is a pointer
9317 to the type of @code{$__}.
9319 @vindex $__@r{, convenience variable}
9321 The variable @code{$__} is automatically set by the @code{x} command
9322 to the value found in the last address examined. Its type is chosen
9323 to match the format in which the data was printed.
9326 @vindex $_exitcode@r{, convenience variable}
9327 The variable @code{$_exitcode} is automatically set to the exit code when
9328 the program being debugged terminates.
9331 @itemx $_probe_arg0@dots{}$_probe_arg11
9332 Arguments to a static probe. @xref{Static Probe Points}.
9335 @vindex $_sdata@r{, inspect, convenience variable}
9336 The variable @code{$_sdata} contains extra collected static tracepoint
9337 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9338 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9339 if extra static tracepoint data has not been collected.
9342 @vindex $_siginfo@r{, convenience variable}
9343 The variable @code{$_siginfo} contains extra signal information
9344 (@pxref{extra signal information}). Note that @code{$_siginfo}
9345 could be empty, if the application has not yet received any signals.
9346 For example, it will be empty before you execute the @code{run} command.
9349 @vindex $_tlb@r{, convenience variable}
9350 The variable @code{$_tlb} is automatically set when debugging
9351 applications running on MS-Windows in native mode or connected to
9352 gdbserver that supports the @code{qGetTIBAddr} request.
9353 @xref{General Query Packets}.
9354 This variable contains the address of the thread information block.
9358 On HP-UX systems, if you refer to a function or variable name that
9359 begins with a dollar sign, @value{GDBN} searches for a user or system
9360 name first, before it searches for a convenience variable.
9362 @node Convenience Funs
9363 @section Convenience Functions
9365 @cindex convenience functions
9366 @value{GDBN} also supplies some @dfn{convenience functions}. These
9367 have a syntax similar to convenience variables. A convenience
9368 function can be used in an expression just like an ordinary function;
9369 however, a convenience function is implemented internally to
9372 These functions require @value{GDBN} to be configured with
9373 @code{Python} support.
9377 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
9378 @findex $_memeq@r{, convenience function}
9379 Returns one if the @var{length} bytes at the addresses given by
9380 @var{buf1} and @var{buf2} are equal.
9381 Otherwise it returns zero.
9383 @item $_regex(@var{str}, @var{regex})
9384 @findex $_regex@r{, convenience function}
9385 Returns one if the string @var{str} matches the regular expression
9386 @var{regex}. Otherwise it returns zero.
9387 The syntax of the regular expression is that specified by @code{Python}'s
9388 regular expression support.
9390 @item $_streq(@var{str1}, @var{str2})
9391 @findex $_streq@r{, convenience function}
9392 Returns one if the strings @var{str1} and @var{str2} are equal.
9393 Otherwise it returns zero.
9395 @item $_strlen(@var{str})
9396 @findex $_strlen@r{, convenience function}
9397 Returns the length of string @var{str}.
9401 @value{GDBN} provides the ability to list and get help on
9402 convenience functions.
9406 @kindex help function
9407 @cindex show all convenience functions
9408 Print a list of all convenience functions.
9415 You can refer to machine register contents, in expressions, as variables
9416 with names starting with @samp{$}. The names of registers are different
9417 for each machine; use @code{info registers} to see the names used on
9421 @kindex info registers
9422 @item info registers
9423 Print the names and values of all registers except floating-point
9424 and vector registers (in the selected stack frame).
9426 @kindex info all-registers
9427 @cindex floating point registers
9428 @item info all-registers
9429 Print the names and values of all registers, including floating-point
9430 and vector registers (in the selected stack frame).
9432 @item info registers @var{regname} @dots{}
9433 Print the @dfn{relativized} value of each specified register @var{regname}.
9434 As discussed in detail below, register values are normally relative to
9435 the selected stack frame. @var{regname} may be any register name valid on
9436 the machine you are using, with or without the initial @samp{$}.
9439 @cindex stack pointer register
9440 @cindex program counter register
9441 @cindex process status register
9442 @cindex frame pointer register
9443 @cindex standard registers
9444 @value{GDBN} has four ``standard'' register names that are available (in
9445 expressions) on most machines---whenever they do not conflict with an
9446 architecture's canonical mnemonics for registers. The register names
9447 @code{$pc} and @code{$sp} are used for the program counter register and
9448 the stack pointer. @code{$fp} is used for a register that contains a
9449 pointer to the current stack frame, and @code{$ps} is used for a
9450 register that contains the processor status. For example,
9451 you could print the program counter in hex with
9458 or print the instruction to be executed next with
9465 or add four to the stack pointer@footnote{This is a way of removing
9466 one word from the stack, on machines where stacks grow downward in
9467 memory (most machines, nowadays). This assumes that the innermost
9468 stack frame is selected; setting @code{$sp} is not allowed when other
9469 stack frames are selected. To pop entire frames off the stack,
9470 regardless of machine architecture, use @code{return};
9471 see @ref{Returning, ,Returning from a Function}.} with
9477 Whenever possible, these four standard register names are available on
9478 your machine even though the machine has different canonical mnemonics,
9479 so long as there is no conflict. The @code{info registers} command
9480 shows the canonical names. For example, on the SPARC, @code{info
9481 registers} displays the processor status register as @code{$psr} but you
9482 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9483 is an alias for the @sc{eflags} register.
9485 @value{GDBN} always considers the contents of an ordinary register as an
9486 integer when the register is examined in this way. Some machines have
9487 special registers which can hold nothing but floating point; these
9488 registers are considered to have floating point values. There is no way
9489 to refer to the contents of an ordinary register as floating point value
9490 (although you can @emph{print} it as a floating point value with
9491 @samp{print/f $@var{regname}}).
9493 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9494 means that the data format in which the register contents are saved by
9495 the operating system is not the same one that your program normally
9496 sees. For example, the registers of the 68881 floating point
9497 coprocessor are always saved in ``extended'' (raw) format, but all C
9498 programs expect to work with ``double'' (virtual) format. In such
9499 cases, @value{GDBN} normally works with the virtual format only (the format
9500 that makes sense for your program), but the @code{info registers} command
9501 prints the data in both formats.
9503 @cindex SSE registers (x86)
9504 @cindex MMX registers (x86)
9505 Some machines have special registers whose contents can be interpreted
9506 in several different ways. For example, modern x86-based machines
9507 have SSE and MMX registers that can hold several values packed
9508 together in several different formats. @value{GDBN} refers to such
9509 registers in @code{struct} notation:
9512 (@value{GDBP}) print $xmm1
9514 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
9515 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
9516 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
9517 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
9518 v4_int32 = @{0, 20657912, 11, 13@},
9519 v2_int64 = @{88725056443645952, 55834574859@},
9520 uint128 = 0x0000000d0000000b013b36f800000000
9525 To set values of such registers, you need to tell @value{GDBN} which
9526 view of the register you wish to change, as if you were assigning
9527 value to a @code{struct} member:
9530 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
9533 Normally, register values are relative to the selected stack frame
9534 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
9535 value that the register would contain if all stack frames farther in
9536 were exited and their saved registers restored. In order to see the
9537 true contents of hardware registers, you must select the innermost
9538 frame (with @samp{frame 0}).
9540 However, @value{GDBN} must deduce where registers are saved, from the machine
9541 code generated by your compiler. If some registers are not saved, or if
9542 @value{GDBN} is unable to locate the saved registers, the selected stack
9543 frame makes no difference.
9545 @node Floating Point Hardware
9546 @section Floating Point Hardware
9547 @cindex floating point
9549 Depending on the configuration, @value{GDBN} may be able to give
9550 you more information about the status of the floating point hardware.
9555 Display hardware-dependent information about the floating
9556 point unit. The exact contents and layout vary depending on the
9557 floating point chip. Currently, @samp{info float} is supported on
9558 the ARM and x86 machines.
9562 @section Vector Unit
9565 Depending on the configuration, @value{GDBN} may be able to give you
9566 more information about the status of the vector unit.
9571 Display information about the vector unit. The exact contents and
9572 layout vary depending on the hardware.
9575 @node OS Information
9576 @section Operating System Auxiliary Information
9577 @cindex OS information
9579 @value{GDBN} provides interfaces to useful OS facilities that can help
9580 you debug your program.
9582 @cindex auxiliary vector
9583 @cindex vector, auxiliary
9584 Some operating systems supply an @dfn{auxiliary vector} to programs at
9585 startup. This is akin to the arguments and environment that you
9586 specify for a program, but contains a system-dependent variety of
9587 binary values that tell system libraries important details about the
9588 hardware, operating system, and process. Each value's purpose is
9589 identified by an integer tag; the meanings are well-known but system-specific.
9590 Depending on the configuration and operating system facilities,
9591 @value{GDBN} may be able to show you this information. For remote
9592 targets, this functionality may further depend on the remote stub's
9593 support of the @samp{qXfer:auxv:read} packet, see
9594 @ref{qXfer auxiliary vector read}.
9599 Display the auxiliary vector of the inferior, which can be either a
9600 live process or a core dump file. @value{GDBN} prints each tag value
9601 numerically, and also shows names and text descriptions for recognized
9602 tags. Some values in the vector are numbers, some bit masks, and some
9603 pointers to strings or other data. @value{GDBN} displays each value in the
9604 most appropriate form for a recognized tag, and in hexadecimal for
9605 an unrecognized tag.
9608 On some targets, @value{GDBN} can access operating system-specific
9609 information and show it to you. The types of information available
9610 will differ depending on the type of operating system running on the
9611 target. The mechanism used to fetch the data is described in
9612 @ref{Operating System Information}. For remote targets, this
9613 functionality depends on the remote stub's support of the
9614 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9618 @item info os @var{infotype}
9620 Display OS information of the requested type.
9622 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
9624 @anchor{linux info os infotypes}
9626 @kindex info os processes
9628 Display the list of processes on the target. For each process,
9629 @value{GDBN} prints the process identifier, the name of the user, the
9630 command corresponding to the process, and the list of processor cores
9631 that the process is currently running on. (To understand what these
9632 properties mean, for this and the following info types, please consult
9633 the general @sc{gnu}/Linux documentation.)
9635 @kindex info os procgroups
9637 Display the list of process groups on the target. For each process,
9638 @value{GDBN} prints the identifier of the process group that it belongs
9639 to, the command corresponding to the process group leader, the process
9640 identifier, and the command line of the process. The list is sorted
9641 first by the process group identifier, then by the process identifier,
9642 so that processes belonging to the same process group are grouped together
9643 and the process group leader is listed first.
9645 @kindex info os threads
9647 Display the list of threads running on the target. For each thread,
9648 @value{GDBN} prints the identifier of the process that the thread
9649 belongs to, the command of the process, the thread identifier, and the
9650 processor core that it is currently running on. The main thread of a
9651 process is not listed.
9653 @kindex info os files
9655 Display the list of open file descriptors on the target. For each
9656 file descriptor, @value{GDBN} prints the identifier of the process
9657 owning the descriptor, the command of the owning process, the value
9658 of the descriptor, and the target of the descriptor.
9660 @kindex info os sockets
9662 Display the list of Internet-domain sockets on the target. For each
9663 socket, @value{GDBN} prints the address and port of the local and
9664 remote endpoints, the current state of the connection, the creator of
9665 the socket, the IP address family of the socket, and the type of the
9670 Display the list of all System V shared-memory regions on the target.
9671 For each shared-memory region, @value{GDBN} prints the region key,
9672 the shared-memory identifier, the access permissions, the size of the
9673 region, the process that created the region, the process that last
9674 attached to or detached from the region, the current number of live
9675 attaches to the region, and the times at which the region was last
9676 attached to, detach from, and changed.
9678 @kindex info os semaphores
9680 Display the list of all System V semaphore sets on the target. For each
9681 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
9682 set identifier, the access permissions, the number of semaphores in the
9683 set, the user and group of the owner and creator of the semaphore set,
9684 and the times at which the semaphore set was operated upon and changed.
9688 Display the list of all System V message queues on the target. For each
9689 message queue, @value{GDBN} prints the message queue key, the message
9690 queue identifier, the access permissions, the current number of bytes
9691 on the queue, the current number of messages on the queue, the processes
9692 that last sent and received a message on the queue, the user and group
9693 of the owner and creator of the message queue, the times at which a
9694 message was last sent and received on the queue, and the time at which
9695 the message queue was last changed.
9697 @kindex info os modules
9699 Display the list of all loaded kernel modules on the target. For each
9700 module, @value{GDBN} prints the module name, the size of the module in
9701 bytes, the number of times the module is used, the dependencies of the
9702 module, the status of the module, and the address of the loaded module
9707 If @var{infotype} is omitted, then list the possible values for
9708 @var{infotype} and the kind of OS information available for each
9709 @var{infotype}. If the target does not return a list of possible
9710 types, this command will report an error.
9713 @node Memory Region Attributes
9714 @section Memory Region Attributes
9715 @cindex memory region attributes
9717 @dfn{Memory region attributes} allow you to describe special handling
9718 required by regions of your target's memory. @value{GDBN} uses
9719 attributes to determine whether to allow certain types of memory
9720 accesses; whether to use specific width accesses; and whether to cache
9721 target memory. By default the description of memory regions is
9722 fetched from the target (if the current target supports this), but the
9723 user can override the fetched regions.
9725 Defined memory regions can be individually enabled and disabled. When a
9726 memory region is disabled, @value{GDBN} uses the default attributes when
9727 accessing memory in that region. Similarly, if no memory regions have
9728 been defined, @value{GDBN} uses the default attributes when accessing
9731 When a memory region is defined, it is given a number to identify it;
9732 to enable, disable, or remove a memory region, you specify that number.
9736 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9737 Define a memory region bounded by @var{lower} and @var{upper} with
9738 attributes @var{attributes}@dots{}, and add it to the list of regions
9739 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9740 case: it is treated as the target's maximum memory address.
9741 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9744 Discard any user changes to the memory regions and use target-supplied
9745 regions, if available, or no regions if the target does not support.
9748 @item delete mem @var{nums}@dots{}
9749 Remove memory regions @var{nums}@dots{} from the list of regions
9750 monitored by @value{GDBN}.
9753 @item disable mem @var{nums}@dots{}
9754 Disable monitoring of memory regions @var{nums}@dots{}.
9755 A disabled memory region is not forgotten.
9756 It may be enabled again later.
9759 @item enable mem @var{nums}@dots{}
9760 Enable monitoring of memory regions @var{nums}@dots{}.
9764 Print a table of all defined memory regions, with the following columns
9768 @item Memory Region Number
9769 @item Enabled or Disabled.
9770 Enabled memory regions are marked with @samp{y}.
9771 Disabled memory regions are marked with @samp{n}.
9774 The address defining the inclusive lower bound of the memory region.
9777 The address defining the exclusive upper bound of the memory region.
9780 The list of attributes set for this memory region.
9785 @subsection Attributes
9787 @subsubsection Memory Access Mode
9788 The access mode attributes set whether @value{GDBN} may make read or
9789 write accesses to a memory region.
9791 While these attributes prevent @value{GDBN} from performing invalid
9792 memory accesses, they do nothing to prevent the target system, I/O DMA,
9793 etc.@: from accessing memory.
9797 Memory is read only.
9799 Memory is write only.
9801 Memory is read/write. This is the default.
9804 @subsubsection Memory Access Size
9805 The access size attribute tells @value{GDBN} to use specific sized
9806 accesses in the memory region. Often memory mapped device registers
9807 require specific sized accesses. If no access size attribute is
9808 specified, @value{GDBN} may use accesses of any size.
9812 Use 8 bit memory accesses.
9814 Use 16 bit memory accesses.
9816 Use 32 bit memory accesses.
9818 Use 64 bit memory accesses.
9821 @c @subsubsection Hardware/Software Breakpoints
9822 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9823 @c will use hardware or software breakpoints for the internal breakpoints
9824 @c used by the step, next, finish, until, etc. commands.
9828 @c Always use hardware breakpoints
9829 @c @item swbreak (default)
9832 @subsubsection Data Cache
9833 The data cache attributes set whether @value{GDBN} will cache target
9834 memory. While this generally improves performance by reducing debug
9835 protocol overhead, it can lead to incorrect results because @value{GDBN}
9836 does not know about volatile variables or memory mapped device
9841 Enable @value{GDBN} to cache target memory.
9843 Disable @value{GDBN} from caching target memory. This is the default.
9846 @subsection Memory Access Checking
9847 @value{GDBN} can be instructed to refuse accesses to memory that is
9848 not explicitly described. This can be useful if accessing such
9849 regions has undesired effects for a specific target, or to provide
9850 better error checking. The following commands control this behaviour.
9853 @kindex set mem inaccessible-by-default
9854 @item set mem inaccessible-by-default [on|off]
9855 If @code{on} is specified, make @value{GDBN} treat memory not
9856 explicitly described by the memory ranges as non-existent and refuse accesses
9857 to such memory. The checks are only performed if there's at least one
9858 memory range defined. If @code{off} is specified, make @value{GDBN}
9859 treat the memory not explicitly described by the memory ranges as RAM.
9860 The default value is @code{on}.
9861 @kindex show mem inaccessible-by-default
9862 @item show mem inaccessible-by-default
9863 Show the current handling of accesses to unknown memory.
9867 @c @subsubsection Memory Write Verification
9868 @c The memory write verification attributes set whether @value{GDBN}
9869 @c will re-reads data after each write to verify the write was successful.
9873 @c @item noverify (default)
9876 @node Dump/Restore Files
9877 @section Copy Between Memory and a File
9878 @cindex dump/restore files
9879 @cindex append data to a file
9880 @cindex dump data to a file
9881 @cindex restore data from a file
9883 You can use the commands @code{dump}, @code{append}, and
9884 @code{restore} to copy data between target memory and a file. The
9885 @code{dump} and @code{append} commands write data to a file, and the
9886 @code{restore} command reads data from a file back into the inferior's
9887 memory. Files may be in binary, Motorola S-record, Intel hex, or
9888 Tektronix Hex format; however, @value{GDBN} can only append to binary
9894 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9895 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9896 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9897 or the value of @var{expr}, to @var{filename} in the given format.
9899 The @var{format} parameter may be any one of:
9906 Motorola S-record format.
9908 Tektronix Hex format.
9911 @value{GDBN} uses the same definitions of these formats as the
9912 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9913 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9917 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9918 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9919 Append the contents of memory from @var{start_addr} to @var{end_addr},
9920 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9921 (@value{GDBN} can only append data to files in raw binary form.)
9924 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9925 Restore the contents of file @var{filename} into memory. The
9926 @code{restore} command can automatically recognize any known @sc{bfd}
9927 file format, except for raw binary. To restore a raw binary file you
9928 must specify the optional keyword @code{binary} after the filename.
9930 If @var{bias} is non-zero, its value will be added to the addresses
9931 contained in the file. Binary files always start at address zero, so
9932 they will be restored at address @var{bias}. Other bfd files have
9933 a built-in location; they will be restored at offset @var{bias}
9936 If @var{start} and/or @var{end} are non-zero, then only data between
9937 file offset @var{start} and file offset @var{end} will be restored.
9938 These offsets are relative to the addresses in the file, before
9939 the @var{bias} argument is applied.
9943 @node Core File Generation
9944 @section How to Produce a Core File from Your Program
9945 @cindex dump core from inferior
9947 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9948 image of a running process and its process status (register values
9949 etc.). Its primary use is post-mortem debugging of a program that
9950 crashed while it ran outside a debugger. A program that crashes
9951 automatically produces a core file, unless this feature is disabled by
9952 the user. @xref{Files}, for information on invoking @value{GDBN} in
9953 the post-mortem debugging mode.
9955 Occasionally, you may wish to produce a core file of the program you
9956 are debugging in order to preserve a snapshot of its state.
9957 @value{GDBN} has a special command for that.
9961 @kindex generate-core-file
9962 @item generate-core-file [@var{file}]
9963 @itemx gcore [@var{file}]
9964 Produce a core dump of the inferior process. The optional argument
9965 @var{file} specifies the file name where to put the core dump. If not
9966 specified, the file name defaults to @file{core.@var{pid}}, where
9967 @var{pid} is the inferior process ID.
9969 Note that this command is implemented only for some systems (as of
9970 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
9973 @node Character Sets
9974 @section Character Sets
9975 @cindex character sets
9977 @cindex translating between character sets
9978 @cindex host character set
9979 @cindex target character set
9981 If the program you are debugging uses a different character set to
9982 represent characters and strings than the one @value{GDBN} uses itself,
9983 @value{GDBN} can automatically translate between the character sets for
9984 you. The character set @value{GDBN} uses we call the @dfn{host
9985 character set}; the one the inferior program uses we call the
9986 @dfn{target character set}.
9988 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9989 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9990 remote protocol (@pxref{Remote Debugging}) to debug a program
9991 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9992 then the host character set is Latin-1, and the target character set is
9993 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9994 target-charset EBCDIC-US}, then @value{GDBN} translates between
9995 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9996 character and string literals in expressions.
9998 @value{GDBN} has no way to automatically recognize which character set
9999 the inferior program uses; you must tell it, using the @code{set
10000 target-charset} command, described below.
10002 Here are the commands for controlling @value{GDBN}'s character set
10006 @item set target-charset @var{charset}
10007 @kindex set target-charset
10008 Set the current target character set to @var{charset}. To display the
10009 list of supported target character sets, type
10010 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10012 @item set host-charset @var{charset}
10013 @kindex set host-charset
10014 Set the current host character set to @var{charset}.
10016 By default, @value{GDBN} uses a host character set appropriate to the
10017 system it is running on; you can override that default using the
10018 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10019 automatically determine the appropriate host character set. In this
10020 case, @value{GDBN} uses @samp{UTF-8}.
10022 @value{GDBN} can only use certain character sets as its host character
10023 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10024 @value{GDBN} will list the host character sets it supports.
10026 @item set charset @var{charset}
10027 @kindex set charset
10028 Set the current host and target character sets to @var{charset}. As
10029 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10030 @value{GDBN} will list the names of the character sets that can be used
10031 for both host and target.
10034 @kindex show charset
10035 Show the names of the current host and target character sets.
10037 @item show host-charset
10038 @kindex show host-charset
10039 Show the name of the current host character set.
10041 @item show target-charset
10042 @kindex show target-charset
10043 Show the name of the current target character set.
10045 @item set target-wide-charset @var{charset}
10046 @kindex set target-wide-charset
10047 Set the current target's wide character set to @var{charset}. This is
10048 the character set used by the target's @code{wchar_t} type. To
10049 display the list of supported wide character sets, type
10050 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10052 @item show target-wide-charset
10053 @kindex show target-wide-charset
10054 Show the name of the current target's wide character set.
10057 Here is an example of @value{GDBN}'s character set support in action.
10058 Assume that the following source code has been placed in the file
10059 @file{charset-test.c}:
10065 = @{72, 101, 108, 108, 111, 44, 32, 119,
10066 111, 114, 108, 100, 33, 10, 0@};
10067 char ibm1047_hello[]
10068 = @{200, 133, 147, 147, 150, 107, 64, 166,
10069 150, 153, 147, 132, 90, 37, 0@};
10073 printf ("Hello, world!\n");
10077 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10078 containing the string @samp{Hello, world!} followed by a newline,
10079 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10081 We compile the program, and invoke the debugger on it:
10084 $ gcc -g charset-test.c -o charset-test
10085 $ gdb -nw charset-test
10086 GNU gdb 2001-12-19-cvs
10087 Copyright 2001 Free Software Foundation, Inc.
10092 We can use the @code{show charset} command to see what character sets
10093 @value{GDBN} is currently using to interpret and display characters and
10097 (@value{GDBP}) show charset
10098 The current host and target character set is `ISO-8859-1'.
10102 For the sake of printing this manual, let's use @sc{ascii} as our
10103 initial character set:
10105 (@value{GDBP}) set charset ASCII
10106 (@value{GDBP}) show charset
10107 The current host and target character set is `ASCII'.
10111 Let's assume that @sc{ascii} is indeed the correct character set for our
10112 host system --- in other words, let's assume that if @value{GDBN} prints
10113 characters using the @sc{ascii} character set, our terminal will display
10114 them properly. Since our current target character set is also
10115 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10118 (@value{GDBP}) print ascii_hello
10119 $1 = 0x401698 "Hello, world!\n"
10120 (@value{GDBP}) print ascii_hello[0]
10125 @value{GDBN} uses the target character set for character and string
10126 literals you use in expressions:
10129 (@value{GDBP}) print '+'
10134 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10137 @value{GDBN} relies on the user to tell it which character set the
10138 target program uses. If we print @code{ibm1047_hello} while our target
10139 character set is still @sc{ascii}, we get jibberish:
10142 (@value{GDBP}) print ibm1047_hello
10143 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10144 (@value{GDBP}) print ibm1047_hello[0]
10149 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10150 @value{GDBN} tells us the character sets it supports:
10153 (@value{GDBP}) set target-charset
10154 ASCII EBCDIC-US IBM1047 ISO-8859-1
10155 (@value{GDBP}) set target-charset
10158 We can select @sc{ibm1047} as our target character set, and examine the
10159 program's strings again. Now the @sc{ascii} string is wrong, but
10160 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10161 target character set, @sc{ibm1047}, to the host character set,
10162 @sc{ascii}, and they display correctly:
10165 (@value{GDBP}) set target-charset IBM1047
10166 (@value{GDBP}) show charset
10167 The current host character set is `ASCII'.
10168 The current target character set is `IBM1047'.
10169 (@value{GDBP}) print ascii_hello
10170 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10171 (@value{GDBP}) print ascii_hello[0]
10173 (@value{GDBP}) print ibm1047_hello
10174 $8 = 0x4016a8 "Hello, world!\n"
10175 (@value{GDBP}) print ibm1047_hello[0]
10180 As above, @value{GDBN} uses the target character set for character and
10181 string literals you use in expressions:
10184 (@value{GDBP}) print '+'
10189 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10192 @node Caching Remote Data
10193 @section Caching Data of Remote Targets
10194 @cindex caching data of remote targets
10196 @value{GDBN} caches data exchanged between the debugger and a
10197 remote target (@pxref{Remote Debugging}). Such caching generally improves
10198 performance, because it reduces the overhead of the remote protocol by
10199 bundling memory reads and writes into large chunks. Unfortunately, simply
10200 caching everything would lead to incorrect results, since @value{GDBN}
10201 does not necessarily know anything about volatile values, memory-mapped I/O
10202 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
10203 memory can be changed @emph{while} a gdb command is executing.
10204 Therefore, by default, @value{GDBN} only caches data
10205 known to be on the stack@footnote{In non-stop mode, it is moderately
10206 rare for a running thread to modify the stack of a stopped thread
10207 in a way that would interfere with a backtrace, and caching of
10208 stack reads provides a significant speed up of remote backtraces.}.
10209 Other regions of memory can be explicitly marked as
10210 cacheable; see @pxref{Memory Region Attributes}.
10213 @kindex set remotecache
10214 @item set remotecache on
10215 @itemx set remotecache off
10216 This option no longer does anything; it exists for compatibility
10219 @kindex show remotecache
10220 @item show remotecache
10221 Show the current state of the obsolete remotecache flag.
10223 @kindex set stack-cache
10224 @item set stack-cache on
10225 @itemx set stack-cache off
10226 Enable or disable caching of stack accesses. When @code{ON}, use
10227 caching. By default, this option is @code{ON}.
10229 @kindex show stack-cache
10230 @item show stack-cache
10231 Show the current state of data caching for memory accesses.
10233 @kindex info dcache
10234 @item info dcache @r{[}line@r{]}
10235 Print the information about the data cache performance. The
10236 information displayed includes the dcache width and depth, and for
10237 each cache line, its number, address, and how many times it was
10238 referenced. This command is useful for debugging the data cache
10241 If a line number is specified, the contents of that line will be
10244 @item set dcache size @var{size}
10245 @cindex dcache size
10246 @kindex set dcache size
10247 Set maximum number of entries in dcache (dcache depth above).
10249 @item set dcache line-size @var{line-size}
10250 @cindex dcache line-size
10251 @kindex set dcache line-size
10252 Set number of bytes each dcache entry caches (dcache width above).
10253 Must be a power of 2.
10255 @item show dcache size
10256 @kindex show dcache size
10257 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
10259 @item show dcache line-size
10260 @kindex show dcache line-size
10261 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
10265 @node Searching Memory
10266 @section Search Memory
10267 @cindex searching memory
10269 Memory can be searched for a particular sequence of bytes with the
10270 @code{find} command.
10274 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10275 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10276 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10277 etc. The search begins at address @var{start_addr} and continues for either
10278 @var{len} bytes or through to @var{end_addr} inclusive.
10281 @var{s} and @var{n} are optional parameters.
10282 They may be specified in either order, apart or together.
10285 @item @var{s}, search query size
10286 The size of each search query value.
10292 halfwords (two bytes)
10296 giant words (eight bytes)
10299 All values are interpreted in the current language.
10300 This means, for example, that if the current source language is C/C@t{++}
10301 then searching for the string ``hello'' includes the trailing '\0'.
10303 If the value size is not specified, it is taken from the
10304 value's type in the current language.
10305 This is useful when one wants to specify the search
10306 pattern as a mixture of types.
10307 Note that this means, for example, that in the case of C-like languages
10308 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10309 which is typically four bytes.
10311 @item @var{n}, maximum number of finds
10312 The maximum number of matches to print. The default is to print all finds.
10315 You can use strings as search values. Quote them with double-quotes
10317 The string value is copied into the search pattern byte by byte,
10318 regardless of the endianness of the target and the size specification.
10320 The address of each match found is printed as well as a count of the
10321 number of matches found.
10323 The address of the last value found is stored in convenience variable
10325 A count of the number of matches is stored in @samp{$numfound}.
10327 For example, if stopped at the @code{printf} in this function:
10333 static char hello[] = "hello-hello";
10334 static struct @{ char c; short s; int i; @}
10335 __attribute__ ((packed)) mixed
10336 = @{ 'c', 0x1234, 0x87654321 @};
10337 printf ("%s\n", hello);
10342 you get during debugging:
10345 (gdb) find &hello[0], +sizeof(hello), "hello"
10346 0x804956d <hello.1620+6>
10348 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10349 0x8049567 <hello.1620>
10350 0x804956d <hello.1620+6>
10352 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10353 0x8049567 <hello.1620>
10355 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10356 0x8049560 <mixed.1625>
10358 (gdb) print $numfound
10361 $2 = (void *) 0x8049560
10364 @node Optimized Code
10365 @chapter Debugging Optimized Code
10366 @cindex optimized code, debugging
10367 @cindex debugging optimized code
10369 Almost all compilers support optimization. With optimization
10370 disabled, the compiler generates assembly code that corresponds
10371 directly to your source code, in a simplistic way. As the compiler
10372 applies more powerful optimizations, the generated assembly code
10373 diverges from your original source code. With help from debugging
10374 information generated by the compiler, @value{GDBN} can map from
10375 the running program back to constructs from your original source.
10377 @value{GDBN} is more accurate with optimization disabled. If you
10378 can recompile without optimization, it is easier to follow the
10379 progress of your program during debugging. But, there are many cases
10380 where you may need to debug an optimized version.
10382 When you debug a program compiled with @samp{-g -O}, remember that the
10383 optimizer has rearranged your code; the debugger shows you what is
10384 really there. Do not be too surprised when the execution path does not
10385 exactly match your source file! An extreme example: if you define a
10386 variable, but never use it, @value{GDBN} never sees that
10387 variable---because the compiler optimizes it out of existence.
10389 Some things do not work as well with @samp{-g -O} as with just
10390 @samp{-g}, particularly on machines with instruction scheduling. If in
10391 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
10392 please report it to us as a bug (including a test case!).
10393 @xref{Variables}, for more information about debugging optimized code.
10396 * Inline Functions:: How @value{GDBN} presents inlining
10397 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
10400 @node Inline Functions
10401 @section Inline Functions
10402 @cindex inline functions, debugging
10404 @dfn{Inlining} is an optimization that inserts a copy of the function
10405 body directly at each call site, instead of jumping to a shared
10406 routine. @value{GDBN} displays inlined functions just like
10407 non-inlined functions. They appear in backtraces. You can view their
10408 arguments and local variables, step into them with @code{step}, skip
10409 them with @code{next}, and escape from them with @code{finish}.
10410 You can check whether a function was inlined by using the
10411 @code{info frame} command.
10413 For @value{GDBN} to support inlined functions, the compiler must
10414 record information about inlining in the debug information ---
10415 @value{NGCC} using the @sc{dwarf 2} format does this, and several
10416 other compilers do also. @value{GDBN} only supports inlined functions
10417 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
10418 do not emit two required attributes (@samp{DW_AT_call_file} and
10419 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
10420 function calls with earlier versions of @value{NGCC}. It instead
10421 displays the arguments and local variables of inlined functions as
10422 local variables in the caller.
10424 The body of an inlined function is directly included at its call site;
10425 unlike a non-inlined function, there are no instructions devoted to
10426 the call. @value{GDBN} still pretends that the call site and the
10427 start of the inlined function are different instructions. Stepping to
10428 the call site shows the call site, and then stepping again shows
10429 the first line of the inlined function, even though no additional
10430 instructions are executed.
10432 This makes source-level debugging much clearer; you can see both the
10433 context of the call and then the effect of the call. Only stepping by
10434 a single instruction using @code{stepi} or @code{nexti} does not do
10435 this; single instruction steps always show the inlined body.
10437 There are some ways that @value{GDBN} does not pretend that inlined
10438 function calls are the same as normal calls:
10442 Setting breakpoints at the call site of an inlined function may not
10443 work, because the call site does not contain any code. @value{GDBN}
10444 may incorrectly move the breakpoint to the next line of the enclosing
10445 function, after the call. This limitation will be removed in a future
10446 version of @value{GDBN}; until then, set a breakpoint on an earlier line
10447 or inside the inlined function instead.
10450 @value{GDBN} cannot locate the return value of inlined calls after
10451 using the @code{finish} command. This is a limitation of compiler-generated
10452 debugging information; after @code{finish}, you can step to the next line
10453 and print a variable where your program stored the return value.
10457 @node Tail Call Frames
10458 @section Tail Call Frames
10459 @cindex tail call frames, debugging
10461 Function @code{B} can call function @code{C} in its very last statement. In
10462 unoptimized compilation the call of @code{C} is immediately followed by return
10463 instruction at the end of @code{B} code. Optimizing compiler may replace the
10464 call and return in function @code{B} into one jump to function @code{C}
10465 instead. Such use of a jump instruction is called @dfn{tail call}.
10467 During execution of function @code{C}, there will be no indication in the
10468 function call stack frames that it was tail-called from @code{B}. If function
10469 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
10470 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
10471 some cases @value{GDBN} can determine that @code{C} was tail-called from
10472 @code{B}, and it will then create fictitious call frame for that, with the
10473 return address set up as if @code{B} called @code{C} normally.
10475 This functionality is currently supported only by DWARF 2 debugging format and
10476 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
10477 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10480 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
10481 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
10485 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
10487 Stack level 1, frame at 0x7fffffffda30:
10488 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
10489 tail call frame, caller of frame at 0x7fffffffda30
10490 source language c++.
10491 Arglist at unknown address.
10492 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
10495 The detection of all the possible code path executions can find them ambiguous.
10496 There is no execution history stored (possible @ref{Reverse Execution} is never
10497 used for this purpose) and the last known caller could have reached the known
10498 callee by multiple different jump sequences. In such case @value{GDBN} still
10499 tries to show at least all the unambiguous top tail callers and all the
10500 unambiguous bottom tail calees, if any.
10503 @anchor{set debug entry-values}
10504 @item set debug entry-values
10505 @kindex set debug entry-values
10506 When set to on, enables printing of analysis messages for both frame argument
10507 values at function entry and tail calls. It will show all the possible valid
10508 tail calls code paths it has considered. It will also print the intersection
10509 of them with the final unambiguous (possibly partial or even empty) code path
10512 @item show debug entry-values
10513 @kindex show debug entry-values
10514 Show the current state of analysis messages printing for both frame argument
10515 values at function entry and tail calls.
10518 The analysis messages for tail calls can for example show why the virtual tail
10519 call frame for function @code{c} has not been recognized (due to the indirect
10520 reference by variable @code{x}):
10523 static void __attribute__((noinline, noclone)) c (void);
10524 void (*x) (void) = c;
10525 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10526 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
10527 int main (void) @{ x (); return 0; @}
10529 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
10530 DW_TAG_GNU_call_site 0x40039a in main
10532 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10535 #1 0x000000000040039a in main () at t.c:5
10538 Another possibility is an ambiguous virtual tail call frames resolution:
10542 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
10543 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
10544 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
10545 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
10546 static void __attribute__((noinline, noclone)) b (void)
10547 @{ if (i) c (); else e (); @}
10548 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
10549 int main (void) @{ a (); return 0; @}
10551 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
10552 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
10553 tailcall: reduced: 0x4004d2(a) |
10556 #1 0x00000000004004d2 in a () at t.c:8
10557 #2 0x0000000000400395 in main () at t.c:9
10560 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
10561 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
10563 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
10564 @ifset HAVE_MAKEINFO_CLICK
10565 @set ARROW @click{}
10566 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
10567 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
10569 @ifclear HAVE_MAKEINFO_CLICK
10571 @set CALLSEQ1B @value{CALLSEQ1A}
10572 @set CALLSEQ2B @value{CALLSEQ2A}
10575 Frames #0 and #2 are real, #1 is a virtual tail call frame.
10576 The code can have possible execution paths @value{CALLSEQ1B} or
10577 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
10579 @code{initial:} state shows some random possible calling sequence @value{GDBN}
10580 has found. It then finds another possible calling sequcen - that one is
10581 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
10582 printed as the @code{reduced:} calling sequence. That one could have many
10583 futher @code{compare:} and @code{reduced:} statements as long as there remain
10584 any non-ambiguous sequence entries.
10586 For the frame of function @code{b} in both cases there are different possible
10587 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
10588 also ambigous. The only non-ambiguous frame is the one for function @code{a},
10589 therefore this one is displayed to the user while the ambiguous frames are
10592 There can be also reasons why printing of frame argument values at function
10597 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
10598 static void __attribute__((noinline, noclone)) a (int i);
10599 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
10600 static void __attribute__((noinline, noclone)) a (int i)
10601 @{ if (i) b (i - 1); else c (0); @}
10602 int main (void) @{ a (5); return 0; @}
10605 #0 c (i=i@@entry=0) at t.c:2
10606 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
10607 function "a" at 0x400420 can call itself via tail calls
10608 i=<optimized out>) at t.c:6
10609 #2 0x000000000040036e in main () at t.c:7
10612 @value{GDBN} cannot find out from the inferior state if and how many times did
10613 function @code{a} call itself (via function @code{b}) as these calls would be
10614 tail calls. Such tail calls would modify thue @code{i} variable, therefore
10615 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
10616 prints @code{<optimized out>} instead.
10619 @chapter C Preprocessor Macros
10621 Some languages, such as C and C@t{++}, provide a way to define and invoke
10622 ``preprocessor macros'' which expand into strings of tokens.
10623 @value{GDBN} can evaluate expressions containing macro invocations, show
10624 the result of macro expansion, and show a macro's definition, including
10625 where it was defined.
10627 You may need to compile your program specially to provide @value{GDBN}
10628 with information about preprocessor macros. Most compilers do not
10629 include macros in their debugging information, even when you compile
10630 with the @option{-g} flag. @xref{Compilation}.
10632 A program may define a macro at one point, remove that definition later,
10633 and then provide a different definition after that. Thus, at different
10634 points in the program, a macro may have different definitions, or have
10635 no definition at all. If there is a current stack frame, @value{GDBN}
10636 uses the macros in scope at that frame's source code line. Otherwise,
10637 @value{GDBN} uses the macros in scope at the current listing location;
10640 Whenever @value{GDBN} evaluates an expression, it always expands any
10641 macro invocations present in the expression. @value{GDBN} also provides
10642 the following commands for working with macros explicitly.
10646 @kindex macro expand
10647 @cindex macro expansion, showing the results of preprocessor
10648 @cindex preprocessor macro expansion, showing the results of
10649 @cindex expanding preprocessor macros
10650 @item macro expand @var{expression}
10651 @itemx macro exp @var{expression}
10652 Show the results of expanding all preprocessor macro invocations in
10653 @var{expression}. Since @value{GDBN} simply expands macros, but does
10654 not parse the result, @var{expression} need not be a valid expression;
10655 it can be any string of tokens.
10658 @item macro expand-once @var{expression}
10659 @itemx macro exp1 @var{expression}
10660 @cindex expand macro once
10661 @i{(This command is not yet implemented.)} Show the results of
10662 expanding those preprocessor macro invocations that appear explicitly in
10663 @var{expression}. Macro invocations appearing in that expansion are
10664 left unchanged. This command allows you to see the effect of a
10665 particular macro more clearly, without being confused by further
10666 expansions. Since @value{GDBN} simply expands macros, but does not
10667 parse the result, @var{expression} need not be a valid expression; it
10668 can be any string of tokens.
10671 @cindex macro definition, showing
10672 @cindex definition of a macro, showing
10673 @cindex macros, from debug info
10674 @item info macro [-a|-all] [--] @var{macro}
10675 Show the current definition or all definitions of the named @var{macro},
10676 and describe the source location or compiler command-line where that
10677 definition was established. The optional double dash is to signify the end of
10678 argument processing and the beginning of @var{macro} for non C-like macros where
10679 the macro may begin with a hyphen.
10681 @kindex info macros
10682 @item info macros @var{linespec}
10683 Show all macro definitions that are in effect at the location specified
10684 by @var{linespec}, and describe the source location or compiler
10685 command-line where those definitions were established.
10687 @kindex macro define
10688 @cindex user-defined macros
10689 @cindex defining macros interactively
10690 @cindex macros, user-defined
10691 @item macro define @var{macro} @var{replacement-list}
10692 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10693 Introduce a definition for a preprocessor macro named @var{macro},
10694 invocations of which are replaced by the tokens given in
10695 @var{replacement-list}. The first form of this command defines an
10696 ``object-like'' macro, which takes no arguments; the second form
10697 defines a ``function-like'' macro, which takes the arguments given in
10700 A definition introduced by this command is in scope in every
10701 expression evaluated in @value{GDBN}, until it is removed with the
10702 @code{macro undef} command, described below. The definition overrides
10703 all definitions for @var{macro} present in the program being debugged,
10704 as well as any previous user-supplied definition.
10706 @kindex macro undef
10707 @item macro undef @var{macro}
10708 Remove any user-supplied definition for the macro named @var{macro}.
10709 This command only affects definitions provided with the @code{macro
10710 define} command, described above; it cannot remove definitions present
10711 in the program being debugged.
10715 List all the macros defined using the @code{macro define} command.
10718 @cindex macros, example of debugging with
10719 Here is a transcript showing the above commands in action. First, we
10720 show our source files:
10725 #include "sample.h"
10728 #define ADD(x) (M + x)
10733 printf ("Hello, world!\n");
10735 printf ("We're so creative.\n");
10737 printf ("Goodbye, world!\n");
10744 Now, we compile the program using the @sc{gnu} C compiler,
10745 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10746 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10747 and @option{-gdwarf-4}; we recommend always choosing the most recent
10748 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10749 includes information about preprocessor macros in the debugging
10753 $ gcc -gdwarf-2 -g3 sample.c -o sample
10757 Now, we start @value{GDBN} on our sample program:
10761 GNU gdb 2002-05-06-cvs
10762 Copyright 2002 Free Software Foundation, Inc.
10763 GDB is free software, @dots{}
10767 We can expand macros and examine their definitions, even when the
10768 program is not running. @value{GDBN} uses the current listing position
10769 to decide which macro definitions are in scope:
10772 (@value{GDBP}) list main
10775 5 #define ADD(x) (M + x)
10780 10 printf ("Hello, world!\n");
10782 12 printf ("We're so creative.\n");
10783 (@value{GDBP}) info macro ADD
10784 Defined at /home/jimb/gdb/macros/play/sample.c:5
10785 #define ADD(x) (M + x)
10786 (@value{GDBP}) info macro Q
10787 Defined at /home/jimb/gdb/macros/play/sample.h:1
10788 included at /home/jimb/gdb/macros/play/sample.c:2
10790 (@value{GDBP}) macro expand ADD(1)
10791 expands to: (42 + 1)
10792 (@value{GDBP}) macro expand-once ADD(1)
10793 expands to: once (M + 1)
10797 In the example above, note that @code{macro expand-once} expands only
10798 the macro invocation explicit in the original text --- the invocation of
10799 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10800 which was introduced by @code{ADD}.
10802 Once the program is running, @value{GDBN} uses the macro definitions in
10803 force at the source line of the current stack frame:
10806 (@value{GDBP}) break main
10807 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10809 Starting program: /home/jimb/gdb/macros/play/sample
10811 Breakpoint 1, main () at sample.c:10
10812 10 printf ("Hello, world!\n");
10816 At line 10, the definition of the macro @code{N} at line 9 is in force:
10819 (@value{GDBP}) info macro N
10820 Defined at /home/jimb/gdb/macros/play/sample.c:9
10822 (@value{GDBP}) macro expand N Q M
10823 expands to: 28 < 42
10824 (@value{GDBP}) print N Q M
10829 As we step over directives that remove @code{N}'s definition, and then
10830 give it a new definition, @value{GDBN} finds the definition (or lack
10831 thereof) in force at each point:
10834 (@value{GDBP}) next
10836 12 printf ("We're so creative.\n");
10837 (@value{GDBP}) info macro N
10838 The symbol `N' has no definition as a C/C++ preprocessor macro
10839 at /home/jimb/gdb/macros/play/sample.c:12
10840 (@value{GDBP}) next
10842 14 printf ("Goodbye, world!\n");
10843 (@value{GDBP}) info macro N
10844 Defined at /home/jimb/gdb/macros/play/sample.c:13
10846 (@value{GDBP}) macro expand N Q M
10847 expands to: 1729 < 42
10848 (@value{GDBP}) print N Q M
10853 In addition to source files, macros can be defined on the compilation command
10854 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10855 such a way, @value{GDBN} displays the location of their definition as line zero
10856 of the source file submitted to the compiler.
10859 (@value{GDBP}) info macro __STDC__
10860 Defined at /home/jimb/gdb/macros/play/sample.c:0
10867 @chapter Tracepoints
10868 @c This chapter is based on the documentation written by Michael
10869 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10871 @cindex tracepoints
10872 In some applications, it is not feasible for the debugger to interrupt
10873 the program's execution long enough for the developer to learn
10874 anything helpful about its behavior. If the program's correctness
10875 depends on its real-time behavior, delays introduced by a debugger
10876 might cause the program to change its behavior drastically, or perhaps
10877 fail, even when the code itself is correct. It is useful to be able
10878 to observe the program's behavior without interrupting it.
10880 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10881 specify locations in the program, called @dfn{tracepoints}, and
10882 arbitrary expressions to evaluate when those tracepoints are reached.
10883 Later, using the @code{tfind} command, you can examine the values
10884 those expressions had when the program hit the tracepoints. The
10885 expressions may also denote objects in memory---structures or arrays,
10886 for example---whose values @value{GDBN} should record; while visiting
10887 a particular tracepoint, you may inspect those objects as if they were
10888 in memory at that moment. However, because @value{GDBN} records these
10889 values without interacting with you, it can do so quickly and
10890 unobtrusively, hopefully not disturbing the program's behavior.
10892 The tracepoint facility is currently available only for remote
10893 targets. @xref{Targets}. In addition, your remote target must know
10894 how to collect trace data. This functionality is implemented in the
10895 remote stub; however, none of the stubs distributed with @value{GDBN}
10896 support tracepoints as of this writing. The format of the remote
10897 packets used to implement tracepoints are described in @ref{Tracepoint
10900 It is also possible to get trace data from a file, in a manner reminiscent
10901 of corefiles; you specify the filename, and use @code{tfind} to search
10902 through the file. @xref{Trace Files}, for more details.
10904 This chapter describes the tracepoint commands and features.
10907 * Set Tracepoints::
10908 * Analyze Collected Data::
10909 * Tracepoint Variables::
10913 @node Set Tracepoints
10914 @section Commands to Set Tracepoints
10916 Before running such a @dfn{trace experiment}, an arbitrary number of
10917 tracepoints can be set. A tracepoint is actually a special type of
10918 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10919 standard breakpoint commands. For instance, as with breakpoints,
10920 tracepoint numbers are successive integers starting from one, and many
10921 of the commands associated with tracepoints take the tracepoint number
10922 as their argument, to identify which tracepoint to work on.
10924 For each tracepoint, you can specify, in advance, some arbitrary set
10925 of data that you want the target to collect in the trace buffer when
10926 it hits that tracepoint. The collected data can include registers,
10927 local variables, or global data. Later, you can use @value{GDBN}
10928 commands to examine the values these data had at the time the
10929 tracepoint was hit.
10931 Tracepoints do not support every breakpoint feature. Ignore counts on
10932 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10933 commands when they are hit. Tracepoints may not be thread-specific
10936 @cindex fast tracepoints
10937 Some targets may support @dfn{fast tracepoints}, which are inserted in
10938 a different way (such as with a jump instead of a trap), that is
10939 faster but possibly restricted in where they may be installed.
10941 @cindex static tracepoints
10942 @cindex markers, static tracepoints
10943 @cindex probing markers, static tracepoints
10944 Regular and fast tracepoints are dynamic tracing facilities, meaning
10945 that they can be used to insert tracepoints at (almost) any location
10946 in the target. Some targets may also support controlling @dfn{static
10947 tracepoints} from @value{GDBN}. With static tracing, a set of
10948 instrumentation points, also known as @dfn{markers}, are embedded in
10949 the target program, and can be activated or deactivated by name or
10950 address. These are usually placed at locations which facilitate
10951 investigating what the target is actually doing. @value{GDBN}'s
10952 support for static tracing includes being able to list instrumentation
10953 points, and attach them with @value{GDBN} defined high level
10954 tracepoints that expose the whole range of convenience of
10955 @value{GDBN}'s tracepoints support. Namely, support for collecting
10956 registers values and values of global or local (to the instrumentation
10957 point) variables; tracepoint conditions and trace state variables.
10958 The act of installing a @value{GDBN} static tracepoint on an
10959 instrumentation point, or marker, is referred to as @dfn{probing} a
10960 static tracepoint marker.
10962 @code{gdbserver} supports tracepoints on some target systems.
10963 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10965 This section describes commands to set tracepoints and associated
10966 conditions and actions.
10969 * Create and Delete Tracepoints::
10970 * Enable and Disable Tracepoints::
10971 * Tracepoint Passcounts::
10972 * Tracepoint Conditions::
10973 * Trace State Variables::
10974 * Tracepoint Actions::
10975 * Listing Tracepoints::
10976 * Listing Static Tracepoint Markers::
10977 * Starting and Stopping Trace Experiments::
10978 * Tracepoint Restrictions::
10981 @node Create and Delete Tracepoints
10982 @subsection Create and Delete Tracepoints
10985 @cindex set tracepoint
10987 @item trace @var{location}
10988 The @code{trace} command is very similar to the @code{break} command.
10989 Its argument @var{location} can be a source line, a function name, or
10990 an address in the target program. @xref{Specify Location}. The
10991 @code{trace} command defines a tracepoint, which is a point in the
10992 target program where the debugger will briefly stop, collect some
10993 data, and then allow the program to continue. Setting a tracepoint or
10994 changing its actions takes effect immediately if the remote stub
10995 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
10997 If remote stub doesn't support the @samp{InstallInTrace} feature, all
10998 these changes don't take effect until the next @code{tstart}
10999 command, and once a trace experiment is running, further changes will
11000 not have any effect until the next trace experiment starts. In addition,
11001 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11002 address is not yet resolved. (This is similar to pending breakpoints.)
11003 Pending tracepoints are not downloaded to the target and not installed
11004 until they are resolved. The resolution of pending tracepoints requires
11005 @value{GDBN} support---when debugging with the remote target, and
11006 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11007 tracing}), pending tracepoints can not be resolved (and downloaded to
11008 the remote stub) while @value{GDBN} is disconnected.
11010 Here are some examples of using the @code{trace} command:
11013 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11015 (@value{GDBP}) @b{trace +2} // 2 lines forward
11017 (@value{GDBP}) @b{trace my_function} // first source line of function
11019 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11021 (@value{GDBP}) @b{trace *0x2117c4} // an address
11025 You can abbreviate @code{trace} as @code{tr}.
11027 @item trace @var{location} if @var{cond}
11028 Set a tracepoint with condition @var{cond}; evaluate the expression
11029 @var{cond} each time the tracepoint is reached, and collect data only
11030 if the value is nonzero---that is, if @var{cond} evaluates as true.
11031 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11032 information on tracepoint conditions.
11034 @item ftrace @var{location} [ if @var{cond} ]
11035 @cindex set fast tracepoint
11036 @cindex fast tracepoints, setting
11038 The @code{ftrace} command sets a fast tracepoint. For targets that
11039 support them, fast tracepoints will use a more efficient but possibly
11040 less general technique to trigger data collection, such as a jump
11041 instruction instead of a trap, or some sort of hardware support. It
11042 may not be possible to create a fast tracepoint at the desired
11043 location, in which case the command will exit with an explanatory
11046 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11049 On 32-bit x86-architecture systems, fast tracepoints normally need to
11050 be placed at an instruction that is 5 bytes or longer, but can be
11051 placed at 4-byte instructions if the low 64K of memory of the target
11052 program is available to install trampolines. Some Unix-type systems,
11053 such as @sc{gnu}/Linux, exclude low addresses from the program's
11054 address space; but for instance with the Linux kernel it is possible
11055 to let @value{GDBN} use this area by doing a @command{sysctl} command
11056 to set the @code{mmap_min_addr} kernel parameter, as in
11059 sudo sysctl -w vm.mmap_min_addr=32768
11063 which sets the low address to 32K, which leaves plenty of room for
11064 trampolines. The minimum address should be set to a page boundary.
11066 @item strace @var{location} [ if @var{cond} ]
11067 @cindex set static tracepoint
11068 @cindex static tracepoints, setting
11069 @cindex probe static tracepoint marker
11071 The @code{strace} command sets a static tracepoint. For targets that
11072 support it, setting a static tracepoint probes a static
11073 instrumentation point, or marker, found at @var{location}. It may not
11074 be possible to set a static tracepoint at the desired location, in
11075 which case the command will exit with an explanatory message.
11077 @value{GDBN} handles arguments to @code{strace} exactly as for
11078 @code{trace}, with the addition that the user can also specify
11079 @code{-m @var{marker}} as @var{location}. This probes the marker
11080 identified by the @var{marker} string identifier. This identifier
11081 depends on the static tracepoint backend library your program is
11082 using. You can find all the marker identifiers in the @samp{ID} field
11083 of the @code{info static-tracepoint-markers} command output.
11084 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11085 Markers}. For example, in the following small program using the UST
11091 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11096 the marker id is composed of joining the first two arguments to the
11097 @code{trace_mark} call with a slash, which translates to:
11100 (@value{GDBP}) info static-tracepoint-markers
11101 Cnt Enb ID Address What
11102 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11108 so you may probe the marker above with:
11111 (@value{GDBP}) strace -m ust/bar33
11114 Static tracepoints accept an extra collect action --- @code{collect
11115 $_sdata}. This collects arbitrary user data passed in the probe point
11116 call to the tracing library. In the UST example above, you'll see
11117 that the third argument to @code{trace_mark} is a printf-like format
11118 string. The user data is then the result of running that formating
11119 string against the following arguments. Note that @code{info
11120 static-tracepoint-markers} command output lists that format string in
11121 the @samp{Data:} field.
11123 You can inspect this data when analyzing the trace buffer, by printing
11124 the $_sdata variable like any other variable available to
11125 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11128 @cindex last tracepoint number
11129 @cindex recent tracepoint number
11130 @cindex tracepoint number
11131 The convenience variable @code{$tpnum} records the tracepoint number
11132 of the most recently set tracepoint.
11134 @kindex delete tracepoint
11135 @cindex tracepoint deletion
11136 @item delete tracepoint @r{[}@var{num}@r{]}
11137 Permanently delete one or more tracepoints. With no argument, the
11138 default is to delete all tracepoints. Note that the regular
11139 @code{delete} command can remove tracepoints also.
11144 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11146 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11150 You can abbreviate this command as @code{del tr}.
11153 @node Enable and Disable Tracepoints
11154 @subsection Enable and Disable Tracepoints
11156 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11159 @kindex disable tracepoint
11160 @item disable tracepoint @r{[}@var{num}@r{]}
11161 Disable tracepoint @var{num}, or all tracepoints if no argument
11162 @var{num} is given. A disabled tracepoint will have no effect during
11163 a trace experiment, but it is not forgotten. You can re-enable
11164 a disabled tracepoint using the @code{enable tracepoint} command.
11165 If the command is issued during a trace experiment and the debug target
11166 has support for disabling tracepoints during a trace experiment, then the
11167 change will be effective immediately. Otherwise, it will be applied to the
11168 next trace experiment.
11170 @kindex enable tracepoint
11171 @item enable tracepoint @r{[}@var{num}@r{]}
11172 Enable tracepoint @var{num}, or all tracepoints. If this command is
11173 issued during a trace experiment and the debug target supports enabling
11174 tracepoints during a trace experiment, then the enabled tracepoints will
11175 become effective immediately. Otherwise, they will become effective the
11176 next time a trace experiment is run.
11179 @node Tracepoint Passcounts
11180 @subsection Tracepoint Passcounts
11184 @cindex tracepoint pass count
11185 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11186 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11187 automatically stop a trace experiment. If a tracepoint's passcount is
11188 @var{n}, then the trace experiment will be automatically stopped on
11189 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11190 @var{num} is not specified, the @code{passcount} command sets the
11191 passcount of the most recently defined tracepoint. If no passcount is
11192 given, the trace experiment will run until stopped explicitly by the
11198 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11199 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11201 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11202 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11203 (@value{GDBP}) @b{trace foo}
11204 (@value{GDBP}) @b{pass 3}
11205 (@value{GDBP}) @b{trace bar}
11206 (@value{GDBP}) @b{pass 2}
11207 (@value{GDBP}) @b{trace baz}
11208 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11209 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11210 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11211 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11215 @node Tracepoint Conditions
11216 @subsection Tracepoint Conditions
11217 @cindex conditional tracepoints
11218 @cindex tracepoint conditions
11220 The simplest sort of tracepoint collects data every time your program
11221 reaches a specified place. You can also specify a @dfn{condition} for
11222 a tracepoint. A condition is just a Boolean expression in your
11223 programming language (@pxref{Expressions, ,Expressions}). A
11224 tracepoint with a condition evaluates the expression each time your
11225 program reaches it, and data collection happens only if the condition
11228 Tracepoint conditions can be specified when a tracepoint is set, by
11229 using @samp{if} in the arguments to the @code{trace} command.
11230 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11231 also be set or changed at any time with the @code{condition} command,
11232 just as with breakpoints.
11234 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11235 the conditional expression itself. Instead, @value{GDBN} encodes the
11236 expression into an agent expression (@pxref{Agent Expressions})
11237 suitable for execution on the target, independently of @value{GDBN}.
11238 Global variables become raw memory locations, locals become stack
11239 accesses, and so forth.
11241 For instance, suppose you have a function that is usually called
11242 frequently, but should not be called after an error has occurred. You
11243 could use the following tracepoint command to collect data about calls
11244 of that function that happen while the error code is propagating
11245 through the program; an unconditional tracepoint could end up
11246 collecting thousands of useless trace frames that you would have to
11250 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11253 @node Trace State Variables
11254 @subsection Trace State Variables
11255 @cindex trace state variables
11257 A @dfn{trace state variable} is a special type of variable that is
11258 created and managed by target-side code. The syntax is the same as
11259 that for GDB's convenience variables (a string prefixed with ``$''),
11260 but they are stored on the target. They must be created explicitly,
11261 using a @code{tvariable} command. They are always 64-bit signed
11264 Trace state variables are remembered by @value{GDBN}, and downloaded
11265 to the target along with tracepoint information when the trace
11266 experiment starts. There are no intrinsic limits on the number of
11267 trace state variables, beyond memory limitations of the target.
11269 @cindex convenience variables, and trace state variables
11270 Although trace state variables are managed by the target, you can use
11271 them in print commands and expressions as if they were convenience
11272 variables; @value{GDBN} will get the current value from the target
11273 while the trace experiment is running. Trace state variables share
11274 the same namespace as other ``$'' variables, which means that you
11275 cannot have trace state variables with names like @code{$23} or
11276 @code{$pc}, nor can you have a trace state variable and a convenience
11277 variable with the same name.
11281 @item tvariable $@var{name} [ = @var{expression} ]
11283 The @code{tvariable} command creates a new trace state variable named
11284 @code{$@var{name}}, and optionally gives it an initial value of
11285 @var{expression}. @var{expression} is evaluated when this command is
11286 entered; the result will be converted to an integer if possible,
11287 otherwise @value{GDBN} will report an error. A subsequent
11288 @code{tvariable} command specifying the same name does not create a
11289 variable, but instead assigns the supplied initial value to the
11290 existing variable of that name, overwriting any previous initial
11291 value. The default initial value is 0.
11293 @item info tvariables
11294 @kindex info tvariables
11295 List all the trace state variables along with their initial values.
11296 Their current values may also be displayed, if the trace experiment is
11299 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11300 @kindex delete tvariable
11301 Delete the given trace state variables, or all of them if no arguments
11306 @node Tracepoint Actions
11307 @subsection Tracepoint Action Lists
11311 @cindex tracepoint actions
11312 @item actions @r{[}@var{num}@r{]}
11313 This command will prompt for a list of actions to be taken when the
11314 tracepoint is hit. If the tracepoint number @var{num} is not
11315 specified, this command sets the actions for the one that was most
11316 recently defined (so that you can define a tracepoint and then say
11317 @code{actions} without bothering about its number). You specify the
11318 actions themselves on the following lines, one action at a time, and
11319 terminate the actions list with a line containing just @code{end}. So
11320 far, the only defined actions are @code{collect}, @code{teval}, and
11321 @code{while-stepping}.
11323 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11324 Commands, ,Breakpoint Command Lists}), except that only the defined
11325 actions are allowed; any other @value{GDBN} command is rejected.
11327 @cindex remove actions from a tracepoint
11328 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11329 and follow it immediately with @samp{end}.
11332 (@value{GDBP}) @b{collect @var{data}} // collect some data
11334 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11336 (@value{GDBP}) @b{end} // signals the end of actions.
11339 In the following example, the action list begins with @code{collect}
11340 commands indicating the things to be collected when the tracepoint is
11341 hit. Then, in order to single-step and collect additional data
11342 following the tracepoint, a @code{while-stepping} command is used,
11343 followed by the list of things to be collected after each step in a
11344 sequence of single steps. The @code{while-stepping} command is
11345 terminated by its own separate @code{end} command. Lastly, the action
11346 list is terminated by an @code{end} command.
11349 (@value{GDBP}) @b{trace foo}
11350 (@value{GDBP}) @b{actions}
11351 Enter actions for tracepoint 1, one per line:
11354 > while-stepping 12
11355 > collect $pc, arr[i]
11360 @kindex collect @r{(tracepoints)}
11361 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11362 Collect values of the given expressions when the tracepoint is hit.
11363 This command accepts a comma-separated list of any valid expressions.
11364 In addition to global, static, or local variables, the following
11365 special arguments are supported:
11369 Collect all registers.
11372 Collect all function arguments.
11375 Collect all local variables.
11378 Collect the return address. This is helpful if you want to see more
11382 Collects the number of arguments from the static probe at which the
11383 tracepoint is located.
11384 @xref{Static Probe Points}.
11386 @item $_probe_arg@var{n}
11387 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
11388 from the static probe at which the tracepoint is located.
11389 @xref{Static Probe Points}.
11392 @vindex $_sdata@r{, collect}
11393 Collect static tracepoint marker specific data. Only available for
11394 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
11395 Lists}. On the UST static tracepoints library backend, an
11396 instrumentation point resembles a @code{printf} function call. The
11397 tracing library is able to collect user specified data formatted to a
11398 character string using the format provided by the programmer that
11399 instrumented the program. Other backends have similar mechanisms.
11400 Here's an example of a UST marker call:
11403 const char master_name[] = "$your_name";
11404 trace_mark(channel1, marker1, "hello %s", master_name)
11407 In this case, collecting @code{$_sdata} collects the string
11408 @samp{hello $yourname}. When analyzing the trace buffer, you can
11409 inspect @samp{$_sdata} like any other variable available to
11413 You can give several consecutive @code{collect} commands, each one
11414 with a single argument, or one @code{collect} command with several
11415 arguments separated by commas; the effect is the same.
11417 The optional @var{mods} changes the usual handling of the arguments.
11418 @code{s} requests that pointers to chars be handled as strings, in
11419 particular collecting the contents of the memory being pointed at, up
11420 to the first zero. The upper bound is by default the value of the
11421 @code{print elements} variable; if @code{s} is followed by a decimal
11422 number, that is the upper bound instead. So for instance
11423 @samp{collect/s25 mystr} collects as many as 25 characters at
11426 The command @code{info scope} (@pxref{Symbols, info scope}) is
11427 particularly useful for figuring out what data to collect.
11429 @kindex teval @r{(tracepoints)}
11430 @item teval @var{expr1}, @var{expr2}, @dots{}
11431 Evaluate the given expressions when the tracepoint is hit. This
11432 command accepts a comma-separated list of expressions. The results
11433 are discarded, so this is mainly useful for assigning values to trace
11434 state variables (@pxref{Trace State Variables}) without adding those
11435 values to the trace buffer, as would be the case if the @code{collect}
11438 @kindex while-stepping @r{(tracepoints)}
11439 @item while-stepping @var{n}
11440 Perform @var{n} single-step instruction traces after the tracepoint,
11441 collecting new data after each step. The @code{while-stepping}
11442 command is followed by the list of what to collect while stepping
11443 (followed by its own @code{end} command):
11446 > while-stepping 12
11447 > collect $regs, myglobal
11453 Note that @code{$pc} is not automatically collected by
11454 @code{while-stepping}; you need to explicitly collect that register if
11455 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
11458 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
11459 @kindex set default-collect
11460 @cindex default collection action
11461 This variable is a list of expressions to collect at each tracepoint
11462 hit. It is effectively an additional @code{collect} action prepended
11463 to every tracepoint action list. The expressions are parsed
11464 individually for each tracepoint, so for instance a variable named
11465 @code{xyz} may be interpreted as a global for one tracepoint, and a
11466 local for another, as appropriate to the tracepoint's location.
11468 @item show default-collect
11469 @kindex show default-collect
11470 Show the list of expressions that are collected by default at each
11475 @node Listing Tracepoints
11476 @subsection Listing Tracepoints
11479 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
11480 @kindex info tp @r{[}@var{n}@dots{}@r{]}
11481 @cindex information about tracepoints
11482 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
11483 Display information about the tracepoint @var{num}. If you don't
11484 specify a tracepoint number, displays information about all the
11485 tracepoints defined so far. The format is similar to that used for
11486 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
11487 command, simply restricting itself to tracepoints.
11489 A tracepoint's listing may include additional information specific to
11494 its passcount as given by the @code{passcount @var{n}} command
11497 the state about installed on target of each location
11501 (@value{GDBP}) @b{info trace}
11502 Num Type Disp Enb Address What
11503 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
11505 collect globfoo, $regs
11510 2 tracepoint keep y <MULTIPLE>
11512 2.1 y 0x0804859c in func4 at change-loc.h:35
11513 installed on target
11514 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
11515 installed on target
11516 2.3 y <PENDING> set_tracepoint
11517 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
11518 not installed on target
11523 This command can be abbreviated @code{info tp}.
11526 @node Listing Static Tracepoint Markers
11527 @subsection Listing Static Tracepoint Markers
11530 @kindex info static-tracepoint-markers
11531 @cindex information about static tracepoint markers
11532 @item info static-tracepoint-markers
11533 Display information about all static tracepoint markers defined in the
11536 For each marker, the following columns are printed:
11540 An incrementing counter, output to help readability. This is not a
11543 The marker ID, as reported by the target.
11544 @item Enabled or Disabled
11545 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
11546 that are not enabled.
11548 Where the marker is in your program, as a memory address.
11550 Where the marker is in the source for your program, as a file and line
11551 number. If the debug information included in the program does not
11552 allow @value{GDBN} to locate the source of the marker, this column
11553 will be left blank.
11557 In addition, the following information may be printed for each marker:
11561 User data passed to the tracing library by the marker call. In the
11562 UST backend, this is the format string passed as argument to the
11564 @item Static tracepoints probing the marker
11565 The list of static tracepoints attached to the marker.
11569 (@value{GDBP}) info static-tracepoint-markers
11570 Cnt ID Enb Address What
11571 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
11572 Data: number1 %d number2 %d
11573 Probed by static tracepoints: #2
11574 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
11580 @node Starting and Stopping Trace Experiments
11581 @subsection Starting and Stopping Trace Experiments
11584 @kindex tstart [ @var{notes} ]
11585 @cindex start a new trace experiment
11586 @cindex collected data discarded
11588 This command starts the trace experiment, and begins collecting data.
11589 It has the side effect of discarding all the data collected in the
11590 trace buffer during the previous trace experiment. If any arguments
11591 are supplied, they are taken as a note and stored with the trace
11592 experiment's state. The notes may be arbitrary text, and are
11593 especially useful with disconnected tracing in a multi-user context;
11594 the notes can explain what the trace is doing, supply user contact
11595 information, and so forth.
11597 @kindex tstop [ @var{notes} ]
11598 @cindex stop a running trace experiment
11600 This command stops the trace experiment. If any arguments are
11601 supplied, they are recorded with the experiment as a note. This is
11602 useful if you are stopping a trace started by someone else, for
11603 instance if the trace is interfering with the system's behavior and
11604 needs to be stopped quickly.
11606 @strong{Note}: a trace experiment and data collection may stop
11607 automatically if any tracepoint's passcount is reached
11608 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
11611 @cindex status of trace data collection
11612 @cindex trace experiment, status of
11614 This command displays the status of the current trace data
11618 Here is an example of the commands we described so far:
11621 (@value{GDBP}) @b{trace gdb_c_test}
11622 (@value{GDBP}) @b{actions}
11623 Enter actions for tracepoint #1, one per line.
11624 > collect $regs,$locals,$args
11625 > while-stepping 11
11629 (@value{GDBP}) @b{tstart}
11630 [time passes @dots{}]
11631 (@value{GDBP}) @b{tstop}
11634 @anchor{disconnected tracing}
11635 @cindex disconnected tracing
11636 You can choose to continue running the trace experiment even if
11637 @value{GDBN} disconnects from the target, voluntarily or
11638 involuntarily. For commands such as @code{detach}, the debugger will
11639 ask what you want to do with the trace. But for unexpected
11640 terminations (@value{GDBN} crash, network outage), it would be
11641 unfortunate to lose hard-won trace data, so the variable
11642 @code{disconnected-tracing} lets you decide whether the trace should
11643 continue running without @value{GDBN}.
11646 @item set disconnected-tracing on
11647 @itemx set disconnected-tracing off
11648 @kindex set disconnected-tracing
11649 Choose whether a tracing run should continue to run if @value{GDBN}
11650 has disconnected from the target. Note that @code{detach} or
11651 @code{quit} will ask you directly what to do about a running trace no
11652 matter what this variable's setting, so the variable is mainly useful
11653 for handling unexpected situations, such as loss of the network.
11655 @item show disconnected-tracing
11656 @kindex show disconnected-tracing
11657 Show the current choice for disconnected tracing.
11661 When you reconnect to the target, the trace experiment may or may not
11662 still be running; it might have filled the trace buffer in the
11663 meantime, or stopped for one of the other reasons. If it is running,
11664 it will continue after reconnection.
11666 Upon reconnection, the target will upload information about the
11667 tracepoints in effect. @value{GDBN} will then compare that
11668 information to the set of tracepoints currently defined, and attempt
11669 to match them up, allowing for the possibility that the numbers may
11670 have changed due to creation and deletion in the meantime. If one of
11671 the target's tracepoints does not match any in @value{GDBN}, the
11672 debugger will create a new tracepoint, so that you have a number with
11673 which to specify that tracepoint. This matching-up process is
11674 necessarily heuristic, and it may result in useless tracepoints being
11675 created; you may simply delete them if they are of no use.
11677 @cindex circular trace buffer
11678 If your target agent supports a @dfn{circular trace buffer}, then you
11679 can run a trace experiment indefinitely without filling the trace
11680 buffer; when space runs out, the agent deletes already-collected trace
11681 frames, oldest first, until there is enough room to continue
11682 collecting. This is especially useful if your tracepoints are being
11683 hit too often, and your trace gets terminated prematurely because the
11684 buffer is full. To ask for a circular trace buffer, simply set
11685 @samp{circular-trace-buffer} to on. You can set this at any time,
11686 including during tracing; if the agent can do it, it will change
11687 buffer handling on the fly, otherwise it will not take effect until
11691 @item set circular-trace-buffer on
11692 @itemx set circular-trace-buffer off
11693 @kindex set circular-trace-buffer
11694 Choose whether a tracing run should use a linear or circular buffer
11695 for trace data. A linear buffer will not lose any trace data, but may
11696 fill up prematurely, while a circular buffer will discard old trace
11697 data, but it will have always room for the latest tracepoint hits.
11699 @item show circular-trace-buffer
11700 @kindex show circular-trace-buffer
11701 Show the current choice for the trace buffer. Note that this may not
11702 match the agent's current buffer handling, nor is it guaranteed to
11703 match the setting that might have been in effect during a past run,
11704 for instance if you are looking at frames from a trace file.
11709 @item set trace-user @var{text}
11710 @kindex set trace-user
11712 @item show trace-user
11713 @kindex show trace-user
11715 @item set trace-notes @var{text}
11716 @kindex set trace-notes
11717 Set the trace run's notes.
11719 @item show trace-notes
11720 @kindex show trace-notes
11721 Show the trace run's notes.
11723 @item set trace-stop-notes @var{text}
11724 @kindex set trace-stop-notes
11725 Set the trace run's stop notes. The handling of the note is as for
11726 @code{tstop} arguments; the set command is convenient way to fix a
11727 stop note that is mistaken or incomplete.
11729 @item show trace-stop-notes
11730 @kindex show trace-stop-notes
11731 Show the trace run's stop notes.
11735 @node Tracepoint Restrictions
11736 @subsection Tracepoint Restrictions
11738 @cindex tracepoint restrictions
11739 There are a number of restrictions on the use of tracepoints. As
11740 described above, tracepoint data gathering occurs on the target
11741 without interaction from @value{GDBN}. Thus the full capabilities of
11742 the debugger are not available during data gathering, and then at data
11743 examination time, you will be limited by only having what was
11744 collected. The following items describe some common problems, but it
11745 is not exhaustive, and you may run into additional difficulties not
11751 Tracepoint expressions are intended to gather objects (lvalues). Thus
11752 the full flexibility of GDB's expression evaluator is not available.
11753 You cannot call functions, cast objects to aggregate types, access
11754 convenience variables or modify values (except by assignment to trace
11755 state variables). Some language features may implicitly call
11756 functions (for instance Objective-C fields with accessors), and therefore
11757 cannot be collected either.
11760 Collection of local variables, either individually or in bulk with
11761 @code{$locals} or @code{$args}, during @code{while-stepping} may
11762 behave erratically. The stepping action may enter a new scope (for
11763 instance by stepping into a function), or the location of the variable
11764 may change (for instance it is loaded into a register). The
11765 tracepoint data recorded uses the location information for the
11766 variables that is correct for the tracepoint location. When the
11767 tracepoint is created, it is not possible, in general, to determine
11768 where the steps of a @code{while-stepping} sequence will advance the
11769 program---particularly if a conditional branch is stepped.
11772 Collection of an incompletely-initialized or partially-destroyed object
11773 may result in something that @value{GDBN} cannot display, or displays
11774 in a misleading way.
11777 When @value{GDBN} displays a pointer to character it automatically
11778 dereferences the pointer to also display characters of the string
11779 being pointed to. However, collecting the pointer during tracing does
11780 not automatically collect the string. You need to explicitly
11781 dereference the pointer and provide size information if you want to
11782 collect not only the pointer, but the memory pointed to. For example,
11783 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11787 It is not possible to collect a complete stack backtrace at a
11788 tracepoint. Instead, you may collect the registers and a few hundred
11789 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11790 (adjust to use the name of the actual stack pointer register on your
11791 target architecture, and the amount of stack you wish to capture).
11792 Then the @code{backtrace} command will show a partial backtrace when
11793 using a trace frame. The number of stack frames that can be examined
11794 depends on the sizes of the frames in the collected stack. Note that
11795 if you ask for a block so large that it goes past the bottom of the
11796 stack, the target agent may report an error trying to read from an
11800 If you do not collect registers at a tracepoint, @value{GDBN} can
11801 infer that the value of @code{$pc} must be the same as the address of
11802 the tracepoint and use that when you are looking at a trace frame
11803 for that tracepoint. However, this cannot work if the tracepoint has
11804 multiple locations (for instance if it was set in a function that was
11805 inlined), or if it has a @code{while-stepping} loop. In those cases
11806 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11811 @node Analyze Collected Data
11812 @section Using the Collected Data
11814 After the tracepoint experiment ends, you use @value{GDBN} commands
11815 for examining the trace data. The basic idea is that each tracepoint
11816 collects a trace @dfn{snapshot} every time it is hit and another
11817 snapshot every time it single-steps. All these snapshots are
11818 consecutively numbered from zero and go into a buffer, and you can
11819 examine them later. The way you examine them is to @dfn{focus} on a
11820 specific trace snapshot. When the remote stub is focused on a trace
11821 snapshot, it will respond to all @value{GDBN} requests for memory and
11822 registers by reading from the buffer which belongs to that snapshot,
11823 rather than from @emph{real} memory or registers of the program being
11824 debugged. This means that @strong{all} @value{GDBN} commands
11825 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11826 behave as if we were currently debugging the program state as it was
11827 when the tracepoint occurred. Any requests for data that are not in
11828 the buffer will fail.
11831 * tfind:: How to select a trace snapshot
11832 * tdump:: How to display all data for a snapshot
11833 * save tracepoints:: How to save tracepoints for a future run
11837 @subsection @code{tfind @var{n}}
11840 @cindex select trace snapshot
11841 @cindex find trace snapshot
11842 The basic command for selecting a trace snapshot from the buffer is
11843 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11844 counting from zero. If no argument @var{n} is given, the next
11845 snapshot is selected.
11847 Here are the various forms of using the @code{tfind} command.
11851 Find the first snapshot in the buffer. This is a synonym for
11852 @code{tfind 0} (since 0 is the number of the first snapshot).
11855 Stop debugging trace snapshots, resume @emph{live} debugging.
11858 Same as @samp{tfind none}.
11861 No argument means find the next trace snapshot.
11864 Find the previous trace snapshot before the current one. This permits
11865 retracing earlier steps.
11867 @item tfind tracepoint @var{num}
11868 Find the next snapshot associated with tracepoint @var{num}. Search
11869 proceeds forward from the last examined trace snapshot. If no
11870 argument @var{num} is given, it means find the next snapshot collected
11871 for the same tracepoint as the current snapshot.
11873 @item tfind pc @var{addr}
11874 Find the next snapshot associated with the value @var{addr} of the
11875 program counter. Search proceeds forward from the last examined trace
11876 snapshot. If no argument @var{addr} is given, it means find the next
11877 snapshot with the same value of PC as the current snapshot.
11879 @item tfind outside @var{addr1}, @var{addr2}
11880 Find the next snapshot whose PC is outside the given range of
11881 addresses (exclusive).
11883 @item tfind range @var{addr1}, @var{addr2}
11884 Find the next snapshot whose PC is between @var{addr1} and
11885 @var{addr2} (inclusive).
11887 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11888 Find the next snapshot associated with the source line @var{n}. If
11889 the optional argument @var{file} is given, refer to line @var{n} in
11890 that source file. Search proceeds forward from the last examined
11891 trace snapshot. If no argument @var{n} is given, it means find the
11892 next line other than the one currently being examined; thus saying
11893 @code{tfind line} repeatedly can appear to have the same effect as
11894 stepping from line to line in a @emph{live} debugging session.
11897 The default arguments for the @code{tfind} commands are specifically
11898 designed to make it easy to scan through the trace buffer. For
11899 instance, @code{tfind} with no argument selects the next trace
11900 snapshot, and @code{tfind -} with no argument selects the previous
11901 trace snapshot. So, by giving one @code{tfind} command, and then
11902 simply hitting @key{RET} repeatedly you can examine all the trace
11903 snapshots in order. Or, by saying @code{tfind -} and then hitting
11904 @key{RET} repeatedly you can examine the snapshots in reverse order.
11905 The @code{tfind line} command with no argument selects the snapshot
11906 for the next source line executed. The @code{tfind pc} command with
11907 no argument selects the next snapshot with the same program counter
11908 (PC) as the current frame. The @code{tfind tracepoint} command with
11909 no argument selects the next trace snapshot collected by the same
11910 tracepoint as the current one.
11912 In addition to letting you scan through the trace buffer manually,
11913 these commands make it easy to construct @value{GDBN} scripts that
11914 scan through the trace buffer and print out whatever collected data
11915 you are interested in. Thus, if we want to examine the PC, FP, and SP
11916 registers from each trace frame in the buffer, we can say this:
11919 (@value{GDBP}) @b{tfind start}
11920 (@value{GDBP}) @b{while ($trace_frame != -1)}
11921 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11922 $trace_frame, $pc, $sp, $fp
11926 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11927 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11928 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11929 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11930 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11931 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11932 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11933 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11934 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11935 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11936 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11939 Or, if we want to examine the variable @code{X} at each source line in
11943 (@value{GDBP}) @b{tfind start}
11944 (@value{GDBP}) @b{while ($trace_frame != -1)}
11945 > printf "Frame %d, X == %d\n", $trace_frame, X
11955 @subsection @code{tdump}
11957 @cindex dump all data collected at tracepoint
11958 @cindex tracepoint data, display
11960 This command takes no arguments. It prints all the data collected at
11961 the current trace snapshot.
11964 (@value{GDBP}) @b{trace 444}
11965 (@value{GDBP}) @b{actions}
11966 Enter actions for tracepoint #2, one per line:
11967 > collect $regs, $locals, $args, gdb_long_test
11970 (@value{GDBP}) @b{tstart}
11972 (@value{GDBP}) @b{tfind line 444}
11973 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11975 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11977 (@value{GDBP}) @b{tdump}
11978 Data collected at tracepoint 2, trace frame 1:
11979 d0 0xc4aa0085 -995491707
11983 d4 0x71aea3d 119204413
11986 d7 0x380035 3670069
11987 a0 0x19e24a 1696330
11988 a1 0x3000668 50333288
11990 a3 0x322000 3284992
11991 a4 0x3000698 50333336
11992 a5 0x1ad3cc 1758156
11993 fp 0x30bf3c 0x30bf3c
11994 sp 0x30bf34 0x30bf34
11996 pc 0x20b2c8 0x20b2c8
12000 p = 0x20e5b4 "gdb-test"
12007 gdb_long_test = 17 '\021'
12012 @code{tdump} works by scanning the tracepoint's current collection
12013 actions and printing the value of each expression listed. So
12014 @code{tdump} can fail, if after a run, you change the tracepoint's
12015 actions to mention variables that were not collected during the run.
12017 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12018 uses the collected value of @code{$pc} to distinguish between trace
12019 frames that were collected at the tracepoint hit, and frames that were
12020 collected while stepping. This allows it to correctly choose whether
12021 to display the basic list of collections, or the collections from the
12022 body of the while-stepping loop. However, if @code{$pc} was not collected,
12023 then @code{tdump} will always attempt to dump using the basic collection
12024 list, and may fail if a while-stepping frame does not include all the
12025 same data that is collected at the tracepoint hit.
12026 @c This is getting pretty arcane, example would be good.
12028 @node save tracepoints
12029 @subsection @code{save tracepoints @var{filename}}
12030 @kindex save tracepoints
12031 @kindex save-tracepoints
12032 @cindex save tracepoints for future sessions
12034 This command saves all current tracepoint definitions together with
12035 their actions and passcounts, into a file @file{@var{filename}}
12036 suitable for use in a later debugging session. To read the saved
12037 tracepoint definitions, use the @code{source} command (@pxref{Command
12038 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12039 alias for @w{@code{save tracepoints}}
12041 @node Tracepoint Variables
12042 @section Convenience Variables for Tracepoints
12043 @cindex tracepoint variables
12044 @cindex convenience variables for tracepoints
12047 @vindex $trace_frame
12048 @item (int) $trace_frame
12049 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12050 snapshot is selected.
12052 @vindex $tracepoint
12053 @item (int) $tracepoint
12054 The tracepoint for the current trace snapshot.
12056 @vindex $trace_line
12057 @item (int) $trace_line
12058 The line number for the current trace snapshot.
12060 @vindex $trace_file
12061 @item (char []) $trace_file
12062 The source file for the current trace snapshot.
12064 @vindex $trace_func
12065 @item (char []) $trace_func
12066 The name of the function containing @code{$tracepoint}.
12069 Note: @code{$trace_file} is not suitable for use in @code{printf},
12070 use @code{output} instead.
12072 Here's a simple example of using these convenience variables for
12073 stepping through all the trace snapshots and printing some of their
12074 data. Note that these are not the same as trace state variables,
12075 which are managed by the target.
12078 (@value{GDBP}) @b{tfind start}
12080 (@value{GDBP}) @b{while $trace_frame != -1}
12081 > output $trace_file
12082 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12088 @section Using Trace Files
12089 @cindex trace files
12091 In some situations, the target running a trace experiment may no
12092 longer be available; perhaps it crashed, or the hardware was needed
12093 for a different activity. To handle these cases, you can arrange to
12094 dump the trace data into a file, and later use that file as a source
12095 of trace data, via the @code{target tfile} command.
12100 @item tsave [ -r ] @var{filename}
12101 Save the trace data to @var{filename}. By default, this command
12102 assumes that @var{filename} refers to the host filesystem, so if
12103 necessary @value{GDBN} will copy raw trace data up from the target and
12104 then save it. If the target supports it, you can also supply the
12105 optional argument @code{-r} (``remote'') to direct the target to save
12106 the data directly into @var{filename} in its own filesystem, which may be
12107 more efficient if the trace buffer is very large. (Note, however, that
12108 @code{target tfile} can only read from files accessible to the host.)
12110 @kindex target tfile
12112 @item target tfile @var{filename}
12113 Use the file named @var{filename} as a source of trace data. Commands
12114 that examine data work as they do with a live target, but it is not
12115 possible to run any new trace experiments. @code{tstatus} will report
12116 the state of the trace run at the moment the data was saved, as well
12117 as the current trace frame you are examining. @var{filename} must be
12118 on a filesystem accessible to the host.
12123 @chapter Debugging Programs That Use Overlays
12126 If your program is too large to fit completely in your target system's
12127 memory, you can sometimes use @dfn{overlays} to work around this
12128 problem. @value{GDBN} provides some support for debugging programs that
12132 * How Overlays Work:: A general explanation of overlays.
12133 * Overlay Commands:: Managing overlays in @value{GDBN}.
12134 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12135 mapped by asking the inferior.
12136 * Overlay Sample Program:: A sample program using overlays.
12139 @node How Overlays Work
12140 @section How Overlays Work
12141 @cindex mapped overlays
12142 @cindex unmapped overlays
12143 @cindex load address, overlay's
12144 @cindex mapped address
12145 @cindex overlay area
12147 Suppose you have a computer whose instruction address space is only 64
12148 kilobytes long, but which has much more memory which can be accessed by
12149 other means: special instructions, segment registers, or memory
12150 management hardware, for example. Suppose further that you want to
12151 adapt a program which is larger than 64 kilobytes to run on this system.
12153 One solution is to identify modules of your program which are relatively
12154 independent, and need not call each other directly; call these modules
12155 @dfn{overlays}. Separate the overlays from the main program, and place
12156 their machine code in the larger memory. Place your main program in
12157 instruction memory, but leave at least enough space there to hold the
12158 largest overlay as well.
12160 Now, to call a function located in an overlay, you must first copy that
12161 overlay's machine code from the large memory into the space set aside
12162 for it in the instruction memory, and then jump to its entry point
12165 @c NB: In the below the mapped area's size is greater or equal to the
12166 @c size of all overlays. This is intentional to remind the developer
12167 @c that overlays don't necessarily need to be the same size.
12171 Data Instruction Larger
12172 Address Space Address Space Address Space
12173 +-----------+ +-----------+ +-----------+
12175 +-----------+ +-----------+ +-----------+<-- overlay 1
12176 | program | | main | .----| overlay 1 | load address
12177 | variables | | program | | +-----------+
12178 | and heap | | | | | |
12179 +-----------+ | | | +-----------+<-- overlay 2
12180 | | +-----------+ | | | load address
12181 +-----------+ | | | .-| overlay 2 |
12183 mapped --->+-----------+ | | +-----------+
12184 address | | | | | |
12185 | overlay | <-' | | |
12186 | area | <---' +-----------+<-- overlay 3
12187 | | <---. | | load address
12188 +-----------+ `--| overlay 3 |
12195 @anchor{A code overlay}A code overlay
12199 The diagram (@pxref{A code overlay}) shows a system with separate data
12200 and instruction address spaces. To map an overlay, the program copies
12201 its code from the larger address space to the instruction address space.
12202 Since the overlays shown here all use the same mapped address, only one
12203 may be mapped at a time. For a system with a single address space for
12204 data and instructions, the diagram would be similar, except that the
12205 program variables and heap would share an address space with the main
12206 program and the overlay area.
12208 An overlay loaded into instruction memory and ready for use is called a
12209 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12210 instruction memory. An overlay not present (or only partially present)
12211 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12212 is its address in the larger memory. The mapped address is also called
12213 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12214 called the @dfn{load memory address}, or @dfn{LMA}.
12216 Unfortunately, overlays are not a completely transparent way to adapt a
12217 program to limited instruction memory. They introduce a new set of
12218 global constraints you must keep in mind as you design your program:
12223 Before calling or returning to a function in an overlay, your program
12224 must make sure that overlay is actually mapped. Otherwise, the call or
12225 return will transfer control to the right address, but in the wrong
12226 overlay, and your program will probably crash.
12229 If the process of mapping an overlay is expensive on your system, you
12230 will need to choose your overlays carefully to minimize their effect on
12231 your program's performance.
12234 The executable file you load onto your system must contain each
12235 overlay's instructions, appearing at the overlay's load address, not its
12236 mapped address. However, each overlay's instructions must be relocated
12237 and its symbols defined as if the overlay were at its mapped address.
12238 You can use GNU linker scripts to specify different load and relocation
12239 addresses for pieces of your program; see @ref{Overlay Description,,,
12240 ld.info, Using ld: the GNU linker}.
12243 The procedure for loading executable files onto your system must be able
12244 to load their contents into the larger address space as well as the
12245 instruction and data spaces.
12249 The overlay system described above is rather simple, and could be
12250 improved in many ways:
12255 If your system has suitable bank switch registers or memory management
12256 hardware, you could use those facilities to make an overlay's load area
12257 contents simply appear at their mapped address in instruction space.
12258 This would probably be faster than copying the overlay to its mapped
12259 area in the usual way.
12262 If your overlays are small enough, you could set aside more than one
12263 overlay area, and have more than one overlay mapped at a time.
12266 You can use overlays to manage data, as well as instructions. In
12267 general, data overlays are even less transparent to your design than
12268 code overlays: whereas code overlays only require care when you call or
12269 return to functions, data overlays require care every time you access
12270 the data. Also, if you change the contents of a data overlay, you
12271 must copy its contents back out to its load address before you can copy a
12272 different data overlay into the same mapped area.
12277 @node Overlay Commands
12278 @section Overlay Commands
12280 To use @value{GDBN}'s overlay support, each overlay in your program must
12281 correspond to a separate section of the executable file. The section's
12282 virtual memory address and load memory address must be the overlay's
12283 mapped and load addresses. Identifying overlays with sections allows
12284 @value{GDBN} to determine the appropriate address of a function or
12285 variable, depending on whether the overlay is mapped or not.
12287 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12288 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12293 Disable @value{GDBN}'s overlay support. When overlay support is
12294 disabled, @value{GDBN} assumes that all functions and variables are
12295 always present at their mapped addresses. By default, @value{GDBN}'s
12296 overlay support is disabled.
12298 @item overlay manual
12299 @cindex manual overlay debugging
12300 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12301 relies on you to tell it which overlays are mapped, and which are not,
12302 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12303 commands described below.
12305 @item overlay map-overlay @var{overlay}
12306 @itemx overlay map @var{overlay}
12307 @cindex map an overlay
12308 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12309 be the name of the object file section containing the overlay. When an
12310 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12311 functions and variables at their mapped addresses. @value{GDBN} assumes
12312 that any other overlays whose mapped ranges overlap that of
12313 @var{overlay} are now unmapped.
12315 @item overlay unmap-overlay @var{overlay}
12316 @itemx overlay unmap @var{overlay}
12317 @cindex unmap an overlay
12318 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
12319 must be the name of the object file section containing the overlay.
12320 When an overlay is unmapped, @value{GDBN} assumes it can find the
12321 overlay's functions and variables at their load addresses.
12324 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
12325 consults a data structure the overlay manager maintains in the inferior
12326 to see which overlays are mapped. For details, see @ref{Automatic
12327 Overlay Debugging}.
12329 @item overlay load-target
12330 @itemx overlay load
12331 @cindex reloading the overlay table
12332 Re-read the overlay table from the inferior. Normally, @value{GDBN}
12333 re-reads the table @value{GDBN} automatically each time the inferior
12334 stops, so this command should only be necessary if you have changed the
12335 overlay mapping yourself using @value{GDBN}. This command is only
12336 useful when using automatic overlay debugging.
12338 @item overlay list-overlays
12339 @itemx overlay list
12340 @cindex listing mapped overlays
12341 Display a list of the overlays currently mapped, along with their mapped
12342 addresses, load addresses, and sizes.
12346 Normally, when @value{GDBN} prints a code address, it includes the name
12347 of the function the address falls in:
12350 (@value{GDBP}) print main
12351 $3 = @{int ()@} 0x11a0 <main>
12354 When overlay debugging is enabled, @value{GDBN} recognizes code in
12355 unmapped overlays, and prints the names of unmapped functions with
12356 asterisks around them. For example, if @code{foo} is a function in an
12357 unmapped overlay, @value{GDBN} prints it this way:
12360 (@value{GDBP}) overlay list
12361 No sections are mapped.
12362 (@value{GDBP}) print foo
12363 $5 = @{int (int)@} 0x100000 <*foo*>
12366 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
12370 (@value{GDBP}) overlay list
12371 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
12372 mapped at 0x1016 - 0x104a
12373 (@value{GDBP}) print foo
12374 $6 = @{int (int)@} 0x1016 <foo>
12377 When overlay debugging is enabled, @value{GDBN} can find the correct
12378 address for functions and variables in an overlay, whether or not the
12379 overlay is mapped. This allows most @value{GDBN} commands, like
12380 @code{break} and @code{disassemble}, to work normally, even on unmapped
12381 code. However, @value{GDBN}'s breakpoint support has some limitations:
12385 @cindex breakpoints in overlays
12386 @cindex overlays, setting breakpoints in
12387 You can set breakpoints in functions in unmapped overlays, as long as
12388 @value{GDBN} can write to the overlay at its load address.
12390 @value{GDBN} can not set hardware or simulator-based breakpoints in
12391 unmapped overlays. However, if you set a breakpoint at the end of your
12392 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
12393 you are using manual overlay management), @value{GDBN} will re-set its
12394 breakpoints properly.
12398 @node Automatic Overlay Debugging
12399 @section Automatic Overlay Debugging
12400 @cindex automatic overlay debugging
12402 @value{GDBN} can automatically track which overlays are mapped and which
12403 are not, given some simple co-operation from the overlay manager in the
12404 inferior. If you enable automatic overlay debugging with the
12405 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
12406 looks in the inferior's memory for certain variables describing the
12407 current state of the overlays.
12409 Here are the variables your overlay manager must define to support
12410 @value{GDBN}'s automatic overlay debugging:
12414 @item @code{_ovly_table}:
12415 This variable must be an array of the following structures:
12420 /* The overlay's mapped address. */
12423 /* The size of the overlay, in bytes. */
12424 unsigned long size;
12426 /* The overlay's load address. */
12429 /* Non-zero if the overlay is currently mapped;
12431 unsigned long mapped;
12435 @item @code{_novlys}:
12436 This variable must be a four-byte signed integer, holding the total
12437 number of elements in @code{_ovly_table}.
12441 To decide whether a particular overlay is mapped or not, @value{GDBN}
12442 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
12443 @code{lma} members equal the VMA and LMA of the overlay's section in the
12444 executable file. When @value{GDBN} finds a matching entry, it consults
12445 the entry's @code{mapped} member to determine whether the overlay is
12448 In addition, your overlay manager may define a function called
12449 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
12450 will silently set a breakpoint there. If the overlay manager then
12451 calls this function whenever it has changed the overlay table, this
12452 will enable @value{GDBN} to accurately keep track of which overlays
12453 are in program memory, and update any breakpoints that may be set
12454 in overlays. This will allow breakpoints to work even if the
12455 overlays are kept in ROM or other non-writable memory while they
12456 are not being executed.
12458 @node Overlay Sample Program
12459 @section Overlay Sample Program
12460 @cindex overlay example program
12462 When linking a program which uses overlays, you must place the overlays
12463 at their load addresses, while relocating them to run at their mapped
12464 addresses. To do this, you must write a linker script (@pxref{Overlay
12465 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
12466 since linker scripts are specific to a particular host system, target
12467 architecture, and target memory layout, this manual cannot provide
12468 portable sample code demonstrating @value{GDBN}'s overlay support.
12470 However, the @value{GDBN} source distribution does contain an overlaid
12471 program, with linker scripts for a few systems, as part of its test
12472 suite. The program consists of the following files from
12473 @file{gdb/testsuite/gdb.base}:
12477 The main program file.
12479 A simple overlay manager, used by @file{overlays.c}.
12484 Overlay modules, loaded and used by @file{overlays.c}.
12487 Linker scripts for linking the test program on the @code{d10v-elf}
12488 and @code{m32r-elf} targets.
12491 You can build the test program using the @code{d10v-elf} GCC
12492 cross-compiler like this:
12495 $ d10v-elf-gcc -g -c overlays.c
12496 $ d10v-elf-gcc -g -c ovlymgr.c
12497 $ d10v-elf-gcc -g -c foo.c
12498 $ d10v-elf-gcc -g -c bar.c
12499 $ d10v-elf-gcc -g -c baz.c
12500 $ d10v-elf-gcc -g -c grbx.c
12501 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
12502 baz.o grbx.o -Wl,-Td10v.ld -o overlays
12505 The build process is identical for any other architecture, except that
12506 you must substitute the appropriate compiler and linker script for the
12507 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
12511 @chapter Using @value{GDBN} with Different Languages
12514 Although programming languages generally have common aspects, they are
12515 rarely expressed in the same manner. For instance, in ANSI C,
12516 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
12517 Modula-2, it is accomplished by @code{p^}. Values can also be
12518 represented (and displayed) differently. Hex numbers in C appear as
12519 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
12521 @cindex working language
12522 Language-specific information is built into @value{GDBN} for some languages,
12523 allowing you to express operations like the above in your program's
12524 native language, and allowing @value{GDBN} to output values in a manner
12525 consistent with the syntax of your program's native language. The
12526 language you use to build expressions is called the @dfn{working
12530 * Setting:: Switching between source languages
12531 * Show:: Displaying the language
12532 * Checks:: Type and range checks
12533 * Supported Languages:: Supported languages
12534 * Unsupported Languages:: Unsupported languages
12538 @section Switching Between Source Languages
12540 There are two ways to control the working language---either have @value{GDBN}
12541 set it automatically, or select it manually yourself. You can use the
12542 @code{set language} command for either purpose. On startup, @value{GDBN}
12543 defaults to setting the language automatically. The working language is
12544 used to determine how expressions you type are interpreted, how values
12547 In addition to the working language, every source file that
12548 @value{GDBN} knows about has its own working language. For some object
12549 file formats, the compiler might indicate which language a particular
12550 source file is in. However, most of the time @value{GDBN} infers the
12551 language from the name of the file. The language of a source file
12552 controls whether C@t{++} names are demangled---this way @code{backtrace} can
12553 show each frame appropriately for its own language. There is no way to
12554 set the language of a source file from within @value{GDBN}, but you can
12555 set the language associated with a filename extension. @xref{Show, ,
12556 Displaying the Language}.
12558 This is most commonly a problem when you use a program, such
12559 as @code{cfront} or @code{f2c}, that generates C but is written in
12560 another language. In that case, make the
12561 program use @code{#line} directives in its C output; that way
12562 @value{GDBN} will know the correct language of the source code of the original
12563 program, and will display that source code, not the generated C code.
12566 * Filenames:: Filename extensions and languages.
12567 * Manually:: Setting the working language manually
12568 * Automatically:: Having @value{GDBN} infer the source language
12572 @subsection List of Filename Extensions and Languages
12574 If a source file name ends in one of the following extensions, then
12575 @value{GDBN} infers that its language is the one indicated.
12593 C@t{++} source file
12599 Objective-C source file
12603 Fortran source file
12606 Modula-2 source file
12610 Assembler source file. This actually behaves almost like C, but
12611 @value{GDBN} does not skip over function prologues when stepping.
12614 In addition, you may set the language associated with a filename
12615 extension. @xref{Show, , Displaying the Language}.
12618 @subsection Setting the Working Language
12620 If you allow @value{GDBN} to set the language automatically,
12621 expressions are interpreted the same way in your debugging session and
12624 @kindex set language
12625 If you wish, you may set the language manually. To do this, issue the
12626 command @samp{set language @var{lang}}, where @var{lang} is the name of
12627 a language, such as
12628 @code{c} or @code{modula-2}.
12629 For a list of the supported languages, type @samp{set language}.
12631 Setting the language manually prevents @value{GDBN} from updating the working
12632 language automatically. This can lead to confusion if you try
12633 to debug a program when the working language is not the same as the
12634 source language, when an expression is acceptable to both
12635 languages---but means different things. For instance, if the current
12636 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12644 might not have the effect you intended. In C, this means to add
12645 @code{b} and @code{c} and place the result in @code{a}. The result
12646 printed would be the value of @code{a}. In Modula-2, this means to compare
12647 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12649 @node Automatically
12650 @subsection Having @value{GDBN} Infer the Source Language
12652 To have @value{GDBN} set the working language automatically, use
12653 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12654 then infers the working language. That is, when your program stops in a
12655 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12656 working language to the language recorded for the function in that
12657 frame. If the language for a frame is unknown (that is, if the function
12658 or block corresponding to the frame was defined in a source file that
12659 does not have a recognized extension), the current working language is
12660 not changed, and @value{GDBN} issues a warning.
12662 This may not seem necessary for most programs, which are written
12663 entirely in one source language. However, program modules and libraries
12664 written in one source language can be used by a main program written in
12665 a different source language. Using @samp{set language auto} in this
12666 case frees you from having to set the working language manually.
12669 @section Displaying the Language
12671 The following commands help you find out which language is the
12672 working language, and also what language source files were written in.
12675 @item show language
12676 @kindex show language
12677 Display the current working language. This is the
12678 language you can use with commands such as @code{print} to
12679 build and compute expressions that may involve variables in your program.
12682 @kindex info frame@r{, show the source language}
12683 Display the source language for this frame. This language becomes the
12684 working language if you use an identifier from this frame.
12685 @xref{Frame Info, ,Information about a Frame}, to identify the other
12686 information listed here.
12689 @kindex info source@r{, show the source language}
12690 Display the source language of this source file.
12691 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12692 information listed here.
12695 In unusual circumstances, you may have source files with extensions
12696 not in the standard list. You can then set the extension associated
12697 with a language explicitly:
12700 @item set extension-language @var{ext} @var{language}
12701 @kindex set extension-language
12702 Tell @value{GDBN} that source files with extension @var{ext} are to be
12703 assumed as written in the source language @var{language}.
12705 @item info extensions
12706 @kindex info extensions
12707 List all the filename extensions and the associated languages.
12711 @section Type and Range Checking
12713 Some languages are designed to guard you against making seemingly common
12714 errors through a series of compile- and run-time checks. These include
12715 checking the type of arguments to functions and operators and making
12716 sure mathematical overflows are caught at run time. Checks such as
12717 these help to ensure a program's correctness once it has been compiled
12718 by eliminating type mismatches and providing active checks for range
12719 errors when your program is running.
12721 By default @value{GDBN} checks for these errors according to the
12722 rules of the current source language. Although @value{GDBN} does not check
12723 the statements in your program, it can check expressions entered directly
12724 into @value{GDBN} for evaluation via the @code{print} command, for example.
12727 * Type Checking:: An overview of type checking
12728 * Range Checking:: An overview of range checking
12731 @cindex type checking
12732 @cindex checks, type
12733 @node Type Checking
12734 @subsection An Overview of Type Checking
12736 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
12737 arguments to operators and functions have to be of the correct type,
12738 otherwise an error occurs. These checks prevent type mismatch
12739 errors from ever causing any run-time problems. For example,
12742 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
12744 (@value{GDBP}) print obj.my_method (0)
12747 (@value{GDBP}) print obj.my_method (0x1234)
12748 Cannot resolve method klass::my_method to any overloaded instance
12751 The second example fails because in C@t{++} the integer constant
12752 @samp{0x1234} is not type-compatible with the pointer parameter type.
12754 For the expressions you use in @value{GDBN} commands, you can tell
12755 @value{GDBN} to not enforce strict type checking or
12756 to treat any mismatches as errors and abandon the expression;
12757 When type checking is disabled, @value{GDBN} successfully evaluates
12758 expressions like the second example above.
12760 Even if type checking is off, there may be other reasons
12761 related to type that prevent @value{GDBN} from evaluating an expression.
12762 For instance, @value{GDBN} does not know how to add an @code{int} and
12763 a @code{struct foo}. These particular type errors have nothing to do
12764 with the language in use and usually arise from expressions which make
12765 little sense to evaluate anyway.
12767 @value{GDBN} provides some additional commands for controlling type checking:
12769 @kindex set check type
12770 @kindex show check type
12772 @item set check type on
12773 @itemx set check type off
12774 Set strict type checking on or off. If any type mismatches occur in
12775 evaluating an expression while type checking is on, @value{GDBN} prints a
12776 message and aborts evaluation of the expression.
12778 @item show check type
12779 Show the current setting of type checking and whether @value{GDBN}
12780 is enforcing strict type checking rules.
12783 @cindex range checking
12784 @cindex checks, range
12785 @node Range Checking
12786 @subsection An Overview of Range Checking
12788 In some languages (such as Modula-2), it is an error to exceed the
12789 bounds of a type; this is enforced with run-time checks. Such range
12790 checking is meant to ensure program correctness by making sure
12791 computations do not overflow, or indices on an array element access do
12792 not exceed the bounds of the array.
12794 For expressions you use in @value{GDBN} commands, you can tell
12795 @value{GDBN} to treat range errors in one of three ways: ignore them,
12796 always treat them as errors and abandon the expression, or issue
12797 warnings but evaluate the expression anyway.
12799 A range error can result from numerical overflow, from exceeding an
12800 array index bound, or when you type a constant that is not a member
12801 of any type. Some languages, however, do not treat overflows as an
12802 error. In many implementations of C, mathematical overflow causes the
12803 result to ``wrap around'' to lower values---for example, if @var{m} is
12804 the largest integer value, and @var{s} is the smallest, then
12807 @var{m} + 1 @result{} @var{s}
12810 This, too, is specific to individual languages, and in some cases
12811 specific to individual compilers or machines. @xref{Supported Languages, ,
12812 Supported Languages}, for further details on specific languages.
12814 @value{GDBN} provides some additional commands for controlling the range checker:
12816 @kindex set check range
12817 @kindex show check range
12819 @item set check range auto
12820 Set range checking on or off based on the current working language.
12821 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12824 @item set check range on
12825 @itemx set check range off
12826 Set range checking on or off, overriding the default setting for the
12827 current working language. A warning is issued if the setting does not
12828 match the language default. If a range error occurs and range checking is on,
12829 then a message is printed and evaluation of the expression is aborted.
12831 @item set check range warn
12832 Output messages when the @value{GDBN} range checker detects a range error,
12833 but attempt to evaluate the expression anyway. Evaluating the
12834 expression may still be impossible for other reasons, such as accessing
12835 memory that the process does not own (a typical example from many Unix
12839 Show the current setting of the range checker, and whether or not it is
12840 being set automatically by @value{GDBN}.
12843 @node Supported Languages
12844 @section Supported Languages
12846 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
12847 OpenCL C, Pascal, assembly, Modula-2, and Ada.
12848 @c This is false ...
12849 Some @value{GDBN} features may be used in expressions regardless of the
12850 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12851 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12852 ,Expressions}) can be used with the constructs of any supported
12855 The following sections detail to what degree each source language is
12856 supported by @value{GDBN}. These sections are not meant to be language
12857 tutorials or references, but serve only as a reference guide to what the
12858 @value{GDBN} expression parser accepts, and what input and output
12859 formats should look like for different languages. There are many good
12860 books written on each of these languages; please look to these for a
12861 language reference or tutorial.
12864 * C:: C and C@t{++}
12867 * Objective-C:: Objective-C
12868 * OpenCL C:: OpenCL C
12869 * Fortran:: Fortran
12871 * Modula-2:: Modula-2
12876 @subsection C and C@t{++}
12878 @cindex C and C@t{++}
12879 @cindex expressions in C or C@t{++}
12881 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12882 to both languages. Whenever this is the case, we discuss those languages
12886 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12887 @cindex @sc{gnu} C@t{++}
12888 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12889 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12890 effectively, you must compile your C@t{++} programs with a supported
12891 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12892 compiler (@code{aCC}).
12895 * C Operators:: C and C@t{++} operators
12896 * C Constants:: C and C@t{++} constants
12897 * C Plus Plus Expressions:: C@t{++} expressions
12898 * C Defaults:: Default settings for C and C@t{++}
12899 * C Checks:: C and C@t{++} type and range checks
12900 * Debugging C:: @value{GDBN} and C
12901 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12902 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12906 @subsubsection C and C@t{++} Operators
12908 @cindex C and C@t{++} operators
12910 Operators must be defined on values of specific types. For instance,
12911 @code{+} is defined on numbers, but not on structures. Operators are
12912 often defined on groups of types.
12914 For the purposes of C and C@t{++}, the following definitions hold:
12919 @emph{Integral types} include @code{int} with any of its storage-class
12920 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12923 @emph{Floating-point types} include @code{float}, @code{double}, and
12924 @code{long double} (if supported by the target platform).
12927 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12930 @emph{Scalar types} include all of the above.
12935 The following operators are supported. They are listed here
12936 in order of increasing precedence:
12940 The comma or sequencing operator. Expressions in a comma-separated list
12941 are evaluated from left to right, with the result of the entire
12942 expression being the last expression evaluated.
12945 Assignment. The value of an assignment expression is the value
12946 assigned. Defined on scalar types.
12949 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12950 and translated to @w{@code{@var{a} = @var{a op b}}}.
12951 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12952 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12953 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12956 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12957 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12961 Logical @sc{or}. Defined on integral types.
12964 Logical @sc{and}. Defined on integral types.
12967 Bitwise @sc{or}. Defined on integral types.
12970 Bitwise exclusive-@sc{or}. Defined on integral types.
12973 Bitwise @sc{and}. Defined on integral types.
12976 Equality and inequality. Defined on scalar types. The value of these
12977 expressions is 0 for false and non-zero for true.
12979 @item <@r{, }>@r{, }<=@r{, }>=
12980 Less than, greater than, less than or equal, greater than or equal.
12981 Defined on scalar types. The value of these expressions is 0 for false
12982 and non-zero for true.
12985 left shift, and right shift. Defined on integral types.
12988 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12991 Addition and subtraction. Defined on integral types, floating-point types and
12994 @item *@r{, }/@r{, }%
12995 Multiplication, division, and modulus. Multiplication and division are
12996 defined on integral and floating-point types. Modulus is defined on
13000 Increment and decrement. When appearing before a variable, the
13001 operation is performed before the variable is used in an expression;
13002 when appearing after it, the variable's value is used before the
13003 operation takes place.
13006 Pointer dereferencing. Defined on pointer types. Same precedence as
13010 Address operator. Defined on variables. Same precedence as @code{++}.
13012 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13013 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13014 to examine the address
13015 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13019 Negative. Defined on integral and floating-point types. Same
13020 precedence as @code{++}.
13023 Logical negation. Defined on integral types. Same precedence as
13027 Bitwise complement operator. Defined on integral types. Same precedence as
13032 Structure member, and pointer-to-structure member. For convenience,
13033 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13034 pointer based on the stored type information.
13035 Defined on @code{struct} and @code{union} data.
13038 Dereferences of pointers to members.
13041 Array indexing. @code{@var{a}[@var{i}]} is defined as
13042 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13045 Function parameter list. Same precedence as @code{->}.
13048 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13049 and @code{class} types.
13052 Doubled colons also represent the @value{GDBN} scope operator
13053 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13057 If an operator is redefined in the user code, @value{GDBN} usually
13058 attempts to invoke the redefined version instead of using the operator's
13059 predefined meaning.
13062 @subsubsection C and C@t{++} Constants
13064 @cindex C and C@t{++} constants
13066 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13071 Integer constants are a sequence of digits. Octal constants are
13072 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13073 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13074 @samp{l}, specifying that the constant should be treated as a
13078 Floating point constants are a sequence of digits, followed by a decimal
13079 point, followed by a sequence of digits, and optionally followed by an
13080 exponent. An exponent is of the form:
13081 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13082 sequence of digits. The @samp{+} is optional for positive exponents.
13083 A floating-point constant may also end with a letter @samp{f} or
13084 @samp{F}, specifying that the constant should be treated as being of
13085 the @code{float} (as opposed to the default @code{double}) type; or with
13086 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13090 Enumerated constants consist of enumerated identifiers, or their
13091 integral equivalents.
13094 Character constants are a single character surrounded by single quotes
13095 (@code{'}), or a number---the ordinal value of the corresponding character
13096 (usually its @sc{ascii} value). Within quotes, the single character may
13097 be represented by a letter or by @dfn{escape sequences}, which are of
13098 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13099 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13100 @samp{@var{x}} is a predefined special character---for example,
13101 @samp{\n} for newline.
13103 Wide character constants can be written by prefixing a character
13104 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13105 form of @samp{x}. The target wide character set is used when
13106 computing the value of this constant (@pxref{Character Sets}).
13109 String constants are a sequence of character constants surrounded by
13110 double quotes (@code{"}). Any valid character constant (as described
13111 above) may appear. Double quotes within the string must be preceded by
13112 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13115 Wide string constants can be written by prefixing a string constant
13116 with @samp{L}, as in C. The target wide character set is used when
13117 computing the value of this constant (@pxref{Character Sets}).
13120 Pointer constants are an integral value. You can also write pointers
13121 to constants using the C operator @samp{&}.
13124 Array constants are comma-separated lists surrounded by braces @samp{@{}
13125 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13126 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13127 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13130 @node C Plus Plus Expressions
13131 @subsubsection C@t{++} Expressions
13133 @cindex expressions in C@t{++}
13134 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13136 @cindex debugging C@t{++} programs
13137 @cindex C@t{++} compilers
13138 @cindex debug formats and C@t{++}
13139 @cindex @value{NGCC} and C@t{++}
13141 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13142 the proper compiler and the proper debug format. Currently,
13143 @value{GDBN} works best when debugging C@t{++} code that is compiled
13144 with the most recent version of @value{NGCC} possible. The DWARF
13145 debugging format is preferred; @value{NGCC} defaults to this on most
13146 popular platforms. Other compilers and/or debug formats are likely to
13147 work badly or not at all when using @value{GDBN} to debug C@t{++}
13148 code. @xref{Compilation}.
13153 @cindex member functions
13155 Member function calls are allowed; you can use expressions like
13158 count = aml->GetOriginal(x, y)
13161 @vindex this@r{, inside C@t{++} member functions}
13162 @cindex namespace in C@t{++}
13164 While a member function is active (in the selected stack frame), your
13165 expressions have the same namespace available as the member function;
13166 that is, @value{GDBN} allows implicit references to the class instance
13167 pointer @code{this} following the same rules as C@t{++}. @code{using}
13168 declarations in the current scope are also respected by @value{GDBN}.
13170 @cindex call overloaded functions
13171 @cindex overloaded functions, calling
13172 @cindex type conversions in C@t{++}
13174 You can call overloaded functions; @value{GDBN} resolves the function
13175 call to the right definition, with some restrictions. @value{GDBN} does not
13176 perform overload resolution involving user-defined type conversions,
13177 calls to constructors, or instantiations of templates that do not exist
13178 in the program. It also cannot handle ellipsis argument lists or
13181 It does perform integral conversions and promotions, floating-point
13182 promotions, arithmetic conversions, pointer conversions, conversions of
13183 class objects to base classes, and standard conversions such as those of
13184 functions or arrays to pointers; it requires an exact match on the
13185 number of function arguments.
13187 Overload resolution is always performed, unless you have specified
13188 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13189 ,@value{GDBN} Features for C@t{++}}.
13191 You must specify @code{set overload-resolution off} in order to use an
13192 explicit function signature to call an overloaded function, as in
13194 p 'foo(char,int)'('x', 13)
13197 The @value{GDBN} command-completion facility can simplify this;
13198 see @ref{Completion, ,Command Completion}.
13200 @cindex reference declarations
13202 @value{GDBN} understands variables declared as C@t{++} references; you can use
13203 them in expressions just as you do in C@t{++} source---they are automatically
13206 In the parameter list shown when @value{GDBN} displays a frame, the values of
13207 reference variables are not displayed (unlike other variables); this
13208 avoids clutter, since references are often used for large structures.
13209 The @emph{address} of a reference variable is always shown, unless
13210 you have specified @samp{set print address off}.
13213 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13214 expressions can use it just as expressions in your program do. Since
13215 one scope may be defined in another, you can use @code{::} repeatedly if
13216 necessary, for example in an expression like
13217 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13218 resolving name scope by reference to source files, in both C and C@t{++}
13219 debugging (@pxref{Variables, ,Program Variables}).
13222 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13227 @subsubsection C and C@t{++} Defaults
13229 @cindex C and C@t{++} defaults
13231 If you allow @value{GDBN} to set range checking automatically, it
13232 defaults to @code{off} whenever the working language changes to
13233 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13234 selects the working language.
13236 If you allow @value{GDBN} to set the language automatically, it
13237 recognizes source files whose names end with @file{.c}, @file{.C}, or
13238 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13239 these files, it sets the working language to C or C@t{++}.
13240 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13241 for further details.
13244 @subsubsection C and C@t{++} Type and Range Checks
13246 @cindex C and C@t{++} checks
13248 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13249 checking is used. However, if you turn type checking off, @value{GDBN}
13250 will allow certain non-standard conversions, such as promoting integer
13251 constants to pointers.
13253 Range checking, if turned on, is done on mathematical operations. Array
13254 indices are not checked, since they are often used to index a pointer
13255 that is not itself an array.
13258 @subsubsection @value{GDBN} and C
13260 The @code{set print union} and @code{show print union} commands apply to
13261 the @code{union} type. When set to @samp{on}, any @code{union} that is
13262 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13263 appears as @samp{@{...@}}.
13265 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13266 with pointers and a memory allocation function. @xref{Expressions,
13269 @node Debugging C Plus Plus
13270 @subsubsection @value{GDBN} Features for C@t{++}
13272 @cindex commands for C@t{++}
13274 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13275 designed specifically for use with C@t{++}. Here is a summary:
13278 @cindex break in overloaded functions
13279 @item @r{breakpoint menus}
13280 When you want a breakpoint in a function whose name is overloaded,
13281 @value{GDBN} has the capability to display a menu of possible breakpoint
13282 locations to help you specify which function definition you want.
13283 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13285 @cindex overloading in C@t{++}
13286 @item rbreak @var{regex}
13287 Setting breakpoints using regular expressions is helpful for setting
13288 breakpoints on overloaded functions that are not members of any special
13290 @xref{Set Breaks, ,Setting Breakpoints}.
13292 @cindex C@t{++} exception handling
13295 Debug C@t{++} exception handling using these commands. @xref{Set
13296 Catchpoints, , Setting Catchpoints}.
13298 @cindex inheritance
13299 @item ptype @var{typename}
13300 Print inheritance relationships as well as other information for type
13302 @xref{Symbols, ,Examining the Symbol Table}.
13304 @item info vtbl @var{expression}.
13305 The @code{info vtbl} command can be used to display the virtual
13306 method tables of the object computed by @var{expression}. This shows
13307 one entry per virtual table; there may be multiple virtual tables when
13308 multiple inheritance is in use.
13310 @cindex C@t{++} symbol display
13311 @item set print demangle
13312 @itemx show print demangle
13313 @itemx set print asm-demangle
13314 @itemx show print asm-demangle
13315 Control whether C@t{++} symbols display in their source form, both when
13316 displaying code as C@t{++} source and when displaying disassemblies.
13317 @xref{Print Settings, ,Print Settings}.
13319 @item set print object
13320 @itemx show print object
13321 Choose whether to print derived (actual) or declared types of objects.
13322 @xref{Print Settings, ,Print Settings}.
13324 @item set print vtbl
13325 @itemx show print vtbl
13326 Control the format for printing virtual function tables.
13327 @xref{Print Settings, ,Print Settings}.
13328 (The @code{vtbl} commands do not work on programs compiled with the HP
13329 ANSI C@t{++} compiler (@code{aCC}).)
13331 @kindex set overload-resolution
13332 @cindex overloaded functions, overload resolution
13333 @item set overload-resolution on
13334 Enable overload resolution for C@t{++} expression evaluation. The default
13335 is on. For overloaded functions, @value{GDBN} evaluates the arguments
13336 and searches for a function whose signature matches the argument types,
13337 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
13338 Expressions, ,C@t{++} Expressions}, for details).
13339 If it cannot find a match, it emits a message.
13341 @item set overload-resolution off
13342 Disable overload resolution for C@t{++} expression evaluation. For
13343 overloaded functions that are not class member functions, @value{GDBN}
13344 chooses the first function of the specified name that it finds in the
13345 symbol table, whether or not its arguments are of the correct type. For
13346 overloaded functions that are class member functions, @value{GDBN}
13347 searches for a function whose signature @emph{exactly} matches the
13350 @kindex show overload-resolution
13351 @item show overload-resolution
13352 Show the current setting of overload resolution.
13354 @item @r{Overloaded symbol names}
13355 You can specify a particular definition of an overloaded symbol, using
13356 the same notation that is used to declare such symbols in C@t{++}: type
13357 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
13358 also use the @value{GDBN} command-line word completion facilities to list the
13359 available choices, or to finish the type list for you.
13360 @xref{Completion,, Command Completion}, for details on how to do this.
13363 @node Decimal Floating Point
13364 @subsubsection Decimal Floating Point format
13365 @cindex decimal floating point format
13367 @value{GDBN} can examine, set and perform computations with numbers in
13368 decimal floating point format, which in the C language correspond to the
13369 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
13370 specified by the extension to support decimal floating-point arithmetic.
13372 There are two encodings in use, depending on the architecture: BID (Binary
13373 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
13374 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
13377 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
13378 to manipulate decimal floating point numbers, it is not possible to convert
13379 (using a cast, for example) integers wider than 32-bit to decimal float.
13381 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
13382 point computations, error checking in decimal float operations ignores
13383 underflow, overflow and divide by zero exceptions.
13385 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
13386 to inspect @code{_Decimal128} values stored in floating point registers.
13387 See @ref{PowerPC,,PowerPC} for more details.
13393 @value{GDBN} can be used to debug programs written in D and compiled with
13394 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
13395 specific feature --- dynamic arrays.
13400 @cindex Go (programming language)
13401 @value{GDBN} can be used to debug programs written in Go and compiled with
13402 @file{gccgo} or @file{6g} compilers.
13404 Here is a summary of the Go-specific features and restrictions:
13407 @cindex current Go package
13408 @item The current Go package
13409 The name of the current package does not need to be specified when
13410 specifying global variables and functions.
13412 For example, given the program:
13416 var myglob = "Shall we?"
13422 When stopped inside @code{main} either of these work:
13426 (gdb) p main.myglob
13429 @cindex builtin Go types
13430 @item Builtin Go types
13431 The @code{string} type is recognized by @value{GDBN} and is printed
13434 @cindex builtin Go functions
13435 @item Builtin Go functions
13436 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
13437 function and handles it internally.
13439 @cindex restrictions on Go expressions
13440 @item Restrictions on Go expressions
13441 All Go operators are supported except @code{&^}.
13442 The Go @code{_} ``blank identifier'' is not supported.
13443 Automatic dereferencing of pointers is not supported.
13447 @subsection Objective-C
13449 @cindex Objective-C
13450 This section provides information about some commands and command
13451 options that are useful for debugging Objective-C code. See also
13452 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
13453 few more commands specific to Objective-C support.
13456 * Method Names in Commands::
13457 * The Print Command with Objective-C::
13460 @node Method Names in Commands
13461 @subsubsection Method Names in Commands
13463 The following commands have been extended to accept Objective-C method
13464 names as line specifications:
13466 @kindex clear@r{, and Objective-C}
13467 @kindex break@r{, and Objective-C}
13468 @kindex info line@r{, and Objective-C}
13469 @kindex jump@r{, and Objective-C}
13470 @kindex list@r{, and Objective-C}
13474 @item @code{info line}
13479 A fully qualified Objective-C method name is specified as
13482 -[@var{Class} @var{methodName}]
13485 where the minus sign is used to indicate an instance method and a
13486 plus sign (not shown) is used to indicate a class method. The class
13487 name @var{Class} and method name @var{methodName} are enclosed in
13488 brackets, similar to the way messages are specified in Objective-C
13489 source code. For example, to set a breakpoint at the @code{create}
13490 instance method of class @code{Fruit} in the program currently being
13494 break -[Fruit create]
13497 To list ten program lines around the @code{initialize} class method,
13501 list +[NSText initialize]
13504 In the current version of @value{GDBN}, the plus or minus sign is
13505 required. In future versions of @value{GDBN}, the plus or minus
13506 sign will be optional, but you can use it to narrow the search. It
13507 is also possible to specify just a method name:
13513 You must specify the complete method name, including any colons. If
13514 your program's source files contain more than one @code{create} method,
13515 you'll be presented with a numbered list of classes that implement that
13516 method. Indicate your choice by number, or type @samp{0} to exit if
13519 As another example, to clear a breakpoint established at the
13520 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
13523 clear -[NSWindow makeKeyAndOrderFront:]
13526 @node The Print Command with Objective-C
13527 @subsubsection The Print Command With Objective-C
13528 @cindex Objective-C, print objects
13529 @kindex print-object
13530 @kindex po @r{(@code{print-object})}
13532 The print command has also been extended to accept methods. For example:
13535 print -[@var{object} hash]
13538 @cindex print an Objective-C object description
13539 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
13541 will tell @value{GDBN} to send the @code{hash} message to @var{object}
13542 and print the result. Also, an additional command has been added,
13543 @code{print-object} or @code{po} for short, which is meant to print
13544 the description of an object. However, this command may only work
13545 with certain Objective-C libraries that have a particular hook
13546 function, @code{_NSPrintForDebugger}, defined.
13549 @subsection OpenCL C
13552 This section provides information about @value{GDBN}s OpenCL C support.
13555 * OpenCL C Datatypes::
13556 * OpenCL C Expressions::
13557 * OpenCL C Operators::
13560 @node OpenCL C Datatypes
13561 @subsubsection OpenCL C Datatypes
13563 @cindex OpenCL C Datatypes
13564 @value{GDBN} supports the builtin scalar and vector datatypes specified
13565 by OpenCL 1.1. In addition the half- and double-precision floating point
13566 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
13567 extensions are also known to @value{GDBN}.
13569 @node OpenCL C Expressions
13570 @subsubsection OpenCL C Expressions
13572 @cindex OpenCL C Expressions
13573 @value{GDBN} supports accesses to vector components including the access as
13574 lvalue where possible. Since OpenCL C is based on C99 most C expressions
13575 supported by @value{GDBN} can be used as well.
13577 @node OpenCL C Operators
13578 @subsubsection OpenCL C Operators
13580 @cindex OpenCL C Operators
13581 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
13585 @subsection Fortran
13586 @cindex Fortran-specific support in @value{GDBN}
13588 @value{GDBN} can be used to debug programs written in Fortran, but it
13589 currently supports only the features of Fortran 77 language.
13591 @cindex trailing underscore, in Fortran symbols
13592 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
13593 among them) append an underscore to the names of variables and
13594 functions. When you debug programs compiled by those compilers, you
13595 will need to refer to variables and functions with a trailing
13599 * Fortran Operators:: Fortran operators and expressions
13600 * Fortran Defaults:: Default settings for Fortran
13601 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
13604 @node Fortran Operators
13605 @subsubsection Fortran Operators and Expressions
13607 @cindex Fortran operators and expressions
13609 Operators must be defined on values of specific types. For instance,
13610 @code{+} is defined on numbers, but not on characters or other non-
13611 arithmetic types. Operators are often defined on groups of types.
13615 The exponentiation operator. It raises the first operand to the power
13619 The range operator. Normally used in the form of array(low:high) to
13620 represent a section of array.
13623 The access component operator. Normally used to access elements in derived
13624 types. Also suitable for unions. As unions aren't part of regular Fortran,
13625 this can only happen when accessing a register that uses a gdbarch-defined
13629 @node Fortran Defaults
13630 @subsubsection Fortran Defaults
13632 @cindex Fortran Defaults
13634 Fortran symbols are usually case-insensitive, so @value{GDBN} by
13635 default uses case-insensitive matches for Fortran symbols. You can
13636 change that with the @samp{set case-insensitive} command, see
13637 @ref{Symbols}, for the details.
13639 @node Special Fortran Commands
13640 @subsubsection Special Fortran Commands
13642 @cindex Special Fortran commands
13644 @value{GDBN} has some commands to support Fortran-specific features,
13645 such as displaying common blocks.
13648 @cindex @code{COMMON} blocks, Fortran
13649 @kindex info common
13650 @item info common @r{[}@var{common-name}@r{]}
13651 This command prints the values contained in the Fortran @code{COMMON}
13652 block whose name is @var{common-name}. With no argument, the names of
13653 all @code{COMMON} blocks visible at the current program location are
13660 @cindex Pascal support in @value{GDBN}, limitations
13661 Debugging Pascal programs which use sets, subranges, file variables, or
13662 nested functions does not currently work. @value{GDBN} does not support
13663 entering expressions, printing values, or similar features using Pascal
13666 The Pascal-specific command @code{set print pascal_static-members}
13667 controls whether static members of Pascal objects are displayed.
13668 @xref{Print Settings, pascal_static-members}.
13671 @subsection Modula-2
13673 @cindex Modula-2, @value{GDBN} support
13675 The extensions made to @value{GDBN} to support Modula-2 only support
13676 output from the @sc{gnu} Modula-2 compiler (which is currently being
13677 developed). Other Modula-2 compilers are not currently supported, and
13678 attempting to debug executables produced by them is most likely
13679 to give an error as @value{GDBN} reads in the executable's symbol
13682 @cindex expressions in Modula-2
13684 * M2 Operators:: Built-in operators
13685 * Built-In Func/Proc:: Built-in functions and procedures
13686 * M2 Constants:: Modula-2 constants
13687 * M2 Types:: Modula-2 types
13688 * M2 Defaults:: Default settings for Modula-2
13689 * Deviations:: Deviations from standard Modula-2
13690 * M2 Checks:: Modula-2 type and range checks
13691 * M2 Scope:: The scope operators @code{::} and @code{.}
13692 * GDB/M2:: @value{GDBN} and Modula-2
13696 @subsubsection Operators
13697 @cindex Modula-2 operators
13699 Operators must be defined on values of specific types. For instance,
13700 @code{+} is defined on numbers, but not on structures. Operators are
13701 often defined on groups of types. For the purposes of Modula-2, the
13702 following definitions hold:
13707 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13711 @emph{Character types} consist of @code{CHAR} and its subranges.
13714 @emph{Floating-point types} consist of @code{REAL}.
13717 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13721 @emph{Scalar types} consist of all of the above.
13724 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13727 @emph{Boolean types} consist of @code{BOOLEAN}.
13731 The following operators are supported, and appear in order of
13732 increasing precedence:
13736 Function argument or array index separator.
13739 Assignment. The value of @var{var} @code{:=} @var{value} is
13743 Less than, greater than on integral, floating-point, or enumerated
13747 Less than or equal to, greater than or equal to
13748 on integral, floating-point and enumerated types, or set inclusion on
13749 set types. Same precedence as @code{<}.
13751 @item =@r{, }<>@r{, }#
13752 Equality and two ways of expressing inequality, valid on scalar types.
13753 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13754 available for inequality, since @code{#} conflicts with the script
13758 Set membership. Defined on set types and the types of their members.
13759 Same precedence as @code{<}.
13762 Boolean disjunction. Defined on boolean types.
13765 Boolean conjunction. Defined on boolean types.
13768 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13771 Addition and subtraction on integral and floating-point types, or union
13772 and difference on set types.
13775 Multiplication on integral and floating-point types, or set intersection
13779 Division on floating-point types, or symmetric set difference on set
13780 types. Same precedence as @code{*}.
13783 Integer division and remainder. Defined on integral types. Same
13784 precedence as @code{*}.
13787 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13790 Pointer dereferencing. Defined on pointer types.
13793 Boolean negation. Defined on boolean types. Same precedence as
13797 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13798 precedence as @code{^}.
13801 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13804 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13808 @value{GDBN} and Modula-2 scope operators.
13812 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13813 treats the use of the operator @code{IN}, or the use of operators
13814 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13815 @code{<=}, and @code{>=} on sets as an error.
13819 @node Built-In Func/Proc
13820 @subsubsection Built-in Functions and Procedures
13821 @cindex Modula-2 built-ins
13823 Modula-2 also makes available several built-in procedures and functions.
13824 In describing these, the following metavariables are used:
13829 represents an @code{ARRAY} variable.
13832 represents a @code{CHAR} constant or variable.
13835 represents a variable or constant of integral type.
13838 represents an identifier that belongs to a set. Generally used in the
13839 same function with the metavariable @var{s}. The type of @var{s} should
13840 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13843 represents a variable or constant of integral or floating-point type.
13846 represents a variable or constant of floating-point type.
13852 represents a variable.
13855 represents a variable or constant of one of many types. See the
13856 explanation of the function for details.
13859 All Modula-2 built-in procedures also return a result, described below.
13863 Returns the absolute value of @var{n}.
13866 If @var{c} is a lower case letter, it returns its upper case
13867 equivalent, otherwise it returns its argument.
13870 Returns the character whose ordinal value is @var{i}.
13873 Decrements the value in the variable @var{v} by one. Returns the new value.
13875 @item DEC(@var{v},@var{i})
13876 Decrements the value in the variable @var{v} by @var{i}. Returns the
13879 @item EXCL(@var{m},@var{s})
13880 Removes the element @var{m} from the set @var{s}. Returns the new
13883 @item FLOAT(@var{i})
13884 Returns the floating point equivalent of the integer @var{i}.
13886 @item HIGH(@var{a})
13887 Returns the index of the last member of @var{a}.
13890 Increments the value in the variable @var{v} by one. Returns the new value.
13892 @item INC(@var{v},@var{i})
13893 Increments the value in the variable @var{v} by @var{i}. Returns the
13896 @item INCL(@var{m},@var{s})
13897 Adds the element @var{m} to the set @var{s} if it is not already
13898 there. Returns the new set.
13901 Returns the maximum value of the type @var{t}.
13904 Returns the minimum value of the type @var{t}.
13907 Returns boolean TRUE if @var{i} is an odd number.
13910 Returns the ordinal value of its argument. For example, the ordinal
13911 value of a character is its @sc{ascii} value (on machines supporting the
13912 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13913 integral, character and enumerated types.
13915 @item SIZE(@var{x})
13916 Returns the size of its argument. @var{x} can be a variable or a type.
13918 @item TRUNC(@var{r})
13919 Returns the integral part of @var{r}.
13921 @item TSIZE(@var{x})
13922 Returns the size of its argument. @var{x} can be a variable or a type.
13924 @item VAL(@var{t},@var{i})
13925 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13929 @emph{Warning:} Sets and their operations are not yet supported, so
13930 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13934 @cindex Modula-2 constants
13936 @subsubsection Constants
13938 @value{GDBN} allows you to express the constants of Modula-2 in the following
13944 Integer constants are simply a sequence of digits. When used in an
13945 expression, a constant is interpreted to be type-compatible with the
13946 rest of the expression. Hexadecimal integers are specified by a
13947 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13950 Floating point constants appear as a sequence of digits, followed by a
13951 decimal point and another sequence of digits. An optional exponent can
13952 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13953 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13954 digits of the floating point constant must be valid decimal (base 10)
13958 Character constants consist of a single character enclosed by a pair of
13959 like quotes, either single (@code{'}) or double (@code{"}). They may
13960 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13961 followed by a @samp{C}.
13964 String constants consist of a sequence of characters enclosed by a
13965 pair of like quotes, either single (@code{'}) or double (@code{"}).
13966 Escape sequences in the style of C are also allowed. @xref{C
13967 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13971 Enumerated constants consist of an enumerated identifier.
13974 Boolean constants consist of the identifiers @code{TRUE} and
13978 Pointer constants consist of integral values only.
13981 Set constants are not yet supported.
13985 @subsubsection Modula-2 Types
13986 @cindex Modula-2 types
13988 Currently @value{GDBN} can print the following data types in Modula-2
13989 syntax: array types, record types, set types, pointer types, procedure
13990 types, enumerated types, subrange types and base types. You can also
13991 print the contents of variables declared using these type.
13992 This section gives a number of simple source code examples together with
13993 sample @value{GDBN} sessions.
13995 The first example contains the following section of code:
14004 and you can request @value{GDBN} to interrogate the type and value of
14005 @code{r} and @code{s}.
14008 (@value{GDBP}) print s
14010 (@value{GDBP}) ptype s
14012 (@value{GDBP}) print r
14014 (@value{GDBP}) ptype r
14019 Likewise if your source code declares @code{s} as:
14023 s: SET ['A'..'Z'] ;
14027 then you may query the type of @code{s} by:
14030 (@value{GDBP}) ptype s
14031 type = SET ['A'..'Z']
14035 Note that at present you cannot interactively manipulate set
14036 expressions using the debugger.
14038 The following example shows how you might declare an array in Modula-2
14039 and how you can interact with @value{GDBN} to print its type and contents:
14043 s: ARRAY [-10..10] OF CHAR ;
14047 (@value{GDBP}) ptype s
14048 ARRAY [-10..10] OF CHAR
14051 Note that the array handling is not yet complete and although the type
14052 is printed correctly, expression handling still assumes that all
14053 arrays have a lower bound of zero and not @code{-10} as in the example
14056 Here are some more type related Modula-2 examples:
14060 colour = (blue, red, yellow, green) ;
14061 t = [blue..yellow] ;
14069 The @value{GDBN} interaction shows how you can query the data type
14070 and value of a variable.
14073 (@value{GDBP}) print s
14075 (@value{GDBP}) ptype t
14076 type = [blue..yellow]
14080 In this example a Modula-2 array is declared and its contents
14081 displayed. Observe that the contents are written in the same way as
14082 their @code{C} counterparts.
14086 s: ARRAY [1..5] OF CARDINAL ;
14092 (@value{GDBP}) print s
14093 $1 = @{1, 0, 0, 0, 0@}
14094 (@value{GDBP}) ptype s
14095 type = ARRAY [1..5] OF CARDINAL
14098 The Modula-2 language interface to @value{GDBN} also understands
14099 pointer types as shown in this example:
14103 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14110 and you can request that @value{GDBN} describes the type of @code{s}.
14113 (@value{GDBP}) ptype s
14114 type = POINTER TO ARRAY [1..5] OF CARDINAL
14117 @value{GDBN} handles compound types as we can see in this example.
14118 Here we combine array types, record types, pointer types and subrange
14129 myarray = ARRAY myrange OF CARDINAL ;
14130 myrange = [-2..2] ;
14132 s: POINTER TO ARRAY myrange OF foo ;
14136 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14140 (@value{GDBP}) ptype s
14141 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14144 f3 : ARRAY [-2..2] OF CARDINAL;
14149 @subsubsection Modula-2 Defaults
14150 @cindex Modula-2 defaults
14152 If type and range checking are set automatically by @value{GDBN}, they
14153 both default to @code{on} whenever the working language changes to
14154 Modula-2. This happens regardless of whether you or @value{GDBN}
14155 selected the working language.
14157 If you allow @value{GDBN} to set the language automatically, then entering
14158 code compiled from a file whose name ends with @file{.mod} sets the
14159 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14160 Infer the Source Language}, for further details.
14163 @subsubsection Deviations from Standard Modula-2
14164 @cindex Modula-2, deviations from
14166 A few changes have been made to make Modula-2 programs easier to debug.
14167 This is done primarily via loosening its type strictness:
14171 Unlike in standard Modula-2, pointer constants can be formed by
14172 integers. This allows you to modify pointer variables during
14173 debugging. (In standard Modula-2, the actual address contained in a
14174 pointer variable is hidden from you; it can only be modified
14175 through direct assignment to another pointer variable or expression that
14176 returned a pointer.)
14179 C escape sequences can be used in strings and characters to represent
14180 non-printable characters. @value{GDBN} prints out strings with these
14181 escape sequences embedded. Single non-printable characters are
14182 printed using the @samp{CHR(@var{nnn})} format.
14185 The assignment operator (@code{:=}) returns the value of its right-hand
14189 All built-in procedures both modify @emph{and} return their argument.
14193 @subsubsection Modula-2 Type and Range Checks
14194 @cindex Modula-2 checks
14197 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14200 @c FIXME remove warning when type/range checks added
14202 @value{GDBN} considers two Modula-2 variables type equivalent if:
14206 They are of types that have been declared equivalent via a @code{TYPE
14207 @var{t1} = @var{t2}} statement
14210 They have been declared on the same line. (Note: This is true of the
14211 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14214 As long as type checking is enabled, any attempt to combine variables
14215 whose types are not equivalent is an error.
14217 Range checking is done on all mathematical operations, assignment, array
14218 index bounds, and all built-in functions and procedures.
14221 @subsubsection The Scope Operators @code{::} and @code{.}
14223 @cindex @code{.}, Modula-2 scope operator
14224 @cindex colon, doubled as scope operator
14226 @vindex colon-colon@r{, in Modula-2}
14227 @c Info cannot handle :: but TeX can.
14230 @vindex ::@r{, in Modula-2}
14233 There are a few subtle differences between the Modula-2 scope operator
14234 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14239 @var{module} . @var{id}
14240 @var{scope} :: @var{id}
14244 where @var{scope} is the name of a module or a procedure,
14245 @var{module} the name of a module, and @var{id} is any declared
14246 identifier within your program, except another module.
14248 Using the @code{::} operator makes @value{GDBN} search the scope
14249 specified by @var{scope} for the identifier @var{id}. If it is not
14250 found in the specified scope, then @value{GDBN} searches all scopes
14251 enclosing the one specified by @var{scope}.
14253 Using the @code{.} operator makes @value{GDBN} search the current scope for
14254 the identifier specified by @var{id} that was imported from the
14255 definition module specified by @var{module}. With this operator, it is
14256 an error if the identifier @var{id} was not imported from definition
14257 module @var{module}, or if @var{id} is not an identifier in
14261 @subsubsection @value{GDBN} and Modula-2
14263 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14264 Five subcommands of @code{set print} and @code{show print} apply
14265 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14266 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14267 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14268 analogue in Modula-2.
14270 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14271 with any language, is not useful with Modula-2. Its
14272 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14273 created in Modula-2 as they can in C or C@t{++}. However, because an
14274 address can be specified by an integral constant, the construct
14275 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14277 @cindex @code{#} in Modula-2
14278 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14279 interpreted as the beginning of a comment. Use @code{<>} instead.
14285 The extensions made to @value{GDBN} for Ada only support
14286 output from the @sc{gnu} Ada (GNAT) compiler.
14287 Other Ada compilers are not currently supported, and
14288 attempting to debug executables produced by them is most likely
14292 @cindex expressions in Ada
14294 * Ada Mode Intro:: General remarks on the Ada syntax
14295 and semantics supported by Ada mode
14297 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14298 * Additions to Ada:: Extensions of the Ada expression syntax.
14299 * Stopping Before Main Program:: Debugging the program during elaboration.
14300 * Ada Tasks:: Listing and setting breakpoints in tasks.
14301 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14302 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14304 * Ada Glitches:: Known peculiarities of Ada mode.
14307 @node Ada Mode Intro
14308 @subsubsection Introduction
14309 @cindex Ada mode, general
14311 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14312 syntax, with some extensions.
14313 The philosophy behind the design of this subset is
14317 That @value{GDBN} should provide basic literals and access to operations for
14318 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
14319 leaving more sophisticated computations to subprograms written into the
14320 program (which therefore may be called from @value{GDBN}).
14323 That type safety and strict adherence to Ada language restrictions
14324 are not particularly important to the @value{GDBN} user.
14327 That brevity is important to the @value{GDBN} user.
14330 Thus, for brevity, the debugger acts as if all names declared in
14331 user-written packages are directly visible, even if they are not visible
14332 according to Ada rules, thus making it unnecessary to fully qualify most
14333 names with their packages, regardless of context. Where this causes
14334 ambiguity, @value{GDBN} asks the user's intent.
14336 The debugger will start in Ada mode if it detects an Ada main program.
14337 As for other languages, it will enter Ada mode when stopped in a program that
14338 was translated from an Ada source file.
14340 While in Ada mode, you may use `@t{--}' for comments. This is useful
14341 mostly for documenting command files. The standard @value{GDBN} comment
14342 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
14343 middle (to allow based literals).
14345 The debugger supports limited overloading. Given a subprogram call in which
14346 the function symbol has multiple definitions, it will use the number of
14347 actual parameters and some information about their types to attempt to narrow
14348 the set of definitions. It also makes very limited use of context, preferring
14349 procedures to functions in the context of the @code{call} command, and
14350 functions to procedures elsewhere.
14352 @node Omissions from Ada
14353 @subsubsection Omissions from Ada
14354 @cindex Ada, omissions from
14356 Here are the notable omissions from the subset:
14360 Only a subset of the attributes are supported:
14364 @t{'First}, @t{'Last}, and @t{'Length}
14365 on array objects (not on types and subtypes).
14368 @t{'Min} and @t{'Max}.
14371 @t{'Pos} and @t{'Val}.
14377 @t{'Range} on array objects (not subtypes), but only as the right
14378 operand of the membership (@code{in}) operator.
14381 @t{'Access}, @t{'Unchecked_Access}, and
14382 @t{'Unrestricted_Access} (a GNAT extension).
14390 @code{Characters.Latin_1} are not available and
14391 concatenation is not implemented. Thus, escape characters in strings are
14392 not currently available.
14395 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
14396 equality of representations. They will generally work correctly
14397 for strings and arrays whose elements have integer or enumeration types.
14398 They may not work correctly for arrays whose element
14399 types have user-defined equality, for arrays of real values
14400 (in particular, IEEE-conformant floating point, because of negative
14401 zeroes and NaNs), and for arrays whose elements contain unused bits with
14402 indeterminate values.
14405 The other component-by-component array operations (@code{and}, @code{or},
14406 @code{xor}, @code{not}, and relational tests other than equality)
14407 are not implemented.
14410 @cindex array aggregates (Ada)
14411 @cindex record aggregates (Ada)
14412 @cindex aggregates (Ada)
14413 There is limited support for array and record aggregates. They are
14414 permitted only on the right sides of assignments, as in these examples:
14417 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
14418 (@value{GDBP}) set An_Array := (1, others => 0)
14419 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
14420 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
14421 (@value{GDBP}) set A_Record := (1, "Peter", True);
14422 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
14426 discriminant's value by assigning an aggregate has an
14427 undefined effect if that discriminant is used within the record.
14428 However, you can first modify discriminants by directly assigning to
14429 them (which normally would not be allowed in Ada), and then performing an
14430 aggregate assignment. For example, given a variable @code{A_Rec}
14431 declared to have a type such as:
14434 type Rec (Len : Small_Integer := 0) is record
14436 Vals : IntArray (1 .. Len);
14440 you can assign a value with a different size of @code{Vals} with two
14444 (@value{GDBP}) set A_Rec.Len := 4
14445 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
14448 As this example also illustrates, @value{GDBN} is very loose about the usual
14449 rules concerning aggregates. You may leave out some of the
14450 components of an array or record aggregate (such as the @code{Len}
14451 component in the assignment to @code{A_Rec} above); they will retain their
14452 original values upon assignment. You may freely use dynamic values as
14453 indices in component associations. You may even use overlapping or
14454 redundant component associations, although which component values are
14455 assigned in such cases is not defined.
14458 Calls to dispatching subprograms are not implemented.
14461 The overloading algorithm is much more limited (i.e., less selective)
14462 than that of real Ada. It makes only limited use of the context in
14463 which a subexpression appears to resolve its meaning, and it is much
14464 looser in its rules for allowing type matches. As a result, some
14465 function calls will be ambiguous, and the user will be asked to choose
14466 the proper resolution.
14469 The @code{new} operator is not implemented.
14472 Entry calls are not implemented.
14475 Aside from printing, arithmetic operations on the native VAX floating-point
14476 formats are not supported.
14479 It is not possible to slice a packed array.
14482 The names @code{True} and @code{False}, when not part of a qualified name,
14483 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
14485 Should your program
14486 redefine these names in a package or procedure (at best a dubious practice),
14487 you will have to use fully qualified names to access their new definitions.
14490 @node Additions to Ada
14491 @subsubsection Additions to Ada
14492 @cindex Ada, deviations from
14494 As it does for other languages, @value{GDBN} makes certain generic
14495 extensions to Ada (@pxref{Expressions}):
14499 If the expression @var{E} is a variable residing in memory (typically
14500 a local variable or array element) and @var{N} is a positive integer,
14501 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
14502 @var{N}-1 adjacent variables following it in memory as an array. In
14503 Ada, this operator is generally not necessary, since its prime use is
14504 in displaying parts of an array, and slicing will usually do this in
14505 Ada. However, there are occasional uses when debugging programs in
14506 which certain debugging information has been optimized away.
14509 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
14510 appears in function or file @var{B}.'' When @var{B} is a file name,
14511 you must typically surround it in single quotes.
14514 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
14515 @var{type} that appears at address @var{addr}.''
14518 A name starting with @samp{$} is a convenience variable
14519 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
14522 In addition, @value{GDBN} provides a few other shortcuts and outright
14523 additions specific to Ada:
14527 The assignment statement is allowed as an expression, returning
14528 its right-hand operand as its value. Thus, you may enter
14531 (@value{GDBP}) set x := y + 3
14532 (@value{GDBP}) print A(tmp := y + 1)
14536 The semicolon is allowed as an ``operator,'' returning as its value
14537 the value of its right-hand operand.
14538 This allows, for example,
14539 complex conditional breaks:
14542 (@value{GDBP}) break f
14543 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
14547 Rather than use catenation and symbolic character names to introduce special
14548 characters into strings, one may instead use a special bracket notation,
14549 which is also used to print strings. A sequence of characters of the form
14550 @samp{["@var{XX}"]} within a string or character literal denotes the
14551 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
14552 sequence of characters @samp{["""]} also denotes a single quotation mark
14553 in strings. For example,
14555 "One line.["0a"]Next line.["0a"]"
14558 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
14562 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
14563 @t{'Max} is optional (and is ignored in any case). For example, it is valid
14567 (@value{GDBP}) print 'max(x, y)
14571 When printing arrays, @value{GDBN} uses positional notation when the
14572 array has a lower bound of 1, and uses a modified named notation otherwise.
14573 For example, a one-dimensional array of three integers with a lower bound
14574 of 3 might print as
14581 That is, in contrast to valid Ada, only the first component has a @code{=>}
14585 You may abbreviate attributes in expressions with any unique,
14586 multi-character subsequence of
14587 their names (an exact match gets preference).
14588 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
14589 in place of @t{a'length}.
14592 @cindex quoting Ada internal identifiers
14593 Since Ada is case-insensitive, the debugger normally maps identifiers you type
14594 to lower case. The GNAT compiler uses upper-case characters for
14595 some of its internal identifiers, which are normally of no interest to users.
14596 For the rare occasions when you actually have to look at them,
14597 enclose them in angle brackets to avoid the lower-case mapping.
14600 (@value{GDBP}) print <JMPBUF_SAVE>[0]
14604 Printing an object of class-wide type or dereferencing an
14605 access-to-class-wide value will display all the components of the object's
14606 specific type (as indicated by its run-time tag). Likewise, component
14607 selection on such a value will operate on the specific type of the
14612 @node Stopping Before Main Program
14613 @subsubsection Stopping at the Very Beginning
14615 @cindex breakpointing Ada elaboration code
14616 It is sometimes necessary to debug the program during elaboration, and
14617 before reaching the main procedure.
14618 As defined in the Ada Reference
14619 Manual, the elaboration code is invoked from a procedure called
14620 @code{adainit}. To run your program up to the beginning of
14621 elaboration, simply use the following two commands:
14622 @code{tbreak adainit} and @code{run}.
14625 @subsubsection Extensions for Ada Tasks
14626 @cindex Ada, tasking
14628 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
14629 @value{GDBN} provides the following task-related commands:
14634 This command shows a list of current Ada tasks, as in the following example:
14641 (@value{GDBP}) info tasks
14642 ID TID P-ID Pri State Name
14643 1 8088000 0 15 Child Activation Wait main_task
14644 2 80a4000 1 15 Accept Statement b
14645 3 809a800 1 15 Child Activation Wait a
14646 * 4 80ae800 3 15 Runnable c
14651 In this listing, the asterisk before the last task indicates it to be the
14652 task currently being inspected.
14656 Represents @value{GDBN}'s internal task number.
14662 The parent's task ID (@value{GDBN}'s internal task number).
14665 The base priority of the task.
14668 Current state of the task.
14672 The task has been created but has not been activated. It cannot be
14676 The task is not blocked for any reason known to Ada. (It may be waiting
14677 for a mutex, though.) It is conceptually "executing" in normal mode.
14680 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14681 that were waiting on terminate alternatives have been awakened and have
14682 terminated themselves.
14684 @item Child Activation Wait
14685 The task is waiting for created tasks to complete activation.
14687 @item Accept Statement
14688 The task is waiting on an accept or selective wait statement.
14690 @item Waiting on entry call
14691 The task is waiting on an entry call.
14693 @item Async Select Wait
14694 The task is waiting to start the abortable part of an asynchronous
14698 The task is waiting on a select statement with only a delay
14701 @item Child Termination Wait
14702 The task is sleeping having completed a master within itself, and is
14703 waiting for the tasks dependent on that master to become terminated or
14704 waiting on a terminate Phase.
14706 @item Wait Child in Term Alt
14707 The task is sleeping waiting for tasks on terminate alternatives to
14708 finish terminating.
14710 @item Accepting RV with @var{taskno}
14711 The task is accepting a rendez-vous with the task @var{taskno}.
14715 Name of the task in the program.
14719 @kindex info task @var{taskno}
14720 @item info task @var{taskno}
14721 This command shows detailled informations on the specified task, as in
14722 the following example:
14727 (@value{GDBP}) info tasks
14728 ID TID P-ID Pri State Name
14729 1 8077880 0 15 Child Activation Wait main_task
14730 * 2 807c468 1 15 Runnable task_1
14731 (@value{GDBP}) info task 2
14732 Ada Task: 0x807c468
14735 Parent: 1 (main_task)
14741 @kindex task@r{ (Ada)}
14742 @cindex current Ada task ID
14743 This command prints the ID of the current task.
14749 (@value{GDBP}) info tasks
14750 ID TID P-ID Pri State Name
14751 1 8077870 0 15 Child Activation Wait main_task
14752 * 2 807c458 1 15 Runnable t
14753 (@value{GDBP}) task
14754 [Current task is 2]
14757 @item task @var{taskno}
14758 @cindex Ada task switching
14759 This command is like the @code{thread @var{threadno}}
14760 command (@pxref{Threads}). It switches the context of debugging
14761 from the current task to the given task.
14767 (@value{GDBP}) info tasks
14768 ID TID P-ID Pri State Name
14769 1 8077870 0 15 Child Activation Wait main_task
14770 * 2 807c458 1 15 Runnable t
14771 (@value{GDBP}) task 1
14772 [Switching to task 1]
14773 #0 0x8067726 in pthread_cond_wait ()
14775 #0 0x8067726 in pthread_cond_wait ()
14776 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14777 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14778 #3 0x806153e in system.tasking.stages.activate_tasks ()
14779 #4 0x804aacc in un () at un.adb:5
14782 @item break @var{linespec} task @var{taskno}
14783 @itemx break @var{linespec} task @var{taskno} if @dots{}
14784 @cindex breakpoints and tasks, in Ada
14785 @cindex task breakpoints, in Ada
14786 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14787 These commands are like the @code{break @dots{} thread @dots{}}
14788 command (@pxref{Thread Stops}).
14789 @var{linespec} specifies source lines, as described
14790 in @ref{Specify Location}.
14792 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14793 to specify that you only want @value{GDBN} to stop the program when a
14794 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14795 numeric task identifiers assigned by @value{GDBN}, shown in the first
14796 column of the @samp{info tasks} display.
14798 If you do not specify @samp{task @var{taskno}} when you set a
14799 breakpoint, the breakpoint applies to @emph{all} tasks of your
14802 You can use the @code{task} qualifier on conditional breakpoints as
14803 well; in this case, place @samp{task @var{taskno}} before the
14804 breakpoint condition (before the @code{if}).
14812 (@value{GDBP}) info tasks
14813 ID TID P-ID Pri State Name
14814 1 140022020 0 15 Child Activation Wait main_task
14815 2 140045060 1 15 Accept/Select Wait t2
14816 3 140044840 1 15 Runnable t1
14817 * 4 140056040 1 15 Runnable t3
14818 (@value{GDBP}) b 15 task 2
14819 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14820 (@value{GDBP}) cont
14825 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14827 (@value{GDBP}) info tasks
14828 ID TID P-ID Pri State Name
14829 1 140022020 0 15 Child Activation Wait main_task
14830 * 2 140045060 1 15 Runnable t2
14831 3 140044840 1 15 Runnable t1
14832 4 140056040 1 15 Delay Sleep t3
14836 @node Ada Tasks and Core Files
14837 @subsubsection Tasking Support when Debugging Core Files
14838 @cindex Ada tasking and core file debugging
14840 When inspecting a core file, as opposed to debugging a live program,
14841 tasking support may be limited or even unavailable, depending on
14842 the platform being used.
14843 For instance, on x86-linux, the list of tasks is available, but task
14844 switching is not supported. On Tru64, however, task switching will work
14847 On certain platforms, including Tru64, the debugger needs to perform some
14848 memory writes in order to provide Ada tasking support. When inspecting
14849 a core file, this means that the core file must be opened with read-write
14850 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14851 Under these circumstances, you should make a backup copy of the core
14852 file before inspecting it with @value{GDBN}.
14854 @node Ravenscar Profile
14855 @subsubsection Tasking Support when using the Ravenscar Profile
14856 @cindex Ravenscar Profile
14858 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14859 specifically designed for systems with safety-critical real-time
14863 @kindex set ravenscar task-switching on
14864 @cindex task switching with program using Ravenscar Profile
14865 @item set ravenscar task-switching on
14866 Allows task switching when debugging a program that uses the Ravenscar
14867 Profile. This is the default.
14869 @kindex set ravenscar task-switching off
14870 @item set ravenscar task-switching off
14871 Turn off task switching when debugging a program that uses the Ravenscar
14872 Profile. This is mostly intended to disable the code that adds support
14873 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14874 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14875 To be effective, this command should be run before the program is started.
14877 @kindex show ravenscar task-switching
14878 @item show ravenscar task-switching
14879 Show whether it is possible to switch from task to task in a program
14880 using the Ravenscar Profile.
14885 @subsubsection Known Peculiarities of Ada Mode
14886 @cindex Ada, problems
14888 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14889 we know of several problems with and limitations of Ada mode in
14891 some of which will be fixed with planned future releases of the debugger
14892 and the GNU Ada compiler.
14896 Static constants that the compiler chooses not to materialize as objects in
14897 storage are invisible to the debugger.
14900 Named parameter associations in function argument lists are ignored (the
14901 argument lists are treated as positional).
14904 Many useful library packages are currently invisible to the debugger.
14907 Fixed-point arithmetic, conversions, input, and output is carried out using
14908 floating-point arithmetic, and may give results that only approximate those on
14912 The GNAT compiler never generates the prefix @code{Standard} for any of
14913 the standard symbols defined by the Ada language. @value{GDBN} knows about
14914 this: it will strip the prefix from names when you use it, and will never
14915 look for a name you have so qualified among local symbols, nor match against
14916 symbols in other packages or subprograms. If you have
14917 defined entities anywhere in your program other than parameters and
14918 local variables whose simple names match names in @code{Standard},
14919 GNAT's lack of qualification here can cause confusion. When this happens,
14920 you can usually resolve the confusion
14921 by qualifying the problematic names with package
14922 @code{Standard} explicitly.
14925 Older versions of the compiler sometimes generate erroneous debugging
14926 information, resulting in the debugger incorrectly printing the value
14927 of affected entities. In some cases, the debugger is able to work
14928 around an issue automatically. In other cases, the debugger is able
14929 to work around the issue, but the work-around has to be specifically
14932 @kindex set ada trust-PAD-over-XVS
14933 @kindex show ada trust-PAD-over-XVS
14936 @item set ada trust-PAD-over-XVS on
14937 Configure GDB to strictly follow the GNAT encoding when computing the
14938 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14939 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14940 a complete description of the encoding used by the GNAT compiler).
14941 This is the default.
14943 @item set ada trust-PAD-over-XVS off
14944 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14945 sometimes prints the wrong value for certain entities, changing @code{ada
14946 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14947 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14948 @code{off}, but this incurs a slight performance penalty, so it is
14949 recommended to leave this setting to @code{on} unless necessary.
14953 @node Unsupported Languages
14954 @section Unsupported Languages
14956 @cindex unsupported languages
14957 @cindex minimal language
14958 In addition to the other fully-supported programming languages,
14959 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14960 It does not represent a real programming language, but provides a set
14961 of capabilities close to what the C or assembly languages provide.
14962 This should allow most simple operations to be performed while debugging
14963 an application that uses a language currently not supported by @value{GDBN}.
14965 If the language is set to @code{auto}, @value{GDBN} will automatically
14966 select this language if the current frame corresponds to an unsupported
14970 @chapter Examining the Symbol Table
14972 The commands described in this chapter allow you to inquire about the
14973 symbols (names of variables, functions and types) defined in your
14974 program. This information is inherent in the text of your program and
14975 does not change as your program executes. @value{GDBN} finds it in your
14976 program's symbol table, in the file indicated when you started @value{GDBN}
14977 (@pxref{File Options, ,Choosing Files}), or by one of the
14978 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14980 @cindex symbol names
14981 @cindex names of symbols
14982 @cindex quoting names
14983 Occasionally, you may need to refer to symbols that contain unusual
14984 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14985 most frequent case is in referring to static variables in other
14986 source files (@pxref{Variables,,Program Variables}). File names
14987 are recorded in object files as debugging symbols, but @value{GDBN} would
14988 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14989 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14990 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14997 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15000 @cindex case-insensitive symbol names
15001 @cindex case sensitivity in symbol names
15002 @kindex set case-sensitive
15003 @item set case-sensitive on
15004 @itemx set case-sensitive off
15005 @itemx set case-sensitive auto
15006 Normally, when @value{GDBN} looks up symbols, it matches their names
15007 with case sensitivity determined by the current source language.
15008 Occasionally, you may wish to control that. The command @code{set
15009 case-sensitive} lets you do that by specifying @code{on} for
15010 case-sensitive matches or @code{off} for case-insensitive ones. If
15011 you specify @code{auto}, case sensitivity is reset to the default
15012 suitable for the source language. The default is case-sensitive
15013 matches for all languages except for Fortran, for which the default is
15014 case-insensitive matches.
15016 @kindex show case-sensitive
15017 @item show case-sensitive
15018 This command shows the current setting of case sensitivity for symbols
15021 @kindex set print type methods
15022 @item set print type methods
15023 @itemx set print type methods on
15024 @itemx set print type methods off
15025 Normally, when @value{GDBN} prints a class, it displays any methods
15026 declared in that class. You can control this behavior either by
15027 passing the appropriate flag to @code{ptype}, or using @command{set
15028 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15029 display the methods; this is the default. Specifying @code{off} will
15030 cause @value{GDBN} to omit the methods.
15032 @kindex show print type methods
15033 @item show print type methods
15034 This command shows the current setting of method display when printing
15037 @kindex set print type typedefs
15038 @item set print type typedefs
15039 @itemx set print type typedefs on
15040 @itemx set print type typedefs off
15042 Normally, when @value{GDBN} prints a class, it displays any typedefs
15043 defined in that class. You can control this behavior either by
15044 passing the appropriate flag to @code{ptype}, or using @command{set
15045 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15046 display the typedef definitions; this is the default. Specifying
15047 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15048 Note that this controls whether the typedef definition itself is
15049 printed, not whether typedef names are substituted when printing other
15052 @kindex show print type typedefs
15053 @item show print type typedefs
15054 This command shows the current setting of typedef display when
15057 @kindex info address
15058 @cindex address of a symbol
15059 @item info address @var{symbol}
15060 Describe where the data for @var{symbol} is stored. For a register
15061 variable, this says which register it is kept in. For a non-register
15062 local variable, this prints the stack-frame offset at which the variable
15065 Note the contrast with @samp{print &@var{symbol}}, which does not work
15066 at all for a register variable, and for a stack local variable prints
15067 the exact address of the current instantiation of the variable.
15069 @kindex info symbol
15070 @cindex symbol from address
15071 @cindex closest symbol and offset for an address
15072 @item info symbol @var{addr}
15073 Print the name of a symbol which is stored at the address @var{addr}.
15074 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15075 nearest symbol and an offset from it:
15078 (@value{GDBP}) info symbol 0x54320
15079 _initialize_vx + 396 in section .text
15083 This is the opposite of the @code{info address} command. You can use
15084 it to find out the name of a variable or a function given its address.
15086 For dynamically linked executables, the name of executable or shared
15087 library containing the symbol is also printed:
15090 (@value{GDBP}) info symbol 0x400225
15091 _start + 5 in section .text of /tmp/a.out
15092 (@value{GDBP}) info symbol 0x2aaaac2811cf
15093 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15097 @item whatis[/@var{flags}] [@var{arg}]
15098 Print the data type of @var{arg}, which can be either an expression
15099 or a name of a data type. With no argument, print the data type of
15100 @code{$}, the last value in the value history.
15102 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15103 is not actually evaluated, and any side-effecting operations (such as
15104 assignments or function calls) inside it do not take place.
15106 If @var{arg} is a variable or an expression, @code{whatis} prints its
15107 literal type as it is used in the source code. If the type was
15108 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15109 the data type underlying the @code{typedef}. If the type of the
15110 variable or the expression is a compound data type, such as
15111 @code{struct} or @code{class}, @code{whatis} never prints their
15112 fields or methods. It just prints the @code{struct}/@code{class}
15113 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15114 such a compound data type, use @code{ptype}.
15116 If @var{arg} is a type name that was defined using @code{typedef},
15117 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15118 Unrolling means that @code{whatis} will show the underlying type used
15119 in the @code{typedef} declaration of @var{arg}. However, if that
15120 underlying type is also a @code{typedef}, @code{whatis} will not
15123 For C code, the type names may also have the form @samp{class
15124 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15125 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15127 @var{flags} can be used to modify how the type is displayed.
15128 Available flags are:
15132 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15133 parameters and typedefs defined in a class when printing the class'
15134 members. The @code{/r} flag disables this.
15137 Do not print methods defined in the class.
15140 Print methods defined in the class. This is the default, but the flag
15141 exists in case you change the default with @command{set print type methods}.
15144 Do not print typedefs defined in the class. Note that this controls
15145 whether the typedef definition itself is printed, not whether typedef
15146 names are substituted when printing other types.
15149 Print typedefs defined in the class. This is the default, but the flag
15150 exists in case you change the default with @command{set print type typedefs}.
15154 @item ptype[/@var{flags}] [@var{arg}]
15155 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15156 detailed description of the type, instead of just the name of the type.
15157 @xref{Expressions, ,Expressions}.
15159 Contrary to @code{whatis}, @code{ptype} always unrolls any
15160 @code{typedef}s in its argument declaration, whether the argument is
15161 a variable, expression, or a data type. This means that @code{ptype}
15162 of a variable or an expression will not print literally its type as
15163 present in the source code---use @code{whatis} for that. @code{typedef}s at
15164 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15165 fields, methods and inner @code{class typedef}s of @code{struct}s,
15166 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15168 For example, for this variable declaration:
15171 typedef double real_t;
15172 struct complex @{ real_t real; double imag; @};
15173 typedef struct complex complex_t;
15175 real_t *real_pointer_var;
15179 the two commands give this output:
15183 (@value{GDBP}) whatis var
15185 (@value{GDBP}) ptype var
15186 type = struct complex @{
15190 (@value{GDBP}) whatis complex_t
15191 type = struct complex
15192 (@value{GDBP}) whatis struct complex
15193 type = struct complex
15194 (@value{GDBP}) ptype struct complex
15195 type = struct complex @{
15199 (@value{GDBP}) whatis real_pointer_var
15201 (@value{GDBP}) ptype real_pointer_var
15207 As with @code{whatis}, using @code{ptype} without an argument refers to
15208 the type of @code{$}, the last value in the value history.
15210 @cindex incomplete type
15211 Sometimes, programs use opaque data types or incomplete specifications
15212 of complex data structure. If the debug information included in the
15213 program does not allow @value{GDBN} to display a full declaration of
15214 the data type, it will say @samp{<incomplete type>}. For example,
15215 given these declarations:
15219 struct foo *fooptr;
15223 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15226 (@value{GDBP}) ptype foo
15227 $1 = <incomplete type>
15231 ``Incomplete type'' is C terminology for data types that are not
15232 completely specified.
15235 @item info types @var{regexp}
15237 Print a brief description of all types whose names match the regular
15238 expression @var{regexp} (or all types in your program, if you supply
15239 no argument). Each complete typename is matched as though it were a
15240 complete line; thus, @samp{i type value} gives information on all
15241 types in your program whose names include the string @code{value}, but
15242 @samp{i type ^value$} gives information only on types whose complete
15243 name is @code{value}.
15245 This command differs from @code{ptype} in two ways: first, like
15246 @code{whatis}, it does not print a detailed description; second, it
15247 lists all source files where a type is defined.
15249 @kindex info type-printers
15250 @item info type-printers
15251 Versions of @value{GDBN} that ship with Python scripting enabled may
15252 have ``type printers'' available. When using @command{ptype} or
15253 @command{whatis}, these printers are consulted when the name of a type
15254 is needed. @xref{Type Printing API}, for more information on writing
15257 @code{info type-printers} displays all the available type printers.
15259 @kindex enable type-printer
15260 @kindex disable type-printer
15261 @item enable type-printer @var{name}@dots{}
15262 @item disable type-printer @var{name}@dots{}
15263 These commands can be used to enable or disable type printers.
15266 @cindex local variables
15267 @item info scope @var{location}
15268 List all the variables local to a particular scope. This command
15269 accepts a @var{location} argument---a function name, a source line, or
15270 an address preceded by a @samp{*}, and prints all the variables local
15271 to the scope defined by that location. (@xref{Specify Location}, for
15272 details about supported forms of @var{location}.) For example:
15275 (@value{GDBP}) @b{info scope command_line_handler}
15276 Scope for command_line_handler:
15277 Symbol rl is an argument at stack/frame offset 8, length 4.
15278 Symbol linebuffer is in static storage at address 0x150a18, length 4.
15279 Symbol linelength is in static storage at address 0x150a1c, length 4.
15280 Symbol p is a local variable in register $esi, length 4.
15281 Symbol p1 is a local variable in register $ebx, length 4.
15282 Symbol nline is a local variable in register $edx, length 4.
15283 Symbol repeat is a local variable at frame offset -8, length 4.
15287 This command is especially useful for determining what data to collect
15288 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
15291 @kindex info source
15293 Show information about the current source file---that is, the source file for
15294 the function containing the current point of execution:
15297 the name of the source file, and the directory containing it,
15299 the directory it was compiled in,
15301 its length, in lines,
15303 which programming language it is written in,
15305 whether the executable includes debugging information for that file, and
15306 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
15308 whether the debugging information includes information about
15309 preprocessor macros.
15313 @kindex info sources
15315 Print the names of all source files in your program for which there is
15316 debugging information, organized into two lists: files whose symbols
15317 have already been read, and files whose symbols will be read when needed.
15319 @kindex info functions
15320 @item info functions
15321 Print the names and data types of all defined functions.
15323 @item info functions @var{regexp}
15324 Print the names and data types of all defined functions
15325 whose names contain a match for regular expression @var{regexp}.
15326 Thus, @samp{info fun step} finds all functions whose names
15327 include @code{step}; @samp{info fun ^step} finds those whose names
15328 start with @code{step}. If a function name contains characters
15329 that conflict with the regular expression language (e.g.@:
15330 @samp{operator*()}), they may be quoted with a backslash.
15332 @kindex info variables
15333 @item info variables
15334 Print the names and data types of all variables that are defined
15335 outside of functions (i.e.@: excluding local variables).
15337 @item info variables @var{regexp}
15338 Print the names and data types of all variables (except for local
15339 variables) whose names contain a match for regular expression
15342 @kindex info classes
15343 @cindex Objective-C, classes and selectors
15345 @itemx info classes @var{regexp}
15346 Display all Objective-C classes in your program, or
15347 (with the @var{regexp} argument) all those matching a particular regular
15350 @kindex info selectors
15351 @item info selectors
15352 @itemx info selectors @var{regexp}
15353 Display all Objective-C selectors in your program, or
15354 (with the @var{regexp} argument) all those matching a particular regular
15358 This was never implemented.
15359 @kindex info methods
15361 @itemx info methods @var{regexp}
15362 The @code{info methods} command permits the user to examine all defined
15363 methods within C@t{++} program, or (with the @var{regexp} argument) a
15364 specific set of methods found in the various C@t{++} classes. Many
15365 C@t{++} classes provide a large number of methods. Thus, the output
15366 from the @code{ptype} command can be overwhelming and hard to use. The
15367 @code{info-methods} command filters the methods, printing only those
15368 which match the regular-expression @var{regexp}.
15371 @cindex opaque data types
15372 @kindex set opaque-type-resolution
15373 @item set opaque-type-resolution on
15374 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
15375 declared as a pointer to a @code{struct}, @code{class}, or
15376 @code{union}---for example, @code{struct MyType *}---that is used in one
15377 source file although the full declaration of @code{struct MyType} is in
15378 another source file. The default is on.
15380 A change in the setting of this subcommand will not take effect until
15381 the next time symbols for a file are loaded.
15383 @item set opaque-type-resolution off
15384 Tell @value{GDBN} not to resolve opaque types. In this case, the type
15385 is printed as follows:
15387 @{<no data fields>@}
15390 @kindex show opaque-type-resolution
15391 @item show opaque-type-resolution
15392 Show whether opaque types are resolved or not.
15394 @kindex maint print symbols
15395 @cindex symbol dump
15396 @kindex maint print psymbols
15397 @cindex partial symbol dump
15398 @item maint print symbols @var{filename}
15399 @itemx maint print psymbols @var{filename}
15400 @itemx maint print msymbols @var{filename}
15401 Write a dump of debugging symbol data into the file @var{filename}.
15402 These commands are used to debug the @value{GDBN} symbol-reading code. Only
15403 symbols with debugging data are included. If you use @samp{maint print
15404 symbols}, @value{GDBN} includes all the symbols for which it has already
15405 collected full details: that is, @var{filename} reflects symbols for
15406 only those files whose symbols @value{GDBN} has read. You can use the
15407 command @code{info sources} to find out which files these are. If you
15408 use @samp{maint print psymbols} instead, the dump shows information about
15409 symbols that @value{GDBN} only knows partially---that is, symbols defined in
15410 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
15411 @samp{maint print msymbols} dumps just the minimal symbol information
15412 required for each object file from which @value{GDBN} has read some symbols.
15413 @xref{Files, ,Commands to Specify Files}, for a discussion of how
15414 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
15416 @kindex maint info symtabs
15417 @kindex maint info psymtabs
15418 @cindex listing @value{GDBN}'s internal symbol tables
15419 @cindex symbol tables, listing @value{GDBN}'s internal
15420 @cindex full symbol tables, listing @value{GDBN}'s internal
15421 @cindex partial symbol tables, listing @value{GDBN}'s internal
15422 @item maint info symtabs @r{[} @var{regexp} @r{]}
15423 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
15425 List the @code{struct symtab} or @code{struct partial_symtab}
15426 structures whose names match @var{regexp}. If @var{regexp} is not
15427 given, list them all. The output includes expressions which you can
15428 copy into a @value{GDBN} debugging this one to examine a particular
15429 structure in more detail. For example:
15432 (@value{GDBP}) maint info psymtabs dwarf2read
15433 @{ objfile /home/gnu/build/gdb/gdb
15434 ((struct objfile *) 0x82e69d0)
15435 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
15436 ((struct partial_symtab *) 0x8474b10)
15439 text addresses 0x814d3c8 -- 0x8158074
15440 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
15441 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
15442 dependencies (none)
15445 (@value{GDBP}) maint info symtabs
15449 We see that there is one partial symbol table whose filename contains
15450 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
15451 and we see that @value{GDBN} has not read in any symtabs yet at all.
15452 If we set a breakpoint on a function, that will cause @value{GDBN} to
15453 read the symtab for the compilation unit containing that function:
15456 (@value{GDBP}) break dwarf2_psymtab_to_symtab
15457 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
15459 (@value{GDBP}) maint info symtabs
15460 @{ objfile /home/gnu/build/gdb/gdb
15461 ((struct objfile *) 0x82e69d0)
15462 @{ symtab /home/gnu/src/gdb/dwarf2read.c
15463 ((struct symtab *) 0x86c1f38)
15466 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
15467 linetable ((struct linetable *) 0x8370fa0)
15468 debugformat DWARF 2
15477 @chapter Altering Execution
15479 Once you think you have found an error in your program, you might want to
15480 find out for certain whether correcting the apparent error would lead to
15481 correct results in the rest of the run. You can find the answer by
15482 experiment, using the @value{GDBN} features for altering execution of the
15485 For example, you can store new values into variables or memory
15486 locations, give your program a signal, restart it at a different
15487 address, or even return prematurely from a function.
15490 * Assignment:: Assignment to variables
15491 * Jumping:: Continuing at a different address
15492 * Signaling:: Giving your program a signal
15493 * Returning:: Returning from a function
15494 * Calling:: Calling your program's functions
15495 * Patching:: Patching your program
15499 @section Assignment to Variables
15502 @cindex setting variables
15503 To alter the value of a variable, evaluate an assignment expression.
15504 @xref{Expressions, ,Expressions}. For example,
15511 stores the value 4 into the variable @code{x}, and then prints the
15512 value of the assignment expression (which is 4).
15513 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
15514 information on operators in supported languages.
15516 @kindex set variable
15517 @cindex variables, setting
15518 If you are not interested in seeing the value of the assignment, use the
15519 @code{set} command instead of the @code{print} command. @code{set} is
15520 really the same as @code{print} except that the expression's value is
15521 not printed and is not put in the value history (@pxref{Value History,
15522 ,Value History}). The expression is evaluated only for its effects.
15524 If the beginning of the argument string of the @code{set} command
15525 appears identical to a @code{set} subcommand, use the @code{set
15526 variable} command instead of just @code{set}. This command is identical
15527 to @code{set} except for its lack of subcommands. For example, if your
15528 program has a variable @code{width}, you get an error if you try to set
15529 a new value with just @samp{set width=13}, because @value{GDBN} has the
15530 command @code{set width}:
15533 (@value{GDBP}) whatis width
15535 (@value{GDBP}) p width
15537 (@value{GDBP}) set width=47
15538 Invalid syntax in expression.
15542 The invalid expression, of course, is @samp{=47}. In
15543 order to actually set the program's variable @code{width}, use
15546 (@value{GDBP}) set var width=47
15549 Because the @code{set} command has many subcommands that can conflict
15550 with the names of program variables, it is a good idea to use the
15551 @code{set variable} command instead of just @code{set}. For example, if
15552 your program has a variable @code{g}, you run into problems if you try
15553 to set a new value with just @samp{set g=4}, because @value{GDBN} has
15554 the command @code{set gnutarget}, abbreviated @code{set g}:
15558 (@value{GDBP}) whatis g
15562 (@value{GDBP}) set g=4
15566 The program being debugged has been started already.
15567 Start it from the beginning? (y or n) y
15568 Starting program: /home/smith/cc_progs/a.out
15569 "/home/smith/cc_progs/a.out": can't open to read symbols:
15570 Invalid bfd target.
15571 (@value{GDBP}) show g
15572 The current BFD target is "=4".
15577 The program variable @code{g} did not change, and you silently set the
15578 @code{gnutarget} to an invalid value. In order to set the variable
15582 (@value{GDBP}) set var g=4
15585 @value{GDBN} allows more implicit conversions in assignments than C; you can
15586 freely store an integer value into a pointer variable or vice versa,
15587 and you can convert any structure to any other structure that is the
15588 same length or shorter.
15589 @comment FIXME: how do structs align/pad in these conversions?
15590 @comment /doc@cygnus.com 18dec1990
15592 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
15593 construct to generate a value of specified type at a specified address
15594 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
15595 to memory location @code{0x83040} as an integer (which implies a certain size
15596 and representation in memory), and
15599 set @{int@}0x83040 = 4
15603 stores the value 4 into that memory location.
15606 @section Continuing at a Different Address
15608 Ordinarily, when you continue your program, you do so at the place where
15609 it stopped, with the @code{continue} command. You can instead continue at
15610 an address of your own choosing, with the following commands:
15614 @kindex j @r{(@code{jump})}
15615 @item jump @var{linespec}
15616 @itemx j @var{linespec}
15617 @itemx jump @var{location}
15618 @itemx j @var{location}
15619 Resume execution at line @var{linespec} or at address given by
15620 @var{location}. Execution stops again immediately if there is a
15621 breakpoint there. @xref{Specify Location}, for a description of the
15622 different forms of @var{linespec} and @var{location}. It is common
15623 practice to use the @code{tbreak} command in conjunction with
15624 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
15626 The @code{jump} command does not change the current stack frame, or
15627 the stack pointer, or the contents of any memory location or any
15628 register other than the program counter. If line @var{linespec} is in
15629 a different function from the one currently executing, the results may
15630 be bizarre if the two functions expect different patterns of arguments or
15631 of local variables. For this reason, the @code{jump} command requests
15632 confirmation if the specified line is not in the function currently
15633 executing. However, even bizarre results are predictable if you are
15634 well acquainted with the machine-language code of your program.
15637 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
15638 On many systems, you can get much the same effect as the @code{jump}
15639 command by storing a new value into the register @code{$pc}. The
15640 difference is that this does not start your program running; it only
15641 changes the address of where it @emph{will} run when you continue. For
15649 makes the next @code{continue} command or stepping command execute at
15650 address @code{0x485}, rather than at the address where your program stopped.
15651 @xref{Continuing and Stepping, ,Continuing and Stepping}.
15653 The most common occasion to use the @code{jump} command is to back
15654 up---perhaps with more breakpoints set---over a portion of a program
15655 that has already executed, in order to examine its execution in more
15660 @section Giving your Program a Signal
15661 @cindex deliver a signal to a program
15665 @item signal @var{signal}
15666 Resume execution where your program stopped, but immediately give it the
15667 signal @var{signal}. @var{signal} can be the name or the number of a
15668 signal. For example, on many systems @code{signal 2} and @code{signal
15669 SIGINT} are both ways of sending an interrupt signal.
15671 Alternatively, if @var{signal} is zero, continue execution without
15672 giving a signal. This is useful when your program stopped on account of
15673 a signal and would ordinarily see the signal when resumed with the
15674 @code{continue} command; @samp{signal 0} causes it to resume without a
15677 @code{signal} does not repeat when you press @key{RET} a second time
15678 after executing the command.
15682 Invoking the @code{signal} command is not the same as invoking the
15683 @code{kill} utility from the shell. Sending a signal with @code{kill}
15684 causes @value{GDBN} to decide what to do with the signal depending on
15685 the signal handling tables (@pxref{Signals}). The @code{signal} command
15686 passes the signal directly to your program.
15690 @section Returning from a Function
15693 @cindex returning from a function
15696 @itemx return @var{expression}
15697 You can cancel execution of a function call with the @code{return}
15698 command. If you give an
15699 @var{expression} argument, its value is used as the function's return
15703 When you use @code{return}, @value{GDBN} discards the selected stack frame
15704 (and all frames within it). You can think of this as making the
15705 discarded frame return prematurely. If you wish to specify a value to
15706 be returned, give that value as the argument to @code{return}.
15708 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15709 Frame}), and any other frames inside of it, leaving its caller as the
15710 innermost remaining frame. That frame becomes selected. The
15711 specified value is stored in the registers used for returning values
15714 The @code{return} command does not resume execution; it leaves the
15715 program stopped in the state that would exist if the function had just
15716 returned. In contrast, the @code{finish} command (@pxref{Continuing
15717 and Stepping, ,Continuing and Stepping}) resumes execution until the
15718 selected stack frame returns naturally.
15720 @value{GDBN} needs to know how the @var{expression} argument should be set for
15721 the inferior. The concrete registers assignment depends on the OS ABI and the
15722 type being returned by the selected stack frame. For example it is common for
15723 OS ABI to return floating point values in FPU registers while integer values in
15724 CPU registers. Still some ABIs return even floating point values in CPU
15725 registers. Larger integer widths (such as @code{long long int}) also have
15726 specific placement rules. @value{GDBN} already knows the OS ABI from its
15727 current target so it needs to find out also the type being returned to make the
15728 assignment into the right register(s).
15730 Normally, the selected stack frame has debug info. @value{GDBN} will always
15731 use the debug info instead of the implicit type of @var{expression} when the
15732 debug info is available. For example, if you type @kbd{return -1}, and the
15733 function in the current stack frame is declared to return a @code{long long
15734 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15735 into a @code{long long int}:
15738 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15740 (@value{GDBP}) return -1
15741 Make func return now? (y or n) y
15742 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15743 43 printf ("result=%lld\n", func ());
15747 However, if the selected stack frame does not have a debug info, e.g., if the
15748 function was compiled without debug info, @value{GDBN} has to find out the type
15749 to return from user. Specifying a different type by mistake may set the value
15750 in different inferior registers than the caller code expects. For example,
15751 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15752 of a @code{long long int} result for a debug info less function (on 32-bit
15753 architectures). Therefore the user is required to specify the return type by
15754 an appropriate cast explicitly:
15757 Breakpoint 2, 0x0040050b in func ()
15758 (@value{GDBP}) return -1
15759 Return value type not available for selected stack frame.
15760 Please use an explicit cast of the value to return.
15761 (@value{GDBP}) return (long long int) -1
15762 Make selected stack frame return now? (y or n) y
15763 #0 0x00400526 in main ()
15768 @section Calling Program Functions
15771 @cindex calling functions
15772 @cindex inferior functions, calling
15773 @item print @var{expr}
15774 Evaluate the expression @var{expr} and display the resulting value.
15775 @var{expr} may include calls to functions in the program being
15779 @item call @var{expr}
15780 Evaluate the expression @var{expr} without displaying @code{void}
15783 You can use this variant of the @code{print} command if you want to
15784 execute a function from your program that does not return anything
15785 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15786 with @code{void} returned values that @value{GDBN} will otherwise
15787 print. If the result is not void, it is printed and saved in the
15791 It is possible for the function you call via the @code{print} or
15792 @code{call} command to generate a signal (e.g., if there's a bug in
15793 the function, or if you passed it incorrect arguments). What happens
15794 in that case is controlled by the @code{set unwindonsignal} command.
15796 Similarly, with a C@t{++} program it is possible for the function you
15797 call via the @code{print} or @code{call} command to generate an
15798 exception that is not handled due to the constraints of the dummy
15799 frame. In this case, any exception that is raised in the frame, but has
15800 an out-of-frame exception handler will not be found. GDB builds a
15801 dummy-frame for the inferior function call, and the unwinder cannot
15802 seek for exception handlers outside of this dummy-frame. What happens
15803 in that case is controlled by the
15804 @code{set unwind-on-terminating-exception} command.
15807 @item set unwindonsignal
15808 @kindex set unwindonsignal
15809 @cindex unwind stack in called functions
15810 @cindex call dummy stack unwinding
15811 Set unwinding of the stack if a signal is received while in a function
15812 that @value{GDBN} called in the program being debugged. If set to on,
15813 @value{GDBN} unwinds the stack it created for the call and restores
15814 the context to what it was before the call. If set to off (the
15815 default), @value{GDBN} stops in the frame where the signal was
15818 @item show unwindonsignal
15819 @kindex show unwindonsignal
15820 Show the current setting of stack unwinding in the functions called by
15823 @item set unwind-on-terminating-exception
15824 @kindex set unwind-on-terminating-exception
15825 @cindex unwind stack in called functions with unhandled exceptions
15826 @cindex call dummy stack unwinding on unhandled exception.
15827 Set unwinding of the stack if a C@t{++} exception is raised, but left
15828 unhandled while in a function that @value{GDBN} called in the program being
15829 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15830 it created for the call and restores the context to what it was before
15831 the call. If set to off, @value{GDBN} the exception is delivered to
15832 the default C@t{++} exception handler and the inferior terminated.
15834 @item show unwind-on-terminating-exception
15835 @kindex show unwind-on-terminating-exception
15836 Show the current setting of stack unwinding in the functions called by
15841 @cindex weak alias functions
15842 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15843 for another function. In such case, @value{GDBN} might not pick up
15844 the type information, including the types of the function arguments,
15845 which causes @value{GDBN} to call the inferior function incorrectly.
15846 As a result, the called function will function erroneously and may
15847 even crash. A solution to that is to use the name of the aliased
15851 @section Patching Programs
15853 @cindex patching binaries
15854 @cindex writing into executables
15855 @cindex writing into corefiles
15857 By default, @value{GDBN} opens the file containing your program's
15858 executable code (or the corefile) read-only. This prevents accidental
15859 alterations to machine code; but it also prevents you from intentionally
15860 patching your program's binary.
15862 If you'd like to be able to patch the binary, you can specify that
15863 explicitly with the @code{set write} command. For example, you might
15864 want to turn on internal debugging flags, or even to make emergency
15870 @itemx set write off
15871 If you specify @samp{set write on}, @value{GDBN} opens executable and
15872 core files for both reading and writing; if you specify @kbd{set write
15873 off} (the default), @value{GDBN} opens them read-only.
15875 If you have already loaded a file, you must load it again (using the
15876 @code{exec-file} or @code{core-file} command) after changing @code{set
15877 write}, for your new setting to take effect.
15881 Display whether executable files and core files are opened for writing
15882 as well as reading.
15886 @chapter @value{GDBN} Files
15888 @value{GDBN} needs to know the file name of the program to be debugged,
15889 both in order to read its symbol table and in order to start your
15890 program. To debug a core dump of a previous run, you must also tell
15891 @value{GDBN} the name of the core dump file.
15894 * Files:: Commands to specify files
15895 * Separate Debug Files:: Debugging information in separate files
15896 * MiniDebugInfo:: Debugging information in a special section
15897 * Index Files:: Index files speed up GDB
15898 * Symbol Errors:: Errors reading symbol files
15899 * Data Files:: GDB data files
15903 @section Commands to Specify Files
15905 @cindex symbol table
15906 @cindex core dump file
15908 You may want to specify executable and core dump file names. The usual
15909 way to do this is at start-up time, using the arguments to
15910 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15911 Out of @value{GDBN}}).
15913 Occasionally it is necessary to change to a different file during a
15914 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15915 specify a file you want to use. Or you are debugging a remote target
15916 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15917 Program}). In these situations the @value{GDBN} commands to specify
15918 new files are useful.
15921 @cindex executable file
15923 @item file @var{filename}
15924 Use @var{filename} as the program to be debugged. It is read for its
15925 symbols and for the contents of pure memory. It is also the program
15926 executed when you use the @code{run} command. If you do not specify a
15927 directory and the file is not found in the @value{GDBN} working directory,
15928 @value{GDBN} uses the environment variable @code{PATH} as a list of
15929 directories to search, just as the shell does when looking for a program
15930 to run. You can change the value of this variable, for both @value{GDBN}
15931 and your program, using the @code{path} command.
15933 @cindex unlinked object files
15934 @cindex patching object files
15935 You can load unlinked object @file{.o} files into @value{GDBN} using
15936 the @code{file} command. You will not be able to ``run'' an object
15937 file, but you can disassemble functions and inspect variables. Also,
15938 if the underlying BFD functionality supports it, you could use
15939 @kbd{gdb -write} to patch object files using this technique. Note
15940 that @value{GDBN} can neither interpret nor modify relocations in this
15941 case, so branches and some initialized variables will appear to go to
15942 the wrong place. But this feature is still handy from time to time.
15945 @code{file} with no argument makes @value{GDBN} discard any information it
15946 has on both executable file and the symbol table.
15949 @item exec-file @r{[} @var{filename} @r{]}
15950 Specify that the program to be run (but not the symbol table) is found
15951 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15952 if necessary to locate your program. Omitting @var{filename} means to
15953 discard information on the executable file.
15955 @kindex symbol-file
15956 @item symbol-file @r{[} @var{filename} @r{]}
15957 Read symbol table information from file @var{filename}. @code{PATH} is
15958 searched when necessary. Use the @code{file} command to get both symbol
15959 table and program to run from the same file.
15961 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15962 program's symbol table.
15964 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15965 some breakpoints and auto-display expressions. This is because they may
15966 contain pointers to the internal data recording symbols and data types,
15967 which are part of the old symbol table data being discarded inside
15970 @code{symbol-file} does not repeat if you press @key{RET} again after
15973 When @value{GDBN} is configured for a particular environment, it
15974 understands debugging information in whatever format is the standard
15975 generated for that environment; you may use either a @sc{gnu} compiler, or
15976 other compilers that adhere to the local conventions.
15977 Best results are usually obtained from @sc{gnu} compilers; for example,
15978 using @code{@value{NGCC}} you can generate debugging information for
15981 For most kinds of object files, with the exception of old SVR3 systems
15982 using COFF, the @code{symbol-file} command does not normally read the
15983 symbol table in full right away. Instead, it scans the symbol table
15984 quickly to find which source files and which symbols are present. The
15985 details are read later, one source file at a time, as they are needed.
15987 The purpose of this two-stage reading strategy is to make @value{GDBN}
15988 start up faster. For the most part, it is invisible except for
15989 occasional pauses while the symbol table details for a particular source
15990 file are being read. (The @code{set verbose} command can turn these
15991 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15992 Warnings and Messages}.)
15994 We have not implemented the two-stage strategy for COFF yet. When the
15995 symbol table is stored in COFF format, @code{symbol-file} reads the
15996 symbol table data in full right away. Note that ``stabs-in-COFF''
15997 still does the two-stage strategy, since the debug info is actually
16001 @cindex reading symbols immediately
16002 @cindex symbols, reading immediately
16003 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16004 @itemx file @r{[} -readnow @r{]} @var{filename}
16005 You can override the @value{GDBN} two-stage strategy for reading symbol
16006 tables by using the @samp{-readnow} option with any of the commands that
16007 load symbol table information, if you want to be sure @value{GDBN} has the
16008 entire symbol table available.
16010 @c FIXME: for now no mention of directories, since this seems to be in
16011 @c flux. 13mar1992 status is that in theory GDB would look either in
16012 @c current dir or in same dir as myprog; but issues like competing
16013 @c GDB's, or clutter in system dirs, mean that in practice right now
16014 @c only current dir is used. FFish says maybe a special GDB hierarchy
16015 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16019 @item core-file @r{[}@var{filename}@r{]}
16021 Specify the whereabouts of a core dump file to be used as the ``contents
16022 of memory''. Traditionally, core files contain only some parts of the
16023 address space of the process that generated them; @value{GDBN} can access the
16024 executable file itself for other parts.
16026 @code{core-file} with no argument specifies that no core file is
16029 Note that the core file is ignored when your program is actually running
16030 under @value{GDBN}. So, if you have been running your program and you
16031 wish to debug a core file instead, you must kill the subprocess in which
16032 the program is running. To do this, use the @code{kill} command
16033 (@pxref{Kill Process, ,Killing the Child Process}).
16035 @kindex add-symbol-file
16036 @cindex dynamic linking
16037 @item add-symbol-file @var{filename} @var{address}
16038 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16039 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16040 The @code{add-symbol-file} command reads additional symbol table
16041 information from the file @var{filename}. You would use this command
16042 when @var{filename} has been dynamically loaded (by some other means)
16043 into the program that is running. @var{address} should be the memory
16044 address at which the file has been loaded; @value{GDBN} cannot figure
16045 this out for itself. You can additionally specify an arbitrary number
16046 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16047 section name and base address for that section. You can specify any
16048 @var{address} as an expression.
16050 The symbol table of the file @var{filename} is added to the symbol table
16051 originally read with the @code{symbol-file} command. You can use the
16052 @code{add-symbol-file} command any number of times; the new symbol data
16053 thus read keeps adding to the old. To discard all old symbol data
16054 instead, use the @code{symbol-file} command without any arguments.
16056 @cindex relocatable object files, reading symbols from
16057 @cindex object files, relocatable, reading symbols from
16058 @cindex reading symbols from relocatable object files
16059 @cindex symbols, reading from relocatable object files
16060 @cindex @file{.o} files, reading symbols from
16061 Although @var{filename} is typically a shared library file, an
16062 executable file, or some other object file which has been fully
16063 relocated for loading into a process, you can also load symbolic
16064 information from relocatable @file{.o} files, as long as:
16068 the file's symbolic information refers only to linker symbols defined in
16069 that file, not to symbols defined by other object files,
16071 every section the file's symbolic information refers to has actually
16072 been loaded into the inferior, as it appears in the file, and
16074 you can determine the address at which every section was loaded, and
16075 provide these to the @code{add-symbol-file} command.
16079 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16080 relocatable files into an already running program; such systems
16081 typically make the requirements above easy to meet. However, it's
16082 important to recognize that many native systems use complex link
16083 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16084 assembly, for example) that make the requirements difficult to meet. In
16085 general, one cannot assume that using @code{add-symbol-file} to read a
16086 relocatable object file's symbolic information will have the same effect
16087 as linking the relocatable object file into the program in the normal
16090 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16092 @kindex add-symbol-file-from-memory
16093 @cindex @code{syscall DSO}
16094 @cindex load symbols from memory
16095 @item add-symbol-file-from-memory @var{address}
16096 Load symbols from the given @var{address} in a dynamically loaded
16097 object file whose image is mapped directly into the inferior's memory.
16098 For example, the Linux kernel maps a @code{syscall DSO} into each
16099 process's address space; this DSO provides kernel-specific code for
16100 some system calls. The argument can be any expression whose
16101 evaluation yields the address of the file's shared object file header.
16102 For this command to work, you must have used @code{symbol-file} or
16103 @code{exec-file} commands in advance.
16105 @kindex add-shared-symbol-files
16107 @item add-shared-symbol-files @var{library-file}
16108 @itemx assf @var{library-file}
16109 The @code{add-shared-symbol-files} command can currently be used only
16110 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16111 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16112 @value{GDBN} automatically looks for shared libraries, however if
16113 @value{GDBN} does not find yours, you can invoke
16114 @code{add-shared-symbol-files}. It takes one argument: the shared
16115 library's file name. @code{assf} is a shorthand alias for
16116 @code{add-shared-symbol-files}.
16119 @item section @var{section} @var{addr}
16120 The @code{section} command changes the base address of the named
16121 @var{section} of the exec file to @var{addr}. This can be used if the
16122 exec file does not contain section addresses, (such as in the
16123 @code{a.out} format), or when the addresses specified in the file
16124 itself are wrong. Each section must be changed separately. The
16125 @code{info files} command, described below, lists all the sections and
16129 @kindex info target
16132 @code{info files} and @code{info target} are synonymous; both print the
16133 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16134 including the names of the executable and core dump files currently in
16135 use by @value{GDBN}, and the files from which symbols were loaded. The
16136 command @code{help target} lists all possible targets rather than
16139 @kindex maint info sections
16140 @item maint info sections
16141 Another command that can give you extra information about program sections
16142 is @code{maint info sections}. In addition to the section information
16143 displayed by @code{info files}, this command displays the flags and file
16144 offset of each section in the executable and core dump files. In addition,
16145 @code{maint info sections} provides the following command options (which
16146 may be arbitrarily combined):
16150 Display sections for all loaded object files, including shared libraries.
16151 @item @var{sections}
16152 Display info only for named @var{sections}.
16153 @item @var{section-flags}
16154 Display info only for sections for which @var{section-flags} are true.
16155 The section flags that @value{GDBN} currently knows about are:
16158 Section will have space allocated in the process when loaded.
16159 Set for all sections except those containing debug information.
16161 Section will be loaded from the file into the child process memory.
16162 Set for pre-initialized code and data, clear for @code{.bss} sections.
16164 Section needs to be relocated before loading.
16166 Section cannot be modified by the child process.
16168 Section contains executable code only.
16170 Section contains data only (no executable code).
16172 Section will reside in ROM.
16174 Section contains data for constructor/destructor lists.
16176 Section is not empty.
16178 An instruction to the linker to not output the section.
16179 @item COFF_SHARED_LIBRARY
16180 A notification to the linker that the section contains
16181 COFF shared library information.
16183 Section contains common symbols.
16186 @kindex set trust-readonly-sections
16187 @cindex read-only sections
16188 @item set trust-readonly-sections on
16189 Tell @value{GDBN} that readonly sections in your object file
16190 really are read-only (i.e.@: that their contents will not change).
16191 In that case, @value{GDBN} can fetch values from these sections
16192 out of the object file, rather than from the target program.
16193 For some targets (notably embedded ones), this can be a significant
16194 enhancement to debugging performance.
16196 The default is off.
16198 @item set trust-readonly-sections off
16199 Tell @value{GDBN} not to trust readonly sections. This means that
16200 the contents of the section might change while the program is running,
16201 and must therefore be fetched from the target when needed.
16203 @item show trust-readonly-sections
16204 Show the current setting of trusting readonly sections.
16207 All file-specifying commands allow both absolute and relative file names
16208 as arguments. @value{GDBN} always converts the file name to an absolute file
16209 name and remembers it that way.
16211 @cindex shared libraries
16212 @anchor{Shared Libraries}
16213 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16214 and IBM RS/6000 AIX shared libraries.
16216 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16217 shared libraries. @xref{Expat}.
16219 @value{GDBN} automatically loads symbol definitions from shared libraries
16220 when you use the @code{run} command, or when you examine a core file.
16221 (Before you issue the @code{run} command, @value{GDBN} does not understand
16222 references to a function in a shared library, however---unless you are
16223 debugging a core file).
16225 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16226 automatically loads the symbols at the time of the @code{shl_load} call.
16228 @c FIXME: some @value{GDBN} release may permit some refs to undef
16229 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16230 @c FIXME...lib; check this from time to time when updating manual
16232 There are times, however, when you may wish to not automatically load
16233 symbol definitions from shared libraries, such as when they are
16234 particularly large or there are many of them.
16236 To control the automatic loading of shared library symbols, use the
16240 @kindex set auto-solib-add
16241 @item set auto-solib-add @var{mode}
16242 If @var{mode} is @code{on}, symbols from all shared object libraries
16243 will be loaded automatically when the inferior begins execution, you
16244 attach to an independently started inferior, or when the dynamic linker
16245 informs @value{GDBN} that a new library has been loaded. If @var{mode}
16246 is @code{off}, symbols must be loaded manually, using the
16247 @code{sharedlibrary} command. The default value is @code{on}.
16249 @cindex memory used for symbol tables
16250 If your program uses lots of shared libraries with debug info that
16251 takes large amounts of memory, you can decrease the @value{GDBN}
16252 memory footprint by preventing it from automatically loading the
16253 symbols from shared libraries. To that end, type @kbd{set
16254 auto-solib-add off} before running the inferior, then load each
16255 library whose debug symbols you do need with @kbd{sharedlibrary
16256 @var{regexp}}, where @var{regexp} is a regular expression that matches
16257 the libraries whose symbols you want to be loaded.
16259 @kindex show auto-solib-add
16260 @item show auto-solib-add
16261 Display the current autoloading mode.
16264 @cindex load shared library
16265 To explicitly load shared library symbols, use the @code{sharedlibrary}
16269 @kindex info sharedlibrary
16271 @item info share @var{regex}
16272 @itemx info sharedlibrary @var{regex}
16273 Print the names of the shared libraries which are currently loaded
16274 that match @var{regex}. If @var{regex} is omitted then print
16275 all shared libraries that are loaded.
16277 @kindex sharedlibrary
16279 @item sharedlibrary @var{regex}
16280 @itemx share @var{regex}
16281 Load shared object library symbols for files matching a
16282 Unix regular expression.
16283 As with files loaded automatically, it only loads shared libraries
16284 required by your program for a core file or after typing @code{run}. If
16285 @var{regex} is omitted all shared libraries required by your program are
16288 @item nosharedlibrary
16289 @kindex nosharedlibrary
16290 @cindex unload symbols from shared libraries
16291 Unload all shared object library symbols. This discards all symbols
16292 that have been loaded from all shared libraries. Symbols from shared
16293 libraries that were loaded by explicit user requests are not
16297 Sometimes you may wish that @value{GDBN} stops and gives you control
16298 when any of shared library events happen. The best way to do this is
16299 to use @code{catch load} and @code{catch unload} (@pxref{Set
16302 @value{GDBN} also supports the the @code{set stop-on-solib-events}
16303 command for this. This command exists for historical reasons. It is
16304 less useful than setting a catchpoint, because it does not allow for
16305 conditions or commands as a catchpoint does.
16308 @item set stop-on-solib-events
16309 @kindex set stop-on-solib-events
16310 This command controls whether @value{GDBN} should give you control
16311 when the dynamic linker notifies it about some shared library event.
16312 The most common event of interest is loading or unloading of a new
16315 @item show stop-on-solib-events
16316 @kindex show stop-on-solib-events
16317 Show whether @value{GDBN} stops and gives you control when shared
16318 library events happen.
16321 Shared libraries are also supported in many cross or remote debugging
16322 configurations. @value{GDBN} needs to have access to the target's libraries;
16323 this can be accomplished either by providing copies of the libraries
16324 on the host system, or by asking @value{GDBN} to automatically retrieve the
16325 libraries from the target. If copies of the target libraries are
16326 provided, they need to be the same as the target libraries, although the
16327 copies on the target can be stripped as long as the copies on the host are
16330 @cindex where to look for shared libraries
16331 For remote debugging, you need to tell @value{GDBN} where the target
16332 libraries are, so that it can load the correct copies---otherwise, it
16333 may try to load the host's libraries. @value{GDBN} has two variables
16334 to specify the search directories for target libraries.
16337 @cindex prefix for shared library file names
16338 @cindex system root, alternate
16339 @kindex set solib-absolute-prefix
16340 @kindex set sysroot
16341 @item set sysroot @var{path}
16342 Use @var{path} as the system root for the program being debugged. Any
16343 absolute shared library paths will be prefixed with @var{path}; many
16344 runtime loaders store the absolute paths to the shared library in the
16345 target program's memory. If you use @code{set sysroot} to find shared
16346 libraries, they need to be laid out in the same way that they are on
16347 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
16350 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
16351 retrieve the target libraries from the remote system. This is only
16352 supported when using a remote target that supports the @code{remote get}
16353 command (@pxref{File Transfer,,Sending files to a remote system}).
16354 The part of @var{path} following the initial @file{remote:}
16355 (if present) is used as system root prefix on the remote file system.
16356 @footnote{If you want to specify a local system root using a directory
16357 that happens to be named @file{remote:}, you need to use some equivalent
16358 variant of the name like @file{./remote:}.}
16360 For targets with an MS-DOS based filesystem, such as MS-Windows and
16361 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
16362 absolute file name with @var{path}. But first, on Unix hosts,
16363 @value{GDBN} converts all backslash directory separators into forward
16364 slashes, because the backslash is not a directory separator on Unix:
16367 c:\foo\bar.dll @result{} c:/foo/bar.dll
16370 Then, @value{GDBN} attempts prefixing the target file name with
16371 @var{path}, and looks for the resulting file name in the host file
16375 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
16378 If that does not find the shared library, @value{GDBN} tries removing
16379 the @samp{:} character from the drive spec, both for convenience, and,
16380 for the case of the host file system not supporting file names with
16384 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
16387 This makes it possible to have a system root that mirrors a target
16388 with more than one drive. E.g., you may want to setup your local
16389 copies of the target system shared libraries like so (note @samp{c} vs
16393 @file{/path/to/sysroot/c/sys/bin/foo.dll}
16394 @file{/path/to/sysroot/c/sys/bin/bar.dll}
16395 @file{/path/to/sysroot/z/sys/bin/bar.dll}
16399 and point the system root at @file{/path/to/sysroot}, so that
16400 @value{GDBN} can find the correct copies of both
16401 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
16403 If that still does not find the shared library, @value{GDBN} tries
16404 removing the whole drive spec from the target file name:
16407 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
16410 This last lookup makes it possible to not care about the drive name,
16411 if you don't want or need to.
16413 The @code{set solib-absolute-prefix} command is an alias for @code{set
16416 @cindex default system root
16417 @cindex @samp{--with-sysroot}
16418 You can set the default system root by using the configure-time
16419 @samp{--with-sysroot} option. If the system root is inside
16420 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16421 @samp{--exec-prefix}), then the default system root will be updated
16422 automatically if the installed @value{GDBN} is moved to a new
16425 @kindex show sysroot
16427 Display the current shared library prefix.
16429 @kindex set solib-search-path
16430 @item set solib-search-path @var{path}
16431 If this variable is set, @var{path} is a colon-separated list of
16432 directories to search for shared libraries. @samp{solib-search-path}
16433 is used after @samp{sysroot} fails to locate the library, or if the
16434 path to the library is relative instead of absolute. If you want to
16435 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
16436 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
16437 finding your host's libraries. @samp{sysroot} is preferred; setting
16438 it to a nonexistent directory may interfere with automatic loading
16439 of shared library symbols.
16441 @kindex show solib-search-path
16442 @item show solib-search-path
16443 Display the current shared library search path.
16445 @cindex DOS file-name semantics of file names.
16446 @kindex set target-file-system-kind (unix|dos-based|auto)
16447 @kindex show target-file-system-kind
16448 @item set target-file-system-kind @var{kind}
16449 Set assumed file system kind for target reported file names.
16451 Shared library file names as reported by the target system may not
16452 make sense as is on the system @value{GDBN} is running on. For
16453 example, when remote debugging a target that has MS-DOS based file
16454 system semantics, from a Unix host, the target may be reporting to
16455 @value{GDBN} a list of loaded shared libraries with file names such as
16456 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
16457 drive letters, so the @samp{c:\} prefix is not normally understood as
16458 indicating an absolute file name, and neither is the backslash
16459 normally considered a directory separator character. In that case,
16460 the native file system would interpret this whole absolute file name
16461 as a relative file name with no directory components. This would make
16462 it impossible to point @value{GDBN} at a copy of the remote target's
16463 shared libraries on the host using @code{set sysroot}, and impractical
16464 with @code{set solib-search-path}. Setting
16465 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
16466 to interpret such file names similarly to how the target would, and to
16467 map them to file names valid on @value{GDBN}'s native file system
16468 semantics. The value of @var{kind} can be @code{"auto"}, in addition
16469 to one of the supported file system kinds. In that case, @value{GDBN}
16470 tries to determine the appropriate file system variant based on the
16471 current target's operating system (@pxref{ABI, ,Configuring the
16472 Current ABI}). The supported file system settings are:
16476 Instruct @value{GDBN} to assume the target file system is of Unix
16477 kind. Only file names starting the forward slash (@samp{/}) character
16478 are considered absolute, and the directory separator character is also
16482 Instruct @value{GDBN} to assume the target file system is DOS based.
16483 File names starting with either a forward slash, or a drive letter
16484 followed by a colon (e.g., @samp{c:}), are considered absolute, and
16485 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
16486 considered directory separators.
16489 Instruct @value{GDBN} to use the file system kind associated with the
16490 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
16491 This is the default.
16495 @cindex file name canonicalization
16496 @cindex base name differences
16497 When processing file names provided by the user, @value{GDBN}
16498 frequently needs to compare them to the file names recorded in the
16499 program's debug info. Normally, @value{GDBN} compares just the
16500 @dfn{base names} of the files as strings, which is reasonably fast
16501 even for very large programs. (The base name of a file is the last
16502 portion of its name, after stripping all the leading directories.)
16503 This shortcut in comparison is based upon the assumption that files
16504 cannot have more than one base name. This is usually true, but
16505 references to files that use symlinks or similar filesystem
16506 facilities violate that assumption. If your program records files
16507 using such facilities, or if you provide file names to @value{GDBN}
16508 using symlinks etc., you can set @code{basenames-may-differ} to
16509 @code{true} to instruct @value{GDBN} to completely canonicalize each
16510 pair of file names it needs to compare. This will make file-name
16511 comparisons accurate, but at a price of a significant slowdown.
16514 @item set basenames-may-differ
16515 @kindex set basenames-may-differ
16516 Set whether a source file may have multiple base names.
16518 @item show basenames-may-differ
16519 @kindex show basenames-may-differ
16520 Show whether a source file may have multiple base names.
16523 @node Separate Debug Files
16524 @section Debugging Information in Separate Files
16525 @cindex separate debugging information files
16526 @cindex debugging information in separate files
16527 @cindex @file{.debug} subdirectories
16528 @cindex debugging information directory, global
16529 @cindex global debugging information directories
16530 @cindex build ID, and separate debugging files
16531 @cindex @file{.build-id} directory
16533 @value{GDBN} allows you to put a program's debugging information in a
16534 file separate from the executable itself, in a way that allows
16535 @value{GDBN} to find and load the debugging information automatically.
16536 Since debugging information can be very large---sometimes larger
16537 than the executable code itself---some systems distribute debugging
16538 information for their executables in separate files, which users can
16539 install only when they need to debug a problem.
16541 @value{GDBN} supports two ways of specifying the separate debug info
16546 The executable contains a @dfn{debug link} that specifies the name of
16547 the separate debug info file. The separate debug file's name is
16548 usually @file{@var{executable}.debug}, where @var{executable} is the
16549 name of the corresponding executable file without leading directories
16550 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
16551 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
16552 checksum for the debug file, which @value{GDBN} uses to validate that
16553 the executable and the debug file came from the same build.
16556 The executable contains a @dfn{build ID}, a unique bit string that is
16557 also present in the corresponding debug info file. (This is supported
16558 only on some operating systems, notably those which use the ELF format
16559 for binary files and the @sc{gnu} Binutils.) For more details about
16560 this feature, see the description of the @option{--build-id}
16561 command-line option in @ref{Options, , Command Line Options, ld.info,
16562 The GNU Linker}. The debug info file's name is not specified
16563 explicitly by the build ID, but can be computed from the build ID, see
16567 Depending on the way the debug info file is specified, @value{GDBN}
16568 uses two different methods of looking for the debug file:
16572 For the ``debug link'' method, @value{GDBN} looks up the named file in
16573 the directory of the executable file, then in a subdirectory of that
16574 directory named @file{.debug}, and finally under each one of the global debug
16575 directories, in a subdirectory whose name is identical to the leading
16576 directories of the executable's absolute file name.
16579 For the ``build ID'' method, @value{GDBN} looks in the
16580 @file{.build-id} subdirectory of each one of the global debug directories for
16581 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
16582 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
16583 are the rest of the bit string. (Real build ID strings are 32 or more
16584 hex characters, not 10.)
16587 So, for example, suppose you ask @value{GDBN} to debug
16588 @file{/usr/bin/ls}, which has a debug link that specifies the
16589 file @file{ls.debug}, and a build ID whose value in hex is
16590 @code{abcdef1234}. If the list of the global debug directories includes
16591 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
16592 debug information files, in the indicated order:
16596 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
16598 @file{/usr/bin/ls.debug}
16600 @file{/usr/bin/.debug/ls.debug}
16602 @file{/usr/lib/debug/usr/bin/ls.debug}.
16605 @anchor{debug-file-directory}
16606 Global debugging info directories default to what is set by @value{GDBN}
16607 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
16608 you can also set the global debugging info directories, and view the list
16609 @value{GDBN} is currently using.
16613 @kindex set debug-file-directory
16614 @item set debug-file-directory @var{directories}
16615 Set the directories which @value{GDBN} searches for separate debugging
16616 information files to @var{directory}. Multiple path components can be set
16617 concatenating them by a path separator.
16619 @kindex show debug-file-directory
16620 @item show debug-file-directory
16621 Show the directories @value{GDBN} searches for separate debugging
16626 @cindex @code{.gnu_debuglink} sections
16627 @cindex debug link sections
16628 A debug link is a special section of the executable file named
16629 @code{.gnu_debuglink}. The section must contain:
16633 A filename, with any leading directory components removed, followed by
16636 zero to three bytes of padding, as needed to reach the next four-byte
16637 boundary within the section, and
16639 a four-byte CRC checksum, stored in the same endianness used for the
16640 executable file itself. The checksum is computed on the debugging
16641 information file's full contents by the function given below, passing
16642 zero as the @var{crc} argument.
16645 Any executable file format can carry a debug link, as long as it can
16646 contain a section named @code{.gnu_debuglink} with the contents
16649 @cindex @code{.note.gnu.build-id} sections
16650 @cindex build ID sections
16651 The build ID is a special section in the executable file (and in other
16652 ELF binary files that @value{GDBN} may consider). This section is
16653 often named @code{.note.gnu.build-id}, but that name is not mandatory.
16654 It contains unique identification for the built files---the ID remains
16655 the same across multiple builds of the same build tree. The default
16656 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
16657 content for the build ID string. The same section with an identical
16658 value is present in the original built binary with symbols, in its
16659 stripped variant, and in the separate debugging information file.
16661 The debugging information file itself should be an ordinary
16662 executable, containing a full set of linker symbols, sections, and
16663 debugging information. The sections of the debugging information file
16664 should have the same names, addresses, and sizes as the original file,
16665 but they need not contain any data---much like a @code{.bss} section
16666 in an ordinary executable.
16668 The @sc{gnu} binary utilities (Binutils) package includes the
16669 @samp{objcopy} utility that can produce
16670 the separated executable / debugging information file pairs using the
16671 following commands:
16674 @kbd{objcopy --only-keep-debug foo foo.debug}
16679 These commands remove the debugging
16680 information from the executable file @file{foo} and place it in the file
16681 @file{foo.debug}. You can use the first, second or both methods to link the
16686 The debug link method needs the following additional command to also leave
16687 behind a debug link in @file{foo}:
16690 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
16693 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
16694 a version of the @code{strip} command such that the command @kbd{strip foo -f
16695 foo.debug} has the same functionality as the two @code{objcopy} commands and
16696 the @code{ln -s} command above, together.
16699 Build ID gets embedded into the main executable using @code{ld --build-id} or
16700 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
16701 compatibility fixes for debug files separation are present in @sc{gnu} binary
16702 utilities (Binutils) package since version 2.18.
16707 @cindex CRC algorithm definition
16708 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16709 IEEE 802.3 using the polynomial:
16711 @c TexInfo requires naked braces for multi-digit exponents for Tex
16712 @c output, but this causes HTML output to barf. HTML has to be set using
16713 @c raw commands. So we end up having to specify this equation in 2
16718 <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>
16719 + <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
16725 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16726 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16730 The function is computed byte at a time, taking the least
16731 significant bit of each byte first. The initial pattern
16732 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16733 the final result is inverted to ensure trailing zeros also affect the
16736 @emph{Note:} This is the same CRC polynomial as used in handling the
16737 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16738 , @value{GDBN} Remote Serial Protocol}). However in the
16739 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16740 significant bit first, and the result is not inverted, so trailing
16741 zeros have no effect on the CRC value.
16743 To complete the description, we show below the code of the function
16744 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16745 initially supplied @code{crc} argument means that an initial call to
16746 this function passing in zero will start computing the CRC using
16749 @kindex gnu_debuglink_crc32
16752 gnu_debuglink_crc32 (unsigned long crc,
16753 unsigned char *buf, size_t len)
16755 static const unsigned long crc32_table[256] =
16757 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16758 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16759 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16760 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16761 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16762 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16763 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16764 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16765 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16766 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16767 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16768 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16769 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16770 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16771 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16772 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16773 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16774 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16775 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16776 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16777 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16778 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16779 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16780 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16781 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16782 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16783 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16784 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16785 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16786 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16787 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16788 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16789 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16790 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16791 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16792 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16793 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16794 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16795 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16796 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16797 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16798 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16799 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16800 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16801 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16802 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16803 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16804 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16805 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16806 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16807 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16810 unsigned char *end;
16812 crc = ~crc & 0xffffffff;
16813 for (end = buf + len; buf < end; ++buf)
16814 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
16815 return ~crc & 0xffffffff;
16820 This computation does not apply to the ``build ID'' method.
16822 @node MiniDebugInfo
16823 @section Debugging information in a special section
16824 @cindex separate debug sections
16825 @cindex @samp{.gnu_debugdata} section
16827 Some systems ship pre-built executables and libraries that have a
16828 special @samp{.gnu_debugdata} section. This feature is called
16829 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
16830 is used to supply extra symbols for backtraces.
16832 The intent of this section is to provide extra minimal debugging
16833 information for use in simple backtraces. It is not intended to be a
16834 replacement for full separate debugging information (@pxref{Separate
16835 Debug Files}). The example below shows the intended use; however,
16836 @value{GDBN} does not currently put restrictions on what sort of
16837 debugging information might be included in the section.
16839 @value{GDBN} has support for this extension. If the section exists,
16840 then it is used provided that no other source of debugging information
16841 can be found, and that @value{GDBN} was configured with LZMA support.
16843 This section can be easily created using @command{objcopy} and other
16844 standard utilities:
16847 # Extract the dynamic symbols from the main binary, there is no need
16848 # to also have these in the normal symbol table
16849 nm -D @var{binary} --format=posix --defined-only \
16850 | awk '@{ print $1 @}' | sort > dynsyms
16852 # Extract all the text (i.e. function) symbols from the debuginfo .
16853 nm @var{binary} --format=posix --defined-only \
16854 | awk '@{ if ($2 == "T" || $2 == "t") print $1 @}' \
16857 # Keep all the function symbols not already in the dynamic symbol
16859 comm -13 dynsyms funcsyms > keep_symbols
16861 # Copy the full debuginfo, keeping only a minimal set of symbols and
16862 # removing some unnecessary sections.
16863 objcopy -S --remove-section .gdb_index --remove-section .comment \
16864 --keep-symbols=keep_symbols @var{binary} mini_debuginfo
16866 # Inject the compressed data into the .gnu_debugdata section of the
16869 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
16873 @section Index Files Speed Up @value{GDBN}
16874 @cindex index files
16875 @cindex @samp{.gdb_index} section
16877 When @value{GDBN} finds a symbol file, it scans the symbols in the
16878 file in order to construct an internal symbol table. This lets most
16879 @value{GDBN} operations work quickly---at the cost of a delay early
16880 on. For large programs, this delay can be quite lengthy, so
16881 @value{GDBN} provides a way to build an index, which speeds up
16884 The index is stored as a section in the symbol file. @value{GDBN} can
16885 write the index to a file, then you can put it into the symbol file
16886 using @command{objcopy}.
16888 To create an index file, use the @code{save gdb-index} command:
16891 @item save gdb-index @var{directory}
16892 @kindex save gdb-index
16893 Create an index file for each symbol file currently known by
16894 @value{GDBN}. Each file is named after its corresponding symbol file,
16895 with @samp{.gdb-index} appended, and is written into the given
16899 Once you have created an index file you can merge it into your symbol
16900 file, here named @file{symfile}, using @command{objcopy}:
16903 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16904 --set-section-flags .gdb_index=readonly symfile symfile
16907 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
16908 sections that have been deprecated. Usually they are deprecated because
16909 they are missing a new feature or have performance issues.
16910 To tell @value{GDBN} to use a deprecated index section anyway
16911 specify @code{set use-deprecated-index-sections on}.
16912 The default is @code{off}.
16913 This can speed up startup, but may result in some functionality being lost.
16914 @xref{Index Section Format}.
16916 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
16917 must be done before gdb reads the file. The following will not work:
16920 $ gdb -ex "set use-deprecated-index-sections on" <program>
16923 Instead you must do, for example,
16926 $ gdb -iex "set use-deprecated-index-sections on" <program>
16929 There are currently some limitation on indices. They only work when
16930 for DWARF debugging information, not stabs. And, they do not
16931 currently work for programs using Ada.
16933 @node Symbol Errors
16934 @section Errors Reading Symbol Files
16936 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16937 such as symbol types it does not recognize, or known bugs in compiler
16938 output. By default, @value{GDBN} does not notify you of such problems, since
16939 they are relatively common and primarily of interest to people
16940 debugging compilers. If you are interested in seeing information
16941 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16942 only one message about each such type of problem, no matter how many
16943 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16944 to see how many times the problems occur, with the @code{set
16945 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16948 The messages currently printed, and their meanings, include:
16951 @item inner block not inside outer block in @var{symbol}
16953 The symbol information shows where symbol scopes begin and end
16954 (such as at the start of a function or a block of statements). This
16955 error indicates that an inner scope block is not fully contained
16956 in its outer scope blocks.
16958 @value{GDBN} circumvents the problem by treating the inner block as if it had
16959 the same scope as the outer block. In the error message, @var{symbol}
16960 may be shown as ``@code{(don't know)}'' if the outer block is not a
16963 @item block at @var{address} out of order
16965 The symbol information for symbol scope blocks should occur in
16966 order of increasing addresses. This error indicates that it does not
16969 @value{GDBN} does not circumvent this problem, and has trouble
16970 locating symbols in the source file whose symbols it is reading. (You
16971 can often determine what source file is affected by specifying
16972 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16975 @item bad block start address patched
16977 The symbol information for a symbol scope block has a start address
16978 smaller than the address of the preceding source line. This is known
16979 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16981 @value{GDBN} circumvents the problem by treating the symbol scope block as
16982 starting on the previous source line.
16984 @item bad string table offset in symbol @var{n}
16987 Symbol number @var{n} contains a pointer into the string table which is
16988 larger than the size of the string table.
16990 @value{GDBN} circumvents the problem by considering the symbol to have the
16991 name @code{foo}, which may cause other problems if many symbols end up
16994 @item unknown symbol type @code{0x@var{nn}}
16996 The symbol information contains new data types that @value{GDBN} does
16997 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16998 uncomprehended information, in hexadecimal.
17000 @value{GDBN} circumvents the error by ignoring this symbol information.
17001 This usually allows you to debug your program, though certain symbols
17002 are not accessible. If you encounter such a problem and feel like
17003 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17004 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17005 and examine @code{*bufp} to see the symbol.
17007 @item stub type has NULL name
17009 @value{GDBN} could not find the full definition for a struct or class.
17011 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17012 The symbol information for a C@t{++} member function is missing some
17013 information that recent versions of the compiler should have output for
17016 @item info mismatch between compiler and debugger
17018 @value{GDBN} could not parse a type specification output by the compiler.
17023 @section GDB Data Files
17025 @cindex prefix for data files
17026 @value{GDBN} will sometimes read an auxiliary data file. These files
17027 are kept in a directory known as the @dfn{data directory}.
17029 You can set the data directory's name, and view the name @value{GDBN}
17030 is currently using.
17033 @kindex set data-directory
17034 @item set data-directory @var{directory}
17035 Set the directory which @value{GDBN} searches for auxiliary data files
17036 to @var{directory}.
17038 @kindex show data-directory
17039 @item show data-directory
17040 Show the directory @value{GDBN} searches for auxiliary data files.
17043 @cindex default data directory
17044 @cindex @samp{--with-gdb-datadir}
17045 You can set the default data directory by using the configure-time
17046 @samp{--with-gdb-datadir} option. If the data directory is inside
17047 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17048 @samp{--exec-prefix}), then the default data directory will be updated
17049 automatically if the installed @value{GDBN} is moved to a new
17052 The data directory may also be specified with the
17053 @code{--data-directory} command line option.
17054 @xref{Mode Options}.
17057 @chapter Specifying a Debugging Target
17059 @cindex debugging target
17060 A @dfn{target} is the execution environment occupied by your program.
17062 Often, @value{GDBN} runs in the same host environment as your program;
17063 in that case, the debugging target is specified as a side effect when
17064 you use the @code{file} or @code{core} commands. When you need more
17065 flexibility---for example, running @value{GDBN} on a physically separate
17066 host, or controlling a standalone system over a serial port or a
17067 realtime system over a TCP/IP connection---you can use the @code{target}
17068 command to specify one of the target types configured for @value{GDBN}
17069 (@pxref{Target Commands, ,Commands for Managing Targets}).
17071 @cindex target architecture
17072 It is possible to build @value{GDBN} for several different @dfn{target
17073 architectures}. When @value{GDBN} is built like that, you can choose
17074 one of the available architectures with the @kbd{set architecture}
17078 @kindex set architecture
17079 @kindex show architecture
17080 @item set architecture @var{arch}
17081 This command sets the current target architecture to @var{arch}. The
17082 value of @var{arch} can be @code{"auto"}, in addition to one of the
17083 supported architectures.
17085 @item show architecture
17086 Show the current target architecture.
17088 @item set processor
17090 @kindex set processor
17091 @kindex show processor
17092 These are alias commands for, respectively, @code{set architecture}
17093 and @code{show architecture}.
17097 * Active Targets:: Active targets
17098 * Target Commands:: Commands for managing targets
17099 * Byte Order:: Choosing target byte order
17102 @node Active Targets
17103 @section Active Targets
17105 @cindex stacking targets
17106 @cindex active targets
17107 @cindex multiple targets
17109 There are multiple classes of targets such as: processes, executable files or
17110 recording sessions. Core files belong to the process class, making core file
17111 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17112 on multiple active targets, one in each class. This allows you to (for
17113 example) start a process and inspect its activity, while still having access to
17114 the executable file after the process finishes. Or if you start process
17115 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17116 presented a virtual layer of the recording target, while the process target
17117 remains stopped at the chronologically last point of the process execution.
17119 Use the @code{core-file} and @code{exec-file} commands to select a new core
17120 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17121 specify as a target a process that is already running, use the @code{attach}
17122 command (@pxref{Attach, ,Debugging an Already-running Process}).
17124 @node Target Commands
17125 @section Commands for Managing Targets
17128 @item target @var{type} @var{parameters}
17129 Connects the @value{GDBN} host environment to a target machine or
17130 process. A target is typically a protocol for talking to debugging
17131 facilities. You use the argument @var{type} to specify the type or
17132 protocol of the target machine.
17134 Further @var{parameters} are interpreted by the target protocol, but
17135 typically include things like device names or host names to connect
17136 with, process numbers, and baud rates.
17138 The @code{target} command does not repeat if you press @key{RET} again
17139 after executing the command.
17141 @kindex help target
17143 Displays the names of all targets available. To display targets
17144 currently selected, use either @code{info target} or @code{info files}
17145 (@pxref{Files, ,Commands to Specify Files}).
17147 @item help target @var{name}
17148 Describe a particular target, including any parameters necessary to
17151 @kindex set gnutarget
17152 @item set gnutarget @var{args}
17153 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17154 knows whether it is reading an @dfn{executable},
17155 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17156 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17157 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17160 @emph{Warning:} To specify a file format with @code{set gnutarget},
17161 you must know the actual BFD name.
17165 @xref{Files, , Commands to Specify Files}.
17167 @kindex show gnutarget
17168 @item show gnutarget
17169 Use the @code{show gnutarget} command to display what file format
17170 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17171 @value{GDBN} will determine the file format for each file automatically,
17172 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
17175 @cindex common targets
17176 Here are some common targets (available, or not, depending on the GDB
17181 @item target exec @var{program}
17182 @cindex executable file target
17183 An executable file. @samp{target exec @var{program}} is the same as
17184 @samp{exec-file @var{program}}.
17186 @item target core @var{filename}
17187 @cindex core dump file target
17188 A core dump file. @samp{target core @var{filename}} is the same as
17189 @samp{core-file @var{filename}}.
17191 @item target remote @var{medium}
17192 @cindex remote target
17193 A remote system connected to @value{GDBN} via a serial line or network
17194 connection. This command tells @value{GDBN} to use its own remote
17195 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17197 For example, if you have a board connected to @file{/dev/ttya} on the
17198 machine running @value{GDBN}, you could say:
17201 target remote /dev/ttya
17204 @code{target remote} supports the @code{load} command. This is only
17205 useful if you have some other way of getting the stub to the target
17206 system, and you can put it somewhere in memory where it won't get
17207 clobbered by the download.
17209 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17210 @cindex built-in simulator target
17211 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17219 works; however, you cannot assume that a specific memory map, device
17220 drivers, or even basic I/O is available, although some simulators do
17221 provide these. For info about any processor-specific simulator details,
17222 see the appropriate section in @ref{Embedded Processors, ,Embedded
17227 Some configurations may include these targets as well:
17231 @item target nrom @var{dev}
17232 @cindex NetROM ROM emulator target
17233 NetROM ROM emulator. This target only supports downloading.
17237 Different targets are available on different configurations of @value{GDBN};
17238 your configuration may have more or fewer targets.
17240 Many remote targets require you to download the executable's code once
17241 you've successfully established a connection. You may wish to control
17242 various aspects of this process.
17247 @kindex set hash@r{, for remote monitors}
17248 @cindex hash mark while downloading
17249 This command controls whether a hash mark @samp{#} is displayed while
17250 downloading a file to the remote monitor. If on, a hash mark is
17251 displayed after each S-record is successfully downloaded to the
17255 @kindex show hash@r{, for remote monitors}
17256 Show the current status of displaying the hash mark.
17258 @item set debug monitor
17259 @kindex set debug monitor
17260 @cindex display remote monitor communications
17261 Enable or disable display of communications messages between
17262 @value{GDBN} and the remote monitor.
17264 @item show debug monitor
17265 @kindex show debug monitor
17266 Show the current status of displaying communications between
17267 @value{GDBN} and the remote monitor.
17272 @kindex load @var{filename}
17273 @item load @var{filename}
17275 Depending on what remote debugging facilities are configured into
17276 @value{GDBN}, the @code{load} command may be available. Where it exists, it
17277 is meant to make @var{filename} (an executable) available for debugging
17278 on the remote system---by downloading, or dynamic linking, for example.
17279 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
17280 the @code{add-symbol-file} command.
17282 If your @value{GDBN} does not have a @code{load} command, attempting to
17283 execute it gets the error message ``@code{You can't do that when your
17284 target is @dots{}}''
17286 The file is loaded at whatever address is specified in the executable.
17287 For some object file formats, you can specify the load address when you
17288 link the program; for other formats, like a.out, the object file format
17289 specifies a fixed address.
17290 @c FIXME! This would be a good place for an xref to the GNU linker doc.
17292 Depending on the remote side capabilities, @value{GDBN} may be able to
17293 load programs into flash memory.
17295 @code{load} does not repeat if you press @key{RET} again after using it.
17299 @section Choosing Target Byte Order
17301 @cindex choosing target byte order
17302 @cindex target byte order
17304 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
17305 offer the ability to run either big-endian or little-endian byte
17306 orders. Usually the executable or symbol will include a bit to
17307 designate the endian-ness, and you will not need to worry about
17308 which to use. However, you may still find it useful to adjust
17309 @value{GDBN}'s idea of processor endian-ness manually.
17313 @item set endian big
17314 Instruct @value{GDBN} to assume the target is big-endian.
17316 @item set endian little
17317 Instruct @value{GDBN} to assume the target is little-endian.
17319 @item set endian auto
17320 Instruct @value{GDBN} to use the byte order associated with the
17324 Display @value{GDBN}'s current idea of the target byte order.
17328 Note that these commands merely adjust interpretation of symbolic
17329 data on the host, and that they have absolutely no effect on the
17333 @node Remote Debugging
17334 @chapter Debugging Remote Programs
17335 @cindex remote debugging
17337 If you are trying to debug a program running on a machine that cannot run
17338 @value{GDBN} in the usual way, it is often useful to use remote debugging.
17339 For example, you might use remote debugging on an operating system kernel,
17340 or on a small system which does not have a general purpose operating system
17341 powerful enough to run a full-featured debugger.
17343 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
17344 to make this work with particular debugging targets. In addition,
17345 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
17346 but not specific to any particular target system) which you can use if you
17347 write the remote stubs---the code that runs on the remote system to
17348 communicate with @value{GDBN}.
17350 Other remote targets may be available in your
17351 configuration of @value{GDBN}; use @code{help target} to list them.
17354 * Connecting:: Connecting to a remote target
17355 * File Transfer:: Sending files to a remote system
17356 * Server:: Using the gdbserver program
17357 * Remote Configuration:: Remote configuration
17358 * Remote Stub:: Implementing a remote stub
17362 @section Connecting to a Remote Target
17364 On the @value{GDBN} host machine, you will need an unstripped copy of
17365 your program, since @value{GDBN} needs symbol and debugging information.
17366 Start up @value{GDBN} as usual, using the name of the local copy of your
17367 program as the first argument.
17369 @cindex @code{target remote}
17370 @value{GDBN} can communicate with the target over a serial line, or
17371 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
17372 each case, @value{GDBN} uses the same protocol for debugging your
17373 program; only the medium carrying the debugging packets varies. The
17374 @code{target remote} command establishes a connection to the target.
17375 Its arguments indicate which medium to use:
17379 @item target remote @var{serial-device}
17380 @cindex serial line, @code{target remote}
17381 Use @var{serial-device} to communicate with the target. For example,
17382 to use a serial line connected to the device named @file{/dev/ttyb}:
17385 target remote /dev/ttyb
17388 If you're using a serial line, you may want to give @value{GDBN} the
17389 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
17390 (@pxref{Remote Configuration, set remotebaud}) before the
17391 @code{target} command.
17393 @item target remote @code{@var{host}:@var{port}}
17394 @itemx target remote @code{tcp:@var{host}:@var{port}}
17395 @cindex @acronym{TCP} port, @code{target remote}
17396 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
17397 The @var{host} may be either a host name or a numeric @acronym{IP}
17398 address; @var{port} must be a decimal number. The @var{host} could be
17399 the target machine itself, if it is directly connected to the net, or
17400 it might be a terminal server which in turn has a serial line to the
17403 For example, to connect to port 2828 on a terminal server named
17407 target remote manyfarms:2828
17410 If your remote target is actually running on the same machine as your
17411 debugger session (e.g.@: a simulator for your target running on the
17412 same host), you can omit the hostname. For example, to connect to
17413 port 1234 on your local machine:
17416 target remote :1234
17420 Note that the colon is still required here.
17422 @item target remote @code{udp:@var{host}:@var{port}}
17423 @cindex @acronym{UDP} port, @code{target remote}
17424 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
17425 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
17428 target remote udp:manyfarms:2828
17431 When using a @acronym{UDP} connection for remote debugging, you should
17432 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
17433 can silently drop packets on busy or unreliable networks, which will
17434 cause havoc with your debugging session.
17436 @item target remote | @var{command}
17437 @cindex pipe, @code{target remote} to
17438 Run @var{command} in the background and communicate with it using a
17439 pipe. The @var{command} is a shell command, to be parsed and expanded
17440 by the system's command shell, @code{/bin/sh}; it should expect remote
17441 protocol packets on its standard input, and send replies on its
17442 standard output. You could use this to run a stand-alone simulator
17443 that speaks the remote debugging protocol, to make net connections
17444 using programs like @code{ssh}, or for other similar tricks.
17446 If @var{command} closes its standard output (perhaps by exiting),
17447 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
17448 program has already exited, this will have no effect.)
17452 Once the connection has been established, you can use all the usual
17453 commands to examine and change data. The remote program is already
17454 running; you can use @kbd{step} and @kbd{continue}, and you do not
17455 need to use @kbd{run}.
17457 @cindex interrupting remote programs
17458 @cindex remote programs, interrupting
17459 Whenever @value{GDBN} is waiting for the remote program, if you type the
17460 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
17461 program. This may or may not succeed, depending in part on the hardware
17462 and the serial drivers the remote system uses. If you type the
17463 interrupt character once again, @value{GDBN} displays this prompt:
17466 Interrupted while waiting for the program.
17467 Give up (and stop debugging it)? (y or n)
17470 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
17471 (If you decide you want to try again later, you can use @samp{target
17472 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
17473 goes back to waiting.
17476 @kindex detach (remote)
17478 When you have finished debugging the remote program, you can use the
17479 @code{detach} command to release it from @value{GDBN} control.
17480 Detaching from the target normally resumes its execution, but the results
17481 will depend on your particular remote stub. After the @code{detach}
17482 command, @value{GDBN} is free to connect to another target.
17486 The @code{disconnect} command behaves like @code{detach}, except that
17487 the target is generally not resumed. It will wait for @value{GDBN}
17488 (this instance or another one) to connect and continue debugging. After
17489 the @code{disconnect} command, @value{GDBN} is again free to connect to
17492 @cindex send command to remote monitor
17493 @cindex extend @value{GDBN} for remote targets
17494 @cindex add new commands for external monitor
17496 @item monitor @var{cmd}
17497 This command allows you to send arbitrary commands directly to the
17498 remote monitor. Since @value{GDBN} doesn't care about the commands it
17499 sends like this, this command is the way to extend @value{GDBN}---you
17500 can add new commands that only the external monitor will understand
17504 @node File Transfer
17505 @section Sending files to a remote system
17506 @cindex remote target, file transfer
17507 @cindex file transfer
17508 @cindex sending files to remote systems
17510 Some remote targets offer the ability to transfer files over the same
17511 connection used to communicate with @value{GDBN}. This is convenient
17512 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
17513 running @code{gdbserver} over a network interface. For other targets,
17514 e.g.@: embedded devices with only a single serial port, this may be
17515 the only way to upload or download files.
17517 Not all remote targets support these commands.
17521 @item remote put @var{hostfile} @var{targetfile}
17522 Copy file @var{hostfile} from the host system (the machine running
17523 @value{GDBN}) to @var{targetfile} on the target system.
17526 @item remote get @var{targetfile} @var{hostfile}
17527 Copy file @var{targetfile} from the target system to @var{hostfile}
17528 on the host system.
17530 @kindex remote delete
17531 @item remote delete @var{targetfile}
17532 Delete @var{targetfile} from the target system.
17537 @section Using the @code{gdbserver} Program
17540 @cindex remote connection without stubs
17541 @code{gdbserver} is a control program for Unix-like systems, which
17542 allows you to connect your program with a remote @value{GDBN} via
17543 @code{target remote}---but without linking in the usual debugging stub.
17545 @code{gdbserver} is not a complete replacement for the debugging stubs,
17546 because it requires essentially the same operating-system facilities
17547 that @value{GDBN} itself does. In fact, a system that can run
17548 @code{gdbserver} to connect to a remote @value{GDBN} could also run
17549 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
17550 because it is a much smaller program than @value{GDBN} itself. It is
17551 also easier to port than all of @value{GDBN}, so you may be able to get
17552 started more quickly on a new system by using @code{gdbserver}.
17553 Finally, if you develop code for real-time systems, you may find that
17554 the tradeoffs involved in real-time operation make it more convenient to
17555 do as much development work as possible on another system, for example
17556 by cross-compiling. You can use @code{gdbserver} to make a similar
17557 choice for debugging.
17559 @value{GDBN} and @code{gdbserver} communicate via either a serial line
17560 or a TCP connection, using the standard @value{GDBN} remote serial
17564 @emph{Warning:} @code{gdbserver} does not have any built-in security.
17565 Do not run @code{gdbserver} connected to any public network; a
17566 @value{GDBN} connection to @code{gdbserver} provides access to the
17567 target system with the same privileges as the user running
17571 @subsection Running @code{gdbserver}
17572 @cindex arguments, to @code{gdbserver}
17573 @cindex @code{gdbserver}, command-line arguments
17575 Run @code{gdbserver} on the target system. You need a copy of the
17576 program you want to debug, including any libraries it requires.
17577 @code{gdbserver} does not need your program's symbol table, so you can
17578 strip the program if necessary to save space. @value{GDBN} on the host
17579 system does all the symbol handling.
17581 To use the server, you must tell it how to communicate with @value{GDBN};
17582 the name of your program; and the arguments for your program. The usual
17586 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
17589 @var{comm} is either a device name (to use a serial line), or a TCP
17590 hostname and portnumber, or @code{-} or @code{stdio} to use
17591 stdin/stdout of @code{gdbserver}.
17592 For example, to debug Emacs with the argument
17593 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
17597 target> gdbserver /dev/com1 emacs foo.txt
17600 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
17603 To use a TCP connection instead of a serial line:
17606 target> gdbserver host:2345 emacs foo.txt
17609 The only difference from the previous example is the first argument,
17610 specifying that you are communicating with the host @value{GDBN} via
17611 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
17612 expect a TCP connection from machine @samp{host} to local TCP port 2345.
17613 (Currently, the @samp{host} part is ignored.) You can choose any number
17614 you want for the port number as long as it does not conflict with any
17615 TCP ports already in use on the target system (for example, @code{23} is
17616 reserved for @code{telnet}).@footnote{If you choose a port number that
17617 conflicts with another service, @code{gdbserver} prints an error message
17618 and exits.} You must use the same port number with the host @value{GDBN}
17619 @code{target remote} command.
17621 The @code{stdio} connection is useful when starting @code{gdbserver}
17625 (gdb) target remote | ssh -T hostname gdbserver - hello
17628 The @samp{-T} option to ssh is provided because we don't need a remote pty,
17629 and we don't want escape-character handling. Ssh does this by default when
17630 a command is provided, the flag is provided to make it explicit.
17631 You could elide it if you want to.
17633 Programs started with stdio-connected gdbserver have @file{/dev/null} for
17634 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
17635 display through a pipe connected to gdbserver.
17636 Both @code{stdout} and @code{stderr} use the same pipe.
17638 @subsubsection Attaching to a Running Program
17639 @cindex attach to a program, @code{gdbserver}
17640 @cindex @option{--attach}, @code{gdbserver} option
17642 On some targets, @code{gdbserver} can also attach to running programs.
17643 This is accomplished via the @code{--attach} argument. The syntax is:
17646 target> gdbserver --attach @var{comm} @var{pid}
17649 @var{pid} is the process ID of a currently running process. It isn't necessary
17650 to point @code{gdbserver} at a binary for the running process.
17653 You can debug processes by name instead of process ID if your target has the
17654 @code{pidof} utility:
17657 target> gdbserver --attach @var{comm} `pidof @var{program}`
17660 In case more than one copy of @var{program} is running, or @var{program}
17661 has multiple threads, most versions of @code{pidof} support the
17662 @code{-s} option to only return the first process ID.
17664 @subsubsection Multi-Process Mode for @code{gdbserver}
17665 @cindex @code{gdbserver}, multiple processes
17666 @cindex multiple processes with @code{gdbserver}
17668 When you connect to @code{gdbserver} using @code{target remote},
17669 @code{gdbserver} debugs the specified program only once. When the
17670 program exits, or you detach from it, @value{GDBN} closes the connection
17671 and @code{gdbserver} exits.
17673 If you connect using @kbd{target extended-remote}, @code{gdbserver}
17674 enters multi-process mode. When the debugged program exits, or you
17675 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
17676 though no program is running. The @code{run} and @code{attach}
17677 commands instruct @code{gdbserver} to run or attach to a new program.
17678 The @code{run} command uses @code{set remote exec-file} (@pxref{set
17679 remote exec-file}) to select the program to run. Command line
17680 arguments are supported, except for wildcard expansion and I/O
17681 redirection (@pxref{Arguments}).
17683 @cindex @option{--multi}, @code{gdbserver} option
17684 To start @code{gdbserver} without supplying an initial command to run
17685 or process ID to attach, use the @option{--multi} command line option.
17686 Then you can connect using @kbd{target extended-remote} and start
17687 the program you want to debug.
17689 In multi-process mode @code{gdbserver} does not automatically exit unless you
17690 use the option @option{--once}. You can terminate it by using
17691 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
17692 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
17693 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
17694 @option{--multi} option to @code{gdbserver} has no influence on that.
17696 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
17698 This section applies only when @code{gdbserver} is run to listen on a TCP port.
17700 @code{gdbserver} normally terminates after all of its debugged processes have
17701 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
17702 extended-remote}, @code{gdbserver} stays running even with no processes left.
17703 @value{GDBN} normally terminates the spawned debugged process on its exit,
17704 which normally also terminates @code{gdbserver} in the @kbd{target remote}
17705 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
17706 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
17707 stays running even in the @kbd{target remote} mode.
17709 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
17710 Such reconnecting is useful for features like @ref{disconnected tracing}. For
17711 completeness, at most one @value{GDBN} can be connected at a time.
17713 @cindex @option{--once}, @code{gdbserver} option
17714 By default, @code{gdbserver} keeps the listening TCP port open, so that
17715 additional connections are possible. However, if you start @code{gdbserver}
17716 with the @option{--once} option, it will stop listening for any further
17717 connection attempts after connecting to the first @value{GDBN} session. This
17718 means no further connections to @code{gdbserver} will be possible after the
17719 first one. It also means @code{gdbserver} will terminate after the first
17720 connection with remote @value{GDBN} has closed, even for unexpectedly closed
17721 connections and even in the @kbd{target extended-remote} mode. The
17722 @option{--once} option allows reusing the same port number for connecting to
17723 multiple instances of @code{gdbserver} running on the same host, since each
17724 instance closes its port after the first connection.
17726 @subsubsection Other Command-Line Arguments for @code{gdbserver}
17728 @cindex @option{--debug}, @code{gdbserver} option
17729 The @option{--debug} option tells @code{gdbserver} to display extra
17730 status information about the debugging process.
17731 @cindex @option{--remote-debug}, @code{gdbserver} option
17732 The @option{--remote-debug} option tells @code{gdbserver} to display
17733 remote protocol debug output. These options are intended for
17734 @code{gdbserver} development and for bug reports to the developers.
17736 @cindex @option{--wrapper}, @code{gdbserver} option
17737 The @option{--wrapper} option specifies a wrapper to launch programs
17738 for debugging. The option should be followed by the name of the
17739 wrapper, then any command-line arguments to pass to the wrapper, then
17740 @kbd{--} indicating the end of the wrapper arguments.
17742 @code{gdbserver} runs the specified wrapper program with a combined
17743 command line including the wrapper arguments, then the name of the
17744 program to debug, then any arguments to the program. The wrapper
17745 runs until it executes your program, and then @value{GDBN} gains control.
17747 You can use any program that eventually calls @code{execve} with
17748 its arguments as a wrapper. Several standard Unix utilities do
17749 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
17750 with @code{exec "$@@"} will also work.
17752 For example, you can use @code{env} to pass an environment variable to
17753 the debugged program, without setting the variable in @code{gdbserver}'s
17757 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
17760 @subsection Connecting to @code{gdbserver}
17762 Run @value{GDBN} on the host system.
17764 First make sure you have the necessary symbol files. Load symbols for
17765 your application using the @code{file} command before you connect. Use
17766 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
17767 was compiled with the correct sysroot using @code{--with-sysroot}).
17769 The symbol file and target libraries must exactly match the executable
17770 and libraries on the target, with one exception: the files on the host
17771 system should not be stripped, even if the files on the target system
17772 are. Mismatched or missing files will lead to confusing results
17773 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
17774 files may also prevent @code{gdbserver} from debugging multi-threaded
17777 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
17778 For TCP connections, you must start up @code{gdbserver} prior to using
17779 the @code{target remote} command. Otherwise you may get an error whose
17780 text depends on the host system, but which usually looks something like
17781 @samp{Connection refused}. Don't use the @code{load}
17782 command in @value{GDBN} when using @code{gdbserver}, since the program is
17783 already on the target.
17785 @subsection Monitor Commands for @code{gdbserver}
17786 @cindex monitor commands, for @code{gdbserver}
17787 @anchor{Monitor Commands for gdbserver}
17789 During a @value{GDBN} session using @code{gdbserver}, you can use the
17790 @code{monitor} command to send special requests to @code{gdbserver}.
17791 Here are the available commands.
17795 List the available monitor commands.
17797 @item monitor set debug 0
17798 @itemx monitor set debug 1
17799 Disable or enable general debugging messages.
17801 @item monitor set remote-debug 0
17802 @itemx monitor set remote-debug 1
17803 Disable or enable specific debugging messages associated with the remote
17804 protocol (@pxref{Remote Protocol}).
17806 @item monitor set libthread-db-search-path [PATH]
17807 @cindex gdbserver, search path for @code{libthread_db}
17808 When this command is issued, @var{path} is a colon-separated list of
17809 directories to search for @code{libthread_db} (@pxref{Threads,,set
17810 libthread-db-search-path}). If you omit @var{path},
17811 @samp{libthread-db-search-path} will be reset to its default value.
17813 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
17814 not supported in @code{gdbserver}.
17817 Tell gdbserver to exit immediately. This command should be followed by
17818 @code{disconnect} to close the debugging session. @code{gdbserver} will
17819 detach from any attached processes and kill any processes it created.
17820 Use @code{monitor exit} to terminate @code{gdbserver} at the end
17821 of a multi-process mode debug session.
17825 @subsection Tracepoints support in @code{gdbserver}
17826 @cindex tracepoints support in @code{gdbserver}
17828 On some targets, @code{gdbserver} supports tracepoints, fast
17829 tracepoints and static tracepoints.
17831 For fast or static tracepoints to work, a special library called the
17832 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
17833 This library is built and distributed as an integral part of
17834 @code{gdbserver}. In addition, support for static tracepoints
17835 requires building the in-process agent library with static tracepoints
17836 support. At present, the UST (LTTng Userspace Tracer,
17837 @url{http://lttng.org/ust}) tracing engine is supported. This support
17838 is automatically available if UST development headers are found in the
17839 standard include path when @code{gdbserver} is built, or if
17840 @code{gdbserver} was explicitly configured using @option{--with-ust}
17841 to point at such headers. You can explicitly disable the support
17842 using @option{--with-ust=no}.
17844 There are several ways to load the in-process agent in your program:
17847 @item Specifying it as dependency at link time
17849 You can link your program dynamically with the in-process agent
17850 library. On most systems, this is accomplished by adding
17851 @code{-linproctrace} to the link command.
17853 @item Using the system's preloading mechanisms
17855 You can force loading the in-process agent at startup time by using
17856 your system's support for preloading shared libraries. Many Unixes
17857 support the concept of preloading user defined libraries. In most
17858 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
17859 in the environment. See also the description of @code{gdbserver}'s
17860 @option{--wrapper} command line option.
17862 @item Using @value{GDBN} to force loading the agent at run time
17864 On some systems, you can force the inferior to load a shared library,
17865 by calling a dynamic loader function in the inferior that takes care
17866 of dynamically looking up and loading a shared library. On most Unix
17867 systems, the function is @code{dlopen}. You'll use the @code{call}
17868 command for that. For example:
17871 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
17874 Note that on most Unix systems, for the @code{dlopen} function to be
17875 available, the program needs to be linked with @code{-ldl}.
17878 On systems that have a userspace dynamic loader, like most Unix
17879 systems, when you connect to @code{gdbserver} using @code{target
17880 remote}, you'll find that the program is stopped at the dynamic
17881 loader's entry point, and no shared library has been loaded in the
17882 program's address space yet, including the in-process agent. In that
17883 case, before being able to use any of the fast or static tracepoints
17884 features, you need to let the loader run and load the shared
17885 libraries. The simplest way to do that is to run the program to the
17886 main procedure. E.g., if debugging a C or C@t{++} program, start
17887 @code{gdbserver} like so:
17890 $ gdbserver :9999 myprogram
17893 Start GDB and connect to @code{gdbserver} like so, and run to main:
17897 (@value{GDBP}) target remote myhost:9999
17898 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
17899 (@value{GDBP}) b main
17900 (@value{GDBP}) continue
17903 The in-process tracing agent library should now be loaded into the
17904 process; you can confirm it with the @code{info sharedlibrary}
17905 command, which will list @file{libinproctrace.so} as loaded in the
17906 process. You are now ready to install fast tracepoints, list static
17907 tracepoint markers, probe static tracepoints markers, and start
17910 @node Remote Configuration
17911 @section Remote Configuration
17914 @kindex show remote
17915 This section documents the configuration options available when
17916 debugging remote programs. For the options related to the File I/O
17917 extensions of the remote protocol, see @ref{system,
17918 system-call-allowed}.
17921 @item set remoteaddresssize @var{bits}
17922 @cindex address size for remote targets
17923 @cindex bits in remote address
17924 Set the maximum size of address in a memory packet to the specified
17925 number of bits. @value{GDBN} will mask off the address bits above
17926 that number, when it passes addresses to the remote target. The
17927 default value is the number of bits in the target's address.
17929 @item show remoteaddresssize
17930 Show the current value of remote address size in bits.
17932 @item set remotebaud @var{n}
17933 @cindex baud rate for remote targets
17934 Set the baud rate for the remote serial I/O to @var{n} baud. The
17935 value is used to set the speed of the serial port used for debugging
17938 @item show remotebaud
17939 Show the current speed of the remote connection.
17941 @item set remotebreak
17942 @cindex interrupt remote programs
17943 @cindex BREAK signal instead of Ctrl-C
17944 @anchor{set remotebreak}
17945 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17946 when you type @kbd{Ctrl-c} to interrupt the program running
17947 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17948 character instead. The default is off, since most remote systems
17949 expect to see @samp{Ctrl-C} as the interrupt signal.
17951 @item show remotebreak
17952 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17953 interrupt the remote program.
17955 @item set remoteflow on
17956 @itemx set remoteflow off
17957 @kindex set remoteflow
17958 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17959 on the serial port used to communicate to the remote target.
17961 @item show remoteflow
17962 @kindex show remoteflow
17963 Show the current setting of hardware flow control.
17965 @item set remotelogbase @var{base}
17966 Set the base (a.k.a.@: radix) of logging serial protocol
17967 communications to @var{base}. Supported values of @var{base} are:
17968 @code{ascii}, @code{octal}, and @code{hex}. The default is
17971 @item show remotelogbase
17972 Show the current setting of the radix for logging remote serial
17975 @item set remotelogfile @var{file}
17976 @cindex record serial communications on file
17977 Record remote serial communications on the named @var{file}. The
17978 default is not to record at all.
17980 @item show remotelogfile.
17981 Show the current setting of the file name on which to record the
17982 serial communications.
17984 @item set remotetimeout @var{num}
17985 @cindex timeout for serial communications
17986 @cindex remote timeout
17987 Set the timeout limit to wait for the remote target to respond to
17988 @var{num} seconds. The default is 2 seconds.
17990 @item show remotetimeout
17991 Show the current number of seconds to wait for the remote target
17994 @cindex limit hardware breakpoints and watchpoints
17995 @cindex remote target, limit break- and watchpoints
17996 @anchor{set remote hardware-watchpoint-limit}
17997 @anchor{set remote hardware-breakpoint-limit}
17998 @item set remote hardware-watchpoint-limit @var{limit}
17999 @itemx set remote hardware-breakpoint-limit @var{limit}
18000 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18001 watchpoints. A limit of -1, the default, is treated as unlimited.
18003 @cindex limit hardware watchpoints length
18004 @cindex remote target, limit watchpoints length
18005 @anchor{set remote hardware-watchpoint-length-limit}
18006 @item set remote hardware-watchpoint-length-limit @var{limit}
18007 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18008 a remote hardware watchpoint. A limit of -1, the default, is treated
18011 @item show remote hardware-watchpoint-length-limit
18012 Show the current limit (in bytes) of the maximum length of
18013 a remote hardware watchpoint.
18015 @item set remote exec-file @var{filename}
18016 @itemx show remote exec-file
18017 @anchor{set remote exec-file}
18018 @cindex executable file, for remote target
18019 Select the file used for @code{run} with @code{target
18020 extended-remote}. This should be set to a filename valid on the
18021 target system. If it is not set, the target will use a default
18022 filename (e.g.@: the last program run).
18024 @item set remote interrupt-sequence
18025 @cindex interrupt remote programs
18026 @cindex select Ctrl-C, BREAK or BREAK-g
18027 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18028 @samp{BREAK-g} as the
18029 sequence to the remote target in order to interrupt the execution.
18030 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18031 is high level of serial line for some certain time.
18032 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18033 It is @code{BREAK} signal followed by character @code{g}.
18035 @item show interrupt-sequence
18036 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18037 is sent by @value{GDBN} to interrupt the remote program.
18038 @code{BREAK-g} is BREAK signal followed by @code{g} and
18039 also known as Magic SysRq g.
18041 @item set remote interrupt-on-connect
18042 @cindex send interrupt-sequence on start
18043 Specify whether interrupt-sequence is sent to remote target when
18044 @value{GDBN} connects to it. This is mostly needed when you debug
18045 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18046 which is known as Magic SysRq g in order to connect @value{GDBN}.
18048 @item show interrupt-on-connect
18049 Show whether interrupt-sequence is sent
18050 to remote target when @value{GDBN} connects to it.
18054 @item set tcp auto-retry on
18055 @cindex auto-retry, for remote TCP target
18056 Enable auto-retry for remote TCP connections. This is useful if the remote
18057 debugging agent is launched in parallel with @value{GDBN}; there is a race
18058 condition because the agent may not become ready to accept the connection
18059 before @value{GDBN} attempts to connect. When auto-retry is
18060 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18061 to establish the connection using the timeout specified by
18062 @code{set tcp connect-timeout}.
18064 @item set tcp auto-retry off
18065 Do not auto-retry failed TCP connections.
18067 @item show tcp auto-retry
18068 Show the current auto-retry setting.
18070 @item set tcp connect-timeout @var{seconds}
18071 @cindex connection timeout, for remote TCP target
18072 @cindex timeout, for remote target connection
18073 Set the timeout for establishing a TCP connection to the remote target to
18074 @var{seconds}. The timeout affects both polling to retry failed connections
18075 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18076 that are merely slow to complete, and represents an approximate cumulative
18079 @item show tcp connect-timeout
18080 Show the current connection timeout setting.
18083 @cindex remote packets, enabling and disabling
18084 The @value{GDBN} remote protocol autodetects the packets supported by
18085 your debugging stub. If you need to override the autodetection, you
18086 can use these commands to enable or disable individual packets. Each
18087 packet can be set to @samp{on} (the remote target supports this
18088 packet), @samp{off} (the remote target does not support this packet),
18089 or @samp{auto} (detect remote target support for this packet). They
18090 all default to @samp{auto}. For more information about each packet,
18091 see @ref{Remote Protocol}.
18093 During normal use, you should not have to use any of these commands.
18094 If you do, that may be a bug in your remote debugging stub, or a bug
18095 in @value{GDBN}. You may want to report the problem to the
18096 @value{GDBN} developers.
18098 For each packet @var{name}, the command to enable or disable the
18099 packet is @code{set remote @var{name}-packet}. The available settings
18102 @multitable @columnfractions 0.28 0.32 0.25
18105 @tab Related Features
18107 @item @code{fetch-register}
18109 @tab @code{info registers}
18111 @item @code{set-register}
18115 @item @code{binary-download}
18117 @tab @code{load}, @code{set}
18119 @item @code{read-aux-vector}
18120 @tab @code{qXfer:auxv:read}
18121 @tab @code{info auxv}
18123 @item @code{symbol-lookup}
18124 @tab @code{qSymbol}
18125 @tab Detecting multiple threads
18127 @item @code{attach}
18128 @tab @code{vAttach}
18131 @item @code{verbose-resume}
18133 @tab Stepping or resuming multiple threads
18139 @item @code{software-breakpoint}
18143 @item @code{hardware-breakpoint}
18147 @item @code{write-watchpoint}
18151 @item @code{read-watchpoint}
18155 @item @code{access-watchpoint}
18159 @item @code{target-features}
18160 @tab @code{qXfer:features:read}
18161 @tab @code{set architecture}
18163 @item @code{library-info}
18164 @tab @code{qXfer:libraries:read}
18165 @tab @code{info sharedlibrary}
18167 @item @code{memory-map}
18168 @tab @code{qXfer:memory-map:read}
18169 @tab @code{info mem}
18171 @item @code{read-sdata-object}
18172 @tab @code{qXfer:sdata:read}
18173 @tab @code{print $_sdata}
18175 @item @code{read-spu-object}
18176 @tab @code{qXfer:spu:read}
18177 @tab @code{info spu}
18179 @item @code{write-spu-object}
18180 @tab @code{qXfer:spu:write}
18181 @tab @code{info spu}
18183 @item @code{read-siginfo-object}
18184 @tab @code{qXfer:siginfo:read}
18185 @tab @code{print $_siginfo}
18187 @item @code{write-siginfo-object}
18188 @tab @code{qXfer:siginfo:write}
18189 @tab @code{set $_siginfo}
18191 @item @code{threads}
18192 @tab @code{qXfer:threads:read}
18193 @tab @code{info threads}
18195 @item @code{get-thread-local-@*storage-address}
18196 @tab @code{qGetTLSAddr}
18197 @tab Displaying @code{__thread} variables
18199 @item @code{get-thread-information-block-address}
18200 @tab @code{qGetTIBAddr}
18201 @tab Display MS-Windows Thread Information Block.
18203 @item @code{search-memory}
18204 @tab @code{qSearch:memory}
18207 @item @code{supported-packets}
18208 @tab @code{qSupported}
18209 @tab Remote communications parameters
18211 @item @code{pass-signals}
18212 @tab @code{QPassSignals}
18213 @tab @code{handle @var{signal}}
18215 @item @code{program-signals}
18216 @tab @code{QProgramSignals}
18217 @tab @code{handle @var{signal}}
18219 @item @code{hostio-close-packet}
18220 @tab @code{vFile:close}
18221 @tab @code{remote get}, @code{remote put}
18223 @item @code{hostio-open-packet}
18224 @tab @code{vFile:open}
18225 @tab @code{remote get}, @code{remote put}
18227 @item @code{hostio-pread-packet}
18228 @tab @code{vFile:pread}
18229 @tab @code{remote get}, @code{remote put}
18231 @item @code{hostio-pwrite-packet}
18232 @tab @code{vFile:pwrite}
18233 @tab @code{remote get}, @code{remote put}
18235 @item @code{hostio-unlink-packet}
18236 @tab @code{vFile:unlink}
18237 @tab @code{remote delete}
18239 @item @code{hostio-readlink-packet}
18240 @tab @code{vFile:readlink}
18243 @item @code{noack-packet}
18244 @tab @code{QStartNoAckMode}
18245 @tab Packet acknowledgment
18247 @item @code{osdata}
18248 @tab @code{qXfer:osdata:read}
18249 @tab @code{info os}
18251 @item @code{query-attached}
18252 @tab @code{qAttached}
18253 @tab Querying remote process attach state.
18255 @item @code{traceframe-info}
18256 @tab @code{qXfer:traceframe-info:read}
18257 @tab Traceframe info
18259 @item @code{install-in-trace}
18260 @tab @code{InstallInTrace}
18261 @tab Install tracepoint in tracing
18263 @item @code{disable-randomization}
18264 @tab @code{QDisableRandomization}
18265 @tab @code{set disable-randomization}
18267 @item @code{conditional-breakpoints-packet}
18268 @tab @code{Z0 and Z1}
18269 @tab @code{Support for target-side breakpoint condition evaluation}
18273 @section Implementing a Remote Stub
18275 @cindex debugging stub, example
18276 @cindex remote stub, example
18277 @cindex stub example, remote debugging
18278 The stub files provided with @value{GDBN} implement the target side of the
18279 communication protocol, and the @value{GDBN} side is implemented in the
18280 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
18281 these subroutines to communicate, and ignore the details. (If you're
18282 implementing your own stub file, you can still ignore the details: start
18283 with one of the existing stub files. @file{sparc-stub.c} is the best
18284 organized, and therefore the easiest to read.)
18286 @cindex remote serial debugging, overview
18287 To debug a program running on another machine (the debugging
18288 @dfn{target} machine), you must first arrange for all the usual
18289 prerequisites for the program to run by itself. For example, for a C
18294 A startup routine to set up the C runtime environment; these usually
18295 have a name like @file{crt0}. The startup routine may be supplied by
18296 your hardware supplier, or you may have to write your own.
18299 A C subroutine library to support your program's
18300 subroutine calls, notably managing input and output.
18303 A way of getting your program to the other machine---for example, a
18304 download program. These are often supplied by the hardware
18305 manufacturer, but you may have to write your own from hardware
18309 The next step is to arrange for your program to use a serial port to
18310 communicate with the machine where @value{GDBN} is running (the @dfn{host}
18311 machine). In general terms, the scheme looks like this:
18315 @value{GDBN} already understands how to use this protocol; when everything
18316 else is set up, you can simply use the @samp{target remote} command
18317 (@pxref{Targets,,Specifying a Debugging Target}).
18319 @item On the target,
18320 you must link with your program a few special-purpose subroutines that
18321 implement the @value{GDBN} remote serial protocol. The file containing these
18322 subroutines is called a @dfn{debugging stub}.
18324 On certain remote targets, you can use an auxiliary program
18325 @code{gdbserver} instead of linking a stub into your program.
18326 @xref{Server,,Using the @code{gdbserver} Program}, for details.
18329 The debugging stub is specific to the architecture of the remote
18330 machine; for example, use @file{sparc-stub.c} to debug programs on
18333 @cindex remote serial stub list
18334 These working remote stubs are distributed with @value{GDBN}:
18339 @cindex @file{i386-stub.c}
18342 For Intel 386 and compatible architectures.
18345 @cindex @file{m68k-stub.c}
18346 @cindex Motorola 680x0
18348 For Motorola 680x0 architectures.
18351 @cindex @file{sh-stub.c}
18354 For Renesas SH architectures.
18357 @cindex @file{sparc-stub.c}
18359 For @sc{sparc} architectures.
18361 @item sparcl-stub.c
18362 @cindex @file{sparcl-stub.c}
18365 For Fujitsu @sc{sparclite} architectures.
18369 The @file{README} file in the @value{GDBN} distribution may list other
18370 recently added stubs.
18373 * Stub Contents:: What the stub can do for you
18374 * Bootstrapping:: What you must do for the stub
18375 * Debug Session:: Putting it all together
18378 @node Stub Contents
18379 @subsection What the Stub Can Do for You
18381 @cindex remote serial stub
18382 The debugging stub for your architecture supplies these three
18386 @item set_debug_traps
18387 @findex set_debug_traps
18388 @cindex remote serial stub, initialization
18389 This routine arranges for @code{handle_exception} to run when your
18390 program stops. You must call this subroutine explicitly in your
18391 program's startup code.
18393 @item handle_exception
18394 @findex handle_exception
18395 @cindex remote serial stub, main routine
18396 This is the central workhorse, but your program never calls it
18397 explicitly---the setup code arranges for @code{handle_exception} to
18398 run when a trap is triggered.
18400 @code{handle_exception} takes control when your program stops during
18401 execution (for example, on a breakpoint), and mediates communications
18402 with @value{GDBN} on the host machine. This is where the communications
18403 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
18404 representative on the target machine. It begins by sending summary
18405 information on the state of your program, then continues to execute,
18406 retrieving and transmitting any information @value{GDBN} needs, until you
18407 execute a @value{GDBN} command that makes your program resume; at that point,
18408 @code{handle_exception} returns control to your own code on the target
18412 @cindex @code{breakpoint} subroutine, remote
18413 Use this auxiliary subroutine to make your program contain a
18414 breakpoint. Depending on the particular situation, this may be the only
18415 way for @value{GDBN} to get control. For instance, if your target
18416 machine has some sort of interrupt button, you won't need to call this;
18417 pressing the interrupt button transfers control to
18418 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
18419 simply receiving characters on the serial port may also trigger a trap;
18420 again, in that situation, you don't need to call @code{breakpoint} from
18421 your own program---simply running @samp{target remote} from the host
18422 @value{GDBN} session gets control.
18424 Call @code{breakpoint} if none of these is true, or if you simply want
18425 to make certain your program stops at a predetermined point for the
18426 start of your debugging session.
18429 @node Bootstrapping
18430 @subsection What You Must Do for the Stub
18432 @cindex remote stub, support routines
18433 The debugging stubs that come with @value{GDBN} are set up for a particular
18434 chip architecture, but they have no information about the rest of your
18435 debugging target machine.
18437 First of all you need to tell the stub how to communicate with the
18441 @item int getDebugChar()
18442 @findex getDebugChar
18443 Write this subroutine to read a single character from the serial port.
18444 It may be identical to @code{getchar} for your target system; a
18445 different name is used to allow you to distinguish the two if you wish.
18447 @item void putDebugChar(int)
18448 @findex putDebugChar
18449 Write this subroutine to write a single character to the serial port.
18450 It may be identical to @code{putchar} for your target system; a
18451 different name is used to allow you to distinguish the two if you wish.
18454 @cindex control C, and remote debugging
18455 @cindex interrupting remote targets
18456 If you want @value{GDBN} to be able to stop your program while it is
18457 running, you need to use an interrupt-driven serial driver, and arrange
18458 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
18459 character). That is the character which @value{GDBN} uses to tell the
18460 remote system to stop.
18462 Getting the debugging target to return the proper status to @value{GDBN}
18463 probably requires changes to the standard stub; one quick and dirty way
18464 is to just execute a breakpoint instruction (the ``dirty'' part is that
18465 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
18467 Other routines you need to supply are:
18470 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
18471 @findex exceptionHandler
18472 Write this function to install @var{exception_address} in the exception
18473 handling tables. You need to do this because the stub does not have any
18474 way of knowing what the exception handling tables on your target system
18475 are like (for example, the processor's table might be in @sc{rom},
18476 containing entries which point to a table in @sc{ram}).
18477 @var{exception_number} is the exception number which should be changed;
18478 its meaning is architecture-dependent (for example, different numbers
18479 might represent divide by zero, misaligned access, etc). When this
18480 exception occurs, control should be transferred directly to
18481 @var{exception_address}, and the processor state (stack, registers,
18482 and so on) should be just as it is when a processor exception occurs. So if
18483 you want to use a jump instruction to reach @var{exception_address}, it
18484 should be a simple jump, not a jump to subroutine.
18486 For the 386, @var{exception_address} should be installed as an interrupt
18487 gate so that interrupts are masked while the handler runs. The gate
18488 should be at privilege level 0 (the most privileged level). The
18489 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
18490 help from @code{exceptionHandler}.
18492 @item void flush_i_cache()
18493 @findex flush_i_cache
18494 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
18495 instruction cache, if any, on your target machine. If there is no
18496 instruction cache, this subroutine may be a no-op.
18498 On target machines that have instruction caches, @value{GDBN} requires this
18499 function to make certain that the state of your program is stable.
18503 You must also make sure this library routine is available:
18506 @item void *memset(void *, int, int)
18508 This is the standard library function @code{memset} that sets an area of
18509 memory to a known value. If you have one of the free versions of
18510 @code{libc.a}, @code{memset} can be found there; otherwise, you must
18511 either obtain it from your hardware manufacturer, or write your own.
18514 If you do not use the GNU C compiler, you may need other standard
18515 library subroutines as well; this varies from one stub to another,
18516 but in general the stubs are likely to use any of the common library
18517 subroutines which @code{@value{NGCC}} generates as inline code.
18520 @node Debug Session
18521 @subsection Putting it All Together
18523 @cindex remote serial debugging summary
18524 In summary, when your program is ready to debug, you must follow these
18529 Make sure you have defined the supporting low-level routines
18530 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
18532 @code{getDebugChar}, @code{putDebugChar},
18533 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
18537 Insert these lines in your program's startup code, before the main
18538 procedure is called:
18545 On some machines, when a breakpoint trap is raised, the hardware
18546 automatically makes the PC point to the instruction after the
18547 breakpoint. If your machine doesn't do that, you may need to adjust
18548 @code{handle_exception} to arrange for it to return to the instruction
18549 after the breakpoint on this first invocation, so that your program
18550 doesn't keep hitting the initial breakpoint instead of making
18554 For the 680x0 stub only, you need to provide a variable called
18555 @code{exceptionHook}. Normally you just use:
18558 void (*exceptionHook)() = 0;
18562 but if before calling @code{set_debug_traps}, you set it to point to a
18563 function in your program, that function is called when
18564 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
18565 error). The function indicated by @code{exceptionHook} is called with
18566 one parameter: an @code{int} which is the exception number.
18569 Compile and link together: your program, the @value{GDBN} debugging stub for
18570 your target architecture, and the supporting subroutines.
18573 Make sure you have a serial connection between your target machine and
18574 the @value{GDBN} host, and identify the serial port on the host.
18577 @c The "remote" target now provides a `load' command, so we should
18578 @c document that. FIXME.
18579 Download your program to your target machine (or get it there by
18580 whatever means the manufacturer provides), and start it.
18583 Start @value{GDBN} on the host, and connect to the target
18584 (@pxref{Connecting,,Connecting to a Remote Target}).
18588 @node Configurations
18589 @chapter Configuration-Specific Information
18591 While nearly all @value{GDBN} commands are available for all native and
18592 cross versions of the debugger, there are some exceptions. This chapter
18593 describes things that are only available in certain configurations.
18595 There are three major categories of configurations: native
18596 configurations, where the host and target are the same, embedded
18597 operating system configurations, which are usually the same for several
18598 different processor architectures, and bare embedded processors, which
18599 are quite different from each other.
18604 * Embedded Processors::
18611 This section describes details specific to particular native
18616 * BSD libkvm Interface:: Debugging BSD kernel memory images
18617 * SVR4 Process Information:: SVR4 process information
18618 * DJGPP Native:: Features specific to the DJGPP port
18619 * Cygwin Native:: Features specific to the Cygwin port
18620 * Hurd Native:: Features specific to @sc{gnu} Hurd
18621 * Darwin:: Features specific to Darwin
18627 On HP-UX systems, if you refer to a function or variable name that
18628 begins with a dollar sign, @value{GDBN} searches for a user or system
18629 name first, before it searches for a convenience variable.
18632 @node BSD libkvm Interface
18633 @subsection BSD libkvm Interface
18636 @cindex kernel memory image
18637 @cindex kernel crash dump
18639 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
18640 interface that provides a uniform interface for accessing kernel virtual
18641 memory images, including live systems and crash dumps. @value{GDBN}
18642 uses this interface to allow you to debug live kernels and kernel crash
18643 dumps on many native BSD configurations. This is implemented as a
18644 special @code{kvm} debugging target. For debugging a live system, load
18645 the currently running kernel into @value{GDBN} and connect to the
18649 (@value{GDBP}) @b{target kvm}
18652 For debugging crash dumps, provide the file name of the crash dump as an
18656 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
18659 Once connected to the @code{kvm} target, the following commands are
18665 Set current context from the @dfn{Process Control Block} (PCB) address.
18668 Set current context from proc address. This command isn't available on
18669 modern FreeBSD systems.
18672 @node SVR4 Process Information
18673 @subsection SVR4 Process Information
18675 @cindex examine process image
18676 @cindex process info via @file{/proc}
18678 Many versions of SVR4 and compatible systems provide a facility called
18679 @samp{/proc} that can be used to examine the image of a running
18680 process using file-system subroutines.
18682 If @value{GDBN} is configured for an operating system with this
18683 facility, the command @code{info proc} is available to report
18684 information about the process running your program, or about any
18685 process running on your system. This includes, as of this writing,
18686 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
18687 not HP-UX, for example.
18689 This command may also work on core files that were created on a system
18690 that has the @samp{/proc} facility.
18696 @itemx info proc @var{process-id}
18697 Summarize available information about any running process. If a
18698 process ID is specified by @var{process-id}, display information about
18699 that process; otherwise display information about the program being
18700 debugged. The summary includes the debugged process ID, the command
18701 line used to invoke it, its current working directory, and its
18702 executable file's absolute file name.
18704 On some systems, @var{process-id} can be of the form
18705 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
18706 within a process. If the optional @var{pid} part is missing, it means
18707 a thread from the process being debugged (the leading @samp{/} still
18708 needs to be present, or else @value{GDBN} will interpret the number as
18709 a process ID rather than a thread ID).
18711 @item info proc cmdline
18712 @cindex info proc cmdline
18713 Show the original command line of the process. This command is
18714 specific to @sc{gnu}/Linux.
18716 @item info proc cwd
18717 @cindex info proc cwd
18718 Show the current working directory of the process. This command is
18719 specific to @sc{gnu}/Linux.
18721 @item info proc exe
18722 @cindex info proc exe
18723 Show the name of executable of the process. This command is specific
18726 @item info proc mappings
18727 @cindex memory address space mappings
18728 Report the memory address space ranges accessible in the program, with
18729 information on whether the process has read, write, or execute access
18730 rights to each range. On @sc{gnu}/Linux systems, each memory range
18731 includes the object file which is mapped to that range, instead of the
18732 memory access rights to that range.
18734 @item info proc stat
18735 @itemx info proc status
18736 @cindex process detailed status information
18737 These subcommands are specific to @sc{gnu}/Linux systems. They show
18738 the process-related information, including the user ID and group ID;
18739 how many threads are there in the process; its virtual memory usage;
18740 the signals that are pending, blocked, and ignored; its TTY; its
18741 consumption of system and user time; its stack size; its @samp{nice}
18742 value; etc. For more information, see the @samp{proc} man page
18743 (type @kbd{man 5 proc} from your shell prompt).
18745 @item info proc all
18746 Show all the information about the process described under all of the
18747 above @code{info proc} subcommands.
18750 @comment These sub-options of 'info proc' were not included when
18751 @comment procfs.c was re-written. Keep their descriptions around
18752 @comment against the day when someone finds the time to put them back in.
18753 @kindex info proc times
18754 @item info proc times
18755 Starting time, user CPU time, and system CPU time for your program and
18758 @kindex info proc id
18760 Report on the process IDs related to your program: its own process ID,
18761 the ID of its parent, the process group ID, and the session ID.
18764 @item set procfs-trace
18765 @kindex set procfs-trace
18766 @cindex @code{procfs} API calls
18767 This command enables and disables tracing of @code{procfs} API calls.
18769 @item show procfs-trace
18770 @kindex show procfs-trace
18771 Show the current state of @code{procfs} API call tracing.
18773 @item set procfs-file @var{file}
18774 @kindex set procfs-file
18775 Tell @value{GDBN} to write @code{procfs} API trace to the named
18776 @var{file}. @value{GDBN} appends the trace info to the previous
18777 contents of the file. The default is to display the trace on the
18780 @item show procfs-file
18781 @kindex show procfs-file
18782 Show the file to which @code{procfs} API trace is written.
18784 @item proc-trace-entry
18785 @itemx proc-trace-exit
18786 @itemx proc-untrace-entry
18787 @itemx proc-untrace-exit
18788 @kindex proc-trace-entry
18789 @kindex proc-trace-exit
18790 @kindex proc-untrace-entry
18791 @kindex proc-untrace-exit
18792 These commands enable and disable tracing of entries into and exits
18793 from the @code{syscall} interface.
18796 @kindex info pidlist
18797 @cindex process list, QNX Neutrino
18798 For QNX Neutrino only, this command displays the list of all the
18799 processes and all the threads within each process.
18802 @kindex info meminfo
18803 @cindex mapinfo list, QNX Neutrino
18804 For QNX Neutrino only, this command displays the list of all mapinfos.
18808 @subsection Features for Debugging @sc{djgpp} Programs
18809 @cindex @sc{djgpp} debugging
18810 @cindex native @sc{djgpp} debugging
18811 @cindex MS-DOS-specific commands
18814 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
18815 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
18816 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
18817 top of real-mode DOS systems and their emulations.
18819 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
18820 defines a few commands specific to the @sc{djgpp} port. This
18821 subsection describes those commands.
18826 This is a prefix of @sc{djgpp}-specific commands which print
18827 information about the target system and important OS structures.
18830 @cindex MS-DOS system info
18831 @cindex free memory information (MS-DOS)
18832 @item info dos sysinfo
18833 This command displays assorted information about the underlying
18834 platform: the CPU type and features, the OS version and flavor, the
18835 DPMI version, and the available conventional and DPMI memory.
18840 @cindex segment descriptor tables
18841 @cindex descriptor tables display
18843 @itemx info dos ldt
18844 @itemx info dos idt
18845 These 3 commands display entries from, respectively, Global, Local,
18846 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
18847 tables are data structures which store a descriptor for each segment
18848 that is currently in use. The segment's selector is an index into a
18849 descriptor table; the table entry for that index holds the
18850 descriptor's base address and limit, and its attributes and access
18853 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
18854 segment (used for both data and the stack), and a DOS segment (which
18855 allows access to DOS/BIOS data structures and absolute addresses in
18856 conventional memory). However, the DPMI host will usually define
18857 additional segments in order to support the DPMI environment.
18859 @cindex garbled pointers
18860 These commands allow to display entries from the descriptor tables.
18861 Without an argument, all entries from the specified table are
18862 displayed. An argument, which should be an integer expression, means
18863 display a single entry whose index is given by the argument. For
18864 example, here's a convenient way to display information about the
18865 debugged program's data segment:
18868 @exdent @code{(@value{GDBP}) info dos ldt $ds}
18869 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
18873 This comes in handy when you want to see whether a pointer is outside
18874 the data segment's limit (i.e.@: @dfn{garbled}).
18876 @cindex page tables display (MS-DOS)
18878 @itemx info dos pte
18879 These two commands display entries from, respectively, the Page
18880 Directory and the Page Tables. Page Directories and Page Tables are
18881 data structures which control how virtual memory addresses are mapped
18882 into physical addresses. A Page Table includes an entry for every
18883 page of memory that is mapped into the program's address space; there
18884 may be several Page Tables, each one holding up to 4096 entries. A
18885 Page Directory has up to 4096 entries, one each for every Page Table
18886 that is currently in use.
18888 Without an argument, @kbd{info dos pde} displays the entire Page
18889 Directory, and @kbd{info dos pte} displays all the entries in all of
18890 the Page Tables. An argument, an integer expression, given to the
18891 @kbd{info dos pde} command means display only that entry from the Page
18892 Directory table. An argument given to the @kbd{info dos pte} command
18893 means display entries from a single Page Table, the one pointed to by
18894 the specified entry in the Page Directory.
18896 @cindex direct memory access (DMA) on MS-DOS
18897 These commands are useful when your program uses @dfn{DMA} (Direct
18898 Memory Access), which needs physical addresses to program the DMA
18901 These commands are supported only with some DPMI servers.
18903 @cindex physical address from linear address
18904 @item info dos address-pte @var{addr}
18905 This command displays the Page Table entry for a specified linear
18906 address. The argument @var{addr} is a linear address which should
18907 already have the appropriate segment's base address added to it,
18908 because this command accepts addresses which may belong to @emph{any}
18909 segment. For example, here's how to display the Page Table entry for
18910 the page where a variable @code{i} is stored:
18913 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
18914 @exdent @code{Page Table entry for address 0x11a00d30:}
18915 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
18919 This says that @code{i} is stored at offset @code{0xd30} from the page
18920 whose physical base address is @code{0x02698000}, and shows all the
18921 attributes of that page.
18923 Note that you must cast the addresses of variables to a @code{char *},
18924 since otherwise the value of @code{__djgpp_base_address}, the base
18925 address of all variables and functions in a @sc{djgpp} program, will
18926 be added using the rules of C pointer arithmetics: if @code{i} is
18927 declared an @code{int}, @value{GDBN} will add 4 times the value of
18928 @code{__djgpp_base_address} to the address of @code{i}.
18930 Here's another example, it displays the Page Table entry for the
18934 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
18935 @exdent @code{Page Table entry for address 0x29110:}
18936 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
18940 (The @code{+ 3} offset is because the transfer buffer's address is the
18941 3rd member of the @code{_go32_info_block} structure.) The output
18942 clearly shows that this DPMI server maps the addresses in conventional
18943 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
18944 linear (@code{0x29110}) addresses are identical.
18946 This command is supported only with some DPMI servers.
18949 @cindex DOS serial data link, remote debugging
18950 In addition to native debugging, the DJGPP port supports remote
18951 debugging via a serial data link. The following commands are specific
18952 to remote serial debugging in the DJGPP port of @value{GDBN}.
18955 @kindex set com1base
18956 @kindex set com1irq
18957 @kindex set com2base
18958 @kindex set com2irq
18959 @kindex set com3base
18960 @kindex set com3irq
18961 @kindex set com4base
18962 @kindex set com4irq
18963 @item set com1base @var{addr}
18964 This command sets the base I/O port address of the @file{COM1} serial
18967 @item set com1irq @var{irq}
18968 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
18969 for the @file{COM1} serial port.
18971 There are similar commands @samp{set com2base}, @samp{set com3irq},
18972 etc.@: for setting the port address and the @code{IRQ} lines for the
18975 @kindex show com1base
18976 @kindex show com1irq
18977 @kindex show com2base
18978 @kindex show com2irq
18979 @kindex show com3base
18980 @kindex show com3irq
18981 @kindex show com4base
18982 @kindex show com4irq
18983 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18984 display the current settings of the base address and the @code{IRQ}
18985 lines used by the COM ports.
18988 @kindex info serial
18989 @cindex DOS serial port status
18990 This command prints the status of the 4 DOS serial ports. For each
18991 port, it prints whether it's active or not, its I/O base address and
18992 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18993 counts of various errors encountered so far.
18997 @node Cygwin Native
18998 @subsection Features for Debugging MS Windows PE Executables
18999 @cindex MS Windows debugging
19000 @cindex native Cygwin debugging
19001 @cindex Cygwin-specific commands
19003 @value{GDBN} supports native debugging of MS Windows programs, including
19004 DLLs with and without symbolic debugging information.
19006 @cindex Ctrl-BREAK, MS-Windows
19007 @cindex interrupt debuggee on MS-Windows
19008 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19009 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19010 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19011 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19012 sequence, which can be used to interrupt the debuggee even if it
19015 There are various additional Cygwin-specific commands, described in
19016 this section. Working with DLLs that have no debugging symbols is
19017 described in @ref{Non-debug DLL Symbols}.
19022 This is a prefix of MS Windows-specific commands which print
19023 information about the target system and important OS structures.
19025 @item info w32 selector
19026 This command displays information returned by
19027 the Win32 API @code{GetThreadSelectorEntry} function.
19028 It takes an optional argument that is evaluated to
19029 a long value to give the information about this given selector.
19030 Without argument, this command displays information
19031 about the six segment registers.
19033 @item info w32 thread-information-block
19034 This command displays thread specific information stored in the
19035 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19036 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19040 This is a Cygwin-specific alias of @code{info shared}.
19042 @kindex dll-symbols
19044 This command loads symbols from a dll similarly to
19045 add-sym command but without the need to specify a base address.
19047 @kindex set cygwin-exceptions
19048 @cindex debugging the Cygwin DLL
19049 @cindex Cygwin DLL, debugging
19050 @item set cygwin-exceptions @var{mode}
19051 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19052 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19053 @value{GDBN} will delay recognition of exceptions, and may ignore some
19054 exceptions which seem to be caused by internal Cygwin DLL
19055 ``bookkeeping''. This option is meant primarily for debugging the
19056 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19057 @value{GDBN} users with false @code{SIGSEGV} signals.
19059 @kindex show cygwin-exceptions
19060 @item show cygwin-exceptions
19061 Displays whether @value{GDBN} will break on exceptions that happen
19062 inside the Cygwin DLL itself.
19064 @kindex set new-console
19065 @item set new-console @var{mode}
19066 If @var{mode} is @code{on} the debuggee will
19067 be started in a new console on next start.
19068 If @var{mode} is @code{off}, the debuggee will
19069 be started in the same console as the debugger.
19071 @kindex show new-console
19072 @item show new-console
19073 Displays whether a new console is used
19074 when the debuggee is started.
19076 @kindex set new-group
19077 @item set new-group @var{mode}
19078 This boolean value controls whether the debuggee should
19079 start a new group or stay in the same group as the debugger.
19080 This affects the way the Windows OS handles
19083 @kindex show new-group
19084 @item show new-group
19085 Displays current value of new-group boolean.
19087 @kindex set debugevents
19088 @item set debugevents
19089 This boolean value adds debug output concerning kernel events related
19090 to the debuggee seen by the debugger. This includes events that
19091 signal thread and process creation and exit, DLL loading and
19092 unloading, console interrupts, and debugging messages produced by the
19093 Windows @code{OutputDebugString} API call.
19095 @kindex set debugexec
19096 @item set debugexec
19097 This boolean value adds debug output concerning execute events
19098 (such as resume thread) seen by the debugger.
19100 @kindex set debugexceptions
19101 @item set debugexceptions
19102 This boolean value adds debug output concerning exceptions in the
19103 debuggee seen by the debugger.
19105 @kindex set debugmemory
19106 @item set debugmemory
19107 This boolean value adds debug output concerning debuggee memory reads
19108 and writes by the debugger.
19112 This boolean values specifies whether the debuggee is called
19113 via a shell or directly (default value is on).
19117 Displays if the debuggee will be started with a shell.
19122 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19125 @node Non-debug DLL Symbols
19126 @subsubsection Support for DLLs without Debugging Symbols
19127 @cindex DLLs with no debugging symbols
19128 @cindex Minimal symbols and DLLs
19130 Very often on windows, some of the DLLs that your program relies on do
19131 not include symbolic debugging information (for example,
19132 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19133 symbols in a DLL, it relies on the minimal amount of symbolic
19134 information contained in the DLL's export table. This section
19135 describes working with such symbols, known internally to @value{GDBN} as
19136 ``minimal symbols''.
19138 Note that before the debugged program has started execution, no DLLs
19139 will have been loaded. The easiest way around this problem is simply to
19140 start the program --- either by setting a breakpoint or letting the
19141 program run once to completion. It is also possible to force
19142 @value{GDBN} to load a particular DLL before starting the executable ---
19143 see the shared library information in @ref{Files}, or the
19144 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19145 explicitly loading symbols from a DLL with no debugging information will
19146 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19147 which may adversely affect symbol lookup performance.
19149 @subsubsection DLL Name Prefixes
19151 In keeping with the naming conventions used by the Microsoft debugging
19152 tools, DLL export symbols are made available with a prefix based on the
19153 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19154 also entered into the symbol table, so @code{CreateFileA} is often
19155 sufficient. In some cases there will be name clashes within a program
19156 (particularly if the executable itself includes full debugging symbols)
19157 necessitating the use of the fully qualified name when referring to the
19158 contents of the DLL. Use single-quotes around the name to avoid the
19159 exclamation mark (``!'') being interpreted as a language operator.
19161 Note that the internal name of the DLL may be all upper-case, even
19162 though the file name of the DLL is lower-case, or vice-versa. Since
19163 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19164 some confusion. If in doubt, try the @code{info functions} and
19165 @code{info variables} commands or even @code{maint print msymbols}
19166 (@pxref{Symbols}). Here's an example:
19169 (@value{GDBP}) info function CreateFileA
19170 All functions matching regular expression "CreateFileA":
19172 Non-debugging symbols:
19173 0x77e885f4 CreateFileA
19174 0x77e885f4 KERNEL32!CreateFileA
19178 (@value{GDBP}) info function !
19179 All functions matching regular expression "!":
19181 Non-debugging symbols:
19182 0x6100114c cygwin1!__assert
19183 0x61004034 cygwin1!_dll_crt0@@0
19184 0x61004240 cygwin1!dll_crt0(per_process *)
19188 @subsubsection Working with Minimal Symbols
19190 Symbols extracted from a DLL's export table do not contain very much
19191 type information. All that @value{GDBN} can do is guess whether a symbol
19192 refers to a function or variable depending on the linker section that
19193 contains the symbol. Also note that the actual contents of the memory
19194 contained in a DLL are not available unless the program is running. This
19195 means that you cannot examine the contents of a variable or disassemble
19196 a function within a DLL without a running program.
19198 Variables are generally treated as pointers and dereferenced
19199 automatically. For this reason, it is often necessary to prefix a
19200 variable name with the address-of operator (``&'') and provide explicit
19201 type information in the command. Here's an example of the type of
19205 (@value{GDBP}) print 'cygwin1!__argv'
19210 (@value{GDBP}) x 'cygwin1!__argv'
19211 0x10021610: "\230y\""
19214 And two possible solutions:
19217 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19218 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19222 (@value{GDBP}) x/2x &'cygwin1!__argv'
19223 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19224 (@value{GDBP}) x/x 0x10021608
19225 0x10021608: 0x0022fd98
19226 (@value{GDBP}) x/s 0x0022fd98
19227 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19230 Setting a break point within a DLL is possible even before the program
19231 starts execution. However, under these circumstances, @value{GDBN} can't
19232 examine the initial instructions of the function in order to skip the
19233 function's frame set-up code. You can work around this by using ``*&''
19234 to set the breakpoint at a raw memory address:
19237 (@value{GDBP}) break *&'python22!PyOS_Readline'
19238 Breakpoint 1 at 0x1e04eff0
19241 The author of these extensions is not entirely convinced that setting a
19242 break point within a shared DLL like @file{kernel32.dll} is completely
19246 @subsection Commands Specific to @sc{gnu} Hurd Systems
19247 @cindex @sc{gnu} Hurd debugging
19249 This subsection describes @value{GDBN} commands specific to the
19250 @sc{gnu} Hurd native debugging.
19255 @kindex set signals@r{, Hurd command}
19256 @kindex set sigs@r{, Hurd command}
19257 This command toggles the state of inferior signal interception by
19258 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
19259 affected by this command. @code{sigs} is a shorthand alias for
19264 @kindex show signals@r{, Hurd command}
19265 @kindex show sigs@r{, Hurd command}
19266 Show the current state of intercepting inferior's signals.
19268 @item set signal-thread
19269 @itemx set sigthread
19270 @kindex set signal-thread
19271 @kindex set sigthread
19272 This command tells @value{GDBN} which thread is the @code{libc} signal
19273 thread. That thread is run when a signal is delivered to a running
19274 process. @code{set sigthread} is the shorthand alias of @code{set
19277 @item show signal-thread
19278 @itemx show sigthread
19279 @kindex show signal-thread
19280 @kindex show sigthread
19281 These two commands show which thread will run when the inferior is
19282 delivered a signal.
19285 @kindex set stopped@r{, Hurd command}
19286 This commands tells @value{GDBN} that the inferior process is stopped,
19287 as with the @code{SIGSTOP} signal. The stopped process can be
19288 continued by delivering a signal to it.
19291 @kindex show stopped@r{, Hurd command}
19292 This command shows whether @value{GDBN} thinks the debuggee is
19295 @item set exceptions
19296 @kindex set exceptions@r{, Hurd command}
19297 Use this command to turn off trapping of exceptions in the inferior.
19298 When exception trapping is off, neither breakpoints nor
19299 single-stepping will work. To restore the default, set exception
19302 @item show exceptions
19303 @kindex show exceptions@r{, Hurd command}
19304 Show the current state of trapping exceptions in the inferior.
19306 @item set task pause
19307 @kindex set task@r{, Hurd commands}
19308 @cindex task attributes (@sc{gnu} Hurd)
19309 @cindex pause current task (@sc{gnu} Hurd)
19310 This command toggles task suspension when @value{GDBN} has control.
19311 Setting it to on takes effect immediately, and the task is suspended
19312 whenever @value{GDBN} gets control. Setting it to off will take
19313 effect the next time the inferior is continued. If this option is set
19314 to off, you can use @code{set thread default pause on} or @code{set
19315 thread pause on} (see below) to pause individual threads.
19317 @item show task pause
19318 @kindex show task@r{, Hurd commands}
19319 Show the current state of task suspension.
19321 @item set task detach-suspend-count
19322 @cindex task suspend count
19323 @cindex detach from task, @sc{gnu} Hurd
19324 This command sets the suspend count the task will be left with when
19325 @value{GDBN} detaches from it.
19327 @item show task detach-suspend-count
19328 Show the suspend count the task will be left with when detaching.
19330 @item set task exception-port
19331 @itemx set task excp
19332 @cindex task exception port, @sc{gnu} Hurd
19333 This command sets the task exception port to which @value{GDBN} will
19334 forward exceptions. The argument should be the value of the @dfn{send
19335 rights} of the task. @code{set task excp} is a shorthand alias.
19337 @item set noninvasive
19338 @cindex noninvasive task options
19339 This command switches @value{GDBN} to a mode that is the least
19340 invasive as far as interfering with the inferior is concerned. This
19341 is the same as using @code{set task pause}, @code{set exceptions}, and
19342 @code{set signals} to values opposite to the defaults.
19344 @item info send-rights
19345 @itemx info receive-rights
19346 @itemx info port-rights
19347 @itemx info port-sets
19348 @itemx info dead-names
19351 @cindex send rights, @sc{gnu} Hurd
19352 @cindex receive rights, @sc{gnu} Hurd
19353 @cindex port rights, @sc{gnu} Hurd
19354 @cindex port sets, @sc{gnu} Hurd
19355 @cindex dead names, @sc{gnu} Hurd
19356 These commands display information about, respectively, send rights,
19357 receive rights, port rights, port sets, and dead names of a task.
19358 There are also shorthand aliases: @code{info ports} for @code{info
19359 port-rights} and @code{info psets} for @code{info port-sets}.
19361 @item set thread pause
19362 @kindex set thread@r{, Hurd command}
19363 @cindex thread properties, @sc{gnu} Hurd
19364 @cindex pause current thread (@sc{gnu} Hurd)
19365 This command toggles current thread suspension when @value{GDBN} has
19366 control. Setting it to on takes effect immediately, and the current
19367 thread is suspended whenever @value{GDBN} gets control. Setting it to
19368 off will take effect the next time the inferior is continued.
19369 Normally, this command has no effect, since when @value{GDBN} has
19370 control, the whole task is suspended. However, if you used @code{set
19371 task pause off} (see above), this command comes in handy to suspend
19372 only the current thread.
19374 @item show thread pause
19375 @kindex show thread@r{, Hurd command}
19376 This command shows the state of current thread suspension.
19378 @item set thread run
19379 This command sets whether the current thread is allowed to run.
19381 @item show thread run
19382 Show whether the current thread is allowed to run.
19384 @item set thread detach-suspend-count
19385 @cindex thread suspend count, @sc{gnu} Hurd
19386 @cindex detach from thread, @sc{gnu} Hurd
19387 This command sets the suspend count @value{GDBN} will leave on a
19388 thread when detaching. This number is relative to the suspend count
19389 found by @value{GDBN} when it notices the thread; use @code{set thread
19390 takeover-suspend-count} to force it to an absolute value.
19392 @item show thread detach-suspend-count
19393 Show the suspend count @value{GDBN} will leave on the thread when
19396 @item set thread exception-port
19397 @itemx set thread excp
19398 Set the thread exception port to which to forward exceptions. This
19399 overrides the port set by @code{set task exception-port} (see above).
19400 @code{set thread excp} is the shorthand alias.
19402 @item set thread takeover-suspend-count
19403 Normally, @value{GDBN}'s thread suspend counts are relative to the
19404 value @value{GDBN} finds when it notices each thread. This command
19405 changes the suspend counts to be absolute instead.
19407 @item set thread default
19408 @itemx show thread default
19409 @cindex thread default settings, @sc{gnu} Hurd
19410 Each of the above @code{set thread} commands has a @code{set thread
19411 default} counterpart (e.g., @code{set thread default pause}, @code{set
19412 thread default exception-port}, etc.). The @code{thread default}
19413 variety of commands sets the default thread properties for all
19414 threads; you can then change the properties of individual threads with
19415 the non-default commands.
19422 @value{GDBN} provides the following commands specific to the Darwin target:
19425 @item set debug darwin @var{num}
19426 @kindex set debug darwin
19427 When set to a non zero value, enables debugging messages specific to
19428 the Darwin support. Higher values produce more verbose output.
19430 @item show debug darwin
19431 @kindex show debug darwin
19432 Show the current state of Darwin messages.
19434 @item set debug mach-o @var{num}
19435 @kindex set debug mach-o
19436 When set to a non zero value, enables debugging messages while
19437 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
19438 file format used on Darwin for object and executable files.) Higher
19439 values produce more verbose output. This is a command to diagnose
19440 problems internal to @value{GDBN} and should not be needed in normal
19443 @item show debug mach-o
19444 @kindex show debug mach-o
19445 Show the current state of Mach-O file messages.
19447 @item set mach-exceptions on
19448 @itemx set mach-exceptions off
19449 @kindex set mach-exceptions
19450 On Darwin, faults are first reported as a Mach exception and are then
19451 mapped to a Posix signal. Use this command to turn on trapping of
19452 Mach exceptions in the inferior. This might be sometimes useful to
19453 better understand the cause of a fault. The default is off.
19455 @item show mach-exceptions
19456 @kindex show mach-exceptions
19457 Show the current state of exceptions trapping.
19462 @section Embedded Operating Systems
19464 This section describes configurations involving the debugging of
19465 embedded operating systems that are available for several different
19469 * VxWorks:: Using @value{GDBN} with VxWorks
19472 @value{GDBN} includes the ability to debug programs running on
19473 various real-time operating systems.
19476 @subsection Using @value{GDBN} with VxWorks
19482 @kindex target vxworks
19483 @item target vxworks @var{machinename}
19484 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
19485 is the target system's machine name or IP address.
19489 On VxWorks, @code{load} links @var{filename} dynamically on the
19490 current target system as well as adding its symbols in @value{GDBN}.
19492 @value{GDBN} enables developers to spawn and debug tasks running on networked
19493 VxWorks targets from a Unix host. Already-running tasks spawned from
19494 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
19495 both the Unix host and on the VxWorks target. The program
19496 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
19497 installed with the name @code{vxgdb}, to distinguish it from a
19498 @value{GDBN} for debugging programs on the host itself.)
19501 @item VxWorks-timeout @var{args}
19502 @kindex vxworks-timeout
19503 All VxWorks-based targets now support the option @code{vxworks-timeout}.
19504 This option is set by the user, and @var{args} represents the number of
19505 seconds @value{GDBN} waits for responses to rpc's. You might use this if
19506 your VxWorks target is a slow software simulator or is on the far side
19507 of a thin network line.
19510 The following information on connecting to VxWorks was current when
19511 this manual was produced; newer releases of VxWorks may use revised
19514 @findex INCLUDE_RDB
19515 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
19516 to include the remote debugging interface routines in the VxWorks
19517 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
19518 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
19519 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
19520 source debugging task @code{tRdbTask} when VxWorks is booted. For more
19521 information on configuring and remaking VxWorks, see the manufacturer's
19523 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
19525 Once you have included @file{rdb.a} in your VxWorks system image and set
19526 your Unix execution search path to find @value{GDBN}, you are ready to
19527 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
19528 @code{vxgdb}, depending on your installation).
19530 @value{GDBN} comes up showing the prompt:
19537 * VxWorks Connection:: Connecting to VxWorks
19538 * VxWorks Download:: VxWorks download
19539 * VxWorks Attach:: Running tasks
19542 @node VxWorks Connection
19543 @subsubsection Connecting to VxWorks
19545 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
19546 network. To connect to a target whose host name is ``@code{tt}'', type:
19549 (vxgdb) target vxworks tt
19553 @value{GDBN} displays messages like these:
19556 Attaching remote machine across net...
19561 @value{GDBN} then attempts to read the symbol tables of any object modules
19562 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
19563 these files by searching the directories listed in the command search
19564 path (@pxref{Environment, ,Your Program's Environment}); if it fails
19565 to find an object file, it displays a message such as:
19568 prog.o: No such file or directory.
19571 When this happens, add the appropriate directory to the search path with
19572 the @value{GDBN} command @code{path}, and execute the @code{target}
19575 @node VxWorks Download
19576 @subsubsection VxWorks Download
19578 @cindex download to VxWorks
19579 If you have connected to the VxWorks target and you want to debug an
19580 object that has not yet been loaded, you can use the @value{GDBN}
19581 @code{load} command to download a file from Unix to VxWorks
19582 incrementally. The object file given as an argument to the @code{load}
19583 command is actually opened twice: first by the VxWorks target in order
19584 to download the code, then by @value{GDBN} in order to read the symbol
19585 table. This can lead to problems if the current working directories on
19586 the two systems differ. If both systems have NFS mounted the same
19587 filesystems, you can avoid these problems by using absolute paths.
19588 Otherwise, it is simplest to set the working directory on both systems
19589 to the directory in which the object file resides, and then to reference
19590 the file by its name, without any path. For instance, a program
19591 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
19592 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
19593 program, type this on VxWorks:
19596 -> cd "@var{vxpath}/vw/demo/rdb"
19600 Then, in @value{GDBN}, type:
19603 (vxgdb) cd @var{hostpath}/vw/demo/rdb
19604 (vxgdb) load prog.o
19607 @value{GDBN} displays a response similar to this:
19610 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
19613 You can also use the @code{load} command to reload an object module
19614 after editing and recompiling the corresponding source file. Note that
19615 this makes @value{GDBN} delete all currently-defined breakpoints,
19616 auto-displays, and convenience variables, and to clear the value
19617 history. (This is necessary in order to preserve the integrity of
19618 debugger's data structures that reference the target system's symbol
19621 @node VxWorks Attach
19622 @subsubsection Running Tasks
19624 @cindex running VxWorks tasks
19625 You can also attach to an existing task using the @code{attach} command as
19629 (vxgdb) attach @var{task}
19633 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
19634 or suspended when you attach to it. Running tasks are suspended at
19635 the time of attachment.
19637 @node Embedded Processors
19638 @section Embedded Processors
19640 This section goes into details specific to particular embedded
19643 @cindex send command to simulator
19644 Whenever a specific embedded processor has a simulator, @value{GDBN}
19645 allows to send an arbitrary command to the simulator.
19648 @item sim @var{command}
19649 @kindex sim@r{, a command}
19650 Send an arbitrary @var{command} string to the simulator. Consult the
19651 documentation for the specific simulator in use for information about
19652 acceptable commands.
19658 * M32R/D:: Renesas M32R/D
19659 * M68K:: Motorola M68K
19660 * MicroBlaze:: Xilinx MicroBlaze
19661 * MIPS Embedded:: MIPS Embedded
19662 * OpenRISC 1000:: OpenRisc 1000
19663 * PowerPC Embedded:: PowerPC Embedded
19664 * PA:: HP PA Embedded
19665 * Sparclet:: Tsqware Sparclet
19666 * Sparclite:: Fujitsu Sparclite
19667 * Z8000:: Zilog Z8000
19670 * Super-H:: Renesas Super-H
19679 @item target rdi @var{dev}
19680 ARM Angel monitor, via RDI library interface to ADP protocol. You may
19681 use this target to communicate with both boards running the Angel
19682 monitor, or with the EmbeddedICE JTAG debug device.
19685 @item target rdp @var{dev}
19690 @value{GDBN} provides the following ARM-specific commands:
19693 @item set arm disassembler
19695 This commands selects from a list of disassembly styles. The
19696 @code{"std"} style is the standard style.
19698 @item show arm disassembler
19700 Show the current disassembly style.
19702 @item set arm apcs32
19703 @cindex ARM 32-bit mode
19704 This command toggles ARM operation mode between 32-bit and 26-bit.
19706 @item show arm apcs32
19707 Display the current usage of the ARM 32-bit mode.
19709 @item set arm fpu @var{fputype}
19710 This command sets the ARM floating-point unit (FPU) type. The
19711 argument @var{fputype} can be one of these:
19715 Determine the FPU type by querying the OS ABI.
19717 Software FPU, with mixed-endian doubles on little-endian ARM
19720 GCC-compiled FPA co-processor.
19722 Software FPU with pure-endian doubles.
19728 Show the current type of the FPU.
19731 This command forces @value{GDBN} to use the specified ABI.
19734 Show the currently used ABI.
19736 @item set arm fallback-mode (arm|thumb|auto)
19737 @value{GDBN} uses the symbol table, when available, to determine
19738 whether instructions are ARM or Thumb. This command controls
19739 @value{GDBN}'s default behavior when the symbol table is not
19740 available. The default is @samp{auto}, which causes @value{GDBN} to
19741 use the current execution mode (from the @code{T} bit in the @code{CPSR}
19744 @item show arm fallback-mode
19745 Show the current fallback instruction mode.
19747 @item set arm force-mode (arm|thumb|auto)
19748 This command overrides use of the symbol table to determine whether
19749 instructions are ARM or Thumb. The default is @samp{auto}, which
19750 causes @value{GDBN} to use the symbol table and then the setting
19751 of @samp{set arm fallback-mode}.
19753 @item show arm force-mode
19754 Show the current forced instruction mode.
19756 @item set debug arm
19757 Toggle whether to display ARM-specific debugging messages from the ARM
19758 target support subsystem.
19760 @item show debug arm
19761 Show whether ARM-specific debugging messages are enabled.
19764 The following commands are available when an ARM target is debugged
19765 using the RDI interface:
19768 @item rdilogfile @r{[}@var{file}@r{]}
19770 @cindex ADP (Angel Debugger Protocol) logging
19771 Set the filename for the ADP (Angel Debugger Protocol) packet log.
19772 With an argument, sets the log file to the specified @var{file}. With
19773 no argument, show the current log file name. The default log file is
19776 @item rdilogenable @r{[}@var{arg}@r{]}
19777 @kindex rdilogenable
19778 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
19779 enables logging, with an argument 0 or @code{"no"} disables it. With
19780 no arguments displays the current setting. When logging is enabled,
19781 ADP packets exchanged between @value{GDBN} and the RDI target device
19782 are logged to a file.
19784 @item set rdiromatzero
19785 @kindex set rdiromatzero
19786 @cindex ROM at zero address, RDI
19787 Tell @value{GDBN} whether the target has ROM at address 0. If on,
19788 vector catching is disabled, so that zero address can be used. If off
19789 (the default), vector catching is enabled. For this command to take
19790 effect, it needs to be invoked prior to the @code{target rdi} command.
19792 @item show rdiromatzero
19793 @kindex show rdiromatzero
19794 Show the current setting of ROM at zero address.
19796 @item set rdiheartbeat
19797 @kindex set rdiheartbeat
19798 @cindex RDI heartbeat
19799 Enable or disable RDI heartbeat packets. It is not recommended to
19800 turn on this option, since it confuses ARM and EPI JTAG interface, as
19801 well as the Angel monitor.
19803 @item show rdiheartbeat
19804 @kindex show rdiheartbeat
19805 Show the setting of RDI heartbeat packets.
19809 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19810 The @value{GDBN} ARM simulator accepts the following optional arguments.
19813 @item --swi-support=@var{type}
19814 Tell the simulator which SWI interfaces to support.
19815 @var{type} may be a comma separated list of the following values.
19816 The default value is @code{all}.
19829 @subsection Renesas M32R/D and M32R/SDI
19832 @kindex target m32r
19833 @item target m32r @var{dev}
19834 Renesas M32R/D ROM monitor.
19836 @kindex target m32rsdi
19837 @item target m32rsdi @var{dev}
19838 Renesas M32R SDI server, connected via parallel port to the board.
19841 The following @value{GDBN} commands are specific to the M32R monitor:
19844 @item set download-path @var{path}
19845 @kindex set download-path
19846 @cindex find downloadable @sc{srec} files (M32R)
19847 Set the default path for finding downloadable @sc{srec} files.
19849 @item show download-path
19850 @kindex show download-path
19851 Show the default path for downloadable @sc{srec} files.
19853 @item set board-address @var{addr}
19854 @kindex set board-address
19855 @cindex M32-EVA target board address
19856 Set the IP address for the M32R-EVA target board.
19858 @item show board-address
19859 @kindex show board-address
19860 Show the current IP address of the target board.
19862 @item set server-address @var{addr}
19863 @kindex set server-address
19864 @cindex download server address (M32R)
19865 Set the IP address for the download server, which is the @value{GDBN}'s
19868 @item show server-address
19869 @kindex show server-address
19870 Display the IP address of the download server.
19872 @item upload @r{[}@var{file}@r{]}
19873 @kindex upload@r{, M32R}
19874 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
19875 upload capability. If no @var{file} argument is given, the current
19876 executable file is uploaded.
19878 @item tload @r{[}@var{file}@r{]}
19879 @kindex tload@r{, M32R}
19880 Test the @code{upload} command.
19883 The following commands are available for M32R/SDI:
19888 @cindex reset SDI connection, M32R
19889 This command resets the SDI connection.
19893 This command shows the SDI connection status.
19896 @kindex debug_chaos
19897 @cindex M32R/Chaos debugging
19898 Instructs the remote that M32R/Chaos debugging is to be used.
19900 @item use_debug_dma
19901 @kindex use_debug_dma
19902 Instructs the remote to use the DEBUG_DMA method of accessing memory.
19905 @kindex use_mon_code
19906 Instructs the remote to use the MON_CODE method of accessing memory.
19909 @kindex use_ib_break
19910 Instructs the remote to set breakpoints by IB break.
19912 @item use_dbt_break
19913 @kindex use_dbt_break
19914 Instructs the remote to set breakpoints by DBT.
19920 The Motorola m68k configuration includes ColdFire support, and a
19921 target command for the following ROM monitor.
19925 @kindex target dbug
19926 @item target dbug @var{dev}
19927 dBUG ROM monitor for Motorola ColdFire.
19932 @subsection MicroBlaze
19933 @cindex Xilinx MicroBlaze
19934 @cindex XMD, Xilinx Microprocessor Debugger
19936 The MicroBlaze is a soft-core processor supported on various Xilinx
19937 FPGAs, such as Spartan or Virtex series. Boards with these processors
19938 usually have JTAG ports which connect to a host system running the Xilinx
19939 Embedded Development Kit (EDK) or Software Development Kit (SDK).
19940 This host system is used to download the configuration bitstream to
19941 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
19942 communicates with the target board using the JTAG interface and
19943 presents a @code{gdbserver} interface to the board. By default
19944 @code{xmd} uses port @code{1234}. (While it is possible to change
19945 this default port, it requires the use of undocumented @code{xmd}
19946 commands. Contact Xilinx support if you need to do this.)
19948 Use these GDB commands to connect to the MicroBlaze target processor.
19951 @item target remote :1234
19952 Use this command to connect to the target if you are running @value{GDBN}
19953 on the same system as @code{xmd}.
19955 @item target remote @var{xmd-host}:1234
19956 Use this command to connect to the target if it is connected to @code{xmd}
19957 running on a different system named @var{xmd-host}.
19960 Use this command to download a program to the MicroBlaze target.
19962 @item set debug microblaze @var{n}
19963 Enable MicroBlaze-specific debugging messages if non-zero.
19965 @item show debug microblaze @var{n}
19966 Show MicroBlaze-specific debugging level.
19969 @node MIPS Embedded
19970 @subsection @acronym{MIPS} Embedded
19972 @cindex @acronym{MIPS} boards
19973 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
19974 @acronym{MIPS} board attached to a serial line. This is available when
19975 you configure @value{GDBN} with @samp{--target=mips-elf}.
19978 Use these @value{GDBN} commands to specify the connection to your target board:
19981 @item target mips @var{port}
19982 @kindex target mips @var{port}
19983 To run a program on the board, start up @code{@value{GDBP}} with the
19984 name of your program as the argument. To connect to the board, use the
19985 command @samp{target mips @var{port}}, where @var{port} is the name of
19986 the serial port connected to the board. If the program has not already
19987 been downloaded to the board, you may use the @code{load} command to
19988 download it. You can then use all the usual @value{GDBN} commands.
19990 For example, this sequence connects to the target board through a serial
19991 port, and loads and runs a program called @var{prog} through the
19995 host$ @value{GDBP} @var{prog}
19996 @value{GDBN} is free software and @dots{}
19997 (@value{GDBP}) target mips /dev/ttyb
19998 (@value{GDBP}) load @var{prog}
20002 @item target mips @var{hostname}:@var{portnumber}
20003 On some @value{GDBN} host configurations, you can specify a TCP
20004 connection (for instance, to a serial line managed by a terminal
20005 concentrator) instead of a serial port, using the syntax
20006 @samp{@var{hostname}:@var{portnumber}}.
20008 @item target pmon @var{port}
20009 @kindex target pmon @var{port}
20012 @item target ddb @var{port}
20013 @kindex target ddb @var{port}
20014 NEC's DDB variant of PMON for Vr4300.
20016 @item target lsi @var{port}
20017 @kindex target lsi @var{port}
20018 LSI variant of PMON.
20020 @kindex target r3900
20021 @item target r3900 @var{dev}
20022 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20024 @kindex target array
20025 @item target array @var{dev}
20026 Array Tech LSI33K RAID controller board.
20032 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20035 @item set mipsfpu double
20036 @itemx set mipsfpu single
20037 @itemx set mipsfpu none
20038 @itemx set mipsfpu auto
20039 @itemx show mipsfpu
20040 @kindex set mipsfpu
20041 @kindex show mipsfpu
20042 @cindex @acronym{MIPS} remote floating point
20043 @cindex floating point, @acronym{MIPS} remote
20044 If your target board does not support the @acronym{MIPS} floating point
20045 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20046 need this, you may wish to put the command in your @value{GDBN} init
20047 file). This tells @value{GDBN} how to find the return value of
20048 functions which return floating point values. It also allows
20049 @value{GDBN} to avoid saving the floating point registers when calling
20050 functions on the board. If you are using a floating point coprocessor
20051 with only single precision floating point support, as on the @sc{r4650}
20052 processor, use the command @samp{set mipsfpu single}. The default
20053 double precision floating point coprocessor may be selected using
20054 @samp{set mipsfpu double}.
20056 In previous versions the only choices were double precision or no
20057 floating point, so @samp{set mipsfpu on} will select double precision
20058 and @samp{set mipsfpu off} will select no floating point.
20060 As usual, you can inquire about the @code{mipsfpu} variable with
20061 @samp{show mipsfpu}.
20063 @item set timeout @var{seconds}
20064 @itemx set retransmit-timeout @var{seconds}
20065 @itemx show timeout
20066 @itemx show retransmit-timeout
20067 @cindex @code{timeout}, @acronym{MIPS} protocol
20068 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20069 @kindex set timeout
20070 @kindex show timeout
20071 @kindex set retransmit-timeout
20072 @kindex show retransmit-timeout
20073 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20074 remote protocol, with the @code{set timeout @var{seconds}} command. The
20075 default is 5 seconds. Similarly, you can control the timeout used while
20076 waiting for an acknowledgment of a packet with the @code{set
20077 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20078 You can inspect both values with @code{show timeout} and @code{show
20079 retransmit-timeout}. (These commands are @emph{only} available when
20080 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20082 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20083 is waiting for your program to stop. In that case, @value{GDBN} waits
20084 forever because it has no way of knowing how long the program is going
20085 to run before stopping.
20087 @item set syn-garbage-limit @var{num}
20088 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20089 @cindex synchronize with remote @acronym{MIPS} target
20090 Limit the maximum number of characters @value{GDBN} should ignore when
20091 it tries to synchronize with the remote target. The default is 10
20092 characters. Setting the limit to -1 means there's no limit.
20094 @item show syn-garbage-limit
20095 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20096 Show the current limit on the number of characters to ignore when
20097 trying to synchronize with the remote system.
20099 @item set monitor-prompt @var{prompt}
20100 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20101 @cindex remote monitor prompt
20102 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20103 remote monitor. The default depends on the target:
20113 @item show monitor-prompt
20114 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20115 Show the current strings @value{GDBN} expects as the prompt from the
20118 @item set monitor-warnings
20119 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20120 Enable or disable monitor warnings about hardware breakpoints. This
20121 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20122 display warning messages whose codes are returned by the @code{lsi}
20123 PMON monitor for breakpoint commands.
20125 @item show monitor-warnings
20126 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20127 Show the current setting of printing monitor warnings.
20129 @item pmon @var{command}
20130 @kindex pmon@r{, @acronym{MIPS} remote}
20131 @cindex send PMON command
20132 This command allows sending an arbitrary @var{command} string to the
20133 monitor. The monitor must be in debug mode for this to work.
20136 @node OpenRISC 1000
20137 @subsection OpenRISC 1000
20138 @cindex OpenRISC 1000
20140 @cindex or1k boards
20141 See OR1k Architecture document (@uref{www.opencores.org}) for more information
20142 about platform and commands.
20146 @kindex target jtag
20147 @item target jtag jtag://@var{host}:@var{port}
20149 Connects to remote JTAG server.
20150 JTAG remote server can be either an or1ksim or JTAG server,
20151 connected via parallel port to the board.
20153 Example: @code{target jtag jtag://localhost:9999}
20156 @item or1ksim @var{command}
20157 If connected to @code{or1ksim} OpenRISC 1000 Architectural
20158 Simulator, proprietary commands can be executed.
20160 @kindex info or1k spr
20161 @item info or1k spr
20162 Displays spr groups.
20164 @item info or1k spr @var{group}
20165 @itemx info or1k spr @var{groupno}
20166 Displays register names in selected group.
20168 @item info or1k spr @var{group} @var{register}
20169 @itemx info or1k spr @var{register}
20170 @itemx info or1k spr @var{groupno} @var{registerno}
20171 @itemx info or1k spr @var{registerno}
20172 Shows information about specified spr register.
20175 @item spr @var{group} @var{register} @var{value}
20176 @itemx spr @var{register @var{value}}
20177 @itemx spr @var{groupno} @var{registerno @var{value}}
20178 @itemx spr @var{registerno @var{value}}
20179 Writes @var{value} to specified spr register.
20182 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
20183 It is very similar to @value{GDBN} trace, except it does not interfere with normal
20184 program execution and is thus much faster. Hardware breakpoints/watchpoint
20185 triggers can be set using:
20188 Load effective address/data
20190 Store effective address/data
20192 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
20197 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
20198 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
20200 @code{htrace} commands:
20201 @cindex OpenRISC 1000 htrace
20204 @item hwatch @var{conditional}
20205 Set hardware watchpoint on combination of Load/Store Effective Address(es)
20206 or Data. For example:
20208 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
20210 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
20214 Display information about current HW trace configuration.
20216 @item htrace trigger @var{conditional}
20217 Set starting criteria for HW trace.
20219 @item htrace qualifier @var{conditional}
20220 Set acquisition qualifier for HW trace.
20222 @item htrace stop @var{conditional}
20223 Set HW trace stopping criteria.
20225 @item htrace record [@var{data}]*
20226 Selects the data to be recorded, when qualifier is met and HW trace was
20229 @item htrace enable
20230 @itemx htrace disable
20231 Enables/disables the HW trace.
20233 @item htrace rewind [@var{filename}]
20234 Clears currently recorded trace data.
20236 If filename is specified, new trace file is made and any newly collected data
20237 will be written there.
20239 @item htrace print [@var{start} [@var{len}]]
20240 Prints trace buffer, using current record configuration.
20242 @item htrace mode continuous
20243 Set continuous trace mode.
20245 @item htrace mode suspend
20246 Set suspend trace mode.
20250 @node PowerPC Embedded
20251 @subsection PowerPC Embedded
20253 @cindex DVC register
20254 @value{GDBN} supports using the DVC (Data Value Compare) register to
20255 implement in hardware simple hardware watchpoint conditions of the form:
20258 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20259 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20262 The DVC register will be automatically used when @value{GDBN} detects
20263 such pattern in a condition expression, and the created watchpoint uses one
20264 debug register (either the @code{exact-watchpoints} option is on and the
20265 variable is scalar, or the variable has a length of one byte). This feature
20266 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20269 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20270 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20271 in which case watchpoints using only one debug register are created when
20272 watching variables of scalar types.
20274 You can create an artificial array to watch an arbitrary memory
20275 region using one of the following commands (@pxref{Expressions}):
20278 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20279 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20282 PowerPC embedded processors support masked watchpoints. See the discussion
20283 about the @code{mask} argument in @ref{Set Watchpoints}.
20285 @cindex ranged breakpoint
20286 PowerPC embedded processors support hardware accelerated
20287 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20288 the inferior whenever it executes an instruction at any address within
20289 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20290 use the @code{break-range} command.
20292 @value{GDBN} provides the following PowerPC-specific commands:
20295 @kindex break-range
20296 @item break-range @var{start-location}, @var{end-location}
20297 Set a breakpoint for an address range.
20298 @var{start-location} and @var{end-location} can specify a function name,
20299 a line number, an offset of lines from the current line or from the start
20300 location, or an address of an instruction (see @ref{Specify Location},
20301 for a list of all the possible ways to specify a @var{location}.)
20302 The breakpoint will stop execution of the inferior whenever it
20303 executes an instruction at any address within the specified range,
20304 (including @var{start-location} and @var{end-location}.)
20306 @kindex set powerpc
20307 @item set powerpc soft-float
20308 @itemx show powerpc soft-float
20309 Force @value{GDBN} to use (or not use) a software floating point calling
20310 convention. By default, @value{GDBN} selects the calling convention based
20311 on the selected architecture and the provided executable file.
20313 @item set powerpc vector-abi
20314 @itemx show powerpc vector-abi
20315 Force @value{GDBN} to use the specified calling convention for vector
20316 arguments and return values. The valid options are @samp{auto};
20317 @samp{generic}, to avoid vector registers even if they are present;
20318 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20319 registers. By default, @value{GDBN} selects the calling convention
20320 based on the selected architecture and the provided executable file.
20322 @item set powerpc exact-watchpoints
20323 @itemx show powerpc exact-watchpoints
20324 Allow @value{GDBN} to use only one debug register when watching a variable
20325 of scalar type, thus assuming that the variable is accessed through the
20326 address of its first byte.
20328 @kindex target dink32
20329 @item target dink32 @var{dev}
20330 DINK32 ROM monitor.
20332 @kindex target ppcbug
20333 @item target ppcbug @var{dev}
20334 @kindex target ppcbug1
20335 @item target ppcbug1 @var{dev}
20336 PPCBUG ROM monitor for PowerPC.
20339 @item target sds @var{dev}
20340 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20343 @cindex SDS protocol
20344 The following commands specific to the SDS protocol are supported
20348 @item set sdstimeout @var{nsec}
20349 @kindex set sdstimeout
20350 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
20351 default is 2 seconds.
20353 @item show sdstimeout
20354 @kindex show sdstimeout
20355 Show the current value of the SDS timeout.
20357 @item sds @var{command}
20358 @kindex sds@r{, a command}
20359 Send the specified @var{command} string to the SDS monitor.
20364 @subsection HP PA Embedded
20368 @kindex target op50n
20369 @item target op50n @var{dev}
20370 OP50N monitor, running on an OKI HPPA board.
20372 @kindex target w89k
20373 @item target w89k @var{dev}
20374 W89K monitor, running on a Winbond HPPA board.
20379 @subsection Tsqware Sparclet
20383 @value{GDBN} enables developers to debug tasks running on
20384 Sparclet targets from a Unix host.
20385 @value{GDBN} uses code that runs on
20386 both the Unix host and on the Sparclet target. The program
20387 @code{@value{GDBP}} is installed and executed on the Unix host.
20390 @item remotetimeout @var{args}
20391 @kindex remotetimeout
20392 @value{GDBN} supports the option @code{remotetimeout}.
20393 This option is set by the user, and @var{args} represents the number of
20394 seconds @value{GDBN} waits for responses.
20397 @cindex compiling, on Sparclet
20398 When compiling for debugging, include the options @samp{-g} to get debug
20399 information and @samp{-Ttext} to relocate the program to where you wish to
20400 load it on the target. You may also want to add the options @samp{-n} or
20401 @samp{-N} in order to reduce the size of the sections. Example:
20404 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
20407 You can use @code{objdump} to verify that the addresses are what you intended:
20410 sparclet-aout-objdump --headers --syms prog
20413 @cindex running, on Sparclet
20415 your Unix execution search path to find @value{GDBN}, you are ready to
20416 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
20417 (or @code{sparclet-aout-gdb}, depending on your installation).
20419 @value{GDBN} comes up showing the prompt:
20426 * Sparclet File:: Setting the file to debug
20427 * Sparclet Connection:: Connecting to Sparclet
20428 * Sparclet Download:: Sparclet download
20429 * Sparclet Execution:: Running and debugging
20432 @node Sparclet File
20433 @subsubsection Setting File to Debug
20435 The @value{GDBN} command @code{file} lets you choose with program to debug.
20438 (gdbslet) file prog
20442 @value{GDBN} then attempts to read the symbol table of @file{prog}.
20443 @value{GDBN} locates
20444 the file by searching the directories listed in the command search
20446 If the file was compiled with debug information (option @samp{-g}), source
20447 files will be searched as well.
20448 @value{GDBN} locates
20449 the source files by searching the directories listed in the directory search
20450 path (@pxref{Environment, ,Your Program's Environment}).
20452 to find a file, it displays a message such as:
20455 prog: No such file or directory.
20458 When this happens, add the appropriate directories to the search paths with
20459 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
20460 @code{target} command again.
20462 @node Sparclet Connection
20463 @subsubsection Connecting to Sparclet
20465 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
20466 To connect to a target on serial port ``@code{ttya}'', type:
20469 (gdbslet) target sparclet /dev/ttya
20470 Remote target sparclet connected to /dev/ttya
20471 main () at ../prog.c:3
20475 @value{GDBN} displays messages like these:
20481 @node Sparclet Download
20482 @subsubsection Sparclet Download
20484 @cindex download to Sparclet
20485 Once connected to the Sparclet target,
20486 you can use the @value{GDBN}
20487 @code{load} command to download the file from the host to the target.
20488 The file name and load offset should be given as arguments to the @code{load}
20490 Since the file format is aout, the program must be loaded to the starting
20491 address. You can use @code{objdump} to find out what this value is. The load
20492 offset is an offset which is added to the VMA (virtual memory address)
20493 of each of the file's sections.
20494 For instance, if the program
20495 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
20496 and bss at 0x12010170, in @value{GDBN}, type:
20499 (gdbslet) load prog 0x12010000
20500 Loading section .text, size 0xdb0 vma 0x12010000
20503 If the code is loaded at a different address then what the program was linked
20504 to, you may need to use the @code{section} and @code{add-symbol-file} commands
20505 to tell @value{GDBN} where to map the symbol table.
20507 @node Sparclet Execution
20508 @subsubsection Running and Debugging
20510 @cindex running and debugging Sparclet programs
20511 You can now begin debugging the task using @value{GDBN}'s execution control
20512 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
20513 manual for the list of commands.
20517 Breakpoint 1 at 0x12010000: file prog.c, line 3.
20519 Starting program: prog
20520 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
20521 3 char *symarg = 0;
20523 4 char *execarg = "hello!";
20528 @subsection Fujitsu Sparclite
20532 @kindex target sparclite
20533 @item target sparclite @var{dev}
20534 Fujitsu sparclite boards, used only for the purpose of loading.
20535 You must use an additional command to debug the program.
20536 For example: target remote @var{dev} using @value{GDBN} standard
20542 @subsection Zilog Z8000
20545 @cindex simulator, Z8000
20546 @cindex Zilog Z8000 simulator
20548 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
20551 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
20552 unsegmented variant of the Z8000 architecture) or the Z8001 (the
20553 segmented variant). The simulator recognizes which architecture is
20554 appropriate by inspecting the object code.
20557 @item target sim @var{args}
20559 @kindex target sim@r{, with Z8000}
20560 Debug programs on a simulated CPU. If the simulator supports setup
20561 options, specify them via @var{args}.
20565 After specifying this target, you can debug programs for the simulated
20566 CPU in the same style as programs for your host computer; use the
20567 @code{file} command to load a new program image, the @code{run} command
20568 to run your program, and so on.
20570 As well as making available all the usual machine registers
20571 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
20572 additional items of information as specially named registers:
20577 Counts clock-ticks in the simulator.
20580 Counts instructions run in the simulator.
20583 Execution time in 60ths of a second.
20587 You can refer to these values in @value{GDBN} expressions with the usual
20588 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
20589 conditional breakpoint that suspends only after at least 5000
20590 simulated clock ticks.
20593 @subsection Atmel AVR
20596 When configured for debugging the Atmel AVR, @value{GDBN} supports the
20597 following AVR-specific commands:
20600 @item info io_registers
20601 @kindex info io_registers@r{, AVR}
20602 @cindex I/O registers (Atmel AVR)
20603 This command displays information about the AVR I/O registers. For
20604 each register, @value{GDBN} prints its number and value.
20611 When configured for debugging CRIS, @value{GDBN} provides the
20612 following CRIS-specific commands:
20615 @item set cris-version @var{ver}
20616 @cindex CRIS version
20617 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
20618 The CRIS version affects register names and sizes. This command is useful in
20619 case autodetection of the CRIS version fails.
20621 @item show cris-version
20622 Show the current CRIS version.
20624 @item set cris-dwarf2-cfi
20625 @cindex DWARF-2 CFI and CRIS
20626 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
20627 Change to @samp{off} when using @code{gcc-cris} whose version is below
20630 @item show cris-dwarf2-cfi
20631 Show the current state of using DWARF-2 CFI.
20633 @item set cris-mode @var{mode}
20635 Set the current CRIS mode to @var{mode}. It should only be changed when
20636 debugging in guru mode, in which case it should be set to
20637 @samp{guru} (the default is @samp{normal}).
20639 @item show cris-mode
20640 Show the current CRIS mode.
20644 @subsection Renesas Super-H
20647 For the Renesas Super-H processor, @value{GDBN} provides these
20651 @item set sh calling-convention @var{convention}
20652 @kindex set sh calling-convention
20653 Set the calling-convention used when calling functions from @value{GDBN}.
20654 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
20655 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
20656 convention. If the DWARF-2 information of the called function specifies
20657 that the function follows the Renesas calling convention, the function
20658 is called using the Renesas calling convention. If the calling convention
20659 is set to @samp{renesas}, the Renesas calling convention is always used,
20660 regardless of the DWARF-2 information. This can be used to override the
20661 default of @samp{gcc} if debug information is missing, or the compiler
20662 does not emit the DWARF-2 calling convention entry for a function.
20664 @item show sh calling-convention
20665 @kindex show sh calling-convention
20666 Show the current calling convention setting.
20671 @node Architectures
20672 @section Architectures
20674 This section describes characteristics of architectures that affect
20675 all uses of @value{GDBN} with the architecture, both native and cross.
20681 * HPPA:: HP PA architecture
20682 * SPU:: Cell Broadband Engine SPU architecture
20687 @subsection x86 Architecture-specific Issues
20690 @item set struct-convention @var{mode}
20691 @kindex set struct-convention
20692 @cindex struct return convention
20693 @cindex struct/union returned in registers
20694 Set the convention used by the inferior to return @code{struct}s and
20695 @code{union}s from functions to @var{mode}. Possible values of
20696 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
20697 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
20698 are returned on the stack, while @code{"reg"} means that a
20699 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
20700 be returned in a register.
20702 @item show struct-convention
20703 @kindex show struct-convention
20704 Show the current setting of the convention to return @code{struct}s
20711 See the following section.
20714 @subsection @acronym{MIPS}
20716 @cindex stack on Alpha
20717 @cindex stack on @acronym{MIPS}
20718 @cindex Alpha stack
20719 @cindex @acronym{MIPS} stack
20720 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
20721 sometimes requires @value{GDBN} to search backward in the object code to
20722 find the beginning of a function.
20724 @cindex response time, @acronym{MIPS} debugging
20725 To improve response time (especially for embedded applications, where
20726 @value{GDBN} may be restricted to a slow serial line for this search)
20727 you may want to limit the size of this search, using one of these
20731 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
20732 @item set heuristic-fence-post @var{limit}
20733 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
20734 search for the beginning of a function. A value of @var{0} (the
20735 default) means there is no limit. However, except for @var{0}, the
20736 larger the limit the more bytes @code{heuristic-fence-post} must search
20737 and therefore the longer it takes to run. You should only need to use
20738 this command when debugging a stripped executable.
20740 @item show heuristic-fence-post
20741 Display the current limit.
20745 These commands are available @emph{only} when @value{GDBN} is configured
20746 for debugging programs on Alpha or @acronym{MIPS} processors.
20748 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
20752 @item set mips abi @var{arg}
20753 @kindex set mips abi
20754 @cindex set ABI for @acronym{MIPS}
20755 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
20756 values of @var{arg} are:
20760 The default ABI associated with the current binary (this is the
20770 @item show mips abi
20771 @kindex show mips abi
20772 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
20774 @item set mips compression @var{arg}
20775 @kindex set mips compression
20776 @cindex code compression, @acronym{MIPS}
20777 Tell @value{GDBN} which @acronym{MIPS} compressed
20778 @acronym{ISA, Instruction Set Architecture} encoding is used by the
20779 inferior. @value{GDBN} uses this for code disassembly and other
20780 internal interpretation purposes. This setting is only referred to
20781 when no executable has been associated with the debugging session or
20782 the executable does not provide information about the encoding it uses.
20783 Otherwise this setting is automatically updated from information
20784 provided by the executable.
20786 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
20787 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
20788 executables containing @acronym{MIPS16} code frequently are not
20789 identified as such.
20791 This setting is ``sticky''; that is, it retains its value across
20792 debugging sessions until reset either explicitly with this command or
20793 implicitly from an executable.
20795 The compiler and/or assembler typically add symbol table annotations to
20796 identify functions compiled for the @acronym{MIPS16} or
20797 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
20798 are present, @value{GDBN} uses them in preference to the global
20799 compressed @acronym{ISA} encoding setting.
20801 @item show mips compression
20802 @kindex show mips compression
20803 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
20804 @value{GDBN} to debug the inferior.
20807 @itemx show mipsfpu
20808 @xref{MIPS Embedded, set mipsfpu}.
20810 @item set mips mask-address @var{arg}
20811 @kindex set mips mask-address
20812 @cindex @acronym{MIPS} addresses, masking
20813 This command determines whether the most-significant 32 bits of 64-bit
20814 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
20815 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20816 setting, which lets @value{GDBN} determine the correct value.
20818 @item show mips mask-address
20819 @kindex show mips mask-address
20820 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
20823 @item set remote-mips64-transfers-32bit-regs
20824 @kindex set remote-mips64-transfers-32bit-regs
20825 This command controls compatibility with 64-bit @acronym{MIPS} targets that
20826 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
20827 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20828 and 64 bits for other registers, set this option to @samp{on}.
20830 @item show remote-mips64-transfers-32bit-regs
20831 @kindex show remote-mips64-transfers-32bit-regs
20832 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
20834 @item set debug mips
20835 @kindex set debug mips
20836 This command turns on and off debugging messages for the @acronym{MIPS}-specific
20837 target code in @value{GDBN}.
20839 @item show debug mips
20840 @kindex show debug mips
20841 Show the current setting of @acronym{MIPS} debugging messages.
20847 @cindex HPPA support
20849 When @value{GDBN} is debugging the HP PA architecture, it provides the
20850 following special commands:
20853 @item set debug hppa
20854 @kindex set debug hppa
20855 This command determines whether HPPA architecture-specific debugging
20856 messages are to be displayed.
20858 @item show debug hppa
20859 Show whether HPPA debugging messages are displayed.
20861 @item maint print unwind @var{address}
20862 @kindex maint print unwind@r{, HPPA}
20863 This command displays the contents of the unwind table entry at the
20864 given @var{address}.
20870 @subsection Cell Broadband Engine SPU architecture
20871 @cindex Cell Broadband Engine
20874 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
20875 it provides the following special commands:
20878 @item info spu event
20880 Display SPU event facility status. Shows current event mask
20881 and pending event status.
20883 @item info spu signal
20884 Display SPU signal notification facility status. Shows pending
20885 signal-control word and signal notification mode of both signal
20886 notification channels.
20888 @item info spu mailbox
20889 Display SPU mailbox facility status. Shows all pending entries,
20890 in order of processing, in each of the SPU Write Outbound,
20891 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
20894 Display MFC DMA status. Shows all pending commands in the MFC
20895 DMA queue. For each entry, opcode, tag, class IDs, effective
20896 and local store addresses and transfer size are shown.
20898 @item info spu proxydma
20899 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
20900 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
20901 and local store addresses and transfer size are shown.
20905 When @value{GDBN} is debugging a combined PowerPC/SPU application
20906 on the Cell Broadband Engine, it provides in addition the following
20910 @item set spu stop-on-load @var{arg}
20912 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
20913 will give control to the user when a new SPE thread enters its @code{main}
20914 function. The default is @code{off}.
20916 @item show spu stop-on-load
20918 Show whether to stop for new SPE threads.
20920 @item set spu auto-flush-cache @var{arg}
20921 Set whether to automatically flush the software-managed cache. When set to
20922 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
20923 cache to be flushed whenever SPE execution stops. This provides a consistent
20924 view of PowerPC memory that is accessed via the cache. If an application
20925 does not use the software-managed cache, this option has no effect.
20927 @item show spu auto-flush-cache
20928 Show whether to automatically flush the software-managed cache.
20933 @subsection PowerPC
20934 @cindex PowerPC architecture
20936 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
20937 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
20938 numbers stored in the floating point registers. These values must be stored
20939 in two consecutive registers, always starting at an even register like
20940 @code{f0} or @code{f2}.
20942 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
20943 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
20944 @code{f2} and @code{f3} for @code{$dl1} and so on.
20946 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
20947 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
20950 @node Controlling GDB
20951 @chapter Controlling @value{GDBN}
20953 You can alter the way @value{GDBN} interacts with you by using the
20954 @code{set} command. For commands controlling how @value{GDBN} displays
20955 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20960 * Editing:: Command editing
20961 * Command History:: Command history
20962 * Screen Size:: Screen size
20963 * Numbers:: Numbers
20964 * ABI:: Configuring the current ABI
20965 * Auto-loading:: Automatically loading associated files
20966 * Messages/Warnings:: Optional warnings and messages
20967 * Debugging Output:: Optional messages about internal happenings
20968 * Other Misc Settings:: Other Miscellaneous Settings
20976 @value{GDBN} indicates its readiness to read a command by printing a string
20977 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20978 can change the prompt string with the @code{set prompt} command. For
20979 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20980 the prompt in one of the @value{GDBN} sessions so that you can always tell
20981 which one you are talking to.
20983 @emph{Note:} @code{set prompt} does not add a space for you after the
20984 prompt you set. This allows you to set a prompt which ends in a space
20985 or a prompt that does not.
20989 @item set prompt @var{newprompt}
20990 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20992 @kindex show prompt
20994 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20997 Versions of @value{GDBN} that ship with Python scripting enabled have
20998 prompt extensions. The commands for interacting with these extensions
21002 @kindex set extended-prompt
21003 @item set extended-prompt @var{prompt}
21004 Set an extended prompt that allows for substitutions.
21005 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21006 substitution. Any escape sequences specified as part of the prompt
21007 string are replaced with the corresponding strings each time the prompt
21013 set extended-prompt Current working directory: \w (gdb)
21016 Note that when an extended-prompt is set, it takes control of the
21017 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21019 @kindex show extended-prompt
21020 @item show extended-prompt
21021 Prints the extended prompt. Any escape sequences specified as part of
21022 the prompt string with @code{set extended-prompt}, are replaced with the
21023 corresponding strings each time the prompt is displayed.
21027 @section Command Editing
21029 @cindex command line editing
21031 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21032 @sc{gnu} library provides consistent behavior for programs which provide a
21033 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21034 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21035 substitution, and a storage and recall of command history across
21036 debugging sessions.
21038 You may control the behavior of command line editing in @value{GDBN} with the
21039 command @code{set}.
21042 @kindex set editing
21045 @itemx set editing on
21046 Enable command line editing (enabled by default).
21048 @item set editing off
21049 Disable command line editing.
21051 @kindex show editing
21053 Show whether command line editing is enabled.
21056 @ifset SYSTEM_READLINE
21057 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21059 @ifclear SYSTEM_READLINE
21060 @xref{Command Line Editing},
21062 for more details about the Readline
21063 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21064 encouraged to read that chapter.
21066 @node Command History
21067 @section Command History
21068 @cindex command history
21070 @value{GDBN} can keep track of the commands you type during your
21071 debugging sessions, so that you can be certain of precisely what
21072 happened. Use these commands to manage the @value{GDBN} command
21075 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21076 package, to provide the history facility.
21077 @ifset SYSTEM_READLINE
21078 @xref{Using History Interactively, , , history, GNU History Library},
21080 @ifclear SYSTEM_READLINE
21081 @xref{Using History Interactively},
21083 for the detailed description of the History library.
21085 To issue a command to @value{GDBN} without affecting certain aspects of
21086 the state which is seen by users, prefix it with @samp{server }
21087 (@pxref{Server Prefix}). This
21088 means that this command will not affect the command history, nor will it
21089 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21090 pressed on a line by itself.
21092 @cindex @code{server}, command prefix
21093 The server prefix does not affect the recording of values into the value
21094 history; to print a value without recording it into the value history,
21095 use the @code{output} command instead of the @code{print} command.
21097 Here is the description of @value{GDBN} commands related to command
21101 @cindex history substitution
21102 @cindex history file
21103 @kindex set history filename
21104 @cindex @env{GDBHISTFILE}, environment variable
21105 @item set history filename @var{fname}
21106 Set the name of the @value{GDBN} command history file to @var{fname}.
21107 This is the file where @value{GDBN} reads an initial command history
21108 list, and where it writes the command history from this session when it
21109 exits. You can access this list through history expansion or through
21110 the history command editing characters listed below. This file defaults
21111 to the value of the environment variable @code{GDBHISTFILE}, or to
21112 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21115 @cindex save command history
21116 @kindex set history save
21117 @item set history save
21118 @itemx set history save on
21119 Record command history in a file, whose name may be specified with the
21120 @code{set history filename} command. By default, this option is disabled.
21122 @item set history save off
21123 Stop recording command history in a file.
21125 @cindex history size
21126 @kindex set history size
21127 @cindex @env{HISTSIZE}, environment variable
21128 @item set history size @var{size}
21129 Set the number of commands which @value{GDBN} keeps in its history list.
21130 This defaults to the value of the environment variable
21131 @code{HISTSIZE}, or to 256 if this variable is not set.
21134 History expansion assigns special meaning to the character @kbd{!}.
21135 @ifset SYSTEM_READLINE
21136 @xref{Event Designators, , , history, GNU History Library},
21138 @ifclear SYSTEM_READLINE
21139 @xref{Event Designators},
21143 @cindex history expansion, turn on/off
21144 Since @kbd{!} is also the logical not operator in C, history expansion
21145 is off by default. If you decide to enable history expansion with the
21146 @code{set history expansion on} command, you may sometimes need to
21147 follow @kbd{!} (when it is used as logical not, in an expression) with
21148 a space or a tab to prevent it from being expanded. The readline
21149 history facilities do not attempt substitution on the strings
21150 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21152 The commands to control history expansion are:
21155 @item set history expansion on
21156 @itemx set history expansion
21157 @kindex set history expansion
21158 Enable history expansion. History expansion is off by default.
21160 @item set history expansion off
21161 Disable history expansion.
21164 @kindex show history
21166 @itemx show history filename
21167 @itemx show history save
21168 @itemx show history size
21169 @itemx show history expansion
21170 These commands display the state of the @value{GDBN} history parameters.
21171 @code{show history} by itself displays all four states.
21176 @kindex show commands
21177 @cindex show last commands
21178 @cindex display command history
21179 @item show commands
21180 Display the last ten commands in the command history.
21182 @item show commands @var{n}
21183 Print ten commands centered on command number @var{n}.
21185 @item show commands +
21186 Print ten commands just after the commands last printed.
21190 @section Screen Size
21191 @cindex size of screen
21192 @cindex pauses in output
21194 Certain commands to @value{GDBN} may produce large amounts of
21195 information output to the screen. To help you read all of it,
21196 @value{GDBN} pauses and asks you for input at the end of each page of
21197 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21198 to discard the remaining output. Also, the screen width setting
21199 determines when to wrap lines of output. Depending on what is being
21200 printed, @value{GDBN} tries to break the line at a readable place,
21201 rather than simply letting it overflow onto the following line.
21203 Normally @value{GDBN} knows the size of the screen from the terminal
21204 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21205 together with the value of the @code{TERM} environment variable and the
21206 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21207 you can override it with the @code{set height} and @code{set
21214 @kindex show height
21215 @item set height @var{lpp}
21217 @itemx set width @var{cpl}
21219 These @code{set} commands specify a screen height of @var{lpp} lines and
21220 a screen width of @var{cpl} characters. The associated @code{show}
21221 commands display the current settings.
21223 If you specify a height of zero lines, @value{GDBN} does not pause during
21224 output no matter how long the output is. This is useful if output is to a
21225 file or to an editor buffer.
21227 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
21228 from wrapping its output.
21230 @item set pagination on
21231 @itemx set pagination off
21232 @kindex set pagination
21233 Turn the output pagination on or off; the default is on. Turning
21234 pagination off is the alternative to @code{set height 0}. Note that
21235 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21236 Options, -batch}) also automatically disables pagination.
21238 @item show pagination
21239 @kindex show pagination
21240 Show the current pagination mode.
21245 @cindex number representation
21246 @cindex entering numbers
21248 You can always enter numbers in octal, decimal, or hexadecimal in
21249 @value{GDBN} by the usual conventions: octal numbers begin with
21250 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21251 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21252 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21253 10; likewise, the default display for numbers---when no particular
21254 format is specified---is base 10. You can change the default base for
21255 both input and output with the commands described below.
21258 @kindex set input-radix
21259 @item set input-radix @var{base}
21260 Set the default base for numeric input. Supported choices
21261 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21262 specified either unambiguously or using the current input radix; for
21266 set input-radix 012
21267 set input-radix 10.
21268 set input-radix 0xa
21272 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21273 leaves the input radix unchanged, no matter what it was, since
21274 @samp{10}, being without any leading or trailing signs of its base, is
21275 interpreted in the current radix. Thus, if the current radix is 16,
21276 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21279 @kindex set output-radix
21280 @item set output-radix @var{base}
21281 Set the default base for numeric display. Supported choices
21282 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21283 specified either unambiguously or using the current input radix.
21285 @kindex show input-radix
21286 @item show input-radix
21287 Display the current default base for numeric input.
21289 @kindex show output-radix
21290 @item show output-radix
21291 Display the current default base for numeric display.
21293 @item set radix @r{[}@var{base}@r{]}
21297 These commands set and show the default base for both input and output
21298 of numbers. @code{set radix} sets the radix of input and output to
21299 the same base; without an argument, it resets the radix back to its
21300 default value of 10.
21305 @section Configuring the Current ABI
21307 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
21308 application automatically. However, sometimes you need to override its
21309 conclusions. Use these commands to manage @value{GDBN}'s view of the
21316 One @value{GDBN} configuration can debug binaries for multiple operating
21317 system targets, either via remote debugging or native emulation.
21318 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
21319 but you can override its conclusion using the @code{set osabi} command.
21320 One example where this is useful is in debugging of binaries which use
21321 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
21322 not have the same identifying marks that the standard C library for your
21327 Show the OS ABI currently in use.
21330 With no argument, show the list of registered available OS ABI's.
21332 @item set osabi @var{abi}
21333 Set the current OS ABI to @var{abi}.
21336 @cindex float promotion
21338 Generally, the way that an argument of type @code{float} is passed to a
21339 function depends on whether the function is prototyped. For a prototyped
21340 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
21341 according to the architecture's convention for @code{float}. For unprototyped
21342 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
21343 @code{double} and then passed.
21345 Unfortunately, some forms of debug information do not reliably indicate whether
21346 a function is prototyped. If @value{GDBN} calls a function that is not marked
21347 as prototyped, it consults @kbd{set coerce-float-to-double}.
21350 @kindex set coerce-float-to-double
21351 @item set coerce-float-to-double
21352 @itemx set coerce-float-to-double on
21353 Arguments of type @code{float} will be promoted to @code{double} when passed
21354 to an unprototyped function. This is the default setting.
21356 @item set coerce-float-to-double off
21357 Arguments of type @code{float} will be passed directly to unprototyped
21360 @kindex show coerce-float-to-double
21361 @item show coerce-float-to-double
21362 Show the current setting of promoting @code{float} to @code{double}.
21366 @kindex show cp-abi
21367 @value{GDBN} needs to know the ABI used for your program's C@t{++}
21368 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
21369 used to build your application. @value{GDBN} only fully supports
21370 programs with a single C@t{++} ABI; if your program contains code using
21371 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
21372 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
21373 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
21374 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
21375 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
21376 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
21381 Show the C@t{++} ABI currently in use.
21384 With no argument, show the list of supported C@t{++} ABI's.
21386 @item set cp-abi @var{abi}
21387 @itemx set cp-abi auto
21388 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
21392 @section Automatically loading associated files
21393 @cindex auto-loading
21395 @value{GDBN} sometimes reads files with commands and settings automatically,
21396 without being explicitly told so by the user. We call this feature
21397 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
21398 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
21399 results or introduce security risks (e.g., if the file comes from untrusted
21402 Note that loading of these associated files (including the local @file{.gdbinit}
21403 file) requires accordingly configured @code{auto-load safe-path}
21404 (@pxref{Auto-loading safe path}).
21406 For these reasons, @value{GDBN} includes commands and options to let you
21407 control when to auto-load files and which files should be auto-loaded.
21410 @anchor{set auto-load off}
21411 @kindex set auto-load off
21412 @item set auto-load off
21413 Globally disable loading of all auto-loaded files.
21414 You may want to use this command with the @samp{-iex} option
21415 (@pxref{Option -init-eval-command}) such as:
21417 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
21420 Be aware that system init file (@pxref{System-wide configuration})
21421 and init files from your home directory (@pxref{Home Directory Init File})
21422 still get read (as they come from generally trusted directories).
21423 To prevent @value{GDBN} from auto-loading even those init files, use the
21424 @option{-nx} option (@pxref{Mode Options}), in addition to
21425 @code{set auto-load no}.
21427 @anchor{show auto-load}
21428 @kindex show auto-load
21429 @item show auto-load
21430 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
21434 (gdb) show auto-load
21435 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
21436 libthread-db: Auto-loading of inferior specific libthread_db is on.
21437 local-gdbinit: Auto-loading of .gdbinit script from current directory
21439 python-scripts: Auto-loading of Python scripts is on.
21440 safe-path: List of directories from which it is safe to auto-load files
21441 is $debugdir:$datadir/auto-load.
21442 scripts-directory: List of directories from which to load auto-loaded scripts
21443 is $debugdir:$datadir/auto-load.
21446 @anchor{info auto-load}
21447 @kindex info auto-load
21448 @item info auto-load
21449 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
21453 (gdb) info auto-load
21456 Yes /home/user/gdb/gdb-gdb.gdb
21457 libthread-db: No auto-loaded libthread-db.
21458 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
21462 Yes /home/user/gdb/gdb-gdb.py
21466 These are various kinds of files @value{GDBN} can automatically load:
21470 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
21472 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
21474 @xref{dotdebug_gdb_scripts section},
21475 controlled by @ref{set auto-load python-scripts}.
21477 @xref{Init File in the Current Directory},
21478 controlled by @ref{set auto-load local-gdbinit}.
21480 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
21483 These are @value{GDBN} control commands for the auto-loading:
21485 @multitable @columnfractions .5 .5
21486 @item @xref{set auto-load off}.
21487 @tab Disable auto-loading globally.
21488 @item @xref{show auto-load}.
21489 @tab Show setting of all kinds of files.
21490 @item @xref{info auto-load}.
21491 @tab Show state of all kinds of files.
21492 @item @xref{set auto-load gdb-scripts}.
21493 @tab Control for @value{GDBN} command scripts.
21494 @item @xref{show auto-load gdb-scripts}.
21495 @tab Show setting of @value{GDBN} command scripts.
21496 @item @xref{info auto-load gdb-scripts}.
21497 @tab Show state of @value{GDBN} command scripts.
21498 @item @xref{set auto-load python-scripts}.
21499 @tab Control for @value{GDBN} Python scripts.
21500 @item @xref{show auto-load python-scripts}.
21501 @tab Show setting of @value{GDBN} Python scripts.
21502 @item @xref{info auto-load python-scripts}.
21503 @tab Show state of @value{GDBN} Python scripts.
21504 @item @xref{set auto-load scripts-directory}.
21505 @tab Control for @value{GDBN} auto-loaded scripts location.
21506 @item @xref{show auto-load scripts-directory}.
21507 @tab Show @value{GDBN} auto-loaded scripts location.
21508 @item @xref{set auto-load local-gdbinit}.
21509 @tab Control for init file in the current directory.
21510 @item @xref{show auto-load local-gdbinit}.
21511 @tab Show setting of init file in the current directory.
21512 @item @xref{info auto-load local-gdbinit}.
21513 @tab Show state of init file in the current directory.
21514 @item @xref{set auto-load libthread-db}.
21515 @tab Control for thread debugging library.
21516 @item @xref{show auto-load libthread-db}.
21517 @tab Show setting of thread debugging library.
21518 @item @xref{info auto-load libthread-db}.
21519 @tab Show state of thread debugging library.
21520 @item @xref{set auto-load safe-path}.
21521 @tab Control directories trusted for automatic loading.
21522 @item @xref{show auto-load safe-path}.
21523 @tab Show directories trusted for automatic loading.
21524 @item @xref{add-auto-load-safe-path}.
21525 @tab Add directory trusted for automatic loading.
21529 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
21530 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
21531 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
21532 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
21533 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
21534 @xref{Python Auto-loading}.
21537 @node Init File in the Current Directory
21538 @subsection Automatically loading init file in the current directory
21539 @cindex auto-loading init file in the current directory
21541 By default, @value{GDBN} reads and executes the canned sequences of commands
21542 from init file (if any) in the current working directory,
21543 see @ref{Init File in the Current Directory during Startup}.
21545 Note that loading of this local @file{.gdbinit} file also requires accordingly
21546 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21549 @anchor{set auto-load local-gdbinit}
21550 @kindex set auto-load local-gdbinit
21551 @item set auto-load local-gdbinit [on|off]
21552 Enable or disable the auto-loading of canned sequences of commands
21553 (@pxref{Sequences}) found in init file in the current directory.
21555 @anchor{show auto-load local-gdbinit}
21556 @kindex show auto-load local-gdbinit
21557 @item show auto-load local-gdbinit
21558 Show whether auto-loading of canned sequences of commands from init file in the
21559 current directory is enabled or disabled.
21561 @anchor{info auto-load local-gdbinit}
21562 @kindex info auto-load local-gdbinit
21563 @item info auto-load local-gdbinit
21564 Print whether canned sequences of commands from init file in the
21565 current directory have been auto-loaded.
21568 @node libthread_db.so.1 file
21569 @subsection Automatically loading thread debugging library
21570 @cindex auto-loading libthread_db.so.1
21572 This feature is currently present only on @sc{gnu}/Linux native hosts.
21574 @value{GDBN} reads in some cases thread debugging library from places specific
21575 to the inferior (@pxref{set libthread-db-search-path}).
21577 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
21578 without checking this @samp{set auto-load libthread-db} switch as system
21579 libraries have to be trusted in general. In all other cases of
21580 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
21581 auto-load libthread-db} is enabled before trying to open such thread debugging
21584 Note that loading of this debugging library also requires accordingly configured
21585 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21588 @anchor{set auto-load libthread-db}
21589 @kindex set auto-load libthread-db
21590 @item set auto-load libthread-db [on|off]
21591 Enable or disable the auto-loading of inferior specific thread debugging library.
21593 @anchor{show auto-load libthread-db}
21594 @kindex show auto-load libthread-db
21595 @item show auto-load libthread-db
21596 Show whether auto-loading of inferior specific thread debugging library is
21597 enabled or disabled.
21599 @anchor{info auto-load libthread-db}
21600 @kindex info auto-load libthread-db
21601 @item info auto-load libthread-db
21602 Print the list of all loaded inferior specific thread debugging libraries and
21603 for each such library print list of inferior @var{pid}s using it.
21606 @node objfile-gdb.gdb file
21607 @subsection The @file{@var{objfile}-gdb.gdb} file
21608 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
21610 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
21611 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
21612 auto-load gdb-scripts} is set to @samp{on}.
21614 Note that loading of this script file also requires accordingly configured
21615 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21617 For more background refer to the similar Python scripts auto-loading
21618 description (@pxref{objfile-gdb.py file}).
21621 @anchor{set auto-load gdb-scripts}
21622 @kindex set auto-load gdb-scripts
21623 @item set auto-load gdb-scripts [on|off]
21624 Enable or disable the auto-loading of canned sequences of commands scripts.
21626 @anchor{show auto-load gdb-scripts}
21627 @kindex show auto-load gdb-scripts
21628 @item show auto-load gdb-scripts
21629 Show whether auto-loading of canned sequences of commands scripts is enabled or
21632 @anchor{info auto-load gdb-scripts}
21633 @kindex info auto-load gdb-scripts
21634 @cindex print list of auto-loaded canned sequences of commands scripts
21635 @item info auto-load gdb-scripts [@var{regexp}]
21636 Print the list of all canned sequences of commands scripts that @value{GDBN}
21640 If @var{regexp} is supplied only canned sequences of commands scripts with
21641 matching names are printed.
21643 @node Auto-loading safe path
21644 @subsection Security restriction for auto-loading
21645 @cindex auto-loading safe-path
21647 As the files of inferior can come from untrusted source (such as submitted by
21648 an application user) @value{GDBN} does not always load any files automatically.
21649 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
21650 directories trusted for loading files not explicitly requested by user.
21651 Each directory can also be a shell wildcard pattern.
21653 If the path is not set properly you will see a warning and the file will not
21658 Reading symbols from /home/user/gdb/gdb...done.
21659 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
21660 declined by your `auto-load safe-path' set
21661 to "$debugdir:$datadir/auto-load".
21662 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
21663 declined by your `auto-load safe-path' set
21664 to "$debugdir:$datadir/auto-load".
21667 The list of trusted directories is controlled by the following commands:
21670 @anchor{set auto-load safe-path}
21671 @kindex set auto-load safe-path
21672 @item set auto-load safe-path @r{[}@var{directories}@r{]}
21673 Set the list of directories (and their subdirectories) trusted for automatic
21674 loading and execution of scripts. You can also enter a specific trusted file.
21675 Each directory can also be a shell wildcard pattern; wildcards do not match
21676 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
21677 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
21678 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
21679 its default value as specified during @value{GDBN} compilation.
21681 The list of directories uses path separator (@samp{:} on GNU and Unix
21682 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
21683 to the @env{PATH} environment variable.
21685 @anchor{show auto-load safe-path}
21686 @kindex show auto-load safe-path
21687 @item show auto-load safe-path
21688 Show the list of directories trusted for automatic loading and execution of
21691 @anchor{add-auto-load-safe-path}
21692 @kindex add-auto-load-safe-path
21693 @item add-auto-load-safe-path
21694 Add an entry (or list of entries) the list of directories trusted for automatic
21695 loading and execution of scripts. Multiple entries may be delimited by the
21696 host platform path separator in use.
21699 This variable defaults to what @code{--with-auto-load-dir} has been configured
21700 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
21701 substitution applies the same as for @ref{set auto-load scripts-directory}.
21702 The default @code{set auto-load safe-path} value can be also overriden by
21703 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
21705 Setting this variable to @file{/} disables this security protection,
21706 corresponding @value{GDBN} configuration option is
21707 @option{--without-auto-load-safe-path}.
21708 This variable is supposed to be set to the system directories writable by the
21709 system superuser only. Users can add their source directories in init files in
21710 their home directories (@pxref{Home Directory Init File}). See also deprecated
21711 init file in the current directory
21712 (@pxref{Init File in the Current Directory during Startup}).
21714 To force @value{GDBN} to load the files it declined to load in the previous
21715 example, you could use one of the following ways:
21718 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
21719 Specify this trusted directory (or a file) as additional component of the list.
21720 You have to specify also any existing directories displayed by
21721 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
21723 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
21724 Specify this directory as in the previous case but just for a single
21725 @value{GDBN} session.
21727 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
21728 Disable auto-loading safety for a single @value{GDBN} session.
21729 This assumes all the files you debug during this @value{GDBN} session will come
21730 from trusted sources.
21732 @item @kbd{./configure --without-auto-load-safe-path}
21733 During compilation of @value{GDBN} you may disable any auto-loading safety.
21734 This assumes all the files you will ever debug with this @value{GDBN} come from
21738 On the other hand you can also explicitly forbid automatic files loading which
21739 also suppresses any such warning messages:
21742 @item @kbd{gdb -iex "set auto-load no" @dots{}}
21743 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
21745 @item @file{~/.gdbinit}: @samp{set auto-load no}
21746 Disable auto-loading globally for the user
21747 (@pxref{Home Directory Init File}). While it is improbable, you could also
21748 use system init file instead (@pxref{System-wide configuration}).
21751 This setting applies to the file names as entered by user. If no entry matches
21752 @value{GDBN} tries as a last resort to also resolve all the file names into
21753 their canonical form (typically resolving symbolic links) and compare the
21754 entries again. @value{GDBN} already canonicalizes most of the filenames on its
21755 own before starting the comparison so a canonical form of directories is
21756 recommended to be entered.
21758 @node Auto-loading verbose mode
21759 @subsection Displaying files tried for auto-load
21760 @cindex auto-loading verbose mode
21762 For better visibility of all the file locations where you can place scripts to
21763 be auto-loaded with inferior --- or to protect yourself against accidental
21764 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
21765 all the files attempted to be loaded. Both existing and non-existing files may
21768 For example the list of directories from which it is safe to auto-load files
21769 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
21770 may not be too obvious while setting it up.
21773 (gdb) set debug auto-load on
21774 (gdb) file ~/src/t/true
21775 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
21776 for objfile "/tmp/true".
21777 auto-load: Updating directories of "/usr:/opt".
21778 auto-load: Using directory "/usr".
21779 auto-load: Using directory "/opt".
21780 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
21781 by your `auto-load safe-path' set to "/usr:/opt".
21785 @anchor{set debug auto-load}
21786 @kindex set debug auto-load
21787 @item set debug auto-load [on|off]
21788 Set whether to print the filenames attempted to be auto-loaded.
21790 @anchor{show debug auto-load}
21791 @kindex show debug auto-load
21792 @item show debug auto-load
21793 Show whether printing of the filenames attempted to be auto-loaded is turned
21797 @node Messages/Warnings
21798 @section Optional Warnings and Messages
21800 @cindex verbose operation
21801 @cindex optional warnings
21802 By default, @value{GDBN} is silent about its inner workings. If you are
21803 running on a slow machine, you may want to use the @code{set verbose}
21804 command. This makes @value{GDBN} tell you when it does a lengthy
21805 internal operation, so you will not think it has crashed.
21807 Currently, the messages controlled by @code{set verbose} are those
21808 which announce that the symbol table for a source file is being read;
21809 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
21812 @kindex set verbose
21813 @item set verbose on
21814 Enables @value{GDBN} output of certain informational messages.
21816 @item set verbose off
21817 Disables @value{GDBN} output of certain informational messages.
21819 @kindex show verbose
21821 Displays whether @code{set verbose} is on or off.
21824 By default, if @value{GDBN} encounters bugs in the symbol table of an
21825 object file, it is silent; but if you are debugging a compiler, you may
21826 find this information useful (@pxref{Symbol Errors, ,Errors Reading
21831 @kindex set complaints
21832 @item set complaints @var{limit}
21833 Permits @value{GDBN} to output @var{limit} complaints about each type of
21834 unusual symbols before becoming silent about the problem. Set
21835 @var{limit} to zero to suppress all complaints; set it to a large number
21836 to prevent complaints from being suppressed.
21838 @kindex show complaints
21839 @item show complaints
21840 Displays how many symbol complaints @value{GDBN} is permitted to produce.
21844 @anchor{confirmation requests}
21845 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
21846 lot of stupid questions to confirm certain commands. For example, if
21847 you try to run a program which is already running:
21851 The program being debugged has been started already.
21852 Start it from the beginning? (y or n)
21855 If you are willing to unflinchingly face the consequences of your own
21856 commands, you can disable this ``feature'':
21860 @kindex set confirm
21862 @cindex confirmation
21863 @cindex stupid questions
21864 @item set confirm off
21865 Disables confirmation requests. Note that running @value{GDBN} with
21866 the @option{--batch} option (@pxref{Mode Options, -batch}) also
21867 automatically disables confirmation requests.
21869 @item set confirm on
21870 Enables confirmation requests (the default).
21872 @kindex show confirm
21874 Displays state of confirmation requests.
21878 @cindex command tracing
21879 If you need to debug user-defined commands or sourced files you may find it
21880 useful to enable @dfn{command tracing}. In this mode each command will be
21881 printed as it is executed, prefixed with one or more @samp{+} symbols, the
21882 quantity denoting the call depth of each command.
21885 @kindex set trace-commands
21886 @cindex command scripts, debugging
21887 @item set trace-commands on
21888 Enable command tracing.
21889 @item set trace-commands off
21890 Disable command tracing.
21891 @item show trace-commands
21892 Display the current state of command tracing.
21895 @node Debugging Output
21896 @section Optional Messages about Internal Happenings
21897 @cindex optional debugging messages
21899 @value{GDBN} has commands that enable optional debugging messages from
21900 various @value{GDBN} subsystems; normally these commands are of
21901 interest to @value{GDBN} maintainers, or when reporting a bug. This
21902 section documents those commands.
21905 @kindex set exec-done-display
21906 @item set exec-done-display
21907 Turns on or off the notification of asynchronous commands'
21908 completion. When on, @value{GDBN} will print a message when an
21909 asynchronous command finishes its execution. The default is off.
21910 @kindex show exec-done-display
21911 @item show exec-done-display
21912 Displays the current setting of asynchronous command completion
21915 @cindex gdbarch debugging info
21916 @cindex architecture debugging info
21917 @item set debug arch
21918 Turns on or off display of gdbarch debugging info. The default is off
21920 @item show debug arch
21921 Displays the current state of displaying gdbarch debugging info.
21922 @item set debug aix-thread
21923 @cindex AIX threads
21924 Display debugging messages about inner workings of the AIX thread
21926 @item show debug aix-thread
21927 Show the current state of AIX thread debugging info display.
21928 @item set debug check-physname
21930 Check the results of the ``physname'' computation. When reading DWARF
21931 debugging information for C@t{++}, @value{GDBN} attempts to compute
21932 each entity's name. @value{GDBN} can do this computation in two
21933 different ways, depending on exactly what information is present.
21934 When enabled, this setting causes @value{GDBN} to compute the names
21935 both ways and display any discrepancies.
21936 @item show debug check-physname
21937 Show the current state of ``physname'' checking.
21938 @item set debug dwarf2-die
21939 @cindex DWARF2 DIEs
21940 Dump DWARF2 DIEs after they are read in.
21941 The value is the number of nesting levels to print.
21942 A value of zero turns off the display.
21943 @item show debug dwarf2-die
21944 Show the current state of DWARF2 DIE debugging.
21945 @item set debug dwarf2-read
21946 @cindex DWARF2 Reading
21947 Turns on or off display of debugging messages related to reading
21948 DWARF debug info. The default is off.
21949 @item show debug dwarf2-read
21950 Show the current state of DWARF2 reader debugging.
21951 @item set debug displaced
21952 @cindex displaced stepping debugging info
21953 Turns on or off display of @value{GDBN} debugging info for the
21954 displaced stepping support. The default is off.
21955 @item show debug displaced
21956 Displays the current state of displaying @value{GDBN} debugging info
21957 related to displaced stepping.
21958 @item set debug event
21959 @cindex event debugging info
21960 Turns on or off display of @value{GDBN} event debugging info. The
21962 @item show debug event
21963 Displays the current state of displaying @value{GDBN} event debugging
21965 @item set debug expression
21966 @cindex expression debugging info
21967 Turns on or off display of debugging info about @value{GDBN}
21968 expression parsing. The default is off.
21969 @item show debug expression
21970 Displays the current state of displaying debugging info about
21971 @value{GDBN} expression parsing.
21972 @item set debug frame
21973 @cindex frame debugging info
21974 Turns on or off display of @value{GDBN} frame debugging info. The
21976 @item show debug frame
21977 Displays the current state of displaying @value{GDBN} frame debugging
21979 @item set debug gnu-nat
21980 @cindex @sc{gnu}/Hurd debug messages
21981 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
21982 @item show debug gnu-nat
21983 Show the current state of @sc{gnu}/Hurd debugging messages.
21984 @item set debug infrun
21985 @cindex inferior debugging info
21986 Turns on or off display of @value{GDBN} debugging info for running the inferior.
21987 The default is off. @file{infrun.c} contains GDB's runtime state machine used
21988 for implementing operations such as single-stepping the inferior.
21989 @item show debug infrun
21990 Displays the current state of @value{GDBN} inferior debugging.
21991 @item set debug jit
21992 @cindex just-in-time compilation, debugging messages
21993 Turns on or off debugging messages from JIT debug support.
21994 @item show debug jit
21995 Displays the current state of @value{GDBN} JIT debugging.
21996 @item set debug lin-lwp
21997 @cindex @sc{gnu}/Linux LWP debug messages
21998 @cindex Linux lightweight processes
21999 Turns on or off debugging messages from the Linux LWP debug support.
22000 @item show debug lin-lwp
22001 Show the current state of Linux LWP debugging messages.
22002 @item set debug notification
22003 @cindex remote async notification debugging info
22004 Turns on or off debugging messages about remote async notification.
22005 The default is off.
22006 @item show debug notification
22007 Displays the current state of remote async notification debugging messages.
22008 @item set debug observer
22009 @cindex observer debugging info
22010 Turns on or off display of @value{GDBN} observer debugging. This
22011 includes info such as the notification of observable events.
22012 @item show debug observer
22013 Displays the current state of observer debugging.
22014 @item set debug overload
22015 @cindex C@t{++} overload debugging info
22016 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22017 info. This includes info such as ranking of functions, etc. The default
22019 @item show debug overload
22020 Displays the current state of displaying @value{GDBN} C@t{++} overload
22022 @cindex expression parser, debugging info
22023 @cindex debug expression parser
22024 @item set debug parser
22025 Turns on or off the display of expression parser debugging output.
22026 Internally, this sets the @code{yydebug} variable in the expression
22027 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22028 details. The default is off.
22029 @item show debug parser
22030 Show the current state of expression parser debugging.
22031 @cindex packets, reporting on stdout
22032 @cindex serial connections, debugging
22033 @cindex debug remote protocol
22034 @cindex remote protocol debugging
22035 @cindex display remote packets
22036 @item set debug remote
22037 Turns on or off display of reports on all packets sent back and forth across
22038 the serial line to the remote machine. The info is printed on the
22039 @value{GDBN} standard output stream. The default is off.
22040 @item show debug remote
22041 Displays the state of display of remote packets.
22042 @item set debug serial
22043 Turns on or off display of @value{GDBN} serial debugging info. The
22045 @item show debug serial
22046 Displays the current state of displaying @value{GDBN} serial debugging
22048 @item set debug solib-frv
22049 @cindex FR-V shared-library debugging
22050 Turns on or off debugging messages for FR-V shared-library code.
22051 @item show debug solib-frv
22052 Display the current state of FR-V shared-library code debugging
22054 @item set debug symtab-create
22055 @cindex symbol table creation
22056 Turns on or off display of debugging messages related to symbol table creation.
22057 The default is off.
22058 @item show debug symtab-create
22059 Show the current state of symbol table creation debugging.
22060 @item set debug target
22061 @cindex target debugging info
22062 Turns on or off display of @value{GDBN} target debugging info. This info
22063 includes what is going on at the target level of GDB, as it happens. The
22064 default is 0. Set it to 1 to track events, and to 2 to also track the
22065 value of large memory transfers. Changes to this flag do not take effect
22066 until the next time you connect to a target or use the @code{run} command.
22067 @item show debug target
22068 Displays the current state of displaying @value{GDBN} target debugging
22070 @item set debug timestamp
22071 @cindex timestampping debugging info
22072 Turns on or off display of timestamps with @value{GDBN} debugging info.
22073 When enabled, seconds and microseconds are displayed before each debugging
22075 @item show debug timestamp
22076 Displays the current state of displaying timestamps with @value{GDBN}
22078 @item set debugvarobj
22079 @cindex variable object debugging info
22080 Turns on or off display of @value{GDBN} variable object debugging
22081 info. The default is off.
22082 @item show debugvarobj
22083 Displays the current state of displaying @value{GDBN} variable object
22085 @item set debug xml
22086 @cindex XML parser debugging
22087 Turns on or off debugging messages for built-in XML parsers.
22088 @item show debug xml
22089 Displays the current state of XML debugging messages.
22092 @node Other Misc Settings
22093 @section Other Miscellaneous Settings
22094 @cindex miscellaneous settings
22097 @kindex set interactive-mode
22098 @item set interactive-mode
22099 If @code{on}, forces @value{GDBN} to assume that GDB was started
22100 in a terminal. In practice, this means that @value{GDBN} should wait
22101 for the user to answer queries generated by commands entered at
22102 the command prompt. If @code{off}, forces @value{GDBN} to operate
22103 in the opposite mode, and it uses the default answers to all queries.
22104 If @code{auto} (the default), @value{GDBN} tries to determine whether
22105 its standard input is a terminal, and works in interactive-mode if it
22106 is, non-interactively otherwise.
22108 In the vast majority of cases, the debugger should be able to guess
22109 correctly which mode should be used. But this setting can be useful
22110 in certain specific cases, such as running a MinGW @value{GDBN}
22111 inside a cygwin window.
22113 @kindex show interactive-mode
22114 @item show interactive-mode
22115 Displays whether the debugger is operating in interactive mode or not.
22118 @node Extending GDB
22119 @chapter Extending @value{GDBN}
22120 @cindex extending GDB
22122 @value{GDBN} provides three mechanisms for extension. The first is based
22123 on composition of @value{GDBN} commands, the second is based on the
22124 Python scripting language, and the third is for defining new aliases of
22127 To facilitate the use of the first two extensions, @value{GDBN} is capable
22128 of evaluating the contents of a file. When doing so, @value{GDBN}
22129 can recognize which scripting language is being used by looking at
22130 the filename extension. Files with an unrecognized filename extension
22131 are always treated as a @value{GDBN} Command Files.
22132 @xref{Command Files,, Command files}.
22134 You can control how @value{GDBN} evaluates these files with the following
22138 @kindex set script-extension
22139 @kindex show script-extension
22140 @item set script-extension off
22141 All scripts are always evaluated as @value{GDBN} Command Files.
22143 @item set script-extension soft
22144 The debugger determines the scripting language based on filename
22145 extension. If this scripting language is supported, @value{GDBN}
22146 evaluates the script using that language. Otherwise, it evaluates
22147 the file as a @value{GDBN} Command File.
22149 @item set script-extension strict
22150 The debugger determines the scripting language based on filename
22151 extension, and evaluates the script using that language. If the
22152 language is not supported, then the evaluation fails.
22154 @item show script-extension
22155 Display the current value of the @code{script-extension} option.
22160 * Sequences:: Canned Sequences of Commands
22161 * Python:: Scripting @value{GDBN} using Python
22162 * Aliases:: Creating new spellings of existing commands
22166 @section Canned Sequences of Commands
22168 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22169 Command Lists}), @value{GDBN} provides two ways to store sequences of
22170 commands for execution as a unit: user-defined commands and command
22174 * Define:: How to define your own commands
22175 * Hooks:: Hooks for user-defined commands
22176 * Command Files:: How to write scripts of commands to be stored in a file
22177 * Output:: Commands for controlled output
22181 @subsection User-defined Commands
22183 @cindex user-defined command
22184 @cindex arguments, to user-defined commands
22185 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22186 which you assign a new name as a command. This is done with the
22187 @code{define} command. User commands may accept up to 10 arguments
22188 separated by whitespace. Arguments are accessed within the user command
22189 via @code{$arg0@dots{}$arg9}. A trivial example:
22193 print $arg0 + $arg1 + $arg2
22198 To execute the command use:
22205 This defines the command @code{adder}, which prints the sum of
22206 its three arguments. Note the arguments are text substitutions, so they may
22207 reference variables, use complex expressions, or even perform inferior
22210 @cindex argument count in user-defined commands
22211 @cindex how many arguments (user-defined commands)
22212 In addition, @code{$argc} may be used to find out how many arguments have
22213 been passed. This expands to a number in the range 0@dots{}10.
22218 print $arg0 + $arg1
22221 print $arg0 + $arg1 + $arg2
22229 @item define @var{commandname}
22230 Define a command named @var{commandname}. If there is already a command
22231 by that name, you are asked to confirm that you want to redefine it.
22232 @var{commandname} may be a bare command name consisting of letters,
22233 numbers, dashes, and underscores. It may also start with any predefined
22234 prefix command. For example, @samp{define target my-target} creates
22235 a user-defined @samp{target my-target} command.
22237 The definition of the command is made up of other @value{GDBN} command lines,
22238 which are given following the @code{define} command. The end of these
22239 commands is marked by a line containing @code{end}.
22242 @kindex end@r{ (user-defined commands)}
22243 @item document @var{commandname}
22244 Document the user-defined command @var{commandname}, so that it can be
22245 accessed by @code{help}. The command @var{commandname} must already be
22246 defined. This command reads lines of documentation just as @code{define}
22247 reads the lines of the command definition, ending with @code{end}.
22248 After the @code{document} command is finished, @code{help} on command
22249 @var{commandname} displays the documentation you have written.
22251 You may use the @code{document} command again to change the
22252 documentation of a command. Redefining the command with @code{define}
22253 does not change the documentation.
22255 @kindex dont-repeat
22256 @cindex don't repeat command
22258 Used inside a user-defined command, this tells @value{GDBN} that this
22259 command should not be repeated when the user hits @key{RET}
22260 (@pxref{Command Syntax, repeat last command}).
22262 @kindex help user-defined
22263 @item help user-defined
22264 List all user-defined commands and all python commands defined in class
22265 COMAND_USER. The first line of the documentation or docstring is
22270 @itemx show user @var{commandname}
22271 Display the @value{GDBN} commands used to define @var{commandname} (but
22272 not its documentation). If no @var{commandname} is given, display the
22273 definitions for all user-defined commands.
22274 This does not work for user-defined python commands.
22276 @cindex infinite recursion in user-defined commands
22277 @kindex show max-user-call-depth
22278 @kindex set max-user-call-depth
22279 @item show max-user-call-depth
22280 @itemx set max-user-call-depth
22281 The value of @code{max-user-call-depth} controls how many recursion
22282 levels are allowed in user-defined commands before @value{GDBN} suspects an
22283 infinite recursion and aborts the command.
22284 This does not apply to user-defined python commands.
22287 In addition to the above commands, user-defined commands frequently
22288 use control flow commands, described in @ref{Command Files}.
22290 When user-defined commands are executed, the
22291 commands of the definition are not printed. An error in any command
22292 stops execution of the user-defined command.
22294 If used interactively, commands that would ask for confirmation proceed
22295 without asking when used inside a user-defined command. Many @value{GDBN}
22296 commands that normally print messages to say what they are doing omit the
22297 messages when used in a user-defined command.
22300 @subsection User-defined Command Hooks
22301 @cindex command hooks
22302 @cindex hooks, for commands
22303 @cindex hooks, pre-command
22306 You may define @dfn{hooks}, which are a special kind of user-defined
22307 command. Whenever you run the command @samp{foo}, if the user-defined
22308 command @samp{hook-foo} exists, it is executed (with no arguments)
22309 before that command.
22311 @cindex hooks, post-command
22313 A hook may also be defined which is run after the command you executed.
22314 Whenever you run the command @samp{foo}, if the user-defined command
22315 @samp{hookpost-foo} exists, it is executed (with no arguments) after
22316 that command. Post-execution hooks may exist simultaneously with
22317 pre-execution hooks, for the same command.
22319 It is valid for a hook to call the command which it hooks. If this
22320 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
22322 @c It would be nice if hookpost could be passed a parameter indicating
22323 @c if the command it hooks executed properly or not. FIXME!
22325 @kindex stop@r{, a pseudo-command}
22326 In addition, a pseudo-command, @samp{stop} exists. Defining
22327 (@samp{hook-stop}) makes the associated commands execute every time
22328 execution stops in your program: before breakpoint commands are run,
22329 displays are printed, or the stack frame is printed.
22331 For example, to ignore @code{SIGALRM} signals while
22332 single-stepping, but treat them normally during normal execution,
22337 handle SIGALRM nopass
22341 handle SIGALRM pass
22344 define hook-continue
22345 handle SIGALRM pass
22349 As a further example, to hook at the beginning and end of the @code{echo}
22350 command, and to add extra text to the beginning and end of the message,
22358 define hookpost-echo
22362 (@value{GDBP}) echo Hello World
22363 <<<---Hello World--->>>
22368 You can define a hook for any single-word command in @value{GDBN}, but
22369 not for command aliases; you should define a hook for the basic command
22370 name, e.g.@: @code{backtrace} rather than @code{bt}.
22371 @c FIXME! So how does Joe User discover whether a command is an alias
22373 You can hook a multi-word command by adding @code{hook-} or
22374 @code{hookpost-} to the last word of the command, e.g.@:
22375 @samp{define target hook-remote} to add a hook to @samp{target remote}.
22377 If an error occurs during the execution of your hook, execution of
22378 @value{GDBN} commands stops and @value{GDBN} issues a prompt
22379 (before the command that you actually typed had a chance to run).
22381 If you try to define a hook which does not match any known command, you
22382 get a warning from the @code{define} command.
22384 @node Command Files
22385 @subsection Command Files
22387 @cindex command files
22388 @cindex scripting commands
22389 A command file for @value{GDBN} is a text file made of lines that are
22390 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
22391 also be included. An empty line in a command file does nothing; it
22392 does not mean to repeat the last command, as it would from the
22395 You can request the execution of a command file with the @code{source}
22396 command. Note that the @code{source} command is also used to evaluate
22397 scripts that are not Command Files. The exact behavior can be configured
22398 using the @code{script-extension} setting.
22399 @xref{Extending GDB,, Extending GDB}.
22403 @cindex execute commands from a file
22404 @item source [-s] [-v] @var{filename}
22405 Execute the command file @var{filename}.
22408 The lines in a command file are generally executed sequentially,
22409 unless the order of execution is changed by one of the
22410 @emph{flow-control commands} described below. The commands are not
22411 printed as they are executed. An error in any command terminates
22412 execution of the command file and control is returned to the console.
22414 @value{GDBN} first searches for @var{filename} in the current directory.
22415 If the file is not found there, and @var{filename} does not specify a
22416 directory, then @value{GDBN} also looks for the file on the source search path
22417 (specified with the @samp{directory} command);
22418 except that @file{$cdir} is not searched because the compilation directory
22419 is not relevant to scripts.
22421 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
22422 on the search path even if @var{filename} specifies a directory.
22423 The search is done by appending @var{filename} to each element of the
22424 search path. So, for example, if @var{filename} is @file{mylib/myscript}
22425 and the search path contains @file{/home/user} then @value{GDBN} will
22426 look for the script @file{/home/user/mylib/myscript}.
22427 The search is also done if @var{filename} is an absolute path.
22428 For example, if @var{filename} is @file{/tmp/myscript} and
22429 the search path contains @file{/home/user} then @value{GDBN} will
22430 look for the script @file{/home/user/tmp/myscript}.
22431 For DOS-like systems, if @var{filename} contains a drive specification,
22432 it is stripped before concatenation. For example, if @var{filename} is
22433 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
22434 will look for the script @file{c:/tmp/myscript}.
22436 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
22437 each command as it is executed. The option must be given before
22438 @var{filename}, and is interpreted as part of the filename anywhere else.
22440 Commands that would ask for confirmation if used interactively proceed
22441 without asking when used in a command file. Many @value{GDBN} commands that
22442 normally print messages to say what they are doing omit the messages
22443 when called from command files.
22445 @value{GDBN} also accepts command input from standard input. In this
22446 mode, normal output goes to standard output and error output goes to
22447 standard error. Errors in a command file supplied on standard input do
22448 not terminate execution of the command file---execution continues with
22452 gdb < cmds > log 2>&1
22455 (The syntax above will vary depending on the shell used.) This example
22456 will execute commands from the file @file{cmds}. All output and errors
22457 would be directed to @file{log}.
22459 Since commands stored on command files tend to be more general than
22460 commands typed interactively, they frequently need to deal with
22461 complicated situations, such as different or unexpected values of
22462 variables and symbols, changes in how the program being debugged is
22463 built, etc. @value{GDBN} provides a set of flow-control commands to
22464 deal with these complexities. Using these commands, you can write
22465 complex scripts that loop over data structures, execute commands
22466 conditionally, etc.
22473 This command allows to include in your script conditionally executed
22474 commands. The @code{if} command takes a single argument, which is an
22475 expression to evaluate. It is followed by a series of commands that
22476 are executed only if the expression is true (its value is nonzero).
22477 There can then optionally be an @code{else} line, followed by a series
22478 of commands that are only executed if the expression was false. The
22479 end of the list is marked by a line containing @code{end}.
22483 This command allows to write loops. Its syntax is similar to
22484 @code{if}: the command takes a single argument, which is an expression
22485 to evaluate, and must be followed by the commands to execute, one per
22486 line, terminated by an @code{end}. These commands are called the
22487 @dfn{body} of the loop. The commands in the body of @code{while} are
22488 executed repeatedly as long as the expression evaluates to true.
22492 This command exits the @code{while} loop in whose body it is included.
22493 Execution of the script continues after that @code{while}s @code{end}
22496 @kindex loop_continue
22497 @item loop_continue
22498 This command skips the execution of the rest of the body of commands
22499 in the @code{while} loop in whose body it is included. Execution
22500 branches to the beginning of the @code{while} loop, where it evaluates
22501 the controlling expression.
22503 @kindex end@r{ (if/else/while commands)}
22505 Terminate the block of commands that are the body of @code{if},
22506 @code{else}, or @code{while} flow-control commands.
22511 @subsection Commands for Controlled Output
22513 During the execution of a command file or a user-defined command, normal
22514 @value{GDBN} output is suppressed; the only output that appears is what is
22515 explicitly printed by the commands in the definition. This section
22516 describes three commands useful for generating exactly the output you
22521 @item echo @var{text}
22522 @c I do not consider backslash-space a standard C escape sequence
22523 @c because it is not in ANSI.
22524 Print @var{text}. Nonprinting characters can be included in
22525 @var{text} using C escape sequences, such as @samp{\n} to print a
22526 newline. @strong{No newline is printed unless you specify one.}
22527 In addition to the standard C escape sequences, a backslash followed
22528 by a space stands for a space. This is useful for displaying a
22529 string with spaces at the beginning or the end, since leading and
22530 trailing spaces are otherwise trimmed from all arguments.
22531 To print @samp{@w{ }and foo =@w{ }}, use the command
22532 @samp{echo \@w{ }and foo = \@w{ }}.
22534 A backslash at the end of @var{text} can be used, as in C, to continue
22535 the command onto subsequent lines. For example,
22538 echo This is some text\n\
22539 which is continued\n\
22540 onto several lines.\n
22543 produces the same output as
22546 echo This is some text\n
22547 echo which is continued\n
22548 echo onto several lines.\n
22552 @item output @var{expression}
22553 Print the value of @var{expression} and nothing but that value: no
22554 newlines, no @samp{$@var{nn} = }. The value is not entered in the
22555 value history either. @xref{Expressions, ,Expressions}, for more information
22558 @item output/@var{fmt} @var{expression}
22559 Print the value of @var{expression} in format @var{fmt}. You can use
22560 the same formats as for @code{print}. @xref{Output Formats,,Output
22561 Formats}, for more information.
22564 @item printf @var{template}, @var{expressions}@dots{}
22565 Print the values of one or more @var{expressions} under the control of
22566 the string @var{template}. To print several values, make
22567 @var{expressions} be a comma-separated list of individual expressions,
22568 which may be either numbers or pointers. Their values are printed as
22569 specified by @var{template}, exactly as a C program would do by
22570 executing the code below:
22573 printf (@var{template}, @var{expressions}@dots{});
22576 As in @code{C} @code{printf}, ordinary characters in @var{template}
22577 are printed verbatim, while @dfn{conversion specification} introduced
22578 by the @samp{%} character cause subsequent @var{expressions} to be
22579 evaluated, their values converted and formatted according to type and
22580 style information encoded in the conversion specifications, and then
22583 For example, you can print two values in hex like this:
22586 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
22589 @code{printf} supports all the standard @code{C} conversion
22590 specifications, including the flags and modifiers between the @samp{%}
22591 character and the conversion letter, with the following exceptions:
22595 The argument-ordering modifiers, such as @samp{2$}, are not supported.
22598 The modifier @samp{*} is not supported for specifying precision or
22602 The @samp{'} flag (for separation of digits into groups according to
22603 @code{LC_NUMERIC'}) is not supported.
22606 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
22610 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
22613 The conversion letters @samp{a} and @samp{A} are not supported.
22617 Note that the @samp{ll} type modifier is supported only if the
22618 underlying @code{C} implementation used to build @value{GDBN} supports
22619 the @code{long long int} type, and the @samp{L} type modifier is
22620 supported only if @code{long double} type is available.
22622 As in @code{C}, @code{printf} supports simple backslash-escape
22623 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
22624 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
22625 single character. Octal and hexadecimal escape sequences are not
22628 Additionally, @code{printf} supports conversion specifications for DFP
22629 (@dfn{Decimal Floating Point}) types using the following length modifiers
22630 together with a floating point specifier.
22635 @samp{H} for printing @code{Decimal32} types.
22638 @samp{D} for printing @code{Decimal64} types.
22641 @samp{DD} for printing @code{Decimal128} types.
22644 If the underlying @code{C} implementation used to build @value{GDBN} has
22645 support for the three length modifiers for DFP types, other modifiers
22646 such as width and precision will also be available for @value{GDBN} to use.
22648 In case there is no such @code{C} support, no additional modifiers will be
22649 available and the value will be printed in the standard way.
22651 Here's an example of printing DFP types using the above conversion letters:
22653 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
22657 @item eval @var{template}, @var{expressions}@dots{}
22658 Convert the values of one or more @var{expressions} under the control of
22659 the string @var{template} to a command line, and call it.
22664 @section Scripting @value{GDBN} using Python
22665 @cindex python scripting
22666 @cindex scripting with python
22668 You can script @value{GDBN} using the @uref{http://www.python.org/,
22669 Python programming language}. This feature is available only if
22670 @value{GDBN} was configured using @option{--with-python}.
22672 @cindex python directory
22673 Python scripts used by @value{GDBN} should be installed in
22674 @file{@var{data-directory}/python}, where @var{data-directory} is
22675 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
22676 This directory, known as the @dfn{python directory},
22677 is automatically added to the Python Search Path in order to allow
22678 the Python interpreter to locate all scripts installed at this location.
22680 Additionally, @value{GDBN} commands and convenience functions which
22681 are written in Python and are located in the
22682 @file{@var{data-directory}/python/gdb/command} or
22683 @file{@var{data-directory}/python/gdb/function} directories are
22684 automatically imported when @value{GDBN} starts.
22687 * Python Commands:: Accessing Python from @value{GDBN}.
22688 * Python API:: Accessing @value{GDBN} from Python.
22689 * Python Auto-loading:: Automatically loading Python code.
22690 * Python modules:: Python modules provided by @value{GDBN}.
22693 @node Python Commands
22694 @subsection Python Commands
22695 @cindex python commands
22696 @cindex commands to access python
22698 @value{GDBN} provides two commands for accessing the Python interpreter,
22699 and one related setting:
22702 @kindex python-interactive
22704 @item python-interactive @r{[}@var{command}@r{]}
22705 @itemx pi @r{[}@var{command}@r{]}
22706 Without an argument, the @code{python-interactive} command can be used
22707 to start an interactive Python prompt. To return to @value{GDBN},
22708 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
22710 Alternatively, a single-line Python command can be given as an
22711 argument and evaluated. If the command is an expression, the result
22712 will be printed; otherwise, nothing will be printed. For example:
22715 (@value{GDBP}) python-interactive 2 + 3
22721 @item python @r{[}@var{command}@r{]}
22722 @itemx py @r{[}@var{command}@r{]}
22723 The @code{python} command can be used to evaluate Python code.
22725 If given an argument, the @code{python} command will evaluate the
22726 argument as a Python command. For example:
22729 (@value{GDBP}) python print 23
22733 If you do not provide an argument to @code{python}, it will act as a
22734 multi-line command, like @code{define}. In this case, the Python
22735 script is made up of subsequent command lines, given after the
22736 @code{python} command. This command list is terminated using a line
22737 containing @code{end}. For example:
22740 (@value{GDBP}) python
22742 End with a line saying just "end".
22748 @kindex set python print-stack
22749 @item set python print-stack
22750 By default, @value{GDBN} will print only the message component of a
22751 Python exception when an error occurs in a Python script. This can be
22752 controlled using @code{set python print-stack}: if @code{full}, then
22753 full Python stack printing is enabled; if @code{none}, then Python stack
22754 and message printing is disabled; if @code{message}, the default, only
22755 the message component of the error is printed.
22758 It is also possible to execute a Python script from the @value{GDBN}
22762 @item source @file{script-name}
22763 The script name must end with @samp{.py} and @value{GDBN} must be configured
22764 to recognize the script language based on filename extension using
22765 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
22767 @item python execfile ("script-name")
22768 This method is based on the @code{execfile} Python built-in function,
22769 and thus is always available.
22773 @subsection Python API
22775 @cindex programming in python
22777 @cindex python stdout
22778 @cindex python pagination
22779 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
22780 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
22781 A Python program which outputs to one of these streams may have its
22782 output interrupted by the user (@pxref{Screen Size}). In this
22783 situation, a Python @code{KeyboardInterrupt} exception is thrown.
22786 * Basic Python:: Basic Python Functions.
22787 * Exception Handling:: How Python exceptions are translated.
22788 * Values From Inferior:: Python representation of values.
22789 * Types In Python:: Python representation of types.
22790 * Pretty Printing API:: Pretty-printing values.
22791 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
22792 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
22793 * Type Printing API:: Pretty-printing types.
22794 * Inferiors In Python:: Python representation of inferiors (processes)
22795 * Events In Python:: Listening for events from @value{GDBN}.
22796 * Threads In Python:: Accessing inferior threads from Python.
22797 * Commands In Python:: Implementing new commands in Python.
22798 * Parameters In Python:: Adding new @value{GDBN} parameters.
22799 * Functions In Python:: Writing new convenience functions.
22800 * Progspaces In Python:: Program spaces.
22801 * Objfiles In Python:: Object files.
22802 * Frames In Python:: Accessing inferior stack frames from Python.
22803 * Blocks In Python:: Accessing frame blocks from Python.
22804 * Symbols In Python:: Python representation of symbols.
22805 * Symbol Tables In Python:: Python representation of symbol tables.
22806 * Breakpoints In Python:: Manipulating breakpoints using Python.
22807 * Finish Breakpoints in Python:: Setting Breakpoints on function return
22809 * Lazy Strings In Python:: Python representation of lazy strings.
22813 @subsubsection Basic Python
22815 @cindex python functions
22816 @cindex python module
22818 @value{GDBN} introduces a new Python module, named @code{gdb}. All
22819 methods and classes added by @value{GDBN} are placed in this module.
22820 @value{GDBN} automatically @code{import}s the @code{gdb} module for
22821 use in all scripts evaluated by the @code{python} command.
22823 @findex gdb.PYTHONDIR
22824 @defvar gdb.PYTHONDIR
22825 A string containing the python directory (@pxref{Python}).
22828 @findex gdb.execute
22829 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
22830 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
22831 If a GDB exception happens while @var{command} runs, it is
22832 translated as described in @ref{Exception Handling,,Exception Handling}.
22834 @var{from_tty} specifies whether @value{GDBN} ought to consider this
22835 command as having originated from the user invoking it interactively.
22836 It must be a boolean value. If omitted, it defaults to @code{False}.
22838 By default, any output produced by @var{command} is sent to
22839 @value{GDBN}'s standard output. If the @var{to_string} parameter is
22840 @code{True}, then output will be collected by @code{gdb.execute} and
22841 returned as a string. The default is @code{False}, in which case the
22842 return value is @code{None}. If @var{to_string} is @code{True}, the
22843 @value{GDBN} virtual terminal will be temporarily set to unlimited width
22844 and height, and its pagination will be disabled; @pxref{Screen Size}.
22847 @findex gdb.breakpoints
22848 @defun gdb.breakpoints ()
22849 Return a sequence holding all of @value{GDBN}'s breakpoints.
22850 @xref{Breakpoints In Python}, for more information.
22853 @findex gdb.parameter
22854 @defun gdb.parameter (parameter)
22855 Return the value of a @value{GDBN} parameter. @var{parameter} is a
22856 string naming the parameter to look up; @var{parameter} may contain
22857 spaces if the parameter has a multi-part name. For example,
22858 @samp{print object} is a valid parameter name.
22860 If the named parameter does not exist, this function throws a
22861 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
22862 parameter's value is converted to a Python value of the appropriate
22863 type, and returned.
22866 @findex gdb.history
22867 @defun gdb.history (number)
22868 Return a value from @value{GDBN}'s value history (@pxref{Value
22869 History}). @var{number} indicates which history element to return.
22870 If @var{number} is negative, then @value{GDBN} will take its absolute value
22871 and count backward from the last element (i.e., the most recent element) to
22872 find the value to return. If @var{number} is zero, then @value{GDBN} will
22873 return the most recent element. If the element specified by @var{number}
22874 doesn't exist in the value history, a @code{gdb.error} exception will be
22877 If no exception is raised, the return value is always an instance of
22878 @code{gdb.Value} (@pxref{Values From Inferior}).
22881 @findex gdb.parse_and_eval
22882 @defun gdb.parse_and_eval (expression)
22883 Parse @var{expression} as an expression in the current language,
22884 evaluate it, and return the result as a @code{gdb.Value}.
22885 @var{expression} must be a string.
22887 This function can be useful when implementing a new command
22888 (@pxref{Commands In Python}), as it provides a way to parse the
22889 command's argument as an expression. It is also useful simply to
22890 compute values, for example, it is the only way to get the value of a
22891 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
22894 @findex gdb.find_pc_line
22895 @defun gdb.find_pc_line (pc)
22896 Return the @code{gdb.Symtab_and_line} object corresponding to the
22897 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
22898 value of @var{pc} is passed as an argument, then the @code{symtab} and
22899 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
22900 will be @code{None} and 0 respectively.
22903 @findex gdb.post_event
22904 @defun gdb.post_event (event)
22905 Put @var{event}, a callable object taking no arguments, into
22906 @value{GDBN}'s internal event queue. This callable will be invoked at
22907 some later point, during @value{GDBN}'s event processing. Events
22908 posted using @code{post_event} will be run in the order in which they
22909 were posted; however, there is no way to know when they will be
22910 processed relative to other events inside @value{GDBN}.
22912 @value{GDBN} is not thread-safe. If your Python program uses multiple
22913 threads, you must be careful to only call @value{GDBN}-specific
22914 functions in the main @value{GDBN} thread. @code{post_event} ensures
22918 (@value{GDBP}) python
22922 > def __init__(self, message):
22923 > self.message = message;
22924 > def __call__(self):
22925 > gdb.write(self.message)
22927 >class MyThread1 (threading.Thread):
22929 > gdb.post_event(Writer("Hello "))
22931 >class MyThread2 (threading.Thread):
22933 > gdb.post_event(Writer("World\n"))
22935 >MyThread1().start()
22936 >MyThread2().start()
22938 (@value{GDBP}) Hello World
22943 @defun gdb.write (string @r{[}, stream{]})
22944 Print a string to @value{GDBN}'s paginated output stream. The
22945 optional @var{stream} determines the stream to print to. The default
22946 stream is @value{GDBN}'s standard output stream. Possible stream
22953 @value{GDBN}'s standard output stream.
22958 @value{GDBN}'s standard error stream.
22963 @value{GDBN}'s log stream (@pxref{Logging Output}).
22966 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
22967 call this function and will automatically direct the output to the
22972 @defun gdb.flush ()
22973 Flush the buffer of a @value{GDBN} paginated stream so that the
22974 contents are displayed immediately. @value{GDBN} will flush the
22975 contents of a stream automatically when it encounters a newline in the
22976 buffer. The optional @var{stream} determines the stream to flush. The
22977 default stream is @value{GDBN}'s standard output stream. Possible
22984 @value{GDBN}'s standard output stream.
22989 @value{GDBN}'s standard error stream.
22994 @value{GDBN}'s log stream (@pxref{Logging Output}).
22998 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
22999 call this function for the relevant stream.
23002 @findex gdb.target_charset
23003 @defun gdb.target_charset ()
23004 Return the name of the current target character set (@pxref{Character
23005 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23006 that @samp{auto} is never returned.
23009 @findex gdb.target_wide_charset
23010 @defun gdb.target_wide_charset ()
23011 Return the name of the current target wide character set
23012 (@pxref{Character Sets}). This differs from
23013 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23017 @findex gdb.solib_name
23018 @defun gdb.solib_name (address)
23019 Return the name of the shared library holding the given @var{address}
23020 as a string, or @code{None}.
23023 @findex gdb.decode_line
23024 @defun gdb.decode_line @r{[}expression@r{]}
23025 Return locations of the line specified by @var{expression}, or of the
23026 current line if no argument was given. This function returns a Python
23027 tuple containing two elements. The first element contains a string
23028 holding any unparsed section of @var{expression} (or @code{None} if
23029 the expression has been fully parsed). The second element contains
23030 either @code{None} or another tuple that contains all the locations
23031 that match the expression represented as @code{gdb.Symtab_and_line}
23032 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23033 provided, it is decoded the way that @value{GDBN}'s inbuilt
23034 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23037 @defun gdb.prompt_hook (current_prompt)
23038 @anchor{prompt_hook}
23040 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23041 assigned to this operation before a prompt is displayed by
23044 The parameter @code{current_prompt} contains the current @value{GDBN}
23045 prompt. This method must return a Python string, or @code{None}. If
23046 a string is returned, the @value{GDBN} prompt will be set to that
23047 string. If @code{None} is returned, @value{GDBN} will continue to use
23048 the current prompt.
23050 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23051 such as those used by readline for command input, and annotation
23052 related prompts are prohibited from being changed.
23055 @node Exception Handling
23056 @subsubsection Exception Handling
23057 @cindex python exceptions
23058 @cindex exceptions, python
23060 When executing the @code{python} command, Python exceptions
23061 uncaught within the Python code are translated to calls to
23062 @value{GDBN} error-reporting mechanism. If the command that called
23063 @code{python} does not handle the error, @value{GDBN} will
23064 terminate it and print an error message containing the Python
23065 exception name, the associated value, and the Python call stack
23066 backtrace at the point where the exception was raised. Example:
23069 (@value{GDBP}) python print foo
23070 Traceback (most recent call last):
23071 File "<string>", line 1, in <module>
23072 NameError: name 'foo' is not defined
23075 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23076 Python code are converted to Python exceptions. The type of the
23077 Python exception depends on the error.
23081 This is the base class for most exceptions generated by @value{GDBN}.
23082 It is derived from @code{RuntimeError}, for compatibility with earlier
23083 versions of @value{GDBN}.
23085 If an error occurring in @value{GDBN} does not fit into some more
23086 specific category, then the generated exception will have this type.
23088 @item gdb.MemoryError
23089 This is a subclass of @code{gdb.error} which is thrown when an
23090 operation tried to access invalid memory in the inferior.
23092 @item KeyboardInterrupt
23093 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23094 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23097 In all cases, your exception handler will see the @value{GDBN} error
23098 message as its value and the Python call stack backtrace at the Python
23099 statement closest to where the @value{GDBN} error occured as the
23102 @findex gdb.GdbError
23103 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23104 it is useful to be able to throw an exception that doesn't cause a
23105 traceback to be printed. For example, the user may have invoked the
23106 command incorrectly. Use the @code{gdb.GdbError} exception
23107 to handle this case. Example:
23111 >class HelloWorld (gdb.Command):
23112 > """Greet the whole world."""
23113 > def __init__ (self):
23114 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23115 > def invoke (self, args, from_tty):
23116 > argv = gdb.string_to_argv (args)
23117 > if len (argv) != 0:
23118 > raise gdb.GdbError ("hello-world takes no arguments")
23119 > print "Hello, World!"
23122 (gdb) hello-world 42
23123 hello-world takes no arguments
23126 @node Values From Inferior
23127 @subsubsection Values From Inferior
23128 @cindex values from inferior, with Python
23129 @cindex python, working with values from inferior
23131 @cindex @code{gdb.Value}
23132 @value{GDBN} provides values it obtains from the inferior program in
23133 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23134 for its internal bookkeeping of the inferior's values, and for
23135 fetching values when necessary.
23137 Inferior values that are simple scalars can be used directly in
23138 Python expressions that are valid for the value's data type. Here's
23139 an example for an integer or floating-point value @code{some_val}:
23146 As result of this, @code{bar} will also be a @code{gdb.Value} object
23147 whose values are of the same type as those of @code{some_val}.
23149 Inferior values that are structures or instances of some class can
23150 be accessed using the Python @dfn{dictionary syntax}. For example, if
23151 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23152 can access its @code{foo} element with:
23155 bar = some_val['foo']
23158 Again, @code{bar} will also be a @code{gdb.Value} object.
23160 A @code{gdb.Value} that represents a function can be executed via
23161 inferior function call. Any arguments provided to the call must match
23162 the function's prototype, and must be provided in the order specified
23165 For example, @code{some_val} is a @code{gdb.Value} instance
23166 representing a function that takes two integers as arguments. To
23167 execute this function, call it like so:
23170 result = some_val (10,20)
23173 Any values returned from a function call will be stored as a
23176 The following attributes are provided:
23179 @defvar Value.address
23180 If this object is addressable, this read-only attribute holds a
23181 @code{gdb.Value} object representing the address. Otherwise,
23182 this attribute holds @code{None}.
23185 @cindex optimized out value in Python
23186 @defvar Value.is_optimized_out
23187 This read-only boolean attribute is true if the compiler optimized out
23188 this value, thus it is not available for fetching from the inferior.
23192 The type of this @code{gdb.Value}. The value of this attribute is a
23193 @code{gdb.Type} object (@pxref{Types In Python}).
23196 @defvar Value.dynamic_type
23197 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
23198 type information (@acronym{RTTI}) to determine the dynamic type of the
23199 value. If this value is of class type, it will return the class in
23200 which the value is embedded, if any. If this value is of pointer or
23201 reference to a class type, it will compute the dynamic type of the
23202 referenced object, and return a pointer or reference to that type,
23203 respectively. In all other cases, it will return the value's static
23206 Note that this feature will only work when debugging a C@t{++} program
23207 that includes @acronym{RTTI} for the object in question. Otherwise,
23208 it will just return the static type of the value as in @kbd{ptype foo}
23209 (@pxref{Symbols, ptype}).
23212 @defvar Value.is_lazy
23213 The value of this read-only boolean attribute is @code{True} if this
23214 @code{gdb.Value} has not yet been fetched from the inferior.
23215 @value{GDBN} does not fetch values until necessary, for efficiency.
23219 myval = gdb.parse_and_eval ('somevar')
23222 The value of @code{somevar} is not fetched at this time. It will be
23223 fetched when the value is needed, or when the @code{fetch_lazy}
23228 The following methods are provided:
23231 @defun Value.__init__ (@var{val})
23232 Many Python values can be converted directly to a @code{gdb.Value} via
23233 this object initializer. Specifically:
23236 @item Python boolean
23237 A Python boolean is converted to the boolean type from the current
23240 @item Python integer
23241 A Python integer is converted to the C @code{long} type for the
23242 current architecture.
23245 A Python long is converted to the C @code{long long} type for the
23246 current architecture.
23249 A Python float is converted to the C @code{double} type for the
23250 current architecture.
23252 @item Python string
23253 A Python string is converted to a target string, using the current
23256 @item @code{gdb.Value}
23257 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
23259 @item @code{gdb.LazyString}
23260 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
23261 Python}), then the lazy string's @code{value} method is called, and
23262 its result is used.
23266 @defun Value.cast (type)
23267 Return a new instance of @code{gdb.Value} that is the result of
23268 casting this instance to the type described by @var{type}, which must
23269 be a @code{gdb.Type} object. If the cast cannot be performed for some
23270 reason, this method throws an exception.
23273 @defun Value.dereference ()
23274 For pointer data types, this method returns a new @code{gdb.Value} object
23275 whose contents is the object pointed to by the pointer. For example, if
23276 @code{foo} is a C pointer to an @code{int}, declared in your C program as
23283 then you can use the corresponding @code{gdb.Value} to access what
23284 @code{foo} points to like this:
23287 bar = foo.dereference ()
23290 The result @code{bar} will be a @code{gdb.Value} object holding the
23291 value pointed to by @code{foo}.
23293 A similar function @code{Value.referenced_value} exists which also
23294 returns @code{gdb.Value} objects corresonding to the values pointed to
23295 by pointer values (and additionally, values referenced by reference
23296 values). However, the behavior of @code{Value.dereference}
23297 differs from @code{Value.referenced_value} by the fact that the
23298 behavior of @code{Value.dereference} is identical to applying the C
23299 unary operator @code{*} on a given value. For example, consider a
23300 reference to a pointer @code{ptrref}, declared in your C@t{++} program
23304 typedef int *intptr;
23308 intptr &ptrref = ptr;
23311 Though @code{ptrref} is a reference value, one can apply the method
23312 @code{Value.dereference} to the @code{gdb.Value} object corresponding
23313 to it and obtain a @code{gdb.Value} which is identical to that
23314 corresponding to @code{val}. However, if you apply the method
23315 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
23316 object identical to that corresponding to @code{ptr}.
23319 py_ptrref = gdb.parse_and_eval ("ptrref")
23320 py_val = py_ptrref.dereference ()
23321 py_ptr = py_ptrref.referenced_value ()
23324 The @code{gdb.Value} object @code{py_val} is identical to that
23325 corresponding to @code{val}, and @code{py_ptr} is identical to that
23326 corresponding to @code{ptr}. In general, @code{Value.dereference} can
23327 be applied whenever the C unary operator @code{*} can be applied
23328 to the corresponding C value. For those cases where applying both
23329 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
23330 the results obtained need not be identical (as we have seen in the above
23331 example). The results are however identical when applied on
23332 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
23333 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
23336 @defun Value.referenced_value ()
23337 For pointer or reference data types, this method returns a new
23338 @code{gdb.Value} object corresponding to the value referenced by the
23339 pointer/reference value. For pointer data types,
23340 @code{Value.dereference} and @code{Value.referenced_value} produce
23341 identical results. The difference between these methods is that
23342 @code{Value.dereference} cannot get the values referenced by reference
23343 values. For example, consider a reference to an @code{int}, declared
23344 in your C@t{++} program as
23352 then applying @code{Value.dereference} to the @code{gdb.Value} object
23353 corresponding to @code{ref} will result in an error, while applying
23354 @code{Value.referenced_value} will result in a @code{gdb.Value} object
23355 identical to that corresponding to @code{val}.
23358 py_ref = gdb.parse_and_eval ("ref")
23359 er_ref = py_ref.dereference () # Results in error
23360 py_val = py_ref.referenced_value () # Returns the referenced value
23363 The @code{gdb.Value} object @code{py_val} is identical to that
23364 corresponding to @code{val}.
23367 @defun Value.dynamic_cast (type)
23368 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
23369 operator were used. Consult a C@t{++} reference for details.
23372 @defun Value.reinterpret_cast (type)
23373 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
23374 operator were used. Consult a C@t{++} reference for details.
23377 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
23378 If this @code{gdb.Value} represents a string, then this method
23379 converts the contents to a Python string. Otherwise, this method will
23380 throw an exception.
23382 Strings are recognized in a language-specific way; whether a given
23383 @code{gdb.Value} represents a string is determined by the current
23386 For C-like languages, a value is a string if it is a pointer to or an
23387 array of characters or ints. The string is assumed to be terminated
23388 by a zero of the appropriate width. However if the optional length
23389 argument is given, the string will be converted to that given length,
23390 ignoring any embedded zeros that the string may contain.
23392 If the optional @var{encoding} argument is given, it must be a string
23393 naming the encoding of the string in the @code{gdb.Value}, such as
23394 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
23395 the same encodings as the corresponding argument to Python's
23396 @code{string.decode} method, and the Python codec machinery will be used
23397 to convert the string. If @var{encoding} is not given, or if
23398 @var{encoding} is the empty string, then either the @code{target-charset}
23399 (@pxref{Character Sets}) will be used, or a language-specific encoding
23400 will be used, if the current language is able to supply one.
23402 The optional @var{errors} argument is the same as the corresponding
23403 argument to Python's @code{string.decode} method.
23405 If the optional @var{length} argument is given, the string will be
23406 fetched and converted to the given length.
23409 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
23410 If this @code{gdb.Value} represents a string, then this method
23411 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
23412 In Python}). Otherwise, this method will throw an exception.
23414 If the optional @var{encoding} argument is given, it must be a string
23415 naming the encoding of the @code{gdb.LazyString}. Some examples are:
23416 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
23417 @var{encoding} argument is an encoding that @value{GDBN} does
23418 recognize, @value{GDBN} will raise an error.
23420 When a lazy string is printed, the @value{GDBN} encoding machinery is
23421 used to convert the string during printing. If the optional
23422 @var{encoding} argument is not provided, or is an empty string,
23423 @value{GDBN} will automatically select the encoding most suitable for
23424 the string type. For further information on encoding in @value{GDBN}
23425 please see @ref{Character Sets}.
23427 If the optional @var{length} argument is given, the string will be
23428 fetched and encoded to the length of characters specified. If
23429 the @var{length} argument is not provided, the string will be fetched
23430 and encoded until a null of appropriate width is found.
23433 @defun Value.fetch_lazy ()
23434 If the @code{gdb.Value} object is currently a lazy value
23435 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
23436 fetched from the inferior. Any errors that occur in the process
23437 will produce a Python exception.
23439 If the @code{gdb.Value} object is not a lazy value, this method
23442 This method does not return a value.
23447 @node Types In Python
23448 @subsubsection Types In Python
23449 @cindex types in Python
23450 @cindex Python, working with types
23453 @value{GDBN} represents types from the inferior using the class
23456 The following type-related functions are available in the @code{gdb}
23459 @findex gdb.lookup_type
23460 @defun gdb.lookup_type (name @r{[}, block@r{]})
23461 This function looks up a type by name. @var{name} is the name of the
23462 type to look up. It must be a string.
23464 If @var{block} is given, then @var{name} is looked up in that scope.
23465 Otherwise, it is searched for globally.
23467 Ordinarily, this function will return an instance of @code{gdb.Type}.
23468 If the named type cannot be found, it will throw an exception.
23471 If the type is a structure or class type, or an enum type, the fields
23472 of that type can be accessed using the Python @dfn{dictionary syntax}.
23473 For example, if @code{some_type} is a @code{gdb.Type} instance holding
23474 a structure type, you can access its @code{foo} field with:
23477 bar = some_type['foo']
23480 @code{bar} will be a @code{gdb.Field} object; see below under the
23481 description of the @code{Type.fields} method for a description of the
23482 @code{gdb.Field} class.
23484 An instance of @code{Type} has the following attributes:
23488 The type code for this type. The type code will be one of the
23489 @code{TYPE_CODE_} constants defined below.
23492 @defvar Type.sizeof
23493 The size of this type, in target @code{char} units. Usually, a
23494 target's @code{char} type will be an 8-bit byte. However, on some
23495 unusual platforms, this type may have a different size.
23499 The tag name for this type. The tag name is the name after
23500 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
23501 languages have this concept. If this type has no tag name, then
23502 @code{None} is returned.
23506 The following methods are provided:
23509 @defun Type.fields ()
23510 For structure and union types, this method returns the fields. Range
23511 types have two fields, the minimum and maximum values. Enum types
23512 have one field per enum constant. Function and method types have one
23513 field per parameter. The base types of C@t{++} classes are also
23514 represented as fields. If the type has no fields, or does not fit
23515 into one of these categories, an empty sequence will be returned.
23517 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
23520 This attribute is not available for @code{static} fields (as in
23521 C@t{++} or Java). For non-@code{static} fields, the value is the bit
23522 position of the field. For @code{enum} fields, the value is the
23523 enumeration member's integer representation.
23526 The name of the field, or @code{None} for anonymous fields.
23529 This is @code{True} if the field is artificial, usually meaning that
23530 it was provided by the compiler and not the user. This attribute is
23531 always provided, and is @code{False} if the field is not artificial.
23533 @item is_base_class
23534 This is @code{True} if the field represents a base class of a C@t{++}
23535 structure. This attribute is always provided, and is @code{False}
23536 if the field is not a base class of the type that is the argument of
23537 @code{fields}, or if that type was not a C@t{++} class.
23540 If the field is packed, or is a bitfield, then this will have a
23541 non-zero value, which is the size of the field in bits. Otherwise,
23542 this will be zero; in this case the field's size is given by its type.
23545 The type of the field. This is usually an instance of @code{Type},
23546 but it can be @code{None} in some situations.
23550 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
23551 Return a new @code{gdb.Type} object which represents an array of this
23552 type. If one argument is given, it is the inclusive upper bound of
23553 the array; in this case the lower bound is zero. If two arguments are
23554 given, the first argument is the lower bound of the array, and the
23555 second argument is the upper bound of the array. An array's length
23556 must not be negative, but the bounds can be.
23559 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
23560 Return a new @code{gdb.Type} object which represents a vector of this
23561 type. If one argument is given, it is the inclusive upper bound of
23562 the vector; in this case the lower bound is zero. If two arguments are
23563 given, the first argument is the lower bound of the vector, and the
23564 second argument is the upper bound of the vector. A vector's length
23565 must not be negative, but the bounds can be.
23567 The difference between an @code{array} and a @code{vector} is that
23568 arrays behave like in C: when used in expressions they decay to a pointer
23569 to the first element whereas vectors are treated as first class values.
23572 @defun Type.const ()
23573 Return a new @code{gdb.Type} object which represents a
23574 @code{const}-qualified variant of this type.
23577 @defun Type.volatile ()
23578 Return a new @code{gdb.Type} object which represents a
23579 @code{volatile}-qualified variant of this type.
23582 @defun Type.unqualified ()
23583 Return a new @code{gdb.Type} object which represents an unqualified
23584 variant of this type. That is, the result is neither @code{const} nor
23588 @defun Type.range ()
23589 Return a Python @code{Tuple} object that contains two elements: the
23590 low bound of the argument type and the high bound of that type. If
23591 the type does not have a range, @value{GDBN} will raise a
23592 @code{gdb.error} exception (@pxref{Exception Handling}).
23595 @defun Type.reference ()
23596 Return a new @code{gdb.Type} object which represents a reference to this
23600 @defun Type.pointer ()
23601 Return a new @code{gdb.Type} object which represents a pointer to this
23605 @defun Type.strip_typedefs ()
23606 Return a new @code{gdb.Type} that represents the real type,
23607 after removing all layers of typedefs.
23610 @defun Type.target ()
23611 Return a new @code{gdb.Type} object which represents the target type
23614 For a pointer type, the target type is the type of the pointed-to
23615 object. For an array type (meaning C-like arrays), the target type is
23616 the type of the elements of the array. For a function or method type,
23617 the target type is the type of the return value. For a complex type,
23618 the target type is the type of the elements. For a typedef, the
23619 target type is the aliased type.
23621 If the type does not have a target, this method will throw an
23625 @defun Type.template_argument (n @r{[}, block@r{]})
23626 If this @code{gdb.Type} is an instantiation of a template, this will
23627 return a new @code{gdb.Type} which represents the type of the
23628 @var{n}th template argument.
23630 If this @code{gdb.Type} is not a template type, this will throw an
23631 exception. Ordinarily, only C@t{++} code will have template types.
23633 If @var{block} is given, then @var{name} is looked up in that scope.
23634 Otherwise, it is searched for globally.
23639 Each type has a code, which indicates what category this type falls
23640 into. The available type categories are represented by constants
23641 defined in the @code{gdb} module:
23644 @findex TYPE_CODE_PTR
23645 @findex gdb.TYPE_CODE_PTR
23646 @item gdb.TYPE_CODE_PTR
23647 The type is a pointer.
23649 @findex TYPE_CODE_ARRAY
23650 @findex gdb.TYPE_CODE_ARRAY
23651 @item gdb.TYPE_CODE_ARRAY
23652 The type is an array.
23654 @findex TYPE_CODE_STRUCT
23655 @findex gdb.TYPE_CODE_STRUCT
23656 @item gdb.TYPE_CODE_STRUCT
23657 The type is a structure.
23659 @findex TYPE_CODE_UNION
23660 @findex gdb.TYPE_CODE_UNION
23661 @item gdb.TYPE_CODE_UNION
23662 The type is a union.
23664 @findex TYPE_CODE_ENUM
23665 @findex gdb.TYPE_CODE_ENUM
23666 @item gdb.TYPE_CODE_ENUM
23667 The type is an enum.
23669 @findex TYPE_CODE_FLAGS
23670 @findex gdb.TYPE_CODE_FLAGS
23671 @item gdb.TYPE_CODE_FLAGS
23672 A bit flags type, used for things such as status registers.
23674 @findex TYPE_CODE_FUNC
23675 @findex gdb.TYPE_CODE_FUNC
23676 @item gdb.TYPE_CODE_FUNC
23677 The type is a function.
23679 @findex TYPE_CODE_INT
23680 @findex gdb.TYPE_CODE_INT
23681 @item gdb.TYPE_CODE_INT
23682 The type is an integer type.
23684 @findex TYPE_CODE_FLT
23685 @findex gdb.TYPE_CODE_FLT
23686 @item gdb.TYPE_CODE_FLT
23687 A floating point type.
23689 @findex TYPE_CODE_VOID
23690 @findex gdb.TYPE_CODE_VOID
23691 @item gdb.TYPE_CODE_VOID
23692 The special type @code{void}.
23694 @findex TYPE_CODE_SET
23695 @findex gdb.TYPE_CODE_SET
23696 @item gdb.TYPE_CODE_SET
23699 @findex TYPE_CODE_RANGE
23700 @findex gdb.TYPE_CODE_RANGE
23701 @item gdb.TYPE_CODE_RANGE
23702 A range type, that is, an integer type with bounds.
23704 @findex TYPE_CODE_STRING
23705 @findex gdb.TYPE_CODE_STRING
23706 @item gdb.TYPE_CODE_STRING
23707 A string type. Note that this is only used for certain languages with
23708 language-defined string types; C strings are not represented this way.
23710 @findex TYPE_CODE_BITSTRING
23711 @findex gdb.TYPE_CODE_BITSTRING
23712 @item gdb.TYPE_CODE_BITSTRING
23713 A string of bits. It is deprecated.
23715 @findex TYPE_CODE_ERROR
23716 @findex gdb.TYPE_CODE_ERROR
23717 @item gdb.TYPE_CODE_ERROR
23718 An unknown or erroneous type.
23720 @findex TYPE_CODE_METHOD
23721 @findex gdb.TYPE_CODE_METHOD
23722 @item gdb.TYPE_CODE_METHOD
23723 A method type, as found in C@t{++} or Java.
23725 @findex TYPE_CODE_METHODPTR
23726 @findex gdb.TYPE_CODE_METHODPTR
23727 @item gdb.TYPE_CODE_METHODPTR
23728 A pointer-to-member-function.
23730 @findex TYPE_CODE_MEMBERPTR
23731 @findex gdb.TYPE_CODE_MEMBERPTR
23732 @item gdb.TYPE_CODE_MEMBERPTR
23733 A pointer-to-member.
23735 @findex TYPE_CODE_REF
23736 @findex gdb.TYPE_CODE_REF
23737 @item gdb.TYPE_CODE_REF
23740 @findex TYPE_CODE_CHAR
23741 @findex gdb.TYPE_CODE_CHAR
23742 @item gdb.TYPE_CODE_CHAR
23745 @findex TYPE_CODE_BOOL
23746 @findex gdb.TYPE_CODE_BOOL
23747 @item gdb.TYPE_CODE_BOOL
23750 @findex TYPE_CODE_COMPLEX
23751 @findex gdb.TYPE_CODE_COMPLEX
23752 @item gdb.TYPE_CODE_COMPLEX
23753 A complex float type.
23755 @findex TYPE_CODE_TYPEDEF
23756 @findex gdb.TYPE_CODE_TYPEDEF
23757 @item gdb.TYPE_CODE_TYPEDEF
23758 A typedef to some other type.
23760 @findex TYPE_CODE_NAMESPACE
23761 @findex gdb.TYPE_CODE_NAMESPACE
23762 @item gdb.TYPE_CODE_NAMESPACE
23763 A C@t{++} namespace.
23765 @findex TYPE_CODE_DECFLOAT
23766 @findex gdb.TYPE_CODE_DECFLOAT
23767 @item gdb.TYPE_CODE_DECFLOAT
23768 A decimal floating point type.
23770 @findex TYPE_CODE_INTERNAL_FUNCTION
23771 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
23772 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
23773 A function internal to @value{GDBN}. This is the type used to represent
23774 convenience functions.
23777 Further support for types is provided in the @code{gdb.types}
23778 Python module (@pxref{gdb.types}).
23780 @node Pretty Printing API
23781 @subsubsection Pretty Printing API
23783 An example output is provided (@pxref{Pretty Printing}).
23785 A pretty-printer is just an object that holds a value and implements a
23786 specific interface, defined here.
23788 @defun pretty_printer.children (self)
23789 @value{GDBN} will call this method on a pretty-printer to compute the
23790 children of the pretty-printer's value.
23792 This method must return an object conforming to the Python iterator
23793 protocol. Each item returned by the iterator must be a tuple holding
23794 two elements. The first element is the ``name'' of the child; the
23795 second element is the child's value. The value can be any Python
23796 object which is convertible to a @value{GDBN} value.
23798 This method is optional. If it does not exist, @value{GDBN} will act
23799 as though the value has no children.
23802 @defun pretty_printer.display_hint (self)
23803 The CLI may call this method and use its result to change the
23804 formatting of a value. The result will also be supplied to an MI
23805 consumer as a @samp{displayhint} attribute of the variable being
23808 This method is optional. If it does exist, this method must return a
23811 Some display hints are predefined by @value{GDBN}:
23815 Indicate that the object being printed is ``array-like''. The CLI
23816 uses this to respect parameters such as @code{set print elements} and
23817 @code{set print array}.
23820 Indicate that the object being printed is ``map-like'', and that the
23821 children of this value can be assumed to alternate between keys and
23825 Indicate that the object being printed is ``string-like''. If the
23826 printer's @code{to_string} method returns a Python string of some
23827 kind, then @value{GDBN} will call its internal language-specific
23828 string-printing function to format the string. For the CLI this means
23829 adding quotation marks, possibly escaping some characters, respecting
23830 @code{set print elements}, and the like.
23834 @defun pretty_printer.to_string (self)
23835 @value{GDBN} will call this method to display the string
23836 representation of the value passed to the object's constructor.
23838 When printing from the CLI, if the @code{to_string} method exists,
23839 then @value{GDBN} will prepend its result to the values returned by
23840 @code{children}. Exactly how this formatting is done is dependent on
23841 the display hint, and may change as more hints are added. Also,
23842 depending on the print settings (@pxref{Print Settings}), the CLI may
23843 print just the result of @code{to_string} in a stack trace, omitting
23844 the result of @code{children}.
23846 If this method returns a string, it is printed verbatim.
23848 Otherwise, if this method returns an instance of @code{gdb.Value},
23849 then @value{GDBN} prints this value. This may result in a call to
23850 another pretty-printer.
23852 If instead the method returns a Python value which is convertible to a
23853 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
23854 the resulting value. Again, this may result in a call to another
23855 pretty-printer. Python scalars (integers, floats, and booleans) and
23856 strings are convertible to @code{gdb.Value}; other types are not.
23858 Finally, if this method returns @code{None} then no further operations
23859 are peformed in this method and nothing is printed.
23861 If the result is not one of these types, an exception is raised.
23864 @value{GDBN} provides a function which can be used to look up the
23865 default pretty-printer for a @code{gdb.Value}:
23867 @findex gdb.default_visualizer
23868 @defun gdb.default_visualizer (value)
23869 This function takes a @code{gdb.Value} object as an argument. If a
23870 pretty-printer for this value exists, then it is returned. If no such
23871 printer exists, then this returns @code{None}.
23874 @node Selecting Pretty-Printers
23875 @subsubsection Selecting Pretty-Printers
23877 The Python list @code{gdb.pretty_printers} contains an array of
23878 functions or callable objects that have been registered via addition
23879 as a pretty-printer. Printers in this list are called @code{global}
23880 printers, they're available when debugging all inferiors.
23881 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
23882 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
23885 Each function on these lists is passed a single @code{gdb.Value}
23886 argument and should return a pretty-printer object conforming to the
23887 interface definition above (@pxref{Pretty Printing API}). If a function
23888 cannot create a pretty-printer for the value, it should return
23891 @value{GDBN} first checks the @code{pretty_printers} attribute of each
23892 @code{gdb.Objfile} in the current program space and iteratively calls
23893 each enabled lookup routine in the list for that @code{gdb.Objfile}
23894 until it receives a pretty-printer object.
23895 If no pretty-printer is found in the objfile lists, @value{GDBN} then
23896 searches the pretty-printer list of the current program space,
23897 calling each enabled function until an object is returned.
23898 After these lists have been exhausted, it tries the global
23899 @code{gdb.pretty_printers} list, again calling each enabled function until an
23900 object is returned.
23902 The order in which the objfiles are searched is not specified. For a
23903 given list, functions are always invoked from the head of the list,
23904 and iterated over sequentially until the end of the list, or a printer
23905 object is returned.
23907 For various reasons a pretty-printer may not work.
23908 For example, the underlying data structure may have changed and
23909 the pretty-printer is out of date.
23911 The consequences of a broken pretty-printer are severe enough that
23912 @value{GDBN} provides support for enabling and disabling individual
23913 printers. For example, if @code{print frame-arguments} is on,
23914 a backtrace can become highly illegible if any argument is printed
23915 with a broken printer.
23917 Pretty-printers are enabled and disabled by attaching an @code{enabled}
23918 attribute to the registered function or callable object. If this attribute
23919 is present and its value is @code{False}, the printer is disabled, otherwise
23920 the printer is enabled.
23922 @node Writing a Pretty-Printer
23923 @subsubsection Writing a Pretty-Printer
23924 @cindex writing a pretty-printer
23926 A pretty-printer consists of two parts: a lookup function to detect
23927 if the type is supported, and the printer itself.
23929 Here is an example showing how a @code{std::string} printer might be
23930 written. @xref{Pretty Printing API}, for details on the API this class
23934 class StdStringPrinter(object):
23935 "Print a std::string"
23937 def __init__(self, val):
23940 def to_string(self):
23941 return self.val['_M_dataplus']['_M_p']
23943 def display_hint(self):
23947 And here is an example showing how a lookup function for the printer
23948 example above might be written.
23951 def str_lookup_function(val):
23952 lookup_tag = val.type.tag
23953 if lookup_tag == None:
23955 regex = re.compile("^std::basic_string<char,.*>$")
23956 if regex.match(lookup_tag):
23957 return StdStringPrinter(val)
23961 The example lookup function extracts the value's type, and attempts to
23962 match it to a type that it can pretty-print. If it is a type the
23963 printer can pretty-print, it will return a printer object. If not, it
23964 returns @code{None}.
23966 We recommend that you put your core pretty-printers into a Python
23967 package. If your pretty-printers are for use with a library, we
23968 further recommend embedding a version number into the package name.
23969 This practice will enable @value{GDBN} to load multiple versions of
23970 your pretty-printers at the same time, because they will have
23973 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
23974 can be evaluated multiple times without changing its meaning. An
23975 ideal auto-load file will consist solely of @code{import}s of your
23976 printer modules, followed by a call to a register pretty-printers with
23977 the current objfile.
23979 Taken as a whole, this approach will scale nicely to multiple
23980 inferiors, each potentially using a different library version.
23981 Embedding a version number in the Python package name will ensure that
23982 @value{GDBN} is able to load both sets of printers simultaneously.
23983 Then, because the search for pretty-printers is done by objfile, and
23984 because your auto-loaded code took care to register your library's
23985 printers with a specific objfile, @value{GDBN} will find the correct
23986 printers for the specific version of the library used by each
23989 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
23990 this code might appear in @code{gdb.libstdcxx.v6}:
23993 def register_printers(objfile):
23994 objfile.pretty_printers.append(str_lookup_function)
23998 And then the corresponding contents of the auto-load file would be:
24001 import gdb.libstdcxx.v6
24002 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24005 The previous example illustrates a basic pretty-printer.
24006 There are a few things that can be improved on.
24007 The printer doesn't have a name, making it hard to identify in a
24008 list of installed printers. The lookup function has a name, but
24009 lookup functions can have arbitrary, even identical, names.
24011 Second, the printer only handles one type, whereas a library typically has
24012 several types. One could install a lookup function for each desired type
24013 in the library, but one could also have a single lookup function recognize
24014 several types. The latter is the conventional way this is handled.
24015 If a pretty-printer can handle multiple data types, then its
24016 @dfn{subprinters} are the printers for the individual data types.
24018 The @code{gdb.printing} module provides a formal way of solving these
24019 problems (@pxref{gdb.printing}).
24020 Here is another example that handles multiple types.
24022 These are the types we are going to pretty-print:
24025 struct foo @{ int a, b; @};
24026 struct bar @{ struct foo x, y; @};
24029 Here are the printers:
24033 """Print a foo object."""
24035 def __init__(self, val):
24038 def to_string(self):
24039 return ("a=<" + str(self.val["a"]) +
24040 "> b=<" + str(self.val["b"]) + ">")
24043 """Print a bar object."""
24045 def __init__(self, val):
24048 def to_string(self):
24049 return ("x=<" + str(self.val["x"]) +
24050 "> y=<" + str(self.val["y"]) + ">")
24053 This example doesn't need a lookup function, that is handled by the
24054 @code{gdb.printing} module. Instead a function is provided to build up
24055 the object that handles the lookup.
24058 import gdb.printing
24060 def build_pretty_printer():
24061 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24063 pp.add_printer('foo', '^foo$', fooPrinter)
24064 pp.add_printer('bar', '^bar$', barPrinter)
24068 And here is the autoload support:
24071 import gdb.printing
24073 gdb.printing.register_pretty_printer(
24074 gdb.current_objfile(),
24075 my_library.build_pretty_printer())
24078 Finally, when this printer is loaded into @value{GDBN}, here is the
24079 corresponding output of @samp{info pretty-printer}:
24082 (gdb) info pretty-printer
24089 @node Type Printing API
24090 @subsubsection Type Printing API
24091 @cindex type printing API for Python
24093 @value{GDBN} provides a way for Python code to customize type display.
24094 This is mainly useful for substituting canonical typedef names for
24097 @cindex type printer
24098 A @dfn{type printer} is just a Python object conforming to a certain
24099 protocol. A simple base class implementing the protocol is provided;
24100 see @ref{gdb.types}. A type printer must supply at least:
24102 @defivar type_printer enabled
24103 A boolean which is True if the printer is enabled, and False
24104 otherwise. This is manipulated by the @code{enable type-printer}
24105 and @code{disable type-printer} commands.
24108 @defivar type_printer name
24109 The name of the type printer. This must be a string. This is used by
24110 the @code{enable type-printer} and @code{disable type-printer}
24114 @defmethod type_printer instantiate (self)
24115 This is called by @value{GDBN} at the start of type-printing. It is
24116 only called if the type printer is enabled. This method must return a
24117 new object that supplies a @code{recognize} method, as described below.
24121 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24122 will compute a list of type recognizers. This is done by iterating
24123 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24124 followed by the per-progspace type printers (@pxref{Progspaces In
24125 Python}), and finally the global type printers.
24127 @value{GDBN} will call the @code{instantiate} method of each enabled
24128 type printer. If this method returns @code{None}, then the result is
24129 ignored; otherwise, it is appended to the list of recognizers.
24131 Then, when @value{GDBN} is going to display a type name, it iterates
24132 over the list of recognizers. For each one, it calls the recognition
24133 function, stopping if the function returns a non-@code{None} value.
24134 The recognition function is defined as:
24136 @defmethod type_recognizer recognize (self, type)
24137 If @var{type} is not recognized, return @code{None}. Otherwise,
24138 return a string which is to be printed as the name of @var{type}.
24139 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24143 @value{GDBN} uses this two-pass approach so that type printers can
24144 efficiently cache information without holding on to it too long. For
24145 example, it can be convenient to look up type information in a type
24146 printer and hold it for a recognizer's lifetime; if a single pass were
24147 done then type printers would have to make use of the event system in
24148 order to avoid holding information that could become stale as the
24151 @node Inferiors In Python
24152 @subsubsection Inferiors In Python
24153 @cindex inferiors in Python
24155 @findex gdb.Inferior
24156 Programs which are being run under @value{GDBN} are called inferiors
24157 (@pxref{Inferiors and Programs}). Python scripts can access
24158 information about and manipulate inferiors controlled by @value{GDBN}
24159 via objects of the @code{gdb.Inferior} class.
24161 The following inferior-related functions are available in the @code{gdb}
24164 @defun gdb.inferiors ()
24165 Return a tuple containing all inferior objects.
24168 @defun gdb.selected_inferior ()
24169 Return an object representing the current inferior.
24172 A @code{gdb.Inferior} object has the following attributes:
24175 @defvar Inferior.num
24176 ID of inferior, as assigned by GDB.
24179 @defvar Inferior.pid
24180 Process ID of the inferior, as assigned by the underlying operating
24184 @defvar Inferior.was_attached
24185 Boolean signaling whether the inferior was created using `attach', or
24186 started by @value{GDBN} itself.
24190 A @code{gdb.Inferior} object has the following methods:
24193 @defun Inferior.is_valid ()
24194 Returns @code{True} if the @code{gdb.Inferior} object is valid,
24195 @code{False} if not. A @code{gdb.Inferior} object will become invalid
24196 if the inferior no longer exists within @value{GDBN}. All other
24197 @code{gdb.Inferior} methods will throw an exception if it is invalid
24198 at the time the method is called.
24201 @defun Inferior.threads ()
24202 This method returns a tuple holding all the threads which are valid
24203 when it is called. If there are no valid threads, the method will
24204 return an empty tuple.
24207 @findex Inferior.read_memory
24208 @defun Inferior.read_memory (address, length)
24209 Read @var{length} bytes of memory from the inferior, starting at
24210 @var{address}. Returns a buffer object, which behaves much like an array
24211 or a string. It can be modified and given to the
24212 @code{Inferior.write_memory} function. In @code{Python} 3, the return
24213 value is a @code{memoryview} object.
24216 @findex Inferior.write_memory
24217 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
24218 Write the contents of @var{buffer} to the inferior, starting at
24219 @var{address}. The @var{buffer} parameter must be a Python object
24220 which supports the buffer protocol, i.e., a string, an array or the
24221 object returned from @code{Inferior.read_memory}. If given, @var{length}
24222 determines the number of bytes from @var{buffer} to be written.
24225 @findex gdb.search_memory
24226 @defun Inferior.search_memory (address, length, pattern)
24227 Search a region of the inferior memory starting at @var{address} with
24228 the given @var{length} using the search pattern supplied in
24229 @var{pattern}. The @var{pattern} parameter must be a Python object
24230 which supports the buffer protocol, i.e., a string, an array or the
24231 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
24232 containing the address where the pattern was found, or @code{None} if
24233 the pattern could not be found.
24237 @node Events In Python
24238 @subsubsection Events In Python
24239 @cindex inferior events in Python
24241 @value{GDBN} provides a general event facility so that Python code can be
24242 notified of various state changes, particularly changes that occur in
24245 An @dfn{event} is just an object that describes some state change. The
24246 type of the object and its attributes will vary depending on the details
24247 of the change. All the existing events are described below.
24249 In order to be notified of an event, you must register an event handler
24250 with an @dfn{event registry}. An event registry is an object in the
24251 @code{gdb.events} module which dispatches particular events. A registry
24252 provides methods to register and unregister event handlers:
24255 @defun EventRegistry.connect (object)
24256 Add the given callable @var{object} to the registry. This object will be
24257 called when an event corresponding to this registry occurs.
24260 @defun EventRegistry.disconnect (object)
24261 Remove the given @var{object} from the registry. Once removed, the object
24262 will no longer receive notifications of events.
24266 Here is an example:
24269 def exit_handler (event):
24270 print "event type: exit"
24271 print "exit code: %d" % (event.exit_code)
24273 gdb.events.exited.connect (exit_handler)
24276 In the above example we connect our handler @code{exit_handler} to the
24277 registry @code{events.exited}. Once connected, @code{exit_handler} gets
24278 called when the inferior exits. The argument @dfn{event} in this example is
24279 of type @code{gdb.ExitedEvent}. As you can see in the example the
24280 @code{ExitedEvent} object has an attribute which indicates the exit code of
24283 The following is a listing of the event registries that are available and
24284 details of the events they emit:
24289 Emits @code{gdb.ThreadEvent}.
24291 Some events can be thread specific when @value{GDBN} is running in non-stop
24292 mode. When represented in Python, these events all extend
24293 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
24294 events which are emitted by this or other modules might extend this event.
24295 Examples of these events are @code{gdb.BreakpointEvent} and
24296 @code{gdb.ContinueEvent}.
24299 @defvar ThreadEvent.inferior_thread
24300 In non-stop mode this attribute will be set to the specific thread which was
24301 involved in the emitted event. Otherwise, it will be set to @code{None}.
24305 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
24307 This event indicates that the inferior has been continued after a stop. For
24308 inherited attribute refer to @code{gdb.ThreadEvent} above.
24310 @item events.exited
24311 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
24312 @code{events.ExitedEvent} has two attributes:
24314 @defvar ExitedEvent.exit_code
24315 An integer representing the exit code, if available, which the inferior
24316 has returned. (The exit code could be unavailable if, for example,
24317 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
24318 the attribute does not exist.
24320 @defvar ExitedEvent inferior
24321 A reference to the inferior which triggered the @code{exited} event.
24326 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
24328 Indicates that the inferior has stopped. All events emitted by this registry
24329 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
24330 will indicate the stopped thread when @value{GDBN} is running in non-stop
24331 mode. Refer to @code{gdb.ThreadEvent} above for more details.
24333 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
24335 This event indicates that the inferior or one of its threads has received as
24336 signal. @code{gdb.SignalEvent} has the following attributes:
24339 @defvar SignalEvent.stop_signal
24340 A string representing the signal received by the inferior. A list of possible
24341 signal values can be obtained by running the command @code{info signals} in
24342 the @value{GDBN} command prompt.
24346 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
24348 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
24349 been hit, and has the following attributes:
24352 @defvar BreakpointEvent.breakpoints
24353 A sequence containing references to all the breakpoints (type
24354 @code{gdb.Breakpoint}) that were hit.
24355 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
24357 @defvar BreakpointEvent.breakpoint
24358 A reference to the first breakpoint that was hit.
24359 This function is maintained for backward compatibility and is now deprecated
24360 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
24364 @item events.new_objfile
24365 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
24366 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
24369 @defvar NewObjFileEvent.new_objfile
24370 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
24371 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
24377 @node Threads In Python
24378 @subsubsection Threads In Python
24379 @cindex threads in python
24381 @findex gdb.InferiorThread
24382 Python scripts can access information about, and manipulate inferior threads
24383 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
24385 The following thread-related functions are available in the @code{gdb}
24388 @findex gdb.selected_thread
24389 @defun gdb.selected_thread ()
24390 This function returns the thread object for the selected thread. If there
24391 is no selected thread, this will return @code{None}.
24394 A @code{gdb.InferiorThread} object has the following attributes:
24397 @defvar InferiorThread.name
24398 The name of the thread. If the user specified a name using
24399 @code{thread name}, then this returns that name. Otherwise, if an
24400 OS-supplied name is available, then it is returned. Otherwise, this
24401 returns @code{None}.
24403 This attribute can be assigned to. The new value must be a string
24404 object, which sets the new name, or @code{None}, which removes any
24405 user-specified thread name.
24408 @defvar InferiorThread.num
24409 ID of the thread, as assigned by GDB.
24412 @defvar InferiorThread.ptid
24413 ID of the thread, as assigned by the operating system. This attribute is a
24414 tuple containing three integers. The first is the Process ID (PID); the second
24415 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
24416 Either the LWPID or TID may be 0, which indicates that the operating system
24417 does not use that identifier.
24421 A @code{gdb.InferiorThread} object has the following methods:
24424 @defun InferiorThread.is_valid ()
24425 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
24426 @code{False} if not. A @code{gdb.InferiorThread} object will become
24427 invalid if the thread exits, or the inferior that the thread belongs
24428 is deleted. All other @code{gdb.InferiorThread} methods will throw an
24429 exception if it is invalid at the time the method is called.
24432 @defun InferiorThread.switch ()
24433 This changes @value{GDBN}'s currently selected thread to the one represented
24437 @defun InferiorThread.is_stopped ()
24438 Return a Boolean indicating whether the thread is stopped.
24441 @defun InferiorThread.is_running ()
24442 Return a Boolean indicating whether the thread is running.
24445 @defun InferiorThread.is_exited ()
24446 Return a Boolean indicating whether the thread is exited.
24450 @node Commands In Python
24451 @subsubsection Commands In Python
24453 @cindex commands in python
24454 @cindex python commands
24455 You can implement new @value{GDBN} CLI commands in Python. A CLI
24456 command is implemented using an instance of the @code{gdb.Command}
24457 class, most commonly using a subclass.
24459 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
24460 The object initializer for @code{Command} registers the new command
24461 with @value{GDBN}. This initializer is normally invoked from the
24462 subclass' own @code{__init__} method.
24464 @var{name} is the name of the command. If @var{name} consists of
24465 multiple words, then the initial words are looked for as prefix
24466 commands. In this case, if one of the prefix commands does not exist,
24467 an exception is raised.
24469 There is no support for multi-line commands.
24471 @var{command_class} should be one of the @samp{COMMAND_} constants
24472 defined below. This argument tells @value{GDBN} how to categorize the
24473 new command in the help system.
24475 @var{completer_class} is an optional argument. If given, it should be
24476 one of the @samp{COMPLETE_} constants defined below. This argument
24477 tells @value{GDBN} how to perform completion for this command. If not
24478 given, @value{GDBN} will attempt to complete using the object's
24479 @code{complete} method (see below); if no such method is found, an
24480 error will occur when completion is attempted.
24482 @var{prefix} is an optional argument. If @code{True}, then the new
24483 command is a prefix command; sub-commands of this command may be
24486 The help text for the new command is taken from the Python
24487 documentation string for the command's class, if there is one. If no
24488 documentation string is provided, the default value ``This command is
24489 not documented.'' is used.
24492 @cindex don't repeat Python command
24493 @defun Command.dont_repeat ()
24494 By default, a @value{GDBN} command is repeated when the user enters a
24495 blank line at the command prompt. A command can suppress this
24496 behavior by invoking the @code{dont_repeat} method. This is similar
24497 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
24500 @defun Command.invoke (argument, from_tty)
24501 This method is called by @value{GDBN} when this command is invoked.
24503 @var{argument} is a string. It is the argument to the command, after
24504 leading and trailing whitespace has been stripped.
24506 @var{from_tty} is a boolean argument. When true, this means that the
24507 command was entered by the user at the terminal; when false it means
24508 that the command came from elsewhere.
24510 If this method throws an exception, it is turned into a @value{GDBN}
24511 @code{error} call. Otherwise, the return value is ignored.
24513 @findex gdb.string_to_argv
24514 To break @var{argument} up into an argv-like string use
24515 @code{gdb.string_to_argv}. This function behaves identically to
24516 @value{GDBN}'s internal argument lexer @code{buildargv}.
24517 It is recommended to use this for consistency.
24518 Arguments are separated by spaces and may be quoted.
24522 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
24523 ['1', '2 "3', '4 "5', "6 '7"]
24528 @cindex completion of Python commands
24529 @defun Command.complete (text, word)
24530 This method is called by @value{GDBN} when the user attempts
24531 completion on this command. All forms of completion are handled by
24532 this method, that is, the @key{TAB} and @key{M-?} key bindings
24533 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
24536 The arguments @var{text} and @var{word} are both strings. @var{text}
24537 holds the complete command line up to the cursor's location.
24538 @var{word} holds the last word of the command line; this is computed
24539 using a word-breaking heuristic.
24541 The @code{complete} method can return several values:
24544 If the return value is a sequence, the contents of the sequence are
24545 used as the completions. It is up to @code{complete} to ensure that the
24546 contents actually do complete the word. A zero-length sequence is
24547 allowed, it means that there were no completions available. Only
24548 string elements of the sequence are used; other elements in the
24549 sequence are ignored.
24552 If the return value is one of the @samp{COMPLETE_} constants defined
24553 below, then the corresponding @value{GDBN}-internal completion
24554 function is invoked, and its result is used.
24557 All other results are treated as though there were no available
24562 When a new command is registered, it must be declared as a member of
24563 some general class of commands. This is used to classify top-level
24564 commands in the on-line help system; note that prefix commands are not
24565 listed under their own category but rather that of their top-level
24566 command. The available classifications are represented by constants
24567 defined in the @code{gdb} module:
24570 @findex COMMAND_NONE
24571 @findex gdb.COMMAND_NONE
24572 @item gdb.COMMAND_NONE
24573 The command does not belong to any particular class. A command in
24574 this category will not be displayed in any of the help categories.
24576 @findex COMMAND_RUNNING
24577 @findex gdb.COMMAND_RUNNING
24578 @item gdb.COMMAND_RUNNING
24579 The command is related to running the inferior. For example,
24580 @code{start}, @code{step}, and @code{continue} are in this category.
24581 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
24582 commands in this category.
24584 @findex COMMAND_DATA
24585 @findex gdb.COMMAND_DATA
24586 @item gdb.COMMAND_DATA
24587 The command is related to data or variables. For example,
24588 @code{call}, @code{find}, and @code{print} are in this category. Type
24589 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
24592 @findex COMMAND_STACK
24593 @findex gdb.COMMAND_STACK
24594 @item gdb.COMMAND_STACK
24595 The command has to do with manipulation of the stack. For example,
24596 @code{backtrace}, @code{frame}, and @code{return} are in this
24597 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
24598 list of commands in this category.
24600 @findex COMMAND_FILES
24601 @findex gdb.COMMAND_FILES
24602 @item gdb.COMMAND_FILES
24603 This class is used for file-related commands. For example,
24604 @code{file}, @code{list} and @code{section} are in this category.
24605 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
24606 commands in this category.
24608 @findex COMMAND_SUPPORT
24609 @findex gdb.COMMAND_SUPPORT
24610 @item gdb.COMMAND_SUPPORT
24611 This should be used for ``support facilities'', generally meaning
24612 things that are useful to the user when interacting with @value{GDBN},
24613 but not related to the state of the inferior. For example,
24614 @code{help}, @code{make}, and @code{shell} are in this category. Type
24615 @kbd{help support} at the @value{GDBN} prompt to see a list of
24616 commands in this category.
24618 @findex COMMAND_STATUS
24619 @findex gdb.COMMAND_STATUS
24620 @item gdb.COMMAND_STATUS
24621 The command is an @samp{info}-related command, that is, related to the
24622 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
24623 and @code{show} are in this category. Type @kbd{help status} at the
24624 @value{GDBN} prompt to see a list of commands in this category.
24626 @findex COMMAND_BREAKPOINTS
24627 @findex gdb.COMMAND_BREAKPOINTS
24628 @item gdb.COMMAND_BREAKPOINTS
24629 The command has to do with breakpoints. For example, @code{break},
24630 @code{clear}, and @code{delete} are in this category. Type @kbd{help
24631 breakpoints} at the @value{GDBN} prompt to see a list of commands in
24634 @findex COMMAND_TRACEPOINTS
24635 @findex gdb.COMMAND_TRACEPOINTS
24636 @item gdb.COMMAND_TRACEPOINTS
24637 The command has to do with tracepoints. For example, @code{trace},
24638 @code{actions}, and @code{tfind} are in this category. Type
24639 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
24640 commands in this category.
24642 @findex COMMAND_USER
24643 @findex gdb.COMMAND_USER
24644 @item gdb.COMMAND_USER
24645 The command is a general purpose command for the user, and typically
24646 does not fit in one of the other categories.
24647 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
24648 a list of commands in this category, as well as the list of gdb macros
24649 (@pxref{Sequences}).
24651 @findex COMMAND_OBSCURE
24652 @findex gdb.COMMAND_OBSCURE
24653 @item gdb.COMMAND_OBSCURE
24654 The command is only used in unusual circumstances, or is not of
24655 general interest to users. For example, @code{checkpoint},
24656 @code{fork}, and @code{stop} are in this category. Type @kbd{help
24657 obscure} at the @value{GDBN} prompt to see a list of commands in this
24660 @findex COMMAND_MAINTENANCE
24661 @findex gdb.COMMAND_MAINTENANCE
24662 @item gdb.COMMAND_MAINTENANCE
24663 The command is only useful to @value{GDBN} maintainers. The
24664 @code{maintenance} and @code{flushregs} commands are in this category.
24665 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
24666 commands in this category.
24669 A new command can use a predefined completion function, either by
24670 specifying it via an argument at initialization, or by returning it
24671 from the @code{complete} method. These predefined completion
24672 constants are all defined in the @code{gdb} module:
24675 @findex COMPLETE_NONE
24676 @findex gdb.COMPLETE_NONE
24677 @item gdb.COMPLETE_NONE
24678 This constant means that no completion should be done.
24680 @findex COMPLETE_FILENAME
24681 @findex gdb.COMPLETE_FILENAME
24682 @item gdb.COMPLETE_FILENAME
24683 This constant means that filename completion should be performed.
24685 @findex COMPLETE_LOCATION
24686 @findex gdb.COMPLETE_LOCATION
24687 @item gdb.COMPLETE_LOCATION
24688 This constant means that location completion should be done.
24689 @xref{Specify Location}.
24691 @findex COMPLETE_COMMAND
24692 @findex gdb.COMPLETE_COMMAND
24693 @item gdb.COMPLETE_COMMAND
24694 This constant means that completion should examine @value{GDBN}
24697 @findex COMPLETE_SYMBOL
24698 @findex gdb.COMPLETE_SYMBOL
24699 @item gdb.COMPLETE_SYMBOL
24700 This constant means that completion should be done using symbol names
24704 The following code snippet shows how a trivial CLI command can be
24705 implemented in Python:
24708 class HelloWorld (gdb.Command):
24709 """Greet the whole world."""
24711 def __init__ (self):
24712 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
24714 def invoke (self, arg, from_tty):
24715 print "Hello, World!"
24720 The last line instantiates the class, and is necessary to trigger the
24721 registration of the command with @value{GDBN}. Depending on how the
24722 Python code is read into @value{GDBN}, you may need to import the
24723 @code{gdb} module explicitly.
24725 @node Parameters In Python
24726 @subsubsection Parameters In Python
24728 @cindex parameters in python
24729 @cindex python parameters
24730 @tindex gdb.Parameter
24732 You can implement new @value{GDBN} parameters using Python. A new
24733 parameter is implemented as an instance of the @code{gdb.Parameter}
24736 Parameters are exposed to the user via the @code{set} and
24737 @code{show} commands. @xref{Help}.
24739 There are many parameters that already exist and can be set in
24740 @value{GDBN}. Two examples are: @code{set follow fork} and
24741 @code{set charset}. Setting these parameters influences certain
24742 behavior in @value{GDBN}. Similarly, you can define parameters that
24743 can be used to influence behavior in custom Python scripts and commands.
24745 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
24746 The object initializer for @code{Parameter} registers the new
24747 parameter with @value{GDBN}. This initializer is normally invoked
24748 from the subclass' own @code{__init__} method.
24750 @var{name} is the name of the new parameter. If @var{name} consists
24751 of multiple words, then the initial words are looked for as prefix
24752 parameters. An example of this can be illustrated with the
24753 @code{set print} set of parameters. If @var{name} is
24754 @code{print foo}, then @code{print} will be searched as the prefix
24755 parameter. In this case the parameter can subsequently be accessed in
24756 @value{GDBN} as @code{set print foo}.
24758 If @var{name} consists of multiple words, and no prefix parameter group
24759 can be found, an exception is raised.
24761 @var{command-class} should be one of the @samp{COMMAND_} constants
24762 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
24763 categorize the new parameter in the help system.
24765 @var{parameter-class} should be one of the @samp{PARAM_} constants
24766 defined below. This argument tells @value{GDBN} the type of the new
24767 parameter; this information is used for input validation and
24770 If @var{parameter-class} is @code{PARAM_ENUM}, then
24771 @var{enum-sequence} must be a sequence of strings. These strings
24772 represent the possible values for the parameter.
24774 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
24775 of a fourth argument will cause an exception to be thrown.
24777 The help text for the new parameter is taken from the Python
24778 documentation string for the parameter's class, if there is one. If
24779 there is no documentation string, a default value is used.
24782 @defvar Parameter.set_doc
24783 If this attribute exists, and is a string, then its value is used as
24784 the help text for this parameter's @code{set} command. The value is
24785 examined when @code{Parameter.__init__} is invoked; subsequent changes
24789 @defvar Parameter.show_doc
24790 If this attribute exists, and is a string, then its value is used as
24791 the help text for this parameter's @code{show} command. The value is
24792 examined when @code{Parameter.__init__} is invoked; subsequent changes
24796 @defvar Parameter.value
24797 The @code{value} attribute holds the underlying value of the
24798 parameter. It can be read and assigned to just as any other
24799 attribute. @value{GDBN} does validation when assignments are made.
24802 There are two methods that should be implemented in any
24803 @code{Parameter} class. These are:
24805 @defun Parameter.get_set_string (self)
24806 @value{GDBN} will call this method when a @var{parameter}'s value has
24807 been changed via the @code{set} API (for example, @kbd{set foo off}).
24808 The @code{value} attribute has already been populated with the new
24809 value and may be used in output. This method must return a string.
24812 @defun Parameter.get_show_string (self, svalue)
24813 @value{GDBN} will call this method when a @var{parameter}'s
24814 @code{show} API has been invoked (for example, @kbd{show foo}). The
24815 argument @code{svalue} receives the string representation of the
24816 current value. This method must return a string.
24819 When a new parameter is defined, its type must be specified. The
24820 available types are represented by constants defined in the @code{gdb}
24824 @findex PARAM_BOOLEAN
24825 @findex gdb.PARAM_BOOLEAN
24826 @item gdb.PARAM_BOOLEAN
24827 The value is a plain boolean. The Python boolean values, @code{True}
24828 and @code{False} are the only valid values.
24830 @findex PARAM_AUTO_BOOLEAN
24831 @findex gdb.PARAM_AUTO_BOOLEAN
24832 @item gdb.PARAM_AUTO_BOOLEAN
24833 The value has three possible states: true, false, and @samp{auto}. In
24834 Python, true and false are represented using boolean constants, and
24835 @samp{auto} is represented using @code{None}.
24837 @findex PARAM_UINTEGER
24838 @findex gdb.PARAM_UINTEGER
24839 @item gdb.PARAM_UINTEGER
24840 The value is an unsigned integer. The value of 0 should be
24841 interpreted to mean ``unlimited''.
24843 @findex PARAM_INTEGER
24844 @findex gdb.PARAM_INTEGER
24845 @item gdb.PARAM_INTEGER
24846 The value is a signed integer. The value of 0 should be interpreted
24847 to mean ``unlimited''.
24849 @findex PARAM_STRING
24850 @findex gdb.PARAM_STRING
24851 @item gdb.PARAM_STRING
24852 The value is a string. When the user modifies the string, any escape
24853 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
24854 translated into corresponding characters and encoded into the current
24857 @findex PARAM_STRING_NOESCAPE
24858 @findex gdb.PARAM_STRING_NOESCAPE
24859 @item gdb.PARAM_STRING_NOESCAPE
24860 The value is a string. When the user modifies the string, escapes are
24861 passed through untranslated.
24863 @findex PARAM_OPTIONAL_FILENAME
24864 @findex gdb.PARAM_OPTIONAL_FILENAME
24865 @item gdb.PARAM_OPTIONAL_FILENAME
24866 The value is a either a filename (a string), or @code{None}.
24868 @findex PARAM_FILENAME
24869 @findex gdb.PARAM_FILENAME
24870 @item gdb.PARAM_FILENAME
24871 The value is a filename. This is just like
24872 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
24874 @findex PARAM_ZINTEGER
24875 @findex gdb.PARAM_ZINTEGER
24876 @item gdb.PARAM_ZINTEGER
24877 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
24878 is interpreted as itself.
24881 @findex gdb.PARAM_ENUM
24882 @item gdb.PARAM_ENUM
24883 The value is a string, which must be one of a collection string
24884 constants provided when the parameter is created.
24887 @node Functions In Python
24888 @subsubsection Writing new convenience functions
24890 @cindex writing convenience functions
24891 @cindex convenience functions in python
24892 @cindex python convenience functions
24893 @tindex gdb.Function
24895 You can implement new convenience functions (@pxref{Convenience Vars})
24896 in Python. A convenience function is an instance of a subclass of the
24897 class @code{gdb.Function}.
24899 @defun Function.__init__ (name)
24900 The initializer for @code{Function} registers the new function with
24901 @value{GDBN}. The argument @var{name} is the name of the function,
24902 a string. The function will be visible to the user as a convenience
24903 variable of type @code{internal function}, whose name is the same as
24904 the given @var{name}.
24906 The documentation for the new function is taken from the documentation
24907 string for the new class.
24910 @defun Function.invoke (@var{*args})
24911 When a convenience function is evaluated, its arguments are converted
24912 to instances of @code{gdb.Value}, and then the function's
24913 @code{invoke} method is called. Note that @value{GDBN} does not
24914 predetermine the arity of convenience functions. Instead, all
24915 available arguments are passed to @code{invoke}, following the
24916 standard Python calling convention. In particular, a convenience
24917 function can have default values for parameters without ill effect.
24919 The return value of this method is used as its value in the enclosing
24920 expression. If an ordinary Python value is returned, it is converted
24921 to a @code{gdb.Value} following the usual rules.
24924 The following code snippet shows how a trivial convenience function can
24925 be implemented in Python:
24928 class Greet (gdb.Function):
24929 """Return string to greet someone.
24930 Takes a name as argument."""
24932 def __init__ (self):
24933 super (Greet, self).__init__ ("greet")
24935 def invoke (self, name):
24936 return "Hello, %s!" % name.string ()
24941 The last line instantiates the class, and is necessary to trigger the
24942 registration of the function with @value{GDBN}. Depending on how the
24943 Python code is read into @value{GDBN}, you may need to import the
24944 @code{gdb} module explicitly.
24946 Now you can use the function in an expression:
24949 (gdb) print $greet("Bob")
24953 @node Progspaces In Python
24954 @subsubsection Program Spaces In Python
24956 @cindex progspaces in python
24957 @tindex gdb.Progspace
24959 A program space, or @dfn{progspace}, represents a symbolic view
24960 of an address space.
24961 It consists of all of the objfiles of the program.
24962 @xref{Objfiles In Python}.
24963 @xref{Inferiors and Programs, program spaces}, for more details
24964 about program spaces.
24966 The following progspace-related functions are available in the
24969 @findex gdb.current_progspace
24970 @defun gdb.current_progspace ()
24971 This function returns the program space of the currently selected inferior.
24972 @xref{Inferiors and Programs}.
24975 @findex gdb.progspaces
24976 @defun gdb.progspaces ()
24977 Return a sequence of all the progspaces currently known to @value{GDBN}.
24980 Each progspace is represented by an instance of the @code{gdb.Progspace}
24983 @defvar Progspace.filename
24984 The file name of the progspace as a string.
24987 @defvar Progspace.pretty_printers
24988 The @code{pretty_printers} attribute is a list of functions. It is
24989 used to look up pretty-printers. A @code{Value} is passed to each
24990 function in order; if the function returns @code{None}, then the
24991 search continues. Otherwise, the return value should be an object
24992 which is used to format the value. @xref{Pretty Printing API}, for more
24996 @defvar Progspace.type_printers
24997 The @code{type_printers} attribute is a list of type printer objects.
24998 @xref{Type Printing API}, for more information.
25001 @node Objfiles In Python
25002 @subsubsection Objfiles In Python
25004 @cindex objfiles in python
25005 @tindex gdb.Objfile
25007 @value{GDBN} loads symbols for an inferior from various
25008 symbol-containing files (@pxref{Files}). These include the primary
25009 executable file, any shared libraries used by the inferior, and any
25010 separate debug info files (@pxref{Separate Debug Files}).
25011 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
25013 The following objfile-related functions are available in the
25016 @findex gdb.current_objfile
25017 @defun gdb.current_objfile ()
25018 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
25019 sets the ``current objfile'' to the corresponding objfile. This
25020 function returns the current objfile. If there is no current objfile,
25021 this function returns @code{None}.
25024 @findex gdb.objfiles
25025 @defun gdb.objfiles ()
25026 Return a sequence of all the objfiles current known to @value{GDBN}.
25027 @xref{Objfiles In Python}.
25030 Each objfile is represented by an instance of the @code{gdb.Objfile}
25033 @defvar Objfile.filename
25034 The file name of the objfile as a string.
25037 @defvar Objfile.pretty_printers
25038 The @code{pretty_printers} attribute is a list of functions. It is
25039 used to look up pretty-printers. A @code{Value} is passed to each
25040 function in order; if the function returns @code{None}, then the
25041 search continues. Otherwise, the return value should be an object
25042 which is used to format the value. @xref{Pretty Printing API}, for more
25046 @defvar Objfile.type_printers
25047 The @code{type_printers} attribute is a list of type printer objects.
25048 @xref{Type Printing API}, for more information.
25051 A @code{gdb.Objfile} object has the following methods:
25053 @defun Objfile.is_valid ()
25054 Returns @code{True} if the @code{gdb.Objfile} object is valid,
25055 @code{False} if not. A @code{gdb.Objfile} object can become invalid
25056 if the object file it refers to is not loaded in @value{GDBN} any
25057 longer. All other @code{gdb.Objfile} methods will throw an exception
25058 if it is invalid at the time the method is called.
25061 @node Frames In Python
25062 @subsubsection Accessing inferior stack frames from Python.
25064 @cindex frames in python
25065 When the debugged program stops, @value{GDBN} is able to analyze its call
25066 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
25067 represents a frame in the stack. A @code{gdb.Frame} object is only valid
25068 while its corresponding frame exists in the inferior's stack. If you try
25069 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
25070 exception (@pxref{Exception Handling}).
25072 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
25076 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
25080 The following frame-related functions are available in the @code{gdb} module:
25082 @findex gdb.selected_frame
25083 @defun gdb.selected_frame ()
25084 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
25087 @findex gdb.newest_frame
25088 @defun gdb.newest_frame ()
25089 Return the newest frame object for the selected thread.
25092 @defun gdb.frame_stop_reason_string (reason)
25093 Return a string explaining the reason why @value{GDBN} stopped unwinding
25094 frames, as expressed by the given @var{reason} code (an integer, see the
25095 @code{unwind_stop_reason} method further down in this section).
25098 A @code{gdb.Frame} object has the following methods:
25101 @defun Frame.is_valid ()
25102 Returns true if the @code{gdb.Frame} object is valid, false if not.
25103 A frame object can become invalid if the frame it refers to doesn't
25104 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
25105 an exception if it is invalid at the time the method is called.
25108 @defun Frame.name ()
25109 Returns the function name of the frame, or @code{None} if it can't be
25113 @defun Frame.type ()
25114 Returns the type of the frame. The value can be one of:
25116 @item gdb.NORMAL_FRAME
25117 An ordinary stack frame.
25119 @item gdb.DUMMY_FRAME
25120 A fake stack frame that was created by @value{GDBN} when performing an
25121 inferior function call.
25123 @item gdb.INLINE_FRAME
25124 A frame representing an inlined function. The function was inlined
25125 into a @code{gdb.NORMAL_FRAME} that is older than this one.
25127 @item gdb.TAILCALL_FRAME
25128 A frame representing a tail call. @xref{Tail Call Frames}.
25130 @item gdb.SIGTRAMP_FRAME
25131 A signal trampoline frame. This is the frame created by the OS when
25132 it calls into a signal handler.
25134 @item gdb.ARCH_FRAME
25135 A fake stack frame representing a cross-architecture call.
25137 @item gdb.SENTINEL_FRAME
25138 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
25143 @defun Frame.unwind_stop_reason ()
25144 Return an integer representing the reason why it's not possible to find
25145 more frames toward the outermost frame. Use
25146 @code{gdb.frame_stop_reason_string} to convert the value returned by this
25147 function to a string. The value can be one of:
25150 @item gdb.FRAME_UNWIND_NO_REASON
25151 No particular reason (older frames should be available).
25153 @item gdb.FRAME_UNWIND_NULL_ID
25154 The previous frame's analyzer returns an invalid result.
25156 @item gdb.FRAME_UNWIND_OUTERMOST
25157 This frame is the outermost.
25159 @item gdb.FRAME_UNWIND_UNAVAILABLE
25160 Cannot unwind further, because that would require knowing the
25161 values of registers or memory that have not been collected.
25163 @item gdb.FRAME_UNWIND_INNER_ID
25164 This frame ID looks like it ought to belong to a NEXT frame,
25165 but we got it for a PREV frame. Normally, this is a sign of
25166 unwinder failure. It could also indicate stack corruption.
25168 @item gdb.FRAME_UNWIND_SAME_ID
25169 This frame has the same ID as the previous one. That means
25170 that unwinding further would almost certainly give us another
25171 frame with exactly the same ID, so break the chain. Normally,
25172 this is a sign of unwinder failure. It could also indicate
25175 @item gdb.FRAME_UNWIND_NO_SAVED_PC
25176 The frame unwinder did not find any saved PC, but we needed
25177 one to unwind further.
25179 @item gdb.FRAME_UNWIND_FIRST_ERROR
25180 Any stop reason greater or equal to this value indicates some kind
25181 of error. This special value facilitates writing code that tests
25182 for errors in unwinding in a way that will work correctly even if
25183 the list of the other values is modified in future @value{GDBN}
25184 versions. Using it, you could write:
25186 reason = gdb.selected_frame().unwind_stop_reason ()
25187 reason_str = gdb.frame_stop_reason_string (reason)
25188 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
25189 print "An error occured: %s" % reason_str
25196 Returns the frame's resume address.
25199 @defun Frame.block ()
25200 Return the frame's code block. @xref{Blocks In Python}.
25203 @defun Frame.function ()
25204 Return the symbol for the function corresponding to this frame.
25205 @xref{Symbols In Python}.
25208 @defun Frame.older ()
25209 Return the frame that called this frame.
25212 @defun Frame.newer ()
25213 Return the frame called by this frame.
25216 @defun Frame.find_sal ()
25217 Return the frame's symtab and line object.
25218 @xref{Symbol Tables In Python}.
25221 @defun Frame.read_var (variable @r{[}, block@r{]})
25222 Return the value of @var{variable} in this frame. If the optional
25223 argument @var{block} is provided, search for the variable from that
25224 block; otherwise start at the frame's current block (which is
25225 determined by the frame's current program counter). @var{variable}
25226 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
25227 @code{gdb.Block} object.
25230 @defun Frame.select ()
25231 Set this frame to be the selected frame. @xref{Stack, ,Examining the
25236 @node Blocks In Python
25237 @subsubsection Accessing frame blocks from Python.
25239 @cindex blocks in python
25242 Within each frame, @value{GDBN} maintains information on each block
25243 stored in that frame. These blocks are organized hierarchically, and
25244 are represented individually in Python as a @code{gdb.Block}.
25245 Please see @ref{Frames In Python}, for a more in-depth discussion on
25246 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
25247 detailed technical information on @value{GDBN}'s book-keeping of the
25250 A @code{gdb.Block} is iterable. The iterator returns the symbols
25251 (@pxref{Symbols In Python}) local to the block. Python programs
25252 should not assume that a specific block object will always contain a
25253 given symbol, since changes in @value{GDBN} features and
25254 infrastructure may cause symbols move across blocks in a symbol
25257 The following block-related functions are available in the @code{gdb}
25260 @findex gdb.block_for_pc
25261 @defun gdb.block_for_pc (pc)
25262 Return the @code{gdb.Block} containing the given @var{pc} value. If the
25263 block cannot be found for the @var{pc} value specified, the function
25264 will return @code{None}.
25267 A @code{gdb.Block} object has the following methods:
25270 @defun Block.is_valid ()
25271 Returns @code{True} if the @code{gdb.Block} object is valid,
25272 @code{False} if not. A block object can become invalid if the block it
25273 refers to doesn't exist anymore in the inferior. All other
25274 @code{gdb.Block} methods will throw an exception if it is invalid at
25275 the time the method is called. The block's validity is also checked
25276 during iteration over symbols of the block.
25280 A @code{gdb.Block} object has the following attributes:
25283 @defvar Block.start
25284 The start address of the block. This attribute is not writable.
25288 The end address of the block. This attribute is not writable.
25291 @defvar Block.function
25292 The name of the block represented as a @code{gdb.Symbol}. If the
25293 block is not named, then this attribute holds @code{None}. This
25294 attribute is not writable.
25297 @defvar Block.superblock
25298 The block containing this block. If this parent block does not exist,
25299 this attribute holds @code{None}. This attribute is not writable.
25302 @defvar Block.global_block
25303 The global block associated with this block. This attribute is not
25307 @defvar Block.static_block
25308 The static block associated with this block. This attribute is not
25312 @defvar Block.is_global
25313 @code{True} if the @code{gdb.Block} object is a global block,
25314 @code{False} if not. This attribute is not
25318 @defvar Block.is_static
25319 @code{True} if the @code{gdb.Block} object is a static block,
25320 @code{False} if not. This attribute is not writable.
25324 @node Symbols In Python
25325 @subsubsection Python representation of Symbols.
25327 @cindex symbols in python
25330 @value{GDBN} represents every variable, function and type as an
25331 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
25332 Similarly, Python represents these symbols in @value{GDBN} with the
25333 @code{gdb.Symbol} object.
25335 The following symbol-related functions are available in the @code{gdb}
25338 @findex gdb.lookup_symbol
25339 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
25340 This function searches for a symbol by name. The search scope can be
25341 restricted to the parameters defined in the optional domain and block
25344 @var{name} is the name of the symbol. It must be a string. The
25345 optional @var{block} argument restricts the search to symbols visible
25346 in that @var{block}. The @var{block} argument must be a
25347 @code{gdb.Block} object. If omitted, the block for the current frame
25348 is used. The optional @var{domain} argument restricts
25349 the search to the domain type. The @var{domain} argument must be a
25350 domain constant defined in the @code{gdb} module and described later
25353 The result is a tuple of two elements.
25354 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
25356 If the symbol is found, the second element is @code{True} if the symbol
25357 is a field of a method's object (e.g., @code{this} in C@t{++}),
25358 otherwise it is @code{False}.
25359 If the symbol is not found, the second element is @code{False}.
25362 @findex gdb.lookup_global_symbol
25363 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
25364 This function searches for a global symbol by name.
25365 The search scope can be restricted to by the domain argument.
25367 @var{name} is the name of the symbol. It must be a string.
25368 The optional @var{domain} argument restricts the search to the domain type.
25369 The @var{domain} argument must be a domain constant defined in the @code{gdb}
25370 module and described later in this chapter.
25372 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
25376 A @code{gdb.Symbol} object has the following attributes:
25379 @defvar Symbol.type
25380 The type of the symbol or @code{None} if no type is recorded.
25381 This attribute is represented as a @code{gdb.Type} object.
25382 @xref{Types In Python}. This attribute is not writable.
25385 @defvar Symbol.symtab
25386 The symbol table in which the symbol appears. This attribute is
25387 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
25388 Python}. This attribute is not writable.
25391 @defvar Symbol.line
25392 The line number in the source code at which the symbol was defined.
25393 This is an integer.
25396 @defvar Symbol.name
25397 The name of the symbol as a string. This attribute is not writable.
25400 @defvar Symbol.linkage_name
25401 The name of the symbol, as used by the linker (i.e., may be mangled).
25402 This attribute is not writable.
25405 @defvar Symbol.print_name
25406 The name of the symbol in a form suitable for output. This is either
25407 @code{name} or @code{linkage_name}, depending on whether the user
25408 asked @value{GDBN} to display demangled or mangled names.
25411 @defvar Symbol.addr_class
25412 The address class of the symbol. This classifies how to find the value
25413 of a symbol. Each address class is a constant defined in the
25414 @code{gdb} module and described later in this chapter.
25417 @defvar Symbol.needs_frame
25418 This is @code{True} if evaluating this symbol's value requires a frame
25419 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
25420 local variables will require a frame, but other symbols will not.
25423 @defvar Symbol.is_argument
25424 @code{True} if the symbol is an argument of a function.
25427 @defvar Symbol.is_constant
25428 @code{True} if the symbol is a constant.
25431 @defvar Symbol.is_function
25432 @code{True} if the symbol is a function or a method.
25435 @defvar Symbol.is_variable
25436 @code{True} if the symbol is a variable.
25440 A @code{gdb.Symbol} object has the following methods:
25443 @defun Symbol.is_valid ()
25444 Returns @code{True} if the @code{gdb.Symbol} object is valid,
25445 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
25446 the symbol it refers to does not exist in @value{GDBN} any longer.
25447 All other @code{gdb.Symbol} methods will throw an exception if it is
25448 invalid at the time the method is called.
25451 @defun Symbol.value (@r{[}frame@r{]})
25452 Compute the value of the symbol, as a @code{gdb.Value}. For
25453 functions, this computes the address of the function, cast to the
25454 appropriate type. If the symbol requires a frame in order to compute
25455 its value, then @var{frame} must be given. If @var{frame} is not
25456 given, or if @var{frame} is invalid, then this method will throw an
25461 The available domain categories in @code{gdb.Symbol} are represented
25462 as constants in the @code{gdb} module:
25465 @findex SYMBOL_UNDEF_DOMAIN
25466 @findex gdb.SYMBOL_UNDEF_DOMAIN
25467 @item gdb.SYMBOL_UNDEF_DOMAIN
25468 This is used when a domain has not been discovered or none of the
25469 following domains apply. This usually indicates an error either
25470 in the symbol information or in @value{GDBN}'s handling of symbols.
25471 @findex SYMBOL_VAR_DOMAIN
25472 @findex gdb.SYMBOL_VAR_DOMAIN
25473 @item gdb.SYMBOL_VAR_DOMAIN
25474 This domain contains variables, function names, typedef names and enum
25476 @findex SYMBOL_STRUCT_DOMAIN
25477 @findex gdb.SYMBOL_STRUCT_DOMAIN
25478 @item gdb.SYMBOL_STRUCT_DOMAIN
25479 This domain holds struct, union and enum type names.
25480 @findex SYMBOL_LABEL_DOMAIN
25481 @findex gdb.SYMBOL_LABEL_DOMAIN
25482 @item gdb.SYMBOL_LABEL_DOMAIN
25483 This domain contains names of labels (for gotos).
25484 @findex SYMBOL_VARIABLES_DOMAIN
25485 @findex gdb.SYMBOL_VARIABLES_DOMAIN
25486 @item gdb.SYMBOL_VARIABLES_DOMAIN
25487 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
25488 contains everything minus functions and types.
25489 @findex SYMBOL_FUNCTIONS_DOMAIN
25490 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
25491 @item gdb.SYMBOL_FUNCTION_DOMAIN
25492 This domain contains all functions.
25493 @findex SYMBOL_TYPES_DOMAIN
25494 @findex gdb.SYMBOL_TYPES_DOMAIN
25495 @item gdb.SYMBOL_TYPES_DOMAIN
25496 This domain contains all types.
25499 The available address class categories in @code{gdb.Symbol} are represented
25500 as constants in the @code{gdb} module:
25503 @findex SYMBOL_LOC_UNDEF
25504 @findex gdb.SYMBOL_LOC_UNDEF
25505 @item gdb.SYMBOL_LOC_UNDEF
25506 If this is returned by address class, it indicates an error either in
25507 the symbol information or in @value{GDBN}'s handling of symbols.
25508 @findex SYMBOL_LOC_CONST
25509 @findex gdb.SYMBOL_LOC_CONST
25510 @item gdb.SYMBOL_LOC_CONST
25511 Value is constant int.
25512 @findex SYMBOL_LOC_STATIC
25513 @findex gdb.SYMBOL_LOC_STATIC
25514 @item gdb.SYMBOL_LOC_STATIC
25515 Value is at a fixed address.
25516 @findex SYMBOL_LOC_REGISTER
25517 @findex gdb.SYMBOL_LOC_REGISTER
25518 @item gdb.SYMBOL_LOC_REGISTER
25519 Value is in a register.
25520 @findex SYMBOL_LOC_ARG
25521 @findex gdb.SYMBOL_LOC_ARG
25522 @item gdb.SYMBOL_LOC_ARG
25523 Value is an argument. This value is at the offset stored within the
25524 symbol inside the frame's argument list.
25525 @findex SYMBOL_LOC_REF_ARG
25526 @findex gdb.SYMBOL_LOC_REF_ARG
25527 @item gdb.SYMBOL_LOC_REF_ARG
25528 Value address is stored in the frame's argument list. Just like
25529 @code{LOC_ARG} except that the value's address is stored at the
25530 offset, not the value itself.
25531 @findex SYMBOL_LOC_REGPARM_ADDR
25532 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
25533 @item gdb.SYMBOL_LOC_REGPARM_ADDR
25534 Value is a specified register. Just like @code{LOC_REGISTER} except
25535 the register holds the address of the argument instead of the argument
25537 @findex SYMBOL_LOC_LOCAL
25538 @findex gdb.SYMBOL_LOC_LOCAL
25539 @item gdb.SYMBOL_LOC_LOCAL
25540 Value is a local variable.
25541 @findex SYMBOL_LOC_TYPEDEF
25542 @findex gdb.SYMBOL_LOC_TYPEDEF
25543 @item gdb.SYMBOL_LOC_TYPEDEF
25544 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
25546 @findex SYMBOL_LOC_BLOCK
25547 @findex gdb.SYMBOL_LOC_BLOCK
25548 @item gdb.SYMBOL_LOC_BLOCK
25550 @findex SYMBOL_LOC_CONST_BYTES
25551 @findex gdb.SYMBOL_LOC_CONST_BYTES
25552 @item gdb.SYMBOL_LOC_CONST_BYTES
25553 Value is a byte-sequence.
25554 @findex SYMBOL_LOC_UNRESOLVED
25555 @findex gdb.SYMBOL_LOC_UNRESOLVED
25556 @item gdb.SYMBOL_LOC_UNRESOLVED
25557 Value is at a fixed address, but the address of the variable has to be
25558 determined from the minimal symbol table whenever the variable is
25560 @findex SYMBOL_LOC_OPTIMIZED_OUT
25561 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
25562 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
25563 The value does not actually exist in the program.
25564 @findex SYMBOL_LOC_COMPUTED
25565 @findex gdb.SYMBOL_LOC_COMPUTED
25566 @item gdb.SYMBOL_LOC_COMPUTED
25567 The value's address is a computed location.
25570 @node Symbol Tables In Python
25571 @subsubsection Symbol table representation in Python.
25573 @cindex symbol tables in python
25575 @tindex gdb.Symtab_and_line
25577 Access to symbol table data maintained by @value{GDBN} on the inferior
25578 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
25579 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
25580 from the @code{find_sal} method in @code{gdb.Frame} object.
25581 @xref{Frames In Python}.
25583 For more information on @value{GDBN}'s symbol table management, see
25584 @ref{Symbols, ,Examining the Symbol Table}, for more information.
25586 A @code{gdb.Symtab_and_line} object has the following attributes:
25589 @defvar Symtab_and_line.symtab
25590 The symbol table object (@code{gdb.Symtab}) for this frame.
25591 This attribute is not writable.
25594 @defvar Symtab_and_line.pc
25595 Indicates the start of the address range occupied by code for the
25596 current source line. This attribute is not writable.
25599 @defvar Symtab_and_line.last
25600 Indicates the end of the address range occupied by code for the current
25601 source line. This attribute is not writable.
25604 @defvar Symtab_and_line.line
25605 Indicates the current line number for this object. This
25606 attribute is not writable.
25610 A @code{gdb.Symtab_and_line} object has the following methods:
25613 @defun Symtab_and_line.is_valid ()
25614 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
25615 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
25616 invalid if the Symbol table and line object it refers to does not
25617 exist in @value{GDBN} any longer. All other
25618 @code{gdb.Symtab_and_line} methods will throw an exception if it is
25619 invalid at the time the method is called.
25623 A @code{gdb.Symtab} object has the following attributes:
25626 @defvar Symtab.filename
25627 The symbol table's source filename. This attribute is not writable.
25630 @defvar Symtab.objfile
25631 The symbol table's backing object file. @xref{Objfiles In Python}.
25632 This attribute is not writable.
25636 A @code{gdb.Symtab} object has the following methods:
25639 @defun Symtab.is_valid ()
25640 Returns @code{True} if the @code{gdb.Symtab} object is valid,
25641 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
25642 the symbol table it refers to does not exist in @value{GDBN} any
25643 longer. All other @code{gdb.Symtab} methods will throw an exception
25644 if it is invalid at the time the method is called.
25647 @defun Symtab.fullname ()
25648 Return the symbol table's source absolute file name.
25651 @defun Symtab.global_block ()
25652 Return the global block of the underlying symbol table.
25653 @xref{Blocks In Python}.
25656 @defun Symtab.static_block ()
25657 Return the static block of the underlying symbol table.
25658 @xref{Blocks In Python}.
25662 @node Breakpoints In Python
25663 @subsubsection Manipulating breakpoints using Python
25665 @cindex breakpoints in python
25666 @tindex gdb.Breakpoint
25668 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
25671 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
25672 Create a new breakpoint. @var{spec} is a string naming the
25673 location of the breakpoint, or an expression that defines a
25674 watchpoint. The contents can be any location recognized by the
25675 @code{break} command, or in the case of a watchpoint, by the @code{watch}
25676 command. The optional @var{type} denotes the breakpoint to create
25677 from the types defined later in this chapter. This argument can be
25678 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
25679 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
25680 allows the breakpoint to become invisible to the user. The breakpoint
25681 will neither be reported when created, nor will it be listed in the
25682 output from @code{info breakpoints} (but will be listed with the
25683 @code{maint info breakpoints} command). The optional @var{wp_class}
25684 argument defines the class of watchpoint to create, if @var{type} is
25685 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
25686 assumed to be a @code{gdb.WP_WRITE} class.
25689 @defun Breakpoint.stop (self)
25690 The @code{gdb.Breakpoint} class can be sub-classed and, in
25691 particular, you may choose to implement the @code{stop} method.
25692 If this method is defined as a sub-class of @code{gdb.Breakpoint},
25693 it will be called when the inferior reaches any location of a
25694 breakpoint which instantiates that sub-class. If the method returns
25695 @code{True}, the inferior will be stopped at the location of the
25696 breakpoint, otherwise the inferior will continue.
25698 If there are multiple breakpoints at the same location with a
25699 @code{stop} method, each one will be called regardless of the
25700 return status of the previous. This ensures that all @code{stop}
25701 methods have a chance to execute at that location. In this scenario
25702 if one of the methods returns @code{True} but the others return
25703 @code{False}, the inferior will still be stopped.
25705 You should not alter the execution state of the inferior (i.e.@:, step,
25706 next, etc.), alter the current frame context (i.e.@:, change the current
25707 active frame), or alter, add or delete any breakpoint. As a general
25708 rule, you should not alter any data within @value{GDBN} or the inferior
25711 Example @code{stop} implementation:
25714 class MyBreakpoint (gdb.Breakpoint):
25716 inf_val = gdb.parse_and_eval("foo")
25723 The available watchpoint types represented by constants are defined in the
25728 @findex gdb.WP_READ
25730 Read only watchpoint.
25733 @findex gdb.WP_WRITE
25735 Write only watchpoint.
25738 @findex gdb.WP_ACCESS
25739 @item gdb.WP_ACCESS
25740 Read/Write watchpoint.
25743 @defun Breakpoint.is_valid ()
25744 Return @code{True} if this @code{Breakpoint} object is valid,
25745 @code{False} otherwise. A @code{Breakpoint} object can become invalid
25746 if the user deletes the breakpoint. In this case, the object still
25747 exists, but the underlying breakpoint does not. In the cases of
25748 watchpoint scope, the watchpoint remains valid even if execution of the
25749 inferior leaves the scope of that watchpoint.
25752 @defun Breakpoint.delete
25753 Permanently deletes the @value{GDBN} breakpoint. This also
25754 invalidates the Python @code{Breakpoint} object. Any further access
25755 to this object's attributes or methods will raise an error.
25758 @defvar Breakpoint.enabled
25759 This attribute is @code{True} if the breakpoint is enabled, and
25760 @code{False} otherwise. This attribute is writable.
25763 @defvar Breakpoint.silent
25764 This attribute is @code{True} if the breakpoint is silent, and
25765 @code{False} otherwise. This attribute is writable.
25767 Note that a breakpoint can also be silent if it has commands and the
25768 first command is @code{silent}. This is not reported by the
25769 @code{silent} attribute.
25772 @defvar Breakpoint.thread
25773 If the breakpoint is thread-specific, this attribute holds the thread
25774 id. If the breakpoint is not thread-specific, this attribute is
25775 @code{None}. This attribute is writable.
25778 @defvar Breakpoint.task
25779 If the breakpoint is Ada task-specific, this attribute holds the Ada task
25780 id. If the breakpoint is not task-specific (or the underlying
25781 language is not Ada), this attribute is @code{None}. This attribute
25785 @defvar Breakpoint.ignore_count
25786 This attribute holds the ignore count for the breakpoint, an integer.
25787 This attribute is writable.
25790 @defvar Breakpoint.number
25791 This attribute holds the breakpoint's number --- the identifier used by
25792 the user to manipulate the breakpoint. This attribute is not writable.
25795 @defvar Breakpoint.type
25796 This attribute holds the breakpoint's type --- the identifier used to
25797 determine the actual breakpoint type or use-case. This attribute is not
25801 @defvar Breakpoint.visible
25802 This attribute tells whether the breakpoint is visible to the user
25803 when set, or when the @samp{info breakpoints} command is run. This
25804 attribute is not writable.
25807 The available types are represented by constants defined in the @code{gdb}
25811 @findex BP_BREAKPOINT
25812 @findex gdb.BP_BREAKPOINT
25813 @item gdb.BP_BREAKPOINT
25814 Normal code breakpoint.
25816 @findex BP_WATCHPOINT
25817 @findex gdb.BP_WATCHPOINT
25818 @item gdb.BP_WATCHPOINT
25819 Watchpoint breakpoint.
25821 @findex BP_HARDWARE_WATCHPOINT
25822 @findex gdb.BP_HARDWARE_WATCHPOINT
25823 @item gdb.BP_HARDWARE_WATCHPOINT
25824 Hardware assisted watchpoint.
25826 @findex BP_READ_WATCHPOINT
25827 @findex gdb.BP_READ_WATCHPOINT
25828 @item gdb.BP_READ_WATCHPOINT
25829 Hardware assisted read watchpoint.
25831 @findex BP_ACCESS_WATCHPOINT
25832 @findex gdb.BP_ACCESS_WATCHPOINT
25833 @item gdb.BP_ACCESS_WATCHPOINT
25834 Hardware assisted access watchpoint.
25837 @defvar Breakpoint.hit_count
25838 This attribute holds the hit count for the breakpoint, an integer.
25839 This attribute is writable, but currently it can only be set to zero.
25842 @defvar Breakpoint.location
25843 This attribute holds the location of the breakpoint, as specified by
25844 the user. It is a string. If the breakpoint does not have a location
25845 (that is, it is a watchpoint) the attribute's value is @code{None}. This
25846 attribute is not writable.
25849 @defvar Breakpoint.expression
25850 This attribute holds a breakpoint expression, as specified by
25851 the user. It is a string. If the breakpoint does not have an
25852 expression (the breakpoint is not a watchpoint) the attribute's value
25853 is @code{None}. This attribute is not writable.
25856 @defvar Breakpoint.condition
25857 This attribute holds the condition of the breakpoint, as specified by
25858 the user. It is a string. If there is no condition, this attribute's
25859 value is @code{None}. This attribute is writable.
25862 @defvar Breakpoint.commands
25863 This attribute holds the commands attached to the breakpoint. If
25864 there are commands, this attribute's value is a string holding all the
25865 commands, separated by newlines. If there are no commands, this
25866 attribute is @code{None}. This attribute is not writable.
25869 @node Finish Breakpoints in Python
25870 @subsubsection Finish Breakpoints
25872 @cindex python finish breakpoints
25873 @tindex gdb.FinishBreakpoint
25875 A finish breakpoint is a temporary breakpoint set at the return address of
25876 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
25877 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
25878 and deleted when the execution will run out of the breakpoint scope (i.e.@:
25879 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
25880 Finish breakpoints are thread specific and must be create with the right
25883 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
25884 Create a finish breakpoint at the return address of the @code{gdb.Frame}
25885 object @var{frame}. If @var{frame} is not provided, this defaults to the
25886 newest frame. The optional @var{internal} argument allows the breakpoint to
25887 become invisible to the user. @xref{Breakpoints In Python}, for further
25888 details about this argument.
25891 @defun FinishBreakpoint.out_of_scope (self)
25892 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
25893 @code{return} command, @dots{}), a function may not properly terminate, and
25894 thus never hit the finish breakpoint. When @value{GDBN} notices such a
25895 situation, the @code{out_of_scope} callback will be triggered.
25897 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
25901 class MyFinishBreakpoint (gdb.FinishBreakpoint)
25903 print "normal finish"
25906 def out_of_scope ():
25907 print "abnormal finish"
25911 @defvar FinishBreakpoint.return_value
25912 When @value{GDBN} is stopped at a finish breakpoint and the frame
25913 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
25914 attribute will contain a @code{gdb.Value} object corresponding to the return
25915 value of the function. The value will be @code{None} if the function return
25916 type is @code{void} or if the return value was not computable. This attribute
25920 @node Lazy Strings In Python
25921 @subsubsection Python representation of lazy strings.
25923 @cindex lazy strings in python
25924 @tindex gdb.LazyString
25926 A @dfn{lazy string} is a string whose contents is not retrieved or
25927 encoded until it is needed.
25929 A @code{gdb.LazyString} is represented in @value{GDBN} as an
25930 @code{address} that points to a region of memory, an @code{encoding}
25931 that will be used to encode that region of memory, and a @code{length}
25932 to delimit the region of memory that represents the string. The
25933 difference between a @code{gdb.LazyString} and a string wrapped within
25934 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
25935 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
25936 retrieved and encoded during printing, while a @code{gdb.Value}
25937 wrapping a string is immediately retrieved and encoded on creation.
25939 A @code{gdb.LazyString} object has the following functions:
25941 @defun LazyString.value ()
25942 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
25943 will point to the string in memory, but will lose all the delayed
25944 retrieval, encoding and handling that @value{GDBN} applies to a
25945 @code{gdb.LazyString}.
25948 @defvar LazyString.address
25949 This attribute holds the address of the string. This attribute is not
25953 @defvar LazyString.length
25954 This attribute holds the length of the string in characters. If the
25955 length is -1, then the string will be fetched and encoded up to the
25956 first null of appropriate width. This attribute is not writable.
25959 @defvar LazyString.encoding
25960 This attribute holds the encoding that will be applied to the string
25961 when the string is printed by @value{GDBN}. If the encoding is not
25962 set, or contains an empty string, then @value{GDBN} will select the
25963 most appropriate encoding when the string is printed. This attribute
25967 @defvar LazyString.type
25968 This attribute holds the type that is represented by the lazy string's
25969 type. For a lazy string this will always be a pointer type. To
25970 resolve this to the lazy string's character type, use the type's
25971 @code{target} method. @xref{Types In Python}. This attribute is not
25975 @node Python Auto-loading
25976 @subsection Python Auto-loading
25977 @cindex Python auto-loading
25979 When a new object file is read (for example, due to the @code{file}
25980 command, or because the inferior has loaded a shared library),
25981 @value{GDBN} will look for Python support scripts in several ways:
25982 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
25983 and @code{.debug_gdb_scripts} section
25984 (@pxref{dotdebug_gdb_scripts section}).
25986 The auto-loading feature is useful for supplying application-specific
25987 debugging commands and scripts.
25989 Auto-loading can be enabled or disabled,
25990 and the list of auto-loaded scripts can be printed.
25993 @anchor{set auto-load python-scripts}
25994 @kindex set auto-load python-scripts
25995 @item set auto-load python-scripts [on|off]
25996 Enable or disable the auto-loading of Python scripts.
25998 @anchor{show auto-load python-scripts}
25999 @kindex show auto-load python-scripts
26000 @item show auto-load python-scripts
26001 Show whether auto-loading of Python scripts is enabled or disabled.
26003 @anchor{info auto-load python-scripts}
26004 @kindex info auto-load python-scripts
26005 @cindex print list of auto-loaded Python scripts
26006 @item info auto-load python-scripts [@var{regexp}]
26007 Print the list of all Python scripts that @value{GDBN} auto-loaded.
26009 Also printed is the list of Python scripts that were mentioned in
26010 the @code{.debug_gdb_scripts} section and were not found
26011 (@pxref{dotdebug_gdb_scripts section}).
26012 This is useful because their names are not printed when @value{GDBN}
26013 tries to load them and fails. There may be many of them, and printing
26014 an error message for each one is problematic.
26016 If @var{regexp} is supplied only Python scripts with matching names are printed.
26021 (gdb) info auto-load python-scripts
26023 Yes py-section-script.py
26024 full name: /tmp/py-section-script.py
26025 No my-foo-pretty-printers.py
26029 When reading an auto-loaded file, @value{GDBN} sets the
26030 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
26031 function (@pxref{Objfiles In Python}). This can be useful for
26032 registering objfile-specific pretty-printers.
26035 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
26036 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
26037 * Which flavor to choose?::
26040 @node objfile-gdb.py file
26041 @subsubsection The @file{@var{objfile}-gdb.py} file
26042 @cindex @file{@var{objfile}-gdb.py}
26044 When a new object file is read, @value{GDBN} looks for
26045 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
26046 where @var{objfile} is the object file's real name, formed by ensuring
26047 that the file name is absolute, following all symlinks, and resolving
26048 @code{.} and @code{..} components. If this file exists and is
26049 readable, @value{GDBN} will evaluate it as a Python script.
26051 If this file does not exist, then @value{GDBN} will look for
26052 @var{script-name} file in all of the directories as specified below.
26054 Note that loading of this script file also requires accordingly configured
26055 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26057 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26058 scripts normally according to its @file{.exe} filename. But if no scripts are
26059 found @value{GDBN} also tries script filenames matching the object file without
26060 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26061 is attempted on any platform. This makes the script filenames compatible
26062 between Unix and MS-Windows hosts.
26065 @anchor{set auto-load scripts-directory}
26066 @kindex set auto-load scripts-directory
26067 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26068 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26069 may be delimited by the host platform path separator in use
26070 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26072 Each entry here needs to be covered also by the security setting
26073 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26075 @anchor{with-auto-load-dir}
26076 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26077 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26078 configuration option @option{--with-auto-load-dir}.
26080 Any reference to @file{$debugdir} will get replaced by
26081 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26082 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26083 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26084 @file{$datadir} must be placed as a directory component --- either alone or
26085 delimited by @file{/} or @file{\} directory separators, depending on the host
26088 The list of directories uses path separator (@samp{:} on GNU and Unix
26089 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26090 to the @env{PATH} environment variable.
26092 @anchor{show auto-load scripts-directory}
26093 @kindex show auto-load scripts-directory
26094 @item show auto-load scripts-directory
26095 Show @value{GDBN} auto-loaded scripts location.
26098 @value{GDBN} does not track which files it has already auto-loaded this way.
26099 @value{GDBN} will load the associated script every time the corresponding
26100 @var{objfile} is opened.
26101 So your @file{-gdb.py} file should be careful to avoid errors if it
26102 is evaluated more than once.
26104 @node dotdebug_gdb_scripts section
26105 @subsubsection The @code{.debug_gdb_scripts} section
26106 @cindex @code{.debug_gdb_scripts} section
26108 For systems using file formats like ELF and COFF,
26109 when @value{GDBN} loads a new object file
26110 it will look for a special section named @samp{.debug_gdb_scripts}.
26111 If this section exists, its contents is a list of names of scripts to load.
26113 @value{GDBN} will look for each specified script file first in the
26114 current directory and then along the source search path
26115 (@pxref{Source Path, ,Specifying Source Directories}),
26116 except that @file{$cdir} is not searched, since the compilation
26117 directory is not relevant to scripts.
26119 Entries can be placed in section @code{.debug_gdb_scripts} with,
26120 for example, this GCC macro:
26123 /* Note: The "MS" section flags are to remove duplicates. */
26124 #define DEFINE_GDB_SCRIPT(script_name) \
26126 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26128 .asciz \"" script_name "\"\n\
26134 Then one can reference the macro in a header or source file like this:
26137 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
26140 The script name may include directories if desired.
26142 Note that loading of this script file also requires accordingly configured
26143 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26145 If the macro is put in a header, any application or library
26146 using this header will get a reference to the specified script.
26148 @node Which flavor to choose?
26149 @subsubsection Which flavor to choose?
26151 Given the multiple ways of auto-loading Python scripts, it might not always
26152 be clear which one to choose. This section provides some guidance.
26154 Benefits of the @file{-gdb.py} way:
26158 Can be used with file formats that don't support multiple sections.
26161 Ease of finding scripts for public libraries.
26163 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
26164 in the source search path.
26165 For publicly installed libraries, e.g., @file{libstdc++}, there typically
26166 isn't a source directory in which to find the script.
26169 Doesn't require source code additions.
26172 Benefits of the @code{.debug_gdb_scripts} way:
26176 Works with static linking.
26178 Scripts for libraries done the @file{-gdb.py} way require an objfile to
26179 trigger their loading. When an application is statically linked the only
26180 objfile available is the executable, and it is cumbersome to attach all the
26181 scripts from all the input libraries to the executable's @file{-gdb.py} script.
26184 Works with classes that are entirely inlined.
26186 Some classes can be entirely inlined, and thus there may not be an associated
26187 shared library to attach a @file{-gdb.py} script to.
26190 Scripts needn't be copied out of the source tree.
26192 In some circumstances, apps can be built out of large collections of internal
26193 libraries, and the build infrastructure necessary to install the
26194 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
26195 cumbersome. It may be easier to specify the scripts in the
26196 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26197 top of the source tree to the source search path.
26200 @node Python modules
26201 @subsection Python modules
26202 @cindex python modules
26204 @value{GDBN} comes with several modules to assist writing Python code.
26207 * gdb.printing:: Building and registering pretty-printers.
26208 * gdb.types:: Utilities for working with types.
26209 * gdb.prompt:: Utilities for prompt value substitution.
26213 @subsubsection gdb.printing
26214 @cindex gdb.printing
26216 This module provides a collection of utilities for working with
26220 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
26221 This class specifies the API that makes @samp{info pretty-printer},
26222 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
26223 Pretty-printers should generally inherit from this class.
26225 @item SubPrettyPrinter (@var{name})
26226 For printers that handle multiple types, this class specifies the
26227 corresponding API for the subprinters.
26229 @item RegexpCollectionPrettyPrinter (@var{name})
26230 Utility class for handling multiple printers, all recognized via
26231 regular expressions.
26232 @xref{Writing a Pretty-Printer}, for an example.
26234 @item FlagEnumerationPrinter (@var{name})
26235 A pretty-printer which handles printing of @code{enum} values. Unlike
26236 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
26237 work properly when there is some overlap between the enumeration
26238 constants. @var{name} is the name of the printer and also the name of
26239 the @code{enum} type to look up.
26241 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
26242 Register @var{printer} with the pretty-printer list of @var{obj}.
26243 If @var{replace} is @code{True} then any existing copy of the printer
26244 is replaced. Otherwise a @code{RuntimeError} exception is raised
26245 if a printer with the same name already exists.
26249 @subsubsection gdb.types
26252 This module provides a collection of utilities for working with
26253 @code{gdb.Type} objects.
26256 @item get_basic_type (@var{type})
26257 Return @var{type} with const and volatile qualifiers stripped,
26258 and with typedefs and C@t{++} references converted to the underlying type.
26263 typedef const int const_int;
26265 const_int& foo_ref (foo);
26266 int main () @{ return 0; @}
26273 (gdb) python import gdb.types
26274 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
26275 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
26279 @item has_field (@var{type}, @var{field})
26280 Return @code{True} if @var{type}, assumed to be a type with fields
26281 (e.g., a structure or union), has field @var{field}.
26283 @item make_enum_dict (@var{enum_type})
26284 Return a Python @code{dictionary} type produced from @var{enum_type}.
26286 @item deep_items (@var{type})
26287 Returns a Python iterator similar to the standard
26288 @code{gdb.Type.iteritems} method, except that the iterator returned
26289 by @code{deep_items} will recursively traverse anonymous struct or
26290 union fields. For example:
26304 Then in @value{GDBN}:
26306 (@value{GDBP}) python import gdb.types
26307 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
26308 (@value{GDBP}) python print struct_a.keys ()
26310 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
26311 @{['a', 'b0', 'b1']@}
26314 @item get_type_recognizers ()
26315 Return a list of the enabled type recognizers for the current context.
26316 This is called by @value{GDBN} during the type-printing process
26317 (@pxref{Type Printing API}).
26319 @item apply_type_recognizers (recognizers, type_obj)
26320 Apply the type recognizers, @var{recognizers}, to the type object
26321 @var{type_obj}. If any recognizer returns a string, return that
26322 string. Otherwise, return @code{None}. This is called by
26323 @value{GDBN} during the type-printing process (@pxref{Type Printing
26326 @item register_type_printer (locus, printer)
26327 This is a convenience function to register a type printer.
26328 @var{printer} is the type printer to register. It must implement the
26329 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
26330 which case the printer is registered with that objfile; a
26331 @code{gdb.Progspace}, in which case the printer is registered with
26332 that progspace; or @code{None}, in which case the printer is
26333 registered globally.
26336 This is a base class that implements the type printer protocol. Type
26337 printers are encouraged, but not required, to derive from this class.
26338 It defines a constructor:
26340 @defmethod TypePrinter __init__ (self, name)
26341 Initialize the type printer with the given name. The new printer
26342 starts in the enabled state.
26348 @subsubsection gdb.prompt
26351 This module provides a method for prompt value-substitution.
26354 @item substitute_prompt (@var{string})
26355 Return @var{string} with escape sequences substituted by values. Some
26356 escape sequences take arguments. You can specify arguments inside
26357 ``@{@}'' immediately following the escape sequence.
26359 The escape sequences you can pass to this function are:
26363 Substitute a backslash.
26365 Substitute an ESC character.
26367 Substitute the selected frame; an argument names a frame parameter.
26369 Substitute a newline.
26371 Substitute a parameter's value; the argument names the parameter.
26373 Substitute a carriage return.
26375 Substitute the selected thread; an argument names a thread parameter.
26377 Substitute the version of GDB.
26379 Substitute the current working directory.
26381 Begin a sequence of non-printing characters. These sequences are
26382 typically used with the ESC character, and are not counted in the string
26383 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
26384 blue-colored ``(gdb)'' prompt where the length is five.
26386 End a sequence of non-printing characters.
26392 substitute_prompt (``frame: \f,
26393 print arguments: \p@{print frame-arguments@}'')
26396 @exdent will return the string:
26399 "frame: main, print arguments: scalars"
26404 @section Creating new spellings of existing commands
26405 @cindex aliases for commands
26407 It is often useful to define alternate spellings of existing commands.
26408 For example, if a new @value{GDBN} command defined in Python has
26409 a long name to type, it is handy to have an abbreviated version of it
26410 that involves less typing.
26412 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26413 of the @samp{step} command even though it is otherwise an ambiguous
26414 abbreviation of other commands like @samp{set} and @samp{show}.
26416 Aliases are also used to provide shortened or more common versions
26417 of multi-word commands. For example, @value{GDBN} provides the
26418 @samp{tty} alias of the @samp{set inferior-tty} command.
26420 You can define a new alias with the @samp{alias} command.
26425 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26429 @var{ALIAS} specifies the name of the new alias.
26430 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26433 @var{COMMAND} specifies the name of an existing command
26434 that is being aliased.
26436 The @samp{-a} option specifies that the new alias is an abbreviation
26437 of the command. Abbreviations are not shown in command
26438 lists displayed by the @samp{help} command.
26440 The @samp{--} option specifies the end of options,
26441 and is useful when @var{ALIAS} begins with a dash.
26443 Here is a simple example showing how to make an abbreviation
26444 of a command so that there is less to type.
26445 Suppose you were tired of typing @samp{disas}, the current
26446 shortest unambiguous abbreviation of the @samp{disassemble} command
26447 and you wanted an even shorter version named @samp{di}.
26448 The following will accomplish this.
26451 (gdb) alias -a di = disas
26454 Note that aliases are different from user-defined commands.
26455 With a user-defined command, you also need to write documentation
26456 for it with the @samp{document} command.
26457 An alias automatically picks up the documentation of the existing command.
26459 Here is an example where we make @samp{elms} an abbreviation of
26460 @samp{elements} in the @samp{set print elements} command.
26461 This is to show that you can make an abbreviation of any part
26465 (gdb) alias -a set print elms = set print elements
26466 (gdb) alias -a show print elms = show print elements
26467 (gdb) set p elms 20
26469 Limit on string chars or array elements to print is 200.
26472 Note that if you are defining an alias of a @samp{set} command,
26473 and you want to have an alias for the corresponding @samp{show}
26474 command, then you need to define the latter separately.
26476 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26477 @var{ALIAS}, just as they are normally.
26480 (gdb) alias -a set pr elms = set p ele
26483 Finally, here is an example showing the creation of a one word
26484 alias for a more complex command.
26485 This creates alias @samp{spe} of the command @samp{set print elements}.
26488 (gdb) alias spe = set print elements
26493 @chapter Command Interpreters
26494 @cindex command interpreters
26496 @value{GDBN} supports multiple command interpreters, and some command
26497 infrastructure to allow users or user interface writers to switch
26498 between interpreters or run commands in other interpreters.
26500 @value{GDBN} currently supports two command interpreters, the console
26501 interpreter (sometimes called the command-line interpreter or @sc{cli})
26502 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26503 describes both of these interfaces in great detail.
26505 By default, @value{GDBN} will start with the console interpreter.
26506 However, the user may choose to start @value{GDBN} with another
26507 interpreter by specifying the @option{-i} or @option{--interpreter}
26508 startup options. Defined interpreters include:
26512 @cindex console interpreter
26513 The traditional console or command-line interpreter. This is the most often
26514 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26515 @value{GDBN} will use this interpreter.
26518 @cindex mi interpreter
26519 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
26520 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26521 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26525 @cindex mi2 interpreter
26526 The current @sc{gdb/mi} interface.
26529 @cindex mi1 interpreter
26530 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
26534 @cindex invoke another interpreter
26535 The interpreter being used by @value{GDBN} may not be dynamically
26536 switched at runtime. Although possible, this could lead to a very
26537 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
26538 enters the command "interpreter-set console" in a console view,
26539 @value{GDBN} would switch to using the console interpreter, rendering
26540 the IDE inoperable!
26542 @kindex interpreter-exec
26543 Although you may only choose a single interpreter at startup, you may execute
26544 commands in any interpreter from the current interpreter using the appropriate
26545 command. If you are running the console interpreter, simply use the
26546 @code{interpreter-exec} command:
26549 interpreter-exec mi "-data-list-register-names"
26552 @sc{gdb/mi} has a similar command, although it is only available in versions of
26553 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26556 @chapter @value{GDBN} Text User Interface
26558 @cindex Text User Interface
26561 * TUI Overview:: TUI overview
26562 * TUI Keys:: TUI key bindings
26563 * TUI Single Key Mode:: TUI single key mode
26564 * TUI Commands:: TUI-specific commands
26565 * TUI Configuration:: TUI configuration variables
26568 The @value{GDBN} Text User Interface (TUI) is a terminal
26569 interface which uses the @code{curses} library to show the source
26570 file, the assembly output, the program registers and @value{GDBN}
26571 commands in separate text windows. The TUI mode is supported only
26572 on platforms where a suitable version of the @code{curses} library
26575 The TUI mode is enabled by default when you invoke @value{GDBN} as
26576 @samp{@value{GDBP} -tui}.
26577 You can also switch in and out of TUI mode while @value{GDBN} runs by
26578 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
26579 @xref{TUI Keys, ,TUI Key Bindings}.
26582 @section TUI Overview
26584 In TUI mode, @value{GDBN} can display several text windows:
26588 This window is the @value{GDBN} command window with the @value{GDBN}
26589 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26590 managed using readline.
26593 The source window shows the source file of the program. The current
26594 line and active breakpoints are displayed in this window.
26597 The assembly window shows the disassembly output of the program.
26600 This window shows the processor registers. Registers are highlighted
26601 when their values change.
26604 The source and assembly windows show the current program position
26605 by highlighting the current line and marking it with a @samp{>} marker.
26606 Breakpoints are indicated with two markers. The first marker
26607 indicates the breakpoint type:
26611 Breakpoint which was hit at least once.
26614 Breakpoint which was never hit.
26617 Hardware breakpoint which was hit at least once.
26620 Hardware breakpoint which was never hit.
26623 The second marker indicates whether the breakpoint is enabled or not:
26627 Breakpoint is enabled.
26630 Breakpoint is disabled.
26633 The source, assembly and register windows are updated when the current
26634 thread changes, when the frame changes, or when the program counter
26637 These windows are not all visible at the same time. The command
26638 window is always visible. The others can be arranged in several
26649 source and assembly,
26652 source and registers, or
26655 assembly and registers.
26658 A status line above the command window shows the following information:
26662 Indicates the current @value{GDBN} target.
26663 (@pxref{Targets, ,Specifying a Debugging Target}).
26666 Gives the current process or thread number.
26667 When no process is being debugged, this field is set to @code{No process}.
26670 Gives the current function name for the selected frame.
26671 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26672 When there is no symbol corresponding to the current program counter,
26673 the string @code{??} is displayed.
26676 Indicates the current line number for the selected frame.
26677 When the current line number is not known, the string @code{??} is displayed.
26680 Indicates the current program counter address.
26684 @section TUI Key Bindings
26685 @cindex TUI key bindings
26687 The TUI installs several key bindings in the readline keymaps
26688 @ifset SYSTEM_READLINE
26689 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26691 @ifclear SYSTEM_READLINE
26692 (@pxref{Command Line Editing}).
26694 The following key bindings are installed for both TUI mode and the
26695 @value{GDBN} standard mode.
26704 Enter or leave the TUI mode. When leaving the TUI mode,
26705 the curses window management stops and @value{GDBN} operates using
26706 its standard mode, writing on the terminal directly. When reentering
26707 the TUI mode, control is given back to the curses windows.
26708 The screen is then refreshed.
26712 Use a TUI layout with only one window. The layout will
26713 either be @samp{source} or @samp{assembly}. When the TUI mode
26714 is not active, it will switch to the TUI mode.
26716 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26720 Use a TUI layout with at least two windows. When the current
26721 layout already has two windows, the next layout with two windows is used.
26722 When a new layout is chosen, one window will always be common to the
26723 previous layout and the new one.
26725 Think of it as the Emacs @kbd{C-x 2} binding.
26729 Change the active window. The TUI associates several key bindings
26730 (like scrolling and arrow keys) with the active window. This command
26731 gives the focus to the next TUI window.
26733 Think of it as the Emacs @kbd{C-x o} binding.
26737 Switch in and out of the TUI SingleKey mode that binds single
26738 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26741 The following key bindings only work in the TUI mode:
26746 Scroll the active window one page up.
26750 Scroll the active window one page down.
26754 Scroll the active window one line up.
26758 Scroll the active window one line down.
26762 Scroll the active window one column left.
26766 Scroll the active window one column right.
26770 Refresh the screen.
26773 Because the arrow keys scroll the active window in the TUI mode, they
26774 are not available for their normal use by readline unless the command
26775 window has the focus. When another window is active, you must use
26776 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26777 and @kbd{C-f} to control the command window.
26779 @node TUI Single Key Mode
26780 @section TUI Single Key Mode
26781 @cindex TUI single key mode
26783 The TUI also provides a @dfn{SingleKey} mode, which binds several
26784 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26785 switch into this mode, where the following key bindings are used:
26788 @kindex c @r{(SingleKey TUI key)}
26792 @kindex d @r{(SingleKey TUI key)}
26796 @kindex f @r{(SingleKey TUI key)}
26800 @kindex n @r{(SingleKey TUI key)}
26804 @kindex q @r{(SingleKey TUI key)}
26806 exit the SingleKey mode.
26808 @kindex r @r{(SingleKey TUI key)}
26812 @kindex s @r{(SingleKey TUI key)}
26816 @kindex u @r{(SingleKey TUI key)}
26820 @kindex v @r{(SingleKey TUI key)}
26824 @kindex w @r{(SingleKey TUI key)}
26829 Other keys temporarily switch to the @value{GDBN} command prompt.
26830 The key that was pressed is inserted in the editing buffer so that
26831 it is possible to type most @value{GDBN} commands without interaction
26832 with the TUI SingleKey mode. Once the command is entered the TUI
26833 SingleKey mode is restored. The only way to permanently leave
26834 this mode is by typing @kbd{q} or @kbd{C-x s}.
26838 @section TUI-specific Commands
26839 @cindex TUI commands
26841 The TUI has specific commands to control the text windows.
26842 These commands are always available, even when @value{GDBN} is not in
26843 the TUI mode. When @value{GDBN} is in the standard mode, most
26844 of these commands will automatically switch to the TUI mode.
26846 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26847 terminal, or @value{GDBN} has been started with the machine interface
26848 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26849 these commands will fail with an error, because it would not be
26850 possible or desirable to enable curses window management.
26855 List and give the size of all displayed windows.
26859 Display the next layout.
26862 Display the previous layout.
26865 Display the source window only.
26868 Display the assembly window only.
26871 Display the source and assembly window.
26874 Display the register window together with the source or assembly window.
26878 Make the next window active for scrolling.
26881 Make the previous window active for scrolling.
26884 Make the source window active for scrolling.
26887 Make the assembly window active for scrolling.
26890 Make the register window active for scrolling.
26893 Make the command window active for scrolling.
26897 Refresh the screen. This is similar to typing @kbd{C-L}.
26899 @item tui reg float
26901 Show the floating point registers in the register window.
26903 @item tui reg general
26904 Show the general registers in the register window.
26907 Show the next register group. The list of register groups as well as
26908 their order is target specific. The predefined register groups are the
26909 following: @code{general}, @code{float}, @code{system}, @code{vector},
26910 @code{all}, @code{save}, @code{restore}.
26912 @item tui reg system
26913 Show the system registers in the register window.
26917 Update the source window and the current execution point.
26919 @item winheight @var{name} +@var{count}
26920 @itemx winheight @var{name} -@var{count}
26922 Change the height of the window @var{name} by @var{count}
26923 lines. Positive counts increase the height, while negative counts
26926 @item tabset @var{nchars}
26928 Set the width of tab stops to be @var{nchars} characters.
26931 @node TUI Configuration
26932 @section TUI Configuration Variables
26933 @cindex TUI configuration variables
26935 Several configuration variables control the appearance of TUI windows.
26938 @item set tui border-kind @var{kind}
26939 @kindex set tui border-kind
26940 Select the border appearance for the source, assembly and register windows.
26941 The possible values are the following:
26944 Use a space character to draw the border.
26947 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
26950 Use the Alternate Character Set to draw the border. The border is
26951 drawn using character line graphics if the terminal supports them.
26954 @item set tui border-mode @var{mode}
26955 @kindex set tui border-mode
26956 @itemx set tui active-border-mode @var{mode}
26957 @kindex set tui active-border-mode
26958 Select the display attributes for the borders of the inactive windows
26959 or the active window. The @var{mode} can be one of the following:
26962 Use normal attributes to display the border.
26968 Use reverse video mode.
26971 Use half bright mode.
26973 @item half-standout
26974 Use half bright and standout mode.
26977 Use extra bright or bold mode.
26979 @item bold-standout
26980 Use extra bright or bold and standout mode.
26985 @chapter Using @value{GDBN} under @sc{gnu} Emacs
26988 @cindex @sc{gnu} Emacs
26989 A special interface allows you to use @sc{gnu} Emacs to view (and
26990 edit) the source files for the program you are debugging with
26993 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
26994 executable file you want to debug as an argument. This command starts
26995 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
26996 created Emacs buffer.
26997 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
26999 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
27004 All ``terminal'' input and output goes through an Emacs buffer, called
27007 This applies both to @value{GDBN} commands and their output, and to the input
27008 and output done by the program you are debugging.
27010 This is useful because it means that you can copy the text of previous
27011 commands and input them again; you can even use parts of the output
27014 All the facilities of Emacs' Shell mode are available for interacting
27015 with your program. In particular, you can send signals the usual
27016 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
27020 @value{GDBN} displays source code through Emacs.
27022 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
27023 source file for that frame and puts an arrow (@samp{=>}) at the
27024 left margin of the current line. Emacs uses a separate buffer for
27025 source display, and splits the screen to show both your @value{GDBN} session
27028 Explicit @value{GDBN} @code{list} or search commands still produce output as
27029 usual, but you probably have no reason to use them from Emacs.
27032 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
27033 a graphical mode, enabled by default, which provides further buffers
27034 that can control the execution and describe the state of your program.
27035 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27037 If you specify an absolute file name when prompted for the @kbd{M-x
27038 gdb} argument, then Emacs sets your current working directory to where
27039 your program resides. If you only specify the file name, then Emacs
27040 sets your current working directory to the directory associated
27041 with the previous buffer. In this case, @value{GDBN} may find your
27042 program by searching your environment's @code{PATH} variable, but on
27043 some operating systems it might not find the source. So, although the
27044 @value{GDBN} input and output session proceeds normally, the auxiliary
27045 buffer does not display the current source and line of execution.
27047 The initial working directory of @value{GDBN} is printed on the top
27048 line of the GUD buffer and this serves as a default for the commands
27049 that specify files for @value{GDBN} to operate on. @xref{Files,
27050 ,Commands to Specify Files}.
27052 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27053 need to call @value{GDBN} by a different name (for example, if you
27054 keep several configurations around, with different names) you can
27055 customize the Emacs variable @code{gud-gdb-command-name} to run the
27058 In the GUD buffer, you can use these special Emacs commands in
27059 addition to the standard Shell mode commands:
27063 Describe the features of Emacs' GUD Mode.
27066 Execute to another source line, like the @value{GDBN} @code{step} command; also
27067 update the display window to show the current file and location.
27070 Execute to next source line in this function, skipping all function
27071 calls, like the @value{GDBN} @code{next} command. Then update the display window
27072 to show the current file and location.
27075 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27076 display window accordingly.
27079 Execute until exit from the selected stack frame, like the @value{GDBN}
27080 @code{finish} command.
27083 Continue execution of your program, like the @value{GDBN} @code{continue}
27087 Go up the number of frames indicated by the numeric argument
27088 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27089 like the @value{GDBN} @code{up} command.
27092 Go down the number of frames indicated by the numeric argument, like the
27093 @value{GDBN} @code{down} command.
27096 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27097 tells @value{GDBN} to set a breakpoint on the source line point is on.
27099 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27100 separate frame which shows a backtrace when the GUD buffer is current.
27101 Move point to any frame in the stack and type @key{RET} to make it
27102 become the current frame and display the associated source in the
27103 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27104 selected frame become the current one. In graphical mode, the
27105 speedbar displays watch expressions.
27107 If you accidentally delete the source-display buffer, an easy way to get
27108 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27109 request a frame display; when you run under Emacs, this recreates
27110 the source buffer if necessary to show you the context of the current
27113 The source files displayed in Emacs are in ordinary Emacs buffers
27114 which are visiting the source files in the usual way. You can edit
27115 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27116 communicates with Emacs in terms of line numbers. If you add or
27117 delete lines from the text, the line numbers that @value{GDBN} knows cease
27118 to correspond properly with the code.
27120 A more detailed description of Emacs' interaction with @value{GDBN} is
27121 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27125 @chapter The @sc{gdb/mi} Interface
27127 @unnumberedsec Function and Purpose
27129 @cindex @sc{gdb/mi}, its purpose
27130 @sc{gdb/mi} is a line based machine oriented text interface to
27131 @value{GDBN} and is activated by specifying using the
27132 @option{--interpreter} command line option (@pxref{Mode Options}). It
27133 is specifically intended to support the development of systems which
27134 use the debugger as just one small component of a larger system.
27136 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27137 in the form of a reference manual.
27139 Note that @sc{gdb/mi} is still under construction, so some of the
27140 features described below are incomplete and subject to change
27141 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27143 @unnumberedsec Notation and Terminology
27145 @cindex notational conventions, for @sc{gdb/mi}
27146 This chapter uses the following notation:
27150 @code{|} separates two alternatives.
27153 @code{[ @var{something} ]} indicates that @var{something} is optional:
27154 it may or may not be given.
27157 @code{( @var{group} )*} means that @var{group} inside the parentheses
27158 may repeat zero or more times.
27161 @code{( @var{group} )+} means that @var{group} inside the parentheses
27162 may repeat one or more times.
27165 @code{"@var{string}"} means a literal @var{string}.
27169 @heading Dependencies
27173 * GDB/MI General Design::
27174 * GDB/MI Command Syntax::
27175 * GDB/MI Compatibility with CLI::
27176 * GDB/MI Development and Front Ends::
27177 * GDB/MI Output Records::
27178 * GDB/MI Simple Examples::
27179 * GDB/MI Command Description Format::
27180 * GDB/MI Breakpoint Commands::
27181 * GDB/MI Catchpoint Commands::
27182 * GDB/MI Program Context::
27183 * GDB/MI Thread Commands::
27184 * GDB/MI Ada Tasking Commands::
27185 * GDB/MI Program Execution::
27186 * GDB/MI Stack Manipulation::
27187 * GDB/MI Variable Objects::
27188 * GDB/MI Data Manipulation::
27189 * GDB/MI Tracepoint Commands::
27190 * GDB/MI Symbol Query::
27191 * GDB/MI File Commands::
27193 * GDB/MI Kod Commands::
27194 * GDB/MI Memory Overlay Commands::
27195 * GDB/MI Signal Handling Commands::
27197 * GDB/MI Target Manipulation::
27198 * GDB/MI File Transfer Commands::
27199 * GDB/MI Miscellaneous Commands::
27202 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27203 @node GDB/MI General Design
27204 @section @sc{gdb/mi} General Design
27205 @cindex GDB/MI General Design
27207 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
27208 parts---commands sent to @value{GDBN}, responses to those commands
27209 and notifications. Each command results in exactly one response,
27210 indicating either successful completion of the command, or an error.
27211 For the commands that do not resume the target, the response contains the
27212 requested information. For the commands that resume the target, the
27213 response only indicates whether the target was successfully resumed.
27214 Notifications is the mechanism for reporting changes in the state of the
27215 target, or in @value{GDBN} state, that cannot conveniently be associated with
27216 a command and reported as part of that command response.
27218 The important examples of notifications are:
27222 Exec notifications. These are used to report changes in
27223 target state---when a target is resumed, or stopped. It would not
27224 be feasible to include this information in response of resuming
27225 commands, because one resume commands can result in multiple events in
27226 different threads. Also, quite some time may pass before any event
27227 happens in the target, while a frontend needs to know whether the resuming
27228 command itself was successfully executed.
27231 Console output, and status notifications. Console output
27232 notifications are used to report output of CLI commands, as well as
27233 diagnostics for other commands. Status notifications are used to
27234 report the progress of a long-running operation. Naturally, including
27235 this information in command response would mean no output is produced
27236 until the command is finished, which is undesirable.
27239 General notifications. Commands may have various side effects on
27240 the @value{GDBN} or target state beyond their official purpose. For example,
27241 a command may change the selected thread. Although such changes can
27242 be included in command response, using notification allows for more
27243 orthogonal frontend design.
27247 There's no guarantee that whenever an MI command reports an error,
27248 @value{GDBN} or the target are in any specific state, and especially,
27249 the state is not reverted to the state before the MI command was
27250 processed. Therefore, whenever an MI command results in an error,
27251 we recommend that the frontend refreshes all the information shown in
27252 the user interface.
27256 * Context management::
27257 * Asynchronous and non-stop modes::
27261 @node Context management
27262 @subsection Context management
27264 In most cases when @value{GDBN} accesses the target, this access is
27265 done in context of a specific thread and frame (@pxref{Frames}).
27266 Often, even when accessing global data, the target requires that a thread
27267 be specified. The CLI interface maintains the selected thread and frame,
27268 and supplies them to target on each command. This is convenient,
27269 because a command line user would not want to specify that information
27270 explicitly on each command, and because user interacts with
27271 @value{GDBN} via a single terminal, so no confusion is possible as
27272 to what thread and frame are the current ones.
27274 In the case of MI, the concept of selected thread and frame is less
27275 useful. First, a frontend can easily remember this information
27276 itself. Second, a graphical frontend can have more than one window,
27277 each one used for debugging a different thread, and the frontend might
27278 want to access additional threads for internal purposes. This
27279 increases the risk that by relying on implicitly selected thread, the
27280 frontend may be operating on a wrong one. Therefore, each MI command
27281 should explicitly specify which thread and frame to operate on. To
27282 make it possible, each MI command accepts the @samp{--thread} and
27283 @samp{--frame} options, the value to each is @value{GDBN} identifier
27284 for thread and frame to operate on.
27286 Usually, each top-level window in a frontend allows the user to select
27287 a thread and a frame, and remembers the user selection for further
27288 operations. However, in some cases @value{GDBN} may suggest that the
27289 current thread be changed. For example, when stopping on a breakpoint
27290 it is reasonable to switch to the thread where breakpoint is hit. For
27291 another example, if the user issues the CLI @samp{thread} command via
27292 the frontend, it is desirable to change the frontend's selected thread to the
27293 one specified by user. @value{GDBN} communicates the suggestion to
27294 change current thread using the @samp{=thread-selected} notification.
27295 No such notification is available for the selected frame at the moment.
27297 Note that historically, MI shares the selected thread with CLI, so
27298 frontends used the @code{-thread-select} to execute commands in the
27299 right context. However, getting this to work right is cumbersome. The
27300 simplest way is for frontend to emit @code{-thread-select} command
27301 before every command. This doubles the number of commands that need
27302 to be sent. The alternative approach is to suppress @code{-thread-select}
27303 if the selected thread in @value{GDBN} is supposed to be identical to the
27304 thread the frontend wants to operate on. However, getting this
27305 optimization right can be tricky. In particular, if the frontend
27306 sends several commands to @value{GDBN}, and one of the commands changes the
27307 selected thread, then the behaviour of subsequent commands will
27308 change. So, a frontend should either wait for response from such
27309 problematic commands, or explicitly add @code{-thread-select} for
27310 all subsequent commands. No frontend is known to do this exactly
27311 right, so it is suggested to just always pass the @samp{--thread} and
27312 @samp{--frame} options.
27314 @node Asynchronous and non-stop modes
27315 @subsection Asynchronous command execution and non-stop mode
27317 On some targets, @value{GDBN} is capable of processing MI commands
27318 even while the target is running. This is called @dfn{asynchronous
27319 command execution} (@pxref{Background Execution}). The frontend may
27320 specify a preferrence for asynchronous execution using the
27321 @code{-gdb-set target-async 1} command, which should be emitted before
27322 either running the executable or attaching to the target. After the
27323 frontend has started the executable or attached to the target, it can
27324 find if asynchronous execution is enabled using the
27325 @code{-list-target-features} command.
27327 Even if @value{GDBN} can accept a command while target is running,
27328 many commands that access the target do not work when the target is
27329 running. Therefore, asynchronous command execution is most useful
27330 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27331 it is possible to examine the state of one thread, while other threads
27334 When a given thread is running, MI commands that try to access the
27335 target in the context of that thread may not work, or may work only on
27336 some targets. In particular, commands that try to operate on thread's
27337 stack will not work, on any target. Commands that read memory, or
27338 modify breakpoints, may work or not work, depending on the target. Note
27339 that even commands that operate on global state, such as @code{print},
27340 @code{set}, and breakpoint commands, still access the target in the
27341 context of a specific thread, so frontend should try to find a
27342 stopped thread and perform the operation on that thread (using the
27343 @samp{--thread} option).
27345 Which commands will work in the context of a running thread is
27346 highly target dependent. However, the two commands
27347 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27348 to find the state of a thread, will always work.
27350 @node Thread groups
27351 @subsection Thread groups
27352 @value{GDBN} may be used to debug several processes at the same time.
27353 On some platfroms, @value{GDBN} may support debugging of several
27354 hardware systems, each one having several cores with several different
27355 processes running on each core. This section describes the MI
27356 mechanism to support such debugging scenarios.
27358 The key observation is that regardless of the structure of the
27359 target, MI can have a global list of threads, because most commands that
27360 accept the @samp{--thread} option do not need to know what process that
27361 thread belongs to. Therefore, it is not necessary to introduce
27362 neither additional @samp{--process} option, nor an notion of the
27363 current process in the MI interface. The only strictly new feature
27364 that is required is the ability to find how the threads are grouped
27367 To allow the user to discover such grouping, and to support arbitrary
27368 hierarchy of machines/cores/processes, MI introduces the concept of a
27369 @dfn{thread group}. Thread group is a collection of threads and other
27370 thread groups. A thread group always has a string identifier, a type,
27371 and may have additional attributes specific to the type. A new
27372 command, @code{-list-thread-groups}, returns the list of top-level
27373 thread groups, which correspond to processes that @value{GDBN} is
27374 debugging at the moment. By passing an identifier of a thread group
27375 to the @code{-list-thread-groups} command, it is possible to obtain
27376 the members of specific thread group.
27378 To allow the user to easily discover processes, and other objects, he
27379 wishes to debug, a concept of @dfn{available thread group} is
27380 introduced. Available thread group is an thread group that
27381 @value{GDBN} is not debugging, but that can be attached to, using the
27382 @code{-target-attach} command. The list of available top-level thread
27383 groups can be obtained using @samp{-list-thread-groups --available}.
27384 In general, the content of a thread group may be only retrieved only
27385 after attaching to that thread group.
27387 Thread groups are related to inferiors (@pxref{Inferiors and
27388 Programs}). Each inferior corresponds to a thread group of a special
27389 type @samp{process}, and some additional operations are permitted on
27390 such thread groups.
27392 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27393 @node GDB/MI Command Syntax
27394 @section @sc{gdb/mi} Command Syntax
27397 * GDB/MI Input Syntax::
27398 * GDB/MI Output Syntax::
27401 @node GDB/MI Input Syntax
27402 @subsection @sc{gdb/mi} Input Syntax
27404 @cindex input syntax for @sc{gdb/mi}
27405 @cindex @sc{gdb/mi}, input syntax
27407 @item @var{command} @expansion{}
27408 @code{@var{cli-command} | @var{mi-command}}
27410 @item @var{cli-command} @expansion{}
27411 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27412 @var{cli-command} is any existing @value{GDBN} CLI command.
27414 @item @var{mi-command} @expansion{}
27415 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27416 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27418 @item @var{token} @expansion{}
27419 "any sequence of digits"
27421 @item @var{option} @expansion{}
27422 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27424 @item @var{parameter} @expansion{}
27425 @code{@var{non-blank-sequence} | @var{c-string}}
27427 @item @var{operation} @expansion{}
27428 @emph{any of the operations described in this chapter}
27430 @item @var{non-blank-sequence} @expansion{}
27431 @emph{anything, provided it doesn't contain special characters such as
27432 "-", @var{nl}, """ and of course " "}
27434 @item @var{c-string} @expansion{}
27435 @code{""" @var{seven-bit-iso-c-string-content} """}
27437 @item @var{nl} @expansion{}
27446 The CLI commands are still handled by the @sc{mi} interpreter; their
27447 output is described below.
27450 The @code{@var{token}}, when present, is passed back when the command
27454 Some @sc{mi} commands accept optional arguments as part of the parameter
27455 list. Each option is identified by a leading @samp{-} (dash) and may be
27456 followed by an optional argument parameter. Options occur first in the
27457 parameter list and can be delimited from normal parameters using
27458 @samp{--} (this is useful when some parameters begin with a dash).
27465 We want easy access to the existing CLI syntax (for debugging).
27468 We want it to be easy to spot a @sc{mi} operation.
27471 @node GDB/MI Output Syntax
27472 @subsection @sc{gdb/mi} Output Syntax
27474 @cindex output syntax of @sc{gdb/mi}
27475 @cindex @sc{gdb/mi}, output syntax
27476 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27477 followed, optionally, by a single result record. This result record
27478 is for the most recent command. The sequence of output records is
27479 terminated by @samp{(gdb)}.
27481 If an input command was prefixed with a @code{@var{token}} then the
27482 corresponding output for that command will also be prefixed by that same
27486 @item @var{output} @expansion{}
27487 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27489 @item @var{result-record} @expansion{}
27490 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27492 @item @var{out-of-band-record} @expansion{}
27493 @code{@var{async-record} | @var{stream-record}}
27495 @item @var{async-record} @expansion{}
27496 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27498 @item @var{exec-async-output} @expansion{}
27499 @code{[ @var{token} ] "*" @var{async-output}}
27501 @item @var{status-async-output} @expansion{}
27502 @code{[ @var{token} ] "+" @var{async-output}}
27504 @item @var{notify-async-output} @expansion{}
27505 @code{[ @var{token} ] "=" @var{async-output}}
27507 @item @var{async-output} @expansion{}
27508 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
27510 @item @var{result-class} @expansion{}
27511 @code{"done" | "running" | "connected" | "error" | "exit"}
27513 @item @var{async-class} @expansion{}
27514 @code{"stopped" | @var{others}} (where @var{others} will be added
27515 depending on the needs---this is still in development).
27517 @item @var{result} @expansion{}
27518 @code{ @var{variable} "=" @var{value}}
27520 @item @var{variable} @expansion{}
27521 @code{ @var{string} }
27523 @item @var{value} @expansion{}
27524 @code{ @var{const} | @var{tuple} | @var{list} }
27526 @item @var{const} @expansion{}
27527 @code{@var{c-string}}
27529 @item @var{tuple} @expansion{}
27530 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27532 @item @var{list} @expansion{}
27533 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27534 @var{result} ( "," @var{result} )* "]" }
27536 @item @var{stream-record} @expansion{}
27537 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27539 @item @var{console-stream-output} @expansion{}
27540 @code{"~" @var{c-string}}
27542 @item @var{target-stream-output} @expansion{}
27543 @code{"@@" @var{c-string}}
27545 @item @var{log-stream-output} @expansion{}
27546 @code{"&" @var{c-string}}
27548 @item @var{nl} @expansion{}
27551 @item @var{token} @expansion{}
27552 @emph{any sequence of digits}.
27560 All output sequences end in a single line containing a period.
27563 The @code{@var{token}} is from the corresponding request. Note that
27564 for all async output, while the token is allowed by the grammar and
27565 may be output by future versions of @value{GDBN} for select async
27566 output messages, it is generally omitted. Frontends should treat
27567 all async output as reporting general changes in the state of the
27568 target and there should be no need to associate async output to any
27572 @cindex status output in @sc{gdb/mi}
27573 @var{status-async-output} contains on-going status information about the
27574 progress of a slow operation. It can be discarded. All status output is
27575 prefixed by @samp{+}.
27578 @cindex async output in @sc{gdb/mi}
27579 @var{exec-async-output} contains asynchronous state change on the target
27580 (stopped, started, disappeared). All async output is prefixed by
27584 @cindex notify output in @sc{gdb/mi}
27585 @var{notify-async-output} contains supplementary information that the
27586 client should handle (e.g., a new breakpoint information). All notify
27587 output is prefixed by @samp{=}.
27590 @cindex console output in @sc{gdb/mi}
27591 @var{console-stream-output} is output that should be displayed as is in the
27592 console. It is the textual response to a CLI command. All the console
27593 output is prefixed by @samp{~}.
27596 @cindex target output in @sc{gdb/mi}
27597 @var{target-stream-output} is the output produced by the target program.
27598 All the target output is prefixed by @samp{@@}.
27601 @cindex log output in @sc{gdb/mi}
27602 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27603 instance messages that should be displayed as part of an error log. All
27604 the log output is prefixed by @samp{&}.
27607 @cindex list output in @sc{gdb/mi}
27608 New @sc{gdb/mi} commands should only output @var{lists} containing
27614 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27615 details about the various output records.
27617 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27618 @node GDB/MI Compatibility with CLI
27619 @section @sc{gdb/mi} Compatibility with CLI
27621 @cindex compatibility, @sc{gdb/mi} and CLI
27622 @cindex @sc{gdb/mi}, compatibility with CLI
27624 For the developers convenience CLI commands can be entered directly,
27625 but there may be some unexpected behaviour. For example, commands
27626 that query the user will behave as if the user replied yes, breakpoint
27627 command lists are not executed and some CLI commands, such as
27628 @code{if}, @code{when} and @code{define}, prompt for further input with
27629 @samp{>}, which is not valid MI output.
27631 This feature may be removed at some stage in the future and it is
27632 recommended that front ends use the @code{-interpreter-exec} command
27633 (@pxref{-interpreter-exec}).
27635 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27636 @node GDB/MI Development and Front Ends
27637 @section @sc{gdb/mi} Development and Front Ends
27638 @cindex @sc{gdb/mi} development
27640 The application which takes the MI output and presents the state of the
27641 program being debugged to the user is called a @dfn{front end}.
27643 Although @sc{gdb/mi} is still incomplete, it is currently being used
27644 by a variety of front ends to @value{GDBN}. This makes it difficult
27645 to introduce new functionality without breaking existing usage. This
27646 section tries to minimize the problems by describing how the protocol
27649 Some changes in MI need not break a carefully designed front end, and
27650 for these the MI version will remain unchanged. The following is a
27651 list of changes that may occur within one level, so front ends should
27652 parse MI output in a way that can handle them:
27656 New MI commands may be added.
27659 New fields may be added to the output of any MI command.
27662 The range of values for fields with specified values, e.g.,
27663 @code{in_scope} (@pxref{-var-update}) may be extended.
27665 @c The format of field's content e.g type prefix, may change so parse it
27666 @c at your own risk. Yes, in general?
27668 @c The order of fields may change? Shouldn't really matter but it might
27669 @c resolve inconsistencies.
27672 If the changes are likely to break front ends, the MI version level
27673 will be increased by one. This will allow the front end to parse the
27674 output according to the MI version. Apart from mi0, new versions of
27675 @value{GDBN} will not support old versions of MI and it will be the
27676 responsibility of the front end to work with the new one.
27678 @c Starting with mi3, add a new command -mi-version that prints the MI
27681 The best way to avoid unexpected changes in MI that might break your front
27682 end is to make your project known to @value{GDBN} developers and
27683 follow development on @email{gdb@@sourceware.org} and
27684 @email{gdb-patches@@sourceware.org}.
27685 @cindex mailing lists
27687 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27688 @node GDB/MI Output Records
27689 @section @sc{gdb/mi} Output Records
27692 * GDB/MI Result Records::
27693 * GDB/MI Stream Records::
27694 * GDB/MI Async Records::
27695 * GDB/MI Breakpoint Information::
27696 * GDB/MI Frame Information::
27697 * GDB/MI Thread Information::
27698 * GDB/MI Ada Exception Information::
27701 @node GDB/MI Result Records
27702 @subsection @sc{gdb/mi} Result Records
27704 @cindex result records in @sc{gdb/mi}
27705 @cindex @sc{gdb/mi}, result records
27706 In addition to a number of out-of-band notifications, the response to a
27707 @sc{gdb/mi} command includes one of the following result indications:
27711 @item "^done" [ "," @var{results} ]
27712 The synchronous operation was successful, @code{@var{results}} are the return
27717 This result record is equivalent to @samp{^done}. Historically, it
27718 was output instead of @samp{^done} if the command has resumed the
27719 target. This behaviour is maintained for backward compatibility, but
27720 all frontends should treat @samp{^done} and @samp{^running}
27721 identically and rely on the @samp{*running} output record to determine
27722 which threads are resumed.
27726 @value{GDBN} has connected to a remote target.
27728 @item "^error" "," @var{c-string}
27730 The operation failed. The @code{@var{c-string}} contains the corresponding
27735 @value{GDBN} has terminated.
27739 @node GDB/MI Stream Records
27740 @subsection @sc{gdb/mi} Stream Records
27742 @cindex @sc{gdb/mi}, stream records
27743 @cindex stream records in @sc{gdb/mi}
27744 @value{GDBN} internally maintains a number of output streams: the console, the
27745 target, and the log. The output intended for each of these streams is
27746 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27748 Each stream record begins with a unique @dfn{prefix character} which
27749 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27750 Syntax}). In addition to the prefix, each stream record contains a
27751 @code{@var{string-output}}. This is either raw text (with an implicit new
27752 line) or a quoted C string (which does not contain an implicit newline).
27755 @item "~" @var{string-output}
27756 The console output stream contains text that should be displayed in the
27757 CLI console window. It contains the textual responses to CLI commands.
27759 @item "@@" @var{string-output}
27760 The target output stream contains any textual output from the running
27761 target. This is only present when GDB's event loop is truly
27762 asynchronous, which is currently only the case for remote targets.
27764 @item "&" @var{string-output}
27765 The log stream contains debugging messages being produced by @value{GDBN}'s
27769 @node GDB/MI Async Records
27770 @subsection @sc{gdb/mi} Async Records
27772 @cindex async records in @sc{gdb/mi}
27773 @cindex @sc{gdb/mi}, async records
27774 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27775 additional changes that have occurred. Those changes can either be a
27776 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27777 target activity (e.g., target stopped).
27779 The following is the list of possible async records:
27783 @item *running,thread-id="@var{thread}"
27784 The target is now running. The @var{thread} field tells which
27785 specific thread is now running, and can be @samp{all} if all threads
27786 are running. The frontend should assume that no interaction with a
27787 running thread is possible after this notification is produced.
27788 The frontend should not assume that this notification is output
27789 only once for any command. @value{GDBN} may emit this notification
27790 several times, either for different threads, because it cannot resume
27791 all threads together, or even for a single thread, if the thread must
27792 be stepped though some code before letting it run freely.
27794 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
27795 The target has stopped. The @var{reason} field can have one of the
27799 @item breakpoint-hit
27800 A breakpoint was reached.
27801 @item watchpoint-trigger
27802 A watchpoint was triggered.
27803 @item read-watchpoint-trigger
27804 A read watchpoint was triggered.
27805 @item access-watchpoint-trigger
27806 An access watchpoint was triggered.
27807 @item function-finished
27808 An -exec-finish or similar CLI command was accomplished.
27809 @item location-reached
27810 An -exec-until or similar CLI command was accomplished.
27811 @item watchpoint-scope
27812 A watchpoint has gone out of scope.
27813 @item end-stepping-range
27814 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
27815 similar CLI command was accomplished.
27816 @item exited-signalled
27817 The inferior exited because of a signal.
27819 The inferior exited.
27820 @item exited-normally
27821 The inferior exited normally.
27822 @item signal-received
27823 A signal was received by the inferior.
27825 The inferior has stopped due to a library being loaded or unloaded.
27826 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
27827 set or when a @code{catch load} or @code{catch unload} catchpoint is
27828 in use (@pxref{Set Catchpoints}).
27830 The inferior has forked. This is reported when @code{catch fork}
27831 (@pxref{Set Catchpoints}) has been used.
27833 The inferior has vforked. This is reported in when @code{catch vfork}
27834 (@pxref{Set Catchpoints}) has been used.
27835 @item syscall-entry
27836 The inferior entered a system call. This is reported when @code{catch
27837 syscall} (@pxref{Set Catchpoints}) has been used.
27838 @item syscall-entry
27839 The inferior returned from a system call. This is reported when
27840 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
27842 The inferior called @code{exec}. This is reported when @code{catch exec}
27843 (@pxref{Set Catchpoints}) has been used.
27846 The @var{id} field identifies the thread that directly caused the stop
27847 -- for example by hitting a breakpoint. Depending on whether all-stop
27848 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
27849 stop all threads, or only the thread that directly triggered the stop.
27850 If all threads are stopped, the @var{stopped} field will have the
27851 value of @code{"all"}. Otherwise, the value of the @var{stopped}
27852 field will be a list of thread identifiers. Presently, this list will
27853 always include a single thread, but frontend should be prepared to see
27854 several threads in the list. The @var{core} field reports the
27855 processor core on which the stop event has happened. This field may be absent
27856 if such information is not available.
27858 @item =thread-group-added,id="@var{id}"
27859 @itemx =thread-group-removed,id="@var{id}"
27860 A thread group was either added or removed. The @var{id} field
27861 contains the @value{GDBN} identifier of the thread group. When a thread
27862 group is added, it generally might not be associated with a running
27863 process. When a thread group is removed, its id becomes invalid and
27864 cannot be used in any way.
27866 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
27867 A thread group became associated with a running program,
27868 either because the program was just started or the thread group
27869 was attached to a program. The @var{id} field contains the
27870 @value{GDBN} identifier of the thread group. The @var{pid} field
27871 contains process identifier, specific to the operating system.
27873 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
27874 A thread group is no longer associated with a running program,
27875 either because the program has exited, or because it was detached
27876 from. The @var{id} field contains the @value{GDBN} identifier of the
27877 thread group. @var{code} is the exit code of the inferior; it exists
27878 only when the inferior exited with some code.
27880 @item =thread-created,id="@var{id}",group-id="@var{gid}"
27881 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
27882 A thread either was created, or has exited. The @var{id} field
27883 contains the @value{GDBN} identifier of the thread. The @var{gid}
27884 field identifies the thread group this thread belongs to.
27886 @item =thread-selected,id="@var{id}"
27887 Informs that the selected thread was changed as result of the last
27888 command. This notification is not emitted as result of @code{-thread-select}
27889 command but is emitted whenever an MI command that is not documented
27890 to change the selected thread actually changes it. In particular,
27891 invoking, directly or indirectly (via user-defined command), the CLI
27892 @code{thread} command, will generate this notification.
27894 We suggest that in response to this notification, front ends
27895 highlight the selected thread and cause subsequent commands to apply to
27898 @item =library-loaded,...
27899 Reports that a new library file was loaded by the program. This
27900 notification has 4 fields---@var{id}, @var{target-name},
27901 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
27902 opaque identifier of the library. For remote debugging case,
27903 @var{target-name} and @var{host-name} fields give the name of the
27904 library file on the target, and on the host respectively. For native
27905 debugging, both those fields have the same value. The
27906 @var{symbols-loaded} field is emitted only for backward compatibility
27907 and should not be relied on to convey any useful information. The
27908 @var{thread-group} field, if present, specifies the id of the thread
27909 group in whose context the library was loaded. If the field is
27910 absent, it means the library was loaded in the context of all present
27913 @item =library-unloaded,...
27914 Reports that a library was unloaded by the program. This notification
27915 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
27916 the same meaning as for the @code{=library-loaded} notification.
27917 The @var{thread-group} field, if present, specifies the id of the
27918 thread group in whose context the library was unloaded. If the field is
27919 absent, it means the library was unloaded in the context of all present
27922 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
27923 @itemx =traceframe-changed,end
27924 Reports that the trace frame was changed and its new number is
27925 @var{tfnum}. The number of the tracepoint associated with this trace
27926 frame is @var{tpnum}.
27928 @item =tsv-created,name=@var{name},value=@var{value}
27929 Reports that the new trace state variable @var{name} is created with
27932 @item =tsv-deleted,name=@var{name}
27933 @itemx =tsv-deleted
27934 Reports that the trace state variable @var{name} is deleted or all
27935 trace state variables are deleted.
27937 @item =breakpoint-created,bkpt=@{...@}
27938 @itemx =breakpoint-modified,bkpt=@{...@}
27939 @itemx =breakpoint-deleted,id=@var{number}
27940 Reports that a breakpoint was created, modified, or deleted,
27941 respectively. Only user-visible breakpoints are reported to the MI
27944 The @var{bkpt} argument is of the same form as returned by the various
27945 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
27946 @var{number} is the ordinal number of the breakpoint.
27948 Note that if a breakpoint is emitted in the result record of a
27949 command, then it will not also be emitted in an async record.
27951 @item =record-started,thread-group="@var{id}"
27952 @itemx =record-stopped,thread-group="@var{id}"
27953 Execution log recording was either started or stopped on an
27954 inferior. The @var{id} is the @value{GDBN} identifier of the thread
27955 group corresponding to the affected inferior.
27957 @item =cmd-param-changed,param=@var{param},value=@var{value}
27958 Reports that a parameter of the command @code{set @var{param}} is
27959 changed to @var{value}. In the multi-word @code{set} command,
27960 the @var{param} is the whole parameter list to @code{set} command.
27961 For example, In command @code{set check type on}, @var{param}
27962 is @code{check type} and @var{value} is @code{on}.
27964 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
27965 Reports that bytes from @var{addr} to @var{data} + @var{len} were
27966 written in an inferior. The @var{id} is the identifier of the
27967 thread group corresponding to the affected inferior. The optional
27968 @code{type="code"} part is reported if the memory written to holds
27972 @node GDB/MI Breakpoint Information
27973 @subsection @sc{gdb/mi} Breakpoint Information
27975 When @value{GDBN} reports information about a breakpoint, a
27976 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
27981 The breakpoint number. For a breakpoint that represents one location
27982 of a multi-location breakpoint, this will be a dotted pair, like
27986 The type of the breakpoint. For ordinary breakpoints this will be
27987 @samp{breakpoint}, but many values are possible.
27990 If the type of the breakpoint is @samp{catchpoint}, then this
27991 indicates the exact type of catchpoint.
27994 This is the breakpoint disposition---either @samp{del}, meaning that
27995 the breakpoint will be deleted at the next stop, or @samp{keep},
27996 meaning that the breakpoint will not be deleted.
27999 This indicates whether the breakpoint is enabled, in which case the
28000 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28001 Note that this is not the same as the field @code{enable}.
28004 The address of the breakpoint. This may be a hexidecimal number,
28005 giving the address; or the string @samp{<PENDING>}, for a pending
28006 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
28007 multiple locations. This field will not be present if no address can
28008 be determined. For example, a watchpoint does not have an address.
28011 If known, the function in which the breakpoint appears.
28012 If not known, this field is not present.
28015 The name of the source file which contains this function, if known.
28016 If not known, this field is not present.
28019 The full file name of the source file which contains this function, if
28020 known. If not known, this field is not present.
28023 The line number at which this breakpoint appears, if known.
28024 If not known, this field is not present.
28027 If the source file is not known, this field may be provided. If
28028 provided, this holds the address of the breakpoint, possibly followed
28032 If this breakpoint is pending, this field is present and holds the
28033 text used to set the breakpoint, as entered by the user.
28036 Where this breakpoint's condition is evaluated, either @samp{host} or
28040 If this is a thread-specific breakpoint, then this identifies the
28041 thread in which the breakpoint can trigger.
28044 If this breakpoint is restricted to a particular Ada task, then this
28045 field will hold the task identifier.
28048 If the breakpoint is conditional, this is the condition expression.
28051 The ignore count of the breakpoint.
28054 The enable count of the breakpoint.
28056 @item traceframe-usage
28059 @item static-tracepoint-marker-string-id
28060 For a static tracepoint, the name of the static tracepoint marker.
28063 For a masked watchpoint, this is the mask.
28066 A tracepoint's pass count.
28068 @item original-location
28069 The location of the breakpoint as originally specified by the user.
28070 This field is optional.
28073 The number of times the breakpoint has been hit.
28076 This field is only given for tracepoints. This is either @samp{y},
28077 meaning that the tracepoint is installed, or @samp{n}, meaning that it
28081 Some extra data, the exact contents of which are type-dependent.
28085 For example, here is what the output of @code{-break-insert}
28086 (@pxref{GDB/MI Breakpoint Commands}) might be:
28089 -> -break-insert main
28090 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28091 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28092 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
28096 @node GDB/MI Frame Information
28097 @subsection @sc{gdb/mi} Frame Information
28099 Response from many MI commands includes an information about stack
28100 frame. This information is a tuple that may have the following
28105 The level of the stack frame. The innermost frame has the level of
28106 zero. This field is always present.
28109 The name of the function corresponding to the frame. This field may
28110 be absent if @value{GDBN} is unable to determine the function name.
28113 The code address for the frame. This field is always present.
28116 The name of the source files that correspond to the frame's code
28117 address. This field may be absent.
28120 The source line corresponding to the frames' code address. This field
28124 The name of the binary file (either executable or shared library) the
28125 corresponds to the frame's code address. This field may be absent.
28129 @node GDB/MI Thread Information
28130 @subsection @sc{gdb/mi} Thread Information
28132 Whenever @value{GDBN} has to report an information about a thread, it
28133 uses a tuple with the following fields:
28137 The numeric id assigned to the thread by @value{GDBN}. This field is
28141 Target-specific string identifying the thread. This field is always present.
28144 Additional information about the thread provided by the target.
28145 It is supposed to be human-readable and not interpreted by the
28146 frontend. This field is optional.
28149 Either @samp{stopped} or @samp{running}, depending on whether the
28150 thread is presently running. This field is always present.
28153 The value of this field is an integer number of the processor core the
28154 thread was last seen on. This field is optional.
28157 @node GDB/MI Ada Exception Information
28158 @subsection @sc{gdb/mi} Ada Exception Information
28160 Whenever a @code{*stopped} record is emitted because the program
28161 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
28162 @value{GDBN} provides the name of the exception that was raised via
28163 the @code{exception-name} field.
28165 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28166 @node GDB/MI Simple Examples
28167 @section Simple Examples of @sc{gdb/mi} Interaction
28168 @cindex @sc{gdb/mi}, simple examples
28170 This subsection presents several simple examples of interaction using
28171 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
28172 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
28173 the output received from @sc{gdb/mi}.
28175 Note the line breaks shown in the examples are here only for
28176 readability, they don't appear in the real output.
28178 @subheading Setting a Breakpoint
28180 Setting a breakpoint generates synchronous output which contains detailed
28181 information of the breakpoint.
28184 -> -break-insert main
28185 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28186 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28187 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
28191 @subheading Program Execution
28193 Program execution generates asynchronous records and MI gives the
28194 reason that execution stopped.
28200 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28201 frame=@{addr="0x08048564",func="main",
28202 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
28203 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
28208 <- *stopped,reason="exited-normally"
28212 @subheading Quitting @value{GDBN}
28214 Quitting @value{GDBN} just prints the result class @samp{^exit}.
28222 Please note that @samp{^exit} is printed immediately, but it might
28223 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
28224 performs necessary cleanups, including killing programs being debugged
28225 or disconnecting from debug hardware, so the frontend should wait till
28226 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
28227 fails to exit in reasonable time.
28229 @subheading A Bad Command
28231 Here's what happens if you pass a non-existent command:
28235 <- ^error,msg="Undefined MI command: rubbish"
28240 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28241 @node GDB/MI Command Description Format
28242 @section @sc{gdb/mi} Command Description Format
28244 The remaining sections describe blocks of commands. Each block of
28245 commands is laid out in a fashion similar to this section.
28247 @subheading Motivation
28249 The motivation for this collection of commands.
28251 @subheading Introduction
28253 A brief introduction to this collection of commands as a whole.
28255 @subheading Commands
28257 For each command in the block, the following is described:
28259 @subsubheading Synopsis
28262 -command @var{args}@dots{}
28265 @subsubheading Result
28267 @subsubheading @value{GDBN} Command
28269 The corresponding @value{GDBN} CLI command(s), if any.
28271 @subsubheading Example
28273 Example(s) formatted for readability. Some of the described commands have
28274 not been implemented yet and these are labeled N.A.@: (not available).
28277 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28278 @node GDB/MI Breakpoint Commands
28279 @section @sc{gdb/mi} Breakpoint Commands
28281 @cindex breakpoint commands for @sc{gdb/mi}
28282 @cindex @sc{gdb/mi}, breakpoint commands
28283 This section documents @sc{gdb/mi} commands for manipulating
28286 @subheading The @code{-break-after} Command
28287 @findex -break-after
28289 @subsubheading Synopsis
28292 -break-after @var{number} @var{count}
28295 The breakpoint number @var{number} is not in effect until it has been
28296 hit @var{count} times. To see how this is reflected in the output of
28297 the @samp{-break-list} command, see the description of the
28298 @samp{-break-list} command below.
28300 @subsubheading @value{GDBN} Command
28302 The corresponding @value{GDBN} command is @samp{ignore}.
28304 @subsubheading Example
28309 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28310 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28311 fullname="/home/foo/hello.c",line="5",times="0"@}
28318 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28319 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28320 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28321 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28322 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28323 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28324 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28325 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28326 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28327 line="5",times="0",ignore="3"@}]@}
28332 @subheading The @code{-break-catch} Command
28333 @findex -break-catch
28336 @subheading The @code{-break-commands} Command
28337 @findex -break-commands
28339 @subsubheading Synopsis
28342 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
28345 Specifies the CLI commands that should be executed when breakpoint
28346 @var{number} is hit. The parameters @var{command1} to @var{commandN}
28347 are the commands. If no command is specified, any previously-set
28348 commands are cleared. @xref{Break Commands}. Typical use of this
28349 functionality is tracing a program, that is, printing of values of
28350 some variables whenever breakpoint is hit and then continuing.
28352 @subsubheading @value{GDBN} Command
28354 The corresponding @value{GDBN} command is @samp{commands}.
28356 @subsubheading Example
28361 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28362 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28363 fullname="/home/foo/hello.c",line="5",times="0"@}
28365 -break-commands 1 "print v" "continue"
28370 @subheading The @code{-break-condition} Command
28371 @findex -break-condition
28373 @subsubheading Synopsis
28376 -break-condition @var{number} @var{expr}
28379 Breakpoint @var{number} will stop the program only if the condition in
28380 @var{expr} is true. The condition becomes part of the
28381 @samp{-break-list} output (see the description of the @samp{-break-list}
28384 @subsubheading @value{GDBN} Command
28386 The corresponding @value{GDBN} command is @samp{condition}.
28388 @subsubheading Example
28392 -break-condition 1 1
28396 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28397 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28398 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28399 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28400 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28401 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28402 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28403 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28404 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28405 line="5",cond="1",times="0",ignore="3"@}]@}
28409 @subheading The @code{-break-delete} Command
28410 @findex -break-delete
28412 @subsubheading Synopsis
28415 -break-delete ( @var{breakpoint} )+
28418 Delete the breakpoint(s) whose number(s) are specified in the argument
28419 list. This is obviously reflected in the breakpoint list.
28421 @subsubheading @value{GDBN} Command
28423 The corresponding @value{GDBN} command is @samp{delete}.
28425 @subsubheading Example
28433 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28434 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28435 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28436 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28437 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28438 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28439 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28444 @subheading The @code{-break-disable} Command
28445 @findex -break-disable
28447 @subsubheading Synopsis
28450 -break-disable ( @var{breakpoint} )+
28453 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28454 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28456 @subsubheading @value{GDBN} Command
28458 The corresponding @value{GDBN} command is @samp{disable}.
28460 @subsubheading Example
28468 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28469 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28470 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28471 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28472 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28473 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28474 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28475 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28476 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28477 line="5",times="0"@}]@}
28481 @subheading The @code{-break-enable} Command
28482 @findex -break-enable
28484 @subsubheading Synopsis
28487 -break-enable ( @var{breakpoint} )+
28490 Enable (previously disabled) @var{breakpoint}(s).
28492 @subsubheading @value{GDBN} Command
28494 The corresponding @value{GDBN} command is @samp{enable}.
28496 @subsubheading Example
28504 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28505 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28506 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28507 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28508 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28509 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28510 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28511 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28512 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28513 line="5",times="0"@}]@}
28517 @subheading The @code{-break-info} Command
28518 @findex -break-info
28520 @subsubheading Synopsis
28523 -break-info @var{breakpoint}
28527 Get information about a single breakpoint.
28529 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28530 Information}, for details on the format of each breakpoint in the
28533 @subsubheading @value{GDBN} Command
28535 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28537 @subsubheading Example
28540 @subheading The @code{-break-insert} Command
28541 @findex -break-insert
28543 @subsubheading Synopsis
28546 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28547 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28548 [ -p @var{thread-id} ] [ @var{location} ]
28552 If specified, @var{location}, can be one of:
28559 @item filename:linenum
28560 @item filename:function
28564 The possible optional parameters of this command are:
28568 Insert a temporary breakpoint.
28570 Insert a hardware breakpoint.
28572 If @var{location} cannot be parsed (for example if it
28573 refers to unknown files or functions), create a pending
28574 breakpoint. Without this flag, @value{GDBN} will report
28575 an error, and won't create a breakpoint, if @var{location}
28578 Create a disabled breakpoint.
28580 Create a tracepoint. @xref{Tracepoints}. When this parameter
28581 is used together with @samp{-h}, a fast tracepoint is created.
28582 @item -c @var{condition}
28583 Make the breakpoint conditional on @var{condition}.
28584 @item -i @var{ignore-count}
28585 Initialize the @var{ignore-count}.
28586 @item -p @var{thread-id}
28587 Restrict the breakpoint to the specified @var{thread-id}.
28590 @subsubheading Result
28592 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28593 resulting breakpoint.
28595 Note: this format is open to change.
28596 @c An out-of-band breakpoint instead of part of the result?
28598 @subsubheading @value{GDBN} Command
28600 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28601 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28603 @subsubheading Example
28608 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28609 fullname="/home/foo/recursive2.c,line="4",times="0"@}
28611 -break-insert -t foo
28612 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28613 fullname="/home/foo/recursive2.c,line="11",times="0"@}
28616 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28617 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28618 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28619 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28620 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28621 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28622 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28623 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28624 addr="0x0001072c", func="main",file="recursive2.c",
28625 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
28626 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28627 addr="0x00010774",func="foo",file="recursive2.c",
28628 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
28630 @c -break-insert -r foo.*
28631 @c ~int foo(int, int);
28632 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28633 @c "fullname="/home/foo/recursive2.c",line="11",times="0"@}
28637 @subheading The @code{-break-list} Command
28638 @findex -break-list
28640 @subsubheading Synopsis
28646 Displays the list of inserted breakpoints, showing the following fields:
28650 number of the breakpoint
28652 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28654 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28657 is the breakpoint enabled or no: @samp{y} or @samp{n}
28659 memory location at which the breakpoint is set
28661 logical location of the breakpoint, expressed by function name, file
28664 number of times the breakpoint has been hit
28667 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28668 @code{body} field is an empty list.
28670 @subsubheading @value{GDBN} Command
28672 The corresponding @value{GDBN} command is @samp{info break}.
28674 @subsubheading Example
28679 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28680 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28681 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28682 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28683 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28684 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28685 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28686 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28687 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
28688 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28689 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28690 line="13",times="0"@}]@}
28694 Here's an example of the result when there are no breakpoints:
28699 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28700 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28701 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28702 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28703 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28704 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28705 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28710 @subheading The @code{-break-passcount} Command
28711 @findex -break-passcount
28713 @subsubheading Synopsis
28716 -break-passcount @var{tracepoint-number} @var{passcount}
28719 Set the passcount for tracepoint @var{tracepoint-number} to
28720 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28721 is not a tracepoint, error is emitted. This corresponds to CLI
28722 command @samp{passcount}.
28724 @subheading The @code{-break-watch} Command
28725 @findex -break-watch
28727 @subsubheading Synopsis
28730 -break-watch [ -a | -r ]
28733 Create a watchpoint. With the @samp{-a} option it will create an
28734 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28735 read from or on a write to the memory location. With the @samp{-r}
28736 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28737 trigger only when the memory location is accessed for reading. Without
28738 either of the options, the watchpoint created is a regular watchpoint,
28739 i.e., it will trigger when the memory location is accessed for writing.
28740 @xref{Set Watchpoints, , Setting Watchpoints}.
28742 Note that @samp{-break-list} will report a single list of watchpoints and
28743 breakpoints inserted.
28745 @subsubheading @value{GDBN} Command
28747 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28750 @subsubheading Example
28752 Setting a watchpoint on a variable in the @code{main} function:
28757 ^done,wpt=@{number="2",exp="x"@}
28762 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28763 value=@{old="-268439212",new="55"@},
28764 frame=@{func="main",args=[],file="recursive2.c",
28765 fullname="/home/foo/bar/recursive2.c",line="5"@}
28769 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28770 the program execution twice: first for the variable changing value, then
28771 for the watchpoint going out of scope.
28776 ^done,wpt=@{number="5",exp="C"@}
28781 *stopped,reason="watchpoint-trigger",
28782 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28783 frame=@{func="callee4",args=[],
28784 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28785 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28790 *stopped,reason="watchpoint-scope",wpnum="5",
28791 frame=@{func="callee3",args=[@{name="strarg",
28792 value="0x11940 \"A string argument.\""@}],
28793 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28794 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28798 Listing breakpoints and watchpoints, at different points in the program
28799 execution. Note that once the watchpoint goes out of scope, it is
28805 ^done,wpt=@{number="2",exp="C"@}
28808 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28809 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28810 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28811 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28812 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28813 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28814 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28815 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28816 addr="0x00010734",func="callee4",
28817 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28818 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
28819 bkpt=@{number="2",type="watchpoint",disp="keep",
28820 enabled="y",addr="",what="C",times="0"@}]@}
28825 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
28826 value=@{old="-276895068",new="3"@},
28827 frame=@{func="callee4",args=[],
28828 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28829 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28832 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28833 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28834 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28835 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28836 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28837 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28838 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28839 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28840 addr="0x00010734",func="callee4",
28841 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28842 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
28843 bkpt=@{number="2",type="watchpoint",disp="keep",
28844 enabled="y",addr="",what="C",times="-5"@}]@}
28848 ^done,reason="watchpoint-scope",wpnum="2",
28849 frame=@{func="callee3",args=[@{name="strarg",
28850 value="0x11940 \"A string argument.\""@}],
28851 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28852 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28855 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28856 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28857 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28858 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28859 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28860 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28861 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28862 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28863 addr="0x00010734",func="callee4",
28864 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28865 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
28871 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28872 @node GDB/MI Catchpoint Commands
28873 @section @sc{gdb/mi} Catchpoint Commands
28875 This section documents @sc{gdb/mi} commands for manipulating
28878 @subheading The @code{-catch-load} Command
28879 @findex -catch-load
28881 @subsubheading Synopsis
28884 -catch-load [ -t ] [ -d ] @var{regexp}
28887 Add a catchpoint for library load events. If the @samp{-t} option is used,
28888 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28889 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
28890 in a disabled state. The @samp{regexp} argument is a regular
28891 expression used to match the name of the loaded library.
28894 @subsubheading @value{GDBN} Command
28896 The corresponding @value{GDBN} command is @samp{catch load}.
28898 @subsubheading Example
28901 -catch-load -t foo.so
28902 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
28903 what="load of library matching foo.so",catch-type="load",times="0"@}
28908 @subheading The @code{-catch-unload} Command
28909 @findex -catch-unload
28911 @subsubheading Synopsis
28914 -catch-unload [ -t ] [ -d ] @var{regexp}
28917 Add a catchpoint for library unload events. If the @samp{-t} option is
28918 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28919 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
28920 created in a disabled state. The @samp{regexp} argument is a regular
28921 expression used to match the name of the unloaded library.
28923 @subsubheading @value{GDBN} Command
28925 The corresponding @value{GDBN} command is @samp{catch unload}.
28927 @subsubheading Example
28930 -catch-unload -d bar.so
28931 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
28932 what="load of library matching bar.so",catch-type="unload",times="0"@}
28937 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28938 @node GDB/MI Program Context
28939 @section @sc{gdb/mi} Program Context
28941 @subheading The @code{-exec-arguments} Command
28942 @findex -exec-arguments
28945 @subsubheading Synopsis
28948 -exec-arguments @var{args}
28951 Set the inferior program arguments, to be used in the next
28954 @subsubheading @value{GDBN} Command
28956 The corresponding @value{GDBN} command is @samp{set args}.
28958 @subsubheading Example
28962 -exec-arguments -v word
28969 @subheading The @code{-exec-show-arguments} Command
28970 @findex -exec-show-arguments
28972 @subsubheading Synopsis
28975 -exec-show-arguments
28978 Print the arguments of the program.
28980 @subsubheading @value{GDBN} Command
28982 The corresponding @value{GDBN} command is @samp{show args}.
28984 @subsubheading Example
28989 @subheading The @code{-environment-cd} Command
28990 @findex -environment-cd
28992 @subsubheading Synopsis
28995 -environment-cd @var{pathdir}
28998 Set @value{GDBN}'s working directory.
29000 @subsubheading @value{GDBN} Command
29002 The corresponding @value{GDBN} command is @samp{cd}.
29004 @subsubheading Example
29008 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29014 @subheading The @code{-environment-directory} Command
29015 @findex -environment-directory
29017 @subsubheading Synopsis
29020 -environment-directory [ -r ] [ @var{pathdir} ]+
29023 Add directories @var{pathdir} to beginning of search path for source files.
29024 If the @samp{-r} option is used, the search path is reset to the default
29025 search path. If directories @var{pathdir} are supplied in addition to the
29026 @samp{-r} option, the search path is first reset and then addition
29028 Multiple directories may be specified, separated by blanks. Specifying
29029 multiple directories in a single command
29030 results in the directories added to the beginning of the
29031 search path in the same order they were presented in the command.
29032 If blanks are needed as
29033 part of a directory name, double-quotes should be used around
29034 the name. In the command output, the path will show up separated
29035 by the system directory-separator character. The directory-separator
29036 character must not be used
29037 in any directory name.
29038 If no directories are specified, the current search path is displayed.
29040 @subsubheading @value{GDBN} Command
29042 The corresponding @value{GDBN} command is @samp{dir}.
29044 @subsubheading Example
29048 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29049 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29051 -environment-directory ""
29052 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29054 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
29055 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
29057 -environment-directory -r
29058 ^done,source-path="$cdir:$cwd"
29063 @subheading The @code{-environment-path} Command
29064 @findex -environment-path
29066 @subsubheading Synopsis
29069 -environment-path [ -r ] [ @var{pathdir} ]+
29072 Add directories @var{pathdir} to beginning of search path for object files.
29073 If the @samp{-r} option is used, the search path is reset to the original
29074 search path that existed at gdb start-up. If directories @var{pathdir} are
29075 supplied in addition to the
29076 @samp{-r} option, the search path is first reset and then addition
29078 Multiple directories may be specified, separated by blanks. Specifying
29079 multiple directories in a single command
29080 results in the directories added to the beginning of the
29081 search path in the same order they were presented in the command.
29082 If blanks are needed as
29083 part of a directory name, double-quotes should be used around
29084 the name. In the command output, the path will show up separated
29085 by the system directory-separator character. The directory-separator
29086 character must not be used
29087 in any directory name.
29088 If no directories are specified, the current path is displayed.
29091 @subsubheading @value{GDBN} Command
29093 The corresponding @value{GDBN} command is @samp{path}.
29095 @subsubheading Example
29100 ^done,path="/usr/bin"
29102 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
29103 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
29105 -environment-path -r /usr/local/bin
29106 ^done,path="/usr/local/bin:/usr/bin"
29111 @subheading The @code{-environment-pwd} Command
29112 @findex -environment-pwd
29114 @subsubheading Synopsis
29120 Show the current working directory.
29122 @subsubheading @value{GDBN} Command
29124 The corresponding @value{GDBN} command is @samp{pwd}.
29126 @subsubheading Example
29131 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
29135 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29136 @node GDB/MI Thread Commands
29137 @section @sc{gdb/mi} Thread Commands
29140 @subheading The @code{-thread-info} Command
29141 @findex -thread-info
29143 @subsubheading Synopsis
29146 -thread-info [ @var{thread-id} ]
29149 Reports information about either a specific thread, if
29150 the @var{thread-id} parameter is present, or about all
29151 threads. When printing information about all threads,
29152 also reports the current thread.
29154 @subsubheading @value{GDBN} Command
29156 The @samp{info thread} command prints the same information
29159 @subsubheading Result
29161 The result is a list of threads. The following attributes are
29162 defined for a given thread:
29166 This field exists only for the current thread. It has the value @samp{*}.
29169 The identifier that @value{GDBN} uses to refer to the thread.
29172 The identifier that the target uses to refer to the thread.
29175 Extra information about the thread, in a target-specific format. This
29179 The name of the thread. If the user specified a name using the
29180 @code{thread name} command, then this name is given. Otherwise, if
29181 @value{GDBN} can extract the thread name from the target, then that
29182 name is given. If @value{GDBN} cannot find the thread name, then this
29186 The stack frame currently executing in the thread.
29189 The thread's state. The @samp{state} field may have the following
29194 The thread is stopped. Frame information is available for stopped
29198 The thread is running. There's no frame information for running
29204 If @value{GDBN} can find the CPU core on which this thread is running,
29205 then this field is the core identifier. This field is optional.
29209 @subsubheading Example
29214 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29215 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
29216 args=[]@},state="running"@},
29217 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29218 frame=@{level="0",addr="0x0804891f",func="foo",
29219 args=[@{name="i",value="10"@}],
29220 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
29221 state="running"@}],
29222 current-thread-id="1"
29226 @subheading The @code{-thread-list-ids} Command
29227 @findex -thread-list-ids
29229 @subsubheading Synopsis
29235 Produces a list of the currently known @value{GDBN} thread ids. At the
29236 end of the list it also prints the total number of such threads.
29238 This command is retained for historical reasons, the
29239 @code{-thread-info} command should be used instead.
29241 @subsubheading @value{GDBN} Command
29243 Part of @samp{info threads} supplies the same information.
29245 @subsubheading Example
29250 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29251 current-thread-id="1",number-of-threads="3"
29256 @subheading The @code{-thread-select} Command
29257 @findex -thread-select
29259 @subsubheading Synopsis
29262 -thread-select @var{threadnum}
29265 Make @var{threadnum} the current thread. It prints the number of the new
29266 current thread, and the topmost frame for that thread.
29268 This command is deprecated in favor of explicitly using the
29269 @samp{--thread} option to each command.
29271 @subsubheading @value{GDBN} Command
29273 The corresponding @value{GDBN} command is @samp{thread}.
29275 @subsubheading Example
29282 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29283 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29287 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29288 number-of-threads="3"
29291 ^done,new-thread-id="3",
29292 frame=@{level="0",func="vprintf",
29293 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29294 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
29298 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29299 @node GDB/MI Ada Tasking Commands
29300 @section @sc{gdb/mi} Ada Tasking Commands
29302 @subheading The @code{-ada-task-info} Command
29303 @findex -ada-task-info
29305 @subsubheading Synopsis
29308 -ada-task-info [ @var{task-id} ]
29311 Reports information about either a specific Ada task, if the
29312 @var{task-id} parameter is present, or about all Ada tasks.
29314 @subsubheading @value{GDBN} Command
29316 The @samp{info tasks} command prints the same information
29317 about all Ada tasks (@pxref{Ada Tasks}).
29319 @subsubheading Result
29321 The result is a table of Ada tasks. The following columns are
29322 defined for each Ada task:
29326 This field exists only for the current thread. It has the value @samp{*}.
29329 The identifier that @value{GDBN} uses to refer to the Ada task.
29332 The identifier that the target uses to refer to the Ada task.
29335 The identifier of the thread corresponding to the Ada task.
29337 This field should always exist, as Ada tasks are always implemented
29338 on top of a thread. But if @value{GDBN} cannot find this corresponding
29339 thread for any reason, the field is omitted.
29342 This field exists only when the task was created by another task.
29343 In this case, it provides the ID of the parent task.
29346 The base priority of the task.
29349 The current state of the task. For a detailed description of the
29350 possible states, see @ref{Ada Tasks}.
29353 The name of the task.
29357 @subsubheading Example
29361 ^done,tasks=@{nr_rows="3",nr_cols="8",
29362 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
29363 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
29364 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
29365 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
29366 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
29367 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
29368 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
29369 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29370 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29371 state="Child Termination Wait",name="main_task"@}]@}
29375 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29376 @node GDB/MI Program Execution
29377 @section @sc{gdb/mi} Program Execution
29379 These are the asynchronous commands which generate the out-of-band
29380 record @samp{*stopped}. Currently @value{GDBN} only really executes
29381 asynchronously with remote targets and this interaction is mimicked in
29384 @subheading The @code{-exec-continue} Command
29385 @findex -exec-continue
29387 @subsubheading Synopsis
29390 -exec-continue [--reverse] [--all|--thread-group N]
29393 Resumes the execution of the inferior program, which will continue
29394 to execute until it reaches a debugger stop event. If the
29395 @samp{--reverse} option is specified, execution resumes in reverse until
29396 it reaches a stop event. Stop events may include
29399 breakpoints or watchpoints
29401 signals or exceptions
29403 the end of the process (or its beginning under @samp{--reverse})
29405 the end or beginning of a replay log if one is being used.
29407 In all-stop mode (@pxref{All-Stop
29408 Mode}), may resume only one thread, or all threads, depending on the
29409 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29410 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29411 ignored in all-stop mode. If the @samp{--thread-group} options is
29412 specified, then all threads in that thread group are resumed.
29414 @subsubheading @value{GDBN} Command
29416 The corresponding @value{GDBN} corresponding is @samp{continue}.
29418 @subsubheading Example
29425 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
29426 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
29432 @subheading The @code{-exec-finish} Command
29433 @findex -exec-finish
29435 @subsubheading Synopsis
29438 -exec-finish [--reverse]
29441 Resumes the execution of the inferior program until the current
29442 function is exited. Displays the results returned by the function.
29443 If the @samp{--reverse} option is specified, resumes the reverse
29444 execution of the inferior program until the point where current
29445 function was called.
29447 @subsubheading @value{GDBN} Command
29449 The corresponding @value{GDBN} command is @samp{finish}.
29451 @subsubheading Example
29453 Function returning @code{void}.
29460 *stopped,reason="function-finished",frame=@{func="main",args=[],
29461 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
29465 Function returning other than @code{void}. The name of the internal
29466 @value{GDBN} variable storing the result is printed, together with the
29473 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29474 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29475 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29476 gdb-result-var="$1",return-value="0"
29481 @subheading The @code{-exec-interrupt} Command
29482 @findex -exec-interrupt
29484 @subsubheading Synopsis
29487 -exec-interrupt [--all|--thread-group N]
29490 Interrupts the background execution of the target. Note how the token
29491 associated with the stop message is the one for the execution command
29492 that has been interrupted. The token for the interrupt itself only
29493 appears in the @samp{^done} output. If the user is trying to
29494 interrupt a non-running program, an error message will be printed.
29496 Note that when asynchronous execution is enabled, this command is
29497 asynchronous just like other execution commands. That is, first the
29498 @samp{^done} response will be printed, and the target stop will be
29499 reported after that using the @samp{*stopped} notification.
29501 In non-stop mode, only the context thread is interrupted by default.
29502 All threads (in all inferiors) will be interrupted if the
29503 @samp{--all} option is specified. If the @samp{--thread-group}
29504 option is specified, all threads in that group will be interrupted.
29506 @subsubheading @value{GDBN} Command
29508 The corresponding @value{GDBN} command is @samp{interrupt}.
29510 @subsubheading Example
29521 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29522 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29523 fullname="/home/foo/bar/try.c",line="13"@}
29528 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29532 @subheading The @code{-exec-jump} Command
29535 @subsubheading Synopsis
29538 -exec-jump @var{location}
29541 Resumes execution of the inferior program at the location specified by
29542 parameter. @xref{Specify Location}, for a description of the
29543 different forms of @var{location}.
29545 @subsubheading @value{GDBN} Command
29547 The corresponding @value{GDBN} command is @samp{jump}.
29549 @subsubheading Example
29552 -exec-jump foo.c:10
29553 *running,thread-id="all"
29558 @subheading The @code{-exec-next} Command
29561 @subsubheading Synopsis
29564 -exec-next [--reverse]
29567 Resumes execution of the inferior program, stopping when the beginning
29568 of the next source line is reached.
29570 If the @samp{--reverse} option is specified, resumes reverse execution
29571 of the inferior program, stopping at the beginning of the previous
29572 source line. If you issue this command on the first line of a
29573 function, it will take you back to the caller of that function, to the
29574 source line where the function was called.
29577 @subsubheading @value{GDBN} Command
29579 The corresponding @value{GDBN} command is @samp{next}.
29581 @subsubheading Example
29587 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29592 @subheading The @code{-exec-next-instruction} Command
29593 @findex -exec-next-instruction
29595 @subsubheading Synopsis
29598 -exec-next-instruction [--reverse]
29601 Executes one machine instruction. If the instruction is a function
29602 call, continues until the function returns. If the program stops at an
29603 instruction in the middle of a source line, the address will be
29606 If the @samp{--reverse} option is specified, resumes reverse execution
29607 of the inferior program, stopping at the previous instruction. If the
29608 previously executed instruction was a return from another function,
29609 it will continue to execute in reverse until the call to that function
29610 (from the current stack frame) is reached.
29612 @subsubheading @value{GDBN} Command
29614 The corresponding @value{GDBN} command is @samp{nexti}.
29616 @subsubheading Example
29620 -exec-next-instruction
29624 *stopped,reason="end-stepping-range",
29625 addr="0x000100d4",line="5",file="hello.c"
29630 @subheading The @code{-exec-return} Command
29631 @findex -exec-return
29633 @subsubheading Synopsis
29639 Makes current function return immediately. Doesn't execute the inferior.
29640 Displays the new current frame.
29642 @subsubheading @value{GDBN} Command
29644 The corresponding @value{GDBN} command is @samp{return}.
29646 @subsubheading Example
29650 200-break-insert callee4
29651 200^done,bkpt=@{number="1",addr="0x00010734",
29652 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29657 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29658 frame=@{func="callee4",args=[],
29659 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29660 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29666 111^done,frame=@{level="0",func="callee3",
29667 args=[@{name="strarg",
29668 value="0x11940 \"A string argument.\""@}],
29669 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29670 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29675 @subheading The @code{-exec-run} Command
29678 @subsubheading Synopsis
29681 -exec-run [--all | --thread-group N]
29684 Starts execution of the inferior from the beginning. The inferior
29685 executes until either a breakpoint is encountered or the program
29686 exits. In the latter case the output will include an exit code, if
29687 the program has exited exceptionally.
29689 When no option is specified, the current inferior is started. If the
29690 @samp{--thread-group} option is specified, it should refer to a thread
29691 group of type @samp{process}, and that thread group will be started.
29692 If the @samp{--all} option is specified, then all inferiors will be started.
29694 @subsubheading @value{GDBN} Command
29696 The corresponding @value{GDBN} command is @samp{run}.
29698 @subsubheading Examples
29703 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29708 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29709 frame=@{func="main",args=[],file="recursive2.c",
29710 fullname="/home/foo/bar/recursive2.c",line="4"@}
29715 Program exited normally:
29723 *stopped,reason="exited-normally"
29728 Program exited exceptionally:
29736 *stopped,reason="exited",exit-code="01"
29740 Another way the program can terminate is if it receives a signal such as
29741 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29745 *stopped,reason="exited-signalled",signal-name="SIGINT",
29746 signal-meaning="Interrupt"
29750 @c @subheading -exec-signal
29753 @subheading The @code{-exec-step} Command
29756 @subsubheading Synopsis
29759 -exec-step [--reverse]
29762 Resumes execution of the inferior program, stopping when the beginning
29763 of the next source line is reached, if the next source line is not a
29764 function call. If it is, stop at the first instruction of the called
29765 function. If the @samp{--reverse} option is specified, resumes reverse
29766 execution of the inferior program, stopping at the beginning of the
29767 previously executed source line.
29769 @subsubheading @value{GDBN} Command
29771 The corresponding @value{GDBN} command is @samp{step}.
29773 @subsubheading Example
29775 Stepping into a function:
29781 *stopped,reason="end-stepping-range",
29782 frame=@{func="foo",args=[@{name="a",value="10"@},
29783 @{name="b",value="0"@}],file="recursive2.c",
29784 fullname="/home/foo/bar/recursive2.c",line="11"@}
29794 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
29799 @subheading The @code{-exec-step-instruction} Command
29800 @findex -exec-step-instruction
29802 @subsubheading Synopsis
29805 -exec-step-instruction [--reverse]
29808 Resumes the inferior which executes one machine instruction. If the
29809 @samp{--reverse} option is specified, resumes reverse execution of the
29810 inferior program, stopping at the previously executed instruction.
29811 The output, once @value{GDBN} has stopped, will vary depending on
29812 whether we have stopped in the middle of a source line or not. In the
29813 former case, the address at which the program stopped will be printed
29816 @subsubheading @value{GDBN} Command
29818 The corresponding @value{GDBN} command is @samp{stepi}.
29820 @subsubheading Example
29824 -exec-step-instruction
29828 *stopped,reason="end-stepping-range",
29829 frame=@{func="foo",args=[],file="try.c",
29830 fullname="/home/foo/bar/try.c",line="10"@}
29832 -exec-step-instruction
29836 *stopped,reason="end-stepping-range",
29837 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
29838 fullname="/home/foo/bar/try.c",line="10"@}
29843 @subheading The @code{-exec-until} Command
29844 @findex -exec-until
29846 @subsubheading Synopsis
29849 -exec-until [ @var{location} ]
29852 Executes the inferior until the @var{location} specified in the
29853 argument is reached. If there is no argument, the inferior executes
29854 until a source line greater than the current one is reached. The
29855 reason for stopping in this case will be @samp{location-reached}.
29857 @subsubheading @value{GDBN} Command
29859 The corresponding @value{GDBN} command is @samp{until}.
29861 @subsubheading Example
29865 -exec-until recursive2.c:6
29869 *stopped,reason="location-reached",frame=@{func="main",args=[],
29870 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
29875 @subheading -file-clear
29876 Is this going away????
29879 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29880 @node GDB/MI Stack Manipulation
29881 @section @sc{gdb/mi} Stack Manipulation Commands
29884 @subheading The @code{-stack-info-frame} Command
29885 @findex -stack-info-frame
29887 @subsubheading Synopsis
29893 Get info on the selected frame.
29895 @subsubheading @value{GDBN} Command
29897 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
29898 (without arguments).
29900 @subsubheading Example
29905 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
29906 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29907 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
29911 @subheading The @code{-stack-info-depth} Command
29912 @findex -stack-info-depth
29914 @subsubheading Synopsis
29917 -stack-info-depth [ @var{max-depth} ]
29920 Return the depth of the stack. If the integer argument @var{max-depth}
29921 is specified, do not count beyond @var{max-depth} frames.
29923 @subsubheading @value{GDBN} Command
29925 There's no equivalent @value{GDBN} command.
29927 @subsubheading Example
29929 For a stack with frame levels 0 through 11:
29936 -stack-info-depth 4
29939 -stack-info-depth 12
29942 -stack-info-depth 11
29945 -stack-info-depth 13
29950 @subheading The @code{-stack-list-arguments} Command
29951 @findex -stack-list-arguments
29953 @subsubheading Synopsis
29956 -stack-list-arguments @var{print-values}
29957 [ @var{low-frame} @var{high-frame} ]
29960 Display a list of the arguments for the frames between @var{low-frame}
29961 and @var{high-frame} (inclusive). If @var{low-frame} and
29962 @var{high-frame} are not provided, list the arguments for the whole
29963 call stack. If the two arguments are equal, show the single frame
29964 at the corresponding level. It is an error if @var{low-frame} is
29965 larger than the actual number of frames. On the other hand,
29966 @var{high-frame} may be larger than the actual number of frames, in
29967 which case only existing frames will be returned.
29969 If @var{print-values} is 0 or @code{--no-values}, print only the names of
29970 the variables; if it is 1 or @code{--all-values}, print also their
29971 values; and if it is 2 or @code{--simple-values}, print the name,
29972 type and value for simple data types, and the name and type for arrays,
29973 structures and unions.
29975 Use of this command to obtain arguments in a single frame is
29976 deprecated in favor of the @samp{-stack-list-variables} command.
29978 @subsubheading @value{GDBN} Command
29980 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
29981 @samp{gdb_get_args} command which partially overlaps with the
29982 functionality of @samp{-stack-list-arguments}.
29984 @subsubheading Example
29991 frame=@{level="0",addr="0x00010734",func="callee4",
29992 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29993 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
29994 frame=@{level="1",addr="0x0001076c",func="callee3",
29995 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29996 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
29997 frame=@{level="2",addr="0x0001078c",func="callee2",
29998 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29999 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
30000 frame=@{level="3",addr="0x000107b4",func="callee1",
30001 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30002 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
30003 frame=@{level="4",addr="0x000107e0",func="main",
30004 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30005 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
30007 -stack-list-arguments 0
30010 frame=@{level="0",args=[]@},
30011 frame=@{level="1",args=[name="strarg"]@},
30012 frame=@{level="2",args=[name="intarg",name="strarg"]@},
30013 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
30014 frame=@{level="4",args=[]@}]
30016 -stack-list-arguments 1
30019 frame=@{level="0",args=[]@},
30021 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30022 frame=@{level="2",args=[
30023 @{name="intarg",value="2"@},
30024 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30025 @{frame=@{level="3",args=[
30026 @{name="intarg",value="2"@},
30027 @{name="strarg",value="0x11940 \"A string argument.\""@},
30028 @{name="fltarg",value="3.5"@}]@},
30029 frame=@{level="4",args=[]@}]
30031 -stack-list-arguments 0 2 2
30032 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
30034 -stack-list-arguments 1 2 2
30035 ^done,stack-args=[frame=@{level="2",
30036 args=[@{name="intarg",value="2"@},
30037 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
30041 @c @subheading -stack-list-exception-handlers
30044 @subheading The @code{-stack-list-frames} Command
30045 @findex -stack-list-frames
30047 @subsubheading Synopsis
30050 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
30053 List the frames currently on the stack. For each frame it displays the
30058 The frame number, 0 being the topmost frame, i.e., the innermost function.
30060 The @code{$pc} value for that frame.
30064 File name of the source file where the function lives.
30065 @item @var{fullname}
30066 The full file name of the source file where the function lives.
30068 Line number corresponding to the @code{$pc}.
30070 The shared library where this function is defined. This is only given
30071 if the frame's function is not known.
30074 If invoked without arguments, this command prints a backtrace for the
30075 whole stack. If given two integer arguments, it shows the frames whose
30076 levels are between the two arguments (inclusive). If the two arguments
30077 are equal, it shows the single frame at the corresponding level. It is
30078 an error if @var{low-frame} is larger than the actual number of
30079 frames. On the other hand, @var{high-frame} may be larger than the
30080 actual number of frames, in which case only existing frames will be returned.
30082 @subsubheading @value{GDBN} Command
30084 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
30086 @subsubheading Example
30088 Full stack backtrace:
30094 [frame=@{level="0",addr="0x0001076c",func="foo",
30095 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
30096 frame=@{level="1",addr="0x000107a4",func="foo",
30097 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30098 frame=@{level="2",addr="0x000107a4",func="foo",
30099 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30100 frame=@{level="3",addr="0x000107a4",func="foo",
30101 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30102 frame=@{level="4",addr="0x000107a4",func="foo",
30103 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30104 frame=@{level="5",addr="0x000107a4",func="foo",
30105 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30106 frame=@{level="6",addr="0x000107a4",func="foo",
30107 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30108 frame=@{level="7",addr="0x000107a4",func="foo",
30109 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30110 frame=@{level="8",addr="0x000107a4",func="foo",
30111 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30112 frame=@{level="9",addr="0x000107a4",func="foo",
30113 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30114 frame=@{level="10",addr="0x000107a4",func="foo",
30115 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30116 frame=@{level="11",addr="0x00010738",func="main",
30117 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
30121 Show frames between @var{low_frame} and @var{high_frame}:
30125 -stack-list-frames 3 5
30127 [frame=@{level="3",addr="0x000107a4",func="foo",
30128 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30129 frame=@{level="4",addr="0x000107a4",func="foo",
30130 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30131 frame=@{level="5",addr="0x000107a4",func="foo",
30132 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30136 Show a single frame:
30140 -stack-list-frames 3 3
30142 [frame=@{level="3",addr="0x000107a4",func="foo",
30143 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30148 @subheading The @code{-stack-list-locals} Command
30149 @findex -stack-list-locals
30151 @subsubheading Synopsis
30154 -stack-list-locals @var{print-values}
30157 Display the local variable names for the selected frame. If
30158 @var{print-values} is 0 or @code{--no-values}, print only the names of
30159 the variables; if it is 1 or @code{--all-values}, print also their
30160 values; and if it is 2 or @code{--simple-values}, print the name,
30161 type and value for simple data types, and the name and type for arrays,
30162 structures and unions. In this last case, a frontend can immediately
30163 display the value of simple data types and create variable objects for
30164 other data types when the user wishes to explore their values in
30167 This command is deprecated in favor of the
30168 @samp{-stack-list-variables} command.
30170 @subsubheading @value{GDBN} Command
30172 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
30174 @subsubheading Example
30178 -stack-list-locals 0
30179 ^done,locals=[name="A",name="B",name="C"]
30181 -stack-list-locals --all-values
30182 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
30183 @{name="C",value="@{1, 2, 3@}"@}]
30184 -stack-list-locals --simple-values
30185 ^done,locals=[@{name="A",type="int",value="1"@},
30186 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
30190 @subheading The @code{-stack-list-variables} Command
30191 @findex -stack-list-variables
30193 @subsubheading Synopsis
30196 -stack-list-variables @var{print-values}
30199 Display the names of local variables and function arguments for the selected frame. If
30200 @var{print-values} is 0 or @code{--no-values}, print only the names of
30201 the variables; if it is 1 or @code{--all-values}, print also their
30202 values; and if it is 2 or @code{--simple-values}, print the name,
30203 type and value for simple data types, and the name and type for arrays,
30204 structures and unions.
30206 @subsubheading Example
30210 -stack-list-variables --thread 1 --frame 0 --all-values
30211 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30216 @subheading The @code{-stack-select-frame} Command
30217 @findex -stack-select-frame
30219 @subsubheading Synopsis
30222 -stack-select-frame @var{framenum}
30225 Change the selected frame. Select a different frame @var{framenum} on
30228 This command in deprecated in favor of passing the @samp{--frame}
30229 option to every command.
30231 @subsubheading @value{GDBN} Command
30233 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30234 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30236 @subsubheading Example
30240 -stack-select-frame 2
30245 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30246 @node GDB/MI Variable Objects
30247 @section @sc{gdb/mi} Variable Objects
30251 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30253 For the implementation of a variable debugger window (locals, watched
30254 expressions, etc.), we are proposing the adaptation of the existing code
30255 used by @code{Insight}.
30257 The two main reasons for that are:
30261 It has been proven in practice (it is already on its second generation).
30264 It will shorten development time (needless to say how important it is
30268 The original interface was designed to be used by Tcl code, so it was
30269 slightly changed so it could be used through @sc{gdb/mi}. This section
30270 describes the @sc{gdb/mi} operations that will be available and gives some
30271 hints about their use.
30273 @emph{Note}: In addition to the set of operations described here, we
30274 expect the @sc{gui} implementation of a variable window to require, at
30275 least, the following operations:
30278 @item @code{-gdb-show} @code{output-radix}
30279 @item @code{-stack-list-arguments}
30280 @item @code{-stack-list-locals}
30281 @item @code{-stack-select-frame}
30286 @subheading Introduction to Variable Objects
30288 @cindex variable objects in @sc{gdb/mi}
30290 Variable objects are "object-oriented" MI interface for examining and
30291 changing values of expressions. Unlike some other MI interfaces that
30292 work with expressions, variable objects are specifically designed for
30293 simple and efficient presentation in the frontend. A variable object
30294 is identified by string name. When a variable object is created, the
30295 frontend specifies the expression for that variable object. The
30296 expression can be a simple variable, or it can be an arbitrary complex
30297 expression, and can even involve CPU registers. After creating a
30298 variable object, the frontend can invoke other variable object
30299 operations---for example to obtain or change the value of a variable
30300 object, or to change display format.
30302 Variable objects have hierarchical tree structure. Any variable object
30303 that corresponds to a composite type, such as structure in C, has
30304 a number of child variable objects, for example corresponding to each
30305 element of a structure. A child variable object can itself have
30306 children, recursively. Recursion ends when we reach
30307 leaf variable objects, which always have built-in types. Child variable
30308 objects are created only by explicit request, so if a frontend
30309 is not interested in the children of a particular variable object, no
30310 child will be created.
30312 For a leaf variable object it is possible to obtain its value as a
30313 string, or set the value from a string. String value can be also
30314 obtained for a non-leaf variable object, but it's generally a string
30315 that only indicates the type of the object, and does not list its
30316 contents. Assignment to a non-leaf variable object is not allowed.
30318 A frontend does not need to read the values of all variable objects each time
30319 the program stops. Instead, MI provides an update command that lists all
30320 variable objects whose values has changed since the last update
30321 operation. This considerably reduces the amount of data that must
30322 be transferred to the frontend. As noted above, children variable
30323 objects are created on demand, and only leaf variable objects have a
30324 real value. As result, gdb will read target memory only for leaf
30325 variables that frontend has created.
30327 The automatic update is not always desirable. For example, a frontend
30328 might want to keep a value of some expression for future reference,
30329 and never update it. For another example, fetching memory is
30330 relatively slow for embedded targets, so a frontend might want
30331 to disable automatic update for the variables that are either not
30332 visible on the screen, or ``closed''. This is possible using so
30333 called ``frozen variable objects''. Such variable objects are never
30334 implicitly updated.
30336 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30337 fixed variable object, the expression is parsed when the variable
30338 object is created, including associating identifiers to specific
30339 variables. The meaning of expression never changes. For a floating
30340 variable object the values of variables whose names appear in the
30341 expressions are re-evaluated every time in the context of the current
30342 frame. Consider this example:
30347 struct work_state state;
30354 If a fixed variable object for the @code{state} variable is created in
30355 this function, and we enter the recursive call, the variable
30356 object will report the value of @code{state} in the top-level
30357 @code{do_work} invocation. On the other hand, a floating variable
30358 object will report the value of @code{state} in the current frame.
30360 If an expression specified when creating a fixed variable object
30361 refers to a local variable, the variable object becomes bound to the
30362 thread and frame in which the variable object is created. When such
30363 variable object is updated, @value{GDBN} makes sure that the
30364 thread/frame combination the variable object is bound to still exists,
30365 and re-evaluates the variable object in context of that thread/frame.
30367 The following is the complete set of @sc{gdb/mi} operations defined to
30368 access this functionality:
30370 @multitable @columnfractions .4 .6
30371 @item @strong{Operation}
30372 @tab @strong{Description}
30374 @item @code{-enable-pretty-printing}
30375 @tab enable Python-based pretty-printing
30376 @item @code{-var-create}
30377 @tab create a variable object
30378 @item @code{-var-delete}
30379 @tab delete the variable object and/or its children
30380 @item @code{-var-set-format}
30381 @tab set the display format of this variable
30382 @item @code{-var-show-format}
30383 @tab show the display format of this variable
30384 @item @code{-var-info-num-children}
30385 @tab tells how many children this object has
30386 @item @code{-var-list-children}
30387 @tab return a list of the object's children
30388 @item @code{-var-info-type}
30389 @tab show the type of this variable object
30390 @item @code{-var-info-expression}
30391 @tab print parent-relative expression that this variable object represents
30392 @item @code{-var-info-path-expression}
30393 @tab print full expression that this variable object represents
30394 @item @code{-var-show-attributes}
30395 @tab is this variable editable? does it exist here?
30396 @item @code{-var-evaluate-expression}
30397 @tab get the value of this variable
30398 @item @code{-var-assign}
30399 @tab set the value of this variable
30400 @item @code{-var-update}
30401 @tab update the variable and its children
30402 @item @code{-var-set-frozen}
30403 @tab set frozeness attribute
30404 @item @code{-var-set-update-range}
30405 @tab set range of children to display on update
30408 In the next subsection we describe each operation in detail and suggest
30409 how it can be used.
30411 @subheading Description And Use of Operations on Variable Objects
30413 @subheading The @code{-enable-pretty-printing} Command
30414 @findex -enable-pretty-printing
30417 -enable-pretty-printing
30420 @value{GDBN} allows Python-based visualizers to affect the output of the
30421 MI variable object commands. However, because there was no way to
30422 implement this in a fully backward-compatible way, a front end must
30423 request that this functionality be enabled.
30425 Once enabled, this feature cannot be disabled.
30427 Note that if Python support has not been compiled into @value{GDBN},
30428 this command will still succeed (and do nothing).
30430 This feature is currently (as of @value{GDBN} 7.0) experimental, and
30431 may work differently in future versions of @value{GDBN}.
30433 @subheading The @code{-var-create} Command
30434 @findex -var-create
30436 @subsubheading Synopsis
30439 -var-create @{@var{name} | "-"@}
30440 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30443 This operation creates a variable object, which allows the monitoring of
30444 a variable, the result of an expression, a memory cell or a CPU
30447 The @var{name} parameter is the string by which the object can be
30448 referenced. It must be unique. If @samp{-} is specified, the varobj
30449 system will generate a string ``varNNNNNN'' automatically. It will be
30450 unique provided that one does not specify @var{name} of that format.
30451 The command fails if a duplicate name is found.
30453 The frame under which the expression should be evaluated can be
30454 specified by @var{frame-addr}. A @samp{*} indicates that the current
30455 frame should be used. A @samp{@@} indicates that a floating variable
30456 object must be created.
30458 @var{expression} is any expression valid on the current language set (must not
30459 begin with a @samp{*}), or one of the following:
30463 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30466 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30469 @samp{$@var{regname}} --- a CPU register name
30472 @cindex dynamic varobj
30473 A varobj's contents may be provided by a Python-based pretty-printer. In this
30474 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30475 have slightly different semantics in some cases. If the
30476 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30477 will never create a dynamic varobj. This ensures backward
30478 compatibility for existing clients.
30480 @subsubheading Result
30482 This operation returns attributes of the newly-created varobj. These
30487 The name of the varobj.
30490 The number of children of the varobj. This number is not necessarily
30491 reliable for a dynamic varobj. Instead, you must examine the
30492 @samp{has_more} attribute.
30495 The varobj's scalar value. For a varobj whose type is some sort of
30496 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30497 will not be interesting.
30500 The varobj's type. This is a string representation of the type, as
30501 would be printed by the @value{GDBN} CLI. If @samp{print object}
30502 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30503 @emph{actual} (derived) type of the object is shown rather than the
30504 @emph{declared} one.
30507 If a variable object is bound to a specific thread, then this is the
30508 thread's identifier.
30511 For a dynamic varobj, this indicates whether there appear to be any
30512 children available. For a non-dynamic varobj, this will be 0.
30515 This attribute will be present and have the value @samp{1} if the
30516 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30517 then this attribute will not be present.
30520 A dynamic varobj can supply a display hint to the front end. The
30521 value comes directly from the Python pretty-printer object's
30522 @code{display_hint} method. @xref{Pretty Printing API}.
30525 Typical output will look like this:
30528 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30529 has_more="@var{has_more}"
30533 @subheading The @code{-var-delete} Command
30534 @findex -var-delete
30536 @subsubheading Synopsis
30539 -var-delete [ -c ] @var{name}
30542 Deletes a previously created variable object and all of its children.
30543 With the @samp{-c} option, just deletes the children.
30545 Returns an error if the object @var{name} is not found.
30548 @subheading The @code{-var-set-format} Command
30549 @findex -var-set-format
30551 @subsubheading Synopsis
30554 -var-set-format @var{name} @var{format-spec}
30557 Sets the output format for the value of the object @var{name} to be
30560 @anchor{-var-set-format}
30561 The syntax for the @var{format-spec} is as follows:
30564 @var{format-spec} @expansion{}
30565 @{binary | decimal | hexadecimal | octal | natural@}
30568 The natural format is the default format choosen automatically
30569 based on the variable type (like decimal for an @code{int}, hex
30570 for pointers, etc.).
30572 For a variable with children, the format is set only on the
30573 variable itself, and the children are not affected.
30575 @subheading The @code{-var-show-format} Command
30576 @findex -var-show-format
30578 @subsubheading Synopsis
30581 -var-show-format @var{name}
30584 Returns the format used to display the value of the object @var{name}.
30587 @var{format} @expansion{}
30592 @subheading The @code{-var-info-num-children} Command
30593 @findex -var-info-num-children
30595 @subsubheading Synopsis
30598 -var-info-num-children @var{name}
30601 Returns the number of children of a variable object @var{name}:
30607 Note that this number is not completely reliable for a dynamic varobj.
30608 It will return the current number of children, but more children may
30612 @subheading The @code{-var-list-children} Command
30613 @findex -var-list-children
30615 @subsubheading Synopsis
30618 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30620 @anchor{-var-list-children}
30622 Return a list of the children of the specified variable object and
30623 create variable objects for them, if they do not already exist. With
30624 a single argument or if @var{print-values} has a value of 0 or
30625 @code{--no-values}, print only the names of the variables; if
30626 @var{print-values} is 1 or @code{--all-values}, also print their
30627 values; and if it is 2 or @code{--simple-values} print the name and
30628 value for simple data types and just the name for arrays, structures
30631 @var{from} and @var{to}, if specified, indicate the range of children
30632 to report. If @var{from} or @var{to} is less than zero, the range is
30633 reset and all children will be reported. Otherwise, children starting
30634 at @var{from} (zero-based) and up to and excluding @var{to} will be
30637 If a child range is requested, it will only affect the current call to
30638 @code{-var-list-children}, but not future calls to @code{-var-update}.
30639 For this, you must instead use @code{-var-set-update-range}. The
30640 intent of this approach is to enable a front end to implement any
30641 update approach it likes; for example, scrolling a view may cause the
30642 front end to request more children with @code{-var-list-children}, and
30643 then the front end could call @code{-var-set-update-range} with a
30644 different range to ensure that future updates are restricted to just
30647 For each child the following results are returned:
30652 Name of the variable object created for this child.
30655 The expression to be shown to the user by the front end to designate this child.
30656 For example this may be the name of a structure member.
30658 For a dynamic varobj, this value cannot be used to form an
30659 expression. There is no way to do this at all with a dynamic varobj.
30661 For C/C@t{++} structures there are several pseudo children returned to
30662 designate access qualifiers. For these pseudo children @var{exp} is
30663 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30664 type and value are not present.
30666 A dynamic varobj will not report the access qualifying
30667 pseudo-children, regardless of the language. This information is not
30668 available at all with a dynamic varobj.
30671 Number of children this child has. For a dynamic varobj, this will be
30675 The type of the child. If @samp{print object}
30676 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30677 @emph{actual} (derived) type of the object is shown rather than the
30678 @emph{declared} one.
30681 If values were requested, this is the value.
30684 If this variable object is associated with a thread, this is the thread id.
30685 Otherwise this result is not present.
30688 If the variable object is frozen, this variable will be present with a value of 1.
30691 The result may have its own attributes:
30695 A dynamic varobj can supply a display hint to the front end. The
30696 value comes directly from the Python pretty-printer object's
30697 @code{display_hint} method. @xref{Pretty Printing API}.
30700 This is an integer attribute which is nonzero if there are children
30701 remaining after the end of the selected range.
30704 @subsubheading Example
30708 -var-list-children n
30709 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30710 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30712 -var-list-children --all-values n
30713 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30714 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30718 @subheading The @code{-var-info-type} Command
30719 @findex -var-info-type
30721 @subsubheading Synopsis
30724 -var-info-type @var{name}
30727 Returns the type of the specified variable @var{name}. The type is
30728 returned as a string in the same format as it is output by the
30732 type=@var{typename}
30736 @subheading The @code{-var-info-expression} Command
30737 @findex -var-info-expression
30739 @subsubheading Synopsis
30742 -var-info-expression @var{name}
30745 Returns a string that is suitable for presenting this
30746 variable object in user interface. The string is generally
30747 not valid expression in the current language, and cannot be evaluated.
30749 For example, if @code{a} is an array, and variable object
30750 @code{A} was created for @code{a}, then we'll get this output:
30753 (gdb) -var-info-expression A.1
30754 ^done,lang="C",exp="1"
30758 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
30760 Note that the output of the @code{-var-list-children} command also
30761 includes those expressions, so the @code{-var-info-expression} command
30764 @subheading The @code{-var-info-path-expression} Command
30765 @findex -var-info-path-expression
30767 @subsubheading Synopsis
30770 -var-info-path-expression @var{name}
30773 Returns an expression that can be evaluated in the current
30774 context and will yield the same value that a variable object has.
30775 Compare this with the @code{-var-info-expression} command, which
30776 result can be used only for UI presentation. Typical use of
30777 the @code{-var-info-path-expression} command is creating a
30778 watchpoint from a variable object.
30780 This command is currently not valid for children of a dynamic varobj,
30781 and will give an error when invoked on one.
30783 For example, suppose @code{C} is a C@t{++} class, derived from class
30784 @code{Base}, and that the @code{Base} class has a member called
30785 @code{m_size}. Assume a variable @code{c} is has the type of
30786 @code{C} and a variable object @code{C} was created for variable
30787 @code{c}. Then, we'll get this output:
30789 (gdb) -var-info-path-expression C.Base.public.m_size
30790 ^done,path_expr=((Base)c).m_size)
30793 @subheading The @code{-var-show-attributes} Command
30794 @findex -var-show-attributes
30796 @subsubheading Synopsis
30799 -var-show-attributes @var{name}
30802 List attributes of the specified variable object @var{name}:
30805 status=@var{attr} [ ( ,@var{attr} )* ]
30809 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
30811 @subheading The @code{-var-evaluate-expression} Command
30812 @findex -var-evaluate-expression
30814 @subsubheading Synopsis
30817 -var-evaluate-expression [-f @var{format-spec}] @var{name}
30820 Evaluates the expression that is represented by the specified variable
30821 object and returns its value as a string. The format of the string
30822 can be specified with the @samp{-f} option. The possible values of
30823 this option are the same as for @code{-var-set-format}
30824 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
30825 the current display format will be used. The current display format
30826 can be changed using the @code{-var-set-format} command.
30832 Note that one must invoke @code{-var-list-children} for a variable
30833 before the value of a child variable can be evaluated.
30835 @subheading The @code{-var-assign} Command
30836 @findex -var-assign
30838 @subsubheading Synopsis
30841 -var-assign @var{name} @var{expression}
30844 Assigns the value of @var{expression} to the variable object specified
30845 by @var{name}. The object must be @samp{editable}. If the variable's
30846 value is altered by the assign, the variable will show up in any
30847 subsequent @code{-var-update} list.
30849 @subsubheading Example
30857 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
30861 @subheading The @code{-var-update} Command
30862 @findex -var-update
30864 @subsubheading Synopsis
30867 -var-update [@var{print-values}] @{@var{name} | "*"@}
30870 Reevaluate the expressions corresponding to the variable object
30871 @var{name} and all its direct and indirect children, and return the
30872 list of variable objects whose values have changed; @var{name} must
30873 be a root variable object. Here, ``changed'' means that the result of
30874 @code{-var-evaluate-expression} before and after the
30875 @code{-var-update} is different. If @samp{*} is used as the variable
30876 object names, all existing variable objects are updated, except
30877 for frozen ones (@pxref{-var-set-frozen}). The option
30878 @var{print-values} determines whether both names and values, or just
30879 names are printed. The possible values of this option are the same
30880 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
30881 recommended to use the @samp{--all-values} option, to reduce the
30882 number of MI commands needed on each program stop.
30884 With the @samp{*} parameter, if a variable object is bound to a
30885 currently running thread, it will not be updated, without any
30888 If @code{-var-set-update-range} was previously used on a varobj, then
30889 only the selected range of children will be reported.
30891 @code{-var-update} reports all the changed varobjs in a tuple named
30894 Each item in the change list is itself a tuple holding:
30898 The name of the varobj.
30901 If values were requested for this update, then this field will be
30902 present and will hold the value of the varobj.
30905 @anchor{-var-update}
30906 This field is a string which may take one of three values:
30910 The variable object's current value is valid.
30913 The variable object does not currently hold a valid value but it may
30914 hold one in the future if its associated expression comes back into
30918 The variable object no longer holds a valid value.
30919 This can occur when the executable file being debugged has changed,
30920 either through recompilation or by using the @value{GDBN} @code{file}
30921 command. The front end should normally choose to delete these variable
30925 In the future new values may be added to this list so the front should
30926 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
30929 This is only present if the varobj is still valid. If the type
30930 changed, then this will be the string @samp{true}; otherwise it will
30933 When a varobj's type changes, its children are also likely to have
30934 become incorrect. Therefore, the varobj's children are automatically
30935 deleted when this attribute is @samp{true}. Also, the varobj's update
30936 range, when set using the @code{-var-set-update-range} command, is
30940 If the varobj's type changed, then this field will be present and will
30943 @item new_num_children
30944 For a dynamic varobj, if the number of children changed, or if the
30945 type changed, this will be the new number of children.
30947 The @samp{numchild} field in other varobj responses is generally not
30948 valid for a dynamic varobj -- it will show the number of children that
30949 @value{GDBN} knows about, but because dynamic varobjs lazily
30950 instantiate their children, this will not reflect the number of
30951 children which may be available.
30953 The @samp{new_num_children} attribute only reports changes to the
30954 number of children known by @value{GDBN}. This is the only way to
30955 detect whether an update has removed children (which necessarily can
30956 only happen at the end of the update range).
30959 The display hint, if any.
30962 This is an integer value, which will be 1 if there are more children
30963 available outside the varobj's update range.
30966 This attribute will be present and have the value @samp{1} if the
30967 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30968 then this attribute will not be present.
30971 If new children were added to a dynamic varobj within the selected
30972 update range (as set by @code{-var-set-update-range}), then they will
30973 be listed in this attribute.
30976 @subsubheading Example
30983 -var-update --all-values var1
30984 ^done,changelist=[@{name="var1",value="3",in_scope="true",
30985 type_changed="false"@}]
30989 @subheading The @code{-var-set-frozen} Command
30990 @findex -var-set-frozen
30991 @anchor{-var-set-frozen}
30993 @subsubheading Synopsis
30996 -var-set-frozen @var{name} @var{flag}
30999 Set the frozenness flag on the variable object @var{name}. The
31000 @var{flag} parameter should be either @samp{1} to make the variable
31001 frozen or @samp{0} to make it unfrozen. If a variable object is
31002 frozen, then neither itself, nor any of its children, are
31003 implicitly updated by @code{-var-update} of
31004 a parent variable or by @code{-var-update *}. Only
31005 @code{-var-update} of the variable itself will update its value and
31006 values of its children. After a variable object is unfrozen, it is
31007 implicitly updated by all subsequent @code{-var-update} operations.
31008 Unfreezing a variable does not update it, only subsequent
31009 @code{-var-update} does.
31011 @subsubheading Example
31015 -var-set-frozen V 1
31020 @subheading The @code{-var-set-update-range} command
31021 @findex -var-set-update-range
31022 @anchor{-var-set-update-range}
31024 @subsubheading Synopsis
31027 -var-set-update-range @var{name} @var{from} @var{to}
31030 Set the range of children to be returned by future invocations of
31031 @code{-var-update}.
31033 @var{from} and @var{to} indicate the range of children to report. If
31034 @var{from} or @var{to} is less than zero, the range is reset and all
31035 children will be reported. Otherwise, children starting at @var{from}
31036 (zero-based) and up to and excluding @var{to} will be reported.
31038 @subsubheading Example
31042 -var-set-update-range V 1 2
31046 @subheading The @code{-var-set-visualizer} command
31047 @findex -var-set-visualizer
31048 @anchor{-var-set-visualizer}
31050 @subsubheading Synopsis
31053 -var-set-visualizer @var{name} @var{visualizer}
31056 Set a visualizer for the variable object @var{name}.
31058 @var{visualizer} is the visualizer to use. The special value
31059 @samp{None} means to disable any visualizer in use.
31061 If not @samp{None}, @var{visualizer} must be a Python expression.
31062 This expression must evaluate to a callable object which accepts a
31063 single argument. @value{GDBN} will call this object with the value of
31064 the varobj @var{name} as an argument (this is done so that the same
31065 Python pretty-printing code can be used for both the CLI and MI).
31066 When called, this object must return an object which conforms to the
31067 pretty-printing interface (@pxref{Pretty Printing API}).
31069 The pre-defined function @code{gdb.default_visualizer} may be used to
31070 select a visualizer by following the built-in process
31071 (@pxref{Selecting Pretty-Printers}). This is done automatically when
31072 a varobj is created, and so ordinarily is not needed.
31074 This feature is only available if Python support is enabled. The MI
31075 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
31076 can be used to check this.
31078 @subsubheading Example
31080 Resetting the visualizer:
31084 -var-set-visualizer V None
31088 Reselecting the default (type-based) visualizer:
31092 -var-set-visualizer V gdb.default_visualizer
31096 Suppose @code{SomeClass} is a visualizer class. A lambda expression
31097 can be used to instantiate this class for a varobj:
31101 -var-set-visualizer V "lambda val: SomeClass()"
31105 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31106 @node GDB/MI Data Manipulation
31107 @section @sc{gdb/mi} Data Manipulation
31109 @cindex data manipulation, in @sc{gdb/mi}
31110 @cindex @sc{gdb/mi}, data manipulation
31111 This section describes the @sc{gdb/mi} commands that manipulate data:
31112 examine memory and registers, evaluate expressions, etc.
31114 @c REMOVED FROM THE INTERFACE.
31115 @c @subheading -data-assign
31116 @c Change the value of a program variable. Plenty of side effects.
31117 @c @subsubheading GDB Command
31119 @c @subsubheading Example
31122 @subheading The @code{-data-disassemble} Command
31123 @findex -data-disassemble
31125 @subsubheading Synopsis
31129 [ -s @var{start-addr} -e @var{end-addr} ]
31130 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
31138 @item @var{start-addr}
31139 is the beginning address (or @code{$pc})
31140 @item @var{end-addr}
31142 @item @var{filename}
31143 is the name of the file to disassemble
31144 @item @var{linenum}
31145 is the line number to disassemble around
31147 is the number of disassembly lines to be produced. If it is -1,
31148 the whole function will be disassembled, in case no @var{end-addr} is
31149 specified. If @var{end-addr} is specified as a non-zero value, and
31150 @var{lines} is lower than the number of disassembly lines between
31151 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
31152 displayed; if @var{lines} is higher than the number of lines between
31153 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
31156 is either 0 (meaning only disassembly), 1 (meaning mixed source and
31157 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
31158 mixed source and disassembly with raw opcodes).
31161 @subsubheading Result
31163 The result of the @code{-data-disassemble} command will be a list named
31164 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31165 used with the @code{-data-disassemble} command.
31167 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31172 The address at which this instruction was disassembled.
31175 The name of the function this instruction is within.
31178 The decimal offset in bytes from the start of @samp{func-name}.
31181 The text disassembly for this @samp{address}.
31184 This field is only present for mode 2. This contains the raw opcode
31185 bytes for the @samp{inst} field.
31189 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
31190 @samp{src_and_asm_line}, each of which has the following fields:
31194 The line number within @samp{file}.
31197 The file name from the compilation unit. This might be an absolute
31198 file name or a relative file name depending on the compile command
31202 Absolute file name of @samp{file}. It is converted to a canonical form
31203 using the source file search path
31204 (@pxref{Source Path, ,Specifying Source Directories})
31205 and after resolving all the symbolic links.
31207 If the source file is not found this field will contain the path as
31208 present in the debug information.
31210 @item line_asm_insn
31211 This is a list of tuples containing the disassembly for @samp{line} in
31212 @samp{file}. The fields of each tuple are the same as for
31213 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31214 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31219 Note that whatever included in the @samp{inst} field, is not
31220 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31223 @subsubheading @value{GDBN} Command
31225 The corresponding @value{GDBN} command is @samp{disassemble}.
31227 @subsubheading Example
31229 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31233 -data-disassemble -s $pc -e "$pc + 20" -- 0
31236 @{address="0x000107c0",func-name="main",offset="4",
31237 inst="mov 2, %o0"@},
31238 @{address="0x000107c4",func-name="main",offset="8",
31239 inst="sethi %hi(0x11800), %o2"@},
31240 @{address="0x000107c8",func-name="main",offset="12",
31241 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31242 @{address="0x000107cc",func-name="main",offset="16",
31243 inst="sethi %hi(0x11800), %o2"@},
31244 @{address="0x000107d0",func-name="main",offset="20",
31245 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31249 Disassemble the whole @code{main} function. Line 32 is part of
31253 -data-disassemble -f basics.c -l 32 -- 0
31255 @{address="0x000107bc",func-name="main",offset="0",
31256 inst="save %sp, -112, %sp"@},
31257 @{address="0x000107c0",func-name="main",offset="4",
31258 inst="mov 2, %o0"@},
31259 @{address="0x000107c4",func-name="main",offset="8",
31260 inst="sethi %hi(0x11800), %o2"@},
31262 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
31263 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
31267 Disassemble 3 instructions from the start of @code{main}:
31271 -data-disassemble -f basics.c -l 32 -n 3 -- 0
31273 @{address="0x000107bc",func-name="main",offset="0",
31274 inst="save %sp, -112, %sp"@},
31275 @{address="0x000107c0",func-name="main",offset="4",
31276 inst="mov 2, %o0"@},
31277 @{address="0x000107c4",func-name="main",offset="8",
31278 inst="sethi %hi(0x11800), %o2"@}]
31282 Disassemble 3 instructions from the start of @code{main} in mixed mode:
31286 -data-disassemble -f basics.c -l 32 -n 3 -- 1
31288 src_and_asm_line=@{line="31",
31289 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31290 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31291 line_asm_insn=[@{address="0x000107bc",
31292 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
31293 src_and_asm_line=@{line="32",
31294 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31295 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31296 line_asm_insn=[@{address="0x000107c0",
31297 func-name="main",offset="4",inst="mov 2, %o0"@},
31298 @{address="0x000107c4",func-name="main",offset="8",
31299 inst="sethi %hi(0x11800), %o2"@}]@}]
31304 @subheading The @code{-data-evaluate-expression} Command
31305 @findex -data-evaluate-expression
31307 @subsubheading Synopsis
31310 -data-evaluate-expression @var{expr}
31313 Evaluate @var{expr} as an expression. The expression could contain an
31314 inferior function call. The function call will execute synchronously.
31315 If the expression contains spaces, it must be enclosed in double quotes.
31317 @subsubheading @value{GDBN} Command
31319 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
31320 @samp{call}. In @code{gdbtk} only, there's a corresponding
31321 @samp{gdb_eval} command.
31323 @subsubheading Example
31325 In the following example, the numbers that precede the commands are the
31326 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
31327 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
31331 211-data-evaluate-expression A
31334 311-data-evaluate-expression &A
31335 311^done,value="0xefffeb7c"
31337 411-data-evaluate-expression A+3
31340 511-data-evaluate-expression "A + 3"
31346 @subheading The @code{-data-list-changed-registers} Command
31347 @findex -data-list-changed-registers
31349 @subsubheading Synopsis
31352 -data-list-changed-registers
31355 Display a list of the registers that have changed.
31357 @subsubheading @value{GDBN} Command
31359 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
31360 has the corresponding command @samp{gdb_changed_register_list}.
31362 @subsubheading Example
31364 On a PPC MBX board:
31372 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
31373 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
31376 -data-list-changed-registers
31377 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
31378 "10","11","13","14","15","16","17","18","19","20","21","22","23",
31379 "24","25","26","27","28","30","31","64","65","66","67","69"]
31384 @subheading The @code{-data-list-register-names} Command
31385 @findex -data-list-register-names
31387 @subsubheading Synopsis
31390 -data-list-register-names [ ( @var{regno} )+ ]
31393 Show a list of register names for the current target. If no arguments
31394 are given, it shows a list of the names of all the registers. If
31395 integer numbers are given as arguments, it will print a list of the
31396 names of the registers corresponding to the arguments. To ensure
31397 consistency between a register name and its number, the output list may
31398 include empty register names.
31400 @subsubheading @value{GDBN} Command
31402 @value{GDBN} does not have a command which corresponds to
31403 @samp{-data-list-register-names}. In @code{gdbtk} there is a
31404 corresponding command @samp{gdb_regnames}.
31406 @subsubheading Example
31408 For the PPC MBX board:
31411 -data-list-register-names
31412 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
31413 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
31414 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
31415 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
31416 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
31417 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
31418 "", "pc","ps","cr","lr","ctr","xer"]
31420 -data-list-register-names 1 2 3
31421 ^done,register-names=["r1","r2","r3"]
31425 @subheading The @code{-data-list-register-values} Command
31426 @findex -data-list-register-values
31428 @subsubheading Synopsis
31431 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
31434 Display the registers' contents. @var{fmt} is the format according to
31435 which the registers' contents are to be returned, followed by an optional
31436 list of numbers specifying the registers to display. A missing list of
31437 numbers indicates that the contents of all the registers must be returned.
31439 Allowed formats for @var{fmt} are:
31456 @subsubheading @value{GDBN} Command
31458 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
31459 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
31461 @subsubheading Example
31463 For a PPC MBX board (note: line breaks are for readability only, they
31464 don't appear in the actual output):
31468 -data-list-register-values r 64 65
31469 ^done,register-values=[@{number="64",value="0xfe00a300"@},
31470 @{number="65",value="0x00029002"@}]
31472 -data-list-register-values x
31473 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
31474 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
31475 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
31476 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
31477 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
31478 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
31479 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
31480 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
31481 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
31482 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
31483 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
31484 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
31485 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
31486 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
31487 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
31488 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
31489 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
31490 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31491 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31492 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31493 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31494 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31495 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31496 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31497 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31498 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31499 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31500 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31501 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31502 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31503 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31504 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31505 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31506 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31507 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31508 @{number="69",value="0x20002b03"@}]
31513 @subheading The @code{-data-read-memory} Command
31514 @findex -data-read-memory
31516 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31518 @subsubheading Synopsis
31521 -data-read-memory [ -o @var{byte-offset} ]
31522 @var{address} @var{word-format} @var{word-size}
31523 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31530 @item @var{address}
31531 An expression specifying the address of the first memory word to be
31532 read. Complex expressions containing embedded white space should be
31533 quoted using the C convention.
31535 @item @var{word-format}
31536 The format to be used to print the memory words. The notation is the
31537 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31540 @item @var{word-size}
31541 The size of each memory word in bytes.
31543 @item @var{nr-rows}
31544 The number of rows in the output table.
31546 @item @var{nr-cols}
31547 The number of columns in the output table.
31550 If present, indicates that each row should include an @sc{ascii} dump. The
31551 value of @var{aschar} is used as a padding character when a byte is not a
31552 member of the printable @sc{ascii} character set (printable @sc{ascii}
31553 characters are those whose code is between 32 and 126, inclusively).
31555 @item @var{byte-offset}
31556 An offset to add to the @var{address} before fetching memory.
31559 This command displays memory contents as a table of @var{nr-rows} by
31560 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31561 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31562 (returned as @samp{total-bytes}). Should less than the requested number
31563 of bytes be returned by the target, the missing words are identified
31564 using @samp{N/A}. The number of bytes read from the target is returned
31565 in @samp{nr-bytes} and the starting address used to read memory in
31568 The address of the next/previous row or page is available in
31569 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31572 @subsubheading @value{GDBN} Command
31574 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31575 @samp{gdb_get_mem} memory read command.
31577 @subsubheading Example
31579 Read six bytes of memory starting at @code{bytes+6} but then offset by
31580 @code{-6} bytes. Format as three rows of two columns. One byte per
31581 word. Display each word in hex.
31585 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31586 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31587 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31588 prev-page="0x0000138a",memory=[
31589 @{addr="0x00001390",data=["0x00","0x01"]@},
31590 @{addr="0x00001392",data=["0x02","0x03"]@},
31591 @{addr="0x00001394",data=["0x04","0x05"]@}]
31595 Read two bytes of memory starting at address @code{shorts + 64} and
31596 display as a single word formatted in decimal.
31600 5-data-read-memory shorts+64 d 2 1 1
31601 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31602 next-row="0x00001512",prev-row="0x0000150e",
31603 next-page="0x00001512",prev-page="0x0000150e",memory=[
31604 @{addr="0x00001510",data=["128"]@}]
31608 Read thirty two bytes of memory starting at @code{bytes+16} and format
31609 as eight rows of four columns. Include a string encoding with @samp{x}
31610 used as the non-printable character.
31614 4-data-read-memory bytes+16 x 1 8 4 x
31615 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31616 next-row="0x000013c0",prev-row="0x0000139c",
31617 next-page="0x000013c0",prev-page="0x00001380",memory=[
31618 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31619 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31620 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31621 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31622 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31623 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31624 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31625 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31629 @subheading The @code{-data-read-memory-bytes} Command
31630 @findex -data-read-memory-bytes
31632 @subsubheading Synopsis
31635 -data-read-memory-bytes [ -o @var{byte-offset} ]
31636 @var{address} @var{count}
31643 @item @var{address}
31644 An expression specifying the address of the first memory word to be
31645 read. Complex expressions containing embedded white space should be
31646 quoted using the C convention.
31649 The number of bytes to read. This should be an integer literal.
31651 @item @var{byte-offset}
31652 The offsets in bytes relative to @var{address} at which to start
31653 reading. This should be an integer literal. This option is provided
31654 so that a frontend is not required to first evaluate address and then
31655 perform address arithmetics itself.
31659 This command attempts to read all accessible memory regions in the
31660 specified range. First, all regions marked as unreadable in the memory
31661 map (if one is defined) will be skipped. @xref{Memory Region
31662 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31663 regions. For each one, if reading full region results in an errors,
31664 @value{GDBN} will try to read a subset of the region.
31666 In general, every single byte in the region may be readable or not,
31667 and the only way to read every readable byte is to try a read at
31668 every address, which is not practical. Therefore, @value{GDBN} will
31669 attempt to read all accessible bytes at either beginning or the end
31670 of the region, using a binary division scheme. This heuristic works
31671 well for reading accross a memory map boundary. Note that if a region
31672 has a readable range that is neither at the beginning or the end,
31673 @value{GDBN} will not read it.
31675 The result record (@pxref{GDB/MI Result Records}) that is output of
31676 the command includes a field named @samp{memory} whose content is a
31677 list of tuples. Each tuple represent a successfully read memory block
31678 and has the following fields:
31682 The start address of the memory block, as hexadecimal literal.
31685 The end address of the memory block, as hexadecimal literal.
31688 The offset of the memory block, as hexadecimal literal, relative to
31689 the start address passed to @code{-data-read-memory-bytes}.
31692 The contents of the memory block, in hex.
31698 @subsubheading @value{GDBN} Command
31700 The corresponding @value{GDBN} command is @samp{x}.
31702 @subsubheading Example
31706 -data-read-memory-bytes &a 10
31707 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31709 contents="01000000020000000300"@}]
31714 @subheading The @code{-data-write-memory-bytes} Command
31715 @findex -data-write-memory-bytes
31717 @subsubheading Synopsis
31720 -data-write-memory-bytes @var{address} @var{contents}
31721 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31728 @item @var{address}
31729 An expression specifying the address of the first memory word to be
31730 read. Complex expressions containing embedded white space should be
31731 quoted using the C convention.
31733 @item @var{contents}
31734 The hex-encoded bytes to write.
31737 Optional argument indicating the number of bytes to be written. If @var{count}
31738 is greater than @var{contents}' length, @value{GDBN} will repeatedly
31739 write @var{contents} until it fills @var{count} bytes.
31743 @subsubheading @value{GDBN} Command
31745 There's no corresponding @value{GDBN} command.
31747 @subsubheading Example
31751 -data-write-memory-bytes &a "aabbccdd"
31758 -data-write-memory-bytes &a "aabbccdd" 16e
31763 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31764 @node GDB/MI Tracepoint Commands
31765 @section @sc{gdb/mi} Tracepoint Commands
31767 The commands defined in this section implement MI support for
31768 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31770 @subheading The @code{-trace-find} Command
31771 @findex -trace-find
31773 @subsubheading Synopsis
31776 -trace-find @var{mode} [@var{parameters}@dots{}]
31779 Find a trace frame using criteria defined by @var{mode} and
31780 @var{parameters}. The following table lists permissible
31781 modes and their parameters. For details of operation, see @ref{tfind}.
31786 No parameters are required. Stops examining trace frames.
31789 An integer is required as parameter. Selects tracepoint frame with
31792 @item tracepoint-number
31793 An integer is required as parameter. Finds next
31794 trace frame that corresponds to tracepoint with the specified number.
31797 An address is required as parameter. Finds
31798 next trace frame that corresponds to any tracepoint at the specified
31801 @item pc-inside-range
31802 Two addresses are required as parameters. Finds next trace
31803 frame that corresponds to a tracepoint at an address inside the
31804 specified range. Both bounds are considered to be inside the range.
31806 @item pc-outside-range
31807 Two addresses are required as parameters. Finds
31808 next trace frame that corresponds to a tracepoint at an address outside
31809 the specified range. Both bounds are considered to be inside the range.
31812 Line specification is required as parameter. @xref{Specify Location}.
31813 Finds next trace frame that corresponds to a tracepoint at
31814 the specified location.
31818 If @samp{none} was passed as @var{mode}, the response does not
31819 have fields. Otherwise, the response may have the following fields:
31823 This field has either @samp{0} or @samp{1} as the value, depending
31824 on whether a matching tracepoint was found.
31827 The index of the found traceframe. This field is present iff
31828 the @samp{found} field has value of @samp{1}.
31831 The index of the found tracepoint. This field is present iff
31832 the @samp{found} field has value of @samp{1}.
31835 The information about the frame corresponding to the found trace
31836 frame. This field is present only if a trace frame was found.
31837 @xref{GDB/MI Frame Information}, for description of this field.
31841 @subsubheading @value{GDBN} Command
31843 The corresponding @value{GDBN} command is @samp{tfind}.
31845 @subheading -trace-define-variable
31846 @findex -trace-define-variable
31848 @subsubheading Synopsis
31851 -trace-define-variable @var{name} [ @var{value} ]
31854 Create trace variable @var{name} if it does not exist. If
31855 @var{value} is specified, sets the initial value of the specified
31856 trace variable to that value. Note that the @var{name} should start
31857 with the @samp{$} character.
31859 @subsubheading @value{GDBN} Command
31861 The corresponding @value{GDBN} command is @samp{tvariable}.
31863 @subheading -trace-list-variables
31864 @findex -trace-list-variables
31866 @subsubheading Synopsis
31869 -trace-list-variables
31872 Return a table of all defined trace variables. Each element of the
31873 table has the following fields:
31877 The name of the trace variable. This field is always present.
31880 The initial value. This is a 64-bit signed integer. This
31881 field is always present.
31884 The value the trace variable has at the moment. This is a 64-bit
31885 signed integer. This field is absent iff current value is
31886 not defined, for example if the trace was never run, or is
31891 @subsubheading @value{GDBN} Command
31893 The corresponding @value{GDBN} command is @samp{tvariables}.
31895 @subsubheading Example
31899 -trace-list-variables
31900 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
31901 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
31902 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
31903 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
31904 body=[variable=@{name="$trace_timestamp",initial="0"@}
31905 variable=@{name="$foo",initial="10",current="15"@}]@}
31909 @subheading -trace-save
31910 @findex -trace-save
31912 @subsubheading Synopsis
31915 -trace-save [-r ] @var{filename}
31918 Saves the collected trace data to @var{filename}. Without the
31919 @samp{-r} option, the data is downloaded from the target and saved
31920 in a local file. With the @samp{-r} option the target is asked
31921 to perform the save.
31923 @subsubheading @value{GDBN} Command
31925 The corresponding @value{GDBN} command is @samp{tsave}.
31928 @subheading -trace-start
31929 @findex -trace-start
31931 @subsubheading Synopsis
31937 Starts a tracing experiments. The result of this command does not
31940 @subsubheading @value{GDBN} Command
31942 The corresponding @value{GDBN} command is @samp{tstart}.
31944 @subheading -trace-status
31945 @findex -trace-status
31947 @subsubheading Synopsis
31953 Obtains the status of a tracing experiment. The result may include
31954 the following fields:
31959 May have a value of either @samp{0}, when no tracing operations are
31960 supported, @samp{1}, when all tracing operations are supported, or
31961 @samp{file} when examining trace file. In the latter case, examining
31962 of trace frame is possible but new tracing experiement cannot be
31963 started. This field is always present.
31966 May have a value of either @samp{0} or @samp{1} depending on whether
31967 tracing experiement is in progress on target. This field is present
31968 if @samp{supported} field is not @samp{0}.
31971 Report the reason why the tracing was stopped last time. This field
31972 may be absent iff tracing was never stopped on target yet. The
31973 value of @samp{request} means the tracing was stopped as result of
31974 the @code{-trace-stop} command. The value of @samp{overflow} means
31975 the tracing buffer is full. The value of @samp{disconnection} means
31976 tracing was automatically stopped when @value{GDBN} has disconnected.
31977 The value of @samp{passcount} means tracing was stopped when a
31978 tracepoint was passed a maximal number of times for that tracepoint.
31979 This field is present if @samp{supported} field is not @samp{0}.
31981 @item stopping-tracepoint
31982 The number of tracepoint whose passcount as exceeded. This field is
31983 present iff the @samp{stop-reason} field has the value of
31987 @itemx frames-created
31988 The @samp{frames} field is a count of the total number of trace frames
31989 in the trace buffer, while @samp{frames-created} is the total created
31990 during the run, including ones that were discarded, such as when a
31991 circular trace buffer filled up. Both fields are optional.
31995 These fields tell the current size of the tracing buffer and the
31996 remaining space. These fields are optional.
31999 The value of the circular trace buffer flag. @code{1} means that the
32000 trace buffer is circular and old trace frames will be discarded if
32001 necessary to make room, @code{0} means that the trace buffer is linear
32005 The value of the disconnected tracing flag. @code{1} means that
32006 tracing will continue after @value{GDBN} disconnects, @code{0} means
32007 that the trace run will stop.
32011 @subsubheading @value{GDBN} Command
32013 The corresponding @value{GDBN} command is @samp{tstatus}.
32015 @subheading -trace-stop
32016 @findex -trace-stop
32018 @subsubheading Synopsis
32024 Stops a tracing experiment. The result of this command has the same
32025 fields as @code{-trace-status}, except that the @samp{supported} and
32026 @samp{running} fields are not output.
32028 @subsubheading @value{GDBN} Command
32030 The corresponding @value{GDBN} command is @samp{tstop}.
32033 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32034 @node GDB/MI Symbol Query
32035 @section @sc{gdb/mi} Symbol Query Commands
32039 @subheading The @code{-symbol-info-address} Command
32040 @findex -symbol-info-address
32042 @subsubheading Synopsis
32045 -symbol-info-address @var{symbol}
32048 Describe where @var{symbol} is stored.
32050 @subsubheading @value{GDBN} Command
32052 The corresponding @value{GDBN} command is @samp{info address}.
32054 @subsubheading Example
32058 @subheading The @code{-symbol-info-file} Command
32059 @findex -symbol-info-file
32061 @subsubheading Synopsis
32067 Show the file for the symbol.
32069 @subsubheading @value{GDBN} Command
32071 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32072 @samp{gdb_find_file}.
32074 @subsubheading Example
32078 @subheading The @code{-symbol-info-function} Command
32079 @findex -symbol-info-function
32081 @subsubheading Synopsis
32084 -symbol-info-function
32087 Show which function the symbol lives in.
32089 @subsubheading @value{GDBN} Command
32091 @samp{gdb_get_function} in @code{gdbtk}.
32093 @subsubheading Example
32097 @subheading The @code{-symbol-info-line} Command
32098 @findex -symbol-info-line
32100 @subsubheading Synopsis
32106 Show the core addresses of the code for a source line.
32108 @subsubheading @value{GDBN} Command
32110 The corresponding @value{GDBN} command is @samp{info line}.
32111 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
32113 @subsubheading Example
32117 @subheading The @code{-symbol-info-symbol} Command
32118 @findex -symbol-info-symbol
32120 @subsubheading Synopsis
32123 -symbol-info-symbol @var{addr}
32126 Describe what symbol is at location @var{addr}.
32128 @subsubheading @value{GDBN} Command
32130 The corresponding @value{GDBN} command is @samp{info symbol}.
32132 @subsubheading Example
32136 @subheading The @code{-symbol-list-functions} Command
32137 @findex -symbol-list-functions
32139 @subsubheading Synopsis
32142 -symbol-list-functions
32145 List the functions in the executable.
32147 @subsubheading @value{GDBN} Command
32149 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
32150 @samp{gdb_search} in @code{gdbtk}.
32152 @subsubheading Example
32157 @subheading The @code{-symbol-list-lines} Command
32158 @findex -symbol-list-lines
32160 @subsubheading Synopsis
32163 -symbol-list-lines @var{filename}
32166 Print the list of lines that contain code and their associated program
32167 addresses for the given source filename. The entries are sorted in
32168 ascending PC order.
32170 @subsubheading @value{GDBN} Command
32172 There is no corresponding @value{GDBN} command.
32174 @subsubheading Example
32177 -symbol-list-lines basics.c
32178 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
32184 @subheading The @code{-symbol-list-types} Command
32185 @findex -symbol-list-types
32187 @subsubheading Synopsis
32193 List all the type names.
32195 @subsubheading @value{GDBN} Command
32197 The corresponding commands are @samp{info types} in @value{GDBN},
32198 @samp{gdb_search} in @code{gdbtk}.
32200 @subsubheading Example
32204 @subheading The @code{-symbol-list-variables} Command
32205 @findex -symbol-list-variables
32207 @subsubheading Synopsis
32210 -symbol-list-variables
32213 List all the global and static variable names.
32215 @subsubheading @value{GDBN} Command
32217 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
32219 @subsubheading Example
32223 @subheading The @code{-symbol-locate} Command
32224 @findex -symbol-locate
32226 @subsubheading Synopsis
32232 @subsubheading @value{GDBN} Command
32234 @samp{gdb_loc} in @code{gdbtk}.
32236 @subsubheading Example
32240 @subheading The @code{-symbol-type} Command
32241 @findex -symbol-type
32243 @subsubheading Synopsis
32246 -symbol-type @var{variable}
32249 Show type of @var{variable}.
32251 @subsubheading @value{GDBN} Command
32253 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
32254 @samp{gdb_obj_variable}.
32256 @subsubheading Example
32261 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32262 @node GDB/MI File Commands
32263 @section @sc{gdb/mi} File Commands
32265 This section describes the GDB/MI commands to specify executable file names
32266 and to read in and obtain symbol table information.
32268 @subheading The @code{-file-exec-and-symbols} Command
32269 @findex -file-exec-and-symbols
32271 @subsubheading Synopsis
32274 -file-exec-and-symbols @var{file}
32277 Specify the executable file to be debugged. This file is the one from
32278 which the symbol table is also read. If no file is specified, the
32279 command clears the executable and symbol information. If breakpoints
32280 are set when using this command with no arguments, @value{GDBN} will produce
32281 error messages. Otherwise, no output is produced, except a completion
32284 @subsubheading @value{GDBN} Command
32286 The corresponding @value{GDBN} command is @samp{file}.
32288 @subsubheading Example
32292 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32298 @subheading The @code{-file-exec-file} Command
32299 @findex -file-exec-file
32301 @subsubheading Synopsis
32304 -file-exec-file @var{file}
32307 Specify the executable file to be debugged. Unlike
32308 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
32309 from this file. If used without argument, @value{GDBN} clears the information
32310 about the executable file. No output is produced, except a completion
32313 @subsubheading @value{GDBN} Command
32315 The corresponding @value{GDBN} command is @samp{exec-file}.
32317 @subsubheading Example
32321 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32328 @subheading The @code{-file-list-exec-sections} Command
32329 @findex -file-list-exec-sections
32331 @subsubheading Synopsis
32334 -file-list-exec-sections
32337 List the sections of the current executable file.
32339 @subsubheading @value{GDBN} Command
32341 The @value{GDBN} command @samp{info file} shows, among the rest, the same
32342 information as this command. @code{gdbtk} has a corresponding command
32343 @samp{gdb_load_info}.
32345 @subsubheading Example
32350 @subheading The @code{-file-list-exec-source-file} Command
32351 @findex -file-list-exec-source-file
32353 @subsubheading Synopsis
32356 -file-list-exec-source-file
32359 List the line number, the current source file, and the absolute path
32360 to the current source file for the current executable. The macro
32361 information field has a value of @samp{1} or @samp{0} depending on
32362 whether or not the file includes preprocessor macro information.
32364 @subsubheading @value{GDBN} Command
32366 The @value{GDBN} equivalent is @samp{info source}
32368 @subsubheading Example
32372 123-file-list-exec-source-file
32373 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
32378 @subheading The @code{-file-list-exec-source-files} Command
32379 @findex -file-list-exec-source-files
32381 @subsubheading Synopsis
32384 -file-list-exec-source-files
32387 List the source files for the current executable.
32389 It will always output both the filename and fullname (absolute file
32390 name) of a source file.
32392 @subsubheading @value{GDBN} Command
32394 The @value{GDBN} equivalent is @samp{info sources}.
32395 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32397 @subsubheading Example
32400 -file-list-exec-source-files
32402 @{file=foo.c,fullname=/home/foo.c@},
32403 @{file=/home/bar.c,fullname=/home/bar.c@},
32404 @{file=gdb_could_not_find_fullpath.c@}]
32409 @subheading The @code{-file-list-shared-libraries} Command
32410 @findex -file-list-shared-libraries
32412 @subsubheading Synopsis
32415 -file-list-shared-libraries
32418 List the shared libraries in the program.
32420 @subsubheading @value{GDBN} Command
32422 The corresponding @value{GDBN} command is @samp{info shared}.
32424 @subsubheading Example
32428 @subheading The @code{-file-list-symbol-files} Command
32429 @findex -file-list-symbol-files
32431 @subsubheading Synopsis
32434 -file-list-symbol-files
32439 @subsubheading @value{GDBN} Command
32441 The corresponding @value{GDBN} command is @samp{info file} (part of it).
32443 @subsubheading Example
32448 @subheading The @code{-file-symbol-file} Command
32449 @findex -file-symbol-file
32451 @subsubheading Synopsis
32454 -file-symbol-file @var{file}
32457 Read symbol table info from the specified @var{file} argument. When
32458 used without arguments, clears @value{GDBN}'s symbol table info. No output is
32459 produced, except for a completion notification.
32461 @subsubheading @value{GDBN} Command
32463 The corresponding @value{GDBN} command is @samp{symbol-file}.
32465 @subsubheading Example
32469 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32475 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32476 @node GDB/MI Memory Overlay Commands
32477 @section @sc{gdb/mi} Memory Overlay Commands
32479 The memory overlay commands are not implemented.
32481 @c @subheading -overlay-auto
32483 @c @subheading -overlay-list-mapping-state
32485 @c @subheading -overlay-list-overlays
32487 @c @subheading -overlay-map
32489 @c @subheading -overlay-off
32491 @c @subheading -overlay-on
32493 @c @subheading -overlay-unmap
32495 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32496 @node GDB/MI Signal Handling Commands
32497 @section @sc{gdb/mi} Signal Handling Commands
32499 Signal handling commands are not implemented.
32501 @c @subheading -signal-handle
32503 @c @subheading -signal-list-handle-actions
32505 @c @subheading -signal-list-signal-types
32509 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32510 @node GDB/MI Target Manipulation
32511 @section @sc{gdb/mi} Target Manipulation Commands
32514 @subheading The @code{-target-attach} Command
32515 @findex -target-attach
32517 @subsubheading Synopsis
32520 -target-attach @var{pid} | @var{gid} | @var{file}
32523 Attach to a process @var{pid} or a file @var{file} outside of
32524 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32525 group, the id previously returned by
32526 @samp{-list-thread-groups --available} must be used.
32528 @subsubheading @value{GDBN} Command
32530 The corresponding @value{GDBN} command is @samp{attach}.
32532 @subsubheading Example
32536 =thread-created,id="1"
32537 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32543 @subheading The @code{-target-compare-sections} Command
32544 @findex -target-compare-sections
32546 @subsubheading Synopsis
32549 -target-compare-sections [ @var{section} ]
32552 Compare data of section @var{section} on target to the exec file.
32553 Without the argument, all sections are compared.
32555 @subsubheading @value{GDBN} Command
32557 The @value{GDBN} equivalent is @samp{compare-sections}.
32559 @subsubheading Example
32564 @subheading The @code{-target-detach} Command
32565 @findex -target-detach
32567 @subsubheading Synopsis
32570 -target-detach [ @var{pid} | @var{gid} ]
32573 Detach from the remote target which normally resumes its execution.
32574 If either @var{pid} or @var{gid} is specified, detaches from either
32575 the specified process, or specified thread group. There's no output.
32577 @subsubheading @value{GDBN} Command
32579 The corresponding @value{GDBN} command is @samp{detach}.
32581 @subsubheading Example
32591 @subheading The @code{-target-disconnect} Command
32592 @findex -target-disconnect
32594 @subsubheading Synopsis
32600 Disconnect from the remote target. There's no output and the target is
32601 generally not resumed.
32603 @subsubheading @value{GDBN} Command
32605 The corresponding @value{GDBN} command is @samp{disconnect}.
32607 @subsubheading Example
32617 @subheading The @code{-target-download} Command
32618 @findex -target-download
32620 @subsubheading Synopsis
32626 Loads the executable onto the remote target.
32627 It prints out an update message every half second, which includes the fields:
32631 The name of the section.
32633 The size of what has been sent so far for that section.
32635 The size of the section.
32637 The total size of what was sent so far (the current and the previous sections).
32639 The size of the overall executable to download.
32643 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32644 @sc{gdb/mi} Output Syntax}).
32646 In addition, it prints the name and size of the sections, as they are
32647 downloaded. These messages include the following fields:
32651 The name of the section.
32653 The size of the section.
32655 The size of the overall executable to download.
32659 At the end, a summary is printed.
32661 @subsubheading @value{GDBN} Command
32663 The corresponding @value{GDBN} command is @samp{load}.
32665 @subsubheading Example
32667 Note: each status message appears on a single line. Here the messages
32668 have been broken down so that they can fit onto a page.
32673 +download,@{section=".text",section-size="6668",total-size="9880"@}
32674 +download,@{section=".text",section-sent="512",section-size="6668",
32675 total-sent="512",total-size="9880"@}
32676 +download,@{section=".text",section-sent="1024",section-size="6668",
32677 total-sent="1024",total-size="9880"@}
32678 +download,@{section=".text",section-sent="1536",section-size="6668",
32679 total-sent="1536",total-size="9880"@}
32680 +download,@{section=".text",section-sent="2048",section-size="6668",
32681 total-sent="2048",total-size="9880"@}
32682 +download,@{section=".text",section-sent="2560",section-size="6668",
32683 total-sent="2560",total-size="9880"@}
32684 +download,@{section=".text",section-sent="3072",section-size="6668",
32685 total-sent="3072",total-size="9880"@}
32686 +download,@{section=".text",section-sent="3584",section-size="6668",
32687 total-sent="3584",total-size="9880"@}
32688 +download,@{section=".text",section-sent="4096",section-size="6668",
32689 total-sent="4096",total-size="9880"@}
32690 +download,@{section=".text",section-sent="4608",section-size="6668",
32691 total-sent="4608",total-size="9880"@}
32692 +download,@{section=".text",section-sent="5120",section-size="6668",
32693 total-sent="5120",total-size="9880"@}
32694 +download,@{section=".text",section-sent="5632",section-size="6668",
32695 total-sent="5632",total-size="9880"@}
32696 +download,@{section=".text",section-sent="6144",section-size="6668",
32697 total-sent="6144",total-size="9880"@}
32698 +download,@{section=".text",section-sent="6656",section-size="6668",
32699 total-sent="6656",total-size="9880"@}
32700 +download,@{section=".init",section-size="28",total-size="9880"@}
32701 +download,@{section=".fini",section-size="28",total-size="9880"@}
32702 +download,@{section=".data",section-size="3156",total-size="9880"@}
32703 +download,@{section=".data",section-sent="512",section-size="3156",
32704 total-sent="7236",total-size="9880"@}
32705 +download,@{section=".data",section-sent="1024",section-size="3156",
32706 total-sent="7748",total-size="9880"@}
32707 +download,@{section=".data",section-sent="1536",section-size="3156",
32708 total-sent="8260",total-size="9880"@}
32709 +download,@{section=".data",section-sent="2048",section-size="3156",
32710 total-sent="8772",total-size="9880"@}
32711 +download,@{section=".data",section-sent="2560",section-size="3156",
32712 total-sent="9284",total-size="9880"@}
32713 +download,@{section=".data",section-sent="3072",section-size="3156",
32714 total-sent="9796",total-size="9880"@}
32715 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32722 @subheading The @code{-target-exec-status} Command
32723 @findex -target-exec-status
32725 @subsubheading Synopsis
32728 -target-exec-status
32731 Provide information on the state of the target (whether it is running or
32732 not, for instance).
32734 @subsubheading @value{GDBN} Command
32736 There's no equivalent @value{GDBN} command.
32738 @subsubheading Example
32742 @subheading The @code{-target-list-available-targets} Command
32743 @findex -target-list-available-targets
32745 @subsubheading Synopsis
32748 -target-list-available-targets
32751 List the possible targets to connect to.
32753 @subsubheading @value{GDBN} Command
32755 The corresponding @value{GDBN} command is @samp{help target}.
32757 @subsubheading Example
32761 @subheading The @code{-target-list-current-targets} Command
32762 @findex -target-list-current-targets
32764 @subsubheading Synopsis
32767 -target-list-current-targets
32770 Describe the current target.
32772 @subsubheading @value{GDBN} Command
32774 The corresponding information is printed by @samp{info file} (among
32777 @subsubheading Example
32781 @subheading The @code{-target-list-parameters} Command
32782 @findex -target-list-parameters
32784 @subsubheading Synopsis
32787 -target-list-parameters
32793 @subsubheading @value{GDBN} Command
32797 @subsubheading Example
32801 @subheading The @code{-target-select} Command
32802 @findex -target-select
32804 @subsubheading Synopsis
32807 -target-select @var{type} @var{parameters @dots{}}
32810 Connect @value{GDBN} to the remote target. This command takes two args:
32814 The type of target, for instance @samp{remote}, etc.
32815 @item @var{parameters}
32816 Device names, host names and the like. @xref{Target Commands, ,
32817 Commands for Managing Targets}, for more details.
32820 The output is a connection notification, followed by the address at
32821 which the target program is, in the following form:
32824 ^connected,addr="@var{address}",func="@var{function name}",
32825 args=[@var{arg list}]
32828 @subsubheading @value{GDBN} Command
32830 The corresponding @value{GDBN} command is @samp{target}.
32832 @subsubheading Example
32836 -target-select remote /dev/ttya
32837 ^connected,addr="0xfe00a300",func="??",args=[]
32841 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32842 @node GDB/MI File Transfer Commands
32843 @section @sc{gdb/mi} File Transfer Commands
32846 @subheading The @code{-target-file-put} Command
32847 @findex -target-file-put
32849 @subsubheading Synopsis
32852 -target-file-put @var{hostfile} @var{targetfile}
32855 Copy file @var{hostfile} from the host system (the machine running
32856 @value{GDBN}) to @var{targetfile} on the target system.
32858 @subsubheading @value{GDBN} Command
32860 The corresponding @value{GDBN} command is @samp{remote put}.
32862 @subsubheading Example
32866 -target-file-put localfile remotefile
32872 @subheading The @code{-target-file-get} Command
32873 @findex -target-file-get
32875 @subsubheading Synopsis
32878 -target-file-get @var{targetfile} @var{hostfile}
32881 Copy file @var{targetfile} from the target system to @var{hostfile}
32882 on the host system.
32884 @subsubheading @value{GDBN} Command
32886 The corresponding @value{GDBN} command is @samp{remote get}.
32888 @subsubheading Example
32892 -target-file-get remotefile localfile
32898 @subheading The @code{-target-file-delete} Command
32899 @findex -target-file-delete
32901 @subsubheading Synopsis
32904 -target-file-delete @var{targetfile}
32907 Delete @var{targetfile} from the target system.
32909 @subsubheading @value{GDBN} Command
32911 The corresponding @value{GDBN} command is @samp{remote delete}.
32913 @subsubheading Example
32917 -target-file-delete remotefile
32923 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32924 @node GDB/MI Miscellaneous Commands
32925 @section Miscellaneous @sc{gdb/mi} Commands
32927 @c @subheading -gdb-complete
32929 @subheading The @code{-gdb-exit} Command
32932 @subsubheading Synopsis
32938 Exit @value{GDBN} immediately.
32940 @subsubheading @value{GDBN} Command
32942 Approximately corresponds to @samp{quit}.
32944 @subsubheading Example
32954 @subheading The @code{-exec-abort} Command
32955 @findex -exec-abort
32957 @subsubheading Synopsis
32963 Kill the inferior running program.
32965 @subsubheading @value{GDBN} Command
32967 The corresponding @value{GDBN} command is @samp{kill}.
32969 @subsubheading Example
32974 @subheading The @code{-gdb-set} Command
32977 @subsubheading Synopsis
32983 Set an internal @value{GDBN} variable.
32984 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32986 @subsubheading @value{GDBN} Command
32988 The corresponding @value{GDBN} command is @samp{set}.
32990 @subsubheading Example
33000 @subheading The @code{-gdb-show} Command
33003 @subsubheading Synopsis
33009 Show the current value of a @value{GDBN} variable.
33011 @subsubheading @value{GDBN} Command
33013 The corresponding @value{GDBN} command is @samp{show}.
33015 @subsubheading Example
33024 @c @subheading -gdb-source
33027 @subheading The @code{-gdb-version} Command
33028 @findex -gdb-version
33030 @subsubheading Synopsis
33036 Show version information for @value{GDBN}. Used mostly in testing.
33038 @subsubheading @value{GDBN} Command
33040 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
33041 default shows this information when you start an interactive session.
33043 @subsubheading Example
33045 @c This example modifies the actual output from GDB to avoid overfull
33051 ~Copyright 2000 Free Software Foundation, Inc.
33052 ~GDB is free software, covered by the GNU General Public License, and
33053 ~you are welcome to change it and/or distribute copies of it under
33054 ~ certain conditions.
33055 ~Type "show copying" to see the conditions.
33056 ~There is absolutely no warranty for GDB. Type "show warranty" for
33058 ~This GDB was configured as
33059 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
33064 @subheading The @code{-list-features} Command
33065 @findex -list-features
33067 Returns a list of particular features of the MI protocol that
33068 this version of gdb implements. A feature can be a command,
33069 or a new field in an output of some command, or even an
33070 important bugfix. While a frontend can sometimes detect presence
33071 of a feature at runtime, it is easier to perform detection at debugger
33074 The command returns a list of strings, with each string naming an
33075 available feature. Each returned string is just a name, it does not
33076 have any internal structure. The list of possible feature names
33082 (gdb) -list-features
33083 ^done,result=["feature1","feature2"]
33086 The current list of features is:
33089 @item frozen-varobjs
33090 Indicates support for the @code{-var-set-frozen} command, as well
33091 as possible presense of the @code{frozen} field in the output
33092 of @code{-varobj-create}.
33093 @item pending-breakpoints
33094 Indicates support for the @option{-f} option to the @code{-break-insert}
33097 Indicates Python scripting support, Python-based
33098 pretty-printing commands, and possible presence of the
33099 @samp{display_hint} field in the output of @code{-var-list-children}
33101 Indicates support for the @code{-thread-info} command.
33102 @item data-read-memory-bytes
33103 Indicates support for the @code{-data-read-memory-bytes} and the
33104 @code{-data-write-memory-bytes} commands.
33105 @item breakpoint-notifications
33106 Indicates that changes to breakpoints and breakpoints created via the
33107 CLI will be announced via async records.
33108 @item ada-task-info
33109 Indicates support for the @code{-ada-task-info} command.
33112 @subheading The @code{-list-target-features} Command
33113 @findex -list-target-features
33115 Returns a list of particular features that are supported by the
33116 target. Those features affect the permitted MI commands, but
33117 unlike the features reported by the @code{-list-features} command, the
33118 features depend on which target GDB is using at the moment. Whenever
33119 a target can change, due to commands such as @code{-target-select},
33120 @code{-target-attach} or @code{-exec-run}, the list of target features
33121 may change, and the frontend should obtain it again.
33125 (gdb) -list-features
33126 ^done,result=["async"]
33129 The current list of features is:
33133 Indicates that the target is capable of asynchronous command
33134 execution, which means that @value{GDBN} will accept further commands
33135 while the target is running.
33138 Indicates that the target is capable of reverse execution.
33139 @xref{Reverse Execution}, for more information.
33143 @subheading The @code{-list-thread-groups} Command
33144 @findex -list-thread-groups
33146 @subheading Synopsis
33149 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
33152 Lists thread groups (@pxref{Thread groups}). When a single thread
33153 group is passed as the argument, lists the children of that group.
33154 When several thread group are passed, lists information about those
33155 thread groups. Without any parameters, lists information about all
33156 top-level thread groups.
33158 Normally, thread groups that are being debugged are reported.
33159 With the @samp{--available} option, @value{GDBN} reports thread groups
33160 available on the target.
33162 The output of this command may have either a @samp{threads} result or
33163 a @samp{groups} result. The @samp{thread} result has a list of tuples
33164 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
33165 Information}). The @samp{groups} result has a list of tuples as value,
33166 each tuple describing a thread group. If top-level groups are
33167 requested (that is, no parameter is passed), or when several groups
33168 are passed, the output always has a @samp{groups} result. The format
33169 of the @samp{group} result is described below.
33171 To reduce the number of roundtrips it's possible to list thread groups
33172 together with their children, by passing the @samp{--recurse} option
33173 and the recursion depth. Presently, only recursion depth of 1 is
33174 permitted. If this option is present, then every reported thread group
33175 will also include its children, either as @samp{group} or
33176 @samp{threads} field.
33178 In general, any combination of option and parameters is permitted, with
33179 the following caveats:
33183 When a single thread group is passed, the output will typically
33184 be the @samp{threads} result. Because threads may not contain
33185 anything, the @samp{recurse} option will be ignored.
33188 When the @samp{--available} option is passed, limited information may
33189 be available. In particular, the list of threads of a process might
33190 be inaccessible. Further, specifying specific thread groups might
33191 not give any performance advantage over listing all thread groups.
33192 The frontend should assume that @samp{-list-thread-groups --available}
33193 is always an expensive operation and cache the results.
33197 The @samp{groups} result is a list of tuples, where each tuple may
33198 have the following fields:
33202 Identifier of the thread group. This field is always present.
33203 The identifier is an opaque string; frontends should not try to
33204 convert it to an integer, even though it might look like one.
33207 The type of the thread group. At present, only @samp{process} is a
33211 The target-specific process identifier. This field is only present
33212 for thread groups of type @samp{process} and only if the process exists.
33215 The number of children this thread group has. This field may be
33216 absent for an available thread group.
33219 This field has a list of tuples as value, each tuple describing a
33220 thread. It may be present if the @samp{--recurse} option is
33221 specified, and it's actually possible to obtain the threads.
33224 This field is a list of integers, each identifying a core that one
33225 thread of the group is running on. This field may be absent if
33226 such information is not available.
33229 The name of the executable file that corresponds to this thread group.
33230 The field is only present for thread groups of type @samp{process},
33231 and only if there is a corresponding executable file.
33235 @subheading Example
33239 -list-thread-groups
33240 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33241 -list-thread-groups 17
33242 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33243 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33244 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33245 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
33246 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
33247 -list-thread-groups --available
33248 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
33249 -list-thread-groups --available --recurse 1
33250 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33251 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33252 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
33253 -list-thread-groups --available --recurse 1 17 18
33254 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33255 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33256 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
33259 @subheading The @code{-info-os} Command
33262 @subsubheading Synopsis
33265 -info-os [ @var{type} ]
33268 If no argument is supplied, the command returns a table of available
33269 operating-system-specific information types. If one of these types is
33270 supplied as an argument @var{type}, then the command returns a table
33271 of data of that type.
33273 The types of information available depend on the target operating
33276 @subsubheading @value{GDBN} Command
33278 The corresponding @value{GDBN} command is @samp{info os}.
33280 @subsubheading Example
33282 When run on a @sc{gnu}/Linux system, the output will look something
33288 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
33289 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
33290 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
33291 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
33292 body=[item=@{col0="processes",col1="Listing of all processes",
33293 col2="Processes"@},
33294 item=@{col0="procgroups",col1="Listing of all process groups",
33295 col2="Process groups"@},
33296 item=@{col0="threads",col1="Listing of all threads",
33298 item=@{col0="files",col1="Listing of all file descriptors",
33299 col2="File descriptors"@},
33300 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
33302 item=@{col0="shm",col1="Listing of all shared-memory regions",
33303 col2="Shared-memory regions"@},
33304 item=@{col0="semaphores",col1="Listing of all semaphores",
33305 col2="Semaphores"@},
33306 item=@{col0="msg",col1="Listing of all message queues",
33307 col2="Message queues"@},
33308 item=@{col0="modules",col1="Listing of all loaded kernel modules",
33309 col2="Kernel modules"@}]@}
33312 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
33313 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33314 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33315 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33316 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33317 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33318 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33319 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33321 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33322 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33326 (Note that the MI output here includes a @code{"Title"} column that
33327 does not appear in command-line @code{info os}; this column is useful
33328 for MI clients that want to enumerate the types of data, such as in a
33329 popup menu, but is needless clutter on the command line, and
33330 @code{info os} omits it.)
33332 @subheading The @code{-add-inferior} Command
33333 @findex -add-inferior
33335 @subheading Synopsis
33341 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33342 inferior is not associated with any executable. Such association may
33343 be established with the @samp{-file-exec-and-symbols} command
33344 (@pxref{GDB/MI File Commands}). The command response has a single
33345 field, @samp{thread-group}, whose value is the identifier of the
33346 thread group corresponding to the new inferior.
33348 @subheading Example
33353 ^done,thread-group="i3"
33356 @subheading The @code{-interpreter-exec} Command
33357 @findex -interpreter-exec
33359 @subheading Synopsis
33362 -interpreter-exec @var{interpreter} @var{command}
33364 @anchor{-interpreter-exec}
33366 Execute the specified @var{command} in the given @var{interpreter}.
33368 @subheading @value{GDBN} Command
33370 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33372 @subheading Example
33376 -interpreter-exec console "break main"
33377 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33378 &"During symbol reading, bad structure-type format.\n"
33379 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33384 @subheading The @code{-inferior-tty-set} Command
33385 @findex -inferior-tty-set
33387 @subheading Synopsis
33390 -inferior-tty-set /dev/pts/1
33393 Set terminal for future runs of the program being debugged.
33395 @subheading @value{GDBN} Command
33397 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33399 @subheading Example
33403 -inferior-tty-set /dev/pts/1
33408 @subheading The @code{-inferior-tty-show} Command
33409 @findex -inferior-tty-show
33411 @subheading Synopsis
33417 Show terminal for future runs of program being debugged.
33419 @subheading @value{GDBN} Command
33421 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33423 @subheading Example
33427 -inferior-tty-set /dev/pts/1
33431 ^done,inferior_tty_terminal="/dev/pts/1"
33435 @subheading The @code{-enable-timings} Command
33436 @findex -enable-timings
33438 @subheading Synopsis
33441 -enable-timings [yes | no]
33444 Toggle the printing of the wallclock, user and system times for an MI
33445 command as a field in its output. This command is to help frontend
33446 developers optimize the performance of their code. No argument is
33447 equivalent to @samp{yes}.
33449 @subheading @value{GDBN} Command
33453 @subheading Example
33461 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33462 addr="0x080484ed",func="main",file="myprog.c",
33463 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
33464 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33472 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33473 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33474 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33475 fullname="/home/nickrob/myprog.c",line="73"@}
33480 @chapter @value{GDBN} Annotations
33482 This chapter describes annotations in @value{GDBN}. Annotations were
33483 designed to interface @value{GDBN} to graphical user interfaces or other
33484 similar programs which want to interact with @value{GDBN} at a
33485 relatively high level.
33487 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33491 This is Edition @value{EDITION}, @value{DATE}.
33495 * Annotations Overview:: What annotations are; the general syntax.
33496 * Server Prefix:: Issuing a command without affecting user state.
33497 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33498 * Errors:: Annotations for error messages.
33499 * Invalidation:: Some annotations describe things now invalid.
33500 * Annotations for Running::
33501 Whether the program is running, how it stopped, etc.
33502 * Source Annotations:: Annotations describing source code.
33505 @node Annotations Overview
33506 @section What is an Annotation?
33507 @cindex annotations
33509 Annotations start with a newline character, two @samp{control-z}
33510 characters, and the name of the annotation. If there is no additional
33511 information associated with this annotation, the name of the annotation
33512 is followed immediately by a newline. If there is additional
33513 information, the name of the annotation is followed by a space, the
33514 additional information, and a newline. The additional information
33515 cannot contain newline characters.
33517 Any output not beginning with a newline and two @samp{control-z}
33518 characters denotes literal output from @value{GDBN}. Currently there is
33519 no need for @value{GDBN} to output a newline followed by two
33520 @samp{control-z} characters, but if there was such a need, the
33521 annotations could be extended with an @samp{escape} annotation which
33522 means those three characters as output.
33524 The annotation @var{level}, which is specified using the
33525 @option{--annotate} command line option (@pxref{Mode Options}), controls
33526 how much information @value{GDBN} prints together with its prompt,
33527 values of expressions, source lines, and other types of output. Level 0
33528 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33529 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33530 for programs that control @value{GDBN}, and level 2 annotations have
33531 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33532 Interface, annotate, GDB's Obsolete Annotations}).
33535 @kindex set annotate
33536 @item set annotate @var{level}
33537 The @value{GDBN} command @code{set annotate} sets the level of
33538 annotations to the specified @var{level}.
33540 @item show annotate
33541 @kindex show annotate
33542 Show the current annotation level.
33545 This chapter describes level 3 annotations.
33547 A simple example of starting up @value{GDBN} with annotations is:
33550 $ @kbd{gdb --annotate=3}
33552 Copyright 2003 Free Software Foundation, Inc.
33553 GDB is free software, covered by the GNU General Public License,
33554 and you are welcome to change it and/or distribute copies of it
33555 under certain conditions.
33556 Type "show copying" to see the conditions.
33557 There is absolutely no warranty for GDB. Type "show warranty"
33559 This GDB was configured as "i386-pc-linux-gnu"
33570 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33571 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33572 denotes a @samp{control-z} character) are annotations; the rest is
33573 output from @value{GDBN}.
33575 @node Server Prefix
33576 @section The Server Prefix
33577 @cindex server prefix
33579 If you prefix a command with @samp{server } then it will not affect
33580 the command history, nor will it affect @value{GDBN}'s notion of which
33581 command to repeat if @key{RET} is pressed on a line by itself. This
33582 means that commands can be run behind a user's back by a front-end in
33583 a transparent manner.
33585 The @code{server } prefix does not affect the recording of values into
33586 the value history; to print a value without recording it into the
33587 value history, use the @code{output} command instead of the
33588 @code{print} command.
33590 Using this prefix also disables confirmation requests
33591 (@pxref{confirmation requests}).
33594 @section Annotation for @value{GDBN} Input
33596 @cindex annotations for prompts
33597 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33598 to know when to send output, when the output from a given command is
33601 Different kinds of input each have a different @dfn{input type}. Each
33602 input type has three annotations: a @code{pre-} annotation, which
33603 denotes the beginning of any prompt which is being output, a plain
33604 annotation, which denotes the end of the prompt, and then a @code{post-}
33605 annotation which denotes the end of any echo which may (or may not) be
33606 associated with the input. For example, the @code{prompt} input type
33607 features the following annotations:
33615 The input types are
33618 @findex pre-prompt annotation
33619 @findex prompt annotation
33620 @findex post-prompt annotation
33622 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33624 @findex pre-commands annotation
33625 @findex commands annotation
33626 @findex post-commands annotation
33628 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33629 command. The annotations are repeated for each command which is input.
33631 @findex pre-overload-choice annotation
33632 @findex overload-choice annotation
33633 @findex post-overload-choice annotation
33634 @item overload-choice
33635 When @value{GDBN} wants the user to select between various overloaded functions.
33637 @findex pre-query annotation
33638 @findex query annotation
33639 @findex post-query annotation
33641 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33643 @findex pre-prompt-for-continue annotation
33644 @findex prompt-for-continue annotation
33645 @findex post-prompt-for-continue annotation
33646 @item prompt-for-continue
33647 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33648 expect this to work well; instead use @code{set height 0} to disable
33649 prompting. This is because the counting of lines is buggy in the
33650 presence of annotations.
33655 @cindex annotations for errors, warnings and interrupts
33657 @findex quit annotation
33662 This annotation occurs right before @value{GDBN} responds to an interrupt.
33664 @findex error annotation
33669 This annotation occurs right before @value{GDBN} responds to an error.
33671 Quit and error annotations indicate that any annotations which @value{GDBN} was
33672 in the middle of may end abruptly. For example, if a
33673 @code{value-history-begin} annotation is followed by a @code{error}, one
33674 cannot expect to receive the matching @code{value-history-end}. One
33675 cannot expect not to receive it either, however; an error annotation
33676 does not necessarily mean that @value{GDBN} is immediately returning all the way
33679 @findex error-begin annotation
33680 A quit or error annotation may be preceded by
33686 Any output between that and the quit or error annotation is the error
33689 Warning messages are not yet annotated.
33690 @c If we want to change that, need to fix warning(), type_error(),
33691 @c range_error(), and possibly other places.
33694 @section Invalidation Notices
33696 @cindex annotations for invalidation messages
33697 The following annotations say that certain pieces of state may have
33701 @findex frames-invalid annotation
33702 @item ^Z^Zframes-invalid
33704 The frames (for example, output from the @code{backtrace} command) may
33707 @findex breakpoints-invalid annotation
33708 @item ^Z^Zbreakpoints-invalid
33710 The breakpoints may have changed. For example, the user just added or
33711 deleted a breakpoint.
33714 @node Annotations for Running
33715 @section Running the Program
33716 @cindex annotations for running programs
33718 @findex starting annotation
33719 @findex stopping annotation
33720 When the program starts executing due to a @value{GDBN} command such as
33721 @code{step} or @code{continue},
33727 is output. When the program stops,
33733 is output. Before the @code{stopped} annotation, a variety of
33734 annotations describe how the program stopped.
33737 @findex exited annotation
33738 @item ^Z^Zexited @var{exit-status}
33739 The program exited, and @var{exit-status} is the exit status (zero for
33740 successful exit, otherwise nonzero).
33742 @findex signalled annotation
33743 @findex signal-name annotation
33744 @findex signal-name-end annotation
33745 @findex signal-string annotation
33746 @findex signal-string-end annotation
33747 @item ^Z^Zsignalled
33748 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33749 annotation continues:
33755 ^Z^Zsignal-name-end
33759 ^Z^Zsignal-string-end
33764 where @var{name} is the name of the signal, such as @code{SIGILL} or
33765 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33766 as @code{Illegal Instruction} or @code{Segmentation fault}.
33767 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33768 user's benefit and have no particular format.
33770 @findex signal annotation
33772 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33773 just saying that the program received the signal, not that it was
33774 terminated with it.
33776 @findex breakpoint annotation
33777 @item ^Z^Zbreakpoint @var{number}
33778 The program hit breakpoint number @var{number}.
33780 @findex watchpoint annotation
33781 @item ^Z^Zwatchpoint @var{number}
33782 The program hit watchpoint number @var{number}.
33785 @node Source Annotations
33786 @section Displaying Source
33787 @cindex annotations for source display
33789 @findex source annotation
33790 The following annotation is used instead of displaying source code:
33793 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
33796 where @var{filename} is an absolute file name indicating which source
33797 file, @var{line} is the line number within that file (where 1 is the
33798 first line in the file), @var{character} is the character position
33799 within the file (where 0 is the first character in the file) (for most
33800 debug formats this will necessarily point to the beginning of a line),
33801 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
33802 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
33803 @var{addr} is the address in the target program associated with the
33804 source which is being displayed. @var{addr} is in the form @samp{0x}
33805 followed by one or more lowercase hex digits (note that this does not
33806 depend on the language).
33808 @node JIT Interface
33809 @chapter JIT Compilation Interface
33810 @cindex just-in-time compilation
33811 @cindex JIT compilation interface
33813 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33814 interface. A JIT compiler is a program or library that generates native
33815 executable code at runtime and executes it, usually in order to achieve good
33816 performance while maintaining platform independence.
33818 Programs that use JIT compilation are normally difficult to debug because
33819 portions of their code are generated at runtime, instead of being loaded from
33820 object files, which is where @value{GDBN} normally finds the program's symbols
33821 and debug information. In order to debug programs that use JIT compilation,
33822 @value{GDBN} has an interface that allows the program to register in-memory
33823 symbol files with @value{GDBN} at runtime.
33825 If you are using @value{GDBN} to debug a program that uses this interface, then
33826 it should work transparently so long as you have not stripped the binary. If
33827 you are developing a JIT compiler, then the interface is documented in the rest
33828 of this chapter. At this time, the only known client of this interface is the
33831 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33832 JIT compiler communicates with @value{GDBN} by writing data into a global
33833 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33834 attaches, it reads a linked list of symbol files from the global variable to
33835 find existing code, and puts a breakpoint in the function so that it can find
33836 out about additional code.
33839 * Declarations:: Relevant C struct declarations
33840 * Registering Code:: Steps to register code
33841 * Unregistering Code:: Steps to unregister code
33842 * Custom Debug Info:: Emit debug information in a custom format
33846 @section JIT Declarations
33848 These are the relevant struct declarations that a C program should include to
33849 implement the interface:
33859 struct jit_code_entry
33861 struct jit_code_entry *next_entry;
33862 struct jit_code_entry *prev_entry;
33863 const char *symfile_addr;
33864 uint64_t symfile_size;
33867 struct jit_descriptor
33870 /* This type should be jit_actions_t, but we use uint32_t
33871 to be explicit about the bitwidth. */
33872 uint32_t action_flag;
33873 struct jit_code_entry *relevant_entry;
33874 struct jit_code_entry *first_entry;
33877 /* GDB puts a breakpoint in this function. */
33878 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33880 /* Make sure to specify the version statically, because the
33881 debugger may check the version before we can set it. */
33882 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
33885 If the JIT is multi-threaded, then it is important that the JIT synchronize any
33886 modifications to this global data properly, which can easily be done by putting
33887 a global mutex around modifications to these structures.
33889 @node Registering Code
33890 @section Registering Code
33892 To register code with @value{GDBN}, the JIT should follow this protocol:
33896 Generate an object file in memory with symbols and other desired debug
33897 information. The file must include the virtual addresses of the sections.
33900 Create a code entry for the file, which gives the start and size of the symbol
33904 Add it to the linked list in the JIT descriptor.
33907 Point the relevant_entry field of the descriptor at the entry.
33910 Set @code{action_flag} to @code{JIT_REGISTER} and call
33911 @code{__jit_debug_register_code}.
33914 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
33915 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
33916 new code. However, the linked list must still be maintained in order to allow
33917 @value{GDBN} to attach to a running process and still find the symbol files.
33919 @node Unregistering Code
33920 @section Unregistering Code
33922 If code is freed, then the JIT should use the following protocol:
33926 Remove the code entry corresponding to the code from the linked list.
33929 Point the @code{relevant_entry} field of the descriptor at the code entry.
33932 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
33933 @code{__jit_debug_register_code}.
33936 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
33937 and the JIT will leak the memory used for the associated symbol files.
33939 @node Custom Debug Info
33940 @section Custom Debug Info
33941 @cindex custom JIT debug info
33942 @cindex JIT debug info reader
33944 Generating debug information in platform-native file formats (like ELF
33945 or COFF) may be an overkill for JIT compilers; especially if all the
33946 debug info is used for is displaying a meaningful backtrace. The
33947 issue can be resolved by having the JIT writers decide on a debug info
33948 format and also provide a reader that parses the debug info generated
33949 by the JIT compiler. This section gives a brief overview on writing
33950 such a parser. More specific details can be found in the source file
33951 @file{gdb/jit-reader.in}, which is also installed as a header at
33952 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
33954 The reader is implemented as a shared object (so this functionality is
33955 not available on platforms which don't allow loading shared objects at
33956 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
33957 @code{jit-reader-unload} are provided, to be used to load and unload
33958 the readers from a preconfigured directory. Once loaded, the shared
33959 object is used the parse the debug information emitted by the JIT
33963 * Using JIT Debug Info Readers:: How to use supplied readers correctly
33964 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33967 @node Using JIT Debug Info Readers
33968 @subsection Using JIT Debug Info Readers
33969 @kindex jit-reader-load
33970 @kindex jit-reader-unload
33972 Readers can be loaded and unloaded using the @code{jit-reader-load}
33973 and @code{jit-reader-unload} commands.
33976 @item jit-reader-load @var{reader}
33977 Load the JIT reader named @var{reader}. @var{reader} is a shared
33978 object specified as either an absolute or a relative file name. In
33979 the latter case, @value{GDBN} will try to load the reader from a
33980 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
33981 system (here @var{libdir} is the system library directory, often
33982 @file{/usr/local/lib}).
33984 Only one reader can be active at a time; trying to load a second
33985 reader when one is already loaded will result in @value{GDBN}
33986 reporting an error. A new JIT reader can be loaded by first unloading
33987 the current one using @code{jit-reader-unload} and then invoking
33988 @code{jit-reader-load}.
33990 @item jit-reader-unload
33991 Unload the currently loaded JIT reader.
33995 @node Writing JIT Debug Info Readers
33996 @subsection Writing JIT Debug Info Readers
33997 @cindex writing JIT debug info readers
33999 As mentioned, a reader is essentially a shared object conforming to a
34000 certain ABI. This ABI is described in @file{jit-reader.h}.
34002 @file{jit-reader.h} defines the structures, macros and functions
34003 required to write a reader. It is installed (along with
34004 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
34005 the system include directory.
34007 Readers need to be released under a GPL compatible license. A reader
34008 can be declared as released under such a license by placing the macro
34009 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
34011 The entry point for readers is the symbol @code{gdb_init_reader},
34012 which is expected to be a function with the prototype
34014 @findex gdb_init_reader
34016 extern struct gdb_reader_funcs *gdb_init_reader (void);
34019 @cindex @code{struct gdb_reader_funcs}
34021 @code{struct gdb_reader_funcs} contains a set of pointers to callback
34022 functions. These functions are executed to read the debug info
34023 generated by the JIT compiler (@code{read}), to unwind stack frames
34024 (@code{unwind}) and to create canonical frame IDs
34025 (@code{get_Frame_id}). It also has a callback that is called when the
34026 reader is being unloaded (@code{destroy}). The struct looks like this
34029 struct gdb_reader_funcs
34031 /* Must be set to GDB_READER_INTERFACE_VERSION. */
34032 int reader_version;
34034 /* For use by the reader. */
34037 gdb_read_debug_info *read;
34038 gdb_unwind_frame *unwind;
34039 gdb_get_frame_id *get_frame_id;
34040 gdb_destroy_reader *destroy;
34044 @cindex @code{struct gdb_symbol_callbacks}
34045 @cindex @code{struct gdb_unwind_callbacks}
34047 The callbacks are provided with another set of callbacks by
34048 @value{GDBN} to do their job. For @code{read}, these callbacks are
34049 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
34050 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
34051 @code{struct gdb_symbol_callbacks} has callbacks to create new object
34052 files and new symbol tables inside those object files. @code{struct
34053 gdb_unwind_callbacks} has callbacks to read registers off the current
34054 frame and to write out the values of the registers in the previous
34055 frame. Both have a callback (@code{target_read}) to read bytes off the
34056 target's address space.
34058 @node In-Process Agent
34059 @chapter In-Process Agent
34060 @cindex debugging agent
34061 The traditional debugging model is conceptually low-speed, but works fine,
34062 because most bugs can be reproduced in debugging-mode execution. However,
34063 as multi-core or many-core processors are becoming mainstream, and
34064 multi-threaded programs become more and more popular, there should be more
34065 and more bugs that only manifest themselves at normal-mode execution, for
34066 example, thread races, because debugger's interference with the program's
34067 timing may conceal the bugs. On the other hand, in some applications,
34068 it is not feasible for the debugger to interrupt the program's execution
34069 long enough for the developer to learn anything helpful about its behavior.
34070 If the program's correctness depends on its real-time behavior, delays
34071 introduced by a debugger might cause the program to fail, even when the
34072 code itself is correct. It is useful to be able to observe the program's
34073 behavior without interrupting it.
34075 Therefore, traditional debugging model is too intrusive to reproduce
34076 some bugs. In order to reduce the interference with the program, we can
34077 reduce the number of operations performed by debugger. The
34078 @dfn{In-Process Agent}, a shared library, is running within the same
34079 process with inferior, and is able to perform some debugging operations
34080 itself. As a result, debugger is only involved when necessary, and
34081 performance of debugging can be improved accordingly. Note that
34082 interference with program can be reduced but can't be removed completely,
34083 because the in-process agent will still stop or slow down the program.
34085 The in-process agent can interpret and execute Agent Expressions
34086 (@pxref{Agent Expressions}) during performing debugging operations. The
34087 agent expressions can be used for different purposes, such as collecting
34088 data in tracepoints, and condition evaluation in breakpoints.
34090 @anchor{Control Agent}
34091 You can control whether the in-process agent is used as an aid for
34092 debugging with the following commands:
34095 @kindex set agent on
34097 Causes the in-process agent to perform some operations on behalf of the
34098 debugger. Just which operations requested by the user will be done
34099 by the in-process agent depends on the its capabilities. For example,
34100 if you request to evaluate breakpoint conditions in the in-process agent,
34101 and the in-process agent has such capability as well, then breakpoint
34102 conditions will be evaluated in the in-process agent.
34104 @kindex set agent off
34105 @item set agent off
34106 Disables execution of debugging operations by the in-process agent. All
34107 of the operations will be performed by @value{GDBN}.
34111 Display the current setting of execution of debugging operations by
34112 the in-process agent.
34116 * In-Process Agent Protocol::
34119 @node In-Process Agent Protocol
34120 @section In-Process Agent Protocol
34121 @cindex in-process agent protocol
34123 The in-process agent is able to communicate with both @value{GDBN} and
34124 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
34125 used for communications between @value{GDBN} or GDBserver and the IPA.
34126 In general, @value{GDBN} or GDBserver sends commands
34127 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
34128 in-process agent replies back with the return result of the command, or
34129 some other information. The data sent to in-process agent is composed
34130 of primitive data types, such as 4-byte or 8-byte type, and composite
34131 types, which are called objects (@pxref{IPA Protocol Objects}).
34134 * IPA Protocol Objects::
34135 * IPA Protocol Commands::
34138 @node IPA Protocol Objects
34139 @subsection IPA Protocol Objects
34140 @cindex ipa protocol objects
34142 The commands sent to and results received from agent may contain some
34143 complex data types called @dfn{objects}.
34145 The in-process agent is running on the same machine with @value{GDBN}
34146 or GDBserver, so it doesn't have to handle as much differences between
34147 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
34148 However, there are still some differences of two ends in two processes:
34152 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
34153 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
34155 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
34156 GDBserver is compiled with one, and in-process agent is compiled with
34160 Here are the IPA Protocol Objects:
34164 agent expression object. It represents an agent expression
34165 (@pxref{Agent Expressions}).
34166 @anchor{agent expression object}
34168 tracepoint action object. It represents a tracepoint action
34169 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
34170 memory, static trace data and to evaluate expression.
34171 @anchor{tracepoint action object}
34173 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
34174 @anchor{tracepoint object}
34178 The following table describes important attributes of each IPA protocol
34181 @multitable @columnfractions .30 .20 .50
34182 @headitem Name @tab Size @tab Description
34183 @item @emph{agent expression object} @tab @tab
34184 @item length @tab 4 @tab length of bytes code
34185 @item byte code @tab @var{length} @tab contents of byte code
34186 @item @emph{tracepoint action for collecting memory} @tab @tab
34187 @item 'M' @tab 1 @tab type of tracepoint action
34188 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
34189 address of the lowest byte to collect, otherwise @var{addr} is the offset
34190 of @var{basereg} for memory collecting.
34191 @item len @tab 8 @tab length of memory for collecting
34192 @item basereg @tab 4 @tab the register number containing the starting
34193 memory address for collecting.
34194 @item @emph{tracepoint action for collecting registers} @tab @tab
34195 @item 'R' @tab 1 @tab type of tracepoint action
34196 @item @emph{tracepoint action for collecting static trace data} @tab @tab
34197 @item 'L' @tab 1 @tab type of tracepoint action
34198 @item @emph{tracepoint action for expression evaluation} @tab @tab
34199 @item 'X' @tab 1 @tab type of tracepoint action
34200 @item agent expression @tab length of @tab @ref{agent expression object}
34201 @item @emph{tracepoint object} @tab @tab
34202 @item number @tab 4 @tab number of tracepoint
34203 @item address @tab 8 @tab address of tracepoint inserted on
34204 @item type @tab 4 @tab type of tracepoint
34205 @item enabled @tab 1 @tab enable or disable of tracepoint
34206 @item step_count @tab 8 @tab step
34207 @item pass_count @tab 8 @tab pass
34208 @item numactions @tab 4 @tab number of tracepoint actions
34209 @item hit count @tab 8 @tab hit count
34210 @item trace frame usage @tab 8 @tab trace frame usage
34211 @item compiled_cond @tab 8 @tab compiled condition
34212 @item orig_size @tab 8 @tab orig size
34213 @item condition @tab 4 if condition is NULL otherwise length of
34214 @ref{agent expression object}
34215 @tab zero if condition is NULL, otherwise is
34216 @ref{agent expression object}
34217 @item actions @tab variable
34218 @tab numactions number of @ref{tracepoint action object}
34221 @node IPA Protocol Commands
34222 @subsection IPA Protocol Commands
34223 @cindex ipa protocol commands
34225 The spaces in each command are delimiters to ease reading this commands
34226 specification. They don't exist in real commands.
34230 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34231 Installs a new fast tracepoint described by @var{tracepoint_object}
34232 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
34233 head of @dfn{jumppad}, which is used to jump to data collection routine
34238 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34239 @var{target_address} is address of tracepoint in the inferior.
34240 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34241 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
34242 @var{fjump} contains a sequence of instructions jump to jumppad entry.
34243 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
34250 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
34251 is about to kill inferiors.
34259 @item probe_marker_at:@var{address}
34260 Asks in-process agent to probe the marker at @var{address}.
34267 @item unprobe_marker_at:@var{address}
34268 Asks in-process agent to unprobe the marker at @var{address}.
34272 @chapter Reporting Bugs in @value{GDBN}
34273 @cindex bugs in @value{GDBN}
34274 @cindex reporting bugs in @value{GDBN}
34276 Your bug reports play an essential role in making @value{GDBN} reliable.
34278 Reporting a bug may help you by bringing a solution to your problem, or it
34279 may not. But in any case the principal function of a bug report is to help
34280 the entire community by making the next version of @value{GDBN} work better. Bug
34281 reports are your contribution to the maintenance of @value{GDBN}.
34283 In order for a bug report to serve its purpose, you must include the
34284 information that enables us to fix the bug.
34287 * Bug Criteria:: Have you found a bug?
34288 * Bug Reporting:: How to report bugs
34292 @section Have You Found a Bug?
34293 @cindex bug criteria
34295 If you are not sure whether you have found a bug, here are some guidelines:
34298 @cindex fatal signal
34299 @cindex debugger crash
34300 @cindex crash of debugger
34302 If the debugger gets a fatal signal, for any input whatever, that is a
34303 @value{GDBN} bug. Reliable debuggers never crash.
34305 @cindex error on valid input
34307 If @value{GDBN} produces an error message for valid input, that is a
34308 bug. (Note that if you're cross debugging, the problem may also be
34309 somewhere in the connection to the target.)
34311 @cindex invalid input
34313 If @value{GDBN} does not produce an error message for invalid input,
34314 that is a bug. However, you should note that your idea of
34315 ``invalid input'' might be our idea of ``an extension'' or ``support
34316 for traditional practice''.
34319 If you are an experienced user of debugging tools, your suggestions
34320 for improvement of @value{GDBN} are welcome in any case.
34323 @node Bug Reporting
34324 @section How to Report Bugs
34325 @cindex bug reports
34326 @cindex @value{GDBN} bugs, reporting
34328 A number of companies and individuals offer support for @sc{gnu} products.
34329 If you obtained @value{GDBN} from a support organization, we recommend you
34330 contact that organization first.
34332 You can find contact information for many support companies and
34333 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34335 @c should add a web page ref...
34338 @ifset BUGURL_DEFAULT
34339 In any event, we also recommend that you submit bug reports for
34340 @value{GDBN}. The preferred method is to submit them directly using
34341 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34342 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34345 @strong{Do not send bug reports to @samp{info-gdb}, or to
34346 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34347 not want to receive bug reports. Those that do have arranged to receive
34350 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34351 serves as a repeater. The mailing list and the newsgroup carry exactly
34352 the same messages. Often people think of posting bug reports to the
34353 newsgroup instead of mailing them. This appears to work, but it has one
34354 problem which can be crucial: a newsgroup posting often lacks a mail
34355 path back to the sender. Thus, if we need to ask for more information,
34356 we may be unable to reach you. For this reason, it is better to send
34357 bug reports to the mailing list.
34359 @ifclear BUGURL_DEFAULT
34360 In any event, we also recommend that you submit bug reports for
34361 @value{GDBN} to @value{BUGURL}.
34365 The fundamental principle of reporting bugs usefully is this:
34366 @strong{report all the facts}. If you are not sure whether to state a
34367 fact or leave it out, state it!
34369 Often people omit facts because they think they know what causes the
34370 problem and assume that some details do not matter. Thus, you might
34371 assume that the name of the variable you use in an example does not matter.
34372 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34373 stray memory reference which happens to fetch from the location where that
34374 name is stored in memory; perhaps, if the name were different, the contents
34375 of that location would fool the debugger into doing the right thing despite
34376 the bug. Play it safe and give a specific, complete example. That is the
34377 easiest thing for you to do, and the most helpful.
34379 Keep in mind that the purpose of a bug report is to enable us to fix the
34380 bug. It may be that the bug has been reported previously, but neither
34381 you nor we can know that unless your bug report is complete and
34384 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34385 bell?'' Those bug reports are useless, and we urge everyone to
34386 @emph{refuse to respond to them} except to chide the sender to report
34389 To enable us to fix the bug, you should include all these things:
34393 The version of @value{GDBN}. @value{GDBN} announces it if you start
34394 with no arguments; you can also print it at any time using @code{show
34397 Without this, we will not know whether there is any point in looking for
34398 the bug in the current version of @value{GDBN}.
34401 The type of machine you are using, and the operating system name and
34405 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34406 ``@value{GCC}--2.8.1''.
34409 What compiler (and its version) was used to compile the program you are
34410 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34411 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34412 to get this information; for other compilers, see the documentation for
34416 The command arguments you gave the compiler to compile your example and
34417 observe the bug. For example, did you use @samp{-O}? To guarantee
34418 you will not omit something important, list them all. A copy of the
34419 Makefile (or the output from make) is sufficient.
34421 If we were to try to guess the arguments, we would probably guess wrong
34422 and then we might not encounter the bug.
34425 A complete input script, and all necessary source files, that will
34429 A description of what behavior you observe that you believe is
34430 incorrect. For example, ``It gets a fatal signal.''
34432 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34433 will certainly notice it. But if the bug is incorrect output, we might
34434 not notice unless it is glaringly wrong. You might as well not give us
34435 a chance to make a mistake.
34437 Even if the problem you experience is a fatal signal, you should still
34438 say so explicitly. Suppose something strange is going on, such as, your
34439 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34440 the C library on your system. (This has happened!) Your copy might
34441 crash and ours would not. If you told us to expect a crash, then when
34442 ours fails to crash, we would know that the bug was not happening for
34443 us. If you had not told us to expect a crash, then we would not be able
34444 to draw any conclusion from our observations.
34447 @cindex recording a session script
34448 To collect all this information, you can use a session recording program
34449 such as @command{script}, which is available on many Unix systems.
34450 Just run your @value{GDBN} session inside @command{script} and then
34451 include the @file{typescript} file with your bug report.
34453 Another way to record a @value{GDBN} session is to run @value{GDBN}
34454 inside Emacs and then save the entire buffer to a file.
34457 If you wish to suggest changes to the @value{GDBN} source, send us context
34458 diffs. If you even discuss something in the @value{GDBN} source, refer to
34459 it by context, not by line number.
34461 The line numbers in our development sources will not match those in your
34462 sources. Your line numbers would convey no useful information to us.
34466 Here are some things that are not necessary:
34470 A description of the envelope of the bug.
34472 Often people who encounter a bug spend a lot of time investigating
34473 which changes to the input file will make the bug go away and which
34474 changes will not affect it.
34476 This is often time consuming and not very useful, because the way we
34477 will find the bug is by running a single example under the debugger
34478 with breakpoints, not by pure deduction from a series of examples.
34479 We recommend that you save your time for something else.
34481 Of course, if you can find a simpler example to report @emph{instead}
34482 of the original one, that is a convenience for us. Errors in the
34483 output will be easier to spot, running under the debugger will take
34484 less time, and so on.
34486 However, simplification is not vital; if you do not want to do this,
34487 report the bug anyway and send us the entire test case you used.
34490 A patch for the bug.
34492 A patch for the bug does help us if it is a good one. But do not omit
34493 the necessary information, such as the test case, on the assumption that
34494 a patch is all we need. We might see problems with your patch and decide
34495 to fix the problem another way, or we might not understand it at all.
34497 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34498 construct an example that will make the program follow a certain path
34499 through the code. If you do not send us the example, we will not be able
34500 to construct one, so we will not be able to verify that the bug is fixed.
34502 And if we cannot understand what bug you are trying to fix, or why your
34503 patch should be an improvement, we will not install it. A test case will
34504 help us to understand.
34507 A guess about what the bug is or what it depends on.
34509 Such guesses are usually wrong. Even we cannot guess right about such
34510 things without first using the debugger to find the facts.
34513 @c The readline documentation is distributed with the readline code
34514 @c and consists of the two following files:
34517 @c Use -I with makeinfo to point to the appropriate directory,
34518 @c environment var TEXINPUTS with TeX.
34519 @ifclear SYSTEM_READLINE
34520 @include rluser.texi
34521 @include hsuser.texi
34525 @appendix In Memoriam
34527 The @value{GDBN} project mourns the loss of the following long-time
34532 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34533 to Free Software in general. Outside of @value{GDBN}, he was known in
34534 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34536 @item Michael Snyder
34537 Michael was one of the Global Maintainers of the @value{GDBN} project,
34538 with contributions recorded as early as 1996, until 2011. In addition
34539 to his day to day participation, he was a large driving force behind
34540 adding Reverse Debugging to @value{GDBN}.
34543 Beyond their technical contributions to the project, they were also
34544 enjoyable members of the Free Software Community. We will miss them.
34546 @node Formatting Documentation
34547 @appendix Formatting Documentation
34549 @cindex @value{GDBN} reference card
34550 @cindex reference card
34551 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34552 for printing with PostScript or Ghostscript, in the @file{gdb}
34553 subdirectory of the main source directory@footnote{In
34554 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34555 release.}. If you can use PostScript or Ghostscript with your printer,
34556 you can print the reference card immediately with @file{refcard.ps}.
34558 The release also includes the source for the reference card. You
34559 can format it, using @TeX{}, by typing:
34565 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34566 mode on US ``letter'' size paper;
34567 that is, on a sheet 11 inches wide by 8.5 inches
34568 high. You will need to specify this form of printing as an option to
34569 your @sc{dvi} output program.
34571 @cindex documentation
34573 All the documentation for @value{GDBN} comes as part of the machine-readable
34574 distribution. The documentation is written in Texinfo format, which is
34575 a documentation system that uses a single source file to produce both
34576 on-line information and a printed manual. You can use one of the Info
34577 formatting commands to create the on-line version of the documentation
34578 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34580 @value{GDBN} includes an already formatted copy of the on-line Info
34581 version of this manual in the @file{gdb} subdirectory. The main Info
34582 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34583 subordinate files matching @samp{gdb.info*} in the same directory. If
34584 necessary, you can print out these files, or read them with any editor;
34585 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34586 Emacs or the standalone @code{info} program, available as part of the
34587 @sc{gnu} Texinfo distribution.
34589 If you want to format these Info files yourself, you need one of the
34590 Info formatting programs, such as @code{texinfo-format-buffer} or
34593 If you have @code{makeinfo} installed, and are in the top level
34594 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34595 version @value{GDBVN}), you can make the Info file by typing:
34602 If you want to typeset and print copies of this manual, you need @TeX{},
34603 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34604 Texinfo definitions file.
34606 @TeX{} is a typesetting program; it does not print files directly, but
34607 produces output files called @sc{dvi} files. To print a typeset
34608 document, you need a program to print @sc{dvi} files. If your system
34609 has @TeX{} installed, chances are it has such a program. The precise
34610 command to use depends on your system; @kbd{lpr -d} is common; another
34611 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34612 require a file name without any extension or a @samp{.dvi} extension.
34614 @TeX{} also requires a macro definitions file called
34615 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34616 written in Texinfo format. On its own, @TeX{} cannot either read or
34617 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34618 and is located in the @file{gdb-@var{version-number}/texinfo}
34621 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34622 typeset and print this manual. First switch to the @file{gdb}
34623 subdirectory of the main source directory (for example, to
34624 @file{gdb-@value{GDBVN}/gdb}) and type:
34630 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34632 @node Installing GDB
34633 @appendix Installing @value{GDBN}
34634 @cindex installation
34637 * Requirements:: Requirements for building @value{GDBN}
34638 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34639 * Separate Objdir:: Compiling @value{GDBN} in another directory
34640 * Config Names:: Specifying names for hosts and targets
34641 * Configure Options:: Summary of options for configure
34642 * System-wide configuration:: Having a system-wide init file
34646 @section Requirements for Building @value{GDBN}
34647 @cindex building @value{GDBN}, requirements for
34649 Building @value{GDBN} requires various tools and packages to be available.
34650 Other packages will be used only if they are found.
34652 @heading Tools/Packages Necessary for Building @value{GDBN}
34654 @item ISO C90 compiler
34655 @value{GDBN} is written in ISO C90. It should be buildable with any
34656 working C90 compiler, e.g.@: GCC.
34660 @heading Tools/Packages Optional for Building @value{GDBN}
34664 @value{GDBN} can use the Expat XML parsing library. This library may be
34665 included with your operating system distribution; if it is not, you
34666 can get the latest version from @url{http://expat.sourceforge.net}.
34667 The @file{configure} script will search for this library in several
34668 standard locations; if it is installed in an unusual path, you can
34669 use the @option{--with-libexpat-prefix} option to specify its location.
34675 Remote protocol memory maps (@pxref{Memory Map Format})
34677 Target descriptions (@pxref{Target Descriptions})
34679 Remote shared library lists (@xref{Library List Format},
34680 or alternatively @pxref{Library List Format for SVR4 Targets})
34682 MS-Windows shared libraries (@pxref{Shared Libraries})
34684 Traceframe info (@pxref{Traceframe Info Format})
34688 @cindex compressed debug sections
34689 @value{GDBN} will use the @samp{zlib} library, if available, to read
34690 compressed debug sections. Some linkers, such as GNU gold, are capable
34691 of producing binaries with compressed debug sections. If @value{GDBN}
34692 is compiled with @samp{zlib}, it will be able to read the debug
34693 information in such binaries.
34695 The @samp{zlib} library is likely included with your operating system
34696 distribution; if it is not, you can get the latest version from
34697 @url{http://zlib.net}.
34700 @value{GDBN}'s features related to character sets (@pxref{Character
34701 Sets}) require a functioning @code{iconv} implementation. If you are
34702 on a GNU system, then this is provided by the GNU C Library. Some
34703 other systems also provide a working @code{iconv}.
34705 If @value{GDBN} is using the @code{iconv} program which is installed
34706 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34707 This is done with @option{--with-iconv-bin} which specifies the
34708 directory that contains the @code{iconv} program.
34710 On systems without @code{iconv}, you can install GNU Libiconv. If you
34711 have previously installed Libiconv, you can use the
34712 @option{--with-libiconv-prefix} option to configure.
34714 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34715 arrange to build Libiconv if a directory named @file{libiconv} appears
34716 in the top-most source directory. If Libiconv is built this way, and
34717 if the operating system does not provide a suitable @code{iconv}
34718 implementation, then the just-built library will automatically be used
34719 by @value{GDBN}. One easy way to set this up is to download GNU
34720 Libiconv, unpack it, and then rename the directory holding the
34721 Libiconv source code to @samp{libiconv}.
34724 @node Running Configure
34725 @section Invoking the @value{GDBN} @file{configure} Script
34726 @cindex configuring @value{GDBN}
34727 @value{GDBN} comes with a @file{configure} script that automates the process
34728 of preparing @value{GDBN} for installation; you can then use @code{make} to
34729 build the @code{gdb} program.
34731 @c irrelevant in info file; it's as current as the code it lives with.
34732 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34733 look at the @file{README} file in the sources; we may have improved the
34734 installation procedures since publishing this manual.}
34737 The @value{GDBN} distribution includes all the source code you need for
34738 @value{GDBN} in a single directory, whose name is usually composed by
34739 appending the version number to @samp{gdb}.
34741 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34742 @file{gdb-@value{GDBVN}} directory. That directory contains:
34745 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34746 script for configuring @value{GDBN} and all its supporting libraries
34748 @item gdb-@value{GDBVN}/gdb
34749 the source specific to @value{GDBN} itself
34751 @item gdb-@value{GDBVN}/bfd
34752 source for the Binary File Descriptor library
34754 @item gdb-@value{GDBVN}/include
34755 @sc{gnu} include files
34757 @item gdb-@value{GDBVN}/libiberty
34758 source for the @samp{-liberty} free software library
34760 @item gdb-@value{GDBVN}/opcodes
34761 source for the library of opcode tables and disassemblers
34763 @item gdb-@value{GDBVN}/readline
34764 source for the @sc{gnu} command-line interface
34766 @item gdb-@value{GDBVN}/glob
34767 source for the @sc{gnu} filename pattern-matching subroutine
34769 @item gdb-@value{GDBVN}/mmalloc
34770 source for the @sc{gnu} memory-mapped malloc package
34773 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34774 from the @file{gdb-@var{version-number}} source directory, which in
34775 this example is the @file{gdb-@value{GDBVN}} directory.
34777 First switch to the @file{gdb-@var{version-number}} source directory
34778 if you are not already in it; then run @file{configure}. Pass the
34779 identifier for the platform on which @value{GDBN} will run as an
34785 cd gdb-@value{GDBVN}
34786 ./configure @var{host}
34791 where @var{host} is an identifier such as @samp{sun4} or
34792 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
34793 (You can often leave off @var{host}; @file{configure} tries to guess the
34794 correct value by examining your system.)
34796 Running @samp{configure @var{host}} and then running @code{make} builds the
34797 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
34798 libraries, then @code{gdb} itself. The configured source files, and the
34799 binaries, are left in the corresponding source directories.
34802 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
34803 system does not recognize this automatically when you run a different
34804 shell, you may need to run @code{sh} on it explicitly:
34807 sh configure @var{host}
34810 If you run @file{configure} from a directory that contains source
34811 directories for multiple libraries or programs, such as the
34812 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34814 creates configuration files for every directory level underneath (unless
34815 you tell it not to, with the @samp{--norecursion} option).
34817 You should run the @file{configure} script from the top directory in the
34818 source tree, the @file{gdb-@var{version-number}} directory. If you run
34819 @file{configure} from one of the subdirectories, you will configure only
34820 that subdirectory. That is usually not what you want. In particular,
34821 if you run the first @file{configure} from the @file{gdb} subdirectory
34822 of the @file{gdb-@var{version-number}} directory, you will omit the
34823 configuration of @file{bfd}, @file{readline}, and other sibling
34824 directories of the @file{gdb} subdirectory. This leads to build errors
34825 about missing include files such as @file{bfd/bfd.h}.
34827 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34828 However, you should make sure that the shell on your path (named by
34829 the @samp{SHELL} environment variable) is publicly readable. Remember
34830 that @value{GDBN} uses the shell to start your program---some systems refuse to
34831 let @value{GDBN} debug child processes whose programs are not readable.
34833 @node Separate Objdir
34834 @section Compiling @value{GDBN} in Another Directory
34836 If you want to run @value{GDBN} versions for several host or target machines,
34837 you need a different @code{gdb} compiled for each combination of
34838 host and target. @file{configure} is designed to make this easy by
34839 allowing you to generate each configuration in a separate subdirectory,
34840 rather than in the source directory. If your @code{make} program
34841 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
34842 @code{make} in each of these directories builds the @code{gdb}
34843 program specified there.
34845 To build @code{gdb} in a separate directory, run @file{configure}
34846 with the @samp{--srcdir} option to specify where to find the source.
34847 (You also need to specify a path to find @file{configure}
34848 itself from your working directory. If the path to @file{configure}
34849 would be the same as the argument to @samp{--srcdir}, you can leave out
34850 the @samp{--srcdir} option; it is assumed.)
34852 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
34853 separate directory for a Sun 4 like this:
34857 cd gdb-@value{GDBVN}
34860 ../gdb-@value{GDBVN}/configure sun4
34865 When @file{configure} builds a configuration using a remote source
34866 directory, it creates a tree for the binaries with the same structure
34867 (and using the same names) as the tree under the source directory. In
34868 the example, you'd find the Sun 4 library @file{libiberty.a} in the
34869 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
34870 @file{gdb-sun4/gdb}.
34872 Make sure that your path to the @file{configure} script has just one
34873 instance of @file{gdb} in it. If your path to @file{configure} looks
34874 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
34875 one subdirectory of @value{GDBN}, not the whole package. This leads to
34876 build errors about missing include files such as @file{bfd/bfd.h}.
34878 One popular reason to build several @value{GDBN} configurations in separate
34879 directories is to configure @value{GDBN} for cross-compiling (where
34880 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
34881 programs that run on another machine---the @dfn{target}).
34882 You specify a cross-debugging target by
34883 giving the @samp{--target=@var{target}} option to @file{configure}.
34885 When you run @code{make} to build a program or library, you must run
34886 it in a configured directory---whatever directory you were in when you
34887 called @file{configure} (or one of its subdirectories).
34889 The @code{Makefile} that @file{configure} generates in each source
34890 directory also runs recursively. If you type @code{make} in a source
34891 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
34892 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
34893 will build all the required libraries, and then build GDB.
34895 When you have multiple hosts or targets configured in separate
34896 directories, you can run @code{make} on them in parallel (for example,
34897 if they are NFS-mounted on each of the hosts); they will not interfere
34901 @section Specifying Names for Hosts and Targets
34903 The specifications used for hosts and targets in the @file{configure}
34904 script are based on a three-part naming scheme, but some short predefined
34905 aliases are also supported. The full naming scheme encodes three pieces
34906 of information in the following pattern:
34909 @var{architecture}-@var{vendor}-@var{os}
34912 For example, you can use the alias @code{sun4} as a @var{host} argument,
34913 or as the value for @var{target} in a @code{--target=@var{target}}
34914 option. The equivalent full name is @samp{sparc-sun-sunos4}.
34916 The @file{configure} script accompanying @value{GDBN} does not provide
34917 any query facility to list all supported host and target names or
34918 aliases. @file{configure} calls the Bourne shell script
34919 @code{config.sub} to map abbreviations to full names; you can read the
34920 script, if you wish, or you can use it to test your guesses on
34921 abbreviations---for example:
34924 % sh config.sub i386-linux
34926 % sh config.sub alpha-linux
34927 alpha-unknown-linux-gnu
34928 % sh config.sub hp9k700
34930 % sh config.sub sun4
34931 sparc-sun-sunos4.1.1
34932 % sh config.sub sun3
34933 m68k-sun-sunos4.1.1
34934 % sh config.sub i986v
34935 Invalid configuration `i986v': machine `i986v' not recognized
34939 @code{config.sub} is also distributed in the @value{GDBN} source
34940 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
34942 @node Configure Options
34943 @section @file{configure} Options
34945 Here is a summary of the @file{configure} options and arguments that
34946 are most often useful for building @value{GDBN}. @file{configure} also has
34947 several other options not listed here. @inforef{What Configure
34948 Does,,configure.info}, for a full explanation of @file{configure}.
34951 configure @r{[}--help@r{]}
34952 @r{[}--prefix=@var{dir}@r{]}
34953 @r{[}--exec-prefix=@var{dir}@r{]}
34954 @r{[}--srcdir=@var{dirname}@r{]}
34955 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
34956 @r{[}--target=@var{target}@r{]}
34961 You may introduce options with a single @samp{-} rather than
34962 @samp{--} if you prefer; but you may abbreviate option names if you use
34967 Display a quick summary of how to invoke @file{configure}.
34969 @item --prefix=@var{dir}
34970 Configure the source to install programs and files under directory
34973 @item --exec-prefix=@var{dir}
34974 Configure the source to install programs under directory
34977 @c avoid splitting the warning from the explanation:
34979 @item --srcdir=@var{dirname}
34980 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
34981 @code{make} that implements the @code{VPATH} feature.}@*
34982 Use this option to make configurations in directories separate from the
34983 @value{GDBN} source directories. Among other things, you can use this to
34984 build (or maintain) several configurations simultaneously, in separate
34985 directories. @file{configure} writes configuration-specific files in
34986 the current directory, but arranges for them to use the source in the
34987 directory @var{dirname}. @file{configure} creates directories under
34988 the working directory in parallel to the source directories below
34991 @item --norecursion
34992 Configure only the directory level where @file{configure} is executed; do not
34993 propagate configuration to subdirectories.
34995 @item --target=@var{target}
34996 Configure @value{GDBN} for cross-debugging programs running on the specified
34997 @var{target}. Without this option, @value{GDBN} is configured to debug
34998 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
35000 There is no convenient way to generate a list of all available targets.
35002 @item @var{host} @dots{}
35003 Configure @value{GDBN} to run on the specified @var{host}.
35005 There is no convenient way to generate a list of all available hosts.
35008 There are many other options available as well, but they are generally
35009 needed for special purposes only.
35011 @node System-wide configuration
35012 @section System-wide configuration and settings
35013 @cindex system-wide init file
35015 @value{GDBN} can be configured to have a system-wide init file;
35016 this file will be read and executed at startup (@pxref{Startup, , What
35017 @value{GDBN} does during startup}).
35019 Here is the corresponding configure option:
35022 @item --with-system-gdbinit=@var{file}
35023 Specify that the default location of the system-wide init file is
35027 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
35028 it may be subject to relocation. Two possible cases:
35032 If the default location of this init file contains @file{$prefix},
35033 it will be subject to relocation. Suppose that the configure options
35034 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
35035 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
35036 init file is looked for as @file{$install/etc/gdbinit} instead of
35037 @file{$prefix/etc/gdbinit}.
35040 By contrast, if the default location does not contain the prefix,
35041 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
35042 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
35043 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
35044 wherever @value{GDBN} is installed.
35047 If the configured location of the system-wide init file (as given by the
35048 @option{--with-system-gdbinit} option at configure time) is in the
35049 data-directory (as specified by @option{--with-gdb-datadir} at configure
35050 time) or in one of its subdirectories, then @value{GDBN} will look for the
35051 system-wide init file in the directory specified by the
35052 @option{--data-directory} command-line option.
35053 Note that the system-wide init file is only read once, during @value{GDBN}
35054 initialization. If the data-directory is changed after @value{GDBN} has
35055 started with the @code{set data-directory} command, the file will not be
35058 @node Maintenance Commands
35059 @appendix Maintenance Commands
35060 @cindex maintenance commands
35061 @cindex internal commands
35063 In addition to commands intended for @value{GDBN} users, @value{GDBN}
35064 includes a number of commands intended for @value{GDBN} developers,
35065 that are not documented elsewhere in this manual. These commands are
35066 provided here for reference. (For commands that turn on debugging
35067 messages, see @ref{Debugging Output}.)
35070 @kindex maint agent
35071 @kindex maint agent-eval
35072 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35073 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35074 Translate the given @var{expression} into remote agent bytecodes.
35075 This command is useful for debugging the Agent Expression mechanism
35076 (@pxref{Agent Expressions}). The @samp{agent} version produces an
35077 expression useful for data collection, such as by tracepoints, while
35078 @samp{maint agent-eval} produces an expression that evaluates directly
35079 to a result. For instance, a collection expression for @code{globa +
35080 globb} will include bytecodes to record four bytes of memory at each
35081 of the addresses of @code{globa} and @code{globb}, while discarding
35082 the result of the addition, while an evaluation expression will do the
35083 addition and return the sum.
35084 If @code{-at} is given, generate remote agent bytecode for @var{location}.
35085 If not, generate remote agent bytecode for current frame PC address.
35087 @kindex maint agent-printf
35088 @item maint agent-printf @var{format},@var{expr},...
35089 Translate the given format string and list of argument expressions
35090 into remote agent bytecodes and display them as a disassembled list.
35091 This command is useful for debugging the agent version of dynamic
35092 printf (@pxref{Dynamic Printf}.
35094 @kindex maint info breakpoints
35095 @item @anchor{maint info breakpoints}maint info breakpoints
35096 Using the same format as @samp{info breakpoints}, display both the
35097 breakpoints you've set explicitly, and those @value{GDBN} is using for
35098 internal purposes. Internal breakpoints are shown with negative
35099 breakpoint numbers. The type column identifies what kind of breakpoint
35104 Normal, explicitly set breakpoint.
35107 Normal, explicitly set watchpoint.
35110 Internal breakpoint, used to handle correctly stepping through
35111 @code{longjmp} calls.
35113 @item longjmp resume
35114 Internal breakpoint at the target of a @code{longjmp}.
35117 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
35120 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
35123 Shared library events.
35127 @kindex maint info bfds
35128 @item maint info bfds
35129 This prints information about each @code{bfd} object that is known to
35130 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
35132 @kindex set displaced-stepping
35133 @kindex show displaced-stepping
35134 @cindex displaced stepping support
35135 @cindex out-of-line single-stepping
35136 @item set displaced-stepping
35137 @itemx show displaced-stepping
35138 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
35139 if the target supports it. Displaced stepping is a way to single-step
35140 over breakpoints without removing them from the inferior, by executing
35141 an out-of-line copy of the instruction that was originally at the
35142 breakpoint location. It is also known as out-of-line single-stepping.
35145 @item set displaced-stepping on
35146 If the target architecture supports it, @value{GDBN} will use
35147 displaced stepping to step over breakpoints.
35149 @item set displaced-stepping off
35150 @value{GDBN} will not use displaced stepping to step over breakpoints,
35151 even if such is supported by the target architecture.
35153 @cindex non-stop mode, and @samp{set displaced-stepping}
35154 @item set displaced-stepping auto
35155 This is the default mode. @value{GDBN} will use displaced stepping
35156 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
35157 architecture supports displaced stepping.
35160 @kindex maint check-symtabs
35161 @item maint check-symtabs
35162 Check the consistency of psymtabs and symtabs.
35164 @kindex maint cplus first_component
35165 @item maint cplus first_component @var{name}
35166 Print the first C@t{++} class/namespace component of @var{name}.
35168 @kindex maint cplus namespace
35169 @item maint cplus namespace
35170 Print the list of possible C@t{++} namespaces.
35172 @kindex maint demangle
35173 @item maint demangle @var{name}
35174 Demangle a C@t{++} or Objective-C mangled @var{name}.
35176 @kindex maint deprecate
35177 @kindex maint undeprecate
35178 @cindex deprecated commands
35179 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35180 @itemx maint undeprecate @var{command}
35181 Deprecate or undeprecate the named @var{command}. Deprecated commands
35182 cause @value{GDBN} to issue a warning when you use them. The optional
35183 argument @var{replacement} says which newer command should be used in
35184 favor of the deprecated one; if it is given, @value{GDBN} will mention
35185 the replacement as part of the warning.
35187 @kindex maint dump-me
35188 @item maint dump-me
35189 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35190 Cause a fatal signal in the debugger and force it to dump its core.
35191 This is supported only on systems which support aborting a program
35192 with the @code{SIGQUIT} signal.
35194 @kindex maint internal-error
35195 @kindex maint internal-warning
35196 @item maint internal-error @r{[}@var{message-text}@r{]}
35197 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35198 Cause @value{GDBN} to call the internal function @code{internal_error}
35199 or @code{internal_warning} and hence behave as though an internal error
35200 or internal warning has been detected. In addition to reporting the
35201 internal problem, these functions give the user the opportunity to
35202 either quit @value{GDBN} or create a core file of the current
35203 @value{GDBN} session.
35205 These commands take an optional parameter @var{message-text} that is
35206 used as the text of the error or warning message.
35208 Here's an example of using @code{internal-error}:
35211 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35212 @dots{}/maint.c:121: internal-error: testing, 1, 2
35213 A problem internal to GDB has been detected. Further
35214 debugging may prove unreliable.
35215 Quit this debugging session? (y or n) @kbd{n}
35216 Create a core file? (y or n) @kbd{n}
35220 @cindex @value{GDBN} internal error
35221 @cindex internal errors, control of @value{GDBN} behavior
35223 @kindex maint set internal-error
35224 @kindex maint show internal-error
35225 @kindex maint set internal-warning
35226 @kindex maint show internal-warning
35227 @item maint set internal-error @var{action} [ask|yes|no]
35228 @itemx maint show internal-error @var{action}
35229 @itemx maint set internal-warning @var{action} [ask|yes|no]
35230 @itemx maint show internal-warning @var{action}
35231 When @value{GDBN} reports an internal problem (error or warning) it
35232 gives the user the opportunity to both quit @value{GDBN} and create a
35233 core file of the current @value{GDBN} session. These commands let you
35234 override the default behaviour for each particular @var{action},
35235 described in the table below.
35239 You can specify that @value{GDBN} should always (yes) or never (no)
35240 quit. The default is to ask the user what to do.
35243 You can specify that @value{GDBN} should always (yes) or never (no)
35244 create a core file. The default is to ask the user what to do.
35247 @kindex maint packet
35248 @item maint packet @var{text}
35249 If @value{GDBN} is talking to an inferior via the serial protocol,
35250 then this command sends the string @var{text} to the inferior, and
35251 displays the response packet. @value{GDBN} supplies the initial
35252 @samp{$} character, the terminating @samp{#} character, and the
35255 @kindex maint print architecture
35256 @item maint print architecture @r{[}@var{file}@r{]}
35257 Print the entire architecture configuration. The optional argument
35258 @var{file} names the file where the output goes.
35260 @kindex maint print c-tdesc
35261 @item maint print c-tdesc
35262 Print the current target description (@pxref{Target Descriptions}) as
35263 a C source file. The created source file can be used in @value{GDBN}
35264 when an XML parser is not available to parse the description.
35266 @kindex maint print dummy-frames
35267 @item maint print dummy-frames
35268 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35271 (@value{GDBP}) @kbd{b add}
35273 (@value{GDBP}) @kbd{print add(2,3)}
35274 Breakpoint 2, add (a=2, b=3) at @dots{}
35276 The program being debugged stopped while in a function called from GDB.
35278 (@value{GDBP}) @kbd{maint print dummy-frames}
35279 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
35280 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
35281 call_lo=0x01014000 call_hi=0x01014001
35285 Takes an optional file parameter.
35287 @kindex maint print registers
35288 @kindex maint print raw-registers
35289 @kindex maint print cooked-registers
35290 @kindex maint print register-groups
35291 @kindex maint print remote-registers
35292 @item maint print registers @r{[}@var{file}@r{]}
35293 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35294 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35295 @itemx maint print register-groups @r{[}@var{file}@r{]}
35296 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35297 Print @value{GDBN}'s internal register data structures.
35299 The command @code{maint print raw-registers} includes the contents of
35300 the raw register cache; the command @code{maint print
35301 cooked-registers} includes the (cooked) value of all registers,
35302 including registers which aren't available on the target nor visible
35303 to user; the command @code{maint print register-groups} includes the
35304 groups that each register is a member of; and the command @code{maint
35305 print remote-registers} includes the remote target's register numbers
35306 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
35307 @value{GDBN} Internals}.
35309 These commands take an optional parameter, a file name to which to
35310 write the information.
35312 @kindex maint print reggroups
35313 @item maint print reggroups @r{[}@var{file}@r{]}
35314 Print @value{GDBN}'s internal register group data structures. The
35315 optional argument @var{file} tells to what file to write the
35318 The register groups info looks like this:
35321 (@value{GDBP}) @kbd{maint print reggroups}
35334 This command forces @value{GDBN} to flush its internal register cache.
35336 @kindex maint print objfiles
35337 @cindex info for known object files
35338 @item maint print objfiles
35339 Print a dump of all known object files. For each object file, this
35340 command prints its name, address in memory, and all of its psymtabs
35343 @kindex maint print section-scripts
35344 @cindex info for known .debug_gdb_scripts-loaded scripts
35345 @item maint print section-scripts [@var{regexp}]
35346 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35347 If @var{regexp} is specified, only print scripts loaded by object files
35348 matching @var{regexp}.
35349 For each script, this command prints its name as specified in the objfile,
35350 and the full path if known.
35351 @xref{dotdebug_gdb_scripts section}.
35353 @kindex maint print statistics
35354 @cindex bcache statistics
35355 @item maint print statistics
35356 This command prints, for each object file in the program, various data
35357 about that object file followed by the byte cache (@dfn{bcache})
35358 statistics for the object file. The objfile data includes the number
35359 of minimal, partial, full, and stabs symbols, the number of types
35360 defined by the objfile, the number of as yet unexpanded psym tables,
35361 the number of line tables and string tables, and the amount of memory
35362 used by the various tables. The bcache statistics include the counts,
35363 sizes, and counts of duplicates of all and unique objects, max,
35364 average, and median entry size, total memory used and its overhead and
35365 savings, and various measures of the hash table size and chain
35368 @kindex maint print target-stack
35369 @cindex target stack description
35370 @item maint print target-stack
35371 A @dfn{target} is an interface between the debugger and a particular
35372 kind of file or process. Targets can be stacked in @dfn{strata},
35373 so that more than one target can potentially respond to a request.
35374 In particular, memory accesses will walk down the stack of targets
35375 until they find a target that is interested in handling that particular
35378 This command prints a short description of each layer that was pushed on
35379 the @dfn{target stack}, starting from the top layer down to the bottom one.
35381 @kindex maint print type
35382 @cindex type chain of a data type
35383 @item maint print type @var{expr}
35384 Print the type chain for a type specified by @var{expr}. The argument
35385 can be either a type name or a symbol. If it is a symbol, the type of
35386 that symbol is described. The type chain produced by this command is
35387 a recursive definition of the data type as stored in @value{GDBN}'s
35388 data structures, including its flags and contained types.
35390 @kindex maint set dwarf2 always-disassemble
35391 @kindex maint show dwarf2 always-disassemble
35392 @item maint set dwarf2 always-disassemble
35393 @item maint show dwarf2 always-disassemble
35394 Control the behavior of @code{info address} when using DWARF debugging
35397 The default is @code{off}, which means that @value{GDBN} should try to
35398 describe a variable's location in an easily readable format. When
35399 @code{on}, @value{GDBN} will instead display the DWARF location
35400 expression in an assembly-like format. Note that some locations are
35401 too complex for @value{GDBN} to describe simply; in this case you will
35402 always see the disassembly form.
35404 Here is an example of the resulting disassembly:
35407 (gdb) info addr argc
35408 Symbol "argc" is a complex DWARF expression:
35412 For more information on these expressions, see
35413 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35415 @kindex maint set dwarf2 max-cache-age
35416 @kindex maint show dwarf2 max-cache-age
35417 @item maint set dwarf2 max-cache-age
35418 @itemx maint show dwarf2 max-cache-age
35419 Control the DWARF 2 compilation unit cache.
35421 @cindex DWARF 2 compilation units cache
35422 In object files with inter-compilation-unit references, such as those
35423 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
35424 reader needs to frequently refer to previously read compilation units.
35425 This setting controls how long a compilation unit will remain in the
35426 cache if it is not referenced. A higher limit means that cached
35427 compilation units will be stored in memory longer, and more total
35428 memory will be used. Setting it to zero disables caching, which will
35429 slow down @value{GDBN} startup, but reduce memory consumption.
35431 @kindex maint set profile
35432 @kindex maint show profile
35433 @cindex profiling GDB
35434 @item maint set profile
35435 @itemx maint show profile
35436 Control profiling of @value{GDBN}.
35438 Profiling will be disabled until you use the @samp{maint set profile}
35439 command to enable it. When you enable profiling, the system will begin
35440 collecting timing and execution count data; when you disable profiling or
35441 exit @value{GDBN}, the results will be written to a log file. Remember that
35442 if you use profiling, @value{GDBN} will overwrite the profiling log file
35443 (often called @file{gmon.out}). If you have a record of important profiling
35444 data in a @file{gmon.out} file, be sure to move it to a safe location.
35446 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35447 compiled with the @samp{-pg} compiler option.
35449 @kindex maint set show-debug-regs
35450 @kindex maint show show-debug-regs
35451 @cindex hardware debug registers
35452 @item maint set show-debug-regs
35453 @itemx maint show show-debug-regs
35454 Control whether to show variables that mirror the hardware debug
35455 registers. Use @code{ON} to enable, @code{OFF} to disable. If
35456 enabled, the debug registers values are shown when @value{GDBN} inserts or
35457 removes a hardware breakpoint or watchpoint, and when the inferior
35458 triggers a hardware-assisted breakpoint or watchpoint.
35460 @kindex maint set show-all-tib
35461 @kindex maint show show-all-tib
35462 @item maint set show-all-tib
35463 @itemx maint show show-all-tib
35464 Control whether to show all non zero areas within a 1k block starting
35465 at thread local base, when using the @samp{info w32 thread-information-block}
35468 @kindex maint space
35469 @cindex memory used by commands
35471 Control whether to display memory usage for each command. If set to a
35472 nonzero value, @value{GDBN} will display how much memory each command
35473 took, following the command's own output. This can also be requested
35474 by invoking @value{GDBN} with the @option{--statistics} command-line
35475 switch (@pxref{Mode Options}).
35478 @cindex time of command execution
35480 Control whether to display the execution time of @value{GDBN} for each command.
35481 If set to a nonzero value, @value{GDBN} will display how much time it
35482 took to execute each command, following the command's own output.
35483 Both CPU time and wallclock time are printed.
35484 Printing both is useful when trying to determine whether the cost is
35485 CPU or, e.g., disk/network, latency.
35486 Note that the CPU time printed is for @value{GDBN} only, it does not include
35487 the execution time of the inferior because there's no mechanism currently
35488 to compute how much time was spent by @value{GDBN} and how much time was
35489 spent by the program been debugged.
35490 This can also be requested by invoking @value{GDBN} with the
35491 @option{--statistics} command-line switch (@pxref{Mode Options}).
35493 @kindex maint translate-address
35494 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35495 Find the symbol stored at the location specified by the address
35496 @var{addr} and an optional section name @var{section}. If found,
35497 @value{GDBN} prints the name of the closest symbol and an offset from
35498 the symbol's location to the specified address. This is similar to
35499 the @code{info address} command (@pxref{Symbols}), except that this
35500 command also allows to find symbols in other sections.
35502 If section was not specified, the section in which the symbol was found
35503 is also printed. For dynamically linked executables, the name of
35504 executable or shared library containing the symbol is printed as well.
35508 The following command is useful for non-interactive invocations of
35509 @value{GDBN}, such as in the test suite.
35512 @item set watchdog @var{nsec}
35513 @kindex set watchdog
35514 @cindex watchdog timer
35515 @cindex timeout for commands
35516 Set the maximum number of seconds @value{GDBN} will wait for the
35517 target operation to finish. If this time expires, @value{GDBN}
35518 reports and error and the command is aborted.
35520 @item show watchdog
35521 Show the current setting of the target wait timeout.
35524 @node Remote Protocol
35525 @appendix @value{GDBN} Remote Serial Protocol
35530 * Stop Reply Packets::
35531 * General Query Packets::
35532 * Architecture-Specific Protocol Details::
35533 * Tracepoint Packets::
35534 * Host I/O Packets::
35536 * Notification Packets::
35537 * Remote Non-Stop::
35538 * Packet Acknowledgment::
35540 * File-I/O Remote Protocol Extension::
35541 * Library List Format::
35542 * Library List Format for SVR4 Targets::
35543 * Memory Map Format::
35544 * Thread List Format::
35545 * Traceframe Info Format::
35551 There may be occasions when you need to know something about the
35552 protocol---for example, if there is only one serial port to your target
35553 machine, you might want your program to do something special if it
35554 recognizes a packet meant for @value{GDBN}.
35556 In the examples below, @samp{->} and @samp{<-} are used to indicate
35557 transmitted and received data, respectively.
35559 @cindex protocol, @value{GDBN} remote serial
35560 @cindex serial protocol, @value{GDBN} remote
35561 @cindex remote serial protocol
35562 All @value{GDBN} commands and responses (other than acknowledgments
35563 and notifications, see @ref{Notification Packets}) are sent as a
35564 @var{packet}. A @var{packet} is introduced with the character
35565 @samp{$}, the actual @var{packet-data}, and the terminating character
35566 @samp{#} followed by a two-digit @var{checksum}:
35569 @code{$}@var{packet-data}@code{#}@var{checksum}
35573 @cindex checksum, for @value{GDBN} remote
35575 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35576 characters between the leading @samp{$} and the trailing @samp{#} (an
35577 eight bit unsigned checksum).
35579 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35580 specification also included an optional two-digit @var{sequence-id}:
35583 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35586 @cindex sequence-id, for @value{GDBN} remote
35588 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35589 has never output @var{sequence-id}s. Stubs that handle packets added
35590 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35592 When either the host or the target machine receives a packet, the first
35593 response expected is an acknowledgment: either @samp{+} (to indicate
35594 the package was received correctly) or @samp{-} (to request
35598 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35603 The @samp{+}/@samp{-} acknowledgments can be disabled
35604 once a connection is established.
35605 @xref{Packet Acknowledgment}, for details.
35607 The host (@value{GDBN}) sends @var{command}s, and the target (the
35608 debugging stub incorporated in your program) sends a @var{response}. In
35609 the case of step and continue @var{command}s, the response is only sent
35610 when the operation has completed, and the target has again stopped all
35611 threads in all attached processes. This is the default all-stop mode
35612 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35613 execution mode; see @ref{Remote Non-Stop}, for details.
35615 @var{packet-data} consists of a sequence of characters with the
35616 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35619 @cindex remote protocol, field separator
35620 Fields within the packet should be separated using @samp{,} @samp{;} or
35621 @samp{:}. Except where otherwise noted all numbers are represented in
35622 @sc{hex} with leading zeros suppressed.
35624 Implementors should note that prior to @value{GDBN} 5.0, the character
35625 @samp{:} could not appear as the third character in a packet (as it
35626 would potentially conflict with the @var{sequence-id}).
35628 @cindex remote protocol, binary data
35629 @anchor{Binary Data}
35630 Binary data in most packets is encoded either as two hexadecimal
35631 digits per byte of binary data. This allowed the traditional remote
35632 protocol to work over connections which were only seven-bit clean.
35633 Some packets designed more recently assume an eight-bit clean
35634 connection, and use a more efficient encoding to send and receive
35637 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35638 as an escape character. Any escaped byte is transmitted as the escape
35639 character followed by the original character XORed with @code{0x20}.
35640 For example, the byte @code{0x7d} would be transmitted as the two
35641 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35642 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35643 @samp{@}}) must always be escaped. Responses sent by the stub
35644 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35645 is not interpreted as the start of a run-length encoded sequence
35648 Response @var{data} can be run-length encoded to save space.
35649 Run-length encoding replaces runs of identical characters with one
35650 instance of the repeated character, followed by a @samp{*} and a
35651 repeat count. The repeat count is itself sent encoded, to avoid
35652 binary characters in @var{data}: a value of @var{n} is sent as
35653 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35654 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35655 code 32) for a repeat count of 3. (This is because run-length
35656 encoding starts to win for counts 3 or more.) Thus, for example,
35657 @samp{0* } is a run-length encoding of ``0000'': the space character
35658 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35661 The printable characters @samp{#} and @samp{$} or with a numeric value
35662 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35663 seven repeats (@samp{$}) can be expanded using a repeat count of only
35664 five (@samp{"}). For example, @samp{00000000} can be encoded as
35667 The error response returned for some packets includes a two character
35668 error number. That number is not well defined.
35670 @cindex empty response, for unsupported packets
35671 For any @var{command} not supported by the stub, an empty response
35672 (@samp{$#00}) should be returned. That way it is possible to extend the
35673 protocol. A newer @value{GDBN} can tell if a packet is supported based
35676 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35677 commands for register access, and the @samp{m} and @samp{M} commands
35678 for memory access. Stubs that only control single-threaded targets
35679 can implement run control with the @samp{c} (continue), and @samp{s}
35680 (step) commands. Stubs that support multi-threading targets should
35681 support the @samp{vCont} command. All other commands are optional.
35686 The following table provides a complete list of all currently defined
35687 @var{command}s and their corresponding response @var{data}.
35688 @xref{File-I/O Remote Protocol Extension}, for details about the File
35689 I/O extension of the remote protocol.
35691 Each packet's description has a template showing the packet's overall
35692 syntax, followed by an explanation of the packet's meaning. We
35693 include spaces in some of the templates for clarity; these are not
35694 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35695 separate its components. For example, a template like @samp{foo
35696 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35697 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35698 @var{baz}. @value{GDBN} does not transmit a space character between the
35699 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35702 @cindex @var{thread-id}, in remote protocol
35703 @anchor{thread-id syntax}
35704 Several packets and replies include a @var{thread-id} field to identify
35705 a thread. Normally these are positive numbers with a target-specific
35706 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35707 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35710 In addition, the remote protocol supports a multiprocess feature in
35711 which the @var{thread-id} syntax is extended to optionally include both
35712 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35713 The @var{pid} (process) and @var{tid} (thread) components each have the
35714 format described above: a positive number with target-specific
35715 interpretation formatted as a big-endian hex string, literal @samp{-1}
35716 to indicate all processes or threads (respectively), or @samp{0} to
35717 indicate an arbitrary process or thread. Specifying just a process, as
35718 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35719 error to specify all processes but a specific thread, such as
35720 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35721 for those packets and replies explicitly documented to include a process
35722 ID, rather than a @var{thread-id}.
35724 The multiprocess @var{thread-id} syntax extensions are only used if both
35725 @value{GDBN} and the stub report support for the @samp{multiprocess}
35726 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35729 Note that all packet forms beginning with an upper- or lower-case
35730 letter, other than those described here, are reserved for future use.
35732 Here are the packet descriptions.
35737 @cindex @samp{!} packet
35738 @anchor{extended mode}
35739 Enable extended mode. In extended mode, the remote server is made
35740 persistent. The @samp{R} packet is used to restart the program being
35746 The remote target both supports and has enabled extended mode.
35750 @cindex @samp{?} packet
35751 Indicate the reason the target halted. The reply is the same as for
35752 step and continue. This packet has a special interpretation when the
35753 target is in non-stop mode; see @ref{Remote Non-Stop}.
35756 @xref{Stop Reply Packets}, for the reply specifications.
35758 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
35759 @cindex @samp{A} packet
35760 Initialized @code{argv[]} array passed into program. @var{arglen}
35761 specifies the number of bytes in the hex encoded byte stream
35762 @var{arg}. See @code{gdbserver} for more details.
35767 The arguments were set.
35773 @cindex @samp{b} packet
35774 (Don't use this packet; its behavior is not well-defined.)
35775 Change the serial line speed to @var{baud}.
35777 JTC: @emph{When does the transport layer state change? When it's
35778 received, or after the ACK is transmitted. In either case, there are
35779 problems if the command or the acknowledgment packet is dropped.}
35781 Stan: @emph{If people really wanted to add something like this, and get
35782 it working for the first time, they ought to modify ser-unix.c to send
35783 some kind of out-of-band message to a specially-setup stub and have the
35784 switch happen "in between" packets, so that from remote protocol's point
35785 of view, nothing actually happened.}
35787 @item B @var{addr},@var{mode}
35788 @cindex @samp{B} packet
35789 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35790 breakpoint at @var{addr}.
35792 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35793 (@pxref{insert breakpoint or watchpoint packet}).
35795 @cindex @samp{bc} packet
35798 Backward continue. Execute the target system in reverse. No parameter.
35799 @xref{Reverse Execution}, for more information.
35802 @xref{Stop Reply Packets}, for the reply specifications.
35804 @cindex @samp{bs} packet
35807 Backward single step. Execute one instruction in reverse. No parameter.
35808 @xref{Reverse Execution}, for more information.
35811 @xref{Stop Reply Packets}, for the reply specifications.
35813 @item c @r{[}@var{addr}@r{]}
35814 @cindex @samp{c} packet
35815 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
35816 resume at current address.
35818 This packet is deprecated for multi-threading support. @xref{vCont
35822 @xref{Stop Reply Packets}, for the reply specifications.
35824 @item C @var{sig}@r{[};@var{addr}@r{]}
35825 @cindex @samp{C} packet
35826 Continue with signal @var{sig} (hex signal number). If
35827 @samp{;@var{addr}} is omitted, resume at same address.
35829 This packet is deprecated for multi-threading support. @xref{vCont
35833 @xref{Stop Reply Packets}, for the reply specifications.
35836 @cindex @samp{d} packet
35839 Don't use this packet; instead, define a general set packet
35840 (@pxref{General Query Packets}).
35844 @cindex @samp{D} packet
35845 The first form of the packet is used to detach @value{GDBN} from the
35846 remote system. It is sent to the remote target
35847 before @value{GDBN} disconnects via the @code{detach} command.
35849 The second form, including a process ID, is used when multiprocess
35850 protocol extensions are enabled (@pxref{multiprocess extensions}), to
35851 detach only a specific process. The @var{pid} is specified as a
35852 big-endian hex string.
35862 @item F @var{RC},@var{EE},@var{CF};@var{XX}
35863 @cindex @samp{F} packet
35864 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
35865 This is part of the File-I/O protocol extension. @xref{File-I/O
35866 Remote Protocol Extension}, for the specification.
35869 @anchor{read registers packet}
35870 @cindex @samp{g} packet
35871 Read general registers.
35875 @item @var{XX@dots{}}
35876 Each byte of register data is described by two hex digits. The bytes
35877 with the register are transmitted in target byte order. The size of
35878 each register and their position within the @samp{g} packet are
35879 determined by the @value{GDBN} internal gdbarch functions
35880 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
35881 specification of several standard @samp{g} packets is specified below.
35883 When reading registers from a trace frame (@pxref{Analyze Collected
35884 Data,,Using the Collected Data}), the stub may also return a string of
35885 literal @samp{x}'s in place of the register data digits, to indicate
35886 that the corresponding register has not been collected, thus its value
35887 is unavailable. For example, for an architecture with 4 registers of
35888 4 bytes each, the following reply indicates to @value{GDBN} that
35889 registers 0 and 2 have not been collected, while registers 1 and 3
35890 have been collected, and both have zero value:
35894 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
35901 @item G @var{XX@dots{}}
35902 @cindex @samp{G} packet
35903 Write general registers. @xref{read registers packet}, for a
35904 description of the @var{XX@dots{}} data.
35914 @item H @var{op} @var{thread-id}
35915 @cindex @samp{H} packet
35916 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
35917 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
35918 it should be @samp{c} for step and continue operations (note that this
35919 is deprecated, supporting the @samp{vCont} command is a better
35920 option), @samp{g} for other operations. The thread designator
35921 @var{thread-id} has the format and interpretation described in
35922 @ref{thread-id syntax}.
35933 @c 'H': How restrictive (or permissive) is the thread model. If a
35934 @c thread is selected and stopped, are other threads allowed
35935 @c to continue to execute? As I mentioned above, I think the
35936 @c semantics of each command when a thread is selected must be
35937 @c described. For example:
35939 @c 'g': If the stub supports threads and a specific thread is
35940 @c selected, returns the register block from that thread;
35941 @c otherwise returns current registers.
35943 @c 'G' If the stub supports threads and a specific thread is
35944 @c selected, sets the registers of the register block of
35945 @c that thread; otherwise sets current registers.
35947 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
35948 @anchor{cycle step packet}
35949 @cindex @samp{i} packet
35950 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
35951 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
35952 step starting at that address.
35955 @cindex @samp{I} packet
35956 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
35960 @cindex @samp{k} packet
35963 FIXME: @emph{There is no description of how to operate when a specific
35964 thread context has been selected (i.e.@: does 'k' kill only that
35967 @item m @var{addr},@var{length}
35968 @cindex @samp{m} packet
35969 Read @var{length} bytes of memory starting at address @var{addr}.
35970 Note that @var{addr} may not be aligned to any particular boundary.
35972 The stub need not use any particular size or alignment when gathering
35973 data from memory for the response; even if @var{addr} is word-aligned
35974 and @var{length} is a multiple of the word size, the stub is free to
35975 use byte accesses, or not. For this reason, this packet may not be
35976 suitable for accessing memory-mapped I/O devices.
35977 @cindex alignment of remote memory accesses
35978 @cindex size of remote memory accesses
35979 @cindex memory, alignment and size of remote accesses
35983 @item @var{XX@dots{}}
35984 Memory contents; each byte is transmitted as a two-digit hexadecimal
35985 number. The reply may contain fewer bytes than requested if the
35986 server was able to read only part of the region of memory.
35991 @item M @var{addr},@var{length}:@var{XX@dots{}}
35992 @cindex @samp{M} packet
35993 Write @var{length} bytes of memory starting at address @var{addr}.
35994 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
35995 hexadecimal number.
36002 for an error (this includes the case where only part of the data was
36007 @cindex @samp{p} packet
36008 Read the value of register @var{n}; @var{n} is in hex.
36009 @xref{read registers packet}, for a description of how the returned
36010 register value is encoded.
36014 @item @var{XX@dots{}}
36015 the register's value
36019 Indicating an unrecognized @var{query}.
36022 @item P @var{n@dots{}}=@var{r@dots{}}
36023 @anchor{write register packet}
36024 @cindex @samp{P} packet
36025 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
36026 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
36027 digits for each byte in the register (target byte order).
36037 @item q @var{name} @var{params}@dots{}
36038 @itemx Q @var{name} @var{params}@dots{}
36039 @cindex @samp{q} packet
36040 @cindex @samp{Q} packet
36041 General query (@samp{q}) and set (@samp{Q}). These packets are
36042 described fully in @ref{General Query Packets}.
36045 @cindex @samp{r} packet
36046 Reset the entire system.
36048 Don't use this packet; use the @samp{R} packet instead.
36051 @cindex @samp{R} packet
36052 Restart the program being debugged. @var{XX}, while needed, is ignored.
36053 This packet is only available in extended mode (@pxref{extended mode}).
36055 The @samp{R} packet has no reply.
36057 @item s @r{[}@var{addr}@r{]}
36058 @cindex @samp{s} packet
36059 Single step. @var{addr} is the address at which to resume. If
36060 @var{addr} is omitted, resume at same address.
36062 This packet is deprecated for multi-threading support. @xref{vCont
36066 @xref{Stop Reply Packets}, for the reply specifications.
36068 @item S @var{sig}@r{[};@var{addr}@r{]}
36069 @anchor{step with signal packet}
36070 @cindex @samp{S} packet
36071 Step with signal. This is analogous to the @samp{C} packet, but
36072 requests a single-step, rather than a normal resumption of execution.
36074 This packet is deprecated for multi-threading support. @xref{vCont
36078 @xref{Stop Reply Packets}, for the reply specifications.
36080 @item t @var{addr}:@var{PP},@var{MM}
36081 @cindex @samp{t} packet
36082 Search backwards starting at address @var{addr} for a match with pattern
36083 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
36084 @var{addr} must be at least 3 digits.
36086 @item T @var{thread-id}
36087 @cindex @samp{T} packet
36088 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
36093 thread is still alive
36099 Packets starting with @samp{v} are identified by a multi-letter name,
36100 up to the first @samp{;} or @samp{?} (or the end of the packet).
36102 @item vAttach;@var{pid}
36103 @cindex @samp{vAttach} packet
36104 Attach to a new process with the specified process ID @var{pid}.
36105 The process ID is a
36106 hexadecimal integer identifying the process. In all-stop mode, all
36107 threads in the attached process are stopped; in non-stop mode, it may be
36108 attached without being stopped if that is supported by the target.
36110 @c In non-stop mode, on a successful vAttach, the stub should set the
36111 @c current thread to a thread of the newly-attached process. After
36112 @c attaching, GDB queries for the attached process's thread ID with qC.
36113 @c Also note that, from a user perspective, whether or not the
36114 @c target is stopped on attach in non-stop mode depends on whether you
36115 @c use the foreground or background version of the attach command, not
36116 @c on what vAttach does; GDB does the right thing with respect to either
36117 @c stopping or restarting threads.
36119 This packet is only available in extended mode (@pxref{extended mode}).
36125 @item @r{Any stop packet}
36126 for success in all-stop mode (@pxref{Stop Reply Packets})
36128 for success in non-stop mode (@pxref{Remote Non-Stop})
36131 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
36132 @cindex @samp{vCont} packet
36133 @anchor{vCont packet}
36134 Resume the inferior, specifying different actions for each thread.
36135 If an action is specified with no @var{thread-id}, then it is applied to any
36136 threads that don't have a specific action specified; if no default action is
36137 specified then other threads should remain stopped in all-stop mode and
36138 in their current state in non-stop mode.
36139 Specifying multiple
36140 default actions is an error; specifying no actions is also an error.
36141 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
36143 Currently supported actions are:
36149 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36153 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36158 The optional argument @var{addr} normally associated with the
36159 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36160 not supported in @samp{vCont}.
36162 The @samp{t} action is only relevant in non-stop mode
36163 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36164 A stop reply should be generated for any affected thread not already stopped.
36165 When a thread is stopped by means of a @samp{t} action,
36166 the corresponding stop reply should indicate that the thread has stopped with
36167 signal @samp{0}, regardless of whether the target uses some other signal
36168 as an implementation detail.
36170 The stub must support @samp{vCont} if it reports support for
36171 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
36172 this case @samp{vCont} actions can be specified to apply to all threads
36173 in a process by using the @samp{p@var{pid}.-1} form of the
36177 @xref{Stop Reply Packets}, for the reply specifications.
36180 @cindex @samp{vCont?} packet
36181 Request a list of actions supported by the @samp{vCont} packet.
36185 @item vCont@r{[};@var{action}@dots{}@r{]}
36186 The @samp{vCont} packet is supported. Each @var{action} is a supported
36187 command in the @samp{vCont} packet.
36189 The @samp{vCont} packet is not supported.
36192 @item vFile:@var{operation}:@var{parameter}@dots{}
36193 @cindex @samp{vFile} packet
36194 Perform a file operation on the target system. For details,
36195 see @ref{Host I/O Packets}.
36197 @item vFlashErase:@var{addr},@var{length}
36198 @cindex @samp{vFlashErase} packet
36199 Direct the stub to erase @var{length} bytes of flash starting at
36200 @var{addr}. The region may enclose any number of flash blocks, but
36201 its start and end must fall on block boundaries, as indicated by the
36202 flash block size appearing in the memory map (@pxref{Memory Map
36203 Format}). @value{GDBN} groups flash memory programming operations
36204 together, and sends a @samp{vFlashDone} request after each group; the
36205 stub is allowed to delay erase operation until the @samp{vFlashDone}
36206 packet is received.
36216 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36217 @cindex @samp{vFlashWrite} packet
36218 Direct the stub to write data to flash address @var{addr}. The data
36219 is passed in binary form using the same encoding as for the @samp{X}
36220 packet (@pxref{Binary Data}). The memory ranges specified by
36221 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36222 not overlap, and must appear in order of increasing addresses
36223 (although @samp{vFlashErase} packets for higher addresses may already
36224 have been received; the ordering is guaranteed only between
36225 @samp{vFlashWrite} packets). If a packet writes to an address that was
36226 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36227 target-specific method, the results are unpredictable.
36235 for vFlashWrite addressing non-flash memory
36241 @cindex @samp{vFlashDone} packet
36242 Indicate to the stub that flash programming operation is finished.
36243 The stub is permitted to delay or batch the effects of a group of
36244 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36245 @samp{vFlashDone} packet is received. The contents of the affected
36246 regions of flash memory are unpredictable until the @samp{vFlashDone}
36247 request is completed.
36249 @item vKill;@var{pid}
36250 @cindex @samp{vKill} packet
36251 Kill the process with the specified process ID. @var{pid} is a
36252 hexadecimal integer identifying the process. This packet is used in
36253 preference to @samp{k} when multiprocess protocol extensions are
36254 supported; see @ref{multiprocess extensions}.
36264 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36265 @cindex @samp{vRun} packet
36266 Run the program @var{filename}, passing it each @var{argument} on its
36267 command line. The file and arguments are hex-encoded strings. If
36268 @var{filename} is an empty string, the stub may use a default program
36269 (e.g.@: the last program run). The program is created in the stopped
36272 @c FIXME: What about non-stop mode?
36274 This packet is only available in extended mode (@pxref{extended mode}).
36280 @item @r{Any stop packet}
36281 for success (@pxref{Stop Reply Packets})
36285 @cindex @samp{vStopped} packet
36286 @xref{Notification Packets}.
36288 @item X @var{addr},@var{length}:@var{XX@dots{}}
36290 @cindex @samp{X} packet
36291 Write data to memory, where the data is transmitted in binary.
36292 @var{addr} is address, @var{length} is number of bytes,
36293 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36303 @item z @var{type},@var{addr},@var{kind}
36304 @itemx Z @var{type},@var{addr},@var{kind}
36305 @anchor{insert breakpoint or watchpoint packet}
36306 @cindex @samp{z} packet
36307 @cindex @samp{Z} packets
36308 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36309 watchpoint starting at address @var{address} of kind @var{kind}.
36311 Each breakpoint and watchpoint packet @var{type} is documented
36314 @emph{Implementation notes: A remote target shall return an empty string
36315 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36316 remote target shall support either both or neither of a given
36317 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36318 avoid potential problems with duplicate packets, the operations should
36319 be implemented in an idempotent way.}
36321 @item z0,@var{addr},@var{kind}
36322 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36323 @cindex @samp{z0} packet
36324 @cindex @samp{Z0} packet
36325 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
36326 @var{addr} of type @var{kind}.
36328 A memory breakpoint is implemented by replacing the instruction at
36329 @var{addr} with a software breakpoint or trap instruction. The
36330 @var{kind} is target-specific and typically indicates the size of
36331 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
36332 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36333 architectures have additional meanings for @var{kind};
36334 @var{cond_list} is an optional list of conditional expressions in bytecode
36335 form that should be evaluated on the target's side. These are the
36336 conditions that should be taken into consideration when deciding if
36337 the breakpoint trigger should be reported back to @var{GDBN}.
36339 The @var{cond_list} parameter is comprised of a series of expressions,
36340 concatenated without separators. Each expression has the following form:
36344 @item X @var{len},@var{expr}
36345 @var{len} is the length of the bytecode expression and @var{expr} is the
36346 actual conditional expression in bytecode form.
36350 The optional @var{cmd_list} parameter introduces commands that may be
36351 run on the target, rather than being reported back to @value{GDBN}.
36352 The parameter starts with a numeric flag @var{persist}; if the flag is
36353 nonzero, then the breakpoint may remain active and the commands
36354 continue to be run even when @value{GDBN} disconnects from the target.
36355 Following this flag is a series of expressions concatenated with no
36356 separators. Each expression has the following form:
36360 @item X @var{len},@var{expr}
36361 @var{len} is the length of the bytecode expression and @var{expr} is the
36362 actual conditional expression in bytecode form.
36366 see @ref{Architecture-Specific Protocol Details}.
36368 @emph{Implementation note: It is possible for a target to copy or move
36369 code that contains memory breakpoints (e.g., when implementing
36370 overlays). The behavior of this packet, in the presence of such a
36371 target, is not defined.}
36383 @item z1,@var{addr},@var{kind}
36384 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
36385 @cindex @samp{z1} packet
36386 @cindex @samp{Z1} packet
36387 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36388 address @var{addr}.
36390 A hardware breakpoint is implemented using a mechanism that is not
36391 dependant on being able to modify the target's memory. @var{kind}
36392 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
36394 @emph{Implementation note: A hardware breakpoint is not affected by code
36407 @item z2,@var{addr},@var{kind}
36408 @itemx Z2,@var{addr},@var{kind}
36409 @cindex @samp{z2} packet
36410 @cindex @samp{Z2} packet
36411 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36412 @var{kind} is interpreted as the number of bytes to watch.
36424 @item z3,@var{addr},@var{kind}
36425 @itemx Z3,@var{addr},@var{kind}
36426 @cindex @samp{z3} packet
36427 @cindex @samp{Z3} packet
36428 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36429 @var{kind} is interpreted as the number of bytes to watch.
36441 @item z4,@var{addr},@var{kind}
36442 @itemx Z4,@var{addr},@var{kind}
36443 @cindex @samp{z4} packet
36444 @cindex @samp{Z4} packet
36445 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36446 @var{kind} is interpreted as the number of bytes to watch.
36460 @node Stop Reply Packets
36461 @section Stop Reply Packets
36462 @cindex stop reply packets
36464 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36465 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36466 receive any of the below as a reply. Except for @samp{?}
36467 and @samp{vStopped}, that reply is only returned
36468 when the target halts. In the below the exact meaning of @dfn{signal
36469 number} is defined by the header @file{include/gdb/signals.h} in the
36470 @value{GDBN} source code.
36472 As in the description of request packets, we include spaces in the
36473 reply templates for clarity; these are not part of the reply packet's
36474 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36480 The program received signal number @var{AA} (a two-digit hexadecimal
36481 number). This is equivalent to a @samp{T} response with no
36482 @var{n}:@var{r} pairs.
36484 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36485 @cindex @samp{T} packet reply
36486 The program received signal number @var{AA} (a two-digit hexadecimal
36487 number). This is equivalent to an @samp{S} response, except that the
36488 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36489 and other information directly in the stop reply packet, reducing
36490 round-trip latency. Single-step and breakpoint traps are reported
36491 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36495 If @var{n} is a hexadecimal number, it is a register number, and the
36496 corresponding @var{r} gives that register's value. @var{r} is a
36497 series of bytes in target byte order, with each byte given by a
36498 two-digit hex number.
36501 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36502 the stopped thread, as specified in @ref{thread-id syntax}.
36505 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36506 the core on which the stop event was detected.
36509 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36510 specific event that stopped the target. The currently defined stop
36511 reasons are listed below. @var{aa} should be @samp{05}, the trap
36512 signal. At most one stop reason should be present.
36515 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36516 and go on to the next; this allows us to extend the protocol in the
36520 The currently defined stop reasons are:
36526 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36529 @cindex shared library events, remote reply
36531 The packet indicates that the loaded libraries have changed.
36532 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36533 list of loaded libraries. @var{r} is ignored.
36535 @cindex replay log events, remote reply
36537 The packet indicates that the target cannot continue replaying
36538 logged execution events, because it has reached the end (or the
36539 beginning when executing backward) of the log. The value of @var{r}
36540 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36541 for more information.
36545 @itemx W @var{AA} ; process:@var{pid}
36546 The process exited, and @var{AA} is the exit status. This is only
36547 applicable to certain targets.
36549 The second form of the response, including the process ID of the exited
36550 process, can be used only when @value{GDBN} has reported support for
36551 multiprocess protocol extensions; see @ref{multiprocess extensions}.
36552 The @var{pid} is formatted as a big-endian hex string.
36555 @itemx X @var{AA} ; process:@var{pid}
36556 The process terminated with signal @var{AA}.
36558 The second form of the response, including the process ID of the
36559 terminated process, can be used only when @value{GDBN} has reported
36560 support for multiprocess protocol extensions; see @ref{multiprocess
36561 extensions}. The @var{pid} is formatted as a big-endian hex string.
36563 @item O @var{XX}@dots{}
36564 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36565 written as the program's console output. This can happen at any time
36566 while the program is running and the debugger should continue to wait
36567 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36569 @item F @var{call-id},@var{parameter}@dots{}
36570 @var{call-id} is the identifier which says which host system call should
36571 be called. This is just the name of the function. Translation into the
36572 correct system call is only applicable as it's defined in @value{GDBN}.
36573 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36576 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36577 this very system call.
36579 The target replies with this packet when it expects @value{GDBN} to
36580 call a host system call on behalf of the target. @value{GDBN} replies
36581 with an appropriate @samp{F} packet and keeps up waiting for the next
36582 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36583 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36584 Protocol Extension}, for more details.
36588 @node General Query Packets
36589 @section General Query Packets
36590 @cindex remote query requests
36592 Packets starting with @samp{q} are @dfn{general query packets};
36593 packets starting with @samp{Q} are @dfn{general set packets}. General
36594 query and set packets are a semi-unified form for retrieving and
36595 sending information to and from the stub.
36597 The initial letter of a query or set packet is followed by a name
36598 indicating what sort of thing the packet applies to. For example,
36599 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36600 definitions with the stub. These packet names follow some
36605 The name must not contain commas, colons or semicolons.
36607 Most @value{GDBN} query and set packets have a leading upper case
36610 The names of custom vendor packets should use a company prefix, in
36611 lower case, followed by a period. For example, packets designed at
36612 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36613 foos) or @samp{Qacme.bar} (for setting bars).
36616 The name of a query or set packet should be separated from any
36617 parameters by a @samp{:}; the parameters themselves should be
36618 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36619 full packet name, and check for a separator or the end of the packet,
36620 in case two packet names share a common prefix. New packets should not begin
36621 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36622 packets predate these conventions, and have arguments without any terminator
36623 for the packet name; we suspect they are in widespread use in places that
36624 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36625 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36628 Like the descriptions of the other packets, each description here
36629 has a template showing the packet's overall syntax, followed by an
36630 explanation of the packet's meaning. We include spaces in some of the
36631 templates for clarity; these are not part of the packet's syntax. No
36632 @value{GDBN} packet uses spaces to separate its components.
36634 Here are the currently defined query and set packets:
36640 Turn on or off the agent as a helper to perform some debugging operations
36641 delegated from @value{GDBN} (@pxref{Control Agent}).
36643 @item QAllow:@var{op}:@var{val}@dots{}
36644 @cindex @samp{QAllow} packet
36645 Specify which operations @value{GDBN} expects to request of the
36646 target, as a semicolon-separated list of operation name and value
36647 pairs. Possible values for @var{op} include @samp{WriteReg},
36648 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36649 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36650 indicating that @value{GDBN} will not request the operation, or 1,
36651 indicating that it may. (The target can then use this to set up its
36652 own internals optimally, for instance if the debugger never expects to
36653 insert breakpoints, it may not need to install its own trap handler.)
36656 @cindex current thread, remote request
36657 @cindex @samp{qC} packet
36658 Return the current thread ID.
36662 @item QC @var{thread-id}
36663 Where @var{thread-id} is a thread ID as documented in
36664 @ref{thread-id syntax}.
36665 @item @r{(anything else)}
36666 Any other reply implies the old thread ID.
36669 @item qCRC:@var{addr},@var{length}
36670 @cindex CRC of memory block, remote request
36671 @cindex @samp{qCRC} packet
36672 Compute the CRC checksum of a block of memory using CRC-32 defined in
36673 IEEE 802.3. The CRC is computed byte at a time, taking the most
36674 significant bit of each byte first. The initial pattern code
36675 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36677 @emph{Note:} This is the same CRC used in validating separate debug
36678 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36679 Files}). However the algorithm is slightly different. When validating
36680 separate debug files, the CRC is computed taking the @emph{least}
36681 significant bit of each byte first, and the final result is inverted to
36682 detect trailing zeros.
36687 An error (such as memory fault)
36688 @item C @var{crc32}
36689 The specified memory region's checksum is @var{crc32}.
36692 @item QDisableRandomization:@var{value}
36693 @cindex disable address space randomization, remote request
36694 @cindex @samp{QDisableRandomization} packet
36695 Some target operating systems will randomize the virtual address space
36696 of the inferior process as a security feature, but provide a feature
36697 to disable such randomization, e.g.@: to allow for a more deterministic
36698 debugging experience. On such systems, this packet with a @var{value}
36699 of 1 directs the target to disable address space randomization for
36700 processes subsequently started via @samp{vRun} packets, while a packet
36701 with a @var{value} of 0 tells the target to enable address space
36704 This packet is only available in extended mode (@pxref{extended mode}).
36709 The request succeeded.
36712 An error occurred. @var{nn} are hex digits.
36715 An empty reply indicates that @samp{QDisableRandomization} is not supported
36719 This packet is not probed by default; the remote stub must request it,
36720 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36721 This should only be done on targets that actually support disabling
36722 address space randomization.
36725 @itemx qsThreadInfo
36726 @cindex list active threads, remote request
36727 @cindex @samp{qfThreadInfo} packet
36728 @cindex @samp{qsThreadInfo} packet
36729 Obtain a list of all active thread IDs from the target (OS). Since there
36730 may be too many active threads to fit into one reply packet, this query
36731 works iteratively: it may require more than one query/reply sequence to
36732 obtain the entire list of threads. The first query of the sequence will
36733 be the @samp{qfThreadInfo} query; subsequent queries in the
36734 sequence will be the @samp{qsThreadInfo} query.
36736 NOTE: This packet replaces the @samp{qL} query (see below).
36740 @item m @var{thread-id}
36742 @item m @var{thread-id},@var{thread-id}@dots{}
36743 a comma-separated list of thread IDs
36745 (lower case letter @samp{L}) denotes end of list.
36748 In response to each query, the target will reply with a list of one or
36749 more thread IDs, separated by commas.
36750 @value{GDBN} will respond to each reply with a request for more thread
36751 ids (using the @samp{qs} form of the query), until the target responds
36752 with @samp{l} (lower-case ell, for @dfn{last}).
36753 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
36756 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
36757 @cindex get thread-local storage address, remote request
36758 @cindex @samp{qGetTLSAddr} packet
36759 Fetch the address associated with thread local storage specified
36760 by @var{thread-id}, @var{offset}, and @var{lm}.
36762 @var{thread-id} is the thread ID associated with the
36763 thread for which to fetch the TLS address. @xref{thread-id syntax}.
36765 @var{offset} is the (big endian, hex encoded) offset associated with the
36766 thread local variable. (This offset is obtained from the debug
36767 information associated with the variable.)
36769 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
36770 load module associated with the thread local storage. For example,
36771 a @sc{gnu}/Linux system will pass the link map address of the shared
36772 object associated with the thread local storage under consideration.
36773 Other operating environments may choose to represent the load module
36774 differently, so the precise meaning of this parameter will vary.
36778 @item @var{XX}@dots{}
36779 Hex encoded (big endian) bytes representing the address of the thread
36780 local storage requested.
36783 An error occurred. @var{nn} are hex digits.
36786 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
36789 @item qGetTIBAddr:@var{thread-id}
36790 @cindex get thread information block address
36791 @cindex @samp{qGetTIBAddr} packet
36792 Fetch address of the Windows OS specific Thread Information Block.
36794 @var{thread-id} is the thread ID associated with the thread.
36798 @item @var{XX}@dots{}
36799 Hex encoded (big endian) bytes representing the linear address of the
36800 thread information block.
36803 An error occured. This means that either the thread was not found, or the
36804 address could not be retrieved.
36807 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
36810 @item qL @var{startflag} @var{threadcount} @var{nextthread}
36811 Obtain thread information from RTOS. Where: @var{startflag} (one hex
36812 digit) is one to indicate the first query and zero to indicate a
36813 subsequent query; @var{threadcount} (two hex digits) is the maximum
36814 number of threads the response packet can contain; and @var{nextthread}
36815 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
36816 returned in the response as @var{argthread}.
36818 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
36822 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
36823 Where: @var{count} (two hex digits) is the number of threads being
36824 returned; @var{done} (one hex digit) is zero to indicate more threads
36825 and one indicates no further threads; @var{argthreadid} (eight hex
36826 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
36827 is a sequence of thread IDs from the target. @var{threadid} (eight hex
36828 digits). See @code{remote.c:parse_threadlist_response()}.
36832 @cindex section offsets, remote request
36833 @cindex @samp{qOffsets} packet
36834 Get section offsets that the target used when relocating the downloaded
36839 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
36840 Relocate the @code{Text} section by @var{xxx} from its original address.
36841 Relocate the @code{Data} section by @var{yyy} from its original address.
36842 If the object file format provides segment information (e.g.@: @sc{elf}
36843 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
36844 segments by the supplied offsets.
36846 @emph{Note: while a @code{Bss} offset may be included in the response,
36847 @value{GDBN} ignores this and instead applies the @code{Data} offset
36848 to the @code{Bss} section.}
36850 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
36851 Relocate the first segment of the object file, which conventionally
36852 contains program code, to a starting address of @var{xxx}. If
36853 @samp{DataSeg} is specified, relocate the second segment, which
36854 conventionally contains modifiable data, to a starting address of
36855 @var{yyy}. @value{GDBN} will report an error if the object file
36856 does not contain segment information, or does not contain at least
36857 as many segments as mentioned in the reply. Extra segments are
36858 kept at fixed offsets relative to the last relocated segment.
36861 @item qP @var{mode} @var{thread-id}
36862 @cindex thread information, remote request
36863 @cindex @samp{qP} packet
36864 Returns information on @var{thread-id}. Where: @var{mode} is a hex
36865 encoded 32 bit mode; @var{thread-id} is a thread ID
36866 (@pxref{thread-id syntax}).
36868 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
36871 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
36875 @cindex non-stop mode, remote request
36876 @cindex @samp{QNonStop} packet
36878 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
36879 @xref{Remote Non-Stop}, for more information.
36884 The request succeeded.
36887 An error occurred. @var{nn} are hex digits.
36890 An empty reply indicates that @samp{QNonStop} is not supported by
36894 This packet is not probed by default; the remote stub must request it,
36895 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36896 Use of this packet is controlled by the @code{set non-stop} command;
36897 @pxref{Non-Stop Mode}.
36899 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36900 @cindex pass signals to inferior, remote request
36901 @cindex @samp{QPassSignals} packet
36902 @anchor{QPassSignals}
36903 Each listed @var{signal} should be passed directly to the inferior process.
36904 Signals are numbered identically to continue packets and stop replies
36905 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36906 strictly greater than the previous item. These signals do not need to stop
36907 the inferior, or be reported to @value{GDBN}. All other signals should be
36908 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
36909 combine; any earlier @samp{QPassSignals} list is completely replaced by the
36910 new list. This packet improves performance when using @samp{handle
36911 @var{signal} nostop noprint pass}.
36916 The request succeeded.
36919 An error occurred. @var{nn} are hex digits.
36922 An empty reply indicates that @samp{QPassSignals} is not supported by
36926 Use of this packet is controlled by the @code{set remote pass-signals}
36927 command (@pxref{Remote Configuration, set remote pass-signals}).
36928 This packet is not probed by default; the remote stub must request it,
36929 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36931 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36932 @cindex signals the inferior may see, remote request
36933 @cindex @samp{QProgramSignals} packet
36934 @anchor{QProgramSignals}
36935 Each listed @var{signal} may be delivered to the inferior process.
36936 Others should be silently discarded.
36938 In some cases, the remote stub may need to decide whether to deliver a
36939 signal to the program or not without @value{GDBN} involvement. One
36940 example of that is while detaching --- the program's threads may have
36941 stopped for signals that haven't yet had a chance of being reported to
36942 @value{GDBN}, and so the remote stub can use the signal list specified
36943 by this packet to know whether to deliver or ignore those pending
36946 This does not influence whether to deliver a signal as requested by a
36947 resumption packet (@pxref{vCont packet}).
36949 Signals are numbered identically to continue packets and stop replies
36950 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36951 strictly greater than the previous item. Multiple
36952 @samp{QProgramSignals} packets do not combine; any earlier
36953 @samp{QProgramSignals} list is completely replaced by the new list.
36958 The request succeeded.
36961 An error occurred. @var{nn} are hex digits.
36964 An empty reply indicates that @samp{QProgramSignals} is not supported
36968 Use of this packet is controlled by the @code{set remote program-signals}
36969 command (@pxref{Remote Configuration, set remote program-signals}).
36970 This packet is not probed by default; the remote stub must request it,
36971 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36973 @item qRcmd,@var{command}
36974 @cindex execute remote command, remote request
36975 @cindex @samp{qRcmd} packet
36976 @var{command} (hex encoded) is passed to the local interpreter for
36977 execution. Invalid commands should be reported using the output
36978 string. Before the final result packet, the target may also respond
36979 with a number of intermediate @samp{O@var{output}} console output
36980 packets. @emph{Implementors should note that providing access to a
36981 stubs's interpreter may have security implications}.
36986 A command response with no output.
36988 A command response with the hex encoded output string @var{OUTPUT}.
36990 Indicate a badly formed request.
36992 An empty reply indicates that @samp{qRcmd} is not recognized.
36995 (Note that the @code{qRcmd} packet's name is separated from the
36996 command by a @samp{,}, not a @samp{:}, contrary to the naming
36997 conventions above. Please don't use this packet as a model for new
37000 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37001 @cindex searching memory, in remote debugging
37002 @cindex @samp{qSearch:memory} packet
37003 @anchor{qSearch memory}
37004 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37005 @var{address} and @var{length} are encoded in hex.
37006 @var{search-pattern} is a sequence of bytes, hex encoded.
37011 The pattern was not found.
37013 The pattern was found at @var{address}.
37015 A badly formed request or an error was encountered while searching memory.
37017 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37020 @item QStartNoAckMode
37021 @cindex @samp{QStartNoAckMode} packet
37022 @anchor{QStartNoAckMode}
37023 Request that the remote stub disable the normal @samp{+}/@samp{-}
37024 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37029 The stub has switched to no-acknowledgment mode.
37030 @value{GDBN} acknowledges this reponse,
37031 but neither the stub nor @value{GDBN} shall send or expect further
37032 @samp{+}/@samp{-} acknowledgments in the current connection.
37034 An empty reply indicates that the stub does not support no-acknowledgment mode.
37037 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37038 @cindex supported packets, remote query
37039 @cindex features of the remote protocol
37040 @cindex @samp{qSupported} packet
37041 @anchor{qSupported}
37042 Tell the remote stub about features supported by @value{GDBN}, and
37043 query the stub for features it supports. This packet allows
37044 @value{GDBN} and the remote stub to take advantage of each others'
37045 features. @samp{qSupported} also consolidates multiple feature probes
37046 at startup, to improve @value{GDBN} performance---a single larger
37047 packet performs better than multiple smaller probe packets on
37048 high-latency links. Some features may enable behavior which must not
37049 be on by default, e.g.@: because it would confuse older clients or
37050 stubs. Other features may describe packets which could be
37051 automatically probed for, but are not. These features must be
37052 reported before @value{GDBN} will use them. This ``default
37053 unsupported'' behavior is not appropriate for all packets, but it
37054 helps to keep the initial connection time under control with new
37055 versions of @value{GDBN} which support increasing numbers of packets.
37059 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37060 The stub supports or does not support each returned @var{stubfeature},
37061 depending on the form of each @var{stubfeature} (see below for the
37064 An empty reply indicates that @samp{qSupported} is not recognized,
37065 or that no features needed to be reported to @value{GDBN}.
37068 The allowed forms for each feature (either a @var{gdbfeature} in the
37069 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37073 @item @var{name}=@var{value}
37074 The remote protocol feature @var{name} is supported, and associated
37075 with the specified @var{value}. The format of @var{value} depends
37076 on the feature, but it must not include a semicolon.
37078 The remote protocol feature @var{name} is supported, and does not
37079 need an associated value.
37081 The remote protocol feature @var{name} is not supported.
37083 The remote protocol feature @var{name} may be supported, and
37084 @value{GDBN} should auto-detect support in some other way when it is
37085 needed. This form will not be used for @var{gdbfeature} notifications,
37086 but may be used for @var{stubfeature} responses.
37089 Whenever the stub receives a @samp{qSupported} request, the
37090 supplied set of @value{GDBN} features should override any previous
37091 request. This allows @value{GDBN} to put the stub in a known
37092 state, even if the stub had previously been communicating with
37093 a different version of @value{GDBN}.
37095 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37100 This feature indicates whether @value{GDBN} supports multiprocess
37101 extensions to the remote protocol. @value{GDBN} does not use such
37102 extensions unless the stub also reports that it supports them by
37103 including @samp{multiprocess+} in its @samp{qSupported} reply.
37104 @xref{multiprocess extensions}, for details.
37107 This feature indicates that @value{GDBN} supports the XML target
37108 description. If the stub sees @samp{xmlRegisters=} with target
37109 specific strings separated by a comma, it will report register
37113 This feature indicates whether @value{GDBN} supports the
37114 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37115 instruction reply packet}).
37118 Stubs should ignore any unknown values for
37119 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37120 packet supports receiving packets of unlimited length (earlier
37121 versions of @value{GDBN} may reject overly long responses). Additional values
37122 for @var{gdbfeature} may be defined in the future to let the stub take
37123 advantage of new features in @value{GDBN}, e.g.@: incompatible
37124 improvements in the remote protocol---the @samp{multiprocess} feature is
37125 an example of such a feature. The stub's reply should be independent
37126 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37127 describes all the features it supports, and then the stub replies with
37128 all the features it supports.
37130 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37131 responses, as long as each response uses one of the standard forms.
37133 Some features are flags. A stub which supports a flag feature
37134 should respond with a @samp{+} form response. Other features
37135 require values, and the stub should respond with an @samp{=}
37138 Each feature has a default value, which @value{GDBN} will use if
37139 @samp{qSupported} is not available or if the feature is not mentioned
37140 in the @samp{qSupported} response. The default values are fixed; a
37141 stub is free to omit any feature responses that match the defaults.
37143 Not all features can be probed, but for those which can, the probing
37144 mechanism is useful: in some cases, a stub's internal
37145 architecture may not allow the protocol layer to know some information
37146 about the underlying target in advance. This is especially common in
37147 stubs which may be configured for multiple targets.
37149 These are the currently defined stub features and their properties:
37151 @multitable @columnfractions 0.35 0.2 0.12 0.2
37152 @c NOTE: The first row should be @headitem, but we do not yet require
37153 @c a new enough version of Texinfo (4.7) to use @headitem.
37155 @tab Value Required
37159 @item @samp{PacketSize}
37164 @item @samp{qXfer:auxv:read}
37169 @item @samp{qXfer:features:read}
37174 @item @samp{qXfer:libraries:read}
37179 @item @samp{qXfer:memory-map:read}
37184 @item @samp{qXfer:sdata:read}
37189 @item @samp{qXfer:spu:read}
37194 @item @samp{qXfer:spu:write}
37199 @item @samp{qXfer:siginfo:read}
37204 @item @samp{qXfer:siginfo:write}
37209 @item @samp{qXfer:threads:read}
37214 @item @samp{qXfer:traceframe-info:read}
37219 @item @samp{qXfer:uib:read}
37224 @item @samp{qXfer:fdpic:read}
37229 @item @samp{QNonStop}
37234 @item @samp{QPassSignals}
37239 @item @samp{QStartNoAckMode}
37244 @item @samp{multiprocess}
37249 @item @samp{ConditionalBreakpoints}
37254 @item @samp{ConditionalTracepoints}
37259 @item @samp{ReverseContinue}
37264 @item @samp{ReverseStep}
37269 @item @samp{TracepointSource}
37274 @item @samp{QAgent}
37279 @item @samp{QAllow}
37284 @item @samp{QDisableRandomization}
37289 @item @samp{EnableDisableTracepoints}
37294 @item @samp{tracenz}
37299 @item @samp{BreakpointCommands}
37306 These are the currently defined stub features, in more detail:
37309 @cindex packet size, remote protocol
37310 @item PacketSize=@var{bytes}
37311 The remote stub can accept packets up to at least @var{bytes} in
37312 length. @value{GDBN} will send packets up to this size for bulk
37313 transfers, and will never send larger packets. This is a limit on the
37314 data characters in the packet, including the frame and checksum.
37315 There is no trailing NUL byte in a remote protocol packet; if the stub
37316 stores packets in a NUL-terminated format, it should allow an extra
37317 byte in its buffer for the NUL. If this stub feature is not supported,
37318 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37320 @item qXfer:auxv:read
37321 The remote stub understands the @samp{qXfer:auxv:read} packet
37322 (@pxref{qXfer auxiliary vector read}).
37324 @item qXfer:features:read
37325 The remote stub understands the @samp{qXfer:features:read} packet
37326 (@pxref{qXfer target description read}).
37328 @item qXfer:libraries:read
37329 The remote stub understands the @samp{qXfer:libraries:read} packet
37330 (@pxref{qXfer library list read}).
37332 @item qXfer:libraries-svr4:read
37333 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37334 (@pxref{qXfer svr4 library list read}).
37336 @item qXfer:memory-map:read
37337 The remote stub understands the @samp{qXfer:memory-map:read} packet
37338 (@pxref{qXfer memory map read}).
37340 @item qXfer:sdata:read
37341 The remote stub understands the @samp{qXfer:sdata:read} packet
37342 (@pxref{qXfer sdata read}).
37344 @item qXfer:spu:read
37345 The remote stub understands the @samp{qXfer:spu:read} packet
37346 (@pxref{qXfer spu read}).
37348 @item qXfer:spu:write
37349 The remote stub understands the @samp{qXfer:spu:write} packet
37350 (@pxref{qXfer spu write}).
37352 @item qXfer:siginfo:read
37353 The remote stub understands the @samp{qXfer:siginfo:read} packet
37354 (@pxref{qXfer siginfo read}).
37356 @item qXfer:siginfo:write
37357 The remote stub understands the @samp{qXfer:siginfo:write} packet
37358 (@pxref{qXfer siginfo write}).
37360 @item qXfer:threads:read
37361 The remote stub understands the @samp{qXfer:threads:read} packet
37362 (@pxref{qXfer threads read}).
37364 @item qXfer:traceframe-info:read
37365 The remote stub understands the @samp{qXfer:traceframe-info:read}
37366 packet (@pxref{qXfer traceframe info read}).
37368 @item qXfer:uib:read
37369 The remote stub understands the @samp{qXfer:uib:read}
37370 packet (@pxref{qXfer unwind info block}).
37372 @item qXfer:fdpic:read
37373 The remote stub understands the @samp{qXfer:fdpic:read}
37374 packet (@pxref{qXfer fdpic loadmap read}).
37377 The remote stub understands the @samp{QNonStop} packet
37378 (@pxref{QNonStop}).
37381 The remote stub understands the @samp{QPassSignals} packet
37382 (@pxref{QPassSignals}).
37384 @item QStartNoAckMode
37385 The remote stub understands the @samp{QStartNoAckMode} packet and
37386 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37389 @anchor{multiprocess extensions}
37390 @cindex multiprocess extensions, in remote protocol
37391 The remote stub understands the multiprocess extensions to the remote
37392 protocol syntax. The multiprocess extensions affect the syntax of
37393 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37394 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37395 replies. Note that reporting this feature indicates support for the
37396 syntactic extensions only, not that the stub necessarily supports
37397 debugging of more than one process at a time. The stub must not use
37398 multiprocess extensions in packet replies unless @value{GDBN} has also
37399 indicated it supports them in its @samp{qSupported} request.
37401 @item qXfer:osdata:read
37402 The remote stub understands the @samp{qXfer:osdata:read} packet
37403 ((@pxref{qXfer osdata read}).
37405 @item ConditionalBreakpoints
37406 The target accepts and implements evaluation of conditional expressions
37407 defined for breakpoints. The target will only report breakpoint triggers
37408 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37410 @item ConditionalTracepoints
37411 The remote stub accepts and implements conditional expressions defined
37412 for tracepoints (@pxref{Tracepoint Conditions}).
37414 @item ReverseContinue
37415 The remote stub accepts and implements the reverse continue packet
37419 The remote stub accepts and implements the reverse step packet
37422 @item TracepointSource
37423 The remote stub understands the @samp{QTDPsrc} packet that supplies
37424 the source form of tracepoint definitions.
37427 The remote stub understands the @samp{QAgent} packet.
37430 The remote stub understands the @samp{QAllow} packet.
37432 @item QDisableRandomization
37433 The remote stub understands the @samp{QDisableRandomization} packet.
37435 @item StaticTracepoint
37436 @cindex static tracepoints, in remote protocol
37437 The remote stub supports static tracepoints.
37439 @item InstallInTrace
37440 @anchor{install tracepoint in tracing}
37441 The remote stub supports installing tracepoint in tracing.
37443 @item EnableDisableTracepoints
37444 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37445 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37446 to be enabled and disabled while a trace experiment is running.
37449 @cindex string tracing, in remote protocol
37450 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
37451 See @ref{Bytecode Descriptions} for details about the bytecode.
37453 @item BreakpointCommands
37454 @cindex breakpoint commands, in remote protocol
37455 The remote stub supports running a breakpoint's command list itself,
37456 rather than reporting the hit to @value{GDBN}.
37461 @cindex symbol lookup, remote request
37462 @cindex @samp{qSymbol} packet
37463 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37464 requests. Accept requests from the target for the values of symbols.
37469 The target does not need to look up any (more) symbols.
37470 @item qSymbol:@var{sym_name}
37471 The target requests the value of symbol @var{sym_name} (hex encoded).
37472 @value{GDBN} may provide the value by using the
37473 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37477 @item qSymbol:@var{sym_value}:@var{sym_name}
37478 Set the value of @var{sym_name} to @var{sym_value}.
37480 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37481 target has previously requested.
37483 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37484 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37490 The target does not need to look up any (more) symbols.
37491 @item qSymbol:@var{sym_name}
37492 The target requests the value of a new symbol @var{sym_name} (hex
37493 encoded). @value{GDBN} will continue to supply the values of symbols
37494 (if available), until the target ceases to request them.
37499 @itemx QTDisconnected
37506 @itemx qTMinFTPILen
37508 @xref{Tracepoint Packets}.
37510 @item qThreadExtraInfo,@var{thread-id}
37511 @cindex thread attributes info, remote request
37512 @cindex @samp{qThreadExtraInfo} packet
37513 Obtain a printable string description of a thread's attributes from
37514 the target OS. @var{thread-id} is a thread ID;
37515 see @ref{thread-id syntax}. This
37516 string may contain anything that the target OS thinks is interesting
37517 for @value{GDBN} to tell the user about the thread. The string is
37518 displayed in @value{GDBN}'s @code{info threads} display. Some
37519 examples of possible thread extra info strings are @samp{Runnable}, or
37520 @samp{Blocked on Mutex}.
37524 @item @var{XX}@dots{}
37525 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37526 comprising the printable string containing the extra information about
37527 the thread's attributes.
37530 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37531 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37532 conventions above. Please don't use this packet as a model for new
37551 @xref{Tracepoint Packets}.
37553 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37554 @cindex read special object, remote request
37555 @cindex @samp{qXfer} packet
37556 @anchor{qXfer read}
37557 Read uninterpreted bytes from the target's special data area
37558 identified by the keyword @var{object}. Request @var{length} bytes
37559 starting at @var{offset} bytes into the data. The content and
37560 encoding of @var{annex} is specific to @var{object}; it can supply
37561 additional details about what data to access.
37563 Here are the specific requests of this form defined so far. All
37564 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37565 formats, listed below.
37568 @item qXfer:auxv:read::@var{offset},@var{length}
37569 @anchor{qXfer auxiliary vector read}
37570 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37571 auxiliary vector}. Note @var{annex} must be empty.
37573 This packet is not probed by default; the remote stub must request it,
37574 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37576 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37577 @anchor{qXfer target description read}
37578 Access the @dfn{target description}. @xref{Target Descriptions}. The
37579 annex specifies which XML document to access. The main description is
37580 always loaded from the @samp{target.xml} annex.
37582 This packet is not probed by default; the remote stub must request it,
37583 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37585 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37586 @anchor{qXfer library list read}
37587 Access the target's list of loaded libraries. @xref{Library List Format}.
37588 The annex part of the generic @samp{qXfer} packet must be empty
37589 (@pxref{qXfer read}).
37591 Targets which maintain a list of libraries in the program's memory do
37592 not need to implement this packet; it is designed for platforms where
37593 the operating system manages the list of loaded libraries.
37595 This packet is not probed by default; the remote stub must request it,
37596 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37598 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37599 @anchor{qXfer svr4 library list read}
37600 Access the target's list of loaded libraries when the target is an SVR4
37601 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37602 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37604 This packet is optional for better performance on SVR4 targets.
37605 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37607 This packet is not probed by default; the remote stub must request it,
37608 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37610 @item qXfer:memory-map:read::@var{offset},@var{length}
37611 @anchor{qXfer memory map read}
37612 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37613 annex part of the generic @samp{qXfer} packet must be empty
37614 (@pxref{qXfer read}).
37616 This packet is not probed by default; the remote stub must request it,
37617 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37619 @item qXfer:sdata:read::@var{offset},@var{length}
37620 @anchor{qXfer sdata read}
37622 Read contents of the extra collected static tracepoint marker
37623 information. The annex part of the generic @samp{qXfer} packet must
37624 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37627 This packet is not probed by default; the remote stub must request it,
37628 by supplying an appropriate @samp{qSupported} response
37629 (@pxref{qSupported}).
37631 @item qXfer:siginfo:read::@var{offset},@var{length}
37632 @anchor{qXfer siginfo read}
37633 Read contents of the extra signal information on the target
37634 system. The annex part of the generic @samp{qXfer} packet must be
37635 empty (@pxref{qXfer read}).
37637 This packet is not probed by default; the remote stub must request it,
37638 by supplying an appropriate @samp{qSupported} response
37639 (@pxref{qSupported}).
37641 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37642 @anchor{qXfer spu read}
37643 Read contents of an @code{spufs} file on the target system. The
37644 annex specifies which file to read; it must be of the form
37645 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37646 in the target process, and @var{name} identifes the @code{spufs} file
37647 in that context to be accessed.
37649 This packet is not probed by default; the remote stub must request it,
37650 by supplying an appropriate @samp{qSupported} response
37651 (@pxref{qSupported}).
37653 @item qXfer:threads:read::@var{offset},@var{length}
37654 @anchor{qXfer threads read}
37655 Access the list of threads on target. @xref{Thread List Format}. The
37656 annex part of the generic @samp{qXfer} packet must be empty
37657 (@pxref{qXfer read}).
37659 This packet is not probed by default; the remote stub must request it,
37660 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37662 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37663 @anchor{qXfer traceframe info read}
37665 Return a description of the current traceframe's contents.
37666 @xref{Traceframe Info Format}. The annex part of the generic
37667 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37669 This packet is not probed by default; the remote stub must request it,
37670 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37672 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37673 @anchor{qXfer unwind info block}
37675 Return the unwind information block for @var{pc}. This packet is used
37676 on OpenVMS/ia64 to ask the kernel unwind information.
37678 This packet is not probed by default.
37680 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37681 @anchor{qXfer fdpic loadmap read}
37682 Read contents of @code{loadmap}s on the target system. The
37683 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37684 executable @code{loadmap} or interpreter @code{loadmap} to read.
37686 This packet is not probed by default; the remote stub must request it,
37687 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37689 @item qXfer:osdata:read::@var{offset},@var{length}
37690 @anchor{qXfer osdata read}
37691 Access the target's @dfn{operating system information}.
37692 @xref{Operating System Information}.
37699 Data @var{data} (@pxref{Binary Data}) has been read from the
37700 target. There may be more data at a higher address (although
37701 it is permitted to return @samp{m} even for the last valid
37702 block of data, as long as at least one byte of data was read).
37703 @var{data} may have fewer bytes than the @var{length} in the
37707 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37708 There is no more data to be read. @var{data} may have fewer bytes
37709 than the @var{length} in the request.
37712 The @var{offset} in the request is at the end of the data.
37713 There is no more data to be read.
37716 The request was malformed, or @var{annex} was invalid.
37719 The offset was invalid, or there was an error encountered reading the data.
37720 @var{nn} is a hex-encoded @code{errno} value.
37723 An empty reply indicates the @var{object} string was not recognized by
37724 the stub, or that the object does not support reading.
37727 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
37728 @cindex write data into object, remote request
37729 @anchor{qXfer write}
37730 Write uninterpreted bytes into the target's special data area
37731 identified by the keyword @var{object}, starting at @var{offset} bytes
37732 into the data. @var{data}@dots{} is the binary-encoded data
37733 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
37734 is specific to @var{object}; it can supply additional details about what data
37737 Here are the specific requests of this form defined so far. All
37738 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
37739 formats, listed below.
37742 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
37743 @anchor{qXfer siginfo write}
37744 Write @var{data} to the extra signal information on the target system.
37745 The annex part of the generic @samp{qXfer} packet must be
37746 empty (@pxref{qXfer write}).
37748 This packet is not probed by default; the remote stub must request it,
37749 by supplying an appropriate @samp{qSupported} response
37750 (@pxref{qSupported}).
37752 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
37753 @anchor{qXfer spu write}
37754 Write @var{data} to an @code{spufs} file on the target system. The
37755 annex specifies which file to write; it must be of the form
37756 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37757 in the target process, and @var{name} identifes the @code{spufs} file
37758 in that context to be accessed.
37760 This packet is not probed by default; the remote stub must request it,
37761 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37767 @var{nn} (hex encoded) is the number of bytes written.
37768 This may be fewer bytes than supplied in the request.
37771 The request was malformed, or @var{annex} was invalid.
37774 The offset was invalid, or there was an error encountered writing the data.
37775 @var{nn} is a hex-encoded @code{errno} value.
37778 An empty reply indicates the @var{object} string was not
37779 recognized by the stub, or that the object does not support writing.
37782 @item qXfer:@var{object}:@var{operation}:@dots{}
37783 Requests of this form may be added in the future. When a stub does
37784 not recognize the @var{object} keyword, or its support for
37785 @var{object} does not recognize the @var{operation} keyword, the stub
37786 must respond with an empty packet.
37788 @item qAttached:@var{pid}
37789 @cindex query attached, remote request
37790 @cindex @samp{qAttached} packet
37791 Return an indication of whether the remote server attached to an
37792 existing process or created a new process. When the multiprocess
37793 protocol extensions are supported (@pxref{multiprocess extensions}),
37794 @var{pid} is an integer in hexadecimal format identifying the target
37795 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
37796 the query packet will be simplified as @samp{qAttached}.
37798 This query is used, for example, to know whether the remote process
37799 should be detached or killed when a @value{GDBN} session is ended with
37800 the @code{quit} command.
37805 The remote server attached to an existing process.
37807 The remote server created a new process.
37809 A badly formed request or an error was encountered.
37814 @node Architecture-Specific Protocol Details
37815 @section Architecture-Specific Protocol Details
37817 This section describes how the remote protocol is applied to specific
37818 target architectures. Also see @ref{Standard Target Features}, for
37819 details of XML target descriptions for each architecture.
37822 * ARM-Specific Protocol Details::
37823 * MIPS-Specific Protocol Details::
37826 @node ARM-Specific Protocol Details
37827 @subsection @acronym{ARM}-specific Protocol Details
37830 * ARM Breakpoint Kinds::
37833 @node ARM Breakpoint Kinds
37834 @subsubsection @acronym{ARM} Breakpoint Kinds
37835 @cindex breakpoint kinds, @acronym{ARM}
37837 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37842 16-bit Thumb mode breakpoint.
37845 32-bit Thumb mode (Thumb-2) breakpoint.
37848 32-bit @acronym{ARM} mode breakpoint.
37852 @node MIPS-Specific Protocol Details
37853 @subsection @acronym{MIPS}-specific Protocol Details
37856 * MIPS Register packet Format::
37857 * MIPS Breakpoint Kinds::
37860 @node MIPS Register packet Format
37861 @subsubsection @acronym{MIPS} Register Packet Format
37862 @cindex register packet format, @acronym{MIPS}
37864 The following @code{g}/@code{G} packets have previously been defined.
37865 In the below, some thirty-two bit registers are transferred as
37866 sixty-four bits. Those registers should be zero/sign extended (which?)
37867 to fill the space allocated. Register bytes are transferred in target
37868 byte order. The two nibbles within a register byte are transferred
37869 most-significant -- least-significant.
37874 All registers are transferred as thirty-two bit quantities in the order:
37875 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37876 registers; fsr; fir; fp.
37879 All registers are transferred as sixty-four bit quantities (including
37880 thirty-two bit registers such as @code{sr}). The ordering is the same
37885 @node MIPS Breakpoint Kinds
37886 @subsubsection @acronym{MIPS} Breakpoint Kinds
37887 @cindex breakpoint kinds, @acronym{MIPS}
37889 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37894 16-bit @acronym{MIPS16} mode breakpoint.
37897 16-bit @acronym{microMIPS} mode breakpoint.
37900 32-bit standard @acronym{MIPS} mode breakpoint.
37903 32-bit @acronym{microMIPS} mode breakpoint.
37907 @node Tracepoint Packets
37908 @section Tracepoint Packets
37909 @cindex tracepoint packets
37910 @cindex packets, tracepoint
37912 Here we describe the packets @value{GDBN} uses to implement
37913 tracepoints (@pxref{Tracepoints}).
37917 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37918 @cindex @samp{QTDP} packet
37919 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37920 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37921 the tracepoint is disabled. @var{step} is the tracepoint's step
37922 count, and @var{pass} is its pass count. If an @samp{F} is present,
37923 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37924 the number of bytes that the target should copy elsewhere to make room
37925 for the tracepoint. If an @samp{X} is present, it introduces a
37926 tracepoint condition, which consists of a hexadecimal length, followed
37927 by a comma and hex-encoded bytes, in a manner similar to action
37928 encodings as described below. If the trailing @samp{-} is present,
37929 further @samp{QTDP} packets will follow to specify this tracepoint's
37935 The packet was understood and carried out.
37937 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37939 The packet was not recognized.
37942 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37943 Define actions to be taken when a tracepoint is hit. @var{n} and
37944 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37945 this tracepoint. This packet may only be sent immediately after
37946 another @samp{QTDP} packet that ended with a @samp{-}. If the
37947 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
37948 specifying more actions for this tracepoint.
37950 In the series of action packets for a given tracepoint, at most one
37951 can have an @samp{S} before its first @var{action}. If such a packet
37952 is sent, it and the following packets define ``while-stepping''
37953 actions. Any prior packets define ordinary actions --- that is, those
37954 taken when the tracepoint is first hit. If no action packet has an
37955 @samp{S}, then all the packets in the series specify ordinary
37956 tracepoint actions.
37958 The @samp{@var{action}@dots{}} portion of the packet is a series of
37959 actions, concatenated without separators. Each action has one of the
37965 Collect the registers whose bits are set in @var{mask}. @var{mask} is
37966 a hexadecimal number whose @var{i}'th bit is set if register number
37967 @var{i} should be collected. (The least significant bit is numbered
37968 zero.) Note that @var{mask} may be any number of digits long; it may
37969 not fit in a 32-bit word.
37971 @item M @var{basereg},@var{offset},@var{len}
37972 Collect @var{len} bytes of memory starting at the address in register
37973 number @var{basereg}, plus @var{offset}. If @var{basereg} is
37974 @samp{-1}, then the range has a fixed address: @var{offset} is the
37975 address of the lowest byte to collect. The @var{basereg},
37976 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
37977 values (the @samp{-1} value for @var{basereg} is a special case).
37979 @item X @var{len},@var{expr}
37980 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
37981 it directs. @var{expr} is an agent expression, as described in
37982 @ref{Agent Expressions}. Each byte of the expression is encoded as a
37983 two-digit hex number in the packet; @var{len} is the number of bytes
37984 in the expression (and thus one-half the number of hex digits in the
37989 Any number of actions may be packed together in a single @samp{QTDP}
37990 packet, as long as the packet does not exceed the maximum packet
37991 length (400 bytes, for many stubs). There may be only one @samp{R}
37992 action per tracepoint, and it must precede any @samp{M} or @samp{X}
37993 actions. Any registers referred to by @samp{M} and @samp{X} actions
37994 must be collected by a preceding @samp{R} action. (The
37995 ``while-stepping'' actions are treated as if they were attached to a
37996 separate tracepoint, as far as these restrictions are concerned.)
38001 The packet was understood and carried out.
38003 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38005 The packet was not recognized.
38008 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38009 @cindex @samp{QTDPsrc} packet
38010 Specify a source string of tracepoint @var{n} at address @var{addr}.
38011 This is useful to get accurate reproduction of the tracepoints
38012 originally downloaded at the beginning of the trace run. @var{type}
38013 is the name of the tracepoint part, such as @samp{cond} for the
38014 tracepoint's conditional expression (see below for a list of types), while
38015 @var{bytes} is the string, encoded in hexadecimal.
38017 @var{start} is the offset of the @var{bytes} within the overall source
38018 string, while @var{slen} is the total length of the source string.
38019 This is intended for handling source strings that are longer than will
38020 fit in a single packet.
38021 @c Add detailed example when this info is moved into a dedicated
38022 @c tracepoint descriptions section.
38024 The available string types are @samp{at} for the location,
38025 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38026 @value{GDBN} sends a separate packet for each command in the action
38027 list, in the same order in which the commands are stored in the list.
38029 The target does not need to do anything with source strings except
38030 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38033 Although this packet is optional, and @value{GDBN} will only send it
38034 if the target replies with @samp{TracepointSource} @xref{General
38035 Query Packets}, it makes both disconnected tracing and trace files
38036 much easier to use. Otherwise the user must be careful that the
38037 tracepoints in effect while looking at trace frames are identical to
38038 the ones in effect during the trace run; even a small discrepancy
38039 could cause @samp{tdump} not to work, or a particular trace frame not
38042 @item QTDV:@var{n}:@var{value}
38043 @cindex define trace state variable, remote request
38044 @cindex @samp{QTDV} packet
38045 Create a new trace state variable, number @var{n}, with an initial
38046 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38047 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38048 the option of not using this packet for initial values of zero; the
38049 target should simply create the trace state variables as they are
38050 mentioned in expressions.
38052 @item QTFrame:@var{n}
38053 @cindex @samp{QTFrame} packet
38054 Select the @var{n}'th tracepoint frame from the buffer, and use the
38055 register and memory contents recorded there to answer subsequent
38056 request packets from @value{GDBN}.
38058 A successful reply from the stub indicates that the stub has found the
38059 requested frame. The response is a series of parts, concatenated
38060 without separators, describing the frame we selected. Each part has
38061 one of the following forms:
38065 The selected frame is number @var{n} in the trace frame buffer;
38066 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38067 was no frame matching the criteria in the request packet.
38070 The selected trace frame records a hit of tracepoint number @var{t};
38071 @var{t} is a hexadecimal number.
38075 @item QTFrame:pc:@var{addr}
38076 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38077 currently selected frame whose PC is @var{addr};
38078 @var{addr} is a hexadecimal number.
38080 @item QTFrame:tdp:@var{t}
38081 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38082 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38083 is a hexadecimal number.
38085 @item QTFrame:range:@var{start}:@var{end}
38086 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38087 currently selected frame whose PC is between @var{start} (inclusive)
38088 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38091 @item QTFrame:outside:@var{start}:@var{end}
38092 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38093 frame @emph{outside} the given range of addresses (exclusive).
38096 @cindex @samp{qTMinFTPILen} packet
38097 This packet requests the minimum length of instruction at which a fast
38098 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38099 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38100 it depends on the target system being able to create trampolines in
38101 the first 64K of memory, which might or might not be possible for that
38102 system. So the reply to this packet will be 4 if it is able to
38109 The minimum instruction length is currently unknown.
38111 The minimum instruction length is @var{length}, where @var{length} is greater
38112 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
38113 that a fast tracepoint may be placed on any instruction regardless of size.
38115 An error has occurred.
38117 An empty reply indicates that the request is not supported by the stub.
38121 @cindex @samp{QTStart} packet
38122 Begin the tracepoint experiment. Begin collecting data from
38123 tracepoint hits in the trace frame buffer. This packet supports the
38124 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38125 instruction reply packet}).
38128 @cindex @samp{QTStop} packet
38129 End the tracepoint experiment. Stop collecting trace frames.
38131 @item QTEnable:@var{n}:@var{addr}
38133 @cindex @samp{QTEnable} packet
38134 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38135 experiment. If the tracepoint was previously disabled, then collection
38136 of data from it will resume.
38138 @item QTDisable:@var{n}:@var{addr}
38140 @cindex @samp{QTDisable} packet
38141 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38142 experiment. No more data will be collected from the tracepoint unless
38143 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38146 @cindex @samp{QTinit} packet
38147 Clear the table of tracepoints, and empty the trace frame buffer.
38149 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38150 @cindex @samp{QTro} packet
38151 Establish the given ranges of memory as ``transparent''. The stub
38152 will answer requests for these ranges from memory's current contents,
38153 if they were not collected as part of the tracepoint hit.
38155 @value{GDBN} uses this to mark read-only regions of memory, like those
38156 containing program code. Since these areas never change, they should
38157 still have the same contents they did when the tracepoint was hit, so
38158 there's no reason for the stub to refuse to provide their contents.
38160 @item QTDisconnected:@var{value}
38161 @cindex @samp{QTDisconnected} packet
38162 Set the choice to what to do with the tracing run when @value{GDBN}
38163 disconnects from the target. A @var{value} of 1 directs the target to
38164 continue the tracing run, while 0 tells the target to stop tracing if
38165 @value{GDBN} is no longer in the picture.
38168 @cindex @samp{qTStatus} packet
38169 Ask the stub if there is a trace experiment running right now.
38171 The reply has the form:
38175 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38176 @var{running} is a single digit @code{1} if the trace is presently
38177 running, or @code{0} if not. It is followed by semicolon-separated
38178 optional fields that an agent may use to report additional status.
38182 If the trace is not running, the agent may report any of several
38183 explanations as one of the optional fields:
38188 No trace has been run yet.
38190 @item tstop[:@var{text}]:0
38191 The trace was stopped by a user-originated stop command. The optional
38192 @var{text} field is a user-supplied string supplied as part of the
38193 stop command (for instance, an explanation of why the trace was
38194 stopped manually). It is hex-encoded.
38197 The trace stopped because the trace buffer filled up.
38199 @item tdisconnected:0
38200 The trace stopped because @value{GDBN} disconnected from the target.
38202 @item tpasscount:@var{tpnum}
38203 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38205 @item terror:@var{text}:@var{tpnum}
38206 The trace stopped because tracepoint @var{tpnum} had an error. The
38207 string @var{text} is available to describe the nature of the error
38208 (for instance, a divide by zero in the condition expression).
38209 @var{text} is hex encoded.
38212 The trace stopped for some other reason.
38216 Additional optional fields supply statistical and other information.
38217 Although not required, they are extremely useful for users monitoring
38218 the progress of a trace run. If a trace has stopped, and these
38219 numbers are reported, they must reflect the state of the just-stopped
38224 @item tframes:@var{n}
38225 The number of trace frames in the buffer.
38227 @item tcreated:@var{n}
38228 The total number of trace frames created during the run. This may
38229 be larger than the trace frame count, if the buffer is circular.
38231 @item tsize:@var{n}
38232 The total size of the trace buffer, in bytes.
38234 @item tfree:@var{n}
38235 The number of bytes still unused in the buffer.
38237 @item circular:@var{n}
38238 The value of the circular trace buffer flag. @code{1} means that the
38239 trace buffer is circular and old trace frames will be discarded if
38240 necessary to make room, @code{0} means that the trace buffer is linear
38243 @item disconn:@var{n}
38244 The value of the disconnected tracing flag. @code{1} means that
38245 tracing will continue after @value{GDBN} disconnects, @code{0} means
38246 that the trace run will stop.
38250 @item qTP:@var{tp}:@var{addr}
38251 @cindex tracepoint status, remote request
38252 @cindex @samp{qTP} packet
38253 Ask the stub for the current state of tracepoint number @var{tp} at
38254 address @var{addr}.
38258 @item V@var{hits}:@var{usage}
38259 The tracepoint has been hit @var{hits} times so far during the trace
38260 run, and accounts for @var{usage} in the trace buffer. Note that
38261 @code{while-stepping} steps are not counted as separate hits, but the
38262 steps' space consumption is added into the usage number.
38266 @item qTV:@var{var}
38267 @cindex trace state variable value, remote request
38268 @cindex @samp{qTV} packet
38269 Ask the stub for the value of the trace state variable number @var{var}.
38274 The value of the variable is @var{value}. This will be the current
38275 value of the variable if the user is examining a running target, or a
38276 saved value if the variable was collected in the trace frame that the
38277 user is looking at. Note that multiple requests may result in
38278 different reply values, such as when requesting values while the
38279 program is running.
38282 The value of the variable is unknown. This would occur, for example,
38283 if the user is examining a trace frame in which the requested variable
38288 @cindex @samp{qTfP} packet
38290 @cindex @samp{qTsP} packet
38291 These packets request data about tracepoints that are being used by
38292 the target. @value{GDBN} sends @code{qTfP} to get the first piece
38293 of data, and multiple @code{qTsP} to get additional pieces. Replies
38294 to these packets generally take the form of the @code{QTDP} packets
38295 that define tracepoints. (FIXME add detailed syntax)
38298 @cindex @samp{qTfV} packet
38300 @cindex @samp{qTsV} packet
38301 These packets request data about trace state variables that are on the
38302 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
38303 and multiple @code{qTsV} to get additional variables. Replies to
38304 these packets follow the syntax of the @code{QTDV} packets that define
38305 trace state variables.
38311 @cindex @samp{qTfSTM} packet
38312 @cindex @samp{qTsSTM} packet
38313 These packets request data about static tracepoint markers that exist
38314 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
38315 first piece of data, and multiple @code{qTsSTM} to get additional
38316 pieces. Replies to these packets take the following form:
38320 @item m @var{address}:@var{id}:@var{extra}
38322 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38323 a comma-separated list of markers
38325 (lower case letter @samp{L}) denotes end of list.
38327 An error occurred. @var{nn} are hex digits.
38329 An empty reply indicates that the request is not supported by the
38333 @var{address} is encoded in hex.
38334 @var{id} and @var{extra} are strings encoded in hex.
38336 In response to each query, the target will reply with a list of one or
38337 more markers, separated by commas. @value{GDBN} will respond to each
38338 reply with a request for more markers (using the @samp{qs} form of the
38339 query), until the target responds with @samp{l} (lower-case ell, for
38342 @item qTSTMat:@var{address}
38344 @cindex @samp{qTSTMat} packet
38345 This packets requests data about static tracepoint markers in the
38346 target program at @var{address}. Replies to this packet follow the
38347 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38348 tracepoint markers.
38350 @item QTSave:@var{filename}
38351 @cindex @samp{QTSave} packet
38352 This packet directs the target to save trace data to the file name
38353 @var{filename} in the target's filesystem. @var{filename} is encoded
38354 as a hex string; the interpretation of the file name (relative vs
38355 absolute, wild cards, etc) is up to the target.
38357 @item qTBuffer:@var{offset},@var{len}
38358 @cindex @samp{qTBuffer} packet
38359 Return up to @var{len} bytes of the current contents of trace buffer,
38360 starting at @var{offset}. The trace buffer is treated as if it were
38361 a contiguous collection of traceframes, as per the trace file format.
38362 The reply consists as many hex-encoded bytes as the target can deliver
38363 in a packet; it is not an error to return fewer than were asked for.
38364 A reply consisting of just @code{l} indicates that no bytes are
38367 @item QTBuffer:circular:@var{value}
38368 This packet directs the target to use a circular trace buffer if
38369 @var{value} is 1, or a linear buffer if the value is 0.
38371 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38372 @cindex @samp{QTNotes} packet
38373 This packet adds optional textual notes to the trace run. Allowable
38374 types include @code{user}, @code{notes}, and @code{tstop}, the
38375 @var{text} fields are arbitrary strings, hex-encoded.
38379 @subsection Relocate instruction reply packet
38380 When installing fast tracepoints in memory, the target may need to
38381 relocate the instruction currently at the tracepoint address to a
38382 different address in memory. For most instructions, a simple copy is
38383 enough, but, for example, call instructions that implicitly push the
38384 return address on the stack, and relative branches or other
38385 PC-relative instructions require offset adjustment, so that the effect
38386 of executing the instruction at a different address is the same as if
38387 it had executed in the original location.
38389 In response to several of the tracepoint packets, the target may also
38390 respond with a number of intermediate @samp{qRelocInsn} request
38391 packets before the final result packet, to have @value{GDBN} handle
38392 this relocation operation. If a packet supports this mechanism, its
38393 documentation will explicitly say so. See for example the above
38394 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38395 format of the request is:
38398 @item qRelocInsn:@var{from};@var{to}
38400 This requests @value{GDBN} to copy instruction at address @var{from}
38401 to address @var{to}, possibly adjusted so that executing the
38402 instruction at @var{to} has the same effect as executing it at
38403 @var{from}. @value{GDBN} writes the adjusted instruction to target
38404 memory starting at @var{to}.
38409 @item qRelocInsn:@var{adjusted_size}
38410 Informs the stub the relocation is complete. @var{adjusted_size} is
38411 the length in bytes of resulting relocated instruction sequence.
38413 A badly formed request was detected, or an error was encountered while
38414 relocating the instruction.
38417 @node Host I/O Packets
38418 @section Host I/O Packets
38419 @cindex Host I/O, remote protocol
38420 @cindex file transfer, remote protocol
38422 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38423 operations on the far side of a remote link. For example, Host I/O is
38424 used to upload and download files to a remote target with its own
38425 filesystem. Host I/O uses the same constant values and data structure
38426 layout as the target-initiated File-I/O protocol. However, the
38427 Host I/O packets are structured differently. The target-initiated
38428 protocol relies on target memory to store parameters and buffers.
38429 Host I/O requests are initiated by @value{GDBN}, and the
38430 target's memory is not involved. @xref{File-I/O Remote Protocol
38431 Extension}, for more details on the target-initiated protocol.
38433 The Host I/O request packets all encode a single operation along with
38434 its arguments. They have this format:
38438 @item vFile:@var{operation}: @var{parameter}@dots{}
38439 @var{operation} is the name of the particular request; the target
38440 should compare the entire packet name up to the second colon when checking
38441 for a supported operation. The format of @var{parameter} depends on
38442 the operation. Numbers are always passed in hexadecimal. Negative
38443 numbers have an explicit minus sign (i.e.@: two's complement is not
38444 used). Strings (e.g.@: filenames) are encoded as a series of
38445 hexadecimal bytes. The last argument to a system call may be a
38446 buffer of escaped binary data (@pxref{Binary Data}).
38450 The valid responses to Host I/O packets are:
38454 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38455 @var{result} is the integer value returned by this operation, usually
38456 non-negative for success and -1 for errors. If an error has occured,
38457 @var{errno} will be included in the result. @var{errno} will have a
38458 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38459 operations which return data, @var{attachment} supplies the data as a
38460 binary buffer. Binary buffers in response packets are escaped in the
38461 normal way (@pxref{Binary Data}). See the individual packet
38462 documentation for the interpretation of @var{result} and
38466 An empty response indicates that this operation is not recognized.
38470 These are the supported Host I/O operations:
38473 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
38474 Open a file at @var{pathname} and return a file descriptor for it, or
38475 return -1 if an error occurs. @var{pathname} is a string,
38476 @var{flags} is an integer indicating a mask of open flags
38477 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38478 of mode bits to use if the file is created (@pxref{mode_t Values}).
38479 @xref{open}, for details of the open flags and mode values.
38481 @item vFile:close: @var{fd}
38482 Close the open file corresponding to @var{fd} and return 0, or
38483 -1 if an error occurs.
38485 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38486 Read data from the open file corresponding to @var{fd}. Up to
38487 @var{count} bytes will be read from the file, starting at @var{offset}
38488 relative to the start of the file. The target may read fewer bytes;
38489 common reasons include packet size limits and an end-of-file
38490 condition. The number of bytes read is returned. Zero should only be
38491 returned for a successful read at the end of the file, or if
38492 @var{count} was zero.
38494 The data read should be returned as a binary attachment on success.
38495 If zero bytes were read, the response should include an empty binary
38496 attachment (i.e.@: a trailing semicolon). The return value is the
38497 number of target bytes read; the binary attachment may be longer if
38498 some characters were escaped.
38500 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38501 Write @var{data} (a binary buffer) to the open file corresponding
38502 to @var{fd}. Start the write at @var{offset} from the start of the
38503 file. Unlike many @code{write} system calls, there is no
38504 separate @var{count} argument; the length of @var{data} in the
38505 packet is used. @samp{vFile:write} returns the number of bytes written,
38506 which may be shorter than the length of @var{data}, or -1 if an
38509 @item vFile:unlink: @var{pathname}
38510 Delete the file at @var{pathname} on the target. Return 0,
38511 or -1 if an error occurs. @var{pathname} is a string.
38513 @item vFile:readlink: @var{filename}
38514 Read value of symbolic link @var{filename} on the target. Return
38515 the number of bytes read, or -1 if an error occurs.
38517 The data read should be returned as a binary attachment on success.
38518 If zero bytes were read, the response should include an empty binary
38519 attachment (i.e.@: a trailing semicolon). The return value is the
38520 number of target bytes read; the binary attachment may be longer if
38521 some characters were escaped.
38526 @section Interrupts
38527 @cindex interrupts (remote protocol)
38529 When a program on the remote target is running, @value{GDBN} may
38530 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
38531 a @code{BREAK} followed by @code{g},
38532 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38534 The precise meaning of @code{BREAK} is defined by the transport
38535 mechanism and may, in fact, be undefined. @value{GDBN} does not
38536 currently define a @code{BREAK} mechanism for any of the network
38537 interfaces except for TCP, in which case @value{GDBN} sends the
38538 @code{telnet} BREAK sequence.
38540 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38541 transport mechanisms. It is represented by sending the single byte
38542 @code{0x03} without any of the usual packet overhead described in
38543 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38544 transmitted as part of a packet, it is considered to be packet data
38545 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38546 (@pxref{X packet}), used for binary downloads, may include an unescaped
38547 @code{0x03} as part of its packet.
38549 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38550 When Linux kernel receives this sequence from serial port,
38551 it stops execution and connects to gdb.
38553 Stubs are not required to recognize these interrupt mechanisms and the
38554 precise meaning associated with receipt of the interrupt is
38555 implementation defined. If the target supports debugging of multiple
38556 threads and/or processes, it should attempt to interrupt all
38557 currently-executing threads and processes.
38558 If the stub is successful at interrupting the
38559 running program, it should send one of the stop
38560 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38561 of successfully stopping the program in all-stop mode, and a stop reply
38562 for each stopped thread in non-stop mode.
38563 Interrupts received while the
38564 program is stopped are discarded.
38566 @node Notification Packets
38567 @section Notification Packets
38568 @cindex notification packets
38569 @cindex packets, notification
38571 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38572 packets that require no acknowledgment. Both the GDB and the stub
38573 may send notifications (although the only notifications defined at
38574 present are sent by the stub). Notifications carry information
38575 without incurring the round-trip latency of an acknowledgment, and so
38576 are useful for low-impact communications where occasional packet loss
38579 A notification packet has the form @samp{% @var{data} #
38580 @var{checksum}}, where @var{data} is the content of the notification,
38581 and @var{checksum} is a checksum of @var{data}, computed and formatted
38582 as for ordinary @value{GDBN} packets. A notification's @var{data}
38583 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38584 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38585 to acknowledge the notification's receipt or to report its corruption.
38587 Every notification's @var{data} begins with a name, which contains no
38588 colon characters, followed by a colon character.
38590 Recipients should silently ignore corrupted notifications and
38591 notifications they do not understand. Recipients should restart
38592 timeout periods on receipt of a well-formed notification, whether or
38593 not they understand it.
38595 Senders should only send the notifications described here when this
38596 protocol description specifies that they are permitted. In the
38597 future, we may extend the protocol to permit existing notifications in
38598 new contexts; this rule helps older senders avoid confusing newer
38601 (Older versions of @value{GDBN} ignore bytes received until they see
38602 the @samp{$} byte that begins an ordinary packet, so new stubs may
38603 transmit notifications without fear of confusing older clients. There
38604 are no notifications defined for @value{GDBN} to send at the moment, but we
38605 assume that most older stubs would ignore them, as well.)
38607 Each notification is comprised of three parts:
38609 @item @var{name}:@var{event}
38610 The notification packet is sent by the side that initiates the
38611 exchange (currently, only the stub does that), with @var{event}
38612 carrying the specific information about the notification.
38613 @var{name} is the name of the notification.
38615 The acknowledge sent by the other side, usually @value{GDBN}, to
38616 acknowledge the exchange and request the event.
38619 The purpose of an asynchronous notification mechanism is to report to
38620 @value{GDBN} that something interesting happened in the remote stub.
38622 The remote stub may send notification @var{name}:@var{event}
38623 at any time, but @value{GDBN} acknowledges the notification when
38624 appropriate. The notification event is pending before @value{GDBN}
38625 acknowledges. Only one notification at a time may be pending; if
38626 additional events occur before @value{GDBN} has acknowledged the
38627 previous notification, they must be queued by the stub for later
38628 synchronous transmission in response to @var{ack} packets from
38629 @value{GDBN}. Because the notification mechanism is unreliable,
38630 the stub is permitted to resend a notification if it believes
38631 @value{GDBN} may not have received it.
38633 Specifically, notifications may appear when @value{GDBN} is not
38634 otherwise reading input from the stub, or when @value{GDBN} is
38635 expecting to read a normal synchronous response or a
38636 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38637 Notification packets are distinct from any other communication from
38638 the stub so there is no ambiguity.
38640 After receiving a notification, @value{GDBN} shall acknowledge it by
38641 sending a @var{ack} packet as a regular, synchronous request to the
38642 stub. Such acknowledgment is not required to happen immediately, as
38643 @value{GDBN} is permitted to send other, unrelated packets to the
38644 stub first, which the stub should process normally.
38646 Upon receiving a @var{ack} packet, if the stub has other queued
38647 events to report to @value{GDBN}, it shall respond by sending a
38648 normal @var{event}. @value{GDBN} shall then send another @var{ack}
38649 packet to solicit further responses; again, it is permitted to send
38650 other, unrelated packets as well which the stub should process
38653 If the stub receives a @var{ack} packet and there are no additional
38654 @var{event} to report, the stub shall return an @samp{OK} response.
38655 At this point, @value{GDBN} has finished processing a notification
38656 and the stub has completed sending any queued events. @value{GDBN}
38657 won't accept any new notifications until the final @samp{OK} is
38658 received . If further notification events occur, the stub shall send
38659 a new notification, @value{GDBN} shall accept the notification, and
38660 the process shall be repeated.
38662 The process of asynchronous notification can be illustrated by the
38665 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
38668 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
38670 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
38675 The following notifications are defined:
38676 @multitable @columnfractions 0.12 0.12 0.38 0.38
38685 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
38686 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
38687 for information on how these notifications are acknowledged by
38689 @tab Report an asynchronous stop event in non-stop mode.
38693 @node Remote Non-Stop
38694 @section Remote Protocol Support for Non-Stop Mode
38696 @value{GDBN}'s remote protocol supports non-stop debugging of
38697 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
38698 supports non-stop mode, it should report that to @value{GDBN} by including
38699 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
38701 @value{GDBN} typically sends a @samp{QNonStop} packet only when
38702 establishing a new connection with the stub. Entering non-stop mode
38703 does not alter the state of any currently-running threads, but targets
38704 must stop all threads in any already-attached processes when entering
38705 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
38706 probe the target state after a mode change.
38708 In non-stop mode, when an attached process encounters an event that
38709 would otherwise be reported with a stop reply, it uses the
38710 asynchronous notification mechanism (@pxref{Notification Packets}) to
38711 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38712 in all processes are stopped when a stop reply is sent, in non-stop
38713 mode only the thread reporting the stop event is stopped. That is,
38714 when reporting a @samp{S} or @samp{T} response to indicate completion
38715 of a step operation, hitting a breakpoint, or a fault, only the
38716 affected thread is stopped; any other still-running threads continue
38717 to run. When reporting a @samp{W} or @samp{X} response, all running
38718 threads belonging to other attached processes continue to run.
38720 In non-stop mode, the target shall respond to the @samp{?} packet as
38721 follows. First, any incomplete stop reply notification/@samp{vStopped}
38722 sequence in progress is abandoned. The target must begin a new
38723 sequence reporting stop events for all stopped threads, whether or not
38724 it has previously reported those events to @value{GDBN}. The first
38725 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38726 subsequent stop replies are sent as responses to @samp{vStopped} packets
38727 using the mechanism described above. The target must not send
38728 asynchronous stop reply notifications until the sequence is complete.
38729 If all threads are running when the target receives the @samp{?} packet,
38730 or if the target is not attached to any process, it shall respond
38733 @node Packet Acknowledgment
38734 @section Packet Acknowledgment
38736 @cindex acknowledgment, for @value{GDBN} remote
38737 @cindex packet acknowledgment, for @value{GDBN} remote
38738 By default, when either the host or the target machine receives a packet,
38739 the first response expected is an acknowledgment: either @samp{+} (to indicate
38740 the package was received correctly) or @samp{-} (to request retransmission).
38741 This mechanism allows the @value{GDBN} remote protocol to operate over
38742 unreliable transport mechanisms, such as a serial line.
38744 In cases where the transport mechanism is itself reliable (such as a pipe or
38745 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38746 It may be desirable to disable them in that case to reduce communication
38747 overhead, or for other reasons. This can be accomplished by means of the
38748 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38750 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38751 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38752 and response format still includes the normal checksum, as described in
38753 @ref{Overview}, but the checksum may be ignored by the receiver.
38755 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38756 no-acknowledgment mode, it should report that to @value{GDBN}
38757 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38758 @pxref{qSupported}.
38759 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38760 disabled via the @code{set remote noack-packet off} command
38761 (@pxref{Remote Configuration}),
38762 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38763 Only then may the stub actually turn off packet acknowledgments.
38764 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38765 response, which can be safely ignored by the stub.
38767 Note that @code{set remote noack-packet} command only affects negotiation
38768 between @value{GDBN} and the stub when subsequent connections are made;
38769 it does not affect the protocol acknowledgment state for any current
38771 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38772 new connection is established,
38773 there is also no protocol request to re-enable the acknowledgments
38774 for the current connection, once disabled.
38779 Example sequence of a target being re-started. Notice how the restart
38780 does not get any direct output:
38785 @emph{target restarts}
38788 <- @code{T001:1234123412341234}
38792 Example sequence of a target being stepped by a single instruction:
38795 -> @code{G1445@dots{}}
38800 <- @code{T001:1234123412341234}
38804 <- @code{1455@dots{}}
38808 @node File-I/O Remote Protocol Extension
38809 @section File-I/O Remote Protocol Extension
38810 @cindex File-I/O remote protocol extension
38813 * File-I/O Overview::
38814 * Protocol Basics::
38815 * The F Request Packet::
38816 * The F Reply Packet::
38817 * The Ctrl-C Message::
38819 * List of Supported Calls::
38820 * Protocol-specific Representation of Datatypes::
38822 * File-I/O Examples::
38825 @node File-I/O Overview
38826 @subsection File-I/O Overview
38827 @cindex file-i/o overview
38829 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38830 target to use the host's file system and console I/O to perform various
38831 system calls. System calls on the target system are translated into a
38832 remote protocol packet to the host system, which then performs the needed
38833 actions and returns a response packet to the target system.
38834 This simulates file system operations even on targets that lack file systems.
38836 The protocol is defined to be independent of both the host and target systems.
38837 It uses its own internal representation of datatypes and values. Both
38838 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38839 translating the system-dependent value representations into the internal
38840 protocol representations when data is transmitted.
38842 The communication is synchronous. A system call is possible only when
38843 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38844 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38845 the target is stopped to allow deterministic access to the target's
38846 memory. Therefore File-I/O is not interruptible by target signals. On
38847 the other hand, it is possible to interrupt File-I/O by a user interrupt
38848 (@samp{Ctrl-C}) within @value{GDBN}.
38850 The target's request to perform a host system call does not finish
38851 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38852 after finishing the system call, the target returns to continuing the
38853 previous activity (continue, step). No additional continue or step
38854 request from @value{GDBN} is required.
38857 (@value{GDBP}) continue
38858 <- target requests 'system call X'
38859 target is stopped, @value{GDBN} executes system call
38860 -> @value{GDBN} returns result
38861 ... target continues, @value{GDBN} returns to wait for the target
38862 <- target hits breakpoint and sends a Txx packet
38865 The protocol only supports I/O on the console and to regular files on
38866 the host file system. Character or block special devices, pipes,
38867 named pipes, sockets or any other communication method on the host
38868 system are not supported by this protocol.
38870 File I/O is not supported in non-stop mode.
38872 @node Protocol Basics
38873 @subsection Protocol Basics
38874 @cindex protocol basics, file-i/o
38876 The File-I/O protocol uses the @code{F} packet as the request as well
38877 as reply packet. Since a File-I/O system call can only occur when
38878 @value{GDBN} is waiting for a response from the continuing or stepping target,
38879 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38880 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38881 This @code{F} packet contains all information needed to allow @value{GDBN}
38882 to call the appropriate host system call:
38886 A unique identifier for the requested system call.
38889 All parameters to the system call. Pointers are given as addresses
38890 in the target memory address space. Pointers to strings are given as
38891 pointer/length pair. Numerical values are given as they are.
38892 Numerical control flags are given in a protocol-specific representation.
38896 At this point, @value{GDBN} has to perform the following actions.
38900 If the parameters include pointer values to data needed as input to a
38901 system call, @value{GDBN} requests this data from the target with a
38902 standard @code{m} packet request. This additional communication has to be
38903 expected by the target implementation and is handled as any other @code{m}
38907 @value{GDBN} translates all value from protocol representation to host
38908 representation as needed. Datatypes are coerced into the host types.
38911 @value{GDBN} calls the system call.
38914 It then coerces datatypes back to protocol representation.
38917 If the system call is expected to return data in buffer space specified
38918 by pointer parameters to the call, the data is transmitted to the
38919 target using a @code{M} or @code{X} packet. This packet has to be expected
38920 by the target implementation and is handled as any other @code{M} or @code{X}
38925 Eventually @value{GDBN} replies with another @code{F} packet which contains all
38926 necessary information for the target to continue. This at least contains
38933 @code{errno}, if has been changed by the system call.
38940 After having done the needed type and value coercion, the target continues
38941 the latest continue or step action.
38943 @node The F Request Packet
38944 @subsection The @code{F} Request Packet
38945 @cindex file-i/o request packet
38946 @cindex @code{F} request packet
38948 The @code{F} request packet has the following format:
38951 @item F@var{call-id},@var{parameter@dots{}}
38953 @var{call-id} is the identifier to indicate the host system call to be called.
38954 This is just the name of the function.
38956 @var{parameter@dots{}} are the parameters to the system call.
38957 Parameters are hexadecimal integer values, either the actual values in case
38958 of scalar datatypes, pointers to target buffer space in case of compound
38959 datatypes and unspecified memory areas, or pointer/length pairs in case
38960 of string parameters. These are appended to the @var{call-id} as a
38961 comma-delimited list. All values are transmitted in ASCII
38962 string representation, pointer/length pairs separated by a slash.
38968 @node The F Reply Packet
38969 @subsection The @code{F} Reply Packet
38970 @cindex file-i/o reply packet
38971 @cindex @code{F} reply packet
38973 The @code{F} reply packet has the following format:
38977 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
38979 @var{retcode} is the return code of the system call as hexadecimal value.
38981 @var{errno} is the @code{errno} set by the call, in protocol-specific
38983 This parameter can be omitted if the call was successful.
38985 @var{Ctrl-C flag} is only sent if the user requested a break. In this
38986 case, @var{errno} must be sent as well, even if the call was successful.
38987 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
38994 or, if the call was interrupted before the host call has been performed:
39001 assuming 4 is the protocol-specific representation of @code{EINTR}.
39006 @node The Ctrl-C Message
39007 @subsection The @samp{Ctrl-C} Message
39008 @cindex ctrl-c message, in file-i/o protocol
39010 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39011 reply packet (@pxref{The F Reply Packet}),
39012 the target should behave as if it had
39013 gotten a break message. The meaning for the target is ``system call
39014 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39015 (as with a break message) and return to @value{GDBN} with a @code{T02}
39018 It's important for the target to know in which
39019 state the system call was interrupted. There are two possible cases:
39023 The system call hasn't been performed on the host yet.
39026 The system call on the host has been finished.
39030 These two states can be distinguished by the target by the value of the
39031 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39032 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39033 on POSIX systems. In any other case, the target may presume that the
39034 system call has been finished --- successfully or not --- and should behave
39035 as if the break message arrived right after the system call.
39037 @value{GDBN} must behave reliably. If the system call has not been called
39038 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39039 @code{errno} in the packet. If the system call on the host has been finished
39040 before the user requests a break, the full action must be finished by
39041 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39042 The @code{F} packet may only be sent when either nothing has happened
39043 or the full action has been completed.
39046 @subsection Console I/O
39047 @cindex console i/o as part of file-i/o
39049 By default and if not explicitly closed by the target system, the file
39050 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39051 on the @value{GDBN} console is handled as any other file output operation
39052 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39053 by @value{GDBN} so that after the target read request from file descriptor
39054 0 all following typing is buffered until either one of the following
39059 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39061 system call is treated as finished.
39064 The user presses @key{RET}. This is treated as end of input with a trailing
39068 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39069 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39073 If the user has typed more characters than fit in the buffer given to
39074 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39075 either another @code{read(0, @dots{})} is requested by the target, or debugging
39076 is stopped at the user's request.
39079 @node List of Supported Calls
39080 @subsection List of Supported Calls
39081 @cindex list of supported file-i/o calls
39098 @unnumberedsubsubsec open
39099 @cindex open, file-i/o system call
39104 int open(const char *pathname, int flags);
39105 int open(const char *pathname, int flags, mode_t mode);
39109 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39112 @var{flags} is the bitwise @code{OR} of the following values:
39116 If the file does not exist it will be created. The host
39117 rules apply as far as file ownership and time stamps
39121 When used with @code{O_CREAT}, if the file already exists it is
39122 an error and open() fails.
39125 If the file already exists and the open mode allows
39126 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39127 truncated to zero length.
39130 The file is opened in append mode.
39133 The file is opened for reading only.
39136 The file is opened for writing only.
39139 The file is opened for reading and writing.
39143 Other bits are silently ignored.
39147 @var{mode} is the bitwise @code{OR} of the following values:
39151 User has read permission.
39154 User has write permission.
39157 Group has read permission.
39160 Group has write permission.
39163 Others have read permission.
39166 Others have write permission.
39170 Other bits are silently ignored.
39173 @item Return value:
39174 @code{open} returns the new file descriptor or -1 if an error
39181 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39184 @var{pathname} refers to a directory.
39187 The requested access is not allowed.
39190 @var{pathname} was too long.
39193 A directory component in @var{pathname} does not exist.
39196 @var{pathname} refers to a device, pipe, named pipe or socket.
39199 @var{pathname} refers to a file on a read-only filesystem and
39200 write access was requested.
39203 @var{pathname} is an invalid pointer value.
39206 No space on device to create the file.
39209 The process already has the maximum number of files open.
39212 The limit on the total number of files open on the system
39216 The call was interrupted by the user.
39222 @unnumberedsubsubsec close
39223 @cindex close, file-i/o system call
39232 @samp{Fclose,@var{fd}}
39234 @item Return value:
39235 @code{close} returns zero on success, or -1 if an error occurred.
39241 @var{fd} isn't a valid open file descriptor.
39244 The call was interrupted by the user.
39250 @unnumberedsubsubsec read
39251 @cindex read, file-i/o system call
39256 int read(int fd, void *buf, unsigned int count);
39260 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
39262 @item Return value:
39263 On success, the number of bytes read is returned.
39264 Zero indicates end of file. If count is zero, read
39265 returns zero as well. On error, -1 is returned.
39271 @var{fd} is not a valid file descriptor or is not open for
39275 @var{bufptr} is an invalid pointer value.
39278 The call was interrupted by the user.
39284 @unnumberedsubsubsec write
39285 @cindex write, file-i/o system call
39290 int write(int fd, const void *buf, unsigned int count);
39294 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39296 @item Return value:
39297 On success, the number of bytes written are returned.
39298 Zero indicates nothing was written. On error, -1
39305 @var{fd} is not a valid file descriptor or is not open for
39309 @var{bufptr} is an invalid pointer value.
39312 An attempt was made to write a file that exceeds the
39313 host-specific maximum file size allowed.
39316 No space on device to write the data.
39319 The call was interrupted by the user.
39325 @unnumberedsubsubsec lseek
39326 @cindex lseek, file-i/o system call
39331 long lseek (int fd, long offset, int flag);
39335 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39337 @var{flag} is one of:
39341 The offset is set to @var{offset} bytes.
39344 The offset is set to its current location plus @var{offset}
39348 The offset is set to the size of the file plus @var{offset}
39352 @item Return value:
39353 On success, the resulting unsigned offset in bytes from
39354 the beginning of the file is returned. Otherwise, a
39355 value of -1 is returned.
39361 @var{fd} is not a valid open file descriptor.
39364 @var{fd} is associated with the @value{GDBN} console.
39367 @var{flag} is not a proper value.
39370 The call was interrupted by the user.
39376 @unnumberedsubsubsec rename
39377 @cindex rename, file-i/o system call
39382 int rename(const char *oldpath, const char *newpath);
39386 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39388 @item Return value:
39389 On success, zero is returned. On error, -1 is returned.
39395 @var{newpath} is an existing directory, but @var{oldpath} is not a
39399 @var{newpath} is a non-empty directory.
39402 @var{oldpath} or @var{newpath} is a directory that is in use by some
39406 An attempt was made to make a directory a subdirectory
39410 A component used as a directory in @var{oldpath} or new
39411 path is not a directory. Or @var{oldpath} is a directory
39412 and @var{newpath} exists but is not a directory.
39415 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39418 No access to the file or the path of the file.
39422 @var{oldpath} or @var{newpath} was too long.
39425 A directory component in @var{oldpath} or @var{newpath} does not exist.
39428 The file is on a read-only filesystem.
39431 The device containing the file has no room for the new
39435 The call was interrupted by the user.
39441 @unnumberedsubsubsec unlink
39442 @cindex unlink, file-i/o system call
39447 int unlink(const char *pathname);
39451 @samp{Funlink,@var{pathnameptr}/@var{len}}
39453 @item Return value:
39454 On success, zero is returned. On error, -1 is returned.
39460 No access to the file or the path of the file.
39463 The system does not allow unlinking of directories.
39466 The file @var{pathname} cannot be unlinked because it's
39467 being used by another process.
39470 @var{pathnameptr} is an invalid pointer value.
39473 @var{pathname} was too long.
39476 A directory component in @var{pathname} does not exist.
39479 A component of the path is not a directory.
39482 The file is on a read-only filesystem.
39485 The call was interrupted by the user.
39491 @unnumberedsubsubsec stat/fstat
39492 @cindex fstat, file-i/o system call
39493 @cindex stat, file-i/o system call
39498 int stat(const char *pathname, struct stat *buf);
39499 int fstat(int fd, struct stat *buf);
39503 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39504 @samp{Ffstat,@var{fd},@var{bufptr}}
39506 @item Return value:
39507 On success, zero is returned. On error, -1 is returned.
39513 @var{fd} is not a valid open file.
39516 A directory component in @var{pathname} does not exist or the
39517 path is an empty string.
39520 A component of the path is not a directory.
39523 @var{pathnameptr} is an invalid pointer value.
39526 No access to the file or the path of the file.
39529 @var{pathname} was too long.
39532 The call was interrupted by the user.
39538 @unnumberedsubsubsec gettimeofday
39539 @cindex gettimeofday, file-i/o system call
39544 int gettimeofday(struct timeval *tv, void *tz);
39548 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39550 @item Return value:
39551 On success, 0 is returned, -1 otherwise.
39557 @var{tz} is a non-NULL pointer.
39560 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39566 @unnumberedsubsubsec isatty
39567 @cindex isatty, file-i/o system call
39572 int isatty(int fd);
39576 @samp{Fisatty,@var{fd}}
39578 @item Return value:
39579 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39585 The call was interrupted by the user.
39590 Note that the @code{isatty} call is treated as a special case: it returns
39591 1 to the target if the file descriptor is attached
39592 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39593 would require implementing @code{ioctl} and would be more complex than
39598 @unnumberedsubsubsec system
39599 @cindex system, file-i/o system call
39604 int system(const char *command);
39608 @samp{Fsystem,@var{commandptr}/@var{len}}
39610 @item Return value:
39611 If @var{len} is zero, the return value indicates whether a shell is
39612 available. A zero return value indicates a shell is not available.
39613 For non-zero @var{len}, the value returned is -1 on error and the
39614 return status of the command otherwise. Only the exit status of the
39615 command is returned, which is extracted from the host's @code{system}
39616 return value by calling @code{WEXITSTATUS(retval)}. In case
39617 @file{/bin/sh} could not be executed, 127 is returned.
39623 The call was interrupted by the user.
39628 @value{GDBN} takes over the full task of calling the necessary host calls
39629 to perform the @code{system} call. The return value of @code{system} on
39630 the host is simplified before it's returned
39631 to the target. Any termination signal information from the child process
39632 is discarded, and the return value consists
39633 entirely of the exit status of the called command.
39635 Due to security concerns, the @code{system} call is by default refused
39636 by @value{GDBN}. The user has to allow this call explicitly with the
39637 @code{set remote system-call-allowed 1} command.
39640 @item set remote system-call-allowed
39641 @kindex set remote system-call-allowed
39642 Control whether to allow the @code{system} calls in the File I/O
39643 protocol for the remote target. The default is zero (disabled).
39645 @item show remote system-call-allowed
39646 @kindex show remote system-call-allowed
39647 Show whether the @code{system} calls are allowed in the File I/O
39651 @node Protocol-specific Representation of Datatypes
39652 @subsection Protocol-specific Representation of Datatypes
39653 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39656 * Integral Datatypes::
39658 * Memory Transfer::
39663 @node Integral Datatypes
39664 @unnumberedsubsubsec Integral Datatypes
39665 @cindex integral datatypes, in file-i/o protocol
39667 The integral datatypes used in the system calls are @code{int},
39668 @code{unsigned int}, @code{long}, @code{unsigned long},
39669 @code{mode_t}, and @code{time_t}.
39671 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
39672 implemented as 32 bit values in this protocol.
39674 @code{long} and @code{unsigned long} are implemented as 64 bit types.
39676 @xref{Limits}, for corresponding MIN and MAX values (similar to those
39677 in @file{limits.h}) to allow range checking on host and target.
39679 @code{time_t} datatypes are defined as seconds since the Epoch.
39681 All integral datatypes transferred as part of a memory read or write of a
39682 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
39685 @node Pointer Values
39686 @unnumberedsubsubsec Pointer Values
39687 @cindex pointer values, in file-i/o protocol
39689 Pointers to target data are transmitted as they are. An exception
39690 is made for pointers to buffers for which the length isn't
39691 transmitted as part of the function call, namely strings. Strings
39692 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39699 which is a pointer to data of length 18 bytes at position 0x1aaf.
39700 The length is defined as the full string length in bytes, including
39701 the trailing null byte. For example, the string @code{"hello world"}
39702 at address 0x123456 is transmitted as
39708 @node Memory Transfer
39709 @unnumberedsubsubsec Memory Transfer
39710 @cindex memory transfer, in file-i/o protocol
39712 Structured data which is transferred using a memory read or write (for
39713 example, a @code{struct stat}) is expected to be in a protocol-specific format
39714 with all scalar multibyte datatypes being big endian. Translation to
39715 this representation needs to be done both by the target before the @code{F}
39716 packet is sent, and by @value{GDBN} before
39717 it transfers memory to the target. Transferred pointers to structured
39718 data should point to the already-coerced data at any time.
39722 @unnumberedsubsubsec struct stat
39723 @cindex struct stat, in file-i/o protocol
39725 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39726 is defined as follows:
39730 unsigned int st_dev; /* device */
39731 unsigned int st_ino; /* inode */
39732 mode_t st_mode; /* protection */
39733 unsigned int st_nlink; /* number of hard links */
39734 unsigned int st_uid; /* user ID of owner */
39735 unsigned int st_gid; /* group ID of owner */
39736 unsigned int st_rdev; /* device type (if inode device) */
39737 unsigned long st_size; /* total size, in bytes */
39738 unsigned long st_blksize; /* blocksize for filesystem I/O */
39739 unsigned long st_blocks; /* number of blocks allocated */
39740 time_t st_atime; /* time of last access */
39741 time_t st_mtime; /* time of last modification */
39742 time_t st_ctime; /* time of last change */
39746 The integral datatypes conform to the definitions given in the
39747 appropriate section (see @ref{Integral Datatypes}, for details) so this
39748 structure is of size 64 bytes.
39750 The values of several fields have a restricted meaning and/or
39756 A value of 0 represents a file, 1 the console.
39759 No valid meaning for the target. Transmitted unchanged.
39762 Valid mode bits are described in @ref{Constants}. Any other
39763 bits have currently no meaning for the target.
39768 No valid meaning for the target. Transmitted unchanged.
39773 These values have a host and file system dependent
39774 accuracy. Especially on Windows hosts, the file system may not
39775 support exact timing values.
39778 The target gets a @code{struct stat} of the above representation and is
39779 responsible for coercing it to the target representation before
39782 Note that due to size differences between the host, target, and protocol
39783 representations of @code{struct stat} members, these members could eventually
39784 get truncated on the target.
39786 @node struct timeval
39787 @unnumberedsubsubsec struct timeval
39788 @cindex struct timeval, in file-i/o protocol
39790 The buffer of type @code{struct timeval} used by the File-I/O protocol
39791 is defined as follows:
39795 time_t tv_sec; /* second */
39796 long tv_usec; /* microsecond */
39800 The integral datatypes conform to the definitions given in the
39801 appropriate section (see @ref{Integral Datatypes}, for details) so this
39802 structure is of size 8 bytes.
39805 @subsection Constants
39806 @cindex constants, in file-i/o protocol
39808 The following values are used for the constants inside of the
39809 protocol. @value{GDBN} and target are responsible for translating these
39810 values before and after the call as needed.
39821 @unnumberedsubsubsec Open Flags
39822 @cindex open flags, in file-i/o protocol
39824 All values are given in hexadecimal representation.
39836 @node mode_t Values
39837 @unnumberedsubsubsec mode_t Values
39838 @cindex mode_t values, in file-i/o protocol
39840 All values are given in octal representation.
39857 @unnumberedsubsubsec Errno Values
39858 @cindex errno values, in file-i/o protocol
39860 All values are given in decimal representation.
39885 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39886 any error value not in the list of supported error numbers.
39889 @unnumberedsubsubsec Lseek Flags
39890 @cindex lseek flags, in file-i/o protocol
39899 @unnumberedsubsubsec Limits
39900 @cindex limits, in file-i/o protocol
39902 All values are given in decimal representation.
39905 INT_MIN -2147483648
39907 UINT_MAX 4294967295
39908 LONG_MIN -9223372036854775808
39909 LONG_MAX 9223372036854775807
39910 ULONG_MAX 18446744073709551615
39913 @node File-I/O Examples
39914 @subsection File-I/O Examples
39915 @cindex file-i/o examples
39917 Example sequence of a write call, file descriptor 3, buffer is at target
39918 address 0x1234, 6 bytes should be written:
39921 <- @code{Fwrite,3,1234,6}
39922 @emph{request memory read from target}
39925 @emph{return "6 bytes written"}
39929 Example sequence of a read call, file descriptor 3, buffer is at target
39930 address 0x1234, 6 bytes should be read:
39933 <- @code{Fread,3,1234,6}
39934 @emph{request memory write to target}
39935 -> @code{X1234,6:XXXXXX}
39936 @emph{return "6 bytes read"}
39940 Example sequence of a read call, call fails on the host due to invalid
39941 file descriptor (@code{EBADF}):
39944 <- @code{Fread,3,1234,6}
39948 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
39952 <- @code{Fread,3,1234,6}
39957 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
39961 <- @code{Fread,3,1234,6}
39962 -> @code{X1234,6:XXXXXX}
39966 @node Library List Format
39967 @section Library List Format
39968 @cindex library list format, remote protocol
39970 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
39971 same process as your application to manage libraries. In this case,
39972 @value{GDBN} can use the loader's symbol table and normal memory
39973 operations to maintain a list of shared libraries. On other
39974 platforms, the operating system manages loaded libraries.
39975 @value{GDBN} can not retrieve the list of currently loaded libraries
39976 through memory operations, so it uses the @samp{qXfer:libraries:read}
39977 packet (@pxref{qXfer library list read}) instead. The remote stub
39978 queries the target's operating system and reports which libraries
39981 The @samp{qXfer:libraries:read} packet returns an XML document which
39982 lists loaded libraries and their offsets. Each library has an
39983 associated name and one or more segment or section base addresses,
39984 which report where the library was loaded in memory.
39986 For the common case of libraries that are fully linked binaries, the
39987 library should have a list of segments. If the target supports
39988 dynamic linking of a relocatable object file, its library XML element
39989 should instead include a list of allocated sections. The segment or
39990 section bases are start addresses, not relocation offsets; they do not
39991 depend on the library's link-time base addresses.
39993 @value{GDBN} must be linked with the Expat library to support XML
39994 library lists. @xref{Expat}.
39996 A simple memory map, with one loaded library relocated by a single
39997 offset, looks like this:
40001 <library name="/lib/libc.so.6">
40002 <segment address="0x10000000"/>
40007 Another simple memory map, with one loaded library with three
40008 allocated sections (.text, .data, .bss), looks like this:
40012 <library name="sharedlib.o">
40013 <section address="0x10000000"/>
40014 <section address="0x20000000"/>
40015 <section address="0x30000000"/>
40020 The format of a library list is described by this DTD:
40023 <!-- library-list: Root element with versioning -->
40024 <!ELEMENT library-list (library)*>
40025 <!ATTLIST library-list version CDATA #FIXED "1.0">
40026 <!ELEMENT library (segment*, section*)>
40027 <!ATTLIST library name CDATA #REQUIRED>
40028 <!ELEMENT segment EMPTY>
40029 <!ATTLIST segment address CDATA #REQUIRED>
40030 <!ELEMENT section EMPTY>
40031 <!ATTLIST section address CDATA #REQUIRED>
40034 In addition, segments and section descriptors cannot be mixed within a
40035 single library element, and you must supply at least one segment or
40036 section for each library.
40038 @node Library List Format for SVR4 Targets
40039 @section Library List Format for SVR4 Targets
40040 @cindex library list format, remote protocol
40042 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40043 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40044 shared libraries. Still a special library list provided by this packet is
40045 more efficient for the @value{GDBN} remote protocol.
40047 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40048 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40049 target, the following parameters are reported:
40053 @code{name}, the absolute file name from the @code{l_name} field of
40054 @code{struct link_map}.
40056 @code{lm} with address of @code{struct link_map} used for TLS
40057 (Thread Local Storage) access.
40059 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40060 @code{struct link_map}. For prelinked libraries this is not an absolute
40061 memory address. It is a displacement of absolute memory address against
40062 address the file was prelinked to during the library load.
40064 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40067 Additionally the single @code{main-lm} attribute specifies address of
40068 @code{struct link_map} used for the main executable. This parameter is used
40069 for TLS access and its presence is optional.
40071 @value{GDBN} must be linked with the Expat library to support XML
40072 SVR4 library lists. @xref{Expat}.
40074 A simple memory map, with two loaded libraries (which do not use prelink),
40078 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40079 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40081 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40083 </library-list-svr>
40086 The format of an SVR4 library list is described by this DTD:
40089 <!-- library-list-svr4: Root element with versioning -->
40090 <!ELEMENT library-list-svr4 (library)*>
40091 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40092 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40093 <!ELEMENT library EMPTY>
40094 <!ATTLIST library name CDATA #REQUIRED>
40095 <!ATTLIST library lm CDATA #REQUIRED>
40096 <!ATTLIST library l_addr CDATA #REQUIRED>
40097 <!ATTLIST library l_ld CDATA #REQUIRED>
40100 @node Memory Map Format
40101 @section Memory Map Format
40102 @cindex memory map format
40104 To be able to write into flash memory, @value{GDBN} needs to obtain a
40105 memory map from the target. This section describes the format of the
40108 The memory map is obtained using the @samp{qXfer:memory-map:read}
40109 (@pxref{qXfer memory map read}) packet and is an XML document that
40110 lists memory regions.
40112 @value{GDBN} must be linked with the Expat library to support XML
40113 memory maps. @xref{Expat}.
40115 The top-level structure of the document is shown below:
40118 <?xml version="1.0"?>
40119 <!DOCTYPE memory-map
40120 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40121 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40127 Each region can be either:
40132 A region of RAM starting at @var{addr} and extending for @var{length}
40136 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40141 A region of read-only memory:
40144 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40149 A region of flash memory, with erasure blocks @var{blocksize}
40153 <memory type="flash" start="@var{addr}" length="@var{length}">
40154 <property name="blocksize">@var{blocksize}</property>
40160 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40161 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40162 packets to write to addresses in such ranges.
40164 The formal DTD for memory map format is given below:
40167 <!-- ................................................... -->
40168 <!-- Memory Map XML DTD ................................ -->
40169 <!-- File: memory-map.dtd .............................. -->
40170 <!-- .................................... .............. -->
40171 <!-- memory-map.dtd -->
40172 <!-- memory-map: Root element with versioning -->
40173 <!ELEMENT memory-map (memory | property)>
40174 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40175 <!ELEMENT memory (property)>
40176 <!-- memory: Specifies a memory region,
40177 and its type, or device. -->
40178 <!ATTLIST memory type CDATA #REQUIRED
40179 start CDATA #REQUIRED
40180 length CDATA #REQUIRED
40181 device CDATA #IMPLIED>
40182 <!-- property: Generic attribute tag -->
40183 <!ELEMENT property (#PCDATA | property)*>
40184 <!ATTLIST property name CDATA #REQUIRED>
40187 @node Thread List Format
40188 @section Thread List Format
40189 @cindex thread list format
40191 To efficiently update the list of threads and their attributes,
40192 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40193 (@pxref{qXfer threads read}) and obtains the XML document with
40194 the following structure:
40197 <?xml version="1.0"?>
40199 <thread id="id" core="0">
40200 ... description ...
40205 Each @samp{thread} element must have the @samp{id} attribute that
40206 identifies the thread (@pxref{thread-id syntax}). The
40207 @samp{core} attribute, if present, specifies which processor core
40208 the thread was last executing on. The content of the of @samp{thread}
40209 element is interpreted as human-readable auxilliary information.
40211 @node Traceframe Info Format
40212 @section Traceframe Info Format
40213 @cindex traceframe info format
40215 To be able to know which objects in the inferior can be examined when
40216 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
40217 memory ranges, registers and trace state variables that have been
40218 collected in a traceframe.
40220 This list is obtained using the @samp{qXfer:traceframe-info:read}
40221 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40223 @value{GDBN} must be linked with the Expat library to support XML
40224 traceframe info discovery. @xref{Expat}.
40226 The top-level structure of the document is shown below:
40229 <?xml version="1.0"?>
40230 <!DOCTYPE traceframe-info
40231 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40232 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
40238 Each traceframe block can be either:
40243 A region of collected memory starting at @var{addr} and extending for
40244 @var{length} bytes from there:
40247 <memory start="@var{addr}" length="@var{length}"/>
40252 The formal DTD for the traceframe info format is given below:
40255 <!ELEMENT traceframe-info (memory)* >
40256 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
40258 <!ELEMENT memory EMPTY>
40259 <!ATTLIST memory start CDATA #REQUIRED
40260 length CDATA #REQUIRED>
40263 @include agentexpr.texi
40265 @node Target Descriptions
40266 @appendix Target Descriptions
40267 @cindex target descriptions
40269 One of the challenges of using @value{GDBN} to debug embedded systems
40270 is that there are so many minor variants of each processor
40271 architecture in use. It is common practice for vendors to start with
40272 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40273 and then make changes to adapt it to a particular market niche. Some
40274 architectures have hundreds of variants, available from dozens of
40275 vendors. This leads to a number of problems:
40279 With so many different customized processors, it is difficult for
40280 the @value{GDBN} maintainers to keep up with the changes.
40282 Since individual variants may have short lifetimes or limited
40283 audiences, it may not be worthwhile to carry information about every
40284 variant in the @value{GDBN} source tree.
40286 When @value{GDBN} does support the architecture of the embedded system
40287 at hand, the task of finding the correct architecture name to give the
40288 @command{set architecture} command can be error-prone.
40291 To address these problems, the @value{GDBN} remote protocol allows a
40292 target system to not only identify itself to @value{GDBN}, but to
40293 actually describe its own features. This lets @value{GDBN} support
40294 processor variants it has never seen before --- to the extent that the
40295 descriptions are accurate, and that @value{GDBN} understands them.
40297 @value{GDBN} must be linked with the Expat library to support XML
40298 target descriptions. @xref{Expat}.
40301 * Retrieving Descriptions:: How descriptions are fetched from a target.
40302 * Target Description Format:: The contents of a target description.
40303 * Predefined Target Types:: Standard types available for target
40305 * Standard Target Features:: Features @value{GDBN} knows about.
40308 @node Retrieving Descriptions
40309 @section Retrieving Descriptions
40311 Target descriptions can be read from the target automatically, or
40312 specified by the user manually. The default behavior is to read the
40313 description from the target. @value{GDBN} retrieves it via the remote
40314 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40315 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40316 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40317 XML document, of the form described in @ref{Target Description
40320 Alternatively, you can specify a file to read for the target description.
40321 If a file is set, the target will not be queried. The commands to
40322 specify a file are:
40325 @cindex set tdesc filename
40326 @item set tdesc filename @var{path}
40327 Read the target description from @var{path}.
40329 @cindex unset tdesc filename
40330 @item unset tdesc filename
40331 Do not read the XML target description from a file. @value{GDBN}
40332 will use the description supplied by the current target.
40334 @cindex show tdesc filename
40335 @item show tdesc filename
40336 Show the filename to read for a target description, if any.
40340 @node Target Description Format
40341 @section Target Description Format
40342 @cindex target descriptions, XML format
40344 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40345 document which complies with the Document Type Definition provided in
40346 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40347 means you can use generally available tools like @command{xmllint} to
40348 check that your feature descriptions are well-formed and valid.
40349 However, to help people unfamiliar with XML write descriptions for
40350 their targets, we also describe the grammar here.
40352 Target descriptions can identify the architecture of the remote target
40353 and (for some architectures) provide information about custom register
40354 sets. They can also identify the OS ABI of the remote target.
40355 @value{GDBN} can use this information to autoconfigure for your
40356 target, or to warn you if you connect to an unsupported target.
40358 Here is a simple target description:
40361 <target version="1.0">
40362 <architecture>i386:x86-64</architecture>
40367 This minimal description only says that the target uses
40368 the x86-64 architecture.
40370 A target description has the following overall form, with [ ] marking
40371 optional elements and @dots{} marking repeatable elements. The elements
40372 are explained further below.
40375 <?xml version="1.0"?>
40376 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40377 <target version="1.0">
40378 @r{[}@var{architecture}@r{]}
40379 @r{[}@var{osabi}@r{]}
40380 @r{[}@var{compatible}@r{]}
40381 @r{[}@var{feature}@dots{}@r{]}
40386 The description is generally insensitive to whitespace and line
40387 breaks, under the usual common-sense rules. The XML version
40388 declaration and document type declaration can generally be omitted
40389 (@value{GDBN} does not require them), but specifying them may be
40390 useful for XML validation tools. The @samp{version} attribute for
40391 @samp{<target>} may also be omitted, but we recommend
40392 including it; if future versions of @value{GDBN} use an incompatible
40393 revision of @file{gdb-target.dtd}, they will detect and report
40394 the version mismatch.
40396 @subsection Inclusion
40397 @cindex target descriptions, inclusion
40400 @cindex <xi:include>
40403 It can sometimes be valuable to split a target description up into
40404 several different annexes, either for organizational purposes, or to
40405 share files between different possible target descriptions. You can
40406 divide a description into multiple files by replacing any element of
40407 the target description with an inclusion directive of the form:
40410 <xi:include href="@var{document}"/>
40414 When @value{GDBN} encounters an element of this form, it will retrieve
40415 the named XML @var{document}, and replace the inclusion directive with
40416 the contents of that document. If the current description was read
40417 using @samp{qXfer}, then so will be the included document;
40418 @var{document} will be interpreted as the name of an annex. If the
40419 current description was read from a file, @value{GDBN} will look for
40420 @var{document} as a file in the same directory where it found the
40421 original description.
40423 @subsection Architecture
40424 @cindex <architecture>
40426 An @samp{<architecture>} element has this form:
40429 <architecture>@var{arch}</architecture>
40432 @var{arch} is one of the architectures from the set accepted by
40433 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40436 @cindex @code{<osabi>}
40438 This optional field was introduced in @value{GDBN} version 7.0.
40439 Previous versions of @value{GDBN} ignore it.
40441 An @samp{<osabi>} element has this form:
40444 <osabi>@var{abi-name}</osabi>
40447 @var{abi-name} is an OS ABI name from the same selection accepted by
40448 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40450 @subsection Compatible Architecture
40451 @cindex @code{<compatible>}
40453 This optional field was introduced in @value{GDBN} version 7.0.
40454 Previous versions of @value{GDBN} ignore it.
40456 A @samp{<compatible>} element has this form:
40459 <compatible>@var{arch}</compatible>
40462 @var{arch} is one of the architectures from the set accepted by
40463 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40465 A @samp{<compatible>} element is used to specify that the target
40466 is able to run binaries in some other than the main target architecture
40467 given by the @samp{<architecture>} element. For example, on the
40468 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40469 or @code{powerpc:common64}, but the system is able to run binaries
40470 in the @code{spu} architecture as well. The way to describe this
40471 capability with @samp{<compatible>} is as follows:
40474 <architecture>powerpc:common</architecture>
40475 <compatible>spu</compatible>
40478 @subsection Features
40481 Each @samp{<feature>} describes some logical portion of the target
40482 system. Features are currently used to describe available CPU
40483 registers and the types of their contents. A @samp{<feature>} element
40487 <feature name="@var{name}">
40488 @r{[}@var{type}@dots{}@r{]}
40494 Each feature's name should be unique within the description. The name
40495 of a feature does not matter unless @value{GDBN} has some special
40496 knowledge of the contents of that feature; if it does, the feature
40497 should have its standard name. @xref{Standard Target Features}.
40501 Any register's value is a collection of bits which @value{GDBN} must
40502 interpret. The default interpretation is a two's complement integer,
40503 but other types can be requested by name in the register description.
40504 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40505 Target Types}), and the description can define additional composite types.
40507 Each type element must have an @samp{id} attribute, which gives
40508 a unique (within the containing @samp{<feature>}) name to the type.
40509 Types must be defined before they are used.
40512 Some targets offer vector registers, which can be treated as arrays
40513 of scalar elements. These types are written as @samp{<vector>} elements,
40514 specifying the array element type, @var{type}, and the number of elements,
40518 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40522 If a register's value is usefully viewed in multiple ways, define it
40523 with a union type containing the useful representations. The
40524 @samp{<union>} element contains one or more @samp{<field>} elements,
40525 each of which has a @var{name} and a @var{type}:
40528 <union id="@var{id}">
40529 <field name="@var{name}" type="@var{type}"/>
40535 If a register's value is composed from several separate values, define
40536 it with a structure type. There are two forms of the @samp{<struct>}
40537 element; a @samp{<struct>} element must either contain only bitfields
40538 or contain no bitfields. If the structure contains only bitfields,
40539 its total size in bytes must be specified, each bitfield must have an
40540 explicit start and end, and bitfields are automatically assigned an
40541 integer type. The field's @var{start} should be less than or
40542 equal to its @var{end}, and zero represents the least significant bit.
40545 <struct id="@var{id}" size="@var{size}">
40546 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40551 If the structure contains no bitfields, then each field has an
40552 explicit type, and no implicit padding is added.
40555 <struct id="@var{id}">
40556 <field name="@var{name}" type="@var{type}"/>
40562 If a register's value is a series of single-bit flags, define it with
40563 a flags type. The @samp{<flags>} element has an explicit @var{size}
40564 and contains one or more @samp{<field>} elements. Each field has a
40565 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
40569 <flags id="@var{id}" size="@var{size}">
40570 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40575 @subsection Registers
40578 Each register is represented as an element with this form:
40581 <reg name="@var{name}"
40582 bitsize="@var{size}"
40583 @r{[}regnum="@var{num}"@r{]}
40584 @r{[}save-restore="@var{save-restore}"@r{]}
40585 @r{[}type="@var{type}"@r{]}
40586 @r{[}group="@var{group}"@r{]}/>
40590 The components are as follows:
40595 The register's name; it must be unique within the target description.
40598 The register's size, in bits.
40601 The register's number. If omitted, a register's number is one greater
40602 than that of the previous register (either in the current feature or in
40603 a preceding feature); the first register in the target description
40604 defaults to zero. This register number is used to read or write
40605 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40606 packets, and registers appear in the @code{g} and @code{G} packets
40607 in order of increasing register number.
40610 Whether the register should be preserved across inferior function
40611 calls; this must be either @code{yes} or @code{no}. The default is
40612 @code{yes}, which is appropriate for most registers except for
40613 some system control registers; this is not related to the target's
40617 The type of the register. @var{type} may be a predefined type, a type
40618 defined in the current feature, or one of the special types @code{int}
40619 and @code{float}. @code{int} is an integer type of the correct size
40620 for @var{bitsize}, and @code{float} is a floating point type (in the
40621 architecture's normal floating point format) of the correct size for
40622 @var{bitsize}. The default is @code{int}.
40625 The register group to which this register belongs. @var{group} must
40626 be either @code{general}, @code{float}, or @code{vector}. If no
40627 @var{group} is specified, @value{GDBN} will not display the register
40628 in @code{info registers}.
40632 @node Predefined Target Types
40633 @section Predefined Target Types
40634 @cindex target descriptions, predefined types
40636 Type definitions in the self-description can build up composite types
40637 from basic building blocks, but can not define fundamental types. Instead,
40638 standard identifiers are provided by @value{GDBN} for the fundamental
40639 types. The currently supported types are:
40648 Signed integer types holding the specified number of bits.
40655 Unsigned integer types holding the specified number of bits.
40659 Pointers to unspecified code and data. The program counter and
40660 any dedicated return address register may be marked as code
40661 pointers; printing a code pointer converts it into a symbolic
40662 address. The stack pointer and any dedicated address registers
40663 may be marked as data pointers.
40666 Single precision IEEE floating point.
40669 Double precision IEEE floating point.
40672 The 12-byte extended precision format used by ARM FPA registers.
40675 The 10-byte extended precision format used by x87 registers.
40678 32bit @sc{eflags} register used by x86.
40681 32bit @sc{mxcsr} register used by x86.
40685 @node Standard Target Features
40686 @section Standard Target Features
40687 @cindex target descriptions, standard features
40689 A target description must contain either no registers or all the
40690 target's registers. If the description contains no registers, then
40691 @value{GDBN} will assume a default register layout, selected based on
40692 the architecture. If the description contains any registers, the
40693 default layout will not be used; the standard registers must be
40694 described in the target description, in such a way that @value{GDBN}
40695 can recognize them.
40697 This is accomplished by giving specific names to feature elements
40698 which contain standard registers. @value{GDBN} will look for features
40699 with those names and verify that they contain the expected registers;
40700 if any known feature is missing required registers, or if any required
40701 feature is missing, @value{GDBN} will reject the target
40702 description. You can add additional registers to any of the
40703 standard features --- @value{GDBN} will display them just as if
40704 they were added to an unrecognized feature.
40706 This section lists the known features and their expected contents.
40707 Sample XML documents for these features are included in the
40708 @value{GDBN} source tree, in the directory @file{gdb/features}.
40710 Names recognized by @value{GDBN} should include the name of the
40711 company or organization which selected the name, and the overall
40712 architecture to which the feature applies; so e.g.@: the feature
40713 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
40715 The names of registers are not case sensitive for the purpose
40716 of recognizing standard features, but @value{GDBN} will only display
40717 registers using the capitalization used in the description.
40724 * PowerPC Features::
40730 @subsection ARM Features
40731 @cindex target descriptions, ARM features
40733 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
40735 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
40736 @samp{lr}, @samp{pc}, and @samp{cpsr}.
40738 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
40739 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
40740 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
40743 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
40744 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
40746 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
40747 it should contain at least registers @samp{wR0} through @samp{wR15} and
40748 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
40749 @samp{wCSSF}, and @samp{wCASF} registers are optional.
40751 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
40752 should contain at least registers @samp{d0} through @samp{d15}. If
40753 they are present, @samp{d16} through @samp{d31} should also be included.
40754 @value{GDBN} will synthesize the single-precision registers from
40755 halves of the double-precision registers.
40757 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
40758 need to contain registers; it instructs @value{GDBN} to display the
40759 VFP double-precision registers as vectors and to synthesize the
40760 quad-precision registers from pairs of double-precision registers.
40761 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
40762 be present and include 32 double-precision registers.
40764 @node i386 Features
40765 @subsection i386 Features
40766 @cindex target descriptions, i386 features
40768 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
40769 targets. It should describe the following registers:
40773 @samp{eax} through @samp{edi} plus @samp{eip} for i386
40775 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
40777 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
40778 @samp{fs}, @samp{gs}
40780 @samp{st0} through @samp{st7}
40782 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
40783 @samp{foseg}, @samp{fooff} and @samp{fop}
40786 The register sets may be different, depending on the target.
40788 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
40789 describe registers:
40793 @samp{xmm0} through @samp{xmm7} for i386
40795 @samp{xmm0} through @samp{xmm15} for amd64
40800 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
40801 @samp{org.gnu.gdb.i386.sse} feature. It should
40802 describe the upper 128 bits of @sc{ymm} registers:
40806 @samp{ymm0h} through @samp{ymm7h} for i386
40808 @samp{ymm0h} through @samp{ymm15h} for amd64
40811 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
40812 describe a single register, @samp{orig_eax}.
40814 @node MIPS Features
40815 @subsection @acronym{MIPS} Features
40816 @cindex target descriptions, @acronym{MIPS} features
40818 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
40819 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
40820 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
40823 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
40824 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
40825 registers. They may be 32-bit or 64-bit depending on the target.
40827 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
40828 it may be optional in a future version of @value{GDBN}. It should
40829 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
40830 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
40832 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
40833 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
40834 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
40835 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
40837 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
40838 contain a single register, @samp{restart}, which is used by the
40839 Linux kernel to control restartable syscalls.
40841 @node M68K Features
40842 @subsection M68K Features
40843 @cindex target descriptions, M68K features
40846 @item @samp{org.gnu.gdb.m68k.core}
40847 @itemx @samp{org.gnu.gdb.coldfire.core}
40848 @itemx @samp{org.gnu.gdb.fido.core}
40849 One of those features must be always present.
40850 The feature that is present determines which flavor of m68k is
40851 used. The feature that is present should contain registers
40852 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
40853 @samp{sp}, @samp{ps} and @samp{pc}.
40855 @item @samp{org.gnu.gdb.coldfire.fp}
40856 This feature is optional. If present, it should contain registers
40857 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
40861 @node PowerPC Features
40862 @subsection PowerPC Features
40863 @cindex target descriptions, PowerPC features
40865 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
40866 targets. It should contain registers @samp{r0} through @samp{r31},
40867 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
40868 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
40870 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
40871 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
40873 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
40874 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
40877 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
40878 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
40879 will combine these registers with the floating point registers
40880 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
40881 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
40882 through @samp{vs63}, the set of vector registers for POWER7.
40884 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
40885 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
40886 @samp{spefscr}. SPE targets should provide 32-bit registers in
40887 @samp{org.gnu.gdb.power.core} and provide the upper halves in
40888 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
40889 these to present registers @samp{ev0} through @samp{ev31} to the
40892 @node TIC6x Features
40893 @subsection TMS320C6x Features
40894 @cindex target descriptions, TIC6x features
40895 @cindex target descriptions, TMS320C6x features
40896 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
40897 targets. It should contain registers @samp{A0} through @samp{A15},
40898 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
40900 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
40901 contain registers @samp{A16} through @samp{A31} and @samp{B16}
40902 through @samp{B31}.
40904 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
40905 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
40907 @node Operating System Information
40908 @appendix Operating System Information
40909 @cindex operating system information
40915 Users of @value{GDBN} often wish to obtain information about the state of
40916 the operating system running on the target---for example the list of
40917 processes, or the list of open files. This section describes the
40918 mechanism that makes it possible. This mechanism is similar to the
40919 target features mechanism (@pxref{Target Descriptions}), but focuses
40920 on a different aspect of target.
40922 Operating system information is retrived from the target via the
40923 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
40924 read}). The object name in the request should be @samp{osdata}, and
40925 the @var{annex} identifies the data to be fetched.
40928 @appendixsection Process list
40929 @cindex operating system information, process list
40931 When requesting the process list, the @var{annex} field in the
40932 @samp{qXfer} request should be @samp{processes}. The returned data is
40933 an XML document. The formal syntax of this document is defined in
40934 @file{gdb/features/osdata.dtd}.
40936 An example document is:
40939 <?xml version="1.0"?>
40940 <!DOCTYPE target SYSTEM "osdata.dtd">
40941 <osdata type="processes">
40943 <column name="pid">1</column>
40944 <column name="user">root</column>
40945 <column name="command">/sbin/init</column>
40946 <column name="cores">1,2,3</column>
40951 Each item should include a column whose name is @samp{pid}. The value
40952 of that column should identify the process on the target. The
40953 @samp{user} and @samp{command} columns are optional, and will be
40954 displayed by @value{GDBN}. The @samp{cores} column, if present,
40955 should contain a comma-separated list of cores that this process
40956 is running on. Target may provide additional columns,
40957 which @value{GDBN} currently ignores.
40959 @node Trace File Format
40960 @appendix Trace File Format
40961 @cindex trace file format
40963 The trace file comes in three parts: a header, a textual description
40964 section, and a trace frame section with binary data.
40966 The header has the form @code{\x7fTRACE0\n}. The first byte is
40967 @code{0x7f} so as to indicate that the file contains binary data,
40968 while the @code{0} is a version number that may have different values
40971 The description section consists of multiple lines of @sc{ascii} text
40972 separated by newline characters (@code{0xa}). The lines may include a
40973 variety of optional descriptive or context-setting information, such
40974 as tracepoint definitions or register set size. @value{GDBN} will
40975 ignore any line that it does not recognize. An empty line marks the end
40978 @c FIXME add some specific types of data
40980 The trace frame section consists of a number of consecutive frames.
40981 Each frame begins with a two-byte tracepoint number, followed by a
40982 four-byte size giving the amount of data in the frame. The data in
40983 the frame consists of a number of blocks, each introduced by a
40984 character indicating its type (at least register, memory, and trace
40985 state variable). The data in this section is raw binary, not a
40986 hexadecimal or other encoding; its endianness matches the target's
40989 @c FIXME bi-arch may require endianness/arch info in description section
40992 @item R @var{bytes}
40993 Register block. The number and ordering of bytes matches that of a
40994 @code{g} packet in the remote protocol. Note that these are the
40995 actual bytes, in target order and @value{GDBN} register order, not a
40996 hexadecimal encoding.
40998 @item M @var{address} @var{length} @var{bytes}...
40999 Memory block. This is a contiguous block of memory, at the 8-byte
41000 address @var{address}, with a 2-byte length @var{length}, followed by
41001 @var{length} bytes.
41003 @item V @var{number} @var{value}
41004 Trace state variable block. This records the 8-byte signed value
41005 @var{value} of trace state variable numbered @var{number}.
41009 Future enhancements of the trace file format may include additional types
41012 @node Index Section Format
41013 @appendix @code{.gdb_index} section format
41014 @cindex .gdb_index section format
41015 @cindex index section format
41017 This section documents the index section that is created by @code{save
41018 gdb-index} (@pxref{Index Files}). The index section is
41019 DWARF-specific; some knowledge of DWARF is assumed in this
41022 The mapped index file format is designed to be directly
41023 @code{mmap}able on any architecture. In most cases, a datum is
41024 represented using a little-endian 32-bit integer value, called an
41025 @code{offset_type}. Big endian machines must byte-swap the values
41026 before using them. Exceptions to this rule are noted. The data is
41027 laid out such that alignment is always respected.
41029 A mapped index consists of several areas, laid out in order.
41033 The file header. This is a sequence of values, of @code{offset_type}
41034 unless otherwise noted:
41038 The version number, currently 7. Versions 1, 2 and 3 are obsolete.
41039 Version 4 uses a different hashing function from versions 5 and 6.
41040 Version 6 includes symbols for inlined functions, whereas versions 4
41041 and 5 do not. Version 7 adds attributes to the CU indices in the
41042 symbol table. @value{GDBN} will only read version 4, 5, or 6 indices
41043 by specifying @code{set use-deprecated-index-sections on}.
41046 The offset, from the start of the file, of the CU list.
41049 The offset, from the start of the file, of the types CU list. Note
41050 that this area can be empty, in which case this offset will be equal
41051 to the next offset.
41054 The offset, from the start of the file, of the address area.
41057 The offset, from the start of the file, of the symbol table.
41060 The offset, from the start of the file, of the constant pool.
41064 The CU list. This is a sequence of pairs of 64-bit little-endian
41065 values, sorted by the CU offset. The first element in each pair is
41066 the offset of a CU in the @code{.debug_info} section. The second
41067 element in each pair is the length of that CU. References to a CU
41068 elsewhere in the map are done using a CU index, which is just the
41069 0-based index into this table. Note that if there are type CUs, then
41070 conceptually CUs and type CUs form a single list for the purposes of
41074 The types CU list. This is a sequence of triplets of 64-bit
41075 little-endian values. In a triplet, the first value is the CU offset,
41076 the second value is the type offset in the CU, and the third value is
41077 the type signature. The types CU list is not sorted.
41080 The address area. The address area consists of a sequence of address
41081 entries. Each address entry has three elements:
41085 The low address. This is a 64-bit little-endian value.
41088 The high address. This is a 64-bit little-endian value. Like
41089 @code{DW_AT_high_pc}, the value is one byte beyond the end.
41092 The CU index. This is an @code{offset_type} value.
41096 The symbol table. This is an open-addressed hash table. The size of
41097 the hash table is always a power of 2.
41099 Each slot in the hash table consists of a pair of @code{offset_type}
41100 values. The first value is the offset of the symbol's name in the
41101 constant pool. The second value is the offset of the CU vector in the
41104 If both values are 0, then this slot in the hash table is empty. This
41105 is ok because while 0 is a valid constant pool index, it cannot be a
41106 valid index for both a string and a CU vector.
41108 The hash value for a table entry is computed by applying an
41109 iterative hash function to the symbol's name. Starting with an
41110 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
41111 the string is incorporated into the hash using the formula depending on the
41116 The formula is @code{r = r * 67 + c - 113}.
41118 @item Versions 5 to 7
41119 The formula is @code{r = r * 67 + tolower (c) - 113}.
41122 The terminating @samp{\0} is not incorporated into the hash.
41124 The step size used in the hash table is computed via
41125 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
41126 value, and @samp{size} is the size of the hash table. The step size
41127 is used to find the next candidate slot when handling a hash
41130 The names of C@t{++} symbols in the hash table are canonicalized. We
41131 don't currently have a simple description of the canonicalization
41132 algorithm; if you intend to create new index sections, you must read
41136 The constant pool. This is simply a bunch of bytes. It is organized
41137 so that alignment is correct: CU vectors are stored first, followed by
41140 A CU vector in the constant pool is a sequence of @code{offset_type}
41141 values. The first value is the number of CU indices in the vector.
41142 Each subsequent value is the index and symbol attributes of a CU in
41143 the CU list. This element in the hash table is used to indicate which
41144 CUs define the symbol and how the symbol is used.
41145 See below for the format of each CU index+attributes entry.
41147 A string in the constant pool is zero-terminated.
41150 Attributes were added to CU index values in @code{.gdb_index} version 7.
41151 If a symbol has multiple uses within a CU then there is one
41152 CU index+attributes value for each use.
41154 The format of each CU index+attributes entry is as follows
41160 This is the index of the CU in the CU list.
41162 These bits are reserved for future purposes and must be zero.
41164 The kind of the symbol in the CU.
41168 This value is reserved and should not be used.
41169 By reserving zero the full @code{offset_type} value is backwards compatible
41170 with previous versions of the index.
41172 The symbol is a type.
41174 The symbol is a variable or an enum value.
41176 The symbol is a function.
41178 Any other kind of symbol.
41180 These values are reserved.
41184 This bit is zero if the value is global and one if it is static.
41186 The determination of whether a symbol is global or static is complicated.
41187 The authorative reference is the file @file{dwarf2read.c} in
41188 @value{GDBN} sources.
41192 This pseudo-code describes the computation of a symbol's kind and
41193 global/static attributes in the index.
41196 is_external = get_attribute (die, DW_AT_external);
41197 language = get_attribute (cu_die, DW_AT_language);
41200 case DW_TAG_typedef:
41201 case DW_TAG_base_type:
41202 case DW_TAG_subrange_type:
41206 case DW_TAG_enumerator:
41208 is_static = (language != CPLUS && language != JAVA);
41210 case DW_TAG_subprogram:
41212 is_static = ! (is_external || language == ADA);
41214 case DW_TAG_constant:
41216 is_static = ! is_external;
41218 case DW_TAG_variable:
41220 is_static = ! is_external;
41222 case DW_TAG_namespace:
41226 case DW_TAG_class_type:
41227 case DW_TAG_interface_type:
41228 case DW_TAG_structure_type:
41229 case DW_TAG_union_type:
41230 case DW_TAG_enumeration_type:
41232 is_static = (language != CPLUS && language != JAVA);
41241 @node GNU Free Documentation License
41242 @appendix GNU Free Documentation License
41245 @node Concept Index
41246 @unnumbered Concept Index
41250 @node Command and Variable Index
41251 @unnumbered Command, Variable, and Function Index
41256 % I think something like @@colophon should be in texinfo. In the
41258 \long\def\colophon{\hbox to0pt{}\vfill
41259 \centerline{The body of this manual is set in}
41260 \centerline{\fontname\tenrm,}
41261 \centerline{with headings in {\bf\fontname\tenbf}}
41262 \centerline{and examples in {\tt\fontname\tentt}.}
41263 \centerline{{\it\fontname\tenit\/},}
41264 \centerline{{\bf\fontname\tenbf}, and}
41265 \centerline{{\sl\fontname\tensl\/}}
41266 \centerline{are used for emphasis.}\vfill}
41268 % Blame: doc@@cygnus.com, 1991.