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 port of @value{GDBN} uses the standard name, but if it finds a
1370 @file{gdb.ini} file in your home directory, it warns you about that
1371 and suggests to rename 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 @kindex fo @r{(@code{forward-search})}
6959 @item forward-search @var{regexp}
6960 @itemx search @var{regexp}
6961 The command @samp{forward-search @var{regexp}} checks each line,
6962 starting with the one following the last line listed, for a match for
6963 @var{regexp}. It lists the line that is found. You can use the
6964 synonym @samp{search @var{regexp}} or abbreviate the command name as
6967 @kindex reverse-search
6968 @item reverse-search @var{regexp}
6969 The command @samp{reverse-search @var{regexp}} checks each line, starting
6970 with the one before the last line listed and going backward, for a match
6971 for @var{regexp}. It lists the line that is found. You can abbreviate
6972 this command as @code{rev}.
6976 @section Specifying Source Directories
6979 @cindex directories for source files
6980 Executable programs sometimes do not record the directories of the source
6981 files from which they were compiled, just the names. Even when they do,
6982 the directories could be moved between the compilation and your debugging
6983 session. @value{GDBN} has a list of directories to search for source files;
6984 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6985 it tries all the directories in the list, in the order they are present
6986 in the list, until it finds a file with the desired name.
6988 For example, suppose an executable references the file
6989 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6990 @file{/mnt/cross}. The file is first looked up literally; if this
6991 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6992 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6993 message is printed. @value{GDBN} does not look up the parts of the
6994 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6995 Likewise, the subdirectories of the source path are not searched: if
6996 the source path is @file{/mnt/cross}, and the binary refers to
6997 @file{foo.c}, @value{GDBN} would not find it under
6998 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7000 Plain file names, relative file names with leading directories, file
7001 names containing dots, etc.@: are all treated as described above; for
7002 instance, if the source path is @file{/mnt/cross}, and the source file
7003 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7004 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7005 that---@file{/mnt/cross/foo.c}.
7007 Note that the executable search path is @emph{not} used to locate the
7010 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7011 any information it has cached about where source files are found and where
7012 each line is in the file.
7016 When you start @value{GDBN}, its source path includes only @samp{cdir}
7017 and @samp{cwd}, in that order.
7018 To add other directories, use the @code{directory} command.
7020 The search path is used to find both program source files and @value{GDBN}
7021 script files (read using the @samp{-command} option and @samp{source} command).
7023 In addition to the source path, @value{GDBN} provides a set of commands
7024 that manage a list of source path substitution rules. A @dfn{substitution
7025 rule} specifies how to rewrite source directories stored in the program's
7026 debug information in case the sources were moved to a different
7027 directory between compilation and debugging. A rule is made of
7028 two strings, the first specifying what needs to be rewritten in
7029 the path, and the second specifying how it should be rewritten.
7030 In @ref{set substitute-path}, we name these two parts @var{from} and
7031 @var{to} respectively. @value{GDBN} does a simple string replacement
7032 of @var{from} with @var{to} at the start of the directory part of the
7033 source file name, and uses that result instead of the original file
7034 name to look up the sources.
7036 Using the previous example, suppose the @file{foo-1.0} tree has been
7037 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7038 @value{GDBN} to replace @file{/usr/src} in all source path names with
7039 @file{/mnt/cross}. The first lookup will then be
7040 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7041 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7042 substitution rule, use the @code{set substitute-path} command
7043 (@pxref{set substitute-path}).
7045 To avoid unexpected substitution results, a rule is applied only if the
7046 @var{from} part of the directory name ends at a directory separator.
7047 For instance, a rule substituting @file{/usr/source} into
7048 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7049 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7050 is applied only at the beginning of the directory name, this rule will
7051 not be applied to @file{/root/usr/source/baz.c} either.
7053 In many cases, you can achieve the same result using the @code{directory}
7054 command. However, @code{set substitute-path} can be more efficient in
7055 the case where the sources are organized in a complex tree with multiple
7056 subdirectories. With the @code{directory} command, you need to add each
7057 subdirectory of your project. If you moved the entire tree while
7058 preserving its internal organization, then @code{set substitute-path}
7059 allows you to direct the debugger to all the sources with one single
7062 @code{set substitute-path} is also more than just a shortcut command.
7063 The source path is only used if the file at the original location no
7064 longer exists. On the other hand, @code{set substitute-path} modifies
7065 the debugger behavior to look at the rewritten location instead. So, if
7066 for any reason a source file that is not relevant to your executable is
7067 located at the original location, a substitution rule is the only
7068 method available to point @value{GDBN} at the new location.
7070 @cindex @samp{--with-relocated-sources}
7071 @cindex default source path substitution
7072 You can configure a default source path substitution rule by
7073 configuring @value{GDBN} with the
7074 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7075 should be the name of a directory under @value{GDBN}'s configured
7076 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7077 directory names in debug information under @var{dir} will be adjusted
7078 automatically if the installed @value{GDBN} is moved to a new
7079 location. This is useful if @value{GDBN}, libraries or executables
7080 with debug information and corresponding source code are being moved
7084 @item directory @var{dirname} @dots{}
7085 @item dir @var{dirname} @dots{}
7086 Add directory @var{dirname} to the front of the source path. Several
7087 directory names may be given to this command, separated by @samp{:}
7088 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7089 part of absolute file names) or
7090 whitespace. You may specify a directory that is already in the source
7091 path; this moves it forward, so @value{GDBN} searches it sooner.
7095 @vindex $cdir@r{, convenience variable}
7096 @vindex $cwd@r{, convenience variable}
7097 @cindex compilation directory
7098 @cindex current directory
7099 @cindex working directory
7100 @cindex directory, current
7101 @cindex directory, compilation
7102 You can use the string @samp{$cdir} to refer to the compilation
7103 directory (if one is recorded), and @samp{$cwd} to refer to the current
7104 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7105 tracks the current working directory as it changes during your @value{GDBN}
7106 session, while the latter is immediately expanded to the current
7107 directory at the time you add an entry to the source path.
7110 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7112 @c RET-repeat for @code{directory} is explicitly disabled, but since
7113 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7115 @item set directories @var{path-list}
7116 @kindex set directories
7117 Set the source path to @var{path-list}.
7118 @samp{$cdir:$cwd} are added if missing.
7120 @item show directories
7121 @kindex show directories
7122 Print the source path: show which directories it contains.
7124 @anchor{set substitute-path}
7125 @item set substitute-path @var{from} @var{to}
7126 @kindex set substitute-path
7127 Define a source path substitution rule, and add it at the end of the
7128 current list of existing substitution rules. If a rule with the same
7129 @var{from} was already defined, then the old rule is also deleted.
7131 For example, if the file @file{/foo/bar/baz.c} was moved to
7132 @file{/mnt/cross/baz.c}, then the command
7135 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7139 will tell @value{GDBN} to replace @samp{/usr/src} with
7140 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7141 @file{baz.c} even though it was moved.
7143 In the case when more than one substitution rule have been defined,
7144 the rules are evaluated one by one in the order where they have been
7145 defined. The first one matching, if any, is selected to perform
7148 For instance, if we had entered the following commands:
7151 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7152 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7156 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7157 @file{/mnt/include/defs.h} by using the first rule. However, it would
7158 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7159 @file{/mnt/src/lib/foo.c}.
7162 @item unset substitute-path [path]
7163 @kindex unset substitute-path
7164 If a path is specified, search the current list of substitution rules
7165 for a rule that would rewrite that path. Delete that rule if found.
7166 A warning is emitted by the debugger if no rule could be found.
7168 If no path is specified, then all substitution rules are deleted.
7170 @item show substitute-path [path]
7171 @kindex show substitute-path
7172 If a path is specified, then print the source path substitution rule
7173 which would rewrite that path, if any.
7175 If no path is specified, then print all existing source path substitution
7180 If your source path is cluttered with directories that are no longer of
7181 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7182 versions of source. You can correct the situation as follows:
7186 Use @code{directory} with no argument to reset the source path to its default value.
7189 Use @code{directory} with suitable arguments to reinstall the
7190 directories you want in the source path. You can add all the
7191 directories in one command.
7195 @section Source and Machine Code
7196 @cindex source line and its code address
7198 You can use the command @code{info line} to map source lines to program
7199 addresses (and vice versa), and the command @code{disassemble} to display
7200 a range of addresses as machine instructions. You can use the command
7201 @code{set disassemble-next-line} to set whether to disassemble next
7202 source line when execution stops. When run under @sc{gnu} Emacs
7203 mode, the @code{info line} command causes the arrow to point to the
7204 line specified. Also, @code{info line} prints addresses in symbolic form as
7209 @item info line @var{linespec}
7210 Print the starting and ending addresses of the compiled code for
7211 source line @var{linespec}. You can specify source lines in any of
7212 the ways documented in @ref{Specify Location}.
7215 For example, we can use @code{info line} to discover the location of
7216 the object code for the first line of function
7217 @code{m4_changequote}:
7219 @c FIXME: I think this example should also show the addresses in
7220 @c symbolic form, as they usually would be displayed.
7222 (@value{GDBP}) info line m4_changequote
7223 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7227 @cindex code address and its source line
7228 We can also inquire (using @code{*@var{addr}} as the form for
7229 @var{linespec}) what source line covers a particular address:
7231 (@value{GDBP}) info line *0x63ff
7232 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7235 @cindex @code{$_} and @code{info line}
7236 @cindex @code{x} command, default address
7237 @kindex x@r{(examine), and} info line
7238 After @code{info line}, the default address for the @code{x} command
7239 is changed to the starting address of the line, so that @samp{x/i} is
7240 sufficient to begin examining the machine code (@pxref{Memory,
7241 ,Examining Memory}). Also, this address is saved as the value of the
7242 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7247 @cindex assembly instructions
7248 @cindex instructions, assembly
7249 @cindex machine instructions
7250 @cindex listing machine instructions
7252 @itemx disassemble /m
7253 @itemx disassemble /r
7254 This specialized command dumps a range of memory as machine
7255 instructions. It can also print mixed source+disassembly by specifying
7256 the @code{/m} modifier and print the raw instructions in hex as well as
7257 in symbolic form by specifying the @code{/r}.
7258 The default memory range is the function surrounding the
7259 program counter of the selected frame. A single argument to this
7260 command is a program counter value; @value{GDBN} dumps the function
7261 surrounding this value. When two arguments are given, they should
7262 be separated by a comma, possibly surrounded by whitespace. The
7263 arguments specify a range of addresses to dump, in one of two forms:
7266 @item @var{start},@var{end}
7267 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7268 @item @var{start},+@var{length}
7269 the addresses from @var{start} (inclusive) to
7270 @code{@var{start}+@var{length}} (exclusive).
7274 When 2 arguments are specified, the name of the function is also
7275 printed (since there could be several functions in the given range).
7277 The argument(s) can be any expression yielding a numeric value, such as
7278 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7280 If the range of memory being disassembled contains current program counter,
7281 the instruction at that location is shown with a @code{=>} marker.
7284 The following example shows the disassembly of a range of addresses of
7285 HP PA-RISC 2.0 code:
7288 (@value{GDBP}) disas 0x32c4, 0x32e4
7289 Dump of assembler code from 0x32c4 to 0x32e4:
7290 0x32c4 <main+204>: addil 0,dp
7291 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7292 0x32cc <main+212>: ldil 0x3000,r31
7293 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7294 0x32d4 <main+220>: ldo 0(r31),rp
7295 0x32d8 <main+224>: addil -0x800,dp
7296 0x32dc <main+228>: ldo 0x588(r1),r26
7297 0x32e0 <main+232>: ldil 0x3000,r31
7298 End of assembler dump.
7301 Here is an example showing mixed source+assembly for Intel x86, when the
7302 program is stopped just after function prologue:
7305 (@value{GDBP}) disas /m main
7306 Dump of assembler code for function main:
7308 0x08048330 <+0>: push %ebp
7309 0x08048331 <+1>: mov %esp,%ebp
7310 0x08048333 <+3>: sub $0x8,%esp
7311 0x08048336 <+6>: and $0xfffffff0,%esp
7312 0x08048339 <+9>: sub $0x10,%esp
7314 6 printf ("Hello.\n");
7315 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7316 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7320 0x08048348 <+24>: mov $0x0,%eax
7321 0x0804834d <+29>: leave
7322 0x0804834e <+30>: ret
7324 End of assembler dump.
7327 Here is another example showing raw instructions in hex for AMD x86-64,
7330 (gdb) disas /r 0x400281,+10
7331 Dump of assembler code from 0x400281 to 0x40028b:
7332 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7333 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7334 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7335 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7336 End of assembler dump.
7339 Some architectures have more than one commonly-used set of instruction
7340 mnemonics or other syntax.
7342 For programs that were dynamically linked and use shared libraries,
7343 instructions that call functions or branch to locations in the shared
7344 libraries might show a seemingly bogus location---it's actually a
7345 location of the relocation table. On some architectures, @value{GDBN}
7346 might be able to resolve these to actual function names.
7349 @kindex set disassembly-flavor
7350 @cindex Intel disassembly flavor
7351 @cindex AT&T disassembly flavor
7352 @item set disassembly-flavor @var{instruction-set}
7353 Select the instruction set to use when disassembling the
7354 program via the @code{disassemble} or @code{x/i} commands.
7356 Currently this command is only defined for the Intel x86 family. You
7357 can set @var{instruction-set} to either @code{intel} or @code{att}.
7358 The default is @code{att}, the AT&T flavor used by default by Unix
7359 assemblers for x86-based targets.
7361 @kindex show disassembly-flavor
7362 @item show disassembly-flavor
7363 Show the current setting of the disassembly flavor.
7367 @kindex set disassemble-next-line
7368 @kindex show disassemble-next-line
7369 @item set disassemble-next-line
7370 @itemx show disassemble-next-line
7371 Control whether or not @value{GDBN} will disassemble the next source
7372 line or instruction when execution stops. If ON, @value{GDBN} will
7373 display disassembly of the next source line when execution of the
7374 program being debugged stops. This is @emph{in addition} to
7375 displaying the source line itself, which @value{GDBN} always does if
7376 possible. If the next source line cannot be displayed for some reason
7377 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7378 info in the debug info), @value{GDBN} will display disassembly of the
7379 next @emph{instruction} instead of showing the next source line. If
7380 AUTO, @value{GDBN} will display disassembly of next instruction only
7381 if the source line cannot be displayed. This setting causes
7382 @value{GDBN} to display some feedback when you step through a function
7383 with no line info or whose source file is unavailable. The default is
7384 OFF, which means never display the disassembly of the next line or
7390 @chapter Examining Data
7392 @cindex printing data
7393 @cindex examining data
7396 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
7397 @c document because it is nonstandard... Under Epoch it displays in a
7398 @c different window or something like that.
7399 The usual way to examine data in your program is with the @code{print}
7400 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7401 evaluates and prints the value of an expression of the language your
7402 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7403 Different Languages}). It may also print the expression using a
7404 Python-based pretty-printer (@pxref{Pretty Printing}).
7407 @item print @var{expr}
7408 @itemx print /@var{f} @var{expr}
7409 @var{expr} is an expression (in the source language). By default the
7410 value of @var{expr} is printed in a format appropriate to its data type;
7411 you can choose a different format by specifying @samp{/@var{f}}, where
7412 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7416 @itemx print /@var{f}
7417 @cindex reprint the last value
7418 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7419 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7420 conveniently inspect the same value in an alternative format.
7423 A more low-level way of examining data is with the @code{x} command.
7424 It examines data in memory at a specified address and prints it in a
7425 specified format. @xref{Memory, ,Examining Memory}.
7427 If you are interested in information about types, or about how the
7428 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7429 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7432 @cindex exploring hierarchical data structures
7434 Another way of examining values of expressions and type information is
7435 through the Python extension command @code{explore} (available only if
7436 the @value{GDBN} build is configured with @code{--with-python}). It
7437 offers an interactive way to start at the highest level (or, the most
7438 abstract level) of the data type of an expression (or, the data type
7439 itself) and explore all the way down to leaf scalar values/fields
7440 embedded in the higher level data types.
7443 @item explore @var{arg}
7444 @var{arg} is either an expression (in the source language), or a type
7445 visible in the current context of the program being debugged.
7448 The working of the @code{explore} command can be illustrated with an
7449 example. If a data type @code{struct ComplexStruct} is defined in your
7459 struct ComplexStruct
7461 struct SimpleStruct *ss_p;
7467 followed by variable declarations as
7470 struct SimpleStruct ss = @{ 10, 1.11 @};
7471 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7475 then, the value of the variable @code{cs} can be explored using the
7476 @code{explore} command as follows.
7480 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7481 the following fields:
7483 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7484 arr = <Enter 1 to explore this field of type `int [10]'>
7486 Enter the field number of choice:
7490 Since the fields of @code{cs} are not scalar values, you are being
7491 prompted to chose the field you want to explore. Let's say you choose
7492 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7493 pointer, you will be asked if it is pointing to a single value. From
7494 the declaration of @code{cs} above, it is indeed pointing to a single
7495 value, hence you enter @code{y}. If you enter @code{n}, then you will
7496 be asked if it were pointing to an array of values, in which case this
7497 field will be explored as if it were an array.
7500 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7501 Continue exploring it as a pointer to a single value [y/n]: y
7502 The value of `*(cs.ss_p)' is a struct/class of type `struct
7503 SimpleStruct' with the following fields:
7505 i = 10 .. (Value of type `int')
7506 d = 1.1100000000000001 .. (Value of type `double')
7508 Press enter to return to parent value:
7512 If the field @code{arr} of @code{cs} was chosen for exploration by
7513 entering @code{1} earlier, then since it is as array, you will be
7514 prompted to enter the index of the element in the array that you want
7518 `cs.arr' is an array of `int'.
7519 Enter the index of the element you want to explore in `cs.arr': 5
7521 `(cs.arr)[5]' is a scalar value of type `int'.
7525 Press enter to return to parent value:
7528 In general, at any stage of exploration, you can go deeper towards the
7529 leaf values by responding to the prompts appropriately, or hit the
7530 return key to return to the enclosing data structure (the @i{higher}
7531 level data structure).
7533 Similar to exploring values, you can use the @code{explore} command to
7534 explore types. Instead of specifying a value (which is typically a
7535 variable name or an expression valid in the current context of the
7536 program being debugged), you specify a type name. If you consider the
7537 same example as above, your can explore the type
7538 @code{struct ComplexStruct} by passing the argument
7539 @code{struct ComplexStruct} to the @code{explore} command.
7542 (gdb) explore struct ComplexStruct
7546 By responding to the prompts appropriately in the subsequent interactive
7547 session, you can explore the type @code{struct ComplexStruct} in a
7548 manner similar to how the value @code{cs} was explored in the above
7551 The @code{explore} command also has two sub-commands,
7552 @code{explore value} and @code{explore type}. The former sub-command is
7553 a way to explicitly specify that value exploration of the argument is
7554 being invoked, while the latter is a way to explicitly specify that type
7555 exploration of the argument is being invoked.
7558 @item explore value @var{expr}
7559 @cindex explore value
7560 This sub-command of @code{explore} explores the value of the
7561 expression @var{expr} (if @var{expr} is an expression valid in the
7562 current context of the program being debugged). The behavior of this
7563 command is identical to that of the behavior of the @code{explore}
7564 command being passed the argument @var{expr}.
7566 @item explore type @var{arg}
7567 @cindex explore type
7568 This sub-command of @code{explore} explores the type of @var{arg} (if
7569 @var{arg} is a type visible in the current context of program being
7570 debugged), or the type of the value/expression @var{arg} (if @var{arg}
7571 is an expression valid in the current context of the program being
7572 debugged). If @var{arg} is a type, then the behavior of this command is
7573 identical to that of the @code{explore} command being passed the
7574 argument @var{arg}. If @var{arg} is an expression, then the behavior of
7575 this command will be identical to that of the @code{explore} command
7576 being passed the type of @var{arg} as the argument.
7580 * Expressions:: Expressions
7581 * Ambiguous Expressions:: Ambiguous Expressions
7582 * Variables:: Program variables
7583 * Arrays:: Artificial arrays
7584 * Output Formats:: Output formats
7585 * Memory:: Examining memory
7586 * Auto Display:: Automatic display
7587 * Print Settings:: Print settings
7588 * Pretty Printing:: Python pretty printing
7589 * Value History:: Value history
7590 * Convenience Vars:: Convenience variables
7591 * Convenience Funs:: Convenience functions
7592 * Registers:: Registers
7593 * Floating Point Hardware:: Floating point hardware
7594 * Vector Unit:: Vector Unit
7595 * OS Information:: Auxiliary data provided by operating system
7596 * Memory Region Attributes:: Memory region attributes
7597 * Dump/Restore Files:: Copy between memory and a file
7598 * Core File Generation:: Cause a program dump its core
7599 * Character Sets:: Debugging programs that use a different
7600 character set than GDB does
7601 * Caching Remote Data:: Data caching for remote targets
7602 * Searching Memory:: Searching memory for a sequence of bytes
7606 @section Expressions
7609 @code{print} and many other @value{GDBN} commands accept an expression and
7610 compute its value. Any kind of constant, variable or operator defined
7611 by the programming language you are using is valid in an expression in
7612 @value{GDBN}. This includes conditional expressions, function calls,
7613 casts, and string constants. It also includes preprocessor macros, if
7614 you compiled your program to include this information; see
7617 @cindex arrays in expressions
7618 @value{GDBN} supports array constants in expressions input by
7619 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7620 you can use the command @code{print @{1, 2, 3@}} to create an array
7621 of three integers. If you pass an array to a function or assign it
7622 to a program variable, @value{GDBN} copies the array to memory that
7623 is @code{malloc}ed in the target program.
7625 Because C is so widespread, most of the expressions shown in examples in
7626 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7627 Languages}, for information on how to use expressions in other
7630 In this section, we discuss operators that you can use in @value{GDBN}
7631 expressions regardless of your programming language.
7633 @cindex casts, in expressions
7634 Casts are supported in all languages, not just in C, because it is so
7635 useful to cast a number into a pointer in order to examine a structure
7636 at that address in memory.
7637 @c FIXME: casts supported---Mod2 true?
7639 @value{GDBN} supports these operators, in addition to those common
7640 to programming languages:
7644 @samp{@@} is a binary operator for treating parts of memory as arrays.
7645 @xref{Arrays, ,Artificial Arrays}, for more information.
7648 @samp{::} allows you to specify a variable in terms of the file or
7649 function where it is defined. @xref{Variables, ,Program Variables}.
7651 @cindex @{@var{type}@}
7652 @cindex type casting memory
7653 @cindex memory, viewing as typed object
7654 @cindex casts, to view memory
7655 @item @{@var{type}@} @var{addr}
7656 Refers to an object of type @var{type} stored at address @var{addr} in
7657 memory. @var{addr} may be any expression whose value is an integer or
7658 pointer (but parentheses are required around binary operators, just as in
7659 a cast). This construct is allowed regardless of what kind of data is
7660 normally supposed to reside at @var{addr}.
7663 @node Ambiguous Expressions
7664 @section Ambiguous Expressions
7665 @cindex ambiguous expressions
7667 Expressions can sometimes contain some ambiguous elements. For instance,
7668 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7669 a single function name to be defined several times, for application in
7670 different contexts. This is called @dfn{overloading}. Another example
7671 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7672 templates and is typically instantiated several times, resulting in
7673 the same function name being defined in different contexts.
7675 In some cases and depending on the language, it is possible to adjust
7676 the expression to remove the ambiguity. For instance in C@t{++}, you
7677 can specify the signature of the function you want to break on, as in
7678 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7679 qualified name of your function often makes the expression unambiguous
7682 When an ambiguity that needs to be resolved is detected, the debugger
7683 has the capability to display a menu of numbered choices for each
7684 possibility, and then waits for the selection with the prompt @samp{>}.
7685 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7686 aborts the current command. If the command in which the expression was
7687 used allows more than one choice to be selected, the next option in the
7688 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7691 For example, the following session excerpt shows an attempt to set a
7692 breakpoint at the overloaded symbol @code{String::after}.
7693 We choose three particular definitions of that function name:
7695 @c FIXME! This is likely to change to show arg type lists, at least
7698 (@value{GDBP}) b String::after
7701 [2] file:String.cc; line number:867
7702 [3] file:String.cc; line number:860
7703 [4] file:String.cc; line number:875
7704 [5] file:String.cc; line number:853
7705 [6] file:String.cc; line number:846
7706 [7] file:String.cc; line number:735
7708 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7709 Breakpoint 2 at 0xb344: file String.cc, line 875.
7710 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7711 Multiple breakpoints were set.
7712 Use the "delete" command to delete unwanted
7719 @kindex set multiple-symbols
7720 @item set multiple-symbols @var{mode}
7721 @cindex multiple-symbols menu
7723 This option allows you to adjust the debugger behavior when an expression
7726 By default, @var{mode} is set to @code{all}. If the command with which
7727 the expression is used allows more than one choice, then @value{GDBN}
7728 automatically selects all possible choices. For instance, inserting
7729 a breakpoint on a function using an ambiguous name results in a breakpoint
7730 inserted on each possible match. However, if a unique choice must be made,
7731 then @value{GDBN} uses the menu to help you disambiguate the expression.
7732 For instance, printing the address of an overloaded function will result
7733 in the use of the menu.
7735 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7736 when an ambiguity is detected.
7738 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7739 an error due to the ambiguity and the command is aborted.
7741 @kindex show multiple-symbols
7742 @item show multiple-symbols
7743 Show the current value of the @code{multiple-symbols} setting.
7747 @section Program Variables
7749 The most common kind of expression to use is the name of a variable
7752 Variables in expressions are understood in the selected stack frame
7753 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7757 global (or file-static)
7764 visible according to the scope rules of the
7765 programming language from the point of execution in that frame
7768 @noindent This means that in the function
7783 you can examine and use the variable @code{a} whenever your program is
7784 executing within the function @code{foo}, but you can only use or
7785 examine the variable @code{b} while your program is executing inside
7786 the block where @code{b} is declared.
7788 @cindex variable name conflict
7789 There is an exception: you can refer to a variable or function whose
7790 scope is a single source file even if the current execution point is not
7791 in this file. But it is possible to have more than one such variable or
7792 function with the same name (in different source files). If that
7793 happens, referring to that name has unpredictable effects. If you wish,
7794 you can specify a static variable in a particular function or file by
7795 using the colon-colon (@code{::}) notation:
7797 @cindex colon-colon, context for variables/functions
7799 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7800 @cindex @code{::}, context for variables/functions
7803 @var{file}::@var{variable}
7804 @var{function}::@var{variable}
7808 Here @var{file} or @var{function} is the name of the context for the
7809 static @var{variable}. In the case of file names, you can use quotes to
7810 make sure @value{GDBN} parses the file name as a single word---for example,
7811 to print a global value of @code{x} defined in @file{f2.c}:
7814 (@value{GDBP}) p 'f2.c'::x
7817 The @code{::} notation is normally used for referring to
7818 static variables, since you typically disambiguate uses of local variables
7819 in functions by selecting the appropriate frame and using the
7820 simple name of the variable. However, you may also use this notation
7821 to refer to local variables in frames enclosing the selected frame:
7830 process (a); /* Stop here */
7841 For example, if there is a breakpoint at the commented line,
7842 here is what you might see
7843 when the program stops after executing the call @code{bar(0)}:
7848 (@value{GDBP}) p bar::a
7851 #2 0x080483d0 in foo (a=5) at foobar.c:12
7854 (@value{GDBP}) p bar::a
7858 @cindex C@t{++} scope resolution
7859 These uses of @samp{::} are very rarely in conflict with the very similar
7860 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7861 scope resolution operator in @value{GDBN} expressions.
7862 @c FIXME: Um, so what happens in one of those rare cases where it's in
7865 @cindex wrong values
7866 @cindex variable values, wrong
7867 @cindex function entry/exit, wrong values of variables
7868 @cindex optimized code, wrong values of variables
7870 @emph{Warning:} Occasionally, a local variable may appear to have the
7871 wrong value at certain points in a function---just after entry to a new
7872 scope, and just before exit.
7874 You may see this problem when you are stepping by machine instructions.
7875 This is because, on most machines, it takes more than one instruction to
7876 set up a stack frame (including local variable definitions); if you are
7877 stepping by machine instructions, variables may appear to have the wrong
7878 values until the stack frame is completely built. On exit, it usually
7879 also takes more than one machine instruction to destroy a stack frame;
7880 after you begin stepping through that group of instructions, local
7881 variable definitions may be gone.
7883 This may also happen when the compiler does significant optimizations.
7884 To be sure of always seeing accurate values, turn off all optimization
7887 @cindex ``No symbol "foo" in current context''
7888 Another possible effect of compiler optimizations is to optimize
7889 unused variables out of existence, or assign variables to registers (as
7890 opposed to memory addresses). Depending on the support for such cases
7891 offered by the debug info format used by the compiler, @value{GDBN}
7892 might not be able to display values for such local variables. If that
7893 happens, @value{GDBN} will print a message like this:
7896 No symbol "foo" in current context.
7899 To solve such problems, either recompile without optimizations, or use a
7900 different debug info format, if the compiler supports several such
7901 formats. @xref{Compilation}, for more information on choosing compiler
7902 options. @xref{C, ,C and C@t{++}}, for more information about debug
7903 info formats that are best suited to C@t{++} programs.
7905 If you ask to print an object whose contents are unknown to
7906 @value{GDBN}, e.g., because its data type is not completely specified
7907 by the debug information, @value{GDBN} will say @samp{<incomplete
7908 type>}. @xref{Symbols, incomplete type}, for more about this.
7910 If you append @kbd{@@entry} string to a function parameter name you get its
7911 value at the time the function got called. If the value is not available an
7912 error message is printed. Entry values are available only with some compilers.
7913 Entry values are normally also printed at the function parameter list according
7914 to @ref{set print entry-values}.
7917 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7923 (gdb) print i@@entry
7927 Strings are identified as arrays of @code{char} values without specified
7928 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7929 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7930 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7931 defines literal string type @code{"char"} as @code{char} without a sign.
7936 signed char var1[] = "A";
7939 You get during debugging
7944 $2 = @{65 'A', 0 '\0'@}
7948 @section Artificial Arrays
7950 @cindex artificial array
7952 @kindex @@@r{, referencing memory as an array}
7953 It is often useful to print out several successive objects of the
7954 same type in memory; a section of an array, or an array of
7955 dynamically determined size for which only a pointer exists in the
7958 You can do this by referring to a contiguous span of memory as an
7959 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7960 operand of @samp{@@} should be the first element of the desired array
7961 and be an individual object. The right operand should be the desired length
7962 of the array. The result is an array value whose elements are all of
7963 the type of the left argument. The first element is actually the left
7964 argument; the second element comes from bytes of memory immediately
7965 following those that hold the first element, and so on. Here is an
7966 example. If a program says
7969 int *array = (int *) malloc (len * sizeof (int));
7973 you can print the contents of @code{array} with
7979 The left operand of @samp{@@} must reside in memory. Array values made
7980 with @samp{@@} in this way behave just like other arrays in terms of
7981 subscripting, and are coerced to pointers when used in expressions.
7982 Artificial arrays most often appear in expressions via the value history
7983 (@pxref{Value History, ,Value History}), after printing one out.
7985 Another way to create an artificial array is to use a cast.
7986 This re-interprets a value as if it were an array.
7987 The value need not be in memory:
7989 (@value{GDBP}) p/x (short[2])0x12345678
7990 $1 = @{0x1234, 0x5678@}
7993 As a convenience, if you leave the array length out (as in
7994 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7995 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7997 (@value{GDBP}) p/x (short[])0x12345678
7998 $2 = @{0x1234, 0x5678@}
8001 Sometimes the artificial array mechanism is not quite enough; in
8002 moderately complex data structures, the elements of interest may not
8003 actually be adjacent---for example, if you are interested in the values
8004 of pointers in an array. One useful work-around in this situation is
8005 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8006 Variables}) as a counter in an expression that prints the first
8007 interesting value, and then repeat that expression via @key{RET}. For
8008 instance, suppose you have an array @code{dtab} of pointers to
8009 structures, and you are interested in the values of a field @code{fv}
8010 in each structure. Here is an example of what you might type:
8020 @node Output Formats
8021 @section Output Formats
8023 @cindex formatted output
8024 @cindex output formats
8025 By default, @value{GDBN} prints a value according to its data type. Sometimes
8026 this is not what you want. For example, you might want to print a number
8027 in hex, or a pointer in decimal. Or you might want to view data in memory
8028 at a certain address as a character string or as an instruction. To do
8029 these things, specify an @dfn{output format} when you print a value.
8031 The simplest use of output formats is to say how to print a value
8032 already computed. This is done by starting the arguments of the
8033 @code{print} command with a slash and a format letter. The format
8034 letters supported are:
8038 Regard the bits of the value as an integer, and print the integer in
8042 Print as integer in signed decimal.
8045 Print as integer in unsigned decimal.
8048 Print as integer in octal.
8051 Print as integer in binary. The letter @samp{t} stands for ``two''.
8052 @footnote{@samp{b} cannot be used because these format letters are also
8053 used with the @code{x} command, where @samp{b} stands for ``byte'';
8054 see @ref{Memory,,Examining Memory}.}
8057 @cindex unknown address, locating
8058 @cindex locate address
8059 Print as an address, both absolute in hexadecimal and as an offset from
8060 the nearest preceding symbol. You can use this format used to discover
8061 where (in what function) an unknown address is located:
8064 (@value{GDBP}) p/a 0x54320
8065 $3 = 0x54320 <_initialize_vx+396>
8069 The command @code{info symbol 0x54320} yields similar results.
8070 @xref{Symbols, info symbol}.
8073 Regard as an integer and print it as a character constant. This
8074 prints both the numerical value and its character representation. The
8075 character representation is replaced with the octal escape @samp{\nnn}
8076 for characters outside the 7-bit @sc{ascii} range.
8078 Without this format, @value{GDBN} displays @code{char},
8079 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8080 constants. Single-byte members of vectors are displayed as integer
8084 Regard the bits of the value as a floating point number and print
8085 using typical floating point syntax.
8088 @cindex printing strings
8089 @cindex printing byte arrays
8090 Regard as a string, if possible. With this format, pointers to single-byte
8091 data are displayed as null-terminated strings and arrays of single-byte data
8092 are displayed as fixed-length strings. Other values are displayed in their
8095 Without this format, @value{GDBN} displays pointers to and arrays of
8096 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8097 strings. Single-byte members of a vector are displayed as an integer
8101 @cindex raw printing
8102 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8103 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8104 Printing}). This typically results in a higher-level display of the
8105 value's contents. The @samp{r} format bypasses any Python
8106 pretty-printer which might exist.
8109 For example, to print the program counter in hex (@pxref{Registers}), type
8116 Note that no space is required before the slash; this is because command
8117 names in @value{GDBN} cannot contain a slash.
8119 To reprint the last value in the value history with a different format,
8120 you can use the @code{print} command with just a format and no
8121 expression. For example, @samp{p/x} reprints the last value in hex.
8124 @section Examining Memory
8126 You can use the command @code{x} (for ``examine'') to examine memory in
8127 any of several formats, independently of your program's data types.
8129 @cindex examining memory
8131 @kindex x @r{(examine memory)}
8132 @item x/@var{nfu} @var{addr}
8135 Use the @code{x} command to examine memory.
8138 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8139 much memory to display and how to format it; @var{addr} is an
8140 expression giving the address where you want to start displaying memory.
8141 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8142 Several commands set convenient defaults for @var{addr}.
8145 @item @var{n}, the repeat count
8146 The repeat count is a decimal integer; the default is 1. It specifies
8147 how much memory (counting by units @var{u}) to display.
8148 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8151 @item @var{f}, the display format
8152 The display format is one of the formats used by @code{print}
8153 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8154 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8155 The default is @samp{x} (hexadecimal) initially. The default changes
8156 each time you use either @code{x} or @code{print}.
8158 @item @var{u}, the unit size
8159 The unit size is any of
8165 Halfwords (two bytes).
8167 Words (four bytes). This is the initial default.
8169 Giant words (eight bytes).
8172 Each time you specify a unit size with @code{x}, that size becomes the
8173 default unit the next time you use @code{x}. For the @samp{i} format,
8174 the unit size is ignored and is normally not written. For the @samp{s} format,
8175 the unit size defaults to @samp{b}, unless it is explicitly given.
8176 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8177 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8178 Note that the results depend on the programming language of the
8179 current compilation unit. If the language is C, the @samp{s}
8180 modifier will use the UTF-16 encoding while @samp{w} will use
8181 UTF-32. The encoding is set by the programming language and cannot
8184 @item @var{addr}, starting display address
8185 @var{addr} is the address where you want @value{GDBN} to begin displaying
8186 memory. The expression need not have a pointer value (though it may);
8187 it is always interpreted as an integer address of a byte of memory.
8188 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8189 @var{addr} is usually just after the last address examined---but several
8190 other commands also set the default address: @code{info breakpoints} (to
8191 the address of the last breakpoint listed), @code{info line} (to the
8192 starting address of a line), and @code{print} (if you use it to display
8193 a value from memory).
8196 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8197 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8198 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8199 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8200 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8202 Since the letters indicating unit sizes are all distinct from the
8203 letters specifying output formats, you do not have to remember whether
8204 unit size or format comes first; either order works. The output
8205 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8206 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8208 Even though the unit size @var{u} is ignored for the formats @samp{s}
8209 and @samp{i}, you might still want to use a count @var{n}; for example,
8210 @samp{3i} specifies that you want to see three machine instructions,
8211 including any operands. For convenience, especially when used with
8212 the @code{display} command, the @samp{i} format also prints branch delay
8213 slot instructions, if any, beyond the count specified, which immediately
8214 follow the last instruction that is within the count. The command
8215 @code{disassemble} gives an alternative way of inspecting machine
8216 instructions; see @ref{Machine Code,,Source and Machine Code}.
8218 All the defaults for the arguments to @code{x} are designed to make it
8219 easy to continue scanning memory with minimal specifications each time
8220 you use @code{x}. For example, after you have inspected three machine
8221 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8222 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8223 the repeat count @var{n} is used again; the other arguments default as
8224 for successive uses of @code{x}.
8226 When examining machine instructions, the instruction at current program
8227 counter is shown with a @code{=>} marker. For example:
8230 (@value{GDBP}) x/5i $pc-6
8231 0x804837f <main+11>: mov %esp,%ebp
8232 0x8048381 <main+13>: push %ecx
8233 0x8048382 <main+14>: sub $0x4,%esp
8234 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8235 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8238 @cindex @code{$_}, @code{$__}, and value history
8239 The addresses and contents printed by the @code{x} command are not saved
8240 in the value history because there is often too much of them and they
8241 would get in the way. Instead, @value{GDBN} makes these values available for
8242 subsequent use in expressions as values of the convenience variables
8243 @code{$_} and @code{$__}. After an @code{x} command, the last address
8244 examined is available for use in expressions in the convenience variable
8245 @code{$_}. The contents of that address, as examined, are available in
8246 the convenience variable @code{$__}.
8248 If the @code{x} command has a repeat count, the address and contents saved
8249 are from the last memory unit printed; this is not the same as the last
8250 address printed if several units were printed on the last line of output.
8252 @cindex remote memory comparison
8253 @cindex verify remote memory image
8254 When you are debugging a program running on a remote target machine
8255 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8256 remote machine's memory against the executable file you downloaded to
8257 the target. The @code{compare-sections} command is provided for such
8261 @kindex compare-sections
8262 @item compare-sections @r{[}@var{section-name}@r{]}
8263 Compare the data of a loadable section @var{section-name} in the
8264 executable file of the program being debugged with the same section in
8265 the remote machine's memory, and report any mismatches. With no
8266 arguments, compares all loadable sections. This command's
8267 availability depends on the target's support for the @code{"qCRC"}
8272 @section Automatic Display
8273 @cindex automatic display
8274 @cindex display of expressions
8276 If you find that you want to print the value of an expression frequently
8277 (to see how it changes), you might want to add it to the @dfn{automatic
8278 display list} so that @value{GDBN} prints its value each time your program stops.
8279 Each expression added to the list is given a number to identify it;
8280 to remove an expression from the list, you specify that number.
8281 The automatic display looks like this:
8285 3: bar[5] = (struct hack *) 0x3804
8289 This display shows item numbers, expressions and their current values. As with
8290 displays you request manually using @code{x} or @code{print}, you can
8291 specify the output format you prefer; in fact, @code{display} decides
8292 whether to use @code{print} or @code{x} depending your format
8293 specification---it uses @code{x} if you specify either the @samp{i}
8294 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8298 @item display @var{expr}
8299 Add the expression @var{expr} to the list of expressions to display
8300 each time your program stops. @xref{Expressions, ,Expressions}.
8302 @code{display} does not repeat if you press @key{RET} again after using it.
8304 @item display/@var{fmt} @var{expr}
8305 For @var{fmt} specifying only a display format and not a size or
8306 count, add the expression @var{expr} to the auto-display list but
8307 arrange to display it each time in the specified format @var{fmt}.
8308 @xref{Output Formats,,Output Formats}.
8310 @item display/@var{fmt} @var{addr}
8311 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8312 number of units, add the expression @var{addr} as a memory address to
8313 be examined each time your program stops. Examining means in effect
8314 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8317 For example, @samp{display/i $pc} can be helpful, to see the machine
8318 instruction about to be executed each time execution stops (@samp{$pc}
8319 is a common name for the program counter; @pxref{Registers, ,Registers}).
8322 @kindex delete display
8324 @item undisplay @var{dnums}@dots{}
8325 @itemx delete display @var{dnums}@dots{}
8326 Remove items from the list of expressions to display. Specify the
8327 numbers of the displays that you want affected with the command
8328 argument @var{dnums}. It can be a single display number, one of the
8329 numbers shown in the first field of the @samp{info display} display;
8330 or it could be a range of display numbers, as in @code{2-4}.
8332 @code{undisplay} does not repeat if you press @key{RET} after using it.
8333 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8335 @kindex disable display
8336 @item disable display @var{dnums}@dots{}
8337 Disable the display of item numbers @var{dnums}. A disabled display
8338 item is not printed automatically, but is not forgotten. It may be
8339 enabled again later. Specify the numbers of the displays that you
8340 want affected with the command argument @var{dnums}. It can be a
8341 single display number, one of the numbers shown in the first field of
8342 the @samp{info display} display; or it could be a range of display
8343 numbers, as in @code{2-4}.
8345 @kindex enable display
8346 @item enable display @var{dnums}@dots{}
8347 Enable display of item numbers @var{dnums}. It becomes effective once
8348 again in auto display of its expression, until you specify otherwise.
8349 Specify the numbers of the displays that you want affected with the
8350 command argument @var{dnums}. It can be a single display number, one
8351 of the numbers shown in the first field of the @samp{info display}
8352 display; or it could be a range of display numbers, as in @code{2-4}.
8355 Display the current values of the expressions on the list, just as is
8356 done when your program stops.
8358 @kindex info display
8360 Print the list of expressions previously set up to display
8361 automatically, each one with its item number, but without showing the
8362 values. This includes disabled expressions, which are marked as such.
8363 It also includes expressions which would not be displayed right now
8364 because they refer to automatic variables not currently available.
8367 @cindex display disabled out of scope
8368 If a display expression refers to local variables, then it does not make
8369 sense outside the lexical context for which it was set up. Such an
8370 expression is disabled when execution enters a context where one of its
8371 variables is not defined. For example, if you give the command
8372 @code{display last_char} while inside a function with an argument
8373 @code{last_char}, @value{GDBN} displays this argument while your program
8374 continues to stop inside that function. When it stops elsewhere---where
8375 there is no variable @code{last_char}---the display is disabled
8376 automatically. The next time your program stops where @code{last_char}
8377 is meaningful, you can enable the display expression once again.
8379 @node Print Settings
8380 @section Print Settings
8382 @cindex format options
8383 @cindex print settings
8384 @value{GDBN} provides the following ways to control how arrays, structures,
8385 and symbols are printed.
8388 These settings are useful for debugging programs in any language:
8392 @item set print address
8393 @itemx set print address on
8394 @cindex print/don't print memory addresses
8395 @value{GDBN} prints memory addresses showing the location of stack
8396 traces, structure values, pointer values, breakpoints, and so forth,
8397 even when it also displays the contents of those addresses. The default
8398 is @code{on}. For example, this is what a stack frame display looks like with
8399 @code{set print address on}:
8404 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8406 530 if (lquote != def_lquote)
8410 @item set print address off
8411 Do not print addresses when displaying their contents. For example,
8412 this is the same stack frame displayed with @code{set print address off}:
8416 (@value{GDBP}) set print addr off
8418 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8419 530 if (lquote != def_lquote)
8423 You can use @samp{set print address off} to eliminate all machine
8424 dependent displays from the @value{GDBN} interface. For example, with
8425 @code{print address off}, you should get the same text for backtraces on
8426 all machines---whether or not they involve pointer arguments.
8429 @item show print address
8430 Show whether or not addresses are to be printed.
8433 When @value{GDBN} prints a symbolic address, it normally prints the
8434 closest earlier symbol plus an offset. If that symbol does not uniquely
8435 identify the address (for example, it is a name whose scope is a single
8436 source file), you may need to clarify. One way to do this is with
8437 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8438 you can set @value{GDBN} to print the source file and line number when
8439 it prints a symbolic address:
8442 @item set print symbol-filename on
8443 @cindex source file and line of a symbol
8444 @cindex symbol, source file and line
8445 Tell @value{GDBN} to print the source file name and line number of a
8446 symbol in the symbolic form of an address.
8448 @item set print symbol-filename off
8449 Do not print source file name and line number of a symbol. This is the
8452 @item show print symbol-filename
8453 Show whether or not @value{GDBN} will print the source file name and
8454 line number of a symbol in the symbolic form of an address.
8457 Another situation where it is helpful to show symbol filenames and line
8458 numbers is when disassembling code; @value{GDBN} shows you the line
8459 number and source file that corresponds to each instruction.
8461 Also, you may wish to see the symbolic form only if the address being
8462 printed is reasonably close to the closest earlier symbol:
8465 @item set print max-symbolic-offset @var{max-offset}
8466 @cindex maximum value for offset of closest symbol
8467 Tell @value{GDBN} to only display the symbolic form of an address if the
8468 offset between the closest earlier symbol and the address is less than
8469 @var{max-offset}. The default is 0, which tells @value{GDBN}
8470 to always print the symbolic form of an address if any symbol precedes it.
8472 @item show print max-symbolic-offset
8473 Ask how large the maximum offset is that @value{GDBN} prints in a
8477 @cindex wild pointer, interpreting
8478 @cindex pointer, finding referent
8479 If you have a pointer and you are not sure where it points, try
8480 @samp{set print symbol-filename on}. Then you can determine the name
8481 and source file location of the variable where it points, using
8482 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8483 For example, here @value{GDBN} shows that a variable @code{ptt} points
8484 at another variable @code{t}, defined in @file{hi2.c}:
8487 (@value{GDBP}) set print symbol-filename on
8488 (@value{GDBP}) p/a ptt
8489 $4 = 0xe008 <t in hi2.c>
8493 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8494 does not show the symbol name and filename of the referent, even with
8495 the appropriate @code{set print} options turned on.
8498 You can also enable @samp{/a}-like formatting all the time using
8499 @samp{set print symbol on}:
8502 @item set print symbol on
8503 Tell @value{GDBN} to print the symbol corresponding to an address, if
8506 @item set print symbol off
8507 Tell @value{GDBN} not to print the symbol corresponding to an
8508 address. In this mode, @value{GDBN} will still print the symbol
8509 corresponding to pointers to functions. This is the default.
8511 @item show print symbol
8512 Show whether @value{GDBN} will display the symbol corresponding to an
8516 Other settings control how different kinds of objects are printed:
8519 @item set print array
8520 @itemx set print array on
8521 @cindex pretty print arrays
8522 Pretty print arrays. This format is more convenient to read,
8523 but uses more space. The default is off.
8525 @item set print array off
8526 Return to compressed format for arrays.
8528 @item show print array
8529 Show whether compressed or pretty format is selected for displaying
8532 @cindex print array indexes
8533 @item set print array-indexes
8534 @itemx set print array-indexes on
8535 Print the index of each element when displaying arrays. May be more
8536 convenient to locate a given element in the array or quickly find the
8537 index of a given element in that printed array. The default is off.
8539 @item set print array-indexes off
8540 Stop printing element indexes when displaying arrays.
8542 @item show print array-indexes
8543 Show whether the index of each element is printed when displaying
8546 @item set print elements @var{number-of-elements}
8547 @cindex number of array elements to print
8548 @cindex limit on number of printed array elements
8549 Set a limit on how many elements of an array @value{GDBN} will print.
8550 If @value{GDBN} is printing a large array, it stops printing after it has
8551 printed the number of elements set by the @code{set print elements} command.
8552 This limit also applies to the display of strings.
8553 When @value{GDBN} starts, this limit is set to 200.
8554 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8556 @item show print elements
8557 Display the number of elements of a large array that @value{GDBN} will print.
8558 If the number is 0, then the printing is unlimited.
8560 @item set print frame-arguments @var{value}
8561 @kindex set print frame-arguments
8562 @cindex printing frame argument values
8563 @cindex print all frame argument values
8564 @cindex print frame argument values for scalars only
8565 @cindex do not print frame argument values
8566 This command allows to control how the values of arguments are printed
8567 when the debugger prints a frame (@pxref{Frames}). The possible
8572 The values of all arguments are printed.
8575 Print the value of an argument only if it is a scalar. The value of more
8576 complex arguments such as arrays, structures, unions, etc, is replaced
8577 by @code{@dots{}}. This is the default. Here is an example where
8578 only scalar arguments are shown:
8581 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8586 None of the argument values are printed. Instead, the value of each argument
8587 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8590 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8595 By default, only scalar arguments are printed. This command can be used
8596 to configure the debugger to print the value of all arguments, regardless
8597 of their type. However, it is often advantageous to not print the value
8598 of more complex parameters. For instance, it reduces the amount of
8599 information printed in each frame, making the backtrace more readable.
8600 Also, it improves performance when displaying Ada frames, because
8601 the computation of large arguments can sometimes be CPU-intensive,
8602 especially in large applications. Setting @code{print frame-arguments}
8603 to @code{scalars} (the default) or @code{none} avoids this computation,
8604 thus speeding up the display of each Ada frame.
8606 @item show print frame-arguments
8607 Show how the value of arguments should be displayed when printing a frame.
8609 @anchor{set print entry-values}
8610 @item set print entry-values @var{value}
8611 @kindex set print entry-values
8612 Set printing of frame argument values at function entry. In some cases
8613 @value{GDBN} can determine the value of function argument which was passed by
8614 the function caller, even if the value was modified inside the called function
8615 and therefore is different. With optimized code, the current value could be
8616 unavailable, but the entry value may still be known.
8618 The default value is @code{default} (see below for its description). Older
8619 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8620 this feature will behave in the @code{default} setting the same way as with the
8623 This functionality is currently supported only by DWARF 2 debugging format and
8624 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8625 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8628 The @var{value} parameter can be one of the following:
8632 Print only actual parameter values, never print values from function entry
8636 #0 different (val=6)
8637 #0 lost (val=<optimized out>)
8639 #0 invalid (val=<optimized out>)
8643 Print only parameter values from function entry point. The actual parameter
8644 values are never printed.
8646 #0 equal (val@@entry=5)
8647 #0 different (val@@entry=5)
8648 #0 lost (val@@entry=5)
8649 #0 born (val@@entry=<optimized out>)
8650 #0 invalid (val@@entry=<optimized out>)
8654 Print only parameter values from function entry point. If value from function
8655 entry point is not known while the actual value is known, print the actual
8656 value for such parameter.
8658 #0 equal (val@@entry=5)
8659 #0 different (val@@entry=5)
8660 #0 lost (val@@entry=5)
8662 #0 invalid (val@@entry=<optimized out>)
8666 Print actual parameter values. If actual parameter value is not known while
8667 value from function entry point is known, print the entry point value for such
8671 #0 different (val=6)
8672 #0 lost (val@@entry=5)
8674 #0 invalid (val=<optimized out>)
8678 Always print both the actual parameter value and its value from function entry
8679 point, even if values of one or both are not available due to compiler
8682 #0 equal (val=5, val@@entry=5)
8683 #0 different (val=6, val@@entry=5)
8684 #0 lost (val=<optimized out>, val@@entry=5)
8685 #0 born (val=10, val@@entry=<optimized out>)
8686 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8690 Print the actual parameter value if it is known and also its value from
8691 function entry point if it is known. If neither is known, print for the actual
8692 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8693 values are known and identical, print the shortened
8694 @code{param=param@@entry=VALUE} notation.
8696 #0 equal (val=val@@entry=5)
8697 #0 different (val=6, val@@entry=5)
8698 #0 lost (val@@entry=5)
8700 #0 invalid (val=<optimized out>)
8704 Always print the actual parameter value. Print also its value from function
8705 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8706 if both values are known and identical, print the shortened
8707 @code{param=param@@entry=VALUE} notation.
8709 #0 equal (val=val@@entry=5)
8710 #0 different (val=6, val@@entry=5)
8711 #0 lost (val=<optimized out>, val@@entry=5)
8713 #0 invalid (val=<optimized out>)
8717 For analysis messages on possible failures of frame argument values at function
8718 entry resolution see @ref{set debug entry-values}.
8720 @item show print entry-values
8721 Show the method being used for printing of frame argument values at function
8724 @item set print repeats
8725 @cindex repeated array elements
8726 Set the threshold for suppressing display of repeated array
8727 elements. When the number of consecutive identical elements of an
8728 array exceeds the threshold, @value{GDBN} prints the string
8729 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8730 identical repetitions, instead of displaying the identical elements
8731 themselves. Setting the threshold to zero will cause all elements to
8732 be individually printed. The default threshold is 10.
8734 @item show print repeats
8735 Display the current threshold for printing repeated identical
8738 @item set print null-stop
8739 @cindex @sc{null} elements in arrays
8740 Cause @value{GDBN} to stop printing the characters of an array when the first
8741 @sc{null} is encountered. This is useful when large arrays actually
8742 contain only short strings.
8745 @item show print null-stop
8746 Show whether @value{GDBN} stops printing an array on the first
8747 @sc{null} character.
8749 @item set print pretty on
8750 @cindex print structures in indented form
8751 @cindex indentation in structure display
8752 Cause @value{GDBN} to print structures in an indented format with one member
8753 per line, like this:
8768 @item set print pretty off
8769 Cause @value{GDBN} to print structures in a compact format, like this:
8773 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8774 meat = 0x54 "Pork"@}
8779 This is the default format.
8781 @item show print pretty
8782 Show which format @value{GDBN} is using to print structures.
8784 @item set print sevenbit-strings on
8785 @cindex eight-bit characters in strings
8786 @cindex octal escapes in strings
8787 Print using only seven-bit characters; if this option is set,
8788 @value{GDBN} displays any eight-bit characters (in strings or
8789 character values) using the notation @code{\}@var{nnn}. This setting is
8790 best if you are working in English (@sc{ascii}) and you use the
8791 high-order bit of characters as a marker or ``meta'' bit.
8793 @item set print sevenbit-strings off
8794 Print full eight-bit characters. This allows the use of more
8795 international character sets, and is the default.
8797 @item show print sevenbit-strings
8798 Show whether or not @value{GDBN} is printing only seven-bit characters.
8800 @item set print union on
8801 @cindex unions in structures, printing
8802 Tell @value{GDBN} to print unions which are contained in structures
8803 and other unions. This is the default setting.
8805 @item set print union off
8806 Tell @value{GDBN} not to print unions which are contained in
8807 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8810 @item show print union
8811 Ask @value{GDBN} whether or not it will print unions which are contained in
8812 structures and other unions.
8814 For example, given the declarations
8817 typedef enum @{Tree, Bug@} Species;
8818 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8819 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8830 struct thing foo = @{Tree, @{Acorn@}@};
8834 with @code{set print union on} in effect @samp{p foo} would print
8837 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8841 and with @code{set print union off} in effect it would print
8844 $1 = @{it = Tree, form = @{...@}@}
8848 @code{set print union} affects programs written in C-like languages
8854 These settings are of interest when debugging C@t{++} programs:
8857 @cindex demangling C@t{++} names
8858 @item set print demangle
8859 @itemx set print demangle on
8860 Print C@t{++} names in their source form rather than in the encoded
8861 (``mangled'') form passed to the assembler and linker for type-safe
8862 linkage. The default is on.
8864 @item show print demangle
8865 Show whether C@t{++} names are printed in mangled or demangled form.
8867 @item set print asm-demangle
8868 @itemx set print asm-demangle on
8869 Print C@t{++} names in their source form rather than their mangled form, even
8870 in assembler code printouts such as instruction disassemblies.
8873 @item show print asm-demangle
8874 Show whether C@t{++} names in assembly listings are printed in mangled
8877 @cindex C@t{++} symbol decoding style
8878 @cindex symbol decoding style, C@t{++}
8879 @kindex set demangle-style
8880 @item set demangle-style @var{style}
8881 Choose among several encoding schemes used by different compilers to
8882 represent C@t{++} names. The choices for @var{style} are currently:
8886 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8887 This is the default.
8890 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8893 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8896 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8899 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8900 @strong{Warning:} this setting alone is not sufficient to allow
8901 debugging @code{cfront}-generated executables. @value{GDBN} would
8902 require further enhancement to permit that.
8905 If you omit @var{style}, you will see a list of possible formats.
8907 @item show demangle-style
8908 Display the encoding style currently in use for decoding C@t{++} symbols.
8910 @item set print object
8911 @itemx set print object on
8912 @cindex derived type of an object, printing
8913 @cindex display derived types
8914 When displaying a pointer to an object, identify the @emph{actual}
8915 (derived) type of the object rather than the @emph{declared} type, using
8916 the virtual function table. Note that the virtual function table is
8917 required---this feature can only work for objects that have run-time
8918 type identification; a single virtual method in the object's declared
8919 type is sufficient. Note that this setting is also taken into account when
8920 working with variable objects via MI (@pxref{GDB/MI}).
8922 @item set print object off
8923 Display only the declared type of objects, without reference to the
8924 virtual function table. This is the default setting.
8926 @item show print object
8927 Show whether actual, or declared, object types are displayed.
8929 @item set print static-members
8930 @itemx set print static-members on
8931 @cindex static members of C@t{++} objects
8932 Print static members when displaying a C@t{++} object. The default is on.
8934 @item set print static-members off
8935 Do not print static members when displaying a C@t{++} object.
8937 @item show print static-members
8938 Show whether C@t{++} static members are printed or not.
8940 @item set print pascal_static-members
8941 @itemx set print pascal_static-members on
8942 @cindex static members of Pascal objects
8943 @cindex Pascal objects, static members display
8944 Print static members when displaying a Pascal object. The default is on.
8946 @item set print pascal_static-members off
8947 Do not print static members when displaying a Pascal object.
8949 @item show print pascal_static-members
8950 Show whether Pascal static members are printed or not.
8952 @c These don't work with HP ANSI C++ yet.
8953 @item set print vtbl
8954 @itemx set print vtbl on
8955 @cindex pretty print C@t{++} virtual function tables
8956 @cindex virtual functions (C@t{++}) display
8957 @cindex VTBL display
8958 Pretty print C@t{++} virtual function tables. The default is off.
8959 (The @code{vtbl} commands do not work on programs compiled with the HP
8960 ANSI C@t{++} compiler (@code{aCC}).)
8962 @item set print vtbl off
8963 Do not pretty print C@t{++} virtual function tables.
8965 @item show print vtbl
8966 Show whether C@t{++} virtual function tables are pretty printed, or not.
8969 @node Pretty Printing
8970 @section Pretty Printing
8972 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8973 Python code. It greatly simplifies the display of complex objects. This
8974 mechanism works for both MI and the CLI.
8977 * Pretty-Printer Introduction:: Introduction to pretty-printers
8978 * Pretty-Printer Example:: An example pretty-printer
8979 * Pretty-Printer Commands:: Pretty-printer commands
8982 @node Pretty-Printer Introduction
8983 @subsection Pretty-Printer Introduction
8985 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8986 registered for the value. If there is then @value{GDBN} invokes the
8987 pretty-printer to print the value. Otherwise the value is printed normally.
8989 Pretty-printers are normally named. This makes them easy to manage.
8990 The @samp{info pretty-printer} command will list all the installed
8991 pretty-printers with their names.
8992 If a pretty-printer can handle multiple data types, then its
8993 @dfn{subprinters} are the printers for the individual data types.
8994 Each such subprinter has its own name.
8995 The format of the name is @var{printer-name};@var{subprinter-name}.
8997 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8998 Typically they are automatically loaded and registered when the corresponding
8999 debug information is loaded, thus making them available without having to
9000 do anything special.
9002 There are three places where a pretty-printer can be registered.
9006 Pretty-printers registered globally are available when debugging
9010 Pretty-printers registered with a program space are available only
9011 when debugging that program.
9012 @xref{Progspaces In Python}, for more details on program spaces in Python.
9015 Pretty-printers registered with an objfile are loaded and unloaded
9016 with the corresponding objfile (e.g., shared library).
9017 @xref{Objfiles In Python}, for more details on objfiles in Python.
9020 @xref{Selecting Pretty-Printers}, for further information on how
9021 pretty-printers are selected,
9023 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9026 @node Pretty-Printer Example
9027 @subsection Pretty-Printer Example
9029 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9032 (@value{GDBP}) print s
9034 static npos = 4294967295,
9036 <std::allocator<char>> = @{
9037 <__gnu_cxx::new_allocator<char>> = @{
9038 <No data fields>@}, <No data fields>
9040 members of std::basic_string<char, std::char_traits<char>,
9041 std::allocator<char> >::_Alloc_hider:
9042 _M_p = 0x804a014 "abcd"
9047 With a pretty-printer for @code{std::string} only the contents are printed:
9050 (@value{GDBP}) print s
9054 @node Pretty-Printer Commands
9055 @subsection Pretty-Printer Commands
9056 @cindex pretty-printer commands
9059 @kindex info pretty-printer
9060 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9061 Print the list of installed pretty-printers.
9062 This includes disabled pretty-printers, which are marked as such.
9064 @var{object-regexp} is a regular expression matching the objects
9065 whose pretty-printers to list.
9066 Objects can be @code{global}, the program space's file
9067 (@pxref{Progspaces In Python}),
9068 and the object files within that program space (@pxref{Objfiles In Python}).
9069 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9070 looks up a printer from these three objects.
9072 @var{name-regexp} is a regular expression matching the name of the printers
9075 @kindex disable pretty-printer
9076 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9077 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9078 A disabled pretty-printer is not forgotten, it may be enabled again later.
9080 @kindex enable pretty-printer
9081 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9082 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9087 Suppose we have three pretty-printers installed: one from library1.so
9088 named @code{foo} that prints objects of type @code{foo}, and
9089 another from library2.so named @code{bar} that prints two types of objects,
9090 @code{bar1} and @code{bar2}.
9093 (gdb) info pretty-printer
9100 (gdb) info pretty-printer library2
9105 (gdb) disable pretty-printer library1
9107 2 of 3 printers enabled
9108 (gdb) info pretty-printer
9115 (gdb) disable pretty-printer library2 bar:bar1
9117 1 of 3 printers enabled
9118 (gdb) info pretty-printer library2
9125 (gdb) disable pretty-printer library2 bar
9127 0 of 3 printers enabled
9128 (gdb) info pretty-printer library2
9137 Note that for @code{bar} the entire printer can be disabled,
9138 as can each individual subprinter.
9141 @section Value History
9143 @cindex value history
9144 @cindex history of values printed by @value{GDBN}
9145 Values printed by the @code{print} command are saved in the @value{GDBN}
9146 @dfn{value history}. This allows you to refer to them in other expressions.
9147 Values are kept until the symbol table is re-read or discarded
9148 (for example with the @code{file} or @code{symbol-file} commands).
9149 When the symbol table changes, the value history is discarded,
9150 since the values may contain pointers back to the types defined in the
9155 @cindex history number
9156 The values printed are given @dfn{history numbers} by which you can
9157 refer to them. These are successive integers starting with one.
9158 @code{print} shows you the history number assigned to a value by
9159 printing @samp{$@var{num} = } before the value; here @var{num} is the
9162 To refer to any previous value, use @samp{$} followed by the value's
9163 history number. The way @code{print} labels its output is designed to
9164 remind you of this. Just @code{$} refers to the most recent value in
9165 the history, and @code{$$} refers to the value before that.
9166 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9167 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9168 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9170 For example, suppose you have just printed a pointer to a structure and
9171 want to see the contents of the structure. It suffices to type
9177 If you have a chain of structures where the component @code{next} points
9178 to the next one, you can print the contents of the next one with this:
9185 You can print successive links in the chain by repeating this
9186 command---which you can do by just typing @key{RET}.
9188 Note that the history records values, not expressions. If the value of
9189 @code{x} is 4 and you type these commands:
9197 then the value recorded in the value history by the @code{print} command
9198 remains 4 even though the value of @code{x} has changed.
9203 Print the last ten values in the value history, with their item numbers.
9204 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9205 values} does not change the history.
9207 @item show values @var{n}
9208 Print ten history values centered on history item number @var{n}.
9211 Print ten history values just after the values last printed. If no more
9212 values are available, @code{show values +} produces no display.
9215 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9216 same effect as @samp{show values +}.
9218 @node Convenience Vars
9219 @section Convenience Variables
9221 @cindex convenience variables
9222 @cindex user-defined variables
9223 @value{GDBN} provides @dfn{convenience variables} that you can use within
9224 @value{GDBN} to hold on to a value and refer to it later. These variables
9225 exist entirely within @value{GDBN}; they are not part of your program, and
9226 setting a convenience variable has no direct effect on further execution
9227 of your program. That is why you can use them freely.
9229 Convenience variables are prefixed with @samp{$}. Any name preceded by
9230 @samp{$} can be used for a convenience variable, unless it is one of
9231 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9232 (Value history references, in contrast, are @emph{numbers} preceded
9233 by @samp{$}. @xref{Value History, ,Value History}.)
9235 You can save a value in a convenience variable with an assignment
9236 expression, just as you would set a variable in your program.
9240 set $foo = *object_ptr
9244 would save in @code{$foo} the value contained in the object pointed to by
9247 Using a convenience variable for the first time creates it, but its
9248 value is @code{void} until you assign a new value. You can alter the
9249 value with another assignment at any time.
9251 Convenience variables have no fixed types. You can assign a convenience
9252 variable any type of value, including structures and arrays, even if
9253 that variable already has a value of a different type. The convenience
9254 variable, when used as an expression, has the type of its current value.
9257 @kindex show convenience
9258 @cindex show all user variables and functions
9259 @item show convenience
9260 Print a list of convenience variables used so far, and their values,
9261 as well as a list of the convenience functions.
9262 Abbreviated @code{show conv}.
9264 @kindex init-if-undefined
9265 @cindex convenience variables, initializing
9266 @item init-if-undefined $@var{variable} = @var{expression}
9267 Set a convenience variable if it has not already been set. This is useful
9268 for user-defined commands that keep some state. It is similar, in concept,
9269 to using local static variables with initializers in C (except that
9270 convenience variables are global). It can also be used to allow users to
9271 override default values used in a command script.
9273 If the variable is already defined then the expression is not evaluated so
9274 any side-effects do not occur.
9277 One of the ways to use a convenience variable is as a counter to be
9278 incremented or a pointer to be advanced. For example, to print
9279 a field from successive elements of an array of structures:
9283 print bar[$i++]->contents
9287 Repeat that command by typing @key{RET}.
9289 Some convenience variables are created automatically by @value{GDBN} and given
9290 values likely to be useful.
9293 @vindex $_@r{, convenience variable}
9295 The variable @code{$_} is automatically set by the @code{x} command to
9296 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9297 commands which provide a default address for @code{x} to examine also
9298 set @code{$_} to that address; these commands include @code{info line}
9299 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9300 except when set by the @code{x} command, in which case it is a pointer
9301 to the type of @code{$__}.
9303 @vindex $__@r{, convenience variable}
9305 The variable @code{$__} is automatically set by the @code{x} command
9306 to the value found in the last address examined. Its type is chosen
9307 to match the format in which the data was printed.
9310 @vindex $_exitcode@r{, convenience variable}
9311 The variable @code{$_exitcode} is automatically set to the exit code when
9312 the program being debugged terminates.
9315 @itemx $_probe_arg0@dots{}$_probe_arg11
9316 Arguments to a static probe. @xref{Static Probe Points}.
9319 @vindex $_sdata@r{, inspect, convenience variable}
9320 The variable @code{$_sdata} contains extra collected static tracepoint
9321 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9322 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9323 if extra static tracepoint data has not been collected.
9326 @vindex $_siginfo@r{, convenience variable}
9327 The variable @code{$_siginfo} contains extra signal information
9328 (@pxref{extra signal information}). Note that @code{$_siginfo}
9329 could be empty, if the application has not yet received any signals.
9330 For example, it will be empty before you execute the @code{run} command.
9333 @vindex $_tlb@r{, convenience variable}
9334 The variable @code{$_tlb} is automatically set when debugging
9335 applications running on MS-Windows in native mode or connected to
9336 gdbserver that supports the @code{qGetTIBAddr} request.
9337 @xref{General Query Packets}.
9338 This variable contains the address of the thread information block.
9342 On HP-UX systems, if you refer to a function or variable name that
9343 begins with a dollar sign, @value{GDBN} searches for a user or system
9344 name first, before it searches for a convenience variable.
9346 @node Convenience Funs
9347 @section Convenience Functions
9349 @cindex convenience functions
9350 @value{GDBN} also supplies some @dfn{convenience functions}. These
9351 have a syntax similar to convenience variables. A convenience
9352 function can be used in an expression just like an ordinary function;
9353 however, a convenience function is implemented internally to
9356 These functions require @value{GDBN} to be configured with
9357 @code{Python} support.
9361 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
9362 @findex $_memeq@r{, convenience function}
9363 Returns one if the @var{length} bytes at the addresses given by
9364 @var{buf1} and @var{buf2} are equal.
9365 Otherwise it returns zero.
9367 @item $_regex(@var{str}, @var{regex})
9368 @findex $_regex@r{, convenience function}
9369 Returns one if the string @var{str} matches the regular expression
9370 @var{regex}. Otherwise it returns zero.
9371 The syntax of the regular expression is that specified by @code{Python}'s
9372 regular expression support.
9374 @item $_streq(@var{str1}, @var{str2})
9375 @findex $_streq@r{, convenience function}
9376 Returns one if the strings @var{str1} and @var{str2} are equal.
9377 Otherwise it returns zero.
9379 @item $_strlen(@var{str})
9380 @findex $_strlen@r{, convenience function}
9381 Returns the length of string @var{str}.
9385 @value{GDBN} provides the ability to list and get help on
9386 convenience functions.
9390 @kindex help function
9391 @cindex show all convenience functions
9392 Print a list of all convenience functions.
9399 You can refer to machine register contents, in expressions, as variables
9400 with names starting with @samp{$}. The names of registers are different
9401 for each machine; use @code{info registers} to see the names used on
9405 @kindex info registers
9406 @item info registers
9407 Print the names and values of all registers except floating-point
9408 and vector registers (in the selected stack frame).
9410 @kindex info all-registers
9411 @cindex floating point registers
9412 @item info all-registers
9413 Print the names and values of all registers, including floating-point
9414 and vector registers (in the selected stack frame).
9416 @item info registers @var{regname} @dots{}
9417 Print the @dfn{relativized} value of each specified register @var{regname}.
9418 As discussed in detail below, register values are normally relative to
9419 the selected stack frame. @var{regname} may be any register name valid on
9420 the machine you are using, with or without the initial @samp{$}.
9423 @cindex stack pointer register
9424 @cindex program counter register
9425 @cindex process status register
9426 @cindex frame pointer register
9427 @cindex standard registers
9428 @value{GDBN} has four ``standard'' register names that are available (in
9429 expressions) on most machines---whenever they do not conflict with an
9430 architecture's canonical mnemonics for registers. The register names
9431 @code{$pc} and @code{$sp} are used for the program counter register and
9432 the stack pointer. @code{$fp} is used for a register that contains a
9433 pointer to the current stack frame, and @code{$ps} is used for a
9434 register that contains the processor status. For example,
9435 you could print the program counter in hex with
9442 or print the instruction to be executed next with
9449 or add four to the stack pointer@footnote{This is a way of removing
9450 one word from the stack, on machines where stacks grow downward in
9451 memory (most machines, nowadays). This assumes that the innermost
9452 stack frame is selected; setting @code{$sp} is not allowed when other
9453 stack frames are selected. To pop entire frames off the stack,
9454 regardless of machine architecture, use @code{return};
9455 see @ref{Returning, ,Returning from a Function}.} with
9461 Whenever possible, these four standard register names are available on
9462 your machine even though the machine has different canonical mnemonics,
9463 so long as there is no conflict. The @code{info registers} command
9464 shows the canonical names. For example, on the SPARC, @code{info
9465 registers} displays the processor status register as @code{$psr} but you
9466 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9467 is an alias for the @sc{eflags} register.
9469 @value{GDBN} always considers the contents of an ordinary register as an
9470 integer when the register is examined in this way. Some machines have
9471 special registers which can hold nothing but floating point; these
9472 registers are considered to have floating point values. There is no way
9473 to refer to the contents of an ordinary register as floating point value
9474 (although you can @emph{print} it as a floating point value with
9475 @samp{print/f $@var{regname}}).
9477 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9478 means that the data format in which the register contents are saved by
9479 the operating system is not the same one that your program normally
9480 sees. For example, the registers of the 68881 floating point
9481 coprocessor are always saved in ``extended'' (raw) format, but all C
9482 programs expect to work with ``double'' (virtual) format. In such
9483 cases, @value{GDBN} normally works with the virtual format only (the format
9484 that makes sense for your program), but the @code{info registers} command
9485 prints the data in both formats.
9487 @cindex SSE registers (x86)
9488 @cindex MMX registers (x86)
9489 Some machines have special registers whose contents can be interpreted
9490 in several different ways. For example, modern x86-based machines
9491 have SSE and MMX registers that can hold several values packed
9492 together in several different formats. @value{GDBN} refers to such
9493 registers in @code{struct} notation:
9496 (@value{GDBP}) print $xmm1
9498 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
9499 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
9500 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
9501 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
9502 v4_int32 = @{0, 20657912, 11, 13@},
9503 v2_int64 = @{88725056443645952, 55834574859@},
9504 uint128 = 0x0000000d0000000b013b36f800000000
9509 To set values of such registers, you need to tell @value{GDBN} which
9510 view of the register you wish to change, as if you were assigning
9511 value to a @code{struct} member:
9514 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
9517 Normally, register values are relative to the selected stack frame
9518 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
9519 value that the register would contain if all stack frames farther in
9520 were exited and their saved registers restored. In order to see the
9521 true contents of hardware registers, you must select the innermost
9522 frame (with @samp{frame 0}).
9524 However, @value{GDBN} must deduce where registers are saved, from the machine
9525 code generated by your compiler. If some registers are not saved, or if
9526 @value{GDBN} is unable to locate the saved registers, the selected stack
9527 frame makes no difference.
9529 @node Floating Point Hardware
9530 @section Floating Point Hardware
9531 @cindex floating point
9533 Depending on the configuration, @value{GDBN} may be able to give
9534 you more information about the status of the floating point hardware.
9539 Display hardware-dependent information about the floating
9540 point unit. The exact contents and layout vary depending on the
9541 floating point chip. Currently, @samp{info float} is supported on
9542 the ARM and x86 machines.
9546 @section Vector Unit
9549 Depending on the configuration, @value{GDBN} may be able to give you
9550 more information about the status of the vector unit.
9555 Display information about the vector unit. The exact contents and
9556 layout vary depending on the hardware.
9559 @node OS Information
9560 @section Operating System Auxiliary Information
9561 @cindex OS information
9563 @value{GDBN} provides interfaces to useful OS facilities that can help
9564 you debug your program.
9566 @cindex auxiliary vector
9567 @cindex vector, auxiliary
9568 Some operating systems supply an @dfn{auxiliary vector} to programs at
9569 startup. This is akin to the arguments and environment that you
9570 specify for a program, but contains a system-dependent variety of
9571 binary values that tell system libraries important details about the
9572 hardware, operating system, and process. Each value's purpose is
9573 identified by an integer tag; the meanings are well-known but system-specific.
9574 Depending on the configuration and operating system facilities,
9575 @value{GDBN} may be able to show you this information. For remote
9576 targets, this functionality may further depend on the remote stub's
9577 support of the @samp{qXfer:auxv:read} packet, see
9578 @ref{qXfer auxiliary vector read}.
9583 Display the auxiliary vector of the inferior, which can be either a
9584 live process or a core dump file. @value{GDBN} prints each tag value
9585 numerically, and also shows names and text descriptions for recognized
9586 tags. Some values in the vector are numbers, some bit masks, and some
9587 pointers to strings or other data. @value{GDBN} displays each value in the
9588 most appropriate form for a recognized tag, and in hexadecimal for
9589 an unrecognized tag.
9592 On some targets, @value{GDBN} can access operating system-specific
9593 information and show it to you. The types of information available
9594 will differ depending on the type of operating system running on the
9595 target. The mechanism used to fetch the data is described in
9596 @ref{Operating System Information}. For remote targets, this
9597 functionality depends on the remote stub's support of the
9598 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9602 @item info os @var{infotype}
9604 Display OS information of the requested type.
9606 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
9608 @anchor{linux info os infotypes}
9610 @kindex info os processes
9612 Display the list of processes on the target. For each process,
9613 @value{GDBN} prints the process identifier, the name of the user, the
9614 command corresponding to the process, and the list of processor cores
9615 that the process is currently running on. (To understand what these
9616 properties mean, for this and the following info types, please consult
9617 the general @sc{gnu}/Linux documentation.)
9619 @kindex info os procgroups
9621 Display the list of process groups on the target. For each process,
9622 @value{GDBN} prints the identifier of the process group that it belongs
9623 to, the command corresponding to the process group leader, the process
9624 identifier, and the command line of the process. The list is sorted
9625 first by the process group identifier, then by the process identifier,
9626 so that processes belonging to the same process group are grouped together
9627 and the process group leader is listed first.
9629 @kindex info os threads
9631 Display the list of threads running on the target. For each thread,
9632 @value{GDBN} prints the identifier of the process that the thread
9633 belongs to, the command of the process, the thread identifier, and the
9634 processor core that it is currently running on. The main thread of a
9635 process is not listed.
9637 @kindex info os files
9639 Display the list of open file descriptors on the target. For each
9640 file descriptor, @value{GDBN} prints the identifier of the process
9641 owning the descriptor, the command of the owning process, the value
9642 of the descriptor, and the target of the descriptor.
9644 @kindex info os sockets
9646 Display the list of Internet-domain sockets on the target. For each
9647 socket, @value{GDBN} prints the address and port of the local and
9648 remote endpoints, the current state of the connection, the creator of
9649 the socket, the IP address family of the socket, and the type of the
9654 Display the list of all System V shared-memory regions on the target.
9655 For each shared-memory region, @value{GDBN} prints the region key,
9656 the shared-memory identifier, the access permissions, the size of the
9657 region, the process that created the region, the process that last
9658 attached to or detached from the region, the current number of live
9659 attaches to the region, and the times at which the region was last
9660 attached to, detach from, and changed.
9662 @kindex info os semaphores
9664 Display the list of all System V semaphore sets on the target. For each
9665 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
9666 set identifier, the access permissions, the number of semaphores in the
9667 set, the user and group of the owner and creator of the semaphore set,
9668 and the times at which the semaphore set was operated upon and changed.
9672 Display the list of all System V message queues on the target. For each
9673 message queue, @value{GDBN} prints the message queue key, the message
9674 queue identifier, the access permissions, the current number of bytes
9675 on the queue, the current number of messages on the queue, the processes
9676 that last sent and received a message on the queue, the user and group
9677 of the owner and creator of the message queue, the times at which a
9678 message was last sent and received on the queue, and the time at which
9679 the message queue was last changed.
9681 @kindex info os modules
9683 Display the list of all loaded kernel modules on the target. For each
9684 module, @value{GDBN} prints the module name, the size of the module in
9685 bytes, the number of times the module is used, the dependencies of the
9686 module, the status of the module, and the address of the loaded module
9691 If @var{infotype} is omitted, then list the possible values for
9692 @var{infotype} and the kind of OS information available for each
9693 @var{infotype}. If the target does not return a list of possible
9694 types, this command will report an error.
9697 @node Memory Region Attributes
9698 @section Memory Region Attributes
9699 @cindex memory region attributes
9701 @dfn{Memory region attributes} allow you to describe special handling
9702 required by regions of your target's memory. @value{GDBN} uses
9703 attributes to determine whether to allow certain types of memory
9704 accesses; whether to use specific width accesses; and whether to cache
9705 target memory. By default the description of memory regions is
9706 fetched from the target (if the current target supports this), but the
9707 user can override the fetched regions.
9709 Defined memory regions can be individually enabled and disabled. When a
9710 memory region is disabled, @value{GDBN} uses the default attributes when
9711 accessing memory in that region. Similarly, if no memory regions have
9712 been defined, @value{GDBN} uses the default attributes when accessing
9715 When a memory region is defined, it is given a number to identify it;
9716 to enable, disable, or remove a memory region, you specify that number.
9720 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9721 Define a memory region bounded by @var{lower} and @var{upper} with
9722 attributes @var{attributes}@dots{}, and add it to the list of regions
9723 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9724 case: it is treated as the target's maximum memory address.
9725 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9728 Discard any user changes to the memory regions and use target-supplied
9729 regions, if available, or no regions if the target does not support.
9732 @item delete mem @var{nums}@dots{}
9733 Remove memory regions @var{nums}@dots{} from the list of regions
9734 monitored by @value{GDBN}.
9737 @item disable mem @var{nums}@dots{}
9738 Disable monitoring of memory regions @var{nums}@dots{}.
9739 A disabled memory region is not forgotten.
9740 It may be enabled again later.
9743 @item enable mem @var{nums}@dots{}
9744 Enable monitoring of memory regions @var{nums}@dots{}.
9748 Print a table of all defined memory regions, with the following columns
9752 @item Memory Region Number
9753 @item Enabled or Disabled.
9754 Enabled memory regions are marked with @samp{y}.
9755 Disabled memory regions are marked with @samp{n}.
9758 The address defining the inclusive lower bound of the memory region.
9761 The address defining the exclusive upper bound of the memory region.
9764 The list of attributes set for this memory region.
9769 @subsection Attributes
9771 @subsubsection Memory Access Mode
9772 The access mode attributes set whether @value{GDBN} may make read or
9773 write accesses to a memory region.
9775 While these attributes prevent @value{GDBN} from performing invalid
9776 memory accesses, they do nothing to prevent the target system, I/O DMA,
9777 etc.@: from accessing memory.
9781 Memory is read only.
9783 Memory is write only.
9785 Memory is read/write. This is the default.
9788 @subsubsection Memory Access Size
9789 The access size attribute tells @value{GDBN} to use specific sized
9790 accesses in the memory region. Often memory mapped device registers
9791 require specific sized accesses. If no access size attribute is
9792 specified, @value{GDBN} may use accesses of any size.
9796 Use 8 bit memory accesses.
9798 Use 16 bit memory accesses.
9800 Use 32 bit memory accesses.
9802 Use 64 bit memory accesses.
9805 @c @subsubsection Hardware/Software Breakpoints
9806 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9807 @c will use hardware or software breakpoints for the internal breakpoints
9808 @c used by the step, next, finish, until, etc. commands.
9812 @c Always use hardware breakpoints
9813 @c @item swbreak (default)
9816 @subsubsection Data Cache
9817 The data cache attributes set whether @value{GDBN} will cache target
9818 memory. While this generally improves performance by reducing debug
9819 protocol overhead, it can lead to incorrect results because @value{GDBN}
9820 does not know about volatile variables or memory mapped device
9825 Enable @value{GDBN} to cache target memory.
9827 Disable @value{GDBN} from caching target memory. This is the default.
9830 @subsection Memory Access Checking
9831 @value{GDBN} can be instructed to refuse accesses to memory that is
9832 not explicitly described. This can be useful if accessing such
9833 regions has undesired effects for a specific target, or to provide
9834 better error checking. The following commands control this behaviour.
9837 @kindex set mem inaccessible-by-default
9838 @item set mem inaccessible-by-default [on|off]
9839 If @code{on} is specified, make @value{GDBN} treat memory not
9840 explicitly described by the memory ranges as non-existent and refuse accesses
9841 to such memory. The checks are only performed if there's at least one
9842 memory range defined. If @code{off} is specified, make @value{GDBN}
9843 treat the memory not explicitly described by the memory ranges as RAM.
9844 The default value is @code{on}.
9845 @kindex show mem inaccessible-by-default
9846 @item show mem inaccessible-by-default
9847 Show the current handling of accesses to unknown memory.
9851 @c @subsubsection Memory Write Verification
9852 @c The memory write verification attributes set whether @value{GDBN}
9853 @c will re-reads data after each write to verify the write was successful.
9857 @c @item noverify (default)
9860 @node Dump/Restore Files
9861 @section Copy Between Memory and a File
9862 @cindex dump/restore files
9863 @cindex append data to a file
9864 @cindex dump data to a file
9865 @cindex restore data from a file
9867 You can use the commands @code{dump}, @code{append}, and
9868 @code{restore} to copy data between target memory and a file. The
9869 @code{dump} and @code{append} commands write data to a file, and the
9870 @code{restore} command reads data from a file back into the inferior's
9871 memory. Files may be in binary, Motorola S-record, Intel hex, or
9872 Tektronix Hex format; however, @value{GDBN} can only append to binary
9878 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9879 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9880 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9881 or the value of @var{expr}, to @var{filename} in the given format.
9883 The @var{format} parameter may be any one of:
9890 Motorola S-record format.
9892 Tektronix Hex format.
9895 @value{GDBN} uses the same definitions of these formats as the
9896 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9897 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9901 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9902 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9903 Append the contents of memory from @var{start_addr} to @var{end_addr},
9904 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9905 (@value{GDBN} can only append data to files in raw binary form.)
9908 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9909 Restore the contents of file @var{filename} into memory. The
9910 @code{restore} command can automatically recognize any known @sc{bfd}
9911 file format, except for raw binary. To restore a raw binary file you
9912 must specify the optional keyword @code{binary} after the filename.
9914 If @var{bias} is non-zero, its value will be added to the addresses
9915 contained in the file. Binary files always start at address zero, so
9916 they will be restored at address @var{bias}. Other bfd files have
9917 a built-in location; they will be restored at offset @var{bias}
9920 If @var{start} and/or @var{end} are non-zero, then only data between
9921 file offset @var{start} and file offset @var{end} will be restored.
9922 These offsets are relative to the addresses in the file, before
9923 the @var{bias} argument is applied.
9927 @node Core File Generation
9928 @section How to Produce a Core File from Your Program
9929 @cindex dump core from inferior
9931 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9932 image of a running process and its process status (register values
9933 etc.). Its primary use is post-mortem debugging of a program that
9934 crashed while it ran outside a debugger. A program that crashes
9935 automatically produces a core file, unless this feature is disabled by
9936 the user. @xref{Files}, for information on invoking @value{GDBN} in
9937 the post-mortem debugging mode.
9939 Occasionally, you may wish to produce a core file of the program you
9940 are debugging in order to preserve a snapshot of its state.
9941 @value{GDBN} has a special command for that.
9945 @kindex generate-core-file
9946 @item generate-core-file [@var{file}]
9947 @itemx gcore [@var{file}]
9948 Produce a core dump of the inferior process. The optional argument
9949 @var{file} specifies the file name where to put the core dump. If not
9950 specified, the file name defaults to @file{core.@var{pid}}, where
9951 @var{pid} is the inferior process ID.
9953 Note that this command is implemented only for some systems (as of
9954 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
9957 @node Character Sets
9958 @section Character Sets
9959 @cindex character sets
9961 @cindex translating between character sets
9962 @cindex host character set
9963 @cindex target character set
9965 If the program you are debugging uses a different character set to
9966 represent characters and strings than the one @value{GDBN} uses itself,
9967 @value{GDBN} can automatically translate between the character sets for
9968 you. The character set @value{GDBN} uses we call the @dfn{host
9969 character set}; the one the inferior program uses we call the
9970 @dfn{target character set}.
9972 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9973 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9974 remote protocol (@pxref{Remote Debugging}) to debug a program
9975 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9976 then the host character set is Latin-1, and the target character set is
9977 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9978 target-charset EBCDIC-US}, then @value{GDBN} translates between
9979 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9980 character and string literals in expressions.
9982 @value{GDBN} has no way to automatically recognize which character set
9983 the inferior program uses; you must tell it, using the @code{set
9984 target-charset} command, described below.
9986 Here are the commands for controlling @value{GDBN}'s character set
9990 @item set target-charset @var{charset}
9991 @kindex set target-charset
9992 Set the current target character set to @var{charset}. To display the
9993 list of supported target character sets, type
9994 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9996 @item set host-charset @var{charset}
9997 @kindex set host-charset
9998 Set the current host character set to @var{charset}.
10000 By default, @value{GDBN} uses a host character set appropriate to the
10001 system it is running on; you can override that default using the
10002 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10003 automatically determine the appropriate host character set. In this
10004 case, @value{GDBN} uses @samp{UTF-8}.
10006 @value{GDBN} can only use certain character sets as its host character
10007 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10008 @value{GDBN} will list the host character sets it supports.
10010 @item set charset @var{charset}
10011 @kindex set charset
10012 Set the current host and target character sets to @var{charset}. As
10013 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10014 @value{GDBN} will list the names of the character sets that can be used
10015 for both host and target.
10018 @kindex show charset
10019 Show the names of the current host and target character sets.
10021 @item show host-charset
10022 @kindex show host-charset
10023 Show the name of the current host character set.
10025 @item show target-charset
10026 @kindex show target-charset
10027 Show the name of the current target character set.
10029 @item set target-wide-charset @var{charset}
10030 @kindex set target-wide-charset
10031 Set the current target's wide character set to @var{charset}. This is
10032 the character set used by the target's @code{wchar_t} type. To
10033 display the list of supported wide character sets, type
10034 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10036 @item show target-wide-charset
10037 @kindex show target-wide-charset
10038 Show the name of the current target's wide character set.
10041 Here is an example of @value{GDBN}'s character set support in action.
10042 Assume that the following source code has been placed in the file
10043 @file{charset-test.c}:
10049 = @{72, 101, 108, 108, 111, 44, 32, 119,
10050 111, 114, 108, 100, 33, 10, 0@};
10051 char ibm1047_hello[]
10052 = @{200, 133, 147, 147, 150, 107, 64, 166,
10053 150, 153, 147, 132, 90, 37, 0@};
10057 printf ("Hello, world!\n");
10061 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10062 containing the string @samp{Hello, world!} followed by a newline,
10063 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10065 We compile the program, and invoke the debugger on it:
10068 $ gcc -g charset-test.c -o charset-test
10069 $ gdb -nw charset-test
10070 GNU gdb 2001-12-19-cvs
10071 Copyright 2001 Free Software Foundation, Inc.
10076 We can use the @code{show charset} command to see what character sets
10077 @value{GDBN} is currently using to interpret and display characters and
10081 (@value{GDBP}) show charset
10082 The current host and target character set is `ISO-8859-1'.
10086 For the sake of printing this manual, let's use @sc{ascii} as our
10087 initial character set:
10089 (@value{GDBP}) set charset ASCII
10090 (@value{GDBP}) show charset
10091 The current host and target character set is `ASCII'.
10095 Let's assume that @sc{ascii} is indeed the correct character set for our
10096 host system --- in other words, let's assume that if @value{GDBN} prints
10097 characters using the @sc{ascii} character set, our terminal will display
10098 them properly. Since our current target character set is also
10099 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10102 (@value{GDBP}) print ascii_hello
10103 $1 = 0x401698 "Hello, world!\n"
10104 (@value{GDBP}) print ascii_hello[0]
10109 @value{GDBN} uses the target character set for character and string
10110 literals you use in expressions:
10113 (@value{GDBP}) print '+'
10118 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10121 @value{GDBN} relies on the user to tell it which character set the
10122 target program uses. If we print @code{ibm1047_hello} while our target
10123 character set is still @sc{ascii}, we get jibberish:
10126 (@value{GDBP}) print ibm1047_hello
10127 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10128 (@value{GDBP}) print ibm1047_hello[0]
10133 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10134 @value{GDBN} tells us the character sets it supports:
10137 (@value{GDBP}) set target-charset
10138 ASCII EBCDIC-US IBM1047 ISO-8859-1
10139 (@value{GDBP}) set target-charset
10142 We can select @sc{ibm1047} as our target character set, and examine the
10143 program's strings again. Now the @sc{ascii} string is wrong, but
10144 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10145 target character set, @sc{ibm1047}, to the host character set,
10146 @sc{ascii}, and they display correctly:
10149 (@value{GDBP}) set target-charset IBM1047
10150 (@value{GDBP}) show charset
10151 The current host character set is `ASCII'.
10152 The current target character set is `IBM1047'.
10153 (@value{GDBP}) print ascii_hello
10154 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10155 (@value{GDBP}) print ascii_hello[0]
10157 (@value{GDBP}) print ibm1047_hello
10158 $8 = 0x4016a8 "Hello, world!\n"
10159 (@value{GDBP}) print ibm1047_hello[0]
10164 As above, @value{GDBN} uses the target character set for character and
10165 string literals you use in expressions:
10168 (@value{GDBP}) print '+'
10173 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10176 @node Caching Remote Data
10177 @section Caching Data of Remote Targets
10178 @cindex caching data of remote targets
10180 @value{GDBN} caches data exchanged between the debugger and a
10181 remote target (@pxref{Remote Debugging}). Such caching generally improves
10182 performance, because it reduces the overhead of the remote protocol by
10183 bundling memory reads and writes into large chunks. Unfortunately, simply
10184 caching everything would lead to incorrect results, since @value{GDBN}
10185 does not necessarily know anything about volatile values, memory-mapped I/O
10186 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
10187 memory can be changed @emph{while} a gdb command is executing.
10188 Therefore, by default, @value{GDBN} only caches data
10189 known to be on the stack@footnote{In non-stop mode, it is moderately
10190 rare for a running thread to modify the stack of a stopped thread
10191 in a way that would interfere with a backtrace, and caching of
10192 stack reads provides a significant speed up of remote backtraces.}.
10193 Other regions of memory can be explicitly marked as
10194 cacheable; see @pxref{Memory Region Attributes}.
10197 @kindex set remotecache
10198 @item set remotecache on
10199 @itemx set remotecache off
10200 This option no longer does anything; it exists for compatibility
10203 @kindex show remotecache
10204 @item show remotecache
10205 Show the current state of the obsolete remotecache flag.
10207 @kindex set stack-cache
10208 @item set stack-cache on
10209 @itemx set stack-cache off
10210 Enable or disable caching of stack accesses. When @code{ON}, use
10211 caching. By default, this option is @code{ON}.
10213 @kindex show stack-cache
10214 @item show stack-cache
10215 Show the current state of data caching for memory accesses.
10217 @kindex info dcache
10218 @item info dcache @r{[}line@r{]}
10219 Print the information about the data cache performance. The
10220 information displayed includes the dcache width and depth, and for
10221 each cache line, its number, address, and how many times it was
10222 referenced. This command is useful for debugging the data cache
10225 If a line number is specified, the contents of that line will be
10228 @item set dcache size @var{size}
10229 @cindex dcache size
10230 @kindex set dcache size
10231 Set maximum number of entries in dcache (dcache depth above).
10233 @item set dcache line-size @var{line-size}
10234 @cindex dcache line-size
10235 @kindex set dcache line-size
10236 Set number of bytes each dcache entry caches (dcache width above).
10237 Must be a power of 2.
10239 @item show dcache size
10240 @kindex show dcache size
10241 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
10243 @item show dcache line-size
10244 @kindex show dcache line-size
10245 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
10249 @node Searching Memory
10250 @section Search Memory
10251 @cindex searching memory
10253 Memory can be searched for a particular sequence of bytes with the
10254 @code{find} command.
10258 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10259 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10260 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10261 etc. The search begins at address @var{start_addr} and continues for either
10262 @var{len} bytes or through to @var{end_addr} inclusive.
10265 @var{s} and @var{n} are optional parameters.
10266 They may be specified in either order, apart or together.
10269 @item @var{s}, search query size
10270 The size of each search query value.
10276 halfwords (two bytes)
10280 giant words (eight bytes)
10283 All values are interpreted in the current language.
10284 This means, for example, that if the current source language is C/C@t{++}
10285 then searching for the string ``hello'' includes the trailing '\0'.
10287 If the value size is not specified, it is taken from the
10288 value's type in the current language.
10289 This is useful when one wants to specify the search
10290 pattern as a mixture of types.
10291 Note that this means, for example, that in the case of C-like languages
10292 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10293 which is typically four bytes.
10295 @item @var{n}, maximum number of finds
10296 The maximum number of matches to print. The default is to print all finds.
10299 You can use strings as search values. Quote them with double-quotes
10301 The string value is copied into the search pattern byte by byte,
10302 regardless of the endianness of the target and the size specification.
10304 The address of each match found is printed as well as a count of the
10305 number of matches found.
10307 The address of the last value found is stored in convenience variable
10309 A count of the number of matches is stored in @samp{$numfound}.
10311 For example, if stopped at the @code{printf} in this function:
10317 static char hello[] = "hello-hello";
10318 static struct @{ char c; short s; int i; @}
10319 __attribute__ ((packed)) mixed
10320 = @{ 'c', 0x1234, 0x87654321 @};
10321 printf ("%s\n", hello);
10326 you get during debugging:
10329 (gdb) find &hello[0], +sizeof(hello), "hello"
10330 0x804956d <hello.1620+6>
10332 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10333 0x8049567 <hello.1620>
10334 0x804956d <hello.1620+6>
10336 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10337 0x8049567 <hello.1620>
10339 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10340 0x8049560 <mixed.1625>
10342 (gdb) print $numfound
10345 $2 = (void *) 0x8049560
10348 @node Optimized Code
10349 @chapter Debugging Optimized Code
10350 @cindex optimized code, debugging
10351 @cindex debugging optimized code
10353 Almost all compilers support optimization. With optimization
10354 disabled, the compiler generates assembly code that corresponds
10355 directly to your source code, in a simplistic way. As the compiler
10356 applies more powerful optimizations, the generated assembly code
10357 diverges from your original source code. With help from debugging
10358 information generated by the compiler, @value{GDBN} can map from
10359 the running program back to constructs from your original source.
10361 @value{GDBN} is more accurate with optimization disabled. If you
10362 can recompile without optimization, it is easier to follow the
10363 progress of your program during debugging. But, there are many cases
10364 where you may need to debug an optimized version.
10366 When you debug a program compiled with @samp{-g -O}, remember that the
10367 optimizer has rearranged your code; the debugger shows you what is
10368 really there. Do not be too surprised when the execution path does not
10369 exactly match your source file! An extreme example: if you define a
10370 variable, but never use it, @value{GDBN} never sees that
10371 variable---because the compiler optimizes it out of existence.
10373 Some things do not work as well with @samp{-g -O} as with just
10374 @samp{-g}, particularly on machines with instruction scheduling. If in
10375 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
10376 please report it to us as a bug (including a test case!).
10377 @xref{Variables}, for more information about debugging optimized code.
10380 * Inline Functions:: How @value{GDBN} presents inlining
10381 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
10384 @node Inline Functions
10385 @section Inline Functions
10386 @cindex inline functions, debugging
10388 @dfn{Inlining} is an optimization that inserts a copy of the function
10389 body directly at each call site, instead of jumping to a shared
10390 routine. @value{GDBN} displays inlined functions just like
10391 non-inlined functions. They appear in backtraces. You can view their
10392 arguments and local variables, step into them with @code{step}, skip
10393 them with @code{next}, and escape from them with @code{finish}.
10394 You can check whether a function was inlined by using the
10395 @code{info frame} command.
10397 For @value{GDBN} to support inlined functions, the compiler must
10398 record information about inlining in the debug information ---
10399 @value{NGCC} using the @sc{dwarf 2} format does this, and several
10400 other compilers do also. @value{GDBN} only supports inlined functions
10401 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
10402 do not emit two required attributes (@samp{DW_AT_call_file} and
10403 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
10404 function calls with earlier versions of @value{NGCC}. It instead
10405 displays the arguments and local variables of inlined functions as
10406 local variables in the caller.
10408 The body of an inlined function is directly included at its call site;
10409 unlike a non-inlined function, there are no instructions devoted to
10410 the call. @value{GDBN} still pretends that the call site and the
10411 start of the inlined function are different instructions. Stepping to
10412 the call site shows the call site, and then stepping again shows
10413 the first line of the inlined function, even though no additional
10414 instructions are executed.
10416 This makes source-level debugging much clearer; you can see both the
10417 context of the call and then the effect of the call. Only stepping by
10418 a single instruction using @code{stepi} or @code{nexti} does not do
10419 this; single instruction steps always show the inlined body.
10421 There are some ways that @value{GDBN} does not pretend that inlined
10422 function calls are the same as normal calls:
10426 Setting breakpoints at the call site of an inlined function may not
10427 work, because the call site does not contain any code. @value{GDBN}
10428 may incorrectly move the breakpoint to the next line of the enclosing
10429 function, after the call. This limitation will be removed in a future
10430 version of @value{GDBN}; until then, set a breakpoint on an earlier line
10431 or inside the inlined function instead.
10434 @value{GDBN} cannot locate the return value of inlined calls after
10435 using the @code{finish} command. This is a limitation of compiler-generated
10436 debugging information; after @code{finish}, you can step to the next line
10437 and print a variable where your program stored the return value.
10441 @node Tail Call Frames
10442 @section Tail Call Frames
10443 @cindex tail call frames, debugging
10445 Function @code{B} can call function @code{C} in its very last statement. In
10446 unoptimized compilation the call of @code{C} is immediately followed by return
10447 instruction at the end of @code{B} code. Optimizing compiler may replace the
10448 call and return in function @code{B} into one jump to function @code{C}
10449 instead. Such use of a jump instruction is called @dfn{tail call}.
10451 During execution of function @code{C}, there will be no indication in the
10452 function call stack frames that it was tail-called from @code{B}. If function
10453 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
10454 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
10455 some cases @value{GDBN} can determine that @code{C} was tail-called from
10456 @code{B}, and it will then create fictitious call frame for that, with the
10457 return address set up as if @code{B} called @code{C} normally.
10459 This functionality is currently supported only by DWARF 2 debugging format and
10460 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
10461 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10464 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
10465 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
10469 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
10471 Stack level 1, frame at 0x7fffffffda30:
10472 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
10473 tail call frame, caller of frame at 0x7fffffffda30
10474 source language c++.
10475 Arglist at unknown address.
10476 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
10479 The detection of all the possible code path executions can find them ambiguous.
10480 There is no execution history stored (possible @ref{Reverse Execution} is never
10481 used for this purpose) and the last known caller could have reached the known
10482 callee by multiple different jump sequences. In such case @value{GDBN} still
10483 tries to show at least all the unambiguous top tail callers and all the
10484 unambiguous bottom tail calees, if any.
10487 @anchor{set debug entry-values}
10488 @item set debug entry-values
10489 @kindex set debug entry-values
10490 When set to on, enables printing of analysis messages for both frame argument
10491 values at function entry and tail calls. It will show all the possible valid
10492 tail calls code paths it has considered. It will also print the intersection
10493 of them with the final unambiguous (possibly partial or even empty) code path
10496 @item show debug entry-values
10497 @kindex show debug entry-values
10498 Show the current state of analysis messages printing for both frame argument
10499 values at function entry and tail calls.
10502 The analysis messages for tail calls can for example show why the virtual tail
10503 call frame for function @code{c} has not been recognized (due to the indirect
10504 reference by variable @code{x}):
10507 static void __attribute__((noinline, noclone)) c (void);
10508 void (*x) (void) = c;
10509 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10510 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
10511 int main (void) @{ x (); return 0; @}
10513 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
10514 DW_TAG_GNU_call_site 0x40039a in main
10516 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10519 #1 0x000000000040039a in main () at t.c:5
10522 Another possibility is an ambiguous virtual tail call frames resolution:
10526 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
10527 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
10528 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
10529 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
10530 static void __attribute__((noinline, noclone)) b (void)
10531 @{ if (i) c (); else e (); @}
10532 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
10533 int main (void) @{ a (); return 0; @}
10535 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
10536 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
10537 tailcall: reduced: 0x4004d2(a) |
10540 #1 0x00000000004004d2 in a () at t.c:8
10541 #2 0x0000000000400395 in main () at t.c:9
10544 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
10545 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
10547 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
10548 @ifset HAVE_MAKEINFO_CLICK
10549 @set ARROW @click{}
10550 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
10551 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
10553 @ifclear HAVE_MAKEINFO_CLICK
10555 @set CALLSEQ1B @value{CALLSEQ1A}
10556 @set CALLSEQ2B @value{CALLSEQ2A}
10559 Frames #0 and #2 are real, #1 is a virtual tail call frame.
10560 The code can have possible execution paths @value{CALLSEQ1B} or
10561 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
10563 @code{initial:} state shows some random possible calling sequence @value{GDBN}
10564 has found. It then finds another possible calling sequcen - that one is
10565 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
10566 printed as the @code{reduced:} calling sequence. That one could have many
10567 futher @code{compare:} and @code{reduced:} statements as long as there remain
10568 any non-ambiguous sequence entries.
10570 For the frame of function @code{b} in both cases there are different possible
10571 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
10572 also ambigous. The only non-ambiguous frame is the one for function @code{a},
10573 therefore this one is displayed to the user while the ambiguous frames are
10576 There can be also reasons why printing of frame argument values at function
10581 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
10582 static void __attribute__((noinline, noclone)) a (int i);
10583 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
10584 static void __attribute__((noinline, noclone)) a (int i)
10585 @{ if (i) b (i - 1); else c (0); @}
10586 int main (void) @{ a (5); return 0; @}
10589 #0 c (i=i@@entry=0) at t.c:2
10590 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
10591 function "a" at 0x400420 can call itself via tail calls
10592 i=<optimized out>) at t.c:6
10593 #2 0x000000000040036e in main () at t.c:7
10596 @value{GDBN} cannot find out from the inferior state if and how many times did
10597 function @code{a} call itself (via function @code{b}) as these calls would be
10598 tail calls. Such tail calls would modify thue @code{i} variable, therefore
10599 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
10600 prints @code{<optimized out>} instead.
10603 @chapter C Preprocessor Macros
10605 Some languages, such as C and C@t{++}, provide a way to define and invoke
10606 ``preprocessor macros'' which expand into strings of tokens.
10607 @value{GDBN} can evaluate expressions containing macro invocations, show
10608 the result of macro expansion, and show a macro's definition, including
10609 where it was defined.
10611 You may need to compile your program specially to provide @value{GDBN}
10612 with information about preprocessor macros. Most compilers do not
10613 include macros in their debugging information, even when you compile
10614 with the @option{-g} flag. @xref{Compilation}.
10616 A program may define a macro at one point, remove that definition later,
10617 and then provide a different definition after that. Thus, at different
10618 points in the program, a macro may have different definitions, or have
10619 no definition at all. If there is a current stack frame, @value{GDBN}
10620 uses the macros in scope at that frame's source code line. Otherwise,
10621 @value{GDBN} uses the macros in scope at the current listing location;
10624 Whenever @value{GDBN} evaluates an expression, it always expands any
10625 macro invocations present in the expression. @value{GDBN} also provides
10626 the following commands for working with macros explicitly.
10630 @kindex macro expand
10631 @cindex macro expansion, showing the results of preprocessor
10632 @cindex preprocessor macro expansion, showing the results of
10633 @cindex expanding preprocessor macros
10634 @item macro expand @var{expression}
10635 @itemx macro exp @var{expression}
10636 Show the results of expanding all preprocessor macro invocations in
10637 @var{expression}. Since @value{GDBN} simply expands macros, but does
10638 not parse the result, @var{expression} need not be a valid expression;
10639 it can be any string of tokens.
10642 @item macro expand-once @var{expression}
10643 @itemx macro exp1 @var{expression}
10644 @cindex expand macro once
10645 @i{(This command is not yet implemented.)} Show the results of
10646 expanding those preprocessor macro invocations that appear explicitly in
10647 @var{expression}. Macro invocations appearing in that expansion are
10648 left unchanged. This command allows you to see the effect of a
10649 particular macro more clearly, without being confused by further
10650 expansions. Since @value{GDBN} simply expands macros, but does not
10651 parse the result, @var{expression} need not be a valid expression; it
10652 can be any string of tokens.
10655 @cindex macro definition, showing
10656 @cindex definition of a macro, showing
10657 @cindex macros, from debug info
10658 @item info macro [-a|-all] [--] @var{macro}
10659 Show the current definition or all definitions of the named @var{macro},
10660 and describe the source location or compiler command-line where that
10661 definition was established. The optional double dash is to signify the end of
10662 argument processing and the beginning of @var{macro} for non C-like macros where
10663 the macro may begin with a hyphen.
10665 @kindex info macros
10666 @item info macros @var{linespec}
10667 Show all macro definitions that are in effect at the location specified
10668 by @var{linespec}, and describe the source location or compiler
10669 command-line where those definitions were established.
10671 @kindex macro define
10672 @cindex user-defined macros
10673 @cindex defining macros interactively
10674 @cindex macros, user-defined
10675 @item macro define @var{macro} @var{replacement-list}
10676 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10677 Introduce a definition for a preprocessor macro named @var{macro},
10678 invocations of which are replaced by the tokens given in
10679 @var{replacement-list}. The first form of this command defines an
10680 ``object-like'' macro, which takes no arguments; the second form
10681 defines a ``function-like'' macro, which takes the arguments given in
10684 A definition introduced by this command is in scope in every
10685 expression evaluated in @value{GDBN}, until it is removed with the
10686 @code{macro undef} command, described below. The definition overrides
10687 all definitions for @var{macro} present in the program being debugged,
10688 as well as any previous user-supplied definition.
10690 @kindex macro undef
10691 @item macro undef @var{macro}
10692 Remove any user-supplied definition for the macro named @var{macro}.
10693 This command only affects definitions provided with the @code{macro
10694 define} command, described above; it cannot remove definitions present
10695 in the program being debugged.
10699 List all the macros defined using the @code{macro define} command.
10702 @cindex macros, example of debugging with
10703 Here is a transcript showing the above commands in action. First, we
10704 show our source files:
10709 #include "sample.h"
10712 #define ADD(x) (M + x)
10717 printf ("Hello, world!\n");
10719 printf ("We're so creative.\n");
10721 printf ("Goodbye, world!\n");
10728 Now, we compile the program using the @sc{gnu} C compiler,
10729 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10730 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10731 and @option{-gdwarf-4}; we recommend always choosing the most recent
10732 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10733 includes information about preprocessor macros in the debugging
10737 $ gcc -gdwarf-2 -g3 sample.c -o sample
10741 Now, we start @value{GDBN} on our sample program:
10745 GNU gdb 2002-05-06-cvs
10746 Copyright 2002 Free Software Foundation, Inc.
10747 GDB is free software, @dots{}
10751 We can expand macros and examine their definitions, even when the
10752 program is not running. @value{GDBN} uses the current listing position
10753 to decide which macro definitions are in scope:
10756 (@value{GDBP}) list main
10759 5 #define ADD(x) (M + x)
10764 10 printf ("Hello, world!\n");
10766 12 printf ("We're so creative.\n");
10767 (@value{GDBP}) info macro ADD
10768 Defined at /home/jimb/gdb/macros/play/sample.c:5
10769 #define ADD(x) (M + x)
10770 (@value{GDBP}) info macro Q
10771 Defined at /home/jimb/gdb/macros/play/sample.h:1
10772 included at /home/jimb/gdb/macros/play/sample.c:2
10774 (@value{GDBP}) macro expand ADD(1)
10775 expands to: (42 + 1)
10776 (@value{GDBP}) macro expand-once ADD(1)
10777 expands to: once (M + 1)
10781 In the example above, note that @code{macro expand-once} expands only
10782 the macro invocation explicit in the original text --- the invocation of
10783 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10784 which was introduced by @code{ADD}.
10786 Once the program is running, @value{GDBN} uses the macro definitions in
10787 force at the source line of the current stack frame:
10790 (@value{GDBP}) break main
10791 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10793 Starting program: /home/jimb/gdb/macros/play/sample
10795 Breakpoint 1, main () at sample.c:10
10796 10 printf ("Hello, world!\n");
10800 At line 10, the definition of the macro @code{N} at line 9 is in force:
10803 (@value{GDBP}) info macro N
10804 Defined at /home/jimb/gdb/macros/play/sample.c:9
10806 (@value{GDBP}) macro expand N Q M
10807 expands to: 28 < 42
10808 (@value{GDBP}) print N Q M
10813 As we step over directives that remove @code{N}'s definition, and then
10814 give it a new definition, @value{GDBN} finds the definition (or lack
10815 thereof) in force at each point:
10818 (@value{GDBP}) next
10820 12 printf ("We're so creative.\n");
10821 (@value{GDBP}) info macro N
10822 The symbol `N' has no definition as a C/C++ preprocessor macro
10823 at /home/jimb/gdb/macros/play/sample.c:12
10824 (@value{GDBP}) next
10826 14 printf ("Goodbye, world!\n");
10827 (@value{GDBP}) info macro N
10828 Defined at /home/jimb/gdb/macros/play/sample.c:13
10830 (@value{GDBP}) macro expand N Q M
10831 expands to: 1729 < 42
10832 (@value{GDBP}) print N Q M
10837 In addition to source files, macros can be defined on the compilation command
10838 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10839 such a way, @value{GDBN} displays the location of their definition as line zero
10840 of the source file submitted to the compiler.
10843 (@value{GDBP}) info macro __STDC__
10844 Defined at /home/jimb/gdb/macros/play/sample.c:0
10851 @chapter Tracepoints
10852 @c This chapter is based on the documentation written by Michael
10853 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10855 @cindex tracepoints
10856 In some applications, it is not feasible for the debugger to interrupt
10857 the program's execution long enough for the developer to learn
10858 anything helpful about its behavior. If the program's correctness
10859 depends on its real-time behavior, delays introduced by a debugger
10860 might cause the program to change its behavior drastically, or perhaps
10861 fail, even when the code itself is correct. It is useful to be able
10862 to observe the program's behavior without interrupting it.
10864 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10865 specify locations in the program, called @dfn{tracepoints}, and
10866 arbitrary expressions to evaluate when those tracepoints are reached.
10867 Later, using the @code{tfind} command, you can examine the values
10868 those expressions had when the program hit the tracepoints. The
10869 expressions may also denote objects in memory---structures or arrays,
10870 for example---whose values @value{GDBN} should record; while visiting
10871 a particular tracepoint, you may inspect those objects as if they were
10872 in memory at that moment. However, because @value{GDBN} records these
10873 values without interacting with you, it can do so quickly and
10874 unobtrusively, hopefully not disturbing the program's behavior.
10876 The tracepoint facility is currently available only for remote
10877 targets. @xref{Targets}. In addition, your remote target must know
10878 how to collect trace data. This functionality is implemented in the
10879 remote stub; however, none of the stubs distributed with @value{GDBN}
10880 support tracepoints as of this writing. The format of the remote
10881 packets used to implement tracepoints are described in @ref{Tracepoint
10884 It is also possible to get trace data from a file, in a manner reminiscent
10885 of corefiles; you specify the filename, and use @code{tfind} to search
10886 through the file. @xref{Trace Files}, for more details.
10888 This chapter describes the tracepoint commands and features.
10891 * Set Tracepoints::
10892 * Analyze Collected Data::
10893 * Tracepoint Variables::
10897 @node Set Tracepoints
10898 @section Commands to Set Tracepoints
10900 Before running such a @dfn{trace experiment}, an arbitrary number of
10901 tracepoints can be set. A tracepoint is actually a special type of
10902 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10903 standard breakpoint commands. For instance, as with breakpoints,
10904 tracepoint numbers are successive integers starting from one, and many
10905 of the commands associated with tracepoints take the tracepoint number
10906 as their argument, to identify which tracepoint to work on.
10908 For each tracepoint, you can specify, in advance, some arbitrary set
10909 of data that you want the target to collect in the trace buffer when
10910 it hits that tracepoint. The collected data can include registers,
10911 local variables, or global data. Later, you can use @value{GDBN}
10912 commands to examine the values these data had at the time the
10913 tracepoint was hit.
10915 Tracepoints do not support every breakpoint feature. Ignore counts on
10916 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10917 commands when they are hit. Tracepoints may not be thread-specific
10920 @cindex fast tracepoints
10921 Some targets may support @dfn{fast tracepoints}, which are inserted in
10922 a different way (such as with a jump instead of a trap), that is
10923 faster but possibly restricted in where they may be installed.
10925 @cindex static tracepoints
10926 @cindex markers, static tracepoints
10927 @cindex probing markers, static tracepoints
10928 Regular and fast tracepoints are dynamic tracing facilities, meaning
10929 that they can be used to insert tracepoints at (almost) any location
10930 in the target. Some targets may also support controlling @dfn{static
10931 tracepoints} from @value{GDBN}. With static tracing, a set of
10932 instrumentation points, also known as @dfn{markers}, are embedded in
10933 the target program, and can be activated or deactivated by name or
10934 address. These are usually placed at locations which facilitate
10935 investigating what the target is actually doing. @value{GDBN}'s
10936 support for static tracing includes being able to list instrumentation
10937 points, and attach them with @value{GDBN} defined high level
10938 tracepoints that expose the whole range of convenience of
10939 @value{GDBN}'s tracepoints support. Namely, support for collecting
10940 registers values and values of global or local (to the instrumentation
10941 point) variables; tracepoint conditions and trace state variables.
10942 The act of installing a @value{GDBN} static tracepoint on an
10943 instrumentation point, or marker, is referred to as @dfn{probing} a
10944 static tracepoint marker.
10946 @code{gdbserver} supports tracepoints on some target systems.
10947 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10949 This section describes commands to set tracepoints and associated
10950 conditions and actions.
10953 * Create and Delete Tracepoints::
10954 * Enable and Disable Tracepoints::
10955 * Tracepoint Passcounts::
10956 * Tracepoint Conditions::
10957 * Trace State Variables::
10958 * Tracepoint Actions::
10959 * Listing Tracepoints::
10960 * Listing Static Tracepoint Markers::
10961 * Starting and Stopping Trace Experiments::
10962 * Tracepoint Restrictions::
10965 @node Create and Delete Tracepoints
10966 @subsection Create and Delete Tracepoints
10969 @cindex set tracepoint
10971 @item trace @var{location}
10972 The @code{trace} command is very similar to the @code{break} command.
10973 Its argument @var{location} can be a source line, a function name, or
10974 an address in the target program. @xref{Specify Location}. The
10975 @code{trace} command defines a tracepoint, which is a point in the
10976 target program where the debugger will briefly stop, collect some
10977 data, and then allow the program to continue. Setting a tracepoint or
10978 changing its actions takes effect immediately if the remote stub
10979 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
10981 If remote stub doesn't support the @samp{InstallInTrace} feature, all
10982 these changes don't take effect until the next @code{tstart}
10983 command, and once a trace experiment is running, further changes will
10984 not have any effect until the next trace experiment starts. In addition,
10985 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
10986 address is not yet resolved. (This is similar to pending breakpoints.)
10987 Pending tracepoints are not downloaded to the target and not installed
10988 until they are resolved. The resolution of pending tracepoints requires
10989 @value{GDBN} support---when debugging with the remote target, and
10990 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
10991 tracing}), pending tracepoints can not be resolved (and downloaded to
10992 the remote stub) while @value{GDBN} is disconnected.
10994 Here are some examples of using the @code{trace} command:
10997 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
10999 (@value{GDBP}) @b{trace +2} // 2 lines forward
11001 (@value{GDBP}) @b{trace my_function} // first source line of function
11003 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11005 (@value{GDBP}) @b{trace *0x2117c4} // an address
11009 You can abbreviate @code{trace} as @code{tr}.
11011 @item trace @var{location} if @var{cond}
11012 Set a tracepoint with condition @var{cond}; evaluate the expression
11013 @var{cond} each time the tracepoint is reached, and collect data only
11014 if the value is nonzero---that is, if @var{cond} evaluates as true.
11015 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11016 information on tracepoint conditions.
11018 @item ftrace @var{location} [ if @var{cond} ]
11019 @cindex set fast tracepoint
11020 @cindex fast tracepoints, setting
11022 The @code{ftrace} command sets a fast tracepoint. For targets that
11023 support them, fast tracepoints will use a more efficient but possibly
11024 less general technique to trigger data collection, such as a jump
11025 instruction instead of a trap, or some sort of hardware support. It
11026 may not be possible to create a fast tracepoint at the desired
11027 location, in which case the command will exit with an explanatory
11030 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11033 On 32-bit x86-architecture systems, fast tracepoints normally need to
11034 be placed at an instruction that is 5 bytes or longer, but can be
11035 placed at 4-byte instructions if the low 64K of memory of the target
11036 program is available to install trampolines. Some Unix-type systems,
11037 such as @sc{gnu}/Linux, exclude low addresses from the program's
11038 address space; but for instance with the Linux kernel it is possible
11039 to let @value{GDBN} use this area by doing a @command{sysctl} command
11040 to set the @code{mmap_min_addr} kernel parameter, as in
11043 sudo sysctl -w vm.mmap_min_addr=32768
11047 which sets the low address to 32K, which leaves plenty of room for
11048 trampolines. The minimum address should be set to a page boundary.
11050 @item strace @var{location} [ if @var{cond} ]
11051 @cindex set static tracepoint
11052 @cindex static tracepoints, setting
11053 @cindex probe static tracepoint marker
11055 The @code{strace} command sets a static tracepoint. For targets that
11056 support it, setting a static tracepoint probes a static
11057 instrumentation point, or marker, found at @var{location}. It may not
11058 be possible to set a static tracepoint at the desired location, in
11059 which case the command will exit with an explanatory message.
11061 @value{GDBN} handles arguments to @code{strace} exactly as for
11062 @code{trace}, with the addition that the user can also specify
11063 @code{-m @var{marker}} as @var{location}. This probes the marker
11064 identified by the @var{marker} string identifier. This identifier
11065 depends on the static tracepoint backend library your program is
11066 using. You can find all the marker identifiers in the @samp{ID} field
11067 of the @code{info static-tracepoint-markers} command output.
11068 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11069 Markers}. For example, in the following small program using the UST
11075 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11080 the marker id is composed of joining the first two arguments to the
11081 @code{trace_mark} call with a slash, which translates to:
11084 (@value{GDBP}) info static-tracepoint-markers
11085 Cnt Enb ID Address What
11086 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11092 so you may probe the marker above with:
11095 (@value{GDBP}) strace -m ust/bar33
11098 Static tracepoints accept an extra collect action --- @code{collect
11099 $_sdata}. This collects arbitrary user data passed in the probe point
11100 call to the tracing library. In the UST example above, you'll see
11101 that the third argument to @code{trace_mark} is a printf-like format
11102 string. The user data is then the result of running that formating
11103 string against the following arguments. Note that @code{info
11104 static-tracepoint-markers} command output lists that format string in
11105 the @samp{Data:} field.
11107 You can inspect this data when analyzing the trace buffer, by printing
11108 the $_sdata variable like any other variable available to
11109 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11112 @cindex last tracepoint number
11113 @cindex recent tracepoint number
11114 @cindex tracepoint number
11115 The convenience variable @code{$tpnum} records the tracepoint number
11116 of the most recently set tracepoint.
11118 @kindex delete tracepoint
11119 @cindex tracepoint deletion
11120 @item delete tracepoint @r{[}@var{num}@r{]}
11121 Permanently delete one or more tracepoints. With no argument, the
11122 default is to delete all tracepoints. Note that the regular
11123 @code{delete} command can remove tracepoints also.
11128 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11130 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11134 You can abbreviate this command as @code{del tr}.
11137 @node Enable and Disable Tracepoints
11138 @subsection Enable and Disable Tracepoints
11140 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11143 @kindex disable tracepoint
11144 @item disable tracepoint @r{[}@var{num}@r{]}
11145 Disable tracepoint @var{num}, or all tracepoints if no argument
11146 @var{num} is given. A disabled tracepoint will have no effect during
11147 a trace experiment, but it is not forgotten. You can re-enable
11148 a disabled tracepoint using the @code{enable tracepoint} command.
11149 If the command is issued during a trace experiment and the debug target
11150 has support for disabling tracepoints during a trace experiment, then the
11151 change will be effective immediately. Otherwise, it will be applied to the
11152 next trace experiment.
11154 @kindex enable tracepoint
11155 @item enable tracepoint @r{[}@var{num}@r{]}
11156 Enable tracepoint @var{num}, or all tracepoints. If this command is
11157 issued during a trace experiment and the debug target supports enabling
11158 tracepoints during a trace experiment, then the enabled tracepoints will
11159 become effective immediately. Otherwise, they will become effective the
11160 next time a trace experiment is run.
11163 @node Tracepoint Passcounts
11164 @subsection Tracepoint Passcounts
11168 @cindex tracepoint pass count
11169 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11170 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11171 automatically stop a trace experiment. If a tracepoint's passcount is
11172 @var{n}, then the trace experiment will be automatically stopped on
11173 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11174 @var{num} is not specified, the @code{passcount} command sets the
11175 passcount of the most recently defined tracepoint. If no passcount is
11176 given, the trace experiment will run until stopped explicitly by the
11182 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11183 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11185 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11186 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11187 (@value{GDBP}) @b{trace foo}
11188 (@value{GDBP}) @b{pass 3}
11189 (@value{GDBP}) @b{trace bar}
11190 (@value{GDBP}) @b{pass 2}
11191 (@value{GDBP}) @b{trace baz}
11192 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11193 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11194 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11195 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11199 @node Tracepoint Conditions
11200 @subsection Tracepoint Conditions
11201 @cindex conditional tracepoints
11202 @cindex tracepoint conditions
11204 The simplest sort of tracepoint collects data every time your program
11205 reaches a specified place. You can also specify a @dfn{condition} for
11206 a tracepoint. A condition is just a Boolean expression in your
11207 programming language (@pxref{Expressions, ,Expressions}). A
11208 tracepoint with a condition evaluates the expression each time your
11209 program reaches it, and data collection happens only if the condition
11212 Tracepoint conditions can be specified when a tracepoint is set, by
11213 using @samp{if} in the arguments to the @code{trace} command.
11214 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11215 also be set or changed at any time with the @code{condition} command,
11216 just as with breakpoints.
11218 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11219 the conditional expression itself. Instead, @value{GDBN} encodes the
11220 expression into an agent expression (@pxref{Agent Expressions})
11221 suitable for execution on the target, independently of @value{GDBN}.
11222 Global variables become raw memory locations, locals become stack
11223 accesses, and so forth.
11225 For instance, suppose you have a function that is usually called
11226 frequently, but should not be called after an error has occurred. You
11227 could use the following tracepoint command to collect data about calls
11228 of that function that happen while the error code is propagating
11229 through the program; an unconditional tracepoint could end up
11230 collecting thousands of useless trace frames that you would have to
11234 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11237 @node Trace State Variables
11238 @subsection Trace State Variables
11239 @cindex trace state variables
11241 A @dfn{trace state variable} is a special type of variable that is
11242 created and managed by target-side code. The syntax is the same as
11243 that for GDB's convenience variables (a string prefixed with ``$''),
11244 but they are stored on the target. They must be created explicitly,
11245 using a @code{tvariable} command. They are always 64-bit signed
11248 Trace state variables are remembered by @value{GDBN}, and downloaded
11249 to the target along with tracepoint information when the trace
11250 experiment starts. There are no intrinsic limits on the number of
11251 trace state variables, beyond memory limitations of the target.
11253 @cindex convenience variables, and trace state variables
11254 Although trace state variables are managed by the target, you can use
11255 them in print commands and expressions as if they were convenience
11256 variables; @value{GDBN} will get the current value from the target
11257 while the trace experiment is running. Trace state variables share
11258 the same namespace as other ``$'' variables, which means that you
11259 cannot have trace state variables with names like @code{$23} or
11260 @code{$pc}, nor can you have a trace state variable and a convenience
11261 variable with the same name.
11265 @item tvariable $@var{name} [ = @var{expression} ]
11267 The @code{tvariable} command creates a new trace state variable named
11268 @code{$@var{name}}, and optionally gives it an initial value of
11269 @var{expression}. @var{expression} is evaluated when this command is
11270 entered; the result will be converted to an integer if possible,
11271 otherwise @value{GDBN} will report an error. A subsequent
11272 @code{tvariable} command specifying the same name does not create a
11273 variable, but instead assigns the supplied initial value to the
11274 existing variable of that name, overwriting any previous initial
11275 value. The default initial value is 0.
11277 @item info tvariables
11278 @kindex info tvariables
11279 List all the trace state variables along with their initial values.
11280 Their current values may also be displayed, if the trace experiment is
11283 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11284 @kindex delete tvariable
11285 Delete the given trace state variables, or all of them if no arguments
11290 @node Tracepoint Actions
11291 @subsection Tracepoint Action Lists
11295 @cindex tracepoint actions
11296 @item actions @r{[}@var{num}@r{]}
11297 This command will prompt for a list of actions to be taken when the
11298 tracepoint is hit. If the tracepoint number @var{num} is not
11299 specified, this command sets the actions for the one that was most
11300 recently defined (so that you can define a tracepoint and then say
11301 @code{actions} without bothering about its number). You specify the
11302 actions themselves on the following lines, one action at a time, and
11303 terminate the actions list with a line containing just @code{end}. So
11304 far, the only defined actions are @code{collect}, @code{teval}, and
11305 @code{while-stepping}.
11307 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11308 Commands, ,Breakpoint Command Lists}), except that only the defined
11309 actions are allowed; any other @value{GDBN} command is rejected.
11311 @cindex remove actions from a tracepoint
11312 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11313 and follow it immediately with @samp{end}.
11316 (@value{GDBP}) @b{collect @var{data}} // collect some data
11318 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11320 (@value{GDBP}) @b{end} // signals the end of actions.
11323 In the following example, the action list begins with @code{collect}
11324 commands indicating the things to be collected when the tracepoint is
11325 hit. Then, in order to single-step and collect additional data
11326 following the tracepoint, a @code{while-stepping} command is used,
11327 followed by the list of things to be collected after each step in a
11328 sequence of single steps. The @code{while-stepping} command is
11329 terminated by its own separate @code{end} command. Lastly, the action
11330 list is terminated by an @code{end} command.
11333 (@value{GDBP}) @b{trace foo}
11334 (@value{GDBP}) @b{actions}
11335 Enter actions for tracepoint 1, one per line:
11338 > while-stepping 12
11339 > collect $pc, arr[i]
11344 @kindex collect @r{(tracepoints)}
11345 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11346 Collect values of the given expressions when the tracepoint is hit.
11347 This command accepts a comma-separated list of any valid expressions.
11348 In addition to global, static, or local variables, the following
11349 special arguments are supported:
11353 Collect all registers.
11356 Collect all function arguments.
11359 Collect all local variables.
11362 Collect the return address. This is helpful if you want to see more
11366 Collects the number of arguments from the static probe at which the
11367 tracepoint is located.
11368 @xref{Static Probe Points}.
11370 @item $_probe_arg@var{n}
11371 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
11372 from the static probe at which the tracepoint is located.
11373 @xref{Static Probe Points}.
11376 @vindex $_sdata@r{, collect}
11377 Collect static tracepoint marker specific data. Only available for
11378 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
11379 Lists}. On the UST static tracepoints library backend, an
11380 instrumentation point resembles a @code{printf} function call. The
11381 tracing library is able to collect user specified data formatted to a
11382 character string using the format provided by the programmer that
11383 instrumented the program. Other backends have similar mechanisms.
11384 Here's an example of a UST marker call:
11387 const char master_name[] = "$your_name";
11388 trace_mark(channel1, marker1, "hello %s", master_name)
11391 In this case, collecting @code{$_sdata} collects the string
11392 @samp{hello $yourname}. When analyzing the trace buffer, you can
11393 inspect @samp{$_sdata} like any other variable available to
11397 You can give several consecutive @code{collect} commands, each one
11398 with a single argument, or one @code{collect} command with several
11399 arguments separated by commas; the effect is the same.
11401 The optional @var{mods} changes the usual handling of the arguments.
11402 @code{s} requests that pointers to chars be handled as strings, in
11403 particular collecting the contents of the memory being pointed at, up
11404 to the first zero. The upper bound is by default the value of the
11405 @code{print elements} variable; if @code{s} is followed by a decimal
11406 number, that is the upper bound instead. So for instance
11407 @samp{collect/s25 mystr} collects as many as 25 characters at
11410 The command @code{info scope} (@pxref{Symbols, info scope}) is
11411 particularly useful for figuring out what data to collect.
11413 @kindex teval @r{(tracepoints)}
11414 @item teval @var{expr1}, @var{expr2}, @dots{}
11415 Evaluate the given expressions when the tracepoint is hit. This
11416 command accepts a comma-separated list of expressions. The results
11417 are discarded, so this is mainly useful for assigning values to trace
11418 state variables (@pxref{Trace State Variables}) without adding those
11419 values to the trace buffer, as would be the case if the @code{collect}
11422 @kindex while-stepping @r{(tracepoints)}
11423 @item while-stepping @var{n}
11424 Perform @var{n} single-step instruction traces after the tracepoint,
11425 collecting new data after each step. The @code{while-stepping}
11426 command is followed by the list of what to collect while stepping
11427 (followed by its own @code{end} command):
11430 > while-stepping 12
11431 > collect $regs, myglobal
11437 Note that @code{$pc} is not automatically collected by
11438 @code{while-stepping}; you need to explicitly collect that register if
11439 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
11442 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
11443 @kindex set default-collect
11444 @cindex default collection action
11445 This variable is a list of expressions to collect at each tracepoint
11446 hit. It is effectively an additional @code{collect} action prepended
11447 to every tracepoint action list. The expressions are parsed
11448 individually for each tracepoint, so for instance a variable named
11449 @code{xyz} may be interpreted as a global for one tracepoint, and a
11450 local for another, as appropriate to the tracepoint's location.
11452 @item show default-collect
11453 @kindex show default-collect
11454 Show the list of expressions that are collected by default at each
11459 @node Listing Tracepoints
11460 @subsection Listing Tracepoints
11463 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
11464 @kindex info tp @r{[}@var{n}@dots{}@r{]}
11465 @cindex information about tracepoints
11466 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
11467 Display information about the tracepoint @var{num}. If you don't
11468 specify a tracepoint number, displays information about all the
11469 tracepoints defined so far. The format is similar to that used for
11470 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
11471 command, simply restricting itself to tracepoints.
11473 A tracepoint's listing may include additional information specific to
11478 its passcount as given by the @code{passcount @var{n}} command
11482 (@value{GDBP}) @b{info trace}
11483 Num Type Disp Enb Address What
11484 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
11486 collect globfoo, $regs
11495 This command can be abbreviated @code{info tp}.
11498 @node Listing Static Tracepoint Markers
11499 @subsection Listing Static Tracepoint Markers
11502 @kindex info static-tracepoint-markers
11503 @cindex information about static tracepoint markers
11504 @item info static-tracepoint-markers
11505 Display information about all static tracepoint markers defined in the
11508 For each marker, the following columns are printed:
11512 An incrementing counter, output to help readability. This is not a
11515 The marker ID, as reported by the target.
11516 @item Enabled or Disabled
11517 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
11518 that are not enabled.
11520 Where the marker is in your program, as a memory address.
11522 Where the marker is in the source for your program, as a file and line
11523 number. If the debug information included in the program does not
11524 allow @value{GDBN} to locate the source of the marker, this column
11525 will be left blank.
11529 In addition, the following information may be printed for each marker:
11533 User data passed to the tracing library by the marker call. In the
11534 UST backend, this is the format string passed as argument to the
11536 @item Static tracepoints probing the marker
11537 The list of static tracepoints attached to the marker.
11541 (@value{GDBP}) info static-tracepoint-markers
11542 Cnt ID Enb Address What
11543 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
11544 Data: number1 %d number2 %d
11545 Probed by static tracepoints: #2
11546 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
11552 @node Starting and Stopping Trace Experiments
11553 @subsection Starting and Stopping Trace Experiments
11556 @kindex tstart [ @var{notes} ]
11557 @cindex start a new trace experiment
11558 @cindex collected data discarded
11560 This command starts the trace experiment, and begins collecting data.
11561 It has the side effect of discarding all the data collected in the
11562 trace buffer during the previous trace experiment. If any arguments
11563 are supplied, they are taken as a note and stored with the trace
11564 experiment's state. The notes may be arbitrary text, and are
11565 especially useful with disconnected tracing in a multi-user context;
11566 the notes can explain what the trace is doing, supply user contact
11567 information, and so forth.
11569 @kindex tstop [ @var{notes} ]
11570 @cindex stop a running trace experiment
11572 This command stops the trace experiment. If any arguments are
11573 supplied, they are recorded with the experiment as a note. This is
11574 useful if you are stopping a trace started by someone else, for
11575 instance if the trace is interfering with the system's behavior and
11576 needs to be stopped quickly.
11578 @strong{Note}: a trace experiment and data collection may stop
11579 automatically if any tracepoint's passcount is reached
11580 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
11583 @cindex status of trace data collection
11584 @cindex trace experiment, status of
11586 This command displays the status of the current trace data
11590 Here is an example of the commands we described so far:
11593 (@value{GDBP}) @b{trace gdb_c_test}
11594 (@value{GDBP}) @b{actions}
11595 Enter actions for tracepoint #1, one per line.
11596 > collect $regs,$locals,$args
11597 > while-stepping 11
11601 (@value{GDBP}) @b{tstart}
11602 [time passes @dots{}]
11603 (@value{GDBP}) @b{tstop}
11606 @anchor{disconnected tracing}
11607 @cindex disconnected tracing
11608 You can choose to continue running the trace experiment even if
11609 @value{GDBN} disconnects from the target, voluntarily or
11610 involuntarily. For commands such as @code{detach}, the debugger will
11611 ask what you want to do with the trace. But for unexpected
11612 terminations (@value{GDBN} crash, network outage), it would be
11613 unfortunate to lose hard-won trace data, so the variable
11614 @code{disconnected-tracing} lets you decide whether the trace should
11615 continue running without @value{GDBN}.
11618 @item set disconnected-tracing on
11619 @itemx set disconnected-tracing off
11620 @kindex set disconnected-tracing
11621 Choose whether a tracing run should continue to run if @value{GDBN}
11622 has disconnected from the target. Note that @code{detach} or
11623 @code{quit} will ask you directly what to do about a running trace no
11624 matter what this variable's setting, so the variable is mainly useful
11625 for handling unexpected situations, such as loss of the network.
11627 @item show disconnected-tracing
11628 @kindex show disconnected-tracing
11629 Show the current choice for disconnected tracing.
11633 When you reconnect to the target, the trace experiment may or may not
11634 still be running; it might have filled the trace buffer in the
11635 meantime, or stopped for one of the other reasons. If it is running,
11636 it will continue after reconnection.
11638 Upon reconnection, the target will upload information about the
11639 tracepoints in effect. @value{GDBN} will then compare that
11640 information to the set of tracepoints currently defined, and attempt
11641 to match them up, allowing for the possibility that the numbers may
11642 have changed due to creation and deletion in the meantime. If one of
11643 the target's tracepoints does not match any in @value{GDBN}, the
11644 debugger will create a new tracepoint, so that you have a number with
11645 which to specify that tracepoint. This matching-up process is
11646 necessarily heuristic, and it may result in useless tracepoints being
11647 created; you may simply delete them if they are of no use.
11649 @cindex circular trace buffer
11650 If your target agent supports a @dfn{circular trace buffer}, then you
11651 can run a trace experiment indefinitely without filling the trace
11652 buffer; when space runs out, the agent deletes already-collected trace
11653 frames, oldest first, until there is enough room to continue
11654 collecting. This is especially useful if your tracepoints are being
11655 hit too often, and your trace gets terminated prematurely because the
11656 buffer is full. To ask for a circular trace buffer, simply set
11657 @samp{circular-trace-buffer} to on. You can set this at any time,
11658 including during tracing; if the agent can do it, it will change
11659 buffer handling on the fly, otherwise it will not take effect until
11663 @item set circular-trace-buffer on
11664 @itemx set circular-trace-buffer off
11665 @kindex set circular-trace-buffer
11666 Choose whether a tracing run should use a linear or circular buffer
11667 for trace data. A linear buffer will not lose any trace data, but may
11668 fill up prematurely, while a circular buffer will discard old trace
11669 data, but it will have always room for the latest tracepoint hits.
11671 @item show circular-trace-buffer
11672 @kindex show circular-trace-buffer
11673 Show the current choice for the trace buffer. Note that this may not
11674 match the agent's current buffer handling, nor is it guaranteed to
11675 match the setting that might have been in effect during a past run,
11676 for instance if you are looking at frames from a trace file.
11681 @item set trace-user @var{text}
11682 @kindex set trace-user
11684 @item show trace-user
11685 @kindex show trace-user
11687 @item set trace-notes @var{text}
11688 @kindex set trace-notes
11689 Set the trace run's notes.
11691 @item show trace-notes
11692 @kindex show trace-notes
11693 Show the trace run's notes.
11695 @item set trace-stop-notes @var{text}
11696 @kindex set trace-stop-notes
11697 Set the trace run's stop notes. The handling of the note is as for
11698 @code{tstop} arguments; the set command is convenient way to fix a
11699 stop note that is mistaken or incomplete.
11701 @item show trace-stop-notes
11702 @kindex show trace-stop-notes
11703 Show the trace run's stop notes.
11707 @node Tracepoint Restrictions
11708 @subsection Tracepoint Restrictions
11710 @cindex tracepoint restrictions
11711 There are a number of restrictions on the use of tracepoints. As
11712 described above, tracepoint data gathering occurs on the target
11713 without interaction from @value{GDBN}. Thus the full capabilities of
11714 the debugger are not available during data gathering, and then at data
11715 examination time, you will be limited by only having what was
11716 collected. The following items describe some common problems, but it
11717 is not exhaustive, and you may run into additional difficulties not
11723 Tracepoint expressions are intended to gather objects (lvalues). Thus
11724 the full flexibility of GDB's expression evaluator is not available.
11725 You cannot call functions, cast objects to aggregate types, access
11726 convenience variables or modify values (except by assignment to trace
11727 state variables). Some language features may implicitly call
11728 functions (for instance Objective-C fields with accessors), and therefore
11729 cannot be collected either.
11732 Collection of local variables, either individually or in bulk with
11733 @code{$locals} or @code{$args}, during @code{while-stepping} may
11734 behave erratically. The stepping action may enter a new scope (for
11735 instance by stepping into a function), or the location of the variable
11736 may change (for instance it is loaded into a register). The
11737 tracepoint data recorded uses the location information for the
11738 variables that is correct for the tracepoint location. When the
11739 tracepoint is created, it is not possible, in general, to determine
11740 where the steps of a @code{while-stepping} sequence will advance the
11741 program---particularly if a conditional branch is stepped.
11744 Collection of an incompletely-initialized or partially-destroyed object
11745 may result in something that @value{GDBN} cannot display, or displays
11746 in a misleading way.
11749 When @value{GDBN} displays a pointer to character it automatically
11750 dereferences the pointer to also display characters of the string
11751 being pointed to. However, collecting the pointer during tracing does
11752 not automatically collect the string. You need to explicitly
11753 dereference the pointer and provide size information if you want to
11754 collect not only the pointer, but the memory pointed to. For example,
11755 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11759 It is not possible to collect a complete stack backtrace at a
11760 tracepoint. Instead, you may collect the registers and a few hundred
11761 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11762 (adjust to use the name of the actual stack pointer register on your
11763 target architecture, and the amount of stack you wish to capture).
11764 Then the @code{backtrace} command will show a partial backtrace when
11765 using a trace frame. The number of stack frames that can be examined
11766 depends on the sizes of the frames in the collected stack. Note that
11767 if you ask for a block so large that it goes past the bottom of the
11768 stack, the target agent may report an error trying to read from an
11772 If you do not collect registers at a tracepoint, @value{GDBN} can
11773 infer that the value of @code{$pc} must be the same as the address of
11774 the tracepoint and use that when you are looking at a trace frame
11775 for that tracepoint. However, this cannot work if the tracepoint has
11776 multiple locations (for instance if it was set in a function that was
11777 inlined), or if it has a @code{while-stepping} loop. In those cases
11778 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11783 @node Analyze Collected Data
11784 @section Using the Collected Data
11786 After the tracepoint experiment ends, you use @value{GDBN} commands
11787 for examining the trace data. The basic idea is that each tracepoint
11788 collects a trace @dfn{snapshot} every time it is hit and another
11789 snapshot every time it single-steps. All these snapshots are
11790 consecutively numbered from zero and go into a buffer, and you can
11791 examine them later. The way you examine them is to @dfn{focus} on a
11792 specific trace snapshot. When the remote stub is focused on a trace
11793 snapshot, it will respond to all @value{GDBN} requests for memory and
11794 registers by reading from the buffer which belongs to that snapshot,
11795 rather than from @emph{real} memory or registers of the program being
11796 debugged. This means that @strong{all} @value{GDBN} commands
11797 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11798 behave as if we were currently debugging the program state as it was
11799 when the tracepoint occurred. Any requests for data that are not in
11800 the buffer will fail.
11803 * tfind:: How to select a trace snapshot
11804 * tdump:: How to display all data for a snapshot
11805 * save tracepoints:: How to save tracepoints for a future run
11809 @subsection @code{tfind @var{n}}
11812 @cindex select trace snapshot
11813 @cindex find trace snapshot
11814 The basic command for selecting a trace snapshot from the buffer is
11815 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11816 counting from zero. If no argument @var{n} is given, the next
11817 snapshot is selected.
11819 Here are the various forms of using the @code{tfind} command.
11823 Find the first snapshot in the buffer. This is a synonym for
11824 @code{tfind 0} (since 0 is the number of the first snapshot).
11827 Stop debugging trace snapshots, resume @emph{live} debugging.
11830 Same as @samp{tfind none}.
11833 No argument means find the next trace snapshot.
11836 Find the previous trace snapshot before the current one. This permits
11837 retracing earlier steps.
11839 @item tfind tracepoint @var{num}
11840 Find the next snapshot associated with tracepoint @var{num}. Search
11841 proceeds forward from the last examined trace snapshot. If no
11842 argument @var{num} is given, it means find the next snapshot collected
11843 for the same tracepoint as the current snapshot.
11845 @item tfind pc @var{addr}
11846 Find the next snapshot associated with the value @var{addr} of the
11847 program counter. Search proceeds forward from the last examined trace
11848 snapshot. If no argument @var{addr} is given, it means find the next
11849 snapshot with the same value of PC as the current snapshot.
11851 @item tfind outside @var{addr1}, @var{addr2}
11852 Find the next snapshot whose PC is outside the given range of
11853 addresses (exclusive).
11855 @item tfind range @var{addr1}, @var{addr2}
11856 Find the next snapshot whose PC is between @var{addr1} and
11857 @var{addr2} (inclusive).
11859 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11860 Find the next snapshot associated with the source line @var{n}. If
11861 the optional argument @var{file} is given, refer to line @var{n} in
11862 that source file. Search proceeds forward from the last examined
11863 trace snapshot. If no argument @var{n} is given, it means find the
11864 next line other than the one currently being examined; thus saying
11865 @code{tfind line} repeatedly can appear to have the same effect as
11866 stepping from line to line in a @emph{live} debugging session.
11869 The default arguments for the @code{tfind} commands are specifically
11870 designed to make it easy to scan through the trace buffer. For
11871 instance, @code{tfind} with no argument selects the next trace
11872 snapshot, and @code{tfind -} with no argument selects the previous
11873 trace snapshot. So, by giving one @code{tfind} command, and then
11874 simply hitting @key{RET} repeatedly you can examine all the trace
11875 snapshots in order. Or, by saying @code{tfind -} and then hitting
11876 @key{RET} repeatedly you can examine the snapshots in reverse order.
11877 The @code{tfind line} command with no argument selects the snapshot
11878 for the next source line executed. The @code{tfind pc} command with
11879 no argument selects the next snapshot with the same program counter
11880 (PC) as the current frame. The @code{tfind tracepoint} command with
11881 no argument selects the next trace snapshot collected by the same
11882 tracepoint as the current one.
11884 In addition to letting you scan through the trace buffer manually,
11885 these commands make it easy to construct @value{GDBN} scripts that
11886 scan through the trace buffer and print out whatever collected data
11887 you are interested in. Thus, if we want to examine the PC, FP, and SP
11888 registers from each trace frame in the buffer, we can say this:
11891 (@value{GDBP}) @b{tfind start}
11892 (@value{GDBP}) @b{while ($trace_frame != -1)}
11893 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11894 $trace_frame, $pc, $sp, $fp
11898 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11899 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11900 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11901 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11902 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11903 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11904 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11905 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11906 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11907 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11908 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11911 Or, if we want to examine the variable @code{X} at each source line in
11915 (@value{GDBP}) @b{tfind start}
11916 (@value{GDBP}) @b{while ($trace_frame != -1)}
11917 > printf "Frame %d, X == %d\n", $trace_frame, X
11927 @subsection @code{tdump}
11929 @cindex dump all data collected at tracepoint
11930 @cindex tracepoint data, display
11932 This command takes no arguments. It prints all the data collected at
11933 the current trace snapshot.
11936 (@value{GDBP}) @b{trace 444}
11937 (@value{GDBP}) @b{actions}
11938 Enter actions for tracepoint #2, one per line:
11939 > collect $regs, $locals, $args, gdb_long_test
11942 (@value{GDBP}) @b{tstart}
11944 (@value{GDBP}) @b{tfind line 444}
11945 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11947 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11949 (@value{GDBP}) @b{tdump}
11950 Data collected at tracepoint 2, trace frame 1:
11951 d0 0xc4aa0085 -995491707
11955 d4 0x71aea3d 119204413
11958 d7 0x380035 3670069
11959 a0 0x19e24a 1696330
11960 a1 0x3000668 50333288
11962 a3 0x322000 3284992
11963 a4 0x3000698 50333336
11964 a5 0x1ad3cc 1758156
11965 fp 0x30bf3c 0x30bf3c
11966 sp 0x30bf34 0x30bf34
11968 pc 0x20b2c8 0x20b2c8
11972 p = 0x20e5b4 "gdb-test"
11979 gdb_long_test = 17 '\021'
11984 @code{tdump} works by scanning the tracepoint's current collection
11985 actions and printing the value of each expression listed. So
11986 @code{tdump} can fail, if after a run, you change the tracepoint's
11987 actions to mention variables that were not collected during the run.
11989 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11990 uses the collected value of @code{$pc} to distinguish between trace
11991 frames that were collected at the tracepoint hit, and frames that were
11992 collected while stepping. This allows it to correctly choose whether
11993 to display the basic list of collections, or the collections from the
11994 body of the while-stepping loop. However, if @code{$pc} was not collected,
11995 then @code{tdump} will always attempt to dump using the basic collection
11996 list, and may fail if a while-stepping frame does not include all the
11997 same data that is collected at the tracepoint hit.
11998 @c This is getting pretty arcane, example would be good.
12000 @node save tracepoints
12001 @subsection @code{save tracepoints @var{filename}}
12002 @kindex save tracepoints
12003 @kindex save-tracepoints
12004 @cindex save tracepoints for future sessions
12006 This command saves all current tracepoint definitions together with
12007 their actions and passcounts, into a file @file{@var{filename}}
12008 suitable for use in a later debugging session. To read the saved
12009 tracepoint definitions, use the @code{source} command (@pxref{Command
12010 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12011 alias for @w{@code{save tracepoints}}
12013 @node Tracepoint Variables
12014 @section Convenience Variables for Tracepoints
12015 @cindex tracepoint variables
12016 @cindex convenience variables for tracepoints
12019 @vindex $trace_frame
12020 @item (int) $trace_frame
12021 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12022 snapshot is selected.
12024 @vindex $tracepoint
12025 @item (int) $tracepoint
12026 The tracepoint for the current trace snapshot.
12028 @vindex $trace_line
12029 @item (int) $trace_line
12030 The line number for the current trace snapshot.
12032 @vindex $trace_file
12033 @item (char []) $trace_file
12034 The source file for the current trace snapshot.
12036 @vindex $trace_func
12037 @item (char []) $trace_func
12038 The name of the function containing @code{$tracepoint}.
12041 Note: @code{$trace_file} is not suitable for use in @code{printf},
12042 use @code{output} instead.
12044 Here's a simple example of using these convenience variables for
12045 stepping through all the trace snapshots and printing some of their
12046 data. Note that these are not the same as trace state variables,
12047 which are managed by the target.
12050 (@value{GDBP}) @b{tfind start}
12052 (@value{GDBP}) @b{while $trace_frame != -1}
12053 > output $trace_file
12054 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12060 @section Using Trace Files
12061 @cindex trace files
12063 In some situations, the target running a trace experiment may no
12064 longer be available; perhaps it crashed, or the hardware was needed
12065 for a different activity. To handle these cases, you can arrange to
12066 dump the trace data into a file, and later use that file as a source
12067 of trace data, via the @code{target tfile} command.
12072 @item tsave [ -r ] @var{filename}
12073 Save the trace data to @var{filename}. By default, this command
12074 assumes that @var{filename} refers to the host filesystem, so if
12075 necessary @value{GDBN} will copy raw trace data up from the target and
12076 then save it. If the target supports it, you can also supply the
12077 optional argument @code{-r} (``remote'') to direct the target to save
12078 the data directly into @var{filename} in its own filesystem, which may be
12079 more efficient if the trace buffer is very large. (Note, however, that
12080 @code{target tfile} can only read from files accessible to the host.)
12082 @kindex target tfile
12084 @item target tfile @var{filename}
12085 Use the file named @var{filename} as a source of trace data. Commands
12086 that examine data work as they do with a live target, but it is not
12087 possible to run any new trace experiments. @code{tstatus} will report
12088 the state of the trace run at the moment the data was saved, as well
12089 as the current trace frame you are examining. @var{filename} must be
12090 on a filesystem accessible to the host.
12095 @chapter Debugging Programs That Use Overlays
12098 If your program is too large to fit completely in your target system's
12099 memory, you can sometimes use @dfn{overlays} to work around this
12100 problem. @value{GDBN} provides some support for debugging programs that
12104 * How Overlays Work:: A general explanation of overlays.
12105 * Overlay Commands:: Managing overlays in @value{GDBN}.
12106 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12107 mapped by asking the inferior.
12108 * Overlay Sample Program:: A sample program using overlays.
12111 @node How Overlays Work
12112 @section How Overlays Work
12113 @cindex mapped overlays
12114 @cindex unmapped overlays
12115 @cindex load address, overlay's
12116 @cindex mapped address
12117 @cindex overlay area
12119 Suppose you have a computer whose instruction address space is only 64
12120 kilobytes long, but which has much more memory which can be accessed by
12121 other means: special instructions, segment registers, or memory
12122 management hardware, for example. Suppose further that you want to
12123 adapt a program which is larger than 64 kilobytes to run on this system.
12125 One solution is to identify modules of your program which are relatively
12126 independent, and need not call each other directly; call these modules
12127 @dfn{overlays}. Separate the overlays from the main program, and place
12128 their machine code in the larger memory. Place your main program in
12129 instruction memory, but leave at least enough space there to hold the
12130 largest overlay as well.
12132 Now, to call a function located in an overlay, you must first copy that
12133 overlay's machine code from the large memory into the space set aside
12134 for it in the instruction memory, and then jump to its entry point
12137 @c NB: In the below the mapped area's size is greater or equal to the
12138 @c size of all overlays. This is intentional to remind the developer
12139 @c that overlays don't necessarily need to be the same size.
12143 Data Instruction Larger
12144 Address Space Address Space Address Space
12145 +-----------+ +-----------+ +-----------+
12147 +-----------+ +-----------+ +-----------+<-- overlay 1
12148 | program | | main | .----| overlay 1 | load address
12149 | variables | | program | | +-----------+
12150 | and heap | | | | | |
12151 +-----------+ | | | +-----------+<-- overlay 2
12152 | | +-----------+ | | | load address
12153 +-----------+ | | | .-| overlay 2 |
12155 mapped --->+-----------+ | | +-----------+
12156 address | | | | | |
12157 | overlay | <-' | | |
12158 | area | <---' +-----------+<-- overlay 3
12159 | | <---. | | load address
12160 +-----------+ `--| overlay 3 |
12167 @anchor{A code overlay}A code overlay
12171 The diagram (@pxref{A code overlay}) shows a system with separate data
12172 and instruction address spaces. To map an overlay, the program copies
12173 its code from the larger address space to the instruction address space.
12174 Since the overlays shown here all use the same mapped address, only one
12175 may be mapped at a time. For a system with a single address space for
12176 data and instructions, the diagram would be similar, except that the
12177 program variables and heap would share an address space with the main
12178 program and the overlay area.
12180 An overlay loaded into instruction memory and ready for use is called a
12181 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12182 instruction memory. An overlay not present (or only partially present)
12183 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12184 is its address in the larger memory. The mapped address is also called
12185 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12186 called the @dfn{load memory address}, or @dfn{LMA}.
12188 Unfortunately, overlays are not a completely transparent way to adapt a
12189 program to limited instruction memory. They introduce a new set of
12190 global constraints you must keep in mind as you design your program:
12195 Before calling or returning to a function in an overlay, your program
12196 must make sure that overlay is actually mapped. Otherwise, the call or
12197 return will transfer control to the right address, but in the wrong
12198 overlay, and your program will probably crash.
12201 If the process of mapping an overlay is expensive on your system, you
12202 will need to choose your overlays carefully to minimize their effect on
12203 your program's performance.
12206 The executable file you load onto your system must contain each
12207 overlay's instructions, appearing at the overlay's load address, not its
12208 mapped address. However, each overlay's instructions must be relocated
12209 and its symbols defined as if the overlay were at its mapped address.
12210 You can use GNU linker scripts to specify different load and relocation
12211 addresses for pieces of your program; see @ref{Overlay Description,,,
12212 ld.info, Using ld: the GNU linker}.
12215 The procedure for loading executable files onto your system must be able
12216 to load their contents into the larger address space as well as the
12217 instruction and data spaces.
12221 The overlay system described above is rather simple, and could be
12222 improved in many ways:
12227 If your system has suitable bank switch registers or memory management
12228 hardware, you could use those facilities to make an overlay's load area
12229 contents simply appear at their mapped address in instruction space.
12230 This would probably be faster than copying the overlay to its mapped
12231 area in the usual way.
12234 If your overlays are small enough, you could set aside more than one
12235 overlay area, and have more than one overlay mapped at a time.
12238 You can use overlays to manage data, as well as instructions. In
12239 general, data overlays are even less transparent to your design than
12240 code overlays: whereas code overlays only require care when you call or
12241 return to functions, data overlays require care every time you access
12242 the data. Also, if you change the contents of a data overlay, you
12243 must copy its contents back out to its load address before you can copy a
12244 different data overlay into the same mapped area.
12249 @node Overlay Commands
12250 @section Overlay Commands
12252 To use @value{GDBN}'s overlay support, each overlay in your program must
12253 correspond to a separate section of the executable file. The section's
12254 virtual memory address and load memory address must be the overlay's
12255 mapped and load addresses. Identifying overlays with sections allows
12256 @value{GDBN} to determine the appropriate address of a function or
12257 variable, depending on whether the overlay is mapped or not.
12259 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12260 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12265 Disable @value{GDBN}'s overlay support. When overlay support is
12266 disabled, @value{GDBN} assumes that all functions and variables are
12267 always present at their mapped addresses. By default, @value{GDBN}'s
12268 overlay support is disabled.
12270 @item overlay manual
12271 @cindex manual overlay debugging
12272 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12273 relies on you to tell it which overlays are mapped, and which are not,
12274 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12275 commands described below.
12277 @item overlay map-overlay @var{overlay}
12278 @itemx overlay map @var{overlay}
12279 @cindex map an overlay
12280 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12281 be the name of the object file section containing the overlay. When an
12282 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12283 functions and variables at their mapped addresses. @value{GDBN} assumes
12284 that any other overlays whose mapped ranges overlap that of
12285 @var{overlay} are now unmapped.
12287 @item overlay unmap-overlay @var{overlay}
12288 @itemx overlay unmap @var{overlay}
12289 @cindex unmap an overlay
12290 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
12291 must be the name of the object file section containing the overlay.
12292 When an overlay is unmapped, @value{GDBN} assumes it can find the
12293 overlay's functions and variables at their load addresses.
12296 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
12297 consults a data structure the overlay manager maintains in the inferior
12298 to see which overlays are mapped. For details, see @ref{Automatic
12299 Overlay Debugging}.
12301 @item overlay load-target
12302 @itemx overlay load
12303 @cindex reloading the overlay table
12304 Re-read the overlay table from the inferior. Normally, @value{GDBN}
12305 re-reads the table @value{GDBN} automatically each time the inferior
12306 stops, so this command should only be necessary if you have changed the
12307 overlay mapping yourself using @value{GDBN}. This command is only
12308 useful when using automatic overlay debugging.
12310 @item overlay list-overlays
12311 @itemx overlay list
12312 @cindex listing mapped overlays
12313 Display a list of the overlays currently mapped, along with their mapped
12314 addresses, load addresses, and sizes.
12318 Normally, when @value{GDBN} prints a code address, it includes the name
12319 of the function the address falls in:
12322 (@value{GDBP}) print main
12323 $3 = @{int ()@} 0x11a0 <main>
12326 When overlay debugging is enabled, @value{GDBN} recognizes code in
12327 unmapped overlays, and prints the names of unmapped functions with
12328 asterisks around them. For example, if @code{foo} is a function in an
12329 unmapped overlay, @value{GDBN} prints it this way:
12332 (@value{GDBP}) overlay list
12333 No sections are mapped.
12334 (@value{GDBP}) print foo
12335 $5 = @{int (int)@} 0x100000 <*foo*>
12338 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
12342 (@value{GDBP}) overlay list
12343 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
12344 mapped at 0x1016 - 0x104a
12345 (@value{GDBP}) print foo
12346 $6 = @{int (int)@} 0x1016 <foo>
12349 When overlay debugging is enabled, @value{GDBN} can find the correct
12350 address for functions and variables in an overlay, whether or not the
12351 overlay is mapped. This allows most @value{GDBN} commands, like
12352 @code{break} and @code{disassemble}, to work normally, even on unmapped
12353 code. However, @value{GDBN}'s breakpoint support has some limitations:
12357 @cindex breakpoints in overlays
12358 @cindex overlays, setting breakpoints in
12359 You can set breakpoints in functions in unmapped overlays, as long as
12360 @value{GDBN} can write to the overlay at its load address.
12362 @value{GDBN} can not set hardware or simulator-based breakpoints in
12363 unmapped overlays. However, if you set a breakpoint at the end of your
12364 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
12365 you are using manual overlay management), @value{GDBN} will re-set its
12366 breakpoints properly.
12370 @node Automatic Overlay Debugging
12371 @section Automatic Overlay Debugging
12372 @cindex automatic overlay debugging
12374 @value{GDBN} can automatically track which overlays are mapped and which
12375 are not, given some simple co-operation from the overlay manager in the
12376 inferior. If you enable automatic overlay debugging with the
12377 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
12378 looks in the inferior's memory for certain variables describing the
12379 current state of the overlays.
12381 Here are the variables your overlay manager must define to support
12382 @value{GDBN}'s automatic overlay debugging:
12386 @item @code{_ovly_table}:
12387 This variable must be an array of the following structures:
12392 /* The overlay's mapped address. */
12395 /* The size of the overlay, in bytes. */
12396 unsigned long size;
12398 /* The overlay's load address. */
12401 /* Non-zero if the overlay is currently mapped;
12403 unsigned long mapped;
12407 @item @code{_novlys}:
12408 This variable must be a four-byte signed integer, holding the total
12409 number of elements in @code{_ovly_table}.
12413 To decide whether a particular overlay is mapped or not, @value{GDBN}
12414 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
12415 @code{lma} members equal the VMA and LMA of the overlay's section in the
12416 executable file. When @value{GDBN} finds a matching entry, it consults
12417 the entry's @code{mapped} member to determine whether the overlay is
12420 In addition, your overlay manager may define a function called
12421 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
12422 will silently set a breakpoint there. If the overlay manager then
12423 calls this function whenever it has changed the overlay table, this
12424 will enable @value{GDBN} to accurately keep track of which overlays
12425 are in program memory, and update any breakpoints that may be set
12426 in overlays. This will allow breakpoints to work even if the
12427 overlays are kept in ROM or other non-writable memory while they
12428 are not being executed.
12430 @node Overlay Sample Program
12431 @section Overlay Sample Program
12432 @cindex overlay example program
12434 When linking a program which uses overlays, you must place the overlays
12435 at their load addresses, while relocating them to run at their mapped
12436 addresses. To do this, you must write a linker script (@pxref{Overlay
12437 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
12438 since linker scripts are specific to a particular host system, target
12439 architecture, and target memory layout, this manual cannot provide
12440 portable sample code demonstrating @value{GDBN}'s overlay support.
12442 However, the @value{GDBN} source distribution does contain an overlaid
12443 program, with linker scripts for a few systems, as part of its test
12444 suite. The program consists of the following files from
12445 @file{gdb/testsuite/gdb.base}:
12449 The main program file.
12451 A simple overlay manager, used by @file{overlays.c}.
12456 Overlay modules, loaded and used by @file{overlays.c}.
12459 Linker scripts for linking the test program on the @code{d10v-elf}
12460 and @code{m32r-elf} targets.
12463 You can build the test program using the @code{d10v-elf} GCC
12464 cross-compiler like this:
12467 $ d10v-elf-gcc -g -c overlays.c
12468 $ d10v-elf-gcc -g -c ovlymgr.c
12469 $ d10v-elf-gcc -g -c foo.c
12470 $ d10v-elf-gcc -g -c bar.c
12471 $ d10v-elf-gcc -g -c baz.c
12472 $ d10v-elf-gcc -g -c grbx.c
12473 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
12474 baz.o grbx.o -Wl,-Td10v.ld -o overlays
12477 The build process is identical for any other architecture, except that
12478 you must substitute the appropriate compiler and linker script for the
12479 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
12483 @chapter Using @value{GDBN} with Different Languages
12486 Although programming languages generally have common aspects, they are
12487 rarely expressed in the same manner. For instance, in ANSI C,
12488 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
12489 Modula-2, it is accomplished by @code{p^}. Values can also be
12490 represented (and displayed) differently. Hex numbers in C appear as
12491 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
12493 @cindex working language
12494 Language-specific information is built into @value{GDBN} for some languages,
12495 allowing you to express operations like the above in your program's
12496 native language, and allowing @value{GDBN} to output values in a manner
12497 consistent with the syntax of your program's native language. The
12498 language you use to build expressions is called the @dfn{working
12502 * Setting:: Switching between source languages
12503 * Show:: Displaying the language
12504 * Checks:: Type and range checks
12505 * Supported Languages:: Supported languages
12506 * Unsupported Languages:: Unsupported languages
12510 @section Switching Between Source Languages
12512 There are two ways to control the working language---either have @value{GDBN}
12513 set it automatically, or select it manually yourself. You can use the
12514 @code{set language} command for either purpose. On startup, @value{GDBN}
12515 defaults to setting the language automatically. The working language is
12516 used to determine how expressions you type are interpreted, how values
12519 In addition to the working language, every source file that
12520 @value{GDBN} knows about has its own working language. For some object
12521 file formats, the compiler might indicate which language a particular
12522 source file is in. However, most of the time @value{GDBN} infers the
12523 language from the name of the file. The language of a source file
12524 controls whether C@t{++} names are demangled---this way @code{backtrace} can
12525 show each frame appropriately for its own language. There is no way to
12526 set the language of a source file from within @value{GDBN}, but you can
12527 set the language associated with a filename extension. @xref{Show, ,
12528 Displaying the Language}.
12530 This is most commonly a problem when you use a program, such
12531 as @code{cfront} or @code{f2c}, that generates C but is written in
12532 another language. In that case, make the
12533 program use @code{#line} directives in its C output; that way
12534 @value{GDBN} will know the correct language of the source code of the original
12535 program, and will display that source code, not the generated C code.
12538 * Filenames:: Filename extensions and languages.
12539 * Manually:: Setting the working language manually
12540 * Automatically:: Having @value{GDBN} infer the source language
12544 @subsection List of Filename Extensions and Languages
12546 If a source file name ends in one of the following extensions, then
12547 @value{GDBN} infers that its language is the one indicated.
12565 C@t{++} source file
12571 Objective-C source file
12575 Fortran source file
12578 Modula-2 source file
12582 Assembler source file. This actually behaves almost like C, but
12583 @value{GDBN} does not skip over function prologues when stepping.
12586 In addition, you may set the language associated with a filename
12587 extension. @xref{Show, , Displaying the Language}.
12590 @subsection Setting the Working Language
12592 If you allow @value{GDBN} to set the language automatically,
12593 expressions are interpreted the same way in your debugging session and
12596 @kindex set language
12597 If you wish, you may set the language manually. To do this, issue the
12598 command @samp{set language @var{lang}}, where @var{lang} is the name of
12599 a language, such as
12600 @code{c} or @code{modula-2}.
12601 For a list of the supported languages, type @samp{set language}.
12603 Setting the language manually prevents @value{GDBN} from updating the working
12604 language automatically. This can lead to confusion if you try
12605 to debug a program when the working language is not the same as the
12606 source language, when an expression is acceptable to both
12607 languages---but means different things. For instance, if the current
12608 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12616 might not have the effect you intended. In C, this means to add
12617 @code{b} and @code{c} and place the result in @code{a}. The result
12618 printed would be the value of @code{a}. In Modula-2, this means to compare
12619 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12621 @node Automatically
12622 @subsection Having @value{GDBN} Infer the Source Language
12624 To have @value{GDBN} set the working language automatically, use
12625 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12626 then infers the working language. That is, when your program stops in a
12627 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12628 working language to the language recorded for the function in that
12629 frame. If the language for a frame is unknown (that is, if the function
12630 or block corresponding to the frame was defined in a source file that
12631 does not have a recognized extension), the current working language is
12632 not changed, and @value{GDBN} issues a warning.
12634 This may not seem necessary for most programs, which are written
12635 entirely in one source language. However, program modules and libraries
12636 written in one source language can be used by a main program written in
12637 a different source language. Using @samp{set language auto} in this
12638 case frees you from having to set the working language manually.
12641 @section Displaying the Language
12643 The following commands help you find out which language is the
12644 working language, and also what language source files were written in.
12647 @item show language
12648 @kindex show language
12649 Display the current working language. This is the
12650 language you can use with commands such as @code{print} to
12651 build and compute expressions that may involve variables in your program.
12654 @kindex info frame@r{, show the source language}
12655 Display the source language for this frame. This language becomes the
12656 working language if you use an identifier from this frame.
12657 @xref{Frame Info, ,Information about a Frame}, to identify the other
12658 information listed here.
12661 @kindex info source@r{, show the source language}
12662 Display the source language of this source file.
12663 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12664 information listed here.
12667 In unusual circumstances, you may have source files with extensions
12668 not in the standard list. You can then set the extension associated
12669 with a language explicitly:
12672 @item set extension-language @var{ext} @var{language}
12673 @kindex set extension-language
12674 Tell @value{GDBN} that source files with extension @var{ext} are to be
12675 assumed as written in the source language @var{language}.
12677 @item info extensions
12678 @kindex info extensions
12679 List all the filename extensions and the associated languages.
12683 @section Type and Range Checking
12685 Some languages are designed to guard you against making seemingly common
12686 errors through a series of compile- and run-time checks. These include
12687 checking the type of arguments to functions and operators and making
12688 sure mathematical overflows are caught at run time. Checks such as
12689 these help to ensure a program's correctness once it has been compiled
12690 by eliminating type mismatches and providing active checks for range
12691 errors when your program is running.
12693 By default @value{GDBN} checks for these errors according to the
12694 rules of the current source language. Although @value{GDBN} does not check
12695 the statements in your program, it can check expressions entered directly
12696 into @value{GDBN} for evaluation via the @code{print} command, for example.
12699 * Type Checking:: An overview of type checking
12700 * Range Checking:: An overview of range checking
12703 @cindex type checking
12704 @cindex checks, type
12705 @node Type Checking
12706 @subsection An Overview of Type Checking
12708 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
12709 arguments to operators and functions have to be of the correct type,
12710 otherwise an error occurs. These checks prevent type mismatch
12711 errors from ever causing any run-time problems. For example,
12714 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
12716 (@value{GDBP}) print obj.my_method (0)
12719 (@value{GDBP}) print obj.my_method (0x1234)
12720 Cannot resolve method klass::my_method to any overloaded instance
12723 The second example fails because in C@t{++} the integer constant
12724 @samp{0x1234} is not type-compatible with the pointer parameter type.
12726 For the expressions you use in @value{GDBN} commands, you can tell
12727 @value{GDBN} to not enforce strict type checking or
12728 to treat any mismatches as errors and abandon the expression;
12729 When type checking is disabled, @value{GDBN} successfully evaluates
12730 expressions like the second example above.
12732 Even if type checking is off, there may be other reasons
12733 related to type that prevent @value{GDBN} from evaluating an expression.
12734 For instance, @value{GDBN} does not know how to add an @code{int} and
12735 a @code{struct foo}. These particular type errors have nothing to do
12736 with the language in use and usually arise from expressions which make
12737 little sense to evaluate anyway.
12739 @value{GDBN} provides some additional commands for controlling type checking:
12741 @kindex set check type
12742 @kindex show check type
12744 @item set check type on
12745 @itemx set check type off
12746 Set strict type checking on or off. If any type mismatches occur in
12747 evaluating an expression while type checking is on, @value{GDBN} prints a
12748 message and aborts evaluation of the expression.
12750 @item show check type
12751 Show the current setting of type checking and whether @value{GDBN}
12752 is enforcing strict type checking rules.
12755 @cindex range checking
12756 @cindex checks, range
12757 @node Range Checking
12758 @subsection An Overview of Range Checking
12760 In some languages (such as Modula-2), it is an error to exceed the
12761 bounds of a type; this is enforced with run-time checks. Such range
12762 checking is meant to ensure program correctness by making sure
12763 computations do not overflow, or indices on an array element access do
12764 not exceed the bounds of the array.
12766 For expressions you use in @value{GDBN} commands, you can tell
12767 @value{GDBN} to treat range errors in one of three ways: ignore them,
12768 always treat them as errors and abandon the expression, or issue
12769 warnings but evaluate the expression anyway.
12771 A range error can result from numerical overflow, from exceeding an
12772 array index bound, or when you type a constant that is not a member
12773 of any type. Some languages, however, do not treat overflows as an
12774 error. In many implementations of C, mathematical overflow causes the
12775 result to ``wrap around'' to lower values---for example, if @var{m} is
12776 the largest integer value, and @var{s} is the smallest, then
12779 @var{m} + 1 @result{} @var{s}
12782 This, too, is specific to individual languages, and in some cases
12783 specific to individual compilers or machines. @xref{Supported Languages, ,
12784 Supported Languages}, for further details on specific languages.
12786 @value{GDBN} provides some additional commands for controlling the range checker:
12788 @kindex set check range
12789 @kindex show check range
12791 @item set check range auto
12792 Set range checking on or off based on the current working language.
12793 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12796 @item set check range on
12797 @itemx set check range off
12798 Set range checking on or off, overriding the default setting for the
12799 current working language. A warning is issued if the setting does not
12800 match the language default. If a range error occurs and range checking is on,
12801 then a message is printed and evaluation of the expression is aborted.
12803 @item set check range warn
12804 Output messages when the @value{GDBN} range checker detects a range error,
12805 but attempt to evaluate the expression anyway. Evaluating the
12806 expression may still be impossible for other reasons, such as accessing
12807 memory that the process does not own (a typical example from many Unix
12811 Show the current setting of the range checker, and whether or not it is
12812 being set automatically by @value{GDBN}.
12815 @node Supported Languages
12816 @section Supported Languages
12818 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
12819 OpenCL C, Pascal, assembly, Modula-2, and Ada.
12820 @c This is false ...
12821 Some @value{GDBN} features may be used in expressions regardless of the
12822 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12823 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12824 ,Expressions}) can be used with the constructs of any supported
12827 The following sections detail to what degree each source language is
12828 supported by @value{GDBN}. These sections are not meant to be language
12829 tutorials or references, but serve only as a reference guide to what the
12830 @value{GDBN} expression parser accepts, and what input and output
12831 formats should look like for different languages. There are many good
12832 books written on each of these languages; please look to these for a
12833 language reference or tutorial.
12836 * C:: C and C@t{++}
12839 * Objective-C:: Objective-C
12840 * OpenCL C:: OpenCL C
12841 * Fortran:: Fortran
12843 * Modula-2:: Modula-2
12848 @subsection C and C@t{++}
12850 @cindex C and C@t{++}
12851 @cindex expressions in C or C@t{++}
12853 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12854 to both languages. Whenever this is the case, we discuss those languages
12858 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12859 @cindex @sc{gnu} C@t{++}
12860 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12861 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12862 effectively, you must compile your C@t{++} programs with a supported
12863 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12864 compiler (@code{aCC}).
12867 * C Operators:: C and C@t{++} operators
12868 * C Constants:: C and C@t{++} constants
12869 * C Plus Plus Expressions:: C@t{++} expressions
12870 * C Defaults:: Default settings for C and C@t{++}
12871 * C Checks:: C and C@t{++} type and range checks
12872 * Debugging C:: @value{GDBN} and C
12873 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12874 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12878 @subsubsection C and C@t{++} Operators
12880 @cindex C and C@t{++} operators
12882 Operators must be defined on values of specific types. For instance,
12883 @code{+} is defined on numbers, but not on structures. Operators are
12884 often defined on groups of types.
12886 For the purposes of C and C@t{++}, the following definitions hold:
12891 @emph{Integral types} include @code{int} with any of its storage-class
12892 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12895 @emph{Floating-point types} include @code{float}, @code{double}, and
12896 @code{long double} (if supported by the target platform).
12899 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12902 @emph{Scalar types} include all of the above.
12907 The following operators are supported. They are listed here
12908 in order of increasing precedence:
12912 The comma or sequencing operator. Expressions in a comma-separated list
12913 are evaluated from left to right, with the result of the entire
12914 expression being the last expression evaluated.
12917 Assignment. The value of an assignment expression is the value
12918 assigned. Defined on scalar types.
12921 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12922 and translated to @w{@code{@var{a} = @var{a op b}}}.
12923 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12924 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12925 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12928 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12929 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12933 Logical @sc{or}. Defined on integral types.
12936 Logical @sc{and}. Defined on integral types.
12939 Bitwise @sc{or}. Defined on integral types.
12942 Bitwise exclusive-@sc{or}. Defined on integral types.
12945 Bitwise @sc{and}. Defined on integral types.
12948 Equality and inequality. Defined on scalar types. The value of these
12949 expressions is 0 for false and non-zero for true.
12951 @item <@r{, }>@r{, }<=@r{, }>=
12952 Less than, greater than, less than or equal, greater than or equal.
12953 Defined on scalar types. The value of these expressions is 0 for false
12954 and non-zero for true.
12957 left shift, and right shift. Defined on integral types.
12960 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12963 Addition and subtraction. Defined on integral types, floating-point types and
12966 @item *@r{, }/@r{, }%
12967 Multiplication, division, and modulus. Multiplication and division are
12968 defined on integral and floating-point types. Modulus is defined on
12972 Increment and decrement. When appearing before a variable, the
12973 operation is performed before the variable is used in an expression;
12974 when appearing after it, the variable's value is used before the
12975 operation takes place.
12978 Pointer dereferencing. Defined on pointer types. Same precedence as
12982 Address operator. Defined on variables. Same precedence as @code{++}.
12984 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
12985 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
12986 to examine the address
12987 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
12991 Negative. Defined on integral and floating-point types. Same
12992 precedence as @code{++}.
12995 Logical negation. Defined on integral types. Same precedence as
12999 Bitwise complement operator. Defined on integral types. Same precedence as
13004 Structure member, and pointer-to-structure member. For convenience,
13005 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13006 pointer based on the stored type information.
13007 Defined on @code{struct} and @code{union} data.
13010 Dereferences of pointers to members.
13013 Array indexing. @code{@var{a}[@var{i}]} is defined as
13014 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13017 Function parameter list. Same precedence as @code{->}.
13020 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13021 and @code{class} types.
13024 Doubled colons also represent the @value{GDBN} scope operator
13025 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13029 If an operator is redefined in the user code, @value{GDBN} usually
13030 attempts to invoke the redefined version instead of using the operator's
13031 predefined meaning.
13034 @subsubsection C and C@t{++} Constants
13036 @cindex C and C@t{++} constants
13038 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13043 Integer constants are a sequence of digits. Octal constants are
13044 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13045 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13046 @samp{l}, specifying that the constant should be treated as a
13050 Floating point constants are a sequence of digits, followed by a decimal
13051 point, followed by a sequence of digits, and optionally followed by an
13052 exponent. An exponent is of the form:
13053 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13054 sequence of digits. The @samp{+} is optional for positive exponents.
13055 A floating-point constant may also end with a letter @samp{f} or
13056 @samp{F}, specifying that the constant should be treated as being of
13057 the @code{float} (as opposed to the default @code{double}) type; or with
13058 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13062 Enumerated constants consist of enumerated identifiers, or their
13063 integral equivalents.
13066 Character constants are a single character surrounded by single quotes
13067 (@code{'}), or a number---the ordinal value of the corresponding character
13068 (usually its @sc{ascii} value). Within quotes, the single character may
13069 be represented by a letter or by @dfn{escape sequences}, which are of
13070 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13071 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13072 @samp{@var{x}} is a predefined special character---for example,
13073 @samp{\n} for newline.
13075 Wide character constants can be written by prefixing a character
13076 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13077 form of @samp{x}. The target wide character set is used when
13078 computing the value of this constant (@pxref{Character Sets}).
13081 String constants are a sequence of character constants surrounded by
13082 double quotes (@code{"}). Any valid character constant (as described
13083 above) may appear. Double quotes within the string must be preceded by
13084 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13087 Wide string constants can be written by prefixing a string constant
13088 with @samp{L}, as in C. The target wide character set is used when
13089 computing the value of this constant (@pxref{Character Sets}).
13092 Pointer constants are an integral value. You can also write pointers
13093 to constants using the C operator @samp{&}.
13096 Array constants are comma-separated lists surrounded by braces @samp{@{}
13097 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13098 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13099 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13102 @node C Plus Plus Expressions
13103 @subsubsection C@t{++} Expressions
13105 @cindex expressions in C@t{++}
13106 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13108 @cindex debugging C@t{++} programs
13109 @cindex C@t{++} compilers
13110 @cindex debug formats and C@t{++}
13111 @cindex @value{NGCC} and C@t{++}
13113 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13114 the proper compiler and the proper debug format. Currently,
13115 @value{GDBN} works best when debugging C@t{++} code that is compiled
13116 with the most recent version of @value{NGCC} possible. The DWARF
13117 debugging format is preferred; @value{NGCC} defaults to this on most
13118 popular platforms. Other compilers and/or debug formats are likely to
13119 work badly or not at all when using @value{GDBN} to debug C@t{++}
13120 code. @xref{Compilation}.
13125 @cindex member functions
13127 Member function calls are allowed; you can use expressions like
13130 count = aml->GetOriginal(x, y)
13133 @vindex this@r{, inside C@t{++} member functions}
13134 @cindex namespace in C@t{++}
13136 While a member function is active (in the selected stack frame), your
13137 expressions have the same namespace available as the member function;
13138 that is, @value{GDBN} allows implicit references to the class instance
13139 pointer @code{this} following the same rules as C@t{++}. @code{using}
13140 declarations in the current scope are also respected by @value{GDBN}.
13142 @cindex call overloaded functions
13143 @cindex overloaded functions, calling
13144 @cindex type conversions in C@t{++}
13146 You can call overloaded functions; @value{GDBN} resolves the function
13147 call to the right definition, with some restrictions. @value{GDBN} does not
13148 perform overload resolution involving user-defined type conversions,
13149 calls to constructors, or instantiations of templates that do not exist
13150 in the program. It also cannot handle ellipsis argument lists or
13153 It does perform integral conversions and promotions, floating-point
13154 promotions, arithmetic conversions, pointer conversions, conversions of
13155 class objects to base classes, and standard conversions such as those of
13156 functions or arrays to pointers; it requires an exact match on the
13157 number of function arguments.
13159 Overload resolution is always performed, unless you have specified
13160 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13161 ,@value{GDBN} Features for C@t{++}}.
13163 You must specify @code{set overload-resolution off} in order to use an
13164 explicit function signature to call an overloaded function, as in
13166 p 'foo(char,int)'('x', 13)
13169 The @value{GDBN} command-completion facility can simplify this;
13170 see @ref{Completion, ,Command Completion}.
13172 @cindex reference declarations
13174 @value{GDBN} understands variables declared as C@t{++} references; you can use
13175 them in expressions just as you do in C@t{++} source---they are automatically
13178 In the parameter list shown when @value{GDBN} displays a frame, the values of
13179 reference variables are not displayed (unlike other variables); this
13180 avoids clutter, since references are often used for large structures.
13181 The @emph{address} of a reference variable is always shown, unless
13182 you have specified @samp{set print address off}.
13185 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13186 expressions can use it just as expressions in your program do. Since
13187 one scope may be defined in another, you can use @code{::} repeatedly if
13188 necessary, for example in an expression like
13189 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13190 resolving name scope by reference to source files, in both C and C@t{++}
13191 debugging (@pxref{Variables, ,Program Variables}).
13194 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13199 @subsubsection C and C@t{++} Defaults
13201 @cindex C and C@t{++} defaults
13203 If you allow @value{GDBN} to set range checking automatically, it
13204 defaults to @code{off} whenever the working language changes to
13205 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13206 selects the working language.
13208 If you allow @value{GDBN} to set the language automatically, it
13209 recognizes source files whose names end with @file{.c}, @file{.C}, or
13210 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13211 these files, it sets the working language to C or C@t{++}.
13212 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13213 for further details.
13216 @subsubsection C and C@t{++} Type and Range Checks
13218 @cindex C and C@t{++} checks
13220 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13221 checking is used. However, if you turn type checking off, @value{GDBN}
13222 will allow certain non-standard conversions, such as promoting integer
13223 constants to pointers.
13225 Range checking, if turned on, is done on mathematical operations. Array
13226 indices are not checked, since they are often used to index a pointer
13227 that is not itself an array.
13230 @subsubsection @value{GDBN} and C
13232 The @code{set print union} and @code{show print union} commands apply to
13233 the @code{union} type. When set to @samp{on}, any @code{union} that is
13234 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13235 appears as @samp{@{...@}}.
13237 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13238 with pointers and a memory allocation function. @xref{Expressions,
13241 @node Debugging C Plus Plus
13242 @subsubsection @value{GDBN} Features for C@t{++}
13244 @cindex commands for C@t{++}
13246 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13247 designed specifically for use with C@t{++}. Here is a summary:
13250 @cindex break in overloaded functions
13251 @item @r{breakpoint menus}
13252 When you want a breakpoint in a function whose name is overloaded,
13253 @value{GDBN} has the capability to display a menu of possible breakpoint
13254 locations to help you specify which function definition you want.
13255 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13257 @cindex overloading in C@t{++}
13258 @item rbreak @var{regex}
13259 Setting breakpoints using regular expressions is helpful for setting
13260 breakpoints on overloaded functions that are not members of any special
13262 @xref{Set Breaks, ,Setting Breakpoints}.
13264 @cindex C@t{++} exception handling
13267 Debug C@t{++} exception handling using these commands. @xref{Set
13268 Catchpoints, , Setting Catchpoints}.
13270 @cindex inheritance
13271 @item ptype @var{typename}
13272 Print inheritance relationships as well as other information for type
13274 @xref{Symbols, ,Examining the Symbol Table}.
13276 @item info vtbl @var{expression}.
13277 The @code{info vtbl} command can be used to display the virtual
13278 method tables of the object computed by @var{expression}. This shows
13279 one entry per virtual table; there may be multiple virtual tables when
13280 multiple inheritance is in use.
13282 @cindex C@t{++} symbol display
13283 @item set print demangle
13284 @itemx show print demangle
13285 @itemx set print asm-demangle
13286 @itemx show print asm-demangle
13287 Control whether C@t{++} symbols display in their source form, both when
13288 displaying code as C@t{++} source and when displaying disassemblies.
13289 @xref{Print Settings, ,Print Settings}.
13291 @item set print object
13292 @itemx show print object
13293 Choose whether to print derived (actual) or declared types of objects.
13294 @xref{Print Settings, ,Print Settings}.
13296 @item set print vtbl
13297 @itemx show print vtbl
13298 Control the format for printing virtual function tables.
13299 @xref{Print Settings, ,Print Settings}.
13300 (The @code{vtbl} commands do not work on programs compiled with the HP
13301 ANSI C@t{++} compiler (@code{aCC}).)
13303 @kindex set overload-resolution
13304 @cindex overloaded functions, overload resolution
13305 @item set overload-resolution on
13306 Enable overload resolution for C@t{++} expression evaluation. The default
13307 is on. For overloaded functions, @value{GDBN} evaluates the arguments
13308 and searches for a function whose signature matches the argument types,
13309 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
13310 Expressions, ,C@t{++} Expressions}, for details).
13311 If it cannot find a match, it emits a message.
13313 @item set overload-resolution off
13314 Disable overload resolution for C@t{++} expression evaluation. For
13315 overloaded functions that are not class member functions, @value{GDBN}
13316 chooses the first function of the specified name that it finds in the
13317 symbol table, whether or not its arguments are of the correct type. For
13318 overloaded functions that are class member functions, @value{GDBN}
13319 searches for a function whose signature @emph{exactly} matches the
13322 @kindex show overload-resolution
13323 @item show overload-resolution
13324 Show the current setting of overload resolution.
13326 @item @r{Overloaded symbol names}
13327 You can specify a particular definition of an overloaded symbol, using
13328 the same notation that is used to declare such symbols in C@t{++}: type
13329 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
13330 also use the @value{GDBN} command-line word completion facilities to list the
13331 available choices, or to finish the type list for you.
13332 @xref{Completion,, Command Completion}, for details on how to do this.
13335 @node Decimal Floating Point
13336 @subsubsection Decimal Floating Point format
13337 @cindex decimal floating point format
13339 @value{GDBN} can examine, set and perform computations with numbers in
13340 decimal floating point format, which in the C language correspond to the
13341 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
13342 specified by the extension to support decimal floating-point arithmetic.
13344 There are two encodings in use, depending on the architecture: BID (Binary
13345 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
13346 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
13349 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
13350 to manipulate decimal floating point numbers, it is not possible to convert
13351 (using a cast, for example) integers wider than 32-bit to decimal float.
13353 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
13354 point computations, error checking in decimal float operations ignores
13355 underflow, overflow and divide by zero exceptions.
13357 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
13358 to inspect @code{_Decimal128} values stored in floating point registers.
13359 See @ref{PowerPC,,PowerPC} for more details.
13365 @value{GDBN} can be used to debug programs written in D and compiled with
13366 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
13367 specific feature --- dynamic arrays.
13372 @cindex Go (programming language)
13373 @value{GDBN} can be used to debug programs written in Go and compiled with
13374 @file{gccgo} or @file{6g} compilers.
13376 Here is a summary of the Go-specific features and restrictions:
13379 @cindex current Go package
13380 @item The current Go package
13381 The name of the current package does not need to be specified when
13382 specifying global variables and functions.
13384 For example, given the program:
13388 var myglob = "Shall we?"
13394 When stopped inside @code{main} either of these work:
13398 (gdb) p main.myglob
13401 @cindex builtin Go types
13402 @item Builtin Go types
13403 The @code{string} type is recognized by @value{GDBN} and is printed
13406 @cindex builtin Go functions
13407 @item Builtin Go functions
13408 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
13409 function and handles it internally.
13411 @cindex restrictions on Go expressions
13412 @item Restrictions on Go expressions
13413 All Go operators are supported except @code{&^}.
13414 The Go @code{_} ``blank identifier'' is not supported.
13415 Automatic dereferencing of pointers is not supported.
13419 @subsection Objective-C
13421 @cindex Objective-C
13422 This section provides information about some commands and command
13423 options that are useful for debugging Objective-C code. See also
13424 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
13425 few more commands specific to Objective-C support.
13428 * Method Names in Commands::
13429 * The Print Command with Objective-C::
13432 @node Method Names in Commands
13433 @subsubsection Method Names in Commands
13435 The following commands have been extended to accept Objective-C method
13436 names as line specifications:
13438 @kindex clear@r{, and Objective-C}
13439 @kindex break@r{, and Objective-C}
13440 @kindex info line@r{, and Objective-C}
13441 @kindex jump@r{, and Objective-C}
13442 @kindex list@r{, and Objective-C}
13446 @item @code{info line}
13451 A fully qualified Objective-C method name is specified as
13454 -[@var{Class} @var{methodName}]
13457 where the minus sign is used to indicate an instance method and a
13458 plus sign (not shown) is used to indicate a class method. The class
13459 name @var{Class} and method name @var{methodName} are enclosed in
13460 brackets, similar to the way messages are specified in Objective-C
13461 source code. For example, to set a breakpoint at the @code{create}
13462 instance method of class @code{Fruit} in the program currently being
13466 break -[Fruit create]
13469 To list ten program lines around the @code{initialize} class method,
13473 list +[NSText initialize]
13476 In the current version of @value{GDBN}, the plus or minus sign is
13477 required. In future versions of @value{GDBN}, the plus or minus
13478 sign will be optional, but you can use it to narrow the search. It
13479 is also possible to specify just a method name:
13485 You must specify the complete method name, including any colons. If
13486 your program's source files contain more than one @code{create} method,
13487 you'll be presented with a numbered list of classes that implement that
13488 method. Indicate your choice by number, or type @samp{0} to exit if
13491 As another example, to clear a breakpoint established at the
13492 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
13495 clear -[NSWindow makeKeyAndOrderFront:]
13498 @node The Print Command with Objective-C
13499 @subsubsection The Print Command With Objective-C
13500 @cindex Objective-C, print objects
13501 @kindex print-object
13502 @kindex po @r{(@code{print-object})}
13504 The print command has also been extended to accept methods. For example:
13507 print -[@var{object} hash]
13510 @cindex print an Objective-C object description
13511 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
13513 will tell @value{GDBN} to send the @code{hash} message to @var{object}
13514 and print the result. Also, an additional command has been added,
13515 @code{print-object} or @code{po} for short, which is meant to print
13516 the description of an object. However, this command may only work
13517 with certain Objective-C libraries that have a particular hook
13518 function, @code{_NSPrintForDebugger}, defined.
13521 @subsection OpenCL C
13524 This section provides information about @value{GDBN}s OpenCL C support.
13527 * OpenCL C Datatypes::
13528 * OpenCL C Expressions::
13529 * OpenCL C Operators::
13532 @node OpenCL C Datatypes
13533 @subsubsection OpenCL C Datatypes
13535 @cindex OpenCL C Datatypes
13536 @value{GDBN} supports the builtin scalar and vector datatypes specified
13537 by OpenCL 1.1. In addition the half- and double-precision floating point
13538 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
13539 extensions are also known to @value{GDBN}.
13541 @node OpenCL C Expressions
13542 @subsubsection OpenCL C Expressions
13544 @cindex OpenCL C Expressions
13545 @value{GDBN} supports accesses to vector components including the access as
13546 lvalue where possible. Since OpenCL C is based on C99 most C expressions
13547 supported by @value{GDBN} can be used as well.
13549 @node OpenCL C Operators
13550 @subsubsection OpenCL C Operators
13552 @cindex OpenCL C Operators
13553 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
13557 @subsection Fortran
13558 @cindex Fortran-specific support in @value{GDBN}
13560 @value{GDBN} can be used to debug programs written in Fortran, but it
13561 currently supports only the features of Fortran 77 language.
13563 @cindex trailing underscore, in Fortran symbols
13564 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
13565 among them) append an underscore to the names of variables and
13566 functions. When you debug programs compiled by those compilers, you
13567 will need to refer to variables and functions with a trailing
13571 * Fortran Operators:: Fortran operators and expressions
13572 * Fortran Defaults:: Default settings for Fortran
13573 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
13576 @node Fortran Operators
13577 @subsubsection Fortran Operators and Expressions
13579 @cindex Fortran operators and expressions
13581 Operators must be defined on values of specific types. For instance,
13582 @code{+} is defined on numbers, but not on characters or other non-
13583 arithmetic types. Operators are often defined on groups of types.
13587 The exponentiation operator. It raises the first operand to the power
13591 The range operator. Normally used in the form of array(low:high) to
13592 represent a section of array.
13595 The access component operator. Normally used to access elements in derived
13596 types. Also suitable for unions. As unions aren't part of regular Fortran,
13597 this can only happen when accessing a register that uses a gdbarch-defined
13601 @node Fortran Defaults
13602 @subsubsection Fortran Defaults
13604 @cindex Fortran Defaults
13606 Fortran symbols are usually case-insensitive, so @value{GDBN} by
13607 default uses case-insensitive matches for Fortran symbols. You can
13608 change that with the @samp{set case-insensitive} command, see
13609 @ref{Symbols}, for the details.
13611 @node Special Fortran Commands
13612 @subsubsection Special Fortran Commands
13614 @cindex Special Fortran commands
13616 @value{GDBN} has some commands to support Fortran-specific features,
13617 such as displaying common blocks.
13620 @cindex @code{COMMON} blocks, Fortran
13621 @kindex info common
13622 @item info common @r{[}@var{common-name}@r{]}
13623 This command prints the values contained in the Fortran @code{COMMON}
13624 block whose name is @var{common-name}. With no argument, the names of
13625 all @code{COMMON} blocks visible at the current program location are
13632 @cindex Pascal support in @value{GDBN}, limitations
13633 Debugging Pascal programs which use sets, subranges, file variables, or
13634 nested functions does not currently work. @value{GDBN} does not support
13635 entering expressions, printing values, or similar features using Pascal
13638 The Pascal-specific command @code{set print pascal_static-members}
13639 controls whether static members of Pascal objects are displayed.
13640 @xref{Print Settings, pascal_static-members}.
13643 @subsection Modula-2
13645 @cindex Modula-2, @value{GDBN} support
13647 The extensions made to @value{GDBN} to support Modula-2 only support
13648 output from the @sc{gnu} Modula-2 compiler (which is currently being
13649 developed). Other Modula-2 compilers are not currently supported, and
13650 attempting to debug executables produced by them is most likely
13651 to give an error as @value{GDBN} reads in the executable's symbol
13654 @cindex expressions in Modula-2
13656 * M2 Operators:: Built-in operators
13657 * Built-In Func/Proc:: Built-in functions and procedures
13658 * M2 Constants:: Modula-2 constants
13659 * M2 Types:: Modula-2 types
13660 * M2 Defaults:: Default settings for Modula-2
13661 * Deviations:: Deviations from standard Modula-2
13662 * M2 Checks:: Modula-2 type and range checks
13663 * M2 Scope:: The scope operators @code{::} and @code{.}
13664 * GDB/M2:: @value{GDBN} and Modula-2
13668 @subsubsection Operators
13669 @cindex Modula-2 operators
13671 Operators must be defined on values of specific types. For instance,
13672 @code{+} is defined on numbers, but not on structures. Operators are
13673 often defined on groups of types. For the purposes of Modula-2, the
13674 following definitions hold:
13679 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13683 @emph{Character types} consist of @code{CHAR} and its subranges.
13686 @emph{Floating-point types} consist of @code{REAL}.
13689 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13693 @emph{Scalar types} consist of all of the above.
13696 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13699 @emph{Boolean types} consist of @code{BOOLEAN}.
13703 The following operators are supported, and appear in order of
13704 increasing precedence:
13708 Function argument or array index separator.
13711 Assignment. The value of @var{var} @code{:=} @var{value} is
13715 Less than, greater than on integral, floating-point, or enumerated
13719 Less than or equal to, greater than or equal to
13720 on integral, floating-point and enumerated types, or set inclusion on
13721 set types. Same precedence as @code{<}.
13723 @item =@r{, }<>@r{, }#
13724 Equality and two ways of expressing inequality, valid on scalar types.
13725 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13726 available for inequality, since @code{#} conflicts with the script
13730 Set membership. Defined on set types and the types of their members.
13731 Same precedence as @code{<}.
13734 Boolean disjunction. Defined on boolean types.
13737 Boolean conjunction. Defined on boolean types.
13740 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13743 Addition and subtraction on integral and floating-point types, or union
13744 and difference on set types.
13747 Multiplication on integral and floating-point types, or set intersection
13751 Division on floating-point types, or symmetric set difference on set
13752 types. Same precedence as @code{*}.
13755 Integer division and remainder. Defined on integral types. Same
13756 precedence as @code{*}.
13759 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13762 Pointer dereferencing. Defined on pointer types.
13765 Boolean negation. Defined on boolean types. Same precedence as
13769 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13770 precedence as @code{^}.
13773 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13776 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13780 @value{GDBN} and Modula-2 scope operators.
13784 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13785 treats the use of the operator @code{IN}, or the use of operators
13786 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13787 @code{<=}, and @code{>=} on sets as an error.
13791 @node Built-In Func/Proc
13792 @subsubsection Built-in Functions and Procedures
13793 @cindex Modula-2 built-ins
13795 Modula-2 also makes available several built-in procedures and functions.
13796 In describing these, the following metavariables are used:
13801 represents an @code{ARRAY} variable.
13804 represents a @code{CHAR} constant or variable.
13807 represents a variable or constant of integral type.
13810 represents an identifier that belongs to a set. Generally used in the
13811 same function with the metavariable @var{s}. The type of @var{s} should
13812 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13815 represents a variable or constant of integral or floating-point type.
13818 represents a variable or constant of floating-point type.
13824 represents a variable.
13827 represents a variable or constant of one of many types. See the
13828 explanation of the function for details.
13831 All Modula-2 built-in procedures also return a result, described below.
13835 Returns the absolute value of @var{n}.
13838 If @var{c} is a lower case letter, it returns its upper case
13839 equivalent, otherwise it returns its argument.
13842 Returns the character whose ordinal value is @var{i}.
13845 Decrements the value in the variable @var{v} by one. Returns the new value.
13847 @item DEC(@var{v},@var{i})
13848 Decrements the value in the variable @var{v} by @var{i}. Returns the
13851 @item EXCL(@var{m},@var{s})
13852 Removes the element @var{m} from the set @var{s}. Returns the new
13855 @item FLOAT(@var{i})
13856 Returns the floating point equivalent of the integer @var{i}.
13858 @item HIGH(@var{a})
13859 Returns the index of the last member of @var{a}.
13862 Increments the value in the variable @var{v} by one. Returns the new value.
13864 @item INC(@var{v},@var{i})
13865 Increments the value in the variable @var{v} by @var{i}. Returns the
13868 @item INCL(@var{m},@var{s})
13869 Adds the element @var{m} to the set @var{s} if it is not already
13870 there. Returns the new set.
13873 Returns the maximum value of the type @var{t}.
13876 Returns the minimum value of the type @var{t}.
13879 Returns boolean TRUE if @var{i} is an odd number.
13882 Returns the ordinal value of its argument. For example, the ordinal
13883 value of a character is its @sc{ascii} value (on machines supporting the
13884 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13885 integral, character and enumerated types.
13887 @item SIZE(@var{x})
13888 Returns the size of its argument. @var{x} can be a variable or a type.
13890 @item TRUNC(@var{r})
13891 Returns the integral part of @var{r}.
13893 @item TSIZE(@var{x})
13894 Returns the size of its argument. @var{x} can be a variable or a type.
13896 @item VAL(@var{t},@var{i})
13897 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13901 @emph{Warning:} Sets and their operations are not yet supported, so
13902 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13906 @cindex Modula-2 constants
13908 @subsubsection Constants
13910 @value{GDBN} allows you to express the constants of Modula-2 in the following
13916 Integer constants are simply a sequence of digits. When used in an
13917 expression, a constant is interpreted to be type-compatible with the
13918 rest of the expression. Hexadecimal integers are specified by a
13919 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13922 Floating point constants appear as a sequence of digits, followed by a
13923 decimal point and another sequence of digits. An optional exponent can
13924 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13925 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13926 digits of the floating point constant must be valid decimal (base 10)
13930 Character constants consist of a single character enclosed by a pair of
13931 like quotes, either single (@code{'}) or double (@code{"}). They may
13932 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13933 followed by a @samp{C}.
13936 String constants consist of a sequence of characters enclosed by a
13937 pair of like quotes, either single (@code{'}) or double (@code{"}).
13938 Escape sequences in the style of C are also allowed. @xref{C
13939 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13943 Enumerated constants consist of an enumerated identifier.
13946 Boolean constants consist of the identifiers @code{TRUE} and
13950 Pointer constants consist of integral values only.
13953 Set constants are not yet supported.
13957 @subsubsection Modula-2 Types
13958 @cindex Modula-2 types
13960 Currently @value{GDBN} can print the following data types in Modula-2
13961 syntax: array types, record types, set types, pointer types, procedure
13962 types, enumerated types, subrange types and base types. You can also
13963 print the contents of variables declared using these type.
13964 This section gives a number of simple source code examples together with
13965 sample @value{GDBN} sessions.
13967 The first example contains the following section of code:
13976 and you can request @value{GDBN} to interrogate the type and value of
13977 @code{r} and @code{s}.
13980 (@value{GDBP}) print s
13982 (@value{GDBP}) ptype s
13984 (@value{GDBP}) print r
13986 (@value{GDBP}) ptype r
13991 Likewise if your source code declares @code{s} as:
13995 s: SET ['A'..'Z'] ;
13999 then you may query the type of @code{s} by:
14002 (@value{GDBP}) ptype s
14003 type = SET ['A'..'Z']
14007 Note that at present you cannot interactively manipulate set
14008 expressions using the debugger.
14010 The following example shows how you might declare an array in Modula-2
14011 and how you can interact with @value{GDBN} to print its type and contents:
14015 s: ARRAY [-10..10] OF CHAR ;
14019 (@value{GDBP}) ptype s
14020 ARRAY [-10..10] OF CHAR
14023 Note that the array handling is not yet complete and although the type
14024 is printed correctly, expression handling still assumes that all
14025 arrays have a lower bound of zero and not @code{-10} as in the example
14028 Here are some more type related Modula-2 examples:
14032 colour = (blue, red, yellow, green) ;
14033 t = [blue..yellow] ;
14041 The @value{GDBN} interaction shows how you can query the data type
14042 and value of a variable.
14045 (@value{GDBP}) print s
14047 (@value{GDBP}) ptype t
14048 type = [blue..yellow]
14052 In this example a Modula-2 array is declared and its contents
14053 displayed. Observe that the contents are written in the same way as
14054 their @code{C} counterparts.
14058 s: ARRAY [1..5] OF CARDINAL ;
14064 (@value{GDBP}) print s
14065 $1 = @{1, 0, 0, 0, 0@}
14066 (@value{GDBP}) ptype s
14067 type = ARRAY [1..5] OF CARDINAL
14070 The Modula-2 language interface to @value{GDBN} also understands
14071 pointer types as shown in this example:
14075 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14082 and you can request that @value{GDBN} describes the type of @code{s}.
14085 (@value{GDBP}) ptype s
14086 type = POINTER TO ARRAY [1..5] OF CARDINAL
14089 @value{GDBN} handles compound types as we can see in this example.
14090 Here we combine array types, record types, pointer types and subrange
14101 myarray = ARRAY myrange OF CARDINAL ;
14102 myrange = [-2..2] ;
14104 s: POINTER TO ARRAY myrange OF foo ;
14108 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14112 (@value{GDBP}) ptype s
14113 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14116 f3 : ARRAY [-2..2] OF CARDINAL;
14121 @subsubsection Modula-2 Defaults
14122 @cindex Modula-2 defaults
14124 If type and range checking are set automatically by @value{GDBN}, they
14125 both default to @code{on} whenever the working language changes to
14126 Modula-2. This happens regardless of whether you or @value{GDBN}
14127 selected the working language.
14129 If you allow @value{GDBN} to set the language automatically, then entering
14130 code compiled from a file whose name ends with @file{.mod} sets the
14131 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14132 Infer the Source Language}, for further details.
14135 @subsubsection Deviations from Standard Modula-2
14136 @cindex Modula-2, deviations from
14138 A few changes have been made to make Modula-2 programs easier to debug.
14139 This is done primarily via loosening its type strictness:
14143 Unlike in standard Modula-2, pointer constants can be formed by
14144 integers. This allows you to modify pointer variables during
14145 debugging. (In standard Modula-2, the actual address contained in a
14146 pointer variable is hidden from you; it can only be modified
14147 through direct assignment to another pointer variable or expression that
14148 returned a pointer.)
14151 C escape sequences can be used in strings and characters to represent
14152 non-printable characters. @value{GDBN} prints out strings with these
14153 escape sequences embedded. Single non-printable characters are
14154 printed using the @samp{CHR(@var{nnn})} format.
14157 The assignment operator (@code{:=}) returns the value of its right-hand
14161 All built-in procedures both modify @emph{and} return their argument.
14165 @subsubsection Modula-2 Type and Range Checks
14166 @cindex Modula-2 checks
14169 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14172 @c FIXME remove warning when type/range checks added
14174 @value{GDBN} considers two Modula-2 variables type equivalent if:
14178 They are of types that have been declared equivalent via a @code{TYPE
14179 @var{t1} = @var{t2}} statement
14182 They have been declared on the same line. (Note: This is true of the
14183 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14186 As long as type checking is enabled, any attempt to combine variables
14187 whose types are not equivalent is an error.
14189 Range checking is done on all mathematical operations, assignment, array
14190 index bounds, and all built-in functions and procedures.
14193 @subsubsection The Scope Operators @code{::} and @code{.}
14195 @cindex @code{.}, Modula-2 scope operator
14196 @cindex colon, doubled as scope operator
14198 @vindex colon-colon@r{, in Modula-2}
14199 @c Info cannot handle :: but TeX can.
14202 @vindex ::@r{, in Modula-2}
14205 There are a few subtle differences between the Modula-2 scope operator
14206 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14211 @var{module} . @var{id}
14212 @var{scope} :: @var{id}
14216 where @var{scope} is the name of a module or a procedure,
14217 @var{module} the name of a module, and @var{id} is any declared
14218 identifier within your program, except another module.
14220 Using the @code{::} operator makes @value{GDBN} search the scope
14221 specified by @var{scope} for the identifier @var{id}. If it is not
14222 found in the specified scope, then @value{GDBN} searches all scopes
14223 enclosing the one specified by @var{scope}.
14225 Using the @code{.} operator makes @value{GDBN} search the current scope for
14226 the identifier specified by @var{id} that was imported from the
14227 definition module specified by @var{module}. With this operator, it is
14228 an error if the identifier @var{id} was not imported from definition
14229 module @var{module}, or if @var{id} is not an identifier in
14233 @subsubsection @value{GDBN} and Modula-2
14235 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14236 Five subcommands of @code{set print} and @code{show print} apply
14237 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14238 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14239 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14240 analogue in Modula-2.
14242 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14243 with any language, is not useful with Modula-2. Its
14244 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14245 created in Modula-2 as they can in C or C@t{++}. However, because an
14246 address can be specified by an integral constant, the construct
14247 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14249 @cindex @code{#} in Modula-2
14250 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14251 interpreted as the beginning of a comment. Use @code{<>} instead.
14257 The extensions made to @value{GDBN} for Ada only support
14258 output from the @sc{gnu} Ada (GNAT) compiler.
14259 Other Ada compilers are not currently supported, and
14260 attempting to debug executables produced by them is most likely
14264 @cindex expressions in Ada
14266 * Ada Mode Intro:: General remarks on the Ada syntax
14267 and semantics supported by Ada mode
14269 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14270 * Additions to Ada:: Extensions of the Ada expression syntax.
14271 * Stopping Before Main Program:: Debugging the program during elaboration.
14272 * Ada Tasks:: Listing and setting breakpoints in tasks.
14273 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14274 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14276 * Ada Glitches:: Known peculiarities of Ada mode.
14279 @node Ada Mode Intro
14280 @subsubsection Introduction
14281 @cindex Ada mode, general
14283 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14284 syntax, with some extensions.
14285 The philosophy behind the design of this subset is
14289 That @value{GDBN} should provide basic literals and access to operations for
14290 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
14291 leaving more sophisticated computations to subprograms written into the
14292 program (which therefore may be called from @value{GDBN}).
14295 That type safety and strict adherence to Ada language restrictions
14296 are not particularly important to the @value{GDBN} user.
14299 That brevity is important to the @value{GDBN} user.
14302 Thus, for brevity, the debugger acts as if all names declared in
14303 user-written packages are directly visible, even if they are not visible
14304 according to Ada rules, thus making it unnecessary to fully qualify most
14305 names with their packages, regardless of context. Where this causes
14306 ambiguity, @value{GDBN} asks the user's intent.
14308 The debugger will start in Ada mode if it detects an Ada main program.
14309 As for other languages, it will enter Ada mode when stopped in a program that
14310 was translated from an Ada source file.
14312 While in Ada mode, you may use `@t{--}' for comments. This is useful
14313 mostly for documenting command files. The standard @value{GDBN} comment
14314 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
14315 middle (to allow based literals).
14317 The debugger supports limited overloading. Given a subprogram call in which
14318 the function symbol has multiple definitions, it will use the number of
14319 actual parameters and some information about their types to attempt to narrow
14320 the set of definitions. It also makes very limited use of context, preferring
14321 procedures to functions in the context of the @code{call} command, and
14322 functions to procedures elsewhere.
14324 @node Omissions from Ada
14325 @subsubsection Omissions from Ada
14326 @cindex Ada, omissions from
14328 Here are the notable omissions from the subset:
14332 Only a subset of the attributes are supported:
14336 @t{'First}, @t{'Last}, and @t{'Length}
14337 on array objects (not on types and subtypes).
14340 @t{'Min} and @t{'Max}.
14343 @t{'Pos} and @t{'Val}.
14349 @t{'Range} on array objects (not subtypes), but only as the right
14350 operand of the membership (@code{in}) operator.
14353 @t{'Access}, @t{'Unchecked_Access}, and
14354 @t{'Unrestricted_Access} (a GNAT extension).
14362 @code{Characters.Latin_1} are not available and
14363 concatenation is not implemented. Thus, escape characters in strings are
14364 not currently available.
14367 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
14368 equality of representations. They will generally work correctly
14369 for strings and arrays whose elements have integer or enumeration types.
14370 They may not work correctly for arrays whose element
14371 types have user-defined equality, for arrays of real values
14372 (in particular, IEEE-conformant floating point, because of negative
14373 zeroes and NaNs), and for arrays whose elements contain unused bits with
14374 indeterminate values.
14377 The other component-by-component array operations (@code{and}, @code{or},
14378 @code{xor}, @code{not}, and relational tests other than equality)
14379 are not implemented.
14382 @cindex array aggregates (Ada)
14383 @cindex record aggregates (Ada)
14384 @cindex aggregates (Ada)
14385 There is limited support for array and record aggregates. They are
14386 permitted only on the right sides of assignments, as in these examples:
14389 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
14390 (@value{GDBP}) set An_Array := (1, others => 0)
14391 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
14392 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
14393 (@value{GDBP}) set A_Record := (1, "Peter", True);
14394 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
14398 discriminant's value by assigning an aggregate has an
14399 undefined effect if that discriminant is used within the record.
14400 However, you can first modify discriminants by directly assigning to
14401 them (which normally would not be allowed in Ada), and then performing an
14402 aggregate assignment. For example, given a variable @code{A_Rec}
14403 declared to have a type such as:
14406 type Rec (Len : Small_Integer := 0) is record
14408 Vals : IntArray (1 .. Len);
14412 you can assign a value with a different size of @code{Vals} with two
14416 (@value{GDBP}) set A_Rec.Len := 4
14417 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
14420 As this example also illustrates, @value{GDBN} is very loose about the usual
14421 rules concerning aggregates. You may leave out some of the
14422 components of an array or record aggregate (such as the @code{Len}
14423 component in the assignment to @code{A_Rec} above); they will retain their
14424 original values upon assignment. You may freely use dynamic values as
14425 indices in component associations. You may even use overlapping or
14426 redundant component associations, although which component values are
14427 assigned in such cases is not defined.
14430 Calls to dispatching subprograms are not implemented.
14433 The overloading algorithm is much more limited (i.e., less selective)
14434 than that of real Ada. It makes only limited use of the context in
14435 which a subexpression appears to resolve its meaning, and it is much
14436 looser in its rules for allowing type matches. As a result, some
14437 function calls will be ambiguous, and the user will be asked to choose
14438 the proper resolution.
14441 The @code{new} operator is not implemented.
14444 Entry calls are not implemented.
14447 Aside from printing, arithmetic operations on the native VAX floating-point
14448 formats are not supported.
14451 It is not possible to slice a packed array.
14454 The names @code{True} and @code{False}, when not part of a qualified name,
14455 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
14457 Should your program
14458 redefine these names in a package or procedure (at best a dubious practice),
14459 you will have to use fully qualified names to access their new definitions.
14462 @node Additions to Ada
14463 @subsubsection Additions to Ada
14464 @cindex Ada, deviations from
14466 As it does for other languages, @value{GDBN} makes certain generic
14467 extensions to Ada (@pxref{Expressions}):
14471 If the expression @var{E} is a variable residing in memory (typically
14472 a local variable or array element) and @var{N} is a positive integer,
14473 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
14474 @var{N}-1 adjacent variables following it in memory as an array. In
14475 Ada, this operator is generally not necessary, since its prime use is
14476 in displaying parts of an array, and slicing will usually do this in
14477 Ada. However, there are occasional uses when debugging programs in
14478 which certain debugging information has been optimized away.
14481 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
14482 appears in function or file @var{B}.'' When @var{B} is a file name,
14483 you must typically surround it in single quotes.
14486 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
14487 @var{type} that appears at address @var{addr}.''
14490 A name starting with @samp{$} is a convenience variable
14491 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
14494 In addition, @value{GDBN} provides a few other shortcuts and outright
14495 additions specific to Ada:
14499 The assignment statement is allowed as an expression, returning
14500 its right-hand operand as its value. Thus, you may enter
14503 (@value{GDBP}) set x := y + 3
14504 (@value{GDBP}) print A(tmp := y + 1)
14508 The semicolon is allowed as an ``operator,'' returning as its value
14509 the value of its right-hand operand.
14510 This allows, for example,
14511 complex conditional breaks:
14514 (@value{GDBP}) break f
14515 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
14519 Rather than use catenation and symbolic character names to introduce special
14520 characters into strings, one may instead use a special bracket notation,
14521 which is also used to print strings. A sequence of characters of the form
14522 @samp{["@var{XX}"]} within a string or character literal denotes the
14523 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
14524 sequence of characters @samp{["""]} also denotes a single quotation mark
14525 in strings. For example,
14527 "One line.["0a"]Next line.["0a"]"
14530 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
14534 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
14535 @t{'Max} is optional (and is ignored in any case). For example, it is valid
14539 (@value{GDBP}) print 'max(x, y)
14543 When printing arrays, @value{GDBN} uses positional notation when the
14544 array has a lower bound of 1, and uses a modified named notation otherwise.
14545 For example, a one-dimensional array of three integers with a lower bound
14546 of 3 might print as
14553 That is, in contrast to valid Ada, only the first component has a @code{=>}
14557 You may abbreviate attributes in expressions with any unique,
14558 multi-character subsequence of
14559 their names (an exact match gets preference).
14560 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
14561 in place of @t{a'length}.
14564 @cindex quoting Ada internal identifiers
14565 Since Ada is case-insensitive, the debugger normally maps identifiers you type
14566 to lower case. The GNAT compiler uses upper-case characters for
14567 some of its internal identifiers, which are normally of no interest to users.
14568 For the rare occasions when you actually have to look at them,
14569 enclose them in angle brackets to avoid the lower-case mapping.
14572 (@value{GDBP}) print <JMPBUF_SAVE>[0]
14576 Printing an object of class-wide type or dereferencing an
14577 access-to-class-wide value will display all the components of the object's
14578 specific type (as indicated by its run-time tag). Likewise, component
14579 selection on such a value will operate on the specific type of the
14584 @node Stopping Before Main Program
14585 @subsubsection Stopping at the Very Beginning
14587 @cindex breakpointing Ada elaboration code
14588 It is sometimes necessary to debug the program during elaboration, and
14589 before reaching the main procedure.
14590 As defined in the Ada Reference
14591 Manual, the elaboration code is invoked from a procedure called
14592 @code{adainit}. To run your program up to the beginning of
14593 elaboration, simply use the following two commands:
14594 @code{tbreak adainit} and @code{run}.
14597 @subsubsection Extensions for Ada Tasks
14598 @cindex Ada, tasking
14600 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
14601 @value{GDBN} provides the following task-related commands:
14606 This command shows a list of current Ada tasks, as in the following example:
14613 (@value{GDBP}) info tasks
14614 ID TID P-ID Pri State Name
14615 1 8088000 0 15 Child Activation Wait main_task
14616 2 80a4000 1 15 Accept Statement b
14617 3 809a800 1 15 Child Activation Wait a
14618 * 4 80ae800 3 15 Runnable c
14623 In this listing, the asterisk before the last task indicates it to be the
14624 task currently being inspected.
14628 Represents @value{GDBN}'s internal task number.
14634 The parent's task ID (@value{GDBN}'s internal task number).
14637 The base priority of the task.
14640 Current state of the task.
14644 The task has been created but has not been activated. It cannot be
14648 The task is not blocked for any reason known to Ada. (It may be waiting
14649 for a mutex, though.) It is conceptually "executing" in normal mode.
14652 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14653 that were waiting on terminate alternatives have been awakened and have
14654 terminated themselves.
14656 @item Child Activation Wait
14657 The task is waiting for created tasks to complete activation.
14659 @item Accept Statement
14660 The task is waiting on an accept or selective wait statement.
14662 @item Waiting on entry call
14663 The task is waiting on an entry call.
14665 @item Async Select Wait
14666 The task is waiting to start the abortable part of an asynchronous
14670 The task is waiting on a select statement with only a delay
14673 @item Child Termination Wait
14674 The task is sleeping having completed a master within itself, and is
14675 waiting for the tasks dependent on that master to become terminated or
14676 waiting on a terminate Phase.
14678 @item Wait Child in Term Alt
14679 The task is sleeping waiting for tasks on terminate alternatives to
14680 finish terminating.
14682 @item Accepting RV with @var{taskno}
14683 The task is accepting a rendez-vous with the task @var{taskno}.
14687 Name of the task in the program.
14691 @kindex info task @var{taskno}
14692 @item info task @var{taskno}
14693 This command shows detailled informations on the specified task, as in
14694 the following example:
14699 (@value{GDBP}) info tasks
14700 ID TID P-ID Pri State Name
14701 1 8077880 0 15 Child Activation Wait main_task
14702 * 2 807c468 1 15 Runnable task_1
14703 (@value{GDBP}) info task 2
14704 Ada Task: 0x807c468
14707 Parent: 1 (main_task)
14713 @kindex task@r{ (Ada)}
14714 @cindex current Ada task ID
14715 This command prints the ID of the current task.
14721 (@value{GDBP}) info tasks
14722 ID TID P-ID Pri State Name
14723 1 8077870 0 15 Child Activation Wait main_task
14724 * 2 807c458 1 15 Runnable t
14725 (@value{GDBP}) task
14726 [Current task is 2]
14729 @item task @var{taskno}
14730 @cindex Ada task switching
14731 This command is like the @code{thread @var{threadno}}
14732 command (@pxref{Threads}). It switches the context of debugging
14733 from the current task to the given task.
14739 (@value{GDBP}) info tasks
14740 ID TID P-ID Pri State Name
14741 1 8077870 0 15 Child Activation Wait main_task
14742 * 2 807c458 1 15 Runnable t
14743 (@value{GDBP}) task 1
14744 [Switching to task 1]
14745 #0 0x8067726 in pthread_cond_wait ()
14747 #0 0x8067726 in pthread_cond_wait ()
14748 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14749 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14750 #3 0x806153e in system.tasking.stages.activate_tasks ()
14751 #4 0x804aacc in un () at un.adb:5
14754 @item break @var{linespec} task @var{taskno}
14755 @itemx break @var{linespec} task @var{taskno} if @dots{}
14756 @cindex breakpoints and tasks, in Ada
14757 @cindex task breakpoints, in Ada
14758 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14759 These commands are like the @code{break @dots{} thread @dots{}}
14760 command (@pxref{Thread Stops}).
14761 @var{linespec} specifies source lines, as described
14762 in @ref{Specify Location}.
14764 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14765 to specify that you only want @value{GDBN} to stop the program when a
14766 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14767 numeric task identifiers assigned by @value{GDBN}, shown in the first
14768 column of the @samp{info tasks} display.
14770 If you do not specify @samp{task @var{taskno}} when you set a
14771 breakpoint, the breakpoint applies to @emph{all} tasks of your
14774 You can use the @code{task} qualifier on conditional breakpoints as
14775 well; in this case, place @samp{task @var{taskno}} before the
14776 breakpoint condition (before the @code{if}).
14784 (@value{GDBP}) info tasks
14785 ID TID P-ID Pri State Name
14786 1 140022020 0 15 Child Activation Wait main_task
14787 2 140045060 1 15 Accept/Select Wait t2
14788 3 140044840 1 15 Runnable t1
14789 * 4 140056040 1 15 Runnable t3
14790 (@value{GDBP}) b 15 task 2
14791 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14792 (@value{GDBP}) cont
14797 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14799 (@value{GDBP}) info tasks
14800 ID TID P-ID Pri State Name
14801 1 140022020 0 15 Child Activation Wait main_task
14802 * 2 140045060 1 15 Runnable t2
14803 3 140044840 1 15 Runnable t1
14804 4 140056040 1 15 Delay Sleep t3
14808 @node Ada Tasks and Core Files
14809 @subsubsection Tasking Support when Debugging Core Files
14810 @cindex Ada tasking and core file debugging
14812 When inspecting a core file, as opposed to debugging a live program,
14813 tasking support may be limited or even unavailable, depending on
14814 the platform being used.
14815 For instance, on x86-linux, the list of tasks is available, but task
14816 switching is not supported. On Tru64, however, task switching will work
14819 On certain platforms, including Tru64, the debugger needs to perform some
14820 memory writes in order to provide Ada tasking support. When inspecting
14821 a core file, this means that the core file must be opened with read-write
14822 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14823 Under these circumstances, you should make a backup copy of the core
14824 file before inspecting it with @value{GDBN}.
14826 @node Ravenscar Profile
14827 @subsubsection Tasking Support when using the Ravenscar Profile
14828 @cindex Ravenscar Profile
14830 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14831 specifically designed for systems with safety-critical real-time
14835 @kindex set ravenscar task-switching on
14836 @cindex task switching with program using Ravenscar Profile
14837 @item set ravenscar task-switching on
14838 Allows task switching when debugging a program that uses the Ravenscar
14839 Profile. This is the default.
14841 @kindex set ravenscar task-switching off
14842 @item set ravenscar task-switching off
14843 Turn off task switching when debugging a program that uses the Ravenscar
14844 Profile. This is mostly intended to disable the code that adds support
14845 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14846 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14847 To be effective, this command should be run before the program is started.
14849 @kindex show ravenscar task-switching
14850 @item show ravenscar task-switching
14851 Show whether it is possible to switch from task to task in a program
14852 using the Ravenscar Profile.
14857 @subsubsection Known Peculiarities of Ada Mode
14858 @cindex Ada, problems
14860 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14861 we know of several problems with and limitations of Ada mode in
14863 some of which will be fixed with planned future releases of the debugger
14864 and the GNU Ada compiler.
14868 Static constants that the compiler chooses not to materialize as objects in
14869 storage are invisible to the debugger.
14872 Named parameter associations in function argument lists are ignored (the
14873 argument lists are treated as positional).
14876 Many useful library packages are currently invisible to the debugger.
14879 Fixed-point arithmetic, conversions, input, and output is carried out using
14880 floating-point arithmetic, and may give results that only approximate those on
14884 The GNAT compiler never generates the prefix @code{Standard} for any of
14885 the standard symbols defined by the Ada language. @value{GDBN} knows about
14886 this: it will strip the prefix from names when you use it, and will never
14887 look for a name you have so qualified among local symbols, nor match against
14888 symbols in other packages or subprograms. If you have
14889 defined entities anywhere in your program other than parameters and
14890 local variables whose simple names match names in @code{Standard},
14891 GNAT's lack of qualification here can cause confusion. When this happens,
14892 you can usually resolve the confusion
14893 by qualifying the problematic names with package
14894 @code{Standard} explicitly.
14897 Older versions of the compiler sometimes generate erroneous debugging
14898 information, resulting in the debugger incorrectly printing the value
14899 of affected entities. In some cases, the debugger is able to work
14900 around an issue automatically. In other cases, the debugger is able
14901 to work around the issue, but the work-around has to be specifically
14904 @kindex set ada trust-PAD-over-XVS
14905 @kindex show ada trust-PAD-over-XVS
14908 @item set ada trust-PAD-over-XVS on
14909 Configure GDB to strictly follow the GNAT encoding when computing the
14910 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14911 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14912 a complete description of the encoding used by the GNAT compiler).
14913 This is the default.
14915 @item set ada trust-PAD-over-XVS off
14916 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14917 sometimes prints the wrong value for certain entities, changing @code{ada
14918 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14919 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14920 @code{off}, but this incurs a slight performance penalty, so it is
14921 recommended to leave this setting to @code{on} unless necessary.
14925 @node Unsupported Languages
14926 @section Unsupported Languages
14928 @cindex unsupported languages
14929 @cindex minimal language
14930 In addition to the other fully-supported programming languages,
14931 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14932 It does not represent a real programming language, but provides a set
14933 of capabilities close to what the C or assembly languages provide.
14934 This should allow most simple operations to be performed while debugging
14935 an application that uses a language currently not supported by @value{GDBN}.
14937 If the language is set to @code{auto}, @value{GDBN} will automatically
14938 select this language if the current frame corresponds to an unsupported
14942 @chapter Examining the Symbol Table
14944 The commands described in this chapter allow you to inquire about the
14945 symbols (names of variables, functions and types) defined in your
14946 program. This information is inherent in the text of your program and
14947 does not change as your program executes. @value{GDBN} finds it in your
14948 program's symbol table, in the file indicated when you started @value{GDBN}
14949 (@pxref{File Options, ,Choosing Files}), or by one of the
14950 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14952 @cindex symbol names
14953 @cindex names of symbols
14954 @cindex quoting names
14955 Occasionally, you may need to refer to symbols that contain unusual
14956 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14957 most frequent case is in referring to static variables in other
14958 source files (@pxref{Variables,,Program Variables}). File names
14959 are recorded in object files as debugging symbols, but @value{GDBN} would
14960 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14961 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14962 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14969 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14972 @cindex case-insensitive symbol names
14973 @cindex case sensitivity in symbol names
14974 @kindex set case-sensitive
14975 @item set case-sensitive on
14976 @itemx set case-sensitive off
14977 @itemx set case-sensitive auto
14978 Normally, when @value{GDBN} looks up symbols, it matches their names
14979 with case sensitivity determined by the current source language.
14980 Occasionally, you may wish to control that. The command @code{set
14981 case-sensitive} lets you do that by specifying @code{on} for
14982 case-sensitive matches or @code{off} for case-insensitive ones. If
14983 you specify @code{auto}, case sensitivity is reset to the default
14984 suitable for the source language. The default is case-sensitive
14985 matches for all languages except for Fortran, for which the default is
14986 case-insensitive matches.
14988 @kindex show case-sensitive
14989 @item show case-sensitive
14990 This command shows the current setting of case sensitivity for symbols
14993 @kindex set print type methods
14994 @item set print type methods
14995 @itemx set print type methods on
14996 @itemx set print type methods off
14997 Normally, when @value{GDBN} prints a class, it displays any methods
14998 declared in that class. You can control this behavior either by
14999 passing the appropriate flag to @code{ptype}, or using @command{set
15000 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15001 display the methods; this is the default. Specifying @code{off} will
15002 cause @value{GDBN} to omit the methods.
15004 @kindex show print type methods
15005 @item show print type methods
15006 This command shows the current setting of method display when printing
15009 @kindex set print type typedefs
15010 @item set print type typedefs
15011 @itemx set print type typedefs on
15012 @itemx set print type typedefs off
15014 Normally, when @value{GDBN} prints a class, it displays any typedefs
15015 defined in that class. You can control this behavior either by
15016 passing the appropriate flag to @code{ptype}, or using @command{set
15017 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15018 display the typedef definitions; this is the default. Specifying
15019 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15020 Note that this controls whether the typedef definition itself is
15021 printed, not whether typedef names are substituted when printing other
15024 @kindex show print type typedefs
15025 @item show print type typedefs
15026 This command shows the current setting of typedef display when
15029 @kindex info address
15030 @cindex address of a symbol
15031 @item info address @var{symbol}
15032 Describe where the data for @var{symbol} is stored. For a register
15033 variable, this says which register it is kept in. For a non-register
15034 local variable, this prints the stack-frame offset at which the variable
15037 Note the contrast with @samp{print &@var{symbol}}, which does not work
15038 at all for a register variable, and for a stack local variable prints
15039 the exact address of the current instantiation of the variable.
15041 @kindex info symbol
15042 @cindex symbol from address
15043 @cindex closest symbol and offset for an address
15044 @item info symbol @var{addr}
15045 Print the name of a symbol which is stored at the address @var{addr}.
15046 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15047 nearest symbol and an offset from it:
15050 (@value{GDBP}) info symbol 0x54320
15051 _initialize_vx + 396 in section .text
15055 This is the opposite of the @code{info address} command. You can use
15056 it to find out the name of a variable or a function given its address.
15058 For dynamically linked executables, the name of executable or shared
15059 library containing the symbol is also printed:
15062 (@value{GDBP}) info symbol 0x400225
15063 _start + 5 in section .text of /tmp/a.out
15064 (@value{GDBP}) info symbol 0x2aaaac2811cf
15065 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15069 @item whatis[/@var{flags}] [@var{arg}]
15070 Print the data type of @var{arg}, which can be either an expression
15071 or a name of a data type. With no argument, print the data type of
15072 @code{$}, the last value in the value history.
15074 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15075 is not actually evaluated, and any side-effecting operations (such as
15076 assignments or function calls) inside it do not take place.
15078 If @var{arg} is a variable or an expression, @code{whatis} prints its
15079 literal type as it is used in the source code. If the type was
15080 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15081 the data type underlying the @code{typedef}. If the type of the
15082 variable or the expression is a compound data type, such as
15083 @code{struct} or @code{class}, @code{whatis} never prints their
15084 fields or methods. It just prints the @code{struct}/@code{class}
15085 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15086 such a compound data type, use @code{ptype}.
15088 If @var{arg} is a type name that was defined using @code{typedef},
15089 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15090 Unrolling means that @code{whatis} will show the underlying type used
15091 in the @code{typedef} declaration of @var{arg}. However, if that
15092 underlying type is also a @code{typedef}, @code{whatis} will not
15095 For C code, the type names may also have the form @samp{class
15096 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15097 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15099 @var{flags} can be used to modify how the type is displayed.
15100 Available flags are:
15104 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15105 parameters and typedefs defined in a class when printing the class'
15106 members. The @code{/r} flag disables this.
15109 Do not print methods defined in the class.
15112 Print methods defined in the class. This is the default, but the flag
15113 exists in case you change the default with @command{set print type methods}.
15116 Do not print typedefs defined in the class. Note that this controls
15117 whether the typedef definition itself is printed, not whether typedef
15118 names are substituted when printing other types.
15121 Print typedefs defined in the class. This is the default, but the flag
15122 exists in case you change the default with @command{set print type typedefs}.
15126 @item ptype[/@var{flags}] [@var{arg}]
15127 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15128 detailed description of the type, instead of just the name of the type.
15129 @xref{Expressions, ,Expressions}.
15131 Contrary to @code{whatis}, @code{ptype} always unrolls any
15132 @code{typedef}s in its argument declaration, whether the argument is
15133 a variable, expression, or a data type. This means that @code{ptype}
15134 of a variable or an expression will not print literally its type as
15135 present in the source code---use @code{whatis} for that. @code{typedef}s at
15136 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15137 fields, methods and inner @code{class typedef}s of @code{struct}s,
15138 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15140 For example, for this variable declaration:
15143 typedef double real_t;
15144 struct complex @{ real_t real; double imag; @};
15145 typedef struct complex complex_t;
15147 real_t *real_pointer_var;
15151 the two commands give this output:
15155 (@value{GDBP}) whatis var
15157 (@value{GDBP}) ptype var
15158 type = struct complex @{
15162 (@value{GDBP}) whatis complex_t
15163 type = struct complex
15164 (@value{GDBP}) whatis struct complex
15165 type = struct complex
15166 (@value{GDBP}) ptype struct complex
15167 type = struct complex @{
15171 (@value{GDBP}) whatis real_pointer_var
15173 (@value{GDBP}) ptype real_pointer_var
15179 As with @code{whatis}, using @code{ptype} without an argument refers to
15180 the type of @code{$}, the last value in the value history.
15182 @cindex incomplete type
15183 Sometimes, programs use opaque data types or incomplete specifications
15184 of complex data structure. If the debug information included in the
15185 program does not allow @value{GDBN} to display a full declaration of
15186 the data type, it will say @samp{<incomplete type>}. For example,
15187 given these declarations:
15191 struct foo *fooptr;
15195 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15198 (@value{GDBP}) ptype foo
15199 $1 = <incomplete type>
15203 ``Incomplete type'' is C terminology for data types that are not
15204 completely specified.
15207 @item info types @var{regexp}
15209 Print a brief description of all types whose names match the regular
15210 expression @var{regexp} (or all types in your program, if you supply
15211 no argument). Each complete typename is matched as though it were a
15212 complete line; thus, @samp{i type value} gives information on all
15213 types in your program whose names include the string @code{value}, but
15214 @samp{i type ^value$} gives information only on types whose complete
15215 name is @code{value}.
15217 This command differs from @code{ptype} in two ways: first, like
15218 @code{whatis}, it does not print a detailed description; second, it
15219 lists all source files where a type is defined.
15221 @kindex info type-printers
15222 @item info type-printers
15223 Versions of @value{GDBN} that ship with Python scripting enabled may
15224 have ``type printers'' available. When using @command{ptype} or
15225 @command{whatis}, these printers are consulted when the name of a type
15226 is needed. @xref{Type Printing API}, for more information on writing
15229 @code{info type-printers} displays all the available type printers.
15231 @kindex enable type-printer
15232 @kindex disable type-printer
15233 @item enable type-printer @var{name}@dots{}
15234 @item disable type-printer @var{name}@dots{}
15235 These commands can be used to enable or disable type printers.
15238 @cindex local variables
15239 @item info scope @var{location}
15240 List all the variables local to a particular scope. This command
15241 accepts a @var{location} argument---a function name, a source line, or
15242 an address preceded by a @samp{*}, and prints all the variables local
15243 to the scope defined by that location. (@xref{Specify Location}, for
15244 details about supported forms of @var{location}.) For example:
15247 (@value{GDBP}) @b{info scope command_line_handler}
15248 Scope for command_line_handler:
15249 Symbol rl is an argument at stack/frame offset 8, length 4.
15250 Symbol linebuffer is in static storage at address 0x150a18, length 4.
15251 Symbol linelength is in static storage at address 0x150a1c, length 4.
15252 Symbol p is a local variable in register $esi, length 4.
15253 Symbol p1 is a local variable in register $ebx, length 4.
15254 Symbol nline is a local variable in register $edx, length 4.
15255 Symbol repeat is a local variable at frame offset -8, length 4.
15259 This command is especially useful for determining what data to collect
15260 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
15263 @kindex info source
15265 Show information about the current source file---that is, the source file for
15266 the function containing the current point of execution:
15269 the name of the source file, and the directory containing it,
15271 the directory it was compiled in,
15273 its length, in lines,
15275 which programming language it is written in,
15277 whether the executable includes debugging information for that file, and
15278 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
15280 whether the debugging information includes information about
15281 preprocessor macros.
15285 @kindex info sources
15287 Print the names of all source files in your program for which there is
15288 debugging information, organized into two lists: files whose symbols
15289 have already been read, and files whose symbols will be read when needed.
15291 @kindex info functions
15292 @item info functions
15293 Print the names and data types of all defined functions.
15295 @item info functions @var{regexp}
15296 Print the names and data types of all defined functions
15297 whose names contain a match for regular expression @var{regexp}.
15298 Thus, @samp{info fun step} finds all functions whose names
15299 include @code{step}; @samp{info fun ^step} finds those whose names
15300 start with @code{step}. If a function name contains characters
15301 that conflict with the regular expression language (e.g.@:
15302 @samp{operator*()}), they may be quoted with a backslash.
15304 @kindex info variables
15305 @item info variables
15306 Print the names and data types of all variables that are defined
15307 outside of functions (i.e.@: excluding local variables).
15309 @item info variables @var{regexp}
15310 Print the names and data types of all variables (except for local
15311 variables) whose names contain a match for regular expression
15314 @kindex info classes
15315 @cindex Objective-C, classes and selectors
15317 @itemx info classes @var{regexp}
15318 Display all Objective-C classes in your program, or
15319 (with the @var{regexp} argument) all those matching a particular regular
15322 @kindex info selectors
15323 @item info selectors
15324 @itemx info selectors @var{regexp}
15325 Display all Objective-C selectors in your program, or
15326 (with the @var{regexp} argument) all those matching a particular regular
15330 This was never implemented.
15331 @kindex info methods
15333 @itemx info methods @var{regexp}
15334 The @code{info methods} command permits the user to examine all defined
15335 methods within C@t{++} program, or (with the @var{regexp} argument) a
15336 specific set of methods found in the various C@t{++} classes. Many
15337 C@t{++} classes provide a large number of methods. Thus, the output
15338 from the @code{ptype} command can be overwhelming and hard to use. The
15339 @code{info-methods} command filters the methods, printing only those
15340 which match the regular-expression @var{regexp}.
15343 @cindex opaque data types
15344 @kindex set opaque-type-resolution
15345 @item set opaque-type-resolution on
15346 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
15347 declared as a pointer to a @code{struct}, @code{class}, or
15348 @code{union}---for example, @code{struct MyType *}---that is used in one
15349 source file although the full declaration of @code{struct MyType} is in
15350 another source file. The default is on.
15352 A change in the setting of this subcommand will not take effect until
15353 the next time symbols for a file are loaded.
15355 @item set opaque-type-resolution off
15356 Tell @value{GDBN} not to resolve opaque types. In this case, the type
15357 is printed as follows:
15359 @{<no data fields>@}
15362 @kindex show opaque-type-resolution
15363 @item show opaque-type-resolution
15364 Show whether opaque types are resolved or not.
15366 @kindex maint print symbols
15367 @cindex symbol dump
15368 @kindex maint print psymbols
15369 @cindex partial symbol dump
15370 @item maint print symbols @var{filename}
15371 @itemx maint print psymbols @var{filename}
15372 @itemx maint print msymbols @var{filename}
15373 Write a dump of debugging symbol data into the file @var{filename}.
15374 These commands are used to debug the @value{GDBN} symbol-reading code. Only
15375 symbols with debugging data are included. If you use @samp{maint print
15376 symbols}, @value{GDBN} includes all the symbols for which it has already
15377 collected full details: that is, @var{filename} reflects symbols for
15378 only those files whose symbols @value{GDBN} has read. You can use the
15379 command @code{info sources} to find out which files these are. If you
15380 use @samp{maint print psymbols} instead, the dump shows information about
15381 symbols that @value{GDBN} only knows partially---that is, symbols defined in
15382 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
15383 @samp{maint print msymbols} dumps just the minimal symbol information
15384 required for each object file from which @value{GDBN} has read some symbols.
15385 @xref{Files, ,Commands to Specify Files}, for a discussion of how
15386 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
15388 @kindex maint info symtabs
15389 @kindex maint info psymtabs
15390 @cindex listing @value{GDBN}'s internal symbol tables
15391 @cindex symbol tables, listing @value{GDBN}'s internal
15392 @cindex full symbol tables, listing @value{GDBN}'s internal
15393 @cindex partial symbol tables, listing @value{GDBN}'s internal
15394 @item maint info symtabs @r{[} @var{regexp} @r{]}
15395 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
15397 List the @code{struct symtab} or @code{struct partial_symtab}
15398 structures whose names match @var{regexp}. If @var{regexp} is not
15399 given, list them all. The output includes expressions which you can
15400 copy into a @value{GDBN} debugging this one to examine a particular
15401 structure in more detail. For example:
15404 (@value{GDBP}) maint info psymtabs dwarf2read
15405 @{ objfile /home/gnu/build/gdb/gdb
15406 ((struct objfile *) 0x82e69d0)
15407 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
15408 ((struct partial_symtab *) 0x8474b10)
15411 text addresses 0x814d3c8 -- 0x8158074
15412 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
15413 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
15414 dependencies (none)
15417 (@value{GDBP}) maint info symtabs
15421 We see that there is one partial symbol table whose filename contains
15422 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
15423 and we see that @value{GDBN} has not read in any symtabs yet at all.
15424 If we set a breakpoint on a function, that will cause @value{GDBN} to
15425 read the symtab for the compilation unit containing that function:
15428 (@value{GDBP}) break dwarf2_psymtab_to_symtab
15429 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
15431 (@value{GDBP}) maint info symtabs
15432 @{ objfile /home/gnu/build/gdb/gdb
15433 ((struct objfile *) 0x82e69d0)
15434 @{ symtab /home/gnu/src/gdb/dwarf2read.c
15435 ((struct symtab *) 0x86c1f38)
15438 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
15439 linetable ((struct linetable *) 0x8370fa0)
15440 debugformat DWARF 2
15449 @chapter Altering Execution
15451 Once you think you have found an error in your program, you might want to
15452 find out for certain whether correcting the apparent error would lead to
15453 correct results in the rest of the run. You can find the answer by
15454 experiment, using the @value{GDBN} features for altering execution of the
15457 For example, you can store new values into variables or memory
15458 locations, give your program a signal, restart it at a different
15459 address, or even return prematurely from a function.
15462 * Assignment:: Assignment to variables
15463 * Jumping:: Continuing at a different address
15464 * Signaling:: Giving your program a signal
15465 * Returning:: Returning from a function
15466 * Calling:: Calling your program's functions
15467 * Patching:: Patching your program
15471 @section Assignment to Variables
15474 @cindex setting variables
15475 To alter the value of a variable, evaluate an assignment expression.
15476 @xref{Expressions, ,Expressions}. For example,
15483 stores the value 4 into the variable @code{x}, and then prints the
15484 value of the assignment expression (which is 4).
15485 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
15486 information on operators in supported languages.
15488 @kindex set variable
15489 @cindex variables, setting
15490 If you are not interested in seeing the value of the assignment, use the
15491 @code{set} command instead of the @code{print} command. @code{set} is
15492 really the same as @code{print} except that the expression's value is
15493 not printed and is not put in the value history (@pxref{Value History,
15494 ,Value History}). The expression is evaluated only for its effects.
15496 If the beginning of the argument string of the @code{set} command
15497 appears identical to a @code{set} subcommand, use the @code{set
15498 variable} command instead of just @code{set}. This command is identical
15499 to @code{set} except for its lack of subcommands. For example, if your
15500 program has a variable @code{width}, you get an error if you try to set
15501 a new value with just @samp{set width=13}, because @value{GDBN} has the
15502 command @code{set width}:
15505 (@value{GDBP}) whatis width
15507 (@value{GDBP}) p width
15509 (@value{GDBP}) set width=47
15510 Invalid syntax in expression.
15514 The invalid expression, of course, is @samp{=47}. In
15515 order to actually set the program's variable @code{width}, use
15518 (@value{GDBP}) set var width=47
15521 Because the @code{set} command has many subcommands that can conflict
15522 with the names of program variables, it is a good idea to use the
15523 @code{set variable} command instead of just @code{set}. For example, if
15524 your program has a variable @code{g}, you run into problems if you try
15525 to set a new value with just @samp{set g=4}, because @value{GDBN} has
15526 the command @code{set gnutarget}, abbreviated @code{set g}:
15530 (@value{GDBP}) whatis g
15534 (@value{GDBP}) set g=4
15538 The program being debugged has been started already.
15539 Start it from the beginning? (y or n) y
15540 Starting program: /home/smith/cc_progs/a.out
15541 "/home/smith/cc_progs/a.out": can't open to read symbols:
15542 Invalid bfd target.
15543 (@value{GDBP}) show g
15544 The current BFD target is "=4".
15549 The program variable @code{g} did not change, and you silently set the
15550 @code{gnutarget} to an invalid value. In order to set the variable
15554 (@value{GDBP}) set var g=4
15557 @value{GDBN} allows more implicit conversions in assignments than C; you can
15558 freely store an integer value into a pointer variable or vice versa,
15559 and you can convert any structure to any other structure that is the
15560 same length or shorter.
15561 @comment FIXME: how do structs align/pad in these conversions?
15562 @comment /doc@cygnus.com 18dec1990
15564 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
15565 construct to generate a value of specified type at a specified address
15566 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
15567 to memory location @code{0x83040} as an integer (which implies a certain size
15568 and representation in memory), and
15571 set @{int@}0x83040 = 4
15575 stores the value 4 into that memory location.
15578 @section Continuing at a Different Address
15580 Ordinarily, when you continue your program, you do so at the place where
15581 it stopped, with the @code{continue} command. You can instead continue at
15582 an address of your own choosing, with the following commands:
15586 @kindex j @r{(@code{jump})}
15587 @item jump @var{linespec}
15588 @itemx j @var{linespec}
15589 @itemx jump @var{location}
15590 @itemx j @var{location}
15591 Resume execution at line @var{linespec} or at address given by
15592 @var{location}. Execution stops again immediately if there is a
15593 breakpoint there. @xref{Specify Location}, for a description of the
15594 different forms of @var{linespec} and @var{location}. It is common
15595 practice to use the @code{tbreak} command in conjunction with
15596 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
15598 The @code{jump} command does not change the current stack frame, or
15599 the stack pointer, or the contents of any memory location or any
15600 register other than the program counter. If line @var{linespec} is in
15601 a different function from the one currently executing, the results may
15602 be bizarre if the two functions expect different patterns of arguments or
15603 of local variables. For this reason, the @code{jump} command requests
15604 confirmation if the specified line is not in the function currently
15605 executing. However, even bizarre results are predictable if you are
15606 well acquainted with the machine-language code of your program.
15609 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
15610 On many systems, you can get much the same effect as the @code{jump}
15611 command by storing a new value into the register @code{$pc}. The
15612 difference is that this does not start your program running; it only
15613 changes the address of where it @emph{will} run when you continue. For
15621 makes the next @code{continue} command or stepping command execute at
15622 address @code{0x485}, rather than at the address where your program stopped.
15623 @xref{Continuing and Stepping, ,Continuing and Stepping}.
15625 The most common occasion to use the @code{jump} command is to back
15626 up---perhaps with more breakpoints set---over a portion of a program
15627 that has already executed, in order to examine its execution in more
15632 @section Giving your Program a Signal
15633 @cindex deliver a signal to a program
15637 @item signal @var{signal}
15638 Resume execution where your program stopped, but immediately give it the
15639 signal @var{signal}. @var{signal} can be the name or the number of a
15640 signal. For example, on many systems @code{signal 2} and @code{signal
15641 SIGINT} are both ways of sending an interrupt signal.
15643 Alternatively, if @var{signal} is zero, continue execution without
15644 giving a signal. This is useful when your program stopped on account of
15645 a signal and would ordinarily see the signal when resumed with the
15646 @code{continue} command; @samp{signal 0} causes it to resume without a
15649 @code{signal} does not repeat when you press @key{RET} a second time
15650 after executing the command.
15654 Invoking the @code{signal} command is not the same as invoking the
15655 @code{kill} utility from the shell. Sending a signal with @code{kill}
15656 causes @value{GDBN} to decide what to do with the signal depending on
15657 the signal handling tables (@pxref{Signals}). The @code{signal} command
15658 passes the signal directly to your program.
15662 @section Returning from a Function
15665 @cindex returning from a function
15668 @itemx return @var{expression}
15669 You can cancel execution of a function call with the @code{return}
15670 command. If you give an
15671 @var{expression} argument, its value is used as the function's return
15675 When you use @code{return}, @value{GDBN} discards the selected stack frame
15676 (and all frames within it). You can think of this as making the
15677 discarded frame return prematurely. If you wish to specify a value to
15678 be returned, give that value as the argument to @code{return}.
15680 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15681 Frame}), and any other frames inside of it, leaving its caller as the
15682 innermost remaining frame. That frame becomes selected. The
15683 specified value is stored in the registers used for returning values
15686 The @code{return} command does not resume execution; it leaves the
15687 program stopped in the state that would exist if the function had just
15688 returned. In contrast, the @code{finish} command (@pxref{Continuing
15689 and Stepping, ,Continuing and Stepping}) resumes execution until the
15690 selected stack frame returns naturally.
15692 @value{GDBN} needs to know how the @var{expression} argument should be set for
15693 the inferior. The concrete registers assignment depends on the OS ABI and the
15694 type being returned by the selected stack frame. For example it is common for
15695 OS ABI to return floating point values in FPU registers while integer values in
15696 CPU registers. Still some ABIs return even floating point values in CPU
15697 registers. Larger integer widths (such as @code{long long int}) also have
15698 specific placement rules. @value{GDBN} already knows the OS ABI from its
15699 current target so it needs to find out also the type being returned to make the
15700 assignment into the right register(s).
15702 Normally, the selected stack frame has debug info. @value{GDBN} will always
15703 use the debug info instead of the implicit type of @var{expression} when the
15704 debug info is available. For example, if you type @kbd{return -1}, and the
15705 function in the current stack frame is declared to return a @code{long long
15706 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15707 into a @code{long long int}:
15710 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15712 (@value{GDBP}) return -1
15713 Make func return now? (y or n) y
15714 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15715 43 printf ("result=%lld\n", func ());
15719 However, if the selected stack frame does not have a debug info, e.g., if the
15720 function was compiled without debug info, @value{GDBN} has to find out the type
15721 to return from user. Specifying a different type by mistake may set the value
15722 in different inferior registers than the caller code expects. For example,
15723 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15724 of a @code{long long int} result for a debug info less function (on 32-bit
15725 architectures). Therefore the user is required to specify the return type by
15726 an appropriate cast explicitly:
15729 Breakpoint 2, 0x0040050b in func ()
15730 (@value{GDBP}) return -1
15731 Return value type not available for selected stack frame.
15732 Please use an explicit cast of the value to return.
15733 (@value{GDBP}) return (long long int) -1
15734 Make selected stack frame return now? (y or n) y
15735 #0 0x00400526 in main ()
15740 @section Calling Program Functions
15743 @cindex calling functions
15744 @cindex inferior functions, calling
15745 @item print @var{expr}
15746 Evaluate the expression @var{expr} and display the resulting value.
15747 @var{expr} may include calls to functions in the program being
15751 @item call @var{expr}
15752 Evaluate the expression @var{expr} without displaying @code{void}
15755 You can use this variant of the @code{print} command if you want to
15756 execute a function from your program that does not return anything
15757 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15758 with @code{void} returned values that @value{GDBN} will otherwise
15759 print. If the result is not void, it is printed and saved in the
15763 It is possible for the function you call via the @code{print} or
15764 @code{call} command to generate a signal (e.g., if there's a bug in
15765 the function, or if you passed it incorrect arguments). What happens
15766 in that case is controlled by the @code{set unwindonsignal} command.
15768 Similarly, with a C@t{++} program it is possible for the function you
15769 call via the @code{print} or @code{call} command to generate an
15770 exception that is not handled due to the constraints of the dummy
15771 frame. In this case, any exception that is raised in the frame, but has
15772 an out-of-frame exception handler will not be found. GDB builds a
15773 dummy-frame for the inferior function call, and the unwinder cannot
15774 seek for exception handlers outside of this dummy-frame. What happens
15775 in that case is controlled by the
15776 @code{set unwind-on-terminating-exception} command.
15779 @item set unwindonsignal
15780 @kindex set unwindonsignal
15781 @cindex unwind stack in called functions
15782 @cindex call dummy stack unwinding
15783 Set unwinding of the stack if a signal is received while in a function
15784 that @value{GDBN} called in the program being debugged. If set to on,
15785 @value{GDBN} unwinds the stack it created for the call and restores
15786 the context to what it was before the call. If set to off (the
15787 default), @value{GDBN} stops in the frame where the signal was
15790 @item show unwindonsignal
15791 @kindex show unwindonsignal
15792 Show the current setting of stack unwinding in the functions called by
15795 @item set unwind-on-terminating-exception
15796 @kindex set unwind-on-terminating-exception
15797 @cindex unwind stack in called functions with unhandled exceptions
15798 @cindex call dummy stack unwinding on unhandled exception.
15799 Set unwinding of the stack if a C@t{++} exception is raised, but left
15800 unhandled while in a function that @value{GDBN} called in the program being
15801 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15802 it created for the call and restores the context to what it was before
15803 the call. If set to off, @value{GDBN} the exception is delivered to
15804 the default C@t{++} exception handler and the inferior terminated.
15806 @item show unwind-on-terminating-exception
15807 @kindex show unwind-on-terminating-exception
15808 Show the current setting of stack unwinding in the functions called by
15813 @cindex weak alias functions
15814 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15815 for another function. In such case, @value{GDBN} might not pick up
15816 the type information, including the types of the function arguments,
15817 which causes @value{GDBN} to call the inferior function incorrectly.
15818 As a result, the called function will function erroneously and may
15819 even crash. A solution to that is to use the name of the aliased
15823 @section Patching Programs
15825 @cindex patching binaries
15826 @cindex writing into executables
15827 @cindex writing into corefiles
15829 By default, @value{GDBN} opens the file containing your program's
15830 executable code (or the corefile) read-only. This prevents accidental
15831 alterations to machine code; but it also prevents you from intentionally
15832 patching your program's binary.
15834 If you'd like to be able to patch the binary, you can specify that
15835 explicitly with the @code{set write} command. For example, you might
15836 want to turn on internal debugging flags, or even to make emergency
15842 @itemx set write off
15843 If you specify @samp{set write on}, @value{GDBN} opens executable and
15844 core files for both reading and writing; if you specify @kbd{set write
15845 off} (the default), @value{GDBN} opens them read-only.
15847 If you have already loaded a file, you must load it again (using the
15848 @code{exec-file} or @code{core-file} command) after changing @code{set
15849 write}, for your new setting to take effect.
15853 Display whether executable files and core files are opened for writing
15854 as well as reading.
15858 @chapter @value{GDBN} Files
15860 @value{GDBN} needs to know the file name of the program to be debugged,
15861 both in order to read its symbol table and in order to start your
15862 program. To debug a core dump of a previous run, you must also tell
15863 @value{GDBN} the name of the core dump file.
15866 * Files:: Commands to specify files
15867 * Separate Debug Files:: Debugging information in separate files
15868 * MiniDebugInfo:: Debugging information in a special section
15869 * Index Files:: Index files speed up GDB
15870 * Symbol Errors:: Errors reading symbol files
15871 * Data Files:: GDB data files
15875 @section Commands to Specify Files
15877 @cindex symbol table
15878 @cindex core dump file
15880 You may want to specify executable and core dump file names. The usual
15881 way to do this is at start-up time, using the arguments to
15882 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15883 Out of @value{GDBN}}).
15885 Occasionally it is necessary to change to a different file during a
15886 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15887 specify a file you want to use. Or you are debugging a remote target
15888 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15889 Program}). In these situations the @value{GDBN} commands to specify
15890 new files are useful.
15893 @cindex executable file
15895 @item file @var{filename}
15896 Use @var{filename} as the program to be debugged. It is read for its
15897 symbols and for the contents of pure memory. It is also the program
15898 executed when you use the @code{run} command. If you do not specify a
15899 directory and the file is not found in the @value{GDBN} working directory,
15900 @value{GDBN} uses the environment variable @code{PATH} as a list of
15901 directories to search, just as the shell does when looking for a program
15902 to run. You can change the value of this variable, for both @value{GDBN}
15903 and your program, using the @code{path} command.
15905 @cindex unlinked object files
15906 @cindex patching object files
15907 You can load unlinked object @file{.o} files into @value{GDBN} using
15908 the @code{file} command. You will not be able to ``run'' an object
15909 file, but you can disassemble functions and inspect variables. Also,
15910 if the underlying BFD functionality supports it, you could use
15911 @kbd{gdb -write} to patch object files using this technique. Note
15912 that @value{GDBN} can neither interpret nor modify relocations in this
15913 case, so branches and some initialized variables will appear to go to
15914 the wrong place. But this feature is still handy from time to time.
15917 @code{file} with no argument makes @value{GDBN} discard any information it
15918 has on both executable file and the symbol table.
15921 @item exec-file @r{[} @var{filename} @r{]}
15922 Specify that the program to be run (but not the symbol table) is found
15923 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15924 if necessary to locate your program. Omitting @var{filename} means to
15925 discard information on the executable file.
15927 @kindex symbol-file
15928 @item symbol-file @r{[} @var{filename} @r{]}
15929 Read symbol table information from file @var{filename}. @code{PATH} is
15930 searched when necessary. Use the @code{file} command to get both symbol
15931 table and program to run from the same file.
15933 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15934 program's symbol table.
15936 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15937 some breakpoints and auto-display expressions. This is because they may
15938 contain pointers to the internal data recording symbols and data types,
15939 which are part of the old symbol table data being discarded inside
15942 @code{symbol-file} does not repeat if you press @key{RET} again after
15945 When @value{GDBN} is configured for a particular environment, it
15946 understands debugging information in whatever format is the standard
15947 generated for that environment; you may use either a @sc{gnu} compiler, or
15948 other compilers that adhere to the local conventions.
15949 Best results are usually obtained from @sc{gnu} compilers; for example,
15950 using @code{@value{NGCC}} you can generate debugging information for
15953 For most kinds of object files, with the exception of old SVR3 systems
15954 using COFF, the @code{symbol-file} command does not normally read the
15955 symbol table in full right away. Instead, it scans the symbol table
15956 quickly to find which source files and which symbols are present. The
15957 details are read later, one source file at a time, as they are needed.
15959 The purpose of this two-stage reading strategy is to make @value{GDBN}
15960 start up faster. For the most part, it is invisible except for
15961 occasional pauses while the symbol table details for a particular source
15962 file are being read. (The @code{set verbose} command can turn these
15963 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15964 Warnings and Messages}.)
15966 We have not implemented the two-stage strategy for COFF yet. When the
15967 symbol table is stored in COFF format, @code{symbol-file} reads the
15968 symbol table data in full right away. Note that ``stabs-in-COFF''
15969 still does the two-stage strategy, since the debug info is actually
15973 @cindex reading symbols immediately
15974 @cindex symbols, reading immediately
15975 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15976 @itemx file @r{[} -readnow @r{]} @var{filename}
15977 You can override the @value{GDBN} two-stage strategy for reading symbol
15978 tables by using the @samp{-readnow} option with any of the commands that
15979 load symbol table information, if you want to be sure @value{GDBN} has the
15980 entire symbol table available.
15982 @c FIXME: for now no mention of directories, since this seems to be in
15983 @c flux. 13mar1992 status is that in theory GDB would look either in
15984 @c current dir or in same dir as myprog; but issues like competing
15985 @c GDB's, or clutter in system dirs, mean that in practice right now
15986 @c only current dir is used. FFish says maybe a special GDB hierarchy
15987 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15991 @item core-file @r{[}@var{filename}@r{]}
15993 Specify the whereabouts of a core dump file to be used as the ``contents
15994 of memory''. Traditionally, core files contain only some parts of the
15995 address space of the process that generated them; @value{GDBN} can access the
15996 executable file itself for other parts.
15998 @code{core-file} with no argument specifies that no core file is
16001 Note that the core file is ignored when your program is actually running
16002 under @value{GDBN}. So, if you have been running your program and you
16003 wish to debug a core file instead, you must kill the subprocess in which
16004 the program is running. To do this, use the @code{kill} command
16005 (@pxref{Kill Process, ,Killing the Child Process}).
16007 @kindex add-symbol-file
16008 @cindex dynamic linking
16009 @item add-symbol-file @var{filename} @var{address}
16010 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16011 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16012 The @code{add-symbol-file} command reads additional symbol table
16013 information from the file @var{filename}. You would use this command
16014 when @var{filename} has been dynamically loaded (by some other means)
16015 into the program that is running. @var{address} should be the memory
16016 address at which the file has been loaded; @value{GDBN} cannot figure
16017 this out for itself. You can additionally specify an arbitrary number
16018 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16019 section name and base address for that section. You can specify any
16020 @var{address} as an expression.
16022 The symbol table of the file @var{filename} is added to the symbol table
16023 originally read with the @code{symbol-file} command. You can use the
16024 @code{add-symbol-file} command any number of times; the new symbol data
16025 thus read keeps adding to the old. To discard all old symbol data
16026 instead, use the @code{symbol-file} command without any arguments.
16028 @cindex relocatable object files, reading symbols from
16029 @cindex object files, relocatable, reading symbols from
16030 @cindex reading symbols from relocatable object files
16031 @cindex symbols, reading from relocatable object files
16032 @cindex @file{.o} files, reading symbols from
16033 Although @var{filename} is typically a shared library file, an
16034 executable file, or some other object file which has been fully
16035 relocated for loading into a process, you can also load symbolic
16036 information from relocatable @file{.o} files, as long as:
16040 the file's symbolic information refers only to linker symbols defined in
16041 that file, not to symbols defined by other object files,
16043 every section the file's symbolic information refers to has actually
16044 been loaded into the inferior, as it appears in the file, and
16046 you can determine the address at which every section was loaded, and
16047 provide these to the @code{add-symbol-file} command.
16051 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16052 relocatable files into an already running program; such systems
16053 typically make the requirements above easy to meet. However, it's
16054 important to recognize that many native systems use complex link
16055 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16056 assembly, for example) that make the requirements difficult to meet. In
16057 general, one cannot assume that using @code{add-symbol-file} to read a
16058 relocatable object file's symbolic information will have the same effect
16059 as linking the relocatable object file into the program in the normal
16062 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16064 @kindex add-symbol-file-from-memory
16065 @cindex @code{syscall DSO}
16066 @cindex load symbols from memory
16067 @item add-symbol-file-from-memory @var{address}
16068 Load symbols from the given @var{address} in a dynamically loaded
16069 object file whose image is mapped directly into the inferior's memory.
16070 For example, the Linux kernel maps a @code{syscall DSO} into each
16071 process's address space; this DSO provides kernel-specific code for
16072 some system calls. The argument can be any expression whose
16073 evaluation yields the address of the file's shared object file header.
16074 For this command to work, you must have used @code{symbol-file} or
16075 @code{exec-file} commands in advance.
16077 @kindex add-shared-symbol-files
16079 @item add-shared-symbol-files @var{library-file}
16080 @itemx assf @var{library-file}
16081 The @code{add-shared-symbol-files} command can currently be used only
16082 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16083 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16084 @value{GDBN} automatically looks for shared libraries, however if
16085 @value{GDBN} does not find yours, you can invoke
16086 @code{add-shared-symbol-files}. It takes one argument: the shared
16087 library's file name. @code{assf} is a shorthand alias for
16088 @code{add-shared-symbol-files}.
16091 @item section @var{section} @var{addr}
16092 The @code{section} command changes the base address of the named
16093 @var{section} of the exec file to @var{addr}. This can be used if the
16094 exec file does not contain section addresses, (such as in the
16095 @code{a.out} format), or when the addresses specified in the file
16096 itself are wrong. Each section must be changed separately. The
16097 @code{info files} command, described below, lists all the sections and
16101 @kindex info target
16104 @code{info files} and @code{info target} are synonymous; both print the
16105 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16106 including the names of the executable and core dump files currently in
16107 use by @value{GDBN}, and the files from which symbols were loaded. The
16108 command @code{help target} lists all possible targets rather than
16111 @kindex maint info sections
16112 @item maint info sections
16113 Another command that can give you extra information about program sections
16114 is @code{maint info sections}. In addition to the section information
16115 displayed by @code{info files}, this command displays the flags and file
16116 offset of each section in the executable and core dump files. In addition,
16117 @code{maint info sections} provides the following command options (which
16118 may be arbitrarily combined):
16122 Display sections for all loaded object files, including shared libraries.
16123 @item @var{sections}
16124 Display info only for named @var{sections}.
16125 @item @var{section-flags}
16126 Display info only for sections for which @var{section-flags} are true.
16127 The section flags that @value{GDBN} currently knows about are:
16130 Section will have space allocated in the process when loaded.
16131 Set for all sections except those containing debug information.
16133 Section will be loaded from the file into the child process memory.
16134 Set for pre-initialized code and data, clear for @code{.bss} sections.
16136 Section needs to be relocated before loading.
16138 Section cannot be modified by the child process.
16140 Section contains executable code only.
16142 Section contains data only (no executable code).
16144 Section will reside in ROM.
16146 Section contains data for constructor/destructor lists.
16148 Section is not empty.
16150 An instruction to the linker to not output the section.
16151 @item COFF_SHARED_LIBRARY
16152 A notification to the linker that the section contains
16153 COFF shared library information.
16155 Section contains common symbols.
16158 @kindex set trust-readonly-sections
16159 @cindex read-only sections
16160 @item set trust-readonly-sections on
16161 Tell @value{GDBN} that readonly sections in your object file
16162 really are read-only (i.e.@: that their contents will not change).
16163 In that case, @value{GDBN} can fetch values from these sections
16164 out of the object file, rather than from the target program.
16165 For some targets (notably embedded ones), this can be a significant
16166 enhancement to debugging performance.
16168 The default is off.
16170 @item set trust-readonly-sections off
16171 Tell @value{GDBN} not to trust readonly sections. This means that
16172 the contents of the section might change while the program is running,
16173 and must therefore be fetched from the target when needed.
16175 @item show trust-readonly-sections
16176 Show the current setting of trusting readonly sections.
16179 All file-specifying commands allow both absolute and relative file names
16180 as arguments. @value{GDBN} always converts the file name to an absolute file
16181 name and remembers it that way.
16183 @cindex shared libraries
16184 @anchor{Shared Libraries}
16185 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16186 and IBM RS/6000 AIX shared libraries.
16188 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16189 shared libraries. @xref{Expat}.
16191 @value{GDBN} automatically loads symbol definitions from shared libraries
16192 when you use the @code{run} command, or when you examine a core file.
16193 (Before you issue the @code{run} command, @value{GDBN} does not understand
16194 references to a function in a shared library, however---unless you are
16195 debugging a core file).
16197 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16198 automatically loads the symbols at the time of the @code{shl_load} call.
16200 @c FIXME: some @value{GDBN} release may permit some refs to undef
16201 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16202 @c FIXME...lib; check this from time to time when updating manual
16204 There are times, however, when you may wish to not automatically load
16205 symbol definitions from shared libraries, such as when they are
16206 particularly large or there are many of them.
16208 To control the automatic loading of shared library symbols, use the
16212 @kindex set auto-solib-add
16213 @item set auto-solib-add @var{mode}
16214 If @var{mode} is @code{on}, symbols from all shared object libraries
16215 will be loaded automatically when the inferior begins execution, you
16216 attach to an independently started inferior, or when the dynamic linker
16217 informs @value{GDBN} that a new library has been loaded. If @var{mode}
16218 is @code{off}, symbols must be loaded manually, using the
16219 @code{sharedlibrary} command. The default value is @code{on}.
16221 @cindex memory used for symbol tables
16222 If your program uses lots of shared libraries with debug info that
16223 takes large amounts of memory, you can decrease the @value{GDBN}
16224 memory footprint by preventing it from automatically loading the
16225 symbols from shared libraries. To that end, type @kbd{set
16226 auto-solib-add off} before running the inferior, then load each
16227 library whose debug symbols you do need with @kbd{sharedlibrary
16228 @var{regexp}}, where @var{regexp} is a regular expression that matches
16229 the libraries whose symbols you want to be loaded.
16231 @kindex show auto-solib-add
16232 @item show auto-solib-add
16233 Display the current autoloading mode.
16236 @cindex load shared library
16237 To explicitly load shared library symbols, use the @code{sharedlibrary}
16241 @kindex info sharedlibrary
16243 @item info share @var{regex}
16244 @itemx info sharedlibrary @var{regex}
16245 Print the names of the shared libraries which are currently loaded
16246 that match @var{regex}. If @var{regex} is omitted then print
16247 all shared libraries that are loaded.
16249 @kindex sharedlibrary
16251 @item sharedlibrary @var{regex}
16252 @itemx share @var{regex}
16253 Load shared object library symbols for files matching a
16254 Unix regular expression.
16255 As with files loaded automatically, it only loads shared libraries
16256 required by your program for a core file or after typing @code{run}. If
16257 @var{regex} is omitted all shared libraries required by your program are
16260 @item nosharedlibrary
16261 @kindex nosharedlibrary
16262 @cindex unload symbols from shared libraries
16263 Unload all shared object library symbols. This discards all symbols
16264 that have been loaded from all shared libraries. Symbols from shared
16265 libraries that were loaded by explicit user requests are not
16269 Sometimes you may wish that @value{GDBN} stops and gives you control
16270 when any of shared library events happen. The best way to do this is
16271 to use @code{catch load} and @code{catch unload} (@pxref{Set
16274 @value{GDBN} also supports the the @code{set stop-on-solib-events}
16275 command for this. This command exists for historical reasons. It is
16276 less useful than setting a catchpoint, because it does not allow for
16277 conditions or commands as a catchpoint does.
16280 @item set stop-on-solib-events
16281 @kindex set stop-on-solib-events
16282 This command controls whether @value{GDBN} should give you control
16283 when the dynamic linker notifies it about some shared library event.
16284 The most common event of interest is loading or unloading of a new
16287 @item show stop-on-solib-events
16288 @kindex show stop-on-solib-events
16289 Show whether @value{GDBN} stops and gives you control when shared
16290 library events happen.
16293 Shared libraries are also supported in many cross or remote debugging
16294 configurations. @value{GDBN} needs to have access to the target's libraries;
16295 this can be accomplished either by providing copies of the libraries
16296 on the host system, or by asking @value{GDBN} to automatically retrieve the
16297 libraries from the target. If copies of the target libraries are
16298 provided, they need to be the same as the target libraries, although the
16299 copies on the target can be stripped as long as the copies on the host are
16302 @cindex where to look for shared libraries
16303 For remote debugging, you need to tell @value{GDBN} where the target
16304 libraries are, so that it can load the correct copies---otherwise, it
16305 may try to load the host's libraries. @value{GDBN} has two variables
16306 to specify the search directories for target libraries.
16309 @cindex prefix for shared library file names
16310 @cindex system root, alternate
16311 @kindex set solib-absolute-prefix
16312 @kindex set sysroot
16313 @item set sysroot @var{path}
16314 Use @var{path} as the system root for the program being debugged. Any
16315 absolute shared library paths will be prefixed with @var{path}; many
16316 runtime loaders store the absolute paths to the shared library in the
16317 target program's memory. If you use @code{set sysroot} to find shared
16318 libraries, they need to be laid out in the same way that they are on
16319 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
16322 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
16323 retrieve the target libraries from the remote system. This is only
16324 supported when using a remote target that supports the @code{remote get}
16325 command (@pxref{File Transfer,,Sending files to a remote system}).
16326 The part of @var{path} following the initial @file{remote:}
16327 (if present) is used as system root prefix on the remote file system.
16328 @footnote{If you want to specify a local system root using a directory
16329 that happens to be named @file{remote:}, you need to use some equivalent
16330 variant of the name like @file{./remote:}.}
16332 For targets with an MS-DOS based filesystem, such as MS-Windows and
16333 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
16334 absolute file name with @var{path}. But first, on Unix hosts,
16335 @value{GDBN} converts all backslash directory separators into forward
16336 slashes, because the backslash is not a directory separator on Unix:
16339 c:\foo\bar.dll @result{} c:/foo/bar.dll
16342 Then, @value{GDBN} attempts prefixing the target file name with
16343 @var{path}, and looks for the resulting file name in the host file
16347 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
16350 If that does not find the shared library, @value{GDBN} tries removing
16351 the @samp{:} character from the drive spec, both for convenience, and,
16352 for the case of the host file system not supporting file names with
16356 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
16359 This makes it possible to have a system root that mirrors a target
16360 with more than one drive. E.g., you may want to setup your local
16361 copies of the target system shared libraries like so (note @samp{c} vs
16365 @file{/path/to/sysroot/c/sys/bin/foo.dll}
16366 @file{/path/to/sysroot/c/sys/bin/bar.dll}
16367 @file{/path/to/sysroot/z/sys/bin/bar.dll}
16371 and point the system root at @file{/path/to/sysroot}, so that
16372 @value{GDBN} can find the correct copies of both
16373 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
16375 If that still does not find the shared library, @value{GDBN} tries
16376 removing the whole drive spec from the target file name:
16379 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
16382 This last lookup makes it possible to not care about the drive name,
16383 if you don't want or need to.
16385 The @code{set solib-absolute-prefix} command is an alias for @code{set
16388 @cindex default system root
16389 @cindex @samp{--with-sysroot}
16390 You can set the default system root by using the configure-time
16391 @samp{--with-sysroot} option. If the system root is inside
16392 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16393 @samp{--exec-prefix}), then the default system root will be updated
16394 automatically if the installed @value{GDBN} is moved to a new
16397 @kindex show sysroot
16399 Display the current shared library prefix.
16401 @kindex set solib-search-path
16402 @item set solib-search-path @var{path}
16403 If this variable is set, @var{path} is a colon-separated list of
16404 directories to search for shared libraries. @samp{solib-search-path}
16405 is used after @samp{sysroot} fails to locate the library, or if the
16406 path to the library is relative instead of absolute. If you want to
16407 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
16408 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
16409 finding your host's libraries. @samp{sysroot} is preferred; setting
16410 it to a nonexistent directory may interfere with automatic loading
16411 of shared library symbols.
16413 @kindex show solib-search-path
16414 @item show solib-search-path
16415 Display the current shared library search path.
16417 @cindex DOS file-name semantics of file names.
16418 @kindex set target-file-system-kind (unix|dos-based|auto)
16419 @kindex show target-file-system-kind
16420 @item set target-file-system-kind @var{kind}
16421 Set assumed file system kind for target reported file names.
16423 Shared library file names as reported by the target system may not
16424 make sense as is on the system @value{GDBN} is running on. For
16425 example, when remote debugging a target that has MS-DOS based file
16426 system semantics, from a Unix host, the target may be reporting to
16427 @value{GDBN} a list of loaded shared libraries with file names such as
16428 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
16429 drive letters, so the @samp{c:\} prefix is not normally understood as
16430 indicating an absolute file name, and neither is the backslash
16431 normally considered a directory separator character. In that case,
16432 the native file system would interpret this whole absolute file name
16433 as a relative file name with no directory components. This would make
16434 it impossible to point @value{GDBN} at a copy of the remote target's
16435 shared libraries on the host using @code{set sysroot}, and impractical
16436 with @code{set solib-search-path}. Setting
16437 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
16438 to interpret such file names similarly to how the target would, and to
16439 map them to file names valid on @value{GDBN}'s native file system
16440 semantics. The value of @var{kind} can be @code{"auto"}, in addition
16441 to one of the supported file system kinds. In that case, @value{GDBN}
16442 tries to determine the appropriate file system variant based on the
16443 current target's operating system (@pxref{ABI, ,Configuring the
16444 Current ABI}). The supported file system settings are:
16448 Instruct @value{GDBN} to assume the target file system is of Unix
16449 kind. Only file names starting the forward slash (@samp{/}) character
16450 are considered absolute, and the directory separator character is also
16454 Instruct @value{GDBN} to assume the target file system is DOS based.
16455 File names starting with either a forward slash, or a drive letter
16456 followed by a colon (e.g., @samp{c:}), are considered absolute, and
16457 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
16458 considered directory separators.
16461 Instruct @value{GDBN} to use the file system kind associated with the
16462 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
16463 This is the default.
16467 @cindex file name canonicalization
16468 @cindex base name differences
16469 When processing file names provided by the user, @value{GDBN}
16470 frequently needs to compare them to the file names recorded in the
16471 program's debug info. Normally, @value{GDBN} compares just the
16472 @dfn{base names} of the files as strings, which is reasonably fast
16473 even for very large programs. (The base name of a file is the last
16474 portion of its name, after stripping all the leading directories.)
16475 This shortcut in comparison is based upon the assumption that files
16476 cannot have more than one base name. This is usually true, but
16477 references to files that use symlinks or similar filesystem
16478 facilities violate that assumption. If your program records files
16479 using such facilities, or if you provide file names to @value{GDBN}
16480 using symlinks etc., you can set @code{basenames-may-differ} to
16481 @code{true} to instruct @value{GDBN} to completely canonicalize each
16482 pair of file names it needs to compare. This will make file-name
16483 comparisons accurate, but at a price of a significant slowdown.
16486 @item set basenames-may-differ
16487 @kindex set basenames-may-differ
16488 Set whether a source file may have multiple base names.
16490 @item show basenames-may-differ
16491 @kindex show basenames-may-differ
16492 Show whether a source file may have multiple base names.
16495 @node Separate Debug Files
16496 @section Debugging Information in Separate Files
16497 @cindex separate debugging information files
16498 @cindex debugging information in separate files
16499 @cindex @file{.debug} subdirectories
16500 @cindex debugging information directory, global
16501 @cindex global debugging information directories
16502 @cindex build ID, and separate debugging files
16503 @cindex @file{.build-id} directory
16505 @value{GDBN} allows you to put a program's debugging information in a
16506 file separate from the executable itself, in a way that allows
16507 @value{GDBN} to find and load the debugging information automatically.
16508 Since debugging information can be very large---sometimes larger
16509 than the executable code itself---some systems distribute debugging
16510 information for their executables in separate files, which users can
16511 install only when they need to debug a problem.
16513 @value{GDBN} supports two ways of specifying the separate debug info
16518 The executable contains a @dfn{debug link} that specifies the name of
16519 the separate debug info file. The separate debug file's name is
16520 usually @file{@var{executable}.debug}, where @var{executable} is the
16521 name of the corresponding executable file without leading directories
16522 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
16523 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
16524 checksum for the debug file, which @value{GDBN} uses to validate that
16525 the executable and the debug file came from the same build.
16528 The executable contains a @dfn{build ID}, a unique bit string that is
16529 also present in the corresponding debug info file. (This is supported
16530 only on some operating systems, notably those which use the ELF format
16531 for binary files and the @sc{gnu} Binutils.) For more details about
16532 this feature, see the description of the @option{--build-id}
16533 command-line option in @ref{Options, , Command Line Options, ld.info,
16534 The GNU Linker}. The debug info file's name is not specified
16535 explicitly by the build ID, but can be computed from the build ID, see
16539 Depending on the way the debug info file is specified, @value{GDBN}
16540 uses two different methods of looking for the debug file:
16544 For the ``debug link'' method, @value{GDBN} looks up the named file in
16545 the directory of the executable file, then in a subdirectory of that
16546 directory named @file{.debug}, and finally under each one of the global debug
16547 directories, in a subdirectory whose name is identical to the leading
16548 directories of the executable's absolute file name.
16551 For the ``build ID'' method, @value{GDBN} looks in the
16552 @file{.build-id} subdirectory of each one of the global debug directories for
16553 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
16554 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
16555 are the rest of the bit string. (Real build ID strings are 32 or more
16556 hex characters, not 10.)
16559 So, for example, suppose you ask @value{GDBN} to debug
16560 @file{/usr/bin/ls}, which has a debug link that specifies the
16561 file @file{ls.debug}, and a build ID whose value in hex is
16562 @code{abcdef1234}. If the list of the global debug directories includes
16563 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
16564 debug information files, in the indicated order:
16568 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
16570 @file{/usr/bin/ls.debug}
16572 @file{/usr/bin/.debug/ls.debug}
16574 @file{/usr/lib/debug/usr/bin/ls.debug}.
16577 @anchor{debug-file-directory}
16578 Global debugging info directories default to what is set by @value{GDBN}
16579 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
16580 you can also set the global debugging info directories, and view the list
16581 @value{GDBN} is currently using.
16585 @kindex set debug-file-directory
16586 @item set debug-file-directory @var{directories}
16587 Set the directories which @value{GDBN} searches for separate debugging
16588 information files to @var{directory}. Multiple path components can be set
16589 concatenating them by a path separator.
16591 @kindex show debug-file-directory
16592 @item show debug-file-directory
16593 Show the directories @value{GDBN} searches for separate debugging
16598 @cindex @code{.gnu_debuglink} sections
16599 @cindex debug link sections
16600 A debug link is a special section of the executable file named
16601 @code{.gnu_debuglink}. The section must contain:
16605 A filename, with any leading directory components removed, followed by
16608 zero to three bytes of padding, as needed to reach the next four-byte
16609 boundary within the section, and
16611 a four-byte CRC checksum, stored in the same endianness used for the
16612 executable file itself. The checksum is computed on the debugging
16613 information file's full contents by the function given below, passing
16614 zero as the @var{crc} argument.
16617 Any executable file format can carry a debug link, as long as it can
16618 contain a section named @code{.gnu_debuglink} with the contents
16621 @cindex @code{.note.gnu.build-id} sections
16622 @cindex build ID sections
16623 The build ID is a special section in the executable file (and in other
16624 ELF binary files that @value{GDBN} may consider). This section is
16625 often named @code{.note.gnu.build-id}, but that name is not mandatory.
16626 It contains unique identification for the built files---the ID remains
16627 the same across multiple builds of the same build tree. The default
16628 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
16629 content for the build ID string. The same section with an identical
16630 value is present in the original built binary with symbols, in its
16631 stripped variant, and in the separate debugging information file.
16633 The debugging information file itself should be an ordinary
16634 executable, containing a full set of linker symbols, sections, and
16635 debugging information. The sections of the debugging information file
16636 should have the same names, addresses, and sizes as the original file,
16637 but they need not contain any data---much like a @code{.bss} section
16638 in an ordinary executable.
16640 The @sc{gnu} binary utilities (Binutils) package includes the
16641 @samp{objcopy} utility that can produce
16642 the separated executable / debugging information file pairs using the
16643 following commands:
16646 @kbd{objcopy --only-keep-debug foo foo.debug}
16651 These commands remove the debugging
16652 information from the executable file @file{foo} and place it in the file
16653 @file{foo.debug}. You can use the first, second or both methods to link the
16658 The debug link method needs the following additional command to also leave
16659 behind a debug link in @file{foo}:
16662 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
16665 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
16666 a version of the @code{strip} command such that the command @kbd{strip foo -f
16667 foo.debug} has the same functionality as the two @code{objcopy} commands and
16668 the @code{ln -s} command above, together.
16671 Build ID gets embedded into the main executable using @code{ld --build-id} or
16672 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
16673 compatibility fixes for debug files separation are present in @sc{gnu} binary
16674 utilities (Binutils) package since version 2.18.
16679 @cindex CRC algorithm definition
16680 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16681 IEEE 802.3 using the polynomial:
16683 @c TexInfo requires naked braces for multi-digit exponents for Tex
16684 @c output, but this causes HTML output to barf. HTML has to be set using
16685 @c raw commands. So we end up having to specify this equation in 2
16690 <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>
16691 + <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
16697 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16698 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16702 The function is computed byte at a time, taking the least
16703 significant bit of each byte first. The initial pattern
16704 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16705 the final result is inverted to ensure trailing zeros also affect the
16708 @emph{Note:} This is the same CRC polynomial as used in handling the
16709 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16710 , @value{GDBN} Remote Serial Protocol}). However in the
16711 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16712 significant bit first, and the result is not inverted, so trailing
16713 zeros have no effect on the CRC value.
16715 To complete the description, we show below the code of the function
16716 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16717 initially supplied @code{crc} argument means that an initial call to
16718 this function passing in zero will start computing the CRC using
16721 @kindex gnu_debuglink_crc32
16724 gnu_debuglink_crc32 (unsigned long crc,
16725 unsigned char *buf, size_t len)
16727 static const unsigned long crc32_table[256] =
16729 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16730 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16731 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16732 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16733 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16734 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16735 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16736 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16737 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16738 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16739 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16740 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16741 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16742 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16743 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16744 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16745 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16746 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16747 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16748 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16749 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16750 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16751 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16752 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16753 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16754 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16755 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16756 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16757 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16758 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16759 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16760 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16761 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16762 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16763 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16764 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16765 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16766 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16767 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16768 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16769 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16770 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16771 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16772 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16773 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16774 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16775 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16776 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16777 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16778 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16779 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16782 unsigned char *end;
16784 crc = ~crc & 0xffffffff;
16785 for (end = buf + len; buf < end; ++buf)
16786 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
16787 return ~crc & 0xffffffff;
16792 This computation does not apply to the ``build ID'' method.
16794 @node MiniDebugInfo
16795 @section Debugging information in a special section
16796 @cindex separate debug sections
16797 @cindex @samp{.gnu_debugdata} section
16799 Some systems ship pre-built executables and libraries that have a
16800 special @samp{.gnu_debugdata} section. This feature is called
16801 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
16802 is used to supply extra symbols for backtraces.
16804 The intent of this section is to provide extra minimal debugging
16805 information for use in simple backtraces. It is not intended to be a
16806 replacement for full separate debugging information (@pxref{Separate
16807 Debug Files}). The example below shows the intended use; however,
16808 @value{GDBN} does not currently put restrictions on what sort of
16809 debugging information might be included in the section.
16811 @value{GDBN} has support for this extension. If the section exists,
16812 then it is used provided that no other source of debugging information
16813 can be found, and that @value{GDBN} was configured with LZMA support.
16815 This section can be easily created using @command{objcopy} and other
16816 standard utilities:
16819 # Extract the dynamic symbols from the main binary, there is no need
16820 # to also have these in the normal symbol table
16821 nm -D @var{binary} --format=posix --defined-only \
16822 | awk '@{ print $1 @}' | sort > dynsyms
16824 # Extract all the text (i.e. function) symbols from the debuginfo .
16825 nm @var{binary} --format=posix --defined-only \
16826 | awk '@{ if ($2 == "T" || $2 == "t") print $1 @}' \
16829 # Keep all the function symbols not already in the dynamic symbol
16831 comm -13 dynsyms funcsyms > keep_symbols
16833 # Copy the full debuginfo, keeping only a minimal set of symbols and
16834 # removing some unnecessary sections.
16835 objcopy -S --remove-section .gdb_index --remove-section .comment \
16836 --keep-symbols=keep_symbols @var{binary} mini_debuginfo
16838 # Inject the compressed data into the .gnu_debugdata section of the
16841 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
16845 @section Index Files Speed Up @value{GDBN}
16846 @cindex index files
16847 @cindex @samp{.gdb_index} section
16849 When @value{GDBN} finds a symbol file, it scans the symbols in the
16850 file in order to construct an internal symbol table. This lets most
16851 @value{GDBN} operations work quickly---at the cost of a delay early
16852 on. For large programs, this delay can be quite lengthy, so
16853 @value{GDBN} provides a way to build an index, which speeds up
16856 The index is stored as a section in the symbol file. @value{GDBN} can
16857 write the index to a file, then you can put it into the symbol file
16858 using @command{objcopy}.
16860 To create an index file, use the @code{save gdb-index} command:
16863 @item save gdb-index @var{directory}
16864 @kindex save gdb-index
16865 Create an index file for each symbol file currently known by
16866 @value{GDBN}. Each file is named after its corresponding symbol file,
16867 with @samp{.gdb-index} appended, and is written into the given
16871 Once you have created an index file you can merge it into your symbol
16872 file, here named @file{symfile}, using @command{objcopy}:
16875 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16876 --set-section-flags .gdb_index=readonly symfile symfile
16879 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
16880 sections that have been deprecated. Usually they are deprecated because
16881 they are missing a new feature or have performance issues.
16882 To tell @value{GDBN} to use a deprecated index section anyway
16883 specify @code{set use-deprecated-index-sections on}.
16884 The default is @code{off}.
16885 This can speed up startup, but may result in some functionality being lost.
16886 @xref{Index Section Format}.
16888 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
16889 must be done before gdb reads the file. The following will not work:
16892 $ gdb -ex "set use-deprecated-index-sections on" <program>
16895 Instead you must do, for example,
16898 $ gdb -iex "set use-deprecated-index-sections on" <program>
16901 There are currently some limitation on indices. They only work when
16902 for DWARF debugging information, not stabs. And, they do not
16903 currently work for programs using Ada.
16905 @node Symbol Errors
16906 @section Errors Reading Symbol Files
16908 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16909 such as symbol types it does not recognize, or known bugs in compiler
16910 output. By default, @value{GDBN} does not notify you of such problems, since
16911 they are relatively common and primarily of interest to people
16912 debugging compilers. If you are interested in seeing information
16913 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16914 only one message about each such type of problem, no matter how many
16915 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16916 to see how many times the problems occur, with the @code{set
16917 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16920 The messages currently printed, and their meanings, include:
16923 @item inner block not inside outer block in @var{symbol}
16925 The symbol information shows where symbol scopes begin and end
16926 (such as at the start of a function or a block of statements). This
16927 error indicates that an inner scope block is not fully contained
16928 in its outer scope blocks.
16930 @value{GDBN} circumvents the problem by treating the inner block as if it had
16931 the same scope as the outer block. In the error message, @var{symbol}
16932 may be shown as ``@code{(don't know)}'' if the outer block is not a
16935 @item block at @var{address} out of order
16937 The symbol information for symbol scope blocks should occur in
16938 order of increasing addresses. This error indicates that it does not
16941 @value{GDBN} does not circumvent this problem, and has trouble
16942 locating symbols in the source file whose symbols it is reading. (You
16943 can often determine what source file is affected by specifying
16944 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16947 @item bad block start address patched
16949 The symbol information for a symbol scope block has a start address
16950 smaller than the address of the preceding source line. This is known
16951 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16953 @value{GDBN} circumvents the problem by treating the symbol scope block as
16954 starting on the previous source line.
16956 @item bad string table offset in symbol @var{n}
16959 Symbol number @var{n} contains a pointer into the string table which is
16960 larger than the size of the string table.
16962 @value{GDBN} circumvents the problem by considering the symbol to have the
16963 name @code{foo}, which may cause other problems if many symbols end up
16966 @item unknown symbol type @code{0x@var{nn}}
16968 The symbol information contains new data types that @value{GDBN} does
16969 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16970 uncomprehended information, in hexadecimal.
16972 @value{GDBN} circumvents the error by ignoring this symbol information.
16973 This usually allows you to debug your program, though certain symbols
16974 are not accessible. If you encounter such a problem and feel like
16975 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16976 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16977 and examine @code{*bufp} to see the symbol.
16979 @item stub type has NULL name
16981 @value{GDBN} could not find the full definition for a struct or class.
16983 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16984 The symbol information for a C@t{++} member function is missing some
16985 information that recent versions of the compiler should have output for
16988 @item info mismatch between compiler and debugger
16990 @value{GDBN} could not parse a type specification output by the compiler.
16995 @section GDB Data Files
16997 @cindex prefix for data files
16998 @value{GDBN} will sometimes read an auxiliary data file. These files
16999 are kept in a directory known as the @dfn{data directory}.
17001 You can set the data directory's name, and view the name @value{GDBN}
17002 is currently using.
17005 @kindex set data-directory
17006 @item set data-directory @var{directory}
17007 Set the directory which @value{GDBN} searches for auxiliary data files
17008 to @var{directory}.
17010 @kindex show data-directory
17011 @item show data-directory
17012 Show the directory @value{GDBN} searches for auxiliary data files.
17015 @cindex default data directory
17016 @cindex @samp{--with-gdb-datadir}
17017 You can set the default data directory by using the configure-time
17018 @samp{--with-gdb-datadir} option. If the data directory is inside
17019 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17020 @samp{--exec-prefix}), then the default data directory will be updated
17021 automatically if the installed @value{GDBN} is moved to a new
17024 The data directory may also be specified with the
17025 @code{--data-directory} command line option.
17026 @xref{Mode Options}.
17029 @chapter Specifying a Debugging Target
17031 @cindex debugging target
17032 A @dfn{target} is the execution environment occupied by your program.
17034 Often, @value{GDBN} runs in the same host environment as your program;
17035 in that case, the debugging target is specified as a side effect when
17036 you use the @code{file} or @code{core} commands. When you need more
17037 flexibility---for example, running @value{GDBN} on a physically separate
17038 host, or controlling a standalone system over a serial port or a
17039 realtime system over a TCP/IP connection---you can use the @code{target}
17040 command to specify one of the target types configured for @value{GDBN}
17041 (@pxref{Target Commands, ,Commands for Managing Targets}).
17043 @cindex target architecture
17044 It is possible to build @value{GDBN} for several different @dfn{target
17045 architectures}. When @value{GDBN} is built like that, you can choose
17046 one of the available architectures with the @kbd{set architecture}
17050 @kindex set architecture
17051 @kindex show architecture
17052 @item set architecture @var{arch}
17053 This command sets the current target architecture to @var{arch}. The
17054 value of @var{arch} can be @code{"auto"}, in addition to one of the
17055 supported architectures.
17057 @item show architecture
17058 Show the current target architecture.
17060 @item set processor
17062 @kindex set processor
17063 @kindex show processor
17064 These are alias commands for, respectively, @code{set architecture}
17065 and @code{show architecture}.
17069 * Active Targets:: Active targets
17070 * Target Commands:: Commands for managing targets
17071 * Byte Order:: Choosing target byte order
17074 @node Active Targets
17075 @section Active Targets
17077 @cindex stacking targets
17078 @cindex active targets
17079 @cindex multiple targets
17081 There are multiple classes of targets such as: processes, executable files or
17082 recording sessions. Core files belong to the process class, making core file
17083 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17084 on multiple active targets, one in each class. This allows you to (for
17085 example) start a process and inspect its activity, while still having access to
17086 the executable file after the process finishes. Or if you start process
17087 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17088 presented a virtual layer of the recording target, while the process target
17089 remains stopped at the chronologically last point of the process execution.
17091 Use the @code{core-file} and @code{exec-file} commands to select a new core
17092 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17093 specify as a target a process that is already running, use the @code{attach}
17094 command (@pxref{Attach, ,Debugging an Already-running Process}).
17096 @node Target Commands
17097 @section Commands for Managing Targets
17100 @item target @var{type} @var{parameters}
17101 Connects the @value{GDBN} host environment to a target machine or
17102 process. A target is typically a protocol for talking to debugging
17103 facilities. You use the argument @var{type} to specify the type or
17104 protocol of the target machine.
17106 Further @var{parameters} are interpreted by the target protocol, but
17107 typically include things like device names or host names to connect
17108 with, process numbers, and baud rates.
17110 The @code{target} command does not repeat if you press @key{RET} again
17111 after executing the command.
17113 @kindex help target
17115 Displays the names of all targets available. To display targets
17116 currently selected, use either @code{info target} or @code{info files}
17117 (@pxref{Files, ,Commands to Specify Files}).
17119 @item help target @var{name}
17120 Describe a particular target, including any parameters necessary to
17123 @kindex set gnutarget
17124 @item set gnutarget @var{args}
17125 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17126 knows whether it is reading an @dfn{executable},
17127 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17128 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17129 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17132 @emph{Warning:} To specify a file format with @code{set gnutarget},
17133 you must know the actual BFD name.
17137 @xref{Files, , Commands to Specify Files}.
17139 @kindex show gnutarget
17140 @item show gnutarget
17141 Use the @code{show gnutarget} command to display what file format
17142 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17143 @value{GDBN} will determine the file format for each file automatically,
17144 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
17147 @cindex common targets
17148 Here are some common targets (available, or not, depending on the GDB
17153 @item target exec @var{program}
17154 @cindex executable file target
17155 An executable file. @samp{target exec @var{program}} is the same as
17156 @samp{exec-file @var{program}}.
17158 @item target core @var{filename}
17159 @cindex core dump file target
17160 A core dump file. @samp{target core @var{filename}} is the same as
17161 @samp{core-file @var{filename}}.
17163 @item target remote @var{medium}
17164 @cindex remote target
17165 A remote system connected to @value{GDBN} via a serial line or network
17166 connection. This command tells @value{GDBN} to use its own remote
17167 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17169 For example, if you have a board connected to @file{/dev/ttya} on the
17170 machine running @value{GDBN}, you could say:
17173 target remote /dev/ttya
17176 @code{target remote} supports the @code{load} command. This is only
17177 useful if you have some other way of getting the stub to the target
17178 system, and you can put it somewhere in memory where it won't get
17179 clobbered by the download.
17181 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17182 @cindex built-in simulator target
17183 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17191 works; however, you cannot assume that a specific memory map, device
17192 drivers, or even basic I/O is available, although some simulators do
17193 provide these. For info about any processor-specific simulator details,
17194 see the appropriate section in @ref{Embedded Processors, ,Embedded
17199 Some configurations may include these targets as well:
17203 @item target nrom @var{dev}
17204 @cindex NetROM ROM emulator target
17205 NetROM ROM emulator. This target only supports downloading.
17209 Different targets are available on different configurations of @value{GDBN};
17210 your configuration may have more or fewer targets.
17212 Many remote targets require you to download the executable's code once
17213 you've successfully established a connection. You may wish to control
17214 various aspects of this process.
17219 @kindex set hash@r{, for remote monitors}
17220 @cindex hash mark while downloading
17221 This command controls whether a hash mark @samp{#} is displayed while
17222 downloading a file to the remote monitor. If on, a hash mark is
17223 displayed after each S-record is successfully downloaded to the
17227 @kindex show hash@r{, for remote monitors}
17228 Show the current status of displaying the hash mark.
17230 @item set debug monitor
17231 @kindex set debug monitor
17232 @cindex display remote monitor communications
17233 Enable or disable display of communications messages between
17234 @value{GDBN} and the remote monitor.
17236 @item show debug monitor
17237 @kindex show debug monitor
17238 Show the current status of displaying communications between
17239 @value{GDBN} and the remote monitor.
17244 @kindex load @var{filename}
17245 @item load @var{filename}
17247 Depending on what remote debugging facilities are configured into
17248 @value{GDBN}, the @code{load} command may be available. Where it exists, it
17249 is meant to make @var{filename} (an executable) available for debugging
17250 on the remote system---by downloading, or dynamic linking, for example.
17251 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
17252 the @code{add-symbol-file} command.
17254 If your @value{GDBN} does not have a @code{load} command, attempting to
17255 execute it gets the error message ``@code{You can't do that when your
17256 target is @dots{}}''
17258 The file is loaded at whatever address is specified in the executable.
17259 For some object file formats, you can specify the load address when you
17260 link the program; for other formats, like a.out, the object file format
17261 specifies a fixed address.
17262 @c FIXME! This would be a good place for an xref to the GNU linker doc.
17264 Depending on the remote side capabilities, @value{GDBN} may be able to
17265 load programs into flash memory.
17267 @code{load} does not repeat if you press @key{RET} again after using it.
17271 @section Choosing Target Byte Order
17273 @cindex choosing target byte order
17274 @cindex target byte order
17276 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
17277 offer the ability to run either big-endian or little-endian byte
17278 orders. Usually the executable or symbol will include a bit to
17279 designate the endian-ness, and you will not need to worry about
17280 which to use. However, you may still find it useful to adjust
17281 @value{GDBN}'s idea of processor endian-ness manually.
17285 @item set endian big
17286 Instruct @value{GDBN} to assume the target is big-endian.
17288 @item set endian little
17289 Instruct @value{GDBN} to assume the target is little-endian.
17291 @item set endian auto
17292 Instruct @value{GDBN} to use the byte order associated with the
17296 Display @value{GDBN}'s current idea of the target byte order.
17300 Note that these commands merely adjust interpretation of symbolic
17301 data on the host, and that they have absolutely no effect on the
17305 @node Remote Debugging
17306 @chapter Debugging Remote Programs
17307 @cindex remote debugging
17309 If you are trying to debug a program running on a machine that cannot run
17310 @value{GDBN} in the usual way, it is often useful to use remote debugging.
17311 For example, you might use remote debugging on an operating system kernel,
17312 or on a small system which does not have a general purpose operating system
17313 powerful enough to run a full-featured debugger.
17315 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
17316 to make this work with particular debugging targets. In addition,
17317 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
17318 but not specific to any particular target system) which you can use if you
17319 write the remote stubs---the code that runs on the remote system to
17320 communicate with @value{GDBN}.
17322 Other remote targets may be available in your
17323 configuration of @value{GDBN}; use @code{help target} to list them.
17326 * Connecting:: Connecting to a remote target
17327 * File Transfer:: Sending files to a remote system
17328 * Server:: Using the gdbserver program
17329 * Remote Configuration:: Remote configuration
17330 * Remote Stub:: Implementing a remote stub
17334 @section Connecting to a Remote Target
17336 On the @value{GDBN} host machine, you will need an unstripped copy of
17337 your program, since @value{GDBN} needs symbol and debugging information.
17338 Start up @value{GDBN} as usual, using the name of the local copy of your
17339 program as the first argument.
17341 @cindex @code{target remote}
17342 @value{GDBN} can communicate with the target over a serial line, or
17343 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
17344 each case, @value{GDBN} uses the same protocol for debugging your
17345 program; only the medium carrying the debugging packets varies. The
17346 @code{target remote} command establishes a connection to the target.
17347 Its arguments indicate which medium to use:
17351 @item target remote @var{serial-device}
17352 @cindex serial line, @code{target remote}
17353 Use @var{serial-device} to communicate with the target. For example,
17354 to use a serial line connected to the device named @file{/dev/ttyb}:
17357 target remote /dev/ttyb
17360 If you're using a serial line, you may want to give @value{GDBN} the
17361 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
17362 (@pxref{Remote Configuration, set remotebaud}) before the
17363 @code{target} command.
17365 @item target remote @code{@var{host}:@var{port}}
17366 @itemx target remote @code{tcp:@var{host}:@var{port}}
17367 @cindex @acronym{TCP} port, @code{target remote}
17368 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
17369 The @var{host} may be either a host name or a numeric @acronym{IP}
17370 address; @var{port} must be a decimal number. The @var{host} could be
17371 the target machine itself, if it is directly connected to the net, or
17372 it might be a terminal server which in turn has a serial line to the
17375 For example, to connect to port 2828 on a terminal server named
17379 target remote manyfarms:2828
17382 If your remote target is actually running on the same machine as your
17383 debugger session (e.g.@: a simulator for your target running on the
17384 same host), you can omit the hostname. For example, to connect to
17385 port 1234 on your local machine:
17388 target remote :1234
17392 Note that the colon is still required here.
17394 @item target remote @code{udp:@var{host}:@var{port}}
17395 @cindex @acronym{UDP} port, @code{target remote}
17396 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
17397 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
17400 target remote udp:manyfarms:2828
17403 When using a @acronym{UDP} connection for remote debugging, you should
17404 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
17405 can silently drop packets on busy or unreliable networks, which will
17406 cause havoc with your debugging session.
17408 @item target remote | @var{command}
17409 @cindex pipe, @code{target remote} to
17410 Run @var{command} in the background and communicate with it using a
17411 pipe. The @var{command} is a shell command, to be parsed and expanded
17412 by the system's command shell, @code{/bin/sh}; it should expect remote
17413 protocol packets on its standard input, and send replies on its
17414 standard output. You could use this to run a stand-alone simulator
17415 that speaks the remote debugging protocol, to make net connections
17416 using programs like @code{ssh}, or for other similar tricks.
17418 If @var{command} closes its standard output (perhaps by exiting),
17419 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
17420 program has already exited, this will have no effect.)
17424 Once the connection has been established, you can use all the usual
17425 commands to examine and change data. The remote program is already
17426 running; you can use @kbd{step} and @kbd{continue}, and you do not
17427 need to use @kbd{run}.
17429 @cindex interrupting remote programs
17430 @cindex remote programs, interrupting
17431 Whenever @value{GDBN} is waiting for the remote program, if you type the
17432 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
17433 program. This may or may not succeed, depending in part on the hardware
17434 and the serial drivers the remote system uses. If you type the
17435 interrupt character once again, @value{GDBN} displays this prompt:
17438 Interrupted while waiting for the program.
17439 Give up (and stop debugging it)? (y or n)
17442 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
17443 (If you decide you want to try again later, you can use @samp{target
17444 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
17445 goes back to waiting.
17448 @kindex detach (remote)
17450 When you have finished debugging the remote program, you can use the
17451 @code{detach} command to release it from @value{GDBN} control.
17452 Detaching from the target normally resumes its execution, but the results
17453 will depend on your particular remote stub. After the @code{detach}
17454 command, @value{GDBN} is free to connect to another target.
17458 The @code{disconnect} command behaves like @code{detach}, except that
17459 the target is generally not resumed. It will wait for @value{GDBN}
17460 (this instance or another one) to connect and continue debugging. After
17461 the @code{disconnect} command, @value{GDBN} is again free to connect to
17464 @cindex send command to remote monitor
17465 @cindex extend @value{GDBN} for remote targets
17466 @cindex add new commands for external monitor
17468 @item monitor @var{cmd}
17469 This command allows you to send arbitrary commands directly to the
17470 remote monitor. Since @value{GDBN} doesn't care about the commands it
17471 sends like this, this command is the way to extend @value{GDBN}---you
17472 can add new commands that only the external monitor will understand
17476 @node File Transfer
17477 @section Sending files to a remote system
17478 @cindex remote target, file transfer
17479 @cindex file transfer
17480 @cindex sending files to remote systems
17482 Some remote targets offer the ability to transfer files over the same
17483 connection used to communicate with @value{GDBN}. This is convenient
17484 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
17485 running @code{gdbserver} over a network interface. For other targets,
17486 e.g.@: embedded devices with only a single serial port, this may be
17487 the only way to upload or download files.
17489 Not all remote targets support these commands.
17493 @item remote put @var{hostfile} @var{targetfile}
17494 Copy file @var{hostfile} from the host system (the machine running
17495 @value{GDBN}) to @var{targetfile} on the target system.
17498 @item remote get @var{targetfile} @var{hostfile}
17499 Copy file @var{targetfile} from the target system to @var{hostfile}
17500 on the host system.
17502 @kindex remote delete
17503 @item remote delete @var{targetfile}
17504 Delete @var{targetfile} from the target system.
17509 @section Using the @code{gdbserver} Program
17512 @cindex remote connection without stubs
17513 @code{gdbserver} is a control program for Unix-like systems, which
17514 allows you to connect your program with a remote @value{GDBN} via
17515 @code{target remote}---but without linking in the usual debugging stub.
17517 @code{gdbserver} is not a complete replacement for the debugging stubs,
17518 because it requires essentially the same operating-system facilities
17519 that @value{GDBN} itself does. In fact, a system that can run
17520 @code{gdbserver} to connect to a remote @value{GDBN} could also run
17521 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
17522 because it is a much smaller program than @value{GDBN} itself. It is
17523 also easier to port than all of @value{GDBN}, so you may be able to get
17524 started more quickly on a new system by using @code{gdbserver}.
17525 Finally, if you develop code for real-time systems, you may find that
17526 the tradeoffs involved in real-time operation make it more convenient to
17527 do as much development work as possible on another system, for example
17528 by cross-compiling. You can use @code{gdbserver} to make a similar
17529 choice for debugging.
17531 @value{GDBN} and @code{gdbserver} communicate via either a serial line
17532 or a TCP connection, using the standard @value{GDBN} remote serial
17536 @emph{Warning:} @code{gdbserver} does not have any built-in security.
17537 Do not run @code{gdbserver} connected to any public network; a
17538 @value{GDBN} connection to @code{gdbserver} provides access to the
17539 target system with the same privileges as the user running
17543 @subsection Running @code{gdbserver}
17544 @cindex arguments, to @code{gdbserver}
17545 @cindex @code{gdbserver}, command-line arguments
17547 Run @code{gdbserver} on the target system. You need a copy of the
17548 program you want to debug, including any libraries it requires.
17549 @code{gdbserver} does not need your program's symbol table, so you can
17550 strip the program if necessary to save space. @value{GDBN} on the host
17551 system does all the symbol handling.
17553 To use the server, you must tell it how to communicate with @value{GDBN};
17554 the name of your program; and the arguments for your program. The usual
17558 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
17561 @var{comm} is either a device name (to use a serial line), or a TCP
17562 hostname and portnumber, or @code{-} or @code{stdio} to use
17563 stdin/stdout of @code{gdbserver}.
17564 For example, to debug Emacs with the argument
17565 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
17569 target> gdbserver /dev/com1 emacs foo.txt
17572 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
17575 To use a TCP connection instead of a serial line:
17578 target> gdbserver host:2345 emacs foo.txt
17581 The only difference from the previous example is the first argument,
17582 specifying that you are communicating with the host @value{GDBN} via
17583 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
17584 expect a TCP connection from machine @samp{host} to local TCP port 2345.
17585 (Currently, the @samp{host} part is ignored.) You can choose any number
17586 you want for the port number as long as it does not conflict with any
17587 TCP ports already in use on the target system (for example, @code{23} is
17588 reserved for @code{telnet}).@footnote{If you choose a port number that
17589 conflicts with another service, @code{gdbserver} prints an error message
17590 and exits.} You must use the same port number with the host @value{GDBN}
17591 @code{target remote} command.
17593 The @code{stdio} connection is useful when starting @code{gdbserver}
17597 (gdb) target remote | ssh -T hostname gdbserver - hello
17600 The @samp{-T} option to ssh is provided because we don't need a remote pty,
17601 and we don't want escape-character handling. Ssh does this by default when
17602 a command is provided, the flag is provided to make it explicit.
17603 You could elide it if you want to.
17605 Programs started with stdio-connected gdbserver have @file{/dev/null} for
17606 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
17607 display through a pipe connected to gdbserver.
17608 Both @code{stdout} and @code{stderr} use the same pipe.
17610 @subsubsection Attaching to a Running Program
17611 @cindex attach to a program, @code{gdbserver}
17612 @cindex @option{--attach}, @code{gdbserver} option
17614 On some targets, @code{gdbserver} can also attach to running programs.
17615 This is accomplished via the @code{--attach} argument. The syntax is:
17618 target> gdbserver --attach @var{comm} @var{pid}
17621 @var{pid} is the process ID of a currently running process. It isn't necessary
17622 to point @code{gdbserver} at a binary for the running process.
17625 You can debug processes by name instead of process ID if your target has the
17626 @code{pidof} utility:
17629 target> gdbserver --attach @var{comm} `pidof @var{program}`
17632 In case more than one copy of @var{program} is running, or @var{program}
17633 has multiple threads, most versions of @code{pidof} support the
17634 @code{-s} option to only return the first process ID.
17636 @subsubsection Multi-Process Mode for @code{gdbserver}
17637 @cindex @code{gdbserver}, multiple processes
17638 @cindex multiple processes with @code{gdbserver}
17640 When you connect to @code{gdbserver} using @code{target remote},
17641 @code{gdbserver} debugs the specified program only once. When the
17642 program exits, or you detach from it, @value{GDBN} closes the connection
17643 and @code{gdbserver} exits.
17645 If you connect using @kbd{target extended-remote}, @code{gdbserver}
17646 enters multi-process mode. When the debugged program exits, or you
17647 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
17648 though no program is running. The @code{run} and @code{attach}
17649 commands instruct @code{gdbserver} to run or attach to a new program.
17650 The @code{run} command uses @code{set remote exec-file} (@pxref{set
17651 remote exec-file}) to select the program to run. Command line
17652 arguments are supported, except for wildcard expansion and I/O
17653 redirection (@pxref{Arguments}).
17655 @cindex @option{--multi}, @code{gdbserver} option
17656 To start @code{gdbserver} without supplying an initial command to run
17657 or process ID to attach, use the @option{--multi} command line option.
17658 Then you can connect using @kbd{target extended-remote} and start
17659 the program you want to debug.
17661 In multi-process mode @code{gdbserver} does not automatically exit unless you
17662 use the option @option{--once}. You can terminate it by using
17663 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
17664 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
17665 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
17666 @option{--multi} option to @code{gdbserver} has no influence on that.
17668 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
17670 This section applies only when @code{gdbserver} is run to listen on a TCP port.
17672 @code{gdbserver} normally terminates after all of its debugged processes have
17673 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
17674 extended-remote}, @code{gdbserver} stays running even with no processes left.
17675 @value{GDBN} normally terminates the spawned debugged process on its exit,
17676 which normally also terminates @code{gdbserver} in the @kbd{target remote}
17677 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
17678 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
17679 stays running even in the @kbd{target remote} mode.
17681 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
17682 Such reconnecting is useful for features like @ref{disconnected tracing}. For
17683 completeness, at most one @value{GDBN} can be connected at a time.
17685 @cindex @option{--once}, @code{gdbserver} option
17686 By default, @code{gdbserver} keeps the listening TCP port open, so that
17687 additional connections are possible. However, if you start @code{gdbserver}
17688 with the @option{--once} option, it will stop listening for any further
17689 connection attempts after connecting to the first @value{GDBN} session. This
17690 means no further connections to @code{gdbserver} will be possible after the
17691 first one. It also means @code{gdbserver} will terminate after the first
17692 connection with remote @value{GDBN} has closed, even for unexpectedly closed
17693 connections and even in the @kbd{target extended-remote} mode. The
17694 @option{--once} option allows reusing the same port number for connecting to
17695 multiple instances of @code{gdbserver} running on the same host, since each
17696 instance closes its port after the first connection.
17698 @subsubsection Other Command-Line Arguments for @code{gdbserver}
17700 @cindex @option{--debug}, @code{gdbserver} option
17701 The @option{--debug} option tells @code{gdbserver} to display extra
17702 status information about the debugging process.
17703 @cindex @option{--remote-debug}, @code{gdbserver} option
17704 The @option{--remote-debug} option tells @code{gdbserver} to display
17705 remote protocol debug output. These options are intended for
17706 @code{gdbserver} development and for bug reports to the developers.
17708 @cindex @option{--wrapper}, @code{gdbserver} option
17709 The @option{--wrapper} option specifies a wrapper to launch programs
17710 for debugging. The option should be followed by the name of the
17711 wrapper, then any command-line arguments to pass to the wrapper, then
17712 @kbd{--} indicating the end of the wrapper arguments.
17714 @code{gdbserver} runs the specified wrapper program with a combined
17715 command line including the wrapper arguments, then the name of the
17716 program to debug, then any arguments to the program. The wrapper
17717 runs until it executes your program, and then @value{GDBN} gains control.
17719 You can use any program that eventually calls @code{execve} with
17720 its arguments as a wrapper. Several standard Unix utilities do
17721 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
17722 with @code{exec "$@@"} will also work.
17724 For example, you can use @code{env} to pass an environment variable to
17725 the debugged program, without setting the variable in @code{gdbserver}'s
17729 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
17732 @subsection Connecting to @code{gdbserver}
17734 Run @value{GDBN} on the host system.
17736 First make sure you have the necessary symbol files. Load symbols for
17737 your application using the @code{file} command before you connect. Use
17738 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
17739 was compiled with the correct sysroot using @code{--with-sysroot}).
17741 The symbol file and target libraries must exactly match the executable
17742 and libraries on the target, with one exception: the files on the host
17743 system should not be stripped, even if the files on the target system
17744 are. Mismatched or missing files will lead to confusing results
17745 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
17746 files may also prevent @code{gdbserver} from debugging multi-threaded
17749 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
17750 For TCP connections, you must start up @code{gdbserver} prior to using
17751 the @code{target remote} command. Otherwise you may get an error whose
17752 text depends on the host system, but which usually looks something like
17753 @samp{Connection refused}. Don't use the @code{load}
17754 command in @value{GDBN} when using @code{gdbserver}, since the program is
17755 already on the target.
17757 @subsection Monitor Commands for @code{gdbserver}
17758 @cindex monitor commands, for @code{gdbserver}
17759 @anchor{Monitor Commands for gdbserver}
17761 During a @value{GDBN} session using @code{gdbserver}, you can use the
17762 @code{monitor} command to send special requests to @code{gdbserver}.
17763 Here are the available commands.
17767 List the available monitor commands.
17769 @item monitor set debug 0
17770 @itemx monitor set debug 1
17771 Disable or enable general debugging messages.
17773 @item monitor set remote-debug 0
17774 @itemx monitor set remote-debug 1
17775 Disable or enable specific debugging messages associated with the remote
17776 protocol (@pxref{Remote Protocol}).
17778 @item monitor set libthread-db-search-path [PATH]
17779 @cindex gdbserver, search path for @code{libthread_db}
17780 When this command is issued, @var{path} is a colon-separated list of
17781 directories to search for @code{libthread_db} (@pxref{Threads,,set
17782 libthread-db-search-path}). If you omit @var{path},
17783 @samp{libthread-db-search-path} will be reset to its default value.
17785 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
17786 not supported in @code{gdbserver}.
17789 Tell gdbserver to exit immediately. This command should be followed by
17790 @code{disconnect} to close the debugging session. @code{gdbserver} will
17791 detach from any attached processes and kill any processes it created.
17792 Use @code{monitor exit} to terminate @code{gdbserver} at the end
17793 of a multi-process mode debug session.
17797 @subsection Tracepoints support in @code{gdbserver}
17798 @cindex tracepoints support in @code{gdbserver}
17800 On some targets, @code{gdbserver} supports tracepoints, fast
17801 tracepoints and static tracepoints.
17803 For fast or static tracepoints to work, a special library called the
17804 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
17805 This library is built and distributed as an integral part of
17806 @code{gdbserver}. In addition, support for static tracepoints
17807 requires building the in-process agent library with static tracepoints
17808 support. At present, the UST (LTTng Userspace Tracer,
17809 @url{http://lttng.org/ust}) tracing engine is supported. This support
17810 is automatically available if UST development headers are found in the
17811 standard include path when @code{gdbserver} is built, or if
17812 @code{gdbserver} was explicitly configured using @option{--with-ust}
17813 to point at such headers. You can explicitly disable the support
17814 using @option{--with-ust=no}.
17816 There are several ways to load the in-process agent in your program:
17819 @item Specifying it as dependency at link time
17821 You can link your program dynamically with the in-process agent
17822 library. On most systems, this is accomplished by adding
17823 @code{-linproctrace} to the link command.
17825 @item Using the system's preloading mechanisms
17827 You can force loading the in-process agent at startup time by using
17828 your system's support for preloading shared libraries. Many Unixes
17829 support the concept of preloading user defined libraries. In most
17830 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
17831 in the environment. See also the description of @code{gdbserver}'s
17832 @option{--wrapper} command line option.
17834 @item Using @value{GDBN} to force loading the agent at run time
17836 On some systems, you can force the inferior to load a shared library,
17837 by calling a dynamic loader function in the inferior that takes care
17838 of dynamically looking up and loading a shared library. On most Unix
17839 systems, the function is @code{dlopen}. You'll use the @code{call}
17840 command for that. For example:
17843 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
17846 Note that on most Unix systems, for the @code{dlopen} function to be
17847 available, the program needs to be linked with @code{-ldl}.
17850 On systems that have a userspace dynamic loader, like most Unix
17851 systems, when you connect to @code{gdbserver} using @code{target
17852 remote}, you'll find that the program is stopped at the dynamic
17853 loader's entry point, and no shared library has been loaded in the
17854 program's address space yet, including the in-process agent. In that
17855 case, before being able to use any of the fast or static tracepoints
17856 features, you need to let the loader run and load the shared
17857 libraries. The simplest way to do that is to run the program to the
17858 main procedure. E.g., if debugging a C or C@t{++} program, start
17859 @code{gdbserver} like so:
17862 $ gdbserver :9999 myprogram
17865 Start GDB and connect to @code{gdbserver} like so, and run to main:
17869 (@value{GDBP}) target remote myhost:9999
17870 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
17871 (@value{GDBP}) b main
17872 (@value{GDBP}) continue
17875 The in-process tracing agent library should now be loaded into the
17876 process; you can confirm it with the @code{info sharedlibrary}
17877 command, which will list @file{libinproctrace.so} as loaded in the
17878 process. You are now ready to install fast tracepoints, list static
17879 tracepoint markers, probe static tracepoints markers, and start
17882 @node Remote Configuration
17883 @section Remote Configuration
17886 @kindex show remote
17887 This section documents the configuration options available when
17888 debugging remote programs. For the options related to the File I/O
17889 extensions of the remote protocol, see @ref{system,
17890 system-call-allowed}.
17893 @item set remoteaddresssize @var{bits}
17894 @cindex address size for remote targets
17895 @cindex bits in remote address
17896 Set the maximum size of address in a memory packet to the specified
17897 number of bits. @value{GDBN} will mask off the address bits above
17898 that number, when it passes addresses to the remote target. The
17899 default value is the number of bits in the target's address.
17901 @item show remoteaddresssize
17902 Show the current value of remote address size in bits.
17904 @item set remotebaud @var{n}
17905 @cindex baud rate for remote targets
17906 Set the baud rate for the remote serial I/O to @var{n} baud. The
17907 value is used to set the speed of the serial port used for debugging
17910 @item show remotebaud
17911 Show the current speed of the remote connection.
17913 @item set remotebreak
17914 @cindex interrupt remote programs
17915 @cindex BREAK signal instead of Ctrl-C
17916 @anchor{set remotebreak}
17917 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17918 when you type @kbd{Ctrl-c} to interrupt the program running
17919 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17920 character instead. The default is off, since most remote systems
17921 expect to see @samp{Ctrl-C} as the interrupt signal.
17923 @item show remotebreak
17924 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17925 interrupt the remote program.
17927 @item set remoteflow on
17928 @itemx set remoteflow off
17929 @kindex set remoteflow
17930 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17931 on the serial port used to communicate to the remote target.
17933 @item show remoteflow
17934 @kindex show remoteflow
17935 Show the current setting of hardware flow control.
17937 @item set remotelogbase @var{base}
17938 Set the base (a.k.a.@: radix) of logging serial protocol
17939 communications to @var{base}. Supported values of @var{base} are:
17940 @code{ascii}, @code{octal}, and @code{hex}. The default is
17943 @item show remotelogbase
17944 Show the current setting of the radix for logging remote serial
17947 @item set remotelogfile @var{file}
17948 @cindex record serial communications on file
17949 Record remote serial communications on the named @var{file}. The
17950 default is not to record at all.
17952 @item show remotelogfile.
17953 Show the current setting of the file name on which to record the
17954 serial communications.
17956 @item set remotetimeout @var{num}
17957 @cindex timeout for serial communications
17958 @cindex remote timeout
17959 Set the timeout limit to wait for the remote target to respond to
17960 @var{num} seconds. The default is 2 seconds.
17962 @item show remotetimeout
17963 Show the current number of seconds to wait for the remote target
17966 @cindex limit hardware breakpoints and watchpoints
17967 @cindex remote target, limit break- and watchpoints
17968 @anchor{set remote hardware-watchpoint-limit}
17969 @anchor{set remote hardware-breakpoint-limit}
17970 @item set remote hardware-watchpoint-limit @var{limit}
17971 @itemx set remote hardware-breakpoint-limit @var{limit}
17972 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17973 watchpoints. A limit of -1, the default, is treated as unlimited.
17975 @cindex limit hardware watchpoints length
17976 @cindex remote target, limit watchpoints length
17977 @anchor{set remote hardware-watchpoint-length-limit}
17978 @item set remote hardware-watchpoint-length-limit @var{limit}
17979 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17980 a remote hardware watchpoint. A limit of -1, the default, is treated
17983 @item show remote hardware-watchpoint-length-limit
17984 Show the current limit (in bytes) of the maximum length of
17985 a remote hardware watchpoint.
17987 @item set remote exec-file @var{filename}
17988 @itemx show remote exec-file
17989 @anchor{set remote exec-file}
17990 @cindex executable file, for remote target
17991 Select the file used for @code{run} with @code{target
17992 extended-remote}. This should be set to a filename valid on the
17993 target system. If it is not set, the target will use a default
17994 filename (e.g.@: the last program run).
17996 @item set remote interrupt-sequence
17997 @cindex interrupt remote programs
17998 @cindex select Ctrl-C, BREAK or BREAK-g
17999 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18000 @samp{BREAK-g} as the
18001 sequence to the remote target in order to interrupt the execution.
18002 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18003 is high level of serial line for some certain time.
18004 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18005 It is @code{BREAK} signal followed by character @code{g}.
18007 @item show interrupt-sequence
18008 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18009 is sent by @value{GDBN} to interrupt the remote program.
18010 @code{BREAK-g} is BREAK signal followed by @code{g} and
18011 also known as Magic SysRq g.
18013 @item set remote interrupt-on-connect
18014 @cindex send interrupt-sequence on start
18015 Specify whether interrupt-sequence is sent to remote target when
18016 @value{GDBN} connects to it. This is mostly needed when you debug
18017 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18018 which is known as Magic SysRq g in order to connect @value{GDBN}.
18020 @item show interrupt-on-connect
18021 Show whether interrupt-sequence is sent
18022 to remote target when @value{GDBN} connects to it.
18026 @item set tcp auto-retry on
18027 @cindex auto-retry, for remote TCP target
18028 Enable auto-retry for remote TCP connections. This is useful if the remote
18029 debugging agent is launched in parallel with @value{GDBN}; there is a race
18030 condition because the agent may not become ready to accept the connection
18031 before @value{GDBN} attempts to connect. When auto-retry is
18032 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18033 to establish the connection using the timeout specified by
18034 @code{set tcp connect-timeout}.
18036 @item set tcp auto-retry off
18037 Do not auto-retry failed TCP connections.
18039 @item show tcp auto-retry
18040 Show the current auto-retry setting.
18042 @item set tcp connect-timeout @var{seconds}
18043 @cindex connection timeout, for remote TCP target
18044 @cindex timeout, for remote target connection
18045 Set the timeout for establishing a TCP connection to the remote target to
18046 @var{seconds}. The timeout affects both polling to retry failed connections
18047 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18048 that are merely slow to complete, and represents an approximate cumulative
18051 @item show tcp connect-timeout
18052 Show the current connection timeout setting.
18055 @cindex remote packets, enabling and disabling
18056 The @value{GDBN} remote protocol autodetects the packets supported by
18057 your debugging stub. If you need to override the autodetection, you
18058 can use these commands to enable or disable individual packets. Each
18059 packet can be set to @samp{on} (the remote target supports this
18060 packet), @samp{off} (the remote target does not support this packet),
18061 or @samp{auto} (detect remote target support for this packet). They
18062 all default to @samp{auto}. For more information about each packet,
18063 see @ref{Remote Protocol}.
18065 During normal use, you should not have to use any of these commands.
18066 If you do, that may be a bug in your remote debugging stub, or a bug
18067 in @value{GDBN}. You may want to report the problem to the
18068 @value{GDBN} developers.
18070 For each packet @var{name}, the command to enable or disable the
18071 packet is @code{set remote @var{name}-packet}. The available settings
18074 @multitable @columnfractions 0.28 0.32 0.25
18077 @tab Related Features
18079 @item @code{fetch-register}
18081 @tab @code{info registers}
18083 @item @code{set-register}
18087 @item @code{binary-download}
18089 @tab @code{load}, @code{set}
18091 @item @code{read-aux-vector}
18092 @tab @code{qXfer:auxv:read}
18093 @tab @code{info auxv}
18095 @item @code{symbol-lookup}
18096 @tab @code{qSymbol}
18097 @tab Detecting multiple threads
18099 @item @code{attach}
18100 @tab @code{vAttach}
18103 @item @code{verbose-resume}
18105 @tab Stepping or resuming multiple threads
18111 @item @code{software-breakpoint}
18115 @item @code{hardware-breakpoint}
18119 @item @code{write-watchpoint}
18123 @item @code{read-watchpoint}
18127 @item @code{access-watchpoint}
18131 @item @code{target-features}
18132 @tab @code{qXfer:features:read}
18133 @tab @code{set architecture}
18135 @item @code{library-info}
18136 @tab @code{qXfer:libraries:read}
18137 @tab @code{info sharedlibrary}
18139 @item @code{memory-map}
18140 @tab @code{qXfer:memory-map:read}
18141 @tab @code{info mem}
18143 @item @code{read-sdata-object}
18144 @tab @code{qXfer:sdata:read}
18145 @tab @code{print $_sdata}
18147 @item @code{read-spu-object}
18148 @tab @code{qXfer:spu:read}
18149 @tab @code{info spu}
18151 @item @code{write-spu-object}
18152 @tab @code{qXfer:spu:write}
18153 @tab @code{info spu}
18155 @item @code{read-siginfo-object}
18156 @tab @code{qXfer:siginfo:read}
18157 @tab @code{print $_siginfo}
18159 @item @code{write-siginfo-object}
18160 @tab @code{qXfer:siginfo:write}
18161 @tab @code{set $_siginfo}
18163 @item @code{threads}
18164 @tab @code{qXfer:threads:read}
18165 @tab @code{info threads}
18167 @item @code{get-thread-local-@*storage-address}
18168 @tab @code{qGetTLSAddr}
18169 @tab Displaying @code{__thread} variables
18171 @item @code{get-thread-information-block-address}
18172 @tab @code{qGetTIBAddr}
18173 @tab Display MS-Windows Thread Information Block.
18175 @item @code{search-memory}
18176 @tab @code{qSearch:memory}
18179 @item @code{supported-packets}
18180 @tab @code{qSupported}
18181 @tab Remote communications parameters
18183 @item @code{pass-signals}
18184 @tab @code{QPassSignals}
18185 @tab @code{handle @var{signal}}
18187 @item @code{program-signals}
18188 @tab @code{QProgramSignals}
18189 @tab @code{handle @var{signal}}
18191 @item @code{hostio-close-packet}
18192 @tab @code{vFile:close}
18193 @tab @code{remote get}, @code{remote put}
18195 @item @code{hostio-open-packet}
18196 @tab @code{vFile:open}
18197 @tab @code{remote get}, @code{remote put}
18199 @item @code{hostio-pread-packet}
18200 @tab @code{vFile:pread}
18201 @tab @code{remote get}, @code{remote put}
18203 @item @code{hostio-pwrite-packet}
18204 @tab @code{vFile:pwrite}
18205 @tab @code{remote get}, @code{remote put}
18207 @item @code{hostio-unlink-packet}
18208 @tab @code{vFile:unlink}
18209 @tab @code{remote delete}
18211 @item @code{hostio-readlink-packet}
18212 @tab @code{vFile:readlink}
18215 @item @code{noack-packet}
18216 @tab @code{QStartNoAckMode}
18217 @tab Packet acknowledgment
18219 @item @code{osdata}
18220 @tab @code{qXfer:osdata:read}
18221 @tab @code{info os}
18223 @item @code{query-attached}
18224 @tab @code{qAttached}
18225 @tab Querying remote process attach state.
18227 @item @code{traceframe-info}
18228 @tab @code{qXfer:traceframe-info:read}
18229 @tab Traceframe info
18231 @item @code{install-in-trace}
18232 @tab @code{InstallInTrace}
18233 @tab Install tracepoint in tracing
18235 @item @code{disable-randomization}
18236 @tab @code{QDisableRandomization}
18237 @tab @code{set disable-randomization}
18239 @item @code{conditional-breakpoints-packet}
18240 @tab @code{Z0 and Z1}
18241 @tab @code{Support for target-side breakpoint condition evaluation}
18245 @section Implementing a Remote Stub
18247 @cindex debugging stub, example
18248 @cindex remote stub, example
18249 @cindex stub example, remote debugging
18250 The stub files provided with @value{GDBN} implement the target side of the
18251 communication protocol, and the @value{GDBN} side is implemented in the
18252 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
18253 these subroutines to communicate, and ignore the details. (If you're
18254 implementing your own stub file, you can still ignore the details: start
18255 with one of the existing stub files. @file{sparc-stub.c} is the best
18256 organized, and therefore the easiest to read.)
18258 @cindex remote serial debugging, overview
18259 To debug a program running on another machine (the debugging
18260 @dfn{target} machine), you must first arrange for all the usual
18261 prerequisites for the program to run by itself. For example, for a C
18266 A startup routine to set up the C runtime environment; these usually
18267 have a name like @file{crt0}. The startup routine may be supplied by
18268 your hardware supplier, or you may have to write your own.
18271 A C subroutine library to support your program's
18272 subroutine calls, notably managing input and output.
18275 A way of getting your program to the other machine---for example, a
18276 download program. These are often supplied by the hardware
18277 manufacturer, but you may have to write your own from hardware
18281 The next step is to arrange for your program to use a serial port to
18282 communicate with the machine where @value{GDBN} is running (the @dfn{host}
18283 machine). In general terms, the scheme looks like this:
18287 @value{GDBN} already understands how to use this protocol; when everything
18288 else is set up, you can simply use the @samp{target remote} command
18289 (@pxref{Targets,,Specifying a Debugging Target}).
18291 @item On the target,
18292 you must link with your program a few special-purpose subroutines that
18293 implement the @value{GDBN} remote serial protocol. The file containing these
18294 subroutines is called a @dfn{debugging stub}.
18296 On certain remote targets, you can use an auxiliary program
18297 @code{gdbserver} instead of linking a stub into your program.
18298 @xref{Server,,Using the @code{gdbserver} Program}, for details.
18301 The debugging stub is specific to the architecture of the remote
18302 machine; for example, use @file{sparc-stub.c} to debug programs on
18305 @cindex remote serial stub list
18306 These working remote stubs are distributed with @value{GDBN}:
18311 @cindex @file{i386-stub.c}
18314 For Intel 386 and compatible architectures.
18317 @cindex @file{m68k-stub.c}
18318 @cindex Motorola 680x0
18320 For Motorola 680x0 architectures.
18323 @cindex @file{sh-stub.c}
18326 For Renesas SH architectures.
18329 @cindex @file{sparc-stub.c}
18331 For @sc{sparc} architectures.
18333 @item sparcl-stub.c
18334 @cindex @file{sparcl-stub.c}
18337 For Fujitsu @sc{sparclite} architectures.
18341 The @file{README} file in the @value{GDBN} distribution may list other
18342 recently added stubs.
18345 * Stub Contents:: What the stub can do for you
18346 * Bootstrapping:: What you must do for the stub
18347 * Debug Session:: Putting it all together
18350 @node Stub Contents
18351 @subsection What the Stub Can Do for You
18353 @cindex remote serial stub
18354 The debugging stub for your architecture supplies these three
18358 @item set_debug_traps
18359 @findex set_debug_traps
18360 @cindex remote serial stub, initialization
18361 This routine arranges for @code{handle_exception} to run when your
18362 program stops. You must call this subroutine explicitly in your
18363 program's startup code.
18365 @item handle_exception
18366 @findex handle_exception
18367 @cindex remote serial stub, main routine
18368 This is the central workhorse, but your program never calls it
18369 explicitly---the setup code arranges for @code{handle_exception} to
18370 run when a trap is triggered.
18372 @code{handle_exception} takes control when your program stops during
18373 execution (for example, on a breakpoint), and mediates communications
18374 with @value{GDBN} on the host machine. This is where the communications
18375 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
18376 representative on the target machine. It begins by sending summary
18377 information on the state of your program, then continues to execute,
18378 retrieving and transmitting any information @value{GDBN} needs, until you
18379 execute a @value{GDBN} command that makes your program resume; at that point,
18380 @code{handle_exception} returns control to your own code on the target
18384 @cindex @code{breakpoint} subroutine, remote
18385 Use this auxiliary subroutine to make your program contain a
18386 breakpoint. Depending on the particular situation, this may be the only
18387 way for @value{GDBN} to get control. For instance, if your target
18388 machine has some sort of interrupt button, you won't need to call this;
18389 pressing the interrupt button transfers control to
18390 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
18391 simply receiving characters on the serial port may also trigger a trap;
18392 again, in that situation, you don't need to call @code{breakpoint} from
18393 your own program---simply running @samp{target remote} from the host
18394 @value{GDBN} session gets control.
18396 Call @code{breakpoint} if none of these is true, or if you simply want
18397 to make certain your program stops at a predetermined point for the
18398 start of your debugging session.
18401 @node Bootstrapping
18402 @subsection What You Must Do for the Stub
18404 @cindex remote stub, support routines
18405 The debugging stubs that come with @value{GDBN} are set up for a particular
18406 chip architecture, but they have no information about the rest of your
18407 debugging target machine.
18409 First of all you need to tell the stub how to communicate with the
18413 @item int getDebugChar()
18414 @findex getDebugChar
18415 Write this subroutine to read a single character from the serial port.
18416 It may be identical to @code{getchar} for your target system; a
18417 different name is used to allow you to distinguish the two if you wish.
18419 @item void putDebugChar(int)
18420 @findex putDebugChar
18421 Write this subroutine to write a single character to the serial port.
18422 It may be identical to @code{putchar} for your target system; a
18423 different name is used to allow you to distinguish the two if you wish.
18426 @cindex control C, and remote debugging
18427 @cindex interrupting remote targets
18428 If you want @value{GDBN} to be able to stop your program while it is
18429 running, you need to use an interrupt-driven serial driver, and arrange
18430 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
18431 character). That is the character which @value{GDBN} uses to tell the
18432 remote system to stop.
18434 Getting the debugging target to return the proper status to @value{GDBN}
18435 probably requires changes to the standard stub; one quick and dirty way
18436 is to just execute a breakpoint instruction (the ``dirty'' part is that
18437 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
18439 Other routines you need to supply are:
18442 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
18443 @findex exceptionHandler
18444 Write this function to install @var{exception_address} in the exception
18445 handling tables. You need to do this because the stub does not have any
18446 way of knowing what the exception handling tables on your target system
18447 are like (for example, the processor's table might be in @sc{rom},
18448 containing entries which point to a table in @sc{ram}).
18449 @var{exception_number} is the exception number which should be changed;
18450 its meaning is architecture-dependent (for example, different numbers
18451 might represent divide by zero, misaligned access, etc). When this
18452 exception occurs, control should be transferred directly to
18453 @var{exception_address}, and the processor state (stack, registers,
18454 and so on) should be just as it is when a processor exception occurs. So if
18455 you want to use a jump instruction to reach @var{exception_address}, it
18456 should be a simple jump, not a jump to subroutine.
18458 For the 386, @var{exception_address} should be installed as an interrupt
18459 gate so that interrupts are masked while the handler runs. The gate
18460 should be at privilege level 0 (the most privileged level). The
18461 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
18462 help from @code{exceptionHandler}.
18464 @item void flush_i_cache()
18465 @findex flush_i_cache
18466 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
18467 instruction cache, if any, on your target machine. If there is no
18468 instruction cache, this subroutine may be a no-op.
18470 On target machines that have instruction caches, @value{GDBN} requires this
18471 function to make certain that the state of your program is stable.
18475 You must also make sure this library routine is available:
18478 @item void *memset(void *, int, int)
18480 This is the standard library function @code{memset} that sets an area of
18481 memory to a known value. If you have one of the free versions of
18482 @code{libc.a}, @code{memset} can be found there; otherwise, you must
18483 either obtain it from your hardware manufacturer, or write your own.
18486 If you do not use the GNU C compiler, you may need other standard
18487 library subroutines as well; this varies from one stub to another,
18488 but in general the stubs are likely to use any of the common library
18489 subroutines which @code{@value{NGCC}} generates as inline code.
18492 @node Debug Session
18493 @subsection Putting it All Together
18495 @cindex remote serial debugging summary
18496 In summary, when your program is ready to debug, you must follow these
18501 Make sure you have defined the supporting low-level routines
18502 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
18504 @code{getDebugChar}, @code{putDebugChar},
18505 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
18509 Insert these lines in your program's startup code, before the main
18510 procedure is called:
18517 On some machines, when a breakpoint trap is raised, the hardware
18518 automatically makes the PC point to the instruction after the
18519 breakpoint. If your machine doesn't do that, you may need to adjust
18520 @code{handle_exception} to arrange for it to return to the instruction
18521 after the breakpoint on this first invocation, so that your program
18522 doesn't keep hitting the initial breakpoint instead of making
18526 For the 680x0 stub only, you need to provide a variable called
18527 @code{exceptionHook}. Normally you just use:
18530 void (*exceptionHook)() = 0;
18534 but if before calling @code{set_debug_traps}, you set it to point to a
18535 function in your program, that function is called when
18536 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
18537 error). The function indicated by @code{exceptionHook} is called with
18538 one parameter: an @code{int} which is the exception number.
18541 Compile and link together: your program, the @value{GDBN} debugging stub for
18542 your target architecture, and the supporting subroutines.
18545 Make sure you have a serial connection between your target machine and
18546 the @value{GDBN} host, and identify the serial port on the host.
18549 @c The "remote" target now provides a `load' command, so we should
18550 @c document that. FIXME.
18551 Download your program to your target machine (or get it there by
18552 whatever means the manufacturer provides), and start it.
18555 Start @value{GDBN} on the host, and connect to the target
18556 (@pxref{Connecting,,Connecting to a Remote Target}).
18560 @node Configurations
18561 @chapter Configuration-Specific Information
18563 While nearly all @value{GDBN} commands are available for all native and
18564 cross versions of the debugger, there are some exceptions. This chapter
18565 describes things that are only available in certain configurations.
18567 There are three major categories of configurations: native
18568 configurations, where the host and target are the same, embedded
18569 operating system configurations, which are usually the same for several
18570 different processor architectures, and bare embedded processors, which
18571 are quite different from each other.
18576 * Embedded Processors::
18583 This section describes details specific to particular native
18588 * BSD libkvm Interface:: Debugging BSD kernel memory images
18589 * SVR4 Process Information:: SVR4 process information
18590 * DJGPP Native:: Features specific to the DJGPP port
18591 * Cygwin Native:: Features specific to the Cygwin port
18592 * Hurd Native:: Features specific to @sc{gnu} Hurd
18593 * Darwin:: Features specific to Darwin
18599 On HP-UX systems, if you refer to a function or variable name that
18600 begins with a dollar sign, @value{GDBN} searches for a user or system
18601 name first, before it searches for a convenience variable.
18604 @node BSD libkvm Interface
18605 @subsection BSD libkvm Interface
18608 @cindex kernel memory image
18609 @cindex kernel crash dump
18611 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
18612 interface that provides a uniform interface for accessing kernel virtual
18613 memory images, including live systems and crash dumps. @value{GDBN}
18614 uses this interface to allow you to debug live kernels and kernel crash
18615 dumps on many native BSD configurations. This is implemented as a
18616 special @code{kvm} debugging target. For debugging a live system, load
18617 the currently running kernel into @value{GDBN} and connect to the
18621 (@value{GDBP}) @b{target kvm}
18624 For debugging crash dumps, provide the file name of the crash dump as an
18628 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
18631 Once connected to the @code{kvm} target, the following commands are
18637 Set current context from the @dfn{Process Control Block} (PCB) address.
18640 Set current context from proc address. This command isn't available on
18641 modern FreeBSD systems.
18644 @node SVR4 Process Information
18645 @subsection SVR4 Process Information
18647 @cindex examine process image
18648 @cindex process info via @file{/proc}
18650 Many versions of SVR4 and compatible systems provide a facility called
18651 @samp{/proc} that can be used to examine the image of a running
18652 process using file-system subroutines.
18654 If @value{GDBN} is configured for an operating system with this
18655 facility, the command @code{info proc} is available to report
18656 information about the process running your program, or about any
18657 process running on your system. This includes, as of this writing,
18658 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
18659 not HP-UX, for example.
18661 This command may also work on core files that were created on a system
18662 that has the @samp{/proc} facility.
18668 @itemx info proc @var{process-id}
18669 Summarize available information about any running process. If a
18670 process ID is specified by @var{process-id}, display information about
18671 that process; otherwise display information about the program being
18672 debugged. The summary includes the debugged process ID, the command
18673 line used to invoke it, its current working directory, and its
18674 executable file's absolute file name.
18676 On some systems, @var{process-id} can be of the form
18677 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
18678 within a process. If the optional @var{pid} part is missing, it means
18679 a thread from the process being debugged (the leading @samp{/} still
18680 needs to be present, or else @value{GDBN} will interpret the number as
18681 a process ID rather than a thread ID).
18683 @item info proc cmdline
18684 @cindex info proc cmdline
18685 Show the original command line of the process. This command is
18686 specific to @sc{gnu}/Linux.
18688 @item info proc cwd
18689 @cindex info proc cwd
18690 Show the current working directory of the process. This command is
18691 specific to @sc{gnu}/Linux.
18693 @item info proc exe
18694 @cindex info proc exe
18695 Show the name of executable of the process. This command is specific
18698 @item info proc mappings
18699 @cindex memory address space mappings
18700 Report the memory address space ranges accessible in the program, with
18701 information on whether the process has read, write, or execute access
18702 rights to each range. On @sc{gnu}/Linux systems, each memory range
18703 includes the object file which is mapped to that range, instead of the
18704 memory access rights to that range.
18706 @item info proc stat
18707 @itemx info proc status
18708 @cindex process detailed status information
18709 These subcommands are specific to @sc{gnu}/Linux systems. They show
18710 the process-related information, including the user ID and group ID;
18711 how many threads are there in the process; its virtual memory usage;
18712 the signals that are pending, blocked, and ignored; its TTY; its
18713 consumption of system and user time; its stack size; its @samp{nice}
18714 value; etc. For more information, see the @samp{proc} man page
18715 (type @kbd{man 5 proc} from your shell prompt).
18717 @item info proc all
18718 Show all the information about the process described under all of the
18719 above @code{info proc} subcommands.
18722 @comment These sub-options of 'info proc' were not included when
18723 @comment procfs.c was re-written. Keep their descriptions around
18724 @comment against the day when someone finds the time to put them back in.
18725 @kindex info proc times
18726 @item info proc times
18727 Starting time, user CPU time, and system CPU time for your program and
18730 @kindex info proc id
18732 Report on the process IDs related to your program: its own process ID,
18733 the ID of its parent, the process group ID, and the session ID.
18736 @item set procfs-trace
18737 @kindex set procfs-trace
18738 @cindex @code{procfs} API calls
18739 This command enables and disables tracing of @code{procfs} API calls.
18741 @item show procfs-trace
18742 @kindex show procfs-trace
18743 Show the current state of @code{procfs} API call tracing.
18745 @item set procfs-file @var{file}
18746 @kindex set procfs-file
18747 Tell @value{GDBN} to write @code{procfs} API trace to the named
18748 @var{file}. @value{GDBN} appends the trace info to the previous
18749 contents of the file. The default is to display the trace on the
18752 @item show procfs-file
18753 @kindex show procfs-file
18754 Show the file to which @code{procfs} API trace is written.
18756 @item proc-trace-entry
18757 @itemx proc-trace-exit
18758 @itemx proc-untrace-entry
18759 @itemx proc-untrace-exit
18760 @kindex proc-trace-entry
18761 @kindex proc-trace-exit
18762 @kindex proc-untrace-entry
18763 @kindex proc-untrace-exit
18764 These commands enable and disable tracing of entries into and exits
18765 from the @code{syscall} interface.
18768 @kindex info pidlist
18769 @cindex process list, QNX Neutrino
18770 For QNX Neutrino only, this command displays the list of all the
18771 processes and all the threads within each process.
18774 @kindex info meminfo
18775 @cindex mapinfo list, QNX Neutrino
18776 For QNX Neutrino only, this command displays the list of all mapinfos.
18780 @subsection Features for Debugging @sc{djgpp} Programs
18781 @cindex @sc{djgpp} debugging
18782 @cindex native @sc{djgpp} debugging
18783 @cindex MS-DOS-specific commands
18786 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
18787 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
18788 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
18789 top of real-mode DOS systems and their emulations.
18791 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
18792 defines a few commands specific to the @sc{djgpp} port. This
18793 subsection describes those commands.
18798 This is a prefix of @sc{djgpp}-specific commands which print
18799 information about the target system and important OS structures.
18802 @cindex MS-DOS system info
18803 @cindex free memory information (MS-DOS)
18804 @item info dos sysinfo
18805 This command displays assorted information about the underlying
18806 platform: the CPU type and features, the OS version and flavor, the
18807 DPMI version, and the available conventional and DPMI memory.
18812 @cindex segment descriptor tables
18813 @cindex descriptor tables display
18815 @itemx info dos ldt
18816 @itemx info dos idt
18817 These 3 commands display entries from, respectively, Global, Local,
18818 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
18819 tables are data structures which store a descriptor for each segment
18820 that is currently in use. The segment's selector is an index into a
18821 descriptor table; the table entry for that index holds the
18822 descriptor's base address and limit, and its attributes and access
18825 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
18826 segment (used for both data and the stack), and a DOS segment (which
18827 allows access to DOS/BIOS data structures and absolute addresses in
18828 conventional memory). However, the DPMI host will usually define
18829 additional segments in order to support the DPMI environment.
18831 @cindex garbled pointers
18832 These commands allow to display entries from the descriptor tables.
18833 Without an argument, all entries from the specified table are
18834 displayed. An argument, which should be an integer expression, means
18835 display a single entry whose index is given by the argument. For
18836 example, here's a convenient way to display information about the
18837 debugged program's data segment:
18840 @exdent @code{(@value{GDBP}) info dos ldt $ds}
18841 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
18845 This comes in handy when you want to see whether a pointer is outside
18846 the data segment's limit (i.e.@: @dfn{garbled}).
18848 @cindex page tables display (MS-DOS)
18850 @itemx info dos pte
18851 These two commands display entries from, respectively, the Page
18852 Directory and the Page Tables. Page Directories and Page Tables are
18853 data structures which control how virtual memory addresses are mapped
18854 into physical addresses. A Page Table includes an entry for every
18855 page of memory that is mapped into the program's address space; there
18856 may be several Page Tables, each one holding up to 4096 entries. A
18857 Page Directory has up to 4096 entries, one each for every Page Table
18858 that is currently in use.
18860 Without an argument, @kbd{info dos pde} displays the entire Page
18861 Directory, and @kbd{info dos pte} displays all the entries in all of
18862 the Page Tables. An argument, an integer expression, given to the
18863 @kbd{info dos pde} command means display only that entry from the Page
18864 Directory table. An argument given to the @kbd{info dos pte} command
18865 means display entries from a single Page Table, the one pointed to by
18866 the specified entry in the Page Directory.
18868 @cindex direct memory access (DMA) on MS-DOS
18869 These commands are useful when your program uses @dfn{DMA} (Direct
18870 Memory Access), which needs physical addresses to program the DMA
18873 These commands are supported only with some DPMI servers.
18875 @cindex physical address from linear address
18876 @item info dos address-pte @var{addr}
18877 This command displays the Page Table entry for a specified linear
18878 address. The argument @var{addr} is a linear address which should
18879 already have the appropriate segment's base address added to it,
18880 because this command accepts addresses which may belong to @emph{any}
18881 segment. For example, here's how to display the Page Table entry for
18882 the page where a variable @code{i} is stored:
18885 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
18886 @exdent @code{Page Table entry for address 0x11a00d30:}
18887 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
18891 This says that @code{i} is stored at offset @code{0xd30} from the page
18892 whose physical base address is @code{0x02698000}, and shows all the
18893 attributes of that page.
18895 Note that you must cast the addresses of variables to a @code{char *},
18896 since otherwise the value of @code{__djgpp_base_address}, the base
18897 address of all variables and functions in a @sc{djgpp} program, will
18898 be added using the rules of C pointer arithmetics: if @code{i} is
18899 declared an @code{int}, @value{GDBN} will add 4 times the value of
18900 @code{__djgpp_base_address} to the address of @code{i}.
18902 Here's another example, it displays the Page Table entry for the
18906 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
18907 @exdent @code{Page Table entry for address 0x29110:}
18908 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
18912 (The @code{+ 3} offset is because the transfer buffer's address is the
18913 3rd member of the @code{_go32_info_block} structure.) The output
18914 clearly shows that this DPMI server maps the addresses in conventional
18915 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
18916 linear (@code{0x29110}) addresses are identical.
18918 This command is supported only with some DPMI servers.
18921 @cindex DOS serial data link, remote debugging
18922 In addition to native debugging, the DJGPP port supports remote
18923 debugging via a serial data link. The following commands are specific
18924 to remote serial debugging in the DJGPP port of @value{GDBN}.
18927 @kindex set com1base
18928 @kindex set com1irq
18929 @kindex set com2base
18930 @kindex set com2irq
18931 @kindex set com3base
18932 @kindex set com3irq
18933 @kindex set com4base
18934 @kindex set com4irq
18935 @item set com1base @var{addr}
18936 This command sets the base I/O port address of the @file{COM1} serial
18939 @item set com1irq @var{irq}
18940 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
18941 for the @file{COM1} serial port.
18943 There are similar commands @samp{set com2base}, @samp{set com3irq},
18944 etc.@: for setting the port address and the @code{IRQ} lines for the
18947 @kindex show com1base
18948 @kindex show com1irq
18949 @kindex show com2base
18950 @kindex show com2irq
18951 @kindex show com3base
18952 @kindex show com3irq
18953 @kindex show com4base
18954 @kindex show com4irq
18955 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18956 display the current settings of the base address and the @code{IRQ}
18957 lines used by the COM ports.
18960 @kindex info serial
18961 @cindex DOS serial port status
18962 This command prints the status of the 4 DOS serial ports. For each
18963 port, it prints whether it's active or not, its I/O base address and
18964 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18965 counts of various errors encountered so far.
18969 @node Cygwin Native
18970 @subsection Features for Debugging MS Windows PE Executables
18971 @cindex MS Windows debugging
18972 @cindex native Cygwin debugging
18973 @cindex Cygwin-specific commands
18975 @value{GDBN} supports native debugging of MS Windows programs, including
18976 DLLs with and without symbolic debugging information.
18978 @cindex Ctrl-BREAK, MS-Windows
18979 @cindex interrupt debuggee on MS-Windows
18980 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18981 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18982 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18983 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18984 sequence, which can be used to interrupt the debuggee even if it
18987 There are various additional Cygwin-specific commands, described in
18988 this section. Working with DLLs that have no debugging symbols is
18989 described in @ref{Non-debug DLL Symbols}.
18994 This is a prefix of MS Windows-specific commands which print
18995 information about the target system and important OS structures.
18997 @item info w32 selector
18998 This command displays information returned by
18999 the Win32 API @code{GetThreadSelectorEntry} function.
19000 It takes an optional argument that is evaluated to
19001 a long value to give the information about this given selector.
19002 Without argument, this command displays information
19003 about the six segment registers.
19005 @item info w32 thread-information-block
19006 This command displays thread specific information stored in the
19007 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19008 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19012 This is a Cygwin-specific alias of @code{info shared}.
19014 @kindex dll-symbols
19016 This command loads symbols from a dll similarly to
19017 add-sym command but without the need to specify a base address.
19019 @kindex set cygwin-exceptions
19020 @cindex debugging the Cygwin DLL
19021 @cindex Cygwin DLL, debugging
19022 @item set cygwin-exceptions @var{mode}
19023 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19024 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19025 @value{GDBN} will delay recognition of exceptions, and may ignore some
19026 exceptions which seem to be caused by internal Cygwin DLL
19027 ``bookkeeping''. This option is meant primarily for debugging the
19028 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19029 @value{GDBN} users with false @code{SIGSEGV} signals.
19031 @kindex show cygwin-exceptions
19032 @item show cygwin-exceptions
19033 Displays whether @value{GDBN} will break on exceptions that happen
19034 inside the Cygwin DLL itself.
19036 @kindex set new-console
19037 @item set new-console @var{mode}
19038 If @var{mode} is @code{on} the debuggee will
19039 be started in a new console on next start.
19040 If @var{mode} is @code{off}, the debuggee will
19041 be started in the same console as the debugger.
19043 @kindex show new-console
19044 @item show new-console
19045 Displays whether a new console is used
19046 when the debuggee is started.
19048 @kindex set new-group
19049 @item set new-group @var{mode}
19050 This boolean value controls whether the debuggee should
19051 start a new group or stay in the same group as the debugger.
19052 This affects the way the Windows OS handles
19055 @kindex show new-group
19056 @item show new-group
19057 Displays current value of new-group boolean.
19059 @kindex set debugevents
19060 @item set debugevents
19061 This boolean value adds debug output concerning kernel events related
19062 to the debuggee seen by the debugger. This includes events that
19063 signal thread and process creation and exit, DLL loading and
19064 unloading, console interrupts, and debugging messages produced by the
19065 Windows @code{OutputDebugString} API call.
19067 @kindex set debugexec
19068 @item set debugexec
19069 This boolean value adds debug output concerning execute events
19070 (such as resume thread) seen by the debugger.
19072 @kindex set debugexceptions
19073 @item set debugexceptions
19074 This boolean value adds debug output concerning exceptions in the
19075 debuggee seen by the debugger.
19077 @kindex set debugmemory
19078 @item set debugmemory
19079 This boolean value adds debug output concerning debuggee memory reads
19080 and writes by the debugger.
19084 This boolean values specifies whether the debuggee is called
19085 via a shell or directly (default value is on).
19089 Displays if the debuggee will be started with a shell.
19094 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19097 @node Non-debug DLL Symbols
19098 @subsubsection Support for DLLs without Debugging Symbols
19099 @cindex DLLs with no debugging symbols
19100 @cindex Minimal symbols and DLLs
19102 Very often on windows, some of the DLLs that your program relies on do
19103 not include symbolic debugging information (for example,
19104 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19105 symbols in a DLL, it relies on the minimal amount of symbolic
19106 information contained in the DLL's export table. This section
19107 describes working with such symbols, known internally to @value{GDBN} as
19108 ``minimal symbols''.
19110 Note that before the debugged program has started execution, no DLLs
19111 will have been loaded. The easiest way around this problem is simply to
19112 start the program --- either by setting a breakpoint or letting the
19113 program run once to completion. It is also possible to force
19114 @value{GDBN} to load a particular DLL before starting the executable ---
19115 see the shared library information in @ref{Files}, or the
19116 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19117 explicitly loading symbols from a DLL with no debugging information will
19118 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19119 which may adversely affect symbol lookup performance.
19121 @subsubsection DLL Name Prefixes
19123 In keeping with the naming conventions used by the Microsoft debugging
19124 tools, DLL export symbols are made available with a prefix based on the
19125 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19126 also entered into the symbol table, so @code{CreateFileA} is often
19127 sufficient. In some cases there will be name clashes within a program
19128 (particularly if the executable itself includes full debugging symbols)
19129 necessitating the use of the fully qualified name when referring to the
19130 contents of the DLL. Use single-quotes around the name to avoid the
19131 exclamation mark (``!'') being interpreted as a language operator.
19133 Note that the internal name of the DLL may be all upper-case, even
19134 though the file name of the DLL is lower-case, or vice-versa. Since
19135 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19136 some confusion. If in doubt, try the @code{info functions} and
19137 @code{info variables} commands or even @code{maint print msymbols}
19138 (@pxref{Symbols}). Here's an example:
19141 (@value{GDBP}) info function CreateFileA
19142 All functions matching regular expression "CreateFileA":
19144 Non-debugging symbols:
19145 0x77e885f4 CreateFileA
19146 0x77e885f4 KERNEL32!CreateFileA
19150 (@value{GDBP}) info function !
19151 All functions matching regular expression "!":
19153 Non-debugging symbols:
19154 0x6100114c cygwin1!__assert
19155 0x61004034 cygwin1!_dll_crt0@@0
19156 0x61004240 cygwin1!dll_crt0(per_process *)
19160 @subsubsection Working with Minimal Symbols
19162 Symbols extracted from a DLL's export table do not contain very much
19163 type information. All that @value{GDBN} can do is guess whether a symbol
19164 refers to a function or variable depending on the linker section that
19165 contains the symbol. Also note that the actual contents of the memory
19166 contained in a DLL are not available unless the program is running. This
19167 means that you cannot examine the contents of a variable or disassemble
19168 a function within a DLL without a running program.
19170 Variables are generally treated as pointers and dereferenced
19171 automatically. For this reason, it is often necessary to prefix a
19172 variable name with the address-of operator (``&'') and provide explicit
19173 type information in the command. Here's an example of the type of
19177 (@value{GDBP}) print 'cygwin1!__argv'
19182 (@value{GDBP}) x 'cygwin1!__argv'
19183 0x10021610: "\230y\""
19186 And two possible solutions:
19189 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19190 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19194 (@value{GDBP}) x/2x &'cygwin1!__argv'
19195 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19196 (@value{GDBP}) x/x 0x10021608
19197 0x10021608: 0x0022fd98
19198 (@value{GDBP}) x/s 0x0022fd98
19199 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19202 Setting a break point within a DLL is possible even before the program
19203 starts execution. However, under these circumstances, @value{GDBN} can't
19204 examine the initial instructions of the function in order to skip the
19205 function's frame set-up code. You can work around this by using ``*&''
19206 to set the breakpoint at a raw memory address:
19209 (@value{GDBP}) break *&'python22!PyOS_Readline'
19210 Breakpoint 1 at 0x1e04eff0
19213 The author of these extensions is not entirely convinced that setting a
19214 break point within a shared DLL like @file{kernel32.dll} is completely
19218 @subsection Commands Specific to @sc{gnu} Hurd Systems
19219 @cindex @sc{gnu} Hurd debugging
19221 This subsection describes @value{GDBN} commands specific to the
19222 @sc{gnu} Hurd native debugging.
19227 @kindex set signals@r{, Hurd command}
19228 @kindex set sigs@r{, Hurd command}
19229 This command toggles the state of inferior signal interception by
19230 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
19231 affected by this command. @code{sigs} is a shorthand alias for
19236 @kindex show signals@r{, Hurd command}
19237 @kindex show sigs@r{, Hurd command}
19238 Show the current state of intercepting inferior's signals.
19240 @item set signal-thread
19241 @itemx set sigthread
19242 @kindex set signal-thread
19243 @kindex set sigthread
19244 This command tells @value{GDBN} which thread is the @code{libc} signal
19245 thread. That thread is run when a signal is delivered to a running
19246 process. @code{set sigthread} is the shorthand alias of @code{set
19249 @item show signal-thread
19250 @itemx show sigthread
19251 @kindex show signal-thread
19252 @kindex show sigthread
19253 These two commands show which thread will run when the inferior is
19254 delivered a signal.
19257 @kindex set stopped@r{, Hurd command}
19258 This commands tells @value{GDBN} that the inferior process is stopped,
19259 as with the @code{SIGSTOP} signal. The stopped process can be
19260 continued by delivering a signal to it.
19263 @kindex show stopped@r{, Hurd command}
19264 This command shows whether @value{GDBN} thinks the debuggee is
19267 @item set exceptions
19268 @kindex set exceptions@r{, Hurd command}
19269 Use this command to turn off trapping of exceptions in the inferior.
19270 When exception trapping is off, neither breakpoints nor
19271 single-stepping will work. To restore the default, set exception
19274 @item show exceptions
19275 @kindex show exceptions@r{, Hurd command}
19276 Show the current state of trapping exceptions in the inferior.
19278 @item set task pause
19279 @kindex set task@r{, Hurd commands}
19280 @cindex task attributes (@sc{gnu} Hurd)
19281 @cindex pause current task (@sc{gnu} Hurd)
19282 This command toggles task suspension when @value{GDBN} has control.
19283 Setting it to on takes effect immediately, and the task is suspended
19284 whenever @value{GDBN} gets control. Setting it to off will take
19285 effect the next time the inferior is continued. If this option is set
19286 to off, you can use @code{set thread default pause on} or @code{set
19287 thread pause on} (see below) to pause individual threads.
19289 @item show task pause
19290 @kindex show task@r{, Hurd commands}
19291 Show the current state of task suspension.
19293 @item set task detach-suspend-count
19294 @cindex task suspend count
19295 @cindex detach from task, @sc{gnu} Hurd
19296 This command sets the suspend count the task will be left with when
19297 @value{GDBN} detaches from it.
19299 @item show task detach-suspend-count
19300 Show the suspend count the task will be left with when detaching.
19302 @item set task exception-port
19303 @itemx set task excp
19304 @cindex task exception port, @sc{gnu} Hurd
19305 This command sets the task exception port to which @value{GDBN} will
19306 forward exceptions. The argument should be the value of the @dfn{send
19307 rights} of the task. @code{set task excp} is a shorthand alias.
19309 @item set noninvasive
19310 @cindex noninvasive task options
19311 This command switches @value{GDBN} to a mode that is the least
19312 invasive as far as interfering with the inferior is concerned. This
19313 is the same as using @code{set task pause}, @code{set exceptions}, and
19314 @code{set signals} to values opposite to the defaults.
19316 @item info send-rights
19317 @itemx info receive-rights
19318 @itemx info port-rights
19319 @itemx info port-sets
19320 @itemx info dead-names
19323 @cindex send rights, @sc{gnu} Hurd
19324 @cindex receive rights, @sc{gnu} Hurd
19325 @cindex port rights, @sc{gnu} Hurd
19326 @cindex port sets, @sc{gnu} Hurd
19327 @cindex dead names, @sc{gnu} Hurd
19328 These commands display information about, respectively, send rights,
19329 receive rights, port rights, port sets, and dead names of a task.
19330 There are also shorthand aliases: @code{info ports} for @code{info
19331 port-rights} and @code{info psets} for @code{info port-sets}.
19333 @item set thread pause
19334 @kindex set thread@r{, Hurd command}
19335 @cindex thread properties, @sc{gnu} Hurd
19336 @cindex pause current thread (@sc{gnu} Hurd)
19337 This command toggles current thread suspension when @value{GDBN} has
19338 control. Setting it to on takes effect immediately, and the current
19339 thread is suspended whenever @value{GDBN} gets control. Setting it to
19340 off will take effect the next time the inferior is continued.
19341 Normally, this command has no effect, since when @value{GDBN} has
19342 control, the whole task is suspended. However, if you used @code{set
19343 task pause off} (see above), this command comes in handy to suspend
19344 only the current thread.
19346 @item show thread pause
19347 @kindex show thread@r{, Hurd command}
19348 This command shows the state of current thread suspension.
19350 @item set thread run
19351 This command sets whether the current thread is allowed to run.
19353 @item show thread run
19354 Show whether the current thread is allowed to run.
19356 @item set thread detach-suspend-count
19357 @cindex thread suspend count, @sc{gnu} Hurd
19358 @cindex detach from thread, @sc{gnu} Hurd
19359 This command sets the suspend count @value{GDBN} will leave on a
19360 thread when detaching. This number is relative to the suspend count
19361 found by @value{GDBN} when it notices the thread; use @code{set thread
19362 takeover-suspend-count} to force it to an absolute value.
19364 @item show thread detach-suspend-count
19365 Show the suspend count @value{GDBN} will leave on the thread when
19368 @item set thread exception-port
19369 @itemx set thread excp
19370 Set the thread exception port to which to forward exceptions. This
19371 overrides the port set by @code{set task exception-port} (see above).
19372 @code{set thread excp} is the shorthand alias.
19374 @item set thread takeover-suspend-count
19375 Normally, @value{GDBN}'s thread suspend counts are relative to the
19376 value @value{GDBN} finds when it notices each thread. This command
19377 changes the suspend counts to be absolute instead.
19379 @item set thread default
19380 @itemx show thread default
19381 @cindex thread default settings, @sc{gnu} Hurd
19382 Each of the above @code{set thread} commands has a @code{set thread
19383 default} counterpart (e.g., @code{set thread default pause}, @code{set
19384 thread default exception-port}, etc.). The @code{thread default}
19385 variety of commands sets the default thread properties for all
19386 threads; you can then change the properties of individual threads with
19387 the non-default commands.
19394 @value{GDBN} provides the following commands specific to the Darwin target:
19397 @item set debug darwin @var{num}
19398 @kindex set debug darwin
19399 When set to a non zero value, enables debugging messages specific to
19400 the Darwin support. Higher values produce more verbose output.
19402 @item show debug darwin
19403 @kindex show debug darwin
19404 Show the current state of Darwin messages.
19406 @item set debug mach-o @var{num}
19407 @kindex set debug mach-o
19408 When set to a non zero value, enables debugging messages while
19409 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
19410 file format used on Darwin for object and executable files.) Higher
19411 values produce more verbose output. This is a command to diagnose
19412 problems internal to @value{GDBN} and should not be needed in normal
19415 @item show debug mach-o
19416 @kindex show debug mach-o
19417 Show the current state of Mach-O file messages.
19419 @item set mach-exceptions on
19420 @itemx set mach-exceptions off
19421 @kindex set mach-exceptions
19422 On Darwin, faults are first reported as a Mach exception and are then
19423 mapped to a Posix signal. Use this command to turn on trapping of
19424 Mach exceptions in the inferior. This might be sometimes useful to
19425 better understand the cause of a fault. The default is off.
19427 @item show mach-exceptions
19428 @kindex show mach-exceptions
19429 Show the current state of exceptions trapping.
19434 @section Embedded Operating Systems
19436 This section describes configurations involving the debugging of
19437 embedded operating systems that are available for several different
19441 * VxWorks:: Using @value{GDBN} with VxWorks
19444 @value{GDBN} includes the ability to debug programs running on
19445 various real-time operating systems.
19448 @subsection Using @value{GDBN} with VxWorks
19454 @kindex target vxworks
19455 @item target vxworks @var{machinename}
19456 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
19457 is the target system's machine name or IP address.
19461 On VxWorks, @code{load} links @var{filename} dynamically on the
19462 current target system as well as adding its symbols in @value{GDBN}.
19464 @value{GDBN} enables developers to spawn and debug tasks running on networked
19465 VxWorks targets from a Unix host. Already-running tasks spawned from
19466 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
19467 both the Unix host and on the VxWorks target. The program
19468 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
19469 installed with the name @code{vxgdb}, to distinguish it from a
19470 @value{GDBN} for debugging programs on the host itself.)
19473 @item VxWorks-timeout @var{args}
19474 @kindex vxworks-timeout
19475 All VxWorks-based targets now support the option @code{vxworks-timeout}.
19476 This option is set by the user, and @var{args} represents the number of
19477 seconds @value{GDBN} waits for responses to rpc's. You might use this if
19478 your VxWorks target is a slow software simulator or is on the far side
19479 of a thin network line.
19482 The following information on connecting to VxWorks was current when
19483 this manual was produced; newer releases of VxWorks may use revised
19486 @findex INCLUDE_RDB
19487 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
19488 to include the remote debugging interface routines in the VxWorks
19489 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
19490 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
19491 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
19492 source debugging task @code{tRdbTask} when VxWorks is booted. For more
19493 information on configuring and remaking VxWorks, see the manufacturer's
19495 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
19497 Once you have included @file{rdb.a} in your VxWorks system image and set
19498 your Unix execution search path to find @value{GDBN}, you are ready to
19499 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
19500 @code{vxgdb}, depending on your installation).
19502 @value{GDBN} comes up showing the prompt:
19509 * VxWorks Connection:: Connecting to VxWorks
19510 * VxWorks Download:: VxWorks download
19511 * VxWorks Attach:: Running tasks
19514 @node VxWorks Connection
19515 @subsubsection Connecting to VxWorks
19517 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
19518 network. To connect to a target whose host name is ``@code{tt}'', type:
19521 (vxgdb) target vxworks tt
19525 @value{GDBN} displays messages like these:
19528 Attaching remote machine across net...
19533 @value{GDBN} then attempts to read the symbol tables of any object modules
19534 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
19535 these files by searching the directories listed in the command search
19536 path (@pxref{Environment, ,Your Program's Environment}); if it fails
19537 to find an object file, it displays a message such as:
19540 prog.o: No such file or directory.
19543 When this happens, add the appropriate directory to the search path with
19544 the @value{GDBN} command @code{path}, and execute the @code{target}
19547 @node VxWorks Download
19548 @subsubsection VxWorks Download
19550 @cindex download to VxWorks
19551 If you have connected to the VxWorks target and you want to debug an
19552 object that has not yet been loaded, you can use the @value{GDBN}
19553 @code{load} command to download a file from Unix to VxWorks
19554 incrementally. The object file given as an argument to the @code{load}
19555 command is actually opened twice: first by the VxWorks target in order
19556 to download the code, then by @value{GDBN} in order to read the symbol
19557 table. This can lead to problems if the current working directories on
19558 the two systems differ. If both systems have NFS mounted the same
19559 filesystems, you can avoid these problems by using absolute paths.
19560 Otherwise, it is simplest to set the working directory on both systems
19561 to the directory in which the object file resides, and then to reference
19562 the file by its name, without any path. For instance, a program
19563 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
19564 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
19565 program, type this on VxWorks:
19568 -> cd "@var{vxpath}/vw/demo/rdb"
19572 Then, in @value{GDBN}, type:
19575 (vxgdb) cd @var{hostpath}/vw/demo/rdb
19576 (vxgdb) load prog.o
19579 @value{GDBN} displays a response similar to this:
19582 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
19585 You can also use the @code{load} command to reload an object module
19586 after editing and recompiling the corresponding source file. Note that
19587 this makes @value{GDBN} delete all currently-defined breakpoints,
19588 auto-displays, and convenience variables, and to clear the value
19589 history. (This is necessary in order to preserve the integrity of
19590 debugger's data structures that reference the target system's symbol
19593 @node VxWorks Attach
19594 @subsubsection Running Tasks
19596 @cindex running VxWorks tasks
19597 You can also attach to an existing task using the @code{attach} command as
19601 (vxgdb) attach @var{task}
19605 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
19606 or suspended when you attach to it. Running tasks are suspended at
19607 the time of attachment.
19609 @node Embedded Processors
19610 @section Embedded Processors
19612 This section goes into details specific to particular embedded
19615 @cindex send command to simulator
19616 Whenever a specific embedded processor has a simulator, @value{GDBN}
19617 allows to send an arbitrary command to the simulator.
19620 @item sim @var{command}
19621 @kindex sim@r{, a command}
19622 Send an arbitrary @var{command} string to the simulator. Consult the
19623 documentation for the specific simulator in use for information about
19624 acceptable commands.
19630 * M32R/D:: Renesas M32R/D
19631 * M68K:: Motorola M68K
19632 * MicroBlaze:: Xilinx MicroBlaze
19633 * MIPS Embedded:: MIPS Embedded
19634 * OpenRISC 1000:: OpenRisc 1000
19635 * PowerPC Embedded:: PowerPC Embedded
19636 * PA:: HP PA Embedded
19637 * Sparclet:: Tsqware Sparclet
19638 * Sparclite:: Fujitsu Sparclite
19639 * Z8000:: Zilog Z8000
19642 * Super-H:: Renesas Super-H
19651 @item target rdi @var{dev}
19652 ARM Angel monitor, via RDI library interface to ADP protocol. You may
19653 use this target to communicate with both boards running the Angel
19654 monitor, or with the EmbeddedICE JTAG debug device.
19657 @item target rdp @var{dev}
19662 @value{GDBN} provides the following ARM-specific commands:
19665 @item set arm disassembler
19667 This commands selects from a list of disassembly styles. The
19668 @code{"std"} style is the standard style.
19670 @item show arm disassembler
19672 Show the current disassembly style.
19674 @item set arm apcs32
19675 @cindex ARM 32-bit mode
19676 This command toggles ARM operation mode between 32-bit and 26-bit.
19678 @item show arm apcs32
19679 Display the current usage of the ARM 32-bit mode.
19681 @item set arm fpu @var{fputype}
19682 This command sets the ARM floating-point unit (FPU) type. The
19683 argument @var{fputype} can be one of these:
19687 Determine the FPU type by querying the OS ABI.
19689 Software FPU, with mixed-endian doubles on little-endian ARM
19692 GCC-compiled FPA co-processor.
19694 Software FPU with pure-endian doubles.
19700 Show the current type of the FPU.
19703 This command forces @value{GDBN} to use the specified ABI.
19706 Show the currently used ABI.
19708 @item set arm fallback-mode (arm|thumb|auto)
19709 @value{GDBN} uses the symbol table, when available, to determine
19710 whether instructions are ARM or Thumb. This command controls
19711 @value{GDBN}'s default behavior when the symbol table is not
19712 available. The default is @samp{auto}, which causes @value{GDBN} to
19713 use the current execution mode (from the @code{T} bit in the @code{CPSR}
19716 @item show arm fallback-mode
19717 Show the current fallback instruction mode.
19719 @item set arm force-mode (arm|thumb|auto)
19720 This command overrides use of the symbol table to determine whether
19721 instructions are ARM or Thumb. The default is @samp{auto}, which
19722 causes @value{GDBN} to use the symbol table and then the setting
19723 of @samp{set arm fallback-mode}.
19725 @item show arm force-mode
19726 Show the current forced instruction mode.
19728 @item set debug arm
19729 Toggle whether to display ARM-specific debugging messages from the ARM
19730 target support subsystem.
19732 @item show debug arm
19733 Show whether ARM-specific debugging messages are enabled.
19736 The following commands are available when an ARM target is debugged
19737 using the RDI interface:
19740 @item rdilogfile @r{[}@var{file}@r{]}
19742 @cindex ADP (Angel Debugger Protocol) logging
19743 Set the filename for the ADP (Angel Debugger Protocol) packet log.
19744 With an argument, sets the log file to the specified @var{file}. With
19745 no argument, show the current log file name. The default log file is
19748 @item rdilogenable @r{[}@var{arg}@r{]}
19749 @kindex rdilogenable
19750 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
19751 enables logging, with an argument 0 or @code{"no"} disables it. With
19752 no arguments displays the current setting. When logging is enabled,
19753 ADP packets exchanged between @value{GDBN} and the RDI target device
19754 are logged to a file.
19756 @item set rdiromatzero
19757 @kindex set rdiromatzero
19758 @cindex ROM at zero address, RDI
19759 Tell @value{GDBN} whether the target has ROM at address 0. If on,
19760 vector catching is disabled, so that zero address can be used. If off
19761 (the default), vector catching is enabled. For this command to take
19762 effect, it needs to be invoked prior to the @code{target rdi} command.
19764 @item show rdiromatzero
19765 @kindex show rdiromatzero
19766 Show the current setting of ROM at zero address.
19768 @item set rdiheartbeat
19769 @kindex set rdiheartbeat
19770 @cindex RDI heartbeat
19771 Enable or disable RDI heartbeat packets. It is not recommended to
19772 turn on this option, since it confuses ARM and EPI JTAG interface, as
19773 well as the Angel monitor.
19775 @item show rdiheartbeat
19776 @kindex show rdiheartbeat
19777 Show the setting of RDI heartbeat packets.
19781 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19782 The @value{GDBN} ARM simulator accepts the following optional arguments.
19785 @item --swi-support=@var{type}
19786 Tell the simulator which SWI interfaces to support.
19787 @var{type} may be a comma separated list of the following values.
19788 The default value is @code{all}.
19801 @subsection Renesas M32R/D and M32R/SDI
19804 @kindex target m32r
19805 @item target m32r @var{dev}
19806 Renesas M32R/D ROM monitor.
19808 @kindex target m32rsdi
19809 @item target m32rsdi @var{dev}
19810 Renesas M32R SDI server, connected via parallel port to the board.
19813 The following @value{GDBN} commands are specific to the M32R monitor:
19816 @item set download-path @var{path}
19817 @kindex set download-path
19818 @cindex find downloadable @sc{srec} files (M32R)
19819 Set the default path for finding downloadable @sc{srec} files.
19821 @item show download-path
19822 @kindex show download-path
19823 Show the default path for downloadable @sc{srec} files.
19825 @item set board-address @var{addr}
19826 @kindex set board-address
19827 @cindex M32-EVA target board address
19828 Set the IP address for the M32R-EVA target board.
19830 @item show board-address
19831 @kindex show board-address
19832 Show the current IP address of the target board.
19834 @item set server-address @var{addr}
19835 @kindex set server-address
19836 @cindex download server address (M32R)
19837 Set the IP address for the download server, which is the @value{GDBN}'s
19840 @item show server-address
19841 @kindex show server-address
19842 Display the IP address of the download server.
19844 @item upload @r{[}@var{file}@r{]}
19845 @kindex upload@r{, M32R}
19846 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
19847 upload capability. If no @var{file} argument is given, the current
19848 executable file is uploaded.
19850 @item tload @r{[}@var{file}@r{]}
19851 @kindex tload@r{, M32R}
19852 Test the @code{upload} command.
19855 The following commands are available for M32R/SDI:
19860 @cindex reset SDI connection, M32R
19861 This command resets the SDI connection.
19865 This command shows the SDI connection status.
19868 @kindex debug_chaos
19869 @cindex M32R/Chaos debugging
19870 Instructs the remote that M32R/Chaos debugging is to be used.
19872 @item use_debug_dma
19873 @kindex use_debug_dma
19874 Instructs the remote to use the DEBUG_DMA method of accessing memory.
19877 @kindex use_mon_code
19878 Instructs the remote to use the MON_CODE method of accessing memory.
19881 @kindex use_ib_break
19882 Instructs the remote to set breakpoints by IB break.
19884 @item use_dbt_break
19885 @kindex use_dbt_break
19886 Instructs the remote to set breakpoints by DBT.
19892 The Motorola m68k configuration includes ColdFire support, and a
19893 target command for the following ROM monitor.
19897 @kindex target dbug
19898 @item target dbug @var{dev}
19899 dBUG ROM monitor for Motorola ColdFire.
19904 @subsection MicroBlaze
19905 @cindex Xilinx MicroBlaze
19906 @cindex XMD, Xilinx Microprocessor Debugger
19908 The MicroBlaze is a soft-core processor supported on various Xilinx
19909 FPGAs, such as Spartan or Virtex series. Boards with these processors
19910 usually have JTAG ports which connect to a host system running the Xilinx
19911 Embedded Development Kit (EDK) or Software Development Kit (SDK).
19912 This host system is used to download the configuration bitstream to
19913 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
19914 communicates with the target board using the JTAG interface and
19915 presents a @code{gdbserver} interface to the board. By default
19916 @code{xmd} uses port @code{1234}. (While it is possible to change
19917 this default port, it requires the use of undocumented @code{xmd}
19918 commands. Contact Xilinx support if you need to do this.)
19920 Use these GDB commands to connect to the MicroBlaze target processor.
19923 @item target remote :1234
19924 Use this command to connect to the target if you are running @value{GDBN}
19925 on the same system as @code{xmd}.
19927 @item target remote @var{xmd-host}:1234
19928 Use this command to connect to the target if it is connected to @code{xmd}
19929 running on a different system named @var{xmd-host}.
19932 Use this command to download a program to the MicroBlaze target.
19934 @item set debug microblaze @var{n}
19935 Enable MicroBlaze-specific debugging messages if non-zero.
19937 @item show debug microblaze @var{n}
19938 Show MicroBlaze-specific debugging level.
19941 @node MIPS Embedded
19942 @subsection @acronym{MIPS} Embedded
19944 @cindex @acronym{MIPS} boards
19945 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
19946 @acronym{MIPS} board attached to a serial line. This is available when
19947 you configure @value{GDBN} with @samp{--target=mips-elf}.
19950 Use these @value{GDBN} commands to specify the connection to your target board:
19953 @item target mips @var{port}
19954 @kindex target mips @var{port}
19955 To run a program on the board, start up @code{@value{GDBP}} with the
19956 name of your program as the argument. To connect to the board, use the
19957 command @samp{target mips @var{port}}, where @var{port} is the name of
19958 the serial port connected to the board. If the program has not already
19959 been downloaded to the board, you may use the @code{load} command to
19960 download it. You can then use all the usual @value{GDBN} commands.
19962 For example, this sequence connects to the target board through a serial
19963 port, and loads and runs a program called @var{prog} through the
19967 host$ @value{GDBP} @var{prog}
19968 @value{GDBN} is free software and @dots{}
19969 (@value{GDBP}) target mips /dev/ttyb
19970 (@value{GDBP}) load @var{prog}
19974 @item target mips @var{hostname}:@var{portnumber}
19975 On some @value{GDBN} host configurations, you can specify a TCP
19976 connection (for instance, to a serial line managed by a terminal
19977 concentrator) instead of a serial port, using the syntax
19978 @samp{@var{hostname}:@var{portnumber}}.
19980 @item target pmon @var{port}
19981 @kindex target pmon @var{port}
19984 @item target ddb @var{port}
19985 @kindex target ddb @var{port}
19986 NEC's DDB variant of PMON for Vr4300.
19988 @item target lsi @var{port}
19989 @kindex target lsi @var{port}
19990 LSI variant of PMON.
19992 @kindex target r3900
19993 @item target r3900 @var{dev}
19994 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19996 @kindex target array
19997 @item target array @var{dev}
19998 Array Tech LSI33K RAID controller board.
20004 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20007 @item set mipsfpu double
20008 @itemx set mipsfpu single
20009 @itemx set mipsfpu none
20010 @itemx set mipsfpu auto
20011 @itemx show mipsfpu
20012 @kindex set mipsfpu
20013 @kindex show mipsfpu
20014 @cindex @acronym{MIPS} remote floating point
20015 @cindex floating point, @acronym{MIPS} remote
20016 If your target board does not support the @acronym{MIPS} floating point
20017 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20018 need this, you may wish to put the command in your @value{GDBN} init
20019 file). This tells @value{GDBN} how to find the return value of
20020 functions which return floating point values. It also allows
20021 @value{GDBN} to avoid saving the floating point registers when calling
20022 functions on the board. If you are using a floating point coprocessor
20023 with only single precision floating point support, as on the @sc{r4650}
20024 processor, use the command @samp{set mipsfpu single}. The default
20025 double precision floating point coprocessor may be selected using
20026 @samp{set mipsfpu double}.
20028 In previous versions the only choices were double precision or no
20029 floating point, so @samp{set mipsfpu on} will select double precision
20030 and @samp{set mipsfpu off} will select no floating point.
20032 As usual, you can inquire about the @code{mipsfpu} variable with
20033 @samp{show mipsfpu}.
20035 @item set timeout @var{seconds}
20036 @itemx set retransmit-timeout @var{seconds}
20037 @itemx show timeout
20038 @itemx show retransmit-timeout
20039 @cindex @code{timeout}, @acronym{MIPS} protocol
20040 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20041 @kindex set timeout
20042 @kindex show timeout
20043 @kindex set retransmit-timeout
20044 @kindex show retransmit-timeout
20045 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20046 remote protocol, with the @code{set timeout @var{seconds}} command. The
20047 default is 5 seconds. Similarly, you can control the timeout used while
20048 waiting for an acknowledgment of a packet with the @code{set
20049 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20050 You can inspect both values with @code{show timeout} and @code{show
20051 retransmit-timeout}. (These commands are @emph{only} available when
20052 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20054 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20055 is waiting for your program to stop. In that case, @value{GDBN} waits
20056 forever because it has no way of knowing how long the program is going
20057 to run before stopping.
20059 @item set syn-garbage-limit @var{num}
20060 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20061 @cindex synchronize with remote @acronym{MIPS} target
20062 Limit the maximum number of characters @value{GDBN} should ignore when
20063 it tries to synchronize with the remote target. The default is 10
20064 characters. Setting the limit to -1 means there's no limit.
20066 @item show syn-garbage-limit
20067 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20068 Show the current limit on the number of characters to ignore when
20069 trying to synchronize with the remote system.
20071 @item set monitor-prompt @var{prompt}
20072 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20073 @cindex remote monitor prompt
20074 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20075 remote monitor. The default depends on the target:
20085 @item show monitor-prompt
20086 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20087 Show the current strings @value{GDBN} expects as the prompt from the
20090 @item set monitor-warnings
20091 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20092 Enable or disable monitor warnings about hardware breakpoints. This
20093 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20094 display warning messages whose codes are returned by the @code{lsi}
20095 PMON monitor for breakpoint commands.
20097 @item show monitor-warnings
20098 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20099 Show the current setting of printing monitor warnings.
20101 @item pmon @var{command}
20102 @kindex pmon@r{, @acronym{MIPS} remote}
20103 @cindex send PMON command
20104 This command allows sending an arbitrary @var{command} string to the
20105 monitor. The monitor must be in debug mode for this to work.
20108 @node OpenRISC 1000
20109 @subsection OpenRISC 1000
20110 @cindex OpenRISC 1000
20112 @cindex or1k boards
20113 See OR1k Architecture document (@uref{www.opencores.org}) for more information
20114 about platform and commands.
20118 @kindex target jtag
20119 @item target jtag jtag://@var{host}:@var{port}
20121 Connects to remote JTAG server.
20122 JTAG remote server can be either an or1ksim or JTAG server,
20123 connected via parallel port to the board.
20125 Example: @code{target jtag jtag://localhost:9999}
20128 @item or1ksim @var{command}
20129 If connected to @code{or1ksim} OpenRISC 1000 Architectural
20130 Simulator, proprietary commands can be executed.
20132 @kindex info or1k spr
20133 @item info or1k spr
20134 Displays spr groups.
20136 @item info or1k spr @var{group}
20137 @itemx info or1k spr @var{groupno}
20138 Displays register names in selected group.
20140 @item info or1k spr @var{group} @var{register}
20141 @itemx info or1k spr @var{register}
20142 @itemx info or1k spr @var{groupno} @var{registerno}
20143 @itemx info or1k spr @var{registerno}
20144 Shows information about specified spr register.
20147 @item spr @var{group} @var{register} @var{value}
20148 @itemx spr @var{register @var{value}}
20149 @itemx spr @var{groupno} @var{registerno @var{value}}
20150 @itemx spr @var{registerno @var{value}}
20151 Writes @var{value} to specified spr register.
20154 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
20155 It is very similar to @value{GDBN} trace, except it does not interfere with normal
20156 program execution and is thus much faster. Hardware breakpoints/watchpoint
20157 triggers can be set using:
20160 Load effective address/data
20162 Store effective address/data
20164 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
20169 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
20170 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
20172 @code{htrace} commands:
20173 @cindex OpenRISC 1000 htrace
20176 @item hwatch @var{conditional}
20177 Set hardware watchpoint on combination of Load/Store Effective Address(es)
20178 or Data. For example:
20180 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
20182 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
20186 Display information about current HW trace configuration.
20188 @item htrace trigger @var{conditional}
20189 Set starting criteria for HW trace.
20191 @item htrace qualifier @var{conditional}
20192 Set acquisition qualifier for HW trace.
20194 @item htrace stop @var{conditional}
20195 Set HW trace stopping criteria.
20197 @item htrace record [@var{data}]*
20198 Selects the data to be recorded, when qualifier is met and HW trace was
20201 @item htrace enable
20202 @itemx htrace disable
20203 Enables/disables the HW trace.
20205 @item htrace rewind [@var{filename}]
20206 Clears currently recorded trace data.
20208 If filename is specified, new trace file is made and any newly collected data
20209 will be written there.
20211 @item htrace print [@var{start} [@var{len}]]
20212 Prints trace buffer, using current record configuration.
20214 @item htrace mode continuous
20215 Set continuous trace mode.
20217 @item htrace mode suspend
20218 Set suspend trace mode.
20222 @node PowerPC Embedded
20223 @subsection PowerPC Embedded
20225 @cindex DVC register
20226 @value{GDBN} supports using the DVC (Data Value Compare) register to
20227 implement in hardware simple hardware watchpoint conditions of the form:
20230 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20231 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20234 The DVC register will be automatically used when @value{GDBN} detects
20235 such pattern in a condition expression, and the created watchpoint uses one
20236 debug register (either the @code{exact-watchpoints} option is on and the
20237 variable is scalar, or the variable has a length of one byte). This feature
20238 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20241 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20242 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20243 in which case watchpoints using only one debug register are created when
20244 watching variables of scalar types.
20246 You can create an artificial array to watch an arbitrary memory
20247 region using one of the following commands (@pxref{Expressions}):
20250 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20251 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20254 PowerPC embedded processors support masked watchpoints. See the discussion
20255 about the @code{mask} argument in @ref{Set Watchpoints}.
20257 @cindex ranged breakpoint
20258 PowerPC embedded processors support hardware accelerated
20259 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20260 the inferior whenever it executes an instruction at any address within
20261 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20262 use the @code{break-range} command.
20264 @value{GDBN} provides the following PowerPC-specific commands:
20267 @kindex break-range
20268 @item break-range @var{start-location}, @var{end-location}
20269 Set a breakpoint for an address range.
20270 @var{start-location} and @var{end-location} can specify a function name,
20271 a line number, an offset of lines from the current line or from the start
20272 location, or an address of an instruction (see @ref{Specify Location},
20273 for a list of all the possible ways to specify a @var{location}.)
20274 The breakpoint will stop execution of the inferior whenever it
20275 executes an instruction at any address within the specified range,
20276 (including @var{start-location} and @var{end-location}.)
20278 @kindex set powerpc
20279 @item set powerpc soft-float
20280 @itemx show powerpc soft-float
20281 Force @value{GDBN} to use (or not use) a software floating point calling
20282 convention. By default, @value{GDBN} selects the calling convention based
20283 on the selected architecture and the provided executable file.
20285 @item set powerpc vector-abi
20286 @itemx show powerpc vector-abi
20287 Force @value{GDBN} to use the specified calling convention for vector
20288 arguments and return values. The valid options are @samp{auto};
20289 @samp{generic}, to avoid vector registers even if they are present;
20290 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20291 registers. By default, @value{GDBN} selects the calling convention
20292 based on the selected architecture and the provided executable file.
20294 @item set powerpc exact-watchpoints
20295 @itemx show powerpc exact-watchpoints
20296 Allow @value{GDBN} to use only one debug register when watching a variable
20297 of scalar type, thus assuming that the variable is accessed through the
20298 address of its first byte.
20300 @kindex target dink32
20301 @item target dink32 @var{dev}
20302 DINK32 ROM monitor.
20304 @kindex target ppcbug
20305 @item target ppcbug @var{dev}
20306 @kindex target ppcbug1
20307 @item target ppcbug1 @var{dev}
20308 PPCBUG ROM monitor for PowerPC.
20311 @item target sds @var{dev}
20312 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20315 @cindex SDS protocol
20316 The following commands specific to the SDS protocol are supported
20320 @item set sdstimeout @var{nsec}
20321 @kindex set sdstimeout
20322 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
20323 default is 2 seconds.
20325 @item show sdstimeout
20326 @kindex show sdstimeout
20327 Show the current value of the SDS timeout.
20329 @item sds @var{command}
20330 @kindex sds@r{, a command}
20331 Send the specified @var{command} string to the SDS monitor.
20336 @subsection HP PA Embedded
20340 @kindex target op50n
20341 @item target op50n @var{dev}
20342 OP50N monitor, running on an OKI HPPA board.
20344 @kindex target w89k
20345 @item target w89k @var{dev}
20346 W89K monitor, running on a Winbond HPPA board.
20351 @subsection Tsqware Sparclet
20355 @value{GDBN} enables developers to debug tasks running on
20356 Sparclet targets from a Unix host.
20357 @value{GDBN} uses code that runs on
20358 both the Unix host and on the Sparclet target. The program
20359 @code{@value{GDBP}} is installed and executed on the Unix host.
20362 @item remotetimeout @var{args}
20363 @kindex remotetimeout
20364 @value{GDBN} supports the option @code{remotetimeout}.
20365 This option is set by the user, and @var{args} represents the number of
20366 seconds @value{GDBN} waits for responses.
20369 @cindex compiling, on Sparclet
20370 When compiling for debugging, include the options @samp{-g} to get debug
20371 information and @samp{-Ttext} to relocate the program to where you wish to
20372 load it on the target. You may also want to add the options @samp{-n} or
20373 @samp{-N} in order to reduce the size of the sections. Example:
20376 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
20379 You can use @code{objdump} to verify that the addresses are what you intended:
20382 sparclet-aout-objdump --headers --syms prog
20385 @cindex running, on Sparclet
20387 your Unix execution search path to find @value{GDBN}, you are ready to
20388 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
20389 (or @code{sparclet-aout-gdb}, depending on your installation).
20391 @value{GDBN} comes up showing the prompt:
20398 * Sparclet File:: Setting the file to debug
20399 * Sparclet Connection:: Connecting to Sparclet
20400 * Sparclet Download:: Sparclet download
20401 * Sparclet Execution:: Running and debugging
20404 @node Sparclet File
20405 @subsubsection Setting File to Debug
20407 The @value{GDBN} command @code{file} lets you choose with program to debug.
20410 (gdbslet) file prog
20414 @value{GDBN} then attempts to read the symbol table of @file{prog}.
20415 @value{GDBN} locates
20416 the file by searching the directories listed in the command search
20418 If the file was compiled with debug information (option @samp{-g}), source
20419 files will be searched as well.
20420 @value{GDBN} locates
20421 the source files by searching the directories listed in the directory search
20422 path (@pxref{Environment, ,Your Program's Environment}).
20424 to find a file, it displays a message such as:
20427 prog: No such file or directory.
20430 When this happens, add the appropriate directories to the search paths with
20431 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
20432 @code{target} command again.
20434 @node Sparclet Connection
20435 @subsubsection Connecting to Sparclet
20437 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
20438 To connect to a target on serial port ``@code{ttya}'', type:
20441 (gdbslet) target sparclet /dev/ttya
20442 Remote target sparclet connected to /dev/ttya
20443 main () at ../prog.c:3
20447 @value{GDBN} displays messages like these:
20453 @node Sparclet Download
20454 @subsubsection Sparclet Download
20456 @cindex download to Sparclet
20457 Once connected to the Sparclet target,
20458 you can use the @value{GDBN}
20459 @code{load} command to download the file from the host to the target.
20460 The file name and load offset should be given as arguments to the @code{load}
20462 Since the file format is aout, the program must be loaded to the starting
20463 address. You can use @code{objdump} to find out what this value is. The load
20464 offset is an offset which is added to the VMA (virtual memory address)
20465 of each of the file's sections.
20466 For instance, if the program
20467 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
20468 and bss at 0x12010170, in @value{GDBN}, type:
20471 (gdbslet) load prog 0x12010000
20472 Loading section .text, size 0xdb0 vma 0x12010000
20475 If the code is loaded at a different address then what the program was linked
20476 to, you may need to use the @code{section} and @code{add-symbol-file} commands
20477 to tell @value{GDBN} where to map the symbol table.
20479 @node Sparclet Execution
20480 @subsubsection Running and Debugging
20482 @cindex running and debugging Sparclet programs
20483 You can now begin debugging the task using @value{GDBN}'s execution control
20484 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
20485 manual for the list of commands.
20489 Breakpoint 1 at 0x12010000: file prog.c, line 3.
20491 Starting program: prog
20492 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
20493 3 char *symarg = 0;
20495 4 char *execarg = "hello!";
20500 @subsection Fujitsu Sparclite
20504 @kindex target sparclite
20505 @item target sparclite @var{dev}
20506 Fujitsu sparclite boards, used only for the purpose of loading.
20507 You must use an additional command to debug the program.
20508 For example: target remote @var{dev} using @value{GDBN} standard
20514 @subsection Zilog Z8000
20517 @cindex simulator, Z8000
20518 @cindex Zilog Z8000 simulator
20520 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
20523 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
20524 unsegmented variant of the Z8000 architecture) or the Z8001 (the
20525 segmented variant). The simulator recognizes which architecture is
20526 appropriate by inspecting the object code.
20529 @item target sim @var{args}
20531 @kindex target sim@r{, with Z8000}
20532 Debug programs on a simulated CPU. If the simulator supports setup
20533 options, specify them via @var{args}.
20537 After specifying this target, you can debug programs for the simulated
20538 CPU in the same style as programs for your host computer; use the
20539 @code{file} command to load a new program image, the @code{run} command
20540 to run your program, and so on.
20542 As well as making available all the usual machine registers
20543 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
20544 additional items of information as specially named registers:
20549 Counts clock-ticks in the simulator.
20552 Counts instructions run in the simulator.
20555 Execution time in 60ths of a second.
20559 You can refer to these values in @value{GDBN} expressions with the usual
20560 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
20561 conditional breakpoint that suspends only after at least 5000
20562 simulated clock ticks.
20565 @subsection Atmel AVR
20568 When configured for debugging the Atmel AVR, @value{GDBN} supports the
20569 following AVR-specific commands:
20572 @item info io_registers
20573 @kindex info io_registers@r{, AVR}
20574 @cindex I/O registers (Atmel AVR)
20575 This command displays information about the AVR I/O registers. For
20576 each register, @value{GDBN} prints its number and value.
20583 When configured for debugging CRIS, @value{GDBN} provides the
20584 following CRIS-specific commands:
20587 @item set cris-version @var{ver}
20588 @cindex CRIS version
20589 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
20590 The CRIS version affects register names and sizes. This command is useful in
20591 case autodetection of the CRIS version fails.
20593 @item show cris-version
20594 Show the current CRIS version.
20596 @item set cris-dwarf2-cfi
20597 @cindex DWARF-2 CFI and CRIS
20598 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
20599 Change to @samp{off} when using @code{gcc-cris} whose version is below
20602 @item show cris-dwarf2-cfi
20603 Show the current state of using DWARF-2 CFI.
20605 @item set cris-mode @var{mode}
20607 Set the current CRIS mode to @var{mode}. It should only be changed when
20608 debugging in guru mode, in which case it should be set to
20609 @samp{guru} (the default is @samp{normal}).
20611 @item show cris-mode
20612 Show the current CRIS mode.
20616 @subsection Renesas Super-H
20619 For the Renesas Super-H processor, @value{GDBN} provides these
20623 @item set sh calling-convention @var{convention}
20624 @kindex set sh calling-convention
20625 Set the calling-convention used when calling functions from @value{GDBN}.
20626 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
20627 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
20628 convention. If the DWARF-2 information of the called function specifies
20629 that the function follows the Renesas calling convention, the function
20630 is called using the Renesas calling convention. If the calling convention
20631 is set to @samp{renesas}, the Renesas calling convention is always used,
20632 regardless of the DWARF-2 information. This can be used to override the
20633 default of @samp{gcc} if debug information is missing, or the compiler
20634 does not emit the DWARF-2 calling convention entry for a function.
20636 @item show sh calling-convention
20637 @kindex show sh calling-convention
20638 Show the current calling convention setting.
20643 @node Architectures
20644 @section Architectures
20646 This section describes characteristics of architectures that affect
20647 all uses of @value{GDBN} with the architecture, both native and cross.
20653 * HPPA:: HP PA architecture
20654 * SPU:: Cell Broadband Engine SPU architecture
20659 @subsection x86 Architecture-specific Issues
20662 @item set struct-convention @var{mode}
20663 @kindex set struct-convention
20664 @cindex struct return convention
20665 @cindex struct/union returned in registers
20666 Set the convention used by the inferior to return @code{struct}s and
20667 @code{union}s from functions to @var{mode}. Possible values of
20668 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
20669 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
20670 are returned on the stack, while @code{"reg"} means that a
20671 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
20672 be returned in a register.
20674 @item show struct-convention
20675 @kindex show struct-convention
20676 Show the current setting of the convention to return @code{struct}s
20683 See the following section.
20686 @subsection @acronym{MIPS}
20688 @cindex stack on Alpha
20689 @cindex stack on @acronym{MIPS}
20690 @cindex Alpha stack
20691 @cindex @acronym{MIPS} stack
20692 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
20693 sometimes requires @value{GDBN} to search backward in the object code to
20694 find the beginning of a function.
20696 @cindex response time, @acronym{MIPS} debugging
20697 To improve response time (especially for embedded applications, where
20698 @value{GDBN} may be restricted to a slow serial line for this search)
20699 you may want to limit the size of this search, using one of these
20703 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
20704 @item set heuristic-fence-post @var{limit}
20705 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
20706 search for the beginning of a function. A value of @var{0} (the
20707 default) means there is no limit. However, except for @var{0}, the
20708 larger the limit the more bytes @code{heuristic-fence-post} must search
20709 and therefore the longer it takes to run. You should only need to use
20710 this command when debugging a stripped executable.
20712 @item show heuristic-fence-post
20713 Display the current limit.
20717 These commands are available @emph{only} when @value{GDBN} is configured
20718 for debugging programs on Alpha or @acronym{MIPS} processors.
20720 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
20724 @item set mips abi @var{arg}
20725 @kindex set mips abi
20726 @cindex set ABI for @acronym{MIPS}
20727 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
20728 values of @var{arg} are:
20732 The default ABI associated with the current binary (this is the
20742 @item show mips abi
20743 @kindex show mips abi
20744 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
20746 @item set mips compression @var{arg}
20747 @kindex set mips compression
20748 @cindex code compression, @acronym{MIPS}
20749 Tell @value{GDBN} which @acronym{MIPS} compressed
20750 @acronym{ISA, Instruction Set Architecture} encoding is used by the
20751 inferior. @value{GDBN} uses this for code disassembly and other
20752 internal interpretation purposes. This setting is only referred to
20753 when no executable has been associated with the debugging session or
20754 the executable does not provide information about the encoding it uses.
20755 Otherwise this setting is automatically updated from information
20756 provided by the executable.
20758 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
20759 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
20760 executables containing @acronym{MIPS16} code frequently are not
20761 identified as such.
20763 This setting is ``sticky''; that is, it retains its value across
20764 debugging sessions until reset either explicitly with this command or
20765 implicitly from an executable.
20767 The compiler and/or assembler typically add symbol table annotations to
20768 identify functions compiled for the @acronym{MIPS16} or
20769 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
20770 are present, @value{GDBN} uses them in preference to the global
20771 compressed @acronym{ISA} encoding setting.
20773 @item show mips compression
20774 @kindex show mips compression
20775 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
20776 @value{GDBN} to debug the inferior.
20779 @itemx show mipsfpu
20780 @xref{MIPS Embedded, set mipsfpu}.
20782 @item set mips mask-address @var{arg}
20783 @kindex set mips mask-address
20784 @cindex @acronym{MIPS} addresses, masking
20785 This command determines whether the most-significant 32 bits of 64-bit
20786 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
20787 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20788 setting, which lets @value{GDBN} determine the correct value.
20790 @item show mips mask-address
20791 @kindex show mips mask-address
20792 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
20795 @item set remote-mips64-transfers-32bit-regs
20796 @kindex set remote-mips64-transfers-32bit-regs
20797 This command controls compatibility with 64-bit @acronym{MIPS} targets that
20798 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
20799 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20800 and 64 bits for other registers, set this option to @samp{on}.
20802 @item show remote-mips64-transfers-32bit-regs
20803 @kindex show remote-mips64-transfers-32bit-regs
20804 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
20806 @item set debug mips
20807 @kindex set debug mips
20808 This command turns on and off debugging messages for the @acronym{MIPS}-specific
20809 target code in @value{GDBN}.
20811 @item show debug mips
20812 @kindex show debug mips
20813 Show the current setting of @acronym{MIPS} debugging messages.
20819 @cindex HPPA support
20821 When @value{GDBN} is debugging the HP PA architecture, it provides the
20822 following special commands:
20825 @item set debug hppa
20826 @kindex set debug hppa
20827 This command determines whether HPPA architecture-specific debugging
20828 messages are to be displayed.
20830 @item show debug hppa
20831 Show whether HPPA debugging messages are displayed.
20833 @item maint print unwind @var{address}
20834 @kindex maint print unwind@r{, HPPA}
20835 This command displays the contents of the unwind table entry at the
20836 given @var{address}.
20842 @subsection Cell Broadband Engine SPU architecture
20843 @cindex Cell Broadband Engine
20846 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
20847 it provides the following special commands:
20850 @item info spu event
20852 Display SPU event facility status. Shows current event mask
20853 and pending event status.
20855 @item info spu signal
20856 Display SPU signal notification facility status. Shows pending
20857 signal-control word and signal notification mode of both signal
20858 notification channels.
20860 @item info spu mailbox
20861 Display SPU mailbox facility status. Shows all pending entries,
20862 in order of processing, in each of the SPU Write Outbound,
20863 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
20866 Display MFC DMA status. Shows all pending commands in the MFC
20867 DMA queue. For each entry, opcode, tag, class IDs, effective
20868 and local store addresses and transfer size are shown.
20870 @item info spu proxydma
20871 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
20872 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
20873 and local store addresses and transfer size are shown.
20877 When @value{GDBN} is debugging a combined PowerPC/SPU application
20878 on the Cell Broadband Engine, it provides in addition the following
20882 @item set spu stop-on-load @var{arg}
20884 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
20885 will give control to the user when a new SPE thread enters its @code{main}
20886 function. The default is @code{off}.
20888 @item show spu stop-on-load
20890 Show whether to stop for new SPE threads.
20892 @item set spu auto-flush-cache @var{arg}
20893 Set whether to automatically flush the software-managed cache. When set to
20894 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
20895 cache to be flushed whenever SPE execution stops. This provides a consistent
20896 view of PowerPC memory that is accessed via the cache. If an application
20897 does not use the software-managed cache, this option has no effect.
20899 @item show spu auto-flush-cache
20900 Show whether to automatically flush the software-managed cache.
20905 @subsection PowerPC
20906 @cindex PowerPC architecture
20908 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
20909 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
20910 numbers stored in the floating point registers. These values must be stored
20911 in two consecutive registers, always starting at an even register like
20912 @code{f0} or @code{f2}.
20914 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
20915 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
20916 @code{f2} and @code{f3} for @code{$dl1} and so on.
20918 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
20919 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
20922 @node Controlling GDB
20923 @chapter Controlling @value{GDBN}
20925 You can alter the way @value{GDBN} interacts with you by using the
20926 @code{set} command. For commands controlling how @value{GDBN} displays
20927 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20932 * Editing:: Command editing
20933 * Command History:: Command history
20934 * Screen Size:: Screen size
20935 * Numbers:: Numbers
20936 * ABI:: Configuring the current ABI
20937 * Auto-loading:: Automatically loading associated files
20938 * Messages/Warnings:: Optional warnings and messages
20939 * Debugging Output:: Optional messages about internal happenings
20940 * Other Misc Settings:: Other Miscellaneous Settings
20948 @value{GDBN} indicates its readiness to read a command by printing a string
20949 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20950 can change the prompt string with the @code{set prompt} command. For
20951 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20952 the prompt in one of the @value{GDBN} sessions so that you can always tell
20953 which one you are talking to.
20955 @emph{Note:} @code{set prompt} does not add a space for you after the
20956 prompt you set. This allows you to set a prompt which ends in a space
20957 or a prompt that does not.
20961 @item set prompt @var{newprompt}
20962 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20964 @kindex show prompt
20966 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20969 Versions of @value{GDBN} that ship with Python scripting enabled have
20970 prompt extensions. The commands for interacting with these extensions
20974 @kindex set extended-prompt
20975 @item set extended-prompt @var{prompt}
20976 Set an extended prompt that allows for substitutions.
20977 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20978 substitution. Any escape sequences specified as part of the prompt
20979 string are replaced with the corresponding strings each time the prompt
20985 set extended-prompt Current working directory: \w (gdb)
20988 Note that when an extended-prompt is set, it takes control of the
20989 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20991 @kindex show extended-prompt
20992 @item show extended-prompt
20993 Prints the extended prompt. Any escape sequences specified as part of
20994 the prompt string with @code{set extended-prompt}, are replaced with the
20995 corresponding strings each time the prompt is displayed.
20999 @section Command Editing
21001 @cindex command line editing
21003 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21004 @sc{gnu} library provides consistent behavior for programs which provide a
21005 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21006 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21007 substitution, and a storage and recall of command history across
21008 debugging sessions.
21010 You may control the behavior of command line editing in @value{GDBN} with the
21011 command @code{set}.
21014 @kindex set editing
21017 @itemx set editing on
21018 Enable command line editing (enabled by default).
21020 @item set editing off
21021 Disable command line editing.
21023 @kindex show editing
21025 Show whether command line editing is enabled.
21028 @ifset SYSTEM_READLINE
21029 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21031 @ifclear SYSTEM_READLINE
21032 @xref{Command Line Editing},
21034 for more details about the Readline
21035 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21036 encouraged to read that chapter.
21038 @node Command History
21039 @section Command History
21040 @cindex command history
21042 @value{GDBN} can keep track of the commands you type during your
21043 debugging sessions, so that you can be certain of precisely what
21044 happened. Use these commands to manage the @value{GDBN} command
21047 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21048 package, to provide the history facility.
21049 @ifset SYSTEM_READLINE
21050 @xref{Using History Interactively, , , history, GNU History Library},
21052 @ifclear SYSTEM_READLINE
21053 @xref{Using History Interactively},
21055 for the detailed description of the History library.
21057 To issue a command to @value{GDBN} without affecting certain aspects of
21058 the state which is seen by users, prefix it with @samp{server }
21059 (@pxref{Server Prefix}). This
21060 means that this command will not affect the command history, nor will it
21061 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21062 pressed on a line by itself.
21064 @cindex @code{server}, command prefix
21065 The server prefix does not affect the recording of values into the value
21066 history; to print a value without recording it into the value history,
21067 use the @code{output} command instead of the @code{print} command.
21069 Here is the description of @value{GDBN} commands related to command
21073 @cindex history substitution
21074 @cindex history file
21075 @kindex set history filename
21076 @cindex @env{GDBHISTFILE}, environment variable
21077 @item set history filename @var{fname}
21078 Set the name of the @value{GDBN} command history file to @var{fname}.
21079 This is the file where @value{GDBN} reads an initial command history
21080 list, and where it writes the command history from this session when it
21081 exits. You can access this list through history expansion or through
21082 the history command editing characters listed below. This file defaults
21083 to the value of the environment variable @code{GDBHISTFILE}, or to
21084 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21087 @cindex save command history
21088 @kindex set history save
21089 @item set history save
21090 @itemx set history save on
21091 Record command history in a file, whose name may be specified with the
21092 @code{set history filename} command. By default, this option is disabled.
21094 @item set history save off
21095 Stop recording command history in a file.
21097 @cindex history size
21098 @kindex set history size
21099 @cindex @env{HISTSIZE}, environment variable
21100 @item set history size @var{size}
21101 Set the number of commands which @value{GDBN} keeps in its history list.
21102 This defaults to the value of the environment variable
21103 @code{HISTSIZE}, or to 256 if this variable is not set.
21106 History expansion assigns special meaning to the character @kbd{!}.
21107 @ifset SYSTEM_READLINE
21108 @xref{Event Designators, , , history, GNU History Library},
21110 @ifclear SYSTEM_READLINE
21111 @xref{Event Designators},
21115 @cindex history expansion, turn on/off
21116 Since @kbd{!} is also the logical not operator in C, history expansion
21117 is off by default. If you decide to enable history expansion with the
21118 @code{set history expansion on} command, you may sometimes need to
21119 follow @kbd{!} (when it is used as logical not, in an expression) with
21120 a space or a tab to prevent it from being expanded. The readline
21121 history facilities do not attempt substitution on the strings
21122 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21124 The commands to control history expansion are:
21127 @item set history expansion on
21128 @itemx set history expansion
21129 @kindex set history expansion
21130 Enable history expansion. History expansion is off by default.
21132 @item set history expansion off
21133 Disable history expansion.
21136 @kindex show history
21138 @itemx show history filename
21139 @itemx show history save
21140 @itemx show history size
21141 @itemx show history expansion
21142 These commands display the state of the @value{GDBN} history parameters.
21143 @code{show history} by itself displays all four states.
21148 @kindex show commands
21149 @cindex show last commands
21150 @cindex display command history
21151 @item show commands
21152 Display the last ten commands in the command history.
21154 @item show commands @var{n}
21155 Print ten commands centered on command number @var{n}.
21157 @item show commands +
21158 Print ten commands just after the commands last printed.
21162 @section Screen Size
21163 @cindex size of screen
21164 @cindex pauses in output
21166 Certain commands to @value{GDBN} may produce large amounts of
21167 information output to the screen. To help you read all of it,
21168 @value{GDBN} pauses and asks you for input at the end of each page of
21169 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21170 to discard the remaining output. Also, the screen width setting
21171 determines when to wrap lines of output. Depending on what is being
21172 printed, @value{GDBN} tries to break the line at a readable place,
21173 rather than simply letting it overflow onto the following line.
21175 Normally @value{GDBN} knows the size of the screen from the terminal
21176 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21177 together with the value of the @code{TERM} environment variable and the
21178 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21179 you can override it with the @code{set height} and @code{set
21186 @kindex show height
21187 @item set height @var{lpp}
21189 @itemx set width @var{cpl}
21191 These @code{set} commands specify a screen height of @var{lpp} lines and
21192 a screen width of @var{cpl} characters. The associated @code{show}
21193 commands display the current settings.
21195 If you specify a height of zero lines, @value{GDBN} does not pause during
21196 output no matter how long the output is. This is useful if output is to a
21197 file or to an editor buffer.
21199 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
21200 from wrapping its output.
21202 @item set pagination on
21203 @itemx set pagination off
21204 @kindex set pagination
21205 Turn the output pagination on or off; the default is on. Turning
21206 pagination off is the alternative to @code{set height 0}. Note that
21207 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21208 Options, -batch}) also automatically disables pagination.
21210 @item show pagination
21211 @kindex show pagination
21212 Show the current pagination mode.
21217 @cindex number representation
21218 @cindex entering numbers
21220 You can always enter numbers in octal, decimal, or hexadecimal in
21221 @value{GDBN} by the usual conventions: octal numbers begin with
21222 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21223 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21224 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21225 10; likewise, the default display for numbers---when no particular
21226 format is specified---is base 10. You can change the default base for
21227 both input and output with the commands described below.
21230 @kindex set input-radix
21231 @item set input-radix @var{base}
21232 Set the default base for numeric input. Supported choices
21233 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21234 specified either unambiguously or using the current input radix; for
21238 set input-radix 012
21239 set input-radix 10.
21240 set input-radix 0xa
21244 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21245 leaves the input radix unchanged, no matter what it was, since
21246 @samp{10}, being without any leading or trailing signs of its base, is
21247 interpreted in the current radix. Thus, if the current radix is 16,
21248 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21251 @kindex set output-radix
21252 @item set output-radix @var{base}
21253 Set the default base for numeric display. Supported choices
21254 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21255 specified either unambiguously or using the current input radix.
21257 @kindex show input-radix
21258 @item show input-radix
21259 Display the current default base for numeric input.
21261 @kindex show output-radix
21262 @item show output-radix
21263 Display the current default base for numeric display.
21265 @item set radix @r{[}@var{base}@r{]}
21269 These commands set and show the default base for both input and output
21270 of numbers. @code{set radix} sets the radix of input and output to
21271 the same base; without an argument, it resets the radix back to its
21272 default value of 10.
21277 @section Configuring the Current ABI
21279 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
21280 application automatically. However, sometimes you need to override its
21281 conclusions. Use these commands to manage @value{GDBN}'s view of the
21288 One @value{GDBN} configuration can debug binaries for multiple operating
21289 system targets, either via remote debugging or native emulation.
21290 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
21291 but you can override its conclusion using the @code{set osabi} command.
21292 One example where this is useful is in debugging of binaries which use
21293 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
21294 not have the same identifying marks that the standard C library for your
21299 Show the OS ABI currently in use.
21302 With no argument, show the list of registered available OS ABI's.
21304 @item set osabi @var{abi}
21305 Set the current OS ABI to @var{abi}.
21308 @cindex float promotion
21310 Generally, the way that an argument of type @code{float} is passed to a
21311 function depends on whether the function is prototyped. For a prototyped
21312 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
21313 according to the architecture's convention for @code{float}. For unprototyped
21314 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
21315 @code{double} and then passed.
21317 Unfortunately, some forms of debug information do not reliably indicate whether
21318 a function is prototyped. If @value{GDBN} calls a function that is not marked
21319 as prototyped, it consults @kbd{set coerce-float-to-double}.
21322 @kindex set coerce-float-to-double
21323 @item set coerce-float-to-double
21324 @itemx set coerce-float-to-double on
21325 Arguments of type @code{float} will be promoted to @code{double} when passed
21326 to an unprototyped function. This is the default setting.
21328 @item set coerce-float-to-double off
21329 Arguments of type @code{float} will be passed directly to unprototyped
21332 @kindex show coerce-float-to-double
21333 @item show coerce-float-to-double
21334 Show the current setting of promoting @code{float} to @code{double}.
21338 @kindex show cp-abi
21339 @value{GDBN} needs to know the ABI used for your program's C@t{++}
21340 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
21341 used to build your application. @value{GDBN} only fully supports
21342 programs with a single C@t{++} ABI; if your program contains code using
21343 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
21344 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
21345 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
21346 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
21347 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
21348 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
21353 Show the C@t{++} ABI currently in use.
21356 With no argument, show the list of supported C@t{++} ABI's.
21358 @item set cp-abi @var{abi}
21359 @itemx set cp-abi auto
21360 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
21364 @section Automatically loading associated files
21365 @cindex auto-loading
21367 @value{GDBN} sometimes reads files with commands and settings automatically,
21368 without being explicitly told so by the user. We call this feature
21369 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
21370 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
21371 results or introduce security risks (e.g., if the file comes from untrusted
21374 Note that loading of these associated files (including the local @file{.gdbinit}
21375 file) requires accordingly configured @code{auto-load safe-path}
21376 (@pxref{Auto-loading safe path}).
21378 For these reasons, @value{GDBN} includes commands and options to let you
21379 control when to auto-load files and which files should be auto-loaded.
21382 @anchor{set auto-load off}
21383 @kindex set auto-load off
21384 @item set auto-load off
21385 Globally disable loading of all auto-loaded files.
21386 You may want to use this command with the @samp{-iex} option
21387 (@pxref{Option -init-eval-command}) such as:
21389 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
21392 Be aware that system init file (@pxref{System-wide configuration})
21393 and init files from your home directory (@pxref{Home Directory Init File})
21394 still get read (as they come from generally trusted directories).
21395 To prevent @value{GDBN} from auto-loading even those init files, use the
21396 @option{-nx} option (@pxref{Mode Options}), in addition to
21397 @code{set auto-load no}.
21399 @anchor{show auto-load}
21400 @kindex show auto-load
21401 @item show auto-load
21402 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
21406 (gdb) show auto-load
21407 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
21408 libthread-db: Auto-loading of inferior specific libthread_db is on.
21409 local-gdbinit: Auto-loading of .gdbinit script from current directory
21411 python-scripts: Auto-loading of Python scripts is on.
21412 safe-path: List of directories from which it is safe to auto-load files
21413 is $debugdir:$datadir/auto-load.
21414 scripts-directory: List of directories from which to load auto-loaded scripts
21415 is $debugdir:$datadir/auto-load.
21418 @anchor{info auto-load}
21419 @kindex info auto-load
21420 @item info auto-load
21421 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
21425 (gdb) info auto-load
21428 Yes /home/user/gdb/gdb-gdb.gdb
21429 libthread-db: No auto-loaded libthread-db.
21430 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
21434 Yes /home/user/gdb/gdb-gdb.py
21438 These are various kinds of files @value{GDBN} can automatically load:
21442 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
21444 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
21446 @xref{dotdebug_gdb_scripts section},
21447 controlled by @ref{set auto-load python-scripts}.
21449 @xref{Init File in the Current Directory},
21450 controlled by @ref{set auto-load local-gdbinit}.
21452 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
21455 These are @value{GDBN} control commands for the auto-loading:
21457 @multitable @columnfractions .5 .5
21458 @item @xref{set auto-load off}.
21459 @tab Disable auto-loading globally.
21460 @item @xref{show auto-load}.
21461 @tab Show setting of all kinds of files.
21462 @item @xref{info auto-load}.
21463 @tab Show state of all kinds of files.
21464 @item @xref{set auto-load gdb-scripts}.
21465 @tab Control for @value{GDBN} command scripts.
21466 @item @xref{show auto-load gdb-scripts}.
21467 @tab Show setting of @value{GDBN} command scripts.
21468 @item @xref{info auto-load gdb-scripts}.
21469 @tab Show state of @value{GDBN} command scripts.
21470 @item @xref{set auto-load python-scripts}.
21471 @tab Control for @value{GDBN} Python scripts.
21472 @item @xref{show auto-load python-scripts}.
21473 @tab Show setting of @value{GDBN} Python scripts.
21474 @item @xref{info auto-load python-scripts}.
21475 @tab Show state of @value{GDBN} Python scripts.
21476 @item @xref{set auto-load scripts-directory}.
21477 @tab Control for @value{GDBN} auto-loaded scripts location.
21478 @item @xref{show auto-load scripts-directory}.
21479 @tab Show @value{GDBN} auto-loaded scripts location.
21480 @item @xref{set auto-load local-gdbinit}.
21481 @tab Control for init file in the current directory.
21482 @item @xref{show auto-load local-gdbinit}.
21483 @tab Show setting of init file in the current directory.
21484 @item @xref{info auto-load local-gdbinit}.
21485 @tab Show state of init file in the current directory.
21486 @item @xref{set auto-load libthread-db}.
21487 @tab Control for thread debugging library.
21488 @item @xref{show auto-load libthread-db}.
21489 @tab Show setting of thread debugging library.
21490 @item @xref{info auto-load libthread-db}.
21491 @tab Show state of thread debugging library.
21492 @item @xref{set auto-load safe-path}.
21493 @tab Control directories trusted for automatic loading.
21494 @item @xref{show auto-load safe-path}.
21495 @tab Show directories trusted for automatic loading.
21496 @item @xref{add-auto-load-safe-path}.
21497 @tab Add directory trusted for automatic loading.
21501 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
21502 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
21503 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
21504 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
21505 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
21506 @xref{Python Auto-loading}.
21509 @node Init File in the Current Directory
21510 @subsection Automatically loading init file in the current directory
21511 @cindex auto-loading init file in the current directory
21513 By default, @value{GDBN} reads and executes the canned sequences of commands
21514 from init file (if any) in the current working directory,
21515 see @ref{Init File in the Current Directory during Startup}.
21517 Note that loading of this local @file{.gdbinit} file also requires accordingly
21518 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21521 @anchor{set auto-load local-gdbinit}
21522 @kindex set auto-load local-gdbinit
21523 @item set auto-load local-gdbinit [on|off]
21524 Enable or disable the auto-loading of canned sequences of commands
21525 (@pxref{Sequences}) found in init file in the current directory.
21527 @anchor{show auto-load local-gdbinit}
21528 @kindex show auto-load local-gdbinit
21529 @item show auto-load local-gdbinit
21530 Show whether auto-loading of canned sequences of commands from init file in the
21531 current directory is enabled or disabled.
21533 @anchor{info auto-load local-gdbinit}
21534 @kindex info auto-load local-gdbinit
21535 @item info auto-load local-gdbinit
21536 Print whether canned sequences of commands from init file in the
21537 current directory have been auto-loaded.
21540 @node libthread_db.so.1 file
21541 @subsection Automatically loading thread debugging library
21542 @cindex auto-loading libthread_db.so.1
21544 This feature is currently present only on @sc{gnu}/Linux native hosts.
21546 @value{GDBN} reads in some cases thread debugging library from places specific
21547 to the inferior (@pxref{set libthread-db-search-path}).
21549 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
21550 without checking this @samp{set auto-load libthread-db} switch as system
21551 libraries have to be trusted in general. In all other cases of
21552 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
21553 auto-load libthread-db} is enabled before trying to open such thread debugging
21556 Note that loading of this debugging library also requires accordingly configured
21557 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21560 @anchor{set auto-load libthread-db}
21561 @kindex set auto-load libthread-db
21562 @item set auto-load libthread-db [on|off]
21563 Enable or disable the auto-loading of inferior specific thread debugging library.
21565 @anchor{show auto-load libthread-db}
21566 @kindex show auto-load libthread-db
21567 @item show auto-load libthread-db
21568 Show whether auto-loading of inferior specific thread debugging library is
21569 enabled or disabled.
21571 @anchor{info auto-load libthread-db}
21572 @kindex info auto-load libthread-db
21573 @item info auto-load libthread-db
21574 Print the list of all loaded inferior specific thread debugging libraries and
21575 for each such library print list of inferior @var{pid}s using it.
21578 @node objfile-gdb.gdb file
21579 @subsection The @file{@var{objfile}-gdb.gdb} file
21580 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
21582 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
21583 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
21584 auto-load gdb-scripts} is set to @samp{on}.
21586 Note that loading of this script file also requires accordingly configured
21587 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21589 For more background refer to the similar Python scripts auto-loading
21590 description (@pxref{objfile-gdb.py file}).
21593 @anchor{set auto-load gdb-scripts}
21594 @kindex set auto-load gdb-scripts
21595 @item set auto-load gdb-scripts [on|off]
21596 Enable or disable the auto-loading of canned sequences of commands scripts.
21598 @anchor{show auto-load gdb-scripts}
21599 @kindex show auto-load gdb-scripts
21600 @item show auto-load gdb-scripts
21601 Show whether auto-loading of canned sequences of commands scripts is enabled or
21604 @anchor{info auto-load gdb-scripts}
21605 @kindex info auto-load gdb-scripts
21606 @cindex print list of auto-loaded canned sequences of commands scripts
21607 @item info auto-load gdb-scripts [@var{regexp}]
21608 Print the list of all canned sequences of commands scripts that @value{GDBN}
21612 If @var{regexp} is supplied only canned sequences of commands scripts with
21613 matching names are printed.
21615 @node Auto-loading safe path
21616 @subsection Security restriction for auto-loading
21617 @cindex auto-loading safe-path
21619 As the files of inferior can come from untrusted source (such as submitted by
21620 an application user) @value{GDBN} does not always load any files automatically.
21621 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
21622 directories trusted for loading files not explicitly requested by user.
21623 Each directory can also be a shell wildcard pattern.
21625 If the path is not set properly you will see a warning and the file will not
21630 Reading symbols from /home/user/gdb/gdb...done.
21631 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
21632 declined by your `auto-load safe-path' set
21633 to "$debugdir:$datadir/auto-load".
21634 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
21635 declined by your `auto-load safe-path' set
21636 to "$debugdir:$datadir/auto-load".
21639 The list of trusted directories is controlled by the following commands:
21642 @anchor{set auto-load safe-path}
21643 @kindex set auto-load safe-path
21644 @item set auto-load safe-path @r{[}@var{directories}@r{]}
21645 Set the list of directories (and their subdirectories) trusted for automatic
21646 loading and execution of scripts. You can also enter a specific trusted file.
21647 Each directory can also be a shell wildcard pattern; wildcards do not match
21648 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
21649 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
21650 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
21651 its default value as specified during @value{GDBN} compilation.
21653 The list of directories uses path separator (@samp{:} on GNU and Unix
21654 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
21655 to the @env{PATH} environment variable.
21657 @anchor{show auto-load safe-path}
21658 @kindex show auto-load safe-path
21659 @item show auto-load safe-path
21660 Show the list of directories trusted for automatic loading and execution of
21663 @anchor{add-auto-load-safe-path}
21664 @kindex add-auto-load-safe-path
21665 @item add-auto-load-safe-path
21666 Add an entry (or list of entries) the list of directories trusted for automatic
21667 loading and execution of scripts. Multiple entries may be delimited by the
21668 host platform path separator in use.
21671 This variable defaults to what @code{--with-auto-load-dir} has been configured
21672 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
21673 substitution applies the same as for @ref{set auto-load scripts-directory}.
21674 The default @code{set auto-load safe-path} value can be also overriden by
21675 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
21677 Setting this variable to @file{/} disables this security protection,
21678 corresponding @value{GDBN} configuration option is
21679 @option{--without-auto-load-safe-path}.
21680 This variable is supposed to be set to the system directories writable by the
21681 system superuser only. Users can add their source directories in init files in
21682 their home directories (@pxref{Home Directory Init File}). See also deprecated
21683 init file in the current directory
21684 (@pxref{Init File in the Current Directory during Startup}).
21686 To force @value{GDBN} to load the files it declined to load in the previous
21687 example, you could use one of the following ways:
21690 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
21691 Specify this trusted directory (or a file) as additional component of the list.
21692 You have to specify also any existing directories displayed by
21693 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
21695 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
21696 Specify this directory as in the previous case but just for a single
21697 @value{GDBN} session.
21699 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
21700 Disable auto-loading safety for a single @value{GDBN} session.
21701 This assumes all the files you debug during this @value{GDBN} session will come
21702 from trusted sources.
21704 @item @kbd{./configure --without-auto-load-safe-path}
21705 During compilation of @value{GDBN} you may disable any auto-loading safety.
21706 This assumes all the files you will ever debug with this @value{GDBN} come from
21710 On the other hand you can also explicitly forbid automatic files loading which
21711 also suppresses any such warning messages:
21714 @item @kbd{gdb -iex "set auto-load no" @dots{}}
21715 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
21717 @item @file{~/.gdbinit}: @samp{set auto-load no}
21718 Disable auto-loading globally for the user
21719 (@pxref{Home Directory Init File}). While it is improbable, you could also
21720 use system init file instead (@pxref{System-wide configuration}).
21723 This setting applies to the file names as entered by user. If no entry matches
21724 @value{GDBN} tries as a last resort to also resolve all the file names into
21725 their canonical form (typically resolving symbolic links) and compare the
21726 entries again. @value{GDBN} already canonicalizes most of the filenames on its
21727 own before starting the comparison so a canonical form of directories is
21728 recommended to be entered.
21730 @node Auto-loading verbose mode
21731 @subsection Displaying files tried for auto-load
21732 @cindex auto-loading verbose mode
21734 For better visibility of all the file locations where you can place scripts to
21735 be auto-loaded with inferior --- or to protect yourself against accidental
21736 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
21737 all the files attempted to be loaded. Both existing and non-existing files may
21740 For example the list of directories from which it is safe to auto-load files
21741 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
21742 may not be too obvious while setting it up.
21745 (gdb) set debug auto-load on
21746 (gdb) file ~/src/t/true
21747 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
21748 for objfile "/tmp/true".
21749 auto-load: Updating directories of "/usr:/opt".
21750 auto-load: Using directory "/usr".
21751 auto-load: Using directory "/opt".
21752 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
21753 by your `auto-load safe-path' set to "/usr:/opt".
21757 @anchor{set debug auto-load}
21758 @kindex set debug auto-load
21759 @item set debug auto-load [on|off]
21760 Set whether to print the filenames attempted to be auto-loaded.
21762 @anchor{show debug auto-load}
21763 @kindex show debug auto-load
21764 @item show debug auto-load
21765 Show whether printing of the filenames attempted to be auto-loaded is turned
21769 @node Messages/Warnings
21770 @section Optional Warnings and Messages
21772 @cindex verbose operation
21773 @cindex optional warnings
21774 By default, @value{GDBN} is silent about its inner workings. If you are
21775 running on a slow machine, you may want to use the @code{set verbose}
21776 command. This makes @value{GDBN} tell you when it does a lengthy
21777 internal operation, so you will not think it has crashed.
21779 Currently, the messages controlled by @code{set verbose} are those
21780 which announce that the symbol table for a source file is being read;
21781 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
21784 @kindex set verbose
21785 @item set verbose on
21786 Enables @value{GDBN} output of certain informational messages.
21788 @item set verbose off
21789 Disables @value{GDBN} output of certain informational messages.
21791 @kindex show verbose
21793 Displays whether @code{set verbose} is on or off.
21796 By default, if @value{GDBN} encounters bugs in the symbol table of an
21797 object file, it is silent; but if you are debugging a compiler, you may
21798 find this information useful (@pxref{Symbol Errors, ,Errors Reading
21803 @kindex set complaints
21804 @item set complaints @var{limit}
21805 Permits @value{GDBN} to output @var{limit} complaints about each type of
21806 unusual symbols before becoming silent about the problem. Set
21807 @var{limit} to zero to suppress all complaints; set it to a large number
21808 to prevent complaints from being suppressed.
21810 @kindex show complaints
21811 @item show complaints
21812 Displays how many symbol complaints @value{GDBN} is permitted to produce.
21816 @anchor{confirmation requests}
21817 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
21818 lot of stupid questions to confirm certain commands. For example, if
21819 you try to run a program which is already running:
21823 The program being debugged has been started already.
21824 Start it from the beginning? (y or n)
21827 If you are willing to unflinchingly face the consequences of your own
21828 commands, you can disable this ``feature'':
21832 @kindex set confirm
21834 @cindex confirmation
21835 @cindex stupid questions
21836 @item set confirm off
21837 Disables confirmation requests. Note that running @value{GDBN} with
21838 the @option{--batch} option (@pxref{Mode Options, -batch}) also
21839 automatically disables confirmation requests.
21841 @item set confirm on
21842 Enables confirmation requests (the default).
21844 @kindex show confirm
21846 Displays state of confirmation requests.
21850 @cindex command tracing
21851 If you need to debug user-defined commands or sourced files you may find it
21852 useful to enable @dfn{command tracing}. In this mode each command will be
21853 printed as it is executed, prefixed with one or more @samp{+} symbols, the
21854 quantity denoting the call depth of each command.
21857 @kindex set trace-commands
21858 @cindex command scripts, debugging
21859 @item set trace-commands on
21860 Enable command tracing.
21861 @item set trace-commands off
21862 Disable command tracing.
21863 @item show trace-commands
21864 Display the current state of command tracing.
21867 @node Debugging Output
21868 @section Optional Messages about Internal Happenings
21869 @cindex optional debugging messages
21871 @value{GDBN} has commands that enable optional debugging messages from
21872 various @value{GDBN} subsystems; normally these commands are of
21873 interest to @value{GDBN} maintainers, or when reporting a bug. This
21874 section documents those commands.
21877 @kindex set exec-done-display
21878 @item set exec-done-display
21879 Turns on or off the notification of asynchronous commands'
21880 completion. When on, @value{GDBN} will print a message when an
21881 asynchronous command finishes its execution. The default is off.
21882 @kindex show exec-done-display
21883 @item show exec-done-display
21884 Displays the current setting of asynchronous command completion
21887 @cindex gdbarch debugging info
21888 @cindex architecture debugging info
21889 @item set debug arch
21890 Turns on or off display of gdbarch debugging info. The default is off
21892 @item show debug arch
21893 Displays the current state of displaying gdbarch debugging info.
21894 @item set debug aix-thread
21895 @cindex AIX threads
21896 Display debugging messages about inner workings of the AIX thread
21898 @item show debug aix-thread
21899 Show the current state of AIX thread debugging info display.
21900 @item set debug check-physname
21902 Check the results of the ``physname'' computation. When reading DWARF
21903 debugging information for C@t{++}, @value{GDBN} attempts to compute
21904 each entity's name. @value{GDBN} can do this computation in two
21905 different ways, depending on exactly what information is present.
21906 When enabled, this setting causes @value{GDBN} to compute the names
21907 both ways and display any discrepancies.
21908 @item show debug check-physname
21909 Show the current state of ``physname'' checking.
21910 @item set debug dwarf2-die
21911 @cindex DWARF2 DIEs
21912 Dump DWARF2 DIEs after they are read in.
21913 The value is the number of nesting levels to print.
21914 A value of zero turns off the display.
21915 @item show debug dwarf2-die
21916 Show the current state of DWARF2 DIE debugging.
21917 @item set debug dwarf2-read
21918 @cindex DWARF2 Reading
21919 Turns on or off display of debugging messages related to reading
21920 DWARF debug info. The default is off.
21921 @item show debug dwarf2-read
21922 Show the current state of DWARF2 reader debugging.
21923 @item set debug displaced
21924 @cindex displaced stepping debugging info
21925 Turns on or off display of @value{GDBN} debugging info for the
21926 displaced stepping support. The default is off.
21927 @item show debug displaced
21928 Displays the current state of displaying @value{GDBN} debugging info
21929 related to displaced stepping.
21930 @item set debug event
21931 @cindex event debugging info
21932 Turns on or off display of @value{GDBN} event debugging info. The
21934 @item show debug event
21935 Displays the current state of displaying @value{GDBN} event debugging
21937 @item set debug expression
21938 @cindex expression debugging info
21939 Turns on or off display of debugging info about @value{GDBN}
21940 expression parsing. The default is off.
21941 @item show debug expression
21942 Displays the current state of displaying debugging info about
21943 @value{GDBN} expression parsing.
21944 @item set debug frame
21945 @cindex frame debugging info
21946 Turns on or off display of @value{GDBN} frame debugging info. The
21948 @item show debug frame
21949 Displays the current state of displaying @value{GDBN} frame debugging
21951 @item set debug gnu-nat
21952 @cindex @sc{gnu}/Hurd debug messages
21953 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
21954 @item show debug gnu-nat
21955 Show the current state of @sc{gnu}/Hurd debugging messages.
21956 @item set debug infrun
21957 @cindex inferior debugging info
21958 Turns on or off display of @value{GDBN} debugging info for running the inferior.
21959 The default is off. @file{infrun.c} contains GDB's runtime state machine used
21960 for implementing operations such as single-stepping the inferior.
21961 @item show debug infrun
21962 Displays the current state of @value{GDBN} inferior debugging.
21963 @item set debug jit
21964 @cindex just-in-time compilation, debugging messages
21965 Turns on or off debugging messages from JIT debug support.
21966 @item show debug jit
21967 Displays the current state of @value{GDBN} JIT debugging.
21968 @item set debug lin-lwp
21969 @cindex @sc{gnu}/Linux LWP debug messages
21970 @cindex Linux lightweight processes
21971 Turns on or off debugging messages from the Linux LWP debug support.
21972 @item show debug lin-lwp
21973 Show the current state of Linux LWP debugging messages.
21974 @item set debug observer
21975 @cindex observer debugging info
21976 Turns on or off display of @value{GDBN} observer debugging. This
21977 includes info such as the notification of observable events.
21978 @item show debug observer
21979 Displays the current state of observer debugging.
21980 @item set debug overload
21981 @cindex C@t{++} overload debugging info
21982 Turns on or off display of @value{GDBN} C@t{++} overload debugging
21983 info. This includes info such as ranking of functions, etc. The default
21985 @item show debug overload
21986 Displays the current state of displaying @value{GDBN} C@t{++} overload
21988 @cindex expression parser, debugging info
21989 @cindex debug expression parser
21990 @item set debug parser
21991 Turns on or off the display of expression parser debugging output.
21992 Internally, this sets the @code{yydebug} variable in the expression
21993 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
21994 details. The default is off.
21995 @item show debug parser
21996 Show the current state of expression parser debugging.
21997 @cindex packets, reporting on stdout
21998 @cindex serial connections, debugging
21999 @cindex debug remote protocol
22000 @cindex remote protocol debugging
22001 @cindex display remote packets
22002 @item set debug remote
22003 Turns on or off display of reports on all packets sent back and forth across
22004 the serial line to the remote machine. The info is printed on the
22005 @value{GDBN} standard output stream. The default is off.
22006 @item show debug remote
22007 Displays the state of display of remote packets.
22008 @item set debug serial
22009 Turns on or off display of @value{GDBN} serial debugging info. The
22011 @item show debug serial
22012 Displays the current state of displaying @value{GDBN} serial debugging
22014 @item set debug solib-frv
22015 @cindex FR-V shared-library debugging
22016 Turns on or off debugging messages for FR-V shared-library code.
22017 @item show debug solib-frv
22018 Display the current state of FR-V shared-library code debugging
22020 @item set debug symtab-create
22021 @cindex symbol table creation
22022 Turns on or off display of debugging messages related to symbol table creation.
22023 The default is off.
22024 @item show debug symtab-create
22025 Show the current state of symbol table creation debugging.
22026 @item set debug target
22027 @cindex target debugging info
22028 Turns on or off display of @value{GDBN} target debugging info. This info
22029 includes what is going on at the target level of GDB, as it happens. The
22030 default is 0. Set it to 1 to track events, and to 2 to also track the
22031 value of large memory transfers. Changes to this flag do not take effect
22032 until the next time you connect to a target or use the @code{run} command.
22033 @item show debug target
22034 Displays the current state of displaying @value{GDBN} target debugging
22036 @item set debug timestamp
22037 @cindex timestampping debugging info
22038 Turns on or off display of timestamps with @value{GDBN} debugging info.
22039 When enabled, seconds and microseconds are displayed before each debugging
22041 @item show debug timestamp
22042 Displays the current state of displaying timestamps with @value{GDBN}
22044 @item set debugvarobj
22045 @cindex variable object debugging info
22046 Turns on or off display of @value{GDBN} variable object debugging
22047 info. The default is off.
22048 @item show debugvarobj
22049 Displays the current state of displaying @value{GDBN} variable object
22051 @item set debug xml
22052 @cindex XML parser debugging
22053 Turns on or off debugging messages for built-in XML parsers.
22054 @item show debug xml
22055 Displays the current state of XML debugging messages.
22058 @node Other Misc Settings
22059 @section Other Miscellaneous Settings
22060 @cindex miscellaneous settings
22063 @kindex set interactive-mode
22064 @item set interactive-mode
22065 If @code{on}, forces @value{GDBN} to assume that GDB was started
22066 in a terminal. In practice, this means that @value{GDBN} should wait
22067 for the user to answer queries generated by commands entered at
22068 the command prompt. If @code{off}, forces @value{GDBN} to operate
22069 in the opposite mode, and it uses the default answers to all queries.
22070 If @code{auto} (the default), @value{GDBN} tries to determine whether
22071 its standard input is a terminal, and works in interactive-mode if it
22072 is, non-interactively otherwise.
22074 In the vast majority of cases, the debugger should be able to guess
22075 correctly which mode should be used. But this setting can be useful
22076 in certain specific cases, such as running a MinGW @value{GDBN}
22077 inside a cygwin window.
22079 @kindex show interactive-mode
22080 @item show interactive-mode
22081 Displays whether the debugger is operating in interactive mode or not.
22084 @node Extending GDB
22085 @chapter Extending @value{GDBN}
22086 @cindex extending GDB
22088 @value{GDBN} provides three mechanisms for extension. The first is based
22089 on composition of @value{GDBN} commands, the second is based on the
22090 Python scripting language, and the third is for defining new aliases of
22093 To facilitate the use of the first two extensions, @value{GDBN} is capable
22094 of evaluating the contents of a file. When doing so, @value{GDBN}
22095 can recognize which scripting language is being used by looking at
22096 the filename extension. Files with an unrecognized filename extension
22097 are always treated as a @value{GDBN} Command Files.
22098 @xref{Command Files,, Command files}.
22100 You can control how @value{GDBN} evaluates these files with the following
22104 @kindex set script-extension
22105 @kindex show script-extension
22106 @item set script-extension off
22107 All scripts are always evaluated as @value{GDBN} Command Files.
22109 @item set script-extension soft
22110 The debugger determines the scripting language based on filename
22111 extension. If this scripting language is supported, @value{GDBN}
22112 evaluates the script using that language. Otherwise, it evaluates
22113 the file as a @value{GDBN} Command File.
22115 @item set script-extension strict
22116 The debugger determines the scripting language based on filename
22117 extension, and evaluates the script using that language. If the
22118 language is not supported, then the evaluation fails.
22120 @item show script-extension
22121 Display the current value of the @code{script-extension} option.
22126 * Sequences:: Canned Sequences of Commands
22127 * Python:: Scripting @value{GDBN} using Python
22128 * Aliases:: Creating new spellings of existing commands
22132 @section Canned Sequences of Commands
22134 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22135 Command Lists}), @value{GDBN} provides two ways to store sequences of
22136 commands for execution as a unit: user-defined commands and command
22140 * Define:: How to define your own commands
22141 * Hooks:: Hooks for user-defined commands
22142 * Command Files:: How to write scripts of commands to be stored in a file
22143 * Output:: Commands for controlled output
22147 @subsection User-defined Commands
22149 @cindex user-defined command
22150 @cindex arguments, to user-defined commands
22151 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22152 which you assign a new name as a command. This is done with the
22153 @code{define} command. User commands may accept up to 10 arguments
22154 separated by whitespace. Arguments are accessed within the user command
22155 via @code{$arg0@dots{}$arg9}. A trivial example:
22159 print $arg0 + $arg1 + $arg2
22164 To execute the command use:
22171 This defines the command @code{adder}, which prints the sum of
22172 its three arguments. Note the arguments are text substitutions, so they may
22173 reference variables, use complex expressions, or even perform inferior
22176 @cindex argument count in user-defined commands
22177 @cindex how many arguments (user-defined commands)
22178 In addition, @code{$argc} may be used to find out how many arguments have
22179 been passed. This expands to a number in the range 0@dots{}10.
22184 print $arg0 + $arg1
22187 print $arg0 + $arg1 + $arg2
22195 @item define @var{commandname}
22196 Define a command named @var{commandname}. If there is already a command
22197 by that name, you are asked to confirm that you want to redefine it.
22198 @var{commandname} may be a bare command name consisting of letters,
22199 numbers, dashes, and underscores. It may also start with any predefined
22200 prefix command. For example, @samp{define target my-target} creates
22201 a user-defined @samp{target my-target} command.
22203 The definition of the command is made up of other @value{GDBN} command lines,
22204 which are given following the @code{define} command. The end of these
22205 commands is marked by a line containing @code{end}.
22208 @kindex end@r{ (user-defined commands)}
22209 @item document @var{commandname}
22210 Document the user-defined command @var{commandname}, so that it can be
22211 accessed by @code{help}. The command @var{commandname} must already be
22212 defined. This command reads lines of documentation just as @code{define}
22213 reads the lines of the command definition, ending with @code{end}.
22214 After the @code{document} command is finished, @code{help} on command
22215 @var{commandname} displays the documentation you have written.
22217 You may use the @code{document} command again to change the
22218 documentation of a command. Redefining the command with @code{define}
22219 does not change the documentation.
22221 @kindex dont-repeat
22222 @cindex don't repeat command
22224 Used inside a user-defined command, this tells @value{GDBN} that this
22225 command should not be repeated when the user hits @key{RET}
22226 (@pxref{Command Syntax, repeat last command}).
22228 @kindex help user-defined
22229 @item help user-defined
22230 List all user-defined commands and all python commands defined in class
22231 COMAND_USER. The first line of the documentation or docstring is
22236 @itemx show user @var{commandname}
22237 Display the @value{GDBN} commands used to define @var{commandname} (but
22238 not its documentation). If no @var{commandname} is given, display the
22239 definitions for all user-defined commands.
22240 This does not work for user-defined python commands.
22242 @cindex infinite recursion in user-defined commands
22243 @kindex show max-user-call-depth
22244 @kindex set max-user-call-depth
22245 @item show max-user-call-depth
22246 @itemx set max-user-call-depth
22247 The value of @code{max-user-call-depth} controls how many recursion
22248 levels are allowed in user-defined commands before @value{GDBN} suspects an
22249 infinite recursion and aborts the command.
22250 This does not apply to user-defined python commands.
22253 In addition to the above commands, user-defined commands frequently
22254 use control flow commands, described in @ref{Command Files}.
22256 When user-defined commands are executed, the
22257 commands of the definition are not printed. An error in any command
22258 stops execution of the user-defined command.
22260 If used interactively, commands that would ask for confirmation proceed
22261 without asking when used inside a user-defined command. Many @value{GDBN}
22262 commands that normally print messages to say what they are doing omit the
22263 messages when used in a user-defined command.
22266 @subsection User-defined Command Hooks
22267 @cindex command hooks
22268 @cindex hooks, for commands
22269 @cindex hooks, pre-command
22272 You may define @dfn{hooks}, which are a special kind of user-defined
22273 command. Whenever you run the command @samp{foo}, if the user-defined
22274 command @samp{hook-foo} exists, it is executed (with no arguments)
22275 before that command.
22277 @cindex hooks, post-command
22279 A hook may also be defined which is run after the command you executed.
22280 Whenever you run the command @samp{foo}, if the user-defined command
22281 @samp{hookpost-foo} exists, it is executed (with no arguments) after
22282 that command. Post-execution hooks may exist simultaneously with
22283 pre-execution hooks, for the same command.
22285 It is valid for a hook to call the command which it hooks. If this
22286 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
22288 @c It would be nice if hookpost could be passed a parameter indicating
22289 @c if the command it hooks executed properly or not. FIXME!
22291 @kindex stop@r{, a pseudo-command}
22292 In addition, a pseudo-command, @samp{stop} exists. Defining
22293 (@samp{hook-stop}) makes the associated commands execute every time
22294 execution stops in your program: before breakpoint commands are run,
22295 displays are printed, or the stack frame is printed.
22297 For example, to ignore @code{SIGALRM} signals while
22298 single-stepping, but treat them normally during normal execution,
22303 handle SIGALRM nopass
22307 handle SIGALRM pass
22310 define hook-continue
22311 handle SIGALRM pass
22315 As a further example, to hook at the beginning and end of the @code{echo}
22316 command, and to add extra text to the beginning and end of the message,
22324 define hookpost-echo
22328 (@value{GDBP}) echo Hello World
22329 <<<---Hello World--->>>
22334 You can define a hook for any single-word command in @value{GDBN}, but
22335 not for command aliases; you should define a hook for the basic command
22336 name, e.g.@: @code{backtrace} rather than @code{bt}.
22337 @c FIXME! So how does Joe User discover whether a command is an alias
22339 You can hook a multi-word command by adding @code{hook-} or
22340 @code{hookpost-} to the last word of the command, e.g.@:
22341 @samp{define target hook-remote} to add a hook to @samp{target remote}.
22343 If an error occurs during the execution of your hook, execution of
22344 @value{GDBN} commands stops and @value{GDBN} issues a prompt
22345 (before the command that you actually typed had a chance to run).
22347 If you try to define a hook which does not match any known command, you
22348 get a warning from the @code{define} command.
22350 @node Command Files
22351 @subsection Command Files
22353 @cindex command files
22354 @cindex scripting commands
22355 A command file for @value{GDBN} is a text file made of lines that are
22356 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
22357 also be included. An empty line in a command file does nothing; it
22358 does not mean to repeat the last command, as it would from the
22361 You can request the execution of a command file with the @code{source}
22362 command. Note that the @code{source} command is also used to evaluate
22363 scripts that are not Command Files. The exact behavior can be configured
22364 using the @code{script-extension} setting.
22365 @xref{Extending GDB,, Extending GDB}.
22369 @cindex execute commands from a file
22370 @item source [-s] [-v] @var{filename}
22371 Execute the command file @var{filename}.
22374 The lines in a command file are generally executed sequentially,
22375 unless the order of execution is changed by one of the
22376 @emph{flow-control commands} described below. The commands are not
22377 printed as they are executed. An error in any command terminates
22378 execution of the command file and control is returned to the console.
22380 @value{GDBN} first searches for @var{filename} in the current directory.
22381 If the file is not found there, and @var{filename} does not specify a
22382 directory, then @value{GDBN} also looks for the file on the source search path
22383 (specified with the @samp{directory} command);
22384 except that @file{$cdir} is not searched because the compilation directory
22385 is not relevant to scripts.
22387 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
22388 on the search path even if @var{filename} specifies a directory.
22389 The search is done by appending @var{filename} to each element of the
22390 search path. So, for example, if @var{filename} is @file{mylib/myscript}
22391 and the search path contains @file{/home/user} then @value{GDBN} will
22392 look for the script @file{/home/user/mylib/myscript}.
22393 The search is also done if @var{filename} is an absolute path.
22394 For example, if @var{filename} is @file{/tmp/myscript} and
22395 the search path contains @file{/home/user} then @value{GDBN} will
22396 look for the script @file{/home/user/tmp/myscript}.
22397 For DOS-like systems, if @var{filename} contains a drive specification,
22398 it is stripped before concatenation. For example, if @var{filename} is
22399 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
22400 will look for the script @file{c:/tmp/myscript}.
22402 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
22403 each command as it is executed. The option must be given before
22404 @var{filename}, and is interpreted as part of the filename anywhere else.
22406 Commands that would ask for confirmation if used interactively proceed
22407 without asking when used in a command file. Many @value{GDBN} commands that
22408 normally print messages to say what they are doing omit the messages
22409 when called from command files.
22411 @value{GDBN} also accepts command input from standard input. In this
22412 mode, normal output goes to standard output and error output goes to
22413 standard error. Errors in a command file supplied on standard input do
22414 not terminate execution of the command file---execution continues with
22418 gdb < cmds > log 2>&1
22421 (The syntax above will vary depending on the shell used.) This example
22422 will execute commands from the file @file{cmds}. All output and errors
22423 would be directed to @file{log}.
22425 Since commands stored on command files tend to be more general than
22426 commands typed interactively, they frequently need to deal with
22427 complicated situations, such as different or unexpected values of
22428 variables and symbols, changes in how the program being debugged is
22429 built, etc. @value{GDBN} provides a set of flow-control commands to
22430 deal with these complexities. Using these commands, you can write
22431 complex scripts that loop over data structures, execute commands
22432 conditionally, etc.
22439 This command allows to include in your script conditionally executed
22440 commands. The @code{if} command takes a single argument, which is an
22441 expression to evaluate. It is followed by a series of commands that
22442 are executed only if the expression is true (its value is nonzero).
22443 There can then optionally be an @code{else} line, followed by a series
22444 of commands that are only executed if the expression was false. The
22445 end of the list is marked by a line containing @code{end}.
22449 This command allows to write loops. Its syntax is similar to
22450 @code{if}: the command takes a single argument, which is an expression
22451 to evaluate, and must be followed by the commands to execute, one per
22452 line, terminated by an @code{end}. These commands are called the
22453 @dfn{body} of the loop. The commands in the body of @code{while} are
22454 executed repeatedly as long as the expression evaluates to true.
22458 This command exits the @code{while} loop in whose body it is included.
22459 Execution of the script continues after that @code{while}s @code{end}
22462 @kindex loop_continue
22463 @item loop_continue
22464 This command skips the execution of the rest of the body of commands
22465 in the @code{while} loop in whose body it is included. Execution
22466 branches to the beginning of the @code{while} loop, where it evaluates
22467 the controlling expression.
22469 @kindex end@r{ (if/else/while commands)}
22471 Terminate the block of commands that are the body of @code{if},
22472 @code{else}, or @code{while} flow-control commands.
22477 @subsection Commands for Controlled Output
22479 During the execution of a command file or a user-defined command, normal
22480 @value{GDBN} output is suppressed; the only output that appears is what is
22481 explicitly printed by the commands in the definition. This section
22482 describes three commands useful for generating exactly the output you
22487 @item echo @var{text}
22488 @c I do not consider backslash-space a standard C escape sequence
22489 @c because it is not in ANSI.
22490 Print @var{text}. Nonprinting characters can be included in
22491 @var{text} using C escape sequences, such as @samp{\n} to print a
22492 newline. @strong{No newline is printed unless you specify one.}
22493 In addition to the standard C escape sequences, a backslash followed
22494 by a space stands for a space. This is useful for displaying a
22495 string with spaces at the beginning or the end, since leading and
22496 trailing spaces are otherwise trimmed from all arguments.
22497 To print @samp{@w{ }and foo =@w{ }}, use the command
22498 @samp{echo \@w{ }and foo = \@w{ }}.
22500 A backslash at the end of @var{text} can be used, as in C, to continue
22501 the command onto subsequent lines. For example,
22504 echo This is some text\n\
22505 which is continued\n\
22506 onto several lines.\n
22509 produces the same output as
22512 echo This is some text\n
22513 echo which is continued\n
22514 echo onto several lines.\n
22518 @item output @var{expression}
22519 Print the value of @var{expression} and nothing but that value: no
22520 newlines, no @samp{$@var{nn} = }. The value is not entered in the
22521 value history either. @xref{Expressions, ,Expressions}, for more information
22524 @item output/@var{fmt} @var{expression}
22525 Print the value of @var{expression} in format @var{fmt}. You can use
22526 the same formats as for @code{print}. @xref{Output Formats,,Output
22527 Formats}, for more information.
22530 @item printf @var{template}, @var{expressions}@dots{}
22531 Print the values of one or more @var{expressions} under the control of
22532 the string @var{template}. To print several values, make
22533 @var{expressions} be a comma-separated list of individual expressions,
22534 which may be either numbers or pointers. Their values are printed as
22535 specified by @var{template}, exactly as a C program would do by
22536 executing the code below:
22539 printf (@var{template}, @var{expressions}@dots{});
22542 As in @code{C} @code{printf}, ordinary characters in @var{template}
22543 are printed verbatim, while @dfn{conversion specification} introduced
22544 by the @samp{%} character cause subsequent @var{expressions} to be
22545 evaluated, their values converted and formatted according to type and
22546 style information encoded in the conversion specifications, and then
22549 For example, you can print two values in hex like this:
22552 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
22555 @code{printf} supports all the standard @code{C} conversion
22556 specifications, including the flags and modifiers between the @samp{%}
22557 character and the conversion letter, with the following exceptions:
22561 The argument-ordering modifiers, such as @samp{2$}, are not supported.
22564 The modifier @samp{*} is not supported for specifying precision or
22568 The @samp{'} flag (for separation of digits into groups according to
22569 @code{LC_NUMERIC'}) is not supported.
22572 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
22576 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
22579 The conversion letters @samp{a} and @samp{A} are not supported.
22583 Note that the @samp{ll} type modifier is supported only if the
22584 underlying @code{C} implementation used to build @value{GDBN} supports
22585 the @code{long long int} type, and the @samp{L} type modifier is
22586 supported only if @code{long double} type is available.
22588 As in @code{C}, @code{printf} supports simple backslash-escape
22589 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
22590 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
22591 single character. Octal and hexadecimal escape sequences are not
22594 Additionally, @code{printf} supports conversion specifications for DFP
22595 (@dfn{Decimal Floating Point}) types using the following length modifiers
22596 together with a floating point specifier.
22601 @samp{H} for printing @code{Decimal32} types.
22604 @samp{D} for printing @code{Decimal64} types.
22607 @samp{DD} for printing @code{Decimal128} types.
22610 If the underlying @code{C} implementation used to build @value{GDBN} has
22611 support for the three length modifiers for DFP types, other modifiers
22612 such as width and precision will also be available for @value{GDBN} to use.
22614 In case there is no such @code{C} support, no additional modifiers will be
22615 available and the value will be printed in the standard way.
22617 Here's an example of printing DFP types using the above conversion letters:
22619 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
22623 @item eval @var{template}, @var{expressions}@dots{}
22624 Convert the values of one or more @var{expressions} under the control of
22625 the string @var{template} to a command line, and call it.
22630 @section Scripting @value{GDBN} using Python
22631 @cindex python scripting
22632 @cindex scripting with python
22634 You can script @value{GDBN} using the @uref{http://www.python.org/,
22635 Python programming language}. This feature is available only if
22636 @value{GDBN} was configured using @option{--with-python}.
22638 @cindex python directory
22639 Python scripts used by @value{GDBN} should be installed in
22640 @file{@var{data-directory}/python}, where @var{data-directory} is
22641 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
22642 This directory, known as the @dfn{python directory},
22643 is automatically added to the Python Search Path in order to allow
22644 the Python interpreter to locate all scripts installed at this location.
22646 Additionally, @value{GDBN} commands and convenience functions which
22647 are written in Python and are located in the
22648 @file{@var{data-directory}/python/gdb/command} or
22649 @file{@var{data-directory}/python/gdb/function} directories are
22650 automatically imported when @value{GDBN} starts.
22653 * Python Commands:: Accessing Python from @value{GDBN}.
22654 * Python API:: Accessing @value{GDBN} from Python.
22655 * Python Auto-loading:: Automatically loading Python code.
22656 * Python modules:: Python modules provided by @value{GDBN}.
22659 @node Python Commands
22660 @subsection Python Commands
22661 @cindex python commands
22662 @cindex commands to access python
22664 @value{GDBN} provides two commands for accessing the Python interpreter,
22665 and one related setting:
22668 @kindex python-interactive
22670 @item python-interactive @r{[}@var{command}@r{]}
22671 @itemx pi @r{[}@var{command}@r{]}
22672 Without an argument, the @code{python-interactive} command can be used
22673 to start an interactive Python prompt. To return to @value{GDBN},
22674 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
22676 Alternatively, a single-line Python command can be given as an
22677 argument and evaluated. If the command is an expression, the result
22678 will be printed; otherwise, nothing will be printed. For example:
22681 (@value{GDBP}) python-interactive 2 + 3
22687 @item python @r{[}@var{command}@r{]}
22688 @itemx py @r{[}@var{command}@r{]}
22689 The @code{python} command can be used to evaluate Python code.
22691 If given an argument, the @code{python} command will evaluate the
22692 argument as a Python command. For example:
22695 (@value{GDBP}) python print 23
22699 If you do not provide an argument to @code{python}, it will act as a
22700 multi-line command, like @code{define}. In this case, the Python
22701 script is made up of subsequent command lines, given after the
22702 @code{python} command. This command list is terminated using a line
22703 containing @code{end}. For example:
22706 (@value{GDBP}) python
22708 End with a line saying just "end".
22714 @kindex set python print-stack
22715 @item set python print-stack
22716 By default, @value{GDBN} will print only the message component of a
22717 Python exception when an error occurs in a Python script. This can be
22718 controlled using @code{set python print-stack}: if @code{full}, then
22719 full Python stack printing is enabled; if @code{none}, then Python stack
22720 and message printing is disabled; if @code{message}, the default, only
22721 the message component of the error is printed.
22724 It is also possible to execute a Python script from the @value{GDBN}
22728 @item source @file{script-name}
22729 The script name must end with @samp{.py} and @value{GDBN} must be configured
22730 to recognize the script language based on filename extension using
22731 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
22733 @item python execfile ("script-name")
22734 This method is based on the @code{execfile} Python built-in function,
22735 and thus is always available.
22739 @subsection Python API
22741 @cindex programming in python
22743 @cindex python stdout
22744 @cindex python pagination
22745 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
22746 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
22747 A Python program which outputs to one of these streams may have its
22748 output interrupted by the user (@pxref{Screen Size}). In this
22749 situation, a Python @code{KeyboardInterrupt} exception is thrown.
22752 * Basic Python:: Basic Python Functions.
22753 * Exception Handling:: How Python exceptions are translated.
22754 * Values From Inferior:: Python representation of values.
22755 * Types In Python:: Python representation of types.
22756 * Pretty Printing API:: Pretty-printing values.
22757 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
22758 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
22759 * Type Printing API:: Pretty-printing types.
22760 * Inferiors In Python:: Python representation of inferiors (processes)
22761 * Events In Python:: Listening for events from @value{GDBN}.
22762 * Threads In Python:: Accessing inferior threads from Python.
22763 * Commands In Python:: Implementing new commands in Python.
22764 * Parameters In Python:: Adding new @value{GDBN} parameters.
22765 * Functions In Python:: Writing new convenience functions.
22766 * Progspaces In Python:: Program spaces.
22767 * Objfiles In Python:: Object files.
22768 * Frames In Python:: Accessing inferior stack frames from Python.
22769 * Blocks In Python:: Accessing frame blocks from Python.
22770 * Symbols In Python:: Python representation of symbols.
22771 * Symbol Tables In Python:: Python representation of symbol tables.
22772 * Breakpoints In Python:: Manipulating breakpoints using Python.
22773 * Finish Breakpoints in Python:: Setting Breakpoints on function return
22775 * Lazy Strings In Python:: Python representation of lazy strings.
22779 @subsubsection Basic Python
22781 @cindex python functions
22782 @cindex python module
22784 @value{GDBN} introduces a new Python module, named @code{gdb}. All
22785 methods and classes added by @value{GDBN} are placed in this module.
22786 @value{GDBN} automatically @code{import}s the @code{gdb} module for
22787 use in all scripts evaluated by the @code{python} command.
22789 @findex gdb.PYTHONDIR
22790 @defvar gdb.PYTHONDIR
22791 A string containing the python directory (@pxref{Python}).
22794 @findex gdb.execute
22795 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
22796 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
22797 If a GDB exception happens while @var{command} runs, it is
22798 translated as described in @ref{Exception Handling,,Exception Handling}.
22800 @var{from_tty} specifies whether @value{GDBN} ought to consider this
22801 command as having originated from the user invoking it interactively.
22802 It must be a boolean value. If omitted, it defaults to @code{False}.
22804 By default, any output produced by @var{command} is sent to
22805 @value{GDBN}'s standard output. If the @var{to_string} parameter is
22806 @code{True}, then output will be collected by @code{gdb.execute} and
22807 returned as a string. The default is @code{False}, in which case the
22808 return value is @code{None}. If @var{to_string} is @code{True}, the
22809 @value{GDBN} virtual terminal will be temporarily set to unlimited width
22810 and height, and its pagination will be disabled; @pxref{Screen Size}.
22813 @findex gdb.breakpoints
22814 @defun gdb.breakpoints ()
22815 Return a sequence holding all of @value{GDBN}'s breakpoints.
22816 @xref{Breakpoints In Python}, for more information.
22819 @findex gdb.parameter
22820 @defun gdb.parameter (parameter)
22821 Return the value of a @value{GDBN} parameter. @var{parameter} is a
22822 string naming the parameter to look up; @var{parameter} may contain
22823 spaces if the parameter has a multi-part name. For example,
22824 @samp{print object} is a valid parameter name.
22826 If the named parameter does not exist, this function throws a
22827 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
22828 parameter's value is converted to a Python value of the appropriate
22829 type, and returned.
22832 @findex gdb.history
22833 @defun gdb.history (number)
22834 Return a value from @value{GDBN}'s value history (@pxref{Value
22835 History}). @var{number} indicates which history element to return.
22836 If @var{number} is negative, then @value{GDBN} will take its absolute value
22837 and count backward from the last element (i.e., the most recent element) to
22838 find the value to return. If @var{number} is zero, then @value{GDBN} will
22839 return the most recent element. If the element specified by @var{number}
22840 doesn't exist in the value history, a @code{gdb.error} exception will be
22843 If no exception is raised, the return value is always an instance of
22844 @code{gdb.Value} (@pxref{Values From Inferior}).
22847 @findex gdb.parse_and_eval
22848 @defun gdb.parse_and_eval (expression)
22849 Parse @var{expression} as an expression in the current language,
22850 evaluate it, and return the result as a @code{gdb.Value}.
22851 @var{expression} must be a string.
22853 This function can be useful when implementing a new command
22854 (@pxref{Commands In Python}), as it provides a way to parse the
22855 command's argument as an expression. It is also useful simply to
22856 compute values, for example, it is the only way to get the value of a
22857 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
22860 @findex gdb.find_pc_line
22861 @defun gdb.find_pc_line (pc)
22862 Return the @code{gdb.Symtab_and_line} object corresponding to the
22863 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
22864 value of @var{pc} is passed as an argument, then the @code{symtab} and
22865 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
22866 will be @code{None} and 0 respectively.
22869 @findex gdb.post_event
22870 @defun gdb.post_event (event)
22871 Put @var{event}, a callable object taking no arguments, into
22872 @value{GDBN}'s internal event queue. This callable will be invoked at
22873 some later point, during @value{GDBN}'s event processing. Events
22874 posted using @code{post_event} will be run in the order in which they
22875 were posted; however, there is no way to know when they will be
22876 processed relative to other events inside @value{GDBN}.
22878 @value{GDBN} is not thread-safe. If your Python program uses multiple
22879 threads, you must be careful to only call @value{GDBN}-specific
22880 functions in the main @value{GDBN} thread. @code{post_event} ensures
22884 (@value{GDBP}) python
22888 > def __init__(self, message):
22889 > self.message = message;
22890 > def __call__(self):
22891 > gdb.write(self.message)
22893 >class MyThread1 (threading.Thread):
22895 > gdb.post_event(Writer("Hello "))
22897 >class MyThread2 (threading.Thread):
22899 > gdb.post_event(Writer("World\n"))
22901 >MyThread1().start()
22902 >MyThread2().start()
22904 (@value{GDBP}) Hello World
22909 @defun gdb.write (string @r{[}, stream{]})
22910 Print a string to @value{GDBN}'s paginated output stream. The
22911 optional @var{stream} determines the stream to print to. The default
22912 stream is @value{GDBN}'s standard output stream. Possible stream
22919 @value{GDBN}'s standard output stream.
22924 @value{GDBN}'s standard error stream.
22929 @value{GDBN}'s log stream (@pxref{Logging Output}).
22932 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
22933 call this function and will automatically direct the output to the
22938 @defun gdb.flush ()
22939 Flush the buffer of a @value{GDBN} paginated stream so that the
22940 contents are displayed immediately. @value{GDBN} will flush the
22941 contents of a stream automatically when it encounters a newline in the
22942 buffer. The optional @var{stream} determines the stream to flush. The
22943 default stream is @value{GDBN}'s standard output stream. Possible
22950 @value{GDBN}'s standard output stream.
22955 @value{GDBN}'s standard error stream.
22960 @value{GDBN}'s log stream (@pxref{Logging Output}).
22964 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
22965 call this function for the relevant stream.
22968 @findex gdb.target_charset
22969 @defun gdb.target_charset ()
22970 Return the name of the current target character set (@pxref{Character
22971 Sets}). This differs from @code{gdb.parameter('target-charset')} in
22972 that @samp{auto} is never returned.
22975 @findex gdb.target_wide_charset
22976 @defun gdb.target_wide_charset ()
22977 Return the name of the current target wide character set
22978 (@pxref{Character Sets}). This differs from
22979 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
22983 @findex gdb.solib_name
22984 @defun gdb.solib_name (address)
22985 Return the name of the shared library holding the given @var{address}
22986 as a string, or @code{None}.
22989 @findex gdb.decode_line
22990 @defun gdb.decode_line @r{[}expression@r{]}
22991 Return locations of the line specified by @var{expression}, or of the
22992 current line if no argument was given. This function returns a Python
22993 tuple containing two elements. The first element contains a string
22994 holding any unparsed section of @var{expression} (or @code{None} if
22995 the expression has been fully parsed). The second element contains
22996 either @code{None} or another tuple that contains all the locations
22997 that match the expression represented as @code{gdb.Symtab_and_line}
22998 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
22999 provided, it is decoded the way that @value{GDBN}'s inbuilt
23000 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23003 @defun gdb.prompt_hook (current_prompt)
23004 @anchor{prompt_hook}
23006 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23007 assigned to this operation before a prompt is displayed by
23010 The parameter @code{current_prompt} contains the current @value{GDBN}
23011 prompt. This method must return a Python string, or @code{None}. If
23012 a string is returned, the @value{GDBN} prompt will be set to that
23013 string. If @code{None} is returned, @value{GDBN} will continue to use
23014 the current prompt.
23016 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23017 such as those used by readline for command input, and annotation
23018 related prompts are prohibited from being changed.
23021 @node Exception Handling
23022 @subsubsection Exception Handling
23023 @cindex python exceptions
23024 @cindex exceptions, python
23026 When executing the @code{python} command, Python exceptions
23027 uncaught within the Python code are translated to calls to
23028 @value{GDBN} error-reporting mechanism. If the command that called
23029 @code{python} does not handle the error, @value{GDBN} will
23030 terminate it and print an error message containing the Python
23031 exception name, the associated value, and the Python call stack
23032 backtrace at the point where the exception was raised. Example:
23035 (@value{GDBP}) python print foo
23036 Traceback (most recent call last):
23037 File "<string>", line 1, in <module>
23038 NameError: name 'foo' is not defined
23041 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23042 Python code are converted to Python exceptions. The type of the
23043 Python exception depends on the error.
23047 This is the base class for most exceptions generated by @value{GDBN}.
23048 It is derived from @code{RuntimeError}, for compatibility with earlier
23049 versions of @value{GDBN}.
23051 If an error occurring in @value{GDBN} does not fit into some more
23052 specific category, then the generated exception will have this type.
23054 @item gdb.MemoryError
23055 This is a subclass of @code{gdb.error} which is thrown when an
23056 operation tried to access invalid memory in the inferior.
23058 @item KeyboardInterrupt
23059 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23060 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23063 In all cases, your exception handler will see the @value{GDBN} error
23064 message as its value and the Python call stack backtrace at the Python
23065 statement closest to where the @value{GDBN} error occured as the
23068 @findex gdb.GdbError
23069 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23070 it is useful to be able to throw an exception that doesn't cause a
23071 traceback to be printed. For example, the user may have invoked the
23072 command incorrectly. Use the @code{gdb.GdbError} exception
23073 to handle this case. Example:
23077 >class HelloWorld (gdb.Command):
23078 > """Greet the whole world."""
23079 > def __init__ (self):
23080 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23081 > def invoke (self, args, from_tty):
23082 > argv = gdb.string_to_argv (args)
23083 > if len (argv) != 0:
23084 > raise gdb.GdbError ("hello-world takes no arguments")
23085 > print "Hello, World!"
23088 (gdb) hello-world 42
23089 hello-world takes no arguments
23092 @node Values From Inferior
23093 @subsubsection Values From Inferior
23094 @cindex values from inferior, with Python
23095 @cindex python, working with values from inferior
23097 @cindex @code{gdb.Value}
23098 @value{GDBN} provides values it obtains from the inferior program in
23099 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23100 for its internal bookkeeping of the inferior's values, and for
23101 fetching values when necessary.
23103 Inferior values that are simple scalars can be used directly in
23104 Python expressions that are valid for the value's data type. Here's
23105 an example for an integer or floating-point value @code{some_val}:
23112 As result of this, @code{bar} will also be a @code{gdb.Value} object
23113 whose values are of the same type as those of @code{some_val}.
23115 Inferior values that are structures or instances of some class can
23116 be accessed using the Python @dfn{dictionary syntax}. For example, if
23117 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23118 can access its @code{foo} element with:
23121 bar = some_val['foo']
23124 Again, @code{bar} will also be a @code{gdb.Value} object.
23126 A @code{gdb.Value} that represents a function can be executed via
23127 inferior function call. Any arguments provided to the call must match
23128 the function's prototype, and must be provided in the order specified
23131 For example, @code{some_val} is a @code{gdb.Value} instance
23132 representing a function that takes two integers as arguments. To
23133 execute this function, call it like so:
23136 result = some_val (10,20)
23139 Any values returned from a function call will be stored as a
23142 The following attributes are provided:
23145 @defvar Value.address
23146 If this object is addressable, this read-only attribute holds a
23147 @code{gdb.Value} object representing the address. Otherwise,
23148 this attribute holds @code{None}.
23151 @cindex optimized out value in Python
23152 @defvar Value.is_optimized_out
23153 This read-only boolean attribute is true if the compiler optimized out
23154 this value, thus it is not available for fetching from the inferior.
23158 The type of this @code{gdb.Value}. The value of this attribute is a
23159 @code{gdb.Type} object (@pxref{Types In Python}).
23162 @defvar Value.dynamic_type
23163 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
23164 type information (@acronym{RTTI}) to determine the dynamic type of the
23165 value. If this value is of class type, it will return the class in
23166 which the value is embedded, if any. If this value is of pointer or
23167 reference to a class type, it will compute the dynamic type of the
23168 referenced object, and return a pointer or reference to that type,
23169 respectively. In all other cases, it will return the value's static
23172 Note that this feature will only work when debugging a C@t{++} program
23173 that includes @acronym{RTTI} for the object in question. Otherwise,
23174 it will just return the static type of the value as in @kbd{ptype foo}
23175 (@pxref{Symbols, ptype}).
23178 @defvar Value.is_lazy
23179 The value of this read-only boolean attribute is @code{True} if this
23180 @code{gdb.Value} has not yet been fetched from the inferior.
23181 @value{GDBN} does not fetch values until necessary, for efficiency.
23185 myval = gdb.parse_and_eval ('somevar')
23188 The value of @code{somevar} is not fetched at this time. It will be
23189 fetched when the value is needed, or when the @code{fetch_lazy}
23194 The following methods are provided:
23197 @defun Value.__init__ (@var{val})
23198 Many Python values can be converted directly to a @code{gdb.Value} via
23199 this object initializer. Specifically:
23202 @item Python boolean
23203 A Python boolean is converted to the boolean type from the current
23206 @item Python integer
23207 A Python integer is converted to the C @code{long} type for the
23208 current architecture.
23211 A Python long is converted to the C @code{long long} type for the
23212 current architecture.
23215 A Python float is converted to the C @code{double} type for the
23216 current architecture.
23218 @item Python string
23219 A Python string is converted to a target string, using the current
23222 @item @code{gdb.Value}
23223 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
23225 @item @code{gdb.LazyString}
23226 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
23227 Python}), then the lazy string's @code{value} method is called, and
23228 its result is used.
23232 @defun Value.cast (type)
23233 Return a new instance of @code{gdb.Value} that is the result of
23234 casting this instance to the type described by @var{type}, which must
23235 be a @code{gdb.Type} object. If the cast cannot be performed for some
23236 reason, this method throws an exception.
23239 @defun Value.dereference ()
23240 For pointer data types, this method returns a new @code{gdb.Value} object
23241 whose contents is the object pointed to by the pointer. For example, if
23242 @code{foo} is a C pointer to an @code{int}, declared in your C program as
23249 then you can use the corresponding @code{gdb.Value} to access what
23250 @code{foo} points to like this:
23253 bar = foo.dereference ()
23256 The result @code{bar} will be a @code{gdb.Value} object holding the
23257 value pointed to by @code{foo}.
23259 A similar function @code{Value.referenced_value} exists which also
23260 returns @code{gdb.Value} objects corresonding to the values pointed to
23261 by pointer values (and additionally, values referenced by reference
23262 values). However, the behavior of @code{Value.dereference}
23263 differs from @code{Value.referenced_value} by the fact that the
23264 behavior of @code{Value.dereference} is identical to applying the C
23265 unary operator @code{*} on a given value. For example, consider a
23266 reference to a pointer @code{ptrref}, declared in your C@t{++} program
23270 typedef int *intptr;
23274 intptr &ptrref = ptr;
23277 Though @code{ptrref} is a reference value, one can apply the method
23278 @code{Value.dereference} to the @code{gdb.Value} object corresponding
23279 to it and obtain a @code{gdb.Value} which is identical to that
23280 corresponding to @code{val}. However, if you apply the method
23281 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
23282 object identical to that corresponding to @code{ptr}.
23285 py_ptrref = gdb.parse_and_eval ("ptrref")
23286 py_val = py_ptrref.dereference ()
23287 py_ptr = py_ptrref.referenced_value ()
23290 The @code{gdb.Value} object @code{py_val} is identical to that
23291 corresponding to @code{val}, and @code{py_ptr} is identical to that
23292 corresponding to @code{ptr}. In general, @code{Value.dereference} can
23293 be applied whenever the C unary operator @code{*} can be applied
23294 to the corresponding C value. For those cases where applying both
23295 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
23296 the results obtained need not be identical (as we have seen in the above
23297 example). The results are however identical when applied on
23298 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
23299 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
23302 @defun Value.referenced_value ()
23303 For pointer or reference data types, this method returns a new
23304 @code{gdb.Value} object corresponding to the value referenced by the
23305 pointer/reference value. For pointer data types,
23306 @code{Value.dereference} and @code{Value.referenced_value} produce
23307 identical results. The difference between these methods is that
23308 @code{Value.dereference} cannot get the values referenced by reference
23309 values. For example, consider a reference to an @code{int}, declared
23310 in your C@t{++} program as
23318 then applying @code{Value.dereference} to the @code{gdb.Value} object
23319 corresponding to @code{ref} will result in an error, while applying
23320 @code{Value.referenced_value} will result in a @code{gdb.Value} object
23321 identical to that corresponding to @code{val}.
23324 py_ref = gdb.parse_and_eval ("ref")
23325 er_ref = py_ref.dereference () # Results in error
23326 py_val = py_ref.referenced_value () # Returns the referenced value
23329 The @code{gdb.Value} object @code{py_val} is identical to that
23330 corresponding to @code{val}.
23333 @defun Value.dynamic_cast (type)
23334 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
23335 operator were used. Consult a C@t{++} reference for details.
23338 @defun Value.reinterpret_cast (type)
23339 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
23340 operator were used. Consult a C@t{++} reference for details.
23343 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
23344 If this @code{gdb.Value} represents a string, then this method
23345 converts the contents to a Python string. Otherwise, this method will
23346 throw an exception.
23348 Strings are recognized in a language-specific way; whether a given
23349 @code{gdb.Value} represents a string is determined by the current
23352 For C-like languages, a value is a string if it is a pointer to or an
23353 array of characters or ints. The string is assumed to be terminated
23354 by a zero of the appropriate width. However if the optional length
23355 argument is given, the string will be converted to that given length,
23356 ignoring any embedded zeros that the string may contain.
23358 If the optional @var{encoding} argument is given, it must be a string
23359 naming the encoding of the string in the @code{gdb.Value}, such as
23360 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
23361 the same encodings as the corresponding argument to Python's
23362 @code{string.decode} method, and the Python codec machinery will be used
23363 to convert the string. If @var{encoding} is not given, or if
23364 @var{encoding} is the empty string, then either the @code{target-charset}
23365 (@pxref{Character Sets}) will be used, or a language-specific encoding
23366 will be used, if the current language is able to supply one.
23368 The optional @var{errors} argument is the same as the corresponding
23369 argument to Python's @code{string.decode} method.
23371 If the optional @var{length} argument is given, the string will be
23372 fetched and converted to the given length.
23375 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
23376 If this @code{gdb.Value} represents a string, then this method
23377 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
23378 In Python}). Otherwise, this method will throw an exception.
23380 If the optional @var{encoding} argument is given, it must be a string
23381 naming the encoding of the @code{gdb.LazyString}. Some examples are:
23382 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
23383 @var{encoding} argument is an encoding that @value{GDBN} does
23384 recognize, @value{GDBN} will raise an error.
23386 When a lazy string is printed, the @value{GDBN} encoding machinery is
23387 used to convert the string during printing. If the optional
23388 @var{encoding} argument is not provided, or is an empty string,
23389 @value{GDBN} will automatically select the encoding most suitable for
23390 the string type. For further information on encoding in @value{GDBN}
23391 please see @ref{Character Sets}.
23393 If the optional @var{length} argument is given, the string will be
23394 fetched and encoded to the length of characters specified. If
23395 the @var{length} argument is not provided, the string will be fetched
23396 and encoded until a null of appropriate width is found.
23399 @defun Value.fetch_lazy ()
23400 If the @code{gdb.Value} object is currently a lazy value
23401 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
23402 fetched from the inferior. Any errors that occur in the process
23403 will produce a Python exception.
23405 If the @code{gdb.Value} object is not a lazy value, this method
23408 This method does not return a value.
23413 @node Types In Python
23414 @subsubsection Types In Python
23415 @cindex types in Python
23416 @cindex Python, working with types
23419 @value{GDBN} represents types from the inferior using the class
23422 The following type-related functions are available in the @code{gdb}
23425 @findex gdb.lookup_type
23426 @defun gdb.lookup_type (name @r{[}, block@r{]})
23427 This function looks up a type by name. @var{name} is the name of the
23428 type to look up. It must be a string.
23430 If @var{block} is given, then @var{name} is looked up in that scope.
23431 Otherwise, it is searched for globally.
23433 Ordinarily, this function will return an instance of @code{gdb.Type}.
23434 If the named type cannot be found, it will throw an exception.
23437 If the type is a structure or class type, or an enum type, the fields
23438 of that type can be accessed using the Python @dfn{dictionary syntax}.
23439 For example, if @code{some_type} is a @code{gdb.Type} instance holding
23440 a structure type, you can access its @code{foo} field with:
23443 bar = some_type['foo']
23446 @code{bar} will be a @code{gdb.Field} object; see below under the
23447 description of the @code{Type.fields} method for a description of the
23448 @code{gdb.Field} class.
23450 An instance of @code{Type} has the following attributes:
23454 The type code for this type. The type code will be one of the
23455 @code{TYPE_CODE_} constants defined below.
23458 @defvar Type.sizeof
23459 The size of this type, in target @code{char} units. Usually, a
23460 target's @code{char} type will be an 8-bit byte. However, on some
23461 unusual platforms, this type may have a different size.
23465 The tag name for this type. The tag name is the name after
23466 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
23467 languages have this concept. If this type has no tag name, then
23468 @code{None} is returned.
23472 The following methods are provided:
23475 @defun Type.fields ()
23476 For structure and union types, this method returns the fields. Range
23477 types have two fields, the minimum and maximum values. Enum types
23478 have one field per enum constant. Function and method types have one
23479 field per parameter. The base types of C@t{++} classes are also
23480 represented as fields. If the type has no fields, or does not fit
23481 into one of these categories, an empty sequence will be returned.
23483 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
23486 This attribute is not available for @code{static} fields (as in
23487 C@t{++} or Java). For non-@code{static} fields, the value is the bit
23488 position of the field. For @code{enum} fields, the value is the
23489 enumeration member's integer representation.
23492 The name of the field, or @code{None} for anonymous fields.
23495 This is @code{True} if the field is artificial, usually meaning that
23496 it was provided by the compiler and not the user. This attribute is
23497 always provided, and is @code{False} if the field is not artificial.
23499 @item is_base_class
23500 This is @code{True} if the field represents a base class of a C@t{++}
23501 structure. This attribute is always provided, and is @code{False}
23502 if the field is not a base class of the type that is the argument of
23503 @code{fields}, or if that type was not a C@t{++} class.
23506 If the field is packed, or is a bitfield, then this will have a
23507 non-zero value, which is the size of the field in bits. Otherwise,
23508 this will be zero; in this case the field's size is given by its type.
23511 The type of the field. This is usually an instance of @code{Type},
23512 but it can be @code{None} in some situations.
23516 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
23517 Return a new @code{gdb.Type} object which represents an array of this
23518 type. If one argument is given, it is the inclusive upper bound of
23519 the array; in this case the lower bound is zero. If two arguments are
23520 given, the first argument is the lower bound of the array, and the
23521 second argument is the upper bound of the array. An array's length
23522 must not be negative, but the bounds can be.
23525 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
23526 Return a new @code{gdb.Type} object which represents a vector of this
23527 type. If one argument is given, it is the inclusive upper bound of
23528 the vector; in this case the lower bound is zero. If two arguments are
23529 given, the first argument is the lower bound of the vector, and the
23530 second argument is the upper bound of the vector. A vector's length
23531 must not be negative, but the bounds can be.
23533 The difference between an @code{array} and a @code{vector} is that
23534 arrays behave like in C: when used in expressions they decay to a pointer
23535 to the first element whereas vectors are treated as first class values.
23538 @defun Type.const ()
23539 Return a new @code{gdb.Type} object which represents a
23540 @code{const}-qualified variant of this type.
23543 @defun Type.volatile ()
23544 Return a new @code{gdb.Type} object which represents a
23545 @code{volatile}-qualified variant of this type.
23548 @defun Type.unqualified ()
23549 Return a new @code{gdb.Type} object which represents an unqualified
23550 variant of this type. That is, the result is neither @code{const} nor
23554 @defun Type.range ()
23555 Return a Python @code{Tuple} object that contains two elements: the
23556 low bound of the argument type and the high bound of that type. If
23557 the type does not have a range, @value{GDBN} will raise a
23558 @code{gdb.error} exception (@pxref{Exception Handling}).
23561 @defun Type.reference ()
23562 Return a new @code{gdb.Type} object which represents a reference to this
23566 @defun Type.pointer ()
23567 Return a new @code{gdb.Type} object which represents a pointer to this
23571 @defun Type.strip_typedefs ()
23572 Return a new @code{gdb.Type} that represents the real type,
23573 after removing all layers of typedefs.
23576 @defun Type.target ()
23577 Return a new @code{gdb.Type} object which represents the target type
23580 For a pointer type, the target type is the type of the pointed-to
23581 object. For an array type (meaning C-like arrays), the target type is
23582 the type of the elements of the array. For a function or method type,
23583 the target type is the type of the return value. For a complex type,
23584 the target type is the type of the elements. For a typedef, the
23585 target type is the aliased type.
23587 If the type does not have a target, this method will throw an
23591 @defun Type.template_argument (n @r{[}, block@r{]})
23592 If this @code{gdb.Type} is an instantiation of a template, this will
23593 return a new @code{gdb.Type} which represents the type of the
23594 @var{n}th template argument.
23596 If this @code{gdb.Type} is not a template type, this will throw an
23597 exception. Ordinarily, only C@t{++} code will have template types.
23599 If @var{block} is given, then @var{name} is looked up in that scope.
23600 Otherwise, it is searched for globally.
23605 Each type has a code, which indicates what category this type falls
23606 into. The available type categories are represented by constants
23607 defined in the @code{gdb} module:
23610 @findex TYPE_CODE_PTR
23611 @findex gdb.TYPE_CODE_PTR
23612 @item gdb.TYPE_CODE_PTR
23613 The type is a pointer.
23615 @findex TYPE_CODE_ARRAY
23616 @findex gdb.TYPE_CODE_ARRAY
23617 @item gdb.TYPE_CODE_ARRAY
23618 The type is an array.
23620 @findex TYPE_CODE_STRUCT
23621 @findex gdb.TYPE_CODE_STRUCT
23622 @item gdb.TYPE_CODE_STRUCT
23623 The type is a structure.
23625 @findex TYPE_CODE_UNION
23626 @findex gdb.TYPE_CODE_UNION
23627 @item gdb.TYPE_CODE_UNION
23628 The type is a union.
23630 @findex TYPE_CODE_ENUM
23631 @findex gdb.TYPE_CODE_ENUM
23632 @item gdb.TYPE_CODE_ENUM
23633 The type is an enum.
23635 @findex TYPE_CODE_FLAGS
23636 @findex gdb.TYPE_CODE_FLAGS
23637 @item gdb.TYPE_CODE_FLAGS
23638 A bit flags type, used for things such as status registers.
23640 @findex TYPE_CODE_FUNC
23641 @findex gdb.TYPE_CODE_FUNC
23642 @item gdb.TYPE_CODE_FUNC
23643 The type is a function.
23645 @findex TYPE_CODE_INT
23646 @findex gdb.TYPE_CODE_INT
23647 @item gdb.TYPE_CODE_INT
23648 The type is an integer type.
23650 @findex TYPE_CODE_FLT
23651 @findex gdb.TYPE_CODE_FLT
23652 @item gdb.TYPE_CODE_FLT
23653 A floating point type.
23655 @findex TYPE_CODE_VOID
23656 @findex gdb.TYPE_CODE_VOID
23657 @item gdb.TYPE_CODE_VOID
23658 The special type @code{void}.
23660 @findex TYPE_CODE_SET
23661 @findex gdb.TYPE_CODE_SET
23662 @item gdb.TYPE_CODE_SET
23665 @findex TYPE_CODE_RANGE
23666 @findex gdb.TYPE_CODE_RANGE
23667 @item gdb.TYPE_CODE_RANGE
23668 A range type, that is, an integer type with bounds.
23670 @findex TYPE_CODE_STRING
23671 @findex gdb.TYPE_CODE_STRING
23672 @item gdb.TYPE_CODE_STRING
23673 A string type. Note that this is only used for certain languages with
23674 language-defined string types; C strings are not represented this way.
23676 @findex TYPE_CODE_BITSTRING
23677 @findex gdb.TYPE_CODE_BITSTRING
23678 @item gdb.TYPE_CODE_BITSTRING
23679 A string of bits. It is deprecated.
23681 @findex TYPE_CODE_ERROR
23682 @findex gdb.TYPE_CODE_ERROR
23683 @item gdb.TYPE_CODE_ERROR
23684 An unknown or erroneous type.
23686 @findex TYPE_CODE_METHOD
23687 @findex gdb.TYPE_CODE_METHOD
23688 @item gdb.TYPE_CODE_METHOD
23689 A method type, as found in C@t{++} or Java.
23691 @findex TYPE_CODE_METHODPTR
23692 @findex gdb.TYPE_CODE_METHODPTR
23693 @item gdb.TYPE_CODE_METHODPTR
23694 A pointer-to-member-function.
23696 @findex TYPE_CODE_MEMBERPTR
23697 @findex gdb.TYPE_CODE_MEMBERPTR
23698 @item gdb.TYPE_CODE_MEMBERPTR
23699 A pointer-to-member.
23701 @findex TYPE_CODE_REF
23702 @findex gdb.TYPE_CODE_REF
23703 @item gdb.TYPE_CODE_REF
23706 @findex TYPE_CODE_CHAR
23707 @findex gdb.TYPE_CODE_CHAR
23708 @item gdb.TYPE_CODE_CHAR
23711 @findex TYPE_CODE_BOOL
23712 @findex gdb.TYPE_CODE_BOOL
23713 @item gdb.TYPE_CODE_BOOL
23716 @findex TYPE_CODE_COMPLEX
23717 @findex gdb.TYPE_CODE_COMPLEX
23718 @item gdb.TYPE_CODE_COMPLEX
23719 A complex float type.
23721 @findex TYPE_CODE_TYPEDEF
23722 @findex gdb.TYPE_CODE_TYPEDEF
23723 @item gdb.TYPE_CODE_TYPEDEF
23724 A typedef to some other type.
23726 @findex TYPE_CODE_NAMESPACE
23727 @findex gdb.TYPE_CODE_NAMESPACE
23728 @item gdb.TYPE_CODE_NAMESPACE
23729 A C@t{++} namespace.
23731 @findex TYPE_CODE_DECFLOAT
23732 @findex gdb.TYPE_CODE_DECFLOAT
23733 @item gdb.TYPE_CODE_DECFLOAT
23734 A decimal floating point type.
23736 @findex TYPE_CODE_INTERNAL_FUNCTION
23737 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
23738 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
23739 A function internal to @value{GDBN}. This is the type used to represent
23740 convenience functions.
23743 Further support for types is provided in the @code{gdb.types}
23744 Python module (@pxref{gdb.types}).
23746 @node Pretty Printing API
23747 @subsubsection Pretty Printing API
23749 An example output is provided (@pxref{Pretty Printing}).
23751 A pretty-printer is just an object that holds a value and implements a
23752 specific interface, defined here.
23754 @defun pretty_printer.children (self)
23755 @value{GDBN} will call this method on a pretty-printer to compute the
23756 children of the pretty-printer's value.
23758 This method must return an object conforming to the Python iterator
23759 protocol. Each item returned by the iterator must be a tuple holding
23760 two elements. The first element is the ``name'' of the child; the
23761 second element is the child's value. The value can be any Python
23762 object which is convertible to a @value{GDBN} value.
23764 This method is optional. If it does not exist, @value{GDBN} will act
23765 as though the value has no children.
23768 @defun pretty_printer.display_hint (self)
23769 The CLI may call this method and use its result to change the
23770 formatting of a value. The result will also be supplied to an MI
23771 consumer as a @samp{displayhint} attribute of the variable being
23774 This method is optional. If it does exist, this method must return a
23777 Some display hints are predefined by @value{GDBN}:
23781 Indicate that the object being printed is ``array-like''. The CLI
23782 uses this to respect parameters such as @code{set print elements} and
23783 @code{set print array}.
23786 Indicate that the object being printed is ``map-like'', and that the
23787 children of this value can be assumed to alternate between keys and
23791 Indicate that the object being printed is ``string-like''. If the
23792 printer's @code{to_string} method returns a Python string of some
23793 kind, then @value{GDBN} will call its internal language-specific
23794 string-printing function to format the string. For the CLI this means
23795 adding quotation marks, possibly escaping some characters, respecting
23796 @code{set print elements}, and the like.
23800 @defun pretty_printer.to_string (self)
23801 @value{GDBN} will call this method to display the string
23802 representation of the value passed to the object's constructor.
23804 When printing from the CLI, if the @code{to_string} method exists,
23805 then @value{GDBN} will prepend its result to the values returned by
23806 @code{children}. Exactly how this formatting is done is dependent on
23807 the display hint, and may change as more hints are added. Also,
23808 depending on the print settings (@pxref{Print Settings}), the CLI may
23809 print just the result of @code{to_string} in a stack trace, omitting
23810 the result of @code{children}.
23812 If this method returns a string, it is printed verbatim.
23814 Otherwise, if this method returns an instance of @code{gdb.Value},
23815 then @value{GDBN} prints this value. This may result in a call to
23816 another pretty-printer.
23818 If instead the method returns a Python value which is convertible to a
23819 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
23820 the resulting value. Again, this may result in a call to another
23821 pretty-printer. Python scalars (integers, floats, and booleans) and
23822 strings are convertible to @code{gdb.Value}; other types are not.
23824 Finally, if this method returns @code{None} then no further operations
23825 are peformed in this method and nothing is printed.
23827 If the result is not one of these types, an exception is raised.
23830 @value{GDBN} provides a function which can be used to look up the
23831 default pretty-printer for a @code{gdb.Value}:
23833 @findex gdb.default_visualizer
23834 @defun gdb.default_visualizer (value)
23835 This function takes a @code{gdb.Value} object as an argument. If a
23836 pretty-printer for this value exists, then it is returned. If no such
23837 printer exists, then this returns @code{None}.
23840 @node Selecting Pretty-Printers
23841 @subsubsection Selecting Pretty-Printers
23843 The Python list @code{gdb.pretty_printers} contains an array of
23844 functions or callable objects that have been registered via addition
23845 as a pretty-printer. Printers in this list are called @code{global}
23846 printers, they're available when debugging all inferiors.
23847 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
23848 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
23851 Each function on these lists is passed a single @code{gdb.Value}
23852 argument and should return a pretty-printer object conforming to the
23853 interface definition above (@pxref{Pretty Printing API}). If a function
23854 cannot create a pretty-printer for the value, it should return
23857 @value{GDBN} first checks the @code{pretty_printers} attribute of each
23858 @code{gdb.Objfile} in the current program space and iteratively calls
23859 each enabled lookup routine in the list for that @code{gdb.Objfile}
23860 until it receives a pretty-printer object.
23861 If no pretty-printer is found in the objfile lists, @value{GDBN} then
23862 searches the pretty-printer list of the current program space,
23863 calling each enabled function until an object is returned.
23864 After these lists have been exhausted, it tries the global
23865 @code{gdb.pretty_printers} list, again calling each enabled function until an
23866 object is returned.
23868 The order in which the objfiles are searched is not specified. For a
23869 given list, functions are always invoked from the head of the list,
23870 and iterated over sequentially until the end of the list, or a printer
23871 object is returned.
23873 For various reasons a pretty-printer may not work.
23874 For example, the underlying data structure may have changed and
23875 the pretty-printer is out of date.
23877 The consequences of a broken pretty-printer are severe enough that
23878 @value{GDBN} provides support for enabling and disabling individual
23879 printers. For example, if @code{print frame-arguments} is on,
23880 a backtrace can become highly illegible if any argument is printed
23881 with a broken printer.
23883 Pretty-printers are enabled and disabled by attaching an @code{enabled}
23884 attribute to the registered function or callable object. If this attribute
23885 is present and its value is @code{False}, the printer is disabled, otherwise
23886 the printer is enabled.
23888 @node Writing a Pretty-Printer
23889 @subsubsection Writing a Pretty-Printer
23890 @cindex writing a pretty-printer
23892 A pretty-printer consists of two parts: a lookup function to detect
23893 if the type is supported, and the printer itself.
23895 Here is an example showing how a @code{std::string} printer might be
23896 written. @xref{Pretty Printing API}, for details on the API this class
23900 class StdStringPrinter(object):
23901 "Print a std::string"
23903 def __init__(self, val):
23906 def to_string(self):
23907 return self.val['_M_dataplus']['_M_p']
23909 def display_hint(self):
23913 And here is an example showing how a lookup function for the printer
23914 example above might be written.
23917 def str_lookup_function(val):
23918 lookup_tag = val.type.tag
23919 if lookup_tag == None:
23921 regex = re.compile("^std::basic_string<char,.*>$")
23922 if regex.match(lookup_tag):
23923 return StdStringPrinter(val)
23927 The example lookup function extracts the value's type, and attempts to
23928 match it to a type that it can pretty-print. If it is a type the
23929 printer can pretty-print, it will return a printer object. If not, it
23930 returns @code{None}.
23932 We recommend that you put your core pretty-printers into a Python
23933 package. If your pretty-printers are for use with a library, we
23934 further recommend embedding a version number into the package name.
23935 This practice will enable @value{GDBN} to load multiple versions of
23936 your pretty-printers at the same time, because they will have
23939 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
23940 can be evaluated multiple times without changing its meaning. An
23941 ideal auto-load file will consist solely of @code{import}s of your
23942 printer modules, followed by a call to a register pretty-printers with
23943 the current objfile.
23945 Taken as a whole, this approach will scale nicely to multiple
23946 inferiors, each potentially using a different library version.
23947 Embedding a version number in the Python package name will ensure that
23948 @value{GDBN} is able to load both sets of printers simultaneously.
23949 Then, because the search for pretty-printers is done by objfile, and
23950 because your auto-loaded code took care to register your library's
23951 printers with a specific objfile, @value{GDBN} will find the correct
23952 printers for the specific version of the library used by each
23955 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
23956 this code might appear in @code{gdb.libstdcxx.v6}:
23959 def register_printers(objfile):
23960 objfile.pretty_printers.append(str_lookup_function)
23964 And then the corresponding contents of the auto-load file would be:
23967 import gdb.libstdcxx.v6
23968 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
23971 The previous example illustrates a basic pretty-printer.
23972 There are a few things that can be improved on.
23973 The printer doesn't have a name, making it hard to identify in a
23974 list of installed printers. The lookup function has a name, but
23975 lookup functions can have arbitrary, even identical, names.
23977 Second, the printer only handles one type, whereas a library typically has
23978 several types. One could install a lookup function for each desired type
23979 in the library, but one could also have a single lookup function recognize
23980 several types. The latter is the conventional way this is handled.
23981 If a pretty-printer can handle multiple data types, then its
23982 @dfn{subprinters} are the printers for the individual data types.
23984 The @code{gdb.printing} module provides a formal way of solving these
23985 problems (@pxref{gdb.printing}).
23986 Here is another example that handles multiple types.
23988 These are the types we are going to pretty-print:
23991 struct foo @{ int a, b; @};
23992 struct bar @{ struct foo x, y; @};
23995 Here are the printers:
23999 """Print a foo object."""
24001 def __init__(self, val):
24004 def to_string(self):
24005 return ("a=<" + str(self.val["a"]) +
24006 "> b=<" + str(self.val["b"]) + ">")
24009 """Print a bar object."""
24011 def __init__(self, val):
24014 def to_string(self):
24015 return ("x=<" + str(self.val["x"]) +
24016 "> y=<" + str(self.val["y"]) + ">")
24019 This example doesn't need a lookup function, that is handled by the
24020 @code{gdb.printing} module. Instead a function is provided to build up
24021 the object that handles the lookup.
24024 import gdb.printing
24026 def build_pretty_printer():
24027 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24029 pp.add_printer('foo', '^foo$', fooPrinter)
24030 pp.add_printer('bar', '^bar$', barPrinter)
24034 And here is the autoload support:
24037 import gdb.printing
24039 gdb.printing.register_pretty_printer(
24040 gdb.current_objfile(),
24041 my_library.build_pretty_printer())
24044 Finally, when this printer is loaded into @value{GDBN}, here is the
24045 corresponding output of @samp{info pretty-printer}:
24048 (gdb) info pretty-printer
24055 @node Type Printing API
24056 @subsubsection Type Printing API
24057 @cindex type printing API for Python
24059 @value{GDBN} provides a way for Python code to customize type display.
24060 This is mainly useful for substituting canonical typedef names for
24063 @cindex type printer
24064 A @dfn{type printer} is just a Python object conforming to a certain
24065 protocol. A simple base class implementing the protocol is provided;
24066 see @ref{gdb.types}. A type printer must supply at least:
24068 @defivar type_printer enabled
24069 A boolean which is True if the printer is enabled, and False
24070 otherwise. This is manipulated by the @code{enable type-printer}
24071 and @code{disable type-printer} commands.
24074 @defivar type_printer name
24075 The name of the type printer. This must be a string. This is used by
24076 the @code{enable type-printer} and @code{disable type-printer}
24080 @defmethod type_printer instantiate (self)
24081 This is called by @value{GDBN} at the start of type-printing. It is
24082 only called if the type printer is enabled. This method must return a
24083 new object that supplies a @code{recognize} method, as described below.
24087 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24088 will compute a list of type recognizers. This is done by iterating
24089 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24090 followed by the per-progspace type printers (@pxref{Progspaces In
24091 Python}), and finally the global type printers.
24093 @value{GDBN} will call the @code{instantiate} method of each enabled
24094 type printer. If this method returns @code{None}, then the result is
24095 ignored; otherwise, it is appended to the list of recognizers.
24097 Then, when @value{GDBN} is going to display a type name, it iterates
24098 over the list of recognizers. For each one, it calls the recognition
24099 function, stopping if the function returns a non-@code{None} value.
24100 The recognition function is defined as:
24102 @defmethod type_recognizer recognize (self, type)
24103 If @var{type} is not recognized, return @code{None}. Otherwise,
24104 return a string which is to be printed as the name of @var{type}.
24105 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24109 @value{GDBN} uses this two-pass approach so that type printers can
24110 efficiently cache information without holding on to it too long. For
24111 example, it can be convenient to look up type information in a type
24112 printer and hold it for a recognizer's lifetime; if a single pass were
24113 done then type printers would have to make use of the event system in
24114 order to avoid holding information that could become stale as the
24117 @node Inferiors In Python
24118 @subsubsection Inferiors In Python
24119 @cindex inferiors in Python
24121 @findex gdb.Inferior
24122 Programs which are being run under @value{GDBN} are called inferiors
24123 (@pxref{Inferiors and Programs}). Python scripts can access
24124 information about and manipulate inferiors controlled by @value{GDBN}
24125 via objects of the @code{gdb.Inferior} class.
24127 The following inferior-related functions are available in the @code{gdb}
24130 @defun gdb.inferiors ()
24131 Return a tuple containing all inferior objects.
24134 @defun gdb.selected_inferior ()
24135 Return an object representing the current inferior.
24138 A @code{gdb.Inferior} object has the following attributes:
24141 @defvar Inferior.num
24142 ID of inferior, as assigned by GDB.
24145 @defvar Inferior.pid
24146 Process ID of the inferior, as assigned by the underlying operating
24150 @defvar Inferior.was_attached
24151 Boolean signaling whether the inferior was created using `attach', or
24152 started by @value{GDBN} itself.
24156 A @code{gdb.Inferior} object has the following methods:
24159 @defun Inferior.is_valid ()
24160 Returns @code{True} if the @code{gdb.Inferior} object is valid,
24161 @code{False} if not. A @code{gdb.Inferior} object will become invalid
24162 if the inferior no longer exists within @value{GDBN}. All other
24163 @code{gdb.Inferior} methods will throw an exception if it is invalid
24164 at the time the method is called.
24167 @defun Inferior.threads ()
24168 This method returns a tuple holding all the threads which are valid
24169 when it is called. If there are no valid threads, the method will
24170 return an empty tuple.
24173 @findex Inferior.read_memory
24174 @defun Inferior.read_memory (address, length)
24175 Read @var{length} bytes of memory from the inferior, starting at
24176 @var{address}. Returns a buffer object, which behaves much like an array
24177 or a string. It can be modified and given to the
24178 @code{Inferior.write_memory} function. In @code{Python} 3, the return
24179 value is a @code{memoryview} object.
24182 @findex Inferior.write_memory
24183 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
24184 Write the contents of @var{buffer} to the inferior, starting at
24185 @var{address}. The @var{buffer} parameter must be a Python object
24186 which supports the buffer protocol, i.e., a string, an array or the
24187 object returned from @code{Inferior.read_memory}. If given, @var{length}
24188 determines the number of bytes from @var{buffer} to be written.
24191 @findex gdb.search_memory
24192 @defun Inferior.search_memory (address, length, pattern)
24193 Search a region of the inferior memory starting at @var{address} with
24194 the given @var{length} using the search pattern supplied in
24195 @var{pattern}. The @var{pattern} parameter must be a Python object
24196 which supports the buffer protocol, i.e., a string, an array or the
24197 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
24198 containing the address where the pattern was found, or @code{None} if
24199 the pattern could not be found.
24203 @node Events In Python
24204 @subsubsection Events In Python
24205 @cindex inferior events in Python
24207 @value{GDBN} provides a general event facility so that Python code can be
24208 notified of various state changes, particularly changes that occur in
24211 An @dfn{event} is just an object that describes some state change. The
24212 type of the object and its attributes will vary depending on the details
24213 of the change. All the existing events are described below.
24215 In order to be notified of an event, you must register an event handler
24216 with an @dfn{event registry}. An event registry is an object in the
24217 @code{gdb.events} module which dispatches particular events. A registry
24218 provides methods to register and unregister event handlers:
24221 @defun EventRegistry.connect (object)
24222 Add the given callable @var{object} to the registry. This object will be
24223 called when an event corresponding to this registry occurs.
24226 @defun EventRegistry.disconnect (object)
24227 Remove the given @var{object} from the registry. Once removed, the object
24228 will no longer receive notifications of events.
24232 Here is an example:
24235 def exit_handler (event):
24236 print "event type: exit"
24237 print "exit code: %d" % (event.exit_code)
24239 gdb.events.exited.connect (exit_handler)
24242 In the above example we connect our handler @code{exit_handler} to the
24243 registry @code{events.exited}. Once connected, @code{exit_handler} gets
24244 called when the inferior exits. The argument @dfn{event} in this example is
24245 of type @code{gdb.ExitedEvent}. As you can see in the example the
24246 @code{ExitedEvent} object has an attribute which indicates the exit code of
24249 The following is a listing of the event registries that are available and
24250 details of the events they emit:
24255 Emits @code{gdb.ThreadEvent}.
24257 Some events can be thread specific when @value{GDBN} is running in non-stop
24258 mode. When represented in Python, these events all extend
24259 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
24260 events which are emitted by this or other modules might extend this event.
24261 Examples of these events are @code{gdb.BreakpointEvent} and
24262 @code{gdb.ContinueEvent}.
24265 @defvar ThreadEvent.inferior_thread
24266 In non-stop mode this attribute will be set to the specific thread which was
24267 involved in the emitted event. Otherwise, it will be set to @code{None}.
24271 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
24273 This event indicates that the inferior has been continued after a stop. For
24274 inherited attribute refer to @code{gdb.ThreadEvent} above.
24276 @item events.exited
24277 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
24278 @code{events.ExitedEvent} has two attributes:
24280 @defvar ExitedEvent.exit_code
24281 An integer representing the exit code, if available, which the inferior
24282 has returned. (The exit code could be unavailable if, for example,
24283 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
24284 the attribute does not exist.
24286 @defvar ExitedEvent inferior
24287 A reference to the inferior which triggered the @code{exited} event.
24292 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
24294 Indicates that the inferior has stopped. All events emitted by this registry
24295 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
24296 will indicate the stopped thread when @value{GDBN} is running in non-stop
24297 mode. Refer to @code{gdb.ThreadEvent} above for more details.
24299 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
24301 This event indicates that the inferior or one of its threads has received as
24302 signal. @code{gdb.SignalEvent} has the following attributes:
24305 @defvar SignalEvent.stop_signal
24306 A string representing the signal received by the inferior. A list of possible
24307 signal values can be obtained by running the command @code{info signals} in
24308 the @value{GDBN} command prompt.
24312 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
24314 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
24315 been hit, and has the following attributes:
24318 @defvar BreakpointEvent.breakpoints
24319 A sequence containing references to all the breakpoints (type
24320 @code{gdb.Breakpoint}) that were hit.
24321 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
24323 @defvar BreakpointEvent.breakpoint
24324 A reference to the first breakpoint that was hit.
24325 This function is maintained for backward compatibility and is now deprecated
24326 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
24330 @item events.new_objfile
24331 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
24332 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
24335 @defvar NewObjFileEvent.new_objfile
24336 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
24337 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
24343 @node Threads In Python
24344 @subsubsection Threads In Python
24345 @cindex threads in python
24347 @findex gdb.InferiorThread
24348 Python scripts can access information about, and manipulate inferior threads
24349 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
24351 The following thread-related functions are available in the @code{gdb}
24354 @findex gdb.selected_thread
24355 @defun gdb.selected_thread ()
24356 This function returns the thread object for the selected thread. If there
24357 is no selected thread, this will return @code{None}.
24360 A @code{gdb.InferiorThread} object has the following attributes:
24363 @defvar InferiorThread.name
24364 The name of the thread. If the user specified a name using
24365 @code{thread name}, then this returns that name. Otherwise, if an
24366 OS-supplied name is available, then it is returned. Otherwise, this
24367 returns @code{None}.
24369 This attribute can be assigned to. The new value must be a string
24370 object, which sets the new name, or @code{None}, which removes any
24371 user-specified thread name.
24374 @defvar InferiorThread.num
24375 ID of the thread, as assigned by GDB.
24378 @defvar InferiorThread.ptid
24379 ID of the thread, as assigned by the operating system. This attribute is a
24380 tuple containing three integers. The first is the Process ID (PID); the second
24381 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
24382 Either the LWPID or TID may be 0, which indicates that the operating system
24383 does not use that identifier.
24387 A @code{gdb.InferiorThread} object has the following methods:
24390 @defun InferiorThread.is_valid ()
24391 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
24392 @code{False} if not. A @code{gdb.InferiorThread} object will become
24393 invalid if the thread exits, or the inferior that the thread belongs
24394 is deleted. All other @code{gdb.InferiorThread} methods will throw an
24395 exception if it is invalid at the time the method is called.
24398 @defun InferiorThread.switch ()
24399 This changes @value{GDBN}'s currently selected thread to the one represented
24403 @defun InferiorThread.is_stopped ()
24404 Return a Boolean indicating whether the thread is stopped.
24407 @defun InferiorThread.is_running ()
24408 Return a Boolean indicating whether the thread is running.
24411 @defun InferiorThread.is_exited ()
24412 Return a Boolean indicating whether the thread is exited.
24416 @node Commands In Python
24417 @subsubsection Commands In Python
24419 @cindex commands in python
24420 @cindex python commands
24421 You can implement new @value{GDBN} CLI commands in Python. A CLI
24422 command is implemented using an instance of the @code{gdb.Command}
24423 class, most commonly using a subclass.
24425 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
24426 The object initializer for @code{Command} registers the new command
24427 with @value{GDBN}. This initializer is normally invoked from the
24428 subclass' own @code{__init__} method.
24430 @var{name} is the name of the command. If @var{name} consists of
24431 multiple words, then the initial words are looked for as prefix
24432 commands. In this case, if one of the prefix commands does not exist,
24433 an exception is raised.
24435 There is no support for multi-line commands.
24437 @var{command_class} should be one of the @samp{COMMAND_} constants
24438 defined below. This argument tells @value{GDBN} how to categorize the
24439 new command in the help system.
24441 @var{completer_class} is an optional argument. If given, it should be
24442 one of the @samp{COMPLETE_} constants defined below. This argument
24443 tells @value{GDBN} how to perform completion for this command. If not
24444 given, @value{GDBN} will attempt to complete using the object's
24445 @code{complete} method (see below); if no such method is found, an
24446 error will occur when completion is attempted.
24448 @var{prefix} is an optional argument. If @code{True}, then the new
24449 command is a prefix command; sub-commands of this command may be
24452 The help text for the new command is taken from the Python
24453 documentation string for the command's class, if there is one. If no
24454 documentation string is provided, the default value ``This command is
24455 not documented.'' is used.
24458 @cindex don't repeat Python command
24459 @defun Command.dont_repeat ()
24460 By default, a @value{GDBN} command is repeated when the user enters a
24461 blank line at the command prompt. A command can suppress this
24462 behavior by invoking the @code{dont_repeat} method. This is similar
24463 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
24466 @defun Command.invoke (argument, from_tty)
24467 This method is called by @value{GDBN} when this command is invoked.
24469 @var{argument} is a string. It is the argument to the command, after
24470 leading and trailing whitespace has been stripped.
24472 @var{from_tty} is a boolean argument. When true, this means that the
24473 command was entered by the user at the terminal; when false it means
24474 that the command came from elsewhere.
24476 If this method throws an exception, it is turned into a @value{GDBN}
24477 @code{error} call. Otherwise, the return value is ignored.
24479 @findex gdb.string_to_argv
24480 To break @var{argument} up into an argv-like string use
24481 @code{gdb.string_to_argv}. This function behaves identically to
24482 @value{GDBN}'s internal argument lexer @code{buildargv}.
24483 It is recommended to use this for consistency.
24484 Arguments are separated by spaces and may be quoted.
24488 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
24489 ['1', '2 "3', '4 "5', "6 '7"]
24494 @cindex completion of Python commands
24495 @defun Command.complete (text, word)
24496 This method is called by @value{GDBN} when the user attempts
24497 completion on this command. All forms of completion are handled by
24498 this method, that is, the @key{TAB} and @key{M-?} key bindings
24499 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
24502 The arguments @var{text} and @var{word} are both strings. @var{text}
24503 holds the complete command line up to the cursor's location.
24504 @var{word} holds the last word of the command line; this is computed
24505 using a word-breaking heuristic.
24507 The @code{complete} method can return several values:
24510 If the return value is a sequence, the contents of the sequence are
24511 used as the completions. It is up to @code{complete} to ensure that the
24512 contents actually do complete the word. A zero-length sequence is
24513 allowed, it means that there were no completions available. Only
24514 string elements of the sequence are used; other elements in the
24515 sequence are ignored.
24518 If the return value is one of the @samp{COMPLETE_} constants defined
24519 below, then the corresponding @value{GDBN}-internal completion
24520 function is invoked, and its result is used.
24523 All other results are treated as though there were no available
24528 When a new command is registered, it must be declared as a member of
24529 some general class of commands. This is used to classify top-level
24530 commands in the on-line help system; note that prefix commands are not
24531 listed under their own category but rather that of their top-level
24532 command. The available classifications are represented by constants
24533 defined in the @code{gdb} module:
24536 @findex COMMAND_NONE
24537 @findex gdb.COMMAND_NONE
24538 @item gdb.COMMAND_NONE
24539 The command does not belong to any particular class. A command in
24540 this category will not be displayed in any of the help categories.
24542 @findex COMMAND_RUNNING
24543 @findex gdb.COMMAND_RUNNING
24544 @item gdb.COMMAND_RUNNING
24545 The command is related to running the inferior. For example,
24546 @code{start}, @code{step}, and @code{continue} are in this category.
24547 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
24548 commands in this category.
24550 @findex COMMAND_DATA
24551 @findex gdb.COMMAND_DATA
24552 @item gdb.COMMAND_DATA
24553 The command is related to data or variables. For example,
24554 @code{call}, @code{find}, and @code{print} are in this category. Type
24555 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
24558 @findex COMMAND_STACK
24559 @findex gdb.COMMAND_STACK
24560 @item gdb.COMMAND_STACK
24561 The command has to do with manipulation of the stack. For example,
24562 @code{backtrace}, @code{frame}, and @code{return} are in this
24563 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
24564 list of commands in this category.
24566 @findex COMMAND_FILES
24567 @findex gdb.COMMAND_FILES
24568 @item gdb.COMMAND_FILES
24569 This class is used for file-related commands. For example,
24570 @code{file}, @code{list} and @code{section} are in this category.
24571 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
24572 commands in this category.
24574 @findex COMMAND_SUPPORT
24575 @findex gdb.COMMAND_SUPPORT
24576 @item gdb.COMMAND_SUPPORT
24577 This should be used for ``support facilities'', generally meaning
24578 things that are useful to the user when interacting with @value{GDBN},
24579 but not related to the state of the inferior. For example,
24580 @code{help}, @code{make}, and @code{shell} are in this category. Type
24581 @kbd{help support} at the @value{GDBN} prompt to see a list of
24582 commands in this category.
24584 @findex COMMAND_STATUS
24585 @findex gdb.COMMAND_STATUS
24586 @item gdb.COMMAND_STATUS
24587 The command is an @samp{info}-related command, that is, related to the
24588 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
24589 and @code{show} are in this category. Type @kbd{help status} at the
24590 @value{GDBN} prompt to see a list of commands in this category.
24592 @findex COMMAND_BREAKPOINTS
24593 @findex gdb.COMMAND_BREAKPOINTS
24594 @item gdb.COMMAND_BREAKPOINTS
24595 The command has to do with breakpoints. For example, @code{break},
24596 @code{clear}, and @code{delete} are in this category. Type @kbd{help
24597 breakpoints} at the @value{GDBN} prompt to see a list of commands in
24600 @findex COMMAND_TRACEPOINTS
24601 @findex gdb.COMMAND_TRACEPOINTS
24602 @item gdb.COMMAND_TRACEPOINTS
24603 The command has to do with tracepoints. For example, @code{trace},
24604 @code{actions}, and @code{tfind} are in this category. Type
24605 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
24606 commands in this category.
24608 @findex COMMAND_USER
24609 @findex gdb.COMMAND_USER
24610 @item gdb.COMMAND_USER
24611 The command is a general purpose command for the user, and typically
24612 does not fit in one of the other categories.
24613 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
24614 a list of commands in this category, as well as the list of gdb macros
24615 (@pxref{Sequences}).
24617 @findex COMMAND_OBSCURE
24618 @findex gdb.COMMAND_OBSCURE
24619 @item gdb.COMMAND_OBSCURE
24620 The command is only used in unusual circumstances, or is not of
24621 general interest to users. For example, @code{checkpoint},
24622 @code{fork}, and @code{stop} are in this category. Type @kbd{help
24623 obscure} at the @value{GDBN} prompt to see a list of commands in this
24626 @findex COMMAND_MAINTENANCE
24627 @findex gdb.COMMAND_MAINTENANCE
24628 @item gdb.COMMAND_MAINTENANCE
24629 The command is only useful to @value{GDBN} maintainers. The
24630 @code{maintenance} and @code{flushregs} commands are in this category.
24631 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
24632 commands in this category.
24635 A new command can use a predefined completion function, either by
24636 specifying it via an argument at initialization, or by returning it
24637 from the @code{complete} method. These predefined completion
24638 constants are all defined in the @code{gdb} module:
24641 @findex COMPLETE_NONE
24642 @findex gdb.COMPLETE_NONE
24643 @item gdb.COMPLETE_NONE
24644 This constant means that no completion should be done.
24646 @findex COMPLETE_FILENAME
24647 @findex gdb.COMPLETE_FILENAME
24648 @item gdb.COMPLETE_FILENAME
24649 This constant means that filename completion should be performed.
24651 @findex COMPLETE_LOCATION
24652 @findex gdb.COMPLETE_LOCATION
24653 @item gdb.COMPLETE_LOCATION
24654 This constant means that location completion should be done.
24655 @xref{Specify Location}.
24657 @findex COMPLETE_COMMAND
24658 @findex gdb.COMPLETE_COMMAND
24659 @item gdb.COMPLETE_COMMAND
24660 This constant means that completion should examine @value{GDBN}
24663 @findex COMPLETE_SYMBOL
24664 @findex gdb.COMPLETE_SYMBOL
24665 @item gdb.COMPLETE_SYMBOL
24666 This constant means that completion should be done using symbol names
24670 The following code snippet shows how a trivial CLI command can be
24671 implemented in Python:
24674 class HelloWorld (gdb.Command):
24675 """Greet the whole world."""
24677 def __init__ (self):
24678 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
24680 def invoke (self, arg, from_tty):
24681 print "Hello, World!"
24686 The last line instantiates the class, and is necessary to trigger the
24687 registration of the command with @value{GDBN}. Depending on how the
24688 Python code is read into @value{GDBN}, you may need to import the
24689 @code{gdb} module explicitly.
24691 @node Parameters In Python
24692 @subsubsection Parameters In Python
24694 @cindex parameters in python
24695 @cindex python parameters
24696 @tindex gdb.Parameter
24698 You can implement new @value{GDBN} parameters using Python. A new
24699 parameter is implemented as an instance of the @code{gdb.Parameter}
24702 Parameters are exposed to the user via the @code{set} and
24703 @code{show} commands. @xref{Help}.
24705 There are many parameters that already exist and can be set in
24706 @value{GDBN}. Two examples are: @code{set follow fork} and
24707 @code{set charset}. Setting these parameters influences certain
24708 behavior in @value{GDBN}. Similarly, you can define parameters that
24709 can be used to influence behavior in custom Python scripts and commands.
24711 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
24712 The object initializer for @code{Parameter} registers the new
24713 parameter with @value{GDBN}. This initializer is normally invoked
24714 from the subclass' own @code{__init__} method.
24716 @var{name} is the name of the new parameter. If @var{name} consists
24717 of multiple words, then the initial words are looked for as prefix
24718 parameters. An example of this can be illustrated with the
24719 @code{set print} set of parameters. If @var{name} is
24720 @code{print foo}, then @code{print} will be searched as the prefix
24721 parameter. In this case the parameter can subsequently be accessed in
24722 @value{GDBN} as @code{set print foo}.
24724 If @var{name} consists of multiple words, and no prefix parameter group
24725 can be found, an exception is raised.
24727 @var{command-class} should be one of the @samp{COMMAND_} constants
24728 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
24729 categorize the new parameter in the help system.
24731 @var{parameter-class} should be one of the @samp{PARAM_} constants
24732 defined below. This argument tells @value{GDBN} the type of the new
24733 parameter; this information is used for input validation and
24736 If @var{parameter-class} is @code{PARAM_ENUM}, then
24737 @var{enum-sequence} must be a sequence of strings. These strings
24738 represent the possible values for the parameter.
24740 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
24741 of a fourth argument will cause an exception to be thrown.
24743 The help text for the new parameter is taken from the Python
24744 documentation string for the parameter's class, if there is one. If
24745 there is no documentation string, a default value is used.
24748 @defvar Parameter.set_doc
24749 If this attribute exists, and is a string, then its value is used as
24750 the help text for this parameter's @code{set} command. The value is
24751 examined when @code{Parameter.__init__} is invoked; subsequent changes
24755 @defvar Parameter.show_doc
24756 If this attribute exists, and is a string, then its value is used as
24757 the help text for this parameter's @code{show} command. The value is
24758 examined when @code{Parameter.__init__} is invoked; subsequent changes
24762 @defvar Parameter.value
24763 The @code{value} attribute holds the underlying value of the
24764 parameter. It can be read and assigned to just as any other
24765 attribute. @value{GDBN} does validation when assignments are made.
24768 There are two methods that should be implemented in any
24769 @code{Parameter} class. These are:
24771 @defun Parameter.get_set_string (self)
24772 @value{GDBN} will call this method when a @var{parameter}'s value has
24773 been changed via the @code{set} API (for example, @kbd{set foo off}).
24774 The @code{value} attribute has already been populated with the new
24775 value and may be used in output. This method must return a string.
24778 @defun Parameter.get_show_string (self, svalue)
24779 @value{GDBN} will call this method when a @var{parameter}'s
24780 @code{show} API has been invoked (for example, @kbd{show foo}). The
24781 argument @code{svalue} receives the string representation of the
24782 current value. This method must return a string.
24785 When a new parameter is defined, its type must be specified. The
24786 available types are represented by constants defined in the @code{gdb}
24790 @findex PARAM_BOOLEAN
24791 @findex gdb.PARAM_BOOLEAN
24792 @item gdb.PARAM_BOOLEAN
24793 The value is a plain boolean. The Python boolean values, @code{True}
24794 and @code{False} are the only valid values.
24796 @findex PARAM_AUTO_BOOLEAN
24797 @findex gdb.PARAM_AUTO_BOOLEAN
24798 @item gdb.PARAM_AUTO_BOOLEAN
24799 The value has three possible states: true, false, and @samp{auto}. In
24800 Python, true and false are represented using boolean constants, and
24801 @samp{auto} is represented using @code{None}.
24803 @findex PARAM_UINTEGER
24804 @findex gdb.PARAM_UINTEGER
24805 @item gdb.PARAM_UINTEGER
24806 The value is an unsigned integer. The value of 0 should be
24807 interpreted to mean ``unlimited''.
24809 @findex PARAM_INTEGER
24810 @findex gdb.PARAM_INTEGER
24811 @item gdb.PARAM_INTEGER
24812 The value is a signed integer. The value of 0 should be interpreted
24813 to mean ``unlimited''.
24815 @findex PARAM_STRING
24816 @findex gdb.PARAM_STRING
24817 @item gdb.PARAM_STRING
24818 The value is a string. When the user modifies the string, any escape
24819 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
24820 translated into corresponding characters and encoded into the current
24823 @findex PARAM_STRING_NOESCAPE
24824 @findex gdb.PARAM_STRING_NOESCAPE
24825 @item gdb.PARAM_STRING_NOESCAPE
24826 The value is a string. When the user modifies the string, escapes are
24827 passed through untranslated.
24829 @findex PARAM_OPTIONAL_FILENAME
24830 @findex gdb.PARAM_OPTIONAL_FILENAME
24831 @item gdb.PARAM_OPTIONAL_FILENAME
24832 The value is a either a filename (a string), or @code{None}.
24834 @findex PARAM_FILENAME
24835 @findex gdb.PARAM_FILENAME
24836 @item gdb.PARAM_FILENAME
24837 The value is a filename. This is just like
24838 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
24840 @findex PARAM_ZINTEGER
24841 @findex gdb.PARAM_ZINTEGER
24842 @item gdb.PARAM_ZINTEGER
24843 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
24844 is interpreted as itself.
24847 @findex gdb.PARAM_ENUM
24848 @item gdb.PARAM_ENUM
24849 The value is a string, which must be one of a collection string
24850 constants provided when the parameter is created.
24853 @node Functions In Python
24854 @subsubsection Writing new convenience functions
24856 @cindex writing convenience functions
24857 @cindex convenience functions in python
24858 @cindex python convenience functions
24859 @tindex gdb.Function
24861 You can implement new convenience functions (@pxref{Convenience Vars})
24862 in Python. A convenience function is an instance of a subclass of the
24863 class @code{gdb.Function}.
24865 @defun Function.__init__ (name)
24866 The initializer for @code{Function} registers the new function with
24867 @value{GDBN}. The argument @var{name} is the name of the function,
24868 a string. The function will be visible to the user as a convenience
24869 variable of type @code{internal function}, whose name is the same as
24870 the given @var{name}.
24872 The documentation for the new function is taken from the documentation
24873 string for the new class.
24876 @defun Function.invoke (@var{*args})
24877 When a convenience function is evaluated, its arguments are converted
24878 to instances of @code{gdb.Value}, and then the function's
24879 @code{invoke} method is called. Note that @value{GDBN} does not
24880 predetermine the arity of convenience functions. Instead, all
24881 available arguments are passed to @code{invoke}, following the
24882 standard Python calling convention. In particular, a convenience
24883 function can have default values for parameters without ill effect.
24885 The return value of this method is used as its value in the enclosing
24886 expression. If an ordinary Python value is returned, it is converted
24887 to a @code{gdb.Value} following the usual rules.
24890 The following code snippet shows how a trivial convenience function can
24891 be implemented in Python:
24894 class Greet (gdb.Function):
24895 """Return string to greet someone.
24896 Takes a name as argument."""
24898 def __init__ (self):
24899 super (Greet, self).__init__ ("greet")
24901 def invoke (self, name):
24902 return "Hello, %s!" % name.string ()
24907 The last line instantiates the class, and is necessary to trigger the
24908 registration of the function with @value{GDBN}. Depending on how the
24909 Python code is read into @value{GDBN}, you may need to import the
24910 @code{gdb} module explicitly.
24912 Now you can use the function in an expression:
24915 (gdb) print $greet("Bob")
24919 @node Progspaces In Python
24920 @subsubsection Program Spaces In Python
24922 @cindex progspaces in python
24923 @tindex gdb.Progspace
24925 A program space, or @dfn{progspace}, represents a symbolic view
24926 of an address space.
24927 It consists of all of the objfiles of the program.
24928 @xref{Objfiles In Python}.
24929 @xref{Inferiors and Programs, program spaces}, for more details
24930 about program spaces.
24932 The following progspace-related functions are available in the
24935 @findex gdb.current_progspace
24936 @defun gdb.current_progspace ()
24937 This function returns the program space of the currently selected inferior.
24938 @xref{Inferiors and Programs}.
24941 @findex gdb.progspaces
24942 @defun gdb.progspaces ()
24943 Return a sequence of all the progspaces currently known to @value{GDBN}.
24946 Each progspace is represented by an instance of the @code{gdb.Progspace}
24949 @defvar Progspace.filename
24950 The file name of the progspace as a string.
24953 @defvar Progspace.pretty_printers
24954 The @code{pretty_printers} attribute is a list of functions. It is
24955 used to look up pretty-printers. A @code{Value} is passed to each
24956 function in order; if the function returns @code{None}, then the
24957 search continues. Otherwise, the return value should be an object
24958 which is used to format the value. @xref{Pretty Printing API}, for more
24962 @defvar Progspace.type_printers
24963 The @code{type_printers} attribute is a list of type printer objects.
24964 @xref{Type Printing API}, for more information.
24967 @node Objfiles In Python
24968 @subsubsection Objfiles In Python
24970 @cindex objfiles in python
24971 @tindex gdb.Objfile
24973 @value{GDBN} loads symbols for an inferior from various
24974 symbol-containing files (@pxref{Files}). These include the primary
24975 executable file, any shared libraries used by the inferior, and any
24976 separate debug info files (@pxref{Separate Debug Files}).
24977 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
24979 The following objfile-related functions are available in the
24982 @findex gdb.current_objfile
24983 @defun gdb.current_objfile ()
24984 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
24985 sets the ``current objfile'' to the corresponding objfile. This
24986 function returns the current objfile. If there is no current objfile,
24987 this function returns @code{None}.
24990 @findex gdb.objfiles
24991 @defun gdb.objfiles ()
24992 Return a sequence of all the objfiles current known to @value{GDBN}.
24993 @xref{Objfiles In Python}.
24996 Each objfile is represented by an instance of the @code{gdb.Objfile}
24999 @defvar Objfile.filename
25000 The file name of the objfile as a string.
25003 @defvar Objfile.pretty_printers
25004 The @code{pretty_printers} attribute is a list of functions. It is
25005 used to look up pretty-printers. A @code{Value} is passed to each
25006 function in order; if the function returns @code{None}, then the
25007 search continues. Otherwise, the return value should be an object
25008 which is used to format the value. @xref{Pretty Printing API}, for more
25012 @defvar Objfile.type_printers
25013 The @code{type_printers} attribute is a list of type printer objects.
25014 @xref{Type Printing API}, for more information.
25017 A @code{gdb.Objfile} object has the following methods:
25019 @defun Objfile.is_valid ()
25020 Returns @code{True} if the @code{gdb.Objfile} object is valid,
25021 @code{False} if not. A @code{gdb.Objfile} object can become invalid
25022 if the object file it refers to is not loaded in @value{GDBN} any
25023 longer. All other @code{gdb.Objfile} methods will throw an exception
25024 if it is invalid at the time the method is called.
25027 @node Frames In Python
25028 @subsubsection Accessing inferior stack frames from Python.
25030 @cindex frames in python
25031 When the debugged program stops, @value{GDBN} is able to analyze its call
25032 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
25033 represents a frame in the stack. A @code{gdb.Frame} object is only valid
25034 while its corresponding frame exists in the inferior's stack. If you try
25035 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
25036 exception (@pxref{Exception Handling}).
25038 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
25042 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
25046 The following frame-related functions are available in the @code{gdb} module:
25048 @findex gdb.selected_frame
25049 @defun gdb.selected_frame ()
25050 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
25053 @findex gdb.newest_frame
25054 @defun gdb.newest_frame ()
25055 Return the newest frame object for the selected thread.
25058 @defun gdb.frame_stop_reason_string (reason)
25059 Return a string explaining the reason why @value{GDBN} stopped unwinding
25060 frames, as expressed by the given @var{reason} code (an integer, see the
25061 @code{unwind_stop_reason} method further down in this section).
25064 A @code{gdb.Frame} object has the following methods:
25067 @defun Frame.is_valid ()
25068 Returns true if the @code{gdb.Frame} object is valid, false if not.
25069 A frame object can become invalid if the frame it refers to doesn't
25070 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
25071 an exception if it is invalid at the time the method is called.
25074 @defun Frame.name ()
25075 Returns the function name of the frame, or @code{None} if it can't be
25079 @defun Frame.type ()
25080 Returns the type of the frame. The value can be one of:
25082 @item gdb.NORMAL_FRAME
25083 An ordinary stack frame.
25085 @item gdb.DUMMY_FRAME
25086 A fake stack frame that was created by @value{GDBN} when performing an
25087 inferior function call.
25089 @item gdb.INLINE_FRAME
25090 A frame representing an inlined function. The function was inlined
25091 into a @code{gdb.NORMAL_FRAME} that is older than this one.
25093 @item gdb.TAILCALL_FRAME
25094 A frame representing a tail call. @xref{Tail Call Frames}.
25096 @item gdb.SIGTRAMP_FRAME
25097 A signal trampoline frame. This is the frame created by the OS when
25098 it calls into a signal handler.
25100 @item gdb.ARCH_FRAME
25101 A fake stack frame representing a cross-architecture call.
25103 @item gdb.SENTINEL_FRAME
25104 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
25109 @defun Frame.unwind_stop_reason ()
25110 Return an integer representing the reason why it's not possible to find
25111 more frames toward the outermost frame. Use
25112 @code{gdb.frame_stop_reason_string} to convert the value returned by this
25113 function to a string. The value can be one of:
25116 @item gdb.FRAME_UNWIND_NO_REASON
25117 No particular reason (older frames should be available).
25119 @item gdb.FRAME_UNWIND_NULL_ID
25120 The previous frame's analyzer returns an invalid result.
25122 @item gdb.FRAME_UNWIND_OUTERMOST
25123 This frame is the outermost.
25125 @item gdb.FRAME_UNWIND_UNAVAILABLE
25126 Cannot unwind further, because that would require knowing the
25127 values of registers or memory that have not been collected.
25129 @item gdb.FRAME_UNWIND_INNER_ID
25130 This frame ID looks like it ought to belong to a NEXT frame,
25131 but we got it for a PREV frame. Normally, this is a sign of
25132 unwinder failure. It could also indicate stack corruption.
25134 @item gdb.FRAME_UNWIND_SAME_ID
25135 This frame has the same ID as the previous one. That means
25136 that unwinding further would almost certainly give us another
25137 frame with exactly the same ID, so break the chain. Normally,
25138 this is a sign of unwinder failure. It could also indicate
25141 @item gdb.FRAME_UNWIND_NO_SAVED_PC
25142 The frame unwinder did not find any saved PC, but we needed
25143 one to unwind further.
25145 @item gdb.FRAME_UNWIND_FIRST_ERROR
25146 Any stop reason greater or equal to this value indicates some kind
25147 of error. This special value facilitates writing code that tests
25148 for errors in unwinding in a way that will work correctly even if
25149 the list of the other values is modified in future @value{GDBN}
25150 versions. Using it, you could write:
25152 reason = gdb.selected_frame().unwind_stop_reason ()
25153 reason_str = gdb.frame_stop_reason_string (reason)
25154 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
25155 print "An error occured: %s" % reason_str
25162 Returns the frame's resume address.
25165 @defun Frame.block ()
25166 Return the frame's code block. @xref{Blocks In Python}.
25169 @defun Frame.function ()
25170 Return the symbol for the function corresponding to this frame.
25171 @xref{Symbols In Python}.
25174 @defun Frame.older ()
25175 Return the frame that called this frame.
25178 @defun Frame.newer ()
25179 Return the frame called by this frame.
25182 @defun Frame.find_sal ()
25183 Return the frame's symtab and line object.
25184 @xref{Symbol Tables In Python}.
25187 @defun Frame.read_var (variable @r{[}, block@r{]})
25188 Return the value of @var{variable} in this frame. If the optional
25189 argument @var{block} is provided, search for the variable from that
25190 block; otherwise start at the frame's current block (which is
25191 determined by the frame's current program counter). @var{variable}
25192 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
25193 @code{gdb.Block} object.
25196 @defun Frame.select ()
25197 Set this frame to be the selected frame. @xref{Stack, ,Examining the
25202 @node Blocks In Python
25203 @subsubsection Accessing frame blocks from Python.
25205 @cindex blocks in python
25208 Within each frame, @value{GDBN} maintains information on each block
25209 stored in that frame. These blocks are organized hierarchically, and
25210 are represented individually in Python as a @code{gdb.Block}.
25211 Please see @ref{Frames In Python}, for a more in-depth discussion on
25212 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
25213 detailed technical information on @value{GDBN}'s book-keeping of the
25216 A @code{gdb.Block} is iterable. The iterator returns the symbols
25217 (@pxref{Symbols In Python}) local to the block. Python programs
25218 should not assume that a specific block object will always contain a
25219 given symbol, since changes in @value{GDBN} features and
25220 infrastructure may cause symbols move across blocks in a symbol
25223 The following block-related functions are available in the @code{gdb}
25226 @findex gdb.block_for_pc
25227 @defun gdb.block_for_pc (pc)
25228 Return the @code{gdb.Block} containing the given @var{pc} value. If the
25229 block cannot be found for the @var{pc} value specified, the function
25230 will return @code{None}.
25233 A @code{gdb.Block} object has the following methods:
25236 @defun Block.is_valid ()
25237 Returns @code{True} if the @code{gdb.Block} object is valid,
25238 @code{False} if not. A block object can become invalid if the block it
25239 refers to doesn't exist anymore in the inferior. All other
25240 @code{gdb.Block} methods will throw an exception if it is invalid at
25241 the time the method is called. The block's validity is also checked
25242 during iteration over symbols of the block.
25246 A @code{gdb.Block} object has the following attributes:
25249 @defvar Block.start
25250 The start address of the block. This attribute is not writable.
25254 The end address of the block. This attribute is not writable.
25257 @defvar Block.function
25258 The name of the block represented as a @code{gdb.Symbol}. If the
25259 block is not named, then this attribute holds @code{None}. This
25260 attribute is not writable.
25263 @defvar Block.superblock
25264 The block containing this block. If this parent block does not exist,
25265 this attribute holds @code{None}. This attribute is not writable.
25268 @defvar Block.global_block
25269 The global block associated with this block. This attribute is not
25273 @defvar Block.static_block
25274 The static block associated with this block. This attribute is not
25278 @defvar Block.is_global
25279 @code{True} if the @code{gdb.Block} object is a global block,
25280 @code{False} if not. This attribute is not
25284 @defvar Block.is_static
25285 @code{True} if the @code{gdb.Block} object is a static block,
25286 @code{False} if not. This attribute is not writable.
25290 @node Symbols In Python
25291 @subsubsection Python representation of Symbols.
25293 @cindex symbols in python
25296 @value{GDBN} represents every variable, function and type as an
25297 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
25298 Similarly, Python represents these symbols in @value{GDBN} with the
25299 @code{gdb.Symbol} object.
25301 The following symbol-related functions are available in the @code{gdb}
25304 @findex gdb.lookup_symbol
25305 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
25306 This function searches for a symbol by name. The search scope can be
25307 restricted to the parameters defined in the optional domain and block
25310 @var{name} is the name of the symbol. It must be a string. The
25311 optional @var{block} argument restricts the search to symbols visible
25312 in that @var{block}. The @var{block} argument must be a
25313 @code{gdb.Block} object. If omitted, the block for the current frame
25314 is used. The optional @var{domain} argument restricts
25315 the search to the domain type. The @var{domain} argument must be a
25316 domain constant defined in the @code{gdb} module and described later
25319 The result is a tuple of two elements.
25320 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
25322 If the symbol is found, the second element is @code{True} if the symbol
25323 is a field of a method's object (e.g., @code{this} in C@t{++}),
25324 otherwise it is @code{False}.
25325 If the symbol is not found, the second element is @code{False}.
25328 @findex gdb.lookup_global_symbol
25329 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
25330 This function searches for a global symbol by name.
25331 The search scope can be restricted to by the domain argument.
25333 @var{name} is the name of the symbol. It must be a string.
25334 The optional @var{domain} argument restricts the search to the domain type.
25335 The @var{domain} argument must be a domain constant defined in the @code{gdb}
25336 module and described later in this chapter.
25338 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
25342 A @code{gdb.Symbol} object has the following attributes:
25345 @defvar Symbol.type
25346 The type of the symbol or @code{None} if no type is recorded.
25347 This attribute is represented as a @code{gdb.Type} object.
25348 @xref{Types In Python}. This attribute is not writable.
25351 @defvar Symbol.symtab
25352 The symbol table in which the symbol appears. This attribute is
25353 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
25354 Python}. This attribute is not writable.
25357 @defvar Symbol.line
25358 The line number in the source code at which the symbol was defined.
25359 This is an integer.
25362 @defvar Symbol.name
25363 The name of the symbol as a string. This attribute is not writable.
25366 @defvar Symbol.linkage_name
25367 The name of the symbol, as used by the linker (i.e., may be mangled).
25368 This attribute is not writable.
25371 @defvar Symbol.print_name
25372 The name of the symbol in a form suitable for output. This is either
25373 @code{name} or @code{linkage_name}, depending on whether the user
25374 asked @value{GDBN} to display demangled or mangled names.
25377 @defvar Symbol.addr_class
25378 The address class of the symbol. This classifies how to find the value
25379 of a symbol. Each address class is a constant defined in the
25380 @code{gdb} module and described later in this chapter.
25383 @defvar Symbol.needs_frame
25384 This is @code{True} if evaluating this symbol's value requires a frame
25385 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
25386 local variables will require a frame, but other symbols will not.
25389 @defvar Symbol.is_argument
25390 @code{True} if the symbol is an argument of a function.
25393 @defvar Symbol.is_constant
25394 @code{True} if the symbol is a constant.
25397 @defvar Symbol.is_function
25398 @code{True} if the symbol is a function or a method.
25401 @defvar Symbol.is_variable
25402 @code{True} if the symbol is a variable.
25406 A @code{gdb.Symbol} object has the following methods:
25409 @defun Symbol.is_valid ()
25410 Returns @code{True} if the @code{gdb.Symbol} object is valid,
25411 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
25412 the symbol it refers to does not exist in @value{GDBN} any longer.
25413 All other @code{gdb.Symbol} methods will throw an exception if it is
25414 invalid at the time the method is called.
25417 @defun Symbol.value (@r{[}frame@r{]})
25418 Compute the value of the symbol, as a @code{gdb.Value}. For
25419 functions, this computes the address of the function, cast to the
25420 appropriate type. If the symbol requires a frame in order to compute
25421 its value, then @var{frame} must be given. If @var{frame} is not
25422 given, or if @var{frame} is invalid, then this method will throw an
25427 The available domain categories in @code{gdb.Symbol} are represented
25428 as constants in the @code{gdb} module:
25431 @findex SYMBOL_UNDEF_DOMAIN
25432 @findex gdb.SYMBOL_UNDEF_DOMAIN
25433 @item gdb.SYMBOL_UNDEF_DOMAIN
25434 This is used when a domain has not been discovered or none of the
25435 following domains apply. This usually indicates an error either
25436 in the symbol information or in @value{GDBN}'s handling of symbols.
25437 @findex SYMBOL_VAR_DOMAIN
25438 @findex gdb.SYMBOL_VAR_DOMAIN
25439 @item gdb.SYMBOL_VAR_DOMAIN
25440 This domain contains variables, function names, typedef names and enum
25442 @findex SYMBOL_STRUCT_DOMAIN
25443 @findex gdb.SYMBOL_STRUCT_DOMAIN
25444 @item gdb.SYMBOL_STRUCT_DOMAIN
25445 This domain holds struct, union and enum type names.
25446 @findex SYMBOL_LABEL_DOMAIN
25447 @findex gdb.SYMBOL_LABEL_DOMAIN
25448 @item gdb.SYMBOL_LABEL_DOMAIN
25449 This domain contains names of labels (for gotos).
25450 @findex SYMBOL_VARIABLES_DOMAIN
25451 @findex gdb.SYMBOL_VARIABLES_DOMAIN
25452 @item gdb.SYMBOL_VARIABLES_DOMAIN
25453 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
25454 contains everything minus functions and types.
25455 @findex SYMBOL_FUNCTIONS_DOMAIN
25456 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
25457 @item gdb.SYMBOL_FUNCTION_DOMAIN
25458 This domain contains all functions.
25459 @findex SYMBOL_TYPES_DOMAIN
25460 @findex gdb.SYMBOL_TYPES_DOMAIN
25461 @item gdb.SYMBOL_TYPES_DOMAIN
25462 This domain contains all types.
25465 The available address class categories in @code{gdb.Symbol} are represented
25466 as constants in the @code{gdb} module:
25469 @findex SYMBOL_LOC_UNDEF
25470 @findex gdb.SYMBOL_LOC_UNDEF
25471 @item gdb.SYMBOL_LOC_UNDEF
25472 If this is returned by address class, it indicates an error either in
25473 the symbol information or in @value{GDBN}'s handling of symbols.
25474 @findex SYMBOL_LOC_CONST
25475 @findex gdb.SYMBOL_LOC_CONST
25476 @item gdb.SYMBOL_LOC_CONST
25477 Value is constant int.
25478 @findex SYMBOL_LOC_STATIC
25479 @findex gdb.SYMBOL_LOC_STATIC
25480 @item gdb.SYMBOL_LOC_STATIC
25481 Value is at a fixed address.
25482 @findex SYMBOL_LOC_REGISTER
25483 @findex gdb.SYMBOL_LOC_REGISTER
25484 @item gdb.SYMBOL_LOC_REGISTER
25485 Value is in a register.
25486 @findex SYMBOL_LOC_ARG
25487 @findex gdb.SYMBOL_LOC_ARG
25488 @item gdb.SYMBOL_LOC_ARG
25489 Value is an argument. This value is at the offset stored within the
25490 symbol inside the frame's argument list.
25491 @findex SYMBOL_LOC_REF_ARG
25492 @findex gdb.SYMBOL_LOC_REF_ARG
25493 @item gdb.SYMBOL_LOC_REF_ARG
25494 Value address is stored in the frame's argument list. Just like
25495 @code{LOC_ARG} except that the value's address is stored at the
25496 offset, not the value itself.
25497 @findex SYMBOL_LOC_REGPARM_ADDR
25498 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
25499 @item gdb.SYMBOL_LOC_REGPARM_ADDR
25500 Value is a specified register. Just like @code{LOC_REGISTER} except
25501 the register holds the address of the argument instead of the argument
25503 @findex SYMBOL_LOC_LOCAL
25504 @findex gdb.SYMBOL_LOC_LOCAL
25505 @item gdb.SYMBOL_LOC_LOCAL
25506 Value is a local variable.
25507 @findex SYMBOL_LOC_TYPEDEF
25508 @findex gdb.SYMBOL_LOC_TYPEDEF
25509 @item gdb.SYMBOL_LOC_TYPEDEF
25510 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
25512 @findex SYMBOL_LOC_BLOCK
25513 @findex gdb.SYMBOL_LOC_BLOCK
25514 @item gdb.SYMBOL_LOC_BLOCK
25516 @findex SYMBOL_LOC_CONST_BYTES
25517 @findex gdb.SYMBOL_LOC_CONST_BYTES
25518 @item gdb.SYMBOL_LOC_CONST_BYTES
25519 Value is a byte-sequence.
25520 @findex SYMBOL_LOC_UNRESOLVED
25521 @findex gdb.SYMBOL_LOC_UNRESOLVED
25522 @item gdb.SYMBOL_LOC_UNRESOLVED
25523 Value is at a fixed address, but the address of the variable has to be
25524 determined from the minimal symbol table whenever the variable is
25526 @findex SYMBOL_LOC_OPTIMIZED_OUT
25527 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
25528 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
25529 The value does not actually exist in the program.
25530 @findex SYMBOL_LOC_COMPUTED
25531 @findex gdb.SYMBOL_LOC_COMPUTED
25532 @item gdb.SYMBOL_LOC_COMPUTED
25533 The value's address is a computed location.
25536 @node Symbol Tables In Python
25537 @subsubsection Symbol table representation in Python.
25539 @cindex symbol tables in python
25541 @tindex gdb.Symtab_and_line
25543 Access to symbol table data maintained by @value{GDBN} on the inferior
25544 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
25545 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
25546 from the @code{find_sal} method in @code{gdb.Frame} object.
25547 @xref{Frames In Python}.
25549 For more information on @value{GDBN}'s symbol table management, see
25550 @ref{Symbols, ,Examining the Symbol Table}, for more information.
25552 A @code{gdb.Symtab_and_line} object has the following attributes:
25555 @defvar Symtab_and_line.symtab
25556 The symbol table object (@code{gdb.Symtab}) for this frame.
25557 This attribute is not writable.
25560 @defvar Symtab_and_line.pc
25561 Indicates the start of the address range occupied by code for the
25562 current source line. This attribute is not writable.
25565 @defvar Symtab_and_line.last
25566 Indicates the end of the address range occupied by code for the current
25567 source line. This attribute is not writable.
25570 @defvar Symtab_and_line.line
25571 Indicates the current line number for this object. This
25572 attribute is not writable.
25576 A @code{gdb.Symtab_and_line} object has the following methods:
25579 @defun Symtab_and_line.is_valid ()
25580 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
25581 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
25582 invalid if the Symbol table and line object it refers to does not
25583 exist in @value{GDBN} any longer. All other
25584 @code{gdb.Symtab_and_line} methods will throw an exception if it is
25585 invalid at the time the method is called.
25589 A @code{gdb.Symtab} object has the following attributes:
25592 @defvar Symtab.filename
25593 The symbol table's source filename. This attribute is not writable.
25596 @defvar Symtab.objfile
25597 The symbol table's backing object file. @xref{Objfiles In Python}.
25598 This attribute is not writable.
25602 A @code{gdb.Symtab} object has the following methods:
25605 @defun Symtab.is_valid ()
25606 Returns @code{True} if the @code{gdb.Symtab} object is valid,
25607 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
25608 the symbol table it refers to does not exist in @value{GDBN} any
25609 longer. All other @code{gdb.Symtab} methods will throw an exception
25610 if it is invalid at the time the method is called.
25613 @defun Symtab.fullname ()
25614 Return the symbol table's source absolute file name.
25617 @defun Symtab.global_block ()
25618 Return the global block of the underlying symbol table.
25619 @xref{Blocks In Python}.
25622 @defun Symtab.static_block ()
25623 Return the static block of the underlying symbol table.
25624 @xref{Blocks In Python}.
25628 @node Breakpoints In Python
25629 @subsubsection Manipulating breakpoints using Python
25631 @cindex breakpoints in python
25632 @tindex gdb.Breakpoint
25634 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
25637 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
25638 Create a new breakpoint. @var{spec} is a string naming the
25639 location of the breakpoint, or an expression that defines a
25640 watchpoint. The contents can be any location recognized by the
25641 @code{break} command, or in the case of a watchpoint, by the @code{watch}
25642 command. The optional @var{type} denotes the breakpoint to create
25643 from the types defined later in this chapter. This argument can be
25644 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
25645 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
25646 allows the breakpoint to become invisible to the user. The breakpoint
25647 will neither be reported when created, nor will it be listed in the
25648 output from @code{info breakpoints} (but will be listed with the
25649 @code{maint info breakpoints} command). The optional @var{wp_class}
25650 argument defines the class of watchpoint to create, if @var{type} is
25651 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
25652 assumed to be a @code{gdb.WP_WRITE} class.
25655 @defun Breakpoint.stop (self)
25656 The @code{gdb.Breakpoint} class can be sub-classed and, in
25657 particular, you may choose to implement the @code{stop} method.
25658 If this method is defined as a sub-class of @code{gdb.Breakpoint},
25659 it will be called when the inferior reaches any location of a
25660 breakpoint which instantiates that sub-class. If the method returns
25661 @code{True}, the inferior will be stopped at the location of the
25662 breakpoint, otherwise the inferior will continue.
25664 If there are multiple breakpoints at the same location with a
25665 @code{stop} method, each one will be called regardless of the
25666 return status of the previous. This ensures that all @code{stop}
25667 methods have a chance to execute at that location. In this scenario
25668 if one of the methods returns @code{True} but the others return
25669 @code{False}, the inferior will still be stopped.
25671 You should not alter the execution state of the inferior (i.e.@:, step,
25672 next, etc.), alter the current frame context (i.e.@:, change the current
25673 active frame), or alter, add or delete any breakpoint. As a general
25674 rule, you should not alter any data within @value{GDBN} or the inferior
25677 Example @code{stop} implementation:
25680 class MyBreakpoint (gdb.Breakpoint):
25682 inf_val = gdb.parse_and_eval("foo")
25689 The available watchpoint types represented by constants are defined in the
25694 @findex gdb.WP_READ
25696 Read only watchpoint.
25699 @findex gdb.WP_WRITE
25701 Write only watchpoint.
25704 @findex gdb.WP_ACCESS
25705 @item gdb.WP_ACCESS
25706 Read/Write watchpoint.
25709 @defun Breakpoint.is_valid ()
25710 Return @code{True} if this @code{Breakpoint} object is valid,
25711 @code{False} otherwise. A @code{Breakpoint} object can become invalid
25712 if the user deletes the breakpoint. In this case, the object still
25713 exists, but the underlying breakpoint does not. In the cases of
25714 watchpoint scope, the watchpoint remains valid even if execution of the
25715 inferior leaves the scope of that watchpoint.
25718 @defun Breakpoint.delete
25719 Permanently deletes the @value{GDBN} breakpoint. This also
25720 invalidates the Python @code{Breakpoint} object. Any further access
25721 to this object's attributes or methods will raise an error.
25724 @defvar Breakpoint.enabled
25725 This attribute is @code{True} if the breakpoint is enabled, and
25726 @code{False} otherwise. This attribute is writable.
25729 @defvar Breakpoint.silent
25730 This attribute is @code{True} if the breakpoint is silent, and
25731 @code{False} otherwise. This attribute is writable.
25733 Note that a breakpoint can also be silent if it has commands and the
25734 first command is @code{silent}. This is not reported by the
25735 @code{silent} attribute.
25738 @defvar Breakpoint.thread
25739 If the breakpoint is thread-specific, this attribute holds the thread
25740 id. If the breakpoint is not thread-specific, this attribute is
25741 @code{None}. This attribute is writable.
25744 @defvar Breakpoint.task
25745 If the breakpoint is Ada task-specific, this attribute holds the Ada task
25746 id. If the breakpoint is not task-specific (or the underlying
25747 language is not Ada), this attribute is @code{None}. This attribute
25751 @defvar Breakpoint.ignore_count
25752 This attribute holds the ignore count for the breakpoint, an integer.
25753 This attribute is writable.
25756 @defvar Breakpoint.number
25757 This attribute holds the breakpoint's number --- the identifier used by
25758 the user to manipulate the breakpoint. This attribute is not writable.
25761 @defvar Breakpoint.type
25762 This attribute holds the breakpoint's type --- the identifier used to
25763 determine the actual breakpoint type or use-case. This attribute is not
25767 @defvar Breakpoint.visible
25768 This attribute tells whether the breakpoint is visible to the user
25769 when set, or when the @samp{info breakpoints} command is run. This
25770 attribute is not writable.
25773 The available types are represented by constants defined in the @code{gdb}
25777 @findex BP_BREAKPOINT
25778 @findex gdb.BP_BREAKPOINT
25779 @item gdb.BP_BREAKPOINT
25780 Normal code breakpoint.
25782 @findex BP_WATCHPOINT
25783 @findex gdb.BP_WATCHPOINT
25784 @item gdb.BP_WATCHPOINT
25785 Watchpoint breakpoint.
25787 @findex BP_HARDWARE_WATCHPOINT
25788 @findex gdb.BP_HARDWARE_WATCHPOINT
25789 @item gdb.BP_HARDWARE_WATCHPOINT
25790 Hardware assisted watchpoint.
25792 @findex BP_READ_WATCHPOINT
25793 @findex gdb.BP_READ_WATCHPOINT
25794 @item gdb.BP_READ_WATCHPOINT
25795 Hardware assisted read watchpoint.
25797 @findex BP_ACCESS_WATCHPOINT
25798 @findex gdb.BP_ACCESS_WATCHPOINT
25799 @item gdb.BP_ACCESS_WATCHPOINT
25800 Hardware assisted access watchpoint.
25803 @defvar Breakpoint.hit_count
25804 This attribute holds the hit count for the breakpoint, an integer.
25805 This attribute is writable, but currently it can only be set to zero.
25808 @defvar Breakpoint.location
25809 This attribute holds the location of the breakpoint, as specified by
25810 the user. It is a string. If the breakpoint does not have a location
25811 (that is, it is a watchpoint) the attribute's value is @code{None}. This
25812 attribute is not writable.
25815 @defvar Breakpoint.expression
25816 This attribute holds a breakpoint expression, as specified by
25817 the user. It is a string. If the breakpoint does not have an
25818 expression (the breakpoint is not a watchpoint) the attribute's value
25819 is @code{None}. This attribute is not writable.
25822 @defvar Breakpoint.condition
25823 This attribute holds the condition of the breakpoint, as specified by
25824 the user. It is a string. If there is no condition, this attribute's
25825 value is @code{None}. This attribute is writable.
25828 @defvar Breakpoint.commands
25829 This attribute holds the commands attached to the breakpoint. If
25830 there are commands, this attribute's value is a string holding all the
25831 commands, separated by newlines. If there are no commands, this
25832 attribute is @code{None}. This attribute is not writable.
25835 @node Finish Breakpoints in Python
25836 @subsubsection Finish Breakpoints
25838 @cindex python finish breakpoints
25839 @tindex gdb.FinishBreakpoint
25841 A finish breakpoint is a temporary breakpoint set at the return address of
25842 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
25843 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
25844 and deleted when the execution will run out of the breakpoint scope (i.e.@:
25845 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
25846 Finish breakpoints are thread specific and must be create with the right
25849 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
25850 Create a finish breakpoint at the return address of the @code{gdb.Frame}
25851 object @var{frame}. If @var{frame} is not provided, this defaults to the
25852 newest frame. The optional @var{internal} argument allows the breakpoint to
25853 become invisible to the user. @xref{Breakpoints In Python}, for further
25854 details about this argument.
25857 @defun FinishBreakpoint.out_of_scope (self)
25858 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
25859 @code{return} command, @dots{}), a function may not properly terminate, and
25860 thus never hit the finish breakpoint. When @value{GDBN} notices such a
25861 situation, the @code{out_of_scope} callback will be triggered.
25863 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
25867 class MyFinishBreakpoint (gdb.FinishBreakpoint)
25869 print "normal finish"
25872 def out_of_scope ():
25873 print "abnormal finish"
25877 @defvar FinishBreakpoint.return_value
25878 When @value{GDBN} is stopped at a finish breakpoint and the frame
25879 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
25880 attribute will contain a @code{gdb.Value} object corresponding to the return
25881 value of the function. The value will be @code{None} if the function return
25882 type is @code{void} or if the return value was not computable. This attribute
25886 @node Lazy Strings In Python
25887 @subsubsection Python representation of lazy strings.
25889 @cindex lazy strings in python
25890 @tindex gdb.LazyString
25892 A @dfn{lazy string} is a string whose contents is not retrieved or
25893 encoded until it is needed.
25895 A @code{gdb.LazyString} is represented in @value{GDBN} as an
25896 @code{address} that points to a region of memory, an @code{encoding}
25897 that will be used to encode that region of memory, and a @code{length}
25898 to delimit the region of memory that represents the string. The
25899 difference between a @code{gdb.LazyString} and a string wrapped within
25900 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
25901 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
25902 retrieved and encoded during printing, while a @code{gdb.Value}
25903 wrapping a string is immediately retrieved and encoded on creation.
25905 A @code{gdb.LazyString} object has the following functions:
25907 @defun LazyString.value ()
25908 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
25909 will point to the string in memory, but will lose all the delayed
25910 retrieval, encoding and handling that @value{GDBN} applies to a
25911 @code{gdb.LazyString}.
25914 @defvar LazyString.address
25915 This attribute holds the address of the string. This attribute is not
25919 @defvar LazyString.length
25920 This attribute holds the length of the string in characters. If the
25921 length is -1, then the string will be fetched and encoded up to the
25922 first null of appropriate width. This attribute is not writable.
25925 @defvar LazyString.encoding
25926 This attribute holds the encoding that will be applied to the string
25927 when the string is printed by @value{GDBN}. If the encoding is not
25928 set, or contains an empty string, then @value{GDBN} will select the
25929 most appropriate encoding when the string is printed. This attribute
25933 @defvar LazyString.type
25934 This attribute holds the type that is represented by the lazy string's
25935 type. For a lazy string this will always be a pointer type. To
25936 resolve this to the lazy string's character type, use the type's
25937 @code{target} method. @xref{Types In Python}. This attribute is not
25941 @node Python Auto-loading
25942 @subsection Python Auto-loading
25943 @cindex Python auto-loading
25945 When a new object file is read (for example, due to the @code{file}
25946 command, or because the inferior has loaded a shared library),
25947 @value{GDBN} will look for Python support scripts in several ways:
25948 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
25949 and @code{.debug_gdb_scripts} section
25950 (@pxref{dotdebug_gdb_scripts section}).
25952 The auto-loading feature is useful for supplying application-specific
25953 debugging commands and scripts.
25955 Auto-loading can be enabled or disabled,
25956 and the list of auto-loaded scripts can be printed.
25959 @anchor{set auto-load python-scripts}
25960 @kindex set auto-load python-scripts
25961 @item set auto-load python-scripts [on|off]
25962 Enable or disable the auto-loading of Python scripts.
25964 @anchor{show auto-load python-scripts}
25965 @kindex show auto-load python-scripts
25966 @item show auto-load python-scripts
25967 Show whether auto-loading of Python scripts is enabled or disabled.
25969 @anchor{info auto-load python-scripts}
25970 @kindex info auto-load python-scripts
25971 @cindex print list of auto-loaded Python scripts
25972 @item info auto-load python-scripts [@var{regexp}]
25973 Print the list of all Python scripts that @value{GDBN} auto-loaded.
25975 Also printed is the list of Python scripts that were mentioned in
25976 the @code{.debug_gdb_scripts} section and were not found
25977 (@pxref{dotdebug_gdb_scripts section}).
25978 This is useful because their names are not printed when @value{GDBN}
25979 tries to load them and fails. There may be many of them, and printing
25980 an error message for each one is problematic.
25982 If @var{regexp} is supplied only Python scripts with matching names are printed.
25987 (gdb) info auto-load python-scripts
25989 Yes py-section-script.py
25990 full name: /tmp/py-section-script.py
25991 No my-foo-pretty-printers.py
25995 When reading an auto-loaded file, @value{GDBN} sets the
25996 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
25997 function (@pxref{Objfiles In Python}). This can be useful for
25998 registering objfile-specific pretty-printers.
26001 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
26002 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
26003 * Which flavor to choose?::
26006 @node objfile-gdb.py file
26007 @subsubsection The @file{@var{objfile}-gdb.py} file
26008 @cindex @file{@var{objfile}-gdb.py}
26010 When a new object file is read, @value{GDBN} looks for
26011 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
26012 where @var{objfile} is the object file's real name, formed by ensuring
26013 that the file name is absolute, following all symlinks, and resolving
26014 @code{.} and @code{..} components. If this file exists and is
26015 readable, @value{GDBN} will evaluate it as a Python script.
26017 If this file does not exist, then @value{GDBN} will look for
26018 @var{script-name} file in all of the directories as specified below.
26020 Note that loading of this script file also requires accordingly configured
26021 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26023 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26024 scripts normally according to its @file{.exe} filename. But if no scripts are
26025 found @value{GDBN} also tries script filenames matching the object file without
26026 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26027 is attempted on any platform. This makes the script filenames compatible
26028 between Unix and MS-Windows hosts.
26031 @anchor{set auto-load scripts-directory}
26032 @kindex set auto-load scripts-directory
26033 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26034 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26035 may be delimited by the host platform path separator in use
26036 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26038 Each entry here needs to be covered also by the security setting
26039 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26041 @anchor{with-auto-load-dir}
26042 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26043 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26044 configuration option @option{--with-auto-load-dir}.
26046 Any reference to @file{$debugdir} will get replaced by
26047 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26048 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26049 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26050 @file{$datadir} must be placed as a directory component --- either alone or
26051 delimited by @file{/} or @file{\} directory separators, depending on the host
26054 The list of directories uses path separator (@samp{:} on GNU and Unix
26055 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26056 to the @env{PATH} environment variable.
26058 @anchor{show auto-load scripts-directory}
26059 @kindex show auto-load scripts-directory
26060 @item show auto-load scripts-directory
26061 Show @value{GDBN} auto-loaded scripts location.
26064 @value{GDBN} does not track which files it has already auto-loaded this way.
26065 @value{GDBN} will load the associated script every time the corresponding
26066 @var{objfile} is opened.
26067 So your @file{-gdb.py} file should be careful to avoid errors if it
26068 is evaluated more than once.
26070 @node dotdebug_gdb_scripts section
26071 @subsubsection The @code{.debug_gdb_scripts} section
26072 @cindex @code{.debug_gdb_scripts} section
26074 For systems using file formats like ELF and COFF,
26075 when @value{GDBN} loads a new object file
26076 it will look for a special section named @samp{.debug_gdb_scripts}.
26077 If this section exists, its contents is a list of names of scripts to load.
26079 @value{GDBN} will look for each specified script file first in the
26080 current directory and then along the source search path
26081 (@pxref{Source Path, ,Specifying Source Directories}),
26082 except that @file{$cdir} is not searched, since the compilation
26083 directory is not relevant to scripts.
26085 Entries can be placed in section @code{.debug_gdb_scripts} with,
26086 for example, this GCC macro:
26089 /* Note: The "MS" section flags are to remove duplicates. */
26090 #define DEFINE_GDB_SCRIPT(script_name) \
26092 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26094 .asciz \"" script_name "\"\n\
26100 Then one can reference the macro in a header or source file like this:
26103 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
26106 The script name may include directories if desired.
26108 Note that loading of this script file also requires accordingly configured
26109 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26111 If the macro is put in a header, any application or library
26112 using this header will get a reference to the specified script.
26114 @node Which flavor to choose?
26115 @subsubsection Which flavor to choose?
26117 Given the multiple ways of auto-loading Python scripts, it might not always
26118 be clear which one to choose. This section provides some guidance.
26120 Benefits of the @file{-gdb.py} way:
26124 Can be used with file formats that don't support multiple sections.
26127 Ease of finding scripts for public libraries.
26129 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
26130 in the source search path.
26131 For publicly installed libraries, e.g., @file{libstdc++}, there typically
26132 isn't a source directory in which to find the script.
26135 Doesn't require source code additions.
26138 Benefits of the @code{.debug_gdb_scripts} way:
26142 Works with static linking.
26144 Scripts for libraries done the @file{-gdb.py} way require an objfile to
26145 trigger their loading. When an application is statically linked the only
26146 objfile available is the executable, and it is cumbersome to attach all the
26147 scripts from all the input libraries to the executable's @file{-gdb.py} script.
26150 Works with classes that are entirely inlined.
26152 Some classes can be entirely inlined, and thus there may not be an associated
26153 shared library to attach a @file{-gdb.py} script to.
26156 Scripts needn't be copied out of the source tree.
26158 In some circumstances, apps can be built out of large collections of internal
26159 libraries, and the build infrastructure necessary to install the
26160 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
26161 cumbersome. It may be easier to specify the scripts in the
26162 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26163 top of the source tree to the source search path.
26166 @node Python modules
26167 @subsection Python modules
26168 @cindex python modules
26170 @value{GDBN} comes with several modules to assist writing Python code.
26173 * gdb.printing:: Building and registering pretty-printers.
26174 * gdb.types:: Utilities for working with types.
26175 * gdb.prompt:: Utilities for prompt value substitution.
26179 @subsubsection gdb.printing
26180 @cindex gdb.printing
26182 This module provides a collection of utilities for working with
26186 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
26187 This class specifies the API that makes @samp{info pretty-printer},
26188 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
26189 Pretty-printers should generally inherit from this class.
26191 @item SubPrettyPrinter (@var{name})
26192 For printers that handle multiple types, this class specifies the
26193 corresponding API for the subprinters.
26195 @item RegexpCollectionPrettyPrinter (@var{name})
26196 Utility class for handling multiple printers, all recognized via
26197 regular expressions.
26198 @xref{Writing a Pretty-Printer}, for an example.
26200 @item FlagEnumerationPrinter (@var{name})
26201 A pretty-printer which handles printing of @code{enum} values. Unlike
26202 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
26203 work properly when there is some overlap between the enumeration
26204 constants. @var{name} is the name of the printer and also the name of
26205 the @code{enum} type to look up.
26207 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
26208 Register @var{printer} with the pretty-printer list of @var{obj}.
26209 If @var{replace} is @code{True} then any existing copy of the printer
26210 is replaced. Otherwise a @code{RuntimeError} exception is raised
26211 if a printer with the same name already exists.
26215 @subsubsection gdb.types
26218 This module provides a collection of utilities for working with
26219 @code{gdb.Type} objects.
26222 @item get_basic_type (@var{type})
26223 Return @var{type} with const and volatile qualifiers stripped,
26224 and with typedefs and C@t{++} references converted to the underlying type.
26229 typedef const int const_int;
26231 const_int& foo_ref (foo);
26232 int main () @{ return 0; @}
26239 (gdb) python import gdb.types
26240 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
26241 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
26245 @item has_field (@var{type}, @var{field})
26246 Return @code{True} if @var{type}, assumed to be a type with fields
26247 (e.g., a structure or union), has field @var{field}.
26249 @item make_enum_dict (@var{enum_type})
26250 Return a Python @code{dictionary} type produced from @var{enum_type}.
26252 @item deep_items (@var{type})
26253 Returns a Python iterator similar to the standard
26254 @code{gdb.Type.iteritems} method, except that the iterator returned
26255 by @code{deep_items} will recursively traverse anonymous struct or
26256 union fields. For example:
26270 Then in @value{GDBN}:
26272 (@value{GDBP}) python import gdb.types
26273 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
26274 (@value{GDBP}) python print struct_a.keys ()
26276 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
26277 @{['a', 'b0', 'b1']@}
26280 @item get_type_recognizers ()
26281 Return a list of the enabled type recognizers for the current context.
26282 This is called by @value{GDBN} during the type-printing process
26283 (@pxref{Type Printing API}).
26285 @item apply_type_recognizers (recognizers, type_obj)
26286 Apply the type recognizers, @var{recognizers}, to the type object
26287 @var{type_obj}. If any recognizer returns a string, return that
26288 string. Otherwise, return @code{None}. This is called by
26289 @value{GDBN} during the type-printing process (@pxref{Type Printing
26292 @item register_type_printer (locus, printer)
26293 This is a convenience function to register a type printer.
26294 @var{printer} is the type printer to register. It must implement the
26295 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
26296 which case the printer is registered with that objfile; a
26297 @code{gdb.Progspace}, in which case the printer is registered with
26298 that progspace; or @code{None}, in which case the printer is
26299 registered globally.
26302 This is a base class that implements the type printer protocol. Type
26303 printers are encouraged, but not required, to derive from this class.
26304 It defines a constructor:
26306 @defmethod TypePrinter __init__ (self, name)
26307 Initialize the type printer with the given name. The new printer
26308 starts in the enabled state.
26314 @subsubsection gdb.prompt
26317 This module provides a method for prompt value-substitution.
26320 @item substitute_prompt (@var{string})
26321 Return @var{string} with escape sequences substituted by values. Some
26322 escape sequences take arguments. You can specify arguments inside
26323 ``@{@}'' immediately following the escape sequence.
26325 The escape sequences you can pass to this function are:
26329 Substitute a backslash.
26331 Substitute an ESC character.
26333 Substitute the selected frame; an argument names a frame parameter.
26335 Substitute a newline.
26337 Substitute a parameter's value; the argument names the parameter.
26339 Substitute a carriage return.
26341 Substitute the selected thread; an argument names a thread parameter.
26343 Substitute the version of GDB.
26345 Substitute the current working directory.
26347 Begin a sequence of non-printing characters. These sequences are
26348 typically used with the ESC character, and are not counted in the string
26349 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
26350 blue-colored ``(gdb)'' prompt where the length is five.
26352 End a sequence of non-printing characters.
26358 substitute_prompt (``frame: \f,
26359 print arguments: \p@{print frame-arguments@}'')
26362 @exdent will return the string:
26365 "frame: main, print arguments: scalars"
26370 @section Creating new spellings of existing commands
26371 @cindex aliases for commands
26373 It is often useful to define alternate spellings of existing commands.
26374 For example, if a new @value{GDBN} command defined in Python has
26375 a long name to type, it is handy to have an abbreviated version of it
26376 that involves less typing.
26378 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26379 of the @samp{step} command even though it is otherwise an ambiguous
26380 abbreviation of other commands like @samp{set} and @samp{show}.
26382 Aliases are also used to provide shortened or more common versions
26383 of multi-word commands. For example, @value{GDBN} provides the
26384 @samp{tty} alias of the @samp{set inferior-tty} command.
26386 You can define a new alias with the @samp{alias} command.
26391 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26395 @var{ALIAS} specifies the name of the new alias.
26396 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26399 @var{COMMAND} specifies the name of an existing command
26400 that is being aliased.
26402 The @samp{-a} option specifies that the new alias is an abbreviation
26403 of the command. Abbreviations are not shown in command
26404 lists displayed by the @samp{help} command.
26406 The @samp{--} option specifies the end of options,
26407 and is useful when @var{ALIAS} begins with a dash.
26409 Here is a simple example showing how to make an abbreviation
26410 of a command so that there is less to type.
26411 Suppose you were tired of typing @samp{disas}, the current
26412 shortest unambiguous abbreviation of the @samp{disassemble} command
26413 and you wanted an even shorter version named @samp{di}.
26414 The following will accomplish this.
26417 (gdb) alias -a di = disas
26420 Note that aliases are different from user-defined commands.
26421 With a user-defined command, you also need to write documentation
26422 for it with the @samp{document} command.
26423 An alias automatically picks up the documentation of the existing command.
26425 Here is an example where we make @samp{elms} an abbreviation of
26426 @samp{elements} in the @samp{set print elements} command.
26427 This is to show that you can make an abbreviation of any part
26431 (gdb) alias -a set print elms = set print elements
26432 (gdb) alias -a show print elms = show print elements
26433 (gdb) set p elms 20
26435 Limit on string chars or array elements to print is 200.
26438 Note that if you are defining an alias of a @samp{set} command,
26439 and you want to have an alias for the corresponding @samp{show}
26440 command, then you need to define the latter separately.
26442 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26443 @var{ALIAS}, just as they are normally.
26446 (gdb) alias -a set pr elms = set p ele
26449 Finally, here is an example showing the creation of a one word
26450 alias for a more complex command.
26451 This creates alias @samp{spe} of the command @samp{set print elements}.
26454 (gdb) alias spe = set print elements
26459 @chapter Command Interpreters
26460 @cindex command interpreters
26462 @value{GDBN} supports multiple command interpreters, and some command
26463 infrastructure to allow users or user interface writers to switch
26464 between interpreters or run commands in other interpreters.
26466 @value{GDBN} currently supports two command interpreters, the console
26467 interpreter (sometimes called the command-line interpreter or @sc{cli})
26468 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26469 describes both of these interfaces in great detail.
26471 By default, @value{GDBN} will start with the console interpreter.
26472 However, the user may choose to start @value{GDBN} with another
26473 interpreter by specifying the @option{-i} or @option{--interpreter}
26474 startup options. Defined interpreters include:
26478 @cindex console interpreter
26479 The traditional console or command-line interpreter. This is the most often
26480 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26481 @value{GDBN} will use this interpreter.
26484 @cindex mi interpreter
26485 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
26486 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26487 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26491 @cindex mi2 interpreter
26492 The current @sc{gdb/mi} interface.
26495 @cindex mi1 interpreter
26496 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
26500 @cindex invoke another interpreter
26501 The interpreter being used by @value{GDBN} may not be dynamically
26502 switched at runtime. Although possible, this could lead to a very
26503 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
26504 enters the command "interpreter-set console" in a console view,
26505 @value{GDBN} would switch to using the console interpreter, rendering
26506 the IDE inoperable!
26508 @kindex interpreter-exec
26509 Although you may only choose a single interpreter at startup, you may execute
26510 commands in any interpreter from the current interpreter using the appropriate
26511 command. If you are running the console interpreter, simply use the
26512 @code{interpreter-exec} command:
26515 interpreter-exec mi "-data-list-register-names"
26518 @sc{gdb/mi} has a similar command, although it is only available in versions of
26519 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26522 @chapter @value{GDBN} Text User Interface
26524 @cindex Text User Interface
26527 * TUI Overview:: TUI overview
26528 * TUI Keys:: TUI key bindings
26529 * TUI Single Key Mode:: TUI single key mode
26530 * TUI Commands:: TUI-specific commands
26531 * TUI Configuration:: TUI configuration variables
26534 The @value{GDBN} Text User Interface (TUI) is a terminal
26535 interface which uses the @code{curses} library to show the source
26536 file, the assembly output, the program registers and @value{GDBN}
26537 commands in separate text windows. The TUI mode is supported only
26538 on platforms where a suitable version of the @code{curses} library
26541 The TUI mode is enabled by default when you invoke @value{GDBN} as
26542 @samp{@value{GDBP} -tui}.
26543 You can also switch in and out of TUI mode while @value{GDBN} runs by
26544 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
26545 @xref{TUI Keys, ,TUI Key Bindings}.
26548 @section TUI Overview
26550 In TUI mode, @value{GDBN} can display several text windows:
26554 This window is the @value{GDBN} command window with the @value{GDBN}
26555 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26556 managed using readline.
26559 The source window shows the source file of the program. The current
26560 line and active breakpoints are displayed in this window.
26563 The assembly window shows the disassembly output of the program.
26566 This window shows the processor registers. Registers are highlighted
26567 when their values change.
26570 The source and assembly windows show the current program position
26571 by highlighting the current line and marking it with a @samp{>} marker.
26572 Breakpoints are indicated with two markers. The first marker
26573 indicates the breakpoint type:
26577 Breakpoint which was hit at least once.
26580 Breakpoint which was never hit.
26583 Hardware breakpoint which was hit at least once.
26586 Hardware breakpoint which was never hit.
26589 The second marker indicates whether the breakpoint is enabled or not:
26593 Breakpoint is enabled.
26596 Breakpoint is disabled.
26599 The source, assembly and register windows are updated when the current
26600 thread changes, when the frame changes, or when the program counter
26603 These windows are not all visible at the same time. The command
26604 window is always visible. The others can be arranged in several
26615 source and assembly,
26618 source and registers, or
26621 assembly and registers.
26624 A status line above the command window shows the following information:
26628 Indicates the current @value{GDBN} target.
26629 (@pxref{Targets, ,Specifying a Debugging Target}).
26632 Gives the current process or thread number.
26633 When no process is being debugged, this field is set to @code{No process}.
26636 Gives the current function name for the selected frame.
26637 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26638 When there is no symbol corresponding to the current program counter,
26639 the string @code{??} is displayed.
26642 Indicates the current line number for the selected frame.
26643 When the current line number is not known, the string @code{??} is displayed.
26646 Indicates the current program counter address.
26650 @section TUI Key Bindings
26651 @cindex TUI key bindings
26653 The TUI installs several key bindings in the readline keymaps
26654 @ifset SYSTEM_READLINE
26655 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26657 @ifclear SYSTEM_READLINE
26658 (@pxref{Command Line Editing}).
26660 The following key bindings are installed for both TUI mode and the
26661 @value{GDBN} standard mode.
26670 Enter or leave the TUI mode. When leaving the TUI mode,
26671 the curses window management stops and @value{GDBN} operates using
26672 its standard mode, writing on the terminal directly. When reentering
26673 the TUI mode, control is given back to the curses windows.
26674 The screen is then refreshed.
26678 Use a TUI layout with only one window. The layout will
26679 either be @samp{source} or @samp{assembly}. When the TUI mode
26680 is not active, it will switch to the TUI mode.
26682 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26686 Use a TUI layout with at least two windows. When the current
26687 layout already has two windows, the next layout with two windows is used.
26688 When a new layout is chosen, one window will always be common to the
26689 previous layout and the new one.
26691 Think of it as the Emacs @kbd{C-x 2} binding.
26695 Change the active window. The TUI associates several key bindings
26696 (like scrolling and arrow keys) with the active window. This command
26697 gives the focus to the next TUI window.
26699 Think of it as the Emacs @kbd{C-x o} binding.
26703 Switch in and out of the TUI SingleKey mode that binds single
26704 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26707 The following key bindings only work in the TUI mode:
26712 Scroll the active window one page up.
26716 Scroll the active window one page down.
26720 Scroll the active window one line up.
26724 Scroll the active window one line down.
26728 Scroll the active window one column left.
26732 Scroll the active window one column right.
26736 Refresh the screen.
26739 Because the arrow keys scroll the active window in the TUI mode, they
26740 are not available for their normal use by readline unless the command
26741 window has the focus. When another window is active, you must use
26742 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26743 and @kbd{C-f} to control the command window.
26745 @node TUI Single Key Mode
26746 @section TUI Single Key Mode
26747 @cindex TUI single key mode
26749 The TUI also provides a @dfn{SingleKey} mode, which binds several
26750 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26751 switch into this mode, where the following key bindings are used:
26754 @kindex c @r{(SingleKey TUI key)}
26758 @kindex d @r{(SingleKey TUI key)}
26762 @kindex f @r{(SingleKey TUI key)}
26766 @kindex n @r{(SingleKey TUI key)}
26770 @kindex q @r{(SingleKey TUI key)}
26772 exit the SingleKey mode.
26774 @kindex r @r{(SingleKey TUI key)}
26778 @kindex s @r{(SingleKey TUI key)}
26782 @kindex u @r{(SingleKey TUI key)}
26786 @kindex v @r{(SingleKey TUI key)}
26790 @kindex w @r{(SingleKey TUI key)}
26795 Other keys temporarily switch to the @value{GDBN} command prompt.
26796 The key that was pressed is inserted in the editing buffer so that
26797 it is possible to type most @value{GDBN} commands without interaction
26798 with the TUI SingleKey mode. Once the command is entered the TUI
26799 SingleKey mode is restored. The only way to permanently leave
26800 this mode is by typing @kbd{q} or @kbd{C-x s}.
26804 @section TUI-specific Commands
26805 @cindex TUI commands
26807 The TUI has specific commands to control the text windows.
26808 These commands are always available, even when @value{GDBN} is not in
26809 the TUI mode. When @value{GDBN} is in the standard mode, most
26810 of these commands will automatically switch to the TUI mode.
26812 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26813 terminal, or @value{GDBN} has been started with the machine interface
26814 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26815 these commands will fail with an error, because it would not be
26816 possible or desirable to enable curses window management.
26821 List and give the size of all displayed windows.
26825 Display the next layout.
26828 Display the previous layout.
26831 Display the source window only.
26834 Display the assembly window only.
26837 Display the source and assembly window.
26840 Display the register window together with the source or assembly window.
26844 Make the next window active for scrolling.
26847 Make the previous window active for scrolling.
26850 Make the source window active for scrolling.
26853 Make the assembly window active for scrolling.
26856 Make the register window active for scrolling.
26859 Make the command window active for scrolling.
26863 Refresh the screen. This is similar to typing @kbd{C-L}.
26865 @item tui reg float
26867 Show the floating point registers in the register window.
26869 @item tui reg general
26870 Show the general registers in the register window.
26873 Show the next register group. The list of register groups as well as
26874 their order is target specific. The predefined register groups are the
26875 following: @code{general}, @code{float}, @code{system}, @code{vector},
26876 @code{all}, @code{save}, @code{restore}.
26878 @item tui reg system
26879 Show the system registers in the register window.
26883 Update the source window and the current execution point.
26885 @item winheight @var{name} +@var{count}
26886 @itemx winheight @var{name} -@var{count}
26888 Change the height of the window @var{name} by @var{count}
26889 lines. Positive counts increase the height, while negative counts
26892 @item tabset @var{nchars}
26894 Set the width of tab stops to be @var{nchars} characters.
26897 @node TUI Configuration
26898 @section TUI Configuration Variables
26899 @cindex TUI configuration variables
26901 Several configuration variables control the appearance of TUI windows.
26904 @item set tui border-kind @var{kind}
26905 @kindex set tui border-kind
26906 Select the border appearance for the source, assembly and register windows.
26907 The possible values are the following:
26910 Use a space character to draw the border.
26913 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
26916 Use the Alternate Character Set to draw the border. The border is
26917 drawn using character line graphics if the terminal supports them.
26920 @item set tui border-mode @var{mode}
26921 @kindex set tui border-mode
26922 @itemx set tui active-border-mode @var{mode}
26923 @kindex set tui active-border-mode
26924 Select the display attributes for the borders of the inactive windows
26925 or the active window. The @var{mode} can be one of the following:
26928 Use normal attributes to display the border.
26934 Use reverse video mode.
26937 Use half bright mode.
26939 @item half-standout
26940 Use half bright and standout mode.
26943 Use extra bright or bold mode.
26945 @item bold-standout
26946 Use extra bright or bold and standout mode.
26951 @chapter Using @value{GDBN} under @sc{gnu} Emacs
26954 @cindex @sc{gnu} Emacs
26955 A special interface allows you to use @sc{gnu} Emacs to view (and
26956 edit) the source files for the program you are debugging with
26959 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
26960 executable file you want to debug as an argument. This command starts
26961 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
26962 created Emacs buffer.
26963 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
26965 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
26970 All ``terminal'' input and output goes through an Emacs buffer, called
26973 This applies both to @value{GDBN} commands and their output, and to the input
26974 and output done by the program you are debugging.
26976 This is useful because it means that you can copy the text of previous
26977 commands and input them again; you can even use parts of the output
26980 All the facilities of Emacs' Shell mode are available for interacting
26981 with your program. In particular, you can send signals the usual
26982 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
26986 @value{GDBN} displays source code through Emacs.
26988 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
26989 source file for that frame and puts an arrow (@samp{=>}) at the
26990 left margin of the current line. Emacs uses a separate buffer for
26991 source display, and splits the screen to show both your @value{GDBN} session
26994 Explicit @value{GDBN} @code{list} or search commands still produce output as
26995 usual, but you probably have no reason to use them from Emacs.
26998 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
26999 a graphical mode, enabled by default, which provides further buffers
27000 that can control the execution and describe the state of your program.
27001 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27003 If you specify an absolute file name when prompted for the @kbd{M-x
27004 gdb} argument, then Emacs sets your current working directory to where
27005 your program resides. If you only specify the file name, then Emacs
27006 sets your current working directory to the directory associated
27007 with the previous buffer. In this case, @value{GDBN} may find your
27008 program by searching your environment's @code{PATH} variable, but on
27009 some operating systems it might not find the source. So, although the
27010 @value{GDBN} input and output session proceeds normally, the auxiliary
27011 buffer does not display the current source and line of execution.
27013 The initial working directory of @value{GDBN} is printed on the top
27014 line of the GUD buffer and this serves as a default for the commands
27015 that specify files for @value{GDBN} to operate on. @xref{Files,
27016 ,Commands to Specify Files}.
27018 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27019 need to call @value{GDBN} by a different name (for example, if you
27020 keep several configurations around, with different names) you can
27021 customize the Emacs variable @code{gud-gdb-command-name} to run the
27024 In the GUD buffer, you can use these special Emacs commands in
27025 addition to the standard Shell mode commands:
27029 Describe the features of Emacs' GUD Mode.
27032 Execute to another source line, like the @value{GDBN} @code{step} command; also
27033 update the display window to show the current file and location.
27036 Execute to next source line in this function, skipping all function
27037 calls, like the @value{GDBN} @code{next} command. Then update the display window
27038 to show the current file and location.
27041 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27042 display window accordingly.
27045 Execute until exit from the selected stack frame, like the @value{GDBN}
27046 @code{finish} command.
27049 Continue execution of your program, like the @value{GDBN} @code{continue}
27053 Go up the number of frames indicated by the numeric argument
27054 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27055 like the @value{GDBN} @code{up} command.
27058 Go down the number of frames indicated by the numeric argument, like the
27059 @value{GDBN} @code{down} command.
27062 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27063 tells @value{GDBN} to set a breakpoint on the source line point is on.
27065 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27066 separate frame which shows a backtrace when the GUD buffer is current.
27067 Move point to any frame in the stack and type @key{RET} to make it
27068 become the current frame and display the associated source in the
27069 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27070 selected frame become the current one. In graphical mode, the
27071 speedbar displays watch expressions.
27073 If you accidentally delete the source-display buffer, an easy way to get
27074 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27075 request a frame display; when you run under Emacs, this recreates
27076 the source buffer if necessary to show you the context of the current
27079 The source files displayed in Emacs are in ordinary Emacs buffers
27080 which are visiting the source files in the usual way. You can edit
27081 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27082 communicates with Emacs in terms of line numbers. If you add or
27083 delete lines from the text, the line numbers that @value{GDBN} knows cease
27084 to correspond properly with the code.
27086 A more detailed description of Emacs' interaction with @value{GDBN} is
27087 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27090 @c The following dropped because Epoch is nonstandard. Reactivate
27091 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
27093 @kindex Emacs Epoch environment
27097 Version 18 of @sc{gnu} Emacs has a built-in window system
27098 called the @code{epoch}
27099 environment. Users of this environment can use a new command,
27100 @code{inspect} which performs identically to @code{print} except that
27101 each value is printed in its own window.
27106 @chapter The @sc{gdb/mi} Interface
27108 @unnumberedsec Function and Purpose
27110 @cindex @sc{gdb/mi}, its purpose
27111 @sc{gdb/mi} is a line based machine oriented text interface to
27112 @value{GDBN} and is activated by specifying using the
27113 @option{--interpreter} command line option (@pxref{Mode Options}). It
27114 is specifically intended to support the development of systems which
27115 use the debugger as just one small component of a larger system.
27117 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27118 in the form of a reference manual.
27120 Note that @sc{gdb/mi} is still under construction, so some of the
27121 features described below are incomplete and subject to change
27122 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27124 @unnumberedsec Notation and Terminology
27126 @cindex notational conventions, for @sc{gdb/mi}
27127 This chapter uses the following notation:
27131 @code{|} separates two alternatives.
27134 @code{[ @var{something} ]} indicates that @var{something} is optional:
27135 it may or may not be given.
27138 @code{( @var{group} )*} means that @var{group} inside the parentheses
27139 may repeat zero or more times.
27142 @code{( @var{group} )+} means that @var{group} inside the parentheses
27143 may repeat one or more times.
27146 @code{"@var{string}"} means a literal @var{string}.
27150 @heading Dependencies
27154 * GDB/MI General Design::
27155 * GDB/MI Command Syntax::
27156 * GDB/MI Compatibility with CLI::
27157 * GDB/MI Development and Front Ends::
27158 * GDB/MI Output Records::
27159 * GDB/MI Simple Examples::
27160 * GDB/MI Command Description Format::
27161 * GDB/MI Breakpoint Commands::
27162 * GDB/MI Catchpoint Commands::
27163 * GDB/MI Program Context::
27164 * GDB/MI Thread Commands::
27165 * GDB/MI Ada Tasking Commands::
27166 * GDB/MI Program Execution::
27167 * GDB/MI Stack Manipulation::
27168 * GDB/MI Variable Objects::
27169 * GDB/MI Data Manipulation::
27170 * GDB/MI Tracepoint Commands::
27171 * GDB/MI Symbol Query::
27172 * GDB/MI File Commands::
27174 * GDB/MI Kod Commands::
27175 * GDB/MI Memory Overlay Commands::
27176 * GDB/MI Signal Handling Commands::
27178 * GDB/MI Target Manipulation::
27179 * GDB/MI File Transfer Commands::
27180 * GDB/MI Miscellaneous Commands::
27183 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27184 @node GDB/MI General Design
27185 @section @sc{gdb/mi} General Design
27186 @cindex GDB/MI General Design
27188 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
27189 parts---commands sent to @value{GDBN}, responses to those commands
27190 and notifications. Each command results in exactly one response,
27191 indicating either successful completion of the command, or an error.
27192 For the commands that do not resume the target, the response contains the
27193 requested information. For the commands that resume the target, the
27194 response only indicates whether the target was successfully resumed.
27195 Notifications is the mechanism for reporting changes in the state of the
27196 target, or in @value{GDBN} state, that cannot conveniently be associated with
27197 a command and reported as part of that command response.
27199 The important examples of notifications are:
27203 Exec notifications. These are used to report changes in
27204 target state---when a target is resumed, or stopped. It would not
27205 be feasible to include this information in response of resuming
27206 commands, because one resume commands can result in multiple events in
27207 different threads. Also, quite some time may pass before any event
27208 happens in the target, while a frontend needs to know whether the resuming
27209 command itself was successfully executed.
27212 Console output, and status notifications. Console output
27213 notifications are used to report output of CLI commands, as well as
27214 diagnostics for other commands. Status notifications are used to
27215 report the progress of a long-running operation. Naturally, including
27216 this information in command response would mean no output is produced
27217 until the command is finished, which is undesirable.
27220 General notifications. Commands may have various side effects on
27221 the @value{GDBN} or target state beyond their official purpose. For example,
27222 a command may change the selected thread. Although such changes can
27223 be included in command response, using notification allows for more
27224 orthogonal frontend design.
27228 There's no guarantee that whenever an MI command reports an error,
27229 @value{GDBN} or the target are in any specific state, and especially,
27230 the state is not reverted to the state before the MI command was
27231 processed. Therefore, whenever an MI command results in an error,
27232 we recommend that the frontend refreshes all the information shown in
27233 the user interface.
27237 * Context management::
27238 * Asynchronous and non-stop modes::
27242 @node Context management
27243 @subsection Context management
27245 In most cases when @value{GDBN} accesses the target, this access is
27246 done in context of a specific thread and frame (@pxref{Frames}).
27247 Often, even when accessing global data, the target requires that a thread
27248 be specified. The CLI interface maintains the selected thread and frame,
27249 and supplies them to target on each command. This is convenient,
27250 because a command line user would not want to specify that information
27251 explicitly on each command, and because user interacts with
27252 @value{GDBN} via a single terminal, so no confusion is possible as
27253 to what thread and frame are the current ones.
27255 In the case of MI, the concept of selected thread and frame is less
27256 useful. First, a frontend can easily remember this information
27257 itself. Second, a graphical frontend can have more than one window,
27258 each one used for debugging a different thread, and the frontend might
27259 want to access additional threads for internal purposes. This
27260 increases the risk that by relying on implicitly selected thread, the
27261 frontend may be operating on a wrong one. Therefore, each MI command
27262 should explicitly specify which thread and frame to operate on. To
27263 make it possible, each MI command accepts the @samp{--thread} and
27264 @samp{--frame} options, the value to each is @value{GDBN} identifier
27265 for thread and frame to operate on.
27267 Usually, each top-level window in a frontend allows the user to select
27268 a thread and a frame, and remembers the user selection for further
27269 operations. However, in some cases @value{GDBN} may suggest that the
27270 current thread be changed. For example, when stopping on a breakpoint
27271 it is reasonable to switch to the thread where breakpoint is hit. For
27272 another example, if the user issues the CLI @samp{thread} command via
27273 the frontend, it is desirable to change the frontend's selected thread to the
27274 one specified by user. @value{GDBN} communicates the suggestion to
27275 change current thread using the @samp{=thread-selected} notification.
27276 No such notification is available for the selected frame at the moment.
27278 Note that historically, MI shares the selected thread with CLI, so
27279 frontends used the @code{-thread-select} to execute commands in the
27280 right context. However, getting this to work right is cumbersome. The
27281 simplest way is for frontend to emit @code{-thread-select} command
27282 before every command. This doubles the number of commands that need
27283 to be sent. The alternative approach is to suppress @code{-thread-select}
27284 if the selected thread in @value{GDBN} is supposed to be identical to the
27285 thread the frontend wants to operate on. However, getting this
27286 optimization right can be tricky. In particular, if the frontend
27287 sends several commands to @value{GDBN}, and one of the commands changes the
27288 selected thread, then the behaviour of subsequent commands will
27289 change. So, a frontend should either wait for response from such
27290 problematic commands, or explicitly add @code{-thread-select} for
27291 all subsequent commands. No frontend is known to do this exactly
27292 right, so it is suggested to just always pass the @samp{--thread} and
27293 @samp{--frame} options.
27295 @node Asynchronous and non-stop modes
27296 @subsection Asynchronous command execution and non-stop mode
27298 On some targets, @value{GDBN} is capable of processing MI commands
27299 even while the target is running. This is called @dfn{asynchronous
27300 command execution} (@pxref{Background Execution}). The frontend may
27301 specify a preferrence for asynchronous execution using the
27302 @code{-gdb-set target-async 1} command, which should be emitted before
27303 either running the executable or attaching to the target. After the
27304 frontend has started the executable or attached to the target, it can
27305 find if asynchronous execution is enabled using the
27306 @code{-list-target-features} command.
27308 Even if @value{GDBN} can accept a command while target is running,
27309 many commands that access the target do not work when the target is
27310 running. Therefore, asynchronous command execution is most useful
27311 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27312 it is possible to examine the state of one thread, while other threads
27315 When a given thread is running, MI commands that try to access the
27316 target in the context of that thread may not work, or may work only on
27317 some targets. In particular, commands that try to operate on thread's
27318 stack will not work, on any target. Commands that read memory, or
27319 modify breakpoints, may work or not work, depending on the target. Note
27320 that even commands that operate on global state, such as @code{print},
27321 @code{set}, and breakpoint commands, still access the target in the
27322 context of a specific thread, so frontend should try to find a
27323 stopped thread and perform the operation on that thread (using the
27324 @samp{--thread} option).
27326 Which commands will work in the context of a running thread is
27327 highly target dependent. However, the two commands
27328 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27329 to find the state of a thread, will always work.
27331 @node Thread groups
27332 @subsection Thread groups
27333 @value{GDBN} may be used to debug several processes at the same time.
27334 On some platfroms, @value{GDBN} may support debugging of several
27335 hardware systems, each one having several cores with several different
27336 processes running on each core. This section describes the MI
27337 mechanism to support such debugging scenarios.
27339 The key observation is that regardless of the structure of the
27340 target, MI can have a global list of threads, because most commands that
27341 accept the @samp{--thread} option do not need to know what process that
27342 thread belongs to. Therefore, it is not necessary to introduce
27343 neither additional @samp{--process} option, nor an notion of the
27344 current process in the MI interface. The only strictly new feature
27345 that is required is the ability to find how the threads are grouped
27348 To allow the user to discover such grouping, and to support arbitrary
27349 hierarchy of machines/cores/processes, MI introduces the concept of a
27350 @dfn{thread group}. Thread group is a collection of threads and other
27351 thread groups. A thread group always has a string identifier, a type,
27352 and may have additional attributes specific to the type. A new
27353 command, @code{-list-thread-groups}, returns the list of top-level
27354 thread groups, which correspond to processes that @value{GDBN} is
27355 debugging at the moment. By passing an identifier of a thread group
27356 to the @code{-list-thread-groups} command, it is possible to obtain
27357 the members of specific thread group.
27359 To allow the user to easily discover processes, and other objects, he
27360 wishes to debug, a concept of @dfn{available thread group} is
27361 introduced. Available thread group is an thread group that
27362 @value{GDBN} is not debugging, but that can be attached to, using the
27363 @code{-target-attach} command. The list of available top-level thread
27364 groups can be obtained using @samp{-list-thread-groups --available}.
27365 In general, the content of a thread group may be only retrieved only
27366 after attaching to that thread group.
27368 Thread groups are related to inferiors (@pxref{Inferiors and
27369 Programs}). Each inferior corresponds to a thread group of a special
27370 type @samp{process}, and some additional operations are permitted on
27371 such thread groups.
27373 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27374 @node GDB/MI Command Syntax
27375 @section @sc{gdb/mi} Command Syntax
27378 * GDB/MI Input Syntax::
27379 * GDB/MI Output Syntax::
27382 @node GDB/MI Input Syntax
27383 @subsection @sc{gdb/mi} Input Syntax
27385 @cindex input syntax for @sc{gdb/mi}
27386 @cindex @sc{gdb/mi}, input syntax
27388 @item @var{command} @expansion{}
27389 @code{@var{cli-command} | @var{mi-command}}
27391 @item @var{cli-command} @expansion{}
27392 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27393 @var{cli-command} is any existing @value{GDBN} CLI command.
27395 @item @var{mi-command} @expansion{}
27396 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27397 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27399 @item @var{token} @expansion{}
27400 "any sequence of digits"
27402 @item @var{option} @expansion{}
27403 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27405 @item @var{parameter} @expansion{}
27406 @code{@var{non-blank-sequence} | @var{c-string}}
27408 @item @var{operation} @expansion{}
27409 @emph{any of the operations described in this chapter}
27411 @item @var{non-blank-sequence} @expansion{}
27412 @emph{anything, provided it doesn't contain special characters such as
27413 "-", @var{nl}, """ and of course " "}
27415 @item @var{c-string} @expansion{}
27416 @code{""" @var{seven-bit-iso-c-string-content} """}
27418 @item @var{nl} @expansion{}
27427 The CLI commands are still handled by the @sc{mi} interpreter; their
27428 output is described below.
27431 The @code{@var{token}}, when present, is passed back when the command
27435 Some @sc{mi} commands accept optional arguments as part of the parameter
27436 list. Each option is identified by a leading @samp{-} (dash) and may be
27437 followed by an optional argument parameter. Options occur first in the
27438 parameter list and can be delimited from normal parameters using
27439 @samp{--} (this is useful when some parameters begin with a dash).
27446 We want easy access to the existing CLI syntax (for debugging).
27449 We want it to be easy to spot a @sc{mi} operation.
27452 @node GDB/MI Output Syntax
27453 @subsection @sc{gdb/mi} Output Syntax
27455 @cindex output syntax of @sc{gdb/mi}
27456 @cindex @sc{gdb/mi}, output syntax
27457 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27458 followed, optionally, by a single result record. This result record
27459 is for the most recent command. The sequence of output records is
27460 terminated by @samp{(gdb)}.
27462 If an input command was prefixed with a @code{@var{token}} then the
27463 corresponding output for that command will also be prefixed by that same
27467 @item @var{output} @expansion{}
27468 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27470 @item @var{result-record} @expansion{}
27471 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27473 @item @var{out-of-band-record} @expansion{}
27474 @code{@var{async-record} | @var{stream-record}}
27476 @item @var{async-record} @expansion{}
27477 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27479 @item @var{exec-async-output} @expansion{}
27480 @code{[ @var{token} ] "*" @var{async-output}}
27482 @item @var{status-async-output} @expansion{}
27483 @code{[ @var{token} ] "+" @var{async-output}}
27485 @item @var{notify-async-output} @expansion{}
27486 @code{[ @var{token} ] "=" @var{async-output}}
27488 @item @var{async-output} @expansion{}
27489 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
27491 @item @var{result-class} @expansion{}
27492 @code{"done" | "running" | "connected" | "error" | "exit"}
27494 @item @var{async-class} @expansion{}
27495 @code{"stopped" | @var{others}} (where @var{others} will be added
27496 depending on the needs---this is still in development).
27498 @item @var{result} @expansion{}
27499 @code{ @var{variable} "=" @var{value}}
27501 @item @var{variable} @expansion{}
27502 @code{ @var{string} }
27504 @item @var{value} @expansion{}
27505 @code{ @var{const} | @var{tuple} | @var{list} }
27507 @item @var{const} @expansion{}
27508 @code{@var{c-string}}
27510 @item @var{tuple} @expansion{}
27511 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27513 @item @var{list} @expansion{}
27514 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27515 @var{result} ( "," @var{result} )* "]" }
27517 @item @var{stream-record} @expansion{}
27518 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27520 @item @var{console-stream-output} @expansion{}
27521 @code{"~" @var{c-string}}
27523 @item @var{target-stream-output} @expansion{}
27524 @code{"@@" @var{c-string}}
27526 @item @var{log-stream-output} @expansion{}
27527 @code{"&" @var{c-string}}
27529 @item @var{nl} @expansion{}
27532 @item @var{token} @expansion{}
27533 @emph{any sequence of digits}.
27541 All output sequences end in a single line containing a period.
27544 The @code{@var{token}} is from the corresponding request. Note that
27545 for all async output, while the token is allowed by the grammar and
27546 may be output by future versions of @value{GDBN} for select async
27547 output messages, it is generally omitted. Frontends should treat
27548 all async output as reporting general changes in the state of the
27549 target and there should be no need to associate async output to any
27553 @cindex status output in @sc{gdb/mi}
27554 @var{status-async-output} contains on-going status information about the
27555 progress of a slow operation. It can be discarded. All status output is
27556 prefixed by @samp{+}.
27559 @cindex async output in @sc{gdb/mi}
27560 @var{exec-async-output} contains asynchronous state change on the target
27561 (stopped, started, disappeared). All async output is prefixed by
27565 @cindex notify output in @sc{gdb/mi}
27566 @var{notify-async-output} contains supplementary information that the
27567 client should handle (e.g., a new breakpoint information). All notify
27568 output is prefixed by @samp{=}.
27571 @cindex console output in @sc{gdb/mi}
27572 @var{console-stream-output} is output that should be displayed as is in the
27573 console. It is the textual response to a CLI command. All the console
27574 output is prefixed by @samp{~}.
27577 @cindex target output in @sc{gdb/mi}
27578 @var{target-stream-output} is the output produced by the target program.
27579 All the target output is prefixed by @samp{@@}.
27582 @cindex log output in @sc{gdb/mi}
27583 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27584 instance messages that should be displayed as part of an error log. All
27585 the log output is prefixed by @samp{&}.
27588 @cindex list output in @sc{gdb/mi}
27589 New @sc{gdb/mi} commands should only output @var{lists} containing
27595 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27596 details about the various output records.
27598 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27599 @node GDB/MI Compatibility with CLI
27600 @section @sc{gdb/mi} Compatibility with CLI
27602 @cindex compatibility, @sc{gdb/mi} and CLI
27603 @cindex @sc{gdb/mi}, compatibility with CLI
27605 For the developers convenience CLI commands can be entered directly,
27606 but there may be some unexpected behaviour. For example, commands
27607 that query the user will behave as if the user replied yes, breakpoint
27608 command lists are not executed and some CLI commands, such as
27609 @code{if}, @code{when} and @code{define}, prompt for further input with
27610 @samp{>}, which is not valid MI output.
27612 This feature may be removed at some stage in the future and it is
27613 recommended that front ends use the @code{-interpreter-exec} command
27614 (@pxref{-interpreter-exec}).
27616 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27617 @node GDB/MI Development and Front Ends
27618 @section @sc{gdb/mi} Development and Front Ends
27619 @cindex @sc{gdb/mi} development
27621 The application which takes the MI output and presents the state of the
27622 program being debugged to the user is called a @dfn{front end}.
27624 Although @sc{gdb/mi} is still incomplete, it is currently being used
27625 by a variety of front ends to @value{GDBN}. This makes it difficult
27626 to introduce new functionality without breaking existing usage. This
27627 section tries to minimize the problems by describing how the protocol
27630 Some changes in MI need not break a carefully designed front end, and
27631 for these the MI version will remain unchanged. The following is a
27632 list of changes that may occur within one level, so front ends should
27633 parse MI output in a way that can handle them:
27637 New MI commands may be added.
27640 New fields may be added to the output of any MI command.
27643 The range of values for fields with specified values, e.g.,
27644 @code{in_scope} (@pxref{-var-update}) may be extended.
27646 @c The format of field's content e.g type prefix, may change so parse it
27647 @c at your own risk. Yes, in general?
27649 @c The order of fields may change? Shouldn't really matter but it might
27650 @c resolve inconsistencies.
27653 If the changes are likely to break front ends, the MI version level
27654 will be increased by one. This will allow the front end to parse the
27655 output according to the MI version. Apart from mi0, new versions of
27656 @value{GDBN} will not support old versions of MI and it will be the
27657 responsibility of the front end to work with the new one.
27659 @c Starting with mi3, add a new command -mi-version that prints the MI
27662 The best way to avoid unexpected changes in MI that might break your front
27663 end is to make your project known to @value{GDBN} developers and
27664 follow development on @email{gdb@@sourceware.org} and
27665 @email{gdb-patches@@sourceware.org}.
27666 @cindex mailing lists
27668 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27669 @node GDB/MI Output Records
27670 @section @sc{gdb/mi} Output Records
27673 * GDB/MI Result Records::
27674 * GDB/MI Stream Records::
27675 * GDB/MI Async Records::
27676 * GDB/MI Frame Information::
27677 * GDB/MI Thread Information::
27678 * GDB/MI Ada Exception Information::
27681 @node GDB/MI Result Records
27682 @subsection @sc{gdb/mi} Result Records
27684 @cindex result records in @sc{gdb/mi}
27685 @cindex @sc{gdb/mi}, result records
27686 In addition to a number of out-of-band notifications, the response to a
27687 @sc{gdb/mi} command includes one of the following result indications:
27691 @item "^done" [ "," @var{results} ]
27692 The synchronous operation was successful, @code{@var{results}} are the return
27697 This result record is equivalent to @samp{^done}. Historically, it
27698 was output instead of @samp{^done} if the command has resumed the
27699 target. This behaviour is maintained for backward compatibility, but
27700 all frontends should treat @samp{^done} and @samp{^running}
27701 identically and rely on the @samp{*running} output record to determine
27702 which threads are resumed.
27706 @value{GDBN} has connected to a remote target.
27708 @item "^error" "," @var{c-string}
27710 The operation failed. The @code{@var{c-string}} contains the corresponding
27715 @value{GDBN} has terminated.
27719 @node GDB/MI Stream Records
27720 @subsection @sc{gdb/mi} Stream Records
27722 @cindex @sc{gdb/mi}, stream records
27723 @cindex stream records in @sc{gdb/mi}
27724 @value{GDBN} internally maintains a number of output streams: the console, the
27725 target, and the log. The output intended for each of these streams is
27726 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27728 Each stream record begins with a unique @dfn{prefix character} which
27729 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27730 Syntax}). In addition to the prefix, each stream record contains a
27731 @code{@var{string-output}}. This is either raw text (with an implicit new
27732 line) or a quoted C string (which does not contain an implicit newline).
27735 @item "~" @var{string-output}
27736 The console output stream contains text that should be displayed in the
27737 CLI console window. It contains the textual responses to CLI commands.
27739 @item "@@" @var{string-output}
27740 The target output stream contains any textual output from the running
27741 target. This is only present when GDB's event loop is truly
27742 asynchronous, which is currently only the case for remote targets.
27744 @item "&" @var{string-output}
27745 The log stream contains debugging messages being produced by @value{GDBN}'s
27749 @node GDB/MI Async Records
27750 @subsection @sc{gdb/mi} Async Records
27752 @cindex async records in @sc{gdb/mi}
27753 @cindex @sc{gdb/mi}, async records
27754 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27755 additional changes that have occurred. Those changes can either be a
27756 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27757 target activity (e.g., target stopped).
27759 The following is the list of possible async records:
27763 @item *running,thread-id="@var{thread}"
27764 The target is now running. The @var{thread} field tells which
27765 specific thread is now running, and can be @samp{all} if all threads
27766 are running. The frontend should assume that no interaction with a
27767 running thread is possible after this notification is produced.
27768 The frontend should not assume that this notification is output
27769 only once for any command. @value{GDBN} may emit this notification
27770 several times, either for different threads, because it cannot resume
27771 all threads together, or even for a single thread, if the thread must
27772 be stepped though some code before letting it run freely.
27774 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
27775 The target has stopped. The @var{reason} field can have one of the
27779 @item breakpoint-hit
27780 A breakpoint was reached.
27781 @item watchpoint-trigger
27782 A watchpoint was triggered.
27783 @item read-watchpoint-trigger
27784 A read watchpoint was triggered.
27785 @item access-watchpoint-trigger
27786 An access watchpoint was triggered.
27787 @item function-finished
27788 An -exec-finish or similar CLI command was accomplished.
27789 @item location-reached
27790 An -exec-until or similar CLI command was accomplished.
27791 @item watchpoint-scope
27792 A watchpoint has gone out of scope.
27793 @item end-stepping-range
27794 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
27795 similar CLI command was accomplished.
27796 @item exited-signalled
27797 The inferior exited because of a signal.
27799 The inferior exited.
27800 @item exited-normally
27801 The inferior exited normally.
27802 @item signal-received
27803 A signal was received by the inferior.
27805 The inferior has stopped due to a library being loaded or unloaded.
27806 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
27807 set or when a @code{catch load} or @code{catch unload} catchpoint is
27808 in use (@pxref{Set Catchpoints}).
27810 The inferior has forked. This is reported when @code{catch fork}
27811 (@pxref{Set Catchpoints}) has been used.
27813 The inferior has vforked. This is reported in when @code{catch vfork}
27814 (@pxref{Set Catchpoints}) has been used.
27815 @item syscall-entry
27816 The inferior entered a system call. This is reported when @code{catch
27817 syscall} (@pxref{Set Catchpoints}) has been used.
27818 @item syscall-entry
27819 The inferior returned from a system call. This is reported when
27820 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
27822 The inferior called @code{exec}. This is reported when @code{catch exec}
27823 (@pxref{Set Catchpoints}) has been used.
27826 The @var{id} field identifies the thread that directly caused the stop
27827 -- for example by hitting a breakpoint. Depending on whether all-stop
27828 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
27829 stop all threads, or only the thread that directly triggered the stop.
27830 If all threads are stopped, the @var{stopped} field will have the
27831 value of @code{"all"}. Otherwise, the value of the @var{stopped}
27832 field will be a list of thread identifiers. Presently, this list will
27833 always include a single thread, but frontend should be prepared to see
27834 several threads in the list. The @var{core} field reports the
27835 processor core on which the stop event has happened. This field may be absent
27836 if such information is not available.
27838 @item =thread-group-added,id="@var{id}"
27839 @itemx =thread-group-removed,id="@var{id}"
27840 A thread group was either added or removed. The @var{id} field
27841 contains the @value{GDBN} identifier of the thread group. When a thread
27842 group is added, it generally might not be associated with a running
27843 process. When a thread group is removed, its id becomes invalid and
27844 cannot be used in any way.
27846 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
27847 A thread group became associated with a running program,
27848 either because the program was just started or the thread group
27849 was attached to a program. The @var{id} field contains the
27850 @value{GDBN} identifier of the thread group. The @var{pid} field
27851 contains process identifier, specific to the operating system.
27853 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
27854 A thread group is no longer associated with a running program,
27855 either because the program has exited, or because it was detached
27856 from. The @var{id} field contains the @value{GDBN} identifier of the
27857 thread group. @var{code} is the exit code of the inferior; it exists
27858 only when the inferior exited with some code.
27860 @item =thread-created,id="@var{id}",group-id="@var{gid}"
27861 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
27862 A thread either was created, or has exited. The @var{id} field
27863 contains the @value{GDBN} identifier of the thread. The @var{gid}
27864 field identifies the thread group this thread belongs to.
27866 @item =thread-selected,id="@var{id}"
27867 Informs that the selected thread was changed as result of the last
27868 command. This notification is not emitted as result of @code{-thread-select}
27869 command but is emitted whenever an MI command that is not documented
27870 to change the selected thread actually changes it. In particular,
27871 invoking, directly or indirectly (via user-defined command), the CLI
27872 @code{thread} command, will generate this notification.
27874 We suggest that in response to this notification, front ends
27875 highlight the selected thread and cause subsequent commands to apply to
27878 @item =library-loaded,...
27879 Reports that a new library file was loaded by the program. This
27880 notification has 4 fields---@var{id}, @var{target-name},
27881 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
27882 opaque identifier of the library. For remote debugging case,
27883 @var{target-name} and @var{host-name} fields give the name of the
27884 library file on the target, and on the host respectively. For native
27885 debugging, both those fields have the same value. The
27886 @var{symbols-loaded} field is emitted only for backward compatibility
27887 and should not be relied on to convey any useful information. The
27888 @var{thread-group} field, if present, specifies the id of the thread
27889 group in whose context the library was loaded. If the field is
27890 absent, it means the library was loaded in the context of all present
27893 @item =library-unloaded,...
27894 Reports that a library was unloaded by the program. This notification
27895 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
27896 the same meaning as for the @code{=library-loaded} notification.
27897 The @var{thread-group} field, if present, specifies the id of the
27898 thread group in whose context the library was unloaded. If the field is
27899 absent, it means the library was unloaded in the context of all present
27902 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
27903 @itemx =traceframe-changed,end
27904 Reports that the trace frame was changed and its new number is
27905 @var{tfnum}. The number of the tracepoint associated with this trace
27906 frame is @var{tpnum}.
27908 @item =tsv-created,name=@var{name},value=@var{value}
27909 Reports that the new trace state variable @var{name} is created with
27912 @item =tsv-deleted,name=@var{name}
27913 @itemx =tsv-deleted
27914 Reports that the trace state variable @var{name} is deleted or all
27915 trace state variables are deleted.
27917 @item =breakpoint-created,bkpt=@{...@}
27918 @itemx =breakpoint-modified,bkpt=@{...@}
27919 @itemx =breakpoint-deleted,id=@var{number}
27920 Reports that a breakpoint was created, modified, or deleted,
27921 respectively. Only user-visible breakpoints are reported to the MI
27924 The @var{bkpt} argument is of the same form as returned by the various
27925 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
27926 @var{number} is the ordinal number of the breakpoint.
27928 Note that if a breakpoint is emitted in the result record of a
27929 command, then it will not also be emitted in an async record.
27931 @item =record-started,thread-group="@var{id}"
27932 @itemx =record-stopped,thread-group="@var{id}"
27933 Execution log recording was either started or stopped on an
27934 inferior. The @var{id} is the @value{GDBN} identifier of the thread
27935 group corresponding to the affected inferior.
27937 @item =cmd-param-changed,param=@var{param},value=@var{value}
27938 Reports that a parameter of the command @code{set @var{param}} is
27939 changed to @var{value}. In the multi-word @code{set} command,
27940 the @var{param} is the whole parameter list to @code{set} command.
27941 For example, In command @code{set check type on}, @var{param}
27942 is @code{check type} and @var{value} is @code{on}.
27944 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
27945 Reports that bytes from @var{addr} to @var{data} + @var{len} were
27946 written in an inferior. The @var{id} is the identifier of the
27947 thread group corresponding to the affected inferior. The optional
27948 @code{type="code"} part is reported if the memory written to holds
27952 @node GDB/MI Frame Information
27953 @subsection @sc{gdb/mi} Frame Information
27955 Response from many MI commands includes an information about stack
27956 frame. This information is a tuple that may have the following
27961 The level of the stack frame. The innermost frame has the level of
27962 zero. This field is always present.
27965 The name of the function corresponding to the frame. This field may
27966 be absent if @value{GDBN} is unable to determine the function name.
27969 The code address for the frame. This field is always present.
27972 The name of the source files that correspond to the frame's code
27973 address. This field may be absent.
27976 The source line corresponding to the frames' code address. This field
27980 The name of the binary file (either executable or shared library) the
27981 corresponds to the frame's code address. This field may be absent.
27985 @node GDB/MI Thread Information
27986 @subsection @sc{gdb/mi} Thread Information
27988 Whenever @value{GDBN} has to report an information about a thread, it
27989 uses a tuple with the following fields:
27993 The numeric id assigned to the thread by @value{GDBN}. This field is
27997 Target-specific string identifying the thread. This field is always present.
28000 Additional information about the thread provided by the target.
28001 It is supposed to be human-readable and not interpreted by the
28002 frontend. This field is optional.
28005 Either @samp{stopped} or @samp{running}, depending on whether the
28006 thread is presently running. This field is always present.
28009 The value of this field is an integer number of the processor core the
28010 thread was last seen on. This field is optional.
28013 @node GDB/MI Ada Exception Information
28014 @subsection @sc{gdb/mi} Ada Exception Information
28016 Whenever a @code{*stopped} record is emitted because the program
28017 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
28018 @value{GDBN} provides the name of the exception that was raised via
28019 the @code{exception-name} field.
28021 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28022 @node GDB/MI Simple Examples
28023 @section Simple Examples of @sc{gdb/mi} Interaction
28024 @cindex @sc{gdb/mi}, simple examples
28026 This subsection presents several simple examples of interaction using
28027 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
28028 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
28029 the output received from @sc{gdb/mi}.
28031 Note the line breaks shown in the examples are here only for
28032 readability, they don't appear in the real output.
28034 @subheading Setting a Breakpoint
28036 Setting a breakpoint generates synchronous output which contains detailed
28037 information of the breakpoint.
28040 -> -break-insert main
28041 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28042 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28043 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
28047 @subheading Program Execution
28049 Program execution generates asynchronous records and MI gives the
28050 reason that execution stopped.
28056 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28057 frame=@{addr="0x08048564",func="main",
28058 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
28059 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
28064 <- *stopped,reason="exited-normally"
28068 @subheading Quitting @value{GDBN}
28070 Quitting @value{GDBN} just prints the result class @samp{^exit}.
28078 Please note that @samp{^exit} is printed immediately, but it might
28079 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
28080 performs necessary cleanups, including killing programs being debugged
28081 or disconnecting from debug hardware, so the frontend should wait till
28082 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
28083 fails to exit in reasonable time.
28085 @subheading A Bad Command
28087 Here's what happens if you pass a non-existent command:
28091 <- ^error,msg="Undefined MI command: rubbish"
28096 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28097 @node GDB/MI Command Description Format
28098 @section @sc{gdb/mi} Command Description Format
28100 The remaining sections describe blocks of commands. Each block of
28101 commands is laid out in a fashion similar to this section.
28103 @subheading Motivation
28105 The motivation for this collection of commands.
28107 @subheading Introduction
28109 A brief introduction to this collection of commands as a whole.
28111 @subheading Commands
28113 For each command in the block, the following is described:
28115 @subsubheading Synopsis
28118 -command @var{args}@dots{}
28121 @subsubheading Result
28123 @subsubheading @value{GDBN} Command
28125 The corresponding @value{GDBN} CLI command(s), if any.
28127 @subsubheading Example
28129 Example(s) formatted for readability. Some of the described commands have
28130 not been implemented yet and these are labeled N.A.@: (not available).
28133 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28134 @node GDB/MI Breakpoint Commands
28135 @section @sc{gdb/mi} Breakpoint Commands
28137 @cindex breakpoint commands for @sc{gdb/mi}
28138 @cindex @sc{gdb/mi}, breakpoint commands
28139 This section documents @sc{gdb/mi} commands for manipulating
28142 @subheading The @code{-break-after} Command
28143 @findex -break-after
28145 @subsubheading Synopsis
28148 -break-after @var{number} @var{count}
28151 The breakpoint number @var{number} is not in effect until it has been
28152 hit @var{count} times. To see how this is reflected in the output of
28153 the @samp{-break-list} command, see the description of the
28154 @samp{-break-list} command below.
28156 @subsubheading @value{GDBN} Command
28158 The corresponding @value{GDBN} command is @samp{ignore}.
28160 @subsubheading Example
28165 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28166 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28167 fullname="/home/foo/hello.c",line="5",times="0"@}
28174 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28175 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28176 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28177 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28178 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28179 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28180 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28181 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28182 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28183 line="5",times="0",ignore="3"@}]@}
28188 @subheading The @code{-break-catch} Command
28189 @findex -break-catch
28192 @subheading The @code{-break-commands} Command
28193 @findex -break-commands
28195 @subsubheading Synopsis
28198 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
28201 Specifies the CLI commands that should be executed when breakpoint
28202 @var{number} is hit. The parameters @var{command1} to @var{commandN}
28203 are the commands. If no command is specified, any previously-set
28204 commands are cleared. @xref{Break Commands}. Typical use of this
28205 functionality is tracing a program, that is, printing of values of
28206 some variables whenever breakpoint is hit and then continuing.
28208 @subsubheading @value{GDBN} Command
28210 The corresponding @value{GDBN} command is @samp{commands}.
28212 @subsubheading Example
28217 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28218 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28219 fullname="/home/foo/hello.c",line="5",times="0"@}
28221 -break-commands 1 "print v" "continue"
28226 @subheading The @code{-break-condition} Command
28227 @findex -break-condition
28229 @subsubheading Synopsis
28232 -break-condition @var{number} @var{expr}
28235 Breakpoint @var{number} will stop the program only if the condition in
28236 @var{expr} is true. The condition becomes part of the
28237 @samp{-break-list} output (see the description of the @samp{-break-list}
28240 @subsubheading @value{GDBN} Command
28242 The corresponding @value{GDBN} command is @samp{condition}.
28244 @subsubheading Example
28248 -break-condition 1 1
28252 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28253 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28254 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28255 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28256 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28257 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28258 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28259 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28260 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28261 line="5",cond="1",times="0",ignore="3"@}]@}
28265 @subheading The @code{-break-delete} Command
28266 @findex -break-delete
28268 @subsubheading Synopsis
28271 -break-delete ( @var{breakpoint} )+
28274 Delete the breakpoint(s) whose number(s) are specified in the argument
28275 list. This is obviously reflected in the breakpoint list.
28277 @subsubheading @value{GDBN} Command
28279 The corresponding @value{GDBN} command is @samp{delete}.
28281 @subsubheading Example
28289 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28290 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28291 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28292 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28293 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28294 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28295 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28300 @subheading The @code{-break-disable} Command
28301 @findex -break-disable
28303 @subsubheading Synopsis
28306 -break-disable ( @var{breakpoint} )+
28309 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28310 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28312 @subsubheading @value{GDBN} Command
28314 The corresponding @value{GDBN} command is @samp{disable}.
28316 @subsubheading Example
28324 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28325 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28326 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28327 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28328 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28329 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28330 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28331 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28332 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28333 line="5",times="0"@}]@}
28337 @subheading The @code{-break-enable} Command
28338 @findex -break-enable
28340 @subsubheading Synopsis
28343 -break-enable ( @var{breakpoint} )+
28346 Enable (previously disabled) @var{breakpoint}(s).
28348 @subsubheading @value{GDBN} Command
28350 The corresponding @value{GDBN} command is @samp{enable}.
28352 @subsubheading Example
28360 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28361 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28362 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28363 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28364 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28365 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28366 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28367 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28368 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28369 line="5",times="0"@}]@}
28373 @subheading The @code{-break-info} Command
28374 @findex -break-info
28376 @subsubheading Synopsis
28379 -break-info @var{breakpoint}
28383 Get information about a single breakpoint.
28385 @subsubheading @value{GDBN} Command
28387 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28389 @subsubheading Example
28392 @subheading The @code{-break-insert} Command
28393 @findex -break-insert
28395 @subsubheading Synopsis
28398 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28399 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28400 [ -p @var{thread-id} ] [ @var{location} ]
28404 If specified, @var{location}, can be one of:
28411 @item filename:linenum
28412 @item filename:function
28416 The possible optional parameters of this command are:
28420 Insert a temporary breakpoint.
28422 Insert a hardware breakpoint.
28424 If @var{location} cannot be parsed (for example if it
28425 refers to unknown files or functions), create a pending
28426 breakpoint. Without this flag, @value{GDBN} will report
28427 an error, and won't create a breakpoint, if @var{location}
28430 Create a disabled breakpoint.
28432 Create a tracepoint. @xref{Tracepoints}. When this parameter
28433 is used together with @samp{-h}, a fast tracepoint is created.
28434 @item -c @var{condition}
28435 Make the breakpoint conditional on @var{condition}.
28436 @item -i @var{ignore-count}
28437 Initialize the @var{ignore-count}.
28438 @item -p @var{thread-id}
28439 Restrict the breakpoint to the specified @var{thread-id}.
28442 @subsubheading Result
28444 The result is in the form:
28447 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
28448 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
28449 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
28450 times="@var{times}"@}
28454 where @var{number} is the @value{GDBN} number for this breakpoint,
28455 @var{funcname} is the name of the function where the breakpoint was
28456 inserted, @var{filename} is the name of the source file which contains
28457 this function, @var{lineno} is the source line number within that file
28458 and @var{times} the number of times that the breakpoint has been hit
28459 (always 0 for -break-insert but may be greater for -break-info or -break-list
28460 which use the same output).
28462 Note: this format is open to change.
28463 @c An out-of-band breakpoint instead of part of the result?
28465 @subsubheading @value{GDBN} Command
28467 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28468 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28470 @subsubheading Example
28475 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28476 fullname="/home/foo/recursive2.c,line="4",times="0"@}
28478 -break-insert -t foo
28479 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28480 fullname="/home/foo/recursive2.c,line="11",times="0"@}
28483 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28484 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28485 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28486 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28487 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28488 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28489 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28490 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28491 addr="0x0001072c", func="main",file="recursive2.c",
28492 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
28493 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28494 addr="0x00010774",func="foo",file="recursive2.c",
28495 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
28497 @c -break-insert -r foo.*
28498 @c ~int foo(int, int);
28499 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28500 @c "fullname="/home/foo/recursive2.c",line="11",times="0"@}
28504 @subheading The @code{-break-list} Command
28505 @findex -break-list
28507 @subsubheading Synopsis
28513 Displays the list of inserted breakpoints, showing the following fields:
28517 number of the breakpoint
28519 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28521 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28524 is the breakpoint enabled or no: @samp{y} or @samp{n}
28526 memory location at which the breakpoint is set
28528 logical location of the breakpoint, expressed by function name, file
28531 number of times the breakpoint has been hit
28534 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28535 @code{body} field is an empty list.
28537 @subsubheading @value{GDBN} Command
28539 The corresponding @value{GDBN} command is @samp{info break}.
28541 @subsubheading Example
28546 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28547 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28548 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28549 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28550 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28551 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28552 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28553 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28554 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
28555 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28556 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28557 line="13",times="0"@}]@}
28561 Here's an example of the result when there are no breakpoints:
28566 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28567 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28568 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28569 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28570 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28571 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28572 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28577 @subheading The @code{-break-passcount} Command
28578 @findex -break-passcount
28580 @subsubheading Synopsis
28583 -break-passcount @var{tracepoint-number} @var{passcount}
28586 Set the passcount for tracepoint @var{tracepoint-number} to
28587 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28588 is not a tracepoint, error is emitted. This corresponds to CLI
28589 command @samp{passcount}.
28591 @subheading The @code{-break-watch} Command
28592 @findex -break-watch
28594 @subsubheading Synopsis
28597 -break-watch [ -a | -r ]
28600 Create a watchpoint. With the @samp{-a} option it will create an
28601 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28602 read from or on a write to the memory location. With the @samp{-r}
28603 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28604 trigger only when the memory location is accessed for reading. Without
28605 either of the options, the watchpoint created is a regular watchpoint,
28606 i.e., it will trigger when the memory location is accessed for writing.
28607 @xref{Set Watchpoints, , Setting Watchpoints}.
28609 Note that @samp{-break-list} will report a single list of watchpoints and
28610 breakpoints inserted.
28612 @subsubheading @value{GDBN} Command
28614 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28617 @subsubheading Example
28619 Setting a watchpoint on a variable in the @code{main} function:
28624 ^done,wpt=@{number="2",exp="x"@}
28629 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28630 value=@{old="-268439212",new="55"@},
28631 frame=@{func="main",args=[],file="recursive2.c",
28632 fullname="/home/foo/bar/recursive2.c",line="5"@}
28636 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28637 the program execution twice: first for the variable changing value, then
28638 for the watchpoint going out of scope.
28643 ^done,wpt=@{number="5",exp="C"@}
28648 *stopped,reason="watchpoint-trigger",
28649 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28650 frame=@{func="callee4",args=[],
28651 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28652 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28657 *stopped,reason="watchpoint-scope",wpnum="5",
28658 frame=@{func="callee3",args=[@{name="strarg",
28659 value="0x11940 \"A string argument.\""@}],
28660 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28661 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28665 Listing breakpoints and watchpoints, at different points in the program
28666 execution. Note that once the watchpoint goes out of scope, it is
28672 ^done,wpt=@{number="2",exp="C"@}
28675 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28676 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28677 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28678 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28679 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28680 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28681 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28682 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28683 addr="0x00010734",func="callee4",
28684 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28685 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
28686 bkpt=@{number="2",type="watchpoint",disp="keep",
28687 enabled="y",addr="",what="C",times="0"@}]@}
28692 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
28693 value=@{old="-276895068",new="3"@},
28694 frame=@{func="callee4",args=[],
28695 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28696 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28699 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28700 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28701 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28702 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28703 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28704 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28705 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28706 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28707 addr="0x00010734",func="callee4",
28708 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28709 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
28710 bkpt=@{number="2",type="watchpoint",disp="keep",
28711 enabled="y",addr="",what="C",times="-5"@}]@}
28715 ^done,reason="watchpoint-scope",wpnum="2",
28716 frame=@{func="callee3",args=[@{name="strarg",
28717 value="0x11940 \"A string argument.\""@}],
28718 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28719 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28722 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28723 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28724 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28725 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28726 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28727 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28728 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28729 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28730 addr="0x00010734",func="callee4",
28731 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28732 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
28738 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28739 @node GDB/MI Catchpoint Commands
28740 @section @sc{gdb/mi} Catchpoint Commands
28742 This section documents @sc{gdb/mi} commands for manipulating
28745 @subheading The @code{-catch-load} Command
28746 @findex -catch-load
28748 @subsubheading Synopsis
28751 -catch-load [ -t ] [ -d ] @var{regexp}
28754 Add a catchpoint for library load events. If the @samp{-t} option is used,
28755 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28756 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
28757 in a disabled state. The @samp{regexp} argument is a regular
28758 expression used to match the name of the loaded library.
28761 @subsubheading @value{GDBN} Command
28763 The corresponding @value{GDBN} command is @samp{catch load}.
28765 @subsubheading Example
28768 -catch-load -t foo.so
28769 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
28770 what="load of library matching foo.so",times="0"@}
28775 @subheading The @code{-catch-unload} Command
28776 @findex -catch-unload
28778 @subsubheading Synopsis
28781 -catch-unload [ -t ] [ -d ] @var{regexp}
28784 Add a catchpoint for library unload events. If the @samp{-t} option is
28785 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28786 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
28787 created in a disabled state. The @samp{regexp} argument is a regular
28788 expression used to match the name of the unloaded library.
28790 @subsubheading @value{GDBN} Command
28792 The corresponding @value{GDBN} command is @samp{catch unload}.
28794 @subsubheading Example
28797 -catch-unload -d bar.so
28798 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
28799 what="load of library matching bar.so",times="0"@}
28804 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28805 @node GDB/MI Program Context
28806 @section @sc{gdb/mi} Program Context
28808 @subheading The @code{-exec-arguments} Command
28809 @findex -exec-arguments
28812 @subsubheading Synopsis
28815 -exec-arguments @var{args}
28818 Set the inferior program arguments, to be used in the next
28821 @subsubheading @value{GDBN} Command
28823 The corresponding @value{GDBN} command is @samp{set args}.
28825 @subsubheading Example
28829 -exec-arguments -v word
28836 @subheading The @code{-exec-show-arguments} Command
28837 @findex -exec-show-arguments
28839 @subsubheading Synopsis
28842 -exec-show-arguments
28845 Print the arguments of the program.
28847 @subsubheading @value{GDBN} Command
28849 The corresponding @value{GDBN} command is @samp{show args}.
28851 @subsubheading Example
28856 @subheading The @code{-environment-cd} Command
28857 @findex -environment-cd
28859 @subsubheading Synopsis
28862 -environment-cd @var{pathdir}
28865 Set @value{GDBN}'s working directory.
28867 @subsubheading @value{GDBN} Command
28869 The corresponding @value{GDBN} command is @samp{cd}.
28871 @subsubheading Example
28875 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28881 @subheading The @code{-environment-directory} Command
28882 @findex -environment-directory
28884 @subsubheading Synopsis
28887 -environment-directory [ -r ] [ @var{pathdir} ]+
28890 Add directories @var{pathdir} to beginning of search path for source files.
28891 If the @samp{-r} option is used, the search path is reset to the default
28892 search path. If directories @var{pathdir} are supplied in addition to the
28893 @samp{-r} option, the search path is first reset and then addition
28895 Multiple directories may be specified, separated by blanks. Specifying
28896 multiple directories in a single command
28897 results in the directories added to the beginning of the
28898 search path in the same order they were presented in the command.
28899 If blanks are needed as
28900 part of a directory name, double-quotes should be used around
28901 the name. In the command output, the path will show up separated
28902 by the system directory-separator character. The directory-separator
28903 character must not be used
28904 in any directory name.
28905 If no directories are specified, the current search path is displayed.
28907 @subsubheading @value{GDBN} Command
28909 The corresponding @value{GDBN} command is @samp{dir}.
28911 @subsubheading Example
28915 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28916 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28918 -environment-directory ""
28919 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28921 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
28922 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
28924 -environment-directory -r
28925 ^done,source-path="$cdir:$cwd"
28930 @subheading The @code{-environment-path} Command
28931 @findex -environment-path
28933 @subsubheading Synopsis
28936 -environment-path [ -r ] [ @var{pathdir} ]+
28939 Add directories @var{pathdir} to beginning of search path for object files.
28940 If the @samp{-r} option is used, the search path is reset to the original
28941 search path that existed at gdb start-up. If directories @var{pathdir} are
28942 supplied in addition to the
28943 @samp{-r} option, the search path is first reset and then addition
28945 Multiple directories may be specified, separated by blanks. Specifying
28946 multiple directories in a single command
28947 results in the directories added to the beginning of the
28948 search path in the same order they were presented in the command.
28949 If blanks are needed as
28950 part of a directory name, double-quotes should be used around
28951 the name. In the command output, the path will show up separated
28952 by the system directory-separator character. The directory-separator
28953 character must not be used
28954 in any directory name.
28955 If no directories are specified, the current path is displayed.
28958 @subsubheading @value{GDBN} Command
28960 The corresponding @value{GDBN} command is @samp{path}.
28962 @subsubheading Example
28967 ^done,path="/usr/bin"
28969 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
28970 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
28972 -environment-path -r /usr/local/bin
28973 ^done,path="/usr/local/bin:/usr/bin"
28978 @subheading The @code{-environment-pwd} Command
28979 @findex -environment-pwd
28981 @subsubheading Synopsis
28987 Show the current working directory.
28989 @subsubheading @value{GDBN} Command
28991 The corresponding @value{GDBN} command is @samp{pwd}.
28993 @subsubheading Example
28998 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
29002 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29003 @node GDB/MI Thread Commands
29004 @section @sc{gdb/mi} Thread Commands
29007 @subheading The @code{-thread-info} Command
29008 @findex -thread-info
29010 @subsubheading Synopsis
29013 -thread-info [ @var{thread-id} ]
29016 Reports information about either a specific thread, if
29017 the @var{thread-id} parameter is present, or about all
29018 threads. When printing information about all threads,
29019 also reports the current thread.
29021 @subsubheading @value{GDBN} Command
29023 The @samp{info thread} command prints the same information
29026 @subsubheading Result
29028 The result is a list of threads. The following attributes are
29029 defined for a given thread:
29033 This field exists only for the current thread. It has the value @samp{*}.
29036 The identifier that @value{GDBN} uses to refer to the thread.
29039 The identifier that the target uses to refer to the thread.
29042 Extra information about the thread, in a target-specific format. This
29046 The name of the thread. If the user specified a name using the
29047 @code{thread name} command, then this name is given. Otherwise, if
29048 @value{GDBN} can extract the thread name from the target, then that
29049 name is given. If @value{GDBN} cannot find the thread name, then this
29053 The stack frame currently executing in the thread.
29056 The thread's state. The @samp{state} field may have the following
29061 The thread is stopped. Frame information is available for stopped
29065 The thread is running. There's no frame information for running
29071 If @value{GDBN} can find the CPU core on which this thread is running,
29072 then this field is the core identifier. This field is optional.
29076 @subsubheading Example
29081 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29082 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
29083 args=[]@},state="running"@},
29084 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29085 frame=@{level="0",addr="0x0804891f",func="foo",
29086 args=[@{name="i",value="10"@}],
29087 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
29088 state="running"@}],
29089 current-thread-id="1"
29093 @subheading The @code{-thread-list-ids} Command
29094 @findex -thread-list-ids
29096 @subsubheading Synopsis
29102 Produces a list of the currently known @value{GDBN} thread ids. At the
29103 end of the list it also prints the total number of such threads.
29105 This command is retained for historical reasons, the
29106 @code{-thread-info} command should be used instead.
29108 @subsubheading @value{GDBN} Command
29110 Part of @samp{info threads} supplies the same information.
29112 @subsubheading Example
29117 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29118 current-thread-id="1",number-of-threads="3"
29123 @subheading The @code{-thread-select} Command
29124 @findex -thread-select
29126 @subsubheading Synopsis
29129 -thread-select @var{threadnum}
29132 Make @var{threadnum} the current thread. It prints the number of the new
29133 current thread, and the topmost frame for that thread.
29135 This command is deprecated in favor of explicitly using the
29136 @samp{--thread} option to each command.
29138 @subsubheading @value{GDBN} Command
29140 The corresponding @value{GDBN} command is @samp{thread}.
29142 @subsubheading Example
29149 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29150 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29154 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29155 number-of-threads="3"
29158 ^done,new-thread-id="3",
29159 frame=@{level="0",func="vprintf",
29160 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29161 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
29165 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29166 @node GDB/MI Ada Tasking Commands
29167 @section @sc{gdb/mi} Ada Tasking Commands
29169 @subheading The @code{-ada-task-info} Command
29170 @findex -ada-task-info
29172 @subsubheading Synopsis
29175 -ada-task-info [ @var{task-id} ]
29178 Reports information about either a specific Ada task, if the
29179 @var{task-id} parameter is present, or about all Ada tasks.
29181 @subsubheading @value{GDBN} Command
29183 The @samp{info tasks} command prints the same information
29184 about all Ada tasks (@pxref{Ada Tasks}).
29186 @subsubheading Result
29188 The result is a table of Ada tasks. The following columns are
29189 defined for each Ada task:
29193 This field exists only for the current thread. It has the value @samp{*}.
29196 The identifier that @value{GDBN} uses to refer to the Ada task.
29199 The identifier that the target uses to refer to the Ada task.
29202 The identifier of the thread corresponding to the Ada task.
29204 This field should always exist, as Ada tasks are always implemented
29205 on top of a thread. But if @value{GDBN} cannot find this corresponding
29206 thread for any reason, the field is omitted.
29209 This field exists only when the task was created by another task.
29210 In this case, it provides the ID of the parent task.
29213 The base priority of the task.
29216 The current state of the task. For a detailed description of the
29217 possible states, see @ref{Ada Tasks}.
29220 The name of the task.
29224 @subsubheading Example
29228 ^done,tasks=@{nr_rows="3",nr_cols="8",
29229 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
29230 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
29231 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
29232 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
29233 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
29234 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
29235 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
29236 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29237 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29238 state="Child Termination Wait",name="main_task"@}]@}
29242 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29243 @node GDB/MI Program Execution
29244 @section @sc{gdb/mi} Program Execution
29246 These are the asynchronous commands which generate the out-of-band
29247 record @samp{*stopped}. Currently @value{GDBN} only really executes
29248 asynchronously with remote targets and this interaction is mimicked in
29251 @subheading The @code{-exec-continue} Command
29252 @findex -exec-continue
29254 @subsubheading Synopsis
29257 -exec-continue [--reverse] [--all|--thread-group N]
29260 Resumes the execution of the inferior program, which will continue
29261 to execute until it reaches a debugger stop event. If the
29262 @samp{--reverse} option is specified, execution resumes in reverse until
29263 it reaches a stop event. Stop events may include
29266 breakpoints or watchpoints
29268 signals or exceptions
29270 the end of the process (or its beginning under @samp{--reverse})
29272 the end or beginning of a replay log if one is being used.
29274 In all-stop mode (@pxref{All-Stop
29275 Mode}), may resume only one thread, or all threads, depending on the
29276 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29277 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29278 ignored in all-stop mode. If the @samp{--thread-group} options is
29279 specified, then all threads in that thread group are resumed.
29281 @subsubheading @value{GDBN} Command
29283 The corresponding @value{GDBN} corresponding is @samp{continue}.
29285 @subsubheading Example
29292 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
29293 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
29299 @subheading The @code{-exec-finish} Command
29300 @findex -exec-finish
29302 @subsubheading Synopsis
29305 -exec-finish [--reverse]
29308 Resumes the execution of the inferior program until the current
29309 function is exited. Displays the results returned by the function.
29310 If the @samp{--reverse} option is specified, resumes the reverse
29311 execution of the inferior program until the point where current
29312 function was called.
29314 @subsubheading @value{GDBN} Command
29316 The corresponding @value{GDBN} command is @samp{finish}.
29318 @subsubheading Example
29320 Function returning @code{void}.
29327 *stopped,reason="function-finished",frame=@{func="main",args=[],
29328 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
29332 Function returning other than @code{void}. The name of the internal
29333 @value{GDBN} variable storing the result is printed, together with the
29340 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29341 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29342 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29343 gdb-result-var="$1",return-value="0"
29348 @subheading The @code{-exec-interrupt} Command
29349 @findex -exec-interrupt
29351 @subsubheading Synopsis
29354 -exec-interrupt [--all|--thread-group N]
29357 Interrupts the background execution of the target. Note how the token
29358 associated with the stop message is the one for the execution command
29359 that has been interrupted. The token for the interrupt itself only
29360 appears in the @samp{^done} output. If the user is trying to
29361 interrupt a non-running program, an error message will be printed.
29363 Note that when asynchronous execution is enabled, this command is
29364 asynchronous just like other execution commands. That is, first the
29365 @samp{^done} response will be printed, and the target stop will be
29366 reported after that using the @samp{*stopped} notification.
29368 In non-stop mode, only the context thread is interrupted by default.
29369 All threads (in all inferiors) will be interrupted if the
29370 @samp{--all} option is specified. If the @samp{--thread-group}
29371 option is specified, all threads in that group will be interrupted.
29373 @subsubheading @value{GDBN} Command
29375 The corresponding @value{GDBN} command is @samp{interrupt}.
29377 @subsubheading Example
29388 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29389 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29390 fullname="/home/foo/bar/try.c",line="13"@}
29395 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29399 @subheading The @code{-exec-jump} Command
29402 @subsubheading Synopsis
29405 -exec-jump @var{location}
29408 Resumes execution of the inferior program at the location specified by
29409 parameter. @xref{Specify Location}, for a description of the
29410 different forms of @var{location}.
29412 @subsubheading @value{GDBN} Command
29414 The corresponding @value{GDBN} command is @samp{jump}.
29416 @subsubheading Example
29419 -exec-jump foo.c:10
29420 *running,thread-id="all"
29425 @subheading The @code{-exec-next} Command
29428 @subsubheading Synopsis
29431 -exec-next [--reverse]
29434 Resumes execution of the inferior program, stopping when the beginning
29435 of the next source line is reached.
29437 If the @samp{--reverse} option is specified, resumes reverse execution
29438 of the inferior program, stopping at the beginning of the previous
29439 source line. If you issue this command on the first line of a
29440 function, it will take you back to the caller of that function, to the
29441 source line where the function was called.
29444 @subsubheading @value{GDBN} Command
29446 The corresponding @value{GDBN} command is @samp{next}.
29448 @subsubheading Example
29454 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29459 @subheading The @code{-exec-next-instruction} Command
29460 @findex -exec-next-instruction
29462 @subsubheading Synopsis
29465 -exec-next-instruction [--reverse]
29468 Executes one machine instruction. If the instruction is a function
29469 call, continues until the function returns. If the program stops at an
29470 instruction in the middle of a source line, the address will be
29473 If the @samp{--reverse} option is specified, resumes reverse execution
29474 of the inferior program, stopping at the previous instruction. If the
29475 previously executed instruction was a return from another function,
29476 it will continue to execute in reverse until the call to that function
29477 (from the current stack frame) is reached.
29479 @subsubheading @value{GDBN} Command
29481 The corresponding @value{GDBN} command is @samp{nexti}.
29483 @subsubheading Example
29487 -exec-next-instruction
29491 *stopped,reason="end-stepping-range",
29492 addr="0x000100d4",line="5",file="hello.c"
29497 @subheading The @code{-exec-return} Command
29498 @findex -exec-return
29500 @subsubheading Synopsis
29506 Makes current function return immediately. Doesn't execute the inferior.
29507 Displays the new current frame.
29509 @subsubheading @value{GDBN} Command
29511 The corresponding @value{GDBN} command is @samp{return}.
29513 @subsubheading Example
29517 200-break-insert callee4
29518 200^done,bkpt=@{number="1",addr="0x00010734",
29519 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29524 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29525 frame=@{func="callee4",args=[],
29526 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29527 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29533 111^done,frame=@{level="0",func="callee3",
29534 args=[@{name="strarg",
29535 value="0x11940 \"A string argument.\""@}],
29536 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29537 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29542 @subheading The @code{-exec-run} Command
29545 @subsubheading Synopsis
29548 -exec-run [--all | --thread-group N]
29551 Starts execution of the inferior from the beginning. The inferior
29552 executes until either a breakpoint is encountered or the program
29553 exits. In the latter case the output will include an exit code, if
29554 the program has exited exceptionally.
29556 When no option is specified, the current inferior is started. If the
29557 @samp{--thread-group} option is specified, it should refer to a thread
29558 group of type @samp{process}, and that thread group will be started.
29559 If the @samp{--all} option is specified, then all inferiors will be started.
29561 @subsubheading @value{GDBN} Command
29563 The corresponding @value{GDBN} command is @samp{run}.
29565 @subsubheading Examples
29570 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29575 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29576 frame=@{func="main",args=[],file="recursive2.c",
29577 fullname="/home/foo/bar/recursive2.c",line="4"@}
29582 Program exited normally:
29590 *stopped,reason="exited-normally"
29595 Program exited exceptionally:
29603 *stopped,reason="exited",exit-code="01"
29607 Another way the program can terminate is if it receives a signal such as
29608 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29612 *stopped,reason="exited-signalled",signal-name="SIGINT",
29613 signal-meaning="Interrupt"
29617 @c @subheading -exec-signal
29620 @subheading The @code{-exec-step} Command
29623 @subsubheading Synopsis
29626 -exec-step [--reverse]
29629 Resumes execution of the inferior program, stopping when the beginning
29630 of the next source line is reached, if the next source line is not a
29631 function call. If it is, stop at the first instruction of the called
29632 function. If the @samp{--reverse} option is specified, resumes reverse
29633 execution of the inferior program, stopping at the beginning of the
29634 previously executed source line.
29636 @subsubheading @value{GDBN} Command
29638 The corresponding @value{GDBN} command is @samp{step}.
29640 @subsubheading Example
29642 Stepping into a function:
29648 *stopped,reason="end-stepping-range",
29649 frame=@{func="foo",args=[@{name="a",value="10"@},
29650 @{name="b",value="0"@}],file="recursive2.c",
29651 fullname="/home/foo/bar/recursive2.c",line="11"@}
29661 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
29666 @subheading The @code{-exec-step-instruction} Command
29667 @findex -exec-step-instruction
29669 @subsubheading Synopsis
29672 -exec-step-instruction [--reverse]
29675 Resumes the inferior which executes one machine instruction. If the
29676 @samp{--reverse} option is specified, resumes reverse execution of the
29677 inferior program, stopping at the previously executed instruction.
29678 The output, once @value{GDBN} has stopped, will vary depending on
29679 whether we have stopped in the middle of a source line or not. In the
29680 former case, the address at which the program stopped will be printed
29683 @subsubheading @value{GDBN} Command
29685 The corresponding @value{GDBN} command is @samp{stepi}.
29687 @subsubheading Example
29691 -exec-step-instruction
29695 *stopped,reason="end-stepping-range",
29696 frame=@{func="foo",args=[],file="try.c",
29697 fullname="/home/foo/bar/try.c",line="10"@}
29699 -exec-step-instruction
29703 *stopped,reason="end-stepping-range",
29704 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
29705 fullname="/home/foo/bar/try.c",line="10"@}
29710 @subheading The @code{-exec-until} Command
29711 @findex -exec-until
29713 @subsubheading Synopsis
29716 -exec-until [ @var{location} ]
29719 Executes the inferior until the @var{location} specified in the
29720 argument is reached. If there is no argument, the inferior executes
29721 until a source line greater than the current one is reached. The
29722 reason for stopping in this case will be @samp{location-reached}.
29724 @subsubheading @value{GDBN} Command
29726 The corresponding @value{GDBN} command is @samp{until}.
29728 @subsubheading Example
29732 -exec-until recursive2.c:6
29736 *stopped,reason="location-reached",frame=@{func="main",args=[],
29737 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
29742 @subheading -file-clear
29743 Is this going away????
29746 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29747 @node GDB/MI Stack Manipulation
29748 @section @sc{gdb/mi} Stack Manipulation Commands
29751 @subheading The @code{-stack-info-frame} Command
29752 @findex -stack-info-frame
29754 @subsubheading Synopsis
29760 Get info on the selected frame.
29762 @subsubheading @value{GDBN} Command
29764 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
29765 (without arguments).
29767 @subsubheading Example
29772 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
29773 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29774 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
29778 @subheading The @code{-stack-info-depth} Command
29779 @findex -stack-info-depth
29781 @subsubheading Synopsis
29784 -stack-info-depth [ @var{max-depth} ]
29787 Return the depth of the stack. If the integer argument @var{max-depth}
29788 is specified, do not count beyond @var{max-depth} frames.
29790 @subsubheading @value{GDBN} Command
29792 There's no equivalent @value{GDBN} command.
29794 @subsubheading Example
29796 For a stack with frame levels 0 through 11:
29803 -stack-info-depth 4
29806 -stack-info-depth 12
29809 -stack-info-depth 11
29812 -stack-info-depth 13
29817 @subheading The @code{-stack-list-arguments} Command
29818 @findex -stack-list-arguments
29820 @subsubheading Synopsis
29823 -stack-list-arguments @var{print-values}
29824 [ @var{low-frame} @var{high-frame} ]
29827 Display a list of the arguments for the frames between @var{low-frame}
29828 and @var{high-frame} (inclusive). If @var{low-frame} and
29829 @var{high-frame} are not provided, list the arguments for the whole
29830 call stack. If the two arguments are equal, show the single frame
29831 at the corresponding level. It is an error if @var{low-frame} is
29832 larger than the actual number of frames. On the other hand,
29833 @var{high-frame} may be larger than the actual number of frames, in
29834 which case only existing frames will be returned.
29836 If @var{print-values} is 0 or @code{--no-values}, print only the names of
29837 the variables; if it is 1 or @code{--all-values}, print also their
29838 values; and if it is 2 or @code{--simple-values}, print the name,
29839 type and value for simple data types, and the name and type for arrays,
29840 structures and unions.
29842 Use of this command to obtain arguments in a single frame is
29843 deprecated in favor of the @samp{-stack-list-variables} command.
29845 @subsubheading @value{GDBN} Command
29847 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
29848 @samp{gdb_get_args} command which partially overlaps with the
29849 functionality of @samp{-stack-list-arguments}.
29851 @subsubheading Example
29858 frame=@{level="0",addr="0x00010734",func="callee4",
29859 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29860 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
29861 frame=@{level="1",addr="0x0001076c",func="callee3",
29862 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29863 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
29864 frame=@{level="2",addr="0x0001078c",func="callee2",
29865 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29866 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
29867 frame=@{level="3",addr="0x000107b4",func="callee1",
29868 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29869 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
29870 frame=@{level="4",addr="0x000107e0",func="main",
29871 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29872 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
29874 -stack-list-arguments 0
29877 frame=@{level="0",args=[]@},
29878 frame=@{level="1",args=[name="strarg"]@},
29879 frame=@{level="2",args=[name="intarg",name="strarg"]@},
29880 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
29881 frame=@{level="4",args=[]@}]
29883 -stack-list-arguments 1
29886 frame=@{level="0",args=[]@},
29888 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29889 frame=@{level="2",args=[
29890 @{name="intarg",value="2"@},
29891 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29892 @{frame=@{level="3",args=[
29893 @{name="intarg",value="2"@},
29894 @{name="strarg",value="0x11940 \"A string argument.\""@},
29895 @{name="fltarg",value="3.5"@}]@},
29896 frame=@{level="4",args=[]@}]
29898 -stack-list-arguments 0 2 2
29899 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
29901 -stack-list-arguments 1 2 2
29902 ^done,stack-args=[frame=@{level="2",
29903 args=[@{name="intarg",value="2"@},
29904 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
29908 @c @subheading -stack-list-exception-handlers
29911 @subheading The @code{-stack-list-frames} Command
29912 @findex -stack-list-frames
29914 @subsubheading Synopsis
29917 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
29920 List the frames currently on the stack. For each frame it displays the
29925 The frame number, 0 being the topmost frame, i.e., the innermost function.
29927 The @code{$pc} value for that frame.
29931 File name of the source file where the function lives.
29932 @item @var{fullname}
29933 The full file name of the source file where the function lives.
29935 Line number corresponding to the @code{$pc}.
29937 The shared library where this function is defined. This is only given
29938 if the frame's function is not known.
29941 If invoked without arguments, this command prints a backtrace for the
29942 whole stack. If given two integer arguments, it shows the frames whose
29943 levels are between the two arguments (inclusive). If the two arguments
29944 are equal, it shows the single frame at the corresponding level. It is
29945 an error if @var{low-frame} is larger than the actual number of
29946 frames. On the other hand, @var{high-frame} may be larger than the
29947 actual number of frames, in which case only existing frames will be returned.
29949 @subsubheading @value{GDBN} Command
29951 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
29953 @subsubheading Example
29955 Full stack backtrace:
29961 [frame=@{level="0",addr="0x0001076c",func="foo",
29962 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
29963 frame=@{level="1",addr="0x000107a4",func="foo",
29964 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29965 frame=@{level="2",addr="0x000107a4",func="foo",
29966 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29967 frame=@{level="3",addr="0x000107a4",func="foo",
29968 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29969 frame=@{level="4",addr="0x000107a4",func="foo",
29970 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29971 frame=@{level="5",addr="0x000107a4",func="foo",
29972 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29973 frame=@{level="6",addr="0x000107a4",func="foo",
29974 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29975 frame=@{level="7",addr="0x000107a4",func="foo",
29976 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29977 frame=@{level="8",addr="0x000107a4",func="foo",
29978 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29979 frame=@{level="9",addr="0x000107a4",func="foo",
29980 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29981 frame=@{level="10",addr="0x000107a4",func="foo",
29982 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29983 frame=@{level="11",addr="0x00010738",func="main",
29984 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
29988 Show frames between @var{low_frame} and @var{high_frame}:
29992 -stack-list-frames 3 5
29994 [frame=@{level="3",addr="0x000107a4",func="foo",
29995 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29996 frame=@{level="4",addr="0x000107a4",func="foo",
29997 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29998 frame=@{level="5",addr="0x000107a4",func="foo",
29999 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30003 Show a single frame:
30007 -stack-list-frames 3 3
30009 [frame=@{level="3",addr="0x000107a4",func="foo",
30010 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30015 @subheading The @code{-stack-list-locals} Command
30016 @findex -stack-list-locals
30018 @subsubheading Synopsis
30021 -stack-list-locals @var{print-values}
30024 Display the local variable names for the selected frame. If
30025 @var{print-values} is 0 or @code{--no-values}, print only the names of
30026 the variables; if it is 1 or @code{--all-values}, print also their
30027 values; and if it is 2 or @code{--simple-values}, print the name,
30028 type and value for simple data types, and the name and type for arrays,
30029 structures and unions. In this last case, a frontend can immediately
30030 display the value of simple data types and create variable objects for
30031 other data types when the user wishes to explore their values in
30034 This command is deprecated in favor of the
30035 @samp{-stack-list-variables} command.
30037 @subsubheading @value{GDBN} Command
30039 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
30041 @subsubheading Example
30045 -stack-list-locals 0
30046 ^done,locals=[name="A",name="B",name="C"]
30048 -stack-list-locals --all-values
30049 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
30050 @{name="C",value="@{1, 2, 3@}"@}]
30051 -stack-list-locals --simple-values
30052 ^done,locals=[@{name="A",type="int",value="1"@},
30053 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
30057 @subheading The @code{-stack-list-variables} Command
30058 @findex -stack-list-variables
30060 @subsubheading Synopsis
30063 -stack-list-variables @var{print-values}
30066 Display the names of local variables and function arguments for the selected frame. If
30067 @var{print-values} is 0 or @code{--no-values}, print only the names of
30068 the variables; if it is 1 or @code{--all-values}, print also their
30069 values; and if it is 2 or @code{--simple-values}, print the name,
30070 type and value for simple data types, and the name and type for arrays,
30071 structures and unions.
30073 @subsubheading Example
30077 -stack-list-variables --thread 1 --frame 0 --all-values
30078 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30083 @subheading The @code{-stack-select-frame} Command
30084 @findex -stack-select-frame
30086 @subsubheading Synopsis
30089 -stack-select-frame @var{framenum}
30092 Change the selected frame. Select a different frame @var{framenum} on
30095 This command in deprecated in favor of passing the @samp{--frame}
30096 option to every command.
30098 @subsubheading @value{GDBN} Command
30100 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30101 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30103 @subsubheading Example
30107 -stack-select-frame 2
30112 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30113 @node GDB/MI Variable Objects
30114 @section @sc{gdb/mi} Variable Objects
30118 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30120 For the implementation of a variable debugger window (locals, watched
30121 expressions, etc.), we are proposing the adaptation of the existing code
30122 used by @code{Insight}.
30124 The two main reasons for that are:
30128 It has been proven in practice (it is already on its second generation).
30131 It will shorten development time (needless to say how important it is
30135 The original interface was designed to be used by Tcl code, so it was
30136 slightly changed so it could be used through @sc{gdb/mi}. This section
30137 describes the @sc{gdb/mi} operations that will be available and gives some
30138 hints about their use.
30140 @emph{Note}: In addition to the set of operations described here, we
30141 expect the @sc{gui} implementation of a variable window to require, at
30142 least, the following operations:
30145 @item @code{-gdb-show} @code{output-radix}
30146 @item @code{-stack-list-arguments}
30147 @item @code{-stack-list-locals}
30148 @item @code{-stack-select-frame}
30153 @subheading Introduction to Variable Objects
30155 @cindex variable objects in @sc{gdb/mi}
30157 Variable objects are "object-oriented" MI interface for examining and
30158 changing values of expressions. Unlike some other MI interfaces that
30159 work with expressions, variable objects are specifically designed for
30160 simple and efficient presentation in the frontend. A variable object
30161 is identified by string name. When a variable object is created, the
30162 frontend specifies the expression for that variable object. The
30163 expression can be a simple variable, or it can be an arbitrary complex
30164 expression, and can even involve CPU registers. After creating a
30165 variable object, the frontend can invoke other variable object
30166 operations---for example to obtain or change the value of a variable
30167 object, or to change display format.
30169 Variable objects have hierarchical tree structure. Any variable object
30170 that corresponds to a composite type, such as structure in C, has
30171 a number of child variable objects, for example corresponding to each
30172 element of a structure. A child variable object can itself have
30173 children, recursively. Recursion ends when we reach
30174 leaf variable objects, which always have built-in types. Child variable
30175 objects are created only by explicit request, so if a frontend
30176 is not interested in the children of a particular variable object, no
30177 child will be created.
30179 For a leaf variable object it is possible to obtain its value as a
30180 string, or set the value from a string. String value can be also
30181 obtained for a non-leaf variable object, but it's generally a string
30182 that only indicates the type of the object, and does not list its
30183 contents. Assignment to a non-leaf variable object is not allowed.
30185 A frontend does not need to read the values of all variable objects each time
30186 the program stops. Instead, MI provides an update command that lists all
30187 variable objects whose values has changed since the last update
30188 operation. This considerably reduces the amount of data that must
30189 be transferred to the frontend. As noted above, children variable
30190 objects are created on demand, and only leaf variable objects have a
30191 real value. As result, gdb will read target memory only for leaf
30192 variables that frontend has created.
30194 The automatic update is not always desirable. For example, a frontend
30195 might want to keep a value of some expression for future reference,
30196 and never update it. For another example, fetching memory is
30197 relatively slow for embedded targets, so a frontend might want
30198 to disable automatic update for the variables that are either not
30199 visible on the screen, or ``closed''. This is possible using so
30200 called ``frozen variable objects''. Such variable objects are never
30201 implicitly updated.
30203 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30204 fixed variable object, the expression is parsed when the variable
30205 object is created, including associating identifiers to specific
30206 variables. The meaning of expression never changes. For a floating
30207 variable object the values of variables whose names appear in the
30208 expressions are re-evaluated every time in the context of the current
30209 frame. Consider this example:
30214 struct work_state state;
30221 If a fixed variable object for the @code{state} variable is created in
30222 this function, and we enter the recursive call, the variable
30223 object will report the value of @code{state} in the top-level
30224 @code{do_work} invocation. On the other hand, a floating variable
30225 object will report the value of @code{state} in the current frame.
30227 If an expression specified when creating a fixed variable object
30228 refers to a local variable, the variable object becomes bound to the
30229 thread and frame in which the variable object is created. When such
30230 variable object is updated, @value{GDBN} makes sure that the
30231 thread/frame combination the variable object is bound to still exists,
30232 and re-evaluates the variable object in context of that thread/frame.
30234 The following is the complete set of @sc{gdb/mi} operations defined to
30235 access this functionality:
30237 @multitable @columnfractions .4 .6
30238 @item @strong{Operation}
30239 @tab @strong{Description}
30241 @item @code{-enable-pretty-printing}
30242 @tab enable Python-based pretty-printing
30243 @item @code{-var-create}
30244 @tab create a variable object
30245 @item @code{-var-delete}
30246 @tab delete the variable object and/or its children
30247 @item @code{-var-set-format}
30248 @tab set the display format of this variable
30249 @item @code{-var-show-format}
30250 @tab show the display format of this variable
30251 @item @code{-var-info-num-children}
30252 @tab tells how many children this object has
30253 @item @code{-var-list-children}
30254 @tab return a list of the object's children
30255 @item @code{-var-info-type}
30256 @tab show the type of this variable object
30257 @item @code{-var-info-expression}
30258 @tab print parent-relative expression that this variable object represents
30259 @item @code{-var-info-path-expression}
30260 @tab print full expression that this variable object represents
30261 @item @code{-var-show-attributes}
30262 @tab is this variable editable? does it exist here?
30263 @item @code{-var-evaluate-expression}
30264 @tab get the value of this variable
30265 @item @code{-var-assign}
30266 @tab set the value of this variable
30267 @item @code{-var-update}
30268 @tab update the variable and its children
30269 @item @code{-var-set-frozen}
30270 @tab set frozeness attribute
30271 @item @code{-var-set-update-range}
30272 @tab set range of children to display on update
30275 In the next subsection we describe each operation in detail and suggest
30276 how it can be used.
30278 @subheading Description And Use of Operations on Variable Objects
30280 @subheading The @code{-enable-pretty-printing} Command
30281 @findex -enable-pretty-printing
30284 -enable-pretty-printing
30287 @value{GDBN} allows Python-based visualizers to affect the output of the
30288 MI variable object commands. However, because there was no way to
30289 implement this in a fully backward-compatible way, a front end must
30290 request that this functionality be enabled.
30292 Once enabled, this feature cannot be disabled.
30294 Note that if Python support has not been compiled into @value{GDBN},
30295 this command will still succeed (and do nothing).
30297 This feature is currently (as of @value{GDBN} 7.0) experimental, and
30298 may work differently in future versions of @value{GDBN}.
30300 @subheading The @code{-var-create} Command
30301 @findex -var-create
30303 @subsubheading Synopsis
30306 -var-create @{@var{name} | "-"@}
30307 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30310 This operation creates a variable object, which allows the monitoring of
30311 a variable, the result of an expression, a memory cell or a CPU
30314 The @var{name} parameter is the string by which the object can be
30315 referenced. It must be unique. If @samp{-} is specified, the varobj
30316 system will generate a string ``varNNNNNN'' automatically. It will be
30317 unique provided that one does not specify @var{name} of that format.
30318 The command fails if a duplicate name is found.
30320 The frame under which the expression should be evaluated can be
30321 specified by @var{frame-addr}. A @samp{*} indicates that the current
30322 frame should be used. A @samp{@@} indicates that a floating variable
30323 object must be created.
30325 @var{expression} is any expression valid on the current language set (must not
30326 begin with a @samp{*}), or one of the following:
30330 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30333 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30336 @samp{$@var{regname}} --- a CPU register name
30339 @cindex dynamic varobj
30340 A varobj's contents may be provided by a Python-based pretty-printer. In this
30341 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30342 have slightly different semantics in some cases. If the
30343 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30344 will never create a dynamic varobj. This ensures backward
30345 compatibility for existing clients.
30347 @subsubheading Result
30349 This operation returns attributes of the newly-created varobj. These
30354 The name of the varobj.
30357 The number of children of the varobj. This number is not necessarily
30358 reliable for a dynamic varobj. Instead, you must examine the
30359 @samp{has_more} attribute.
30362 The varobj's scalar value. For a varobj whose type is some sort of
30363 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30364 will not be interesting.
30367 The varobj's type. This is a string representation of the type, as
30368 would be printed by the @value{GDBN} CLI. If @samp{print object}
30369 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30370 @emph{actual} (derived) type of the object is shown rather than the
30371 @emph{declared} one.
30374 If a variable object is bound to a specific thread, then this is the
30375 thread's identifier.
30378 For a dynamic varobj, this indicates whether there appear to be any
30379 children available. For a non-dynamic varobj, this will be 0.
30382 This attribute will be present and have the value @samp{1} if the
30383 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30384 then this attribute will not be present.
30387 A dynamic varobj can supply a display hint to the front end. The
30388 value comes directly from the Python pretty-printer object's
30389 @code{display_hint} method. @xref{Pretty Printing API}.
30392 Typical output will look like this:
30395 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30396 has_more="@var{has_more}"
30400 @subheading The @code{-var-delete} Command
30401 @findex -var-delete
30403 @subsubheading Synopsis
30406 -var-delete [ -c ] @var{name}
30409 Deletes a previously created variable object and all of its children.
30410 With the @samp{-c} option, just deletes the children.
30412 Returns an error if the object @var{name} is not found.
30415 @subheading The @code{-var-set-format} Command
30416 @findex -var-set-format
30418 @subsubheading Synopsis
30421 -var-set-format @var{name} @var{format-spec}
30424 Sets the output format for the value of the object @var{name} to be
30427 @anchor{-var-set-format}
30428 The syntax for the @var{format-spec} is as follows:
30431 @var{format-spec} @expansion{}
30432 @{binary | decimal | hexadecimal | octal | natural@}
30435 The natural format is the default format choosen automatically
30436 based on the variable type (like decimal for an @code{int}, hex
30437 for pointers, etc.).
30439 For a variable with children, the format is set only on the
30440 variable itself, and the children are not affected.
30442 @subheading The @code{-var-show-format} Command
30443 @findex -var-show-format
30445 @subsubheading Synopsis
30448 -var-show-format @var{name}
30451 Returns the format used to display the value of the object @var{name}.
30454 @var{format} @expansion{}
30459 @subheading The @code{-var-info-num-children} Command
30460 @findex -var-info-num-children
30462 @subsubheading Synopsis
30465 -var-info-num-children @var{name}
30468 Returns the number of children of a variable object @var{name}:
30474 Note that this number is not completely reliable for a dynamic varobj.
30475 It will return the current number of children, but more children may
30479 @subheading The @code{-var-list-children} Command
30480 @findex -var-list-children
30482 @subsubheading Synopsis
30485 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30487 @anchor{-var-list-children}
30489 Return a list of the children of the specified variable object and
30490 create variable objects for them, if they do not already exist. With
30491 a single argument or if @var{print-values} has a value of 0 or
30492 @code{--no-values}, print only the names of the variables; if
30493 @var{print-values} is 1 or @code{--all-values}, also print their
30494 values; and if it is 2 or @code{--simple-values} print the name and
30495 value for simple data types and just the name for arrays, structures
30498 @var{from} and @var{to}, if specified, indicate the range of children
30499 to report. If @var{from} or @var{to} is less than zero, the range is
30500 reset and all children will be reported. Otherwise, children starting
30501 at @var{from} (zero-based) and up to and excluding @var{to} will be
30504 If a child range is requested, it will only affect the current call to
30505 @code{-var-list-children}, but not future calls to @code{-var-update}.
30506 For this, you must instead use @code{-var-set-update-range}. The
30507 intent of this approach is to enable a front end to implement any
30508 update approach it likes; for example, scrolling a view may cause the
30509 front end to request more children with @code{-var-list-children}, and
30510 then the front end could call @code{-var-set-update-range} with a
30511 different range to ensure that future updates are restricted to just
30514 For each child the following results are returned:
30519 Name of the variable object created for this child.
30522 The expression to be shown to the user by the front end to designate this child.
30523 For example this may be the name of a structure member.
30525 For a dynamic varobj, this value cannot be used to form an
30526 expression. There is no way to do this at all with a dynamic varobj.
30528 For C/C@t{++} structures there are several pseudo children returned to
30529 designate access qualifiers. For these pseudo children @var{exp} is
30530 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30531 type and value are not present.
30533 A dynamic varobj will not report the access qualifying
30534 pseudo-children, regardless of the language. This information is not
30535 available at all with a dynamic varobj.
30538 Number of children this child has. For a dynamic varobj, this will be
30542 The type of the child. If @samp{print object}
30543 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30544 @emph{actual} (derived) type of the object is shown rather than the
30545 @emph{declared} one.
30548 If values were requested, this is the value.
30551 If this variable object is associated with a thread, this is the thread id.
30552 Otherwise this result is not present.
30555 If the variable object is frozen, this variable will be present with a value of 1.
30558 The result may have its own attributes:
30562 A dynamic varobj can supply a display hint to the front end. The
30563 value comes directly from the Python pretty-printer object's
30564 @code{display_hint} method. @xref{Pretty Printing API}.
30567 This is an integer attribute which is nonzero if there are children
30568 remaining after the end of the selected range.
30571 @subsubheading Example
30575 -var-list-children n
30576 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30577 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30579 -var-list-children --all-values n
30580 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30581 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30585 @subheading The @code{-var-info-type} Command
30586 @findex -var-info-type
30588 @subsubheading Synopsis
30591 -var-info-type @var{name}
30594 Returns the type of the specified variable @var{name}. The type is
30595 returned as a string in the same format as it is output by the
30599 type=@var{typename}
30603 @subheading The @code{-var-info-expression} Command
30604 @findex -var-info-expression
30606 @subsubheading Synopsis
30609 -var-info-expression @var{name}
30612 Returns a string that is suitable for presenting this
30613 variable object in user interface. The string is generally
30614 not valid expression in the current language, and cannot be evaluated.
30616 For example, if @code{a} is an array, and variable object
30617 @code{A} was created for @code{a}, then we'll get this output:
30620 (gdb) -var-info-expression A.1
30621 ^done,lang="C",exp="1"
30625 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
30627 Note that the output of the @code{-var-list-children} command also
30628 includes those expressions, so the @code{-var-info-expression} command
30631 @subheading The @code{-var-info-path-expression} Command
30632 @findex -var-info-path-expression
30634 @subsubheading Synopsis
30637 -var-info-path-expression @var{name}
30640 Returns an expression that can be evaluated in the current
30641 context and will yield the same value that a variable object has.
30642 Compare this with the @code{-var-info-expression} command, which
30643 result can be used only for UI presentation. Typical use of
30644 the @code{-var-info-path-expression} command is creating a
30645 watchpoint from a variable object.
30647 This command is currently not valid for children of a dynamic varobj,
30648 and will give an error when invoked on one.
30650 For example, suppose @code{C} is a C@t{++} class, derived from class
30651 @code{Base}, and that the @code{Base} class has a member called
30652 @code{m_size}. Assume a variable @code{c} is has the type of
30653 @code{C} and a variable object @code{C} was created for variable
30654 @code{c}. Then, we'll get this output:
30656 (gdb) -var-info-path-expression C.Base.public.m_size
30657 ^done,path_expr=((Base)c).m_size)
30660 @subheading The @code{-var-show-attributes} Command
30661 @findex -var-show-attributes
30663 @subsubheading Synopsis
30666 -var-show-attributes @var{name}
30669 List attributes of the specified variable object @var{name}:
30672 status=@var{attr} [ ( ,@var{attr} )* ]
30676 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
30678 @subheading The @code{-var-evaluate-expression} Command
30679 @findex -var-evaluate-expression
30681 @subsubheading Synopsis
30684 -var-evaluate-expression [-f @var{format-spec}] @var{name}
30687 Evaluates the expression that is represented by the specified variable
30688 object and returns its value as a string. The format of the string
30689 can be specified with the @samp{-f} option. The possible values of
30690 this option are the same as for @code{-var-set-format}
30691 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
30692 the current display format will be used. The current display format
30693 can be changed using the @code{-var-set-format} command.
30699 Note that one must invoke @code{-var-list-children} for a variable
30700 before the value of a child variable can be evaluated.
30702 @subheading The @code{-var-assign} Command
30703 @findex -var-assign
30705 @subsubheading Synopsis
30708 -var-assign @var{name} @var{expression}
30711 Assigns the value of @var{expression} to the variable object specified
30712 by @var{name}. The object must be @samp{editable}. If the variable's
30713 value is altered by the assign, the variable will show up in any
30714 subsequent @code{-var-update} list.
30716 @subsubheading Example
30724 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
30728 @subheading The @code{-var-update} Command
30729 @findex -var-update
30731 @subsubheading Synopsis
30734 -var-update [@var{print-values}] @{@var{name} | "*"@}
30737 Reevaluate the expressions corresponding to the variable object
30738 @var{name} and all its direct and indirect children, and return the
30739 list of variable objects whose values have changed; @var{name} must
30740 be a root variable object. Here, ``changed'' means that the result of
30741 @code{-var-evaluate-expression} before and after the
30742 @code{-var-update} is different. If @samp{*} is used as the variable
30743 object names, all existing variable objects are updated, except
30744 for frozen ones (@pxref{-var-set-frozen}). The option
30745 @var{print-values} determines whether both names and values, or just
30746 names are printed. The possible values of this option are the same
30747 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
30748 recommended to use the @samp{--all-values} option, to reduce the
30749 number of MI commands needed on each program stop.
30751 With the @samp{*} parameter, if a variable object is bound to a
30752 currently running thread, it will not be updated, without any
30755 If @code{-var-set-update-range} was previously used on a varobj, then
30756 only the selected range of children will be reported.
30758 @code{-var-update} reports all the changed varobjs in a tuple named
30761 Each item in the change list is itself a tuple holding:
30765 The name of the varobj.
30768 If values were requested for this update, then this field will be
30769 present and will hold the value of the varobj.
30772 @anchor{-var-update}
30773 This field is a string which may take one of three values:
30777 The variable object's current value is valid.
30780 The variable object does not currently hold a valid value but it may
30781 hold one in the future if its associated expression comes back into
30785 The variable object no longer holds a valid value.
30786 This can occur when the executable file being debugged has changed,
30787 either through recompilation or by using the @value{GDBN} @code{file}
30788 command. The front end should normally choose to delete these variable
30792 In the future new values may be added to this list so the front should
30793 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
30796 This is only present if the varobj is still valid. If the type
30797 changed, then this will be the string @samp{true}; otherwise it will
30800 When a varobj's type changes, its children are also likely to have
30801 become incorrect. Therefore, the varobj's children are automatically
30802 deleted when this attribute is @samp{true}. Also, the varobj's update
30803 range, when set using the @code{-var-set-update-range} command, is
30807 If the varobj's type changed, then this field will be present and will
30810 @item new_num_children
30811 For a dynamic varobj, if the number of children changed, or if the
30812 type changed, this will be the new number of children.
30814 The @samp{numchild} field in other varobj responses is generally not
30815 valid for a dynamic varobj -- it will show the number of children that
30816 @value{GDBN} knows about, but because dynamic varobjs lazily
30817 instantiate their children, this will not reflect the number of
30818 children which may be available.
30820 The @samp{new_num_children} attribute only reports changes to the
30821 number of children known by @value{GDBN}. This is the only way to
30822 detect whether an update has removed children (which necessarily can
30823 only happen at the end of the update range).
30826 The display hint, if any.
30829 This is an integer value, which will be 1 if there are more children
30830 available outside the varobj's update range.
30833 This attribute will be present and have the value @samp{1} if the
30834 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30835 then this attribute will not be present.
30838 If new children were added to a dynamic varobj within the selected
30839 update range (as set by @code{-var-set-update-range}), then they will
30840 be listed in this attribute.
30843 @subsubheading Example
30850 -var-update --all-values var1
30851 ^done,changelist=[@{name="var1",value="3",in_scope="true",
30852 type_changed="false"@}]
30856 @subheading The @code{-var-set-frozen} Command
30857 @findex -var-set-frozen
30858 @anchor{-var-set-frozen}
30860 @subsubheading Synopsis
30863 -var-set-frozen @var{name} @var{flag}
30866 Set the frozenness flag on the variable object @var{name}. The
30867 @var{flag} parameter should be either @samp{1} to make the variable
30868 frozen or @samp{0} to make it unfrozen. If a variable object is
30869 frozen, then neither itself, nor any of its children, are
30870 implicitly updated by @code{-var-update} of
30871 a parent variable or by @code{-var-update *}. Only
30872 @code{-var-update} of the variable itself will update its value and
30873 values of its children. After a variable object is unfrozen, it is
30874 implicitly updated by all subsequent @code{-var-update} operations.
30875 Unfreezing a variable does not update it, only subsequent
30876 @code{-var-update} does.
30878 @subsubheading Example
30882 -var-set-frozen V 1
30887 @subheading The @code{-var-set-update-range} command
30888 @findex -var-set-update-range
30889 @anchor{-var-set-update-range}
30891 @subsubheading Synopsis
30894 -var-set-update-range @var{name} @var{from} @var{to}
30897 Set the range of children to be returned by future invocations of
30898 @code{-var-update}.
30900 @var{from} and @var{to} indicate the range of children to report. If
30901 @var{from} or @var{to} is less than zero, the range is reset and all
30902 children will be reported. Otherwise, children starting at @var{from}
30903 (zero-based) and up to and excluding @var{to} will be reported.
30905 @subsubheading Example
30909 -var-set-update-range V 1 2
30913 @subheading The @code{-var-set-visualizer} command
30914 @findex -var-set-visualizer
30915 @anchor{-var-set-visualizer}
30917 @subsubheading Synopsis
30920 -var-set-visualizer @var{name} @var{visualizer}
30923 Set a visualizer for the variable object @var{name}.
30925 @var{visualizer} is the visualizer to use. The special value
30926 @samp{None} means to disable any visualizer in use.
30928 If not @samp{None}, @var{visualizer} must be a Python expression.
30929 This expression must evaluate to a callable object which accepts a
30930 single argument. @value{GDBN} will call this object with the value of
30931 the varobj @var{name} as an argument (this is done so that the same
30932 Python pretty-printing code can be used for both the CLI and MI).
30933 When called, this object must return an object which conforms to the
30934 pretty-printing interface (@pxref{Pretty Printing API}).
30936 The pre-defined function @code{gdb.default_visualizer} may be used to
30937 select a visualizer by following the built-in process
30938 (@pxref{Selecting Pretty-Printers}). This is done automatically when
30939 a varobj is created, and so ordinarily is not needed.
30941 This feature is only available if Python support is enabled. The MI
30942 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
30943 can be used to check this.
30945 @subsubheading Example
30947 Resetting the visualizer:
30951 -var-set-visualizer V None
30955 Reselecting the default (type-based) visualizer:
30959 -var-set-visualizer V gdb.default_visualizer
30963 Suppose @code{SomeClass} is a visualizer class. A lambda expression
30964 can be used to instantiate this class for a varobj:
30968 -var-set-visualizer V "lambda val: SomeClass()"
30972 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30973 @node GDB/MI Data Manipulation
30974 @section @sc{gdb/mi} Data Manipulation
30976 @cindex data manipulation, in @sc{gdb/mi}
30977 @cindex @sc{gdb/mi}, data manipulation
30978 This section describes the @sc{gdb/mi} commands that manipulate data:
30979 examine memory and registers, evaluate expressions, etc.
30981 @c REMOVED FROM THE INTERFACE.
30982 @c @subheading -data-assign
30983 @c Change the value of a program variable. Plenty of side effects.
30984 @c @subsubheading GDB Command
30986 @c @subsubheading Example
30989 @subheading The @code{-data-disassemble} Command
30990 @findex -data-disassemble
30992 @subsubheading Synopsis
30996 [ -s @var{start-addr} -e @var{end-addr} ]
30997 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
31005 @item @var{start-addr}
31006 is the beginning address (or @code{$pc})
31007 @item @var{end-addr}
31009 @item @var{filename}
31010 is the name of the file to disassemble
31011 @item @var{linenum}
31012 is the line number to disassemble around
31014 is the number of disassembly lines to be produced. If it is -1,
31015 the whole function will be disassembled, in case no @var{end-addr} is
31016 specified. If @var{end-addr} is specified as a non-zero value, and
31017 @var{lines} is lower than the number of disassembly lines between
31018 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
31019 displayed; if @var{lines} is higher than the number of lines between
31020 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
31023 is either 0 (meaning only disassembly), 1 (meaning mixed source and
31024 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
31025 mixed source and disassembly with raw opcodes).
31028 @subsubheading Result
31030 The result of the @code{-data-disassemble} command will be a list named
31031 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31032 used with the @code{-data-disassemble} command.
31034 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31039 The address at which this instruction was disassembled.
31042 The name of the function this instruction is within.
31045 The decimal offset in bytes from the start of @samp{func-name}.
31048 The text disassembly for this @samp{address}.
31051 This field is only present for mode 2. This contains the raw opcode
31052 bytes for the @samp{inst} field.
31056 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
31057 @samp{src_and_asm_line}, each of which has the following fields:
31061 The line number within @samp{file}.
31064 The file name from the compilation unit. This might be an absolute
31065 file name or a relative file name depending on the compile command
31069 This field is optional. If it is present it will contain an absolute
31070 file name of @samp{file}. If this field is not present then
31071 @value{GDBN} was unable to determine the absolute file name.
31073 @item line_asm_insn
31074 This is a list of tuples containing the disassembly for @samp{line} in
31075 @samp{file}. The fields of each tuple are the same as for
31076 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31077 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31082 Note that whatever included in the @samp{inst} field, is not
31083 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31086 @subsubheading @value{GDBN} Command
31088 The corresponding @value{GDBN} command is @samp{disassemble}.
31090 @subsubheading Example
31092 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31096 -data-disassemble -s $pc -e "$pc + 20" -- 0
31099 @{address="0x000107c0",func-name="main",offset="4",
31100 inst="mov 2, %o0"@},
31101 @{address="0x000107c4",func-name="main",offset="8",
31102 inst="sethi %hi(0x11800), %o2"@},
31103 @{address="0x000107c8",func-name="main",offset="12",
31104 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31105 @{address="0x000107cc",func-name="main",offset="16",
31106 inst="sethi %hi(0x11800), %o2"@},
31107 @{address="0x000107d0",func-name="main",offset="20",
31108 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31112 Disassemble the whole @code{main} function. Line 32 is part of
31116 -data-disassemble -f basics.c -l 32 -- 0
31118 @{address="0x000107bc",func-name="main",offset="0",
31119 inst="save %sp, -112, %sp"@},
31120 @{address="0x000107c0",func-name="main",offset="4",
31121 inst="mov 2, %o0"@},
31122 @{address="0x000107c4",func-name="main",offset="8",
31123 inst="sethi %hi(0x11800), %o2"@},
31125 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
31126 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
31130 Disassemble 3 instructions from the start of @code{main}:
31134 -data-disassemble -f basics.c -l 32 -n 3 -- 0
31136 @{address="0x000107bc",func-name="main",offset="0",
31137 inst="save %sp, -112, %sp"@},
31138 @{address="0x000107c0",func-name="main",offset="4",
31139 inst="mov 2, %o0"@},
31140 @{address="0x000107c4",func-name="main",offset="8",
31141 inst="sethi %hi(0x11800), %o2"@}]
31145 Disassemble 3 instructions from the start of @code{main} in mixed mode:
31149 -data-disassemble -f basics.c -l 32 -n 3 -- 1
31151 src_and_asm_line=@{line="31",
31152 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31153 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31154 line_asm_insn=[@{address="0x000107bc",
31155 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
31156 src_and_asm_line=@{line="32",
31157 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31158 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31159 line_asm_insn=[@{address="0x000107c0",
31160 func-name="main",offset="4",inst="mov 2, %o0"@},
31161 @{address="0x000107c4",func-name="main",offset="8",
31162 inst="sethi %hi(0x11800), %o2"@}]@}]
31167 @subheading The @code{-data-evaluate-expression} Command
31168 @findex -data-evaluate-expression
31170 @subsubheading Synopsis
31173 -data-evaluate-expression @var{expr}
31176 Evaluate @var{expr} as an expression. The expression could contain an
31177 inferior function call. The function call will execute synchronously.
31178 If the expression contains spaces, it must be enclosed in double quotes.
31180 @subsubheading @value{GDBN} Command
31182 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
31183 @samp{call}. In @code{gdbtk} only, there's a corresponding
31184 @samp{gdb_eval} command.
31186 @subsubheading Example
31188 In the following example, the numbers that precede the commands are the
31189 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
31190 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
31194 211-data-evaluate-expression A
31197 311-data-evaluate-expression &A
31198 311^done,value="0xefffeb7c"
31200 411-data-evaluate-expression A+3
31203 511-data-evaluate-expression "A + 3"
31209 @subheading The @code{-data-list-changed-registers} Command
31210 @findex -data-list-changed-registers
31212 @subsubheading Synopsis
31215 -data-list-changed-registers
31218 Display a list of the registers that have changed.
31220 @subsubheading @value{GDBN} Command
31222 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
31223 has the corresponding command @samp{gdb_changed_register_list}.
31225 @subsubheading Example
31227 On a PPC MBX board:
31235 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
31236 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
31239 -data-list-changed-registers
31240 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
31241 "10","11","13","14","15","16","17","18","19","20","21","22","23",
31242 "24","25","26","27","28","30","31","64","65","66","67","69"]
31247 @subheading The @code{-data-list-register-names} Command
31248 @findex -data-list-register-names
31250 @subsubheading Synopsis
31253 -data-list-register-names [ ( @var{regno} )+ ]
31256 Show a list of register names for the current target. If no arguments
31257 are given, it shows a list of the names of all the registers. If
31258 integer numbers are given as arguments, it will print a list of the
31259 names of the registers corresponding to the arguments. To ensure
31260 consistency between a register name and its number, the output list may
31261 include empty register names.
31263 @subsubheading @value{GDBN} Command
31265 @value{GDBN} does not have a command which corresponds to
31266 @samp{-data-list-register-names}. In @code{gdbtk} there is a
31267 corresponding command @samp{gdb_regnames}.
31269 @subsubheading Example
31271 For the PPC MBX board:
31274 -data-list-register-names
31275 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
31276 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
31277 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
31278 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
31279 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
31280 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
31281 "", "pc","ps","cr","lr","ctr","xer"]
31283 -data-list-register-names 1 2 3
31284 ^done,register-names=["r1","r2","r3"]
31288 @subheading The @code{-data-list-register-values} Command
31289 @findex -data-list-register-values
31291 @subsubheading Synopsis
31294 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
31297 Display the registers' contents. @var{fmt} is the format according to
31298 which the registers' contents are to be returned, followed by an optional
31299 list of numbers specifying the registers to display. A missing list of
31300 numbers indicates that the contents of all the registers must be returned.
31302 Allowed formats for @var{fmt} are:
31319 @subsubheading @value{GDBN} Command
31321 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
31322 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
31324 @subsubheading Example
31326 For a PPC MBX board (note: line breaks are for readability only, they
31327 don't appear in the actual output):
31331 -data-list-register-values r 64 65
31332 ^done,register-values=[@{number="64",value="0xfe00a300"@},
31333 @{number="65",value="0x00029002"@}]
31335 -data-list-register-values x
31336 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
31337 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
31338 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
31339 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
31340 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
31341 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
31342 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
31343 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
31344 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
31345 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
31346 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
31347 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
31348 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
31349 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
31350 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
31351 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
31352 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
31353 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31354 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31355 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31356 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31357 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31358 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31359 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31360 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31361 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31362 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31363 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31364 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31365 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31366 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31367 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31368 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31369 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31370 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31371 @{number="69",value="0x20002b03"@}]
31376 @subheading The @code{-data-read-memory} Command
31377 @findex -data-read-memory
31379 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31381 @subsubheading Synopsis
31384 -data-read-memory [ -o @var{byte-offset} ]
31385 @var{address} @var{word-format} @var{word-size}
31386 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31393 @item @var{address}
31394 An expression specifying the address of the first memory word to be
31395 read. Complex expressions containing embedded white space should be
31396 quoted using the C convention.
31398 @item @var{word-format}
31399 The format to be used to print the memory words. The notation is the
31400 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31403 @item @var{word-size}
31404 The size of each memory word in bytes.
31406 @item @var{nr-rows}
31407 The number of rows in the output table.
31409 @item @var{nr-cols}
31410 The number of columns in the output table.
31413 If present, indicates that each row should include an @sc{ascii} dump. The
31414 value of @var{aschar} is used as a padding character when a byte is not a
31415 member of the printable @sc{ascii} character set (printable @sc{ascii}
31416 characters are those whose code is between 32 and 126, inclusively).
31418 @item @var{byte-offset}
31419 An offset to add to the @var{address} before fetching memory.
31422 This command displays memory contents as a table of @var{nr-rows} by
31423 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31424 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31425 (returned as @samp{total-bytes}). Should less than the requested number
31426 of bytes be returned by the target, the missing words are identified
31427 using @samp{N/A}. The number of bytes read from the target is returned
31428 in @samp{nr-bytes} and the starting address used to read memory in
31431 The address of the next/previous row or page is available in
31432 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31435 @subsubheading @value{GDBN} Command
31437 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31438 @samp{gdb_get_mem} memory read command.
31440 @subsubheading Example
31442 Read six bytes of memory starting at @code{bytes+6} but then offset by
31443 @code{-6} bytes. Format as three rows of two columns. One byte per
31444 word. Display each word in hex.
31448 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31449 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31450 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31451 prev-page="0x0000138a",memory=[
31452 @{addr="0x00001390",data=["0x00","0x01"]@},
31453 @{addr="0x00001392",data=["0x02","0x03"]@},
31454 @{addr="0x00001394",data=["0x04","0x05"]@}]
31458 Read two bytes of memory starting at address @code{shorts + 64} and
31459 display as a single word formatted in decimal.
31463 5-data-read-memory shorts+64 d 2 1 1
31464 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31465 next-row="0x00001512",prev-row="0x0000150e",
31466 next-page="0x00001512",prev-page="0x0000150e",memory=[
31467 @{addr="0x00001510",data=["128"]@}]
31471 Read thirty two bytes of memory starting at @code{bytes+16} and format
31472 as eight rows of four columns. Include a string encoding with @samp{x}
31473 used as the non-printable character.
31477 4-data-read-memory bytes+16 x 1 8 4 x
31478 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31479 next-row="0x000013c0",prev-row="0x0000139c",
31480 next-page="0x000013c0",prev-page="0x00001380",memory=[
31481 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31482 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31483 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31484 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31485 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31486 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31487 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31488 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31492 @subheading The @code{-data-read-memory-bytes} Command
31493 @findex -data-read-memory-bytes
31495 @subsubheading Synopsis
31498 -data-read-memory-bytes [ -o @var{byte-offset} ]
31499 @var{address} @var{count}
31506 @item @var{address}
31507 An expression specifying the address of the first memory word to be
31508 read. Complex expressions containing embedded white space should be
31509 quoted using the C convention.
31512 The number of bytes to read. This should be an integer literal.
31514 @item @var{byte-offset}
31515 The offsets in bytes relative to @var{address} at which to start
31516 reading. This should be an integer literal. This option is provided
31517 so that a frontend is not required to first evaluate address and then
31518 perform address arithmetics itself.
31522 This command attempts to read all accessible memory regions in the
31523 specified range. First, all regions marked as unreadable in the memory
31524 map (if one is defined) will be skipped. @xref{Memory Region
31525 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31526 regions. For each one, if reading full region results in an errors,
31527 @value{GDBN} will try to read a subset of the region.
31529 In general, every single byte in the region may be readable or not,
31530 and the only way to read every readable byte is to try a read at
31531 every address, which is not practical. Therefore, @value{GDBN} will
31532 attempt to read all accessible bytes at either beginning or the end
31533 of the region, using a binary division scheme. This heuristic works
31534 well for reading accross a memory map boundary. Note that if a region
31535 has a readable range that is neither at the beginning or the end,
31536 @value{GDBN} will not read it.
31538 The result record (@pxref{GDB/MI Result Records}) that is output of
31539 the command includes a field named @samp{memory} whose content is a
31540 list of tuples. Each tuple represent a successfully read memory block
31541 and has the following fields:
31545 The start address of the memory block, as hexadecimal literal.
31548 The end address of the memory block, as hexadecimal literal.
31551 The offset of the memory block, as hexadecimal literal, relative to
31552 the start address passed to @code{-data-read-memory-bytes}.
31555 The contents of the memory block, in hex.
31561 @subsubheading @value{GDBN} Command
31563 The corresponding @value{GDBN} command is @samp{x}.
31565 @subsubheading Example
31569 -data-read-memory-bytes &a 10
31570 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31572 contents="01000000020000000300"@}]
31577 @subheading The @code{-data-write-memory-bytes} Command
31578 @findex -data-write-memory-bytes
31580 @subsubheading Synopsis
31583 -data-write-memory-bytes @var{address} @var{contents}
31584 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31591 @item @var{address}
31592 An expression specifying the address of the first memory word to be
31593 read. Complex expressions containing embedded white space should be
31594 quoted using the C convention.
31596 @item @var{contents}
31597 The hex-encoded bytes to write.
31600 Optional argument indicating the number of bytes to be written. If @var{count}
31601 is greater than @var{contents}' length, @value{GDBN} will repeatedly
31602 write @var{contents} until it fills @var{count} bytes.
31606 @subsubheading @value{GDBN} Command
31608 There's no corresponding @value{GDBN} command.
31610 @subsubheading Example
31614 -data-write-memory-bytes &a "aabbccdd"
31621 -data-write-memory-bytes &a "aabbccdd" 16e
31626 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31627 @node GDB/MI Tracepoint Commands
31628 @section @sc{gdb/mi} Tracepoint Commands
31630 The commands defined in this section implement MI support for
31631 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31633 @subheading The @code{-trace-find} Command
31634 @findex -trace-find
31636 @subsubheading Synopsis
31639 -trace-find @var{mode} [@var{parameters}@dots{}]
31642 Find a trace frame using criteria defined by @var{mode} and
31643 @var{parameters}. The following table lists permissible
31644 modes and their parameters. For details of operation, see @ref{tfind}.
31649 No parameters are required. Stops examining trace frames.
31652 An integer is required as parameter. Selects tracepoint frame with
31655 @item tracepoint-number
31656 An integer is required as parameter. Finds next
31657 trace frame that corresponds to tracepoint with the specified number.
31660 An address is required as parameter. Finds
31661 next trace frame that corresponds to any tracepoint at the specified
31664 @item pc-inside-range
31665 Two addresses are required as parameters. Finds next trace
31666 frame that corresponds to a tracepoint at an address inside the
31667 specified range. Both bounds are considered to be inside the range.
31669 @item pc-outside-range
31670 Two addresses are required as parameters. Finds
31671 next trace frame that corresponds to a tracepoint at an address outside
31672 the specified range. Both bounds are considered to be inside the range.
31675 Line specification is required as parameter. @xref{Specify Location}.
31676 Finds next trace frame that corresponds to a tracepoint at
31677 the specified location.
31681 If @samp{none} was passed as @var{mode}, the response does not
31682 have fields. Otherwise, the response may have the following fields:
31686 This field has either @samp{0} or @samp{1} as the value, depending
31687 on whether a matching tracepoint was found.
31690 The index of the found traceframe. This field is present iff
31691 the @samp{found} field has value of @samp{1}.
31694 The index of the found tracepoint. This field is present iff
31695 the @samp{found} field has value of @samp{1}.
31698 The information about the frame corresponding to the found trace
31699 frame. This field is present only if a trace frame was found.
31700 @xref{GDB/MI Frame Information}, for description of this field.
31704 @subsubheading @value{GDBN} Command
31706 The corresponding @value{GDBN} command is @samp{tfind}.
31708 @subheading -trace-define-variable
31709 @findex -trace-define-variable
31711 @subsubheading Synopsis
31714 -trace-define-variable @var{name} [ @var{value} ]
31717 Create trace variable @var{name} if it does not exist. If
31718 @var{value} is specified, sets the initial value of the specified
31719 trace variable to that value. Note that the @var{name} should start
31720 with the @samp{$} character.
31722 @subsubheading @value{GDBN} Command
31724 The corresponding @value{GDBN} command is @samp{tvariable}.
31726 @subheading -trace-list-variables
31727 @findex -trace-list-variables
31729 @subsubheading Synopsis
31732 -trace-list-variables
31735 Return a table of all defined trace variables. Each element of the
31736 table has the following fields:
31740 The name of the trace variable. This field is always present.
31743 The initial value. This is a 64-bit signed integer. This
31744 field is always present.
31747 The value the trace variable has at the moment. This is a 64-bit
31748 signed integer. This field is absent iff current value is
31749 not defined, for example if the trace was never run, or is
31754 @subsubheading @value{GDBN} Command
31756 The corresponding @value{GDBN} command is @samp{tvariables}.
31758 @subsubheading Example
31762 -trace-list-variables
31763 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
31764 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
31765 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
31766 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
31767 body=[variable=@{name="$trace_timestamp",initial="0"@}
31768 variable=@{name="$foo",initial="10",current="15"@}]@}
31772 @subheading -trace-save
31773 @findex -trace-save
31775 @subsubheading Synopsis
31778 -trace-save [-r ] @var{filename}
31781 Saves the collected trace data to @var{filename}. Without the
31782 @samp{-r} option, the data is downloaded from the target and saved
31783 in a local file. With the @samp{-r} option the target is asked
31784 to perform the save.
31786 @subsubheading @value{GDBN} Command
31788 The corresponding @value{GDBN} command is @samp{tsave}.
31791 @subheading -trace-start
31792 @findex -trace-start
31794 @subsubheading Synopsis
31800 Starts a tracing experiments. The result of this command does not
31803 @subsubheading @value{GDBN} Command
31805 The corresponding @value{GDBN} command is @samp{tstart}.
31807 @subheading -trace-status
31808 @findex -trace-status
31810 @subsubheading Synopsis
31816 Obtains the status of a tracing experiment. The result may include
31817 the following fields:
31822 May have a value of either @samp{0}, when no tracing operations are
31823 supported, @samp{1}, when all tracing operations are supported, or
31824 @samp{file} when examining trace file. In the latter case, examining
31825 of trace frame is possible but new tracing experiement cannot be
31826 started. This field is always present.
31829 May have a value of either @samp{0} or @samp{1} depending on whether
31830 tracing experiement is in progress on target. This field is present
31831 if @samp{supported} field is not @samp{0}.
31834 Report the reason why the tracing was stopped last time. This field
31835 may be absent iff tracing was never stopped on target yet. The
31836 value of @samp{request} means the tracing was stopped as result of
31837 the @code{-trace-stop} command. The value of @samp{overflow} means
31838 the tracing buffer is full. The value of @samp{disconnection} means
31839 tracing was automatically stopped when @value{GDBN} has disconnected.
31840 The value of @samp{passcount} means tracing was stopped when a
31841 tracepoint was passed a maximal number of times for that tracepoint.
31842 This field is present if @samp{supported} field is not @samp{0}.
31844 @item stopping-tracepoint
31845 The number of tracepoint whose passcount as exceeded. This field is
31846 present iff the @samp{stop-reason} field has the value of
31850 @itemx frames-created
31851 The @samp{frames} field is a count of the total number of trace frames
31852 in the trace buffer, while @samp{frames-created} is the total created
31853 during the run, including ones that were discarded, such as when a
31854 circular trace buffer filled up. Both fields are optional.
31858 These fields tell the current size of the tracing buffer and the
31859 remaining space. These fields are optional.
31862 The value of the circular trace buffer flag. @code{1} means that the
31863 trace buffer is circular and old trace frames will be discarded if
31864 necessary to make room, @code{0} means that the trace buffer is linear
31868 The value of the disconnected tracing flag. @code{1} means that
31869 tracing will continue after @value{GDBN} disconnects, @code{0} means
31870 that the trace run will stop.
31874 @subsubheading @value{GDBN} Command
31876 The corresponding @value{GDBN} command is @samp{tstatus}.
31878 @subheading -trace-stop
31879 @findex -trace-stop
31881 @subsubheading Synopsis
31887 Stops a tracing experiment. The result of this command has the same
31888 fields as @code{-trace-status}, except that the @samp{supported} and
31889 @samp{running} fields are not output.
31891 @subsubheading @value{GDBN} Command
31893 The corresponding @value{GDBN} command is @samp{tstop}.
31896 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31897 @node GDB/MI Symbol Query
31898 @section @sc{gdb/mi} Symbol Query Commands
31902 @subheading The @code{-symbol-info-address} Command
31903 @findex -symbol-info-address
31905 @subsubheading Synopsis
31908 -symbol-info-address @var{symbol}
31911 Describe where @var{symbol} is stored.
31913 @subsubheading @value{GDBN} Command
31915 The corresponding @value{GDBN} command is @samp{info address}.
31917 @subsubheading Example
31921 @subheading The @code{-symbol-info-file} Command
31922 @findex -symbol-info-file
31924 @subsubheading Synopsis
31930 Show the file for the symbol.
31932 @subsubheading @value{GDBN} Command
31934 There's no equivalent @value{GDBN} command. @code{gdbtk} has
31935 @samp{gdb_find_file}.
31937 @subsubheading Example
31941 @subheading The @code{-symbol-info-function} Command
31942 @findex -symbol-info-function
31944 @subsubheading Synopsis
31947 -symbol-info-function
31950 Show which function the symbol lives in.
31952 @subsubheading @value{GDBN} Command
31954 @samp{gdb_get_function} in @code{gdbtk}.
31956 @subsubheading Example
31960 @subheading The @code{-symbol-info-line} Command
31961 @findex -symbol-info-line
31963 @subsubheading Synopsis
31969 Show the core addresses of the code for a source line.
31971 @subsubheading @value{GDBN} Command
31973 The corresponding @value{GDBN} command is @samp{info line}.
31974 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31976 @subsubheading Example
31980 @subheading The @code{-symbol-info-symbol} Command
31981 @findex -symbol-info-symbol
31983 @subsubheading Synopsis
31986 -symbol-info-symbol @var{addr}
31989 Describe what symbol is at location @var{addr}.
31991 @subsubheading @value{GDBN} Command
31993 The corresponding @value{GDBN} command is @samp{info symbol}.
31995 @subsubheading Example
31999 @subheading The @code{-symbol-list-functions} Command
32000 @findex -symbol-list-functions
32002 @subsubheading Synopsis
32005 -symbol-list-functions
32008 List the functions in the executable.
32010 @subsubheading @value{GDBN} Command
32012 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
32013 @samp{gdb_search} in @code{gdbtk}.
32015 @subsubheading Example
32020 @subheading The @code{-symbol-list-lines} Command
32021 @findex -symbol-list-lines
32023 @subsubheading Synopsis
32026 -symbol-list-lines @var{filename}
32029 Print the list of lines that contain code and their associated program
32030 addresses for the given source filename. The entries are sorted in
32031 ascending PC order.
32033 @subsubheading @value{GDBN} Command
32035 There is no corresponding @value{GDBN} command.
32037 @subsubheading Example
32040 -symbol-list-lines basics.c
32041 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
32047 @subheading The @code{-symbol-list-types} Command
32048 @findex -symbol-list-types
32050 @subsubheading Synopsis
32056 List all the type names.
32058 @subsubheading @value{GDBN} Command
32060 The corresponding commands are @samp{info types} in @value{GDBN},
32061 @samp{gdb_search} in @code{gdbtk}.
32063 @subsubheading Example
32067 @subheading The @code{-symbol-list-variables} Command
32068 @findex -symbol-list-variables
32070 @subsubheading Synopsis
32073 -symbol-list-variables
32076 List all the global and static variable names.
32078 @subsubheading @value{GDBN} Command
32080 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
32082 @subsubheading Example
32086 @subheading The @code{-symbol-locate} Command
32087 @findex -symbol-locate
32089 @subsubheading Synopsis
32095 @subsubheading @value{GDBN} Command
32097 @samp{gdb_loc} in @code{gdbtk}.
32099 @subsubheading Example
32103 @subheading The @code{-symbol-type} Command
32104 @findex -symbol-type
32106 @subsubheading Synopsis
32109 -symbol-type @var{variable}
32112 Show type of @var{variable}.
32114 @subsubheading @value{GDBN} Command
32116 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
32117 @samp{gdb_obj_variable}.
32119 @subsubheading Example
32124 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32125 @node GDB/MI File Commands
32126 @section @sc{gdb/mi} File Commands
32128 This section describes the GDB/MI commands to specify executable file names
32129 and to read in and obtain symbol table information.
32131 @subheading The @code{-file-exec-and-symbols} Command
32132 @findex -file-exec-and-symbols
32134 @subsubheading Synopsis
32137 -file-exec-and-symbols @var{file}
32140 Specify the executable file to be debugged. This file is the one from
32141 which the symbol table is also read. If no file is specified, the
32142 command clears the executable and symbol information. If breakpoints
32143 are set when using this command with no arguments, @value{GDBN} will produce
32144 error messages. Otherwise, no output is produced, except a completion
32147 @subsubheading @value{GDBN} Command
32149 The corresponding @value{GDBN} command is @samp{file}.
32151 @subsubheading Example
32155 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32161 @subheading The @code{-file-exec-file} Command
32162 @findex -file-exec-file
32164 @subsubheading Synopsis
32167 -file-exec-file @var{file}
32170 Specify the executable file to be debugged. Unlike
32171 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
32172 from this file. If used without argument, @value{GDBN} clears the information
32173 about the executable file. No output is produced, except a completion
32176 @subsubheading @value{GDBN} Command
32178 The corresponding @value{GDBN} command is @samp{exec-file}.
32180 @subsubheading Example
32184 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32191 @subheading The @code{-file-list-exec-sections} Command
32192 @findex -file-list-exec-sections
32194 @subsubheading Synopsis
32197 -file-list-exec-sections
32200 List the sections of the current executable file.
32202 @subsubheading @value{GDBN} Command
32204 The @value{GDBN} command @samp{info file} shows, among the rest, the same
32205 information as this command. @code{gdbtk} has a corresponding command
32206 @samp{gdb_load_info}.
32208 @subsubheading Example
32213 @subheading The @code{-file-list-exec-source-file} Command
32214 @findex -file-list-exec-source-file
32216 @subsubheading Synopsis
32219 -file-list-exec-source-file
32222 List the line number, the current source file, and the absolute path
32223 to the current source file for the current executable. The macro
32224 information field has a value of @samp{1} or @samp{0} depending on
32225 whether or not the file includes preprocessor macro information.
32227 @subsubheading @value{GDBN} Command
32229 The @value{GDBN} equivalent is @samp{info source}
32231 @subsubheading Example
32235 123-file-list-exec-source-file
32236 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
32241 @subheading The @code{-file-list-exec-source-files} Command
32242 @findex -file-list-exec-source-files
32244 @subsubheading Synopsis
32247 -file-list-exec-source-files
32250 List the source files for the current executable.
32252 It will always output the filename, but only when @value{GDBN} can find
32253 the absolute file name of a source file, will it output the fullname.
32255 @subsubheading @value{GDBN} Command
32257 The @value{GDBN} equivalent is @samp{info sources}.
32258 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32260 @subsubheading Example
32263 -file-list-exec-source-files
32265 @{file=foo.c,fullname=/home/foo.c@},
32266 @{file=/home/bar.c,fullname=/home/bar.c@},
32267 @{file=gdb_could_not_find_fullpath.c@}]
32272 @subheading The @code{-file-list-shared-libraries} Command
32273 @findex -file-list-shared-libraries
32275 @subsubheading Synopsis
32278 -file-list-shared-libraries
32281 List the shared libraries in the program.
32283 @subsubheading @value{GDBN} Command
32285 The corresponding @value{GDBN} command is @samp{info shared}.
32287 @subsubheading Example
32291 @subheading The @code{-file-list-symbol-files} Command
32292 @findex -file-list-symbol-files
32294 @subsubheading Synopsis
32297 -file-list-symbol-files
32302 @subsubheading @value{GDBN} Command
32304 The corresponding @value{GDBN} command is @samp{info file} (part of it).
32306 @subsubheading Example
32311 @subheading The @code{-file-symbol-file} Command
32312 @findex -file-symbol-file
32314 @subsubheading Synopsis
32317 -file-symbol-file @var{file}
32320 Read symbol table info from the specified @var{file} argument. When
32321 used without arguments, clears @value{GDBN}'s symbol table info. No output is
32322 produced, except for a completion notification.
32324 @subsubheading @value{GDBN} Command
32326 The corresponding @value{GDBN} command is @samp{symbol-file}.
32328 @subsubheading Example
32332 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32338 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32339 @node GDB/MI Memory Overlay Commands
32340 @section @sc{gdb/mi} Memory Overlay Commands
32342 The memory overlay commands are not implemented.
32344 @c @subheading -overlay-auto
32346 @c @subheading -overlay-list-mapping-state
32348 @c @subheading -overlay-list-overlays
32350 @c @subheading -overlay-map
32352 @c @subheading -overlay-off
32354 @c @subheading -overlay-on
32356 @c @subheading -overlay-unmap
32358 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32359 @node GDB/MI Signal Handling Commands
32360 @section @sc{gdb/mi} Signal Handling Commands
32362 Signal handling commands are not implemented.
32364 @c @subheading -signal-handle
32366 @c @subheading -signal-list-handle-actions
32368 @c @subheading -signal-list-signal-types
32372 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32373 @node GDB/MI Target Manipulation
32374 @section @sc{gdb/mi} Target Manipulation Commands
32377 @subheading The @code{-target-attach} Command
32378 @findex -target-attach
32380 @subsubheading Synopsis
32383 -target-attach @var{pid} | @var{gid} | @var{file}
32386 Attach to a process @var{pid} or a file @var{file} outside of
32387 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32388 group, the id previously returned by
32389 @samp{-list-thread-groups --available} must be used.
32391 @subsubheading @value{GDBN} Command
32393 The corresponding @value{GDBN} command is @samp{attach}.
32395 @subsubheading Example
32399 =thread-created,id="1"
32400 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32406 @subheading The @code{-target-compare-sections} Command
32407 @findex -target-compare-sections
32409 @subsubheading Synopsis
32412 -target-compare-sections [ @var{section} ]
32415 Compare data of section @var{section} on target to the exec file.
32416 Without the argument, all sections are compared.
32418 @subsubheading @value{GDBN} Command
32420 The @value{GDBN} equivalent is @samp{compare-sections}.
32422 @subsubheading Example
32427 @subheading The @code{-target-detach} Command
32428 @findex -target-detach
32430 @subsubheading Synopsis
32433 -target-detach [ @var{pid} | @var{gid} ]
32436 Detach from the remote target which normally resumes its execution.
32437 If either @var{pid} or @var{gid} is specified, detaches from either
32438 the specified process, or specified thread group. There's no output.
32440 @subsubheading @value{GDBN} Command
32442 The corresponding @value{GDBN} command is @samp{detach}.
32444 @subsubheading Example
32454 @subheading The @code{-target-disconnect} Command
32455 @findex -target-disconnect
32457 @subsubheading Synopsis
32463 Disconnect from the remote target. There's no output and the target is
32464 generally not resumed.
32466 @subsubheading @value{GDBN} Command
32468 The corresponding @value{GDBN} command is @samp{disconnect}.
32470 @subsubheading Example
32480 @subheading The @code{-target-download} Command
32481 @findex -target-download
32483 @subsubheading Synopsis
32489 Loads the executable onto the remote target.
32490 It prints out an update message every half second, which includes the fields:
32494 The name of the section.
32496 The size of what has been sent so far for that section.
32498 The size of the section.
32500 The total size of what was sent so far (the current and the previous sections).
32502 The size of the overall executable to download.
32506 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32507 @sc{gdb/mi} Output Syntax}).
32509 In addition, it prints the name and size of the sections, as they are
32510 downloaded. These messages include the following fields:
32514 The name of the section.
32516 The size of the section.
32518 The size of the overall executable to download.
32522 At the end, a summary is printed.
32524 @subsubheading @value{GDBN} Command
32526 The corresponding @value{GDBN} command is @samp{load}.
32528 @subsubheading Example
32530 Note: each status message appears on a single line. Here the messages
32531 have been broken down so that they can fit onto a page.
32536 +download,@{section=".text",section-size="6668",total-size="9880"@}
32537 +download,@{section=".text",section-sent="512",section-size="6668",
32538 total-sent="512",total-size="9880"@}
32539 +download,@{section=".text",section-sent="1024",section-size="6668",
32540 total-sent="1024",total-size="9880"@}
32541 +download,@{section=".text",section-sent="1536",section-size="6668",
32542 total-sent="1536",total-size="9880"@}
32543 +download,@{section=".text",section-sent="2048",section-size="6668",
32544 total-sent="2048",total-size="9880"@}
32545 +download,@{section=".text",section-sent="2560",section-size="6668",
32546 total-sent="2560",total-size="9880"@}
32547 +download,@{section=".text",section-sent="3072",section-size="6668",
32548 total-sent="3072",total-size="9880"@}
32549 +download,@{section=".text",section-sent="3584",section-size="6668",
32550 total-sent="3584",total-size="9880"@}
32551 +download,@{section=".text",section-sent="4096",section-size="6668",
32552 total-sent="4096",total-size="9880"@}
32553 +download,@{section=".text",section-sent="4608",section-size="6668",
32554 total-sent="4608",total-size="9880"@}
32555 +download,@{section=".text",section-sent="5120",section-size="6668",
32556 total-sent="5120",total-size="9880"@}
32557 +download,@{section=".text",section-sent="5632",section-size="6668",
32558 total-sent="5632",total-size="9880"@}
32559 +download,@{section=".text",section-sent="6144",section-size="6668",
32560 total-sent="6144",total-size="9880"@}
32561 +download,@{section=".text",section-sent="6656",section-size="6668",
32562 total-sent="6656",total-size="9880"@}
32563 +download,@{section=".init",section-size="28",total-size="9880"@}
32564 +download,@{section=".fini",section-size="28",total-size="9880"@}
32565 +download,@{section=".data",section-size="3156",total-size="9880"@}
32566 +download,@{section=".data",section-sent="512",section-size="3156",
32567 total-sent="7236",total-size="9880"@}
32568 +download,@{section=".data",section-sent="1024",section-size="3156",
32569 total-sent="7748",total-size="9880"@}
32570 +download,@{section=".data",section-sent="1536",section-size="3156",
32571 total-sent="8260",total-size="9880"@}
32572 +download,@{section=".data",section-sent="2048",section-size="3156",
32573 total-sent="8772",total-size="9880"@}
32574 +download,@{section=".data",section-sent="2560",section-size="3156",
32575 total-sent="9284",total-size="9880"@}
32576 +download,@{section=".data",section-sent="3072",section-size="3156",
32577 total-sent="9796",total-size="9880"@}
32578 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32585 @subheading The @code{-target-exec-status} Command
32586 @findex -target-exec-status
32588 @subsubheading Synopsis
32591 -target-exec-status
32594 Provide information on the state of the target (whether it is running or
32595 not, for instance).
32597 @subsubheading @value{GDBN} Command
32599 There's no equivalent @value{GDBN} command.
32601 @subsubheading Example
32605 @subheading The @code{-target-list-available-targets} Command
32606 @findex -target-list-available-targets
32608 @subsubheading Synopsis
32611 -target-list-available-targets
32614 List the possible targets to connect to.
32616 @subsubheading @value{GDBN} Command
32618 The corresponding @value{GDBN} command is @samp{help target}.
32620 @subsubheading Example
32624 @subheading The @code{-target-list-current-targets} Command
32625 @findex -target-list-current-targets
32627 @subsubheading Synopsis
32630 -target-list-current-targets
32633 Describe the current target.
32635 @subsubheading @value{GDBN} Command
32637 The corresponding information is printed by @samp{info file} (among
32640 @subsubheading Example
32644 @subheading The @code{-target-list-parameters} Command
32645 @findex -target-list-parameters
32647 @subsubheading Synopsis
32650 -target-list-parameters
32656 @subsubheading @value{GDBN} Command
32660 @subsubheading Example
32664 @subheading The @code{-target-select} Command
32665 @findex -target-select
32667 @subsubheading Synopsis
32670 -target-select @var{type} @var{parameters @dots{}}
32673 Connect @value{GDBN} to the remote target. This command takes two args:
32677 The type of target, for instance @samp{remote}, etc.
32678 @item @var{parameters}
32679 Device names, host names and the like. @xref{Target Commands, ,
32680 Commands for Managing Targets}, for more details.
32683 The output is a connection notification, followed by the address at
32684 which the target program is, in the following form:
32687 ^connected,addr="@var{address}",func="@var{function name}",
32688 args=[@var{arg list}]
32691 @subsubheading @value{GDBN} Command
32693 The corresponding @value{GDBN} command is @samp{target}.
32695 @subsubheading Example
32699 -target-select remote /dev/ttya
32700 ^connected,addr="0xfe00a300",func="??",args=[]
32704 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32705 @node GDB/MI File Transfer Commands
32706 @section @sc{gdb/mi} File Transfer Commands
32709 @subheading The @code{-target-file-put} Command
32710 @findex -target-file-put
32712 @subsubheading Synopsis
32715 -target-file-put @var{hostfile} @var{targetfile}
32718 Copy file @var{hostfile} from the host system (the machine running
32719 @value{GDBN}) to @var{targetfile} on the target system.
32721 @subsubheading @value{GDBN} Command
32723 The corresponding @value{GDBN} command is @samp{remote put}.
32725 @subsubheading Example
32729 -target-file-put localfile remotefile
32735 @subheading The @code{-target-file-get} Command
32736 @findex -target-file-get
32738 @subsubheading Synopsis
32741 -target-file-get @var{targetfile} @var{hostfile}
32744 Copy file @var{targetfile} from the target system to @var{hostfile}
32745 on the host system.
32747 @subsubheading @value{GDBN} Command
32749 The corresponding @value{GDBN} command is @samp{remote get}.
32751 @subsubheading Example
32755 -target-file-get remotefile localfile
32761 @subheading The @code{-target-file-delete} Command
32762 @findex -target-file-delete
32764 @subsubheading Synopsis
32767 -target-file-delete @var{targetfile}
32770 Delete @var{targetfile} from the target system.
32772 @subsubheading @value{GDBN} Command
32774 The corresponding @value{GDBN} command is @samp{remote delete}.
32776 @subsubheading Example
32780 -target-file-delete remotefile
32786 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32787 @node GDB/MI Miscellaneous Commands
32788 @section Miscellaneous @sc{gdb/mi} Commands
32790 @c @subheading -gdb-complete
32792 @subheading The @code{-gdb-exit} Command
32795 @subsubheading Synopsis
32801 Exit @value{GDBN} immediately.
32803 @subsubheading @value{GDBN} Command
32805 Approximately corresponds to @samp{quit}.
32807 @subsubheading Example
32817 @subheading The @code{-exec-abort} Command
32818 @findex -exec-abort
32820 @subsubheading Synopsis
32826 Kill the inferior running program.
32828 @subsubheading @value{GDBN} Command
32830 The corresponding @value{GDBN} command is @samp{kill}.
32832 @subsubheading Example
32837 @subheading The @code{-gdb-set} Command
32840 @subsubheading Synopsis
32846 Set an internal @value{GDBN} variable.
32847 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32849 @subsubheading @value{GDBN} Command
32851 The corresponding @value{GDBN} command is @samp{set}.
32853 @subsubheading Example
32863 @subheading The @code{-gdb-show} Command
32866 @subsubheading Synopsis
32872 Show the current value of a @value{GDBN} variable.
32874 @subsubheading @value{GDBN} Command
32876 The corresponding @value{GDBN} command is @samp{show}.
32878 @subsubheading Example
32887 @c @subheading -gdb-source
32890 @subheading The @code{-gdb-version} Command
32891 @findex -gdb-version
32893 @subsubheading Synopsis
32899 Show version information for @value{GDBN}. Used mostly in testing.
32901 @subsubheading @value{GDBN} Command
32903 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
32904 default shows this information when you start an interactive session.
32906 @subsubheading Example
32908 @c This example modifies the actual output from GDB to avoid overfull
32914 ~Copyright 2000 Free Software Foundation, Inc.
32915 ~GDB is free software, covered by the GNU General Public License, and
32916 ~you are welcome to change it and/or distribute copies of it under
32917 ~ certain conditions.
32918 ~Type "show copying" to see the conditions.
32919 ~There is absolutely no warranty for GDB. Type "show warranty" for
32921 ~This GDB was configured as
32922 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32927 @subheading The @code{-list-features} Command
32928 @findex -list-features
32930 Returns a list of particular features of the MI protocol that
32931 this version of gdb implements. A feature can be a command,
32932 or a new field in an output of some command, or even an
32933 important bugfix. While a frontend can sometimes detect presence
32934 of a feature at runtime, it is easier to perform detection at debugger
32937 The command returns a list of strings, with each string naming an
32938 available feature. Each returned string is just a name, it does not
32939 have any internal structure. The list of possible feature names
32945 (gdb) -list-features
32946 ^done,result=["feature1","feature2"]
32949 The current list of features is:
32952 @item frozen-varobjs
32953 Indicates support for the @code{-var-set-frozen} command, as well
32954 as possible presense of the @code{frozen} field in the output
32955 of @code{-varobj-create}.
32956 @item pending-breakpoints
32957 Indicates support for the @option{-f} option to the @code{-break-insert}
32960 Indicates Python scripting support, Python-based
32961 pretty-printing commands, and possible presence of the
32962 @samp{display_hint} field in the output of @code{-var-list-children}
32964 Indicates support for the @code{-thread-info} command.
32965 @item data-read-memory-bytes
32966 Indicates support for the @code{-data-read-memory-bytes} and the
32967 @code{-data-write-memory-bytes} commands.
32968 @item breakpoint-notifications
32969 Indicates that changes to breakpoints and breakpoints created via the
32970 CLI will be announced via async records.
32971 @item ada-task-info
32972 Indicates support for the @code{-ada-task-info} command.
32975 @subheading The @code{-list-target-features} Command
32976 @findex -list-target-features
32978 Returns a list of particular features that are supported by the
32979 target. Those features affect the permitted MI commands, but
32980 unlike the features reported by the @code{-list-features} command, the
32981 features depend on which target GDB is using at the moment. Whenever
32982 a target can change, due to commands such as @code{-target-select},
32983 @code{-target-attach} or @code{-exec-run}, the list of target features
32984 may change, and the frontend should obtain it again.
32988 (gdb) -list-features
32989 ^done,result=["async"]
32992 The current list of features is:
32996 Indicates that the target is capable of asynchronous command
32997 execution, which means that @value{GDBN} will accept further commands
32998 while the target is running.
33001 Indicates that the target is capable of reverse execution.
33002 @xref{Reverse Execution}, for more information.
33006 @subheading The @code{-list-thread-groups} Command
33007 @findex -list-thread-groups
33009 @subheading Synopsis
33012 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
33015 Lists thread groups (@pxref{Thread groups}). When a single thread
33016 group is passed as the argument, lists the children of that group.
33017 When several thread group are passed, lists information about those
33018 thread groups. Without any parameters, lists information about all
33019 top-level thread groups.
33021 Normally, thread groups that are being debugged are reported.
33022 With the @samp{--available} option, @value{GDBN} reports thread groups
33023 available on the target.
33025 The output of this command may have either a @samp{threads} result or
33026 a @samp{groups} result. The @samp{thread} result has a list of tuples
33027 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
33028 Information}). The @samp{groups} result has a list of tuples as value,
33029 each tuple describing a thread group. If top-level groups are
33030 requested (that is, no parameter is passed), or when several groups
33031 are passed, the output always has a @samp{groups} result. The format
33032 of the @samp{group} result is described below.
33034 To reduce the number of roundtrips it's possible to list thread groups
33035 together with their children, by passing the @samp{--recurse} option
33036 and the recursion depth. Presently, only recursion depth of 1 is
33037 permitted. If this option is present, then every reported thread group
33038 will also include its children, either as @samp{group} or
33039 @samp{threads} field.
33041 In general, any combination of option and parameters is permitted, with
33042 the following caveats:
33046 When a single thread group is passed, the output will typically
33047 be the @samp{threads} result. Because threads may not contain
33048 anything, the @samp{recurse} option will be ignored.
33051 When the @samp{--available} option is passed, limited information may
33052 be available. In particular, the list of threads of a process might
33053 be inaccessible. Further, specifying specific thread groups might
33054 not give any performance advantage over listing all thread groups.
33055 The frontend should assume that @samp{-list-thread-groups --available}
33056 is always an expensive operation and cache the results.
33060 The @samp{groups} result is a list of tuples, where each tuple may
33061 have the following fields:
33065 Identifier of the thread group. This field is always present.
33066 The identifier is an opaque string; frontends should not try to
33067 convert it to an integer, even though it might look like one.
33070 The type of the thread group. At present, only @samp{process} is a
33074 The target-specific process identifier. This field is only present
33075 for thread groups of type @samp{process} and only if the process exists.
33078 The number of children this thread group has. This field may be
33079 absent for an available thread group.
33082 This field has a list of tuples as value, each tuple describing a
33083 thread. It may be present if the @samp{--recurse} option is
33084 specified, and it's actually possible to obtain the threads.
33087 This field is a list of integers, each identifying a core that one
33088 thread of the group is running on. This field may be absent if
33089 such information is not available.
33092 The name of the executable file that corresponds to this thread group.
33093 The field is only present for thread groups of type @samp{process},
33094 and only if there is a corresponding executable file.
33098 @subheading Example
33102 -list-thread-groups
33103 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33104 -list-thread-groups 17
33105 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33106 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33107 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33108 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
33109 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
33110 -list-thread-groups --available
33111 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
33112 -list-thread-groups --available --recurse 1
33113 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33114 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33115 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
33116 -list-thread-groups --available --recurse 1 17 18
33117 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33118 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33119 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
33122 @subheading The @code{-info-os} Command
33125 @subsubheading Synopsis
33128 -info-os [ @var{type} ]
33131 If no argument is supplied, the command returns a table of available
33132 operating-system-specific information types. If one of these types is
33133 supplied as an argument @var{type}, then the command returns a table
33134 of data of that type.
33136 The types of information available depend on the target operating
33139 @subsubheading @value{GDBN} Command
33141 The corresponding @value{GDBN} command is @samp{info os}.
33143 @subsubheading Example
33145 When run on a @sc{gnu}/Linux system, the output will look something
33151 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
33152 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
33153 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
33154 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
33155 body=[item=@{col0="processes",col1="Listing of all processes",
33156 col2="Processes"@},
33157 item=@{col0="procgroups",col1="Listing of all process groups",
33158 col2="Process groups"@},
33159 item=@{col0="threads",col1="Listing of all threads",
33161 item=@{col0="files",col1="Listing of all file descriptors",
33162 col2="File descriptors"@},
33163 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
33165 item=@{col0="shm",col1="Listing of all shared-memory regions",
33166 col2="Shared-memory regions"@},
33167 item=@{col0="semaphores",col1="Listing of all semaphores",
33168 col2="Semaphores"@},
33169 item=@{col0="msg",col1="Listing of all message queues",
33170 col2="Message queues"@},
33171 item=@{col0="modules",col1="Listing of all loaded kernel modules",
33172 col2="Kernel modules"@}]@}
33175 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
33176 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33177 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33178 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33179 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33180 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33181 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33182 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33184 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33185 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33189 (Note that the MI output here includes a @code{"Title"} column that
33190 does not appear in command-line @code{info os}; this column is useful
33191 for MI clients that want to enumerate the types of data, such as in a
33192 popup menu, but is needless clutter on the command line, and
33193 @code{info os} omits it.)
33195 @subheading The @code{-add-inferior} Command
33196 @findex -add-inferior
33198 @subheading Synopsis
33204 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33205 inferior is not associated with any executable. Such association may
33206 be established with the @samp{-file-exec-and-symbols} command
33207 (@pxref{GDB/MI File Commands}). The command response has a single
33208 field, @samp{thread-group}, whose value is the identifier of the
33209 thread group corresponding to the new inferior.
33211 @subheading Example
33216 ^done,thread-group="i3"
33219 @subheading The @code{-interpreter-exec} Command
33220 @findex -interpreter-exec
33222 @subheading Synopsis
33225 -interpreter-exec @var{interpreter} @var{command}
33227 @anchor{-interpreter-exec}
33229 Execute the specified @var{command} in the given @var{interpreter}.
33231 @subheading @value{GDBN} Command
33233 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33235 @subheading Example
33239 -interpreter-exec console "break main"
33240 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33241 &"During symbol reading, bad structure-type format.\n"
33242 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33247 @subheading The @code{-inferior-tty-set} Command
33248 @findex -inferior-tty-set
33250 @subheading Synopsis
33253 -inferior-tty-set /dev/pts/1
33256 Set terminal for future runs of the program being debugged.
33258 @subheading @value{GDBN} Command
33260 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33262 @subheading Example
33266 -inferior-tty-set /dev/pts/1
33271 @subheading The @code{-inferior-tty-show} Command
33272 @findex -inferior-tty-show
33274 @subheading Synopsis
33280 Show terminal for future runs of program being debugged.
33282 @subheading @value{GDBN} Command
33284 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33286 @subheading Example
33290 -inferior-tty-set /dev/pts/1
33294 ^done,inferior_tty_terminal="/dev/pts/1"
33298 @subheading The @code{-enable-timings} Command
33299 @findex -enable-timings
33301 @subheading Synopsis
33304 -enable-timings [yes | no]
33307 Toggle the printing of the wallclock, user and system times for an MI
33308 command as a field in its output. This command is to help frontend
33309 developers optimize the performance of their code. No argument is
33310 equivalent to @samp{yes}.
33312 @subheading @value{GDBN} Command
33316 @subheading Example
33324 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33325 addr="0x080484ed",func="main",file="myprog.c",
33326 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
33327 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33335 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33336 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33337 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33338 fullname="/home/nickrob/myprog.c",line="73"@}
33343 @chapter @value{GDBN} Annotations
33345 This chapter describes annotations in @value{GDBN}. Annotations were
33346 designed to interface @value{GDBN} to graphical user interfaces or other
33347 similar programs which want to interact with @value{GDBN} at a
33348 relatively high level.
33350 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33354 This is Edition @value{EDITION}, @value{DATE}.
33358 * Annotations Overview:: What annotations are; the general syntax.
33359 * Server Prefix:: Issuing a command without affecting user state.
33360 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33361 * Errors:: Annotations for error messages.
33362 * Invalidation:: Some annotations describe things now invalid.
33363 * Annotations for Running::
33364 Whether the program is running, how it stopped, etc.
33365 * Source Annotations:: Annotations describing source code.
33368 @node Annotations Overview
33369 @section What is an Annotation?
33370 @cindex annotations
33372 Annotations start with a newline character, two @samp{control-z}
33373 characters, and the name of the annotation. If there is no additional
33374 information associated with this annotation, the name of the annotation
33375 is followed immediately by a newline. If there is additional
33376 information, the name of the annotation is followed by a space, the
33377 additional information, and a newline. The additional information
33378 cannot contain newline characters.
33380 Any output not beginning with a newline and two @samp{control-z}
33381 characters denotes literal output from @value{GDBN}. Currently there is
33382 no need for @value{GDBN} to output a newline followed by two
33383 @samp{control-z} characters, but if there was such a need, the
33384 annotations could be extended with an @samp{escape} annotation which
33385 means those three characters as output.
33387 The annotation @var{level}, which is specified using the
33388 @option{--annotate} command line option (@pxref{Mode Options}), controls
33389 how much information @value{GDBN} prints together with its prompt,
33390 values of expressions, source lines, and other types of output. Level 0
33391 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33392 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33393 for programs that control @value{GDBN}, and level 2 annotations have
33394 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33395 Interface, annotate, GDB's Obsolete Annotations}).
33398 @kindex set annotate
33399 @item set annotate @var{level}
33400 The @value{GDBN} command @code{set annotate} sets the level of
33401 annotations to the specified @var{level}.
33403 @item show annotate
33404 @kindex show annotate
33405 Show the current annotation level.
33408 This chapter describes level 3 annotations.
33410 A simple example of starting up @value{GDBN} with annotations is:
33413 $ @kbd{gdb --annotate=3}
33415 Copyright 2003 Free Software Foundation, Inc.
33416 GDB is free software, covered by the GNU General Public License,
33417 and you are welcome to change it and/or distribute copies of it
33418 under certain conditions.
33419 Type "show copying" to see the conditions.
33420 There is absolutely no warranty for GDB. Type "show warranty"
33422 This GDB was configured as "i386-pc-linux-gnu"
33433 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33434 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33435 denotes a @samp{control-z} character) are annotations; the rest is
33436 output from @value{GDBN}.
33438 @node Server Prefix
33439 @section The Server Prefix
33440 @cindex server prefix
33442 If you prefix a command with @samp{server } then it will not affect
33443 the command history, nor will it affect @value{GDBN}'s notion of which
33444 command to repeat if @key{RET} is pressed on a line by itself. This
33445 means that commands can be run behind a user's back by a front-end in
33446 a transparent manner.
33448 The @code{server } prefix does not affect the recording of values into
33449 the value history; to print a value without recording it into the
33450 value history, use the @code{output} command instead of the
33451 @code{print} command.
33453 Using this prefix also disables confirmation requests
33454 (@pxref{confirmation requests}).
33457 @section Annotation for @value{GDBN} Input
33459 @cindex annotations for prompts
33460 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33461 to know when to send output, when the output from a given command is
33464 Different kinds of input each have a different @dfn{input type}. Each
33465 input type has three annotations: a @code{pre-} annotation, which
33466 denotes the beginning of any prompt which is being output, a plain
33467 annotation, which denotes the end of the prompt, and then a @code{post-}
33468 annotation which denotes the end of any echo which may (or may not) be
33469 associated with the input. For example, the @code{prompt} input type
33470 features the following annotations:
33478 The input types are
33481 @findex pre-prompt annotation
33482 @findex prompt annotation
33483 @findex post-prompt annotation
33485 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33487 @findex pre-commands annotation
33488 @findex commands annotation
33489 @findex post-commands annotation
33491 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33492 command. The annotations are repeated for each command which is input.
33494 @findex pre-overload-choice annotation
33495 @findex overload-choice annotation
33496 @findex post-overload-choice annotation
33497 @item overload-choice
33498 When @value{GDBN} wants the user to select between various overloaded functions.
33500 @findex pre-query annotation
33501 @findex query annotation
33502 @findex post-query annotation
33504 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33506 @findex pre-prompt-for-continue annotation
33507 @findex prompt-for-continue annotation
33508 @findex post-prompt-for-continue annotation
33509 @item prompt-for-continue
33510 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33511 expect this to work well; instead use @code{set height 0} to disable
33512 prompting. This is because the counting of lines is buggy in the
33513 presence of annotations.
33518 @cindex annotations for errors, warnings and interrupts
33520 @findex quit annotation
33525 This annotation occurs right before @value{GDBN} responds to an interrupt.
33527 @findex error annotation
33532 This annotation occurs right before @value{GDBN} responds to an error.
33534 Quit and error annotations indicate that any annotations which @value{GDBN} was
33535 in the middle of may end abruptly. For example, if a
33536 @code{value-history-begin} annotation is followed by a @code{error}, one
33537 cannot expect to receive the matching @code{value-history-end}. One
33538 cannot expect not to receive it either, however; an error annotation
33539 does not necessarily mean that @value{GDBN} is immediately returning all the way
33542 @findex error-begin annotation
33543 A quit or error annotation may be preceded by
33549 Any output between that and the quit or error annotation is the error
33552 Warning messages are not yet annotated.
33553 @c If we want to change that, need to fix warning(), type_error(),
33554 @c range_error(), and possibly other places.
33557 @section Invalidation Notices
33559 @cindex annotations for invalidation messages
33560 The following annotations say that certain pieces of state may have
33564 @findex frames-invalid annotation
33565 @item ^Z^Zframes-invalid
33567 The frames (for example, output from the @code{backtrace} command) may
33570 @findex breakpoints-invalid annotation
33571 @item ^Z^Zbreakpoints-invalid
33573 The breakpoints may have changed. For example, the user just added or
33574 deleted a breakpoint.
33577 @node Annotations for Running
33578 @section Running the Program
33579 @cindex annotations for running programs
33581 @findex starting annotation
33582 @findex stopping annotation
33583 When the program starts executing due to a @value{GDBN} command such as
33584 @code{step} or @code{continue},
33590 is output. When the program stops,
33596 is output. Before the @code{stopped} annotation, a variety of
33597 annotations describe how the program stopped.
33600 @findex exited annotation
33601 @item ^Z^Zexited @var{exit-status}
33602 The program exited, and @var{exit-status} is the exit status (zero for
33603 successful exit, otherwise nonzero).
33605 @findex signalled annotation
33606 @findex signal-name annotation
33607 @findex signal-name-end annotation
33608 @findex signal-string annotation
33609 @findex signal-string-end annotation
33610 @item ^Z^Zsignalled
33611 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33612 annotation continues:
33618 ^Z^Zsignal-name-end
33622 ^Z^Zsignal-string-end
33627 where @var{name} is the name of the signal, such as @code{SIGILL} or
33628 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33629 as @code{Illegal Instruction} or @code{Segmentation fault}.
33630 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33631 user's benefit and have no particular format.
33633 @findex signal annotation
33635 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33636 just saying that the program received the signal, not that it was
33637 terminated with it.
33639 @findex breakpoint annotation
33640 @item ^Z^Zbreakpoint @var{number}
33641 The program hit breakpoint number @var{number}.
33643 @findex watchpoint annotation
33644 @item ^Z^Zwatchpoint @var{number}
33645 The program hit watchpoint number @var{number}.
33648 @node Source Annotations
33649 @section Displaying Source
33650 @cindex annotations for source display
33652 @findex source annotation
33653 The following annotation is used instead of displaying source code:
33656 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
33659 where @var{filename} is an absolute file name indicating which source
33660 file, @var{line} is the line number within that file (where 1 is the
33661 first line in the file), @var{character} is the character position
33662 within the file (where 0 is the first character in the file) (for most
33663 debug formats this will necessarily point to the beginning of a line),
33664 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
33665 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
33666 @var{addr} is the address in the target program associated with the
33667 source which is being displayed. @var{addr} is in the form @samp{0x}
33668 followed by one or more lowercase hex digits (note that this does not
33669 depend on the language).
33671 @node JIT Interface
33672 @chapter JIT Compilation Interface
33673 @cindex just-in-time compilation
33674 @cindex JIT compilation interface
33676 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33677 interface. A JIT compiler is a program or library that generates native
33678 executable code at runtime and executes it, usually in order to achieve good
33679 performance while maintaining platform independence.
33681 Programs that use JIT compilation are normally difficult to debug because
33682 portions of their code are generated at runtime, instead of being loaded from
33683 object files, which is where @value{GDBN} normally finds the program's symbols
33684 and debug information. In order to debug programs that use JIT compilation,
33685 @value{GDBN} has an interface that allows the program to register in-memory
33686 symbol files with @value{GDBN} at runtime.
33688 If you are using @value{GDBN} to debug a program that uses this interface, then
33689 it should work transparently so long as you have not stripped the binary. If
33690 you are developing a JIT compiler, then the interface is documented in the rest
33691 of this chapter. At this time, the only known client of this interface is the
33694 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33695 JIT compiler communicates with @value{GDBN} by writing data into a global
33696 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33697 attaches, it reads a linked list of symbol files from the global variable to
33698 find existing code, and puts a breakpoint in the function so that it can find
33699 out about additional code.
33702 * Declarations:: Relevant C struct declarations
33703 * Registering Code:: Steps to register code
33704 * Unregistering Code:: Steps to unregister code
33705 * Custom Debug Info:: Emit debug information in a custom format
33709 @section JIT Declarations
33711 These are the relevant struct declarations that a C program should include to
33712 implement the interface:
33722 struct jit_code_entry
33724 struct jit_code_entry *next_entry;
33725 struct jit_code_entry *prev_entry;
33726 const char *symfile_addr;
33727 uint64_t symfile_size;
33730 struct jit_descriptor
33733 /* This type should be jit_actions_t, but we use uint32_t
33734 to be explicit about the bitwidth. */
33735 uint32_t action_flag;
33736 struct jit_code_entry *relevant_entry;
33737 struct jit_code_entry *first_entry;
33740 /* GDB puts a breakpoint in this function. */
33741 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33743 /* Make sure to specify the version statically, because the
33744 debugger may check the version before we can set it. */
33745 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
33748 If the JIT is multi-threaded, then it is important that the JIT synchronize any
33749 modifications to this global data properly, which can easily be done by putting
33750 a global mutex around modifications to these structures.
33752 @node Registering Code
33753 @section Registering Code
33755 To register code with @value{GDBN}, the JIT should follow this protocol:
33759 Generate an object file in memory with symbols and other desired debug
33760 information. The file must include the virtual addresses of the sections.
33763 Create a code entry for the file, which gives the start and size of the symbol
33767 Add it to the linked list in the JIT descriptor.
33770 Point the relevant_entry field of the descriptor at the entry.
33773 Set @code{action_flag} to @code{JIT_REGISTER} and call
33774 @code{__jit_debug_register_code}.
33777 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
33778 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
33779 new code. However, the linked list must still be maintained in order to allow
33780 @value{GDBN} to attach to a running process and still find the symbol files.
33782 @node Unregistering Code
33783 @section Unregistering Code
33785 If code is freed, then the JIT should use the following protocol:
33789 Remove the code entry corresponding to the code from the linked list.
33792 Point the @code{relevant_entry} field of the descriptor at the code entry.
33795 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
33796 @code{__jit_debug_register_code}.
33799 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
33800 and the JIT will leak the memory used for the associated symbol files.
33802 @node Custom Debug Info
33803 @section Custom Debug Info
33804 @cindex custom JIT debug info
33805 @cindex JIT debug info reader
33807 Generating debug information in platform-native file formats (like ELF
33808 or COFF) may be an overkill for JIT compilers; especially if all the
33809 debug info is used for is displaying a meaningful backtrace. The
33810 issue can be resolved by having the JIT writers decide on a debug info
33811 format and also provide a reader that parses the debug info generated
33812 by the JIT compiler. This section gives a brief overview on writing
33813 such a parser. More specific details can be found in the source file
33814 @file{gdb/jit-reader.in}, which is also installed as a header at
33815 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
33817 The reader is implemented as a shared object (so this functionality is
33818 not available on platforms which don't allow loading shared objects at
33819 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
33820 @code{jit-reader-unload} are provided, to be used to load and unload
33821 the readers from a preconfigured directory. Once loaded, the shared
33822 object is used the parse the debug information emitted by the JIT
33826 * Using JIT Debug Info Readers:: How to use supplied readers correctly
33827 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33830 @node Using JIT Debug Info Readers
33831 @subsection Using JIT Debug Info Readers
33832 @kindex jit-reader-load
33833 @kindex jit-reader-unload
33835 Readers can be loaded and unloaded using the @code{jit-reader-load}
33836 and @code{jit-reader-unload} commands.
33839 @item jit-reader-load @var{reader-name}
33840 Load the JIT reader named @var{reader-name}. On a UNIX system, this
33841 will usually load @file{@var{libdir}/gdb/@var{reader-name}}, where
33842 @var{libdir} is the system library directory, usually
33843 @file{/usr/local/lib}. Only one reader can be active at a time;
33844 trying to load a second reader when one is already loaded will result
33845 in @value{GDBN} reporting an error. A new JIT reader can be loaded by
33846 first unloading the current one using @code{jit-reader-load} and then
33847 invoking @code{jit-reader-load}.
33849 @item jit-reader-unload
33850 Unload the currently loaded JIT reader.
33854 @node Writing JIT Debug Info Readers
33855 @subsection Writing JIT Debug Info Readers
33856 @cindex writing JIT debug info readers
33858 As mentioned, a reader is essentially a shared object conforming to a
33859 certain ABI. This ABI is described in @file{jit-reader.h}.
33861 @file{jit-reader.h} defines the structures, macros and functions
33862 required to write a reader. It is installed (along with
33863 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
33864 the system include directory.
33866 Readers need to be released under a GPL compatible license. A reader
33867 can be declared as released under such a license by placing the macro
33868 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
33870 The entry point for readers is the symbol @code{gdb_init_reader},
33871 which is expected to be a function with the prototype
33873 @findex gdb_init_reader
33875 extern struct gdb_reader_funcs *gdb_init_reader (void);
33878 @cindex @code{struct gdb_reader_funcs}
33880 @code{struct gdb_reader_funcs} contains a set of pointers to callback
33881 functions. These functions are executed to read the debug info
33882 generated by the JIT compiler (@code{read}), to unwind stack frames
33883 (@code{unwind}) and to create canonical frame IDs
33884 (@code{get_Frame_id}). It also has a callback that is called when the
33885 reader is being unloaded (@code{destroy}). The struct looks like this
33888 struct gdb_reader_funcs
33890 /* Must be set to GDB_READER_INTERFACE_VERSION. */
33891 int reader_version;
33893 /* For use by the reader. */
33896 gdb_read_debug_info *read;
33897 gdb_unwind_frame *unwind;
33898 gdb_get_frame_id *get_frame_id;
33899 gdb_destroy_reader *destroy;
33903 @cindex @code{struct gdb_symbol_callbacks}
33904 @cindex @code{struct gdb_unwind_callbacks}
33906 The callbacks are provided with another set of callbacks by
33907 @value{GDBN} to do their job. For @code{read}, these callbacks are
33908 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
33909 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
33910 @code{struct gdb_symbol_callbacks} has callbacks to create new object
33911 files and new symbol tables inside those object files. @code{struct
33912 gdb_unwind_callbacks} has callbacks to read registers off the current
33913 frame and to write out the values of the registers in the previous
33914 frame. Both have a callback (@code{target_read}) to read bytes off the
33915 target's address space.
33917 @node In-Process Agent
33918 @chapter In-Process Agent
33919 @cindex debugging agent
33920 The traditional debugging model is conceptually low-speed, but works fine,
33921 because most bugs can be reproduced in debugging-mode execution. However,
33922 as multi-core or many-core processors are becoming mainstream, and
33923 multi-threaded programs become more and more popular, there should be more
33924 and more bugs that only manifest themselves at normal-mode execution, for
33925 example, thread races, because debugger's interference with the program's
33926 timing may conceal the bugs. On the other hand, in some applications,
33927 it is not feasible for the debugger to interrupt the program's execution
33928 long enough for the developer to learn anything helpful about its behavior.
33929 If the program's correctness depends on its real-time behavior, delays
33930 introduced by a debugger might cause the program to fail, even when the
33931 code itself is correct. It is useful to be able to observe the program's
33932 behavior without interrupting it.
33934 Therefore, traditional debugging model is too intrusive to reproduce
33935 some bugs. In order to reduce the interference with the program, we can
33936 reduce the number of operations performed by debugger. The
33937 @dfn{In-Process Agent}, a shared library, is running within the same
33938 process with inferior, and is able to perform some debugging operations
33939 itself. As a result, debugger is only involved when necessary, and
33940 performance of debugging can be improved accordingly. Note that
33941 interference with program can be reduced but can't be removed completely,
33942 because the in-process agent will still stop or slow down the program.
33944 The in-process agent can interpret and execute Agent Expressions
33945 (@pxref{Agent Expressions}) during performing debugging operations. The
33946 agent expressions can be used for different purposes, such as collecting
33947 data in tracepoints, and condition evaluation in breakpoints.
33949 @anchor{Control Agent}
33950 You can control whether the in-process agent is used as an aid for
33951 debugging with the following commands:
33954 @kindex set agent on
33956 Causes the in-process agent to perform some operations on behalf of the
33957 debugger. Just which operations requested by the user will be done
33958 by the in-process agent depends on the its capabilities. For example,
33959 if you request to evaluate breakpoint conditions in the in-process agent,
33960 and the in-process agent has such capability as well, then breakpoint
33961 conditions will be evaluated in the in-process agent.
33963 @kindex set agent off
33964 @item set agent off
33965 Disables execution of debugging operations by the in-process agent. All
33966 of the operations will be performed by @value{GDBN}.
33970 Display the current setting of execution of debugging operations by
33971 the in-process agent.
33975 * In-Process Agent Protocol::
33978 @node In-Process Agent Protocol
33979 @section In-Process Agent Protocol
33980 @cindex in-process agent protocol
33982 The in-process agent is able to communicate with both @value{GDBN} and
33983 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
33984 used for communications between @value{GDBN} or GDBserver and the IPA.
33985 In general, @value{GDBN} or GDBserver sends commands
33986 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
33987 in-process agent replies back with the return result of the command, or
33988 some other information. The data sent to in-process agent is composed
33989 of primitive data types, such as 4-byte or 8-byte type, and composite
33990 types, which are called objects (@pxref{IPA Protocol Objects}).
33993 * IPA Protocol Objects::
33994 * IPA Protocol Commands::
33997 @node IPA Protocol Objects
33998 @subsection IPA Protocol Objects
33999 @cindex ipa protocol objects
34001 The commands sent to and results received from agent may contain some
34002 complex data types called @dfn{objects}.
34004 The in-process agent is running on the same machine with @value{GDBN}
34005 or GDBserver, so it doesn't have to handle as much differences between
34006 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
34007 However, there are still some differences of two ends in two processes:
34011 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
34012 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
34014 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
34015 GDBserver is compiled with one, and in-process agent is compiled with
34019 Here are the IPA Protocol Objects:
34023 agent expression object. It represents an agent expression
34024 (@pxref{Agent Expressions}).
34025 @anchor{agent expression object}
34027 tracepoint action object. It represents a tracepoint action
34028 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
34029 memory, static trace data and to evaluate expression.
34030 @anchor{tracepoint action object}
34032 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
34033 @anchor{tracepoint object}
34037 The following table describes important attributes of each IPA protocol
34040 @multitable @columnfractions .30 .20 .50
34041 @headitem Name @tab Size @tab Description
34042 @item @emph{agent expression object} @tab @tab
34043 @item length @tab 4 @tab length of bytes code
34044 @item byte code @tab @var{length} @tab contents of byte code
34045 @item @emph{tracepoint action for collecting memory} @tab @tab
34046 @item 'M' @tab 1 @tab type of tracepoint action
34047 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
34048 address of the lowest byte to collect, otherwise @var{addr} is the offset
34049 of @var{basereg} for memory collecting.
34050 @item len @tab 8 @tab length of memory for collecting
34051 @item basereg @tab 4 @tab the register number containing the starting
34052 memory address for collecting.
34053 @item @emph{tracepoint action for collecting registers} @tab @tab
34054 @item 'R' @tab 1 @tab type of tracepoint action
34055 @item @emph{tracepoint action for collecting static trace data} @tab @tab
34056 @item 'L' @tab 1 @tab type of tracepoint action
34057 @item @emph{tracepoint action for expression evaluation} @tab @tab
34058 @item 'X' @tab 1 @tab type of tracepoint action
34059 @item agent expression @tab length of @tab @ref{agent expression object}
34060 @item @emph{tracepoint object} @tab @tab
34061 @item number @tab 4 @tab number of tracepoint
34062 @item address @tab 8 @tab address of tracepoint inserted on
34063 @item type @tab 4 @tab type of tracepoint
34064 @item enabled @tab 1 @tab enable or disable of tracepoint
34065 @item step_count @tab 8 @tab step
34066 @item pass_count @tab 8 @tab pass
34067 @item numactions @tab 4 @tab number of tracepoint actions
34068 @item hit count @tab 8 @tab hit count
34069 @item trace frame usage @tab 8 @tab trace frame usage
34070 @item compiled_cond @tab 8 @tab compiled condition
34071 @item orig_size @tab 8 @tab orig size
34072 @item condition @tab 4 if condition is NULL otherwise length of
34073 @ref{agent expression object}
34074 @tab zero if condition is NULL, otherwise is
34075 @ref{agent expression object}
34076 @item actions @tab variable
34077 @tab numactions number of @ref{tracepoint action object}
34080 @node IPA Protocol Commands
34081 @subsection IPA Protocol Commands
34082 @cindex ipa protocol commands
34084 The spaces in each command are delimiters to ease reading this commands
34085 specification. They don't exist in real commands.
34089 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34090 Installs a new fast tracepoint described by @var{tracepoint_object}
34091 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
34092 head of @dfn{jumppad}, which is used to jump to data collection routine
34097 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34098 @var{target_address} is address of tracepoint in the inferior.
34099 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34100 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
34101 @var{fjump} contains a sequence of instructions jump to jumppad entry.
34102 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
34109 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
34110 is about to kill inferiors.
34118 @item probe_marker_at:@var{address}
34119 Asks in-process agent to probe the marker at @var{address}.
34126 @item unprobe_marker_at:@var{address}
34127 Asks in-process agent to unprobe the marker at @var{address}.
34131 @chapter Reporting Bugs in @value{GDBN}
34132 @cindex bugs in @value{GDBN}
34133 @cindex reporting bugs in @value{GDBN}
34135 Your bug reports play an essential role in making @value{GDBN} reliable.
34137 Reporting a bug may help you by bringing a solution to your problem, or it
34138 may not. But in any case the principal function of a bug report is to help
34139 the entire community by making the next version of @value{GDBN} work better. Bug
34140 reports are your contribution to the maintenance of @value{GDBN}.
34142 In order for a bug report to serve its purpose, you must include the
34143 information that enables us to fix the bug.
34146 * Bug Criteria:: Have you found a bug?
34147 * Bug Reporting:: How to report bugs
34151 @section Have You Found a Bug?
34152 @cindex bug criteria
34154 If you are not sure whether you have found a bug, here are some guidelines:
34157 @cindex fatal signal
34158 @cindex debugger crash
34159 @cindex crash of debugger
34161 If the debugger gets a fatal signal, for any input whatever, that is a
34162 @value{GDBN} bug. Reliable debuggers never crash.
34164 @cindex error on valid input
34166 If @value{GDBN} produces an error message for valid input, that is a
34167 bug. (Note that if you're cross debugging, the problem may also be
34168 somewhere in the connection to the target.)
34170 @cindex invalid input
34172 If @value{GDBN} does not produce an error message for invalid input,
34173 that is a bug. However, you should note that your idea of
34174 ``invalid input'' might be our idea of ``an extension'' or ``support
34175 for traditional practice''.
34178 If you are an experienced user of debugging tools, your suggestions
34179 for improvement of @value{GDBN} are welcome in any case.
34182 @node Bug Reporting
34183 @section How to Report Bugs
34184 @cindex bug reports
34185 @cindex @value{GDBN} bugs, reporting
34187 A number of companies and individuals offer support for @sc{gnu} products.
34188 If you obtained @value{GDBN} from a support organization, we recommend you
34189 contact that organization first.
34191 You can find contact information for many support companies and
34192 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34194 @c should add a web page ref...
34197 @ifset BUGURL_DEFAULT
34198 In any event, we also recommend that you submit bug reports for
34199 @value{GDBN}. The preferred method is to submit them directly using
34200 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34201 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34204 @strong{Do not send bug reports to @samp{info-gdb}, or to
34205 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34206 not want to receive bug reports. Those that do have arranged to receive
34209 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34210 serves as a repeater. The mailing list and the newsgroup carry exactly
34211 the same messages. Often people think of posting bug reports to the
34212 newsgroup instead of mailing them. This appears to work, but it has one
34213 problem which can be crucial: a newsgroup posting often lacks a mail
34214 path back to the sender. Thus, if we need to ask for more information,
34215 we may be unable to reach you. For this reason, it is better to send
34216 bug reports to the mailing list.
34218 @ifclear BUGURL_DEFAULT
34219 In any event, we also recommend that you submit bug reports for
34220 @value{GDBN} to @value{BUGURL}.
34224 The fundamental principle of reporting bugs usefully is this:
34225 @strong{report all the facts}. If you are not sure whether to state a
34226 fact or leave it out, state it!
34228 Often people omit facts because they think they know what causes the
34229 problem and assume that some details do not matter. Thus, you might
34230 assume that the name of the variable you use in an example does not matter.
34231 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34232 stray memory reference which happens to fetch from the location where that
34233 name is stored in memory; perhaps, if the name were different, the contents
34234 of that location would fool the debugger into doing the right thing despite
34235 the bug. Play it safe and give a specific, complete example. That is the
34236 easiest thing for you to do, and the most helpful.
34238 Keep in mind that the purpose of a bug report is to enable us to fix the
34239 bug. It may be that the bug has been reported previously, but neither
34240 you nor we can know that unless your bug report is complete and
34243 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34244 bell?'' Those bug reports are useless, and we urge everyone to
34245 @emph{refuse to respond to them} except to chide the sender to report
34248 To enable us to fix the bug, you should include all these things:
34252 The version of @value{GDBN}. @value{GDBN} announces it if you start
34253 with no arguments; you can also print it at any time using @code{show
34256 Without this, we will not know whether there is any point in looking for
34257 the bug in the current version of @value{GDBN}.
34260 The type of machine you are using, and the operating system name and
34264 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34265 ``@value{GCC}--2.8.1''.
34268 What compiler (and its version) was used to compile the program you are
34269 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34270 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34271 to get this information; for other compilers, see the documentation for
34275 The command arguments you gave the compiler to compile your example and
34276 observe the bug. For example, did you use @samp{-O}? To guarantee
34277 you will not omit something important, list them all. A copy of the
34278 Makefile (or the output from make) is sufficient.
34280 If we were to try to guess the arguments, we would probably guess wrong
34281 and then we might not encounter the bug.
34284 A complete input script, and all necessary source files, that will
34288 A description of what behavior you observe that you believe is
34289 incorrect. For example, ``It gets a fatal signal.''
34291 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34292 will certainly notice it. But if the bug is incorrect output, we might
34293 not notice unless it is glaringly wrong. You might as well not give us
34294 a chance to make a mistake.
34296 Even if the problem you experience is a fatal signal, you should still
34297 say so explicitly. Suppose something strange is going on, such as, your
34298 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34299 the C library on your system. (This has happened!) Your copy might
34300 crash and ours would not. If you told us to expect a crash, then when
34301 ours fails to crash, we would know that the bug was not happening for
34302 us. If you had not told us to expect a crash, then we would not be able
34303 to draw any conclusion from our observations.
34306 @cindex recording a session script
34307 To collect all this information, you can use a session recording program
34308 such as @command{script}, which is available on many Unix systems.
34309 Just run your @value{GDBN} session inside @command{script} and then
34310 include the @file{typescript} file with your bug report.
34312 Another way to record a @value{GDBN} session is to run @value{GDBN}
34313 inside Emacs and then save the entire buffer to a file.
34316 If you wish to suggest changes to the @value{GDBN} source, send us context
34317 diffs. If you even discuss something in the @value{GDBN} source, refer to
34318 it by context, not by line number.
34320 The line numbers in our development sources will not match those in your
34321 sources. Your line numbers would convey no useful information to us.
34325 Here are some things that are not necessary:
34329 A description of the envelope of the bug.
34331 Often people who encounter a bug spend a lot of time investigating
34332 which changes to the input file will make the bug go away and which
34333 changes will not affect it.
34335 This is often time consuming and not very useful, because the way we
34336 will find the bug is by running a single example under the debugger
34337 with breakpoints, not by pure deduction from a series of examples.
34338 We recommend that you save your time for something else.
34340 Of course, if you can find a simpler example to report @emph{instead}
34341 of the original one, that is a convenience for us. Errors in the
34342 output will be easier to spot, running under the debugger will take
34343 less time, and so on.
34345 However, simplification is not vital; if you do not want to do this,
34346 report the bug anyway and send us the entire test case you used.
34349 A patch for the bug.
34351 A patch for the bug does help us if it is a good one. But do not omit
34352 the necessary information, such as the test case, on the assumption that
34353 a patch is all we need. We might see problems with your patch and decide
34354 to fix the problem another way, or we might not understand it at all.
34356 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34357 construct an example that will make the program follow a certain path
34358 through the code. If you do not send us the example, we will not be able
34359 to construct one, so we will not be able to verify that the bug is fixed.
34361 And if we cannot understand what bug you are trying to fix, or why your
34362 patch should be an improvement, we will not install it. A test case will
34363 help us to understand.
34366 A guess about what the bug is or what it depends on.
34368 Such guesses are usually wrong. Even we cannot guess right about such
34369 things without first using the debugger to find the facts.
34372 @c The readline documentation is distributed with the readline code
34373 @c and consists of the two following files:
34376 @c Use -I with makeinfo to point to the appropriate directory,
34377 @c environment var TEXINPUTS with TeX.
34378 @ifclear SYSTEM_READLINE
34379 @include rluser.texi
34380 @include hsuser.texi
34384 @appendix In Memoriam
34386 The @value{GDBN} project mourns the loss of the following long-time
34391 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34392 to Free Software in general. Outside of @value{GDBN}, he was known in
34393 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34395 @item Michael Snyder
34396 Michael was one of the Global Maintainers of the @value{GDBN} project,
34397 with contributions recorded as early as 1996, until 2011. In addition
34398 to his day to day participation, he was a large driving force behind
34399 adding Reverse Debugging to @value{GDBN}.
34402 Beyond their technical contributions to the project, they were also
34403 enjoyable members of the Free Software Community. We will miss them.
34405 @node Formatting Documentation
34406 @appendix Formatting Documentation
34408 @cindex @value{GDBN} reference card
34409 @cindex reference card
34410 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34411 for printing with PostScript or Ghostscript, in the @file{gdb}
34412 subdirectory of the main source directory@footnote{In
34413 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34414 release.}. If you can use PostScript or Ghostscript with your printer,
34415 you can print the reference card immediately with @file{refcard.ps}.
34417 The release also includes the source for the reference card. You
34418 can format it, using @TeX{}, by typing:
34424 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34425 mode on US ``letter'' size paper;
34426 that is, on a sheet 11 inches wide by 8.5 inches
34427 high. You will need to specify this form of printing as an option to
34428 your @sc{dvi} output program.
34430 @cindex documentation
34432 All the documentation for @value{GDBN} comes as part of the machine-readable
34433 distribution. The documentation is written in Texinfo format, which is
34434 a documentation system that uses a single source file to produce both
34435 on-line information and a printed manual. You can use one of the Info
34436 formatting commands to create the on-line version of the documentation
34437 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34439 @value{GDBN} includes an already formatted copy of the on-line Info
34440 version of this manual in the @file{gdb} subdirectory. The main Info
34441 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34442 subordinate files matching @samp{gdb.info*} in the same directory. If
34443 necessary, you can print out these files, or read them with any editor;
34444 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34445 Emacs or the standalone @code{info} program, available as part of the
34446 @sc{gnu} Texinfo distribution.
34448 If you want to format these Info files yourself, you need one of the
34449 Info formatting programs, such as @code{texinfo-format-buffer} or
34452 If you have @code{makeinfo} installed, and are in the top level
34453 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34454 version @value{GDBVN}), you can make the Info file by typing:
34461 If you want to typeset and print copies of this manual, you need @TeX{},
34462 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34463 Texinfo definitions file.
34465 @TeX{} is a typesetting program; it does not print files directly, but
34466 produces output files called @sc{dvi} files. To print a typeset
34467 document, you need a program to print @sc{dvi} files. If your system
34468 has @TeX{} installed, chances are it has such a program. The precise
34469 command to use depends on your system; @kbd{lpr -d} is common; another
34470 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34471 require a file name without any extension or a @samp{.dvi} extension.
34473 @TeX{} also requires a macro definitions file called
34474 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34475 written in Texinfo format. On its own, @TeX{} cannot either read or
34476 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34477 and is located in the @file{gdb-@var{version-number}/texinfo}
34480 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34481 typeset and print this manual. First switch to the @file{gdb}
34482 subdirectory of the main source directory (for example, to
34483 @file{gdb-@value{GDBVN}/gdb}) and type:
34489 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34491 @node Installing GDB
34492 @appendix Installing @value{GDBN}
34493 @cindex installation
34496 * Requirements:: Requirements for building @value{GDBN}
34497 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34498 * Separate Objdir:: Compiling @value{GDBN} in another directory
34499 * Config Names:: Specifying names for hosts and targets
34500 * Configure Options:: Summary of options for configure
34501 * System-wide configuration:: Having a system-wide init file
34505 @section Requirements for Building @value{GDBN}
34506 @cindex building @value{GDBN}, requirements for
34508 Building @value{GDBN} requires various tools and packages to be available.
34509 Other packages will be used only if they are found.
34511 @heading Tools/Packages Necessary for Building @value{GDBN}
34513 @item ISO C90 compiler
34514 @value{GDBN} is written in ISO C90. It should be buildable with any
34515 working C90 compiler, e.g.@: GCC.
34519 @heading Tools/Packages Optional for Building @value{GDBN}
34523 @value{GDBN} can use the Expat XML parsing library. This library may be
34524 included with your operating system distribution; if it is not, you
34525 can get the latest version from @url{http://expat.sourceforge.net}.
34526 The @file{configure} script will search for this library in several
34527 standard locations; if it is installed in an unusual path, you can
34528 use the @option{--with-libexpat-prefix} option to specify its location.
34534 Remote protocol memory maps (@pxref{Memory Map Format})
34536 Target descriptions (@pxref{Target Descriptions})
34538 Remote shared library lists (@xref{Library List Format},
34539 or alternatively @pxref{Library List Format for SVR4 Targets})
34541 MS-Windows shared libraries (@pxref{Shared Libraries})
34543 Traceframe info (@pxref{Traceframe Info Format})
34547 @cindex compressed debug sections
34548 @value{GDBN} will use the @samp{zlib} library, if available, to read
34549 compressed debug sections. Some linkers, such as GNU gold, are capable
34550 of producing binaries with compressed debug sections. If @value{GDBN}
34551 is compiled with @samp{zlib}, it will be able to read the debug
34552 information in such binaries.
34554 The @samp{zlib} library is likely included with your operating system
34555 distribution; if it is not, you can get the latest version from
34556 @url{http://zlib.net}.
34559 @value{GDBN}'s features related to character sets (@pxref{Character
34560 Sets}) require a functioning @code{iconv} implementation. If you are
34561 on a GNU system, then this is provided by the GNU C Library. Some
34562 other systems also provide a working @code{iconv}.
34564 If @value{GDBN} is using the @code{iconv} program which is installed
34565 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34566 This is done with @option{--with-iconv-bin} which specifies the
34567 directory that contains the @code{iconv} program.
34569 On systems without @code{iconv}, you can install GNU Libiconv. If you
34570 have previously installed Libiconv, you can use the
34571 @option{--with-libiconv-prefix} option to configure.
34573 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34574 arrange to build Libiconv if a directory named @file{libiconv} appears
34575 in the top-most source directory. If Libiconv is built this way, and
34576 if the operating system does not provide a suitable @code{iconv}
34577 implementation, then the just-built library will automatically be used
34578 by @value{GDBN}. One easy way to set this up is to download GNU
34579 Libiconv, unpack it, and then rename the directory holding the
34580 Libiconv source code to @samp{libiconv}.
34583 @node Running Configure
34584 @section Invoking the @value{GDBN} @file{configure} Script
34585 @cindex configuring @value{GDBN}
34586 @value{GDBN} comes with a @file{configure} script that automates the process
34587 of preparing @value{GDBN} for installation; you can then use @code{make} to
34588 build the @code{gdb} program.
34590 @c irrelevant in info file; it's as current as the code it lives with.
34591 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34592 look at the @file{README} file in the sources; we may have improved the
34593 installation procedures since publishing this manual.}
34596 The @value{GDBN} distribution includes all the source code you need for
34597 @value{GDBN} in a single directory, whose name is usually composed by
34598 appending the version number to @samp{gdb}.
34600 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34601 @file{gdb-@value{GDBVN}} directory. That directory contains:
34604 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34605 script for configuring @value{GDBN} and all its supporting libraries
34607 @item gdb-@value{GDBVN}/gdb
34608 the source specific to @value{GDBN} itself
34610 @item gdb-@value{GDBVN}/bfd
34611 source for the Binary File Descriptor library
34613 @item gdb-@value{GDBVN}/include
34614 @sc{gnu} include files
34616 @item gdb-@value{GDBVN}/libiberty
34617 source for the @samp{-liberty} free software library
34619 @item gdb-@value{GDBVN}/opcodes
34620 source for the library of opcode tables and disassemblers
34622 @item gdb-@value{GDBVN}/readline
34623 source for the @sc{gnu} command-line interface
34625 @item gdb-@value{GDBVN}/glob
34626 source for the @sc{gnu} filename pattern-matching subroutine
34628 @item gdb-@value{GDBVN}/mmalloc
34629 source for the @sc{gnu} memory-mapped malloc package
34632 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34633 from the @file{gdb-@var{version-number}} source directory, which in
34634 this example is the @file{gdb-@value{GDBVN}} directory.
34636 First switch to the @file{gdb-@var{version-number}} source directory
34637 if you are not already in it; then run @file{configure}. Pass the
34638 identifier for the platform on which @value{GDBN} will run as an
34644 cd gdb-@value{GDBVN}
34645 ./configure @var{host}
34650 where @var{host} is an identifier such as @samp{sun4} or
34651 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
34652 (You can often leave off @var{host}; @file{configure} tries to guess the
34653 correct value by examining your system.)
34655 Running @samp{configure @var{host}} and then running @code{make} builds the
34656 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
34657 libraries, then @code{gdb} itself. The configured source files, and the
34658 binaries, are left in the corresponding source directories.
34661 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
34662 system does not recognize this automatically when you run a different
34663 shell, you may need to run @code{sh} on it explicitly:
34666 sh configure @var{host}
34669 If you run @file{configure} from a directory that contains source
34670 directories for multiple libraries or programs, such as the
34671 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34673 creates configuration files for every directory level underneath (unless
34674 you tell it not to, with the @samp{--norecursion} option).
34676 You should run the @file{configure} script from the top directory in the
34677 source tree, the @file{gdb-@var{version-number}} directory. If you run
34678 @file{configure} from one of the subdirectories, you will configure only
34679 that subdirectory. That is usually not what you want. In particular,
34680 if you run the first @file{configure} from the @file{gdb} subdirectory
34681 of the @file{gdb-@var{version-number}} directory, you will omit the
34682 configuration of @file{bfd}, @file{readline}, and other sibling
34683 directories of the @file{gdb} subdirectory. This leads to build errors
34684 about missing include files such as @file{bfd/bfd.h}.
34686 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34687 However, you should make sure that the shell on your path (named by
34688 the @samp{SHELL} environment variable) is publicly readable. Remember
34689 that @value{GDBN} uses the shell to start your program---some systems refuse to
34690 let @value{GDBN} debug child processes whose programs are not readable.
34692 @node Separate Objdir
34693 @section Compiling @value{GDBN} in Another Directory
34695 If you want to run @value{GDBN} versions for several host or target machines,
34696 you need a different @code{gdb} compiled for each combination of
34697 host and target. @file{configure} is designed to make this easy by
34698 allowing you to generate each configuration in a separate subdirectory,
34699 rather than in the source directory. If your @code{make} program
34700 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
34701 @code{make} in each of these directories builds the @code{gdb}
34702 program specified there.
34704 To build @code{gdb} in a separate directory, run @file{configure}
34705 with the @samp{--srcdir} option to specify where to find the source.
34706 (You also need to specify a path to find @file{configure}
34707 itself from your working directory. If the path to @file{configure}
34708 would be the same as the argument to @samp{--srcdir}, you can leave out
34709 the @samp{--srcdir} option; it is assumed.)
34711 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
34712 separate directory for a Sun 4 like this:
34716 cd gdb-@value{GDBVN}
34719 ../gdb-@value{GDBVN}/configure sun4
34724 When @file{configure} builds a configuration using a remote source
34725 directory, it creates a tree for the binaries with the same structure
34726 (and using the same names) as the tree under the source directory. In
34727 the example, you'd find the Sun 4 library @file{libiberty.a} in the
34728 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
34729 @file{gdb-sun4/gdb}.
34731 Make sure that your path to the @file{configure} script has just one
34732 instance of @file{gdb} in it. If your path to @file{configure} looks
34733 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
34734 one subdirectory of @value{GDBN}, not the whole package. This leads to
34735 build errors about missing include files such as @file{bfd/bfd.h}.
34737 One popular reason to build several @value{GDBN} configurations in separate
34738 directories is to configure @value{GDBN} for cross-compiling (where
34739 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
34740 programs that run on another machine---the @dfn{target}).
34741 You specify a cross-debugging target by
34742 giving the @samp{--target=@var{target}} option to @file{configure}.
34744 When you run @code{make} to build a program or library, you must run
34745 it in a configured directory---whatever directory you were in when you
34746 called @file{configure} (or one of its subdirectories).
34748 The @code{Makefile} that @file{configure} generates in each source
34749 directory also runs recursively. If you type @code{make} in a source
34750 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
34751 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
34752 will build all the required libraries, and then build GDB.
34754 When you have multiple hosts or targets configured in separate
34755 directories, you can run @code{make} on them in parallel (for example,
34756 if they are NFS-mounted on each of the hosts); they will not interfere
34760 @section Specifying Names for Hosts and Targets
34762 The specifications used for hosts and targets in the @file{configure}
34763 script are based on a three-part naming scheme, but some short predefined
34764 aliases are also supported. The full naming scheme encodes three pieces
34765 of information in the following pattern:
34768 @var{architecture}-@var{vendor}-@var{os}
34771 For example, you can use the alias @code{sun4} as a @var{host} argument,
34772 or as the value for @var{target} in a @code{--target=@var{target}}
34773 option. The equivalent full name is @samp{sparc-sun-sunos4}.
34775 The @file{configure} script accompanying @value{GDBN} does not provide
34776 any query facility to list all supported host and target names or
34777 aliases. @file{configure} calls the Bourne shell script
34778 @code{config.sub} to map abbreviations to full names; you can read the
34779 script, if you wish, or you can use it to test your guesses on
34780 abbreviations---for example:
34783 % sh config.sub i386-linux
34785 % sh config.sub alpha-linux
34786 alpha-unknown-linux-gnu
34787 % sh config.sub hp9k700
34789 % sh config.sub sun4
34790 sparc-sun-sunos4.1.1
34791 % sh config.sub sun3
34792 m68k-sun-sunos4.1.1
34793 % sh config.sub i986v
34794 Invalid configuration `i986v': machine `i986v' not recognized
34798 @code{config.sub} is also distributed in the @value{GDBN} source
34799 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
34801 @node Configure Options
34802 @section @file{configure} Options
34804 Here is a summary of the @file{configure} options and arguments that
34805 are most often useful for building @value{GDBN}. @file{configure} also has
34806 several other options not listed here. @inforef{What Configure
34807 Does,,configure.info}, for a full explanation of @file{configure}.
34810 configure @r{[}--help@r{]}
34811 @r{[}--prefix=@var{dir}@r{]}
34812 @r{[}--exec-prefix=@var{dir}@r{]}
34813 @r{[}--srcdir=@var{dirname}@r{]}
34814 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
34815 @r{[}--target=@var{target}@r{]}
34820 You may introduce options with a single @samp{-} rather than
34821 @samp{--} if you prefer; but you may abbreviate option names if you use
34826 Display a quick summary of how to invoke @file{configure}.
34828 @item --prefix=@var{dir}
34829 Configure the source to install programs and files under directory
34832 @item --exec-prefix=@var{dir}
34833 Configure the source to install programs under directory
34836 @c avoid splitting the warning from the explanation:
34838 @item --srcdir=@var{dirname}
34839 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
34840 @code{make} that implements the @code{VPATH} feature.}@*
34841 Use this option to make configurations in directories separate from the
34842 @value{GDBN} source directories. Among other things, you can use this to
34843 build (or maintain) several configurations simultaneously, in separate
34844 directories. @file{configure} writes configuration-specific files in
34845 the current directory, but arranges for them to use the source in the
34846 directory @var{dirname}. @file{configure} creates directories under
34847 the working directory in parallel to the source directories below
34850 @item --norecursion
34851 Configure only the directory level where @file{configure} is executed; do not
34852 propagate configuration to subdirectories.
34854 @item --target=@var{target}
34855 Configure @value{GDBN} for cross-debugging programs running on the specified
34856 @var{target}. Without this option, @value{GDBN} is configured to debug
34857 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
34859 There is no convenient way to generate a list of all available targets.
34861 @item @var{host} @dots{}
34862 Configure @value{GDBN} to run on the specified @var{host}.
34864 There is no convenient way to generate a list of all available hosts.
34867 There are many other options available as well, but they are generally
34868 needed for special purposes only.
34870 @node System-wide configuration
34871 @section System-wide configuration and settings
34872 @cindex system-wide init file
34874 @value{GDBN} can be configured to have a system-wide init file;
34875 this file will be read and executed at startup (@pxref{Startup, , What
34876 @value{GDBN} does during startup}).
34878 Here is the corresponding configure option:
34881 @item --with-system-gdbinit=@var{file}
34882 Specify that the default location of the system-wide init file is
34886 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
34887 it may be subject to relocation. Two possible cases:
34891 If the default location of this init file contains @file{$prefix},
34892 it will be subject to relocation. Suppose that the configure options
34893 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
34894 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
34895 init file is looked for as @file{$install/etc/gdbinit} instead of
34896 @file{$prefix/etc/gdbinit}.
34899 By contrast, if the default location does not contain the prefix,
34900 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
34901 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
34902 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
34903 wherever @value{GDBN} is installed.
34906 If the configured location of the system-wide init file (as given by the
34907 @option{--with-system-gdbinit} option at configure time) is in the
34908 data-directory (as specified by @option{--with-gdb-datadir} at configure
34909 time) or in one of its subdirectories, then @value{GDBN} will look for the
34910 system-wide init file in the directory specified by the
34911 @option{--data-directory} command-line option.
34912 Note that the system-wide init file is only read once, during @value{GDBN}
34913 initialization. If the data-directory is changed after @value{GDBN} has
34914 started with the @code{set data-directory} command, the file will not be
34917 @node Maintenance Commands
34918 @appendix Maintenance Commands
34919 @cindex maintenance commands
34920 @cindex internal commands
34922 In addition to commands intended for @value{GDBN} users, @value{GDBN}
34923 includes a number of commands intended for @value{GDBN} developers,
34924 that are not documented elsewhere in this manual. These commands are
34925 provided here for reference. (For commands that turn on debugging
34926 messages, see @ref{Debugging Output}.)
34929 @kindex maint agent
34930 @kindex maint agent-eval
34931 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34932 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34933 Translate the given @var{expression} into remote agent bytecodes.
34934 This command is useful for debugging the Agent Expression mechanism
34935 (@pxref{Agent Expressions}). The @samp{agent} version produces an
34936 expression useful for data collection, such as by tracepoints, while
34937 @samp{maint agent-eval} produces an expression that evaluates directly
34938 to a result. For instance, a collection expression for @code{globa +
34939 globb} will include bytecodes to record four bytes of memory at each
34940 of the addresses of @code{globa} and @code{globb}, while discarding
34941 the result of the addition, while an evaluation expression will do the
34942 addition and return the sum.
34943 If @code{-at} is given, generate remote agent bytecode for @var{location}.
34944 If not, generate remote agent bytecode for current frame PC address.
34946 @kindex maint agent-printf
34947 @item maint agent-printf @var{format},@var{expr},...
34948 Translate the given format string and list of argument expressions
34949 into remote agent bytecodes and display them as a disassembled list.
34950 This command is useful for debugging the agent version of dynamic
34951 printf (@pxref{Dynamic Printf}.
34953 @kindex maint info breakpoints
34954 @item @anchor{maint info breakpoints}maint info breakpoints
34955 Using the same format as @samp{info breakpoints}, display both the
34956 breakpoints you've set explicitly, and those @value{GDBN} is using for
34957 internal purposes. Internal breakpoints are shown with negative
34958 breakpoint numbers. The type column identifies what kind of breakpoint
34963 Normal, explicitly set breakpoint.
34966 Normal, explicitly set watchpoint.
34969 Internal breakpoint, used to handle correctly stepping through
34970 @code{longjmp} calls.
34972 @item longjmp resume
34973 Internal breakpoint at the target of a @code{longjmp}.
34976 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
34979 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
34982 Shared library events.
34986 @kindex maint info bfds
34987 @item maint info bfds
34988 This prints information about each @code{bfd} object that is known to
34989 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
34991 @kindex set displaced-stepping
34992 @kindex show displaced-stepping
34993 @cindex displaced stepping support
34994 @cindex out-of-line single-stepping
34995 @item set displaced-stepping
34996 @itemx show displaced-stepping
34997 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
34998 if the target supports it. Displaced stepping is a way to single-step
34999 over breakpoints without removing them from the inferior, by executing
35000 an out-of-line copy of the instruction that was originally at the
35001 breakpoint location. It is also known as out-of-line single-stepping.
35004 @item set displaced-stepping on
35005 If the target architecture supports it, @value{GDBN} will use
35006 displaced stepping to step over breakpoints.
35008 @item set displaced-stepping off
35009 @value{GDBN} will not use displaced stepping to step over breakpoints,
35010 even if such is supported by the target architecture.
35012 @cindex non-stop mode, and @samp{set displaced-stepping}
35013 @item set displaced-stepping auto
35014 This is the default mode. @value{GDBN} will use displaced stepping
35015 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
35016 architecture supports displaced stepping.
35019 @kindex maint check-symtabs
35020 @item maint check-symtabs
35021 Check the consistency of psymtabs and symtabs.
35023 @kindex maint cplus first_component
35024 @item maint cplus first_component @var{name}
35025 Print the first C@t{++} class/namespace component of @var{name}.
35027 @kindex maint cplus namespace
35028 @item maint cplus namespace
35029 Print the list of possible C@t{++} namespaces.
35031 @kindex maint demangle
35032 @item maint demangle @var{name}
35033 Demangle a C@t{++} or Objective-C mangled @var{name}.
35035 @kindex maint deprecate
35036 @kindex maint undeprecate
35037 @cindex deprecated commands
35038 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35039 @itemx maint undeprecate @var{command}
35040 Deprecate or undeprecate the named @var{command}. Deprecated commands
35041 cause @value{GDBN} to issue a warning when you use them. The optional
35042 argument @var{replacement} says which newer command should be used in
35043 favor of the deprecated one; if it is given, @value{GDBN} will mention
35044 the replacement as part of the warning.
35046 @kindex maint dump-me
35047 @item maint dump-me
35048 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35049 Cause a fatal signal in the debugger and force it to dump its core.
35050 This is supported only on systems which support aborting a program
35051 with the @code{SIGQUIT} signal.
35053 @kindex maint internal-error
35054 @kindex maint internal-warning
35055 @item maint internal-error @r{[}@var{message-text}@r{]}
35056 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35057 Cause @value{GDBN} to call the internal function @code{internal_error}
35058 or @code{internal_warning} and hence behave as though an internal error
35059 or internal warning has been detected. In addition to reporting the
35060 internal problem, these functions give the user the opportunity to
35061 either quit @value{GDBN} or create a core file of the current
35062 @value{GDBN} session.
35064 These commands take an optional parameter @var{message-text} that is
35065 used as the text of the error or warning message.
35067 Here's an example of using @code{internal-error}:
35070 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35071 @dots{}/maint.c:121: internal-error: testing, 1, 2
35072 A problem internal to GDB has been detected. Further
35073 debugging may prove unreliable.
35074 Quit this debugging session? (y or n) @kbd{n}
35075 Create a core file? (y or n) @kbd{n}
35079 @cindex @value{GDBN} internal error
35080 @cindex internal errors, control of @value{GDBN} behavior
35082 @kindex maint set internal-error
35083 @kindex maint show internal-error
35084 @kindex maint set internal-warning
35085 @kindex maint show internal-warning
35086 @item maint set internal-error @var{action} [ask|yes|no]
35087 @itemx maint show internal-error @var{action}
35088 @itemx maint set internal-warning @var{action} [ask|yes|no]
35089 @itemx maint show internal-warning @var{action}
35090 When @value{GDBN} reports an internal problem (error or warning) it
35091 gives the user the opportunity to both quit @value{GDBN} and create a
35092 core file of the current @value{GDBN} session. These commands let you
35093 override the default behaviour for each particular @var{action},
35094 described in the table below.
35098 You can specify that @value{GDBN} should always (yes) or never (no)
35099 quit. The default is to ask the user what to do.
35102 You can specify that @value{GDBN} should always (yes) or never (no)
35103 create a core file. The default is to ask the user what to do.
35106 @kindex maint packet
35107 @item maint packet @var{text}
35108 If @value{GDBN} is talking to an inferior via the serial protocol,
35109 then this command sends the string @var{text} to the inferior, and
35110 displays the response packet. @value{GDBN} supplies the initial
35111 @samp{$} character, the terminating @samp{#} character, and the
35114 @kindex maint print architecture
35115 @item maint print architecture @r{[}@var{file}@r{]}
35116 Print the entire architecture configuration. The optional argument
35117 @var{file} names the file where the output goes.
35119 @kindex maint print c-tdesc
35120 @item maint print c-tdesc
35121 Print the current target description (@pxref{Target Descriptions}) as
35122 a C source file. The created source file can be used in @value{GDBN}
35123 when an XML parser is not available to parse the description.
35125 @kindex maint print dummy-frames
35126 @item maint print dummy-frames
35127 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35130 (@value{GDBP}) @kbd{b add}
35132 (@value{GDBP}) @kbd{print add(2,3)}
35133 Breakpoint 2, add (a=2, b=3) at @dots{}
35135 The program being debugged stopped while in a function called from GDB.
35137 (@value{GDBP}) @kbd{maint print dummy-frames}
35138 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
35139 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
35140 call_lo=0x01014000 call_hi=0x01014001
35144 Takes an optional file parameter.
35146 @kindex maint print registers
35147 @kindex maint print raw-registers
35148 @kindex maint print cooked-registers
35149 @kindex maint print register-groups
35150 @kindex maint print remote-registers
35151 @item maint print registers @r{[}@var{file}@r{]}
35152 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35153 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35154 @itemx maint print register-groups @r{[}@var{file}@r{]}
35155 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35156 Print @value{GDBN}'s internal register data structures.
35158 The command @code{maint print raw-registers} includes the contents of
35159 the raw register cache; the command @code{maint print
35160 cooked-registers} includes the (cooked) value of all registers,
35161 including registers which aren't available on the target nor visible
35162 to user; the command @code{maint print register-groups} includes the
35163 groups that each register is a member of; and the command @code{maint
35164 print remote-registers} includes the remote target's register numbers
35165 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
35166 @value{GDBN} Internals}.
35168 These commands take an optional parameter, a file name to which to
35169 write the information.
35171 @kindex maint print reggroups
35172 @item maint print reggroups @r{[}@var{file}@r{]}
35173 Print @value{GDBN}'s internal register group data structures. The
35174 optional argument @var{file} tells to what file to write the
35177 The register groups info looks like this:
35180 (@value{GDBP}) @kbd{maint print reggroups}
35193 This command forces @value{GDBN} to flush its internal register cache.
35195 @kindex maint print objfiles
35196 @cindex info for known object files
35197 @item maint print objfiles
35198 Print a dump of all known object files. For each object file, this
35199 command prints its name, address in memory, and all of its psymtabs
35202 @kindex maint print section-scripts
35203 @cindex info for known .debug_gdb_scripts-loaded scripts
35204 @item maint print section-scripts [@var{regexp}]
35205 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35206 If @var{regexp} is specified, only print scripts loaded by object files
35207 matching @var{regexp}.
35208 For each script, this command prints its name as specified in the objfile,
35209 and the full path if known.
35210 @xref{dotdebug_gdb_scripts section}.
35212 @kindex maint print statistics
35213 @cindex bcache statistics
35214 @item maint print statistics
35215 This command prints, for each object file in the program, various data
35216 about that object file followed by the byte cache (@dfn{bcache})
35217 statistics for the object file. The objfile data includes the number
35218 of minimal, partial, full, and stabs symbols, the number of types
35219 defined by the objfile, the number of as yet unexpanded psym tables,
35220 the number of line tables and string tables, and the amount of memory
35221 used by the various tables. The bcache statistics include the counts,
35222 sizes, and counts of duplicates of all and unique objects, max,
35223 average, and median entry size, total memory used and its overhead and
35224 savings, and various measures of the hash table size and chain
35227 @kindex maint print target-stack
35228 @cindex target stack description
35229 @item maint print target-stack
35230 A @dfn{target} is an interface between the debugger and a particular
35231 kind of file or process. Targets can be stacked in @dfn{strata},
35232 so that more than one target can potentially respond to a request.
35233 In particular, memory accesses will walk down the stack of targets
35234 until they find a target that is interested in handling that particular
35237 This command prints a short description of each layer that was pushed on
35238 the @dfn{target stack}, starting from the top layer down to the bottom one.
35240 @kindex maint print type
35241 @cindex type chain of a data type
35242 @item maint print type @var{expr}
35243 Print the type chain for a type specified by @var{expr}. The argument
35244 can be either a type name or a symbol. If it is a symbol, the type of
35245 that symbol is described. The type chain produced by this command is
35246 a recursive definition of the data type as stored in @value{GDBN}'s
35247 data structures, including its flags and contained types.
35249 @kindex maint set dwarf2 always-disassemble
35250 @kindex maint show dwarf2 always-disassemble
35251 @item maint set dwarf2 always-disassemble
35252 @item maint show dwarf2 always-disassemble
35253 Control the behavior of @code{info address} when using DWARF debugging
35256 The default is @code{off}, which means that @value{GDBN} should try to
35257 describe a variable's location in an easily readable format. When
35258 @code{on}, @value{GDBN} will instead display the DWARF location
35259 expression in an assembly-like format. Note that some locations are
35260 too complex for @value{GDBN} to describe simply; in this case you will
35261 always see the disassembly form.
35263 Here is an example of the resulting disassembly:
35266 (gdb) info addr argc
35267 Symbol "argc" is a complex DWARF expression:
35271 For more information on these expressions, see
35272 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35274 @kindex maint set dwarf2 max-cache-age
35275 @kindex maint show dwarf2 max-cache-age
35276 @item maint set dwarf2 max-cache-age
35277 @itemx maint show dwarf2 max-cache-age
35278 Control the DWARF 2 compilation unit cache.
35280 @cindex DWARF 2 compilation units cache
35281 In object files with inter-compilation-unit references, such as those
35282 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
35283 reader needs to frequently refer to previously read compilation units.
35284 This setting controls how long a compilation unit will remain in the
35285 cache if it is not referenced. A higher limit means that cached
35286 compilation units will be stored in memory longer, and more total
35287 memory will be used. Setting it to zero disables caching, which will
35288 slow down @value{GDBN} startup, but reduce memory consumption.
35290 @kindex maint set profile
35291 @kindex maint show profile
35292 @cindex profiling GDB
35293 @item maint set profile
35294 @itemx maint show profile
35295 Control profiling of @value{GDBN}.
35297 Profiling will be disabled until you use the @samp{maint set profile}
35298 command to enable it. When you enable profiling, the system will begin
35299 collecting timing and execution count data; when you disable profiling or
35300 exit @value{GDBN}, the results will be written to a log file. Remember that
35301 if you use profiling, @value{GDBN} will overwrite the profiling log file
35302 (often called @file{gmon.out}). If you have a record of important profiling
35303 data in a @file{gmon.out} file, be sure to move it to a safe location.
35305 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35306 compiled with the @samp{-pg} compiler option.
35308 @kindex maint set show-debug-regs
35309 @kindex maint show show-debug-regs
35310 @cindex hardware debug registers
35311 @item maint set show-debug-regs
35312 @itemx maint show show-debug-regs
35313 Control whether to show variables that mirror the hardware debug
35314 registers. Use @code{ON} to enable, @code{OFF} to disable. If
35315 enabled, the debug registers values are shown when @value{GDBN} inserts or
35316 removes a hardware breakpoint or watchpoint, and when the inferior
35317 triggers a hardware-assisted breakpoint or watchpoint.
35319 @kindex maint set show-all-tib
35320 @kindex maint show show-all-tib
35321 @item maint set show-all-tib
35322 @itemx maint show show-all-tib
35323 Control whether to show all non zero areas within a 1k block starting
35324 at thread local base, when using the @samp{info w32 thread-information-block}
35327 @kindex maint space
35328 @cindex memory used by commands
35330 Control whether to display memory usage for each command. If set to a
35331 nonzero value, @value{GDBN} will display how much memory each command
35332 took, following the command's own output. This can also be requested
35333 by invoking @value{GDBN} with the @option{--statistics} command-line
35334 switch (@pxref{Mode Options}).
35337 @cindex time of command execution
35339 Control whether to display the execution time of @value{GDBN} for each command.
35340 If set to a nonzero value, @value{GDBN} will display how much time it
35341 took to execute each command, following the command's own output.
35342 Both CPU time and wallclock time are printed.
35343 Printing both is useful when trying to determine whether the cost is
35344 CPU or, e.g., disk/network, latency.
35345 Note that the CPU time printed is for @value{GDBN} only, it does not include
35346 the execution time of the inferior because there's no mechanism currently
35347 to compute how much time was spent by @value{GDBN} and how much time was
35348 spent by the program been debugged.
35349 This can also be requested by invoking @value{GDBN} with the
35350 @option{--statistics} command-line switch (@pxref{Mode Options}).
35352 @kindex maint translate-address
35353 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35354 Find the symbol stored at the location specified by the address
35355 @var{addr} and an optional section name @var{section}. If found,
35356 @value{GDBN} prints the name of the closest symbol and an offset from
35357 the symbol's location to the specified address. This is similar to
35358 the @code{info address} command (@pxref{Symbols}), except that this
35359 command also allows to find symbols in other sections.
35361 If section was not specified, the section in which the symbol was found
35362 is also printed. For dynamically linked executables, the name of
35363 executable or shared library containing the symbol is printed as well.
35367 The following command is useful for non-interactive invocations of
35368 @value{GDBN}, such as in the test suite.
35371 @item set watchdog @var{nsec}
35372 @kindex set watchdog
35373 @cindex watchdog timer
35374 @cindex timeout for commands
35375 Set the maximum number of seconds @value{GDBN} will wait for the
35376 target operation to finish. If this time expires, @value{GDBN}
35377 reports and error and the command is aborted.
35379 @item show watchdog
35380 Show the current setting of the target wait timeout.
35383 @node Remote Protocol
35384 @appendix @value{GDBN} Remote Serial Protocol
35389 * Stop Reply Packets::
35390 * General Query Packets::
35391 * Architecture-Specific Protocol Details::
35392 * Tracepoint Packets::
35393 * Host I/O Packets::
35395 * Notification Packets::
35396 * Remote Non-Stop::
35397 * Packet Acknowledgment::
35399 * File-I/O Remote Protocol Extension::
35400 * Library List Format::
35401 * Library List Format for SVR4 Targets::
35402 * Memory Map Format::
35403 * Thread List Format::
35404 * Traceframe Info Format::
35410 There may be occasions when you need to know something about the
35411 protocol---for example, if there is only one serial port to your target
35412 machine, you might want your program to do something special if it
35413 recognizes a packet meant for @value{GDBN}.
35415 In the examples below, @samp{->} and @samp{<-} are used to indicate
35416 transmitted and received data, respectively.
35418 @cindex protocol, @value{GDBN} remote serial
35419 @cindex serial protocol, @value{GDBN} remote
35420 @cindex remote serial protocol
35421 All @value{GDBN} commands and responses (other than acknowledgments
35422 and notifications, see @ref{Notification Packets}) are sent as a
35423 @var{packet}. A @var{packet} is introduced with the character
35424 @samp{$}, the actual @var{packet-data}, and the terminating character
35425 @samp{#} followed by a two-digit @var{checksum}:
35428 @code{$}@var{packet-data}@code{#}@var{checksum}
35432 @cindex checksum, for @value{GDBN} remote
35434 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35435 characters between the leading @samp{$} and the trailing @samp{#} (an
35436 eight bit unsigned checksum).
35438 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35439 specification also included an optional two-digit @var{sequence-id}:
35442 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35445 @cindex sequence-id, for @value{GDBN} remote
35447 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35448 has never output @var{sequence-id}s. Stubs that handle packets added
35449 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35451 When either the host or the target machine receives a packet, the first
35452 response expected is an acknowledgment: either @samp{+} (to indicate
35453 the package was received correctly) or @samp{-} (to request
35457 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35462 The @samp{+}/@samp{-} acknowledgments can be disabled
35463 once a connection is established.
35464 @xref{Packet Acknowledgment}, for details.
35466 The host (@value{GDBN}) sends @var{command}s, and the target (the
35467 debugging stub incorporated in your program) sends a @var{response}. In
35468 the case of step and continue @var{command}s, the response is only sent
35469 when the operation has completed, and the target has again stopped all
35470 threads in all attached processes. This is the default all-stop mode
35471 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35472 execution mode; see @ref{Remote Non-Stop}, for details.
35474 @var{packet-data} consists of a sequence of characters with the
35475 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35478 @cindex remote protocol, field separator
35479 Fields within the packet should be separated using @samp{,} @samp{;} or
35480 @samp{:}. Except where otherwise noted all numbers are represented in
35481 @sc{hex} with leading zeros suppressed.
35483 Implementors should note that prior to @value{GDBN} 5.0, the character
35484 @samp{:} could not appear as the third character in a packet (as it
35485 would potentially conflict with the @var{sequence-id}).
35487 @cindex remote protocol, binary data
35488 @anchor{Binary Data}
35489 Binary data in most packets is encoded either as two hexadecimal
35490 digits per byte of binary data. This allowed the traditional remote
35491 protocol to work over connections which were only seven-bit clean.
35492 Some packets designed more recently assume an eight-bit clean
35493 connection, and use a more efficient encoding to send and receive
35496 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35497 as an escape character. Any escaped byte is transmitted as the escape
35498 character followed by the original character XORed with @code{0x20}.
35499 For example, the byte @code{0x7d} would be transmitted as the two
35500 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35501 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35502 @samp{@}}) must always be escaped. Responses sent by the stub
35503 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35504 is not interpreted as the start of a run-length encoded sequence
35507 Response @var{data} can be run-length encoded to save space.
35508 Run-length encoding replaces runs of identical characters with one
35509 instance of the repeated character, followed by a @samp{*} and a
35510 repeat count. The repeat count is itself sent encoded, to avoid
35511 binary characters in @var{data}: a value of @var{n} is sent as
35512 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35513 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35514 code 32) for a repeat count of 3. (This is because run-length
35515 encoding starts to win for counts 3 or more.) Thus, for example,
35516 @samp{0* } is a run-length encoding of ``0000'': the space character
35517 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35520 The printable characters @samp{#} and @samp{$} or with a numeric value
35521 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35522 seven repeats (@samp{$}) can be expanded using a repeat count of only
35523 five (@samp{"}). For example, @samp{00000000} can be encoded as
35526 The error response returned for some packets includes a two character
35527 error number. That number is not well defined.
35529 @cindex empty response, for unsupported packets
35530 For any @var{command} not supported by the stub, an empty response
35531 (@samp{$#00}) should be returned. That way it is possible to extend the
35532 protocol. A newer @value{GDBN} can tell if a packet is supported based
35535 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35536 commands for register access, and the @samp{m} and @samp{M} commands
35537 for memory access. Stubs that only control single-threaded targets
35538 can implement run control with the @samp{c} (continue), and @samp{s}
35539 (step) commands. Stubs that support multi-threading targets should
35540 support the @samp{vCont} command. All other commands are optional.
35545 The following table provides a complete list of all currently defined
35546 @var{command}s and their corresponding response @var{data}.
35547 @xref{File-I/O Remote Protocol Extension}, for details about the File
35548 I/O extension of the remote protocol.
35550 Each packet's description has a template showing the packet's overall
35551 syntax, followed by an explanation of the packet's meaning. We
35552 include spaces in some of the templates for clarity; these are not
35553 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35554 separate its components. For example, a template like @samp{foo
35555 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35556 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35557 @var{baz}. @value{GDBN} does not transmit a space character between the
35558 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35561 @cindex @var{thread-id}, in remote protocol
35562 @anchor{thread-id syntax}
35563 Several packets and replies include a @var{thread-id} field to identify
35564 a thread. Normally these are positive numbers with a target-specific
35565 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35566 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35569 In addition, the remote protocol supports a multiprocess feature in
35570 which the @var{thread-id} syntax is extended to optionally include both
35571 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35572 The @var{pid} (process) and @var{tid} (thread) components each have the
35573 format described above: a positive number with target-specific
35574 interpretation formatted as a big-endian hex string, literal @samp{-1}
35575 to indicate all processes or threads (respectively), or @samp{0} to
35576 indicate an arbitrary process or thread. Specifying just a process, as
35577 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35578 error to specify all processes but a specific thread, such as
35579 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35580 for those packets and replies explicitly documented to include a process
35581 ID, rather than a @var{thread-id}.
35583 The multiprocess @var{thread-id} syntax extensions are only used if both
35584 @value{GDBN} and the stub report support for the @samp{multiprocess}
35585 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35588 Note that all packet forms beginning with an upper- or lower-case
35589 letter, other than those described here, are reserved for future use.
35591 Here are the packet descriptions.
35596 @cindex @samp{!} packet
35597 @anchor{extended mode}
35598 Enable extended mode. In extended mode, the remote server is made
35599 persistent. The @samp{R} packet is used to restart the program being
35605 The remote target both supports and has enabled extended mode.
35609 @cindex @samp{?} packet
35610 Indicate the reason the target halted. The reply is the same as for
35611 step and continue. This packet has a special interpretation when the
35612 target is in non-stop mode; see @ref{Remote Non-Stop}.
35615 @xref{Stop Reply Packets}, for the reply specifications.
35617 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
35618 @cindex @samp{A} packet
35619 Initialized @code{argv[]} array passed into program. @var{arglen}
35620 specifies the number of bytes in the hex encoded byte stream
35621 @var{arg}. See @code{gdbserver} for more details.
35626 The arguments were set.
35632 @cindex @samp{b} packet
35633 (Don't use this packet; its behavior is not well-defined.)
35634 Change the serial line speed to @var{baud}.
35636 JTC: @emph{When does the transport layer state change? When it's
35637 received, or after the ACK is transmitted. In either case, there are
35638 problems if the command or the acknowledgment packet is dropped.}
35640 Stan: @emph{If people really wanted to add something like this, and get
35641 it working for the first time, they ought to modify ser-unix.c to send
35642 some kind of out-of-band message to a specially-setup stub and have the
35643 switch happen "in between" packets, so that from remote protocol's point
35644 of view, nothing actually happened.}
35646 @item B @var{addr},@var{mode}
35647 @cindex @samp{B} packet
35648 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35649 breakpoint at @var{addr}.
35651 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35652 (@pxref{insert breakpoint or watchpoint packet}).
35654 @cindex @samp{bc} packet
35657 Backward continue. Execute the target system in reverse. No parameter.
35658 @xref{Reverse Execution}, for more information.
35661 @xref{Stop Reply Packets}, for the reply specifications.
35663 @cindex @samp{bs} packet
35666 Backward single step. Execute one instruction in reverse. No parameter.
35667 @xref{Reverse Execution}, for more information.
35670 @xref{Stop Reply Packets}, for the reply specifications.
35672 @item c @r{[}@var{addr}@r{]}
35673 @cindex @samp{c} packet
35674 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
35675 resume at current address.
35677 This packet is deprecated for multi-threading support. @xref{vCont
35681 @xref{Stop Reply Packets}, for the reply specifications.
35683 @item C @var{sig}@r{[};@var{addr}@r{]}
35684 @cindex @samp{C} packet
35685 Continue with signal @var{sig} (hex signal number). If
35686 @samp{;@var{addr}} is omitted, resume at same address.
35688 This packet is deprecated for multi-threading support. @xref{vCont
35692 @xref{Stop Reply Packets}, for the reply specifications.
35695 @cindex @samp{d} packet
35698 Don't use this packet; instead, define a general set packet
35699 (@pxref{General Query Packets}).
35703 @cindex @samp{D} packet
35704 The first form of the packet is used to detach @value{GDBN} from the
35705 remote system. It is sent to the remote target
35706 before @value{GDBN} disconnects via the @code{detach} command.
35708 The second form, including a process ID, is used when multiprocess
35709 protocol extensions are enabled (@pxref{multiprocess extensions}), to
35710 detach only a specific process. The @var{pid} is specified as a
35711 big-endian hex string.
35721 @item F @var{RC},@var{EE},@var{CF};@var{XX}
35722 @cindex @samp{F} packet
35723 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
35724 This is part of the File-I/O protocol extension. @xref{File-I/O
35725 Remote Protocol Extension}, for the specification.
35728 @anchor{read registers packet}
35729 @cindex @samp{g} packet
35730 Read general registers.
35734 @item @var{XX@dots{}}
35735 Each byte of register data is described by two hex digits. The bytes
35736 with the register are transmitted in target byte order. The size of
35737 each register and their position within the @samp{g} packet are
35738 determined by the @value{GDBN} internal gdbarch functions
35739 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
35740 specification of several standard @samp{g} packets is specified below.
35742 When reading registers from a trace frame (@pxref{Analyze Collected
35743 Data,,Using the Collected Data}), the stub may also return a string of
35744 literal @samp{x}'s in place of the register data digits, to indicate
35745 that the corresponding register has not been collected, thus its value
35746 is unavailable. For example, for an architecture with 4 registers of
35747 4 bytes each, the following reply indicates to @value{GDBN} that
35748 registers 0 and 2 have not been collected, while registers 1 and 3
35749 have been collected, and both have zero value:
35753 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
35760 @item G @var{XX@dots{}}
35761 @cindex @samp{G} packet
35762 Write general registers. @xref{read registers packet}, for a
35763 description of the @var{XX@dots{}} data.
35773 @item H @var{op} @var{thread-id}
35774 @cindex @samp{H} packet
35775 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
35776 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
35777 it should be @samp{c} for step and continue operations (note that this
35778 is deprecated, supporting the @samp{vCont} command is a better
35779 option), @samp{g} for other operations. The thread designator
35780 @var{thread-id} has the format and interpretation described in
35781 @ref{thread-id syntax}.
35792 @c 'H': How restrictive (or permissive) is the thread model. If a
35793 @c thread is selected and stopped, are other threads allowed
35794 @c to continue to execute? As I mentioned above, I think the
35795 @c semantics of each command when a thread is selected must be
35796 @c described. For example:
35798 @c 'g': If the stub supports threads and a specific thread is
35799 @c selected, returns the register block from that thread;
35800 @c otherwise returns current registers.
35802 @c 'G' If the stub supports threads and a specific thread is
35803 @c selected, sets the registers of the register block of
35804 @c that thread; otherwise sets current registers.
35806 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
35807 @anchor{cycle step packet}
35808 @cindex @samp{i} packet
35809 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
35810 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
35811 step starting at that address.
35814 @cindex @samp{I} packet
35815 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
35819 @cindex @samp{k} packet
35822 FIXME: @emph{There is no description of how to operate when a specific
35823 thread context has been selected (i.e.@: does 'k' kill only that
35826 @item m @var{addr},@var{length}
35827 @cindex @samp{m} packet
35828 Read @var{length} bytes of memory starting at address @var{addr}.
35829 Note that @var{addr} may not be aligned to any particular boundary.
35831 The stub need not use any particular size or alignment when gathering
35832 data from memory for the response; even if @var{addr} is word-aligned
35833 and @var{length} is a multiple of the word size, the stub is free to
35834 use byte accesses, or not. For this reason, this packet may not be
35835 suitable for accessing memory-mapped I/O devices.
35836 @cindex alignment of remote memory accesses
35837 @cindex size of remote memory accesses
35838 @cindex memory, alignment and size of remote accesses
35842 @item @var{XX@dots{}}
35843 Memory contents; each byte is transmitted as a two-digit hexadecimal
35844 number. The reply may contain fewer bytes than requested if the
35845 server was able to read only part of the region of memory.
35850 @item M @var{addr},@var{length}:@var{XX@dots{}}
35851 @cindex @samp{M} packet
35852 Write @var{length} bytes of memory starting at address @var{addr}.
35853 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
35854 hexadecimal number.
35861 for an error (this includes the case where only part of the data was
35866 @cindex @samp{p} packet
35867 Read the value of register @var{n}; @var{n} is in hex.
35868 @xref{read registers packet}, for a description of how the returned
35869 register value is encoded.
35873 @item @var{XX@dots{}}
35874 the register's value
35878 Indicating an unrecognized @var{query}.
35881 @item P @var{n@dots{}}=@var{r@dots{}}
35882 @anchor{write register packet}
35883 @cindex @samp{P} packet
35884 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
35885 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
35886 digits for each byte in the register (target byte order).
35896 @item q @var{name} @var{params}@dots{}
35897 @itemx Q @var{name} @var{params}@dots{}
35898 @cindex @samp{q} packet
35899 @cindex @samp{Q} packet
35900 General query (@samp{q}) and set (@samp{Q}). These packets are
35901 described fully in @ref{General Query Packets}.
35904 @cindex @samp{r} packet
35905 Reset the entire system.
35907 Don't use this packet; use the @samp{R} packet instead.
35910 @cindex @samp{R} packet
35911 Restart the program being debugged. @var{XX}, while needed, is ignored.
35912 This packet is only available in extended mode (@pxref{extended mode}).
35914 The @samp{R} packet has no reply.
35916 @item s @r{[}@var{addr}@r{]}
35917 @cindex @samp{s} packet
35918 Single step. @var{addr} is the address at which to resume. If
35919 @var{addr} is omitted, resume at same address.
35921 This packet is deprecated for multi-threading support. @xref{vCont
35925 @xref{Stop Reply Packets}, for the reply specifications.
35927 @item S @var{sig}@r{[};@var{addr}@r{]}
35928 @anchor{step with signal packet}
35929 @cindex @samp{S} packet
35930 Step with signal. This is analogous to the @samp{C} packet, but
35931 requests a single-step, rather than a normal resumption of execution.
35933 This packet is deprecated for multi-threading support. @xref{vCont
35937 @xref{Stop Reply Packets}, for the reply specifications.
35939 @item t @var{addr}:@var{PP},@var{MM}
35940 @cindex @samp{t} packet
35941 Search backwards starting at address @var{addr} for a match with pattern
35942 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
35943 @var{addr} must be at least 3 digits.
35945 @item T @var{thread-id}
35946 @cindex @samp{T} packet
35947 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
35952 thread is still alive
35958 Packets starting with @samp{v} are identified by a multi-letter name,
35959 up to the first @samp{;} or @samp{?} (or the end of the packet).
35961 @item vAttach;@var{pid}
35962 @cindex @samp{vAttach} packet
35963 Attach to a new process with the specified process ID @var{pid}.
35964 The process ID is a
35965 hexadecimal integer identifying the process. In all-stop mode, all
35966 threads in the attached process are stopped; in non-stop mode, it may be
35967 attached without being stopped if that is supported by the target.
35969 @c In non-stop mode, on a successful vAttach, the stub should set the
35970 @c current thread to a thread of the newly-attached process. After
35971 @c attaching, GDB queries for the attached process's thread ID with qC.
35972 @c Also note that, from a user perspective, whether or not the
35973 @c target is stopped on attach in non-stop mode depends on whether you
35974 @c use the foreground or background version of the attach command, not
35975 @c on what vAttach does; GDB does the right thing with respect to either
35976 @c stopping or restarting threads.
35978 This packet is only available in extended mode (@pxref{extended mode}).
35984 @item @r{Any stop packet}
35985 for success in all-stop mode (@pxref{Stop Reply Packets})
35987 for success in non-stop mode (@pxref{Remote Non-Stop})
35990 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35991 @cindex @samp{vCont} packet
35992 @anchor{vCont packet}
35993 Resume the inferior, specifying different actions for each thread.
35994 If an action is specified with no @var{thread-id}, then it is applied to any
35995 threads that don't have a specific action specified; if no default action is
35996 specified then other threads should remain stopped in all-stop mode and
35997 in their current state in non-stop mode.
35998 Specifying multiple
35999 default actions is an error; specifying no actions is also an error.
36000 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
36002 Currently supported actions are:
36008 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36012 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36017 The optional argument @var{addr} normally associated with the
36018 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36019 not supported in @samp{vCont}.
36021 The @samp{t} action is only relevant in non-stop mode
36022 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36023 A stop reply should be generated for any affected thread not already stopped.
36024 When a thread is stopped by means of a @samp{t} action,
36025 the corresponding stop reply should indicate that the thread has stopped with
36026 signal @samp{0}, regardless of whether the target uses some other signal
36027 as an implementation detail.
36029 The stub must support @samp{vCont} if it reports support for
36030 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
36031 this case @samp{vCont} actions can be specified to apply to all threads
36032 in a process by using the @samp{p@var{pid}.-1} form of the
36036 @xref{Stop Reply Packets}, for the reply specifications.
36039 @cindex @samp{vCont?} packet
36040 Request a list of actions supported by the @samp{vCont} packet.
36044 @item vCont@r{[};@var{action}@dots{}@r{]}
36045 The @samp{vCont} packet is supported. Each @var{action} is a supported
36046 command in the @samp{vCont} packet.
36048 The @samp{vCont} packet is not supported.
36051 @item vFile:@var{operation}:@var{parameter}@dots{}
36052 @cindex @samp{vFile} packet
36053 Perform a file operation on the target system. For details,
36054 see @ref{Host I/O Packets}.
36056 @item vFlashErase:@var{addr},@var{length}
36057 @cindex @samp{vFlashErase} packet
36058 Direct the stub to erase @var{length} bytes of flash starting at
36059 @var{addr}. The region may enclose any number of flash blocks, but
36060 its start and end must fall on block boundaries, as indicated by the
36061 flash block size appearing in the memory map (@pxref{Memory Map
36062 Format}). @value{GDBN} groups flash memory programming operations
36063 together, and sends a @samp{vFlashDone} request after each group; the
36064 stub is allowed to delay erase operation until the @samp{vFlashDone}
36065 packet is received.
36075 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36076 @cindex @samp{vFlashWrite} packet
36077 Direct the stub to write data to flash address @var{addr}. The data
36078 is passed in binary form using the same encoding as for the @samp{X}
36079 packet (@pxref{Binary Data}). The memory ranges specified by
36080 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36081 not overlap, and must appear in order of increasing addresses
36082 (although @samp{vFlashErase} packets for higher addresses may already
36083 have been received; the ordering is guaranteed only between
36084 @samp{vFlashWrite} packets). If a packet writes to an address that was
36085 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36086 target-specific method, the results are unpredictable.
36094 for vFlashWrite addressing non-flash memory
36100 @cindex @samp{vFlashDone} packet
36101 Indicate to the stub that flash programming operation is finished.
36102 The stub is permitted to delay or batch the effects of a group of
36103 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36104 @samp{vFlashDone} packet is received. The contents of the affected
36105 regions of flash memory are unpredictable until the @samp{vFlashDone}
36106 request is completed.
36108 @item vKill;@var{pid}
36109 @cindex @samp{vKill} packet
36110 Kill the process with the specified process ID. @var{pid} is a
36111 hexadecimal integer identifying the process. This packet is used in
36112 preference to @samp{k} when multiprocess protocol extensions are
36113 supported; see @ref{multiprocess extensions}.
36123 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36124 @cindex @samp{vRun} packet
36125 Run the program @var{filename}, passing it each @var{argument} on its
36126 command line. The file and arguments are hex-encoded strings. If
36127 @var{filename} is an empty string, the stub may use a default program
36128 (e.g.@: the last program run). The program is created in the stopped
36131 @c FIXME: What about non-stop mode?
36133 This packet is only available in extended mode (@pxref{extended mode}).
36139 @item @r{Any stop packet}
36140 for success (@pxref{Stop Reply Packets})
36144 @anchor{vStopped packet}
36145 @cindex @samp{vStopped} packet
36147 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
36148 reply and prompt for the stub to report another one.
36152 @item @r{Any stop packet}
36153 if there is another unreported stop event (@pxref{Stop Reply Packets})
36155 if there are no unreported stop events
36158 @item X @var{addr},@var{length}:@var{XX@dots{}}
36160 @cindex @samp{X} packet
36161 Write data to memory, where the data is transmitted in binary.
36162 @var{addr} is address, @var{length} is number of bytes,
36163 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36173 @item z @var{type},@var{addr},@var{kind}
36174 @itemx Z @var{type},@var{addr},@var{kind}
36175 @anchor{insert breakpoint or watchpoint packet}
36176 @cindex @samp{z} packet
36177 @cindex @samp{Z} packets
36178 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36179 watchpoint starting at address @var{address} of kind @var{kind}.
36181 Each breakpoint and watchpoint packet @var{type} is documented
36184 @emph{Implementation notes: A remote target shall return an empty string
36185 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36186 remote target shall support either both or neither of a given
36187 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36188 avoid potential problems with duplicate packets, the operations should
36189 be implemented in an idempotent way.}
36191 @item z0,@var{addr},@var{kind}
36192 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36193 @cindex @samp{z0} packet
36194 @cindex @samp{Z0} packet
36195 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
36196 @var{addr} of type @var{kind}.
36198 A memory breakpoint is implemented by replacing the instruction at
36199 @var{addr} with a software breakpoint or trap instruction. The
36200 @var{kind} is target-specific and typically indicates the size of
36201 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
36202 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36203 architectures have additional meanings for @var{kind};
36204 @var{cond_list} is an optional list of conditional expressions in bytecode
36205 form that should be evaluated on the target's side. These are the
36206 conditions that should be taken into consideration when deciding if
36207 the breakpoint trigger should be reported back to @var{GDBN}.
36209 The @var{cond_list} parameter is comprised of a series of expressions,
36210 concatenated without separators. Each expression has the following form:
36214 @item X @var{len},@var{expr}
36215 @var{len} is the length of the bytecode expression and @var{expr} is the
36216 actual conditional expression in bytecode form.
36220 The optional @var{cmd_list} parameter introduces commands that may be
36221 run on the target, rather than being reported back to @value{GDBN}.
36222 The parameter starts with a numeric flag @var{persist}; if the flag is
36223 nonzero, then the breakpoint may remain active and the commands
36224 continue to be run even when @value{GDBN} disconnects from the target.
36225 Following this flag is a series of expressions concatenated with no
36226 separators. Each expression has the following form:
36230 @item X @var{len},@var{expr}
36231 @var{len} is the length of the bytecode expression and @var{expr} is the
36232 actual conditional expression in bytecode form.
36236 see @ref{Architecture-Specific Protocol Details}.
36238 @emph{Implementation note: It is possible for a target to copy or move
36239 code that contains memory breakpoints (e.g., when implementing
36240 overlays). The behavior of this packet, in the presence of such a
36241 target, is not defined.}
36253 @item z1,@var{addr},@var{kind}
36254 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
36255 @cindex @samp{z1} packet
36256 @cindex @samp{Z1} packet
36257 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36258 address @var{addr}.
36260 A hardware breakpoint is implemented using a mechanism that is not
36261 dependant on being able to modify the target's memory. @var{kind}
36262 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
36264 @emph{Implementation note: A hardware breakpoint is not affected by code
36277 @item z2,@var{addr},@var{kind}
36278 @itemx Z2,@var{addr},@var{kind}
36279 @cindex @samp{z2} packet
36280 @cindex @samp{Z2} packet
36281 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36282 @var{kind} is interpreted as the number of bytes to watch.
36294 @item z3,@var{addr},@var{kind}
36295 @itemx Z3,@var{addr},@var{kind}
36296 @cindex @samp{z3} packet
36297 @cindex @samp{Z3} packet
36298 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36299 @var{kind} is interpreted as the number of bytes to watch.
36311 @item z4,@var{addr},@var{kind}
36312 @itemx Z4,@var{addr},@var{kind}
36313 @cindex @samp{z4} packet
36314 @cindex @samp{Z4} packet
36315 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36316 @var{kind} is interpreted as the number of bytes to watch.
36330 @node Stop Reply Packets
36331 @section Stop Reply Packets
36332 @cindex stop reply packets
36334 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36335 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36336 receive any of the below as a reply. Except for @samp{?}
36337 and @samp{vStopped}, that reply is only returned
36338 when the target halts. In the below the exact meaning of @dfn{signal
36339 number} is defined by the header @file{include/gdb/signals.h} in the
36340 @value{GDBN} source code.
36342 As in the description of request packets, we include spaces in the
36343 reply templates for clarity; these are not part of the reply packet's
36344 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36350 The program received signal number @var{AA} (a two-digit hexadecimal
36351 number). This is equivalent to a @samp{T} response with no
36352 @var{n}:@var{r} pairs.
36354 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36355 @cindex @samp{T} packet reply
36356 The program received signal number @var{AA} (a two-digit hexadecimal
36357 number). This is equivalent to an @samp{S} response, except that the
36358 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36359 and other information directly in the stop reply packet, reducing
36360 round-trip latency. Single-step and breakpoint traps are reported
36361 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36365 If @var{n} is a hexadecimal number, it is a register number, and the
36366 corresponding @var{r} gives that register's value. @var{r} is a
36367 series of bytes in target byte order, with each byte given by a
36368 two-digit hex number.
36371 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36372 the stopped thread, as specified in @ref{thread-id syntax}.
36375 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36376 the core on which the stop event was detected.
36379 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36380 specific event that stopped the target. The currently defined stop
36381 reasons are listed below. @var{aa} should be @samp{05}, the trap
36382 signal. At most one stop reason should be present.
36385 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36386 and go on to the next; this allows us to extend the protocol in the
36390 The currently defined stop reasons are:
36396 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36399 @cindex shared library events, remote reply
36401 The packet indicates that the loaded libraries have changed.
36402 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36403 list of loaded libraries. @var{r} is ignored.
36405 @cindex replay log events, remote reply
36407 The packet indicates that the target cannot continue replaying
36408 logged execution events, because it has reached the end (or the
36409 beginning when executing backward) of the log. The value of @var{r}
36410 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36411 for more information.
36415 @itemx W @var{AA} ; process:@var{pid}
36416 The process exited, and @var{AA} is the exit status. This is only
36417 applicable to certain targets.
36419 The second form of the response, including the process ID of the exited
36420 process, can be used only when @value{GDBN} has reported support for
36421 multiprocess protocol extensions; see @ref{multiprocess extensions}.
36422 The @var{pid} is formatted as a big-endian hex string.
36425 @itemx X @var{AA} ; process:@var{pid}
36426 The process terminated with signal @var{AA}.
36428 The second form of the response, including the process ID of the
36429 terminated process, can be used only when @value{GDBN} has reported
36430 support for multiprocess protocol extensions; see @ref{multiprocess
36431 extensions}. The @var{pid} is formatted as a big-endian hex string.
36433 @item O @var{XX}@dots{}
36434 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36435 written as the program's console output. This can happen at any time
36436 while the program is running and the debugger should continue to wait
36437 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36439 @item F @var{call-id},@var{parameter}@dots{}
36440 @var{call-id} is the identifier which says which host system call should
36441 be called. This is just the name of the function. Translation into the
36442 correct system call is only applicable as it's defined in @value{GDBN}.
36443 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36446 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36447 this very system call.
36449 The target replies with this packet when it expects @value{GDBN} to
36450 call a host system call on behalf of the target. @value{GDBN} replies
36451 with an appropriate @samp{F} packet and keeps up waiting for the next
36452 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36453 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36454 Protocol Extension}, for more details.
36458 @node General Query Packets
36459 @section General Query Packets
36460 @cindex remote query requests
36462 Packets starting with @samp{q} are @dfn{general query packets};
36463 packets starting with @samp{Q} are @dfn{general set packets}. General
36464 query and set packets are a semi-unified form for retrieving and
36465 sending information to and from the stub.
36467 The initial letter of a query or set packet is followed by a name
36468 indicating what sort of thing the packet applies to. For example,
36469 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36470 definitions with the stub. These packet names follow some
36475 The name must not contain commas, colons or semicolons.
36477 Most @value{GDBN} query and set packets have a leading upper case
36480 The names of custom vendor packets should use a company prefix, in
36481 lower case, followed by a period. For example, packets designed at
36482 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36483 foos) or @samp{Qacme.bar} (for setting bars).
36486 The name of a query or set packet should be separated from any
36487 parameters by a @samp{:}; the parameters themselves should be
36488 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36489 full packet name, and check for a separator or the end of the packet,
36490 in case two packet names share a common prefix. New packets should not begin
36491 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36492 packets predate these conventions, and have arguments without any terminator
36493 for the packet name; we suspect they are in widespread use in places that
36494 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36495 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36498 Like the descriptions of the other packets, each description here
36499 has a template showing the packet's overall syntax, followed by an
36500 explanation of the packet's meaning. We include spaces in some of the
36501 templates for clarity; these are not part of the packet's syntax. No
36502 @value{GDBN} packet uses spaces to separate its components.
36504 Here are the currently defined query and set packets:
36510 Turn on or off the agent as a helper to perform some debugging operations
36511 delegated from @value{GDBN} (@pxref{Control Agent}).
36513 @item QAllow:@var{op}:@var{val}@dots{}
36514 @cindex @samp{QAllow} packet
36515 Specify which operations @value{GDBN} expects to request of the
36516 target, as a semicolon-separated list of operation name and value
36517 pairs. Possible values for @var{op} include @samp{WriteReg},
36518 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36519 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36520 indicating that @value{GDBN} will not request the operation, or 1,
36521 indicating that it may. (The target can then use this to set up its
36522 own internals optimally, for instance if the debugger never expects to
36523 insert breakpoints, it may not need to install its own trap handler.)
36526 @cindex current thread, remote request
36527 @cindex @samp{qC} packet
36528 Return the current thread ID.
36532 @item QC @var{thread-id}
36533 Where @var{thread-id} is a thread ID as documented in
36534 @ref{thread-id syntax}.
36535 @item @r{(anything else)}
36536 Any other reply implies the old thread ID.
36539 @item qCRC:@var{addr},@var{length}
36540 @cindex CRC of memory block, remote request
36541 @cindex @samp{qCRC} packet
36542 Compute the CRC checksum of a block of memory using CRC-32 defined in
36543 IEEE 802.3. The CRC is computed byte at a time, taking the most
36544 significant bit of each byte first. The initial pattern code
36545 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36547 @emph{Note:} This is the same CRC used in validating separate debug
36548 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36549 Files}). However the algorithm is slightly different. When validating
36550 separate debug files, the CRC is computed taking the @emph{least}
36551 significant bit of each byte first, and the final result is inverted to
36552 detect trailing zeros.
36557 An error (such as memory fault)
36558 @item C @var{crc32}
36559 The specified memory region's checksum is @var{crc32}.
36562 @item QDisableRandomization:@var{value}
36563 @cindex disable address space randomization, remote request
36564 @cindex @samp{QDisableRandomization} packet
36565 Some target operating systems will randomize the virtual address space
36566 of the inferior process as a security feature, but provide a feature
36567 to disable such randomization, e.g.@: to allow for a more deterministic
36568 debugging experience. On such systems, this packet with a @var{value}
36569 of 1 directs the target to disable address space randomization for
36570 processes subsequently started via @samp{vRun} packets, while a packet
36571 with a @var{value} of 0 tells the target to enable address space
36574 This packet is only available in extended mode (@pxref{extended mode}).
36579 The request succeeded.
36582 An error occurred. @var{nn} are hex digits.
36585 An empty reply indicates that @samp{QDisableRandomization} is not supported
36589 This packet is not probed by default; the remote stub must request it,
36590 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36591 This should only be done on targets that actually support disabling
36592 address space randomization.
36595 @itemx qsThreadInfo
36596 @cindex list active threads, remote request
36597 @cindex @samp{qfThreadInfo} packet
36598 @cindex @samp{qsThreadInfo} packet
36599 Obtain a list of all active thread IDs from the target (OS). Since there
36600 may be too many active threads to fit into one reply packet, this query
36601 works iteratively: it may require more than one query/reply sequence to
36602 obtain the entire list of threads. The first query of the sequence will
36603 be the @samp{qfThreadInfo} query; subsequent queries in the
36604 sequence will be the @samp{qsThreadInfo} query.
36606 NOTE: This packet replaces the @samp{qL} query (see below).
36610 @item m @var{thread-id}
36612 @item m @var{thread-id},@var{thread-id}@dots{}
36613 a comma-separated list of thread IDs
36615 (lower case letter @samp{L}) denotes end of list.
36618 In response to each query, the target will reply with a list of one or
36619 more thread IDs, separated by commas.
36620 @value{GDBN} will respond to each reply with a request for more thread
36621 ids (using the @samp{qs} form of the query), until the target responds
36622 with @samp{l} (lower-case ell, for @dfn{last}).
36623 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
36626 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
36627 @cindex get thread-local storage address, remote request
36628 @cindex @samp{qGetTLSAddr} packet
36629 Fetch the address associated with thread local storage specified
36630 by @var{thread-id}, @var{offset}, and @var{lm}.
36632 @var{thread-id} is the thread ID associated with the
36633 thread for which to fetch the TLS address. @xref{thread-id syntax}.
36635 @var{offset} is the (big endian, hex encoded) offset associated with the
36636 thread local variable. (This offset is obtained from the debug
36637 information associated with the variable.)
36639 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
36640 load module associated with the thread local storage. For example,
36641 a @sc{gnu}/Linux system will pass the link map address of the shared
36642 object associated with the thread local storage under consideration.
36643 Other operating environments may choose to represent the load module
36644 differently, so the precise meaning of this parameter will vary.
36648 @item @var{XX}@dots{}
36649 Hex encoded (big endian) bytes representing the address of the thread
36650 local storage requested.
36653 An error occurred. @var{nn} are hex digits.
36656 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
36659 @item qGetTIBAddr:@var{thread-id}
36660 @cindex get thread information block address
36661 @cindex @samp{qGetTIBAddr} packet
36662 Fetch address of the Windows OS specific Thread Information Block.
36664 @var{thread-id} is the thread ID associated with the thread.
36668 @item @var{XX}@dots{}
36669 Hex encoded (big endian) bytes representing the linear address of the
36670 thread information block.
36673 An error occured. This means that either the thread was not found, or the
36674 address could not be retrieved.
36677 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
36680 @item qL @var{startflag} @var{threadcount} @var{nextthread}
36681 Obtain thread information from RTOS. Where: @var{startflag} (one hex
36682 digit) is one to indicate the first query and zero to indicate a
36683 subsequent query; @var{threadcount} (two hex digits) is the maximum
36684 number of threads the response packet can contain; and @var{nextthread}
36685 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
36686 returned in the response as @var{argthread}.
36688 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
36692 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
36693 Where: @var{count} (two hex digits) is the number of threads being
36694 returned; @var{done} (one hex digit) is zero to indicate more threads
36695 and one indicates no further threads; @var{argthreadid} (eight hex
36696 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
36697 is a sequence of thread IDs from the target. @var{threadid} (eight hex
36698 digits). See @code{remote.c:parse_threadlist_response()}.
36702 @cindex section offsets, remote request
36703 @cindex @samp{qOffsets} packet
36704 Get section offsets that the target used when relocating the downloaded
36709 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
36710 Relocate the @code{Text} section by @var{xxx} from its original address.
36711 Relocate the @code{Data} section by @var{yyy} from its original address.
36712 If the object file format provides segment information (e.g.@: @sc{elf}
36713 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
36714 segments by the supplied offsets.
36716 @emph{Note: while a @code{Bss} offset may be included in the response,
36717 @value{GDBN} ignores this and instead applies the @code{Data} offset
36718 to the @code{Bss} section.}
36720 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
36721 Relocate the first segment of the object file, which conventionally
36722 contains program code, to a starting address of @var{xxx}. If
36723 @samp{DataSeg} is specified, relocate the second segment, which
36724 conventionally contains modifiable data, to a starting address of
36725 @var{yyy}. @value{GDBN} will report an error if the object file
36726 does not contain segment information, or does not contain at least
36727 as many segments as mentioned in the reply. Extra segments are
36728 kept at fixed offsets relative to the last relocated segment.
36731 @item qP @var{mode} @var{thread-id}
36732 @cindex thread information, remote request
36733 @cindex @samp{qP} packet
36734 Returns information on @var{thread-id}. Where: @var{mode} is a hex
36735 encoded 32 bit mode; @var{thread-id} is a thread ID
36736 (@pxref{thread-id syntax}).
36738 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
36741 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
36745 @cindex non-stop mode, remote request
36746 @cindex @samp{QNonStop} packet
36748 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
36749 @xref{Remote Non-Stop}, for more information.
36754 The request succeeded.
36757 An error occurred. @var{nn} are hex digits.
36760 An empty reply indicates that @samp{QNonStop} is not supported by
36764 This packet is not probed by default; the remote stub must request it,
36765 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36766 Use of this packet is controlled by the @code{set non-stop} command;
36767 @pxref{Non-Stop Mode}.
36769 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36770 @cindex pass signals to inferior, remote request
36771 @cindex @samp{QPassSignals} packet
36772 @anchor{QPassSignals}
36773 Each listed @var{signal} should be passed directly to the inferior process.
36774 Signals are numbered identically to continue packets and stop replies
36775 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36776 strictly greater than the previous item. These signals do not need to stop
36777 the inferior, or be reported to @value{GDBN}. All other signals should be
36778 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
36779 combine; any earlier @samp{QPassSignals} list is completely replaced by the
36780 new list. This packet improves performance when using @samp{handle
36781 @var{signal} nostop noprint pass}.
36786 The request succeeded.
36789 An error occurred. @var{nn} are hex digits.
36792 An empty reply indicates that @samp{QPassSignals} is not supported by
36796 Use of this packet is controlled by the @code{set remote pass-signals}
36797 command (@pxref{Remote Configuration, set remote pass-signals}).
36798 This packet is not probed by default; the remote stub must request it,
36799 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36801 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36802 @cindex signals the inferior may see, remote request
36803 @cindex @samp{QProgramSignals} packet
36804 @anchor{QProgramSignals}
36805 Each listed @var{signal} may be delivered to the inferior process.
36806 Others should be silently discarded.
36808 In some cases, the remote stub may need to decide whether to deliver a
36809 signal to the program or not without @value{GDBN} involvement. One
36810 example of that is while detaching --- the program's threads may have
36811 stopped for signals that haven't yet had a chance of being reported to
36812 @value{GDBN}, and so the remote stub can use the signal list specified
36813 by this packet to know whether to deliver or ignore those pending
36816 This does not influence whether to deliver a signal as requested by a
36817 resumption packet (@pxref{vCont packet}).
36819 Signals are numbered identically to continue packets and stop replies
36820 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36821 strictly greater than the previous item. Multiple
36822 @samp{QProgramSignals} packets do not combine; any earlier
36823 @samp{QProgramSignals} list is completely replaced by the new list.
36828 The request succeeded.
36831 An error occurred. @var{nn} are hex digits.
36834 An empty reply indicates that @samp{QProgramSignals} is not supported
36838 Use of this packet is controlled by the @code{set remote program-signals}
36839 command (@pxref{Remote Configuration, set remote program-signals}).
36840 This packet is not probed by default; the remote stub must request it,
36841 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36843 @item qRcmd,@var{command}
36844 @cindex execute remote command, remote request
36845 @cindex @samp{qRcmd} packet
36846 @var{command} (hex encoded) is passed to the local interpreter for
36847 execution. Invalid commands should be reported using the output
36848 string. Before the final result packet, the target may also respond
36849 with a number of intermediate @samp{O@var{output}} console output
36850 packets. @emph{Implementors should note that providing access to a
36851 stubs's interpreter may have security implications}.
36856 A command response with no output.
36858 A command response with the hex encoded output string @var{OUTPUT}.
36860 Indicate a badly formed request.
36862 An empty reply indicates that @samp{qRcmd} is not recognized.
36865 (Note that the @code{qRcmd} packet's name is separated from the
36866 command by a @samp{,}, not a @samp{:}, contrary to the naming
36867 conventions above. Please don't use this packet as a model for new
36870 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
36871 @cindex searching memory, in remote debugging
36872 @cindex @samp{qSearch:memory} packet
36873 @anchor{qSearch memory}
36874 Search @var{length} bytes at @var{address} for @var{search-pattern}.
36875 @var{address} and @var{length} are encoded in hex.
36876 @var{search-pattern} is a sequence of bytes, hex encoded.
36881 The pattern was not found.
36883 The pattern was found at @var{address}.
36885 A badly formed request or an error was encountered while searching memory.
36887 An empty reply indicates that @samp{qSearch:memory} is not recognized.
36890 @item QStartNoAckMode
36891 @cindex @samp{QStartNoAckMode} packet
36892 @anchor{QStartNoAckMode}
36893 Request that the remote stub disable the normal @samp{+}/@samp{-}
36894 protocol acknowledgments (@pxref{Packet Acknowledgment}).
36899 The stub has switched to no-acknowledgment mode.
36900 @value{GDBN} acknowledges this reponse,
36901 but neither the stub nor @value{GDBN} shall send or expect further
36902 @samp{+}/@samp{-} acknowledgments in the current connection.
36904 An empty reply indicates that the stub does not support no-acknowledgment mode.
36907 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
36908 @cindex supported packets, remote query
36909 @cindex features of the remote protocol
36910 @cindex @samp{qSupported} packet
36911 @anchor{qSupported}
36912 Tell the remote stub about features supported by @value{GDBN}, and
36913 query the stub for features it supports. This packet allows
36914 @value{GDBN} and the remote stub to take advantage of each others'
36915 features. @samp{qSupported} also consolidates multiple feature probes
36916 at startup, to improve @value{GDBN} performance---a single larger
36917 packet performs better than multiple smaller probe packets on
36918 high-latency links. Some features may enable behavior which must not
36919 be on by default, e.g.@: because it would confuse older clients or
36920 stubs. Other features may describe packets which could be
36921 automatically probed for, but are not. These features must be
36922 reported before @value{GDBN} will use them. This ``default
36923 unsupported'' behavior is not appropriate for all packets, but it
36924 helps to keep the initial connection time under control with new
36925 versions of @value{GDBN} which support increasing numbers of packets.
36929 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
36930 The stub supports or does not support each returned @var{stubfeature},
36931 depending on the form of each @var{stubfeature} (see below for the
36934 An empty reply indicates that @samp{qSupported} is not recognized,
36935 or that no features needed to be reported to @value{GDBN}.
36938 The allowed forms for each feature (either a @var{gdbfeature} in the
36939 @samp{qSupported} packet, or a @var{stubfeature} in the response)
36943 @item @var{name}=@var{value}
36944 The remote protocol feature @var{name} is supported, and associated
36945 with the specified @var{value}. The format of @var{value} depends
36946 on the feature, but it must not include a semicolon.
36948 The remote protocol feature @var{name} is supported, and does not
36949 need an associated value.
36951 The remote protocol feature @var{name} is not supported.
36953 The remote protocol feature @var{name} may be supported, and
36954 @value{GDBN} should auto-detect support in some other way when it is
36955 needed. This form will not be used for @var{gdbfeature} notifications,
36956 but may be used for @var{stubfeature} responses.
36959 Whenever the stub receives a @samp{qSupported} request, the
36960 supplied set of @value{GDBN} features should override any previous
36961 request. This allows @value{GDBN} to put the stub in a known
36962 state, even if the stub had previously been communicating with
36963 a different version of @value{GDBN}.
36965 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
36970 This feature indicates whether @value{GDBN} supports multiprocess
36971 extensions to the remote protocol. @value{GDBN} does not use such
36972 extensions unless the stub also reports that it supports them by
36973 including @samp{multiprocess+} in its @samp{qSupported} reply.
36974 @xref{multiprocess extensions}, for details.
36977 This feature indicates that @value{GDBN} supports the XML target
36978 description. If the stub sees @samp{xmlRegisters=} with target
36979 specific strings separated by a comma, it will report register
36983 This feature indicates whether @value{GDBN} supports the
36984 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
36985 instruction reply packet}).
36988 Stubs should ignore any unknown values for
36989 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
36990 packet supports receiving packets of unlimited length (earlier
36991 versions of @value{GDBN} may reject overly long responses). Additional values
36992 for @var{gdbfeature} may be defined in the future to let the stub take
36993 advantage of new features in @value{GDBN}, e.g.@: incompatible
36994 improvements in the remote protocol---the @samp{multiprocess} feature is
36995 an example of such a feature. The stub's reply should be independent
36996 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
36997 describes all the features it supports, and then the stub replies with
36998 all the features it supports.
37000 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37001 responses, as long as each response uses one of the standard forms.
37003 Some features are flags. A stub which supports a flag feature
37004 should respond with a @samp{+} form response. Other features
37005 require values, and the stub should respond with an @samp{=}
37008 Each feature has a default value, which @value{GDBN} will use if
37009 @samp{qSupported} is not available or if the feature is not mentioned
37010 in the @samp{qSupported} response. The default values are fixed; a
37011 stub is free to omit any feature responses that match the defaults.
37013 Not all features can be probed, but for those which can, the probing
37014 mechanism is useful: in some cases, a stub's internal
37015 architecture may not allow the protocol layer to know some information
37016 about the underlying target in advance. This is especially common in
37017 stubs which may be configured for multiple targets.
37019 These are the currently defined stub features and their properties:
37021 @multitable @columnfractions 0.35 0.2 0.12 0.2
37022 @c NOTE: The first row should be @headitem, but we do not yet require
37023 @c a new enough version of Texinfo (4.7) to use @headitem.
37025 @tab Value Required
37029 @item @samp{PacketSize}
37034 @item @samp{qXfer:auxv:read}
37039 @item @samp{qXfer:features:read}
37044 @item @samp{qXfer:libraries:read}
37049 @item @samp{qXfer:memory-map:read}
37054 @item @samp{qXfer:sdata:read}
37059 @item @samp{qXfer:spu:read}
37064 @item @samp{qXfer:spu:write}
37069 @item @samp{qXfer:siginfo:read}
37074 @item @samp{qXfer:siginfo:write}
37079 @item @samp{qXfer:threads:read}
37084 @item @samp{qXfer:traceframe-info:read}
37089 @item @samp{qXfer:uib:read}
37094 @item @samp{qXfer:fdpic:read}
37099 @item @samp{QNonStop}
37104 @item @samp{QPassSignals}
37109 @item @samp{QStartNoAckMode}
37114 @item @samp{multiprocess}
37119 @item @samp{ConditionalBreakpoints}
37124 @item @samp{ConditionalTracepoints}
37129 @item @samp{ReverseContinue}
37134 @item @samp{ReverseStep}
37139 @item @samp{TracepointSource}
37144 @item @samp{QAgent}
37149 @item @samp{QAllow}
37154 @item @samp{QDisableRandomization}
37159 @item @samp{EnableDisableTracepoints}
37164 @item @samp{tracenz}
37169 @item @samp{BreakpointCommands}
37176 These are the currently defined stub features, in more detail:
37179 @cindex packet size, remote protocol
37180 @item PacketSize=@var{bytes}
37181 The remote stub can accept packets up to at least @var{bytes} in
37182 length. @value{GDBN} will send packets up to this size for bulk
37183 transfers, and will never send larger packets. This is a limit on the
37184 data characters in the packet, including the frame and checksum.
37185 There is no trailing NUL byte in a remote protocol packet; if the stub
37186 stores packets in a NUL-terminated format, it should allow an extra
37187 byte in its buffer for the NUL. If this stub feature is not supported,
37188 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37190 @item qXfer:auxv:read
37191 The remote stub understands the @samp{qXfer:auxv:read} packet
37192 (@pxref{qXfer auxiliary vector read}).
37194 @item qXfer:features:read
37195 The remote stub understands the @samp{qXfer:features:read} packet
37196 (@pxref{qXfer target description read}).
37198 @item qXfer:libraries:read
37199 The remote stub understands the @samp{qXfer:libraries:read} packet
37200 (@pxref{qXfer library list read}).
37202 @item qXfer:libraries-svr4:read
37203 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37204 (@pxref{qXfer svr4 library list read}).
37206 @item qXfer:memory-map:read
37207 The remote stub understands the @samp{qXfer:memory-map:read} packet
37208 (@pxref{qXfer memory map read}).
37210 @item qXfer:sdata:read
37211 The remote stub understands the @samp{qXfer:sdata:read} packet
37212 (@pxref{qXfer sdata read}).
37214 @item qXfer:spu:read
37215 The remote stub understands the @samp{qXfer:spu:read} packet
37216 (@pxref{qXfer spu read}).
37218 @item qXfer:spu:write
37219 The remote stub understands the @samp{qXfer:spu:write} packet
37220 (@pxref{qXfer spu write}).
37222 @item qXfer:siginfo:read
37223 The remote stub understands the @samp{qXfer:siginfo:read} packet
37224 (@pxref{qXfer siginfo read}).
37226 @item qXfer:siginfo:write
37227 The remote stub understands the @samp{qXfer:siginfo:write} packet
37228 (@pxref{qXfer siginfo write}).
37230 @item qXfer:threads:read
37231 The remote stub understands the @samp{qXfer:threads:read} packet
37232 (@pxref{qXfer threads read}).
37234 @item qXfer:traceframe-info:read
37235 The remote stub understands the @samp{qXfer:traceframe-info:read}
37236 packet (@pxref{qXfer traceframe info read}).
37238 @item qXfer:uib:read
37239 The remote stub understands the @samp{qXfer:uib:read}
37240 packet (@pxref{qXfer unwind info block}).
37242 @item qXfer:fdpic:read
37243 The remote stub understands the @samp{qXfer:fdpic:read}
37244 packet (@pxref{qXfer fdpic loadmap read}).
37247 The remote stub understands the @samp{QNonStop} packet
37248 (@pxref{QNonStop}).
37251 The remote stub understands the @samp{QPassSignals} packet
37252 (@pxref{QPassSignals}).
37254 @item QStartNoAckMode
37255 The remote stub understands the @samp{QStartNoAckMode} packet and
37256 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37259 @anchor{multiprocess extensions}
37260 @cindex multiprocess extensions, in remote protocol
37261 The remote stub understands the multiprocess extensions to the remote
37262 protocol syntax. The multiprocess extensions affect the syntax of
37263 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37264 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37265 replies. Note that reporting this feature indicates support for the
37266 syntactic extensions only, not that the stub necessarily supports
37267 debugging of more than one process at a time. The stub must not use
37268 multiprocess extensions in packet replies unless @value{GDBN} has also
37269 indicated it supports them in its @samp{qSupported} request.
37271 @item qXfer:osdata:read
37272 The remote stub understands the @samp{qXfer:osdata:read} packet
37273 ((@pxref{qXfer osdata read}).
37275 @item ConditionalBreakpoints
37276 The target accepts and implements evaluation of conditional expressions
37277 defined for breakpoints. The target will only report breakpoint triggers
37278 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37280 @item ConditionalTracepoints
37281 The remote stub accepts and implements conditional expressions defined
37282 for tracepoints (@pxref{Tracepoint Conditions}).
37284 @item ReverseContinue
37285 The remote stub accepts and implements the reverse continue packet
37289 The remote stub accepts and implements the reverse step packet
37292 @item TracepointSource
37293 The remote stub understands the @samp{QTDPsrc} packet that supplies
37294 the source form of tracepoint definitions.
37297 The remote stub understands the @samp{QAgent} packet.
37300 The remote stub understands the @samp{QAllow} packet.
37302 @item QDisableRandomization
37303 The remote stub understands the @samp{QDisableRandomization} packet.
37305 @item StaticTracepoint
37306 @cindex static tracepoints, in remote protocol
37307 The remote stub supports static tracepoints.
37309 @item InstallInTrace
37310 @anchor{install tracepoint in tracing}
37311 The remote stub supports installing tracepoint in tracing.
37313 @item EnableDisableTracepoints
37314 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37315 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37316 to be enabled and disabled while a trace experiment is running.
37319 @cindex string tracing, in remote protocol
37320 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
37321 See @ref{Bytecode Descriptions} for details about the bytecode.
37323 @item BreakpointCommands
37324 @cindex breakpoint commands, in remote protocol
37325 The remote stub supports running a breakpoint's command list itself,
37326 rather than reporting the hit to @value{GDBN}.
37331 @cindex symbol lookup, remote request
37332 @cindex @samp{qSymbol} packet
37333 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37334 requests. Accept requests from the target for the values of symbols.
37339 The target does not need to look up any (more) symbols.
37340 @item qSymbol:@var{sym_name}
37341 The target requests the value of symbol @var{sym_name} (hex encoded).
37342 @value{GDBN} may provide the value by using the
37343 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37347 @item qSymbol:@var{sym_value}:@var{sym_name}
37348 Set the value of @var{sym_name} to @var{sym_value}.
37350 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37351 target has previously requested.
37353 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37354 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37360 The target does not need to look up any (more) symbols.
37361 @item qSymbol:@var{sym_name}
37362 The target requests the value of a new symbol @var{sym_name} (hex
37363 encoded). @value{GDBN} will continue to supply the values of symbols
37364 (if available), until the target ceases to request them.
37369 @itemx QTDisconnected
37376 @itemx qTMinFTPILen
37378 @xref{Tracepoint Packets}.
37380 @item qThreadExtraInfo,@var{thread-id}
37381 @cindex thread attributes info, remote request
37382 @cindex @samp{qThreadExtraInfo} packet
37383 Obtain a printable string description of a thread's attributes from
37384 the target OS. @var{thread-id} is a thread ID;
37385 see @ref{thread-id syntax}. This
37386 string may contain anything that the target OS thinks is interesting
37387 for @value{GDBN} to tell the user about the thread. The string is
37388 displayed in @value{GDBN}'s @code{info threads} display. Some
37389 examples of possible thread extra info strings are @samp{Runnable}, or
37390 @samp{Blocked on Mutex}.
37394 @item @var{XX}@dots{}
37395 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37396 comprising the printable string containing the extra information about
37397 the thread's attributes.
37400 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37401 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37402 conventions above. Please don't use this packet as a model for new
37421 @xref{Tracepoint Packets}.
37423 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37424 @cindex read special object, remote request
37425 @cindex @samp{qXfer} packet
37426 @anchor{qXfer read}
37427 Read uninterpreted bytes from the target's special data area
37428 identified by the keyword @var{object}. Request @var{length} bytes
37429 starting at @var{offset} bytes into the data. The content and
37430 encoding of @var{annex} is specific to @var{object}; it can supply
37431 additional details about what data to access.
37433 Here are the specific requests of this form defined so far. All
37434 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37435 formats, listed below.
37438 @item qXfer:auxv:read::@var{offset},@var{length}
37439 @anchor{qXfer auxiliary vector read}
37440 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37441 auxiliary vector}. Note @var{annex} must be empty.
37443 This packet is not probed by default; the remote stub must request it,
37444 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37446 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37447 @anchor{qXfer target description read}
37448 Access the @dfn{target description}. @xref{Target Descriptions}. The
37449 annex specifies which XML document to access. The main description is
37450 always loaded from the @samp{target.xml} annex.
37452 This packet is not probed by default; the remote stub must request it,
37453 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37455 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37456 @anchor{qXfer library list read}
37457 Access the target's list of loaded libraries. @xref{Library List Format}.
37458 The annex part of the generic @samp{qXfer} packet must be empty
37459 (@pxref{qXfer read}).
37461 Targets which maintain a list of libraries in the program's memory do
37462 not need to implement this packet; it is designed for platforms where
37463 the operating system manages the list of loaded libraries.
37465 This packet is not probed by default; the remote stub must request it,
37466 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37468 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37469 @anchor{qXfer svr4 library list read}
37470 Access the target's list of loaded libraries when the target is an SVR4
37471 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37472 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37474 This packet is optional for better performance on SVR4 targets.
37475 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37477 This packet is not probed by default; the remote stub must request it,
37478 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37480 @item qXfer:memory-map:read::@var{offset},@var{length}
37481 @anchor{qXfer memory map read}
37482 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37483 annex part of the generic @samp{qXfer} packet must be empty
37484 (@pxref{qXfer read}).
37486 This packet is not probed by default; the remote stub must request it,
37487 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37489 @item qXfer:sdata:read::@var{offset},@var{length}
37490 @anchor{qXfer sdata read}
37492 Read contents of the extra collected static tracepoint marker
37493 information. The annex part of the generic @samp{qXfer} packet must
37494 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37497 This packet is not probed by default; the remote stub must request it,
37498 by supplying an appropriate @samp{qSupported} response
37499 (@pxref{qSupported}).
37501 @item qXfer:siginfo:read::@var{offset},@var{length}
37502 @anchor{qXfer siginfo read}
37503 Read contents of the extra signal information on the target
37504 system. The annex part of the generic @samp{qXfer} packet must be
37505 empty (@pxref{qXfer read}).
37507 This packet is not probed by default; the remote stub must request it,
37508 by supplying an appropriate @samp{qSupported} response
37509 (@pxref{qSupported}).
37511 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37512 @anchor{qXfer spu read}
37513 Read contents of an @code{spufs} file on the target system. The
37514 annex specifies which file to read; it must be of the form
37515 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37516 in the target process, and @var{name} identifes the @code{spufs} file
37517 in that context to be accessed.
37519 This packet is not probed by default; the remote stub must request it,
37520 by supplying an appropriate @samp{qSupported} response
37521 (@pxref{qSupported}).
37523 @item qXfer:threads:read::@var{offset},@var{length}
37524 @anchor{qXfer threads read}
37525 Access the list of threads on target. @xref{Thread List Format}. The
37526 annex part of the generic @samp{qXfer} packet must be empty
37527 (@pxref{qXfer read}).
37529 This packet is not probed by default; the remote stub must request it,
37530 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37532 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37533 @anchor{qXfer traceframe info read}
37535 Return a description of the current traceframe's contents.
37536 @xref{Traceframe Info Format}. The annex part of the generic
37537 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37539 This packet is not probed by default; the remote stub must request it,
37540 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37542 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37543 @anchor{qXfer unwind info block}
37545 Return the unwind information block for @var{pc}. This packet is used
37546 on OpenVMS/ia64 to ask the kernel unwind information.
37548 This packet is not probed by default.
37550 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37551 @anchor{qXfer fdpic loadmap read}
37552 Read contents of @code{loadmap}s on the target system. The
37553 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37554 executable @code{loadmap} or interpreter @code{loadmap} to read.
37556 This packet is not probed by default; the remote stub must request it,
37557 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37559 @item qXfer:osdata:read::@var{offset},@var{length}
37560 @anchor{qXfer osdata read}
37561 Access the target's @dfn{operating system information}.
37562 @xref{Operating System Information}.
37569 Data @var{data} (@pxref{Binary Data}) has been read from the
37570 target. There may be more data at a higher address (although
37571 it is permitted to return @samp{m} even for the last valid
37572 block of data, as long as at least one byte of data was read).
37573 @var{data} may have fewer bytes than the @var{length} in the
37577 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37578 There is no more data to be read. @var{data} may have fewer bytes
37579 than the @var{length} in the request.
37582 The @var{offset} in the request is at the end of the data.
37583 There is no more data to be read.
37586 The request was malformed, or @var{annex} was invalid.
37589 The offset was invalid, or there was an error encountered reading the data.
37590 @var{nn} is a hex-encoded @code{errno} value.
37593 An empty reply indicates the @var{object} string was not recognized by
37594 the stub, or that the object does not support reading.
37597 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
37598 @cindex write data into object, remote request
37599 @anchor{qXfer write}
37600 Write uninterpreted bytes into the target's special data area
37601 identified by the keyword @var{object}, starting at @var{offset} bytes
37602 into the data. @var{data}@dots{} is the binary-encoded data
37603 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
37604 is specific to @var{object}; it can supply additional details about what data
37607 Here are the specific requests of this form defined so far. All
37608 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
37609 formats, listed below.
37612 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
37613 @anchor{qXfer siginfo write}
37614 Write @var{data} to the extra signal information on the target system.
37615 The annex part of the generic @samp{qXfer} packet must be
37616 empty (@pxref{qXfer write}).
37618 This packet is not probed by default; the remote stub must request it,
37619 by supplying an appropriate @samp{qSupported} response
37620 (@pxref{qSupported}).
37622 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
37623 @anchor{qXfer spu write}
37624 Write @var{data} to an @code{spufs} file on the target system. The
37625 annex specifies which file to write; it must be of the form
37626 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37627 in the target process, and @var{name} identifes the @code{spufs} file
37628 in that context to be accessed.
37630 This packet is not probed by default; the remote stub must request it,
37631 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37637 @var{nn} (hex encoded) is the number of bytes written.
37638 This may be fewer bytes than supplied in the request.
37641 The request was malformed, or @var{annex} was invalid.
37644 The offset was invalid, or there was an error encountered writing the data.
37645 @var{nn} is a hex-encoded @code{errno} value.
37648 An empty reply indicates the @var{object} string was not
37649 recognized by the stub, or that the object does not support writing.
37652 @item qXfer:@var{object}:@var{operation}:@dots{}
37653 Requests of this form may be added in the future. When a stub does
37654 not recognize the @var{object} keyword, or its support for
37655 @var{object} does not recognize the @var{operation} keyword, the stub
37656 must respond with an empty packet.
37658 @item qAttached:@var{pid}
37659 @cindex query attached, remote request
37660 @cindex @samp{qAttached} packet
37661 Return an indication of whether the remote server attached to an
37662 existing process or created a new process. When the multiprocess
37663 protocol extensions are supported (@pxref{multiprocess extensions}),
37664 @var{pid} is an integer in hexadecimal format identifying the target
37665 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
37666 the query packet will be simplified as @samp{qAttached}.
37668 This query is used, for example, to know whether the remote process
37669 should be detached or killed when a @value{GDBN} session is ended with
37670 the @code{quit} command.
37675 The remote server attached to an existing process.
37677 The remote server created a new process.
37679 A badly formed request or an error was encountered.
37684 @node Architecture-Specific Protocol Details
37685 @section Architecture-Specific Protocol Details
37687 This section describes how the remote protocol is applied to specific
37688 target architectures. Also see @ref{Standard Target Features}, for
37689 details of XML target descriptions for each architecture.
37692 * ARM-Specific Protocol Details::
37693 * MIPS-Specific Protocol Details::
37696 @node ARM-Specific Protocol Details
37697 @subsection @acronym{ARM}-specific Protocol Details
37700 * ARM Breakpoint Kinds::
37703 @node ARM Breakpoint Kinds
37704 @subsubsection @acronym{ARM} Breakpoint Kinds
37705 @cindex breakpoint kinds, @acronym{ARM}
37707 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37712 16-bit Thumb mode breakpoint.
37715 32-bit Thumb mode (Thumb-2) breakpoint.
37718 32-bit @acronym{ARM} mode breakpoint.
37722 @node MIPS-Specific Protocol Details
37723 @subsection @acronym{MIPS}-specific Protocol Details
37726 * MIPS Register packet Format::
37727 * MIPS Breakpoint Kinds::
37730 @node MIPS Register packet Format
37731 @subsubsection @acronym{MIPS} Register Packet Format
37732 @cindex register packet format, @acronym{MIPS}
37734 The following @code{g}/@code{G} packets have previously been defined.
37735 In the below, some thirty-two bit registers are transferred as
37736 sixty-four bits. Those registers should be zero/sign extended (which?)
37737 to fill the space allocated. Register bytes are transferred in target
37738 byte order. The two nibbles within a register byte are transferred
37739 most-significant -- least-significant.
37744 All registers are transferred as thirty-two bit quantities in the order:
37745 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37746 registers; fsr; fir; fp.
37749 All registers are transferred as sixty-four bit quantities (including
37750 thirty-two bit registers such as @code{sr}). The ordering is the same
37755 @node MIPS Breakpoint Kinds
37756 @subsubsection @acronym{MIPS} Breakpoint Kinds
37757 @cindex breakpoint kinds, @acronym{MIPS}
37759 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37764 16-bit @acronym{MIPS16} mode breakpoint.
37767 16-bit @acronym{microMIPS} mode breakpoint.
37770 32-bit standard @acronym{MIPS} mode breakpoint.
37773 32-bit @acronym{microMIPS} mode breakpoint.
37777 @node Tracepoint Packets
37778 @section Tracepoint Packets
37779 @cindex tracepoint packets
37780 @cindex packets, tracepoint
37782 Here we describe the packets @value{GDBN} uses to implement
37783 tracepoints (@pxref{Tracepoints}).
37787 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37788 @cindex @samp{QTDP} packet
37789 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37790 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37791 the tracepoint is disabled. @var{step} is the tracepoint's step
37792 count, and @var{pass} is its pass count. If an @samp{F} is present,
37793 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37794 the number of bytes that the target should copy elsewhere to make room
37795 for the tracepoint. If an @samp{X} is present, it introduces a
37796 tracepoint condition, which consists of a hexadecimal length, followed
37797 by a comma and hex-encoded bytes, in a manner similar to action
37798 encodings as described below. If the trailing @samp{-} is present,
37799 further @samp{QTDP} packets will follow to specify this tracepoint's
37805 The packet was understood and carried out.
37807 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37809 The packet was not recognized.
37812 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37813 Define actions to be taken when a tracepoint is hit. @var{n} and
37814 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37815 this tracepoint. This packet may only be sent immediately after
37816 another @samp{QTDP} packet that ended with a @samp{-}. If the
37817 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
37818 specifying more actions for this tracepoint.
37820 In the series of action packets for a given tracepoint, at most one
37821 can have an @samp{S} before its first @var{action}. If such a packet
37822 is sent, it and the following packets define ``while-stepping''
37823 actions. Any prior packets define ordinary actions --- that is, those
37824 taken when the tracepoint is first hit. If no action packet has an
37825 @samp{S}, then all the packets in the series specify ordinary
37826 tracepoint actions.
37828 The @samp{@var{action}@dots{}} portion of the packet is a series of
37829 actions, concatenated without separators. Each action has one of the
37835 Collect the registers whose bits are set in @var{mask}. @var{mask} is
37836 a hexadecimal number whose @var{i}'th bit is set if register number
37837 @var{i} should be collected. (The least significant bit is numbered
37838 zero.) Note that @var{mask} may be any number of digits long; it may
37839 not fit in a 32-bit word.
37841 @item M @var{basereg},@var{offset},@var{len}
37842 Collect @var{len} bytes of memory starting at the address in register
37843 number @var{basereg}, plus @var{offset}. If @var{basereg} is
37844 @samp{-1}, then the range has a fixed address: @var{offset} is the
37845 address of the lowest byte to collect. The @var{basereg},
37846 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
37847 values (the @samp{-1} value for @var{basereg} is a special case).
37849 @item X @var{len},@var{expr}
37850 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
37851 it directs. @var{expr} is an agent expression, as described in
37852 @ref{Agent Expressions}. Each byte of the expression is encoded as a
37853 two-digit hex number in the packet; @var{len} is the number of bytes
37854 in the expression (and thus one-half the number of hex digits in the
37859 Any number of actions may be packed together in a single @samp{QTDP}
37860 packet, as long as the packet does not exceed the maximum packet
37861 length (400 bytes, for many stubs). There may be only one @samp{R}
37862 action per tracepoint, and it must precede any @samp{M} or @samp{X}
37863 actions. Any registers referred to by @samp{M} and @samp{X} actions
37864 must be collected by a preceding @samp{R} action. (The
37865 ``while-stepping'' actions are treated as if they were attached to a
37866 separate tracepoint, as far as these restrictions are concerned.)
37871 The packet was understood and carried out.
37873 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37875 The packet was not recognized.
37878 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
37879 @cindex @samp{QTDPsrc} packet
37880 Specify a source string of tracepoint @var{n} at address @var{addr}.
37881 This is useful to get accurate reproduction of the tracepoints
37882 originally downloaded at the beginning of the trace run. @var{type}
37883 is the name of the tracepoint part, such as @samp{cond} for the
37884 tracepoint's conditional expression (see below for a list of types), while
37885 @var{bytes} is the string, encoded in hexadecimal.
37887 @var{start} is the offset of the @var{bytes} within the overall source
37888 string, while @var{slen} is the total length of the source string.
37889 This is intended for handling source strings that are longer than will
37890 fit in a single packet.
37891 @c Add detailed example when this info is moved into a dedicated
37892 @c tracepoint descriptions section.
37894 The available string types are @samp{at} for the location,
37895 @samp{cond} for the conditional, and @samp{cmd} for an action command.
37896 @value{GDBN} sends a separate packet for each command in the action
37897 list, in the same order in which the commands are stored in the list.
37899 The target does not need to do anything with source strings except
37900 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
37903 Although this packet is optional, and @value{GDBN} will only send it
37904 if the target replies with @samp{TracepointSource} @xref{General
37905 Query Packets}, it makes both disconnected tracing and trace files
37906 much easier to use. Otherwise the user must be careful that the
37907 tracepoints in effect while looking at trace frames are identical to
37908 the ones in effect during the trace run; even a small discrepancy
37909 could cause @samp{tdump} not to work, or a particular trace frame not
37912 @item QTDV:@var{n}:@var{value}
37913 @cindex define trace state variable, remote request
37914 @cindex @samp{QTDV} packet
37915 Create a new trace state variable, number @var{n}, with an initial
37916 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
37917 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
37918 the option of not using this packet for initial values of zero; the
37919 target should simply create the trace state variables as they are
37920 mentioned in expressions.
37922 @item QTFrame:@var{n}
37923 @cindex @samp{QTFrame} packet
37924 Select the @var{n}'th tracepoint frame from the buffer, and use the
37925 register and memory contents recorded there to answer subsequent
37926 request packets from @value{GDBN}.
37928 A successful reply from the stub indicates that the stub has found the
37929 requested frame. The response is a series of parts, concatenated
37930 without separators, describing the frame we selected. Each part has
37931 one of the following forms:
37935 The selected frame is number @var{n} in the trace frame buffer;
37936 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
37937 was no frame matching the criteria in the request packet.
37940 The selected trace frame records a hit of tracepoint number @var{t};
37941 @var{t} is a hexadecimal number.
37945 @item QTFrame:pc:@var{addr}
37946 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37947 currently selected frame whose PC is @var{addr};
37948 @var{addr} is a hexadecimal number.
37950 @item QTFrame:tdp:@var{t}
37951 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37952 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
37953 is a hexadecimal number.
37955 @item QTFrame:range:@var{start}:@var{end}
37956 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37957 currently selected frame whose PC is between @var{start} (inclusive)
37958 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
37961 @item QTFrame:outside:@var{start}:@var{end}
37962 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
37963 frame @emph{outside} the given range of addresses (exclusive).
37966 @cindex @samp{qTMinFTPILen} packet
37967 This packet requests the minimum length of instruction at which a fast
37968 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
37969 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
37970 it depends on the target system being able to create trampolines in
37971 the first 64K of memory, which might or might not be possible for that
37972 system. So the reply to this packet will be 4 if it is able to
37979 The minimum instruction length is currently unknown.
37981 The minimum instruction length is @var{length}, where @var{length} is greater
37982 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
37983 that a fast tracepoint may be placed on any instruction regardless of size.
37985 An error has occurred.
37987 An empty reply indicates that the request is not supported by the stub.
37991 @cindex @samp{QTStart} packet
37992 Begin the tracepoint experiment. Begin collecting data from
37993 tracepoint hits in the trace frame buffer. This packet supports the
37994 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
37995 instruction reply packet}).
37998 @cindex @samp{QTStop} packet
37999 End the tracepoint experiment. Stop collecting trace frames.
38001 @item QTEnable:@var{n}:@var{addr}
38003 @cindex @samp{QTEnable} packet
38004 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38005 experiment. If the tracepoint was previously disabled, then collection
38006 of data from it will resume.
38008 @item QTDisable:@var{n}:@var{addr}
38010 @cindex @samp{QTDisable} packet
38011 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38012 experiment. No more data will be collected from the tracepoint unless
38013 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38016 @cindex @samp{QTinit} packet
38017 Clear the table of tracepoints, and empty the trace frame buffer.
38019 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38020 @cindex @samp{QTro} packet
38021 Establish the given ranges of memory as ``transparent''. The stub
38022 will answer requests for these ranges from memory's current contents,
38023 if they were not collected as part of the tracepoint hit.
38025 @value{GDBN} uses this to mark read-only regions of memory, like those
38026 containing program code. Since these areas never change, they should
38027 still have the same contents they did when the tracepoint was hit, so
38028 there's no reason for the stub to refuse to provide their contents.
38030 @item QTDisconnected:@var{value}
38031 @cindex @samp{QTDisconnected} packet
38032 Set the choice to what to do with the tracing run when @value{GDBN}
38033 disconnects from the target. A @var{value} of 1 directs the target to
38034 continue the tracing run, while 0 tells the target to stop tracing if
38035 @value{GDBN} is no longer in the picture.
38038 @cindex @samp{qTStatus} packet
38039 Ask the stub if there is a trace experiment running right now.
38041 The reply has the form:
38045 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38046 @var{running} is a single digit @code{1} if the trace is presently
38047 running, or @code{0} if not. It is followed by semicolon-separated
38048 optional fields that an agent may use to report additional status.
38052 If the trace is not running, the agent may report any of several
38053 explanations as one of the optional fields:
38058 No trace has been run yet.
38060 @item tstop[:@var{text}]:0
38061 The trace was stopped by a user-originated stop command. The optional
38062 @var{text} field is a user-supplied string supplied as part of the
38063 stop command (for instance, an explanation of why the trace was
38064 stopped manually). It is hex-encoded.
38067 The trace stopped because the trace buffer filled up.
38069 @item tdisconnected:0
38070 The trace stopped because @value{GDBN} disconnected from the target.
38072 @item tpasscount:@var{tpnum}
38073 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38075 @item terror:@var{text}:@var{tpnum}
38076 The trace stopped because tracepoint @var{tpnum} had an error. The
38077 string @var{text} is available to describe the nature of the error
38078 (for instance, a divide by zero in the condition expression).
38079 @var{text} is hex encoded.
38082 The trace stopped for some other reason.
38086 Additional optional fields supply statistical and other information.
38087 Although not required, they are extremely useful for users monitoring
38088 the progress of a trace run. If a trace has stopped, and these
38089 numbers are reported, they must reflect the state of the just-stopped
38094 @item tframes:@var{n}
38095 The number of trace frames in the buffer.
38097 @item tcreated:@var{n}
38098 The total number of trace frames created during the run. This may
38099 be larger than the trace frame count, if the buffer is circular.
38101 @item tsize:@var{n}
38102 The total size of the trace buffer, in bytes.
38104 @item tfree:@var{n}
38105 The number of bytes still unused in the buffer.
38107 @item circular:@var{n}
38108 The value of the circular trace buffer flag. @code{1} means that the
38109 trace buffer is circular and old trace frames will be discarded if
38110 necessary to make room, @code{0} means that the trace buffer is linear
38113 @item disconn:@var{n}
38114 The value of the disconnected tracing flag. @code{1} means that
38115 tracing will continue after @value{GDBN} disconnects, @code{0} means
38116 that the trace run will stop.
38120 @item qTP:@var{tp}:@var{addr}
38121 @cindex tracepoint status, remote request
38122 @cindex @samp{qTP} packet
38123 Ask the stub for the current state of tracepoint number @var{tp} at
38124 address @var{addr}.
38128 @item V@var{hits}:@var{usage}
38129 The tracepoint has been hit @var{hits} times so far during the trace
38130 run, and accounts for @var{usage} in the trace buffer. Note that
38131 @code{while-stepping} steps are not counted as separate hits, but the
38132 steps' space consumption is added into the usage number.
38136 @item qTV:@var{var}
38137 @cindex trace state variable value, remote request
38138 @cindex @samp{qTV} packet
38139 Ask the stub for the value of the trace state variable number @var{var}.
38144 The value of the variable is @var{value}. This will be the current
38145 value of the variable if the user is examining a running target, or a
38146 saved value if the variable was collected in the trace frame that the
38147 user is looking at. Note that multiple requests may result in
38148 different reply values, such as when requesting values while the
38149 program is running.
38152 The value of the variable is unknown. This would occur, for example,
38153 if the user is examining a trace frame in which the requested variable
38158 @cindex @samp{qTfP} packet
38160 @cindex @samp{qTsP} packet
38161 These packets request data about tracepoints that are being used by
38162 the target. @value{GDBN} sends @code{qTfP} to get the first piece
38163 of data, and multiple @code{qTsP} to get additional pieces. Replies
38164 to these packets generally take the form of the @code{QTDP} packets
38165 that define tracepoints. (FIXME add detailed syntax)
38168 @cindex @samp{qTfV} packet
38170 @cindex @samp{qTsV} packet
38171 These packets request data about trace state variables that are on the
38172 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
38173 and multiple @code{qTsV} to get additional variables. Replies to
38174 these packets follow the syntax of the @code{QTDV} packets that define
38175 trace state variables.
38181 @cindex @samp{qTfSTM} packet
38182 @cindex @samp{qTsSTM} packet
38183 These packets request data about static tracepoint markers that exist
38184 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
38185 first piece of data, and multiple @code{qTsSTM} to get additional
38186 pieces. Replies to these packets take the following form:
38190 @item m @var{address}:@var{id}:@var{extra}
38192 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38193 a comma-separated list of markers
38195 (lower case letter @samp{L}) denotes end of list.
38197 An error occurred. @var{nn} are hex digits.
38199 An empty reply indicates that the request is not supported by the
38203 @var{address} is encoded in hex.
38204 @var{id} and @var{extra} are strings encoded in hex.
38206 In response to each query, the target will reply with a list of one or
38207 more markers, separated by commas. @value{GDBN} will respond to each
38208 reply with a request for more markers (using the @samp{qs} form of the
38209 query), until the target responds with @samp{l} (lower-case ell, for
38212 @item qTSTMat:@var{address}
38214 @cindex @samp{qTSTMat} packet
38215 This packets requests data about static tracepoint markers in the
38216 target program at @var{address}. Replies to this packet follow the
38217 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38218 tracepoint markers.
38220 @item QTSave:@var{filename}
38221 @cindex @samp{QTSave} packet
38222 This packet directs the target to save trace data to the file name
38223 @var{filename} in the target's filesystem. @var{filename} is encoded
38224 as a hex string; the interpretation of the file name (relative vs
38225 absolute, wild cards, etc) is up to the target.
38227 @item qTBuffer:@var{offset},@var{len}
38228 @cindex @samp{qTBuffer} packet
38229 Return up to @var{len} bytes of the current contents of trace buffer,
38230 starting at @var{offset}. The trace buffer is treated as if it were
38231 a contiguous collection of traceframes, as per the trace file format.
38232 The reply consists as many hex-encoded bytes as the target can deliver
38233 in a packet; it is not an error to return fewer than were asked for.
38234 A reply consisting of just @code{l} indicates that no bytes are
38237 @item QTBuffer:circular:@var{value}
38238 This packet directs the target to use a circular trace buffer if
38239 @var{value} is 1, or a linear buffer if the value is 0.
38241 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38242 @cindex @samp{QTNotes} packet
38243 This packet adds optional textual notes to the trace run. Allowable
38244 types include @code{user}, @code{notes}, and @code{tstop}, the
38245 @var{text} fields are arbitrary strings, hex-encoded.
38249 @subsection Relocate instruction reply packet
38250 When installing fast tracepoints in memory, the target may need to
38251 relocate the instruction currently at the tracepoint address to a
38252 different address in memory. For most instructions, a simple copy is
38253 enough, but, for example, call instructions that implicitly push the
38254 return address on the stack, and relative branches or other
38255 PC-relative instructions require offset adjustment, so that the effect
38256 of executing the instruction at a different address is the same as if
38257 it had executed in the original location.
38259 In response to several of the tracepoint packets, the target may also
38260 respond with a number of intermediate @samp{qRelocInsn} request
38261 packets before the final result packet, to have @value{GDBN} handle
38262 this relocation operation. If a packet supports this mechanism, its
38263 documentation will explicitly say so. See for example the above
38264 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38265 format of the request is:
38268 @item qRelocInsn:@var{from};@var{to}
38270 This requests @value{GDBN} to copy instruction at address @var{from}
38271 to address @var{to}, possibly adjusted so that executing the
38272 instruction at @var{to} has the same effect as executing it at
38273 @var{from}. @value{GDBN} writes the adjusted instruction to target
38274 memory starting at @var{to}.
38279 @item qRelocInsn:@var{adjusted_size}
38280 Informs the stub the relocation is complete. @var{adjusted_size} is
38281 the length in bytes of resulting relocated instruction sequence.
38283 A badly formed request was detected, or an error was encountered while
38284 relocating the instruction.
38287 @node Host I/O Packets
38288 @section Host I/O Packets
38289 @cindex Host I/O, remote protocol
38290 @cindex file transfer, remote protocol
38292 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38293 operations on the far side of a remote link. For example, Host I/O is
38294 used to upload and download files to a remote target with its own
38295 filesystem. Host I/O uses the same constant values and data structure
38296 layout as the target-initiated File-I/O protocol. However, the
38297 Host I/O packets are structured differently. The target-initiated
38298 protocol relies on target memory to store parameters and buffers.
38299 Host I/O requests are initiated by @value{GDBN}, and the
38300 target's memory is not involved. @xref{File-I/O Remote Protocol
38301 Extension}, for more details on the target-initiated protocol.
38303 The Host I/O request packets all encode a single operation along with
38304 its arguments. They have this format:
38308 @item vFile:@var{operation}: @var{parameter}@dots{}
38309 @var{operation} is the name of the particular request; the target
38310 should compare the entire packet name up to the second colon when checking
38311 for a supported operation. The format of @var{parameter} depends on
38312 the operation. Numbers are always passed in hexadecimal. Negative
38313 numbers have an explicit minus sign (i.e.@: two's complement is not
38314 used). Strings (e.g.@: filenames) are encoded as a series of
38315 hexadecimal bytes. The last argument to a system call may be a
38316 buffer of escaped binary data (@pxref{Binary Data}).
38320 The valid responses to Host I/O packets are:
38324 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38325 @var{result} is the integer value returned by this operation, usually
38326 non-negative for success and -1 for errors. If an error has occured,
38327 @var{errno} will be included in the result. @var{errno} will have a
38328 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38329 operations which return data, @var{attachment} supplies the data as a
38330 binary buffer. Binary buffers in response packets are escaped in the
38331 normal way (@pxref{Binary Data}). See the individual packet
38332 documentation for the interpretation of @var{result} and
38336 An empty response indicates that this operation is not recognized.
38340 These are the supported Host I/O operations:
38343 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
38344 Open a file at @var{pathname} and return a file descriptor for it, or
38345 return -1 if an error occurs. @var{pathname} is a string,
38346 @var{flags} is an integer indicating a mask of open flags
38347 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38348 of mode bits to use if the file is created (@pxref{mode_t Values}).
38349 @xref{open}, for details of the open flags and mode values.
38351 @item vFile:close: @var{fd}
38352 Close the open file corresponding to @var{fd} and return 0, or
38353 -1 if an error occurs.
38355 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38356 Read data from the open file corresponding to @var{fd}. Up to
38357 @var{count} bytes will be read from the file, starting at @var{offset}
38358 relative to the start of the file. The target may read fewer bytes;
38359 common reasons include packet size limits and an end-of-file
38360 condition. The number of bytes read is returned. Zero should only be
38361 returned for a successful read at the end of the file, or if
38362 @var{count} was zero.
38364 The data read should be returned as a binary attachment on success.
38365 If zero bytes were read, the response should include an empty binary
38366 attachment (i.e.@: a trailing semicolon). The return value is the
38367 number of target bytes read; the binary attachment may be longer if
38368 some characters were escaped.
38370 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38371 Write @var{data} (a binary buffer) to the open file corresponding
38372 to @var{fd}. Start the write at @var{offset} from the start of the
38373 file. Unlike many @code{write} system calls, there is no
38374 separate @var{count} argument; the length of @var{data} in the
38375 packet is used. @samp{vFile:write} returns the number of bytes written,
38376 which may be shorter than the length of @var{data}, or -1 if an
38379 @item vFile:unlink: @var{pathname}
38380 Delete the file at @var{pathname} on the target. Return 0,
38381 or -1 if an error occurs. @var{pathname} is a string.
38383 @item vFile:readlink: @var{filename}
38384 Read value of symbolic link @var{filename} on the target. Return
38385 the number of bytes read, or -1 if an error occurs.
38387 The data read should be returned as a binary attachment on success.
38388 If zero bytes were read, the response should include an empty binary
38389 attachment (i.e.@: a trailing semicolon). The return value is the
38390 number of target bytes read; the binary attachment may be longer if
38391 some characters were escaped.
38396 @section Interrupts
38397 @cindex interrupts (remote protocol)
38399 When a program on the remote target is running, @value{GDBN} may
38400 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
38401 a @code{BREAK} followed by @code{g},
38402 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38404 The precise meaning of @code{BREAK} is defined by the transport
38405 mechanism and may, in fact, be undefined. @value{GDBN} does not
38406 currently define a @code{BREAK} mechanism for any of the network
38407 interfaces except for TCP, in which case @value{GDBN} sends the
38408 @code{telnet} BREAK sequence.
38410 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38411 transport mechanisms. It is represented by sending the single byte
38412 @code{0x03} without any of the usual packet overhead described in
38413 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38414 transmitted as part of a packet, it is considered to be packet data
38415 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38416 (@pxref{X packet}), used for binary downloads, may include an unescaped
38417 @code{0x03} as part of its packet.
38419 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38420 When Linux kernel receives this sequence from serial port,
38421 it stops execution and connects to gdb.
38423 Stubs are not required to recognize these interrupt mechanisms and the
38424 precise meaning associated with receipt of the interrupt is
38425 implementation defined. If the target supports debugging of multiple
38426 threads and/or processes, it should attempt to interrupt all
38427 currently-executing threads and processes.
38428 If the stub is successful at interrupting the
38429 running program, it should send one of the stop
38430 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38431 of successfully stopping the program in all-stop mode, and a stop reply
38432 for each stopped thread in non-stop mode.
38433 Interrupts received while the
38434 program is stopped are discarded.
38436 @node Notification Packets
38437 @section Notification Packets
38438 @cindex notification packets
38439 @cindex packets, notification
38441 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38442 packets that require no acknowledgment. Both the GDB and the stub
38443 may send notifications (although the only notifications defined at
38444 present are sent by the stub). Notifications carry information
38445 without incurring the round-trip latency of an acknowledgment, and so
38446 are useful for low-impact communications where occasional packet loss
38449 A notification packet has the form @samp{% @var{data} #
38450 @var{checksum}}, where @var{data} is the content of the notification,
38451 and @var{checksum} is a checksum of @var{data}, computed and formatted
38452 as for ordinary @value{GDBN} packets. A notification's @var{data}
38453 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38454 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38455 to acknowledge the notification's receipt or to report its corruption.
38457 Every notification's @var{data} begins with a name, which contains no
38458 colon characters, followed by a colon character.
38460 Recipients should silently ignore corrupted notifications and
38461 notifications they do not understand. Recipients should restart
38462 timeout periods on receipt of a well-formed notification, whether or
38463 not they understand it.
38465 Senders should only send the notifications described here when this
38466 protocol description specifies that they are permitted. In the
38467 future, we may extend the protocol to permit existing notifications in
38468 new contexts; this rule helps older senders avoid confusing newer
38471 (Older versions of @value{GDBN} ignore bytes received until they see
38472 the @samp{$} byte that begins an ordinary packet, so new stubs may
38473 transmit notifications without fear of confusing older clients. There
38474 are no notifications defined for @value{GDBN} to send at the moment, but we
38475 assume that most older stubs would ignore them, as well.)
38477 The following notification packets from the stub to @value{GDBN} are
38481 @item Stop: @var{reply}
38482 Report an asynchronous stop event in non-stop mode.
38483 The @var{reply} has the form of a stop reply, as
38484 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
38485 for information on how these notifications are acknowledged by
38489 @node Remote Non-Stop
38490 @section Remote Protocol Support for Non-Stop Mode
38492 @value{GDBN}'s remote protocol supports non-stop debugging of
38493 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
38494 supports non-stop mode, it should report that to @value{GDBN} by including
38495 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
38497 @value{GDBN} typically sends a @samp{QNonStop} packet only when
38498 establishing a new connection with the stub. Entering non-stop mode
38499 does not alter the state of any currently-running threads, but targets
38500 must stop all threads in any already-attached processes when entering
38501 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
38502 probe the target state after a mode change.
38504 In non-stop mode, when an attached process encounters an event that
38505 would otherwise be reported with a stop reply, it uses the
38506 asynchronous notification mechanism (@pxref{Notification Packets}) to
38507 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38508 in all processes are stopped when a stop reply is sent, in non-stop
38509 mode only the thread reporting the stop event is stopped. That is,
38510 when reporting a @samp{S} or @samp{T} response to indicate completion
38511 of a step operation, hitting a breakpoint, or a fault, only the
38512 affected thread is stopped; any other still-running threads continue
38513 to run. When reporting a @samp{W} or @samp{X} response, all running
38514 threads belonging to other attached processes continue to run.
38516 Only one stop reply notification at a time may be pending; if
38517 additional stop events occur before @value{GDBN} has acknowledged the
38518 previous notification, they must be queued by the stub for later
38519 synchronous transmission in response to @samp{vStopped} packets from
38520 @value{GDBN}. Because the notification mechanism is unreliable,
38521 the stub is permitted to resend a stop reply notification
38522 if it believes @value{GDBN} may not have received it. @value{GDBN}
38523 ignores additional stop reply notifications received before it has
38524 finished processing a previous notification and the stub has completed
38525 sending any queued stop events.
38527 Otherwise, @value{GDBN} must be prepared to receive a stop reply
38528 notification at any time. Specifically, they may appear when
38529 @value{GDBN} is not otherwise reading input from the stub, or when
38530 @value{GDBN} is expecting to read a normal synchronous response or a
38531 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38532 Notification packets are distinct from any other communication from
38533 the stub so there is no ambiguity.
38535 After receiving a stop reply notification, @value{GDBN} shall
38536 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
38537 as a regular, synchronous request to the stub. Such acknowledgment
38538 is not required to happen immediately, as @value{GDBN} is permitted to
38539 send other, unrelated packets to the stub first, which the stub should
38542 Upon receiving a @samp{vStopped} packet, if the stub has other queued
38543 stop events to report to @value{GDBN}, it shall respond by sending a
38544 normal stop reply response. @value{GDBN} shall then send another
38545 @samp{vStopped} packet to solicit further responses; again, it is
38546 permitted to send other, unrelated packets as well which the stub
38547 should process normally.
38549 If the stub receives a @samp{vStopped} packet and there are no
38550 additional stop events to report, the stub shall return an @samp{OK}
38551 response. At this point, if further stop events occur, the stub shall
38552 send a new stop reply notification, @value{GDBN} shall accept the
38553 notification, and the process shall be repeated.
38555 In non-stop mode, the target shall respond to the @samp{?} packet as
38556 follows. First, any incomplete stop reply notification/@samp{vStopped}
38557 sequence in progress is abandoned. The target must begin a new
38558 sequence reporting stop events for all stopped threads, whether or not
38559 it has previously reported those events to @value{GDBN}. The first
38560 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38561 subsequent stop replies are sent as responses to @samp{vStopped} packets
38562 using the mechanism described above. The target must not send
38563 asynchronous stop reply notifications until the sequence is complete.
38564 If all threads are running when the target receives the @samp{?} packet,
38565 or if the target is not attached to any process, it shall respond
38568 @node Packet Acknowledgment
38569 @section Packet Acknowledgment
38571 @cindex acknowledgment, for @value{GDBN} remote
38572 @cindex packet acknowledgment, for @value{GDBN} remote
38573 By default, when either the host or the target machine receives a packet,
38574 the first response expected is an acknowledgment: either @samp{+} (to indicate
38575 the package was received correctly) or @samp{-} (to request retransmission).
38576 This mechanism allows the @value{GDBN} remote protocol to operate over
38577 unreliable transport mechanisms, such as a serial line.
38579 In cases where the transport mechanism is itself reliable (such as a pipe or
38580 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38581 It may be desirable to disable them in that case to reduce communication
38582 overhead, or for other reasons. This can be accomplished by means of the
38583 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38585 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38586 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38587 and response format still includes the normal checksum, as described in
38588 @ref{Overview}, but the checksum may be ignored by the receiver.
38590 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38591 no-acknowledgment mode, it should report that to @value{GDBN}
38592 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38593 @pxref{qSupported}.
38594 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38595 disabled via the @code{set remote noack-packet off} command
38596 (@pxref{Remote Configuration}),
38597 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38598 Only then may the stub actually turn off packet acknowledgments.
38599 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38600 response, which can be safely ignored by the stub.
38602 Note that @code{set remote noack-packet} command only affects negotiation
38603 between @value{GDBN} and the stub when subsequent connections are made;
38604 it does not affect the protocol acknowledgment state for any current
38606 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38607 new connection is established,
38608 there is also no protocol request to re-enable the acknowledgments
38609 for the current connection, once disabled.
38614 Example sequence of a target being re-started. Notice how the restart
38615 does not get any direct output:
38620 @emph{target restarts}
38623 <- @code{T001:1234123412341234}
38627 Example sequence of a target being stepped by a single instruction:
38630 -> @code{G1445@dots{}}
38635 <- @code{T001:1234123412341234}
38639 <- @code{1455@dots{}}
38643 @node File-I/O Remote Protocol Extension
38644 @section File-I/O Remote Protocol Extension
38645 @cindex File-I/O remote protocol extension
38648 * File-I/O Overview::
38649 * Protocol Basics::
38650 * The F Request Packet::
38651 * The F Reply Packet::
38652 * The Ctrl-C Message::
38654 * List of Supported Calls::
38655 * Protocol-specific Representation of Datatypes::
38657 * File-I/O Examples::
38660 @node File-I/O Overview
38661 @subsection File-I/O Overview
38662 @cindex file-i/o overview
38664 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38665 target to use the host's file system and console I/O to perform various
38666 system calls. System calls on the target system are translated into a
38667 remote protocol packet to the host system, which then performs the needed
38668 actions and returns a response packet to the target system.
38669 This simulates file system operations even on targets that lack file systems.
38671 The protocol is defined to be independent of both the host and target systems.
38672 It uses its own internal representation of datatypes and values. Both
38673 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38674 translating the system-dependent value representations into the internal
38675 protocol representations when data is transmitted.
38677 The communication is synchronous. A system call is possible only when
38678 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38679 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38680 the target is stopped to allow deterministic access to the target's
38681 memory. Therefore File-I/O is not interruptible by target signals. On
38682 the other hand, it is possible to interrupt File-I/O by a user interrupt
38683 (@samp{Ctrl-C}) within @value{GDBN}.
38685 The target's request to perform a host system call does not finish
38686 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38687 after finishing the system call, the target returns to continuing the
38688 previous activity (continue, step). No additional continue or step
38689 request from @value{GDBN} is required.
38692 (@value{GDBP}) continue
38693 <- target requests 'system call X'
38694 target is stopped, @value{GDBN} executes system call
38695 -> @value{GDBN} returns result
38696 ... target continues, @value{GDBN} returns to wait for the target
38697 <- target hits breakpoint and sends a Txx packet
38700 The protocol only supports I/O on the console and to regular files on
38701 the host file system. Character or block special devices, pipes,
38702 named pipes, sockets or any other communication method on the host
38703 system are not supported by this protocol.
38705 File I/O is not supported in non-stop mode.
38707 @node Protocol Basics
38708 @subsection Protocol Basics
38709 @cindex protocol basics, file-i/o
38711 The File-I/O protocol uses the @code{F} packet as the request as well
38712 as reply packet. Since a File-I/O system call can only occur when
38713 @value{GDBN} is waiting for a response from the continuing or stepping target,
38714 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38715 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38716 This @code{F} packet contains all information needed to allow @value{GDBN}
38717 to call the appropriate host system call:
38721 A unique identifier for the requested system call.
38724 All parameters to the system call. Pointers are given as addresses
38725 in the target memory address space. Pointers to strings are given as
38726 pointer/length pair. Numerical values are given as they are.
38727 Numerical control flags are given in a protocol-specific representation.
38731 At this point, @value{GDBN} has to perform the following actions.
38735 If the parameters include pointer values to data needed as input to a
38736 system call, @value{GDBN} requests this data from the target with a
38737 standard @code{m} packet request. This additional communication has to be
38738 expected by the target implementation and is handled as any other @code{m}
38742 @value{GDBN} translates all value from protocol representation to host
38743 representation as needed. Datatypes are coerced into the host types.
38746 @value{GDBN} calls the system call.
38749 It then coerces datatypes back to protocol representation.
38752 If the system call is expected to return data in buffer space specified
38753 by pointer parameters to the call, the data is transmitted to the
38754 target using a @code{M} or @code{X} packet. This packet has to be expected
38755 by the target implementation and is handled as any other @code{M} or @code{X}
38760 Eventually @value{GDBN} replies with another @code{F} packet which contains all
38761 necessary information for the target to continue. This at least contains
38768 @code{errno}, if has been changed by the system call.
38775 After having done the needed type and value coercion, the target continues
38776 the latest continue or step action.
38778 @node The F Request Packet
38779 @subsection The @code{F} Request Packet
38780 @cindex file-i/o request packet
38781 @cindex @code{F} request packet
38783 The @code{F} request packet has the following format:
38786 @item F@var{call-id},@var{parameter@dots{}}
38788 @var{call-id} is the identifier to indicate the host system call to be called.
38789 This is just the name of the function.
38791 @var{parameter@dots{}} are the parameters to the system call.
38792 Parameters are hexadecimal integer values, either the actual values in case
38793 of scalar datatypes, pointers to target buffer space in case of compound
38794 datatypes and unspecified memory areas, or pointer/length pairs in case
38795 of string parameters. These are appended to the @var{call-id} as a
38796 comma-delimited list. All values are transmitted in ASCII
38797 string representation, pointer/length pairs separated by a slash.
38803 @node The F Reply Packet
38804 @subsection The @code{F} Reply Packet
38805 @cindex file-i/o reply packet
38806 @cindex @code{F} reply packet
38808 The @code{F} reply packet has the following format:
38812 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
38814 @var{retcode} is the return code of the system call as hexadecimal value.
38816 @var{errno} is the @code{errno} set by the call, in protocol-specific
38818 This parameter can be omitted if the call was successful.
38820 @var{Ctrl-C flag} is only sent if the user requested a break. In this
38821 case, @var{errno} must be sent as well, even if the call was successful.
38822 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
38829 or, if the call was interrupted before the host call has been performed:
38836 assuming 4 is the protocol-specific representation of @code{EINTR}.
38841 @node The Ctrl-C Message
38842 @subsection The @samp{Ctrl-C} Message
38843 @cindex ctrl-c message, in file-i/o protocol
38845 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
38846 reply packet (@pxref{The F Reply Packet}),
38847 the target should behave as if it had
38848 gotten a break message. The meaning for the target is ``system call
38849 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
38850 (as with a break message) and return to @value{GDBN} with a @code{T02}
38853 It's important for the target to know in which
38854 state the system call was interrupted. There are two possible cases:
38858 The system call hasn't been performed on the host yet.
38861 The system call on the host has been finished.
38865 These two states can be distinguished by the target by the value of the
38866 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
38867 call hasn't been performed. This is equivalent to the @code{EINTR} handling
38868 on POSIX systems. In any other case, the target may presume that the
38869 system call has been finished --- successfully or not --- and should behave
38870 as if the break message arrived right after the system call.
38872 @value{GDBN} must behave reliably. If the system call has not been called
38873 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
38874 @code{errno} in the packet. If the system call on the host has been finished
38875 before the user requests a break, the full action must be finished by
38876 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
38877 The @code{F} packet may only be sent when either nothing has happened
38878 or the full action has been completed.
38881 @subsection Console I/O
38882 @cindex console i/o as part of file-i/o
38884 By default and if not explicitly closed by the target system, the file
38885 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
38886 on the @value{GDBN} console is handled as any other file output operation
38887 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
38888 by @value{GDBN} so that after the target read request from file descriptor
38889 0 all following typing is buffered until either one of the following
38894 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
38896 system call is treated as finished.
38899 The user presses @key{RET}. This is treated as end of input with a trailing
38903 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
38904 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
38908 If the user has typed more characters than fit in the buffer given to
38909 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
38910 either another @code{read(0, @dots{})} is requested by the target, or debugging
38911 is stopped at the user's request.
38914 @node List of Supported Calls
38915 @subsection List of Supported Calls
38916 @cindex list of supported file-i/o calls
38933 @unnumberedsubsubsec open
38934 @cindex open, file-i/o system call
38939 int open(const char *pathname, int flags);
38940 int open(const char *pathname, int flags, mode_t mode);
38944 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
38947 @var{flags} is the bitwise @code{OR} of the following values:
38951 If the file does not exist it will be created. The host
38952 rules apply as far as file ownership and time stamps
38956 When used with @code{O_CREAT}, if the file already exists it is
38957 an error and open() fails.
38960 If the file already exists and the open mode allows
38961 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
38962 truncated to zero length.
38965 The file is opened in append mode.
38968 The file is opened for reading only.
38971 The file is opened for writing only.
38974 The file is opened for reading and writing.
38978 Other bits are silently ignored.
38982 @var{mode} is the bitwise @code{OR} of the following values:
38986 User has read permission.
38989 User has write permission.
38992 Group has read permission.
38995 Group has write permission.
38998 Others have read permission.
39001 Others have write permission.
39005 Other bits are silently ignored.
39008 @item Return value:
39009 @code{open} returns the new file descriptor or -1 if an error
39016 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39019 @var{pathname} refers to a directory.
39022 The requested access is not allowed.
39025 @var{pathname} was too long.
39028 A directory component in @var{pathname} does not exist.
39031 @var{pathname} refers to a device, pipe, named pipe or socket.
39034 @var{pathname} refers to a file on a read-only filesystem and
39035 write access was requested.
39038 @var{pathname} is an invalid pointer value.
39041 No space on device to create the file.
39044 The process already has the maximum number of files open.
39047 The limit on the total number of files open on the system
39051 The call was interrupted by the user.
39057 @unnumberedsubsubsec close
39058 @cindex close, file-i/o system call
39067 @samp{Fclose,@var{fd}}
39069 @item Return value:
39070 @code{close} returns zero on success, or -1 if an error occurred.
39076 @var{fd} isn't a valid open file descriptor.
39079 The call was interrupted by the user.
39085 @unnumberedsubsubsec read
39086 @cindex read, file-i/o system call
39091 int read(int fd, void *buf, unsigned int count);
39095 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
39097 @item Return value:
39098 On success, the number of bytes read is returned.
39099 Zero indicates end of file. If count is zero, read
39100 returns zero as well. On error, -1 is returned.
39106 @var{fd} is not a valid file descriptor or is not open for
39110 @var{bufptr} is an invalid pointer value.
39113 The call was interrupted by the user.
39119 @unnumberedsubsubsec write
39120 @cindex write, file-i/o system call
39125 int write(int fd, const void *buf, unsigned int count);
39129 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39131 @item Return value:
39132 On success, the number of bytes written are returned.
39133 Zero indicates nothing was written. On error, -1
39140 @var{fd} is not a valid file descriptor or is not open for
39144 @var{bufptr} is an invalid pointer value.
39147 An attempt was made to write a file that exceeds the
39148 host-specific maximum file size allowed.
39151 No space on device to write the data.
39154 The call was interrupted by the user.
39160 @unnumberedsubsubsec lseek
39161 @cindex lseek, file-i/o system call
39166 long lseek (int fd, long offset, int flag);
39170 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39172 @var{flag} is one of:
39176 The offset is set to @var{offset} bytes.
39179 The offset is set to its current location plus @var{offset}
39183 The offset is set to the size of the file plus @var{offset}
39187 @item Return value:
39188 On success, the resulting unsigned offset in bytes from
39189 the beginning of the file is returned. Otherwise, a
39190 value of -1 is returned.
39196 @var{fd} is not a valid open file descriptor.
39199 @var{fd} is associated with the @value{GDBN} console.
39202 @var{flag} is not a proper value.
39205 The call was interrupted by the user.
39211 @unnumberedsubsubsec rename
39212 @cindex rename, file-i/o system call
39217 int rename(const char *oldpath, const char *newpath);
39221 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39223 @item Return value:
39224 On success, zero is returned. On error, -1 is returned.
39230 @var{newpath} is an existing directory, but @var{oldpath} is not a
39234 @var{newpath} is a non-empty directory.
39237 @var{oldpath} or @var{newpath} is a directory that is in use by some
39241 An attempt was made to make a directory a subdirectory
39245 A component used as a directory in @var{oldpath} or new
39246 path is not a directory. Or @var{oldpath} is a directory
39247 and @var{newpath} exists but is not a directory.
39250 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39253 No access to the file or the path of the file.
39257 @var{oldpath} or @var{newpath} was too long.
39260 A directory component in @var{oldpath} or @var{newpath} does not exist.
39263 The file is on a read-only filesystem.
39266 The device containing the file has no room for the new
39270 The call was interrupted by the user.
39276 @unnumberedsubsubsec unlink
39277 @cindex unlink, file-i/o system call
39282 int unlink(const char *pathname);
39286 @samp{Funlink,@var{pathnameptr}/@var{len}}
39288 @item Return value:
39289 On success, zero is returned. On error, -1 is returned.
39295 No access to the file or the path of the file.
39298 The system does not allow unlinking of directories.
39301 The file @var{pathname} cannot be unlinked because it's
39302 being used by another process.
39305 @var{pathnameptr} is an invalid pointer value.
39308 @var{pathname} was too long.
39311 A directory component in @var{pathname} does not exist.
39314 A component of the path is not a directory.
39317 The file is on a read-only filesystem.
39320 The call was interrupted by the user.
39326 @unnumberedsubsubsec stat/fstat
39327 @cindex fstat, file-i/o system call
39328 @cindex stat, file-i/o system call
39333 int stat(const char *pathname, struct stat *buf);
39334 int fstat(int fd, struct stat *buf);
39338 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39339 @samp{Ffstat,@var{fd},@var{bufptr}}
39341 @item Return value:
39342 On success, zero is returned. On error, -1 is returned.
39348 @var{fd} is not a valid open file.
39351 A directory component in @var{pathname} does not exist or the
39352 path is an empty string.
39355 A component of the path is not a directory.
39358 @var{pathnameptr} is an invalid pointer value.
39361 No access to the file or the path of the file.
39364 @var{pathname} was too long.
39367 The call was interrupted by the user.
39373 @unnumberedsubsubsec gettimeofday
39374 @cindex gettimeofday, file-i/o system call
39379 int gettimeofday(struct timeval *tv, void *tz);
39383 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39385 @item Return value:
39386 On success, 0 is returned, -1 otherwise.
39392 @var{tz} is a non-NULL pointer.
39395 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39401 @unnumberedsubsubsec isatty
39402 @cindex isatty, file-i/o system call
39407 int isatty(int fd);
39411 @samp{Fisatty,@var{fd}}
39413 @item Return value:
39414 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39420 The call was interrupted by the user.
39425 Note that the @code{isatty} call is treated as a special case: it returns
39426 1 to the target if the file descriptor is attached
39427 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39428 would require implementing @code{ioctl} and would be more complex than
39433 @unnumberedsubsubsec system
39434 @cindex system, file-i/o system call
39439 int system(const char *command);
39443 @samp{Fsystem,@var{commandptr}/@var{len}}
39445 @item Return value:
39446 If @var{len} is zero, the return value indicates whether a shell is
39447 available. A zero return value indicates a shell is not available.
39448 For non-zero @var{len}, the value returned is -1 on error and the
39449 return status of the command otherwise. Only the exit status of the
39450 command is returned, which is extracted from the host's @code{system}
39451 return value by calling @code{WEXITSTATUS(retval)}. In case
39452 @file{/bin/sh} could not be executed, 127 is returned.
39458 The call was interrupted by the user.
39463 @value{GDBN} takes over the full task of calling the necessary host calls
39464 to perform the @code{system} call. The return value of @code{system} on
39465 the host is simplified before it's returned
39466 to the target. Any termination signal information from the child process
39467 is discarded, and the return value consists
39468 entirely of the exit status of the called command.
39470 Due to security concerns, the @code{system} call is by default refused
39471 by @value{GDBN}. The user has to allow this call explicitly with the
39472 @code{set remote system-call-allowed 1} command.
39475 @item set remote system-call-allowed
39476 @kindex set remote system-call-allowed
39477 Control whether to allow the @code{system} calls in the File I/O
39478 protocol for the remote target. The default is zero (disabled).
39480 @item show remote system-call-allowed
39481 @kindex show remote system-call-allowed
39482 Show whether the @code{system} calls are allowed in the File I/O
39486 @node Protocol-specific Representation of Datatypes
39487 @subsection Protocol-specific Representation of Datatypes
39488 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39491 * Integral Datatypes::
39493 * Memory Transfer::
39498 @node Integral Datatypes
39499 @unnumberedsubsubsec Integral Datatypes
39500 @cindex integral datatypes, in file-i/o protocol
39502 The integral datatypes used in the system calls are @code{int},
39503 @code{unsigned int}, @code{long}, @code{unsigned long},
39504 @code{mode_t}, and @code{time_t}.
39506 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
39507 implemented as 32 bit values in this protocol.
39509 @code{long} and @code{unsigned long} are implemented as 64 bit types.
39511 @xref{Limits}, for corresponding MIN and MAX values (similar to those
39512 in @file{limits.h}) to allow range checking on host and target.
39514 @code{time_t} datatypes are defined as seconds since the Epoch.
39516 All integral datatypes transferred as part of a memory read or write of a
39517 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
39520 @node Pointer Values
39521 @unnumberedsubsubsec Pointer Values
39522 @cindex pointer values, in file-i/o protocol
39524 Pointers to target data are transmitted as they are. An exception
39525 is made for pointers to buffers for which the length isn't
39526 transmitted as part of the function call, namely strings. Strings
39527 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39534 which is a pointer to data of length 18 bytes at position 0x1aaf.
39535 The length is defined as the full string length in bytes, including
39536 the trailing null byte. For example, the string @code{"hello world"}
39537 at address 0x123456 is transmitted as
39543 @node Memory Transfer
39544 @unnumberedsubsubsec Memory Transfer
39545 @cindex memory transfer, in file-i/o protocol
39547 Structured data which is transferred using a memory read or write (for
39548 example, a @code{struct stat}) is expected to be in a protocol-specific format
39549 with all scalar multibyte datatypes being big endian. Translation to
39550 this representation needs to be done both by the target before the @code{F}
39551 packet is sent, and by @value{GDBN} before
39552 it transfers memory to the target. Transferred pointers to structured
39553 data should point to the already-coerced data at any time.
39557 @unnumberedsubsubsec struct stat
39558 @cindex struct stat, in file-i/o protocol
39560 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39561 is defined as follows:
39565 unsigned int st_dev; /* device */
39566 unsigned int st_ino; /* inode */
39567 mode_t st_mode; /* protection */
39568 unsigned int st_nlink; /* number of hard links */
39569 unsigned int st_uid; /* user ID of owner */
39570 unsigned int st_gid; /* group ID of owner */
39571 unsigned int st_rdev; /* device type (if inode device) */
39572 unsigned long st_size; /* total size, in bytes */
39573 unsigned long st_blksize; /* blocksize for filesystem I/O */
39574 unsigned long st_blocks; /* number of blocks allocated */
39575 time_t st_atime; /* time of last access */
39576 time_t st_mtime; /* time of last modification */
39577 time_t st_ctime; /* time of last change */
39581 The integral datatypes conform to the definitions given in the
39582 appropriate section (see @ref{Integral Datatypes}, for details) so this
39583 structure is of size 64 bytes.
39585 The values of several fields have a restricted meaning and/or
39591 A value of 0 represents a file, 1 the console.
39594 No valid meaning for the target. Transmitted unchanged.
39597 Valid mode bits are described in @ref{Constants}. Any other
39598 bits have currently no meaning for the target.
39603 No valid meaning for the target. Transmitted unchanged.
39608 These values have a host and file system dependent
39609 accuracy. Especially on Windows hosts, the file system may not
39610 support exact timing values.
39613 The target gets a @code{struct stat} of the above representation and is
39614 responsible for coercing it to the target representation before
39617 Note that due to size differences between the host, target, and protocol
39618 representations of @code{struct stat} members, these members could eventually
39619 get truncated on the target.
39621 @node struct timeval
39622 @unnumberedsubsubsec struct timeval
39623 @cindex struct timeval, in file-i/o protocol
39625 The buffer of type @code{struct timeval} used by the File-I/O protocol
39626 is defined as follows:
39630 time_t tv_sec; /* second */
39631 long tv_usec; /* microsecond */
39635 The integral datatypes conform to the definitions given in the
39636 appropriate section (see @ref{Integral Datatypes}, for details) so this
39637 structure is of size 8 bytes.
39640 @subsection Constants
39641 @cindex constants, in file-i/o protocol
39643 The following values are used for the constants inside of the
39644 protocol. @value{GDBN} and target are responsible for translating these
39645 values before and after the call as needed.
39656 @unnumberedsubsubsec Open Flags
39657 @cindex open flags, in file-i/o protocol
39659 All values are given in hexadecimal representation.
39671 @node mode_t Values
39672 @unnumberedsubsubsec mode_t Values
39673 @cindex mode_t values, in file-i/o protocol
39675 All values are given in octal representation.
39692 @unnumberedsubsubsec Errno Values
39693 @cindex errno values, in file-i/o protocol
39695 All values are given in decimal representation.
39720 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39721 any error value not in the list of supported error numbers.
39724 @unnumberedsubsubsec Lseek Flags
39725 @cindex lseek flags, in file-i/o protocol
39734 @unnumberedsubsubsec Limits
39735 @cindex limits, in file-i/o protocol
39737 All values are given in decimal representation.
39740 INT_MIN -2147483648
39742 UINT_MAX 4294967295
39743 LONG_MIN -9223372036854775808
39744 LONG_MAX 9223372036854775807
39745 ULONG_MAX 18446744073709551615
39748 @node File-I/O Examples
39749 @subsection File-I/O Examples
39750 @cindex file-i/o examples
39752 Example sequence of a write call, file descriptor 3, buffer is at target
39753 address 0x1234, 6 bytes should be written:
39756 <- @code{Fwrite,3,1234,6}
39757 @emph{request memory read from target}
39760 @emph{return "6 bytes written"}
39764 Example sequence of a read call, file descriptor 3, buffer is at target
39765 address 0x1234, 6 bytes should be read:
39768 <- @code{Fread,3,1234,6}
39769 @emph{request memory write to target}
39770 -> @code{X1234,6:XXXXXX}
39771 @emph{return "6 bytes read"}
39775 Example sequence of a read call, call fails on the host due to invalid
39776 file descriptor (@code{EBADF}):
39779 <- @code{Fread,3,1234,6}
39783 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
39787 <- @code{Fread,3,1234,6}
39792 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
39796 <- @code{Fread,3,1234,6}
39797 -> @code{X1234,6:XXXXXX}
39801 @node Library List Format
39802 @section Library List Format
39803 @cindex library list format, remote protocol
39805 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
39806 same process as your application to manage libraries. In this case,
39807 @value{GDBN} can use the loader's symbol table and normal memory
39808 operations to maintain a list of shared libraries. On other
39809 platforms, the operating system manages loaded libraries.
39810 @value{GDBN} can not retrieve the list of currently loaded libraries
39811 through memory operations, so it uses the @samp{qXfer:libraries:read}
39812 packet (@pxref{qXfer library list read}) instead. The remote stub
39813 queries the target's operating system and reports which libraries
39816 The @samp{qXfer:libraries:read} packet returns an XML document which
39817 lists loaded libraries and their offsets. Each library has an
39818 associated name and one or more segment or section base addresses,
39819 which report where the library was loaded in memory.
39821 For the common case of libraries that are fully linked binaries, the
39822 library should have a list of segments. If the target supports
39823 dynamic linking of a relocatable object file, its library XML element
39824 should instead include a list of allocated sections. The segment or
39825 section bases are start addresses, not relocation offsets; they do not
39826 depend on the library's link-time base addresses.
39828 @value{GDBN} must be linked with the Expat library to support XML
39829 library lists. @xref{Expat}.
39831 A simple memory map, with one loaded library relocated by a single
39832 offset, looks like this:
39836 <library name="/lib/libc.so.6">
39837 <segment address="0x10000000"/>
39842 Another simple memory map, with one loaded library with three
39843 allocated sections (.text, .data, .bss), looks like this:
39847 <library name="sharedlib.o">
39848 <section address="0x10000000"/>
39849 <section address="0x20000000"/>
39850 <section address="0x30000000"/>
39855 The format of a library list is described by this DTD:
39858 <!-- library-list: Root element with versioning -->
39859 <!ELEMENT library-list (library)*>
39860 <!ATTLIST library-list version CDATA #FIXED "1.0">
39861 <!ELEMENT library (segment*, section*)>
39862 <!ATTLIST library name CDATA #REQUIRED>
39863 <!ELEMENT segment EMPTY>
39864 <!ATTLIST segment address CDATA #REQUIRED>
39865 <!ELEMENT section EMPTY>
39866 <!ATTLIST section address CDATA #REQUIRED>
39869 In addition, segments and section descriptors cannot be mixed within a
39870 single library element, and you must supply at least one segment or
39871 section for each library.
39873 @node Library List Format for SVR4 Targets
39874 @section Library List Format for SVR4 Targets
39875 @cindex library list format, remote protocol
39877 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
39878 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
39879 shared libraries. Still a special library list provided by this packet is
39880 more efficient for the @value{GDBN} remote protocol.
39882 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
39883 loaded libraries and their SVR4 linker parameters. For each library on SVR4
39884 target, the following parameters are reported:
39888 @code{name}, the absolute file name from the @code{l_name} field of
39889 @code{struct link_map}.
39891 @code{lm} with address of @code{struct link_map} used for TLS
39892 (Thread Local Storage) access.
39894 @code{l_addr}, the displacement as read from the field @code{l_addr} of
39895 @code{struct link_map}. For prelinked libraries this is not an absolute
39896 memory address. It is a displacement of absolute memory address against
39897 address the file was prelinked to during the library load.
39899 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
39902 Additionally the single @code{main-lm} attribute specifies address of
39903 @code{struct link_map} used for the main executable. This parameter is used
39904 for TLS access and its presence is optional.
39906 @value{GDBN} must be linked with the Expat library to support XML
39907 SVR4 library lists. @xref{Expat}.
39909 A simple memory map, with two loaded libraries (which do not use prelink),
39913 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
39914 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
39916 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
39918 </library-list-svr>
39921 The format of an SVR4 library list is described by this DTD:
39924 <!-- library-list-svr4: Root element with versioning -->
39925 <!ELEMENT library-list-svr4 (library)*>
39926 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
39927 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
39928 <!ELEMENT library EMPTY>
39929 <!ATTLIST library name CDATA #REQUIRED>
39930 <!ATTLIST library lm CDATA #REQUIRED>
39931 <!ATTLIST library l_addr CDATA #REQUIRED>
39932 <!ATTLIST library l_ld CDATA #REQUIRED>
39935 @node Memory Map Format
39936 @section Memory Map Format
39937 @cindex memory map format
39939 To be able to write into flash memory, @value{GDBN} needs to obtain a
39940 memory map from the target. This section describes the format of the
39943 The memory map is obtained using the @samp{qXfer:memory-map:read}
39944 (@pxref{qXfer memory map read}) packet and is an XML document that
39945 lists memory regions.
39947 @value{GDBN} must be linked with the Expat library to support XML
39948 memory maps. @xref{Expat}.
39950 The top-level structure of the document is shown below:
39953 <?xml version="1.0"?>
39954 <!DOCTYPE memory-map
39955 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39956 "http://sourceware.org/gdb/gdb-memory-map.dtd">
39962 Each region can be either:
39967 A region of RAM starting at @var{addr} and extending for @var{length}
39971 <memory type="ram" start="@var{addr}" length="@var{length}"/>
39976 A region of read-only memory:
39979 <memory type="rom" start="@var{addr}" length="@var{length}"/>
39984 A region of flash memory, with erasure blocks @var{blocksize}
39988 <memory type="flash" start="@var{addr}" length="@var{length}">
39989 <property name="blocksize">@var{blocksize}</property>
39995 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
39996 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
39997 packets to write to addresses in such ranges.
39999 The formal DTD for memory map format is given below:
40002 <!-- ................................................... -->
40003 <!-- Memory Map XML DTD ................................ -->
40004 <!-- File: memory-map.dtd .............................. -->
40005 <!-- .................................... .............. -->
40006 <!-- memory-map.dtd -->
40007 <!-- memory-map: Root element with versioning -->
40008 <!ELEMENT memory-map (memory | property)>
40009 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40010 <!ELEMENT memory (property)>
40011 <!-- memory: Specifies a memory region,
40012 and its type, or device. -->
40013 <!ATTLIST memory type CDATA #REQUIRED
40014 start CDATA #REQUIRED
40015 length CDATA #REQUIRED
40016 device CDATA #IMPLIED>
40017 <!-- property: Generic attribute tag -->
40018 <!ELEMENT property (#PCDATA | property)*>
40019 <!ATTLIST property name CDATA #REQUIRED>
40022 @node Thread List Format
40023 @section Thread List Format
40024 @cindex thread list format
40026 To efficiently update the list of threads and their attributes,
40027 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40028 (@pxref{qXfer threads read}) and obtains the XML document with
40029 the following structure:
40032 <?xml version="1.0"?>
40034 <thread id="id" core="0">
40035 ... description ...
40040 Each @samp{thread} element must have the @samp{id} attribute that
40041 identifies the thread (@pxref{thread-id syntax}). The
40042 @samp{core} attribute, if present, specifies which processor core
40043 the thread was last executing on. The content of the of @samp{thread}
40044 element is interpreted as human-readable auxilliary information.
40046 @node Traceframe Info Format
40047 @section Traceframe Info Format
40048 @cindex traceframe info format
40050 To be able to know which objects in the inferior can be examined when
40051 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
40052 memory ranges, registers and trace state variables that have been
40053 collected in a traceframe.
40055 This list is obtained using the @samp{qXfer:traceframe-info:read}
40056 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40058 @value{GDBN} must be linked with the Expat library to support XML
40059 traceframe info discovery. @xref{Expat}.
40061 The top-level structure of the document is shown below:
40064 <?xml version="1.0"?>
40065 <!DOCTYPE traceframe-info
40066 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40067 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
40073 Each traceframe block can be either:
40078 A region of collected memory starting at @var{addr} and extending for
40079 @var{length} bytes from there:
40082 <memory start="@var{addr}" length="@var{length}"/>
40087 The formal DTD for the traceframe info format is given below:
40090 <!ELEMENT traceframe-info (memory)* >
40091 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
40093 <!ELEMENT memory EMPTY>
40094 <!ATTLIST memory start CDATA #REQUIRED
40095 length CDATA #REQUIRED>
40098 @include agentexpr.texi
40100 @node Target Descriptions
40101 @appendix Target Descriptions
40102 @cindex target descriptions
40104 One of the challenges of using @value{GDBN} to debug embedded systems
40105 is that there are so many minor variants of each processor
40106 architecture in use. It is common practice for vendors to start with
40107 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40108 and then make changes to adapt it to a particular market niche. Some
40109 architectures have hundreds of variants, available from dozens of
40110 vendors. This leads to a number of problems:
40114 With so many different customized processors, it is difficult for
40115 the @value{GDBN} maintainers to keep up with the changes.
40117 Since individual variants may have short lifetimes or limited
40118 audiences, it may not be worthwhile to carry information about every
40119 variant in the @value{GDBN} source tree.
40121 When @value{GDBN} does support the architecture of the embedded system
40122 at hand, the task of finding the correct architecture name to give the
40123 @command{set architecture} command can be error-prone.
40126 To address these problems, the @value{GDBN} remote protocol allows a
40127 target system to not only identify itself to @value{GDBN}, but to
40128 actually describe its own features. This lets @value{GDBN} support
40129 processor variants it has never seen before --- to the extent that the
40130 descriptions are accurate, and that @value{GDBN} understands them.
40132 @value{GDBN} must be linked with the Expat library to support XML
40133 target descriptions. @xref{Expat}.
40136 * Retrieving Descriptions:: How descriptions are fetched from a target.
40137 * Target Description Format:: The contents of a target description.
40138 * Predefined Target Types:: Standard types available for target
40140 * Standard Target Features:: Features @value{GDBN} knows about.
40143 @node Retrieving Descriptions
40144 @section Retrieving Descriptions
40146 Target descriptions can be read from the target automatically, or
40147 specified by the user manually. The default behavior is to read the
40148 description from the target. @value{GDBN} retrieves it via the remote
40149 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40150 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40151 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40152 XML document, of the form described in @ref{Target Description
40155 Alternatively, you can specify a file to read for the target description.
40156 If a file is set, the target will not be queried. The commands to
40157 specify a file are:
40160 @cindex set tdesc filename
40161 @item set tdesc filename @var{path}
40162 Read the target description from @var{path}.
40164 @cindex unset tdesc filename
40165 @item unset tdesc filename
40166 Do not read the XML target description from a file. @value{GDBN}
40167 will use the description supplied by the current target.
40169 @cindex show tdesc filename
40170 @item show tdesc filename
40171 Show the filename to read for a target description, if any.
40175 @node Target Description Format
40176 @section Target Description Format
40177 @cindex target descriptions, XML format
40179 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40180 document which complies with the Document Type Definition provided in
40181 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40182 means you can use generally available tools like @command{xmllint} to
40183 check that your feature descriptions are well-formed and valid.
40184 However, to help people unfamiliar with XML write descriptions for
40185 their targets, we also describe the grammar here.
40187 Target descriptions can identify the architecture of the remote target
40188 and (for some architectures) provide information about custom register
40189 sets. They can also identify the OS ABI of the remote target.
40190 @value{GDBN} can use this information to autoconfigure for your
40191 target, or to warn you if you connect to an unsupported target.
40193 Here is a simple target description:
40196 <target version="1.0">
40197 <architecture>i386:x86-64</architecture>
40202 This minimal description only says that the target uses
40203 the x86-64 architecture.
40205 A target description has the following overall form, with [ ] marking
40206 optional elements and @dots{} marking repeatable elements. The elements
40207 are explained further below.
40210 <?xml version="1.0"?>
40211 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40212 <target version="1.0">
40213 @r{[}@var{architecture}@r{]}
40214 @r{[}@var{osabi}@r{]}
40215 @r{[}@var{compatible}@r{]}
40216 @r{[}@var{feature}@dots{}@r{]}
40221 The description is generally insensitive to whitespace and line
40222 breaks, under the usual common-sense rules. The XML version
40223 declaration and document type declaration can generally be omitted
40224 (@value{GDBN} does not require them), but specifying them may be
40225 useful for XML validation tools. The @samp{version} attribute for
40226 @samp{<target>} may also be omitted, but we recommend
40227 including it; if future versions of @value{GDBN} use an incompatible
40228 revision of @file{gdb-target.dtd}, they will detect and report
40229 the version mismatch.
40231 @subsection Inclusion
40232 @cindex target descriptions, inclusion
40235 @cindex <xi:include>
40238 It can sometimes be valuable to split a target description up into
40239 several different annexes, either for organizational purposes, or to
40240 share files between different possible target descriptions. You can
40241 divide a description into multiple files by replacing any element of
40242 the target description with an inclusion directive of the form:
40245 <xi:include href="@var{document}"/>
40249 When @value{GDBN} encounters an element of this form, it will retrieve
40250 the named XML @var{document}, and replace the inclusion directive with
40251 the contents of that document. If the current description was read
40252 using @samp{qXfer}, then so will be the included document;
40253 @var{document} will be interpreted as the name of an annex. If the
40254 current description was read from a file, @value{GDBN} will look for
40255 @var{document} as a file in the same directory where it found the
40256 original description.
40258 @subsection Architecture
40259 @cindex <architecture>
40261 An @samp{<architecture>} element has this form:
40264 <architecture>@var{arch}</architecture>
40267 @var{arch} is one of the architectures from the set accepted by
40268 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40271 @cindex @code{<osabi>}
40273 This optional field was introduced in @value{GDBN} version 7.0.
40274 Previous versions of @value{GDBN} ignore it.
40276 An @samp{<osabi>} element has this form:
40279 <osabi>@var{abi-name}</osabi>
40282 @var{abi-name} is an OS ABI name from the same selection accepted by
40283 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40285 @subsection Compatible Architecture
40286 @cindex @code{<compatible>}
40288 This optional field was introduced in @value{GDBN} version 7.0.
40289 Previous versions of @value{GDBN} ignore it.
40291 A @samp{<compatible>} element has this form:
40294 <compatible>@var{arch}</compatible>
40297 @var{arch} is one of the architectures from the set accepted by
40298 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40300 A @samp{<compatible>} element is used to specify that the target
40301 is able to run binaries in some other than the main target architecture
40302 given by the @samp{<architecture>} element. For example, on the
40303 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40304 or @code{powerpc:common64}, but the system is able to run binaries
40305 in the @code{spu} architecture as well. The way to describe this
40306 capability with @samp{<compatible>} is as follows:
40309 <architecture>powerpc:common</architecture>
40310 <compatible>spu</compatible>
40313 @subsection Features
40316 Each @samp{<feature>} describes some logical portion of the target
40317 system. Features are currently used to describe available CPU
40318 registers and the types of their contents. A @samp{<feature>} element
40322 <feature name="@var{name}">
40323 @r{[}@var{type}@dots{}@r{]}
40329 Each feature's name should be unique within the description. The name
40330 of a feature does not matter unless @value{GDBN} has some special
40331 knowledge of the contents of that feature; if it does, the feature
40332 should have its standard name. @xref{Standard Target Features}.
40336 Any register's value is a collection of bits which @value{GDBN} must
40337 interpret. The default interpretation is a two's complement integer,
40338 but other types can be requested by name in the register description.
40339 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40340 Target Types}), and the description can define additional composite types.
40342 Each type element must have an @samp{id} attribute, which gives
40343 a unique (within the containing @samp{<feature>}) name to the type.
40344 Types must be defined before they are used.
40347 Some targets offer vector registers, which can be treated as arrays
40348 of scalar elements. These types are written as @samp{<vector>} elements,
40349 specifying the array element type, @var{type}, and the number of elements,
40353 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40357 If a register's value is usefully viewed in multiple ways, define it
40358 with a union type containing the useful representations. The
40359 @samp{<union>} element contains one or more @samp{<field>} elements,
40360 each of which has a @var{name} and a @var{type}:
40363 <union id="@var{id}">
40364 <field name="@var{name}" type="@var{type}"/>
40370 If a register's value is composed from several separate values, define
40371 it with a structure type. There are two forms of the @samp{<struct>}
40372 element; a @samp{<struct>} element must either contain only bitfields
40373 or contain no bitfields. If the structure contains only bitfields,
40374 its total size in bytes must be specified, each bitfield must have an
40375 explicit start and end, and bitfields are automatically assigned an
40376 integer type. The field's @var{start} should be less than or
40377 equal to its @var{end}, and zero represents the least significant bit.
40380 <struct id="@var{id}" size="@var{size}">
40381 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40386 If the structure contains no bitfields, then each field has an
40387 explicit type, and no implicit padding is added.
40390 <struct id="@var{id}">
40391 <field name="@var{name}" type="@var{type}"/>
40397 If a register's value is a series of single-bit flags, define it with
40398 a flags type. The @samp{<flags>} element has an explicit @var{size}
40399 and contains one or more @samp{<field>} elements. Each field has a
40400 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
40404 <flags id="@var{id}" size="@var{size}">
40405 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40410 @subsection Registers
40413 Each register is represented as an element with this form:
40416 <reg name="@var{name}"
40417 bitsize="@var{size}"
40418 @r{[}regnum="@var{num}"@r{]}
40419 @r{[}save-restore="@var{save-restore}"@r{]}
40420 @r{[}type="@var{type}"@r{]}
40421 @r{[}group="@var{group}"@r{]}/>
40425 The components are as follows:
40430 The register's name; it must be unique within the target description.
40433 The register's size, in bits.
40436 The register's number. If omitted, a register's number is one greater
40437 than that of the previous register (either in the current feature or in
40438 a preceding feature); the first register in the target description
40439 defaults to zero. This register number is used to read or write
40440 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40441 packets, and registers appear in the @code{g} and @code{G} packets
40442 in order of increasing register number.
40445 Whether the register should be preserved across inferior function
40446 calls; this must be either @code{yes} or @code{no}. The default is
40447 @code{yes}, which is appropriate for most registers except for
40448 some system control registers; this is not related to the target's
40452 The type of the register. @var{type} may be a predefined type, a type
40453 defined in the current feature, or one of the special types @code{int}
40454 and @code{float}. @code{int} is an integer type of the correct size
40455 for @var{bitsize}, and @code{float} is a floating point type (in the
40456 architecture's normal floating point format) of the correct size for
40457 @var{bitsize}. The default is @code{int}.
40460 The register group to which this register belongs. @var{group} must
40461 be either @code{general}, @code{float}, or @code{vector}. If no
40462 @var{group} is specified, @value{GDBN} will not display the register
40463 in @code{info registers}.
40467 @node Predefined Target Types
40468 @section Predefined Target Types
40469 @cindex target descriptions, predefined types
40471 Type definitions in the self-description can build up composite types
40472 from basic building blocks, but can not define fundamental types. Instead,
40473 standard identifiers are provided by @value{GDBN} for the fundamental
40474 types. The currently supported types are:
40483 Signed integer types holding the specified number of bits.
40490 Unsigned integer types holding the specified number of bits.
40494 Pointers to unspecified code and data. The program counter and
40495 any dedicated return address register may be marked as code
40496 pointers; printing a code pointer converts it into a symbolic
40497 address. The stack pointer and any dedicated address registers
40498 may be marked as data pointers.
40501 Single precision IEEE floating point.
40504 Double precision IEEE floating point.
40507 The 12-byte extended precision format used by ARM FPA registers.
40510 The 10-byte extended precision format used by x87 registers.
40513 32bit @sc{eflags} register used by x86.
40516 32bit @sc{mxcsr} register used by x86.
40520 @node Standard Target Features
40521 @section Standard Target Features
40522 @cindex target descriptions, standard features
40524 A target description must contain either no registers or all the
40525 target's registers. If the description contains no registers, then
40526 @value{GDBN} will assume a default register layout, selected based on
40527 the architecture. If the description contains any registers, the
40528 default layout will not be used; the standard registers must be
40529 described in the target description, in such a way that @value{GDBN}
40530 can recognize them.
40532 This is accomplished by giving specific names to feature elements
40533 which contain standard registers. @value{GDBN} will look for features
40534 with those names and verify that they contain the expected registers;
40535 if any known feature is missing required registers, or if any required
40536 feature is missing, @value{GDBN} will reject the target
40537 description. You can add additional registers to any of the
40538 standard features --- @value{GDBN} will display them just as if
40539 they were added to an unrecognized feature.
40541 This section lists the known features and their expected contents.
40542 Sample XML documents for these features are included in the
40543 @value{GDBN} source tree, in the directory @file{gdb/features}.
40545 Names recognized by @value{GDBN} should include the name of the
40546 company or organization which selected the name, and the overall
40547 architecture to which the feature applies; so e.g.@: the feature
40548 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
40550 The names of registers are not case sensitive for the purpose
40551 of recognizing standard features, but @value{GDBN} will only display
40552 registers using the capitalization used in the description.
40559 * PowerPC Features::
40565 @subsection ARM Features
40566 @cindex target descriptions, ARM features
40568 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
40570 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
40571 @samp{lr}, @samp{pc}, and @samp{cpsr}.
40573 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
40574 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
40575 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
40578 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
40579 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
40581 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
40582 it should contain at least registers @samp{wR0} through @samp{wR15} and
40583 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
40584 @samp{wCSSF}, and @samp{wCASF} registers are optional.
40586 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
40587 should contain at least registers @samp{d0} through @samp{d15}. If
40588 they are present, @samp{d16} through @samp{d31} should also be included.
40589 @value{GDBN} will synthesize the single-precision registers from
40590 halves of the double-precision registers.
40592 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
40593 need to contain registers; it instructs @value{GDBN} to display the
40594 VFP double-precision registers as vectors and to synthesize the
40595 quad-precision registers from pairs of double-precision registers.
40596 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
40597 be present and include 32 double-precision registers.
40599 @node i386 Features
40600 @subsection i386 Features
40601 @cindex target descriptions, i386 features
40603 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
40604 targets. It should describe the following registers:
40608 @samp{eax} through @samp{edi} plus @samp{eip} for i386
40610 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
40612 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
40613 @samp{fs}, @samp{gs}
40615 @samp{st0} through @samp{st7}
40617 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
40618 @samp{foseg}, @samp{fooff} and @samp{fop}
40621 The register sets may be different, depending on the target.
40623 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
40624 describe registers:
40628 @samp{xmm0} through @samp{xmm7} for i386
40630 @samp{xmm0} through @samp{xmm15} for amd64
40635 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
40636 @samp{org.gnu.gdb.i386.sse} feature. It should
40637 describe the upper 128 bits of @sc{ymm} registers:
40641 @samp{ymm0h} through @samp{ymm7h} for i386
40643 @samp{ymm0h} through @samp{ymm15h} for amd64
40646 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
40647 describe a single register, @samp{orig_eax}.
40649 @node MIPS Features
40650 @subsection @acronym{MIPS} Features
40651 @cindex target descriptions, @acronym{MIPS} features
40653 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
40654 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
40655 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
40658 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
40659 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
40660 registers. They may be 32-bit or 64-bit depending on the target.
40662 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
40663 it may be optional in a future version of @value{GDBN}. It should
40664 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
40665 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
40667 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
40668 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
40669 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
40670 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
40672 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
40673 contain a single register, @samp{restart}, which is used by the
40674 Linux kernel to control restartable syscalls.
40676 @node M68K Features
40677 @subsection M68K Features
40678 @cindex target descriptions, M68K features
40681 @item @samp{org.gnu.gdb.m68k.core}
40682 @itemx @samp{org.gnu.gdb.coldfire.core}
40683 @itemx @samp{org.gnu.gdb.fido.core}
40684 One of those features must be always present.
40685 The feature that is present determines which flavor of m68k is
40686 used. The feature that is present should contain registers
40687 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
40688 @samp{sp}, @samp{ps} and @samp{pc}.
40690 @item @samp{org.gnu.gdb.coldfire.fp}
40691 This feature is optional. If present, it should contain registers
40692 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
40696 @node PowerPC Features
40697 @subsection PowerPC Features
40698 @cindex target descriptions, PowerPC features
40700 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
40701 targets. It should contain registers @samp{r0} through @samp{r31},
40702 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
40703 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
40705 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
40706 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
40708 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
40709 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
40712 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
40713 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
40714 will combine these registers with the floating point registers
40715 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
40716 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
40717 through @samp{vs63}, the set of vector registers for POWER7.
40719 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
40720 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
40721 @samp{spefscr}. SPE targets should provide 32-bit registers in
40722 @samp{org.gnu.gdb.power.core} and provide the upper halves in
40723 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
40724 these to present registers @samp{ev0} through @samp{ev31} to the
40727 @node TIC6x Features
40728 @subsection TMS320C6x Features
40729 @cindex target descriptions, TIC6x features
40730 @cindex target descriptions, TMS320C6x features
40731 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
40732 targets. It should contain registers @samp{A0} through @samp{A15},
40733 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
40735 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
40736 contain registers @samp{A16} through @samp{A31} and @samp{B16}
40737 through @samp{B31}.
40739 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
40740 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
40742 @node Operating System Information
40743 @appendix Operating System Information
40744 @cindex operating system information
40750 Users of @value{GDBN} often wish to obtain information about the state of
40751 the operating system running on the target---for example the list of
40752 processes, or the list of open files. This section describes the
40753 mechanism that makes it possible. This mechanism is similar to the
40754 target features mechanism (@pxref{Target Descriptions}), but focuses
40755 on a different aspect of target.
40757 Operating system information is retrived from the target via the
40758 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
40759 read}). The object name in the request should be @samp{osdata}, and
40760 the @var{annex} identifies the data to be fetched.
40763 @appendixsection Process list
40764 @cindex operating system information, process list
40766 When requesting the process list, the @var{annex} field in the
40767 @samp{qXfer} request should be @samp{processes}. The returned data is
40768 an XML document. The formal syntax of this document is defined in
40769 @file{gdb/features/osdata.dtd}.
40771 An example document is:
40774 <?xml version="1.0"?>
40775 <!DOCTYPE target SYSTEM "osdata.dtd">
40776 <osdata type="processes">
40778 <column name="pid">1</column>
40779 <column name="user">root</column>
40780 <column name="command">/sbin/init</column>
40781 <column name="cores">1,2,3</column>
40786 Each item should include a column whose name is @samp{pid}. The value
40787 of that column should identify the process on the target. The
40788 @samp{user} and @samp{command} columns are optional, and will be
40789 displayed by @value{GDBN}. The @samp{cores} column, if present,
40790 should contain a comma-separated list of cores that this process
40791 is running on. Target may provide additional columns,
40792 which @value{GDBN} currently ignores.
40794 @node Trace File Format
40795 @appendix Trace File Format
40796 @cindex trace file format
40798 The trace file comes in three parts: a header, a textual description
40799 section, and a trace frame section with binary data.
40801 The header has the form @code{\x7fTRACE0\n}. The first byte is
40802 @code{0x7f} so as to indicate that the file contains binary data,
40803 while the @code{0} is a version number that may have different values
40806 The description section consists of multiple lines of @sc{ascii} text
40807 separated by newline characters (@code{0xa}). The lines may include a
40808 variety of optional descriptive or context-setting information, such
40809 as tracepoint definitions or register set size. @value{GDBN} will
40810 ignore any line that it does not recognize. An empty line marks the end
40813 @c FIXME add some specific types of data
40815 The trace frame section consists of a number of consecutive frames.
40816 Each frame begins with a two-byte tracepoint number, followed by a
40817 four-byte size giving the amount of data in the frame. The data in
40818 the frame consists of a number of blocks, each introduced by a
40819 character indicating its type (at least register, memory, and trace
40820 state variable). The data in this section is raw binary, not a
40821 hexadecimal or other encoding; its endianness matches the target's
40824 @c FIXME bi-arch may require endianness/arch info in description section
40827 @item R @var{bytes}
40828 Register block. The number and ordering of bytes matches that of a
40829 @code{g} packet in the remote protocol. Note that these are the
40830 actual bytes, in target order and @value{GDBN} register order, not a
40831 hexadecimal encoding.
40833 @item M @var{address} @var{length} @var{bytes}...
40834 Memory block. This is a contiguous block of memory, at the 8-byte
40835 address @var{address}, with a 2-byte length @var{length}, followed by
40836 @var{length} bytes.
40838 @item V @var{number} @var{value}
40839 Trace state variable block. This records the 8-byte signed value
40840 @var{value} of trace state variable numbered @var{number}.
40844 Future enhancements of the trace file format may include additional types
40847 @node Index Section Format
40848 @appendix @code{.gdb_index} section format
40849 @cindex .gdb_index section format
40850 @cindex index section format
40852 This section documents the index section that is created by @code{save
40853 gdb-index} (@pxref{Index Files}). The index section is
40854 DWARF-specific; some knowledge of DWARF is assumed in this
40857 The mapped index file format is designed to be directly
40858 @code{mmap}able on any architecture. In most cases, a datum is
40859 represented using a little-endian 32-bit integer value, called an
40860 @code{offset_type}. Big endian machines must byte-swap the values
40861 before using them. Exceptions to this rule are noted. The data is
40862 laid out such that alignment is always respected.
40864 A mapped index consists of several areas, laid out in order.
40868 The file header. This is a sequence of values, of @code{offset_type}
40869 unless otherwise noted:
40873 The version number, currently 7. Versions 1, 2 and 3 are obsolete.
40874 Version 4 uses a different hashing function from versions 5 and 6.
40875 Version 6 includes symbols for inlined functions, whereas versions 4
40876 and 5 do not. Version 7 adds attributes to the CU indices in the
40877 symbol table. @value{GDBN} will only read version 4, 5, or 6 indices
40878 by specifying @code{set use-deprecated-index-sections on}.
40881 The offset, from the start of the file, of the CU list.
40884 The offset, from the start of the file, of the types CU list. Note
40885 that this area can be empty, in which case this offset will be equal
40886 to the next offset.
40889 The offset, from the start of the file, of the address area.
40892 The offset, from the start of the file, of the symbol table.
40895 The offset, from the start of the file, of the constant pool.
40899 The CU list. This is a sequence of pairs of 64-bit little-endian
40900 values, sorted by the CU offset. The first element in each pair is
40901 the offset of a CU in the @code{.debug_info} section. The second
40902 element in each pair is the length of that CU. References to a CU
40903 elsewhere in the map are done using a CU index, which is just the
40904 0-based index into this table. Note that if there are type CUs, then
40905 conceptually CUs and type CUs form a single list for the purposes of
40909 The types CU list. This is a sequence of triplets of 64-bit
40910 little-endian values. In a triplet, the first value is the CU offset,
40911 the second value is the type offset in the CU, and the third value is
40912 the type signature. The types CU list is not sorted.
40915 The address area. The address area consists of a sequence of address
40916 entries. Each address entry has three elements:
40920 The low address. This is a 64-bit little-endian value.
40923 The high address. This is a 64-bit little-endian value. Like
40924 @code{DW_AT_high_pc}, the value is one byte beyond the end.
40927 The CU index. This is an @code{offset_type} value.
40931 The symbol table. This is an open-addressed hash table. The size of
40932 the hash table is always a power of 2.
40934 Each slot in the hash table consists of a pair of @code{offset_type}
40935 values. The first value is the offset of the symbol's name in the
40936 constant pool. The second value is the offset of the CU vector in the
40939 If both values are 0, then this slot in the hash table is empty. This
40940 is ok because while 0 is a valid constant pool index, it cannot be a
40941 valid index for both a string and a CU vector.
40943 The hash value for a table entry is computed by applying an
40944 iterative hash function to the symbol's name. Starting with an
40945 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
40946 the string is incorporated into the hash using the formula depending on the
40951 The formula is @code{r = r * 67 + c - 113}.
40953 @item Versions 5 to 7
40954 The formula is @code{r = r * 67 + tolower (c) - 113}.
40957 The terminating @samp{\0} is not incorporated into the hash.
40959 The step size used in the hash table is computed via
40960 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
40961 value, and @samp{size} is the size of the hash table. The step size
40962 is used to find the next candidate slot when handling a hash
40965 The names of C@t{++} symbols in the hash table are canonicalized. We
40966 don't currently have a simple description of the canonicalization
40967 algorithm; if you intend to create new index sections, you must read
40971 The constant pool. This is simply a bunch of bytes. It is organized
40972 so that alignment is correct: CU vectors are stored first, followed by
40975 A CU vector in the constant pool is a sequence of @code{offset_type}
40976 values. The first value is the number of CU indices in the vector.
40977 Each subsequent value is the index and symbol attributes of a CU in
40978 the CU list. This element in the hash table is used to indicate which
40979 CUs define the symbol and how the symbol is used.
40980 See below for the format of each CU index+attributes entry.
40982 A string in the constant pool is zero-terminated.
40985 Attributes were added to CU index values in @code{.gdb_index} version 7.
40986 If a symbol has multiple uses within a CU then there is one
40987 CU index+attributes value for each use.
40989 The format of each CU index+attributes entry is as follows
40995 This is the index of the CU in the CU list.
40997 These bits are reserved for future purposes and must be zero.
40999 The kind of the symbol in the CU.
41003 This value is reserved and should not be used.
41004 By reserving zero the full @code{offset_type} value is backwards compatible
41005 with previous versions of the index.
41007 The symbol is a type.
41009 The symbol is a variable or an enum value.
41011 The symbol is a function.
41013 Any other kind of symbol.
41015 These values are reserved.
41019 This bit is zero if the value is global and one if it is static.
41021 The determination of whether a symbol is global or static is complicated.
41022 The authorative reference is the file @file{dwarf2read.c} in
41023 @value{GDBN} sources.
41027 This pseudo-code describes the computation of a symbol's kind and
41028 global/static attributes in the index.
41031 is_external = get_attribute (die, DW_AT_external);
41032 language = get_attribute (cu_die, DW_AT_language);
41035 case DW_TAG_typedef:
41036 case DW_TAG_base_type:
41037 case DW_TAG_subrange_type:
41041 case DW_TAG_enumerator:
41043 is_static = (language != CPLUS && language != JAVA);
41045 case DW_TAG_subprogram:
41047 is_static = ! (is_external || language == ADA);
41049 case DW_TAG_constant:
41051 is_static = ! is_external;
41053 case DW_TAG_variable:
41055 is_static = ! is_external;
41057 case DW_TAG_namespace:
41061 case DW_TAG_class_type:
41062 case DW_TAG_interface_type:
41063 case DW_TAG_structure_type:
41064 case DW_TAG_union_type:
41065 case DW_TAG_enumeration_type:
41067 is_static = (language != CPLUS && language != JAVA);
41076 @node GNU Free Documentation License
41077 @appendix GNU Free Documentation License
41080 @node Concept Index
41081 @unnumbered Concept Index
41085 @node Command and Variable Index
41086 @unnumbered Command, Variable, and Function Index
41091 % I think something like @@colophon should be in texinfo. In the
41093 \long\def\colophon{\hbox to0pt{}\vfill
41094 \centerline{The body of this manual is set in}
41095 \centerline{\fontname\tenrm,}
41096 \centerline{with headings in {\bf\fontname\tenbf}}
41097 \centerline{and examples in {\tt\fontname\tentt}.}
41098 \centerline{{\it\fontname\tenit\/},}
41099 \centerline{{\bf\fontname\tenbf}, and}
41100 \centerline{{\sl\fontname\tensl\/}}
41101 \centerline{are used for emphasis.}\vfill}
41103 % Blame: doc@@cygnus.com, 1991.