1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-1996, 1998-2012 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, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
51 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
53 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
68 This file documents the @sc{gnu} debugger @value{GDBN}.
70 This is the @value{EDITION} Edition, of @cite{Debugging with
71 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
72 @ifset VERSION_PACKAGE
73 @value{VERSION_PACKAGE}
75 Version @value{GDBVN}.
81 @title Debugging with @value{GDBN}
82 @subtitle The @sc{gnu} Source-Level Debugger
84 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
85 @ifset VERSION_PACKAGE
87 @subtitle @value{VERSION_PACKAGE}
89 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
93 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
94 \hfill {\it Debugging with @value{GDBN}}\par
95 \hfill \TeX{}info \texinfoversion\par
99 @vskip 0pt plus 1filll
100 Published by the Free Software Foundation @*
101 51 Franklin Street, Fifth Floor,
102 Boston, MA 02110-1301, USA@*
103 ISBN 978-0-9831592-3-0 @*
110 @node Top, Summary, (dir), (dir)
112 @top Debugging with @value{GDBN}
114 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
116 This is the @value{EDITION} Edition, for @value{GDBN}
117 @ifset VERSION_PACKAGE
118 @value{VERSION_PACKAGE}
120 Version @value{GDBVN}.
122 Copyright (C) 1988-2012 Free Software Foundation, Inc.
124 This edition of the GDB manual is dedicated to the memory of Fred
125 Fish. Fred was a long-standing contributor to GDB and to Free
126 software in general. We will miss him.
129 * Summary:: Summary of @value{GDBN}
130 * Sample Session:: A sample @value{GDBN} session
132 * Invocation:: Getting in and out of @value{GDBN}
133 * Commands:: @value{GDBN} commands
134 * Running:: Running programs under @value{GDBN}
135 * Stopping:: Stopping and continuing
136 * Reverse Execution:: Running programs backward
137 * Process Record and Replay:: Recording inferior's execution and replaying it
138 * Stack:: Examining the stack
139 * Source:: Examining source files
140 * Data:: Examining data
141 * Optimized Code:: Debugging optimized code
142 * Macros:: Preprocessor Macros
143 * Tracepoints:: Debugging remote targets non-intrusively
144 * Overlays:: Debugging programs that use overlays
146 * Languages:: Using @value{GDBN} with different languages
148 * Symbols:: Examining the symbol table
149 * Altering:: Altering execution
150 * GDB Files:: @value{GDBN} files
151 * Targets:: Specifying a debugging target
152 * Remote Debugging:: Debugging remote programs
153 * Configurations:: Configuration-specific information
154 * Controlling GDB:: Controlling @value{GDBN}
155 * Extending GDB:: Extending @value{GDBN}
156 * Interpreters:: Command Interpreters
157 * TUI:: @value{GDBN} Text User Interface
158 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
159 * GDB/MI:: @value{GDBN}'s Machine Interface.
160 * Annotations:: @value{GDBN}'s annotation interface.
161 * JIT Interface:: Using the JIT debugging interface.
162 * In-Process Agent:: In-Process Agent
164 * GDB Bugs:: Reporting bugs in @value{GDBN}
166 @ifset SYSTEM_READLINE
167 * Command Line Editing: (rluserman). Command Line Editing
168 * Using History Interactively: (history). Using History Interactively
170 @ifclear SYSTEM_READLINE
171 * Command Line Editing:: Command Line Editing
172 * Using History Interactively:: Using History Interactively
174 * In Memoriam:: In Memoriam
175 * Formatting Documentation:: How to format and print @value{GDBN} documentation
176 * Installing GDB:: Installing GDB
177 * Maintenance Commands:: Maintenance Commands
178 * Remote Protocol:: GDB Remote Serial Protocol
179 * Agent Expressions:: The GDB Agent Expression Mechanism
180 * Target Descriptions:: How targets can describe themselves to
182 * Operating System Information:: Getting additional information from
184 * Trace File Format:: GDB trace file format
185 * Index Section Format:: .gdb_index section format
186 * Copying:: GNU General Public License says
187 how you can copy and share GDB
188 * GNU Free Documentation License:: The license for this documentation
189 * Concept Index:: Index of @value{GDBN} concepts
190 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
191 functions, and Python data types
199 @unnumbered Summary of @value{GDBN}
201 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
202 going on ``inside'' another program while it executes---or what another
203 program was doing at the moment it crashed.
205 @value{GDBN} can do four main kinds of things (plus other things in support of
206 these) to help you catch bugs in the act:
210 Start your program, specifying anything that might affect its behavior.
213 Make your program stop on specified conditions.
216 Examine what has happened, when your program has stopped.
219 Change things in your program, so you can experiment with correcting the
220 effects of one bug and go on to learn about another.
223 You can use @value{GDBN} to debug programs written in C and C@t{++}.
224 For more information, see @ref{Supported Languages,,Supported Languages}.
225 For more information, see @ref{C,,C and C++}.
227 Support for D is partial. For information on D, see
231 Support for Modula-2 is partial. For information on Modula-2, see
232 @ref{Modula-2,,Modula-2}.
234 Support for OpenCL C is partial. For information on OpenCL C, see
235 @ref{OpenCL C,,OpenCL C}.
238 Debugging Pascal programs which use sets, subranges, file variables, or
239 nested functions does not currently work. @value{GDBN} does not support
240 entering expressions, printing values, or similar features using Pascal
244 @value{GDBN} can be used to debug programs written in Fortran, although
245 it may be necessary to refer to some variables with a trailing
248 @value{GDBN} can be used to debug programs written in Objective-C,
249 using either the Apple/NeXT or the GNU Objective-C runtime.
252 * Free Software:: Freely redistributable software
253 * Free Documentation:: Free Software Needs Free Documentation
254 * Contributors:: Contributors to GDB
258 @unnumberedsec Free Software
260 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
261 General Public License
262 (GPL). The GPL gives you the freedom to copy or adapt a licensed
263 program---but every person getting a copy also gets with it the
264 freedom to modify that copy (which means that they must get access to
265 the source code), and the freedom to distribute further copies.
266 Typical software companies use copyrights to limit your freedoms; the
267 Free Software Foundation uses the GPL to preserve these freedoms.
269 Fundamentally, the General Public License is a license which says that
270 you have these freedoms and that you cannot take these freedoms away
273 @node Free Documentation
274 @unnumberedsec Free Software Needs Free Documentation
276 The biggest deficiency in the free software community today is not in
277 the software---it is the lack of good free documentation that we can
278 include with the free software. Many of our most important
279 programs do not come with free reference manuals and free introductory
280 texts. Documentation is an essential part of any software package;
281 when an important free software package does not come with a free
282 manual and a free tutorial, that is a major gap. We have many such
285 Consider Perl, for instance. The tutorial manuals that people
286 normally use are non-free. How did this come about? Because the
287 authors of those manuals published them with restrictive terms---no
288 copying, no modification, source files not available---which exclude
289 them from the free software world.
291 That wasn't the first time this sort of thing happened, and it was far
292 from the last. Many times we have heard a GNU user eagerly describe a
293 manual that he is writing, his intended contribution to the community,
294 only to learn that he had ruined everything by signing a publication
295 contract to make it non-free.
297 Free documentation, like free software, is a matter of freedom, not
298 price. The problem with the non-free manual is not that publishers
299 charge a price for printed copies---that in itself is fine. (The Free
300 Software Foundation sells printed copies of manuals, too.) The
301 problem is the restrictions on the use of the manual. Free manuals
302 are available in source code form, and give you permission to copy and
303 modify. Non-free manuals do not allow this.
305 The criteria of freedom for a free manual are roughly the same as for
306 free software. Redistribution (including the normal kinds of
307 commercial redistribution) must be permitted, so that the manual can
308 accompany every copy of the program, both on-line and on paper.
310 Permission for modification of the technical content is crucial too.
311 When people modify the software, adding or changing features, if they
312 are conscientious they will change the manual too---so they can
313 provide accurate and clear documentation for the modified program. A
314 manual that leaves you no choice but to write a new manual to document
315 a changed version of the program is not really available to our
318 Some kinds of limits on the way modification is handled are
319 acceptable. For example, requirements to preserve the original
320 author's copyright notice, the distribution terms, or the list of
321 authors, are ok. It is also no problem to require modified versions
322 to include notice that they were modified. Even entire sections that
323 may not be deleted or changed are acceptable, as long as they deal
324 with nontechnical topics (like this one). These kinds of restrictions
325 are acceptable because they don't obstruct the community's normal use
328 However, it must be possible to modify all the @emph{technical}
329 content of the manual, and then distribute the result in all the usual
330 media, through all the usual channels. Otherwise, the restrictions
331 obstruct the use of the manual, it is not free, and we need another
332 manual to replace it.
334 Please spread the word about this issue. Our community continues to
335 lose manuals to proprietary publishing. If we spread the word that
336 free software needs free reference manuals and free tutorials, perhaps
337 the next person who wants to contribute by writing documentation will
338 realize, before it is too late, that only free manuals contribute to
339 the free software community.
341 If you are writing documentation, please insist on publishing it under
342 the GNU Free Documentation License or another free documentation
343 license. Remember that this decision requires your approval---you
344 don't have to let the publisher decide. Some commercial publishers
345 will use a free license if you insist, but they will not propose the
346 option; it is up to you to raise the issue and say firmly that this is
347 what you want. If the publisher you are dealing with refuses, please
348 try other publishers. If you're not sure whether a proposed license
349 is free, write to @email{licensing@@gnu.org}.
351 You can encourage commercial publishers to sell more free, copylefted
352 manuals and tutorials by buying them, and particularly by buying
353 copies from the publishers that paid for their writing or for major
354 improvements. Meanwhile, try to avoid buying non-free documentation
355 at all. Check the distribution terms of a manual before you buy it,
356 and insist that whoever seeks your business must respect your freedom.
357 Check the history of the book, and try to reward the publishers that
358 have paid or pay the authors to work on it.
360 The Free Software Foundation maintains a list of free documentation
361 published by other publishers, at
362 @url{http://www.fsf.org/doc/other-free-books.html}.
365 @unnumberedsec Contributors to @value{GDBN}
367 Richard Stallman was the original author of @value{GDBN}, and of many
368 other @sc{gnu} programs. Many others have contributed to its
369 development. This section attempts to credit major contributors. One
370 of the virtues of free software is that everyone is free to contribute
371 to it; with regret, we cannot actually acknowledge everyone here. The
372 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
373 blow-by-blow account.
375 Changes much prior to version 2.0 are lost in the mists of time.
378 @emph{Plea:} Additions to this section are particularly welcome. If you
379 or your friends (or enemies, to be evenhanded) have been unfairly
380 omitted from this list, we would like to add your names!
383 So that they may not regard their many labors as thankless, we
384 particularly thank those who shepherded @value{GDBN} through major
386 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
387 Jim Blandy (release 4.18);
388 Jason Molenda (release 4.17);
389 Stan Shebs (release 4.14);
390 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
391 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
392 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
393 Jim Kingdon (releases 3.5, 3.4, and 3.3);
394 and Randy Smith (releases 3.2, 3.1, and 3.0).
396 Richard Stallman, assisted at various times by Peter TerMaat, Chris
397 Hanson, and Richard Mlynarik, handled releases through 2.8.
399 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
400 in @value{GDBN}, with significant additional contributions from Per
401 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
402 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
403 much general update work leading to release 3.0).
405 @value{GDBN} uses the BFD subroutine library to examine multiple
406 object-file formats; BFD was a joint project of David V.
407 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
409 David Johnson wrote the original COFF support; Pace Willison did
410 the original support for encapsulated COFF.
412 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
414 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
415 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
417 Jean-Daniel Fekete contributed Sun 386i support.
418 Chris Hanson improved the HP9000 support.
419 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
420 David Johnson contributed Encore Umax support.
421 Jyrki Kuoppala contributed Altos 3068 support.
422 Jeff Law contributed HP PA and SOM support.
423 Keith Packard contributed NS32K support.
424 Doug Rabson contributed Acorn Risc Machine support.
425 Bob Rusk contributed Harris Nighthawk CX-UX support.
426 Chris Smith contributed Convex support (and Fortran debugging).
427 Jonathan Stone contributed Pyramid support.
428 Michael Tiemann contributed SPARC support.
429 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
430 Pace Willison contributed Intel 386 support.
431 Jay Vosburgh contributed Symmetry support.
432 Marko Mlinar contributed OpenRISC 1000 support.
434 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
436 Rich Schaefer and Peter Schauer helped with support of SunOS shared
439 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
440 about several machine instruction sets.
442 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
443 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
444 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
445 and RDI targets, respectively.
447 Brian Fox is the author of the readline libraries providing
448 command-line editing and command history.
450 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
451 Modula-2 support, and contributed the Languages chapter of this manual.
453 Fred Fish wrote most of the support for Unix System Vr4.
454 He also enhanced the command-completion support to cover C@t{++} overloaded
457 Hitachi America (now Renesas America), Ltd. sponsored the support for
458 H8/300, H8/500, and Super-H processors.
460 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
462 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
465 Toshiba sponsored the support for the TX39 Mips processor.
467 Matsushita sponsored the support for the MN10200 and MN10300 processors.
469 Fujitsu sponsored the support for SPARClite and FR30 processors.
471 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
474 Michael Snyder added support for tracepoints.
476 Stu Grossman wrote gdbserver.
478 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
479 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
481 The following people at the Hewlett-Packard Company contributed
482 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
483 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
484 compiler, and the Text User Interface (nee Terminal User Interface):
485 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
486 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
487 provided HP-specific information in this manual.
489 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
490 Robert Hoehne made significant contributions to the DJGPP port.
492 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
493 development since 1991. Cygnus engineers who have worked on @value{GDBN}
494 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
495 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
496 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
497 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
498 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
499 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
500 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
501 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
502 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
503 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
504 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
505 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
506 Zuhn have made contributions both large and small.
508 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
509 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
511 Jim Blandy added support for preprocessor macros, while working for Red
514 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
515 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
516 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
517 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
518 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
519 with the migration of old architectures to this new framework.
521 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
522 unwinder framework, this consisting of a fresh new design featuring
523 frame IDs, independent frame sniffers, and the sentinel frame. Mark
524 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
525 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
526 trad unwinders. The architecture-specific changes, each involving a
527 complete rewrite of the architecture's frame code, were carried out by
528 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
529 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
530 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
531 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
534 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
535 Tensilica, Inc.@: contributed support for Xtensa processors. Others
536 who have worked on the Xtensa port of @value{GDBN} in the past include
537 Steve Tjiang, John Newlin, and Scott Foehner.
539 Michael Eager and staff of Xilinx, Inc., contributed support for the
540 Xilinx MicroBlaze architecture.
543 @chapter A Sample @value{GDBN} Session
545 You can use this manual at your leisure to read all about @value{GDBN}.
546 However, a handful of commands are enough to get started using the
547 debugger. This chapter illustrates those commands.
550 In this sample session, we emphasize user input like this: @b{input},
551 to make it easier to pick out from the surrounding output.
554 @c FIXME: this example may not be appropriate for some configs, where
555 @c FIXME...primary interest is in remote use.
557 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
558 processor) exhibits the following bug: sometimes, when we change its
559 quote strings from the default, the commands used to capture one macro
560 definition within another stop working. In the following short @code{m4}
561 session, we define a macro @code{foo} which expands to @code{0000}; we
562 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
563 same thing. However, when we change the open quote string to
564 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
565 procedure fails to define a new synonym @code{baz}:
574 @b{define(bar,defn(`foo'))}
578 @b{changequote(<QUOTE>,<UNQUOTE>)}
580 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
583 m4: End of input: 0: fatal error: EOF in string
587 Let us use @value{GDBN} to try to see what is going on.
590 $ @b{@value{GDBP} m4}
591 @c FIXME: this falsifies the exact text played out, to permit smallbook
592 @c FIXME... format to come out better.
593 @value{GDBN} is free software and you are welcome to distribute copies
594 of it under certain conditions; type "show copying" to see
596 There is absolutely no warranty for @value{GDBN}; type "show warranty"
599 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
604 @value{GDBN} reads only enough symbol data to know where to find the
605 rest when needed; as a result, the first prompt comes up very quickly.
606 We now tell @value{GDBN} to use a narrower display width than usual, so
607 that examples fit in this manual.
610 (@value{GDBP}) @b{set width 70}
614 We need to see how the @code{m4} built-in @code{changequote} works.
615 Having looked at the source, we know the relevant subroutine is
616 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
617 @code{break} command.
620 (@value{GDBP}) @b{break m4_changequote}
621 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
625 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
626 control; as long as control does not reach the @code{m4_changequote}
627 subroutine, the program runs as usual:
630 (@value{GDBP}) @b{run}
631 Starting program: /work/Editorial/gdb/gnu/m4/m4
639 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
640 suspends execution of @code{m4}, displaying information about the
641 context where it stops.
644 @b{changequote(<QUOTE>,<UNQUOTE>)}
646 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
648 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
652 Now we use the command @code{n} (@code{next}) to advance execution to
653 the next line of the current function.
657 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
662 @code{set_quotes} looks like a promising subroutine. We can go into it
663 by using the command @code{s} (@code{step}) instead of @code{next}.
664 @code{step} goes to the next line to be executed in @emph{any}
665 subroutine, so it steps into @code{set_quotes}.
669 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
671 530 if (lquote != def_lquote)
675 The display that shows the subroutine where @code{m4} is now
676 suspended (and its arguments) is called a stack frame display. It
677 shows a summary of the stack. We can use the @code{backtrace}
678 command (which can also be spelled @code{bt}), to see where we are
679 in the stack as a whole: the @code{backtrace} command displays a
680 stack frame for each active subroutine.
683 (@value{GDBP}) @b{bt}
684 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
686 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
688 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
689 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
691 #4 0x79dc in expand_input () at macro.c:40
692 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
696 We step through a few more lines to see what happens. The first two
697 times, we can use @samp{s}; the next two times we use @code{n} to avoid
698 falling into the @code{xstrdup} subroutine.
702 0x3b5c 532 if (rquote != def_rquote)
704 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
705 def_lquote : xstrdup(lq);
707 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
710 538 len_lquote = strlen(rquote);
714 The last line displayed looks a little odd; we can examine the variables
715 @code{lquote} and @code{rquote} to see if they are in fact the new left
716 and right quotes we specified. We use the command @code{p}
717 (@code{print}) to see their values.
720 (@value{GDBP}) @b{p lquote}
721 $1 = 0x35d40 "<QUOTE>"
722 (@value{GDBP}) @b{p rquote}
723 $2 = 0x35d50 "<UNQUOTE>"
727 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
728 To look at some context, we can display ten lines of source
729 surrounding the current line with the @code{l} (@code{list}) command.
735 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
737 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
740 538 len_lquote = strlen(rquote);
741 539 len_rquote = strlen(lquote);
748 Let us step past the two lines that set @code{len_lquote} and
749 @code{len_rquote}, and then examine the values of those variables.
753 539 len_rquote = strlen(lquote);
756 (@value{GDBP}) @b{p len_lquote}
758 (@value{GDBP}) @b{p len_rquote}
763 That certainly looks wrong, assuming @code{len_lquote} and
764 @code{len_rquote} are meant to be the lengths of @code{lquote} and
765 @code{rquote} respectively. We can set them to better values using
766 the @code{p} command, since it can print the value of
767 any expression---and that expression can include subroutine calls and
771 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
773 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
778 Is that enough to fix the problem of using the new quotes with the
779 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
780 executing with the @code{c} (@code{continue}) command, and then try the
781 example that caused trouble initially:
787 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
794 Success! The new quotes now work just as well as the default ones. The
795 problem seems to have been just the two typos defining the wrong
796 lengths. We allow @code{m4} exit by giving it an EOF as input:
800 Program exited normally.
804 The message @samp{Program exited normally.} is from @value{GDBN}; it
805 indicates @code{m4} has finished executing. We can end our @value{GDBN}
806 session with the @value{GDBN} @code{quit} command.
809 (@value{GDBP}) @b{quit}
813 @chapter Getting In and Out of @value{GDBN}
815 This chapter discusses how to start @value{GDBN}, and how to get out of it.
819 type @samp{@value{GDBP}} to start @value{GDBN}.
821 type @kbd{quit} or @kbd{Ctrl-d} to exit.
825 * Invoking GDB:: How to start @value{GDBN}
826 * Quitting GDB:: How to quit @value{GDBN}
827 * Shell Commands:: How to use shell commands inside @value{GDBN}
828 * Logging Output:: How to log @value{GDBN}'s output to a file
832 @section Invoking @value{GDBN}
834 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
835 @value{GDBN} reads commands from the terminal until you tell it to exit.
837 You can also run @code{@value{GDBP}} with a variety of arguments and options,
838 to specify more of your debugging environment at the outset.
840 The command-line options described here are designed
841 to cover a variety of situations; in some environments, some of these
842 options may effectively be unavailable.
844 The most usual way to start @value{GDBN} is with one argument,
845 specifying an executable program:
848 @value{GDBP} @var{program}
852 You can also start with both an executable program and a core file
856 @value{GDBP} @var{program} @var{core}
859 You can, instead, specify a process ID as a second argument, if you want
860 to debug a running process:
863 @value{GDBP} @var{program} 1234
867 would attach @value{GDBN} to process @code{1234} (unless you also have a file
868 named @file{1234}; @value{GDBN} does check for a core file first).
870 Taking advantage of the second command-line argument requires a fairly
871 complete operating system; when you use @value{GDBN} as a remote
872 debugger attached to a bare board, there may not be any notion of
873 ``process'', and there is often no way to get a core dump. @value{GDBN}
874 will warn you if it is unable to attach or to read core dumps.
876 You can optionally have @code{@value{GDBP}} pass any arguments after the
877 executable file to the inferior using @code{--args}. This option stops
880 @value{GDBP} --args gcc -O2 -c foo.c
882 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
883 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
885 You can run @code{@value{GDBP}} without printing the front material, which describes
886 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
893 You can further control how @value{GDBN} starts up by using command-line
894 options. @value{GDBN} itself can remind you of the options available.
904 to display all available options and briefly describe their use
905 (@samp{@value{GDBP} -h} is a shorter equivalent).
907 All options and command line arguments you give are processed
908 in sequential order. The order makes a difference when the
909 @samp{-x} option is used.
913 * File Options:: Choosing files
914 * Mode Options:: Choosing modes
915 * Startup:: What @value{GDBN} does during startup
919 @subsection Choosing Files
921 When @value{GDBN} starts, it reads any arguments other than options as
922 specifying an executable file and core file (or process ID). This is
923 the same as if the arguments were specified by the @samp{-se} and
924 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
925 first argument that does not have an associated option flag as
926 equivalent to the @samp{-se} option followed by that argument; and the
927 second argument that does not have an associated option flag, if any, as
928 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
929 If the second argument begins with a decimal digit, @value{GDBN} will
930 first attempt to attach to it as a process, and if that fails, attempt
931 to open it as a corefile. If you have a corefile whose name begins with
932 a digit, you can prevent @value{GDBN} from treating it as a pid by
933 prefixing it with @file{./}, e.g.@: @file{./12345}.
935 If @value{GDBN} has not been configured to included core file support,
936 such as for most embedded targets, then it will complain about a second
937 argument and ignore it.
939 Many options have both long and short forms; both are shown in the
940 following list. @value{GDBN} also recognizes the long forms if you truncate
941 them, so long as enough of the option is present to be unambiguous.
942 (If you prefer, you can flag option arguments with @samp{--} rather
943 than @samp{-}, though we illustrate the more usual convention.)
945 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
946 @c way, both those who look for -foo and --foo in the index, will find
950 @item -symbols @var{file}
952 @cindex @code{--symbols}
954 Read symbol table from file @var{file}.
956 @item -exec @var{file}
958 @cindex @code{--exec}
960 Use file @var{file} as the executable file to execute when appropriate,
961 and for examining pure data in conjunction with a core dump.
965 Read symbol table from file @var{file} and use it as the executable
968 @item -core @var{file}
970 @cindex @code{--core}
972 Use file @var{file} as a core dump to examine.
974 @item -pid @var{number}
975 @itemx -p @var{number}
978 Connect to process ID @var{number}, as with the @code{attach} command.
980 @item -command @var{file}
982 @cindex @code{--command}
984 Execute commands from file @var{file}. The contents of this file is
985 evaluated exactly as the @code{source} command would.
986 @xref{Command Files,, Command files}.
988 @item -eval-command @var{command}
989 @itemx -ex @var{command}
990 @cindex @code{--eval-command}
992 Execute a single @value{GDBN} command.
994 This option may be used multiple times to call multiple commands. It may
995 also be interleaved with @samp{-command} as required.
998 @value{GDBP} -ex 'target sim' -ex 'load' \
999 -x setbreakpoints -ex 'run' a.out
1002 @item -init-command @var{file}
1003 @itemx -ix @var{file}
1004 @cindex @code{--init-command}
1006 Execute commands from file @var{file} before loading the inferior (but
1007 after loading gdbinit files).
1010 @item -init-eval-command @var{command}
1011 @itemx -iex @var{command}
1012 @cindex @code{--init-eval-command}
1014 Execute a single @value{GDBN} command before loading the inferior (but
1015 after loading gdbinit files).
1018 @item -directory @var{directory}
1019 @itemx -d @var{directory}
1020 @cindex @code{--directory}
1022 Add @var{directory} to the path to search for source and script files.
1026 @cindex @code{--readnow}
1028 Read each symbol file's entire symbol table immediately, rather than
1029 the default, which is to read it incrementally as it is needed.
1030 This makes startup slower, but makes future operations faster.
1035 @subsection Choosing Modes
1037 You can run @value{GDBN} in various alternative modes---for example, in
1038 batch mode or quiet mode.
1046 Do not execute commands found in any initialization file.
1047 There are three init files, loaded in the following order:
1050 @item @file{system.gdbinit}
1051 This is the system-wide init file.
1052 Its location is specified with the @code{--with-system-gdbinit}
1053 configure option (@pxref{System-wide configuration}).
1054 It is loaded first when @value{GDBN} starts, before command line options
1055 have been processed.
1056 @item @file{~/.gdbinit}
1057 This is the init file in your home directory.
1058 It is loaded next, after @file{system.gdbinit}, and before
1059 command options have been processed.
1060 @item @file{./.gdbinit}
1061 This is the init file in the current directory.
1062 It is loaded last, after command line options other than @code{-x} and
1063 @code{-ex} have been processed. Command line options @code{-x} and
1064 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1067 For further documentation on startup processing, @xref{Startup}.
1068 For documentation on how to write command files,
1069 @xref{Command Files,,Command Files}.
1074 Do not execute commands found in @file{~/.gdbinit}, the init file
1075 in your home directory.
1081 @cindex @code{--quiet}
1082 @cindex @code{--silent}
1084 ``Quiet''. Do not print the introductory and copyright messages. These
1085 messages are also suppressed in batch mode.
1088 @cindex @code{--batch}
1089 Run in batch mode. Exit with status @code{0} after processing all the
1090 command files specified with @samp{-x} (and all commands from
1091 initialization files, if not inhibited with @samp{-n}). Exit with
1092 nonzero status if an error occurs in executing the @value{GDBN} commands
1093 in the command files. Batch mode also disables pagination, sets unlimited
1094 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1095 off} were in effect (@pxref{Messages/Warnings}).
1097 Batch mode may be useful for running @value{GDBN} as a filter, for
1098 example to download and run a program on another computer; in order to
1099 make this more useful, the message
1102 Program exited normally.
1106 (which is ordinarily issued whenever a program running under
1107 @value{GDBN} control terminates) is not issued when running in batch
1111 @cindex @code{--batch-silent}
1112 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1113 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1114 unaffected). This is much quieter than @samp{-silent} and would be useless
1115 for an interactive session.
1117 This is particularly useful when using targets that give @samp{Loading section}
1118 messages, for example.
1120 Note that targets that give their output via @value{GDBN}, as opposed to
1121 writing directly to @code{stdout}, will also be made silent.
1123 @item -return-child-result
1124 @cindex @code{--return-child-result}
1125 The return code from @value{GDBN} will be the return code from the child
1126 process (the process being debugged), with the following exceptions:
1130 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1131 internal error. In this case the exit code is the same as it would have been
1132 without @samp{-return-child-result}.
1134 The user quits with an explicit value. E.g., @samp{quit 1}.
1136 The child process never runs, or is not allowed to terminate, in which case
1137 the exit code will be -1.
1140 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1141 when @value{GDBN} is being used as a remote program loader or simulator
1146 @cindex @code{--nowindows}
1148 ``No windows''. If @value{GDBN} comes with a graphical user interface
1149 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1150 interface. If no GUI is available, this option has no effect.
1154 @cindex @code{--windows}
1156 If @value{GDBN} includes a GUI, then this option requires it to be
1159 @item -cd @var{directory}
1161 Run @value{GDBN} using @var{directory} as its working directory,
1162 instead of the current directory.
1164 @item -data-directory @var{directory}
1165 @cindex @code{--data-directory}
1166 Run @value{GDBN} using @var{directory} as its data directory.
1167 The data directory is where @value{GDBN} searches for its
1168 auxiliary files. @xref{Data Files}.
1172 @cindex @code{--fullname}
1174 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1175 subprocess. It tells @value{GDBN} to output the full file name and line
1176 number in a standard, recognizable fashion each time a stack frame is
1177 displayed (which includes each time your program stops). This
1178 recognizable format looks like two @samp{\032} characters, followed by
1179 the file name, line number and character position separated by colons,
1180 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1181 @samp{\032} characters as a signal to display the source code for the
1185 @cindex @code{--epoch}
1186 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1187 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1188 routines so as to allow Epoch to display values of expressions in a
1191 @item -annotate @var{level}
1192 @cindex @code{--annotate}
1193 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1194 effect is identical to using @samp{set annotate @var{level}}
1195 (@pxref{Annotations}). The annotation @var{level} controls how much
1196 information @value{GDBN} prints together with its prompt, values of
1197 expressions, source lines, and other types of output. Level 0 is the
1198 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1199 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1200 that control @value{GDBN}, and level 2 has been deprecated.
1202 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1206 @cindex @code{--args}
1207 Change interpretation of command line so that arguments following the
1208 executable file are passed as command line arguments to the inferior.
1209 This option stops option processing.
1211 @item -baud @var{bps}
1213 @cindex @code{--baud}
1215 Set the line speed (baud rate or bits per second) of any serial
1216 interface used by @value{GDBN} for remote debugging.
1218 @item -l @var{timeout}
1220 Set the timeout (in seconds) of any communication used by @value{GDBN}
1221 for remote debugging.
1223 @item -tty @var{device}
1224 @itemx -t @var{device}
1225 @cindex @code{--tty}
1227 Run using @var{device} for your program's standard input and output.
1228 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1230 @c resolve the situation of these eventually
1232 @cindex @code{--tui}
1233 Activate the @dfn{Text User Interface} when starting. The Text User
1234 Interface manages several text windows on the terminal, showing
1235 source, assembly, registers and @value{GDBN} command outputs
1236 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1237 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1238 Using @value{GDBN} under @sc{gnu} Emacs}).
1241 @c @cindex @code{--xdb}
1242 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1243 @c For information, see the file @file{xdb_trans.html}, which is usually
1244 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1247 @item -interpreter @var{interp}
1248 @cindex @code{--interpreter}
1249 Use the interpreter @var{interp} for interface with the controlling
1250 program or device. This option is meant to be set by programs which
1251 communicate with @value{GDBN} using it as a back end.
1252 @xref{Interpreters, , Command Interpreters}.
1254 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1255 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1256 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1257 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1258 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1259 @sc{gdb/mi} interfaces are no longer supported.
1262 @cindex @code{--write}
1263 Open the executable and core files for both reading and writing. This
1264 is equivalent to the @samp{set write on} command inside @value{GDBN}
1268 @cindex @code{--statistics}
1269 This option causes @value{GDBN} to print statistics about time and
1270 memory usage after it completes each command and returns to the prompt.
1273 @cindex @code{--version}
1274 This option causes @value{GDBN} to print its version number and
1275 no-warranty blurb, and exit.
1280 @subsection What @value{GDBN} Does During Startup
1281 @cindex @value{GDBN} startup
1283 Here's the description of what @value{GDBN} does during session startup:
1287 Sets up the command interpreter as specified by the command line
1288 (@pxref{Mode Options, interpreter}).
1292 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1293 used when building @value{GDBN}; @pxref{System-wide configuration,
1294 ,System-wide configuration and settings}) and executes all the commands in
1297 @anchor{Home Directory Init File}
1299 Reads the init file (if any) in your home directory@footnote{On
1300 DOS/Windows systems, the home directory is the one pointed to by the
1301 @code{HOME} environment variable.} and executes all the commands in
1304 @anchor{Option -init-eval-command}
1306 Executes commands and command files specified by the @samp{-iex} and
1307 @samp{-ix} options in their specified order. Usually you should use the
1308 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1309 settings before @value{GDBN} init files get executed and before inferior
1313 Processes command line options and operands.
1315 @anchor{Init File in the Current Directory during Startup}
1317 Reads and executes the commands from init file (if any) in the current
1318 working directory as long as @samp{set auto-load local-gdbinit} is set to
1319 @samp{on} (@pxref{Init File in the Current Directory}).
1320 This is only done if the current directory is
1321 different from your home directory. Thus, you can have more than one
1322 init file, one generic in your home directory, and another, specific
1323 to the program you are debugging, in the directory where you invoke
1327 If the command line specified a program to debug, or a process to
1328 attach to, or a core file, @value{GDBN} loads any auto-loaded
1329 scripts provided for the program or for its loaded shared libraries.
1330 @xref{Auto-loading}.
1332 If you wish to disable the auto-loading during startup,
1333 you must do something like the following:
1336 $ gdb -iex "set auto-load python-scripts off" myprogram
1339 Option @samp{-ex} does not work because the auto-loading is then turned
1343 Executes commands and command files specified by the @samp{-ex} and
1344 @samp{-x} options in their specified order. @xref{Command Files}, for
1345 more details about @value{GDBN} command files.
1348 Reads the command history recorded in the @dfn{history file}.
1349 @xref{Command History}, for more details about the command history and the
1350 files where @value{GDBN} records it.
1353 Init files use the same syntax as @dfn{command files} (@pxref{Command
1354 Files}) and are processed by @value{GDBN} in the same way. The init
1355 file in your home directory can set options (such as @samp{set
1356 complaints}) that affect subsequent processing of command line options
1357 and operands. Init files are not executed if you use the @samp{-nx}
1358 option (@pxref{Mode Options, ,Choosing Modes}).
1360 To display the list of init files loaded by gdb at startup, you
1361 can use @kbd{gdb --help}.
1363 @cindex init file name
1364 @cindex @file{.gdbinit}
1365 @cindex @file{gdb.ini}
1366 The @value{GDBN} init files are normally called @file{.gdbinit}.
1367 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1368 the limitations of file names imposed by DOS filesystems. The Windows
1369 ports of @value{GDBN} use the standard name, but if they find a
1370 @file{gdb.ini} file, they warn you about that and suggest to rename
1371 the file to the standard name.
1375 @section Quitting @value{GDBN}
1376 @cindex exiting @value{GDBN}
1377 @cindex leaving @value{GDBN}
1380 @kindex quit @r{[}@var{expression}@r{]}
1381 @kindex q @r{(@code{quit})}
1382 @item quit @r{[}@var{expression}@r{]}
1384 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1385 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1386 do not supply @var{expression}, @value{GDBN} will terminate normally;
1387 otherwise it will terminate using the result of @var{expression} as the
1392 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1393 terminates the action of any @value{GDBN} command that is in progress and
1394 returns to @value{GDBN} command level. It is safe to type the interrupt
1395 character at any time because @value{GDBN} does not allow it to take effect
1396 until a time when it is safe.
1398 If you have been using @value{GDBN} to control an attached process or
1399 device, you can release it with the @code{detach} command
1400 (@pxref{Attach, ,Debugging an Already-running Process}).
1402 @node Shell Commands
1403 @section Shell Commands
1405 If you need to execute occasional shell commands during your
1406 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1407 just use the @code{shell} command.
1412 @cindex shell escape
1413 @item shell @var{command-string}
1414 @itemx !@var{command-string}
1415 Invoke a standard shell to execute @var{command-string}.
1416 Note that no space is needed between @code{!} and @var{command-string}.
1417 If it exists, the environment variable @code{SHELL} determines which
1418 shell to run. Otherwise @value{GDBN} uses the default shell
1419 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1422 The utility @code{make} is often needed in development environments.
1423 You do not have to use the @code{shell} command for this purpose in
1428 @cindex calling make
1429 @item make @var{make-args}
1430 Execute the @code{make} program with the specified
1431 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1434 @node Logging Output
1435 @section Logging Output
1436 @cindex logging @value{GDBN} output
1437 @cindex save @value{GDBN} output to a file
1439 You may want to save the output of @value{GDBN} commands to a file.
1440 There are several commands to control @value{GDBN}'s logging.
1444 @item set logging on
1446 @item set logging off
1448 @cindex logging file name
1449 @item set logging file @var{file}
1450 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1451 @item set logging overwrite [on|off]
1452 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1453 you want @code{set logging on} to overwrite the logfile instead.
1454 @item set logging redirect [on|off]
1455 By default, @value{GDBN} output will go to both the terminal and the logfile.
1456 Set @code{redirect} if you want output to go only to the log file.
1457 @kindex show logging
1459 Show the current values of the logging settings.
1463 @chapter @value{GDBN} Commands
1465 You can abbreviate a @value{GDBN} command to the first few letters of the command
1466 name, if that abbreviation is unambiguous; and you can repeat certain
1467 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1468 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1469 show you the alternatives available, if there is more than one possibility).
1472 * Command Syntax:: How to give commands to @value{GDBN}
1473 * Completion:: Command completion
1474 * Help:: How to ask @value{GDBN} for help
1477 @node Command Syntax
1478 @section Command Syntax
1480 A @value{GDBN} command is a single line of input. There is no limit on
1481 how long it can be. It starts with a command name, which is followed by
1482 arguments whose meaning depends on the command name. For example, the
1483 command @code{step} accepts an argument which is the number of times to
1484 step, as in @samp{step 5}. You can also use the @code{step} command
1485 with no arguments. Some commands do not allow any arguments.
1487 @cindex abbreviation
1488 @value{GDBN} command names may always be truncated if that abbreviation is
1489 unambiguous. Other possible command abbreviations are listed in the
1490 documentation for individual commands. In some cases, even ambiguous
1491 abbreviations are allowed; for example, @code{s} is specially defined as
1492 equivalent to @code{step} even though there are other commands whose
1493 names start with @code{s}. You can test abbreviations by using them as
1494 arguments to the @code{help} command.
1496 @cindex repeating commands
1497 @kindex RET @r{(repeat last command)}
1498 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1499 repeat the previous command. Certain commands (for example, @code{run})
1500 will not repeat this way; these are commands whose unintentional
1501 repetition might cause trouble and which you are unlikely to want to
1502 repeat. User-defined commands can disable this feature; see
1503 @ref{Define, dont-repeat}.
1505 The @code{list} and @code{x} commands, when you repeat them with
1506 @key{RET}, construct new arguments rather than repeating
1507 exactly as typed. This permits easy scanning of source or memory.
1509 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1510 output, in a way similar to the common utility @code{more}
1511 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1512 @key{RET} too many in this situation, @value{GDBN} disables command
1513 repetition after any command that generates this sort of display.
1515 @kindex # @r{(a comment)}
1517 Any text from a @kbd{#} to the end of the line is a comment; it does
1518 nothing. This is useful mainly in command files (@pxref{Command
1519 Files,,Command Files}).
1521 @cindex repeating command sequences
1522 @kindex Ctrl-o @r{(operate-and-get-next)}
1523 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1524 commands. This command accepts the current line, like @key{RET}, and
1525 then fetches the next line relative to the current line from the history
1529 @section Command Completion
1532 @cindex word completion
1533 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1534 only one possibility; it can also show you what the valid possibilities
1535 are for the next word in a command, at any time. This works for @value{GDBN}
1536 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1538 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1539 of a word. If there is only one possibility, @value{GDBN} fills in the
1540 word, and waits for you to finish the command (or press @key{RET} to
1541 enter it). For example, if you type
1543 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1544 @c complete accuracy in these examples; space introduced for clarity.
1545 @c If texinfo enhancements make it unnecessary, it would be nice to
1546 @c replace " @key" by "@key" in the following...
1548 (@value{GDBP}) info bre @key{TAB}
1552 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1553 the only @code{info} subcommand beginning with @samp{bre}:
1556 (@value{GDBP}) info breakpoints
1560 You can either press @key{RET} at this point, to run the @code{info
1561 breakpoints} command, or backspace and enter something else, if
1562 @samp{breakpoints} does not look like the command you expected. (If you
1563 were sure you wanted @code{info breakpoints} in the first place, you
1564 might as well just type @key{RET} immediately after @samp{info bre},
1565 to exploit command abbreviations rather than command completion).
1567 If there is more than one possibility for the next word when you press
1568 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1569 characters and try again, or just press @key{TAB} a second time;
1570 @value{GDBN} displays all the possible completions for that word. For
1571 example, you might want to set a breakpoint on a subroutine whose name
1572 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1573 just sounds the bell. Typing @key{TAB} again displays all the
1574 function names in your program that begin with those characters, for
1578 (@value{GDBP}) b make_ @key{TAB}
1579 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1580 make_a_section_from_file make_environ
1581 make_abs_section make_function_type
1582 make_blockvector make_pointer_type
1583 make_cleanup make_reference_type
1584 make_command make_symbol_completion_list
1585 (@value{GDBP}) b make_
1589 After displaying the available possibilities, @value{GDBN} copies your
1590 partial input (@samp{b make_} in the example) so you can finish the
1593 If you just want to see the list of alternatives in the first place, you
1594 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1595 means @kbd{@key{META} ?}. You can type this either by holding down a
1596 key designated as the @key{META} shift on your keyboard (if there is
1597 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1599 @cindex quotes in commands
1600 @cindex completion of quoted strings
1601 Sometimes the string you need, while logically a ``word'', may contain
1602 parentheses or other characters that @value{GDBN} normally excludes from
1603 its notion of a word. To permit word completion to work in this
1604 situation, you may enclose words in @code{'} (single quote marks) in
1605 @value{GDBN} commands.
1607 The most likely situation where you might need this is in typing the
1608 name of a C@t{++} function. This is because C@t{++} allows function
1609 overloading (multiple definitions of the same function, distinguished
1610 by argument type). For example, when you want to set a breakpoint you
1611 may need to distinguish whether you mean the version of @code{name}
1612 that takes an @code{int} parameter, @code{name(int)}, or the version
1613 that takes a @code{float} parameter, @code{name(float)}. To use the
1614 word-completion facilities in this situation, type a single quote
1615 @code{'} at the beginning of the function name. This alerts
1616 @value{GDBN} that it may need to consider more information than usual
1617 when you press @key{TAB} or @kbd{M-?} to request word completion:
1620 (@value{GDBP}) b 'bubble( @kbd{M-?}
1621 bubble(double,double) bubble(int,int)
1622 (@value{GDBP}) b 'bubble(
1625 In some cases, @value{GDBN} can tell that completing a name requires using
1626 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1627 completing as much as it can) if you do not type the quote in the first
1631 (@value{GDBP}) b bub @key{TAB}
1632 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1633 (@value{GDBP}) b 'bubble(
1637 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1638 you have not yet started typing the argument list when you ask for
1639 completion on an overloaded symbol.
1641 For more information about overloaded functions, see @ref{C Plus Plus
1642 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1643 overload-resolution off} to disable overload resolution;
1644 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1646 @cindex completion of structure field names
1647 @cindex structure field name completion
1648 @cindex completion of union field names
1649 @cindex union field name completion
1650 When completing in an expression which looks up a field in a
1651 structure, @value{GDBN} also tries@footnote{The completer can be
1652 confused by certain kinds of invalid expressions. Also, it only
1653 examines the static type of the expression, not the dynamic type.} to
1654 limit completions to the field names available in the type of the
1658 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1659 magic to_fputs to_rewind
1660 to_data to_isatty to_write
1661 to_delete to_put to_write_async_safe
1666 This is because the @code{gdb_stdout} is a variable of the type
1667 @code{struct ui_file} that is defined in @value{GDBN} sources as
1674 ui_file_flush_ftype *to_flush;
1675 ui_file_write_ftype *to_write;
1676 ui_file_write_async_safe_ftype *to_write_async_safe;
1677 ui_file_fputs_ftype *to_fputs;
1678 ui_file_read_ftype *to_read;
1679 ui_file_delete_ftype *to_delete;
1680 ui_file_isatty_ftype *to_isatty;
1681 ui_file_rewind_ftype *to_rewind;
1682 ui_file_put_ftype *to_put;
1689 @section Getting Help
1690 @cindex online documentation
1693 You can always ask @value{GDBN} itself for information on its commands,
1694 using the command @code{help}.
1697 @kindex h @r{(@code{help})}
1700 You can use @code{help} (abbreviated @code{h}) with no arguments to
1701 display a short list of named classes of commands:
1705 List of classes of commands:
1707 aliases -- Aliases of other commands
1708 breakpoints -- Making program stop at certain points
1709 data -- Examining data
1710 files -- Specifying and examining files
1711 internals -- Maintenance commands
1712 obscure -- Obscure features
1713 running -- Running the program
1714 stack -- Examining the stack
1715 status -- Status inquiries
1716 support -- Support facilities
1717 tracepoints -- Tracing of program execution without
1718 stopping the program
1719 user-defined -- User-defined commands
1721 Type "help" followed by a class name for a list of
1722 commands in that class.
1723 Type "help" followed by command name for full
1725 Command name abbreviations are allowed if unambiguous.
1728 @c the above line break eliminates huge line overfull...
1730 @item help @var{class}
1731 Using one of the general help classes as an argument, you can get a
1732 list of the individual commands in that class. For example, here is the
1733 help display for the class @code{status}:
1736 (@value{GDBP}) help status
1741 @c Line break in "show" line falsifies real output, but needed
1742 @c to fit in smallbook page size.
1743 info -- Generic command for showing things
1744 about the program being debugged
1745 show -- Generic command for showing things
1748 Type "help" followed by command name for full
1750 Command name abbreviations are allowed if unambiguous.
1754 @item help @var{command}
1755 With a command name as @code{help} argument, @value{GDBN} displays a
1756 short paragraph on how to use that command.
1759 @item apropos @var{args}
1760 The @code{apropos} command searches through all of the @value{GDBN}
1761 commands, and their documentation, for the regular expression specified in
1762 @var{args}. It prints out all matches found. For example:
1773 alias -- Define a new command that is an alias of an existing command
1774 aliases -- Aliases of other commands
1775 d -- Delete some breakpoints or auto-display expressions
1776 del -- Delete some breakpoints or auto-display expressions
1777 delete -- Delete some breakpoints or auto-display expressions
1782 @item complete @var{args}
1783 The @code{complete @var{args}} command lists all the possible completions
1784 for the beginning of a command. Use @var{args} to specify the beginning of the
1785 command you want completed. For example:
1791 @noindent results in:
1802 @noindent This is intended for use by @sc{gnu} Emacs.
1805 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1806 and @code{show} to inquire about the state of your program, or the state
1807 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1808 manual introduces each of them in the appropriate context. The listings
1809 under @code{info} and under @code{show} in the Command, Variable, and
1810 Function Index point to all the sub-commands. @xref{Command and Variable
1816 @kindex i @r{(@code{info})}
1818 This command (abbreviated @code{i}) is for describing the state of your
1819 program. For example, you can show the arguments passed to a function
1820 with @code{info args}, list the registers currently in use with @code{info
1821 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1822 You can get a complete list of the @code{info} sub-commands with
1823 @w{@code{help info}}.
1827 You can assign the result of an expression to an environment variable with
1828 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1829 @code{set prompt $}.
1833 In contrast to @code{info}, @code{show} is for describing the state of
1834 @value{GDBN} itself.
1835 You can change most of the things you can @code{show}, by using the
1836 related command @code{set}; for example, you can control what number
1837 system is used for displays with @code{set radix}, or simply inquire
1838 which is currently in use with @code{show radix}.
1841 To display all the settable parameters and their current
1842 values, you can use @code{show} with no arguments; you may also use
1843 @code{info set}. Both commands produce the same display.
1844 @c FIXME: "info set" violates the rule that "info" is for state of
1845 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1846 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1850 Here are three miscellaneous @code{show} subcommands, all of which are
1851 exceptional in lacking corresponding @code{set} commands:
1854 @kindex show version
1855 @cindex @value{GDBN} version number
1857 Show what version of @value{GDBN} is running. You should include this
1858 information in @value{GDBN} bug-reports. If multiple versions of
1859 @value{GDBN} are in use at your site, you may need to determine which
1860 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1861 commands are introduced, and old ones may wither away. Also, many
1862 system vendors ship variant versions of @value{GDBN}, and there are
1863 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1864 The version number is the same as the one announced when you start
1867 @kindex show copying
1868 @kindex info copying
1869 @cindex display @value{GDBN} copyright
1872 Display information about permission for copying @value{GDBN}.
1874 @kindex show warranty
1875 @kindex info warranty
1877 @itemx info warranty
1878 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1879 if your version of @value{GDBN} comes with one.
1884 @chapter Running Programs Under @value{GDBN}
1886 When you run a program under @value{GDBN}, you must first generate
1887 debugging information when you compile it.
1889 You may start @value{GDBN} with its arguments, if any, in an environment
1890 of your choice. If you are doing native debugging, you may redirect
1891 your program's input and output, debug an already running process, or
1892 kill a child process.
1895 * Compilation:: Compiling for debugging
1896 * Starting:: Starting your program
1897 * Arguments:: Your program's arguments
1898 * Environment:: Your program's environment
1900 * Working Directory:: Your program's working directory
1901 * Input/Output:: Your program's input and output
1902 * Attach:: Debugging an already-running process
1903 * Kill Process:: Killing the child process
1905 * Inferiors and Programs:: Debugging multiple inferiors and programs
1906 * Threads:: Debugging programs with multiple threads
1907 * Forks:: Debugging forks
1908 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1912 @section Compiling for Debugging
1914 In order to debug a program effectively, you need to generate
1915 debugging information when you compile it. This debugging information
1916 is stored in the object file; it describes the data type of each
1917 variable or function and the correspondence between source line numbers
1918 and addresses in the executable code.
1920 To request debugging information, specify the @samp{-g} option when you run
1923 Programs that are to be shipped to your customers are compiled with
1924 optimizations, using the @samp{-O} compiler option. However, some
1925 compilers are unable to handle the @samp{-g} and @samp{-O} options
1926 together. Using those compilers, you cannot generate optimized
1927 executables containing debugging information.
1929 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1930 without @samp{-O}, making it possible to debug optimized code. We
1931 recommend that you @emph{always} use @samp{-g} whenever you compile a
1932 program. You may think your program is correct, but there is no sense
1933 in pushing your luck. For more information, see @ref{Optimized Code}.
1935 Older versions of the @sc{gnu} C compiler permitted a variant option
1936 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1937 format; if your @sc{gnu} C compiler has this option, do not use it.
1939 @value{GDBN} knows about preprocessor macros and can show you their
1940 expansion (@pxref{Macros}). Most compilers do not include information
1941 about preprocessor macros in the debugging information if you specify
1942 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1943 the @sc{gnu} C compiler, provides macro information if you are using
1944 the DWARF debugging format, and specify the option @option{-g3}.
1946 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1947 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1948 information on @value{NGCC} options affecting debug information.
1950 You will have the best debugging experience if you use the latest
1951 version of the DWARF debugging format that your compiler supports.
1952 DWARF is currently the most expressive and best supported debugging
1953 format in @value{GDBN}.
1957 @section Starting your Program
1963 @kindex r @r{(@code{run})}
1966 Use the @code{run} command to start your program under @value{GDBN}.
1967 You must first specify the program name (except on VxWorks) with an
1968 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1969 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1970 (@pxref{Files, ,Commands to Specify Files}).
1974 If you are running your program in an execution environment that
1975 supports processes, @code{run} creates an inferior process and makes
1976 that process run your program. In some environments without processes,
1977 @code{run} jumps to the start of your program. Other targets,
1978 like @samp{remote}, are always running. If you get an error
1979 message like this one:
1982 The "remote" target does not support "run".
1983 Try "help target" or "continue".
1987 then use @code{continue} to run your program. You may need @code{load}
1988 first (@pxref{load}).
1990 The execution of a program is affected by certain information it
1991 receives from its superior. @value{GDBN} provides ways to specify this
1992 information, which you must do @emph{before} starting your program. (You
1993 can change it after starting your program, but such changes only affect
1994 your program the next time you start it.) This information may be
1995 divided into four categories:
1998 @item The @emph{arguments.}
1999 Specify the arguments to give your program as the arguments of the
2000 @code{run} command. If a shell is available on your target, the shell
2001 is used to pass the arguments, so that you may use normal conventions
2002 (such as wildcard expansion or variable substitution) in describing
2004 In Unix systems, you can control which shell is used with the
2005 @code{SHELL} environment variable.
2006 @xref{Arguments, ,Your Program's Arguments}.
2008 @item The @emph{environment.}
2009 Your program normally inherits its environment from @value{GDBN}, but you can
2010 use the @value{GDBN} commands @code{set environment} and @code{unset
2011 environment} to change parts of the environment that affect
2012 your program. @xref{Environment, ,Your Program's Environment}.
2014 @item The @emph{working directory.}
2015 Your program inherits its working directory from @value{GDBN}. You can set
2016 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2017 @xref{Working Directory, ,Your Program's Working Directory}.
2019 @item The @emph{standard input and output.}
2020 Your program normally uses the same device for standard input and
2021 standard output as @value{GDBN} is using. You can redirect input and output
2022 in the @code{run} command line, or you can use the @code{tty} command to
2023 set a different device for your program.
2024 @xref{Input/Output, ,Your Program's Input and Output}.
2027 @emph{Warning:} While input and output redirection work, you cannot use
2028 pipes to pass the output of the program you are debugging to another
2029 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2033 When you issue the @code{run} command, your program begins to execute
2034 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2035 of how to arrange for your program to stop. Once your program has
2036 stopped, you may call functions in your program, using the @code{print}
2037 or @code{call} commands. @xref{Data, ,Examining Data}.
2039 If the modification time of your symbol file has changed since the last
2040 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2041 table, and reads it again. When it does this, @value{GDBN} tries to retain
2042 your current breakpoints.
2047 @cindex run to main procedure
2048 The name of the main procedure can vary from language to language.
2049 With C or C@t{++}, the main procedure name is always @code{main}, but
2050 other languages such as Ada do not require a specific name for their
2051 main procedure. The debugger provides a convenient way to start the
2052 execution of the program and to stop at the beginning of the main
2053 procedure, depending on the language used.
2055 The @samp{start} command does the equivalent of setting a temporary
2056 breakpoint at the beginning of the main procedure and then invoking
2057 the @samp{run} command.
2059 @cindex elaboration phase
2060 Some programs contain an @dfn{elaboration} phase where some startup code is
2061 executed before the main procedure is called. This depends on the
2062 languages used to write your program. In C@t{++}, for instance,
2063 constructors for static and global objects are executed before
2064 @code{main} is called. It is therefore possible that the debugger stops
2065 before reaching the main procedure. However, the temporary breakpoint
2066 will remain to halt execution.
2068 Specify the arguments to give to your program as arguments to the
2069 @samp{start} command. These arguments will be given verbatim to the
2070 underlying @samp{run} command. Note that the same arguments will be
2071 reused if no argument is provided during subsequent calls to
2072 @samp{start} or @samp{run}.
2074 It is sometimes necessary to debug the program during elaboration. In
2075 these cases, using the @code{start} command would stop the execution of
2076 your program too late, as the program would have already completed the
2077 elaboration phase. Under these circumstances, insert breakpoints in your
2078 elaboration code before running your program.
2080 @kindex set exec-wrapper
2081 @item set exec-wrapper @var{wrapper}
2082 @itemx show exec-wrapper
2083 @itemx unset exec-wrapper
2084 When @samp{exec-wrapper} is set, the specified wrapper is used to
2085 launch programs for debugging. @value{GDBN} starts your program
2086 with a shell command of the form @kbd{exec @var{wrapper}
2087 @var{program}}. Quoting is added to @var{program} and its
2088 arguments, but not to @var{wrapper}, so you should add quotes if
2089 appropriate for your shell. The wrapper runs until it executes
2090 your program, and then @value{GDBN} takes control.
2092 You can use any program that eventually calls @code{execve} with
2093 its arguments as a wrapper. Several standard Unix utilities do
2094 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2095 with @code{exec "$@@"} will also work.
2097 For example, you can use @code{env} to pass an environment variable to
2098 the debugged program, without setting the variable in your shell's
2102 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2106 This command is available when debugging locally on most targets, excluding
2107 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2109 @kindex set disable-randomization
2110 @item set disable-randomization
2111 @itemx set disable-randomization on
2112 This option (enabled by default in @value{GDBN}) will turn off the native
2113 randomization of the virtual address space of the started program. This option
2114 is useful for multiple debugging sessions to make the execution better
2115 reproducible and memory addresses reusable across debugging sessions.
2117 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2118 On @sc{gnu}/Linux you can get the same behavior using
2121 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2124 @item set disable-randomization off
2125 Leave the behavior of the started executable unchanged. Some bugs rear their
2126 ugly heads only when the program is loaded at certain addresses. If your bug
2127 disappears when you run the program under @value{GDBN}, that might be because
2128 @value{GDBN} by default disables the address randomization on platforms, such
2129 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2130 disable-randomization off} to try to reproduce such elusive bugs.
2132 On targets where it is available, virtual address space randomization
2133 protects the programs against certain kinds of security attacks. In these
2134 cases the attacker needs to know the exact location of a concrete executable
2135 code. Randomizing its location makes it impossible to inject jumps misusing
2136 a code at its expected addresses.
2138 Prelinking shared libraries provides a startup performance advantage but it
2139 makes addresses in these libraries predictable for privileged processes by
2140 having just unprivileged access at the target system. Reading the shared
2141 library binary gives enough information for assembling the malicious code
2142 misusing it. Still even a prelinked shared library can get loaded at a new
2143 random address just requiring the regular relocation process during the
2144 startup. Shared libraries not already prelinked are always loaded at
2145 a randomly chosen address.
2147 Position independent executables (PIE) contain position independent code
2148 similar to the shared libraries and therefore such executables get loaded at
2149 a randomly chosen address upon startup. PIE executables always load even
2150 already prelinked shared libraries at a random address. You can build such
2151 executable using @command{gcc -fPIE -pie}.
2153 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2154 (as long as the randomization is enabled).
2156 @item show disable-randomization
2157 Show the current setting of the explicit disable of the native randomization of
2158 the virtual address space of the started program.
2163 @section Your Program's Arguments
2165 @cindex arguments (to your program)
2166 The arguments to your program can be specified by the arguments of the
2168 They are passed to a shell, which expands wildcard characters and
2169 performs redirection of I/O, and thence to your program. Your
2170 @code{SHELL} environment variable (if it exists) specifies what shell
2171 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2172 the default shell (@file{/bin/sh} on Unix).
2174 On non-Unix systems, the program is usually invoked directly by
2175 @value{GDBN}, which emulates I/O redirection via the appropriate system
2176 calls, and the wildcard characters are expanded by the startup code of
2177 the program, not by the shell.
2179 @code{run} with no arguments uses the same arguments used by the previous
2180 @code{run}, or those set by the @code{set args} command.
2185 Specify the arguments to be used the next time your program is run. If
2186 @code{set args} has no arguments, @code{run} executes your program
2187 with no arguments. Once you have run your program with arguments,
2188 using @code{set args} before the next @code{run} is the only way to run
2189 it again without arguments.
2193 Show the arguments to give your program when it is started.
2197 @section Your Program's Environment
2199 @cindex environment (of your program)
2200 The @dfn{environment} consists of a set of environment variables and
2201 their values. Environment variables conventionally record such things as
2202 your user name, your home directory, your terminal type, and your search
2203 path for programs to run. Usually you set up environment variables with
2204 the shell and they are inherited by all the other programs you run. When
2205 debugging, it can be useful to try running your program with a modified
2206 environment without having to start @value{GDBN} over again.
2210 @item path @var{directory}
2211 Add @var{directory} to the front of the @code{PATH} environment variable
2212 (the search path for executables) that will be passed to your program.
2213 The value of @code{PATH} used by @value{GDBN} does not change.
2214 You may specify several directory names, separated by whitespace or by a
2215 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2216 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2217 is moved to the front, so it is searched sooner.
2219 You can use the string @samp{$cwd} to refer to whatever is the current
2220 working directory at the time @value{GDBN} searches the path. If you
2221 use @samp{.} instead, it refers to the directory where you executed the
2222 @code{path} command. @value{GDBN} replaces @samp{.} in the
2223 @var{directory} argument (with the current path) before adding
2224 @var{directory} to the search path.
2225 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2226 @c document that, since repeating it would be a no-op.
2230 Display the list of search paths for executables (the @code{PATH}
2231 environment variable).
2233 @kindex show environment
2234 @item show environment @r{[}@var{varname}@r{]}
2235 Print the value of environment variable @var{varname} to be given to
2236 your program when it starts. If you do not supply @var{varname},
2237 print the names and values of all environment variables to be given to
2238 your program. You can abbreviate @code{environment} as @code{env}.
2240 @kindex set environment
2241 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2242 Set environment variable @var{varname} to @var{value}. The value
2243 changes for your program only, not for @value{GDBN} itself. @var{value} may
2244 be any string; the values of environment variables are just strings, and
2245 any interpretation is supplied by your program itself. The @var{value}
2246 parameter is optional; if it is eliminated, the variable is set to a
2248 @c "any string" here does not include leading, trailing
2249 @c blanks. Gnu asks: does anyone care?
2251 For example, this command:
2258 tells the debugged program, when subsequently run, that its user is named
2259 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2260 are not actually required.)
2262 @kindex unset environment
2263 @item unset environment @var{varname}
2264 Remove variable @var{varname} from the environment to be passed to your
2265 program. This is different from @samp{set env @var{varname} =};
2266 @code{unset environment} removes the variable from the environment,
2267 rather than assigning it an empty value.
2270 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2272 by your @code{SHELL} environment variable if it exists (or
2273 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2274 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2275 @file{.bashrc} for BASH---any variables you set in that file affect
2276 your program. You may wish to move setting of environment variables to
2277 files that are only run when you sign on, such as @file{.login} or
2280 @node Working Directory
2281 @section Your Program's Working Directory
2283 @cindex working directory (of your program)
2284 Each time you start your program with @code{run}, it inherits its
2285 working directory from the current working directory of @value{GDBN}.
2286 The @value{GDBN} working directory is initially whatever it inherited
2287 from its parent process (typically the shell), but you can specify a new
2288 working directory in @value{GDBN} with the @code{cd} command.
2290 The @value{GDBN} working directory also serves as a default for the commands
2291 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2296 @cindex change working directory
2297 @item cd @r{[}@var{directory}@r{]}
2298 Set the @value{GDBN} working directory to @var{directory}. If not
2299 given, @var{directory} uses @file{'~'}.
2303 Print the @value{GDBN} working directory.
2306 It is generally impossible to find the current working directory of
2307 the process being debugged (since a program can change its directory
2308 during its run). If you work on a system where @value{GDBN} is
2309 configured with the @file{/proc} support, you can use the @code{info
2310 proc} command (@pxref{SVR4 Process Information}) to find out the
2311 current working directory of the debuggee.
2314 @section Your Program's Input and Output
2319 By default, the program you run under @value{GDBN} does input and output to
2320 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2321 to its own terminal modes to interact with you, but it records the terminal
2322 modes your program was using and switches back to them when you continue
2323 running your program.
2326 @kindex info terminal
2328 Displays information recorded by @value{GDBN} about the terminal modes your
2332 You can redirect your program's input and/or output using shell
2333 redirection with the @code{run} command. For example,
2340 starts your program, diverting its output to the file @file{outfile}.
2343 @cindex controlling terminal
2344 Another way to specify where your program should do input and output is
2345 with the @code{tty} command. This command accepts a file name as
2346 argument, and causes this file to be the default for future @code{run}
2347 commands. It also resets the controlling terminal for the child
2348 process, for future @code{run} commands. For example,
2355 directs that processes started with subsequent @code{run} commands
2356 default to do input and output on the terminal @file{/dev/ttyb} and have
2357 that as their controlling terminal.
2359 An explicit redirection in @code{run} overrides the @code{tty} command's
2360 effect on the input/output device, but not its effect on the controlling
2363 When you use the @code{tty} command or redirect input in the @code{run}
2364 command, only the input @emph{for your program} is affected. The input
2365 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2366 for @code{set inferior-tty}.
2368 @cindex inferior tty
2369 @cindex set inferior controlling terminal
2370 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2371 display the name of the terminal that will be used for future runs of your
2375 @item set inferior-tty /dev/ttyb
2376 @kindex set inferior-tty
2377 Set the tty for the program being debugged to /dev/ttyb.
2379 @item show inferior-tty
2380 @kindex show inferior-tty
2381 Show the current tty for the program being debugged.
2385 @section Debugging an Already-running Process
2390 @item attach @var{process-id}
2391 This command attaches to a running process---one that was started
2392 outside @value{GDBN}. (@code{info files} shows your active
2393 targets.) The command takes as argument a process ID. The usual way to
2394 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2395 or with the @samp{jobs -l} shell command.
2397 @code{attach} does not repeat if you press @key{RET} a second time after
2398 executing the command.
2401 To use @code{attach}, your program must be running in an environment
2402 which supports processes; for example, @code{attach} does not work for
2403 programs on bare-board targets that lack an operating system. You must
2404 also have permission to send the process a signal.
2406 When you use @code{attach}, the debugger finds the program running in
2407 the process first by looking in the current working directory, then (if
2408 the program is not found) by using the source file search path
2409 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2410 the @code{file} command to load the program. @xref{Files, ,Commands to
2413 The first thing @value{GDBN} does after arranging to debug the specified
2414 process is to stop it. You can examine and modify an attached process
2415 with all the @value{GDBN} commands that are ordinarily available when
2416 you start processes with @code{run}. You can insert breakpoints; you
2417 can step and continue; you can modify storage. If you would rather the
2418 process continue running, you may use the @code{continue} command after
2419 attaching @value{GDBN} to the process.
2424 When you have finished debugging the attached process, you can use the
2425 @code{detach} command to release it from @value{GDBN} control. Detaching
2426 the process continues its execution. After the @code{detach} command,
2427 that process and @value{GDBN} become completely independent once more, and you
2428 are ready to @code{attach} another process or start one with @code{run}.
2429 @code{detach} does not repeat if you press @key{RET} again after
2430 executing the command.
2433 If you exit @value{GDBN} while you have an attached process, you detach
2434 that process. If you use the @code{run} command, you kill that process.
2435 By default, @value{GDBN} asks for confirmation if you try to do either of these
2436 things; you can control whether or not you need to confirm by using the
2437 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2441 @section Killing the Child Process
2446 Kill the child process in which your program is running under @value{GDBN}.
2449 This command is useful if you wish to debug a core dump instead of a
2450 running process. @value{GDBN} ignores any core dump file while your program
2453 On some operating systems, a program cannot be executed outside @value{GDBN}
2454 while you have breakpoints set on it inside @value{GDBN}. You can use the
2455 @code{kill} command in this situation to permit running your program
2456 outside the debugger.
2458 The @code{kill} command is also useful if you wish to recompile and
2459 relink your program, since on many systems it is impossible to modify an
2460 executable file while it is running in a process. In this case, when you
2461 next type @code{run}, @value{GDBN} notices that the file has changed, and
2462 reads the symbol table again (while trying to preserve your current
2463 breakpoint settings).
2465 @node Inferiors and Programs
2466 @section Debugging Multiple Inferiors and Programs
2468 @value{GDBN} lets you run and debug multiple programs in a single
2469 session. In addition, @value{GDBN} on some systems may let you run
2470 several programs simultaneously (otherwise you have to exit from one
2471 before starting another). In the most general case, you can have
2472 multiple threads of execution in each of multiple processes, launched
2473 from multiple executables.
2476 @value{GDBN} represents the state of each program execution with an
2477 object called an @dfn{inferior}. An inferior typically corresponds to
2478 a process, but is more general and applies also to targets that do not
2479 have processes. Inferiors may be created before a process runs, and
2480 may be retained after a process exits. Inferiors have unique
2481 identifiers that are different from process ids. Usually each
2482 inferior will also have its own distinct address space, although some
2483 embedded targets may have several inferiors running in different parts
2484 of a single address space. Each inferior may in turn have multiple
2485 threads running in it.
2487 To find out what inferiors exist at any moment, use @w{@code{info
2491 @kindex info inferiors
2492 @item info inferiors
2493 Print a list of all inferiors currently being managed by @value{GDBN}.
2495 @value{GDBN} displays for each inferior (in this order):
2499 the inferior number assigned by @value{GDBN}
2502 the target system's inferior identifier
2505 the name of the executable the inferior is running.
2510 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2511 indicates the current inferior.
2515 @c end table here to get a little more width for example
2518 (@value{GDBP}) info inferiors
2519 Num Description Executable
2520 2 process 2307 hello
2521 * 1 process 3401 goodbye
2524 To switch focus between inferiors, use the @code{inferior} command:
2527 @kindex inferior @var{infno}
2528 @item inferior @var{infno}
2529 Make inferior number @var{infno} the current inferior. The argument
2530 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2531 in the first field of the @samp{info inferiors} display.
2535 You can get multiple executables into a debugging session via the
2536 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2537 systems @value{GDBN} can add inferiors to the debug session
2538 automatically by following calls to @code{fork} and @code{exec}. To
2539 remove inferiors from the debugging session use the
2540 @w{@code{remove-inferiors}} command.
2543 @kindex add-inferior
2544 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2545 Adds @var{n} inferiors to be run using @var{executable} as the
2546 executable. @var{n} defaults to 1. If no executable is specified,
2547 the inferiors begins empty, with no program. You can still assign or
2548 change the program assigned to the inferior at any time by using the
2549 @code{file} command with the executable name as its argument.
2551 @kindex clone-inferior
2552 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2553 Adds @var{n} inferiors ready to execute the same program as inferior
2554 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2555 number of the current inferior. This is a convenient command when you
2556 want to run another instance of the inferior you are debugging.
2559 (@value{GDBP}) info inferiors
2560 Num Description Executable
2561 * 1 process 29964 helloworld
2562 (@value{GDBP}) clone-inferior
2565 (@value{GDBP}) info inferiors
2566 Num Description Executable
2568 * 1 process 29964 helloworld
2571 You can now simply switch focus to inferior 2 and run it.
2573 @kindex remove-inferiors
2574 @item remove-inferiors @var{infno}@dots{}
2575 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2576 possible to remove an inferior that is running with this command. For
2577 those, use the @code{kill} or @code{detach} command first.
2581 To quit debugging one of the running inferiors that is not the current
2582 inferior, you can either detach from it by using the @w{@code{detach
2583 inferior}} command (allowing it to run independently), or kill it
2584 using the @w{@code{kill inferiors}} command:
2587 @kindex detach inferiors @var{infno}@dots{}
2588 @item detach inferior @var{infno}@dots{}
2589 Detach from the inferior or inferiors identified by @value{GDBN}
2590 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2591 still stays on the list of inferiors shown by @code{info inferiors},
2592 but its Description will show @samp{<null>}.
2594 @kindex kill inferiors @var{infno}@dots{}
2595 @item kill inferiors @var{infno}@dots{}
2596 Kill the inferior or inferiors identified by @value{GDBN} inferior
2597 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2598 stays on the list of inferiors shown by @code{info inferiors}, but its
2599 Description will show @samp{<null>}.
2602 After the successful completion of a command such as @code{detach},
2603 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2604 a normal process exit, the inferior is still valid and listed with
2605 @code{info inferiors}, ready to be restarted.
2608 To be notified when inferiors are started or exit under @value{GDBN}'s
2609 control use @w{@code{set print inferior-events}}:
2612 @kindex set print inferior-events
2613 @cindex print messages on inferior start and exit
2614 @item set print inferior-events
2615 @itemx set print inferior-events on
2616 @itemx set print inferior-events off
2617 The @code{set print inferior-events} command allows you to enable or
2618 disable printing of messages when @value{GDBN} notices that new
2619 inferiors have started or that inferiors have exited or have been
2620 detached. By default, these messages will not be printed.
2622 @kindex show print inferior-events
2623 @item show print inferior-events
2624 Show whether messages will be printed when @value{GDBN} detects that
2625 inferiors have started, exited or have been detached.
2628 Many commands will work the same with multiple programs as with a
2629 single program: e.g., @code{print myglobal} will simply display the
2630 value of @code{myglobal} in the current inferior.
2633 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2634 get more info about the relationship of inferiors, programs, address
2635 spaces in a debug session. You can do that with the @w{@code{maint
2636 info program-spaces}} command.
2639 @kindex maint info program-spaces
2640 @item maint info program-spaces
2641 Print a list of all program spaces currently being managed by
2644 @value{GDBN} displays for each program space (in this order):
2648 the program space number assigned by @value{GDBN}
2651 the name of the executable loaded into the program space, with e.g.,
2652 the @code{file} command.
2657 An asterisk @samp{*} preceding the @value{GDBN} program space number
2658 indicates the current program space.
2660 In addition, below each program space line, @value{GDBN} prints extra
2661 information that isn't suitable to display in tabular form. For
2662 example, the list of inferiors bound to the program space.
2665 (@value{GDBP}) maint info program-spaces
2668 Bound inferiors: ID 1 (process 21561)
2672 Here we can see that no inferior is running the program @code{hello},
2673 while @code{process 21561} is running the program @code{goodbye}. On
2674 some targets, it is possible that multiple inferiors are bound to the
2675 same program space. The most common example is that of debugging both
2676 the parent and child processes of a @code{vfork} call. For example,
2679 (@value{GDBP}) maint info program-spaces
2682 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2685 Here, both inferior 2 and inferior 1 are running in the same program
2686 space as a result of inferior 1 having executed a @code{vfork} call.
2690 @section Debugging Programs with Multiple Threads
2692 @cindex threads of execution
2693 @cindex multiple threads
2694 @cindex switching threads
2695 In some operating systems, such as HP-UX and Solaris, a single program
2696 may have more than one @dfn{thread} of execution. The precise semantics
2697 of threads differ from one operating system to another, but in general
2698 the threads of a single program are akin to multiple processes---except
2699 that they share one address space (that is, they can all examine and
2700 modify the same variables). On the other hand, each thread has its own
2701 registers and execution stack, and perhaps private memory.
2703 @value{GDBN} provides these facilities for debugging multi-thread
2707 @item automatic notification of new threads
2708 @item @samp{thread @var{threadno}}, a command to switch among threads
2709 @item @samp{info threads}, a command to inquire about existing threads
2710 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2711 a command to apply a command to a list of threads
2712 @item thread-specific breakpoints
2713 @item @samp{set print thread-events}, which controls printing of
2714 messages on thread start and exit.
2715 @item @samp{set libthread-db-search-path @var{path}}, which lets
2716 the user specify which @code{libthread_db} to use if the default choice
2717 isn't compatible with the program.
2721 @emph{Warning:} These facilities are not yet available on every
2722 @value{GDBN} configuration where the operating system supports threads.
2723 If your @value{GDBN} does not support threads, these commands have no
2724 effect. For example, a system without thread support shows no output
2725 from @samp{info threads}, and always rejects the @code{thread} command,
2729 (@value{GDBP}) info threads
2730 (@value{GDBP}) thread 1
2731 Thread ID 1 not known. Use the "info threads" command to
2732 see the IDs of currently known threads.
2734 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2735 @c doesn't support threads"?
2738 @cindex focus of debugging
2739 @cindex current thread
2740 The @value{GDBN} thread debugging facility allows you to observe all
2741 threads while your program runs---but whenever @value{GDBN} takes
2742 control, one thread in particular is always the focus of debugging.
2743 This thread is called the @dfn{current thread}. Debugging commands show
2744 program information from the perspective of the current thread.
2746 @cindex @code{New} @var{systag} message
2747 @cindex thread identifier (system)
2748 @c FIXME-implementors!! It would be more helpful if the [New...] message
2749 @c included GDB's numeric thread handle, so you could just go to that
2750 @c thread without first checking `info threads'.
2751 Whenever @value{GDBN} detects a new thread in your program, it displays
2752 the target system's identification for the thread with a message in the
2753 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2754 whose form varies depending on the particular system. For example, on
2755 @sc{gnu}/Linux, you might see
2758 [New Thread 0x41e02940 (LWP 25582)]
2762 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2763 the @var{systag} is simply something like @samp{process 368}, with no
2766 @c FIXME!! (1) Does the [New...] message appear even for the very first
2767 @c thread of a program, or does it only appear for the
2768 @c second---i.e.@: when it becomes obvious we have a multithread
2770 @c (2) *Is* there necessarily a first thread always? Or do some
2771 @c multithread systems permit starting a program with multiple
2772 @c threads ab initio?
2774 @cindex thread number
2775 @cindex thread identifier (GDB)
2776 For debugging purposes, @value{GDBN} associates its own thread
2777 number---always a single integer---with each thread in your program.
2780 @kindex info threads
2781 @item info threads @r{[}@var{id}@dots{}@r{]}
2782 Display a summary of all threads currently in your program. Optional
2783 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2784 means to print information only about the specified thread or threads.
2785 @value{GDBN} displays for each thread (in this order):
2789 the thread number assigned by @value{GDBN}
2792 the target system's thread identifier (@var{systag})
2795 the thread's name, if one is known. A thread can either be named by
2796 the user (see @code{thread name}, below), or, in some cases, by the
2800 the current stack frame summary for that thread
2804 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2805 indicates the current thread.
2809 @c end table here to get a little more width for example
2812 (@value{GDBP}) info threads
2814 3 process 35 thread 27 0x34e5 in sigpause ()
2815 2 process 35 thread 23 0x34e5 in sigpause ()
2816 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2820 On Solaris, you can display more information about user threads with a
2821 Solaris-specific command:
2824 @item maint info sol-threads
2825 @kindex maint info sol-threads
2826 @cindex thread info (Solaris)
2827 Display info on Solaris user threads.
2831 @kindex thread @var{threadno}
2832 @item thread @var{threadno}
2833 Make thread number @var{threadno} the current thread. The command
2834 argument @var{threadno} is the internal @value{GDBN} thread number, as
2835 shown in the first field of the @samp{info threads} display.
2836 @value{GDBN} responds by displaying the system identifier of the thread
2837 you selected, and its current stack frame summary:
2840 (@value{GDBP}) thread 2
2841 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2842 #0 some_function (ignore=0x0) at example.c:8
2843 8 printf ("hello\n");
2847 As with the @samp{[New @dots{}]} message, the form of the text after
2848 @samp{Switching to} depends on your system's conventions for identifying
2851 @vindex $_thread@r{, convenience variable}
2852 The debugger convenience variable @samp{$_thread} contains the number
2853 of the current thread. You may find this useful in writing breakpoint
2854 conditional expressions, command scripts, and so forth. See
2855 @xref{Convenience Vars,, Convenience Variables}, for general
2856 information on convenience variables.
2858 @kindex thread apply
2859 @cindex apply command to several threads
2860 @item thread apply [@var{threadno} | all] @var{command}
2861 The @code{thread apply} command allows you to apply the named
2862 @var{command} to one or more threads. Specify the numbers of the
2863 threads that you want affected with the command argument
2864 @var{threadno}. It can be a single thread number, one of the numbers
2865 shown in the first field of the @samp{info threads} display; or it
2866 could be a range of thread numbers, as in @code{2-4}. To apply a
2867 command to all threads, type @kbd{thread apply all @var{command}}.
2870 @cindex name a thread
2871 @item thread name [@var{name}]
2872 This command assigns a name to the current thread. If no argument is
2873 given, any existing user-specified name is removed. The thread name
2874 appears in the @samp{info threads} display.
2876 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2877 determine the name of the thread as given by the OS. On these
2878 systems, a name specified with @samp{thread name} will override the
2879 system-give name, and removing the user-specified name will cause
2880 @value{GDBN} to once again display the system-specified name.
2883 @cindex search for a thread
2884 @item thread find [@var{regexp}]
2885 Search for and display thread ids whose name or @var{systag}
2886 matches the supplied regular expression.
2888 As well as being the complement to the @samp{thread name} command,
2889 this command also allows you to identify a thread by its target
2890 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2894 (@value{GDBN}) thread find 26688
2895 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2896 (@value{GDBN}) info thread 4
2898 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2901 @kindex set print thread-events
2902 @cindex print messages on thread start and exit
2903 @item set print thread-events
2904 @itemx set print thread-events on
2905 @itemx set print thread-events off
2906 The @code{set print thread-events} command allows you to enable or
2907 disable printing of messages when @value{GDBN} notices that new threads have
2908 started or that threads have exited. By default, these messages will
2909 be printed if detection of these events is supported by the target.
2910 Note that these messages cannot be disabled on all targets.
2912 @kindex show print thread-events
2913 @item show print thread-events
2914 Show whether messages will be printed when @value{GDBN} detects that threads
2915 have started and exited.
2918 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2919 more information about how @value{GDBN} behaves when you stop and start
2920 programs with multiple threads.
2922 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2923 watchpoints in programs with multiple threads.
2925 @anchor{set libthread-db-search-path}
2927 @kindex set libthread-db-search-path
2928 @cindex search path for @code{libthread_db}
2929 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2930 If this variable is set, @var{path} is a colon-separated list of
2931 directories @value{GDBN} will use to search for @code{libthread_db}.
2932 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2933 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2934 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2937 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2938 @code{libthread_db} library to obtain information about threads in the
2939 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2940 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
2941 specific thread debugging library loading is enabled
2942 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
2944 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2945 refers to the default system directories that are
2946 normally searched for loading shared libraries. The @samp{$sdir} entry
2947 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
2948 (@pxref{libthread_db.so.1 file}).
2950 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2951 refers to the directory from which @code{libpthread}
2952 was loaded in the inferior process.
2954 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2955 @value{GDBN} attempts to initialize it with the current inferior process.
2956 If this initialization fails (which could happen because of a version
2957 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2958 will unload @code{libthread_db}, and continue with the next directory.
2959 If none of @code{libthread_db} libraries initialize successfully,
2960 @value{GDBN} will issue a warning and thread debugging will be disabled.
2962 Setting @code{libthread-db-search-path} is currently implemented
2963 only on some platforms.
2965 @kindex show libthread-db-search-path
2966 @item show libthread-db-search-path
2967 Display current libthread_db search path.
2969 @kindex set debug libthread-db
2970 @kindex show debug libthread-db
2971 @cindex debugging @code{libthread_db}
2972 @item set debug libthread-db
2973 @itemx show debug libthread-db
2974 Turns on or off display of @code{libthread_db}-related events.
2975 Use @code{1} to enable, @code{0} to disable.
2979 @section Debugging Forks
2981 @cindex fork, debugging programs which call
2982 @cindex multiple processes
2983 @cindex processes, multiple
2984 On most systems, @value{GDBN} has no special support for debugging
2985 programs which create additional processes using the @code{fork}
2986 function. When a program forks, @value{GDBN} will continue to debug the
2987 parent process and the child process will run unimpeded. If you have
2988 set a breakpoint in any code which the child then executes, the child
2989 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2990 will cause it to terminate.
2992 However, if you want to debug the child process there is a workaround
2993 which isn't too painful. Put a call to @code{sleep} in the code which
2994 the child process executes after the fork. It may be useful to sleep
2995 only if a certain environment variable is set, or a certain file exists,
2996 so that the delay need not occur when you don't want to run @value{GDBN}
2997 on the child. While the child is sleeping, use the @code{ps} program to
2998 get its process ID. Then tell @value{GDBN} (a new invocation of
2999 @value{GDBN} if you are also debugging the parent process) to attach to
3000 the child process (@pxref{Attach}). From that point on you can debug
3001 the child process just like any other process which you attached to.
3003 On some systems, @value{GDBN} provides support for debugging programs that
3004 create additional processes using the @code{fork} or @code{vfork} functions.
3005 Currently, the only platforms with this feature are HP-UX (11.x and later
3006 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3008 By default, when a program forks, @value{GDBN} will continue to debug
3009 the parent process and the child process will run unimpeded.
3011 If you want to follow the child process instead of the parent process,
3012 use the command @w{@code{set follow-fork-mode}}.
3015 @kindex set follow-fork-mode
3016 @item set follow-fork-mode @var{mode}
3017 Set the debugger response to a program call of @code{fork} or
3018 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3019 process. The @var{mode} argument can be:
3023 The original process is debugged after a fork. The child process runs
3024 unimpeded. This is the default.
3027 The new process is debugged after a fork. The parent process runs
3032 @kindex show follow-fork-mode
3033 @item show follow-fork-mode
3034 Display the current debugger response to a @code{fork} or @code{vfork} call.
3037 @cindex debugging multiple processes
3038 On Linux, if you want to debug both the parent and child processes, use the
3039 command @w{@code{set detach-on-fork}}.
3042 @kindex set detach-on-fork
3043 @item set detach-on-fork @var{mode}
3044 Tells gdb whether to detach one of the processes after a fork, or
3045 retain debugger control over them both.
3049 The child process (or parent process, depending on the value of
3050 @code{follow-fork-mode}) will be detached and allowed to run
3051 independently. This is the default.
3054 Both processes will be held under the control of @value{GDBN}.
3055 One process (child or parent, depending on the value of
3056 @code{follow-fork-mode}) is debugged as usual, while the other
3061 @kindex show detach-on-fork
3062 @item show detach-on-fork
3063 Show whether detach-on-fork mode is on/off.
3066 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3067 will retain control of all forked processes (including nested forks).
3068 You can list the forked processes under the control of @value{GDBN} by
3069 using the @w{@code{info inferiors}} command, and switch from one fork
3070 to another by using the @code{inferior} command (@pxref{Inferiors and
3071 Programs, ,Debugging Multiple Inferiors and Programs}).
3073 To quit debugging one of the forked processes, you can either detach
3074 from it by using the @w{@code{detach inferiors}} command (allowing it
3075 to run independently), or kill it using the @w{@code{kill inferiors}}
3076 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3079 If you ask to debug a child process and a @code{vfork} is followed by an
3080 @code{exec}, @value{GDBN} executes the new target up to the first
3081 breakpoint in the new target. If you have a breakpoint set on
3082 @code{main} in your original program, the breakpoint will also be set on
3083 the child process's @code{main}.
3085 On some systems, when a child process is spawned by @code{vfork}, you
3086 cannot debug the child or parent until an @code{exec} call completes.
3088 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3089 call executes, the new target restarts. To restart the parent
3090 process, use the @code{file} command with the parent executable name
3091 as its argument. By default, after an @code{exec} call executes,
3092 @value{GDBN} discards the symbols of the previous executable image.
3093 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3097 @kindex set follow-exec-mode
3098 @item set follow-exec-mode @var{mode}
3100 Set debugger response to a program call of @code{exec}. An
3101 @code{exec} call replaces the program image of a process.
3103 @code{follow-exec-mode} can be:
3107 @value{GDBN} creates a new inferior and rebinds the process to this
3108 new inferior. The program the process was running before the
3109 @code{exec} call can be restarted afterwards by restarting the
3115 (@value{GDBP}) info inferiors
3117 Id Description Executable
3120 process 12020 is executing new program: prog2
3121 Program exited normally.
3122 (@value{GDBP}) info inferiors
3123 Id Description Executable
3129 @value{GDBN} keeps the process bound to the same inferior. The new
3130 executable image replaces the previous executable loaded in the
3131 inferior. Restarting the inferior after the @code{exec} call, with
3132 e.g., the @code{run} command, restarts the executable the process was
3133 running after the @code{exec} call. This is the default mode.
3138 (@value{GDBP}) info inferiors
3139 Id Description Executable
3142 process 12020 is executing new program: prog2
3143 Program exited normally.
3144 (@value{GDBP}) info inferiors
3145 Id Description Executable
3152 You can use the @code{catch} command to make @value{GDBN} stop whenever
3153 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3154 Catchpoints, ,Setting Catchpoints}.
3156 @node Checkpoint/Restart
3157 @section Setting a @emph{Bookmark} to Return to Later
3162 @cindex snapshot of a process
3163 @cindex rewind program state
3165 On certain operating systems@footnote{Currently, only
3166 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3167 program's state, called a @dfn{checkpoint}, and come back to it
3170 Returning to a checkpoint effectively undoes everything that has
3171 happened in the program since the @code{checkpoint} was saved. This
3172 includes changes in memory, registers, and even (within some limits)
3173 system state. Effectively, it is like going back in time to the
3174 moment when the checkpoint was saved.
3176 Thus, if you're stepping thru a program and you think you're
3177 getting close to the point where things go wrong, you can save
3178 a checkpoint. Then, if you accidentally go too far and miss
3179 the critical statement, instead of having to restart your program
3180 from the beginning, you can just go back to the checkpoint and
3181 start again from there.
3183 This can be especially useful if it takes a lot of time or
3184 steps to reach the point where you think the bug occurs.
3186 To use the @code{checkpoint}/@code{restart} method of debugging:
3191 Save a snapshot of the debugged program's current execution state.
3192 The @code{checkpoint} command takes no arguments, but each checkpoint
3193 is assigned a small integer id, similar to a breakpoint id.
3195 @kindex info checkpoints
3196 @item info checkpoints
3197 List the checkpoints that have been saved in the current debugging
3198 session. For each checkpoint, the following information will be
3205 @item Source line, or label
3208 @kindex restart @var{checkpoint-id}
3209 @item restart @var{checkpoint-id}
3210 Restore the program state that was saved as checkpoint number
3211 @var{checkpoint-id}. All program variables, registers, stack frames
3212 etc.@: will be returned to the values that they had when the checkpoint
3213 was saved. In essence, gdb will ``wind back the clock'' to the point
3214 in time when the checkpoint was saved.
3216 Note that breakpoints, @value{GDBN} variables, command history etc.
3217 are not affected by restoring a checkpoint. In general, a checkpoint
3218 only restores things that reside in the program being debugged, not in
3221 @kindex delete checkpoint @var{checkpoint-id}
3222 @item delete checkpoint @var{checkpoint-id}
3223 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3227 Returning to a previously saved checkpoint will restore the user state
3228 of the program being debugged, plus a significant subset of the system
3229 (OS) state, including file pointers. It won't ``un-write'' data from
3230 a file, but it will rewind the file pointer to the previous location,
3231 so that the previously written data can be overwritten. For files
3232 opened in read mode, the pointer will also be restored so that the
3233 previously read data can be read again.
3235 Of course, characters that have been sent to a printer (or other
3236 external device) cannot be ``snatched back'', and characters received
3237 from eg.@: a serial device can be removed from internal program buffers,
3238 but they cannot be ``pushed back'' into the serial pipeline, ready to
3239 be received again. Similarly, the actual contents of files that have
3240 been changed cannot be restored (at this time).
3242 However, within those constraints, you actually can ``rewind'' your
3243 program to a previously saved point in time, and begin debugging it
3244 again --- and you can change the course of events so as to debug a
3245 different execution path this time.
3247 @cindex checkpoints and process id
3248 Finally, there is one bit of internal program state that will be
3249 different when you return to a checkpoint --- the program's process
3250 id. Each checkpoint will have a unique process id (or @var{pid}),
3251 and each will be different from the program's original @var{pid}.
3252 If your program has saved a local copy of its process id, this could
3253 potentially pose a problem.
3255 @subsection A Non-obvious Benefit of Using Checkpoints
3257 On some systems such as @sc{gnu}/Linux, address space randomization
3258 is performed on new processes for security reasons. This makes it
3259 difficult or impossible to set a breakpoint, or watchpoint, on an
3260 absolute address if you have to restart the program, since the
3261 absolute location of a symbol will change from one execution to the
3264 A checkpoint, however, is an @emph{identical} copy of a process.
3265 Therefore if you create a checkpoint at (eg.@:) the start of main,
3266 and simply return to that checkpoint instead of restarting the
3267 process, you can avoid the effects of address randomization and
3268 your symbols will all stay in the same place.
3271 @chapter Stopping and Continuing
3273 The principal purposes of using a debugger are so that you can stop your
3274 program before it terminates; or so that, if your program runs into
3275 trouble, you can investigate and find out why.
3277 Inside @value{GDBN}, your program may stop for any of several reasons,
3278 such as a signal, a breakpoint, or reaching a new line after a
3279 @value{GDBN} command such as @code{step}. You may then examine and
3280 change variables, set new breakpoints or remove old ones, and then
3281 continue execution. Usually, the messages shown by @value{GDBN} provide
3282 ample explanation of the status of your program---but you can also
3283 explicitly request this information at any time.
3286 @kindex info program
3288 Display information about the status of your program: whether it is
3289 running or not, what process it is, and why it stopped.
3293 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3294 * Continuing and Stepping:: Resuming execution
3295 * Skipping Over Functions and Files::
3296 Skipping over functions and files
3298 * Thread Stops:: Stopping and starting multi-thread programs
3302 @section Breakpoints, Watchpoints, and Catchpoints
3305 A @dfn{breakpoint} makes your program stop whenever a certain point in
3306 the program is reached. For each breakpoint, you can add conditions to
3307 control in finer detail whether your program stops. You can set
3308 breakpoints with the @code{break} command and its variants (@pxref{Set
3309 Breaks, ,Setting Breakpoints}), to specify the place where your program
3310 should stop by line number, function name or exact address in the
3313 On some systems, you can set breakpoints in shared libraries before
3314 the executable is run. There is a minor limitation on HP-UX systems:
3315 you must wait until the executable is run in order to set breakpoints
3316 in shared library routines that are not called directly by the program
3317 (for example, routines that are arguments in a @code{pthread_create}
3321 @cindex data breakpoints
3322 @cindex memory tracing
3323 @cindex breakpoint on memory address
3324 @cindex breakpoint on variable modification
3325 A @dfn{watchpoint} is a special breakpoint that stops your program
3326 when the value of an expression changes. The expression may be a value
3327 of a variable, or it could involve values of one or more variables
3328 combined by operators, such as @samp{a + b}. This is sometimes called
3329 @dfn{data breakpoints}. You must use a different command to set
3330 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3331 from that, you can manage a watchpoint like any other breakpoint: you
3332 enable, disable, and delete both breakpoints and watchpoints using the
3335 You can arrange to have values from your program displayed automatically
3336 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3340 @cindex breakpoint on events
3341 A @dfn{catchpoint} is another special breakpoint that stops your program
3342 when a certain kind of event occurs, such as the throwing of a C@t{++}
3343 exception or the loading of a library. As with watchpoints, you use a
3344 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3345 Catchpoints}), but aside from that, you can manage a catchpoint like any
3346 other breakpoint. (To stop when your program receives a signal, use the
3347 @code{handle} command; see @ref{Signals, ,Signals}.)
3349 @cindex breakpoint numbers
3350 @cindex numbers for breakpoints
3351 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3352 catchpoint when you create it; these numbers are successive integers
3353 starting with one. In many of the commands for controlling various
3354 features of breakpoints you use the breakpoint number to say which
3355 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3356 @dfn{disabled}; if disabled, it has no effect on your program until you
3359 @cindex breakpoint ranges
3360 @cindex ranges of breakpoints
3361 Some @value{GDBN} commands accept a range of breakpoints on which to
3362 operate. A breakpoint range is either a single breakpoint number, like
3363 @samp{5}, or two such numbers, in increasing order, separated by a
3364 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3365 all breakpoints in that range are operated on.
3368 * Set Breaks:: Setting breakpoints
3369 * Set Watchpoints:: Setting watchpoints
3370 * Set Catchpoints:: Setting catchpoints
3371 * Delete Breaks:: Deleting breakpoints
3372 * Disabling:: Disabling breakpoints
3373 * Conditions:: Break conditions
3374 * Break Commands:: Breakpoint command lists
3375 * Dynamic Printf:: Dynamic printf
3376 * Save Breakpoints:: How to save breakpoints in a file
3377 * Static Probe Points:: Listing static probe points
3378 * Error in Breakpoints:: ``Cannot insert breakpoints''
3379 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3383 @subsection Setting Breakpoints
3385 @c FIXME LMB what does GDB do if no code on line of breakpt?
3386 @c consider in particular declaration with/without initialization.
3388 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3391 @kindex b @r{(@code{break})}
3392 @vindex $bpnum@r{, convenience variable}
3393 @cindex latest breakpoint
3394 Breakpoints are set with the @code{break} command (abbreviated
3395 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3396 number of the breakpoint you've set most recently; see @ref{Convenience
3397 Vars,, Convenience Variables}, for a discussion of what you can do with
3398 convenience variables.
3401 @item break @var{location}
3402 Set a breakpoint at the given @var{location}, which can specify a
3403 function name, a line number, or an address of an instruction.
3404 (@xref{Specify Location}, for a list of all the possible ways to
3405 specify a @var{location}.) The breakpoint will stop your program just
3406 before it executes any of the code in the specified @var{location}.
3408 When using source languages that permit overloading of symbols, such as
3409 C@t{++}, a function name may refer to more than one possible place to break.
3410 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3413 It is also possible to insert a breakpoint that will stop the program
3414 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3415 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3418 When called without any arguments, @code{break} sets a breakpoint at
3419 the next instruction to be executed in the selected stack frame
3420 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3421 innermost, this makes your program stop as soon as control
3422 returns to that frame. This is similar to the effect of a
3423 @code{finish} command in the frame inside the selected frame---except
3424 that @code{finish} does not leave an active breakpoint. If you use
3425 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3426 the next time it reaches the current location; this may be useful
3429 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3430 least one instruction has been executed. If it did not do this, you
3431 would be unable to proceed past a breakpoint without first disabling the
3432 breakpoint. This rule applies whether or not the breakpoint already
3433 existed when your program stopped.
3435 @item break @dots{} if @var{cond}
3436 Set a breakpoint with condition @var{cond}; evaluate the expression
3437 @var{cond} each time the breakpoint is reached, and stop only if the
3438 value is nonzero---that is, if @var{cond} evaluates as true.
3439 @samp{@dots{}} stands for one of the possible arguments described
3440 above (or no argument) specifying where to break. @xref{Conditions,
3441 ,Break Conditions}, for more information on breakpoint conditions.
3444 @item tbreak @var{args}
3445 Set a breakpoint enabled only for one stop. @var{args} are the
3446 same as for the @code{break} command, and the breakpoint is set in the same
3447 way, but the breakpoint is automatically deleted after the first time your
3448 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3451 @cindex hardware breakpoints
3452 @item hbreak @var{args}
3453 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3454 @code{break} command and the breakpoint is set in the same way, but the
3455 breakpoint requires hardware support and some target hardware may not
3456 have this support. The main purpose of this is EPROM/ROM code
3457 debugging, so you can set a breakpoint at an instruction without
3458 changing the instruction. This can be used with the new trap-generation
3459 provided by SPARClite DSU and most x86-based targets. These targets
3460 will generate traps when a program accesses some data or instruction
3461 address that is assigned to the debug registers. However the hardware
3462 breakpoint registers can take a limited number of breakpoints. For
3463 example, on the DSU, only two data breakpoints can be set at a time, and
3464 @value{GDBN} will reject this command if more than two are used. Delete
3465 or disable unused hardware breakpoints before setting new ones
3466 (@pxref{Disabling, ,Disabling Breakpoints}).
3467 @xref{Conditions, ,Break Conditions}.
3468 For remote targets, you can restrict the number of hardware
3469 breakpoints @value{GDBN} will use, see @ref{set remote
3470 hardware-breakpoint-limit}.
3473 @item thbreak @var{args}
3474 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3475 are the same as for the @code{hbreak} command and the breakpoint is set in
3476 the same way. However, like the @code{tbreak} command,
3477 the breakpoint is automatically deleted after the
3478 first time your program stops there. Also, like the @code{hbreak}
3479 command, the breakpoint requires hardware support and some target hardware
3480 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3481 See also @ref{Conditions, ,Break Conditions}.
3484 @cindex regular expression
3485 @cindex breakpoints at functions matching a regexp
3486 @cindex set breakpoints in many functions
3487 @item rbreak @var{regex}
3488 Set breakpoints on all functions matching the regular expression
3489 @var{regex}. This command sets an unconditional breakpoint on all
3490 matches, printing a list of all breakpoints it set. Once these
3491 breakpoints are set, they are treated just like the breakpoints set with
3492 the @code{break} command. You can delete them, disable them, or make
3493 them conditional the same way as any other breakpoint.
3495 The syntax of the regular expression is the standard one used with tools
3496 like @file{grep}. Note that this is different from the syntax used by
3497 shells, so for instance @code{foo*} matches all functions that include
3498 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3499 @code{.*} leading and trailing the regular expression you supply, so to
3500 match only functions that begin with @code{foo}, use @code{^foo}.
3502 @cindex non-member C@t{++} functions, set breakpoint in
3503 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3504 breakpoints on overloaded functions that are not members of any special
3507 @cindex set breakpoints on all functions
3508 The @code{rbreak} command can be used to set breakpoints in
3509 @strong{all} the functions in a program, like this:
3512 (@value{GDBP}) rbreak .
3515 @item rbreak @var{file}:@var{regex}
3516 If @code{rbreak} is called with a filename qualification, it limits
3517 the search for functions matching the given regular expression to the
3518 specified @var{file}. This can be used, for example, to set breakpoints on
3519 every function in a given file:
3522 (@value{GDBP}) rbreak file.c:.
3525 The colon separating the filename qualifier from the regex may
3526 optionally be surrounded by spaces.
3528 @kindex info breakpoints
3529 @cindex @code{$_} and @code{info breakpoints}
3530 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3531 @itemx info break @r{[}@var{n}@dots{}@r{]}
3532 Print a table of all breakpoints, watchpoints, and catchpoints set and
3533 not deleted. Optional argument @var{n} means print information only
3534 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3535 For each breakpoint, following columns are printed:
3538 @item Breakpoint Numbers
3540 Breakpoint, watchpoint, or catchpoint.
3542 Whether the breakpoint is marked to be disabled or deleted when hit.
3543 @item Enabled or Disabled
3544 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3545 that are not enabled.
3547 Where the breakpoint is in your program, as a memory address. For a
3548 pending breakpoint whose address is not yet known, this field will
3549 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3550 library that has the symbol or line referred by breakpoint is loaded.
3551 See below for details. A breakpoint with several locations will
3552 have @samp{<MULTIPLE>} in this field---see below for details.
3554 Where the breakpoint is in the source for your program, as a file and
3555 line number. For a pending breakpoint, the original string passed to
3556 the breakpoint command will be listed as it cannot be resolved until
3557 the appropriate shared library is loaded in the future.
3561 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3562 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3563 @value{GDBN} on the host's side. If it is ``target'', then the condition
3564 is evaluated by the target. The @code{info break} command shows
3565 the condition on the line following the affected breakpoint, together with
3566 its condition evaluation mode in between parentheses.
3568 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3569 allowed to have a condition specified for it. The condition is not parsed for
3570 validity until a shared library is loaded that allows the pending
3571 breakpoint to resolve to a valid location.
3574 @code{info break} with a breakpoint
3575 number @var{n} as argument lists only that breakpoint. The
3576 convenience variable @code{$_} and the default examining-address for
3577 the @code{x} command are set to the address of the last breakpoint
3578 listed (@pxref{Memory, ,Examining Memory}).
3581 @code{info break} displays a count of the number of times the breakpoint
3582 has been hit. This is especially useful in conjunction with the
3583 @code{ignore} command. You can ignore a large number of breakpoint
3584 hits, look at the breakpoint info to see how many times the breakpoint
3585 was hit, and then run again, ignoring one less than that number. This
3586 will get you quickly to the last hit of that breakpoint.
3589 For a breakpoints with an enable count (xref) greater than 1,
3590 @code{info break} also displays that count.
3594 @value{GDBN} allows you to set any number of breakpoints at the same place in
3595 your program. There is nothing silly or meaningless about this. When
3596 the breakpoints are conditional, this is even useful
3597 (@pxref{Conditions, ,Break Conditions}).
3599 @cindex multiple locations, breakpoints
3600 @cindex breakpoints, multiple locations
3601 It is possible that a breakpoint corresponds to several locations
3602 in your program. Examples of this situation are:
3606 Multiple functions in the program may have the same name.
3609 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3610 instances of the function body, used in different cases.
3613 For a C@t{++} template function, a given line in the function can
3614 correspond to any number of instantiations.
3617 For an inlined function, a given source line can correspond to
3618 several places where that function is inlined.
3621 In all those cases, @value{GDBN} will insert a breakpoint at all
3622 the relevant locations.
3624 A breakpoint with multiple locations is displayed in the breakpoint
3625 table using several rows---one header row, followed by one row for
3626 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3627 address column. The rows for individual locations contain the actual
3628 addresses for locations, and show the functions to which those
3629 locations belong. The number column for a location is of the form
3630 @var{breakpoint-number}.@var{location-number}.
3635 Num Type Disp Enb Address What
3636 1 breakpoint keep y <MULTIPLE>
3638 breakpoint already hit 1 time
3639 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3640 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3643 Each location can be individually enabled or disabled by passing
3644 @var{breakpoint-number}.@var{location-number} as argument to the
3645 @code{enable} and @code{disable} commands. Note that you cannot
3646 delete the individual locations from the list, you can only delete the
3647 entire list of locations that belong to their parent breakpoint (with
3648 the @kbd{delete @var{num}} command, where @var{num} is the number of
3649 the parent breakpoint, 1 in the above example). Disabling or enabling
3650 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3651 that belong to that breakpoint.
3653 @cindex pending breakpoints
3654 It's quite common to have a breakpoint inside a shared library.
3655 Shared libraries can be loaded and unloaded explicitly,
3656 and possibly repeatedly, as the program is executed. To support
3657 this use case, @value{GDBN} updates breakpoint locations whenever
3658 any shared library is loaded or unloaded. Typically, you would
3659 set a breakpoint in a shared library at the beginning of your
3660 debugging session, when the library is not loaded, and when the
3661 symbols from the library are not available. When you try to set
3662 breakpoint, @value{GDBN} will ask you if you want to set
3663 a so called @dfn{pending breakpoint}---breakpoint whose address
3664 is not yet resolved.
3666 After the program is run, whenever a new shared library is loaded,
3667 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3668 shared library contains the symbol or line referred to by some
3669 pending breakpoint, that breakpoint is resolved and becomes an
3670 ordinary breakpoint. When a library is unloaded, all breakpoints
3671 that refer to its symbols or source lines become pending again.
3673 This logic works for breakpoints with multiple locations, too. For
3674 example, if you have a breakpoint in a C@t{++} template function, and
3675 a newly loaded shared library has an instantiation of that template,
3676 a new location is added to the list of locations for the breakpoint.
3678 Except for having unresolved address, pending breakpoints do not
3679 differ from regular breakpoints. You can set conditions or commands,
3680 enable and disable them and perform other breakpoint operations.
3682 @value{GDBN} provides some additional commands for controlling what
3683 happens when the @samp{break} command cannot resolve breakpoint
3684 address specification to an address:
3686 @kindex set breakpoint pending
3687 @kindex show breakpoint pending
3689 @item set breakpoint pending auto
3690 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3691 location, it queries you whether a pending breakpoint should be created.
3693 @item set breakpoint pending on
3694 This indicates that an unrecognized breakpoint location should automatically
3695 result in a pending breakpoint being created.
3697 @item set breakpoint pending off
3698 This indicates that pending breakpoints are not to be created. Any
3699 unrecognized breakpoint location results in an error. This setting does
3700 not affect any pending breakpoints previously created.
3702 @item show breakpoint pending
3703 Show the current behavior setting for creating pending breakpoints.
3706 The settings above only affect the @code{break} command and its
3707 variants. Once breakpoint is set, it will be automatically updated
3708 as shared libraries are loaded and unloaded.
3710 @cindex automatic hardware breakpoints
3711 For some targets, @value{GDBN} can automatically decide if hardware or
3712 software breakpoints should be used, depending on whether the
3713 breakpoint address is read-only or read-write. This applies to
3714 breakpoints set with the @code{break} command as well as to internal
3715 breakpoints set by commands like @code{next} and @code{finish}. For
3716 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3719 You can control this automatic behaviour with the following commands::
3721 @kindex set breakpoint auto-hw
3722 @kindex show breakpoint auto-hw
3724 @item set breakpoint auto-hw on
3725 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3726 will try to use the target memory map to decide if software or hardware
3727 breakpoint must be used.
3729 @item set breakpoint auto-hw off
3730 This indicates @value{GDBN} should not automatically select breakpoint
3731 type. If the target provides a memory map, @value{GDBN} will warn when
3732 trying to set software breakpoint at a read-only address.
3735 @value{GDBN} normally implements breakpoints by replacing the program code
3736 at the breakpoint address with a special instruction, which, when
3737 executed, given control to the debugger. By default, the program
3738 code is so modified only when the program is resumed. As soon as
3739 the program stops, @value{GDBN} restores the original instructions. This
3740 behaviour guards against leaving breakpoints inserted in the
3741 target should gdb abrubptly disconnect. However, with slow remote
3742 targets, inserting and removing breakpoint can reduce the performance.
3743 This behavior can be controlled with the following commands::
3745 @kindex set breakpoint always-inserted
3746 @kindex show breakpoint always-inserted
3748 @item set breakpoint always-inserted off
3749 All breakpoints, including newly added by the user, are inserted in
3750 the target only when the target is resumed. All breakpoints are
3751 removed from the target when it stops.
3753 @item set breakpoint always-inserted on
3754 Causes all breakpoints to be inserted in the target at all times. If
3755 the user adds a new breakpoint, or changes an existing breakpoint, the
3756 breakpoints in the target are updated immediately. A breakpoint is
3757 removed from the target only when breakpoint itself is removed.
3759 @cindex non-stop mode, and @code{breakpoint always-inserted}
3760 @item set breakpoint always-inserted auto
3761 This is the default mode. If @value{GDBN} is controlling the inferior
3762 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3763 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3764 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3765 @code{breakpoint always-inserted} mode is off.
3768 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3769 when a breakpoint breaks. If the condition is true, then the process being
3770 debugged stops, otherwise the process is resumed.
3772 If the target supports evaluating conditions on its end, @value{GDBN} may
3773 download the breakpoint, together with its conditions, to it.
3775 This feature can be controlled via the following commands:
3777 @kindex set breakpoint condition-evaluation
3778 @kindex show breakpoint condition-evaluation
3780 @item set breakpoint condition-evaluation host
3781 This option commands @value{GDBN} to evaluate the breakpoint
3782 conditions on the host's side. Unconditional breakpoints are sent to
3783 the target which in turn receives the triggers and reports them back to GDB
3784 for condition evaluation. This is the standard evaluation mode.
3786 @item set breakpoint condition-evaluation target
3787 This option commands @value{GDBN} to download breakpoint conditions
3788 to the target at the moment of their insertion. The target
3789 is responsible for evaluating the conditional expression and reporting
3790 breakpoint stop events back to @value{GDBN} whenever the condition
3791 is true. Due to limitations of target-side evaluation, some conditions
3792 cannot be evaluated there, e.g., conditions that depend on local data
3793 that is only known to the host. Examples include
3794 conditional expressions involving convenience variables, complex types
3795 that cannot be handled by the agent expression parser and expressions
3796 that are too long to be sent over to the target, specially when the
3797 target is a remote system. In these cases, the conditions will be
3798 evaluated by @value{GDBN}.
3800 @item set breakpoint condition-evaluation auto
3801 This is the default mode. If the target supports evaluating breakpoint
3802 conditions on its end, @value{GDBN} will download breakpoint conditions to
3803 the target (limitations mentioned previously apply). If the target does
3804 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3805 to evaluating all these conditions on the host's side.
3809 @cindex negative breakpoint numbers
3810 @cindex internal @value{GDBN} breakpoints
3811 @value{GDBN} itself sometimes sets breakpoints in your program for
3812 special purposes, such as proper handling of @code{longjmp} (in C
3813 programs). These internal breakpoints are assigned negative numbers,
3814 starting with @code{-1}; @samp{info breakpoints} does not display them.
3815 You can see these breakpoints with the @value{GDBN} maintenance command
3816 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3819 @node Set Watchpoints
3820 @subsection Setting Watchpoints
3822 @cindex setting watchpoints
3823 You can use a watchpoint to stop execution whenever the value of an
3824 expression changes, without having to predict a particular place where
3825 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3826 The expression may be as simple as the value of a single variable, or
3827 as complex as many variables combined by operators. Examples include:
3831 A reference to the value of a single variable.
3834 An address cast to an appropriate data type. For example,
3835 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3836 address (assuming an @code{int} occupies 4 bytes).
3839 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3840 expression can use any operators valid in the program's native
3841 language (@pxref{Languages}).
3844 You can set a watchpoint on an expression even if the expression can
3845 not be evaluated yet. For instance, you can set a watchpoint on
3846 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3847 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3848 the expression produces a valid value. If the expression becomes
3849 valid in some other way than changing a variable (e.g.@: if the memory
3850 pointed to by @samp{*global_ptr} becomes readable as the result of a
3851 @code{malloc} call), @value{GDBN} may not stop until the next time
3852 the expression changes.
3854 @cindex software watchpoints
3855 @cindex hardware watchpoints
3856 Depending on your system, watchpoints may be implemented in software or
3857 hardware. @value{GDBN} does software watchpointing by single-stepping your
3858 program and testing the variable's value each time, which is hundreds of
3859 times slower than normal execution. (But this may still be worth it, to
3860 catch errors where you have no clue what part of your program is the
3863 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3864 x86-based targets, @value{GDBN} includes support for hardware
3865 watchpoints, which do not slow down the running of your program.
3869 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3870 Set a watchpoint for an expression. @value{GDBN} will break when the
3871 expression @var{expr} is written into by the program and its value
3872 changes. The simplest (and the most popular) use of this command is
3873 to watch the value of a single variable:
3876 (@value{GDBP}) watch foo
3879 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3880 argument, @value{GDBN} breaks only when the thread identified by
3881 @var{threadnum} changes the value of @var{expr}. If any other threads
3882 change the value of @var{expr}, @value{GDBN} will not break. Note
3883 that watchpoints restricted to a single thread in this way only work
3884 with Hardware Watchpoints.
3886 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3887 (see below). The @code{-location} argument tells @value{GDBN} to
3888 instead watch the memory referred to by @var{expr}. In this case,
3889 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3890 and watch the memory at that address. The type of the result is used
3891 to determine the size of the watched memory. If the expression's
3892 result does not have an address, then @value{GDBN} will print an
3895 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3896 of masked watchpoints, if the current architecture supports this
3897 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3898 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3899 to an address to watch. The mask specifies that some bits of an address
3900 (the bits which are reset in the mask) should be ignored when matching
3901 the address accessed by the inferior against the watchpoint address.
3902 Thus, a masked watchpoint watches many addresses simultaneously---those
3903 addresses whose unmasked bits are identical to the unmasked bits in the
3904 watchpoint address. The @code{mask} argument implies @code{-location}.
3908 (@value{GDBP}) watch foo mask 0xffff00ff
3909 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3913 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3914 Set a watchpoint that will break when the value of @var{expr} is read
3918 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3919 Set a watchpoint that will break when @var{expr} is either read from
3920 or written into by the program.
3922 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3923 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3924 This command prints a list of watchpoints, using the same format as
3925 @code{info break} (@pxref{Set Breaks}).
3928 If you watch for a change in a numerically entered address you need to
3929 dereference it, as the address itself is just a constant number which will
3930 never change. @value{GDBN} refuses to create a watchpoint that watches
3931 a never-changing value:
3934 (@value{GDBP}) watch 0x600850
3935 Cannot watch constant value 0x600850.
3936 (@value{GDBP}) watch *(int *) 0x600850
3937 Watchpoint 1: *(int *) 6293584
3940 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3941 watchpoints execute very quickly, and the debugger reports a change in
3942 value at the exact instruction where the change occurs. If @value{GDBN}
3943 cannot set a hardware watchpoint, it sets a software watchpoint, which
3944 executes more slowly and reports the change in value at the next
3945 @emph{statement}, not the instruction, after the change occurs.
3947 @cindex use only software watchpoints
3948 You can force @value{GDBN} to use only software watchpoints with the
3949 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3950 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3951 the underlying system supports them. (Note that hardware-assisted
3952 watchpoints that were set @emph{before} setting
3953 @code{can-use-hw-watchpoints} to zero will still use the hardware
3954 mechanism of watching expression values.)
3957 @item set can-use-hw-watchpoints
3958 @kindex set can-use-hw-watchpoints
3959 Set whether or not to use hardware watchpoints.
3961 @item show can-use-hw-watchpoints
3962 @kindex show can-use-hw-watchpoints
3963 Show the current mode of using hardware watchpoints.
3966 For remote targets, you can restrict the number of hardware
3967 watchpoints @value{GDBN} will use, see @ref{set remote
3968 hardware-breakpoint-limit}.
3970 When you issue the @code{watch} command, @value{GDBN} reports
3973 Hardware watchpoint @var{num}: @var{expr}
3977 if it was able to set a hardware watchpoint.
3979 Currently, the @code{awatch} and @code{rwatch} commands can only set
3980 hardware watchpoints, because accesses to data that don't change the
3981 value of the watched expression cannot be detected without examining
3982 every instruction as it is being executed, and @value{GDBN} does not do
3983 that currently. If @value{GDBN} finds that it is unable to set a
3984 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3985 will print a message like this:
3988 Expression cannot be implemented with read/access watchpoint.
3991 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3992 data type of the watched expression is wider than what a hardware
3993 watchpoint on the target machine can handle. For example, some systems
3994 can only watch regions that are up to 4 bytes wide; on such systems you
3995 cannot set hardware watchpoints for an expression that yields a
3996 double-precision floating-point number (which is typically 8 bytes
3997 wide). As a work-around, it might be possible to break the large region
3998 into a series of smaller ones and watch them with separate watchpoints.
4000 If you set too many hardware watchpoints, @value{GDBN} might be unable
4001 to insert all of them when you resume the execution of your program.
4002 Since the precise number of active watchpoints is unknown until such
4003 time as the program is about to be resumed, @value{GDBN} might not be
4004 able to warn you about this when you set the watchpoints, and the
4005 warning will be printed only when the program is resumed:
4008 Hardware watchpoint @var{num}: Could not insert watchpoint
4012 If this happens, delete or disable some of the watchpoints.
4014 Watching complex expressions that reference many variables can also
4015 exhaust the resources available for hardware-assisted watchpoints.
4016 That's because @value{GDBN} needs to watch every variable in the
4017 expression with separately allocated resources.
4019 If you call a function interactively using @code{print} or @code{call},
4020 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4021 kind of breakpoint or the call completes.
4023 @value{GDBN} automatically deletes watchpoints that watch local
4024 (automatic) variables, or expressions that involve such variables, when
4025 they go out of scope, that is, when the execution leaves the block in
4026 which these variables were defined. In particular, when the program
4027 being debugged terminates, @emph{all} local variables go out of scope,
4028 and so only watchpoints that watch global variables remain set. If you
4029 rerun the program, you will need to set all such watchpoints again. One
4030 way of doing that would be to set a code breakpoint at the entry to the
4031 @code{main} function and when it breaks, set all the watchpoints.
4033 @cindex watchpoints and threads
4034 @cindex threads and watchpoints
4035 In multi-threaded programs, watchpoints will detect changes to the
4036 watched expression from every thread.
4039 @emph{Warning:} In multi-threaded programs, software watchpoints
4040 have only limited usefulness. If @value{GDBN} creates a software
4041 watchpoint, it can only watch the value of an expression @emph{in a
4042 single thread}. If you are confident that the expression can only
4043 change due to the current thread's activity (and if you are also
4044 confident that no other thread can become current), then you can use
4045 software watchpoints as usual. However, @value{GDBN} may not notice
4046 when a non-current thread's activity changes the expression. (Hardware
4047 watchpoints, in contrast, watch an expression in all threads.)
4050 @xref{set remote hardware-watchpoint-limit}.
4052 @node Set Catchpoints
4053 @subsection Setting Catchpoints
4054 @cindex catchpoints, setting
4055 @cindex exception handlers
4056 @cindex event handling
4058 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4059 kinds of program events, such as C@t{++} exceptions or the loading of a
4060 shared library. Use the @code{catch} command to set a catchpoint.
4064 @item catch @var{event}
4065 Stop when @var{event} occurs. @var{event} can be any of the following:
4068 @cindex stop on C@t{++} exceptions
4069 The throwing of a C@t{++} exception.
4072 The catching of a C@t{++} exception.
4075 @cindex Ada exception catching
4076 @cindex catch Ada exceptions
4077 An Ada exception being raised. If an exception name is specified
4078 at the end of the command (eg @code{catch exception Program_Error}),
4079 the debugger will stop only when this specific exception is raised.
4080 Otherwise, the debugger stops execution when any Ada exception is raised.
4082 When inserting an exception catchpoint on a user-defined exception whose
4083 name is identical to one of the exceptions defined by the language, the
4084 fully qualified name must be used as the exception name. Otherwise,
4085 @value{GDBN} will assume that it should stop on the pre-defined exception
4086 rather than the user-defined one. For instance, assuming an exception
4087 called @code{Constraint_Error} is defined in package @code{Pck}, then
4088 the command to use to catch such exceptions is @kbd{catch exception
4089 Pck.Constraint_Error}.
4091 @item exception unhandled
4092 An exception that was raised but is not handled by the program.
4095 A failed Ada assertion.
4098 @cindex break on fork/exec
4099 A call to @code{exec}. This is currently only available for HP-UX
4103 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4104 @cindex break on a system call.
4105 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4106 syscall is a mechanism for application programs to request a service
4107 from the operating system (OS) or one of the OS system services.
4108 @value{GDBN} can catch some or all of the syscalls issued by the
4109 debuggee, and show the related information for each syscall. If no
4110 argument is specified, calls to and returns from all system calls
4113 @var{name} can be any system call name that is valid for the
4114 underlying OS. Just what syscalls are valid depends on the OS. On
4115 GNU and Unix systems, you can find the full list of valid syscall
4116 names on @file{/usr/include/asm/unistd.h}.
4118 @c For MS-Windows, the syscall names and the corresponding numbers
4119 @c can be found, e.g., on this URL:
4120 @c http://www.metasploit.com/users/opcode/syscalls.html
4121 @c but we don't support Windows syscalls yet.
4123 Normally, @value{GDBN} knows in advance which syscalls are valid for
4124 each OS, so you can use the @value{GDBN} command-line completion
4125 facilities (@pxref{Completion,, command completion}) to list the
4128 You may also specify the system call numerically. A syscall's
4129 number is the value passed to the OS's syscall dispatcher to
4130 identify the requested service. When you specify the syscall by its
4131 name, @value{GDBN} uses its database of syscalls to convert the name
4132 into the corresponding numeric code, but using the number directly
4133 may be useful if @value{GDBN}'s database does not have the complete
4134 list of syscalls on your system (e.g., because @value{GDBN} lags
4135 behind the OS upgrades).
4137 The example below illustrates how this command works if you don't provide
4141 (@value{GDBP}) catch syscall
4142 Catchpoint 1 (syscall)
4144 Starting program: /tmp/catch-syscall
4146 Catchpoint 1 (call to syscall 'close'), \
4147 0xffffe424 in __kernel_vsyscall ()
4151 Catchpoint 1 (returned from syscall 'close'), \
4152 0xffffe424 in __kernel_vsyscall ()
4156 Here is an example of catching a system call by name:
4159 (@value{GDBP}) catch syscall chroot
4160 Catchpoint 1 (syscall 'chroot' [61])
4162 Starting program: /tmp/catch-syscall
4164 Catchpoint 1 (call to syscall 'chroot'), \
4165 0xffffe424 in __kernel_vsyscall ()
4169 Catchpoint 1 (returned from syscall 'chroot'), \
4170 0xffffe424 in __kernel_vsyscall ()
4174 An example of specifying a system call numerically. In the case
4175 below, the syscall number has a corresponding entry in the XML
4176 file, so @value{GDBN} finds its name and prints it:
4179 (@value{GDBP}) catch syscall 252
4180 Catchpoint 1 (syscall(s) 'exit_group')
4182 Starting program: /tmp/catch-syscall
4184 Catchpoint 1 (call to syscall 'exit_group'), \
4185 0xffffe424 in __kernel_vsyscall ()
4189 Program exited normally.
4193 However, there can be situations when there is no corresponding name
4194 in XML file for that syscall number. In this case, @value{GDBN} prints
4195 a warning message saying that it was not able to find the syscall name,
4196 but the catchpoint will be set anyway. See the example below:
4199 (@value{GDBP}) catch syscall 764
4200 warning: The number '764' does not represent a known syscall.
4201 Catchpoint 2 (syscall 764)
4205 If you configure @value{GDBN} using the @samp{--without-expat} option,
4206 it will not be able to display syscall names. Also, if your
4207 architecture does not have an XML file describing its system calls,
4208 you will not be able to see the syscall names. It is important to
4209 notice that these two features are used for accessing the syscall
4210 name database. In either case, you will see a warning like this:
4213 (@value{GDBP}) catch syscall
4214 warning: Could not open "syscalls/i386-linux.xml"
4215 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4216 GDB will not be able to display syscall names.
4217 Catchpoint 1 (syscall)
4221 Of course, the file name will change depending on your architecture and system.
4223 Still using the example above, you can also try to catch a syscall by its
4224 number. In this case, you would see something like:
4227 (@value{GDBP}) catch syscall 252
4228 Catchpoint 1 (syscall(s) 252)
4231 Again, in this case @value{GDBN} would not be able to display syscall's names.
4234 A call to @code{fork}. This is currently only available for HP-UX
4238 A call to @code{vfork}. This is currently only available for HP-UX
4241 @item load @r{[}regexp@r{]}
4242 @itemx unload @r{[}regexp@r{]}
4243 The loading or unloading of a shared library. If @var{regexp} is
4244 given, then the catchpoint will stop only if the regular expression
4245 matches one of the affected libraries.
4249 @item tcatch @var{event}
4250 Set a catchpoint that is enabled only for one stop. The catchpoint is
4251 automatically deleted after the first time the event is caught.
4255 Use the @code{info break} command to list the current catchpoints.
4257 There are currently some limitations to C@t{++} exception handling
4258 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4262 If you call a function interactively, @value{GDBN} normally returns
4263 control to you when the function has finished executing. If the call
4264 raises an exception, however, the call may bypass the mechanism that
4265 returns control to you and cause your program either to abort or to
4266 simply continue running until it hits a breakpoint, catches a signal
4267 that @value{GDBN} is listening for, or exits. This is the case even if
4268 you set a catchpoint for the exception; catchpoints on exceptions are
4269 disabled within interactive calls.
4272 You cannot raise an exception interactively.
4275 You cannot install an exception handler interactively.
4278 @cindex raise exceptions
4279 Sometimes @code{catch} is not the best way to debug exception handling:
4280 if you need to know exactly where an exception is raised, it is better to
4281 stop @emph{before} the exception handler is called, since that way you
4282 can see the stack before any unwinding takes place. If you set a
4283 breakpoint in an exception handler instead, it may not be easy to find
4284 out where the exception was raised.
4286 To stop just before an exception handler is called, you need some
4287 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4288 raised by calling a library function named @code{__raise_exception}
4289 which has the following ANSI C interface:
4292 /* @var{addr} is where the exception identifier is stored.
4293 @var{id} is the exception identifier. */
4294 void __raise_exception (void **addr, void *id);
4298 To make the debugger catch all exceptions before any stack
4299 unwinding takes place, set a breakpoint on @code{__raise_exception}
4300 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4302 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4303 that depends on the value of @var{id}, you can stop your program when
4304 a specific exception is raised. You can use multiple conditional
4305 breakpoints to stop your program when any of a number of exceptions are
4310 @subsection Deleting Breakpoints
4312 @cindex clearing breakpoints, watchpoints, catchpoints
4313 @cindex deleting breakpoints, watchpoints, catchpoints
4314 It is often necessary to eliminate a breakpoint, watchpoint, or
4315 catchpoint once it has done its job and you no longer want your program
4316 to stop there. This is called @dfn{deleting} the breakpoint. A
4317 breakpoint that has been deleted no longer exists; it is forgotten.
4319 With the @code{clear} command you can delete breakpoints according to
4320 where they are in your program. With the @code{delete} command you can
4321 delete individual breakpoints, watchpoints, or catchpoints by specifying
4322 their breakpoint numbers.
4324 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4325 automatically ignores breakpoints on the first instruction to be executed
4326 when you continue execution without changing the execution address.
4331 Delete any breakpoints at the next instruction to be executed in the
4332 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4333 the innermost frame is selected, this is a good way to delete a
4334 breakpoint where your program just stopped.
4336 @item clear @var{location}
4337 Delete any breakpoints set at the specified @var{location}.
4338 @xref{Specify Location}, for the various forms of @var{location}; the
4339 most useful ones are listed below:
4342 @item clear @var{function}
4343 @itemx clear @var{filename}:@var{function}
4344 Delete any breakpoints set at entry to the named @var{function}.
4346 @item clear @var{linenum}
4347 @itemx clear @var{filename}:@var{linenum}
4348 Delete any breakpoints set at or within the code of the specified
4349 @var{linenum} of the specified @var{filename}.
4352 @cindex delete breakpoints
4354 @kindex d @r{(@code{delete})}
4355 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4356 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4357 ranges specified as arguments. If no argument is specified, delete all
4358 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4359 confirm off}). You can abbreviate this command as @code{d}.
4363 @subsection Disabling Breakpoints
4365 @cindex enable/disable a breakpoint
4366 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4367 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4368 it had been deleted, but remembers the information on the breakpoint so
4369 that you can @dfn{enable} it again later.
4371 You disable and enable breakpoints, watchpoints, and catchpoints with
4372 the @code{enable} and @code{disable} commands, optionally specifying
4373 one or more breakpoint numbers as arguments. Use @code{info break} to
4374 print a list of all breakpoints, watchpoints, and catchpoints if you
4375 do not know which numbers to use.
4377 Disabling and enabling a breakpoint that has multiple locations
4378 affects all of its locations.
4380 A breakpoint, watchpoint, or catchpoint can have any of several
4381 different states of enablement:
4385 Enabled. The breakpoint stops your program. A breakpoint set
4386 with the @code{break} command starts out in this state.
4388 Disabled. The breakpoint has no effect on your program.
4390 Enabled once. The breakpoint stops your program, but then becomes
4393 Enabled for a count. The breakpoint stops your program for the next
4394 N times, then becomes disabled.
4396 Enabled for deletion. The breakpoint stops your program, but
4397 immediately after it does so it is deleted permanently. A breakpoint
4398 set with the @code{tbreak} command starts out in this state.
4401 You can use the following commands to enable or disable breakpoints,
4402 watchpoints, and catchpoints:
4406 @kindex dis @r{(@code{disable})}
4407 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4408 Disable the specified breakpoints---or all breakpoints, if none are
4409 listed. A disabled breakpoint has no effect but is not forgotten. All
4410 options such as ignore-counts, conditions and commands are remembered in
4411 case the breakpoint is enabled again later. You may abbreviate
4412 @code{disable} as @code{dis}.
4415 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4416 Enable the specified breakpoints (or all defined breakpoints). They
4417 become effective once again in stopping your program.
4419 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4420 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4421 of these breakpoints immediately after stopping your program.
4423 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4424 Enable the specified breakpoints temporarily. @value{GDBN} records
4425 @var{count} with each of the specified breakpoints, and decrements a
4426 breakpoint's count when it is hit. When any count reaches 0,
4427 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4428 count (@pxref{Conditions, ,Break Conditions}), that will be
4429 decremented to 0 before @var{count} is affected.
4431 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4432 Enable the specified breakpoints to work once, then die. @value{GDBN}
4433 deletes any of these breakpoints as soon as your program stops there.
4434 Breakpoints set by the @code{tbreak} command start out in this state.
4437 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4438 @c confusing: tbreak is also initially enabled.
4439 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4440 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4441 subsequently, they become disabled or enabled only when you use one of
4442 the commands above. (The command @code{until} can set and delete a
4443 breakpoint of its own, but it does not change the state of your other
4444 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4448 @subsection Break Conditions
4449 @cindex conditional breakpoints
4450 @cindex breakpoint conditions
4452 @c FIXME what is scope of break condition expr? Context where wanted?
4453 @c in particular for a watchpoint?
4454 The simplest sort of breakpoint breaks every time your program reaches a
4455 specified place. You can also specify a @dfn{condition} for a
4456 breakpoint. A condition is just a Boolean expression in your
4457 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4458 a condition evaluates the expression each time your program reaches it,
4459 and your program stops only if the condition is @emph{true}.
4461 This is the converse of using assertions for program validation; in that
4462 situation, you want to stop when the assertion is violated---that is,
4463 when the condition is false. In C, if you want to test an assertion expressed
4464 by the condition @var{assert}, you should set the condition
4465 @samp{! @var{assert}} on the appropriate breakpoint.
4467 Conditions are also accepted for watchpoints; you may not need them,
4468 since a watchpoint is inspecting the value of an expression anyhow---but
4469 it might be simpler, say, to just set a watchpoint on a variable name,
4470 and specify a condition that tests whether the new value is an interesting
4473 Break conditions can have side effects, and may even call functions in
4474 your program. This can be useful, for example, to activate functions
4475 that log program progress, or to use your own print functions to
4476 format special data structures. The effects are completely predictable
4477 unless there is another enabled breakpoint at the same address. (In
4478 that case, @value{GDBN} might see the other breakpoint first and stop your
4479 program without checking the condition of this one.) Note that
4480 breakpoint commands are usually more convenient and flexible than break
4482 purpose of performing side effects when a breakpoint is reached
4483 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4485 Breakpoint conditions can also be evaluated on the target's side if
4486 the target supports it. Instead of evaluating the conditions locally,
4487 @value{GDBN} encodes the expression into an agent expression
4488 (@pxref{Agent Expressions}) suitable for execution on the target,
4489 independently of @value{GDBN}. Global variables become raw memory
4490 locations, locals become stack accesses, and so forth.
4492 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4493 when its condition evaluates to true. This mechanism may provide faster
4494 response times depending on the performance characteristics of the target
4495 since it does not need to keep @value{GDBN} informed about
4496 every breakpoint trigger, even those with false conditions.
4498 Break conditions can be specified when a breakpoint is set, by using
4499 @samp{if} in the arguments to the @code{break} command. @xref{Set
4500 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4501 with the @code{condition} command.
4503 You can also use the @code{if} keyword with the @code{watch} command.
4504 The @code{catch} command does not recognize the @code{if} keyword;
4505 @code{condition} is the only way to impose a further condition on a
4510 @item condition @var{bnum} @var{expression}
4511 Specify @var{expression} as the break condition for breakpoint,
4512 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4513 breakpoint @var{bnum} stops your program only if the value of
4514 @var{expression} is true (nonzero, in C). When you use
4515 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4516 syntactic correctness, and to determine whether symbols in it have
4517 referents in the context of your breakpoint. If @var{expression} uses
4518 symbols not referenced in the context of the breakpoint, @value{GDBN}
4519 prints an error message:
4522 No symbol "foo" in current context.
4527 not actually evaluate @var{expression} at the time the @code{condition}
4528 command (or a command that sets a breakpoint with a condition, like
4529 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4531 @item condition @var{bnum}
4532 Remove the condition from breakpoint number @var{bnum}. It becomes
4533 an ordinary unconditional breakpoint.
4536 @cindex ignore count (of breakpoint)
4537 A special case of a breakpoint condition is to stop only when the
4538 breakpoint has been reached a certain number of times. This is so
4539 useful that there is a special way to do it, using the @dfn{ignore
4540 count} of the breakpoint. Every breakpoint has an ignore count, which
4541 is an integer. Most of the time, the ignore count is zero, and
4542 therefore has no effect. But if your program reaches a breakpoint whose
4543 ignore count is positive, then instead of stopping, it just decrements
4544 the ignore count by one and continues. As a result, if the ignore count
4545 value is @var{n}, the breakpoint does not stop the next @var{n} times
4546 your program reaches it.
4550 @item ignore @var{bnum} @var{count}
4551 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4552 The next @var{count} times the breakpoint is reached, your program's
4553 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4556 To make the breakpoint stop the next time it is reached, specify
4559 When you use @code{continue} to resume execution of your program from a
4560 breakpoint, you can specify an ignore count directly as an argument to
4561 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4562 Stepping,,Continuing and Stepping}.
4564 If a breakpoint has a positive ignore count and a condition, the
4565 condition is not checked. Once the ignore count reaches zero,
4566 @value{GDBN} resumes checking the condition.
4568 You could achieve the effect of the ignore count with a condition such
4569 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4570 is decremented each time. @xref{Convenience Vars, ,Convenience
4574 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4577 @node Break Commands
4578 @subsection Breakpoint Command Lists
4580 @cindex breakpoint commands
4581 You can give any breakpoint (or watchpoint or catchpoint) a series of
4582 commands to execute when your program stops due to that breakpoint. For
4583 example, you might want to print the values of certain expressions, or
4584 enable other breakpoints.
4588 @kindex end@r{ (breakpoint commands)}
4589 @item commands @r{[}@var{range}@dots{}@r{]}
4590 @itemx @dots{} @var{command-list} @dots{}
4592 Specify a list of commands for the given breakpoints. The commands
4593 themselves appear on the following lines. Type a line containing just
4594 @code{end} to terminate the commands.
4596 To remove all commands from a breakpoint, type @code{commands} and
4597 follow it immediately with @code{end}; that is, give no commands.
4599 With no argument, @code{commands} refers to the last breakpoint,
4600 watchpoint, or catchpoint set (not to the breakpoint most recently
4601 encountered). If the most recent breakpoints were set with a single
4602 command, then the @code{commands} will apply to all the breakpoints
4603 set by that command. This applies to breakpoints set by
4604 @code{rbreak}, and also applies when a single @code{break} command
4605 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4609 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4610 disabled within a @var{command-list}.
4612 You can use breakpoint commands to start your program up again. Simply
4613 use the @code{continue} command, or @code{step}, or any other command
4614 that resumes execution.
4616 Any other commands in the command list, after a command that resumes
4617 execution, are ignored. This is because any time you resume execution
4618 (even with a simple @code{next} or @code{step}), you may encounter
4619 another breakpoint---which could have its own command list, leading to
4620 ambiguities about which list to execute.
4623 If the first command you specify in a command list is @code{silent}, the
4624 usual message about stopping at a breakpoint is not printed. This may
4625 be desirable for breakpoints that are to print a specific message and
4626 then continue. If none of the remaining commands print anything, you
4627 see no sign that the breakpoint was reached. @code{silent} is
4628 meaningful only at the beginning of a breakpoint command list.
4630 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4631 print precisely controlled output, and are often useful in silent
4632 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4634 For example, here is how you could use breakpoint commands to print the
4635 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4641 printf "x is %d\n",x
4646 One application for breakpoint commands is to compensate for one bug so
4647 you can test for another. Put a breakpoint just after the erroneous line
4648 of code, give it a condition to detect the case in which something
4649 erroneous has been done, and give it commands to assign correct values
4650 to any variables that need them. End with the @code{continue} command
4651 so that your program does not stop, and start with the @code{silent}
4652 command so that no output is produced. Here is an example:
4663 @node Dynamic Printf
4664 @subsection Dynamic Printf
4666 @cindex dynamic printf
4668 The dynamic printf command @code{dprintf} combines a breakpoint with
4669 formatted printing of your program's data to give you the effect of
4670 inserting @code{printf} calls into your program on-the-fly, without
4671 having to recompile it.
4673 In its most basic form, the output goes to the GDB console. However,
4674 you can set the variable @code{dprintf-style} for alternate handling.
4675 For instance, you can ask to format the output by calling your
4676 program's @code{printf} function. This has the advantage that the
4677 characters go to the program's output device, so they can recorded in
4678 redirects to files and so forth.
4680 If you are doing remote debugging with a stub or agent, you can also
4681 ask to have the printf handled by the remote agent. In addition to
4682 ensuring that the output goes to the remote program's device along
4683 with any other output the program might produce, you can also ask that
4684 the dprintf remain active even after disconnecting from the remote
4685 target. Using the stub/agent is also more efficient, as it can do
4686 everything without needing to communicate with @value{GDBN}.
4690 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4691 Whenever execution reaches @var{location}, print the values of one or
4692 more @var{expressions} under the control of the string @var{template}.
4693 To print several values, separate them with commas.
4695 @item set dprintf-style @var{style}
4696 Set the dprintf output to be handled in one of several different
4697 styles enumerated below. A change of style affects all existing
4698 dynamic printfs immediately. (If you need individual control over the
4699 print commands, simply define normal breakpoints with
4700 explicitly-supplied command lists.)
4703 @kindex dprintf-style gdb
4704 Handle the output using the @value{GDBN} @code{printf} command.
4707 @kindex dprintf-style call
4708 Handle the output by calling a function in your program (normally
4712 @kindex dprintf-style agent
4713 Have the remote debugging agent (such as @code{gdbserver}) handle
4714 the output itself. This style is only available for agents that
4715 support running commands on the target.
4717 @item set dprintf-function @var{function}
4718 Set the function to call if the dprintf style is @code{call}. By
4719 default its value is @code{printf}. You may set it to any expression.
4720 that @value{GDBN} can evaluate to a function, as per the @code{call}
4723 @item set dprintf-channel @var{channel}
4724 Set a ``channel'' for dprintf. If set to a non-empty value,
4725 @value{GDBN} will evaluate it as an expression and pass the result as
4726 a first argument to the @code{dprintf-function}, in the manner of
4727 @code{fprintf} and similar functions. Otherwise, the dprintf format
4728 string will be the first argument, in the manner of @code{printf}.
4730 As an example, if you wanted @code{dprintf} output to go to a logfile
4731 that is a standard I/O stream assigned to the variable @code{mylog},
4732 you could do the following:
4735 (gdb) set dprintf-style call
4736 (gdb) set dprintf-function fprintf
4737 (gdb) set dprintf-channel mylog
4738 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4739 Dprintf 1 at 0x123456: file main.c, line 25.
4741 1 dprintf keep y 0x00123456 in main at main.c:25
4742 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4747 Note that the @code{info break} displays the dynamic printf commands
4748 as normal breakpoint commands; you can thus easily see the effect of
4749 the variable settings.
4751 @item set disconnected-dprintf on
4752 @itemx set disconnected-dprintf off
4753 @kindex set disconnected-dprintf
4754 Choose whether @code{dprintf} commands should continue to run if
4755 @value{GDBN} has disconnected from the target. This only applies
4756 if the @code{dprintf-style} is @code{agent}.
4758 @item show disconnected-dprintf off
4759 @kindex show disconnected-dprintf
4760 Show the current choice for disconnected @code{dprintf}.
4764 @value{GDBN} does not check the validity of function and channel,
4765 relying on you to supply values that are meaningful for the contexts
4766 in which they are being used. For instance, the function and channel
4767 may be the values of local variables, but if that is the case, then
4768 all enabled dynamic prints must be at locations within the scope of
4769 those locals. If evaluation fails, @value{GDBN} will report an error.
4771 @node Save Breakpoints
4772 @subsection How to save breakpoints to a file
4774 To save breakpoint definitions to a file use the @w{@code{save
4775 breakpoints}} command.
4778 @kindex save breakpoints
4779 @cindex save breakpoints to a file for future sessions
4780 @item save breakpoints [@var{filename}]
4781 This command saves all current breakpoint definitions together with
4782 their commands and ignore counts, into a file @file{@var{filename}}
4783 suitable for use in a later debugging session. This includes all
4784 types of breakpoints (breakpoints, watchpoints, catchpoints,
4785 tracepoints). To read the saved breakpoint definitions, use the
4786 @code{source} command (@pxref{Command Files}). Note that watchpoints
4787 with expressions involving local variables may fail to be recreated
4788 because it may not be possible to access the context where the
4789 watchpoint is valid anymore. Because the saved breakpoint definitions
4790 are simply a sequence of @value{GDBN} commands that recreate the
4791 breakpoints, you can edit the file in your favorite editing program,
4792 and remove the breakpoint definitions you're not interested in, or
4793 that can no longer be recreated.
4796 @node Static Probe Points
4797 @subsection Static Probe Points
4799 @cindex static probe point, SystemTap
4800 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4801 for Statically Defined Tracing, and the probes are designed to have a tiny
4802 runtime code and data footprint, and no dynamic relocations. They are
4803 usable from assembly, C and C@t{++} languages. See
4804 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4805 for a good reference on how the @acronym{SDT} probes are implemented.
4807 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4808 @acronym{SDT} probes are supported on ELF-compatible systems. See
4809 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4810 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4811 in your applications.
4813 @cindex semaphores on static probe points
4814 Some probes have an associated semaphore variable; for instance, this
4815 happens automatically if you defined your probe using a DTrace-style
4816 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4817 automatically enable it when you specify a breakpoint using the
4818 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4819 location by some other method (e.g., @code{break file:line}), then
4820 @value{GDBN} will not automatically set the semaphore.
4822 You can examine the available static static probes using @code{info
4823 probes}, with optional arguments:
4827 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4828 If given, @var{provider} is a regular expression used to match against provider
4829 names when selecting which probes to list. If omitted, probes by all
4830 probes from all providers are listed.
4832 If given, @var{name} is a regular expression to match against probe names
4833 when selecting which probes to list. If omitted, probe names are not
4834 considered when deciding whether to display them.
4836 If given, @var{objfile} is a regular expression used to select which
4837 object files (executable or shared libraries) to examine. If not
4838 given, all object files are considered.
4840 @item info probes all
4841 List the available static probes, from all types.
4844 @vindex $_probe_arg@r{, convenience variable}
4845 A probe may specify up to twelve arguments. These are available at the
4846 point at which the probe is defined---that is, when the current PC is
4847 at the probe's location. The arguments are available using the
4848 convenience variables (@pxref{Convenience Vars})
4849 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4850 an integer of the appropriate size; types are not preserved. The
4851 convenience variable @code{$_probe_argc} holds the number of arguments
4852 at the current probe point.
4854 These variables are always available, but attempts to access them at
4855 any location other than a probe point will cause @value{GDBN} to give
4859 @c @ifclear BARETARGET
4860 @node Error in Breakpoints
4861 @subsection ``Cannot insert breakpoints''
4863 If you request too many active hardware-assisted breakpoints and
4864 watchpoints, you will see this error message:
4866 @c FIXME: the precise wording of this message may change; the relevant
4867 @c source change is not committed yet (Sep 3, 1999).
4869 Stopped; cannot insert breakpoints.
4870 You may have requested too many hardware breakpoints and watchpoints.
4874 This message is printed when you attempt to resume the program, since
4875 only then @value{GDBN} knows exactly how many hardware breakpoints and
4876 watchpoints it needs to insert.
4878 When this message is printed, you need to disable or remove some of the
4879 hardware-assisted breakpoints and watchpoints, and then continue.
4881 @node Breakpoint-related Warnings
4882 @subsection ``Breakpoint address adjusted...''
4883 @cindex breakpoint address adjusted
4885 Some processor architectures place constraints on the addresses at
4886 which breakpoints may be placed. For architectures thus constrained,
4887 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4888 with the constraints dictated by the architecture.
4890 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4891 a VLIW architecture in which a number of RISC-like instructions may be
4892 bundled together for parallel execution. The FR-V architecture
4893 constrains the location of a breakpoint instruction within such a
4894 bundle to the instruction with the lowest address. @value{GDBN}
4895 honors this constraint by adjusting a breakpoint's address to the
4896 first in the bundle.
4898 It is not uncommon for optimized code to have bundles which contain
4899 instructions from different source statements, thus it may happen that
4900 a breakpoint's address will be adjusted from one source statement to
4901 another. Since this adjustment may significantly alter @value{GDBN}'s
4902 breakpoint related behavior from what the user expects, a warning is
4903 printed when the breakpoint is first set and also when the breakpoint
4906 A warning like the one below is printed when setting a breakpoint
4907 that's been subject to address adjustment:
4910 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4913 Such warnings are printed both for user settable and @value{GDBN}'s
4914 internal breakpoints. If you see one of these warnings, you should
4915 verify that a breakpoint set at the adjusted address will have the
4916 desired affect. If not, the breakpoint in question may be removed and
4917 other breakpoints may be set which will have the desired behavior.
4918 E.g., it may be sufficient to place the breakpoint at a later
4919 instruction. A conditional breakpoint may also be useful in some
4920 cases to prevent the breakpoint from triggering too often.
4922 @value{GDBN} will also issue a warning when stopping at one of these
4923 adjusted breakpoints:
4926 warning: Breakpoint 1 address previously adjusted from 0x00010414
4930 When this warning is encountered, it may be too late to take remedial
4931 action except in cases where the breakpoint is hit earlier or more
4932 frequently than expected.
4934 @node Continuing and Stepping
4935 @section Continuing and Stepping
4939 @cindex resuming execution
4940 @dfn{Continuing} means resuming program execution until your program
4941 completes normally. In contrast, @dfn{stepping} means executing just
4942 one more ``step'' of your program, where ``step'' may mean either one
4943 line of source code, or one machine instruction (depending on what
4944 particular command you use). Either when continuing or when stepping,
4945 your program may stop even sooner, due to a breakpoint or a signal. (If
4946 it stops due to a signal, you may want to use @code{handle}, or use
4947 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4951 @kindex c @r{(@code{continue})}
4952 @kindex fg @r{(resume foreground execution)}
4953 @item continue @r{[}@var{ignore-count}@r{]}
4954 @itemx c @r{[}@var{ignore-count}@r{]}
4955 @itemx fg @r{[}@var{ignore-count}@r{]}
4956 Resume program execution, at the address where your program last stopped;
4957 any breakpoints set at that address are bypassed. The optional argument
4958 @var{ignore-count} allows you to specify a further number of times to
4959 ignore a breakpoint at this location; its effect is like that of
4960 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4962 The argument @var{ignore-count} is meaningful only when your program
4963 stopped due to a breakpoint. At other times, the argument to
4964 @code{continue} is ignored.
4966 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4967 debugged program is deemed to be the foreground program) are provided
4968 purely for convenience, and have exactly the same behavior as
4972 To resume execution at a different place, you can use @code{return}
4973 (@pxref{Returning, ,Returning from a Function}) to go back to the
4974 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4975 Different Address}) to go to an arbitrary location in your program.
4977 A typical technique for using stepping is to set a breakpoint
4978 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4979 beginning of the function or the section of your program where a problem
4980 is believed to lie, run your program until it stops at that breakpoint,
4981 and then step through the suspect area, examining the variables that are
4982 interesting, until you see the problem happen.
4986 @kindex s @r{(@code{step})}
4988 Continue running your program until control reaches a different source
4989 line, then stop it and return control to @value{GDBN}. This command is
4990 abbreviated @code{s}.
4993 @c "without debugging information" is imprecise; actually "without line
4994 @c numbers in the debugging information". (gcc -g1 has debugging info but
4995 @c not line numbers). But it seems complex to try to make that
4996 @c distinction here.
4997 @emph{Warning:} If you use the @code{step} command while control is
4998 within a function that was compiled without debugging information,
4999 execution proceeds until control reaches a function that does have
5000 debugging information. Likewise, it will not step into a function which
5001 is compiled without debugging information. To step through functions
5002 without debugging information, use the @code{stepi} command, described
5006 The @code{step} command only stops at the first instruction of a source
5007 line. This prevents the multiple stops that could otherwise occur in
5008 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5009 to stop if a function that has debugging information is called within
5010 the line. In other words, @code{step} @emph{steps inside} any functions
5011 called within the line.
5013 Also, the @code{step} command only enters a function if there is line
5014 number information for the function. Otherwise it acts like the
5015 @code{next} command. This avoids problems when using @code{cc -gl}
5016 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5017 was any debugging information about the routine.
5019 @item step @var{count}
5020 Continue running as in @code{step}, but do so @var{count} times. If a
5021 breakpoint is reached, or a signal not related to stepping occurs before
5022 @var{count} steps, stepping stops right away.
5025 @kindex n @r{(@code{next})}
5026 @item next @r{[}@var{count}@r{]}
5027 Continue to the next source line in the current (innermost) stack frame.
5028 This is similar to @code{step}, but function calls that appear within
5029 the line of code are executed without stopping. Execution stops when
5030 control reaches a different line of code at the original stack level
5031 that was executing when you gave the @code{next} command. This command
5032 is abbreviated @code{n}.
5034 An argument @var{count} is a repeat count, as for @code{step}.
5037 @c FIX ME!! Do we delete this, or is there a way it fits in with
5038 @c the following paragraph? --- Vctoria
5040 @c @code{next} within a function that lacks debugging information acts like
5041 @c @code{step}, but any function calls appearing within the code of the
5042 @c function are executed without stopping.
5044 The @code{next} command only stops at the first instruction of a
5045 source line. This prevents multiple stops that could otherwise occur in
5046 @code{switch} statements, @code{for} loops, etc.
5048 @kindex set step-mode
5050 @cindex functions without line info, and stepping
5051 @cindex stepping into functions with no line info
5052 @itemx set step-mode on
5053 The @code{set step-mode on} command causes the @code{step} command to
5054 stop at the first instruction of a function which contains no debug line
5055 information rather than stepping over it.
5057 This is useful in cases where you may be interested in inspecting the
5058 machine instructions of a function which has no symbolic info and do not
5059 want @value{GDBN} to automatically skip over this function.
5061 @item set step-mode off
5062 Causes the @code{step} command to step over any functions which contains no
5063 debug information. This is the default.
5065 @item show step-mode
5066 Show whether @value{GDBN} will stop in or step over functions without
5067 source line debug information.
5070 @kindex fin @r{(@code{finish})}
5072 Continue running until just after function in the selected stack frame
5073 returns. Print the returned value (if any). This command can be
5074 abbreviated as @code{fin}.
5076 Contrast this with the @code{return} command (@pxref{Returning,
5077 ,Returning from a Function}).
5080 @kindex u @r{(@code{until})}
5081 @cindex run until specified location
5084 Continue running until a source line past the current line, in the
5085 current stack frame, is reached. This command is used to avoid single
5086 stepping through a loop more than once. It is like the @code{next}
5087 command, except that when @code{until} encounters a jump, it
5088 automatically continues execution until the program counter is greater
5089 than the address of the jump.
5091 This means that when you reach the end of a loop after single stepping
5092 though it, @code{until} makes your program continue execution until it
5093 exits the loop. In contrast, a @code{next} command at the end of a loop
5094 simply steps back to the beginning of the loop, which forces you to step
5095 through the next iteration.
5097 @code{until} always stops your program if it attempts to exit the current
5100 @code{until} may produce somewhat counterintuitive results if the order
5101 of machine code does not match the order of the source lines. For
5102 example, in the following excerpt from a debugging session, the @code{f}
5103 (@code{frame}) command shows that execution is stopped at line
5104 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5108 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5110 (@value{GDBP}) until
5111 195 for ( ; argc > 0; NEXTARG) @{
5114 This happened because, for execution efficiency, the compiler had
5115 generated code for the loop closure test at the end, rather than the
5116 start, of the loop---even though the test in a C @code{for}-loop is
5117 written before the body of the loop. The @code{until} command appeared
5118 to step back to the beginning of the loop when it advanced to this
5119 expression; however, it has not really gone to an earlier
5120 statement---not in terms of the actual machine code.
5122 @code{until} with no argument works by means of single
5123 instruction stepping, and hence is slower than @code{until} with an
5126 @item until @var{location}
5127 @itemx u @var{location}
5128 Continue running your program until either the specified location is
5129 reached, or the current stack frame returns. @var{location} is any of
5130 the forms described in @ref{Specify Location}.
5131 This form of the command uses temporary breakpoints, and
5132 hence is quicker than @code{until} without an argument. The specified
5133 location is actually reached only if it is in the current frame. This
5134 implies that @code{until} can be used to skip over recursive function
5135 invocations. For instance in the code below, if the current location is
5136 line @code{96}, issuing @code{until 99} will execute the program up to
5137 line @code{99} in the same invocation of factorial, i.e., after the inner
5138 invocations have returned.
5141 94 int factorial (int value)
5143 96 if (value > 1) @{
5144 97 value *= factorial (value - 1);
5151 @kindex advance @var{location}
5152 @item advance @var{location}
5153 Continue running the program up to the given @var{location}. An argument is
5154 required, which should be of one of the forms described in
5155 @ref{Specify Location}.
5156 Execution will also stop upon exit from the current stack
5157 frame. This command is similar to @code{until}, but @code{advance} will
5158 not skip over recursive function calls, and the target location doesn't
5159 have to be in the same frame as the current one.
5163 @kindex si @r{(@code{stepi})}
5165 @itemx stepi @var{arg}
5167 Execute one machine instruction, then stop and return to the debugger.
5169 It is often useful to do @samp{display/i $pc} when stepping by machine
5170 instructions. This makes @value{GDBN} automatically display the next
5171 instruction to be executed, each time your program stops. @xref{Auto
5172 Display,, Automatic Display}.
5174 An argument is a repeat count, as in @code{step}.
5178 @kindex ni @r{(@code{nexti})}
5180 @itemx nexti @var{arg}
5182 Execute one machine instruction, but if it is a function call,
5183 proceed until the function returns.
5185 An argument is a repeat count, as in @code{next}.
5188 @node Skipping Over Functions and Files
5189 @section Skipping Over Functions and Files
5190 @cindex skipping over functions and files
5192 The program you are debugging may contain some functions which are
5193 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5194 skip a function or all functions in a file when stepping.
5196 For example, consider the following C function:
5207 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5208 are not interested in stepping through @code{boring}. If you run @code{step}
5209 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5210 step over both @code{foo} and @code{boring}!
5212 One solution is to @code{step} into @code{boring} and use the @code{finish}
5213 command to immediately exit it. But this can become tedious if @code{boring}
5214 is called from many places.
5216 A more flexible solution is to execute @kbd{skip boring}. This instructs
5217 @value{GDBN} never to step into @code{boring}. Now when you execute
5218 @code{step} at line 103, you'll step over @code{boring} and directly into
5221 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5222 example, @code{skip file boring.c}.
5225 @kindex skip function
5226 @item skip @r{[}@var{linespec}@r{]}
5227 @itemx skip function @r{[}@var{linespec}@r{]}
5228 After running this command, the function named by @var{linespec} or the
5229 function containing the line named by @var{linespec} will be skipped over when
5230 stepping. @xref{Specify Location}.
5232 If you do not specify @var{linespec}, the function you're currently debugging
5235 (If you have a function called @code{file} that you want to skip, use
5236 @kbd{skip function file}.)
5239 @item skip file @r{[}@var{filename}@r{]}
5240 After running this command, any function whose source lives in @var{filename}
5241 will be skipped over when stepping.
5243 If you do not specify @var{filename}, functions whose source lives in the file
5244 you're currently debugging will be skipped.
5247 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5248 These are the commands for managing your list of skips:
5252 @item info skip @r{[}@var{range}@r{]}
5253 Print details about the specified skip(s). If @var{range} is not specified,
5254 print a table with details about all functions and files marked for skipping.
5255 @code{info skip} prints the following information about each skip:
5259 A number identifying this skip.
5261 The type of this skip, either @samp{function} or @samp{file}.
5262 @item Enabled or Disabled
5263 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5265 For function skips, this column indicates the address in memory of the function
5266 being skipped. If you've set a function skip on a function which has not yet
5267 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5268 which has the function is loaded, @code{info skip} will show the function's
5271 For file skips, this field contains the filename being skipped. For functions
5272 skips, this field contains the function name and its line number in the file
5273 where it is defined.
5277 @item skip delete @r{[}@var{range}@r{]}
5278 Delete the specified skip(s). If @var{range} is not specified, delete all
5282 @item skip enable @r{[}@var{range}@r{]}
5283 Enable the specified skip(s). If @var{range} is not specified, enable all
5286 @kindex skip disable
5287 @item skip disable @r{[}@var{range}@r{]}
5288 Disable the specified skip(s). If @var{range} is not specified, disable all
5297 A signal is an asynchronous event that can happen in a program. The
5298 operating system defines the possible kinds of signals, and gives each
5299 kind a name and a number. For example, in Unix @code{SIGINT} is the
5300 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5301 @code{SIGSEGV} is the signal a program gets from referencing a place in
5302 memory far away from all the areas in use; @code{SIGALRM} occurs when
5303 the alarm clock timer goes off (which happens only if your program has
5304 requested an alarm).
5306 @cindex fatal signals
5307 Some signals, including @code{SIGALRM}, are a normal part of the
5308 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5309 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5310 program has not specified in advance some other way to handle the signal.
5311 @code{SIGINT} does not indicate an error in your program, but it is normally
5312 fatal so it can carry out the purpose of the interrupt: to kill the program.
5314 @value{GDBN} has the ability to detect any occurrence of a signal in your
5315 program. You can tell @value{GDBN} in advance what to do for each kind of
5318 @cindex handling signals
5319 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5320 @code{SIGALRM} be silently passed to your program
5321 (so as not to interfere with their role in the program's functioning)
5322 but to stop your program immediately whenever an error signal happens.
5323 You can change these settings with the @code{handle} command.
5326 @kindex info signals
5330 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5331 handle each one. You can use this to see the signal numbers of all
5332 the defined types of signals.
5334 @item info signals @var{sig}
5335 Similar, but print information only about the specified signal number.
5337 @code{info handle} is an alias for @code{info signals}.
5340 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5341 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5342 can be the number of a signal or its name (with or without the
5343 @samp{SIG} at the beginning); a list of signal numbers of the form
5344 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5345 known signals. Optional arguments @var{keywords}, described below,
5346 say what change to make.
5350 The keywords allowed by the @code{handle} command can be abbreviated.
5351 Their full names are:
5355 @value{GDBN} should not stop your program when this signal happens. It may
5356 still print a message telling you that the signal has come in.
5359 @value{GDBN} should stop your program when this signal happens. This implies
5360 the @code{print} keyword as well.
5363 @value{GDBN} should print a message when this signal happens.
5366 @value{GDBN} should not mention the occurrence of the signal at all. This
5367 implies the @code{nostop} keyword as well.
5371 @value{GDBN} should allow your program to see this signal; your program
5372 can handle the signal, or else it may terminate if the signal is fatal
5373 and not handled. @code{pass} and @code{noignore} are synonyms.
5377 @value{GDBN} should not allow your program to see this signal.
5378 @code{nopass} and @code{ignore} are synonyms.
5382 When a signal stops your program, the signal is not visible to the
5384 continue. Your program sees the signal then, if @code{pass} is in
5385 effect for the signal in question @emph{at that time}. In other words,
5386 after @value{GDBN} reports a signal, you can use the @code{handle}
5387 command with @code{pass} or @code{nopass} to control whether your
5388 program sees that signal when you continue.
5390 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5391 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5392 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5395 You can also use the @code{signal} command to prevent your program from
5396 seeing a signal, or cause it to see a signal it normally would not see,
5397 or to give it any signal at any time. For example, if your program stopped
5398 due to some sort of memory reference error, you might store correct
5399 values into the erroneous variables and continue, hoping to see more
5400 execution; but your program would probably terminate immediately as
5401 a result of the fatal signal once it saw the signal. To prevent this,
5402 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5405 @cindex extra signal information
5406 @anchor{extra signal information}
5408 On some targets, @value{GDBN} can inspect extra signal information
5409 associated with the intercepted signal, before it is actually
5410 delivered to the program being debugged. This information is exported
5411 by the convenience variable @code{$_siginfo}, and consists of data
5412 that is passed by the kernel to the signal handler at the time of the
5413 receipt of a signal. The data type of the information itself is
5414 target dependent. You can see the data type using the @code{ptype
5415 $_siginfo} command. On Unix systems, it typically corresponds to the
5416 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5419 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5420 referenced address that raised a segmentation fault.
5424 (@value{GDBP}) continue
5425 Program received signal SIGSEGV, Segmentation fault.
5426 0x0000000000400766 in main ()
5428 (@value{GDBP}) ptype $_siginfo
5435 struct @{...@} _kill;
5436 struct @{...@} _timer;
5438 struct @{...@} _sigchld;
5439 struct @{...@} _sigfault;
5440 struct @{...@} _sigpoll;
5443 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5447 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5448 $1 = (void *) 0x7ffff7ff7000
5452 Depending on target support, @code{$_siginfo} may also be writable.
5455 @section Stopping and Starting Multi-thread Programs
5457 @cindex stopped threads
5458 @cindex threads, stopped
5460 @cindex continuing threads
5461 @cindex threads, continuing
5463 @value{GDBN} supports debugging programs with multiple threads
5464 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5465 are two modes of controlling execution of your program within the
5466 debugger. In the default mode, referred to as @dfn{all-stop mode},
5467 when any thread in your program stops (for example, at a breakpoint
5468 or while being stepped), all other threads in the program are also stopped by
5469 @value{GDBN}. On some targets, @value{GDBN} also supports
5470 @dfn{non-stop mode}, in which other threads can continue to run freely while
5471 you examine the stopped thread in the debugger.
5474 * All-Stop Mode:: All threads stop when GDB takes control
5475 * Non-Stop Mode:: Other threads continue to execute
5476 * Background Execution:: Running your program asynchronously
5477 * Thread-Specific Breakpoints:: Controlling breakpoints
5478 * Interrupted System Calls:: GDB may interfere with system calls
5479 * Observer Mode:: GDB does not alter program behavior
5483 @subsection All-Stop Mode
5485 @cindex all-stop mode
5487 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5488 @emph{all} threads of execution stop, not just the current thread. This
5489 allows you to examine the overall state of the program, including
5490 switching between threads, without worrying that things may change
5493 Conversely, whenever you restart the program, @emph{all} threads start
5494 executing. @emph{This is true even when single-stepping} with commands
5495 like @code{step} or @code{next}.
5497 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5498 Since thread scheduling is up to your debugging target's operating
5499 system (not controlled by @value{GDBN}), other threads may
5500 execute more than one statement while the current thread completes a
5501 single step. Moreover, in general other threads stop in the middle of a
5502 statement, rather than at a clean statement boundary, when the program
5505 You might even find your program stopped in another thread after
5506 continuing or even single-stepping. This happens whenever some other
5507 thread runs into a breakpoint, a signal, or an exception before the
5508 first thread completes whatever you requested.
5510 @cindex automatic thread selection
5511 @cindex switching threads automatically
5512 @cindex threads, automatic switching
5513 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5514 signal, it automatically selects the thread where that breakpoint or
5515 signal happened. @value{GDBN} alerts you to the context switch with a
5516 message such as @samp{[Switching to Thread @var{n}]} to identify the
5519 On some OSes, you can modify @value{GDBN}'s default behavior by
5520 locking the OS scheduler to allow only a single thread to run.
5523 @item set scheduler-locking @var{mode}
5524 @cindex scheduler locking mode
5525 @cindex lock scheduler
5526 Set the scheduler locking mode. If it is @code{off}, then there is no
5527 locking and any thread may run at any time. If @code{on}, then only the
5528 current thread may run when the inferior is resumed. The @code{step}
5529 mode optimizes for single-stepping; it prevents other threads
5530 from preempting the current thread while you are stepping, so that
5531 the focus of debugging does not change unexpectedly.
5532 Other threads only rarely (or never) get a chance to run
5533 when you step. They are more likely to run when you @samp{next} over a
5534 function call, and they are completely free to run when you use commands
5535 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5536 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5537 the current thread away from the thread that you are debugging.
5539 @item show scheduler-locking
5540 Display the current scheduler locking mode.
5543 @cindex resume threads of multiple processes simultaneously
5544 By default, when you issue one of the execution commands such as
5545 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5546 threads of the current inferior to run. For example, if @value{GDBN}
5547 is attached to two inferiors, each with two threads, the
5548 @code{continue} command resumes only the two threads of the current
5549 inferior. This is useful, for example, when you debug a program that
5550 forks and you want to hold the parent stopped (so that, for instance,
5551 it doesn't run to exit), while you debug the child. In other
5552 situations, you may not be interested in inspecting the current state
5553 of any of the processes @value{GDBN} is attached to, and you may want
5554 to resume them all until some breakpoint is hit. In the latter case,
5555 you can instruct @value{GDBN} to allow all threads of all the
5556 inferiors to run with the @w{@code{set schedule-multiple}} command.
5559 @kindex set schedule-multiple
5560 @item set schedule-multiple
5561 Set the mode for allowing threads of multiple processes to be resumed
5562 when an execution command is issued. When @code{on}, all threads of
5563 all processes are allowed to run. When @code{off}, only the threads
5564 of the current process are resumed. The default is @code{off}. The
5565 @code{scheduler-locking} mode takes precedence when set to @code{on},
5566 or while you are stepping and set to @code{step}.
5568 @item show schedule-multiple
5569 Display the current mode for resuming the execution of threads of
5574 @subsection Non-Stop Mode
5576 @cindex non-stop mode
5578 @c This section is really only a place-holder, and needs to be expanded
5579 @c with more details.
5581 For some multi-threaded targets, @value{GDBN} supports an optional
5582 mode of operation in which you can examine stopped program threads in
5583 the debugger while other threads continue to execute freely. This
5584 minimizes intrusion when debugging live systems, such as programs
5585 where some threads have real-time constraints or must continue to
5586 respond to external events. This is referred to as @dfn{non-stop} mode.
5588 In non-stop mode, when a thread stops to report a debugging event,
5589 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5590 threads as well, in contrast to the all-stop mode behavior. Additionally,
5591 execution commands such as @code{continue} and @code{step} apply by default
5592 only to the current thread in non-stop mode, rather than all threads as
5593 in all-stop mode. This allows you to control threads explicitly in
5594 ways that are not possible in all-stop mode --- for example, stepping
5595 one thread while allowing others to run freely, stepping
5596 one thread while holding all others stopped, or stepping several threads
5597 independently and simultaneously.
5599 To enter non-stop mode, use this sequence of commands before you run
5600 or attach to your program:
5603 # Enable the async interface.
5606 # If using the CLI, pagination breaks non-stop.
5609 # Finally, turn it on!
5613 You can use these commands to manipulate the non-stop mode setting:
5616 @kindex set non-stop
5617 @item set non-stop on
5618 Enable selection of non-stop mode.
5619 @item set non-stop off
5620 Disable selection of non-stop mode.
5621 @kindex show non-stop
5623 Show the current non-stop enablement setting.
5626 Note these commands only reflect whether non-stop mode is enabled,
5627 not whether the currently-executing program is being run in non-stop mode.
5628 In particular, the @code{set non-stop} preference is only consulted when
5629 @value{GDBN} starts or connects to the target program, and it is generally
5630 not possible to switch modes once debugging has started. Furthermore,
5631 since not all targets support non-stop mode, even when you have enabled
5632 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5635 In non-stop mode, all execution commands apply only to the current thread
5636 by default. That is, @code{continue} only continues one thread.
5637 To continue all threads, issue @code{continue -a} or @code{c -a}.
5639 You can use @value{GDBN}'s background execution commands
5640 (@pxref{Background Execution}) to run some threads in the background
5641 while you continue to examine or step others from @value{GDBN}.
5642 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5643 always executed asynchronously in non-stop mode.
5645 Suspending execution is done with the @code{interrupt} command when
5646 running in the background, or @kbd{Ctrl-c} during foreground execution.
5647 In all-stop mode, this stops the whole process;
5648 but in non-stop mode the interrupt applies only to the current thread.
5649 To stop the whole program, use @code{interrupt -a}.
5651 Other execution commands do not currently support the @code{-a} option.
5653 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5654 that thread current, as it does in all-stop mode. This is because the
5655 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5656 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5657 changed to a different thread just as you entered a command to operate on the
5658 previously current thread.
5660 @node Background Execution
5661 @subsection Background Execution
5663 @cindex foreground execution
5664 @cindex background execution
5665 @cindex asynchronous execution
5666 @cindex execution, foreground, background and asynchronous
5668 @value{GDBN}'s execution commands have two variants: the normal
5669 foreground (synchronous) behavior, and a background
5670 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5671 the program to report that some thread has stopped before prompting for
5672 another command. In background execution, @value{GDBN} immediately gives
5673 a command prompt so that you can issue other commands while your program runs.
5675 You need to explicitly enable asynchronous mode before you can use
5676 background execution commands. You can use these commands to
5677 manipulate the asynchronous mode setting:
5680 @kindex set target-async
5681 @item set target-async on
5682 Enable asynchronous mode.
5683 @item set target-async off
5684 Disable asynchronous mode.
5685 @kindex show target-async
5686 @item show target-async
5687 Show the current target-async setting.
5690 If the target doesn't support async mode, @value{GDBN} issues an error
5691 message if you attempt to use the background execution commands.
5693 To specify background execution, add a @code{&} to the command. For example,
5694 the background form of the @code{continue} command is @code{continue&}, or
5695 just @code{c&}. The execution commands that accept background execution
5701 @xref{Starting, , Starting your Program}.
5705 @xref{Attach, , Debugging an Already-running Process}.
5709 @xref{Continuing and Stepping, step}.
5713 @xref{Continuing and Stepping, stepi}.
5717 @xref{Continuing and Stepping, next}.
5721 @xref{Continuing and Stepping, nexti}.
5725 @xref{Continuing and Stepping, continue}.
5729 @xref{Continuing and Stepping, finish}.
5733 @xref{Continuing and Stepping, until}.
5737 Background execution is especially useful in conjunction with non-stop
5738 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5739 However, you can also use these commands in the normal all-stop mode with
5740 the restriction that you cannot issue another execution command until the
5741 previous one finishes. Examples of commands that are valid in all-stop
5742 mode while the program is running include @code{help} and @code{info break}.
5744 You can interrupt your program while it is running in the background by
5745 using the @code{interrupt} command.
5752 Suspend execution of the running program. In all-stop mode,
5753 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5754 only the current thread. To stop the whole program in non-stop mode,
5755 use @code{interrupt -a}.
5758 @node Thread-Specific Breakpoints
5759 @subsection Thread-Specific Breakpoints
5761 When your program has multiple threads (@pxref{Threads,, Debugging
5762 Programs with Multiple Threads}), you can choose whether to set
5763 breakpoints on all threads, or on a particular thread.
5766 @cindex breakpoints and threads
5767 @cindex thread breakpoints
5768 @kindex break @dots{} thread @var{threadno}
5769 @item break @var{linespec} thread @var{threadno}
5770 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5771 @var{linespec} specifies source lines; there are several ways of
5772 writing them (@pxref{Specify Location}), but the effect is always to
5773 specify some source line.
5775 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5776 to specify that you only want @value{GDBN} to stop the program when a
5777 particular thread reaches this breakpoint. @var{threadno} is one of the
5778 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5779 column of the @samp{info threads} display.
5781 If you do not specify @samp{thread @var{threadno}} when you set a
5782 breakpoint, the breakpoint applies to @emph{all} threads of your
5785 You can use the @code{thread} qualifier on conditional breakpoints as
5786 well; in this case, place @samp{thread @var{threadno}} before or
5787 after the breakpoint condition, like this:
5790 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5795 @node Interrupted System Calls
5796 @subsection Interrupted System Calls
5798 @cindex thread breakpoints and system calls
5799 @cindex system calls and thread breakpoints
5800 @cindex premature return from system calls
5801 There is an unfortunate side effect when using @value{GDBN} to debug
5802 multi-threaded programs. If one thread stops for a
5803 breakpoint, or for some other reason, and another thread is blocked in a
5804 system call, then the system call may return prematurely. This is a
5805 consequence of the interaction between multiple threads and the signals
5806 that @value{GDBN} uses to implement breakpoints and other events that
5809 To handle this problem, your program should check the return value of
5810 each system call and react appropriately. This is good programming
5813 For example, do not write code like this:
5819 The call to @code{sleep} will return early if a different thread stops
5820 at a breakpoint or for some other reason.
5822 Instead, write this:
5827 unslept = sleep (unslept);
5830 A system call is allowed to return early, so the system is still
5831 conforming to its specification. But @value{GDBN} does cause your
5832 multi-threaded program to behave differently than it would without
5835 Also, @value{GDBN} uses internal breakpoints in the thread library to
5836 monitor certain events such as thread creation and thread destruction.
5837 When such an event happens, a system call in another thread may return
5838 prematurely, even though your program does not appear to stop.
5841 @subsection Observer Mode
5843 If you want to build on non-stop mode and observe program behavior
5844 without any chance of disruption by @value{GDBN}, you can set
5845 variables to disable all of the debugger's attempts to modify state,
5846 whether by writing memory, inserting breakpoints, etc. These operate
5847 at a low level, intercepting operations from all commands.
5849 When all of these are set to @code{off}, then @value{GDBN} is said to
5850 be @dfn{observer mode}. As a convenience, the variable
5851 @code{observer} can be set to disable these, plus enable non-stop
5854 Note that @value{GDBN} will not prevent you from making nonsensical
5855 combinations of these settings. For instance, if you have enabled
5856 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5857 then breakpoints that work by writing trap instructions into the code
5858 stream will still not be able to be placed.
5863 @item set observer on
5864 @itemx set observer off
5865 When set to @code{on}, this disables all the permission variables
5866 below (except for @code{insert-fast-tracepoints}), plus enables
5867 non-stop debugging. Setting this to @code{off} switches back to
5868 normal debugging, though remaining in non-stop mode.
5871 Show whether observer mode is on or off.
5873 @kindex may-write-registers
5874 @item set may-write-registers on
5875 @itemx set may-write-registers off
5876 This controls whether @value{GDBN} will attempt to alter the values of
5877 registers, such as with assignment expressions in @code{print}, or the
5878 @code{jump} command. It defaults to @code{on}.
5880 @item show may-write-registers
5881 Show the current permission to write registers.
5883 @kindex may-write-memory
5884 @item set may-write-memory on
5885 @itemx set may-write-memory off
5886 This controls whether @value{GDBN} will attempt to alter the contents
5887 of memory, such as with assignment expressions in @code{print}. It
5888 defaults to @code{on}.
5890 @item show may-write-memory
5891 Show the current permission to write memory.
5893 @kindex may-insert-breakpoints
5894 @item set may-insert-breakpoints on
5895 @itemx set may-insert-breakpoints off
5896 This controls whether @value{GDBN} will attempt to insert breakpoints.
5897 This affects all breakpoints, including internal breakpoints defined
5898 by @value{GDBN}. It defaults to @code{on}.
5900 @item show may-insert-breakpoints
5901 Show the current permission to insert breakpoints.
5903 @kindex may-insert-tracepoints
5904 @item set may-insert-tracepoints on
5905 @itemx set may-insert-tracepoints off
5906 This controls whether @value{GDBN} will attempt to insert (regular)
5907 tracepoints at the beginning of a tracing experiment. It affects only
5908 non-fast tracepoints, fast tracepoints being under the control of
5909 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5911 @item show may-insert-tracepoints
5912 Show the current permission to insert tracepoints.
5914 @kindex may-insert-fast-tracepoints
5915 @item set may-insert-fast-tracepoints on
5916 @itemx set may-insert-fast-tracepoints off
5917 This controls whether @value{GDBN} will attempt to insert fast
5918 tracepoints at the beginning of a tracing experiment. It affects only
5919 fast tracepoints, regular (non-fast) tracepoints being under the
5920 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5922 @item show may-insert-fast-tracepoints
5923 Show the current permission to insert fast tracepoints.
5925 @kindex may-interrupt
5926 @item set may-interrupt on
5927 @itemx set may-interrupt off
5928 This controls whether @value{GDBN} will attempt to interrupt or stop
5929 program execution. When this variable is @code{off}, the
5930 @code{interrupt} command will have no effect, nor will
5931 @kbd{Ctrl-c}. It defaults to @code{on}.
5933 @item show may-interrupt
5934 Show the current permission to interrupt or stop the program.
5938 @node Reverse Execution
5939 @chapter Running programs backward
5940 @cindex reverse execution
5941 @cindex running programs backward
5943 When you are debugging a program, it is not unusual to realize that
5944 you have gone too far, and some event of interest has already happened.
5945 If the target environment supports it, @value{GDBN} can allow you to
5946 ``rewind'' the program by running it backward.
5948 A target environment that supports reverse execution should be able
5949 to ``undo'' the changes in machine state that have taken place as the
5950 program was executing normally. Variables, registers etc.@: should
5951 revert to their previous values. Obviously this requires a great
5952 deal of sophistication on the part of the target environment; not
5953 all target environments can support reverse execution.
5955 When a program is executed in reverse, the instructions that
5956 have most recently been executed are ``un-executed'', in reverse
5957 order. The program counter runs backward, following the previous
5958 thread of execution in reverse. As each instruction is ``un-executed'',
5959 the values of memory and/or registers that were changed by that
5960 instruction are reverted to their previous states. After executing
5961 a piece of source code in reverse, all side effects of that code
5962 should be ``undone'', and all variables should be returned to their
5963 prior values@footnote{
5964 Note that some side effects are easier to undo than others. For instance,
5965 memory and registers are relatively easy, but device I/O is hard. Some
5966 targets may be able undo things like device I/O, and some may not.
5968 The contract between @value{GDBN} and the reverse executing target
5969 requires only that the target do something reasonable when
5970 @value{GDBN} tells it to execute backwards, and then report the
5971 results back to @value{GDBN}. Whatever the target reports back to
5972 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5973 assumes that the memory and registers that the target reports are in a
5974 consistant state, but @value{GDBN} accepts whatever it is given.
5977 If you are debugging in a target environment that supports
5978 reverse execution, @value{GDBN} provides the following commands.
5981 @kindex reverse-continue
5982 @kindex rc @r{(@code{reverse-continue})}
5983 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5984 @itemx rc @r{[}@var{ignore-count}@r{]}
5985 Beginning at the point where your program last stopped, start executing
5986 in reverse. Reverse execution will stop for breakpoints and synchronous
5987 exceptions (signals), just like normal execution. Behavior of
5988 asynchronous signals depends on the target environment.
5990 @kindex reverse-step
5991 @kindex rs @r{(@code{step})}
5992 @item reverse-step @r{[}@var{count}@r{]}
5993 Run the program backward until control reaches the start of a
5994 different source line; then stop it, and return control to @value{GDBN}.
5996 Like the @code{step} command, @code{reverse-step} will only stop
5997 at the beginning of a source line. It ``un-executes'' the previously
5998 executed source line. If the previous source line included calls to
5999 debuggable functions, @code{reverse-step} will step (backward) into
6000 the called function, stopping at the beginning of the @emph{last}
6001 statement in the called function (typically a return statement).
6003 Also, as with the @code{step} command, if non-debuggable functions are
6004 called, @code{reverse-step} will run thru them backward without stopping.
6006 @kindex reverse-stepi
6007 @kindex rsi @r{(@code{reverse-stepi})}
6008 @item reverse-stepi @r{[}@var{count}@r{]}
6009 Reverse-execute one machine instruction. Note that the instruction
6010 to be reverse-executed is @emph{not} the one pointed to by the program
6011 counter, but the instruction executed prior to that one. For instance,
6012 if the last instruction was a jump, @code{reverse-stepi} will take you
6013 back from the destination of the jump to the jump instruction itself.
6015 @kindex reverse-next
6016 @kindex rn @r{(@code{reverse-next})}
6017 @item reverse-next @r{[}@var{count}@r{]}
6018 Run backward to the beginning of the previous line executed in
6019 the current (innermost) stack frame. If the line contains function
6020 calls, they will be ``un-executed'' without stopping. Starting from
6021 the first line of a function, @code{reverse-next} will take you back
6022 to the caller of that function, @emph{before} the function was called,
6023 just as the normal @code{next} command would take you from the last
6024 line of a function back to its return to its caller
6025 @footnote{Unless the code is too heavily optimized.}.
6027 @kindex reverse-nexti
6028 @kindex rni @r{(@code{reverse-nexti})}
6029 @item reverse-nexti @r{[}@var{count}@r{]}
6030 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6031 in reverse, except that called functions are ``un-executed'' atomically.
6032 That is, if the previously executed instruction was a return from
6033 another function, @code{reverse-nexti} will continue to execute
6034 in reverse until the call to that function (from the current stack
6037 @kindex reverse-finish
6038 @item reverse-finish
6039 Just as the @code{finish} command takes you to the point where the
6040 current function returns, @code{reverse-finish} takes you to the point
6041 where it was called. Instead of ending up at the end of the current
6042 function invocation, you end up at the beginning.
6044 @kindex set exec-direction
6045 @item set exec-direction
6046 Set the direction of target execution.
6047 @item set exec-direction reverse
6048 @cindex execute forward or backward in time
6049 @value{GDBN} will perform all execution commands in reverse, until the
6050 exec-direction mode is changed to ``forward''. Affected commands include
6051 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6052 command cannot be used in reverse mode.
6053 @item set exec-direction forward
6054 @value{GDBN} will perform all execution commands in the normal fashion.
6055 This is the default.
6059 @node Process Record and Replay
6060 @chapter Recording Inferior's Execution and Replaying It
6061 @cindex process record and replay
6062 @cindex recording inferior's execution and replaying it
6064 On some platforms, @value{GDBN} provides a special @dfn{process record
6065 and replay} target that can record a log of the process execution, and
6066 replay it later with both forward and reverse execution commands.
6069 When this target is in use, if the execution log includes the record
6070 for the next instruction, @value{GDBN} will debug in @dfn{replay
6071 mode}. In the replay mode, the inferior does not really execute code
6072 instructions. Instead, all the events that normally happen during
6073 code execution are taken from the execution log. While code is not
6074 really executed in replay mode, the values of registers (including the
6075 program counter register) and the memory of the inferior are still
6076 changed as they normally would. Their contents are taken from the
6080 If the record for the next instruction is not in the execution log,
6081 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6082 inferior executes normally, and @value{GDBN} records the execution log
6085 The process record and replay target supports reverse execution
6086 (@pxref{Reverse Execution}), even if the platform on which the
6087 inferior runs does not. However, the reverse execution is limited in
6088 this case by the range of the instructions recorded in the execution
6089 log. In other words, reverse execution on platforms that don't
6090 support it directly can only be done in the replay mode.
6092 When debugging in the reverse direction, @value{GDBN} will work in
6093 replay mode as long as the execution log includes the record for the
6094 previous instruction; otherwise, it will work in record mode, if the
6095 platform supports reverse execution, or stop if not.
6097 For architecture environments that support process record and replay,
6098 @value{GDBN} provides the following commands:
6101 @kindex target record
6105 This command starts the process record and replay target. The process
6106 record and replay target can only debug a process that is already
6107 running. Therefore, you need first to start the process with the
6108 @kbd{run} or @kbd{start} commands, and then start the recording with
6109 the @kbd{target record} command.
6111 Both @code{record} and @code{rec} are aliases of @code{target record}.
6113 @cindex displaced stepping, and process record and replay
6114 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6115 will be automatically disabled when process record and replay target
6116 is started. That's because the process record and replay target
6117 doesn't support displaced stepping.
6119 @cindex non-stop mode, and process record and replay
6120 @cindex asynchronous execution, and process record and replay
6121 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6122 the asynchronous execution mode (@pxref{Background Execution}), the
6123 process record and replay target cannot be started because it doesn't
6124 support these two modes.
6129 Stop the process record and replay target. When process record and
6130 replay target stops, the entire execution log will be deleted and the
6131 inferior will either be terminated, or will remain in its final state.
6133 When you stop the process record and replay target in record mode (at
6134 the end of the execution log), the inferior will be stopped at the
6135 next instruction that would have been recorded. In other words, if
6136 you record for a while and then stop recording, the inferior process
6137 will be left in the same state as if the recording never happened.
6139 On the other hand, if the process record and replay target is stopped
6140 while in replay mode (that is, not at the end of the execution log,
6141 but at some earlier point), the inferior process will become ``live''
6142 at that earlier state, and it will then be possible to continue the
6143 usual ``live'' debugging of the process from that state.
6145 When the inferior process exits, or @value{GDBN} detaches from it,
6146 process record and replay target will automatically stop itself.
6149 @item record save @var{filename}
6150 Save the execution log to a file @file{@var{filename}}.
6151 Default filename is @file{gdb_record.@var{process_id}}, where
6152 @var{process_id} is the process ID of the inferior.
6154 @kindex record restore
6155 @item record restore @var{filename}
6156 Restore the execution log from a file @file{@var{filename}}.
6157 File must have been created with @code{record save}.
6159 @kindex set record insn-number-max
6160 @item set record insn-number-max @var{limit}
6161 Set the limit of instructions to be recorded. Default value is 200000.
6163 If @var{limit} is a positive number, then @value{GDBN} will start
6164 deleting instructions from the log once the number of the record
6165 instructions becomes greater than @var{limit}. For every new recorded
6166 instruction, @value{GDBN} will delete the earliest recorded
6167 instruction to keep the number of recorded instructions at the limit.
6168 (Since deleting recorded instructions loses information, @value{GDBN}
6169 lets you control what happens when the limit is reached, by means of
6170 the @code{stop-at-limit} option, described below.)
6172 If @var{limit} is zero, @value{GDBN} will never delete recorded
6173 instructions from the execution log. The number of recorded
6174 instructions is unlimited in this case.
6176 @kindex show record insn-number-max
6177 @item show record insn-number-max
6178 Show the limit of instructions to be recorded.
6180 @kindex set record stop-at-limit
6181 @item set record stop-at-limit
6182 Control the behavior when the number of recorded instructions reaches
6183 the limit. If ON (the default), @value{GDBN} will stop when the limit
6184 is reached for the first time and ask you whether you want to stop the
6185 inferior or continue running it and recording the execution log. If
6186 you decide to continue recording, each new recorded instruction will
6187 cause the oldest one to be deleted.
6189 If this option is OFF, @value{GDBN} will automatically delete the
6190 oldest record to make room for each new one, without asking.
6192 @kindex show record stop-at-limit
6193 @item show record stop-at-limit
6194 Show the current setting of @code{stop-at-limit}.
6196 @kindex set record memory-query
6197 @item set record memory-query
6198 Control the behavior when @value{GDBN} is unable to record memory
6199 changes caused by an instruction. If ON, @value{GDBN} will query
6200 whether to stop the inferior in that case.
6202 If this option is OFF (the default), @value{GDBN} will automatically
6203 ignore the effect of such instructions on memory. Later, when
6204 @value{GDBN} replays this execution log, it will mark the log of this
6205 instruction as not accessible, and it will not affect the replay
6208 @kindex show record memory-query
6209 @item show record memory-query
6210 Show the current setting of @code{memory-query}.
6214 Show various statistics about the state of process record and its
6215 in-memory execution log buffer, including:
6219 Whether in record mode or replay mode.
6221 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6223 Highest recorded instruction number.
6225 Current instruction about to be replayed (if in replay mode).
6227 Number of instructions contained in the execution log.
6229 Maximum number of instructions that may be contained in the execution log.
6232 @kindex record delete
6235 When record target runs in replay mode (``in the past''), delete the
6236 subsequent execution log and begin to record a new execution log starting
6237 from the current address. This means you will abandon the previously
6238 recorded ``future'' and begin recording a new ``future''.
6243 @chapter Examining the Stack
6245 When your program has stopped, the first thing you need to know is where it
6246 stopped and how it got there.
6249 Each time your program performs a function call, information about the call
6251 That information includes the location of the call in your program,
6252 the arguments of the call,
6253 and the local variables of the function being called.
6254 The information is saved in a block of data called a @dfn{stack frame}.
6255 The stack frames are allocated in a region of memory called the @dfn{call
6258 When your program stops, the @value{GDBN} commands for examining the
6259 stack allow you to see all of this information.
6261 @cindex selected frame
6262 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6263 @value{GDBN} commands refer implicitly to the selected frame. In
6264 particular, whenever you ask @value{GDBN} for the value of a variable in
6265 your program, the value is found in the selected frame. There are
6266 special @value{GDBN} commands to select whichever frame you are
6267 interested in. @xref{Selection, ,Selecting a Frame}.
6269 When your program stops, @value{GDBN} automatically selects the
6270 currently executing frame and describes it briefly, similar to the
6271 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6274 * Frames:: Stack frames
6275 * Backtrace:: Backtraces
6276 * Selection:: Selecting a frame
6277 * Frame Info:: Information on a frame
6282 @section Stack Frames
6284 @cindex frame, definition
6286 The call stack is divided up into contiguous pieces called @dfn{stack
6287 frames}, or @dfn{frames} for short; each frame is the data associated
6288 with one call to one function. The frame contains the arguments given
6289 to the function, the function's local variables, and the address at
6290 which the function is executing.
6292 @cindex initial frame
6293 @cindex outermost frame
6294 @cindex innermost frame
6295 When your program is started, the stack has only one frame, that of the
6296 function @code{main}. This is called the @dfn{initial} frame or the
6297 @dfn{outermost} frame. Each time a function is called, a new frame is
6298 made. Each time a function returns, the frame for that function invocation
6299 is eliminated. If a function is recursive, there can be many frames for
6300 the same function. The frame for the function in which execution is
6301 actually occurring is called the @dfn{innermost} frame. This is the most
6302 recently created of all the stack frames that still exist.
6304 @cindex frame pointer
6305 Inside your program, stack frames are identified by their addresses. A
6306 stack frame consists of many bytes, each of which has its own address; each
6307 kind of computer has a convention for choosing one byte whose
6308 address serves as the address of the frame. Usually this address is kept
6309 in a register called the @dfn{frame pointer register}
6310 (@pxref{Registers, $fp}) while execution is going on in that frame.
6312 @cindex frame number
6313 @value{GDBN} assigns numbers to all existing stack frames, starting with
6314 zero for the innermost frame, one for the frame that called it,
6315 and so on upward. These numbers do not really exist in your program;
6316 they are assigned by @value{GDBN} to give you a way of designating stack
6317 frames in @value{GDBN} commands.
6319 @c The -fomit-frame-pointer below perennially causes hbox overflow
6320 @c underflow problems.
6321 @cindex frameless execution
6322 Some compilers provide a way to compile functions so that they operate
6323 without stack frames. (For example, the @value{NGCC} option
6325 @samp{-fomit-frame-pointer}
6327 generates functions without a frame.)
6328 This is occasionally done with heavily used library functions to save
6329 the frame setup time. @value{GDBN} has limited facilities for dealing
6330 with these function invocations. If the innermost function invocation
6331 has no stack frame, @value{GDBN} nevertheless regards it as though
6332 it had a separate frame, which is numbered zero as usual, allowing
6333 correct tracing of the function call chain. However, @value{GDBN} has
6334 no provision for frameless functions elsewhere in the stack.
6337 @kindex frame@r{, command}
6338 @cindex current stack frame
6339 @item frame @var{args}
6340 The @code{frame} command allows you to move from one stack frame to another,
6341 and to print the stack frame you select. @var{args} may be either the
6342 address of the frame or the stack frame number. Without an argument,
6343 @code{frame} prints the current stack frame.
6345 @kindex select-frame
6346 @cindex selecting frame silently
6348 The @code{select-frame} command allows you to move from one stack frame
6349 to another without printing the frame. This is the silent version of
6357 @cindex call stack traces
6358 A backtrace is a summary of how your program got where it is. It shows one
6359 line per frame, for many frames, starting with the currently executing
6360 frame (frame zero), followed by its caller (frame one), and on up the
6365 @kindex bt @r{(@code{backtrace})}
6368 Print a backtrace of the entire stack: one line per frame for all
6369 frames in the stack.
6371 You can stop the backtrace at any time by typing the system interrupt
6372 character, normally @kbd{Ctrl-c}.
6374 @item backtrace @var{n}
6376 Similar, but print only the innermost @var{n} frames.
6378 @item backtrace -@var{n}
6380 Similar, but print only the outermost @var{n} frames.
6382 @item backtrace full
6384 @itemx bt full @var{n}
6385 @itemx bt full -@var{n}
6386 Print the values of the local variables also. @var{n} specifies the
6387 number of frames to print, as described above.
6392 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6393 are additional aliases for @code{backtrace}.
6395 @cindex multiple threads, backtrace
6396 In a multi-threaded program, @value{GDBN} by default shows the
6397 backtrace only for the current thread. To display the backtrace for
6398 several or all of the threads, use the command @code{thread apply}
6399 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6400 apply all backtrace}, @value{GDBN} will display the backtrace for all
6401 the threads; this is handy when you debug a core dump of a
6402 multi-threaded program.
6404 Each line in the backtrace shows the frame number and the function name.
6405 The program counter value is also shown---unless you use @code{set
6406 print address off}. The backtrace also shows the source file name and
6407 line number, as well as the arguments to the function. The program
6408 counter value is omitted if it is at the beginning of the code for that
6411 Here is an example of a backtrace. It was made with the command
6412 @samp{bt 3}, so it shows the innermost three frames.
6416 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6418 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6419 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6421 (More stack frames follow...)
6426 The display for frame zero does not begin with a program counter
6427 value, indicating that your program has stopped at the beginning of the
6428 code for line @code{993} of @code{builtin.c}.
6431 The value of parameter @code{data} in frame 1 has been replaced by
6432 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6433 only if it is a scalar (integer, pointer, enumeration, etc). See command
6434 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6435 on how to configure the way function parameter values are printed.
6437 @cindex optimized out, in backtrace
6438 @cindex function call arguments, optimized out
6439 If your program was compiled with optimizations, some compilers will
6440 optimize away arguments passed to functions if those arguments are
6441 never used after the call. Such optimizations generate code that
6442 passes arguments through registers, but doesn't store those arguments
6443 in the stack frame. @value{GDBN} has no way of displaying such
6444 arguments in stack frames other than the innermost one. Here's what
6445 such a backtrace might look like:
6449 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6451 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6452 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6454 (More stack frames follow...)
6459 The values of arguments that were not saved in their stack frames are
6460 shown as @samp{<optimized out>}.
6462 If you need to display the values of such optimized-out arguments,
6463 either deduce that from other variables whose values depend on the one
6464 you are interested in, or recompile without optimizations.
6466 @cindex backtrace beyond @code{main} function
6467 @cindex program entry point
6468 @cindex startup code, and backtrace
6469 Most programs have a standard user entry point---a place where system
6470 libraries and startup code transition into user code. For C this is
6471 @code{main}@footnote{
6472 Note that embedded programs (the so-called ``free-standing''
6473 environment) are not required to have a @code{main} function as the
6474 entry point. They could even have multiple entry points.}.
6475 When @value{GDBN} finds the entry function in a backtrace
6476 it will terminate the backtrace, to avoid tracing into highly
6477 system-specific (and generally uninteresting) code.
6479 If you need to examine the startup code, or limit the number of levels
6480 in a backtrace, you can change this behavior:
6483 @item set backtrace past-main
6484 @itemx set backtrace past-main on
6485 @kindex set backtrace
6486 Backtraces will continue past the user entry point.
6488 @item set backtrace past-main off
6489 Backtraces will stop when they encounter the user entry point. This is the
6492 @item show backtrace past-main
6493 @kindex show backtrace
6494 Display the current user entry point backtrace policy.
6496 @item set backtrace past-entry
6497 @itemx set backtrace past-entry on
6498 Backtraces will continue past the internal entry point of an application.
6499 This entry point is encoded by the linker when the application is built,
6500 and is likely before the user entry point @code{main} (or equivalent) is called.
6502 @item set backtrace past-entry off
6503 Backtraces will stop when they encounter the internal entry point of an
6504 application. This is the default.
6506 @item show backtrace past-entry
6507 Display the current internal entry point backtrace policy.
6509 @item set backtrace limit @var{n}
6510 @itemx set backtrace limit 0
6511 @cindex backtrace limit
6512 Limit the backtrace to @var{n} levels. A value of zero means
6515 @item show backtrace limit
6516 Display the current limit on backtrace levels.
6520 @section Selecting a Frame
6522 Most commands for examining the stack and other data in your program work on
6523 whichever stack frame is selected at the moment. Here are the commands for
6524 selecting a stack frame; all of them finish by printing a brief description
6525 of the stack frame just selected.
6528 @kindex frame@r{, selecting}
6529 @kindex f @r{(@code{frame})}
6532 Select frame number @var{n}. Recall that frame zero is the innermost
6533 (currently executing) frame, frame one is the frame that called the
6534 innermost one, and so on. The highest-numbered frame is the one for
6537 @item frame @var{addr}
6539 Select the frame at address @var{addr}. This is useful mainly if the
6540 chaining of stack frames has been damaged by a bug, making it
6541 impossible for @value{GDBN} to assign numbers properly to all frames. In
6542 addition, this can be useful when your program has multiple stacks and
6543 switches between them.
6545 On the SPARC architecture, @code{frame} needs two addresses to
6546 select an arbitrary frame: a frame pointer and a stack pointer.
6548 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
6549 pointer and a program counter.
6551 On the 29k architecture, it needs three addresses: a register stack
6552 pointer, a program counter, and a memory stack pointer.
6556 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6557 advances toward the outermost frame, to higher frame numbers, to frames
6558 that have existed longer. @var{n} defaults to one.
6561 @kindex do @r{(@code{down})}
6563 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6564 advances toward the innermost frame, to lower frame numbers, to frames
6565 that were created more recently. @var{n} defaults to one. You may
6566 abbreviate @code{down} as @code{do}.
6569 All of these commands end by printing two lines of output describing the
6570 frame. The first line shows the frame number, the function name, the
6571 arguments, and the source file and line number of execution in that
6572 frame. The second line shows the text of that source line.
6580 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6582 10 read_input_file (argv[i]);
6586 After such a printout, the @code{list} command with no arguments
6587 prints ten lines centered on the point of execution in the frame.
6588 You can also edit the program at the point of execution with your favorite
6589 editing program by typing @code{edit}.
6590 @xref{List, ,Printing Source Lines},
6594 @kindex down-silently
6596 @item up-silently @var{n}
6597 @itemx down-silently @var{n}
6598 These two commands are variants of @code{up} and @code{down},
6599 respectively; they differ in that they do their work silently, without
6600 causing display of the new frame. They are intended primarily for use
6601 in @value{GDBN} command scripts, where the output might be unnecessary and
6606 @section Information About a Frame
6608 There are several other commands to print information about the selected
6614 When used without any argument, this command does not change which
6615 frame is selected, but prints a brief description of the currently
6616 selected stack frame. It can be abbreviated @code{f}. With an
6617 argument, this command is used to select a stack frame.
6618 @xref{Selection, ,Selecting a Frame}.
6621 @kindex info f @r{(@code{info frame})}
6624 This command prints a verbose description of the selected stack frame,
6629 the address of the frame
6631 the address of the next frame down (called by this frame)
6633 the address of the next frame up (caller of this frame)
6635 the language in which the source code corresponding to this frame is written
6637 the address of the frame's arguments
6639 the address of the frame's local variables
6641 the program counter saved in it (the address of execution in the caller frame)
6643 which registers were saved in the frame
6646 @noindent The verbose description is useful when
6647 something has gone wrong that has made the stack format fail to fit
6648 the usual conventions.
6650 @item info frame @var{addr}
6651 @itemx info f @var{addr}
6652 Print a verbose description of the frame at address @var{addr}, without
6653 selecting that frame. The selected frame remains unchanged by this
6654 command. This requires the same kind of address (more than one for some
6655 architectures) that you specify in the @code{frame} command.
6656 @xref{Selection, ,Selecting a Frame}.
6660 Print the arguments of the selected frame, each on a separate line.
6664 Print the local variables of the selected frame, each on a separate
6665 line. These are all variables (declared either static or automatic)
6666 accessible at the point of execution of the selected frame.
6672 @chapter Examining Source Files
6674 @value{GDBN} can print parts of your program's source, since the debugging
6675 information recorded in the program tells @value{GDBN} what source files were
6676 used to build it. When your program stops, @value{GDBN} spontaneously prints
6677 the line where it stopped. Likewise, when you select a stack frame
6678 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6679 execution in that frame has stopped. You can print other portions of
6680 source files by explicit command.
6682 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6683 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6684 @value{GDBN} under @sc{gnu} Emacs}.
6687 * List:: Printing source lines
6688 * Specify Location:: How to specify code locations
6689 * Edit:: Editing source files
6690 * Search:: Searching source files
6691 * Source Path:: Specifying source directories
6692 * Machine Code:: Source and machine code
6696 @section Printing Source Lines
6699 @kindex l @r{(@code{list})}
6700 To print lines from a source file, use the @code{list} command
6701 (abbreviated @code{l}). By default, ten lines are printed.
6702 There are several ways to specify what part of the file you want to
6703 print; see @ref{Specify Location}, for the full list.
6705 Here are the forms of the @code{list} command most commonly used:
6708 @item list @var{linenum}
6709 Print lines centered around line number @var{linenum} in the
6710 current source file.
6712 @item list @var{function}
6713 Print lines centered around the beginning of function
6717 Print more lines. If the last lines printed were printed with a
6718 @code{list} command, this prints lines following the last lines
6719 printed; however, if the last line printed was a solitary line printed
6720 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6721 Stack}), this prints lines centered around that line.
6724 Print lines just before the lines last printed.
6727 @cindex @code{list}, how many lines to display
6728 By default, @value{GDBN} prints ten source lines with any of these forms of
6729 the @code{list} command. You can change this using @code{set listsize}:
6732 @kindex set listsize
6733 @item set listsize @var{count}
6734 Make the @code{list} command display @var{count} source lines (unless
6735 the @code{list} argument explicitly specifies some other number).
6736 Setting @var{count} to -1 means there's no limit and 0 means suppress
6737 display of source lines.
6739 @kindex show listsize
6741 Display the number of lines that @code{list} prints.
6744 Repeating a @code{list} command with @key{RET} discards the argument,
6745 so it is equivalent to typing just @code{list}. This is more useful
6746 than listing the same lines again. An exception is made for an
6747 argument of @samp{-}; that argument is preserved in repetition so that
6748 each repetition moves up in the source file.
6750 In general, the @code{list} command expects you to supply zero, one or two
6751 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6752 of writing them (@pxref{Specify Location}), but the effect is always
6753 to specify some source line.
6755 Here is a complete description of the possible arguments for @code{list}:
6758 @item list @var{linespec}
6759 Print lines centered around the line specified by @var{linespec}.
6761 @item list @var{first},@var{last}
6762 Print lines from @var{first} to @var{last}. Both arguments are
6763 linespecs. When a @code{list} command has two linespecs, and the
6764 source file of the second linespec is omitted, this refers to
6765 the same source file as the first linespec.
6767 @item list ,@var{last}
6768 Print lines ending with @var{last}.
6770 @item list @var{first},
6771 Print lines starting with @var{first}.
6774 Print lines just after the lines last printed.
6777 Print lines just before the lines last printed.
6780 As described in the preceding table.
6783 @node Specify Location
6784 @section Specifying a Location
6785 @cindex specifying location
6788 Several @value{GDBN} commands accept arguments that specify a location
6789 of your program's code. Since @value{GDBN} is a source-level
6790 debugger, a location usually specifies some line in the source code;
6791 for that reason, locations are also known as @dfn{linespecs}.
6793 Here are all the different ways of specifying a code location that
6794 @value{GDBN} understands:
6798 Specifies the line number @var{linenum} of the current source file.
6801 @itemx +@var{offset}
6802 Specifies the line @var{offset} lines before or after the @dfn{current
6803 line}. For the @code{list} command, the current line is the last one
6804 printed; for the breakpoint commands, this is the line at which
6805 execution stopped in the currently selected @dfn{stack frame}
6806 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6807 used as the second of the two linespecs in a @code{list} command,
6808 this specifies the line @var{offset} lines up or down from the first
6811 @item @var{filename}:@var{linenum}
6812 Specifies the line @var{linenum} in the source file @var{filename}.
6813 If @var{filename} is a relative file name, then it will match any
6814 source file name with the same trailing components. For example, if
6815 @var{filename} is @samp{gcc/expr.c}, then it will match source file
6816 name of @file{/build/trunk/gcc/expr.c}, but not
6817 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
6819 @item @var{function}
6820 Specifies the line that begins the body of the function @var{function}.
6821 For example, in C, this is the line with the open brace.
6823 @item @var{function}:@var{label}
6824 Specifies the line where @var{label} appears in @var{function}.
6826 @item @var{filename}:@var{function}
6827 Specifies the line that begins the body of the function @var{function}
6828 in the file @var{filename}. You only need the file name with a
6829 function name to avoid ambiguity when there are identically named
6830 functions in different source files.
6833 Specifies the line at which the label named @var{label} appears.
6834 @value{GDBN} searches for the label in the function corresponding to
6835 the currently selected stack frame. If there is no current selected
6836 stack frame (for instance, if the inferior is not running), then
6837 @value{GDBN} will not search for a label.
6839 @item *@var{address}
6840 Specifies the program address @var{address}. For line-oriented
6841 commands, such as @code{list} and @code{edit}, this specifies a source
6842 line that contains @var{address}. For @code{break} and other
6843 breakpoint oriented commands, this can be used to set breakpoints in
6844 parts of your program which do not have debugging information or
6847 Here @var{address} may be any expression valid in the current working
6848 language (@pxref{Languages, working language}) that specifies a code
6849 address. In addition, as a convenience, @value{GDBN} extends the
6850 semantics of expressions used in locations to cover the situations
6851 that frequently happen during debugging. Here are the various forms
6855 @item @var{expression}
6856 Any expression valid in the current working language.
6858 @item @var{funcaddr}
6859 An address of a function or procedure derived from its name. In C,
6860 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6861 simply the function's name @var{function} (and actually a special case
6862 of a valid expression). In Pascal and Modula-2, this is
6863 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6864 (although the Pascal form also works).
6866 This form specifies the address of the function's first instruction,
6867 before the stack frame and arguments have been set up.
6869 @item '@var{filename}'::@var{funcaddr}
6870 Like @var{funcaddr} above, but also specifies the name of the source
6871 file explicitly. This is useful if the name of the function does not
6872 specify the function unambiguously, e.g., if there are several
6873 functions with identical names in different source files.
6876 @cindex breakpoint at static probe point
6877 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
6878 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
6879 applications to embed static probes. @xref{Static Probe Points}, for more
6880 information on finding and using static probes. This form of linespec
6881 specifies the location of such a static probe.
6883 If @var{objfile} is given, only probes coming from that shared library
6884 or executable matching @var{objfile} as a regular expression are considered.
6885 If @var{provider} is given, then only probes from that provider are considered.
6886 If several probes match the spec, @value{GDBN} will insert a breakpoint at
6887 each one of those probes.
6893 @section Editing Source Files
6894 @cindex editing source files
6897 @kindex e @r{(@code{edit})}
6898 To edit the lines in a source file, use the @code{edit} command.
6899 The editing program of your choice
6900 is invoked with the current line set to
6901 the active line in the program.
6902 Alternatively, there are several ways to specify what part of the file you
6903 want to print if you want to see other parts of the program:
6906 @item edit @var{location}
6907 Edit the source file specified by @code{location}. Editing starts at
6908 that @var{location}, e.g., at the specified source line of the
6909 specified file. @xref{Specify Location}, for all the possible forms
6910 of the @var{location} argument; here are the forms of the @code{edit}
6911 command most commonly used:
6914 @item edit @var{number}
6915 Edit the current source file with @var{number} as the active line number.
6917 @item edit @var{function}
6918 Edit the file containing @var{function} at the beginning of its definition.
6923 @subsection Choosing your Editor
6924 You can customize @value{GDBN} to use any editor you want
6926 The only restriction is that your editor (say @code{ex}), recognizes the
6927 following command-line syntax:
6929 ex +@var{number} file
6931 The optional numeric value +@var{number} specifies the number of the line in
6932 the file where to start editing.}.
6933 By default, it is @file{@value{EDITOR}}, but you can change this
6934 by setting the environment variable @code{EDITOR} before using
6935 @value{GDBN}. For example, to configure @value{GDBN} to use the
6936 @code{vi} editor, you could use these commands with the @code{sh} shell:
6942 or in the @code{csh} shell,
6944 setenv EDITOR /usr/bin/vi
6949 @section Searching Source Files
6950 @cindex searching source files
6952 There are two commands for searching through the current source file for a
6957 @kindex forward-search
6958 @item forward-search @var{regexp}
6959 @itemx search @var{regexp}
6960 The command @samp{forward-search @var{regexp}} checks each line,
6961 starting with the one following the last line listed, for a match for
6962 @var{regexp}. It lists the line that is found. You can use the
6963 synonym @samp{search @var{regexp}} or abbreviate the command name as
6966 @kindex reverse-search
6967 @item reverse-search @var{regexp}
6968 The command @samp{reverse-search @var{regexp}} checks each line, starting
6969 with the one before the last line listed and going backward, for a match
6970 for @var{regexp}. It lists the line that is found. You can abbreviate
6971 this command as @code{rev}.
6975 @section Specifying Source Directories
6978 @cindex directories for source files
6979 Executable programs sometimes do not record the directories of the source
6980 files from which they were compiled, just the names. Even when they do,
6981 the directories could be moved between the compilation and your debugging
6982 session. @value{GDBN} has a list of directories to search for source files;
6983 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6984 it tries all the directories in the list, in the order they are present
6985 in the list, until it finds a file with the desired name.
6987 For example, suppose an executable references the file
6988 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6989 @file{/mnt/cross}. The file is first looked up literally; if this
6990 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6991 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6992 message is printed. @value{GDBN} does not look up the parts of the
6993 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6994 Likewise, the subdirectories of the source path are not searched: if
6995 the source path is @file{/mnt/cross}, and the binary refers to
6996 @file{foo.c}, @value{GDBN} would not find it under
6997 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6999 Plain file names, relative file names with leading directories, file
7000 names containing dots, etc.@: are all treated as described above; for
7001 instance, if the source path is @file{/mnt/cross}, and the source file
7002 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7003 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7004 that---@file{/mnt/cross/foo.c}.
7006 Note that the executable search path is @emph{not} used to locate the
7009 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7010 any information it has cached about where source files are found and where
7011 each line is in the file.
7015 When you start @value{GDBN}, its source path includes only @samp{cdir}
7016 and @samp{cwd}, in that order.
7017 To add other directories, use the @code{directory} command.
7019 The search path is used to find both program source files and @value{GDBN}
7020 script files (read using the @samp{-command} option and @samp{source} command).
7022 In addition to the source path, @value{GDBN} provides a set of commands
7023 that manage a list of source path substitution rules. A @dfn{substitution
7024 rule} specifies how to rewrite source directories stored in the program's
7025 debug information in case the sources were moved to a different
7026 directory between compilation and debugging. A rule is made of
7027 two strings, the first specifying what needs to be rewritten in
7028 the path, and the second specifying how it should be rewritten.
7029 In @ref{set substitute-path}, we name these two parts @var{from} and
7030 @var{to} respectively. @value{GDBN} does a simple string replacement
7031 of @var{from} with @var{to} at the start of the directory part of the
7032 source file name, and uses that result instead of the original file
7033 name to look up the sources.
7035 Using the previous example, suppose the @file{foo-1.0} tree has been
7036 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7037 @value{GDBN} to replace @file{/usr/src} in all source path names with
7038 @file{/mnt/cross}. The first lookup will then be
7039 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7040 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7041 substitution rule, use the @code{set substitute-path} command
7042 (@pxref{set substitute-path}).
7044 To avoid unexpected substitution results, a rule is applied only if the
7045 @var{from} part of the directory name ends at a directory separator.
7046 For instance, a rule substituting @file{/usr/source} into
7047 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7048 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7049 is applied only at the beginning of the directory name, this rule will
7050 not be applied to @file{/root/usr/source/baz.c} either.
7052 In many cases, you can achieve the same result using the @code{directory}
7053 command. However, @code{set substitute-path} can be more efficient in
7054 the case where the sources are organized in a complex tree with multiple
7055 subdirectories. With the @code{directory} command, you need to add each
7056 subdirectory of your project. If you moved the entire tree while
7057 preserving its internal organization, then @code{set substitute-path}
7058 allows you to direct the debugger to all the sources with one single
7061 @code{set substitute-path} is also more than just a shortcut command.
7062 The source path is only used if the file at the original location no
7063 longer exists. On the other hand, @code{set substitute-path} modifies
7064 the debugger behavior to look at the rewritten location instead. So, if
7065 for any reason a source file that is not relevant to your executable is
7066 located at the original location, a substitution rule is the only
7067 method available to point @value{GDBN} at the new location.
7069 @cindex @samp{--with-relocated-sources}
7070 @cindex default source path substitution
7071 You can configure a default source path substitution rule by
7072 configuring @value{GDBN} with the
7073 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7074 should be the name of a directory under @value{GDBN}'s configured
7075 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7076 directory names in debug information under @var{dir} will be adjusted
7077 automatically if the installed @value{GDBN} is moved to a new
7078 location. This is useful if @value{GDBN}, libraries or executables
7079 with debug information and corresponding source code are being moved
7083 @item directory @var{dirname} @dots{}
7084 @item dir @var{dirname} @dots{}
7085 Add directory @var{dirname} to the front of the source path. Several
7086 directory names may be given to this command, separated by @samp{:}
7087 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7088 part of absolute file names) or
7089 whitespace. You may specify a directory that is already in the source
7090 path; this moves it forward, so @value{GDBN} searches it sooner.
7094 @vindex $cdir@r{, convenience variable}
7095 @vindex $cwd@r{, convenience variable}
7096 @cindex compilation directory
7097 @cindex current directory
7098 @cindex working directory
7099 @cindex directory, current
7100 @cindex directory, compilation
7101 You can use the string @samp{$cdir} to refer to the compilation
7102 directory (if one is recorded), and @samp{$cwd} to refer to the current
7103 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7104 tracks the current working directory as it changes during your @value{GDBN}
7105 session, while the latter is immediately expanded to the current
7106 directory at the time you add an entry to the source path.
7109 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7111 @c RET-repeat for @code{directory} is explicitly disabled, but since
7112 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7114 @item set directories @var{path-list}
7115 @kindex set directories
7116 Set the source path to @var{path-list}.
7117 @samp{$cdir:$cwd} are added if missing.
7119 @item show directories
7120 @kindex show directories
7121 Print the source path: show which directories it contains.
7123 @anchor{set substitute-path}
7124 @item set substitute-path @var{from} @var{to}
7125 @kindex set substitute-path
7126 Define a source path substitution rule, and add it at the end of the
7127 current list of existing substitution rules. If a rule with the same
7128 @var{from} was already defined, then the old rule is also deleted.
7130 For example, if the file @file{/foo/bar/baz.c} was moved to
7131 @file{/mnt/cross/baz.c}, then the command
7134 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7138 will tell @value{GDBN} to replace @samp{/usr/src} with
7139 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7140 @file{baz.c} even though it was moved.
7142 In the case when more than one substitution rule have been defined,
7143 the rules are evaluated one by one in the order where they have been
7144 defined. The first one matching, if any, is selected to perform
7147 For instance, if we had entered the following commands:
7150 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7151 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7155 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7156 @file{/mnt/include/defs.h} by using the first rule. However, it would
7157 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7158 @file{/mnt/src/lib/foo.c}.
7161 @item unset substitute-path [path]
7162 @kindex unset substitute-path
7163 If a path is specified, search the current list of substitution rules
7164 for a rule that would rewrite that path. Delete that rule if found.
7165 A warning is emitted by the debugger if no rule could be found.
7167 If no path is specified, then all substitution rules are deleted.
7169 @item show substitute-path [path]
7170 @kindex show substitute-path
7171 If a path is specified, then print the source path substitution rule
7172 which would rewrite that path, if any.
7174 If no path is specified, then print all existing source path substitution
7179 If your source path is cluttered with directories that are no longer of
7180 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7181 versions of source. You can correct the situation as follows:
7185 Use @code{directory} with no argument to reset the source path to its default value.
7188 Use @code{directory} with suitable arguments to reinstall the
7189 directories you want in the source path. You can add all the
7190 directories in one command.
7194 @section Source and Machine Code
7195 @cindex source line and its code address
7197 You can use the command @code{info line} to map source lines to program
7198 addresses (and vice versa), and the command @code{disassemble} to display
7199 a range of addresses as machine instructions. You can use the command
7200 @code{set disassemble-next-line} to set whether to disassemble next
7201 source line when execution stops. When run under @sc{gnu} Emacs
7202 mode, the @code{info line} command causes the arrow to point to the
7203 line specified. Also, @code{info line} prints addresses in symbolic form as
7208 @item info line @var{linespec}
7209 Print the starting and ending addresses of the compiled code for
7210 source line @var{linespec}. You can specify source lines in any of
7211 the ways documented in @ref{Specify Location}.
7214 For example, we can use @code{info line} to discover the location of
7215 the object code for the first line of function
7216 @code{m4_changequote}:
7218 @c FIXME: I think this example should also show the addresses in
7219 @c symbolic form, as they usually would be displayed.
7221 (@value{GDBP}) info line m4_changequote
7222 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7226 @cindex code address and its source line
7227 We can also inquire (using @code{*@var{addr}} as the form for
7228 @var{linespec}) what source line covers a particular address:
7230 (@value{GDBP}) info line *0x63ff
7231 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7234 @cindex @code{$_} and @code{info line}
7235 @cindex @code{x} command, default address
7236 @kindex x@r{(examine), and} info line
7237 After @code{info line}, the default address for the @code{x} command
7238 is changed to the starting address of the line, so that @samp{x/i} is
7239 sufficient to begin examining the machine code (@pxref{Memory,
7240 ,Examining Memory}). Also, this address is saved as the value of the
7241 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7246 @cindex assembly instructions
7247 @cindex instructions, assembly
7248 @cindex machine instructions
7249 @cindex listing machine instructions
7251 @itemx disassemble /m
7252 @itemx disassemble /r
7253 This specialized command dumps a range of memory as machine
7254 instructions. It can also print mixed source+disassembly by specifying
7255 the @code{/m} modifier and print the raw instructions in hex as well as
7256 in symbolic form by specifying the @code{/r}.
7257 The default memory range is the function surrounding the
7258 program counter of the selected frame. A single argument to this
7259 command is a program counter value; @value{GDBN} dumps the function
7260 surrounding this value. When two arguments are given, they should
7261 be separated by a comma, possibly surrounded by whitespace. The
7262 arguments specify a range of addresses to dump, in one of two forms:
7265 @item @var{start},@var{end}
7266 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7267 @item @var{start},+@var{length}
7268 the addresses from @var{start} (inclusive) to
7269 @code{@var{start}+@var{length}} (exclusive).
7273 When 2 arguments are specified, the name of the function is also
7274 printed (since there could be several functions in the given range).
7276 The argument(s) can be any expression yielding a numeric value, such as
7277 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7279 If the range of memory being disassembled contains current program counter,
7280 the instruction at that location is shown with a @code{=>} marker.
7283 The following example shows the disassembly of a range of addresses of
7284 HP PA-RISC 2.0 code:
7287 (@value{GDBP}) disas 0x32c4, 0x32e4
7288 Dump of assembler code from 0x32c4 to 0x32e4:
7289 0x32c4 <main+204>: addil 0,dp
7290 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7291 0x32cc <main+212>: ldil 0x3000,r31
7292 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7293 0x32d4 <main+220>: ldo 0(r31),rp
7294 0x32d8 <main+224>: addil -0x800,dp
7295 0x32dc <main+228>: ldo 0x588(r1),r26
7296 0x32e0 <main+232>: ldil 0x3000,r31
7297 End of assembler dump.
7300 Here is an example showing mixed source+assembly for Intel x86, when the
7301 program is stopped just after function prologue:
7304 (@value{GDBP}) disas /m main
7305 Dump of assembler code for function main:
7307 0x08048330 <+0>: push %ebp
7308 0x08048331 <+1>: mov %esp,%ebp
7309 0x08048333 <+3>: sub $0x8,%esp
7310 0x08048336 <+6>: and $0xfffffff0,%esp
7311 0x08048339 <+9>: sub $0x10,%esp
7313 6 printf ("Hello.\n");
7314 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7315 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7319 0x08048348 <+24>: mov $0x0,%eax
7320 0x0804834d <+29>: leave
7321 0x0804834e <+30>: ret
7323 End of assembler dump.
7326 Here is another example showing raw instructions in hex for AMD x86-64,
7329 (gdb) disas /r 0x400281,+10
7330 Dump of assembler code from 0x400281 to 0x40028b:
7331 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7332 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7333 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7334 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7335 End of assembler dump.
7338 Some architectures have more than one commonly-used set of instruction
7339 mnemonics or other syntax.
7341 For programs that were dynamically linked and use shared libraries,
7342 instructions that call functions or branch to locations in the shared
7343 libraries might show a seemingly bogus location---it's actually a
7344 location of the relocation table. On some architectures, @value{GDBN}
7345 might be able to resolve these to actual function names.
7348 @kindex set disassembly-flavor
7349 @cindex Intel disassembly flavor
7350 @cindex AT&T disassembly flavor
7351 @item set disassembly-flavor @var{instruction-set}
7352 Select the instruction set to use when disassembling the
7353 program via the @code{disassemble} or @code{x/i} commands.
7355 Currently this command is only defined for the Intel x86 family. You
7356 can set @var{instruction-set} to either @code{intel} or @code{att}.
7357 The default is @code{att}, the AT&T flavor used by default by Unix
7358 assemblers for x86-based targets.
7360 @kindex show disassembly-flavor
7361 @item show disassembly-flavor
7362 Show the current setting of the disassembly flavor.
7366 @kindex set disassemble-next-line
7367 @kindex show disassemble-next-line
7368 @item set disassemble-next-line
7369 @itemx show disassemble-next-line
7370 Control whether or not @value{GDBN} will disassemble the next source
7371 line or instruction when execution stops. If ON, @value{GDBN} will
7372 display disassembly of the next source line when execution of the
7373 program being debugged stops. This is @emph{in addition} to
7374 displaying the source line itself, which @value{GDBN} always does if
7375 possible. If the next source line cannot be displayed for some reason
7376 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7377 info in the debug info), @value{GDBN} will display disassembly of the
7378 next @emph{instruction} instead of showing the next source line. If
7379 AUTO, @value{GDBN} will display disassembly of next instruction only
7380 if the source line cannot be displayed. This setting causes
7381 @value{GDBN} to display some feedback when you step through a function
7382 with no line info or whose source file is unavailable. The default is
7383 OFF, which means never display the disassembly of the next line or
7389 @chapter Examining Data
7391 @cindex printing data
7392 @cindex examining data
7395 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
7396 @c document because it is nonstandard... Under Epoch it displays in a
7397 @c different window or something like that.
7398 The usual way to examine data in your program is with the @code{print}
7399 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7400 evaluates and prints the value of an expression of the language your
7401 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7402 Different Languages}). It may also print the expression using a
7403 Python-based pretty-printer (@pxref{Pretty Printing}).
7406 @item print @var{expr}
7407 @itemx print /@var{f} @var{expr}
7408 @var{expr} is an expression (in the source language). By default the
7409 value of @var{expr} is printed in a format appropriate to its data type;
7410 you can choose a different format by specifying @samp{/@var{f}}, where
7411 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7415 @itemx print /@var{f}
7416 @cindex reprint the last value
7417 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7418 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7419 conveniently inspect the same value in an alternative format.
7422 A more low-level way of examining data is with the @code{x} command.
7423 It examines data in memory at a specified address and prints it in a
7424 specified format. @xref{Memory, ,Examining Memory}.
7426 If you are interested in information about types, or about how the
7427 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7428 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7431 @cindex exploring hierarchical data structures
7433 Another way of examining values of expressions and type information is
7434 through the Python extension command @code{explore} (available only if
7435 the @value{GDBN} build is configured with @code{--with-python}). It
7436 offers an interactive way to start at the highest level (or, the most
7437 abstract level) of the data type of an expression (or, the data type
7438 itself) and explore all the way down to leaf scalar values/fields
7439 embedded in the higher level data types.
7442 @item explore @var{arg}
7443 @var{arg} is either an expression (in the source language), or a type
7444 visible in the current context of the program being debugged.
7447 The working of the @code{explore} command can be illustrated with an
7448 example. If a data type @code{struct ComplexStruct} is defined in your
7458 struct ComplexStruct
7460 struct SimpleStruct *ss_p;
7466 followed by variable declarations as
7469 struct SimpleStruct ss = @{ 10, 1.11 @};
7470 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7474 then, the value of the variable @code{cs} can be explored using the
7475 @code{explore} command as follows.
7479 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7480 the following fields:
7482 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7483 arr = <Enter 1 to explore this field of type `int [10]'>
7485 Enter the field number of choice:
7489 Since the fields of @code{cs} are not scalar values, you are being
7490 prompted to chose the field you want to explore. Let's say you choose
7491 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7492 pointer, you will be asked if it is pointing to a single value. From
7493 the declaration of @code{cs} above, it is indeed pointing to a single
7494 value, hence you enter @code{y}. If you enter @code{n}, then you will
7495 be asked if it were pointing to an array of values, in which case this
7496 field will be explored as if it were an array.
7499 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7500 Continue exploring it as a pointer to a single value [y/n]: y
7501 The value of `*(cs.ss_p)' is a struct/class of type `struct
7502 SimpleStruct' with the following fields:
7504 i = 10 .. (Value of type `int')
7505 d = 1.1100000000000001 .. (Value of type `double')
7507 Press enter to return to parent value:
7511 If the field @code{arr} of @code{cs} was chosen for exploration by
7512 entering @code{1} earlier, then since it is as array, you will be
7513 prompted to enter the index of the element in the array that you want
7517 `cs.arr' is an array of `int'.
7518 Enter the index of the element you want to explore in `cs.arr': 5
7520 `(cs.arr)[5]' is a scalar value of type `int'.
7524 Press enter to return to parent value:
7527 In general, at any stage of exploration, you can go deeper towards the
7528 leaf values by responding to the prompts appropriately, or hit the
7529 return key to return to the enclosing data structure (the @i{higher}
7530 level data structure).
7532 Similar to exploring values, you can use the @code{explore} command to
7533 explore types. Instead of specifying a value (which is typically a
7534 variable name or an expression valid in the current context of the
7535 program being debugged), you specify a type name. If you consider the
7536 same example as above, your can explore the type
7537 @code{struct ComplexStruct} by passing the argument
7538 @code{struct ComplexStruct} to the @code{explore} command.
7541 (gdb) explore struct ComplexStruct
7545 By responding to the prompts appropriately in the subsequent interactive
7546 session, you can explore the type @code{struct ComplexStruct} in a
7547 manner similar to how the value @code{cs} was explored in the above
7550 The @code{explore} command also has two sub-commands,
7551 @code{explore value} and @code{explore type}. The former sub-command is
7552 a way to explicitly specify that value exploration of the argument is
7553 being invoked, while the latter is a way to explicitly specify that type
7554 exploration of the argument is being invoked.
7557 @item explore value @var{expr}
7558 @cindex explore value
7559 This sub-command of @code{explore} explores the value of the
7560 expression @var{expr} (if @var{expr} is an expression valid in the
7561 current context of the program being debugged). The behavior of this
7562 command is identical to that of the behavior of the @code{explore}
7563 command being passed the argument @var{expr}.
7565 @item explore type @var{arg}
7566 @cindex explore type
7567 This sub-command of @code{explore} explores the type of @var{arg} (if
7568 @var{arg} is a type visible in the current context of program being
7569 debugged), or the type of the value/expression @var{arg} (if @var{arg}
7570 is an expression valid in the current context of the program being
7571 debugged). If @var{arg} is a type, then the behavior of this command is
7572 identical to that of the @code{explore} command being passed the
7573 argument @var{arg}. If @var{arg} is an expression, then the behavior of
7574 this command will be identical to that of the @code{explore} command
7575 being passed the type of @var{arg} as the argument.
7579 * Expressions:: Expressions
7580 * Ambiguous Expressions:: Ambiguous Expressions
7581 * Variables:: Program variables
7582 * Arrays:: Artificial arrays
7583 * Output Formats:: Output formats
7584 * Memory:: Examining memory
7585 * Auto Display:: Automatic display
7586 * Print Settings:: Print settings
7587 * Pretty Printing:: Python pretty printing
7588 * Value History:: Value history
7589 * Convenience Vars:: Convenience variables
7590 * Convenience Funs:: Convenience functions
7591 * Registers:: Registers
7592 * Floating Point Hardware:: Floating point hardware
7593 * Vector Unit:: Vector Unit
7594 * OS Information:: Auxiliary data provided by operating system
7595 * Memory Region Attributes:: Memory region attributes
7596 * Dump/Restore Files:: Copy between memory and a file
7597 * Core File Generation:: Cause a program dump its core
7598 * Character Sets:: Debugging programs that use a different
7599 character set than GDB does
7600 * Caching Remote Data:: Data caching for remote targets
7601 * Searching Memory:: Searching memory for a sequence of bytes
7605 @section Expressions
7608 @code{print} and many other @value{GDBN} commands accept an expression and
7609 compute its value. Any kind of constant, variable or operator defined
7610 by the programming language you are using is valid in an expression in
7611 @value{GDBN}. This includes conditional expressions, function calls,
7612 casts, and string constants. It also includes preprocessor macros, if
7613 you compiled your program to include this information; see
7616 @cindex arrays in expressions
7617 @value{GDBN} supports array constants in expressions input by
7618 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7619 you can use the command @code{print @{1, 2, 3@}} to create an array
7620 of three integers. If you pass an array to a function or assign it
7621 to a program variable, @value{GDBN} copies the array to memory that
7622 is @code{malloc}ed in the target program.
7624 Because C is so widespread, most of the expressions shown in examples in
7625 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7626 Languages}, for information on how to use expressions in other
7629 In this section, we discuss operators that you can use in @value{GDBN}
7630 expressions regardless of your programming language.
7632 @cindex casts, in expressions
7633 Casts are supported in all languages, not just in C, because it is so
7634 useful to cast a number into a pointer in order to examine a structure
7635 at that address in memory.
7636 @c FIXME: casts supported---Mod2 true?
7638 @value{GDBN} supports these operators, in addition to those common
7639 to programming languages:
7643 @samp{@@} is a binary operator for treating parts of memory as arrays.
7644 @xref{Arrays, ,Artificial Arrays}, for more information.
7647 @samp{::} allows you to specify a variable in terms of the file or
7648 function where it is defined. @xref{Variables, ,Program Variables}.
7650 @cindex @{@var{type}@}
7651 @cindex type casting memory
7652 @cindex memory, viewing as typed object
7653 @cindex casts, to view memory
7654 @item @{@var{type}@} @var{addr}
7655 Refers to an object of type @var{type} stored at address @var{addr} in
7656 memory. @var{addr} may be any expression whose value is an integer or
7657 pointer (but parentheses are required around binary operators, just as in
7658 a cast). This construct is allowed regardless of what kind of data is
7659 normally supposed to reside at @var{addr}.
7662 @node Ambiguous Expressions
7663 @section Ambiguous Expressions
7664 @cindex ambiguous expressions
7666 Expressions can sometimes contain some ambiguous elements. For instance,
7667 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7668 a single function name to be defined several times, for application in
7669 different contexts. This is called @dfn{overloading}. Another example
7670 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7671 templates and is typically instantiated several times, resulting in
7672 the same function name being defined in different contexts.
7674 In some cases and depending on the language, it is possible to adjust
7675 the expression to remove the ambiguity. For instance in C@t{++}, you
7676 can specify the signature of the function you want to break on, as in
7677 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7678 qualified name of your function often makes the expression unambiguous
7681 When an ambiguity that needs to be resolved is detected, the debugger
7682 has the capability to display a menu of numbered choices for each
7683 possibility, and then waits for the selection with the prompt @samp{>}.
7684 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7685 aborts the current command. If the command in which the expression was
7686 used allows more than one choice to be selected, the next option in the
7687 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7690 For example, the following session excerpt shows an attempt to set a
7691 breakpoint at the overloaded symbol @code{String::after}.
7692 We choose three particular definitions of that function name:
7694 @c FIXME! This is likely to change to show arg type lists, at least
7697 (@value{GDBP}) b String::after
7700 [2] file:String.cc; line number:867
7701 [3] file:String.cc; line number:860
7702 [4] file:String.cc; line number:875
7703 [5] file:String.cc; line number:853
7704 [6] file:String.cc; line number:846
7705 [7] file:String.cc; line number:735
7707 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7708 Breakpoint 2 at 0xb344: file String.cc, line 875.
7709 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7710 Multiple breakpoints were set.
7711 Use the "delete" command to delete unwanted
7718 @kindex set multiple-symbols
7719 @item set multiple-symbols @var{mode}
7720 @cindex multiple-symbols menu
7722 This option allows you to adjust the debugger behavior when an expression
7725 By default, @var{mode} is set to @code{all}. If the command with which
7726 the expression is used allows more than one choice, then @value{GDBN}
7727 automatically selects all possible choices. For instance, inserting
7728 a breakpoint on a function using an ambiguous name results in a breakpoint
7729 inserted on each possible match. However, if a unique choice must be made,
7730 then @value{GDBN} uses the menu to help you disambiguate the expression.
7731 For instance, printing the address of an overloaded function will result
7732 in the use of the menu.
7734 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7735 when an ambiguity is detected.
7737 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7738 an error due to the ambiguity and the command is aborted.
7740 @kindex show multiple-symbols
7741 @item show multiple-symbols
7742 Show the current value of the @code{multiple-symbols} setting.
7746 @section Program Variables
7748 The most common kind of expression to use is the name of a variable
7751 Variables in expressions are understood in the selected stack frame
7752 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7756 global (or file-static)
7763 visible according to the scope rules of the
7764 programming language from the point of execution in that frame
7767 @noindent This means that in the function
7782 you can examine and use the variable @code{a} whenever your program is
7783 executing within the function @code{foo}, but you can only use or
7784 examine the variable @code{b} while your program is executing inside
7785 the block where @code{b} is declared.
7787 @cindex variable name conflict
7788 There is an exception: you can refer to a variable or function whose
7789 scope is a single source file even if the current execution point is not
7790 in this file. But it is possible to have more than one such variable or
7791 function with the same name (in different source files). If that
7792 happens, referring to that name has unpredictable effects. If you wish,
7793 you can specify a static variable in a particular function or file by
7794 using the colon-colon (@code{::}) notation:
7796 @cindex colon-colon, context for variables/functions
7798 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7799 @cindex @code{::}, context for variables/functions
7802 @var{file}::@var{variable}
7803 @var{function}::@var{variable}
7807 Here @var{file} or @var{function} is the name of the context for the
7808 static @var{variable}. In the case of file names, you can use quotes to
7809 make sure @value{GDBN} parses the file name as a single word---for example,
7810 to print a global value of @code{x} defined in @file{f2.c}:
7813 (@value{GDBP}) p 'f2.c'::x
7816 The @code{::} notation is normally used for referring to
7817 static variables, since you typically disambiguate uses of local variables
7818 in functions by selecting the appropriate frame and using the
7819 simple name of the variable. However, you may also use this notation
7820 to refer to local variables in frames enclosing the selected frame:
7829 process (a); /* Stop here */
7840 For example, if there is a breakpoint at the commented line,
7841 here is what you might see
7842 when the program stops after executing the call @code{bar(0)}:
7847 (@value{GDBP}) p bar::a
7850 #2 0x080483d0 in foo (a=5) at foobar.c:12
7853 (@value{GDBP}) p bar::a
7857 @cindex C@t{++} scope resolution
7858 These uses of @samp{::} are very rarely in conflict with the very similar
7859 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7860 scope resolution operator in @value{GDBN} expressions.
7861 @c FIXME: Um, so what happens in one of those rare cases where it's in
7864 @cindex wrong values
7865 @cindex variable values, wrong
7866 @cindex function entry/exit, wrong values of variables
7867 @cindex optimized code, wrong values of variables
7869 @emph{Warning:} Occasionally, a local variable may appear to have the
7870 wrong value at certain points in a function---just after entry to a new
7871 scope, and just before exit.
7873 You may see this problem when you are stepping by machine instructions.
7874 This is because, on most machines, it takes more than one instruction to
7875 set up a stack frame (including local variable definitions); if you are
7876 stepping by machine instructions, variables may appear to have the wrong
7877 values until the stack frame is completely built. On exit, it usually
7878 also takes more than one machine instruction to destroy a stack frame;
7879 after you begin stepping through that group of instructions, local
7880 variable definitions may be gone.
7882 This may also happen when the compiler does significant optimizations.
7883 To be sure of always seeing accurate values, turn off all optimization
7886 @cindex ``No symbol "foo" in current context''
7887 Another possible effect of compiler optimizations is to optimize
7888 unused variables out of existence, or assign variables to registers (as
7889 opposed to memory addresses). Depending on the support for such cases
7890 offered by the debug info format used by the compiler, @value{GDBN}
7891 might not be able to display values for such local variables. If that
7892 happens, @value{GDBN} will print a message like this:
7895 No symbol "foo" in current context.
7898 To solve such problems, either recompile without optimizations, or use a
7899 different debug info format, if the compiler supports several such
7900 formats. @xref{Compilation}, for more information on choosing compiler
7901 options. @xref{C, ,C and C@t{++}}, for more information about debug
7902 info formats that are best suited to C@t{++} programs.
7904 If you ask to print an object whose contents are unknown to
7905 @value{GDBN}, e.g., because its data type is not completely specified
7906 by the debug information, @value{GDBN} will say @samp{<incomplete
7907 type>}. @xref{Symbols, incomplete type}, for more about this.
7909 If you append @kbd{@@entry} string to a function parameter name you get its
7910 value at the time the function got called. If the value is not available an
7911 error message is printed. Entry values are available only with some compilers.
7912 Entry values are normally also printed at the function parameter list according
7913 to @ref{set print entry-values}.
7916 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7922 (gdb) print i@@entry
7926 Strings are identified as arrays of @code{char} values without specified
7927 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7928 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7929 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7930 defines literal string type @code{"char"} as @code{char} without a sign.
7935 signed char var1[] = "A";
7938 You get during debugging
7943 $2 = @{65 'A', 0 '\0'@}
7947 @section Artificial Arrays
7949 @cindex artificial array
7951 @kindex @@@r{, referencing memory as an array}
7952 It is often useful to print out several successive objects of the
7953 same type in memory; a section of an array, or an array of
7954 dynamically determined size for which only a pointer exists in the
7957 You can do this by referring to a contiguous span of memory as an
7958 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7959 operand of @samp{@@} should be the first element of the desired array
7960 and be an individual object. The right operand should be the desired length
7961 of the array. The result is an array value whose elements are all of
7962 the type of the left argument. The first element is actually the left
7963 argument; the second element comes from bytes of memory immediately
7964 following those that hold the first element, and so on. Here is an
7965 example. If a program says
7968 int *array = (int *) malloc (len * sizeof (int));
7972 you can print the contents of @code{array} with
7978 The left operand of @samp{@@} must reside in memory. Array values made
7979 with @samp{@@} in this way behave just like other arrays in terms of
7980 subscripting, and are coerced to pointers when used in expressions.
7981 Artificial arrays most often appear in expressions via the value history
7982 (@pxref{Value History, ,Value History}), after printing one out.
7984 Another way to create an artificial array is to use a cast.
7985 This re-interprets a value as if it were an array.
7986 The value need not be in memory:
7988 (@value{GDBP}) p/x (short[2])0x12345678
7989 $1 = @{0x1234, 0x5678@}
7992 As a convenience, if you leave the array length out (as in
7993 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7994 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7996 (@value{GDBP}) p/x (short[])0x12345678
7997 $2 = @{0x1234, 0x5678@}
8000 Sometimes the artificial array mechanism is not quite enough; in
8001 moderately complex data structures, the elements of interest may not
8002 actually be adjacent---for example, if you are interested in the values
8003 of pointers in an array. One useful work-around in this situation is
8004 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8005 Variables}) as a counter in an expression that prints the first
8006 interesting value, and then repeat that expression via @key{RET}. For
8007 instance, suppose you have an array @code{dtab} of pointers to
8008 structures, and you are interested in the values of a field @code{fv}
8009 in each structure. Here is an example of what you might type:
8019 @node Output Formats
8020 @section Output Formats
8022 @cindex formatted output
8023 @cindex output formats
8024 By default, @value{GDBN} prints a value according to its data type. Sometimes
8025 this is not what you want. For example, you might want to print a number
8026 in hex, or a pointer in decimal. Or you might want to view data in memory
8027 at a certain address as a character string or as an instruction. To do
8028 these things, specify an @dfn{output format} when you print a value.
8030 The simplest use of output formats is to say how to print a value
8031 already computed. This is done by starting the arguments of the
8032 @code{print} command with a slash and a format letter. The format
8033 letters supported are:
8037 Regard the bits of the value as an integer, and print the integer in
8041 Print as integer in signed decimal.
8044 Print as integer in unsigned decimal.
8047 Print as integer in octal.
8050 Print as integer in binary. The letter @samp{t} stands for ``two''.
8051 @footnote{@samp{b} cannot be used because these format letters are also
8052 used with the @code{x} command, where @samp{b} stands for ``byte'';
8053 see @ref{Memory,,Examining Memory}.}
8056 @cindex unknown address, locating
8057 @cindex locate address
8058 Print as an address, both absolute in hexadecimal and as an offset from
8059 the nearest preceding symbol. You can use this format used to discover
8060 where (in what function) an unknown address is located:
8063 (@value{GDBP}) p/a 0x54320
8064 $3 = 0x54320 <_initialize_vx+396>
8068 The command @code{info symbol 0x54320} yields similar results.
8069 @xref{Symbols, info symbol}.
8072 Regard as an integer and print it as a character constant. This
8073 prints both the numerical value and its character representation. The
8074 character representation is replaced with the octal escape @samp{\nnn}
8075 for characters outside the 7-bit @sc{ascii} range.
8077 Without this format, @value{GDBN} displays @code{char},
8078 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8079 constants. Single-byte members of vectors are displayed as integer
8083 Regard the bits of the value as a floating point number and print
8084 using typical floating point syntax.
8087 @cindex printing strings
8088 @cindex printing byte arrays
8089 Regard as a string, if possible. With this format, pointers to single-byte
8090 data are displayed as null-terminated strings and arrays of single-byte data
8091 are displayed as fixed-length strings. Other values are displayed in their
8094 Without this format, @value{GDBN} displays pointers to and arrays of
8095 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8096 strings. Single-byte members of a vector are displayed as an integer
8100 @cindex raw printing
8101 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8102 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8103 Printing}). This typically results in a higher-level display of the
8104 value's contents. The @samp{r} format bypasses any Python
8105 pretty-printer which might exist.
8108 For example, to print the program counter in hex (@pxref{Registers}), type
8115 Note that no space is required before the slash; this is because command
8116 names in @value{GDBN} cannot contain a slash.
8118 To reprint the last value in the value history with a different format,
8119 you can use the @code{print} command with just a format and no
8120 expression. For example, @samp{p/x} reprints the last value in hex.
8123 @section Examining Memory
8125 You can use the command @code{x} (for ``examine'') to examine memory in
8126 any of several formats, independently of your program's data types.
8128 @cindex examining memory
8130 @kindex x @r{(examine memory)}
8131 @item x/@var{nfu} @var{addr}
8134 Use the @code{x} command to examine memory.
8137 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8138 much memory to display and how to format it; @var{addr} is an
8139 expression giving the address where you want to start displaying memory.
8140 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8141 Several commands set convenient defaults for @var{addr}.
8144 @item @var{n}, the repeat count
8145 The repeat count is a decimal integer; the default is 1. It specifies
8146 how much memory (counting by units @var{u}) to display.
8147 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8150 @item @var{f}, the display format
8151 The display format is one of the formats used by @code{print}
8152 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8153 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8154 The default is @samp{x} (hexadecimal) initially. The default changes
8155 each time you use either @code{x} or @code{print}.
8157 @item @var{u}, the unit size
8158 The unit size is any of
8164 Halfwords (two bytes).
8166 Words (four bytes). This is the initial default.
8168 Giant words (eight bytes).
8171 Each time you specify a unit size with @code{x}, that size becomes the
8172 default unit the next time you use @code{x}. For the @samp{i} format,
8173 the unit size is ignored and is normally not written. For the @samp{s} format,
8174 the unit size defaults to @samp{b}, unless it is explicitly given.
8175 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8176 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8177 Note that the results depend on the programming language of the
8178 current compilation unit. If the language is C, the @samp{s}
8179 modifier will use the UTF-16 encoding while @samp{w} will use
8180 UTF-32. The encoding is set by the programming language and cannot
8183 @item @var{addr}, starting display address
8184 @var{addr} is the address where you want @value{GDBN} to begin displaying
8185 memory. The expression need not have a pointer value (though it may);
8186 it is always interpreted as an integer address of a byte of memory.
8187 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8188 @var{addr} is usually just after the last address examined---but several
8189 other commands also set the default address: @code{info breakpoints} (to
8190 the address of the last breakpoint listed), @code{info line} (to the
8191 starting address of a line), and @code{print} (if you use it to display
8192 a value from memory).
8195 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8196 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8197 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8198 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8199 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8201 Since the letters indicating unit sizes are all distinct from the
8202 letters specifying output formats, you do not have to remember whether
8203 unit size or format comes first; either order works. The output
8204 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8205 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8207 Even though the unit size @var{u} is ignored for the formats @samp{s}
8208 and @samp{i}, you might still want to use a count @var{n}; for example,
8209 @samp{3i} specifies that you want to see three machine instructions,
8210 including any operands. For convenience, especially when used with
8211 the @code{display} command, the @samp{i} format also prints branch delay
8212 slot instructions, if any, beyond the count specified, which immediately
8213 follow the last instruction that is within the count. The command
8214 @code{disassemble} gives an alternative way of inspecting machine
8215 instructions; see @ref{Machine Code,,Source and Machine Code}.
8217 All the defaults for the arguments to @code{x} are designed to make it
8218 easy to continue scanning memory with minimal specifications each time
8219 you use @code{x}. For example, after you have inspected three machine
8220 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8221 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8222 the repeat count @var{n} is used again; the other arguments default as
8223 for successive uses of @code{x}.
8225 When examining machine instructions, the instruction at current program
8226 counter is shown with a @code{=>} marker. For example:
8229 (@value{GDBP}) x/5i $pc-6
8230 0x804837f <main+11>: mov %esp,%ebp
8231 0x8048381 <main+13>: push %ecx
8232 0x8048382 <main+14>: sub $0x4,%esp
8233 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8234 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8237 @cindex @code{$_}, @code{$__}, and value history
8238 The addresses and contents printed by the @code{x} command are not saved
8239 in the value history because there is often too much of them and they
8240 would get in the way. Instead, @value{GDBN} makes these values available for
8241 subsequent use in expressions as values of the convenience variables
8242 @code{$_} and @code{$__}. After an @code{x} command, the last address
8243 examined is available for use in expressions in the convenience variable
8244 @code{$_}. The contents of that address, as examined, are available in
8245 the convenience variable @code{$__}.
8247 If the @code{x} command has a repeat count, the address and contents saved
8248 are from the last memory unit printed; this is not the same as the last
8249 address printed if several units were printed on the last line of output.
8251 @cindex remote memory comparison
8252 @cindex verify remote memory image
8253 When you are debugging a program running on a remote target machine
8254 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8255 remote machine's memory against the executable file you downloaded to
8256 the target. The @code{compare-sections} command is provided for such
8260 @kindex compare-sections
8261 @item compare-sections @r{[}@var{section-name}@r{]}
8262 Compare the data of a loadable section @var{section-name} in the
8263 executable file of the program being debugged with the same section in
8264 the remote machine's memory, and report any mismatches. With no
8265 arguments, compares all loadable sections. This command's
8266 availability depends on the target's support for the @code{"qCRC"}
8271 @section Automatic Display
8272 @cindex automatic display
8273 @cindex display of expressions
8275 If you find that you want to print the value of an expression frequently
8276 (to see how it changes), you might want to add it to the @dfn{automatic
8277 display list} so that @value{GDBN} prints its value each time your program stops.
8278 Each expression added to the list is given a number to identify it;
8279 to remove an expression from the list, you specify that number.
8280 The automatic display looks like this:
8284 3: bar[5] = (struct hack *) 0x3804
8288 This display shows item numbers, expressions and their current values. As with
8289 displays you request manually using @code{x} or @code{print}, you can
8290 specify the output format you prefer; in fact, @code{display} decides
8291 whether to use @code{print} or @code{x} depending your format
8292 specification---it uses @code{x} if you specify either the @samp{i}
8293 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8297 @item display @var{expr}
8298 Add the expression @var{expr} to the list of expressions to display
8299 each time your program stops. @xref{Expressions, ,Expressions}.
8301 @code{display} does not repeat if you press @key{RET} again after using it.
8303 @item display/@var{fmt} @var{expr}
8304 For @var{fmt} specifying only a display format and not a size or
8305 count, add the expression @var{expr} to the auto-display list but
8306 arrange to display it each time in the specified format @var{fmt}.
8307 @xref{Output Formats,,Output Formats}.
8309 @item display/@var{fmt} @var{addr}
8310 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8311 number of units, add the expression @var{addr} as a memory address to
8312 be examined each time your program stops. Examining means in effect
8313 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8316 For example, @samp{display/i $pc} can be helpful, to see the machine
8317 instruction about to be executed each time execution stops (@samp{$pc}
8318 is a common name for the program counter; @pxref{Registers, ,Registers}).
8321 @kindex delete display
8323 @item undisplay @var{dnums}@dots{}
8324 @itemx delete display @var{dnums}@dots{}
8325 Remove items from the list of expressions to display. Specify the
8326 numbers of the displays that you want affected with the command
8327 argument @var{dnums}. It can be a single display number, one of the
8328 numbers shown in the first field of the @samp{info display} display;
8329 or it could be a range of display numbers, as in @code{2-4}.
8331 @code{undisplay} does not repeat if you press @key{RET} after using it.
8332 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8334 @kindex disable display
8335 @item disable display @var{dnums}@dots{}
8336 Disable the display of item numbers @var{dnums}. A disabled display
8337 item is not printed automatically, but is not forgotten. It may be
8338 enabled again later. Specify the numbers of the displays that you
8339 want affected with the command argument @var{dnums}. It can be a
8340 single display number, one of the numbers shown in the first field of
8341 the @samp{info display} display; or it could be a range of display
8342 numbers, as in @code{2-4}.
8344 @kindex enable display
8345 @item enable display @var{dnums}@dots{}
8346 Enable display of item numbers @var{dnums}. It becomes effective once
8347 again in auto display of its expression, until you specify otherwise.
8348 Specify the numbers of the displays that you want affected with the
8349 command argument @var{dnums}. It can be a single display number, one
8350 of the numbers shown in the first field of the @samp{info display}
8351 display; or it could be a range of display numbers, as in @code{2-4}.
8354 Display the current values of the expressions on the list, just as is
8355 done when your program stops.
8357 @kindex info display
8359 Print the list of expressions previously set up to display
8360 automatically, each one with its item number, but without showing the
8361 values. This includes disabled expressions, which are marked as such.
8362 It also includes expressions which would not be displayed right now
8363 because they refer to automatic variables not currently available.
8366 @cindex display disabled out of scope
8367 If a display expression refers to local variables, then it does not make
8368 sense outside the lexical context for which it was set up. Such an
8369 expression is disabled when execution enters a context where one of its
8370 variables is not defined. For example, if you give the command
8371 @code{display last_char} while inside a function with an argument
8372 @code{last_char}, @value{GDBN} displays this argument while your program
8373 continues to stop inside that function. When it stops elsewhere---where
8374 there is no variable @code{last_char}---the display is disabled
8375 automatically. The next time your program stops where @code{last_char}
8376 is meaningful, you can enable the display expression once again.
8378 @node Print Settings
8379 @section Print Settings
8381 @cindex format options
8382 @cindex print settings
8383 @value{GDBN} provides the following ways to control how arrays, structures,
8384 and symbols are printed.
8387 These settings are useful for debugging programs in any language:
8391 @item set print address
8392 @itemx set print address on
8393 @cindex print/don't print memory addresses
8394 @value{GDBN} prints memory addresses showing the location of stack
8395 traces, structure values, pointer values, breakpoints, and so forth,
8396 even when it also displays the contents of those addresses. The default
8397 is @code{on}. For example, this is what a stack frame display looks like with
8398 @code{set print address on}:
8403 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8405 530 if (lquote != def_lquote)
8409 @item set print address off
8410 Do not print addresses when displaying their contents. For example,
8411 this is the same stack frame displayed with @code{set print address off}:
8415 (@value{GDBP}) set print addr off
8417 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8418 530 if (lquote != def_lquote)
8422 You can use @samp{set print address off} to eliminate all machine
8423 dependent displays from the @value{GDBN} interface. For example, with
8424 @code{print address off}, you should get the same text for backtraces on
8425 all machines---whether or not they involve pointer arguments.
8428 @item show print address
8429 Show whether or not addresses are to be printed.
8432 When @value{GDBN} prints a symbolic address, it normally prints the
8433 closest earlier symbol plus an offset. If that symbol does not uniquely
8434 identify the address (for example, it is a name whose scope is a single
8435 source file), you may need to clarify. One way to do this is with
8436 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8437 you can set @value{GDBN} to print the source file and line number when
8438 it prints a symbolic address:
8441 @item set print symbol-filename on
8442 @cindex source file and line of a symbol
8443 @cindex symbol, source file and line
8444 Tell @value{GDBN} to print the source file name and line number of a
8445 symbol in the symbolic form of an address.
8447 @item set print symbol-filename off
8448 Do not print source file name and line number of a symbol. This is the
8451 @item show print symbol-filename
8452 Show whether or not @value{GDBN} will print the source file name and
8453 line number of a symbol in the symbolic form of an address.
8456 Another situation where it is helpful to show symbol filenames and line
8457 numbers is when disassembling code; @value{GDBN} shows you the line
8458 number and source file that corresponds to each instruction.
8460 Also, you may wish to see the symbolic form only if the address being
8461 printed is reasonably close to the closest earlier symbol:
8464 @item set print max-symbolic-offset @var{max-offset}
8465 @cindex maximum value for offset of closest symbol
8466 Tell @value{GDBN} to only display the symbolic form of an address if the
8467 offset between the closest earlier symbol and the address is less than
8468 @var{max-offset}. The default is 0, which tells @value{GDBN}
8469 to always print the symbolic form of an address if any symbol precedes it.
8471 @item show print max-symbolic-offset
8472 Ask how large the maximum offset is that @value{GDBN} prints in a
8476 @cindex wild pointer, interpreting
8477 @cindex pointer, finding referent
8478 If you have a pointer and you are not sure where it points, try
8479 @samp{set print symbol-filename on}. Then you can determine the name
8480 and source file location of the variable where it points, using
8481 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8482 For example, here @value{GDBN} shows that a variable @code{ptt} points
8483 at another variable @code{t}, defined in @file{hi2.c}:
8486 (@value{GDBP}) set print symbol-filename on
8487 (@value{GDBP}) p/a ptt
8488 $4 = 0xe008 <t in hi2.c>
8492 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8493 does not show the symbol name and filename of the referent, even with
8494 the appropriate @code{set print} options turned on.
8497 You can also enable @samp{/a}-like formatting all the time using
8498 @samp{set print symbol on}:
8501 @item set print symbol on
8502 Tell @value{GDBN} to print the symbol corresponding to an address, if
8505 @item set print symbol off
8506 Tell @value{GDBN} not to print the symbol corresponding to an
8507 address. In this mode, @value{GDBN} will still print the symbol
8508 corresponding to pointers to functions. This is the default.
8510 @item show print symbol
8511 Show whether @value{GDBN} will display the symbol corresponding to an
8515 Other settings control how different kinds of objects are printed:
8518 @item set print array
8519 @itemx set print array on
8520 @cindex pretty print arrays
8521 Pretty print arrays. This format is more convenient to read,
8522 but uses more space. The default is off.
8524 @item set print array off
8525 Return to compressed format for arrays.
8527 @item show print array
8528 Show whether compressed or pretty format is selected for displaying
8531 @cindex print array indexes
8532 @item set print array-indexes
8533 @itemx set print array-indexes on
8534 Print the index of each element when displaying arrays. May be more
8535 convenient to locate a given element in the array or quickly find the
8536 index of a given element in that printed array. The default is off.
8538 @item set print array-indexes off
8539 Stop printing element indexes when displaying arrays.
8541 @item show print array-indexes
8542 Show whether the index of each element is printed when displaying
8545 @item set print elements @var{number-of-elements}
8546 @cindex number of array elements to print
8547 @cindex limit on number of printed array elements
8548 Set a limit on how many elements of an array @value{GDBN} will print.
8549 If @value{GDBN} is printing a large array, it stops printing after it has
8550 printed the number of elements set by the @code{set print elements} command.
8551 This limit also applies to the display of strings.
8552 When @value{GDBN} starts, this limit is set to 200.
8553 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8555 @item show print elements
8556 Display the number of elements of a large array that @value{GDBN} will print.
8557 If the number is 0, then the printing is unlimited.
8559 @item set print frame-arguments @var{value}
8560 @kindex set print frame-arguments
8561 @cindex printing frame argument values
8562 @cindex print all frame argument values
8563 @cindex print frame argument values for scalars only
8564 @cindex do not print frame argument values
8565 This command allows to control how the values of arguments are printed
8566 when the debugger prints a frame (@pxref{Frames}). The possible
8571 The values of all arguments are printed.
8574 Print the value of an argument only if it is a scalar. The value of more
8575 complex arguments such as arrays, structures, unions, etc, is replaced
8576 by @code{@dots{}}. This is the default. Here is an example where
8577 only scalar arguments are shown:
8580 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8585 None of the argument values are printed. Instead, the value of each argument
8586 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8589 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8594 By default, only scalar arguments are printed. This command can be used
8595 to configure the debugger to print the value of all arguments, regardless
8596 of their type. However, it is often advantageous to not print the value
8597 of more complex parameters. For instance, it reduces the amount of
8598 information printed in each frame, making the backtrace more readable.
8599 Also, it improves performance when displaying Ada frames, because
8600 the computation of large arguments can sometimes be CPU-intensive,
8601 especially in large applications. Setting @code{print frame-arguments}
8602 to @code{scalars} (the default) or @code{none} avoids this computation,
8603 thus speeding up the display of each Ada frame.
8605 @item show print frame-arguments
8606 Show how the value of arguments should be displayed when printing a frame.
8608 @anchor{set print entry-values}
8609 @item set print entry-values @var{value}
8610 @kindex set print entry-values
8611 Set printing of frame argument values at function entry. In some cases
8612 @value{GDBN} can determine the value of function argument which was passed by
8613 the function caller, even if the value was modified inside the called function
8614 and therefore is different. With optimized code, the current value could be
8615 unavailable, but the entry value may still be known.
8617 The default value is @code{default} (see below for its description). Older
8618 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8619 this feature will behave in the @code{default} setting the same way as with the
8622 This functionality is currently supported only by DWARF 2 debugging format and
8623 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8624 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8627 The @var{value} parameter can be one of the following:
8631 Print only actual parameter values, never print values from function entry
8635 #0 different (val=6)
8636 #0 lost (val=<optimized out>)
8638 #0 invalid (val=<optimized out>)
8642 Print only parameter values from function entry point. The actual parameter
8643 values are never printed.
8645 #0 equal (val@@entry=5)
8646 #0 different (val@@entry=5)
8647 #0 lost (val@@entry=5)
8648 #0 born (val@@entry=<optimized out>)
8649 #0 invalid (val@@entry=<optimized out>)
8653 Print only parameter values from function entry point. If value from function
8654 entry point is not known while the actual value is known, print the actual
8655 value for such parameter.
8657 #0 equal (val@@entry=5)
8658 #0 different (val@@entry=5)
8659 #0 lost (val@@entry=5)
8661 #0 invalid (val@@entry=<optimized out>)
8665 Print actual parameter values. If actual parameter value is not known while
8666 value from function entry point is known, print the entry point value for such
8670 #0 different (val=6)
8671 #0 lost (val@@entry=5)
8673 #0 invalid (val=<optimized out>)
8677 Always print both the actual parameter value and its value from function entry
8678 point, even if values of one or both are not available due to compiler
8681 #0 equal (val=5, val@@entry=5)
8682 #0 different (val=6, val@@entry=5)
8683 #0 lost (val=<optimized out>, val@@entry=5)
8684 #0 born (val=10, val@@entry=<optimized out>)
8685 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8689 Print the actual parameter value if it is known and also its value from
8690 function entry point if it is known. If neither is known, print for the actual
8691 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8692 values are known and identical, print the shortened
8693 @code{param=param@@entry=VALUE} notation.
8695 #0 equal (val=val@@entry=5)
8696 #0 different (val=6, val@@entry=5)
8697 #0 lost (val@@entry=5)
8699 #0 invalid (val=<optimized out>)
8703 Always print the actual parameter value. Print also its value from function
8704 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8705 if both values are known and identical, print the shortened
8706 @code{param=param@@entry=VALUE} notation.
8708 #0 equal (val=val@@entry=5)
8709 #0 different (val=6, val@@entry=5)
8710 #0 lost (val=<optimized out>, val@@entry=5)
8712 #0 invalid (val=<optimized out>)
8716 For analysis messages on possible failures of frame argument values at function
8717 entry resolution see @ref{set debug entry-values}.
8719 @item show print entry-values
8720 Show the method being used for printing of frame argument values at function
8723 @item set print repeats
8724 @cindex repeated array elements
8725 Set the threshold for suppressing display of repeated array
8726 elements. When the number of consecutive identical elements of an
8727 array exceeds the threshold, @value{GDBN} prints the string
8728 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8729 identical repetitions, instead of displaying the identical elements
8730 themselves. Setting the threshold to zero will cause all elements to
8731 be individually printed. The default threshold is 10.
8733 @item show print repeats
8734 Display the current threshold for printing repeated identical
8737 @item set print null-stop
8738 @cindex @sc{null} elements in arrays
8739 Cause @value{GDBN} to stop printing the characters of an array when the first
8740 @sc{null} is encountered. This is useful when large arrays actually
8741 contain only short strings.
8744 @item show print null-stop
8745 Show whether @value{GDBN} stops printing an array on the first
8746 @sc{null} character.
8748 @item set print pretty on
8749 @cindex print structures in indented form
8750 @cindex indentation in structure display
8751 Cause @value{GDBN} to print structures in an indented format with one member
8752 per line, like this:
8767 @item set print pretty off
8768 Cause @value{GDBN} to print structures in a compact format, like this:
8772 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8773 meat = 0x54 "Pork"@}
8778 This is the default format.
8780 @item show print pretty
8781 Show which format @value{GDBN} is using to print structures.
8783 @item set print sevenbit-strings on
8784 @cindex eight-bit characters in strings
8785 @cindex octal escapes in strings
8786 Print using only seven-bit characters; if this option is set,
8787 @value{GDBN} displays any eight-bit characters (in strings or
8788 character values) using the notation @code{\}@var{nnn}. This setting is
8789 best if you are working in English (@sc{ascii}) and you use the
8790 high-order bit of characters as a marker or ``meta'' bit.
8792 @item set print sevenbit-strings off
8793 Print full eight-bit characters. This allows the use of more
8794 international character sets, and is the default.
8796 @item show print sevenbit-strings
8797 Show whether or not @value{GDBN} is printing only seven-bit characters.
8799 @item set print union on
8800 @cindex unions in structures, printing
8801 Tell @value{GDBN} to print unions which are contained in structures
8802 and other unions. This is the default setting.
8804 @item set print union off
8805 Tell @value{GDBN} not to print unions which are contained in
8806 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8809 @item show print union
8810 Ask @value{GDBN} whether or not it will print unions which are contained in
8811 structures and other unions.
8813 For example, given the declarations
8816 typedef enum @{Tree, Bug@} Species;
8817 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8818 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8829 struct thing foo = @{Tree, @{Acorn@}@};
8833 with @code{set print union on} in effect @samp{p foo} would print
8836 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8840 and with @code{set print union off} in effect it would print
8843 $1 = @{it = Tree, form = @{...@}@}
8847 @code{set print union} affects programs written in C-like languages
8853 These settings are of interest when debugging C@t{++} programs:
8856 @cindex demangling C@t{++} names
8857 @item set print demangle
8858 @itemx set print demangle on
8859 Print C@t{++} names in their source form rather than in the encoded
8860 (``mangled'') form passed to the assembler and linker for type-safe
8861 linkage. The default is on.
8863 @item show print demangle
8864 Show whether C@t{++} names are printed in mangled or demangled form.
8866 @item set print asm-demangle
8867 @itemx set print asm-demangle on
8868 Print C@t{++} names in their source form rather than their mangled form, even
8869 in assembler code printouts such as instruction disassemblies.
8872 @item show print asm-demangle
8873 Show whether C@t{++} names in assembly listings are printed in mangled
8876 @cindex C@t{++} symbol decoding style
8877 @cindex symbol decoding style, C@t{++}
8878 @kindex set demangle-style
8879 @item set demangle-style @var{style}
8880 Choose among several encoding schemes used by different compilers to
8881 represent C@t{++} names. The choices for @var{style} are currently:
8885 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8888 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8889 This is the default.
8892 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8895 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8898 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8899 @strong{Warning:} this setting alone is not sufficient to allow
8900 debugging @code{cfront}-generated executables. @value{GDBN} would
8901 require further enhancement to permit that.
8904 If you omit @var{style}, you will see a list of possible formats.
8906 @item show demangle-style
8907 Display the encoding style currently in use for decoding C@t{++} symbols.
8909 @item set print object
8910 @itemx set print object on
8911 @cindex derived type of an object, printing
8912 @cindex display derived types
8913 When displaying a pointer to an object, identify the @emph{actual}
8914 (derived) type of the object rather than the @emph{declared} type, using
8915 the virtual function table. Note that the virtual function table is
8916 required---this feature can only work for objects that have run-time
8917 type identification; a single virtual method in the object's declared
8918 type is sufficient. Note that this setting is also taken into account when
8919 working with variable objects via MI (@pxref{GDB/MI}).
8921 @item set print object off
8922 Display only the declared type of objects, without reference to the
8923 virtual function table. This is the default setting.
8925 @item show print object
8926 Show whether actual, or declared, object types are displayed.
8928 @item set print static-members
8929 @itemx set print static-members on
8930 @cindex static members of C@t{++} objects
8931 Print static members when displaying a C@t{++} object. The default is on.
8933 @item set print static-members off
8934 Do not print static members when displaying a C@t{++} object.
8936 @item show print static-members
8937 Show whether C@t{++} static members are printed or not.
8939 @item set print pascal_static-members
8940 @itemx set print pascal_static-members on
8941 @cindex static members of Pascal objects
8942 @cindex Pascal objects, static members display
8943 Print static members when displaying a Pascal object. The default is on.
8945 @item set print pascal_static-members off
8946 Do not print static members when displaying a Pascal object.
8948 @item show print pascal_static-members
8949 Show whether Pascal static members are printed or not.
8951 @c These don't work with HP ANSI C++ yet.
8952 @item set print vtbl
8953 @itemx set print vtbl on
8954 @cindex pretty print C@t{++} virtual function tables
8955 @cindex virtual functions (C@t{++}) display
8956 @cindex VTBL display
8957 Pretty print C@t{++} virtual function tables. The default is off.
8958 (The @code{vtbl} commands do not work on programs compiled with the HP
8959 ANSI C@t{++} compiler (@code{aCC}).)
8961 @item set print vtbl off
8962 Do not pretty print C@t{++} virtual function tables.
8964 @item show print vtbl
8965 Show whether C@t{++} virtual function tables are pretty printed, or not.
8968 @node Pretty Printing
8969 @section Pretty Printing
8971 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8972 Python code. It greatly simplifies the display of complex objects. This
8973 mechanism works for both MI and the CLI.
8976 * Pretty-Printer Introduction:: Introduction to pretty-printers
8977 * Pretty-Printer Example:: An example pretty-printer
8978 * Pretty-Printer Commands:: Pretty-printer commands
8981 @node Pretty-Printer Introduction
8982 @subsection Pretty-Printer Introduction
8984 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8985 registered for the value. If there is then @value{GDBN} invokes the
8986 pretty-printer to print the value. Otherwise the value is printed normally.
8988 Pretty-printers are normally named. This makes them easy to manage.
8989 The @samp{info pretty-printer} command will list all the installed
8990 pretty-printers with their names.
8991 If a pretty-printer can handle multiple data types, then its
8992 @dfn{subprinters} are the printers for the individual data types.
8993 Each such subprinter has its own name.
8994 The format of the name is @var{printer-name};@var{subprinter-name}.
8996 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8997 Typically they are automatically loaded and registered when the corresponding
8998 debug information is loaded, thus making them available without having to
8999 do anything special.
9001 There are three places where a pretty-printer can be registered.
9005 Pretty-printers registered globally are available when debugging
9009 Pretty-printers registered with a program space are available only
9010 when debugging that program.
9011 @xref{Progspaces In Python}, for more details on program spaces in Python.
9014 Pretty-printers registered with an objfile are loaded and unloaded
9015 with the corresponding objfile (e.g., shared library).
9016 @xref{Objfiles In Python}, for more details on objfiles in Python.
9019 @xref{Selecting Pretty-Printers}, for further information on how
9020 pretty-printers are selected,
9022 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9025 @node Pretty-Printer Example
9026 @subsection Pretty-Printer Example
9028 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9031 (@value{GDBP}) print s
9033 static npos = 4294967295,
9035 <std::allocator<char>> = @{
9036 <__gnu_cxx::new_allocator<char>> = @{
9037 <No data fields>@}, <No data fields>
9039 members of std::basic_string<char, std::char_traits<char>,
9040 std::allocator<char> >::_Alloc_hider:
9041 _M_p = 0x804a014 "abcd"
9046 With a pretty-printer for @code{std::string} only the contents are printed:
9049 (@value{GDBP}) print s
9053 @node Pretty-Printer Commands
9054 @subsection Pretty-Printer Commands
9055 @cindex pretty-printer commands
9058 @kindex info pretty-printer
9059 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9060 Print the list of installed pretty-printers.
9061 This includes disabled pretty-printers, which are marked as such.
9063 @var{object-regexp} is a regular expression matching the objects
9064 whose pretty-printers to list.
9065 Objects can be @code{global}, the program space's file
9066 (@pxref{Progspaces In Python}),
9067 and the object files within that program space (@pxref{Objfiles In Python}).
9068 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9069 looks up a printer from these three objects.
9071 @var{name-regexp} is a regular expression matching the name of the printers
9074 @kindex disable pretty-printer
9075 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9076 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9077 A disabled pretty-printer is not forgotten, it may be enabled again later.
9079 @kindex enable pretty-printer
9080 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9081 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9086 Suppose we have three pretty-printers installed: one from library1.so
9087 named @code{foo} that prints objects of type @code{foo}, and
9088 another from library2.so named @code{bar} that prints two types of objects,
9089 @code{bar1} and @code{bar2}.
9092 (gdb) info pretty-printer
9099 (gdb) info pretty-printer library2
9104 (gdb) disable pretty-printer library1
9106 2 of 3 printers enabled
9107 (gdb) info pretty-printer
9114 (gdb) disable pretty-printer library2 bar:bar1
9116 1 of 3 printers enabled
9117 (gdb) info pretty-printer library2
9124 (gdb) disable pretty-printer library2 bar
9126 0 of 3 printers enabled
9127 (gdb) info pretty-printer library2
9136 Note that for @code{bar} the entire printer can be disabled,
9137 as can each individual subprinter.
9140 @section Value History
9142 @cindex value history
9143 @cindex history of values printed by @value{GDBN}
9144 Values printed by the @code{print} command are saved in the @value{GDBN}
9145 @dfn{value history}. This allows you to refer to them in other expressions.
9146 Values are kept until the symbol table is re-read or discarded
9147 (for example with the @code{file} or @code{symbol-file} commands).
9148 When the symbol table changes, the value history is discarded,
9149 since the values may contain pointers back to the types defined in the
9154 @cindex history number
9155 The values printed are given @dfn{history numbers} by which you can
9156 refer to them. These are successive integers starting with one.
9157 @code{print} shows you the history number assigned to a value by
9158 printing @samp{$@var{num} = } before the value; here @var{num} is the
9161 To refer to any previous value, use @samp{$} followed by the value's
9162 history number. The way @code{print} labels its output is designed to
9163 remind you of this. Just @code{$} refers to the most recent value in
9164 the history, and @code{$$} refers to the value before that.
9165 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9166 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9167 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9169 For example, suppose you have just printed a pointer to a structure and
9170 want to see the contents of the structure. It suffices to type
9176 If you have a chain of structures where the component @code{next} points
9177 to the next one, you can print the contents of the next one with this:
9184 You can print successive links in the chain by repeating this
9185 command---which you can do by just typing @key{RET}.
9187 Note that the history records values, not expressions. If the value of
9188 @code{x} is 4 and you type these commands:
9196 then the value recorded in the value history by the @code{print} command
9197 remains 4 even though the value of @code{x} has changed.
9202 Print the last ten values in the value history, with their item numbers.
9203 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9204 values} does not change the history.
9206 @item show values @var{n}
9207 Print ten history values centered on history item number @var{n}.
9210 Print ten history values just after the values last printed. If no more
9211 values are available, @code{show values +} produces no display.
9214 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9215 same effect as @samp{show values +}.
9217 @node Convenience Vars
9218 @section Convenience Variables
9220 @cindex convenience variables
9221 @cindex user-defined variables
9222 @value{GDBN} provides @dfn{convenience variables} that you can use within
9223 @value{GDBN} to hold on to a value and refer to it later. These variables
9224 exist entirely within @value{GDBN}; they are not part of your program, and
9225 setting a convenience variable has no direct effect on further execution
9226 of your program. That is why you can use them freely.
9228 Convenience variables are prefixed with @samp{$}. Any name preceded by
9229 @samp{$} can be used for a convenience variable, unless it is one of
9230 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9231 (Value history references, in contrast, are @emph{numbers} preceded
9232 by @samp{$}. @xref{Value History, ,Value History}.)
9234 You can save a value in a convenience variable with an assignment
9235 expression, just as you would set a variable in your program.
9239 set $foo = *object_ptr
9243 would save in @code{$foo} the value contained in the object pointed to by
9246 Using a convenience variable for the first time creates it, but its
9247 value is @code{void} until you assign a new value. You can alter the
9248 value with another assignment at any time.
9250 Convenience variables have no fixed types. You can assign a convenience
9251 variable any type of value, including structures and arrays, even if
9252 that variable already has a value of a different type. The convenience
9253 variable, when used as an expression, has the type of its current value.
9256 @kindex show convenience
9257 @cindex show all user variables and functions
9258 @item show convenience
9259 Print a list of convenience variables used so far, and their values,
9260 as well as a list of the convenience functions.
9261 Abbreviated @code{show conv}.
9263 @kindex init-if-undefined
9264 @cindex convenience variables, initializing
9265 @item init-if-undefined $@var{variable} = @var{expression}
9266 Set a convenience variable if it has not already been set. This is useful
9267 for user-defined commands that keep some state. It is similar, in concept,
9268 to using local static variables with initializers in C (except that
9269 convenience variables are global). It can also be used to allow users to
9270 override default values used in a command script.
9272 If the variable is already defined then the expression is not evaluated so
9273 any side-effects do not occur.
9276 One of the ways to use a convenience variable is as a counter to be
9277 incremented or a pointer to be advanced. For example, to print
9278 a field from successive elements of an array of structures:
9282 print bar[$i++]->contents
9286 Repeat that command by typing @key{RET}.
9288 Some convenience variables are created automatically by @value{GDBN} and given
9289 values likely to be useful.
9292 @vindex $_@r{, convenience variable}
9294 The variable @code{$_} is automatically set by the @code{x} command to
9295 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9296 commands which provide a default address for @code{x} to examine also
9297 set @code{$_} to that address; these commands include @code{info line}
9298 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9299 except when set by the @code{x} command, in which case it is a pointer
9300 to the type of @code{$__}.
9302 @vindex $__@r{, convenience variable}
9304 The variable @code{$__} is automatically set by the @code{x} command
9305 to the value found in the last address examined. Its type is chosen
9306 to match the format in which the data was printed.
9309 @vindex $_exitcode@r{, convenience variable}
9310 The variable @code{$_exitcode} is automatically set to the exit code when
9311 the program being debugged terminates.
9314 @itemx $_probe_arg0@dots{}$_probe_arg11
9315 Arguments to a static probe. @xref{Static Probe Points}.
9318 @vindex $_sdata@r{, inspect, convenience variable}
9319 The variable @code{$_sdata} contains extra collected static tracepoint
9320 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9321 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9322 if extra static tracepoint data has not been collected.
9325 @vindex $_siginfo@r{, convenience variable}
9326 The variable @code{$_siginfo} contains extra signal information
9327 (@pxref{extra signal information}). Note that @code{$_siginfo}
9328 could be empty, if the application has not yet received any signals.
9329 For example, it will be empty before you execute the @code{run} command.
9332 @vindex $_tlb@r{, convenience variable}
9333 The variable @code{$_tlb} is automatically set when debugging
9334 applications running on MS-Windows in native mode or connected to
9335 gdbserver that supports the @code{qGetTIBAddr} request.
9336 @xref{General Query Packets}.
9337 This variable contains the address of the thread information block.
9341 On HP-UX systems, if you refer to a function or variable name that
9342 begins with a dollar sign, @value{GDBN} searches for a user or system
9343 name first, before it searches for a convenience variable.
9345 @node Convenience Funs
9346 @section Convenience Functions
9348 @cindex convenience functions
9349 @value{GDBN} also supplies some @dfn{convenience functions}. These
9350 have a syntax similar to convenience variables. A convenience
9351 function can be used in an expression just like an ordinary function;
9352 however, a convenience function is implemented internally to
9355 These functions require @value{GDBN} to be configured with
9356 @code{Python} support.
9360 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
9361 @findex $_memeq@r{, convenience function}
9362 Returns one if the @var{length} bytes at the addresses given by
9363 @var{buf1} and @var{buf2} are equal.
9364 Otherwise it returns zero.
9366 @item $_regex(@var{str}, @var{regex})
9367 @findex $_regex@r{, convenience function}
9368 Returns one if the string @var{str} matches the regular expression
9369 @var{regex}. Otherwise it returns zero.
9370 The syntax of the regular expression is that specified by @code{Python}'s
9371 regular expression support.
9373 @item $_streq(@var{str1}, @var{str2})
9374 @findex $_streq@r{, convenience function}
9375 Returns one if the strings @var{str1} and @var{str2} are equal.
9376 Otherwise it returns zero.
9378 @item $_strlen(@var{str})
9379 @findex $_strlen@r{, convenience function}
9380 Returns the length of string @var{str}.
9384 @value{GDBN} provides the ability to list and get help on
9385 convenience functions.
9389 @kindex help function
9390 @cindex show all convenience functions
9391 Print a list of all convenience functions.
9398 You can refer to machine register contents, in expressions, as variables
9399 with names starting with @samp{$}. The names of registers are different
9400 for each machine; use @code{info registers} to see the names used on
9404 @kindex info registers
9405 @item info registers
9406 Print the names and values of all registers except floating-point
9407 and vector registers (in the selected stack frame).
9409 @kindex info all-registers
9410 @cindex floating point registers
9411 @item info all-registers
9412 Print the names and values of all registers, including floating-point
9413 and vector registers (in the selected stack frame).
9415 @item info registers @var{regname} @dots{}
9416 Print the @dfn{relativized} value of each specified register @var{regname}.
9417 As discussed in detail below, register values are normally relative to
9418 the selected stack frame. @var{regname} may be any register name valid on
9419 the machine you are using, with or without the initial @samp{$}.
9422 @cindex stack pointer register
9423 @cindex program counter register
9424 @cindex process status register
9425 @cindex frame pointer register
9426 @cindex standard registers
9427 @value{GDBN} has four ``standard'' register names that are available (in
9428 expressions) on most machines---whenever they do not conflict with an
9429 architecture's canonical mnemonics for registers. The register names
9430 @code{$pc} and @code{$sp} are used for the program counter register and
9431 the stack pointer. @code{$fp} is used for a register that contains a
9432 pointer to the current stack frame, and @code{$ps} is used for a
9433 register that contains the processor status. For example,
9434 you could print the program counter in hex with
9441 or print the instruction to be executed next with
9448 or add four to the stack pointer@footnote{This is a way of removing
9449 one word from the stack, on machines where stacks grow downward in
9450 memory (most machines, nowadays). This assumes that the innermost
9451 stack frame is selected; setting @code{$sp} is not allowed when other
9452 stack frames are selected. To pop entire frames off the stack,
9453 regardless of machine architecture, use @code{return};
9454 see @ref{Returning, ,Returning from a Function}.} with
9460 Whenever possible, these four standard register names are available on
9461 your machine even though the machine has different canonical mnemonics,
9462 so long as there is no conflict. The @code{info registers} command
9463 shows the canonical names. For example, on the SPARC, @code{info
9464 registers} displays the processor status register as @code{$psr} but you
9465 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9466 is an alias for the @sc{eflags} register.
9468 @value{GDBN} always considers the contents of an ordinary register as an
9469 integer when the register is examined in this way. Some machines have
9470 special registers which can hold nothing but floating point; these
9471 registers are considered to have floating point values. There is no way
9472 to refer to the contents of an ordinary register as floating point value
9473 (although you can @emph{print} it as a floating point value with
9474 @samp{print/f $@var{regname}}).
9476 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9477 means that the data format in which the register contents are saved by
9478 the operating system is not the same one that your program normally
9479 sees. For example, the registers of the 68881 floating point
9480 coprocessor are always saved in ``extended'' (raw) format, but all C
9481 programs expect to work with ``double'' (virtual) format. In such
9482 cases, @value{GDBN} normally works with the virtual format only (the format
9483 that makes sense for your program), but the @code{info registers} command
9484 prints the data in both formats.
9486 @cindex SSE registers (x86)
9487 @cindex MMX registers (x86)
9488 Some machines have special registers whose contents can be interpreted
9489 in several different ways. For example, modern x86-based machines
9490 have SSE and MMX registers that can hold several values packed
9491 together in several different formats. @value{GDBN} refers to such
9492 registers in @code{struct} notation:
9495 (@value{GDBP}) print $xmm1
9497 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
9498 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
9499 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
9500 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
9501 v4_int32 = @{0, 20657912, 11, 13@},
9502 v2_int64 = @{88725056443645952, 55834574859@},
9503 uint128 = 0x0000000d0000000b013b36f800000000
9508 To set values of such registers, you need to tell @value{GDBN} which
9509 view of the register you wish to change, as if you were assigning
9510 value to a @code{struct} member:
9513 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
9516 Normally, register values are relative to the selected stack frame
9517 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
9518 value that the register would contain if all stack frames farther in
9519 were exited and their saved registers restored. In order to see the
9520 true contents of hardware registers, you must select the innermost
9521 frame (with @samp{frame 0}).
9523 However, @value{GDBN} must deduce where registers are saved, from the machine
9524 code generated by your compiler. If some registers are not saved, or if
9525 @value{GDBN} is unable to locate the saved registers, the selected stack
9526 frame makes no difference.
9528 @node Floating Point Hardware
9529 @section Floating Point Hardware
9530 @cindex floating point
9532 Depending on the configuration, @value{GDBN} may be able to give
9533 you more information about the status of the floating point hardware.
9538 Display hardware-dependent information about the floating
9539 point unit. The exact contents and layout vary depending on the
9540 floating point chip. Currently, @samp{info float} is supported on
9541 the ARM and x86 machines.
9545 @section Vector Unit
9548 Depending on the configuration, @value{GDBN} may be able to give you
9549 more information about the status of the vector unit.
9554 Display information about the vector unit. The exact contents and
9555 layout vary depending on the hardware.
9558 @node OS Information
9559 @section Operating System Auxiliary Information
9560 @cindex OS information
9562 @value{GDBN} provides interfaces to useful OS facilities that can help
9563 you debug your program.
9565 @cindex @code{ptrace} system call
9566 @cindex @code{struct user} contents
9567 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
9568 machines), it interfaces with the inferior via the @code{ptrace}
9569 system call. The operating system creates a special sata structure,
9570 called @code{struct user}, for this interface. You can use the
9571 command @code{info udot} to display the contents of this data
9577 Display the contents of the @code{struct user} maintained by the OS
9578 kernel for the program being debugged. @value{GDBN} displays the
9579 contents of @code{struct user} as a list of hex numbers, similar to
9580 the @code{examine} command.
9583 @cindex auxiliary vector
9584 @cindex vector, auxiliary
9585 Some operating systems supply an @dfn{auxiliary vector} to programs at
9586 startup. This is akin to the arguments and environment that you
9587 specify for a program, but contains a system-dependent variety of
9588 binary values that tell system libraries important details about the
9589 hardware, operating system, and process. Each value's purpose is
9590 identified by an integer tag; the meanings are well-known but system-specific.
9591 Depending on the configuration and operating system facilities,
9592 @value{GDBN} may be able to show you this information. For remote
9593 targets, this functionality may further depend on the remote stub's
9594 support of the @samp{qXfer:auxv:read} packet, see
9595 @ref{qXfer auxiliary vector read}.
9600 Display the auxiliary vector of the inferior, which can be either a
9601 live process or a core dump file. @value{GDBN} prints each tag value
9602 numerically, and also shows names and text descriptions for recognized
9603 tags. Some values in the vector are numbers, some bit masks, and some
9604 pointers to strings or other data. @value{GDBN} displays each value in the
9605 most appropriate form for a recognized tag, and in hexadecimal for
9606 an unrecognized tag.
9609 On some targets, @value{GDBN} can access operating system-specific
9610 information and show it to you. The types of information available
9611 will differ depending on the type of operating system running on the
9612 target. The mechanism used to fetch the data is described in
9613 @ref{Operating System Information}. For remote targets, this
9614 functionality depends on the remote stub's support of the
9615 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9619 @item info os @var{infotype}
9621 Display OS information of the requested type.
9623 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
9625 @anchor{linux info os infotypes}
9627 @kindex info os processes
9629 Display the list of processes on the target. For each process,
9630 @value{GDBN} prints the process identifier, the name of the user, the
9631 command corresponding to the process, and the list of processor cores
9632 that the process is currently running on. (To understand what these
9633 properties mean, for this and the following info types, please consult
9634 the general @sc{gnu}/Linux documentation.)
9636 @kindex info os procgroups
9638 Display the list of process groups on the target. For each process,
9639 @value{GDBN} prints the identifier of the process group that it belongs
9640 to, the command corresponding to the process group leader, the process
9641 identifier, and the command line of the process. The list is sorted
9642 first by the process group identifier, then by the process identifier,
9643 so that processes belonging to the same process group are grouped together
9644 and the process group leader is listed first.
9646 @kindex info os threads
9648 Display the list of threads running on the target. For each thread,
9649 @value{GDBN} prints the identifier of the process that the thread
9650 belongs to, the command of the process, the thread identifier, and the
9651 processor core that it is currently running on. The main thread of a
9652 process is not listed.
9654 @kindex info os files
9656 Display the list of open file descriptors on the target. For each
9657 file descriptor, @value{GDBN} prints the identifier of the process
9658 owning the descriptor, the command of the owning process, the value
9659 of the descriptor, and the target of the descriptor.
9661 @kindex info os sockets
9663 Display the list of Internet-domain sockets on the target. For each
9664 socket, @value{GDBN} prints the address and port of the local and
9665 remote endpoints, the current state of the connection, the creator of
9666 the socket, the IP address family of the socket, and the type of the
9671 Display the list of all System V shared-memory regions on the target.
9672 For each shared-memory region, @value{GDBN} prints the region key,
9673 the shared-memory identifier, the access permissions, the size of the
9674 region, the process that created the region, the process that last
9675 attached to or detached from the region, the current number of live
9676 attaches to the region, and the times at which the region was last
9677 attached to, detach from, and changed.
9679 @kindex info os semaphores
9681 Display the list of all System V semaphore sets on the target. For each
9682 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
9683 set identifier, the access permissions, the number of semaphores in the
9684 set, the user and group of the owner and creator of the semaphore set,
9685 and the times at which the semaphore set was operated upon and changed.
9689 Display the list of all System V message queues on the target. For each
9690 message queue, @value{GDBN} prints the message queue key, the message
9691 queue identifier, the access permissions, the current number of bytes
9692 on the queue, the current number of messages on the queue, the processes
9693 that last sent and received a message on the queue, the user and group
9694 of the owner and creator of the message queue, the times at which a
9695 message was last sent and received on the queue, and the time at which
9696 the message queue was last changed.
9698 @kindex info os modules
9700 Display the list of all loaded kernel modules on the target. For each
9701 module, @value{GDBN} prints the module name, the size of the module in
9702 bytes, the number of times the module is used, the dependencies of the
9703 module, the status of the module, and the address of the loaded module
9708 If @var{infotype} is omitted, then list the possible values for
9709 @var{infotype} and the kind of OS information available for each
9710 @var{infotype}. If the target does not return a list of possible
9711 types, this command will report an error.
9714 @node Memory Region Attributes
9715 @section Memory Region Attributes
9716 @cindex memory region attributes
9718 @dfn{Memory region attributes} allow you to describe special handling
9719 required by regions of your target's memory. @value{GDBN} uses
9720 attributes to determine whether to allow certain types of memory
9721 accesses; whether to use specific width accesses; and whether to cache
9722 target memory. By default the description of memory regions is
9723 fetched from the target (if the current target supports this), but the
9724 user can override the fetched regions.
9726 Defined memory regions can be individually enabled and disabled. When a
9727 memory region is disabled, @value{GDBN} uses the default attributes when
9728 accessing memory in that region. Similarly, if no memory regions have
9729 been defined, @value{GDBN} uses the default attributes when accessing
9732 When a memory region is defined, it is given a number to identify it;
9733 to enable, disable, or remove a memory region, you specify that number.
9737 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9738 Define a memory region bounded by @var{lower} and @var{upper} with
9739 attributes @var{attributes}@dots{}, and add it to the list of regions
9740 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9741 case: it is treated as the target's maximum memory address.
9742 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9745 Discard any user changes to the memory regions and use target-supplied
9746 regions, if available, or no regions if the target does not support.
9749 @item delete mem @var{nums}@dots{}
9750 Remove memory regions @var{nums}@dots{} from the list of regions
9751 monitored by @value{GDBN}.
9754 @item disable mem @var{nums}@dots{}
9755 Disable monitoring of memory regions @var{nums}@dots{}.
9756 A disabled memory region is not forgotten.
9757 It may be enabled again later.
9760 @item enable mem @var{nums}@dots{}
9761 Enable monitoring of memory regions @var{nums}@dots{}.
9765 Print a table of all defined memory regions, with the following columns
9769 @item Memory Region Number
9770 @item Enabled or Disabled.
9771 Enabled memory regions are marked with @samp{y}.
9772 Disabled memory regions are marked with @samp{n}.
9775 The address defining the inclusive lower bound of the memory region.
9778 The address defining the exclusive upper bound of the memory region.
9781 The list of attributes set for this memory region.
9786 @subsection Attributes
9788 @subsubsection Memory Access Mode
9789 The access mode attributes set whether @value{GDBN} may make read or
9790 write accesses to a memory region.
9792 While these attributes prevent @value{GDBN} from performing invalid
9793 memory accesses, they do nothing to prevent the target system, I/O DMA,
9794 etc.@: from accessing memory.
9798 Memory is read only.
9800 Memory is write only.
9802 Memory is read/write. This is the default.
9805 @subsubsection Memory Access Size
9806 The access size attribute tells @value{GDBN} to use specific sized
9807 accesses in the memory region. Often memory mapped device registers
9808 require specific sized accesses. If no access size attribute is
9809 specified, @value{GDBN} may use accesses of any size.
9813 Use 8 bit memory accesses.
9815 Use 16 bit memory accesses.
9817 Use 32 bit memory accesses.
9819 Use 64 bit memory accesses.
9822 @c @subsubsection Hardware/Software Breakpoints
9823 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9824 @c will use hardware or software breakpoints for the internal breakpoints
9825 @c used by the step, next, finish, until, etc. commands.
9829 @c Always use hardware breakpoints
9830 @c @item swbreak (default)
9833 @subsubsection Data Cache
9834 The data cache attributes set whether @value{GDBN} will cache target
9835 memory. While this generally improves performance by reducing debug
9836 protocol overhead, it can lead to incorrect results because @value{GDBN}
9837 does not know about volatile variables or memory mapped device
9842 Enable @value{GDBN} to cache target memory.
9844 Disable @value{GDBN} from caching target memory. This is the default.
9847 @subsection Memory Access Checking
9848 @value{GDBN} can be instructed to refuse accesses to memory that is
9849 not explicitly described. This can be useful if accessing such
9850 regions has undesired effects for a specific target, or to provide
9851 better error checking. The following commands control this behaviour.
9854 @kindex set mem inaccessible-by-default
9855 @item set mem inaccessible-by-default [on|off]
9856 If @code{on} is specified, make @value{GDBN} treat memory not
9857 explicitly described by the memory ranges as non-existent and refuse accesses
9858 to such memory. The checks are only performed if there's at least one
9859 memory range defined. If @code{off} is specified, make @value{GDBN}
9860 treat the memory not explicitly described by the memory ranges as RAM.
9861 The default value is @code{on}.
9862 @kindex show mem inaccessible-by-default
9863 @item show mem inaccessible-by-default
9864 Show the current handling of accesses to unknown memory.
9868 @c @subsubsection Memory Write Verification
9869 @c The memory write verification attributes set whether @value{GDBN}
9870 @c will re-reads data after each write to verify the write was successful.
9874 @c @item noverify (default)
9877 @node Dump/Restore Files
9878 @section Copy Between Memory and a File
9879 @cindex dump/restore files
9880 @cindex append data to a file
9881 @cindex dump data to a file
9882 @cindex restore data from a file
9884 You can use the commands @code{dump}, @code{append}, and
9885 @code{restore} to copy data between target memory and a file. The
9886 @code{dump} and @code{append} commands write data to a file, and the
9887 @code{restore} command reads data from a file back into the inferior's
9888 memory. Files may be in binary, Motorola S-record, Intel hex, or
9889 Tektronix Hex format; however, @value{GDBN} can only append to binary
9895 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9896 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9897 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9898 or the value of @var{expr}, to @var{filename} in the given format.
9900 The @var{format} parameter may be any one of:
9907 Motorola S-record format.
9909 Tektronix Hex format.
9912 @value{GDBN} uses the same definitions of these formats as the
9913 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9914 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9918 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9919 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9920 Append the contents of memory from @var{start_addr} to @var{end_addr},
9921 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9922 (@value{GDBN} can only append data to files in raw binary form.)
9925 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9926 Restore the contents of file @var{filename} into memory. The
9927 @code{restore} command can automatically recognize any known @sc{bfd}
9928 file format, except for raw binary. To restore a raw binary file you
9929 must specify the optional keyword @code{binary} after the filename.
9931 If @var{bias} is non-zero, its value will be added to the addresses
9932 contained in the file. Binary files always start at address zero, so
9933 they will be restored at address @var{bias}. Other bfd files have
9934 a built-in location; they will be restored at offset @var{bias}
9937 If @var{start} and/or @var{end} are non-zero, then only data between
9938 file offset @var{start} and file offset @var{end} will be restored.
9939 These offsets are relative to the addresses in the file, before
9940 the @var{bias} argument is applied.
9944 @node Core File Generation
9945 @section How to Produce a Core File from Your Program
9946 @cindex dump core from inferior
9948 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9949 image of a running process and its process status (register values
9950 etc.). Its primary use is post-mortem debugging of a program that
9951 crashed while it ran outside a debugger. A program that crashes
9952 automatically produces a core file, unless this feature is disabled by
9953 the user. @xref{Files}, for information on invoking @value{GDBN} in
9954 the post-mortem debugging mode.
9956 Occasionally, you may wish to produce a core file of the program you
9957 are debugging in order to preserve a snapshot of its state.
9958 @value{GDBN} has a special command for that.
9962 @kindex generate-core-file
9963 @item generate-core-file [@var{file}]
9964 @itemx gcore [@var{file}]
9965 Produce a core dump of the inferior process. The optional argument
9966 @var{file} specifies the file name where to put the core dump. If not
9967 specified, the file name defaults to @file{core.@var{pid}}, where
9968 @var{pid} is the inferior process ID.
9970 Note that this command is implemented only for some systems (as of
9971 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9974 @node Character Sets
9975 @section Character Sets
9976 @cindex character sets
9978 @cindex translating between character sets
9979 @cindex host character set
9980 @cindex target character set
9982 If the program you are debugging uses a different character set to
9983 represent characters and strings than the one @value{GDBN} uses itself,
9984 @value{GDBN} can automatically translate between the character sets for
9985 you. The character set @value{GDBN} uses we call the @dfn{host
9986 character set}; the one the inferior program uses we call the
9987 @dfn{target character set}.
9989 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9990 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9991 remote protocol (@pxref{Remote Debugging}) to debug a program
9992 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9993 then the host character set is Latin-1, and the target character set is
9994 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9995 target-charset EBCDIC-US}, then @value{GDBN} translates between
9996 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9997 character and string literals in expressions.
9999 @value{GDBN} has no way to automatically recognize which character set
10000 the inferior program uses; you must tell it, using the @code{set
10001 target-charset} command, described below.
10003 Here are the commands for controlling @value{GDBN}'s character set
10007 @item set target-charset @var{charset}
10008 @kindex set target-charset
10009 Set the current target character set to @var{charset}. To display the
10010 list of supported target character sets, type
10011 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10013 @item set host-charset @var{charset}
10014 @kindex set host-charset
10015 Set the current host character set to @var{charset}.
10017 By default, @value{GDBN} uses a host character set appropriate to the
10018 system it is running on; you can override that default using the
10019 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10020 automatically determine the appropriate host character set. In this
10021 case, @value{GDBN} uses @samp{UTF-8}.
10023 @value{GDBN} can only use certain character sets as its host character
10024 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10025 @value{GDBN} will list the host character sets it supports.
10027 @item set charset @var{charset}
10028 @kindex set charset
10029 Set the current host and target character sets to @var{charset}. As
10030 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10031 @value{GDBN} will list the names of the character sets that can be used
10032 for both host and target.
10035 @kindex show charset
10036 Show the names of the current host and target character sets.
10038 @item show host-charset
10039 @kindex show host-charset
10040 Show the name of the current host character set.
10042 @item show target-charset
10043 @kindex show target-charset
10044 Show the name of the current target character set.
10046 @item set target-wide-charset @var{charset}
10047 @kindex set target-wide-charset
10048 Set the current target's wide character set to @var{charset}. This is
10049 the character set used by the target's @code{wchar_t} type. To
10050 display the list of supported wide character sets, type
10051 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10053 @item show target-wide-charset
10054 @kindex show target-wide-charset
10055 Show the name of the current target's wide character set.
10058 Here is an example of @value{GDBN}'s character set support in action.
10059 Assume that the following source code has been placed in the file
10060 @file{charset-test.c}:
10066 = @{72, 101, 108, 108, 111, 44, 32, 119,
10067 111, 114, 108, 100, 33, 10, 0@};
10068 char ibm1047_hello[]
10069 = @{200, 133, 147, 147, 150, 107, 64, 166,
10070 150, 153, 147, 132, 90, 37, 0@};
10074 printf ("Hello, world!\n");
10078 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10079 containing the string @samp{Hello, world!} followed by a newline,
10080 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10082 We compile the program, and invoke the debugger on it:
10085 $ gcc -g charset-test.c -o charset-test
10086 $ gdb -nw charset-test
10087 GNU gdb 2001-12-19-cvs
10088 Copyright 2001 Free Software Foundation, Inc.
10093 We can use the @code{show charset} command to see what character sets
10094 @value{GDBN} is currently using to interpret and display characters and
10098 (@value{GDBP}) show charset
10099 The current host and target character set is `ISO-8859-1'.
10103 For the sake of printing this manual, let's use @sc{ascii} as our
10104 initial character set:
10106 (@value{GDBP}) set charset ASCII
10107 (@value{GDBP}) show charset
10108 The current host and target character set is `ASCII'.
10112 Let's assume that @sc{ascii} is indeed the correct character set for our
10113 host system --- in other words, let's assume that if @value{GDBN} prints
10114 characters using the @sc{ascii} character set, our terminal will display
10115 them properly. Since our current target character set is also
10116 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10119 (@value{GDBP}) print ascii_hello
10120 $1 = 0x401698 "Hello, world!\n"
10121 (@value{GDBP}) print ascii_hello[0]
10126 @value{GDBN} uses the target character set for character and string
10127 literals you use in expressions:
10130 (@value{GDBP}) print '+'
10135 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10138 @value{GDBN} relies on the user to tell it which character set the
10139 target program uses. If we print @code{ibm1047_hello} while our target
10140 character set is still @sc{ascii}, we get jibberish:
10143 (@value{GDBP}) print ibm1047_hello
10144 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10145 (@value{GDBP}) print ibm1047_hello[0]
10150 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10151 @value{GDBN} tells us the character sets it supports:
10154 (@value{GDBP}) set target-charset
10155 ASCII EBCDIC-US IBM1047 ISO-8859-1
10156 (@value{GDBP}) set target-charset
10159 We can select @sc{ibm1047} as our target character set, and examine the
10160 program's strings again. Now the @sc{ascii} string is wrong, but
10161 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10162 target character set, @sc{ibm1047}, to the host character set,
10163 @sc{ascii}, and they display correctly:
10166 (@value{GDBP}) set target-charset IBM1047
10167 (@value{GDBP}) show charset
10168 The current host character set is `ASCII'.
10169 The current target character set is `IBM1047'.
10170 (@value{GDBP}) print ascii_hello
10171 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10172 (@value{GDBP}) print ascii_hello[0]
10174 (@value{GDBP}) print ibm1047_hello
10175 $8 = 0x4016a8 "Hello, world!\n"
10176 (@value{GDBP}) print ibm1047_hello[0]
10181 As above, @value{GDBN} uses the target character set for character and
10182 string literals you use in expressions:
10185 (@value{GDBP}) print '+'
10190 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10193 @node Caching Remote Data
10194 @section Caching Data of Remote Targets
10195 @cindex caching data of remote targets
10197 @value{GDBN} caches data exchanged between the debugger and a
10198 remote target (@pxref{Remote Debugging}). Such caching generally improves
10199 performance, because it reduces the overhead of the remote protocol by
10200 bundling memory reads and writes into large chunks. Unfortunately, simply
10201 caching everything would lead to incorrect results, since @value{GDBN}
10202 does not necessarily know anything about volatile values, memory-mapped I/O
10203 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
10204 memory can be changed @emph{while} a gdb command is executing.
10205 Therefore, by default, @value{GDBN} only caches data
10206 known to be on the stack@footnote{In non-stop mode, it is moderately
10207 rare for a running thread to modify the stack of a stopped thread
10208 in a way that would interfere with a backtrace, and caching of
10209 stack reads provides a significant speed up of remote backtraces.}.
10210 Other regions of memory can be explicitly marked as
10211 cacheable; see @pxref{Memory Region Attributes}.
10214 @kindex set remotecache
10215 @item set remotecache on
10216 @itemx set remotecache off
10217 This option no longer does anything; it exists for compatibility
10220 @kindex show remotecache
10221 @item show remotecache
10222 Show the current state of the obsolete remotecache flag.
10224 @kindex set stack-cache
10225 @item set stack-cache on
10226 @itemx set stack-cache off
10227 Enable or disable caching of stack accesses. When @code{ON}, use
10228 caching. By default, this option is @code{ON}.
10230 @kindex show stack-cache
10231 @item show stack-cache
10232 Show the current state of data caching for memory accesses.
10234 @kindex info dcache
10235 @item info dcache @r{[}line@r{]}
10236 Print the information about the data cache performance. The
10237 information displayed includes the dcache width and depth, and for
10238 each cache line, its number, address, and how many times it was
10239 referenced. This command is useful for debugging the data cache
10242 If a line number is specified, the contents of that line will be
10245 @item set dcache size @var{size}
10246 @cindex dcache size
10247 @kindex set dcache size
10248 Set maximum number of entries in dcache (dcache depth above).
10250 @item set dcache line-size @var{line-size}
10251 @cindex dcache line-size
10252 @kindex set dcache line-size
10253 Set number of bytes each dcache entry caches (dcache width above).
10254 Must be a power of 2.
10256 @item show dcache size
10257 @kindex show dcache size
10258 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
10260 @item show dcache line-size
10261 @kindex show dcache line-size
10262 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
10266 @node Searching Memory
10267 @section Search Memory
10268 @cindex searching memory
10270 Memory can be searched for a particular sequence of bytes with the
10271 @code{find} command.
10275 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10276 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10277 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10278 etc. The search begins at address @var{start_addr} and continues for either
10279 @var{len} bytes or through to @var{end_addr} inclusive.
10282 @var{s} and @var{n} are optional parameters.
10283 They may be specified in either order, apart or together.
10286 @item @var{s}, search query size
10287 The size of each search query value.
10293 halfwords (two bytes)
10297 giant words (eight bytes)
10300 All values are interpreted in the current language.
10301 This means, for example, that if the current source language is C/C@t{++}
10302 then searching for the string ``hello'' includes the trailing '\0'.
10304 If the value size is not specified, it is taken from the
10305 value's type in the current language.
10306 This is useful when one wants to specify the search
10307 pattern as a mixture of types.
10308 Note that this means, for example, that in the case of C-like languages
10309 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10310 which is typically four bytes.
10312 @item @var{n}, maximum number of finds
10313 The maximum number of matches to print. The default is to print all finds.
10316 You can use strings as search values. Quote them with double-quotes
10318 The string value is copied into the search pattern byte by byte,
10319 regardless of the endianness of the target and the size specification.
10321 The address of each match found is printed as well as a count of the
10322 number of matches found.
10324 The address of the last value found is stored in convenience variable
10326 A count of the number of matches is stored in @samp{$numfound}.
10328 For example, if stopped at the @code{printf} in this function:
10334 static char hello[] = "hello-hello";
10335 static struct @{ char c; short s; int i; @}
10336 __attribute__ ((packed)) mixed
10337 = @{ 'c', 0x1234, 0x87654321 @};
10338 printf ("%s\n", hello);
10343 you get during debugging:
10346 (gdb) find &hello[0], +sizeof(hello), "hello"
10347 0x804956d <hello.1620+6>
10349 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10350 0x8049567 <hello.1620>
10351 0x804956d <hello.1620+6>
10353 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10354 0x8049567 <hello.1620>
10356 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10357 0x8049560 <mixed.1625>
10359 (gdb) print $numfound
10362 $2 = (void *) 0x8049560
10365 @node Optimized Code
10366 @chapter Debugging Optimized Code
10367 @cindex optimized code, debugging
10368 @cindex debugging optimized code
10370 Almost all compilers support optimization. With optimization
10371 disabled, the compiler generates assembly code that corresponds
10372 directly to your source code, in a simplistic way. As the compiler
10373 applies more powerful optimizations, the generated assembly code
10374 diverges from your original source code. With help from debugging
10375 information generated by the compiler, @value{GDBN} can map from
10376 the running program back to constructs from your original source.
10378 @value{GDBN} is more accurate with optimization disabled. If you
10379 can recompile without optimization, it is easier to follow the
10380 progress of your program during debugging. But, there are many cases
10381 where you may need to debug an optimized version.
10383 When you debug a program compiled with @samp{-g -O}, remember that the
10384 optimizer has rearranged your code; the debugger shows you what is
10385 really there. Do not be too surprised when the execution path does not
10386 exactly match your source file! An extreme example: if you define a
10387 variable, but never use it, @value{GDBN} never sees that
10388 variable---because the compiler optimizes it out of existence.
10390 Some things do not work as well with @samp{-g -O} as with just
10391 @samp{-g}, particularly on machines with instruction scheduling. If in
10392 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
10393 please report it to us as a bug (including a test case!).
10394 @xref{Variables}, for more information about debugging optimized code.
10397 * Inline Functions:: How @value{GDBN} presents inlining
10398 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
10401 @node Inline Functions
10402 @section Inline Functions
10403 @cindex inline functions, debugging
10405 @dfn{Inlining} is an optimization that inserts a copy of the function
10406 body directly at each call site, instead of jumping to a shared
10407 routine. @value{GDBN} displays inlined functions just like
10408 non-inlined functions. They appear in backtraces. You can view their
10409 arguments and local variables, step into them with @code{step}, skip
10410 them with @code{next}, and escape from them with @code{finish}.
10411 You can check whether a function was inlined by using the
10412 @code{info frame} command.
10414 For @value{GDBN} to support inlined functions, the compiler must
10415 record information about inlining in the debug information ---
10416 @value{NGCC} using the @sc{dwarf 2} format does this, and several
10417 other compilers do also. @value{GDBN} only supports inlined functions
10418 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
10419 do not emit two required attributes (@samp{DW_AT_call_file} and
10420 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
10421 function calls with earlier versions of @value{NGCC}. It instead
10422 displays the arguments and local variables of inlined functions as
10423 local variables in the caller.
10425 The body of an inlined function is directly included at its call site;
10426 unlike a non-inlined function, there are no instructions devoted to
10427 the call. @value{GDBN} still pretends that the call site and the
10428 start of the inlined function are different instructions. Stepping to
10429 the call site shows the call site, and then stepping again shows
10430 the first line of the inlined function, even though no additional
10431 instructions are executed.
10433 This makes source-level debugging much clearer; you can see both the
10434 context of the call and then the effect of the call. Only stepping by
10435 a single instruction using @code{stepi} or @code{nexti} does not do
10436 this; single instruction steps always show the inlined body.
10438 There are some ways that @value{GDBN} does not pretend that inlined
10439 function calls are the same as normal calls:
10443 Setting breakpoints at the call site of an inlined function may not
10444 work, because the call site does not contain any code. @value{GDBN}
10445 may incorrectly move the breakpoint to the next line of the enclosing
10446 function, after the call. This limitation will be removed in a future
10447 version of @value{GDBN}; until then, set a breakpoint on an earlier line
10448 or inside the inlined function instead.
10451 @value{GDBN} cannot locate the return value of inlined calls after
10452 using the @code{finish} command. This is a limitation of compiler-generated
10453 debugging information; after @code{finish}, you can step to the next line
10454 and print a variable where your program stored the return value.
10458 @node Tail Call Frames
10459 @section Tail Call Frames
10460 @cindex tail call frames, debugging
10462 Function @code{B} can call function @code{C} in its very last statement. In
10463 unoptimized compilation the call of @code{C} is immediately followed by return
10464 instruction at the end of @code{B} code. Optimizing compiler may replace the
10465 call and return in function @code{B} into one jump to function @code{C}
10466 instead. Such use of a jump instruction is called @dfn{tail call}.
10468 During execution of function @code{C}, there will be no indication in the
10469 function call stack frames that it was tail-called from @code{B}. If function
10470 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
10471 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
10472 some cases @value{GDBN} can determine that @code{C} was tail-called from
10473 @code{B}, and it will then create fictitious call frame for that, with the
10474 return address set up as if @code{B} called @code{C} normally.
10476 This functionality is currently supported only by DWARF 2 debugging format and
10477 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
10478 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10481 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
10482 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
10486 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
10488 Stack level 1, frame at 0x7fffffffda30:
10489 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
10490 tail call frame, caller of frame at 0x7fffffffda30
10491 source language c++.
10492 Arglist at unknown address.
10493 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
10496 The detection of all the possible code path executions can find them ambiguous.
10497 There is no execution history stored (possible @ref{Reverse Execution} is never
10498 used for this purpose) and the last known caller could have reached the known
10499 callee by multiple different jump sequences. In such case @value{GDBN} still
10500 tries to show at least all the unambiguous top tail callers and all the
10501 unambiguous bottom tail calees, if any.
10504 @anchor{set debug entry-values}
10505 @item set debug entry-values
10506 @kindex set debug entry-values
10507 When set to on, enables printing of analysis messages for both frame argument
10508 values at function entry and tail calls. It will show all the possible valid
10509 tail calls code paths it has considered. It will also print the intersection
10510 of them with the final unambiguous (possibly partial or even empty) code path
10513 @item show debug entry-values
10514 @kindex show debug entry-values
10515 Show the current state of analysis messages printing for both frame argument
10516 values at function entry and tail calls.
10519 The analysis messages for tail calls can for example show why the virtual tail
10520 call frame for function @code{c} has not been recognized (due to the indirect
10521 reference by variable @code{x}):
10524 static void __attribute__((noinline, noclone)) c (void);
10525 void (*x) (void) = c;
10526 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10527 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
10528 int main (void) @{ x (); return 0; @}
10530 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
10531 DW_TAG_GNU_call_site 0x40039a in main
10533 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10536 #1 0x000000000040039a in main () at t.c:5
10539 Another possibility is an ambiguous virtual tail call frames resolution:
10543 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
10544 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
10545 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
10546 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
10547 static void __attribute__((noinline, noclone)) b (void)
10548 @{ if (i) c (); else e (); @}
10549 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
10550 int main (void) @{ a (); return 0; @}
10552 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
10553 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
10554 tailcall: reduced: 0x4004d2(a) |
10557 #1 0x00000000004004d2 in a () at t.c:8
10558 #2 0x0000000000400395 in main () at t.c:9
10561 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
10562 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
10564 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
10565 @ifset HAVE_MAKEINFO_CLICK
10566 @set ARROW @click{}
10567 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
10568 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
10570 @ifclear HAVE_MAKEINFO_CLICK
10572 @set CALLSEQ1B @value{CALLSEQ1A}
10573 @set CALLSEQ2B @value{CALLSEQ2A}
10576 Frames #0 and #2 are real, #1 is a virtual tail call frame.
10577 The code can have possible execution paths @value{CALLSEQ1B} or
10578 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
10580 @code{initial:} state shows some random possible calling sequence @value{GDBN}
10581 has found. It then finds another possible calling sequcen - that one is
10582 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
10583 printed as the @code{reduced:} calling sequence. That one could have many
10584 futher @code{compare:} and @code{reduced:} statements as long as there remain
10585 any non-ambiguous sequence entries.
10587 For the frame of function @code{b} in both cases there are different possible
10588 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
10589 also ambigous. The only non-ambiguous frame is the one for function @code{a},
10590 therefore this one is displayed to the user while the ambiguous frames are
10593 There can be also reasons why printing of frame argument values at function
10598 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
10599 static void __attribute__((noinline, noclone)) a (int i);
10600 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
10601 static void __attribute__((noinline, noclone)) a (int i)
10602 @{ if (i) b (i - 1); else c (0); @}
10603 int main (void) @{ a (5); return 0; @}
10606 #0 c (i=i@@entry=0) at t.c:2
10607 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
10608 function "a" at 0x400420 can call itself via tail calls
10609 i=<optimized out>) at t.c:6
10610 #2 0x000000000040036e in main () at t.c:7
10613 @value{GDBN} cannot find out from the inferior state if and how many times did
10614 function @code{a} call itself (via function @code{b}) as these calls would be
10615 tail calls. Such tail calls would modify thue @code{i} variable, therefore
10616 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
10617 prints @code{<optimized out>} instead.
10620 @chapter C Preprocessor Macros
10622 Some languages, such as C and C@t{++}, provide a way to define and invoke
10623 ``preprocessor macros'' which expand into strings of tokens.
10624 @value{GDBN} can evaluate expressions containing macro invocations, show
10625 the result of macro expansion, and show a macro's definition, including
10626 where it was defined.
10628 You may need to compile your program specially to provide @value{GDBN}
10629 with information about preprocessor macros. Most compilers do not
10630 include macros in their debugging information, even when you compile
10631 with the @option{-g} flag. @xref{Compilation}.
10633 A program may define a macro at one point, remove that definition later,
10634 and then provide a different definition after that. Thus, at different
10635 points in the program, a macro may have different definitions, or have
10636 no definition at all. If there is a current stack frame, @value{GDBN}
10637 uses the macros in scope at that frame's source code line. Otherwise,
10638 @value{GDBN} uses the macros in scope at the current listing location;
10641 Whenever @value{GDBN} evaluates an expression, it always expands any
10642 macro invocations present in the expression. @value{GDBN} also provides
10643 the following commands for working with macros explicitly.
10647 @kindex macro expand
10648 @cindex macro expansion, showing the results of preprocessor
10649 @cindex preprocessor macro expansion, showing the results of
10650 @cindex expanding preprocessor macros
10651 @item macro expand @var{expression}
10652 @itemx macro exp @var{expression}
10653 Show the results of expanding all preprocessor macro invocations in
10654 @var{expression}. Since @value{GDBN} simply expands macros, but does
10655 not parse the result, @var{expression} need not be a valid expression;
10656 it can be any string of tokens.
10659 @item macro expand-once @var{expression}
10660 @itemx macro exp1 @var{expression}
10661 @cindex expand macro once
10662 @i{(This command is not yet implemented.)} Show the results of
10663 expanding those preprocessor macro invocations that appear explicitly in
10664 @var{expression}. Macro invocations appearing in that expansion are
10665 left unchanged. This command allows you to see the effect of a
10666 particular macro more clearly, without being confused by further
10667 expansions. Since @value{GDBN} simply expands macros, but does not
10668 parse the result, @var{expression} need not be a valid expression; it
10669 can be any string of tokens.
10672 @cindex macro definition, showing
10673 @cindex definition of a macro, showing
10674 @cindex macros, from debug info
10675 @item info macro [-a|-all] [--] @var{macro}
10676 Show the current definition or all definitions of the named @var{macro},
10677 and describe the source location or compiler command-line where that
10678 definition was established. The optional double dash is to signify the end of
10679 argument processing and the beginning of @var{macro} for non C-like macros where
10680 the macro may begin with a hyphen.
10682 @kindex info macros
10683 @item info macros @var{linespec}
10684 Show all macro definitions that are in effect at the location specified
10685 by @var{linespec}, and describe the source location or compiler
10686 command-line where those definitions were established.
10688 @kindex macro define
10689 @cindex user-defined macros
10690 @cindex defining macros interactively
10691 @cindex macros, user-defined
10692 @item macro define @var{macro} @var{replacement-list}
10693 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10694 Introduce a definition for a preprocessor macro named @var{macro},
10695 invocations of which are replaced by the tokens given in
10696 @var{replacement-list}. The first form of this command defines an
10697 ``object-like'' macro, which takes no arguments; the second form
10698 defines a ``function-like'' macro, which takes the arguments given in
10701 A definition introduced by this command is in scope in every
10702 expression evaluated in @value{GDBN}, until it is removed with the
10703 @code{macro undef} command, described below. The definition overrides
10704 all definitions for @var{macro} present in the program being debugged,
10705 as well as any previous user-supplied definition.
10707 @kindex macro undef
10708 @item macro undef @var{macro}
10709 Remove any user-supplied definition for the macro named @var{macro}.
10710 This command only affects definitions provided with the @code{macro
10711 define} command, described above; it cannot remove definitions present
10712 in the program being debugged.
10716 List all the macros defined using the @code{macro define} command.
10719 @cindex macros, example of debugging with
10720 Here is a transcript showing the above commands in action. First, we
10721 show our source files:
10726 #include "sample.h"
10729 #define ADD(x) (M + x)
10734 printf ("Hello, world!\n");
10736 printf ("We're so creative.\n");
10738 printf ("Goodbye, world!\n");
10745 Now, we compile the program using the @sc{gnu} C compiler,
10746 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10747 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10748 and @option{-gdwarf-4}; we recommend always choosing the most recent
10749 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10750 includes information about preprocessor macros in the debugging
10754 $ gcc -gdwarf-2 -g3 sample.c -o sample
10758 Now, we start @value{GDBN} on our sample program:
10762 GNU gdb 2002-05-06-cvs
10763 Copyright 2002 Free Software Foundation, Inc.
10764 GDB is free software, @dots{}
10768 We can expand macros and examine their definitions, even when the
10769 program is not running. @value{GDBN} uses the current listing position
10770 to decide which macro definitions are in scope:
10773 (@value{GDBP}) list main
10776 5 #define ADD(x) (M + x)
10781 10 printf ("Hello, world!\n");
10783 12 printf ("We're so creative.\n");
10784 (@value{GDBP}) info macro ADD
10785 Defined at /home/jimb/gdb/macros/play/sample.c:5
10786 #define ADD(x) (M + x)
10787 (@value{GDBP}) info macro Q
10788 Defined at /home/jimb/gdb/macros/play/sample.h:1
10789 included at /home/jimb/gdb/macros/play/sample.c:2
10791 (@value{GDBP}) macro expand ADD(1)
10792 expands to: (42 + 1)
10793 (@value{GDBP}) macro expand-once ADD(1)
10794 expands to: once (M + 1)
10798 In the example above, note that @code{macro expand-once} expands only
10799 the macro invocation explicit in the original text --- the invocation of
10800 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10801 which was introduced by @code{ADD}.
10803 Once the program is running, @value{GDBN} uses the macro definitions in
10804 force at the source line of the current stack frame:
10807 (@value{GDBP}) break main
10808 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10810 Starting program: /home/jimb/gdb/macros/play/sample
10812 Breakpoint 1, main () at sample.c:10
10813 10 printf ("Hello, world!\n");
10817 At line 10, the definition of the macro @code{N} at line 9 is in force:
10820 (@value{GDBP}) info macro N
10821 Defined at /home/jimb/gdb/macros/play/sample.c:9
10823 (@value{GDBP}) macro expand N Q M
10824 expands to: 28 < 42
10825 (@value{GDBP}) print N Q M
10830 As we step over directives that remove @code{N}'s definition, and then
10831 give it a new definition, @value{GDBN} finds the definition (or lack
10832 thereof) in force at each point:
10835 (@value{GDBP}) next
10837 12 printf ("We're so creative.\n");
10838 (@value{GDBP}) info macro N
10839 The symbol `N' has no definition as a C/C++ preprocessor macro
10840 at /home/jimb/gdb/macros/play/sample.c:12
10841 (@value{GDBP}) next
10843 14 printf ("Goodbye, world!\n");
10844 (@value{GDBP}) info macro N
10845 Defined at /home/jimb/gdb/macros/play/sample.c:13
10847 (@value{GDBP}) macro expand N Q M
10848 expands to: 1729 < 42
10849 (@value{GDBP}) print N Q M
10854 In addition to source files, macros can be defined on the compilation command
10855 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10856 such a way, @value{GDBN} displays the location of their definition as line zero
10857 of the source file submitted to the compiler.
10860 (@value{GDBP}) info macro __STDC__
10861 Defined at /home/jimb/gdb/macros/play/sample.c:0
10868 @chapter Tracepoints
10869 @c This chapter is based on the documentation written by Michael
10870 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10872 @cindex tracepoints
10873 In some applications, it is not feasible for the debugger to interrupt
10874 the program's execution long enough for the developer to learn
10875 anything helpful about its behavior. If the program's correctness
10876 depends on its real-time behavior, delays introduced by a debugger
10877 might cause the program to change its behavior drastically, or perhaps
10878 fail, even when the code itself is correct. It is useful to be able
10879 to observe the program's behavior without interrupting it.
10881 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10882 specify locations in the program, called @dfn{tracepoints}, and
10883 arbitrary expressions to evaluate when those tracepoints are reached.
10884 Later, using the @code{tfind} command, you can examine the values
10885 those expressions had when the program hit the tracepoints. The
10886 expressions may also denote objects in memory---structures or arrays,
10887 for example---whose values @value{GDBN} should record; while visiting
10888 a particular tracepoint, you may inspect those objects as if they were
10889 in memory at that moment. However, because @value{GDBN} records these
10890 values without interacting with you, it can do so quickly and
10891 unobtrusively, hopefully not disturbing the program's behavior.
10893 The tracepoint facility is currently available only for remote
10894 targets. @xref{Targets}. In addition, your remote target must know
10895 how to collect trace data. This functionality is implemented in the
10896 remote stub; however, none of the stubs distributed with @value{GDBN}
10897 support tracepoints as of this writing. The format of the remote
10898 packets used to implement tracepoints are described in @ref{Tracepoint
10901 It is also possible to get trace data from a file, in a manner reminiscent
10902 of corefiles; you specify the filename, and use @code{tfind} to search
10903 through the file. @xref{Trace Files}, for more details.
10905 This chapter describes the tracepoint commands and features.
10908 * Set Tracepoints::
10909 * Analyze Collected Data::
10910 * Tracepoint Variables::
10914 @node Set Tracepoints
10915 @section Commands to Set Tracepoints
10917 Before running such a @dfn{trace experiment}, an arbitrary number of
10918 tracepoints can be set. A tracepoint is actually a special type of
10919 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10920 standard breakpoint commands. For instance, as with breakpoints,
10921 tracepoint numbers are successive integers starting from one, and many
10922 of the commands associated with tracepoints take the tracepoint number
10923 as their argument, to identify which tracepoint to work on.
10925 For each tracepoint, you can specify, in advance, some arbitrary set
10926 of data that you want the target to collect in the trace buffer when
10927 it hits that tracepoint. The collected data can include registers,
10928 local variables, or global data. Later, you can use @value{GDBN}
10929 commands to examine the values these data had at the time the
10930 tracepoint was hit.
10932 Tracepoints do not support every breakpoint feature. Ignore counts on
10933 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10934 commands when they are hit. Tracepoints may not be thread-specific
10937 @cindex fast tracepoints
10938 Some targets may support @dfn{fast tracepoints}, which are inserted in
10939 a different way (such as with a jump instead of a trap), that is
10940 faster but possibly restricted in where they may be installed.
10942 @cindex static tracepoints
10943 @cindex markers, static tracepoints
10944 @cindex probing markers, static tracepoints
10945 Regular and fast tracepoints are dynamic tracing facilities, meaning
10946 that they can be used to insert tracepoints at (almost) any location
10947 in the target. Some targets may also support controlling @dfn{static
10948 tracepoints} from @value{GDBN}. With static tracing, a set of
10949 instrumentation points, also known as @dfn{markers}, are embedded in
10950 the target program, and can be activated or deactivated by name or
10951 address. These are usually placed at locations which facilitate
10952 investigating what the target is actually doing. @value{GDBN}'s
10953 support for static tracing includes being able to list instrumentation
10954 points, and attach them with @value{GDBN} defined high level
10955 tracepoints that expose the whole range of convenience of
10956 @value{GDBN}'s tracepoints support. Namely, support for collecting
10957 registers values and values of global or local (to the instrumentation
10958 point) variables; tracepoint conditions and trace state variables.
10959 The act of installing a @value{GDBN} static tracepoint on an
10960 instrumentation point, or marker, is referred to as @dfn{probing} a
10961 static tracepoint marker.
10963 @code{gdbserver} supports tracepoints on some target systems.
10964 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10966 This section describes commands to set tracepoints and associated
10967 conditions and actions.
10970 * Create and Delete Tracepoints::
10971 * Enable and Disable Tracepoints::
10972 * Tracepoint Passcounts::
10973 * Tracepoint Conditions::
10974 * Trace State Variables::
10975 * Tracepoint Actions::
10976 * Listing Tracepoints::
10977 * Listing Static Tracepoint Markers::
10978 * Starting and Stopping Trace Experiments::
10979 * Tracepoint Restrictions::
10982 @node Create and Delete Tracepoints
10983 @subsection Create and Delete Tracepoints
10986 @cindex set tracepoint
10988 @item trace @var{location}
10989 The @code{trace} command is very similar to the @code{break} command.
10990 Its argument @var{location} can be a source line, a function name, or
10991 an address in the target program. @xref{Specify Location}. The
10992 @code{trace} command defines a tracepoint, which is a point in the
10993 target program where the debugger will briefly stop, collect some
10994 data, and then allow the program to continue. Setting a tracepoint or
10995 changing its actions takes effect immediately if the remote stub
10996 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
10998 If remote stub doesn't support the @samp{InstallInTrace} feature, all
10999 these changes don't take effect until the next @code{tstart}
11000 command, and once a trace experiment is running, further changes will
11001 not have any effect until the next trace experiment starts. In addition,
11002 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11003 address is not yet resolved. (This is similar to pending breakpoints.)
11004 Pending tracepoints are not downloaded to the target and not installed
11005 until they are resolved. The resolution of pending tracepoints requires
11006 @value{GDBN} support---when debugging with the remote target, and
11007 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11008 tracing}), pending tracepoints can not be resolved (and downloaded to
11009 the remote stub) while @value{GDBN} is disconnected.
11011 Here are some examples of using the @code{trace} command:
11014 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11016 (@value{GDBP}) @b{trace +2} // 2 lines forward
11018 (@value{GDBP}) @b{trace my_function} // first source line of function
11020 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11022 (@value{GDBP}) @b{trace *0x2117c4} // an address
11026 You can abbreviate @code{trace} as @code{tr}.
11028 @item trace @var{location} if @var{cond}
11029 Set a tracepoint with condition @var{cond}; evaluate the expression
11030 @var{cond} each time the tracepoint is reached, and collect data only
11031 if the value is nonzero---that is, if @var{cond} evaluates as true.
11032 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11033 information on tracepoint conditions.
11035 @item ftrace @var{location} [ if @var{cond} ]
11036 @cindex set fast tracepoint
11037 @cindex fast tracepoints, setting
11039 The @code{ftrace} command sets a fast tracepoint. For targets that
11040 support them, fast tracepoints will use a more efficient but possibly
11041 less general technique to trigger data collection, such as a jump
11042 instruction instead of a trap, or some sort of hardware support. It
11043 may not be possible to create a fast tracepoint at the desired
11044 location, in which case the command will exit with an explanatory
11047 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11050 On 32-bit x86-architecture systems, fast tracepoints normally need to
11051 be placed at an instruction that is 5 bytes or longer, but can be
11052 placed at 4-byte instructions if the low 64K of memory of the target
11053 program is available to install trampolines. Some Unix-type systems,
11054 such as @sc{gnu}/Linux, exclude low addresses from the program's
11055 address space; but for instance with the Linux kernel it is possible
11056 to let @value{GDBN} use this area by doing a @command{sysctl} command
11057 to set the @code{mmap_min_addr} kernel parameter, as in
11060 sudo sysctl -w vm.mmap_min_addr=32768
11064 which sets the low address to 32K, which leaves plenty of room for
11065 trampolines. The minimum address should be set to a page boundary.
11067 @item strace @var{location} [ if @var{cond} ]
11068 @cindex set static tracepoint
11069 @cindex static tracepoints, setting
11070 @cindex probe static tracepoint marker
11072 The @code{strace} command sets a static tracepoint. For targets that
11073 support it, setting a static tracepoint probes a static
11074 instrumentation point, or marker, found at @var{location}. It may not
11075 be possible to set a static tracepoint at the desired location, in
11076 which case the command will exit with an explanatory message.
11078 @value{GDBN} handles arguments to @code{strace} exactly as for
11079 @code{trace}, with the addition that the user can also specify
11080 @code{-m @var{marker}} as @var{location}. This probes the marker
11081 identified by the @var{marker} string identifier. This identifier
11082 depends on the static tracepoint backend library your program is
11083 using. You can find all the marker identifiers in the @samp{ID} field
11084 of the @code{info static-tracepoint-markers} command output.
11085 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11086 Markers}. For example, in the following small program using the UST
11092 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11097 the marker id is composed of joining the first two arguments to the
11098 @code{trace_mark} call with a slash, which translates to:
11101 (@value{GDBP}) info static-tracepoint-markers
11102 Cnt Enb ID Address What
11103 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11109 so you may probe the marker above with:
11112 (@value{GDBP}) strace -m ust/bar33
11115 Static tracepoints accept an extra collect action --- @code{collect
11116 $_sdata}. This collects arbitrary user data passed in the probe point
11117 call to the tracing library. In the UST example above, you'll see
11118 that the third argument to @code{trace_mark} is a printf-like format
11119 string. The user data is then the result of running that formating
11120 string against the following arguments. Note that @code{info
11121 static-tracepoint-markers} command output lists that format string in
11122 the @samp{Data:} field.
11124 You can inspect this data when analyzing the trace buffer, by printing
11125 the $_sdata variable like any other variable available to
11126 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11129 @cindex last tracepoint number
11130 @cindex recent tracepoint number
11131 @cindex tracepoint number
11132 The convenience variable @code{$tpnum} records the tracepoint number
11133 of the most recently set tracepoint.
11135 @kindex delete tracepoint
11136 @cindex tracepoint deletion
11137 @item delete tracepoint @r{[}@var{num}@r{]}
11138 Permanently delete one or more tracepoints. With no argument, the
11139 default is to delete all tracepoints. Note that the regular
11140 @code{delete} command can remove tracepoints also.
11145 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11147 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11151 You can abbreviate this command as @code{del tr}.
11154 @node Enable and Disable Tracepoints
11155 @subsection Enable and Disable Tracepoints
11157 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11160 @kindex disable tracepoint
11161 @item disable tracepoint @r{[}@var{num}@r{]}
11162 Disable tracepoint @var{num}, or all tracepoints if no argument
11163 @var{num} is given. A disabled tracepoint will have no effect during
11164 a trace experiment, but it is not forgotten. You can re-enable
11165 a disabled tracepoint using the @code{enable tracepoint} command.
11166 If the command is issued during a trace experiment and the debug target
11167 has support for disabling tracepoints during a trace experiment, then the
11168 change will be effective immediately. Otherwise, it will be applied to the
11169 next trace experiment.
11171 @kindex enable tracepoint
11172 @item enable tracepoint @r{[}@var{num}@r{]}
11173 Enable tracepoint @var{num}, or all tracepoints. If this command is
11174 issued during a trace experiment and the debug target supports enabling
11175 tracepoints during a trace experiment, then the enabled tracepoints will
11176 become effective immediately. Otherwise, they will become effective the
11177 next time a trace experiment is run.
11180 @node Tracepoint Passcounts
11181 @subsection Tracepoint Passcounts
11185 @cindex tracepoint pass count
11186 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11187 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11188 automatically stop a trace experiment. If a tracepoint's passcount is
11189 @var{n}, then the trace experiment will be automatically stopped on
11190 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11191 @var{num} is not specified, the @code{passcount} command sets the
11192 passcount of the most recently defined tracepoint. If no passcount is
11193 given, the trace experiment will run until stopped explicitly by the
11199 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11200 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11202 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11203 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11204 (@value{GDBP}) @b{trace foo}
11205 (@value{GDBP}) @b{pass 3}
11206 (@value{GDBP}) @b{trace bar}
11207 (@value{GDBP}) @b{pass 2}
11208 (@value{GDBP}) @b{trace baz}
11209 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11210 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11211 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11212 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11216 @node Tracepoint Conditions
11217 @subsection Tracepoint Conditions
11218 @cindex conditional tracepoints
11219 @cindex tracepoint conditions
11221 The simplest sort of tracepoint collects data every time your program
11222 reaches a specified place. You can also specify a @dfn{condition} for
11223 a tracepoint. A condition is just a Boolean expression in your
11224 programming language (@pxref{Expressions, ,Expressions}). A
11225 tracepoint with a condition evaluates the expression each time your
11226 program reaches it, and data collection happens only if the condition
11229 Tracepoint conditions can be specified when a tracepoint is set, by
11230 using @samp{if} in the arguments to the @code{trace} command.
11231 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11232 also be set or changed at any time with the @code{condition} command,
11233 just as with breakpoints.
11235 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11236 the conditional expression itself. Instead, @value{GDBN} encodes the
11237 expression into an agent expression (@pxref{Agent Expressions})
11238 suitable for execution on the target, independently of @value{GDBN}.
11239 Global variables become raw memory locations, locals become stack
11240 accesses, and so forth.
11242 For instance, suppose you have a function that is usually called
11243 frequently, but should not be called after an error has occurred. You
11244 could use the following tracepoint command to collect data about calls
11245 of that function that happen while the error code is propagating
11246 through the program; an unconditional tracepoint could end up
11247 collecting thousands of useless trace frames that you would have to
11251 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11254 @node Trace State Variables
11255 @subsection Trace State Variables
11256 @cindex trace state variables
11258 A @dfn{trace state variable} is a special type of variable that is
11259 created and managed by target-side code. The syntax is the same as
11260 that for GDB's convenience variables (a string prefixed with ``$''),
11261 but they are stored on the target. They must be created explicitly,
11262 using a @code{tvariable} command. They are always 64-bit signed
11265 Trace state variables are remembered by @value{GDBN}, and downloaded
11266 to the target along with tracepoint information when the trace
11267 experiment starts. There are no intrinsic limits on the number of
11268 trace state variables, beyond memory limitations of the target.
11270 @cindex convenience variables, and trace state variables
11271 Although trace state variables are managed by the target, you can use
11272 them in print commands and expressions as if they were convenience
11273 variables; @value{GDBN} will get the current value from the target
11274 while the trace experiment is running. Trace state variables share
11275 the same namespace as other ``$'' variables, which means that you
11276 cannot have trace state variables with names like @code{$23} or
11277 @code{$pc}, nor can you have a trace state variable and a convenience
11278 variable with the same name.
11282 @item tvariable $@var{name} [ = @var{expression} ]
11284 The @code{tvariable} command creates a new trace state variable named
11285 @code{$@var{name}}, and optionally gives it an initial value of
11286 @var{expression}. @var{expression} is evaluated when this command is
11287 entered; the result will be converted to an integer if possible,
11288 otherwise @value{GDBN} will report an error. A subsequent
11289 @code{tvariable} command specifying the same name does not create a
11290 variable, but instead assigns the supplied initial value to the
11291 existing variable of that name, overwriting any previous initial
11292 value. The default initial value is 0.
11294 @item info tvariables
11295 @kindex info tvariables
11296 List all the trace state variables along with their initial values.
11297 Their current values may also be displayed, if the trace experiment is
11300 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11301 @kindex delete tvariable
11302 Delete the given trace state variables, or all of them if no arguments
11307 @node Tracepoint Actions
11308 @subsection Tracepoint Action Lists
11312 @cindex tracepoint actions
11313 @item actions @r{[}@var{num}@r{]}
11314 This command will prompt for a list of actions to be taken when the
11315 tracepoint is hit. If the tracepoint number @var{num} is not
11316 specified, this command sets the actions for the one that was most
11317 recently defined (so that you can define a tracepoint and then say
11318 @code{actions} without bothering about its number). You specify the
11319 actions themselves on the following lines, one action at a time, and
11320 terminate the actions list with a line containing just @code{end}. So
11321 far, the only defined actions are @code{collect}, @code{teval}, and
11322 @code{while-stepping}.
11324 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11325 Commands, ,Breakpoint Command Lists}), except that only the defined
11326 actions are allowed; any other @value{GDBN} command is rejected.
11328 @cindex remove actions from a tracepoint
11329 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11330 and follow it immediately with @samp{end}.
11333 (@value{GDBP}) @b{collect @var{data}} // collect some data
11335 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11337 (@value{GDBP}) @b{end} // signals the end of actions.
11340 In the following example, the action list begins with @code{collect}
11341 commands indicating the things to be collected when the tracepoint is
11342 hit. Then, in order to single-step and collect additional data
11343 following the tracepoint, a @code{while-stepping} command is used,
11344 followed by the list of things to be collected after each step in a
11345 sequence of single steps. The @code{while-stepping} command is
11346 terminated by its own separate @code{end} command. Lastly, the action
11347 list is terminated by an @code{end} command.
11350 (@value{GDBP}) @b{trace foo}
11351 (@value{GDBP}) @b{actions}
11352 Enter actions for tracepoint 1, one per line:
11355 > while-stepping 12
11356 > collect $pc, arr[i]
11361 @kindex collect @r{(tracepoints)}
11362 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11363 Collect values of the given expressions when the tracepoint is hit.
11364 This command accepts a comma-separated list of any valid expressions.
11365 In addition to global, static, or local variables, the following
11366 special arguments are supported:
11370 Collect all registers.
11373 Collect all function arguments.
11376 Collect all local variables.
11379 Collect the return address. This is helpful if you want to see more
11383 Collects the number of arguments from the static probe at which the
11384 tracepoint is located.
11385 @xref{Static Probe Points}.
11387 @item $_probe_arg@var{n}
11388 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
11389 from the static probe at which the tracepoint is located.
11390 @xref{Static Probe Points}.
11393 @vindex $_sdata@r{, collect}
11394 Collect static tracepoint marker specific data. Only available for
11395 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
11396 Lists}. On the UST static tracepoints library backend, an
11397 instrumentation point resembles a @code{printf} function call. The
11398 tracing library is able to collect user specified data formatted to a
11399 character string using the format provided by the programmer that
11400 instrumented the program. Other backends have similar mechanisms.
11401 Here's an example of a UST marker call:
11404 const char master_name[] = "$your_name";
11405 trace_mark(channel1, marker1, "hello %s", master_name)
11408 In this case, collecting @code{$_sdata} collects the string
11409 @samp{hello $yourname}. When analyzing the trace buffer, you can
11410 inspect @samp{$_sdata} like any other variable available to
11414 You can give several consecutive @code{collect} commands, each one
11415 with a single argument, or one @code{collect} command with several
11416 arguments separated by commas; the effect is the same.
11418 The optional @var{mods} changes the usual handling of the arguments.
11419 @code{s} requests that pointers to chars be handled as strings, in
11420 particular collecting the contents of the memory being pointed at, up
11421 to the first zero. The upper bound is by default the value of the
11422 @code{print elements} variable; if @code{s} is followed by a decimal
11423 number, that is the upper bound instead. So for instance
11424 @samp{collect/s25 mystr} collects as many as 25 characters at
11427 The command @code{info scope} (@pxref{Symbols, info scope}) is
11428 particularly useful for figuring out what data to collect.
11430 @kindex teval @r{(tracepoints)}
11431 @item teval @var{expr1}, @var{expr2}, @dots{}
11432 Evaluate the given expressions when the tracepoint is hit. This
11433 command accepts a comma-separated list of expressions. The results
11434 are discarded, so this is mainly useful for assigning values to trace
11435 state variables (@pxref{Trace State Variables}) without adding those
11436 values to the trace buffer, as would be the case if the @code{collect}
11439 @kindex while-stepping @r{(tracepoints)}
11440 @item while-stepping @var{n}
11441 Perform @var{n} single-step instruction traces after the tracepoint,
11442 collecting new data after each step. The @code{while-stepping}
11443 command is followed by the list of what to collect while stepping
11444 (followed by its own @code{end} command):
11447 > while-stepping 12
11448 > collect $regs, myglobal
11454 Note that @code{$pc} is not automatically collected by
11455 @code{while-stepping}; you need to explicitly collect that register if
11456 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
11459 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
11460 @kindex set default-collect
11461 @cindex default collection action
11462 This variable is a list of expressions to collect at each tracepoint
11463 hit. It is effectively an additional @code{collect} action prepended
11464 to every tracepoint action list. The expressions are parsed
11465 individually for each tracepoint, so for instance a variable named
11466 @code{xyz} may be interpreted as a global for one tracepoint, and a
11467 local for another, as appropriate to the tracepoint's location.
11469 @item show default-collect
11470 @kindex show default-collect
11471 Show the list of expressions that are collected by default at each
11476 @node Listing Tracepoints
11477 @subsection Listing Tracepoints
11480 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
11481 @kindex info tp @r{[}@var{n}@dots{}@r{]}
11482 @cindex information about tracepoints
11483 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
11484 Display information about the tracepoint @var{num}. If you don't
11485 specify a tracepoint number, displays information about all the
11486 tracepoints defined so far. The format is similar to that used for
11487 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
11488 command, simply restricting itself to tracepoints.
11490 A tracepoint's listing may include additional information specific to
11495 its passcount as given by the @code{passcount @var{n}} command
11499 (@value{GDBP}) @b{info trace}
11500 Num Type Disp Enb Address What
11501 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
11503 collect globfoo, $regs
11512 This command can be abbreviated @code{info tp}.
11515 @node Listing Static Tracepoint Markers
11516 @subsection Listing Static Tracepoint Markers
11519 @kindex info static-tracepoint-markers
11520 @cindex information about static tracepoint markers
11521 @item info static-tracepoint-markers
11522 Display information about all static tracepoint markers defined in the
11525 For each marker, the following columns are printed:
11529 An incrementing counter, output to help readability. This is not a
11532 The marker ID, as reported by the target.
11533 @item Enabled or Disabled
11534 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
11535 that are not enabled.
11537 Where the marker is in your program, as a memory address.
11539 Where the marker is in the source for your program, as a file and line
11540 number. If the debug information included in the program does not
11541 allow @value{GDBN} to locate the source of the marker, this column
11542 will be left blank.
11546 In addition, the following information may be printed for each marker:
11550 User data passed to the tracing library by the marker call. In the
11551 UST backend, this is the format string passed as argument to the
11553 @item Static tracepoints probing the marker
11554 The list of static tracepoints attached to the marker.
11558 (@value{GDBP}) info static-tracepoint-markers
11559 Cnt ID Enb Address What
11560 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
11561 Data: number1 %d number2 %d
11562 Probed by static tracepoints: #2
11563 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
11569 @node Starting and Stopping Trace Experiments
11570 @subsection Starting and Stopping Trace Experiments
11573 @kindex tstart [ @var{notes} ]
11574 @cindex start a new trace experiment
11575 @cindex collected data discarded
11577 This command starts the trace experiment, and begins collecting data.
11578 It has the side effect of discarding all the data collected in the
11579 trace buffer during the previous trace experiment. If any arguments
11580 are supplied, they are taken as a note and stored with the trace
11581 experiment's state. The notes may be arbitrary text, and are
11582 especially useful with disconnected tracing in a multi-user context;
11583 the notes can explain what the trace is doing, supply user contact
11584 information, and so forth.
11586 @kindex tstop [ @var{notes} ]
11587 @cindex stop a running trace experiment
11589 This command stops the trace experiment. If any arguments are
11590 supplied, they are recorded with the experiment as a note. This is
11591 useful if you are stopping a trace started by someone else, for
11592 instance if the trace is interfering with the system's behavior and
11593 needs to be stopped quickly.
11595 @strong{Note}: a trace experiment and data collection may stop
11596 automatically if any tracepoint's passcount is reached
11597 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
11600 @cindex status of trace data collection
11601 @cindex trace experiment, status of
11603 This command displays the status of the current trace data
11607 Here is an example of the commands we described so far:
11610 (@value{GDBP}) @b{trace gdb_c_test}
11611 (@value{GDBP}) @b{actions}
11612 Enter actions for tracepoint #1, one per line.
11613 > collect $regs,$locals,$args
11614 > while-stepping 11
11618 (@value{GDBP}) @b{tstart}
11619 [time passes @dots{}]
11620 (@value{GDBP}) @b{tstop}
11623 @anchor{disconnected tracing}
11624 @cindex disconnected tracing
11625 You can choose to continue running the trace experiment even if
11626 @value{GDBN} disconnects from the target, voluntarily or
11627 involuntarily. For commands such as @code{detach}, the debugger will
11628 ask what you want to do with the trace. But for unexpected
11629 terminations (@value{GDBN} crash, network outage), it would be
11630 unfortunate to lose hard-won trace data, so the variable
11631 @code{disconnected-tracing} lets you decide whether the trace should
11632 continue running without @value{GDBN}.
11635 @item set disconnected-tracing on
11636 @itemx set disconnected-tracing off
11637 @kindex set disconnected-tracing
11638 Choose whether a tracing run should continue to run if @value{GDBN}
11639 has disconnected from the target. Note that @code{detach} or
11640 @code{quit} will ask you directly what to do about a running trace no
11641 matter what this variable's setting, so the variable is mainly useful
11642 for handling unexpected situations, such as loss of the network.
11644 @item show disconnected-tracing
11645 @kindex show disconnected-tracing
11646 Show the current choice for disconnected tracing.
11650 When you reconnect to the target, the trace experiment may or may not
11651 still be running; it might have filled the trace buffer in the
11652 meantime, or stopped for one of the other reasons. If it is running,
11653 it will continue after reconnection.
11655 Upon reconnection, the target will upload information about the
11656 tracepoints in effect. @value{GDBN} will then compare that
11657 information to the set of tracepoints currently defined, and attempt
11658 to match them up, allowing for the possibility that the numbers may
11659 have changed due to creation and deletion in the meantime. If one of
11660 the target's tracepoints does not match any in @value{GDBN}, the
11661 debugger will create a new tracepoint, so that you have a number with
11662 which to specify that tracepoint. This matching-up process is
11663 necessarily heuristic, and it may result in useless tracepoints being
11664 created; you may simply delete them if they are of no use.
11666 @cindex circular trace buffer
11667 If your target agent supports a @dfn{circular trace buffer}, then you
11668 can run a trace experiment indefinitely without filling the trace
11669 buffer; when space runs out, the agent deletes already-collected trace
11670 frames, oldest first, until there is enough room to continue
11671 collecting. This is especially useful if your tracepoints are being
11672 hit too often, and your trace gets terminated prematurely because the
11673 buffer is full. To ask for a circular trace buffer, simply set
11674 @samp{circular-trace-buffer} to on. You can set this at any time,
11675 including during tracing; if the agent can do it, it will change
11676 buffer handling on the fly, otherwise it will not take effect until
11680 @item set circular-trace-buffer on
11681 @itemx set circular-trace-buffer off
11682 @kindex set circular-trace-buffer
11683 Choose whether a tracing run should use a linear or circular buffer
11684 for trace data. A linear buffer will not lose any trace data, but may
11685 fill up prematurely, while a circular buffer will discard old trace
11686 data, but it will have always room for the latest tracepoint hits.
11688 @item show circular-trace-buffer
11689 @kindex show circular-trace-buffer
11690 Show the current choice for the trace buffer. Note that this may not
11691 match the agent's current buffer handling, nor is it guaranteed to
11692 match the setting that might have been in effect during a past run,
11693 for instance if you are looking at frames from a trace file.
11698 @item set trace-user @var{text}
11699 @kindex set trace-user
11701 @item show trace-user
11702 @kindex show trace-user
11704 @item set trace-notes @var{text}
11705 @kindex set trace-notes
11706 Set the trace run's notes.
11708 @item show trace-notes
11709 @kindex show trace-notes
11710 Show the trace run's notes.
11712 @item set trace-stop-notes @var{text}
11713 @kindex set trace-stop-notes
11714 Set the trace run's stop notes. The handling of the note is as for
11715 @code{tstop} arguments; the set command is convenient way to fix a
11716 stop note that is mistaken or incomplete.
11718 @item show trace-stop-notes
11719 @kindex show trace-stop-notes
11720 Show the trace run's stop notes.
11724 @node Tracepoint Restrictions
11725 @subsection Tracepoint Restrictions
11727 @cindex tracepoint restrictions
11728 There are a number of restrictions on the use of tracepoints. As
11729 described above, tracepoint data gathering occurs on the target
11730 without interaction from @value{GDBN}. Thus the full capabilities of
11731 the debugger are not available during data gathering, and then at data
11732 examination time, you will be limited by only having what was
11733 collected. The following items describe some common problems, but it
11734 is not exhaustive, and you may run into additional difficulties not
11740 Tracepoint expressions are intended to gather objects (lvalues). Thus
11741 the full flexibility of GDB's expression evaluator is not available.
11742 You cannot call functions, cast objects to aggregate types, access
11743 convenience variables or modify values (except by assignment to trace
11744 state variables). Some language features may implicitly call
11745 functions (for instance Objective-C fields with accessors), and therefore
11746 cannot be collected either.
11749 Collection of local variables, either individually or in bulk with
11750 @code{$locals} or @code{$args}, during @code{while-stepping} may
11751 behave erratically. The stepping action may enter a new scope (for
11752 instance by stepping into a function), or the location of the variable
11753 may change (for instance it is loaded into a register). The
11754 tracepoint data recorded uses the location information for the
11755 variables that is correct for the tracepoint location. When the
11756 tracepoint is created, it is not possible, in general, to determine
11757 where the steps of a @code{while-stepping} sequence will advance the
11758 program---particularly if a conditional branch is stepped.
11761 Collection of an incompletely-initialized or partially-destroyed object
11762 may result in something that @value{GDBN} cannot display, or displays
11763 in a misleading way.
11766 When @value{GDBN} displays a pointer to character it automatically
11767 dereferences the pointer to also display characters of the string
11768 being pointed to. However, collecting the pointer during tracing does
11769 not automatically collect the string. You need to explicitly
11770 dereference the pointer and provide size information if you want to
11771 collect not only the pointer, but the memory pointed to. For example,
11772 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11776 It is not possible to collect a complete stack backtrace at a
11777 tracepoint. Instead, you may collect the registers and a few hundred
11778 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11779 (adjust to use the name of the actual stack pointer register on your
11780 target architecture, and the amount of stack you wish to capture).
11781 Then the @code{backtrace} command will show a partial backtrace when
11782 using a trace frame. The number of stack frames that can be examined
11783 depends on the sizes of the frames in the collected stack. Note that
11784 if you ask for a block so large that it goes past the bottom of the
11785 stack, the target agent may report an error trying to read from an
11789 If you do not collect registers at a tracepoint, @value{GDBN} can
11790 infer that the value of @code{$pc} must be the same as the address of
11791 the tracepoint and use that when you are looking at a trace frame
11792 for that tracepoint. However, this cannot work if the tracepoint has
11793 multiple locations (for instance if it was set in a function that was
11794 inlined), or if it has a @code{while-stepping} loop. In those cases
11795 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11800 @node Analyze Collected Data
11801 @section Using the Collected Data
11803 After the tracepoint experiment ends, you use @value{GDBN} commands
11804 for examining the trace data. The basic idea is that each tracepoint
11805 collects a trace @dfn{snapshot} every time it is hit and another
11806 snapshot every time it single-steps. All these snapshots are
11807 consecutively numbered from zero and go into a buffer, and you can
11808 examine them later. The way you examine them is to @dfn{focus} on a
11809 specific trace snapshot. When the remote stub is focused on a trace
11810 snapshot, it will respond to all @value{GDBN} requests for memory and
11811 registers by reading from the buffer which belongs to that snapshot,
11812 rather than from @emph{real} memory or registers of the program being
11813 debugged. This means that @strong{all} @value{GDBN} commands
11814 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11815 behave as if we were currently debugging the program state as it was
11816 when the tracepoint occurred. Any requests for data that are not in
11817 the buffer will fail.
11820 * tfind:: How to select a trace snapshot
11821 * tdump:: How to display all data for a snapshot
11822 * save tracepoints:: How to save tracepoints for a future run
11826 @subsection @code{tfind @var{n}}
11829 @cindex select trace snapshot
11830 @cindex find trace snapshot
11831 The basic command for selecting a trace snapshot from the buffer is
11832 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11833 counting from zero. If no argument @var{n} is given, the next
11834 snapshot is selected.
11836 Here are the various forms of using the @code{tfind} command.
11840 Find the first snapshot in the buffer. This is a synonym for
11841 @code{tfind 0} (since 0 is the number of the first snapshot).
11844 Stop debugging trace snapshots, resume @emph{live} debugging.
11847 Same as @samp{tfind none}.
11850 No argument means find the next trace snapshot.
11853 Find the previous trace snapshot before the current one. This permits
11854 retracing earlier steps.
11856 @item tfind tracepoint @var{num}
11857 Find the next snapshot associated with tracepoint @var{num}. Search
11858 proceeds forward from the last examined trace snapshot. If no
11859 argument @var{num} is given, it means find the next snapshot collected
11860 for the same tracepoint as the current snapshot.
11862 @item tfind pc @var{addr}
11863 Find the next snapshot associated with the value @var{addr} of the
11864 program counter. Search proceeds forward from the last examined trace
11865 snapshot. If no argument @var{addr} is given, it means find the next
11866 snapshot with the same value of PC as the current snapshot.
11868 @item tfind outside @var{addr1}, @var{addr2}
11869 Find the next snapshot whose PC is outside the given range of
11870 addresses (exclusive).
11872 @item tfind range @var{addr1}, @var{addr2}
11873 Find the next snapshot whose PC is between @var{addr1} and
11874 @var{addr2} (inclusive).
11876 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11877 Find the next snapshot associated with the source line @var{n}. If
11878 the optional argument @var{file} is given, refer to line @var{n} in
11879 that source file. Search proceeds forward from the last examined
11880 trace snapshot. If no argument @var{n} is given, it means find the
11881 next line other than the one currently being examined; thus saying
11882 @code{tfind line} repeatedly can appear to have the same effect as
11883 stepping from line to line in a @emph{live} debugging session.
11886 The default arguments for the @code{tfind} commands are specifically
11887 designed to make it easy to scan through the trace buffer. For
11888 instance, @code{tfind} with no argument selects the next trace
11889 snapshot, and @code{tfind -} with no argument selects the previous
11890 trace snapshot. So, by giving one @code{tfind} command, and then
11891 simply hitting @key{RET} repeatedly you can examine all the trace
11892 snapshots in order. Or, by saying @code{tfind -} and then hitting
11893 @key{RET} repeatedly you can examine the snapshots in reverse order.
11894 The @code{tfind line} command with no argument selects the snapshot
11895 for the next source line executed. The @code{tfind pc} command with
11896 no argument selects the next snapshot with the same program counter
11897 (PC) as the current frame. The @code{tfind tracepoint} command with
11898 no argument selects the next trace snapshot collected by the same
11899 tracepoint as the current one.
11901 In addition to letting you scan through the trace buffer manually,
11902 these commands make it easy to construct @value{GDBN} scripts that
11903 scan through the trace buffer and print out whatever collected data
11904 you are interested in. Thus, if we want to examine the PC, FP, and SP
11905 registers from each trace frame in the buffer, we can say this:
11908 (@value{GDBP}) @b{tfind start}
11909 (@value{GDBP}) @b{while ($trace_frame != -1)}
11910 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11911 $trace_frame, $pc, $sp, $fp
11915 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11916 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11917 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11918 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11919 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11920 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11921 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11922 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11923 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11924 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11925 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11928 Or, if we want to examine the variable @code{X} at each source line in
11932 (@value{GDBP}) @b{tfind start}
11933 (@value{GDBP}) @b{while ($trace_frame != -1)}
11934 > printf "Frame %d, X == %d\n", $trace_frame, X
11944 @subsection @code{tdump}
11946 @cindex dump all data collected at tracepoint
11947 @cindex tracepoint data, display
11949 This command takes no arguments. It prints all the data collected at
11950 the current trace snapshot.
11953 (@value{GDBP}) @b{trace 444}
11954 (@value{GDBP}) @b{actions}
11955 Enter actions for tracepoint #2, one per line:
11956 > collect $regs, $locals, $args, gdb_long_test
11959 (@value{GDBP}) @b{tstart}
11961 (@value{GDBP}) @b{tfind line 444}
11962 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11964 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11966 (@value{GDBP}) @b{tdump}
11967 Data collected at tracepoint 2, trace frame 1:
11968 d0 0xc4aa0085 -995491707
11972 d4 0x71aea3d 119204413
11975 d7 0x380035 3670069
11976 a0 0x19e24a 1696330
11977 a1 0x3000668 50333288
11979 a3 0x322000 3284992
11980 a4 0x3000698 50333336
11981 a5 0x1ad3cc 1758156
11982 fp 0x30bf3c 0x30bf3c
11983 sp 0x30bf34 0x30bf34
11985 pc 0x20b2c8 0x20b2c8
11989 p = 0x20e5b4 "gdb-test"
11996 gdb_long_test = 17 '\021'
12001 @code{tdump} works by scanning the tracepoint's current collection
12002 actions and printing the value of each expression listed. So
12003 @code{tdump} can fail, if after a run, you change the tracepoint's
12004 actions to mention variables that were not collected during the run.
12006 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12007 uses the collected value of @code{$pc} to distinguish between trace
12008 frames that were collected at the tracepoint hit, and frames that were
12009 collected while stepping. This allows it to correctly choose whether
12010 to display the basic list of collections, or the collections from the
12011 body of the while-stepping loop. However, if @code{$pc} was not collected,
12012 then @code{tdump} will always attempt to dump using the basic collection
12013 list, and may fail if a while-stepping frame does not include all the
12014 same data that is collected at the tracepoint hit.
12015 @c This is getting pretty arcane, example would be good.
12017 @node save tracepoints
12018 @subsection @code{save tracepoints @var{filename}}
12019 @kindex save tracepoints
12020 @kindex save-tracepoints
12021 @cindex save tracepoints for future sessions
12023 This command saves all current tracepoint definitions together with
12024 their actions and passcounts, into a file @file{@var{filename}}
12025 suitable for use in a later debugging session. To read the saved
12026 tracepoint definitions, use the @code{source} command (@pxref{Command
12027 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12028 alias for @w{@code{save tracepoints}}
12030 @node Tracepoint Variables
12031 @section Convenience Variables for Tracepoints
12032 @cindex tracepoint variables
12033 @cindex convenience variables for tracepoints
12036 @vindex $trace_frame
12037 @item (int) $trace_frame
12038 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12039 snapshot is selected.
12041 @vindex $tracepoint
12042 @item (int) $tracepoint
12043 The tracepoint for the current trace snapshot.
12045 @vindex $trace_line
12046 @item (int) $trace_line
12047 The line number for the current trace snapshot.
12049 @vindex $trace_file
12050 @item (char []) $trace_file
12051 The source file for the current trace snapshot.
12053 @vindex $trace_func
12054 @item (char []) $trace_func
12055 The name of the function containing @code{$tracepoint}.
12058 Note: @code{$trace_file} is not suitable for use in @code{printf},
12059 use @code{output} instead.
12061 Here's a simple example of using these convenience variables for
12062 stepping through all the trace snapshots and printing some of their
12063 data. Note that these are not the same as trace state variables,
12064 which are managed by the target.
12067 (@value{GDBP}) @b{tfind start}
12069 (@value{GDBP}) @b{while $trace_frame != -1}
12070 > output $trace_file
12071 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12077 @section Using Trace Files
12078 @cindex trace files
12080 In some situations, the target running a trace experiment may no
12081 longer be available; perhaps it crashed, or the hardware was needed
12082 for a different activity. To handle these cases, you can arrange to
12083 dump the trace data into a file, and later use that file as a source
12084 of trace data, via the @code{target tfile} command.
12089 @item tsave [ -r ] @var{filename}
12090 Save the trace data to @var{filename}. By default, this command
12091 assumes that @var{filename} refers to the host filesystem, so if
12092 necessary @value{GDBN} will copy raw trace data up from the target and
12093 then save it. If the target supports it, you can also supply the
12094 optional argument @code{-r} (``remote'') to direct the target to save
12095 the data directly into @var{filename} in its own filesystem, which may be
12096 more efficient if the trace buffer is very large. (Note, however, that
12097 @code{target tfile} can only read from files accessible to the host.)
12099 @kindex target tfile
12101 @item target tfile @var{filename}
12102 Use the file named @var{filename} as a source of trace data. Commands
12103 that examine data work as they do with a live target, but it is not
12104 possible to run any new trace experiments. @code{tstatus} will report
12105 the state of the trace run at the moment the data was saved, as well
12106 as the current trace frame you are examining. @var{filename} must be
12107 on a filesystem accessible to the host.
12112 @chapter Debugging Programs That Use Overlays
12115 If your program is too large to fit completely in your target system's
12116 memory, you can sometimes use @dfn{overlays} to work around this
12117 problem. @value{GDBN} provides some support for debugging programs that
12121 * How Overlays Work:: A general explanation of overlays.
12122 * Overlay Commands:: Managing overlays in @value{GDBN}.
12123 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12124 mapped by asking the inferior.
12125 * Overlay Sample Program:: A sample program using overlays.
12128 @node How Overlays Work
12129 @section How Overlays Work
12130 @cindex mapped overlays
12131 @cindex unmapped overlays
12132 @cindex load address, overlay's
12133 @cindex mapped address
12134 @cindex overlay area
12136 Suppose you have a computer whose instruction address space is only 64
12137 kilobytes long, but which has much more memory which can be accessed by
12138 other means: special instructions, segment registers, or memory
12139 management hardware, for example. Suppose further that you want to
12140 adapt a program which is larger than 64 kilobytes to run on this system.
12142 One solution is to identify modules of your program which are relatively
12143 independent, and need not call each other directly; call these modules
12144 @dfn{overlays}. Separate the overlays from the main program, and place
12145 their machine code in the larger memory. Place your main program in
12146 instruction memory, but leave at least enough space there to hold the
12147 largest overlay as well.
12149 Now, to call a function located in an overlay, you must first copy that
12150 overlay's machine code from the large memory into the space set aside
12151 for it in the instruction memory, and then jump to its entry point
12154 @c NB: In the below the mapped area's size is greater or equal to the
12155 @c size of all overlays. This is intentional to remind the developer
12156 @c that overlays don't necessarily need to be the same size.
12160 Data Instruction Larger
12161 Address Space Address Space Address Space
12162 +-----------+ +-----------+ +-----------+
12164 +-----------+ +-----------+ +-----------+<-- overlay 1
12165 | program | | main | .----| overlay 1 | load address
12166 | variables | | program | | +-----------+
12167 | and heap | | | | | |
12168 +-----------+ | | | +-----------+<-- overlay 2
12169 | | +-----------+ | | | load address
12170 +-----------+ | | | .-| overlay 2 |
12172 mapped --->+-----------+ | | +-----------+
12173 address | | | | | |
12174 | overlay | <-' | | |
12175 | area | <---' +-----------+<-- overlay 3
12176 | | <---. | | load address
12177 +-----------+ `--| overlay 3 |
12184 @anchor{A code overlay}A code overlay
12188 The diagram (@pxref{A code overlay}) shows a system with separate data
12189 and instruction address spaces. To map an overlay, the program copies
12190 its code from the larger address space to the instruction address space.
12191 Since the overlays shown here all use the same mapped address, only one
12192 may be mapped at a time. For a system with a single address space for
12193 data and instructions, the diagram would be similar, except that the
12194 program variables and heap would share an address space with the main
12195 program and the overlay area.
12197 An overlay loaded into instruction memory and ready for use is called a
12198 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12199 instruction memory. An overlay not present (or only partially present)
12200 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12201 is its address in the larger memory. The mapped address is also called
12202 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12203 called the @dfn{load memory address}, or @dfn{LMA}.
12205 Unfortunately, overlays are not a completely transparent way to adapt a
12206 program to limited instruction memory. They introduce a new set of
12207 global constraints you must keep in mind as you design your program:
12212 Before calling or returning to a function in an overlay, your program
12213 must make sure that overlay is actually mapped. Otherwise, the call or
12214 return will transfer control to the right address, but in the wrong
12215 overlay, and your program will probably crash.
12218 If the process of mapping an overlay is expensive on your system, you
12219 will need to choose your overlays carefully to minimize their effect on
12220 your program's performance.
12223 The executable file you load onto your system must contain each
12224 overlay's instructions, appearing at the overlay's load address, not its
12225 mapped address. However, each overlay's instructions must be relocated
12226 and its symbols defined as if the overlay were at its mapped address.
12227 You can use GNU linker scripts to specify different load and relocation
12228 addresses for pieces of your program; see @ref{Overlay Description,,,
12229 ld.info, Using ld: the GNU linker}.
12232 The procedure for loading executable files onto your system must be able
12233 to load their contents into the larger address space as well as the
12234 instruction and data spaces.
12238 The overlay system described above is rather simple, and could be
12239 improved in many ways:
12244 If your system has suitable bank switch registers or memory management
12245 hardware, you could use those facilities to make an overlay's load area
12246 contents simply appear at their mapped address in instruction space.
12247 This would probably be faster than copying the overlay to its mapped
12248 area in the usual way.
12251 If your overlays are small enough, you could set aside more than one
12252 overlay area, and have more than one overlay mapped at a time.
12255 You can use overlays to manage data, as well as instructions. In
12256 general, data overlays are even less transparent to your design than
12257 code overlays: whereas code overlays only require care when you call or
12258 return to functions, data overlays require care every time you access
12259 the data. Also, if you change the contents of a data overlay, you
12260 must copy its contents back out to its load address before you can copy a
12261 different data overlay into the same mapped area.
12266 @node Overlay Commands
12267 @section Overlay Commands
12269 To use @value{GDBN}'s overlay support, each overlay in your program must
12270 correspond to a separate section of the executable file. The section's
12271 virtual memory address and load memory address must be the overlay's
12272 mapped and load addresses. Identifying overlays with sections allows
12273 @value{GDBN} to determine the appropriate address of a function or
12274 variable, depending on whether the overlay is mapped or not.
12276 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12277 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12282 Disable @value{GDBN}'s overlay support. When overlay support is
12283 disabled, @value{GDBN} assumes that all functions and variables are
12284 always present at their mapped addresses. By default, @value{GDBN}'s
12285 overlay support is disabled.
12287 @item overlay manual
12288 @cindex manual overlay debugging
12289 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12290 relies on you to tell it which overlays are mapped, and which are not,
12291 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12292 commands described below.
12294 @item overlay map-overlay @var{overlay}
12295 @itemx overlay map @var{overlay}
12296 @cindex map an overlay
12297 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12298 be the name of the object file section containing the overlay. When an
12299 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12300 functions and variables at their mapped addresses. @value{GDBN} assumes
12301 that any other overlays whose mapped ranges overlap that of
12302 @var{overlay} are now unmapped.
12304 @item overlay unmap-overlay @var{overlay}
12305 @itemx overlay unmap @var{overlay}
12306 @cindex unmap an overlay
12307 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
12308 must be the name of the object file section containing the overlay.
12309 When an overlay is unmapped, @value{GDBN} assumes it can find the
12310 overlay's functions and variables at their load addresses.
12313 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
12314 consults a data structure the overlay manager maintains in the inferior
12315 to see which overlays are mapped. For details, see @ref{Automatic
12316 Overlay Debugging}.
12318 @item overlay load-target
12319 @itemx overlay load
12320 @cindex reloading the overlay table
12321 Re-read the overlay table from the inferior. Normally, @value{GDBN}
12322 re-reads the table @value{GDBN} automatically each time the inferior
12323 stops, so this command should only be necessary if you have changed the
12324 overlay mapping yourself using @value{GDBN}. This command is only
12325 useful when using automatic overlay debugging.
12327 @item overlay list-overlays
12328 @itemx overlay list
12329 @cindex listing mapped overlays
12330 Display a list of the overlays currently mapped, along with their mapped
12331 addresses, load addresses, and sizes.
12335 Normally, when @value{GDBN} prints a code address, it includes the name
12336 of the function the address falls in:
12339 (@value{GDBP}) print main
12340 $3 = @{int ()@} 0x11a0 <main>
12343 When overlay debugging is enabled, @value{GDBN} recognizes code in
12344 unmapped overlays, and prints the names of unmapped functions with
12345 asterisks around them. For example, if @code{foo} is a function in an
12346 unmapped overlay, @value{GDBN} prints it this way:
12349 (@value{GDBP}) overlay list
12350 No sections are mapped.
12351 (@value{GDBP}) print foo
12352 $5 = @{int (int)@} 0x100000 <*foo*>
12355 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
12359 (@value{GDBP}) overlay list
12360 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
12361 mapped at 0x1016 - 0x104a
12362 (@value{GDBP}) print foo
12363 $6 = @{int (int)@} 0x1016 <foo>
12366 When overlay debugging is enabled, @value{GDBN} can find the correct
12367 address for functions and variables in an overlay, whether or not the
12368 overlay is mapped. This allows most @value{GDBN} commands, like
12369 @code{break} and @code{disassemble}, to work normally, even on unmapped
12370 code. However, @value{GDBN}'s breakpoint support has some limitations:
12374 @cindex breakpoints in overlays
12375 @cindex overlays, setting breakpoints in
12376 You can set breakpoints in functions in unmapped overlays, as long as
12377 @value{GDBN} can write to the overlay at its load address.
12379 @value{GDBN} can not set hardware or simulator-based breakpoints in
12380 unmapped overlays. However, if you set a breakpoint at the end of your
12381 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
12382 you are using manual overlay management), @value{GDBN} will re-set its
12383 breakpoints properly.
12387 @node Automatic Overlay Debugging
12388 @section Automatic Overlay Debugging
12389 @cindex automatic overlay debugging
12391 @value{GDBN} can automatically track which overlays are mapped and which
12392 are not, given some simple co-operation from the overlay manager in the
12393 inferior. If you enable automatic overlay debugging with the
12394 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
12395 looks in the inferior's memory for certain variables describing the
12396 current state of the overlays.
12398 Here are the variables your overlay manager must define to support
12399 @value{GDBN}'s automatic overlay debugging:
12403 @item @code{_ovly_table}:
12404 This variable must be an array of the following structures:
12409 /* The overlay's mapped address. */
12412 /* The size of the overlay, in bytes. */
12413 unsigned long size;
12415 /* The overlay's load address. */
12418 /* Non-zero if the overlay is currently mapped;
12420 unsigned long mapped;
12424 @item @code{_novlys}:
12425 This variable must be a four-byte signed integer, holding the total
12426 number of elements in @code{_ovly_table}.
12430 To decide whether a particular overlay is mapped or not, @value{GDBN}
12431 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
12432 @code{lma} members equal the VMA and LMA of the overlay's section in the
12433 executable file. When @value{GDBN} finds a matching entry, it consults
12434 the entry's @code{mapped} member to determine whether the overlay is
12437 In addition, your overlay manager may define a function called
12438 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
12439 will silently set a breakpoint there. If the overlay manager then
12440 calls this function whenever it has changed the overlay table, this
12441 will enable @value{GDBN} to accurately keep track of which overlays
12442 are in program memory, and update any breakpoints that may be set
12443 in overlays. This will allow breakpoints to work even if the
12444 overlays are kept in ROM or other non-writable memory while they
12445 are not being executed.
12447 @node Overlay Sample Program
12448 @section Overlay Sample Program
12449 @cindex overlay example program
12451 When linking a program which uses overlays, you must place the overlays
12452 at their load addresses, while relocating them to run at their mapped
12453 addresses. To do this, you must write a linker script (@pxref{Overlay
12454 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
12455 since linker scripts are specific to a particular host system, target
12456 architecture, and target memory layout, this manual cannot provide
12457 portable sample code demonstrating @value{GDBN}'s overlay support.
12459 However, the @value{GDBN} source distribution does contain an overlaid
12460 program, with linker scripts for a few systems, as part of its test
12461 suite. The program consists of the following files from
12462 @file{gdb/testsuite/gdb.base}:
12466 The main program file.
12468 A simple overlay manager, used by @file{overlays.c}.
12473 Overlay modules, loaded and used by @file{overlays.c}.
12476 Linker scripts for linking the test program on the @code{d10v-elf}
12477 and @code{m32r-elf} targets.
12480 You can build the test program using the @code{d10v-elf} GCC
12481 cross-compiler like this:
12484 $ d10v-elf-gcc -g -c overlays.c
12485 $ d10v-elf-gcc -g -c ovlymgr.c
12486 $ d10v-elf-gcc -g -c foo.c
12487 $ d10v-elf-gcc -g -c bar.c
12488 $ d10v-elf-gcc -g -c baz.c
12489 $ d10v-elf-gcc -g -c grbx.c
12490 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
12491 baz.o grbx.o -Wl,-Td10v.ld -o overlays
12494 The build process is identical for any other architecture, except that
12495 you must substitute the appropriate compiler and linker script for the
12496 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
12500 @chapter Using @value{GDBN} with Different Languages
12503 Although programming languages generally have common aspects, they are
12504 rarely expressed in the same manner. For instance, in ANSI C,
12505 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
12506 Modula-2, it is accomplished by @code{p^}. Values can also be
12507 represented (and displayed) differently. Hex numbers in C appear as
12508 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
12510 @cindex working language
12511 Language-specific information is built into @value{GDBN} for some languages,
12512 allowing you to express operations like the above in your program's
12513 native language, and allowing @value{GDBN} to output values in a manner
12514 consistent with the syntax of your program's native language. The
12515 language you use to build expressions is called the @dfn{working
12519 * Setting:: Switching between source languages
12520 * Show:: Displaying the language
12521 * Checks:: Type and range checks
12522 * Supported Languages:: Supported languages
12523 * Unsupported Languages:: Unsupported languages
12527 @section Switching Between Source Languages
12529 There are two ways to control the working language---either have @value{GDBN}
12530 set it automatically, or select it manually yourself. You can use the
12531 @code{set language} command for either purpose. On startup, @value{GDBN}
12532 defaults to setting the language automatically. The working language is
12533 used to determine how expressions you type are interpreted, how values
12536 In addition to the working language, every source file that
12537 @value{GDBN} knows about has its own working language. For some object
12538 file formats, the compiler might indicate which language a particular
12539 source file is in. However, most of the time @value{GDBN} infers the
12540 language from the name of the file. The language of a source file
12541 controls whether C@t{++} names are demangled---this way @code{backtrace} can
12542 show each frame appropriately for its own language. There is no way to
12543 set the language of a source file from within @value{GDBN}, but you can
12544 set the language associated with a filename extension. @xref{Show, ,
12545 Displaying the Language}.
12547 This is most commonly a problem when you use a program, such
12548 as @code{cfront} or @code{f2c}, that generates C but is written in
12549 another language. In that case, make the
12550 program use @code{#line} directives in its C output; that way
12551 @value{GDBN} will know the correct language of the source code of the original
12552 program, and will display that source code, not the generated C code.
12555 * Filenames:: Filename extensions and languages.
12556 * Manually:: Setting the working language manually
12557 * Automatically:: Having @value{GDBN} infer the source language
12561 @subsection List of Filename Extensions and Languages
12563 If a source file name ends in one of the following extensions, then
12564 @value{GDBN} infers that its language is the one indicated.
12582 C@t{++} source file
12588 Objective-C source file
12592 Fortran source file
12595 Modula-2 source file
12599 Assembler source file. This actually behaves almost like C, but
12600 @value{GDBN} does not skip over function prologues when stepping.
12603 In addition, you may set the language associated with a filename
12604 extension. @xref{Show, , Displaying the Language}.
12607 @subsection Setting the Working Language
12609 If you allow @value{GDBN} to set the language automatically,
12610 expressions are interpreted the same way in your debugging session and
12613 @kindex set language
12614 If you wish, you may set the language manually. To do this, issue the
12615 command @samp{set language @var{lang}}, where @var{lang} is the name of
12616 a language, such as
12617 @code{c} or @code{modula-2}.
12618 For a list of the supported languages, type @samp{set language}.
12620 Setting the language manually prevents @value{GDBN} from updating the working
12621 language automatically. This can lead to confusion if you try
12622 to debug a program when the working language is not the same as the
12623 source language, when an expression is acceptable to both
12624 languages---but means different things. For instance, if the current
12625 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12633 might not have the effect you intended. In C, this means to add
12634 @code{b} and @code{c} and place the result in @code{a}. The result
12635 printed would be the value of @code{a}. In Modula-2, this means to compare
12636 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12638 @node Automatically
12639 @subsection Having @value{GDBN} Infer the Source Language
12641 To have @value{GDBN} set the working language automatically, use
12642 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12643 then infers the working language. That is, when your program stops in a
12644 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12645 working language to the language recorded for the function in that
12646 frame. If the language for a frame is unknown (that is, if the function
12647 or block corresponding to the frame was defined in a source file that
12648 does not have a recognized extension), the current working language is
12649 not changed, and @value{GDBN} issues a warning.
12651 This may not seem necessary for most programs, which are written
12652 entirely in one source language. However, program modules and libraries
12653 written in one source language can be used by a main program written in
12654 a different source language. Using @samp{set language auto} in this
12655 case frees you from having to set the working language manually.
12658 @section Displaying the Language
12660 The following commands help you find out which language is the
12661 working language, and also what language source files were written in.
12664 @item show language
12665 @kindex show language
12666 Display the current working language. This is the
12667 language you can use with commands such as @code{print} to
12668 build and compute expressions that may involve variables in your program.
12671 @kindex info frame@r{, show the source language}
12672 Display the source language for this frame. This language becomes the
12673 working language if you use an identifier from this frame.
12674 @xref{Frame Info, ,Information about a Frame}, to identify the other
12675 information listed here.
12678 @kindex info source@r{, show the source language}
12679 Display the source language of this source file.
12680 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12681 information listed here.
12684 In unusual circumstances, you may have source files with extensions
12685 not in the standard list. You can then set the extension associated
12686 with a language explicitly:
12689 @item set extension-language @var{ext} @var{language}
12690 @kindex set extension-language
12691 Tell @value{GDBN} that source files with extension @var{ext} are to be
12692 assumed as written in the source language @var{language}.
12694 @item info extensions
12695 @kindex info extensions
12696 List all the filename extensions and the associated languages.
12700 @section Type and Range Checking
12702 Some languages are designed to guard you against making seemingly common
12703 errors through a series of compile- and run-time checks. These include
12704 checking the type of arguments to functions and operators and making
12705 sure mathematical overflows are caught at run time. Checks such as
12706 these help to ensure a program's correctness once it has been compiled
12707 by eliminating type mismatches and providing active checks for range
12708 errors when your program is running.
12710 By default @value{GDBN} checks for these errors according to the
12711 rules of the current source language. Although @value{GDBN} does not check
12712 the statements in your program, it can check expressions entered directly
12713 into @value{GDBN} for evaluation via the @code{print} command, for example.
12716 * Type Checking:: An overview of type checking
12717 * Range Checking:: An overview of range checking
12720 @cindex type checking
12721 @cindex checks, type
12722 @node Type Checking
12723 @subsection An Overview of Type Checking
12725 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
12726 arguments to operators and functions have to be of the correct type,
12727 otherwise an error occurs. These checks prevent type mismatch
12728 errors from ever causing any run-time problems. For example,
12731 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
12733 (@value{GDBP}) print obj.my_method (0)
12736 (@value{GDBP}) print obj.my_method (0x1234)
12737 Cannot resolve method klass::my_method to any overloaded instance
12740 The second example fails because in C@t{++} the integer constant
12741 @samp{0x1234} is not type-compatible with the pointer parameter type.
12743 For the expressions you use in @value{GDBN} commands, you can tell
12744 @value{GDBN} to not enforce strict type checking or
12745 to treat any mismatches as errors and abandon the expression;
12746 When type checking is disabled, @value{GDBN} successfully evaluates
12747 expressions like the second example above.
12749 Even if type checking is off, there may be other reasons
12750 related to type that prevent @value{GDBN} from evaluating an expression.
12751 For instance, @value{GDBN} does not know how to add an @code{int} and
12752 a @code{struct foo}. These particular type errors have nothing to do
12753 with the language in use and usually arise from expressions which make
12754 little sense to evaluate anyway.
12756 @value{GDBN} provides some additional commands for controlling type checking:
12758 @kindex set check type
12759 @kindex show check type
12761 @item set check type on
12762 @itemx set check type off
12763 Set strict type checking on or off. If any type mismatches occur in
12764 evaluating an expression while type checking is on, @value{GDBN} prints a
12765 message and aborts evaluation of the expression.
12767 @item show check type
12768 Show the current setting of type checking and whether @value{GDBN}
12769 is enforcing strict type checking rules.
12772 @cindex range checking
12773 @cindex checks, range
12774 @node Range Checking
12775 @subsection An Overview of Range Checking
12777 In some languages (such as Modula-2), it is an error to exceed the
12778 bounds of a type; this is enforced with run-time checks. Such range
12779 checking is meant to ensure program correctness by making sure
12780 computations do not overflow, or indices on an array element access do
12781 not exceed the bounds of the array.
12783 For expressions you use in @value{GDBN} commands, you can tell
12784 @value{GDBN} to treat range errors in one of three ways: ignore them,
12785 always treat them as errors and abandon the expression, or issue
12786 warnings but evaluate the expression anyway.
12788 A range error can result from numerical overflow, from exceeding an
12789 array index bound, or when you type a constant that is not a member
12790 of any type. Some languages, however, do not treat overflows as an
12791 error. In many implementations of C, mathematical overflow causes the
12792 result to ``wrap around'' to lower values---for example, if @var{m} is
12793 the largest integer value, and @var{s} is the smallest, then
12796 @var{m} + 1 @result{} @var{s}
12799 This, too, is specific to individual languages, and in some cases
12800 specific to individual compilers or machines. @xref{Supported Languages, ,
12801 Supported Languages}, for further details on specific languages.
12803 @value{GDBN} provides some additional commands for controlling the range checker:
12805 @kindex set check range
12806 @kindex show check range
12808 @item set check range auto
12809 Set range checking on or off based on the current working language.
12810 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12813 @item set check range on
12814 @itemx set check range off
12815 Set range checking on or off, overriding the default setting for the
12816 current working language. A warning is issued if the setting does not
12817 match the language default. If a range error occurs and range checking is on,
12818 then a message is printed and evaluation of the expression is aborted.
12820 @item set check range warn
12821 Output messages when the @value{GDBN} range checker detects a range error,
12822 but attempt to evaluate the expression anyway. Evaluating the
12823 expression may still be impossible for other reasons, such as accessing
12824 memory that the process does not own (a typical example from many Unix
12828 Show the current setting of the range checker, and whether or not it is
12829 being set automatically by @value{GDBN}.
12832 @node Supported Languages
12833 @section Supported Languages
12835 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
12836 OpenCL C, Pascal, assembly, Modula-2, and Ada.
12837 @c This is false ...
12838 Some @value{GDBN} features may be used in expressions regardless of the
12839 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12840 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12841 ,Expressions}) can be used with the constructs of any supported
12844 The following sections detail to what degree each source language is
12845 supported by @value{GDBN}. These sections are not meant to be language
12846 tutorials or references, but serve only as a reference guide to what the
12847 @value{GDBN} expression parser accepts, and what input and output
12848 formats should look like for different languages. There are many good
12849 books written on each of these languages; please look to these for a
12850 language reference or tutorial.
12853 * C:: C and C@t{++}
12856 * Objective-C:: Objective-C
12857 * OpenCL C:: OpenCL C
12858 * Fortran:: Fortran
12860 * Modula-2:: Modula-2
12865 @subsection C and C@t{++}
12867 @cindex C and C@t{++}
12868 @cindex expressions in C or C@t{++}
12870 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12871 to both languages. Whenever this is the case, we discuss those languages
12875 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12876 @cindex @sc{gnu} C@t{++}
12877 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12878 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12879 effectively, you must compile your C@t{++} programs with a supported
12880 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12881 compiler (@code{aCC}).
12884 * C Operators:: C and C@t{++} operators
12885 * C Constants:: C and C@t{++} constants
12886 * C Plus Plus Expressions:: C@t{++} expressions
12887 * C Defaults:: Default settings for C and C@t{++}
12888 * C Checks:: C and C@t{++} type and range checks
12889 * Debugging C:: @value{GDBN} and C
12890 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12891 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12895 @subsubsection C and C@t{++} Operators
12897 @cindex C and C@t{++} operators
12899 Operators must be defined on values of specific types. For instance,
12900 @code{+} is defined on numbers, but not on structures. Operators are
12901 often defined on groups of types.
12903 For the purposes of C and C@t{++}, the following definitions hold:
12908 @emph{Integral types} include @code{int} with any of its storage-class
12909 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12912 @emph{Floating-point types} include @code{float}, @code{double}, and
12913 @code{long double} (if supported by the target platform).
12916 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12919 @emph{Scalar types} include all of the above.
12924 The following operators are supported. They are listed here
12925 in order of increasing precedence:
12929 The comma or sequencing operator. Expressions in a comma-separated list
12930 are evaluated from left to right, with the result of the entire
12931 expression being the last expression evaluated.
12934 Assignment. The value of an assignment expression is the value
12935 assigned. Defined on scalar types.
12938 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12939 and translated to @w{@code{@var{a} = @var{a op b}}}.
12940 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12941 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12942 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12945 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12946 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12950 Logical @sc{or}. Defined on integral types.
12953 Logical @sc{and}. Defined on integral types.
12956 Bitwise @sc{or}. Defined on integral types.
12959 Bitwise exclusive-@sc{or}. Defined on integral types.
12962 Bitwise @sc{and}. Defined on integral types.
12965 Equality and inequality. Defined on scalar types. The value of these
12966 expressions is 0 for false and non-zero for true.
12968 @item <@r{, }>@r{, }<=@r{, }>=
12969 Less than, greater than, less than or equal, greater than or equal.
12970 Defined on scalar types. The value of these expressions is 0 for false
12971 and non-zero for true.
12974 left shift, and right shift. Defined on integral types.
12977 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12980 Addition and subtraction. Defined on integral types, floating-point types and
12983 @item *@r{, }/@r{, }%
12984 Multiplication, division, and modulus. Multiplication and division are
12985 defined on integral and floating-point types. Modulus is defined on
12989 Increment and decrement. When appearing before a variable, the
12990 operation is performed before the variable is used in an expression;
12991 when appearing after it, the variable's value is used before the
12992 operation takes place.
12995 Pointer dereferencing. Defined on pointer types. Same precedence as
12999 Address operator. Defined on variables. Same precedence as @code{++}.
13001 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13002 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13003 to examine the address
13004 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13008 Negative. Defined on integral and floating-point types. Same
13009 precedence as @code{++}.
13012 Logical negation. Defined on integral types. Same precedence as
13016 Bitwise complement operator. Defined on integral types. Same precedence as
13021 Structure member, and pointer-to-structure member. For convenience,
13022 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13023 pointer based on the stored type information.
13024 Defined on @code{struct} and @code{union} data.
13027 Dereferences of pointers to members.
13030 Array indexing. @code{@var{a}[@var{i}]} is defined as
13031 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13034 Function parameter list. Same precedence as @code{->}.
13037 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13038 and @code{class} types.
13041 Doubled colons also represent the @value{GDBN} scope operator
13042 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13046 If an operator is redefined in the user code, @value{GDBN} usually
13047 attempts to invoke the redefined version instead of using the operator's
13048 predefined meaning.
13051 @subsubsection C and C@t{++} Constants
13053 @cindex C and C@t{++} constants
13055 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13060 Integer constants are a sequence of digits. Octal constants are
13061 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13062 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13063 @samp{l}, specifying that the constant should be treated as a
13067 Floating point constants are a sequence of digits, followed by a decimal
13068 point, followed by a sequence of digits, and optionally followed by an
13069 exponent. An exponent is of the form:
13070 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13071 sequence of digits. The @samp{+} is optional for positive exponents.
13072 A floating-point constant may also end with a letter @samp{f} or
13073 @samp{F}, specifying that the constant should be treated as being of
13074 the @code{float} (as opposed to the default @code{double}) type; or with
13075 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13079 Enumerated constants consist of enumerated identifiers, or their
13080 integral equivalents.
13083 Character constants are a single character surrounded by single quotes
13084 (@code{'}), or a number---the ordinal value of the corresponding character
13085 (usually its @sc{ascii} value). Within quotes, the single character may
13086 be represented by a letter or by @dfn{escape sequences}, which are of
13087 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13088 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13089 @samp{@var{x}} is a predefined special character---for example,
13090 @samp{\n} for newline.
13092 Wide character constants can be written by prefixing a character
13093 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13094 form of @samp{x}. The target wide character set is used when
13095 computing the value of this constant (@pxref{Character Sets}).
13098 String constants are a sequence of character constants surrounded by
13099 double quotes (@code{"}). Any valid character constant (as described
13100 above) may appear. Double quotes within the string must be preceded by
13101 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13104 Wide string constants can be written by prefixing a string constant
13105 with @samp{L}, as in C. The target wide character set is used when
13106 computing the value of this constant (@pxref{Character Sets}).
13109 Pointer constants are an integral value. You can also write pointers
13110 to constants using the C operator @samp{&}.
13113 Array constants are comma-separated lists surrounded by braces @samp{@{}
13114 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13115 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13116 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13119 @node C Plus Plus Expressions
13120 @subsubsection C@t{++} Expressions
13122 @cindex expressions in C@t{++}
13123 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13125 @cindex debugging C@t{++} programs
13126 @cindex C@t{++} compilers
13127 @cindex debug formats and C@t{++}
13128 @cindex @value{NGCC} and C@t{++}
13130 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13131 the proper compiler and the proper debug format. Currently,
13132 @value{GDBN} works best when debugging C@t{++} code that is compiled
13133 with the most recent version of @value{NGCC} possible. The DWARF
13134 debugging format is preferred; @value{NGCC} defaults to this on most
13135 popular platforms. Other compilers and/or debug formats are likely to
13136 work badly or not at all when using @value{GDBN} to debug C@t{++}
13137 code. @xref{Compilation}.
13142 @cindex member functions
13144 Member function calls are allowed; you can use expressions like
13147 count = aml->GetOriginal(x, y)
13150 @vindex this@r{, inside C@t{++} member functions}
13151 @cindex namespace in C@t{++}
13153 While a member function is active (in the selected stack frame), your
13154 expressions have the same namespace available as the member function;
13155 that is, @value{GDBN} allows implicit references to the class instance
13156 pointer @code{this} following the same rules as C@t{++}. @code{using}
13157 declarations in the current scope are also respected by @value{GDBN}.
13159 @cindex call overloaded functions
13160 @cindex overloaded functions, calling
13161 @cindex type conversions in C@t{++}
13163 You can call overloaded functions; @value{GDBN} resolves the function
13164 call to the right definition, with some restrictions. @value{GDBN} does not
13165 perform overload resolution involving user-defined type conversions,
13166 calls to constructors, or instantiations of templates that do not exist
13167 in the program. It also cannot handle ellipsis argument lists or
13170 It does perform integral conversions and promotions, floating-point
13171 promotions, arithmetic conversions, pointer conversions, conversions of
13172 class objects to base classes, and standard conversions such as those of
13173 functions or arrays to pointers; it requires an exact match on the
13174 number of function arguments.
13176 Overload resolution is always performed, unless you have specified
13177 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13178 ,@value{GDBN} Features for C@t{++}}.
13180 You must specify @code{set overload-resolution off} in order to use an
13181 explicit function signature to call an overloaded function, as in
13183 p 'foo(char,int)'('x', 13)
13186 The @value{GDBN} command-completion facility can simplify this;
13187 see @ref{Completion, ,Command Completion}.
13189 @cindex reference declarations
13191 @value{GDBN} understands variables declared as C@t{++} references; you can use
13192 them in expressions just as you do in C@t{++} source---they are automatically
13195 In the parameter list shown when @value{GDBN} displays a frame, the values of
13196 reference variables are not displayed (unlike other variables); this
13197 avoids clutter, since references are often used for large structures.
13198 The @emph{address} of a reference variable is always shown, unless
13199 you have specified @samp{set print address off}.
13202 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13203 expressions can use it just as expressions in your program do. Since
13204 one scope may be defined in another, you can use @code{::} repeatedly if
13205 necessary, for example in an expression like
13206 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13207 resolving name scope by reference to source files, in both C and C@t{++}
13208 debugging (@pxref{Variables, ,Program Variables}).
13211 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13216 @subsubsection C and C@t{++} Defaults
13218 @cindex C and C@t{++} defaults
13220 If you allow @value{GDBN} to set range checking automatically, it
13221 defaults to @code{off} whenever the working language changes to
13222 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13223 selects the working language.
13225 If you allow @value{GDBN} to set the language automatically, it
13226 recognizes source files whose names end with @file{.c}, @file{.C}, or
13227 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13228 these files, it sets the working language to C or C@t{++}.
13229 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13230 for further details.
13233 @subsubsection C and C@t{++} Type and Range Checks
13235 @cindex C and C@t{++} checks
13237 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13238 checking is used. However, if you turn type checking off, @value{GDBN}
13239 will allow certain non-standard conversions, such as promoting integer
13240 constants to pointers.
13242 Range checking, if turned on, is done on mathematical operations. Array
13243 indices are not checked, since they are often used to index a pointer
13244 that is not itself an array.
13247 @subsubsection @value{GDBN} and C
13249 The @code{set print union} and @code{show print union} commands apply to
13250 the @code{union} type. When set to @samp{on}, any @code{union} that is
13251 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13252 appears as @samp{@{...@}}.
13254 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13255 with pointers and a memory allocation function. @xref{Expressions,
13258 @node Debugging C Plus Plus
13259 @subsubsection @value{GDBN} Features for C@t{++}
13261 @cindex commands for C@t{++}
13263 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13264 designed specifically for use with C@t{++}. Here is a summary:
13267 @cindex break in overloaded functions
13268 @item @r{breakpoint menus}
13269 When you want a breakpoint in a function whose name is overloaded,
13270 @value{GDBN} has the capability to display a menu of possible breakpoint
13271 locations to help you specify which function definition you want.
13272 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13274 @cindex overloading in C@t{++}
13275 @item rbreak @var{regex}
13276 Setting breakpoints using regular expressions is helpful for setting
13277 breakpoints on overloaded functions that are not members of any special
13279 @xref{Set Breaks, ,Setting Breakpoints}.
13281 @cindex C@t{++} exception handling
13284 Debug C@t{++} exception handling using these commands. @xref{Set
13285 Catchpoints, , Setting Catchpoints}.
13287 @cindex inheritance
13288 @item ptype @var{typename}
13289 Print inheritance relationships as well as other information for type
13291 @xref{Symbols, ,Examining the Symbol Table}.
13293 @item info vtbl @var{expression}.
13294 The @code{info vtbl} command can be used to display the virtual
13295 method tables of the object computed by @var{expression}. This shows
13296 one entry per virtual table; there may be multiple virtual tables when
13297 multiple inheritance is in use.
13299 @cindex C@t{++} symbol display
13300 @item set print demangle
13301 @itemx show print demangle
13302 @itemx set print asm-demangle
13303 @itemx show print asm-demangle
13304 Control whether C@t{++} symbols display in their source form, both when
13305 displaying code as C@t{++} source and when displaying disassemblies.
13306 @xref{Print Settings, ,Print Settings}.
13308 @item set print object
13309 @itemx show print object
13310 Choose whether to print derived (actual) or declared types of objects.
13311 @xref{Print Settings, ,Print Settings}.
13313 @item set print vtbl
13314 @itemx show print vtbl
13315 Control the format for printing virtual function tables.
13316 @xref{Print Settings, ,Print Settings}.
13317 (The @code{vtbl} commands do not work on programs compiled with the HP
13318 ANSI C@t{++} compiler (@code{aCC}).)
13320 @kindex set overload-resolution
13321 @cindex overloaded functions, overload resolution
13322 @item set overload-resolution on
13323 Enable overload resolution for C@t{++} expression evaluation. The default
13324 is on. For overloaded functions, @value{GDBN} evaluates the arguments
13325 and searches for a function whose signature matches the argument types,
13326 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
13327 Expressions, ,C@t{++} Expressions}, for details).
13328 If it cannot find a match, it emits a message.
13330 @item set overload-resolution off
13331 Disable overload resolution for C@t{++} expression evaluation. For
13332 overloaded functions that are not class member functions, @value{GDBN}
13333 chooses the first function of the specified name that it finds in the
13334 symbol table, whether or not its arguments are of the correct type. For
13335 overloaded functions that are class member functions, @value{GDBN}
13336 searches for a function whose signature @emph{exactly} matches the
13339 @kindex show overload-resolution
13340 @item show overload-resolution
13341 Show the current setting of overload resolution.
13343 @item @r{Overloaded symbol names}
13344 You can specify a particular definition of an overloaded symbol, using
13345 the same notation that is used to declare such symbols in C@t{++}: type
13346 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
13347 also use the @value{GDBN} command-line word completion facilities to list the
13348 available choices, or to finish the type list for you.
13349 @xref{Completion,, Command Completion}, for details on how to do this.
13352 @node Decimal Floating Point
13353 @subsubsection Decimal Floating Point format
13354 @cindex decimal floating point format
13356 @value{GDBN} can examine, set and perform computations with numbers in
13357 decimal floating point format, which in the C language correspond to the
13358 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
13359 specified by the extension to support decimal floating-point arithmetic.
13361 There are two encodings in use, depending on the architecture: BID (Binary
13362 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
13363 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
13366 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
13367 to manipulate decimal floating point numbers, it is not possible to convert
13368 (using a cast, for example) integers wider than 32-bit to decimal float.
13370 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
13371 point computations, error checking in decimal float operations ignores
13372 underflow, overflow and divide by zero exceptions.
13374 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
13375 to inspect @code{_Decimal128} values stored in floating point registers.
13376 See @ref{PowerPC,,PowerPC} for more details.
13382 @value{GDBN} can be used to debug programs written in D and compiled with
13383 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
13384 specific feature --- dynamic arrays.
13389 @cindex Go (programming language)
13390 @value{GDBN} can be used to debug programs written in Go and compiled with
13391 @file{gccgo} or @file{6g} compilers.
13393 Here is a summary of the Go-specific features and restrictions:
13396 @cindex current Go package
13397 @item The current Go package
13398 The name of the current package does not need to be specified when
13399 specifying global variables and functions.
13401 For example, given the program:
13405 var myglob = "Shall we?"
13411 When stopped inside @code{main} either of these work:
13415 (gdb) p main.myglob
13418 @cindex builtin Go types
13419 @item Builtin Go types
13420 The @code{string} type is recognized by @value{GDBN} and is printed
13423 @cindex builtin Go functions
13424 @item Builtin Go functions
13425 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
13426 function and handles it internally.
13428 @cindex restrictions on Go expressions
13429 @item Restrictions on Go expressions
13430 All Go operators are supported except @code{&^}.
13431 The Go @code{_} ``blank identifier'' is not supported.
13432 Automatic dereferencing of pointers is not supported.
13436 @subsection Objective-C
13438 @cindex Objective-C
13439 This section provides information about some commands and command
13440 options that are useful for debugging Objective-C code. See also
13441 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
13442 few more commands specific to Objective-C support.
13445 * Method Names in Commands::
13446 * The Print Command with Objective-C::
13449 @node Method Names in Commands
13450 @subsubsection Method Names in Commands
13452 The following commands have been extended to accept Objective-C method
13453 names as line specifications:
13455 @kindex clear@r{, and Objective-C}
13456 @kindex break@r{, and Objective-C}
13457 @kindex info line@r{, and Objective-C}
13458 @kindex jump@r{, and Objective-C}
13459 @kindex list@r{, and Objective-C}
13463 @item @code{info line}
13468 A fully qualified Objective-C method name is specified as
13471 -[@var{Class} @var{methodName}]
13474 where the minus sign is used to indicate an instance method and a
13475 plus sign (not shown) is used to indicate a class method. The class
13476 name @var{Class} and method name @var{methodName} are enclosed in
13477 brackets, similar to the way messages are specified in Objective-C
13478 source code. For example, to set a breakpoint at the @code{create}
13479 instance method of class @code{Fruit} in the program currently being
13483 break -[Fruit create]
13486 To list ten program lines around the @code{initialize} class method,
13490 list +[NSText initialize]
13493 In the current version of @value{GDBN}, the plus or minus sign is
13494 required. In future versions of @value{GDBN}, the plus or minus
13495 sign will be optional, but you can use it to narrow the search. It
13496 is also possible to specify just a method name:
13502 You must specify the complete method name, including any colons. If
13503 your program's source files contain more than one @code{create} method,
13504 you'll be presented with a numbered list of classes that implement that
13505 method. Indicate your choice by number, or type @samp{0} to exit if
13508 As another example, to clear a breakpoint established at the
13509 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
13512 clear -[NSWindow makeKeyAndOrderFront:]
13515 @node The Print Command with Objective-C
13516 @subsubsection The Print Command With Objective-C
13517 @cindex Objective-C, print objects
13518 @kindex print-object
13519 @kindex po @r{(@code{print-object})}
13521 The print command has also been extended to accept methods. For example:
13524 print -[@var{object} hash]
13527 @cindex print an Objective-C object description
13528 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
13530 will tell @value{GDBN} to send the @code{hash} message to @var{object}
13531 and print the result. Also, an additional command has been added,
13532 @code{print-object} or @code{po} for short, which is meant to print
13533 the description of an object. However, this command may only work
13534 with certain Objective-C libraries that have a particular hook
13535 function, @code{_NSPrintForDebugger}, defined.
13538 @subsection OpenCL C
13541 This section provides information about @value{GDBN}s OpenCL C support.
13544 * OpenCL C Datatypes::
13545 * OpenCL C Expressions::
13546 * OpenCL C Operators::
13549 @node OpenCL C Datatypes
13550 @subsubsection OpenCL C Datatypes
13552 @cindex OpenCL C Datatypes
13553 @value{GDBN} supports the builtin scalar and vector datatypes specified
13554 by OpenCL 1.1. In addition the half- and double-precision floating point
13555 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
13556 extensions are also known to @value{GDBN}.
13558 @node OpenCL C Expressions
13559 @subsubsection OpenCL C Expressions
13561 @cindex OpenCL C Expressions
13562 @value{GDBN} supports accesses to vector components including the access as
13563 lvalue where possible. Since OpenCL C is based on C99 most C expressions
13564 supported by @value{GDBN} can be used as well.
13566 @node OpenCL C Operators
13567 @subsubsection OpenCL C Operators
13569 @cindex OpenCL C Operators
13570 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
13574 @subsection Fortran
13575 @cindex Fortran-specific support in @value{GDBN}
13577 @value{GDBN} can be used to debug programs written in Fortran, but it
13578 currently supports only the features of Fortran 77 language.
13580 @cindex trailing underscore, in Fortran symbols
13581 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
13582 among them) append an underscore to the names of variables and
13583 functions. When you debug programs compiled by those compilers, you
13584 will need to refer to variables and functions with a trailing
13588 * Fortran Operators:: Fortran operators and expressions
13589 * Fortran Defaults:: Default settings for Fortran
13590 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
13593 @node Fortran Operators
13594 @subsubsection Fortran Operators and Expressions
13596 @cindex Fortran operators and expressions
13598 Operators must be defined on values of specific types. For instance,
13599 @code{+} is defined on numbers, but not on characters or other non-
13600 arithmetic types. Operators are often defined on groups of types.
13604 The exponentiation operator. It raises the first operand to the power
13608 The range operator. Normally used in the form of array(low:high) to
13609 represent a section of array.
13612 The access component operator. Normally used to access elements in derived
13613 types. Also suitable for unions. As unions aren't part of regular Fortran,
13614 this can only happen when accessing a register that uses a gdbarch-defined
13618 @node Fortran Defaults
13619 @subsubsection Fortran Defaults
13621 @cindex Fortran Defaults
13623 Fortran symbols are usually case-insensitive, so @value{GDBN} by
13624 default uses case-insensitive matches for Fortran symbols. You can
13625 change that with the @samp{set case-insensitive} command, see
13626 @ref{Symbols}, for the details.
13628 @node Special Fortran Commands
13629 @subsubsection Special Fortran Commands
13631 @cindex Special Fortran commands
13633 @value{GDBN} has some commands to support Fortran-specific features,
13634 such as displaying common blocks.
13637 @cindex @code{COMMON} blocks, Fortran
13638 @kindex info common
13639 @item info common @r{[}@var{common-name}@r{]}
13640 This command prints the values contained in the Fortran @code{COMMON}
13641 block whose name is @var{common-name}. With no argument, the names of
13642 all @code{COMMON} blocks visible at the current program location are
13649 @cindex Pascal support in @value{GDBN}, limitations
13650 Debugging Pascal programs which use sets, subranges, file variables, or
13651 nested functions does not currently work. @value{GDBN} does not support
13652 entering expressions, printing values, or similar features using Pascal
13655 The Pascal-specific command @code{set print pascal_static-members}
13656 controls whether static members of Pascal objects are displayed.
13657 @xref{Print Settings, pascal_static-members}.
13660 @subsection Modula-2
13662 @cindex Modula-2, @value{GDBN} support
13664 The extensions made to @value{GDBN} to support Modula-2 only support
13665 output from the @sc{gnu} Modula-2 compiler (which is currently being
13666 developed). Other Modula-2 compilers are not currently supported, and
13667 attempting to debug executables produced by them is most likely
13668 to give an error as @value{GDBN} reads in the executable's symbol
13671 @cindex expressions in Modula-2
13673 * M2 Operators:: Built-in operators
13674 * Built-In Func/Proc:: Built-in functions and procedures
13675 * M2 Constants:: Modula-2 constants
13676 * M2 Types:: Modula-2 types
13677 * M2 Defaults:: Default settings for Modula-2
13678 * Deviations:: Deviations from standard Modula-2
13679 * M2 Checks:: Modula-2 type and range checks
13680 * M2 Scope:: The scope operators @code{::} and @code{.}
13681 * GDB/M2:: @value{GDBN} and Modula-2
13685 @subsubsection Operators
13686 @cindex Modula-2 operators
13688 Operators must be defined on values of specific types. For instance,
13689 @code{+} is defined on numbers, but not on structures. Operators are
13690 often defined on groups of types. For the purposes of Modula-2, the
13691 following definitions hold:
13696 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13700 @emph{Character types} consist of @code{CHAR} and its subranges.
13703 @emph{Floating-point types} consist of @code{REAL}.
13706 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13710 @emph{Scalar types} consist of all of the above.
13713 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13716 @emph{Boolean types} consist of @code{BOOLEAN}.
13720 The following operators are supported, and appear in order of
13721 increasing precedence:
13725 Function argument or array index separator.
13728 Assignment. The value of @var{var} @code{:=} @var{value} is
13732 Less than, greater than on integral, floating-point, or enumerated
13736 Less than or equal to, greater than or equal to
13737 on integral, floating-point and enumerated types, or set inclusion on
13738 set types. Same precedence as @code{<}.
13740 @item =@r{, }<>@r{, }#
13741 Equality and two ways of expressing inequality, valid on scalar types.
13742 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13743 available for inequality, since @code{#} conflicts with the script
13747 Set membership. Defined on set types and the types of their members.
13748 Same precedence as @code{<}.
13751 Boolean disjunction. Defined on boolean types.
13754 Boolean conjunction. Defined on boolean types.
13757 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13760 Addition and subtraction on integral and floating-point types, or union
13761 and difference on set types.
13764 Multiplication on integral and floating-point types, or set intersection
13768 Division on floating-point types, or symmetric set difference on set
13769 types. Same precedence as @code{*}.
13772 Integer division and remainder. Defined on integral types. Same
13773 precedence as @code{*}.
13776 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13779 Pointer dereferencing. Defined on pointer types.
13782 Boolean negation. Defined on boolean types. Same precedence as
13786 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13787 precedence as @code{^}.
13790 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13793 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13797 @value{GDBN} and Modula-2 scope operators.
13801 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13802 treats the use of the operator @code{IN}, or the use of operators
13803 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13804 @code{<=}, and @code{>=} on sets as an error.
13808 @node Built-In Func/Proc
13809 @subsubsection Built-in Functions and Procedures
13810 @cindex Modula-2 built-ins
13812 Modula-2 also makes available several built-in procedures and functions.
13813 In describing these, the following metavariables are used:
13818 represents an @code{ARRAY} variable.
13821 represents a @code{CHAR} constant or variable.
13824 represents a variable or constant of integral type.
13827 represents an identifier that belongs to a set. Generally used in the
13828 same function with the metavariable @var{s}. The type of @var{s} should
13829 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13832 represents a variable or constant of integral or floating-point type.
13835 represents a variable or constant of floating-point type.
13841 represents a variable.
13844 represents a variable or constant of one of many types. See the
13845 explanation of the function for details.
13848 All Modula-2 built-in procedures also return a result, described below.
13852 Returns the absolute value of @var{n}.
13855 If @var{c} is a lower case letter, it returns its upper case
13856 equivalent, otherwise it returns its argument.
13859 Returns the character whose ordinal value is @var{i}.
13862 Decrements the value in the variable @var{v} by one. Returns the new value.
13864 @item DEC(@var{v},@var{i})
13865 Decrements the value in the variable @var{v} by @var{i}. Returns the
13868 @item EXCL(@var{m},@var{s})
13869 Removes the element @var{m} from the set @var{s}. Returns the new
13872 @item FLOAT(@var{i})
13873 Returns the floating point equivalent of the integer @var{i}.
13875 @item HIGH(@var{a})
13876 Returns the index of the last member of @var{a}.
13879 Increments the value in the variable @var{v} by one. Returns the new value.
13881 @item INC(@var{v},@var{i})
13882 Increments the value in the variable @var{v} by @var{i}. Returns the
13885 @item INCL(@var{m},@var{s})
13886 Adds the element @var{m} to the set @var{s} if it is not already
13887 there. Returns the new set.
13890 Returns the maximum value of the type @var{t}.
13893 Returns the minimum value of the type @var{t}.
13896 Returns boolean TRUE if @var{i} is an odd number.
13899 Returns the ordinal value of its argument. For example, the ordinal
13900 value of a character is its @sc{ascii} value (on machines supporting the
13901 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13902 integral, character and enumerated types.
13904 @item SIZE(@var{x})
13905 Returns the size of its argument. @var{x} can be a variable or a type.
13907 @item TRUNC(@var{r})
13908 Returns the integral part of @var{r}.
13910 @item TSIZE(@var{x})
13911 Returns the size of its argument. @var{x} can be a variable or a type.
13913 @item VAL(@var{t},@var{i})
13914 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13918 @emph{Warning:} Sets and their operations are not yet supported, so
13919 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13923 @cindex Modula-2 constants
13925 @subsubsection Constants
13927 @value{GDBN} allows you to express the constants of Modula-2 in the following
13933 Integer constants are simply a sequence of digits. When used in an
13934 expression, a constant is interpreted to be type-compatible with the
13935 rest of the expression. Hexadecimal integers are specified by a
13936 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13939 Floating point constants appear as a sequence of digits, followed by a
13940 decimal point and another sequence of digits. An optional exponent can
13941 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13942 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13943 digits of the floating point constant must be valid decimal (base 10)
13947 Character constants consist of a single character enclosed by a pair of
13948 like quotes, either single (@code{'}) or double (@code{"}). They may
13949 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13950 followed by a @samp{C}.
13953 String constants consist of a sequence of characters enclosed by a
13954 pair of like quotes, either single (@code{'}) or double (@code{"}).
13955 Escape sequences in the style of C are also allowed. @xref{C
13956 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13960 Enumerated constants consist of an enumerated identifier.
13963 Boolean constants consist of the identifiers @code{TRUE} and
13967 Pointer constants consist of integral values only.
13970 Set constants are not yet supported.
13974 @subsubsection Modula-2 Types
13975 @cindex Modula-2 types
13977 Currently @value{GDBN} can print the following data types in Modula-2
13978 syntax: array types, record types, set types, pointer types, procedure
13979 types, enumerated types, subrange types and base types. You can also
13980 print the contents of variables declared using these type.
13981 This section gives a number of simple source code examples together with
13982 sample @value{GDBN} sessions.
13984 The first example contains the following section of code:
13993 and you can request @value{GDBN} to interrogate the type and value of
13994 @code{r} and @code{s}.
13997 (@value{GDBP}) print s
13999 (@value{GDBP}) ptype s
14001 (@value{GDBP}) print r
14003 (@value{GDBP}) ptype r
14008 Likewise if your source code declares @code{s} as:
14012 s: SET ['A'..'Z'] ;
14016 then you may query the type of @code{s} by:
14019 (@value{GDBP}) ptype s
14020 type = SET ['A'..'Z']
14024 Note that at present you cannot interactively manipulate set
14025 expressions using the debugger.
14027 The following example shows how you might declare an array in Modula-2
14028 and how you can interact with @value{GDBN} to print its type and contents:
14032 s: ARRAY [-10..10] OF CHAR ;
14036 (@value{GDBP}) ptype s
14037 ARRAY [-10..10] OF CHAR
14040 Note that the array handling is not yet complete and although the type
14041 is printed correctly, expression handling still assumes that all
14042 arrays have a lower bound of zero and not @code{-10} as in the example
14045 Here are some more type related Modula-2 examples:
14049 colour = (blue, red, yellow, green) ;
14050 t = [blue..yellow] ;
14058 The @value{GDBN} interaction shows how you can query the data type
14059 and value of a variable.
14062 (@value{GDBP}) print s
14064 (@value{GDBP}) ptype t
14065 type = [blue..yellow]
14069 In this example a Modula-2 array is declared and its contents
14070 displayed. Observe that the contents are written in the same way as
14071 their @code{C} counterparts.
14075 s: ARRAY [1..5] OF CARDINAL ;
14081 (@value{GDBP}) print s
14082 $1 = @{1, 0, 0, 0, 0@}
14083 (@value{GDBP}) ptype s
14084 type = ARRAY [1..5] OF CARDINAL
14087 The Modula-2 language interface to @value{GDBN} also understands
14088 pointer types as shown in this example:
14092 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14099 and you can request that @value{GDBN} describes the type of @code{s}.
14102 (@value{GDBP}) ptype s
14103 type = POINTER TO ARRAY [1..5] OF CARDINAL
14106 @value{GDBN} handles compound types as we can see in this example.
14107 Here we combine array types, record types, pointer types and subrange
14118 myarray = ARRAY myrange OF CARDINAL ;
14119 myrange = [-2..2] ;
14121 s: POINTER TO ARRAY myrange OF foo ;
14125 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14129 (@value{GDBP}) ptype s
14130 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14133 f3 : ARRAY [-2..2] OF CARDINAL;
14138 @subsubsection Modula-2 Defaults
14139 @cindex Modula-2 defaults
14141 If type and range checking are set automatically by @value{GDBN}, they
14142 both default to @code{on} whenever the working language changes to
14143 Modula-2. This happens regardless of whether you or @value{GDBN}
14144 selected the working language.
14146 If you allow @value{GDBN} to set the language automatically, then entering
14147 code compiled from a file whose name ends with @file{.mod} sets the
14148 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14149 Infer the Source Language}, for further details.
14152 @subsubsection Deviations from Standard Modula-2
14153 @cindex Modula-2, deviations from
14155 A few changes have been made to make Modula-2 programs easier to debug.
14156 This is done primarily via loosening its type strictness:
14160 Unlike in standard Modula-2, pointer constants can be formed by
14161 integers. This allows you to modify pointer variables during
14162 debugging. (In standard Modula-2, the actual address contained in a
14163 pointer variable is hidden from you; it can only be modified
14164 through direct assignment to another pointer variable or expression that
14165 returned a pointer.)
14168 C escape sequences can be used in strings and characters to represent
14169 non-printable characters. @value{GDBN} prints out strings with these
14170 escape sequences embedded. Single non-printable characters are
14171 printed using the @samp{CHR(@var{nnn})} format.
14174 The assignment operator (@code{:=}) returns the value of its right-hand
14178 All built-in procedures both modify @emph{and} return their argument.
14182 @subsubsection Modula-2 Type and Range Checks
14183 @cindex Modula-2 checks
14186 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14189 @c FIXME remove warning when type/range checks added
14191 @value{GDBN} considers two Modula-2 variables type equivalent if:
14195 They are of types that have been declared equivalent via a @code{TYPE
14196 @var{t1} = @var{t2}} statement
14199 They have been declared on the same line. (Note: This is true of the
14200 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14203 As long as type checking is enabled, any attempt to combine variables
14204 whose types are not equivalent is an error.
14206 Range checking is done on all mathematical operations, assignment, array
14207 index bounds, and all built-in functions and procedures.
14210 @subsubsection The Scope Operators @code{::} and @code{.}
14212 @cindex @code{.}, Modula-2 scope operator
14213 @cindex colon, doubled as scope operator
14215 @vindex colon-colon@r{, in Modula-2}
14216 @c Info cannot handle :: but TeX can.
14219 @vindex ::@r{, in Modula-2}
14222 There are a few subtle differences between the Modula-2 scope operator
14223 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14228 @var{module} . @var{id}
14229 @var{scope} :: @var{id}
14233 where @var{scope} is the name of a module or a procedure,
14234 @var{module} the name of a module, and @var{id} is any declared
14235 identifier within your program, except another module.
14237 Using the @code{::} operator makes @value{GDBN} search the scope
14238 specified by @var{scope} for the identifier @var{id}. If it is not
14239 found in the specified scope, then @value{GDBN} searches all scopes
14240 enclosing the one specified by @var{scope}.
14242 Using the @code{.} operator makes @value{GDBN} search the current scope for
14243 the identifier specified by @var{id} that was imported from the
14244 definition module specified by @var{module}. With this operator, it is
14245 an error if the identifier @var{id} was not imported from definition
14246 module @var{module}, or if @var{id} is not an identifier in
14250 @subsubsection @value{GDBN} and Modula-2
14252 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14253 Five subcommands of @code{set print} and @code{show print} apply
14254 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14255 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14256 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14257 analogue in Modula-2.
14259 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14260 with any language, is not useful with Modula-2. Its
14261 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14262 created in Modula-2 as they can in C or C@t{++}. However, because an
14263 address can be specified by an integral constant, the construct
14264 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14266 @cindex @code{#} in Modula-2
14267 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14268 interpreted as the beginning of a comment. Use @code{<>} instead.
14274 The extensions made to @value{GDBN} for Ada only support
14275 output from the @sc{gnu} Ada (GNAT) compiler.
14276 Other Ada compilers are not currently supported, and
14277 attempting to debug executables produced by them is most likely
14281 @cindex expressions in Ada
14283 * Ada Mode Intro:: General remarks on the Ada syntax
14284 and semantics supported by Ada mode
14286 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14287 * Additions to Ada:: Extensions of the Ada expression syntax.
14288 * Stopping Before Main Program:: Debugging the program during elaboration.
14289 * Ada Tasks:: Listing and setting breakpoints in tasks.
14290 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14291 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14293 * Ada Glitches:: Known peculiarities of Ada mode.
14296 @node Ada Mode Intro
14297 @subsubsection Introduction
14298 @cindex Ada mode, general
14300 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14301 syntax, with some extensions.
14302 The philosophy behind the design of this subset is
14306 That @value{GDBN} should provide basic literals and access to operations for
14307 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
14308 leaving more sophisticated computations to subprograms written into the
14309 program (which therefore may be called from @value{GDBN}).
14312 That type safety and strict adherence to Ada language restrictions
14313 are not particularly important to the @value{GDBN} user.
14316 That brevity is important to the @value{GDBN} user.
14319 Thus, for brevity, the debugger acts as if all names declared in
14320 user-written packages are directly visible, even if they are not visible
14321 according to Ada rules, thus making it unnecessary to fully qualify most
14322 names with their packages, regardless of context. Where this causes
14323 ambiguity, @value{GDBN} asks the user's intent.
14325 The debugger will start in Ada mode if it detects an Ada main program.
14326 As for other languages, it will enter Ada mode when stopped in a program that
14327 was translated from an Ada source file.
14329 While in Ada mode, you may use `@t{--}' for comments. This is useful
14330 mostly for documenting command files. The standard @value{GDBN} comment
14331 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
14332 middle (to allow based literals).
14334 The debugger supports limited overloading. Given a subprogram call in which
14335 the function symbol has multiple definitions, it will use the number of
14336 actual parameters and some information about their types to attempt to narrow
14337 the set of definitions. It also makes very limited use of context, preferring
14338 procedures to functions in the context of the @code{call} command, and
14339 functions to procedures elsewhere.
14341 @node Omissions from Ada
14342 @subsubsection Omissions from Ada
14343 @cindex Ada, omissions from
14345 Here are the notable omissions from the subset:
14349 Only a subset of the attributes are supported:
14353 @t{'First}, @t{'Last}, and @t{'Length}
14354 on array objects (not on types and subtypes).
14357 @t{'Min} and @t{'Max}.
14360 @t{'Pos} and @t{'Val}.
14366 @t{'Range} on array objects (not subtypes), but only as the right
14367 operand of the membership (@code{in}) operator.
14370 @t{'Access}, @t{'Unchecked_Access}, and
14371 @t{'Unrestricted_Access} (a GNAT extension).
14379 @code{Characters.Latin_1} are not available and
14380 concatenation is not implemented. Thus, escape characters in strings are
14381 not currently available.
14384 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
14385 equality of representations. They will generally work correctly
14386 for strings and arrays whose elements have integer or enumeration types.
14387 They may not work correctly for arrays whose element
14388 types have user-defined equality, for arrays of real values
14389 (in particular, IEEE-conformant floating point, because of negative
14390 zeroes and NaNs), and for arrays whose elements contain unused bits with
14391 indeterminate values.
14394 The other component-by-component array operations (@code{and}, @code{or},
14395 @code{xor}, @code{not}, and relational tests other than equality)
14396 are not implemented.
14399 @cindex array aggregates (Ada)
14400 @cindex record aggregates (Ada)
14401 @cindex aggregates (Ada)
14402 There is limited support for array and record aggregates. They are
14403 permitted only on the right sides of assignments, as in these examples:
14406 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
14407 (@value{GDBP}) set An_Array := (1, others => 0)
14408 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
14409 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
14410 (@value{GDBP}) set A_Record := (1, "Peter", True);
14411 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
14415 discriminant's value by assigning an aggregate has an
14416 undefined effect if that discriminant is used within the record.
14417 However, you can first modify discriminants by directly assigning to
14418 them (which normally would not be allowed in Ada), and then performing an
14419 aggregate assignment. For example, given a variable @code{A_Rec}
14420 declared to have a type such as:
14423 type Rec (Len : Small_Integer := 0) is record
14425 Vals : IntArray (1 .. Len);
14429 you can assign a value with a different size of @code{Vals} with two
14433 (@value{GDBP}) set A_Rec.Len := 4
14434 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
14437 As this example also illustrates, @value{GDBN} is very loose about the usual
14438 rules concerning aggregates. You may leave out some of the
14439 components of an array or record aggregate (such as the @code{Len}
14440 component in the assignment to @code{A_Rec} above); they will retain their
14441 original values upon assignment. You may freely use dynamic values as
14442 indices in component associations. You may even use overlapping or
14443 redundant component associations, although which component values are
14444 assigned in such cases is not defined.
14447 Calls to dispatching subprograms are not implemented.
14450 The overloading algorithm is much more limited (i.e., less selective)
14451 than that of real Ada. It makes only limited use of the context in
14452 which a subexpression appears to resolve its meaning, and it is much
14453 looser in its rules for allowing type matches. As a result, some
14454 function calls will be ambiguous, and the user will be asked to choose
14455 the proper resolution.
14458 The @code{new} operator is not implemented.
14461 Entry calls are not implemented.
14464 Aside from printing, arithmetic operations on the native VAX floating-point
14465 formats are not supported.
14468 It is not possible to slice a packed array.
14471 The names @code{True} and @code{False}, when not part of a qualified name,
14472 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
14474 Should your program
14475 redefine these names in a package or procedure (at best a dubious practice),
14476 you will have to use fully qualified names to access their new definitions.
14479 @node Additions to Ada
14480 @subsubsection Additions to Ada
14481 @cindex Ada, deviations from
14483 As it does for other languages, @value{GDBN} makes certain generic
14484 extensions to Ada (@pxref{Expressions}):
14488 If the expression @var{E} is a variable residing in memory (typically
14489 a local variable or array element) and @var{N} is a positive integer,
14490 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
14491 @var{N}-1 adjacent variables following it in memory as an array. In
14492 Ada, this operator is generally not necessary, since its prime use is
14493 in displaying parts of an array, and slicing will usually do this in
14494 Ada. However, there are occasional uses when debugging programs in
14495 which certain debugging information has been optimized away.
14498 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
14499 appears in function or file @var{B}.'' When @var{B} is a file name,
14500 you must typically surround it in single quotes.
14503 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
14504 @var{type} that appears at address @var{addr}.''
14507 A name starting with @samp{$} is a convenience variable
14508 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
14511 In addition, @value{GDBN} provides a few other shortcuts and outright
14512 additions specific to Ada:
14516 The assignment statement is allowed as an expression, returning
14517 its right-hand operand as its value. Thus, you may enter
14520 (@value{GDBP}) set x := y + 3
14521 (@value{GDBP}) print A(tmp := y + 1)
14525 The semicolon is allowed as an ``operator,'' returning as its value
14526 the value of its right-hand operand.
14527 This allows, for example,
14528 complex conditional breaks:
14531 (@value{GDBP}) break f
14532 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
14536 Rather than use catenation and symbolic character names to introduce special
14537 characters into strings, one may instead use a special bracket notation,
14538 which is also used to print strings. A sequence of characters of the form
14539 @samp{["@var{XX}"]} within a string or character literal denotes the
14540 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
14541 sequence of characters @samp{["""]} also denotes a single quotation mark
14542 in strings. For example,
14544 "One line.["0a"]Next line.["0a"]"
14547 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
14551 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
14552 @t{'Max} is optional (and is ignored in any case). For example, it is valid
14556 (@value{GDBP}) print 'max(x, y)
14560 When printing arrays, @value{GDBN} uses positional notation when the
14561 array has a lower bound of 1, and uses a modified named notation otherwise.
14562 For example, a one-dimensional array of three integers with a lower bound
14563 of 3 might print as
14570 That is, in contrast to valid Ada, only the first component has a @code{=>}
14574 You may abbreviate attributes in expressions with any unique,
14575 multi-character subsequence of
14576 their names (an exact match gets preference).
14577 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
14578 in place of @t{a'length}.
14581 @cindex quoting Ada internal identifiers
14582 Since Ada is case-insensitive, the debugger normally maps identifiers you type
14583 to lower case. The GNAT compiler uses upper-case characters for
14584 some of its internal identifiers, which are normally of no interest to users.
14585 For the rare occasions when you actually have to look at them,
14586 enclose them in angle brackets to avoid the lower-case mapping.
14589 (@value{GDBP}) print <JMPBUF_SAVE>[0]
14593 Printing an object of class-wide type or dereferencing an
14594 access-to-class-wide value will display all the components of the object's
14595 specific type (as indicated by its run-time tag). Likewise, component
14596 selection on such a value will operate on the specific type of the
14601 @node Stopping Before Main Program
14602 @subsubsection Stopping at the Very Beginning
14604 @cindex breakpointing Ada elaboration code
14605 It is sometimes necessary to debug the program during elaboration, and
14606 before reaching the main procedure.
14607 As defined in the Ada Reference
14608 Manual, the elaboration code is invoked from a procedure called
14609 @code{adainit}. To run your program up to the beginning of
14610 elaboration, simply use the following two commands:
14611 @code{tbreak adainit} and @code{run}.
14614 @subsubsection Extensions for Ada Tasks
14615 @cindex Ada, tasking
14617 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
14618 @value{GDBN} provides the following task-related commands:
14623 This command shows a list of current Ada tasks, as in the following example:
14630 (@value{GDBP}) info tasks
14631 ID TID P-ID Pri State Name
14632 1 8088000 0 15 Child Activation Wait main_task
14633 2 80a4000 1 15 Accept Statement b
14634 3 809a800 1 15 Child Activation Wait a
14635 * 4 80ae800 3 15 Runnable c
14640 In this listing, the asterisk before the last task indicates it to be the
14641 task currently being inspected.
14645 Represents @value{GDBN}'s internal task number.
14651 The parent's task ID (@value{GDBN}'s internal task number).
14654 The base priority of the task.
14657 Current state of the task.
14661 The task has been created but has not been activated. It cannot be
14665 The task is not blocked for any reason known to Ada. (It may be waiting
14666 for a mutex, though.) It is conceptually "executing" in normal mode.
14669 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14670 that were waiting on terminate alternatives have been awakened and have
14671 terminated themselves.
14673 @item Child Activation Wait
14674 The task is waiting for created tasks to complete activation.
14676 @item Accept Statement
14677 The task is waiting on an accept or selective wait statement.
14679 @item Waiting on entry call
14680 The task is waiting on an entry call.
14682 @item Async Select Wait
14683 The task is waiting to start the abortable part of an asynchronous
14687 The task is waiting on a select statement with only a delay
14690 @item Child Termination Wait
14691 The task is sleeping having completed a master within itself, and is
14692 waiting for the tasks dependent on that master to become terminated or
14693 waiting on a terminate Phase.
14695 @item Wait Child in Term Alt
14696 The task is sleeping waiting for tasks on terminate alternatives to
14697 finish terminating.
14699 @item Accepting RV with @var{taskno}
14700 The task is accepting a rendez-vous with the task @var{taskno}.
14704 Name of the task in the program.
14708 @kindex info task @var{taskno}
14709 @item info task @var{taskno}
14710 This command shows detailled informations on the specified task, as in
14711 the following example:
14716 (@value{GDBP}) info tasks
14717 ID TID P-ID Pri State Name
14718 1 8077880 0 15 Child Activation Wait main_task
14719 * 2 807c468 1 15 Runnable task_1
14720 (@value{GDBP}) info task 2
14721 Ada Task: 0x807c468
14724 Parent: 1 (main_task)
14730 @kindex task@r{ (Ada)}
14731 @cindex current Ada task ID
14732 This command prints the ID of the current task.
14738 (@value{GDBP}) info tasks
14739 ID TID P-ID Pri State Name
14740 1 8077870 0 15 Child Activation Wait main_task
14741 * 2 807c458 1 15 Runnable t
14742 (@value{GDBP}) task
14743 [Current task is 2]
14746 @item task @var{taskno}
14747 @cindex Ada task switching
14748 This command is like the @code{thread @var{threadno}}
14749 command (@pxref{Threads}). It switches the context of debugging
14750 from the current task to the given task.
14756 (@value{GDBP}) info tasks
14757 ID TID P-ID Pri State Name
14758 1 8077870 0 15 Child Activation Wait main_task
14759 * 2 807c458 1 15 Runnable t
14760 (@value{GDBP}) task 1
14761 [Switching to task 1]
14762 #0 0x8067726 in pthread_cond_wait ()
14764 #0 0x8067726 in pthread_cond_wait ()
14765 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14766 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14767 #3 0x806153e in system.tasking.stages.activate_tasks ()
14768 #4 0x804aacc in un () at un.adb:5
14771 @item break @var{linespec} task @var{taskno}
14772 @itemx break @var{linespec} task @var{taskno} if @dots{}
14773 @cindex breakpoints and tasks, in Ada
14774 @cindex task breakpoints, in Ada
14775 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14776 These commands are like the @code{break @dots{} thread @dots{}}
14777 command (@pxref{Thread Stops}).
14778 @var{linespec} specifies source lines, as described
14779 in @ref{Specify Location}.
14781 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14782 to specify that you only want @value{GDBN} to stop the program when a
14783 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14784 numeric task identifiers assigned by @value{GDBN}, shown in the first
14785 column of the @samp{info tasks} display.
14787 If you do not specify @samp{task @var{taskno}} when you set a
14788 breakpoint, the breakpoint applies to @emph{all} tasks of your
14791 You can use the @code{task} qualifier on conditional breakpoints as
14792 well; in this case, place @samp{task @var{taskno}} before the
14793 breakpoint condition (before the @code{if}).
14801 (@value{GDBP}) info tasks
14802 ID TID P-ID Pri State Name
14803 1 140022020 0 15 Child Activation Wait main_task
14804 2 140045060 1 15 Accept/Select Wait t2
14805 3 140044840 1 15 Runnable t1
14806 * 4 140056040 1 15 Runnable t3
14807 (@value{GDBP}) b 15 task 2
14808 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14809 (@value{GDBP}) cont
14814 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14816 (@value{GDBP}) info tasks
14817 ID TID P-ID Pri State Name
14818 1 140022020 0 15 Child Activation Wait main_task
14819 * 2 140045060 1 15 Runnable t2
14820 3 140044840 1 15 Runnable t1
14821 4 140056040 1 15 Delay Sleep t3
14825 @node Ada Tasks and Core Files
14826 @subsubsection Tasking Support when Debugging Core Files
14827 @cindex Ada tasking and core file debugging
14829 When inspecting a core file, as opposed to debugging a live program,
14830 tasking support may be limited or even unavailable, depending on
14831 the platform being used.
14832 For instance, on x86-linux, the list of tasks is available, but task
14833 switching is not supported. On Tru64, however, task switching will work
14836 On certain platforms, including Tru64, the debugger needs to perform some
14837 memory writes in order to provide Ada tasking support. When inspecting
14838 a core file, this means that the core file must be opened with read-write
14839 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14840 Under these circumstances, you should make a backup copy of the core
14841 file before inspecting it with @value{GDBN}.
14843 @node Ravenscar Profile
14844 @subsubsection Tasking Support when using the Ravenscar Profile
14845 @cindex Ravenscar Profile
14847 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14848 specifically designed for systems with safety-critical real-time
14852 @kindex set ravenscar task-switching on
14853 @cindex task switching with program using Ravenscar Profile
14854 @item set ravenscar task-switching on
14855 Allows task switching when debugging a program that uses the Ravenscar
14856 Profile. This is the default.
14858 @kindex set ravenscar task-switching off
14859 @item set ravenscar task-switching off
14860 Turn off task switching when debugging a program that uses the Ravenscar
14861 Profile. This is mostly intended to disable the code that adds support
14862 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14863 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14864 To be effective, this command should be run before the program is started.
14866 @kindex show ravenscar task-switching
14867 @item show ravenscar task-switching
14868 Show whether it is possible to switch from task to task in a program
14869 using the Ravenscar Profile.
14874 @subsubsection Known Peculiarities of Ada Mode
14875 @cindex Ada, problems
14877 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14878 we know of several problems with and limitations of Ada mode in
14880 some of which will be fixed with planned future releases of the debugger
14881 and the GNU Ada compiler.
14885 Static constants that the compiler chooses not to materialize as objects in
14886 storage are invisible to the debugger.
14889 Named parameter associations in function argument lists are ignored (the
14890 argument lists are treated as positional).
14893 Many useful library packages are currently invisible to the debugger.
14896 Fixed-point arithmetic, conversions, input, and output is carried out using
14897 floating-point arithmetic, and may give results that only approximate those on
14901 The GNAT compiler never generates the prefix @code{Standard} for any of
14902 the standard symbols defined by the Ada language. @value{GDBN} knows about
14903 this: it will strip the prefix from names when you use it, and will never
14904 look for a name you have so qualified among local symbols, nor match against
14905 symbols in other packages or subprograms. If you have
14906 defined entities anywhere in your program other than parameters and
14907 local variables whose simple names match names in @code{Standard},
14908 GNAT's lack of qualification here can cause confusion. When this happens,
14909 you can usually resolve the confusion
14910 by qualifying the problematic names with package
14911 @code{Standard} explicitly.
14914 Older versions of the compiler sometimes generate erroneous debugging
14915 information, resulting in the debugger incorrectly printing the value
14916 of affected entities. In some cases, the debugger is able to work
14917 around an issue automatically. In other cases, the debugger is able
14918 to work around the issue, but the work-around has to be specifically
14921 @kindex set ada trust-PAD-over-XVS
14922 @kindex show ada trust-PAD-over-XVS
14925 @item set ada trust-PAD-over-XVS on
14926 Configure GDB to strictly follow the GNAT encoding when computing the
14927 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14928 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14929 a complete description of the encoding used by the GNAT compiler).
14930 This is the default.
14932 @item set ada trust-PAD-over-XVS off
14933 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14934 sometimes prints the wrong value for certain entities, changing @code{ada
14935 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14936 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14937 @code{off}, but this incurs a slight performance penalty, so it is
14938 recommended to leave this setting to @code{on} unless necessary.
14942 @node Unsupported Languages
14943 @section Unsupported Languages
14945 @cindex unsupported languages
14946 @cindex minimal language
14947 In addition to the other fully-supported programming languages,
14948 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14949 It does not represent a real programming language, but provides a set
14950 of capabilities close to what the C or assembly languages provide.
14951 This should allow most simple operations to be performed while debugging
14952 an application that uses a language currently not supported by @value{GDBN}.
14954 If the language is set to @code{auto}, @value{GDBN} will automatically
14955 select this language if the current frame corresponds to an unsupported
14959 @chapter Examining the Symbol Table
14961 The commands described in this chapter allow you to inquire about the
14962 symbols (names of variables, functions and types) defined in your
14963 program. This information is inherent in the text of your program and
14964 does not change as your program executes. @value{GDBN} finds it in your
14965 program's symbol table, in the file indicated when you started @value{GDBN}
14966 (@pxref{File Options, ,Choosing Files}), or by one of the
14967 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14969 @cindex symbol names
14970 @cindex names of symbols
14971 @cindex quoting names
14972 Occasionally, you may need to refer to symbols that contain unusual
14973 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14974 most frequent case is in referring to static variables in other
14975 source files (@pxref{Variables,,Program Variables}). File names
14976 are recorded in object files as debugging symbols, but @value{GDBN} would
14977 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14978 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14979 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14986 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14989 @cindex case-insensitive symbol names
14990 @cindex case sensitivity in symbol names
14991 @kindex set case-sensitive
14992 @item set case-sensitive on
14993 @itemx set case-sensitive off
14994 @itemx set case-sensitive auto
14995 Normally, when @value{GDBN} looks up symbols, it matches their names
14996 with case sensitivity determined by the current source language.
14997 Occasionally, you may wish to control that. The command @code{set
14998 case-sensitive} lets you do that by specifying @code{on} for
14999 case-sensitive matches or @code{off} for case-insensitive ones. If
15000 you specify @code{auto}, case sensitivity is reset to the default
15001 suitable for the source language. The default is case-sensitive
15002 matches for all languages except for Fortran, for which the default is
15003 case-insensitive matches.
15005 @kindex show case-sensitive
15006 @item show case-sensitive
15007 This command shows the current setting of case sensitivity for symbols
15010 @kindex info address
15011 @cindex address of a symbol
15012 @item info address @var{symbol}
15013 Describe where the data for @var{symbol} is stored. For a register
15014 variable, this says which register it is kept in. For a non-register
15015 local variable, this prints the stack-frame offset at which the variable
15018 Note the contrast with @samp{print &@var{symbol}}, which does not work
15019 at all for a register variable, and for a stack local variable prints
15020 the exact address of the current instantiation of the variable.
15022 @kindex info symbol
15023 @cindex symbol from address
15024 @cindex closest symbol and offset for an address
15025 @item info symbol @var{addr}
15026 Print the name of a symbol which is stored at the address @var{addr}.
15027 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15028 nearest symbol and an offset from it:
15031 (@value{GDBP}) info symbol 0x54320
15032 _initialize_vx + 396 in section .text
15036 This is the opposite of the @code{info address} command. You can use
15037 it to find out the name of a variable or a function given its address.
15039 For dynamically linked executables, the name of executable or shared
15040 library containing the symbol is also printed:
15043 (@value{GDBP}) info symbol 0x400225
15044 _start + 5 in section .text of /tmp/a.out
15045 (@value{GDBP}) info symbol 0x2aaaac2811cf
15046 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15050 @item whatis [@var{arg}]
15051 Print the data type of @var{arg}, which can be either an expression
15052 or a name of a data type. With no argument, print the data type of
15053 @code{$}, the last value in the value history.
15055 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15056 is not actually evaluated, and any side-effecting operations (such as
15057 assignments or function calls) inside it do not take place.
15059 If @var{arg} is a variable or an expression, @code{whatis} prints its
15060 literal type as it is used in the source code. If the type was
15061 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15062 the data type underlying the @code{typedef}. If the type of the
15063 variable or the expression is a compound data type, such as
15064 @code{struct} or @code{class}, @code{whatis} never prints their
15065 fields or methods. It just prints the @code{struct}/@code{class}
15066 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15067 such a compound data type, use @code{ptype}.
15069 If @var{arg} is a type name that was defined using @code{typedef},
15070 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15071 Unrolling means that @code{whatis} will show the underlying type used
15072 in the @code{typedef} declaration of @var{arg}. However, if that
15073 underlying type is also a @code{typedef}, @code{whatis} will not
15076 For C code, the type names may also have the form @samp{class
15077 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15078 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15081 @item ptype [@var{arg}]
15082 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15083 detailed description of the type, instead of just the name of the type.
15084 @xref{Expressions, ,Expressions}.
15086 Contrary to @code{whatis}, @code{ptype} always unrolls any
15087 @code{typedef}s in its argument declaration, whether the argument is
15088 a variable, expression, or a data type. This means that @code{ptype}
15089 of a variable or an expression will not print literally its type as
15090 present in the source code---use @code{whatis} for that. @code{typedef}s at
15091 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15092 fields, methods and inner @code{class typedef}s of @code{struct}s,
15093 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15095 For example, for this variable declaration:
15098 typedef double real_t;
15099 struct complex @{ real_t real; double imag; @};
15100 typedef struct complex complex_t;
15102 real_t *real_pointer_var;
15106 the two commands give this output:
15110 (@value{GDBP}) whatis var
15112 (@value{GDBP}) ptype var
15113 type = struct complex @{
15117 (@value{GDBP}) whatis complex_t
15118 type = struct complex
15119 (@value{GDBP}) whatis struct complex
15120 type = struct complex
15121 (@value{GDBP}) ptype struct complex
15122 type = struct complex @{
15126 (@value{GDBP}) whatis real_pointer_var
15128 (@value{GDBP}) ptype real_pointer_var
15134 As with @code{whatis}, using @code{ptype} without an argument refers to
15135 the type of @code{$}, the last value in the value history.
15137 @cindex incomplete type
15138 Sometimes, programs use opaque data types or incomplete specifications
15139 of complex data structure. If the debug information included in the
15140 program does not allow @value{GDBN} to display a full declaration of
15141 the data type, it will say @samp{<incomplete type>}. For example,
15142 given these declarations:
15146 struct foo *fooptr;
15150 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15153 (@value{GDBP}) ptype foo
15154 $1 = <incomplete type>
15158 ``Incomplete type'' is C terminology for data types that are not
15159 completely specified.
15162 @item info types @var{regexp}
15164 Print a brief description of all types whose names match the regular
15165 expression @var{regexp} (or all types in your program, if you supply
15166 no argument). Each complete typename is matched as though it were a
15167 complete line; thus, @samp{i type value} gives information on all
15168 types in your program whose names include the string @code{value}, but
15169 @samp{i type ^value$} gives information only on types whose complete
15170 name is @code{value}.
15172 This command differs from @code{ptype} in two ways: first, like
15173 @code{whatis}, it does not print a detailed description; second, it
15174 lists all source files where a type is defined.
15177 @cindex local variables
15178 @item info scope @var{location}
15179 List all the variables local to a particular scope. This command
15180 accepts a @var{location} argument---a function name, a source line, or
15181 an address preceded by a @samp{*}, and prints all the variables local
15182 to the scope defined by that location. (@xref{Specify Location}, for
15183 details about supported forms of @var{location}.) For example:
15186 (@value{GDBP}) @b{info scope command_line_handler}
15187 Scope for command_line_handler:
15188 Symbol rl is an argument at stack/frame offset 8, length 4.
15189 Symbol linebuffer is in static storage at address 0x150a18, length 4.
15190 Symbol linelength is in static storage at address 0x150a1c, length 4.
15191 Symbol p is a local variable in register $esi, length 4.
15192 Symbol p1 is a local variable in register $ebx, length 4.
15193 Symbol nline is a local variable in register $edx, length 4.
15194 Symbol repeat is a local variable at frame offset -8, length 4.
15198 This command is especially useful for determining what data to collect
15199 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
15202 @kindex info source
15204 Show information about the current source file---that is, the source file for
15205 the function containing the current point of execution:
15208 the name of the source file, and the directory containing it,
15210 the directory it was compiled in,
15212 its length, in lines,
15214 which programming language it is written in,
15216 whether the executable includes debugging information for that file, and
15217 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
15219 whether the debugging information includes information about
15220 preprocessor macros.
15224 @kindex info sources
15226 Print the names of all source files in your program for which there is
15227 debugging information, organized into two lists: files whose symbols
15228 have already been read, and files whose symbols will be read when needed.
15230 @kindex info functions
15231 @item info functions
15232 Print the names and data types of all defined functions.
15234 @item info functions @var{regexp}
15235 Print the names and data types of all defined functions
15236 whose names contain a match for regular expression @var{regexp}.
15237 Thus, @samp{info fun step} finds all functions whose names
15238 include @code{step}; @samp{info fun ^step} finds those whose names
15239 start with @code{step}. If a function name contains characters
15240 that conflict with the regular expression language (e.g.@:
15241 @samp{operator*()}), they may be quoted with a backslash.
15243 @kindex info variables
15244 @item info variables
15245 Print the names and data types of all variables that are defined
15246 outside of functions (i.e.@: excluding local variables).
15248 @item info variables @var{regexp}
15249 Print the names and data types of all variables (except for local
15250 variables) whose names contain a match for regular expression
15253 @kindex info classes
15254 @cindex Objective-C, classes and selectors
15256 @itemx info classes @var{regexp}
15257 Display all Objective-C classes in your program, or
15258 (with the @var{regexp} argument) all those matching a particular regular
15261 @kindex info selectors
15262 @item info selectors
15263 @itemx info selectors @var{regexp}
15264 Display all Objective-C selectors in your program, or
15265 (with the @var{regexp} argument) all those matching a particular regular
15269 This was never implemented.
15270 @kindex info methods
15272 @itemx info methods @var{regexp}
15273 The @code{info methods} command permits the user to examine all defined
15274 methods within C@t{++} program, or (with the @var{regexp} argument) a
15275 specific set of methods found in the various C@t{++} classes. Many
15276 C@t{++} classes provide a large number of methods. Thus, the output
15277 from the @code{ptype} command can be overwhelming and hard to use. The
15278 @code{info-methods} command filters the methods, printing only those
15279 which match the regular-expression @var{regexp}.
15282 @cindex opaque data types
15283 @kindex set opaque-type-resolution
15284 @item set opaque-type-resolution on
15285 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
15286 declared as a pointer to a @code{struct}, @code{class}, or
15287 @code{union}---for example, @code{struct MyType *}---that is used in one
15288 source file although the full declaration of @code{struct MyType} is in
15289 another source file. The default is on.
15291 A change in the setting of this subcommand will not take effect until
15292 the next time symbols for a file are loaded.
15294 @item set opaque-type-resolution off
15295 Tell @value{GDBN} not to resolve opaque types. In this case, the type
15296 is printed as follows:
15298 @{<no data fields>@}
15301 @kindex show opaque-type-resolution
15302 @item show opaque-type-resolution
15303 Show whether opaque types are resolved or not.
15305 @kindex maint print symbols
15306 @cindex symbol dump
15307 @kindex maint print psymbols
15308 @cindex partial symbol dump
15309 @item maint print symbols @var{filename}
15310 @itemx maint print psymbols @var{filename}
15311 @itemx maint print msymbols @var{filename}
15312 Write a dump of debugging symbol data into the file @var{filename}.
15313 These commands are used to debug the @value{GDBN} symbol-reading code. Only
15314 symbols with debugging data are included. If you use @samp{maint print
15315 symbols}, @value{GDBN} includes all the symbols for which it has already
15316 collected full details: that is, @var{filename} reflects symbols for
15317 only those files whose symbols @value{GDBN} has read. You can use the
15318 command @code{info sources} to find out which files these are. If you
15319 use @samp{maint print psymbols} instead, the dump shows information about
15320 symbols that @value{GDBN} only knows partially---that is, symbols defined in
15321 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
15322 @samp{maint print msymbols} dumps just the minimal symbol information
15323 required for each object file from which @value{GDBN} has read some symbols.
15324 @xref{Files, ,Commands to Specify Files}, for a discussion of how
15325 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
15327 @kindex maint info symtabs
15328 @kindex maint info psymtabs
15329 @cindex listing @value{GDBN}'s internal symbol tables
15330 @cindex symbol tables, listing @value{GDBN}'s internal
15331 @cindex full symbol tables, listing @value{GDBN}'s internal
15332 @cindex partial symbol tables, listing @value{GDBN}'s internal
15333 @item maint info symtabs @r{[} @var{regexp} @r{]}
15334 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
15336 List the @code{struct symtab} or @code{struct partial_symtab}
15337 structures whose names match @var{regexp}. If @var{regexp} is not
15338 given, list them all. The output includes expressions which you can
15339 copy into a @value{GDBN} debugging this one to examine a particular
15340 structure in more detail. For example:
15343 (@value{GDBP}) maint info psymtabs dwarf2read
15344 @{ objfile /home/gnu/build/gdb/gdb
15345 ((struct objfile *) 0x82e69d0)
15346 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
15347 ((struct partial_symtab *) 0x8474b10)
15350 text addresses 0x814d3c8 -- 0x8158074
15351 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
15352 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
15353 dependencies (none)
15356 (@value{GDBP}) maint info symtabs
15360 We see that there is one partial symbol table whose filename contains
15361 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
15362 and we see that @value{GDBN} has not read in any symtabs yet at all.
15363 If we set a breakpoint on a function, that will cause @value{GDBN} to
15364 read the symtab for the compilation unit containing that function:
15367 (@value{GDBP}) break dwarf2_psymtab_to_symtab
15368 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
15370 (@value{GDBP}) maint info symtabs
15371 @{ objfile /home/gnu/build/gdb/gdb
15372 ((struct objfile *) 0x82e69d0)
15373 @{ symtab /home/gnu/src/gdb/dwarf2read.c
15374 ((struct symtab *) 0x86c1f38)
15377 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
15378 linetable ((struct linetable *) 0x8370fa0)
15379 debugformat DWARF 2
15388 @chapter Altering Execution
15390 Once you think you have found an error in your program, you might want to
15391 find out for certain whether correcting the apparent error would lead to
15392 correct results in the rest of the run. You can find the answer by
15393 experiment, using the @value{GDBN} features for altering execution of the
15396 For example, you can store new values into variables or memory
15397 locations, give your program a signal, restart it at a different
15398 address, or even return prematurely from a function.
15401 * Assignment:: Assignment to variables
15402 * Jumping:: Continuing at a different address
15403 * Signaling:: Giving your program a signal
15404 * Returning:: Returning from a function
15405 * Calling:: Calling your program's functions
15406 * Patching:: Patching your program
15410 @section Assignment to Variables
15413 @cindex setting variables
15414 To alter the value of a variable, evaluate an assignment expression.
15415 @xref{Expressions, ,Expressions}. For example,
15422 stores the value 4 into the variable @code{x}, and then prints the
15423 value of the assignment expression (which is 4).
15424 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
15425 information on operators in supported languages.
15427 @kindex set variable
15428 @cindex variables, setting
15429 If you are not interested in seeing the value of the assignment, use the
15430 @code{set} command instead of the @code{print} command. @code{set} is
15431 really the same as @code{print} except that the expression's value is
15432 not printed and is not put in the value history (@pxref{Value History,
15433 ,Value History}). The expression is evaluated only for its effects.
15435 If the beginning of the argument string of the @code{set} command
15436 appears identical to a @code{set} subcommand, use the @code{set
15437 variable} command instead of just @code{set}. This command is identical
15438 to @code{set} except for its lack of subcommands. For example, if your
15439 program has a variable @code{width}, you get an error if you try to set
15440 a new value with just @samp{set width=13}, because @value{GDBN} has the
15441 command @code{set width}:
15444 (@value{GDBP}) whatis width
15446 (@value{GDBP}) p width
15448 (@value{GDBP}) set width=47
15449 Invalid syntax in expression.
15453 The invalid expression, of course, is @samp{=47}. In
15454 order to actually set the program's variable @code{width}, use
15457 (@value{GDBP}) set var width=47
15460 Because the @code{set} command has many subcommands that can conflict
15461 with the names of program variables, it is a good idea to use the
15462 @code{set variable} command instead of just @code{set}. For example, if
15463 your program has a variable @code{g}, you run into problems if you try
15464 to set a new value with just @samp{set g=4}, because @value{GDBN} has
15465 the command @code{set gnutarget}, abbreviated @code{set g}:
15469 (@value{GDBP}) whatis g
15473 (@value{GDBP}) set g=4
15477 The program being debugged has been started already.
15478 Start it from the beginning? (y or n) y
15479 Starting program: /home/smith/cc_progs/a.out
15480 "/home/smith/cc_progs/a.out": can't open to read symbols:
15481 Invalid bfd target.
15482 (@value{GDBP}) show g
15483 The current BFD target is "=4".
15488 The program variable @code{g} did not change, and you silently set the
15489 @code{gnutarget} to an invalid value. In order to set the variable
15493 (@value{GDBP}) set var g=4
15496 @value{GDBN} allows more implicit conversions in assignments than C; you can
15497 freely store an integer value into a pointer variable or vice versa,
15498 and you can convert any structure to any other structure that is the
15499 same length or shorter.
15500 @comment FIXME: how do structs align/pad in these conversions?
15501 @comment /doc@cygnus.com 18dec1990
15503 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
15504 construct to generate a value of specified type at a specified address
15505 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
15506 to memory location @code{0x83040} as an integer (which implies a certain size
15507 and representation in memory), and
15510 set @{int@}0x83040 = 4
15514 stores the value 4 into that memory location.
15517 @section Continuing at a Different Address
15519 Ordinarily, when you continue your program, you do so at the place where
15520 it stopped, with the @code{continue} command. You can instead continue at
15521 an address of your own choosing, with the following commands:
15525 @kindex j @r{(@code{jump})}
15526 @item jump @var{linespec}
15527 @itemx j @var{linespec}
15528 @itemx jump @var{location}
15529 @itemx j @var{location}
15530 Resume execution at line @var{linespec} or at address given by
15531 @var{location}. Execution stops again immediately if there is a
15532 breakpoint there. @xref{Specify Location}, for a description of the
15533 different forms of @var{linespec} and @var{location}. It is common
15534 practice to use the @code{tbreak} command in conjunction with
15535 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
15537 The @code{jump} command does not change the current stack frame, or
15538 the stack pointer, or the contents of any memory location or any
15539 register other than the program counter. If line @var{linespec} is in
15540 a different function from the one currently executing, the results may
15541 be bizarre if the two functions expect different patterns of arguments or
15542 of local variables. For this reason, the @code{jump} command requests
15543 confirmation if the specified line is not in the function currently
15544 executing. However, even bizarre results are predictable if you are
15545 well acquainted with the machine-language code of your program.
15548 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
15549 On many systems, you can get much the same effect as the @code{jump}
15550 command by storing a new value into the register @code{$pc}. The
15551 difference is that this does not start your program running; it only
15552 changes the address of where it @emph{will} run when you continue. For
15560 makes the next @code{continue} command or stepping command execute at
15561 address @code{0x485}, rather than at the address where your program stopped.
15562 @xref{Continuing and Stepping, ,Continuing and Stepping}.
15564 The most common occasion to use the @code{jump} command is to back
15565 up---perhaps with more breakpoints set---over a portion of a program
15566 that has already executed, in order to examine its execution in more
15571 @section Giving your Program a Signal
15572 @cindex deliver a signal to a program
15576 @item signal @var{signal}
15577 Resume execution where your program stopped, but immediately give it the
15578 signal @var{signal}. @var{signal} can be the name or the number of a
15579 signal. For example, on many systems @code{signal 2} and @code{signal
15580 SIGINT} are both ways of sending an interrupt signal.
15582 Alternatively, if @var{signal} is zero, continue execution without
15583 giving a signal. This is useful when your program stopped on account of
15584 a signal and would ordinary see the signal when resumed with the
15585 @code{continue} command; @samp{signal 0} causes it to resume without a
15588 @code{signal} does not repeat when you press @key{RET} a second time
15589 after executing the command.
15593 Invoking the @code{signal} command is not the same as invoking the
15594 @code{kill} utility from the shell. Sending a signal with @code{kill}
15595 causes @value{GDBN} to decide what to do with the signal depending on
15596 the signal handling tables (@pxref{Signals}). The @code{signal} command
15597 passes the signal directly to your program.
15601 @section Returning from a Function
15604 @cindex returning from a function
15607 @itemx return @var{expression}
15608 You can cancel execution of a function call with the @code{return}
15609 command. If you give an
15610 @var{expression} argument, its value is used as the function's return
15614 When you use @code{return}, @value{GDBN} discards the selected stack frame
15615 (and all frames within it). You can think of this as making the
15616 discarded frame return prematurely. If you wish to specify a value to
15617 be returned, give that value as the argument to @code{return}.
15619 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15620 Frame}), and any other frames inside of it, leaving its caller as the
15621 innermost remaining frame. That frame becomes selected. The
15622 specified value is stored in the registers used for returning values
15625 The @code{return} command does not resume execution; it leaves the
15626 program stopped in the state that would exist if the function had just
15627 returned. In contrast, the @code{finish} command (@pxref{Continuing
15628 and Stepping, ,Continuing and Stepping}) resumes execution until the
15629 selected stack frame returns naturally.
15631 @value{GDBN} needs to know how the @var{expression} argument should be set for
15632 the inferior. The concrete registers assignment depends on the OS ABI and the
15633 type being returned by the selected stack frame. For example it is common for
15634 OS ABI to return floating point values in FPU registers while integer values in
15635 CPU registers. Still some ABIs return even floating point values in CPU
15636 registers. Larger integer widths (such as @code{long long int}) also have
15637 specific placement rules. @value{GDBN} already knows the OS ABI from its
15638 current target so it needs to find out also the type being returned to make the
15639 assignment into the right register(s).
15641 Normally, the selected stack frame has debug info. @value{GDBN} will always
15642 use the debug info instead of the implicit type of @var{expression} when the
15643 debug info is available. For example, if you type @kbd{return -1}, and the
15644 function in the current stack frame is declared to return a @code{long long
15645 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15646 into a @code{long long int}:
15649 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15651 (@value{GDBP}) return -1
15652 Make func return now? (y or n) y
15653 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15654 43 printf ("result=%lld\n", func ());
15658 However, if the selected stack frame does not have a debug info, e.g., if the
15659 function was compiled without debug info, @value{GDBN} has to find out the type
15660 to return from user. Specifying a different type by mistake may set the value
15661 in different inferior registers than the caller code expects. For example,
15662 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15663 of a @code{long long int} result for a debug info less function (on 32-bit
15664 architectures). Therefore the user is required to specify the return type by
15665 an appropriate cast explicitly:
15668 Breakpoint 2, 0x0040050b in func ()
15669 (@value{GDBP}) return -1
15670 Return value type not available for selected stack frame.
15671 Please use an explicit cast of the value to return.
15672 (@value{GDBP}) return (long long int) -1
15673 Make selected stack frame return now? (y or n) y
15674 #0 0x00400526 in main ()
15679 @section Calling Program Functions
15682 @cindex calling functions
15683 @cindex inferior functions, calling
15684 @item print @var{expr}
15685 Evaluate the expression @var{expr} and display the resulting value.
15686 @var{expr} may include calls to functions in the program being
15690 @item call @var{expr}
15691 Evaluate the expression @var{expr} without displaying @code{void}
15694 You can use this variant of the @code{print} command if you want to
15695 execute a function from your program that does not return anything
15696 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15697 with @code{void} returned values that @value{GDBN} will otherwise
15698 print. If the result is not void, it is printed and saved in the
15702 It is possible for the function you call via the @code{print} or
15703 @code{call} command to generate a signal (e.g., if there's a bug in
15704 the function, or if you passed it incorrect arguments). What happens
15705 in that case is controlled by the @code{set unwindonsignal} command.
15707 Similarly, with a C@t{++} program it is possible for the function you
15708 call via the @code{print} or @code{call} command to generate an
15709 exception that is not handled due to the constraints of the dummy
15710 frame. In this case, any exception that is raised in the frame, but has
15711 an out-of-frame exception handler will not be found. GDB builds a
15712 dummy-frame for the inferior function call, and the unwinder cannot
15713 seek for exception handlers outside of this dummy-frame. What happens
15714 in that case is controlled by the
15715 @code{set unwind-on-terminating-exception} command.
15718 @item set unwindonsignal
15719 @kindex set unwindonsignal
15720 @cindex unwind stack in called functions
15721 @cindex call dummy stack unwinding
15722 Set unwinding of the stack if a signal is received while in a function
15723 that @value{GDBN} called in the program being debugged. If set to on,
15724 @value{GDBN} unwinds the stack it created for the call and restores
15725 the context to what it was before the call. If set to off (the
15726 default), @value{GDBN} stops in the frame where the signal was
15729 @item show unwindonsignal
15730 @kindex show unwindonsignal
15731 Show the current setting of stack unwinding in the functions called by
15734 @item set unwind-on-terminating-exception
15735 @kindex set unwind-on-terminating-exception
15736 @cindex unwind stack in called functions with unhandled exceptions
15737 @cindex call dummy stack unwinding on unhandled exception.
15738 Set unwinding of the stack if a C@t{++} exception is raised, but left
15739 unhandled while in a function that @value{GDBN} called in the program being
15740 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15741 it created for the call and restores the context to what it was before
15742 the call. If set to off, @value{GDBN} the exception is delivered to
15743 the default C@t{++} exception handler and the inferior terminated.
15745 @item show unwind-on-terminating-exception
15746 @kindex show unwind-on-terminating-exception
15747 Show the current setting of stack unwinding in the functions called by
15752 @cindex weak alias functions
15753 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15754 for another function. In such case, @value{GDBN} might not pick up
15755 the type information, including the types of the function arguments,
15756 which causes @value{GDBN} to call the inferior function incorrectly.
15757 As a result, the called function will function erroneously and may
15758 even crash. A solution to that is to use the name of the aliased
15762 @section Patching Programs
15764 @cindex patching binaries
15765 @cindex writing into executables
15766 @cindex writing into corefiles
15768 By default, @value{GDBN} opens the file containing your program's
15769 executable code (or the corefile) read-only. This prevents accidental
15770 alterations to machine code; but it also prevents you from intentionally
15771 patching your program's binary.
15773 If you'd like to be able to patch the binary, you can specify that
15774 explicitly with the @code{set write} command. For example, you might
15775 want to turn on internal debugging flags, or even to make emergency
15781 @itemx set write off
15782 If you specify @samp{set write on}, @value{GDBN} opens executable and
15783 core files for both reading and writing; if you specify @kbd{set write
15784 off} (the default), @value{GDBN} opens them read-only.
15786 If you have already loaded a file, you must load it again (using the
15787 @code{exec-file} or @code{core-file} command) after changing @code{set
15788 write}, for your new setting to take effect.
15792 Display whether executable files and core files are opened for writing
15793 as well as reading.
15797 @chapter @value{GDBN} Files
15799 @value{GDBN} needs to know the file name of the program to be debugged,
15800 both in order to read its symbol table and in order to start your
15801 program. To debug a core dump of a previous run, you must also tell
15802 @value{GDBN} the name of the core dump file.
15805 * Files:: Commands to specify files
15806 * Separate Debug Files:: Debugging information in separate files
15807 * Index Files:: Index files speed up GDB
15808 * Symbol Errors:: Errors reading symbol files
15809 * Data Files:: GDB data files
15813 @section Commands to Specify Files
15815 @cindex symbol table
15816 @cindex core dump file
15818 You may want to specify executable and core dump file names. The usual
15819 way to do this is at start-up time, using the arguments to
15820 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15821 Out of @value{GDBN}}).
15823 Occasionally it is necessary to change to a different file during a
15824 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15825 specify a file you want to use. Or you are debugging a remote target
15826 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15827 Program}). In these situations the @value{GDBN} commands to specify
15828 new files are useful.
15831 @cindex executable file
15833 @item file @var{filename}
15834 Use @var{filename} as the program to be debugged. It is read for its
15835 symbols and for the contents of pure memory. It is also the program
15836 executed when you use the @code{run} command. If you do not specify a
15837 directory and the file is not found in the @value{GDBN} working directory,
15838 @value{GDBN} uses the environment variable @code{PATH} as a list of
15839 directories to search, just as the shell does when looking for a program
15840 to run. You can change the value of this variable, for both @value{GDBN}
15841 and your program, using the @code{path} command.
15843 @cindex unlinked object files
15844 @cindex patching object files
15845 You can load unlinked object @file{.o} files into @value{GDBN} using
15846 the @code{file} command. You will not be able to ``run'' an object
15847 file, but you can disassemble functions and inspect variables. Also,
15848 if the underlying BFD functionality supports it, you could use
15849 @kbd{gdb -write} to patch object files using this technique. Note
15850 that @value{GDBN} can neither interpret nor modify relocations in this
15851 case, so branches and some initialized variables will appear to go to
15852 the wrong place. But this feature is still handy from time to time.
15855 @code{file} with no argument makes @value{GDBN} discard any information it
15856 has on both executable file and the symbol table.
15859 @item exec-file @r{[} @var{filename} @r{]}
15860 Specify that the program to be run (but not the symbol table) is found
15861 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15862 if necessary to locate your program. Omitting @var{filename} means to
15863 discard information on the executable file.
15865 @kindex symbol-file
15866 @item symbol-file @r{[} @var{filename} @r{]}
15867 Read symbol table information from file @var{filename}. @code{PATH} is
15868 searched when necessary. Use the @code{file} command to get both symbol
15869 table and program to run from the same file.
15871 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15872 program's symbol table.
15874 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15875 some breakpoints and auto-display expressions. This is because they may
15876 contain pointers to the internal data recording symbols and data types,
15877 which are part of the old symbol table data being discarded inside
15880 @code{symbol-file} does not repeat if you press @key{RET} again after
15883 When @value{GDBN} is configured for a particular environment, it
15884 understands debugging information in whatever format is the standard
15885 generated for that environment; you may use either a @sc{gnu} compiler, or
15886 other compilers that adhere to the local conventions.
15887 Best results are usually obtained from @sc{gnu} compilers; for example,
15888 using @code{@value{NGCC}} you can generate debugging information for
15891 For most kinds of object files, with the exception of old SVR3 systems
15892 using COFF, the @code{symbol-file} command does not normally read the
15893 symbol table in full right away. Instead, it scans the symbol table
15894 quickly to find which source files and which symbols are present. The
15895 details are read later, one source file at a time, as they are needed.
15897 The purpose of this two-stage reading strategy is to make @value{GDBN}
15898 start up faster. For the most part, it is invisible except for
15899 occasional pauses while the symbol table details for a particular source
15900 file are being read. (The @code{set verbose} command can turn these
15901 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15902 Warnings and Messages}.)
15904 We have not implemented the two-stage strategy for COFF yet. When the
15905 symbol table is stored in COFF format, @code{symbol-file} reads the
15906 symbol table data in full right away. Note that ``stabs-in-COFF''
15907 still does the two-stage strategy, since the debug info is actually
15911 @cindex reading symbols immediately
15912 @cindex symbols, reading immediately
15913 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15914 @itemx file @r{[} -readnow @r{]} @var{filename}
15915 You can override the @value{GDBN} two-stage strategy for reading symbol
15916 tables by using the @samp{-readnow} option with any of the commands that
15917 load symbol table information, if you want to be sure @value{GDBN} has the
15918 entire symbol table available.
15920 @c FIXME: for now no mention of directories, since this seems to be in
15921 @c flux. 13mar1992 status is that in theory GDB would look either in
15922 @c current dir or in same dir as myprog; but issues like competing
15923 @c GDB's, or clutter in system dirs, mean that in practice right now
15924 @c only current dir is used. FFish says maybe a special GDB hierarchy
15925 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15929 @item core-file @r{[}@var{filename}@r{]}
15931 Specify the whereabouts of a core dump file to be used as the ``contents
15932 of memory''. Traditionally, core files contain only some parts of the
15933 address space of the process that generated them; @value{GDBN} can access the
15934 executable file itself for other parts.
15936 @code{core-file} with no argument specifies that no core file is
15939 Note that the core file is ignored when your program is actually running
15940 under @value{GDBN}. So, if you have been running your program and you
15941 wish to debug a core file instead, you must kill the subprocess in which
15942 the program is running. To do this, use the @code{kill} command
15943 (@pxref{Kill Process, ,Killing the Child Process}).
15945 @kindex add-symbol-file
15946 @cindex dynamic linking
15947 @item add-symbol-file @var{filename} @var{address}
15948 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15949 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15950 The @code{add-symbol-file} command reads additional symbol table
15951 information from the file @var{filename}. You would use this command
15952 when @var{filename} has been dynamically loaded (by some other means)
15953 into the program that is running. @var{address} should be the memory
15954 address at which the file has been loaded; @value{GDBN} cannot figure
15955 this out for itself. You can additionally specify an arbitrary number
15956 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15957 section name and base address for that section. You can specify any
15958 @var{address} as an expression.
15960 The symbol table of the file @var{filename} is added to the symbol table
15961 originally read with the @code{symbol-file} command. You can use the
15962 @code{add-symbol-file} command any number of times; the new symbol data
15963 thus read keeps adding to the old. To discard all old symbol data
15964 instead, use the @code{symbol-file} command without any arguments.
15966 @cindex relocatable object files, reading symbols from
15967 @cindex object files, relocatable, reading symbols from
15968 @cindex reading symbols from relocatable object files
15969 @cindex symbols, reading from relocatable object files
15970 @cindex @file{.o} files, reading symbols from
15971 Although @var{filename} is typically a shared library file, an
15972 executable file, or some other object file which has been fully
15973 relocated for loading into a process, you can also load symbolic
15974 information from relocatable @file{.o} files, as long as:
15978 the file's symbolic information refers only to linker symbols defined in
15979 that file, not to symbols defined by other object files,
15981 every section the file's symbolic information refers to has actually
15982 been loaded into the inferior, as it appears in the file, and
15984 you can determine the address at which every section was loaded, and
15985 provide these to the @code{add-symbol-file} command.
15989 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15990 relocatable files into an already running program; such systems
15991 typically make the requirements above easy to meet. However, it's
15992 important to recognize that many native systems use complex link
15993 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15994 assembly, for example) that make the requirements difficult to meet. In
15995 general, one cannot assume that using @code{add-symbol-file} to read a
15996 relocatable object file's symbolic information will have the same effect
15997 as linking the relocatable object file into the program in the normal
16000 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16002 @kindex add-symbol-file-from-memory
16003 @cindex @code{syscall DSO}
16004 @cindex load symbols from memory
16005 @item add-symbol-file-from-memory @var{address}
16006 Load symbols from the given @var{address} in a dynamically loaded
16007 object file whose image is mapped directly into the inferior's memory.
16008 For example, the Linux kernel maps a @code{syscall DSO} into each
16009 process's address space; this DSO provides kernel-specific code for
16010 some system calls. The argument can be any expression whose
16011 evaluation yields the address of the file's shared object file header.
16012 For this command to work, you must have used @code{symbol-file} or
16013 @code{exec-file} commands in advance.
16015 @kindex add-shared-symbol-files
16017 @item add-shared-symbol-files @var{library-file}
16018 @itemx assf @var{library-file}
16019 The @code{add-shared-symbol-files} command can currently be used only
16020 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16021 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16022 @value{GDBN} automatically looks for shared libraries, however if
16023 @value{GDBN} does not find yours, you can invoke
16024 @code{add-shared-symbol-files}. It takes one argument: the shared
16025 library's file name. @code{assf} is a shorthand alias for
16026 @code{add-shared-symbol-files}.
16029 @item section @var{section} @var{addr}
16030 The @code{section} command changes the base address of the named
16031 @var{section} of the exec file to @var{addr}. This can be used if the
16032 exec file does not contain section addresses, (such as in the
16033 @code{a.out} format), or when the addresses specified in the file
16034 itself are wrong. Each section must be changed separately. The
16035 @code{info files} command, described below, lists all the sections and
16039 @kindex info target
16042 @code{info files} and @code{info target} are synonymous; both print the
16043 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16044 including the names of the executable and core dump files currently in
16045 use by @value{GDBN}, and the files from which symbols were loaded. The
16046 command @code{help target} lists all possible targets rather than
16049 @kindex maint info sections
16050 @item maint info sections
16051 Another command that can give you extra information about program sections
16052 is @code{maint info sections}. In addition to the section information
16053 displayed by @code{info files}, this command displays the flags and file
16054 offset of each section in the executable and core dump files. In addition,
16055 @code{maint info sections} provides the following command options (which
16056 may be arbitrarily combined):
16060 Display sections for all loaded object files, including shared libraries.
16061 @item @var{sections}
16062 Display info only for named @var{sections}.
16063 @item @var{section-flags}
16064 Display info only for sections for which @var{section-flags} are true.
16065 The section flags that @value{GDBN} currently knows about are:
16068 Section will have space allocated in the process when loaded.
16069 Set for all sections except those containing debug information.
16071 Section will be loaded from the file into the child process memory.
16072 Set for pre-initialized code and data, clear for @code{.bss} sections.
16074 Section needs to be relocated before loading.
16076 Section cannot be modified by the child process.
16078 Section contains executable code only.
16080 Section contains data only (no executable code).
16082 Section will reside in ROM.
16084 Section contains data for constructor/destructor lists.
16086 Section is not empty.
16088 An instruction to the linker to not output the section.
16089 @item COFF_SHARED_LIBRARY
16090 A notification to the linker that the section contains
16091 COFF shared library information.
16093 Section contains common symbols.
16096 @kindex set trust-readonly-sections
16097 @cindex read-only sections
16098 @item set trust-readonly-sections on
16099 Tell @value{GDBN} that readonly sections in your object file
16100 really are read-only (i.e.@: that their contents will not change).
16101 In that case, @value{GDBN} can fetch values from these sections
16102 out of the object file, rather than from the target program.
16103 For some targets (notably embedded ones), this can be a significant
16104 enhancement to debugging performance.
16106 The default is off.
16108 @item set trust-readonly-sections off
16109 Tell @value{GDBN} not to trust readonly sections. This means that
16110 the contents of the section might change while the program is running,
16111 and must therefore be fetched from the target when needed.
16113 @item show trust-readonly-sections
16114 Show the current setting of trusting readonly sections.
16117 All file-specifying commands allow both absolute and relative file names
16118 as arguments. @value{GDBN} always converts the file name to an absolute file
16119 name and remembers it that way.
16121 @cindex shared libraries
16122 @anchor{Shared Libraries}
16123 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16124 and IBM RS/6000 AIX shared libraries.
16126 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16127 shared libraries. @xref{Expat}.
16129 @value{GDBN} automatically loads symbol definitions from shared libraries
16130 when you use the @code{run} command, or when you examine a core file.
16131 (Before you issue the @code{run} command, @value{GDBN} does not understand
16132 references to a function in a shared library, however---unless you are
16133 debugging a core file).
16135 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16136 automatically loads the symbols at the time of the @code{shl_load} call.
16138 @c FIXME: some @value{GDBN} release may permit some refs to undef
16139 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16140 @c FIXME...lib; check this from time to time when updating manual
16142 There are times, however, when you may wish to not automatically load
16143 symbol definitions from shared libraries, such as when they are
16144 particularly large or there are many of them.
16146 To control the automatic loading of shared library symbols, use the
16150 @kindex set auto-solib-add
16151 @item set auto-solib-add @var{mode}
16152 If @var{mode} is @code{on}, symbols from all shared object libraries
16153 will be loaded automatically when the inferior begins execution, you
16154 attach to an independently started inferior, or when the dynamic linker
16155 informs @value{GDBN} that a new library has been loaded. If @var{mode}
16156 is @code{off}, symbols must be loaded manually, using the
16157 @code{sharedlibrary} command. The default value is @code{on}.
16159 @cindex memory used for symbol tables
16160 If your program uses lots of shared libraries with debug info that
16161 takes large amounts of memory, you can decrease the @value{GDBN}
16162 memory footprint by preventing it from automatically loading the
16163 symbols from shared libraries. To that end, type @kbd{set
16164 auto-solib-add off} before running the inferior, then load each
16165 library whose debug symbols you do need with @kbd{sharedlibrary
16166 @var{regexp}}, where @var{regexp} is a regular expression that matches
16167 the libraries whose symbols you want to be loaded.
16169 @kindex show auto-solib-add
16170 @item show auto-solib-add
16171 Display the current autoloading mode.
16174 @cindex load shared library
16175 To explicitly load shared library symbols, use the @code{sharedlibrary}
16179 @kindex info sharedlibrary
16181 @item info share @var{regex}
16182 @itemx info sharedlibrary @var{regex}
16183 Print the names of the shared libraries which are currently loaded
16184 that match @var{regex}. If @var{regex} is omitted then print
16185 all shared libraries that are loaded.
16187 @kindex sharedlibrary
16189 @item sharedlibrary @var{regex}
16190 @itemx share @var{regex}
16191 Load shared object library symbols for files matching a
16192 Unix regular expression.
16193 As with files loaded automatically, it only loads shared libraries
16194 required by your program for a core file or after typing @code{run}. If
16195 @var{regex} is omitted all shared libraries required by your program are
16198 @item nosharedlibrary
16199 @kindex nosharedlibrary
16200 @cindex unload symbols from shared libraries
16201 Unload all shared object library symbols. This discards all symbols
16202 that have been loaded from all shared libraries. Symbols from shared
16203 libraries that were loaded by explicit user requests are not
16207 Sometimes you may wish that @value{GDBN} stops and gives you control
16208 when any of shared library events happen. The best way to do this is
16209 to use @code{catch load} and @code{catch unload} (@pxref{Set
16212 @value{GDBN} also supports the the @code{set stop-on-solib-events}
16213 command for this. This command exists for historical reasons. It is
16214 less useful than setting a catchpoint, because it does not allow for
16215 conditions or commands as a catchpoint does.
16218 @item set stop-on-solib-events
16219 @kindex set stop-on-solib-events
16220 This command controls whether @value{GDBN} should give you control
16221 when the dynamic linker notifies it about some shared library event.
16222 The most common event of interest is loading or unloading of a new
16225 @item show stop-on-solib-events
16226 @kindex show stop-on-solib-events
16227 Show whether @value{GDBN} stops and gives you control when shared
16228 library events happen.
16231 Shared libraries are also supported in many cross or remote debugging
16232 configurations. @value{GDBN} needs to have access to the target's libraries;
16233 this can be accomplished either by providing copies of the libraries
16234 on the host system, or by asking @value{GDBN} to automatically retrieve the
16235 libraries from the target. If copies of the target libraries are
16236 provided, they need to be the same as the target libraries, although the
16237 copies on the target can be stripped as long as the copies on the host are
16240 @cindex where to look for shared libraries
16241 For remote debugging, you need to tell @value{GDBN} where the target
16242 libraries are, so that it can load the correct copies---otherwise, it
16243 may try to load the host's libraries. @value{GDBN} has two variables
16244 to specify the search directories for target libraries.
16247 @cindex prefix for shared library file names
16248 @cindex system root, alternate
16249 @kindex set solib-absolute-prefix
16250 @kindex set sysroot
16251 @item set sysroot @var{path}
16252 Use @var{path} as the system root for the program being debugged. Any
16253 absolute shared library paths will be prefixed with @var{path}; many
16254 runtime loaders store the absolute paths to the shared library in the
16255 target program's memory. If you use @code{set sysroot} to find shared
16256 libraries, they need to be laid out in the same way that they are on
16257 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
16260 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
16261 retrieve the target libraries from the remote system. This is only
16262 supported when using a remote target that supports the @code{remote get}
16263 command (@pxref{File Transfer,,Sending files to a remote system}).
16264 The part of @var{path} following the initial @file{remote:}
16265 (if present) is used as system root prefix on the remote file system.
16266 @footnote{If you want to specify a local system root using a directory
16267 that happens to be named @file{remote:}, you need to use some equivalent
16268 variant of the name like @file{./remote:}.}
16270 For targets with an MS-DOS based filesystem, such as MS-Windows and
16271 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
16272 absolute file name with @var{path}. But first, on Unix hosts,
16273 @value{GDBN} converts all backslash directory separators into forward
16274 slashes, because the backslash is not a directory separator on Unix:
16277 c:\foo\bar.dll @result{} c:/foo/bar.dll
16280 Then, @value{GDBN} attempts prefixing the target file name with
16281 @var{path}, and looks for the resulting file name in the host file
16285 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
16288 If that does not find the shared library, @value{GDBN} tries removing
16289 the @samp{:} character from the drive spec, both for convenience, and,
16290 for the case of the host file system not supporting file names with
16294 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
16297 This makes it possible to have a system root that mirrors a target
16298 with more than one drive. E.g., you may want to setup your local
16299 copies of the target system shared libraries like so (note @samp{c} vs
16303 @file{/path/to/sysroot/c/sys/bin/foo.dll}
16304 @file{/path/to/sysroot/c/sys/bin/bar.dll}
16305 @file{/path/to/sysroot/z/sys/bin/bar.dll}
16309 and point the system root at @file{/path/to/sysroot}, so that
16310 @value{GDBN} can find the correct copies of both
16311 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
16313 If that still does not find the shared library, @value{GDBN} tries
16314 removing the whole drive spec from the target file name:
16317 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
16320 This last lookup makes it possible to not care about the drive name,
16321 if you don't want or need to.
16323 The @code{set solib-absolute-prefix} command is an alias for @code{set
16326 @cindex default system root
16327 @cindex @samp{--with-sysroot}
16328 You can set the default system root by using the configure-time
16329 @samp{--with-sysroot} option. If the system root is inside
16330 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16331 @samp{--exec-prefix}), then the default system root will be updated
16332 automatically if the installed @value{GDBN} is moved to a new
16335 @kindex show sysroot
16337 Display the current shared library prefix.
16339 @kindex set solib-search-path
16340 @item set solib-search-path @var{path}
16341 If this variable is set, @var{path} is a colon-separated list of
16342 directories to search for shared libraries. @samp{solib-search-path}
16343 is used after @samp{sysroot} fails to locate the library, or if the
16344 path to the library is relative instead of absolute. If you want to
16345 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
16346 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
16347 finding your host's libraries. @samp{sysroot} is preferred; setting
16348 it to a nonexistent directory may interfere with automatic loading
16349 of shared library symbols.
16351 @kindex show solib-search-path
16352 @item show solib-search-path
16353 Display the current shared library search path.
16355 @cindex DOS file-name semantics of file names.
16356 @kindex set target-file-system-kind (unix|dos-based|auto)
16357 @kindex show target-file-system-kind
16358 @item set target-file-system-kind @var{kind}
16359 Set assumed file system kind for target reported file names.
16361 Shared library file names as reported by the target system may not
16362 make sense as is on the system @value{GDBN} is running on. For
16363 example, when remote debugging a target that has MS-DOS based file
16364 system semantics, from a Unix host, the target may be reporting to
16365 @value{GDBN} a list of loaded shared libraries with file names such as
16366 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
16367 drive letters, so the @samp{c:\} prefix is not normally understood as
16368 indicating an absolute file name, and neither is the backslash
16369 normally considered a directory separator character. In that case,
16370 the native file system would interpret this whole absolute file name
16371 as a relative file name with no directory components. This would make
16372 it impossible to point @value{GDBN} at a copy of the remote target's
16373 shared libraries on the host using @code{set sysroot}, and impractical
16374 with @code{set solib-search-path}. Setting
16375 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
16376 to interpret such file names similarly to how the target would, and to
16377 map them to file names valid on @value{GDBN}'s native file system
16378 semantics. The value of @var{kind} can be @code{"auto"}, in addition
16379 to one of the supported file system kinds. In that case, @value{GDBN}
16380 tries to determine the appropriate file system variant based on the
16381 current target's operating system (@pxref{ABI, ,Configuring the
16382 Current ABI}). The supported file system settings are:
16386 Instruct @value{GDBN} to assume the target file system is of Unix
16387 kind. Only file names starting the forward slash (@samp{/}) character
16388 are considered absolute, and the directory separator character is also
16392 Instruct @value{GDBN} to assume the target file system is DOS based.
16393 File names starting with either a forward slash, or a drive letter
16394 followed by a colon (e.g., @samp{c:}), are considered absolute, and
16395 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
16396 considered directory separators.
16399 Instruct @value{GDBN} to use the file system kind associated with the
16400 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
16401 This is the default.
16405 @cindex file name canonicalization
16406 @cindex base name differences
16407 When processing file names provided by the user, @value{GDBN}
16408 frequently needs to compare them to the file names recorded in the
16409 program's debug info. Normally, @value{GDBN} compares just the
16410 @dfn{base names} of the files as strings, which is reasonably fast
16411 even for very large programs. (The base name of a file is the last
16412 portion of its name, after stripping all the leading directories.)
16413 This shortcut in comparison is based upon the assumption that files
16414 cannot have more than one base name. This is usually true, but
16415 references to files that use symlinks or similar filesystem
16416 facilities violate that assumption. If your program records files
16417 using such facilities, or if you provide file names to @value{GDBN}
16418 using symlinks etc., you can set @code{basenames-may-differ} to
16419 @code{true} to instruct @value{GDBN} to completely canonicalize each
16420 pair of file names it needs to compare. This will make file-name
16421 comparisons accurate, but at a price of a significant slowdown.
16424 @item set basenames-may-differ
16425 @kindex set basenames-may-differ
16426 Set whether a source file may have multiple base names.
16428 @item show basenames-may-differ
16429 @kindex show basenames-may-differ
16430 Show whether a source file may have multiple base names.
16433 @node Separate Debug Files
16434 @section Debugging Information in Separate Files
16435 @cindex separate debugging information files
16436 @cindex debugging information in separate files
16437 @cindex @file{.debug} subdirectories
16438 @cindex debugging information directory, global
16439 @cindex global debugging information directories
16440 @cindex build ID, and separate debugging files
16441 @cindex @file{.build-id} directory
16443 @value{GDBN} allows you to put a program's debugging information in a
16444 file separate from the executable itself, in a way that allows
16445 @value{GDBN} to find and load the debugging information automatically.
16446 Since debugging information can be very large---sometimes larger
16447 than the executable code itself---some systems distribute debugging
16448 information for their executables in separate files, which users can
16449 install only when they need to debug a problem.
16451 @value{GDBN} supports two ways of specifying the separate debug info
16456 The executable contains a @dfn{debug link} that specifies the name of
16457 the separate debug info file. The separate debug file's name is
16458 usually @file{@var{executable}.debug}, where @var{executable} is the
16459 name of the corresponding executable file without leading directories
16460 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
16461 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
16462 checksum for the debug file, which @value{GDBN} uses to validate that
16463 the executable and the debug file came from the same build.
16466 The executable contains a @dfn{build ID}, a unique bit string that is
16467 also present in the corresponding debug info file. (This is supported
16468 only on some operating systems, notably those which use the ELF format
16469 for binary files and the @sc{gnu} Binutils.) For more details about
16470 this feature, see the description of the @option{--build-id}
16471 command-line option in @ref{Options, , Command Line Options, ld.info,
16472 The GNU Linker}. The debug info file's name is not specified
16473 explicitly by the build ID, but can be computed from the build ID, see
16477 Depending on the way the debug info file is specified, @value{GDBN}
16478 uses two different methods of looking for the debug file:
16482 For the ``debug link'' method, @value{GDBN} looks up the named file in
16483 the directory of the executable file, then in a subdirectory of that
16484 directory named @file{.debug}, and finally under each one of the global debug
16485 directories, in a subdirectory whose name is identical to the leading
16486 directories of the executable's absolute file name.
16489 For the ``build ID'' method, @value{GDBN} looks in the
16490 @file{.build-id} subdirectory of each one of the global debug directories for
16491 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
16492 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
16493 are the rest of the bit string. (Real build ID strings are 32 or more
16494 hex characters, not 10.)
16497 So, for example, suppose you ask @value{GDBN} to debug
16498 @file{/usr/bin/ls}, which has a debug link that specifies the
16499 file @file{ls.debug}, and a build ID whose value in hex is
16500 @code{abcdef1234}. If the list of the global debug directories includes
16501 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
16502 debug information files, in the indicated order:
16506 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
16508 @file{/usr/bin/ls.debug}
16510 @file{/usr/bin/.debug/ls.debug}
16512 @file{/usr/lib/debug/usr/bin/ls.debug}.
16515 @anchor{debug-file-directory}
16516 Global debugging info directories default to what is set by @value{GDBN}
16517 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
16518 you can also set the global debugging info directories, and view the list
16519 @value{GDBN} is currently using.
16523 @kindex set debug-file-directory
16524 @item set debug-file-directory @var{directories}
16525 Set the directories which @value{GDBN} searches for separate debugging
16526 information files to @var{directory}. Multiple path components can be set
16527 concatenating them by a path separator.
16529 @kindex show debug-file-directory
16530 @item show debug-file-directory
16531 Show the directories @value{GDBN} searches for separate debugging
16536 @cindex @code{.gnu_debuglink} sections
16537 @cindex debug link sections
16538 A debug link is a special section of the executable file named
16539 @code{.gnu_debuglink}. The section must contain:
16543 A filename, with any leading directory components removed, followed by
16546 zero to three bytes of padding, as needed to reach the next four-byte
16547 boundary within the section, and
16549 a four-byte CRC checksum, stored in the same endianness used for the
16550 executable file itself. The checksum is computed on the debugging
16551 information file's full contents by the function given below, passing
16552 zero as the @var{crc} argument.
16555 Any executable file format can carry a debug link, as long as it can
16556 contain a section named @code{.gnu_debuglink} with the contents
16559 @cindex @code{.note.gnu.build-id} sections
16560 @cindex build ID sections
16561 The build ID is a special section in the executable file (and in other
16562 ELF binary files that @value{GDBN} may consider). This section is
16563 often named @code{.note.gnu.build-id}, but that name is not mandatory.
16564 It contains unique identification for the built files---the ID remains
16565 the same across multiple builds of the same build tree. The default
16566 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
16567 content for the build ID string. The same section with an identical
16568 value is present in the original built binary with symbols, in its
16569 stripped variant, and in the separate debugging information file.
16571 The debugging information file itself should be an ordinary
16572 executable, containing a full set of linker symbols, sections, and
16573 debugging information. The sections of the debugging information file
16574 should have the same names, addresses, and sizes as the original file,
16575 but they need not contain any data---much like a @code{.bss} section
16576 in an ordinary executable.
16578 The @sc{gnu} binary utilities (Binutils) package includes the
16579 @samp{objcopy} utility that can produce
16580 the separated executable / debugging information file pairs using the
16581 following commands:
16584 @kbd{objcopy --only-keep-debug foo foo.debug}
16589 These commands remove the debugging
16590 information from the executable file @file{foo} and place it in the file
16591 @file{foo.debug}. You can use the first, second or both methods to link the
16596 The debug link method needs the following additional command to also leave
16597 behind a debug link in @file{foo}:
16600 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
16603 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
16604 a version of the @code{strip} command such that the command @kbd{strip foo -f
16605 foo.debug} has the same functionality as the two @code{objcopy} commands and
16606 the @code{ln -s} command above, together.
16609 Build ID gets embedded into the main executable using @code{ld --build-id} or
16610 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
16611 compatibility fixes for debug files separation are present in @sc{gnu} binary
16612 utilities (Binutils) package since version 2.18.
16617 @cindex CRC algorithm definition
16618 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16619 IEEE 802.3 using the polynomial:
16621 @c TexInfo requires naked braces for multi-digit exponents for Tex
16622 @c output, but this causes HTML output to barf. HTML has to be set using
16623 @c raw commands. So we end up having to specify this equation in 2
16628 <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>
16629 + <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
16635 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16636 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16640 The function is computed byte at a time, taking the least
16641 significant bit of each byte first. The initial pattern
16642 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16643 the final result is inverted to ensure trailing zeros also affect the
16646 @emph{Note:} This is the same CRC polynomial as used in handling the
16647 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16648 , @value{GDBN} Remote Serial Protocol}). However in the
16649 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16650 significant bit first, and the result is not inverted, so trailing
16651 zeros have no effect on the CRC value.
16653 To complete the description, we show below the code of the function
16654 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16655 initially supplied @code{crc} argument means that an initial call to
16656 this function passing in zero will start computing the CRC using
16659 @kindex gnu_debuglink_crc32
16662 gnu_debuglink_crc32 (unsigned long crc,
16663 unsigned char *buf, size_t len)
16665 static const unsigned long crc32_table[256] =
16667 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16668 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16669 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16670 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16671 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16672 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16673 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16674 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16675 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16676 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16677 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16678 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16679 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16680 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16681 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16682 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16683 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16684 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16685 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16686 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16687 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16688 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16689 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16690 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16691 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16692 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16693 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16694 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16695 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16696 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16697 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16698 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16699 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16700 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16701 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16702 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16703 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16704 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16705 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16706 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16707 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16708 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16709 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16710 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16711 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16712 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16713 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16714 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16715 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16716 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16717 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16720 unsigned char *end;
16722 crc = ~crc & 0xffffffff;
16723 for (end = buf + len; buf < end; ++buf)
16724 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
16725 return ~crc & 0xffffffff;
16730 This computation does not apply to the ``build ID'' method.
16734 @section Index Files Speed Up @value{GDBN}
16735 @cindex index files
16736 @cindex @samp{.gdb_index} section
16738 When @value{GDBN} finds a symbol file, it scans the symbols in the
16739 file in order to construct an internal symbol table. This lets most
16740 @value{GDBN} operations work quickly---at the cost of a delay early
16741 on. For large programs, this delay can be quite lengthy, so
16742 @value{GDBN} provides a way to build an index, which speeds up
16745 The index is stored as a section in the symbol file. @value{GDBN} can
16746 write the index to a file, then you can put it into the symbol file
16747 using @command{objcopy}.
16749 To create an index file, use the @code{save gdb-index} command:
16752 @item save gdb-index @var{directory}
16753 @kindex save gdb-index
16754 Create an index file for each symbol file currently known by
16755 @value{GDBN}. Each file is named after its corresponding symbol file,
16756 with @samp{.gdb-index} appended, and is written into the given
16760 Once you have created an index file you can merge it into your symbol
16761 file, here named @file{symfile}, using @command{objcopy}:
16764 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16765 --set-section-flags .gdb_index=readonly symfile symfile
16768 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
16769 sections that have been deprecated. Usually they are deprecated because
16770 they are missing a new feature or have performance issues.
16771 To tell @value{GDBN} to use a deprecated index section anyway
16772 specify @code{set use-deprecated-index-sections on}.
16773 The default is @code{off}.
16774 This can speed up startup, but may result in some functionality being lost.
16775 @xref{Index Section Format}.
16777 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
16778 must be done before gdb reads the file. The following will not work:
16781 $ gdb -ex "set use-deprecated-index-sections on" <program>
16784 Instead you must do, for example,
16787 $ gdb -iex "set use-deprecated-index-sections on" <program>
16790 There are currently some limitation on indices. They only work when
16791 for DWARF debugging information, not stabs. And, they do not
16792 currently work for programs using Ada.
16794 @node Symbol Errors
16795 @section Errors Reading Symbol Files
16797 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16798 such as symbol types it does not recognize, or known bugs in compiler
16799 output. By default, @value{GDBN} does not notify you of such problems, since
16800 they are relatively common and primarily of interest to people
16801 debugging compilers. If you are interested in seeing information
16802 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16803 only one message about each such type of problem, no matter how many
16804 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16805 to see how many times the problems occur, with the @code{set
16806 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16809 The messages currently printed, and their meanings, include:
16812 @item inner block not inside outer block in @var{symbol}
16814 The symbol information shows where symbol scopes begin and end
16815 (such as at the start of a function or a block of statements). This
16816 error indicates that an inner scope block is not fully contained
16817 in its outer scope blocks.
16819 @value{GDBN} circumvents the problem by treating the inner block as if it had
16820 the same scope as the outer block. In the error message, @var{symbol}
16821 may be shown as ``@code{(don't know)}'' if the outer block is not a
16824 @item block at @var{address} out of order
16826 The symbol information for symbol scope blocks should occur in
16827 order of increasing addresses. This error indicates that it does not
16830 @value{GDBN} does not circumvent this problem, and has trouble
16831 locating symbols in the source file whose symbols it is reading. (You
16832 can often determine what source file is affected by specifying
16833 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16836 @item bad block start address patched
16838 The symbol information for a symbol scope block has a start address
16839 smaller than the address of the preceding source line. This is known
16840 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16842 @value{GDBN} circumvents the problem by treating the symbol scope block as
16843 starting on the previous source line.
16845 @item bad string table offset in symbol @var{n}
16848 Symbol number @var{n} contains a pointer into the string table which is
16849 larger than the size of the string table.
16851 @value{GDBN} circumvents the problem by considering the symbol to have the
16852 name @code{foo}, which may cause other problems if many symbols end up
16855 @item unknown symbol type @code{0x@var{nn}}
16857 The symbol information contains new data types that @value{GDBN} does
16858 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16859 uncomprehended information, in hexadecimal.
16861 @value{GDBN} circumvents the error by ignoring this symbol information.
16862 This usually allows you to debug your program, though certain symbols
16863 are not accessible. If you encounter such a problem and feel like
16864 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16865 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16866 and examine @code{*bufp} to see the symbol.
16868 @item stub type has NULL name
16870 @value{GDBN} could not find the full definition for a struct or class.
16872 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16873 The symbol information for a C@t{++} member function is missing some
16874 information that recent versions of the compiler should have output for
16877 @item info mismatch between compiler and debugger
16879 @value{GDBN} could not parse a type specification output by the compiler.
16884 @section GDB Data Files
16886 @cindex prefix for data files
16887 @value{GDBN} will sometimes read an auxiliary data file. These files
16888 are kept in a directory known as the @dfn{data directory}.
16890 You can set the data directory's name, and view the name @value{GDBN}
16891 is currently using.
16894 @kindex set data-directory
16895 @item set data-directory @var{directory}
16896 Set the directory which @value{GDBN} searches for auxiliary data files
16897 to @var{directory}.
16899 @kindex show data-directory
16900 @item show data-directory
16901 Show the directory @value{GDBN} searches for auxiliary data files.
16904 @cindex default data directory
16905 @cindex @samp{--with-gdb-datadir}
16906 You can set the default data directory by using the configure-time
16907 @samp{--with-gdb-datadir} option. If the data directory is inside
16908 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16909 @samp{--exec-prefix}), then the default data directory will be updated
16910 automatically if the installed @value{GDBN} is moved to a new
16913 The data directory may also be specified with the
16914 @code{--data-directory} command line option.
16915 @xref{Mode Options}.
16918 @chapter Specifying a Debugging Target
16920 @cindex debugging target
16921 A @dfn{target} is the execution environment occupied by your program.
16923 Often, @value{GDBN} runs in the same host environment as your program;
16924 in that case, the debugging target is specified as a side effect when
16925 you use the @code{file} or @code{core} commands. When you need more
16926 flexibility---for example, running @value{GDBN} on a physically separate
16927 host, or controlling a standalone system over a serial port or a
16928 realtime system over a TCP/IP connection---you can use the @code{target}
16929 command to specify one of the target types configured for @value{GDBN}
16930 (@pxref{Target Commands, ,Commands for Managing Targets}).
16932 @cindex target architecture
16933 It is possible to build @value{GDBN} for several different @dfn{target
16934 architectures}. When @value{GDBN} is built like that, you can choose
16935 one of the available architectures with the @kbd{set architecture}
16939 @kindex set architecture
16940 @kindex show architecture
16941 @item set architecture @var{arch}
16942 This command sets the current target architecture to @var{arch}. The
16943 value of @var{arch} can be @code{"auto"}, in addition to one of the
16944 supported architectures.
16946 @item show architecture
16947 Show the current target architecture.
16949 @item set processor
16951 @kindex set processor
16952 @kindex show processor
16953 These are alias commands for, respectively, @code{set architecture}
16954 and @code{show architecture}.
16958 * Active Targets:: Active targets
16959 * Target Commands:: Commands for managing targets
16960 * Byte Order:: Choosing target byte order
16963 @node Active Targets
16964 @section Active Targets
16966 @cindex stacking targets
16967 @cindex active targets
16968 @cindex multiple targets
16970 There are multiple classes of targets such as: processes, executable files or
16971 recording sessions. Core files belong to the process class, making core file
16972 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16973 on multiple active targets, one in each class. This allows you to (for
16974 example) start a process and inspect its activity, while still having access to
16975 the executable file after the process finishes. Or if you start process
16976 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16977 presented a virtual layer of the recording target, while the process target
16978 remains stopped at the chronologically last point of the process execution.
16980 Use the @code{core-file} and @code{exec-file} commands to select a new core
16981 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16982 specify as a target a process that is already running, use the @code{attach}
16983 command (@pxref{Attach, ,Debugging an Already-running Process}).
16985 @node Target Commands
16986 @section Commands for Managing Targets
16989 @item target @var{type} @var{parameters}
16990 Connects the @value{GDBN} host environment to a target machine or
16991 process. A target is typically a protocol for talking to debugging
16992 facilities. You use the argument @var{type} to specify the type or
16993 protocol of the target machine.
16995 Further @var{parameters} are interpreted by the target protocol, but
16996 typically include things like device names or host names to connect
16997 with, process numbers, and baud rates.
16999 The @code{target} command does not repeat if you press @key{RET} again
17000 after executing the command.
17002 @kindex help target
17004 Displays the names of all targets available. To display targets
17005 currently selected, use either @code{info target} or @code{info files}
17006 (@pxref{Files, ,Commands to Specify Files}).
17008 @item help target @var{name}
17009 Describe a particular target, including any parameters necessary to
17012 @kindex set gnutarget
17013 @item set gnutarget @var{args}
17014 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17015 knows whether it is reading an @dfn{executable},
17016 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17017 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17018 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17021 @emph{Warning:} To specify a file format with @code{set gnutarget},
17022 you must know the actual BFD name.
17026 @xref{Files, , Commands to Specify Files}.
17028 @kindex show gnutarget
17029 @item show gnutarget
17030 Use the @code{show gnutarget} command to display what file format
17031 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17032 @value{GDBN} will determine the file format for each file automatically,
17033 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
17036 @cindex common targets
17037 Here are some common targets (available, or not, depending on the GDB
17042 @item target exec @var{program}
17043 @cindex executable file target
17044 An executable file. @samp{target exec @var{program}} is the same as
17045 @samp{exec-file @var{program}}.
17047 @item target core @var{filename}
17048 @cindex core dump file target
17049 A core dump file. @samp{target core @var{filename}} is the same as
17050 @samp{core-file @var{filename}}.
17052 @item target remote @var{medium}
17053 @cindex remote target
17054 A remote system connected to @value{GDBN} via a serial line or network
17055 connection. This command tells @value{GDBN} to use its own remote
17056 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17058 For example, if you have a board connected to @file{/dev/ttya} on the
17059 machine running @value{GDBN}, you could say:
17062 target remote /dev/ttya
17065 @code{target remote} supports the @code{load} command. This is only
17066 useful if you have some other way of getting the stub to the target
17067 system, and you can put it somewhere in memory where it won't get
17068 clobbered by the download.
17070 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17071 @cindex built-in simulator target
17072 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17080 works; however, you cannot assume that a specific memory map, device
17081 drivers, or even basic I/O is available, although some simulators do
17082 provide these. For info about any processor-specific simulator details,
17083 see the appropriate section in @ref{Embedded Processors, ,Embedded
17088 Some configurations may include these targets as well:
17092 @item target nrom @var{dev}
17093 @cindex NetROM ROM emulator target
17094 NetROM ROM emulator. This target only supports downloading.
17098 Different targets are available on different configurations of @value{GDBN};
17099 your configuration may have more or fewer targets.
17101 Many remote targets require you to download the executable's code once
17102 you've successfully established a connection. You may wish to control
17103 various aspects of this process.
17108 @kindex set hash@r{, for remote monitors}
17109 @cindex hash mark while downloading
17110 This command controls whether a hash mark @samp{#} is displayed while
17111 downloading a file to the remote monitor. If on, a hash mark is
17112 displayed after each S-record is successfully downloaded to the
17116 @kindex show hash@r{, for remote monitors}
17117 Show the current status of displaying the hash mark.
17119 @item set debug monitor
17120 @kindex set debug monitor
17121 @cindex display remote monitor communications
17122 Enable or disable display of communications messages between
17123 @value{GDBN} and the remote monitor.
17125 @item show debug monitor
17126 @kindex show debug monitor
17127 Show the current status of displaying communications between
17128 @value{GDBN} and the remote monitor.
17133 @kindex load @var{filename}
17134 @item load @var{filename}
17136 Depending on what remote debugging facilities are configured into
17137 @value{GDBN}, the @code{load} command may be available. Where it exists, it
17138 is meant to make @var{filename} (an executable) available for debugging
17139 on the remote system---by downloading, or dynamic linking, for example.
17140 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
17141 the @code{add-symbol-file} command.
17143 If your @value{GDBN} does not have a @code{load} command, attempting to
17144 execute it gets the error message ``@code{You can't do that when your
17145 target is @dots{}}''
17147 The file is loaded at whatever address is specified in the executable.
17148 For some object file formats, you can specify the load address when you
17149 link the program; for other formats, like a.out, the object file format
17150 specifies a fixed address.
17151 @c FIXME! This would be a good place for an xref to the GNU linker doc.
17153 Depending on the remote side capabilities, @value{GDBN} may be able to
17154 load programs into flash memory.
17156 @code{load} does not repeat if you press @key{RET} again after using it.
17160 @section Choosing Target Byte Order
17162 @cindex choosing target byte order
17163 @cindex target byte order
17165 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
17166 offer the ability to run either big-endian or little-endian byte
17167 orders. Usually the executable or symbol will include a bit to
17168 designate the endian-ness, and you will not need to worry about
17169 which to use. However, you may still find it useful to adjust
17170 @value{GDBN}'s idea of processor endian-ness manually.
17174 @item set endian big
17175 Instruct @value{GDBN} to assume the target is big-endian.
17177 @item set endian little
17178 Instruct @value{GDBN} to assume the target is little-endian.
17180 @item set endian auto
17181 Instruct @value{GDBN} to use the byte order associated with the
17185 Display @value{GDBN}'s current idea of the target byte order.
17189 Note that these commands merely adjust interpretation of symbolic
17190 data on the host, and that they have absolutely no effect on the
17194 @node Remote Debugging
17195 @chapter Debugging Remote Programs
17196 @cindex remote debugging
17198 If you are trying to debug a program running on a machine that cannot run
17199 @value{GDBN} in the usual way, it is often useful to use remote debugging.
17200 For example, you might use remote debugging on an operating system kernel,
17201 or on a small system which does not have a general purpose operating system
17202 powerful enough to run a full-featured debugger.
17204 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
17205 to make this work with particular debugging targets. In addition,
17206 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
17207 but not specific to any particular target system) which you can use if you
17208 write the remote stubs---the code that runs on the remote system to
17209 communicate with @value{GDBN}.
17211 Other remote targets may be available in your
17212 configuration of @value{GDBN}; use @code{help target} to list them.
17215 * Connecting:: Connecting to a remote target
17216 * File Transfer:: Sending files to a remote system
17217 * Server:: Using the gdbserver program
17218 * Remote Configuration:: Remote configuration
17219 * Remote Stub:: Implementing a remote stub
17223 @section Connecting to a Remote Target
17225 On the @value{GDBN} host machine, you will need an unstripped copy of
17226 your program, since @value{GDBN} needs symbol and debugging information.
17227 Start up @value{GDBN} as usual, using the name of the local copy of your
17228 program as the first argument.
17230 @cindex @code{target remote}
17231 @value{GDBN} can communicate with the target over a serial line, or
17232 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
17233 each case, @value{GDBN} uses the same protocol for debugging your
17234 program; only the medium carrying the debugging packets varies. The
17235 @code{target remote} command establishes a connection to the target.
17236 Its arguments indicate which medium to use:
17240 @item target remote @var{serial-device}
17241 @cindex serial line, @code{target remote}
17242 Use @var{serial-device} to communicate with the target. For example,
17243 to use a serial line connected to the device named @file{/dev/ttyb}:
17246 target remote /dev/ttyb
17249 If you're using a serial line, you may want to give @value{GDBN} the
17250 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
17251 (@pxref{Remote Configuration, set remotebaud}) before the
17252 @code{target} command.
17254 @item target remote @code{@var{host}:@var{port}}
17255 @itemx target remote @code{tcp:@var{host}:@var{port}}
17256 @cindex @acronym{TCP} port, @code{target remote}
17257 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
17258 The @var{host} may be either a host name or a numeric @acronym{IP}
17259 address; @var{port} must be a decimal number. The @var{host} could be
17260 the target machine itself, if it is directly connected to the net, or
17261 it might be a terminal server which in turn has a serial line to the
17264 For example, to connect to port 2828 on a terminal server named
17268 target remote manyfarms:2828
17271 If your remote target is actually running on the same machine as your
17272 debugger session (e.g.@: a simulator for your target running on the
17273 same host), you can omit the hostname. For example, to connect to
17274 port 1234 on your local machine:
17277 target remote :1234
17281 Note that the colon is still required here.
17283 @item target remote @code{udp:@var{host}:@var{port}}
17284 @cindex @acronym{UDP} port, @code{target remote}
17285 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
17286 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
17289 target remote udp:manyfarms:2828
17292 When using a @acronym{UDP} connection for remote debugging, you should
17293 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
17294 can silently drop packets on busy or unreliable networks, which will
17295 cause havoc with your debugging session.
17297 @item target remote | @var{command}
17298 @cindex pipe, @code{target remote} to
17299 Run @var{command} in the background and communicate with it using a
17300 pipe. The @var{command} is a shell command, to be parsed and expanded
17301 by the system's command shell, @code{/bin/sh}; it should expect remote
17302 protocol packets on its standard input, and send replies on its
17303 standard output. You could use this to run a stand-alone simulator
17304 that speaks the remote debugging protocol, to make net connections
17305 using programs like @code{ssh}, or for other similar tricks.
17307 If @var{command} closes its standard output (perhaps by exiting),
17308 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
17309 program has already exited, this will have no effect.)
17313 Once the connection has been established, you can use all the usual
17314 commands to examine and change data. The remote program is already
17315 running; you can use @kbd{step} and @kbd{continue}, and you do not
17316 need to use @kbd{run}.
17318 @cindex interrupting remote programs
17319 @cindex remote programs, interrupting
17320 Whenever @value{GDBN} is waiting for the remote program, if you type the
17321 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
17322 program. This may or may not succeed, depending in part on the hardware
17323 and the serial drivers the remote system uses. If you type the
17324 interrupt character once again, @value{GDBN} displays this prompt:
17327 Interrupted while waiting for the program.
17328 Give up (and stop debugging it)? (y or n)
17331 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
17332 (If you decide you want to try again later, you can use @samp{target
17333 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
17334 goes back to waiting.
17337 @kindex detach (remote)
17339 When you have finished debugging the remote program, you can use the
17340 @code{detach} command to release it from @value{GDBN} control.
17341 Detaching from the target normally resumes its execution, but the results
17342 will depend on your particular remote stub. After the @code{detach}
17343 command, @value{GDBN} is free to connect to another target.
17347 The @code{disconnect} command behaves like @code{detach}, except that
17348 the target is generally not resumed. It will wait for @value{GDBN}
17349 (this instance or another one) to connect and continue debugging. After
17350 the @code{disconnect} command, @value{GDBN} is again free to connect to
17353 @cindex send command to remote monitor
17354 @cindex extend @value{GDBN} for remote targets
17355 @cindex add new commands for external monitor
17357 @item monitor @var{cmd}
17358 This command allows you to send arbitrary commands directly to the
17359 remote monitor. Since @value{GDBN} doesn't care about the commands it
17360 sends like this, this command is the way to extend @value{GDBN}---you
17361 can add new commands that only the external monitor will understand
17365 @node File Transfer
17366 @section Sending files to a remote system
17367 @cindex remote target, file transfer
17368 @cindex file transfer
17369 @cindex sending files to remote systems
17371 Some remote targets offer the ability to transfer files over the same
17372 connection used to communicate with @value{GDBN}. This is convenient
17373 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
17374 running @code{gdbserver} over a network interface. For other targets,
17375 e.g.@: embedded devices with only a single serial port, this may be
17376 the only way to upload or download files.
17378 Not all remote targets support these commands.
17382 @item remote put @var{hostfile} @var{targetfile}
17383 Copy file @var{hostfile} from the host system (the machine running
17384 @value{GDBN}) to @var{targetfile} on the target system.
17387 @item remote get @var{targetfile} @var{hostfile}
17388 Copy file @var{targetfile} from the target system to @var{hostfile}
17389 on the host system.
17391 @kindex remote delete
17392 @item remote delete @var{targetfile}
17393 Delete @var{targetfile} from the target system.
17398 @section Using the @code{gdbserver} Program
17401 @cindex remote connection without stubs
17402 @code{gdbserver} is a control program for Unix-like systems, which
17403 allows you to connect your program with a remote @value{GDBN} via
17404 @code{target remote}---but without linking in the usual debugging stub.
17406 @code{gdbserver} is not a complete replacement for the debugging stubs,
17407 because it requires essentially the same operating-system facilities
17408 that @value{GDBN} itself does. In fact, a system that can run
17409 @code{gdbserver} to connect to a remote @value{GDBN} could also run
17410 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
17411 because it is a much smaller program than @value{GDBN} itself. It is
17412 also easier to port than all of @value{GDBN}, so you may be able to get
17413 started more quickly on a new system by using @code{gdbserver}.
17414 Finally, if you develop code for real-time systems, you may find that
17415 the tradeoffs involved in real-time operation make it more convenient to
17416 do as much development work as possible on another system, for example
17417 by cross-compiling. You can use @code{gdbserver} to make a similar
17418 choice for debugging.
17420 @value{GDBN} and @code{gdbserver} communicate via either a serial line
17421 or a TCP connection, using the standard @value{GDBN} remote serial
17425 @emph{Warning:} @code{gdbserver} does not have any built-in security.
17426 Do not run @code{gdbserver} connected to any public network; a
17427 @value{GDBN} connection to @code{gdbserver} provides access to the
17428 target system with the same privileges as the user running
17432 @subsection Running @code{gdbserver}
17433 @cindex arguments, to @code{gdbserver}
17434 @cindex @code{gdbserver}, command-line arguments
17436 Run @code{gdbserver} on the target system. You need a copy of the
17437 program you want to debug, including any libraries it requires.
17438 @code{gdbserver} does not need your program's symbol table, so you can
17439 strip the program if necessary to save space. @value{GDBN} on the host
17440 system does all the symbol handling.
17442 To use the server, you must tell it how to communicate with @value{GDBN};
17443 the name of your program; and the arguments for your program. The usual
17447 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
17450 @var{comm} is either a device name (to use a serial line), or a TCP
17451 hostname and portnumber, or @code{-} or @code{stdio} to use
17452 stdin/stdout of @code{gdbserver}.
17453 For example, to debug Emacs with the argument
17454 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
17458 target> gdbserver /dev/com1 emacs foo.txt
17461 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
17464 To use a TCP connection instead of a serial line:
17467 target> gdbserver host:2345 emacs foo.txt
17470 The only difference from the previous example is the first argument,
17471 specifying that you are communicating with the host @value{GDBN} via
17472 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
17473 expect a TCP connection from machine @samp{host} to local TCP port 2345.
17474 (Currently, the @samp{host} part is ignored.) You can choose any number
17475 you want for the port number as long as it does not conflict with any
17476 TCP ports already in use on the target system (for example, @code{23} is
17477 reserved for @code{telnet}).@footnote{If you choose a port number that
17478 conflicts with another service, @code{gdbserver} prints an error message
17479 and exits.} You must use the same port number with the host @value{GDBN}
17480 @code{target remote} command.
17482 The @code{stdio} connection is useful when starting @code{gdbserver}
17486 (gdb) target remote | ssh -T hostname gdbserver - hello
17489 The @samp{-T} option to ssh is provided because we don't need a remote pty,
17490 and we don't want escape-character handling. Ssh does this by default when
17491 a command is provided, the flag is provided to make it explicit.
17492 You could elide it if you want to.
17494 Programs started with stdio-connected gdbserver have @file{/dev/null} for
17495 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
17496 display through a pipe connected to gdbserver.
17497 Both @code{stdout} and @code{stderr} use the same pipe.
17499 @subsubsection Attaching to a Running Program
17500 @cindex attach to a program, @code{gdbserver}
17501 @cindex @option{--attach}, @code{gdbserver} option
17503 On some targets, @code{gdbserver} can also attach to running programs.
17504 This is accomplished via the @code{--attach} argument. The syntax is:
17507 target> gdbserver --attach @var{comm} @var{pid}
17510 @var{pid} is the process ID of a currently running process. It isn't necessary
17511 to point @code{gdbserver} at a binary for the running process.
17514 You can debug processes by name instead of process ID if your target has the
17515 @code{pidof} utility:
17518 target> gdbserver --attach @var{comm} `pidof @var{program}`
17521 In case more than one copy of @var{program} is running, or @var{program}
17522 has multiple threads, most versions of @code{pidof} support the
17523 @code{-s} option to only return the first process ID.
17525 @subsubsection Multi-Process Mode for @code{gdbserver}
17526 @cindex @code{gdbserver}, multiple processes
17527 @cindex multiple processes with @code{gdbserver}
17529 When you connect to @code{gdbserver} using @code{target remote},
17530 @code{gdbserver} debugs the specified program only once. When the
17531 program exits, or you detach from it, @value{GDBN} closes the connection
17532 and @code{gdbserver} exits.
17534 If you connect using @kbd{target extended-remote}, @code{gdbserver}
17535 enters multi-process mode. When the debugged program exits, or you
17536 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
17537 though no program is running. The @code{run} and @code{attach}
17538 commands instruct @code{gdbserver} to run or attach to a new program.
17539 The @code{run} command uses @code{set remote exec-file} (@pxref{set
17540 remote exec-file}) to select the program to run. Command line
17541 arguments are supported, except for wildcard expansion and I/O
17542 redirection (@pxref{Arguments}).
17544 @cindex @option{--multi}, @code{gdbserver} option
17545 To start @code{gdbserver} without supplying an initial command to run
17546 or process ID to attach, use the @option{--multi} command line option.
17547 Then you can connect using @kbd{target extended-remote} and start
17548 the program you want to debug.
17550 In multi-process mode @code{gdbserver} does not automatically exit unless you
17551 use the option @option{--once}. You can terminate it by using
17552 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
17553 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
17554 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
17555 @option{--multi} option to @code{gdbserver} has no influence on that.
17557 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
17559 This section applies only when @code{gdbserver} is run to listen on a TCP port.
17561 @code{gdbserver} normally terminates after all of its debugged processes have
17562 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
17563 extended-remote}, @code{gdbserver} stays running even with no processes left.
17564 @value{GDBN} normally terminates the spawned debugged process on its exit,
17565 which normally also terminates @code{gdbserver} in the @kbd{target remote}
17566 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
17567 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
17568 stays running even in the @kbd{target remote} mode.
17570 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
17571 Such reconnecting is useful for features like @ref{disconnected tracing}. For
17572 completeness, at most one @value{GDBN} can be connected at a time.
17574 @cindex @option{--once}, @code{gdbserver} option
17575 By default, @code{gdbserver} keeps the listening TCP port open, so that
17576 additional connections are possible. However, if you start @code{gdbserver}
17577 with the @option{--once} option, it will stop listening for any further
17578 connection attempts after connecting to the first @value{GDBN} session. This
17579 means no further connections to @code{gdbserver} will be possible after the
17580 first one. It also means @code{gdbserver} will terminate after the first
17581 connection with remote @value{GDBN} has closed, even for unexpectedly closed
17582 connections and even in the @kbd{target extended-remote} mode. The
17583 @option{--once} option allows reusing the same port number for connecting to
17584 multiple instances of @code{gdbserver} running on the same host, since each
17585 instance closes its port after the first connection.
17587 @subsubsection Other Command-Line Arguments for @code{gdbserver}
17589 @cindex @option{--debug}, @code{gdbserver} option
17590 The @option{--debug} option tells @code{gdbserver} to display extra
17591 status information about the debugging process.
17592 @cindex @option{--remote-debug}, @code{gdbserver} option
17593 The @option{--remote-debug} option tells @code{gdbserver} to display
17594 remote protocol debug output. These options are intended for
17595 @code{gdbserver} development and for bug reports to the developers.
17597 @cindex @option{--wrapper}, @code{gdbserver} option
17598 The @option{--wrapper} option specifies a wrapper to launch programs
17599 for debugging. The option should be followed by the name of the
17600 wrapper, then any command-line arguments to pass to the wrapper, then
17601 @kbd{--} indicating the end of the wrapper arguments.
17603 @code{gdbserver} runs the specified wrapper program with a combined
17604 command line including the wrapper arguments, then the name of the
17605 program to debug, then any arguments to the program. The wrapper
17606 runs until it executes your program, and then @value{GDBN} gains control.
17608 You can use any program that eventually calls @code{execve} with
17609 its arguments as a wrapper. Several standard Unix utilities do
17610 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
17611 with @code{exec "$@@"} will also work.
17613 For example, you can use @code{env} to pass an environment variable to
17614 the debugged program, without setting the variable in @code{gdbserver}'s
17618 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
17621 @subsection Connecting to @code{gdbserver}
17623 Run @value{GDBN} on the host system.
17625 First make sure you have the necessary symbol files. Load symbols for
17626 your application using the @code{file} command before you connect. Use
17627 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
17628 was compiled with the correct sysroot using @code{--with-sysroot}).
17630 The symbol file and target libraries must exactly match the executable
17631 and libraries on the target, with one exception: the files on the host
17632 system should not be stripped, even if the files on the target system
17633 are. Mismatched or missing files will lead to confusing results
17634 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
17635 files may also prevent @code{gdbserver} from debugging multi-threaded
17638 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
17639 For TCP connections, you must start up @code{gdbserver} prior to using
17640 the @code{target remote} command. Otherwise you may get an error whose
17641 text depends on the host system, but which usually looks something like
17642 @samp{Connection refused}. Don't use the @code{load}
17643 command in @value{GDBN} when using @code{gdbserver}, since the program is
17644 already on the target.
17646 @subsection Monitor Commands for @code{gdbserver}
17647 @cindex monitor commands, for @code{gdbserver}
17648 @anchor{Monitor Commands for gdbserver}
17650 During a @value{GDBN} session using @code{gdbserver}, you can use the
17651 @code{monitor} command to send special requests to @code{gdbserver}.
17652 Here are the available commands.
17656 List the available monitor commands.
17658 @item monitor set debug 0
17659 @itemx monitor set debug 1
17660 Disable or enable general debugging messages.
17662 @item monitor set remote-debug 0
17663 @itemx monitor set remote-debug 1
17664 Disable or enable specific debugging messages associated with the remote
17665 protocol (@pxref{Remote Protocol}).
17667 @item monitor set libthread-db-search-path [PATH]
17668 @cindex gdbserver, search path for @code{libthread_db}
17669 When this command is issued, @var{path} is a colon-separated list of
17670 directories to search for @code{libthread_db} (@pxref{Threads,,set
17671 libthread-db-search-path}). If you omit @var{path},
17672 @samp{libthread-db-search-path} will be reset to its default value.
17674 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
17675 not supported in @code{gdbserver}.
17678 Tell gdbserver to exit immediately. This command should be followed by
17679 @code{disconnect} to close the debugging session. @code{gdbserver} will
17680 detach from any attached processes and kill any processes it created.
17681 Use @code{monitor exit} to terminate @code{gdbserver} at the end
17682 of a multi-process mode debug session.
17686 @subsection Tracepoints support in @code{gdbserver}
17687 @cindex tracepoints support in @code{gdbserver}
17689 On some targets, @code{gdbserver} supports tracepoints, fast
17690 tracepoints and static tracepoints.
17692 For fast or static tracepoints to work, a special library called the
17693 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
17694 This library is built and distributed as an integral part of
17695 @code{gdbserver}. In addition, support for static tracepoints
17696 requires building the in-process agent library with static tracepoints
17697 support. At present, the UST (LTTng Userspace Tracer,
17698 @url{http://lttng.org/ust}) tracing engine is supported. This support
17699 is automatically available if UST development headers are found in the
17700 standard include path when @code{gdbserver} is built, or if
17701 @code{gdbserver} was explicitly configured using @option{--with-ust}
17702 to point at such headers. You can explicitly disable the support
17703 using @option{--with-ust=no}.
17705 There are several ways to load the in-process agent in your program:
17708 @item Specifying it as dependency at link time
17710 You can link your program dynamically with the in-process agent
17711 library. On most systems, this is accomplished by adding
17712 @code{-linproctrace} to the link command.
17714 @item Using the system's preloading mechanisms
17716 You can force loading the in-process agent at startup time by using
17717 your system's support for preloading shared libraries. Many Unixes
17718 support the concept of preloading user defined libraries. In most
17719 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
17720 in the environment. See also the description of @code{gdbserver}'s
17721 @option{--wrapper} command line option.
17723 @item Using @value{GDBN} to force loading the agent at run time
17725 On some systems, you can force the inferior to load a shared library,
17726 by calling a dynamic loader function in the inferior that takes care
17727 of dynamically looking up and loading a shared library. On most Unix
17728 systems, the function is @code{dlopen}. You'll use the @code{call}
17729 command for that. For example:
17732 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
17735 Note that on most Unix systems, for the @code{dlopen} function to be
17736 available, the program needs to be linked with @code{-ldl}.
17739 On systems that have a userspace dynamic loader, like most Unix
17740 systems, when you connect to @code{gdbserver} using @code{target
17741 remote}, you'll find that the program is stopped at the dynamic
17742 loader's entry point, and no shared library has been loaded in the
17743 program's address space yet, including the in-process agent. In that
17744 case, before being able to use any of the fast or static tracepoints
17745 features, you need to let the loader run and load the shared
17746 libraries. The simplest way to do that is to run the program to the
17747 main procedure. E.g., if debugging a C or C@t{++} program, start
17748 @code{gdbserver} like so:
17751 $ gdbserver :9999 myprogram
17754 Start GDB and connect to @code{gdbserver} like so, and run to main:
17758 (@value{GDBP}) target remote myhost:9999
17759 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
17760 (@value{GDBP}) b main
17761 (@value{GDBP}) continue
17764 The in-process tracing agent library should now be loaded into the
17765 process; you can confirm it with the @code{info sharedlibrary}
17766 command, which will list @file{libinproctrace.so} as loaded in the
17767 process. You are now ready to install fast tracepoints, list static
17768 tracepoint markers, probe static tracepoints markers, and start
17771 @node Remote Configuration
17772 @section Remote Configuration
17775 @kindex show remote
17776 This section documents the configuration options available when
17777 debugging remote programs. For the options related to the File I/O
17778 extensions of the remote protocol, see @ref{system,
17779 system-call-allowed}.
17782 @item set remoteaddresssize @var{bits}
17783 @cindex address size for remote targets
17784 @cindex bits in remote address
17785 Set the maximum size of address in a memory packet to the specified
17786 number of bits. @value{GDBN} will mask off the address bits above
17787 that number, when it passes addresses to the remote target. The
17788 default value is the number of bits in the target's address.
17790 @item show remoteaddresssize
17791 Show the current value of remote address size in bits.
17793 @item set remotebaud @var{n}
17794 @cindex baud rate for remote targets
17795 Set the baud rate for the remote serial I/O to @var{n} baud. The
17796 value is used to set the speed of the serial port used for debugging
17799 @item show remotebaud
17800 Show the current speed of the remote connection.
17802 @item set remotebreak
17803 @cindex interrupt remote programs
17804 @cindex BREAK signal instead of Ctrl-C
17805 @anchor{set remotebreak}
17806 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17807 when you type @kbd{Ctrl-c} to interrupt the program running
17808 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17809 character instead. The default is off, since most remote systems
17810 expect to see @samp{Ctrl-C} as the interrupt signal.
17812 @item show remotebreak
17813 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17814 interrupt the remote program.
17816 @item set remoteflow on
17817 @itemx set remoteflow off
17818 @kindex set remoteflow
17819 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17820 on the serial port used to communicate to the remote target.
17822 @item show remoteflow
17823 @kindex show remoteflow
17824 Show the current setting of hardware flow control.
17826 @item set remotelogbase @var{base}
17827 Set the base (a.k.a.@: radix) of logging serial protocol
17828 communications to @var{base}. Supported values of @var{base} are:
17829 @code{ascii}, @code{octal}, and @code{hex}. The default is
17832 @item show remotelogbase
17833 Show the current setting of the radix for logging remote serial
17836 @item set remotelogfile @var{file}
17837 @cindex record serial communications on file
17838 Record remote serial communications on the named @var{file}. The
17839 default is not to record at all.
17841 @item show remotelogfile.
17842 Show the current setting of the file name on which to record the
17843 serial communications.
17845 @item set remotetimeout @var{num}
17846 @cindex timeout for serial communications
17847 @cindex remote timeout
17848 Set the timeout limit to wait for the remote target to respond to
17849 @var{num} seconds. The default is 2 seconds.
17851 @item show remotetimeout
17852 Show the current number of seconds to wait for the remote target
17855 @cindex limit hardware breakpoints and watchpoints
17856 @cindex remote target, limit break- and watchpoints
17857 @anchor{set remote hardware-watchpoint-limit}
17858 @anchor{set remote hardware-breakpoint-limit}
17859 @item set remote hardware-watchpoint-limit @var{limit}
17860 @itemx set remote hardware-breakpoint-limit @var{limit}
17861 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17862 watchpoints. A limit of -1, the default, is treated as unlimited.
17864 @cindex limit hardware watchpoints length
17865 @cindex remote target, limit watchpoints length
17866 @anchor{set remote hardware-watchpoint-length-limit}
17867 @item set remote hardware-watchpoint-length-limit @var{limit}
17868 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17869 a remote hardware watchpoint. A limit of -1, the default, is treated
17872 @item show remote hardware-watchpoint-length-limit
17873 Show the current limit (in bytes) of the maximum length of
17874 a remote hardware watchpoint.
17876 @item set remote exec-file @var{filename}
17877 @itemx show remote exec-file
17878 @anchor{set remote exec-file}
17879 @cindex executable file, for remote target
17880 Select the file used for @code{run} with @code{target
17881 extended-remote}. This should be set to a filename valid on the
17882 target system. If it is not set, the target will use a default
17883 filename (e.g.@: the last program run).
17885 @item set remote interrupt-sequence
17886 @cindex interrupt remote programs
17887 @cindex select Ctrl-C, BREAK or BREAK-g
17888 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
17889 @samp{BREAK-g} as the
17890 sequence to the remote target in order to interrupt the execution.
17891 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
17892 is high level of serial line for some certain time.
17893 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
17894 It is @code{BREAK} signal followed by character @code{g}.
17896 @item show interrupt-sequence
17897 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
17898 is sent by @value{GDBN} to interrupt the remote program.
17899 @code{BREAK-g} is BREAK signal followed by @code{g} and
17900 also known as Magic SysRq g.
17902 @item set remote interrupt-on-connect
17903 @cindex send interrupt-sequence on start
17904 Specify whether interrupt-sequence is sent to remote target when
17905 @value{GDBN} connects to it. This is mostly needed when you debug
17906 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
17907 which is known as Magic SysRq g in order to connect @value{GDBN}.
17909 @item show interrupt-on-connect
17910 Show whether interrupt-sequence is sent
17911 to remote target when @value{GDBN} connects to it.
17915 @item set tcp auto-retry on
17916 @cindex auto-retry, for remote TCP target
17917 Enable auto-retry for remote TCP connections. This is useful if the remote
17918 debugging agent is launched in parallel with @value{GDBN}; there is a race
17919 condition because the agent may not become ready to accept the connection
17920 before @value{GDBN} attempts to connect. When auto-retry is
17921 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17922 to establish the connection using the timeout specified by
17923 @code{set tcp connect-timeout}.
17925 @item set tcp auto-retry off
17926 Do not auto-retry failed TCP connections.
17928 @item show tcp auto-retry
17929 Show the current auto-retry setting.
17931 @item set tcp connect-timeout @var{seconds}
17932 @cindex connection timeout, for remote TCP target
17933 @cindex timeout, for remote target connection
17934 Set the timeout for establishing a TCP connection to the remote target to
17935 @var{seconds}. The timeout affects both polling to retry failed connections
17936 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17937 that are merely slow to complete, and represents an approximate cumulative
17940 @item show tcp connect-timeout
17941 Show the current connection timeout setting.
17944 @cindex remote packets, enabling and disabling
17945 The @value{GDBN} remote protocol autodetects the packets supported by
17946 your debugging stub. If you need to override the autodetection, you
17947 can use these commands to enable or disable individual packets. Each
17948 packet can be set to @samp{on} (the remote target supports this
17949 packet), @samp{off} (the remote target does not support this packet),
17950 or @samp{auto} (detect remote target support for this packet). They
17951 all default to @samp{auto}. For more information about each packet,
17952 see @ref{Remote Protocol}.
17954 During normal use, you should not have to use any of these commands.
17955 If you do, that may be a bug in your remote debugging stub, or a bug
17956 in @value{GDBN}. You may want to report the problem to the
17957 @value{GDBN} developers.
17959 For each packet @var{name}, the command to enable or disable the
17960 packet is @code{set remote @var{name}-packet}. The available settings
17963 @multitable @columnfractions 0.28 0.32 0.25
17966 @tab Related Features
17968 @item @code{fetch-register}
17970 @tab @code{info registers}
17972 @item @code{set-register}
17976 @item @code{binary-download}
17978 @tab @code{load}, @code{set}
17980 @item @code{read-aux-vector}
17981 @tab @code{qXfer:auxv:read}
17982 @tab @code{info auxv}
17984 @item @code{symbol-lookup}
17985 @tab @code{qSymbol}
17986 @tab Detecting multiple threads
17988 @item @code{attach}
17989 @tab @code{vAttach}
17992 @item @code{verbose-resume}
17994 @tab Stepping or resuming multiple threads
18000 @item @code{software-breakpoint}
18004 @item @code{hardware-breakpoint}
18008 @item @code{write-watchpoint}
18012 @item @code{read-watchpoint}
18016 @item @code{access-watchpoint}
18020 @item @code{target-features}
18021 @tab @code{qXfer:features:read}
18022 @tab @code{set architecture}
18024 @item @code{library-info}
18025 @tab @code{qXfer:libraries:read}
18026 @tab @code{info sharedlibrary}
18028 @item @code{memory-map}
18029 @tab @code{qXfer:memory-map:read}
18030 @tab @code{info mem}
18032 @item @code{read-sdata-object}
18033 @tab @code{qXfer:sdata:read}
18034 @tab @code{print $_sdata}
18036 @item @code{read-spu-object}
18037 @tab @code{qXfer:spu:read}
18038 @tab @code{info spu}
18040 @item @code{write-spu-object}
18041 @tab @code{qXfer:spu:write}
18042 @tab @code{info spu}
18044 @item @code{read-siginfo-object}
18045 @tab @code{qXfer:siginfo:read}
18046 @tab @code{print $_siginfo}
18048 @item @code{write-siginfo-object}
18049 @tab @code{qXfer:siginfo:write}
18050 @tab @code{set $_siginfo}
18052 @item @code{threads}
18053 @tab @code{qXfer:threads:read}
18054 @tab @code{info threads}
18056 @item @code{get-thread-local-@*storage-address}
18057 @tab @code{qGetTLSAddr}
18058 @tab Displaying @code{__thread} variables
18060 @item @code{get-thread-information-block-address}
18061 @tab @code{qGetTIBAddr}
18062 @tab Display MS-Windows Thread Information Block.
18064 @item @code{search-memory}
18065 @tab @code{qSearch:memory}
18068 @item @code{supported-packets}
18069 @tab @code{qSupported}
18070 @tab Remote communications parameters
18072 @item @code{pass-signals}
18073 @tab @code{QPassSignals}
18074 @tab @code{handle @var{signal}}
18076 @item @code{program-signals}
18077 @tab @code{QProgramSignals}
18078 @tab @code{handle @var{signal}}
18080 @item @code{hostio-close-packet}
18081 @tab @code{vFile:close}
18082 @tab @code{remote get}, @code{remote put}
18084 @item @code{hostio-open-packet}
18085 @tab @code{vFile:open}
18086 @tab @code{remote get}, @code{remote put}
18088 @item @code{hostio-pread-packet}
18089 @tab @code{vFile:pread}
18090 @tab @code{remote get}, @code{remote put}
18092 @item @code{hostio-pwrite-packet}
18093 @tab @code{vFile:pwrite}
18094 @tab @code{remote get}, @code{remote put}
18096 @item @code{hostio-unlink-packet}
18097 @tab @code{vFile:unlink}
18098 @tab @code{remote delete}
18100 @item @code{hostio-readlink-packet}
18101 @tab @code{vFile:readlink}
18104 @item @code{noack-packet}
18105 @tab @code{QStartNoAckMode}
18106 @tab Packet acknowledgment
18108 @item @code{osdata}
18109 @tab @code{qXfer:osdata:read}
18110 @tab @code{info os}
18112 @item @code{query-attached}
18113 @tab @code{qAttached}
18114 @tab Querying remote process attach state.
18116 @item @code{traceframe-info}
18117 @tab @code{qXfer:traceframe-info:read}
18118 @tab Traceframe info
18120 @item @code{install-in-trace}
18121 @tab @code{InstallInTrace}
18122 @tab Install tracepoint in tracing
18124 @item @code{disable-randomization}
18125 @tab @code{QDisableRandomization}
18126 @tab @code{set disable-randomization}
18128 @item @code{conditional-breakpoints-packet}
18129 @tab @code{Z0 and Z1}
18130 @tab @code{Support for target-side breakpoint condition evaluation}
18134 @section Implementing a Remote Stub
18136 @cindex debugging stub, example
18137 @cindex remote stub, example
18138 @cindex stub example, remote debugging
18139 The stub files provided with @value{GDBN} implement the target side of the
18140 communication protocol, and the @value{GDBN} side is implemented in the
18141 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
18142 these subroutines to communicate, and ignore the details. (If you're
18143 implementing your own stub file, you can still ignore the details: start
18144 with one of the existing stub files. @file{sparc-stub.c} is the best
18145 organized, and therefore the easiest to read.)
18147 @cindex remote serial debugging, overview
18148 To debug a program running on another machine (the debugging
18149 @dfn{target} machine), you must first arrange for all the usual
18150 prerequisites for the program to run by itself. For example, for a C
18155 A startup routine to set up the C runtime environment; these usually
18156 have a name like @file{crt0}. The startup routine may be supplied by
18157 your hardware supplier, or you may have to write your own.
18160 A C subroutine library to support your program's
18161 subroutine calls, notably managing input and output.
18164 A way of getting your program to the other machine---for example, a
18165 download program. These are often supplied by the hardware
18166 manufacturer, but you may have to write your own from hardware
18170 The next step is to arrange for your program to use a serial port to
18171 communicate with the machine where @value{GDBN} is running (the @dfn{host}
18172 machine). In general terms, the scheme looks like this:
18176 @value{GDBN} already understands how to use this protocol; when everything
18177 else is set up, you can simply use the @samp{target remote} command
18178 (@pxref{Targets,,Specifying a Debugging Target}).
18180 @item On the target,
18181 you must link with your program a few special-purpose subroutines that
18182 implement the @value{GDBN} remote serial protocol. The file containing these
18183 subroutines is called a @dfn{debugging stub}.
18185 On certain remote targets, you can use an auxiliary program
18186 @code{gdbserver} instead of linking a stub into your program.
18187 @xref{Server,,Using the @code{gdbserver} Program}, for details.
18190 The debugging stub is specific to the architecture of the remote
18191 machine; for example, use @file{sparc-stub.c} to debug programs on
18194 @cindex remote serial stub list
18195 These working remote stubs are distributed with @value{GDBN}:
18200 @cindex @file{i386-stub.c}
18203 For Intel 386 and compatible architectures.
18206 @cindex @file{m68k-stub.c}
18207 @cindex Motorola 680x0
18209 For Motorola 680x0 architectures.
18212 @cindex @file{sh-stub.c}
18215 For Renesas SH architectures.
18218 @cindex @file{sparc-stub.c}
18220 For @sc{sparc} architectures.
18222 @item sparcl-stub.c
18223 @cindex @file{sparcl-stub.c}
18226 For Fujitsu @sc{sparclite} architectures.
18230 The @file{README} file in the @value{GDBN} distribution may list other
18231 recently added stubs.
18234 * Stub Contents:: What the stub can do for you
18235 * Bootstrapping:: What you must do for the stub
18236 * Debug Session:: Putting it all together
18239 @node Stub Contents
18240 @subsection What the Stub Can Do for You
18242 @cindex remote serial stub
18243 The debugging stub for your architecture supplies these three
18247 @item set_debug_traps
18248 @findex set_debug_traps
18249 @cindex remote serial stub, initialization
18250 This routine arranges for @code{handle_exception} to run when your
18251 program stops. You must call this subroutine explicitly in your
18252 program's startup code.
18254 @item handle_exception
18255 @findex handle_exception
18256 @cindex remote serial stub, main routine
18257 This is the central workhorse, but your program never calls it
18258 explicitly---the setup code arranges for @code{handle_exception} to
18259 run when a trap is triggered.
18261 @code{handle_exception} takes control when your program stops during
18262 execution (for example, on a breakpoint), and mediates communications
18263 with @value{GDBN} on the host machine. This is where the communications
18264 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
18265 representative on the target machine. It begins by sending summary
18266 information on the state of your program, then continues to execute,
18267 retrieving and transmitting any information @value{GDBN} needs, until you
18268 execute a @value{GDBN} command that makes your program resume; at that point,
18269 @code{handle_exception} returns control to your own code on the target
18273 @cindex @code{breakpoint} subroutine, remote
18274 Use this auxiliary subroutine to make your program contain a
18275 breakpoint. Depending on the particular situation, this may be the only
18276 way for @value{GDBN} to get control. For instance, if your target
18277 machine has some sort of interrupt button, you won't need to call this;
18278 pressing the interrupt button transfers control to
18279 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
18280 simply receiving characters on the serial port may also trigger a trap;
18281 again, in that situation, you don't need to call @code{breakpoint} from
18282 your own program---simply running @samp{target remote} from the host
18283 @value{GDBN} session gets control.
18285 Call @code{breakpoint} if none of these is true, or if you simply want
18286 to make certain your program stops at a predetermined point for the
18287 start of your debugging session.
18290 @node Bootstrapping
18291 @subsection What You Must Do for the Stub
18293 @cindex remote stub, support routines
18294 The debugging stubs that come with @value{GDBN} are set up for a particular
18295 chip architecture, but they have no information about the rest of your
18296 debugging target machine.
18298 First of all you need to tell the stub how to communicate with the
18302 @item int getDebugChar()
18303 @findex getDebugChar
18304 Write this subroutine to read a single character from the serial port.
18305 It may be identical to @code{getchar} for your target system; a
18306 different name is used to allow you to distinguish the two if you wish.
18308 @item void putDebugChar(int)
18309 @findex putDebugChar
18310 Write this subroutine to write a single character to the serial port.
18311 It may be identical to @code{putchar} for your target system; a
18312 different name is used to allow you to distinguish the two if you wish.
18315 @cindex control C, and remote debugging
18316 @cindex interrupting remote targets
18317 If you want @value{GDBN} to be able to stop your program while it is
18318 running, you need to use an interrupt-driven serial driver, and arrange
18319 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
18320 character). That is the character which @value{GDBN} uses to tell the
18321 remote system to stop.
18323 Getting the debugging target to return the proper status to @value{GDBN}
18324 probably requires changes to the standard stub; one quick and dirty way
18325 is to just execute a breakpoint instruction (the ``dirty'' part is that
18326 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
18328 Other routines you need to supply are:
18331 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
18332 @findex exceptionHandler
18333 Write this function to install @var{exception_address} in the exception
18334 handling tables. You need to do this because the stub does not have any
18335 way of knowing what the exception handling tables on your target system
18336 are like (for example, the processor's table might be in @sc{rom},
18337 containing entries which point to a table in @sc{ram}).
18338 @var{exception_number} is the exception number which should be changed;
18339 its meaning is architecture-dependent (for example, different numbers
18340 might represent divide by zero, misaligned access, etc). When this
18341 exception occurs, control should be transferred directly to
18342 @var{exception_address}, and the processor state (stack, registers,
18343 and so on) should be just as it is when a processor exception occurs. So if
18344 you want to use a jump instruction to reach @var{exception_address}, it
18345 should be a simple jump, not a jump to subroutine.
18347 For the 386, @var{exception_address} should be installed as an interrupt
18348 gate so that interrupts are masked while the handler runs. The gate
18349 should be at privilege level 0 (the most privileged level). The
18350 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
18351 help from @code{exceptionHandler}.
18353 @item void flush_i_cache()
18354 @findex flush_i_cache
18355 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
18356 instruction cache, if any, on your target machine. If there is no
18357 instruction cache, this subroutine may be a no-op.
18359 On target machines that have instruction caches, @value{GDBN} requires this
18360 function to make certain that the state of your program is stable.
18364 You must also make sure this library routine is available:
18367 @item void *memset(void *, int, int)
18369 This is the standard library function @code{memset} that sets an area of
18370 memory to a known value. If you have one of the free versions of
18371 @code{libc.a}, @code{memset} can be found there; otherwise, you must
18372 either obtain it from your hardware manufacturer, or write your own.
18375 If you do not use the GNU C compiler, you may need other standard
18376 library subroutines as well; this varies from one stub to another,
18377 but in general the stubs are likely to use any of the common library
18378 subroutines which @code{@value{NGCC}} generates as inline code.
18381 @node Debug Session
18382 @subsection Putting it All Together
18384 @cindex remote serial debugging summary
18385 In summary, when your program is ready to debug, you must follow these
18390 Make sure you have defined the supporting low-level routines
18391 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
18393 @code{getDebugChar}, @code{putDebugChar},
18394 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
18398 Insert these lines in your program's startup code, before the main
18399 procedure is called:
18406 On some machines, when a breakpoint trap is raised, the hardware
18407 automatically makes the PC point to the instruction after the
18408 breakpoint. If your machine doesn't do that, you may need to adjust
18409 @code{handle_exception} to arrange for it to return to the instruction
18410 after the breakpoint on this first invocation, so that your program
18411 doesn't keep hitting the initial breakpoint instead of making
18415 For the 680x0 stub only, you need to provide a variable called
18416 @code{exceptionHook}. Normally you just use:
18419 void (*exceptionHook)() = 0;
18423 but if before calling @code{set_debug_traps}, you set it to point to a
18424 function in your program, that function is called when
18425 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
18426 error). The function indicated by @code{exceptionHook} is called with
18427 one parameter: an @code{int} which is the exception number.
18430 Compile and link together: your program, the @value{GDBN} debugging stub for
18431 your target architecture, and the supporting subroutines.
18434 Make sure you have a serial connection between your target machine and
18435 the @value{GDBN} host, and identify the serial port on the host.
18438 @c The "remote" target now provides a `load' command, so we should
18439 @c document that. FIXME.
18440 Download your program to your target machine (or get it there by
18441 whatever means the manufacturer provides), and start it.
18444 Start @value{GDBN} on the host, and connect to the target
18445 (@pxref{Connecting,,Connecting to a Remote Target}).
18449 @node Configurations
18450 @chapter Configuration-Specific Information
18452 While nearly all @value{GDBN} commands are available for all native and
18453 cross versions of the debugger, there are some exceptions. This chapter
18454 describes things that are only available in certain configurations.
18456 There are three major categories of configurations: native
18457 configurations, where the host and target are the same, embedded
18458 operating system configurations, which are usually the same for several
18459 different processor architectures, and bare embedded processors, which
18460 are quite different from each other.
18465 * Embedded Processors::
18472 This section describes details specific to particular native
18477 * BSD libkvm Interface:: Debugging BSD kernel memory images
18478 * SVR4 Process Information:: SVR4 process information
18479 * DJGPP Native:: Features specific to the DJGPP port
18480 * Cygwin Native:: Features specific to the Cygwin port
18481 * Hurd Native:: Features specific to @sc{gnu} Hurd
18482 * Darwin:: Features specific to Darwin
18488 On HP-UX systems, if you refer to a function or variable name that
18489 begins with a dollar sign, @value{GDBN} searches for a user or system
18490 name first, before it searches for a convenience variable.
18493 @node BSD libkvm Interface
18494 @subsection BSD libkvm Interface
18497 @cindex kernel memory image
18498 @cindex kernel crash dump
18500 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
18501 interface that provides a uniform interface for accessing kernel virtual
18502 memory images, including live systems and crash dumps. @value{GDBN}
18503 uses this interface to allow you to debug live kernels and kernel crash
18504 dumps on many native BSD configurations. This is implemented as a
18505 special @code{kvm} debugging target. For debugging a live system, load
18506 the currently running kernel into @value{GDBN} and connect to the
18510 (@value{GDBP}) @b{target kvm}
18513 For debugging crash dumps, provide the file name of the crash dump as an
18517 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
18520 Once connected to the @code{kvm} target, the following commands are
18526 Set current context from the @dfn{Process Control Block} (PCB) address.
18529 Set current context from proc address. This command isn't available on
18530 modern FreeBSD systems.
18533 @node SVR4 Process Information
18534 @subsection SVR4 Process Information
18536 @cindex examine process image
18537 @cindex process info via @file{/proc}
18539 Many versions of SVR4 and compatible systems provide a facility called
18540 @samp{/proc} that can be used to examine the image of a running
18541 process using file-system subroutines. If @value{GDBN} is configured
18542 for an operating system with this facility, the command @code{info
18543 proc} is available to report information about the process running
18544 your program, or about any process running on your system. @code{info
18545 proc} works only on SVR4 systems that include the @code{procfs} code.
18546 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
18547 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
18553 @itemx info proc @var{process-id}
18554 Summarize available information about any running process. If a
18555 process ID is specified by @var{process-id}, display information about
18556 that process; otherwise display information about the program being
18557 debugged. The summary includes the debugged process ID, the command
18558 line used to invoke it, its current working directory, and its
18559 executable file's absolute file name.
18561 On some systems, @var{process-id} can be of the form
18562 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
18563 within a process. If the optional @var{pid} part is missing, it means
18564 a thread from the process being debugged (the leading @samp{/} still
18565 needs to be present, or else @value{GDBN} will interpret the number as
18566 a process ID rather than a thread ID).
18568 @item info proc mappings
18569 @cindex memory address space mappings
18570 Report the memory address space ranges accessible in the program, with
18571 information on whether the process has read, write, or execute access
18572 rights to each range. On @sc{gnu}/Linux systems, each memory range
18573 includes the object file which is mapped to that range, instead of the
18574 memory access rights to that range.
18576 @item info proc stat
18577 @itemx info proc status
18578 @cindex process detailed status information
18579 These subcommands are specific to @sc{gnu}/Linux systems. They show
18580 the process-related information, including the user ID and group ID;
18581 how many threads are there in the process; its virtual memory usage;
18582 the signals that are pending, blocked, and ignored; its TTY; its
18583 consumption of system and user time; its stack size; its @samp{nice}
18584 value; etc. For more information, see the @samp{proc} man page
18585 (type @kbd{man 5 proc} from your shell prompt).
18587 @item info proc all
18588 Show all the information about the process described under all of the
18589 above @code{info proc} subcommands.
18592 @comment These sub-options of 'info proc' were not included when
18593 @comment procfs.c was re-written. Keep their descriptions around
18594 @comment against the day when someone finds the time to put them back in.
18595 @kindex info proc times
18596 @item info proc times
18597 Starting time, user CPU time, and system CPU time for your program and
18600 @kindex info proc id
18602 Report on the process IDs related to your program: its own process ID,
18603 the ID of its parent, the process group ID, and the session ID.
18606 @item set procfs-trace
18607 @kindex set procfs-trace
18608 @cindex @code{procfs} API calls
18609 This command enables and disables tracing of @code{procfs} API calls.
18611 @item show procfs-trace
18612 @kindex show procfs-trace
18613 Show the current state of @code{procfs} API call tracing.
18615 @item set procfs-file @var{file}
18616 @kindex set procfs-file
18617 Tell @value{GDBN} to write @code{procfs} API trace to the named
18618 @var{file}. @value{GDBN} appends the trace info to the previous
18619 contents of the file. The default is to display the trace on the
18622 @item show procfs-file
18623 @kindex show procfs-file
18624 Show the file to which @code{procfs} API trace is written.
18626 @item proc-trace-entry
18627 @itemx proc-trace-exit
18628 @itemx proc-untrace-entry
18629 @itemx proc-untrace-exit
18630 @kindex proc-trace-entry
18631 @kindex proc-trace-exit
18632 @kindex proc-untrace-entry
18633 @kindex proc-untrace-exit
18634 These commands enable and disable tracing of entries into and exits
18635 from the @code{syscall} interface.
18638 @kindex info pidlist
18639 @cindex process list, QNX Neutrino
18640 For QNX Neutrino only, this command displays the list of all the
18641 processes and all the threads within each process.
18644 @kindex info meminfo
18645 @cindex mapinfo list, QNX Neutrino
18646 For QNX Neutrino only, this command displays the list of all mapinfos.
18650 @subsection Features for Debugging @sc{djgpp} Programs
18651 @cindex @sc{djgpp} debugging
18652 @cindex native @sc{djgpp} debugging
18653 @cindex MS-DOS-specific commands
18656 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
18657 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
18658 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
18659 top of real-mode DOS systems and their emulations.
18661 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
18662 defines a few commands specific to the @sc{djgpp} port. This
18663 subsection describes those commands.
18668 This is a prefix of @sc{djgpp}-specific commands which print
18669 information about the target system and important OS structures.
18672 @cindex MS-DOS system info
18673 @cindex free memory information (MS-DOS)
18674 @item info dos sysinfo
18675 This command displays assorted information about the underlying
18676 platform: the CPU type and features, the OS version and flavor, the
18677 DPMI version, and the available conventional and DPMI memory.
18682 @cindex segment descriptor tables
18683 @cindex descriptor tables display
18685 @itemx info dos ldt
18686 @itemx info dos idt
18687 These 3 commands display entries from, respectively, Global, Local,
18688 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
18689 tables are data structures which store a descriptor for each segment
18690 that is currently in use. The segment's selector is an index into a
18691 descriptor table; the table entry for that index holds the
18692 descriptor's base address and limit, and its attributes and access
18695 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
18696 segment (used for both data and the stack), and a DOS segment (which
18697 allows access to DOS/BIOS data structures and absolute addresses in
18698 conventional memory). However, the DPMI host will usually define
18699 additional segments in order to support the DPMI environment.
18701 @cindex garbled pointers
18702 These commands allow to display entries from the descriptor tables.
18703 Without an argument, all entries from the specified table are
18704 displayed. An argument, which should be an integer expression, means
18705 display a single entry whose index is given by the argument. For
18706 example, here's a convenient way to display information about the
18707 debugged program's data segment:
18710 @exdent @code{(@value{GDBP}) info dos ldt $ds}
18711 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
18715 This comes in handy when you want to see whether a pointer is outside
18716 the data segment's limit (i.e.@: @dfn{garbled}).
18718 @cindex page tables display (MS-DOS)
18720 @itemx info dos pte
18721 These two commands display entries from, respectively, the Page
18722 Directory and the Page Tables. Page Directories and Page Tables are
18723 data structures which control how virtual memory addresses are mapped
18724 into physical addresses. A Page Table includes an entry for every
18725 page of memory that is mapped into the program's address space; there
18726 may be several Page Tables, each one holding up to 4096 entries. A
18727 Page Directory has up to 4096 entries, one each for every Page Table
18728 that is currently in use.
18730 Without an argument, @kbd{info dos pde} displays the entire Page
18731 Directory, and @kbd{info dos pte} displays all the entries in all of
18732 the Page Tables. An argument, an integer expression, given to the
18733 @kbd{info dos pde} command means display only that entry from the Page
18734 Directory table. An argument given to the @kbd{info dos pte} command
18735 means display entries from a single Page Table, the one pointed to by
18736 the specified entry in the Page Directory.
18738 @cindex direct memory access (DMA) on MS-DOS
18739 These commands are useful when your program uses @dfn{DMA} (Direct
18740 Memory Access), which needs physical addresses to program the DMA
18743 These commands are supported only with some DPMI servers.
18745 @cindex physical address from linear address
18746 @item info dos address-pte @var{addr}
18747 This command displays the Page Table entry for a specified linear
18748 address. The argument @var{addr} is a linear address which should
18749 already have the appropriate segment's base address added to it,
18750 because this command accepts addresses which may belong to @emph{any}
18751 segment. For example, here's how to display the Page Table entry for
18752 the page where a variable @code{i} is stored:
18755 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
18756 @exdent @code{Page Table entry for address 0x11a00d30:}
18757 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
18761 This says that @code{i} is stored at offset @code{0xd30} from the page
18762 whose physical base address is @code{0x02698000}, and shows all the
18763 attributes of that page.
18765 Note that you must cast the addresses of variables to a @code{char *},
18766 since otherwise the value of @code{__djgpp_base_address}, the base
18767 address of all variables and functions in a @sc{djgpp} program, will
18768 be added using the rules of C pointer arithmetics: if @code{i} is
18769 declared an @code{int}, @value{GDBN} will add 4 times the value of
18770 @code{__djgpp_base_address} to the address of @code{i}.
18772 Here's another example, it displays the Page Table entry for the
18776 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
18777 @exdent @code{Page Table entry for address 0x29110:}
18778 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
18782 (The @code{+ 3} offset is because the transfer buffer's address is the
18783 3rd member of the @code{_go32_info_block} structure.) The output
18784 clearly shows that this DPMI server maps the addresses in conventional
18785 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
18786 linear (@code{0x29110}) addresses are identical.
18788 This command is supported only with some DPMI servers.
18791 @cindex DOS serial data link, remote debugging
18792 In addition to native debugging, the DJGPP port supports remote
18793 debugging via a serial data link. The following commands are specific
18794 to remote serial debugging in the DJGPP port of @value{GDBN}.
18797 @kindex set com1base
18798 @kindex set com1irq
18799 @kindex set com2base
18800 @kindex set com2irq
18801 @kindex set com3base
18802 @kindex set com3irq
18803 @kindex set com4base
18804 @kindex set com4irq
18805 @item set com1base @var{addr}
18806 This command sets the base I/O port address of the @file{COM1} serial
18809 @item set com1irq @var{irq}
18810 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
18811 for the @file{COM1} serial port.
18813 There are similar commands @samp{set com2base}, @samp{set com3irq},
18814 etc.@: for setting the port address and the @code{IRQ} lines for the
18817 @kindex show com1base
18818 @kindex show com1irq
18819 @kindex show com2base
18820 @kindex show com2irq
18821 @kindex show com3base
18822 @kindex show com3irq
18823 @kindex show com4base
18824 @kindex show com4irq
18825 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18826 display the current settings of the base address and the @code{IRQ}
18827 lines used by the COM ports.
18830 @kindex info serial
18831 @cindex DOS serial port status
18832 This command prints the status of the 4 DOS serial ports. For each
18833 port, it prints whether it's active or not, its I/O base address and
18834 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18835 counts of various errors encountered so far.
18839 @node Cygwin Native
18840 @subsection Features for Debugging MS Windows PE Executables
18841 @cindex MS Windows debugging
18842 @cindex native Cygwin debugging
18843 @cindex Cygwin-specific commands
18845 @value{GDBN} supports native debugging of MS Windows programs, including
18846 DLLs with and without symbolic debugging information.
18848 @cindex Ctrl-BREAK, MS-Windows
18849 @cindex interrupt debuggee on MS-Windows
18850 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18851 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18852 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18853 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18854 sequence, which can be used to interrupt the debuggee even if it
18857 There are various additional Cygwin-specific commands, described in
18858 this section. Working with DLLs that have no debugging symbols is
18859 described in @ref{Non-debug DLL Symbols}.
18864 This is a prefix of MS Windows-specific commands which print
18865 information about the target system and important OS structures.
18867 @item info w32 selector
18868 This command displays information returned by
18869 the Win32 API @code{GetThreadSelectorEntry} function.
18870 It takes an optional argument that is evaluated to
18871 a long value to give the information about this given selector.
18872 Without argument, this command displays information
18873 about the six segment registers.
18875 @item info w32 thread-information-block
18876 This command displays thread specific information stored in the
18877 Thread Information Block (readable on the X86 CPU family using @code{$fs}
18878 selector for 32-bit programs and @code{$gs} for 64-bit programs).
18882 This is a Cygwin-specific alias of @code{info shared}.
18884 @kindex dll-symbols
18886 This command loads symbols from a dll similarly to
18887 add-sym command but without the need to specify a base address.
18889 @kindex set cygwin-exceptions
18890 @cindex debugging the Cygwin DLL
18891 @cindex Cygwin DLL, debugging
18892 @item set cygwin-exceptions @var{mode}
18893 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
18894 happen inside the Cygwin DLL. If @var{mode} is @code{off},
18895 @value{GDBN} will delay recognition of exceptions, and may ignore some
18896 exceptions which seem to be caused by internal Cygwin DLL
18897 ``bookkeeping''. This option is meant primarily for debugging the
18898 Cygwin DLL itself; the default value is @code{off} to avoid annoying
18899 @value{GDBN} users with false @code{SIGSEGV} signals.
18901 @kindex show cygwin-exceptions
18902 @item show cygwin-exceptions
18903 Displays whether @value{GDBN} will break on exceptions that happen
18904 inside the Cygwin DLL itself.
18906 @kindex set new-console
18907 @item set new-console @var{mode}
18908 If @var{mode} is @code{on} the debuggee will
18909 be started in a new console on next start.
18910 If @var{mode} is @code{off}, the debuggee will
18911 be started in the same console as the debugger.
18913 @kindex show new-console
18914 @item show new-console
18915 Displays whether a new console is used
18916 when the debuggee is started.
18918 @kindex set new-group
18919 @item set new-group @var{mode}
18920 This boolean value controls whether the debuggee should
18921 start a new group or stay in the same group as the debugger.
18922 This affects the way the Windows OS handles
18925 @kindex show new-group
18926 @item show new-group
18927 Displays current value of new-group boolean.
18929 @kindex set debugevents
18930 @item set debugevents
18931 This boolean value adds debug output concerning kernel events related
18932 to the debuggee seen by the debugger. This includes events that
18933 signal thread and process creation and exit, DLL loading and
18934 unloading, console interrupts, and debugging messages produced by the
18935 Windows @code{OutputDebugString} API call.
18937 @kindex set debugexec
18938 @item set debugexec
18939 This boolean value adds debug output concerning execute events
18940 (such as resume thread) seen by the debugger.
18942 @kindex set debugexceptions
18943 @item set debugexceptions
18944 This boolean value adds debug output concerning exceptions in the
18945 debuggee seen by the debugger.
18947 @kindex set debugmemory
18948 @item set debugmemory
18949 This boolean value adds debug output concerning debuggee memory reads
18950 and writes by the debugger.
18954 This boolean values specifies whether the debuggee is called
18955 via a shell or directly (default value is on).
18959 Displays if the debuggee will be started with a shell.
18964 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18967 @node Non-debug DLL Symbols
18968 @subsubsection Support for DLLs without Debugging Symbols
18969 @cindex DLLs with no debugging symbols
18970 @cindex Minimal symbols and DLLs
18972 Very often on windows, some of the DLLs that your program relies on do
18973 not include symbolic debugging information (for example,
18974 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18975 symbols in a DLL, it relies on the minimal amount of symbolic
18976 information contained in the DLL's export table. This section
18977 describes working with such symbols, known internally to @value{GDBN} as
18978 ``minimal symbols''.
18980 Note that before the debugged program has started execution, no DLLs
18981 will have been loaded. The easiest way around this problem is simply to
18982 start the program --- either by setting a breakpoint or letting the
18983 program run once to completion. It is also possible to force
18984 @value{GDBN} to load a particular DLL before starting the executable ---
18985 see the shared library information in @ref{Files}, or the
18986 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18987 explicitly loading symbols from a DLL with no debugging information will
18988 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18989 which may adversely affect symbol lookup performance.
18991 @subsubsection DLL Name Prefixes
18993 In keeping with the naming conventions used by the Microsoft debugging
18994 tools, DLL export symbols are made available with a prefix based on the
18995 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18996 also entered into the symbol table, so @code{CreateFileA} is often
18997 sufficient. In some cases there will be name clashes within a program
18998 (particularly if the executable itself includes full debugging symbols)
18999 necessitating the use of the fully qualified name when referring to the
19000 contents of the DLL. Use single-quotes around the name to avoid the
19001 exclamation mark (``!'') being interpreted as a language operator.
19003 Note that the internal name of the DLL may be all upper-case, even
19004 though the file name of the DLL is lower-case, or vice-versa. Since
19005 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19006 some confusion. If in doubt, try the @code{info functions} and
19007 @code{info variables} commands or even @code{maint print msymbols}
19008 (@pxref{Symbols}). Here's an example:
19011 (@value{GDBP}) info function CreateFileA
19012 All functions matching regular expression "CreateFileA":
19014 Non-debugging symbols:
19015 0x77e885f4 CreateFileA
19016 0x77e885f4 KERNEL32!CreateFileA
19020 (@value{GDBP}) info function !
19021 All functions matching regular expression "!":
19023 Non-debugging symbols:
19024 0x6100114c cygwin1!__assert
19025 0x61004034 cygwin1!_dll_crt0@@0
19026 0x61004240 cygwin1!dll_crt0(per_process *)
19030 @subsubsection Working with Minimal Symbols
19032 Symbols extracted from a DLL's export table do not contain very much
19033 type information. All that @value{GDBN} can do is guess whether a symbol
19034 refers to a function or variable depending on the linker section that
19035 contains the symbol. Also note that the actual contents of the memory
19036 contained in a DLL are not available unless the program is running. This
19037 means that you cannot examine the contents of a variable or disassemble
19038 a function within a DLL without a running program.
19040 Variables are generally treated as pointers and dereferenced
19041 automatically. For this reason, it is often necessary to prefix a
19042 variable name with the address-of operator (``&'') and provide explicit
19043 type information in the command. Here's an example of the type of
19047 (@value{GDBP}) print 'cygwin1!__argv'
19052 (@value{GDBP}) x 'cygwin1!__argv'
19053 0x10021610: "\230y\""
19056 And two possible solutions:
19059 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19060 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19064 (@value{GDBP}) x/2x &'cygwin1!__argv'
19065 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19066 (@value{GDBP}) x/x 0x10021608
19067 0x10021608: 0x0022fd98
19068 (@value{GDBP}) x/s 0x0022fd98
19069 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19072 Setting a break point within a DLL is possible even before the program
19073 starts execution. However, under these circumstances, @value{GDBN} can't
19074 examine the initial instructions of the function in order to skip the
19075 function's frame set-up code. You can work around this by using ``*&''
19076 to set the breakpoint at a raw memory address:
19079 (@value{GDBP}) break *&'python22!PyOS_Readline'
19080 Breakpoint 1 at 0x1e04eff0
19083 The author of these extensions is not entirely convinced that setting a
19084 break point within a shared DLL like @file{kernel32.dll} is completely
19088 @subsection Commands Specific to @sc{gnu} Hurd Systems
19089 @cindex @sc{gnu} Hurd debugging
19091 This subsection describes @value{GDBN} commands specific to the
19092 @sc{gnu} Hurd native debugging.
19097 @kindex set signals@r{, Hurd command}
19098 @kindex set sigs@r{, Hurd command}
19099 This command toggles the state of inferior signal interception by
19100 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
19101 affected by this command. @code{sigs} is a shorthand alias for
19106 @kindex show signals@r{, Hurd command}
19107 @kindex show sigs@r{, Hurd command}
19108 Show the current state of intercepting inferior's signals.
19110 @item set signal-thread
19111 @itemx set sigthread
19112 @kindex set signal-thread
19113 @kindex set sigthread
19114 This command tells @value{GDBN} which thread is the @code{libc} signal
19115 thread. That thread is run when a signal is delivered to a running
19116 process. @code{set sigthread} is the shorthand alias of @code{set
19119 @item show signal-thread
19120 @itemx show sigthread
19121 @kindex show signal-thread
19122 @kindex show sigthread
19123 These two commands show which thread will run when the inferior is
19124 delivered a signal.
19127 @kindex set stopped@r{, Hurd command}
19128 This commands tells @value{GDBN} that the inferior process is stopped,
19129 as with the @code{SIGSTOP} signal. The stopped process can be
19130 continued by delivering a signal to it.
19133 @kindex show stopped@r{, Hurd command}
19134 This command shows whether @value{GDBN} thinks the debuggee is
19137 @item set exceptions
19138 @kindex set exceptions@r{, Hurd command}
19139 Use this command to turn off trapping of exceptions in the inferior.
19140 When exception trapping is off, neither breakpoints nor
19141 single-stepping will work. To restore the default, set exception
19144 @item show exceptions
19145 @kindex show exceptions@r{, Hurd command}
19146 Show the current state of trapping exceptions in the inferior.
19148 @item set task pause
19149 @kindex set task@r{, Hurd commands}
19150 @cindex task attributes (@sc{gnu} Hurd)
19151 @cindex pause current task (@sc{gnu} Hurd)
19152 This command toggles task suspension when @value{GDBN} has control.
19153 Setting it to on takes effect immediately, and the task is suspended
19154 whenever @value{GDBN} gets control. Setting it to off will take
19155 effect the next time the inferior is continued. If this option is set
19156 to off, you can use @code{set thread default pause on} or @code{set
19157 thread pause on} (see below) to pause individual threads.
19159 @item show task pause
19160 @kindex show task@r{, Hurd commands}
19161 Show the current state of task suspension.
19163 @item set task detach-suspend-count
19164 @cindex task suspend count
19165 @cindex detach from task, @sc{gnu} Hurd
19166 This command sets the suspend count the task will be left with when
19167 @value{GDBN} detaches from it.
19169 @item show task detach-suspend-count
19170 Show the suspend count the task will be left with when detaching.
19172 @item set task exception-port
19173 @itemx set task excp
19174 @cindex task exception port, @sc{gnu} Hurd
19175 This command sets the task exception port to which @value{GDBN} will
19176 forward exceptions. The argument should be the value of the @dfn{send
19177 rights} of the task. @code{set task excp} is a shorthand alias.
19179 @item set noninvasive
19180 @cindex noninvasive task options
19181 This command switches @value{GDBN} to a mode that is the least
19182 invasive as far as interfering with the inferior is concerned. This
19183 is the same as using @code{set task pause}, @code{set exceptions}, and
19184 @code{set signals} to values opposite to the defaults.
19186 @item info send-rights
19187 @itemx info receive-rights
19188 @itemx info port-rights
19189 @itemx info port-sets
19190 @itemx info dead-names
19193 @cindex send rights, @sc{gnu} Hurd
19194 @cindex receive rights, @sc{gnu} Hurd
19195 @cindex port rights, @sc{gnu} Hurd
19196 @cindex port sets, @sc{gnu} Hurd
19197 @cindex dead names, @sc{gnu} Hurd
19198 These commands display information about, respectively, send rights,
19199 receive rights, port rights, port sets, and dead names of a task.
19200 There are also shorthand aliases: @code{info ports} for @code{info
19201 port-rights} and @code{info psets} for @code{info port-sets}.
19203 @item set thread pause
19204 @kindex set thread@r{, Hurd command}
19205 @cindex thread properties, @sc{gnu} Hurd
19206 @cindex pause current thread (@sc{gnu} Hurd)
19207 This command toggles current thread suspension when @value{GDBN} has
19208 control. Setting it to on takes effect immediately, and the current
19209 thread is suspended whenever @value{GDBN} gets control. Setting it to
19210 off will take effect the next time the inferior is continued.
19211 Normally, this command has no effect, since when @value{GDBN} has
19212 control, the whole task is suspended. However, if you used @code{set
19213 task pause off} (see above), this command comes in handy to suspend
19214 only the current thread.
19216 @item show thread pause
19217 @kindex show thread@r{, Hurd command}
19218 This command shows the state of current thread suspension.
19220 @item set thread run
19221 This command sets whether the current thread is allowed to run.
19223 @item show thread run
19224 Show whether the current thread is allowed to run.
19226 @item set thread detach-suspend-count
19227 @cindex thread suspend count, @sc{gnu} Hurd
19228 @cindex detach from thread, @sc{gnu} Hurd
19229 This command sets the suspend count @value{GDBN} will leave on a
19230 thread when detaching. This number is relative to the suspend count
19231 found by @value{GDBN} when it notices the thread; use @code{set thread
19232 takeover-suspend-count} to force it to an absolute value.
19234 @item show thread detach-suspend-count
19235 Show the suspend count @value{GDBN} will leave on the thread when
19238 @item set thread exception-port
19239 @itemx set thread excp
19240 Set the thread exception port to which to forward exceptions. This
19241 overrides the port set by @code{set task exception-port} (see above).
19242 @code{set thread excp} is the shorthand alias.
19244 @item set thread takeover-suspend-count
19245 Normally, @value{GDBN}'s thread suspend counts are relative to the
19246 value @value{GDBN} finds when it notices each thread. This command
19247 changes the suspend counts to be absolute instead.
19249 @item set thread default
19250 @itemx show thread default
19251 @cindex thread default settings, @sc{gnu} Hurd
19252 Each of the above @code{set thread} commands has a @code{set thread
19253 default} counterpart (e.g., @code{set thread default pause}, @code{set
19254 thread default exception-port}, etc.). The @code{thread default}
19255 variety of commands sets the default thread properties for all
19256 threads; you can then change the properties of individual threads with
19257 the non-default commands.
19264 @value{GDBN} provides the following commands specific to the Darwin target:
19267 @item set debug darwin @var{num}
19268 @kindex set debug darwin
19269 When set to a non zero value, enables debugging messages specific to
19270 the Darwin support. Higher values produce more verbose output.
19272 @item show debug darwin
19273 @kindex show debug darwin
19274 Show the current state of Darwin messages.
19276 @item set debug mach-o @var{num}
19277 @kindex set debug mach-o
19278 When set to a non zero value, enables debugging messages while
19279 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
19280 file format used on Darwin for object and executable files.) Higher
19281 values produce more verbose output. This is a command to diagnose
19282 problems internal to @value{GDBN} and should not be needed in normal
19285 @item show debug mach-o
19286 @kindex show debug mach-o
19287 Show the current state of Mach-O file messages.
19289 @item set mach-exceptions on
19290 @itemx set mach-exceptions off
19291 @kindex set mach-exceptions
19292 On Darwin, faults are first reported as a Mach exception and are then
19293 mapped to a Posix signal. Use this command to turn on trapping of
19294 Mach exceptions in the inferior. This might be sometimes useful to
19295 better understand the cause of a fault. The default is off.
19297 @item show mach-exceptions
19298 @kindex show mach-exceptions
19299 Show the current state of exceptions trapping.
19304 @section Embedded Operating Systems
19306 This section describes configurations involving the debugging of
19307 embedded operating systems that are available for several different
19311 * VxWorks:: Using @value{GDBN} with VxWorks
19314 @value{GDBN} includes the ability to debug programs running on
19315 various real-time operating systems.
19318 @subsection Using @value{GDBN} with VxWorks
19324 @kindex target vxworks
19325 @item target vxworks @var{machinename}
19326 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
19327 is the target system's machine name or IP address.
19331 On VxWorks, @code{load} links @var{filename} dynamically on the
19332 current target system as well as adding its symbols in @value{GDBN}.
19334 @value{GDBN} enables developers to spawn and debug tasks running on networked
19335 VxWorks targets from a Unix host. Already-running tasks spawned from
19336 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
19337 both the Unix host and on the VxWorks target. The program
19338 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
19339 installed with the name @code{vxgdb}, to distinguish it from a
19340 @value{GDBN} for debugging programs on the host itself.)
19343 @item VxWorks-timeout @var{args}
19344 @kindex vxworks-timeout
19345 All VxWorks-based targets now support the option @code{vxworks-timeout}.
19346 This option is set by the user, and @var{args} represents the number of
19347 seconds @value{GDBN} waits for responses to rpc's. You might use this if
19348 your VxWorks target is a slow software simulator or is on the far side
19349 of a thin network line.
19352 The following information on connecting to VxWorks was current when
19353 this manual was produced; newer releases of VxWorks may use revised
19356 @findex INCLUDE_RDB
19357 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
19358 to include the remote debugging interface routines in the VxWorks
19359 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
19360 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
19361 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
19362 source debugging task @code{tRdbTask} when VxWorks is booted. For more
19363 information on configuring and remaking VxWorks, see the manufacturer's
19365 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
19367 Once you have included @file{rdb.a} in your VxWorks system image and set
19368 your Unix execution search path to find @value{GDBN}, you are ready to
19369 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
19370 @code{vxgdb}, depending on your installation).
19372 @value{GDBN} comes up showing the prompt:
19379 * VxWorks Connection:: Connecting to VxWorks
19380 * VxWorks Download:: VxWorks download
19381 * VxWorks Attach:: Running tasks
19384 @node VxWorks Connection
19385 @subsubsection Connecting to VxWorks
19387 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
19388 network. To connect to a target whose host name is ``@code{tt}'', type:
19391 (vxgdb) target vxworks tt
19395 @value{GDBN} displays messages like these:
19398 Attaching remote machine across net...
19403 @value{GDBN} then attempts to read the symbol tables of any object modules
19404 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
19405 these files by searching the directories listed in the command search
19406 path (@pxref{Environment, ,Your Program's Environment}); if it fails
19407 to find an object file, it displays a message such as:
19410 prog.o: No such file or directory.
19413 When this happens, add the appropriate directory to the search path with
19414 the @value{GDBN} command @code{path}, and execute the @code{target}
19417 @node VxWorks Download
19418 @subsubsection VxWorks Download
19420 @cindex download to VxWorks
19421 If you have connected to the VxWorks target and you want to debug an
19422 object that has not yet been loaded, you can use the @value{GDBN}
19423 @code{load} command to download a file from Unix to VxWorks
19424 incrementally. The object file given as an argument to the @code{load}
19425 command is actually opened twice: first by the VxWorks target in order
19426 to download the code, then by @value{GDBN} in order to read the symbol
19427 table. This can lead to problems if the current working directories on
19428 the two systems differ. If both systems have NFS mounted the same
19429 filesystems, you can avoid these problems by using absolute paths.
19430 Otherwise, it is simplest to set the working directory on both systems
19431 to the directory in which the object file resides, and then to reference
19432 the file by its name, without any path. For instance, a program
19433 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
19434 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
19435 program, type this on VxWorks:
19438 -> cd "@var{vxpath}/vw/demo/rdb"
19442 Then, in @value{GDBN}, type:
19445 (vxgdb) cd @var{hostpath}/vw/demo/rdb
19446 (vxgdb) load prog.o
19449 @value{GDBN} displays a response similar to this:
19452 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
19455 You can also use the @code{load} command to reload an object module
19456 after editing and recompiling the corresponding source file. Note that
19457 this makes @value{GDBN} delete all currently-defined breakpoints,
19458 auto-displays, and convenience variables, and to clear the value
19459 history. (This is necessary in order to preserve the integrity of
19460 debugger's data structures that reference the target system's symbol
19463 @node VxWorks Attach
19464 @subsubsection Running Tasks
19466 @cindex running VxWorks tasks
19467 You can also attach to an existing task using the @code{attach} command as
19471 (vxgdb) attach @var{task}
19475 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
19476 or suspended when you attach to it. Running tasks are suspended at
19477 the time of attachment.
19479 @node Embedded Processors
19480 @section Embedded Processors
19482 This section goes into details specific to particular embedded
19485 @cindex send command to simulator
19486 Whenever a specific embedded processor has a simulator, @value{GDBN}
19487 allows to send an arbitrary command to the simulator.
19490 @item sim @var{command}
19491 @kindex sim@r{, a command}
19492 Send an arbitrary @var{command} string to the simulator. Consult the
19493 documentation for the specific simulator in use for information about
19494 acceptable commands.
19500 * M32R/D:: Renesas M32R/D
19501 * M68K:: Motorola M68K
19502 * MicroBlaze:: Xilinx MicroBlaze
19503 * MIPS Embedded:: MIPS Embedded
19504 * OpenRISC 1000:: OpenRisc 1000
19505 * PowerPC Embedded:: PowerPC Embedded
19506 * PA:: HP PA Embedded
19507 * Sparclet:: Tsqware Sparclet
19508 * Sparclite:: Fujitsu Sparclite
19509 * Z8000:: Zilog Z8000
19512 * Super-H:: Renesas Super-H
19521 @item target rdi @var{dev}
19522 ARM Angel monitor, via RDI library interface to ADP protocol. You may
19523 use this target to communicate with both boards running the Angel
19524 monitor, or with the EmbeddedICE JTAG debug device.
19527 @item target rdp @var{dev}
19532 @value{GDBN} provides the following ARM-specific commands:
19535 @item set arm disassembler
19537 This commands selects from a list of disassembly styles. The
19538 @code{"std"} style is the standard style.
19540 @item show arm disassembler
19542 Show the current disassembly style.
19544 @item set arm apcs32
19545 @cindex ARM 32-bit mode
19546 This command toggles ARM operation mode between 32-bit and 26-bit.
19548 @item show arm apcs32
19549 Display the current usage of the ARM 32-bit mode.
19551 @item set arm fpu @var{fputype}
19552 This command sets the ARM floating-point unit (FPU) type. The
19553 argument @var{fputype} can be one of these:
19557 Determine the FPU type by querying the OS ABI.
19559 Software FPU, with mixed-endian doubles on little-endian ARM
19562 GCC-compiled FPA co-processor.
19564 Software FPU with pure-endian doubles.
19570 Show the current type of the FPU.
19573 This command forces @value{GDBN} to use the specified ABI.
19576 Show the currently used ABI.
19578 @item set arm fallback-mode (arm|thumb|auto)
19579 @value{GDBN} uses the symbol table, when available, to determine
19580 whether instructions are ARM or Thumb. This command controls
19581 @value{GDBN}'s default behavior when the symbol table is not
19582 available. The default is @samp{auto}, which causes @value{GDBN} to
19583 use the current execution mode (from the @code{T} bit in the @code{CPSR}
19586 @item show arm fallback-mode
19587 Show the current fallback instruction mode.
19589 @item set arm force-mode (arm|thumb|auto)
19590 This command overrides use of the symbol table to determine whether
19591 instructions are ARM or Thumb. The default is @samp{auto}, which
19592 causes @value{GDBN} to use the symbol table and then the setting
19593 of @samp{set arm fallback-mode}.
19595 @item show arm force-mode
19596 Show the current forced instruction mode.
19598 @item set debug arm
19599 Toggle whether to display ARM-specific debugging messages from the ARM
19600 target support subsystem.
19602 @item show debug arm
19603 Show whether ARM-specific debugging messages are enabled.
19606 The following commands are available when an ARM target is debugged
19607 using the RDI interface:
19610 @item rdilogfile @r{[}@var{file}@r{]}
19612 @cindex ADP (Angel Debugger Protocol) logging
19613 Set the filename for the ADP (Angel Debugger Protocol) packet log.
19614 With an argument, sets the log file to the specified @var{file}. With
19615 no argument, show the current log file name. The default log file is
19618 @item rdilogenable @r{[}@var{arg}@r{]}
19619 @kindex rdilogenable
19620 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
19621 enables logging, with an argument 0 or @code{"no"} disables it. With
19622 no arguments displays the current setting. When logging is enabled,
19623 ADP packets exchanged between @value{GDBN} and the RDI target device
19624 are logged to a file.
19626 @item set rdiromatzero
19627 @kindex set rdiromatzero
19628 @cindex ROM at zero address, RDI
19629 Tell @value{GDBN} whether the target has ROM at address 0. If on,
19630 vector catching is disabled, so that zero address can be used. If off
19631 (the default), vector catching is enabled. For this command to take
19632 effect, it needs to be invoked prior to the @code{target rdi} command.
19634 @item show rdiromatzero
19635 @kindex show rdiromatzero
19636 Show the current setting of ROM at zero address.
19638 @item set rdiheartbeat
19639 @kindex set rdiheartbeat
19640 @cindex RDI heartbeat
19641 Enable or disable RDI heartbeat packets. It is not recommended to
19642 turn on this option, since it confuses ARM and EPI JTAG interface, as
19643 well as the Angel monitor.
19645 @item show rdiheartbeat
19646 @kindex show rdiheartbeat
19647 Show the setting of RDI heartbeat packets.
19651 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19652 The @value{GDBN} ARM simulator accepts the following optional arguments.
19655 @item --swi-support=@var{type}
19656 Tell the simulator which SWI interfaces to support.
19657 @var{type} may be a comma separated list of the following values.
19658 The default value is @code{all}.
19671 @subsection Renesas M32R/D and M32R/SDI
19674 @kindex target m32r
19675 @item target m32r @var{dev}
19676 Renesas M32R/D ROM monitor.
19678 @kindex target m32rsdi
19679 @item target m32rsdi @var{dev}
19680 Renesas M32R SDI server, connected via parallel port to the board.
19683 The following @value{GDBN} commands are specific to the M32R monitor:
19686 @item set download-path @var{path}
19687 @kindex set download-path
19688 @cindex find downloadable @sc{srec} files (M32R)
19689 Set the default path for finding downloadable @sc{srec} files.
19691 @item show download-path
19692 @kindex show download-path
19693 Show the default path for downloadable @sc{srec} files.
19695 @item set board-address @var{addr}
19696 @kindex set board-address
19697 @cindex M32-EVA target board address
19698 Set the IP address for the M32R-EVA target board.
19700 @item show board-address
19701 @kindex show board-address
19702 Show the current IP address of the target board.
19704 @item set server-address @var{addr}
19705 @kindex set server-address
19706 @cindex download server address (M32R)
19707 Set the IP address for the download server, which is the @value{GDBN}'s
19710 @item show server-address
19711 @kindex show server-address
19712 Display the IP address of the download server.
19714 @item upload @r{[}@var{file}@r{]}
19715 @kindex upload@r{, M32R}
19716 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
19717 upload capability. If no @var{file} argument is given, the current
19718 executable file is uploaded.
19720 @item tload @r{[}@var{file}@r{]}
19721 @kindex tload@r{, M32R}
19722 Test the @code{upload} command.
19725 The following commands are available for M32R/SDI:
19730 @cindex reset SDI connection, M32R
19731 This command resets the SDI connection.
19735 This command shows the SDI connection status.
19738 @kindex debug_chaos
19739 @cindex M32R/Chaos debugging
19740 Instructs the remote that M32R/Chaos debugging is to be used.
19742 @item use_debug_dma
19743 @kindex use_debug_dma
19744 Instructs the remote to use the DEBUG_DMA method of accessing memory.
19747 @kindex use_mon_code
19748 Instructs the remote to use the MON_CODE method of accessing memory.
19751 @kindex use_ib_break
19752 Instructs the remote to set breakpoints by IB break.
19754 @item use_dbt_break
19755 @kindex use_dbt_break
19756 Instructs the remote to set breakpoints by DBT.
19762 The Motorola m68k configuration includes ColdFire support, and a
19763 target command for the following ROM monitor.
19767 @kindex target dbug
19768 @item target dbug @var{dev}
19769 dBUG ROM monitor for Motorola ColdFire.
19774 @subsection MicroBlaze
19775 @cindex Xilinx MicroBlaze
19776 @cindex XMD, Xilinx Microprocessor Debugger
19778 The MicroBlaze is a soft-core processor supported on various Xilinx
19779 FPGAs, such as Spartan or Virtex series. Boards with these processors
19780 usually have JTAG ports which connect to a host system running the Xilinx
19781 Embedded Development Kit (EDK) or Software Development Kit (SDK).
19782 This host system is used to download the configuration bitstream to
19783 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
19784 communicates with the target board using the JTAG interface and
19785 presents a @code{gdbserver} interface to the board. By default
19786 @code{xmd} uses port @code{1234}. (While it is possible to change
19787 this default port, it requires the use of undocumented @code{xmd}
19788 commands. Contact Xilinx support if you need to do this.)
19790 Use these GDB commands to connect to the MicroBlaze target processor.
19793 @item target remote :1234
19794 Use this command to connect to the target if you are running @value{GDBN}
19795 on the same system as @code{xmd}.
19797 @item target remote @var{xmd-host}:1234
19798 Use this command to connect to the target if it is connected to @code{xmd}
19799 running on a different system named @var{xmd-host}.
19802 Use this command to download a program to the MicroBlaze target.
19804 @item set debug microblaze @var{n}
19805 Enable MicroBlaze-specific debugging messages if non-zero.
19807 @item show debug microblaze @var{n}
19808 Show MicroBlaze-specific debugging level.
19811 @node MIPS Embedded
19812 @subsection @acronym{MIPS} Embedded
19814 @cindex @acronym{MIPS} boards
19815 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
19816 @acronym{MIPS} board attached to a serial line. This is available when
19817 you configure @value{GDBN} with @samp{--target=mips-elf}.
19820 Use these @value{GDBN} commands to specify the connection to your target board:
19823 @item target mips @var{port}
19824 @kindex target mips @var{port}
19825 To run a program on the board, start up @code{@value{GDBP}} with the
19826 name of your program as the argument. To connect to the board, use the
19827 command @samp{target mips @var{port}}, where @var{port} is the name of
19828 the serial port connected to the board. If the program has not already
19829 been downloaded to the board, you may use the @code{load} command to
19830 download it. You can then use all the usual @value{GDBN} commands.
19832 For example, this sequence connects to the target board through a serial
19833 port, and loads and runs a program called @var{prog} through the
19837 host$ @value{GDBP} @var{prog}
19838 @value{GDBN} is free software and @dots{}
19839 (@value{GDBP}) target mips /dev/ttyb
19840 (@value{GDBP}) load @var{prog}
19844 @item target mips @var{hostname}:@var{portnumber}
19845 On some @value{GDBN} host configurations, you can specify a TCP
19846 connection (for instance, to a serial line managed by a terminal
19847 concentrator) instead of a serial port, using the syntax
19848 @samp{@var{hostname}:@var{portnumber}}.
19850 @item target pmon @var{port}
19851 @kindex target pmon @var{port}
19854 @item target ddb @var{port}
19855 @kindex target ddb @var{port}
19856 NEC's DDB variant of PMON for Vr4300.
19858 @item target lsi @var{port}
19859 @kindex target lsi @var{port}
19860 LSI variant of PMON.
19862 @kindex target r3900
19863 @item target r3900 @var{dev}
19864 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19866 @kindex target array
19867 @item target array @var{dev}
19868 Array Tech LSI33K RAID controller board.
19874 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
19877 @item set mipsfpu double
19878 @itemx set mipsfpu single
19879 @itemx set mipsfpu none
19880 @itemx set mipsfpu auto
19881 @itemx show mipsfpu
19882 @kindex set mipsfpu
19883 @kindex show mipsfpu
19884 @cindex @acronym{MIPS} remote floating point
19885 @cindex floating point, @acronym{MIPS} remote
19886 If your target board does not support the @acronym{MIPS} floating point
19887 coprocessor, you should use the command @samp{set mipsfpu none} (if you
19888 need this, you may wish to put the command in your @value{GDBN} init
19889 file). This tells @value{GDBN} how to find the return value of
19890 functions which return floating point values. It also allows
19891 @value{GDBN} to avoid saving the floating point registers when calling
19892 functions on the board. If you are using a floating point coprocessor
19893 with only single precision floating point support, as on the @sc{r4650}
19894 processor, use the command @samp{set mipsfpu single}. The default
19895 double precision floating point coprocessor may be selected using
19896 @samp{set mipsfpu double}.
19898 In previous versions the only choices were double precision or no
19899 floating point, so @samp{set mipsfpu on} will select double precision
19900 and @samp{set mipsfpu off} will select no floating point.
19902 As usual, you can inquire about the @code{mipsfpu} variable with
19903 @samp{show mipsfpu}.
19905 @item set timeout @var{seconds}
19906 @itemx set retransmit-timeout @var{seconds}
19907 @itemx show timeout
19908 @itemx show retransmit-timeout
19909 @cindex @code{timeout}, @acronym{MIPS} protocol
19910 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
19911 @kindex set timeout
19912 @kindex show timeout
19913 @kindex set retransmit-timeout
19914 @kindex show retransmit-timeout
19915 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
19916 remote protocol, with the @code{set timeout @var{seconds}} command. The
19917 default is 5 seconds. Similarly, you can control the timeout used while
19918 waiting for an acknowledgment of a packet with the @code{set
19919 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19920 You can inspect both values with @code{show timeout} and @code{show
19921 retransmit-timeout}. (These commands are @emph{only} available when
19922 @value{GDBN} is configured for @samp{--target=mips-elf}.)
19924 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19925 is waiting for your program to stop. In that case, @value{GDBN} waits
19926 forever because it has no way of knowing how long the program is going
19927 to run before stopping.
19929 @item set syn-garbage-limit @var{num}
19930 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
19931 @cindex synchronize with remote @acronym{MIPS} target
19932 Limit the maximum number of characters @value{GDBN} should ignore when
19933 it tries to synchronize with the remote target. The default is 10
19934 characters. Setting the limit to -1 means there's no limit.
19936 @item show syn-garbage-limit
19937 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
19938 Show the current limit on the number of characters to ignore when
19939 trying to synchronize with the remote system.
19941 @item set monitor-prompt @var{prompt}
19942 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
19943 @cindex remote monitor prompt
19944 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19945 remote monitor. The default depends on the target:
19955 @item show monitor-prompt
19956 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
19957 Show the current strings @value{GDBN} expects as the prompt from the
19960 @item set monitor-warnings
19961 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
19962 Enable or disable monitor warnings about hardware breakpoints. This
19963 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19964 display warning messages whose codes are returned by the @code{lsi}
19965 PMON monitor for breakpoint commands.
19967 @item show monitor-warnings
19968 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
19969 Show the current setting of printing monitor warnings.
19971 @item pmon @var{command}
19972 @kindex pmon@r{, @acronym{MIPS} remote}
19973 @cindex send PMON command
19974 This command allows sending an arbitrary @var{command} string to the
19975 monitor. The monitor must be in debug mode for this to work.
19978 @node OpenRISC 1000
19979 @subsection OpenRISC 1000
19980 @cindex OpenRISC 1000
19982 @cindex or1k boards
19983 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19984 about platform and commands.
19988 @kindex target jtag
19989 @item target jtag jtag://@var{host}:@var{port}
19991 Connects to remote JTAG server.
19992 JTAG remote server can be either an or1ksim or JTAG server,
19993 connected via parallel port to the board.
19995 Example: @code{target jtag jtag://localhost:9999}
19998 @item or1ksim @var{command}
19999 If connected to @code{or1ksim} OpenRISC 1000 Architectural
20000 Simulator, proprietary commands can be executed.
20002 @kindex info or1k spr
20003 @item info or1k spr
20004 Displays spr groups.
20006 @item info or1k spr @var{group}
20007 @itemx info or1k spr @var{groupno}
20008 Displays register names in selected group.
20010 @item info or1k spr @var{group} @var{register}
20011 @itemx info or1k spr @var{register}
20012 @itemx info or1k spr @var{groupno} @var{registerno}
20013 @itemx info or1k spr @var{registerno}
20014 Shows information about specified spr register.
20017 @item spr @var{group} @var{register} @var{value}
20018 @itemx spr @var{register @var{value}}
20019 @itemx spr @var{groupno} @var{registerno @var{value}}
20020 @itemx spr @var{registerno @var{value}}
20021 Writes @var{value} to specified spr register.
20024 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
20025 It is very similar to @value{GDBN} trace, except it does not interfere with normal
20026 program execution and is thus much faster. Hardware breakpoints/watchpoint
20027 triggers can be set using:
20030 Load effective address/data
20032 Store effective address/data
20034 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
20039 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
20040 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
20042 @code{htrace} commands:
20043 @cindex OpenRISC 1000 htrace
20046 @item hwatch @var{conditional}
20047 Set hardware watchpoint on combination of Load/Store Effective Address(es)
20048 or Data. For example:
20050 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
20052 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
20056 Display information about current HW trace configuration.
20058 @item htrace trigger @var{conditional}
20059 Set starting criteria for HW trace.
20061 @item htrace qualifier @var{conditional}
20062 Set acquisition qualifier for HW trace.
20064 @item htrace stop @var{conditional}
20065 Set HW trace stopping criteria.
20067 @item htrace record [@var{data}]*
20068 Selects the data to be recorded, when qualifier is met and HW trace was
20071 @item htrace enable
20072 @itemx htrace disable
20073 Enables/disables the HW trace.
20075 @item htrace rewind [@var{filename}]
20076 Clears currently recorded trace data.
20078 If filename is specified, new trace file is made and any newly collected data
20079 will be written there.
20081 @item htrace print [@var{start} [@var{len}]]
20082 Prints trace buffer, using current record configuration.
20084 @item htrace mode continuous
20085 Set continuous trace mode.
20087 @item htrace mode suspend
20088 Set suspend trace mode.
20092 @node PowerPC Embedded
20093 @subsection PowerPC Embedded
20095 @cindex DVC register
20096 @value{GDBN} supports using the DVC (Data Value Compare) register to
20097 implement in hardware simple hardware watchpoint conditions of the form:
20100 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20101 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20104 The DVC register will be automatically used when @value{GDBN} detects
20105 such pattern in a condition expression, and the created watchpoint uses one
20106 debug register (either the @code{exact-watchpoints} option is on and the
20107 variable is scalar, or the variable has a length of one byte). This feature
20108 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20111 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20112 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20113 in which case watchpoints using only one debug register are created when
20114 watching variables of scalar types.
20116 You can create an artificial array to watch an arbitrary memory
20117 region using one of the following commands (@pxref{Expressions}):
20120 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20121 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20124 PowerPC embedded processors support masked watchpoints. See the discussion
20125 about the @code{mask} argument in @ref{Set Watchpoints}.
20127 @cindex ranged breakpoint
20128 PowerPC embedded processors support hardware accelerated
20129 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20130 the inferior whenever it executes an instruction at any address within
20131 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20132 use the @code{break-range} command.
20134 @value{GDBN} provides the following PowerPC-specific commands:
20137 @kindex break-range
20138 @item break-range @var{start-location}, @var{end-location}
20139 Set a breakpoint for an address range.
20140 @var{start-location} and @var{end-location} can specify a function name,
20141 a line number, an offset of lines from the current line or from the start
20142 location, or an address of an instruction (see @ref{Specify Location},
20143 for a list of all the possible ways to specify a @var{location}.)
20144 The breakpoint will stop execution of the inferior whenever it
20145 executes an instruction at any address within the specified range,
20146 (including @var{start-location} and @var{end-location}.)
20148 @kindex set powerpc
20149 @item set powerpc soft-float
20150 @itemx show powerpc soft-float
20151 Force @value{GDBN} to use (or not use) a software floating point calling
20152 convention. By default, @value{GDBN} selects the calling convention based
20153 on the selected architecture and the provided executable file.
20155 @item set powerpc vector-abi
20156 @itemx show powerpc vector-abi
20157 Force @value{GDBN} to use the specified calling convention for vector
20158 arguments and return values. The valid options are @samp{auto};
20159 @samp{generic}, to avoid vector registers even if they are present;
20160 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20161 registers. By default, @value{GDBN} selects the calling convention
20162 based on the selected architecture and the provided executable file.
20164 @item set powerpc exact-watchpoints
20165 @itemx show powerpc exact-watchpoints
20166 Allow @value{GDBN} to use only one debug register when watching a variable
20167 of scalar type, thus assuming that the variable is accessed through the
20168 address of its first byte.
20170 @kindex target dink32
20171 @item target dink32 @var{dev}
20172 DINK32 ROM monitor.
20174 @kindex target ppcbug
20175 @item target ppcbug @var{dev}
20176 @kindex target ppcbug1
20177 @item target ppcbug1 @var{dev}
20178 PPCBUG ROM monitor for PowerPC.
20181 @item target sds @var{dev}
20182 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20185 @cindex SDS protocol
20186 The following commands specific to the SDS protocol are supported
20190 @item set sdstimeout @var{nsec}
20191 @kindex set sdstimeout
20192 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
20193 default is 2 seconds.
20195 @item show sdstimeout
20196 @kindex show sdstimeout
20197 Show the current value of the SDS timeout.
20199 @item sds @var{command}
20200 @kindex sds@r{, a command}
20201 Send the specified @var{command} string to the SDS monitor.
20206 @subsection HP PA Embedded
20210 @kindex target op50n
20211 @item target op50n @var{dev}
20212 OP50N monitor, running on an OKI HPPA board.
20214 @kindex target w89k
20215 @item target w89k @var{dev}
20216 W89K monitor, running on a Winbond HPPA board.
20221 @subsection Tsqware Sparclet
20225 @value{GDBN} enables developers to debug tasks running on
20226 Sparclet targets from a Unix host.
20227 @value{GDBN} uses code that runs on
20228 both the Unix host and on the Sparclet target. The program
20229 @code{@value{GDBP}} is installed and executed on the Unix host.
20232 @item remotetimeout @var{args}
20233 @kindex remotetimeout
20234 @value{GDBN} supports the option @code{remotetimeout}.
20235 This option is set by the user, and @var{args} represents the number of
20236 seconds @value{GDBN} waits for responses.
20239 @cindex compiling, on Sparclet
20240 When compiling for debugging, include the options @samp{-g} to get debug
20241 information and @samp{-Ttext} to relocate the program to where you wish to
20242 load it on the target. You may also want to add the options @samp{-n} or
20243 @samp{-N} in order to reduce the size of the sections. Example:
20246 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
20249 You can use @code{objdump} to verify that the addresses are what you intended:
20252 sparclet-aout-objdump --headers --syms prog
20255 @cindex running, on Sparclet
20257 your Unix execution search path to find @value{GDBN}, you are ready to
20258 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
20259 (or @code{sparclet-aout-gdb}, depending on your installation).
20261 @value{GDBN} comes up showing the prompt:
20268 * Sparclet File:: Setting the file to debug
20269 * Sparclet Connection:: Connecting to Sparclet
20270 * Sparclet Download:: Sparclet download
20271 * Sparclet Execution:: Running and debugging
20274 @node Sparclet File
20275 @subsubsection Setting File to Debug
20277 The @value{GDBN} command @code{file} lets you choose with program to debug.
20280 (gdbslet) file prog
20284 @value{GDBN} then attempts to read the symbol table of @file{prog}.
20285 @value{GDBN} locates
20286 the file by searching the directories listed in the command search
20288 If the file was compiled with debug information (option @samp{-g}), source
20289 files will be searched as well.
20290 @value{GDBN} locates
20291 the source files by searching the directories listed in the directory search
20292 path (@pxref{Environment, ,Your Program's Environment}).
20294 to find a file, it displays a message such as:
20297 prog: No such file or directory.
20300 When this happens, add the appropriate directories to the search paths with
20301 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
20302 @code{target} command again.
20304 @node Sparclet Connection
20305 @subsubsection Connecting to Sparclet
20307 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
20308 To connect to a target on serial port ``@code{ttya}'', type:
20311 (gdbslet) target sparclet /dev/ttya
20312 Remote target sparclet connected to /dev/ttya
20313 main () at ../prog.c:3
20317 @value{GDBN} displays messages like these:
20323 @node Sparclet Download
20324 @subsubsection Sparclet Download
20326 @cindex download to Sparclet
20327 Once connected to the Sparclet target,
20328 you can use the @value{GDBN}
20329 @code{load} command to download the file from the host to the target.
20330 The file name and load offset should be given as arguments to the @code{load}
20332 Since the file format is aout, the program must be loaded to the starting
20333 address. You can use @code{objdump} to find out what this value is. The load
20334 offset is an offset which is added to the VMA (virtual memory address)
20335 of each of the file's sections.
20336 For instance, if the program
20337 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
20338 and bss at 0x12010170, in @value{GDBN}, type:
20341 (gdbslet) load prog 0x12010000
20342 Loading section .text, size 0xdb0 vma 0x12010000
20345 If the code is loaded at a different address then what the program was linked
20346 to, you may need to use the @code{section} and @code{add-symbol-file} commands
20347 to tell @value{GDBN} where to map the symbol table.
20349 @node Sparclet Execution
20350 @subsubsection Running and Debugging
20352 @cindex running and debugging Sparclet programs
20353 You can now begin debugging the task using @value{GDBN}'s execution control
20354 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
20355 manual for the list of commands.
20359 Breakpoint 1 at 0x12010000: file prog.c, line 3.
20361 Starting program: prog
20362 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
20363 3 char *symarg = 0;
20365 4 char *execarg = "hello!";
20370 @subsection Fujitsu Sparclite
20374 @kindex target sparclite
20375 @item target sparclite @var{dev}
20376 Fujitsu sparclite boards, used only for the purpose of loading.
20377 You must use an additional command to debug the program.
20378 For example: target remote @var{dev} using @value{GDBN} standard
20384 @subsection Zilog Z8000
20387 @cindex simulator, Z8000
20388 @cindex Zilog Z8000 simulator
20390 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
20393 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
20394 unsegmented variant of the Z8000 architecture) or the Z8001 (the
20395 segmented variant). The simulator recognizes which architecture is
20396 appropriate by inspecting the object code.
20399 @item target sim @var{args}
20401 @kindex target sim@r{, with Z8000}
20402 Debug programs on a simulated CPU. If the simulator supports setup
20403 options, specify them via @var{args}.
20407 After specifying this target, you can debug programs for the simulated
20408 CPU in the same style as programs for your host computer; use the
20409 @code{file} command to load a new program image, the @code{run} command
20410 to run your program, and so on.
20412 As well as making available all the usual machine registers
20413 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
20414 additional items of information as specially named registers:
20419 Counts clock-ticks in the simulator.
20422 Counts instructions run in the simulator.
20425 Execution time in 60ths of a second.
20429 You can refer to these values in @value{GDBN} expressions with the usual
20430 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
20431 conditional breakpoint that suspends only after at least 5000
20432 simulated clock ticks.
20435 @subsection Atmel AVR
20438 When configured for debugging the Atmel AVR, @value{GDBN} supports the
20439 following AVR-specific commands:
20442 @item info io_registers
20443 @kindex info io_registers@r{, AVR}
20444 @cindex I/O registers (Atmel AVR)
20445 This command displays information about the AVR I/O registers. For
20446 each register, @value{GDBN} prints its number and value.
20453 When configured for debugging CRIS, @value{GDBN} provides the
20454 following CRIS-specific commands:
20457 @item set cris-version @var{ver}
20458 @cindex CRIS version
20459 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
20460 The CRIS version affects register names and sizes. This command is useful in
20461 case autodetection of the CRIS version fails.
20463 @item show cris-version
20464 Show the current CRIS version.
20466 @item set cris-dwarf2-cfi
20467 @cindex DWARF-2 CFI and CRIS
20468 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
20469 Change to @samp{off} when using @code{gcc-cris} whose version is below
20472 @item show cris-dwarf2-cfi
20473 Show the current state of using DWARF-2 CFI.
20475 @item set cris-mode @var{mode}
20477 Set the current CRIS mode to @var{mode}. It should only be changed when
20478 debugging in guru mode, in which case it should be set to
20479 @samp{guru} (the default is @samp{normal}).
20481 @item show cris-mode
20482 Show the current CRIS mode.
20486 @subsection Renesas Super-H
20489 For the Renesas Super-H processor, @value{GDBN} provides these
20493 @item set sh calling-convention @var{convention}
20494 @kindex set sh calling-convention
20495 Set the calling-convention used when calling functions from @value{GDBN}.
20496 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
20497 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
20498 convention. If the DWARF-2 information of the called function specifies
20499 that the function follows the Renesas calling convention, the function
20500 is called using the Renesas calling convention. If the calling convention
20501 is set to @samp{renesas}, the Renesas calling convention is always used,
20502 regardless of the DWARF-2 information. This can be used to override the
20503 default of @samp{gcc} if debug information is missing, or the compiler
20504 does not emit the DWARF-2 calling convention entry for a function.
20506 @item show sh calling-convention
20507 @kindex show sh calling-convention
20508 Show the current calling convention setting.
20513 @node Architectures
20514 @section Architectures
20516 This section describes characteristics of architectures that affect
20517 all uses of @value{GDBN} with the architecture, both native and cross.
20523 * HPPA:: HP PA architecture
20524 * SPU:: Cell Broadband Engine SPU architecture
20529 @subsection x86 Architecture-specific Issues
20532 @item set struct-convention @var{mode}
20533 @kindex set struct-convention
20534 @cindex struct return convention
20535 @cindex struct/union returned in registers
20536 Set the convention used by the inferior to return @code{struct}s and
20537 @code{union}s from functions to @var{mode}. Possible values of
20538 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
20539 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
20540 are returned on the stack, while @code{"reg"} means that a
20541 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
20542 be returned in a register.
20544 @item show struct-convention
20545 @kindex show struct-convention
20546 Show the current setting of the convention to return @code{struct}s
20553 See the following section.
20556 @subsection @acronym{MIPS}
20558 @cindex stack on Alpha
20559 @cindex stack on @acronym{MIPS}
20560 @cindex Alpha stack
20561 @cindex @acronym{MIPS} stack
20562 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
20563 sometimes requires @value{GDBN} to search backward in the object code to
20564 find the beginning of a function.
20566 @cindex response time, @acronym{MIPS} debugging
20567 To improve response time (especially for embedded applications, where
20568 @value{GDBN} may be restricted to a slow serial line for this search)
20569 you may want to limit the size of this search, using one of these
20573 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
20574 @item set heuristic-fence-post @var{limit}
20575 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
20576 search for the beginning of a function. A value of @var{0} (the
20577 default) means there is no limit. However, except for @var{0}, the
20578 larger the limit the more bytes @code{heuristic-fence-post} must search
20579 and therefore the longer it takes to run. You should only need to use
20580 this command when debugging a stripped executable.
20582 @item show heuristic-fence-post
20583 Display the current limit.
20587 These commands are available @emph{only} when @value{GDBN} is configured
20588 for debugging programs on Alpha or @acronym{MIPS} processors.
20590 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
20594 @item set mips abi @var{arg}
20595 @kindex set mips abi
20596 @cindex set ABI for @acronym{MIPS}
20597 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
20598 values of @var{arg} are:
20602 The default ABI associated with the current binary (this is the
20612 @item show mips abi
20613 @kindex show mips abi
20614 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
20616 @item set mips compression @var{arg}
20617 @kindex set mips compression
20618 @cindex code compression, @acronym{MIPS}
20619 Tell @value{GDBN} which @acronym{MIPS} compressed
20620 @acronym{ISA, Instruction Set Architecture} encoding is used by the
20621 inferior. @value{GDBN} uses this for code disassembly and other
20622 internal interpretation purposes. This setting is only referred to
20623 when no executable has been associated with the debugging session or
20624 the executable does not provide information about the encoding it uses.
20625 Otherwise this setting is automatically updated from information
20626 provided by the executable.
20628 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
20629 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
20630 executables containing @acronym{MIPS16} code frequently are not
20631 identified as such.
20633 This setting is ``sticky''; that is, it retains its value across
20634 debugging sessions until reset either explicitly with this command or
20635 implicitly from an executable.
20637 The compiler and/or assembler typically add symbol table annotations to
20638 identify functions compiled for the @acronym{MIPS16} or
20639 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
20640 are present, @value{GDBN} uses them in preference to the global
20641 compressed @acronym{ISA} encoding setting.
20643 @item show mips compression
20644 @kindex show mips compression
20645 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
20646 @value{GDBN} to debug the inferior.
20649 @itemx show mipsfpu
20650 @xref{MIPS Embedded, set mipsfpu}.
20652 @item set mips mask-address @var{arg}
20653 @kindex set mips mask-address
20654 @cindex @acronym{MIPS} addresses, masking
20655 This command determines whether the most-significant 32 bits of 64-bit
20656 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
20657 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20658 setting, which lets @value{GDBN} determine the correct value.
20660 @item show mips mask-address
20661 @kindex show mips mask-address
20662 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
20665 @item set remote-mips64-transfers-32bit-regs
20666 @kindex set remote-mips64-transfers-32bit-regs
20667 This command controls compatibility with 64-bit @acronym{MIPS} targets that
20668 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
20669 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20670 and 64 bits for other registers, set this option to @samp{on}.
20672 @item show remote-mips64-transfers-32bit-regs
20673 @kindex show remote-mips64-transfers-32bit-regs
20674 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
20676 @item set debug mips
20677 @kindex set debug mips
20678 This command turns on and off debugging messages for the @acronym{MIPS}-specific
20679 target code in @value{GDBN}.
20681 @item show debug mips
20682 @kindex show debug mips
20683 Show the current setting of @acronym{MIPS} debugging messages.
20689 @cindex HPPA support
20691 When @value{GDBN} is debugging the HP PA architecture, it provides the
20692 following special commands:
20695 @item set debug hppa
20696 @kindex set debug hppa
20697 This command determines whether HPPA architecture-specific debugging
20698 messages are to be displayed.
20700 @item show debug hppa
20701 Show whether HPPA debugging messages are displayed.
20703 @item maint print unwind @var{address}
20704 @kindex maint print unwind@r{, HPPA}
20705 This command displays the contents of the unwind table entry at the
20706 given @var{address}.
20712 @subsection Cell Broadband Engine SPU architecture
20713 @cindex Cell Broadband Engine
20716 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
20717 it provides the following special commands:
20720 @item info spu event
20722 Display SPU event facility status. Shows current event mask
20723 and pending event status.
20725 @item info spu signal
20726 Display SPU signal notification facility status. Shows pending
20727 signal-control word and signal notification mode of both signal
20728 notification channels.
20730 @item info spu mailbox
20731 Display SPU mailbox facility status. Shows all pending entries,
20732 in order of processing, in each of the SPU Write Outbound,
20733 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
20736 Display MFC DMA status. Shows all pending commands in the MFC
20737 DMA queue. For each entry, opcode, tag, class IDs, effective
20738 and local store addresses and transfer size are shown.
20740 @item info spu proxydma
20741 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
20742 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
20743 and local store addresses and transfer size are shown.
20747 When @value{GDBN} is debugging a combined PowerPC/SPU application
20748 on the Cell Broadband Engine, it provides in addition the following
20752 @item set spu stop-on-load @var{arg}
20754 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
20755 will give control to the user when a new SPE thread enters its @code{main}
20756 function. The default is @code{off}.
20758 @item show spu stop-on-load
20760 Show whether to stop for new SPE threads.
20762 @item set spu auto-flush-cache @var{arg}
20763 Set whether to automatically flush the software-managed cache. When set to
20764 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
20765 cache to be flushed whenever SPE execution stops. This provides a consistent
20766 view of PowerPC memory that is accessed via the cache. If an application
20767 does not use the software-managed cache, this option has no effect.
20769 @item show spu auto-flush-cache
20770 Show whether to automatically flush the software-managed cache.
20775 @subsection PowerPC
20776 @cindex PowerPC architecture
20778 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
20779 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
20780 numbers stored in the floating point registers. These values must be stored
20781 in two consecutive registers, always starting at an even register like
20782 @code{f0} or @code{f2}.
20784 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
20785 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
20786 @code{f2} and @code{f3} for @code{$dl1} and so on.
20788 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
20789 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
20792 @node Controlling GDB
20793 @chapter Controlling @value{GDBN}
20795 You can alter the way @value{GDBN} interacts with you by using the
20796 @code{set} command. For commands controlling how @value{GDBN} displays
20797 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20802 * Editing:: Command editing
20803 * Command History:: Command history
20804 * Screen Size:: Screen size
20805 * Numbers:: Numbers
20806 * ABI:: Configuring the current ABI
20807 * Auto-loading:: Automatically loading associated files
20808 * Messages/Warnings:: Optional warnings and messages
20809 * Debugging Output:: Optional messages about internal happenings
20810 * Other Misc Settings:: Other Miscellaneous Settings
20818 @value{GDBN} indicates its readiness to read a command by printing a string
20819 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20820 can change the prompt string with the @code{set prompt} command. For
20821 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20822 the prompt in one of the @value{GDBN} sessions so that you can always tell
20823 which one you are talking to.
20825 @emph{Note:} @code{set prompt} does not add a space for you after the
20826 prompt you set. This allows you to set a prompt which ends in a space
20827 or a prompt that does not.
20831 @item set prompt @var{newprompt}
20832 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20834 @kindex show prompt
20836 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20839 Versions of @value{GDBN} that ship with Python scripting enabled have
20840 prompt extensions. The commands for interacting with these extensions
20844 @kindex set extended-prompt
20845 @item set extended-prompt @var{prompt}
20846 Set an extended prompt that allows for substitutions.
20847 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20848 substitution. Any escape sequences specified as part of the prompt
20849 string are replaced with the corresponding strings each time the prompt
20855 set extended-prompt Current working directory: \w (gdb)
20858 Note that when an extended-prompt is set, it takes control of the
20859 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20861 @kindex show extended-prompt
20862 @item show extended-prompt
20863 Prints the extended prompt. Any escape sequences specified as part of
20864 the prompt string with @code{set extended-prompt}, are replaced with the
20865 corresponding strings each time the prompt is displayed.
20869 @section Command Editing
20871 @cindex command line editing
20873 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
20874 @sc{gnu} library provides consistent behavior for programs which provide a
20875 command line interface to the user. Advantages are @sc{gnu} Emacs-style
20876 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
20877 substitution, and a storage and recall of command history across
20878 debugging sessions.
20880 You may control the behavior of command line editing in @value{GDBN} with the
20881 command @code{set}.
20884 @kindex set editing
20887 @itemx set editing on
20888 Enable command line editing (enabled by default).
20890 @item set editing off
20891 Disable command line editing.
20893 @kindex show editing
20895 Show whether command line editing is enabled.
20898 @ifset SYSTEM_READLINE
20899 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
20901 @ifclear SYSTEM_READLINE
20902 @xref{Command Line Editing},
20904 for more details about the Readline
20905 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
20906 encouraged to read that chapter.
20908 @node Command History
20909 @section Command History
20910 @cindex command history
20912 @value{GDBN} can keep track of the commands you type during your
20913 debugging sessions, so that you can be certain of precisely what
20914 happened. Use these commands to manage the @value{GDBN} command
20917 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20918 package, to provide the history facility.
20919 @ifset SYSTEM_READLINE
20920 @xref{Using History Interactively, , , history, GNU History Library},
20922 @ifclear SYSTEM_READLINE
20923 @xref{Using History Interactively},
20925 for the detailed description of the History library.
20927 To issue a command to @value{GDBN} without affecting certain aspects of
20928 the state which is seen by users, prefix it with @samp{server }
20929 (@pxref{Server Prefix}). This
20930 means that this command will not affect the command history, nor will it
20931 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20932 pressed on a line by itself.
20934 @cindex @code{server}, command prefix
20935 The server prefix does not affect the recording of values into the value
20936 history; to print a value without recording it into the value history,
20937 use the @code{output} command instead of the @code{print} command.
20939 Here is the description of @value{GDBN} commands related to command
20943 @cindex history substitution
20944 @cindex history file
20945 @kindex set history filename
20946 @cindex @env{GDBHISTFILE}, environment variable
20947 @item set history filename @var{fname}
20948 Set the name of the @value{GDBN} command history file to @var{fname}.
20949 This is the file where @value{GDBN} reads an initial command history
20950 list, and where it writes the command history from this session when it
20951 exits. You can access this list through history expansion or through
20952 the history command editing characters listed below. This file defaults
20953 to the value of the environment variable @code{GDBHISTFILE}, or to
20954 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20957 @cindex save command history
20958 @kindex set history save
20959 @item set history save
20960 @itemx set history save on
20961 Record command history in a file, whose name may be specified with the
20962 @code{set history filename} command. By default, this option is disabled.
20964 @item set history save off
20965 Stop recording command history in a file.
20967 @cindex history size
20968 @kindex set history size
20969 @cindex @env{HISTSIZE}, environment variable
20970 @item set history size @var{size}
20971 Set the number of commands which @value{GDBN} keeps in its history list.
20972 This defaults to the value of the environment variable
20973 @code{HISTSIZE}, or to 256 if this variable is not set.
20976 History expansion assigns special meaning to the character @kbd{!}.
20977 @ifset SYSTEM_READLINE
20978 @xref{Event Designators, , , history, GNU History Library},
20980 @ifclear SYSTEM_READLINE
20981 @xref{Event Designators},
20985 @cindex history expansion, turn on/off
20986 Since @kbd{!} is also the logical not operator in C, history expansion
20987 is off by default. If you decide to enable history expansion with the
20988 @code{set history expansion on} command, you may sometimes need to
20989 follow @kbd{!} (when it is used as logical not, in an expression) with
20990 a space or a tab to prevent it from being expanded. The readline
20991 history facilities do not attempt substitution on the strings
20992 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20994 The commands to control history expansion are:
20997 @item set history expansion on
20998 @itemx set history expansion
20999 @kindex set history expansion
21000 Enable history expansion. History expansion is off by default.
21002 @item set history expansion off
21003 Disable history expansion.
21006 @kindex show history
21008 @itemx show history filename
21009 @itemx show history save
21010 @itemx show history size
21011 @itemx show history expansion
21012 These commands display the state of the @value{GDBN} history parameters.
21013 @code{show history} by itself displays all four states.
21018 @kindex show commands
21019 @cindex show last commands
21020 @cindex display command history
21021 @item show commands
21022 Display the last ten commands in the command history.
21024 @item show commands @var{n}
21025 Print ten commands centered on command number @var{n}.
21027 @item show commands +
21028 Print ten commands just after the commands last printed.
21032 @section Screen Size
21033 @cindex size of screen
21034 @cindex pauses in output
21036 Certain commands to @value{GDBN} may produce large amounts of
21037 information output to the screen. To help you read all of it,
21038 @value{GDBN} pauses and asks you for input at the end of each page of
21039 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21040 to discard the remaining output. Also, the screen width setting
21041 determines when to wrap lines of output. Depending on what is being
21042 printed, @value{GDBN} tries to break the line at a readable place,
21043 rather than simply letting it overflow onto the following line.
21045 Normally @value{GDBN} knows the size of the screen from the terminal
21046 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21047 together with the value of the @code{TERM} environment variable and the
21048 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21049 you can override it with the @code{set height} and @code{set
21056 @kindex show height
21057 @item set height @var{lpp}
21059 @itemx set width @var{cpl}
21061 These @code{set} commands specify a screen height of @var{lpp} lines and
21062 a screen width of @var{cpl} characters. The associated @code{show}
21063 commands display the current settings.
21065 If you specify a height of zero lines, @value{GDBN} does not pause during
21066 output no matter how long the output is. This is useful if output is to a
21067 file or to an editor buffer.
21069 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
21070 from wrapping its output.
21072 @item set pagination on
21073 @itemx set pagination off
21074 @kindex set pagination
21075 Turn the output pagination on or off; the default is on. Turning
21076 pagination off is the alternative to @code{set height 0}. Note that
21077 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21078 Options, -batch}) also automatically disables pagination.
21080 @item show pagination
21081 @kindex show pagination
21082 Show the current pagination mode.
21087 @cindex number representation
21088 @cindex entering numbers
21090 You can always enter numbers in octal, decimal, or hexadecimal in
21091 @value{GDBN} by the usual conventions: octal numbers begin with
21092 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21093 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21094 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21095 10; likewise, the default display for numbers---when no particular
21096 format is specified---is base 10. You can change the default base for
21097 both input and output with the commands described below.
21100 @kindex set input-radix
21101 @item set input-radix @var{base}
21102 Set the default base for numeric input. Supported choices
21103 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21104 specified either unambiguously or using the current input radix; for
21108 set input-radix 012
21109 set input-radix 10.
21110 set input-radix 0xa
21114 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21115 leaves the input radix unchanged, no matter what it was, since
21116 @samp{10}, being without any leading or trailing signs of its base, is
21117 interpreted in the current radix. Thus, if the current radix is 16,
21118 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21121 @kindex set output-radix
21122 @item set output-radix @var{base}
21123 Set the default base for numeric display. Supported choices
21124 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21125 specified either unambiguously or using the current input radix.
21127 @kindex show input-radix
21128 @item show input-radix
21129 Display the current default base for numeric input.
21131 @kindex show output-radix
21132 @item show output-radix
21133 Display the current default base for numeric display.
21135 @item set radix @r{[}@var{base}@r{]}
21139 These commands set and show the default base for both input and output
21140 of numbers. @code{set radix} sets the radix of input and output to
21141 the same base; without an argument, it resets the radix back to its
21142 default value of 10.
21147 @section Configuring the Current ABI
21149 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
21150 application automatically. However, sometimes you need to override its
21151 conclusions. Use these commands to manage @value{GDBN}'s view of the
21158 One @value{GDBN} configuration can debug binaries for multiple operating
21159 system targets, either via remote debugging or native emulation.
21160 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
21161 but you can override its conclusion using the @code{set osabi} command.
21162 One example where this is useful is in debugging of binaries which use
21163 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
21164 not have the same identifying marks that the standard C library for your
21169 Show the OS ABI currently in use.
21172 With no argument, show the list of registered available OS ABI's.
21174 @item set osabi @var{abi}
21175 Set the current OS ABI to @var{abi}.
21178 @cindex float promotion
21180 Generally, the way that an argument of type @code{float} is passed to a
21181 function depends on whether the function is prototyped. For a prototyped
21182 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
21183 according to the architecture's convention for @code{float}. For unprototyped
21184 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
21185 @code{double} and then passed.
21187 Unfortunately, some forms of debug information do not reliably indicate whether
21188 a function is prototyped. If @value{GDBN} calls a function that is not marked
21189 as prototyped, it consults @kbd{set coerce-float-to-double}.
21192 @kindex set coerce-float-to-double
21193 @item set coerce-float-to-double
21194 @itemx set coerce-float-to-double on
21195 Arguments of type @code{float} will be promoted to @code{double} when passed
21196 to an unprototyped function. This is the default setting.
21198 @item set coerce-float-to-double off
21199 Arguments of type @code{float} will be passed directly to unprototyped
21202 @kindex show coerce-float-to-double
21203 @item show coerce-float-to-double
21204 Show the current setting of promoting @code{float} to @code{double}.
21208 @kindex show cp-abi
21209 @value{GDBN} needs to know the ABI used for your program's C@t{++}
21210 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
21211 used to build your application. @value{GDBN} only fully supports
21212 programs with a single C@t{++} ABI; if your program contains code using
21213 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
21214 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
21215 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
21216 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
21217 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
21218 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
21223 Show the C@t{++} ABI currently in use.
21226 With no argument, show the list of supported C@t{++} ABI's.
21228 @item set cp-abi @var{abi}
21229 @itemx set cp-abi auto
21230 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
21234 @section Automatically loading associated files
21235 @cindex auto-loading
21237 @value{GDBN} sometimes reads files with commands and settings automatically,
21238 without being explicitly told so by the user. We call this feature
21239 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
21240 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
21241 results or introduce security risks (e.g., if the file comes from untrusted
21244 Note that loading of these associated files (including the local @file{.gdbinit}
21245 file) requires accordingly configured @code{auto-load safe-path}
21246 (@pxref{Auto-loading safe path}).
21248 For these reasons, @value{GDBN} includes commands and options to let you
21249 control when to auto-load files and which files should be auto-loaded.
21252 @anchor{set auto-load off}
21253 @kindex set auto-load off
21254 @item set auto-load off
21255 Globally disable loading of all auto-loaded files.
21256 You may want to use this command with the @samp{-iex} option
21257 (@pxref{Option -init-eval-command}) such as:
21259 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
21262 Be aware that system init file (@pxref{System-wide configuration})
21263 and init files from your home directory (@pxref{Home Directory Init File})
21264 still get read (as they come from generally trusted directories).
21265 To prevent @value{GDBN} from auto-loading even those init files, use the
21266 @option{-nx} option (@pxref{Mode Options}), in addition to
21267 @code{set auto-load no}.
21269 @anchor{show auto-load}
21270 @kindex show auto-load
21271 @item show auto-load
21272 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
21276 (gdb) show auto-load
21277 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
21278 libthread-db: Auto-loading of inferior specific libthread_db is on.
21279 local-gdbinit: Auto-loading of .gdbinit script from current directory
21281 python-scripts: Auto-loading of Python scripts is on.
21282 safe-path: List of directories from which it is safe to auto-load files
21283 is $debugdir:$datadir/auto-load.
21284 scripts-directory: List of directories from which to load auto-loaded scripts
21285 is $debugdir:$datadir/auto-load.
21288 @anchor{info auto-load}
21289 @kindex info auto-load
21290 @item info auto-load
21291 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
21295 (gdb) info auto-load
21298 Yes /home/user/gdb/gdb-gdb.gdb
21299 libthread-db: No auto-loaded libthread-db.
21300 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
21304 Yes /home/user/gdb/gdb-gdb.py
21308 These are various kinds of files @value{GDBN} can automatically load:
21312 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
21314 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
21316 @xref{dotdebug_gdb_scripts section},
21317 controlled by @ref{set auto-load python-scripts}.
21319 @xref{Init File in the Current Directory},
21320 controlled by @ref{set auto-load local-gdbinit}.
21322 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
21325 These are @value{GDBN} control commands for the auto-loading:
21327 @multitable @columnfractions .5 .5
21328 @item @xref{set auto-load off}.
21329 @tab Disable auto-loading globally.
21330 @item @xref{show auto-load}.
21331 @tab Show setting of all kinds of files.
21332 @item @xref{info auto-load}.
21333 @tab Show state of all kinds of files.
21334 @item @xref{set auto-load gdb-scripts}.
21335 @tab Control for @value{GDBN} command scripts.
21336 @item @xref{show auto-load gdb-scripts}.
21337 @tab Show setting of @value{GDBN} command scripts.
21338 @item @xref{info auto-load gdb-scripts}.
21339 @tab Show state of @value{GDBN} command scripts.
21340 @item @xref{set auto-load python-scripts}.
21341 @tab Control for @value{GDBN} Python scripts.
21342 @item @xref{show auto-load python-scripts}.
21343 @tab Show setting of @value{GDBN} Python scripts.
21344 @item @xref{info auto-load python-scripts}.
21345 @tab Show state of @value{GDBN} Python scripts.
21346 @item @xref{set auto-load scripts-directory}.
21347 @tab Control for @value{GDBN} auto-loaded scripts location.
21348 @item @xref{show auto-load scripts-directory}.
21349 @tab Show @value{GDBN} auto-loaded scripts location.
21350 @item @xref{set auto-load local-gdbinit}.
21351 @tab Control for init file in the current directory.
21352 @item @xref{show auto-load local-gdbinit}.
21353 @tab Show setting of init file in the current directory.
21354 @item @xref{info auto-load local-gdbinit}.
21355 @tab Show state of init file in the current directory.
21356 @item @xref{set auto-load libthread-db}.
21357 @tab Control for thread debugging library.
21358 @item @xref{show auto-load libthread-db}.
21359 @tab Show setting of thread debugging library.
21360 @item @xref{info auto-load libthread-db}.
21361 @tab Show state of thread debugging library.
21362 @item @xref{set auto-load safe-path}.
21363 @tab Control directories trusted for automatic loading.
21364 @item @xref{show auto-load safe-path}.
21365 @tab Show directories trusted for automatic loading.
21366 @item @xref{add-auto-load-safe-path}.
21367 @tab Add directory trusted for automatic loading.
21371 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
21372 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
21373 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
21374 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
21375 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
21376 @xref{Python Auto-loading}.
21379 @node Init File in the Current Directory
21380 @subsection Automatically loading init file in the current directory
21381 @cindex auto-loading init file in the current directory
21383 By default, @value{GDBN} reads and executes the canned sequences of commands
21384 from init file (if any) in the current working directory,
21385 see @ref{Init File in the Current Directory during Startup}.
21387 Note that loading of this local @file{.gdbinit} file also requires accordingly
21388 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21391 @anchor{set auto-load local-gdbinit}
21392 @kindex set auto-load local-gdbinit
21393 @item set auto-load local-gdbinit [on|off]
21394 Enable or disable the auto-loading of canned sequences of commands
21395 (@pxref{Sequences}) found in init file in the current directory.
21397 @anchor{show auto-load local-gdbinit}
21398 @kindex show auto-load local-gdbinit
21399 @item show auto-load local-gdbinit
21400 Show whether auto-loading of canned sequences of commands from init file in the
21401 current directory is enabled or disabled.
21403 @anchor{info auto-load local-gdbinit}
21404 @kindex info auto-load local-gdbinit
21405 @item info auto-load local-gdbinit
21406 Print whether canned sequences of commands from init file in the
21407 current directory have been auto-loaded.
21410 @node libthread_db.so.1 file
21411 @subsection Automatically loading thread debugging library
21412 @cindex auto-loading libthread_db.so.1
21414 This feature is currently present only on @sc{gnu}/Linux native hosts.
21416 @value{GDBN} reads in some cases thread debugging library from places specific
21417 to the inferior (@pxref{set libthread-db-search-path}).
21419 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
21420 without checking this @samp{set auto-load libthread-db} switch as system
21421 libraries have to be trusted in general. In all other cases of
21422 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
21423 auto-load libthread-db} is enabled before trying to open such thread debugging
21426 Note that loading of this debugging library also requires accordingly configured
21427 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21430 @anchor{set auto-load libthread-db}
21431 @kindex set auto-load libthread-db
21432 @item set auto-load libthread-db [on|off]
21433 Enable or disable the auto-loading of inferior specific thread debugging library.
21435 @anchor{show auto-load libthread-db}
21436 @kindex show auto-load libthread-db
21437 @item show auto-load libthread-db
21438 Show whether auto-loading of inferior specific thread debugging library is
21439 enabled or disabled.
21441 @anchor{info auto-load libthread-db}
21442 @kindex info auto-load libthread-db
21443 @item info auto-load libthread-db
21444 Print the list of all loaded inferior specific thread debugging libraries and
21445 for each such library print list of inferior @var{pid}s using it.
21448 @node objfile-gdb.gdb file
21449 @subsection The @file{@var{objfile}-gdb.gdb} file
21450 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
21452 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
21453 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
21454 auto-load gdb-scripts} is set to @samp{on}.
21456 Note that loading of this script file also requires accordingly configured
21457 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21459 For more background refer to the similar Python scripts auto-loading
21460 description (@pxref{objfile-gdb.py file}).
21463 @anchor{set auto-load gdb-scripts}
21464 @kindex set auto-load gdb-scripts
21465 @item set auto-load gdb-scripts [on|off]
21466 Enable or disable the auto-loading of canned sequences of commands scripts.
21468 @anchor{show auto-load gdb-scripts}
21469 @kindex show auto-load gdb-scripts
21470 @item show auto-load gdb-scripts
21471 Show whether auto-loading of canned sequences of commands scripts is enabled or
21474 @anchor{info auto-load gdb-scripts}
21475 @kindex info auto-load gdb-scripts
21476 @cindex print list of auto-loaded canned sequences of commands scripts
21477 @item info auto-load gdb-scripts [@var{regexp}]
21478 Print the list of all canned sequences of commands scripts that @value{GDBN}
21482 If @var{regexp} is supplied only canned sequences of commands scripts with
21483 matching names are printed.
21485 @node Auto-loading safe path
21486 @subsection Security restriction for auto-loading
21487 @cindex auto-loading safe-path
21489 As the files of inferior can come from untrusted source (such as submitted by
21490 an application user) @value{GDBN} does not always load any files automatically.
21491 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
21492 directories trusted for loading files not explicitly requested by user.
21493 Each directory can also be a shell wildcard pattern.
21495 If the path is not set properly you will see a warning and the file will not
21500 Reading symbols from /home/user/gdb/gdb...done.
21501 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
21502 declined by your `auto-load safe-path' set
21503 to "$debugdir:$datadir/auto-load".
21504 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
21505 declined by your `auto-load safe-path' set
21506 to "$debugdir:$datadir/auto-load".
21509 The list of trusted directories is controlled by the following commands:
21512 @anchor{set auto-load safe-path}
21513 @kindex set auto-load safe-path
21514 @item set auto-load safe-path @r{[}@var{directories}@r{]}
21515 Set the list of directories (and their subdirectories) trusted for automatic
21516 loading and execution of scripts. You can also enter a specific trusted file.
21517 Each directory can also be a shell wildcard pattern; wildcards do not match
21518 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
21519 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
21520 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
21521 its default value as specified during @value{GDBN} compilation.
21523 The list of directories uses path separator (@samp{:} on GNU and Unix
21524 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
21525 to the @env{PATH} environment variable.
21527 @anchor{show auto-load safe-path}
21528 @kindex show auto-load safe-path
21529 @item show auto-load safe-path
21530 Show the list of directories trusted for automatic loading and execution of
21533 @anchor{add-auto-load-safe-path}
21534 @kindex add-auto-load-safe-path
21535 @item add-auto-load-safe-path
21536 Add an entry (or list of entries) the list of directories trusted for automatic
21537 loading and execution of scripts. Multiple entries may be delimited by the
21538 host platform path separator in use.
21541 This variable defaults to what @code{--with-auto-load-dir} has been configured
21542 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
21543 substitution applies the same as for @ref{set auto-load scripts-directory}.
21544 The default @code{set auto-load safe-path} value can be also overriden by
21545 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
21547 Setting this variable to @file{/} disables this security protection,
21548 corresponding @value{GDBN} configuration option is
21549 @option{--without-auto-load-safe-path}.
21550 This variable is supposed to be set to the system directories writable by the
21551 system superuser only. Users can add their source directories in init files in
21552 their home directories (@pxref{Home Directory Init File}). See also deprecated
21553 init file in the current directory
21554 (@pxref{Init File in the Current Directory during Startup}).
21556 To force @value{GDBN} to load the files it declined to load in the previous
21557 example, you could use one of the following ways:
21560 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
21561 Specify this trusted directory (or a file) as additional component of the list.
21562 You have to specify also any existing directories displayed by
21563 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
21565 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
21566 Specify this directory as in the previous case but just for a single
21567 @value{GDBN} session.
21569 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
21570 Disable auto-loading safety for a single @value{GDBN} session.
21571 This assumes all the files you debug during this @value{GDBN} session will come
21572 from trusted sources.
21574 @item @kbd{./configure --without-auto-load-safe-path}
21575 During compilation of @value{GDBN} you may disable any auto-loading safety.
21576 This assumes all the files you will ever debug with this @value{GDBN} come from
21580 On the other hand you can also explicitly forbid automatic files loading which
21581 also suppresses any such warning messages:
21584 @item @kbd{gdb -iex "set auto-load no" @dots{}}
21585 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
21587 @item @file{~/.gdbinit}: @samp{set auto-load no}
21588 Disable auto-loading globally for the user
21589 (@pxref{Home Directory Init File}). While it is improbable, you could also
21590 use system init file instead (@pxref{System-wide configuration}).
21593 This setting applies to the file names as entered by user. If no entry matches
21594 @value{GDBN} tries as a last resort to also resolve all the file names into
21595 their canonical form (typically resolving symbolic links) and compare the
21596 entries again. @value{GDBN} already canonicalizes most of the filenames on its
21597 own before starting the comparison so a canonical form of directories is
21598 recommended to be entered.
21600 @node Auto-loading verbose mode
21601 @subsection Displaying files tried for auto-load
21602 @cindex auto-loading verbose mode
21604 For better visibility of all the file locations where you can place scripts to
21605 be auto-loaded with inferior --- or to protect yourself against accidental
21606 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
21607 all the files attempted to be loaded. Both existing and non-existing files may
21610 For example the list of directories from which it is safe to auto-load files
21611 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
21612 may not be too obvious while setting it up.
21615 (gdb) set debug auto-load on
21616 (gdb) file ~/src/t/true
21617 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
21618 for objfile "/tmp/true".
21619 auto-load: Updating directories of "/usr:/opt".
21620 auto-load: Using directory "/usr".
21621 auto-load: Using directory "/opt".
21622 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
21623 by your `auto-load safe-path' set to "/usr:/opt".
21627 @anchor{set debug auto-load}
21628 @kindex set debug auto-load
21629 @item set debug auto-load [on|off]
21630 Set whether to print the filenames attempted to be auto-loaded.
21632 @anchor{show debug auto-load}
21633 @kindex show debug auto-load
21634 @item show debug auto-load
21635 Show whether printing of the filenames attempted to be auto-loaded is turned
21639 @node Messages/Warnings
21640 @section Optional Warnings and Messages
21642 @cindex verbose operation
21643 @cindex optional warnings
21644 By default, @value{GDBN} is silent about its inner workings. If you are
21645 running on a slow machine, you may want to use the @code{set verbose}
21646 command. This makes @value{GDBN} tell you when it does a lengthy
21647 internal operation, so you will not think it has crashed.
21649 Currently, the messages controlled by @code{set verbose} are those
21650 which announce that the symbol table for a source file is being read;
21651 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
21654 @kindex set verbose
21655 @item set verbose on
21656 Enables @value{GDBN} output of certain informational messages.
21658 @item set verbose off
21659 Disables @value{GDBN} output of certain informational messages.
21661 @kindex show verbose
21663 Displays whether @code{set verbose} is on or off.
21666 By default, if @value{GDBN} encounters bugs in the symbol table of an
21667 object file, it is silent; but if you are debugging a compiler, you may
21668 find this information useful (@pxref{Symbol Errors, ,Errors Reading
21673 @kindex set complaints
21674 @item set complaints @var{limit}
21675 Permits @value{GDBN} to output @var{limit} complaints about each type of
21676 unusual symbols before becoming silent about the problem. Set
21677 @var{limit} to zero to suppress all complaints; set it to a large number
21678 to prevent complaints from being suppressed.
21680 @kindex show complaints
21681 @item show complaints
21682 Displays how many symbol complaints @value{GDBN} is permitted to produce.
21686 @anchor{confirmation requests}
21687 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
21688 lot of stupid questions to confirm certain commands. For example, if
21689 you try to run a program which is already running:
21693 The program being debugged has been started already.
21694 Start it from the beginning? (y or n)
21697 If you are willing to unflinchingly face the consequences of your own
21698 commands, you can disable this ``feature'':
21702 @kindex set confirm
21704 @cindex confirmation
21705 @cindex stupid questions
21706 @item set confirm off
21707 Disables confirmation requests. Note that running @value{GDBN} with
21708 the @option{--batch} option (@pxref{Mode Options, -batch}) also
21709 automatically disables confirmation requests.
21711 @item set confirm on
21712 Enables confirmation requests (the default).
21714 @kindex show confirm
21716 Displays state of confirmation requests.
21720 @cindex command tracing
21721 If you need to debug user-defined commands or sourced files you may find it
21722 useful to enable @dfn{command tracing}. In this mode each command will be
21723 printed as it is executed, prefixed with one or more @samp{+} symbols, the
21724 quantity denoting the call depth of each command.
21727 @kindex set trace-commands
21728 @cindex command scripts, debugging
21729 @item set trace-commands on
21730 Enable command tracing.
21731 @item set trace-commands off
21732 Disable command tracing.
21733 @item show trace-commands
21734 Display the current state of command tracing.
21737 @node Debugging Output
21738 @section Optional Messages about Internal Happenings
21739 @cindex optional debugging messages
21741 @value{GDBN} has commands that enable optional debugging messages from
21742 various @value{GDBN} subsystems; normally these commands are of
21743 interest to @value{GDBN} maintainers, or when reporting a bug. This
21744 section documents those commands.
21747 @kindex set exec-done-display
21748 @item set exec-done-display
21749 Turns on or off the notification of asynchronous commands'
21750 completion. When on, @value{GDBN} will print a message when an
21751 asynchronous command finishes its execution. The default is off.
21752 @kindex show exec-done-display
21753 @item show exec-done-display
21754 Displays the current setting of asynchronous command completion
21757 @cindex gdbarch debugging info
21758 @cindex architecture debugging info
21759 @item set debug arch
21760 Turns on or off display of gdbarch debugging info. The default is off
21762 @item show debug arch
21763 Displays the current state of displaying gdbarch debugging info.
21764 @item set debug aix-thread
21765 @cindex AIX threads
21766 Display debugging messages about inner workings of the AIX thread
21768 @item show debug aix-thread
21769 Show the current state of AIX thread debugging info display.
21770 @item set debug check-physname
21772 Check the results of the ``physname'' computation. When reading DWARF
21773 debugging information for C@t{++}, @value{GDBN} attempts to compute
21774 each entity's name. @value{GDBN} can do this computation in two
21775 different ways, depending on exactly what information is present.
21776 When enabled, this setting causes @value{GDBN} to compute the names
21777 both ways and display any discrepancies.
21778 @item show debug check-physname
21779 Show the current state of ``physname'' checking.
21780 @item set debug dwarf2-die
21781 @cindex DWARF2 DIEs
21782 Dump DWARF2 DIEs after they are read in.
21783 The value is the number of nesting levels to print.
21784 A value of zero turns off the display.
21785 @item show debug dwarf2-die
21786 Show the current state of DWARF2 DIE debugging.
21787 @item set debug dwarf2-read
21788 @cindex DWARF2 Reading
21789 Turns on or off display of debugging messages related to reading
21790 DWARF debug info. The default is off.
21791 @item show debug dwarf2-read
21792 Show the current state of DWARF2 reader debugging.
21793 @item set debug displaced
21794 @cindex displaced stepping debugging info
21795 Turns on or off display of @value{GDBN} debugging info for the
21796 displaced stepping support. The default is off.
21797 @item show debug displaced
21798 Displays the current state of displaying @value{GDBN} debugging info
21799 related to displaced stepping.
21800 @item set debug event
21801 @cindex event debugging info
21802 Turns on or off display of @value{GDBN} event debugging info. The
21804 @item show debug event
21805 Displays the current state of displaying @value{GDBN} event debugging
21807 @item set debug expression
21808 @cindex expression debugging info
21809 Turns on or off display of debugging info about @value{GDBN}
21810 expression parsing. The default is off.
21811 @item show debug expression
21812 Displays the current state of displaying debugging info about
21813 @value{GDBN} expression parsing.
21814 @item set debug frame
21815 @cindex frame debugging info
21816 Turns on or off display of @value{GDBN} frame debugging info. The
21818 @item show debug frame
21819 Displays the current state of displaying @value{GDBN} frame debugging
21821 @item set debug gnu-nat
21822 @cindex @sc{gnu}/Hurd debug messages
21823 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
21824 @item show debug gnu-nat
21825 Show the current state of @sc{gnu}/Hurd debugging messages.
21826 @item set debug infrun
21827 @cindex inferior debugging info
21828 Turns on or off display of @value{GDBN} debugging info for running the inferior.
21829 The default is off. @file{infrun.c} contains GDB's runtime state machine used
21830 for implementing operations such as single-stepping the inferior.
21831 @item show debug infrun
21832 Displays the current state of @value{GDBN} inferior debugging.
21833 @item set debug jit
21834 @cindex just-in-time compilation, debugging messages
21835 Turns on or off debugging messages from JIT debug support.
21836 @item show debug jit
21837 Displays the current state of @value{GDBN} JIT debugging.
21838 @item set debug lin-lwp
21839 @cindex @sc{gnu}/Linux LWP debug messages
21840 @cindex Linux lightweight processes
21841 Turns on or off debugging messages from the Linux LWP debug support.
21842 @item show debug lin-lwp
21843 Show the current state of Linux LWP debugging messages.
21844 @item set debug observer
21845 @cindex observer debugging info
21846 Turns on or off display of @value{GDBN} observer debugging. This
21847 includes info such as the notification of observable events.
21848 @item show debug observer
21849 Displays the current state of observer debugging.
21850 @item set debug overload
21851 @cindex C@t{++} overload debugging info
21852 Turns on or off display of @value{GDBN} C@t{++} overload debugging
21853 info. This includes info such as ranking of functions, etc. The default
21855 @item show debug overload
21856 Displays the current state of displaying @value{GDBN} C@t{++} overload
21858 @cindex expression parser, debugging info
21859 @cindex debug expression parser
21860 @item set debug parser
21861 Turns on or off the display of expression parser debugging output.
21862 Internally, this sets the @code{yydebug} variable in the expression
21863 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
21864 details. The default is off.
21865 @item show debug parser
21866 Show the current state of expression parser debugging.
21867 @cindex packets, reporting on stdout
21868 @cindex serial connections, debugging
21869 @cindex debug remote protocol
21870 @cindex remote protocol debugging
21871 @cindex display remote packets
21872 @item set debug remote
21873 Turns on or off display of reports on all packets sent back and forth across
21874 the serial line to the remote machine. The info is printed on the
21875 @value{GDBN} standard output stream. The default is off.
21876 @item show debug remote
21877 Displays the state of display of remote packets.
21878 @item set debug serial
21879 Turns on or off display of @value{GDBN} serial debugging info. The
21881 @item show debug serial
21882 Displays the current state of displaying @value{GDBN} serial debugging
21884 @item set debug solib-frv
21885 @cindex FR-V shared-library debugging
21886 Turns on or off debugging messages for FR-V shared-library code.
21887 @item show debug solib-frv
21888 Display the current state of FR-V shared-library code debugging
21890 @item set debug symtab-create
21891 @cindex symbol table creation
21892 Turns on or off display of debugging messages related to symbol table creation.
21893 The default is off.
21894 @item show debug symtab-create
21895 Show the current state of symbol table creation debugging.
21896 @item set debug target
21897 @cindex target debugging info
21898 Turns on or off display of @value{GDBN} target debugging info. This info
21899 includes what is going on at the target level of GDB, as it happens. The
21900 default is 0. Set it to 1 to track events, and to 2 to also track the
21901 value of large memory transfers. Changes to this flag do not take effect
21902 until the next time you connect to a target or use the @code{run} command.
21903 @item show debug target
21904 Displays the current state of displaying @value{GDBN} target debugging
21906 @item set debug timestamp
21907 @cindex timestampping debugging info
21908 Turns on or off display of timestamps with @value{GDBN} debugging info.
21909 When enabled, seconds and microseconds are displayed before each debugging
21911 @item show debug timestamp
21912 Displays the current state of displaying timestamps with @value{GDBN}
21914 @item set debugvarobj
21915 @cindex variable object debugging info
21916 Turns on or off display of @value{GDBN} variable object debugging
21917 info. The default is off.
21918 @item show debugvarobj
21919 Displays the current state of displaying @value{GDBN} variable object
21921 @item set debug xml
21922 @cindex XML parser debugging
21923 Turns on or off debugging messages for built-in XML parsers.
21924 @item show debug xml
21925 Displays the current state of XML debugging messages.
21928 @node Other Misc Settings
21929 @section Other Miscellaneous Settings
21930 @cindex miscellaneous settings
21933 @kindex set interactive-mode
21934 @item set interactive-mode
21935 If @code{on}, forces @value{GDBN} to assume that GDB was started
21936 in a terminal. In practice, this means that @value{GDBN} should wait
21937 for the user to answer queries generated by commands entered at
21938 the command prompt. If @code{off}, forces @value{GDBN} to operate
21939 in the opposite mode, and it uses the default answers to all queries.
21940 If @code{auto} (the default), @value{GDBN} tries to determine whether
21941 its standard input is a terminal, and works in interactive-mode if it
21942 is, non-interactively otherwise.
21944 In the vast majority of cases, the debugger should be able to guess
21945 correctly which mode should be used. But this setting can be useful
21946 in certain specific cases, such as running a MinGW @value{GDBN}
21947 inside a cygwin window.
21949 @kindex show interactive-mode
21950 @item show interactive-mode
21951 Displays whether the debugger is operating in interactive mode or not.
21954 @node Extending GDB
21955 @chapter Extending @value{GDBN}
21956 @cindex extending GDB
21958 @value{GDBN} provides three mechanisms for extension. The first is based
21959 on composition of @value{GDBN} commands, the second is based on the
21960 Python scripting language, and the third is for defining new aliases of
21963 To facilitate the use of the first two extensions, @value{GDBN} is capable
21964 of evaluating the contents of a file. When doing so, @value{GDBN}
21965 can recognize which scripting language is being used by looking at
21966 the filename extension. Files with an unrecognized filename extension
21967 are always treated as a @value{GDBN} Command Files.
21968 @xref{Command Files,, Command files}.
21970 You can control how @value{GDBN} evaluates these files with the following
21974 @kindex set script-extension
21975 @kindex show script-extension
21976 @item set script-extension off
21977 All scripts are always evaluated as @value{GDBN} Command Files.
21979 @item set script-extension soft
21980 The debugger determines the scripting language based on filename
21981 extension. If this scripting language is supported, @value{GDBN}
21982 evaluates the script using that language. Otherwise, it evaluates
21983 the file as a @value{GDBN} Command File.
21985 @item set script-extension strict
21986 The debugger determines the scripting language based on filename
21987 extension, and evaluates the script using that language. If the
21988 language is not supported, then the evaluation fails.
21990 @item show script-extension
21991 Display the current value of the @code{script-extension} option.
21996 * Sequences:: Canned Sequences of Commands
21997 * Python:: Scripting @value{GDBN} using Python
21998 * Aliases:: Creating new spellings of existing commands
22002 @section Canned Sequences of Commands
22004 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22005 Command Lists}), @value{GDBN} provides two ways to store sequences of
22006 commands for execution as a unit: user-defined commands and command
22010 * Define:: How to define your own commands
22011 * Hooks:: Hooks for user-defined commands
22012 * Command Files:: How to write scripts of commands to be stored in a file
22013 * Output:: Commands for controlled output
22017 @subsection User-defined Commands
22019 @cindex user-defined command
22020 @cindex arguments, to user-defined commands
22021 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22022 which you assign a new name as a command. This is done with the
22023 @code{define} command. User commands may accept up to 10 arguments
22024 separated by whitespace. Arguments are accessed within the user command
22025 via @code{$arg0@dots{}$arg9}. A trivial example:
22029 print $arg0 + $arg1 + $arg2
22034 To execute the command use:
22041 This defines the command @code{adder}, which prints the sum of
22042 its three arguments. Note the arguments are text substitutions, so they may
22043 reference variables, use complex expressions, or even perform inferior
22046 @cindex argument count in user-defined commands
22047 @cindex how many arguments (user-defined commands)
22048 In addition, @code{$argc} may be used to find out how many arguments have
22049 been passed. This expands to a number in the range 0@dots{}10.
22054 print $arg0 + $arg1
22057 print $arg0 + $arg1 + $arg2
22065 @item define @var{commandname}
22066 Define a command named @var{commandname}. If there is already a command
22067 by that name, you are asked to confirm that you want to redefine it.
22068 @var{commandname} may be a bare command name consisting of letters,
22069 numbers, dashes, and underscores. It may also start with any predefined
22070 prefix command. For example, @samp{define target my-target} creates
22071 a user-defined @samp{target my-target} command.
22073 The definition of the command is made up of other @value{GDBN} command lines,
22074 which are given following the @code{define} command. The end of these
22075 commands is marked by a line containing @code{end}.
22078 @kindex end@r{ (user-defined commands)}
22079 @item document @var{commandname}
22080 Document the user-defined command @var{commandname}, so that it can be
22081 accessed by @code{help}. The command @var{commandname} must already be
22082 defined. This command reads lines of documentation just as @code{define}
22083 reads the lines of the command definition, ending with @code{end}.
22084 After the @code{document} command is finished, @code{help} on command
22085 @var{commandname} displays the documentation you have written.
22087 You may use the @code{document} command again to change the
22088 documentation of a command. Redefining the command with @code{define}
22089 does not change the documentation.
22091 @kindex dont-repeat
22092 @cindex don't repeat command
22094 Used inside a user-defined command, this tells @value{GDBN} that this
22095 command should not be repeated when the user hits @key{RET}
22096 (@pxref{Command Syntax, repeat last command}).
22098 @kindex help user-defined
22099 @item help user-defined
22100 List all user-defined commands and all python commands defined in class
22101 COMAND_USER. The first line of the documentation or docstring is
22106 @itemx show user @var{commandname}
22107 Display the @value{GDBN} commands used to define @var{commandname} (but
22108 not its documentation). If no @var{commandname} is given, display the
22109 definitions for all user-defined commands.
22110 This does not work for user-defined python commands.
22112 @cindex infinite recursion in user-defined commands
22113 @kindex show max-user-call-depth
22114 @kindex set max-user-call-depth
22115 @item show max-user-call-depth
22116 @itemx set max-user-call-depth
22117 The value of @code{max-user-call-depth} controls how many recursion
22118 levels are allowed in user-defined commands before @value{GDBN} suspects an
22119 infinite recursion and aborts the command.
22120 This does not apply to user-defined python commands.
22123 In addition to the above commands, user-defined commands frequently
22124 use control flow commands, described in @ref{Command Files}.
22126 When user-defined commands are executed, the
22127 commands of the definition are not printed. An error in any command
22128 stops execution of the user-defined command.
22130 If used interactively, commands that would ask for confirmation proceed
22131 without asking when used inside a user-defined command. Many @value{GDBN}
22132 commands that normally print messages to say what they are doing omit the
22133 messages when used in a user-defined command.
22136 @subsection User-defined Command Hooks
22137 @cindex command hooks
22138 @cindex hooks, for commands
22139 @cindex hooks, pre-command
22142 You may define @dfn{hooks}, which are a special kind of user-defined
22143 command. Whenever you run the command @samp{foo}, if the user-defined
22144 command @samp{hook-foo} exists, it is executed (with no arguments)
22145 before that command.
22147 @cindex hooks, post-command
22149 A hook may also be defined which is run after the command you executed.
22150 Whenever you run the command @samp{foo}, if the user-defined command
22151 @samp{hookpost-foo} exists, it is executed (with no arguments) after
22152 that command. Post-execution hooks may exist simultaneously with
22153 pre-execution hooks, for the same command.
22155 It is valid for a hook to call the command which it hooks. If this
22156 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
22158 @c It would be nice if hookpost could be passed a parameter indicating
22159 @c if the command it hooks executed properly or not. FIXME!
22161 @kindex stop@r{, a pseudo-command}
22162 In addition, a pseudo-command, @samp{stop} exists. Defining
22163 (@samp{hook-stop}) makes the associated commands execute every time
22164 execution stops in your program: before breakpoint commands are run,
22165 displays are printed, or the stack frame is printed.
22167 For example, to ignore @code{SIGALRM} signals while
22168 single-stepping, but treat them normally during normal execution,
22173 handle SIGALRM nopass
22177 handle SIGALRM pass
22180 define hook-continue
22181 handle SIGALRM pass
22185 As a further example, to hook at the beginning and end of the @code{echo}
22186 command, and to add extra text to the beginning and end of the message,
22194 define hookpost-echo
22198 (@value{GDBP}) echo Hello World
22199 <<<---Hello World--->>>
22204 You can define a hook for any single-word command in @value{GDBN}, but
22205 not for command aliases; you should define a hook for the basic command
22206 name, e.g.@: @code{backtrace} rather than @code{bt}.
22207 @c FIXME! So how does Joe User discover whether a command is an alias
22209 You can hook a multi-word command by adding @code{hook-} or
22210 @code{hookpost-} to the last word of the command, e.g.@:
22211 @samp{define target hook-remote} to add a hook to @samp{target remote}.
22213 If an error occurs during the execution of your hook, execution of
22214 @value{GDBN} commands stops and @value{GDBN} issues a prompt
22215 (before the command that you actually typed had a chance to run).
22217 If you try to define a hook which does not match any known command, you
22218 get a warning from the @code{define} command.
22220 @node Command Files
22221 @subsection Command Files
22223 @cindex command files
22224 @cindex scripting commands
22225 A command file for @value{GDBN} is a text file made of lines that are
22226 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
22227 also be included. An empty line in a command file does nothing; it
22228 does not mean to repeat the last command, as it would from the
22231 You can request the execution of a command file with the @code{source}
22232 command. Note that the @code{source} command is also used to evaluate
22233 scripts that are not Command Files. The exact behavior can be configured
22234 using the @code{script-extension} setting.
22235 @xref{Extending GDB,, Extending GDB}.
22239 @cindex execute commands from a file
22240 @item source [-s] [-v] @var{filename}
22241 Execute the command file @var{filename}.
22244 The lines in a command file are generally executed sequentially,
22245 unless the order of execution is changed by one of the
22246 @emph{flow-control commands} described below. The commands are not
22247 printed as they are executed. An error in any command terminates
22248 execution of the command file and control is returned to the console.
22250 @value{GDBN} first searches for @var{filename} in the current directory.
22251 If the file is not found there, and @var{filename} does not specify a
22252 directory, then @value{GDBN} also looks for the file on the source search path
22253 (specified with the @samp{directory} command);
22254 except that @file{$cdir} is not searched because the compilation directory
22255 is not relevant to scripts.
22257 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
22258 on the search path even if @var{filename} specifies a directory.
22259 The search is done by appending @var{filename} to each element of the
22260 search path. So, for example, if @var{filename} is @file{mylib/myscript}
22261 and the search path contains @file{/home/user} then @value{GDBN} will
22262 look for the script @file{/home/user/mylib/myscript}.
22263 The search is also done if @var{filename} is an absolute path.
22264 For example, if @var{filename} is @file{/tmp/myscript} and
22265 the search path contains @file{/home/user} then @value{GDBN} will
22266 look for the script @file{/home/user/tmp/myscript}.
22267 For DOS-like systems, if @var{filename} contains a drive specification,
22268 it is stripped before concatenation. For example, if @var{filename} is
22269 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
22270 will look for the script @file{c:/tmp/myscript}.
22272 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
22273 each command as it is executed. The option must be given before
22274 @var{filename}, and is interpreted as part of the filename anywhere else.
22276 Commands that would ask for confirmation if used interactively proceed
22277 without asking when used in a command file. Many @value{GDBN} commands that
22278 normally print messages to say what they are doing omit the messages
22279 when called from command files.
22281 @value{GDBN} also accepts command input from standard input. In this
22282 mode, normal output goes to standard output and error output goes to
22283 standard error. Errors in a command file supplied on standard input do
22284 not terminate execution of the command file---execution continues with
22288 gdb < cmds > log 2>&1
22291 (The syntax above will vary depending on the shell used.) This example
22292 will execute commands from the file @file{cmds}. All output and errors
22293 would be directed to @file{log}.
22295 Since commands stored on command files tend to be more general than
22296 commands typed interactively, they frequently need to deal with
22297 complicated situations, such as different or unexpected values of
22298 variables and symbols, changes in how the program being debugged is
22299 built, etc. @value{GDBN} provides a set of flow-control commands to
22300 deal with these complexities. Using these commands, you can write
22301 complex scripts that loop over data structures, execute commands
22302 conditionally, etc.
22309 This command allows to include in your script conditionally executed
22310 commands. The @code{if} command takes a single argument, which is an
22311 expression to evaluate. It is followed by a series of commands that
22312 are executed only if the expression is true (its value is nonzero).
22313 There can then optionally be an @code{else} line, followed by a series
22314 of commands that are only executed if the expression was false. The
22315 end of the list is marked by a line containing @code{end}.
22319 This command allows to write loops. Its syntax is similar to
22320 @code{if}: the command takes a single argument, which is an expression
22321 to evaluate, and must be followed by the commands to execute, one per
22322 line, terminated by an @code{end}. These commands are called the
22323 @dfn{body} of the loop. The commands in the body of @code{while} are
22324 executed repeatedly as long as the expression evaluates to true.
22328 This command exits the @code{while} loop in whose body it is included.
22329 Execution of the script continues after that @code{while}s @code{end}
22332 @kindex loop_continue
22333 @item loop_continue
22334 This command skips the execution of the rest of the body of commands
22335 in the @code{while} loop in whose body it is included. Execution
22336 branches to the beginning of the @code{while} loop, where it evaluates
22337 the controlling expression.
22339 @kindex end@r{ (if/else/while commands)}
22341 Terminate the block of commands that are the body of @code{if},
22342 @code{else}, or @code{while} flow-control commands.
22347 @subsection Commands for Controlled Output
22349 During the execution of a command file or a user-defined command, normal
22350 @value{GDBN} output is suppressed; the only output that appears is what is
22351 explicitly printed by the commands in the definition. This section
22352 describes three commands useful for generating exactly the output you
22357 @item echo @var{text}
22358 @c I do not consider backslash-space a standard C escape sequence
22359 @c because it is not in ANSI.
22360 Print @var{text}. Nonprinting characters can be included in
22361 @var{text} using C escape sequences, such as @samp{\n} to print a
22362 newline. @strong{No newline is printed unless you specify one.}
22363 In addition to the standard C escape sequences, a backslash followed
22364 by a space stands for a space. This is useful for displaying a
22365 string with spaces at the beginning or the end, since leading and
22366 trailing spaces are otherwise trimmed from all arguments.
22367 To print @samp{@w{ }and foo =@w{ }}, use the command
22368 @samp{echo \@w{ }and foo = \@w{ }}.
22370 A backslash at the end of @var{text} can be used, as in C, to continue
22371 the command onto subsequent lines. For example,
22374 echo This is some text\n\
22375 which is continued\n\
22376 onto several lines.\n
22379 produces the same output as
22382 echo This is some text\n
22383 echo which is continued\n
22384 echo onto several lines.\n
22388 @item output @var{expression}
22389 Print the value of @var{expression} and nothing but that value: no
22390 newlines, no @samp{$@var{nn} = }. The value is not entered in the
22391 value history either. @xref{Expressions, ,Expressions}, for more information
22394 @item output/@var{fmt} @var{expression}
22395 Print the value of @var{expression} in format @var{fmt}. You can use
22396 the same formats as for @code{print}. @xref{Output Formats,,Output
22397 Formats}, for more information.
22400 @item printf @var{template}, @var{expressions}@dots{}
22401 Print the values of one or more @var{expressions} under the control of
22402 the string @var{template}. To print several values, make
22403 @var{expressions} be a comma-separated list of individual expressions,
22404 which may be either numbers or pointers. Their values are printed as
22405 specified by @var{template}, exactly as a C program would do by
22406 executing the code below:
22409 printf (@var{template}, @var{expressions}@dots{});
22412 As in @code{C} @code{printf}, ordinary characters in @var{template}
22413 are printed verbatim, while @dfn{conversion specification} introduced
22414 by the @samp{%} character cause subsequent @var{expressions} to be
22415 evaluated, their values converted and formatted according to type and
22416 style information encoded in the conversion specifications, and then
22419 For example, you can print two values in hex like this:
22422 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
22425 @code{printf} supports all the standard @code{C} conversion
22426 specifications, including the flags and modifiers between the @samp{%}
22427 character and the conversion letter, with the following exceptions:
22431 The argument-ordering modifiers, such as @samp{2$}, are not supported.
22434 The modifier @samp{*} is not supported for specifying precision or
22438 The @samp{'} flag (for separation of digits into groups according to
22439 @code{LC_NUMERIC'}) is not supported.
22442 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
22446 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
22449 The conversion letters @samp{a} and @samp{A} are not supported.
22453 Note that the @samp{ll} type modifier is supported only if the
22454 underlying @code{C} implementation used to build @value{GDBN} supports
22455 the @code{long long int} type, and the @samp{L} type modifier is
22456 supported only if @code{long double} type is available.
22458 As in @code{C}, @code{printf} supports simple backslash-escape
22459 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
22460 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
22461 single character. Octal and hexadecimal escape sequences are not
22464 Additionally, @code{printf} supports conversion specifications for DFP
22465 (@dfn{Decimal Floating Point}) types using the following length modifiers
22466 together with a floating point specifier.
22471 @samp{H} for printing @code{Decimal32} types.
22474 @samp{D} for printing @code{Decimal64} types.
22477 @samp{DD} for printing @code{Decimal128} types.
22480 If the underlying @code{C} implementation used to build @value{GDBN} has
22481 support for the three length modifiers for DFP types, other modifiers
22482 such as width and precision will also be available for @value{GDBN} to use.
22484 In case there is no such @code{C} support, no additional modifiers will be
22485 available and the value will be printed in the standard way.
22487 Here's an example of printing DFP types using the above conversion letters:
22489 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
22493 @item eval @var{template}, @var{expressions}@dots{}
22494 Convert the values of one or more @var{expressions} under the control of
22495 the string @var{template} to a command line, and call it.
22500 @section Scripting @value{GDBN} using Python
22501 @cindex python scripting
22502 @cindex scripting with python
22504 You can script @value{GDBN} using the @uref{http://www.python.org/,
22505 Python programming language}. This feature is available only if
22506 @value{GDBN} was configured using @option{--with-python}.
22508 @cindex python directory
22509 Python scripts used by @value{GDBN} should be installed in
22510 @file{@var{data-directory}/python}, where @var{data-directory} is
22511 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
22512 This directory, known as the @dfn{python directory},
22513 is automatically added to the Python Search Path in order to allow
22514 the Python interpreter to locate all scripts installed at this location.
22516 Additionally, @value{GDBN} commands and convenience functions which
22517 are written in Python and are located in the
22518 @file{@var{data-directory}/python/gdb/command} or
22519 @file{@var{data-directory}/python/gdb/function} directories are
22520 automatically imported when @value{GDBN} starts.
22523 * Python Commands:: Accessing Python from @value{GDBN}.
22524 * Python API:: Accessing @value{GDBN} from Python.
22525 * Python Auto-loading:: Automatically loading Python code.
22526 * Python modules:: Python modules provided by @value{GDBN}.
22529 @node Python Commands
22530 @subsection Python Commands
22531 @cindex python commands
22532 @cindex commands to access python
22534 @value{GDBN} provides two commands for accessing the Python interpreter,
22535 and one related setting:
22538 @kindex python-interactive
22540 @item python-interactive @r{[}@var{command}@r{]}
22541 @itemx pi @r{[}@var{command}@r{]}
22542 Without an argument, the @code{python-interactive} command can be used
22543 to start an interactive Python prompt. To return to @value{GDBN},
22544 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
22546 Alternatively, a single-line Python command can be given as an
22547 argument and evaluated. If the command is an expression, the result
22548 will be printed; otherwise, nothing will be printed. For example:
22551 (@value{GDBP}) python-interactive 2 + 3
22557 @item python @r{[}@var{command}@r{]}
22558 @itemx py @r{[}@var{command}@r{]}
22559 The @code{python} command can be used to evaluate Python code.
22561 If given an argument, the @code{python} command will evaluate the
22562 argument as a Python command. For example:
22565 (@value{GDBP}) python print 23
22569 If you do not provide an argument to @code{python}, it will act as a
22570 multi-line command, like @code{define}. In this case, the Python
22571 script is made up of subsequent command lines, given after the
22572 @code{python} command. This command list is terminated using a line
22573 containing @code{end}. For example:
22576 (@value{GDBP}) python
22578 End with a line saying just "end".
22584 @kindex set python print-stack
22585 @item set python print-stack
22586 By default, @value{GDBN} will print only the message component of a
22587 Python exception when an error occurs in a Python script. This can be
22588 controlled using @code{set python print-stack}: if @code{full}, then
22589 full Python stack printing is enabled; if @code{none}, then Python stack
22590 and message printing is disabled; if @code{message}, the default, only
22591 the message component of the error is printed.
22594 It is also possible to execute a Python script from the @value{GDBN}
22598 @item source @file{script-name}
22599 The script name must end with @samp{.py} and @value{GDBN} must be configured
22600 to recognize the script language based on filename extension using
22601 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
22603 @item python execfile ("script-name")
22604 This method is based on the @code{execfile} Python built-in function,
22605 and thus is always available.
22609 @subsection Python API
22611 @cindex programming in python
22613 @cindex python stdout
22614 @cindex python pagination
22615 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
22616 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
22617 A Python program which outputs to one of these streams may have its
22618 output interrupted by the user (@pxref{Screen Size}). In this
22619 situation, a Python @code{KeyboardInterrupt} exception is thrown.
22622 * Basic Python:: Basic Python Functions.
22623 * Exception Handling:: How Python exceptions are translated.
22624 * Values From Inferior:: Python representation of values.
22625 * Types In Python:: Python representation of types.
22626 * Pretty Printing API:: Pretty-printing values.
22627 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
22628 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
22629 * Inferiors In Python:: Python representation of inferiors (processes)
22630 * Events In Python:: Listening for events from @value{GDBN}.
22631 * Threads In Python:: Accessing inferior threads from Python.
22632 * Commands In Python:: Implementing new commands in Python.
22633 * Parameters In Python:: Adding new @value{GDBN} parameters.
22634 * Functions In Python:: Writing new convenience functions.
22635 * Progspaces In Python:: Program spaces.
22636 * Objfiles In Python:: Object files.
22637 * Frames In Python:: Accessing inferior stack frames from Python.
22638 * Blocks In Python:: Accessing frame blocks from Python.
22639 * Symbols In Python:: Python representation of symbols.
22640 * Symbol Tables In Python:: Python representation of symbol tables.
22641 * Breakpoints In Python:: Manipulating breakpoints using Python.
22642 * Finish Breakpoints in Python:: Setting Breakpoints on function return
22644 * Lazy Strings In Python:: Python representation of lazy strings.
22648 @subsubsection Basic Python
22650 @cindex python functions
22651 @cindex python module
22653 @value{GDBN} introduces a new Python module, named @code{gdb}. All
22654 methods and classes added by @value{GDBN} are placed in this module.
22655 @value{GDBN} automatically @code{import}s the @code{gdb} module for
22656 use in all scripts evaluated by the @code{python} command.
22658 @findex gdb.PYTHONDIR
22659 @defvar gdb.PYTHONDIR
22660 A string containing the python directory (@pxref{Python}).
22663 @findex gdb.execute
22664 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
22665 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
22666 If a GDB exception happens while @var{command} runs, it is
22667 translated as described in @ref{Exception Handling,,Exception Handling}.
22669 @var{from_tty} specifies whether @value{GDBN} ought to consider this
22670 command as having originated from the user invoking it interactively.
22671 It must be a boolean value. If omitted, it defaults to @code{False}.
22673 By default, any output produced by @var{command} is sent to
22674 @value{GDBN}'s standard output. If the @var{to_string} parameter is
22675 @code{True}, then output will be collected by @code{gdb.execute} and
22676 returned as a string. The default is @code{False}, in which case the
22677 return value is @code{None}. If @var{to_string} is @code{True}, the
22678 @value{GDBN} virtual terminal will be temporarily set to unlimited width
22679 and height, and its pagination will be disabled; @pxref{Screen Size}.
22682 @findex gdb.breakpoints
22683 @defun gdb.breakpoints ()
22684 Return a sequence holding all of @value{GDBN}'s breakpoints.
22685 @xref{Breakpoints In Python}, for more information.
22688 @findex gdb.parameter
22689 @defun gdb.parameter (parameter)
22690 Return the value of a @value{GDBN} parameter. @var{parameter} is a
22691 string naming the parameter to look up; @var{parameter} may contain
22692 spaces if the parameter has a multi-part name. For example,
22693 @samp{print object} is a valid parameter name.
22695 If the named parameter does not exist, this function throws a
22696 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
22697 parameter's value is converted to a Python value of the appropriate
22698 type, and returned.
22701 @findex gdb.history
22702 @defun gdb.history (number)
22703 Return a value from @value{GDBN}'s value history (@pxref{Value
22704 History}). @var{number} indicates which history element to return.
22705 If @var{number} is negative, then @value{GDBN} will take its absolute value
22706 and count backward from the last element (i.e., the most recent element) to
22707 find the value to return. If @var{number} is zero, then @value{GDBN} will
22708 return the most recent element. If the element specified by @var{number}
22709 doesn't exist in the value history, a @code{gdb.error} exception will be
22712 If no exception is raised, the return value is always an instance of
22713 @code{gdb.Value} (@pxref{Values From Inferior}).
22716 @findex gdb.parse_and_eval
22717 @defun gdb.parse_and_eval (expression)
22718 Parse @var{expression} as an expression in the current language,
22719 evaluate it, and return the result as a @code{gdb.Value}.
22720 @var{expression} must be a string.
22722 This function can be useful when implementing a new command
22723 (@pxref{Commands In Python}), as it provides a way to parse the
22724 command's argument as an expression. It is also useful simply to
22725 compute values, for example, it is the only way to get the value of a
22726 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
22729 @findex gdb.find_pc_line
22730 @defun gdb.find_pc_line (pc)
22731 Return the @code{gdb.Symtab_and_line} object corresponding to the
22732 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
22733 value of @var{pc} is passed as an argument, then the @code{symtab} and
22734 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
22735 will be @code{None} and 0 respectively.
22738 @findex gdb.post_event
22739 @defun gdb.post_event (event)
22740 Put @var{event}, a callable object taking no arguments, into
22741 @value{GDBN}'s internal event queue. This callable will be invoked at
22742 some later point, during @value{GDBN}'s event processing. Events
22743 posted using @code{post_event} will be run in the order in which they
22744 were posted; however, there is no way to know when they will be
22745 processed relative to other events inside @value{GDBN}.
22747 @value{GDBN} is not thread-safe. If your Python program uses multiple
22748 threads, you must be careful to only call @value{GDBN}-specific
22749 functions in the main @value{GDBN} thread. @code{post_event} ensures
22753 (@value{GDBP}) python
22757 > def __init__(self, message):
22758 > self.message = message;
22759 > def __call__(self):
22760 > gdb.write(self.message)
22762 >class MyThread1 (threading.Thread):
22764 > gdb.post_event(Writer("Hello "))
22766 >class MyThread2 (threading.Thread):
22768 > gdb.post_event(Writer("World\n"))
22770 >MyThread1().start()
22771 >MyThread2().start()
22773 (@value{GDBP}) Hello World
22778 @defun gdb.write (string @r{[}, stream{]})
22779 Print a string to @value{GDBN}'s paginated output stream. The
22780 optional @var{stream} determines the stream to print to. The default
22781 stream is @value{GDBN}'s standard output stream. Possible stream
22788 @value{GDBN}'s standard output stream.
22793 @value{GDBN}'s standard error stream.
22798 @value{GDBN}'s log stream (@pxref{Logging Output}).
22801 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
22802 call this function and will automatically direct the output to the
22807 @defun gdb.flush ()
22808 Flush the buffer of a @value{GDBN} paginated stream so that the
22809 contents are displayed immediately. @value{GDBN} will flush the
22810 contents of a stream automatically when it encounters a newline in the
22811 buffer. The optional @var{stream} determines the stream to flush. The
22812 default stream is @value{GDBN}'s standard output stream. Possible
22819 @value{GDBN}'s standard output stream.
22824 @value{GDBN}'s standard error stream.
22829 @value{GDBN}'s log stream (@pxref{Logging Output}).
22833 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
22834 call this function for the relevant stream.
22837 @findex gdb.target_charset
22838 @defun gdb.target_charset ()
22839 Return the name of the current target character set (@pxref{Character
22840 Sets}). This differs from @code{gdb.parameter('target-charset')} in
22841 that @samp{auto} is never returned.
22844 @findex gdb.target_wide_charset
22845 @defun gdb.target_wide_charset ()
22846 Return the name of the current target wide character set
22847 (@pxref{Character Sets}). This differs from
22848 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
22852 @findex gdb.solib_name
22853 @defun gdb.solib_name (address)
22854 Return the name of the shared library holding the given @var{address}
22855 as a string, or @code{None}.
22858 @findex gdb.decode_line
22859 @defun gdb.decode_line @r{[}expression@r{]}
22860 Return locations of the line specified by @var{expression}, or of the
22861 current line if no argument was given. This function returns a Python
22862 tuple containing two elements. The first element contains a string
22863 holding any unparsed section of @var{expression} (or @code{None} if
22864 the expression has been fully parsed). The second element contains
22865 either @code{None} or another tuple that contains all the locations
22866 that match the expression represented as @code{gdb.Symtab_and_line}
22867 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
22868 provided, it is decoded the way that @value{GDBN}'s inbuilt
22869 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
22872 @defun gdb.prompt_hook (current_prompt)
22873 @anchor{prompt_hook}
22875 If @var{prompt_hook} is callable, @value{GDBN} will call the method
22876 assigned to this operation before a prompt is displayed by
22879 The parameter @code{current_prompt} contains the current @value{GDBN}
22880 prompt. This method must return a Python string, or @code{None}. If
22881 a string is returned, the @value{GDBN} prompt will be set to that
22882 string. If @code{None} is returned, @value{GDBN} will continue to use
22883 the current prompt.
22885 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
22886 such as those used by readline for command input, and annotation
22887 related prompts are prohibited from being changed.
22890 @node Exception Handling
22891 @subsubsection Exception Handling
22892 @cindex python exceptions
22893 @cindex exceptions, python
22895 When executing the @code{python} command, Python exceptions
22896 uncaught within the Python code are translated to calls to
22897 @value{GDBN} error-reporting mechanism. If the command that called
22898 @code{python} does not handle the error, @value{GDBN} will
22899 terminate it and print an error message containing the Python
22900 exception name, the associated value, and the Python call stack
22901 backtrace at the point where the exception was raised. Example:
22904 (@value{GDBP}) python print foo
22905 Traceback (most recent call last):
22906 File "<string>", line 1, in <module>
22907 NameError: name 'foo' is not defined
22910 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
22911 Python code are converted to Python exceptions. The type of the
22912 Python exception depends on the error.
22916 This is the base class for most exceptions generated by @value{GDBN}.
22917 It is derived from @code{RuntimeError}, for compatibility with earlier
22918 versions of @value{GDBN}.
22920 If an error occurring in @value{GDBN} does not fit into some more
22921 specific category, then the generated exception will have this type.
22923 @item gdb.MemoryError
22924 This is a subclass of @code{gdb.error} which is thrown when an
22925 operation tried to access invalid memory in the inferior.
22927 @item KeyboardInterrupt
22928 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
22929 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
22932 In all cases, your exception handler will see the @value{GDBN} error
22933 message as its value and the Python call stack backtrace at the Python
22934 statement closest to where the @value{GDBN} error occured as the
22937 @findex gdb.GdbError
22938 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
22939 it is useful to be able to throw an exception that doesn't cause a
22940 traceback to be printed. For example, the user may have invoked the
22941 command incorrectly. Use the @code{gdb.GdbError} exception
22942 to handle this case. Example:
22946 >class HelloWorld (gdb.Command):
22947 > """Greet the whole world."""
22948 > def __init__ (self):
22949 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
22950 > def invoke (self, args, from_tty):
22951 > argv = gdb.string_to_argv (args)
22952 > if len (argv) != 0:
22953 > raise gdb.GdbError ("hello-world takes no arguments")
22954 > print "Hello, World!"
22957 (gdb) hello-world 42
22958 hello-world takes no arguments
22961 @node Values From Inferior
22962 @subsubsection Values From Inferior
22963 @cindex values from inferior, with Python
22964 @cindex python, working with values from inferior
22966 @cindex @code{gdb.Value}
22967 @value{GDBN} provides values it obtains from the inferior program in
22968 an object of type @code{gdb.Value}. @value{GDBN} uses this object
22969 for its internal bookkeeping of the inferior's values, and for
22970 fetching values when necessary.
22972 Inferior values that are simple scalars can be used directly in
22973 Python expressions that are valid for the value's data type. Here's
22974 an example for an integer or floating-point value @code{some_val}:
22981 As result of this, @code{bar} will also be a @code{gdb.Value} object
22982 whose values are of the same type as those of @code{some_val}.
22984 Inferior values that are structures or instances of some class can
22985 be accessed using the Python @dfn{dictionary syntax}. For example, if
22986 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
22987 can access its @code{foo} element with:
22990 bar = some_val['foo']
22993 Again, @code{bar} will also be a @code{gdb.Value} object.
22995 A @code{gdb.Value} that represents a function can be executed via
22996 inferior function call. Any arguments provided to the call must match
22997 the function's prototype, and must be provided in the order specified
23000 For example, @code{some_val} is a @code{gdb.Value} instance
23001 representing a function that takes two integers as arguments. To
23002 execute this function, call it like so:
23005 result = some_val (10,20)
23008 Any values returned from a function call will be stored as a
23011 The following attributes are provided:
23014 @defvar Value.address
23015 If this object is addressable, this read-only attribute holds a
23016 @code{gdb.Value} object representing the address. Otherwise,
23017 this attribute holds @code{None}.
23020 @cindex optimized out value in Python
23021 @defvar Value.is_optimized_out
23022 This read-only boolean attribute is true if the compiler optimized out
23023 this value, thus it is not available for fetching from the inferior.
23027 The type of this @code{gdb.Value}. The value of this attribute is a
23028 @code{gdb.Type} object (@pxref{Types In Python}).
23031 @defvar Value.dynamic_type
23032 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
23033 type information (@acronym{RTTI}) to determine the dynamic type of the
23034 value. If this value is of class type, it will return the class in
23035 which the value is embedded, if any. If this value is of pointer or
23036 reference to a class type, it will compute the dynamic type of the
23037 referenced object, and return a pointer or reference to that type,
23038 respectively. In all other cases, it will return the value's static
23041 Note that this feature will only work when debugging a C@t{++} program
23042 that includes @acronym{RTTI} for the object in question. Otherwise,
23043 it will just return the static type of the value as in @kbd{ptype foo}
23044 (@pxref{Symbols, ptype}).
23047 @defvar Value.is_lazy
23048 The value of this read-only boolean attribute is @code{True} if this
23049 @code{gdb.Value} has not yet been fetched from the inferior.
23050 @value{GDBN} does not fetch values until necessary, for efficiency.
23054 myval = gdb.parse_and_eval ('somevar')
23057 The value of @code{somevar} is not fetched at this time. It will be
23058 fetched when the value is needed, or when the @code{fetch_lazy}
23063 The following methods are provided:
23066 @defun Value.__init__ (@var{val})
23067 Many Python values can be converted directly to a @code{gdb.Value} via
23068 this object initializer. Specifically:
23071 @item Python boolean
23072 A Python boolean is converted to the boolean type from the current
23075 @item Python integer
23076 A Python integer is converted to the C @code{long} type for the
23077 current architecture.
23080 A Python long is converted to the C @code{long long} type for the
23081 current architecture.
23084 A Python float is converted to the C @code{double} type for the
23085 current architecture.
23087 @item Python string
23088 A Python string is converted to a target string, using the current
23091 @item @code{gdb.Value}
23092 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
23094 @item @code{gdb.LazyString}
23095 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
23096 Python}), then the lazy string's @code{value} method is called, and
23097 its result is used.
23101 @defun Value.cast (type)
23102 Return a new instance of @code{gdb.Value} that is the result of
23103 casting this instance to the type described by @var{type}, which must
23104 be a @code{gdb.Type} object. If the cast cannot be performed for some
23105 reason, this method throws an exception.
23108 @defun Value.dereference ()
23109 For pointer data types, this method returns a new @code{gdb.Value} object
23110 whose contents is the object pointed to by the pointer. For example, if
23111 @code{foo} is a C pointer to an @code{int}, declared in your C program as
23118 then you can use the corresponding @code{gdb.Value} to access what
23119 @code{foo} points to like this:
23122 bar = foo.dereference ()
23125 The result @code{bar} will be a @code{gdb.Value} object holding the
23126 value pointed to by @code{foo}.
23128 A similar function @code{Value.referenced_value} exists which also
23129 returns @code{gdb.Value} objects corresonding to the values pointed to
23130 by pointer values (and additionally, values referenced by reference
23131 values). However, the behavior of @code{Value.dereference}
23132 differs from @code{Value.referenced_value} by the fact that the
23133 behavior of @code{Value.dereference} is identical to applying the C
23134 unary operator @code{*} on a given value. For example, consider a
23135 reference to a pointer @code{ptrref}, declared in your C@t{++} program
23139 typedef int *intptr;
23143 intptr &ptrref = ptr;
23146 Though @code{ptrref} is a reference value, one can apply the method
23147 @code{Value.dereference} to the @code{gdb.Value} object corresponding
23148 to it and obtain a @code{gdb.Value} which is identical to that
23149 corresponding to @code{val}. However, if you apply the method
23150 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
23151 object identical to that corresponding to @code{ptr}.
23154 py_ptrref = gdb.parse_and_eval ("ptrref")
23155 py_val = py_ptrref.dereference ()
23156 py_ptr = py_ptrref.referenced_value ()
23159 The @code{gdb.Value} object @code{py_val} is identical to that
23160 corresponding to @code{val}, and @code{py_ptr} is identical to that
23161 corresponding to @code{ptr}. In general, @code{Value.dereference} can
23162 be applied whenever the C unary operator @code{*} can be applied
23163 to the corresponding C value. For those cases where applying both
23164 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
23165 the results obtained need not be identical (as we have seen in the above
23166 example). The results are however identical when applied on
23167 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
23168 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
23171 @defun Value.referenced_value ()
23172 For pointer or reference data types, this method returns a new
23173 @code{gdb.Value} object corresponding to the value referenced by the
23174 pointer/reference value. For pointer data types,
23175 @code{Value.dereference} and @code{Value.referenced_value} produce
23176 identical results. The difference between these methods is that
23177 @code{Value.dereference} cannot get the values referenced by reference
23178 values. For example, consider a reference to an @code{int}, declared
23179 in your C@t{++} program as
23187 then applying @code{Value.dereference} to the @code{gdb.Value} object
23188 corresponding to @code{ref} will result in an error, while applying
23189 @code{Value.referenced_value} will result in a @code{gdb.Value} object
23190 identical to that corresponding to @code{val}.
23193 py_ref = gdb.parse_and_eval ("ref")
23194 er_ref = py_ref.dereference () # Results in error
23195 py_val = py_ref.referenced_value () # Returns the referenced value
23198 The @code{gdb.Value} object @code{py_val} is identical to that
23199 corresponding to @code{val}.
23202 @defun Value.dynamic_cast (type)
23203 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
23204 operator were used. Consult a C@t{++} reference for details.
23207 @defun Value.reinterpret_cast (type)
23208 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
23209 operator were used. Consult a C@t{++} reference for details.
23212 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
23213 If this @code{gdb.Value} represents a string, then this method
23214 converts the contents to a Python string. Otherwise, this method will
23215 throw an exception.
23217 Strings are recognized in a language-specific way; whether a given
23218 @code{gdb.Value} represents a string is determined by the current
23221 For C-like languages, a value is a string if it is a pointer to or an
23222 array of characters or ints. The string is assumed to be terminated
23223 by a zero of the appropriate width. However if the optional length
23224 argument is given, the string will be converted to that given length,
23225 ignoring any embedded zeros that the string may contain.
23227 If the optional @var{encoding} argument is given, it must be a string
23228 naming the encoding of the string in the @code{gdb.Value}, such as
23229 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
23230 the same encodings as the corresponding argument to Python's
23231 @code{string.decode} method, and the Python codec machinery will be used
23232 to convert the string. If @var{encoding} is not given, or if
23233 @var{encoding} is the empty string, then either the @code{target-charset}
23234 (@pxref{Character Sets}) will be used, or a language-specific encoding
23235 will be used, if the current language is able to supply one.
23237 The optional @var{errors} argument is the same as the corresponding
23238 argument to Python's @code{string.decode} method.
23240 If the optional @var{length} argument is given, the string will be
23241 fetched and converted to the given length.
23244 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
23245 If this @code{gdb.Value} represents a string, then this method
23246 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
23247 In Python}). Otherwise, this method will throw an exception.
23249 If the optional @var{encoding} argument is given, it must be a string
23250 naming the encoding of the @code{gdb.LazyString}. Some examples are:
23251 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
23252 @var{encoding} argument is an encoding that @value{GDBN} does
23253 recognize, @value{GDBN} will raise an error.
23255 When a lazy string is printed, the @value{GDBN} encoding machinery is
23256 used to convert the string during printing. If the optional
23257 @var{encoding} argument is not provided, or is an empty string,
23258 @value{GDBN} will automatically select the encoding most suitable for
23259 the string type. For further information on encoding in @value{GDBN}
23260 please see @ref{Character Sets}.
23262 If the optional @var{length} argument is given, the string will be
23263 fetched and encoded to the length of characters specified. If
23264 the @var{length} argument is not provided, the string will be fetched
23265 and encoded until a null of appropriate width is found.
23268 @defun Value.fetch_lazy ()
23269 If the @code{gdb.Value} object is currently a lazy value
23270 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
23271 fetched from the inferior. Any errors that occur in the process
23272 will produce a Python exception.
23274 If the @code{gdb.Value} object is not a lazy value, this method
23277 This method does not return a value.
23282 @node Types In Python
23283 @subsubsection Types In Python
23284 @cindex types in Python
23285 @cindex Python, working with types
23288 @value{GDBN} represents types from the inferior using the class
23291 The following type-related functions are available in the @code{gdb}
23294 @findex gdb.lookup_type
23295 @defun gdb.lookup_type (name @r{[}, block@r{]})
23296 This function looks up a type by name. @var{name} is the name of the
23297 type to look up. It must be a string.
23299 If @var{block} is given, then @var{name} is looked up in that scope.
23300 Otherwise, it is searched for globally.
23302 Ordinarily, this function will return an instance of @code{gdb.Type}.
23303 If the named type cannot be found, it will throw an exception.
23306 If the type is a structure or class type, or an enum type, the fields
23307 of that type can be accessed using the Python @dfn{dictionary syntax}.
23308 For example, if @code{some_type} is a @code{gdb.Type} instance holding
23309 a structure type, you can access its @code{foo} field with:
23312 bar = some_type['foo']
23315 @code{bar} will be a @code{gdb.Field} object; see below under the
23316 description of the @code{Type.fields} method for a description of the
23317 @code{gdb.Field} class.
23319 An instance of @code{Type} has the following attributes:
23323 The type code for this type. The type code will be one of the
23324 @code{TYPE_CODE_} constants defined below.
23327 @defvar Type.sizeof
23328 The size of this type, in target @code{char} units. Usually, a
23329 target's @code{char} type will be an 8-bit byte. However, on some
23330 unusual platforms, this type may have a different size.
23334 The tag name for this type. The tag name is the name after
23335 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
23336 languages have this concept. If this type has no tag name, then
23337 @code{None} is returned.
23341 The following methods are provided:
23344 @defun Type.fields ()
23345 For structure and union types, this method returns the fields. Range
23346 types have two fields, the minimum and maximum values. Enum types
23347 have one field per enum constant. Function and method types have one
23348 field per parameter. The base types of C@t{++} classes are also
23349 represented as fields. If the type has no fields, or does not fit
23350 into one of these categories, an empty sequence will be returned.
23352 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
23355 This attribute is not available for @code{static} fields (as in
23356 C@t{++} or Java). For non-@code{static} fields, the value is the bit
23357 position of the field. For @code{enum} fields, the value is the
23358 enumeration member's integer representation.
23361 The name of the field, or @code{None} for anonymous fields.
23364 This is @code{True} if the field is artificial, usually meaning that
23365 it was provided by the compiler and not the user. This attribute is
23366 always provided, and is @code{False} if the field is not artificial.
23368 @item is_base_class
23369 This is @code{True} if the field represents a base class of a C@t{++}
23370 structure. This attribute is always provided, and is @code{False}
23371 if the field is not a base class of the type that is the argument of
23372 @code{fields}, or if that type was not a C@t{++} class.
23375 If the field is packed, or is a bitfield, then this will have a
23376 non-zero value, which is the size of the field in bits. Otherwise,
23377 this will be zero; in this case the field's size is given by its type.
23380 The type of the field. This is usually an instance of @code{Type},
23381 but it can be @code{None} in some situations.
23385 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
23386 Return a new @code{gdb.Type} object which represents an array of this
23387 type. If one argument is given, it is the inclusive upper bound of
23388 the array; in this case the lower bound is zero. If two arguments are
23389 given, the first argument is the lower bound of the array, and the
23390 second argument is the upper bound of the array. An array's length
23391 must not be negative, but the bounds can be.
23394 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
23395 Return a new @code{gdb.Type} object which represents a vector of this
23396 type. If one argument is given, it is the inclusive upper bound of
23397 the vector; in this case the lower bound is zero. If two arguments are
23398 given, the first argument is the lower bound of the vector, and the
23399 second argument is the upper bound of the vector. A vector's length
23400 must not be negative, but the bounds can be.
23402 The difference between an @code{array} and a @code{vector} is that
23403 arrays behave like in C: when used in expressions they decay to a pointer
23404 to the first element whereas vectors are treated as first class values.
23407 @defun Type.const ()
23408 Return a new @code{gdb.Type} object which represents a
23409 @code{const}-qualified variant of this type.
23412 @defun Type.volatile ()
23413 Return a new @code{gdb.Type} object which represents a
23414 @code{volatile}-qualified variant of this type.
23417 @defun Type.unqualified ()
23418 Return a new @code{gdb.Type} object which represents an unqualified
23419 variant of this type. That is, the result is neither @code{const} nor
23423 @defun Type.range ()
23424 Return a Python @code{Tuple} object that contains two elements: the
23425 low bound of the argument type and the high bound of that type. If
23426 the type does not have a range, @value{GDBN} will raise a
23427 @code{gdb.error} exception (@pxref{Exception Handling}).
23430 @defun Type.reference ()
23431 Return a new @code{gdb.Type} object which represents a reference to this
23435 @defun Type.pointer ()
23436 Return a new @code{gdb.Type} object which represents a pointer to this
23440 @defun Type.strip_typedefs ()
23441 Return a new @code{gdb.Type} that represents the real type,
23442 after removing all layers of typedefs.
23445 @defun Type.target ()
23446 Return a new @code{gdb.Type} object which represents the target type
23449 For a pointer type, the target type is the type of the pointed-to
23450 object. For an array type (meaning C-like arrays), the target type is
23451 the type of the elements of the array. For a function or method type,
23452 the target type is the type of the return value. For a complex type,
23453 the target type is the type of the elements. For a typedef, the
23454 target type is the aliased type.
23456 If the type does not have a target, this method will throw an
23460 @defun Type.template_argument (n @r{[}, block@r{]})
23461 If this @code{gdb.Type} is an instantiation of a template, this will
23462 return a new @code{gdb.Type} which represents the type of the
23463 @var{n}th template argument.
23465 If this @code{gdb.Type} is not a template type, this will throw an
23466 exception. Ordinarily, only C@t{++} code will have template types.
23468 If @var{block} is given, then @var{name} is looked up in that scope.
23469 Otherwise, it is searched for globally.
23474 Each type has a code, which indicates what category this type falls
23475 into. The available type categories are represented by constants
23476 defined in the @code{gdb} module:
23479 @findex TYPE_CODE_PTR
23480 @findex gdb.TYPE_CODE_PTR
23481 @item gdb.TYPE_CODE_PTR
23482 The type is a pointer.
23484 @findex TYPE_CODE_ARRAY
23485 @findex gdb.TYPE_CODE_ARRAY
23486 @item gdb.TYPE_CODE_ARRAY
23487 The type is an array.
23489 @findex TYPE_CODE_STRUCT
23490 @findex gdb.TYPE_CODE_STRUCT
23491 @item gdb.TYPE_CODE_STRUCT
23492 The type is a structure.
23494 @findex TYPE_CODE_UNION
23495 @findex gdb.TYPE_CODE_UNION
23496 @item gdb.TYPE_CODE_UNION
23497 The type is a union.
23499 @findex TYPE_CODE_ENUM
23500 @findex gdb.TYPE_CODE_ENUM
23501 @item gdb.TYPE_CODE_ENUM
23502 The type is an enum.
23504 @findex TYPE_CODE_FLAGS
23505 @findex gdb.TYPE_CODE_FLAGS
23506 @item gdb.TYPE_CODE_FLAGS
23507 A bit flags type, used for things such as status registers.
23509 @findex TYPE_CODE_FUNC
23510 @findex gdb.TYPE_CODE_FUNC
23511 @item gdb.TYPE_CODE_FUNC
23512 The type is a function.
23514 @findex TYPE_CODE_INT
23515 @findex gdb.TYPE_CODE_INT
23516 @item gdb.TYPE_CODE_INT
23517 The type is an integer type.
23519 @findex TYPE_CODE_FLT
23520 @findex gdb.TYPE_CODE_FLT
23521 @item gdb.TYPE_CODE_FLT
23522 A floating point type.
23524 @findex TYPE_CODE_VOID
23525 @findex gdb.TYPE_CODE_VOID
23526 @item gdb.TYPE_CODE_VOID
23527 The special type @code{void}.
23529 @findex TYPE_CODE_SET
23530 @findex gdb.TYPE_CODE_SET
23531 @item gdb.TYPE_CODE_SET
23534 @findex TYPE_CODE_RANGE
23535 @findex gdb.TYPE_CODE_RANGE
23536 @item gdb.TYPE_CODE_RANGE
23537 A range type, that is, an integer type with bounds.
23539 @findex TYPE_CODE_STRING
23540 @findex gdb.TYPE_CODE_STRING
23541 @item gdb.TYPE_CODE_STRING
23542 A string type. Note that this is only used for certain languages with
23543 language-defined string types; C strings are not represented this way.
23545 @findex TYPE_CODE_BITSTRING
23546 @findex gdb.TYPE_CODE_BITSTRING
23547 @item gdb.TYPE_CODE_BITSTRING
23548 A string of bits. It is deprecated.
23550 @findex TYPE_CODE_ERROR
23551 @findex gdb.TYPE_CODE_ERROR
23552 @item gdb.TYPE_CODE_ERROR
23553 An unknown or erroneous type.
23555 @findex TYPE_CODE_METHOD
23556 @findex gdb.TYPE_CODE_METHOD
23557 @item gdb.TYPE_CODE_METHOD
23558 A method type, as found in C@t{++} or Java.
23560 @findex TYPE_CODE_METHODPTR
23561 @findex gdb.TYPE_CODE_METHODPTR
23562 @item gdb.TYPE_CODE_METHODPTR
23563 A pointer-to-member-function.
23565 @findex TYPE_CODE_MEMBERPTR
23566 @findex gdb.TYPE_CODE_MEMBERPTR
23567 @item gdb.TYPE_CODE_MEMBERPTR
23568 A pointer-to-member.
23570 @findex TYPE_CODE_REF
23571 @findex gdb.TYPE_CODE_REF
23572 @item gdb.TYPE_CODE_REF
23575 @findex TYPE_CODE_CHAR
23576 @findex gdb.TYPE_CODE_CHAR
23577 @item gdb.TYPE_CODE_CHAR
23580 @findex TYPE_CODE_BOOL
23581 @findex gdb.TYPE_CODE_BOOL
23582 @item gdb.TYPE_CODE_BOOL
23585 @findex TYPE_CODE_COMPLEX
23586 @findex gdb.TYPE_CODE_COMPLEX
23587 @item gdb.TYPE_CODE_COMPLEX
23588 A complex float type.
23590 @findex TYPE_CODE_TYPEDEF
23591 @findex gdb.TYPE_CODE_TYPEDEF
23592 @item gdb.TYPE_CODE_TYPEDEF
23593 A typedef to some other type.
23595 @findex TYPE_CODE_NAMESPACE
23596 @findex gdb.TYPE_CODE_NAMESPACE
23597 @item gdb.TYPE_CODE_NAMESPACE
23598 A C@t{++} namespace.
23600 @findex TYPE_CODE_DECFLOAT
23601 @findex gdb.TYPE_CODE_DECFLOAT
23602 @item gdb.TYPE_CODE_DECFLOAT
23603 A decimal floating point type.
23605 @findex TYPE_CODE_INTERNAL_FUNCTION
23606 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
23607 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
23608 A function internal to @value{GDBN}. This is the type used to represent
23609 convenience functions.
23612 Further support for types is provided in the @code{gdb.types}
23613 Python module (@pxref{gdb.types}).
23615 @node Pretty Printing API
23616 @subsubsection Pretty Printing API
23618 An example output is provided (@pxref{Pretty Printing}).
23620 A pretty-printer is just an object that holds a value and implements a
23621 specific interface, defined here.
23623 @defun pretty_printer.children (self)
23624 @value{GDBN} will call this method on a pretty-printer to compute the
23625 children of the pretty-printer's value.
23627 This method must return an object conforming to the Python iterator
23628 protocol. Each item returned by the iterator must be a tuple holding
23629 two elements. The first element is the ``name'' of the child; the
23630 second element is the child's value. The value can be any Python
23631 object which is convertible to a @value{GDBN} value.
23633 This method is optional. If it does not exist, @value{GDBN} will act
23634 as though the value has no children.
23637 @defun pretty_printer.display_hint (self)
23638 The CLI may call this method and use its result to change the
23639 formatting of a value. The result will also be supplied to an MI
23640 consumer as a @samp{displayhint} attribute of the variable being
23643 This method is optional. If it does exist, this method must return a
23646 Some display hints are predefined by @value{GDBN}:
23650 Indicate that the object being printed is ``array-like''. The CLI
23651 uses this to respect parameters such as @code{set print elements} and
23652 @code{set print array}.
23655 Indicate that the object being printed is ``map-like'', and that the
23656 children of this value can be assumed to alternate between keys and
23660 Indicate that the object being printed is ``string-like''. If the
23661 printer's @code{to_string} method returns a Python string of some
23662 kind, then @value{GDBN} will call its internal language-specific
23663 string-printing function to format the string. For the CLI this means
23664 adding quotation marks, possibly escaping some characters, respecting
23665 @code{set print elements}, and the like.
23669 @defun pretty_printer.to_string (self)
23670 @value{GDBN} will call this method to display the string
23671 representation of the value passed to the object's constructor.
23673 When printing from the CLI, if the @code{to_string} method exists,
23674 then @value{GDBN} will prepend its result to the values returned by
23675 @code{children}. Exactly how this formatting is done is dependent on
23676 the display hint, and may change as more hints are added. Also,
23677 depending on the print settings (@pxref{Print Settings}), the CLI may
23678 print just the result of @code{to_string} in a stack trace, omitting
23679 the result of @code{children}.
23681 If this method returns a string, it is printed verbatim.
23683 Otherwise, if this method returns an instance of @code{gdb.Value},
23684 then @value{GDBN} prints this value. This may result in a call to
23685 another pretty-printer.
23687 If instead the method returns a Python value which is convertible to a
23688 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
23689 the resulting value. Again, this may result in a call to another
23690 pretty-printer. Python scalars (integers, floats, and booleans) and
23691 strings are convertible to @code{gdb.Value}; other types are not.
23693 Finally, if this method returns @code{None} then no further operations
23694 are peformed in this method and nothing is printed.
23696 If the result is not one of these types, an exception is raised.
23699 @value{GDBN} provides a function which can be used to look up the
23700 default pretty-printer for a @code{gdb.Value}:
23702 @findex gdb.default_visualizer
23703 @defun gdb.default_visualizer (value)
23704 This function takes a @code{gdb.Value} object as an argument. If a
23705 pretty-printer for this value exists, then it is returned. If no such
23706 printer exists, then this returns @code{None}.
23709 @node Selecting Pretty-Printers
23710 @subsubsection Selecting Pretty-Printers
23712 The Python list @code{gdb.pretty_printers} contains an array of
23713 functions or callable objects that have been registered via addition
23714 as a pretty-printer. Printers in this list are called @code{global}
23715 printers, they're available when debugging all inferiors.
23716 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
23717 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
23720 Each function on these lists is passed a single @code{gdb.Value}
23721 argument and should return a pretty-printer object conforming to the
23722 interface definition above (@pxref{Pretty Printing API}). If a function
23723 cannot create a pretty-printer for the value, it should return
23726 @value{GDBN} first checks the @code{pretty_printers} attribute of each
23727 @code{gdb.Objfile} in the current program space and iteratively calls
23728 each enabled lookup routine in the list for that @code{gdb.Objfile}
23729 until it receives a pretty-printer object.
23730 If no pretty-printer is found in the objfile lists, @value{GDBN} then
23731 searches the pretty-printer list of the current program space,
23732 calling each enabled function until an object is returned.
23733 After these lists have been exhausted, it tries the global
23734 @code{gdb.pretty_printers} list, again calling each enabled function until an
23735 object is returned.
23737 The order in which the objfiles are searched is not specified. For a
23738 given list, functions are always invoked from the head of the list,
23739 and iterated over sequentially until the end of the list, or a printer
23740 object is returned.
23742 For various reasons a pretty-printer may not work.
23743 For example, the underlying data structure may have changed and
23744 the pretty-printer is out of date.
23746 The consequences of a broken pretty-printer are severe enough that
23747 @value{GDBN} provides support for enabling and disabling individual
23748 printers. For example, if @code{print frame-arguments} is on,
23749 a backtrace can become highly illegible if any argument is printed
23750 with a broken printer.
23752 Pretty-printers are enabled and disabled by attaching an @code{enabled}
23753 attribute to the registered function or callable object. If this attribute
23754 is present and its value is @code{False}, the printer is disabled, otherwise
23755 the printer is enabled.
23757 @node Writing a Pretty-Printer
23758 @subsubsection Writing a Pretty-Printer
23759 @cindex writing a pretty-printer
23761 A pretty-printer consists of two parts: a lookup function to detect
23762 if the type is supported, and the printer itself.
23764 Here is an example showing how a @code{std::string} printer might be
23765 written. @xref{Pretty Printing API}, for details on the API this class
23769 class StdStringPrinter(object):
23770 "Print a std::string"
23772 def __init__(self, val):
23775 def to_string(self):
23776 return self.val['_M_dataplus']['_M_p']
23778 def display_hint(self):
23782 And here is an example showing how a lookup function for the printer
23783 example above might be written.
23786 def str_lookup_function(val):
23787 lookup_tag = val.type.tag
23788 if lookup_tag == None:
23790 regex = re.compile("^std::basic_string<char,.*>$")
23791 if regex.match(lookup_tag):
23792 return StdStringPrinter(val)
23796 The example lookup function extracts the value's type, and attempts to
23797 match it to a type that it can pretty-print. If it is a type the
23798 printer can pretty-print, it will return a printer object. If not, it
23799 returns @code{None}.
23801 We recommend that you put your core pretty-printers into a Python
23802 package. If your pretty-printers are for use with a library, we
23803 further recommend embedding a version number into the package name.
23804 This practice will enable @value{GDBN} to load multiple versions of
23805 your pretty-printers at the same time, because they will have
23808 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
23809 can be evaluated multiple times without changing its meaning. An
23810 ideal auto-load file will consist solely of @code{import}s of your
23811 printer modules, followed by a call to a register pretty-printers with
23812 the current objfile.
23814 Taken as a whole, this approach will scale nicely to multiple
23815 inferiors, each potentially using a different library version.
23816 Embedding a version number in the Python package name will ensure that
23817 @value{GDBN} is able to load both sets of printers simultaneously.
23818 Then, because the search for pretty-printers is done by objfile, and
23819 because your auto-loaded code took care to register your library's
23820 printers with a specific objfile, @value{GDBN} will find the correct
23821 printers for the specific version of the library used by each
23824 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
23825 this code might appear in @code{gdb.libstdcxx.v6}:
23828 def register_printers(objfile):
23829 objfile.pretty_printers.append(str_lookup_function)
23833 And then the corresponding contents of the auto-load file would be:
23836 import gdb.libstdcxx.v6
23837 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
23840 The previous example illustrates a basic pretty-printer.
23841 There are a few things that can be improved on.
23842 The printer doesn't have a name, making it hard to identify in a
23843 list of installed printers. The lookup function has a name, but
23844 lookup functions can have arbitrary, even identical, names.
23846 Second, the printer only handles one type, whereas a library typically has
23847 several types. One could install a lookup function for each desired type
23848 in the library, but one could also have a single lookup function recognize
23849 several types. The latter is the conventional way this is handled.
23850 If a pretty-printer can handle multiple data types, then its
23851 @dfn{subprinters} are the printers for the individual data types.
23853 The @code{gdb.printing} module provides a formal way of solving these
23854 problems (@pxref{gdb.printing}).
23855 Here is another example that handles multiple types.
23857 These are the types we are going to pretty-print:
23860 struct foo @{ int a, b; @};
23861 struct bar @{ struct foo x, y; @};
23864 Here are the printers:
23868 """Print a foo object."""
23870 def __init__(self, val):
23873 def to_string(self):
23874 return ("a=<" + str(self.val["a"]) +
23875 "> b=<" + str(self.val["b"]) + ">")
23878 """Print a bar object."""
23880 def __init__(self, val):
23883 def to_string(self):
23884 return ("x=<" + str(self.val["x"]) +
23885 "> y=<" + str(self.val["y"]) + ">")
23888 This example doesn't need a lookup function, that is handled by the
23889 @code{gdb.printing} module. Instead a function is provided to build up
23890 the object that handles the lookup.
23893 import gdb.printing
23895 def build_pretty_printer():
23896 pp = gdb.printing.RegexpCollectionPrettyPrinter(
23898 pp.add_printer('foo', '^foo$', fooPrinter)
23899 pp.add_printer('bar', '^bar$', barPrinter)
23903 And here is the autoload support:
23906 import gdb.printing
23908 gdb.printing.register_pretty_printer(
23909 gdb.current_objfile(),
23910 my_library.build_pretty_printer())
23913 Finally, when this printer is loaded into @value{GDBN}, here is the
23914 corresponding output of @samp{info pretty-printer}:
23917 (gdb) info pretty-printer
23924 @node Inferiors In Python
23925 @subsubsection Inferiors In Python
23926 @cindex inferiors in Python
23928 @findex gdb.Inferior
23929 Programs which are being run under @value{GDBN} are called inferiors
23930 (@pxref{Inferiors and Programs}). Python scripts can access
23931 information about and manipulate inferiors controlled by @value{GDBN}
23932 via objects of the @code{gdb.Inferior} class.
23934 The following inferior-related functions are available in the @code{gdb}
23937 @defun gdb.inferiors ()
23938 Return a tuple containing all inferior objects.
23941 @defun gdb.selected_inferior ()
23942 Return an object representing the current inferior.
23945 A @code{gdb.Inferior} object has the following attributes:
23948 @defvar Inferior.num
23949 ID of inferior, as assigned by GDB.
23952 @defvar Inferior.pid
23953 Process ID of the inferior, as assigned by the underlying operating
23957 @defvar Inferior.was_attached
23958 Boolean signaling whether the inferior was created using `attach', or
23959 started by @value{GDBN} itself.
23963 A @code{gdb.Inferior} object has the following methods:
23966 @defun Inferior.is_valid ()
23967 Returns @code{True} if the @code{gdb.Inferior} object is valid,
23968 @code{False} if not. A @code{gdb.Inferior} object will become invalid
23969 if the inferior no longer exists within @value{GDBN}. All other
23970 @code{gdb.Inferior} methods will throw an exception if it is invalid
23971 at the time the method is called.
23974 @defun Inferior.threads ()
23975 This method returns a tuple holding all the threads which are valid
23976 when it is called. If there are no valid threads, the method will
23977 return an empty tuple.
23980 @findex Inferior.read_memory
23981 @defun Inferior.read_memory (address, length)
23982 Read @var{length} bytes of memory from the inferior, starting at
23983 @var{address}. Returns a buffer object, which behaves much like an array
23984 or a string. It can be modified and given to the
23985 @code{Inferior.write_memory} function.
23988 @findex Inferior.write_memory
23989 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
23990 Write the contents of @var{buffer} to the inferior, starting at
23991 @var{address}. The @var{buffer} parameter must be a Python object
23992 which supports the buffer protocol, i.e., a string, an array or the
23993 object returned from @code{Inferior.read_memory}. If given, @var{length}
23994 determines the number of bytes from @var{buffer} to be written.
23997 @findex gdb.search_memory
23998 @defun Inferior.search_memory (address, length, pattern)
23999 Search a region of the inferior memory starting at @var{address} with
24000 the given @var{length} using the search pattern supplied in
24001 @var{pattern}. The @var{pattern} parameter must be a Python object
24002 which supports the buffer protocol, i.e., a string, an array or the
24003 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
24004 containing the address where the pattern was found, or @code{None} if
24005 the pattern could not be found.
24009 @node Events In Python
24010 @subsubsection Events In Python
24011 @cindex inferior events in Python
24013 @value{GDBN} provides a general event facility so that Python code can be
24014 notified of various state changes, particularly changes that occur in
24017 An @dfn{event} is just an object that describes some state change. The
24018 type of the object and its attributes will vary depending on the details
24019 of the change. All the existing events are described below.
24021 In order to be notified of an event, you must register an event handler
24022 with an @dfn{event registry}. An event registry is an object in the
24023 @code{gdb.events} module which dispatches particular events. A registry
24024 provides methods to register and unregister event handlers:
24027 @defun EventRegistry.connect (object)
24028 Add the given callable @var{object} to the registry. This object will be
24029 called when an event corresponding to this registry occurs.
24032 @defun EventRegistry.disconnect (object)
24033 Remove the given @var{object} from the registry. Once removed, the object
24034 will no longer receive notifications of events.
24038 Here is an example:
24041 def exit_handler (event):
24042 print "event type: exit"
24043 print "exit code: %d" % (event.exit_code)
24045 gdb.events.exited.connect (exit_handler)
24048 In the above example we connect our handler @code{exit_handler} to the
24049 registry @code{events.exited}. Once connected, @code{exit_handler} gets
24050 called when the inferior exits. The argument @dfn{event} in this example is
24051 of type @code{gdb.ExitedEvent}. As you can see in the example the
24052 @code{ExitedEvent} object has an attribute which indicates the exit code of
24055 The following is a listing of the event registries that are available and
24056 details of the events they emit:
24061 Emits @code{gdb.ThreadEvent}.
24063 Some events can be thread specific when @value{GDBN} is running in non-stop
24064 mode. When represented in Python, these events all extend
24065 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
24066 events which are emitted by this or other modules might extend this event.
24067 Examples of these events are @code{gdb.BreakpointEvent} and
24068 @code{gdb.ContinueEvent}.
24071 @defvar ThreadEvent.inferior_thread
24072 In non-stop mode this attribute will be set to the specific thread which was
24073 involved in the emitted event. Otherwise, it will be set to @code{None}.
24077 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
24079 This event indicates that the inferior has been continued after a stop. For
24080 inherited attribute refer to @code{gdb.ThreadEvent} above.
24082 @item events.exited
24083 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
24084 @code{events.ExitedEvent} has two attributes:
24086 @defvar ExitedEvent.exit_code
24087 An integer representing the exit code, if available, which the inferior
24088 has returned. (The exit code could be unavailable if, for example,
24089 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
24090 the attribute does not exist.
24092 @defvar ExitedEvent inferior
24093 A reference to the inferior which triggered the @code{exited} event.
24098 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
24100 Indicates that the inferior has stopped. All events emitted by this registry
24101 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
24102 will indicate the stopped thread when @value{GDBN} is running in non-stop
24103 mode. Refer to @code{gdb.ThreadEvent} above for more details.
24105 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
24107 This event indicates that the inferior or one of its threads has received as
24108 signal. @code{gdb.SignalEvent} has the following attributes:
24111 @defvar SignalEvent.stop_signal
24112 A string representing the signal received by the inferior. A list of possible
24113 signal values can be obtained by running the command @code{info signals} in
24114 the @value{GDBN} command prompt.
24118 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
24120 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
24121 been hit, and has the following attributes:
24124 @defvar BreakpointEvent.breakpoints
24125 A sequence containing references to all the breakpoints (type
24126 @code{gdb.Breakpoint}) that were hit.
24127 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
24129 @defvar BreakpointEvent.breakpoint
24130 A reference to the first breakpoint that was hit.
24131 This function is maintained for backward compatibility and is now deprecated
24132 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
24136 @item events.new_objfile
24137 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
24138 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
24141 @defvar NewObjFileEvent.new_objfile
24142 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
24143 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
24149 @node Threads In Python
24150 @subsubsection Threads In Python
24151 @cindex threads in python
24153 @findex gdb.InferiorThread
24154 Python scripts can access information about, and manipulate inferior threads
24155 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
24157 The following thread-related functions are available in the @code{gdb}
24160 @findex gdb.selected_thread
24161 @defun gdb.selected_thread ()
24162 This function returns the thread object for the selected thread. If there
24163 is no selected thread, this will return @code{None}.
24166 A @code{gdb.InferiorThread} object has the following attributes:
24169 @defvar InferiorThread.name
24170 The name of the thread. If the user specified a name using
24171 @code{thread name}, then this returns that name. Otherwise, if an
24172 OS-supplied name is available, then it is returned. Otherwise, this
24173 returns @code{None}.
24175 This attribute can be assigned to. The new value must be a string
24176 object, which sets the new name, or @code{None}, which removes any
24177 user-specified thread name.
24180 @defvar InferiorThread.num
24181 ID of the thread, as assigned by GDB.
24184 @defvar InferiorThread.ptid
24185 ID of the thread, as assigned by the operating system. This attribute is a
24186 tuple containing three integers. The first is the Process ID (PID); the second
24187 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
24188 Either the LWPID or TID may be 0, which indicates that the operating system
24189 does not use that identifier.
24193 A @code{gdb.InferiorThread} object has the following methods:
24196 @defun InferiorThread.is_valid ()
24197 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
24198 @code{False} if not. A @code{gdb.InferiorThread} object will become
24199 invalid if the thread exits, or the inferior that the thread belongs
24200 is deleted. All other @code{gdb.InferiorThread} methods will throw an
24201 exception if it is invalid at the time the method is called.
24204 @defun InferiorThread.switch ()
24205 This changes @value{GDBN}'s currently selected thread to the one represented
24209 @defun InferiorThread.is_stopped ()
24210 Return a Boolean indicating whether the thread is stopped.
24213 @defun InferiorThread.is_running ()
24214 Return a Boolean indicating whether the thread is running.
24217 @defun InferiorThread.is_exited ()
24218 Return a Boolean indicating whether the thread is exited.
24222 @node Commands In Python
24223 @subsubsection Commands In Python
24225 @cindex commands in python
24226 @cindex python commands
24227 You can implement new @value{GDBN} CLI commands in Python. A CLI
24228 command is implemented using an instance of the @code{gdb.Command}
24229 class, most commonly using a subclass.
24231 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
24232 The object initializer for @code{Command} registers the new command
24233 with @value{GDBN}. This initializer is normally invoked from the
24234 subclass' own @code{__init__} method.
24236 @var{name} is the name of the command. If @var{name} consists of
24237 multiple words, then the initial words are looked for as prefix
24238 commands. In this case, if one of the prefix commands does not exist,
24239 an exception is raised.
24241 There is no support for multi-line commands.
24243 @var{command_class} should be one of the @samp{COMMAND_} constants
24244 defined below. This argument tells @value{GDBN} how to categorize the
24245 new command in the help system.
24247 @var{completer_class} is an optional argument. If given, it should be
24248 one of the @samp{COMPLETE_} constants defined below. This argument
24249 tells @value{GDBN} how to perform completion for this command. If not
24250 given, @value{GDBN} will attempt to complete using the object's
24251 @code{complete} method (see below); if no such method is found, an
24252 error will occur when completion is attempted.
24254 @var{prefix} is an optional argument. If @code{True}, then the new
24255 command is a prefix command; sub-commands of this command may be
24258 The help text for the new command is taken from the Python
24259 documentation string for the command's class, if there is one. If no
24260 documentation string is provided, the default value ``This command is
24261 not documented.'' is used.
24264 @cindex don't repeat Python command
24265 @defun Command.dont_repeat ()
24266 By default, a @value{GDBN} command is repeated when the user enters a
24267 blank line at the command prompt. A command can suppress this
24268 behavior by invoking the @code{dont_repeat} method. This is similar
24269 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
24272 @defun Command.invoke (argument, from_tty)
24273 This method is called by @value{GDBN} when this command is invoked.
24275 @var{argument} is a string. It is the argument to the command, after
24276 leading and trailing whitespace has been stripped.
24278 @var{from_tty} is a boolean argument. When true, this means that the
24279 command was entered by the user at the terminal; when false it means
24280 that the command came from elsewhere.
24282 If this method throws an exception, it is turned into a @value{GDBN}
24283 @code{error} call. Otherwise, the return value is ignored.
24285 @findex gdb.string_to_argv
24286 To break @var{argument} up into an argv-like string use
24287 @code{gdb.string_to_argv}. This function behaves identically to
24288 @value{GDBN}'s internal argument lexer @code{buildargv}.
24289 It is recommended to use this for consistency.
24290 Arguments are separated by spaces and may be quoted.
24294 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
24295 ['1', '2 "3', '4 "5', "6 '7"]
24300 @cindex completion of Python commands
24301 @defun Command.complete (text, word)
24302 This method is called by @value{GDBN} when the user attempts
24303 completion on this command. All forms of completion are handled by
24304 this method, that is, the @key{TAB} and @key{M-?} key bindings
24305 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
24308 The arguments @var{text} and @var{word} are both strings. @var{text}
24309 holds the complete command line up to the cursor's location.
24310 @var{word} holds the last word of the command line; this is computed
24311 using a word-breaking heuristic.
24313 The @code{complete} method can return several values:
24316 If the return value is a sequence, the contents of the sequence are
24317 used as the completions. It is up to @code{complete} to ensure that the
24318 contents actually do complete the word. A zero-length sequence is
24319 allowed, it means that there were no completions available. Only
24320 string elements of the sequence are used; other elements in the
24321 sequence are ignored.
24324 If the return value is one of the @samp{COMPLETE_} constants defined
24325 below, then the corresponding @value{GDBN}-internal completion
24326 function is invoked, and its result is used.
24329 All other results are treated as though there were no available
24334 When a new command is registered, it must be declared as a member of
24335 some general class of commands. This is used to classify top-level
24336 commands in the on-line help system; note that prefix commands are not
24337 listed under their own category but rather that of their top-level
24338 command. The available classifications are represented by constants
24339 defined in the @code{gdb} module:
24342 @findex COMMAND_NONE
24343 @findex gdb.COMMAND_NONE
24344 @item gdb.COMMAND_NONE
24345 The command does not belong to any particular class. A command in
24346 this category will not be displayed in any of the help categories.
24348 @findex COMMAND_RUNNING
24349 @findex gdb.COMMAND_RUNNING
24350 @item gdb.COMMAND_RUNNING
24351 The command is related to running the inferior. For example,
24352 @code{start}, @code{step}, and @code{continue} are in this category.
24353 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
24354 commands in this category.
24356 @findex COMMAND_DATA
24357 @findex gdb.COMMAND_DATA
24358 @item gdb.COMMAND_DATA
24359 The command is related to data or variables. For example,
24360 @code{call}, @code{find}, and @code{print} are in this category. Type
24361 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
24364 @findex COMMAND_STACK
24365 @findex gdb.COMMAND_STACK
24366 @item gdb.COMMAND_STACK
24367 The command has to do with manipulation of the stack. For example,
24368 @code{backtrace}, @code{frame}, and @code{return} are in this
24369 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
24370 list of commands in this category.
24372 @findex COMMAND_FILES
24373 @findex gdb.COMMAND_FILES
24374 @item gdb.COMMAND_FILES
24375 This class is used for file-related commands. For example,
24376 @code{file}, @code{list} and @code{section} are in this category.
24377 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
24378 commands in this category.
24380 @findex COMMAND_SUPPORT
24381 @findex gdb.COMMAND_SUPPORT
24382 @item gdb.COMMAND_SUPPORT
24383 This should be used for ``support facilities'', generally meaning
24384 things that are useful to the user when interacting with @value{GDBN},
24385 but not related to the state of the inferior. For example,
24386 @code{help}, @code{make}, and @code{shell} are in this category. Type
24387 @kbd{help support} at the @value{GDBN} prompt to see a list of
24388 commands in this category.
24390 @findex COMMAND_STATUS
24391 @findex gdb.COMMAND_STATUS
24392 @item gdb.COMMAND_STATUS
24393 The command is an @samp{info}-related command, that is, related to the
24394 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
24395 and @code{show} are in this category. Type @kbd{help status} at the
24396 @value{GDBN} prompt to see a list of commands in this category.
24398 @findex COMMAND_BREAKPOINTS
24399 @findex gdb.COMMAND_BREAKPOINTS
24400 @item gdb.COMMAND_BREAKPOINTS
24401 The command has to do with breakpoints. For example, @code{break},
24402 @code{clear}, and @code{delete} are in this category. Type @kbd{help
24403 breakpoints} at the @value{GDBN} prompt to see a list of commands in
24406 @findex COMMAND_TRACEPOINTS
24407 @findex gdb.COMMAND_TRACEPOINTS
24408 @item gdb.COMMAND_TRACEPOINTS
24409 The command has to do with tracepoints. For example, @code{trace},
24410 @code{actions}, and @code{tfind} are in this category. Type
24411 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
24412 commands in this category.
24414 @findex COMMAND_USER
24415 @findex gdb.COMMAND_USER
24416 @item gdb.COMMAND_USER
24417 The command is a general purpose command for the user, and typically
24418 does not fit in one of the other categories.
24419 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
24420 a list of commands in this category, as well as the list of gdb macros
24421 (@pxref{Sequences}).
24423 @findex COMMAND_OBSCURE
24424 @findex gdb.COMMAND_OBSCURE
24425 @item gdb.COMMAND_OBSCURE
24426 The command is only used in unusual circumstances, or is not of
24427 general interest to users. For example, @code{checkpoint},
24428 @code{fork}, and @code{stop} are in this category. Type @kbd{help
24429 obscure} at the @value{GDBN} prompt to see a list of commands in this
24432 @findex COMMAND_MAINTENANCE
24433 @findex gdb.COMMAND_MAINTENANCE
24434 @item gdb.COMMAND_MAINTENANCE
24435 The command is only useful to @value{GDBN} maintainers. The
24436 @code{maintenance} and @code{flushregs} commands are in this category.
24437 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
24438 commands in this category.
24441 A new command can use a predefined completion function, either by
24442 specifying it via an argument at initialization, or by returning it
24443 from the @code{complete} method. These predefined completion
24444 constants are all defined in the @code{gdb} module:
24447 @findex COMPLETE_NONE
24448 @findex gdb.COMPLETE_NONE
24449 @item gdb.COMPLETE_NONE
24450 This constant means that no completion should be done.
24452 @findex COMPLETE_FILENAME
24453 @findex gdb.COMPLETE_FILENAME
24454 @item gdb.COMPLETE_FILENAME
24455 This constant means that filename completion should be performed.
24457 @findex COMPLETE_LOCATION
24458 @findex gdb.COMPLETE_LOCATION
24459 @item gdb.COMPLETE_LOCATION
24460 This constant means that location completion should be done.
24461 @xref{Specify Location}.
24463 @findex COMPLETE_COMMAND
24464 @findex gdb.COMPLETE_COMMAND
24465 @item gdb.COMPLETE_COMMAND
24466 This constant means that completion should examine @value{GDBN}
24469 @findex COMPLETE_SYMBOL
24470 @findex gdb.COMPLETE_SYMBOL
24471 @item gdb.COMPLETE_SYMBOL
24472 This constant means that completion should be done using symbol names
24476 The following code snippet shows how a trivial CLI command can be
24477 implemented in Python:
24480 class HelloWorld (gdb.Command):
24481 """Greet the whole world."""
24483 def __init__ (self):
24484 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
24486 def invoke (self, arg, from_tty):
24487 print "Hello, World!"
24492 The last line instantiates the class, and is necessary to trigger the
24493 registration of the command with @value{GDBN}. Depending on how the
24494 Python code is read into @value{GDBN}, you may need to import the
24495 @code{gdb} module explicitly.
24497 @node Parameters In Python
24498 @subsubsection Parameters In Python
24500 @cindex parameters in python
24501 @cindex python parameters
24502 @tindex gdb.Parameter
24504 You can implement new @value{GDBN} parameters using Python. A new
24505 parameter is implemented as an instance of the @code{gdb.Parameter}
24508 Parameters are exposed to the user via the @code{set} and
24509 @code{show} commands. @xref{Help}.
24511 There are many parameters that already exist and can be set in
24512 @value{GDBN}. Two examples are: @code{set follow fork} and
24513 @code{set charset}. Setting these parameters influences certain
24514 behavior in @value{GDBN}. Similarly, you can define parameters that
24515 can be used to influence behavior in custom Python scripts and commands.
24517 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
24518 The object initializer for @code{Parameter} registers the new
24519 parameter with @value{GDBN}. This initializer is normally invoked
24520 from the subclass' own @code{__init__} method.
24522 @var{name} is the name of the new parameter. If @var{name} consists
24523 of multiple words, then the initial words are looked for as prefix
24524 parameters. An example of this can be illustrated with the
24525 @code{set print} set of parameters. If @var{name} is
24526 @code{print foo}, then @code{print} will be searched as the prefix
24527 parameter. In this case the parameter can subsequently be accessed in
24528 @value{GDBN} as @code{set print foo}.
24530 If @var{name} consists of multiple words, and no prefix parameter group
24531 can be found, an exception is raised.
24533 @var{command-class} should be one of the @samp{COMMAND_} constants
24534 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
24535 categorize the new parameter in the help system.
24537 @var{parameter-class} should be one of the @samp{PARAM_} constants
24538 defined below. This argument tells @value{GDBN} the type of the new
24539 parameter; this information is used for input validation and
24542 If @var{parameter-class} is @code{PARAM_ENUM}, then
24543 @var{enum-sequence} must be a sequence of strings. These strings
24544 represent the possible values for the parameter.
24546 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
24547 of a fourth argument will cause an exception to be thrown.
24549 The help text for the new parameter is taken from the Python
24550 documentation string for the parameter's class, if there is one. If
24551 there is no documentation string, a default value is used.
24554 @defvar Parameter.set_doc
24555 If this attribute exists, and is a string, then its value is used as
24556 the help text for this parameter's @code{set} command. The value is
24557 examined when @code{Parameter.__init__} is invoked; subsequent changes
24561 @defvar Parameter.show_doc
24562 If this attribute exists, and is a string, then its value is used as
24563 the help text for this parameter's @code{show} command. The value is
24564 examined when @code{Parameter.__init__} is invoked; subsequent changes
24568 @defvar Parameter.value
24569 The @code{value} attribute holds the underlying value of the
24570 parameter. It can be read and assigned to just as any other
24571 attribute. @value{GDBN} does validation when assignments are made.
24574 There are two methods that should be implemented in any
24575 @code{Parameter} class. These are:
24577 @defun Parameter.get_set_string (self)
24578 @value{GDBN} will call this method when a @var{parameter}'s value has
24579 been changed via the @code{set} API (for example, @kbd{set foo off}).
24580 The @code{value} attribute has already been populated with the new
24581 value and may be used in output. This method must return a string.
24584 @defun Parameter.get_show_string (self, svalue)
24585 @value{GDBN} will call this method when a @var{parameter}'s
24586 @code{show} API has been invoked (for example, @kbd{show foo}). The
24587 argument @code{svalue} receives the string representation of the
24588 current value. This method must return a string.
24591 When a new parameter is defined, its type must be specified. The
24592 available types are represented by constants defined in the @code{gdb}
24596 @findex PARAM_BOOLEAN
24597 @findex gdb.PARAM_BOOLEAN
24598 @item gdb.PARAM_BOOLEAN
24599 The value is a plain boolean. The Python boolean values, @code{True}
24600 and @code{False} are the only valid values.
24602 @findex PARAM_AUTO_BOOLEAN
24603 @findex gdb.PARAM_AUTO_BOOLEAN
24604 @item gdb.PARAM_AUTO_BOOLEAN
24605 The value has three possible states: true, false, and @samp{auto}. In
24606 Python, true and false are represented using boolean constants, and
24607 @samp{auto} is represented using @code{None}.
24609 @findex PARAM_UINTEGER
24610 @findex gdb.PARAM_UINTEGER
24611 @item gdb.PARAM_UINTEGER
24612 The value is an unsigned integer. The value of 0 should be
24613 interpreted to mean ``unlimited''.
24615 @findex PARAM_INTEGER
24616 @findex gdb.PARAM_INTEGER
24617 @item gdb.PARAM_INTEGER
24618 The value is a signed integer. The value of 0 should be interpreted
24619 to mean ``unlimited''.
24621 @findex PARAM_STRING
24622 @findex gdb.PARAM_STRING
24623 @item gdb.PARAM_STRING
24624 The value is a string. When the user modifies the string, any escape
24625 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
24626 translated into corresponding characters and encoded into the current
24629 @findex PARAM_STRING_NOESCAPE
24630 @findex gdb.PARAM_STRING_NOESCAPE
24631 @item gdb.PARAM_STRING_NOESCAPE
24632 The value is a string. When the user modifies the string, escapes are
24633 passed through untranslated.
24635 @findex PARAM_OPTIONAL_FILENAME
24636 @findex gdb.PARAM_OPTIONAL_FILENAME
24637 @item gdb.PARAM_OPTIONAL_FILENAME
24638 The value is a either a filename (a string), or @code{None}.
24640 @findex PARAM_FILENAME
24641 @findex gdb.PARAM_FILENAME
24642 @item gdb.PARAM_FILENAME
24643 The value is a filename. This is just like
24644 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
24646 @findex PARAM_ZINTEGER
24647 @findex gdb.PARAM_ZINTEGER
24648 @item gdb.PARAM_ZINTEGER
24649 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
24650 is interpreted as itself.
24653 @findex gdb.PARAM_ENUM
24654 @item gdb.PARAM_ENUM
24655 The value is a string, which must be one of a collection string
24656 constants provided when the parameter is created.
24659 @node Functions In Python
24660 @subsubsection Writing new convenience functions
24662 @cindex writing convenience functions
24663 @cindex convenience functions in python
24664 @cindex python convenience functions
24665 @tindex gdb.Function
24667 You can implement new convenience functions (@pxref{Convenience Vars})
24668 in Python. A convenience function is an instance of a subclass of the
24669 class @code{gdb.Function}.
24671 @defun Function.__init__ (name)
24672 The initializer for @code{Function} registers the new function with
24673 @value{GDBN}. The argument @var{name} is the name of the function,
24674 a string. The function will be visible to the user as a convenience
24675 variable of type @code{internal function}, whose name is the same as
24676 the given @var{name}.
24678 The documentation for the new function is taken from the documentation
24679 string for the new class.
24682 @defun Function.invoke (@var{*args})
24683 When a convenience function is evaluated, its arguments are converted
24684 to instances of @code{gdb.Value}, and then the function's
24685 @code{invoke} method is called. Note that @value{GDBN} does not
24686 predetermine the arity of convenience functions. Instead, all
24687 available arguments are passed to @code{invoke}, following the
24688 standard Python calling convention. In particular, a convenience
24689 function can have default values for parameters without ill effect.
24691 The return value of this method is used as its value in the enclosing
24692 expression. If an ordinary Python value is returned, it is converted
24693 to a @code{gdb.Value} following the usual rules.
24696 The following code snippet shows how a trivial convenience function can
24697 be implemented in Python:
24700 class Greet (gdb.Function):
24701 """Return string to greet someone.
24702 Takes a name as argument."""
24704 def __init__ (self):
24705 super (Greet, self).__init__ ("greet")
24707 def invoke (self, name):
24708 return "Hello, %s!" % name.string ()
24713 The last line instantiates the class, and is necessary to trigger the
24714 registration of the function with @value{GDBN}. Depending on how the
24715 Python code is read into @value{GDBN}, you may need to import the
24716 @code{gdb} module explicitly.
24718 @node Progspaces In Python
24719 @subsubsection Program Spaces In Python
24721 @cindex progspaces in python
24722 @tindex gdb.Progspace
24724 A program space, or @dfn{progspace}, represents a symbolic view
24725 of an address space.
24726 It consists of all of the objfiles of the program.
24727 @xref{Objfiles In Python}.
24728 @xref{Inferiors and Programs, program spaces}, for more details
24729 about program spaces.
24731 The following progspace-related functions are available in the
24734 @findex gdb.current_progspace
24735 @defun gdb.current_progspace ()
24736 This function returns the program space of the currently selected inferior.
24737 @xref{Inferiors and Programs}.
24740 @findex gdb.progspaces
24741 @defun gdb.progspaces ()
24742 Return a sequence of all the progspaces currently known to @value{GDBN}.
24745 Each progspace is represented by an instance of the @code{gdb.Progspace}
24748 @defvar Progspace.filename
24749 The file name of the progspace as a string.
24752 @defvar Progspace.pretty_printers
24753 The @code{pretty_printers} attribute is a list of functions. It is
24754 used to look up pretty-printers. A @code{Value} is passed to each
24755 function in order; if the function returns @code{None}, then the
24756 search continues. Otherwise, the return value should be an object
24757 which is used to format the value. @xref{Pretty Printing API}, for more
24761 @node Objfiles In Python
24762 @subsubsection Objfiles In Python
24764 @cindex objfiles in python
24765 @tindex gdb.Objfile
24767 @value{GDBN} loads symbols for an inferior from various
24768 symbol-containing files (@pxref{Files}). These include the primary
24769 executable file, any shared libraries used by the inferior, and any
24770 separate debug info files (@pxref{Separate Debug Files}).
24771 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
24773 The following objfile-related functions are available in the
24776 @findex gdb.current_objfile
24777 @defun gdb.current_objfile ()
24778 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
24779 sets the ``current objfile'' to the corresponding objfile. This
24780 function returns the current objfile. If there is no current objfile,
24781 this function returns @code{None}.
24784 @findex gdb.objfiles
24785 @defun gdb.objfiles ()
24786 Return a sequence of all the objfiles current known to @value{GDBN}.
24787 @xref{Objfiles In Python}.
24790 Each objfile is represented by an instance of the @code{gdb.Objfile}
24793 @defvar Objfile.filename
24794 The file name of the objfile as a string.
24797 @defvar Objfile.pretty_printers
24798 The @code{pretty_printers} attribute is a list of functions. It is
24799 used to look up pretty-printers. A @code{Value} is passed to each
24800 function in order; if the function returns @code{None}, then the
24801 search continues. Otherwise, the return value should be an object
24802 which is used to format the value. @xref{Pretty Printing API}, for more
24806 A @code{gdb.Objfile} object has the following methods:
24808 @defun Objfile.is_valid ()
24809 Returns @code{True} if the @code{gdb.Objfile} object is valid,
24810 @code{False} if not. A @code{gdb.Objfile} object can become invalid
24811 if the object file it refers to is not loaded in @value{GDBN} any
24812 longer. All other @code{gdb.Objfile} methods will throw an exception
24813 if it is invalid at the time the method is called.
24816 @node Frames In Python
24817 @subsubsection Accessing inferior stack frames from Python.
24819 @cindex frames in python
24820 When the debugged program stops, @value{GDBN} is able to analyze its call
24821 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
24822 represents a frame in the stack. A @code{gdb.Frame} object is only valid
24823 while its corresponding frame exists in the inferior's stack. If you try
24824 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
24825 exception (@pxref{Exception Handling}).
24827 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
24831 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
24835 The following frame-related functions are available in the @code{gdb} module:
24837 @findex gdb.selected_frame
24838 @defun gdb.selected_frame ()
24839 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
24842 @findex gdb.newest_frame
24843 @defun gdb.newest_frame ()
24844 Return the newest frame object for the selected thread.
24847 @defun gdb.frame_stop_reason_string (reason)
24848 Return a string explaining the reason why @value{GDBN} stopped unwinding
24849 frames, as expressed by the given @var{reason} code (an integer, see the
24850 @code{unwind_stop_reason} method further down in this section).
24853 A @code{gdb.Frame} object has the following methods:
24856 @defun Frame.is_valid ()
24857 Returns true if the @code{gdb.Frame} object is valid, false if not.
24858 A frame object can become invalid if the frame it refers to doesn't
24859 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
24860 an exception if it is invalid at the time the method is called.
24863 @defun Frame.name ()
24864 Returns the function name of the frame, or @code{None} if it can't be
24868 @defun Frame.type ()
24869 Returns the type of the frame. The value can be one of:
24871 @item gdb.NORMAL_FRAME
24872 An ordinary stack frame.
24874 @item gdb.DUMMY_FRAME
24875 A fake stack frame that was created by @value{GDBN} when performing an
24876 inferior function call.
24878 @item gdb.INLINE_FRAME
24879 A frame representing an inlined function. The function was inlined
24880 into a @code{gdb.NORMAL_FRAME} that is older than this one.
24882 @item gdb.TAILCALL_FRAME
24883 A frame representing a tail call. @xref{Tail Call Frames}.
24885 @item gdb.SIGTRAMP_FRAME
24886 A signal trampoline frame. This is the frame created by the OS when
24887 it calls into a signal handler.
24889 @item gdb.ARCH_FRAME
24890 A fake stack frame representing a cross-architecture call.
24892 @item gdb.SENTINEL_FRAME
24893 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
24898 @defun Frame.unwind_stop_reason ()
24899 Return an integer representing the reason why it's not possible to find
24900 more frames toward the outermost frame. Use
24901 @code{gdb.frame_stop_reason_string} to convert the value returned by this
24902 function to a string. The value can be one of:
24905 @item gdb.FRAME_UNWIND_NO_REASON
24906 No particular reason (older frames should be available).
24908 @item gdb.FRAME_UNWIND_NULL_ID
24909 The previous frame's analyzer returns an invalid result.
24911 @item gdb.FRAME_UNWIND_OUTERMOST
24912 This frame is the outermost.
24914 @item gdb.FRAME_UNWIND_UNAVAILABLE
24915 Cannot unwind further, because that would require knowing the
24916 values of registers or memory that have not been collected.
24918 @item gdb.FRAME_UNWIND_INNER_ID
24919 This frame ID looks like it ought to belong to a NEXT frame,
24920 but we got it for a PREV frame. Normally, this is a sign of
24921 unwinder failure. It could also indicate stack corruption.
24923 @item gdb.FRAME_UNWIND_SAME_ID
24924 This frame has the same ID as the previous one. That means
24925 that unwinding further would almost certainly give us another
24926 frame with exactly the same ID, so break the chain. Normally,
24927 this is a sign of unwinder failure. It could also indicate
24930 @item gdb.FRAME_UNWIND_NO_SAVED_PC
24931 The frame unwinder did not find any saved PC, but we needed
24932 one to unwind further.
24934 @item gdb.FRAME_UNWIND_FIRST_ERROR
24935 Any stop reason greater or equal to this value indicates some kind
24936 of error. This special value facilitates writing code that tests
24937 for errors in unwinding in a way that will work correctly even if
24938 the list of the other values is modified in future @value{GDBN}
24939 versions. Using it, you could write:
24941 reason = gdb.selected_frame().unwind_stop_reason ()
24942 reason_str = gdb.frame_stop_reason_string (reason)
24943 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
24944 print "An error occured: %s" % reason_str
24951 Returns the frame's resume address.
24954 @defun Frame.block ()
24955 Return the frame's code block. @xref{Blocks In Python}.
24958 @defun Frame.function ()
24959 Return the symbol for the function corresponding to this frame.
24960 @xref{Symbols In Python}.
24963 @defun Frame.older ()
24964 Return the frame that called this frame.
24967 @defun Frame.newer ()
24968 Return the frame called by this frame.
24971 @defun Frame.find_sal ()
24972 Return the frame's symtab and line object.
24973 @xref{Symbol Tables In Python}.
24976 @defun Frame.read_var (variable @r{[}, block@r{]})
24977 Return the value of @var{variable} in this frame. If the optional
24978 argument @var{block} is provided, search for the variable from that
24979 block; otherwise start at the frame's current block (which is
24980 determined by the frame's current program counter). @var{variable}
24981 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
24982 @code{gdb.Block} object.
24985 @defun Frame.select ()
24986 Set this frame to be the selected frame. @xref{Stack, ,Examining the
24991 @node Blocks In Python
24992 @subsubsection Accessing frame blocks from Python.
24994 @cindex blocks in python
24997 Within each frame, @value{GDBN} maintains information on each block
24998 stored in that frame. These blocks are organized hierarchically, and
24999 are represented individually in Python as a @code{gdb.Block}.
25000 Please see @ref{Frames In Python}, for a more in-depth discussion on
25001 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
25002 detailed technical information on @value{GDBN}'s book-keeping of the
25005 A @code{gdb.Block} is iterable. The iterator returns the symbols
25006 (@pxref{Symbols In Python}) local to the block. Python programs
25007 should not assume that a specific block object will always contain a
25008 given symbol, since changes in @value{GDBN} features and
25009 infrastructure may cause symbols move across blocks in a symbol
25012 The following block-related functions are available in the @code{gdb}
25015 @findex gdb.block_for_pc
25016 @defun gdb.block_for_pc (pc)
25017 Return the @code{gdb.Block} containing the given @var{pc} value. If the
25018 block cannot be found for the @var{pc} value specified, the function
25019 will return @code{None}.
25022 A @code{gdb.Block} object has the following methods:
25025 @defun Block.is_valid ()
25026 Returns @code{True} if the @code{gdb.Block} object is valid,
25027 @code{False} if not. A block object can become invalid if the block it
25028 refers to doesn't exist anymore in the inferior. All other
25029 @code{gdb.Block} methods will throw an exception if it is invalid at
25030 the time the method is called. The block's validity is also checked
25031 during iteration over symbols of the block.
25035 A @code{gdb.Block} object has the following attributes:
25038 @defvar Block.start
25039 The start address of the block. This attribute is not writable.
25043 The end address of the block. This attribute is not writable.
25046 @defvar Block.function
25047 The name of the block represented as a @code{gdb.Symbol}. If the
25048 block is not named, then this attribute holds @code{None}. This
25049 attribute is not writable.
25052 @defvar Block.superblock
25053 The block containing this block. If this parent block does not exist,
25054 this attribute holds @code{None}. This attribute is not writable.
25057 @defvar Block.global_block
25058 The global block associated with this block. This attribute is not
25062 @defvar Block.static_block
25063 The static block associated with this block. This attribute is not
25067 @defvar Block.is_global
25068 @code{True} if the @code{gdb.Block} object is a global block,
25069 @code{False} if not. This attribute is not
25073 @defvar Block.is_static
25074 @code{True} if the @code{gdb.Block} object is a static block,
25075 @code{False} if not. This attribute is not writable.
25079 @node Symbols In Python
25080 @subsubsection Python representation of Symbols.
25082 @cindex symbols in python
25085 @value{GDBN} represents every variable, function and type as an
25086 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
25087 Similarly, Python represents these symbols in @value{GDBN} with the
25088 @code{gdb.Symbol} object.
25090 The following symbol-related functions are available in the @code{gdb}
25093 @findex gdb.lookup_symbol
25094 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
25095 This function searches for a symbol by name. The search scope can be
25096 restricted to the parameters defined in the optional domain and block
25099 @var{name} is the name of the symbol. It must be a string. The
25100 optional @var{block} argument restricts the search to symbols visible
25101 in that @var{block}. The @var{block} argument must be a
25102 @code{gdb.Block} object. If omitted, the block for the current frame
25103 is used. The optional @var{domain} argument restricts
25104 the search to the domain type. The @var{domain} argument must be a
25105 domain constant defined in the @code{gdb} module and described later
25108 The result is a tuple of two elements.
25109 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
25111 If the symbol is found, the second element is @code{True} if the symbol
25112 is a field of a method's object (e.g., @code{this} in C@t{++}),
25113 otherwise it is @code{False}.
25114 If the symbol is not found, the second element is @code{False}.
25117 @findex gdb.lookup_global_symbol
25118 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
25119 This function searches for a global symbol by name.
25120 The search scope can be restricted to by the domain argument.
25122 @var{name} is the name of the symbol. It must be a string.
25123 The optional @var{domain} argument restricts the search to the domain type.
25124 The @var{domain} argument must be a domain constant defined in the @code{gdb}
25125 module and described later in this chapter.
25127 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
25131 A @code{gdb.Symbol} object has the following attributes:
25134 @defvar Symbol.type
25135 The type of the symbol or @code{None} if no type is recorded.
25136 This attribute is represented as a @code{gdb.Type} object.
25137 @xref{Types In Python}. This attribute is not writable.
25140 @defvar Symbol.symtab
25141 The symbol table in which the symbol appears. This attribute is
25142 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
25143 Python}. This attribute is not writable.
25146 @defvar Symbol.line
25147 The line number in the source code at which the symbol was defined.
25148 This is an integer.
25151 @defvar Symbol.name
25152 The name of the symbol as a string. This attribute is not writable.
25155 @defvar Symbol.linkage_name
25156 The name of the symbol, as used by the linker (i.e., may be mangled).
25157 This attribute is not writable.
25160 @defvar Symbol.print_name
25161 The name of the symbol in a form suitable for output. This is either
25162 @code{name} or @code{linkage_name}, depending on whether the user
25163 asked @value{GDBN} to display demangled or mangled names.
25166 @defvar Symbol.addr_class
25167 The address class of the symbol. This classifies how to find the value
25168 of a symbol. Each address class is a constant defined in the
25169 @code{gdb} module and described later in this chapter.
25172 @defvar Symbol.needs_frame
25173 This is @code{True} if evaluating this symbol's value requires a frame
25174 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
25175 local variables will require a frame, but other symbols will not.
25178 @defvar Symbol.is_argument
25179 @code{True} if the symbol is an argument of a function.
25182 @defvar Symbol.is_constant
25183 @code{True} if the symbol is a constant.
25186 @defvar Symbol.is_function
25187 @code{True} if the symbol is a function or a method.
25190 @defvar Symbol.is_variable
25191 @code{True} if the symbol is a variable.
25195 A @code{gdb.Symbol} object has the following methods:
25198 @defun Symbol.is_valid ()
25199 Returns @code{True} if the @code{gdb.Symbol} object is valid,
25200 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
25201 the symbol it refers to does not exist in @value{GDBN} any longer.
25202 All other @code{gdb.Symbol} methods will throw an exception if it is
25203 invalid at the time the method is called.
25206 @defun Symbol.value (@r{[}frame@r{]})
25207 Compute the value of the symbol, as a @code{gdb.Value}. For
25208 functions, this computes the address of the function, cast to the
25209 appropriate type. If the symbol requires a frame in order to compute
25210 its value, then @var{frame} must be given. If @var{frame} is not
25211 given, or if @var{frame} is invalid, then this method will throw an
25216 The available domain categories in @code{gdb.Symbol} are represented
25217 as constants in the @code{gdb} module:
25220 @findex SYMBOL_UNDEF_DOMAIN
25221 @findex gdb.SYMBOL_UNDEF_DOMAIN
25222 @item gdb.SYMBOL_UNDEF_DOMAIN
25223 This is used when a domain has not been discovered or none of the
25224 following domains apply. This usually indicates an error either
25225 in the symbol information or in @value{GDBN}'s handling of symbols.
25226 @findex SYMBOL_VAR_DOMAIN
25227 @findex gdb.SYMBOL_VAR_DOMAIN
25228 @item gdb.SYMBOL_VAR_DOMAIN
25229 This domain contains variables, function names, typedef names and enum
25231 @findex SYMBOL_STRUCT_DOMAIN
25232 @findex gdb.SYMBOL_STRUCT_DOMAIN
25233 @item gdb.SYMBOL_STRUCT_DOMAIN
25234 This domain holds struct, union and enum type names.
25235 @findex SYMBOL_LABEL_DOMAIN
25236 @findex gdb.SYMBOL_LABEL_DOMAIN
25237 @item gdb.SYMBOL_LABEL_DOMAIN
25238 This domain contains names of labels (for gotos).
25239 @findex SYMBOL_VARIABLES_DOMAIN
25240 @findex gdb.SYMBOL_VARIABLES_DOMAIN
25241 @item gdb.SYMBOL_VARIABLES_DOMAIN
25242 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
25243 contains everything minus functions and types.
25244 @findex SYMBOL_FUNCTIONS_DOMAIN
25245 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
25246 @item gdb.SYMBOL_FUNCTION_DOMAIN
25247 This domain contains all functions.
25248 @findex SYMBOL_TYPES_DOMAIN
25249 @findex gdb.SYMBOL_TYPES_DOMAIN
25250 @item gdb.SYMBOL_TYPES_DOMAIN
25251 This domain contains all types.
25254 The available address class categories in @code{gdb.Symbol} are represented
25255 as constants in the @code{gdb} module:
25258 @findex SYMBOL_LOC_UNDEF
25259 @findex gdb.SYMBOL_LOC_UNDEF
25260 @item gdb.SYMBOL_LOC_UNDEF
25261 If this is returned by address class, it indicates an error either in
25262 the symbol information or in @value{GDBN}'s handling of symbols.
25263 @findex SYMBOL_LOC_CONST
25264 @findex gdb.SYMBOL_LOC_CONST
25265 @item gdb.SYMBOL_LOC_CONST
25266 Value is constant int.
25267 @findex SYMBOL_LOC_STATIC
25268 @findex gdb.SYMBOL_LOC_STATIC
25269 @item gdb.SYMBOL_LOC_STATIC
25270 Value is at a fixed address.
25271 @findex SYMBOL_LOC_REGISTER
25272 @findex gdb.SYMBOL_LOC_REGISTER
25273 @item gdb.SYMBOL_LOC_REGISTER
25274 Value is in a register.
25275 @findex SYMBOL_LOC_ARG
25276 @findex gdb.SYMBOL_LOC_ARG
25277 @item gdb.SYMBOL_LOC_ARG
25278 Value is an argument. This value is at the offset stored within the
25279 symbol inside the frame's argument list.
25280 @findex SYMBOL_LOC_REF_ARG
25281 @findex gdb.SYMBOL_LOC_REF_ARG
25282 @item gdb.SYMBOL_LOC_REF_ARG
25283 Value address is stored in the frame's argument list. Just like
25284 @code{LOC_ARG} except that the value's address is stored at the
25285 offset, not the value itself.
25286 @findex SYMBOL_LOC_REGPARM_ADDR
25287 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
25288 @item gdb.SYMBOL_LOC_REGPARM_ADDR
25289 Value is a specified register. Just like @code{LOC_REGISTER} except
25290 the register holds the address of the argument instead of the argument
25292 @findex SYMBOL_LOC_LOCAL
25293 @findex gdb.SYMBOL_LOC_LOCAL
25294 @item gdb.SYMBOL_LOC_LOCAL
25295 Value is a local variable.
25296 @findex SYMBOL_LOC_TYPEDEF
25297 @findex gdb.SYMBOL_LOC_TYPEDEF
25298 @item gdb.SYMBOL_LOC_TYPEDEF
25299 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
25301 @findex SYMBOL_LOC_BLOCK
25302 @findex gdb.SYMBOL_LOC_BLOCK
25303 @item gdb.SYMBOL_LOC_BLOCK
25305 @findex SYMBOL_LOC_CONST_BYTES
25306 @findex gdb.SYMBOL_LOC_CONST_BYTES
25307 @item gdb.SYMBOL_LOC_CONST_BYTES
25308 Value is a byte-sequence.
25309 @findex SYMBOL_LOC_UNRESOLVED
25310 @findex gdb.SYMBOL_LOC_UNRESOLVED
25311 @item gdb.SYMBOL_LOC_UNRESOLVED
25312 Value is at a fixed address, but the address of the variable has to be
25313 determined from the minimal symbol table whenever the variable is
25315 @findex SYMBOL_LOC_OPTIMIZED_OUT
25316 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
25317 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
25318 The value does not actually exist in the program.
25319 @findex SYMBOL_LOC_COMPUTED
25320 @findex gdb.SYMBOL_LOC_COMPUTED
25321 @item gdb.SYMBOL_LOC_COMPUTED
25322 The value's address is a computed location.
25325 @node Symbol Tables In Python
25326 @subsubsection Symbol table representation in Python.
25328 @cindex symbol tables in python
25330 @tindex gdb.Symtab_and_line
25332 Access to symbol table data maintained by @value{GDBN} on the inferior
25333 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
25334 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
25335 from the @code{find_sal} method in @code{gdb.Frame} object.
25336 @xref{Frames In Python}.
25338 For more information on @value{GDBN}'s symbol table management, see
25339 @ref{Symbols, ,Examining the Symbol Table}, for more information.
25341 A @code{gdb.Symtab_and_line} object has the following attributes:
25344 @defvar Symtab_and_line.symtab
25345 The symbol table object (@code{gdb.Symtab}) for this frame.
25346 This attribute is not writable.
25349 @defvar Symtab_and_line.pc
25350 Indicates the start of the address range occupied by code for the
25351 current source line. This attribute is not writable.
25354 @defvar Symtab_and_line.last
25355 Indicates the end of the address range occupied by code for the current
25356 source line. This attribute is not writable.
25359 @defvar Symtab_and_line.line
25360 Indicates the current line number for this object. This
25361 attribute is not writable.
25365 A @code{gdb.Symtab_and_line} object has the following methods:
25368 @defun Symtab_and_line.is_valid ()
25369 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
25370 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
25371 invalid if the Symbol table and line object it refers to does not
25372 exist in @value{GDBN} any longer. All other
25373 @code{gdb.Symtab_and_line} methods will throw an exception if it is
25374 invalid at the time the method is called.
25378 A @code{gdb.Symtab} object has the following attributes:
25381 @defvar Symtab.filename
25382 The symbol table's source filename. This attribute is not writable.
25385 @defvar Symtab.objfile
25386 The symbol table's backing object file. @xref{Objfiles In Python}.
25387 This attribute is not writable.
25391 A @code{gdb.Symtab} object has the following methods:
25394 @defun Symtab.is_valid ()
25395 Returns @code{True} if the @code{gdb.Symtab} object is valid,
25396 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
25397 the symbol table it refers to does not exist in @value{GDBN} any
25398 longer. All other @code{gdb.Symtab} methods will throw an exception
25399 if it is invalid at the time the method is called.
25402 @defun Symtab.fullname ()
25403 Return the symbol table's source absolute file name.
25406 @defun Symtab.global_block ()
25407 Return the global block of the underlying symbol table.
25408 @xref{Blocks In Python}.
25411 @defun Symtab.static_block ()
25412 Return the static block of the underlying symbol table.
25413 @xref{Blocks In Python}.
25417 @node Breakpoints In Python
25418 @subsubsection Manipulating breakpoints using Python
25420 @cindex breakpoints in python
25421 @tindex gdb.Breakpoint
25423 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
25426 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
25427 Create a new breakpoint. @var{spec} is a string naming the
25428 location of the breakpoint, or an expression that defines a
25429 watchpoint. The contents can be any location recognized by the
25430 @code{break} command, or in the case of a watchpoint, by the @code{watch}
25431 command. The optional @var{type} denotes the breakpoint to create
25432 from the types defined later in this chapter. This argument can be
25433 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
25434 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
25435 allows the breakpoint to become invisible to the user. The breakpoint
25436 will neither be reported when created, nor will it be listed in the
25437 output from @code{info breakpoints} (but will be listed with the
25438 @code{maint info breakpoints} command). The optional @var{wp_class}
25439 argument defines the class of watchpoint to create, if @var{type} is
25440 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
25441 assumed to be a @code{gdb.WP_WRITE} class.
25444 @defun Breakpoint.stop (self)
25445 The @code{gdb.Breakpoint} class can be sub-classed and, in
25446 particular, you may choose to implement the @code{stop} method.
25447 If this method is defined as a sub-class of @code{gdb.Breakpoint},
25448 it will be called when the inferior reaches any location of a
25449 breakpoint which instantiates that sub-class. If the method returns
25450 @code{True}, the inferior will be stopped at the location of the
25451 breakpoint, otherwise the inferior will continue.
25453 If there are multiple breakpoints at the same location with a
25454 @code{stop} method, each one will be called regardless of the
25455 return status of the previous. This ensures that all @code{stop}
25456 methods have a chance to execute at that location. In this scenario
25457 if one of the methods returns @code{True} but the others return
25458 @code{False}, the inferior will still be stopped.
25460 You should not alter the execution state of the inferior (i.e.@:, step,
25461 next, etc.), alter the current frame context (i.e.@:, change the current
25462 active frame), or alter, add or delete any breakpoint. As a general
25463 rule, you should not alter any data within @value{GDBN} or the inferior
25466 Example @code{stop} implementation:
25469 class MyBreakpoint (gdb.Breakpoint):
25471 inf_val = gdb.parse_and_eval("foo")
25478 The available watchpoint types represented by constants are defined in the
25483 @findex gdb.WP_READ
25485 Read only watchpoint.
25488 @findex gdb.WP_WRITE
25490 Write only watchpoint.
25493 @findex gdb.WP_ACCESS
25494 @item gdb.WP_ACCESS
25495 Read/Write watchpoint.
25498 @defun Breakpoint.is_valid ()
25499 Return @code{True} if this @code{Breakpoint} object is valid,
25500 @code{False} otherwise. A @code{Breakpoint} object can become invalid
25501 if the user deletes the breakpoint. In this case, the object still
25502 exists, but the underlying breakpoint does not. In the cases of
25503 watchpoint scope, the watchpoint remains valid even if execution of the
25504 inferior leaves the scope of that watchpoint.
25507 @defun Breakpoint.delete
25508 Permanently deletes the @value{GDBN} breakpoint. This also
25509 invalidates the Python @code{Breakpoint} object. Any further access
25510 to this object's attributes or methods will raise an error.
25513 @defvar Breakpoint.enabled
25514 This attribute is @code{True} if the breakpoint is enabled, and
25515 @code{False} otherwise. This attribute is writable.
25518 @defvar Breakpoint.silent
25519 This attribute is @code{True} if the breakpoint is silent, and
25520 @code{False} otherwise. This attribute is writable.
25522 Note that a breakpoint can also be silent if it has commands and the
25523 first command is @code{silent}. This is not reported by the
25524 @code{silent} attribute.
25527 @defvar Breakpoint.thread
25528 If the breakpoint is thread-specific, this attribute holds the thread
25529 id. If the breakpoint is not thread-specific, this attribute is
25530 @code{None}. This attribute is writable.
25533 @defvar Breakpoint.task
25534 If the breakpoint is Ada task-specific, this attribute holds the Ada task
25535 id. If the breakpoint is not task-specific (or the underlying
25536 language is not Ada), this attribute is @code{None}. This attribute
25540 @defvar Breakpoint.ignore_count
25541 This attribute holds the ignore count for the breakpoint, an integer.
25542 This attribute is writable.
25545 @defvar Breakpoint.number
25546 This attribute holds the breakpoint's number --- the identifier used by
25547 the user to manipulate the breakpoint. This attribute is not writable.
25550 @defvar Breakpoint.type
25551 This attribute holds the breakpoint's type --- the identifier used to
25552 determine the actual breakpoint type or use-case. This attribute is not
25556 @defvar Breakpoint.visible
25557 This attribute tells whether the breakpoint is visible to the user
25558 when set, or when the @samp{info breakpoints} command is run. This
25559 attribute is not writable.
25562 The available types are represented by constants defined in the @code{gdb}
25566 @findex BP_BREAKPOINT
25567 @findex gdb.BP_BREAKPOINT
25568 @item gdb.BP_BREAKPOINT
25569 Normal code breakpoint.
25571 @findex BP_WATCHPOINT
25572 @findex gdb.BP_WATCHPOINT
25573 @item gdb.BP_WATCHPOINT
25574 Watchpoint breakpoint.
25576 @findex BP_HARDWARE_WATCHPOINT
25577 @findex gdb.BP_HARDWARE_WATCHPOINT
25578 @item gdb.BP_HARDWARE_WATCHPOINT
25579 Hardware assisted watchpoint.
25581 @findex BP_READ_WATCHPOINT
25582 @findex gdb.BP_READ_WATCHPOINT
25583 @item gdb.BP_READ_WATCHPOINT
25584 Hardware assisted read watchpoint.
25586 @findex BP_ACCESS_WATCHPOINT
25587 @findex gdb.BP_ACCESS_WATCHPOINT
25588 @item gdb.BP_ACCESS_WATCHPOINT
25589 Hardware assisted access watchpoint.
25592 @defvar Breakpoint.hit_count
25593 This attribute holds the hit count for the breakpoint, an integer.
25594 This attribute is writable, but currently it can only be set to zero.
25597 @defvar Breakpoint.location
25598 This attribute holds the location of the breakpoint, as specified by
25599 the user. It is a string. If the breakpoint does not have a location
25600 (that is, it is a watchpoint) the attribute's value is @code{None}. This
25601 attribute is not writable.
25604 @defvar Breakpoint.expression
25605 This attribute holds a breakpoint expression, as specified by
25606 the user. It is a string. If the breakpoint does not have an
25607 expression (the breakpoint is not a watchpoint) the attribute's value
25608 is @code{None}. This attribute is not writable.
25611 @defvar Breakpoint.condition
25612 This attribute holds the condition of the breakpoint, as specified by
25613 the user. It is a string. If there is no condition, this attribute's
25614 value is @code{None}. This attribute is writable.
25617 @defvar Breakpoint.commands
25618 This attribute holds the commands attached to the breakpoint. If
25619 there are commands, this attribute's value is a string holding all the
25620 commands, separated by newlines. If there are no commands, this
25621 attribute is @code{None}. This attribute is not writable.
25624 @node Finish Breakpoints in Python
25625 @subsubsection Finish Breakpoints
25627 @cindex python finish breakpoints
25628 @tindex gdb.FinishBreakpoint
25630 A finish breakpoint is a temporary breakpoint set at the return address of
25631 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
25632 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
25633 and deleted when the execution will run out of the breakpoint scope (i.e.@:
25634 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
25635 Finish breakpoints are thread specific and must be create with the right
25638 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
25639 Create a finish breakpoint at the return address of the @code{gdb.Frame}
25640 object @var{frame}. If @var{frame} is not provided, this defaults to the
25641 newest frame. The optional @var{internal} argument allows the breakpoint to
25642 become invisible to the user. @xref{Breakpoints In Python}, for further
25643 details about this argument.
25646 @defun FinishBreakpoint.out_of_scope (self)
25647 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
25648 @code{return} command, @dots{}), a function may not properly terminate, and
25649 thus never hit the finish breakpoint. When @value{GDBN} notices such a
25650 situation, the @code{out_of_scope} callback will be triggered.
25652 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
25656 class MyFinishBreakpoint (gdb.FinishBreakpoint)
25658 print "normal finish"
25661 def out_of_scope ():
25662 print "abnormal finish"
25666 @defvar FinishBreakpoint.return_value
25667 When @value{GDBN} is stopped at a finish breakpoint and the frame
25668 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
25669 attribute will contain a @code{gdb.Value} object corresponding to the return
25670 value of the function. The value will be @code{None} if the function return
25671 type is @code{void} or if the return value was not computable. This attribute
25675 @node Lazy Strings In Python
25676 @subsubsection Python representation of lazy strings.
25678 @cindex lazy strings in python
25679 @tindex gdb.LazyString
25681 A @dfn{lazy string} is a string whose contents is not retrieved or
25682 encoded until it is needed.
25684 A @code{gdb.LazyString} is represented in @value{GDBN} as an
25685 @code{address} that points to a region of memory, an @code{encoding}
25686 that will be used to encode that region of memory, and a @code{length}
25687 to delimit the region of memory that represents the string. The
25688 difference between a @code{gdb.LazyString} and a string wrapped within
25689 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
25690 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
25691 retrieved and encoded during printing, while a @code{gdb.Value}
25692 wrapping a string is immediately retrieved and encoded on creation.
25694 A @code{gdb.LazyString} object has the following functions:
25696 @defun LazyString.value ()
25697 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
25698 will point to the string in memory, but will lose all the delayed
25699 retrieval, encoding and handling that @value{GDBN} applies to a
25700 @code{gdb.LazyString}.
25703 @defvar LazyString.address
25704 This attribute holds the address of the string. This attribute is not
25708 @defvar LazyString.length
25709 This attribute holds the length of the string in characters. If the
25710 length is -1, then the string will be fetched and encoded up to the
25711 first null of appropriate width. This attribute is not writable.
25714 @defvar LazyString.encoding
25715 This attribute holds the encoding that will be applied to the string
25716 when the string is printed by @value{GDBN}. If the encoding is not
25717 set, or contains an empty string, then @value{GDBN} will select the
25718 most appropriate encoding when the string is printed. This attribute
25722 @defvar LazyString.type
25723 This attribute holds the type that is represented by the lazy string's
25724 type. For a lazy string this will always be a pointer type. To
25725 resolve this to the lazy string's character type, use the type's
25726 @code{target} method. @xref{Types In Python}. This attribute is not
25730 @node Python Auto-loading
25731 @subsection Python Auto-loading
25732 @cindex Python auto-loading
25734 When a new object file is read (for example, due to the @code{file}
25735 command, or because the inferior has loaded a shared library),
25736 @value{GDBN} will look for Python support scripts in several ways:
25737 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
25738 and @code{.debug_gdb_scripts} section
25739 (@pxref{dotdebug_gdb_scripts section}).
25741 The auto-loading feature is useful for supplying application-specific
25742 debugging commands and scripts.
25744 Auto-loading can be enabled or disabled,
25745 and the list of auto-loaded scripts can be printed.
25748 @anchor{set auto-load python-scripts}
25749 @kindex set auto-load python-scripts
25750 @item set auto-load python-scripts [on|off]
25751 Enable or disable the auto-loading of Python scripts.
25753 @anchor{show auto-load python-scripts}
25754 @kindex show auto-load python-scripts
25755 @item show auto-load python-scripts
25756 Show whether auto-loading of Python scripts is enabled or disabled.
25758 @anchor{info auto-load python-scripts}
25759 @kindex info auto-load python-scripts
25760 @cindex print list of auto-loaded Python scripts
25761 @item info auto-load python-scripts [@var{regexp}]
25762 Print the list of all Python scripts that @value{GDBN} auto-loaded.
25764 Also printed is the list of Python scripts that were mentioned in
25765 the @code{.debug_gdb_scripts} section and were not found
25766 (@pxref{dotdebug_gdb_scripts section}).
25767 This is useful because their names are not printed when @value{GDBN}
25768 tries to load them and fails. There may be many of them, and printing
25769 an error message for each one is problematic.
25771 If @var{regexp} is supplied only Python scripts with matching names are printed.
25776 (gdb) info auto-load python-scripts
25778 Yes py-section-script.py
25779 full name: /tmp/py-section-script.py
25780 No my-foo-pretty-printers.py
25784 When reading an auto-loaded file, @value{GDBN} sets the
25785 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
25786 function (@pxref{Objfiles In Python}). This can be useful for
25787 registering objfile-specific pretty-printers.
25790 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
25791 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
25792 * Which flavor to choose?::
25795 @node objfile-gdb.py file
25796 @subsubsection The @file{@var{objfile}-gdb.py} file
25797 @cindex @file{@var{objfile}-gdb.py}
25799 When a new object file is read, @value{GDBN} looks for
25800 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
25801 where @var{objfile} is the object file's real name, formed by ensuring
25802 that the file name is absolute, following all symlinks, and resolving
25803 @code{.} and @code{..} components. If this file exists and is
25804 readable, @value{GDBN} will evaluate it as a Python script.
25806 If this file does not exist, then @value{GDBN} will look for
25807 @var{script-name} file in all of the directories as specified below.
25809 Note that loading of this script file also requires accordingly configured
25810 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25812 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
25813 scripts normally according to its @file{.exe} filename. But if no scripts are
25814 found @value{GDBN} also tries script filenames matching the object file without
25815 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
25816 is attempted on any platform. This makes the script filenames compatible
25817 between Unix and MS-Windows hosts.
25820 @anchor{set auto-load scripts-directory}
25821 @kindex set auto-load scripts-directory
25822 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
25823 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
25824 may be delimited by the host platform path separator in use
25825 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
25827 Each entry here needs to be covered also by the security setting
25828 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
25830 @anchor{with-auto-load-dir}
25831 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
25832 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
25833 configuration option @option{--with-auto-load-dir}.
25835 Any reference to @file{$debugdir} will get replaced by
25836 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
25837 reference to @file{$datadir} will get replaced by @var{data-directory} which is
25838 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
25839 @file{$datadir} must be placed as a directory component --- either alone or
25840 delimited by @file{/} or @file{\} directory separators, depending on the host
25843 The list of directories uses path separator (@samp{:} on GNU and Unix
25844 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25845 to the @env{PATH} environment variable.
25847 @anchor{show auto-load scripts-directory}
25848 @kindex show auto-load scripts-directory
25849 @item show auto-load scripts-directory
25850 Show @value{GDBN} auto-loaded scripts location.
25853 @value{GDBN} does not track which files it has already auto-loaded this way.
25854 @value{GDBN} will load the associated script every time the corresponding
25855 @var{objfile} is opened.
25856 So your @file{-gdb.py} file should be careful to avoid errors if it
25857 is evaluated more than once.
25859 @node dotdebug_gdb_scripts section
25860 @subsubsection The @code{.debug_gdb_scripts} section
25861 @cindex @code{.debug_gdb_scripts} section
25863 For systems using file formats like ELF and COFF,
25864 when @value{GDBN} loads a new object file
25865 it will look for a special section named @samp{.debug_gdb_scripts}.
25866 If this section exists, its contents is a list of names of scripts to load.
25868 @value{GDBN} will look for each specified script file first in the
25869 current directory and then along the source search path
25870 (@pxref{Source Path, ,Specifying Source Directories}),
25871 except that @file{$cdir} is not searched, since the compilation
25872 directory is not relevant to scripts.
25874 Entries can be placed in section @code{.debug_gdb_scripts} with,
25875 for example, this GCC macro:
25878 /* Note: The "MS" section flags are to remove duplicates. */
25879 #define DEFINE_GDB_SCRIPT(script_name) \
25881 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
25883 .asciz \"" script_name "\"\n\
25889 Then one can reference the macro in a header or source file like this:
25892 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
25895 The script name may include directories if desired.
25897 Note that loading of this script file also requires accordingly configured
25898 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25900 If the macro is put in a header, any application or library
25901 using this header will get a reference to the specified script.
25903 @node Which flavor to choose?
25904 @subsubsection Which flavor to choose?
25906 Given the multiple ways of auto-loading Python scripts, it might not always
25907 be clear which one to choose. This section provides some guidance.
25909 Benefits of the @file{-gdb.py} way:
25913 Can be used with file formats that don't support multiple sections.
25916 Ease of finding scripts for public libraries.
25918 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
25919 in the source search path.
25920 For publicly installed libraries, e.g., @file{libstdc++}, there typically
25921 isn't a source directory in which to find the script.
25924 Doesn't require source code additions.
25927 Benefits of the @code{.debug_gdb_scripts} way:
25931 Works with static linking.
25933 Scripts for libraries done the @file{-gdb.py} way require an objfile to
25934 trigger their loading. When an application is statically linked the only
25935 objfile available is the executable, and it is cumbersome to attach all the
25936 scripts from all the input libraries to the executable's @file{-gdb.py} script.
25939 Works with classes that are entirely inlined.
25941 Some classes can be entirely inlined, and thus there may not be an associated
25942 shared library to attach a @file{-gdb.py} script to.
25945 Scripts needn't be copied out of the source tree.
25947 In some circumstances, apps can be built out of large collections of internal
25948 libraries, and the build infrastructure necessary to install the
25949 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
25950 cumbersome. It may be easier to specify the scripts in the
25951 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
25952 top of the source tree to the source search path.
25955 @node Python modules
25956 @subsection Python modules
25957 @cindex python modules
25959 @value{GDBN} comes with several modules to assist writing Python code.
25962 * gdb.printing:: Building and registering pretty-printers.
25963 * gdb.types:: Utilities for working with types.
25964 * gdb.prompt:: Utilities for prompt value substitution.
25968 @subsubsection gdb.printing
25969 @cindex gdb.printing
25971 This module provides a collection of utilities for working with
25975 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
25976 This class specifies the API that makes @samp{info pretty-printer},
25977 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
25978 Pretty-printers should generally inherit from this class.
25980 @item SubPrettyPrinter (@var{name})
25981 For printers that handle multiple types, this class specifies the
25982 corresponding API for the subprinters.
25984 @item RegexpCollectionPrettyPrinter (@var{name})
25985 Utility class for handling multiple printers, all recognized via
25986 regular expressions.
25987 @xref{Writing a Pretty-Printer}, for an example.
25989 @item FlagEnumerationPrinter (@var{name})
25990 A pretty-printer which handles printing of @code{enum} values. Unlike
25991 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
25992 work properly when there is some overlap between the enumeration
25993 constants. @var{name} is the name of the printer and also the name of
25994 the @code{enum} type to look up.
25996 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
25997 Register @var{printer} with the pretty-printer list of @var{obj}.
25998 If @var{replace} is @code{True} then any existing copy of the printer
25999 is replaced. Otherwise a @code{RuntimeError} exception is raised
26000 if a printer with the same name already exists.
26004 @subsubsection gdb.types
26007 This module provides a collection of utilities for working with
26008 @code{gdb.Types} objects.
26011 @item get_basic_type (@var{type})
26012 Return @var{type} with const and volatile qualifiers stripped,
26013 and with typedefs and C@t{++} references converted to the underlying type.
26018 typedef const int const_int;
26020 const_int& foo_ref (foo);
26021 int main () @{ return 0; @}
26028 (gdb) python import gdb.types
26029 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
26030 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
26034 @item has_field (@var{type}, @var{field})
26035 Return @code{True} if @var{type}, assumed to be a type with fields
26036 (e.g., a structure or union), has field @var{field}.
26038 @item make_enum_dict (@var{enum_type})
26039 Return a Python @code{dictionary} type produced from @var{enum_type}.
26041 @item deep_items (@var{type})
26042 Returns a Python iterator similar to the standard
26043 @code{gdb.Type.iteritems} method, except that the iterator returned
26044 by @code{deep_items} will recursively traverse anonymous struct or
26045 union fields. For example:
26059 Then in @value{GDBN}:
26061 (@value{GDBP}) python import gdb.types
26062 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
26063 (@value{GDBP}) python print struct_a.keys ()
26065 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
26066 @{['a', 'b0', 'b1']@}
26072 @subsubsection gdb.prompt
26075 This module provides a method for prompt value-substitution.
26078 @item substitute_prompt (@var{string})
26079 Return @var{string} with escape sequences substituted by values. Some
26080 escape sequences take arguments. You can specify arguments inside
26081 ``@{@}'' immediately following the escape sequence.
26083 The escape sequences you can pass to this function are:
26087 Substitute a backslash.
26089 Substitute an ESC character.
26091 Substitute the selected frame; an argument names a frame parameter.
26093 Substitute a newline.
26095 Substitute a parameter's value; the argument names the parameter.
26097 Substitute a carriage return.
26099 Substitute the selected thread; an argument names a thread parameter.
26101 Substitute the version of GDB.
26103 Substitute the current working directory.
26105 Begin a sequence of non-printing characters. These sequences are
26106 typically used with the ESC character, and are not counted in the string
26107 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
26108 blue-colored ``(gdb)'' prompt where the length is five.
26110 End a sequence of non-printing characters.
26116 substitute_prompt (``frame: \f,
26117 print arguments: \p@{print frame-arguments@}'')
26120 @exdent will return the string:
26123 "frame: main, print arguments: scalars"
26128 @section Creating new spellings of existing commands
26129 @cindex aliases for commands
26131 It is often useful to define alternate spellings of existing commands.
26132 For example, if a new @value{GDBN} command defined in Python has
26133 a long name to type, it is handy to have an abbreviated version of it
26134 that involves less typing.
26136 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26137 of the @samp{step} command even though it is otherwise an ambiguous
26138 abbreviation of other commands like @samp{set} and @samp{show}.
26140 Aliases are also used to provide shortened or more common versions
26141 of multi-word commands. For example, @value{GDBN} provides the
26142 @samp{tty} alias of the @samp{set inferior-tty} command.
26144 You can define a new alias with the @samp{alias} command.
26149 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26153 @var{ALIAS} specifies the name of the new alias.
26154 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26157 @var{COMMAND} specifies the name of an existing command
26158 that is being aliased.
26160 The @samp{-a} option specifies that the new alias is an abbreviation
26161 of the command. Abbreviations are not shown in command
26162 lists displayed by the @samp{help} command.
26164 The @samp{--} option specifies the end of options,
26165 and is useful when @var{ALIAS} begins with a dash.
26167 Here is a simple example showing how to make an abbreviation
26168 of a command so that there is less to type.
26169 Suppose you were tired of typing @samp{disas}, the current
26170 shortest unambiguous abbreviation of the @samp{disassemble} command
26171 and you wanted an even shorter version named @samp{di}.
26172 The following will accomplish this.
26175 (gdb) alias -a di = disas
26178 Note that aliases are different from user-defined commands.
26179 With a user-defined command, you also need to write documentation
26180 for it with the @samp{document} command.
26181 An alias automatically picks up the documentation of the existing command.
26183 Here is an example where we make @samp{elms} an abbreviation of
26184 @samp{elements} in the @samp{set print elements} command.
26185 This is to show that you can make an abbreviation of any part
26189 (gdb) alias -a set print elms = set print elements
26190 (gdb) alias -a show print elms = show print elements
26191 (gdb) set p elms 20
26193 Limit on string chars or array elements to print is 200.
26196 Note that if you are defining an alias of a @samp{set} command,
26197 and you want to have an alias for the corresponding @samp{show}
26198 command, then you need to define the latter separately.
26200 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26201 @var{ALIAS}, just as they are normally.
26204 (gdb) alias -a set pr elms = set p ele
26207 Finally, here is an example showing the creation of a one word
26208 alias for a more complex command.
26209 This creates alias @samp{spe} of the command @samp{set print elements}.
26212 (gdb) alias spe = set print elements
26217 @chapter Command Interpreters
26218 @cindex command interpreters
26220 @value{GDBN} supports multiple command interpreters, and some command
26221 infrastructure to allow users or user interface writers to switch
26222 between interpreters or run commands in other interpreters.
26224 @value{GDBN} currently supports two command interpreters, the console
26225 interpreter (sometimes called the command-line interpreter or @sc{cli})
26226 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26227 describes both of these interfaces in great detail.
26229 By default, @value{GDBN} will start with the console interpreter.
26230 However, the user may choose to start @value{GDBN} with another
26231 interpreter by specifying the @option{-i} or @option{--interpreter}
26232 startup options. Defined interpreters include:
26236 @cindex console interpreter
26237 The traditional console or command-line interpreter. This is the most often
26238 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26239 @value{GDBN} will use this interpreter.
26242 @cindex mi interpreter
26243 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
26244 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26245 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26249 @cindex mi2 interpreter
26250 The current @sc{gdb/mi} interface.
26253 @cindex mi1 interpreter
26254 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
26258 @cindex invoke another interpreter
26259 The interpreter being used by @value{GDBN} may not be dynamically
26260 switched at runtime. Although possible, this could lead to a very
26261 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
26262 enters the command "interpreter-set console" in a console view,
26263 @value{GDBN} would switch to using the console interpreter, rendering
26264 the IDE inoperable!
26266 @kindex interpreter-exec
26267 Although you may only choose a single interpreter at startup, you may execute
26268 commands in any interpreter from the current interpreter using the appropriate
26269 command. If you are running the console interpreter, simply use the
26270 @code{interpreter-exec} command:
26273 interpreter-exec mi "-data-list-register-names"
26276 @sc{gdb/mi} has a similar command, although it is only available in versions of
26277 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26280 @chapter @value{GDBN} Text User Interface
26282 @cindex Text User Interface
26285 * TUI Overview:: TUI overview
26286 * TUI Keys:: TUI key bindings
26287 * TUI Single Key Mode:: TUI single key mode
26288 * TUI Commands:: TUI-specific commands
26289 * TUI Configuration:: TUI configuration variables
26292 The @value{GDBN} Text User Interface (TUI) is a terminal
26293 interface which uses the @code{curses} library to show the source
26294 file, the assembly output, the program registers and @value{GDBN}
26295 commands in separate text windows. The TUI mode is supported only
26296 on platforms where a suitable version of the @code{curses} library
26299 The TUI mode is enabled by default when you invoke @value{GDBN} as
26300 @samp{@value{GDBP} -tui}.
26301 You can also switch in and out of TUI mode while @value{GDBN} runs by
26302 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
26303 @xref{TUI Keys, ,TUI Key Bindings}.
26306 @section TUI Overview
26308 In TUI mode, @value{GDBN} can display several text windows:
26312 This window is the @value{GDBN} command window with the @value{GDBN}
26313 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26314 managed using readline.
26317 The source window shows the source file of the program. The current
26318 line and active breakpoints are displayed in this window.
26321 The assembly window shows the disassembly output of the program.
26324 This window shows the processor registers. Registers are highlighted
26325 when their values change.
26328 The source and assembly windows show the current program position
26329 by highlighting the current line and marking it with a @samp{>} marker.
26330 Breakpoints are indicated with two markers. The first marker
26331 indicates the breakpoint type:
26335 Breakpoint which was hit at least once.
26338 Breakpoint which was never hit.
26341 Hardware breakpoint which was hit at least once.
26344 Hardware breakpoint which was never hit.
26347 The second marker indicates whether the breakpoint is enabled or not:
26351 Breakpoint is enabled.
26354 Breakpoint is disabled.
26357 The source, assembly and register windows are updated when the current
26358 thread changes, when the frame changes, or when the program counter
26361 These windows are not all visible at the same time. The command
26362 window is always visible. The others can be arranged in several
26373 source and assembly,
26376 source and registers, or
26379 assembly and registers.
26382 A status line above the command window shows the following information:
26386 Indicates the current @value{GDBN} target.
26387 (@pxref{Targets, ,Specifying a Debugging Target}).
26390 Gives the current process or thread number.
26391 When no process is being debugged, this field is set to @code{No process}.
26394 Gives the current function name for the selected frame.
26395 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26396 When there is no symbol corresponding to the current program counter,
26397 the string @code{??} is displayed.
26400 Indicates the current line number for the selected frame.
26401 When the current line number is not known, the string @code{??} is displayed.
26404 Indicates the current program counter address.
26408 @section TUI Key Bindings
26409 @cindex TUI key bindings
26411 The TUI installs several key bindings in the readline keymaps
26412 @ifset SYSTEM_READLINE
26413 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26415 @ifclear SYSTEM_READLINE
26416 (@pxref{Command Line Editing}).
26418 The following key bindings are installed for both TUI mode and the
26419 @value{GDBN} standard mode.
26428 Enter or leave the TUI mode. When leaving the TUI mode,
26429 the curses window management stops and @value{GDBN} operates using
26430 its standard mode, writing on the terminal directly. When reentering
26431 the TUI mode, control is given back to the curses windows.
26432 The screen is then refreshed.
26436 Use a TUI layout with only one window. The layout will
26437 either be @samp{source} or @samp{assembly}. When the TUI mode
26438 is not active, it will switch to the TUI mode.
26440 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26444 Use a TUI layout with at least two windows. When the current
26445 layout already has two windows, the next layout with two windows is used.
26446 When a new layout is chosen, one window will always be common to the
26447 previous layout and the new one.
26449 Think of it as the Emacs @kbd{C-x 2} binding.
26453 Change the active window. The TUI associates several key bindings
26454 (like scrolling and arrow keys) with the active window. This command
26455 gives the focus to the next TUI window.
26457 Think of it as the Emacs @kbd{C-x o} binding.
26461 Switch in and out of the TUI SingleKey mode that binds single
26462 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26465 The following key bindings only work in the TUI mode:
26470 Scroll the active window one page up.
26474 Scroll the active window one page down.
26478 Scroll the active window one line up.
26482 Scroll the active window one line down.
26486 Scroll the active window one column left.
26490 Scroll the active window one column right.
26494 Refresh the screen.
26497 Because the arrow keys scroll the active window in the TUI mode, they
26498 are not available for their normal use by readline unless the command
26499 window has the focus. When another window is active, you must use
26500 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26501 and @kbd{C-f} to control the command window.
26503 @node TUI Single Key Mode
26504 @section TUI Single Key Mode
26505 @cindex TUI single key mode
26507 The TUI also provides a @dfn{SingleKey} mode, which binds several
26508 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26509 switch into this mode, where the following key bindings are used:
26512 @kindex c @r{(SingleKey TUI key)}
26516 @kindex d @r{(SingleKey TUI key)}
26520 @kindex f @r{(SingleKey TUI key)}
26524 @kindex n @r{(SingleKey TUI key)}
26528 @kindex q @r{(SingleKey TUI key)}
26530 exit the SingleKey mode.
26532 @kindex r @r{(SingleKey TUI key)}
26536 @kindex s @r{(SingleKey TUI key)}
26540 @kindex u @r{(SingleKey TUI key)}
26544 @kindex v @r{(SingleKey TUI key)}
26548 @kindex w @r{(SingleKey TUI key)}
26553 Other keys temporarily switch to the @value{GDBN} command prompt.
26554 The key that was pressed is inserted in the editing buffer so that
26555 it is possible to type most @value{GDBN} commands without interaction
26556 with the TUI SingleKey mode. Once the command is entered the TUI
26557 SingleKey mode is restored. The only way to permanently leave
26558 this mode is by typing @kbd{q} or @kbd{C-x s}.
26562 @section TUI-specific Commands
26563 @cindex TUI commands
26565 The TUI has specific commands to control the text windows.
26566 These commands are always available, even when @value{GDBN} is not in
26567 the TUI mode. When @value{GDBN} is in the standard mode, most
26568 of these commands will automatically switch to the TUI mode.
26570 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26571 terminal, or @value{GDBN} has been started with the machine interface
26572 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26573 these commands will fail with an error, because it would not be
26574 possible or desirable to enable curses window management.
26579 List and give the size of all displayed windows.
26583 Display the next layout.
26586 Display the previous layout.
26589 Display the source window only.
26592 Display the assembly window only.
26595 Display the source and assembly window.
26598 Display the register window together with the source or assembly window.
26602 Make the next window active for scrolling.
26605 Make the previous window active for scrolling.
26608 Make the source window active for scrolling.
26611 Make the assembly window active for scrolling.
26614 Make the register window active for scrolling.
26617 Make the command window active for scrolling.
26621 Refresh the screen. This is similar to typing @kbd{C-L}.
26623 @item tui reg float
26625 Show the floating point registers in the register window.
26627 @item tui reg general
26628 Show the general registers in the register window.
26631 Show the next register group. The list of register groups as well as
26632 their order is target specific. The predefined register groups are the
26633 following: @code{general}, @code{float}, @code{system}, @code{vector},
26634 @code{all}, @code{save}, @code{restore}.
26636 @item tui reg system
26637 Show the system registers in the register window.
26641 Update the source window and the current execution point.
26643 @item winheight @var{name} +@var{count}
26644 @itemx winheight @var{name} -@var{count}
26646 Change the height of the window @var{name} by @var{count}
26647 lines. Positive counts increase the height, while negative counts
26650 @item tabset @var{nchars}
26652 Set the width of tab stops to be @var{nchars} characters.
26655 @node TUI Configuration
26656 @section TUI Configuration Variables
26657 @cindex TUI configuration variables
26659 Several configuration variables control the appearance of TUI windows.
26662 @item set tui border-kind @var{kind}
26663 @kindex set tui border-kind
26664 Select the border appearance for the source, assembly and register windows.
26665 The possible values are the following:
26668 Use a space character to draw the border.
26671 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
26674 Use the Alternate Character Set to draw the border. The border is
26675 drawn using character line graphics if the terminal supports them.
26678 @item set tui border-mode @var{mode}
26679 @kindex set tui border-mode
26680 @itemx set tui active-border-mode @var{mode}
26681 @kindex set tui active-border-mode
26682 Select the display attributes for the borders of the inactive windows
26683 or the active window. The @var{mode} can be one of the following:
26686 Use normal attributes to display the border.
26692 Use reverse video mode.
26695 Use half bright mode.
26697 @item half-standout
26698 Use half bright and standout mode.
26701 Use extra bright or bold mode.
26703 @item bold-standout
26704 Use extra bright or bold and standout mode.
26709 @chapter Using @value{GDBN} under @sc{gnu} Emacs
26712 @cindex @sc{gnu} Emacs
26713 A special interface allows you to use @sc{gnu} Emacs to view (and
26714 edit) the source files for the program you are debugging with
26717 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
26718 executable file you want to debug as an argument. This command starts
26719 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
26720 created Emacs buffer.
26721 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
26723 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
26728 All ``terminal'' input and output goes through an Emacs buffer, called
26731 This applies both to @value{GDBN} commands and their output, and to the input
26732 and output done by the program you are debugging.
26734 This is useful because it means that you can copy the text of previous
26735 commands and input them again; you can even use parts of the output
26738 All the facilities of Emacs' Shell mode are available for interacting
26739 with your program. In particular, you can send signals the usual
26740 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
26744 @value{GDBN} displays source code through Emacs.
26746 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
26747 source file for that frame and puts an arrow (@samp{=>}) at the
26748 left margin of the current line. Emacs uses a separate buffer for
26749 source display, and splits the screen to show both your @value{GDBN} session
26752 Explicit @value{GDBN} @code{list} or search commands still produce output as
26753 usual, but you probably have no reason to use them from Emacs.
26756 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
26757 a graphical mode, enabled by default, which provides further buffers
26758 that can control the execution and describe the state of your program.
26759 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
26761 If you specify an absolute file name when prompted for the @kbd{M-x
26762 gdb} argument, then Emacs sets your current working directory to where
26763 your program resides. If you only specify the file name, then Emacs
26764 sets your current working directory to the directory associated
26765 with the previous buffer. In this case, @value{GDBN} may find your
26766 program by searching your environment's @code{PATH} variable, but on
26767 some operating systems it might not find the source. So, although the
26768 @value{GDBN} input and output session proceeds normally, the auxiliary
26769 buffer does not display the current source and line of execution.
26771 The initial working directory of @value{GDBN} is printed on the top
26772 line of the GUD buffer and this serves as a default for the commands
26773 that specify files for @value{GDBN} to operate on. @xref{Files,
26774 ,Commands to Specify Files}.
26776 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
26777 need to call @value{GDBN} by a different name (for example, if you
26778 keep several configurations around, with different names) you can
26779 customize the Emacs variable @code{gud-gdb-command-name} to run the
26782 In the GUD buffer, you can use these special Emacs commands in
26783 addition to the standard Shell mode commands:
26787 Describe the features of Emacs' GUD Mode.
26790 Execute to another source line, like the @value{GDBN} @code{step} command; also
26791 update the display window to show the current file and location.
26794 Execute to next source line in this function, skipping all function
26795 calls, like the @value{GDBN} @code{next} command. Then update the display window
26796 to show the current file and location.
26799 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
26800 display window accordingly.
26803 Execute until exit from the selected stack frame, like the @value{GDBN}
26804 @code{finish} command.
26807 Continue execution of your program, like the @value{GDBN} @code{continue}
26811 Go up the number of frames indicated by the numeric argument
26812 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
26813 like the @value{GDBN} @code{up} command.
26816 Go down the number of frames indicated by the numeric argument, like the
26817 @value{GDBN} @code{down} command.
26820 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
26821 tells @value{GDBN} to set a breakpoint on the source line point is on.
26823 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
26824 separate frame which shows a backtrace when the GUD buffer is current.
26825 Move point to any frame in the stack and type @key{RET} to make it
26826 become the current frame and display the associated source in the
26827 source buffer. Alternatively, click @kbd{Mouse-2} to make the
26828 selected frame become the current one. In graphical mode, the
26829 speedbar displays watch expressions.
26831 If you accidentally delete the source-display buffer, an easy way to get
26832 it back is to type the command @code{f} in the @value{GDBN} buffer, to
26833 request a frame display; when you run under Emacs, this recreates
26834 the source buffer if necessary to show you the context of the current
26837 The source files displayed in Emacs are in ordinary Emacs buffers
26838 which are visiting the source files in the usual way. You can edit
26839 the files with these buffers if you wish; but keep in mind that @value{GDBN}
26840 communicates with Emacs in terms of line numbers. If you add or
26841 delete lines from the text, the line numbers that @value{GDBN} knows cease
26842 to correspond properly with the code.
26844 A more detailed description of Emacs' interaction with @value{GDBN} is
26845 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
26848 @c The following dropped because Epoch is nonstandard. Reactivate
26849 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
26851 @kindex Emacs Epoch environment
26855 Version 18 of @sc{gnu} Emacs has a built-in window system
26856 called the @code{epoch}
26857 environment. Users of this environment can use a new command,
26858 @code{inspect} which performs identically to @code{print} except that
26859 each value is printed in its own window.
26864 @chapter The @sc{gdb/mi} Interface
26866 @unnumberedsec Function and Purpose
26868 @cindex @sc{gdb/mi}, its purpose
26869 @sc{gdb/mi} is a line based machine oriented text interface to
26870 @value{GDBN} and is activated by specifying using the
26871 @option{--interpreter} command line option (@pxref{Mode Options}). It
26872 is specifically intended to support the development of systems which
26873 use the debugger as just one small component of a larger system.
26875 This chapter is a specification of the @sc{gdb/mi} interface. It is written
26876 in the form of a reference manual.
26878 Note that @sc{gdb/mi} is still under construction, so some of the
26879 features described below are incomplete and subject to change
26880 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
26882 @unnumberedsec Notation and Terminology
26884 @cindex notational conventions, for @sc{gdb/mi}
26885 This chapter uses the following notation:
26889 @code{|} separates two alternatives.
26892 @code{[ @var{something} ]} indicates that @var{something} is optional:
26893 it may or may not be given.
26896 @code{( @var{group} )*} means that @var{group} inside the parentheses
26897 may repeat zero or more times.
26900 @code{( @var{group} )+} means that @var{group} inside the parentheses
26901 may repeat one or more times.
26904 @code{"@var{string}"} means a literal @var{string}.
26908 @heading Dependencies
26912 * GDB/MI General Design::
26913 * GDB/MI Command Syntax::
26914 * GDB/MI Compatibility with CLI::
26915 * GDB/MI Development and Front Ends::
26916 * GDB/MI Output Records::
26917 * GDB/MI Simple Examples::
26918 * GDB/MI Command Description Format::
26919 * GDB/MI Breakpoint Commands::
26920 * GDB/MI Program Context::
26921 * GDB/MI Thread Commands::
26922 * GDB/MI Ada Tasking Commands::
26923 * GDB/MI Program Execution::
26924 * GDB/MI Stack Manipulation::
26925 * GDB/MI Variable Objects::
26926 * GDB/MI Data Manipulation::
26927 * GDB/MI Tracepoint Commands::
26928 * GDB/MI Symbol Query::
26929 * GDB/MI File Commands::
26931 * GDB/MI Kod Commands::
26932 * GDB/MI Memory Overlay Commands::
26933 * GDB/MI Signal Handling Commands::
26935 * GDB/MI Target Manipulation::
26936 * GDB/MI File Transfer Commands::
26937 * GDB/MI Miscellaneous Commands::
26940 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26941 @node GDB/MI General Design
26942 @section @sc{gdb/mi} General Design
26943 @cindex GDB/MI General Design
26945 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
26946 parts---commands sent to @value{GDBN}, responses to those commands
26947 and notifications. Each command results in exactly one response,
26948 indicating either successful completion of the command, or an error.
26949 For the commands that do not resume the target, the response contains the
26950 requested information. For the commands that resume the target, the
26951 response only indicates whether the target was successfully resumed.
26952 Notifications is the mechanism for reporting changes in the state of the
26953 target, or in @value{GDBN} state, that cannot conveniently be associated with
26954 a command and reported as part of that command response.
26956 The important examples of notifications are:
26960 Exec notifications. These are used to report changes in
26961 target state---when a target is resumed, or stopped. It would not
26962 be feasible to include this information in response of resuming
26963 commands, because one resume commands can result in multiple events in
26964 different threads. Also, quite some time may pass before any event
26965 happens in the target, while a frontend needs to know whether the resuming
26966 command itself was successfully executed.
26969 Console output, and status notifications. Console output
26970 notifications are used to report output of CLI commands, as well as
26971 diagnostics for other commands. Status notifications are used to
26972 report the progress of a long-running operation. Naturally, including
26973 this information in command response would mean no output is produced
26974 until the command is finished, which is undesirable.
26977 General notifications. Commands may have various side effects on
26978 the @value{GDBN} or target state beyond their official purpose. For example,
26979 a command may change the selected thread. Although such changes can
26980 be included in command response, using notification allows for more
26981 orthogonal frontend design.
26985 There's no guarantee that whenever an MI command reports an error,
26986 @value{GDBN} or the target are in any specific state, and especially,
26987 the state is not reverted to the state before the MI command was
26988 processed. Therefore, whenever an MI command results in an error,
26989 we recommend that the frontend refreshes all the information shown in
26990 the user interface.
26994 * Context management::
26995 * Asynchronous and non-stop modes::
26999 @node Context management
27000 @subsection Context management
27002 In most cases when @value{GDBN} accesses the target, this access is
27003 done in context of a specific thread and frame (@pxref{Frames}).
27004 Often, even when accessing global data, the target requires that a thread
27005 be specified. The CLI interface maintains the selected thread and frame,
27006 and supplies them to target on each command. This is convenient,
27007 because a command line user would not want to specify that information
27008 explicitly on each command, and because user interacts with
27009 @value{GDBN} via a single terminal, so no confusion is possible as
27010 to what thread and frame are the current ones.
27012 In the case of MI, the concept of selected thread and frame is less
27013 useful. First, a frontend can easily remember this information
27014 itself. Second, a graphical frontend can have more than one window,
27015 each one used for debugging a different thread, and the frontend might
27016 want to access additional threads for internal purposes. This
27017 increases the risk that by relying on implicitly selected thread, the
27018 frontend may be operating on a wrong one. Therefore, each MI command
27019 should explicitly specify which thread and frame to operate on. To
27020 make it possible, each MI command accepts the @samp{--thread} and
27021 @samp{--frame} options, the value to each is @value{GDBN} identifier
27022 for thread and frame to operate on.
27024 Usually, each top-level window in a frontend allows the user to select
27025 a thread and a frame, and remembers the user selection for further
27026 operations. However, in some cases @value{GDBN} may suggest that the
27027 current thread be changed. For example, when stopping on a breakpoint
27028 it is reasonable to switch to the thread where breakpoint is hit. For
27029 another example, if the user issues the CLI @samp{thread} command via
27030 the frontend, it is desirable to change the frontend's selected thread to the
27031 one specified by user. @value{GDBN} communicates the suggestion to
27032 change current thread using the @samp{=thread-selected} notification.
27033 No such notification is available for the selected frame at the moment.
27035 Note that historically, MI shares the selected thread with CLI, so
27036 frontends used the @code{-thread-select} to execute commands in the
27037 right context. However, getting this to work right is cumbersome. The
27038 simplest way is for frontend to emit @code{-thread-select} command
27039 before every command. This doubles the number of commands that need
27040 to be sent. The alternative approach is to suppress @code{-thread-select}
27041 if the selected thread in @value{GDBN} is supposed to be identical to the
27042 thread the frontend wants to operate on. However, getting this
27043 optimization right can be tricky. In particular, if the frontend
27044 sends several commands to @value{GDBN}, and one of the commands changes the
27045 selected thread, then the behaviour of subsequent commands will
27046 change. So, a frontend should either wait for response from such
27047 problematic commands, or explicitly add @code{-thread-select} for
27048 all subsequent commands. No frontend is known to do this exactly
27049 right, so it is suggested to just always pass the @samp{--thread} and
27050 @samp{--frame} options.
27052 @node Asynchronous and non-stop modes
27053 @subsection Asynchronous command execution and non-stop mode
27055 On some targets, @value{GDBN} is capable of processing MI commands
27056 even while the target is running. This is called @dfn{asynchronous
27057 command execution} (@pxref{Background Execution}). The frontend may
27058 specify a preferrence for asynchronous execution using the
27059 @code{-gdb-set target-async 1} command, which should be emitted before
27060 either running the executable or attaching to the target. After the
27061 frontend has started the executable or attached to the target, it can
27062 find if asynchronous execution is enabled using the
27063 @code{-list-target-features} command.
27065 Even if @value{GDBN} can accept a command while target is running,
27066 many commands that access the target do not work when the target is
27067 running. Therefore, asynchronous command execution is most useful
27068 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27069 it is possible to examine the state of one thread, while other threads
27072 When a given thread is running, MI commands that try to access the
27073 target in the context of that thread may not work, or may work only on
27074 some targets. In particular, commands that try to operate on thread's
27075 stack will not work, on any target. Commands that read memory, or
27076 modify breakpoints, may work or not work, depending on the target. Note
27077 that even commands that operate on global state, such as @code{print},
27078 @code{set}, and breakpoint commands, still access the target in the
27079 context of a specific thread, so frontend should try to find a
27080 stopped thread and perform the operation on that thread (using the
27081 @samp{--thread} option).
27083 Which commands will work in the context of a running thread is
27084 highly target dependent. However, the two commands
27085 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27086 to find the state of a thread, will always work.
27088 @node Thread groups
27089 @subsection Thread groups
27090 @value{GDBN} may be used to debug several processes at the same time.
27091 On some platfroms, @value{GDBN} may support debugging of several
27092 hardware systems, each one having several cores with several different
27093 processes running on each core. This section describes the MI
27094 mechanism to support such debugging scenarios.
27096 The key observation is that regardless of the structure of the
27097 target, MI can have a global list of threads, because most commands that
27098 accept the @samp{--thread} option do not need to know what process that
27099 thread belongs to. Therefore, it is not necessary to introduce
27100 neither additional @samp{--process} option, nor an notion of the
27101 current process in the MI interface. The only strictly new feature
27102 that is required is the ability to find how the threads are grouped
27105 To allow the user to discover such grouping, and to support arbitrary
27106 hierarchy of machines/cores/processes, MI introduces the concept of a
27107 @dfn{thread group}. Thread group is a collection of threads and other
27108 thread groups. A thread group always has a string identifier, a type,
27109 and may have additional attributes specific to the type. A new
27110 command, @code{-list-thread-groups}, returns the list of top-level
27111 thread groups, which correspond to processes that @value{GDBN} is
27112 debugging at the moment. By passing an identifier of a thread group
27113 to the @code{-list-thread-groups} command, it is possible to obtain
27114 the members of specific thread group.
27116 To allow the user to easily discover processes, and other objects, he
27117 wishes to debug, a concept of @dfn{available thread group} is
27118 introduced. Available thread group is an thread group that
27119 @value{GDBN} is not debugging, but that can be attached to, using the
27120 @code{-target-attach} command. The list of available top-level thread
27121 groups can be obtained using @samp{-list-thread-groups --available}.
27122 In general, the content of a thread group may be only retrieved only
27123 after attaching to that thread group.
27125 Thread groups are related to inferiors (@pxref{Inferiors and
27126 Programs}). Each inferior corresponds to a thread group of a special
27127 type @samp{process}, and some additional operations are permitted on
27128 such thread groups.
27130 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27131 @node GDB/MI Command Syntax
27132 @section @sc{gdb/mi} Command Syntax
27135 * GDB/MI Input Syntax::
27136 * GDB/MI Output Syntax::
27139 @node GDB/MI Input Syntax
27140 @subsection @sc{gdb/mi} Input Syntax
27142 @cindex input syntax for @sc{gdb/mi}
27143 @cindex @sc{gdb/mi}, input syntax
27145 @item @var{command} @expansion{}
27146 @code{@var{cli-command} | @var{mi-command}}
27148 @item @var{cli-command} @expansion{}
27149 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27150 @var{cli-command} is any existing @value{GDBN} CLI command.
27152 @item @var{mi-command} @expansion{}
27153 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27154 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27156 @item @var{token} @expansion{}
27157 "any sequence of digits"
27159 @item @var{option} @expansion{}
27160 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27162 @item @var{parameter} @expansion{}
27163 @code{@var{non-blank-sequence} | @var{c-string}}
27165 @item @var{operation} @expansion{}
27166 @emph{any of the operations described in this chapter}
27168 @item @var{non-blank-sequence} @expansion{}
27169 @emph{anything, provided it doesn't contain special characters such as
27170 "-", @var{nl}, """ and of course " "}
27172 @item @var{c-string} @expansion{}
27173 @code{""" @var{seven-bit-iso-c-string-content} """}
27175 @item @var{nl} @expansion{}
27184 The CLI commands are still handled by the @sc{mi} interpreter; their
27185 output is described below.
27188 The @code{@var{token}}, when present, is passed back when the command
27192 Some @sc{mi} commands accept optional arguments as part of the parameter
27193 list. Each option is identified by a leading @samp{-} (dash) and may be
27194 followed by an optional argument parameter. Options occur first in the
27195 parameter list and can be delimited from normal parameters using
27196 @samp{--} (this is useful when some parameters begin with a dash).
27203 We want easy access to the existing CLI syntax (for debugging).
27206 We want it to be easy to spot a @sc{mi} operation.
27209 @node GDB/MI Output Syntax
27210 @subsection @sc{gdb/mi} Output Syntax
27212 @cindex output syntax of @sc{gdb/mi}
27213 @cindex @sc{gdb/mi}, output syntax
27214 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27215 followed, optionally, by a single result record. This result record
27216 is for the most recent command. The sequence of output records is
27217 terminated by @samp{(gdb)}.
27219 If an input command was prefixed with a @code{@var{token}} then the
27220 corresponding output for that command will also be prefixed by that same
27224 @item @var{output} @expansion{}
27225 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27227 @item @var{result-record} @expansion{}
27228 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27230 @item @var{out-of-band-record} @expansion{}
27231 @code{@var{async-record} | @var{stream-record}}
27233 @item @var{async-record} @expansion{}
27234 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27236 @item @var{exec-async-output} @expansion{}
27237 @code{[ @var{token} ] "*" @var{async-output}}
27239 @item @var{status-async-output} @expansion{}
27240 @code{[ @var{token} ] "+" @var{async-output}}
27242 @item @var{notify-async-output} @expansion{}
27243 @code{[ @var{token} ] "=" @var{async-output}}
27245 @item @var{async-output} @expansion{}
27246 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
27248 @item @var{result-class} @expansion{}
27249 @code{"done" | "running" | "connected" | "error" | "exit"}
27251 @item @var{async-class} @expansion{}
27252 @code{"stopped" | @var{others}} (where @var{others} will be added
27253 depending on the needs---this is still in development).
27255 @item @var{result} @expansion{}
27256 @code{ @var{variable} "=" @var{value}}
27258 @item @var{variable} @expansion{}
27259 @code{ @var{string} }
27261 @item @var{value} @expansion{}
27262 @code{ @var{const} | @var{tuple} | @var{list} }
27264 @item @var{const} @expansion{}
27265 @code{@var{c-string}}
27267 @item @var{tuple} @expansion{}
27268 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27270 @item @var{list} @expansion{}
27271 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27272 @var{result} ( "," @var{result} )* "]" }
27274 @item @var{stream-record} @expansion{}
27275 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27277 @item @var{console-stream-output} @expansion{}
27278 @code{"~" @var{c-string}}
27280 @item @var{target-stream-output} @expansion{}
27281 @code{"@@" @var{c-string}}
27283 @item @var{log-stream-output} @expansion{}
27284 @code{"&" @var{c-string}}
27286 @item @var{nl} @expansion{}
27289 @item @var{token} @expansion{}
27290 @emph{any sequence of digits}.
27298 All output sequences end in a single line containing a period.
27301 The @code{@var{token}} is from the corresponding request. Note that
27302 for all async output, while the token is allowed by the grammar and
27303 may be output by future versions of @value{GDBN} for select async
27304 output messages, it is generally omitted. Frontends should treat
27305 all async output as reporting general changes in the state of the
27306 target and there should be no need to associate async output to any
27310 @cindex status output in @sc{gdb/mi}
27311 @var{status-async-output} contains on-going status information about the
27312 progress of a slow operation. It can be discarded. All status output is
27313 prefixed by @samp{+}.
27316 @cindex async output in @sc{gdb/mi}
27317 @var{exec-async-output} contains asynchronous state change on the target
27318 (stopped, started, disappeared). All async output is prefixed by
27322 @cindex notify output in @sc{gdb/mi}
27323 @var{notify-async-output} contains supplementary information that the
27324 client should handle (e.g., a new breakpoint information). All notify
27325 output is prefixed by @samp{=}.
27328 @cindex console output in @sc{gdb/mi}
27329 @var{console-stream-output} is output that should be displayed as is in the
27330 console. It is the textual response to a CLI command. All the console
27331 output is prefixed by @samp{~}.
27334 @cindex target output in @sc{gdb/mi}
27335 @var{target-stream-output} is the output produced by the target program.
27336 All the target output is prefixed by @samp{@@}.
27339 @cindex log output in @sc{gdb/mi}
27340 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27341 instance messages that should be displayed as part of an error log. All
27342 the log output is prefixed by @samp{&}.
27345 @cindex list output in @sc{gdb/mi}
27346 New @sc{gdb/mi} commands should only output @var{lists} containing
27352 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27353 details about the various output records.
27355 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27356 @node GDB/MI Compatibility with CLI
27357 @section @sc{gdb/mi} Compatibility with CLI
27359 @cindex compatibility, @sc{gdb/mi} and CLI
27360 @cindex @sc{gdb/mi}, compatibility with CLI
27362 For the developers convenience CLI commands can be entered directly,
27363 but there may be some unexpected behaviour. For example, commands
27364 that query the user will behave as if the user replied yes, breakpoint
27365 command lists are not executed and some CLI commands, such as
27366 @code{if}, @code{when} and @code{define}, prompt for further input with
27367 @samp{>}, which is not valid MI output.
27369 This feature may be removed at some stage in the future and it is
27370 recommended that front ends use the @code{-interpreter-exec} command
27371 (@pxref{-interpreter-exec}).
27373 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27374 @node GDB/MI Development and Front Ends
27375 @section @sc{gdb/mi} Development and Front Ends
27376 @cindex @sc{gdb/mi} development
27378 The application which takes the MI output and presents the state of the
27379 program being debugged to the user is called a @dfn{front end}.
27381 Although @sc{gdb/mi} is still incomplete, it is currently being used
27382 by a variety of front ends to @value{GDBN}. This makes it difficult
27383 to introduce new functionality without breaking existing usage. This
27384 section tries to minimize the problems by describing how the protocol
27387 Some changes in MI need not break a carefully designed front end, and
27388 for these the MI version will remain unchanged. The following is a
27389 list of changes that may occur within one level, so front ends should
27390 parse MI output in a way that can handle them:
27394 New MI commands may be added.
27397 New fields may be added to the output of any MI command.
27400 The range of values for fields with specified values, e.g.,
27401 @code{in_scope} (@pxref{-var-update}) may be extended.
27403 @c The format of field's content e.g type prefix, may change so parse it
27404 @c at your own risk. Yes, in general?
27406 @c The order of fields may change? Shouldn't really matter but it might
27407 @c resolve inconsistencies.
27410 If the changes are likely to break front ends, the MI version level
27411 will be increased by one. This will allow the front end to parse the
27412 output according to the MI version. Apart from mi0, new versions of
27413 @value{GDBN} will not support old versions of MI and it will be the
27414 responsibility of the front end to work with the new one.
27416 @c Starting with mi3, add a new command -mi-version that prints the MI
27419 The best way to avoid unexpected changes in MI that might break your front
27420 end is to make your project known to @value{GDBN} developers and
27421 follow development on @email{gdb@@sourceware.org} and
27422 @email{gdb-patches@@sourceware.org}.
27423 @cindex mailing lists
27425 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27426 @node GDB/MI Output Records
27427 @section @sc{gdb/mi} Output Records
27430 * GDB/MI Result Records::
27431 * GDB/MI Stream Records::
27432 * GDB/MI Async Records::
27433 * GDB/MI Frame Information::
27434 * GDB/MI Thread Information::
27435 * GDB/MI Ada Exception Information::
27438 @node GDB/MI Result Records
27439 @subsection @sc{gdb/mi} Result Records
27441 @cindex result records in @sc{gdb/mi}
27442 @cindex @sc{gdb/mi}, result records
27443 In addition to a number of out-of-band notifications, the response to a
27444 @sc{gdb/mi} command includes one of the following result indications:
27448 @item "^done" [ "," @var{results} ]
27449 The synchronous operation was successful, @code{@var{results}} are the return
27454 This result record is equivalent to @samp{^done}. Historically, it
27455 was output instead of @samp{^done} if the command has resumed the
27456 target. This behaviour is maintained for backward compatibility, but
27457 all frontends should treat @samp{^done} and @samp{^running}
27458 identically and rely on the @samp{*running} output record to determine
27459 which threads are resumed.
27463 @value{GDBN} has connected to a remote target.
27465 @item "^error" "," @var{c-string}
27467 The operation failed. The @code{@var{c-string}} contains the corresponding
27472 @value{GDBN} has terminated.
27476 @node GDB/MI Stream Records
27477 @subsection @sc{gdb/mi} Stream Records
27479 @cindex @sc{gdb/mi}, stream records
27480 @cindex stream records in @sc{gdb/mi}
27481 @value{GDBN} internally maintains a number of output streams: the console, the
27482 target, and the log. The output intended for each of these streams is
27483 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27485 Each stream record begins with a unique @dfn{prefix character} which
27486 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27487 Syntax}). In addition to the prefix, each stream record contains a
27488 @code{@var{string-output}}. This is either raw text (with an implicit new
27489 line) or a quoted C string (which does not contain an implicit newline).
27492 @item "~" @var{string-output}
27493 The console output stream contains text that should be displayed in the
27494 CLI console window. It contains the textual responses to CLI commands.
27496 @item "@@" @var{string-output}
27497 The target output stream contains any textual output from the running
27498 target. This is only present when GDB's event loop is truly
27499 asynchronous, which is currently only the case for remote targets.
27501 @item "&" @var{string-output}
27502 The log stream contains debugging messages being produced by @value{GDBN}'s
27506 @node GDB/MI Async Records
27507 @subsection @sc{gdb/mi} Async Records
27509 @cindex async records in @sc{gdb/mi}
27510 @cindex @sc{gdb/mi}, async records
27511 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27512 additional changes that have occurred. Those changes can either be a
27513 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27514 target activity (e.g., target stopped).
27516 The following is the list of possible async records:
27520 @item *running,thread-id="@var{thread}"
27521 The target is now running. The @var{thread} field tells which
27522 specific thread is now running, and can be @samp{all} if all threads
27523 are running. The frontend should assume that no interaction with a
27524 running thread is possible after this notification is produced.
27525 The frontend should not assume that this notification is output
27526 only once for any command. @value{GDBN} may emit this notification
27527 several times, either for different threads, because it cannot resume
27528 all threads together, or even for a single thread, if the thread must
27529 be stepped though some code before letting it run freely.
27531 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
27532 The target has stopped. The @var{reason} field can have one of the
27536 @item breakpoint-hit
27537 A breakpoint was reached.
27538 @item watchpoint-trigger
27539 A watchpoint was triggered.
27540 @item read-watchpoint-trigger
27541 A read watchpoint was triggered.
27542 @item access-watchpoint-trigger
27543 An access watchpoint was triggered.
27544 @item function-finished
27545 An -exec-finish or similar CLI command was accomplished.
27546 @item location-reached
27547 An -exec-until or similar CLI command was accomplished.
27548 @item watchpoint-scope
27549 A watchpoint has gone out of scope.
27550 @item end-stepping-range
27551 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
27552 similar CLI command was accomplished.
27553 @item exited-signalled
27554 The inferior exited because of a signal.
27556 The inferior exited.
27557 @item exited-normally
27558 The inferior exited normally.
27559 @item signal-received
27560 A signal was received by the inferior.
27562 The inferior has stopped due to a library being loaded or unloaded.
27563 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
27564 set or when a @code{catch load} or @code{catch unload} catchpoint is
27565 in use (@pxref{Set Catchpoints}).
27567 The inferior has forked. This is reported when @code{catch fork}
27568 (@pxref{Set Catchpoints}) has been used.
27570 The inferior has vforked. This is reported in when @code{catch vfork}
27571 (@pxref{Set Catchpoints}) has been used.
27572 @item syscall-entry
27573 The inferior entered a system call. This is reported when @code{catch
27574 syscall} (@pxref{Set Catchpoints}) has been used.
27575 @item syscall-entry
27576 The inferior returned from a system call. This is reported when
27577 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
27579 The inferior called @code{exec}. This is reported when @code{catch exec}
27580 (@pxref{Set Catchpoints}) has been used.
27583 The @var{id} field identifies the thread that directly caused the stop
27584 -- for example by hitting a breakpoint. Depending on whether all-stop
27585 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
27586 stop all threads, or only the thread that directly triggered the stop.
27587 If all threads are stopped, the @var{stopped} field will have the
27588 value of @code{"all"}. Otherwise, the value of the @var{stopped}
27589 field will be a list of thread identifiers. Presently, this list will
27590 always include a single thread, but frontend should be prepared to see
27591 several threads in the list. The @var{core} field reports the
27592 processor core on which the stop event has happened. This field may be absent
27593 if such information is not available.
27595 @item =thread-group-added,id="@var{id}"
27596 @itemx =thread-group-removed,id="@var{id}"
27597 A thread group was either added or removed. The @var{id} field
27598 contains the @value{GDBN} identifier of the thread group. When a thread
27599 group is added, it generally might not be associated with a running
27600 process. When a thread group is removed, its id becomes invalid and
27601 cannot be used in any way.
27603 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
27604 A thread group became associated with a running program,
27605 either because the program was just started or the thread group
27606 was attached to a program. The @var{id} field contains the
27607 @value{GDBN} identifier of the thread group. The @var{pid} field
27608 contains process identifier, specific to the operating system.
27610 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
27611 A thread group is no longer associated with a running program,
27612 either because the program has exited, or because it was detached
27613 from. The @var{id} field contains the @value{GDBN} identifier of the
27614 thread group. @var{code} is the exit code of the inferior; it exists
27615 only when the inferior exited with some code.
27617 @item =thread-created,id="@var{id}",group-id="@var{gid}"
27618 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
27619 A thread either was created, or has exited. The @var{id} field
27620 contains the @value{GDBN} identifier of the thread. The @var{gid}
27621 field identifies the thread group this thread belongs to.
27623 @item =thread-selected,id="@var{id}"
27624 Informs that the selected thread was changed as result of the last
27625 command. This notification is not emitted as result of @code{-thread-select}
27626 command but is emitted whenever an MI command that is not documented
27627 to change the selected thread actually changes it. In particular,
27628 invoking, directly or indirectly (via user-defined command), the CLI
27629 @code{thread} command, will generate this notification.
27631 We suggest that in response to this notification, front ends
27632 highlight the selected thread and cause subsequent commands to apply to
27635 @item =library-loaded,...
27636 Reports that a new library file was loaded by the program. This
27637 notification has 4 fields---@var{id}, @var{target-name},
27638 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
27639 opaque identifier of the library. For remote debugging case,
27640 @var{target-name} and @var{host-name} fields give the name of the
27641 library file on the target, and on the host respectively. For native
27642 debugging, both those fields have the same value. The
27643 @var{symbols-loaded} field is emitted only for backward compatibility
27644 and should not be relied on to convey any useful information. The
27645 @var{thread-group} field, if present, specifies the id of the thread
27646 group in whose context the library was loaded. If the field is
27647 absent, it means the library was loaded in the context of all present
27650 @item =library-unloaded,...
27651 Reports that a library was unloaded by the program. This notification
27652 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
27653 the same meaning as for the @code{=library-loaded} notification.
27654 The @var{thread-group} field, if present, specifies the id of the
27655 thread group in whose context the library was unloaded. If the field is
27656 absent, it means the library was unloaded in the context of all present
27659 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
27660 @itemx =traceframe-changed,end
27661 Reports that the trace frame was changed and its new number is
27662 @var{tfnum}. The number of the tracepoint associated with this trace
27663 frame is @var{tpnum}.
27665 @item =tsv-created,name=@var{name},value=@var{value}
27666 Reports that the new trace state variable @var{name} is created with
27669 @item =tsv-deleted,name=@var{name}
27670 @itemx =tsv-deleted
27671 Reports that the trace state variable @var{name} is deleted or all
27672 trace state variables are deleted.
27674 @item =breakpoint-created,bkpt=@{...@}
27675 @itemx =breakpoint-modified,bkpt=@{...@}
27676 @itemx =breakpoint-deleted,id=@var{number}
27677 Reports that a breakpoint was created, modified, or deleted,
27678 respectively. Only user-visible breakpoints are reported to the MI
27681 The @var{bkpt} argument is of the same form as returned by the various
27682 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
27683 @var{number} is the ordinal number of the breakpoint.
27685 Note that if a breakpoint is emitted in the result record of a
27686 command, then it will not also be emitted in an async record.
27688 @item =record-started,thread-group="@var{id}"
27689 @itemx =record-stopped,thread-group="@var{id}"
27690 Execution log recording was either started or stopped on an
27691 inferior. The @var{id} is the @value{GDBN} identifier of the thread
27692 group corresponding to the affected inferior.
27694 @item =cmd-param-changed,param=@var{param},value=@var{value}
27695 Reports that a parameter of the command @code{set @var{param}} is
27696 changed to @var{value}. In the multi-word @code{set} command,
27697 the @var{param} is the whole parameter list to @code{set} command.
27698 For example, In command @code{set check type on}, @var{param}
27699 is @code{check type} and @var{value} is @code{on}.
27701 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
27702 Reports that bytes from @var{addr} to @var{data} + @var{len} were
27703 written in an inferior. The @var{id} is the identifier of the
27704 thread group corresponding to the affected inferior. The optional
27705 @code{type="code"} part is reported if the memory written to holds
27709 @node GDB/MI Frame Information
27710 @subsection @sc{gdb/mi} Frame Information
27712 Response from many MI commands includes an information about stack
27713 frame. This information is a tuple that may have the following
27718 The level of the stack frame. The innermost frame has the level of
27719 zero. This field is always present.
27722 The name of the function corresponding to the frame. This field may
27723 be absent if @value{GDBN} is unable to determine the function name.
27726 The code address for the frame. This field is always present.
27729 The name of the source files that correspond to the frame's code
27730 address. This field may be absent.
27733 The source line corresponding to the frames' code address. This field
27737 The name of the binary file (either executable or shared library) the
27738 corresponds to the frame's code address. This field may be absent.
27742 @node GDB/MI Thread Information
27743 @subsection @sc{gdb/mi} Thread Information
27745 Whenever @value{GDBN} has to report an information about a thread, it
27746 uses a tuple with the following fields:
27750 The numeric id assigned to the thread by @value{GDBN}. This field is
27754 Target-specific string identifying the thread. This field is always present.
27757 Additional information about the thread provided by the target.
27758 It is supposed to be human-readable and not interpreted by the
27759 frontend. This field is optional.
27762 Either @samp{stopped} or @samp{running}, depending on whether the
27763 thread is presently running. This field is always present.
27766 The value of this field is an integer number of the processor core the
27767 thread was last seen on. This field is optional.
27770 @node GDB/MI Ada Exception Information
27771 @subsection @sc{gdb/mi} Ada Exception Information
27773 Whenever a @code{*stopped} record is emitted because the program
27774 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
27775 @value{GDBN} provides the name of the exception that was raised via
27776 the @code{exception-name} field.
27778 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27779 @node GDB/MI Simple Examples
27780 @section Simple Examples of @sc{gdb/mi} Interaction
27781 @cindex @sc{gdb/mi}, simple examples
27783 This subsection presents several simple examples of interaction using
27784 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
27785 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
27786 the output received from @sc{gdb/mi}.
27788 Note the line breaks shown in the examples are here only for
27789 readability, they don't appear in the real output.
27791 @subheading Setting a Breakpoint
27793 Setting a breakpoint generates synchronous output which contains detailed
27794 information of the breakpoint.
27797 -> -break-insert main
27798 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27799 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27800 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
27804 @subheading Program Execution
27806 Program execution generates asynchronous records and MI gives the
27807 reason that execution stopped.
27813 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27814 frame=@{addr="0x08048564",func="main",
27815 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
27816 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
27821 <- *stopped,reason="exited-normally"
27825 @subheading Quitting @value{GDBN}
27827 Quitting @value{GDBN} just prints the result class @samp{^exit}.
27835 Please note that @samp{^exit} is printed immediately, but it might
27836 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
27837 performs necessary cleanups, including killing programs being debugged
27838 or disconnecting from debug hardware, so the frontend should wait till
27839 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
27840 fails to exit in reasonable time.
27842 @subheading A Bad Command
27844 Here's what happens if you pass a non-existent command:
27848 <- ^error,msg="Undefined MI command: rubbish"
27853 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27854 @node GDB/MI Command Description Format
27855 @section @sc{gdb/mi} Command Description Format
27857 The remaining sections describe blocks of commands. Each block of
27858 commands is laid out in a fashion similar to this section.
27860 @subheading Motivation
27862 The motivation for this collection of commands.
27864 @subheading Introduction
27866 A brief introduction to this collection of commands as a whole.
27868 @subheading Commands
27870 For each command in the block, the following is described:
27872 @subsubheading Synopsis
27875 -command @var{args}@dots{}
27878 @subsubheading Result
27880 @subsubheading @value{GDBN} Command
27882 The corresponding @value{GDBN} CLI command(s), if any.
27884 @subsubheading Example
27886 Example(s) formatted for readability. Some of the described commands have
27887 not been implemented yet and these are labeled N.A.@: (not available).
27890 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27891 @node GDB/MI Breakpoint Commands
27892 @section @sc{gdb/mi} Breakpoint Commands
27894 @cindex breakpoint commands for @sc{gdb/mi}
27895 @cindex @sc{gdb/mi}, breakpoint commands
27896 This section documents @sc{gdb/mi} commands for manipulating
27899 @subheading The @code{-break-after} Command
27900 @findex -break-after
27902 @subsubheading Synopsis
27905 -break-after @var{number} @var{count}
27908 The breakpoint number @var{number} is not in effect until it has been
27909 hit @var{count} times. To see how this is reflected in the output of
27910 the @samp{-break-list} command, see the description of the
27911 @samp{-break-list} command below.
27913 @subsubheading @value{GDBN} Command
27915 The corresponding @value{GDBN} command is @samp{ignore}.
27917 @subsubheading Example
27922 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27923 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27924 fullname="/home/foo/hello.c",line="5",times="0"@}
27931 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27932 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27933 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27934 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27935 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27936 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27937 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27938 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27939 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27940 line="5",times="0",ignore="3"@}]@}
27945 @subheading The @code{-break-catch} Command
27946 @findex -break-catch
27949 @subheading The @code{-break-commands} Command
27950 @findex -break-commands
27952 @subsubheading Synopsis
27955 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
27958 Specifies the CLI commands that should be executed when breakpoint
27959 @var{number} is hit. The parameters @var{command1} to @var{commandN}
27960 are the commands. If no command is specified, any previously-set
27961 commands are cleared. @xref{Break Commands}. Typical use of this
27962 functionality is tracing a program, that is, printing of values of
27963 some variables whenever breakpoint is hit and then continuing.
27965 @subsubheading @value{GDBN} Command
27967 The corresponding @value{GDBN} command is @samp{commands}.
27969 @subsubheading Example
27974 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27975 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27976 fullname="/home/foo/hello.c",line="5",times="0"@}
27978 -break-commands 1 "print v" "continue"
27983 @subheading The @code{-break-condition} Command
27984 @findex -break-condition
27986 @subsubheading Synopsis
27989 -break-condition @var{number} @var{expr}
27992 Breakpoint @var{number} will stop the program only if the condition in
27993 @var{expr} is true. The condition becomes part of the
27994 @samp{-break-list} output (see the description of the @samp{-break-list}
27997 @subsubheading @value{GDBN} Command
27999 The corresponding @value{GDBN} command is @samp{condition}.
28001 @subsubheading Example
28005 -break-condition 1 1
28009 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28010 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28011 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28012 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28013 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28014 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28015 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28016 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28017 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28018 line="5",cond="1",times="0",ignore="3"@}]@}
28022 @subheading The @code{-break-delete} Command
28023 @findex -break-delete
28025 @subsubheading Synopsis
28028 -break-delete ( @var{breakpoint} )+
28031 Delete the breakpoint(s) whose number(s) are specified in the argument
28032 list. This is obviously reflected in the breakpoint list.
28034 @subsubheading @value{GDBN} Command
28036 The corresponding @value{GDBN} command is @samp{delete}.
28038 @subsubheading Example
28046 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28047 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28048 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28049 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28050 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28051 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28052 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28057 @subheading The @code{-break-disable} Command
28058 @findex -break-disable
28060 @subsubheading Synopsis
28063 -break-disable ( @var{breakpoint} )+
28066 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28067 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28069 @subsubheading @value{GDBN} Command
28071 The corresponding @value{GDBN} command is @samp{disable}.
28073 @subsubheading Example
28081 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28082 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28083 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28084 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28085 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28086 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28087 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28088 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28089 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28090 line="5",times="0"@}]@}
28094 @subheading The @code{-break-enable} Command
28095 @findex -break-enable
28097 @subsubheading Synopsis
28100 -break-enable ( @var{breakpoint} )+
28103 Enable (previously disabled) @var{breakpoint}(s).
28105 @subsubheading @value{GDBN} Command
28107 The corresponding @value{GDBN} command is @samp{enable}.
28109 @subsubheading Example
28117 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28118 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28119 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28120 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28121 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28122 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28123 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28124 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28125 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28126 line="5",times="0"@}]@}
28130 @subheading The @code{-break-info} Command
28131 @findex -break-info
28133 @subsubheading Synopsis
28136 -break-info @var{breakpoint}
28140 Get information about a single breakpoint.
28142 @subsubheading @value{GDBN} Command
28144 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28146 @subsubheading Example
28149 @subheading The @code{-break-insert} Command
28150 @findex -break-insert
28152 @subsubheading Synopsis
28155 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28156 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28157 [ -p @var{thread-id} ] [ @var{location} ]
28161 If specified, @var{location}, can be one of:
28168 @item filename:linenum
28169 @item filename:function
28173 The possible optional parameters of this command are:
28177 Insert a temporary breakpoint.
28179 Insert a hardware breakpoint.
28181 If @var{location} cannot be parsed (for example if it
28182 refers to unknown files or functions), create a pending
28183 breakpoint. Without this flag, @value{GDBN} will report
28184 an error, and won't create a breakpoint, if @var{location}
28187 Create a disabled breakpoint.
28189 Create a tracepoint. @xref{Tracepoints}. When this parameter
28190 is used together with @samp{-h}, a fast tracepoint is created.
28191 @item -c @var{condition}
28192 Make the breakpoint conditional on @var{condition}.
28193 @item -i @var{ignore-count}
28194 Initialize the @var{ignore-count}.
28195 @item -p @var{thread-id}
28196 Restrict the breakpoint to the specified @var{thread-id}.
28199 @subsubheading Result
28201 The result is in the form:
28204 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
28205 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
28206 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
28207 times="@var{times}"@}
28211 where @var{number} is the @value{GDBN} number for this breakpoint,
28212 @var{funcname} is the name of the function where the breakpoint was
28213 inserted, @var{filename} is the name of the source file which contains
28214 this function, @var{lineno} is the source line number within that file
28215 and @var{times} the number of times that the breakpoint has been hit
28216 (always 0 for -break-insert but may be greater for -break-info or -break-list
28217 which use the same output).
28219 Note: this format is open to change.
28220 @c An out-of-band breakpoint instead of part of the result?
28222 @subsubheading @value{GDBN} Command
28224 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28225 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28227 @subsubheading Example
28232 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28233 fullname="/home/foo/recursive2.c,line="4",times="0"@}
28235 -break-insert -t foo
28236 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28237 fullname="/home/foo/recursive2.c,line="11",times="0"@}
28240 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28241 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28242 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28243 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28244 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28245 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28246 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28247 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28248 addr="0x0001072c", func="main",file="recursive2.c",
28249 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
28250 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28251 addr="0x00010774",func="foo",file="recursive2.c",
28252 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
28254 @c -break-insert -r foo.*
28255 @c ~int foo(int, int);
28256 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28257 @c "fullname="/home/foo/recursive2.c",line="11",times="0"@}
28261 @subheading The @code{-break-list} Command
28262 @findex -break-list
28264 @subsubheading Synopsis
28270 Displays the list of inserted breakpoints, showing the following fields:
28274 number of the breakpoint
28276 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28278 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28281 is the breakpoint enabled or no: @samp{y} or @samp{n}
28283 memory location at which the breakpoint is set
28285 logical location of the breakpoint, expressed by function name, file
28288 number of times the breakpoint has been hit
28291 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28292 @code{body} field is an empty list.
28294 @subsubheading @value{GDBN} Command
28296 The corresponding @value{GDBN} command is @samp{info break}.
28298 @subsubheading Example
28303 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28304 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28305 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28306 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28307 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28308 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28309 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28310 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28311 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
28312 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28313 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28314 line="13",times="0"@}]@}
28318 Here's an example of the result when there are no breakpoints:
28323 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28324 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28325 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28326 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28327 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28328 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28329 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28334 @subheading The @code{-break-passcount} Command
28335 @findex -break-passcount
28337 @subsubheading Synopsis
28340 -break-passcount @var{tracepoint-number} @var{passcount}
28343 Set the passcount for tracepoint @var{tracepoint-number} to
28344 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28345 is not a tracepoint, error is emitted. This corresponds to CLI
28346 command @samp{passcount}.
28348 @subheading The @code{-break-watch} Command
28349 @findex -break-watch
28351 @subsubheading Synopsis
28354 -break-watch [ -a | -r ]
28357 Create a watchpoint. With the @samp{-a} option it will create an
28358 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28359 read from or on a write to the memory location. With the @samp{-r}
28360 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28361 trigger only when the memory location is accessed for reading. Without
28362 either of the options, the watchpoint created is a regular watchpoint,
28363 i.e., it will trigger when the memory location is accessed for writing.
28364 @xref{Set Watchpoints, , Setting Watchpoints}.
28366 Note that @samp{-break-list} will report a single list of watchpoints and
28367 breakpoints inserted.
28369 @subsubheading @value{GDBN} Command
28371 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28374 @subsubheading Example
28376 Setting a watchpoint on a variable in the @code{main} function:
28381 ^done,wpt=@{number="2",exp="x"@}
28386 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28387 value=@{old="-268439212",new="55"@},
28388 frame=@{func="main",args=[],file="recursive2.c",
28389 fullname="/home/foo/bar/recursive2.c",line="5"@}
28393 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28394 the program execution twice: first for the variable changing value, then
28395 for the watchpoint going out of scope.
28400 ^done,wpt=@{number="5",exp="C"@}
28405 *stopped,reason="watchpoint-trigger",
28406 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28407 frame=@{func="callee4",args=[],
28408 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28409 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28414 *stopped,reason="watchpoint-scope",wpnum="5",
28415 frame=@{func="callee3",args=[@{name="strarg",
28416 value="0x11940 \"A string argument.\""@}],
28417 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28418 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28422 Listing breakpoints and watchpoints, at different points in the program
28423 execution. Note that once the watchpoint goes out of scope, it is
28429 ^done,wpt=@{number="2",exp="C"@}
28432 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28433 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28434 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28435 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28436 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28437 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28438 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28439 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28440 addr="0x00010734",func="callee4",
28441 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28442 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
28443 bkpt=@{number="2",type="watchpoint",disp="keep",
28444 enabled="y",addr="",what="C",times="0"@}]@}
28449 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
28450 value=@{old="-276895068",new="3"@},
28451 frame=@{func="callee4",args=[],
28452 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28453 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28456 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28457 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28458 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28459 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28460 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28461 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28462 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28463 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28464 addr="0x00010734",func="callee4",
28465 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28466 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
28467 bkpt=@{number="2",type="watchpoint",disp="keep",
28468 enabled="y",addr="",what="C",times="-5"@}]@}
28472 ^done,reason="watchpoint-scope",wpnum="2",
28473 frame=@{func="callee3",args=[@{name="strarg",
28474 value="0x11940 \"A string argument.\""@}],
28475 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28476 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28479 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28480 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28481 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28482 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28483 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28484 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28485 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28486 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28487 addr="0x00010734",func="callee4",
28488 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28489 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
28494 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28495 @node GDB/MI Program Context
28496 @section @sc{gdb/mi} Program Context
28498 @subheading The @code{-exec-arguments} Command
28499 @findex -exec-arguments
28502 @subsubheading Synopsis
28505 -exec-arguments @var{args}
28508 Set the inferior program arguments, to be used in the next
28511 @subsubheading @value{GDBN} Command
28513 The corresponding @value{GDBN} command is @samp{set args}.
28515 @subsubheading Example
28519 -exec-arguments -v word
28526 @subheading The @code{-exec-show-arguments} Command
28527 @findex -exec-show-arguments
28529 @subsubheading Synopsis
28532 -exec-show-arguments
28535 Print the arguments of the program.
28537 @subsubheading @value{GDBN} Command
28539 The corresponding @value{GDBN} command is @samp{show args}.
28541 @subsubheading Example
28546 @subheading The @code{-environment-cd} Command
28547 @findex -environment-cd
28549 @subsubheading Synopsis
28552 -environment-cd @var{pathdir}
28555 Set @value{GDBN}'s working directory.
28557 @subsubheading @value{GDBN} Command
28559 The corresponding @value{GDBN} command is @samp{cd}.
28561 @subsubheading Example
28565 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28571 @subheading The @code{-environment-directory} Command
28572 @findex -environment-directory
28574 @subsubheading Synopsis
28577 -environment-directory [ -r ] [ @var{pathdir} ]+
28580 Add directories @var{pathdir} to beginning of search path for source files.
28581 If the @samp{-r} option is used, the search path is reset to the default
28582 search path. If directories @var{pathdir} are supplied in addition to the
28583 @samp{-r} option, the search path is first reset and then addition
28585 Multiple directories may be specified, separated by blanks. Specifying
28586 multiple directories in a single command
28587 results in the directories added to the beginning of the
28588 search path in the same order they were presented in the command.
28589 If blanks are needed as
28590 part of a directory name, double-quotes should be used around
28591 the name. In the command output, the path will show up separated
28592 by the system directory-separator character. The directory-separator
28593 character must not be used
28594 in any directory name.
28595 If no directories are specified, the current search path is displayed.
28597 @subsubheading @value{GDBN} Command
28599 The corresponding @value{GDBN} command is @samp{dir}.
28601 @subsubheading Example
28605 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28606 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28608 -environment-directory ""
28609 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28611 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
28612 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
28614 -environment-directory -r
28615 ^done,source-path="$cdir:$cwd"
28620 @subheading The @code{-environment-path} Command
28621 @findex -environment-path
28623 @subsubheading Synopsis
28626 -environment-path [ -r ] [ @var{pathdir} ]+
28629 Add directories @var{pathdir} to beginning of search path for object files.
28630 If the @samp{-r} option is used, the search path is reset to the original
28631 search path that existed at gdb start-up. If directories @var{pathdir} are
28632 supplied in addition to the
28633 @samp{-r} option, the search path is first reset and then addition
28635 Multiple directories may be specified, separated by blanks. Specifying
28636 multiple directories in a single command
28637 results in the directories added to the beginning of the
28638 search path in the same order they were presented in the command.
28639 If blanks are needed as
28640 part of a directory name, double-quotes should be used around
28641 the name. In the command output, the path will show up separated
28642 by the system directory-separator character. The directory-separator
28643 character must not be used
28644 in any directory name.
28645 If no directories are specified, the current path is displayed.
28648 @subsubheading @value{GDBN} Command
28650 The corresponding @value{GDBN} command is @samp{path}.
28652 @subsubheading Example
28657 ^done,path="/usr/bin"
28659 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
28660 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
28662 -environment-path -r /usr/local/bin
28663 ^done,path="/usr/local/bin:/usr/bin"
28668 @subheading The @code{-environment-pwd} Command
28669 @findex -environment-pwd
28671 @subsubheading Synopsis
28677 Show the current working directory.
28679 @subsubheading @value{GDBN} Command
28681 The corresponding @value{GDBN} command is @samp{pwd}.
28683 @subsubheading Example
28688 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
28692 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28693 @node GDB/MI Thread Commands
28694 @section @sc{gdb/mi} Thread Commands
28697 @subheading The @code{-thread-info} Command
28698 @findex -thread-info
28700 @subsubheading Synopsis
28703 -thread-info [ @var{thread-id} ]
28706 Reports information about either a specific thread, if
28707 the @var{thread-id} parameter is present, or about all
28708 threads. When printing information about all threads,
28709 also reports the current thread.
28711 @subsubheading @value{GDBN} Command
28713 The @samp{info thread} command prints the same information
28716 @subsubheading Result
28718 The result is a list of threads. The following attributes are
28719 defined for a given thread:
28723 This field exists only for the current thread. It has the value @samp{*}.
28726 The identifier that @value{GDBN} uses to refer to the thread.
28729 The identifier that the target uses to refer to the thread.
28732 Extra information about the thread, in a target-specific format. This
28736 The name of the thread. If the user specified a name using the
28737 @code{thread name} command, then this name is given. Otherwise, if
28738 @value{GDBN} can extract the thread name from the target, then that
28739 name is given. If @value{GDBN} cannot find the thread name, then this
28743 The stack frame currently executing in the thread.
28746 The thread's state. The @samp{state} field may have the following
28751 The thread is stopped. Frame information is available for stopped
28755 The thread is running. There's no frame information for running
28761 If @value{GDBN} can find the CPU core on which this thread is running,
28762 then this field is the core identifier. This field is optional.
28766 @subsubheading Example
28771 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28772 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28773 args=[]@},state="running"@},
28774 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28775 frame=@{level="0",addr="0x0804891f",func="foo",
28776 args=[@{name="i",value="10"@}],
28777 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28778 state="running"@}],
28779 current-thread-id="1"
28783 @subheading The @code{-thread-list-ids} Command
28784 @findex -thread-list-ids
28786 @subsubheading Synopsis
28792 Produces a list of the currently known @value{GDBN} thread ids. At the
28793 end of the list it also prints the total number of such threads.
28795 This command is retained for historical reasons, the
28796 @code{-thread-info} command should be used instead.
28798 @subsubheading @value{GDBN} Command
28800 Part of @samp{info threads} supplies the same information.
28802 @subsubheading Example
28807 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28808 current-thread-id="1",number-of-threads="3"
28813 @subheading The @code{-thread-select} Command
28814 @findex -thread-select
28816 @subsubheading Synopsis
28819 -thread-select @var{threadnum}
28822 Make @var{threadnum} the current thread. It prints the number of the new
28823 current thread, and the topmost frame for that thread.
28825 This command is deprecated in favor of explicitly using the
28826 @samp{--thread} option to each command.
28828 @subsubheading @value{GDBN} Command
28830 The corresponding @value{GDBN} command is @samp{thread}.
28832 @subsubheading Example
28839 *stopped,reason="end-stepping-range",thread-id="2",line="187",
28840 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
28844 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28845 number-of-threads="3"
28848 ^done,new-thread-id="3",
28849 frame=@{level="0",func="vprintf",
28850 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
28851 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
28855 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28856 @node GDB/MI Ada Tasking Commands
28857 @section @sc{gdb/mi} Ada Tasking Commands
28859 @subheading The @code{-ada-task-info} Command
28860 @findex -ada-task-info
28862 @subsubheading Synopsis
28865 -ada-task-info [ @var{task-id} ]
28868 Reports information about either a specific Ada task, if the
28869 @var{task-id} parameter is present, or about all Ada tasks.
28871 @subsubheading @value{GDBN} Command
28873 The @samp{info tasks} command prints the same information
28874 about all Ada tasks (@pxref{Ada Tasks}).
28876 @subsubheading Result
28878 The result is a table of Ada tasks. The following columns are
28879 defined for each Ada task:
28883 This field exists only for the current thread. It has the value @samp{*}.
28886 The identifier that @value{GDBN} uses to refer to the Ada task.
28889 The identifier that the target uses to refer to the Ada task.
28892 The identifier of the thread corresponding to the Ada task.
28894 This field should always exist, as Ada tasks are always implemented
28895 on top of a thread. But if @value{GDBN} cannot find this corresponding
28896 thread for any reason, the field is omitted.
28899 This field exists only when the task was created by another task.
28900 In this case, it provides the ID of the parent task.
28903 The base priority of the task.
28906 The current state of the task. For a detailed description of the
28907 possible states, see @ref{Ada Tasks}.
28910 The name of the task.
28914 @subsubheading Example
28918 ^done,tasks=@{nr_rows="3",nr_cols="8",
28919 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28920 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28921 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28922 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28923 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28924 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28925 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28926 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
28927 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
28928 state="Child Termination Wait",name="main_task"@}]@}
28932 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28933 @node GDB/MI Program Execution
28934 @section @sc{gdb/mi} Program Execution
28936 These are the asynchronous commands which generate the out-of-band
28937 record @samp{*stopped}. Currently @value{GDBN} only really executes
28938 asynchronously with remote targets and this interaction is mimicked in
28941 @subheading The @code{-exec-continue} Command
28942 @findex -exec-continue
28944 @subsubheading Synopsis
28947 -exec-continue [--reverse] [--all|--thread-group N]
28950 Resumes the execution of the inferior program, which will continue
28951 to execute until it reaches a debugger stop event. If the
28952 @samp{--reverse} option is specified, execution resumes in reverse until
28953 it reaches a stop event. Stop events may include
28956 breakpoints or watchpoints
28958 signals or exceptions
28960 the end of the process (or its beginning under @samp{--reverse})
28962 the end or beginning of a replay log if one is being used.
28964 In all-stop mode (@pxref{All-Stop
28965 Mode}), may resume only one thread, or all threads, depending on the
28966 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28967 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28968 ignored in all-stop mode. If the @samp{--thread-group} options is
28969 specified, then all threads in that thread group are resumed.
28971 @subsubheading @value{GDBN} Command
28973 The corresponding @value{GDBN} corresponding is @samp{continue}.
28975 @subsubheading Example
28982 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28983 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28989 @subheading The @code{-exec-finish} Command
28990 @findex -exec-finish
28992 @subsubheading Synopsis
28995 -exec-finish [--reverse]
28998 Resumes the execution of the inferior program until the current
28999 function is exited. Displays the results returned by the function.
29000 If the @samp{--reverse} option is specified, resumes the reverse
29001 execution of the inferior program until the point where current
29002 function was called.
29004 @subsubheading @value{GDBN} Command
29006 The corresponding @value{GDBN} command is @samp{finish}.
29008 @subsubheading Example
29010 Function returning @code{void}.
29017 *stopped,reason="function-finished",frame=@{func="main",args=[],
29018 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
29022 Function returning other than @code{void}. The name of the internal
29023 @value{GDBN} variable storing the result is printed, together with the
29030 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29031 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29032 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29033 gdb-result-var="$1",return-value="0"
29038 @subheading The @code{-exec-interrupt} Command
29039 @findex -exec-interrupt
29041 @subsubheading Synopsis
29044 -exec-interrupt [--all|--thread-group N]
29047 Interrupts the background execution of the target. Note how the token
29048 associated with the stop message is the one for the execution command
29049 that has been interrupted. The token for the interrupt itself only
29050 appears in the @samp{^done} output. If the user is trying to
29051 interrupt a non-running program, an error message will be printed.
29053 Note that when asynchronous execution is enabled, this command is
29054 asynchronous just like other execution commands. That is, first the
29055 @samp{^done} response will be printed, and the target stop will be
29056 reported after that using the @samp{*stopped} notification.
29058 In non-stop mode, only the context thread is interrupted by default.
29059 All threads (in all inferiors) will be interrupted if the
29060 @samp{--all} option is specified. If the @samp{--thread-group}
29061 option is specified, all threads in that group will be interrupted.
29063 @subsubheading @value{GDBN} Command
29065 The corresponding @value{GDBN} command is @samp{interrupt}.
29067 @subsubheading Example
29078 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29079 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29080 fullname="/home/foo/bar/try.c",line="13"@}
29085 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29089 @subheading The @code{-exec-jump} Command
29092 @subsubheading Synopsis
29095 -exec-jump @var{location}
29098 Resumes execution of the inferior program at the location specified by
29099 parameter. @xref{Specify Location}, for a description of the
29100 different forms of @var{location}.
29102 @subsubheading @value{GDBN} Command
29104 The corresponding @value{GDBN} command is @samp{jump}.
29106 @subsubheading Example
29109 -exec-jump foo.c:10
29110 *running,thread-id="all"
29115 @subheading The @code{-exec-next} Command
29118 @subsubheading Synopsis
29121 -exec-next [--reverse]
29124 Resumes execution of the inferior program, stopping when the beginning
29125 of the next source line is reached.
29127 If the @samp{--reverse} option is specified, resumes reverse execution
29128 of the inferior program, stopping at the beginning of the previous
29129 source line. If you issue this command on the first line of a
29130 function, it will take you back to the caller of that function, to the
29131 source line where the function was called.
29134 @subsubheading @value{GDBN} Command
29136 The corresponding @value{GDBN} command is @samp{next}.
29138 @subsubheading Example
29144 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29149 @subheading The @code{-exec-next-instruction} Command
29150 @findex -exec-next-instruction
29152 @subsubheading Synopsis
29155 -exec-next-instruction [--reverse]
29158 Executes one machine instruction. If the instruction is a function
29159 call, continues until the function returns. If the program stops at an
29160 instruction in the middle of a source line, the address will be
29163 If the @samp{--reverse} option is specified, resumes reverse execution
29164 of the inferior program, stopping at the previous instruction. If the
29165 previously executed instruction was a return from another function,
29166 it will continue to execute in reverse until the call to that function
29167 (from the current stack frame) is reached.
29169 @subsubheading @value{GDBN} Command
29171 The corresponding @value{GDBN} command is @samp{nexti}.
29173 @subsubheading Example
29177 -exec-next-instruction
29181 *stopped,reason="end-stepping-range",
29182 addr="0x000100d4",line="5",file="hello.c"
29187 @subheading The @code{-exec-return} Command
29188 @findex -exec-return
29190 @subsubheading Synopsis
29196 Makes current function return immediately. Doesn't execute the inferior.
29197 Displays the new current frame.
29199 @subsubheading @value{GDBN} Command
29201 The corresponding @value{GDBN} command is @samp{return}.
29203 @subsubheading Example
29207 200-break-insert callee4
29208 200^done,bkpt=@{number="1",addr="0x00010734",
29209 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29214 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29215 frame=@{func="callee4",args=[],
29216 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29217 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29223 111^done,frame=@{level="0",func="callee3",
29224 args=[@{name="strarg",
29225 value="0x11940 \"A string argument.\""@}],
29226 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29227 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29232 @subheading The @code{-exec-run} Command
29235 @subsubheading Synopsis
29238 -exec-run [--all | --thread-group N]
29241 Starts execution of the inferior from the beginning. The inferior
29242 executes until either a breakpoint is encountered or the program
29243 exits. In the latter case the output will include an exit code, if
29244 the program has exited exceptionally.
29246 When no option is specified, the current inferior is started. If the
29247 @samp{--thread-group} option is specified, it should refer to a thread
29248 group of type @samp{process}, and that thread group will be started.
29249 If the @samp{--all} option is specified, then all inferiors will be started.
29251 @subsubheading @value{GDBN} Command
29253 The corresponding @value{GDBN} command is @samp{run}.
29255 @subsubheading Examples
29260 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29265 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29266 frame=@{func="main",args=[],file="recursive2.c",
29267 fullname="/home/foo/bar/recursive2.c",line="4"@}
29272 Program exited normally:
29280 *stopped,reason="exited-normally"
29285 Program exited exceptionally:
29293 *stopped,reason="exited",exit-code="01"
29297 Another way the program can terminate is if it receives a signal such as
29298 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29302 *stopped,reason="exited-signalled",signal-name="SIGINT",
29303 signal-meaning="Interrupt"
29307 @c @subheading -exec-signal
29310 @subheading The @code{-exec-step} Command
29313 @subsubheading Synopsis
29316 -exec-step [--reverse]
29319 Resumes execution of the inferior program, stopping when the beginning
29320 of the next source line is reached, if the next source line is not a
29321 function call. If it is, stop at the first instruction of the called
29322 function. If the @samp{--reverse} option is specified, resumes reverse
29323 execution of the inferior program, stopping at the beginning of the
29324 previously executed source line.
29326 @subsubheading @value{GDBN} Command
29328 The corresponding @value{GDBN} command is @samp{step}.
29330 @subsubheading Example
29332 Stepping into a function:
29338 *stopped,reason="end-stepping-range",
29339 frame=@{func="foo",args=[@{name="a",value="10"@},
29340 @{name="b",value="0"@}],file="recursive2.c",
29341 fullname="/home/foo/bar/recursive2.c",line="11"@}
29351 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
29356 @subheading The @code{-exec-step-instruction} Command
29357 @findex -exec-step-instruction
29359 @subsubheading Synopsis
29362 -exec-step-instruction [--reverse]
29365 Resumes the inferior which executes one machine instruction. If the
29366 @samp{--reverse} option is specified, resumes reverse execution of the
29367 inferior program, stopping at the previously executed instruction.
29368 The output, once @value{GDBN} has stopped, will vary depending on
29369 whether we have stopped in the middle of a source line or not. In the
29370 former case, the address at which the program stopped will be printed
29373 @subsubheading @value{GDBN} Command
29375 The corresponding @value{GDBN} command is @samp{stepi}.
29377 @subsubheading Example
29381 -exec-step-instruction
29385 *stopped,reason="end-stepping-range",
29386 frame=@{func="foo",args=[],file="try.c",
29387 fullname="/home/foo/bar/try.c",line="10"@}
29389 -exec-step-instruction
29393 *stopped,reason="end-stepping-range",
29394 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
29395 fullname="/home/foo/bar/try.c",line="10"@}
29400 @subheading The @code{-exec-until} Command
29401 @findex -exec-until
29403 @subsubheading Synopsis
29406 -exec-until [ @var{location} ]
29409 Executes the inferior until the @var{location} specified in the
29410 argument is reached. If there is no argument, the inferior executes
29411 until a source line greater than the current one is reached. The
29412 reason for stopping in this case will be @samp{location-reached}.
29414 @subsubheading @value{GDBN} Command
29416 The corresponding @value{GDBN} command is @samp{until}.
29418 @subsubheading Example
29422 -exec-until recursive2.c:6
29426 *stopped,reason="location-reached",frame=@{func="main",args=[],
29427 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
29432 @subheading -file-clear
29433 Is this going away????
29436 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29437 @node GDB/MI Stack Manipulation
29438 @section @sc{gdb/mi} Stack Manipulation Commands
29441 @subheading The @code{-stack-info-frame} Command
29442 @findex -stack-info-frame
29444 @subsubheading Synopsis
29450 Get info on the selected frame.
29452 @subsubheading @value{GDBN} Command
29454 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
29455 (without arguments).
29457 @subsubheading Example
29462 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
29463 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29464 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
29468 @subheading The @code{-stack-info-depth} Command
29469 @findex -stack-info-depth
29471 @subsubheading Synopsis
29474 -stack-info-depth [ @var{max-depth} ]
29477 Return the depth of the stack. If the integer argument @var{max-depth}
29478 is specified, do not count beyond @var{max-depth} frames.
29480 @subsubheading @value{GDBN} Command
29482 There's no equivalent @value{GDBN} command.
29484 @subsubheading Example
29486 For a stack with frame levels 0 through 11:
29493 -stack-info-depth 4
29496 -stack-info-depth 12
29499 -stack-info-depth 11
29502 -stack-info-depth 13
29507 @subheading The @code{-stack-list-arguments} Command
29508 @findex -stack-list-arguments
29510 @subsubheading Synopsis
29513 -stack-list-arguments @var{print-values}
29514 [ @var{low-frame} @var{high-frame} ]
29517 Display a list of the arguments for the frames between @var{low-frame}
29518 and @var{high-frame} (inclusive). If @var{low-frame} and
29519 @var{high-frame} are not provided, list the arguments for the whole
29520 call stack. If the two arguments are equal, show the single frame
29521 at the corresponding level. It is an error if @var{low-frame} is
29522 larger than the actual number of frames. On the other hand,
29523 @var{high-frame} may be larger than the actual number of frames, in
29524 which case only existing frames will be returned.
29526 If @var{print-values} is 0 or @code{--no-values}, print only the names of
29527 the variables; if it is 1 or @code{--all-values}, print also their
29528 values; and if it is 2 or @code{--simple-values}, print the name,
29529 type and value for simple data types, and the name and type for arrays,
29530 structures and unions.
29532 Use of this command to obtain arguments in a single frame is
29533 deprecated in favor of the @samp{-stack-list-variables} command.
29535 @subsubheading @value{GDBN} Command
29537 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
29538 @samp{gdb_get_args} command which partially overlaps with the
29539 functionality of @samp{-stack-list-arguments}.
29541 @subsubheading Example
29548 frame=@{level="0",addr="0x00010734",func="callee4",
29549 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29550 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
29551 frame=@{level="1",addr="0x0001076c",func="callee3",
29552 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29553 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
29554 frame=@{level="2",addr="0x0001078c",func="callee2",
29555 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29556 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
29557 frame=@{level="3",addr="0x000107b4",func="callee1",
29558 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29559 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
29560 frame=@{level="4",addr="0x000107e0",func="main",
29561 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29562 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
29564 -stack-list-arguments 0
29567 frame=@{level="0",args=[]@},
29568 frame=@{level="1",args=[name="strarg"]@},
29569 frame=@{level="2",args=[name="intarg",name="strarg"]@},
29570 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
29571 frame=@{level="4",args=[]@}]
29573 -stack-list-arguments 1
29576 frame=@{level="0",args=[]@},
29578 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29579 frame=@{level="2",args=[
29580 @{name="intarg",value="2"@},
29581 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29582 @{frame=@{level="3",args=[
29583 @{name="intarg",value="2"@},
29584 @{name="strarg",value="0x11940 \"A string argument.\""@},
29585 @{name="fltarg",value="3.5"@}]@},
29586 frame=@{level="4",args=[]@}]
29588 -stack-list-arguments 0 2 2
29589 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
29591 -stack-list-arguments 1 2 2
29592 ^done,stack-args=[frame=@{level="2",
29593 args=[@{name="intarg",value="2"@},
29594 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
29598 @c @subheading -stack-list-exception-handlers
29601 @subheading The @code{-stack-list-frames} Command
29602 @findex -stack-list-frames
29604 @subsubheading Synopsis
29607 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
29610 List the frames currently on the stack. For each frame it displays the
29615 The frame number, 0 being the topmost frame, i.e., the innermost function.
29617 The @code{$pc} value for that frame.
29621 File name of the source file where the function lives.
29622 @item @var{fullname}
29623 The full file name of the source file where the function lives.
29625 Line number corresponding to the @code{$pc}.
29627 The shared library where this function is defined. This is only given
29628 if the frame's function is not known.
29631 If invoked without arguments, this command prints a backtrace for the
29632 whole stack. If given two integer arguments, it shows the frames whose
29633 levels are between the two arguments (inclusive). If the two arguments
29634 are equal, it shows the single frame at the corresponding level. It is
29635 an error if @var{low-frame} is larger than the actual number of
29636 frames. On the other hand, @var{high-frame} may be larger than the
29637 actual number of frames, in which case only existing frames will be returned.
29639 @subsubheading @value{GDBN} Command
29641 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
29643 @subsubheading Example
29645 Full stack backtrace:
29651 [frame=@{level="0",addr="0x0001076c",func="foo",
29652 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
29653 frame=@{level="1",addr="0x000107a4",func="foo",
29654 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29655 frame=@{level="2",addr="0x000107a4",func="foo",
29656 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29657 frame=@{level="3",addr="0x000107a4",func="foo",
29658 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29659 frame=@{level="4",addr="0x000107a4",func="foo",
29660 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29661 frame=@{level="5",addr="0x000107a4",func="foo",
29662 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29663 frame=@{level="6",addr="0x000107a4",func="foo",
29664 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29665 frame=@{level="7",addr="0x000107a4",func="foo",
29666 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29667 frame=@{level="8",addr="0x000107a4",func="foo",
29668 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29669 frame=@{level="9",addr="0x000107a4",func="foo",
29670 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29671 frame=@{level="10",addr="0x000107a4",func="foo",
29672 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29673 frame=@{level="11",addr="0x00010738",func="main",
29674 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
29678 Show frames between @var{low_frame} and @var{high_frame}:
29682 -stack-list-frames 3 5
29684 [frame=@{level="3",addr="0x000107a4",func="foo",
29685 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29686 frame=@{level="4",addr="0x000107a4",func="foo",
29687 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29688 frame=@{level="5",addr="0x000107a4",func="foo",
29689 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29693 Show a single frame:
29697 -stack-list-frames 3 3
29699 [frame=@{level="3",addr="0x000107a4",func="foo",
29700 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29705 @subheading The @code{-stack-list-locals} Command
29706 @findex -stack-list-locals
29708 @subsubheading Synopsis
29711 -stack-list-locals @var{print-values}
29714 Display the local variable names for the selected frame. If
29715 @var{print-values} is 0 or @code{--no-values}, print only the names of
29716 the variables; if it is 1 or @code{--all-values}, print also their
29717 values; and if it is 2 or @code{--simple-values}, print the name,
29718 type and value for simple data types, and the name and type for arrays,
29719 structures and unions. In this last case, a frontend can immediately
29720 display the value of simple data types and create variable objects for
29721 other data types when the user wishes to explore their values in
29724 This command is deprecated in favor of the
29725 @samp{-stack-list-variables} command.
29727 @subsubheading @value{GDBN} Command
29729 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29731 @subsubheading Example
29735 -stack-list-locals 0
29736 ^done,locals=[name="A",name="B",name="C"]
29738 -stack-list-locals --all-values
29739 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29740 @{name="C",value="@{1, 2, 3@}"@}]
29741 -stack-list-locals --simple-values
29742 ^done,locals=[@{name="A",type="int",value="1"@},
29743 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29747 @subheading The @code{-stack-list-variables} Command
29748 @findex -stack-list-variables
29750 @subsubheading Synopsis
29753 -stack-list-variables @var{print-values}
29756 Display the names of local variables and function arguments for the selected frame. If
29757 @var{print-values} is 0 or @code{--no-values}, print only the names of
29758 the variables; if it is 1 or @code{--all-values}, print also their
29759 values; and if it is 2 or @code{--simple-values}, print the name,
29760 type and value for simple data types, and the name and type for arrays,
29761 structures and unions.
29763 @subsubheading Example
29767 -stack-list-variables --thread 1 --frame 0 --all-values
29768 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
29773 @subheading The @code{-stack-select-frame} Command
29774 @findex -stack-select-frame
29776 @subsubheading Synopsis
29779 -stack-select-frame @var{framenum}
29782 Change the selected frame. Select a different frame @var{framenum} on
29785 This command in deprecated in favor of passing the @samp{--frame}
29786 option to every command.
29788 @subsubheading @value{GDBN} Command
29790 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
29791 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
29793 @subsubheading Example
29797 -stack-select-frame 2
29802 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29803 @node GDB/MI Variable Objects
29804 @section @sc{gdb/mi} Variable Objects
29808 @subheading Motivation for Variable Objects in @sc{gdb/mi}
29810 For the implementation of a variable debugger window (locals, watched
29811 expressions, etc.), we are proposing the adaptation of the existing code
29812 used by @code{Insight}.
29814 The two main reasons for that are:
29818 It has been proven in practice (it is already on its second generation).
29821 It will shorten development time (needless to say how important it is
29825 The original interface was designed to be used by Tcl code, so it was
29826 slightly changed so it could be used through @sc{gdb/mi}. This section
29827 describes the @sc{gdb/mi} operations that will be available and gives some
29828 hints about their use.
29830 @emph{Note}: In addition to the set of operations described here, we
29831 expect the @sc{gui} implementation of a variable window to require, at
29832 least, the following operations:
29835 @item @code{-gdb-show} @code{output-radix}
29836 @item @code{-stack-list-arguments}
29837 @item @code{-stack-list-locals}
29838 @item @code{-stack-select-frame}
29843 @subheading Introduction to Variable Objects
29845 @cindex variable objects in @sc{gdb/mi}
29847 Variable objects are "object-oriented" MI interface for examining and
29848 changing values of expressions. Unlike some other MI interfaces that
29849 work with expressions, variable objects are specifically designed for
29850 simple and efficient presentation in the frontend. A variable object
29851 is identified by string name. When a variable object is created, the
29852 frontend specifies the expression for that variable object. The
29853 expression can be a simple variable, or it can be an arbitrary complex
29854 expression, and can even involve CPU registers. After creating a
29855 variable object, the frontend can invoke other variable object
29856 operations---for example to obtain or change the value of a variable
29857 object, or to change display format.
29859 Variable objects have hierarchical tree structure. Any variable object
29860 that corresponds to a composite type, such as structure in C, has
29861 a number of child variable objects, for example corresponding to each
29862 element of a structure. A child variable object can itself have
29863 children, recursively. Recursion ends when we reach
29864 leaf variable objects, which always have built-in types. Child variable
29865 objects are created only by explicit request, so if a frontend
29866 is not interested in the children of a particular variable object, no
29867 child will be created.
29869 For a leaf variable object it is possible to obtain its value as a
29870 string, or set the value from a string. String value can be also
29871 obtained for a non-leaf variable object, but it's generally a string
29872 that only indicates the type of the object, and does not list its
29873 contents. Assignment to a non-leaf variable object is not allowed.
29875 A frontend does not need to read the values of all variable objects each time
29876 the program stops. Instead, MI provides an update command that lists all
29877 variable objects whose values has changed since the last update
29878 operation. This considerably reduces the amount of data that must
29879 be transferred to the frontend. As noted above, children variable
29880 objects are created on demand, and only leaf variable objects have a
29881 real value. As result, gdb will read target memory only for leaf
29882 variables that frontend has created.
29884 The automatic update is not always desirable. For example, a frontend
29885 might want to keep a value of some expression for future reference,
29886 and never update it. For another example, fetching memory is
29887 relatively slow for embedded targets, so a frontend might want
29888 to disable automatic update for the variables that are either not
29889 visible on the screen, or ``closed''. This is possible using so
29890 called ``frozen variable objects''. Such variable objects are never
29891 implicitly updated.
29893 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
29894 fixed variable object, the expression is parsed when the variable
29895 object is created, including associating identifiers to specific
29896 variables. The meaning of expression never changes. For a floating
29897 variable object the values of variables whose names appear in the
29898 expressions are re-evaluated every time in the context of the current
29899 frame. Consider this example:
29904 struct work_state state;
29911 If a fixed variable object for the @code{state} variable is created in
29912 this function, and we enter the recursive call, the variable
29913 object will report the value of @code{state} in the top-level
29914 @code{do_work} invocation. On the other hand, a floating variable
29915 object will report the value of @code{state} in the current frame.
29917 If an expression specified when creating a fixed variable object
29918 refers to a local variable, the variable object becomes bound to the
29919 thread and frame in which the variable object is created. When such
29920 variable object is updated, @value{GDBN} makes sure that the
29921 thread/frame combination the variable object is bound to still exists,
29922 and re-evaluates the variable object in context of that thread/frame.
29924 The following is the complete set of @sc{gdb/mi} operations defined to
29925 access this functionality:
29927 @multitable @columnfractions .4 .6
29928 @item @strong{Operation}
29929 @tab @strong{Description}
29931 @item @code{-enable-pretty-printing}
29932 @tab enable Python-based pretty-printing
29933 @item @code{-var-create}
29934 @tab create a variable object
29935 @item @code{-var-delete}
29936 @tab delete the variable object and/or its children
29937 @item @code{-var-set-format}
29938 @tab set the display format of this variable
29939 @item @code{-var-show-format}
29940 @tab show the display format of this variable
29941 @item @code{-var-info-num-children}
29942 @tab tells how many children this object has
29943 @item @code{-var-list-children}
29944 @tab return a list of the object's children
29945 @item @code{-var-info-type}
29946 @tab show the type of this variable object
29947 @item @code{-var-info-expression}
29948 @tab print parent-relative expression that this variable object represents
29949 @item @code{-var-info-path-expression}
29950 @tab print full expression that this variable object represents
29951 @item @code{-var-show-attributes}
29952 @tab is this variable editable? does it exist here?
29953 @item @code{-var-evaluate-expression}
29954 @tab get the value of this variable
29955 @item @code{-var-assign}
29956 @tab set the value of this variable
29957 @item @code{-var-update}
29958 @tab update the variable and its children
29959 @item @code{-var-set-frozen}
29960 @tab set frozeness attribute
29961 @item @code{-var-set-update-range}
29962 @tab set range of children to display on update
29965 In the next subsection we describe each operation in detail and suggest
29966 how it can be used.
29968 @subheading Description And Use of Operations on Variable Objects
29970 @subheading The @code{-enable-pretty-printing} Command
29971 @findex -enable-pretty-printing
29974 -enable-pretty-printing
29977 @value{GDBN} allows Python-based visualizers to affect the output of the
29978 MI variable object commands. However, because there was no way to
29979 implement this in a fully backward-compatible way, a front end must
29980 request that this functionality be enabled.
29982 Once enabled, this feature cannot be disabled.
29984 Note that if Python support has not been compiled into @value{GDBN},
29985 this command will still succeed (and do nothing).
29987 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29988 may work differently in future versions of @value{GDBN}.
29990 @subheading The @code{-var-create} Command
29991 @findex -var-create
29993 @subsubheading Synopsis
29996 -var-create @{@var{name} | "-"@}
29997 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30000 This operation creates a variable object, which allows the monitoring of
30001 a variable, the result of an expression, a memory cell or a CPU
30004 The @var{name} parameter is the string by which the object can be
30005 referenced. It must be unique. If @samp{-} is specified, the varobj
30006 system will generate a string ``varNNNNNN'' automatically. It will be
30007 unique provided that one does not specify @var{name} of that format.
30008 The command fails if a duplicate name is found.
30010 The frame under which the expression should be evaluated can be
30011 specified by @var{frame-addr}. A @samp{*} indicates that the current
30012 frame should be used. A @samp{@@} indicates that a floating variable
30013 object must be created.
30015 @var{expression} is any expression valid on the current language set (must not
30016 begin with a @samp{*}), or one of the following:
30020 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30023 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30026 @samp{$@var{regname}} --- a CPU register name
30029 @cindex dynamic varobj
30030 A varobj's contents may be provided by a Python-based pretty-printer. In this
30031 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30032 have slightly different semantics in some cases. If the
30033 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30034 will never create a dynamic varobj. This ensures backward
30035 compatibility for existing clients.
30037 @subsubheading Result
30039 This operation returns attributes of the newly-created varobj. These
30044 The name of the varobj.
30047 The number of children of the varobj. This number is not necessarily
30048 reliable for a dynamic varobj. Instead, you must examine the
30049 @samp{has_more} attribute.
30052 The varobj's scalar value. For a varobj whose type is some sort of
30053 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30054 will not be interesting.
30057 The varobj's type. This is a string representation of the type, as
30058 would be printed by the @value{GDBN} CLI. If @samp{print object}
30059 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30060 @emph{actual} (derived) type of the object is shown rather than the
30061 @emph{declared} one.
30064 If a variable object is bound to a specific thread, then this is the
30065 thread's identifier.
30068 For a dynamic varobj, this indicates whether there appear to be any
30069 children available. For a non-dynamic varobj, this will be 0.
30072 This attribute will be present and have the value @samp{1} if the
30073 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30074 then this attribute will not be present.
30077 A dynamic varobj can supply a display hint to the front end. The
30078 value comes directly from the Python pretty-printer object's
30079 @code{display_hint} method. @xref{Pretty Printing API}.
30082 Typical output will look like this:
30085 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30086 has_more="@var{has_more}"
30090 @subheading The @code{-var-delete} Command
30091 @findex -var-delete
30093 @subsubheading Synopsis
30096 -var-delete [ -c ] @var{name}
30099 Deletes a previously created variable object and all of its children.
30100 With the @samp{-c} option, just deletes the children.
30102 Returns an error if the object @var{name} is not found.
30105 @subheading The @code{-var-set-format} Command
30106 @findex -var-set-format
30108 @subsubheading Synopsis
30111 -var-set-format @var{name} @var{format-spec}
30114 Sets the output format for the value of the object @var{name} to be
30117 @anchor{-var-set-format}
30118 The syntax for the @var{format-spec} is as follows:
30121 @var{format-spec} @expansion{}
30122 @{binary | decimal | hexadecimal | octal | natural@}
30125 The natural format is the default format choosen automatically
30126 based on the variable type (like decimal for an @code{int}, hex
30127 for pointers, etc.).
30129 For a variable with children, the format is set only on the
30130 variable itself, and the children are not affected.
30132 @subheading The @code{-var-show-format} Command
30133 @findex -var-show-format
30135 @subsubheading Synopsis
30138 -var-show-format @var{name}
30141 Returns the format used to display the value of the object @var{name}.
30144 @var{format} @expansion{}
30149 @subheading The @code{-var-info-num-children} Command
30150 @findex -var-info-num-children
30152 @subsubheading Synopsis
30155 -var-info-num-children @var{name}
30158 Returns the number of children of a variable object @var{name}:
30164 Note that this number is not completely reliable for a dynamic varobj.
30165 It will return the current number of children, but more children may
30169 @subheading The @code{-var-list-children} Command
30170 @findex -var-list-children
30172 @subsubheading Synopsis
30175 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30177 @anchor{-var-list-children}
30179 Return a list of the children of the specified variable object and
30180 create variable objects for them, if they do not already exist. With
30181 a single argument or if @var{print-values} has a value of 0 or
30182 @code{--no-values}, print only the names of the variables; if
30183 @var{print-values} is 1 or @code{--all-values}, also print their
30184 values; and if it is 2 or @code{--simple-values} print the name and
30185 value for simple data types and just the name for arrays, structures
30188 @var{from} and @var{to}, if specified, indicate the range of children
30189 to report. If @var{from} or @var{to} is less than zero, the range is
30190 reset and all children will be reported. Otherwise, children starting
30191 at @var{from} (zero-based) and up to and excluding @var{to} will be
30194 If a child range is requested, it will only affect the current call to
30195 @code{-var-list-children}, but not future calls to @code{-var-update}.
30196 For this, you must instead use @code{-var-set-update-range}. The
30197 intent of this approach is to enable a front end to implement any
30198 update approach it likes; for example, scrolling a view may cause the
30199 front end to request more children with @code{-var-list-children}, and
30200 then the front end could call @code{-var-set-update-range} with a
30201 different range to ensure that future updates are restricted to just
30204 For each child the following results are returned:
30209 Name of the variable object created for this child.
30212 The expression to be shown to the user by the front end to designate this child.
30213 For example this may be the name of a structure member.
30215 For a dynamic varobj, this value cannot be used to form an
30216 expression. There is no way to do this at all with a dynamic varobj.
30218 For C/C@t{++} structures there are several pseudo children returned to
30219 designate access qualifiers. For these pseudo children @var{exp} is
30220 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30221 type and value are not present.
30223 A dynamic varobj will not report the access qualifying
30224 pseudo-children, regardless of the language. This information is not
30225 available at all with a dynamic varobj.
30228 Number of children this child has. For a dynamic varobj, this will be
30232 The type of the child. If @samp{print object}
30233 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30234 @emph{actual} (derived) type of the object is shown rather than the
30235 @emph{declared} one.
30238 If values were requested, this is the value.
30241 If this variable object is associated with a thread, this is the thread id.
30242 Otherwise this result is not present.
30245 If the variable object is frozen, this variable will be present with a value of 1.
30248 The result may have its own attributes:
30252 A dynamic varobj can supply a display hint to the front end. The
30253 value comes directly from the Python pretty-printer object's
30254 @code{display_hint} method. @xref{Pretty Printing API}.
30257 This is an integer attribute which is nonzero if there are children
30258 remaining after the end of the selected range.
30261 @subsubheading Example
30265 -var-list-children n
30266 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30267 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30269 -var-list-children --all-values n
30270 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30271 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30275 @subheading The @code{-var-info-type} Command
30276 @findex -var-info-type
30278 @subsubheading Synopsis
30281 -var-info-type @var{name}
30284 Returns the type of the specified variable @var{name}. The type is
30285 returned as a string in the same format as it is output by the
30289 type=@var{typename}
30293 @subheading The @code{-var-info-expression} Command
30294 @findex -var-info-expression
30296 @subsubheading Synopsis
30299 -var-info-expression @var{name}
30302 Returns a string that is suitable for presenting this
30303 variable object in user interface. The string is generally
30304 not valid expression in the current language, and cannot be evaluated.
30306 For example, if @code{a} is an array, and variable object
30307 @code{A} was created for @code{a}, then we'll get this output:
30310 (gdb) -var-info-expression A.1
30311 ^done,lang="C",exp="1"
30315 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
30317 Note that the output of the @code{-var-list-children} command also
30318 includes those expressions, so the @code{-var-info-expression} command
30321 @subheading The @code{-var-info-path-expression} Command
30322 @findex -var-info-path-expression
30324 @subsubheading Synopsis
30327 -var-info-path-expression @var{name}
30330 Returns an expression that can be evaluated in the current
30331 context and will yield the same value that a variable object has.
30332 Compare this with the @code{-var-info-expression} command, which
30333 result can be used only for UI presentation. Typical use of
30334 the @code{-var-info-path-expression} command is creating a
30335 watchpoint from a variable object.
30337 This command is currently not valid for children of a dynamic varobj,
30338 and will give an error when invoked on one.
30340 For example, suppose @code{C} is a C@t{++} class, derived from class
30341 @code{Base}, and that the @code{Base} class has a member called
30342 @code{m_size}. Assume a variable @code{c} is has the type of
30343 @code{C} and a variable object @code{C} was created for variable
30344 @code{c}. Then, we'll get this output:
30346 (gdb) -var-info-path-expression C.Base.public.m_size
30347 ^done,path_expr=((Base)c).m_size)
30350 @subheading The @code{-var-show-attributes} Command
30351 @findex -var-show-attributes
30353 @subsubheading Synopsis
30356 -var-show-attributes @var{name}
30359 List attributes of the specified variable object @var{name}:
30362 status=@var{attr} [ ( ,@var{attr} )* ]
30366 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
30368 @subheading The @code{-var-evaluate-expression} Command
30369 @findex -var-evaluate-expression
30371 @subsubheading Synopsis
30374 -var-evaluate-expression [-f @var{format-spec}] @var{name}
30377 Evaluates the expression that is represented by the specified variable
30378 object and returns its value as a string. The format of the string
30379 can be specified with the @samp{-f} option. The possible values of
30380 this option are the same as for @code{-var-set-format}
30381 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
30382 the current display format will be used. The current display format
30383 can be changed using the @code{-var-set-format} command.
30389 Note that one must invoke @code{-var-list-children} for a variable
30390 before the value of a child variable can be evaluated.
30392 @subheading The @code{-var-assign} Command
30393 @findex -var-assign
30395 @subsubheading Synopsis
30398 -var-assign @var{name} @var{expression}
30401 Assigns the value of @var{expression} to the variable object specified
30402 by @var{name}. The object must be @samp{editable}. If the variable's
30403 value is altered by the assign, the variable will show up in any
30404 subsequent @code{-var-update} list.
30406 @subsubheading Example
30414 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
30418 @subheading The @code{-var-update} Command
30419 @findex -var-update
30421 @subsubheading Synopsis
30424 -var-update [@var{print-values}] @{@var{name} | "*"@}
30427 Reevaluate the expressions corresponding to the variable object
30428 @var{name} and all its direct and indirect children, and return the
30429 list of variable objects whose values have changed; @var{name} must
30430 be a root variable object. Here, ``changed'' means that the result of
30431 @code{-var-evaluate-expression} before and after the
30432 @code{-var-update} is different. If @samp{*} is used as the variable
30433 object names, all existing variable objects are updated, except
30434 for frozen ones (@pxref{-var-set-frozen}). The option
30435 @var{print-values} determines whether both names and values, or just
30436 names are printed. The possible values of this option are the same
30437 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
30438 recommended to use the @samp{--all-values} option, to reduce the
30439 number of MI commands needed on each program stop.
30441 With the @samp{*} parameter, if a variable object is bound to a
30442 currently running thread, it will not be updated, without any
30445 If @code{-var-set-update-range} was previously used on a varobj, then
30446 only the selected range of children will be reported.
30448 @code{-var-update} reports all the changed varobjs in a tuple named
30451 Each item in the change list is itself a tuple holding:
30455 The name of the varobj.
30458 If values were requested for this update, then this field will be
30459 present and will hold the value of the varobj.
30462 @anchor{-var-update}
30463 This field is a string which may take one of three values:
30467 The variable object's current value is valid.
30470 The variable object does not currently hold a valid value but it may
30471 hold one in the future if its associated expression comes back into
30475 The variable object no longer holds a valid value.
30476 This can occur when the executable file being debugged has changed,
30477 either through recompilation or by using the @value{GDBN} @code{file}
30478 command. The front end should normally choose to delete these variable
30482 In the future new values may be added to this list so the front should
30483 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
30486 This is only present if the varobj is still valid. If the type
30487 changed, then this will be the string @samp{true}; otherwise it will
30490 When a varobj's type changes, its children are also likely to have
30491 become incorrect. Therefore, the varobj's children are automatically
30492 deleted when this attribute is @samp{true}. Also, the varobj's update
30493 range, when set using the @code{-var-set-update-range} command, is
30497 If the varobj's type changed, then this field will be present and will
30500 @item new_num_children
30501 For a dynamic varobj, if the number of children changed, or if the
30502 type changed, this will be the new number of children.
30504 The @samp{numchild} field in other varobj responses is generally not
30505 valid for a dynamic varobj -- it will show the number of children that
30506 @value{GDBN} knows about, but because dynamic varobjs lazily
30507 instantiate their children, this will not reflect the number of
30508 children which may be available.
30510 The @samp{new_num_children} attribute only reports changes to the
30511 number of children known by @value{GDBN}. This is the only way to
30512 detect whether an update has removed children (which necessarily can
30513 only happen at the end of the update range).
30516 The display hint, if any.
30519 This is an integer value, which will be 1 if there are more children
30520 available outside the varobj's update range.
30523 This attribute will be present and have the value @samp{1} if the
30524 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30525 then this attribute will not be present.
30528 If new children were added to a dynamic varobj within the selected
30529 update range (as set by @code{-var-set-update-range}), then they will
30530 be listed in this attribute.
30533 @subsubheading Example
30540 -var-update --all-values var1
30541 ^done,changelist=[@{name="var1",value="3",in_scope="true",
30542 type_changed="false"@}]
30546 @subheading The @code{-var-set-frozen} Command
30547 @findex -var-set-frozen
30548 @anchor{-var-set-frozen}
30550 @subsubheading Synopsis
30553 -var-set-frozen @var{name} @var{flag}
30556 Set the frozenness flag on the variable object @var{name}. The
30557 @var{flag} parameter should be either @samp{1} to make the variable
30558 frozen or @samp{0} to make it unfrozen. If a variable object is
30559 frozen, then neither itself, nor any of its children, are
30560 implicitly updated by @code{-var-update} of
30561 a parent variable or by @code{-var-update *}. Only
30562 @code{-var-update} of the variable itself will update its value and
30563 values of its children. After a variable object is unfrozen, it is
30564 implicitly updated by all subsequent @code{-var-update} operations.
30565 Unfreezing a variable does not update it, only subsequent
30566 @code{-var-update} does.
30568 @subsubheading Example
30572 -var-set-frozen V 1
30577 @subheading The @code{-var-set-update-range} command
30578 @findex -var-set-update-range
30579 @anchor{-var-set-update-range}
30581 @subsubheading Synopsis
30584 -var-set-update-range @var{name} @var{from} @var{to}
30587 Set the range of children to be returned by future invocations of
30588 @code{-var-update}.
30590 @var{from} and @var{to} indicate the range of children to report. If
30591 @var{from} or @var{to} is less than zero, the range is reset and all
30592 children will be reported. Otherwise, children starting at @var{from}
30593 (zero-based) and up to and excluding @var{to} will be reported.
30595 @subsubheading Example
30599 -var-set-update-range V 1 2
30603 @subheading The @code{-var-set-visualizer} command
30604 @findex -var-set-visualizer
30605 @anchor{-var-set-visualizer}
30607 @subsubheading Synopsis
30610 -var-set-visualizer @var{name} @var{visualizer}
30613 Set a visualizer for the variable object @var{name}.
30615 @var{visualizer} is the visualizer to use. The special value
30616 @samp{None} means to disable any visualizer in use.
30618 If not @samp{None}, @var{visualizer} must be a Python expression.
30619 This expression must evaluate to a callable object which accepts a
30620 single argument. @value{GDBN} will call this object with the value of
30621 the varobj @var{name} as an argument (this is done so that the same
30622 Python pretty-printing code can be used for both the CLI and MI).
30623 When called, this object must return an object which conforms to the
30624 pretty-printing interface (@pxref{Pretty Printing API}).
30626 The pre-defined function @code{gdb.default_visualizer} may be used to
30627 select a visualizer by following the built-in process
30628 (@pxref{Selecting Pretty-Printers}). This is done automatically when
30629 a varobj is created, and so ordinarily is not needed.
30631 This feature is only available if Python support is enabled. The MI
30632 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
30633 can be used to check this.
30635 @subsubheading Example
30637 Resetting the visualizer:
30641 -var-set-visualizer V None
30645 Reselecting the default (type-based) visualizer:
30649 -var-set-visualizer V gdb.default_visualizer
30653 Suppose @code{SomeClass} is a visualizer class. A lambda expression
30654 can be used to instantiate this class for a varobj:
30658 -var-set-visualizer V "lambda val: SomeClass()"
30662 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30663 @node GDB/MI Data Manipulation
30664 @section @sc{gdb/mi} Data Manipulation
30666 @cindex data manipulation, in @sc{gdb/mi}
30667 @cindex @sc{gdb/mi}, data manipulation
30668 This section describes the @sc{gdb/mi} commands that manipulate data:
30669 examine memory and registers, evaluate expressions, etc.
30671 @c REMOVED FROM THE INTERFACE.
30672 @c @subheading -data-assign
30673 @c Change the value of a program variable. Plenty of side effects.
30674 @c @subsubheading GDB Command
30676 @c @subsubheading Example
30679 @subheading The @code{-data-disassemble} Command
30680 @findex -data-disassemble
30682 @subsubheading Synopsis
30686 [ -s @var{start-addr} -e @var{end-addr} ]
30687 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
30695 @item @var{start-addr}
30696 is the beginning address (or @code{$pc})
30697 @item @var{end-addr}
30699 @item @var{filename}
30700 is the name of the file to disassemble
30701 @item @var{linenum}
30702 is the line number to disassemble around
30704 is the number of disassembly lines to be produced. If it is -1,
30705 the whole function will be disassembled, in case no @var{end-addr} is
30706 specified. If @var{end-addr} is specified as a non-zero value, and
30707 @var{lines} is lower than the number of disassembly lines between
30708 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30709 displayed; if @var{lines} is higher than the number of lines between
30710 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30713 is either 0 (meaning only disassembly), 1 (meaning mixed source and
30714 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
30715 mixed source and disassembly with raw opcodes).
30718 @subsubheading Result
30720 The output for each instruction is composed of four fields:
30729 Note that whatever included in the instruction field, is not manipulated
30730 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
30732 @subsubheading @value{GDBN} Command
30734 There's no direct mapping from this command to the CLI.
30736 @subsubheading Example
30738 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
30742 -data-disassemble -s $pc -e "$pc + 20" -- 0
30745 @{address="0x000107c0",func-name="main",offset="4",
30746 inst="mov 2, %o0"@},
30747 @{address="0x000107c4",func-name="main",offset="8",
30748 inst="sethi %hi(0x11800), %o2"@},
30749 @{address="0x000107c8",func-name="main",offset="12",
30750 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30751 @{address="0x000107cc",func-name="main",offset="16",
30752 inst="sethi %hi(0x11800), %o2"@},
30753 @{address="0x000107d0",func-name="main",offset="20",
30754 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30758 Disassemble the whole @code{main} function. Line 32 is part of
30762 -data-disassemble -f basics.c -l 32 -- 0
30764 @{address="0x000107bc",func-name="main",offset="0",
30765 inst="save %sp, -112, %sp"@},
30766 @{address="0x000107c0",func-name="main",offset="4",
30767 inst="mov 2, %o0"@},
30768 @{address="0x000107c4",func-name="main",offset="8",
30769 inst="sethi %hi(0x11800), %o2"@},
30771 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30772 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30776 Disassemble 3 instructions from the start of @code{main}:
30780 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30782 @{address="0x000107bc",func-name="main",offset="0",
30783 inst="save %sp, -112, %sp"@},
30784 @{address="0x000107c0",func-name="main",offset="4",
30785 inst="mov 2, %o0"@},
30786 @{address="0x000107c4",func-name="main",offset="8",
30787 inst="sethi %hi(0x11800), %o2"@}]
30791 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30795 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30797 src_and_asm_line=@{line="31",
30798 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
30799 testsuite/gdb.mi/basics.c",line_asm_insn=[
30800 @{address="0x000107bc",func-name="main",offset="0",
30801 inst="save %sp, -112, %sp"@}]@},
30802 src_and_asm_line=@{line="32",
30803 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
30804 testsuite/gdb.mi/basics.c",line_asm_insn=[
30805 @{address="0x000107c0",func-name="main",offset="4",
30806 inst="mov 2, %o0"@},
30807 @{address="0x000107c4",func-name="main",offset="8",
30808 inst="sethi %hi(0x11800), %o2"@}]@}]
30813 @subheading The @code{-data-evaluate-expression} Command
30814 @findex -data-evaluate-expression
30816 @subsubheading Synopsis
30819 -data-evaluate-expression @var{expr}
30822 Evaluate @var{expr} as an expression. The expression could contain an
30823 inferior function call. The function call will execute synchronously.
30824 If the expression contains spaces, it must be enclosed in double quotes.
30826 @subsubheading @value{GDBN} Command
30828 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
30829 @samp{call}. In @code{gdbtk} only, there's a corresponding
30830 @samp{gdb_eval} command.
30832 @subsubheading Example
30834 In the following example, the numbers that precede the commands are the
30835 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
30836 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
30840 211-data-evaluate-expression A
30843 311-data-evaluate-expression &A
30844 311^done,value="0xefffeb7c"
30846 411-data-evaluate-expression A+3
30849 511-data-evaluate-expression "A + 3"
30855 @subheading The @code{-data-list-changed-registers} Command
30856 @findex -data-list-changed-registers
30858 @subsubheading Synopsis
30861 -data-list-changed-registers
30864 Display a list of the registers that have changed.
30866 @subsubheading @value{GDBN} Command
30868 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30869 has the corresponding command @samp{gdb_changed_register_list}.
30871 @subsubheading Example
30873 On a PPC MBX board:
30881 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
30882 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
30885 -data-list-changed-registers
30886 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
30887 "10","11","13","14","15","16","17","18","19","20","21","22","23",
30888 "24","25","26","27","28","30","31","64","65","66","67","69"]
30893 @subheading The @code{-data-list-register-names} Command
30894 @findex -data-list-register-names
30896 @subsubheading Synopsis
30899 -data-list-register-names [ ( @var{regno} )+ ]
30902 Show a list of register names for the current target. If no arguments
30903 are given, it shows a list of the names of all the registers. If
30904 integer numbers are given as arguments, it will print a list of the
30905 names of the registers corresponding to the arguments. To ensure
30906 consistency between a register name and its number, the output list may
30907 include empty register names.
30909 @subsubheading @value{GDBN} Command
30911 @value{GDBN} does not have a command which corresponds to
30912 @samp{-data-list-register-names}. In @code{gdbtk} there is a
30913 corresponding command @samp{gdb_regnames}.
30915 @subsubheading Example
30917 For the PPC MBX board:
30920 -data-list-register-names
30921 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
30922 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
30923 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
30924 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
30925 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
30926 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
30927 "", "pc","ps","cr","lr","ctr","xer"]
30929 -data-list-register-names 1 2 3
30930 ^done,register-names=["r1","r2","r3"]
30934 @subheading The @code{-data-list-register-values} Command
30935 @findex -data-list-register-values
30937 @subsubheading Synopsis
30940 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
30943 Display the registers' contents. @var{fmt} is the format according to
30944 which the registers' contents are to be returned, followed by an optional
30945 list of numbers specifying the registers to display. A missing list of
30946 numbers indicates that the contents of all the registers must be returned.
30948 Allowed formats for @var{fmt} are:
30965 @subsubheading @value{GDBN} Command
30967 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30968 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30970 @subsubheading Example
30972 For a PPC MBX board (note: line breaks are for readability only, they
30973 don't appear in the actual output):
30977 -data-list-register-values r 64 65
30978 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30979 @{number="65",value="0x00029002"@}]
30981 -data-list-register-values x
30982 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30983 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30984 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30985 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30986 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30987 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30988 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30989 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30990 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30991 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30992 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30993 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30994 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30995 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30996 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30997 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30998 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30999 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31000 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31001 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31002 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31003 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31004 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31005 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31006 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31007 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31008 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31009 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31010 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31011 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31012 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31013 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31014 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31015 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31016 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31017 @{number="69",value="0x20002b03"@}]
31022 @subheading The @code{-data-read-memory} Command
31023 @findex -data-read-memory
31025 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31027 @subsubheading Synopsis
31030 -data-read-memory [ -o @var{byte-offset} ]
31031 @var{address} @var{word-format} @var{word-size}
31032 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31039 @item @var{address}
31040 An expression specifying the address of the first memory word to be
31041 read. Complex expressions containing embedded white space should be
31042 quoted using the C convention.
31044 @item @var{word-format}
31045 The format to be used to print the memory words. The notation is the
31046 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31049 @item @var{word-size}
31050 The size of each memory word in bytes.
31052 @item @var{nr-rows}
31053 The number of rows in the output table.
31055 @item @var{nr-cols}
31056 The number of columns in the output table.
31059 If present, indicates that each row should include an @sc{ascii} dump. The
31060 value of @var{aschar} is used as a padding character when a byte is not a
31061 member of the printable @sc{ascii} character set (printable @sc{ascii}
31062 characters are those whose code is between 32 and 126, inclusively).
31064 @item @var{byte-offset}
31065 An offset to add to the @var{address} before fetching memory.
31068 This command displays memory contents as a table of @var{nr-rows} by
31069 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31070 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31071 (returned as @samp{total-bytes}). Should less than the requested number
31072 of bytes be returned by the target, the missing words are identified
31073 using @samp{N/A}. The number of bytes read from the target is returned
31074 in @samp{nr-bytes} and the starting address used to read memory in
31077 The address of the next/previous row or page is available in
31078 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31081 @subsubheading @value{GDBN} Command
31083 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31084 @samp{gdb_get_mem} memory read command.
31086 @subsubheading Example
31088 Read six bytes of memory starting at @code{bytes+6} but then offset by
31089 @code{-6} bytes. Format as three rows of two columns. One byte per
31090 word. Display each word in hex.
31094 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31095 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31096 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31097 prev-page="0x0000138a",memory=[
31098 @{addr="0x00001390",data=["0x00","0x01"]@},
31099 @{addr="0x00001392",data=["0x02","0x03"]@},
31100 @{addr="0x00001394",data=["0x04","0x05"]@}]
31104 Read two bytes of memory starting at address @code{shorts + 64} and
31105 display as a single word formatted in decimal.
31109 5-data-read-memory shorts+64 d 2 1 1
31110 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31111 next-row="0x00001512",prev-row="0x0000150e",
31112 next-page="0x00001512",prev-page="0x0000150e",memory=[
31113 @{addr="0x00001510",data=["128"]@}]
31117 Read thirty two bytes of memory starting at @code{bytes+16} and format
31118 as eight rows of four columns. Include a string encoding with @samp{x}
31119 used as the non-printable character.
31123 4-data-read-memory bytes+16 x 1 8 4 x
31124 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31125 next-row="0x000013c0",prev-row="0x0000139c",
31126 next-page="0x000013c0",prev-page="0x00001380",memory=[
31127 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31128 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31129 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31130 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31131 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31132 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31133 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31134 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31138 @subheading The @code{-data-read-memory-bytes} Command
31139 @findex -data-read-memory-bytes
31141 @subsubheading Synopsis
31144 -data-read-memory-bytes [ -o @var{byte-offset} ]
31145 @var{address} @var{count}
31152 @item @var{address}
31153 An expression specifying the address of the first memory word to be
31154 read. Complex expressions containing embedded white space should be
31155 quoted using the C convention.
31158 The number of bytes to read. This should be an integer literal.
31160 @item @var{byte-offset}
31161 The offsets in bytes relative to @var{address} at which to start
31162 reading. This should be an integer literal. This option is provided
31163 so that a frontend is not required to first evaluate address and then
31164 perform address arithmetics itself.
31168 This command attempts to read all accessible memory regions in the
31169 specified range. First, all regions marked as unreadable in the memory
31170 map (if one is defined) will be skipped. @xref{Memory Region
31171 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31172 regions. For each one, if reading full region results in an errors,
31173 @value{GDBN} will try to read a subset of the region.
31175 In general, every single byte in the region may be readable or not,
31176 and the only way to read every readable byte is to try a read at
31177 every address, which is not practical. Therefore, @value{GDBN} will
31178 attempt to read all accessible bytes at either beginning or the end
31179 of the region, using a binary division scheme. This heuristic works
31180 well for reading accross a memory map boundary. Note that if a region
31181 has a readable range that is neither at the beginning or the end,
31182 @value{GDBN} will not read it.
31184 The result record (@pxref{GDB/MI Result Records}) that is output of
31185 the command includes a field named @samp{memory} whose content is a
31186 list of tuples. Each tuple represent a successfully read memory block
31187 and has the following fields:
31191 The start address of the memory block, as hexadecimal literal.
31194 The end address of the memory block, as hexadecimal literal.
31197 The offset of the memory block, as hexadecimal literal, relative to
31198 the start address passed to @code{-data-read-memory-bytes}.
31201 The contents of the memory block, in hex.
31207 @subsubheading @value{GDBN} Command
31209 The corresponding @value{GDBN} command is @samp{x}.
31211 @subsubheading Example
31215 -data-read-memory-bytes &a 10
31216 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31218 contents="01000000020000000300"@}]
31223 @subheading The @code{-data-write-memory-bytes} Command
31224 @findex -data-write-memory-bytes
31226 @subsubheading Synopsis
31229 -data-write-memory-bytes @var{address} @var{contents}
31236 @item @var{address}
31237 An expression specifying the address of the first memory word to be
31238 read. Complex expressions containing embedded white space should be
31239 quoted using the C convention.
31241 @item @var{contents}
31242 The hex-encoded bytes to write.
31246 @subsubheading @value{GDBN} Command
31248 There's no corresponding @value{GDBN} command.
31250 @subsubheading Example
31254 -data-write-memory-bytes &a "aabbccdd"
31260 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31261 @node GDB/MI Tracepoint Commands
31262 @section @sc{gdb/mi} Tracepoint Commands
31264 The commands defined in this section implement MI support for
31265 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31267 @subheading The @code{-trace-find} Command
31268 @findex -trace-find
31270 @subsubheading Synopsis
31273 -trace-find @var{mode} [@var{parameters}@dots{}]
31276 Find a trace frame using criteria defined by @var{mode} and
31277 @var{parameters}. The following table lists permissible
31278 modes and their parameters. For details of operation, see @ref{tfind}.
31283 No parameters are required. Stops examining trace frames.
31286 An integer is required as parameter. Selects tracepoint frame with
31289 @item tracepoint-number
31290 An integer is required as parameter. Finds next
31291 trace frame that corresponds to tracepoint with the specified number.
31294 An address is required as parameter. Finds
31295 next trace frame that corresponds to any tracepoint at the specified
31298 @item pc-inside-range
31299 Two addresses are required as parameters. Finds next trace
31300 frame that corresponds to a tracepoint at an address inside the
31301 specified range. Both bounds are considered to be inside the range.
31303 @item pc-outside-range
31304 Two addresses are required as parameters. Finds
31305 next trace frame that corresponds to a tracepoint at an address outside
31306 the specified range. Both bounds are considered to be inside the range.
31309 Line specification is required as parameter. @xref{Specify Location}.
31310 Finds next trace frame that corresponds to a tracepoint at
31311 the specified location.
31315 If @samp{none} was passed as @var{mode}, the response does not
31316 have fields. Otherwise, the response may have the following fields:
31320 This field has either @samp{0} or @samp{1} as the value, depending
31321 on whether a matching tracepoint was found.
31324 The index of the found traceframe. This field is present iff
31325 the @samp{found} field has value of @samp{1}.
31328 The index of the found tracepoint. This field is present iff
31329 the @samp{found} field has value of @samp{1}.
31332 The information about the frame corresponding to the found trace
31333 frame. This field is present only if a trace frame was found.
31334 @xref{GDB/MI Frame Information}, for description of this field.
31338 @subsubheading @value{GDBN} Command
31340 The corresponding @value{GDBN} command is @samp{tfind}.
31342 @subheading -trace-define-variable
31343 @findex -trace-define-variable
31345 @subsubheading Synopsis
31348 -trace-define-variable @var{name} [ @var{value} ]
31351 Create trace variable @var{name} if it does not exist. If
31352 @var{value} is specified, sets the initial value of the specified
31353 trace variable to that value. Note that the @var{name} should start
31354 with the @samp{$} character.
31356 @subsubheading @value{GDBN} Command
31358 The corresponding @value{GDBN} command is @samp{tvariable}.
31360 @subheading -trace-list-variables
31361 @findex -trace-list-variables
31363 @subsubheading Synopsis
31366 -trace-list-variables
31369 Return a table of all defined trace variables. Each element of the
31370 table has the following fields:
31374 The name of the trace variable. This field is always present.
31377 The initial value. This is a 64-bit signed integer. This
31378 field is always present.
31381 The value the trace variable has at the moment. This is a 64-bit
31382 signed integer. This field is absent iff current value is
31383 not defined, for example if the trace was never run, or is
31388 @subsubheading @value{GDBN} Command
31390 The corresponding @value{GDBN} command is @samp{tvariables}.
31392 @subsubheading Example
31396 -trace-list-variables
31397 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
31398 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
31399 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
31400 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
31401 body=[variable=@{name="$trace_timestamp",initial="0"@}
31402 variable=@{name="$foo",initial="10",current="15"@}]@}
31406 @subheading -trace-save
31407 @findex -trace-save
31409 @subsubheading Synopsis
31412 -trace-save [-r ] @var{filename}
31415 Saves the collected trace data to @var{filename}. Without the
31416 @samp{-r} option, the data is downloaded from the target and saved
31417 in a local file. With the @samp{-r} option the target is asked
31418 to perform the save.
31420 @subsubheading @value{GDBN} Command
31422 The corresponding @value{GDBN} command is @samp{tsave}.
31425 @subheading -trace-start
31426 @findex -trace-start
31428 @subsubheading Synopsis
31434 Starts a tracing experiments. The result of this command does not
31437 @subsubheading @value{GDBN} Command
31439 The corresponding @value{GDBN} command is @samp{tstart}.
31441 @subheading -trace-status
31442 @findex -trace-status
31444 @subsubheading Synopsis
31450 Obtains the status of a tracing experiment. The result may include
31451 the following fields:
31456 May have a value of either @samp{0}, when no tracing operations are
31457 supported, @samp{1}, when all tracing operations are supported, or
31458 @samp{file} when examining trace file. In the latter case, examining
31459 of trace frame is possible but new tracing experiement cannot be
31460 started. This field is always present.
31463 May have a value of either @samp{0} or @samp{1} depending on whether
31464 tracing experiement is in progress on target. This field is present
31465 if @samp{supported} field is not @samp{0}.
31468 Report the reason why the tracing was stopped last time. This field
31469 may be absent iff tracing was never stopped on target yet. The
31470 value of @samp{request} means the tracing was stopped as result of
31471 the @code{-trace-stop} command. The value of @samp{overflow} means
31472 the tracing buffer is full. The value of @samp{disconnection} means
31473 tracing was automatically stopped when @value{GDBN} has disconnected.
31474 The value of @samp{passcount} means tracing was stopped when a
31475 tracepoint was passed a maximal number of times for that tracepoint.
31476 This field is present if @samp{supported} field is not @samp{0}.
31478 @item stopping-tracepoint
31479 The number of tracepoint whose passcount as exceeded. This field is
31480 present iff the @samp{stop-reason} field has the value of
31484 @itemx frames-created
31485 The @samp{frames} field is a count of the total number of trace frames
31486 in the trace buffer, while @samp{frames-created} is the total created
31487 during the run, including ones that were discarded, such as when a
31488 circular trace buffer filled up. Both fields are optional.
31492 These fields tell the current size of the tracing buffer and the
31493 remaining space. These fields are optional.
31496 The value of the circular trace buffer flag. @code{1} means that the
31497 trace buffer is circular and old trace frames will be discarded if
31498 necessary to make room, @code{0} means that the trace buffer is linear
31502 The value of the disconnected tracing flag. @code{1} means that
31503 tracing will continue after @value{GDBN} disconnects, @code{0} means
31504 that the trace run will stop.
31508 @subsubheading @value{GDBN} Command
31510 The corresponding @value{GDBN} command is @samp{tstatus}.
31512 @subheading -trace-stop
31513 @findex -trace-stop
31515 @subsubheading Synopsis
31521 Stops a tracing experiment. The result of this command has the same
31522 fields as @code{-trace-status}, except that the @samp{supported} and
31523 @samp{running} fields are not output.
31525 @subsubheading @value{GDBN} Command
31527 The corresponding @value{GDBN} command is @samp{tstop}.
31530 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31531 @node GDB/MI Symbol Query
31532 @section @sc{gdb/mi} Symbol Query Commands
31536 @subheading The @code{-symbol-info-address} Command
31537 @findex -symbol-info-address
31539 @subsubheading Synopsis
31542 -symbol-info-address @var{symbol}
31545 Describe where @var{symbol} is stored.
31547 @subsubheading @value{GDBN} Command
31549 The corresponding @value{GDBN} command is @samp{info address}.
31551 @subsubheading Example
31555 @subheading The @code{-symbol-info-file} Command
31556 @findex -symbol-info-file
31558 @subsubheading Synopsis
31564 Show the file for the symbol.
31566 @subsubheading @value{GDBN} Command
31568 There's no equivalent @value{GDBN} command. @code{gdbtk} has
31569 @samp{gdb_find_file}.
31571 @subsubheading Example
31575 @subheading The @code{-symbol-info-function} Command
31576 @findex -symbol-info-function
31578 @subsubheading Synopsis
31581 -symbol-info-function
31584 Show which function the symbol lives in.
31586 @subsubheading @value{GDBN} Command
31588 @samp{gdb_get_function} in @code{gdbtk}.
31590 @subsubheading Example
31594 @subheading The @code{-symbol-info-line} Command
31595 @findex -symbol-info-line
31597 @subsubheading Synopsis
31603 Show the core addresses of the code for a source line.
31605 @subsubheading @value{GDBN} Command
31607 The corresponding @value{GDBN} command is @samp{info line}.
31608 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31610 @subsubheading Example
31614 @subheading The @code{-symbol-info-symbol} Command
31615 @findex -symbol-info-symbol
31617 @subsubheading Synopsis
31620 -symbol-info-symbol @var{addr}
31623 Describe what symbol is at location @var{addr}.
31625 @subsubheading @value{GDBN} Command
31627 The corresponding @value{GDBN} command is @samp{info symbol}.
31629 @subsubheading Example
31633 @subheading The @code{-symbol-list-functions} Command
31634 @findex -symbol-list-functions
31636 @subsubheading Synopsis
31639 -symbol-list-functions
31642 List the functions in the executable.
31644 @subsubheading @value{GDBN} Command
31646 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31647 @samp{gdb_search} in @code{gdbtk}.
31649 @subsubheading Example
31654 @subheading The @code{-symbol-list-lines} Command
31655 @findex -symbol-list-lines
31657 @subsubheading Synopsis
31660 -symbol-list-lines @var{filename}
31663 Print the list of lines that contain code and their associated program
31664 addresses for the given source filename. The entries are sorted in
31665 ascending PC order.
31667 @subsubheading @value{GDBN} Command
31669 There is no corresponding @value{GDBN} command.
31671 @subsubheading Example
31674 -symbol-list-lines basics.c
31675 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
31681 @subheading The @code{-symbol-list-types} Command
31682 @findex -symbol-list-types
31684 @subsubheading Synopsis
31690 List all the type names.
31692 @subsubheading @value{GDBN} Command
31694 The corresponding commands are @samp{info types} in @value{GDBN},
31695 @samp{gdb_search} in @code{gdbtk}.
31697 @subsubheading Example
31701 @subheading The @code{-symbol-list-variables} Command
31702 @findex -symbol-list-variables
31704 @subsubheading Synopsis
31707 -symbol-list-variables
31710 List all the global and static variable names.
31712 @subsubheading @value{GDBN} Command
31714 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31716 @subsubheading Example
31720 @subheading The @code{-symbol-locate} Command
31721 @findex -symbol-locate
31723 @subsubheading Synopsis
31729 @subsubheading @value{GDBN} Command
31731 @samp{gdb_loc} in @code{gdbtk}.
31733 @subsubheading Example
31737 @subheading The @code{-symbol-type} Command
31738 @findex -symbol-type
31740 @subsubheading Synopsis
31743 -symbol-type @var{variable}
31746 Show type of @var{variable}.
31748 @subsubheading @value{GDBN} Command
31750 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
31751 @samp{gdb_obj_variable}.
31753 @subsubheading Example
31758 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31759 @node GDB/MI File Commands
31760 @section @sc{gdb/mi} File Commands
31762 This section describes the GDB/MI commands to specify executable file names
31763 and to read in and obtain symbol table information.
31765 @subheading The @code{-file-exec-and-symbols} Command
31766 @findex -file-exec-and-symbols
31768 @subsubheading Synopsis
31771 -file-exec-and-symbols @var{file}
31774 Specify the executable file to be debugged. This file is the one from
31775 which the symbol table is also read. If no file is specified, the
31776 command clears the executable and symbol information. If breakpoints
31777 are set when using this command with no arguments, @value{GDBN} will produce
31778 error messages. Otherwise, no output is produced, except a completion
31781 @subsubheading @value{GDBN} Command
31783 The corresponding @value{GDBN} command is @samp{file}.
31785 @subsubheading Example
31789 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31795 @subheading The @code{-file-exec-file} Command
31796 @findex -file-exec-file
31798 @subsubheading Synopsis
31801 -file-exec-file @var{file}
31804 Specify the executable file to be debugged. Unlike
31805 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
31806 from this file. If used without argument, @value{GDBN} clears the information
31807 about the executable file. No output is produced, except a completion
31810 @subsubheading @value{GDBN} Command
31812 The corresponding @value{GDBN} command is @samp{exec-file}.
31814 @subsubheading Example
31818 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31825 @subheading The @code{-file-list-exec-sections} Command
31826 @findex -file-list-exec-sections
31828 @subsubheading Synopsis
31831 -file-list-exec-sections
31834 List the sections of the current executable file.
31836 @subsubheading @value{GDBN} Command
31838 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31839 information as this command. @code{gdbtk} has a corresponding command
31840 @samp{gdb_load_info}.
31842 @subsubheading Example
31847 @subheading The @code{-file-list-exec-source-file} Command
31848 @findex -file-list-exec-source-file
31850 @subsubheading Synopsis
31853 -file-list-exec-source-file
31856 List the line number, the current source file, and the absolute path
31857 to the current source file for the current executable. The macro
31858 information field has a value of @samp{1} or @samp{0} depending on
31859 whether or not the file includes preprocessor macro information.
31861 @subsubheading @value{GDBN} Command
31863 The @value{GDBN} equivalent is @samp{info source}
31865 @subsubheading Example
31869 123-file-list-exec-source-file
31870 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31875 @subheading The @code{-file-list-exec-source-files} Command
31876 @findex -file-list-exec-source-files
31878 @subsubheading Synopsis
31881 -file-list-exec-source-files
31884 List the source files for the current executable.
31886 It will always output the filename, but only when @value{GDBN} can find
31887 the absolute file name of a source file, will it output the fullname.
31889 @subsubheading @value{GDBN} Command
31891 The @value{GDBN} equivalent is @samp{info sources}.
31892 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31894 @subsubheading Example
31897 -file-list-exec-source-files
31899 @{file=foo.c,fullname=/home/foo.c@},
31900 @{file=/home/bar.c,fullname=/home/bar.c@},
31901 @{file=gdb_could_not_find_fullpath.c@}]
31906 @subheading The @code{-file-list-shared-libraries} Command
31907 @findex -file-list-shared-libraries
31909 @subsubheading Synopsis
31912 -file-list-shared-libraries
31915 List the shared libraries in the program.
31917 @subsubheading @value{GDBN} Command
31919 The corresponding @value{GDBN} command is @samp{info shared}.
31921 @subsubheading Example
31925 @subheading The @code{-file-list-symbol-files} Command
31926 @findex -file-list-symbol-files
31928 @subsubheading Synopsis
31931 -file-list-symbol-files
31936 @subsubheading @value{GDBN} Command
31938 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31940 @subsubheading Example
31945 @subheading The @code{-file-symbol-file} Command
31946 @findex -file-symbol-file
31948 @subsubheading Synopsis
31951 -file-symbol-file @var{file}
31954 Read symbol table info from the specified @var{file} argument. When
31955 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31956 produced, except for a completion notification.
31958 @subsubheading @value{GDBN} Command
31960 The corresponding @value{GDBN} command is @samp{symbol-file}.
31962 @subsubheading Example
31966 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31972 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31973 @node GDB/MI Memory Overlay Commands
31974 @section @sc{gdb/mi} Memory Overlay Commands
31976 The memory overlay commands are not implemented.
31978 @c @subheading -overlay-auto
31980 @c @subheading -overlay-list-mapping-state
31982 @c @subheading -overlay-list-overlays
31984 @c @subheading -overlay-map
31986 @c @subheading -overlay-off
31988 @c @subheading -overlay-on
31990 @c @subheading -overlay-unmap
31992 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31993 @node GDB/MI Signal Handling Commands
31994 @section @sc{gdb/mi} Signal Handling Commands
31996 Signal handling commands are not implemented.
31998 @c @subheading -signal-handle
32000 @c @subheading -signal-list-handle-actions
32002 @c @subheading -signal-list-signal-types
32006 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32007 @node GDB/MI Target Manipulation
32008 @section @sc{gdb/mi} Target Manipulation Commands
32011 @subheading The @code{-target-attach} Command
32012 @findex -target-attach
32014 @subsubheading Synopsis
32017 -target-attach @var{pid} | @var{gid} | @var{file}
32020 Attach to a process @var{pid} or a file @var{file} outside of
32021 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32022 group, the id previously returned by
32023 @samp{-list-thread-groups --available} must be used.
32025 @subsubheading @value{GDBN} Command
32027 The corresponding @value{GDBN} command is @samp{attach}.
32029 @subsubheading Example
32033 =thread-created,id="1"
32034 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32040 @subheading The @code{-target-compare-sections} Command
32041 @findex -target-compare-sections
32043 @subsubheading Synopsis
32046 -target-compare-sections [ @var{section} ]
32049 Compare data of section @var{section} on target to the exec file.
32050 Without the argument, all sections are compared.
32052 @subsubheading @value{GDBN} Command
32054 The @value{GDBN} equivalent is @samp{compare-sections}.
32056 @subsubheading Example
32061 @subheading The @code{-target-detach} Command
32062 @findex -target-detach
32064 @subsubheading Synopsis
32067 -target-detach [ @var{pid} | @var{gid} ]
32070 Detach from the remote target which normally resumes its execution.
32071 If either @var{pid} or @var{gid} is specified, detaches from either
32072 the specified process, or specified thread group. There's no output.
32074 @subsubheading @value{GDBN} Command
32076 The corresponding @value{GDBN} command is @samp{detach}.
32078 @subsubheading Example
32088 @subheading The @code{-target-disconnect} Command
32089 @findex -target-disconnect
32091 @subsubheading Synopsis
32097 Disconnect from the remote target. There's no output and the target is
32098 generally not resumed.
32100 @subsubheading @value{GDBN} Command
32102 The corresponding @value{GDBN} command is @samp{disconnect}.
32104 @subsubheading Example
32114 @subheading The @code{-target-download} Command
32115 @findex -target-download
32117 @subsubheading Synopsis
32123 Loads the executable onto the remote target.
32124 It prints out an update message every half second, which includes the fields:
32128 The name of the section.
32130 The size of what has been sent so far for that section.
32132 The size of the section.
32134 The total size of what was sent so far (the current and the previous sections).
32136 The size of the overall executable to download.
32140 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32141 @sc{gdb/mi} Output Syntax}).
32143 In addition, it prints the name and size of the sections, as they are
32144 downloaded. These messages include the following fields:
32148 The name of the section.
32150 The size of the section.
32152 The size of the overall executable to download.
32156 At the end, a summary is printed.
32158 @subsubheading @value{GDBN} Command
32160 The corresponding @value{GDBN} command is @samp{load}.
32162 @subsubheading Example
32164 Note: each status message appears on a single line. Here the messages
32165 have been broken down so that they can fit onto a page.
32170 +download,@{section=".text",section-size="6668",total-size="9880"@}
32171 +download,@{section=".text",section-sent="512",section-size="6668",
32172 total-sent="512",total-size="9880"@}
32173 +download,@{section=".text",section-sent="1024",section-size="6668",
32174 total-sent="1024",total-size="9880"@}
32175 +download,@{section=".text",section-sent="1536",section-size="6668",
32176 total-sent="1536",total-size="9880"@}
32177 +download,@{section=".text",section-sent="2048",section-size="6668",
32178 total-sent="2048",total-size="9880"@}
32179 +download,@{section=".text",section-sent="2560",section-size="6668",
32180 total-sent="2560",total-size="9880"@}
32181 +download,@{section=".text",section-sent="3072",section-size="6668",
32182 total-sent="3072",total-size="9880"@}
32183 +download,@{section=".text",section-sent="3584",section-size="6668",
32184 total-sent="3584",total-size="9880"@}
32185 +download,@{section=".text",section-sent="4096",section-size="6668",
32186 total-sent="4096",total-size="9880"@}
32187 +download,@{section=".text",section-sent="4608",section-size="6668",
32188 total-sent="4608",total-size="9880"@}
32189 +download,@{section=".text",section-sent="5120",section-size="6668",
32190 total-sent="5120",total-size="9880"@}
32191 +download,@{section=".text",section-sent="5632",section-size="6668",
32192 total-sent="5632",total-size="9880"@}
32193 +download,@{section=".text",section-sent="6144",section-size="6668",
32194 total-sent="6144",total-size="9880"@}
32195 +download,@{section=".text",section-sent="6656",section-size="6668",
32196 total-sent="6656",total-size="9880"@}
32197 +download,@{section=".init",section-size="28",total-size="9880"@}
32198 +download,@{section=".fini",section-size="28",total-size="9880"@}
32199 +download,@{section=".data",section-size="3156",total-size="9880"@}
32200 +download,@{section=".data",section-sent="512",section-size="3156",
32201 total-sent="7236",total-size="9880"@}
32202 +download,@{section=".data",section-sent="1024",section-size="3156",
32203 total-sent="7748",total-size="9880"@}
32204 +download,@{section=".data",section-sent="1536",section-size="3156",
32205 total-sent="8260",total-size="9880"@}
32206 +download,@{section=".data",section-sent="2048",section-size="3156",
32207 total-sent="8772",total-size="9880"@}
32208 +download,@{section=".data",section-sent="2560",section-size="3156",
32209 total-sent="9284",total-size="9880"@}
32210 +download,@{section=".data",section-sent="3072",section-size="3156",
32211 total-sent="9796",total-size="9880"@}
32212 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32219 @subheading The @code{-target-exec-status} Command
32220 @findex -target-exec-status
32222 @subsubheading Synopsis
32225 -target-exec-status
32228 Provide information on the state of the target (whether it is running or
32229 not, for instance).
32231 @subsubheading @value{GDBN} Command
32233 There's no equivalent @value{GDBN} command.
32235 @subsubheading Example
32239 @subheading The @code{-target-list-available-targets} Command
32240 @findex -target-list-available-targets
32242 @subsubheading Synopsis
32245 -target-list-available-targets
32248 List the possible targets to connect to.
32250 @subsubheading @value{GDBN} Command
32252 The corresponding @value{GDBN} command is @samp{help target}.
32254 @subsubheading Example
32258 @subheading The @code{-target-list-current-targets} Command
32259 @findex -target-list-current-targets
32261 @subsubheading Synopsis
32264 -target-list-current-targets
32267 Describe the current target.
32269 @subsubheading @value{GDBN} Command
32271 The corresponding information is printed by @samp{info file} (among
32274 @subsubheading Example
32278 @subheading The @code{-target-list-parameters} Command
32279 @findex -target-list-parameters
32281 @subsubheading Synopsis
32284 -target-list-parameters
32290 @subsubheading @value{GDBN} Command
32294 @subsubheading Example
32298 @subheading The @code{-target-select} Command
32299 @findex -target-select
32301 @subsubheading Synopsis
32304 -target-select @var{type} @var{parameters @dots{}}
32307 Connect @value{GDBN} to the remote target. This command takes two args:
32311 The type of target, for instance @samp{remote}, etc.
32312 @item @var{parameters}
32313 Device names, host names and the like. @xref{Target Commands, ,
32314 Commands for Managing Targets}, for more details.
32317 The output is a connection notification, followed by the address at
32318 which the target program is, in the following form:
32321 ^connected,addr="@var{address}",func="@var{function name}",
32322 args=[@var{arg list}]
32325 @subsubheading @value{GDBN} Command
32327 The corresponding @value{GDBN} command is @samp{target}.
32329 @subsubheading Example
32333 -target-select remote /dev/ttya
32334 ^connected,addr="0xfe00a300",func="??",args=[]
32338 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32339 @node GDB/MI File Transfer Commands
32340 @section @sc{gdb/mi} File Transfer Commands
32343 @subheading The @code{-target-file-put} Command
32344 @findex -target-file-put
32346 @subsubheading Synopsis
32349 -target-file-put @var{hostfile} @var{targetfile}
32352 Copy file @var{hostfile} from the host system (the machine running
32353 @value{GDBN}) to @var{targetfile} on the target system.
32355 @subsubheading @value{GDBN} Command
32357 The corresponding @value{GDBN} command is @samp{remote put}.
32359 @subsubheading Example
32363 -target-file-put localfile remotefile
32369 @subheading The @code{-target-file-get} Command
32370 @findex -target-file-get
32372 @subsubheading Synopsis
32375 -target-file-get @var{targetfile} @var{hostfile}
32378 Copy file @var{targetfile} from the target system to @var{hostfile}
32379 on the host system.
32381 @subsubheading @value{GDBN} Command
32383 The corresponding @value{GDBN} command is @samp{remote get}.
32385 @subsubheading Example
32389 -target-file-get remotefile localfile
32395 @subheading The @code{-target-file-delete} Command
32396 @findex -target-file-delete
32398 @subsubheading Synopsis
32401 -target-file-delete @var{targetfile}
32404 Delete @var{targetfile} from the target system.
32406 @subsubheading @value{GDBN} Command
32408 The corresponding @value{GDBN} command is @samp{remote delete}.
32410 @subsubheading Example
32414 -target-file-delete remotefile
32420 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32421 @node GDB/MI Miscellaneous Commands
32422 @section Miscellaneous @sc{gdb/mi} Commands
32424 @c @subheading -gdb-complete
32426 @subheading The @code{-gdb-exit} Command
32429 @subsubheading Synopsis
32435 Exit @value{GDBN} immediately.
32437 @subsubheading @value{GDBN} Command
32439 Approximately corresponds to @samp{quit}.
32441 @subsubheading Example
32451 @subheading The @code{-exec-abort} Command
32452 @findex -exec-abort
32454 @subsubheading Synopsis
32460 Kill the inferior running program.
32462 @subsubheading @value{GDBN} Command
32464 The corresponding @value{GDBN} command is @samp{kill}.
32466 @subsubheading Example
32471 @subheading The @code{-gdb-set} Command
32474 @subsubheading Synopsis
32480 Set an internal @value{GDBN} variable.
32481 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32483 @subsubheading @value{GDBN} Command
32485 The corresponding @value{GDBN} command is @samp{set}.
32487 @subsubheading Example
32497 @subheading The @code{-gdb-show} Command
32500 @subsubheading Synopsis
32506 Show the current value of a @value{GDBN} variable.
32508 @subsubheading @value{GDBN} Command
32510 The corresponding @value{GDBN} command is @samp{show}.
32512 @subsubheading Example
32521 @c @subheading -gdb-source
32524 @subheading The @code{-gdb-version} Command
32525 @findex -gdb-version
32527 @subsubheading Synopsis
32533 Show version information for @value{GDBN}. Used mostly in testing.
32535 @subsubheading @value{GDBN} Command
32537 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
32538 default shows this information when you start an interactive session.
32540 @subsubheading Example
32542 @c This example modifies the actual output from GDB to avoid overfull
32548 ~Copyright 2000 Free Software Foundation, Inc.
32549 ~GDB is free software, covered by the GNU General Public License, and
32550 ~you are welcome to change it and/or distribute copies of it under
32551 ~ certain conditions.
32552 ~Type "show copying" to see the conditions.
32553 ~There is absolutely no warranty for GDB. Type "show warranty" for
32555 ~This GDB was configured as
32556 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32561 @subheading The @code{-list-features} Command
32562 @findex -list-features
32564 Returns a list of particular features of the MI protocol that
32565 this version of gdb implements. A feature can be a command,
32566 or a new field in an output of some command, or even an
32567 important bugfix. While a frontend can sometimes detect presence
32568 of a feature at runtime, it is easier to perform detection at debugger
32571 The command returns a list of strings, with each string naming an
32572 available feature. Each returned string is just a name, it does not
32573 have any internal structure. The list of possible feature names
32579 (gdb) -list-features
32580 ^done,result=["feature1","feature2"]
32583 The current list of features is:
32586 @item frozen-varobjs
32587 Indicates support for the @code{-var-set-frozen} command, as well
32588 as possible presense of the @code{frozen} field in the output
32589 of @code{-varobj-create}.
32590 @item pending-breakpoints
32591 Indicates support for the @option{-f} option to the @code{-break-insert}
32594 Indicates Python scripting support, Python-based
32595 pretty-printing commands, and possible presence of the
32596 @samp{display_hint} field in the output of @code{-var-list-children}
32598 Indicates support for the @code{-thread-info} command.
32599 @item data-read-memory-bytes
32600 Indicates support for the @code{-data-read-memory-bytes} and the
32601 @code{-data-write-memory-bytes} commands.
32602 @item breakpoint-notifications
32603 Indicates that changes to breakpoints and breakpoints created via the
32604 CLI will be announced via async records.
32605 @item ada-task-info
32606 Indicates support for the @code{-ada-task-info} command.
32609 @subheading The @code{-list-target-features} Command
32610 @findex -list-target-features
32612 Returns a list of particular features that are supported by the
32613 target. Those features affect the permitted MI commands, but
32614 unlike the features reported by the @code{-list-features} command, the
32615 features depend on which target GDB is using at the moment. Whenever
32616 a target can change, due to commands such as @code{-target-select},
32617 @code{-target-attach} or @code{-exec-run}, the list of target features
32618 may change, and the frontend should obtain it again.
32622 (gdb) -list-features
32623 ^done,result=["async"]
32626 The current list of features is:
32630 Indicates that the target is capable of asynchronous command
32631 execution, which means that @value{GDBN} will accept further commands
32632 while the target is running.
32635 Indicates that the target is capable of reverse execution.
32636 @xref{Reverse Execution}, for more information.
32640 @subheading The @code{-list-thread-groups} Command
32641 @findex -list-thread-groups
32643 @subheading Synopsis
32646 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
32649 Lists thread groups (@pxref{Thread groups}). When a single thread
32650 group is passed as the argument, lists the children of that group.
32651 When several thread group are passed, lists information about those
32652 thread groups. Without any parameters, lists information about all
32653 top-level thread groups.
32655 Normally, thread groups that are being debugged are reported.
32656 With the @samp{--available} option, @value{GDBN} reports thread groups
32657 available on the target.
32659 The output of this command may have either a @samp{threads} result or
32660 a @samp{groups} result. The @samp{thread} result has a list of tuples
32661 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
32662 Information}). The @samp{groups} result has a list of tuples as value,
32663 each tuple describing a thread group. If top-level groups are
32664 requested (that is, no parameter is passed), or when several groups
32665 are passed, the output always has a @samp{groups} result. The format
32666 of the @samp{group} result is described below.
32668 To reduce the number of roundtrips it's possible to list thread groups
32669 together with their children, by passing the @samp{--recurse} option
32670 and the recursion depth. Presently, only recursion depth of 1 is
32671 permitted. If this option is present, then every reported thread group
32672 will also include its children, either as @samp{group} or
32673 @samp{threads} field.
32675 In general, any combination of option and parameters is permitted, with
32676 the following caveats:
32680 When a single thread group is passed, the output will typically
32681 be the @samp{threads} result. Because threads may not contain
32682 anything, the @samp{recurse} option will be ignored.
32685 When the @samp{--available} option is passed, limited information may
32686 be available. In particular, the list of threads of a process might
32687 be inaccessible. Further, specifying specific thread groups might
32688 not give any performance advantage over listing all thread groups.
32689 The frontend should assume that @samp{-list-thread-groups --available}
32690 is always an expensive operation and cache the results.
32694 The @samp{groups} result is a list of tuples, where each tuple may
32695 have the following fields:
32699 Identifier of the thread group. This field is always present.
32700 The identifier is an opaque string; frontends should not try to
32701 convert it to an integer, even though it might look like one.
32704 The type of the thread group. At present, only @samp{process} is a
32708 The target-specific process identifier. This field is only present
32709 for thread groups of type @samp{process} and only if the process exists.
32712 The number of children this thread group has. This field may be
32713 absent for an available thread group.
32716 This field has a list of tuples as value, each tuple describing a
32717 thread. It may be present if the @samp{--recurse} option is
32718 specified, and it's actually possible to obtain the threads.
32721 This field is a list of integers, each identifying a core that one
32722 thread of the group is running on. This field may be absent if
32723 such information is not available.
32726 The name of the executable file that corresponds to this thread group.
32727 The field is only present for thread groups of type @samp{process},
32728 and only if there is a corresponding executable file.
32732 @subheading Example
32736 -list-thread-groups
32737 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32738 -list-thread-groups 17
32739 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32740 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32741 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32742 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32743 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32744 -list-thread-groups --available
32745 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32746 -list-thread-groups --available --recurse 1
32747 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32748 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32749 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32750 -list-thread-groups --available --recurse 1 17 18
32751 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32752 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32753 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32756 @subheading The @code{-info-os} Command
32759 @subsubheading Synopsis
32762 -info-os [ @var{type} ]
32765 If no argument is supplied, the command returns a table of available
32766 operating-system-specific information types. If one of these types is
32767 supplied as an argument @var{type}, then the command returns a table
32768 of data of that type.
32770 The types of information available depend on the target operating
32773 @subsubheading @value{GDBN} Command
32775 The corresponding @value{GDBN} command is @samp{info os}.
32777 @subsubheading Example
32779 When run on a @sc{gnu}/Linux system, the output will look something
32785 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
32786 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
32787 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
32788 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
32789 body=[item=@{col0="processes",col1="Listing of all processes",
32790 col2="Processes"@},
32791 item=@{col0="procgroups",col1="Listing of all process groups",
32792 col2="Process groups"@},
32793 item=@{col0="threads",col1="Listing of all threads",
32795 item=@{col0="files",col1="Listing of all file descriptors",
32796 col2="File descriptors"@},
32797 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
32799 item=@{col0="shm",col1="Listing of all shared-memory regions",
32800 col2="Shared-memory regions"@},
32801 item=@{col0="semaphores",col1="Listing of all semaphores",
32802 col2="Semaphores"@},
32803 item=@{col0="msg",col1="Listing of all message queues",
32804 col2="Message queues"@},
32805 item=@{col0="modules",col1="Listing of all loaded kernel modules",
32806 col2="Kernel modules"@}]@}
32809 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
32810 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
32811 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
32812 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
32813 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
32814 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
32815 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
32816 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
32818 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
32819 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
32823 (Note that the MI output here includes a @code{"Title"} column that
32824 does not appear in command-line @code{info os}; this column is useful
32825 for MI clients that want to enumerate the types of data, such as in a
32826 popup menu, but is needless clutter on the command line, and
32827 @code{info os} omits it.)
32829 @subheading The @code{-add-inferior} Command
32830 @findex -add-inferior
32832 @subheading Synopsis
32838 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32839 inferior is not associated with any executable. Such association may
32840 be established with the @samp{-file-exec-and-symbols} command
32841 (@pxref{GDB/MI File Commands}). The command response has a single
32842 field, @samp{thread-group}, whose value is the identifier of the
32843 thread group corresponding to the new inferior.
32845 @subheading Example
32850 ^done,thread-group="i3"
32853 @subheading The @code{-interpreter-exec} Command
32854 @findex -interpreter-exec
32856 @subheading Synopsis
32859 -interpreter-exec @var{interpreter} @var{command}
32861 @anchor{-interpreter-exec}
32863 Execute the specified @var{command} in the given @var{interpreter}.
32865 @subheading @value{GDBN} Command
32867 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32869 @subheading Example
32873 -interpreter-exec console "break main"
32874 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32875 &"During symbol reading, bad structure-type format.\n"
32876 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32881 @subheading The @code{-inferior-tty-set} Command
32882 @findex -inferior-tty-set
32884 @subheading Synopsis
32887 -inferior-tty-set /dev/pts/1
32890 Set terminal for future runs of the program being debugged.
32892 @subheading @value{GDBN} Command
32894 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32896 @subheading Example
32900 -inferior-tty-set /dev/pts/1
32905 @subheading The @code{-inferior-tty-show} Command
32906 @findex -inferior-tty-show
32908 @subheading Synopsis
32914 Show terminal for future runs of program being debugged.
32916 @subheading @value{GDBN} Command
32918 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32920 @subheading Example
32924 -inferior-tty-set /dev/pts/1
32928 ^done,inferior_tty_terminal="/dev/pts/1"
32932 @subheading The @code{-enable-timings} Command
32933 @findex -enable-timings
32935 @subheading Synopsis
32938 -enable-timings [yes | no]
32941 Toggle the printing of the wallclock, user and system times for an MI
32942 command as a field in its output. This command is to help frontend
32943 developers optimize the performance of their code. No argument is
32944 equivalent to @samp{yes}.
32946 @subheading @value{GDBN} Command
32950 @subheading Example
32958 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32959 addr="0x080484ed",func="main",file="myprog.c",
32960 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
32961 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32969 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32970 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32971 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32972 fullname="/home/nickrob/myprog.c",line="73"@}
32977 @chapter @value{GDBN} Annotations
32979 This chapter describes annotations in @value{GDBN}. Annotations were
32980 designed to interface @value{GDBN} to graphical user interfaces or other
32981 similar programs which want to interact with @value{GDBN} at a
32982 relatively high level.
32984 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32988 This is Edition @value{EDITION}, @value{DATE}.
32992 * Annotations Overview:: What annotations are; the general syntax.
32993 * Server Prefix:: Issuing a command without affecting user state.
32994 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32995 * Errors:: Annotations for error messages.
32996 * Invalidation:: Some annotations describe things now invalid.
32997 * Annotations for Running::
32998 Whether the program is running, how it stopped, etc.
32999 * Source Annotations:: Annotations describing source code.
33002 @node Annotations Overview
33003 @section What is an Annotation?
33004 @cindex annotations
33006 Annotations start with a newline character, two @samp{control-z}
33007 characters, and the name of the annotation. If there is no additional
33008 information associated with this annotation, the name of the annotation
33009 is followed immediately by a newline. If there is additional
33010 information, the name of the annotation is followed by a space, the
33011 additional information, and a newline. The additional information
33012 cannot contain newline characters.
33014 Any output not beginning with a newline and two @samp{control-z}
33015 characters denotes literal output from @value{GDBN}. Currently there is
33016 no need for @value{GDBN} to output a newline followed by two
33017 @samp{control-z} characters, but if there was such a need, the
33018 annotations could be extended with an @samp{escape} annotation which
33019 means those three characters as output.
33021 The annotation @var{level}, which is specified using the
33022 @option{--annotate} command line option (@pxref{Mode Options}), controls
33023 how much information @value{GDBN} prints together with its prompt,
33024 values of expressions, source lines, and other types of output. Level 0
33025 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33026 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33027 for programs that control @value{GDBN}, and level 2 annotations have
33028 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33029 Interface, annotate, GDB's Obsolete Annotations}).
33032 @kindex set annotate
33033 @item set annotate @var{level}
33034 The @value{GDBN} command @code{set annotate} sets the level of
33035 annotations to the specified @var{level}.
33037 @item show annotate
33038 @kindex show annotate
33039 Show the current annotation level.
33042 This chapter describes level 3 annotations.
33044 A simple example of starting up @value{GDBN} with annotations is:
33047 $ @kbd{gdb --annotate=3}
33049 Copyright 2003 Free Software Foundation, Inc.
33050 GDB is free software, covered by the GNU General Public License,
33051 and you are welcome to change it and/or distribute copies of it
33052 under certain conditions.
33053 Type "show copying" to see the conditions.
33054 There is absolutely no warranty for GDB. Type "show warranty"
33056 This GDB was configured as "i386-pc-linux-gnu"
33067 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33068 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33069 denotes a @samp{control-z} character) are annotations; the rest is
33070 output from @value{GDBN}.
33072 @node Server Prefix
33073 @section The Server Prefix
33074 @cindex server prefix
33076 If you prefix a command with @samp{server } then it will not affect
33077 the command history, nor will it affect @value{GDBN}'s notion of which
33078 command to repeat if @key{RET} is pressed on a line by itself. This
33079 means that commands can be run behind a user's back by a front-end in
33080 a transparent manner.
33082 The @code{server } prefix does not affect the recording of values into
33083 the value history; to print a value without recording it into the
33084 value history, use the @code{output} command instead of the
33085 @code{print} command.
33087 Using this prefix also disables confirmation requests
33088 (@pxref{confirmation requests}).
33091 @section Annotation for @value{GDBN} Input
33093 @cindex annotations for prompts
33094 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33095 to know when to send output, when the output from a given command is
33098 Different kinds of input each have a different @dfn{input type}. Each
33099 input type has three annotations: a @code{pre-} annotation, which
33100 denotes the beginning of any prompt which is being output, a plain
33101 annotation, which denotes the end of the prompt, and then a @code{post-}
33102 annotation which denotes the end of any echo which may (or may not) be
33103 associated with the input. For example, the @code{prompt} input type
33104 features the following annotations:
33112 The input types are
33115 @findex pre-prompt annotation
33116 @findex prompt annotation
33117 @findex post-prompt annotation
33119 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33121 @findex pre-commands annotation
33122 @findex commands annotation
33123 @findex post-commands annotation
33125 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33126 command. The annotations are repeated for each command which is input.
33128 @findex pre-overload-choice annotation
33129 @findex overload-choice annotation
33130 @findex post-overload-choice annotation
33131 @item overload-choice
33132 When @value{GDBN} wants the user to select between various overloaded functions.
33134 @findex pre-query annotation
33135 @findex query annotation
33136 @findex post-query annotation
33138 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33140 @findex pre-prompt-for-continue annotation
33141 @findex prompt-for-continue annotation
33142 @findex post-prompt-for-continue annotation
33143 @item prompt-for-continue
33144 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33145 expect this to work well; instead use @code{set height 0} to disable
33146 prompting. This is because the counting of lines is buggy in the
33147 presence of annotations.
33152 @cindex annotations for errors, warnings and interrupts
33154 @findex quit annotation
33159 This annotation occurs right before @value{GDBN} responds to an interrupt.
33161 @findex error annotation
33166 This annotation occurs right before @value{GDBN} responds to an error.
33168 Quit and error annotations indicate that any annotations which @value{GDBN} was
33169 in the middle of may end abruptly. For example, if a
33170 @code{value-history-begin} annotation is followed by a @code{error}, one
33171 cannot expect to receive the matching @code{value-history-end}. One
33172 cannot expect not to receive it either, however; an error annotation
33173 does not necessarily mean that @value{GDBN} is immediately returning all the way
33176 @findex error-begin annotation
33177 A quit or error annotation may be preceded by
33183 Any output between that and the quit or error annotation is the error
33186 Warning messages are not yet annotated.
33187 @c If we want to change that, need to fix warning(), type_error(),
33188 @c range_error(), and possibly other places.
33191 @section Invalidation Notices
33193 @cindex annotations for invalidation messages
33194 The following annotations say that certain pieces of state may have
33198 @findex frames-invalid annotation
33199 @item ^Z^Zframes-invalid
33201 The frames (for example, output from the @code{backtrace} command) may
33204 @findex breakpoints-invalid annotation
33205 @item ^Z^Zbreakpoints-invalid
33207 The breakpoints may have changed. For example, the user just added or
33208 deleted a breakpoint.
33211 @node Annotations for Running
33212 @section Running the Program
33213 @cindex annotations for running programs
33215 @findex starting annotation
33216 @findex stopping annotation
33217 When the program starts executing due to a @value{GDBN} command such as
33218 @code{step} or @code{continue},
33224 is output. When the program stops,
33230 is output. Before the @code{stopped} annotation, a variety of
33231 annotations describe how the program stopped.
33234 @findex exited annotation
33235 @item ^Z^Zexited @var{exit-status}
33236 The program exited, and @var{exit-status} is the exit status (zero for
33237 successful exit, otherwise nonzero).
33239 @findex signalled annotation
33240 @findex signal-name annotation
33241 @findex signal-name-end annotation
33242 @findex signal-string annotation
33243 @findex signal-string-end annotation
33244 @item ^Z^Zsignalled
33245 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33246 annotation continues:
33252 ^Z^Zsignal-name-end
33256 ^Z^Zsignal-string-end
33261 where @var{name} is the name of the signal, such as @code{SIGILL} or
33262 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33263 as @code{Illegal Instruction} or @code{Segmentation fault}.
33264 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33265 user's benefit and have no particular format.
33267 @findex signal annotation
33269 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33270 just saying that the program received the signal, not that it was
33271 terminated with it.
33273 @findex breakpoint annotation
33274 @item ^Z^Zbreakpoint @var{number}
33275 The program hit breakpoint number @var{number}.
33277 @findex watchpoint annotation
33278 @item ^Z^Zwatchpoint @var{number}
33279 The program hit watchpoint number @var{number}.
33282 @node Source Annotations
33283 @section Displaying Source
33284 @cindex annotations for source display
33286 @findex source annotation
33287 The following annotation is used instead of displaying source code:
33290 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
33293 where @var{filename} is an absolute file name indicating which source
33294 file, @var{line} is the line number within that file (where 1 is the
33295 first line in the file), @var{character} is the character position
33296 within the file (where 0 is the first character in the file) (for most
33297 debug formats this will necessarily point to the beginning of a line),
33298 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
33299 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
33300 @var{addr} is the address in the target program associated with the
33301 source which is being displayed. @var{addr} is in the form @samp{0x}
33302 followed by one or more lowercase hex digits (note that this does not
33303 depend on the language).
33305 @node JIT Interface
33306 @chapter JIT Compilation Interface
33307 @cindex just-in-time compilation
33308 @cindex JIT compilation interface
33310 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33311 interface. A JIT compiler is a program or library that generates native
33312 executable code at runtime and executes it, usually in order to achieve good
33313 performance while maintaining platform independence.
33315 Programs that use JIT compilation are normally difficult to debug because
33316 portions of their code are generated at runtime, instead of being loaded from
33317 object files, which is where @value{GDBN} normally finds the program's symbols
33318 and debug information. In order to debug programs that use JIT compilation,
33319 @value{GDBN} has an interface that allows the program to register in-memory
33320 symbol files with @value{GDBN} at runtime.
33322 If you are using @value{GDBN} to debug a program that uses this interface, then
33323 it should work transparently so long as you have not stripped the binary. If
33324 you are developing a JIT compiler, then the interface is documented in the rest
33325 of this chapter. At this time, the only known client of this interface is the
33328 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33329 JIT compiler communicates with @value{GDBN} by writing data into a global
33330 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33331 attaches, it reads a linked list of symbol files from the global variable to
33332 find existing code, and puts a breakpoint in the function so that it can find
33333 out about additional code.
33336 * Declarations:: Relevant C struct declarations
33337 * Registering Code:: Steps to register code
33338 * Unregistering Code:: Steps to unregister code
33339 * Custom Debug Info:: Emit debug information in a custom format
33343 @section JIT Declarations
33345 These are the relevant struct declarations that a C program should include to
33346 implement the interface:
33356 struct jit_code_entry
33358 struct jit_code_entry *next_entry;
33359 struct jit_code_entry *prev_entry;
33360 const char *symfile_addr;
33361 uint64_t symfile_size;
33364 struct jit_descriptor
33367 /* This type should be jit_actions_t, but we use uint32_t
33368 to be explicit about the bitwidth. */
33369 uint32_t action_flag;
33370 struct jit_code_entry *relevant_entry;
33371 struct jit_code_entry *first_entry;
33374 /* GDB puts a breakpoint in this function. */
33375 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33377 /* Make sure to specify the version statically, because the
33378 debugger may check the version before we can set it. */
33379 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
33382 If the JIT is multi-threaded, then it is important that the JIT synchronize any
33383 modifications to this global data properly, which can easily be done by putting
33384 a global mutex around modifications to these structures.
33386 @node Registering Code
33387 @section Registering Code
33389 To register code with @value{GDBN}, the JIT should follow this protocol:
33393 Generate an object file in memory with symbols and other desired debug
33394 information. The file must include the virtual addresses of the sections.
33397 Create a code entry for the file, which gives the start and size of the symbol
33401 Add it to the linked list in the JIT descriptor.
33404 Point the relevant_entry field of the descriptor at the entry.
33407 Set @code{action_flag} to @code{JIT_REGISTER} and call
33408 @code{__jit_debug_register_code}.
33411 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
33412 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
33413 new code. However, the linked list must still be maintained in order to allow
33414 @value{GDBN} to attach to a running process and still find the symbol files.
33416 @node Unregistering Code
33417 @section Unregistering Code
33419 If code is freed, then the JIT should use the following protocol:
33423 Remove the code entry corresponding to the code from the linked list.
33426 Point the @code{relevant_entry} field of the descriptor at the code entry.
33429 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
33430 @code{__jit_debug_register_code}.
33433 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
33434 and the JIT will leak the memory used for the associated symbol files.
33436 @node Custom Debug Info
33437 @section Custom Debug Info
33438 @cindex custom JIT debug info
33439 @cindex JIT debug info reader
33441 Generating debug information in platform-native file formats (like ELF
33442 or COFF) may be an overkill for JIT compilers; especially if all the
33443 debug info is used for is displaying a meaningful backtrace. The
33444 issue can be resolved by having the JIT writers decide on a debug info
33445 format and also provide a reader that parses the debug info generated
33446 by the JIT compiler. This section gives a brief overview on writing
33447 such a parser. More specific details can be found in the source file
33448 @file{gdb/jit-reader.in}, which is also installed as a header at
33449 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
33451 The reader is implemented as a shared object (so this functionality is
33452 not available on platforms which don't allow loading shared objects at
33453 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
33454 @code{jit-reader-unload} are provided, to be used to load and unload
33455 the readers from a preconfigured directory. Once loaded, the shared
33456 object is used the parse the debug information emitted by the JIT
33460 * Using JIT Debug Info Readers:: How to use supplied readers correctly
33461 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33464 @node Using JIT Debug Info Readers
33465 @subsection Using JIT Debug Info Readers
33466 @kindex jit-reader-load
33467 @kindex jit-reader-unload
33469 Readers can be loaded and unloaded using the @code{jit-reader-load}
33470 and @code{jit-reader-unload} commands.
33473 @item jit-reader-load @var{reader-name}
33474 Load the JIT reader named @var{reader-name}. On a UNIX system, this
33475 will usually load @file{@var{libdir}/gdb/@var{reader-name}}, where
33476 @var{libdir} is the system library directory, usually
33477 @file{/usr/local/lib}. Only one reader can be active at a time;
33478 trying to load a second reader when one is already loaded will result
33479 in @value{GDBN} reporting an error. A new JIT reader can be loaded by
33480 first unloading the current one using @code{jit-reader-load} and then
33481 invoking @code{jit-reader-load}.
33483 @item jit-reader-unload
33484 Unload the currently loaded JIT reader.
33488 @node Writing JIT Debug Info Readers
33489 @subsection Writing JIT Debug Info Readers
33490 @cindex writing JIT debug info readers
33492 As mentioned, a reader is essentially a shared object conforming to a
33493 certain ABI. This ABI is described in @file{jit-reader.h}.
33495 @file{jit-reader.h} defines the structures, macros and functions
33496 required to write a reader. It is installed (along with
33497 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
33498 the system include directory.
33500 Readers need to be released under a GPL compatible license. A reader
33501 can be declared as released under such a license by placing the macro
33502 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
33504 The entry point for readers is the symbol @code{gdb_init_reader},
33505 which is expected to be a function with the prototype
33507 @findex gdb_init_reader
33509 extern struct gdb_reader_funcs *gdb_init_reader (void);
33512 @cindex @code{struct gdb_reader_funcs}
33514 @code{struct gdb_reader_funcs} contains a set of pointers to callback
33515 functions. These functions are executed to read the debug info
33516 generated by the JIT compiler (@code{read}), to unwind stack frames
33517 (@code{unwind}) and to create canonical frame IDs
33518 (@code{get_Frame_id}). It also has a callback that is called when the
33519 reader is being unloaded (@code{destroy}). The struct looks like this
33522 struct gdb_reader_funcs
33524 /* Must be set to GDB_READER_INTERFACE_VERSION. */
33525 int reader_version;
33527 /* For use by the reader. */
33530 gdb_read_debug_info *read;
33531 gdb_unwind_frame *unwind;
33532 gdb_get_frame_id *get_frame_id;
33533 gdb_destroy_reader *destroy;
33537 @cindex @code{struct gdb_symbol_callbacks}
33538 @cindex @code{struct gdb_unwind_callbacks}
33540 The callbacks are provided with another set of callbacks by
33541 @value{GDBN} to do their job. For @code{read}, these callbacks are
33542 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
33543 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
33544 @code{struct gdb_symbol_callbacks} has callbacks to create new object
33545 files and new symbol tables inside those object files. @code{struct
33546 gdb_unwind_callbacks} has callbacks to read registers off the current
33547 frame and to write out the values of the registers in the previous
33548 frame. Both have a callback (@code{target_read}) to read bytes off the
33549 target's address space.
33551 @node In-Process Agent
33552 @chapter In-Process Agent
33553 @cindex debugging agent
33554 The traditional debugging model is conceptually low-speed, but works fine,
33555 because most bugs can be reproduced in debugging-mode execution. However,
33556 as multi-core or many-core processors are becoming mainstream, and
33557 multi-threaded programs become more and more popular, there should be more
33558 and more bugs that only manifest themselves at normal-mode execution, for
33559 example, thread races, because debugger's interference with the program's
33560 timing may conceal the bugs. On the other hand, in some applications,
33561 it is not feasible for the debugger to interrupt the program's execution
33562 long enough for the developer to learn anything helpful about its behavior.
33563 If the program's correctness depends on its real-time behavior, delays
33564 introduced by a debugger might cause the program to fail, even when the
33565 code itself is correct. It is useful to be able to observe the program's
33566 behavior without interrupting it.
33568 Therefore, traditional debugging model is too intrusive to reproduce
33569 some bugs. In order to reduce the interference with the program, we can
33570 reduce the number of operations performed by debugger. The
33571 @dfn{In-Process Agent}, a shared library, is running within the same
33572 process with inferior, and is able to perform some debugging operations
33573 itself. As a result, debugger is only involved when necessary, and
33574 performance of debugging can be improved accordingly. Note that
33575 interference with program can be reduced but can't be removed completely,
33576 because the in-process agent will still stop or slow down the program.
33578 The in-process agent can interpret and execute Agent Expressions
33579 (@pxref{Agent Expressions}) during performing debugging operations. The
33580 agent expressions can be used for different purposes, such as collecting
33581 data in tracepoints, and condition evaluation in breakpoints.
33583 @anchor{Control Agent}
33584 You can control whether the in-process agent is used as an aid for
33585 debugging with the following commands:
33588 @kindex set agent on
33590 Causes the in-process agent to perform some operations on behalf of the
33591 debugger. Just which operations requested by the user will be done
33592 by the in-process agent depends on the its capabilities. For example,
33593 if you request to evaluate breakpoint conditions in the in-process agent,
33594 and the in-process agent has such capability as well, then breakpoint
33595 conditions will be evaluated in the in-process agent.
33597 @kindex set agent off
33598 @item set agent off
33599 Disables execution of debugging operations by the in-process agent. All
33600 of the operations will be performed by @value{GDBN}.
33604 Display the current setting of execution of debugging operations by
33605 the in-process agent.
33609 * In-Process Agent Protocol::
33612 @node In-Process Agent Protocol
33613 @section In-Process Agent Protocol
33614 @cindex in-process agent protocol
33616 The in-process agent is able to communicate with both @value{GDBN} and
33617 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
33618 used for communications between @value{GDBN} or GDBserver and the IPA.
33619 In general, @value{GDBN} or GDBserver sends commands
33620 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
33621 in-process agent replies back with the return result of the command, or
33622 some other information. The data sent to in-process agent is composed
33623 of primitive data types, such as 4-byte or 8-byte type, and composite
33624 types, which are called objects (@pxref{IPA Protocol Objects}).
33627 * IPA Protocol Objects::
33628 * IPA Protocol Commands::
33631 @node IPA Protocol Objects
33632 @subsection IPA Protocol Objects
33633 @cindex ipa protocol objects
33635 The commands sent to and results received from agent may contain some
33636 complex data types called @dfn{objects}.
33638 The in-process agent is running on the same machine with @value{GDBN}
33639 or GDBserver, so it doesn't have to handle as much differences between
33640 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
33641 However, there are still some differences of two ends in two processes:
33645 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
33646 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
33648 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
33649 GDBserver is compiled with one, and in-process agent is compiled with
33653 Here are the IPA Protocol Objects:
33657 agent expression object. It represents an agent expression
33658 (@pxref{Agent Expressions}).
33659 @anchor{agent expression object}
33661 tracepoint action object. It represents a tracepoint action
33662 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
33663 memory, static trace data and to evaluate expression.
33664 @anchor{tracepoint action object}
33666 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
33667 @anchor{tracepoint object}
33671 The following table describes important attributes of each IPA protocol
33674 @multitable @columnfractions .30 .20 .50
33675 @headitem Name @tab Size @tab Description
33676 @item @emph{agent expression object} @tab @tab
33677 @item length @tab 4 @tab length of bytes code
33678 @item byte code @tab @var{length} @tab contents of byte code
33679 @item @emph{tracepoint action for collecting memory} @tab @tab
33680 @item 'M' @tab 1 @tab type of tracepoint action
33681 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
33682 address of the lowest byte to collect, otherwise @var{addr} is the offset
33683 of @var{basereg} for memory collecting.
33684 @item len @tab 8 @tab length of memory for collecting
33685 @item basereg @tab 4 @tab the register number containing the starting
33686 memory address for collecting.
33687 @item @emph{tracepoint action for collecting registers} @tab @tab
33688 @item 'R' @tab 1 @tab type of tracepoint action
33689 @item @emph{tracepoint action for collecting static trace data} @tab @tab
33690 @item 'L' @tab 1 @tab type of tracepoint action
33691 @item @emph{tracepoint action for expression evaluation} @tab @tab
33692 @item 'X' @tab 1 @tab type of tracepoint action
33693 @item agent expression @tab length of @tab @ref{agent expression object}
33694 @item @emph{tracepoint object} @tab @tab
33695 @item number @tab 4 @tab number of tracepoint
33696 @item address @tab 8 @tab address of tracepoint inserted on
33697 @item type @tab 4 @tab type of tracepoint
33698 @item enabled @tab 1 @tab enable or disable of tracepoint
33699 @item step_count @tab 8 @tab step
33700 @item pass_count @tab 8 @tab pass
33701 @item numactions @tab 4 @tab number of tracepoint actions
33702 @item hit count @tab 8 @tab hit count
33703 @item trace frame usage @tab 8 @tab trace frame usage
33704 @item compiled_cond @tab 8 @tab compiled condition
33705 @item orig_size @tab 8 @tab orig size
33706 @item condition @tab 4 if condition is NULL otherwise length of
33707 @ref{agent expression object}
33708 @tab zero if condition is NULL, otherwise is
33709 @ref{agent expression object}
33710 @item actions @tab variable
33711 @tab numactions number of @ref{tracepoint action object}
33714 @node IPA Protocol Commands
33715 @subsection IPA Protocol Commands
33716 @cindex ipa protocol commands
33718 The spaces in each command are delimiters to ease reading this commands
33719 specification. They don't exist in real commands.
33723 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
33724 Installs a new fast tracepoint described by @var{tracepoint_object}
33725 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
33726 head of @dfn{jumppad}, which is used to jump to data collection routine
33731 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
33732 @var{target_address} is address of tracepoint in the inferior.
33733 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
33734 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
33735 @var{fjump} contains a sequence of instructions jump to jumppad entry.
33736 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
33743 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
33744 is about to kill inferiors.
33752 @item probe_marker_at:@var{address}
33753 Asks in-process agent to probe the marker at @var{address}.
33760 @item unprobe_marker_at:@var{address}
33761 Asks in-process agent to unprobe the marker at @var{address}.
33765 @chapter Reporting Bugs in @value{GDBN}
33766 @cindex bugs in @value{GDBN}
33767 @cindex reporting bugs in @value{GDBN}
33769 Your bug reports play an essential role in making @value{GDBN} reliable.
33771 Reporting a bug may help you by bringing a solution to your problem, or it
33772 may not. But in any case the principal function of a bug report is to help
33773 the entire community by making the next version of @value{GDBN} work better. Bug
33774 reports are your contribution to the maintenance of @value{GDBN}.
33776 In order for a bug report to serve its purpose, you must include the
33777 information that enables us to fix the bug.
33780 * Bug Criteria:: Have you found a bug?
33781 * Bug Reporting:: How to report bugs
33785 @section Have You Found a Bug?
33786 @cindex bug criteria
33788 If you are not sure whether you have found a bug, here are some guidelines:
33791 @cindex fatal signal
33792 @cindex debugger crash
33793 @cindex crash of debugger
33795 If the debugger gets a fatal signal, for any input whatever, that is a
33796 @value{GDBN} bug. Reliable debuggers never crash.
33798 @cindex error on valid input
33800 If @value{GDBN} produces an error message for valid input, that is a
33801 bug. (Note that if you're cross debugging, the problem may also be
33802 somewhere in the connection to the target.)
33804 @cindex invalid input
33806 If @value{GDBN} does not produce an error message for invalid input,
33807 that is a bug. However, you should note that your idea of
33808 ``invalid input'' might be our idea of ``an extension'' or ``support
33809 for traditional practice''.
33812 If you are an experienced user of debugging tools, your suggestions
33813 for improvement of @value{GDBN} are welcome in any case.
33816 @node Bug Reporting
33817 @section How to Report Bugs
33818 @cindex bug reports
33819 @cindex @value{GDBN} bugs, reporting
33821 A number of companies and individuals offer support for @sc{gnu} products.
33822 If you obtained @value{GDBN} from a support organization, we recommend you
33823 contact that organization first.
33825 You can find contact information for many support companies and
33826 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33828 @c should add a web page ref...
33831 @ifset BUGURL_DEFAULT
33832 In any event, we also recommend that you submit bug reports for
33833 @value{GDBN}. The preferred method is to submit them directly using
33834 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33835 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33838 @strong{Do not send bug reports to @samp{info-gdb}, or to
33839 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33840 not want to receive bug reports. Those that do have arranged to receive
33843 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33844 serves as a repeater. The mailing list and the newsgroup carry exactly
33845 the same messages. Often people think of posting bug reports to the
33846 newsgroup instead of mailing them. This appears to work, but it has one
33847 problem which can be crucial: a newsgroup posting often lacks a mail
33848 path back to the sender. Thus, if we need to ask for more information,
33849 we may be unable to reach you. For this reason, it is better to send
33850 bug reports to the mailing list.
33852 @ifclear BUGURL_DEFAULT
33853 In any event, we also recommend that you submit bug reports for
33854 @value{GDBN} to @value{BUGURL}.
33858 The fundamental principle of reporting bugs usefully is this:
33859 @strong{report all the facts}. If you are not sure whether to state a
33860 fact or leave it out, state it!
33862 Often people omit facts because they think they know what causes the
33863 problem and assume that some details do not matter. Thus, you might
33864 assume that the name of the variable you use in an example does not matter.
33865 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33866 stray memory reference which happens to fetch from the location where that
33867 name is stored in memory; perhaps, if the name were different, the contents
33868 of that location would fool the debugger into doing the right thing despite
33869 the bug. Play it safe and give a specific, complete example. That is the
33870 easiest thing for you to do, and the most helpful.
33872 Keep in mind that the purpose of a bug report is to enable us to fix the
33873 bug. It may be that the bug has been reported previously, but neither
33874 you nor we can know that unless your bug report is complete and
33877 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33878 bell?'' Those bug reports are useless, and we urge everyone to
33879 @emph{refuse to respond to them} except to chide the sender to report
33882 To enable us to fix the bug, you should include all these things:
33886 The version of @value{GDBN}. @value{GDBN} announces it if you start
33887 with no arguments; you can also print it at any time using @code{show
33890 Without this, we will not know whether there is any point in looking for
33891 the bug in the current version of @value{GDBN}.
33894 The type of machine you are using, and the operating system name and
33898 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33899 ``@value{GCC}--2.8.1''.
33902 What compiler (and its version) was used to compile the program you are
33903 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33904 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33905 to get this information; for other compilers, see the documentation for
33909 The command arguments you gave the compiler to compile your example and
33910 observe the bug. For example, did you use @samp{-O}? To guarantee
33911 you will not omit something important, list them all. A copy of the
33912 Makefile (or the output from make) is sufficient.
33914 If we were to try to guess the arguments, we would probably guess wrong
33915 and then we might not encounter the bug.
33918 A complete input script, and all necessary source files, that will
33922 A description of what behavior you observe that you believe is
33923 incorrect. For example, ``It gets a fatal signal.''
33925 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33926 will certainly notice it. But if the bug is incorrect output, we might
33927 not notice unless it is glaringly wrong. You might as well not give us
33928 a chance to make a mistake.
33930 Even if the problem you experience is a fatal signal, you should still
33931 say so explicitly. Suppose something strange is going on, such as, your
33932 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33933 the C library on your system. (This has happened!) Your copy might
33934 crash and ours would not. If you told us to expect a crash, then when
33935 ours fails to crash, we would know that the bug was not happening for
33936 us. If you had not told us to expect a crash, then we would not be able
33937 to draw any conclusion from our observations.
33940 @cindex recording a session script
33941 To collect all this information, you can use a session recording program
33942 such as @command{script}, which is available on many Unix systems.
33943 Just run your @value{GDBN} session inside @command{script} and then
33944 include the @file{typescript} file with your bug report.
33946 Another way to record a @value{GDBN} session is to run @value{GDBN}
33947 inside Emacs and then save the entire buffer to a file.
33950 If you wish to suggest changes to the @value{GDBN} source, send us context
33951 diffs. If you even discuss something in the @value{GDBN} source, refer to
33952 it by context, not by line number.
33954 The line numbers in our development sources will not match those in your
33955 sources. Your line numbers would convey no useful information to us.
33959 Here are some things that are not necessary:
33963 A description of the envelope of the bug.
33965 Often people who encounter a bug spend a lot of time investigating
33966 which changes to the input file will make the bug go away and which
33967 changes will not affect it.
33969 This is often time consuming and not very useful, because the way we
33970 will find the bug is by running a single example under the debugger
33971 with breakpoints, not by pure deduction from a series of examples.
33972 We recommend that you save your time for something else.
33974 Of course, if you can find a simpler example to report @emph{instead}
33975 of the original one, that is a convenience for us. Errors in the
33976 output will be easier to spot, running under the debugger will take
33977 less time, and so on.
33979 However, simplification is not vital; if you do not want to do this,
33980 report the bug anyway and send us the entire test case you used.
33983 A patch for the bug.
33985 A patch for the bug does help us if it is a good one. But do not omit
33986 the necessary information, such as the test case, on the assumption that
33987 a patch is all we need. We might see problems with your patch and decide
33988 to fix the problem another way, or we might not understand it at all.
33990 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33991 construct an example that will make the program follow a certain path
33992 through the code. If you do not send us the example, we will not be able
33993 to construct one, so we will not be able to verify that the bug is fixed.
33995 And if we cannot understand what bug you are trying to fix, or why your
33996 patch should be an improvement, we will not install it. A test case will
33997 help us to understand.
34000 A guess about what the bug is or what it depends on.
34002 Such guesses are usually wrong. Even we cannot guess right about such
34003 things without first using the debugger to find the facts.
34006 @c The readline documentation is distributed with the readline code
34007 @c and consists of the two following files:
34010 @c Use -I with makeinfo to point to the appropriate directory,
34011 @c environment var TEXINPUTS with TeX.
34012 @ifclear SYSTEM_READLINE
34013 @include rluser.texi
34014 @include hsuser.texi
34018 @appendix In Memoriam
34020 The @value{GDBN} project mourns the loss of the following long-time
34025 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34026 to Free Software in general. Outside of @value{GDBN}, he was known in
34027 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34029 @item Michael Snyder
34030 Michael was one of the Global Maintainers of the @value{GDBN} project,
34031 with contributions recorded as early as 1996, until 2011. In addition
34032 to his day to day participation, he was a large driving force behind
34033 adding Reverse Debugging to @value{GDBN}.
34036 Beyond their technical contributions to the project, they were also
34037 enjoyable members of the Free Software Community. We will miss them.
34039 @node Formatting Documentation
34040 @appendix Formatting Documentation
34042 @cindex @value{GDBN} reference card
34043 @cindex reference card
34044 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34045 for printing with PostScript or Ghostscript, in the @file{gdb}
34046 subdirectory of the main source directory@footnote{In
34047 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34048 release.}. If you can use PostScript or Ghostscript with your printer,
34049 you can print the reference card immediately with @file{refcard.ps}.
34051 The release also includes the source for the reference card. You
34052 can format it, using @TeX{}, by typing:
34058 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34059 mode on US ``letter'' size paper;
34060 that is, on a sheet 11 inches wide by 8.5 inches
34061 high. You will need to specify this form of printing as an option to
34062 your @sc{dvi} output program.
34064 @cindex documentation
34066 All the documentation for @value{GDBN} comes as part of the machine-readable
34067 distribution. The documentation is written in Texinfo format, which is
34068 a documentation system that uses a single source file to produce both
34069 on-line information and a printed manual. You can use one of the Info
34070 formatting commands to create the on-line version of the documentation
34071 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34073 @value{GDBN} includes an already formatted copy of the on-line Info
34074 version of this manual in the @file{gdb} subdirectory. The main Info
34075 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34076 subordinate files matching @samp{gdb.info*} in the same directory. If
34077 necessary, you can print out these files, or read them with any editor;
34078 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34079 Emacs or the standalone @code{info} program, available as part of the
34080 @sc{gnu} Texinfo distribution.
34082 If you want to format these Info files yourself, you need one of the
34083 Info formatting programs, such as @code{texinfo-format-buffer} or
34086 If you have @code{makeinfo} installed, and are in the top level
34087 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34088 version @value{GDBVN}), you can make the Info file by typing:
34095 If you want to typeset and print copies of this manual, you need @TeX{},
34096 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34097 Texinfo definitions file.
34099 @TeX{} is a typesetting program; it does not print files directly, but
34100 produces output files called @sc{dvi} files. To print a typeset
34101 document, you need a program to print @sc{dvi} files. If your system
34102 has @TeX{} installed, chances are it has such a program. The precise
34103 command to use depends on your system; @kbd{lpr -d} is common; another
34104 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34105 require a file name without any extension or a @samp{.dvi} extension.
34107 @TeX{} also requires a macro definitions file called
34108 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34109 written in Texinfo format. On its own, @TeX{} cannot either read or
34110 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34111 and is located in the @file{gdb-@var{version-number}/texinfo}
34114 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34115 typeset and print this manual. First switch to the @file{gdb}
34116 subdirectory of the main source directory (for example, to
34117 @file{gdb-@value{GDBVN}/gdb}) and type:
34123 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34125 @node Installing GDB
34126 @appendix Installing @value{GDBN}
34127 @cindex installation
34130 * Requirements:: Requirements for building @value{GDBN}
34131 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34132 * Separate Objdir:: Compiling @value{GDBN} in another directory
34133 * Config Names:: Specifying names for hosts and targets
34134 * Configure Options:: Summary of options for configure
34135 * System-wide configuration:: Having a system-wide init file
34139 @section Requirements for Building @value{GDBN}
34140 @cindex building @value{GDBN}, requirements for
34142 Building @value{GDBN} requires various tools and packages to be available.
34143 Other packages will be used only if they are found.
34145 @heading Tools/Packages Necessary for Building @value{GDBN}
34147 @item ISO C90 compiler
34148 @value{GDBN} is written in ISO C90. It should be buildable with any
34149 working C90 compiler, e.g.@: GCC.
34153 @heading Tools/Packages Optional for Building @value{GDBN}
34157 @value{GDBN} can use the Expat XML parsing library. This library may be
34158 included with your operating system distribution; if it is not, you
34159 can get the latest version from @url{http://expat.sourceforge.net}.
34160 The @file{configure} script will search for this library in several
34161 standard locations; if it is installed in an unusual path, you can
34162 use the @option{--with-libexpat-prefix} option to specify its location.
34168 Remote protocol memory maps (@pxref{Memory Map Format})
34170 Target descriptions (@pxref{Target Descriptions})
34172 Remote shared library lists (@xref{Library List Format},
34173 or alternatively @pxref{Library List Format for SVR4 Targets})
34175 MS-Windows shared libraries (@pxref{Shared Libraries})
34177 Traceframe info (@pxref{Traceframe Info Format})
34181 @cindex compressed debug sections
34182 @value{GDBN} will use the @samp{zlib} library, if available, to read
34183 compressed debug sections. Some linkers, such as GNU gold, are capable
34184 of producing binaries with compressed debug sections. If @value{GDBN}
34185 is compiled with @samp{zlib}, it will be able to read the debug
34186 information in such binaries.
34188 The @samp{zlib} library is likely included with your operating system
34189 distribution; if it is not, you can get the latest version from
34190 @url{http://zlib.net}.
34193 @value{GDBN}'s features related to character sets (@pxref{Character
34194 Sets}) require a functioning @code{iconv} implementation. If you are
34195 on a GNU system, then this is provided by the GNU C Library. Some
34196 other systems also provide a working @code{iconv}.
34198 If @value{GDBN} is using the @code{iconv} program which is installed
34199 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34200 This is done with @option{--with-iconv-bin} which specifies the
34201 directory that contains the @code{iconv} program.
34203 On systems without @code{iconv}, you can install GNU Libiconv. If you
34204 have previously installed Libiconv, you can use the
34205 @option{--with-libiconv-prefix} option to configure.
34207 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34208 arrange to build Libiconv if a directory named @file{libiconv} appears
34209 in the top-most source directory. If Libiconv is built this way, and
34210 if the operating system does not provide a suitable @code{iconv}
34211 implementation, then the just-built library will automatically be used
34212 by @value{GDBN}. One easy way to set this up is to download GNU
34213 Libiconv, unpack it, and then rename the directory holding the
34214 Libiconv source code to @samp{libiconv}.
34217 @node Running Configure
34218 @section Invoking the @value{GDBN} @file{configure} Script
34219 @cindex configuring @value{GDBN}
34220 @value{GDBN} comes with a @file{configure} script that automates the process
34221 of preparing @value{GDBN} for installation; you can then use @code{make} to
34222 build the @code{gdb} program.
34224 @c irrelevant in info file; it's as current as the code it lives with.
34225 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34226 look at the @file{README} file in the sources; we may have improved the
34227 installation procedures since publishing this manual.}
34230 The @value{GDBN} distribution includes all the source code you need for
34231 @value{GDBN} in a single directory, whose name is usually composed by
34232 appending the version number to @samp{gdb}.
34234 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34235 @file{gdb-@value{GDBVN}} directory. That directory contains:
34238 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34239 script for configuring @value{GDBN} and all its supporting libraries
34241 @item gdb-@value{GDBVN}/gdb
34242 the source specific to @value{GDBN} itself
34244 @item gdb-@value{GDBVN}/bfd
34245 source for the Binary File Descriptor library
34247 @item gdb-@value{GDBVN}/include
34248 @sc{gnu} include files
34250 @item gdb-@value{GDBVN}/libiberty
34251 source for the @samp{-liberty} free software library
34253 @item gdb-@value{GDBVN}/opcodes
34254 source for the library of opcode tables and disassemblers
34256 @item gdb-@value{GDBVN}/readline
34257 source for the @sc{gnu} command-line interface
34259 @item gdb-@value{GDBVN}/glob
34260 source for the @sc{gnu} filename pattern-matching subroutine
34262 @item gdb-@value{GDBVN}/mmalloc
34263 source for the @sc{gnu} memory-mapped malloc package
34266 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34267 from the @file{gdb-@var{version-number}} source directory, which in
34268 this example is the @file{gdb-@value{GDBVN}} directory.
34270 First switch to the @file{gdb-@var{version-number}} source directory
34271 if you are not already in it; then run @file{configure}. Pass the
34272 identifier for the platform on which @value{GDBN} will run as an
34278 cd gdb-@value{GDBVN}
34279 ./configure @var{host}
34284 where @var{host} is an identifier such as @samp{sun4} or
34285 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
34286 (You can often leave off @var{host}; @file{configure} tries to guess the
34287 correct value by examining your system.)
34289 Running @samp{configure @var{host}} and then running @code{make} builds the
34290 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
34291 libraries, then @code{gdb} itself. The configured source files, and the
34292 binaries, are left in the corresponding source directories.
34295 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
34296 system does not recognize this automatically when you run a different
34297 shell, you may need to run @code{sh} on it explicitly:
34300 sh configure @var{host}
34303 If you run @file{configure} from a directory that contains source
34304 directories for multiple libraries or programs, such as the
34305 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34307 creates configuration files for every directory level underneath (unless
34308 you tell it not to, with the @samp{--norecursion} option).
34310 You should run the @file{configure} script from the top directory in the
34311 source tree, the @file{gdb-@var{version-number}} directory. If you run
34312 @file{configure} from one of the subdirectories, you will configure only
34313 that subdirectory. That is usually not what you want. In particular,
34314 if you run the first @file{configure} from the @file{gdb} subdirectory
34315 of the @file{gdb-@var{version-number}} directory, you will omit the
34316 configuration of @file{bfd}, @file{readline}, and other sibling
34317 directories of the @file{gdb} subdirectory. This leads to build errors
34318 about missing include files such as @file{bfd/bfd.h}.
34320 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34321 However, you should make sure that the shell on your path (named by
34322 the @samp{SHELL} environment variable) is publicly readable. Remember
34323 that @value{GDBN} uses the shell to start your program---some systems refuse to
34324 let @value{GDBN} debug child processes whose programs are not readable.
34326 @node Separate Objdir
34327 @section Compiling @value{GDBN} in Another Directory
34329 If you want to run @value{GDBN} versions for several host or target machines,
34330 you need a different @code{gdb} compiled for each combination of
34331 host and target. @file{configure} is designed to make this easy by
34332 allowing you to generate each configuration in a separate subdirectory,
34333 rather than in the source directory. If your @code{make} program
34334 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
34335 @code{make} in each of these directories builds the @code{gdb}
34336 program specified there.
34338 To build @code{gdb} in a separate directory, run @file{configure}
34339 with the @samp{--srcdir} option to specify where to find the source.
34340 (You also need to specify a path to find @file{configure}
34341 itself from your working directory. If the path to @file{configure}
34342 would be the same as the argument to @samp{--srcdir}, you can leave out
34343 the @samp{--srcdir} option; it is assumed.)
34345 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
34346 separate directory for a Sun 4 like this:
34350 cd gdb-@value{GDBVN}
34353 ../gdb-@value{GDBVN}/configure sun4
34358 When @file{configure} builds a configuration using a remote source
34359 directory, it creates a tree for the binaries with the same structure
34360 (and using the same names) as the tree under the source directory. In
34361 the example, you'd find the Sun 4 library @file{libiberty.a} in the
34362 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
34363 @file{gdb-sun4/gdb}.
34365 Make sure that your path to the @file{configure} script has just one
34366 instance of @file{gdb} in it. If your path to @file{configure} looks
34367 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
34368 one subdirectory of @value{GDBN}, not the whole package. This leads to
34369 build errors about missing include files such as @file{bfd/bfd.h}.
34371 One popular reason to build several @value{GDBN} configurations in separate
34372 directories is to configure @value{GDBN} for cross-compiling (where
34373 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
34374 programs that run on another machine---the @dfn{target}).
34375 You specify a cross-debugging target by
34376 giving the @samp{--target=@var{target}} option to @file{configure}.
34378 When you run @code{make} to build a program or library, you must run
34379 it in a configured directory---whatever directory you were in when you
34380 called @file{configure} (or one of its subdirectories).
34382 The @code{Makefile} that @file{configure} generates in each source
34383 directory also runs recursively. If you type @code{make} in a source
34384 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
34385 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
34386 will build all the required libraries, and then build GDB.
34388 When you have multiple hosts or targets configured in separate
34389 directories, you can run @code{make} on them in parallel (for example,
34390 if they are NFS-mounted on each of the hosts); they will not interfere
34394 @section Specifying Names for Hosts and Targets
34396 The specifications used for hosts and targets in the @file{configure}
34397 script are based on a three-part naming scheme, but some short predefined
34398 aliases are also supported. The full naming scheme encodes three pieces
34399 of information in the following pattern:
34402 @var{architecture}-@var{vendor}-@var{os}
34405 For example, you can use the alias @code{sun4} as a @var{host} argument,
34406 or as the value for @var{target} in a @code{--target=@var{target}}
34407 option. The equivalent full name is @samp{sparc-sun-sunos4}.
34409 The @file{configure} script accompanying @value{GDBN} does not provide
34410 any query facility to list all supported host and target names or
34411 aliases. @file{configure} calls the Bourne shell script
34412 @code{config.sub} to map abbreviations to full names; you can read the
34413 script, if you wish, or you can use it to test your guesses on
34414 abbreviations---for example:
34417 % sh config.sub i386-linux
34419 % sh config.sub alpha-linux
34420 alpha-unknown-linux-gnu
34421 % sh config.sub hp9k700
34423 % sh config.sub sun4
34424 sparc-sun-sunos4.1.1
34425 % sh config.sub sun3
34426 m68k-sun-sunos4.1.1
34427 % sh config.sub i986v
34428 Invalid configuration `i986v': machine `i986v' not recognized
34432 @code{config.sub} is also distributed in the @value{GDBN} source
34433 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
34435 @node Configure Options
34436 @section @file{configure} Options
34438 Here is a summary of the @file{configure} options and arguments that
34439 are most often useful for building @value{GDBN}. @file{configure} also has
34440 several other options not listed here. @inforef{What Configure
34441 Does,,configure.info}, for a full explanation of @file{configure}.
34444 configure @r{[}--help@r{]}
34445 @r{[}--prefix=@var{dir}@r{]}
34446 @r{[}--exec-prefix=@var{dir}@r{]}
34447 @r{[}--srcdir=@var{dirname}@r{]}
34448 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
34449 @r{[}--target=@var{target}@r{]}
34454 You may introduce options with a single @samp{-} rather than
34455 @samp{--} if you prefer; but you may abbreviate option names if you use
34460 Display a quick summary of how to invoke @file{configure}.
34462 @item --prefix=@var{dir}
34463 Configure the source to install programs and files under directory
34466 @item --exec-prefix=@var{dir}
34467 Configure the source to install programs under directory
34470 @c avoid splitting the warning from the explanation:
34472 @item --srcdir=@var{dirname}
34473 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
34474 @code{make} that implements the @code{VPATH} feature.}@*
34475 Use this option to make configurations in directories separate from the
34476 @value{GDBN} source directories. Among other things, you can use this to
34477 build (or maintain) several configurations simultaneously, in separate
34478 directories. @file{configure} writes configuration-specific files in
34479 the current directory, but arranges for them to use the source in the
34480 directory @var{dirname}. @file{configure} creates directories under
34481 the working directory in parallel to the source directories below
34484 @item --norecursion
34485 Configure only the directory level where @file{configure} is executed; do not
34486 propagate configuration to subdirectories.
34488 @item --target=@var{target}
34489 Configure @value{GDBN} for cross-debugging programs running on the specified
34490 @var{target}. Without this option, @value{GDBN} is configured to debug
34491 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
34493 There is no convenient way to generate a list of all available targets.
34495 @item @var{host} @dots{}
34496 Configure @value{GDBN} to run on the specified @var{host}.
34498 There is no convenient way to generate a list of all available hosts.
34501 There are many other options available as well, but they are generally
34502 needed for special purposes only.
34504 @node System-wide configuration
34505 @section System-wide configuration and settings
34506 @cindex system-wide init file
34508 @value{GDBN} can be configured to have a system-wide init file;
34509 this file will be read and executed at startup (@pxref{Startup, , What
34510 @value{GDBN} does during startup}).
34512 Here is the corresponding configure option:
34515 @item --with-system-gdbinit=@var{file}
34516 Specify that the default location of the system-wide init file is
34520 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
34521 it may be subject to relocation. Two possible cases:
34525 If the default location of this init file contains @file{$prefix},
34526 it will be subject to relocation. Suppose that the configure options
34527 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
34528 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
34529 init file is looked for as @file{$install/etc/gdbinit} instead of
34530 @file{$prefix/etc/gdbinit}.
34533 By contrast, if the default location does not contain the prefix,
34534 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
34535 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
34536 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
34537 wherever @value{GDBN} is installed.
34540 @node Maintenance Commands
34541 @appendix Maintenance Commands
34542 @cindex maintenance commands
34543 @cindex internal commands
34545 In addition to commands intended for @value{GDBN} users, @value{GDBN}
34546 includes a number of commands intended for @value{GDBN} developers,
34547 that are not documented elsewhere in this manual. These commands are
34548 provided here for reference. (For commands that turn on debugging
34549 messages, see @ref{Debugging Output}.)
34552 @kindex maint agent
34553 @kindex maint agent-eval
34554 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34555 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34556 Translate the given @var{expression} into remote agent bytecodes.
34557 This command is useful for debugging the Agent Expression mechanism
34558 (@pxref{Agent Expressions}). The @samp{agent} version produces an
34559 expression useful for data collection, such as by tracepoints, while
34560 @samp{maint agent-eval} produces an expression that evaluates directly
34561 to a result. For instance, a collection expression for @code{globa +
34562 globb} will include bytecodes to record four bytes of memory at each
34563 of the addresses of @code{globa} and @code{globb}, while discarding
34564 the result of the addition, while an evaluation expression will do the
34565 addition and return the sum.
34566 If @code{-at} is given, generate remote agent bytecode for @var{location}.
34567 If not, generate remote agent bytecode for current frame PC address.
34569 @kindex maint agent-printf
34570 @item maint agent-printf @var{format},@var{expr},...
34571 Translate the given format string and list of argument expressions
34572 into remote agent bytecodes and display them as a disassembled list.
34573 This command is useful for debugging the agent version of dynamic
34574 printf (@pxref{Dynamic Printf}.
34576 @kindex maint info breakpoints
34577 @item @anchor{maint info breakpoints}maint info breakpoints
34578 Using the same format as @samp{info breakpoints}, display both the
34579 breakpoints you've set explicitly, and those @value{GDBN} is using for
34580 internal purposes. Internal breakpoints are shown with negative
34581 breakpoint numbers. The type column identifies what kind of breakpoint
34586 Normal, explicitly set breakpoint.
34589 Normal, explicitly set watchpoint.
34592 Internal breakpoint, used to handle correctly stepping through
34593 @code{longjmp} calls.
34595 @item longjmp resume
34596 Internal breakpoint at the target of a @code{longjmp}.
34599 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
34602 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
34605 Shared library events.
34609 @kindex maint info bfds
34610 @item maint info bfds
34611 This prints information about each @code{bfd} object that is known to
34612 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
34614 @kindex set displaced-stepping
34615 @kindex show displaced-stepping
34616 @cindex displaced stepping support
34617 @cindex out-of-line single-stepping
34618 @item set displaced-stepping
34619 @itemx show displaced-stepping
34620 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
34621 if the target supports it. Displaced stepping is a way to single-step
34622 over breakpoints without removing them from the inferior, by executing
34623 an out-of-line copy of the instruction that was originally at the
34624 breakpoint location. It is also known as out-of-line single-stepping.
34627 @item set displaced-stepping on
34628 If the target architecture supports it, @value{GDBN} will use
34629 displaced stepping to step over breakpoints.
34631 @item set displaced-stepping off
34632 @value{GDBN} will not use displaced stepping to step over breakpoints,
34633 even if such is supported by the target architecture.
34635 @cindex non-stop mode, and @samp{set displaced-stepping}
34636 @item set displaced-stepping auto
34637 This is the default mode. @value{GDBN} will use displaced stepping
34638 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
34639 architecture supports displaced stepping.
34642 @kindex maint check-symtabs
34643 @item maint check-symtabs
34644 Check the consistency of psymtabs and symtabs.
34646 @kindex maint cplus first_component
34647 @item maint cplus first_component @var{name}
34648 Print the first C@t{++} class/namespace component of @var{name}.
34650 @kindex maint cplus namespace
34651 @item maint cplus namespace
34652 Print the list of possible C@t{++} namespaces.
34654 @kindex maint demangle
34655 @item maint demangle @var{name}
34656 Demangle a C@t{++} or Objective-C mangled @var{name}.
34658 @kindex maint deprecate
34659 @kindex maint undeprecate
34660 @cindex deprecated commands
34661 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
34662 @itemx maint undeprecate @var{command}
34663 Deprecate or undeprecate the named @var{command}. Deprecated commands
34664 cause @value{GDBN} to issue a warning when you use them. The optional
34665 argument @var{replacement} says which newer command should be used in
34666 favor of the deprecated one; if it is given, @value{GDBN} will mention
34667 the replacement as part of the warning.
34669 @kindex maint dump-me
34670 @item maint dump-me
34671 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
34672 Cause a fatal signal in the debugger and force it to dump its core.
34673 This is supported only on systems which support aborting a program
34674 with the @code{SIGQUIT} signal.
34676 @kindex maint internal-error
34677 @kindex maint internal-warning
34678 @item maint internal-error @r{[}@var{message-text}@r{]}
34679 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
34680 Cause @value{GDBN} to call the internal function @code{internal_error}
34681 or @code{internal_warning} and hence behave as though an internal error
34682 or internal warning has been detected. In addition to reporting the
34683 internal problem, these functions give the user the opportunity to
34684 either quit @value{GDBN} or create a core file of the current
34685 @value{GDBN} session.
34687 These commands take an optional parameter @var{message-text} that is
34688 used as the text of the error or warning message.
34690 Here's an example of using @code{internal-error}:
34693 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
34694 @dots{}/maint.c:121: internal-error: testing, 1, 2
34695 A problem internal to GDB has been detected. Further
34696 debugging may prove unreliable.
34697 Quit this debugging session? (y or n) @kbd{n}
34698 Create a core file? (y or n) @kbd{n}
34702 @cindex @value{GDBN} internal error
34703 @cindex internal errors, control of @value{GDBN} behavior
34705 @kindex maint set internal-error
34706 @kindex maint show internal-error
34707 @kindex maint set internal-warning
34708 @kindex maint show internal-warning
34709 @item maint set internal-error @var{action} [ask|yes|no]
34710 @itemx maint show internal-error @var{action}
34711 @itemx maint set internal-warning @var{action} [ask|yes|no]
34712 @itemx maint show internal-warning @var{action}
34713 When @value{GDBN} reports an internal problem (error or warning) it
34714 gives the user the opportunity to both quit @value{GDBN} and create a
34715 core file of the current @value{GDBN} session. These commands let you
34716 override the default behaviour for each particular @var{action},
34717 described in the table below.
34721 You can specify that @value{GDBN} should always (yes) or never (no)
34722 quit. The default is to ask the user what to do.
34725 You can specify that @value{GDBN} should always (yes) or never (no)
34726 create a core file. The default is to ask the user what to do.
34729 @kindex maint packet
34730 @item maint packet @var{text}
34731 If @value{GDBN} is talking to an inferior via the serial protocol,
34732 then this command sends the string @var{text} to the inferior, and
34733 displays the response packet. @value{GDBN} supplies the initial
34734 @samp{$} character, the terminating @samp{#} character, and the
34737 @kindex maint print architecture
34738 @item maint print architecture @r{[}@var{file}@r{]}
34739 Print the entire architecture configuration. The optional argument
34740 @var{file} names the file where the output goes.
34742 @kindex maint print c-tdesc
34743 @item maint print c-tdesc
34744 Print the current target description (@pxref{Target Descriptions}) as
34745 a C source file. The created source file can be used in @value{GDBN}
34746 when an XML parser is not available to parse the description.
34748 @kindex maint print dummy-frames
34749 @item maint print dummy-frames
34750 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34753 (@value{GDBP}) @kbd{b add}
34755 (@value{GDBP}) @kbd{print add(2,3)}
34756 Breakpoint 2, add (a=2, b=3) at @dots{}
34758 The program being debugged stopped while in a function called from GDB.
34760 (@value{GDBP}) @kbd{maint print dummy-frames}
34761 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
34762 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
34763 call_lo=0x01014000 call_hi=0x01014001
34767 Takes an optional file parameter.
34769 @kindex maint print registers
34770 @kindex maint print raw-registers
34771 @kindex maint print cooked-registers
34772 @kindex maint print register-groups
34773 @kindex maint print remote-registers
34774 @item maint print registers @r{[}@var{file}@r{]}
34775 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34776 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34777 @itemx maint print register-groups @r{[}@var{file}@r{]}
34778 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34779 Print @value{GDBN}'s internal register data structures.
34781 The command @code{maint print raw-registers} includes the contents of
34782 the raw register cache; the command @code{maint print
34783 cooked-registers} includes the (cooked) value of all registers,
34784 including registers which aren't available on the target nor visible
34785 to user; the command @code{maint print register-groups} includes the
34786 groups that each register is a member of; and the command @code{maint
34787 print remote-registers} includes the remote target's register numbers
34788 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
34789 @value{GDBN} Internals}.
34791 These commands take an optional parameter, a file name to which to
34792 write the information.
34794 @kindex maint print reggroups
34795 @item maint print reggroups @r{[}@var{file}@r{]}
34796 Print @value{GDBN}'s internal register group data structures. The
34797 optional argument @var{file} tells to what file to write the
34800 The register groups info looks like this:
34803 (@value{GDBP}) @kbd{maint print reggroups}
34816 This command forces @value{GDBN} to flush its internal register cache.
34818 @kindex maint print objfiles
34819 @cindex info for known object files
34820 @item maint print objfiles
34821 Print a dump of all known object files. For each object file, this
34822 command prints its name, address in memory, and all of its psymtabs
34825 @kindex maint print section-scripts
34826 @cindex info for known .debug_gdb_scripts-loaded scripts
34827 @item maint print section-scripts [@var{regexp}]
34828 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34829 If @var{regexp} is specified, only print scripts loaded by object files
34830 matching @var{regexp}.
34831 For each script, this command prints its name as specified in the objfile,
34832 and the full path if known.
34833 @xref{dotdebug_gdb_scripts section}.
34835 @kindex maint print statistics
34836 @cindex bcache statistics
34837 @item maint print statistics
34838 This command prints, for each object file in the program, various data
34839 about that object file followed by the byte cache (@dfn{bcache})
34840 statistics for the object file. The objfile data includes the number
34841 of minimal, partial, full, and stabs symbols, the number of types
34842 defined by the objfile, the number of as yet unexpanded psym tables,
34843 the number of line tables and string tables, and the amount of memory
34844 used by the various tables. The bcache statistics include the counts,
34845 sizes, and counts of duplicates of all and unique objects, max,
34846 average, and median entry size, total memory used and its overhead and
34847 savings, and various measures of the hash table size and chain
34850 @kindex maint print target-stack
34851 @cindex target stack description
34852 @item maint print target-stack
34853 A @dfn{target} is an interface between the debugger and a particular
34854 kind of file or process. Targets can be stacked in @dfn{strata},
34855 so that more than one target can potentially respond to a request.
34856 In particular, memory accesses will walk down the stack of targets
34857 until they find a target that is interested in handling that particular
34860 This command prints a short description of each layer that was pushed on
34861 the @dfn{target stack}, starting from the top layer down to the bottom one.
34863 @kindex maint print type
34864 @cindex type chain of a data type
34865 @item maint print type @var{expr}
34866 Print the type chain for a type specified by @var{expr}. The argument
34867 can be either a type name or a symbol. If it is a symbol, the type of
34868 that symbol is described. The type chain produced by this command is
34869 a recursive definition of the data type as stored in @value{GDBN}'s
34870 data structures, including its flags and contained types.
34872 @kindex maint set dwarf2 always-disassemble
34873 @kindex maint show dwarf2 always-disassemble
34874 @item maint set dwarf2 always-disassemble
34875 @item maint show dwarf2 always-disassemble
34876 Control the behavior of @code{info address} when using DWARF debugging
34879 The default is @code{off}, which means that @value{GDBN} should try to
34880 describe a variable's location in an easily readable format. When
34881 @code{on}, @value{GDBN} will instead display the DWARF location
34882 expression in an assembly-like format. Note that some locations are
34883 too complex for @value{GDBN} to describe simply; in this case you will
34884 always see the disassembly form.
34886 Here is an example of the resulting disassembly:
34889 (gdb) info addr argc
34890 Symbol "argc" is a complex DWARF expression:
34894 For more information on these expressions, see
34895 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34897 @kindex maint set dwarf2 max-cache-age
34898 @kindex maint show dwarf2 max-cache-age
34899 @item maint set dwarf2 max-cache-age
34900 @itemx maint show dwarf2 max-cache-age
34901 Control the DWARF 2 compilation unit cache.
34903 @cindex DWARF 2 compilation units cache
34904 In object files with inter-compilation-unit references, such as those
34905 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
34906 reader needs to frequently refer to previously read compilation units.
34907 This setting controls how long a compilation unit will remain in the
34908 cache if it is not referenced. A higher limit means that cached
34909 compilation units will be stored in memory longer, and more total
34910 memory will be used. Setting it to zero disables caching, which will
34911 slow down @value{GDBN} startup, but reduce memory consumption.
34913 @kindex maint set profile
34914 @kindex maint show profile
34915 @cindex profiling GDB
34916 @item maint set profile
34917 @itemx maint show profile
34918 Control profiling of @value{GDBN}.
34920 Profiling will be disabled until you use the @samp{maint set profile}
34921 command to enable it. When you enable profiling, the system will begin
34922 collecting timing and execution count data; when you disable profiling or
34923 exit @value{GDBN}, the results will be written to a log file. Remember that
34924 if you use profiling, @value{GDBN} will overwrite the profiling log file
34925 (often called @file{gmon.out}). If you have a record of important profiling
34926 data in a @file{gmon.out} file, be sure to move it to a safe location.
34928 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34929 compiled with the @samp{-pg} compiler option.
34931 @kindex maint set show-debug-regs
34932 @kindex maint show show-debug-regs
34933 @cindex hardware debug registers
34934 @item maint set show-debug-regs
34935 @itemx maint show show-debug-regs
34936 Control whether to show variables that mirror the hardware debug
34937 registers. Use @code{ON} to enable, @code{OFF} to disable. If
34938 enabled, the debug registers values are shown when @value{GDBN} inserts or
34939 removes a hardware breakpoint or watchpoint, and when the inferior
34940 triggers a hardware-assisted breakpoint or watchpoint.
34942 @kindex maint set show-all-tib
34943 @kindex maint show show-all-tib
34944 @item maint set show-all-tib
34945 @itemx maint show show-all-tib
34946 Control whether to show all non zero areas within a 1k block starting
34947 at thread local base, when using the @samp{info w32 thread-information-block}
34950 @kindex maint space
34951 @cindex memory used by commands
34953 Control whether to display memory usage for each command. If set to a
34954 nonzero value, @value{GDBN} will display how much memory each command
34955 took, following the command's own output. This can also be requested
34956 by invoking @value{GDBN} with the @option{--statistics} command-line
34957 switch (@pxref{Mode Options}).
34960 @cindex time of command execution
34962 Control whether to display the execution time of @value{GDBN} for each command.
34963 If set to a nonzero value, @value{GDBN} will display how much time it
34964 took to execute each command, following the command's own output.
34965 Both CPU time and wallclock time are printed.
34966 Printing both is useful when trying to determine whether the cost is
34967 CPU or, e.g., disk/network, latency.
34968 Note that the CPU time printed is for @value{GDBN} only, it does not include
34969 the execution time of the inferior because there's no mechanism currently
34970 to compute how much time was spent by @value{GDBN} and how much time was
34971 spent by the program been debugged.
34972 This can also be requested by invoking @value{GDBN} with the
34973 @option{--statistics} command-line switch (@pxref{Mode Options}).
34975 @kindex maint translate-address
34976 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34977 Find the symbol stored at the location specified by the address
34978 @var{addr} and an optional section name @var{section}. If found,
34979 @value{GDBN} prints the name of the closest symbol and an offset from
34980 the symbol's location to the specified address. This is similar to
34981 the @code{info address} command (@pxref{Symbols}), except that this
34982 command also allows to find symbols in other sections.
34984 If section was not specified, the section in which the symbol was found
34985 is also printed. For dynamically linked executables, the name of
34986 executable or shared library containing the symbol is printed as well.
34990 The following command is useful for non-interactive invocations of
34991 @value{GDBN}, such as in the test suite.
34994 @item set watchdog @var{nsec}
34995 @kindex set watchdog
34996 @cindex watchdog timer
34997 @cindex timeout for commands
34998 Set the maximum number of seconds @value{GDBN} will wait for the
34999 target operation to finish. If this time expires, @value{GDBN}
35000 reports and error and the command is aborted.
35002 @item show watchdog
35003 Show the current setting of the target wait timeout.
35006 @node Remote Protocol
35007 @appendix @value{GDBN} Remote Serial Protocol
35012 * Stop Reply Packets::
35013 * General Query Packets::
35014 * Architecture-Specific Protocol Details::
35015 * Tracepoint Packets::
35016 * Host I/O Packets::
35018 * Notification Packets::
35019 * Remote Non-Stop::
35020 * Packet Acknowledgment::
35022 * File-I/O Remote Protocol Extension::
35023 * Library List Format::
35024 * Library List Format for SVR4 Targets::
35025 * Memory Map Format::
35026 * Thread List Format::
35027 * Traceframe Info Format::
35033 There may be occasions when you need to know something about the
35034 protocol---for example, if there is only one serial port to your target
35035 machine, you might want your program to do something special if it
35036 recognizes a packet meant for @value{GDBN}.
35038 In the examples below, @samp{->} and @samp{<-} are used to indicate
35039 transmitted and received data, respectively.
35041 @cindex protocol, @value{GDBN} remote serial
35042 @cindex serial protocol, @value{GDBN} remote
35043 @cindex remote serial protocol
35044 All @value{GDBN} commands and responses (other than acknowledgments
35045 and notifications, see @ref{Notification Packets}) are sent as a
35046 @var{packet}. A @var{packet} is introduced with the character
35047 @samp{$}, the actual @var{packet-data}, and the terminating character
35048 @samp{#} followed by a two-digit @var{checksum}:
35051 @code{$}@var{packet-data}@code{#}@var{checksum}
35055 @cindex checksum, for @value{GDBN} remote
35057 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35058 characters between the leading @samp{$} and the trailing @samp{#} (an
35059 eight bit unsigned checksum).
35061 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35062 specification also included an optional two-digit @var{sequence-id}:
35065 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35068 @cindex sequence-id, for @value{GDBN} remote
35070 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35071 has never output @var{sequence-id}s. Stubs that handle packets added
35072 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35074 When either the host or the target machine receives a packet, the first
35075 response expected is an acknowledgment: either @samp{+} (to indicate
35076 the package was received correctly) or @samp{-} (to request
35080 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35085 The @samp{+}/@samp{-} acknowledgments can be disabled
35086 once a connection is established.
35087 @xref{Packet Acknowledgment}, for details.
35089 The host (@value{GDBN}) sends @var{command}s, and the target (the
35090 debugging stub incorporated in your program) sends a @var{response}. In
35091 the case of step and continue @var{command}s, the response is only sent
35092 when the operation has completed, and the target has again stopped all
35093 threads in all attached processes. This is the default all-stop mode
35094 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35095 execution mode; see @ref{Remote Non-Stop}, for details.
35097 @var{packet-data} consists of a sequence of characters with the
35098 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35101 @cindex remote protocol, field separator
35102 Fields within the packet should be separated using @samp{,} @samp{;} or
35103 @samp{:}. Except where otherwise noted all numbers are represented in
35104 @sc{hex} with leading zeros suppressed.
35106 Implementors should note that prior to @value{GDBN} 5.0, the character
35107 @samp{:} could not appear as the third character in a packet (as it
35108 would potentially conflict with the @var{sequence-id}).
35110 @cindex remote protocol, binary data
35111 @anchor{Binary Data}
35112 Binary data in most packets is encoded either as two hexadecimal
35113 digits per byte of binary data. This allowed the traditional remote
35114 protocol to work over connections which were only seven-bit clean.
35115 Some packets designed more recently assume an eight-bit clean
35116 connection, and use a more efficient encoding to send and receive
35119 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35120 as an escape character. Any escaped byte is transmitted as the escape
35121 character followed by the original character XORed with @code{0x20}.
35122 For example, the byte @code{0x7d} would be transmitted as the two
35123 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35124 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35125 @samp{@}}) must always be escaped. Responses sent by the stub
35126 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35127 is not interpreted as the start of a run-length encoded sequence
35130 Response @var{data} can be run-length encoded to save space.
35131 Run-length encoding replaces runs of identical characters with one
35132 instance of the repeated character, followed by a @samp{*} and a
35133 repeat count. The repeat count is itself sent encoded, to avoid
35134 binary characters in @var{data}: a value of @var{n} is sent as
35135 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35136 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35137 code 32) for a repeat count of 3. (This is because run-length
35138 encoding starts to win for counts 3 or more.) Thus, for example,
35139 @samp{0* } is a run-length encoding of ``0000'': the space character
35140 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35143 The printable characters @samp{#} and @samp{$} or with a numeric value
35144 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35145 seven repeats (@samp{$}) can be expanded using a repeat count of only
35146 five (@samp{"}). For example, @samp{00000000} can be encoded as
35149 The error response returned for some packets includes a two character
35150 error number. That number is not well defined.
35152 @cindex empty response, for unsupported packets
35153 For any @var{command} not supported by the stub, an empty response
35154 (@samp{$#00}) should be returned. That way it is possible to extend the
35155 protocol. A newer @value{GDBN} can tell if a packet is supported based
35158 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35159 commands for register access, and the @samp{m} and @samp{M} commands
35160 for memory access. Stubs that only control single-threaded targets
35161 can implement run control with the @samp{c} (continue), and @samp{s}
35162 (step) commands. Stubs that support multi-threading targets should
35163 support the @samp{vCont} command. All other commands are optional.
35168 The following table provides a complete list of all currently defined
35169 @var{command}s and their corresponding response @var{data}.
35170 @xref{File-I/O Remote Protocol Extension}, for details about the File
35171 I/O extension of the remote protocol.
35173 Each packet's description has a template showing the packet's overall
35174 syntax, followed by an explanation of the packet's meaning. We
35175 include spaces in some of the templates for clarity; these are not
35176 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35177 separate its components. For example, a template like @samp{foo
35178 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35179 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35180 @var{baz}. @value{GDBN} does not transmit a space character between the
35181 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35184 @cindex @var{thread-id}, in remote protocol
35185 @anchor{thread-id syntax}
35186 Several packets and replies include a @var{thread-id} field to identify
35187 a thread. Normally these are positive numbers with a target-specific
35188 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35189 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35192 In addition, the remote protocol supports a multiprocess feature in
35193 which the @var{thread-id} syntax is extended to optionally include both
35194 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35195 The @var{pid} (process) and @var{tid} (thread) components each have the
35196 format described above: a positive number with target-specific
35197 interpretation formatted as a big-endian hex string, literal @samp{-1}
35198 to indicate all processes or threads (respectively), or @samp{0} to
35199 indicate an arbitrary process or thread. Specifying just a process, as
35200 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35201 error to specify all processes but a specific thread, such as
35202 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35203 for those packets and replies explicitly documented to include a process
35204 ID, rather than a @var{thread-id}.
35206 The multiprocess @var{thread-id} syntax extensions are only used if both
35207 @value{GDBN} and the stub report support for the @samp{multiprocess}
35208 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35211 Note that all packet forms beginning with an upper- or lower-case
35212 letter, other than those described here, are reserved for future use.
35214 Here are the packet descriptions.
35219 @cindex @samp{!} packet
35220 @anchor{extended mode}
35221 Enable extended mode. In extended mode, the remote server is made
35222 persistent. The @samp{R} packet is used to restart the program being
35228 The remote target both supports and has enabled extended mode.
35232 @cindex @samp{?} packet
35233 Indicate the reason the target halted. The reply is the same as for
35234 step and continue. This packet has a special interpretation when the
35235 target is in non-stop mode; see @ref{Remote Non-Stop}.
35238 @xref{Stop Reply Packets}, for the reply specifications.
35240 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
35241 @cindex @samp{A} packet
35242 Initialized @code{argv[]} array passed into program. @var{arglen}
35243 specifies the number of bytes in the hex encoded byte stream
35244 @var{arg}. See @code{gdbserver} for more details.
35249 The arguments were set.
35255 @cindex @samp{b} packet
35256 (Don't use this packet; its behavior is not well-defined.)
35257 Change the serial line speed to @var{baud}.
35259 JTC: @emph{When does the transport layer state change? When it's
35260 received, or after the ACK is transmitted. In either case, there are
35261 problems if the command or the acknowledgment packet is dropped.}
35263 Stan: @emph{If people really wanted to add something like this, and get
35264 it working for the first time, they ought to modify ser-unix.c to send
35265 some kind of out-of-band message to a specially-setup stub and have the
35266 switch happen "in between" packets, so that from remote protocol's point
35267 of view, nothing actually happened.}
35269 @item B @var{addr},@var{mode}
35270 @cindex @samp{B} packet
35271 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35272 breakpoint at @var{addr}.
35274 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35275 (@pxref{insert breakpoint or watchpoint packet}).
35277 @cindex @samp{bc} packet
35280 Backward continue. Execute the target system in reverse. No parameter.
35281 @xref{Reverse Execution}, for more information.
35284 @xref{Stop Reply Packets}, for the reply specifications.
35286 @cindex @samp{bs} packet
35289 Backward single step. Execute one instruction in reverse. No parameter.
35290 @xref{Reverse Execution}, for more information.
35293 @xref{Stop Reply Packets}, for the reply specifications.
35295 @item c @r{[}@var{addr}@r{]}
35296 @cindex @samp{c} packet
35297 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
35298 resume at current address.
35300 This packet is deprecated for multi-threading support. @xref{vCont
35304 @xref{Stop Reply Packets}, for the reply specifications.
35306 @item C @var{sig}@r{[};@var{addr}@r{]}
35307 @cindex @samp{C} packet
35308 Continue with signal @var{sig} (hex signal number). If
35309 @samp{;@var{addr}} is omitted, resume at same address.
35311 This packet is deprecated for multi-threading support. @xref{vCont
35315 @xref{Stop Reply Packets}, for the reply specifications.
35318 @cindex @samp{d} packet
35321 Don't use this packet; instead, define a general set packet
35322 (@pxref{General Query Packets}).
35326 @cindex @samp{D} packet
35327 The first form of the packet is used to detach @value{GDBN} from the
35328 remote system. It is sent to the remote target
35329 before @value{GDBN} disconnects via the @code{detach} command.
35331 The second form, including a process ID, is used when multiprocess
35332 protocol extensions are enabled (@pxref{multiprocess extensions}), to
35333 detach only a specific process. The @var{pid} is specified as a
35334 big-endian hex string.
35344 @item F @var{RC},@var{EE},@var{CF};@var{XX}
35345 @cindex @samp{F} packet
35346 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
35347 This is part of the File-I/O protocol extension. @xref{File-I/O
35348 Remote Protocol Extension}, for the specification.
35351 @anchor{read registers packet}
35352 @cindex @samp{g} packet
35353 Read general registers.
35357 @item @var{XX@dots{}}
35358 Each byte of register data is described by two hex digits. The bytes
35359 with the register are transmitted in target byte order. The size of
35360 each register and their position within the @samp{g} packet are
35361 determined by the @value{GDBN} internal gdbarch functions
35362 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
35363 specification of several standard @samp{g} packets is specified below.
35365 When reading registers from a trace frame (@pxref{Analyze Collected
35366 Data,,Using the Collected Data}), the stub may also return a string of
35367 literal @samp{x}'s in place of the register data digits, to indicate
35368 that the corresponding register has not been collected, thus its value
35369 is unavailable. For example, for an architecture with 4 registers of
35370 4 bytes each, the following reply indicates to @value{GDBN} that
35371 registers 0 and 2 have not been collected, while registers 1 and 3
35372 have been collected, and both have zero value:
35376 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
35383 @item G @var{XX@dots{}}
35384 @cindex @samp{G} packet
35385 Write general registers. @xref{read registers packet}, for a
35386 description of the @var{XX@dots{}} data.
35396 @item H @var{op} @var{thread-id}
35397 @cindex @samp{H} packet
35398 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
35399 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
35400 it should be @samp{c} for step and continue operations (note that this
35401 is deprecated, supporting the @samp{vCont} command is a better
35402 option), @samp{g} for other operations. The thread designator
35403 @var{thread-id} has the format and interpretation described in
35404 @ref{thread-id syntax}.
35415 @c 'H': How restrictive (or permissive) is the thread model. If a
35416 @c thread is selected and stopped, are other threads allowed
35417 @c to continue to execute? As I mentioned above, I think the
35418 @c semantics of each command when a thread is selected must be
35419 @c described. For example:
35421 @c 'g': If the stub supports threads and a specific thread is
35422 @c selected, returns the register block from that thread;
35423 @c otherwise returns current registers.
35425 @c 'G' If the stub supports threads and a specific thread is
35426 @c selected, sets the registers of the register block of
35427 @c that thread; otherwise sets current registers.
35429 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
35430 @anchor{cycle step packet}
35431 @cindex @samp{i} packet
35432 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
35433 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
35434 step starting at that address.
35437 @cindex @samp{I} packet
35438 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
35442 @cindex @samp{k} packet
35445 FIXME: @emph{There is no description of how to operate when a specific
35446 thread context has been selected (i.e.@: does 'k' kill only that
35449 @item m @var{addr},@var{length}
35450 @cindex @samp{m} packet
35451 Read @var{length} bytes of memory starting at address @var{addr}.
35452 Note that @var{addr} may not be aligned to any particular boundary.
35454 The stub need not use any particular size or alignment when gathering
35455 data from memory for the response; even if @var{addr} is word-aligned
35456 and @var{length} is a multiple of the word size, the stub is free to
35457 use byte accesses, or not. For this reason, this packet may not be
35458 suitable for accessing memory-mapped I/O devices.
35459 @cindex alignment of remote memory accesses
35460 @cindex size of remote memory accesses
35461 @cindex memory, alignment and size of remote accesses
35465 @item @var{XX@dots{}}
35466 Memory contents; each byte is transmitted as a two-digit hexadecimal
35467 number. The reply may contain fewer bytes than requested if the
35468 server was able to read only part of the region of memory.
35473 @item M @var{addr},@var{length}:@var{XX@dots{}}
35474 @cindex @samp{M} packet
35475 Write @var{length} bytes of memory starting at address @var{addr}.
35476 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
35477 hexadecimal number.
35484 for an error (this includes the case where only part of the data was
35489 @cindex @samp{p} packet
35490 Read the value of register @var{n}; @var{n} is in hex.
35491 @xref{read registers packet}, for a description of how the returned
35492 register value is encoded.
35496 @item @var{XX@dots{}}
35497 the register's value
35501 Indicating an unrecognized @var{query}.
35504 @item P @var{n@dots{}}=@var{r@dots{}}
35505 @anchor{write register packet}
35506 @cindex @samp{P} packet
35507 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
35508 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
35509 digits for each byte in the register (target byte order).
35519 @item q @var{name} @var{params}@dots{}
35520 @itemx Q @var{name} @var{params}@dots{}
35521 @cindex @samp{q} packet
35522 @cindex @samp{Q} packet
35523 General query (@samp{q}) and set (@samp{Q}). These packets are
35524 described fully in @ref{General Query Packets}.
35527 @cindex @samp{r} packet
35528 Reset the entire system.
35530 Don't use this packet; use the @samp{R} packet instead.
35533 @cindex @samp{R} packet
35534 Restart the program being debugged. @var{XX}, while needed, is ignored.
35535 This packet is only available in extended mode (@pxref{extended mode}).
35537 The @samp{R} packet has no reply.
35539 @item s @r{[}@var{addr}@r{]}
35540 @cindex @samp{s} packet
35541 Single step. @var{addr} is the address at which to resume. If
35542 @var{addr} is omitted, resume at same address.
35544 This packet is deprecated for multi-threading support. @xref{vCont
35548 @xref{Stop Reply Packets}, for the reply specifications.
35550 @item S @var{sig}@r{[};@var{addr}@r{]}
35551 @anchor{step with signal packet}
35552 @cindex @samp{S} packet
35553 Step with signal. This is analogous to the @samp{C} packet, but
35554 requests a single-step, rather than a normal resumption of execution.
35556 This packet is deprecated for multi-threading support. @xref{vCont
35560 @xref{Stop Reply Packets}, for the reply specifications.
35562 @item t @var{addr}:@var{PP},@var{MM}
35563 @cindex @samp{t} packet
35564 Search backwards starting at address @var{addr} for a match with pattern
35565 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
35566 @var{addr} must be at least 3 digits.
35568 @item T @var{thread-id}
35569 @cindex @samp{T} packet
35570 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
35575 thread is still alive
35581 Packets starting with @samp{v} are identified by a multi-letter name,
35582 up to the first @samp{;} or @samp{?} (or the end of the packet).
35584 @item vAttach;@var{pid}
35585 @cindex @samp{vAttach} packet
35586 Attach to a new process with the specified process ID @var{pid}.
35587 The process ID is a
35588 hexadecimal integer identifying the process. In all-stop mode, all
35589 threads in the attached process are stopped; in non-stop mode, it may be
35590 attached without being stopped if that is supported by the target.
35592 @c In non-stop mode, on a successful vAttach, the stub should set the
35593 @c current thread to a thread of the newly-attached process. After
35594 @c attaching, GDB queries for the attached process's thread ID with qC.
35595 @c Also note that, from a user perspective, whether or not the
35596 @c target is stopped on attach in non-stop mode depends on whether you
35597 @c use the foreground or background version of the attach command, not
35598 @c on what vAttach does; GDB does the right thing with respect to either
35599 @c stopping or restarting threads.
35601 This packet is only available in extended mode (@pxref{extended mode}).
35607 @item @r{Any stop packet}
35608 for success in all-stop mode (@pxref{Stop Reply Packets})
35610 for success in non-stop mode (@pxref{Remote Non-Stop})
35613 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35614 @cindex @samp{vCont} packet
35615 @anchor{vCont packet}
35616 Resume the inferior, specifying different actions for each thread.
35617 If an action is specified with no @var{thread-id}, then it is applied to any
35618 threads that don't have a specific action specified; if no default action is
35619 specified then other threads should remain stopped in all-stop mode and
35620 in their current state in non-stop mode.
35621 Specifying multiple
35622 default actions is an error; specifying no actions is also an error.
35623 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
35625 Currently supported actions are:
35631 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35635 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35640 The optional argument @var{addr} normally associated with the
35641 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35642 not supported in @samp{vCont}.
35644 The @samp{t} action is only relevant in non-stop mode
35645 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35646 A stop reply should be generated for any affected thread not already stopped.
35647 When a thread is stopped by means of a @samp{t} action,
35648 the corresponding stop reply should indicate that the thread has stopped with
35649 signal @samp{0}, regardless of whether the target uses some other signal
35650 as an implementation detail.
35652 The stub must support @samp{vCont} if it reports support for
35653 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
35654 this case @samp{vCont} actions can be specified to apply to all threads
35655 in a process by using the @samp{p@var{pid}.-1} form of the
35659 @xref{Stop Reply Packets}, for the reply specifications.
35662 @cindex @samp{vCont?} packet
35663 Request a list of actions supported by the @samp{vCont} packet.
35667 @item vCont@r{[};@var{action}@dots{}@r{]}
35668 The @samp{vCont} packet is supported. Each @var{action} is a supported
35669 command in the @samp{vCont} packet.
35671 The @samp{vCont} packet is not supported.
35674 @item vFile:@var{operation}:@var{parameter}@dots{}
35675 @cindex @samp{vFile} packet
35676 Perform a file operation on the target system. For details,
35677 see @ref{Host I/O Packets}.
35679 @item vFlashErase:@var{addr},@var{length}
35680 @cindex @samp{vFlashErase} packet
35681 Direct the stub to erase @var{length} bytes of flash starting at
35682 @var{addr}. The region may enclose any number of flash blocks, but
35683 its start and end must fall on block boundaries, as indicated by the
35684 flash block size appearing in the memory map (@pxref{Memory Map
35685 Format}). @value{GDBN} groups flash memory programming operations
35686 together, and sends a @samp{vFlashDone} request after each group; the
35687 stub is allowed to delay erase operation until the @samp{vFlashDone}
35688 packet is received.
35698 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35699 @cindex @samp{vFlashWrite} packet
35700 Direct the stub to write data to flash address @var{addr}. The data
35701 is passed in binary form using the same encoding as for the @samp{X}
35702 packet (@pxref{Binary Data}). The memory ranges specified by
35703 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35704 not overlap, and must appear in order of increasing addresses
35705 (although @samp{vFlashErase} packets for higher addresses may already
35706 have been received; the ordering is guaranteed only between
35707 @samp{vFlashWrite} packets). If a packet writes to an address that was
35708 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35709 target-specific method, the results are unpredictable.
35717 for vFlashWrite addressing non-flash memory
35723 @cindex @samp{vFlashDone} packet
35724 Indicate to the stub that flash programming operation is finished.
35725 The stub is permitted to delay or batch the effects of a group of
35726 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35727 @samp{vFlashDone} packet is received. The contents of the affected
35728 regions of flash memory are unpredictable until the @samp{vFlashDone}
35729 request is completed.
35731 @item vKill;@var{pid}
35732 @cindex @samp{vKill} packet
35733 Kill the process with the specified process ID. @var{pid} is a
35734 hexadecimal integer identifying the process. This packet is used in
35735 preference to @samp{k} when multiprocess protocol extensions are
35736 supported; see @ref{multiprocess extensions}.
35746 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35747 @cindex @samp{vRun} packet
35748 Run the program @var{filename}, passing it each @var{argument} on its
35749 command line. The file and arguments are hex-encoded strings. If
35750 @var{filename} is an empty string, the stub may use a default program
35751 (e.g.@: the last program run). The program is created in the stopped
35754 @c FIXME: What about non-stop mode?
35756 This packet is only available in extended mode (@pxref{extended mode}).
35762 @item @r{Any stop packet}
35763 for success (@pxref{Stop Reply Packets})
35767 @anchor{vStopped packet}
35768 @cindex @samp{vStopped} packet
35770 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
35771 reply and prompt for the stub to report another one.
35775 @item @r{Any stop packet}
35776 if there is another unreported stop event (@pxref{Stop Reply Packets})
35778 if there are no unreported stop events
35781 @item X @var{addr},@var{length}:@var{XX@dots{}}
35783 @cindex @samp{X} packet
35784 Write data to memory, where the data is transmitted in binary.
35785 @var{addr} is address, @var{length} is number of bytes,
35786 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35796 @item z @var{type},@var{addr},@var{kind}
35797 @itemx Z @var{type},@var{addr},@var{kind}
35798 @anchor{insert breakpoint or watchpoint packet}
35799 @cindex @samp{z} packet
35800 @cindex @samp{Z} packets
35801 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35802 watchpoint starting at address @var{address} of kind @var{kind}.
35804 Each breakpoint and watchpoint packet @var{type} is documented
35807 @emph{Implementation notes: A remote target shall return an empty string
35808 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35809 remote target shall support either both or neither of a given
35810 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35811 avoid potential problems with duplicate packets, the operations should
35812 be implemented in an idempotent way.}
35814 @item z0,@var{addr},@var{kind}
35815 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35816 @cindex @samp{z0} packet
35817 @cindex @samp{Z0} packet
35818 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
35819 @var{addr} of type @var{kind}.
35821 A memory breakpoint is implemented by replacing the instruction at
35822 @var{addr} with a software breakpoint or trap instruction. The
35823 @var{kind} is target-specific and typically indicates the size of
35824 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
35825 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35826 architectures have additional meanings for @var{kind};
35827 @var{cond_list} is an optional list of conditional expressions in bytecode
35828 form that should be evaluated on the target's side. These are the
35829 conditions that should be taken into consideration when deciding if
35830 the breakpoint trigger should be reported back to @var{GDBN}.
35832 The @var{cond_list} parameter is comprised of a series of expressions,
35833 concatenated without separators. Each expression has the following form:
35837 @item X @var{len},@var{expr}
35838 @var{len} is the length of the bytecode expression and @var{expr} is the
35839 actual conditional expression in bytecode form.
35843 The optional @var{cmd_list} parameter introduces commands that may be
35844 run on the target, rather than being reported back to @value{GDBN}.
35845 The parameter starts with a numeric flag @var{persist}; if the flag is
35846 nonzero, then the breakpoint may remain active and the commands
35847 continue to be run even when @value{GDBN} disconnects from the target.
35848 Following this flag is a series of expressions concatenated with no
35849 separators. Each expression has the following form:
35853 @item X @var{len},@var{expr}
35854 @var{len} is the length of the bytecode expression and @var{expr} is the
35855 actual conditional expression in bytecode form.
35859 see @ref{Architecture-Specific Protocol Details}.
35861 @emph{Implementation note: It is possible for a target to copy or move
35862 code that contains memory breakpoints (e.g., when implementing
35863 overlays). The behavior of this packet, in the presence of such a
35864 target, is not defined.}
35876 @item z1,@var{addr},@var{kind}
35877 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35878 @cindex @samp{z1} packet
35879 @cindex @samp{Z1} packet
35880 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35881 address @var{addr}.
35883 A hardware breakpoint is implemented using a mechanism that is not
35884 dependant on being able to modify the target's memory. @var{kind}
35885 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35887 @emph{Implementation note: A hardware breakpoint is not affected by code
35900 @item z2,@var{addr},@var{kind}
35901 @itemx Z2,@var{addr},@var{kind}
35902 @cindex @samp{z2} packet
35903 @cindex @samp{Z2} packet
35904 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35905 @var{kind} is interpreted as the number of bytes to watch.
35917 @item z3,@var{addr},@var{kind}
35918 @itemx Z3,@var{addr},@var{kind}
35919 @cindex @samp{z3} packet
35920 @cindex @samp{Z3} packet
35921 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35922 @var{kind} is interpreted as the number of bytes to watch.
35934 @item z4,@var{addr},@var{kind}
35935 @itemx Z4,@var{addr},@var{kind}
35936 @cindex @samp{z4} packet
35937 @cindex @samp{Z4} packet
35938 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35939 @var{kind} is interpreted as the number of bytes to watch.
35953 @node Stop Reply Packets
35954 @section Stop Reply Packets
35955 @cindex stop reply packets
35957 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35958 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35959 receive any of the below as a reply. Except for @samp{?}
35960 and @samp{vStopped}, that reply is only returned
35961 when the target halts. In the below the exact meaning of @dfn{signal
35962 number} is defined by the header @file{include/gdb/signals.h} in the
35963 @value{GDBN} source code.
35965 As in the description of request packets, we include spaces in the
35966 reply templates for clarity; these are not part of the reply packet's
35967 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35973 The program received signal number @var{AA} (a two-digit hexadecimal
35974 number). This is equivalent to a @samp{T} response with no
35975 @var{n}:@var{r} pairs.
35977 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35978 @cindex @samp{T} packet reply
35979 The program received signal number @var{AA} (a two-digit hexadecimal
35980 number). This is equivalent to an @samp{S} response, except that the
35981 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35982 and other information directly in the stop reply packet, reducing
35983 round-trip latency. Single-step and breakpoint traps are reported
35984 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35988 If @var{n} is a hexadecimal number, it is a register number, and the
35989 corresponding @var{r} gives that register's value. @var{r} is a
35990 series of bytes in target byte order, with each byte given by a
35991 two-digit hex number.
35994 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35995 the stopped thread, as specified in @ref{thread-id syntax}.
35998 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35999 the core on which the stop event was detected.
36002 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36003 specific event that stopped the target. The currently defined stop
36004 reasons are listed below. @var{aa} should be @samp{05}, the trap
36005 signal. At most one stop reason should be present.
36008 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36009 and go on to the next; this allows us to extend the protocol in the
36013 The currently defined stop reasons are:
36019 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36022 @cindex shared library events, remote reply
36024 The packet indicates that the loaded libraries have changed.
36025 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36026 list of loaded libraries. @var{r} is ignored.
36028 @cindex replay log events, remote reply
36030 The packet indicates that the target cannot continue replaying
36031 logged execution events, because it has reached the end (or the
36032 beginning when executing backward) of the log. The value of @var{r}
36033 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36034 for more information.
36038 @itemx W @var{AA} ; process:@var{pid}
36039 The process exited, and @var{AA} is the exit status. This is only
36040 applicable to certain targets.
36042 The second form of the response, including the process ID of the exited
36043 process, can be used only when @value{GDBN} has reported support for
36044 multiprocess protocol extensions; see @ref{multiprocess extensions}.
36045 The @var{pid} is formatted as a big-endian hex string.
36048 @itemx X @var{AA} ; process:@var{pid}
36049 The process terminated with signal @var{AA}.
36051 The second form of the response, including the process ID of the
36052 terminated process, can be used only when @value{GDBN} has reported
36053 support for multiprocess protocol extensions; see @ref{multiprocess
36054 extensions}. The @var{pid} is formatted as a big-endian hex string.
36056 @item O @var{XX}@dots{}
36057 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36058 written as the program's console output. This can happen at any time
36059 while the program is running and the debugger should continue to wait
36060 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36062 @item F @var{call-id},@var{parameter}@dots{}
36063 @var{call-id} is the identifier which says which host system call should
36064 be called. This is just the name of the function. Translation into the
36065 correct system call is only applicable as it's defined in @value{GDBN}.
36066 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36069 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36070 this very system call.
36072 The target replies with this packet when it expects @value{GDBN} to
36073 call a host system call on behalf of the target. @value{GDBN} replies
36074 with an appropriate @samp{F} packet and keeps up waiting for the next
36075 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36076 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36077 Protocol Extension}, for more details.
36081 @node General Query Packets
36082 @section General Query Packets
36083 @cindex remote query requests
36085 Packets starting with @samp{q} are @dfn{general query packets};
36086 packets starting with @samp{Q} are @dfn{general set packets}. General
36087 query and set packets are a semi-unified form for retrieving and
36088 sending information to and from the stub.
36090 The initial letter of a query or set packet is followed by a name
36091 indicating what sort of thing the packet applies to. For example,
36092 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36093 definitions with the stub. These packet names follow some
36098 The name must not contain commas, colons or semicolons.
36100 Most @value{GDBN} query and set packets have a leading upper case
36103 The names of custom vendor packets should use a company prefix, in
36104 lower case, followed by a period. For example, packets designed at
36105 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36106 foos) or @samp{Qacme.bar} (for setting bars).
36109 The name of a query or set packet should be separated from any
36110 parameters by a @samp{:}; the parameters themselves should be
36111 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36112 full packet name, and check for a separator or the end of the packet,
36113 in case two packet names share a common prefix. New packets should not begin
36114 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36115 packets predate these conventions, and have arguments without any terminator
36116 for the packet name; we suspect they are in widespread use in places that
36117 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36118 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36121 Like the descriptions of the other packets, each description here
36122 has a template showing the packet's overall syntax, followed by an
36123 explanation of the packet's meaning. We include spaces in some of the
36124 templates for clarity; these are not part of the packet's syntax. No
36125 @value{GDBN} packet uses spaces to separate its components.
36127 Here are the currently defined query and set packets:
36133 Turn on or off the agent as a helper to perform some debugging operations
36134 delegated from @value{GDBN} (@pxref{Control Agent}).
36136 @item QAllow:@var{op}:@var{val}@dots{}
36137 @cindex @samp{QAllow} packet
36138 Specify which operations @value{GDBN} expects to request of the
36139 target, as a semicolon-separated list of operation name and value
36140 pairs. Possible values for @var{op} include @samp{WriteReg},
36141 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36142 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36143 indicating that @value{GDBN} will not request the operation, or 1,
36144 indicating that it may. (The target can then use this to set up its
36145 own internals optimally, for instance if the debugger never expects to
36146 insert breakpoints, it may not need to install its own trap handler.)
36149 @cindex current thread, remote request
36150 @cindex @samp{qC} packet
36151 Return the current thread ID.
36155 @item QC @var{thread-id}
36156 Where @var{thread-id} is a thread ID as documented in
36157 @ref{thread-id syntax}.
36158 @item @r{(anything else)}
36159 Any other reply implies the old thread ID.
36162 @item qCRC:@var{addr},@var{length}
36163 @cindex CRC of memory block, remote request
36164 @cindex @samp{qCRC} packet
36165 Compute the CRC checksum of a block of memory using CRC-32 defined in
36166 IEEE 802.3. The CRC is computed byte at a time, taking the most
36167 significant bit of each byte first. The initial pattern code
36168 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36170 @emph{Note:} This is the same CRC used in validating separate debug
36171 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36172 Files}). However the algorithm is slightly different. When validating
36173 separate debug files, the CRC is computed taking the @emph{least}
36174 significant bit of each byte first, and the final result is inverted to
36175 detect trailing zeros.
36180 An error (such as memory fault)
36181 @item C @var{crc32}
36182 The specified memory region's checksum is @var{crc32}.
36185 @item QDisableRandomization:@var{value}
36186 @cindex disable address space randomization, remote request
36187 @cindex @samp{QDisableRandomization} packet
36188 Some target operating systems will randomize the virtual address space
36189 of the inferior process as a security feature, but provide a feature
36190 to disable such randomization, e.g.@: to allow for a more deterministic
36191 debugging experience. On such systems, this packet with a @var{value}
36192 of 1 directs the target to disable address space randomization for
36193 processes subsequently started via @samp{vRun} packets, while a packet
36194 with a @var{value} of 0 tells the target to enable address space
36197 This packet is only available in extended mode (@pxref{extended mode}).
36202 The request succeeded.
36205 An error occurred. @var{nn} are hex digits.
36208 An empty reply indicates that @samp{QDisableRandomization} is not supported
36212 This packet is not probed by default; the remote stub must request it,
36213 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36214 This should only be done on targets that actually support disabling
36215 address space randomization.
36218 @itemx qsThreadInfo
36219 @cindex list active threads, remote request
36220 @cindex @samp{qfThreadInfo} packet
36221 @cindex @samp{qsThreadInfo} packet
36222 Obtain a list of all active thread IDs from the target (OS). Since there
36223 may be too many active threads to fit into one reply packet, this query
36224 works iteratively: it may require more than one query/reply sequence to
36225 obtain the entire list of threads. The first query of the sequence will
36226 be the @samp{qfThreadInfo} query; subsequent queries in the
36227 sequence will be the @samp{qsThreadInfo} query.
36229 NOTE: This packet replaces the @samp{qL} query (see below).
36233 @item m @var{thread-id}
36235 @item m @var{thread-id},@var{thread-id}@dots{}
36236 a comma-separated list of thread IDs
36238 (lower case letter @samp{L}) denotes end of list.
36241 In response to each query, the target will reply with a list of one or
36242 more thread IDs, separated by commas.
36243 @value{GDBN} will respond to each reply with a request for more thread
36244 ids (using the @samp{qs} form of the query), until the target responds
36245 with @samp{l} (lower-case ell, for @dfn{last}).
36246 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
36249 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
36250 @cindex get thread-local storage address, remote request
36251 @cindex @samp{qGetTLSAddr} packet
36252 Fetch the address associated with thread local storage specified
36253 by @var{thread-id}, @var{offset}, and @var{lm}.
36255 @var{thread-id} is the thread ID associated with the
36256 thread for which to fetch the TLS address. @xref{thread-id syntax}.
36258 @var{offset} is the (big endian, hex encoded) offset associated with the
36259 thread local variable. (This offset is obtained from the debug
36260 information associated with the variable.)
36262 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
36263 load module associated with the thread local storage. For example,
36264 a @sc{gnu}/Linux system will pass the link map address of the shared
36265 object associated with the thread local storage under consideration.
36266 Other operating environments may choose to represent the load module
36267 differently, so the precise meaning of this parameter will vary.
36271 @item @var{XX}@dots{}
36272 Hex encoded (big endian) bytes representing the address of the thread
36273 local storage requested.
36276 An error occurred. @var{nn} are hex digits.
36279 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
36282 @item qGetTIBAddr:@var{thread-id}
36283 @cindex get thread information block address
36284 @cindex @samp{qGetTIBAddr} packet
36285 Fetch address of the Windows OS specific Thread Information Block.
36287 @var{thread-id} is the thread ID associated with the thread.
36291 @item @var{XX}@dots{}
36292 Hex encoded (big endian) bytes representing the linear address of the
36293 thread information block.
36296 An error occured. This means that either the thread was not found, or the
36297 address could not be retrieved.
36300 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
36303 @item qL @var{startflag} @var{threadcount} @var{nextthread}
36304 Obtain thread information from RTOS. Where: @var{startflag} (one hex
36305 digit) is one to indicate the first query and zero to indicate a
36306 subsequent query; @var{threadcount} (two hex digits) is the maximum
36307 number of threads the response packet can contain; and @var{nextthread}
36308 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
36309 returned in the response as @var{argthread}.
36311 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
36315 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
36316 Where: @var{count} (two hex digits) is the number of threads being
36317 returned; @var{done} (one hex digit) is zero to indicate more threads
36318 and one indicates no further threads; @var{argthreadid} (eight hex
36319 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
36320 is a sequence of thread IDs from the target. @var{threadid} (eight hex
36321 digits). See @code{remote.c:parse_threadlist_response()}.
36325 @cindex section offsets, remote request
36326 @cindex @samp{qOffsets} packet
36327 Get section offsets that the target used when relocating the downloaded
36332 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
36333 Relocate the @code{Text} section by @var{xxx} from its original address.
36334 Relocate the @code{Data} section by @var{yyy} from its original address.
36335 If the object file format provides segment information (e.g.@: @sc{elf}
36336 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
36337 segments by the supplied offsets.
36339 @emph{Note: while a @code{Bss} offset may be included in the response,
36340 @value{GDBN} ignores this and instead applies the @code{Data} offset
36341 to the @code{Bss} section.}
36343 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
36344 Relocate the first segment of the object file, which conventionally
36345 contains program code, to a starting address of @var{xxx}. If
36346 @samp{DataSeg} is specified, relocate the second segment, which
36347 conventionally contains modifiable data, to a starting address of
36348 @var{yyy}. @value{GDBN} will report an error if the object file
36349 does not contain segment information, or does not contain at least
36350 as many segments as mentioned in the reply. Extra segments are
36351 kept at fixed offsets relative to the last relocated segment.
36354 @item qP @var{mode} @var{thread-id}
36355 @cindex thread information, remote request
36356 @cindex @samp{qP} packet
36357 Returns information on @var{thread-id}. Where: @var{mode} is a hex
36358 encoded 32 bit mode; @var{thread-id} is a thread ID
36359 (@pxref{thread-id syntax}).
36361 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
36364 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
36368 @cindex non-stop mode, remote request
36369 @cindex @samp{QNonStop} packet
36371 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
36372 @xref{Remote Non-Stop}, for more information.
36377 The request succeeded.
36380 An error occurred. @var{nn} are hex digits.
36383 An empty reply indicates that @samp{QNonStop} is not supported by
36387 This packet is not probed by default; the remote stub must request it,
36388 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36389 Use of this packet is controlled by the @code{set non-stop} command;
36390 @pxref{Non-Stop Mode}.
36392 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36393 @cindex pass signals to inferior, remote request
36394 @cindex @samp{QPassSignals} packet
36395 @anchor{QPassSignals}
36396 Each listed @var{signal} should be passed directly to the inferior process.
36397 Signals are numbered identically to continue packets and stop replies
36398 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36399 strictly greater than the previous item. These signals do not need to stop
36400 the inferior, or be reported to @value{GDBN}. All other signals should be
36401 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
36402 combine; any earlier @samp{QPassSignals} list is completely replaced by the
36403 new list. This packet improves performance when using @samp{handle
36404 @var{signal} nostop noprint pass}.
36409 The request succeeded.
36412 An error occurred. @var{nn} are hex digits.
36415 An empty reply indicates that @samp{QPassSignals} is not supported by
36419 Use of this packet is controlled by the @code{set remote pass-signals}
36420 command (@pxref{Remote Configuration, set remote pass-signals}).
36421 This packet is not probed by default; the remote stub must request it,
36422 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36424 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36425 @cindex signals the inferior may see, remote request
36426 @cindex @samp{QProgramSignals} packet
36427 @anchor{QProgramSignals}
36428 Each listed @var{signal} may be delivered to the inferior process.
36429 Others should be silently discarded.
36431 In some cases, the remote stub may need to decide whether to deliver a
36432 signal to the program or not without @value{GDBN} involvement. One
36433 example of that is while detaching --- the program's threads may have
36434 stopped for signals that haven't yet had a chance of being reported to
36435 @value{GDBN}, and so the remote stub can use the signal list specified
36436 by this packet to know whether to deliver or ignore those pending
36439 This does not influence whether to deliver a signal as requested by a
36440 resumption packet (@pxref{vCont packet}).
36442 Signals are numbered identically to continue packets and stop replies
36443 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36444 strictly greater than the previous item. Multiple
36445 @samp{QProgramSignals} packets do not combine; any earlier
36446 @samp{QProgramSignals} list is completely replaced by the new list.
36451 The request succeeded.
36454 An error occurred. @var{nn} are hex digits.
36457 An empty reply indicates that @samp{QProgramSignals} is not supported
36461 Use of this packet is controlled by the @code{set remote program-signals}
36462 command (@pxref{Remote Configuration, set remote program-signals}).
36463 This packet is not probed by default; the remote stub must request it,
36464 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36466 @item qRcmd,@var{command}
36467 @cindex execute remote command, remote request
36468 @cindex @samp{qRcmd} packet
36469 @var{command} (hex encoded) is passed to the local interpreter for
36470 execution. Invalid commands should be reported using the output
36471 string. Before the final result packet, the target may also respond
36472 with a number of intermediate @samp{O@var{output}} console output
36473 packets. @emph{Implementors should note that providing access to a
36474 stubs's interpreter may have security implications}.
36479 A command response with no output.
36481 A command response with the hex encoded output string @var{OUTPUT}.
36483 Indicate a badly formed request.
36485 An empty reply indicates that @samp{qRcmd} is not recognized.
36488 (Note that the @code{qRcmd} packet's name is separated from the
36489 command by a @samp{,}, not a @samp{:}, contrary to the naming
36490 conventions above. Please don't use this packet as a model for new
36493 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
36494 @cindex searching memory, in remote debugging
36495 @cindex @samp{qSearch:memory} packet
36496 @anchor{qSearch memory}
36497 Search @var{length} bytes at @var{address} for @var{search-pattern}.
36498 @var{address} and @var{length} are encoded in hex.
36499 @var{search-pattern} is a sequence of bytes, hex encoded.
36504 The pattern was not found.
36506 The pattern was found at @var{address}.
36508 A badly formed request or an error was encountered while searching memory.
36510 An empty reply indicates that @samp{qSearch:memory} is not recognized.
36513 @item QStartNoAckMode
36514 @cindex @samp{QStartNoAckMode} packet
36515 @anchor{QStartNoAckMode}
36516 Request that the remote stub disable the normal @samp{+}/@samp{-}
36517 protocol acknowledgments (@pxref{Packet Acknowledgment}).
36522 The stub has switched to no-acknowledgment mode.
36523 @value{GDBN} acknowledges this reponse,
36524 but neither the stub nor @value{GDBN} shall send or expect further
36525 @samp{+}/@samp{-} acknowledgments in the current connection.
36527 An empty reply indicates that the stub does not support no-acknowledgment mode.
36530 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
36531 @cindex supported packets, remote query
36532 @cindex features of the remote protocol
36533 @cindex @samp{qSupported} packet
36534 @anchor{qSupported}
36535 Tell the remote stub about features supported by @value{GDBN}, and
36536 query the stub for features it supports. This packet allows
36537 @value{GDBN} and the remote stub to take advantage of each others'
36538 features. @samp{qSupported} also consolidates multiple feature probes
36539 at startup, to improve @value{GDBN} performance---a single larger
36540 packet performs better than multiple smaller probe packets on
36541 high-latency links. Some features may enable behavior which must not
36542 be on by default, e.g.@: because it would confuse older clients or
36543 stubs. Other features may describe packets which could be
36544 automatically probed for, but are not. These features must be
36545 reported before @value{GDBN} will use them. This ``default
36546 unsupported'' behavior is not appropriate for all packets, but it
36547 helps to keep the initial connection time under control with new
36548 versions of @value{GDBN} which support increasing numbers of packets.
36552 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
36553 The stub supports or does not support each returned @var{stubfeature},
36554 depending on the form of each @var{stubfeature} (see below for the
36557 An empty reply indicates that @samp{qSupported} is not recognized,
36558 or that no features needed to be reported to @value{GDBN}.
36561 The allowed forms for each feature (either a @var{gdbfeature} in the
36562 @samp{qSupported} packet, or a @var{stubfeature} in the response)
36566 @item @var{name}=@var{value}
36567 The remote protocol feature @var{name} is supported, and associated
36568 with the specified @var{value}. The format of @var{value} depends
36569 on the feature, but it must not include a semicolon.
36571 The remote protocol feature @var{name} is supported, and does not
36572 need an associated value.
36574 The remote protocol feature @var{name} is not supported.
36576 The remote protocol feature @var{name} may be supported, and
36577 @value{GDBN} should auto-detect support in some other way when it is
36578 needed. This form will not be used for @var{gdbfeature} notifications,
36579 but may be used for @var{stubfeature} responses.
36582 Whenever the stub receives a @samp{qSupported} request, the
36583 supplied set of @value{GDBN} features should override any previous
36584 request. This allows @value{GDBN} to put the stub in a known
36585 state, even if the stub had previously been communicating with
36586 a different version of @value{GDBN}.
36588 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
36593 This feature indicates whether @value{GDBN} supports multiprocess
36594 extensions to the remote protocol. @value{GDBN} does not use such
36595 extensions unless the stub also reports that it supports them by
36596 including @samp{multiprocess+} in its @samp{qSupported} reply.
36597 @xref{multiprocess extensions}, for details.
36600 This feature indicates that @value{GDBN} supports the XML target
36601 description. If the stub sees @samp{xmlRegisters=} with target
36602 specific strings separated by a comma, it will report register
36606 This feature indicates whether @value{GDBN} supports the
36607 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
36608 instruction reply packet}).
36611 Stubs should ignore any unknown values for
36612 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
36613 packet supports receiving packets of unlimited length (earlier
36614 versions of @value{GDBN} may reject overly long responses). Additional values
36615 for @var{gdbfeature} may be defined in the future to let the stub take
36616 advantage of new features in @value{GDBN}, e.g.@: incompatible
36617 improvements in the remote protocol---the @samp{multiprocess} feature is
36618 an example of such a feature. The stub's reply should be independent
36619 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
36620 describes all the features it supports, and then the stub replies with
36621 all the features it supports.
36623 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
36624 responses, as long as each response uses one of the standard forms.
36626 Some features are flags. A stub which supports a flag feature
36627 should respond with a @samp{+} form response. Other features
36628 require values, and the stub should respond with an @samp{=}
36631 Each feature has a default value, which @value{GDBN} will use if
36632 @samp{qSupported} is not available or if the feature is not mentioned
36633 in the @samp{qSupported} response. The default values are fixed; a
36634 stub is free to omit any feature responses that match the defaults.
36636 Not all features can be probed, but for those which can, the probing
36637 mechanism is useful: in some cases, a stub's internal
36638 architecture may not allow the protocol layer to know some information
36639 about the underlying target in advance. This is especially common in
36640 stubs which may be configured for multiple targets.
36642 These are the currently defined stub features and their properties:
36644 @multitable @columnfractions 0.35 0.2 0.12 0.2
36645 @c NOTE: The first row should be @headitem, but we do not yet require
36646 @c a new enough version of Texinfo (4.7) to use @headitem.
36648 @tab Value Required
36652 @item @samp{PacketSize}
36657 @item @samp{qXfer:auxv:read}
36662 @item @samp{qXfer:features:read}
36667 @item @samp{qXfer:libraries:read}
36672 @item @samp{qXfer:memory-map:read}
36677 @item @samp{qXfer:sdata:read}
36682 @item @samp{qXfer:spu:read}
36687 @item @samp{qXfer:spu:write}
36692 @item @samp{qXfer:siginfo:read}
36697 @item @samp{qXfer:siginfo:write}
36702 @item @samp{qXfer:threads:read}
36707 @item @samp{qXfer:traceframe-info:read}
36712 @item @samp{qXfer:uib:read}
36717 @item @samp{qXfer:fdpic:read}
36722 @item @samp{QNonStop}
36727 @item @samp{QPassSignals}
36732 @item @samp{QStartNoAckMode}
36737 @item @samp{multiprocess}
36742 @item @samp{ConditionalBreakpoints}
36747 @item @samp{ConditionalTracepoints}
36752 @item @samp{ReverseContinue}
36757 @item @samp{ReverseStep}
36762 @item @samp{TracepointSource}
36767 @item @samp{QAgent}
36772 @item @samp{QAllow}
36777 @item @samp{QDisableRandomization}
36782 @item @samp{EnableDisableTracepoints}
36787 @item @samp{tracenz}
36792 @item @samp{BreakpointCommands}
36799 These are the currently defined stub features, in more detail:
36802 @cindex packet size, remote protocol
36803 @item PacketSize=@var{bytes}
36804 The remote stub can accept packets up to at least @var{bytes} in
36805 length. @value{GDBN} will send packets up to this size for bulk
36806 transfers, and will never send larger packets. This is a limit on the
36807 data characters in the packet, including the frame and checksum.
36808 There is no trailing NUL byte in a remote protocol packet; if the stub
36809 stores packets in a NUL-terminated format, it should allow an extra
36810 byte in its buffer for the NUL. If this stub feature is not supported,
36811 @value{GDBN} guesses based on the size of the @samp{g} packet response.
36813 @item qXfer:auxv:read
36814 The remote stub understands the @samp{qXfer:auxv:read} packet
36815 (@pxref{qXfer auxiliary vector read}).
36817 @item qXfer:features:read
36818 The remote stub understands the @samp{qXfer:features:read} packet
36819 (@pxref{qXfer target description read}).
36821 @item qXfer:libraries:read
36822 The remote stub understands the @samp{qXfer:libraries:read} packet
36823 (@pxref{qXfer library list read}).
36825 @item qXfer:libraries-svr4:read
36826 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
36827 (@pxref{qXfer svr4 library list read}).
36829 @item qXfer:memory-map:read
36830 The remote stub understands the @samp{qXfer:memory-map:read} packet
36831 (@pxref{qXfer memory map read}).
36833 @item qXfer:sdata:read
36834 The remote stub understands the @samp{qXfer:sdata:read} packet
36835 (@pxref{qXfer sdata read}).
36837 @item qXfer:spu:read
36838 The remote stub understands the @samp{qXfer:spu:read} packet
36839 (@pxref{qXfer spu read}).
36841 @item qXfer:spu:write
36842 The remote stub understands the @samp{qXfer:spu:write} packet
36843 (@pxref{qXfer spu write}).
36845 @item qXfer:siginfo:read
36846 The remote stub understands the @samp{qXfer:siginfo:read} packet
36847 (@pxref{qXfer siginfo read}).
36849 @item qXfer:siginfo:write
36850 The remote stub understands the @samp{qXfer:siginfo:write} packet
36851 (@pxref{qXfer siginfo write}).
36853 @item qXfer:threads:read
36854 The remote stub understands the @samp{qXfer:threads:read} packet
36855 (@pxref{qXfer threads read}).
36857 @item qXfer:traceframe-info:read
36858 The remote stub understands the @samp{qXfer:traceframe-info:read}
36859 packet (@pxref{qXfer traceframe info read}).
36861 @item qXfer:uib:read
36862 The remote stub understands the @samp{qXfer:uib:read}
36863 packet (@pxref{qXfer unwind info block}).
36865 @item qXfer:fdpic:read
36866 The remote stub understands the @samp{qXfer:fdpic:read}
36867 packet (@pxref{qXfer fdpic loadmap read}).
36870 The remote stub understands the @samp{QNonStop} packet
36871 (@pxref{QNonStop}).
36874 The remote stub understands the @samp{QPassSignals} packet
36875 (@pxref{QPassSignals}).
36877 @item QStartNoAckMode
36878 The remote stub understands the @samp{QStartNoAckMode} packet and
36879 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
36882 @anchor{multiprocess extensions}
36883 @cindex multiprocess extensions, in remote protocol
36884 The remote stub understands the multiprocess extensions to the remote
36885 protocol syntax. The multiprocess extensions affect the syntax of
36886 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
36887 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
36888 replies. Note that reporting this feature indicates support for the
36889 syntactic extensions only, not that the stub necessarily supports
36890 debugging of more than one process at a time. The stub must not use
36891 multiprocess extensions in packet replies unless @value{GDBN} has also
36892 indicated it supports them in its @samp{qSupported} request.
36894 @item qXfer:osdata:read
36895 The remote stub understands the @samp{qXfer:osdata:read} packet
36896 ((@pxref{qXfer osdata read}).
36898 @item ConditionalBreakpoints
36899 The target accepts and implements evaluation of conditional expressions
36900 defined for breakpoints. The target will only report breakpoint triggers
36901 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
36903 @item ConditionalTracepoints
36904 The remote stub accepts and implements conditional expressions defined
36905 for tracepoints (@pxref{Tracepoint Conditions}).
36907 @item ReverseContinue
36908 The remote stub accepts and implements the reverse continue packet
36912 The remote stub accepts and implements the reverse step packet
36915 @item TracepointSource
36916 The remote stub understands the @samp{QTDPsrc} packet that supplies
36917 the source form of tracepoint definitions.
36920 The remote stub understands the @samp{QAgent} packet.
36923 The remote stub understands the @samp{QAllow} packet.
36925 @item QDisableRandomization
36926 The remote stub understands the @samp{QDisableRandomization} packet.
36928 @item StaticTracepoint
36929 @cindex static tracepoints, in remote protocol
36930 The remote stub supports static tracepoints.
36932 @item InstallInTrace
36933 @anchor{install tracepoint in tracing}
36934 The remote stub supports installing tracepoint in tracing.
36936 @item EnableDisableTracepoints
36937 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
36938 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
36939 to be enabled and disabled while a trace experiment is running.
36942 @cindex string tracing, in remote protocol
36943 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
36944 See @ref{Bytecode Descriptions} for details about the bytecode.
36946 @item BreakpointCommands
36947 @cindex breakpoint commands, in remote protocol
36948 The remote stub supports running a breakpoint's command list itself,
36949 rather than reporting the hit to @value{GDBN}.
36954 @cindex symbol lookup, remote request
36955 @cindex @samp{qSymbol} packet
36956 Notify the target that @value{GDBN} is prepared to serve symbol lookup
36957 requests. Accept requests from the target for the values of symbols.
36962 The target does not need to look up any (more) symbols.
36963 @item qSymbol:@var{sym_name}
36964 The target requests the value of symbol @var{sym_name} (hex encoded).
36965 @value{GDBN} may provide the value by using the
36966 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
36970 @item qSymbol:@var{sym_value}:@var{sym_name}
36971 Set the value of @var{sym_name} to @var{sym_value}.
36973 @var{sym_name} (hex encoded) is the name of a symbol whose value the
36974 target has previously requested.
36976 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
36977 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
36983 The target does not need to look up any (more) symbols.
36984 @item qSymbol:@var{sym_name}
36985 The target requests the value of a new symbol @var{sym_name} (hex
36986 encoded). @value{GDBN} will continue to supply the values of symbols
36987 (if available), until the target ceases to request them.
36992 @item QTDisconnected
36999 @itemx qTMinFTPILen
37001 @xref{Tracepoint Packets}.
37003 @item qThreadExtraInfo,@var{thread-id}
37004 @cindex thread attributes info, remote request
37005 @cindex @samp{qThreadExtraInfo} packet
37006 Obtain a printable string description of a thread's attributes from
37007 the target OS. @var{thread-id} is a thread ID;
37008 see @ref{thread-id syntax}. This
37009 string may contain anything that the target OS thinks is interesting
37010 for @value{GDBN} to tell the user about the thread. The string is
37011 displayed in @value{GDBN}'s @code{info threads} display. Some
37012 examples of possible thread extra info strings are @samp{Runnable}, or
37013 @samp{Blocked on Mutex}.
37017 @item @var{XX}@dots{}
37018 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37019 comprising the printable string containing the extra information about
37020 the thread's attributes.
37023 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37024 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37025 conventions above. Please don't use this packet as a model for new
37044 @xref{Tracepoint Packets}.
37046 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37047 @cindex read special object, remote request
37048 @cindex @samp{qXfer} packet
37049 @anchor{qXfer read}
37050 Read uninterpreted bytes from the target's special data area
37051 identified by the keyword @var{object}. Request @var{length} bytes
37052 starting at @var{offset} bytes into the data. The content and
37053 encoding of @var{annex} is specific to @var{object}; it can supply
37054 additional details about what data to access.
37056 Here are the specific requests of this form defined so far. All
37057 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37058 formats, listed below.
37061 @item qXfer:auxv:read::@var{offset},@var{length}
37062 @anchor{qXfer auxiliary vector read}
37063 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37064 auxiliary vector}. Note @var{annex} must be empty.
37066 This packet is not probed by default; the remote stub must request it,
37067 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37069 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37070 @anchor{qXfer target description read}
37071 Access the @dfn{target description}. @xref{Target Descriptions}. The
37072 annex specifies which XML document to access. The main description is
37073 always loaded from the @samp{target.xml} annex.
37075 This packet is not probed by default; the remote stub must request it,
37076 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37078 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37079 @anchor{qXfer library list read}
37080 Access the target's list of loaded libraries. @xref{Library List Format}.
37081 The annex part of the generic @samp{qXfer} packet must be empty
37082 (@pxref{qXfer read}).
37084 Targets which maintain a list of libraries in the program's memory do
37085 not need to implement this packet; it is designed for platforms where
37086 the operating system manages the list of loaded libraries.
37088 This packet is not probed by default; the remote stub must request it,
37089 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37091 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37092 @anchor{qXfer svr4 library list read}
37093 Access the target's list of loaded libraries when the target is an SVR4
37094 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37095 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37097 This packet is optional for better performance on SVR4 targets.
37098 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37100 This packet is not probed by default; the remote stub must request it,
37101 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37103 @item qXfer:memory-map:read::@var{offset},@var{length}
37104 @anchor{qXfer memory map read}
37105 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37106 annex part of the generic @samp{qXfer} packet must be empty
37107 (@pxref{qXfer read}).
37109 This packet is not probed by default; the remote stub must request it,
37110 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37112 @item qXfer:sdata:read::@var{offset},@var{length}
37113 @anchor{qXfer sdata read}
37115 Read contents of the extra collected static tracepoint marker
37116 information. The annex part of the generic @samp{qXfer} packet must
37117 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37120 This packet is not probed by default; the remote stub must request it,
37121 by supplying an appropriate @samp{qSupported} response
37122 (@pxref{qSupported}).
37124 @item qXfer:siginfo:read::@var{offset},@var{length}
37125 @anchor{qXfer siginfo read}
37126 Read contents of the extra signal information on the target
37127 system. The annex part of the generic @samp{qXfer} packet must be
37128 empty (@pxref{qXfer read}).
37130 This packet is not probed by default; the remote stub must request it,
37131 by supplying an appropriate @samp{qSupported} response
37132 (@pxref{qSupported}).
37134 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37135 @anchor{qXfer spu read}
37136 Read contents of an @code{spufs} file on the target system. The
37137 annex specifies which file to read; it must be of the form
37138 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37139 in the target process, and @var{name} identifes the @code{spufs} file
37140 in that context to be accessed.
37142 This packet is not probed by default; the remote stub must request it,
37143 by supplying an appropriate @samp{qSupported} response
37144 (@pxref{qSupported}).
37146 @item qXfer:threads:read::@var{offset},@var{length}
37147 @anchor{qXfer threads read}
37148 Access the list of threads on target. @xref{Thread List Format}. The
37149 annex part of the generic @samp{qXfer} packet must be empty
37150 (@pxref{qXfer read}).
37152 This packet is not probed by default; the remote stub must request it,
37153 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37155 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37156 @anchor{qXfer traceframe info read}
37158 Return a description of the current traceframe's contents.
37159 @xref{Traceframe Info Format}. The annex part of the generic
37160 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37162 This packet is not probed by default; the remote stub must request it,
37163 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37165 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37166 @anchor{qXfer unwind info block}
37168 Return the unwind information block for @var{pc}. This packet is used
37169 on OpenVMS/ia64 to ask the kernel unwind information.
37171 This packet is not probed by default.
37173 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37174 @anchor{qXfer fdpic loadmap read}
37175 Read contents of @code{loadmap}s on the target system. The
37176 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37177 executable @code{loadmap} or interpreter @code{loadmap} to read.
37179 This packet is not probed by default; the remote stub must request it,
37180 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37182 @item qXfer:osdata:read::@var{offset},@var{length}
37183 @anchor{qXfer osdata read}
37184 Access the target's @dfn{operating system information}.
37185 @xref{Operating System Information}.
37192 Data @var{data} (@pxref{Binary Data}) has been read from the
37193 target. There may be more data at a higher address (although
37194 it is permitted to return @samp{m} even for the last valid
37195 block of data, as long as at least one byte of data was read).
37196 @var{data} may have fewer bytes than the @var{length} in the
37200 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37201 There is no more data to be read. @var{data} may have fewer bytes
37202 than the @var{length} in the request.
37205 The @var{offset} in the request is at the end of the data.
37206 There is no more data to be read.
37209 The request was malformed, or @var{annex} was invalid.
37212 The offset was invalid, or there was an error encountered reading the data.
37213 @var{nn} is a hex-encoded @code{errno} value.
37216 An empty reply indicates the @var{object} string was not recognized by
37217 the stub, or that the object does not support reading.
37220 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
37221 @cindex write data into object, remote request
37222 @anchor{qXfer write}
37223 Write uninterpreted bytes into the target's special data area
37224 identified by the keyword @var{object}, starting at @var{offset} bytes
37225 into the data. @var{data}@dots{} is the binary-encoded data
37226 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
37227 is specific to @var{object}; it can supply additional details about what data
37230 Here are the specific requests of this form defined so far. All
37231 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
37232 formats, listed below.
37235 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
37236 @anchor{qXfer siginfo write}
37237 Write @var{data} to the extra signal information on the target system.
37238 The annex part of the generic @samp{qXfer} packet must be
37239 empty (@pxref{qXfer write}).
37241 This packet is not probed by default; the remote stub must request it,
37242 by supplying an appropriate @samp{qSupported} response
37243 (@pxref{qSupported}).
37245 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
37246 @anchor{qXfer spu write}
37247 Write @var{data} to an @code{spufs} file on the target system. The
37248 annex specifies which file to write; it must be of the form
37249 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37250 in the target process, and @var{name} identifes the @code{spufs} file
37251 in that context to be accessed.
37253 This packet is not probed by default; the remote stub must request it,
37254 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37260 @var{nn} (hex encoded) is the number of bytes written.
37261 This may be fewer bytes than supplied in the request.
37264 The request was malformed, or @var{annex} was invalid.
37267 The offset was invalid, or there was an error encountered writing the data.
37268 @var{nn} is a hex-encoded @code{errno} value.
37271 An empty reply indicates the @var{object} string was not
37272 recognized by the stub, or that the object does not support writing.
37275 @item qXfer:@var{object}:@var{operation}:@dots{}
37276 Requests of this form may be added in the future. When a stub does
37277 not recognize the @var{object} keyword, or its support for
37278 @var{object} does not recognize the @var{operation} keyword, the stub
37279 must respond with an empty packet.
37281 @item qAttached:@var{pid}
37282 @cindex query attached, remote request
37283 @cindex @samp{qAttached} packet
37284 Return an indication of whether the remote server attached to an
37285 existing process or created a new process. When the multiprocess
37286 protocol extensions are supported (@pxref{multiprocess extensions}),
37287 @var{pid} is an integer in hexadecimal format identifying the target
37288 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
37289 the query packet will be simplified as @samp{qAttached}.
37291 This query is used, for example, to know whether the remote process
37292 should be detached or killed when a @value{GDBN} session is ended with
37293 the @code{quit} command.
37298 The remote server attached to an existing process.
37300 The remote server created a new process.
37302 A badly formed request or an error was encountered.
37307 @node Architecture-Specific Protocol Details
37308 @section Architecture-Specific Protocol Details
37310 This section describes how the remote protocol is applied to specific
37311 target architectures. Also see @ref{Standard Target Features}, for
37312 details of XML target descriptions for each architecture.
37315 * ARM-Specific Protocol Details::
37316 * MIPS-Specific Protocol Details::
37319 @node ARM-Specific Protocol Details
37320 @subsection @acronym{ARM}-specific Protocol Details
37323 * ARM Breakpoint Kinds::
37326 @node ARM Breakpoint Kinds
37327 @subsubsection @acronym{ARM} Breakpoint Kinds
37328 @cindex breakpoint kinds, @acronym{ARM}
37330 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37335 16-bit Thumb mode breakpoint.
37338 32-bit Thumb mode (Thumb-2) breakpoint.
37341 32-bit @acronym{ARM} mode breakpoint.
37345 @node MIPS-Specific Protocol Details
37346 @subsection @acronym{MIPS}-specific Protocol Details
37349 * MIPS Register packet Format::
37350 * MIPS Breakpoint Kinds::
37353 @node MIPS Register packet Format
37354 @subsubsection @acronym{MIPS} Register Packet Format
37355 @cindex register packet format, @acronym{MIPS}
37357 The following @code{g}/@code{G} packets have previously been defined.
37358 In the below, some thirty-two bit registers are transferred as
37359 sixty-four bits. Those registers should be zero/sign extended (which?)
37360 to fill the space allocated. Register bytes are transferred in target
37361 byte order. The two nibbles within a register byte are transferred
37362 most-significant -- least-significant.
37367 All registers are transferred as thirty-two bit quantities in the order:
37368 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37369 registers; fsr; fir; fp.
37372 All registers are transferred as sixty-four bit quantities (including
37373 thirty-two bit registers such as @code{sr}). The ordering is the same
37378 @node MIPS Breakpoint Kinds
37379 @subsubsection @acronym{MIPS} Breakpoint Kinds
37380 @cindex breakpoint kinds, @acronym{MIPS}
37382 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37387 16-bit @acronym{MIPS16} mode breakpoint.
37390 16-bit @acronym{microMIPS} mode breakpoint.
37393 32-bit standard @acronym{MIPS} mode breakpoint.
37396 32-bit @acronym{microMIPS} mode breakpoint.
37400 @node Tracepoint Packets
37401 @section Tracepoint Packets
37402 @cindex tracepoint packets
37403 @cindex packets, tracepoint
37405 Here we describe the packets @value{GDBN} uses to implement
37406 tracepoints (@pxref{Tracepoints}).
37410 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37411 @cindex @samp{QTDP} packet
37412 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37413 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37414 the tracepoint is disabled. @var{step} is the tracepoint's step
37415 count, and @var{pass} is its pass count. If an @samp{F} is present,
37416 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37417 the number of bytes that the target should copy elsewhere to make room
37418 for the tracepoint. If an @samp{X} is present, it introduces a
37419 tracepoint condition, which consists of a hexadecimal length, followed
37420 by a comma and hex-encoded bytes, in a manner similar to action
37421 encodings as described below. If the trailing @samp{-} is present,
37422 further @samp{QTDP} packets will follow to specify this tracepoint's
37428 The packet was understood and carried out.
37430 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37432 The packet was not recognized.
37435 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37436 Define actions to be taken when a tracepoint is hit. @var{n} and
37437 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37438 this tracepoint. This packet may only be sent immediately after
37439 another @samp{QTDP} packet that ended with a @samp{-}. If the
37440 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
37441 specifying more actions for this tracepoint.
37443 In the series of action packets for a given tracepoint, at most one
37444 can have an @samp{S} before its first @var{action}. If such a packet
37445 is sent, it and the following packets define ``while-stepping''
37446 actions. Any prior packets define ordinary actions --- that is, those
37447 taken when the tracepoint is first hit. If no action packet has an
37448 @samp{S}, then all the packets in the series specify ordinary
37449 tracepoint actions.
37451 The @samp{@var{action}@dots{}} portion of the packet is a series of
37452 actions, concatenated without separators. Each action has one of the
37458 Collect the registers whose bits are set in @var{mask}. @var{mask} is
37459 a hexadecimal number whose @var{i}'th bit is set if register number
37460 @var{i} should be collected. (The least significant bit is numbered
37461 zero.) Note that @var{mask} may be any number of digits long; it may
37462 not fit in a 32-bit word.
37464 @item M @var{basereg},@var{offset},@var{len}
37465 Collect @var{len} bytes of memory starting at the address in register
37466 number @var{basereg}, plus @var{offset}. If @var{basereg} is
37467 @samp{-1}, then the range has a fixed address: @var{offset} is the
37468 address of the lowest byte to collect. The @var{basereg},
37469 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
37470 values (the @samp{-1} value for @var{basereg} is a special case).
37472 @item X @var{len},@var{expr}
37473 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
37474 it directs. @var{expr} is an agent expression, as described in
37475 @ref{Agent Expressions}. Each byte of the expression is encoded as a
37476 two-digit hex number in the packet; @var{len} is the number of bytes
37477 in the expression (and thus one-half the number of hex digits in the
37482 Any number of actions may be packed together in a single @samp{QTDP}
37483 packet, as long as the packet does not exceed the maximum packet
37484 length (400 bytes, for many stubs). There may be only one @samp{R}
37485 action per tracepoint, and it must precede any @samp{M} or @samp{X}
37486 actions. Any registers referred to by @samp{M} and @samp{X} actions
37487 must be collected by a preceding @samp{R} action. (The
37488 ``while-stepping'' actions are treated as if they were attached to a
37489 separate tracepoint, as far as these restrictions are concerned.)
37494 The packet was understood and carried out.
37496 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37498 The packet was not recognized.
37501 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
37502 @cindex @samp{QTDPsrc} packet
37503 Specify a source string of tracepoint @var{n} at address @var{addr}.
37504 This is useful to get accurate reproduction of the tracepoints
37505 originally downloaded at the beginning of the trace run. @var{type}
37506 is the name of the tracepoint part, such as @samp{cond} for the
37507 tracepoint's conditional expression (see below for a list of types), while
37508 @var{bytes} is the string, encoded in hexadecimal.
37510 @var{start} is the offset of the @var{bytes} within the overall source
37511 string, while @var{slen} is the total length of the source string.
37512 This is intended for handling source strings that are longer than will
37513 fit in a single packet.
37514 @c Add detailed example when this info is moved into a dedicated
37515 @c tracepoint descriptions section.
37517 The available string types are @samp{at} for the location,
37518 @samp{cond} for the conditional, and @samp{cmd} for an action command.
37519 @value{GDBN} sends a separate packet for each command in the action
37520 list, in the same order in which the commands are stored in the list.
37522 The target does not need to do anything with source strings except
37523 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
37526 Although this packet is optional, and @value{GDBN} will only send it
37527 if the target replies with @samp{TracepointSource} @xref{General
37528 Query Packets}, it makes both disconnected tracing and trace files
37529 much easier to use. Otherwise the user must be careful that the
37530 tracepoints in effect while looking at trace frames are identical to
37531 the ones in effect during the trace run; even a small discrepancy
37532 could cause @samp{tdump} not to work, or a particular trace frame not
37535 @item QTDV:@var{n}:@var{value}
37536 @cindex define trace state variable, remote request
37537 @cindex @samp{QTDV} packet
37538 Create a new trace state variable, number @var{n}, with an initial
37539 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
37540 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
37541 the option of not using this packet for initial values of zero; the
37542 target should simply create the trace state variables as they are
37543 mentioned in expressions.
37545 @item QTFrame:@var{n}
37546 @cindex @samp{QTFrame} packet
37547 Select the @var{n}'th tracepoint frame from the buffer, and use the
37548 register and memory contents recorded there to answer subsequent
37549 request packets from @value{GDBN}.
37551 A successful reply from the stub indicates that the stub has found the
37552 requested frame. The response is a series of parts, concatenated
37553 without separators, describing the frame we selected. Each part has
37554 one of the following forms:
37558 The selected frame is number @var{n} in the trace frame buffer;
37559 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
37560 was no frame matching the criteria in the request packet.
37563 The selected trace frame records a hit of tracepoint number @var{t};
37564 @var{t} is a hexadecimal number.
37568 @item QTFrame:pc:@var{addr}
37569 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37570 currently selected frame whose PC is @var{addr};
37571 @var{addr} is a hexadecimal number.
37573 @item QTFrame:tdp:@var{t}
37574 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37575 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
37576 is a hexadecimal number.
37578 @item QTFrame:range:@var{start}:@var{end}
37579 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37580 currently selected frame whose PC is between @var{start} (inclusive)
37581 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
37584 @item QTFrame:outside:@var{start}:@var{end}
37585 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
37586 frame @emph{outside} the given range of addresses (exclusive).
37589 @cindex @samp{qTMinFTPILen} packet
37590 This packet requests the minimum length of instruction at which a fast
37591 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
37592 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
37593 it depends on the target system being able to create trampolines in
37594 the first 64K of memory, which might or might not be possible for that
37595 system. So the reply to this packet will be 4 if it is able to
37602 The minimum instruction length is currently unknown.
37604 The minimum instruction length is @var{length}, where @var{length} is greater
37605 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
37606 that a fast tracepoint may be placed on any instruction regardless of size.
37608 An error has occurred.
37610 An empty reply indicates that the request is not supported by the stub.
37614 @cindex @samp{QTStart} packet
37615 Begin the tracepoint experiment. Begin collecting data from
37616 tracepoint hits in the trace frame buffer. This packet supports the
37617 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
37618 instruction reply packet}).
37621 @cindex @samp{QTStop} packet
37622 End the tracepoint experiment. Stop collecting trace frames.
37624 @item QTEnable:@var{n}:@var{addr}
37626 @cindex @samp{QTEnable} packet
37627 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
37628 experiment. If the tracepoint was previously disabled, then collection
37629 of data from it will resume.
37631 @item QTDisable:@var{n}:@var{addr}
37633 @cindex @samp{QTDisable} packet
37634 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
37635 experiment. No more data will be collected from the tracepoint unless
37636 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
37639 @cindex @samp{QTinit} packet
37640 Clear the table of tracepoints, and empty the trace frame buffer.
37642 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
37643 @cindex @samp{QTro} packet
37644 Establish the given ranges of memory as ``transparent''. The stub
37645 will answer requests for these ranges from memory's current contents,
37646 if they were not collected as part of the tracepoint hit.
37648 @value{GDBN} uses this to mark read-only regions of memory, like those
37649 containing program code. Since these areas never change, they should
37650 still have the same contents they did when the tracepoint was hit, so
37651 there's no reason for the stub to refuse to provide their contents.
37653 @item QTDisconnected:@var{value}
37654 @cindex @samp{QTDisconnected} packet
37655 Set the choice to what to do with the tracing run when @value{GDBN}
37656 disconnects from the target. A @var{value} of 1 directs the target to
37657 continue the tracing run, while 0 tells the target to stop tracing if
37658 @value{GDBN} is no longer in the picture.
37661 @cindex @samp{qTStatus} packet
37662 Ask the stub if there is a trace experiment running right now.
37664 The reply has the form:
37668 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
37669 @var{running} is a single digit @code{1} if the trace is presently
37670 running, or @code{0} if not. It is followed by semicolon-separated
37671 optional fields that an agent may use to report additional status.
37675 If the trace is not running, the agent may report any of several
37676 explanations as one of the optional fields:
37681 No trace has been run yet.
37683 @item tstop[:@var{text}]:0
37684 The trace was stopped by a user-originated stop command. The optional
37685 @var{text} field is a user-supplied string supplied as part of the
37686 stop command (for instance, an explanation of why the trace was
37687 stopped manually). It is hex-encoded.
37690 The trace stopped because the trace buffer filled up.
37692 @item tdisconnected:0
37693 The trace stopped because @value{GDBN} disconnected from the target.
37695 @item tpasscount:@var{tpnum}
37696 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
37698 @item terror:@var{text}:@var{tpnum}
37699 The trace stopped because tracepoint @var{tpnum} had an error. The
37700 string @var{text} is available to describe the nature of the error
37701 (for instance, a divide by zero in the condition expression).
37702 @var{text} is hex encoded.
37705 The trace stopped for some other reason.
37709 Additional optional fields supply statistical and other information.
37710 Although not required, they are extremely useful for users monitoring
37711 the progress of a trace run. If a trace has stopped, and these
37712 numbers are reported, they must reflect the state of the just-stopped
37717 @item tframes:@var{n}
37718 The number of trace frames in the buffer.
37720 @item tcreated:@var{n}
37721 The total number of trace frames created during the run. This may
37722 be larger than the trace frame count, if the buffer is circular.
37724 @item tsize:@var{n}
37725 The total size of the trace buffer, in bytes.
37727 @item tfree:@var{n}
37728 The number of bytes still unused in the buffer.
37730 @item circular:@var{n}
37731 The value of the circular trace buffer flag. @code{1} means that the
37732 trace buffer is circular and old trace frames will be discarded if
37733 necessary to make room, @code{0} means that the trace buffer is linear
37736 @item disconn:@var{n}
37737 The value of the disconnected tracing flag. @code{1} means that
37738 tracing will continue after @value{GDBN} disconnects, @code{0} means
37739 that the trace run will stop.
37743 @item qTP:@var{tp}:@var{addr}
37744 @cindex tracepoint status, remote request
37745 @cindex @samp{qTP} packet
37746 Ask the stub for the current state of tracepoint number @var{tp} at
37747 address @var{addr}.
37751 @item V@var{hits}:@var{usage}
37752 The tracepoint has been hit @var{hits} times so far during the trace
37753 run, and accounts for @var{usage} in the trace buffer. Note that
37754 @code{while-stepping} steps are not counted as separate hits, but the
37755 steps' space consumption is added into the usage number.
37759 @item qTV:@var{var}
37760 @cindex trace state variable value, remote request
37761 @cindex @samp{qTV} packet
37762 Ask the stub for the value of the trace state variable number @var{var}.
37767 The value of the variable is @var{value}. This will be the current
37768 value of the variable if the user is examining a running target, or a
37769 saved value if the variable was collected in the trace frame that the
37770 user is looking at. Note that multiple requests may result in
37771 different reply values, such as when requesting values while the
37772 program is running.
37775 The value of the variable is unknown. This would occur, for example,
37776 if the user is examining a trace frame in which the requested variable
37781 @cindex @samp{qTfP} packet
37783 @cindex @samp{qTsP} packet
37784 These packets request data about tracepoints that are being used by
37785 the target. @value{GDBN} sends @code{qTfP} to get the first piece
37786 of data, and multiple @code{qTsP} to get additional pieces. Replies
37787 to these packets generally take the form of the @code{QTDP} packets
37788 that define tracepoints. (FIXME add detailed syntax)
37791 @cindex @samp{qTfV} packet
37793 @cindex @samp{qTsV} packet
37794 These packets request data about trace state variables that are on the
37795 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
37796 and multiple @code{qTsV} to get additional variables. Replies to
37797 these packets follow the syntax of the @code{QTDV} packets that define
37798 trace state variables.
37804 @cindex @samp{qTfSTM} packet
37805 @cindex @samp{qTsSTM} packet
37806 These packets request data about static tracepoint markers that exist
37807 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
37808 first piece of data, and multiple @code{qTsSTM} to get additional
37809 pieces. Replies to these packets take the following form:
37813 @item m @var{address}:@var{id}:@var{extra}
37815 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
37816 a comma-separated list of markers
37818 (lower case letter @samp{L}) denotes end of list.
37820 An error occurred. @var{nn} are hex digits.
37822 An empty reply indicates that the request is not supported by the
37826 @var{address} is encoded in hex.
37827 @var{id} and @var{extra} are strings encoded in hex.
37829 In response to each query, the target will reply with a list of one or
37830 more markers, separated by commas. @value{GDBN} will respond to each
37831 reply with a request for more markers (using the @samp{qs} form of the
37832 query), until the target responds with @samp{l} (lower-case ell, for
37835 @item qTSTMat:@var{address}
37837 @cindex @samp{qTSTMat} packet
37838 This packets requests data about static tracepoint markers in the
37839 target program at @var{address}. Replies to this packet follow the
37840 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
37841 tracepoint markers.
37843 @item QTSave:@var{filename}
37844 @cindex @samp{QTSave} packet
37845 This packet directs the target to save trace data to the file name
37846 @var{filename} in the target's filesystem. @var{filename} is encoded
37847 as a hex string; the interpretation of the file name (relative vs
37848 absolute, wild cards, etc) is up to the target.
37850 @item qTBuffer:@var{offset},@var{len}
37851 @cindex @samp{qTBuffer} packet
37852 Return up to @var{len} bytes of the current contents of trace buffer,
37853 starting at @var{offset}. The trace buffer is treated as if it were
37854 a contiguous collection of traceframes, as per the trace file format.
37855 The reply consists as many hex-encoded bytes as the target can deliver
37856 in a packet; it is not an error to return fewer than were asked for.
37857 A reply consisting of just @code{l} indicates that no bytes are
37860 @item QTBuffer:circular:@var{value}
37861 This packet directs the target to use a circular trace buffer if
37862 @var{value} is 1, or a linear buffer if the value is 0.
37864 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
37865 @cindex @samp{QTNotes} packet
37866 This packet adds optional textual notes to the trace run. Allowable
37867 types include @code{user}, @code{notes}, and @code{tstop}, the
37868 @var{text} fields are arbitrary strings, hex-encoded.
37872 @subsection Relocate instruction reply packet
37873 When installing fast tracepoints in memory, the target may need to
37874 relocate the instruction currently at the tracepoint address to a
37875 different address in memory. For most instructions, a simple copy is
37876 enough, but, for example, call instructions that implicitly push the
37877 return address on the stack, and relative branches or other
37878 PC-relative instructions require offset adjustment, so that the effect
37879 of executing the instruction at a different address is the same as if
37880 it had executed in the original location.
37882 In response to several of the tracepoint packets, the target may also
37883 respond with a number of intermediate @samp{qRelocInsn} request
37884 packets before the final result packet, to have @value{GDBN} handle
37885 this relocation operation. If a packet supports this mechanism, its
37886 documentation will explicitly say so. See for example the above
37887 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
37888 format of the request is:
37891 @item qRelocInsn:@var{from};@var{to}
37893 This requests @value{GDBN} to copy instruction at address @var{from}
37894 to address @var{to}, possibly adjusted so that executing the
37895 instruction at @var{to} has the same effect as executing it at
37896 @var{from}. @value{GDBN} writes the adjusted instruction to target
37897 memory starting at @var{to}.
37902 @item qRelocInsn:@var{adjusted_size}
37903 Informs the stub the relocation is complete. @var{adjusted_size} is
37904 the length in bytes of resulting relocated instruction sequence.
37906 A badly formed request was detected, or an error was encountered while
37907 relocating the instruction.
37910 @node Host I/O Packets
37911 @section Host I/O Packets
37912 @cindex Host I/O, remote protocol
37913 @cindex file transfer, remote protocol
37915 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
37916 operations on the far side of a remote link. For example, Host I/O is
37917 used to upload and download files to a remote target with its own
37918 filesystem. Host I/O uses the same constant values and data structure
37919 layout as the target-initiated File-I/O protocol. However, the
37920 Host I/O packets are structured differently. The target-initiated
37921 protocol relies on target memory to store parameters and buffers.
37922 Host I/O requests are initiated by @value{GDBN}, and the
37923 target's memory is not involved. @xref{File-I/O Remote Protocol
37924 Extension}, for more details on the target-initiated protocol.
37926 The Host I/O request packets all encode a single operation along with
37927 its arguments. They have this format:
37931 @item vFile:@var{operation}: @var{parameter}@dots{}
37932 @var{operation} is the name of the particular request; the target
37933 should compare the entire packet name up to the second colon when checking
37934 for a supported operation. The format of @var{parameter} depends on
37935 the operation. Numbers are always passed in hexadecimal. Negative
37936 numbers have an explicit minus sign (i.e.@: two's complement is not
37937 used). Strings (e.g.@: filenames) are encoded as a series of
37938 hexadecimal bytes. The last argument to a system call may be a
37939 buffer of escaped binary data (@pxref{Binary Data}).
37943 The valid responses to Host I/O packets are:
37947 @item F @var{result} [, @var{errno}] [; @var{attachment}]
37948 @var{result} is the integer value returned by this operation, usually
37949 non-negative for success and -1 for errors. If an error has occured,
37950 @var{errno} will be included in the result. @var{errno} will have a
37951 value defined by the File-I/O protocol (@pxref{Errno Values}). For
37952 operations which return data, @var{attachment} supplies the data as a
37953 binary buffer. Binary buffers in response packets are escaped in the
37954 normal way (@pxref{Binary Data}). See the individual packet
37955 documentation for the interpretation of @var{result} and
37959 An empty response indicates that this operation is not recognized.
37963 These are the supported Host I/O operations:
37966 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
37967 Open a file at @var{pathname} and return a file descriptor for it, or
37968 return -1 if an error occurs. @var{pathname} is a string,
37969 @var{flags} is an integer indicating a mask of open flags
37970 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
37971 of mode bits to use if the file is created (@pxref{mode_t Values}).
37972 @xref{open}, for details of the open flags and mode values.
37974 @item vFile:close: @var{fd}
37975 Close the open file corresponding to @var{fd} and return 0, or
37976 -1 if an error occurs.
37978 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
37979 Read data from the open file corresponding to @var{fd}. Up to
37980 @var{count} bytes will be read from the file, starting at @var{offset}
37981 relative to the start of the file. The target may read fewer bytes;
37982 common reasons include packet size limits and an end-of-file
37983 condition. The number of bytes read is returned. Zero should only be
37984 returned for a successful read at the end of the file, or if
37985 @var{count} was zero.
37987 The data read should be returned as a binary attachment on success.
37988 If zero bytes were read, the response should include an empty binary
37989 attachment (i.e.@: a trailing semicolon). The return value is the
37990 number of target bytes read; the binary attachment may be longer if
37991 some characters were escaped.
37993 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
37994 Write @var{data} (a binary buffer) to the open file corresponding
37995 to @var{fd}. Start the write at @var{offset} from the start of the
37996 file. Unlike many @code{write} system calls, there is no
37997 separate @var{count} argument; the length of @var{data} in the
37998 packet is used. @samp{vFile:write} returns the number of bytes written,
37999 which may be shorter than the length of @var{data}, or -1 if an
38002 @item vFile:unlink: @var{pathname}
38003 Delete the file at @var{pathname} on the target. Return 0,
38004 or -1 if an error occurs. @var{pathname} is a string.
38006 @item vFile:readlink: @var{filename}
38007 Read value of symbolic link @var{filename} on the target. Return
38008 the number of bytes read, or -1 if an error occurs.
38010 The data read should be returned as a binary attachment on success.
38011 If zero bytes were read, the response should include an empty binary
38012 attachment (i.e.@: a trailing semicolon). The return value is the
38013 number of target bytes read; the binary attachment may be longer if
38014 some characters were escaped.
38019 @section Interrupts
38020 @cindex interrupts (remote protocol)
38022 When a program on the remote target is running, @value{GDBN} may
38023 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
38024 a @code{BREAK} followed by @code{g},
38025 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38027 The precise meaning of @code{BREAK} is defined by the transport
38028 mechanism and may, in fact, be undefined. @value{GDBN} does not
38029 currently define a @code{BREAK} mechanism for any of the network
38030 interfaces except for TCP, in which case @value{GDBN} sends the
38031 @code{telnet} BREAK sequence.
38033 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38034 transport mechanisms. It is represented by sending the single byte
38035 @code{0x03} without any of the usual packet overhead described in
38036 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38037 transmitted as part of a packet, it is considered to be packet data
38038 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38039 (@pxref{X packet}), used for binary downloads, may include an unescaped
38040 @code{0x03} as part of its packet.
38042 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38043 When Linux kernel receives this sequence from serial port,
38044 it stops execution and connects to gdb.
38046 Stubs are not required to recognize these interrupt mechanisms and the
38047 precise meaning associated with receipt of the interrupt is
38048 implementation defined. If the target supports debugging of multiple
38049 threads and/or processes, it should attempt to interrupt all
38050 currently-executing threads and processes.
38051 If the stub is successful at interrupting the
38052 running program, it should send one of the stop
38053 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38054 of successfully stopping the program in all-stop mode, and a stop reply
38055 for each stopped thread in non-stop mode.
38056 Interrupts received while the
38057 program is stopped are discarded.
38059 @node Notification Packets
38060 @section Notification Packets
38061 @cindex notification packets
38062 @cindex packets, notification
38064 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38065 packets that require no acknowledgment. Both the GDB and the stub
38066 may send notifications (although the only notifications defined at
38067 present are sent by the stub). Notifications carry information
38068 without incurring the round-trip latency of an acknowledgment, and so
38069 are useful for low-impact communications where occasional packet loss
38072 A notification packet has the form @samp{% @var{data} #
38073 @var{checksum}}, where @var{data} is the content of the notification,
38074 and @var{checksum} is a checksum of @var{data}, computed and formatted
38075 as for ordinary @value{GDBN} packets. A notification's @var{data}
38076 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38077 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38078 to acknowledge the notification's receipt or to report its corruption.
38080 Every notification's @var{data} begins with a name, which contains no
38081 colon characters, followed by a colon character.
38083 Recipients should silently ignore corrupted notifications and
38084 notifications they do not understand. Recipients should restart
38085 timeout periods on receipt of a well-formed notification, whether or
38086 not they understand it.
38088 Senders should only send the notifications described here when this
38089 protocol description specifies that they are permitted. In the
38090 future, we may extend the protocol to permit existing notifications in
38091 new contexts; this rule helps older senders avoid confusing newer
38094 (Older versions of @value{GDBN} ignore bytes received until they see
38095 the @samp{$} byte that begins an ordinary packet, so new stubs may
38096 transmit notifications without fear of confusing older clients. There
38097 are no notifications defined for @value{GDBN} to send at the moment, but we
38098 assume that most older stubs would ignore them, as well.)
38100 The following notification packets from the stub to @value{GDBN} are
38104 @item Stop: @var{reply}
38105 Report an asynchronous stop event in non-stop mode.
38106 The @var{reply} has the form of a stop reply, as
38107 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
38108 for information on how these notifications are acknowledged by
38112 @node Remote Non-Stop
38113 @section Remote Protocol Support for Non-Stop Mode
38115 @value{GDBN}'s remote protocol supports non-stop debugging of
38116 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
38117 supports non-stop mode, it should report that to @value{GDBN} by including
38118 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
38120 @value{GDBN} typically sends a @samp{QNonStop} packet only when
38121 establishing a new connection with the stub. Entering non-stop mode
38122 does not alter the state of any currently-running threads, but targets
38123 must stop all threads in any already-attached processes when entering
38124 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
38125 probe the target state after a mode change.
38127 In non-stop mode, when an attached process encounters an event that
38128 would otherwise be reported with a stop reply, it uses the
38129 asynchronous notification mechanism (@pxref{Notification Packets}) to
38130 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38131 in all processes are stopped when a stop reply is sent, in non-stop
38132 mode only the thread reporting the stop event is stopped. That is,
38133 when reporting a @samp{S} or @samp{T} response to indicate completion
38134 of a step operation, hitting a breakpoint, or a fault, only the
38135 affected thread is stopped; any other still-running threads continue
38136 to run. When reporting a @samp{W} or @samp{X} response, all running
38137 threads belonging to other attached processes continue to run.
38139 Only one stop reply notification at a time may be pending; if
38140 additional stop events occur before @value{GDBN} has acknowledged the
38141 previous notification, they must be queued by the stub for later
38142 synchronous transmission in response to @samp{vStopped} packets from
38143 @value{GDBN}. Because the notification mechanism is unreliable,
38144 the stub is permitted to resend a stop reply notification
38145 if it believes @value{GDBN} may not have received it. @value{GDBN}
38146 ignores additional stop reply notifications received before it has
38147 finished processing a previous notification and the stub has completed
38148 sending any queued stop events.
38150 Otherwise, @value{GDBN} must be prepared to receive a stop reply
38151 notification at any time. Specifically, they may appear when
38152 @value{GDBN} is not otherwise reading input from the stub, or when
38153 @value{GDBN} is expecting to read a normal synchronous response or a
38154 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38155 Notification packets are distinct from any other communication from
38156 the stub so there is no ambiguity.
38158 After receiving a stop reply notification, @value{GDBN} shall
38159 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
38160 as a regular, synchronous request to the stub. Such acknowledgment
38161 is not required to happen immediately, as @value{GDBN} is permitted to
38162 send other, unrelated packets to the stub first, which the stub should
38165 Upon receiving a @samp{vStopped} packet, if the stub has other queued
38166 stop events to report to @value{GDBN}, it shall respond by sending a
38167 normal stop reply response. @value{GDBN} shall then send another
38168 @samp{vStopped} packet to solicit further responses; again, it is
38169 permitted to send other, unrelated packets as well which the stub
38170 should process normally.
38172 If the stub receives a @samp{vStopped} packet and there are no
38173 additional stop events to report, the stub shall return an @samp{OK}
38174 response. At this point, if further stop events occur, the stub shall
38175 send a new stop reply notification, @value{GDBN} shall accept the
38176 notification, and the process shall be repeated.
38178 In non-stop mode, the target shall respond to the @samp{?} packet as
38179 follows. First, any incomplete stop reply notification/@samp{vStopped}
38180 sequence in progress is abandoned. The target must begin a new
38181 sequence reporting stop events for all stopped threads, whether or not
38182 it has previously reported those events to @value{GDBN}. The first
38183 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38184 subsequent stop replies are sent as responses to @samp{vStopped} packets
38185 using the mechanism described above. The target must not send
38186 asynchronous stop reply notifications until the sequence is complete.
38187 If all threads are running when the target receives the @samp{?} packet,
38188 or if the target is not attached to any process, it shall respond
38191 @node Packet Acknowledgment
38192 @section Packet Acknowledgment
38194 @cindex acknowledgment, for @value{GDBN} remote
38195 @cindex packet acknowledgment, for @value{GDBN} remote
38196 By default, when either the host or the target machine receives a packet,
38197 the first response expected is an acknowledgment: either @samp{+} (to indicate
38198 the package was received correctly) or @samp{-} (to request retransmission).
38199 This mechanism allows the @value{GDBN} remote protocol to operate over
38200 unreliable transport mechanisms, such as a serial line.
38202 In cases where the transport mechanism is itself reliable (such as a pipe or
38203 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38204 It may be desirable to disable them in that case to reduce communication
38205 overhead, or for other reasons. This can be accomplished by means of the
38206 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38208 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38209 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38210 and response format still includes the normal checksum, as described in
38211 @ref{Overview}, but the checksum may be ignored by the receiver.
38213 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38214 no-acknowledgment mode, it should report that to @value{GDBN}
38215 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38216 @pxref{qSupported}.
38217 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38218 disabled via the @code{set remote noack-packet off} command
38219 (@pxref{Remote Configuration}),
38220 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38221 Only then may the stub actually turn off packet acknowledgments.
38222 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38223 response, which can be safely ignored by the stub.
38225 Note that @code{set remote noack-packet} command only affects negotiation
38226 between @value{GDBN} and the stub when subsequent connections are made;
38227 it does not affect the protocol acknowledgment state for any current
38229 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38230 new connection is established,
38231 there is also no protocol request to re-enable the acknowledgments
38232 for the current connection, once disabled.
38237 Example sequence of a target being re-started. Notice how the restart
38238 does not get any direct output:
38243 @emph{target restarts}
38246 <- @code{T001:1234123412341234}
38250 Example sequence of a target being stepped by a single instruction:
38253 -> @code{G1445@dots{}}
38258 <- @code{T001:1234123412341234}
38262 <- @code{1455@dots{}}
38266 @node File-I/O Remote Protocol Extension
38267 @section File-I/O Remote Protocol Extension
38268 @cindex File-I/O remote protocol extension
38271 * File-I/O Overview::
38272 * Protocol Basics::
38273 * The F Request Packet::
38274 * The F Reply Packet::
38275 * The Ctrl-C Message::
38277 * List of Supported Calls::
38278 * Protocol-specific Representation of Datatypes::
38280 * File-I/O Examples::
38283 @node File-I/O Overview
38284 @subsection File-I/O Overview
38285 @cindex file-i/o overview
38287 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38288 target to use the host's file system and console I/O to perform various
38289 system calls. System calls on the target system are translated into a
38290 remote protocol packet to the host system, which then performs the needed
38291 actions and returns a response packet to the target system.
38292 This simulates file system operations even on targets that lack file systems.
38294 The protocol is defined to be independent of both the host and target systems.
38295 It uses its own internal representation of datatypes and values. Both
38296 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38297 translating the system-dependent value representations into the internal
38298 protocol representations when data is transmitted.
38300 The communication is synchronous. A system call is possible only when
38301 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38302 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38303 the target is stopped to allow deterministic access to the target's
38304 memory. Therefore File-I/O is not interruptible by target signals. On
38305 the other hand, it is possible to interrupt File-I/O by a user interrupt
38306 (@samp{Ctrl-C}) within @value{GDBN}.
38308 The target's request to perform a host system call does not finish
38309 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38310 after finishing the system call, the target returns to continuing the
38311 previous activity (continue, step). No additional continue or step
38312 request from @value{GDBN} is required.
38315 (@value{GDBP}) continue
38316 <- target requests 'system call X'
38317 target is stopped, @value{GDBN} executes system call
38318 -> @value{GDBN} returns result
38319 ... target continues, @value{GDBN} returns to wait for the target
38320 <- target hits breakpoint and sends a Txx packet
38323 The protocol only supports I/O on the console and to regular files on
38324 the host file system. Character or block special devices, pipes,
38325 named pipes, sockets or any other communication method on the host
38326 system are not supported by this protocol.
38328 File I/O is not supported in non-stop mode.
38330 @node Protocol Basics
38331 @subsection Protocol Basics
38332 @cindex protocol basics, file-i/o
38334 The File-I/O protocol uses the @code{F} packet as the request as well
38335 as reply packet. Since a File-I/O system call can only occur when
38336 @value{GDBN} is waiting for a response from the continuing or stepping target,
38337 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38338 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38339 This @code{F} packet contains all information needed to allow @value{GDBN}
38340 to call the appropriate host system call:
38344 A unique identifier for the requested system call.
38347 All parameters to the system call. Pointers are given as addresses
38348 in the target memory address space. Pointers to strings are given as
38349 pointer/length pair. Numerical values are given as they are.
38350 Numerical control flags are given in a protocol-specific representation.
38354 At this point, @value{GDBN} has to perform the following actions.
38358 If the parameters include pointer values to data needed as input to a
38359 system call, @value{GDBN} requests this data from the target with a
38360 standard @code{m} packet request. This additional communication has to be
38361 expected by the target implementation and is handled as any other @code{m}
38365 @value{GDBN} translates all value from protocol representation to host
38366 representation as needed. Datatypes are coerced into the host types.
38369 @value{GDBN} calls the system call.
38372 It then coerces datatypes back to protocol representation.
38375 If the system call is expected to return data in buffer space specified
38376 by pointer parameters to the call, the data is transmitted to the
38377 target using a @code{M} or @code{X} packet. This packet has to be expected
38378 by the target implementation and is handled as any other @code{M} or @code{X}
38383 Eventually @value{GDBN} replies with another @code{F} packet which contains all
38384 necessary information for the target to continue. This at least contains
38391 @code{errno}, if has been changed by the system call.
38398 After having done the needed type and value coercion, the target continues
38399 the latest continue or step action.
38401 @node The F Request Packet
38402 @subsection The @code{F} Request Packet
38403 @cindex file-i/o request packet
38404 @cindex @code{F} request packet
38406 The @code{F} request packet has the following format:
38409 @item F@var{call-id},@var{parameter@dots{}}
38411 @var{call-id} is the identifier to indicate the host system call to be called.
38412 This is just the name of the function.
38414 @var{parameter@dots{}} are the parameters to the system call.
38415 Parameters are hexadecimal integer values, either the actual values in case
38416 of scalar datatypes, pointers to target buffer space in case of compound
38417 datatypes and unspecified memory areas, or pointer/length pairs in case
38418 of string parameters. These are appended to the @var{call-id} as a
38419 comma-delimited list. All values are transmitted in ASCII
38420 string representation, pointer/length pairs separated by a slash.
38426 @node The F Reply Packet
38427 @subsection The @code{F} Reply Packet
38428 @cindex file-i/o reply packet
38429 @cindex @code{F} reply packet
38431 The @code{F} reply packet has the following format:
38435 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
38437 @var{retcode} is the return code of the system call as hexadecimal value.
38439 @var{errno} is the @code{errno} set by the call, in protocol-specific
38441 This parameter can be omitted if the call was successful.
38443 @var{Ctrl-C flag} is only sent if the user requested a break. In this
38444 case, @var{errno} must be sent as well, even if the call was successful.
38445 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
38452 or, if the call was interrupted before the host call has been performed:
38459 assuming 4 is the protocol-specific representation of @code{EINTR}.
38464 @node The Ctrl-C Message
38465 @subsection The @samp{Ctrl-C} Message
38466 @cindex ctrl-c message, in file-i/o protocol
38468 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
38469 reply packet (@pxref{The F Reply Packet}),
38470 the target should behave as if it had
38471 gotten a break message. The meaning for the target is ``system call
38472 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
38473 (as with a break message) and return to @value{GDBN} with a @code{T02}
38476 It's important for the target to know in which
38477 state the system call was interrupted. There are two possible cases:
38481 The system call hasn't been performed on the host yet.
38484 The system call on the host has been finished.
38488 These two states can be distinguished by the target by the value of the
38489 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
38490 call hasn't been performed. This is equivalent to the @code{EINTR} handling
38491 on POSIX systems. In any other case, the target may presume that the
38492 system call has been finished --- successfully or not --- and should behave
38493 as if the break message arrived right after the system call.
38495 @value{GDBN} must behave reliably. If the system call has not been called
38496 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
38497 @code{errno} in the packet. If the system call on the host has been finished
38498 before the user requests a break, the full action must be finished by
38499 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
38500 The @code{F} packet may only be sent when either nothing has happened
38501 or the full action has been completed.
38504 @subsection Console I/O
38505 @cindex console i/o as part of file-i/o
38507 By default and if not explicitly closed by the target system, the file
38508 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
38509 on the @value{GDBN} console is handled as any other file output operation
38510 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
38511 by @value{GDBN} so that after the target read request from file descriptor
38512 0 all following typing is buffered until either one of the following
38517 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
38519 system call is treated as finished.
38522 The user presses @key{RET}. This is treated as end of input with a trailing
38526 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
38527 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
38531 If the user has typed more characters than fit in the buffer given to
38532 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
38533 either another @code{read(0, @dots{})} is requested by the target, or debugging
38534 is stopped at the user's request.
38537 @node List of Supported Calls
38538 @subsection List of Supported Calls
38539 @cindex list of supported file-i/o calls
38556 @unnumberedsubsubsec open
38557 @cindex open, file-i/o system call
38562 int open(const char *pathname, int flags);
38563 int open(const char *pathname, int flags, mode_t mode);
38567 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
38570 @var{flags} is the bitwise @code{OR} of the following values:
38574 If the file does not exist it will be created. The host
38575 rules apply as far as file ownership and time stamps
38579 When used with @code{O_CREAT}, if the file already exists it is
38580 an error and open() fails.
38583 If the file already exists and the open mode allows
38584 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
38585 truncated to zero length.
38588 The file is opened in append mode.
38591 The file is opened for reading only.
38594 The file is opened for writing only.
38597 The file is opened for reading and writing.
38601 Other bits are silently ignored.
38605 @var{mode} is the bitwise @code{OR} of the following values:
38609 User has read permission.
38612 User has write permission.
38615 Group has read permission.
38618 Group has write permission.
38621 Others have read permission.
38624 Others have write permission.
38628 Other bits are silently ignored.
38631 @item Return value:
38632 @code{open} returns the new file descriptor or -1 if an error
38639 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
38642 @var{pathname} refers to a directory.
38645 The requested access is not allowed.
38648 @var{pathname} was too long.
38651 A directory component in @var{pathname} does not exist.
38654 @var{pathname} refers to a device, pipe, named pipe or socket.
38657 @var{pathname} refers to a file on a read-only filesystem and
38658 write access was requested.
38661 @var{pathname} is an invalid pointer value.
38664 No space on device to create the file.
38667 The process already has the maximum number of files open.
38670 The limit on the total number of files open on the system
38674 The call was interrupted by the user.
38680 @unnumberedsubsubsec close
38681 @cindex close, file-i/o system call
38690 @samp{Fclose,@var{fd}}
38692 @item Return value:
38693 @code{close} returns zero on success, or -1 if an error occurred.
38699 @var{fd} isn't a valid open file descriptor.
38702 The call was interrupted by the user.
38708 @unnumberedsubsubsec read
38709 @cindex read, file-i/o system call
38714 int read(int fd, void *buf, unsigned int count);
38718 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
38720 @item Return value:
38721 On success, the number of bytes read is returned.
38722 Zero indicates end of file. If count is zero, read
38723 returns zero as well. On error, -1 is returned.
38729 @var{fd} is not a valid file descriptor or is not open for
38733 @var{bufptr} is an invalid pointer value.
38736 The call was interrupted by the user.
38742 @unnumberedsubsubsec write
38743 @cindex write, file-i/o system call
38748 int write(int fd, const void *buf, unsigned int count);
38752 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
38754 @item Return value:
38755 On success, the number of bytes written are returned.
38756 Zero indicates nothing was written. On error, -1
38763 @var{fd} is not a valid file descriptor or is not open for
38767 @var{bufptr} is an invalid pointer value.
38770 An attempt was made to write a file that exceeds the
38771 host-specific maximum file size allowed.
38774 No space on device to write the data.
38777 The call was interrupted by the user.
38783 @unnumberedsubsubsec lseek
38784 @cindex lseek, file-i/o system call
38789 long lseek (int fd, long offset, int flag);
38793 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
38795 @var{flag} is one of:
38799 The offset is set to @var{offset} bytes.
38802 The offset is set to its current location plus @var{offset}
38806 The offset is set to the size of the file plus @var{offset}
38810 @item Return value:
38811 On success, the resulting unsigned offset in bytes from
38812 the beginning of the file is returned. Otherwise, a
38813 value of -1 is returned.
38819 @var{fd} is not a valid open file descriptor.
38822 @var{fd} is associated with the @value{GDBN} console.
38825 @var{flag} is not a proper value.
38828 The call was interrupted by the user.
38834 @unnumberedsubsubsec rename
38835 @cindex rename, file-i/o system call
38840 int rename(const char *oldpath, const char *newpath);
38844 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
38846 @item Return value:
38847 On success, zero is returned. On error, -1 is returned.
38853 @var{newpath} is an existing directory, but @var{oldpath} is not a
38857 @var{newpath} is a non-empty directory.
38860 @var{oldpath} or @var{newpath} is a directory that is in use by some
38864 An attempt was made to make a directory a subdirectory
38868 A component used as a directory in @var{oldpath} or new
38869 path is not a directory. Or @var{oldpath} is a directory
38870 and @var{newpath} exists but is not a directory.
38873 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
38876 No access to the file or the path of the file.
38880 @var{oldpath} or @var{newpath} was too long.
38883 A directory component in @var{oldpath} or @var{newpath} does not exist.
38886 The file is on a read-only filesystem.
38889 The device containing the file has no room for the new
38893 The call was interrupted by the user.
38899 @unnumberedsubsubsec unlink
38900 @cindex unlink, file-i/o system call
38905 int unlink(const char *pathname);
38909 @samp{Funlink,@var{pathnameptr}/@var{len}}
38911 @item Return value:
38912 On success, zero is returned. On error, -1 is returned.
38918 No access to the file or the path of the file.
38921 The system does not allow unlinking of directories.
38924 The file @var{pathname} cannot be unlinked because it's
38925 being used by another process.
38928 @var{pathnameptr} is an invalid pointer value.
38931 @var{pathname} was too long.
38934 A directory component in @var{pathname} does not exist.
38937 A component of the path is not a directory.
38940 The file is on a read-only filesystem.
38943 The call was interrupted by the user.
38949 @unnumberedsubsubsec stat/fstat
38950 @cindex fstat, file-i/o system call
38951 @cindex stat, file-i/o system call
38956 int stat(const char *pathname, struct stat *buf);
38957 int fstat(int fd, struct stat *buf);
38961 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
38962 @samp{Ffstat,@var{fd},@var{bufptr}}
38964 @item Return value:
38965 On success, zero is returned. On error, -1 is returned.
38971 @var{fd} is not a valid open file.
38974 A directory component in @var{pathname} does not exist or the
38975 path is an empty string.
38978 A component of the path is not a directory.
38981 @var{pathnameptr} is an invalid pointer value.
38984 No access to the file or the path of the file.
38987 @var{pathname} was too long.
38990 The call was interrupted by the user.
38996 @unnumberedsubsubsec gettimeofday
38997 @cindex gettimeofday, file-i/o system call
39002 int gettimeofday(struct timeval *tv, void *tz);
39006 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39008 @item Return value:
39009 On success, 0 is returned, -1 otherwise.
39015 @var{tz} is a non-NULL pointer.
39018 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39024 @unnumberedsubsubsec isatty
39025 @cindex isatty, file-i/o system call
39030 int isatty(int fd);
39034 @samp{Fisatty,@var{fd}}
39036 @item Return value:
39037 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39043 The call was interrupted by the user.
39048 Note that the @code{isatty} call is treated as a special case: it returns
39049 1 to the target if the file descriptor is attached
39050 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39051 would require implementing @code{ioctl} and would be more complex than
39056 @unnumberedsubsubsec system
39057 @cindex system, file-i/o system call
39062 int system(const char *command);
39066 @samp{Fsystem,@var{commandptr}/@var{len}}
39068 @item Return value:
39069 If @var{len} is zero, the return value indicates whether a shell is
39070 available. A zero return value indicates a shell is not available.
39071 For non-zero @var{len}, the value returned is -1 on error and the
39072 return status of the command otherwise. Only the exit status of the
39073 command is returned, which is extracted from the host's @code{system}
39074 return value by calling @code{WEXITSTATUS(retval)}. In case
39075 @file{/bin/sh} could not be executed, 127 is returned.
39081 The call was interrupted by the user.
39086 @value{GDBN} takes over the full task of calling the necessary host calls
39087 to perform the @code{system} call. The return value of @code{system} on
39088 the host is simplified before it's returned
39089 to the target. Any termination signal information from the child process
39090 is discarded, and the return value consists
39091 entirely of the exit status of the called command.
39093 Due to security concerns, the @code{system} call is by default refused
39094 by @value{GDBN}. The user has to allow this call explicitly with the
39095 @code{set remote system-call-allowed 1} command.
39098 @item set remote system-call-allowed
39099 @kindex set remote system-call-allowed
39100 Control whether to allow the @code{system} calls in the File I/O
39101 protocol for the remote target. The default is zero (disabled).
39103 @item show remote system-call-allowed
39104 @kindex show remote system-call-allowed
39105 Show whether the @code{system} calls are allowed in the File I/O
39109 @node Protocol-specific Representation of Datatypes
39110 @subsection Protocol-specific Representation of Datatypes
39111 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39114 * Integral Datatypes::
39116 * Memory Transfer::
39121 @node Integral Datatypes
39122 @unnumberedsubsubsec Integral Datatypes
39123 @cindex integral datatypes, in file-i/o protocol
39125 The integral datatypes used in the system calls are @code{int},
39126 @code{unsigned int}, @code{long}, @code{unsigned long},
39127 @code{mode_t}, and @code{time_t}.
39129 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
39130 implemented as 32 bit values in this protocol.
39132 @code{long} and @code{unsigned long} are implemented as 64 bit types.
39134 @xref{Limits}, for corresponding MIN and MAX values (similar to those
39135 in @file{limits.h}) to allow range checking on host and target.
39137 @code{time_t} datatypes are defined as seconds since the Epoch.
39139 All integral datatypes transferred as part of a memory read or write of a
39140 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
39143 @node Pointer Values
39144 @unnumberedsubsubsec Pointer Values
39145 @cindex pointer values, in file-i/o protocol
39147 Pointers to target data are transmitted as they are. An exception
39148 is made for pointers to buffers for which the length isn't
39149 transmitted as part of the function call, namely strings. Strings
39150 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39157 which is a pointer to data of length 18 bytes at position 0x1aaf.
39158 The length is defined as the full string length in bytes, including
39159 the trailing null byte. For example, the string @code{"hello world"}
39160 at address 0x123456 is transmitted as
39166 @node Memory Transfer
39167 @unnumberedsubsubsec Memory Transfer
39168 @cindex memory transfer, in file-i/o protocol
39170 Structured data which is transferred using a memory read or write (for
39171 example, a @code{struct stat}) is expected to be in a protocol-specific format
39172 with all scalar multibyte datatypes being big endian. Translation to
39173 this representation needs to be done both by the target before the @code{F}
39174 packet is sent, and by @value{GDBN} before
39175 it transfers memory to the target. Transferred pointers to structured
39176 data should point to the already-coerced data at any time.
39180 @unnumberedsubsubsec struct stat
39181 @cindex struct stat, in file-i/o protocol
39183 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39184 is defined as follows:
39188 unsigned int st_dev; /* device */
39189 unsigned int st_ino; /* inode */
39190 mode_t st_mode; /* protection */
39191 unsigned int st_nlink; /* number of hard links */
39192 unsigned int st_uid; /* user ID of owner */
39193 unsigned int st_gid; /* group ID of owner */
39194 unsigned int st_rdev; /* device type (if inode device) */
39195 unsigned long st_size; /* total size, in bytes */
39196 unsigned long st_blksize; /* blocksize for filesystem I/O */
39197 unsigned long st_blocks; /* number of blocks allocated */
39198 time_t st_atime; /* time of last access */
39199 time_t st_mtime; /* time of last modification */
39200 time_t st_ctime; /* time of last change */
39204 The integral datatypes conform to the definitions given in the
39205 appropriate section (see @ref{Integral Datatypes}, for details) so this
39206 structure is of size 64 bytes.
39208 The values of several fields have a restricted meaning and/or
39214 A value of 0 represents a file, 1 the console.
39217 No valid meaning for the target. Transmitted unchanged.
39220 Valid mode bits are described in @ref{Constants}. Any other
39221 bits have currently no meaning for the target.
39226 No valid meaning for the target. Transmitted unchanged.
39231 These values have a host and file system dependent
39232 accuracy. Especially on Windows hosts, the file system may not
39233 support exact timing values.
39236 The target gets a @code{struct stat} of the above representation and is
39237 responsible for coercing it to the target representation before
39240 Note that due to size differences between the host, target, and protocol
39241 representations of @code{struct stat} members, these members could eventually
39242 get truncated on the target.
39244 @node struct timeval
39245 @unnumberedsubsubsec struct timeval
39246 @cindex struct timeval, in file-i/o protocol
39248 The buffer of type @code{struct timeval} used by the File-I/O protocol
39249 is defined as follows:
39253 time_t tv_sec; /* second */
39254 long tv_usec; /* microsecond */
39258 The integral datatypes conform to the definitions given in the
39259 appropriate section (see @ref{Integral Datatypes}, for details) so this
39260 structure is of size 8 bytes.
39263 @subsection Constants
39264 @cindex constants, in file-i/o protocol
39266 The following values are used for the constants inside of the
39267 protocol. @value{GDBN} and target are responsible for translating these
39268 values before and after the call as needed.
39279 @unnumberedsubsubsec Open Flags
39280 @cindex open flags, in file-i/o protocol
39282 All values are given in hexadecimal representation.
39294 @node mode_t Values
39295 @unnumberedsubsubsec mode_t Values
39296 @cindex mode_t values, in file-i/o protocol
39298 All values are given in octal representation.
39315 @unnumberedsubsubsec Errno Values
39316 @cindex errno values, in file-i/o protocol
39318 All values are given in decimal representation.
39343 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39344 any error value not in the list of supported error numbers.
39347 @unnumberedsubsubsec Lseek Flags
39348 @cindex lseek flags, in file-i/o protocol
39357 @unnumberedsubsubsec Limits
39358 @cindex limits, in file-i/o protocol
39360 All values are given in decimal representation.
39363 INT_MIN -2147483648
39365 UINT_MAX 4294967295
39366 LONG_MIN -9223372036854775808
39367 LONG_MAX 9223372036854775807
39368 ULONG_MAX 18446744073709551615
39371 @node File-I/O Examples
39372 @subsection File-I/O Examples
39373 @cindex file-i/o examples
39375 Example sequence of a write call, file descriptor 3, buffer is at target
39376 address 0x1234, 6 bytes should be written:
39379 <- @code{Fwrite,3,1234,6}
39380 @emph{request memory read from target}
39383 @emph{return "6 bytes written"}
39387 Example sequence of a read call, file descriptor 3, buffer is at target
39388 address 0x1234, 6 bytes should be read:
39391 <- @code{Fread,3,1234,6}
39392 @emph{request memory write to target}
39393 -> @code{X1234,6:XXXXXX}
39394 @emph{return "6 bytes read"}
39398 Example sequence of a read call, call fails on the host due to invalid
39399 file descriptor (@code{EBADF}):
39402 <- @code{Fread,3,1234,6}
39406 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
39410 <- @code{Fread,3,1234,6}
39415 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
39419 <- @code{Fread,3,1234,6}
39420 -> @code{X1234,6:XXXXXX}
39424 @node Library List Format
39425 @section Library List Format
39426 @cindex library list format, remote protocol
39428 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
39429 same process as your application to manage libraries. In this case,
39430 @value{GDBN} can use the loader's symbol table and normal memory
39431 operations to maintain a list of shared libraries. On other
39432 platforms, the operating system manages loaded libraries.
39433 @value{GDBN} can not retrieve the list of currently loaded libraries
39434 through memory operations, so it uses the @samp{qXfer:libraries:read}
39435 packet (@pxref{qXfer library list read}) instead. The remote stub
39436 queries the target's operating system and reports which libraries
39439 The @samp{qXfer:libraries:read} packet returns an XML document which
39440 lists loaded libraries and their offsets. Each library has an
39441 associated name and one or more segment or section base addresses,
39442 which report where the library was loaded in memory.
39444 For the common case of libraries that are fully linked binaries, the
39445 library should have a list of segments. If the target supports
39446 dynamic linking of a relocatable object file, its library XML element
39447 should instead include a list of allocated sections. The segment or
39448 section bases are start addresses, not relocation offsets; they do not
39449 depend on the library's link-time base addresses.
39451 @value{GDBN} must be linked with the Expat library to support XML
39452 library lists. @xref{Expat}.
39454 A simple memory map, with one loaded library relocated by a single
39455 offset, looks like this:
39459 <library name="/lib/libc.so.6">
39460 <segment address="0x10000000"/>
39465 Another simple memory map, with one loaded library with three
39466 allocated sections (.text, .data, .bss), looks like this:
39470 <library name="sharedlib.o">
39471 <section address="0x10000000"/>
39472 <section address="0x20000000"/>
39473 <section address="0x30000000"/>
39478 The format of a library list is described by this DTD:
39481 <!-- library-list: Root element with versioning -->
39482 <!ELEMENT library-list (library)*>
39483 <!ATTLIST library-list version CDATA #FIXED "1.0">
39484 <!ELEMENT library (segment*, section*)>
39485 <!ATTLIST library name CDATA #REQUIRED>
39486 <!ELEMENT segment EMPTY>
39487 <!ATTLIST segment address CDATA #REQUIRED>
39488 <!ELEMENT section EMPTY>
39489 <!ATTLIST section address CDATA #REQUIRED>
39492 In addition, segments and section descriptors cannot be mixed within a
39493 single library element, and you must supply at least one segment or
39494 section for each library.
39496 @node Library List Format for SVR4 Targets
39497 @section Library List Format for SVR4 Targets
39498 @cindex library list format, remote protocol
39500 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
39501 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
39502 shared libraries. Still a special library list provided by this packet is
39503 more efficient for the @value{GDBN} remote protocol.
39505 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
39506 loaded libraries and their SVR4 linker parameters. For each library on SVR4
39507 target, the following parameters are reported:
39511 @code{name}, the absolute file name from the @code{l_name} field of
39512 @code{struct link_map}.
39514 @code{lm} with address of @code{struct link_map} used for TLS
39515 (Thread Local Storage) access.
39517 @code{l_addr}, the displacement as read from the field @code{l_addr} of
39518 @code{struct link_map}. For prelinked libraries this is not an absolute
39519 memory address. It is a displacement of absolute memory address against
39520 address the file was prelinked to during the library load.
39522 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
39525 Additionally the single @code{main-lm} attribute specifies address of
39526 @code{struct link_map} used for the main executable. This parameter is used
39527 for TLS access and its presence is optional.
39529 @value{GDBN} must be linked with the Expat library to support XML
39530 SVR4 library lists. @xref{Expat}.
39532 A simple memory map, with two loaded libraries (which do not use prelink),
39536 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
39537 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
39539 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
39541 </library-list-svr>
39544 The format of an SVR4 library list is described by this DTD:
39547 <!-- library-list-svr4: Root element with versioning -->
39548 <!ELEMENT library-list-svr4 (library)*>
39549 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
39550 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
39551 <!ELEMENT library EMPTY>
39552 <!ATTLIST library name CDATA #REQUIRED>
39553 <!ATTLIST library lm CDATA #REQUIRED>
39554 <!ATTLIST library l_addr CDATA #REQUIRED>
39555 <!ATTLIST library l_ld CDATA #REQUIRED>
39558 @node Memory Map Format
39559 @section Memory Map Format
39560 @cindex memory map format
39562 To be able to write into flash memory, @value{GDBN} needs to obtain a
39563 memory map from the target. This section describes the format of the
39566 The memory map is obtained using the @samp{qXfer:memory-map:read}
39567 (@pxref{qXfer memory map read}) packet and is an XML document that
39568 lists memory regions.
39570 @value{GDBN} must be linked with the Expat library to support XML
39571 memory maps. @xref{Expat}.
39573 The top-level structure of the document is shown below:
39576 <?xml version="1.0"?>
39577 <!DOCTYPE memory-map
39578 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39579 "http://sourceware.org/gdb/gdb-memory-map.dtd">
39585 Each region can be either:
39590 A region of RAM starting at @var{addr} and extending for @var{length}
39594 <memory type="ram" start="@var{addr}" length="@var{length}"/>
39599 A region of read-only memory:
39602 <memory type="rom" start="@var{addr}" length="@var{length}"/>
39607 A region of flash memory, with erasure blocks @var{blocksize}
39611 <memory type="flash" start="@var{addr}" length="@var{length}">
39612 <property name="blocksize">@var{blocksize}</property>
39618 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
39619 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
39620 packets to write to addresses in such ranges.
39622 The formal DTD for memory map format is given below:
39625 <!-- ................................................... -->
39626 <!-- Memory Map XML DTD ................................ -->
39627 <!-- File: memory-map.dtd .............................. -->
39628 <!-- .................................... .............. -->
39629 <!-- memory-map.dtd -->
39630 <!-- memory-map: Root element with versioning -->
39631 <!ELEMENT memory-map (memory | property)>
39632 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
39633 <!ELEMENT memory (property)>
39634 <!-- memory: Specifies a memory region,
39635 and its type, or device. -->
39636 <!ATTLIST memory type CDATA #REQUIRED
39637 start CDATA #REQUIRED
39638 length CDATA #REQUIRED
39639 device CDATA #IMPLIED>
39640 <!-- property: Generic attribute tag -->
39641 <!ELEMENT property (#PCDATA | property)*>
39642 <!ATTLIST property name CDATA #REQUIRED>
39645 @node Thread List Format
39646 @section Thread List Format
39647 @cindex thread list format
39649 To efficiently update the list of threads and their attributes,
39650 @value{GDBN} issues the @samp{qXfer:threads:read} packet
39651 (@pxref{qXfer threads read}) and obtains the XML document with
39652 the following structure:
39655 <?xml version="1.0"?>
39657 <thread id="id" core="0">
39658 ... description ...
39663 Each @samp{thread} element must have the @samp{id} attribute that
39664 identifies the thread (@pxref{thread-id syntax}). The
39665 @samp{core} attribute, if present, specifies which processor core
39666 the thread was last executing on. The content of the of @samp{thread}
39667 element is interpreted as human-readable auxilliary information.
39669 @node Traceframe Info Format
39670 @section Traceframe Info Format
39671 @cindex traceframe info format
39673 To be able to know which objects in the inferior can be examined when
39674 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
39675 memory ranges, registers and trace state variables that have been
39676 collected in a traceframe.
39678 This list is obtained using the @samp{qXfer:traceframe-info:read}
39679 (@pxref{qXfer traceframe info read}) packet and is an XML document.
39681 @value{GDBN} must be linked with the Expat library to support XML
39682 traceframe info discovery. @xref{Expat}.
39684 The top-level structure of the document is shown below:
39687 <?xml version="1.0"?>
39688 <!DOCTYPE traceframe-info
39689 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39690 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
39696 Each traceframe block can be either:
39701 A region of collected memory starting at @var{addr} and extending for
39702 @var{length} bytes from there:
39705 <memory start="@var{addr}" length="@var{length}"/>
39710 The formal DTD for the traceframe info format is given below:
39713 <!ELEMENT traceframe-info (memory)* >
39714 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
39716 <!ELEMENT memory EMPTY>
39717 <!ATTLIST memory start CDATA #REQUIRED
39718 length CDATA #REQUIRED>
39721 @include agentexpr.texi
39723 @node Target Descriptions
39724 @appendix Target Descriptions
39725 @cindex target descriptions
39727 One of the challenges of using @value{GDBN} to debug embedded systems
39728 is that there are so many minor variants of each processor
39729 architecture in use. It is common practice for vendors to start with
39730 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
39731 and then make changes to adapt it to a particular market niche. Some
39732 architectures have hundreds of variants, available from dozens of
39733 vendors. This leads to a number of problems:
39737 With so many different customized processors, it is difficult for
39738 the @value{GDBN} maintainers to keep up with the changes.
39740 Since individual variants may have short lifetimes or limited
39741 audiences, it may not be worthwhile to carry information about every
39742 variant in the @value{GDBN} source tree.
39744 When @value{GDBN} does support the architecture of the embedded system
39745 at hand, the task of finding the correct architecture name to give the
39746 @command{set architecture} command can be error-prone.
39749 To address these problems, the @value{GDBN} remote protocol allows a
39750 target system to not only identify itself to @value{GDBN}, but to
39751 actually describe its own features. This lets @value{GDBN} support
39752 processor variants it has never seen before --- to the extent that the
39753 descriptions are accurate, and that @value{GDBN} understands them.
39755 @value{GDBN} must be linked with the Expat library to support XML
39756 target descriptions. @xref{Expat}.
39759 * Retrieving Descriptions:: How descriptions are fetched from a target.
39760 * Target Description Format:: The contents of a target description.
39761 * Predefined Target Types:: Standard types available for target
39763 * Standard Target Features:: Features @value{GDBN} knows about.
39766 @node Retrieving Descriptions
39767 @section Retrieving Descriptions
39769 Target descriptions can be read from the target automatically, or
39770 specified by the user manually. The default behavior is to read the
39771 description from the target. @value{GDBN} retrieves it via the remote
39772 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
39773 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
39774 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
39775 XML document, of the form described in @ref{Target Description
39778 Alternatively, you can specify a file to read for the target description.
39779 If a file is set, the target will not be queried. The commands to
39780 specify a file are:
39783 @cindex set tdesc filename
39784 @item set tdesc filename @var{path}
39785 Read the target description from @var{path}.
39787 @cindex unset tdesc filename
39788 @item unset tdesc filename
39789 Do not read the XML target description from a file. @value{GDBN}
39790 will use the description supplied by the current target.
39792 @cindex show tdesc filename
39793 @item show tdesc filename
39794 Show the filename to read for a target description, if any.
39798 @node Target Description Format
39799 @section Target Description Format
39800 @cindex target descriptions, XML format
39802 A target description annex is an @uref{http://www.w3.org/XML/, XML}
39803 document which complies with the Document Type Definition provided in
39804 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
39805 means you can use generally available tools like @command{xmllint} to
39806 check that your feature descriptions are well-formed and valid.
39807 However, to help people unfamiliar with XML write descriptions for
39808 their targets, we also describe the grammar here.
39810 Target descriptions can identify the architecture of the remote target
39811 and (for some architectures) provide information about custom register
39812 sets. They can also identify the OS ABI of the remote target.
39813 @value{GDBN} can use this information to autoconfigure for your
39814 target, or to warn you if you connect to an unsupported target.
39816 Here is a simple target description:
39819 <target version="1.0">
39820 <architecture>i386:x86-64</architecture>
39825 This minimal description only says that the target uses
39826 the x86-64 architecture.
39828 A target description has the following overall form, with [ ] marking
39829 optional elements and @dots{} marking repeatable elements. The elements
39830 are explained further below.
39833 <?xml version="1.0"?>
39834 <!DOCTYPE target SYSTEM "gdb-target.dtd">
39835 <target version="1.0">
39836 @r{[}@var{architecture}@r{]}
39837 @r{[}@var{osabi}@r{]}
39838 @r{[}@var{compatible}@r{]}
39839 @r{[}@var{feature}@dots{}@r{]}
39844 The description is generally insensitive to whitespace and line
39845 breaks, under the usual common-sense rules. The XML version
39846 declaration and document type declaration can generally be omitted
39847 (@value{GDBN} does not require them), but specifying them may be
39848 useful for XML validation tools. The @samp{version} attribute for
39849 @samp{<target>} may also be omitted, but we recommend
39850 including it; if future versions of @value{GDBN} use an incompatible
39851 revision of @file{gdb-target.dtd}, they will detect and report
39852 the version mismatch.
39854 @subsection Inclusion
39855 @cindex target descriptions, inclusion
39858 @cindex <xi:include>
39861 It can sometimes be valuable to split a target description up into
39862 several different annexes, either for organizational purposes, or to
39863 share files between different possible target descriptions. You can
39864 divide a description into multiple files by replacing any element of
39865 the target description with an inclusion directive of the form:
39868 <xi:include href="@var{document}"/>
39872 When @value{GDBN} encounters an element of this form, it will retrieve
39873 the named XML @var{document}, and replace the inclusion directive with
39874 the contents of that document. If the current description was read
39875 using @samp{qXfer}, then so will be the included document;
39876 @var{document} will be interpreted as the name of an annex. If the
39877 current description was read from a file, @value{GDBN} will look for
39878 @var{document} as a file in the same directory where it found the
39879 original description.
39881 @subsection Architecture
39882 @cindex <architecture>
39884 An @samp{<architecture>} element has this form:
39887 <architecture>@var{arch}</architecture>
39890 @var{arch} is one of the architectures from the set accepted by
39891 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39894 @cindex @code{<osabi>}
39896 This optional field was introduced in @value{GDBN} version 7.0.
39897 Previous versions of @value{GDBN} ignore it.
39899 An @samp{<osabi>} element has this form:
39902 <osabi>@var{abi-name}</osabi>
39905 @var{abi-name} is an OS ABI name from the same selection accepted by
39906 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
39908 @subsection Compatible Architecture
39909 @cindex @code{<compatible>}
39911 This optional field was introduced in @value{GDBN} version 7.0.
39912 Previous versions of @value{GDBN} ignore it.
39914 A @samp{<compatible>} element has this form:
39917 <compatible>@var{arch}</compatible>
39920 @var{arch} is one of the architectures from the set accepted by
39921 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39923 A @samp{<compatible>} element is used to specify that the target
39924 is able to run binaries in some other than the main target architecture
39925 given by the @samp{<architecture>} element. For example, on the
39926 Cell Broadband Engine, the main architecture is @code{powerpc:common}
39927 or @code{powerpc:common64}, but the system is able to run binaries
39928 in the @code{spu} architecture as well. The way to describe this
39929 capability with @samp{<compatible>} is as follows:
39932 <architecture>powerpc:common</architecture>
39933 <compatible>spu</compatible>
39936 @subsection Features
39939 Each @samp{<feature>} describes some logical portion of the target
39940 system. Features are currently used to describe available CPU
39941 registers and the types of their contents. A @samp{<feature>} element
39945 <feature name="@var{name}">
39946 @r{[}@var{type}@dots{}@r{]}
39952 Each feature's name should be unique within the description. The name
39953 of a feature does not matter unless @value{GDBN} has some special
39954 knowledge of the contents of that feature; if it does, the feature
39955 should have its standard name. @xref{Standard Target Features}.
39959 Any register's value is a collection of bits which @value{GDBN} must
39960 interpret. The default interpretation is a two's complement integer,
39961 but other types can be requested by name in the register description.
39962 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
39963 Target Types}), and the description can define additional composite types.
39965 Each type element must have an @samp{id} attribute, which gives
39966 a unique (within the containing @samp{<feature>}) name to the type.
39967 Types must be defined before they are used.
39970 Some targets offer vector registers, which can be treated as arrays
39971 of scalar elements. These types are written as @samp{<vector>} elements,
39972 specifying the array element type, @var{type}, and the number of elements,
39976 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
39980 If a register's value is usefully viewed in multiple ways, define it
39981 with a union type containing the useful representations. The
39982 @samp{<union>} element contains one or more @samp{<field>} elements,
39983 each of which has a @var{name} and a @var{type}:
39986 <union id="@var{id}">
39987 <field name="@var{name}" type="@var{type}"/>
39993 If a register's value is composed from several separate values, define
39994 it with a structure type. There are two forms of the @samp{<struct>}
39995 element; a @samp{<struct>} element must either contain only bitfields
39996 or contain no bitfields. If the structure contains only bitfields,
39997 its total size in bytes must be specified, each bitfield must have an
39998 explicit start and end, and bitfields are automatically assigned an
39999 integer type. The field's @var{start} should be less than or
40000 equal to its @var{end}, and zero represents the least significant bit.
40003 <struct id="@var{id}" size="@var{size}">
40004 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40009 If the structure contains no bitfields, then each field has an
40010 explicit type, and no implicit padding is added.
40013 <struct id="@var{id}">
40014 <field name="@var{name}" type="@var{type}"/>
40020 If a register's value is a series of single-bit flags, define it with
40021 a flags type. The @samp{<flags>} element has an explicit @var{size}
40022 and contains one or more @samp{<field>} elements. Each field has a
40023 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
40027 <flags id="@var{id}" size="@var{size}">
40028 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40033 @subsection Registers
40036 Each register is represented as an element with this form:
40039 <reg name="@var{name}"
40040 bitsize="@var{size}"
40041 @r{[}regnum="@var{num}"@r{]}
40042 @r{[}save-restore="@var{save-restore}"@r{]}
40043 @r{[}type="@var{type}"@r{]}
40044 @r{[}group="@var{group}"@r{]}/>
40048 The components are as follows:
40053 The register's name; it must be unique within the target description.
40056 The register's size, in bits.
40059 The register's number. If omitted, a register's number is one greater
40060 than that of the previous register (either in the current feature or in
40061 a preceding feature); the first register in the target description
40062 defaults to zero. This register number is used to read or write
40063 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40064 packets, and registers appear in the @code{g} and @code{G} packets
40065 in order of increasing register number.
40068 Whether the register should be preserved across inferior function
40069 calls; this must be either @code{yes} or @code{no}. The default is
40070 @code{yes}, which is appropriate for most registers except for
40071 some system control registers; this is not related to the target's
40075 The type of the register. @var{type} may be a predefined type, a type
40076 defined in the current feature, or one of the special types @code{int}
40077 and @code{float}. @code{int} is an integer type of the correct size
40078 for @var{bitsize}, and @code{float} is a floating point type (in the
40079 architecture's normal floating point format) of the correct size for
40080 @var{bitsize}. The default is @code{int}.
40083 The register group to which this register belongs. @var{group} must
40084 be either @code{general}, @code{float}, or @code{vector}. If no
40085 @var{group} is specified, @value{GDBN} will not display the register
40086 in @code{info registers}.
40090 @node Predefined Target Types
40091 @section Predefined Target Types
40092 @cindex target descriptions, predefined types
40094 Type definitions in the self-description can build up composite types
40095 from basic building blocks, but can not define fundamental types. Instead,
40096 standard identifiers are provided by @value{GDBN} for the fundamental
40097 types. The currently supported types are:
40106 Signed integer types holding the specified number of bits.
40113 Unsigned integer types holding the specified number of bits.
40117 Pointers to unspecified code and data. The program counter and
40118 any dedicated return address register may be marked as code
40119 pointers; printing a code pointer converts it into a symbolic
40120 address. The stack pointer and any dedicated address registers
40121 may be marked as data pointers.
40124 Single precision IEEE floating point.
40127 Double precision IEEE floating point.
40130 The 12-byte extended precision format used by ARM FPA registers.
40133 The 10-byte extended precision format used by x87 registers.
40136 32bit @sc{eflags} register used by x86.
40139 32bit @sc{mxcsr} register used by x86.
40143 @node Standard Target Features
40144 @section Standard Target Features
40145 @cindex target descriptions, standard features
40147 A target description must contain either no registers or all the
40148 target's registers. If the description contains no registers, then
40149 @value{GDBN} will assume a default register layout, selected based on
40150 the architecture. If the description contains any registers, the
40151 default layout will not be used; the standard registers must be
40152 described in the target description, in such a way that @value{GDBN}
40153 can recognize them.
40155 This is accomplished by giving specific names to feature elements
40156 which contain standard registers. @value{GDBN} will look for features
40157 with those names and verify that they contain the expected registers;
40158 if any known feature is missing required registers, or if any required
40159 feature is missing, @value{GDBN} will reject the target
40160 description. You can add additional registers to any of the
40161 standard features --- @value{GDBN} will display them just as if
40162 they were added to an unrecognized feature.
40164 This section lists the known features and their expected contents.
40165 Sample XML documents for these features are included in the
40166 @value{GDBN} source tree, in the directory @file{gdb/features}.
40168 Names recognized by @value{GDBN} should include the name of the
40169 company or organization which selected the name, and the overall
40170 architecture to which the feature applies; so e.g.@: the feature
40171 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
40173 The names of registers are not case sensitive for the purpose
40174 of recognizing standard features, but @value{GDBN} will only display
40175 registers using the capitalization used in the description.
40182 * PowerPC Features::
40188 @subsection ARM Features
40189 @cindex target descriptions, ARM features
40191 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
40193 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
40194 @samp{lr}, @samp{pc}, and @samp{cpsr}.
40196 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
40197 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
40198 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
40201 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
40202 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
40204 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
40205 it should contain at least registers @samp{wR0} through @samp{wR15} and
40206 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
40207 @samp{wCSSF}, and @samp{wCASF} registers are optional.
40209 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
40210 should contain at least registers @samp{d0} through @samp{d15}. If
40211 they are present, @samp{d16} through @samp{d31} should also be included.
40212 @value{GDBN} will synthesize the single-precision registers from
40213 halves of the double-precision registers.
40215 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
40216 need to contain registers; it instructs @value{GDBN} to display the
40217 VFP double-precision registers as vectors and to synthesize the
40218 quad-precision registers from pairs of double-precision registers.
40219 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
40220 be present and include 32 double-precision registers.
40222 @node i386 Features
40223 @subsection i386 Features
40224 @cindex target descriptions, i386 features
40226 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
40227 targets. It should describe the following registers:
40231 @samp{eax} through @samp{edi} plus @samp{eip} for i386
40233 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
40235 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
40236 @samp{fs}, @samp{gs}
40238 @samp{st0} through @samp{st7}
40240 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
40241 @samp{foseg}, @samp{fooff} and @samp{fop}
40244 The register sets may be different, depending on the target.
40246 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
40247 describe registers:
40251 @samp{xmm0} through @samp{xmm7} for i386
40253 @samp{xmm0} through @samp{xmm15} for amd64
40258 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
40259 @samp{org.gnu.gdb.i386.sse} feature. It should
40260 describe the upper 128 bits of @sc{ymm} registers:
40264 @samp{ymm0h} through @samp{ymm7h} for i386
40266 @samp{ymm0h} through @samp{ymm15h} for amd64
40269 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
40270 describe a single register, @samp{orig_eax}.
40272 @node MIPS Features
40273 @subsection @acronym{MIPS} Features
40274 @cindex target descriptions, @acronym{MIPS} features
40276 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
40277 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
40278 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
40281 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
40282 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
40283 registers. They may be 32-bit or 64-bit depending on the target.
40285 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
40286 it may be optional in a future version of @value{GDBN}. It should
40287 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
40288 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
40290 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
40291 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
40292 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
40293 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
40295 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
40296 contain a single register, @samp{restart}, which is used by the
40297 Linux kernel to control restartable syscalls.
40299 @node M68K Features
40300 @subsection M68K Features
40301 @cindex target descriptions, M68K features
40304 @item @samp{org.gnu.gdb.m68k.core}
40305 @itemx @samp{org.gnu.gdb.coldfire.core}
40306 @itemx @samp{org.gnu.gdb.fido.core}
40307 One of those features must be always present.
40308 The feature that is present determines which flavor of m68k is
40309 used. The feature that is present should contain registers
40310 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
40311 @samp{sp}, @samp{ps} and @samp{pc}.
40313 @item @samp{org.gnu.gdb.coldfire.fp}
40314 This feature is optional. If present, it should contain registers
40315 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
40319 @node PowerPC Features
40320 @subsection PowerPC Features
40321 @cindex target descriptions, PowerPC features
40323 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
40324 targets. It should contain registers @samp{r0} through @samp{r31},
40325 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
40326 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
40328 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
40329 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
40331 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
40332 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
40335 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
40336 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
40337 will combine these registers with the floating point registers
40338 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
40339 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
40340 through @samp{vs63}, the set of vector registers for POWER7.
40342 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
40343 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
40344 @samp{spefscr}. SPE targets should provide 32-bit registers in
40345 @samp{org.gnu.gdb.power.core} and provide the upper halves in
40346 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
40347 these to present registers @samp{ev0} through @samp{ev31} to the
40350 @node TIC6x Features
40351 @subsection TMS320C6x Features
40352 @cindex target descriptions, TIC6x features
40353 @cindex target descriptions, TMS320C6x features
40354 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
40355 targets. It should contain registers @samp{A0} through @samp{A15},
40356 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
40358 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
40359 contain registers @samp{A16} through @samp{A31} and @samp{B16}
40360 through @samp{B31}.
40362 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
40363 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
40365 @node Operating System Information
40366 @appendix Operating System Information
40367 @cindex operating system information
40373 Users of @value{GDBN} often wish to obtain information about the state of
40374 the operating system running on the target---for example the list of
40375 processes, or the list of open files. This section describes the
40376 mechanism that makes it possible. This mechanism is similar to the
40377 target features mechanism (@pxref{Target Descriptions}), but focuses
40378 on a different aspect of target.
40380 Operating system information is retrived from the target via the
40381 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
40382 read}). The object name in the request should be @samp{osdata}, and
40383 the @var{annex} identifies the data to be fetched.
40386 @appendixsection Process list
40387 @cindex operating system information, process list
40389 When requesting the process list, the @var{annex} field in the
40390 @samp{qXfer} request should be @samp{processes}. The returned data is
40391 an XML document. The formal syntax of this document is defined in
40392 @file{gdb/features/osdata.dtd}.
40394 An example document is:
40397 <?xml version="1.0"?>
40398 <!DOCTYPE target SYSTEM "osdata.dtd">
40399 <osdata type="processes">
40401 <column name="pid">1</column>
40402 <column name="user">root</column>
40403 <column name="command">/sbin/init</column>
40404 <column name="cores">1,2,3</column>
40409 Each item should include a column whose name is @samp{pid}. The value
40410 of that column should identify the process on the target. The
40411 @samp{user} and @samp{command} columns are optional, and will be
40412 displayed by @value{GDBN}. The @samp{cores} column, if present,
40413 should contain a comma-separated list of cores that this process
40414 is running on. Target may provide additional columns,
40415 which @value{GDBN} currently ignores.
40417 @node Trace File Format
40418 @appendix Trace File Format
40419 @cindex trace file format
40421 The trace file comes in three parts: a header, a textual description
40422 section, and a trace frame section with binary data.
40424 The header has the form @code{\x7fTRACE0\n}. The first byte is
40425 @code{0x7f} so as to indicate that the file contains binary data,
40426 while the @code{0} is a version number that may have different values
40429 The description section consists of multiple lines of @sc{ascii} text
40430 separated by newline characters (@code{0xa}). The lines may include a
40431 variety of optional descriptive or context-setting information, such
40432 as tracepoint definitions or register set size. @value{GDBN} will
40433 ignore any line that it does not recognize. An empty line marks the end
40436 @c FIXME add some specific types of data
40438 The trace frame section consists of a number of consecutive frames.
40439 Each frame begins with a two-byte tracepoint number, followed by a
40440 four-byte size giving the amount of data in the frame. The data in
40441 the frame consists of a number of blocks, each introduced by a
40442 character indicating its type (at least register, memory, and trace
40443 state variable). The data in this section is raw binary, not a
40444 hexadecimal or other encoding; its endianness matches the target's
40447 @c FIXME bi-arch may require endianness/arch info in description section
40450 @item R @var{bytes}
40451 Register block. The number and ordering of bytes matches that of a
40452 @code{g} packet in the remote protocol. Note that these are the
40453 actual bytes, in target order and @value{GDBN} register order, not a
40454 hexadecimal encoding.
40456 @item M @var{address} @var{length} @var{bytes}...
40457 Memory block. This is a contiguous block of memory, at the 8-byte
40458 address @var{address}, with a 2-byte length @var{length}, followed by
40459 @var{length} bytes.
40461 @item V @var{number} @var{value}
40462 Trace state variable block. This records the 8-byte signed value
40463 @var{value} of trace state variable numbered @var{number}.
40467 Future enhancements of the trace file format may include additional types
40470 @node Index Section Format
40471 @appendix @code{.gdb_index} section format
40472 @cindex .gdb_index section format
40473 @cindex index section format
40475 This section documents the index section that is created by @code{save
40476 gdb-index} (@pxref{Index Files}). The index section is
40477 DWARF-specific; some knowledge of DWARF is assumed in this
40480 The mapped index file format is designed to be directly
40481 @code{mmap}able on any architecture. In most cases, a datum is
40482 represented using a little-endian 32-bit integer value, called an
40483 @code{offset_type}. Big endian machines must byte-swap the values
40484 before using them. Exceptions to this rule are noted. The data is
40485 laid out such that alignment is always respected.
40487 A mapped index consists of several areas, laid out in order.
40491 The file header. This is a sequence of values, of @code{offset_type}
40492 unless otherwise noted:
40496 The version number, currently 7. Versions 1, 2 and 3 are obsolete.
40497 Version 4 uses a different hashing function from versions 5 and 6.
40498 Version 6 includes symbols for inlined functions, whereas versions 4
40499 and 5 do not. Version 7 adds attributes to the CU indices in the
40500 symbol table. @value{GDBN} will only read version 4, 5, or 6 indices
40501 by specifying @code{set use-deprecated-index-sections on}.
40504 The offset, from the start of the file, of the CU list.
40507 The offset, from the start of the file, of the types CU list. Note
40508 that this area can be empty, in which case this offset will be equal
40509 to the next offset.
40512 The offset, from the start of the file, of the address area.
40515 The offset, from the start of the file, of the symbol table.
40518 The offset, from the start of the file, of the constant pool.
40522 The CU list. This is a sequence of pairs of 64-bit little-endian
40523 values, sorted by the CU offset. The first element in each pair is
40524 the offset of a CU in the @code{.debug_info} section. The second
40525 element in each pair is the length of that CU. References to a CU
40526 elsewhere in the map are done using a CU index, which is just the
40527 0-based index into this table. Note that if there are type CUs, then
40528 conceptually CUs and type CUs form a single list for the purposes of
40532 The types CU list. This is a sequence of triplets of 64-bit
40533 little-endian values. In a triplet, the first value is the CU offset,
40534 the second value is the type offset in the CU, and the third value is
40535 the type signature. The types CU list is not sorted.
40538 The address area. The address area consists of a sequence of address
40539 entries. Each address entry has three elements:
40543 The low address. This is a 64-bit little-endian value.
40546 The high address. This is a 64-bit little-endian value. Like
40547 @code{DW_AT_high_pc}, the value is one byte beyond the end.
40550 The CU index. This is an @code{offset_type} value.
40554 The symbol table. This is an open-addressed hash table. The size of
40555 the hash table is always a power of 2.
40557 Each slot in the hash table consists of a pair of @code{offset_type}
40558 values. The first value is the offset of the symbol's name in the
40559 constant pool. The second value is the offset of the CU vector in the
40562 If both values are 0, then this slot in the hash table is empty. This
40563 is ok because while 0 is a valid constant pool index, it cannot be a
40564 valid index for both a string and a CU vector.
40566 The hash value for a table entry is computed by applying an
40567 iterative hash function to the symbol's name. Starting with an
40568 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
40569 the string is incorporated into the hash using the formula depending on the
40574 The formula is @code{r = r * 67 + c - 113}.
40576 @item Versions 5 to 7
40577 The formula is @code{r = r * 67 + tolower (c) - 113}.
40580 The terminating @samp{\0} is not incorporated into the hash.
40582 The step size used in the hash table is computed via
40583 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
40584 value, and @samp{size} is the size of the hash table. The step size
40585 is used to find the next candidate slot when handling a hash
40588 The names of C@t{++} symbols in the hash table are canonicalized. We
40589 don't currently have a simple description of the canonicalization
40590 algorithm; if you intend to create new index sections, you must read
40594 The constant pool. This is simply a bunch of bytes. It is organized
40595 so that alignment is correct: CU vectors are stored first, followed by
40598 A CU vector in the constant pool is a sequence of @code{offset_type}
40599 values. The first value is the number of CU indices in the vector.
40600 Each subsequent value is the index and symbol attributes of a CU in
40601 the CU list. This element in the hash table is used to indicate which
40602 CUs define the symbol and how the symbol is used.
40603 See below for the format of each CU index+attributes entry.
40605 A string in the constant pool is zero-terminated.
40608 Attributes were added to CU index values in @code{.gdb_index} version 7.
40609 If a symbol has multiple uses within a CU then there is one
40610 CU index+attributes value for each use.
40612 The format of each CU index+attributes entry is as follows
40618 This is the index of the CU in the CU list.
40620 These bits are reserved for future purposes and must be zero.
40622 The kind of the symbol in the CU.
40626 This value is reserved and should not be used.
40627 By reserving zero the full @code{offset_type} value is backwards compatible
40628 with previous versions of the index.
40630 The symbol is a type.
40632 The symbol is a variable or an enum value.
40634 The symbol is a function.
40636 Any other kind of symbol.
40638 These values are reserved.
40642 This bit is zero if the value is global and one if it is static.
40644 The determination of whether a symbol is global or static is complicated.
40645 The authorative reference is the file @file{dwarf2read.c} in
40646 @value{GDBN} sources.
40650 This pseudo-code describes the computation of a symbol's kind and
40651 global/static attributes in the index.
40654 is_external = get_attribute (die, DW_AT_external);
40655 language = get_attribute (cu_die, DW_AT_language);
40658 case DW_TAG_typedef:
40659 case DW_TAG_base_type:
40660 case DW_TAG_subrange_type:
40664 case DW_TAG_enumerator:
40666 is_static = (language != CPLUS && language != JAVA);
40668 case DW_TAG_subprogram:
40670 is_static = ! (is_external || language == ADA);
40672 case DW_TAG_constant:
40674 is_static = ! is_external;
40676 case DW_TAG_variable:
40678 is_static = ! is_external;
40680 case DW_TAG_namespace:
40684 case DW_TAG_class_type:
40685 case DW_TAG_interface_type:
40686 case DW_TAG_structure_type:
40687 case DW_TAG_union_type:
40688 case DW_TAG_enumeration_type:
40690 is_static = (language != CPLUS && language != JAVA);
40699 @node GNU Free Documentation License
40700 @appendix GNU Free Documentation License
40703 @node Concept Index
40704 @unnumbered Concept Index
40708 @node Command and Variable Index
40709 @unnumbered Command, Variable, and Function Index
40714 % I think something like @@colophon should be in texinfo. In the
40716 \long\def\colophon{\hbox to0pt{}\vfill
40717 \centerline{The body of this manual is set in}
40718 \centerline{\fontname\tenrm,}
40719 \centerline{with headings in {\bf\fontname\tenbf}}
40720 \centerline{and examples in {\tt\fontname\tentt}.}
40721 \centerline{{\it\fontname\tenit\/},}
40722 \centerline{{\bf\fontname\tenbf}, and}
40723 \centerline{{\sl\fontname\tensl\/}}
40724 \centerline{are used for emphasis.}\vfill}
40726 % Blame: doc@@cygnus.com, 1991.